bluuebunny/crossref_metadata_2025 huggingface dataset:
Control System Design and Optimization Using LabVIEW for a Plug in Hybrid Electric Vehicle as Part of EcoCar: The NeXt Competition
Authors: Harries Brian , Smith Brandon , Carter Sean , White Darris , Compere Marc
Published: August 2012

Embry Riddle Aeronautical University is part of EcoCar: The NeXt Challenge, an advanced vehicle competition run by Argonne National Labs and sponsored by General Motors and the Department of Energy. The competition tasks 16 schools around the country with designing and implementing the most efficient vehicle architecture. As part of the EcoCar Challenge, Embry Riddle Aeronautical University is working on developing a controls strategy for a Plug in Hybrid Electric Vehicle. The control system is designed to optimize efficiency and consumer acceptability by allowing the EcoEagles to control each of the cars sub-systems. Control is done using CAN bus communication that utilizes National Instruments (NI) single board reconfigurable input / output (sbRIO) real time hardware. The EcoEagles powertrain architecture includes GM’s two-mode hybrid electric transmission which contains two 55kW electric motors, a 1.3 liter turbo diesel engine running on B20 biodiesel, and a 12.8 kWh lithium-ion battery pack produced by A123 Systems. Each component has a control module that interfaces directly with the subsystems and hardware on the vehicle. These controllers are: the Traction Power Inverter Module (TPIM), the Engine Control Module (ECM), and the Battery Pack Control Module (BPCM). Vehicle control and communication between these modules is managed by the EcoEagles, two controllers called the Supervisory Control Unit (SCU) and the Gateway (GW). The purpose of the gateway is to control the flow of CAN communication between modules and to isolate the ECM and BPCM from the vehicle to avoid data interference. Communication is done on two separate CAN buses, the Power Train Expansion Bus (PTEB), and the High Speed Bus (HS). The controls diagram can be seen in Figure 1. The paper will go into detail on shift strategy and engine operation where optimization was used to maintain efficient operation of the engine. The paper will also describe the control strategy that was developed using coupled LabVIEW Statecharts [1] with CAN messaging inputs from all of the control modules in order to maintain safe efficient operation.
Modeling of Thermal Transport in Phononic Crystals Using Finite Difference Time Domain Method
Authors: Dechaumphai Edward , Chen Renkun
Published: August 2012

Phonon transport in two dimensional nano-membranes with periodic variations in acoustic properties, a.k.a. phononic crystals, has drawn tremendous interests recently due to their novel properties and potential applications in thermal energy conversion. Recent experiments have demonstrated drastically lower thermal conductivity than what one would expect from the Boltzmann transport equations (BTE) that describe phonon transport as particle diffusion. To understand the intriguing behavior, we used a partially coherent picture to model thermal transport in 2D phononic crystals. In this model, phonons with mean free paths longer than the characteristic size of the phononic crystals are treated as coherent waves. The finite difference time domain method is utilized to simulate the wave behavior and to obtain the phonon dispersion relations in phononic crystals. On the other hand, phonons with mean free paths shorter than the characteristic size are considered particles and are treated by BTE after taking the diffusive boundary scattering into account. Our result shows that the thermal conductivity reduces as the characteristic sizes decrease due to both the zone folding effect and the diffusive boundary scattering, which is consistent with the recent experimental results.
Electrohydrodynamic (EHD) Enhanced Separation of Fine Liquid Droplets From Gas Flows
Authors: Acharya B. , Dessiatoun S. , Shooshtari A. , Fody J. , Ohadi M. M.
Published: August 2012

Experimental studies were undertaken to investigate separation of fine water particles from a stream of air-water droplet mixture using the electrohydrodynamic (EHD) effect. Air-water droplets mixture flows through a prototype consisting of 7 tubes arranged in a circular pattern which is enclosed in bigger tube. Wire electrodes placed in the center of each tube were charged with DC high-voltage. Corona discharge resulted from the application of high-voltage. Corona generated by the wires gave rise to the EHD effect, causing the water particles to move radially outwards towards the sides of the tube, where they were collected from specially designed beveled holes on the bottom. Near complete separation was achieved with 38W power input requirement for air-flows up to 303 CFM with 0.079 gpm water input. The pressure drop across the system was seen to be only 5.4 Pa.
Progression Over the Years: The EcoEagles Student-Designed Biodiesel Plug-In Hybrid Electric Vehicle
Authors: Carter Sean , Beckwith Jenna , Compere Marc , White Darris , Smith Brandon , Karstetter Zachary , Harries Brian
Published: August 2012

The Embry-Riddle Aeronautical University (ERAU) EcoEagles are participating in the EcoCar: The NeXt Challenge competition. The competition is a three-year collegiate event where 16 teams from North America compete to build a more efficient and better performing GM production vehicle. The three year collegiate competition is sponsored by the Department of Energy (DOE), General Motors (GM), and Argonne National Labs (ANL). The advanced vehicle technology competition has a history, and has been organized and ran for the past 20 years. The competition challenges collegiate minds to reduce the environmental impact of a Chevrolet EcoCAR by minimizing fuel consumption and reducing emissions while retaining the vehicle’s performance, safety, and consumer appeal. The main focus of the competition is to use real world vehicle development strategies and processes that would meet GM’s standard practices and safety protocols. All of the sponsors of the competition provide teams with engineering tools, equipment needed to create a realistic vehicle, and project design support to the teams throughout the competition. The ERAU team, the EcoEagles, has successfully devised a Plug-In Hybrid Electric Vehicle (PHEV) propulsion system that meets those requirements. The electrification of the powertrain and the use of biodiesel fuel are central themes in the EcoEagles’ strategy for improving fuel economy and tailpipe emissions. The team selected an electric range of approximately 25 miles based on the average commuter driving less than 33 miles per day [1]; meaning that most of the vehicle operation will be conducted using either fully electric or electric-assisted propulsion. The vehicle design consideration was accomplished by implementing a 1.3L GM Turbo Diesel coupled with a 2-Mode electrically variable transmission (EVT) and an A123 Lithium-Ion Iron-Phosphate 330V 12.8kWhr battery pack. The EcoEagles design will reduce petroleum energy consumption by 78%, improve fuel economy by 66%, and reduce well-to-wheel greenhouse gas (WTWGHG) emissions by 30%. The paper will focus on the 99% production readiness. The paper will also discuss and include vehicle test data supporting the energy efficiency, emissions, and performance / utility capabilities of the vehicle as determined by the first two years of vehicle development. The vehicle architecture and background information will also be presented to help the reader understand why the given architecture was chosen and how it might compare to the Chevrolet EcoCAR. Performance predictions made from simulations will be contrasted against those from the Hardware-in-the-Loop (HIL) development. Finally, on-road testing will also be compared with the same predictions with the goal of showing why the model-based, HIL enhanced, and vehicle technical specifications (VTS) did or did not agree.
Modeling the Transition From Conventional to Auxetic Behavior in Compressed Foams
Authors: Matheny J. C. , Berhan L. M.
Published: August 2012

In theory, a negative Poisson’s ratio (i.e. auxetic) material has improved hardness, impact resistance, fracture toughness, and shear modulus over one with a positive Poisson’s ratio and comparable stiffness. These enhanced properties make them attractive candidates for a wide range of applications, including ones in the biomedical industry. Over the past two decades there has been increasing interest in auxetic materials leading to the discovery and development of new auxetic materials at the micro- and macro-scales. It has been reported in the literature that some human trabecular bone is auxetic; however verification of this claim and measurement of the Poisson’s ratio of biological materials remains a challenge. This research need is the motivation for the current work. The central research objective of this project is to develop an approach to gain fundamental insight into the geometric characteristics of auxetic open cell materials by studying the underpinning mechanics behind the transition from positive to negative Poisson’s ratio that takes place when open-cell foam is compressed and heat treated. The approach involves detailed image analysis and finite element modeling of the microstructure of polyurethane foam, which is commonly used as a test material to model the structure of human cancellous bone. By studying both conventional and auxetic foam, and the process by which conventional foams are transformed to auxetic, we seek to identify the critical features of auxetic open-cell structures. The results will lead to a better understanding of auxetic cellular materials in general, and will be used to develop a framework for use in determining the mechanical properties and potential auxeticity of human trabecular bone and to aid in the design of synthetic auxetic biomaterials. In this paper we report on preliminary results of our modeling efforts.
Hydrophobicity of Hierarchical Structured Super-Hydrophobic Surfaces With the Secondary Pillars: A Lattice Boltzmann Method With High-Density Ratio
Authors: Lee Jung Shin , Kim Yong Hyun , Choi Won Jae , Lee Joon Sang
Published: August 2012

This paper studies the enhanced super-hydrophobicity on surfaces with hierarchical textures. Surface roughness increases the Contact angle (CA). Recently hierarchical structure surface, which is secondary structures established on the simple pillars or pyramids array, has gained lot of interest from researchers because hydrophobicity of hierarchical structure was found to be greater than in simple structure. In this paper, CA for two surface cases are measured with the computational fluid dynamics (CFD) modeling, known as lattice Boltzmann method (LBM). The first case is “simple structure”, which is composed of square cross section pillar array. The second one is “hierarchical structure”, which is composed of secondary pillar structure added on the base pillar array. Secondary pillar structure is comparatively small, about 50∼100 times smaller than base pillar. Simulation of water droplets, which are statically placed on each of the surfaces, is carried out using the projection method of LBM. Projection method is used to in this study to be able to model the large density difference between air and water. Two phase immiscible fluids flow consisting of air and water (density ratio of air to water = 1:1000) is built in 3D space by using the projection method. CAs and the Cassie, Wenzel regime characteristic for hierarchical structured surface case are compared to that of simple structured surface. We were succeeded in quantifying the benefit of having hierarchical textures; the addition of the secondary structure enhances both the apparent contact angle and the robustness of the non-wetting regime.
Dynamic Brittle Fracture Captured With Peridynamics
Authors: Ha Youn D. , Bobaru Florin
Published: August 2012

The bond-based peridynamic model is able to capture many of the essential characteristics of dynamic brittle fracture observed in experiments: crack branching, crack-path instability, asymmetries of crack paths, successive branching, secondary cracking at right angles from existing crack surfaces, etc. In this paper we investigate the influence of the stress waves on the crack branching angle and the velocity profile. We observe that crack branching in peridynamics evolves as the phenomenology proposed by the experimental evidence [1]: when a crack reaches a critical stage (macroscopically identified by its stress intensity factor) it splits into two or more branches, each propagating with the same speed as the parent crack, but with a much reduced process zone.
Vibration Rectification and Thermal Disturbances in Ultra Precision Inertial Sensors
Authors: Zaiss Curtis , Spiewak Swavik
Published: August 2012

Advanced inertial MEMS sensors facilitate achieving superb precision and resolution in measuring translational and rotational displacements, down to femtometers and milli-arcseconds. At present such performance is possible only in measurements of a very short duration, typically below 1 second. As this duration increases, the precision rapidly deteriorates. However, experimental accelerometers indicate the possibility of measurements with sub-micron precision for up to 30 seconds. For longer measurements, e.g., up to 5 minutes, the errors increase. However they still remain below 100 μm. The main cause of errors is a strong amplification of low frequency disturbances and distortions introduced by the sensors. It occurs when acceleration and angular rate are converted to the translational and angular displacement, i.e., during the integration. Thus, the key to maximizing the performance of inertial displacement sensors is a reduction of their low frequency disturbances. In the top tier sensors the key components of the disturbances include (1) the inherent thermodynamic and electrical noise, (2) chaotic mechanical phenomena, and (3) nonlinear distortion. The presented research is concerned with these three areas. It focuses on the identification and correction of errors which deteriorate a stability of the sensors’ bias, in particular on the vibration rectification error (VRE) and temperature variations due to the actuation in servo accelerometers. The investigated accelerometers are high performance sensors, digital and analog, whose total harmonic distortion is in the range from 1% down to a few parts-per-million (i.e., <0.001%). The objective is to develop on-line corrective filters capable of reducing the overall low frequency distortion below 0.00001%.
Computational Modeling of Post-Sutured Tissue Performance
Authors: Kasavajhala Ananth Ram Mahanth , Gu Linxia
Published: August 2012

Efficiency of post-operative sutured tissues depends on the state stress and strain, affecting the rate of wound healing. The objective of this study was to examine, the effect of suture size and stiffness, on the deformation of an incised continuous tissue. A simple running suture configuration was modeled and analyzed using 3D Finite Element Method (FEM). Prolene suture thread (Ethicon Inc.) of size 7-0 and 8-0 with varying material stiffness in the range of 6240 MPa to 30 MPa have been used whereas CryoValve aorta graft (Cryo Life Inc.) is considered as tissue material. Results show that the suture size has major impact on the deformation state of the tissue than the suture stiffness. Even though the difference in material stiffness caused a negligible change in strain, there is 55% increase in max principal strain away from suture line. Moreover, altering the suture size from 7-0 to 8-0 resulted in a 12% reduction in max tissue stresses. Because of the localization of max stress around the corner holes of the flaw, there is a fair chance of damage initiation at this location.
Prediction of Boiling and Critical Heat Flux Using an Eulerian Multiphase Boiling Model
Authors: Li Huiying , Vasquez Sergio A. , Punekar Hemant , Muralikrishnan R.
Published: August 2012

The present paper concerns the development and validation of an Eulerian multiphase boiling model to predict boiling and critical heat flux within the general-purpose computational fluid dynamics (CFD) solver FLUENT. The governing equations solved are generalized phase continuity, momentum and energy equations. Turbulence effects are accounted for using mixture, dispersed or per-phase multiphase turbulence models. Wall boiling phenomena are modeled using the baseline mechanistic nucleate boiling model, developed in Rensselaer Polytechnic Institute (RPI). Modifications have been introduced to the quenching heat flux model to achieve mesh-independent solutions. The influences of boiling model parameters have also been systematically investigated. To model non-equilibrium boiling and critical heat flux, the PRI model is extended to the departure from nucleate boiling (DNB) by partitioning wall heat flux to both liquid and vapor phases and considering the existence of thin liquid wall film. Topological functions are introduced to consider the wall boiling regime transition from the nucleate boiling to critical heat flux (CHF), and the corresponding flow regime change from bubbly flows to mist flows. A range of sub-models are implemented to model the interfacial momentum, mass and heat transfer and turbulence-bubble interactions. To validate the Eulerian multiphase boiling model, it has been used to predict nucleating boiling and critical heat flux in a range of 2D and 3D boiling flows. The examples presented in the paper include: (1). Nucleate boiling of sub-cooled water in an upward heated pipe; (2) R113 liquid flows through a vertical annulus with internal heated walls; (3). 3D boiling flows in a rectangular-sectioned duct; and (4). Critical heat flux and post dryout in vertical pipes. The results demonstrate that the model is able to predict reasonably well the distributions of wall temperature, the bulk fluid sub-cooling temperature and cross-sectional averaged vapor volume fraction in the vertical pipe. The computed profiles of the vapor volume fraction, liquid temperature, and the liquid and vapor velocity profiles are generally in good agreement with available experiments in the 2D annular case. In the 3D rectangular duct, the cross-sectional averaged vapor volume fractions are well captured in all the ten cases under investigation. In the case of critical heat flux and post dryout, the model is also able to predict reasonably well the location and the temperature rise under critical heat flux conditions. The computed wall temperature distributions along the pipes are in overall good agreement with available experiments.
Optimal Hardware Placement in a Minitower Computer Enclosure System
Authors: Cano M. Alfaro , Hernandez-Guerrero A. , Rubio Arana C. , Popescu Aristotel
Published: August 2012

One of the requirements for existing personal computers, PCs, is that the hardware inside must maintain an operating temperature as low as possible. One way to achieve that is to place the hardware components at locations with enough airflow around it. However, the relationship between the airflow and temperature of the components is unknown before they are placed at specific locations inside a PC. In this work a Computational Fluid Dynamics (CFD) analysis is coupled to a Design of Experiment (DOE) methodology to answer typical minitower key questions: a) how do the possible positions of hardware components affect their temperature?, and b) is it possible to get an optimal placement for these hardware components using the data collected by the CFD simulation results? The DOE methodology is used to optimize the analysis for a very large number of possible configurations. The results help in identifying where the efforts need to be placed in order to optimize the positioning of the hardware components for similar configurations at the designing stage. Somehow the results show that general conclusions could be drawn, but that there are not specific rules that could be applied to every configuration.
Fabrication and Characterization of Hybrid Nano-Polymer Solar Cells
Authors: Kelkar Rohit , Timmavajjala Satwik , Mitra Kunal , Baum Clayton
Published: August 2012

Hybrid solar cells consist of organic as well as inorganic substances. An organic compound absorbs light and transports holes whereas an inorganic compound is an acceptor and transports electrons. Hybrid solar cells were fabricated on glass slides pre-coated with indium tin oxide (ITO) which itself acts as a cathode. Poly(3,4 ethylenedioxythiophene)polystyrenesulfonate (PEDOT:PSS) was coated in order to avoid a short circuit between the layers and also to smooth the surface of ITO. A photoactive layer which consisted of poly(3-hexathiophene) (P3HT), TiO2 and star dispersant was coated over the PEDOT:PSS layer. Gold/molybdenum was sputtered as an anode material. Star dispersant was added to the active layer in order to improve the performance of the solar cell. Introduction of star dispersant increases the interfacial area and in turn the exciton dissociation. Atomic force microscopy (AFM) was used to measure the thicknesses of the individual layers and also to obtain a topographical view of the cell surface to ensure the uniformity of the deposited layers. Absorption and photoluminescence spectra were measured to characterize the solar cell. Finally, current–voltage characteristics were measured to ensure that the solar cell acts as a diode.
MRI-Based Three Dimensional Modeling of Stenting Procedure
Authors: Zhao Shijia , Gu Linxia , Ganpule Shailesh
Published: August 2012

In this work, the stents-induced mechanical responses of a patient-specific common carotid artery (CCA) were evaluated through computational simulation. The realistic 3D geometry of the artery was constructed from the MRI data. Two types of self-expanding stent design (open-cell and closed-cell) were used to restore the blood flow inside the 60% stenosed artery. The resulting lumen gain, dog-boning effect and arterial stress were estimated. Results suggested that the artery was straightened after stent implantation, and the open-cell design led to bigger lumen gain, better conformability, and less dog-boning effect. This work may facilitate the development of new stent designs.
Numerical Study on the Thermal Performance of a Substrate Integrated Thermal Buffer Heat Sink
Authors: Jankowski Nicholas R. , McCluskey F. Patrick
Published: August 2012

This report describes a parametric numerical study of a substrate integrated Thermal Buffer Heat Sink (TBHS) used to reduce transient temperature rise of power electronic devices. Linear and non-linear finite element models of the substrate unit cell are developed including a polynomial smoothing function to approximate phase change using the apparent capacity method (ACM). Parameters investigated include substrate geometry, convection rate and heat load. These parameters are examined for steady state and transient thermal loading conditions, and substrate thermal performance is evaluated for each case. Specifically the TBHS design tradeoff between thermal resistance and thermal capacity is quantified, and the ability of the TBHS structure to reduce peak temperature rise for certain transient load conditions is evaluated. It is demonstrated that for short thermal transients a particular TBHS design can suppress temperature rise by 19.6°C (35%) when compared to an equivalent standard microchannel heat sink.
Numerical Study of the Endwall Effects on Water Single-Phase Pressure Drop Across a Circular Micro-Pin-Fin Array
Authors: Mita Jonathan R. , Qu Weilin , Pfefferkorn Frank E.
Published: August 2012

This paper presents a numerical study of pressure drop associated with water liquid single-phase flow across an array of staggered micro-pin-fins having circular cross-section. The numerical simulations were validated against previously obtained experimental results using an array of staggered circular micro-pin-fins having the following dimensions: 180 micron diameter and 683 micron height. The longitudinal pitch and transverse pitch of the micro-pin-fins are equal to 399 microns. The effects of endwalls on pressure drop characteristics were then explored numerically. Six different micro-pin-fin height to diameter ratios were studied with seven different Reynolds numbers. All simulations were performed at room temperature (23°C). It was seen that for any given Reynolds number, as the pin height to diameter ratio increased, the pressure drop and resulting non-dimensional friction factor decreased.
Heat and Mass Transfer in Double-Filmwise Heat Exchanger for Industrial Food Processing Applications
Authors: Skop Helen , Pezzuto James , Oleynikov-White Valeriy G. , Cavallo John F. , Fesjian Robert
Published: August 2012

The baking industry is considered as one of the major energy consuming food industries in North America. More than 40% of bakery fuel consumption is used to evaporate water in the processes [1]. In addition to the baking process’ vapor the oven stack gas contains water vapor from combustion products. Overall the content of water vapor in the typical oven stack gas is about 20% by volume. Most bakeries waste this vapor and its latent heat. Bakeries’ ovens have wide diversity in power and design. Off-the-shelve heat exchangers are not considered as cost effective equipment for stack gas cooling below gas’ dew point temperature. At typical oven stack gas composition water vapor condensation begins to condense at about 72° C. Not using the latent heat of stack water vapor and the heat from gas cooling from dew point temperature to ambient temperature results in low effectiveness of waste heat recovery. Mainly the effect from the recovery of stack gas cooling prior to condensation is considered as non cost effective and waste heat recovery is neglected.
Computational Modeling of Anisotropic Thermal Conductivity and Joule Heating on Printed Circuit Boards
Authors: Dogruoz M. Baris , Shankaran Gokul , Pitner Gregory , Nagulapally Manoj
Published: August 2012

A printed circuit board (PCB) consists of consecutive layers of dielectric material and current carrying traces and vias. Conducting system level simulations of PCB’s with detailed trace and via geometries is computationally very expensive. In the present study, the effects of the trace and via geometry in the physical model are taken into account by importing the corresponding ECAD data with which locally varying anisotrpoic thermal conductivity on the PCB is determined accordingly. Moreover, the effects of Joule heating in the current carrying traces are included by using a number of planar heat sources representing individual metal trace layers. The powermap on each of these layers is determined by solving the relevant electric field equations where the temperature dependency of the electrical field is also taken into account. The results are presented on a sample PCB and comparisons are made with the previous studies and conventional models. It is demonstrated that temperature values differ substantially depending on the method of Joule heating treatment used.
Heat Conduction in High Thermal Conductivity Networked Composite Films for Thermal Interface Materials
Authors: Fard Hafez Raeisi , Pashayi Kamyar , Lai Fengyuan , Plawsky Joel , Borca-Tasciuc Theodorian
Published: August 2012

Fast and efficient exchange of thermal energy plays a vital role in the thermal management of electronic and optoelectronic devices. A critical component for thermal management is a thermal interface material (TIM) that is used to minimize the contact thermal resistance between surfaces and to provide a low resistance pathway to spread and remove heat. Ideal TIMs must pass several key requirements: 1) high thermal conductivity κ and low thermal contact resistance with the mating surfaces; 2) easy to apply with controlled thickness; 3) low temperature processing; 4) able to accommodate thermally induced mechanical stresses during on-off cycling of the device1. Particle-based composites have reasonable slurry viscosities, however their thermal conductivity are usually very low (<10 Wm−1K−1), even when high κ nanofillers are employed, due to the thermal interface resistance between nanoparticles and the polymer matrix2 or the absence of high κ pathways.
A Rotary-Leg Robot Model That Predicts Both Leg Revolution and Oscillation Behavior
Authors: Lu Xiaoxiao , Seipel Justin
Published: August 2012

The Clock-Torqued Spring-Loaded Inverted Pendulum (CT-SLIP) model is extended to predict both leg revolution and oscillation behaviors. With this model we demonstrate that the center-of-mass locomotion dynamics of both leg revolution and oscillation cases have identical local stability with respect to small perturbations, while global stability (with respect to large perturbations) shows differences. This extension of the CT-SLIP model and comparative analysis has potential benefits in robot path planning where there may be a choice between a leg revolution or oscillation. Further, this analysis helps relate mathematical models and physical models based on leg revolution to animal locomotion that is dependent on leg retraction and oscillation.
Optimization of Phononic Crystals for the Simultaneous Attenuation of Out-of-Plane and In-Plane Waves
Authors: Bilal Osama R. , Hussein Mahmoud I.
Published: August 2012

The topological distribution of the material phases inside the unit cell composing a phononic crystal has a significant effect on its dispersion characteristics. This topology can be engineered to produce application-specific requirements. In this paper, a specialized genetic-algorithm-based topology optimization methodology for the design of two-dimensional phononic crystals is presented. Specifically the target is the opening and maximization of band gap size for (i) out-of-plane waves, (ii) in-plane waves and (iii) both out-of-plane and in-plane waves simultaneously. The methodology as well as the resulting designs are presented.
Thermal Modeling and Heat Management of Supercapacitor Modules by High Velocity Impinging Fan Flow
Authors: Xu Xinqiang , Sammakia Bahgat G. , Murray Bruce T. , Jung DaeYoung , Eilertsen Thor
Published: August 2012

Supercapacitors are a strong candidate for high-power applications such as electric/hybrid vehicles due to their high power densities and high efficiency. In these applications, supercapacitors are used in large stacks (modules) to provide the peak-power requirement. They are subject to heavy duty cycling conditions, which results in significant heat generation inside each cell. Under such conditions, natural convection air cooling is found to be an ineffective method for removing heat from the supercapacitor modules. Therefore, utilizing an appropriate forced convection cooling system becomes necessary for the lifetime and performance of supercapacitor modules. The objective of this paper is to study the cooling of supercapacitor modules under high velocity impinging fan flow. A three-dimensional computational model was developed using the commercial FEM software package COMSOL. The κ-ε two equation turbulence model is employed to account for turbulent transport. The supercapacitor module studied in this paper was composed of 18 cells, which were connected in series. The parameters studied include the Reynolds number of the impinging flow, the spacing between cells and the impingement distance. The results show how the forced convection cooling varies with the Reynolds number and that the Nusselt number increases with the Reynolds number. In addition, the variation of the temperature profile within the module with the spacing arrangement between cells was investigated.
Failure Analysis of Redundant Escalator Chain Pin Retention Mechanisms
Authors: Klopp Richard W.
Published: August 2012

The pins in new escalator chains were observed to have drifted laterally out of the chain side plates within a few hours of startup. The force driving this movement was sufficient to overcome a light interference fit and retaining rings intended to restrain the pins. Neither pins with heavy interference fit nor connector pins with sliding fits exhibited this tendency to drift. A failure analysis showed that even if the pins and side plates had been manufactured with a heavy interference fit, the sharp edge of the retaining ring groove acted as a broaching tool during assembly, shaving out and enlarging the side plate hole, and destroying the intended fit. The driving force for pin drift was traced to the hysteretic force and rotation sequence as the chain traveled around the escalator sprockets, which led to a walking mechanism that imparted a lateral force sufficient to move the pins and overcome the retaining rings.
Particle Effects on Gas-Liquid-Solid Flows
Authors: Zhang Xinyu , Ahmadi Goodarz
Published: August 2012

A numerical simulation is carried out to study the role of particles in gas-liquid-solid flows in bubble columns. An Eulerian-Lagrangian model is used and the liquid flow is modeled using a volume-averaged system of governing equations, while motions of bubbles and particles are evaluated using Lagrangian trajectory analysis. It is assumed that the bubbles remain spherical. The interactions between bubble-liquid and particle-liquid are included in the study. The discrete phase equations include drag, lift, buoyancy, and virtual mass forces. Particle-particle interactions and bubble-bubble interactions are accounted for by the hard sphere model approach. The bubble coalescence is also included in the model. Neutrally buoyant particles are used in the study. A parcel approach is used and a parcel represents a certain number of particles of same size, velocity, and other properties. Variation of particle loading is modeled by changing the corresponding number of particles in every parcel. In a previous work, the predicted results were compared with the experimental data, and good agreement was obtained. The transient flow characteristics of the three-phase flow are studied and the effects of particle loading on flow characteristics are discussed. The simulations show that the transient characteristics of the three-phase flow in a column are dominated by time-dependent vortices. The particle loading can affect the characteristics of the three-phase flows and flows with high particle loading evolve faster.
Blast Response Characteristics for an Instrumented Helmet on a Skull-Brain Surrogate
Authors: Ford Matthew , Simmonds Kirth , Horner David , Gauvin John , Bagchi Amit
Published: August 2012

In current US Military operations, warfighters are frequently subjected to blast events, which can lead to traumatic brain injury (TBI). In response to this recent and increasingly prevalent threat, helmet systems must protect the head against high velocity, short duration overpressures in addition to blunt and ballistic impacts. Understanding the blast impact response characteristics of helmet systems may improve the design and selection process for headborne equipment and contribute to reducing blast-related brain injury.
Levels of Ethics Education in University Graduate Programs
Authors: Filush Austin , Barakat Nael
Published: August 2012

Professional ethics are critical in guiding how professionals conduct themselves as they apply their knowledge for providing services to the public. Therefore it should be without question that during education, professional degree seeking students should be taught ethics pertaining to their field of study. However, in many graduate programs in the field of engineering sciences throughout the country, professional ethics is not required for a degree, particularly beyond undergraduate degrees. A study was performed in 2006 polling some major universities, covering most of the geographical areas and states of the United States, on the content of their graduate engineering programs pertaining to professional ethics. The results showed that only a very small percentage of universities had a full course or a subject of a course pertaining to professional ethics. These numbers reflect a significant shortage in the students’ education on how to perform in a professional setting. Five years later in 2011, the same universities were polled again to see if any change has been made to improve the ethics education at the graduate level. The data showed a small increase in the number of schools mentioning professional ethics at the graduate level, but the numbers are still very low. This paper covers the poll results along with an analysis of the findings and attempts to explore the reasons behind this lack of emphases on ethics education in engineering at the graduate level. It also discusses what Universities should be teaching students in regards to professional ethics. The analysis includes skills needed in industry as well as the supporting arguments for the importance of ethics education.
Refractive Devices Based on Acoustic Metamaterials
Authors: Gracia´ Rogelio , Torrent Daniel , Sa´nchez-Dehesa Jose´
Published: August 2012

The t matrix of a hole in an acoustic waveguide is here obtained and applied to study the scattering of sound waves propagating inside a waveguide. It is found that a hole drilled in a waveguide behaves as a cylindrical unit whose dynamical mass density is lower than that of the surrounded background. This property has been used here to design an acoustic refractive lens. Numerical experiments based on multiple scattering simulations confirm the sound focusing by the designed device.
Impact of Permeation Properties and Back Sheet/ Encapsulation Interactions on the Reliability of PV Modules
Authors: Hu¨lsmann Philip , Peike Cornelia , Blu¨ml Matthias , Schmid Philipp , Weiß Karl-Anders , Ko¨hl Michael
Published: August 2012

The interaction of different types of new encapsulation and back sheet materials for PV modules was investigated. Therefore, various types of laminates were made in order to examine the environmental impact on such materials during the materials aging process with special attention to the permeability of the back sheet. The laminates were characterized by Raman Spectroscopy, FT-IR/VIS reflectance measurements before and after different accelerated aging procedures. The water vapor and oxygen permeation properties were measured. A clear correlation between the permeation properties and the observed aging behavior was found. The degradation, especially of the encapsulant, resulted in increasing background fluorescence in the Raman Spectra and in a change of transmittance of the encapsulants which is also known as yellowing. It could be shown that the encapsulation/cell/back-sheet system should be optimized in order to minimize the stress on the PV-module components.
Closed Form Solutions for Electrostatically Actuated Micromirrors Considering the Bending Effect
Authors: Moeenfard Hamid , Ahmadian Mohammad Taghi , Moeenfard Hosein
Published: August 2012

In the current paper, analytical solutions are presented for the nonlinear problem of electrostatically actuated torsional micromirrors considering the bending of the torsional beams. Energy method is used for finding the equilibrium equations. Then the explicit function theorem is utilized for finding the equations governing the instability mode of the mirror. The presented results show that neglecting the bending effect in electrostatic torsion micro actuators can cause to several hundred percent of overestimation of the stability limits of the device. In order to study the voltage-angle and voltage-displacement behavior of the micromirror, equilibrium equations are solved using HPM. Presented results are in good agreement with numerical simulations and experimental findings.
Experimental Validation of an Elastic-Plastic Contact Model
Authors: Brake M. R. , Reu P. L. , VanGoethem D. J. , Bejarano M. V. , Sumali A.
Published: August 2012

In many engineered structures and components, impact events frequently occur between sub-components. Numerical models are able to adequately capture the salient features of these events; however, with high fidelity finite element models, an unreasonably large number of elements are needed to accurately model just the elastic regime when arbitrary contact is considered. In order to solve real engineering problems with elastic-plastic impacts in complex or built up systems, an analytical expression is needed to make solutions practical. To this end, a series of experiments are designed to test a new elastic plastic model for impact dynamics. A hard metal ball is attached as the end of a pendulum, and is struck against a relatively compliant metal puck. Digital image analysis is used to measure the displacement and velocity of the metal ball across the impact events. Frictional losses in the system are minimized, and the coefficient of restitution is calculated as a function of velocity. These measurements are used to validate an elastic-plastic impact model, which is further compared to and other models from the literature. Good agreement is found between the new analytical model and the experiments.
Investigation of Tumor Growth Based on Phase Field Model
Authors: He Zhi Zhu , Liu Jing
Published: August 2012

This paper presents and investigates the tumor growth based on a phase model. The tumor core is necrotic and inhibitor chemical species are considered. The interface of tumor and health tissue is tracked using a phase field equation. The reformulation of a classical model, accounting for cell-proliferation, apoptosis, cell-to-cell and cell-to-matrix adhesion, is derived. The advantages of the finite difference methodology employed are generality and relative simplicity implication. We present simulations of the nonlinear evolution of growing tumors morphology and discuss the effects of tumor microenvironment. Mechanisms reflecting the tumor growth and development behavior was preliminarily interpreted. Recently numerous mathematical have been developed to investigate the growth dynamics of tumor [1–8]. One of most significant model developed by Wise [8] is based on Cahn-Hilliard equation, which is conservation phase field method. Allen-Chan nonconservation phase field has been developed to track the moving interface for multiphase simulation by Sun [9]. Allen-Chan equation is second order, while Cahn-Hilliard equation is fourth order in space. Thus, we introduce the Allen-Chan phase method [9–10] to simulate the tumor growth, which is very simple for numerical simulation The computation domain is illustrated in Fig. 1, where ΩH denotes host tissue, the tumor domains is comprised of viable tumor cell ΩV and dead tumor cell ΩD. The numerical results are presented at Fig. (2–4). One can find that the growth of tumor strongly depend on the nutrients and nonlinear unstable growth may lead to finger shaped pattern, which is in agreement with recent experimental observations [7] of in vivo tumor. In summary, a phase method has been developed to study diffusion and consumption of the nutrients and tumor cell proliferation, necrosis and migration, which discloses the evolution of complex shape of tumor.
Growth-Induced Stress Inside Solid Tumor Using Thermoelasticity Model
Authors: He Zhi Zhu , Liu Jing
Published: August 2012

The tumor growth strongly depends upon the availability of nutrients. Many experimental evidences recently indicated that stress play important role in tumor invasion. The growth-induced stress is from pressure imposed on tumor by surrounding tissues due to tumor expansion invasion. This paper introduces a model to characterize growth-induced stress in solid tumor by analogy with thermoelasticity theory. The model is composed of a nutrients diffusion equation and a stress evolution equation. The solid spheroid tumor stress distribution induced by tumor spatial non-uniformity growth is studied. Moreover, the mechanical interactions between the solid tumor and the surrounding host tissue are discussed detailed.
Numerical Modelling of the Effective Thermal Conductivities of Composite Materials
Authors: He Zhi Zhu , Liu Jing
Published: August 2012

Nanoparticles with high thermal conductivity are often impregnated within fluids or biological tissue for heat transfer enhancement. Prediction of effective thermal conductivity of such nanocomposite plays an important role in evaluating thermal effects induced by nanoparticles. In this article, an order parameter is introduced to characterize the domain of nanoparticles so that a unified conduction heat transfer equation is established. An effective numerical technology alternate direction implicit finite difference is adopted to solve the heat transfer equation. The present approach could potentially account for the effect of nanoparticle shape and size.
Development of a Belt Conveyor Cooling System for Concrete Aggregates
Authors: Ahmed Khaled I. E. , Hamouda A. M. S. , Gadala M. S.
Published: August 2012

Using hot aggregates, in concrete production, results in a drop in compressive strength of the produced concrete. Various methods have been proposed for cooling concrete aggregates. This paper proposes a new design for a conveyor system for cooling the aggregates during hot seasons. Simulation of the heat flow during the cooling process over the conveyor is analyzed with the objective of understanding the effect of the various design parameters and achieving minimum cooling time with the least possible power. A finite element model for the new design is proposed and discussed. Challenges facing numerical simulation are addressed in this paper. The results of the finite element analysis of the new design are presented for various initial conditions and cooling rates.
A System Performance and Economics Analysis of IGCC With Supercritical Steam Bottom Cycle Supplied With Varying Blends of Coal and Biomass Feedstock
Authors: Long Henry A. , Wang Ting
Published: August 2012

In recent years, Integrated Gasification Combined Cycle Technology (IGCC) has been gaining steady popularity for use in clean coal power operations with carbon capture and sequestration. Great efforts have been continuously spent on investigating various ways to improve the efficiency and further reduce the greenhouse gas (GHG) emissions of such plants. This study focuses on investigating two approaches to achieve these goals. First, replace the traditional subcritical Rankine steam cycle portion of the overall plant with a supercritical steam cycle. Second, add different amounts of biomass as co-feedstock to reduce carbon footprint as well as SOx and NOx emissions. Employing biomass as a feedstock to generate fuels or power has the advantage of being carbon neutral or even becoming carbon negative if carbon is captured and sequestered. Due to a limited supply of feedstock, biomass plants are usually small, which results in higher capital and production costs. In addition, biomass can only be obtained at specific times in the year, meaning the plant cannot feasibly operate year-round, resulting in fairly low capacity factors. Considering these challenges, it is more economically attractive and less technically challenging to co-combust or co-gasify biomass wastes with coal. The results show that supercritical IGCC the net plant efficiency increases with increased biomass blending in the all cases. For both subcritical and supercritical cases, the efficiency increases initially from 0% to 10% (wt.) biomass, and decreases thereafter. However, the efficiency of the blended cases always remains higher than that of the pure coal baseline cases. The emissions (NOx, SOx, and effective CO2) and the capital cost all decrease as biomass ratio increases, but the cost of electricity increases with biomass ratio due to the high cost of the biomass used. Finally, implementing a supercritical steam cycle is shown to increase the net plant output power by 13% and the thermal efficiency by about 1.6 percentage points (or 4.56%) with a 6.7% reduction in capital cost, and a 3.5% decrease in cost of electricity.