bluuebunny/crossref_metadata_2025 huggingface dataset:
Near Wall Turbulence Characteristics of a Drag Reducing Polymer Fluid Flow in Concentric Annulus Using CFD
Authors: Rahman Aziz , Rodriguez Corredor Fabio Ernesto , Bizhani Majid , Kuru Ergun
Published: April 2014

A CFD simulation was conducted to analyze the near wall turbulence characteristics of a drag reducing (DR) polymer fluid (0.12% V/V) flow through concentric annulus. The continuity and momentum equations were solved by using a commercial CFD package (CFX 14) with the Shear-Stress-Transport (SST) model option. The simulation results were compared to the experimental data obtained by using high resolution Particle Image Velocimetry (PIV) analyses of drag reducing polymer fluid flow in a horizontal concentric annulus. A fully developed turbulent flow of water through a horizontal flow loop (ID = 9.5 cm) with concentric annular geometry (inner to outer pipe radius ratio = 0.4) was used for comparison purpose. The flow rates ranged from 3.92 to 5.95 kg/s. Drag reducing PHPA solutions behaved as a power law fluid with the rheological model (μ = Kγn−1) for the shear rate of 1/s to 600/s.

Bulk and near wall velocity profile obtained from simulation showed good agreements with the experimental data. Drag reducing polymer reduce the Reynolds stresses level due to weaker and fewer turbulent eddies formation near the wall. Results of the simulation study also showed that if the flow rates of power law fluid increased from 3.92 to 5.95 kg/s, the drag reduction in the annuli is increased from 10% to 20% compared to water case indicating the strong damping to turbulent kinetic energy in the flow. The CFD analyses using SST model is computationally inexpensive and, therefore, can be conveniently used for investigating the flow characteristics of drag reducing polymer fluids in concentric annulus.
Numerical Study of Single Phase Liquid Mixing in Stirred Tanks Fitted With Rushton Turbine and Flotation Impeller
Authors: Basavarajappa Manjunath , Miskovic Sanja
Published: April 2014

Mixing is a complex process and usually involves continuous reduction of length and time scales associated with fluid(s) being mixed. Mixing is an essential process and finds widespread application in a range of industries. Due to lack of understanding of the mixing process, industries lose a significant amount of money contributed by increased power consumption and longer process times. In this work a thorough comparison of flow, mixing, and turbulence characteristics of Rushton turbine (RT) and a flotation impeller, variation of disc turbine, is performed for single phase flows using Computational Fluid Dynamics (CFD). The fluid used is water. Base case validation and model verification is performed by comparing our CFD results with widely accepted Laser Doppler Anemometry (LDA) experimental results for the Rushton Turbine. Multiple reference frame (MRF) technique, a pseudo-steady modeling method, is used to model the impeller motion on flow characteristics at different Reynolds numbers (Re). Turbulence closure is provided using RANS based two equation realizable k-ε turbulence model. Grid independence studies are carried out a sufficiently fine grid is selected to capture the fine flow structures close to the impeller, though radial velocity close to impeller was under-predicted compared to experimental results. Effects of finite impeller blade and disc thicknesses on the local flow field, which are commonly modeled as thin surfaces, are explored. Various tank geometric variations, like different impeller clearances, and impeller diameter to tank diameter ratios (DI/DT), are also investigated. The numerical results will help in understanding the effect of impeller design on local and bulk flow characteristics and turbulence anisotropy close to the impeller. The results from this work will direct the tank and impeller design choices for two phase solid-liquid flows for future investigations.
Formula Electric System: Thermal Management Design
Authors: Smith Jackson , Bidwell Bryan , Beitelmal Abdlmonem , Hight Timothy
Published: April 2014

This paper presents the thermal management analysis performed on lithium polymer cells designed for High Performance Electric Vehicle (HPEV) applications. The objective was to choose an optimum temperature range for the cells to operate at, determine the thermal response of the cells under their full spectrum of discharge capabilities, calculate the necessary convective heat transfer necessary to maintain the cells within said temperature range, then to create a thermal management solution to incorporate into a battery pack composed of 288 cells. Thermal testing and modeling on individual lithium polymer cells determined the thermal response and amount of convection cooling required for the cells over their intended duty cycles. A convective heat transfer coefficient of 50 W/m2K was determined to be sufficient to prevent the proposed cell from exceeding the optimum temperature range during its most strenuous duty cycle. The proposed design scheme utilized a fan to force air circulation up along the side of modules where each module consists of four cells connected in series. A proposed feedback control loop system allowed for active control of the battery cell’s temperature resulting in an increase in efficiency and overall performance for HPEV applications.
CFD Simulation of Gas-Liquid Two-Phase Flow Through an Orifice in Millimeter-Scale Rectangular Channel
Authors: Ismayilov Fuad , Ilegbusi Olusegun J.
Published: April 2014

A numerical model is developed and used to simulate gas-liquid two-phase flow through a plate orifice in a millimeter-scale channel. The channel width is 50 mm and the height is varied from 1.00 mm to 2.00 mm. The contraction ratio and thickness of the orifice are varied over the range 0.04–0.4 and 5–20 mm respectively. The model utilized is based on the multiphase-mixture principle in which transport equations are solved for the mixed phase velocities with allowance for interpenetration of phases and intra-phase transfer processes. The predicted velocity profiles are successfully validated by comparison with the available experimental data for the mixture velocity. The predictions also extend beyond the experimental data to provide the detailed effect of contraction ratio on the flow and gas fraction distribution in the channel. In the range of parameters investigated, the predictions indicate that the flow in such channels will produce no wake in the lee of the orifice for contraction ratios >0.2.
Self-Assembly of Monolayers of Submicron Sized Particles on Thin Liquid Films
Authors: Pillapakkam Shriram , Musunuri N. A. , Singh P.
Published: April 2014

In this paper, we present a technique for freezing monolayers of micron and sub-micron sized particles onto the surface of a flexible thin film after the self-assembly of a particle monolayer on fluid-liquid interfaces has been improved by the process we have developed where an electric field is applied in the direction normal to the interface. Particles smaller than about 10 microns do not self-assemble under the action of lateral capillary forces alone since capillary forces amongst them are small compared to Brownian forces. We have overcome this problem by applying an electric field in the direction normal to the interface which gives rise to dipoledipole and capillary forces which cause the particles to arrange in a triangular pattern. The technique involves assembling the monolayer on the interface between a UV-curable resin and another liquid by applying an electric field, and then curing the resin by applying UV light. The monolayer becomes embedded on the surface of the solidified resin film.
Design Principles for the Conceptual Design of Low-Cost Prosthetic Knee
Authors: Duenas Victor H. , Vargas-Hernandez Noe
Published: April 2014

The objective of this paper is to document design lessons learned in the development of low-cost lower-limb prosthetic devices. Four design principles are introduced based on the authors′ experience redesigning a low-cost prosthetic knee mechanism. These design principles are valuable sources to complete the conceptual design of the knee mechanism in the absence of a unique or exact methodology that comprises all the aspects concerning engineering design.

The paper defines the motivation to improve life quality by restoring knee functionality in terms of mobility and stability. Subsequent sections explore the state of the art, design constraints, gait analysis, and 3-D modeling using CAD. The model is validated using kinematic and structural simulation in NX 7.5™ covering basic geometric parameters and motion assumptions. The four conceptual design principles are: Hybrid Design Model, Simultaneous Modeling, Multidisciplinary Pulses, and Built-in and Post-design Optimization. Each principle is presented to exemplify its contribution in the knee mechanism redesign. Finally, the design principles are intended to assist the designer with empirical guidelines in the development of prosthetic devices.
Understanding Why Engineering Students Take Too Long to Graduate
Authors: Karimi Amir , Manteufel Randall D.
Published: April 2014

There is growing pressure on public colleges and universities to decrease the time students take to earn an undergraduate degree. There are many factors that slow students’ progress towards graduation. For example, urban universities may have a significant number of non-traditional students who don’t take a full load of courses required to graduate in four years. Also, some freshman students interested in engineering may not be prepared for college and are required to take remedial math and science courses. Engineering is a highly-structured program, often with a long sequence of courses requiring one or more prerequisites. If some courses aren’t offered each semester, this can delay progress toward graduation for some students. This paper examines graduating students’ academic records and surveys senior-level mechanical engineering students to identify some of the causes for the increased graduation times. Students provided detailed information such as their full- or part-time status, how many semesters left to graduation, whether they attended summer school, the courses they had difficulty passing, and other issues related to the length of time required to complete their degrees. Feedback from students is essential as universities look to improve graduation rates. The results presented are based on the data for the mechanical engineering program at a public institution in Texas. Although each institution is unique, the findings presented in this paper are expected to apply to similar institutions throughout the nation.
Instrumentation to Monitor Transient Periodic Developing Flow in Non-Newtonian Slurries
Authors: Bamberger Judith Ann , Enderlin Carl W.
Published: April 2014

Staff at Pacific Northwest National Laboratory have conducted mixing and mobilization experiments with both transparent and opaque non-Newtonian slurries that poses a yield stress and exhibit Bingham plastic and shear thinning behavior. This paper describes measurement techniques applied to identify the interface between flowing (i.e. mobilized) and stationary regions of non-Newtonian slurries that are subjected to transient, periodic, developing flows. Techniques were identified or developed to determine the mobilized and stagnant regions of a vessel, characteristic mixing times, and characteristic velocities of the flow field and mixing process. Instruments and techniques included electromagnetic (EM) and Doppler velocity probes, camera wells, radio frequency tags, dye tracers, and core sampling. Testing focused on mixing vessels using intermitent jet mixers oriented vertically downward. Descriptions of the instruments and instrument performance are presented. These techniques were an effective approach to characterize mixing phenomena, determine mixing energy required to fully mobilize vessel contents and to determine mixing times for process evaluation.
Guided Wave Propagation in Tubular Section With Multi-Layered Viscoelastic Coating: Part I — Axial Waves
Authors: Kuo Chi-Wei , Suh C. Steve
Published: April 2014

Propagating waves physically admissible in a tubular section are derived to establish their dispersion characteristics in response to the presence of multi-layered viscoelastic coatings. Longitudinal waves that propagate in the axial direction are studied. To characterize the hollow cylinder with coating layers, wave dispersion and attenuation are studied using the “global matrix” technique. Since each layer is considered to be perfectly bonded to each other, displacement and strain continuity are imposed as the interfacial boundary conditions. Viscoelastic coating materials such as bitumen and epoxy serve to improve pipeline reliability, but they also dampen and dissipate wave energy. The viscoelastic materials are studied as well. By replacing the real material constants with complex material constants in the characteristic equation, the impact of the viscoelastic coatings on wave dispersion is established. Bisection method is followed to find the real and complex roots of the three characteristic equations derived. Roots thus obtained are manipulated to allow the phase velocity and attenuation dispersion to be plotted against frequency. The dispersion of phase velocity and wave attenuation for coated pipes are evaluated against a baseline model which is the bare, uncoated tubing to establish the propagation characteristics of the guided shear and longitudinal waves in the presence of multiple coating layers. The effects of increasing attenuation parameter and coating thickness are also investigated.
CFD Analysis of a Cryogenic Pressure Vessel Hydrogen Leak
Authors: Ledesma-Orozco E. R. , Salazar-Garibay A. , Aceves S. M. , Espinosa-Loza F.
Published: April 2014

This paper reports the numerical simulation of the sudden hydrogen release from a cryogenic pressure vessel due to a broken tube where hydrogen vents into the vacuum jacket. Real gas effects are considered and the specific “vessel within vessel” geometry of cryogenic vessels. For practical reasons, this study focuses on hydrogen release from 34.5 MPa, with initial temperatures of 62 K and 300 K. The high pressure vessel internal volume is 151 L. Pressure versus time graphs indicate that the vacuum jacket resist the pressure build up until reaching the rupture disc setting to finally release into the atmosphere, and a comparative of this result with the ASME Code burst pressure calculation is presented.
Elastoplastic Analysis of a Cantilever Beam Under Combined Compressive and Bending Load
Authors: Boix Salazar Julio A. , de Lange Dirk F. , Cruz Alberto Torres , Medellín Castillo Hugo I. , Rodríguez Gilberto Mejía
Published: April 2014

In this study the elastoplastic behavior of cantilever beams under a combined compressive axial load and an imposed lateral bending deflection are analyzed. Eventhough the particular condition of elastoplastic buckling has been studied before, the developed theories are limited to the prediction of the initial failure of the beam. In the current study the elastoplastic behavior of cantilever beams under compressive load at levels below the critical buckling load are studied in order to determine the remaining load bearing capacity of the beam under combined bending and axial loads, including the behavior at progressive levels of plastic deformation.

The elastoplastic bending process is analyzed using the finite element method. In particular, the analysis is focused on the evaluation of the limiting bending force necessary to increase or reduce the curvature of the beam in the plastic zone. The bending force depends on the compressive axial load, the geometrical dimensions of the beam, material coefficients, such as Young’s modulus and yield stress, and the hardening model. The large number of variables involved, is reduced by introducing two dimensionless load parameters.

The results of the analysis are presented and discussed for a wide range of dimensionless loads. Also the influence of work hardening on the obtained bending force is analyzed, comparing between an ideal plastic behavior and a bilinear plasticity model with a linear hardening behavior.
Integrating Experimental Data Analysis Through Online Modules
Authors: Singh Kumer V. , Khan Fazeel , Birchfield Neal S.
Published: April 2014

In various universities, including Miami University (MU), an undergraduate course in vibrations may be offered in a lecture-only format. However, several concepts in vibrations, such as natural frequencies, damping, mode shapes etc., may be improved immensely from experimental demonstrations and hands-on activities for students to fully grasp the concept and its application. In recent years, several online experiments and resources have been developed in the area of dynamical systems and controls in order to provide an experiential learning environment. With the support of the National Science Foundation, a series of Computational-Experimental (ComEx) learning modules are being developed for integrating experimental, computational and validation studies in the mechanical and manufacturing engineering curriculum at MU. These learning modules are web based and are intended for dissemination to a wide audience extending beyond the students at MU. In this paper, salient features of these online learning modules, which integrate experimental data analysis for mechanical vibration course, are presented. Three different group activities associated with these modules are presented with specific details of the activities, assessment plans, and student perceptions of the modules. The content of these modules is evolving based on feedback from students and external, expert evaluators. It is anticipated that such learning studios can be used by instructors who teach lecture based vibration and control courses, and this resource will yield more insight into the theory, computation and practical applications of essential concepts in this area.
Influence of Modeling Assumptions on the Simulated EDM Performance
Authors: Escobar Agustín Márquez , de Lange Dirk F. , Medellín Castillo Hugo I. , Pérez Gutiérrez Francisco G.
Published: April 2014

Electrical Discharge Machining (EDM) is a non-conventional machining process widely used to manufacture hard material components which are not easily machined by conventional machining processes. Several modeling approaches have since long been proposed to characterize the EDM process, based on the electro-thermal phenomena that occur. Several of these early models are analytical models that have the major advantage of providing predictions of process performance based on analytical solutions. Unfortunately, their derivation often demands a number of assumptions and simplifications, which can limit the scope and precision of the predictions obtained. Two of the most known analytical models are based on different heat sources: a point heat source [1], and a uniform disk heat source [2].

In this paper, these two analytical EDM models are analyzed and compared with more elaborated numerical models in which specific modeling assumptions are lifted; the objective is to quantify the influence of each of these assumptions on the final result. Numerical simulations are based on the finite element method, which enables to study the influence of different temporal pulse shapes, the spatial intensity distribution, the temperature dependency of the thermal coefficients, and in particular the influence of the way latent heat is taken into account. The results are analyzed in terms of the predicted material removal rate (MRR), depth and radius of the crater. A comparison is presented between the two theoretical results [1], [2], and those obtained by the more elaborated numerical models. At the same time, a comparison is also made with some experimental data from literature.
Topology Optimization for the Single Phase Flow Using Two Point Flux Approximation Model
Authors: Dong Guang , Song Yulan
Published: April 2014

The topology optimization method is extended to solve a single phase flow in porous media optimization problem based on the Two Point Flux Approximation model. In particular, this paper discusses both strong form and matrix form equations for the flow in porous media. The design variables and design objective are well defined for this topology optimization problem, which is based on the Solid Isotropic Material with Penalization approach. The optimization problem is solved by the Generalized Sequential Approximate Optimization algorithm iteratively. To show the effectiveness of the topology optimization in solving the single phase flow in porous media, the examples of two-dimensional grid cell TPFA model with impermeable regions as constrains are presented in the numerical example section.
Numerical Simulation of Heat Pipe-Assisted Latent Heat Thermal Energy Storage Unit for Dish-Stirling Systems
Authors: Shabgard Hamidreza , Faghri Amir , Bergman Theodore L. , Andraka Charles E.
Published: April 2014

A two-dimensional model is developed to simulate the transient response of a heat pipe-assisted latent heat thermal energy storage (LHTES) unit that is combined with dish-Stirling solar power generation systems. The unit consists of a container which houses a phase change material (PCM) and two sets of interlaced input and output heat pipes (HPs) embedded in the PCM. The LHTES unit is exposed to time-varying concentrated solar irradiance. A three-stage operating scenario is investigated that includes: (i) charging only, (ii) simultaneous charging and discharging, and (iii) discharging only. In general, it was found that the PCM damps the temporal variations of the input solar irradiance, and provides relatively smooth thermal power to the engine over a time period that can extend to after-sunset hours. Heat pipe spacing was identified as a key parameter to control the dynamic response of the unit. The system with the greatest (smallest) heat pipe spacing was found to have the greatest (smallest) temperature drops across the LHTES, as well as the maximum (minimum) amount of PCM melting and solidification. Exergy analyses were also performed, and it was found that the exergy efficiencies of all the systems considered were greater than 97%, with the maximum exergy efficiency associated with the system having the minimum heat pipe spacing.
Nonlinear Dynamics of Axially Moving Plates With Rotational Springs
Authors: Ghayesh Mergen H. , Amabili Marco
Published: April 2014

In this paper, the in-plane and out-of-plane nonlinear dynamics of an axially moving plate with distributed rotational springs at boundaries is examined numerically. The Von Kármán plate theory along with the Kirchhoff’s hypothesis are employed to construct the kinetic and potential energies of the system. The Lagrange equation is used so as to obtain the equations of motion which are in the form of a set of second-order nonlinear ordinary differential equations. This set is recast into a set of first-order nonlinear ordinary differential equations with coupled terms. Gear’s backward-differentiation-formula is employed to integrate this set of equations numerically, yielding the generalized coordinates of the system as a function of time. The bifurcation diagrams of Poincaré maps are then constructed by sectioning these time histories in every period of the external excitation force. The results are shown in the form of time histories, phase-plane portraits, and Poincaré sections. The effect of the stiffness of the rotational springs on the global dynamics of the system is also investigated.
A Lattice Boltzmann Approach for Directional Transporting of Droplets Using Heterogeneous Surface Roughness
Authors: Lee Jung Shin , Lee Joon Sang
Published: April 2014

Fluid droplet on a surface with roughness has been simulated to investigate the hydrophobicity of surface and also measure the increase in contact angle (CA). Surface roughness increases the area of solid-liquid interface and this increase in composite interface makes the water to repel solid surface, thus causing an increase of the CA. Recently heterogeneous structure surface, which is pillar or rib structures with gradually changing pitches in certain direction, has gained lot of interest from researchers because wetting characteristics of those structures allow droplet movement without external forces. In this paper, droplet movement for heterogeneous surface cases are simulated with the computational fluid dynamics (CFD) modeling, known as Lattice Boltzmann method (LBM). First part of the study concentrates on droplet transportation. Half of the surface is more-hydrophobic region, textured with microscopic pillars and the other part of surface is less-hydrophobic, textured or smooth surface. Second part of the study concentrates on droplet breakup. More-hydrophobic textured band is located at center of less-hydrophobic textured surface. To see the effect of surface structure only, we choose same chemical property for all surfaces. Water droplets are spatially placed on border line of the different textures of surface. The simulations are carried out using projection method of LBM. Projection method has been used to in this study to be able to model the large density difference between air and water. Two phase immiscible fluids flow consisting of air and water (density ratio of air to water = 1:1000) is built in 3D space by using Projection method. This method can calculate solid-liquid-gas composite interface.
Incorporating Micro-Thermo-Mechanical Damage Model in Life Prediction Analysis of a Turbine Engine Blade to Disk Attachment
Authors: Naboulsi Sam
Published: April 2014

Fretting is an important problem for the operators of turbine engines, and it occurs when the blade and disk are pressed together in contact and experience a small oscillating relative displacement due to variations in engine speed and vibratory loading. It is a significant driver of fatigue damage and failure risk of disks. The present effort focuses on the damage initiation and propagation due to fretting fatigue. It introduces a micro-thermo-mechanical damage model that is capable of capturing the micro-scale nature of the fretting small oscillatory relative displacement. The micro-scale capability of the damage model is required to capture the effect of very high local stress near the edge of contact, which results in wear, nucleation of cracks, and their growth. It also provides a high fidelity approach to capture the significant reduction in the life of the material at the blade to disk attachment. To further understand the role of damage in the fretting initiated fracture, a specially developed novel fretting crack initiation model is incorporated in the analysis. Such combination makes it possible to simulate the realistic mechanism associated with fretting. The models are incorporated in a fretting fatigue simulation of an actual blade and disk attachment configuration. The results are validated with data obtained from an actual blade and disk attachment test using a representative loading mission. The results show consistency and accuracy with experimental data.
Viscoelastic Strain Response (ViSR) Ultrasound in Pre-Clinical and Clinical Application
Authors: Scola Mallory R. , Kornegay Joe N. , Howard James F. , Nichols Timothy C. , Gallippi Caterina M.
Published: April 2014

Viscoelastic Strain Response (ViSR) ultrasound is a novel acoustic radiation force (ARF)-based imaging method that noninvasively interrogates the viscoelastic properties of tissue by measuring the relaxation time constant for constant stress in the Voigt biomechanical model. The time constant is defined as the ratio of coefficient of viscosity to elastic modulus, so ViSR differentiates tissue with disparate viscosities and elasticities. ViSR ultrasound is performed by delivering two successive ARF impulses to a single region of exciation (ROE) and tracking the micrometer-scale displacements induced by the propagating longitudinal waves. ViSR does not rely on transverse wave propagation, which can be disrupted and difficult to track in heterogeneous and/or geometrically complex media. Another advantage to ViSR ultrasound is a large axial range relative to conventional ARF Impulse (ARFI) ultrasound.

In this overview, ViSR methods are discussed and demonstrated in calibrated viscoelastic tissue mimicking materials. ViSR ultrasound is then applied to differentiating fatty and fibrous deposition in muscle in a golden retriever muscular dystrophy (GRMD) dog model and in boys with Duchenne muscular dystrophy (DMD) with correlation to standard physical testing. ViSR is also applied to delineating the structure and composition of atherosclerotic plaques in a hypercholesterolemic pig model with histochemical validation. ViSR’s key advantages and disadvantages are discussed in regard to its general clinical utility.
High Pressure Turbine Rotor Stage Endwall Cooling and Passage Thermal Fields as Affected by Leakage Flow and Combustor Liner Coolant Streams
Authors: Ayaskanta Arya , Simon Terrence W. , Erickson Ryan , Moon Hee Koo , Zhang Luzeng
Published: April 2014

The effects of an engine-representative combustor exit temperature profile and different disc cavity leakage flow rates on endwall adiabatic effectiveness distributions and passage temperature fields in a high pressure turbine rotor stage of a gas turbine are experimentally documented. The measurements are made on a stationary linear blade row cascade with an axisymmetrically-contoured endwall of modern engine geometry and with engine-representative approach flow thermal and fluid mechanics characteristics. The measurements give insight into mixing of coolant emerging as leakage flow and combustor liner coolant mix with hot core gases ahead of the airfoil row. Reported results are thermal fields in the passage, adiabatic wall temperatures and adiabatic effectiveness values in using an engine-representative approach flow temperature profile and with approach flow temperature profiles with 1) no coolant in the approach flow (flat profile) and 2) coolant only within 10% of the span (approach flow profile with a thin thermal boundary layer).The results give insight into mixing between the leakage flow and the mainstream passage flow and its effects on endwall cooling. The results demonstrate that for the conditions studied; much of the endwall cooling is contributed by the coolant in the approach flow. This is an important result that has previously not been well documented.
Effect of Lubrication in Nano-Indentation Process: A Molecular Dynamics Simulation Study
Authors: Wang Yachao , Shi Jing
Published: April 2014

Molecular dynamics (MD) simulation is an effective numerical approach to study nano-indentation processes on many intriguing issues such as material deformation response, mechanical properties of materials such as hardness, and phase transformation. Lubrication is an important consideration for many types of tool-based manufacturing processes including indentation, scratching, and machining. It adds complexity to the system, affects the friction condition, and changes material behavior. For indentation process, the existence of lubrication liquid may also influence mechanical property measurements. Unfortunately, lubrication effect in tool-material interactions has not been addressed by the existing MD simulation literature. In this study, we construct 3D MD simulation models for nano-indentation of single crystal copper using a cylindrical diamond indenter under wet and dry conditions, respectively. The wet condition is realized by adding water molecules to the simulation system to separate the indenter and copper surface, while the dry condition does not have water molecule in the system. The tribological effects of water are investigated at two different indentation speeds. The results indicate that wet indentation with water eliminates the reverse indentation size effect, which however occurs in the dry nano-indentation process. Also, the existence of water results in higher computed hardness values under low indentation loads. Meanwhile, friction forces along the indenter/work interface are reduced under wet indentation condition. It is found that lubrication is helpful for preserving the size and shape of residual indentation. In addition, the increase of indentation speed increases the indentation force.
Preliminary Performance Test of Mechanical Pump for a Stella-1
Authors: Han Ji-Woong , Ko Bock Seong , Park Sang-Jun , Lee YoonSang , Jeong Ji-Young , Lee Yong Bum
Published: April 2014

In the process of sodium-cooled fast reactor (SFR) design, it is very important to verify thermo-hydraulic performance of each component in the sodium environment. In KAERI (Korea Atomic Energy Research Institute) STELLA (Sodium Integral Effect Test Loop for Safety Simulation and Assessment) project is under a Mid- and Long-term Nuclear R&D Program. The STELLA project is composed of two stages. In the 1st stage the performance for heat exchangers such as DHX (Decay heat exchanger) and AHX (Air heat exchanger) and for PHTS (Primary heat transport system) mechanical pump will be evaluated. The detailed design of each component is based on that of a 600MWe demonstration reactor.

Since full-scale components could not be installed in STELLA-1 [1], the model pump is designed to be scaled-down based on the scaling law. Various pump tests have been done in water environment by using model pump.

In this study the design features of model pump were described and the scaling parameters were examined. The results of pump performance tests have been also introduced which is essential to perform safety analysis.
Performance Analysis of Two HVAC Systems for Zero Energy Research Laboratory, Denton, TX
Authors: Hasib Naimee , Mun Junghyon , Tao Yong X.
Published: April 2014

HVAC (Heating, Ventilation & Air Conditioning) system is the most significant part of a building which directly associated with human comfort. Modern HVAC system optimizes all the parameters like temperature, humidity and indoor air quality to give the occupant the best comfort. Beside human comfort some other crucial factors like installation, maintenance & operational cost, efficiency, availability and controlling method of the system need to be taken into consideration. This paper covers the study and comparison among two different HVAC systems to achieve the goal of finding the better effective HVAC system in terms of human comfort, efficiency considering North Texas climate. In this paper; power consumption, human comfort & efficiency analysis is done for the existing WWHP & WAHP system (in UNT ZØE) using Energy Plus simulation software. Calibration of the simulation data of the existing system is done comparing with the real data. After the baseline model is calibrated, simulation for other HVAC systems like evaporative cooler (EC) is conducted. The comparison analysis of both the HVAC systems shows the better effective HVAC system in North Texas weather considering all the relevant issues and challenges. The result will make UNT Zero Energy lab more energy efficient and a standard model towards a sustainable green future.
Integration of a Reliability Model Within a Virtual Analysis System for Printed Circuit Boards
Authors: Goerdt Benjamin B. , Dababneh Amer , Marler Timothy , Ozbolat Ibrahim , Weibtraub Benjamin , Johnson Ross
Published: April 2014

The field of modeling and simulation continues to grow and help reduce costs and increase development speed in the engineering community, but use of such capabilities has been minimal with respect to circuit board visualization and reliability. This work responds to this gap with a new simulation-based reliability model for electrical components and systems, integrated within a software platform for concurrent analysis. While statistics-based reliability analysis is common, this work presents the integration of such models in a comprehensive system. The results coupled with a user-friendly interface and display in a virtual environment combine to create a novel tool for the identification of problem areas and planning for future maintenance of electromechanical systems.
Micro Double Pressure Sensor for Measuring the Applying Forces in Balloon Angioplasty
Authors: Dabiri Arman
Published: April 2014

This paper describes a new catheter based on double pressure sensor for measuring reaction forces of cardiovascular vessel walls in balloon angioplasty. This medical device is based on Wheatstone bridge and a passive transformer module. It assists cardiologists to measure reaction forces exiting between the catheter and the vascular wall. Reaction forces on the catheter can be grouped into two types: 1) reaction forces on the catheter head and 2) reaction forces between the balloon and the vascular wall. Its new proposed transducer module aids doctors decrease cardiology steps leading to the reduction of patients’ pains from inputting consecutive catheters into their bodies. Moreover, its special circuit design reduces needing wires for power supplying of the sensors, and simplifies the fabrication processes. Finally, mechanical behaviors of the sensor have been simulated in SolidWorks and its electrical circuit is modeled in Simulink\electrical. Also, Fabrication processes are projected in the final step of designing.
A Review of Nuclear Power in China
Authors: Catlow Fred
Published: April 2014

Whilst nuclear power does not seem to have the support of public opinion in many parts of the world China is forging ahead with its ambitious nuclear programme. Some might argue that this is to support their weapons programme but that clearly is not the case and is undoubtedly to provide a stable source of energy for the generation of electricity but also for alternative peaceful uses such as desalination.

This paper covers the history of nuclear power in China over more than thirty years and addresses what impact, if any, their policy of continued expansion of nuclear power will have on the rest of the world. The different reactor types installed in China is reviewed, the infrastructure and the overall strategy is surveyed.
Application of Thermal Hydraulic and Severe Accident Code SOCRAT/V3 for Calculation of Air Ingress Experiment QUENCH-16
Authors: Vasiliev Alexander
Published: April 2014

The thermal hydraulic and SFD (Severe Fuel Damage) best estimate computer modelling code SOCRAT/V3 has been used for the calculation of QUENCH-16 experiment which was performed in the frame of the EC supported LACOMECO programme.

The QUENCH-16 test conditions simulated a representative scenario of LOCA (Loss of Coolant Accident) nuclear power plant accident sequence in which the overheated up to 1800K core would be reflooded from the bottom by ECCS (Emergency Core Cooling System). The QUENCH-16 experiment included the following phases: first heat-up phase, pre-oxidation phase, slow cool-down phase (preparatory to air ingress), air ingress phase and bottom water flooding phase.

The test QUENCH-16 was successfully conducted at the Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany, on July 27, 2011. The primary objective of this test was to investigate the oxidation of Zircaloy in the air following a limited pre-oxidation in the steam and to achieve a long period of oxygen starvation to promote the interaction with the nitrogen. Unexpectedly high cladding oxidation rate was detected during flooding phase which resulted in huge hydrogen production in QUENCH-16. It was due to zirconium nitride (ZrN) formation in a cladding which induced a diffusion transparency of zirconium dioxide layer.

QUENCH facility is designed for studies of the PWR fuel assemblies behaviour under conditions simulating design basis, beyond design basis and severe accidents.

SOCRAT/V3 computer modelling code was used for estimation of basic thermal hydraulic, oxidation and air ingress parameters in QUENCH-16.

The calculated results are in a reasonable agreement with experimental data which justifies the adequacy of modeling capabilities of SOCRAT code for application to such a complicated test as QUENCH-16.
Cancellation of Physiological Hand Tremors Using Compliant Robotic Assist
Authors: Bobade Rupesh S. , Gandhi Prasanna S. , Bhagat Nikunj A. , Chen Chao
Published: April 2014

Physiological hand tremors are unwanted involuntary motions which affect the precision of surgeons during microsurgery. For precision surgical procedures, the magnitude of tremors is high as compared to the thickness of vessel or tissue being operated at surgical site. Hence the chances of causing irreversible damages in the nearby locations is very high, particularly in case of neural and vitreoretinal surgeries. Furthermore, human hand stability is a skill to be acquired with extensive training, it decreases with age and limits the number of surgeons qualified to perform microsurgery. Control of tremors is therefore, a major challenge for the surgeons at global level. In this paper, we have shown an effective implementation of a compliant manipulator system to successfully measure and suppress tremors. The compliant manipulators offer inherent advantageous over rigid systems, for example, more accuracy, no friction, no wear and tear, flexibility which would help preserving surgical feel and easy controllability from microsurgical point of view. Three different control schemes include feedback from lowpass filtering and an adaptive filtering are implemented and compared. The effective adaptive control scheme shows promising results in reducing tremors at the surgeon’s tool tip by ∼96%, when holding at a point and by ∼68% while carrying out a voluntary motion.
A Coupled Finite Volume Method for Particle Scale Electrochemical Modeling of Lithium-Ion Batteries
Authors: Trembacki Bradley L. , Vadakkepatt Ajay , Mathur Sanjay R. , Murthy Jayathi Y.
Published: April 2014

Lithium-ion batteries are commonly simulated using a volume-averaged formulation (porous electrode theory), using effective properties such as conductivity and diffusivity and assuming a simplified spherical geometry of the electrode particles. Microscopic scans show that the shape, size, and orientation of the particles is highly variable, which can significantly alter pathways for ionic, electronic, or thermal transport. Unlike a volume-averaged spherical formulation, a particle-scale simulation applied to a real electrode geometry is able to predict localized phenomena and enables the optimization of material morphology to maximize battery performance. The physical processes involved in lithium-ion battery simulations are electron, ion, mass, and thermal transport, and a particle-scale simulation yields the spatial variation of Li concentration, electrostatic potential, and temperature throughout time as the battery discharges. In this paper we develop a fully-coupled finite volume methodology for the simulation of the electrochemical equations in a lithium ion battery cell. An unstructured mesh of arbitrary convex polyhedral cells is used to mesh synthetic spherical particles and electrolyte. Second-order discrete conservation equations for Li ion transport and electrostatic potential are developed. Butler-Volmer kinetics are included at the electrode/electrolyte interface. A block-sparse unstructured linear system results from the discretization of the governing equations, and is solved using a BiCGSTAB solver with an algebraic multigrid pre-conditioner. A fully-implicit time stepping scheme is used to compute transients. Our methodology fully couples species, electrostatics, and Butler-Volmer kinetics in a stable and efficient computational algorithm. We demonstrate that it is more stable and takes less time to converge than a conventional sequential solution procedure.
Gravity-Assisted, Passive Cancellation of Disturbances for Inertial Sensors
Authors: Karpachevskyy Taras , Spiewak Swavik
Published: April 2014

Continuing enhancements in Microsystem Technologies facilitate the development of inertial sensors — accelerometers and gyroscopes — of unprecedented performance to cost ratio and broaden the frontiers of their application. Of particular interest, because of their immunity to ambient disturbances, are sensors equipped with high resolution Electro-Mechanical ΣΔ converters and with a high speed, digital serial signal transmission. The digital circuitry of these sensors reaches the accuracy of 0.02 parts-per-million (ppm). However, the analogue transducers of measured physical quantities into electrical signals inside of the even best inertial sensors are prone to inherent imperfections of analog systems such as nonlinearity, cross-sensitivity, or noise. The best accuracy of these transducers is about two orders of magnitude worse than that of the electrical circuitry. The overall accuracy can be greatly improved by using corrective filters that cancel the effects of imperfections in the analogue transducers. The effectiveness of these filters hinges upon the accuracy of identifying comprehensive models of the analogue transducers.

Ambient disturbances, in particular mechanical vibrations, greatly deteriorate the accuracy of identification. Their impact can be attenuated to some extent by using vibration isolation platforms. The effectiveness of attenuation is usually good at the frequencies above 5–10 Hz, however it is poor at low frequencies. This poor attenuation is a significant disadvantage since the low frequency phenomena in inertial sensors have pronounced impact on their suitability for a broad class of applications (e.g., navigation).

The presented research focuses on the design of a passive vibration isolation device in which horizontal movement is coupled to tilt in a way that a component of the gravity perceived by the tested inertial sensor effectively cancels out the horizontal acceleration coming from the ambient vibrations.
A Method for Computation of Wave Propagation in Heterogeneous Solids: Implementation and Performance
Authors: Cho S. S. , Park K. C. , Kolman R.
Published: April 2014

Computer implementation of the new algorithm developed in [1, 2, 3] and its numerical performance is presented, with detailed discussions of the element-by-element decomposition of the extensional and shear components and step-by-step algorithmic procedures. Numerical results as applied to wave propagating through cracked plane stress problems, three-dimensional problems and elasto-plastic problems illustrate high-fidelity of the present algorithm compared with existing ones, and the new algorithm is implemented into an open source research code TAHOE[4] code along with the further computational performance.
Vibration Damping Enhancement of Fiber Reinforced Polymer Composites With Surface Grown Zinc Oxide Nanorods
Authors: Masghouni Nejib , Al-Haik Marwan
Published: April 2014

The use of zinc oxide (ZnO) nanostructures with fiber reinforced polymer composites has gained more applications recently due to the additive benefits of the semi-conductivity and piezoelectricity of ZnO. In this study, we suggest growing ZnO nanowires (NWs) on the surface of woven carbon fibers using low temperature (c.a. 80°C) hydrothermal technique and integrating the modified fibers in composite structures based on epoxy matrix. Mechanical vibrations tests based on samples with and without surface-grown ZnO established the enhanced damping of the hybrid composite structures through measuring the damping ratio and the vibration amplitude. We hypothesize that, besides the piezoelectric induced damping, the large aspect ratio of ZnO nanowires could provide higher interfacial friction with the epoxy matrix and in between the neighboring nanowires which in return could provide more energy dissipation.