bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Warpage Measurement Capabilities and Results Obtained by Using Laser and Digital Fringe Projection Methods
Authors: Kang Sungbum , Ume I. Charles
Published: April 2014

Electronic packaged devices are becoming increasingly smaller in size and higher in density while requiring higher performance and superior reliability. Warpage is one of the crucial factors for the thermo-mechanical reliability of electronic packages and warpage control becomes a more crucial process during the printed wiring board (PWB) fabrication and package assembly processes. This requirement necessitates more accurate methods of measuring warpage. The fringe projection methods are recent trends for measuring the warpage of chip packages, PWBs, and PWB assemblies because of their noncontact, full-field, and high-resolution measurement capabilities. This paper presents a comparison of two fringe projection methods: laser fringe projection (projection moiré) and digital fringe projection. Experimental results show that digital fringe projection has higher practical resolution, and better accuracy and precision than laser fringe projection.
Large Eddy Simulation of a Swirl-Stabilized Flame
Authors: Zhang Cheng , Zhao Wei
Published: April 2014

Swirl is used in a wide range of combustions systems such as engines, furnaces, gasifiers, and boilers, to enhance mixing, stabilize flames, and reduce pollutant emissions. Numerical modeling of swirling flows remains a challenging task, since there may exist complex recirculating flow patterns and flow instabilities associated with vortex breakdown, precessing vortex core, and jet precession. In swirling flames, the situation becomes more complex because the unsteady heat release can add other modes of instability. The origins and nature of these instabilities are still not well understood despite many experimental and numerical studies have been conducted in the area. The Sydney swirl burner flame series provide an excellent platform for validating numerical methods for turbulence-chemistry interactions and have been target flames for the TNF workshop series. The burner has well-defined boundary conditions and comprehensive experimental data sets have been documented for different fuel compositions and flow conditions. Compared with the piloted and bluff-body stabilized flames, swirl-stabilized flames pose an additional challenge to numerical modeling because of the complex flow patterns and inherent flow instabilities. In this study, a large eddy simulation (LES)-based multi-environment turbulent combustion model is used to model the Sydney swirl burner flame SMH1. The multi-environment filtered density function model (MEFDF) depicts the filtered density function (FDF) as a weighted summation of a small number of multi-dimensional Dirac delta functions in composition space. It is derived from the transport FDF equation using the direct quadrature method of moments (DQMOM). The MEFDF method with multiple reactive scalars retains the unique property of the joint FDF model of treating the chemical source term exactly. A 19-species mechanism reduced from GRI-Mech 2.11 is employed for chemical kinetics. The in situ adaptive tabulation algorithm (ISAT) is used to speed-up the evaluation of the chemical source term. The predicted radial profiles of the axial velocity, azimuthal velocity, mixture fraction, temperature, and species mass fractions of CO2, CO, and NO are in reasonable agreement with the experimental data. It has been found that, compared with the experimental data, the profiles of the temperature and species mass fractions shifted slightly outward in the radial direction at downstream locations and NO mass fraction is slightly over-predicted at most locations. Further work will be needed to find out possible reasons for these discrepancies.
Evaluation of Head Injury Criteria Under Different Impact Loading
Authors: Saboori Parisa , Mansoor-Baghaei Shahab , Sadegh Ali M.
Published: April 2014

The Head Injury Criterion (HIC) has been employed as a measure of traumatic brain injury arising from an impact involving linear acceleration. Some investigators have been reported the shortcomings of the HIC regarding the angular accelerations, head mass and the precise threshold of injury level [1, 2]. In this study the effect of acceleration curves, as a frontal impact, and the HIC values on the strain in the brain was critically analyzed. Specifically in this paper, the strains in the brain for three sets of acceleration pulses, where the peak of the curve takes place early or later (advanced or delayed) during the pulse time, were investigated. The results of this study indicate that for two different acceleration pulses, with the same peak value, duration and the same HIC values the strains in the brain are different. Therefore there is a need for further research leading to better criteria or modification of the HIC as it relates to the Traumatic Brain Injury (TBI).
Design and Analysis of Ejector Powerplant System
Authors: Berana Menandro S. , Bermido Edward T.
Published: April 2014

An ejector is a device with no moving components and is made up of four main parts: converging-diverging nozzle, suction chamber, mixing section and diffuser. It has become popular in refrigeration system as it gives the advantage of recovering expansion energy from high pressure difference into compression energy.

In this study, the potential use of ejector in powerplants that use low-grade or low temperature heat sources was conceptualized and analytically investigated. A novel combination of the ejector and the organic Rankine cycle (ORC) was proposed. The driving fluid in the ejector of the proposed powerplant cycle is the high-pressure liquid in the separator that is just circulated back to the evaporator in the ORC. Further increase in turbine temperature drop (TTD), which can increase the power output and efficiency of the plant, can be achieved through expansion, mixing and recompression processes in the ejector. Ocean thermal energy conversion (OTEC), solar-boosted OTEC (SOTEC), solar-thermal, waste-heat driven, biomass and geothermal powerplants were considered in the analysis.

Mathematical models in our previous studies were developed and used to calculate for nozzle and ejector parameters. The geometric profile of the ejector for optimization with categorized heat sources was determined. Isentropic, internally reversible, and irreversible two-phase nozzle expansions were analyzed. Two-phase flow calculations were continued in the mixing section. It was assumed that the constant-pressure mixing of the primary and secondary fluids occur at the hypothetical throat inside the constant-area section. Calculation for shock wave in the mixing section was also done. The diffuser was analyzed in a similar manner with the nozzle.

Calculation for other components and plant efficiencies was finally conducted. Ammonia and propane which are both natural working fluids were used in the analysis. Evaporator temperature range from 293.15 K to 393.15 K and condenser and ambient temperatures range from 283.15 K to 308.15 K were used in the analysis. The lowest ambient temperature of 283.15 K was used for the OTEC and SOTEC powerplants. It was shown that ammonia and propane can operate up to 11 K and 12 K below the ambient temperature, respectively. Ejector efficiency ranged from 90 to 95% for both working fluids. The maximum efficiencies of the ejector powerplant were 19.2% for ammonia and 14.9% for propane, compared to 11.7% and 9.8% of the conventional ORC. It was analytically determined that the efficiency of the ejector powerplant is higher than that of the ORC powerplant for the same working fluid and conditions of the evaporator, condenser and the ambient.
The Blast Gauge™ System as a Research Tool to Quantify Blast Overpressure in Complex Environments
Authors: Ostertag Michael H. , Kenyon Matthew , Borkholder David A. , Lee General , da Silva Uade , Kamimori Gary
Published: April 2014

Tactical officers and military personnel who train in explosive entry techniques regularly put themselves at risk of blast exposure. The overpressure conditions in complex military and law enforcement environments, such as interior doors, hallways, and stairwells, cannot be accurately predicted by standard blast models which were developed from outdoor, free-field blasts. In both training and operations, small, low-cost blast overpressure sensors would provide the benefit of tracking exposure levels of at-risk individuals. The sensors would allow, for the first time, direct determination of safe stand-off distances and positioning for personnel during explosive breaching. Overpressure, impulse, and acceleration data has been captured for a series of interior and exterior blasts, demonstrating the utility of the Blast Gauge system as a training and research tool to quantify blast overpressure in complex environments.
Development of an Adaptive Human-Machine-Interface to Minimize Driver Distraction and Workload
Authors: Westin Matthew , Dougherty Ronald , Depcik Christopher , Hausmann Austin , Sprouse Charles
Published: April 2014

The original use of the vehicle dashboard was to provide enough sensory information to inform the driver of the current engine and vehicle status and performance. Over time, it has evolved into an entertainment system that includes person-to-person communication, global positioning information, and the Internet, just to name a few. Each of these new features adds to the amount of information that drivers must absorb, leading to potential distraction and possible increases in the number and types of accidents. In order to provide an overview of these issues, this paper summarizes previous work on driver distraction and workload, demonstrating the importance of addressing those issues that compete for driver attention and action. In addition, a test platform vehicle is introduced which has the capability of assessing modified dashboards and consoles, as well as the ability to acquire relevant driving performance data. Future efforts with this test platform will be directed toward helping to resolve the critical tug-of-war between providing more information and entertainment while keeping drivers and their passengers safe. The long-term goal of this research is to evaluate the various technological innovations available for inclusion in the driving environment and determining how to optimize driver information delivery without excessive distraction and workload. The information presented herein is the first step in that effort of developing an adaptive distraction/workload management system that monitors performance metrics and provides selected feedback to drivers.

The test platform (1973 VW Beetle converted to a plug-in series hybrid) can provide speed, location (GPS), 3-D acceleration, and rear proximity detection. The test drive route was a 2 km × 3 km city street circuit which took approximately 25 minutes to complete. Data is provided herein to demonstrate these capabilities. In addition, the platform has driver selectable layouts for the instrument cluster and console (LCD screens). The test platform is planned for use to determine driver preferences (e.g., dashboard/console configurations) and attention performance in addition to identifying optimal real-time feedback for drivers with different demographics.
The Effects of Retesting on the Mechanical Properties of Brain Tissue
Authors: Rezaei A. , Salimi Jazi M. , Karami G. , Ziejewski M.
Published: April 2014

Traumatic brain injury (TBI) is one of the most important problems in biomechanical engineering, and there have been many experiments conducted in order to characterize the mechanical properties of brain tissue. However, obtaining fresh human brain tissue is difficult, if not impossible. Also, the sample preparation and testing protocols must be carried out with great delicacy because brain tissue is very soft and vulnerable to being deformed under a very small amount of load. Most importantly, according to several researchers, each sample must be tested only one time as the tissue may be damaged and its characteristics subsequently changed. This paper is intended to examine the amount of decay that can happen in material characteristics due to retesting. A stress relaxation test is conducted on the same samples of the swine brain tissue multiple times in small and large deformations. The mechanical properties of the substance are calculated before and after retesting, and the constants of the tissue, as mechanical characteristics, are determined and compared. Short- and long-term moduli, relaxation times and relaxation functions are calculated and compared to understand how much they decay after repeating the experiments. The results show that retesting does not significantly change the elastic part of the tissue characteristics, but the viscous behavior shows a relatively sizeable change. The ability to account for the material decay of the samples due to repetition of the experiments results in the need for fewer samples and less preparation time and effort.
Lateral Impact Validation of a Probabilistic Statistical Shape Finite Element Model of the Head and Neck
Authors: Eliason Travis , Francis Loren , Bredbenner Todd , Stemper Brian , Nicolella Dan , Shender Barry , Paskoff Glenn
Published: April 2014

Injury prediction and mitigation are common overarching goals of modern biomechanical research. This research is fundamental to preventing and mitigating injuries sustained by those exposed to dangerous conditions including but not limited to occupational hazards, warfighter risks, automotive accidents, etc. Unlike traditional mechanical system research, biological systems are difficult and costly to test resulting in a need for robust and accurate numerical simulations. Models of the cervical spine are complex, nonlinear systems that must accurately model dynamic loading, large deflections, elastic, and viscoelastic behavior. In addition to individual complexities, population variance in both material properties and shape must be taken into account for accurate injury prediction.

As part of a hierarchical validation and verification (V&V) methodology, lateral impact cadaveric cervical spine experiments were compared to a high fidelity statistical shape finite element model (SSFEM) of the cervical spine and head. Specimens were mounted to a sled and accelerated using a pendulum impact with 1, 2, and 3 m/s impact velocities. The kinematics of the head and all individual cervical vertebrae were recorded with a Vicon motion capture system along with sled acceleration data. Sled accelerations were used as input boundary conditions for the probabilistic study using the SSFEM. Head and vertebrae rotations between the experimental and model responses were then compared.

A latin hypercube probabilistic analysis was performed for each impact velocity to determine the probabilistic response of each rotation metric. When comparing these responses, both the average and variation must be taken into consideration. This is accomplished using a quantitative validation metric based on the area between the cumulative distribution functions (CDF) of experimental response and the computed probabilistic response. Our results showed a very good match between the model and experiment at the higher impact velocities and a slightly stiffer response at lower rates. These results are consistent with previous validation studies performed with this SSFEM.

By expanding the validation data set with lateral impact loading, greater confidence in the model is obtained under different loading modes. This confidence allows the model to be used for probability of injury predictions as well as to identify important system variables in preventing injuries. High fidelity numeric modeling allows for rapid and cost effective assessment of hazardous loading conditions and safety equipment compared to experimental modeling. The knowledge gained from these modeling studies is fundamental and necessary for safe and effective design and injury mitigation.
Modeling the Ductile Brittle Fracture Transition in Reactor Pressure Vessel Steels Using a Cohesive Zone Model Based Approach
Authors: Chakraborty Pritam , Biner S. Bulent
Published: April 2014

Fracture properties of Reactor Pressure Vessel (RPV) steels show large variations with changes in temperature and irradiation levels. Brittle behavior is observed at lower temperatures and/or higher irradiation levels whereas ductile mode of failure is predominant at higher temperatures and/or lower irradiation levels. In addition to such temperature and radiation dependent fracture behavior, significant scatter in fracture toughness has also been observed. As a consequence of such variability in fracture behavior, accurate estimates of fracture properties of RPV steels are of utmost importance for safe and reliable operation of reactor pressure vessels.

A cohesive zone based approach is being pursued in the present study where an attempt is made to obtain a unified law capturing both stable crack growth (ductile fracture) and unstable failure (cleavage fracture). The parameters of the constitutive model are dependent on both temperature and failure probability. The effect of irradiation has not been considered in the present study. The use of such a cohesive zone based approach would allow the modeling of explicit crack growth at both stable and unstable regimes of fracture. Also it would provide the possibility to incorporate more physical lower length scale models to predict DBT. Such a multi-scale approach would significantly improve the predictive capabilities of the model, which is still largely empirical.
Pumping Cost Minimization in an Existing District Heating Network
Authors: Sciacovelli Adriano , Guelpa Elisa , Verda Vittorio
Published: April 2014

District heating is expected to significantly contribute to the reduction of primary energy needs for heating in urban areas. This result is obtained through use of such as CHP systems, residual heat from industries or waste-to-energy plants, as well as the integration of renewable energies. The pumping system plays a crucial role and may significantly affect its performances. In this paper a large district heating system is considered. Various operating conditions corresponding with partial load operation are analyzed through a thermo-fluid dynamic model of the network. For each condition, the optimal set point of the various pumps is obtained. The set of optimal operating conditions is finally used to obtain a control strategy for the network. Results show that with respect to conventional control strategy significant reductions in primary energy consumption can be achieved.
The Effects of Orifice Sizes on a Hydraulic Servo Valve Control System
Authors: McNea Marshall , Duan Shanzhong (Shawn)
Published: April 2014

Precision control for a force controlled hydraulic system can be achieved through the use of a flow controlled servo valve. Servo valves can be manufactured with a spool that is overlapped, an under lapped, or has a zero lap. A servo valve with a zero lap is desirable for a responsive hydraulic system without leakage, but has the disadvantage of creating a pressure pulse upon opening the valve. The hydraulic system for this setup involves having a double end, double action actuator that will have a cyclic motion generating multiple pressure waves in the system. Including an orifice in the system, which will function as a dampener, can reduce the pressure pulses. Traditional locations for orifices have been in the spool and on the actuator piston. For this hydraulic system design an external orifice will be introduced into the system via the use of an orifice plate included in the hydraulic fittings. This change allows for the ability to change the orifice size. Changing the orifice size to determine the effects on the systems control will be analyzed. The intended outcome is to demonstrate that different sized orifice plates will cause changes to the control system behavior so that an experimental formula will be established for this approach of a zero lap valve with an external damper for reduction of overshooting of dynamical behavior of the valve spool.
Ash Sintering in a Biomass Pellet Boiler
Authors: Ribeiro Pedro , Teixeira José , Ferreira Manuel Eduardo
Published: April 2014

The market for residential pellet burning equipments is well developed in some European countries like Germany, Austria and Italy and rapidly expanding in others. As a consequence the pellet production has also grown, although a large fraction is destined for industrial applications such as coal co-combustion. Due to the existence of chemical elements such as Na, K and Si, the pellet combustion can lead to agglomerated ashes on the grate of the burner causing problems for its proper operation.

The present work aimed to study the influence of temperature and air flows in the ash agglomeration at the grate. For this purpose, it was assembled an experimental setup that, in a brief, description consists of: i) boiler, whose burner allows the regulation of the primary and secondary air flow, ii) variable flow exhaust gases extraction system, iii) controllable feeding system, iv) heat dissipation system, v) data acquisition and control system, vi) exhaust gases analysis system.

The results indicate an increased formation of agglomerated ash with increasing of temperature. In addition, they also suggest the influence of excess air and primary air fraction in that formation, and the existence of an optimum working condition for high excess air and a primary air fraction of around 30%. The application of swirl in the secondary air improves both the flame stability and enables an efficient combustion into regions where the ash agglomeration is reduced. Moreover, they also show that there are other factors that influence the ash agglomeration, mostly related to the changing of the chemical elements ratio due to vaporization of the more volatile species.
Sizing and Positioning Algorithm for 1 µm to 10 µm Particles Using Shadowgraphy
Authors: Robinson Michael J. , Mahmud Zakaria , Swenson Orven F. , Hoey Justin
Published: April 2014

Measuring flows of aerosol particles of less than 10 μm diameter has proven a challenge in the past. Previously, our work included a brief review of the current state-of-art for aerosol measurements where accurate sizing was limited to particles greater than 5 μm. We developed a sizing and positioning algorithm (SPA) to accurately calculate both the diameter of a spherical particle, and the relative position of that particle to the object plane of the imaging camera for particles down to 3 μm in diameter. Our current work further extends the measurement range down to 1 μm particles. This algorithm has great benefit for the scientific community interested in small-particle aerosol flows.
AC Electrothermal Pumping for Medical Applications
Authors: Islam Nazmul
Published: April 2014

While AC electroosmosis (AC-EO) micropumps have advantages of easy implementation and compatibility with microchip fabrication, it has been observed that the pumping rate is decreased for high conductive bio-fluids [1]. To expand our applications to biomedical area we propose here the AC electrothermal (ACET) effect, which can also improve the pumping rate by multiple fold compare to AC-EO. When utilized in biomedical applications, these micropumps can be used to administer small amounts of medication (e.g. insulin) at regular time intervals. ACET generates temperature gradients in the fluids, and consequently induces space charges that move in electric fields and produce microflows. To demonstrate the fluid manipulation in high conductive bio-fluids, we have developed an AC electrothermal micropump using asymmetrical electrode arrays.
Molecular Dynamics Simulation of Electrically-Assisted Spreading of an Ionically Conducting Water Droplet
Authors: Song Fenhong , Li Ben Q. , Liu Chao
Published: April 2014

Molecular dynamics simulations are performed to study the spreading behavior of a nanosized water droplet that contains freely moving ions subject to an imposed electric field parallel to a solid surface. Results show that positive and negative ions respond to the applied electric field in a different manner, whereas water molecules are polarized by realigning themselves in the electric field. These localized behaviors of the ions and polarized molecules define the droplet deformation and spreading on a solid substrate. Both the ion concentration and the strength of the applied field play an important role in re-alignment of the polarized water molecules and in the movement of ions. The existence of the freely moving ions causes the droplet to spread differently from the pure liquid. It is observed that an ionically conducting water droplet undergoes the asymmetric-to-symmetric spreading transition at about the field strength of 0.05V/Å, which is considerably smaller than the same sized water droplet without ions. Also, the ionically conducting droplet completely wets the solid surface in the presence of a strong electric field.
The J and M Integrals for a Cylindrical Cavity in a Time-Harmonic Wave Field
Authors: Gommerstadt B. Y.
Published: April 2014

The invariant integrals are being widely used in the study of defects and fracture mechanics, mostly in elastostatics. However, the properties and the interpretation of these integrals in elastodynamics, especially in the case of time-harmonic excitation, have remained unexplored. Their study has a variety of engineering and geophysical implications, in particular, for the further development of non-destructive evaluation techniques. This contribution is focused on the derivation of the time average J integral for a cylindrical inhomogeneity and M integral for a cylindrical cavity placed in a monochromatic plane elastic wave of arbitrary wavelength. It is shown in the context of antiplane linear elasticity, that the J integral or the material force acting on the inhomogeneity resembles the radiation pressure force exerted on a dielectric cylinder by the normally incident electromagnetic wave. Based on the existing solution of this electrodynamic problem and the corresponding acoustic problem, the J integral is expressed as a function of the nondimensional wave number in the form of the partial wave expansion of the scattering theory. Employing the same classical method as for the J integral, the closed-form solution for the time average M integral for a traction-free cavity is also obtained as a function of the nondimensional wave number. The M integral, i.e., the expansion moment per unit length on an infinitely long circular cavity, is represented in terms of the scattering phase shifts as in the case of the J integral. Rather different expressions for the cavity are also derived for both integrals, which can be used more conveniently for numerical calculations, and these calculations are carried out for J and M integrals in a wide spectrum of frequencies. Asymptotic approximations of both integrals for low and high frequencies are presented. The long wavelength approximation, including the monopole and dipole contributions, has been provided for the J integral in the form of simple analytical expression. The value of M integral in the vanishing frequency limit is also presented. In the opposite short wavelength limit, the corresponding asymptotic values are derived for both integrals. These solutions which are valid for the empty cavity are extended to the case of inviscid fluid-filled cavity. The obtained results can be used in the area of non-destructive evaluation for the flaw characterization by ultrasonic scattering methods. The derived frequency dependence of the J and M integral can be related to the measurable far-field scattering amplitudes. This relationship is relevant to the inverse-scattering approach, which can be applied to the characterization of materials in an attempt to infer geometrical characteristics of flow structures.
Control of Friction-Induced Instability in Simultaneous Time-Frequency Domain
Authors: Liu Meng-Kun , Suh C. Steve
Published: April 2014

A flexible cantilever beam pressed against a rigid rotating disk is explored for studying self-excited friction-induced vibrations that are inherently unstable due to alternating friction conditions and decreasing dynamic friction characteristics. Because no linearization or approximation scheme is followed, the genuine characteristics of the system including stick-slip and inherent discontinuities are fully disclosed without any distortion. It is shown that the system dynamics is stable only within certain ranges of the relative velocity. With increasing relative velocity, the response loses its stability with diverging amplitude and broadening spectrum. A novel time-frequency controller is subsequently applied to negate the chaotic vibrations at high relative velocity by adjusting the applied normal force. The controller design requires no closed-form solution or transfer function, hence allowing the underlying features of the discontinuous system to be fully established and properly controlled. The inception of chaotic response at high relative velocity is effectively denied to result in a restoration of the system back to a relatively stable state of limit-cycle.
Channel Flow of a Mixture of Granular Materials and a Fluid
Authors: Wu Wei-Tao , Aubry Nadine , Massoudi Mehrdad
Published: April 2014

In this paper, we consider the three dimensional flow of granular materials and a viscous fluid in a channel. We use Mixture Theory to treat this problem as a two-component system [1]: One component is the solid particles (granular materials), such as sand, coal particles or red blood cells; the solid particles are modeled as a generalized Reiner-Rivlin type fluid derived by Massoudi [2], which not only considers the effects of volume fraction but also has a viscosity which is shear rate dependent. The other component, the host fluid, is assumed to behave as a linear viscous fluid, such as water, oil or plasma. For the interaction forces, the effect of different hindrance functions for the drag force is studied; moreover a generalized form of the expression for the hindrance function is suggested. For studying this two-component system numerically, a three dimensional CFD solver based on OpenFOAM® has been developed. Applying this solver, a specific problem (blood flow) has been studied for which our numerical results and experimental data [3] show good agreement.
Maximizing Strength of Bimaterial Interfaces
Authors: Nasiri P. , Dargush Gary F.
Published: April 2014

Bi-material interfaces are prevalent in a broad range of natural and man-made components and systems. Failures often occur on the interface at a free edge, especially when the corresponding linear elastic solution exhibits a singularity in stress, which depends upon the material properties and the included angles of the two material bodies. In this paper, we combine finite element analysis and a compact self-organizing cellular automata-based genetic algorithm for topology optimization of the bi-material system. The objective is to eliminate stress singularities and furthermore to reduce peak interface stresses. The developed algorithm is applied to a simple bi-material plate in an attempt to maximize strength through geometric design.
Non-Concentrated Solar Collector for Solarthermal Chemical Reactions
Authors: Hotz Nico
Published: April 2014

The purpose of this study is the proof that non-concentrating solar-thermal collectors can supply the thermal energy needed to power endothermic chemical reactions such as steam reforming of alcoholic (bio-) fuels. Traditional steam reformers require the combustion of up to 50% of the primary fuel to enable the endothermic reforming reaction. Our goal is to use a selective solar absorber coating on top of a collector-reactor surrounded by vacuum insulation. For methanol reforming, a reaction temperature of 220–250°C is required for effective methanol-to-hydrogen conversion. A multilayer absorber coating (TiNOX) is used, as well as a turbomolecular pump to reach ultra-high. The collector-reactor is made of copper tubes and plates and a Cu/ZnO/Al2O3 catalyst is integrated in a porous ceramic structure towards the end of the reactor tube. The device is tested under 1000 W/m2 solar irradiation (using an ABB class solar simulator, air mass 1.5).

Numerical and experimental results show that convective and conductive heat losses are eliminated at vacuum pressures of <10−4 Torr. By reducing radiative losses through chemical polishing of the non-absorbing surfaces, the methanol-water mixture can be effectively heated to 240–250°C and converted to hydrogen-rich gas mixture. For liquid methanol-water inlet flow rates up to 1 ml/min per m2 of solar collector area can be converted to hydrogen with a methanol conversion rate above 90%.

This study will present the design and fabrication of the solar collector-reactor, its testing and optimization, and its integration into an entire hydrogen-fed Polymer Electrolyte Membrane fuel cell system.
Current Situation of Design Criteria for Intervertebral Disc Prosthesis
Authors: Vargas-Alcaraz Epifanio , Espinosa-Bautista Adrián , López-Parra Marcelo
Published: April 2014

This paper presents the literature review on the design criteria for intervertebral disc prosthesis. The design criteria relate to the design features that intervertebral prosthesis must accomplish (i.e. fixation to bones, spine mobility, energy absorption and etcetera). The need to improve the performance has led to changes in the features which reflect in the current design criteria.

Currently, the disc prosthesis technology is experiencing a generational change. The first generation was thoroughly studied while the second generation is in the clinical tests stage. During the time the first generation prostheses were applied in patients there was not a clear trend in the clinical results which produced a lack of trust and reliability in the performance of the disc prosthesis. The changes in the design features of one generation compared to the next generation are based in the deepening in the knowledge of the problem and the results obtained with the first generation prostheses.

Some design criteria were identified for the first generation. These criteria were not completely characterized since there was not enough information to be used by the designer. This lack of characterization of most design criteria produced many different versions without a clear focus which help to define the basic design features of disc prostheses. This document presents the necessary information to thoroughly characterize the design criteria outlining the missing information for the design criteria found. An analysis is done of the design criteria in the second generation of prosthesis.

Finally if the information contained in the design criteria is enough, the clinical results would be better focused to achieve a more repeatable, reproducible and reliable process for a total disc intervertebral prosthesis replacement as now is considered the vertebral fusion, this is a gold standard.
Using TRIZ Tools at Early Stages of a User Centered Design Process
Authors: Ávila Javier , González Silvia , Borja Vicente , Espinosa Adrián
Published: April 2014

An innovative product may not be successful when launched to the market arena; this paper explores the use of TRIZ tools at early stages of the user centered design approach (UCD) to develop new products. This paper proposes an application of TRIZ tools through an abstract analysis of the customer’s interactions and the context; this allows a deeper understanding and a comprehensive definition of customer requirements. The authors’ proposal is aimed at identifying innovative commercial successful opportunities. The main contribution of this paper is centered on the integration of the value creation and innovation tools of the UCD approach and TRIZ at early design stages. The first part of the paper describes the link between relevant design methodologies and innovation tools applied by UCD and TRIZ. The next section discusses the integration of UCD and TRIZ. The third section presents applications of this integration. Finally conclusions are presented and further work is described.
Transitional and Turbulent Flow Modeling in a Tesla Valve
Authors: Thompson Scott M. , Jamal Tausif , Paudel Basil J. , Walters D. Keith
Published: April 2014

A Tesla valve is a fluidic dioide that may be used in a variety of mini/micro channel applications for passive flow rectification and/or control. The valve’s effectiveness is quantified by the diodicity, which is primarily governed by the incoming flow speed, its design and direction-dependent minor losses throughout its structure during forward and reverse flows. It has been previously shown that the Reynolds number at the valve inlet is not representative of the entire flow regime throughout the Tesla structure. Therefore, pure-laminar solving methods are not necessarily accurate. Local flow instabilities exist and exhibit both transitional and turbulent characteristics. Therefore, the current investigation seeks to identify a suitable RANS-based flow modeling approach to predict Tesla valve diodicity via three-dimensional (3D) computational fluid dynamics (CFD) for inlet Reynolds numbers up to Re = 2,000. Using ANSYS FLUENT (v. 14), a variety of models were employed, including: the Realizable k-ε, k-kL-ω and SST k-ω models. All numerical simulations were validated against available experimental data obtained from an identically-shaped Tesla valve structure. It was found that the k-ε model drastically under-predicts experimental data for the entire range of Reynolds numbers investigated and cannot accurately model the Tesla valve flow. The k-kL-ω and SST k-ω models approach the experimentally-measured diodicity better than regular 2D CFD. The k-kL-ω demonstrates exceptional agreement with experimental data for Reynolds numbers up to approximately 1,500. However, both the k-kL-ω and k-ω SST models over-predict experimental data for Re = 2,000.
Evaluation of Bimanual Stretched String Control of Haptic Workspace Mapping for Virtual Assembly
Authors: Vyawahare Vikram S. , Stone Richard T.
Published: April 2014

Kinesthetic haptic devices due to their typically small workspaces have limitations to their reach in virtual environments. In order to overcome this limitation a new interaction technique ‘Bimanual Stretched String Control of Haptic Workspace Mapping’ (BS-SCHWM) is developed using a unique combination of spatial interaction devices; namely a kinesthetic haptic device (Phantom Omni®) and a magnetically tracked device (Razer Hydra) each held in one of the user hands. The technique is implemented in the domain of virtual assembly. The virtual assembly simulation implemented in this research is based on physically based modeling approach using Voxmap PointShell library. Immersive stereo vision and spatial interaction devices enable natural interactions with the CAD models within the virtual assembly environment. The BS-SCHWM technique uses scene motion to map the haptic device workspace to different parts of the scene and provides means of controlling the direction and speed of scene motion. A bimanual cursor helps the user in visualizing the bimanual interaction paradigm. The facility of transporting objects using the technique is implemented. Schemes of measuring task completion and metrics for analyzing the interaction characteristics are designed. A preliminary evaluation of the BS-SCHWM technique with comparative analysis of its characteristics with an existing unimanual technique of haptic workspace expansion was achieved by conducting a within subject user study experiment. Participants were screened for normal visual acuity, stereopsis and manual dexterity. Analysis of the generated data provide good indicators for evaluation of hypotheses regarding participant performance, ease of use, hand motion and intuitiveness.
Ductile Failure in Processed Thin Sheet Metals
Authors: Ding Huafeng , Zhu Caichao , Zhou Zhong , Qian Dong
Published: April 2014

Ductile fracture in thin sheet metals is a common failure mechanism that governs many important industrial applications. A variety of simulation methods, ranging from the atomistic to continuum scales, have been proposed and demonstrated. To assess the capabilities of the existing simulation tools, a group of researchers presented their modeling predictions on the so-called Sandia Fracture Challenge problem at the 2012 ASME IMECE conference. The discrepancies between the simulation and experimental results, and among the experimental results themselves led to consensus that more needs to be done to improve the understanding of this complex phenomenon. Following the participation of the Sandia Fracture challenge, further simulations are performed to study the ductile failure in thin sheet metals with conditions that are commonly used for processing. It is shown that failure pattern and load are significantly influenced by the processing conditions.
Thermo-Mechanical Analysis of Structural Elements Incorporating Nanocomposites
Authors: Hasan Zeaid , Chattopadhyay Aditi
Published: April 2014

The paper presents the use of nanocompsoites in structural level components to improve their overall performance against unique composite failure modes. A multiscale approach is adopted in order to obtain the overall effective mechanical and thermal properties of the nanocomposite. Those effective properties are used in analyzing the structural components using finite element analysis. The results are demonstrated on a composite T stringer that is widely used as a stiffener for composite panels in aerospace structures. The existence of tows in the manufacturing of such components often results in delamination which reduces the structural integrity. In addition, the bondline interface between the skin and stringer is considered a hot spot where delmaination is susceptible to occur. In this study, we propose the use of nanocompsoites to address this issue and improve their overall performance. Thermal cure and temperature variation is considered in this study and its effect on the failure initiation load will be highlighted. A quantitative comparison from using various CNT weight percentages in the epoxy matrix on the initial damage is provided.
Pressure Drop and Heat Transfer Characteristics of Pin Fin Enhanced Microgaps in Single Phase Microfluidic Cooling
Authors: Wan Zhimin , Joshi Yogendra K.
Published: April 2014

Three dimensional (3D) stacking of semiconductor chips is an emerging technology which promises improved electrical performance including improved bandwidth, reduced wire interconnection lengths, and reduced signal delay. However, due to the higher power density per unit volume of the stacking, it poses great challenge for thermal management. Inter-tier microfluidic cooling with microgaps with surface area enhancements such as pin fins can potentially achieve superior thermal performance. As such, the hydraulic and thermal characteristics of this configuration over parametric ranges of practical interest are important. Conventional correlations developed in the literature for macropin fins show large errors for dense arrays of micropins.

In this work, the hydraulic and thermal characteristics of a microgap with pin fin were investigated for a large range of Reynolds number (Re) based on pin fin diameter (Dp) by numerical modeling. The effects of the pin fin dimensions including diameter, transversal spacing, longitudinal spacing, height and Re on the friction factor (f) and colburn j factor were studied. Correlations of the f and j for dense arrays of micro pins are developed based on parametric runs over 22< Re <357, pin fin diameter of 100 μm, pitch/ diameter ratios of 1.5 ∼ 2.25, and height/ diameter ratios of 1.5 ∼ 2.25. The validity of the correlations is confirmed by experiments. Lastly, a parametric optimization was done and the thermal resistance of the microgap with 150 W heat generation is reduced by 28.5% with the optimized dimensions for a given pumping power compared to an un-optimized pin fin configuration.
Infusion of Green Energy Manufacturing Into Engineering and Technology Curricula
Authors: Chiou Richard Y. , Belu Radian , Tseng Tzu-Liang (Bill)
Published: April 2014

This paper discusses a joint educational effort that incorporates sustainability in engineering and technology curricula at Drexel University (DU) and University of Texas at El Paso (UTEP). A critical component of a national “green industries/green jobs” effort is to motivate our citizenry to become proficient in STEM and associated manufacturing fields and societies, thus ensuring we have a 21st century workforce. Sustainable engineering is about design that recognizes the constraints applied by natural resources and the environmental system. The needs for engineering students and practicing engineers to understand sustainability concepts and concerns have been noted by many educators, scientists or engineers, and it is the philosophy of the authors that all engineering students need to become versed in sustainability ideas. This paper describes key factors in enhancing the ability of future engineering graduates to better contribute to a more sustainable future, preserving natural resources and advancing technological and societal development. Two approaches are used to incorporate sustainability into the undergraduate engineering and technology curricula that can be adopted or adapted by science and engineering faculty for this purpose. The two approaches described in the paper include: (1) redesigning existing courses through development of new materials that meet the objectives of the original courses and (2) developing upper division elective courses that address specific topics related to sustainability, such as green manufacturing, clean energy, and life-cycle assessment. The efforts presented in the paper also include an increase in social responsibility, development of innovative thinking skills, better understanding of sustainability issues, and increasing students’ interests in the engineering and technology programs. Projects, included in the senior courses or in the senior design project course sequence have been also part of them.
Passivation and Performance of Inorganic Aqueous Solutions in a Grooved, Aluminum Flat Heat Pipe
Authors: Stubblebine Michael , Amouzegar Ladan , Catton Ivan
Published: April 2014

Aluminum heat pipes have traditionally been incompatible with water and water-based fluids because they quickly react with the casing to generate non-condensable hydrogen gas (NCG). The NCGs inhibit the operation of evaporation and condensation based devices, eventually plugging the condenser end of the heat pipe. The heat pipe is then unable to remove heat from the condenser and the device fails. Terdtoon [1] found that these events often happen so rapidly between aluminum and water that measurements cannot even be taken. The present work tested two different, patented inorganic aqueous solutions (IAS) in a flat heat pipe setup. Grooved aluminum plates were used as the heat pipe wick and the tests were run with the heating section raised above the condenser. Compatibility between the working fluid and aluminum heat pipe was established by running the device to dryout and then reducing the heat flux to check for hysteresis. De-ionized water (DI water) was also tested, as a baseline, to establish that it did indeed fail as expected. Operating performance of each mixture was obtained from zero heat input until dryout was reached for multiple angles of inclination. The data show that both IAS mixtures are compatible with aluminum heat pipes and exhibit performance similar to that of a copper and water heat pipe. IAS and aluminum heat pipes could replace existing copper and water devices and deliver similar performance while reducing overall weight by more than three times. An IAS and aluminum heat pipe could also replace existing aluminum and ammonia combinations, currently favored in aerospace applications, to allow for increased performance and a larger operating temperature range while maintaining low device weight.