Sensor networks constitute a field of research which combines many challenges of modern computer science, wireless communication and mobile computing. The resource limitations of a sensor network, especially in terms of energy, require an integrated approach for the different layers of communication. In particular, this work aims to present an overview of the benefits and of the most recent advances in antenna technologies, investigating the possibility of integrating these solutions in a large distributed wireless sensor network for the extensive monitoring of the natural environment. An integrated design technique of the wireless device, built with printed patches on a dielectric substrates is here presented.

Microstrip patch antenna arrangements offer many advantages. They provide low profiles, are light-weight and are easily integrated with the monolithic circuitry that has been embraced for miniaturised RF sensing systems. This paper presents the designs of 8-16 GHz bandwidth log-periodic and aperture-stacked based antenna arrangements. These antennas are examined in the light of the existence of alternatives (e.g., a Vivaldi tapered slot sensor) for operation as broadband sensing elements.

Ultra-wideband (UWB) technology dates back to early 1980s and was originally employed in radar applications. Unlike any narrowband or broadband communication systems, an UWB system does not employ any radio frequency (RF) carrier for data transmission. Instead it uses very short period electrical pulses in the order of hundreds of pico-seconds to few nano-seconds, which justifies the availability of an ultra-high bandwidth. From a hardware implementation viewpoint, UWB system design presents many challenges such as synchronisation, power limitation and receiver design. However, the design of an UWB transceiver is less complex given the fact that the RF carrier is eliminated. In an UWB transceiver, most of the processing is performed in the digital baseband while the analog front end is responsible for amplification, filtering and quantisation. A bank of matched filters constitutes the major portion of digital baseband section in an UWB transceiver. This paper presents the design, optimisation and field programmable gate array (FPGA) implementation of the matched filter bank as an attempt to minimise the overall circuit complexity, achieve higher data rates and low power consumption in UWB radios.

The design of common source (CS) Low Noise Amplifiers (LNA) for wireless receivers is presented. The design trade-offs between main criteria are discussed. An extra gate-to-source capacitor is added to the input transistor to reduce the transistor dimension while still satisfying the noise matching. The small MOSFET also improves the LNA linearity with comparatively small drain-source current. The extra gate-to-source capacitor is introduced by the bonding-pad parasitic capacitor; hence a negative effect parasitic capacitance is turned into a useful capacitor. The simulated Noise Figure (NF) of two single-ended LNAs using 0.18 μm CMOS process achieve 0.62 dB and 0.92 dB at 2.4 GHz and 5.25 GHz respectively while matching a 50 ohm impedance.

This paper presents the design of a 1536 x 1536 pixel silicon backplane for dynamic holography in an all-optical 64 x 64 switch. Each pixel consists of two 6T-SRAM cells, a 4-to-1 multiplexer, and a high voltage buffer. A special driving technique using digital driving of the ITO and reflector devices has enabled the chip to control the voltage across the liquid crystal sandwich with zero DC bias. The chip has been fabricated in a 0.25 μm 2.5V/5V with a special high reflectivity top metal process. The pixel dimensions is 10.8 μm X 10.8 μm with a 0.6 μm spacing between the top metals. The total chip area is 21.9 mm X 21.7 mm. At typical driving frequencies of 10 KHz the chip consumes only 100 mW.

This paper presents a fully differential ultra low power successive approximation (SA) Analog-to-digital converter (ADC) for biomedical application. In order to reduce the system power consumption, the building block components of the SA ADC architecture has been optimised. In addition, the ADC the input voltage swing is scaled down to in order to reduce the slope gain error and the nonlinearity errors. The SA ADC has been implemented in Cadence Analog Design Environment using 0.18-micron CMOS technology. The designed SA ADC operates at a sampling rate of 200S/s at 3V power supply and consumes only 12µW of power at this frequency. The ADC standby power consumption is less than 1µW. The designed 16-bit ADC occupies an area of 0.1 mm² and is the smallest in size among its 16-bit counter parts reported in the literature. The proposed 16-bit ADC achieves the differential-non-linearity (DNL) and integral-non-linearity errors (INL) of ± 0.5 LSB and ± 0.3 LSB respectively.

We present an analysis of the use of suprathreshold stochastic resonance for analog to digital conversion. Suprathreshold stochastic resonance is a phenomenon where the presence of internal or input noise provides the optimal response from a system of identical parallel threshold devices such as comparators or neurons. Under the conditions where this occurs, such a system is effectively a non-deterministic analog to digital converter. In this paper we compare the suprathreshold stochastic resonance effect to conventional analog to digital conversion by analysing the rate-distortion trade-off of each.

The analysis of full-chip IR and di/dt drop as well as package and on-chip resonance is very important for the system-on-chip design. Algorithms to optimize power distribution networks (PDNs) iteratively require fast methods to estimate the power supply noise. Additionally an efficient way to provide the complex input data for such a simulation is required. The simulation method used is based on a macromodel of the off-chip power supply and a 2D signal line model of the on-chip PDN. The on-chip PDN gets discretized in 2D signal line cells. We use admittance functions in each direction instead of resistances and inductances for these cells. Therefore, the frequency dependence due to the multiple return paths in different layers and further high frequency effects can be incorporated. One of the merits of this approach is that these admittance functions, which may vary all over the chip, can be efficiently calculated with a model order reduction algorithm directly from a Partial Element Equivalent Circuit (PEEC) model. The currents of the nonlinear devices are modeled as time varying current sources in parallel to capacitances and conductances. We use a fast transient simulation algorithm closely related to the Finite-Difference Time-Domain schemes to simulate the model. The method is well suited for iterative design improvements and irregular power grids. Combining the macromodel of the off-chip PDN with the reduced order model of the IC we investigate the effect of damping resistors and the possibility to optimize the power integrity by increasing the damping resistors.

The architecture of an analog recurrent neural network that can learn a continuous-time trajectory is presented. The proposed learning circuit does not distinguish parameters based on a presumed model of the signal or system for identification. The synaptic weights are modeled as variable gain cells that can be implemented with a few MOS transistors. The network output consists primarily of neuron signals which portray the periodic characteristics of the input signal in unsupervised mode. For the specific purpose of demonstrating the trajectory learning capabilities, a periodic signal with varying characteristics is used. The developed architecture, however, allows for more general learning tasks typical in applications of identification and control. The periodicity of the input signal ensures consistency in the outcome of the error and convergence speed at different instances in time. While alternative on-line versions of the synaptic update measures can be formulated, which allow for faster learning speed and better convergence behavior, the architecture of the analog RNN used here is easier to implement while still allowing to demonstrate the general principle. Because the architecture depends on the network generating a stable limit cycle, and consequently a periodic solution which is robust over an interval of parameter uncertainties, we currently place the restriction of a periodic format for the input signals. The simulated network contains interconnected recurrent neurons with continuous-time dynamics. The system basically performs random-direction descent of the error as a multidimensional extension to the stochastic approximation. To achieve unsupervised learning in recurrent dynamical systems we propose a synapse circuit which has a very simple structure and is suitable for implementation in VLSI.

Reconfigurable Circuit (RC) platforms can be configured to implement complex combinatorial and sequential logic. In this paper we investigate various RC technologies and discuss possible methods to optimise their power, speed and area. To address the drawbacks of existing RC technologies we propose a generic architecture we call "OFRL" (On-the-Fly Reconfigurable Logic). Our objective is to provide a low power, high speed platform for reconfigurable circuit and dynamically reconfigurable logic applications that use fewer transistors than existing technologies.

In this paper, a first order TDTL system is designed, simulated and implemented on a reconfigurable FPGA system. Initially the loop was designed and simulated using Matlab/Simulink. Subsequently some novel modifications were introduced to the TDTL in order to allow an optimized reconfigurable implementation, which eases the design process and allows for dynamic parameter and design modifications. The reconfigurable TDTL was tested in real time conditions under the same operating conditions of the simulated loop. Comparison between the simulated and real time results indicate a high degree of correlation, making the loop attractive for various practical applications.

A new hardware architecture is described to perform multiplication and modular multiplication with a modulus of variable wordlength. It is intended for a microprocessor datapath to support efficient implementation of long wordlength operations using the residue number system.

Fully-adiabatic (thermodynamically reversible) logic is one of the few promising approaches to low-power logic design. To maximize the system power-performance of an adiabatic circuit requires an ultra low-loss on-chip clock source, which can generate an output signal with a quasi-trapezoidal (flat-topped) voltage waveform. In this paper, we propose to use high-Q MEMS resonators to generate the custom waveform. The big challenge in the MEMS resonator design is that a non-sinusoidal (quasi-trapezoidal) waveform needs to be generated even though the resonator oscillates sinusoidally. Our solution is to customize the shape of the sensing comb fingers of the resonator, with the result that the sensing capacitance varies quasi-trapezoidally. The effective quality factor and the area-efficiency of the microstructure have been optimized so as to minimize the whole system’s power dissipation and cost at a given frequency. A resonator design with a 100 kHz resonant frequency based on a standard TSMC 0.35μm CMOS process has been fabricated. The resonator has an area of 300 μm by 160 μm with a thickness of 30 μm. Three-dimensional field simulation shows that the resonator generates a quasi-trapezoidal waveform when it operates at its resonance. An on-chip buffer is also designed for monitoring the waveform generated by the MEMS resonator. The post-CMOS fabrication process is compatible with standard CMOS processes. Thus the custom clock generator can be integrated with logic circuits on the same CMOS chip. The size of the MEMS resonator can be further reduced by design optimization and advances in micro/nano-fabrication technology.

Polythiophene, one of the most extensively studied conducting polymers, was selected as an actuator material due to its chemical and electrochemical stability both in air and moisture. In this work, poly(3-methylthiophene) based actuators were constructed electrochemically with a tubular geometrical configuration. The actuation behaviour was investigated regarding to the actuation strain generated, the stress produced and work per cycle performed by poly(3-methylthiophene) actuators. The effect of potential sweep rate and different electrolytes (ionic liquid and organic solvent) on the actuation performance were also explored. Poly(3-methylthiophene) actuators show an increase in actuation strain with an increase in applied load.

TiNi films were deposited on silicon by co-sputtering TiNi target and a separate Ti target at a temperature of 450°C. Results from differential scanning calorimeter, in-situ X-ray diffraction and curvature measurement revealed clearly martensitic transformation upon heating and cooling. Two types of TiNi/Si optical micromirror structures with a Si mirror cap (20 micron thick) and TiNi/Si actuation beams were designed and fabricated. For the first design, three elbow shaped Si beams with TiNi electrodes were used as the arms to actuate the mirror. In the second design, a V-shaped cantilever based on TiNi/Si bimorph beams was used as the actuation mechanism for micromirror. TiNi electrodes were patterned and wet-etched in a solutions of HF:HNO₃:H₂O (1:1:20) with an etch rate of 0.6 μm/min. The TiNi/Si microbeams were flat at room temperature, and bent up with applying voltage in TiNi electrodes (due to phase transformation and shape memory effect), thus causing the changes in angles of micromirror.

Optical switches are among key devices for implementation of DWDM in optical networks. There are a number of technologies available to realize optical switches, including Micro-Electro-Mechanical System (MEMS) switches, Bubble-Based Waveguide Switches, Liquid Crystal on Silicon (LCOS) Switches, Electro-Optic Switches, and Thermo-Optic Switches. Among these technologies MEMS has received particular attention in recent years, initially using 2 dimensional (2D) switches and later progressing to 3D switches. This paper evaluates Liquid Crystal on Silicon (LCOS) as an alternative to MEMS for implementation of optical switches. The opportunities and challenges for LCOS in optical networking are discussed. Issues related to availability of LCs, switching speeds, voltage requirements, scalability, wavelength range, packaging and crosstalk are considered.

This paper demonstrates the use of modern electromagnetic simulation software to design and develop a selection of three novel transmission line transitions, for operation at mm-wavelengths, and an improvement in the performance of existing transitions. Specifically, our three case studies analyse (i) a microstrip-to-stripline transition, (ii) an inverted microstrip transition, and (iii) a mtripline-to-finline transition. The important concepts are described and the tools available are explained. A number of novel and effective designs are presented as examples.

A silica microlens has been proposed which can be integrated with planar optical waveguide circuits. In order to fabricate the microlens, two deep silica etches must be performed. RIE is the prefered process as under certain conditions it is anisotropic. This paper reports on a study of different masking materials and plasma etch conditions trialed for the deep silica etch.

The spin-on photoresist SU8 from MicroChem has a relatively high refractive index (n=1.57 at 1550nm) compared with other polymers. It is stable and has high optical transmission at optical communication wavelengths. In this paper we study rib waveguides fabricated using SU8 as the core layer and thermoset polymers UV15 (n=1.50 at 1550nm) from Master Bond and NOA61 (n=1.54 at 1550nm) from Gentec as the cladding layers. The rib height is varied from 0.3 to 1.7μm high. This is part of the SU8 layer sandwiched between the cladding layers. The waveguides are tested to determine the effects of varying this geometry for single mode optical transmission. The lengths of the waveguides were 1.5 cm to 5 cm.

In this study, the geometry of the handlebars of bicycle is simulated as a hollow cylindrical rod, subjected to flexural vibration transmitted from a head tube. Analytical prediction as well as experimental investigation are implemented to evaluate the effectiveness of active control of flexural vibration of the handlebars using Macro-Fiber Composite (MFC) actuators. The newly developed MFC actuators are typically directional or anisotropic, and more flexible and conformable as compared to traditional monolithic isotropic piezoceramic actuators. Predictions of the finite element model are validated experimentally using a cantilevered cylindrical rod surface bonded with three flexible MFC actuators, two placed at the clamped end and the third at the bend location. A primary disturbance is assumed to be transmitted from the clamped end, while a secondary force from the MFC actuators. The velocity feedback and the LQR controller are utilized to determine appropriate voltage inputs into the MFC actuators. Close agreement is found between theoretical assumptions and experiments. The results obtained suggest that using the MFC actuators in controlling the flexural wave transmission through hollow cylindrical rod has been effective.

The evolution of the optical beam profile along a high-power tapered semiconductor amplifier has been demonstrated by using a rigorous finite element-based and full-vectorial modal approach, coupled with the beam propagation method. Numerically simulated results indicate that many higher order modes are generated and propagate along the tapered structure and their interference with the fundamental mode causes variations of the optical beam, both along the transverse and the axial directions, which significantly modifies the output beam quality.

Vibrations from a target provide a difficult to mask target signature. Vibrometry shows potential for long-range target identification whilst a fibre implementation may lead to a smaller, more compact system when compared with an equivalent solid-state source solution. A prototype fibre LDV system and electronic demodulation scheme using low-cost telecommunications components is described and tested. The aim of the system is to remove the velocity component of a target signature for target identification purposes. Signal processing methods and signature measurements are described which demonstrate the utility of the system for target recognition.

A novel 2-bit optical-input optical-output analog-to-digital converter (ADC) is demonstrated in self electro-optic device (SEED) technology using a threshold logic technique. The threshold gate was constructed using a resistor-SEED (R-SEED) which is composed of a large value resistor and a SEED area of 500 um x 500 um. Each gate operates as a majority function that has a threshold level controlled by a fixed optical input. The ADC was constructed using two R-SEED gates operating at wavelength of 846 nm. The test bench set-up operates at 100 Hz. However, as the proposed architecture is scalable, it can operate at much higher speeds and generate larger number of bits. This architecture is only limited by the switching speed of the SEED and propagation delay through each threshold gate.

Miniaturization of laboratory sensors has been enabled by continued evolution of technology. Field portable systems are often desired, because they reduce sample handling, provide rapid feedback capability, and enhance convenience. Fieldable sensor systems should include a method for initiating the analysis, storing and displaying the results, while consuming minimal power and being compact and portable. Low cost will allow widespread usage of these systems. In this paper, we discuss a reconfigurable Personal Data Assistant (PDA) based control and data collection system for use with miniature sensors. The system is based on the Handspring visor PDA and a custom designed motherboard, which connects directly to the PDA microprocessor. The PDA provides a convenient and low cost graphical user interface, moderate processing capability, and integrated battery power. The low power motherboard provides the voltage levels, data collection, and input/output (I/O) capabilities required by many MEMS and miniature sensors. These capabilities are relayed to connectors, where an application specific daughterboard is attached. In this paper, two applications are demonstrated. First, a handheld nucleic acid sequence-based amplification (NASBA) detection sensor consisting of a heated and optical fluorescence detection system is discussed. Second, an electrostatically actuated MEMS micro mirror controller is realized.

This paper presents the fabrication process of a MEMS-based cantilever flow sensor (CFS) with double cantilever beams and the test results of CFS in a wind-tunnel. Four boron-doped piezoresistive strain gauges at the base of each cantilever beam compose the four arms of the Wheatstone bridge. The output of CFS will change signs as piezoresistors at the base of the cantilever beam undergo compressive or tensile stresses. Analyses and experimental results suggest that double-beam CFS can be applied not only as a flow direction discriminator but also as a wall skin-friction sensor, which could be used in the system of active flow control for drag reduction and separation suppression in the boundary layers on a wing section. Temperature effect is commonly encountered in the application of MEMS-based piezoresistive strain gauges. By comparing the outputs of CFS when front side and back side of it facing the flow respectively, we are able to clarify the contribution of temperature effect on the output of CFS sensor and give more accurate results on flow measurement.

Microcantilevers are commonly used as part of sensor elements in Microelectromechanical Systems (MEMS). Deflection or the shift of resonance frequency of microcantilever beams are regularly used to measure chemical, physical or biological quantities. An important characteristic of any sensor is its sensitivity to a given input. This paper explores the possibility of improving the sensitivity of a microcantilever by modifying the mechanical properties using partial perforations on the surface of the microcantilever. This paper presents two analytical models that quantify the deflection and the fundamental resonant frequency in terms of the perforation dimensions for a microcantilever beam. Beams with a single partial perforation are considered first, and the models are then expanded to include multi-perforated cantilevers. Results obtained from the analytical models are compared to Finite Element Analysis (FEA) simulations of perforated microcantilever beams. The analytical models of a microcantilever with a single perforation show high accuracies compared to the FEA, while the accuracy of results for a cantilever beam with many perforations decrease as the number and size of perforations are increased. The results of the models are used to design a cantilever beam with the desired mechanical properties.

A process management and development system for MEMS design is introduced. It allows the specification of processes for specific applications and the tracking of the development procedures. The system is based on a dedicated database environment that is able to store and manage all process related design constraints and development related data linked to the fabrication process data itself. The interdependencies between application specific processes and all stages of the design flow will be discussed and a software system will be introduced meeting the requirements of this new approach. Although initially dedicated to microsystem processes this environment may also support nanoelectronic fabrication technologies.

This paper presents a wafer level packaging solution for MEMS devices using wafer to wafer bonding with SU8-5 negative photoresist. A sensitive piezoelectric pressure sensor with the pressure range between 0 and 0.4 bar was chosen to test the quality of the solution. As stress induced by the packaging technique is the main challenge in MEMS encapsulation, the piezoresistive pressure sensors with its tensometric bridge offer a good opportunity for testing the packaging solution. The offset modification of the diffused piezoresistive Wheatstone bridge fabricated on a 15 μm thin diaphragm is directly influenced by the value of the stress induced by the packaging. In our paper the silicon wafer with pressure sensors is sandwiched between a bottom silicon wafer with etched holes for the applied pressure and a top glass wafer with via-holes and metallization leads. Silicon and Pyrex glass (Corning 7740) was used as materials for packaging mainly due to their thermal coefficient of expansion. The results, variation of tensometric bridge in the range between -5 mV to +5 mV at 10 VDC power supply shows that the packaging solution can be applied for MEMS packaging.

Over the last three years we have demonstrated key milestones in the fabrication of buried nano-scale devices in silicon using an ultra-high vacuum scanning tunnelling microscope (STM) and silicon molecular beam epitaxy (MBE). Recently we have achieved the final step of connecting the STM-patterned buried phosphorus devices to the outside world to perform electrical measurements. The results of our low temperature magnetotransport measurements highlight the potential of this approach for the creation of atomic-scale devices.

The radio-frequency single-electron-transistor (rf-SET) is an electrometer that can sense a fraction of an electron charge on microsecond timescales. At present this device is prevented from reaching quantum limits by the noise contribution of the post-amplifier, generally a cryogenic high-electron mobility transistor (HEMT). We present results to date in our effort to construct an alternative post-amplifier based on the dc superconducting quantum interference device (SQUID). These SQUID-based amplifiers, which are fabricated in aluminium via electron beam lithography and shadow mask evaporation open the possibility of near-quantum-limited electrometry with the rf-SET.

The possible role of self-assembled monolayers (SAMs) as the dielectric component of nanoscale capacitors is considered. SAMs of two rather different molecules, α,α’-p-xylyldithiol ('XYL’) and dodecanedithiol ('C12’) were produced on a gold {111} substrate, and characterized with respect to their conductivity. The data were fitted with a double tunnel barrier model, in which the two SAMs are primarily differentiated by barrier height and thickness with that of XYL having a thickness of 1.0 nm and a barrier height of 0.78 eV compared to 1.69 nm and 1.39 eV for C12. The remaining parameters of the model were determined by Monte Carlo optimization. Assuming perfect connection of top and bottom electrodes, the leakage current through the XYL at 1 volt is calculated to be 1.4x10⁵ A/cm², compared to 2.7x10⁴ A/cm² through C12. These values are not as low as can be obtained with SiO₂ of the same thickness. However, SAMs are readily and precisely produced by simple, low temperature processes, a factor which may allow them a niche in the future.

In this paper, we present and analyze the most fundamental constraint of RFID systems, power rectification. This issue plays an important role in development of long-range RFID systems. Rectifiers are the key components in power rectifications and efficiency of an RFID system. Therefore this paper is concentrated in investigating this major issue. To tackle this problem a novel Schottky Barrier Diode (SBD) has been proposed. The proposed SBD provides good power conversion rate and switching properties.

We enunciate the general principles that govern the transport of charge and heat in a thermionic device. We illustrate the application of these principles to the subject of domestic refrigeration. A complementary application is power generation. We distinguish Class 2 devices, in which the potential barrier on the hot side plays a role, from Class 1 devices, in which this barrier is irrelevant. We show that the effect of heat backflow is to drastically reduce the efficiency of thermionic devices in both GaAs and InSb representative semiconductor systems. We conclude that practical devices are not likely with bulk, single-barrier devices.

The ultimate goal of micro-systems is ad hoc arrays of wireless, self powered intelligent sensors which self-assemble on installation and adjust to a changing number of sensors and/or changing sensor location. The sensors and the network infrastructure must be low cost, disposable (recyclable), unobtrusive and these ultimate goals impact on all aspects of sensor design and network protocols. In this paper, a number of strategies employed to achieve these goals are outlined. In particular, some recent technological developments have facilitated more efficient sensor networks. These include smart antennas, low power electronics and sensors, creative methods of data reduction and "tipping bucket" data streaming. Sensor networks with lifetimes of more than one year are now possible.

The ability to supply power at the micro level from the ambient energy is an increasingly important area of MEMS. This paper presents a methodology for the design of an electromagnetic micro generator that converts mechanical energy associated with the low amplitude vibration present in structures such us tall buildings and bridges to electrical power. The generator consists of a rigid housing and a moving magnet suspended on a flat spring that induces a voltage on a stationary coil attached to the housing. Finite Element Analysis (FEA) software (ANSYS5.7) has been used to analyse different designs of flat springs and to select one that is capable of large deflection. The effects of the main design parameters: length, width, thickness and material properties on the spring deflection were modelled. Maximum static deflection of 13.43μm is achieved under the gravitational force. Furthermore, Free vibration characteristics of the suspended magnet are also presented. Maximum electric power of 14.5nW is calculated for the spring with natural frequency of 18.56 Hz when the input vibration frequency and its amplitude are assumed to be 3kHz and 5μm. An outline of how the design can proceed in a logical manner is discussed.

The rapidly decreasing size, cost, and power consumption of wireless sensors has opened up the relatively new research field of energy harvesting. Recent years have seen an increasing amount of research on using ambient vibrations as a power source. An important feature of all of these generators is that they depend on the resonance frequency of the generator device being matched with the frequency of the input vibrations. The goal of this paper, therefore, is to explore solutions to the problem of self-tuning vibration based energy harvesters. A distinction is made between “active” tuning actuators that must continuously supply power to achieve the resonance frequency change, and “passive” tuning actuators that supply power initially to tune the frequency, and then are able to “turn off” while maintaining the new resonance frequency. This paper analyzes the feasibility of tuning the resonance frequency of vibration based generators with “active” tuning actuators. Actuators that can tune the effective stiffness, mass, and damping are analyzed theoretically. Numerical results based for each type of actuator are presented. It is shown that only actuators that tune the effective damping will result in a net increase in power output, and only under the circumstance that no actuation power is needed to add damping. The net increase in power occurs when the mismatch between driving vibrations the mismatch between driving vibrations the resonance frequency of the device is more than 5%. Finally, the theory and numerical results are validated by experiments done on a piezoelectric generator with a smart material “active” tuning actuator.

This paper presents a smart suit, water impermeable, containing sensors and electronics for monitoring handicapped people at hydrotherapy sessions in swimming-pools. For integration into textiles, electronic components should be designed in a functional, robust and inexpensive way. Therefore, small-size electronics microsystems are a promising approach. The smart suit allows the monitoring of individual biometric data, such as heart rate, temperature and movement of the body. Two solutions for transmitting the data wirelessly are presented: through a low-voltage (3.0 V), low-power, CMOS RF IC (1.6 mm x 1.5 mm size dimensions) operating at 433 MHz, with ASK modulation and a patch antenna built on lossy substrates compatible with integrated circuits fabrication. Two different substrates were used for antenna implementation: high-resistivity silicon (HRS) and Corning Pyrex #7740 glass. The antenna prototypes were built to operate close to the 5 GHz ISM band. They operate at a center frequency of 5.705 GHz (HRS) and 5.995 GHz (Pyrex). The studied parameters were: substrate thickness, substrate losses, oxide thickness, metal conductivity and thickness. The antenna on HRS uses an area of 8 mm², providing a 90 MHz bandwidth and ~0.3 dBi of gain. On a glass substrate, the antenna uses 12 mm², provides 100 MHz bandwidth and ~3 dBi of gain.

Thin metal foil sensors for corrosion monitoring are being developed for applications under paints, sealants and in lap joints. These sensors are two electrode electrochemical devices. A fundamental consideration for these sensors is that they reflect the corrosion activity of the structure to be monitored. To this end, fine milling, chemical etching and laser micromachining are used to fabricate the sensors from the same material as the structure of interest. Details of the fabrication, characterisation and micro-circuit instrumentation of the sensors will be presented.

Although historically among the most popular of sports, today, combative sports are often viewed as an expression of our savage past. Of primary concern are the long term effects of participating in these sports on the health of participants. The scoring of such sports has also been the subject of much debate, with a panel of judges making decisions about very quick events involving large sums of prize money. This paper describes an electronic system for use primarily in the sport of boxing, though it is suitable for martial arts such as karate and taekwondo. The technology is based on a previously described sensor platform and integrates a network of sensors on the athlete’s head, body and hands. Using a Bluetooth network, physical contacts are monitored in near real-time or post event on a remote computer to determine legal hits and hence derivative measures like scoring and final outcomes. It is hoped that this system can be applied to reduce the need for full contact contests as well as provide a more reliable method of determining the outcome of a bout. Other benefits presented here include the ability to analyse an athlete's performance post match or training session, such as assessing the efficacy of training drills and effects of fatigue.

The measurement of sport specific performance characteristics is an important part of an athletes training and preparation for competition. Thus automated measurement, extraction and analysis of performance measures is desired and addressed in this paper. A tri-axial accelerometer based system was located on the lower back or swimmers to record acceleration profiles. The accelerometer system contained two ADXL202 bi-axial accelerometers positioned perpendicular to one another, and can store over 6 hours of data at 150Hz per channel using internal flash memory. The simultaneous collection of video and electronics touch pad timing was used to validate the algorithm results. Using the tri-axial accelerometer data, algorithms have been developed to derive lap times and stroke count. Comparison against electronic touch pad timing against accelerometer lap times has produced results with a typical error of better than ±0.5 seconds. Video comparison of the stroke count algorithm for freestyle also produced results with an average error of ±1 stroke. The developed algorithms have a higher level of reliability compared to hand timed and counted date that is commonly used during training.

Optical fiber sensors can be used to measure many different parameters including strain, temperature, pressure, displacement, electrical field, refractive index, rotation, position and vibrations. Among a variety of fiber sensors, fiber Bragg grating (FBG) has numerous advantages over other optical fiber sensors. One of the major advantages of this type of sensors is attributed to wavelength-encoded information given by the Bragg grating. Since the wavelength is an absolute parameter, signal from FBG may be processed such that its information remains immune to power fluctuations along the optical path. This inherent characteristic makes the FBG sensors very attractive for application in harsh environment, and on-site measurements. But FBG sensors can measure temperature and strain simultaneously; it is necessary to decouple measurement information. In the present paper, A distributed fiber Bragg grating sensors measurement system that measures global deformations of large surface online-based FBG sensors is introduced. Short overview of the measurement principle and the signal processing realized and fusion method as well as the application of the sensor in the field of large surface will be presented. A new fusion method based on the federal Kalman filter to decouple information of the temperature and strain is proposed. The algorithm of optimum estimation fusion for distributed FBG systems based on the model of deformation of beam is studied. Simulation results and experimental results show algorithm of fusion and decoupling is an efficient method for improving performance of distributed FBG sensors system.

A structure using the two-way shape memory effect (TWSME) returns to its initial shape by increasing or decreasing temperature under initial residual stress. Through the thermo-mechanical constitutive equation of shape memory alloy (SMA) proposed by Lagoudas et al., we simulate the behavior of a double actuator in which two SMA wires are attached to the tip of bar under the initially given residual stress. Through the numerical results conducted in the present study, the proposed actuator device is suitable for repeated actuation. The simulation algorithm proposed in the present study can be applied extensively to the analysis of the assembled system of SMA-actuator and host structure in practical applications.

The phase inversion technique was used to produce polyaniline (PAn) actuators with different geometries that cannot be obtained by PAn cast from N-methyl-2-pyrrolidinone (NMP) solution in a conventional way. PAn was cast and coagulated in a water bath forming films and tubes with or without a platinum (Pt) wire helix as an interconnect. PAn was doped with hydrochloric solution (HCl, 1 M) (PAn/HCl) or methanesulfonic acid (MSA, 1 M) (PAn/MSA). In nitric acid (HNO₃, 1 M) aqueous electrolyte, the actuation strain of PAn/HCl was 0.9% which increased to 2.0% and 2.7% for the tubes without and with the Pt helix, respectively. The Pt helix helped prevent the IR drop along the actuator. Comparing with NaNO₃ (1 M) aqueous electrolyte, the use of HNO₃ aqueous electrolyte gave better actuation stability where at least 100 cycles were observed and the final actuation strain was determined by the size of dopant. Change of coagulation bath from water to NMP (30% w/w)/water resulted in subtle difference in the Young’s modulus of PAn/MSA in oxidized and reduced states. PAn prepared by phase inversion technique is porous by nature, consequently it is brittle and exhibits a low actuation stress (0.3 - 0.4 MPa).

Piezoelectric (PZT) actuators are commonly employed to drive flexure-jointed mechanisms with a nanometer resolution. There are three issues related to piezoelectric actuators; hysteresis, creep and vibration. Although the first two problems have been studied widely, a little attention has been given to the vibration analysis of piezoelectric actuators and elastic (compliant) mechanisms they drive. When a piezoelectric actuator is coupled with an elastic system (e.g. a flexure-jointed mechanism), the effect of the resulting vibration on the accuracy of the piezo-actuated flexure-jointed mechanism is significant, and therefore, the vibration problem deserves a systematic investigation. In this paper, we report on vibration analysis of such systems, and the influence of the actuator and mechanism dynamics on the system accuracy through a numerical analysis. A flexure jointed Scott-Russell mechanism is considered as the mechanism driven by a piezoelectric actuator. This mechanism can be used not only to change the direction of a translation motion by 90° but also to be a mechanical displacement amplifier. Numerical results are provided to quantify the interaction between the actuator dynamics and the mechanism dynamics from vibration and positioning accuracy points of view. Further, the influence of the type of input signals on the positioning accuracy of the piezo-electric actuated flexure-jointed micromanipulation systems is elaborated with extensive numerical results.

This paper deals with feature of the magnetostrictive actuator. The current-displacement hysteresis loop has been modeled mathematically. Based on the experimental data, this model has then been predigested into a linear one. And then several experiments have been carried on to validate this model. By putting the actuator into a certain testing platform, the correct results of the system which is excited by a single current input signal, a single mechanical input signal and the co current-mechanical signal have been achieved. Through a serial of given experiments by using diverse current and mechanical exciters, the actuator has been put into applications and the dynamic characteristics of the vibration responses of certain situations of the “electro-magneto-elastic integral system” has been gained. Based on all the study of the dynamic characteristic of the actuator’s vibration output, and from the aspect of minimizing the output displacement of the actuator, the method of vibration control has been carried on. We have measure to input a control current to make the vibration of mechanical exciting system lowest. This is the basis of designing a smart structure and carrying on vibration control.

Multi-wire steel strands have been widely used in various prestressed concrete structures. In this study, experimental evaluation of fiber Bragg grating (FBG) sensors for strain measurements in a seven-wire prestressed steel strand has been carried out. An installation technique of FBG sensors has been developed to fulfill the special requirements of the prestressed steel strand. The experiment results show that fiber Bragg gratings can represent the overall stress of the prestressed steel strand without being affected by the specific structure of the strand when it is only fixed on one wire. It is also demonstrated that the maximum strain that the FBG sensor can measure is 6260 με, while the prestressed steel strand usually endures the strain greater than 10000 με. This means that an offset of about 4000 με is necessary to measure the maximum strain that the strand could experience in its applications.

Nondestructive evaluation (NDE) is essential in civil and building engineering. Impedance-based method uses the electro-mechanical coupling effect of piezoceramic lead-zirconate-titanate (PZT) materials to measure the force impedance of the structure. By comparing the impedance spectra of the damaged structure with the baseline (the impedance spectra for the pristine structure), the damage in the structure can be assessed. The impedance-based method has shown some advantages over the traditional NDE methods. However, it is not able to identify the location and quantity of the damage simultaneously. This paper presents a technique to overcome this limitation. The technique first measures the variations of the electro-mechanical impedance of the structure, which is similar to the impedance-based method, so that it can inherit the advantage of convenience in operation from the impedance-based method. The damage is then identified by a system identification technique which is generally employed in the vibration-based method. Due to the numerous local optima in the search space, the traditional optimization strategies may not be able to find the correct solution. This paper selects evolutionary programming (EP) as the system identification technique for its robustness in finding the global optimum. Thus, the location and the quantity of the damage can be simultaneously identified. In order to enhance the feasibility of the integrated EP and impedance-based (inEPIB) technique, a fitness function, which can be generally applied to other methods, is proposed to discriminate the variations caused by damages from the discrepancies caused by modeling errors. Experiments are carried out on beams and plates to verify the damage detection results. The results demonstrate that both the location and extent of damage can be simultaneously identified.

In this paper, we present work on a surface micromachined opto-mechanical microaccelerometer employing Ni seimic mass. The device uses optical detection to sense motion. The microaccelerometer consists of a 500 um x 500 um electrodeposited nickel suspended by a folded beam spring on each corner over 10 pairs of 30 um x 400 um rectangular photodiodes. The seismic mass also has an array of rectangular holes parallel to the photodiodes. Each hole partially exposes a pair of adjacent photodiodes to to be illuminated by an LED. Once the mass experiences acceleration, it will act as a mechanical shutter and alters the amount of exposed area of photodiodes. For each pair of the photodiodes, as the shutter moves, it will increase the exposed area of one diode and at the same time will at the same time reduce the exposed area of the other diode by the same amount. Fully differential current signals can then be taken by appropriately biasing the photodiodes. By using differential sensing arrangement, the effects of noise and dark current can be reduced significantly. The microaccelerometer is tested on a rotating disc. The frequency response of the accelerometer is relatively flat up to 1500 Hz, then, it rise sharply at resonant frequency of approximately 1700 Hz. An open loop sensitivity of 9.2mV/g in the direction of acceleration is obtained. Cross axial sensitivity was below the noise level.

Sensor packaging has been identified as one of the most significant areas of research for enabling sensor usage in harsh environments for several application fields. Protection is one of the primary goals of sensor packaging; however, research deals not only with robust and resistant packages optimization, but also with electromagnetic performance. On the other hand, from the economic point of view, wireless sensor networks present hundreds of thousands of small sensors, namely motes, whose costs should be reduced at the lowest level, thus driving low the packaging cost also. So far, packaging issues have not been extended to such topics because these products are not yet in the advanced production cycle. However, in order to guarantee high EMC performance and low packaging costs, it is necessary to address the packaging strategy from the very beginning. Technological improvements that impacts on production time and costs can be suitable organized by anticipating the above mentioned issues in the development and design of the motes, obtaining in this way a significant reduction of final efforts for optimization. The paper addresses the development and production techniques necessary to identify the real needs in such a field and provides the suitable strategies to enhance industrial performance of high-volumes productions. Moreover the electrical and mechanical characteristics of these devices are reviewed and better identified in function of the environmental requirements and electromagnetic compatibility. Future developments complete the scenario and introduce the next mote generation characterized by a cost lower by an order of magnitude.

In a sensor employing changes in capacitance the introduction of two additional reference electrodes can assist in the minimization and correction of errors introduced in the manufacturing process and from changes in environmental conditions. The two extra electrodes that reflect the maximum and minimum values of the measuring electrode are constructed during the same lithographic process and in close proximity to the active electrode. In preliminary trials of 79 sensors the uncorrected error in reading was nearly 20% of full scale and dropped to 4% of full scale after applying the correction. The technique with support electronics printed on flexible substrates allow the sensor to be small, integrated and “smart”.

This paper presents the application specific integrated circuit (ASIC) implementation of an intelligent controller for a reconfigurable data acquisition (DAQ) system. The DAQ system is employed in a digital relay for power system protection application. The controller is the intelligence behind the reconfigurable architecture. It continuously monitors the voltages and currents to detect the appearance of an abnormal condition on the power transmission network. Then it will send signals to adjust DAQ system sampling speed and filter cut-off frequency for properly detecting the fault location and properly analysing the fault. A novel approach to determine the line impedance angle has been proposed. This approach eliminates the square-root and arc-tan operations to reduce the cost of the semi-custom ASIC implementation of the intelligent controller. Analysis revealed that the intelligent controller achieved a maximum operating frequency of 100MHz, with 10ns critical path delay. The controller core utilises an area of 1.9mm².

High-frequency (HF) communications is undergoing resurgence despite advances in long-range satellite communication systems. Defense agencies are using the HF spectrum for backup communications as well as for spectrum surveillance applications. Spectrum management organizations are monitoring the HF spectrum to control and enforce licensing. These activities usually require systems capable of determining the location of a source of transmissions, separating valid signals from interference and noise, and recognizing signal modulation. Our ultimate aim is to develop robust modulation recognition algorithms for real HF signals, that is, signals propagating by multiple ionospheric modes. One aspect of modulation recognition is the extraction of signal identifying features. The most common features for modulation recognition are instantaneous phase, amplitude, and frequency. However, this paper focuses on two feature parameters: coherence and entropy. Signal entropy and the coherence function show potential for robust recognition of HF modulation types in the presence of HF noise and multi-path. Specifically, it is shown that the methods of calculation of coherence and entropy are important and that appropriate calculations ensure stability in the parameters. For the first time a new metric, called Coherence-Median Difference (CMD), is introduced that provides a measure of the dominance of coherence at specific frequencies to coherence at all other frequencies in a particular bandwidth.

This paper explores the authorship of the Letter to the Hebrews using a number of different measures of relationship between different texts of the New Testament. The methods used in the study include file zipping and compression techniques, prediction by the partial matching technique and the word recurrence interval technique. The long term motivation is that the techniques employed in this study may find applicability in future generation web search engines, email authorship identification, detection of plagiarism and terrorist email traffic filtration.

We have developed an analytical model that describes the steady-state thermal behavior of a 1-D electrothermal bimorph MEMS micromirror. The steady-state 1-D heat transport equation is used to solve for the temperature distribution of the device upon actuation. Three models are developed using different thermal conditions on the device. The models consider heat dissipation from conduction and convection and the temperature dependence of the actuator electrical resistor. The temperature distribution equation of each model is analyzed to find critical thermal parameters such as the position of maximum temperature, maximum temperature, average temperature, and equivalent thermal resistance. The simplest model, called the Case 1 model, is used to develop an electrothermal lumped element model that uses a single thermal power source. In the Case 1 model, it is shown that a parameter called the “balancing factor” predicts where the maximum temperature is located, the distribution of power flow, and the division of thermal resistances. The analytical models are compared to FEM simulations and agree within 20% for all of the actuation ranges and thermal conditions tested.

Although multiplication and addition can be very efficiently implemented in a Residue Number System (RNS), scaling (division by a constant) is much more computationally complex. This limitation has prevented wider adoption of RNS. In this paper, different RNS scaling schemes are surveyed and compared. It is found that scaling in RNS has been performed with the aid of conversions to and from RNS, bse extensions between modulus sets, and redundant RNS channels. Recent advances in RNS scaling theory have reduced the overhead of such measures but RNS scaling still falls short of the ideal: a simple operation performed entirely within the RNS channels.

In this paper, for the first time to our knowledge, we report a novel FBG-type two-dimensional sensor that is able to simultaneously measure two-dimension (2-D) force and temperature, and the 2-D force sensing process can be tuned by applying rectangular cantilever beam (RCB). In the vertical directions of the RCB axis, the wavelengths shifts of two FBGs bonded to the surface of the RCB are quasi-linear with respect to the 2-D force and temperature, respectively. Two FBGs are experimentally demonstrated to have the 2-D force sensitivities of ~5.32 nm/N and 3.21 nm/N, a temperature sensitivity of ~0.095nm/°C between 0°C and 70°C, respectively.

A shear mode PZT actuator for the microdroplet ejecting system is proposed. The plate-shaped actuator poled with remnant polarization perpendicular to actuating field induces piezoelectric shear effect. Two poling designs for the shear mode piezoelectric actuator are compared by both the analysis and experiment. The two poling designs are single-surface poling design and dual-surface poling design. The single-surface poling design arranges poling electrodes only on one surface, while the dual-surface poling design arranges poling electrodes on the opposite surfaces. Although the single-surface poling design is convenient for poling process, its requirement of the higher poling voltage for achieving coercive field induces specimen failure of surface cracks. So, the dual-surface poling design is preferred because the higher yield and better electromechanical coupling characteristic can be obtained. In both poling designs, the relations of shear piezoelectric coefficient, d₁₅, and actuating electric field are obtained with three kinds of sample thicknesses.

It is shown that the dynamic behaviour of a disk-type magnetorheological (MR) fluid damper developed on shear mode for rotational machinery can be controlled by application of an external DC magnetic field produced by a low voltage electromagnetic coil and that the disk-type MR fluid damper can effectively attenuate the rotor vibration. In this paper, the dynamic behaviour of the disk-type MR fluid damper for attenuating rotor vibration under AC sinusoidal magnetic field is experimentally studied on a flexible rotor. It is shown that as the frequency of applied AC sinusoidal magnetic field increases, the capability of the disk-type MR fluid damper to attenuate rotor vibration significantly reduces. There is a maximum frequency of AC sinusoidal magnetic field for a given applied magnetic field strength to realize the MR effect. When the frequency of AC sinusoidal magnetic field is over the maximum frequency, the MR activity almost completely disappears and the dynamic behaviour of the disk-type MR fluid dampers under a high frequency AC magnetic field is the same as that without magnetic field. For a given sinusoidal magnetic field frequency, there is also a minimum AC sinusoidal magnetic field to active the MR effect. In the rotor vibration control of view, it is not necessary to use the AC power supply for disk-type MR fluid dampers.

Nanoscale particles of metals such as gold can interact with light by means of a plasmon resonance, even though they are much smaller than the wavelengths of visible light. The proportions of light that are absorbed and scattered vary with wavelength. Any light that is absorbed will cause heating of the particles, and this effect may potentially be exploited for solar glazing coatings, nanoscale lithography or medical treatments. The position of maximum absorption of an isolated spherical nanoparticle is 518 nm, but this may be significantly red-shifted by means of decreasing the symmetry to an prolate spheroid or 'nanorod’, or by producing a metal 'nanoshell’ on a dielectric core, or by aggregating insulated spherical particles. Absorption peaks in the vicinity of 655 nm for aggregated particles and 780 nm for prolate spheroids are demonstrated here. Absorbed energy is released as heat into the environment of the particles, and will cause a temperature rise within the particle the magnitude of which depends upon the value of the effective heat transfer coefficient between particle and environment. The latter is not known, but we show how highly localized temperature rises of some tens of Celsius might be conceivable in systems illuminated by sunlight.

We explore emergent behavior in an agent-based model of a complex system. The particular complex system we consider is a battlefield simulation. These agents are modeled in the RePast agent-based modeling environment. We will explore how agents of various capabilities and differing task sets affect the outcome of a battle. The capabilities of these agents include, but are not limited to, the ability to maneuver on the battlefield, receive and understand messages, formulate and send messages and attack enemy agents.

Velocity of Detonation (VoD) is an important measured characteristic parameter of explosive materials. When new explosives are developed, their VoD must be determined. Devices used to measure VoD are always destroyed in the process, however replacing these devices represents a considerable cost in the characterisation of new explosives. This paper reports the design and performance of three low-cost implementations of a point-to-point VoD measurement system, two using optical fibre and a third using piezoelectric polymers (PolyVinyliDine Flouride, PVDF). The devices were designed for short charges used under controlled laboratory conditions and were tested using the common explosive 'Composition B'. These new devices are a fraction of the cost of currently available VoD sensors and show promise in achieving comparable accuracy. Their future development will dramatically reduce the cost of testing and aid the characterisation of new explosives.

Despite their limited information processing capabilities, insects (with brains smaller than a pinhead) are able to manoeuvre with precision through environments that are highly-crowded and contain moving objects. Their ability to avoid collisions using limited computing power forms the basis for this project, in which we attempt to simulate the motion detection ability of insects using two models - the Horridge Template Model and the Reichardt Correlation Model. In this project, the direction of motion of a moving object and its angular speed are determined by capturing visual data using a web camera focussed on a moving pattern generated by VisionEgg software. The performance of both the models is quantitatively compared and various error-reducing techniques are investigated.

A polymer blend incorporating polyaniline (PAn) was used as a sensing medium in the construction of a resistance based humidity sensor. Aniline monomer was polymerised to PAn emeraldine salt (ES) in the presence of poly (butyl acrylate-co-vinyl acetate) and the processable blend was developed by redissolving 1-2 w/w% of the resulting sensing polymer residue in dichloromethane (DCM). Some of this residue was washed in ammonia solution to de-dope the PAn to emeraldine base (EB) to act as a protective layer on the surface of the sensing polymer. This residue was then washed with distilled water until a neutral pH was realised with the waste water, dried and redissolved in DCM at 1-2 w/w% to create a processable blend barrier polymer solution. The final sensor design utilised 125μm polyester insulated platinum wire as conducting electrodes that were dip coated in the PAn ES blend solution and dried in a desiccator. A protective coating was then applied by dip coating in the EB blend solution. The sensors had an overall final thickness of less than 200μm and showed high sensitivity to humidity, low resistance, and good reversibility without hysteresis. The EB protective layer was shown to give more stable and predictable responses to the sensors when placed inside curing epoxies. Polymer based thin film humidity sensors have the advantage that the high processability of the material allows for simple fabrication of a range of geometries including smaller sensor designs. Such sensors may find uses in detecting water content in a number of areas including composite materials, electronic textiles, food/electronics packaging and corrosion detection.

Lumogen Yellow S0790 is a commercial azomethine based pigment and is used for enhancing CCD devices for detecting ultraviolet radiation. In this work we report on the crystal structure and morphology of the raw material, as-deposited and post-annealed films, as well as the influence these have on the subsequent optical properties. Our measurements of physical vapour deposited (PVD) Lumogen films indicate that commercial Lumogen powder is crystalline in its as-received state, with a melting point of 273.3°C and boiling point of 328.6°C. Furthermore, we have found that as-deposited films on room temperature substrates possess an inherent crystalline structure, which has not been reported previously, but also that the material’s structure changes into a completely different crystalline form upon annealing for 90 hours at 80°C.

A hardware random number generator is different from a pseudo-random number generator; a pseudo-random number generator approximates the assumed behavior of a real hardware random number generator. Simple pseudo random number generators suffices for most applications, however for demanding situations such as the generation of cryptographic keys, requires an efficient and a cost effective source of random numbers. Arbiter-based Physical Unclonable Functions (PUFs) proposed for physical authentication of ICs exploits statistical delay variation of wires and transistors across integrated circuits, as a result of process variations, to build a secret key unique to each IC. Experimental results and theoretical studies show that a sufficient amount of variation exits across IC’s. This variation enables each IC to be identified securely. It is possible to exploit the unreliability of these PUF responses to build a physical random number generator. There exists measurement noise, which comes from the instability of an arbiter when it is in a racing condition. There exist challenges whose responses are unpredictable. Without environmental variations, the responses of these challenges are random in repeated measurements. Compared to other physical random number generators, the PUF-based random number generators can be a compact and a low-power solution since the generator need only be turned on when required. A 64-stage PUF circuit costs less than 1000 gates and the circuit can be implemented using a standard IC manufacturing processes. In this paper we have presented a fast and an efficient random number generator, and analysed the quality of random numbers produced using an array of tests used by the National Institute of Standards and Technology to evaluate the randomness of random number generators designed for cryptographic applications.

In this paper, the design of a thin film thermoelectric microcooler module is examined. The module consists of n-type bismuth telluride and p-type antimony telluride thermoelectric materials. The commercial software CFD-ACE+ is used to implement and analyse the model. A two-dimensional coupled electrical and thermal synthesis was performed. The influence of the thickness of the thermoelectric materials on the change in temperature has been investigated. The thickness of the thermoelements was varied between 0.5 and 20 μm. The device performance in terms of change in temperature with and without a load has been studied. The optimal thickness for the thermoelements was found to be 2μm. At 30mA, a temperature difference of 3K below ambient was obtained.

Glaucoma is one of the leading causes of blindness affecting millions of people worldwide. Regular monitoring of intra ocular pressure (IOP) in the eyes is an important component in the treatment of this affliction. Current manual measurements do not give room for continuous indication of the progression of the disease. Microelectromechanical System (MEMS) technology lends itself to the development of devices capable of in-situ monitoring of the phenomenon that occur at the micro and nano scales, inside the human body. The paper reports on the complex flow and pressure relationships in the eye and the current methods of monitoring Glaucoma. The comparison highlights the requirements of an implantable miniature device that can indicate the changes leading to an increase of IOP inside the eye. An analysis of the pressures in the anterior chamber of the eye was undertaken to estimate the out put voltages that could be obtained from a micro structure implanted in the eye.

In the proposed work, an adaptive first order zero-crossing digital phase locked loop (AZC-DPLL) for rapid acquisition, reliable locking, and independent of input signal level is designed, simulated and subsequently implemented on an FPGA based reconfigurable system. The finite state machine controller of the AZC-DPLL senses any changes in input signal frequency and amplitude level, that may cause the loop to loose lock, and accordingly adjusts the loop gain to bring the loop in lock within a few samples. Through this adaptation process, the conflicting requirement of fast acquisition and reliable locking is achieved.

In this paper, we propose a novel and simple method to measure the force vector by bonding the uniform fiber Bragg grating along the erect main strain line of the structure. With the same direction but various magnitudes or with the same magnitude but different directions, the center wavelength and bandwidth may both change. Based on the different responses of the reflection spectrum, we can measure the direction as well as magnitude of various forces in theory. We also offer some elementary experiment results to demonstrate the feasibility of this sensing principle. The experimental results are in agreement with our theoretical analysis.

Bipolar/MOSFET hybrid mode lateral transistor is a transistor in which both bipolar and MOSFET currents flow simultaneously. Because of (1) Good compatibility with CMOS technology; (2) Larger current driving capability and transconductance than MOSFET. So, it is suitable to be taken as a bipolar device in BiCMOS element. In this paper, the Si/SiGe heterostructure, under the gate, is introduced into the conventional bipolar/MOSFET hybrid mode transistor. So a hybrid mode transistor with a lateral n⁺-Si/p-SiGe/n⁺-Si structure parallel in base is formed, in which the heterostructure of E-B junction n⁺-Si/p-SiGe has a high injection electron current from E to B region and a low injection hole current from B to E region (result in by higher barrier for hole), then the total injection efficiency will increase. When this effect becomes a main mechanism than that of the barrier lowering in the surface depletion layer, the characteristics of the device will be dependent on the parameters of SiGe alloy, such as the mole number of Germanium etc. The device simulation of Si/SiGe heterojunction base hybrid mode transistor has been carried out by MEDICI program. The simulation results show that I_C and h_FE increase with Mole number of Ge increasing and W_B decreasing, then the current gain and current capability are improved than that of conventional bipolar/MOSFET hybrid Mode transistor.

The two main sources of power dissipation in CMOS circuits are dynamic and static power dissipation. Static power dissipation is due to leakage current when the transistor is normally off. The improvement in technology scaling has introduced very large subthreshold leakage current, therefore careful design techniques are very important in order to reduce subthreshold leakage current for low power design. Leakage current occurs in both active and standby modes. It is recommended to switch off the leakage current when the circuit is in standby mode, however it is not always possible to shut off the leakage current completely during this mode. Unlike gate leakage, subthreshold leakage cannot be solved by MOS structures nor by introducing new material. One of the feasible solutions is by combinational use of Low-V_t transistors for its high-speed capability and High-V_t transistors for very small leakage current. Multi-Threshold CMOS (MTCMOS) and Variable-Threshold CMOS (VTCMOS) are biasing techniques that uses combinations of different threshold voltage and are suitable for SRAM design. Ideally the larger the threshold level the lower the leakage current, however, one must decide the optimum value of threshold level between the power switch (High-V_t devices) and (Low-V_t devices), as recovery delay tends to increase in higher threshold level. The full paper will discuss the design and performance of SRAM implemented using MTCMOS and VTCMOS biasing techniques. An improved sensing amplifier in the memory cell was incorporated to enhance the circuit performance.

Shape memory alloys (SMAs) find many applications in smart composite structural systems as the active components. Their ability to provide a high force and large displacement makes them an excellent candidate for an actuator for controlling the shape of smart structures. In this paper, using a macroscopic model that captures the thermo-mechanical behaviors and the two-way shape memory effect (TWSME) of SMAs smart morphing polymeric composite shell structures like shape-changeable UAV wings is demonstrated and analyzed numerically and experimentally when subjected to various kinds of pressure loads. The controllable shapes of the morphing shells to that thin SMA strip actuator are attached are investigated depending on various phase transformation temperatures. SMA strips start to transform from the martensitic into the austenitic state upon actuation through resistive heating, simultaneously recover the prestrain, and thus cause the shell structures to deform three dimensionally. The behaviors of composite shells attached with SMA strip actuators are analyzed using the finite element methods and 3-D constitutive equations of SMAs. Several morphing composite shell structures are fabricated and their experimental shape changes depending on temperatures are compared to the numerical results. That two results show good correlations indicates the finite element analysis and 3-D constitutive equations are accurate enough to utilize them for the design of smart composite shell structures for various applications.

In order to simulate the thermally-induced vibration phenomenon of the flexible thin boom structure of the spacecraft such as the thin solar panel and the flexible cantilever with the attached tip mass in space, the thermally-induced vibration including thermal flutter of the flexible thin boom with the concentrated tip mass was experimentally investigated at various thermal environments using a heat lamp and both vacuum and air condition using the vacuum chamber. In this experimental study, divergence speed, natural frequency and thermal strains of the thermally-induced vibration were comparatively evaluated at various thermal environment conditions. Finally the thermally-induced vibration of the flexible boom structure of the earth orbit satellite in solar radiation environment from the earth eclipse region including umbra and penumbra was simulated using the vacuum chamber and power control of the heating lamp.

A motor that can be powered up by either a DC or AC supply and rotates in either direction, based on the so-called Huber effect, is investigated. For the first time, this paper examines the motor characteristics under both DC and AC conditions, for quantitative comparisons. Earlier work has not examined, in detail, the effect of an AC supply on the Huber motor operation. Previous work on the Huber or ball-bearing motor suffered from alignment problems and here we describe a new methodology to address this. The new construction is also a step toward a micromotor realization. The motor, with its reduced dimensions, also has the advantage of reduced operating current. Since 1959, the principle of operation of this motor has remained an unsolved mystery and various theories exist in the literature. We show various empirical findings that shed some light on the hotly contested debate. The discovery of carbon on the bearings, under AC supply conditions, reported here creates a new open question. Motor acceleration versus torque characteristics are obtained, using a data acquisition system to facilitate dynamic real-time recording.

A novel two-way bistable bimorph bridge actuator for out of plane deflection is reported in this paper. The device has a 1200μm long, 50μm wide and 4μm thick composite bimorph beam consists of PECVD SiO2 and titanium layers. The end supports of the beam consist of 2 pairs of spring and are provided by 2 pairs of long titanium 'legs’ alongside the beam. 10mW and 4mW in the beam and legs for 3ms respectively is needed for 50 micron of out-of-plane deflection travel. By applying the appropriate joule heating sequence to the device, it is possible to snap the buckled beam upward or downward between two equilibrium states. An analytical and simulation models of heat transfer and tunable snapping are developed for the system. This paper presents the working principal, analysis, simulations of the device. The actuator will be used to move a micromirror, located at the centre of beam, for optical switching. This novel mechanism can have useful application in relays, optical switching and threshold sensors.

In this paper, we present a finite difference based one-dimensional dynamic modeling, which includes electro-thermal coupled with thermo-mechanical behavior of a multi-layered micro-bridge. The electro-thermal model includes the heat transfer from the joule-heated layer to the other layers, and establishes the transient temperature gradient through the thickness of the bridge. The thermal moment and axial load resulting from the transient temperature gradient are used to couple electro-thermal with thermo-mechanical behavior. The dynamic modeling takes into account buckling, and damping effects, asymmetry residual stresses in the layers, and lateral movement at the support ends. The proposed model is applied to a tri-layer micro-bridge of 1000μm length, made of 2μm silicon dioxide sandwiched in between 2μm thick epi-silicon, and 2μm thick poly silicon, with four 400μm long legs, and springs at the four corners the bridge. The beam, and legs are 40μm, and 10μm wide respectively. Results demonstrate the bi-stability of the structure, and a large movement of 40μm between the up and down stable states can easily be obtained. Application of only 21mA electrical current for 15μs to the legs is required to switch buckled-up position to buckled-down position. An additional trapezoidal waveform electrical current of 100mA amplitude for 4μs, and 100μs falling time needs to be applied for the reverse actuation. The switching speed in both cases is less than 500μs.

A multi-layered micro-bridge buckles due to residual stresses in the layers of the beam when it is released during fabrication, and the axial load due to this stress exceeds the Euler load. This residual stress renders intrinsic bi-stability behavior to the bridge. In this paper, the effect of axial, rotational stiffness, and residual moment on the buckled shape, snapping, and bi-stability of multi-layered bridge when it is thermally actuated is studied both theoretically, and experimentally. Theoretical analysis, and ANSYS finite element simulation have been carried out to investigate these effects. Deflection versus temperature plots for different axial, rotational stiffness, and residual moment are obtained. The theoretical investigations are applied to bi-morph micro-bridges of 1000um length, and 40um wide made of PECVD silicon dioxide, and epi-taxial silicon, and a tri-layer structure of Poly/SiO₂/epi-silicon. The bi-layer structure is fabricated, and its buckled shape is obtained from SEM. Results show that axial, rotational stiffness, and residual moment strongly affect the buckled shape, and bi-stability of the micro-bridge. It is also shown that for thermally actuated micro-bridge, better bi-stability, and snapping characteristics can be obtained when both rotational and axial stiffnesses are reduced, and the residual moment must not exceed a certain threshold value if bi-stability is to be preserved.

Periodic structures with minimum feature sizes in the scale of the mean radiation wavelength or less attract considerable interest due to the peculiarity of their electromagnetic (EM) response. When interference and diffraction effects become sufficiently strong, novel and interesting phenomena emerge in reflectivity, transmissivity, absorbance and even infrared thermal emission. The nanotechnology processing enables the production of high-efficiency diffraction gratings with quite small periods, down to the nanometer range, with aspect ratios higher than in spectroscopic gratings. In this paper we present the spectral measurements (transmission and thermal emission) of GaAs and silicon samples with lamella 1D gratings and mesa 2D structures. We also present the theoretical and simulation tools developed for the design and analysis of multilayer lamellar grating structures.

This paper presents the theory, design, and evaluation of a smart device for the enhanced separation of particles mixed in fluid. The smart device takes advantage of the ultrasonic standing wave, which was generated by the operation of a piezoceramic PZT patch installed in the smart device. The details of the device design including the electro-acoustical modelling for separation and PZT transducer are described at first. Based on this design, the separation device was fabricated and evaluated. In the experiments, an optical camera with a zoom lense was used to monitor the position of interested particles within the separation channel layer in the device. The electric impedance of the PZT patch bonded on the separation device was measured. The device shows a strong levitation force against 50μm diameter sand particles mixed with water at the separation channel in the device. Experimetal results also showed that the device can levitate both heavy and light settled sand particles clouds on the bottom to the nodal lines of the generated standing wave field in the separation channel.

The inward flow piezo poppet valve (PZP) is examined by the use of CFD (Computational Fluid Dynamics) over a range of displacements and pressures consistent with the use of an actuating piezo driver, for conical head poppets in steady flow conditions. No tendency to unsteady fluid forcing of the poppet is seen in the computational output. A simple sizing technique is indicated.

Terahertz imaging is presently in its exploratory stage. Although plots of time versus terahertz amplitude, and frequency versus terahertz magnitude are some of the most common ways of analyzing terahertz data, no standard rendering technique has been established. While existing methods are indispensable, improvements to how terahertz data is rendered and analyzed should be explored so that new techniques can complement existing ones and/or provide a means of displaying new information that existing methods cannot. This paper reports on one solution to terahertz imaging: an implementation of a new form of phase contrast imaging, which is based on a well-established technique for optical microscopy. This will provide us with a further way of interpreting information from terahertz imaging systems.

Technology advances tend to reduce minimum dimensions and source voltages to maintain scaling rules. Both scaling trends make noise more critical, reduce yield and increase device parameter fluctuations. This paper presents a statistical model that permits the study of noise and parameter deviations on gates. Using this model stochastic resonance (SR) is studied both in single devices and arrays for subthreshold and suprathreshold input signals. The SR is measured by the signal-to-noise ratio (SNR) in the time domain and a modified SNR is proposed to take into account all the effects induced by noise in gates. With this measure subthreshold and suprathreshold SR is reviewed. Finally, a discussion of the possibility of considering noise a part of the electronic circuits is presented, suggesting that it could be a solution to some of the emerging problems in future nanotechnologies.

Numerical increment of analog circuits causes power consumption to increase and requires a larger chip area. In designing an analog complementary-metal-oxide-semiconductor (CMOS) vision chip for edge detection, power consumption should be considered. It restricts the number of the edge detection circuit which is based on the edge detection mechanism of vertebrate retina. In this paper, we applied electronic switches to an analog CMOS vision chip for edge detection to reduce the power consumption. Also, we propose a method to implement vision chip with higher resolution, which is to separate pixels for edge detection into a 128×128 photodetector array and a 1×128 edge detection driving circuit array. The capability to minimize power consumption was investigated by SPICE. Estimated power consumption with 128×128 pixels was below 20mW.

Recently, decimal arithmetic has become attractive in the financial and commercial world including banking, tax calculation, currency conversion, insurance and accounting. Although computers are still carrying out decimal calculation using software libraries and binary floating-point numbers, it is likely that in the near future, all processors will be equipped with units performing decimal operations directly on decimal operands. One critical building block for some complex decimal operations is the decimal carry-free adder. This paper discusses the mathematical framework of the addition, introduces a new signed-digit format for representing decimal numbers and presents an efficient architectural implementation. Delay estimation analysis shows that the adder offers improved performance over earlier designs.

Motion detection and velocity estimation systems based on the study of insects tries to emulate the extraordinary visual system of insects with the aim of coming up with low power, computationally simple, highly efficient and robust devices. The Reichardt correlator model is one of the earliest and the most prominent models of motion detection based on insect vision. In this paper we try to extend the Reichardt correlator model to include an additional non-linearity which has been seen to be present in the fly visual system and we study its effect on the contrast dependance of the response and also try to understand its influence on pattern noise. Experiments are carried out by adding this compressive non-linearity at different positions in the model as has been postulated by previous works and comparison of the physiological data with modelling results is done.

Insects perform highly complicated navigational tasks even though their visual system is relatively simple. The main idea of work in this area is to study the visual system of insects and to incorporate algorithms used by them in electronic circuits to produce low power, computationally simple, highly efficient, robust devices capable of accurate motion detection and velocity estimation. The Reichardt correlator model is one of the earliest and the most prominent biologically inspired models of motion detection developed by Hassentein and Reichardt in 1956. In an attempt to get accurate estimates of yaw velocity using an elaborated Reichardt correlator, we have investigated the effect of pattern noise (deviation of the correlator output resulting from the structure of the visual scene) on the correlator response. We have tested different sampling methods here and it is found that a circular sampled array of elementary motion detectors (EMDs) reduces pattern noise effectively compared to an array of rectangular or randomly selected EMDs for measuring rotational motion.

Terahertz wavelengths can pass through dry, non-polar, non-metallic materials that are opaque at visible wavelengths. Moreover they can be manipulated using millimeter wave and quasi-optical techniques to form an image. Sensing in this band potentially provides advantages in a number of areas of interest for security and defense, such as screening of personnel for hidden objects, and the detection of chemical and biological agents. This paper reviews recent research into THz applications by groups across Europe, the US, Australasia, and the UK. Several private companies are developing smaller and cheaper reliable devices allowing for commercialisation of these applications. While there are a number of challenges to be overcome there is little doubt that THz technologies will play a major role in the near future for advancement of security, public health and defense.

An adaptive non-linear photodetector circuit is implemented using electronic discrete components to describe the response of blowfly photoreceptor cells. The photodetector circuit consists of a cascade of a linear photodetector, two divisive feedback loops and a static non-linearity stage. The circuit is rigorously evaluated using an ultra bright Light Emitting Diode. Detailed comparison is done between the photodetector circuit and the actual neurobiological data of the blowfly photoreceptor cells to fine tune the parameters of the circuit.

Recent advances in biological Microelectromechanical Systems (MEMS) have resulted in significant research being carried out to improve minimally invasive surgical procedures (MIS). Surgeons familar with MIS often complain of inadequate tactile and visual feedback. Hence, there is a need for better surgical instrumentation or procedures. This paper presents a survey on the applications of MEMS sensors in surgical instruments during in vivo diagnosis and treatment. Several applications of MEMS sensors are discussed. It is evident that MEMS can increase the functionalities of surgical tools and improve the performance of surgeons. MEMS sensors not only can help to reduce patient trauma, but also lower health care cost.

A scanning near-field microscope provides nano-scale imaging capability of field induced THz wave emission spectra from semiconductor surfaces and interfaces. Combined with a scanning probe tip and femtosecond optical pulse excitation, THz wave emission with sub-100 nm spatial resolution has been demonstrated. The scanning probe tip modulates semiconductor surface field with nano-scale accuracy through the imaging charge dipole, the tunneling current, or the contact current. The modulated THz wave from the highly localized area under the scanning tip is detected in time-domain. This aperture-less imaging method leads the way to study nano-scale to atomic level emission spectroscopy at THz frequency range.