bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on Boiling Heat Transfer and Critical Heat Flux in Mist Cooling: Effect of Droplet Size on Heat Transfer Characteristics
Authors: Ohtake Hiroyasu , Tanaki Tomoyasu , Koizumi Yasuo
Published: April 2008

Boiling heat transfer and critical heat flux—CHF—in mist cooling were investigated experimentally and analytically. Especially, the heat transfer in the mist cooling was examined focusing on the effects of droplet size and droplet velocity on the heat transfer characteristics. Steady state experiments of heat transfer were conducted using a pure copper cylinder and mist flow of water-air at room temperature. Liquid flow rate was 0.3, 0.9, 1.8, 4 and 8 l/hr, respectively; each air flow rate on normal condition was 0, 40, 75 and 120 lN/min. Furthermore, liquid mass flux on the heater surface for each experimental condition was measured by using a cylinder with a scale and the same diameter as the heater. Distribution of air velocity, average velocity of droplets and average diameter of droplets were measured by using a fine Pitot tube, laser doppler anemometry and immersion method, respectively. Three correlations of the mist cooling rate for non-boiling, evaporation of droplets and evaporation of the liquid film were developed by using the measured liquid mass flux, characteristic droplet velocity and wall superheat. A CHF model was presented by focusing on maximum evaporation rate of the liquid mass flux on a heater. A droplet evaporation model was proposed by using the transient heat conduction in a sphere. Finally, three dimensionless correlations for the mist cooling were presented.
Modeling the Effects of Interstitial Fluid Flow on a Single Osteocyte and Its Processes
Authors: Anderson Eric J. , Kaliyamoorthy Sathya , Knothe Tate Melissa L.
Published: April 2008

In order to understand the manner in which local changes in mechanical environment are translated into cellular activity underlying tissue level bone adaptation, there is a need to explore fluid flow regimes at small scales such as the osteocyte. Recent developments provide impetus to model periosteocytic flow using computational fluid dynamics. In building this model, the local effects of fluid flow on the osteocyte cell body and its processes were analyzed. For each model, fluid flow was induced via a pressure gradient, and the CFD calculated, based on the Navier-Stokes equations, the shear stress at the cell-fluid interface and radial stress, acting normal to the cell surface. Based on the model, the osteocyte cell body is exposed primarily to effects of hydrodynamic pressure and the cell processes are exposed primarily to shear and radial stress, with highest stress gradients at sites where the process and the cell body intersect and where two cell processes join at the gap junction. Hence, this model simulates subcellular effects of fluid flow and suggests, for the first time to our knowledge, major differences in modes of loading between the domain of the cell body and that of the cell process.
Robotic Enhancement of Human Motor Learning Based on Computational Modeling of Neural Adaptation
Authors: Reinkensmeyer David J. , Liu Jiayin , Emken Jeremy L.
Published: April 2008

Robotic devices could potentially retrain movement following neurologic injuries such as stroke and spinal cord injury, or train surgeons or athletes to make skillful movements. However, the optimal forms of robot assistance for enhancing human motor learning remain unknown. Here we present a model of motor learning in which the nervous system learns to move by adjusting motor commands in proportion to trajectory errors. We then provide experimental evidence that motor adaptation can be accelerated by transiently increasing trajectory errors, based on identification of such a motor learning model. We also demonstrate how a robotic training algorithm that mimics the adaptive features of human motor learning could theoretically improve movement recovery following a neurologic injury. Such a robotic training algorithm can limit movement errors while allowing the nervous system to learn an internal model of its altered dynamic environment.
Integrating Advanced Composite Materials Into the Chassis of a Sports Car
Authors: Osborn Christopher J. , Kennedy John M.
Published: April 2008

This work evaluated the feasibility of replacing the current stamped-steel floor-pan bulkhead assembly (FBA) of a popular street car with one made of fiber reinforced polymer matrix composite material. To evaluate the feasibility, a finite element model was constructed which incorporated much of the midsection of the vehicle’s chassis. Each part of the chassis section assembly was modeled, meshed, and constrained such that the actual physical assembly relations were upheld. Shell elements were used to model the FBA, and brick and tetrahedron elements modeled the surrounding chassis. Six loading cases were considered: a torsion case, a bending case, and four seat load cases. The chosen composite consisted of an intermediate modulus fiber (AS4) and a typical thermal-set epoxy (3501-6). Four laminate stacking sequences were studied: two quasi-isotropic laminates, a zero-dominated laminate, and a symmetric laminate. A sandwich laminate case was also studied, which utilized quasi-isotropic face-sheets and an isotropic foam core. For comparison a steel case was also simulated. The overall result of the model showed that the sandwich case proved to be superior with the smallest displacements and stresses while reducing weight. The overall weight saving was an astonishing 3% of total vehicle weight which represents a significant savings for an automobile. Based on the results it was determined that the replacement of the steel FBA with a composite FBA is feasible.
Impact Damage Monitoring in Composite Plates
Authors: Shih Frank J. , Banerjee Sauvik , Mal Ajit K.
Published: April 2008

This paper is concerned with the real-time detection of internal damage in composite structural components during impact using the far-field surface motion generated by these events. Impact tests are carried out on graphite epoxy composite plates using an instrumented impact testing system. Contact force and surface motion are measured at several locations on the plate surface. The far-field surface motions, both flexural and extensional waves in the composite plate, are modeled using both approximate and exact solution methods. Postimpact test were performed to determine the extent of internal damage caused by the impact load. Further research on the detection method can lead to the development of a viable impact monitoring system for composite aerospace structures using distributed sensors.
Innovative Design of Secondary Emergency Egress Systems for Railroad Locomotives
Authors: Parida Basant K. , Kidd W. John , Punwani Swamidas
Published: April 2008

In a locomotive cab structural damage due to collision, derailment or rollover may often block the normal egress routes. These situations require suitable emergency egress systems that provide access both from interior by the crew and from exterior by the rescue team. After incorporation of a removable roof hatch as the primary egress system, a removable windshield and emergency hinge release of the rear door were selected as potential secondary emergency egress alternatives. Simple innovative concepts and cost-effective hardware systems have been developed at Foster-Miller laboratories and installed on mockup assemblies to provide viable solutions to the above two secondary egress systems. Proof of concept demonstration and functionality evaluation were successfully carried out. This paper presents the salient design features and functional evaluation of these novel emergency egress concepts. Feasibility of incorporating these secondary egress systems into new railroad locomotive cab design is briefly discussed.
Parallel Computation of a Mixed Convection Problem Using Fully-Coupled and Segregated Algorithms
Authors: Darbandi Masoud , Banaeizadeh Araz , Schneider Gerry E.
Published: April 2008

In this work, parallel solution of the Navier-Stokes equations for a mixed convection heat problem is achieved using a finite-element-based finite-volume method in fully coupled and semi coupled algorithms. A major drawback with the implicit methods is the need for solving the huge set of linear algebraic equations in large scale problems. The current parallel computation is developed on distributed memory machines. The matrix decomposition and solution are carried out using PETSc library. In the fully coupled algorithm, there is a 36-diagonal global matrix for the two-dimensional governing equations. In order to reduce the computational time, the matrix is suitably broken in several sub-matrices and they are subsequently solved in a segregated manner. This approach results in four 9-diagonal matrices. Different sparse solver algorithms are utilized to solve a mixed natural-forced convection problem using either fully-coupled or semi-coupled algorithms. The performance of the solvers are then investigated in solving on a distributed computing environment. The study shows that the iteration run time considerably decreases although the overall run time of the fully coupled algorithm still looks better.
Utilizing Multimedia Tools to Create Virtual Laboratory Experiments in an Introduction to Materials Course
Authors: Workman-Germann Jamie
Published: April 2008

Work is currently being done using multimedia tools to create virtual laboratory experiments for the Introduction to Materials course (MET 141) at Indiana University Purdue University at Indianapolis (IUPUI). These efforts are part of a larger project to incorporate the entire class; lecture, laboratory, homework, exams, and quizzes into an online environment. Video, audio, data capture and analysis, hardware, and software tools are being utilized and developed to create this new method of performing and analyzing laboratory experiments. The foundation for this project was created during the 2001–2002 school year. During that time, a CD-ROM laboratory supplement was developed to accompany the lab manual used in the Introduction to Materials course. The CD-ROM combined video, audio, text, and graphics to help students understand the procedures and equipment being used in the experiments. With this start, the idea of converting the entire course into a distance-learning format was formed. While many courses are delivered in a distance-learning format, incorporating laboratory experiments in the same manner can present several new challenges. This paper will detail the development of this project, the tools used to create the virtual experiments, and give additional details on the materials created for this course.
Evaluation of Machine-Vision Based Profile Measurements for Rolling Railcar Wheels
Authors: Robeda James , Morgan Richard
Published: April 2008

In an effort to increase the number of wheels with measured profile parameters and reduce the number of condemnable wheels in service, machine vision-based wayside inspection systems are being developed to “virtually” gage all wheels of passing trains. In 2003, Transportation Technology Center, Inc. (TTCI), a wholly owned subsidiary of the Association of American Railroads (AAR), evaluated a pair of these wheel profile monitoring systems from two different vendors. Wheel-related expenses (inspection, maintenance, and replacement) make up about 37 percent of annual car maintenance costs. A significant portion of these expenses is directly related to maintenance actions associated with worn wheels. The primary indicators of worn wheels are wheel profile parameters that reach condemnable limits imposed by industry maintenance standards. These parameters include flange thickness, flange height, rim thickness, and tread hollow (hollow-worn wheels). To monitor profile parameters, inspectors attempt to visually check each wheel on inbound and outbound trains. They also measure wheel profile parameter values with steel gages on about 5 percent of the wheels annually. Each system TTCI evaluated used a different method to measure wheel profiles and determine the four primary parameters of interest. One system used lasers to highlight the wheel profile, and the other used high intensity strobes to take a picture of the wheel. Both systems used video frame capture technology and proprietary algorithms to analyze the data and calculate profile parameters. Both systems were installed at wayside locations at the Federal Railroad Administration’s Transportation Technology Center (TTC), Pueblo, Colorado. The systems were set up and evaluated over a period of several months. For each system evaluation, a test consist was assembled and run by the system at various speeds and lighting conditions. The profiles for test wheels were measured with a MiniProf® profilometer, and the four primary profile parameters were determined for each wheel prior to testing. Both systems were used during the tests to measure the wheel profiles and associated profile parameters. Through subsequent analysis, the system-derived parameters were compared to MiniProf parameter values for each test wheel to determine the tested system measurement accuracy. Both systems were found to be capable of delivering measurement accuracies of greater than 90 percent for three of the four parameters.
A Study on the Thermal Management of the Electronic Parts and Systems
Authors: Teng Jyh-Tong , Tsang Shih-Cheng , Chen Jiunn-Shyang , Fung Tien-Juinn
Published: April 2008

The rapid developments of computer industry and semiconductor processes lead to high component density, high-energy dissipation, and compact volume of the electronic components in systems. Those are especially true for the high-energy density of the CPUs, resulting in high temperature rise for the electronic chips. To preserve the life span of the integrated circuits and to ensure their proper functions, it is necessary to develop proper means for evaluating the related thermal management in order to effectively dissipate the energy released from these electronic parts and systems. This project used Icepak 4.0, developed by Fluent, to determine thermal-fluidic behaviors of the notebook computer, desktop computer, and switch power supply, under an environmental temperature of 35°C. In addition, parametric studies were carried out to evaluate the distribution of temperature inside the systems under investigation and the effectiveness of overall thermal management for the systems. Icepak uses the unstructured grid generation technique for the three-dimensional modeling of the electronic components and systems. With the computational fluid dynamics (CFD) solver employed by Fluent and using the finite volume method, Icepak simulates the flow and temperature fields inside the system or component of concern. Parametric studies — including the positions for venting, the locations for the cooling fans, the directions of flow for the fans (either by blowing or suction), and the number of fins used for heat dissipation — were carried out to determine the effectiveness of the thermal management designs of the desktop computer, notebook computer, and switch power supply under an environment temperature of 35 °C. Results of this study indicated that the peak component temperatures for the three systems under study are 84 °C, 80 °C, and 81 °C, respectively, while the maximum allowable temperatures suggested by the manufacturers of these three items are 85 °C, 90 °C, and 85 °C, respectively.
Adaptive Input Estimation Methods for High Bandwidth Microgyros
Authors: Fan M. , Feng Z. C. , Chellaboina V.
Published: April 2008

The vibratory microgyro senses the angular motion by detecting the Coriolis force acting on a vibratory structure when the supporting frame is undergoing angular motion. Two unique circumstances arise. First, the input to the governing equation of motion is a product of a time periodic function and the angular input. Consequently, the detection of the angular motion involves a demodulation process. Second, force actuators are required to generate the “energizing” vibratory motion; however, force actuators that can be implemented through microfabrication mostly have very small force output. Therefore, mechanical resonance is used to achieve desired amplitude in the driven-mode. These special circumstances lead to poor sensor dynamic characteristics such as the narrow bandwidth. In this paper, we present adaptive input estimation methods to achieve high bandwidth of microgyros. Specifically, we present an adaptive observer-based technique to estimate the angular motion by providing the Coriolis force as the input to the adaptive observer. In this paper, we consider two methods, namely, the open-loop method and the closed-loop method. While the closed-loop method can allow for uncertainties in the parameters it requires an additional actuator when compared to the open-loop method. The results of these techniques will be compared with that of the demodulation input estimation method.
An Improved Lattice Boltzmann Method for Steady Fluid Flows
Authors: Velivelli Aditya C. , Bryden Kenneth M.
Published: April 2008

The use of the lattice Boltzmann method in computational fluid dynamics has been steadily increasing. The highly local nature of lattice Boltzmann computations have allowed for easy cache optimization and parallelization. This bestows the lattice Boltzmann method with considerable superiority in computational performance over traditional finite difference methods for solving unsteady flow problems. When solving steady flow problems, the explicit nature of the lattice Boltzmann discretization limits the time step size. The time step size is limited by the Courant-Friedrichs-Lewy (CFL) condition and local gradients in the solution, the latter limitation being more extreme. This paper describes a novel explicit discretization for the lattice Boltzmann method that can perform simulations with larger time step sizes. The new algorithm is applid to the steady Burger’s equation, uux = μ(uxx + uyy), which is a nonlinear partial differential equation containing both convection and diffusion terms. A comparison between the original lattice Boltzmann method and the new algorithm is performed with regard to time for computation and accuracy.
Entrance Length of Low Reynolds Number Flow in Microchannel
Authors: Lee Sang-Youp , Jang Jaesung , Wereley Steve T.
Published: April 2008

The entrance lengths in rectangular microchannels with planar reservoirs, geometries typically produced with microfabrication techniques, have been investigated in the low Reynolds number range, 1 < ReD < 100. Two microchannels having the complementary aspect ratios (H/W) of 2.75 and 0.37 are fabricated and tested. The hydraulic diameters of two microchannels are ~370 μm and ~56.4 μm. μPIV is used to measure the velocity profiles and the entrance lengths are found from the curve fitted centerline velocity growth. The entrance lengths in the channels with planar upstream reservoirs are found to be significantly different from those with infinite upstream reservoirs.
Fabrication of Ultra Thick Ferromagnetic Structures in Silicon
Authors: Jones Debbie G. , Pisano Albert P.
Published: April 2008

A novel fabrication process is presented to create ultra thick ferromagnetic structures in silicon. The structures are fabricated by electroforming NiFe into silicon templates patterned with deep reactive ion etching (DRIE). Thin films are deposited into photoresist molds for characterization of an electroplating cell. Results show that electroplated films with a saturation magnetization above 1.6 tesla and compositions of approximately 50/50 NiFe can be obtained through agitation of the electrolyte. Scanning electron microscopy (SEM) images show that NiFe structures embedded in a 500 μm thick silicon wafer are realized and the roughening of the mold sidewalls during the DRIE aids in adhesion of the NiFe to the silicon.
A Shell Formulation to Model the Three-Dimensional Deformation Response of Woven Fabrics
Authors: King Michael J. , Socrate Simona
Published: April 2008

We capture the out-of-plane mechanical response of woven fabrics through a nonlinear anisotropic shell implementation of a continuum constitutive model. For the membrane response, we rely on a previously developed model for the in-plane behavior of woven fabrics. This planar model captured both the macroscopic response and the interactions of the yarns at the structural level, but was limited to two dimensions. The two-dimensional model is here extended to capture three-dimensional modes of deformations through a shell formulation. We assume that the effects of out-of-plane bending and shear on the established in-plane behavior are negligible; however, we do consider the effects that in-plane deformation and the resulting evolution of the fabric structure have on the out-of-plane response. For example, the formulation accounts for the evolving anisotropy of the out-of-plane bending behavior, which reflects the changing orientations of the yarn families within the fabric surface. This three-dimensional model permits the analysis of complex modes of fabric deformation such as wrinkling at large shear strains or transverse identation. We present experiments and detailed finite element analyses used to understand and characterize the out-of-plane responses of the fabric, including bending and twist, and we discuss the underlying physical phenomena that control these responses. Finally, we compare model predictions of complex loading modes to experimental findings.
CFD Studies on Burner Secondary Air Flow
Authors: Purimetla Anil K. , Cui Jie , Idem Stephen , Munukutla Sastry
Published: April 2008

In many fossil power plants operating today, there is insufficient means to assure the proper balancing of the secondary airflows between the individual burners of wall-fired units in addition there is a problem of dust deposition on the floor. This mismatch leads to decreased boiler efficiency and increased emissions. In this study, a Computational Fluid Dynamics (CFD) modeling of a fossil power plant wind box scale model is performed using the commercial software CFX5.6. The model solves the three dimensional Reynolds averaged Navier-Stokes equations with the K-epsilon turbulence model. The CFD results are validated by the experimental data taken from a 1/8th scale model of a wall fired fossil unit. Simulations under various flow conditions are obtained to identify the optimum design in terms of the equalization of the secondary airflow through the burners.
Permeability of Cortical Bone to Large Molecular Weight Proteins Under Diffusive and Load-Induced Convective Transport Mechanisms
Authors: Patel R. B. , Tami A. E. , Knothe Tate M. L.
Published: April 2008

The composition of bone is 75% mineral and organic components and 25% fluid; yet until the past 30 years, the fluid component of bone had been ignored [1]. The idea of load induced fluid flow via pressure gradients was hypothesized for the first time by Piekarski et al in his application of Biot’s poroelasticity theory [2]. Poroelasticity theory mathematically describes the sponge-like behavior of bone: when bone is squeezed(loaded) fluid will be induced to flow. However although the concept of load induced fluid flow is well accepted in the orhopedic field, our study is the first to provide quantitative evidence of the effect of load induced fluid on macromolecular transport. Hence the goals of this study include observing permeability of large molecular weight tracers in cortical bone, ii.) comparing molecular size dependence on tracer permeability in cortical bone, and iii.) comparing effects of convective and diffusive transport mechanisms on permeability.
Fixed Order Positive Real Control Using Genetic Algorithms
Authors: Chellaboina VijaySekhar , Ranga Mithun K.
Published: April 2008

In this paper, we present a case study of several examples involving optimal positive real control design for positive real plants. Specifically, we apply genetic algorithms to obtain low order optimal control designs with and without the strict positive real constraint on the compensator. This study shows that genetic search strategy is an effective approach for designing low order optimal controllers with complex constraints such as strict positive realness of the compensator. Furthermore, the examples studied also shed some new light on optimal positive real control problems.
3-Dimensional Electrodes for Microbatteries
Authors: Chamran Fardad , Yeh Yuting , Dunn Bruce , Kim Chang-Jin
Published: April 2008

A general micro-molding approach based on MEMS fabrication has been introduced to fabricate 3-dimensional (3-D) electrodes for microbatteries. Batteries based on 3-D microstructure are shown to offer significant advantages (e.g., small areal footprint and short diffusion lengths) in comparison to the conventional 2-D thin film batteries. In this paper, microelectrodes for Li-ion and Ni-Zn batteries have been fabricated and tested
Numerical and Experimental Study of Pressure Drop Reduction in a Power Plant Stack
Authors: Lakshmiraju Murthy , Cui Jie , Idem Stephen , Munukutla Sastry
Published: April 2008

As governmental regulations on the emission of the power industry became more restrictive, many power plants operating today experience severe problems. The fans that handle the flow through the stack, that were originally designed to handle a certain maximum flow rate, are now required to handle even higher flow rates due to the introduction of emission control devices. In this study, computational fluid dynamics (CFD) and experimental studies have been carried out on the scale model of a stack to identify means for pressure drop reduction. The CFD model was constructed using the commercial software CFX-5.6. The model solves the Reynolds averaged Navier-Stokes equation with Shear-Stress turbulence model (SST) and the CFD results are validated by data taken from the scale model. Baffles of different orientation have been installed in the stack under different flow conditions. Both numerical and experimental results confirm that adding baffles can reduce the pressure drop in a stack significantly. Thus, with minimum effort, power plants can keep running the stacks at a higher flow rate.
A Split-Flux Model for Phonon Transport Near Hotspots
Authors: Sinha S. , Pop E. , Goodson K. E.
Published: April 2008

Intense electron-phonon scattering near the peak electric field in a semiconductor device results in nanometer-scale phonon hotspots with power densities on the order of 1 W/μm3. To study the impact of the hotspot on phonon transport, we solve the phonon Boltzmann transport equation under the relaxation time approximation to yield the departure from equilibrium amongst phonon modes. The departure function is split into two contributions: one arising from the far-from-equilibrium emitted phonons and the other from the near-equilibrium thermal phonons. The model predictions are compared with existing data on ballistic phonon transport in silicon. Computations of transient and steady state phonon occupation numbers for a device geometry show the predominance of longitudinal optical phonons for electric fields on the order of 1 MV/m. Due to the low group velocity of these modes, there is an energy stagnation at the hotspot which results in an excess temperature rise of about 13% for a 90 nm bulk silicon device. During device switching, emitted phonons have sufficient time to relax completely when the duty cycle is 30% on a period of 100 ps.
A Microfabrication Process for Polymer Microchannel With Embedded Vertical Electrodes for Microfluidic Applications
Authors: Wang Lisen , Lee Abraham P.
Published: April 2008

In this paper, we will report the use of SU-8 to make an all polymer microchannel with vertical platinum electrodes, which is fabricated by a multilayer SU-8 coating and electroplating process. The first layer is spun to increase the adhesion of the channel and the substrate, the second layer is the microchannel structure. The third layer is spun on another substrate and then capped onto the second channel layer to make a completely sealed SU-8 Channel. The PDMS substrate we used to spin the third layer on is flexible to enable conformably sealing to the microchannel substrate. A process that makes vertical microelectrodes inside the channels is also developed, which makes it a powerful process to make a complicate microfluidic network.
Analytical and Experimental Investigation of Laser-Nanosphere Interaction for Nanoscale Surface Modification
Authors: Heltzel Alex J. , Theppakuttai Senthil , Howell John R. , Chen Shaochen
Published: April 2008

An investigation on the features created on a silicon substrate by the irradiation of nanospheres on the substrate surface with a pulsed laser is presented. Silica nanospheres of diameter on the order of laser wavelength are deposited on silicon substrate and irradiated with a pulsed Nd: YAG laser. As a result, nanofeatures are created on the surface by the melting and resolidification of silicon. The experiment is repeated for different laser wavelengths (532 nm, and 355 nm), sphere diameters (640 nm, and 1.76 μm) and laser energies, and the effect of each of these parameters on the features created are studied. An analytical model based on Mie Theory complements the results. The model includes all evanescent terms and does not rely on either far field or size-parameter approximations. The predicted intensity distributions on the substrate indicate a strong near field enhancement confined to a very small area (nanometer scale). The results correlate well with the feature geometries obtained in the experiment.
Piezoelectric Modal Sensors for Two-Dimensional Structures
Authors: Chou Yuan-Fang , Yang Ming-Yi
Published: April 2008

Using the orthogonal property of eigenfunctions, piezoelectric modal sensors for one-dimensional members were created by shaping electrode patterns proportional to modal strains. However, it is not easy to apply the same concept to two-dimensional structures due to the difficulty in implementing location weight needed for signals. Therefore, nonlinear optimization scheme is employed in this paper to design modal sensors for two-dimensional structures. For a given electrode pattern, the signal contributed from each mode is found by integrating the corresponding free surface charges on the sensing electrode. Then the modal sensor is obtained by modifying electrode pattern to achieve required relative signal strength for different modes. Sensors that are capable to sense or filter out the signal generated by a specific mode can be developed. A two-dimensional aluminum plate coated with PZT layer is adopted as an example. Mode shapes are found with finite element analysis. Modal sensors are designed successfully and mode- reject filters are also demonstrated.
The Development of a Computer-Based Teaching Tool for Internal Combustion Engine Courses
Authors: Zeng Pin , Assanis Dennis N.
Published: April 2008

In this paper, the authors introduce the development of a computer-based internal combustion engine teaching tool for the undergraduate and professional training courses. The teaching tool simulates a SI (Spark Ignition) engine running in a testing facility. The physical and mathematical models, as well as the control strategies that govern the engine’s operation are embedded within the tool. It works as a virtual engine, and at the same time it displays and explains the physics behind each working process of the engine using graphical and animation features. The teaching tool serves as an assistant for the instructor of the internal combustion engine course. It provides the students with a visual and interactive environment to learn the physical processes of the internal combustion engines faster and easier.
Segmented Binary Control of Shape Memory Alloy Actuators — Feedforward Servo Control
Authors: Selden Brian , Cho Kyu-Jin , Asada H. Harry
Published: April 2008

A new approach to the design and control of shape memory alloy (SMA) actuators, called Segmented Binary Control (SBC), is extended from previous work. The transient response of SBC is examined and is discovered to be inadequate in real time servo control because of significant latency times. A dramatic improvement is shown using a feedforward method in which a predetermined path is known and appropriate actions are calculated beforehand. In addition, this feedforward servo control of SMA is accomplished with only internal local feedback loops and no global feedback of position.
The Development, Implementation, and Changes in Engineering Courses, at a Large State University, Sponsored Through an NSF Coalition
Authors: Griffin Richard , Svec Courtney , Caso Rita , Froyd Jeff
Published: April 2008

Since 1988, with support from the Foundation Coalition, one of the Engineering Education Coalitions supported by the National Science Foundation, the Dwight Look College of Engineering has invested considerable time and energy in renewing its sophomore engineering courses. The excitement which accompanies the receipt of a large NSF funded program results in an initial enthusiasm and energy that is contagious for both faculty and students. The initial results of a “pilot” program are almost always improved course content, better student attitudes, better retention, etc. However, when the rush wears off and the new courses have to be institutionalized, what happens? What can be learned from consistent, long-term efforts to assess and improve the sophomore engineering science courses? This paper focuses on the introductory sophomore materials science course, Principles of Materials Engineering (ENGR 213). Using data collected from students and evaluation of student performance as measured by course grades and a standardized test, the authors will examine what has been learned since the inception of the course.
Micro Pulsatile Jets for Thrust Optimization
Authors: Finley Tiffany J. , Mohseni Kamran
Published: April 2008

Thrust optimization of micro-synthetic pulsatile jets is studied. Cylindrical cavities with a small circular orifice at one end, and a vibrating diaphragm at the other are used for thrust generation. The governing parameters are identified and the tradeoffs between electrostatic, piezoelectric, and electromagnetic actuation methods are investigated. Optimization of the micro jets requires a solution that gives maximum diaphragm displacement while minimizing voltage. The size of the orifice diameter is chosen to maintain a formation number of 4, at which the length of an expelled slug of fluid from the exit orifice is four times the diameter of orifice. This relationship maximizes the circulation and impulse in the leading vortex rings generated by the actuator. To examine the effects of cavity dimensions, a number of actuators are constructed out of aluminum with various cavity diameter, cavity height, and orifice diameters. Piezoelectric disks bonded to brass shims are used for actuation. The jets are tested in air at various actuation voltage and wave-shape functions. Maximum thrust generation is achieved at the resonant frequency of the cavity. Hot wire anemometry is used to further characterize the jet flow field. An investigation into electrostatic, piezoelectric, and electromagnetic diaphragm actuation methods revealed that electromagnetic actuation provides the maximum diaphragm displacement using a constant voltage.
CFD Investigation of an Oscillating Structure Placed in a Liquid Medium
Authors: Srinivasan Vedanth , Salazar Abraham J. , Saito Kozo
Published: April 2008

Investigation of flow structure in a system comprising of an oscillating structure immersed in a liquid medium has been extensively studied by researchers. Their applications in industrial processing are generally based on the non-linear effects produced by finite amplitude pressure variations created by the oscillating structure. The high frequency oscillations of the structure placed in the liquid medium creates a rapid series of alternating contractions and expansions pressure fields. These amplitudes associated with the high frequency oscillations are accompanied by a series of phenomena such as highly intensified radiation pressure, heat generation, acoustic streaming, agitation, cavitation, interface instabilities and friction, diffusion and mechanical rupture. The high frequency oscillations impart the translation momentum into the liquid during the first half of the cycle and absorb the same in the remainder of the cycle. This paper investigates the cavitation phenomenon, defined as creation of vapor pockets when the liquid pressure falls below the vaporization pressure of the liquid, associated with high frequency oscillations of a structure placed in a liquid medium. This has been performed using CFD analysis of such high frequency oscillations of a structure in a liquid medium using commercially available software. The grids used in the simulations are resolved fine enough to capture the physics of the flow and numerically stabilize the simulation. This transient simulation reveals high pressure gradients close to the oscillating structure due to their rapid motion, which is a function of frequency and amplitude of the vibration. The inception of cavitation phenomenon is associated with highly non-linear vapor bubble dynamics. Discussions on the velocity contours and the distribution of phases in the flow have been carried out in detail with highlights on the bubble dynamics. The use of CFD in simulating fluid structure interaction as in the case above, help us understand the nonlinear effects originating from the generation of high intensity pressure driven fields and their interaction with the medium.
Mechanics of Multi-Walled Carbon Nanotubes Under Uniaxial Compression
Authors: Waters Julie F. , Riester Laura , Jouzi Maryam , Guduru Pradeep R. , Xu J. M.
Published: April 2008

We report shell buckling instabilities observed experimentally in multi-walled carbon nanotubes subjected to uniaxial compression and interpret the results using insights from elasticity theory and molecular dynamics simulations. Uniform hexagonal arrays of vertically-oriented, freestanding multi-walled carbon nanotubes were grown in a self-assembled, highly-ordered nanoporous alumina matrix and then placed under uniaxial compression using a nanoindenter. Both flat and spherical nanoindenter tips were used to compress many nanotubes at once, and individual nanotube behavior could be deduced from the bulk force-vs.-displacement data by using the uniformity of the nanotube arrays and the geometry of the tips. Buckling instabilities are evident in the measured force-vs.-displacement behavior. A consideration of thin shell elasticity theory and molecular dynamics models provides guidelines for interpreting the experimental results. Excellent agreement is found between the experimentally measured critical buckling loads and those predicted by theory.
Simulation of Empirical Correlations Between Temperatures and Blood Perfusion During Heating Using a Temperature-Dependent Blood Perfusion Model
Authors: Chen Cuiye , Roemer Robert B.
Published: April 2008

This study applies a recently developed temperature-dependent blood perfusion model (TDBPM) coupled with a modified, one-dimensional Pennes bioheat transfer equation to predict the blood perfusion and temperature responses to step function microwave heating applied in the in vivo experiments performed by Sekins’ et al. [1] on human thigh muscle. The TDBPM model links the perfusion increase to the tissue temperature elevation based on physiological mechanisms underlying this temperature-blood-perfusion change phenomenon, i.e., a pharmacokinetic compartmental model. This physiology-based model avoids using ad hoc time delays between blood perfusion increases and tissue temperature elevations as done in previous efforts. It also includes a mechanism that produces the threshold temperature for blood flow increases that has been observed in vivo. In our recent study [2], the TDBPM model was used to simulate both the constant temperature water bath heating used in the in vivo experiments on rat leg muscle performed by Song et al. [3], and the step function microwave heating applied in the in vivo experiments on canine thigh muscle performed by Roemer et al. [4]. The blood perfusion rates predicted by the model are compared with those in vivo experimental data obtained in rat muscle and human muscle and good agreement was obtained. The TDBPM provides a possible explanation to the biochemical and biophysical origins of the relationships between temperature and blood flow that observed in rat muscle and human muscle. The physiology-based TDBPM is a simple, generic model of muscle blood flow responses of different animals to different heating conditions, which provides the type of fundamental information needed for the design of methods to thermally control blood flow in medical applications.
Computing Phase Change Front and Temperature Histories in Stochastic Media
Authors: Emery A. F. , Bardot D.
Published: April 2008

Although many phase change problems involve uncertain or stochastic properties, the computation of temperatures and front position is typically based on known properties. This paper considers the effect of uncertain or noisy properties, particularly the latent heat, and investigates the application of perturbation techniques, polynomial chaos, and Wick products in computing the temperatures and front position. These methods are dependent upon formulating the problem in a manner in which the uncertain properties appear in the differential equations and are thus limited in their applicability.
Optimized Design, Fabrication and Characterization of PZT Unimorph Microactuators for Deformable Mirrors
Authors: Hishinuma Yoshikazu , Yang Eui-Hyeok , Cheng Jian-Gong , Trolier-McKinstry Susan
Published: April 2008

This paper describes an optimization of PZT unimorph membrane microactuators in view of their application to deformable mirrors (DMs). PZT unimorph actuators of various electrode designs, silicon membrane thickness, and membrane sizes were fabricated and characterized. A mathematical model was developed to further assist the optimization of membrane thickness and electrode sizes, and excellent agreement with experiment was obtained. For a 2.5mm diameter actuator with 2μm thick PZT and 15μm thick silicon membrane, the measured vertical stroke was 5.4μm at 50V. The measured resonant frequency of the unimorph actuator was 47kHz, far exceeding the bandwidth requirement of most DMs (~1kHz).
Analytical Solution for BGA Modules Under Thermal/Mechanical Loading
Authors: Qian Zhengfang , Tomase Joe
Published: April 2008

This paper presents an advanced approach to obtain analytical solutions for BGA-type package or module under both thermal loading and mechanical bending. The theoretical framework is based on two-dimensional theory of plate pure bending. Solder joint shear strain distribution has been derived analytically. Specifically, the joint strain has been correlated with measured board strain. The approach developed and analytical solutions obtained are very useful for rapid component qualification in terms of solder joint reliability.
Modeling Strategy in Evaluating Thermal Performance of an RF Module for Wireless Communications
Authors: Chiriac Victor , Lee Tien-Yu Tom
Published: April 2008

A detailed study was performed to evaluate the thermal performance of RF Modules and to identify meaningful correlations between specific design characteristics and the power dissipation needed to satisfy the required thermal budget under various critical operating conditions. The investigation focuses on the thermal characteristics of the RF module die layout and transistor cells, and on the thermal impact of the metallic air bridges connecting the load cells to the collector pads/vias to the overall thermal performance of the RF module. A first-pass modeling predicts higher temperatures than IR measurement, by ~20–30%. The addition of the die layout air bridges connecting the load cells in the detailed simulation models leads to a predicted air bridge temperature of ~9% higher than the IR measurement. Additional modeling reveals that between the open (not encapsulated) and the closed module, the die peak temperature differs by less than 3 °C, most of the heat being dissipated through the substrate and board to the heat stage. Thus, the impact of mold compound is insignificant. For a closed module, the mold compound helps dissipate the heat, so the die temperature is slightly cooler than for the open module (<<3°C). This suggests that the die peak temperature measured in an open module can be adjusted (by subtracting 2–3°C) to represent the die temperature in a closed module.
A Microfluidic Tensiometer
Authors: Mayer Hans C. , Anna Shelley L.
Published: April 2008

Recent theoretical predictions indicate that a shift in surfactant transport mechanism from diffusion controlled to kinetically controlled occurs at highly curved interfaces where the length scale is on the same order as feature sizes in microfluidic devices. At present, experimental evidence of this shift in transport mechanism is lacking and this is due to the limitations on degree of interface curvature imposed by traditional methods of surface tension measurement. We show that the measurement of dynamic surface tension is possible at highly curved interfaces using a microfluidic tensiometer that utilizes glass micropipettes to control curvature dimension. Comparison of dynamic surface tension data from our microfluidic tensiometer with data obtained from traditional techniques will validate the theoretical arguments reported, and will improve understanding of two phase flows in microfluidic devices.
Thermal Conductivity of Ultra Thin Single Crystal Silicon Layers: Part I — Experimental Measurements at Room and Cryogenic Temperatures
Authors: Liu Wenjun , Asheghi Mehdi
Published: April 2008

Self-heating in deep submicron transistors (e.g., Silicon-on-insulator and strained-Si) and thermal engineering of many nanoscale devices such as nanocalorimeters and high-density thermomechanical data storage are strongly influenced by thermal conduction in ultra-thin silicon layers. The lateral thermal conductivity of single-crystal silicon layers of thicknesses 20 and 100 nm at temperatures between 30 and 300 K was measured using Joule heating and electrical-resistance thermometry in suspended microfabricated structures. In general, a large reduction in thermal conductivity resulting from phonon-boundary scattering, particularly at low temperatures, is observed. Thermal conductivity of the 20 nm thick silicon layer at room temperature is nearly 22 W m−1K−1, compared to the bulk value, 148 W m−1K−1. The predictions of the classical thermal conductivity theory that accounts for the reduced phonon mean free paths based on a solution of the Boltzmann transport equation along a layer agrees well with the experimental results.
Effect of Cooled and Hot EGR on Performance and Emission Characteristics of S-I Engine
Authors: Salehi-Khojin Amin , Pirouzpanah Vahab , Mahinfalah Mohammad , Weinzierd Steve
Published: April 2008

Exhaust gas recirculation (EGR) is the most effective and practical method for reduction of NOx emission in Internal Combustion Engines. However, improper application of EGR in the engine causes higher power loss, excessive specific fuel consumption (SFC) and an increase in the concentration of other pollutants. For this reason, the amount and temperature of EGR must be tailored for each engine in order to get optimum performance and emission results. In this research work, after comparison of hot and cooled EGR for an S-I engine, pollutant behavior has also been studied around Dew point temperature of exhaust gasses. Results indicate that the pollutant’s behavior depend on the EGR mixture (amount and temperature), thermal capacity of EGR and amount of water condensation. For example, when the amount of EGR is 10% there is a higher reduction of NOx with ignorable power loss. Results also showed that the optimum temperature in experimental conditions and in this particular engine is about 340–343 Kelvin, which is just above the Dew point of exhaust gases.