bluuebunny/crossref_metadata_2025 huggingface dataset:
The Stacked Amplified Thermomechanical In-Plane Microactuator (StATIM)
Authors: Wilcox Daniel L. , Howell Larry L. , Lyon Scott
Published: April 2008

A compact large-displacement staged thermal actuator, the Stacked Amplified Thermomechanical In-plane Microactuator (StATIM), is introduced in this paper. The StATIM has a large ratio of output displacement to device area, while still providing significant output force. The device utilizes the multi-layer, planarized nature of Sandia National Laboratories’ SUMMiT V surface micromachining process. The StATIM is derived from the Amplified Thermomechanical In-plane Microactuator, or ATIM, which is described briefly. Two configurations of the StATIM fabricated in the SUMMiT V process are presented. The first device has a footprint of 0.40 mm2 and an output displacement of 39.3 μm, for a displacement density of 97.8 μm/mm2. The second, with a footprint of 0.26 mm2, has a 43.9 μm displacement and a displacement density of 169.8 μm/mm2. The fully compliant nature of the StATIM results in reliable, low-friction performance. The output displacement and force of the StATIM are sufficient for a wide range of applications, and its compact design preserves die space.
A Compressible Fluid Power Dynamic Model of a Liquid Propellant Powered Rifle
Authors: Adams Mark , Barth Eric J.
Published: April 2008

This paper presents a dynamic model of the interior ballistics of an experimental liquid propellant-powered rifle. The liquid propellant-powered rifle described utilizes a misture of Hydroxyl Ammonium Nitrate (HAN) and hydrocarbon fuel to replace gunpowder typically used in such firearms. The motivation for such a development is to discard the need for a shell casing whereby carrying only propellant and bullets will reduce both the mass and volume per shot carried by the soldier. A first-principles dynamic model of the interior ballistics is derived as a compressible fluid power problem with the chemical liberation of heat within the chamber modeled via a condensed-phase reaction rate law. The model is used to predict the overall performance in terms of ballistic kinetic energy as well as draw design insight regarding the role of friction, chamber geometry, and the profile of chamber pressure with respect to time. Simulation results are presented as well as preliminary experimental results from a proof-of concept device.
Development of an Advanced High Temperature Heat Exchanger Design for Hydrogen Production
Authors: Subramanian Sundaresan , Akberove Roald , Chen Yitung , Hechanova Anthony E. , De Losier Clayton Ray
Published: April 2008

This paper deals with the development of an advanced high temperature heat exchanger design for hydrogen production by the sulfur iodine thermochemical cycle from advanced nuclear reactor concepts. The offset strip-fin hybrid plate type compact heat exchanger concept is chosen, and the material of manufacture is the liquid silicon impregnated carbon composite. The offset strip-fin is chosen as a method of heat transfer enhancement due to the boundary layer restart mechanism between the fins that has a direct effect on enhancing heat transfer. The effect of the fin thickness, pitch in flow direction, and the aspect ratio of the offset fins on the flow field and heat transfer are studied in 2-D using Computational Fluid Dynamics (CFD) techniques, and the results are then compared with the analytical calculation results. The preprocessor GAMBIT is used to create a computational mesh, and the CFD software package FLUENT, that is based on the finite volume method is used to produce numerical results. Proper dimensions of the strip fins need to be chosen in order to have an optimized heat transfer enhancement coupled with a reduced pressure drop. The study is conducted with helium gas as the working fluid with varied of Reynolds number values. The flow and heat transfer is considered to become periodically fully developed after a certain entrance length hence numerical simulations were performed using periodic boundary conditions. Two-dimensional numerical simulations were also performed for the whole length of the heat exchanger which has 37 such periodic modules. Comparison study was performed between the cases of fins with rectangular and curved geometry. Attempt has also been made in order to validate the coefficient of fin thickness (Cfin) value using CFD techniques, which has been used in the existing empirical correlations to suit this type of heat exchanger geometry. The model developed in this paper is used to investigate the heat exchanger design parameters in order to find an optimal design.
Dynamics of a Coulomb Damped Helical Spring: A Finite Element Approach
Authors: Rashidi Majid , Budhabhatti Sachin P. , Frater John L.
Published: April 2008

This work presents the results of a mathematical modeling to study the dynamic behavior of a helical spring under a periodic excitation induced by a rotating cam. The spring is sleeved over a mandrel; thereby it is further subjected to a Coulomb damping force as it oscillates. Helical springs expand radially when they are compressed. The effect of this radial expansion is included in the mathematical model. Standard wave equation that includes variable Coulomb damping was used to examine the vibratory behavior of the spring. Numerical solution to the no-friction, constant-friction, and varying-friction forces were obtained from the wave equation, using Explicit Finite Difference method. Finite Element was used to model the radial expansion of the spring to determine the variations of the Coulomb friction force. The spring response to the prescribed cam excitation, under the variable Coulomb friction force, was found not to be significantly different from that of a previously assumed constant friction force, for the cases that were studied in this work. In case of postulating a variable damping force the residual vibrations of spring loops are slightly higher than of the constant damping force.
Performance Analysis of an IMM-Based Obstacle Detection Algorithm
Authors: Kang Yeonsik , Caveney Derek S. , Hedrick J. K.
Published: April 2008

In this paper, two approaches for obstacle detection and position estimation are presented. One is an algorithm based on M out of N detection logic and the other is an algorithm based on the probabilistic Interacting Multiple Model (IMM) method. The M out of N threshold-based algorithm declares that there is an obstacle present if it gets M validated measurements out of N consecutive measurements. IMM algorithm runs two different models in parallel, each based on a different hypothesis. One model assumes that there is an obstacle present while the other model assumes that there is no obstacle present in the sensor field of view. The performances of the two algorithms are compared based on their false alarm rate and detection speed. At first, Monte Carlo simulations are performed using only the false measurements to determine the thresholds for each method that generate a similar number of false detections. Using these thresholds, the detection speed of each method is compared and it is shown that the IMM-based algorithm is superior to the M out of N logic-based algorithm.
Evaluation of Sub-Zero and Residence Times After Continuous Versus Multiple Intermittent Cryogen Spray Cooling Exposure on Human Skin Phantom
Authors: Ramirez-San-Juan Julio C. , Tuqan Alia T. , Kelly Kristen M. , Nelson J. Stuart , Aguilar Guillermo
Published: April 2008

Cryogen spray cooling (CSC) is used to minimize the risk of epidermal damage during various laser dermatologic surgeries. However, as the application of single or multiple cryogen spurts becomes available on some commercial lasers devices, it is necessary to determine the optimal CSC parameters for different laser surgeries. The objective of this study was to measure the time the sprayed surface of a human skin phantom (HSP) remains below water freezing temperature 0°C, referred to as subzero time (ts), and below the cryogen boiling temperature −26°C, referred to as residence time (tr), as well as the minimum surface temperature (Tmin) and the time at which Tmin occurs (tTmin) for two HSP-initial temperatures (20 °C and 70 °C) during and after the application of single (SCS) and multiple cryogen spurts (MCS). For this propose, a HSP was used to measure ts, tr, Tmin, and tTmin for nine sequences: one SCS of ΔtT = TCT = 40 ms; four MCS sequences, all adding to a ΔtT of 40 ms but with different TCT up to 110 ms and, finally; four SCS that matched the TCT of the four MCS sequences, but lead to different ΔtT. Our results show that the differences between SCS and MCS sequences with the same TCT are negligible for all variables measured (ts, tr, Tmin, tTmin). Moreover, in this interval (40 ms ≤ TCT ≤ 110 ms), this variables show a remarkable linear dependence with the TCT.
Modifying the Heat Transfer Characteristics of a Residential Oven to Promote Favorable Baking Results
Authors: Breen Mark A. , Schneider Judith A. , Walters D. Keith , Chamra Louay
Published: April 2008

Baking has historically been a trial and error method of cooking. Little research has been conducted to determine the heat transfer characteristics that promote good baking results, and previous research studies have focused on commercial baking applications and the quantities of radiation, convection and conduction that are delivered to the food after a favorable baking process has been defined. The objective of the present work is to experimentally explore the feasibility of modifying a residential oven to mimic commercial baking products. The first step in the solution process was to define the thermo-physical conditions that promote favorable baking results. Next, by defining the current residential oven’s baking characteristics through experimentation, the optimal geometric and material properties were determined. Experimentation included single thermocouple testing, multiple thermocouple testing, and ‘bake’ testing. It was found that a stacked wall structure created by layering various materials in a sandwich like configuration, placed between the lower resistive heating element and the oven cavity, improved the heat transfer characteristics of the oven.
Numerical Modeling of Unsteady Gas Flow Around the Projectile in the Light Gas Gun
Authors: Ponyavin Valery , Chen Yitung , Pepper Darrell W. , Hsieh Hsuan-Tsung
Published: April 2008

In this study, an attempt to calculate the characteristics of gas flow around a projectile during the motion of the projectile in the Joint Actinide Shock Physics Experimental Research (JASPER) light-gas gun is undertaken. The flow is considered as axisymmetric, nonstationary, nonisothermal, compressible, and turbulent. For calculating the flow around the projectile, the finite volume method was employed. A comparison between two launch tube exit geometries was made. The first case was standard muzzle geometry, where the wall of the bore and the outer surface of the launch tube form a 90 degree angle. The second case included a 26.6 degree bevel transition from the wall of the bore to the outer surface of the launch tube. The results of the calculations are represented in figures depicting the flow at different moments of time. The figures show the fields of velocity, pressure and density, as well as the appearance of shock waves inside the geometry. Some comparisons with calculations of the same problem but using finite-element method were made. The obtained results can be further used for optimization JASPER geometry. The results also can be used for calculating the gun barrels for the strength and the oscillatory stability. In our future study we will couple structural analysis of the gun barrel material with the gas dynamic calculation of motion of the projectile in the gun barrel with the use of advanced computational methods.
Control of the Mechanical Property on Machined Surface by a New Tool for Cutting-Burnishing Combined Process
Authors: Segawa Toshiaki , Sasahara Hiroyuki , Tsutsumi Masaomi
Published: April 2008

We have developed a new tool that is called as the “Compressive Residual Stress Generating cutter” (CRSG cutter)[1]. The CRSG cutter can generate effective compressive residual stress within the machined surface concurrently with the milling process. It is expected to improve mechanical properties such as the fatigue life and the resistance to stress corrosion cracking. The purpose of this study is to investigate the possibility of controlling the residual stress state within the machined surface with varying the machining conditions using the CRSG cutter. It was shown that the quantity of the plastic deformation of the machined surface affects the residual stress. The setting of the machining conditions with the CRSG cutter can control the plastic deformation quantity. The cross feed width can change plastic deformation on the machined surface that is the key factor in order to control the residual stress within the machined surface.
Steady-State Energy Transfer of a Semi-Active Suspension Under Hybrid Control
Authors: Boggs Christopher M. , Goncalves Fernando D. , Ahmadian Mehdi
Published: April 2008

Magnetorheological (MR) fluids are often characterized by their field-dependent yield stress. Upon the activation of a magnetic field, the fluid has the ability to change from a fluid state to a semi-solid state in milliseconds. The field-dependent yield stress and the fluid’s fast response time make MR fluid an attractive technology for many applications. One such application that has gained considerable attention is in MR fluid dampers. The real-time control possibilities make MR dampers attractive alternatives to conventional viscous dampers. In comparing passive dampers with MR dampers, an equivalent viscous damping coefficient is often found from the energy dissipated by the MR damper with a fixed current applied to the damper. In contrast, this study investigates energy dissipation of the MR damper under a semi-active hybrid control policy. Hybrid control is a linear combination of skyhook and groundhook control. This study investigates the system energy under steady-state conditions at three frequencies, and how the system energy varies with varying contributions from skyhook and groundhook. A quarter-car rig was used to evaluate the dynamics of the hybrid suspension using an MR damper. Previous studies have shown that hybrid control can offer advantages to both the sprung and unsprung masses; however the relationship between energy dissipation and performance is not clear. In this study, we compare control policy performance to several energy-based measures. Results indicate that there is a strong correlation between sprung mass RMS acceleration and unsprung mass RMS acceleration to several of the energy-based measures.
Using Musculoskeletal Properties to Develop a “Normalized Potential Moment Contribution Index” for Individual Arm Muscles
Authors: Hunt Betsy V. , Gonzalez Roger V.
Published: April 2008

Musculoskeletal models serve as research tools to study the effect of individual muscle forces across multiple joints. Models are already used as diagnostic tools for treatment and rehabilitation such as in tendon transfer surgeries [1,2].
Process Analysis and Simulation of the Solar Thermo-Chemical Hydrogen Generation
Authors: Khan Mohammad Arif , Chen Yitung , Boehm Robert , Hsieh Sean
Published: April 2008

A process analysis and simulation model has been developed in the framework of the process simulator ASPEN PLUSTM in order to produce solar thermo-chemical hydrogen. Hydrogen is an environmentally attractive transportation fuel that has the potential to replace fossil fuels. Chemical mass balance, conversion rate, operating temperature and pressure are comparatively assessed for a wide range of hydrogen production processes, including processes which are hydrocarbon based (methane cracking and steam methane reforming), non-hydrocarbon based (water electrolysis) and integrated process (combined hydrocarbon and non-hydrocarbon based processes). The process analysis and simulation also provide a quantitative tool for insight and understanding the process. The project collaborators among General Atomics, NREL, SNL, UCB and UNLV have done the selection screening from all available thermochemical processes. Then a process analysis and simulation model by using ASPEN PLUS has been built up with the help of detailed reactions, additional data, reactor dimensions, rate laws, parameter values and specific reaction rate and equilibrium constants to find an economically feasible and environmentally suitable process to generate pure hydrogen gas which can be used in fuel cell and automobiles.
Pulsatile Flow and Deformation in Curved Stenosis Models of Arterial Disease
Authors: Kobayashi Shunichi , Fukuzawa Yutaka , Ayama Yuuki , Morikawa Hirohisa , Tang Dalin , Ku David N.
Published: April 2008

Blood flow through the constricted area of a severe stenosis is similar to that through a venturi or flow nozzle. In the contraction section, the blood can accelerate to high speed. In this situation, the external pressure may be greater than the internal fluid pressure, and the artery could collapse. This collapse may be important in the development of atherosclerotic plaque fracture and subsequent thrombosis or distal embolization. We have developed an experimental model that closely approximates the arterial disease situation and performed steady and pulsatile flow experiments, and the characteristics of flow and compression concerned with the geometry and compliance of the model were discussed [1]. But we had not focused on the coronary stenosis. As the first step to develop the experimental model of coronary stenosis, the curved stenosis model was made. This paper was to examine the influence of curvature and stretch of the stenosis model on flow and collapse under pulsatile flow.
Modeling of Convective Drying of Trehalose Solution
Authors: Chen Bingyan , Bhowmick Sankha
Published: April 2008

Prediction of trehalose solution desiccation is required for understanding the protocol for preservation of biological materials, including mammalian cells[1]. The purpose of present work is to develop a numerical model for simulating the drying process of thin trehalose solution films by forced and natural convection. Changes in concentration profile in the solution during the drying process, and the influence of the transport properties of trehalose/water system on the drying kinetics were evaluated using this model. The end point of the simulation was reached by the formation of glass at the surface.
Experimental Characterization and Simulation of Three Dimensional Plastic Deformation Induced by Microscale Laser Shock Peening
Authors: Chen Hongqiang , Kysar Jeffrey W. , Yao Y. Lawrence , Wang Youneng
Published: April 2008

Different experimental techniques and 3D FEM simulations are employed to characterize and analyze the three dimensional plastic deformation and residual strain/stress distribution for single crystal Aluminum under microscale laser shock peening assuming finite geometry. Single pulse shock peening at individual locations was studied. X-ray micro-diffraction techniques based on a synchrotron light source affords micron scale spatial resolution and is used to measure the residual stress spatial distribution along different crystalline directions on the shocked surface. Crystal lattice rotation due to plastic deformation is also measured with electron backscatter diffraction (EBSD). The result is experimentally quantified and compared with the simulation result obtained from FEM analysis. The influence of the finite size effect, crystalline orientation are investigated using single crystal plasticity in FEM analysis. The result of the 3D simulations of a single shock peened indentation are compared with the FEM results for a shocked line under 2D plain strain deformation assumption. The prediction of overall character of the deformation and lattice rotation fields in three dimensions will lay the ground work for practical application of μLSP.
Human Vocal Tract Modeling and Geometric Parameterization
Authors: Tameem Hussain Z. , Mehta Bhavin V.
Published: April 2008

This investigation uses a multi disciplinary approach to standardize a non-invasive method for measuring human vocal tract morphology. A series of Magnetic Resonance Imaging (MRI) scans are performed on the subject’s vocal tract and a detailed three-dimensional model is created through image processing and computer modeling. This information is compared with the vocal tract measurements obtained with Eccovision Acoustic Pharyngometer, in order to establish the accuracy of the instrument. The model is then used to develop other specific models through parametric modeling. This method is useful in creating solid models with limited geometrical information and helps researchers study the human vocal tract changes due to aging and degenerative diseases.
Effects of Swelling Conditions on the Compressive Properties of Nucleus Pulposus From Bovine Intervertebral Discs
Authors: Korda David T. , Perie Delphine , Iatridis James C.
Published: April 2008

The intervertebral disc provides flexibility and load support for the spine. It consists of two main regions; the outer annulus fibrosus which is a highly organized collagen matrix and the inner nucleus pulposus which (in a healthy disc) is a proteoglycan rich gelatinous material. The predominant mode of loading on the intervertebral disc is axial compression, which generates hydrostatic pressures within the disc. The high water content of the nucleus plays a major role in supporting these loads. With age and degeneration, the water content of the nucleus changes, and is believed to significantly impact its ability to bear load. The purpose of this study therefore, was to define the effects of swelling conditions (which affect disc hydration) on the material properties of the disc under compressive loading.
Induced Flow and Motions of Fine Solid Particles in Water With Irradiation of YAG Laser
Authors: Watanabe Kazunori , Ota Masahiro , Takikawa Shigeru
Published: April 2008

Induced flow and motions of fine solid particles with irradiation of YAG laser beam in water droplet, often called laser trapping, are discussed in this paper. While the absorption of the near infrared laser beam into glass plate and water can be generally small as they have high transmissivity, the absorption should be effective for the high intensity of laser beam by being focused under a microscope. A micro-sized heat spot could be produced by the absorption of the laser beam, and heat transfer occurred from the heated glass plate to the water droplet with the particles. The local flow was induced by the effect of the heat transfer. The force of the flow exerting the particles was so great that the radiation pressure on the particle would not be effective any more. The local flow caused the motions of the particles far from the laser beam, e.g., rotating, clustering and unexpected motions induced by a produced bubble on the bottom of the glass plate. These interesting phenomena were observed under microscope and recorded by a VHS connecting to a CCD camera. The particles were rotated with the irradiation of the laser beam, the revolution was too high compared to the VHS capture rate. Also one of these interesting phenomena was that the scattered particles in the water droplet were clustered around the focal spot of the laser beam. The theoretical backgrounds on the induced flow and the motion of the fine particles are also discussed.
Deformation Behaviors of Aluminum Pipes Compressed in the Direction of Pipe Axis
Authors: Kurosawa Takahiro , Naoi Hisashi
Published: April 2008

Recently there are strong demands for reduction of carbon dioxide exhausted from cars on the viewpoint of global warming prevention. And, improvement in safety of cars is needed with increase of its speed. The main method to satisfy the former demand is to reduce the mass of cars, and main procedure to solve the latter subjects is to protect lives of crews in the head-on collision of automobiles. Lightweight members to absorb the energy at the collision have been installed in the engine room in order to satisfy abovementioned both demands. The purpose of this study is to optimize cross sectional size and shape of the aluminum pipe as the lightweight members for energy absorption.(1)(2)(3) In this report, the specimens are aluminum pipes whose shapes are hexagon and octagon. And ribs that connect one corner to opposite corner of the specimens in order to increase the energy absorption at the collision are installed inside the hexagonal and octagonal pipes. We also prepared the other specimens where the ribs are removed from the pipes. These specimens are compressed in the direction of the pipe axis, and deformation behaviors are observed. We investigate the effect of cross sectional shape on the performance of energy absorption, being measured from the force-displacement diagram obtained by compressive test. The results are as follows. (1) The plastic deformation by compressive test of the aluminum pipes starts from initiations machined at the vicinity of the pipe end then the folds results one after another in the pipes. (2) When we start to compress the pipe from which the ribs are removed, compressive force reaches at its maximum value, thereafter the force rapidly and greatly drops with large plastic deformation. And the force moves repeatedly up and down at its lower values with the progress of folds. (3) When we start to compress the pipes in which the ribs are installed, the drop of the force is smaller than that of the pipes without ribs and the force moves repeatedly up and down at its higher values. (4) The amounts of energy absorption at the octagonal pipe are bigger than those of the hexagonal pipe. And, the amounts of energy absorption of the pipes in which the ribs are installed are bigger than those of the pipes from which the ribs are removed.
Swirling Flow of a Viscoelastic Fluid With Free Surface: Part I — Experimental Analysis of Vortex Motion by PIV
Authors: Wei Jinjia , Li Fengchen , Yu Bo , Kawaguchi Yasuo
Published: April 2008

The swirling flows of water and CTAC (cetyltrimethyl ammonium chloride) surfactant solutions in an open cylindrical container with a rotating disc at the bottom were experimentally investigated by use of a double-pulsed PIV (particle image velocimetry) system. The mass concentrations of CTAC solutions were in the range of 50–1000 ppm, and the Reynolds number based on angular velocity, kinematic viscosity of water and radius of rotating disc was fixed at 4.3 × 104. The aspect ratio of the height of the liquid filled into the cylindrical vessel to the radius of the vessel was set to 1.0. The secondary flow patterns in the meridional plane and the tangential velocities were obtained. The flow pattern in the meridional plane for water at the present high Reynolds number differed greatly from that at low Reynolds numbers, and an inertia-driven vortex was pushed to the corner between the free surface and the cylindrical wall by a counter-rotating vortex caused by vortex breakdown. For the 1000-ppm surfactant solution flow, the inertia-driven vortex located at the corner between the bottom and the cylindrical wall whereas an elasticity-driven reverse vortex governed the majority of the flow field. The radial distributions of the time-averaged tangential velocities also differed for water and surfactant solutions. The rotation of the fluid caused a deformation of the free surface with a dip at the center. The dip was largest for the water case and decreased with increasing surfactant concentration.
Numerical Simulation of the Interfacial Growth of the Stratified Wavy Two-Phase Flow in the Horizontal Rectangular Channel
Authors: Ebihara Ken-ichi , Watanabe Tadashi
Published: April 2008

Two-phase flow is one of the important phenomena that are found in nuclear reactors. It is required for the design and the safe operation of nuclear reactors to understand and predict the two-phase flow phenomenon by numerical analyses. This paper describes the numerical simulation of the interfacial growth of the stratified wavy two-phase flow in the horizontal rectangular channel. This flow is the cocurrent flow separated by gravity and a fundamental flow pattern of two-phase flow. The influence of the channel width upon the growth of the interfacial wave was evaluated by carrying out several simulations for the different channel width. The numerical simulation model adopted in this paper is a one-component two-phase fluid model of the lattice Boltzmann method. This model has been developed and utilized for numerical analyses of two-phase flow in recent years because it has the capability of simulating spontaneous phenomena of the interface between phases. The wave growth was observed and the dimensionless numbers that characterize the two-phase flow state were measured during the computations. The relation between the wave growth and the dimensionless numbers, which were obtained as the computational results was compared with that in the flow pattern map proposed on the basis of theoretical consideration by Taitel and Dukler. It was verified in the case of the wide channel width that the simulated relation was in agreement with that in the theoretical flow pattern map. It was shown that the narrower the channel width became, the more mass flow rate of the rare phase the interfacial growth needed and the obtained relation deviated from that in the flow pattern map.
Experimental and Numerical Evaluation of SnAgCu and SnPb Solders Using a MicroBGA Under Accelerated Temperature Cycling Conditions
Authors: Rodgers Bryan , Punch Jeff , Ryan Claire , Waldron Finbarr , Floyd Liam
Published: April 2008

A comparative evaluation of the leading lead-free solder candidate (95.5Sn3.8Ag0.7Cu) and traditional tin-lead solder (63Sn37Pb) under thermal cycling conditions was carried out. A test vehicle consisting of four daisy chained 10×10 array 0.8mm pitch plastic micro ball grid arrays (microBGA) mounted on an 8-layer FR4 printed wiring board was designed. The board finish was organic solder preservative (OSP) for the lead-free devices and hot air solder levelled (HASL) in the case of the eutectic devices. An event detector was used to monitor the continuity of each daisy chain during accelerated temperature cycling, where the test vehicles were cycled with a ramp rate of approximately 3°C per minute from −40°C to 125°C, with 10-minute dwells and a total cycle time of 2 hours 10 minutes. Results to date plotted using a Weibull distribution indicate that the SnAgCu solder is more reliable under these conditions. Experiments were also carried out on large-scale lead-free solder specimens to determine the parameters required for the Anand viscoplasticity model. The Anand model was then implemented in finite element analysis using ANSYS®, where the submodelling technique was employed to determine the viscoplastic work per thermal cycle for each solder joint along the package diagonal. Schubert’s fatigue life model was used to predict the number of cycles to failure of each joint, although it should be noted that the necessary model parameters for the may need to be calibrated. Results indicate that the joint under the die edge is likely to fail first and that the SnAgCu solder is more fatigue resistant. The numerical predictions underestimate the fatigue life in both cases.
Machine Tool Chatter and Surface Quality in Milling Processes
Authors: Insperger Tama´s , Gradisek Janez , Kalveram Martin , Ste´pa´n Ga´bor , Weinert Klaus , Govekar Edvard
Published: April 2008

Two degree of freedom model of milling process is investigated. The governing equation of motion is decomposed into two parts: an ordinary differential equation describing the stable periodic motion of the tool and a delay-differential equation describing chatter. Stability chart is derived by using semi-discretization method for the delay-differential equation corresponding to the chatter motion. The stable periodic motion of the tool and the associated surface location error are obtained by a conventional solution technique of ordinary differential equations. Stability chart and surface location error are determined for milling process. It is shown that at spindle speeds, where high depths of cut are available through stable machining, the surface location error is large. The phase portrait of the tool is also analyzed for different spindle speeds. Theoretical predictions are qualitatively confirmed by experiments.
Modelling the Ageing Behavior of New Environmentally Friendly Fluids Using Correlation Analysis and Neural Networks
Authors: Go¨hler Oliver-Carlos , Schmidt Martin , Murrenhoff Hubertus
Published: April 2008

One main focus of the development of a new, environmentally friendly biodegradable fluid is put on the oxidative stability of the fluid. A rotary bomb test apparatus (RBT) is used to investigate the ageing of the fluid. A correlation analysis of test results shows that the degree of saturation of the used fatty acids plays an important role in the ageing process. The influence of temperature and different distributions of fatty acids on the operating time of the fluid is simulated by means of a neural network. The paper presents the state of the current work.
Ultrasonic Wave Interaction for NDE of Inhomogeneous Prestress in Materials
Authors: Ravasoo Arvi
Published: April 2008

The problem of ultrasonic nondestructive evaluation (NDE) of inhomogeneous prestress field is studied theoretically for an elastic material and plane strain. The nonlinear effects of ultrasonic wave propagation and interaction are shown to be additional sources of information for NDE. A model problem of simultaneous propagation of two ultrasonic longitudinal waves in physically nonlinear elastic material undergoing two-parametric prestress state is solved. The corresponding analytical solution is derived. Results of numerical simulations lead to the conclusion that it is possible to propose an algorithm for NDE of the inhomogeneous prestress field on the basis of the recorded data of boundary oscillations evoked by simultaneous propagation of two ultrasonic waves. The analysis of the oscillating boundary profiles permits to determine qualitatively the presence of prestress in the material and to distinguish special cases of the prestress state, for example, to evaluate quantitatively the parameters of the prestress.
Proprioception Evaluation of Patients Undergoing Anterior Shoulder Stabilization
Authors: Nowak Michael , Joseph Mick , Nissen Carl , Asaki Takafumi
Published: April 2008

This paper presents the initial data from the first clinical usage of a 2nd generation device to measure proprioception of the shoulder or knee. The device was used to evaluate the surgical stabilization of subjects with anterior shoulder instability. Two types of shoulder proprioception were evaluated: Threshold to Detection of Passive Motion (TTDPM) and Reproduction of Passive Position (RPP). Data is presented for 12 subjects 1 year post-surgery. The data demonstrated that the involved limb TTDPM and RPP approached that of the uninvolved limb, and that the values improved as the shoulder was rotated upwards. Both results point to the efficacy of the repair method and the ability of the device to evaluate proprioception.
Determination of Anisotropic Absorption and Extinction Coefficients of a Tomographed Real Porous Medium
Authors: Zeghondy Barbar , Taine Jean , Iacona Estelle
Published: April 2008

The direct general identification method of the radiative properties of high porosity media, developed and validated for virtual statistically isotropic media in [1], has been applied to a real statistically anisotropic medium. This medium has a transparent fluid phase and an opaque gray diffuse solid phase. It is modelled by a semi-transparent equivalent medium characterized by extinction and absorption coefficients β and κ. These quantities are directly determined from the morphology data obtained by X-ray tomography and from the absorptivity of the solid phase. The application of this approach to a mullite sample has established that β and κ are homogeneous but depend on direction. This last feature has to be accounted for by a radiative transfer method for this type of medium.
Predicting Hydraulic Valve Flow Forces Using CFD
Authors: Yang Roger
Published: April 2008

This paper presents a method of using Computational Fluid Dynamics (CFD) computer simulations for hydraulic oil flow inside hydraulic valves. The main objective is to study “flow forces” - the hydraulic forces induced by oil flow on the actuators of hydraulic valves, with the aim of minimizing their effects or use their effects towards improving valve performance. Integration of solved pressure distribution and velocity fields from CFD simulation solutions over related valve component surface areas is employed to obtain the desirable flow forces and viscous flow wall drag effect has also been included. Different valve metering geometry has been simulated using a commercially available CFD software program. The hydraulic oil flow inside valves is assumed steady-state and normally in a turbulent mode. The complete simulation procedure is presented from parametric geometry creation with a 3-D solid CAD through final post-processing of results. Simulation results of several hydraulic valve applications, both spool valves and poppet valves, are included. Tests have been performed to measure flow force and oil flow rates. CFD results are compared to experimental results, in some cases, with good correlation.
Independent and Dependent Scattering for Semitransparent Media Containing Bubbles
Authors: Randrianalisoa Jaona H. , Baillis Dominique
Published: April 2008

The objective of this present work is to provide a new approach for the radiative characteristics computation of semitransparent media containing spherical bubbles. The bubble size is considred much larger than the wavelength. First, previous models from the literature based on the independent theory are reviewed and established in the Geometric optic limit. Second, a predictive model using the Monte Carlo method is developed. The results obtained from the independent theory models and the Monte Carlo approach are compared. In addition, by varying the bubbles volume fraction, we investigate the limit of validity of the independent theory in such medium.
Design and Characterization of a Rotary Actuated Hot Gas Servovalve
Authors: Fite Kevin B. , Mitchell Jason E. , Barth Eric J. , Goldfarb Michael
Published: April 2008

This paper describes the design and characterization of a unique three-way hot gas servovalve designed for the flow control of steam at 235°C. The valve incorporates a pressure-balanced rotary spool coupled to a servomotor/gearbox/encoder combination to achieve high-bandwidth and high-precision operation, and also incorporates several design elements in order to accommodate the high temperatures associated with the working fluid. The spool and sleeve entail geometries of low aspect ratio and are mechanically isolated from the manifold with Viton O-rings to ensure uniform thermal expansion and contraction. To thermally isolate the DC motor, a PEEK motor mount is used to connect the motor housing with the valve manifold. Additionally, the motor shaft is coupled to the spool with an Oldham coupling that incorporates a PEEK center disk to further insulate the motor from the high temperature spool. The desing is presented, along with experimental data that characterizes the dynamic performance and flow characteristics of the valve.
Simulation of Thermionic Emission From a Quantum Wire Using the Non-Equilibrium Green’s Function Method
Authors: Liu Yang , Raza Hassan , Fisher Timothy S.
Published: April 2008

Even though the theory of thermionic emission of electrons from bulk metals is well understood, discrete electron energy states exist when material length scales approach one nanometer, and the traditional treatment must be revised. This paper presents a theoretical development of thermionic emission from nanoscale materials. A general expression for the emitted current as a function of field, temperature and work function is established for a quantum wire. The results differ from those of 3-D bulk materials. Simulation of thermionic emission from a quantum wire is achieved with the non-equilibrium Green’s function (NEGF) method, which includes relevant mesocopic physics and has been widely applied to transport problems in nanostructures. The NEGF approach provides a powerful solution to modeling problems when interfacial transport effects between bulk and confined conductors are important. Both the theoretical and simulated results indicate a higher current density and thus higher energy conversion capacity than that of a bulk material with the same work function. Thus the quantum confined materials may provide a method for improving the capacity of direct energy conversion devices and systems.
Exact Modal Analysis and Its Applications to Transverse Vibrations of Axially Travelling Strings
Authors: Wang Yuefang , Ren Xichun , Huang Lihua
Published: April 2008

The Hamiltonian dynamics based on symplectic mathematics is used to solve the transverse vibration of axially traveling strings. The Hamiltonian function is formulated and the canonical equation is developed. The exact modal functions are obtained through a linear eigenvalue analysis, and the symplectic-type orthogonality conditions of modes are derived. The expansion theorem is applied to solve the displacement response to free and forced vibrations. Unlike traditional modes of transporting strings, the exact modal functions do not suffer divergence instability, or singularity, at the critical speed, and can be easily used as the base or trial functions for solving linear and nonlinear vibration.
Application of Robust Design Techniques to the Parallel Design of Engineering Systems
Authors: Mahmoud Haitham A. , Kabamba Pierre T. , Ulsoy A. Galip , Brusher Gerald A.
Published: April 2008

The problem of designing complex systems, with performance specifications from multiple disciplines, was cast within the framework of robust control design in a previous publication. In that work, the overall system design problem was decomposed into several subsystem design problems. Robust controller analysis techniques were used to determine limits on the magnitudes of the uncertain parameters that would enable the design of the subsystems to proceed in parallel. In this paper, we extend that previous work, formulate the subsystem design problems in a robust controller design framework and use nonlinear optimization to design subsystems that are robust with respect to the uncertainties arising from designing the subsystems in parallel. This requires that the uncertain parameters for a given subsystem include, in addition to its own uncertain design parameters, the design variables and outputs from other subsystems that are needed in that subsystem analysis. Incorporating the uncertainties arising from parallel subsystem design into robust controller design framework will ensure that, upon assembly of the subsystems, the system-level performance requirements are met. The results are illustrated using a simple example representing a corner-car model.
A Game Theoretic Based Scheme for Multidisciplinary Optimization With Uncertainty
Authors: Gupta Amit , Krishnamurthy K.
Published: April 2008

A game theoretic based scheme is considered in this study for multidisciplinary design optimization under uncertain conditions. The methodology developed is illustrated by considering the example of an internal combustion (IC) engine. Various game protocols are used to model the optimization process and the results obtained are compared with each other. A genetic algorithm (GA) is used as an optimization and constraining tool. Convergence, constraint handling and processing time are considered to evaluate the efficacy of the methodology developed.
Practical Structure Design and Control for Digital Clay
Authors: Zhu Haihong , Book Wayne J.
Published: April 2008

Digital Clay is a proposed novel three-dimensional computer input and output device for surface shape and haptic effects. The device consists of an array of fluidic actuators under the control of valves connected to two pressure reservoirs in a manner ultimately suitable to an implementation in MEMS technology. The challenges to build this device lie in both the kinematical structure design and the control architecture. Though it is proposed to ultimately build the actuators and control valves using MEMS technology, conventional methods are used at the current prototype stage. In this paper, several designs of the practical kinematical structure will be discussed and the proposed control architecture for the Digital Clay will be introduced.
Nonlinear Vibrations of Doubly Curved Shallow Shells
Authors: Amabili M.
Published: April 2008

Large amplitude (geometrically non-linear) vibrations of doubly curved shallow shells with rectangular boundary, simply supported at the four edges and subjected to harmonic excitation normal to the surface in the spectral neighbourhood of the fundamental mode are investigated. Two different non-linear strain-displacement relationships, from the Donnell’s and Novozhilov’s shell theories, are used to calculate the elastic strain energy. In-plane inertia and geometric imperfections are taken into account. The solution is obtained by Lagrangian approach. The non-linear equations of motion are studied by using (i) a code based on arclength continuation method that allows bifurcation analysis and (ii) direct time integration. Numerical results are compared to those available in the literature and convergence of the solution is shown. Interaction of modes having integer ratio among their natural frequencies, giving rise to internal resonances, is discussed. Shell stability under dynamic load is also investigated by using continuation method, bifurcation diagram from direct time integration and calculation of the Lyapunov exponents and Lyapunov dimension. Interesting phenomena such as (i) snap-through instability, (ii) subharmonic response, (iii) period doubling bifurcations and (iv) chaotic behavior have been observed.
A Study of Enthalpic Relaxation of Trehalose-Water Glasses
Authors: Green James , Fowler Alex , Toner Mehmet , Bhowmick Sankha
Published: April 2008

Trehalose has been shown to be an effective biostabilizer, one explanation for this is that it can easily form glass at near ambient temperatures. Enthalpic relaxation is a physical aging process that occurs in glasses held near, but below, their Tg and is an indicator of the amount of molecular mobility of a particular glass. Since molecular mobility is key to long-term storage biologics in a glassy matrix this study was developed to gain a fundamental understanding of the enthalpic relaxation kinetics of trehalose-water glasses. Through the use of DSC, enthalpic peaks were quantitatively measured for water-trehalose glasses as a function of aging time and aging temperature for three different mass percentages (Mwater/Mtrehalose%, ~0%, ~1.5%, & ~10%). From this data the total amount of relaxation and the relaxation time have been determined using the Cowie-Ferguson equation. Understanding the effects of water on enthalpic relaxation kinetics will help lead to optimized drying protocols and storage parameters.
Modeling and Control of an Electro-Hydraulic Poppet Valve
Authors: Opdenbosch Patrick , Sadegh Nader , Book Wayne J.
Published: April 2008

This paper explores the dynamic modeling of a novel two stage bidirectional poppet valve and proposes a control scheme that uses a Nodal Link Perceptron Network (NLPN). The dynamic nonlinear mathematical model of this Electro-Hydraulic Control Valve (EHCV) is based on the analysis of the interactions among its mechanical, hydraulic, and electromagnetic subsystems. A discussion on experimental approaches to determine the model parameters is included along with model validation results. Finally, the control scheme is developed by proposing that the states of the EHCV follow a set of desired states, which are calculated based upon the desired valve flow conductance coefficient KV. A simulation is presented at the end to verify the proposed control scheme.