bluuebunny/crossref_metadata_2025 huggingface dataset:
Lean Manufacturing and Cycle Time Variability Analysis for Factory Automation Using Simulation Tools
Authors: Andrecioli Ricardo , Lin Y. J.
Published: August 2009

This paper presents the influence of cycle time variation and number of kanban cards on the throughput of manufacturing cell supported by simulation tools. The ultimate goal of the work is for attaining factory automation. Based on this analysis the paper will introduce the concept of “Moving Bottleneck”. We also propose an optimization function to enable manufacturing processes optimization outcomes by employing the proposed function. The results show that the analysis performed and methodology proposed are effective tools towards lean factory manufacturing automation.
Optimal Attainment of Production Rates for a Multi-Stage Kanban Managed Production System With Time Varying Demand
Authors: Fang Yunmei , Lin Y. J.
Published: August 2009

This paper delves into the evaluation of an operation planning for a realistic multi-stage, single-product Kanban managed production system with time varying production rates and finished goods demands. The study pursued is to dynamically and systematically manipulate the production rate of each stage and the raw material orders at the first stage which are corresponding to the minimum integrated inventory costs incurred due to raw materials, finished products and work-in-process (WIP) inventories under a varying demand of finished product. Simulation results verify the effectiveness of the proposed operation planning methodology for a multistage Kanban managed production and supply chain system.
Loading and Unloading Processes in Elastic-Plastic Contact of a Rough Surface With a Flat
Authors: Sepehri Ali , Farhang Kambiz
Published: August 2009

Three dimensional elastic-plastic contact of two nominally flat rough surfaces is considered. Equations governing the shoulder-shoulder contact of asperities are derived based on the Chang, Etsion and Bogy (CEB) model of contact in which volume conservation is assumed in the plastic flow regime. Shoulder-shoulder asperity contact yields a slanted contact force consisting of both tangential (parallel to mean plane) and normal components. Each force component comprises elastic and elastic-plastic parts. Statistical summation of normal force components leads to the derivation of the normal contact force for the elastic-plastic contact akin to the CEB model. Half-plane tangential force due to elastic-plastic contact is derived through the statistical summation of tangential force component along an arbitrary tangential direction.
Comparison of High and Low Speed Rear-Impact Head and Neck Injury Risk Measures Related to Occupant Size and Vehicle Seat Strength Characteristics
Authors: Saczalski Kenneth J. , Pozzi Mark C. , Burton Joseph Lawson
Published: August 2009

This study demonstrates the use of efficient inferred statistical “factorial methods” for scientifically evaluating, with a relatively few tests, the rear-impact occupant “head and neck injury risk” performance of 2 different types of vehicle front seats, with adjustable headrests, when various size occupants are subjected to high and low impact severities. The 2 seat types studied included the stronger “belt-integrated seat” (BIS) designs, with restraints attached and having strength levels beyond 14 kN, and the more common but weaker single recliner (SR) seats, without attached restraints and having only about 3.2 kN strength. Sled-body-buck systems and full vehicle to barrier tests were run with “matched pairs” of surrogates in the 2 seat types at speed changes of 12.5 to 50 kph. Three sizes of Hybrid-III adult surrogates (i.e. 52 kg small female, 80 kg average male, and an average male surrogate ballasted to about 110 kg) were used in the evaluations. Also, some tests were run with 6 year-old Hybrid-III child surrogates located behind the front seats due to interest in potential child injury from collapsing front seats. The 2-level factorial method, combined with a biomechanical ratio comparison and a “student-t” test evaluation, were used to compare safety performance of the 2 seat designs. The resulting data analysis indicates that, in the mid to high range of rear impact severity (i.e. 20 to 50 kph), the stronger BIS seat systems tend to provide greatly improved “head-neck” protection over the weaker SR type seats for both the front seated adult occupants and rear seated children. At the low range of impact severity (i.e. 12.5 to 19 kph) there was no significant statistical difference between either seat types, except that the headrests of both could be improved.
Evaluation Methods for Linked-Course PBL in Engineering
Authors: Hunt Emily M. , Lockwood-Cooke Pamela , Kelley Judy
Published: August 2009

Problem-Based Learning (PBL) has become an increasingly popular method across disciplines in K-12 and higher education worldwide since it was first introduced to medical education in the late 1960’s. However, it has not gained significant popularity in engineering curricula due to the large time-scale needed to solve complex engineering problems. Previous work by the authors in this area has developed a method for combining problem solving opportunities on a small time scale in linked courses that culminate to solve a challenging problem that would normally take a significant amount of class time. This method of problem-based learning provides a practical application that can be used in engineering curricula. While this method has produced favorable response from both students and faculty involved, there is a need for a more comprehensive effort to develop strategies for evaluation of PBL in mathematics, science and engineering courses, both directly and indirectly. In this study, Engineering Statics, Engineering Physics, and Calculus II are linked using PBL to increase both student engagement and success. For smaller problems, group work with directed individual or interactive tasks is facilitated through teacher-guided discussions. Students who are in these linked (co-enrolled) classes work on small mathematics, physics, and engineering problems that are used to solve a challenging engineering problem. The project addresses concepts taught in class, reinforces connections among the courses, and provides real-world applications. A mixed method evaluation approach was utilized by the external evaluators, the West Texas Office of Evaluation and Research (WTER) including surveys, focus groups, and personal interviews.
Influence of Heat Treatment on Gas Metal Arc Welded Aluminum 6063 Alloy for Automotive Aluminum Spaceframe Architectures
Authors: Koganti Ramakrishna , Elliott Adrian , Zaluzec Matthew , Caliskan Ari , Joaquin Armando
Published: August 2009

An aluminum structure has many advantages over steel for automotive application, but the combination of lower weight, with high torsional stiffness and good energy management performance in crash is perhaps the most beneficial. Hybrid architectures, consisting of a combination of aluminum products including stampings, extrusions (straight and hydroformed) and castings, are becoming more common. The Ford GT represents the first Ford Motor Company hybrid aluminum spaceframe. The frame is comprised of castings, extrusions and stamped, flat and roll-bonded, panels. All structural connections between the extrusions and the castings are fusion welded with the exception of the front and rear crush structures. Ford R&AE supported the Ford GT program in the joining and assembly of the hybrid aluminum body architecture, with responsibility for the development of the Gas Metal Arc Welding (GMAW) process. Recognizing that the heat input from the GMA welding process is significant, it is necessary to understand the aluminum material properties after temperature exposure during welding. The frame is subject to further temperature exposure during manufacture during the painting operations. Additionally, those areas of the frame around the engine will be exposed to high temperatures in service. The objective of this study, in support of the Ford GT, was to evaluate the mechanical properties of GMA welded 6063-T6 extruded coupons after different heat treatments simulating the paint ovens during vehicle build and extreme engine temperatures when in service. This information was critical for use in the program Finite Element Models (FEM) developed for Noise, Vibration, and Harshness (NVH), Crash and Durability. The study was successful in showing that the tensile strength of the welded aluminum was not affected by thermal exposure for the range of different temperatures and times, chosen to represent vehicle build and in service temperature conditions. The most consistent results were obtained for tests simulating the paint bake (180 °C for 30 minutes). The ‘as welded’ and engine bay temperature exposures (24 hour at 150 °C and 200 °C) showed higher variability. The failure mode for the 24 hour exposures was in the weld, as compared to the HAZ for the other samples.
Derivation of Fractional Differential Equations for Modeling Diffusion in Porous Media of Fractal Geometry
Authors: Fomin Sergei , Chugunov Vladimir , Hashida Toshiyuki
Published: August 2009

Utilizing the double-porosity approach it is assumed that porous medium is constituted by two groups of pores in such way that major mass transport takes place mostly along the network of larger pores (group 1) and these larger (stem) pores are surrounded by the medium formed by the dead-end porous of fractal geometry (group 2). Solving analytically equation for the stem pore from the group 1 and accounting for the mass exchange with pores from the group 2, it is proved that diffusion in a stem pore should be described by the fractional differential equation. Based on this result, equation of mass flux that models non-Fickian diffusion in complex fractal medium is proposed. Applying this generalized form of mass transfer equation for modeling the contaminant transport in fractured porous aquifer leads to a fractional order differential equation, where mass exchange between blocks and fractures is modeled by the temporal fractional derivatives. This equation is solved analytically.
Simulation Study on the Control Valve in Hydraulic Operating Mechanism of the High Voltage Circuit Breaker
Authors: Liu Wei , Yang Huayong , Xu Bing , Wu Zhongyu
Published: August 2009

High voltage circuit breaker is an important interrupting device in a power system network. The operating mechanism is a key component of circuit breakers. The action of hydraulic operating mechanism in circuit breaker is different from general hydraulic mechanism for its high speed, short operating time and high pressure. In this paper, the working principle of hydraulic operating mechanism of 252kv high voltage circuit breaker is introduced. The high response speed solenoid pilot direction control valve is analyzed. The dynamic characteristic of the valve affects the performance of the hydraulic operating mechanism. Mathematical models of the valve and system have been developed. Simulations are carried out with AMESIM, hydraulic simulation software, and ANSOFT, electromagnetic simulation software. The characteristics of the operating mechanism control valve are discussed with the consideration of the influence of the geometry and environmental parameters. As the result of the research work, the simulation models and results provide the effectively theoretical guidance for the design and optimization of hydraulic operating mechanism.
Numerical Study of Laminar Fluid Flow Around Two Cubes of Arbitrary Configuration Mounted on a Surface
Authors: Eslami Mohammad , Tavakol Mohammad Mehdi , Goshtasbi Rad Ebrahim
Published: August 2009

The problem of flow field around single or multiple bluff bodies mounted on a surface is of great importance in different fields of engineering. The case of a single surface mounted cube has been studied extensively but unfortunately, little attention has been paid to the flow around two or more rectangular blocks in array. Therefore, A CFD code is developed to calculate three dimensional steady state laminar fluid flow around two cuboids of arbitrary size and configuration mounted on a surface in free stream conditions. The employed numerical scheme is finite volume and SIMPLE algorithm is used to treat pressure and velocity coupling. Results are presented for two cubes of the same size mounted on a surface for various inline and staggered arrangements. Streamlines at different planes are plotted for various combinations of the distance between the two cubes and Reynolds number. Velocity and pressure distributions are also plotted in the wake region behind the cubes. It is shown that presence of the second cube completely changes the flow field and vortical structures in comparison with the case of a single cube. Effects of the both stream-wise and spanwise distances between the two cubes and Reynolds number are also discussed.
The Synchronic Influence of the Effective Parameters on the External Surface Roughness and Changes of the External Diameter in Tube Spinning Process Using Design of Experiments and Optimizing the Process
Authors: Sharifi Tashnizi E. , Fazeli Nahrekhalaji A. R.
Published: August 2009

Tube spinning process is considered to be a very effective way for fabricating a long thick-walled part. In this research, the influences of major parameters of the thermomechanical tube spinning process such as preform thickness, percent of thickness reduction, rotational speed, feed rate, solution and aging treatment time on the external surface roughness and changes of the external diameter for fabricating of 2024 aluminum spun tubes using design of experiments is studied. The effect of the basic input parameters on the external surface roughness and changes of the external diameter was investigated synchronically by designing the experiments. After conducting the experiments, results are analyzed by variance analysis and by obtaining predicted mathematic models. Finally, by using these models and multivariate optimization, input parameters for optimum production are achieved.
Modeling and Studying the Impacts of Effective Parameters on the Parts Hardness During the Tube Spinning Process by the Design of Experiments
Authors: Fazeli Nahrkhalaji A. R. , Sharifi Tashnizi E.
Published: August 2009

The spinning process is recognized as an effective process for fabrication of thin wall cylindrical parts with precision tolerances. In this paper, the influences of major parameters of thermomechanical tube spinning process such as preform’s thickness, percentage of thickness reduction, mandrel rotational speed, feed rate, solution treatment time and aging treatment time on hardness for fabricating 2024 aluminum spun tubes using the design of experiments (DOE) are studied. Experimental data is analyzed by analysis of variance and an empirical model. It is found that, increasing the mandrel rotational speed and percentage of thickness reduction in addition to decreasing in aging treatment time causes increasing in hardness.
Influence of Track Properties on Railway Vehicles Wheel Rolling Contact Fatigue
Authors: Mehrgou Mahdi , Nasr Asghar
Published: August 2009

Track properties such as rail inclination, cant and gage width have significant effects on the shape and size of the contact area, actual rolling radius and also on the contact forces. These effects have an important role on rolling contact fatigue (RCF) which is known to be the main reason for large portion of wheel set failures and expenses. In this study the wheel/rail dynamic interaction of an Iranian railway passenger wagon under different track features are investigated through simulations using ADAMS\Rail commercial software. The calculated results regarding contact load data and contact properties of the wheel and rail are used for fatigue analysis to calculate RCF damage to the wheels using damage criteria based on previous studies. Two major parameters believed to have serious roles on RCF are the contact stress and the tangential force in the contact patch. These parameters are obtained from vehicle dynamic simulation studies. This paper describes and compares effects of different track geometries in curved and tangent tracks on RCF of three different wheel profiles S1002, P8 and IR1002. It is to identify which combinations of wheel load, wheel and rail profiles and vehicle dynamic characteristics cause RCF more severely.
An Embedded Elliptic Nano-Fiber in Anti-Plane Strain Couple Stress Elasticity
Authors: Shodja Hossein M. , Haftbaradaran Hamed
Published: August 2009

The application of higher order continuum theories, with size effect considerations, have recently been spread in the micro and nano-scale studies. One famous version of these theories is the couple stress theory. This paper utilizes this theory to study the anti-plane problem of an elliptic nano-fiber, embedded in an infinite medium, both made of centrosymmetric isotropic material. In this framework, a characteristic length appears in the formulation, by which examination of the size effect is possible. This work presents an analytical solution for the proposed problem.
Reduction of Oxygen Consumption in a Blast Furnace Through the Improvement of Heat Exchangers Efficiency
Authors: Assunc¸a˜o Charles So´stenes
Published: August 2009

This paper concerns the performance improvement study of three heat exchangers. The objective is to reduce the consumption of oxygen used to enrich the blown air into a Blast Furnace through the improvement of the energetic efficiency of these heat exchangers. A CFD (Computer Fluids Dynamics) model was developed in order to simulate the thermodynamic behavior of the fluids inside the heat exchangers. Some geometric modifications were simulated with the objective of change the combustion gases flow characteristics. The simulation showed a potential of energetic efficiency improvement of 15, 25%, which means an increase of 115°C in the outlet air temperature. The simulated modifications were implemented in one of three heat exchangers and the actual temperature increase was 135°C. After the implementation of the modifications in the others heat exchangers, the expected reduction of the oxygen consumption in the Blast Furnace is about 4.400.000 Nm3 per year.
Analytical and Numerical Study of the Evaporation of a Single Fuel Droplet With a Vaporized Fuel Background
Authors: Abarham Mehdi , Wichman Indrek S.
Published: August 2009

A simplified set of equations is examined for the problem of droplet evaporation. The equations employ the Clausius-Clapeyron boundary condition for the surface fuel-vapor condensation, which is responsible for numerous interesting mathematical behaviors, including the existence of an initial condensation stage followed by the classical d2-evaporation stage. Numerical methods of analysis are used, in conjunction with asymptotic analysis of each stage: (I) condensation; (II) transition; (III) evaporation. Comparisons are made with previous experiments. A brief discussion is provided of effective droplet evaporation in partial condensation environments.
Nonlinear Adaptive Control of Dynamic Systems Driven by Shape Memory Alloy (SMA) Actuators
Authors: Chen Shuo , Craft William J. , Song David Y.
Published: August 2009

This work describes the development and analysis of nonlinear adaptive based control algorithms for composite structures/systems operated with Shape Memory Alloy (SMA) actuators. A mathematical model charactering the motion of the composite systems is established, and by using Lyapunov stability theory, algorithms for linear displacement tracking control are derived. Actuation and control is achieved by adjusting the supply current to the SMA actuators. It is shown that with the proposed strategy for both linear displacement and velocity requires that the desired trajectory is tracked precisely. The novelty of the proposed approach also lies in the fact that it is fairly easy to set up and the computation involved as compared with other strategies. An example is used to verify the validity of the proposed approach. Simulation results using Matlab are presented.
Eexperimental Investigation of Heat Characteristics of Liquid Flow With Micro-Encapsulated Phase Change Material
Authors: Sabbah Rami , Yagoobi Jamal , Al Hallaj Said
Published: August 2009

This experimental study investigates the effect of presence of Micro-Encapsulated Phase Change Material (MEPCM) within the working fluid on thermal performances of the cooling system. To conduct this study, an experimental setup consisting of a steel tube with an inner diameter of 4.3mm, outer diameter of 6.3mm and a length of 1,016mm is selected. 5%, 10% and 20% mass concentration MEPCM slurries with particle diameter ranging between 5–15μm were included in this study. Tube wall temperature profile, fluid inlet, outlet temperatures, the pressure drop across the tube are measured and corresponding heat transfer coefficients are determined for various operating conditions. Differential Scanning Calometery (DSC) test results for an iterative method for local variables calculation. The experimental results showed significant enhancement in heat transfer coefficient higher than 50% and reduction in tube wall temperature higher than 35%. The controlling parameters are identified and their effects on the heat transfer characteristics are evaluated and analyzed.
Dynamic Behaviour of a MEMS-Gyroscope Subjected to Stochastic Angular Rate Perturbations
Authors: Wang Tianfu , Asokanthan Samuel F.
Published: August 2009

Instabilities in a vibratory MEMS gyroscope that is subject to stochastic fluctuations in input angular rates are investigated. The vibratory-type gyroscope considered in the present study is of the spring-mass type. For the purpose of acquiring stability conditions, when the angular rate input is subject to small intensity stochastic fluctuations, dynamic behaviour of stochastically perturbed linear gyroscopic systems is studied in detail. An asymptotic approach based on the method of stochastic averaging has been employed for this purpose, and closed-form conditions for mean square stability of dynamic response are obtained for the case of exponentially correlated noise. Results are shown to depend only on those values of the excitation spectral density near twice the natural frequencies and the combination frequencies of the system. The presented results remain valid if the stochastic parametric excitation has a small correlation time compared with the system relaxation time. Stability predictions have been illustrated via stability diagrams in the power-spectral–density-damping-ratio space. Further, to illustrate the applicability of the results in practice, conditions for varying input angular rates are mapped. Although, the above conditions are predicted for the spring-mass type gyroscope, the predictions can be easily translated to other vibratory gyroscope designs.
Bubble Rise and Departure From a Viscous Liquid Free Surface
Authors: Mohammadi Farhangi Mehran , Passandideh-Fard Mohammad , Bagherian Behtash
Published: August 2009

In this paper, the rising of a single bubble in a viscous liquid and its departure from the free-surface are simulated using a transient 2D/axisymmetric model. To predict the shape of the bubble deformation, the Navier-Stokes equations in addition to an advection equation for liquid volume fraction are solved. A modified Volume-of-Fluid (VOF) technique based on Youngs’ algorithm is used to track the bubble deformation. To validate the model, the results of simulations for terminal rise velocity and bubble shape are compared with those of the experiments. Next, the effect of different parameters such as initial bubble radius, channel height, and liquid viscosity and surface tension on the shape and rise velocity of the bubble is investigated. Finally, the interaction of the bubble with the free surface during its departure from the liquid is simulated, and the results are compared qualitatively with experimental photographs.
Influence of Parametric Resonance on a Bubble Driven by Intensive Sound During Stable Cavitation
Authors: Wang Ruimin , Zong Fengde , Yang Yang
Published: August 2009

Ultrasonic cavitation is a well-known phenomenon that plays an important role in several physical systems and its applications are commonly utilized in different fields of physics and technology. The cavitation phenomena can be described by means of a field theory that should be able to predict the values of the macroscopic quantities, introducing physical parameters specifically for the bubbly liquid to be considered as a continuum; while on the other hand, the goal is to solve the problem of single bubble dynamics in an ultrasonic field as a starting point towards a multibubble theory. Usually the theory of single bubble dynamics in ultrasonic cavitation is constructed by primarily imposing the conditions of spherical symmetry on the bubble interface and a viscoelastic liquid, thus obtaining a significant simplification of the equations of motion and a single nonlinear equation for the interface. This approach can be satisfactory in several cases, but the situations in which the bubble deviates from its spherical shape (i.e. the collapse on a rigid boundary) and the problem of the stability of the interface motion, which turns out to be very important in sonoluminescence, cannot be treated by this theory. In the field of ultrasonic cavitation numerical analysis is a further means of investigation besides the analytical approach and experimental measurements, and it is necessary at least for two reasons. Specifically, an exact analytical treatment of the equations that model this phenomenon is substantially impossible due to their high nonlinearity; and furthermore the typical order of magnitude of the measurable quantities (object sizes in the range of microns, time intervals in the range of microseconds with nanosecond resolution) makes experiments difficult to perform. Hence we numerically analyze the relationships between amplitude and frequency by the use of SPECTRA PLUS software. The method is tested analyzing forced oscillations of cavitation bubbles excited by ultrasonic standing waves at different pressure amplitudes, showing characteristic behaviour of nonlinear dynamical systems; frequency spectra are obtained, stability analysis is performed. It is important to note that we observe subharmonic behaviour of the volume mode of the bubble prior to the instabilities due to shape modes. If one further increases the value of pressure amplitudes, one can clearly observe surface instabilities and deformations that lead to the destruction of the bubble. This evidence may suggest that the subharmonic behaviour leads to chaos in ultrasonic cavitation.
Development and Validation of a High Fidelity 3-D Computational Spine Model That Incorporates Spatial Material Density Variations
Authors: Diaz-Silva Ricardo A. , Sarigul-Klijn Nesrin
Published: August 2009

Anatomically accurate high fidelity computational model of human spine is developed from Computed Tomography scans of a healthy subject and validated against experimental and other computational results. Procedures developed in this work will serve useful in noninvasive evaluation of patients with back problems. The advantage of this approach is that the model can be tailored to specific individual or specimen.
Scaled Acoustics Experiments and Vibration Prediction Based Structural Health Monitoring
Authors: Sarigul-Klijn Nesrin , Lopez Israel , Baek Seung-Il
Published: August 2009

Vibration and acoustic-based health monitoring techniques are presented to monitor structural health under dynamic environment. In order to extract damage sensitive features, linear and nonlinear dimensional reduction techniques are applied and compared. First, a vibration numerical study based on the damage index method is used to provide both location and severity of impact damage. Next, controlled scaled experimental measurements are taken to investigate the aeroacoustic properties of sub-scale wings under known damage conditions. The aeroacoustic nature of the flow field in and around generic aircraft wing damage is determined to characterize the physical mechanism of noise generated by the damage and its applicability to battle damage detection. Simulated battle damage is investigated using a baseline, and two damage models introduced; namely, (1) an undamaged wing as baseline, (2) chordwise-spanwise-partial-penetration (SCPP), and (3) spanwise-chordwise-full-penetration (SCFP). Dimensional reduction techniques are employed to extract time-frequency domain features, which can be used to detect the presence of structural damage. Results are given to illustrate effectiveness of this approach.
Occupant Protection via Frontal Crash Testing Analysis
Authors: Thorbole Chandrashekhar K. , Batzer Stephen A.
Published: August 2009

During frontal collisions, two central characteristics that define a vehicle’s crashworthiness are the occupant compartment deceleration magnitude and the level of occupant compartment intrusion. The deceleration severity determines seat belt loading for restrained occupants and the severity of secondary impacts of occupants against interior structures. Occupant compartment intrusion diminishes the survival space and increases the probability of individual occupants receiving worst injuries. Proper evaluation of a vehicle’s crashworthiness requires full scale crash testing as per standards defined by FMVSS 208, and this physical testing could be supplemented by virtual testing. The 208 standard specifies performance requirements for the vehicle in order to reduce the number and severity of the occupant injuries. FMVSS 208 crash testing involves rigid barrier impact tests at 30 mph, and the vehicle must be certified for all impact angles from −30 to +30 degrees. Allowance is made for the manufacturer to substitute engineering judgement for actual testing at each angle. The agreement of the vehicle to the test requirements ensures a reasonable degree of occupant safety. This study investigates virtual frontal testing to replicate severe crashes resulting in occupant compartment intrusion. The study is conducted using a validated FEA model of a 1998 Chevrolet S-10 standard cab pickup truck. It details simulation results from a variety of impact angles and velocities in order to determine the best potential test procedure for a frontal crash scenario. The results of this computational analysis demonstrate the offset frontal MDB (vehicle-to-vehicle) impact test procedure to be rigorous and capable of evaluating both the aspect of crashworthy performance of the vehicle. This test procedure resulted significant cabin intrusion along with cabin deceleration severity comparable to frontal rigid barrier 30 mph full width test.
Migration of Nanoclay in PP/PS Blend and Effect of Its Localization on Cell Structure
Authors: Zhao Jun-Feng , Huang Han-Xiong
Published: August 2009

In this work, the migration of clay in polypropylene/polystyrene (PP/PS) blend and the effect of its final localization on cell structure of microcellular foamed blend nanocomposites were studied. To observe the clay migration, a multilayered blend, alternatively superposed PS and PP/clay films with a thickness of 0.2 mm, was subjected to low shear flow. Batch foaming was performed on obtained blend nanocomposites to study the influence of the nanoclay localization on cell structure by using CO2 as the foaming agent. When subjected to flow, most clay dispersed in PP phase migrated into PS gradually. The migration of nanoclay caused smaller mean cell diameter and higher cell density to foamed PS. With the reduction of nanoclay content in PP phase, the cell density of PP foam decreased due to the reduction of heterogeneous nucleation sites and the mean cell diameter became smaller.
Numerical Study of Natural Convective Diffusion of VOCs With Soret and Dufour Effects in Ternary-Component System
Authors: Chen Baoming , Geng Wenguang , Tian Maocheng , Liu Fang
Published: August 2009

The effect of cross diffusion namely Soret effect and Dufour effect on the convective diffusion of volatile organic compounds (VOCs) indoor environment is investigated in this paper. Based on the principle of thermodynamics of irreversible processes, a mathematical model is developed for the ternary component system (VOCs, dry air and water vapor) with compensating thermal and solute gradients, and this mathematical model is solved numerically by commercial CFD (Fluent) code. Profiles of the dimensionless velocity, temperature and concentration are shown graphically with Soret and Dufour coefficients. Furthermore, the cross diffusion effects on the mass transfer induced by two different solute (VOCs and water vapor) concentration gradients is numerical studied. Finally, numerical values of physical quantities, such as the average Nusselt number and Sherwood number are presented. The numerical results show that the temperature gradient and the water vapor concentration gradient have an effect on the convective diffusion of VOCs indoor environment, and the cross diffusion effects would be taken into consideration for the problem of simultaneous heat and mass transfer especially in the presence of large temperature and concentration gradients.
Precise Bipolar Micro Dissection Means of an Adjustable Virtual Loop
Authors: Wenzel R. , Wulfsberg J.-P.
Published: August 2009

This paper presents the development of a bipolar probe for RF surgery which allows a precise coagulation or vaporization of tissue in microsurgical dimensions. Differently from established technologies, that base on excoriation with an active metal loop or punctual dissection with needles, the new technology uses additional electromagnetic fields for arching a bundled current path to a virtual loop, which affords no mechanical but only electrical controlled ablation of tissue volumina.
Bifurcation of Spatiotemporal Cardiac Alternans
Authors: Zhao Xiaopeng
Published: August 2009

Cardiac alternans is an initiator of ventricular fibrillation, a fatal heart rhythm disorder that kills hundreds of thousands people in the US each year. Alternans manifests as a pattern with beat-to-beat long-short variations in action potential duration. In an isolated cardiac cell, alternans arises as a supercritical period-doubling bifurcation. In cardiac tissue (coupled cells), propagation effect leads to more complicated bifurcation structures. Specifically, there may coexist multiple spatiotemporal patterns of alternans in tissue due to the interaction between electrotonic coupling and intrinsic instability in the dynamics of action potential. In this work, we carry out a detailed bifurcation analysis to illustrate the mechanism that leads to this phenomenon. The results on this analysis may shed light on the onset and control of the dreadful instability of cardiac alternans.
3D Simulations and Experimental Validation Using the Molecular Strain Function Model With Convective Constraint Release
Authors: Olley P. , Gough T. , Coates P. D.
Published: August 2009

The Molecular Strain Function model with Convective Constraint Release has been demonstrated by Wagner to fit elongational and shear viscosities, and First and Second Normal stress differences for a variety of polymer melts, when used with a Convective Constraint Release mechanism [J. Rheol. 45 (2001), 1387]. A modification to the CCR mechanism was shown to give more accurate representation of corner vortices in an abrupt contraction flow [JNNFM 135 (2006), 68] for both planar and axisymmetric contraction flows. It is highly desirable to assess the model against 3D flows. A primary advantage of 3D simulation in assessing a constitutive model is that, experimentally, it is very difficult to produce truly 2D data; the side walls of a finite die affect stress birefringence measurements (since this is a ‘line of sight’ cumulative measurement), and also induce significant 3D motion into the flow. The existing 2-dimensional code has been extended to fully 3-dimensional flows using 27-node ‘brick’ elements, and using a number of developments to deal with tracking and storage problems inherent in 3D time-integral solution. The 3D code is assessed against known 2-dimensional solutions to verify its accuracy; the constitutive model is then assessed against experimental data for a 4:1 contraction ratio die, which has finite width (5:3 depth to inlet height), inducing 3D effects. Stress birefringence, vortex size, and cross-sectional flow rate data at a number of flow rates are compared. The model is shown to give good accuracy against this flow.
Drag Reduction on SUVs and Trucks by Wake Control
Authors: Maazouddin Amarddin Z. , Zhou Dongmei
Published: August 2009

Road vehicles such as SUVs or pickup trucks are described as bluff bodies. When the air flow passes over the road vehicles the flow will separate at the rear of the vehicle, forming a large low pressure turbulent wake region behind the vehicle. The formed pressure drag posts resistance on the road vehicles and thus increases the work done by the engine to propel the vehicle. The purpose of this paper is to present the development and design of drag reducing devices for SUVs by studying the SUV’s aerodynamics. Numerical simulations using commercial software package — FLUENT were performed in order to study the aerodynamics behind the vehicles. A computer model of the Ahmed Vehicle Model was selected as a benchmark test. This Ahmed Model is a simple geometric body that retains major flow features where most part of the drag is concentrated. Seven different spoiler designs for the SUV have been studied. Their results for the SUV’s aerodynamics have been presented through velocity vectors, pressure contours, and aerodynamic lift and drag plots. One spoiler design was found to be able to reduce aerodynamic drag and others were found to be able to reduce the lift.
Occupant Injuries and Roof Strength in Rollover Crashes
Authors: Grzebieta Raphael , Young David , McIntosh Andrew , Bambach Michael
Published: August 2009

This paper shows how a mathematical relationship can be derived linking serious neck injuries to excessive roof deformation and that this relationship depends on the vehicle’s Centre of Gravity (COG) lateral velocity at the moment of touchdown of the vehicle’s roof structure. The relationships have been greatly simplified for an idealized condition to facilitate derivation of the equations. In the case of a very strong roof, occupant neck loading resulting from torso augmentation reaches a threshold value that depends on the coefficient of friction between the road surface and the vehicle’s steel body or tires and the height the vehicle’s COG drops during a quarter turn impact sequence.
Modeling and Parametric Analysis of Plasma Spray Particle State Distribution for Deposition Rate Control
Authors: Wroblewski Donald , Ghosh Onomitra , Lum Annie , Willoughby David , VanHout Michael , Hogstrom Kristina , Basu Soumendra N. , Gevelber Michael
Published: August 2009

Plasma spray for depositing thermal barrier coatings features large distributions of particle states that result in significant variations in coating quality. These variations arise from distributions of particle sizes, large spatial gradients of plasma thermal-fluid fields, and temporal variations of the arc and jet. This paper describes a simplified approach for studying how particle state distributions are influenced by torch conditions and powder distributions, and the implications for deposition rate monitoring and control. The approach combines a simplified jet model with a more detailed particle model. The important fluid-thermal spatial gradients in the plasma jet are captured using a three zone model: a core region, modeled by growth of a turbulent shear layer around a laminar core, a transition region and a similarity region. Plasma-particle momentum and thermal interactions, particle phase transitions, internal particle temperature gradients, and collapse of in-flight hollow particles have been modeled using a multi-lumped particle model. Effects of distributions of particle size, particle morphology, injection velocity, and carrier gas flow were studied for YSZ spray in an Ar-He plasma. The results provide guidance on sensor design and operation and on approaches for plume location control.
Two Hindrances to More Accurate Automotive Crash Simulations
Authors: Krauss Ryan W.
Published: August 2009

Automobile crashes cost the lives of 30,000 Americans in an average year. Some of these deaths might be prevented through the design of safer automobiles. Crashworthiness design relies heavily on computer simulations because reliable physical tests cannot be run until very late in the design of a vehicle. There are often discrepancies between simulations and the results of physical tests and these differences can lead to failures of critical tests late in the design cycle when correcting the problem is often costly and difficult. This paper discusses two hindrances to more accurate crash simulations: not being able to get accurate material data at impact speeds and the difficulty of modeling the contact between two colliding bodies during a crash. Getting accurate material properties at impact speeds is difficult because the testing often excites vibrations within the test device. The natural frequencies of the test device can lead to mechanical ringing that contaminates the impact response data. If the frequency of this ringing is not sufficiently high, it is very difficult to filter out this mechanical noise without affecting the material response data. Initial investigations have lead to the discovery of a test device whose internal resonances are well separated in frequency from the material response data, allowing material data to be filtered without adversely affecting the data. Two designs for an improved device are also being pursued. This paper also presents an open-source software module that is being developed for modeling impact and contact problems using the finite element method. The software is being written in Python and will be freely distributed. The open-source nature of the software will allow others to review, modify, and build on the algorithms for contact modeling. The software module and contact algorithms will be verified by comparison with experimental results.
Theoretical Prediction of Run Speed Distribution for a Molecular Motor
Authors: Walcott Sam , Kad Neil M.
Published: August 2009

Processive molecular motors are large proteins that “walk” along filaments in a cell, transforming chemical energy into mechanical work. These microscopic motors behave, at least qualitatively, like macroscopic walking machines. The dynamics and stability of macroscopic walkers are understood by analysis of “stride functions” (Poincare´ maps from one step to the next). We show that molecular motors have linear, probabilistic stride functions. Using these functions, we derive expressions for three measurable distributions: step period, run length and average run speed. The former two distributions are well known, the latter is new. We validate our calculation with simulations of a realistic model for Myosin Va (a molecular motor). The parameters of the run speed distribution specify both the run-length and step period distributions. As step-period distributions are difficult to measure under physiologically relevant conditions, this technique provides new information. Finally, we discuss the effects of variable step size and experimental error.
Finishing of Flat Parts Led by Lapping Kinematics on Abrasive Disc Dressed in Agreement With Overlap Factors
Authors: Sanchez L. E. A. , Jun N. Z. X. , Fiocchi A. A.
Published: August 2009

This paper discusses the investigation of an abrasive process for finishing flat workpieces, based on the combination of important grinding and lapping characteristics. Instead of loose abrasive grains between the workpiece and the lapping plate, a resinoid grinding wheel of hot-pressed silicon carbide is placed on the plate of a device resembling a lapping machine. The resin bond grinding wheel is dressed with a single-point diamond. In addition to keeping the plate flat, dressing also plays the role of interfering in the behavior of the process by varying the overlap factor (Ud). It was found that the studied process simplify the set-up and can be controlled more easily than in lapping, whose is a painstaking process. The surface roughness and flatness deviation proved comparable to those of lapping, or even finer than it, with the additional advantage of a less contaminated workpiece surface with a shiny appearance. The process was also monitored by acoustic emission (AE), which indicates to be a promissing and suitable technique for use in this process.
Reduction of Pollutants Emissions From Domestic Boilers: CFD Study
Authors: Hassan Gasser , Pourkashanian Mohamed , Ingham Derek , Ma Lin , Taylor Stephen
Published: August 2009

This study is concerned with building a computational fluid dynamics (CFD) model to simulate the combustion process occurring in the combustion chamber of some domestic boilers. The burner used in this boiler is a conventional cylindrical premix burner with small inlet holes on its surface. A two-dimensional (2D) CFD model is built to simulate the combustion chamber domain and the partially premixed combustion model with a postprocessor for NOx calculations is used to simulate the combustion process inside the combustion chamber. A complete description of the formation characteristics of NOx produced from the boiler is discussed in detail. A comparison between the CFD numerical results and the experimental measurements at different boiler loads is performed in order to validate the numerical model and investigate the accuracy of the CFD model. The validated CFD model is used to investigate the effect of different boundaries temperatures and the mixture inlet velocity on the flue gas average temperature, residence time and hence the CO and NOx concentrations produced from the combustion chamber. The concept of changing the mixture inlet velocity is found to be an effective method to improve the design of the burner in order to reduce the pollutant emissions produced from the boiler with no effect on the boiler efficiency.
Effect of Synthetic Jets Over Natural Convection Heat Sinks
Authors: Arik Mehmet , Utturkar Yogen , Ozmusul Murat
Published: August 2009

In moderate power electronics applications, the most preferred way of thermal management is natural convection to air with or without heat sinks. Though the use of heat sinks is fairly adequate for modest heat dissipation needs, it suffers from some serious performance limitations. Firstly, a large volume of the heat sink is required to keep the junction temperature at an allowable limit. This need arises because of the low convective film coefficients due to close spacing. In the present computational and experimental study, we propose a synthetic jet embedded heat sink to enhance the performance levels beyond two times within the same volume of a regular passive heat sink. Synthetic jets are meso-scale devices producing high velocity periodic jet streams at high velocities. As a result, by carefully positioning of these jets in the thermal real estate, the heat transfer over the surfaces can be dramatically augmented. This increase in the heat transfer rate is able to compensate for the loss of fin area happening due to the embedding of the jet within the heat sink volume, thus causing an overall increase in the heat dissipation. Heat transfer enhancements of 2.2 times over baseline natural convection cooled heat sinks are measured. Thermal resistances are compared for a range of jet operating conditions and found to be less than 0.9 K/W. Local temperatures obtained from experimental and computational agreed within ± 5%.