Formation of Embedded Microstructures by Thermal Activated Solvent Bonding

Abstract: We present a thermal activated solvent bonding technique for the formation of embedded microstrucutres in polymer. It is based on the temperature dependent solubility of polymer in a liquid that is not a solvent at room temperature. With thermal activation, the liquid is transformed into a solvent of the polymer, creating a bonding capability through segmental or chain interdiffusion at the bonding interface. The technique has advantages over the more commonly used thermal bonding due to its much lower operation temperature (30 degrees C lower than the material's Tg), lower load, as well as shorter time. Lap shear test indicated bonding shear strength of up to 2.9 MPa. Leak test based on the bubble emission technique showed that the bonded microfluidic device can withstand at least 6 bars (87 psi) of internal pressure (gauge) in the microchannel. This technique can be applied to other systems of polymer and solvent.


Design and Modeling of Micromechanical GaAs based Hot Plate for Gas Sensors

Abstract: For modern Gas sensors, high sensitivity and low power are expected. This paper discusses design, simulation and fabrication of new Micromachined Thermal Converters (MTCs) based on GaAs developed for Gas sensors. Metal oxide gas sensors generally work in high temperature mode that is required for chemical reactions to be performed between molecules of the specified gas and the surface of sensing material. There is a low power consumption required to obtain the operation temperatures in the range of 200 to 500 oC. High thermal isolation of these devices solves consumption problem and can be made by designing of free standing micromechanical hot plates. Mechanical stability and a fast thermal response are especially significant parameters that can not be neglected. These characteristics can be achieved with new concept of GaAs thermal converter.


Set-up and characterization of a humidity sensor realized in LTCC-technology

Abstract: A new type of integrated temperature and humidity sensor applying LTCC-technology has been developed and characterized. In this approach, sensing elements are implemented using heated metal resistors (Pt-elements), where one is exposed to the humid environment that causes the sensor element to cool down with increased humidity, while the other one is sealed from the environment. Sensor design is based on FEA (Finite Element Analyses) where the critical design parameters have been analyzed with regard to the performance characteristic of the device. The set-up of sensor element will be shown and the functional capability will be demonstrated by experimental results.


Micromachined Polycrystalline Sige-Based Thermopiles for Micropower Generation on Human Body

Abstract: This paper presents a polycrystalline silicon germanium (poly-SiGe) thermopile specially designed for thermoelectric generators used on human body. Both the design of the single thermocouple and the arrangement of the thermocouple array have been described. A rim structure has been introduced in order to increase the temperature difference across the thermocouple junctions. The modeling of the thermocouple and the thermopile has been performed analytically and numerically. An output power of about 1 $\mu$W at an output voltage of more than 1 V is expected from the current design of thermopiles in a watch-size generator. The key material properties of the poly-SiGe have been measured. The thermopile has been fabricated and tested. Experimental results clearly demonstrate the advantage of the rim structure in increasing output voltage. In presence of forced convection, the output voltage of a non-released thermopile can increase from about 53 mV/K/cm2 to about 130 mV/K/cm2 after the rim structure is formed. A larger output voltage from the thermopile is expected upon process completion.


Silicon microneedles array with biodegradable tips for transdermal drug delivery

Abstract: This paper presents the fabrication process, characterization results and basic functionality of silicon microneedles array with biodegradable tips. In order to avoid the main problems related to silicon microneedles : broking of the top part of the needles inside the skin, a simple solution can be fabrication of microneedles array with biodegradable tips. The silicon microneedles array was fabricated by using reactive ion etching while the biodegradable tips were performed using and anodization process that generates selectively porous silicon only on the top part of the skin. The paper presents also the results of in vitro release of calcein using microneedles array with biodegradable tips


2-D Analysis of Enhancement of Analytes Adsorption Due to Flow Stirring by Electrothermal Force in The Microcantilever Sensor

Abstract: Ac electrokinetic flows are commonly used for manipulating micron-scale particles in a biosensor system. At the solid-liquid state there are two kinds of processes in the reaction between analytes and ligands: the mass transport process and the chemical reaction process. The mass transport process is related to convection and diffusion. Total or partial limit of mass transport would retard the diffusion from the bulk fluid to the interface of reaction. This effect decreases the possibility of adsorption of analyte and ligand because the chemical reaction is faster than the diffusion. In order to solve this problem, we apply an ac electric field to induce a vortex field by the electrothermal effect, which helps in increasing the rate of diffusion. By using the finite element analysis software, COMSOL Multiphysics, we optimized several parameters of the microelectrode structures and the position of the reacting surface, i.e. the microcantilever, by a simplified 2-D model and a 3-D model. It is successful in accelerating the reacting rate of the molecule which is limited by mass transport. The factor of the efficiency is about 1.429 when the operating voltage is 15 Vrms peak-to-peak. In addition, the surface concentration of the complex on the microcantilever has been simulated.


Development and Application of a Diaphragm Micro-Pump with Piezoelectric Device

Abstract: In this study, a new type of thin, compact, and light weighed diaphragm micro-pump has been successfully developed to actuate the liquid by the vibration of a diaphragm. The micro-diaphragm pump with two valves is fabricated in an aluminum case by using highly accurate CNC machine, and the cross-section dimension is 5mm x 8mm. Both valves and diaphragm are manufactured from PDMS. The amplitude of vibration by a piezoelectric device produces an oscillating flow which may change the chamber volume by changing the curvature of a diaphragm. Several experimental set-ups for performance test in a single micro-diaphragm pump, isothermal flow open system, and a closed liquid cooling system is designed and implemented. The performance of one-side actuating micro-diaphragm pump is affected by the design of check valves, diaphragm, piezoelectric device, chamber volume, input voltage and frequency. The measured maximum flow rate of present design is 72 ml/min at zero total pump head in the range of operation frequency 70-180 Hz.


Simulation of valveless micropump and mode analysis

Abstract: In this work, a 3-D simulation is performed to study for the solid-fluid coupling effect driven by piezoelectric materials and utilizes asymmetric obstacles to control the flow direction. The result of simulation is also verified. For a micropump, it is crucial to find the optimal working frequency which produce maximum net flow rate. The PZT plate vibrates under the first mode, which is symmetric. Adjusting the working frequency, the maximum flow rate can be obtained. For the micrpump we studied, the optimal working frequency is 3.2K Hz. At higher working frequency, say 20K Hz, the fluid-solid membrane may come out a intermediate mode, which is different from the first mode and the second mode. It is observed that the center of the mode drifts. Meanwhile, the result shows that a phase shift lagging when the excitation force exists in the vibration response. Finally, at even higher working frequency, say 30K Hz, a second vibration mode is observed.


Enhanced Sensing Characteristics in MEMS-based Formaldehyde Gas Sensor

Abstract: This study has successfully demonstrated a novel self-heating formaldehyde gas sensor based on a thin film of NiO sensing layer. A new fabrication process has been developed in which the Pt micro heater and electrodes are deposited directly on the substrate and the NiO thin film is deposited above on the micro heater to serve as sensing layer. Pt electrodes are formed below the sensing layer to measure the electrical conductivity changes caused by formaldehyde oxidation at the oxide surface. Furthermore, the upper sensing layer and NiO/Al2O3 co-sputtering significantly increases the sensitivity of the gas sensor, improves its detection limit capability. The microfabricated formaldehyde gas sensor presented in this study is suitable not only for industrial process monitoring, but also for the detection of formaldehyde concentrations in buildings in order to safeguard human health.


Mems Q-Factor Enhancement Using Parametric Amplification: Theoretical Study and Design of a Parametric Device

Abstract: Parametric amplification is an interesting way of artificially increasing a MEMS Quality factor and could be helpful in many kinds of applications. This paper presents a theoretical study of this principle, based on Matlab/Simulink simulations, and proposes design guidelines for parametric structures. A new device designed with this approach is presented together with the corresponding FEM simulation results.


Biodegradable Polylactic Acid (PLA) Microstructures for Scaffold Applications

Abstract: In this research, we present a simple and cost effective soft lithographic process to fabricate PLA scaffolds for tissue engineering. In which, the negative photoresist JSR THB-120N was spun on a glass subtract followed by conventional UV lithographic processes to fabricate the master to cast the PDMS elastomeric mold. A thin poly(vinyl alcohol) (PVA) layer was used as a mode release such that the PLA scaffold can be easily peeled off. The PLA precursor solution was then cast onto the PDMS mold to form the PLA microstructures. After evaporating the solvent, the PLA microstructures can be easily peeled off from the PDMS mold. Experimental results show that the desired microvessels scaffold can be successfully transferred to the biodegradable polymer PLA.


Solving functional reliability issue for an optical electrostatic switch

Abstract: In this paper, we report the advantage of using AC actuating signal for driving MEMS actuators instead of DC voltages. The study is based upon micro mirror devices used in digital mode for optical switching operation. When the pull-in effect is used, charge injection occurs when the micro mirror is maintained in the deflected position. To avoid this effect, a geometrical solution is to realize grounded landing electrodes which are electro-statically separated from the control electrodes. Another solution is the use of AC signal which eliminates charge injection particularly if a bipolar signal is used. Long term experiments have demonstrated the reliability of such a signal command to avoid injection of electric charges.


Identification of Test Structures for Reduced Order Modeling of the Squeeze Film Damping in Mems

Abstract: In this study the dynamic behaviour of perforated microplates oscillating under the effect of squeeze film damping is analyzed. A numerical approach is adopted to predict the effects of damping and stiffness transferred from the surrounding ambient air to oscillating structures ; the effect of hole's cross section and plate's extension is observed. Results obtained by F.E.M. models are compared with experimental measurements performed by an optical interferometric microscope.


Out-of-Plane Cmos Compatible Magnetometers

Abstract: Three-dimensional MEMS magnetometers with use of residual stresses in thin multilayers cantilevers are presented. Half-loop cantilevers based on Lorentz-force deflection convert magnetic flux in changes, thanks to piezoresistive transducers mounted in Wheatstone bridge. Magnetic field in the order of 10 Gauss was measured with a sensitivity of 0.015 mV/Gauss. A Finite Element Model of the device has been developed with Ansys for static and dynamic simulations. Novel out-of-plane ferromagnetic nickel plate magnetometer is also presented.


Tuneable Capacitor based on dual picks profile of the sacrificial layer

Abstract: In this paper, we present a novel dual gap tuneable capacitor process based on the profile of the sacrificial layer. This profile involves a tri-layer photo-resist process with only one mask level. This realization is based on a special profile of the sacrificial layer designed by two picks. The mechanism of the sacrificial layer realisation is dependent on resist thickness, resist formulation (viscosity, type of polymer and/or solvent, additives...), design of the patterned layer (size or width) and the conditions under which this layer is prepared: thermal treatment, etch back processes... In this communication we demonstrate influence of the later parameters and discuss how a dual pick profile was achieved.


Reduced 30% scanning time 3D multiplexer integrated circuit applied to large array format 20KHZ frequency inkjet print heads

Abstract: Enhancement of the number and array density of nozzles within an inkjet head chip is one of the keys to raise the printing speed and printing resolutions. However, traditional 2D architecture of driving circuits can not meet the requirement for high scanning speed and low data accessing points when nozzle numbers greater than 1000. This paper proposes a novel architecture of high-selection-speed three-dimensional data registration for inkjet applications. With the configuration of three-dimensional data registration, the number of data accessing points as well as the scanning lines can be greatly reduced for large array inkjet printheads with nozzles numbering more than 1000. This IC (Integrated Circuit) architecture involves three-dimensional multiplexing with the provision of a gating transistor for each ink firing resistor, where ink firing resistors are triggered only by the selection of their associated gating transistors. Three signals: selection (S), address (A), and power supply (P), are employed together to activate a nozzle for droplet ejection. The smart printhead controller has been designed by a 0.35 um CMOS process with a total circuit area, 2500 x 500 microm2, which is 80% of the cirucuit area by 2D configuration for 1000 nozzles. Experiment results demonstrate the functionality of the fabricated IC in operation, signal transmission and a potential to control more than 1000 nozzles with only 31 data access points and reduced 30% scanning time.


Analysis of Asymmetric Piezoelectric Composite Beam

Abstract: This paper deals with the vibration analysis of an asymmetric composite beam composed of glass a piezoelectric material. The Bernoulli's beam theory is adopted for mechanical deformations, and the electric potential field of the piezoelectric material is assumed such that the divergence-free requirement of the electrical displacements is satisfied. The accuracy of the analytic model is assessed by comparing the resonance frequencies obtained by the analytic model with those obtained by the finite element method. The model developed can be used as a tool for designing piezoelectric actuators such as micro-pumps.


A High-Q Microwave MEMS Resonator

Abstract: A High-Q microwave (K band) MEMS resonator is presented, which empolys substrate integrated waveguide (SIW) and micromachined via-hole arrays by ICP process. Nonradiation dielectric waveguide (NRD) is formed by metal filled via-hole arrays and grounded planes. The three dimensional (3D) high resistivity silicon substrate filled cavity resonator is fed by current probes using CPW line. This monolithic resonator results in low cost, high performance and easy integration with planar cicuits. The measured quality factor is beyond 180 and the resonance frequency is 21GHz.It shows a good agreement with the simulation results. The chip size is only 4.7mm x 4.6mm x 0.5mm. Finally, as an example of applications, a filter using two SIW resonators is designed.


Lamination And Microstructuring Technology for a Bio-Cell Multiwell array

Abstract: Microtechnology becomes a versatile tool for biological and biomedical applications. Microwells have been established long but remained non-intelligent up to now. Merging new fabrication techniques and handling concepts with microelectronics enables to realize intelligent microwells suitable for future improved cancer treatment. The described technology depicts the basis for the fabrication of a elecronically enhanced microwell. Thin aluminium sheets are structured by laser micro machining and laminated successively to obtain registration tolerances of the respective layers of 5..10\^A$\mu$m. The microwells lasermachined into the laminate are with 50..80\^A$\mu$m diameter, allowing to hold individual cells within the well. The individual process steps are described and results on the microstructuring are given.


Monotonic and fatigue testing of spring-bridged freestanding microbeams application for MEMS

Abstract: Microelectromechanical systems (MEMS) technologies are developing rapidly with increasing study of the design, fabrication and commercialization of microscale systems and devices. Accurate knowledge on the mechanical behaviors of thin film materials used for MEMS is important for successful design and development of MEMS. Here a novel electroplating spring-bridge micro-tensile specimen integrates pin-pin align holes, misalignment compensate spring, load sensor beam and freestanding thin film is demonstrated and fabricated. The specimen is fit into a specially designed micro-mechanical apparatus to carry out a series of monotonic tensile testing on sub-micron freestanding thin films. Certain thin films applicable as structure or motion gears in MEMS were tested including sputtered gold, copper and tantalum nitride thin films. Metal specimens were fabricated by sputtering; for tantalum nitride film samples, nitrogen gas was introduced into the chamber during sputtering tantalum films on the silicon wafer. The sample fabrication method involves three steps of lithography and two steps of electroplating copper to hold a dog bone freestanding thin film. Using standard wet etching or lift off techniques, a series of microtensile specimens were patterned in metal thin films, holes, and seed layer for spring and frame structure on the underlying silicon oxide coated silicon substrate. Two steps of electroplating processing to distinct spring and frame portion of the test chip. Finally, chemical etched away the silicon oxide to separated electroplated specimen and silicon substrate.


Profile Control of a Borosilicate-Glass Groove Formed by Deep Reactive Ion Etching

Abstract: Deep reactive ion etching (DRIE) of borosilicate glass and profile control of an etched groove are reported. DRIE was carried out using an anodically bonded silicon wafer as an etching mask. We controlled the groove profile, namely improving its sidewall angle, by removing excessively thick polymer film produced by carbonfluoride etching gases during DRIE. Two fabrication processes were experimentally compared for effective removal of the film : DRIE with the addition of argon to the etching gases and a novel combined process in which DRIE and subsequent ultrasonic cleaning in DI water were alternately carried out. Both processes improved the sidewall angle, and it reached 85o independent of the mask-opening width. The results showed the processes can remove excessive polymer film on sidewalls. Accordingly, the processes are an effective way to control the groove profile of borosilicate glass.


Selection of High Strength Encapsulant for MEMS Devices Undergoing High Pressure Packaging

Abstract: Deflection behavior of several encapsulant materials under uniform pressure was studied to determine the best encapsulant for MEMS device. Encapsulation is needed to protect movable parts of MEMS devices during high pressure transfer molded packaging process. The selected encapsulant material has to have surface deflection of less than 5 ?m under 100 atm vertical loading. Deflection was simulated using CoventorWare ver.2005 software and verified with calculation results obtained using shell bending theory. Screening design was used to construct a systematic approach for selecting the best encapsulant material and thickness under uniform pressure up to 100 atm. Materials considered for this study were polyimide, parylene C and carbon based epoxy resin. It was observed that carbon based epoxy resin has deflection of less than 5 ?m for all thickness and pressure variations. Parylene C is acceptable and polyimide is unsuitable as high strength encapsulant. Carbon based epoxy resin is considered the best encapsulation material for MEMS under high pressure packaging process due to its high strength.


A Two-Step Etching Method to Fabricate Nanopores in Silicon

Abstract: A cost effectively method to fabricate nanopores in silicon by only using the conventional wet-etching technique is developed in this research. The main concept of the proposed method is a two-step etching process, including a premier double-sided wet etching and a succeeding track-etching. A special fixture is designed to hold the pre-etched silicon wafer inside it such that the track-etching can be effectively carried out. An electrochemical system is employed to detect and record the ion diffusion current once the pre-etched cavities are etched into a through nanopore. Experimental results indicate that the proposed method can cost effectively fabricate nanopores in silicon.


A Reconfigurable Impedance Matching Network Employing RF-MEMS Switches

Abstract: We propose the design of a reconfigurable impedance matching network for the lower RF frequency band, based on a developed RF-MEMS technology. The circuit is composed of RF-MEMS ohmic relays, metal-insulator-metal (MIM) capacitors and suspended spiral inductors, all integrated on a high resistivity Silicon substrate. The presented circuit is well-suited for all applications requiring adaptive impedance matching between two in principle unknown cascaded RF-circuits. The fabrication and testing of a monolithic integrated prototype in RF-MEMS technology from ITC-irst is currently underway.


Towards a Methodology for Analysis of Interconnect Structures for 3D-Integration of Micro Systems

Abstract: Functional aspects as well as the influence of integration technology on the system behavior have to be considered in the 3D integration design process of micro systems. Therefore, information from different physical domains has to be provided to designers. Due to the variety of structures and effects of different physical domains, efficient modeling approaches and simulation algorithms have to be combined. The paper describes a modular approach which covers detailed analysis with PDE solvers and model generation for system level simulation.


Modeling of a piezoelectric micro-scanner

Abstract: Micro-scanners have been widely used in many optical applications. The micro-scanner presented in this paper uses multimorph-type bending actuators to tilt a square plate mirror. This paper presents a complete analytical model of the piezoelectric micro-scanner. This theoretical model based on strength of material equations calculates the force generated by the multimorphs on the mirror, the profile of the structure and the angular deflection of the mirror. The proposed model, used to optimize the design of the piezoelectric silicon micro-scanner, is intended for further HDL integration, allowing in this way system level simulation and optimization.


A novel method for fatigue testing of MEMS devices containing movable elements

Abstract: In this paper we present an electronic circuit for position or capacitance estimation of MEMS electrostatic actuators based on a switched capacitor technique. The circuit uses a capacitive divider configuration composed by a fixed capacitor and the variable capacitance of the electrostatic actuator for generating a signal that is a function of the input voltage and capacitive ratio. The proposed circuit can be used to actuate and to sense position of an electrostatic MEMS actuator without extra sensing elements. This approach is compatible with the requirements of most analog feedback systems and the circuit topology of pulsed digital oscillators (PDO).


Noise and thermal stability of vibrating micro-gyrometers preamplifiers

Abstract: The preamplifier is a critical component of gyrometer's electronics. Indeed the resolution of the sensor is limited by its signal to noise ratio, and the gyrometer's thermal stability is limited by its gain drift. In this paper, five different kinds of preamplifiers are presented and compared. Finally, the design of an integrated preamplifier is shown in order to increase the gain stability while reducing its noise and size.


0-level Vacuum Packaging RT Process for MEMS Resonators

Abstract: A new Room Temperature (RT) 0-level vacuum package is demonstrated in this work, using amorphous silicon (aSi) as sacrificial layer and SiO2 as structural layer. The process is compatible with most of MEMS resonators and Resonant Suspended-Gate MOSFET [1] fabrication processes. This paper presents a study on the influence of releasing hole dimensions on the releasing time and hole clogging. It discusses mass production compatibility in terms of packaging stress during back-end plastic injection process. The packaging is done at room temperature making it fully compatible with IC-processed wafers and avoiding any subsequent degradation of the active devices.


From MEMS Devices to Smart Integrated Systems

Abstract: The smart integrated systems of tomorrow would demand a combination of micromechanical components and traditional electronics. On-chip solutions will be the ultimate goal. One way of making such systems is to implement the mechanical parts in an ordinary CMOS process. This procedure has been used to design an oscillator consisting of a resonating cantilever beam and a CMOS Pierce feedback amplifier. The resonating frequency is changed if the beam is bent by external forces. The paper describes central features of this procedure and highlights the design considerations for the CMOS-MEMS oscillator. The circuit is used as an example of a "VLSI designer" way of making future integrated micromechanical and microelectronic systems on-chip. The possibility for expansion to larger systems is reviewed.


Interconnect Challenges in Highly Integrated MEMS/ASIC Subsystems

Abstract: Micromechanical devices like accelerometers or rotation sensors form an increasing segment beneath the devices supplying the consumer market. A hybrid integration approach to build smart sensor clusters for the precise detection of movements in all spatial dimensions requires a large toolbox of interconnect technologies, each with its own constraints regarding the total process integration. Specific challenges described in this paper are post-CMOS feedthroughs, front-to-front die contact arrays, vacuum-compliant lateral interconnect and fine-pitch solder balling to finally form a Chip-Scale System-in-Package (CSSiP).


Experimental Characterization of the static behaviour of microcatntilevers electrostatically actuated

Abstract: This paper concerns the experimental validation of some mathematical models previously developed by the authors, to predict the static behaviour of microelectrostatic actuators, basically free-clamped microbeams. This layout is currently used in RF-MEMS design operation or even in material testing at microscale. The analysis investigates preliminarily the static behaviour of a set of microcantilevers bending in-plane. This investigation is aimed to distinguish the geometrical linear behaviour, exhibited under small displacement assumption, from the geometrical nonlinearity, caused by large deflection. The applied electromechanical force, which nonlinearly depends on displacement, charge and voltage, is predicted by a coupled-field approach, based on numerical methods and herewith experimentally validated, by means of a Fogale Zoomsurf 3D. Model performance is evaluated on pull-in prediction and on the curve displacement vs. voltage. In fact, FEM nonlinear solution performed by a coupled-field approach, available on commercial codes, and by a FEM non-incremental approach are compared with linear solution, for different values of the design parameters.


Nanobiosensors based on individual olfactory receptors

Abstract: In the SPOT-NOSED European project, nanoscale sensing elements bearing olfactory receptors and grafted onto functionalized gold substrates are used as odorant detectors to develop a new concept of nanobioelectronic nose, through sensitive impedancemetric measurement of single receptor conformational change upon ligand binding, with a better specificity and lower detection threshold than traditional physical sensors.


Bridge configurations in piezoresistive two-axis accelerometers

Abstract: In piezoresisitive two-axis accelerometers with two proof masses suspended by cantilever beams, there are generally many ways to configure the Wheatstone bridges. The configurations are different both with respect to functionality and performance. The main distinction is between bridges that contain resistors belonging to both proof masses, and the one bridge that doesn't. We compare the different bridge configurations by analytical calculations of bridge non-linearity, robustness towards manufacturing variations and electronic noise. We consider accelerometers where the ratio between the sensitivity to acceleration normal and parallel to the chip plane vary over a wide range. For numerical examples we use representative values for p-type silicon. The performance of the configuration with one bridge connected to each proof mass is superior to those that combine resistors belonging to different proof masses.


Online Sensor Testing through Superposition of Encoded Stimulus

Abstract: Online monitoring remains an important requirement for a range of microsystems. The solution based on the injection of an actuating test stimulus into the bias structure of active devices holds great potential. This paper presents an improved solution that aims to remove the measurand-induced signal from the sensor output. It involves encoding the test stimulus and using a covariance algorithm to reject the signal that does not contain the code. The trade-off between the sine wave rejection ratio of the technique and the test time response is studied and, in the case of a MEMS accelerometer, it is demonstrated that the rejection is higher than 14dB for a test time of about 0.7s. Furthermore, the accuracy of the test signal can be evaluated to guarantee the integrity of the online test output.


Modeling of T-Shaped Microcantilever Resonators

Abstract: The extensive research and development of micromechanical resonators is trying to allow the use of these devices for highly sensitive applications. Microcantilevers are some of the simplest MEMS structure and had been proved to be a good platform due to its excellent mechanical properties. A cantilever working in dynamic mode, adjust its resonance frequency depending on changes in both the spring constant (k) and mass (m) of the resonator. The aim of this work was to model a cantilever structure to determine the optimal dimensions in which the resonance frequency would be a function dominated by mass changes and not stiffness changes. In order to validate the model a set of microcantilevers were fabricated and characterized.


Novel Bonding technologies for wafer-level transparent packaging of MOEMS

Abstract: Depending on the type of Micro-Electro-Mechanical System (MEMS), packaging costs are contributing up to 80% of the total device cost. Each MEMS device category, its function and operational environment will individually dictate the packaging requirement. Due to the lack of standardized testing procedures, the reliability of those MEMS packages sometimes can only be proven by taking into consideration its functionality over lifetime. Innovation with regards to cost reduction and standardization in the field of packaging is therefore of utmost importance to the speed of commercialisation of MEMS devices. Nowadays heavily driven by consumer applications the MEMS device market is forecasted to enjoy a compound annual growth rate (CAGR) above 13%, which is when compared to the IC device market, an outstanding growth rate. Nevertheless this forecasted value can drift upwards or downwards depending on the rate of innovation in the field of packaging. MEMS devices typically require a specific fabrication process where the device wafer is bonded to a second wafer which effectively encapsulates the MEMS structure. This method leaves the device free to move within a vacuum or an inert gas atmosphere.


Design and Fabrication of the Suspended High-Q Spiral Inductors with X-Beams

Abstract: In this paper, deep sub-micron CMOS process compatible high Q on chip spiral inductors with air gap structure were designed and fabricated. In the design the electromagnetic were used for electrical-characteristics and maximum mechanical strength, respectively. The copper wires were capped with electroless Ni plating to prevent the copper from oxidizing. A Si3N4/ SiO2 X-beam was designed to increase the mechanical strength of the inductor in air gap. The enhancement of maximum mechanical strength of a spiral inductor with X-beams is more than 4500 times. Among these structures, the measured maximum quality factor (Q) of the suspending inductor and frequency at maximum Q are improved from 5.2 and 1.6GHz of conventional spiral inductor to 7.3 and 2.1 GHz, respectively.


One MEMS Design Tool with Maximal Six Design Flows

Abstract: This paper presents one MEMS design tool with total six design flows, which makes it possible that the MEMS designers are able to choose the most suitable design flow for their specific devices. The design tool is divided into three levels and interconnected by six interfaces. The three levels are lumped-element model based system level, finite element analysis based device level and process level, which covers nearly all modeling and simulation functions for MEMS design. The six interfaces are proposed to automatically transmit the design data between every two levels, thus the maximal six design flows could be realized. The interfaces take the netlist, solid model and layout as the data inlet and outlet for the system, device and process level respectively. The realization of these interfaces are presented and verified by design examples, which also proves that the enough flexibility in the design flow can really increase the design efficiency.


Studies of Polymer Deformation and Recovery in Hot Embossing

Abstract: In large area micro hot embossing, the process temperature plays a critical role to both the local fidelity of microstructure formation and global uniformity. The significance of low temperature hot embossing is to improve global flatness of embossed devices. This paper reports on experimental studies of polymer deformation and relaxation in micro embossing when the process temperatures are below or near its glass transition temperature (Tg). In this investigation, an indentation system and a micro embosser were used to investigate the relationship of microstructure formation versus process temperature and load pressure. The depth of indentation was controlled and the load force at a certain indentation depth was measured. Experiments were carried out using 1 mm thick PMMA films with the process temperature ranging from Tg-55 degrees C to Tg +20 degrees C. The embossed structures included a single micro cavity and groups of micro cavity arrays. It was found that at temperature of Tg-55 degrees C, elastic deformation dominated the formation of microstructures and significant relaxation happened after embossing. From Tg-20 degrees C to Tg, plastic deformation dominated polymer deformation, and permanent cavities could be formed on PMMA substrates without obvious relaxation. However, the formation of protrusive structures as micro pillars was not complete since there was little polymer flow. With an increase in process temperature, microstructure could be formed under lower loading pressure. Considering the fidelity of a single microstructure and global flatness of embossed substrates, micro hot embossing at a low process temperature, but with good fidelity, should be preferred.


Evaluation of the thermal and hydraulic performances of a very thin sintered copper flat heat pipe for 3D microsystem packages

Abstract: The reported research work presents numerical studies validated by experimental results of a flat micro heat pipe with sintered copper wick structure. The objectives of this project are to produce and demonstrate the efficiency of the passive cooling technology (heat pipe) integrated in a very thin electronic substrate that is a part of a multifunctional 3-D electronic package. The enhanced technology is dedicated to the thermal management of high dissipative microsystems having heat densities of more than 10W/cm2. Future applications are envisaged in the avionics sector. In this research 2D numerical hydraulic model has been developed to investigate the performance of a very thin flat micro heat pipe with sintered copper wick structure, using water as a refrigerant. Finite difference method has been used to develop the model. The model has been used to determine the mass transfer and fluid flow in order to evaluate the limits of heat transport capacity as functions of the dimensions of the wick and the vapour space and for various copper spheres radii. The results are presented in terms of liquid and vapour pressures within the heat pipe. The simulated results are validated by experiments and proved that the method can be further used to predict thermal performance of the heat pipe and to optimise its design.


Design and Implementation of Aggregate Functions in the DLV System

Abstract: Disjunctive Logic Programming (DLP) is a very expressive formalism: it allows for expressing every property of finite structures that is decidable in the complexity class SigmaP2 (= NP^NP). Despite this high expressiveness, there are some simple properties, often arising in real-world applications, which cannot be encoded in a simple and natural manner. Especially properties that require the use of arithmetic operators (like sum, times, or count) on a set or multiset of elements, which satisfy some conditions, cannot be naturally expressed in classic DLP. To overcome this deficiency, we extend DLP by aggregate functions in a conservative way. In particular, we avoid the introduction of constructs with disputed semantics, by requiring aggregates to be stratified. We formally define the semantics of the extended language (called DLP^A), and illustrate how it can be profitably used for representing knowledge. Furthermore, we analyze the computational complexity of DLP^A, showing that the addition of aggregates does not bring a higher cost in that respect. Finally, we provide an implementation of DLP^A in DLV -- a state-of-the-art DLP system -- and report on experiments which confirm the usefulness of the proposed extension also for the efficiency of computation.


General Algorithms for Testing the Ambiguity of Finite Automata

Abstract: This paper presents efficient algorithms for testing the finite, polynomial, and exponential ambiguity of finite automata with $\epsilon$-transitions. It gives an algorithm for testing the exponential ambiguity of an automaton $A$ in time $O(|A|_E^2)$, and finite or polynomial ambiguity in time $O(|A|_E^3)$. These complexities significantly improve over the previous best complexities given for the same problem. Furthermore, the algorithms presented are simple and are based on a general algorithm for the composition or intersection of automata. We also give an algorithm to determine the degree of polynomial ambiguity of a finite automaton $A$ that is polynomially ambiguous in time $O(|A|_E^3)$. Finally, we present an application of our algorithms to an approximate computation of the entropy of a probabilistic automaton.


The Forgiving Tree: A Self-Healing Distributed Data Structure

Abstract: We consider the problem of self-healing in peer-to-peer networks that are under repeated attack by an omniscient adversary. We assume that the following process continues for up to n rounds where n is the total number of nodes initially in the network: the adversary deletes an arbitrary node from the network, then the network responds by quickly adding a small number of new edges. We present a distributed data structure that ensures two key properties. First, the diameter of the network is never more than $O(\log \Delta)$ times its original diameter, where $\Delta$ is the maximum degree of the network initially. We note that for many peer-to-peer systems, $\Delta$ is polylogarithmic, so the diameter increase would be a O(log log n) multiplicative factor. Second, the degree of any node never increases by more than 3 over its original degree. Our data structure is fully distributed, has O(1) latency per round and requires each node to send and receive O(1) messages per round. The data structure requires an initial setup phase that has latency equal to the diameter of the original network, and requires, with high probability, each node v to send O(log n) messages along every edge incident to v. Our approach is orthogonal and complementary to traditional topology-based approaches to defending against attack.


An integrated model of traffic, geography and economy in the Internet

Abstract: Modeling Internet growth is important both for understanding the current network and to predict and improve its future. To date, Internet models have typically attempted to explain a subset of the following characteristics: network structure, traffic flow, geography, and economy. In this paper we present a discrete, agent-based model, that integrates all of them. We show that the model generates networks with topologies, dynamics, and (more speculatively) spatial distributions that are similar to the Internet.


Tur\'an Graphs, Stability Number, and Fibonacci Index

Abstract: The Fibonacci index of a graph is the number of its stable sets. This parameter is widely studied and has applications in chemical graph theory. In this paper, we establish tight upper bounds for the Fibonacci index in terms of the stability number and the order of general graphs and connected graphs. Tur\'an graphs frequently appear in extremal graph theory. We show that Tur\'an graphs and a connected variant of them are also extremal for these particular problems.


Some Aspects of Testing Process for Transport Streams in Digital Video Broadcasting

Abstract: This paper presents some aspects related to the DVB (Digital Video Broadcasting) investigation. The basic aspects of DVB are presented, with an emphasis on DVB-T version of standard. The main purpose of this research is to analyze the way that the transmission of the transport streams is realized in case of the Terrestrial Digital Video Broadcasting (DVB-T). To accomplish this, first, Digital Video Broadcasting standard is presented, and then the main aspects of DVB testing and analysis of the transport streams are investigated. The paper presents also the results obtained using two programs designed for DVB analysis: Mosalina and TSA.


Implementing a Test Strategy for an Advanced Video Acquisition and Processing Architecture

Abstract: This paper presents some aspects related to test process of an advanced video system used in remote IP surveillance. The system is based on a Pentium compatible architecture using the industrial standard PC104+. First the overall architecture of the system is presented, involving both hardware or software aspects. The acquisition board which is developed in a special, nonstandard architecture, is also briefly presented. The main purpose of this research was to set a coherent set of procedures in order to test all the aspects of the video acquisition board. To accomplish this, it was necessary to set-up a procedure in two steps: stand alone video board test (functional test) and an in-system test procedure verifying the compatibility with both OS: Linux and Windows. The paper presents also the results obtained using this procedure.


Use of Rapid Probabilistic Argumentation for Ranking on Large Complex Networks

Abstract: We introduce a family of novel ranking algorithms called ERank which run in linear/near linear time and build on explicitly modeling a network as uncertain evidence. The model uses Probabilistic Argumentation Systems (PAS) which are a combination of probability theory and propositional logic, and also a special case of Dempster-Shafer Theory of Evidence. ERank rapidly generates approximate results for the NP-complete problem involved enabling the use of the technique in large networks. We use a previously introduced PAS model for citation networks generalizing it for all networks. We propose a statistical test to be used for comparing the performances of different ranking algorithms based on a clustering validity test. Our experimentation using this test on a real-world network shows ERank to have the best performance in comparison to well-known algorithms including PageRank, closeness, and betweenness.


An Algebraic Characterization of Security of Cryptographic Protocols

Abstract: Several of the basic cryptographic constructs have associated algebraic structures. Formal models proposed by Dolev and Yao to study the (unconditional) security of public key protocols form a group. The security of some types of protocols can be neatly formulated in this algebraic setting. We investigate classes of two-party protocols. We then consider extension of the formal algebraic framework to private-key protocols. We also discuss concrete realization of the formal models. In this case, we propose a definition in terms of pseudo-free groups.


PVM-Distributed Implementation of the Radiance Code

Abstract: The Parallel Virtual Machine (PVM) tool has been used for a distributed implementation of Greg Ward's Radiance code. In order to generate exactly the same primary rays with both the sequential and the parallel codes, the quincunx sampling technique used in Radiance for the reduction of the number of primary rays by interpolation, must be left untouched in the parallel implementation. The octree of local ambient values used in Radiance for the indirect illumination has been shared among all the processors. Both static and dynamic image partitioning techniques which replicate the octree of the complete scene in all the processors and have load-balancing, have been developed for one frame rendering. Speedups larger than 7.5 have been achieved in a network of 8 workstations. For animation sequences, a new dynamic partitioning distribution technique with superlinear speedups has also been developed.


Universal Reconfiguration of (Hyper-)cubic Robots

Abstract: We study a simple reconfigurable robot model which has not been previously examined: cubic robots comprised of three-dimensional cubic modules which can slide across each other and rotate about each others' edges. We demonstrate that the cubic robot model is universal, i.e., that an n-module cubic robot can reconfigure itself into any specified n-module configuration. Additionally, we provide an algorithm that efficiently plans and executes cubic robot motion. Our results directly extend to a d-dimensional model.


Efficient implementation of GALS systems over commercial synchronous FPGAs: a new approach

Abstract: The new vision presented is aimed to overcome the logic overhead issues that previous works exhibit when applying GALS techniques to programmable logic devices. The proposed new view relies in a 2-phase, bundled data parity based protocol for data transfer and clock generation tasks. The ability of the introduced methodology for smart real-time delay selection allows the implementation of a variety of new methodologies for electromagnetic interference mitigation and device environment changes adaptation.


Automatic Verification of Correspondences for Security Protocols

Abstract: We present a new technique for verifying correspondences in security protocols. In particular, correspondences can be used to formalize authentication. Our technique is fully automatic, it can handle an unbounded number of sessions of the protocol, and it is efficient in practice. It significantly extends a previous technique for the verification of secrecy. The protocol is represented in an extension of the pi calculus with fairly arbitrary cryptographic primitives. This protocol representation includes the specification of the correspondence to be verified, but no other annotation. This representation is then translated into an abstract representation by Horn clauses, which is used to prove the desired correspondence. Our technique has been proved correct and implemented. We have tested it on various protocols from the literature. The experimental results show that these protocols can be verified by our technique in less than 1 s.


Sketch-Based Estimation of Subpopulation-Weight

Abstract: Summaries of massive data sets support approximate query processing over the original data. A basic aggregate over a set of records is the weight of subpopulations specified as a predicate over records' attributes. Bottom-k sketches are a powerful summarization format of weighted items that includes priority sampling and the classic weighted sampling without replacement. They can be computed efficiently for many representations of the data including distributed databases and data streams. We derive novel unbiased estimators and efficient confidence bounds for subpopulation weight. Our estimators and bounds are tailored by distinguishing between applications (such as data streams) where the total weight of the sketched set can be computed by the summarization algorithm without a significant use of additional resources, and applications (such as sketches of network neighborhoods) where this is not the case. Our rigorous derivations are based on clever applications of the Horvitz-Thompson estimator, and are complemented by efficient computational methods. We demonstrate their benefit on a wide range of Pareto distributions.


Spreadsheet Errors: What We Know. What We Think We Can Do

Abstract: Fifteen years of research studies have concluded unanimously that spreadsheet errors are both common and non-trivial. Now we must seek ways to reduce spreadsheet errors. Several approaches have been suggested, some of which are promising and others, while appealing because they are easy to do, are not likely to be effective. To date, only one technique, cell-by-cell code inspection, has been demonstrated to be effective. We need to conduct further research to determine the degree to which other techniques can reduce spreadsheet errors.


Spreadsheet Development Methodologies using Resolver: Moving spreadsheets into the 21st Century

Abstract: We intend to demonstrate the innate problems with existing spreadsheet products and to show how to tackle these issues using a new type of spreadsheet program called Resolver. It addresses the issues head-on and thereby moves the 1980's "VisiCalc paradigm" on to match the advances in computer languages and user requirements. Continuous display of the spreadsheet grid and the equivalent computer program, together with the ability to interact and add code through either interface, provides a number of new methodologies for spreadsheet development.


Fun Boy Three Were Wrong: it is what you do, not the way that you do it

Abstract: I revisit some classic publications on modularity, to show what problems its pioneers wanted to solve. These problems occur with spreadsheets too: to recognise them may help us avoid them.


Concerning the Feasibility of Example-driven Modelling Techniques

Abstract: We report on a series of experiments concerning the feasibility of example driven modelling. The main aim was to establish experimentally within an academic environment: the relationship between error and task complexity using a) Traditional spreadsheet modelling; b) example driven techniques. We report on the experimental design, sampling, research methods and the tasks set for both control and treatment groups. Analysis of the completed tasks allows comparison of several different variables. The experimental results compare the performance indicators for the treatment and control groups by comparing accuracy, experience, training, confidence measures, perceived difficulty and perceived completeness. The various results are thoroughly tested for statistical significance using: the Chi squared test, Fisher's exact test for significance, Cochran's Q test and McNemar's test on difficulty.


It Ain't What You View, But The Way That You View It: documenting spreadsheets with Excelsior, semantic wikis, and literate programming

Abstract: I describe preliminary experiments in documenting Excelsior versions of spreadsheets using semantic wikis and literate programming. The objective is to create well-structured and comprehensive documentation, easy to use by those unfamiliar with the spreadsheets documented. I discuss why so much documentation is hard to use, and briefly explain semantic wikis and literate programming; although parts of the paper are Excelsior-specific, these sections may be of more general interest.


An Empirical Study of End-User Behaviour in Spreadsheet Error Detection & Correction

Abstract: Very little is known about the process by which end-user developers detect and correct spreadsheet errors. Any research pertaining to the development of spreadsheet testing methodologies or auditing tools would benefit from information on how end-users perform the debugging process in practice. Thirteen industry-based professionals and thirty-four accounting & finance students took part in a current ongoing experiment designed to record and analyse end-user behaviour in spreadsheet error detection and correction. Professionals significantly outperformed students in correcting certain error types. Time-based cell activity analysis showed that a strong correlation exists between the percentage of cells inspected and the number of errors corrected. The cell activity data was gathered through a purpose written VBA Excel plug-in that records the time and detail of all cell selection and cell change actions of individuals.


Why Task-Based Training is Superior to Traditional Training Methods

Abstract: The risks of spreadsheet use do not just come from the misuse of formulae. As such, training needs to go beyond this technical aspect of spreadsheet use and look at the spreadsheet in its full business context. While standard training is by and large unable to do this, task-based training is perfectly suited to a contextual approach to training.


Establishing A Minimum Generic Skill Set For Risk Management Teaching In A Spreadsheet Training Course

Abstract: Past research shows that spreadsheet models are prone to such a high frequency of errors and data security implications that the risk management of spreadsheet development and spreadsheet use is of great importance to both industry and academia. The underlying rationale for this paper is that spreadsheet training courses should specifically address risk management in the development process both from a generic and a domain-specific viewpoint. This research specifically focuses on one of these namely those generic issues of risk management that should be present in a training course that attempts to meet good-practice within industry. A pilot questionnaire was constructed showing a possible minimum set of risk management issues and sent to academics and industry practitioners for feedback. The findings from this pilot survey will be used to refine the questionnaire for sending to a larger body of possible respondents. It is expected these findings will form the basis of a risk management teaching approach to be trialled in a number of selected ongoing spreadsheet training courses.


Voice-controlled Debugging of Spreadsheets

Abstract: Developments in Mobile Computing are putting pressure on the software industry to research new modes of interaction that do not rely on the traditional keyboard and mouse combination. Computer users suffering from Repetitive Strain Injury also seek an alternative to keyboard and mouse devices to reduce suffering in wrist and finger joints. Voice-control is an alternative approach to spreadsheet development and debugging that has been researched and used successfully in other domains. While voice-control technology for spreadsheets is available its effectiveness has not been investigated. This study is the first to compare the performance of a set of expert spreadsheet developers that debugged a spreadsheet using voice-control technology and another set that debugged the same spreadsheet using keyboard and mouse. The study showed that voice, despite its advantages, proved to be slower and less accurate. However, it also revealed ways in which the technology might be improved to redress this imbalance.


The RDF Virtual Machine

Abstract: The Resource Description Framework (RDF) is a semantic network data model that is used to create machine-understandable descriptions of the world and is the basis of the Semantic Web. This article discusses the application of RDF to the representation of computer software and virtual computing machines. The Semantic Web is posited as not only a web of data, but also as a web of programs and processes.


The Complexity of Node Blocking for Dags

Abstract: We consider the following modification of annihilation game called node blocking. Given a directed graph, each vertex can be occupied by at most one token. There are two types of tokens, each player can move his type of tokens. The players alternate their moves and the current player $i$ selects one token of type $i$ and moves the token along a directed edge to an unoccupied vertex. If a player cannot make a move then he loses. We consider the problem of determining the complexity of the game: given an arbitrary configuration of tokens in a directed acyclic graph, does the current player has a winning strategy? We prove that the problem is PSPACE-complete.


Time Warp Edit Distance

Abstract: This technical report details a family of time warp distances on the set of discrete time series. This family is constructed as an editing distance whose elementary operations apply on linear segments. A specific parameter allows controlling the stiffness of the elastic matching. It is well suited for the processing of event data for which each data sample is associated with a timestamp, not necessarily obtained according to a constant sampling rate. Some properties verified by these distances are proposed and proved in this report.


Wavelet and Curvelet Moments for Image Classification: Application to Aggregate Mixture Grading

Abstract: We show the potential for classifying images of mixtures of aggregate, based themselves on varying, albeit well-defined, sizes and shapes, in order to provide a far more effective approach compared to the classification of individual sizes and shapes. While a dominant (additive, stationary) Gaussian noise component in image data will ensure that wavelet coefficients are of Gaussian distribution, long tailed distributions (symptomatic, for example, of extreme values) may well hold in practice for wavelet coefficients. Energy (2nd order moment) has often been used for image characterization for image content-based retrieval, and higher order moments may be important also, not least for capturing long tailed distributional behavior. In this work, we assess 2nd, 3rd and 4th order moments of multiresolution transform -- wavelet and curvelet transform -- coefficients as features. As analysis methodology, taking account of image types, multiresolution transforms, and moments of coefficients in the scales or bands, we use correspondence analysis as well as k-nearest neighbors supervised classification.


Data Traffic Dynamics and Saturation on a Single Link

Abstract: The dynamics of User Datagram Protocol (UDP) traffic over Ethernet between two computers are analyzed using nonlinear dynamics which shows that there are two clear regimes in the data flow: free flow and saturated. The two most important variables affecting this are the packet size and packet flow rate. However, this transition is due to a transcritical bifurcation rather than phase transition in models such as in vehicle traffic or theorized large-scale computer network congestion. It is hoped this model will help lay the groundwork for further research on the dynamics of networks, especially computer networks.


Delay Analysis for Wireless Local Area Networks with Multipacket Reception under Finite Load

Abstract: To date, most analysis of WLANs has been focused on their operation under saturation condition. This work is an attempt to understand the fundamental performance of WLANs under unsaturated condition. In particular, we are interested in the delay performance when collisions of packets are resolved by an exponential backoff mechanism. Using a multiple-vacation queueing model, we derive an explicit expression for packet delay distribution, from which necessary conditions for finite mean delay and delay jitter are established. It is found that under some circumstances, mean delay and delay jitter may approach infinity even when the traffic load is way below the saturation throughput. Saturation throughput is therefore not a sound measure of WLAN capacity when the underlying applications are delay sensitive. To bridge the gap, we define safe-bounded-mean-delay (SBMD) throughput and safe-bounded-delay-jitter (SBDJ) throughput that reflect the actual network capacity users can enjoy when they require bounded mean delay and delay jitter, respectively. The analytical model in this paper is general enough to cover both single-packet reception (SPR) and multi-packet reception (MPR) WLANs, as well as carrier-sensing and non-carrier-sensing networks. We show that the SBMD and SBDJ throughputs scale super-linearly with the MPR capability of a network. Together with our earlier work that proves super-linear throughput scaling under saturation condition, our results here complete the demonstration of MPR as a powerful capacity-enhancement technique for both delay-sensitive and delay-tolerant applications.


Neural Networks and Database Systems

Abstract: Object-oriented database systems proved very valuable at handling and administrating complex objects. In the following guidelines for embedding neural networks into such systems are presented. It is our goal to treat networks as normal data in the database system. From the logical point of view, a neural network is a complex data value and can be stored as a normal data object. It is generally accepted that rule-based reasoning will play an important role in future database applications. The knowledge base consists of facts and rules, which are both stored and handled by the underlying database system. Neural networks can be seen as representation of intensional knowledge of intelligent database systems. So they are part of a rule based knowledge pool and can be used like conventional rules. The user has a unified view about his knowledge base regardless of the origin of the unique rules.


Towards a formalization of budgets

Abstract: We go into the need for, and the requirements on, a formal theory of budgets. We present a simple algebraic theory of rational budgets, i.e., budgets in which amounts of money are specified by functions on the rational numbers. This theory is based on the tuplix calculus. We go into the importance of using totalized models for the rational numbers. We present a case study on the educational budget of a university department offering master programs.


Color Graphs: An Efficient Model For Two-Dimensional Cellular Automata Linear Rules

Abstract: Two-dimensional nine neighbor hood rectangular Cellular Automata rules can be modeled using many different techniques like Rule matrices, State Transition Diagrams, Boolean functions, Algebraic Normal Form etc. In this paper, a new model is introduced using color graphs to model all the 512 linear rules. The graph theoretic properties therefore studied in this paper simplifies the analysis of all linear rules in comparison with other ways of its study.


Dynamic data models: an application of MOP-based persistence in Common Lisp

Abstract: The data model of an application, the nature and format of data stored across executions, is typically a very rigid part of its early specification, even when prototyping, and changing it after code that relies on it was written can prove quite expensive and error-prone. Code and data in a running Lisp image can be dynamically modified. A MOP-based persistence library can bring this dynamicity to the data model. This enables to extend the easy prototyping way of development to the storage of data and helps avoiding interruptions of service. This article presents the conditions to do this portably and transparently.


Local Information Based Algorithms for Packet Transport in Complex Networks

Abstract: We introduce four algorithms for packet transport in complex networks. These algorithms use deterministic rules which depend, in different ways, on the degree of the node, the number of packets posted down each edge, the mean delivery time of packets sent down each edge to each destination and the time since an edge last transmitted a packet. On scale-free networks all our algorithms are considerably more efficient and can handle a larger load than the random walk algorithm. We consider in detail various attributes of our algorithms, for instance we show that an algorithm that bases its decisions on the mean delivery time jams unless it incorporates information about the degree of the destination node.


Outward Accessibility in Urban Street Networks: Characterization and Improvements

Abstract: The dynamics of transportation through towns and cities is strongly affected by the topology of the connections and routes. The current work describes an approach combining complex networks and self-avoiding random walk dynamics in order to quantify in objective and accurate manner, along a range of spatial scales, the accessibility of places in towns and cities. The transition probabilities are estimated for several lengths of the walks and used to calculate the outward accessibility of each node. The potential of the methodology is illustrated with respect to the characterization and improvements of the accessibility of the town of Sao Carlos.


Preventing Coordinated Attacks Via Distributed Alert Exchange

Abstract: Attacks on information systems followed by intrusions may cause large revenue losses. The prevention of both is not always possible by just considering information from isolated sources of the network. A global view of the whole system is necessary to recognize and react to the different actions of such an attack. The design and deployment of a decentralized system targeted at detecting as well as reacting to information system attacks might benefit from the loose coupling realized by publish/subscribe middleware. In this paper, we present the advantages and convenience in using this communication paradigm for a general decentralized attack prevention framework. Furthermore, we present the design and implementation of our approach based on existing publish/subscribe middleware and evaluate our approach for GNU/Linux systems.


Generic case complexity and One-Way functions

Abstract: The goal of this paper is to introduce ideas and methodology of the generic case complexity to cryptography community. This relatively new approach allows one to analyze the behavior of an algorithm on ''most'' inputs in a simple and intuitive fashion which has some practical advantages over classical methods based on averaging. We present an alternative definition of one-way function using the concepts of generic case complexity and show its equivalence to the standard definition. In addition we demonstrate the convenience of the new approach by giving a short proof that extending adversaries to a larger class of partial algorithms with errors does not change the strength of the security assumption.


Information Hiding Techniques: A Tutorial Review

Abstract: The purpose of this tutorial is to present an overview of various information hiding techniques. A brief history of steganography is provided along with techniques that were used to hide information. Text, image and audio based information hiding techniques are discussed. This paper also provides a basic introduction to digital watermarking.


Architecture for Integrated Mems Resonators Quality Factor Measurement

Abstract: In this paper, an architecture designed for electrical measurement of the quality factor of MEMS resonators is proposed. An estimation of the measurement performance is made using PSPICE simulations taking into account the component's non-idealities. An error on the measured Q value of only several percent is achievable, at a small integration cost, for sufficiently high quality factor values (Q > 100).


Optimization of Cricket-inspired, Biomimetic Artificial Hair Sensors for Flow Sensing

Abstract: High density arrays of artificial hair sensors, biomimicking the extremely sensitive mechanoreceptive filiform hairs found on cerci of crickets have been fabricated successfully. We assess the sensitivity of these artificial sensors and present a scheme for further optimization addressing the deteriorating effects of stress in the structures. We show that, by removing a portion of chromium electrodes close to the torsional beams, the upward lift at the edges of the membrane due to the stress, will decrease hence increase the sensitivity.


Knowledge Technologies

Abstract: Several technologies are emerging that provide new ways to capture, store, present and use knowledge. This book is the first to provide a comprehensive introduction to five of the most important of these technologies: Knowledge Engineering, Knowledge Based Engineering, Knowledge Webs, Ontologies and Semantic Webs. For each of these, answers are given to a number of key questions (What is it? How does it operate? How is a system developed? What can it be used for? What tools are available? What are the main issues?). The book is aimed at students, researchers and practitioners interested in Knowledge Management, Artificial Intelligence, Design Engineering and Web Technologies. During the 1990s, Nick worked at the University of Nottingham on the application of AI techniques to knowledge management and on various knowledge acquisition projects to develop expert systems for military applications. In 1999, he joined Epistemics where he worked on numerous knowledge projects and helped establish knowledge management programmes at large organisations in the engineering, technology and legal sectors. He is author of the book "Knowledge Acquisition in Practice", which describes a step-by-step procedure for acquiring and implementing expertise. He maintains strong links with leading research organisations working on knowledge technologies, such as knowledge-based engineering, ontologies and semantic technologies.


The Discrete Hilbert Transform for Non-Periodic Signals

Abstract: This note investigates the size of the guard band for non-periodic discrete Hilbert transform, which has recently been proposed for data hiding and security applications. It is shown that a guard band equal to the duration of the message is sufficient for a variety of analog signals and is, therefore, likely to be adequate for discrete or digital data.


Separating NOF communication complexity classes RP and NP

Abstract: We provide a non-explicit separation of the number-on-forehead communication complexity classes RP and NP when the number of players is up to \delta log(n) for any \delta<1. Recent lower bounds on Set-Disjointness [LS08,CA08] provide an explicit separation between these classes when the number of players is only up to o(loglog(n)).


Are complex systems hard to evolve?

Abstract: Evolutionary complexity is here measured by the number of trials/evaluations needed for evolving a logical gate in a non-linear medium. Behavioural complexity of the gates evolved is characterised in terms of cellular automata behaviour. We speculate that hierarchies of behavioural and evolutionary complexities are isomorphic up to some degree, subject to substrate specificity of evolution and the spectrum of evolution parameters.


Deriving Sorting Algorithms

Abstract: This paper proposes new derivations of three well-known sorting algorithms, in their functional formulation. The approach we use is based on three main ingredients: first, the algorithms are derived from a simpler algorithm, i.e. the specification is already a solution to the problem (in this sense our derivations are program transformations). Secondly, a mixture of inductive and coinductive arguments are used in a uniform, algebraic style in our reasoning. Finally, the approach uses structural invariants so as to strengthen the equational reasoning with logical arguments that cannot be captured in the algebraic framework.


Complexity Metrics for Spreadsheet Models

Abstract: Several complexity metrics are described which are related to logic structure, data structure and size of spreadsheet models. They primarily concentrate on the dispersion of cell references and cell paths. Most metrics are newly defined, while some are adapted from traditional software engineering. Their purpose is the identification of cells which are liable to errors. In addition, they can be used to estimate the values of dependent process metrics, such as the development duration and effort, and especially to adjust the cell error rate in accordance with the contents of each individual cell, in order to accurately asses the reliability of a model. Finally, two conceptual constructs - the reference branching condition cell and the condition block - are discussed, aiming at improving the reliability, modifiability, auditability and comprehensibility of logical tests.


A Paradigm for Spreadsheet Engineering Methodologies

Abstract: Spreadsheet engineering methodologies are diverse and sometimes contradictory. It is difficult for spreadsheet developers to identify a spreadsheet engineering methodology that is appropriate for their class of spreadsheet, with its unique combination of goals, type of problem, and available time and resources. There is a lack of well-organized, proven methodologies with known costs and benefits for well-defined spreadsheet classes. It is difficult to compare and critically evaluate methodologies. We present a paradigm for organizing and interpreting spreadsheet engineering recommendations. It systematically addresses the myriad choices made when developing a spreadsheet, and explicitly considers resource constraints and other development parameters. This paradigm provides a framework for evaluation, comparison, and selection of methodologies, and a list of essential elements for developers or codifiers of new methodologies. This paradigm identifies gaps in our knowledge that merit further research.


A Toolkit for Scalable Spreadsheet Visualization

Abstract: This paper presents a toolkit for spreadsheet visualization based on logical areas, semantic classes and data modules. Logical areas, semantic classes and data modules are abstract representations of spreadsheet programs that are meant to reduce the auditing and comprehension effort, especially for large and regular spreadsheets. The toolkit is integrated as a plug-in in the Gnumeric spreadsheet system for Linux. It can process large, industry scale spreadsheet programs in reasonable time and is tightly integrated with its host spreadsheet system. Users can generate hierarchical and graph-based representations of their spreadsheets. This allows them to spot conceptual similarities in different regions of the spreadsheet, that would otherwise not fit on a screen. As it is assumed that the learning effort for effective use of such a tool should be kept low, we aim for intuitive handling of most of the tool's functions.


Using Layout Information for Spreadsheet Visualization

Abstract: This paper extends a spreadsheet visualization technique by using layout information. The original approach identifies logically or semantically related cells by relying exclusively on the content of cells for identifying semantic classes. A disadvantage of semantic classes is that users have to supply parameters which describe the possible shapes of these blocks. The correct parametrization requires a certain degree of experience and is thus not suitable for untrained users. To avoid this constraint, the approach reported in this paper uses row/column-labels as well as common format information for locating areas with common, recurring semantics. Heuristics are provided to distinguish between cell groups with intended common semantics and cell groups related in an ad-hoc manner.


Spreadsheet Structure Discovery with Logic Programming

Abstract: Our term "structure discovery" denotes the recovery of structure, such as the grouping of cells, that was intended by a spreadsheet's author but is not explicit in the spreadsheet. We are implementing structure discovery tools in the logic-programming language Prolog for our spreadsheet analysis program Model Master, by writing grammars for spreadsheet structures. The objective is an "intelligent structure monitor" to run beside Excel, allowing users to reconfigure spreadsheets to the representational needs of the task at hand. This could revolutionise spreadsheet "best practice". We also describe a formulation of spreadsheet reverse-engineering based on "arrows".


Syntax diagrams as a formalism for representation of syntactic relations of formal languages

Abstract: The new approach to representation of syntax of formal languages-- a formalism of syntax diagrams is offered. Syntax diagrams look a convenient language for the description of syntactic relations in the languages having nonlinear representation of texts, for example, for representation of syntax lows of the language of structural chemical formulas. The formalism of neighbourhood grammar is used to describe the set of correct syntax constructs. The neighbourhood the grammar consists of a set of families of "neighbourhoods"-- the diagrams defined for each symbol of the language's alphabet. The syntax diagram is correct if each symbol is included into this diagram together with some neighbourhood. In other words, correct diagrams are needed to be covered by elements of the neighbourhood grammar. Thus, the grammar of formal language can be represented as system of the covers defined for each correct syntax diagram.


Sensing Danger: Innate Immunology for Intrusion Detection

Abstract: The immune system provides an ideal metaphor for anomaly detection in general and computer security in particular. Based on this idea, artificial immune systems have been used for a number of years for intrusion detection, unfortunately so far with little success. However, these previous systems were largely based on immunological theory from the 1970s and 1980s and over the last decade our understanding of immunological processes has vastly improved. In this paper we present two new immune inspired algorithms based on the latest immunological discoveries, such as the behaviour of Dendritic Cells. The resultant algorithms are applied to real world intrusion problems and show encouraging results. Overall, we believe there is a bright future for these next generation artificial immune algorithms.


Algebraic Pattern Matching in Join Calculus

Abstract: We propose an extension of the join calculus with pattern matching on algebraic data types. Our initial motivation is twofold: to provide an intuitive semantics of the interaction between concurrency and pattern matching; to define a practical compilation scheme from extended join definitions into ordinary ones plus ML pattern matching. To assess the correctness of our compilation scheme, we develop a theory of the applied join calculus, a calculus with value passing and value matching. We implement this calculus as an extension of the current JoCaml system.


A Qualitative Modal Representation of Quantum Register Transformations

Abstract: We introduce two modal natural deduction systems that are suitable to represent and reason about transformations of quantum registers in an abstract, qualitative, way. Quantum registers represent quantum systems, and can be viewed as the structure of quantum data for quantum operations. Our systems provide a modal framework for reasoning about operations on quantum registers (unitary transformations and measurements), in terms of possible worlds (as abstractions of quantum registers) and accessibility relations between these worlds. We give a Kripke--style semantics that formally describes quantum register transformations and prove the soundness and completeness of our systems with respect to this semantics.


Hospital Case Cost Estimates Modelling - Algorithm Comparison

Abstract: Ontario (Canada) Health System stakeholders support the idea and necessity of the integrated source of data that would include both clinical (e.g. diagnosis, intervention, length of stay, case mix group) and financial (e.g. cost per weighted case, cost per diem) characteristics of the Ontario healthcare system activities at the patient-specific level. At present, the actual patient-level case costs in the explicit form are not available in the financial databases for all hospitals. The goal of this research effort is to develop financial models that will assign each clinical case in the patient-specific data warehouse a dollar value, representing the cost incurred by the Ontario health care facility which treated the patient. Five mathematical models have been developed and verified using real dataset. All models can be classified into two groups based on their underlying method: 1. Models based on using relative intensity weights of the cases, and 2. Models based on using cost per diem.


Language of Boolean functions its Grammar and Machine

Abstract: In this paper an algorithm is designed which generates in-equivalent Boolean functions of any number of variables from the four Boolean functions of single variable. The grammar for such set of Boolean function is provided. The Turing Machine that accepts such set is constructed.


Some properties of the Ukrainian writing system

Abstract: We investigate the grapheme-phoneme relation in Ukrainian and some properties of the Ukrainian version of the Cyrillic alphabet.


Safety alternating automata on data words

Abstract: A data word is a sequence of pairs of a letter from a finite alphabet and an element from an infinite set, where the latter can only be compared for equality. Safety one-way alternating automata with one register on infinite data words are considered, their nonemptiness is shown EXPSPACE-complete, and their inclusion decidable but not primitive recursive. The same complexity bounds are obtained for satisfiability and refinement, respectively, for the safety fragment of linear temporal logic with freeze quantification. Dropping the safety restriction, adding past temporal operators, or adding one more register, each causes undecidability.


Call Admission Control Algorithm for pre-stored VBR video streams

Abstract: We examine the problem of accepting a new request for a pre-stored VBR video stream that has been smoothed using any of the smoothing algorithms found in the literature. The output of these algorithms is a piecewise constant-rate schedule for a Variable Bit-Rate (VBR) stream. The schedule guarantees that the decoder buffer does not overflow or underflow. The problem addressed in this paper is the determination of the minimal time displacement of each new requested VBR stream so that it can be accomodated by the network and/or the video server without overbooking the committed traffic. We prove that this call-admission control problem for multiple requested VBR streams is NP-complete and inapproximable within a constant factor, by reducing it from the VERTEX COLOR problem. We also present a deterministic morphology-sensitive algorithm that calculates the minimal time displacement of a VBR stream request. The complexity of the proposed algorithm make it suitable for real-time determination of the time displacement parameter during the call admission phase.


A O(n^8) X O(n^7) Linear Programming Model of the Quadratic Assignment Problem

Abstract: This paper has been withdrawn because Theorem 21 and Corollary 22 are in error; The modeling idea is OK, but it needs 9-dimensional variables instead of the 8-dimensional variables defined in notations 6.9. Examples of the correct model (with 9-index variables) are: (1) Diaby, M., "Linear Programming Formulation of the Set Partitioning Problem," International Journal of Operational Research 8:4 (August 2010) pp. 399-427; (2) Diaby, M., "Linear Programming Formulation of the Vertex Coloring Problem," International Journal of Mathematics in Operational Research 2:3 (May 2010) pp. 259-289; (3) Diaby, M., "The Traveling Salesman Problem: A Linear Programming Formulation," WSEAS Transactions on Mathematics, 6:6 (June 2007) pp. 745-754.


Curves That Must Be Retraced

Abstract: We exhibit a polynomial time computable plane curve GAMMA that has finite length, does not intersect itself, and is smooth except at one endpoint, but has the following property. For every computable parametrization f of GAMMA and every positive integer n, there is some positive-length subcurve of GAMMA that f retraces at least n times. In contrast, every computable curve of finite length that does not intersect itself has a constant-speed (hence non-retracing) parametrization that is computable relative to the halting problem.


A Simple Yao-Yao-Based Spanner of Bounded Degree

Abstract: It is a standing open question to decide whether the Yao-Yao structure for unit disk graphs (UDGs) is a length spanner of not. This question is highly relevant to the topology control problem for wireless ad hoc networks. In this paper we make progress towards resolving this question by showing that the Yao-Yao structure is a length spanner for UDGs of bounded aspect ratio. We also propose a new local algorithm, called Yao-Sparse-Sink, based on the Yao-Sink method introduced by Li, Wan, Wang and Frieder, that computes a (1+e)-spanner of bounded degree for a given UDG and for given e > 0. The Yao-Sparse-Sink method enables an efficient local computation of sparse sink trees. Finally, we show that all these structures for UDGs -- Yao, Yao-Yao, Yao-Sink and Yao-Sparse-Sink -- have arbitrarily large weight.


The Generation of Textual Entailment with NLML in an Intelligent Dialogue system for Language Learning CSIEC

Abstract: This research report introduces the generation of textual entailment within the project CSIEC (Computer Simulation in Educational Communication), an interactive web-based human-computer dialogue system with natural language for English instruction. The generation of textual entailment (GTE) is critical to the further improvement of CSIEC project. Up to now we have found few literatures related with GTE. Simulating the process that a human being learns English as a foreign language we explore our naive approach to tackle the GTE problem and its algorithm within the framework of CSIEC, i.e. rule annotation in NLML, pattern recognition (matching), and entailment transformation. The time and space complexity of our algorithm is tested with some entailment examples. Further works include the rules annotation based on the English textbooks and a GUI interface for normal users to edit the entailment rules.


A Study On Distributed Model Predictive Consensus

Abstract: We investigate convergence properties of a proposed distributed model predictive control (DMPC) scheme, where agents negotiate to compute an optimal consensus point using an incremental subgradient method based on primal decomposition as described in Johansson et al. [2006, 2007]. The objective of the distributed control strategy is to agree upon and achieve an optimal common output value for a group of agents in the presence of constraints on the agent dynamics using local predictive controllers. Stability analysis using a receding horizon implementation of the distributed optimal consensus scheme is performed. Conditions are given under which convergence can be obtained even if the negotiations do not reach full consensus.


Qtier-Rapor: Managing Spreadsheet Systems & Improving Corporate Performance, Compliance and Governance

Abstract: Much of what EuSpRIG discusses is concerned with the integrity of individual spreadsheets. In businesses, interlocking spreadsheets are regularly used to fill functional gaps in core administrative systems. The growth and deployment of such integrated spreadsheet SYSTEMS raises the scale of issues to a whole new level. The correct management of spreadsheet systems is necessary to ensure that the business achieves its goals of improved performance and good corporate governance, within the constraints of legislative compliance - poor management will deliver the opposite. This paper is an anatomy of the real-life issues of the commercial use of spreadsheets in business, and demonstrates how Qtier-Rapor has been used to instil best practice in the use of integrated commercial spreadsheet systems.


Automated Termination Proofs for Logic Programs by Term Rewriting

Abstract: There are two kinds of approaches for termination analysis of logic programs: "transformational" and "direct" ones. Direct approaches prove termination directly on the basis of the logic program. Transformational approaches transform a logic program into a term rewrite system (TRS) and then analyze termination of the resulting TRS instead. Thus, transformational approaches make all methods previously developed for TRSs available for logic programs as well. However, the applicability of most existing transformations is quite restricted, as they can only be used for certain subclasses of logic programs. (Most of them are restricted to well-moded programs.) In this paper we improve these transformations such that they become applicable for any definite logic program. To simulate the behavior of logic programs by TRSs, we slightly modify the notion of rewriting by permitting infinite terms. We show that our transformation results in TRSs which are indeed suitable for automated termination analysis. In contrast to most other methods for termination of logic programs, our technique is also sound for logic programming without occur check, which is typically used in practice. We implemented our approach in the termination prover AProVE and successfully evaluated it on a large collection of examples.


EuSpRIG 2006 Commercial Spreadsheet Review

Abstract: This management summary provides an outline of a commercial spreadsheet review process. The aim of this process is to ensure remedial or enhancement work can safely be undertaken on a spreadsheet with a commercially acceptable level of risk of introducing new errors.


Another approach to decide on real root existence for univariate Polynomials, and a multivariate extension for 3-SAT

Abstract: We present six Theorems on the univariate real Polynomial, using which we develop a new algorithm for deciding the existence of atleast one real root for univariate integer Polynomials. Our algorithm outputs that no positive real root exists, if and only if, the given Polynomial is a factor of a real Polynomial with positive coefficients. Next, we define a transformation that transforms any instance of 3-SAT into a multivariate real Polynomial with positive coefficients, if and only if, the instance is not satisfiable.


Composition Attacks and Auxiliary Information in Data Privacy

Abstract: Privacy is an increasingly important aspect of data publishing. Reasoning about privacy, however, is fraught with pitfalls. One of the most significant is the auxiliary information (also called external knowledge, background knowledge, or side information) that an adversary gleans from other channels such as the web, public records, or domain knowledge. This paper explores how one can reason about privacy in the face of rich, realistic sources of auxiliary information. Specifically, we investigate the effectiveness of current anonymization schemes in preserving privacy when multiple organizations independently release anonymized data about overlapping populations. 1. We investigate composition attacks, in which an adversary uses independent anonymized releases to breach privacy. We explain why recently proposed models of limited auxiliary information fail to capture composition attacks. Our experiments demonstrate that even a simple instance of a composition attack can breach privacy in practice, for a large class of currently proposed techniques. The class includes k-anonymity and several recent variants. 2. On a more positive note, certain randomization-based notions of privacy (such as differential privacy) provably resist composition attacks and, in fact, the use of arbitrary side information. This resistance enables stand-alone design of anonymization schemes, without the need for explicitly keeping track of other releases. We provide a precise formulation of this property, and prove that an important class of relaxations of differential privacy also satisfy the property. This significantly enlarges the class of protocols known to enable modular design.


From a set of parts to an indivisible whole. Part I: Operations in a closed mode

Abstract: This paper provides a description of a new method for information processing based on holistic approach wherein analysis is a direct product of synthesis. The core of the method is iterative averaging of all the elements of a system according to all the parameters describing the elements. Contrary to common logic, the iterative averaging of a system's elements does not result in homogenization of the system; instead, it causes an obligatory subdivision of the system into two alternative subgroups, leaving no outliers. Within each of the formed subgroups, similarity coefficients between the elements reach the value of 1, whereas similarity coefficients between the elements of different subgroups equal a certain constant value greater than 0 but lower than 1. When subjected to iterative averaging, any system consisting of three or more elements of which at least two elements are not completely identical undergo such a process of bifurcation that occurs non-linearly. Successive iterative averaging of each of the forming subgroups eventually provides a hierarchical system that reflects relationships between the elements of an input system under analysis. We propose a definition of a natural hierarchy that can exist only in conditions of closeness of a system and can be discovered upon providing such an effect onto a system which allows its elements interact with each other based on the principle of self-organization. Self-organization can be achieved through an overall and total cross-averaging of a system's elements. We demonstrate the application potentials of the proposed technology on a number of examples, including a system of scattered points, randomized datasets, as well as meteorological and demographical datasets.


A Survey on Deep Packet Inspection for Intrusion Detection Systems

Abstract: Deep packet inspection is widely recognized as a powerful way which is used for intrusion detection systems for inspecting, deterring and deflecting malicious attacks over the network. Fundamentally, almost intrusion detection systems have the ability to search through packets and identify contents that match with known attacks. In this paper, we survey the deep packet inspection implementations techniques, research challenges and algorithms. Finally, we provide a comparison between the different applied systems.


A Bit-Compatible Shared Memory Parallelization for ILU(k) Preconditioning and a Bit-Compatible Generalization to Distributed Memory

Abstract: ILU(k) is a commonly used preconditioner for iterative linear solvers for sparse, non-symmetric systems. It is often preferred for the sake of its stability. We present TPILU(k), the first efficiently parallelized ILU(k) preconditioner that maintains this important stability property. Even better, TPILU(k) preconditioning produces an answer that is bit-compatible with the sequential ILU(k) preconditioning. In terms of performance, the TPILU(k) preconditioning is shown to run faster whenever more cores are made available to it --- while continuing to be as stable as sequential ILU(k). This is in contrast to some competing methods that may become unstable if the degree of thread parallelism is raised too far. Where Block Jacobi ILU(k) fails in an application, it can be replaced by TPILU(k) in order to maintain good performance, while also achieving full stability. As a further optimization, TPILU(k) offers an optional level-based incomplete inverse method as a fast approximation for the original ILU(k) preconditioned matrix. Although this enhancement is not bit-compatible with classical ILU(k), it is bit-compatible with the output from the single-threaded version of the same algorithm. In experiments on a 16-core computer, the enhanced TPILU(k)-based iterative linear solver performed up to 9 times faster. As we approach an era of many-core computing, the ability to efficiently take advantage of many cores will become ever more important. TPILU(k) also demonstrates good performance on cluster or Grid. For example, the new algorithm achieves 50 times speedup with 80 nodes for general sparse matrices of dimension 160,000 that are diagonally dominant.