bluuebunny/crossref_metadata_2025 huggingface dataset:
Biocompatible, Superparamagnetic, Flame Synthesized Iron Oxide Nanoparticles: Cellular Uptake and Toxicity Studies
Authors: Buyukhatipoglu Kivilcim , Miller Tiffany A. , Morss Clyne Alisa
Published: August 2009

Superparamagnetic iron oxide nanoparticles, including magnetite (Fe3O4), are widely used in applications such as targeted drug delivery, magnetic resonance imaging, tissue engineering, gene therapy, hyperthermic malignant cell treatment, and cell membrane manipulation. These nanoparticles are particularly interesting for in vivo and in vitro applications since they do not exhibit magnetic behavior once the magnetic field has been removed. In the current work, superparamagnetic iron oxide nanoparticles were produced using a flame synthesis method, which provides significant advantages over other material synthesis processes such as solgel processing, chemical vapor deposition, and laser ablation. Flame synthesis allows control of particle size, size distribution, phase and composition by altering flame operating conditions. Flame synthesis is further capable of commercial production rates with minimal post-processing of the final product materials. This study focuses on the interaction of flame synthesized iron oxide nanoparticles with porcine aortic endothelial cells and compares the results to those obtained using commercially available iron oxide nanoparticles. The materials characteristics of the flame synthesized iron oxide nanoparticles, including morphology, elemental composition, particle size, were analyzed by electron microscopy (TEM, ESEM, EDS), and Raman Spectroscopy. The data verified production of a heterogenous mixture of hematite and magnetite nanoparticles, which exhibit superparamagnetic properties. Monodisperse iron oxide particles of 6–12 nm diameter and aggregated clusters of these 6–12nm nanoparticles have been synthesized. Nanoparticle biocompatibility was assessed by incubating flame synthesized and commercially available iron oxide nanoparticles with endothelial cells for 24 hours. Both alamar blue and Live/Dead cell assays showed no significant toxicity difference between flame synthesized and commercially available nanoparticles. Cells exposed to both types of nanoparticles maintained membrane integrity, as indicated by minimal lactase dehydrogenase release. Endothelial cells imaged by ESEM and confirmed by EDS demonstrated that uncoated flame synthesized nanoparticles are ingested into cells in a similar manner to commercially available nanoparticles. These data suggest that flame synthesized iron oxide nanoparticles are comparable to commercially available nanoparticles for biological applications. Flame synthesis has the advantage of a relatively simple synthesis process with higher purity products and lower time and energy manufacturing costs. Future work will include functionalizing the nanoparticle surfaces for specific biological applications, including specific cell targeting and bioactive factor delivery.
Fractional Order Models for Viscoelasticity of Soft Biological Tissues
Authors: Meral Faik Can , Royston Thomas J. , Magin Richard L.
Published: August 2009

Dynamic mechanical properties of soft tissues provide information that may be used in medical diagnosis. Developing a better fundamental understanding of the governing constitutive relations could improve diagnostic techniques. The mechanical behavior of soft tissues and tissue mimicking phantoms, such as gels, can be represented by viscoelastic material models. Static loading of viscoelastic materials yields information related to elasticity, creep and stress relaxation. However, a broader measure of rate-dependent properties that affect mechanical wave propagation and wave attenuation in such materials can only be extracted from measured response to dynamic excitation. The well known linear viscoelastic material models of Voigt, Maxwell and Kelvin cannot represent the more complicated frequency dependency of these materials over a broad spectral range. Therefore, fractional calculus methods have been considered to model the viscoelastic behavior of soft tissue-like materials. Fractional order models capture the viscoelastic material behavior using fractional orders of differential equations that may yield a more accurate representation of viscoelastic material behavior. This paper focuses on experimental measurements on the tissue mimicking phantom, CF11. Surface waves on the phantom material are studied experimentally and theoretically. Theoretical calculations using linear and fractional order methods are compared with experimental measurements.
Effects of Shock Waves on Acceleration of Cell Growth Rate by Shock Tube
Authors: Tamagawa Masaaki , Ishimatsu Norikazu
Published: August 2009

This paper describes effects of shock waves on cells to certificate the angiogenesis by shock wave (pressure wave) in the clinical application such as ESW (Extracorporeal Shock Wave). Especially, to investigate the effects of shock waves on the endothelial cells in vitro, the cells worked by plane shock waves using shock tube apparatus are observed and measured in the microscope. The peak pressure working on the endothelial cells at the test case is 0.4 MPa. After working shock waves on suspended cells, growth rate (area per one cell and population of cells) are measured by image processing. It is found that the growth rate of the shock-worked cells from 0 to 4h is clearly high compared with control one. It is concluded that once shock waves worked, the cells have capacity to increase growth rate in vitro. This preliminary result will be applied to fundamental investigations about shock wave stimulus on several kinds of cells in future.
A Similarity Measure Based on Extension Distance and Its Application in CBR
Authors: Zhao Yanwei , Zhang Feng , Su Nan , Tang Huijun , Chen Jian
Published: August 2009

Case-based reasoning (CBR) is an effective method that integrates reasoning methodology and represents related knowledge in a domain. The success of a CBR system largely depends on case retrieval, and the similarity and determination of weight for each case features have a significant influence on the efficiency and accuracy of case retrieval. The aim of the research is to improve the efficiency and accuracy of case retrieval. Analyzing the deficiency of similarity measures based on the classical distance, different similarity measures are proposed for different kinds of attribute values based on the extension distance, especially the similarity model between numerical and set considered the customer’s preference. The standard deviation related with the similarity is introduced to distribute the dynamic attribute’s weights which also considered the customer’s interest, but not the traditional methods that the weight is a constant if determined. The presented methods will enable the system to retrieve the more similar case correctly so that reducing case adaptation. In this study, an electric drill is used as a case to verify the usefulness and effectiveness of the similarity measurements and weight assignments. It is demonstrated that this method is more beneficial to case retrieval compared with other methods.
The Research on Dynamic Lubrication Between Complicated Surfaces With Simplified Elastic Contact Theory
Authors: Liu Hu Ran
Published: August 2009

This paper applied the simplified elastic contact theory into the research on dynamic lubrication between complicated surfaces. The simplified elastic contact theory is relevant to my work in that both theories assume: there are no effects the adjacent “slices” of a body have on each other. The simplified elastic contact theory is different to my work in that: one is aimed at the contact stress between wheel of the train and the railway; another is aimed at the dynamic lubrication between complicated surfaces.
Curve-Curve Contact in 5-Axis NC Machining of Sculptured Surfaces Using Flat-End Cutter
Authors: Liu Hu Ran
Published: August 2009

The concept of “contact” in differential geometry is creatively applied into the machining of the sculptured surface; the contact principle of the machining of complicated surfaces is presented. The circumference circle of the cylindrical cutter instead of ball-end milling cutter is used to sweep the curved surface. This is the highly effective method. In this paper an innovative theory for machining complicated surface is presented. By using a flat-end mill instead of ball-end mill, and by adjusting the axis of cutter relative to the surface, the two surfaces, the swept surface and the required surface, have the same curvatures, up to as high as 3rd order. It shows how aspects of 5-axos machining can be achieved through 3-axis methods. This is useful as not all shops can afford 5-axis machining.
Automatic Speed Control System for Vehicle Approaching and Driving on a Curve
Authors: Lee Yong H.
Published: August 2009

Based on the curvature information for an upcoming road, an automatic speed control system regulates vehicle speed to improve vehicle curve following performance. The road information is extracted from a digitally stored map using the current vehicle position obtained from Global Positioning System (GPS) data. Then, a safe curve speed is determined using the lateral dynamics of vehicle in turn to ensure proper curve handling. Other factors, such as vehicle characteristics, driver preferences, and road and environment conditions are also considered so that vehicle safety and driver comfort are enhanced. An acceleration command is generated from the current vehicle speed and the desired curve speed profile. Driving mode, such as conservative, normal, or aggressive mode, can be selected from the console for a desired driving style. The gain and preview time to determine the vehicle cornering speed are selected according to driver’s preference. The functional blocks of the system include computation of the road curvature, determination of a desired curve speed profile for the best cornering performance for an upcoming curve, and regulation of vehicle speed toward the desired speed. Signal input blocks and actuator control blocks are added to interface with the bus oriented sensors and actuators. The entrance and exit conditions block checks for various vehicle status signals to enter or exit the curve speed control mode gracefully. It also generates a diagnostic message when map data is absent or an error occurs on acceleration command computation. The vehicle studies indicated that the curve speed control system is effective in regulating vehicle speed during curve following maneuvers.
Progress in the Development of Chemical Kinetics Databases for the Combustion of Real Fuels
Authors: Tsang Wing
Published: August 2009

Modern Computational Fluid Dynamics codes have increasing capabilities for taking into account detailed chemical kinetics [1, 2]. This opens the possibility of simulating the combustion of real fuels in industrial devices. This will bring combustion technology in line with modern developments in cutting edge science. One could not design VLSI circuits without simulations. Similarly, the design of modern airplanes depends on simulations before final wind tunnel testing. A key to the proper simulation of the chemistry in combustion is the kinetics database. The aim of this paper is to describe the current situation in this area. We will begin by discussing the special problems posed by the nature of the fuel. We will then define the elements in a proper chemical kinetic database. Currently used databases for the simulation of combustion will be critically examined. The importance of a more fundamentally based database will be emphasized. Finally some recent work pertaining to the chemical kinetics of real liquid fuel molecules will be described.
Flow Regime Evolution in Long, Serpentine Microchannels With a Porous Carbon Paper Wall
Authors: Steinbrenner Julie E. , Lee Eon Soo , Wang Fu-Min , Fang Chen , Hidrovo Carlos H. , Goodson Kenneth E.
Published: August 2009

An important function of the gas delivery channels in Proton Exchange Membrane (PEM) fuel cells is the evacuation of liquid water created at the cathode. The resulting two-phase flow can become an obstacle to reactant transport and a source of parasitic losses. The present work examines the behavior of two-phase flow in 500 μm × 500 μm × 60 cm channels with distributed water injection through a porous carbon paper wall to gain understanding of the physics of flows relevant to fuel cell water management challenges. Flow regime maps based on local gas and liquid flow rates are constructed for experimental conditions corresponding to current densities between 0.5 and 1 A/cm2 and stoichiometric coefficients from 1 to 4. Flow structures are analyzed along the entire length of the channel. It is observed that slug flow is favored to plug flow at high air flow rates and low liquid flow rates. Stratified flow dominates at high liquid flow rates. Along the axial flow direction, the flow regime consistently transitions from intermittent to wavy to stable stratified flow. This progression is quantified using a parameter of flow progression which characterizes the degree of development of the two-phase flow toward the stable stratified condition. This parameter is discussed in relation to fuel cell operating conditions. It provides a metric for analyzing liquid water removal mechanisms in the cathode channels of PEM fuel cells.
Mathematical and Optimization for a Non-Linear Yeast Cell Proliferation Problem Using Genetic Algorithm
Authors: Ghaffari A. , Ghanizadeh Chenarbon S. , Rahmani Vahid P.
Published: August 2009

We consider an age-maturity structured model arising from a yeast cell proliferation problem. This model is a new study in the filed of analysis of cell kinetics and cell division using mathematical modeling and optimized by Genetic Algorithm. We use our mathematical analysis in conjunction with experimental data from the division analysis of primitive cells to characterize the maturation/proliferation process.
Dynamic Simulation and Technologic Parameter Optimization of Ultra-Precision, Double-Sided Planar Polishing Machine
Authors: Zhao Yanwei , Kim Gap-Yong , Du Jianfeng , Wen Siwei
Published: August 2009

The mechanical movement in ultra-precision polishing process is an important factor which influences the polishing quality. Based on chemical-mechanical polishing (CMP) principle of PE-1 type ultra-precision polishing machine, dynamic simulation and technologic parameter optimization was studied. Firstly, a virtual prototype was built. And this prototype was validated by comparing the testing values with theoretical results. Secondly, the dynamic and kinematics characteristics of the polishing process was simulated and analyzed. Through the study of the relationship between the input velocity ratio of planetary system and workpiece movement, researcher found that the movement of workpiece is only influenced by input velocity ratio of planetary system, not involve the load of cylinder and velocity of plate. Through the simulation of point moving on workpiece surface, researcher found that the average velocity of points along the radius is increase while the radius increases, and the average velocity of points on the same circle is equal. Through the simulation of movement route, researcher found that the points along the radius have similar route style considering the same input speed ratio of planetary system. Thirdly, technologic parameter optimization was studied. The optimization research of non-uniformity revealed that the speed of plate has effect on both removal rate and the amount of material. High velocity of plate can make for getting high removing quantity. And the optimization research of material removal rate revealed that the higher pressure can get higher removal rate. At last, on the condition of same pressure and speed of plate, the optimum result is gained. The results indicated that high velocity of plate can make for getting high removing quantity, and high pressure can make for getting high removal rate.
Resistance Spot Welding (RSW) Process Optimization for Uncoated 2.0mm Dual Phase 780 to 2.0 mm Uncoated 2.0 mm Dual Phase 780 (DP780) Steel for Automotive Applications
Authors: Koganti Ramakrishna , Angotti Sergio , Wexler Arnon , Maatz Donald F.
Published: August 2009

There has been a substantial increase in the use of advanced high strength steel in automotive structures in the last few years. The usage of these materials is projected to grow significantly in the next 5–10 years with new safety and fuel economy regulations. Advanced High Strength Steels (AHSS) are getting popular with superior mechanical properties and weight advantages compared to mild steel materials. These new materials have significant manufacturing challenges, particularly for welding and stamping. Proper understanding of the weldability of these materials is critical for successful application in future vehicle programs. Due to high strength nature of AHSS materials, higher weld forces and longer weld times are needed to weld AHSS materials. This work is in support of lightweight structures development and during the weld development phase various gages of coated and uncoated AHSS materials (DP780, DP980, TRIP780, Boron, Algoma 700B) were investigated. Both 2T and 3T stack-up conditions were investigated. Also, some combination of AHSS materials with High Strength Low Alloy (HSLA) and Bake Hardenable 210 (BH210) electro galvanized (EG) steels were also investigated. In this paper, weld lobe development for 2.0 mm DP780 bare to 2.0 mm DP780 bare 2T stack-up combination is discussed. Weld lobes were developed with Mid Frequency Direct Current (MFDC) equipment, ISO type B-20 tip, constant weld force of 6.36 kN (1430 lbf), hold time of 5 cycles and the weld times were varied 21, 24 and 27 cycles. Based on the tensile, cross-tension and nugget data, there were no correlations were observed between tensile load and button size and also between cross-tension and button size. Weld cross section data indicated heat affected zone (HAZ) at the weld nugget area and hardness drop of 17% was observed at the HAZ area. Irrespective of weld cycles, similar HAZ was observed close to the weld nugget. The weld lobes, mechanical properties (tensile shear and cross tension), cross-section examination, and microhardness of 2.0 mm DP780 bare to 2.0 mm DP780 bare weld 2T stack-up results are discussed.
Hybrid Contact Search Algorithm for Wheel/Rail Contact Problems
Authors: Sugiyama Hiroyuki , Suda Yoshihiro
Published: August 2009

In this investigation, the on-line and off-line hybrid contact algorithm for modeling wheel/rail contact problems is developed based on the elastic contact formulation. In the tabular contact search used in existing specialized railroad vehicle dynamics codes, contact points are predicted using an assumption of rigid contacts. For this reason, the contact points can be different from those predicted by the on-line based contact search used in general elastic contact formulations. The difference in the contact point becomes significant when flange contacts that have large contact angles are considered. In the hybrid algorithm developed in this investigation, the off-line tabular search is used for treating tread contacts, while the on-line iterative search is used for treating flange contacts. By so doing, a computationally efficient procedure is achieved while keeping accurate predictions of contact points on the wheel flange. Furthermore, the use of the proposed hybrid algorithm can eliminate the use of time-consuming on-line search procedures for the second points of contact as well. Since the location of second points of contact is pre-computed in the contact geometry analysis, the occurrence of two-point contact can be predicted using the look-up table in a straightforward manner. For the two-point contact scenarios encountered in curve negotiations, the online search is used for flange contacts, while the off-line search is used for tread contacts simultaneously. The on-line one-point contact search is also important for flange climb scenarios. It is demonstrated by several numerical examples that the proposed hybrid contact search algorithm can be effectively used for modeling wheel/rail contacts in the analysis of general multibody railroad vehicle systems.
The Potential of Using Betelnut Fibres for Tribo-Polyester Composites Considering Three Different Orientations
Authors: Yousif B. F. , Gill Nirmal Singh , Lau Saijod T. W. , Devadas Alvin
Published: August 2009

This paper presents an attempt to use betelnut fibres as reinforcement for tribo-polyester composites in bearing applications. The composite was fabricated using the hand lay-up technique, and contains 15 layers of randomly distributed chopped fibres and 17 layers of polyester. The adhesive wear and frictional behavior of the composites were studied against a polished stainless steel counterface using block-on-disc (BOD) machine at different applied loads (5–30N) and sliding distance (0–7km). In addition to that, the orientation of the fibre layers with respect to the sliding direction of the counterface was considered, i.e. parallel (P-O), anti-parallel (AP-O) and normal (N-O). Studies on worn surfaces, using a scanning electron microscope (SEM), and roughness profiles of the composite and counterface assisted to explain the results. As a result of this work, it was found that applied load has less effect on the specific wear rate and friction coefficient of the composite especially in P-O and AP-O. Meanwhile, in both orientations (P-O and AP-O), the steady state of specific wear rate was reached after 5 km sliding distance. On the other hand, the composite behaved differently in N-O, where the wear and friction increased when the load and sliding distance increased. This was due to the poor support of the fibres in that orientation, where delamination, pull out and breakage in the fibres were observed. In P-O and AP-O, the wear mechanism was predominated by plastic deformation and micro-cracks.
Development of a High Temperature Oxidation Mechanism for Bio-Aviation Fuels
Authors: Catalanotti E. , Hughes K. J. , Pourkashanian M. , Uryga-Bugajska I. , Williams A.
Published: August 2009

Almost all current civil and military aviation around the world use a kerosene-type fuel. However one of the alternatives is to use a mixture of petrochemicals and biofuel, especially methyl esters derived from vegetable oil (Fatty Acid Methyl Esters, FAMEs) that given their properties appear to be one of the most suitable for Aviation fuels. Studies were conducted to develop a fundamental and detailed reaction mechanism for the combustion of bio-aviation fuel through a combination of the existing kerosene based reaction mechanism developed previously by the authors (Aviation Fuel Reaction Mechanism v1.1), along with published chemical kinetic mechanisms for methylbutanoate (MB). Methylbutanoate is the simplest FAME that exhibits similar patterns of reactivity to FAME’s of longer carbon chain length typical of those derived from vegetable oils, furthermore it has been the subject of several studies to provide chemical kinetic mechanisms to predict its oxidation behavior. Evaluations of the combined reaction mechanism have been performed using CHEMKIN™ and similar software simulating high temperature/pressure conditions. A comparison between the oxidation processes of the Kerosene and Bio-Aviation fuel was carried out, along with sensitivity analysis to provide insight into some of the differences observed. A similar behaviour was observed for blends of 20%MB/80%Kerosene in the combustion conditions studied, indicating that combustion in current aircraft engines would not be adversely affected by using such a blend.
Feasibility of Thermoelectric Waste Heat Recovery in Large Scale Systems
Authors: LaManna Jacob , Ortiz David , Livelli Mark , Haas Samuel , Chikwem Chinedu , Ray Brittany , Stevens Robert
Published: August 2009

With the growing emphasis on energy efficiency because of environmental, political, and economic reasons and the fact there has been significant advances in thermoelectric materials, there is a renewed interest in using thermoelectrics for waste heat recovery. A mathematical model of a thermoelectric power system is developed from a heat transfer analysis of a waste heat recovery system. The model is validated by altering design parameters of a small prototype thermoelectric system that converts heat into electricity. A heated air stream is produced using an exhaust simulation test stand and provides the waste heat source for the prototype. The prototype is designed to be able to change several system parameters such as different heat sinks, thermoelectric module counts, and module configurations to better validate the developed model. The model does predict the electrical performance with typical accuracy of 30% error from the prototype over a range of configurations and operating conditions. A feasibility study using the validated model was used to determine under what conditions this technology will become economically viable, such as remote power generation with 20 year payback.
Design of Robotic Arm Using Delay Based Operation of DC Geared Motors With a Microcontroller
Authors: Sulaiman Dilshad A. , Pandey Akash B.
Published: August 2009

This paper provides the design of a simple robotic arm for pick and place operations as well as other material handling operations. The movements of the arm are anthropometric i.e. resembling the human arm with respect to degrees of freedom so as to provide a human touch in industrial and space operations. This system operates using controlled motion of DC geared motors along with a microcontroller based system (8051 or PIC based). Use of PWM (Pulse Width Modulation) can be used to control the RPM of DC geared motors. This system has the advantage of being simple and low cost with a varied flexibility of operation. A collective array of sensors viz. voice sensor, infrared light sensors, proximity sensors etc. can be incorporated to form a feedback induced closed loop system. Whereas for tasks of picking and placing at a fixed location from another location the system can be operational at open-loop. The material for the robotic arm can be polypropylene or acrylic or aluminium to reduce weight without compromising on the strength and lifting capacity of the robotic arm, such that the torque of the DC geared motors (actuators) at each joint are sufficient to lift the arm along with the weight at the end effector. Clutch and gear shifting mechanism can be used to increase the degrees of freedom per actuator. The driving circuit mainly consists of the microcontroller and H-bridge drivers using an 8-bit port to control 4 DC geared motors per port simultaneously or one at a time using delay commands. DC geared motors are quite cheaper than stepper motors and RC Servos thus reducing the total cost of the system drastically. Plus being light weight, DC geared motors reduce the total weight of the system. This paper will also throw light on the programming aspects for the microcontroller (8051 or PIC based) along with the compatible flash programmers and HEX code generators. This project will further explain on the approach followed in the mechanical design of the robotic arm (motion, work volume etc.) as well as the possible future applications of the robotic arm. Also the design of the robotic arm on CAD tools like Solidworks will be discussed in brief along with the modeling and simulation of the various links of the arm as well as the whole assembly of the system. With increasing popularity of Automation, robotic arms are the present and future of all industrial operations. Finally the paper concludes on the further improvements in design and technology.
Integrating Professional Skills in the 21st Century Engineering and Technical Curriculum
Authors: Birch John , Jaramillo Paola , Wosczyna-Birch Karen , Adrezin Ronald , Richards Beth
Published: August 2009

The Engineering Challenge for the 21st Century Program was initially based on concepts from the Transferable Integrated Design Engineering Education (TIDEE) model. The TIDEE model was developed in the mid 1990s to focus on continuous improvement of engineering design education. The primary thrust of the TIDEE model focuses on team-based activities that allow students to effectively develop the necessary skills to become qualified, productive, and successful engineers and technologists of the future. The Engineering Challenge Program focuses on project based learning in a team environment and targets two important educational groups: underrepresented students as well as faculty from high schools and community colleges in Connecticut. In order to further develop the students’ interpersonal and organizational skills, the Engineering Challenge Program expands on the TIDEE model through development of technical writing and professional skills including project management, teamwork skills, understanding behavioral diversity using DISC behavioral profiles, and personal accountability. Interdisciplinary teams of high school teachers and college faculty work with a CT-based management consultant group to deliver the program by “teaching teachers” effective methods to assess and coach teamwork in the classroom and labs. The Engineering Challenge Program has impacted over 250 students composed of high school and undergraduate students from community colleges and to a lesser degree four-year universities. By targeting underrepresented student participants, the program has been effective in engaging its participants in pursuing education and careers in STEM-related disciplines. Approximately 35% of the participants have been females and 53% of the participants’ non-Caucasian.
Damage of Thermo-Elasto-Plastic Multimaterial Under Thermal Cycling Conditions
Authors: Taher Bilal , Abboudi Said , Youness Rafic
Published: August 2009

The increasing of the temperature in the multi-material solicited with thermal and mechanical charges leads to surpass the load of elastic constraint, so we have to apply the thermo-elasto-plastic behavior. The increasing need of structures having multiple functions orientates designers to combine materials in order to obtain, according to coupling scales, multi-materials structures. The lifetime of these structures represents a one of the main decisive element for offices and manufacturers studies. The results of this work should be added to the set of functional charges to obtain an optimal and final decision on the design of the product. In this study, a numerical analysis conducted by finite elements method of thermo-elasto-plastic behavior of these type of materials and their damage under thermal cyclic solicitations. The study is led in two dimensions (r, z) on a cylindrical material constituted of two layers (stainless steel, Steel), subjected to a variable heat flux at the internal surface and an exchange with the ambient at the external surface. Other faces are isolated. The sample is fixed in the axial direction and free in the radial direction. The damage model is based on the works of Lemaiˆtre and Chaboche. Numerical results are presented for periodic heat flux and for different thickness of the material. The study is concluded by optimizing of the thickness of materials according to the total lifetime caused by thermo-elasto-plastic effect.
Thermal and Thermomechanical Analysis of Custom Engineered Ag-Nanoparticle Thermal Interface Materials
Authors: Chhasatia Viral , Sun Ying , Zhou Fan , Huang Liwei , Wang Howard
Published: August 2009

Thermal interface material (TIM) is a major hurdle in heat flow for typical chip/heat sink assemblies. In many electronic devices, hot spots occur in areas of high activity during the device operation. These hot spots can lead to high thermal gradients, which in turn result in performance and reliability hindrances. The elevated, non-uniform power density confronted with conventional TIMs that contain a uniform layer of high thermal conductivity material for the entire chip can be extremely insufficient in many applications. In this paper, a custom engineered, Ag-nanoparticle (Ag-NP) TIM that targets directly to the high power density region is introduced for achieving better thermal-mechanical-electrical performance at a low cost. These nanoparticles can be inkjet printed on hot spots and sintered at a relative low temperature (∼120°C) to create a continuous metallic layer that is in good contact with both the chip and heat sink, whereas the conventional particle-laden TIM covers the lower power density area. A computational model is developed to examine the overall thermal performance and reliability of the hybrid Ag-NP/conventional TIM as a function of the bondline thickness, applied pressure, deposition pattern, and surface roughness. The results show great improvements compared with a high-performance indium solder.
Nonlinear Feedback Control and Dynamics of an Electrostatically Actuated Microbeam Filter
Authors: Ouakad H. M. , Nayfeh A. H. , Choura S. , Abdel-Rahman E. M. , Najar F. , Hammad B.
Published: August 2009

This work is concerned with the modeling, nonlinear dynamic analysis and control design of an electrostatically actuated clamped-clamped microbeam filter. The model accounts for the mid-plane stretching and nonlinear form of the electrostatic force actuated along the microbeam span. A reduced-order model is constructed, using the method of multiple scales, to examine the microsystem static and dynamics behaviors. To improve the microbeam behavior, a nonlinear feedback controller is proposed. The main control objective is to make it behave like commonly known one-degree-of-freedom self-excited oscillators, such as the van der Pol and Rayleigh oscillators, which depict attractive filtering features. We present a novel control design that regulates the pass band of the fixed-fixed microbeam and derive analytical expressions that approximate the nonlinear resonance frequencies and amplitudes of the periodic solutions when the microbeam is subjected to one-point and fully-distributed feedback forces.
A New LuGre Friction Model for MR-9000 Type MR Damper
Authors: Yang Fan , Sedaghati Ramin , Esmailzadeh Ebrahim
Published: August 2009

This paper presents a new hysteresis model, based on the LuGre friction model, to analyze the dynamic behavior of large-scale Magneto-Rheological (MR) damper (MR-9000 type MR-damper [1]) accurately and efficiently. The gradient based optimization technique and the least square method will be utilized to identify the modal parameters. The dynamic behavior of MR-damper under different types of excitation and input current have been predicted using the proposed model and then compared with those predicted using modified Bouc-Wen model to verify the validity of the proposed model.
A Takagi-Sugeno Fuzzy Model of a Concentric-Tubes Heat Exchanger
Authors: Ruiz-Mercado Claudia , Pacheco-Vega Arturo , Palacios Elvia
Published: August 2009

In the present study we develop a Takagi-Sugeno (TS) fuzzy model of a concentric-tubes heat exchanger. The model is structured on fuzzy logic reasoning with sets of linguistic rules describing the dynamic characteristics of the thermal system. Using a system identification technique based on adaptive neural networks, the fuzzy rules are derived from experimental data of the flow rates and fluid temperatures in the heat exchanger. The accuracy of the resulting model is assessed by predicting the time-dependent response of the outlet hot- and cold-water temperatures under a step-change in the mass flow rate of the cold fluid. The results indicate that the TS fuzzy model is able to estimate the behavior of the physical system with very little predicting errors. Upon the basis of this empirical model, in the near future we will report on a control strategy for the regulation and tracking of the outlet temperatures in the heat exchanger.
Cu Pillar Bump FCBGA Package Design and Reliability Assessments
Authors: Kao Nicholas , Hu Yen-Chang , Tseng Yuan-Lin , Chen Eason , Lai Jeng-Yuan , Wang Yu-Po
Published: August 2009

With the trend of electronic consumer product toward more functionality, high performance and miniaturization, IC chip is required to deliver more Input/Output (I/O) and better electrical characteristics under same package form factor. Flip Chip BGA (FCBGA) package was developed to meet those requirements offering better electrical performance, more I/O pin accommodation and high transmission speed. However, the flip chip technology is encountering its structure limitation as the bump pitch is getting smaller and smaller because the spherical geometry bump shape is to limit the fine bump pitch arrangement and it’s also difficult to fill by underfill between narrow gaps. As this demand, a new fine bump pitch technology is developed as “Cu pillar bump” with the structure of Cu post and solder tip. The Cu pillar bump is plating process manufactured structure and composes with copper cylinder (Cu post) and mushroom shape solder cap (Solder tip). The geometry of Cu pillar bump not only provides a finer bump pitch, but also enhances the thermal performances due to the higher conductivity than conventional solder material. This paper mainly characterized the Cu pillar bump structure stress performances of FCBGA package to prevent reliability failures by finite element models. First, the bump stress and Cu/low-k stress of Cu pillar bump were studied to compare with conventional bump structure. The purpose is to investigate the potential reliability risk of Cu pillar bump structure. Secondly, the bump stress and Cu/low-k stress distribution were evaluated for different Polyimide (PI) layer, Under Bump Metallization (UBM) size and solder mask opening (SMO) size. This study can show the stress contribution of each design factor. Thirdly, a matrix which combination UBM size, Cu post thickness, SMO size, PI opening and PI thickness were studied to observe the stress distribution. Finally, the stress simulation results were experimentally validated by reliability tests.
A Numerical Study of Geometrical Effects on the Strouhal Number of a Circular Cylinder
Authors: Kazemifar Farzan , Molai Mehdi , Firoozabadi Bahar , Ahmadi Goodarz
Published: August 2009

In this paper, reducing the Strouhal number of a circular cylinder is studied numerically. Two-dimensional numerical simulations of flow over a normal circular cylinder and various modified circular cylinders are carried out using FLUENT® soft ware. Two small blades are attached to a circular cylinder and the effects of variation of the blades length and the blade angle are studied numerically. The blade angle is chosen 2α = 0°, 30°, 90°, 120° and 150°. The blades length is chosen l/d = 0.125, 0.25, 0.375. Effects of blade angles and blade lengths were studied for both 2α = 0° and 150°. Results show that increasing in blade lengths decreases the Strouhal number. Moreover, as the blade angle was increased from zero to 90°, the percentage reduction in Strouhal number decreased; however, as the blade angle was further increased from 90° to 150°, the percentage reduction in Strouhal number increased. Although the modifications studied here decrease the vortex shedding frequency they make the vortices shed from the cylinder farther and stronger hence increasing the magnitude of the fluctuating forces.
The Effect of H2S on Production of Carbon Black From Sub-Quality Natural Gas
Authors: Moghiman M. , Javadi M. , Raad M. H. , Hosseini N. , Soleimani M.
Published: August 2009

The objective of this paper is computational investigation of the carbon black production through thermal decomposition of waste gases containing CH4 and H2S, without requiring a H2S separation process. The chemical reaction model, which involves solid carbon, sulfur compounds and precursor species for formation carbon black, based on an assumed Probability Density Function (PDF) parameterized by the mean and variance of mixture fraction and β-PDF shape. The soot formation is modeled by using the soot particle number density and the mass density based on acetylene concentrations. The effects of feedstock mass flow rate and reactor temperature on carbon black, soot, CO, S2, SO2, COS and CS2 formation are investigated. The results show that the major factor influencing CH4 and H2S conversions is reactor temperature. The results reveal that at any temperature, H2S conversion is less than that of CH4. For temperatures higher than 1100°K, the reactor CH4 conversion reaches 100%. At temperatures below 1300°K, H2S conversion is too low and usually less than 5%. For temperatures higher than 1300°K, H2S conversion increases sharply with temperature and the major products of the process are S2 and SO2 while COS and CS2 are minor products. The results also show that the production of carbon black from sub-quality natural gas, process involving the formation of carbon monoxide which is occurring in parallel, play a very significant role. For lower values of feedstock flow rate, CH4 mostly burns to CO and consequently, the production of carbon black is low.
The Steady-State Modeling and Static System Design of a Refrigeration System for High Heat Flux Removal
Authors: Zhou Rongliang , Catano Juan , Zhang Tiejun , Wen John T. , Michna Greg , Peles Yoav , Jensen Michael K.
Published: August 2009

This paper investigates the steady-state modeling and static system design of a refrigeration system for high heat flux removal of high power electronics system. The refrigeration cycle considered consists of multiple evaporators, liquid accumulator, compressor, condenser and expansion valves. In contrast with conventional refrigeration systems with liquid-to-liquid heat exchangers for temperature control where the critical heat flux (CHF) is not a major concern, refrigeration systems for high heat flux removal have to ensure that the incoming heat flux is lower than the CHF to prevent device burnout. Since the superheated region in the evaporator has much lower heat transfer coefficient than the two-phase region, the evaporator exit should be two-phase for ensure sufficiently high CHF. The two-phase evaporator exit necessitates the inclusion of a heated liquid accumulator for the safe operation of the compressor to ensure only saturated vapor enters the compressor. The evaporators and condenser of the cycle are modeled by the mass balance, momentum balance, and energy balance equations. Due to the future utilization of microchannels to enhance heat transfer in heat exchangers, the momentum equation, rarely seen in previous modeling efforts, is included here to capture potentially significant pressure drops. The expansion valve and compressor are modeled as static components. The accumulator is modeled to regulate the active refrigeration charge of the system and to provide just enough heat to the outflow of the evaporator such that the inflow of the compressor is always saturated vapor. Based on the steady-state model, the static system design issues include determining the total refrigerant charge of the system to accommodate the varying operation conditions, sizing of the compressor and accumulator, and finding the optimal operation condition for given incoming heat flux to optimize the Coefficient of Performance (COP) while satisfying the CHF and other constraints. The steady-state model will be validated on a testbed currently in construction. The testbed consists of a reciprocating compressor with variable frequency drive, a plate condenser, a heated accumulator (tank with electric heater), three evaporators with immersed electrically controlled heaters, and one electronic expansion valve for each evaporator.
Assessment of Loss Correlations for Performance Prediction of Low Reaction Gas Turbine Stages
Authors: Benini Ernesto , Boscolo Giovanni , Garavello Andrea
Published: August 2009

In spite of the remarkable advances in the field of the Computational Fluid Dynamics, algebraic models built upon empirical loss and deviation correlations are still one of the most reliable and effective tools to predict the performance of gas turbine stages with reasonable accuracy, especially when low-reaction, multi-stage architectures are considered. This paper deals with a comparison among some of the most popular loss correlations used by gas turbine manufacturers; such comparison is performed on a two-stage low-reaction turbine for which detailed experimental data are available. An overall assessment on the validity of loss correlations is carried out to help the designer/analyst using the most accurate model when both on- and off-design are to be carried out.
Optimal Control of a Quasi-Linearized On Demand All Wheel Drive System
Authors: Reyhart Delon , Anwar Sohel
Published: August 2009

This paper presents an optimal algorithm to enhance the performance of an On-demand All Wheel Drive (ODAWD) vehicle by traction improvement through regulation of wheel slip. A “Minimum Fuel Problem” is developed with a cost function minimizing the slip error and the control action which is the ratio of the torque transmitted to the non driven wheels (rear wheels) to the total torque from engine. A simplified vehicle model (bicycle model) is used for the derivation and the system produces a Two Point Boundary Value Problem (TPBVP) once the Hamiltonian is formed and Pontryagin minimum Principle is used. An iterative algorithm based on the “Shooting Method” is then used to arrive at the optimal control action. The proposed controller optimally reduces the wheel slip error by engaging and dynamically controlling a hydraulic clutch which transmits the optimal torque to the rear wheels, thus reducing the vehicle longitudinal slip and enhancing vehicle traction. The controller was simulated in two phases where the first phase was an open loop simulation for a desired vehicle speed profile and the second phase, a closed loop system where the controller was integrated on a validated 14 degree-of-freedom detailed vehicle model in SIMULINK. The two phased simulation results provide high promise of the controller performance on low friction coefficient surfaces with enhanced traction and reduced vehicle longitudinal slip in an acceleration event.
Battery Disconnect Devices Related to Vehicle Safety
Authors: Cope Cam
Published: August 2009

In many vehicles, the largest electrical cable, located between the battery and the starter/alternator, is not fused and has limited mechanical protection. Being generally located in the front of the engine compartment, this cable poses a serious fire risk in cases of a crash, collision, or rollover. Vehicle deformation during a collision or rollover can damage the insulation of electrical cables and ground the wires. The high current caused by short circuits can produce elevated temperatures as well as electrical sparks or arcing that can ignite the cable’s insulation, ignite released flammable liquids or vapors, and can ignite nearby plastic components inside the engine compartment. Circuit protection devices are designed to disconnect the main power supply (battery) to cables and other electrical components, thereby reducing the occurrence of such fires. This paper reviews these devices and reports on the test results of a pyrotechnically driven safety switch engineered by Delphi.