bluuebunny/crossref_metadata_2025 huggingface dataset:
Dual Mode Locomotives: Systems Study of New Freight Locomotives for Sweden
Authors: Skoglund Mattias , O¨stlund Stefan , Bark Peter
Published: June 2009

A conceptual study for a Swedish dual-mode locomotive is presented. The primary energy sources are AC electricity from an overhead catenary system or a diesel-electric generator system. The study focuses on analysing how freight operations and locomotive utilisation can be improved and how it can affect environmental aspects of freight operations. Based on project experiences and operative demands, a system proposal has been presented. The rated power output is considerably higher in electric mode compared to diesel mode. The reason for this being higher power demand on electrified main lines compared to branch lines and yards lacking overhead catenary where the power need is lower. The starting tractive effort will however be the same regardless of electric mode or diesel mode, making it possible to haul the same train weight in both propulsion modes. The study has shown that dual-mode locomotives for Swedish freight operations are most interesting in order to improve operations, degree of utilisation and environmental performance.
Microsimulation Analysis of Highway-Rail Grade Crossings: A Case Study in Lincoln, Nebraska
Authors: Rilett Laurence R. , Appiah Justice
Published: June 2009

This paper examines the usefulness of supplementing railroad preemption operations at highway-rail grade crossings with variable message signs. Using the microscopic traffic simulation model, VISSIM, the effects on grade crossing operations of different train dwell times as well as different levels of driver response to a variable message sign in the vicinity of the crossing are assessed. The results affirm the potential usefulness of variable message signs for preventing lengthy queues and illustrate the importance of explicitly considering the delay experienced by vehicles on the blocked roadway in developing a traffic control strategy for highway-rail grade crossings.
Real-Time Estimation of Temporal Word Boundaries Without Linguistic Knowledge
Authors: Shahidi Parham , Southward Steve C. , Ahmadian Mehdi
Published: June 2009

A novel real-time algorithm has been developed for estimating temporal word boundaries in measured speech without the need for interpretation of individual words. This algorithm is the foundational building block of a method for estimating a variety of key metrics such as word production rate, phrase production rate, words per phrase, etc., that are indicative of human mental states. In particular, we are interested in developing a system for monitoring locomotive crew alertness. The majority of existing speech processing algorithms relies on pre-recorded speech corpora. The real-time algorithm presented here is unique in that it employs a simple and efficient pattern matching method to identify temporal word boundaries by monitoring threshold crossings in the speech power signal. This algorithm eliminates the need to interpret the speech, and still produces reasonable estimates of word boundaries. The proposed algorithm has been tested with a batch of experimentally recorded speech data and with real time speech data. The results from the testing are outlined in this paper.
Track-to-Earth Potentials and Stray Current Monitoring on Portland TriMet MAX Light Rail System
Authors: Pham Kinh D. , Looijenga Kai , Wallis Gene , Heilig Thomas
Published: June 2009

The track is insulated in a DC railway system. Even when the track is new, the insulation between track and earth is never ideal. The insulating capacity of the new track diminishes in the course of time due to ageing and dirt. The insulation can also be affected due to improper track construction. It is, therefore, necessary to monitor stray current activity to detect early insulation deficiencies to prevent any possible damage due to stray current corrosion of metal objects such as underground utility pipelines or building reinforcements. One approach to monitoring stray current activities is through the measurement of track-to-earth potentials. Dynamic stray current effects can normally be identified by fluctuations in the track-to-earth potentials with time. This paper describes the Siemens SITRAS SMS stray current monitoring system used on the Portland IMAX Light Rail extension. The SITRAS SMS system consists of a central evaluation PC located at TriMet Systems Engineering Office with track-to-earth voltage sensors installed at each of the six traction power substations on the IMAX line rail extension. The sensors and the PC are connected to each other through an ETHERNET network. The measured data are stored and archived in three different stages: instantaneous, short-term, and long term average values. This paper will present and analyze the data colleted on the IMAX line rail extension. Basic stray current modeling and analysis will also be discussed.
Design of Nanocrystalline Materials for Structural Applications
Authors: Saxena Ashok , Rajgarhia Rahul , Bansal Shubhra
Published: June 2009

The unique and desirable behavior of nanocrystalline materials (NCMs) is singularly attributed to the large number of grain boundaries relative to their coarse grain material (CGM) counterparts, which translates into a significant fraction of atoms (up to 50%) located in interfacial regions. Thus, the atomic structure and properties of the grain boundaries are of extreme importance in dictating the macroscopic physical and mechanical properties of NCMs. However, one of the biggest challenges is to produce durable nanostructures that will not lose their properties during service. Hardness, strength, fracture toughness, creep and fatigue experiments have been conducted to assess the properties of nanostructured Cu and their durability under temperature and stress. Molecular dynamics studies have been used to investigate how segregated dopant atoms affect the energetics of grain boundaries and their implications on grain growth in nanocrystalline metals by our group.
Indentation Mechanics for Micro- and Nano-Layered Composites
Authors: Tang G. , Shen Y.-L.
Published: June 2009

The effect of micro- and nano-scale heterogeneity on the indentation behavior of the composite structure was studied numerically using the finite element method. The material system of concern is the aluminum (Al)/silicon carbide (SiC) multilayered thin films above the silicon (Si) substrate. The numerical model features the explicit composite structure indented by a conical diamond indenter within the axisymmetric simulation framework. Attention is devoted to the evolution of stress and deformation fields in the layered composite during the indentation loading and unloading processes. It was found that the layered composite, consisting of materials with distinctly different mechanical properties, results in unique deformation patterns. Significant tensile stresses can be generated locally along certain directions, which offers a mechanistic rationale for the indentation-induced internal cracking observed experimentally. The unloading process also leads to an expansion of the tension-stressed area, as well as continued plastic flow in parts of the Al layers. Implications of these numerical findings to the nanoindentation response of metal-ceramic laminates are discussed.
Capillary Flow in Microchannel With Pillars
Authors: Saha Auro Ashish , Tweedie Mark , Roy Susanta , Mitra Sushanta K. , McLaughlin Jim
Published: June 2009

Numerical simulation and experimental results of free surface flow in microfluidic channel containing 10 × 15 array of 350 micron circular cross-section pillars is presented here. Passive capillary driven transport of de-ionized (DI) water and isopropyl alcohol is considered in the study. The channel is fabricated from glass microscope slides patterned with SU8 photoresist using an SF 100 maskless lithography system. Subsequently, microscope slide have been adhered with cyanoacrylate adhesive for sealing the device. The pillars are 120 micron deep, with adjacent pillars being separated by 300 micron. The three-dimensional free surface phenomena is simulated by volume of fluid (VOF) technique and microfluidic imaging is used to experimentally visualize the interface movement. This helps in understanding how free surface is modified by the presence of pillars for performing microfluidic analysis. The effectiveness of using pillars in the fluidic channel to enhance capillary flow and create a more uniform wavefront is demonstrated.
A New Design of Large Stroke Micro-Deformable Mirror Actuated by Electrostatic Repulsive Force
Authors: Hu Fangrong , Yao Jun , Qiu Chuankai , Wang Dajia
Published: June 2009

In this paper, a MEMS mirror actuated by an electrostatic repulsive force has been proposed and analyzed. The mirror consists of four U-shape springs, a fixed bottom electrode and a movable top electrode, there are many comb fingers on the edges of both electrodes. When the voltage is applied to the top and bottom electrodes, an asymmetric electric field is generated to the top movable fingers and springs, thus a net electrostatic force is produced to move the top plate out of plane. This designed micro-mirror is different from conventional MDM based on electrostatic-attractive-force, which is restricted by one-third thickness of the sacrificial layer for the pull-in phenomenon. The characteristic of this MDM has been analyzed, the result shows that the resonant frequency of the first mode is 8 kHz, and the stroke reaches 10μm at 200V, a MDM with large strokes can be realized for the application of adaptive optics in optical aberrations correction.
Investigation on Multiple Piezoelectric Effect of Piezoelectric Crystal Under Applied Electric Field
Authors: Sun Baoyuan , Shi Yinhui , Qian Min , Zhang Jun , Zhang Zhonghua
Published: June 2009

Based on the theory of classical piezoelectricity, the relationship between the generation of multiple piezoelectric effect under applied electric field and boundary conditions is analyzed. The generating process of multiple piezoelectric effect is elaborated and the formulas of secondary direct and tertiary converse piezoelectric effect are deduced. The displacement or voltage generated by primary converse, secondary direct and tertiary converse piezoelectric effect is calculated by using coupled-field analysis function in the Finite Element Analysis software-ANSYS. Experimental research of multiple piezoelectric effect under applied electric field is performed through PZT-5 stack. The experimental result verifies the existence of multiple piezoelectric effect. Experimental data shows that voltage and displacement generated by secondary direct and tertiary converse piezoelectric effect respectively are linear with the applied voltage. Both the simulation and experimental results prove that the theoretical analysis is accurate.
Study on the Shockwave Pressure Testing Method for Detonating Cords
Authors: Bai Ying-Wei , Jiang Zhuang-De , Zhao Yu-Long , Chu En-Yi , Wang Kexuan
Published: June 2009

When detonation cords are used in explosive trains such as explosive circuits, the output performance can be obtained by destructive tests of matching samples from common production lots. In this paper the shockwave pressure testing method for Detonating Cords is studied. Two types of sensors are used to test the shockwave pressure. One is a thin film Mn-Cu sensor which is a standard testing method for output performance of explosive devices. The other sensor is a high pressure sensor with a microcircuit in it; this sensor can be used many times. The testing results are verified in the detonation equation.
Fabrication of a Novel Resonant Pressure Sensor Based on SOI Wafer
Authors: Ma Zhibo , Ren Sen , Qiao Dayong , Yuan Weizheng
Published: June 2009

Based on the silicon-on-insulator (SOI) silicon, a novel resonant pressure sensor for atmosphere pressure detection is designed and fabricated. The resonator suspended by four beams at four pedestals on the diaphragm is encapsulated between two glass lids. The diaphragm shape changes with the change of ambient gas pressure; thereby the resonator’s nature frequency also is changes. To prevent the undesired etching of resonator during the wet etching, a protective process using silicon nitride and silicon oxide is adopted. Experiments show that after wet etching 10 hours in tetramethyl ammonium hydroxide (TMAH) solution, the resonator is successfully released. This protection technology shows a high practical value especially for the release of a movable microstructure by wet silicon etchants. Initial performance test results of the device yield a natural frequency of 9.932 KHz at atmospheric pressure and the Q-factor of 34 rising to over 7293 in high vacuum (<10 Pa). The relative pressure sensitivity of the sensor is measured to be 5.88% for a 10μm diaphragm.
Simulation and Improvement of 5GHz Power Divider on FR-4 PCB
Authors: Wang Mu-Chun , Kuo Chung-Hsin , Hsieh Zhen-Ying , Huang Chun-Wei , Chen Shuang-Yuan
Published: June 2009

In the recent electronic industry, the fiber-resin (FR-4) material is commonly and usually applied to printed circuit board (PCB). Below 3GHz radio-frequency operation range, the FR-4 material board demonstrates a good stability with frequency variation. However, while the central frequency shifts to 5GHz, the characteristic of this material shows some unstable phenomenon with frequency due to the material integrity. For a real FR-4 material, dielectric constant, dissipation factor, coefficient of thermal expansion, and thermal conductivity, basically, are not uniform in each part. In order to overcome these difficulties, this team adopts the simulation concept of the Wilkinson power divider and experimentally adjusts the micro-strip lines in 5GHz power divider. Shortening the metal-line length on the PCB means that the operation wavelength is also reduced. Using this idea and carefully compensating for extra connection effects with real circuit operation, we successfully provide a lower power-loss 5GHz power divider in commercial IC system applications, especially in wireless local-area network (WLAN).
Improvement of Printed Circuit Board Assembly Process in 2.4GHz RF Circuit Products
Authors: Wang Mu-Chun , Hsieh Zhen-Ying , Yang Ting-Yu , Tu Chia-Hao , Chen Shuang-Yuan
Published: June 2009

The semiconductor process technology and the circuit design concept are continuously improved at the recent era. The product cost is gradually decreased, too. The commercial electronic products generally cover ICs, external components and printed circuit board (PCB). After the circuit layout blueprints are completed, engineers will transfer them into PCB as a prototype. The next step is to integrate some contributed electronic components to form a functional product. This second step is called as PCB assembly (PCBA). However, the bigger copper area on PCB will provide a good thermal dissipation. This effect will degrade the solderability and increase the contact resistance while the electronic components are integrated on PCB. The product performance, therefore, is deteriorated. Contriving some special empty boundary shapes neighboring the connected pins of integrated electronic components to soften the thermal dissipation ability of copper layer on printed circuit substrate is a good method. We design some useful patterns to conquer this issue and increase the PCB assembly yield from 70% to 95%. The other efforts are to study the flow rate of isolated ink in PCBA production line and suitably control the solder temperature. Because some electronic components are composed by plastic materials, higher temperature will damage the external shapes of them and the PCB has the bending possibility. These two beneficial efforts also contribute the assembly yield well in 2.4GHz radio-frequency (RF) products.
Failure Modes Model of MEMS Accelerometers Based on Neural Networks
Authors: Bai Yanping , An Ping , Hao Yilong
Published: June 2009

Fabrication of a MEMS system involves design, testing, packaging and reliability related issues. However, reliability issues that are discovered at a late phase may cause major delays in the product development going together with high costs. In this paper we study the failure modes and Mechanisms of MEMS accelerometers products and present the classification modeling of failure modes based on neural networks. In ours MEMS accelerometers, there are six failure mechanisms that have been found to be the primary sources of failure nodes. We introduce nonlinear BP network with a hidden layer and linear perception to classify for MEMS accelerometers products. Classification results show that nonlinear BP network seem to be most appropriate to approach the problem of failure modes classification than linear perception. BP neural network is capable of learning the intrinsic relations of the patterns with which they were trained. For all experiments results, the training success of rate is 100% for both methods. BP networks obtained a high forecast success of rate of over 99.5%. The linear perception model obtained a success of rate of over 95.5%. We also analyze the technology stability of MEMS products.
Simulation and Signal Processing of a Decoupled Bulk-Micromachined Z-Axis Gyroscope
Authors: Cui Jian , Chi Xiaozhu , Ding Haitao , Yan Guizhen
Published: June 2009

In this paper, a kind of control strategy with an effective zero bias compensation method for a symmetrical and highly doubly decoupled bulk micromachined single crystal z-axis gyroscope is presented with the details. Simulation of behavior level with Labview are carried on before the real signal processing. In order to realize the closed loop control and self-oscillation, an automatic gain control (AGC) model is constructed and simulated with the sense axis signal processing. A measurement system is design to test the performance of the gyroscope. The drive and the sense mode resonant frequencies are measured to be 3.044 kHz and 3.258 kHz respectively which agrees well with the simulation results. The scale factor is 0.21mv/deg/s in the range of ±500deg/ s with the non-linearity 0.7% at atmospheric pressure. The test results also reveal that the gyroscope can provide a rate resolution approximately 0.011deg/s in 10Hz bandwidth.
A Bulk Micromachined Cantilever Array for Uncooled Infrared Imaging
Authors: Yi Yuliang , Ma Shenglin , Yu Xiaomei , Liu Ming , Liu Xiaohua
Published: June 2009

This paper presents a bi-material microcantilever focal plane array (FPA) for uncooled infrared (IR) imaging. The FPA was fabricated by a bulk silicon micromachining method with substrate silicon selectively removed by deep reactive ion etching (DRIE) technique at the area where each cantilever pixel is located. The absorbance of the IR radiation can be improved by 48% due to the selective removal of the substrate, and hence the noise equivalent temperature difference (NETD) of the FPA can be reduced by 32% compared to the one fabricated by sacrificial layer technique, approaching 60mK. The thermomechanical sensitivity and the response time of the FPA were measured and calculated to be 112nm/K and 15ms, respectively. An image of human bodies was captured by an optical readout method.
Design and Fabrication of Uncooled MEMS Capacitive FPA for IR Imaging
Authors: Ma Shenglin , Yi Yuliang , Tang Yaquan , Yu Xiaomei
Published: June 2009

A new structure of MEMS Uncooled capacitive focal plane array (FPA) is presented and its thermo-mechanical behaviors are studied. A surface process with poly-silicon as a sacrificial layer was developed, and in which poly-silicon was dry etched by SF6 in an ICP system of STS. The etching rates of poly-silicon in lateral and vertical can reach 3.8 and 5.6μm/min after the optimization of the process. The process is simple and compatible with most of the IC processes.
Fabrication of Nanoscale Vias by Offset Patterning
Authors: Lau Chi Ho , Lee S. W. Ricky
Published: June 2009

Patterning of features with photolithography technique by overlying multiple exposure patterns with intentional offset reduces the effective size of the resultant opening when the openings overlap incompletely. The size of resultant opening depends on the size of the parental opening and the degree of overlap. Overlapping via patterns helps to achieve small via size from photolithography. In the present study, two oxide layers with via pattern were involved. The bottom oxide layer was deposited and patterned first. The top oxide layer and the poly-Si sandwich layer were then deposited on the patterned bottom oxide layer and patterned with an offset afterwards. Experimental results show resultant vias with size reduction by more than 50% compared with the parental vias. The equivalent diameter of the resultant vias goes down to as small as 400 nm. It was found that the equivalent diameter decreases with reduction in parental via size. The length-to-width ratio of the resultant vias opening increases as the parental via size becomes larger. The offset distance is also found to contribute significant effect to the size of the resultant via. The large offset distance leads to small but high-aspect ratio resultant vias.
Investigation on the Effects of Copper Electroplating Process
Authors: Chen Yue , Li Xiuhan , Chen Shi Qing , Zhang Haixia
Published: June 2009

This paper mainly discusses DC electroplating process parameter, especially the current density, affects the electroplating result (such as copper grain, surface smooth, resistivity). A positive relationship has been found between the current density and the electrodepositing speed, copper grain diameter, core cluster as well as square resistivity. Furthermore, testing structures are designed to monitor the process on line. And an observation of fluctuation along the transection has been found which is also increased with the current density.
MEMS Based Dew Point Hygrometer With Optimal Self Adjusted Detection Threshold
Authors: Jachowicz Ryszard , Weremczuk Jerzy , Paczesny Daniel , Tarapata Grzegorz
Published: June 2009

A new system of dew point temperature hygrometer, based on semiconductor MEMS detector is presented in the paper. Many details of MEMS detector construction are given with details in the report. Basic idea of algorithms of detector control is also discussed. More attention is devoted to subalgorithm for self-adjusted detector threshold operation. Excellent dynamic parameters of the new hygrometer (i.e. 2÷5 dew point detections and temperature measurements per second), proved by the hygrometer tests, will be presented and described in the report. It means that presented hygrometer is 10÷100 times faster than conventional hygrometers. In the end of the paper two medical applications are demonstrated with clinical test results. The first application is for dermatology for TransEpidermal Water Loss (TEWL) factor of human skin. The second is focused on measurement of humidity in human nose cavity and human throat during breathing. In both case fast humidity measurements, with time constant of some 0.5s, have been required.
Optical Feedback Interferometry and Its Application in MEMS Sensing
Authors: Liu Huilan , Wang Yong , Pan Zaiyou , Feng Lishuang
Published: June 2009

Optical feedback interferometry is a novel optical testing method. The self-mixing effect in laser diodes is a useful tool for testing the movement of a reflector and realizing high-precision measurement using a simple configuration. The operating principle of the optical feedback interferometry is introduced. Optical feedback interferometer experiments were carried out using a He-Ne laser and laser diode as light sources respectively, and the results were analyzed. The experiments validated the conclusion of the simulation. Discussion was made to the applications of optical feedback interferometry in MEMS sensing. A novel MOEMS accelerometer based on optical feedback interferometry was proposed. The accelerometer is simple and can make acceleration measurement with precision on a scale of light wavelength.
High Q Circular-Section Solenoid-Type Inductor
Authors: Li Xiuhan , Shu Guanghua , Sao Jinan , Zhang Xiongwei
Published: June 2009

A* high Q-factor circular-section solenoid-type inductor is designed and fabricated through micro electro mechanical system (MEMS) technology. The radius of the circular-section is 100μm. Ansoft HFSS is used to design and optimize the structure parameters of the inductor. The stable inductance of 10nH and maximum Q-factor of 46 is gained at the N of 10, wire width w of 10μm, space between wires d of 15μm and the self-resonance frequency of the inductor is above 10GHz. A novel fabrication method—flip chip bonding is proposed to bond the two parts of the inductor, and the process is compatible with CMOS process.
Fabrication of Superhydrophilic Surfaces by Aluminum-Induced Crystallization of Amorphous Silicon
Authors: Kollias Kenneth , Wang Hengyu , Zou Min
Published: June 2009

Aluminum-induced crystallization (AIC) of amorphous silicon (a-Si) was, for the first time, used to produce textured surfaces to increase the wettability of solid substrates. It was found that glass substrates textured by AIC of a-Si technique exhibit highly stable superhydrophilic property. The water contact angle (WCA) of the textured glass surfaces became less than 5° in 0.5 second immediately after the AIC of a-process and remained less than 10° in 1 second even after the samples were stored in air for 192 hours.
Development of RF Power Attenuation Model With MEMS Coils
Authors: Yuan Quan , Li Xiuhan , Li Dan , Zhang Haixia
Published: June 2009

This paper presents an experiment system to study the characteristics of RF power delivery in HBSS (Hanks’ Balanced Salt Solutions), which is similar with Bio-body. The high Q MEMS inductor is used for inductive coupling, testing frequency from 1MHz to 200MHz. An attenuation model of the lateral, vertical and angular factors was fitted and verified by surgical implantation in animal, which matched very well.
The Effect of Surface Nano/Micro-Texturing on Escherichia Coli Cell Adhesion
Authors: Wang Hengyu , Kim Jeong-Hwan , Zou Min , Tung Steve , Kim Jin-Woo
Published: June 2009

Control of cell-to-surface adhesion has significant impacts on various biological and biomedical applications. In this study, the adhesion of Escherichia coli (E. coli) cells on nano/micro-textured surfaces produced by a unique surface texturing technique, aluminum-induced crystallization (AIC) of amorphous silicon (a-Si), was studied in order to control E. coli cell adhesion on glass substrates in an E. coli-based whole-cell chemical sensor. It was found that textured surfaces significantly enhanced cell-to-surface adhesion. Among the textured surfaces, nano/micro-textured surfaces showed advantage over micro-textured surfaces on the cell-to-surface adhesion. Study of the cell-to-surface adhesion mechanism suggests that the cell adhesion efficiency was controlled by the particle density of the textured surfaces.
Laser Direct-Write Micro Dents Using Laser Shock Peening: Experimental Study and Numerical Simulations
Authors: Sealy M. P. , Guo Y. B. , Dumitrescu C. , Puzinauskas P. V. , Chen S. C.
Published: June 2009

Laser shock peening (LSP) is an innovative surface treatment developed to improve surface integrity. The primary purpose of LSP in the literature is to impart compressive residual stresses below the surface of a material. This study explores the feasibility using LSP to direct-write surface micro dents for lubricant retention. Micro dents have been successfully fabricated on the aluminum 6061-T6 surfaces. LSP is a highly transient process with a pulse duration of 10 – 100 ns. As a consequence, the real time in-situ measurements of laser/material interaction is challenging. Therefore, FEA simulations of LSP were performed via 3D spatial and temporal shock pressure using user material and load subroutines. The results suggested there is an optimal peening time that produces the deepest dent.
Finite Element Modeling of Carbon Nanotube Composites for Vibration Damping
Authors: Dai R. L. , Liao W. H.
Published: June 2009

It was found that with carbon nanotube (CNT) addition, epoxy resin composites could greatly enhance damping ability while the stiffness is kept high. A composite unit cell model containing single CNT segment is developed by using finite element method (FEM). CNT orientation is varied in order to describe the behaviors of the randomly oriented CNTs inside the epoxy matrix. Composite loss factors are calculated based on the ratio of the unit cell energy loss to the unit cell energy input. Calculated loss factors under different strain levels are compared to experimental data. As the CNT/matrix model gives smaller loss factors as compared with experimental data, a CNT/CNT model is further developed in order to improve model accuracy.
Nonlinear Responses and Optical Limiting Behavior of Ag Nano-Particles
Authors: Majles Ara M. H. , Dehghani Z. , Saievar Iranizad E. , Salmani S.
Published: June 2009

Ag nano-particles have been synthesized and the formation and microstructure of Ag particles, were monitored by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Visible spectrum and z-scan technique. XRD pattern confirmed the cubic structure of the synthesized material. The UV-Visible spectrum of this material shows an absorption peak about 200 nm wavelengths. Optical limiting (OL) property of Ag nano-particles is studied. The nonlinear refractive indices of Ag nano-particles were defined by the z-scan technique using CW He-Ne laser (λ = 632.8 nm) at different incident intensities. The results reveal that the new complex exhibits strong nonlinear optics refraction effect such as self-focusing and the magnitude of n2 was measured in order of 10−7 (cm2/W) with a negative sign.
Effect of the Molecular Weight and Density of Ambient Gas on Shock Wave in Laser-Assisted Nanostructuring
Authors: Guo Liying , Wang Xinwei
Published: June 2009

This paper presents the results from molecular dynamics simulations that are performed to explore the properties of the shock wave during laser-assisted near field surface nanostructuring. A quasi-three dimensional model is constructed to study systems consisting of over 2 million atoms. This work includes studies on the velocity as well as pressure evolution of shock wave front with respect to different solid/gas molecular mass ratios and different ambient gas densities. The limitation on shock wave formation under the same laser fluence is also investigated. The results show that lower ratio of the solid/gas molecular weight weakens the strength of the shock wave during the nanostructuring process. Additionally, the formation and attenuation of the shock wave under different ambient gas conditions is studied in substantial detail.
Micro Cooling Based on Acoustic Streaming
Authors: Sun Hongming , Guo Hang
Published: June 2009

Heat transfer due to forced convection caused by acoustic streaming in microfluidic devices is shown to have potential in cooling effect. However, few studies are made for theoretically studying the fluid motion induced by the acoustic field and forced heat transfer for micro cooling in microdevices. In this paper, Navier-Stokes equations are first employed to study acoustic radiation force and acoustic streaming in microchannel actuated by ultrasonic vibration. Then, an analytical study of fluid motion acoustically induced and the temperature field in microchannel is investigated to determine the enhancement of cooling effect in microchannel with acoustic streaming.
The Capillary Force Between an AFM Tip and a Surface at Different Humidity
Authors: Chen Sheng Chau , Lin Jen Fin
Published: June 2009

In the present study, the meniscus profiles of water bridges formed at different relative humidity are determined using the geometric relationships including the Kelvin equation and the force equilibrium formula established for the meniscus. The pull-off forces predicted by the present model show good agreement with the experimental results reported in the literatures. When the contact angles at two solid bodies are equal, the pull-off force is slightly elevated by an increase of the relative humidity of air, and is significantly elevated by an increase of the asperity radius. Furthermore, two hydrophobic surfaces with equally large contact angles lower the pull-off force. If a difference exists between the contact angles of two solid surfaces, the asperity with a hydrophilic surface incorporating with a smooth flat plate with a hydrophobic surface reduces the pull-off force.
1.331μm Narrow-Bandwidth Light Source Based on Polymer Micro-Blazed Grating
Authors: Wang Hairong , Gao Xianni , Sun Guoliang , Zhao Yulong , Jiang Zhuangde
Published: June 2009

In order to detect methane (CH4) accurately and reliably, this paper presents a sensor which consists of infrared diode, fixtures, blazed grating, to realize the extremely narrow-bandwidth light at wavelength of 1.331μm. Based on factors such as compatibility with the transmission characteristics of silica fiber and the cost, a LED (light-emitting diode) with center wavelength of 1.3μm is selected. The LED light is modulated as the parallel light beam. As the light is incident in a micro-blazed grating with certain angle, by diffraction and interference, the light will output the maximum light intensity of its diffraction order at 1.331 μm, which just is an absorption peak of CH4. Micro-blazed grating applied here is low cost and easy replication by various ways, which makes extreme narrow width wavelength possible. Simulation and analysis indicate the designed prototype can output 1.331μm with bandwidth from 1.32907μm to 1.332495μm. With the light source basing on light dividing system, more reliable and higher sensitive measurement of the dangerous gases such as methane and carbon monoxide (CO) can be realized.
High Sensitive Sensor for Micro and Nano Particles Detection Based on DeFET
Authors: Ibrahim Mohamed F. , Elsayed Fahmi , Ghalab Yehya H. , Badawy Wael
Published: June 2009

This paper presents a new configuration of an electric field sensor, named “Differential Electric-Field Sensitive Field Effect Transistor” (DeFET). The new configuration which has different gate distances of DeFET is designed to detect tiny particles. The new design can be used in environmental applications such as one can detect carbon dioxide concentration in air. This paper also reviews the DeFET’s theory of operation and presents simulation which confirms the basic idea of the DeFET.
The Study on Position Accuracy of Micro-Coordinate Measuring Machine
Authors: Yang Chuan , Zhao Qiang , Zhao Yu-Long , Jing Wei-Xuan
Published: June 2009

In order to measure the microcosmic profiles of ultra-smooth surfaces, a high-accuracy noncontact micro-Coordinate Measuring Machine (micro-Coordinate Measuring Machine, micro-CMM) is developed in this paper. The working table of this measurement device is located by a macro-micro dual-drive system. A closed-loop control system, which is composed by a laser interferometer and stepper motors, is adopted to improve the positioning accuracy of the macro-positioning stage. The experimental results show that the positioning accuracy of this system is obviously improved and satisfies the positioning requirement of the macro-positioning stage. Because the positioning accuracy of the flexure-based micro-positioning stage can not satisfy the design requirement under the control of the traditional PID control, A PID control system based on Adaptive Neural-Fuzzy Inference is proposed to improve the control accuracy of the micro-positioning stage. The experimental results show that this system can improve the positioning accuracy of the micro-positioning stage, and basically meets the requirement of the design.
Visualization of Micro Vapor Bubble Dynamic Behaviors in Open Capillary Microgrooves
Authors: Hu Xuegong , Wu Liyuan , Tang Dawei
Published: June 2009

In this paper, a visualization investigation on micro bubble dynamic behaviors in vertical rectangular capillary microgrooves is conducted. With the help of a high-speed digital camera with the maximum speed of 30000 frames per second, a CCD camera and a stereomicroscope, the processes of formation, growth, coalescence and collapse of micro vapor bubbles in the microgrooves are observed. Bubble profile and size can be determined by image processing technique with MATLAB. The results show that micro vapor bubbles have four evolution modes. They include individual micro bubble growth and collapse along a microgroove, individual micro bubble growth and collapse across neighboring microgrooves, micro bubble coalescence and collapse along the same microgroove, and micro bubble coalescence and collapse across neighboring microgrooves. Whichever mode occurs, micro bubble doesn’t depart from the bottom of microgroove before it collapses. Experimental results about time-varying micro bubble sizes are distinctly different from those of theoretical calculation results by dynamic microlayer model for nucleate boiling heat transfer. Micro bubble breakup always occurs during the initial growing stage of bubble and collapse time is far shorter than the end time of the initial growth of individual bubble obtained by the dynamic microlayer model. Theoretical analysis indicates that interface effect and geometric structures of the microgrooves are responsible for the differences.
Designing an Intelligent Controller for a Molecular Valve
Authors: Momeni Kasra , Alasty Aria
Published: June 2009

Too much effort has been done for manipulating individual atoms, using nano-manipulators and Scanning Tunneling Microscopes (STM). On the other hand, characterization and manipulation of nano-flows is of great concern. In the current work a molecular valve has been considered, which is made up of six atoms placed on the circumstance of a circle. A fuzzy controller has been designed for controlling the diameter of this molecular valve. The designed fuzzy controller used singleton fuzzifier, Mamdani inference engine, center average defuzzifier and exponential membership functions. A model based on the classical Molecular Dynamics (MD) is used for modeling the nano-system and passing the states to the fuzzy controller. Then the fuzzy controller sets the actuators positions in order to control the diameter of the molecular valve. It has been shown that the designed controller can control the radius with an appropriate accuracy. Dimensionless equations of motion are used for designing the controller; therefore the designed controller is versatile and applicable to all the cases that the interactions between actuators and molecules can be modeled by Lennard-Jones potential. Using such a controller makes the molecular valve become applicable in the real world which has great applications such as drug delivery and controlling nano-flows with single molecule accuracy.
Modeling of Light Scattering by Silica Nanoporous Structures
Authors: Zhu Qunzhi , Li Yongguang , Chen Dawei
Published: June 2009

Study of light scattering by nanoscale structures is essential to evaluate the radiative heat transfer in silica aerogels. For the purpose of simplification and feasibility regular structures are proposed to substitute irregular structures in silica aerogels to obtain average results of light scattering. The differential scattering cross section increases with density and decrease dramatically with wavelength in the visible spectrum. An inverse power-law relation can be observed between the differential scattering cross section and the incident wavelength. Furthermore, a power-law relation can be obtained for dimensionless scattering cross section and density. These findings are very helpful to understand the influences of structural parameters on light scattering.
The Effects of Large Blood Vessels on Three-Dimensional Tissue Temperature Distributions During Electromagnetic Induced Nano-Hyperthermia: Numerical Simulation
Authors: Deng Zhong-Shan , Liu Jing
Published: June 2009

As is well known, the blood flowing through large blood vessels acts as a heat sink and plays an important role in affecting temperature profiles of heated tissues [1]. In hyperthermia, heating is usually limited to the tumor and a small margin of the surrounding tissue. Since the temperatures in the rest of the body remain normal, the blood that supplies the tumor will be relatively cold. Consequently, the blood flow inside a large vessel will represent a sink which cools the nearby heated tissues and then limits heating lesion during tumor hyperthermia. Under this adverse condition, a part of vital tumor cells may remain in the thermally lethal area and lead to recurrence of tumors after hyperthermia treatment. More specifically, tumor cell survival in the vicinity of large blood vessels is often correlated with tumor recurrence after thermal therapy. Therefore, it is difficult to implement an effective hyperthermia treatment when a tumor is contiguous to a large blood vessel or such vessel transits the tumor. How to totally destroy tumor cells in the vicinity of large blood vessels has been a major challenge in hyperthermia [2].
Rapid Electromagnetic Rewarming of Cryopreserved Tissues Using Nano-Magnetoparticles: Feasibility Study
Authors: Deng Zhong-Shan , Liu Jing
Published: June 2009

Cryopreservation and banking of biological cells and tissues have been widely utilized in scientific research and clinical applications. All practical cryopreservation protocols require biomaterials to survive two processes: cooling down to cryogenic storage temperature and the subsequent rewarming. Many investigations have shown that both cooling and rewarming rates are critical to the survival of cryopreserved cells, tissues, and organs [1]. Experimental evidence from a range of cell and organ model systems has suggested that better results may sometimes be obtained by rapid rewarming, particularly if the biomaterials have been cryopreserved via vitrification [2]. Unfortunately, the vitrification also introduces a new hazard — the formation of ice crystals during thawing the samples. By rewarming the vitrified biomaterials rapidly, it is possible to avoid recrystallization of the numerous micro ice nuclei formed during the cooling process [2]. For tissue samples with dimensions more than a few millimeters, the need for rapid rewarming precludes the use of the traditional approaches such as heat convection and conduction because the low thermal diffusivity of biomaterials prevents energy from conducting into the centre sufficiently quickly. Electromagnetic heating may be the only feasible method, which offers a significant advantage (i.e., heat is generated volumetrically) over conventional heating methods. However, for bulk tissue sample, the warming rate of tissue at the center of sample will inevitably be much less than that close to the surface. Such undesired results will lead to non-uniform heating, and may further result in thermal runaway, which is localized as exponential increase in temperature due to the temperature dependence of water’s dielectric properties [3]. In addition, for some cases, the warming rate of cryopreserved tissue by electromagnetic heating may still be not large enough. To solve the above problems, this study proposed an effective approach to perform rapid and uniform electromagnetic rewarming for cryopreserved bulk tissues through adjuvant use of nano-magnetoparticles. The principle of the present method is similar to that of electromagnetic induced nano-hyperthermia.
Hermetic Packaging Technique Featuring Through-Wafer Interconnects and Low Temperature Direct Bond
Authors: Lee James , Rogers Tony
Published: June 2009

A novel wafer level packaging method suitable for low production volumes, R&D, and multi-project wafers is presented, providing a hermetic seal suitable for vacuum encapsulation with wafers bonded at a low temperature. Hermetic through-wafer interconnects are bump bonded to a CMOS chip encapsulated by bonding a cap wafer after activating surfaces with free radicals, the Silicon-Silicon direct bond is then annealed to a high strength at 200°C to avoid chip damage. The application for which this system is proposed is an implantable multi-contact active nerve electrode for the treatment of epilepsy via vagus nerve stimulation. Although intended for human implantation of integrated systems, this technology may be applied across a range of devices requiring hermetic or vacuum sealing and through-wafer interconnection. Solid electroplated through-wafer interconnects (aspect ratio 5) enable hermetic interconnection of direct bonded packages with low connection impedance, offering benefits across a range of packaging applications. A key feature of this packaging method is it’s versatility, the proposed embodiment features chip to wafer bonding with an ASIC, but the package is equally suitable for MEMS devices and also for wafer to wafer bonding.
Wafer Bonding Processes for the Manufacture of Microsystems
Authors: Rogers Tony , Aitken Nick
Published: June 2009

Wafer bonding is a widely used step in the manufacture of Microsystems, and serves several purposes: • Structural component of the MEMS device. • First level packaging. • Encapsulation of vacuum or controlled gas. In addition the technology is becoming more widely used in IC fabrication for wafer level packaging (WLP) and 3D integration. It is also widely used for the fabrication of micro fluidic structures and in the manufacture of high efficiency LED’s. Depending on the application, temperature constraints, material compatibility etc. different wafer bonding processes are available, each with their own benefits and drawbacks. This paper describes various wafer bonding processes that are applicable, not only to silicon, but other materials such as glass and quartz that are commonly used in MEMS devices. The process of selecting the most appropriate bonding process for the particular application is presented along with examples of anodic, glass frit, eutectic, direct, adhesive and thermo-compression bonding. The examples include appropriate metrology for bond strength and quality. The paper also addresses the benefits of being able to treat the wafer surfaces in-situ prior to bonding in order to improve yield and bond strength, and also discusses equipment requirements for achieving high yield wafer bonding, along with high precision alignment accuracy, good force and temperature uniformity, high wafer throughput, etc. Some common problems that can affect yield are identified and discussed. These include local temperature variations, that can occur with anodic bonding, and how to eliminate them; how to cope with materials of different thermal expansion coefficient; how best to deal with out-gassing and achieve vacuum encapsulation; and procedures for multi-stacking wafers of differing thicknesses. The presentation includes infra-red and scanning acoustic microscopy images of various bond types, plus some examples of what can go wrong if the correct manufacturing protocol is not maintained.
Glass-Glass Wafer Bonding for Microfluidic Devices
Authors: Aitken Nick , Rogers Tony
Published: June 2009

The AML AWB04 wafer bonding platform has been used to develop glass – glass bonding processes for both quartz and Pyrex substrates. This allows the accurate wafer to wafer alignment and bonding of two microfluidic (or any other glass device) wafers. In the case of Quartz, the process is also useful in the field of SAW (Surface Acoustic Wave) device fabrication. Although there are simpler and cheaper ways of creating micro fluidic devices (e.g adhesive bonded glass wafers, or all polymer devices), Pyrex is often required as the material is qualified for use in pharmaceutical and medical industries. The transmission properties of glass are also often needed where optical sensing and measurement is required. Pyrex is often needed for chemical compatibility, and is commonly used for glassware. Using the AML equipment, Pyrex and Quartz devices can be sealed at the wafer level with placement accuracies approaching ±1μm. The bonding process can also seal vacuum cavities, or seal controlled atmosphere cavities (e.g. reference cavities for optical absorption measurements). It is sometimes important to maintain precise glass micromachining dimensions and therefore it is necessary to bond at a temperature substantially less than the strain point of the glass: the AML equipment and processes can achieve this. The sealing strength is sufficient to withstand high pressure fluidic applications.