bluuebunny/crossref_metadata_2025 huggingface dataset:
Capturing Assembly Constraints of Experimental Setups in a Virtual Laboratory Environment
Authors: Aziz El-Sayed , Chang Yizhe , Esche Sven K. , Chassapis Constantin
Published: October 2013

Recently, multi-player game engines have been explored regarding their potential for implementing virtual laboratory environments for engineering and science education. In these developments, the virtual assembly process of the laboratory equipment is a critical step, and a detailed formalized description of how different components of the experimental equipment are to be joined in the assembly process is necessary. This description includes the joint types (lower and upper kinematic pairs) and the associated degrees of freedom, the resulting mobility of the assembly as well as the joint fit requirements.

In this paper, a formalized representation of the assembly process that captures the information on the joint kinematics and the components’ degrees of freedom generated when assembling laboratory equipment in a virtual laboratory environment will be discussed. A planetary gear train system will be used as an example to illustrate the proposed method. In particular, the structure of the assembly of a planetary gear train system involves assembly constraints between a group of components (sun, planet and ring gears, shafts, planet carrier assembly, etc.) that generate the desired relationship between the input and output motions. This paper will identify important requirements for modeling different configurations of planetary gear train assemblies within a game-based virtual laboratory environment. These requirements include the positioning and the orienting of the components, the verification of the kinematic joints, the propagation of the mating constraints and the capturing of the joint attributes.
Infrared Assessment of an Optimized Vane Pressure Side Film Cooling Array
Authors: Johnson J. J. , King P. I. , Clark J. P. , Lethander A. T. , Posada N. A.
Published: October 2013

The following experimental work described here entails the investigation by infrared thermography (IRT) of full-scale flat plates intended to model the pressure side (PS) of a modern fully-cooled turbine inlet vane called the High-Impact Technologies (HIT) Research Turbine Vane (RTV). The imaging system is used to make detailed full-coverage, two-dimensional, steady-state measurements of flat plate surface temperature. The PS has a total of 282 film cooling holes including three rows of showerhead holes near the leading edge and a handful of rows downstream depending on the design. The flat plates precisely match the material, thickness, and cooling hole sizes on the RTV, however they are not intended to match the external pressure field or the characteristics of internal cooling beneath the airfoil surface. Surface temperature relative to individual trial freestream gas temperatures is reported for an uncooled plate, a plate with the baseline RTV cooling scheme, and for four different hole types on a plate with a 3D-optimized cooling array designed for the RTV in previous work using genetic algorithms and computational fluid dynamics (CFD). The four different cooling hole shapes tested on the downstream rows of the optimized array plates include cylindrical holes, fan-shaped holes, Vehr holes, and a new cooling hole called a mini-trench shaped (MTS) hole. Experimentation on flat plate models using infrared thermography provides large amounts of valuable data, is inexpensive and highly repeatable relative to large rotating blowdown rigs. The results provide key insights into the differences between full-PS film cooling performance on the plate versus the 3D RTV and suggests to designers the best cooling hole shape for the next build of the RTV which will soon be tested in a full-scale blowdown rig instrumented with heat flux gauges. Overall, results clearly corroborate how cooling was redistributed and improved over the PS of the RTV in the original computational design effort and suggest that certain hole shapes are best suited for certain locations on the flat plate models.
Fast Converging Model for Load and Shear of Molecularly Thin Surface Films
Authors: Chong W. W. F. , Teodorescu M.
Published: October 2013

Predicting the contact load and the shear losses in a narrow conjunction separated by a molecularly thin fluid layer must account for a significant number of factors: the chemical composition of the fluid and solid boundaries, the length of molecular chains, the intermolecular forces, the concentration of different species of molecules in the mixture, molecule-to-surface adsorption and surface topography. The most commonly used solutions to this problem either neglect a significant part of the participating phenomena or are computationally expensive (e.g. molecular dynamics simulations).

The current paper proposes a statistical mechanics model, which predicts the behavior of a molecularly thin film confined within a nano-scale conjunction. The advantage of this approach is that it is fast converging (semi-analytic) and all the aforementioned phenomena could be accounted for, within a single frame-work. The model is tested for an idealized bimolecular fluid and it was found that it can predict the influence of the packing fraction and the concentration ratio over the discontinuous discharge of fluid out of the a nano-scale conjunction.

The main application is accurate prediction of the shear stress-induced losses in a nano-scale contact (e.g. between asperities on opposite sides of a tribological conjunction) and modern drug delivery techniques (e.g. transdermal drug delivery patches).
Microfluidic Photocatalytic Water-Splitting Reactors
Authors: Ahsan Syed Saad , Erickson David
Published: October 2013

In this work, we present a novel microfluidic photocatalytic water-splitting reactor. Optofluidics offers advantages over conventional reactors in terms of improved photon transfer efficiency and mass transfer efficiency and are therefore the ideal platform for photocatalytic reactions. Our device is a planar optofluidic device which we used to study the kinetics of Platinum-Impregnated Titanium Oxide as the oxygen and hydrogen producing photocatalyst redox mediated by Iodide/Iodate species. We deposit our catalysts via a sol-gel method while the platinum co-catalyst is added by wet impregnation via reduction in Sodium Borohydride. The reactions are performed under a 100W Hg lamp and reaction rates are inferred by measuring the depletion of the two Iodine species via UV-vis absorption spectrophotometry. Our results indicate that reaction rates and efficiencies can be enhanced by using an optofluidic platform as opposed to the conventional slurry reactor used in previous experiments for this class of reaction. We believe that the micro-optofluidic platform of our device offers the benefit of measuring the kinetic properties of these class of reactions quickly and cheaply for the goals of further optimization.
Dendritic Nanotip for Low-Cost Detection of Mycobacterium Tuberculosis
Authors: Kim Jong-Hoon , Hiraiwa Morgan , Gao Dayong , Lee Kyong-Hoon , Chung Jae-Hyun
Published: October 2013

Rapid diagnosis of tuberculosis, one of the most widely spread diseases on the globe today, has been critically demanded for over a century. One of the major challenges for screening Mycobacterium tuberculosis (MTB) is in low-cost detection of MTB. In this study, we present an electrical detection method of MTB cells using a dendritic nanotip composed of single-walled carbon nanotubes (SWCNTs) and Si micro- and nanowires. The novelty is in the direct measurement of electric current with a minimal capacitance effect on dendritic nanotip surface. Upon binding of target cells, a gating effect on the nanotip surface decreases the electric current, which is measured directly by a dendritic nanotip. The measurement resolution is aided by reduced interference of an electrical double layer effect, due to the dendritic nanostructure. Using the nanotip, BCG cells could be electrically detected within 15 minutes, which is validated by fluorescence detection. The sensitivity is 1000 cfu/ml for both methods. The presented tip sensor demonstrated the potential for rapid and low-cost detection of MTB.
Towards the Realization of a Conveyor Platform for Microparts Employing a Deformable Surface
Authors: Rizwan Mohsin , Shiakolas Panos S.
Published: October 2013

Various approaches ranging from micro-sized air-nozzles to direct manipulation through bimetallic actuators have been proposed to displace/orient sub-millimeter sized parts for automatic assembly of homogeneous and/or heterogeneous microdevices Keeping in view the micromanipulation requirements, based on the concept of active surface, a new approach for micromanipulation has been proposed by the authors which comprises of controlled deformation of a flexible continuous surface [1]. A single actuator system has limited micropart translocation capability and multiple sequential actuators need to be used if the required translocation distance is more than the capability of an actuator. For a single actuator system, the parameters of the system and their influence on the system output (translocation distance or travel distance) have already been discussed as function of the input frequency, actuator stroke, surface roughness and deformation wavelength [2]. In a multiactuator system, the subsequent actuators engage the micropart with a finite initial velocity and at some position relative to the actuator. Therefore, a sequential array of actuators exhibits a different set of overall operational characteristics. This manuscript describes the operational characteristics of sequential actuators towards a microconveyor system over a range of actuator frequencies and other system parameters and estimates the system output i.e. the micropart distance travelled or translocation. The discussion is based on a two actuator system with the conclusions generalized for a multi-actuator system.
Toward Better Integration of Vehicle Assembly Production Systems
Authors: Arinez Jorge , Yen Jerry , Michaloski John , Proctor Frederick , Rippey William
Published: October 2013

In today’s manufacturing world, system integration often necessitates composing systems of technology that are not designed to interoperate with each other. This inherent incompatibility results in redundant, non–value added work that is required for information to be properly transferred and processed in order for the total system to function properly. As a result, current approaches to systems integration tend to be complicated, costly, time–consuming, and error–prone. In the automotive industry, this integration predicament is found most dramatically in vehicle assembly systems, which are built from a collection of different, incompatible, and multi–vendor “silo” subsystems. This paper will investigate the problems associated with integration of vehicle assembly systems and propose a standard information and communication model to address the integration problems due to incompatible data models. Benefits to the standard information and communication model, including better integration, improvements to the efficiency of the existing vehicle assembly operations, and additional capabilities to increase productivity, is discussed.
Approximation of a Random Process by Inversion of a Kernel Density Estimator
Authors: Lloyd George M.
Published: October 2013

A random process is frequently defined entirely by outcomes measured from it. Generally an important goal is to be able to approximate the random process sufficiently accurately in some sense. Common reasons for doing so are to provide surrogate variates for performing tests of hypothesis, and also to provide a model of the random process computationally suitable for inputs to or as stochastic coefficients for a numerical model. In cases of concern here the context is not limited to univariate random process, nor to Gaussian processes. This paper examines an alternative approach for modeling an arbitrary random process known only through its source variates. In this new method the kernel density estimator is inverted to provide a functional in the space of standard normal random variables. This functional can be expanded into a series representation of the random process using Wiener expansions. Several benefits accrue to this method. First, the computation expense of evaluating a KDE (and computing its inverse) need only be done once. Secondly, the rate of convergence of the series representation yields information on the departure of the random process from a strictly Gaussian one.
Input Force Identification in Time Domain Using Optimally Placed Accelerometers
Authors: Gupta Deepak K. , Dhingra Anoop K.
Published: October 2013

A technique in time domain is presented that aims at identifying dynamic loads acting on a structure from acceleration time response measured experimentally at finite number of locations on the structure. The structure essentially gets transformed into its own load transducer. The approach is based on the standard equilibrium equation in dynamics in time domain. For measurement of the acceleration response, there can be a large number of combinations of locations on the structure where the accelerometers can be mounted and the recovered loads may be quite sensitive to the locations selected for accelerometer placements. In fact, the precision with which the applied loads are estimated from measured acceleration response depends on the number of accelerometers utilized and their locations on the component. Implementation of a methodology to determine the optimum set of accelerometer locations, based on the sparse nature of the mass, damping and stiffness matrices, is presented to guide the selection of number and locations of accelerometers that will provide the most precise load estimates. A numerical validation that helps understand the main characteristics of the proposed approach is also presented. The numerical results reveal the effectiveness and utility of the proposed technique.
Estimating the Position and Size of a Cavity in a Plate by Means of Boundary Element Method and Conduction Heat Transfer
Authors: Karganroudi Sasan Sattarpanah , Roshani Mohammad R. , Aligoodarz Mohammad R. , Tehrani Mohammad Reza Soleimani
Published: October 2013

This study proves the possibility of predicting the existence of a cavity inside a homogenous body based on the geometrical parameters and the position of cavity by means of the boundary element method. Regarding the extensive use of steel plates in heavy and huge industries, this project focuses on two-dimensional plates and studies the thermal effects of shape and position of the existing cavity by solving the two-dimensional Laplace’s equation on conduction heat transfer over the body. The thermal changes on some boundaries affected by shape and position of cavity give an appropriate estimate of cavity. Considering the bulky and big amount of calculation and iteration and also the type of boundary conditions the fast and accurate numerical method proper to the mentioned problem, Boundary Element Method, is applied to simulate the experiments. The conclusion is taken due to the results of simulation. Based on the theory of Boundary Element method, the problem is simulated as a rectangular plate with two constant temperature and two constant flux boundary conditions while the cavity is inside, so concerning the position of cavity the variation of decreasing temperature on the boundaries with constant flux rate is changing. In order to reach the idea, the proper programming code has been written in Visual Fortran programming language and the results of the program output has been compared and interpreted.
A Search-Based Approach for Prediction of Flexible Hose Shapes
Authors: Hermann Tristan , Patil Lalit , Srinivas Lakshmi , Murthy Krishna , Dutta Debasish
Published: October 2013

Flexible hoses and cables are vital components used in a variety of artifacts, including complex products such as automobiles. When designing a vehicle, it is important to know the shape that a flexible component will take between its two endpoints. Incorrect information regarding hose shapes can lead to shortened component lifespans and even costly recalls. Several efforts have attempted to predict the shape of flexible components. In the past, Computer Aided Engineering (CAE) simulations using mathematical models have been used to predict hose and cable shapes, providing fairly accurate results. However, CAE simulations of hoses and cables are extremely time-consuming, often taking several hours to weeks for completion. In this paper, we propose an approach to dramatically reduce this time burden. We propose the idea of “looking up” a solution. Rather than mathematically calculating a hose shape, our approach called Search-based Real-time Prediction of CAE Solutions (SRPCS) relies on a large database of intelligently represented problems and solutions. The query problem is then intelligently decomposed into problems with known solutions and the individual solutions are then recombined to obtain the overall shape, i.e., solution to the problem. We generated real hose shapes in a test rig and stored in a database. Analysis of the results shows that the SRPCS provides an accurate and rapid solution to obtain the shape of flexible components.
A Physics-Based Modeling Approach of a Natural Gas HCCI Engine
Authors: AbdelGawad Marwa W. , Tafreshi Reza , Langari Reza
Published: October 2013

Homogeneous Charge Compression Ignition (HCCI) Engines hold promises of being the next generation of internal combustion engines due to their ability to produce high thermal efficiencies, in addition to low nitric oxides and particulate matter. HCCI combustion is achieved through the auto-ignition of a compressed homogenous fuel-air mixture, thus making it a “fusion” between spark-ignition and compression-ignition engines. The main challenge in developing HCCI engines is the absence of a combustion trigger hence making the control of combustion timing difficult.

To be able to control ignition timing, a physics-based model is developed to model the full HCCI engine cycle while taking into consideration cycle-to-cycle transitions. Exhaust Gas Recirculation is used to control combustion timing while the temperature at intake valve closure will serve as the parameter that represents the desired ignition timing. The Modified Knock Integral model defines the necessary relationship between ignition timing and temperature at intake valve closure. Validation of the developed model is performed by determining the ignition timing under varying conditions. Results are shown to be in accordance with data acquired from a single-cylinder model developed using a sophisticated engine simulation program, GT-Power.
Simultaneous Time-Frequency Control of Multi-Dimensional Micro-Milling Instability
Authors: Liu Meng-Kun , Halfmann Eric B. , Suh C. Steve
Published: October 2013

A novel control concept is presented for the online control of a high-speed micro-milling model system in the time and frequency domains concurrently. Micro-milling response at high-speed is highly sensitive to machining condition and external perturbation, easily deteriorating from bifurcation to chaos. When losing stability, milling time response is no longer periodic and the frequency response becomes broadband, rendering aberrational tool chatter and probable tool damage. The controller effectively mitigates the nonlinear vibration of the tool in the time domain and at the same time confines the frequency response from expanding and becoming chaotically broadband. The simultaneous time-frequency control is achieved through manipulating wavelet coefficients, thus not limited by the increasing bandwidth of the chaotic system — a fundamental restraint that deprives contemporary controller designs of validity and effectiveness. The feedforward feature of the control concept prevents errors from re-entering the control loop and inadvertently perturbing the sensitive micro-milling system. Because neither closed-form nor linearization is required, the innate, genuine features of the micro-milling response are faithfully retained.
3D Micromixer
Authors: Farshchian Bahador , Choi Junseo , Park Sunggook
Published: October 2013

This paper presents the fabrication of a 3D microchannel whose sidewalls and bottom surface are patterned with ratchets using a modified 3D molding process. In the modified 3D molding process the surface of poly(methyl methacrylate) (PMMA) is first patterned using a brass mold having ratchet structures. Then PDMS prepolymer was spin coated over the surface of micropatterned PMMA and cured followed by the primary molding using a brass mold having a T-conjunction protrusion. After primary molding demolding was done by first demolding the brass mold and then peeling off PDMS stamp from PMMA substrate. By setting a 45° angle between direction of ratchets patterned on the surface of PMMA and the brass mold protrusion prior to primary molding 45° slanted ratchets were formed on the sidewall and bottom surface of microchannel using the modified 3D molding. The scanning electron microscope (SEM) micrographs show a successful integration of micropatterns inside the microchannel. Holes were drilled in the inlet and outlet area of the 3D channel before bonding. A solvent bonding technique was used for bonding of 3D channel to a plain cover plate. After bonding capillary tubes were inserted into the holes and glued to the chip using an epoxy glue. For characterization of mixing fluorescence intensity was quantified in the 3D microchannel as deionized water and fluorescein dye injected from different inlets of 3D micromixer were mixed along the 3D microchannel and mixing efficiency was calculated. The results were compared with the data obtained for similar microdevice whose surfaces were not patterned. The results demonstrate at a specific flow rate a faster mixing occurs in a microdevice whose sidewall and bottom surface are patterned with slanted 45° ratchets.
CFD for Cyclone Optimization for Liquid Extraction From Solid Particles in Turbulent Air Flows
Authors: He Anpeng , Zhang Ning
Published: October 2013

CFD based design optimization for liquid extraction using cyclone is presented in this paper. The extraction process is liquid extraction from solid particles in turbulent air flows. The solid particles contain a certain amount of liquid, so call wet-particles. The simulations were performed using commercial ANSYS-FLUENT software. The software is an excellent tool for simulating turbulent flows. However, the software does not have the direct capability of simulating this particular liquid-extraction process. External user defined functions and subroutines (UDFs) were developed and incorporated in the software to conduct the simulation for this particular process. Several design configurations were tested to obtain the best extraction performance. Investigations of the physics of the extraction process in turbulent flows were also conducted using the new “hybrid” software tool.
Length Scale Dependent Deformation in Polymers
Authors: Alisafaei F. , Sanei Seyed Hamid Reza , Han Chung-Souk
Published: October 2013

Length scale dependent deformation of polymers has been observed in different experiments including micro-beam bending and indentation tests. Here the length scale dependent deformation of polydimethylsiloxane is examined in indentation testing at length scales from microns down to hundreds of nanometers. Strong indentation size effects have been observed in these experiments which are rationalized with rotation gradients that can be related to Frank elasticity type molecular energies known from liquid crystal polymers. To support this notion additional experiments have been conducted where Berkovich and spherical indenter tips results have been compared with each other.
A Computer-Based Design System for Lightweight Grippers in the Automotive Industry
Authors: Petersson Håkan , Motte Damien , Eriksson Martin , Bjärnemo Robert
Published: October 2013

This paper presents the development as well as the architecture of a computer-aided dedicated fixture design system intended to support the design of lightweight (carbon fiber composite) grippers for a major truck company. Lightweight grippers were required due to the increasing production rates in the automotive industry. The current robotic equipment was facing diverse problems during transportation and aligning of the parts, problems related to mass inertia, accuracy and stability. Moreover, the increased demands for truck customization and fast release of new product versions required a computer-based support for the design of the appropriate fixtures.

This application is believed to be of interest for fixture research because the design of such complex fixtures is likely to appear more and more often. Specifically, such fixtures are subject to specific requirements that necessitate a systematic requirement elicitation method; they also require extensive conceptual design work as well as careful analysis activity planning.

The main steps requisite for the development of the design system are reported: setup planning, fixture planning, conceptual design of the gripper. The architecture, the process and the constituent elements of the design system are also described and illustrated.
Conducting Heterointerface of Polar-Nonpolar Band Gap Insulators
Authors: Su Shanshan , You Jeong Ho
Published: October 2013

Recently, the heterointerface between two band insulators, LaAlO3 and SrTiO3 has received much attention due to its high conducting behavior. The origin of conducting carriers at the LaAlO3/SrTiO3 heterointerface has been mainly explained by two distinct models: the polar catastrophe model and the atomic inter-diffusion model. The polar catastrophe model is based on a half electron transferred from polar LaAlO3 to nonpolar SrTiO3 to avoid the divergence of electric field without any atomic diffusions. The atomic inter-diffusion model is based on the transfer of dopants from LaAlO3 to SrTiO3 near the interface. However, the origin of the conducting carriers is still under debate and needs to be investigated further. In this study, we have examined the origin of conducting carriers at the LaAlO3/SrTiO3 heterointerface using the self-consistency calculations of Schrödinger equation and Poisson equation. We have studied the LaAlO3/SrTiO3 heterointerfaces with and without atomic diffusions. From the self-consistency calculations, carrier distributions, band structures, energy levels, and wavefunctions have been obtained. It has been found that the majority of electron is localized within a few nm from the interface forming two-dimensional electron gas, and multi-subbands are occupied indicating a multi-channel conducting behavior. We also calculated the electron mobility at the interface using the linearized Boltzmann equation including various scattering mechanisms, such as acoustic phonon, polar optical phonon, and remote charged layers in LaAlO3. The calculated mobility has been compared with available experimental data as a function of temperature and thickness of LaAlO3.
Natural Convection Within an Elongated Vertical Cylinder: Heat Loss From Bore of Oil Well Christmas Tree
Authors: Sanchez Mauricio A. , Marotta Egidio (Ed) , Arora Sumit
Published: October 2013

Internal natural convective heat transfer from a thin walled, vertical cylinder with an exposed vertical surface is investigated numerically. The top and bottom end faces are assumed isothermal. This setup approximates the vertical wellbore of a christmas tree for simulating cool-down of subsea oil and gas equipment during shutdown operations. The primary objective of this study is to determine the cooling rate of the interior fluid and the onset of fluid rotation caused by the two non-adiabatic surfaces as a function of Biot (Bi) at the vertical cylindrical wall. The flow is assumed to be three-dimensional, non-steady, and transitional with constant fluid properties except for the density variation with temperature. This latter effect gives rise to the buoyancy forces; being treated by using the Boussinesq approach. The solution is obtained by numerically solving the governing equations; these equations were written in terms of dimensionless variables. The solution is obtained using a commercial finite element method based-code, COMSOL Multiphysics. The specific application that motivated this investigation involved a range of Prandtl numbers (Pr) from 0.7, to 168. The results for these cases are presented herein. In addition, a range of other governing parameters has been considered. From the numerical results for small and moderate values of Rayleigh number, it is observed that steady state solutions (i.e. temperature and velocity) are stratified at the source temperature region regardless of the Biot number.
Modeling a Stirling Engine for Cogeneration Applications
Authors: Ferreira Ana C. , Teixeira Senhorinha , Teixeira José C. , Nunes Manuel L. , Martins Luís B.
Published: October 2013

The interest on decentralized power generation technology has been drastically increasing over the last few years. This great interest is due to the necessity of achieving new ways for improving energy efficiency, the national security of energy supply and the reduction of carbon dioxide emissions. Combined heat and power generation (CHP) systems can be a good option to achieve those goals. In Europe and for the building sector, this fact can be translated in the development of low power systems (micro-CHP), designed to fulfill building equivalent loads. These systems will replace the usual boilers that satisfy the dwelling’s heat requirements and, additionally, generate electricity for own consumption or export back to the electricity grid. The most cited technologies in small and micro-scale are Fuel Cells, Internal Combustion Engines, and Stirling Engines. Stirling Engines are gaining some attention due to their advantages: high total efficiency, fuel flexibility, low emissions, low noise/vibration levels and good performance at partial load. Due to these characteristics, Stirling engines seem to be a good alternative for residential energy conversion, and thus, a pathway for more energy-efficient systems that rise to the challenges of increasing market competition. Many studies have been conducted in order to assess Stirling Engines performance, but the integration of technical and economic evaluation for micro-CHP systems applications is an issue that is not focused in literature, and is the final objective of this project.
The Shockwave Response of Thin Composite Materials
Authors: Jahnke Douglas , Andreopoulos Yiannis
Published: October 2013

Impingement of blast or shock waves on structures is characterized by a substantial transient aerodynamic load that develops over the short time associated with the shock reflection time scale. This mutual interaction between the shock wave and the structure can cause significant deformation of the structure and high strain rates within the material resulting in damage. An experimental investigation was carried out to determine the aeroelastic response of thin flat plates of composite materials during face-on impact with planar shock waves. The experiments were performed in a large-scale shock tube research facility, which had a working section of 12 inches in diameter and a length of 80 ft.

Phenolic composite S2-HJ1 plates of 1/8 inch nominal thickness consisting of 12 layers of fibers and epoxy composite S2 plates of 1/8 inch nominal thickness consisting of 10 layers of fibers were tested in the present investigation. Miniature semi-conductor strain-gauges of high frequency response, high speed photography and Digital Image Correlation techniques were employed to measure locally the strain on the exterior side of the plates and high frequency response pressure transducers were used to measure time-dependent wall and total pressure. In order to provide comparison with the response of monolithic material to similar compressive loadings, aluminum and stainless steel plates were also tested under the same conditions. The application of shock loading on the specimen causes significant permanent deformation on the plates which has been measured immediately after the experiment while the specimen is still mounted on the end flange of the shock tube. These experimental data obtained in the present experiments include the measured displacement of the external surface of the plates from their original position in the normal to the plate direction along the radius of the specimen. This displacement is highest at the center of the plate and zero at the location of clamping. The results show that the deformations of the thicker plates are still considerably lower than those obtained in the steel and thinner composite plates although the loading pressure is more than triple in magnitude and the corresponding impulse is about 2.3 times higher. Composite plates were found to suppress several of the modes of the wave patterns while metallic ones demonstrate a rich variety of interacting modes. The frequency content of the strain signals on the surface of composite plates was not always the same with the content of the surface acceleration measured in free vibration experiments.
Impact Characterization of Polyurethane Composites Manufactured Using Vacuum Assisted Resin Transfer Molding
Authors: Mohamed M. , Vuppalapati R. R. , Hawkins S. , Chandrashekhara K. , Schuman T.
Published: October 2013

Glass fiber reinforced composites are finding various applications due to their high specific stiffness/strength, and corrosion resistance. Vacuum assisted resin transfer molding (VARTM) is one of the commonly used low cost composite manufacturing processes. Polyurethane (PU) resin system has been observed to have better mechanical properties and higher impact strength when compared to conventional resin systems such as polyester and vinyl ester. Until recently, PU could not be used in composite manufacturing processes such as VARTM due to its low pot life. In the present work, a thermoset PU resin systems with longer pot life developed by Bayer MaterialScience is used. Glass fiber reinforced PU composites have been manufactured using one part PU resin system. Performance evaluation was conducted on these composites using tensile, flexure and impact tests. Finite element simulation was conducted to validate the mechanical tests. Results showed that PU composites manufactured using novel thermoset PU resins and VARTM process will have significant applications in infrastructure and automotive industries.
Electrothermal Blinking Vortices for Chaotic Mixing
Authors: Loire Sophie , Kauffmann Paul , Gimenez Paul , Mezić Igor , Meinhart Carl
Published: October 2013

Thanks to its favorable reduction scale law, and its easy integration, electrokinetics has emerged over the last fifteen years as one of the major solution to drive flows in fully integrated lab-on-chip. At microscale, an efficient mixing is a keystep which can dramatically accelerate bio-reactions. For thirty years, Dynamical System theory has predicted that chaotic mixing must involve at least 3 dimensions (either time dependent 2D flows or 3D flows). However, in microfluidics, few works have yet presented efficient embedded micromixers. This paper presents experimental and theoretical study of 2D time dependent chaotic mixing using AC electrothermal fluid flows. Experiments and numerical simulations are performed on a top view device and a sideview device. In both devices, a sinusoidal electric signal is applied between 3 interdigitated gold electrodes. A phase signal Vpp = 11V and a ground are switched between the two side electrodes using a step function, whereas the opposite phase signal –Vpp is steadily applied to the center electrode (Figure 1). Flow velocity is measured by micro particle image velocimetry μ PIV. The velocity profile shows a dramatic asymmetry between the two vortices. Therefore, during the switch, vortices overlap, leading to stretching and folding flows required to obtain chaotic mixing (Figure 3 and 4). The experimental measurements validate our electrothermal models based on our previous work [1]. The mixing efficiency of low diffusive particles is studied at multiscale using the mix-variance coefficient (MVC) [2] to evaluate mixing at different scales (Figure 4). To do so, the domain is successively divided in boxes along the x and y direction up to nx and ny boxes, respectively. For each box configuration, average bead concentration is computed. The variance of these concentrations is then evaluated: MVCs=1nxny∑i=1ny∑j=1nxρij-0.52. The result of numerically evaluated MVC in Figure 2 show a dramatic increase of mixing efficiency with blinking vortices compared to steady flow.

Theoretical, experimental and simulation results of the mixing process will be presented.
Effects of the Light Source on the Signal Quality for Photonic and Microfluidic Nanohole Sensor Calorimeter
Authors: Sen Mehmet , Kowalski Gregory , Fiering Jason , Larson Dale
Published: October 2013

Our research focuses on the development of a calorimeter device utilizing a photonic temperature sensor based on the extraordinary optical tranmission (EOT) signals through nanohole array (NHA) sensors on metallic films in combination with a continuous coflow reactor clamped to the sensor chip. The fluid was in direct contact with the gold. The incident light traversed the layers of the flowcell assembly to illuminate the sensors, and was measured using a CCD camera. Here, the effect of the light source and the flowcell material and design on the signal quality is reported. Using an incoherent light source and eliminating elastic deformation from the illumination path resulted in an interference-free, fringe-free optical configuration. Using the improved apparatus, EOT signal temperature dependence for different liquids (DI water and ethanol) was presented. EOT signal gain due to a temperature change was 3.810 times higher in the ethanol than the DI water signal gain. This behavior was explained by the difference in the volumetric expansion coefficient, which is a factor in the change of dielectric constant due to temperature changes. This trend was in agreement with the analytical relations and supports the use of EOT as a measurement signal in a miniaturized calorimeter.
High Heat Flux Phase Change on Silicon Wick Structures
Authors: Cai Qingjun , Bhunia Avijit , Zhao Yuan
Published: October 2013

Silicon is the major material in IC manufacture. It has high thermal conductivity and is compatible with precision micro-fabrication. It also has decent thermal expansion coefficient to most semiconductor materials. These characteristics make it an ideally underlying material for fabricating micro/mini heat pipes and their wick structures. In this paper, we focus our research investigations on high heat flux phase change capacity of the silicon wick structures. The experimental wick sample is composed of silicon pillars 320μm in height and 30 ∼ 100μm in diameter. In a stainless steel test chamber, synchronized visualizations and measurements are performed to crosscheck experimental phenomena and data. Using the mono-wick structure with large silicon pillar of 100μm in diameter, the phase change on the silicon wick structure reaches its maximum heat flux at 1,130W/cm2 over a 2mm×2mm heating area. The wick structure can fully utilize the wick pump capability to supply liquid from all 360° directions to the center heating area. In contrast, the large heating area and fine silicon pillars 10μm in diameter significantly reduces liquid transport capability and suppresses generation of nucleate boiling. As a result, phase change completely relies on evaporation, and the CHF of the wick structure is reduced to 180W/cm2. An analytical model based on high heat flux phase change of mono-porous wick structures indicates that heat transfer capability is subjected to the ratio between the wick particle radius and the heater dimensions, as well as vapor occupation ratio of the porous volume. In contrast, phase change heat transfer coefficients of the wick structures essentially reflect material properties of wick structure and mechanism of two-phase interactions within wick structures.
Detailed Experimental Characterisation of Gas-Liquid Two-Phase Slug Flow in Horizontal Pipes
Authors: do Amaral Carlos E. F. , Castillo Fernando , da Silva Marco José , Santos Eduardo N. , Morales Rigoberto E. M.
Published: October 2013

Two phase flow occurs in many applications in industry, mainly in the transport of mixtures in pipes. The identification of these patterns is of fundamental importance in the design of piping systems and equipments. In this scenario, this work proposes an experimental study to identify multiphase flow patterns of water and air in horizontal tubes. The study was developed using an experimental circuit of 26 mm diameter and 9.2 m length pipe, at Thermal Sciences Lab at Federal Technological University of Paraná. To characterize the parameters one used an intrusive mesh electrodes sensor, a tomographic technique that allows details of the distribution of phases with good temporal and special resolution. Tests were conducted using several experimental settings of water and gas superficial flows, mostly with slug flow characteristics. Measurements were compared to models and the temporal void fraction series were analyzed to produce bubble velocity and frequency information, showing the characteristics for each two-phase pattern.
Simulation Based Optimization of Microfluidic Devices Used for Molecular Enrichment
Authors: Xia Hui , Mathew Bobby , Hegab Hisham , Feng June
Published: October 2013

Microfluidic devices are used in several engineering fields ranging from biomedical to chemical to engineering for applications such as micro reactor, target molecular enriching and cell capturing. With regard to related applications, microfluidic devices offer advantages such as high surface area to volume ratio, increased mass transfer coefficient and portability in addition to their requirement of low analytes. Affinity based microfluidic devices with microscale posts have high compactness and mass transfer coefficient. In order to maximize the benefits offered by employing microfluidic devices, it is important to apply parametric study in the device designing work. This study is aimed at studying the operating and geometric parameters of microfluidic devices with square/rectangular microscale posts. The geometric parameters, such as aspect ratio of the microposts used, could possibly decide the performance of the device. Operating parameters studied are Reynolds number, Peclet number, Damköhler number, and equilibrium reaction constant. These parameters encompass the influence of velocity, diffusivity, density, viscosity, hydraulic diameter, inlet concentration of species and absorption/desorption reaction constants.

This work theoretically analyzes the influence of the above mentioned parameters using COMSOL Multiphysics 4.2.a. The governing equations of microfluidic devices, i.e. Navier-Stokes equations and the advection-diffusion equation, subjected to the above mentioned operating parameters, are solved to obtain the velocity profile, pressure drop and concentration profile of the species. The metric used for analyzing the influence of each operating parameter is the capture efficiency, i.e. the ratio of outlet concentration to inlet concentration as well the pressure drop. The results of this study would improve the design of microfluidic devices used for chemical reactions as well as that used for protein enrichment.
Analysis of Secondary Features From Visualization of Two-Phase Refrigerant Flow
Authors: Field Brandon S.
Published: October 2013

Flow visualizations of refrigerant flows were made in a 0.5 mm glass channel. High speed videos of two-phase R134a flows were used to examine the secondary features within the two-phase flow and categorize the flow regimes present. Essentially, in small diameter channels, there are only two major observed flow regimes: inertia dominated (annular flow) and surface tension dominated (intermittent flow: slug or bubble). Image analysis was used to measure the velocities of the slugs and bubbles, and measurements of secondary features of the flow, such as the velocity of the surface waves that arose in slug-annular flow and the smaller bubbles that could be seen in the wakes of larger bubbles.

The secondary features of the two-phase flow are discussed with regard to their contribution to the flow regimes that are observed as the flow moves through the channel. Rings of liquid were observed to form into liquid slugs, dividing the longer bubbles into two. This is believed to be one of the transition mechanisms between the two flow regimes. Small droplets were also observed within the vapor core, which demonstrated velocity gradients within the vapor bubbles. Velocity measurements of the secondary features within the liquid films are used in the analysis of the dynamics within these flows that lead to pressure drop and flow regime transition.
Heavy Truck Rollover Testing Methods
Authors: Herbst Brian R. , Bish Jack O. , Meyer Steven E. , Nelson Arin O. , Forrest Stephen M. , Bell Lauren D. , Clarke Christopher C.
Published: October 2013

Rollovers continue to be a major source of heavy truck fatalities when compared to other accident modes. Real world rollover accidents are analyzed and two distinct damage patterns are identified. Damage to heavy truck roofs can occur from lateral loading that transitions to vertical roof loading as the vehicle rolls onto its side and then over onto its roof. A second load path can occur when the vehicle has rolled onto its side and furrows into the ground generating large longitudinal friction forces between the roof and ground. A review of the previous literature and various test methodologies are presented. A sled impact test methodology is presented which allows for structural assessment of a heavy truck cab’s crashworthiness in both of these loading environments. Two test series are presented using the sled impact test methodology in order to analyze real world truck rollovers using varying impact platen and contact angles. The structural deformation and failure patterns were found to be consistent with damage seen in real world accident vehicles. In each case, a second equivalent truck cab was then reinforced and tested under similar conditions to evaluate the energy management and crush resistance of a stronger cab structure. These structural reinforcements demonstrated a substantial reduction in roof crush and protected the survival space of the occupant compartment.