bluuebunny/crossref_metadata_2025 huggingface dataset:
Corrosion Rates and Changes in Mechanical Properties of Copper Alloys due to Seawater Exposure
Authors: Drach Andrew , Tsukrov Igor , Gross Todd , Hofmann Uwe , Aufrecht Jochen , Grohbauer Adolf
Published: October 2013

A field study on corrosion was conducted on several copper alloys subjected to prolonged exposure in seawater. Rectangular plates made of nine alloys were deployed for a year in the North Atlantic Ocean. Material loss rates were quantified by measuring the difference in weight between the initial virgin specimens and the cleaned specimens after recovery. Changes in mechanical properties due to the seawater exposure were quantified by performing standard uniaxial tension tests. Stress-strain dependence was obtained for each of the tested materials using the digital image correlation technique. Some degradation of tensile strength was observed in all alloys, but for most of them it was not substantial.
Biotemplated Superhydrophobic Surfaces for Enhanced Dropwise Condensation
Authors: Olceroglu Emre , King Stephen M. , Rahman Md. Mahamudur , McCarthy Matthew
Published: October 2013

The increased heat transfer achieved through dropwise condensation, as compared to filmwise condensation, has the potential to substantially impact a variety of applications including high-heat flux thermal management systems, integrated electronics cooling, and various industrial and chemical processes. Here, we report stable dropwise condensation onto biotemplated nanostructured super-hydrophobic surfaces. We have demonstrated continuous droplet coalescence and ejection at diameters of less than 20 μm and compared directly with flat hydrophobic surfaces. The self-ejection mechanism characteristic of dropwise condensation has been shown using a simple bio-nano-fabrication technique based on the self-assembly and mineralization of the Tobacco mosaic virus (TMV). This process is extendable to commercially relevant nanomanufacturing of both microscale electronics devices as well as large-scale large-area industrial equipment. This manufacturing flexibility is unique as compared to many other micro/nano-structured surfaces fabricated to demonstrate similar increases in condensation heat transfer.
Quantification of Uncertainty in Creep Failure in RF-MEMS Switches
Authors: Kolis Peter A. , Koslowski Marisol , Bajaj Anil K.
Published: October 2013

We present simulations of the dynamic response of radio frequency micro-electro-mechanical-systems (RF-MEMS) switches undergoing creep deformation. The model includes a microscale-informed Coble creep formulation incorporated in a beam model of an electrostatically actuated RF-MEMS switch, and it is solved using a Ritz-Galerkin based modal expansion. The resulting effects on the long-term device behavior as well as the implications of uncertainty in the device geometry and material parameters are studied. We find that the addition of creep to the beam model results in an undesired degradation of the device performance, as evidenced by decreases in the closing and release voltages.
Steady State Numerical Modeling of Non-Conventional Loop Heat Pipes (LHPs)
Authors: Remella Karthik S. , Gerner Frank M. , Shuja Ahmed , Medis Praveen
Published: October 2013

Loop heat pipes (LHPs) transport energy from an evaporator to a condenser in the form of latent heat. In conventional LHPs, the vapor pressure is significantly higher than the liquid pressure across the liquid-vapor interface due to the small pores and the corresponding capillary forces in the wick. This large pressure difference transports the single phase vapor after evaporation from the evaporator to the condenser and once the vapor is condensed, a single phase liquid from the condenser back to the evaporator. This current work involves the development of a steady state design model of the LHP system consisting of a planar evaporator package and a finned copper tube loop, which serves as an air-cooled condenser. Although evaporation due to the heat transfer creates the pressure in the vapor which drives the flow, contrasting to the conventional loop heat pipes, the pressure drop across the liquid-vapor interface is much smaller. A positive hydrostatic head is applied to the liquid above the wick and there is entrainment of liquid from the wick in the evaporator. Therefore, the fluid flow leaving the evaporator package is a two-phase flow, assumed to be saturated liquid and saturated vapor in equilibrium. The primary objective of this non-conventional LHP device is to remove the thermal energy dissipated from a Light Emitting Diode (LED) array. A major portion of this energy causes evaporation of the working fluid within the wick. The remaining energy reheats the liquid in both the liquid return line and within the evaporator package. The evaporator package is modeled as a one-dimensional thermal resistance network and these resistances are empirically determined from experiments. It is found that the convective heat transfer co-efficient of air plays a pivotal role in the heat dissipation and hence, is empirically determined in this work. This value is fairly agreeable with the Nusselt number correlation on the air side developed by Hahne et al. [1]. A mass balance relates the fill volume with the length of the condenser. The temperatures within the LHP are predicted by applying the principle of conservation of energy over the evaporator, the condenser and the sub-cooler sections of the heat exchanger loop. Finally, this LHP model predicts an approximate fill volume necessary for the LHP to operate properly.
Feasibility Study of Using Thermoelectric Cooling Modules for Active Cooling of Photovoltaic Panels
Authors: Najafi Hamidreza , Woodbury Keith
Published: October 2013

Temperature increment is one of the main challenges for solar concentrating photovoltaic (CPV) systems which cause cell degradation and significant efficiency loss. To overcome this issue, a novel cooling method by using Peltier effect is proposed and investigated. In this approach, thermoelectric cooling (TEC) modules are considered to be installed on the back side of the photovoltaic (PV) module. The required power to run the TEC module is provided by the PV panel itself. A comprehensive model is developed and simulated via MATLAB in order to determine the values of temperatures in different sections of the system and calculate the required power to run the TEC module and the extra generated power by PV panels due to the cooling effect. The result shows that using TEC modules can successfully keep the PV cell temperature within the desired temperature range during a hot day when limited temperature reduction is needed.
Modeling Flow Recirculation Inside a Holding Chamber
Authors: Oliveira Ricardo F. , Teixeira José Carlos , Marques Helena Maria Cabral , Teixeira Senhorinha
Published: October 2013

The present project analyses the streamlines patterns that influence the efficiency of the holding chambers (used in asthma treatment) and relate it with the geometric dimensions of the device. According to some unpublished observations, the utmost significant drug delivery faction for the treatment (the fine particle fraction below 6.0 μm in diameter) gets trapped in the recirculation areas of the holding chamber. Reducing the size of these recirculation areas will improve the device efficiency. This paper makes use of computational fluid dynamic techniques, as a method to avoid the need for the construction of traditional prototypes, thus reducing the cost of the research process. It was possible to obtain the size of the recirculation area in an automatic way and to relate such pattern with the geometric details of the holding chamber. An alternative design is compared with the Volumatic®, which is the widest used device. Results support the possibility in reducing the recirculation area inside the device by changing the wall geometry. By analyzing the influence of the length and diameter ratio of the expansion section of the holding chamber, it was concluded that longer lengths and lower diameter ratios yield a reduction of the recirculation area. The results bring a better understanding of the influence of geometry in the recirculation area and therefore in the holding chamber efficiency.
Stress Analysis of Peripheral Stents Using Photogrammetric Deformation Tracking
Authors: Avdeev Ilya V. , Shams Mir Z. , Hastert Andrew L.
Published: October 2013

Peripheral artery stents are commonly used as an alternative to invasive treatment for atherosclerosis. Design of stents has traditionally relied on structural Finite Element Analysis (FEA). Correct representation of kinematic boundary conditions in FEA models is very important for stent design. Moreover, real-time tracking of stent deformations and subsequent calculations of stresses can be potentially used during the endovascular procedures. The medical imaging data stream can be used for photogrammetric measurements of stent deformations. In this study, a method is proposed to couple FEA stress simulations with real-time image analysis. A customized testing machine was designed and fabricated to apply tension, twisting, and three points bending to various stents. A CCD camera was used to capture stent deflection images at 30 frames per second. Image processing algorithms and code were developed to identify stent boundaries and to measure deformation modes. The obtained deformations were applied as boundary conditions to FEA stent models. Stresses developed at different regions in the stent structure were observed and points of maximum stresses were recorded.
Experimental Investigation and Finite Element Modeling Analysis of Photostrictive Optical Actuators
Authors: Rahman Mosfequr , Nawaz Masud , Mitra Aniruddha , Bassiri-Gharb Nazanin , Jackson John E.
Published: October 2013

Photostrictive materials are lanthanum-modified lead zirconatetitanate (Pb, La)(Zr, Ti) O3 ceramics doped with WO3, called PLZT, exhibit large photostriction under uniform illumination of high-energy light. Photostrictive materials are ferrodielectric ceramics that have a photostrictive effect. Photostriction arises from a superposition of the photovoltaic effect, i.e. the generation of large voltage from the irradiation of light, and the converse-piezoelectric effect, i.e. expansion or contraction under the voltage applied. Photostrictive materials offer the potential for actuators with many advantages over traditional transducing electromechanical actuators made of shape memory alloys and electroceramics (piezoelectric and electrostrictive). Drawback of traditional actuators is that they require hard-wired connections to transmit the control signals which introduce electrical noise into the control signals; on the other hand PLZT actuators offer non-contact actuation, remote control, and are immune from electric/magnetic disturbances.

The main goal of the research work is to investigate the feasibility of utilizing photostrictive materials as an optical actuator for Micro-Electro-Mechanical-Systems (MEMS) applications. In this investigation process both experimental and computational approaches have been implemented. In the experimental part of this research, a test set-up has been designed and developed to measure the photostriction effect of a PLZT thin film on a silicon wafer as smart beams. The experimental set-up includes high pressure short arc xenon lamp with lamp housing, power supply, lamp igniter, hot mirror, band pass filters, optical chopper, and laser sensor with sensor head and controller.1 μm PLZT thin film on the silicon wafer sample has been tested as a cantilever beam with different light intensities, and focusing the light at the different locations on the PLZT cantilever beam. The experiment has been performed for continuous and pulses of lights focusing on the PLZT optical actuator. An optical chopper was used to make pulses of light on the PLZT cantilever beam. Also, a computational finite element method useful for design of systems incorporating thin film photostrictive actuators has already been developed by the authors. The element has been implemented in an in-house finite element code. This derived finite element for continuous illumination of light on the photostrictive thin film has been used to investigate the application of photostrictive actuators for the different structures and various boundary conditions of microbeams with various actuator locations and length intensities. A successful conclusion of these tasks will affirm the potential of the PLZT optical actuator to use in the MEMS devices.
Acquiring “Working” Skills and Experience Through Hands-On Multidisciplinary Design Projects
Authors: Zhang Andy S. , Heng Iem , Zia Farrukh
Published: October 2013

One of the problems that many engineering graduates face when looking for their first job is: do you have experience? Employers prefer graduates with relevant experience to those without. Why is experience so important to employers? Can students accumulate “working” experience while studying in college? This paper discusses the use of design projects inside and outside of classrooms to help students gain “working” experience and skills through hands-on design activities that simulate the actual design activities that occur in the industry. Faculty members from the Mechanical Engineering Technology and Computer Engineering Technology departments were involved in creating multidisciplinary design projects. The design projects give students new insights into what they learn in their coursework and provide students the valuable experiences in analytical skills, concurrent engineering approach, people skills, and management skills needed for the students when looking for employment.
Leading Edge Jet Impingement Under High Rotation Numbers
Authors: Elston Cassius A. , Wright Lesley M.
Published: October 2013

The effect of rotation on jet impingement cooling is experimentally investigated in this study. Pressurized cooling air is supplied to a smooth, square channel in the radial outward direction. To model leading edge impingement in a gas turbine, jets are formed from a single row of discrete holes. The cooling air from the first pass is expelled through the holes, with the jets impinging on a semi-circular, concave surface. The inlet Reynolds number varied from 10000–40000 in the square supply channel. The rotation number and buoyancy parameter varied from 0–1.4 and 0–6.6 near the inlet of the channel, and as coolant is extracted for jet impingement, the rotation and buoyancy numbers can exceed 10 and 500 near the end of the passage. The average jet Reynolds number varied from 6000–24000, and the jet rotation number varied from 0–0.13. For all test cases, the jet-to-jet spacing (s/djet = 4), the jet-to-target surface spacing (l/djet = 3.2), and the impingement surface diameter-to-diameter (D/djet = 6.4) were held constant. A steady state technique was implemented to determine regionally averaged Nusselt numbers on the leading and trailing surfaces inside the supply channel and three spanwise locations on the concave target surface. It was observed that in all rotating test cases, the Nusselt numbers deviated from those measured in a non-rotating channel. The degree of separation between the leading and trailing surface increased with increasing rotation number. Near the inlet of the channel, heat transfer was dominated by entrance effects, however moving downstream, the local rotation number increased and the effect of rotation was more pronounced. The effect of rotation on the target surface was most clearly seen in the absence of crossflow. With pure jet impingement, the deflection of the impinging jet combined with the rotation induced secondary flows offered increased mixing within the impingement cavity and enhanced heat transfer. In the presence of strong crossflow of the spent air, the same level of heat transfer is measured in both the stationary and rotating channels.
Visual Feedback Navigation and Control of a Quadrotor Using Fuzzy Expert Systems
Authors: Brech Dale E. , Liu Jiayi , Brech Alex A. , Hoover Randy C.
Published: October 2013

This paper proposes a novel tele-autonomous control method of a quadrotor miniature air vehicle (MAV) that utilizes visual feedback mechanisms. The controller navigates a commercially available quadrotor to different Region-Of-Interests (ROI) as determined by the user. Visual feedback and state estimation is accomplished via vanishing point estimation for corridor centering and navigation. Speeded-Up Robust Feature (SURF) algorithms are used for feature selection, distance estimation, and approaching the ROI. The results of these visual feedback mechanisms are then fed into multiple Fuzzy Expert Systems for navigation and control. Experimental results are presented validating the approach using an unmanned quadrotor in an unknown indoor environment.
Behavior of Internal Energy and Enthalpy of Fluids Along Isotherms and Isentropic Lines in the Compressed Liquid Region
Authors: Karimi Amir , McGill Karen , Manteufel Randall D.
Published: October 2013

It is a common practice to approximate the thermodynamics properties of fluids in the compressed liquid regions from their saturation properties. Most thermodynamics textbooks state that the specific volume, specific internal energy, and specific entropy in the compressed liquid region are functions of temperature only and are independent of pressure. Therefore, compressed liquid property tables are not provided for any substance, except for water, and compressed liquid properties are approximated by their saturated liquid properties at a given temperature. Recent examination of current practice in approximating compressed liquid properties has shown that the internal energy of fluids exhibits growing dependency on pressure with increases in temperature. This paper compares the behavior of internal energy and enthalpy four compressed fluids along isotherms with those behaviors along isentropic lines. Water, ammonia, methane, and propane are examined in this study. It is shown that effects of pressure on the internal energy and enthalpy of compressed liquids are much lower along isentropic lines than those along isotherms.
An Investigation on Hot Corrosion Resistance of Plasma Sprayed Composite YSZ-Gd2Zr2O7 and Gd2Zr2O7 Thermal Barrier Coatings in Simulated Turbine Environment at 1050°C
Authors: Habibi M. H. , Wang Li , Guo Shengmin
Published: October 2013

Thermal barrier coatings (TBCs) are frequently used on hot section components in gas turbines. Rare-earth zirconate ceramics used as thermal barrier coatings have attracted increasing interest in recent years due to their distinctly lower thermal conductivity than common TBC material; Yttria stabilized zirconia (YSZ). This paper investigates the hot corrosion resistance of composite YSZ+Gd2Zr2O7 and Gd2Zr2O7 coating, in Na2SO4+V2O5 at 1050°C. Chemical interaction is found to be the major corrosive mechanism for the deterioration of these coatings. Characterizations using X-ray diffraction (XRD) and scanning electron microscope (SEM) indicate that the reaction between NaVO3 and Y2O3 in YSZ produces YVO4 and leads to the transformation of tetragonal ZrO2 to monoclinic ZrO2. Then For the Gd2Zr2O7+YSZ composite coating, by the formation of GdVO4, the amount of YVO4 formed on the YSZ+Gd2Zr2O7 composite coating is significantly reduced, thus the amount of monoclinic phase in the TBC coating is substantially reduced. Comparing to YSZ, under a high temperature of 1050°C, Gd2Zr2O7 is more stable, both thermally and chemically, So Gd2Zr2O7 exhibits a better hot corrosion resistance than YSZ+Gd2Zr2O7 composite coating.
A Fluid Flow Characterization Device for an Educational Desktop Learning Module
Authors: Peterson Kirsten L. , Compere Marc D. , Allam Yosef S. , Van Wie Bernard J.
Published: October 2013

This paper presents the design and testing of a fluid loss characterization device for use in engineering education as a classroom or laboratory demonstration in a core curriculum fluid dynamics course. The design is specifically tailored for clear demonstration of the abstract concept of fluid loss in a way that supports collaborative, hands-on, active, and problem-based learning.

This stand-alone device is intended as a prototype for a Desktop Learning Module (DLM) cartridge. The DLM module framework was developed by engineering educators at Washington State University as part of a collaborative NSF-sponsored program. The fluid loss characterization device was sponsored by the Embry-Riddle Aeronautical University Honors Program in Daytona Beach, Florida.

The purpose of the experiment is to have students determine the loss coefficients and friction factors of different piping components in a fluid flow system. The experiment involves measuring volumetric flowrate changes in the system due to the introduction of minor and major losses. A pump circulates water at a specified rate tunable by the students to achieve a steady state flow condition. Height sensors report tank heights and a flow meter shows volumetric flow rate which is verifiable with student’s data collection. A graphical computer interface allows students to control pump rate and also reports tank height in real time. The computer and height sensors are not critical to the learning objectives and may be replaced with rulers and a potentiometer for motor control.

The educational goals are for students to gain a better understanding of the transition between Bernoulli’s flow equation and the Energy equation, to study major and minor losses, and experimentally determine volumetric flowrate. Fluid flow loss concepts can be reinforced by experimentally verifying these concepts immediately after presenting them on the whiteboard.

Educational assessments measuring gains with pre- and post-tests and a conceptual test one week later were performed with a control group and experimental group. Results are presented that allow direct comparison between a hands-on activity versus conventional lecture-based instruction alone. The results indicate no statistically significant differences in gains between control and treatment groups; however the trend indicates improved ability to describe abstract concepts on the material 1 week later in the experiment group. The most promising results show that a greater percentage of students who were actively involved with the demonstration increased their scores from post- to conceptual assessment. This agrees with previously published results on CHAPL [1]. The majority of passive observers showed decreased scores. These results warrant more devices be built and tested to engage the entire class in the hands-on collaborative experiment.
Development of a Variable Electromotive-Force Generator for a Wind Turbine
Authors: Zhu W. D. , Goudarzi N. , Wang X. F. , Kendrick P.
Published: October 2013

To improve the power production and the overall operational range of a wind turbine, a modified generator called a variable electromotive-force generator (VEG), which has an adjustable overlap between the rotor and the stator, is proposed. Theoretical analysis of employing a VEG relies on numerous assumptions about the aerodynamic and electromagnetic models of a wind turbine drivetrain. In this work, a novel test stand for a VEG prototype, including a 12 V DC synchronous generator with an adjustable overlap between the rotor and the stator, a 700 W electric motor as the prime mover, and a stepper motor as the actuator for an active control system, is designed and fabricated. The performance of the VEG prototype is studied experimentally, and the active control system to adjust the overlap between the rotor and the stator based on the desired output power at different input speeds is developed. A variable factor is used to condition the desired and real output powers to improve the stability of the control system. The results show that decreasing the overlap between the rotor and the stator of the generator at low speeds results in decreasing the torque loss of the generator and increasing the rotational speed of the generator rotor. Having a VEG in a wind turbine operating under a lower input power than that of a regular generator means the VEG can start working at a lower wind speed than the current cut-in speed of the regular generator.
Experimental Study of an Airfoil Heat Pipe Subjected to an Impingement of Hot Gases
Authors: Carbajal Gerardo , Vázquez Ramos Alberto
Published: October 2013

An experimental study was performed to an airfoil heat pipe. The airfoil was subjected to a jet impingement of hot gases at the leading edge. The airfoil was also tested first with air and later with water as the working fluid. The experimental result shown that the heat pipe spread better the heat input from the leading edge at very high heat input rate than the air filled airfoil design. The case material was brass, the porous media was nickel foam with 1.70 mm thickness and average pore size of 590 × 10−6 m. Distilled water was used as the working fluid. The experimental data indicate the proposed design can reduce the temperature at the leading edge surface. The temperature reduction in the leading edge airfoil heat pipe was approximately 33 percent compared with the air filled airfoil. The phase change mechanism inside the heat pipe was the key factor to spread better the localized energy input and thus reducing the temperature distribution on the leading edge.
Use Multi-Objective Optimization for Designing Cloaks With Acoustic and Elastic Materials
Authors: Bao Chunyan , Cai Liang-Wu
Published: October 2013

The various optimization schemes have been recently shown to be a capable tool for designing acoustic cloaks based on Cummer-Schurig prescription without requiring material singularity. However, when using an optimization scheme to optimize a cloak at one specified frequency, sometimes it is observed that the cloaking effect deteriorate at other frequencies. This paper explores the use of multi-objective optimization approach such that the cloaking performance is maintained over a wide range of frequencies. Two examples are presented. The first cloak is comprised of all aocustic layers, and the second cloak is comprised of a mixture of acoustic and elastic layers. The results show the effectiveness of the multi-objective optimization approach on maintaining cloaking performance over a specified frequency range.
On the Design of a Biodegradable POC-HA Polymeric Cardiovascular Stent
Authors: Ponkala Joonas , Rizwan Mohsin , Shiakolas Panos S.
Published: October 2013

The current state of the art in coronary stent technology, tubular structures used to keep the lumen open, is mainly populated by metallic stents coated with certain drugs to increase biocompatibility, even though experimental biodegradable stents have appeared in the horizon. Biodegradable polymeric stent design necessitates accurate characterization of time dependent polymer material properties and mechanical behavior for analysis and optimization. This manuscript presents the process for evaluating material properties for biodegradable biocompatible polymeric composite poly(diol citrate) hydroxyapatite (POC-HA), approaches for identifying material models and three dimensional solid models for finite element analysis and fabrication of a stent. The developed material models were utilized in a nonlinear finite element analysis to evaluate the suitability of the POC-HA material for coronary stent application. In addition, the advantages of using femtosecond laser machining to fabricate the POC-HA stent are discussed showing a machined stent. The methodology presented with additional steps can be applied in the development of a biocompatible and biodegradable polymeric stents.
Friction Between Steel and Asphalt Without Gouging Under Representative Rollover Impact Pressures
Authors: Mihora Dennis , Friedman Keith , Hutchinson John
Published: October 2013

This paper describes a study examining the friction loads resulting from cylindrical structure sliding contact with asphalt without gouging. During a rollover event the vehicle roof structure interacts with the ground. Friction can account for a large portion of the dissipation of vehicle energy during these events. Only friction values at low pressures have been reported previously. Determination of the friction values observed under the higher pressure values expected during certain A-pillar to asphalt interactions was addressed in this study. First, sections of asphalt roadways were obtained. Both new and used portions of roadway were used. A smooth, elliptically shaped counterface representative of a roof structure component was utilized. A robotic test device allowing control of speed, compressive forces, and temperature and measurement of traction forces was utilized under controlled conditions [1]. Studies were conducted at 21° C and 68° C. The results show that an average friction of .70 is observed across all the samples with a range of up to 1.2 in metal to asphalt interaction without gouging.
Wind Power Generating Potential at the University of North Texas Campus
Authors: Rayegan Rambod , Tao Yong X. , Fang Frank Y.
Published: October 2013

This study utilizes two sets of wind speed data at 3 m above the ground surface level retrieved from two on-campus weather stations to study the wind power generating potential at the University of North Texas Campus. Weather stations have been installed approximately 5 miles away from each other. The mean wind speed data of 10 minute intervals in a one-year period from February 1st 2011 to January 31st 2012 has been adopted and analyzed. The numerical values of the dimensionless Weibull shape parameter (k) and Weibull scale parameter (c) have been determined. Monthly average wind speed and standard deviation, power generation, and power density at the sensor level for both locations has been discussed. Lower values of wind speed were found during summer months and higher during spring months. The results show that the wind power density in the area is fair enough to be considered as a renewable power source for the University. Thereafter annual energy production by using two wind turbines with nominal capacities of 100 and 3.5 kW for both weather stations has been studied. Initial costs of using each turbine to maintain power demands of selected buildings have been compared. In order to utilize wind energy, it is recommended to install highly efficient wind turbines for electricity supply of campus buildings with lower power demands. Using grant monies to maintain the initial costs of the installation of wind turbines make them economically more desirable. Since wind power potential is low during summer, PV panels as proper supplements to the power generating system are suggested.
Hydraulic Jump due to Jet Impingement on Micro-Patterned Surfaces Exhibiting Ribs and Cavities
Authors: Johnson M. , Maynes D. , Vanderhoff J. C. , Webb B. W.
Published: October 2013

This paper reports experimental results characterizing the hydraulic jumps that form due to liquid jet impingement on micro-patterned surfaces with alternating micro-ribs and cavities. The surfaces are characterized by the cavity fraction, which is defined as the width of a cavity divided by the combined width of a cavity and an adjoining rib. The surfaces are all hydrophilic and thus the cavity regions are wetted during the impingement process. Four different surface designs were studied, with respective cavity fractions of 0 (smooth surface), 0.5, 0.8, and 0.93. The experimental data spans a Weber number range (based on the jet velocity and diameter) of 600 to 2100 and a corresponding Reynolds number range of 11500 to 21400. As with jet impingement on a smooth surface, when a liquid jet strikes a ribbed surface it then moves radially outward in a thin film and eventually experiences a hydraulic jump, where the thickness of the film increases by an order of magnitude, and the velocity decreases accordingly. However, the anisotropy of the patterned surface causes a disparity in frictional resistance dependent upon the direction of the flow relative to the orientation of the ribs. This results in a hydraulic jump which is elliptical rather than circular in shape, where the major axis of the ellipse is aligned parallel to the ribs, concomitant with the frictional resistance being smallest parallel to the ribs and greatest perpendicular to the ribs. When the water depth downstream of the jump was imposed at a predetermined value, the major and minor axis of the jump decreased with increasing water depth, following classical hydraulic jump behavior. The experimental results indicate that for a given cavity fraction and downstream depth, the radius of the jump increases with increasing Reynolds number. At a specified Reynolds number and downstream depth, the hydraulic jump radius in the direction parallel to the ribs of a patterned surface is nominally equal to the jump radius for a smooth surface, regardless of cavity fraction. The jump radius perpendicular to the ribs is notably less than that for a smooth surface, and this radius decreases with increasing cavity fraction.
Numerical Simulation of Accident Scenario in High Temperature Gas Cooled (Pebble Bed) Nuclear Reactors
Authors: Peter Geoffrey J.
Published: October 2013

The accident scenario resulting from blockages due to the retention of dust in the coolant gas or from the rupture of one or more fuel particles used in the High Temperature Gas Cooled (Pebble Bed) Nuclear Reactors considered for the next generation of Advanced High Temperature Reactors (AHTR), for nuclear power production, and for high-temperature hydrogen production using nuclear reactors to reduce the carbon footprint is examined in this paper.

Blockages can cause local variations in flow and heat transfer that may lead to hot spots within the bed that could compromise reactor safety. Therefore, it is important to know the void fraction distribution and the interstitial velocity field in the packed bed. The blockage for this numerical study simulated a region with significantly lower void than that in the rest of the bed. Finite difference technique solved the simplified continuity, momentum, and energy equations.

Any meaningful outcome of the solution depended largely upon the validity of the boundary conditions. Among them, the inlet and outlet velocity profiles required special attention. Thus, a close approximation to these profiles obtained from an experimental set-up established the boundary conditions.

This paper presents the development of the elliptic-partial differential equation for a bed of pebbles, and the solution procedure. The paper also discusses velocity and temperature profiles obtained from both numerical and experimental setup, with and without effect of blockage. In addition, the paper compares the results obtained from the experimental set-up with numerical simulation using a commercially available code that uses finite element techniques.
A Diffusion Model in a Two-Phase Interfacial Zone for Nanoscale Lithium-Ion Battery Materials
Authors: ChiuHuang Cheng-Kai , Huang Hsiao-Ying Shadow
Published: October 2013

The development of lithium-ion batteries plays an important role to stimulate electric vehicle (EV) and plug-in electric vehicle (PHEV) industries and it is one of many solutions to reduce US oil import dependence. To develop advanced vehicle technologies that use energy more efficiently, retaining the lithium-ion battery capacity is one of major challenges facing by the electrochemical community today. During electrochemical processes, lithium ions diffuse from and insert into nanoscaled cathode materials in which stresses are formed. It is considered that diffusion-induced stress is one of the factors causing electrode material capacity loss and failure. In this study, we present a model which is capable for describing diffusion mechanisms and stress formation in nano-platelike cathode materials, LiFePO4 (Lithium-iron-phosphate). We consider particle size >100 nm in this study since it has been suggested that very small nanoparticles (<100 nm) may not undergo phase separation during fast diffusion. To evaluate diffusion-induced stress accurately, factors such as the diffusivity and phase boundary movements are considered. Our result provides quantitative lithium concentrations inside LiFePO4 nanoparticles. The result could be used for evaluating stress formation and provides potential cues for precursors of capacity loss in lithium-ion batteries. This study contributes to the fundamental understanding of lithium ion diffusion in electrode materials, and results from this model help better electrode materials design in lithium-ion batteries.
Evaluation System of Tooth Contact Patterns of Hypoid Gears Using Artificial Intelligence
Authors: Nakamura Morimasa , Kojima Keisuke , Moriwaki Ichiro
Published: October 2013

Tooth contact inspection is one of the most common methods for checking qualities of hypoid gear pairs. A change in machine setting parameters for cutting and lapping processes of a hypoid gear pair enables a tooth contact pattern of a hypoid gear pair to be varied. The deviation of the pattern from the target one is represented by a grade point. In the inspection, the qualities of hypoid gear pairs are usually classified into only two grades; OK or NG. However, in order to conduct a follow-up survey on problems of the products and to be useful to be trouble shooting tasks of the end products, finer classifications and more quantitative evaluations of tooth contact patterns could be effective. Such approaches have been tried, however, only experienced and well-trained technicians for the inspection of hypoid gear pairs can determine the point of each tooth contact pattern. And it is difficult to make this evaluation method automatic. To overcome this problem, an application of artificial intelligence system must be useful. The present paper describes a computer evaluation system using the neural network, which is a kind of the artificial intelligence systems, for tooth contact patterns of hypoid gear pairs which can evaluate the results of the inspections instead of experienced hypoid gear technicians. This system with the neural network has a capability to learn relationships between evaluation grade points of tooth contact patterns given by the hypoid gear technicians and graphics of tooth contact patterns of hypoid gear pairs. Moreover, it can return the evaluation grade points when a tooth contact pattern is input into the system. The evaluation performance of the developed system was discussed. And a quality of normative tooth contact patterns, which were used as the teacher signals for training the neural network system, greatly affected its performance. The comparison of evaluated grade points obtained from developed system with the technician’s ones showed that the correct answer ratio obtained from the developed system was about 90% in the best case.
Cultivating Emerging and Black Swan Technologies
Authors: Mahajan Roop L. , Mueller Rolf , Williams Christopher B. , Reed Jeff , Campbell Thomas A. , Ramakrishnan Naren
Published: October 2013

Emerging technologies, defined as contemporary cutting-edge developments in various fields of technology, are generally associated with the potential for large impact on society. In a recent op-ed, “The coming Tech-led Boom” (Wall Street Journal, January 30, 2012), Mills and Ottino list three grand technological transformations — big data, smart manufacturing, and the wireless revolution — poised to transform this century as much as telephony and electricity did in the 20th century. This list is by no means comprehensive and most likely misses technologies that are not yet recognized, but may still carry an extreme impact — i.e., the so-called Black Swans, as defined by New York Times best-selling author, Nassim Nicholas Taleb, in his book, The Black Swan. Taleb cites the example of three recently implemented technologies that most impact our world today — the Internet, the computer, and the laser — and notes that all three were unplanned, unpredicted, and unappreciated upon their discovery, and remained unappreciated well after initial use.

In this paper, we will examine several emerging technologies, present a methodology to create a breeding ground for potential Black Swans, and finally discuss the societal and ethical aspects of these technologies.
Numerical Modelling of Mixed Flow Impeller in Stirred Vessel
Authors: Mohiuddin A. K. M. , Adeyemi Nabeel , Jameel Ahmad Tariq
Published: October 2013

Flow characteristics of a single mixed flow impeller in baffled and unbaffled vessel have been experimentally and numerically investigated at 600 rpm. The mean, radial and axial velocity components obtained using particle image velocimetry (PIV) were compared with three turbulence models (κ-ε, κ-ε shear stress transport (sst) and Reynold’s stress model (RSM)) based on the Reynold’s averaging Navier-Stokes equation at two planes, above (x/R = 0.46) and below (x/R = 0.38) the impeller. Numerical results of mean and axial velocity for the RSM turbulence model compared better to PIV below the impeller against other models in the baffled vessel. However, the axial and radial velocity components from the κ-ε model compare well to PIV result at a distance away from the wall. Associated power number and energy of the impeller were also observed to be better predicted with the RSM, although at a higher computational cost. Trade-offs in using the RSM as a tool for simulation of the mixed flow impeller is suggested.
Experimental Comparison of GCC-Based Time Delay Estimation Methods for Ultrasonic Leak Detection in Compressed Air System
Authors: Liao Pingping , Cai Maolin , Fu Xiangheng
Published: October 2013

Air leakage is one of the most significant energy waste factors in compressed air systems which account for about 10% of total industrial energy consumption. It is estimated that about 10%∼40% of the compressed air is wasted through leakage in most plants. A new ultrasonic leak detection method based on time delay estimation (TDE) is proposed to locate the compressed air leak for preventing energy waste in pneumatic systems. The accuracy of detection is highly dependent on the performance of the TDE method. Performances of six typical TDE methods based on generalized cross correlation (GCC) are compared, and these methods are the basic cross correlation (BCC), the Roth impulse response, the phase transform (PHAT), the smoothed coherence transform (SCOT), the WEINER processor, and the Hannan-Thomson (HT) processor. The experimental results show that: Firstly, the accuracy and precision of time delay estimation increases with the observation interval for all these methods. Secondly, the success rates of Roth, PHAT, SCOT and HT are much higher than that of BCC and WEINER, among which the HT processor performs best with a highest success rates closely followed by the PHAT processor. Thirdly, the HT processor which is a maximum likelihood estimator gives the minimum standard deviation of the time delay estimate; however, the standard deviations of all these GCC methods are very small. The HT processor outperforms other GCC methods in terms of success rate and standard deviation. Consequently, it is preferable to apply the HT processor for this particular purpose.
A Methodology Based on Interactive Virtual Prototypes for a Better Design of Consumer-Product Interaction
Authors: Ferrise Francesco , Bordegoni Monica , Cugini Umberto
Published: October 2013

The paper describes the preliminary results of a research activity on the design of consumer-product interaction by means of interactive Virtual Prototypes (iVPs). Differently from Virtual Prototypes (VPs), which can be defined as an integration of geometries and functional multi-domain and multi-physics models, interactive Virtual Prototypes can be implemented as an integration of functional models for each sense — in this case vision, touch and hearing — which are parametric and independent from each other, so that they can be modified on request. Thanks to the use of iVPs the interaction design approach can be reversed. In fact, first the iVP can be used for the design and evaluation with final users of the consumer-product interaction, and then the resulting interaction parameters can be mapped back to the functional models of the VPs by following a sort of reverse engineering activity. So, the interaction specifications are not derived by questionnaires and focus groups with potential customers, but products are shown, tested, and customised directly with the potential buyers. This method presents several advantages for companies. It allows designers to more easily and directly capture the voice of the customers by gathering an immediate feedback about new interaction modalities, and also to design and validate at the same time the emotional response of their products. Besides, these studies and validations can be performed when the product design is in its infancy and technical decisions have not been taken, with the consequent advantage that design changes are not too expensive. The paper demonstrates the validity and potentiality of the methodology through some case studies.
Resonant Frequency of an MR Compatible Rotating Anode X-Ray Tube
Authors: Shin M. , Lillaney P. , Hinshaw W. , Fahrig R.
Published: October 2013

Switching between X-ray and MR imaging with the systems in close proximity can facilitate accurate image-guided interventional procedures using their complementary advantages. Conventional X-ray tubes use induction motors whose functionality fails within MR fringe field environments; thus we developed a novel MR compatible X-ray tube motor.

Vibrations from the structural instability of a motor can lead to mechanical failure, as well as image artifacts due to shaking X-ray focal spot on the anode target; hence it is important for proper X-ray tube motor operation to identify the resonant frequencies that cause large amplitude vibrations. The ability to model rotor dynamics and how they change with the motor design is valuable because it allows us to optimize the motor structure. A finite element model has been developed and validated by experiments measuring the acceleration change and the power spectrum of the motor response.
Design and Process Development Concerns for the Assembly of Very Small Solder Joints
Authors: Alazzam A. , Obaidat M. , Perfecto E. , Lu M. , Kentner S. , O’Brien N. , Arfaei B. , Borgesen P.
Published: October 2013

This work reports a systematic study that addresses the evolution of the solder and intermetallic bond layer microstructure and resulting properties in microbump based assemblies during reflow and subsequent aging. So far, pure Sn as well as alloys with two different initial concentrations of Ag were considered. Thicknesses down to 5μm were deposited and reflowed on Cu, Ni, and Ni/Au pads of different thicknesses and diameters ranging from 150μm to 11μm. Flip chips with these structures were finally assembled onto different substrate pads using a fine pitch bonder and aged at different elevated temperatures for various lengths of time. Solder and intermetallic layer microstructures were characterized by cross polarizer microscopy and scanning electron microscope (SEM). Different combinations led to size and composition dependent effects including different solder composition and microstructure as well as much faster growth of intermetallic layers, and different ratios of intermetallic layer thicknesses.