bluuebunny/crossref_metadata_2025 huggingface dataset:
Data Center Modeling Using Response Surface With Multi-Parameters Approach
Authors: Phan Long , Lin Cheng-Xian , Telusma Mackenson
Published: March 2016

Energy consumption and thermal management have become key challenges in the design of large-scale data centers, where perforated tiles are used together with cold and hot aisles configuration to improve thermal management. Although full-field simulations using computational fluid dynamics and heat transfer (CFD/HT) tools can be applied to predict the flow and temperature fields inside data centers, their running time remains the biggest challenge to most modelers. In this paper, response surface methodology based on radial basis function is used to drastically reduce the running time while preserving the accuracy of the model. Response surface method with data interpolation allows the study of many design parameters of data center model more feasible and economical in terms of modeling time. Three scenarios of response surface construction are investigated (5%, 10%, and 20%). The method shows very good agreement with the simulation results obtained from CFD/HT model as in the case of 20% of the original CFD data points used for response surface training. Error analysis is carried out to quantify the error associated with each scenario. Case 20% shows superb accuracy as compared to others. With only 2.12 × 104 in mean relative error and R2 = 0.970, the case can capture most of the aspects of the original CFD model.
Effects of Lingualized and Linear Occlusion Schemes on the Stress Distribution of an Implant Retained Overdenture Using Finite Element Analysis
Authors: Hasan Md Abu
Published: March 2016

This study compares the effects of lingualized and linear occlusion schemes on the stress distribution of an implant retained mandibular overdenture (IRO) using finite element analysis (FEA). A high fidelity solid model of mandibular overdenture incorporating cusps and fossae of occlusal surface with two anterior implants in the canine regions and residual ridge support in the posterior region of the alveolar bone was modeled in SolidWorks and imported to ANSYS for stress analysis. The load was applied vertically to the central grooves and buccal cusp tips of the premolars and molar teeth for the lingualized and linear occlusion respectively. The loading magnitudes were 200 N on the premolars and 200 N on the molar teeth with multiple contact locations. The results show that the linear occlusion scheme generated higher stress in the implants and the prosthetic bar than the lingualized occlusion. The locations of high stress concentrations were the neck of the implants and the implant-prosthetic bar intersection for both the occlusion schemes. However, in the cortical bone lingualized occlusion loading scheme generated higher stress (max principal stress) than the linear one suggesting possibility of greater bone loss. The results of this study could be used to comprehend the stress distribution in the denture teeth, base, bone-implant interface and surrounding bone for the two occlusion concepts and may be of help to the clinicians in choosing the right scheme for the edentulous patients.
Assessment of Natural Convection Heat Transfer in an Isochoric Thermal Energy Storage System
Authors: Baghaei Lakeh Reza , Guerrero Yetlanezi B. , Nithyanandam Karthik , Wirz Richard E.
Published: March 2016

Most of the renewable energy sources, including solar and wind suffer from significant intermittency due to day/night cycles and unpredictable weather patterns. Energy Storage systems are required to enable the renewable energy sources to continuously generate energy for the power grid. Thermal Energy Storage (TES) is one of the most promising forms of energy storage due to simplicity and economic reasons. However, heat transfer is a well-known problem of most TES systems that utilize solid state or phase change. Insufficient heat transfer impairs the functionality of the system by imposing an upper limit on the power generation. Isochoric thermal energy storage system is suggested as a low-cost alternative for salt-based thermal energy storage systems. The isochoric thermal energy storage systems utilize a liquid storage medium and benefit from enhanced heat transfer due to the presence of buoyancy-driven flows. In this study, the effect of buoyancy-driven flows on the heat transfer characteristics of an Isochoric Thermal Energy Storage system is studied computationally. The storage fluid is molten elemental sulfur which has promising cost benefits. For this study, the storage fluid is stored in horizontal storage tubes. A computational model was developed to study the effect of buoyancy-driven flow and natural convection heat transfer on the charge/discharge times. The computational model is developed using an unsteady Finite Volume Method to model the transient heat transfer from the constant-temperature tube wall to the storage fluid. The results of this study show that the heat transfer process in Isochoric thermal energy storage system is dominated by natural convection and the buoyancy-driven flow reduces the charge time of the storage tube by 72–93%.
Parametric Study on Dynamics of Breathing Cracked Rotor via Laser Scanner
Authors: Zhao J. , DeSmidt H. A. , Peng M. , Yao W.
Published: March 2016

The study is based on the finite element model which was developed to investigate the nonlinear breathing behavior of transverse cracks in terms of crack location and rotation speed. The crack model is built using the released strain energy concept in fracture mechanics. Zero Stress Intensity Factor (SIF) method is employed to determine the crack closure line at each time step by calculating the stress intensity factor of opening mode for prescribed resolutions in crack area. The crack is considered open at the points where the stress intensity factor for opening mode is larger than zero. The stiffness matrix is updated at every time step by integrating compliant coefficients over instantly calculated crack open area. With the updated stiffness and force matrices, the vibration response at next time step is solved by Newmark integration method. To investigate the effectiveness of laser scanner, parametric study is conducted to analyze the vibration responses collected by the laser scanner with different scanning functions and frequencies. With this model, the displacement or velocity along the shaft can be extracted to form time based data sets for different scanning function or scanning frequency to explore its usefulness for damage identification.
Transient Double-Diffusive Convection in a Vertical Cavity With Soret and Dufour Effects by Lattice Boltzmann Method on CUDA Platform
Authors: Ren Qinlong , Chan Cho Lik
Published: March 2016

Double diffusive flow in a cavity has attracted lots of attention due to its importance in many engineering fields such as ocean circulation, crystal growth, pollution transportation in air, metal manufacturing process and so on. When heat and mass transfer occur simultaneously in the double diffusive flow, the fluid flow is not only driven by the temperature gradient but also by the concentration gradient as well. In some cases, the Dufour and Soret effects will play a significant role in the double diffusive flow process. The energy flux created by the concentration gradient is called Dufour effect and the temperature gradient can cause the mass flux which is Soret effect. When taking the Soret and Dufour effects into account, the temperature and concentration equations become coupled with each other. However, the coupling diffusivities matrix can be diagonalized. The coupled system can then be transformed to two uncoupled diffusion-advection equations of two independent species. The temperature and concentration can be obtained by the inverse transformation of these two independent species. As a numerical method developed in the past two decades, lattice Boltzmann method (LBM) is powerful in simulating complex heat transfer and fluid mechanics problems. In the current study, a lattice Boltzmann model was developed and implemented for the double-diffusive convection with Soret and Dufour effects. Three distribution functions were used to compute the fluid velocity, specie 1, and specie 2, respectively. Specifically, a rectangular enclosure with horizontal temperature and concentration gradients was investigated. On the other hand, the graphics processing units (GPU) computing becomes popular since the advent of the NVIDIA’s CUDA platform, which includes both hardware components and software programming environment. The developed LBM code was adapted on the CUDA platform to accelerate the computation for parametric studies. The GPU is responsible for the parallel tasks while CPU tackles the sequential steps in the computation. To verify the improvement on computation ability by using GPU, the ratio of the computational time between CPU code and CUDA code is presented by simulating the classical natural convection process in a cavity. The computational speed can be accelerated by more than 20 times when large number of nodes is used. The fluid flow, temperature field and concentration field are presented for different Rayleigh numbers, buoyancy ratios, Prandtl numbers, Lewis numbers, aspect ratios, as well as Soret and Dufour coefficients. In addition, the results of Nusselt and Sherwood numbers are shown for different parametric conditions. As a result, lattice Boltzmann method was demonstrated as a good option to study the complex double-diffusive convection with Soret and Dufour effects in a vertical cavity.
Intermittent Contact Dynamics of a Micro-Cantilever in High Speed Contact Mode Scanning Probe Microscopy
Authors: Dey Somnath , Kartik V.
Published: March 2016

The intermittent contact dynamics of a scanning probe microscopy (SPM) micro-cantilever are investigated in the context of high speed imaging in contact mode. At high scan speeds the cantilever can completely detach from the sample surface, and this lowers the achievable image resolution and limits the imaging speed. An analysis is performed, modeling the micro-cantilever as an Euler-Bernoulli beam and approximating the effect of the tip’s contact with the surface by an attached spring with an end mass that is subjected to attractive/repulsive interaction force. At low scan speeds, the cantilever follows the surface profile, while the frequency spectra exhibit a number of side-bands, while at higher speeds, the contact is intermittent. The sensitivity of the cantilever’s deflection varies along the length and hence the image resolution strongly depends on the point selected for optical laser deflection.
Negotiation in Collaborative Working Environment for the Next Generation of Product Design
Authors: Coutinho Carlos , Cretan Adina , Agostinho Carlos , Jardim-Goncalves Ricardo
Published: March 2016

Negotiation in collaborative manufacturing environments drive new ways to perform interoperability between industrial companies. The networks of SMEs are a novel segment in a highly competitive area, supported by numerous partners and applications which need to collaborate and to be interoperable. Particularly, the subcontracted small and medium enterprises (SMEs) need to be flexible towards the changes that are imposed by the major contractors, doing so at the lowest cost. This paper proposes a framework which advocates negotiations as a pillar mechanism to support innovation during the development of services in industrial collaborative working environments, and reflects the results of the European research project H2020 C2NET.
Thermal Stress Analysis of Gypsum Shell Cracking in Polyjet-Based Rapid Casting of Cellular Metals
Authors: Heo Hyeonu , Tessema Addis , Iqbal Shaheer , Ju Jaehyung , Kidane Addis
Published: March 2016

Cellular (or lattice) metals are increasingly gaining attention for their having combinations of mechanical, thermal, and acoustic properties that provide potential opportunities for diverse multifunctional structural implementations. These include ultra-light structures with high specific strength and high specific strain, excellent impact absorption, acoustic insulation, heat dissipation media and compact heat exchangers. The emerging 3D printing technologies including direct and indirect additive manufacturing processes may accelerate the realization of their structural applications of cellular metals. For indirect additive manufacturing processes, sacrificial patterns are 3D printed with castable polymers, followed by metal filling into a mold cavity to make final cellular metals. With a high stiffness of a castable polymer, e.g., VisiJet® Procast, it is possible to build network lattice cellular structures, replacing wax which has been used for traditional investment casting processes. In general, a high thermal stress is expected during burning-out process of the rapid casing. Due to the castable polymer’s new properties, no literature is available on thermal stress between the castable polymer and ceramic shells for indirect additive manufacturing of cellular structures. The objective of this study is to investigate i) thermal stress by thermal expansion mismatch between a sacrificial pattern made of a castable polymer and a coated gypsum shell and ii) an effect of the thickness of the coated gypsum shell on thermal cracking. Starting with thermal analysis, glass transition temperature, melting temperature and thermal expansion coefficient are obtained from experiments. An analytical model for thermal stress analysis is constructed with thermo-mechanical constitutive equations and compatibility equations, followed by a failure analysis at the coated shells where gypsum is used for coating the sacrificial pattern. The thermo-mechanical analysis is conducted as a function of temperature and coated shell thickness followed by a numerical validation with a finite element (FE) based simulation. The castable polymer has the potential to be used as a base material for manufacturing 3D network cellular sacrificial patterns with thin cell walls over conventional wax materials due to its high modulus and low thermal expansion coefficient during the burning out process of the sacrificial pattern.
Effect of Vehicle Front End Profile on Pedestrian Kinematics and Biomechanical Responses Using a Validated Numerical Model
Authors: Gupta Vishal , Kalra Anil , Shen Ming , Chou Clifford C. , Yang King H.
Published: March 2016

Traumatic injuries and biomechanical responses of a pedestrian depend on vehicle front end characteristics as well as the pedestrian anthropometric details in vehicle-pedestrian crashes. A number of laboratory experiments were conducted using post mortem human subjects (PMHS) to understand the biomechanics behind the injuries in a pedestrian crash. However, different vehicular front ends were used in these studies making comparisons among studies impossible. The current research work focuses on validating simulated pedestrian kinematics and accelerations responses of MADYMO full body pedestrian model with the experimental results. In general, overall kinematics of the body for pedestrian models were also compared with that recorded in the video snapshots from the cadaveric experimental tests at 50 ms time intervals. Along with the validation of kinematics of pedestrian, the acceleration responses of head, chest, pelvic and lower leg of the pedestrians were also validated against the corresponding experimental data. Other responses like head angle as well as head impact velocity during primary impact with the hood were analyzed at different impact speeds. Once the responses were validated for a particular front end of the vehicle, a series of numerical parametric studies were further conducted using several front end profiles based off a mid-sized sedan. For the parametric study, different pedestrian models representing three pedestrian sizes, a 50th male, a 5th female, and a 6 years-old child, were used in the simulations. Finite element model of a vehicle front end was changed in terms of the heights of bumper, bonnet leading-edge, and bonnet rear reference-line using a mesh-morphing technique. In most simulations, primary head impact location depends on the pedestrian size, and the secondary impact with ground at the head region is affected by type of vehicle and its front end profile. Kinematics of the pedestrians as well as the angle of primary head impact varies a great deal based upon the front-end profile of the striking vehicle (e.g., raised front-end profile or lowered front-end profile). Leg and pelvis accelerations were found to be high in vehicles with raised front end profiles. Chest and head accelerations were also found to be affected by vehicle front end profile and pedestrian size. However, it should be noted that there were some front-end profiles that help in avoiding pedestrian secondary head impact with the ground.
Vehicle Pose Estimation and SONAR Sensor Based Mapping
Authors: Ismail Hesham , Balachandran Balakumar
Published: March 2016

In carrying out simultaneous localization and mapping, a mobile vehicle is used to simultaneously estimate its position and build a map of the environment. The long-term goal of this work is to build an autonomous inspection mobile vehicle for oil storage tanks and pipelines. The harsh environmental conditions in storage tanks and pipelines limit the types of feature extraction sensors and vehicle pose estimation sensors that one can use. Here, a SOund Navigation And Ranging (SONAR) sensor will be used for feature extraction, and a gyroscope and an encoder will be used for vehicle pose estimation. The integration of these sensors (SONAR, encoder, and gyroscope) will be discussed in this paper, along with the use of a recently developed algorithm fusion for SONAR sensors. The integration of the sensors represents a step towards implementation of concurrent localization and mapping progress in harsh environments.
An Analytical and Computational Investigation of Room Heating due to Complex Geometry Heat Sources
Authors: Friedrich Fabian , Epple Philipp , Steber Michael , Delgado Antonio
Published: March 2016

The compressed air generated by a compressor, is one of the most expensive known energy forms. The reason therefore is that electrical energy is converted directly into heat. The dissipation of the heat has a decisive influence on the performance of a compressor. Due to lack of standards during the planning phase of new production halls the heat balance, i.e. the supply and removal of the generated heat, very often the compressor is not considered proper. Even the German Engineering Association Directive VDMA 4363 “Lüftung der Betriebsräume luftgekühlter Kompressoren” (Ventilation of Industrial Premises Air-Cooled Compressors) [4] does not answer this question. In order to close this gap the impact of the volume of the room in order to keep the compressor running at a proper temperature is investigated. The influence of the orientation and size of the hot surfaces on the room heating is analyzed in detail as well.
CFD Modeling of Fast Transient Processes in Drilling Fluid
Authors: Golbabaei-Asl Mona , Povitsky Alex , Ring Lev
Published: March 2016

The current paper presents the numerical simulation of the wave propagation phenomena in the Newtonian and non-Newtonian drilling mud flow associated with oil/gas drilling activities. The formation of wave due to back pressure changes by means of a choke is investigated. Numerical schemes with second- and forth-order accuracy have been applied to the non-linear Euler and Navier-Stokes equations to demonstrate the advantage of high-order approximation in numerical modeling. A grid refinement study is performed to observe the convergence of the solution with respect to various time steps and grid sizes. Conservative and non-conservative formulations of momentum equations were explored to evaluate the accuracy of reflection and transmission of pressure pulse at the areal discontinuity in the conduit.
The Effects of Material Properties on Pillar-Based QCM Sensors
Authors: Esmaeilzadeh Hamed , Cernigliaro George , Su Junwei , Gong Lin , Mirzaee Iman , Charmchi Majid , Sun Hongwei
Published: March 2016

Quartz crystal microbalance (QCM) device is a highly sensitive mass sensor (sensitivity: 0.5 ng/cm2) with a wide range of applications including biosensing, thin film deposition, surface chemistry, volatile organic compounds (VOC) and gaseous analytes detection. A recent study shows that several orders of magnitude improvement in sensitivity can be achieved by attaching microscale Polymethyl methacrylate (PMMA) pillars onto the surface of the QCM (QCM-P) to form a two-degree of freedom coupled resonant system. In this research, the effects of residual layer from the nanoimprinting process of micro-pillars and polydispersity index (Pd) of PMMA molecules on the sensitivity of QCM-P devices are investigated both experimentally and theoretically. The results show the residual layer behaves as an additional mass and significantly reduces the frequency shift of QCM-P sensor while a low polydispersity of PMMA improves the sensor responses. The outcome of this research leads to an in-depth understanding of the effects of material and fabrication process on QCM-P sensors which will build a solid foundation for the further improvement of QCM-P devices for a variety of applications such as protein binding measurement in drug discovery, gas detection for environmental monitoring and protection.
Cost Effectiveness Optimization of Component Improvements of a Turbofan Engine Using Genetic Algorithm
Authors: Yobby Jason , Raja Daniel S. , Yan Terry X.
Published: March 2016

In this paper, we examined an imaginary underperforming prototype of a real high bypass-ratio turbofan gas turbine engine that has been assembled to specifications. The prototype was designed and assembled to generate a predetermined value of specific thrust while consuming fuel at a predefined specific fuel consumption value. To meet the required performance targets, improvements needed to be made to one or more of the engine components. In most real world scenarios, the improvement of any or all engine parameters pertaining to its performance is tied to a cost per percentages of improvements of individual component in the engine. There is always a narrow room for improvement in each or all of the components. However, the improvements come with high costs, since the engine has been designed in an efficient way to begin with. The cost of improvement of each component is indexed by a dollar cost per percent value of the component performance characteristics. It is of technical and economic importance to find a combination of performance improvements of each of the components that yields the lowest overall rework cost, thereby the total design cost, given the specified engine performance criteria. To achieve this goal, simulations for a real gas turbine turbofan cycle are performed in conjunction with the genetic algorithm (GA). A single objective (i.e. total improvement cost) GA with two constraints (i.e. desired values of specific thrust and specific fuel consumption) and eight degrees of freedom (i.e. diffuser pressure ratio, fan polytropic efficiency, compressor polytropic efficiency, burner efficiency, burner pressure drop ratio, turbine polytropic efficiency, fan duct exit nozzle pressure ratio, core duct exit nozzle pressure ratio) is employed. As a result, we have found the lowest overall cost associated with the improvements for each of the components.
Closed-Loop Control of Soft Active Composites
Authors: Ahmed Numair , Ferreira Placid
Published: March 2016

This paper presents the possibility of closed-loop regulation of position or force at features (posts) on an active composite membrane. Active composite membranes are multilayered membranes with different functions, actuation, sensing, interconnect, mechanical compliance tuning assigned to them. Here we demonstrate the ability to perform closed-loop control on an array of four posts on a membrane stamp designed for micro-transfer printing. The paper also assesses the positioning and force resolution obtaining from such membranes.
Virtual Simulation of Blast, Behind-Armor Blunt Trauma, and Projectile Penetration Leading to Injury of Life-Critical Organs in the Human Torso
Authors: Cooper Candice F. , Taylor Paul A.
Published: March 2016

Light body armor development for the warfighter is based on trial-and-error testing of prototype designs against ballistic projectiles. Torso armor testing against blast is virtually nonexistent but necessary to ensure adequate mitigation against injury to the heart and lungs. In this paper, we discuss the development of a high-fidelity human torso model and the associated modeling & simulation (M&S) capabilities. Using this torso model, we demonstrate the advantage of virtual simulation in the investigation of wound injury as it relates to the warfighter experience. Here, we present the results of virtual simulations of blast loading and ballistic projectile impact to the torso with and without notional protective armor. Our intent here is to demonstrate the advantages of applying a modeling and simulation approach to the investigation of wound injury and relative merit assessments of protective body armor.
Coupled Fluid-Chemical Computational Modeling of Anticoagulation Therapies in a Stented Artery
Authors: Ghosh Anirban , Seo Jung-Hee , Mittal Rajat
Published: March 2016

Stent thrombosis is a major complication that occurs after the placement of stents in the coronary artery through balloon angioplasty. The common treatment for stent thrombosis is to provide patients with anticoagulant and antiplatelet therapy through the bloodstream. This study uses numerical modeling to compare two delivery methods of heparin anticoagulant to the arterial wall to reduce thrombus formation: through the flow and via a drug-eluting stent. A unique computational fluid dynamics model is developed that couples an incompressible flow solver with a convection-diffusion-reaction equation solver. The flow solver uses a sharp-interface immersed boundary method on a Cartesian grid to characterize pulsatile flow over the curved wires of the stent. Concurrently, the convection-diffusion-reaction equations are solved for the 19 coupled reactions that make up the coagulation cascade and heparin interactions, as well as reaction and transport equations for both active and inactive platelet species. The simulation is run with input boundary conditions of steady flow, pulsatile Poiseuille flow, and a Womersley flow profile. Results are collected for the bare metal stent case, anticoagulant delivered through the bloodstream, and anticoagulant delivered through a drug-eluting stent. The results generally find that the drug-eluting stent delivery of anticoagulant is more effective in reducing platelet activation and clotting, while also providing a more localized anticoagulant distribution.
Performance of Temperature Controlled Perimeter and Row-Based Cooling Systems in Open and Containment Environment
Authors: Nemati Kourosh , Alissa Husam , Sammakia Bahgat
Published: March 2016

The continuous increase of data center usage is leading the industry to increase the load density per square foot of existing facilities. High density (HD) IT load per rack demands bringing the cooling source closer to the heat load in contrast to room level air cooling. For high density racks, the use of in-row cooling systems is becoming increasingly popular. In-row cooling can be the main source of cooling for a data center or work jointly with perimeter cooling in what is called a hybrid cooled room level system. Also, hot or cold aisle containment can be integrated with perimeter cooling and used throughout the data center to reduce the mixing of hot and cold air. Currently, there has not been much work comparing the performance of in-row cooling in open versus contained environments.

The present work builds on a previous study where the interaction of perimeter and row-based cooling was evaluated for a cold-aisle containment (CAC) environment. Previously, the benefit of using row-based cooled in an aisle has not been compared with an aisle in open conditions. Here, we numerically investigate the performance of in-row coolers in both opened and cold-aisle contained environments. Groups of IT equipment that differ in air flow strength are used to provide the heat load. Empirically measured flow curves for common IT equipment are employed to provide simplified models of the IT equipment in the CFD software used. The steady state analysis includes information provided in the manufacturer’s specifications such as heat exchanger performance characteristics. The model was validated using a new data center laboratory with perimeter cooling. A single aisle of the data center is modeled to reduce the computational time, and the results are generalized. The cold aisle contains 16 racks of IT equipment distributed on both sides. In addition, the aisle contains 2 power distribution units. Full details are incorporated in the computational model. A single Liebert® CW114 CRAC unit provides the perimeter cooling in the data center. The model captures the particular air flow behavior in the cold aisle when row-based cooling is utilized. Correlations are derived to predict the ability of air cooling units to maintain set points at different air flow rates. The effect of leakage is also considered.
Investigation of Non-Destructive Examination for Mechanical Damage of FRP
Authors: Ono Keisuke , Fujii Yoshimichi , Wada Akihiro
Published: March 2016

Nowadays, fiber reinforced plastic (FRP) has been widely used in many areas such as auto mobile, airplane and marine vessel due to its high specific strength, good corrosion resistance, relatively low cost and so on. However, it still remains unknown that what kind of damage will happen in the internal structure when an automobile, which is made from FRP, has a slight impact with something such as a wall. Then the following road safety of the automobile cannot be guaranteed because certain parts may be exposed to damage in what seems even like a slight impact. In addition, it is well known that initial fracture can bring damage and great effect to the mechanical properties of the FRP material. The novelty of this paper is that the object of this research is micro crack such as transverse crack. While, almost previous report is aimed at delamination. Actually, before the delamination happens, micro crack has already occurred. The mechanical property of FRP is beginning to decrease by delamination. However, when the delamination occurred in the FRP is examined, it is already too late because the delamination can bring great influence to the safety of the FRP products. Therefore, it is important to investigate and detect the presence of micro crack with ultrasonic wave. In this way, some accidents might be avoided. While, because of the variety of the constraints in the fracture mechanism, the damage behavior is very difficult to evaluate and there are rarely researches and data on it. Although damage assessment by visual observation and the durable service life on FRP has become a general tendency in these recent years, the appropriate way of non-destructive examination has not been confirmed yet.

The purpose of this study is to investigate the possibility of non-destructive examination with ultrasonic wave testing for mechanical damage of glass fiber reinforced plastics (GFRP). The possibility of dividing of Lamb wave modes by reducing the thickness of samples was confirmed and the variance of distribution of frequency of S0 mode wave by micro fracture in GFRP.
Convective Electronic Device Cooling Using Microencapsulated Phase Change Material Slurry in Planar Spiral Coil
Authors: Rokni Houman B. , Languri Ehsan M. , Johnson Wayne
Published: March 2016

The current trend in miniaturization of electronic devises requires more effective thermal management techniques to remove the heat to ensure the maximum performance of the devise. Among all available thermal management techniques for electronic cooling, convective heat transfer cooling has gained attentions due to low cost and maturity in the market. The single-phase convective heat removal technique suffers from the low heat carrying capacity since there is no phase change occurs during the process. On the other hand, Microencapsulated phase change materials (MPCMs) are gaining attention due to their high heat carrying capacity. MPCMs are composed of phase change material (PCM) as the core material that is encapsulated with micrometer size shell materials. The PCM inside the capsules may undergo a phase change as the temperature varies around the melting and freezing temperature points of the PCM. This leads to a significant heat gain/release due to the phase change of the PCM.

In this paper, we are performing a numerical modeling on the performance of MPCMs mixed with single-phase base fluid when pumped through planar spiral coils. From electronic thermal management point of view, it is ideal to have an enhanced coolant that maintain the operating temperature under an allowable level uniformly. The behavior of MPCM slurry when pumped through planar spiral coils reveals unique patterns due to the centrifugal forces. The available data on MPCM slurry through spiral coil heat exchangers show the new patterns of velocity and heat transfer curves that require further investigation and scientific explanations. The current paper studies the steady conditions of flows under laminar regimes at different boundary conditions. A CAD model of a planar coil heat exchanger is developed in SolidWorks. The model is meshed and discretized in order to apply the governing equations into the model. ANSYS Fluent package is used to solve the fluid flow and heat transfer equations inside the geometry. The velocity and temperature profiles along the coil are studied and discussed to quantify the roles of different forces in such flows. The ultimate goal of this study to evaluate the efficacy of utilizing such formulated microencapsulated PCM slurry at different mass concentrations on electronic thermal management considering the cost associated to the added pressure drop when using MPCM slurry.
Numerical Simulation of Air Vortex Interaction With Porous Screen
Authors: An Xudong , Hassanipour Fatemeh
Published: March 2016

In this paper, numerical analysis of a two-dimensional vortex ring impinging through porous screen surface is investigated. The vortex ring is generated by a piston-cylinder assembly. The objective is to study the flow behavior of vortex ring when passing through porous screen and especially to obtain the values which are difficult to achieve in experiment method, such as kinetic energy and vorticity. A variety of parameters are set to be control groups, including porosity of porous screen (ϕ = 0.3, 0.6 and 0.8), Reynolds number of vortex ring (Re = 700 – 3000), piston diameter (D = 20mm, 34mm and 50mm) and gap between piston and porous screen (L = 50mm, 100mm and 150mm). The following results are acquired: (1) Porosity plays an important role on the vortex ring structure and flow behavior, (2) Reynolds number have notable influence on the vorticity evolution of vortex ring in the situation of low porosity, (3) Larger piston dimension results in slower progress of vortex ring transmission and sharper reduction of vortex ring kinetic energy, and (4) The gap length has significant effect on kinetic energy of vortex ring only in the situation of low porosity.
Axiomatic Design: 30 Years After
Authors: Nordlund Mats , Lee Taesik , Kim Sang-Gook
Published: March 2016

In 1977, Nam P Suh proposed a different approach to design research. Suh’s approach was different in that it introduced the notions of domains and layers in a 2-D design thinking and stipulated a set of axioms that describes what is a good design. Following Suh’s 2-D reasoning structure in a zigzagging manner and applying these axioms through the design process should enable the designer to arrive at a good design.

In this paper, we present our own experiences in applying Suh’s theories to software design, product design, organizational design, process design, and more in both academic and industrial settings. We also share our experience from teaching the Axiomatic Design theory to students at universities and engineers in industry, and draw conclusions on how best to teach and use this approach, and what results one can expect.

The merits of the design axioms are discussed based on the practical experiences that the authors have had in their application. The process developed around the axioms to derive maximum value (solution neutral environment, design domains, what-how relationship, zig-zag process, decomposition, and design matrices) is also discussed and some updates are proposed.
Wettability Effect on Droplet Growth Behaviors During Dropwise Condensation
Authors: Lee Jae Bin , Lee Seong Hyuk , Choi Chang Kyoung , Lee Jungho
Published: March 2016

The present study examines the transient characteristics of droplet growth and heat transfer during dropwise condensation process on different hydrophobic surfaces. The self-assembled monolayer (SAM) of n-octadecyl mercaptan was coated on the surface to change the surface wettability with the contact angles of 148° and 124°. A Canon EOS 7D camera and an Infinity K2 lens were used to capture the spontaneous images during condensation. From the experiment, three regimes were observed: in the first regime where the droplets were formed with nearly homogenous pattern, the heat transfer coefficient increased rapidly. In the second regime, both the droplet size and the liquid area fraction increased. In the third regime, coalescence among larger droplets was dominant, causing the decrease in the liquid area fraction with time. Moreover, the measured fall-off time was faster in the case with higher contact angle because of relatively low surface energy.
Reliability Analysis and Design Considering Disjointed Active Failure Regions
Authors: Wang Pingfeng , Cui Xiaolong
Published: March 2016

Failure of practical engineering systems could be induced by several correlated failure modes, and consequently reliability analysis are conducted with multiple disjointed failure regions in the system random input space. Problems with disjointed failure regions create a great challenge for existing reliability analysis approaches due to the discontinuity of the system performance function between these regions. This paper presents a new enhanced Monte Carlo simulation (EMCS) approach for reliability analysis and design considering disjointed failure regions. The ordinary Kriging method is adopted to construct surrogate model for the performance function so that Monte Carlo simulation (MCS) can be used to estimate the reliability. A maximum failure potential based sampling scheme is developed to iteratively search failure samples and update the Kriging model. Two case studies are used to demonstrate the efficacy of the proposed methodology.
Shock Tube Design for High Fidelity Blast Wave Simulation
Authors: Ostoich Christopher , Rapo Mark , Powell Brian , Sainz Humberto , Chan Philemon
Published: March 2016

Traumatic brain injury (TBI) has been recognized as the signature wound of the current conflicts and it has been hypothesized that blast overpressure can contribute a significant pathway to TBI. As such, there are many ongoing research efforts to understand the mechanism to blast induced TBI, which all require blast testing using physical and biological surrogates either in the field or in the laboratory. The use of shock tubes to generate blast-like pressure waves in a laboratory can effectively produce the large amounts of data needed for research into blast induced TBI. A combined analytical, computational, and experimental approach was developed to design an advanced shock tube capable of generating high quality out-of-tube blast waves. The selected tube design was fabricated and laboratory tests at various blast wave levels were conducted. Comparisons of tube-generated laboratory data with explosive-generated field data indicated that the shock tube could accurately reproduce blast wave loading on test surrogates. High fidelity blast wave simulation in the laboratory presents an avenue to rapidly and inexpensively generate the large volumes of data necessary to validate and develop theories linking blast exposure to TBI.
Evaluation of the Dynamic Performance for Five-Axis CNC Machine Tools Based on RTCP
Authors: Jiang Zhong , Wang Wei , Li Qingzhao , Zhou Zhipeng , Ding Jiexiong , Deng Meng
Published: March 2016

RTCP (rotation tool center point), which is one of the necessary functions for high-grade CNC machine tools, can effectively decrease nonlinear errors caused by the motion of the rotation axis and improve the accuracy of the machinery. Based on the characteristic that the cutting tool tip point is relative to the manufacturing workpiece, the RTCP trajectory is proposed to conveniently measure the displacement of the tool tip point. The scheme is utilized to study the dynamic performance of machine tools, and a simulation that shows the relationship between the tool tip error trajectory and the factors influencing the dynamic performance of the machine tool is presented based on the servo system model. Then, the experiment is carried out, and the tool tip point error variation is found to be consistent with the simulation result. This study provides theoretical support for dynamic performance detection of five-axis CNC machine tools.
Frictional Torque Transfer Behaviors of Friction Pads in Wet Clutch Engagement
Authors: Jang Siyoul
Published: March 2016

For stable frictional torque transfer, wet clutch pads have the functional requirements of a high traction and a low wear rate with positive μ-V frictional characteristics. However, because of the intrinsic negative μ-V frictional characteristics of a friction material that has a static friction coefficient greater than its kinetic friction coefficient, the frictional torque transfer has unstable vibrations during the clutch-pad engagement.

To reduce the vibration mode during the engagement of wet clutch pads, the kinetic friction coefficient should be made greater than the static friction coefficient through modifications in the design parameters as well as in the characteristics of the friction materials. To obtain positive μ-V frictional characteristics, it is important to manipulate the static-friction coefficient, which largely develops in the boundary lubrication stage during the clutch-pad engagement. The formation of the boundary film is described by slip boundary conditions and hydrodynamic lubrication films. It also includes the elastic deformation of the wet pad material due to the contact pressure. The wet clutch pad material is made of a porous structure through which the lubricant can easily spread when the applied load and sliding speed are imposed. The lubrication and the direct contact of the surfaces are simultaneously considered for a frictional torque transfer that lasts for less than one second, depending on the working conditions.

In this study, some of the computational results with a measured μ-V friction coefficient covering both the static and kinetic friction during the wet-clutch engagement are obtained for the lubrication and the direct-contact pressures.
Free-Field Blast Loading for TBI and Lung Injury Correlation
Authors: Rapo Mark , Ostoich Christopher , Juhas Brett , Powell Brian , Chan Philemon
Published: March 2016

This paper presents a study to provide guidance on the use of body-worn blast overpressure sensors to predict the risk of blast induced closed head trauma and lung injury. Data collected from blast sensor systems, when used in combination with modeling and simulation, can recreate the full loading on the warfighter [1]. Using field blast data from a 4 sensor time-synched blast system, the incident blast wave and direction was reconstructed and used as input to computational fluid dynamic (CFD) simulations of blast impacting an outfitted warfighter. Pressures around the head and underneath the helmet were found to be in agreement with experimental data. The peak resultant head velocity, which is shown to be a correlate of concussion, was also found to correlate with incident impulse over a wide range of blast conditions. Lung injury was assessed for every blast condition, revealing that some blast directions and intensities more readily engage multiple modes of injury. With the accurate reconstruction of the true blast loading to a warfighter, damage correlates obtained from biomechanical modeling analysis can be calculated for correlation with medical outcomes.
Dynamic Behavior of Acrylonitrile Butadiene Styrene Under Impact Loads
Authors: Peterson Alex , Bolling Denzell , Olasumboye Adewale , Habtour Ed , Riddick Jaret C. , Coatney Michael , Owolabi Gbadebo
Published: March 2016

This paper is aimed at providing a better understanding of the potential energy absorption benefits of components fabricated using fused deposition modeling (FDM) additive manufacturing. Using FDM, it is possible to print three-dimensional (3-D) objects created through the use of computer-aided design and computer-aided manufacturing software coupled with computer codes that enable the layer-by-layer deposition of material to form the 3-D component. Also known as direct digital manufacturing or 3-D printing, AM offers the benefit of being able to rotate printing orientation during processing to manipulate the design build and ultimately control mechanical and structural properties when subjected to dynamic loads. In this work, tensile test specimens were first fabricated to characterize the general mechanical behavior of the of 3D-printed Acrylonitrile Butadiene Styrene (ABS) material to assess its potential strain rate dependency. The mechanical evaluation under the quasi-static load was also necessary to determine the properties necessary to characterize the dynamic evolution of ABS in compression at various strain rates. ABS specimens were subsequently subjected to high strain rate deformation through the use of the Split Hopkinson Pressure Bar. During compression a new phenomenon described as a multistage collapse in which the samples undergo multiple stages of contraction and expansion was observed as the impact load was applied.
Theoretical Analysis of Pyroelectric Harvesting of Low-Grade Exhaust Waste Heat
Authors: Ju Y. Sungtaek
Published: March 2016

Efficient and cost-effective harvesting of exhaust waste heat represents significant opportunities for improving the overall energy efficiency of combined heat and power cycles, transportation vehicles, and industrial processes. Pyroelectric thermal energy harvesting is interesting for its potentially high efficiency. We report a design concept and related thermal models for harvesting of exhaust waste heat based on the pyroelectric effect. The design concept utilizes switchable thermal interfaces formed on duct walls of exhaust gas and liquid coolants to achieve temporal thermal cycling of pyroelectric materials. Our thermal model explicitly accounts for spatial variations in the exhaust gas and coolant temperatures for practical waste heat harvesting systems, for example, those that can be incorporated into micro-CHP (combined heat and power) units. Model prediction results for example cases are presented to illustrate the impact of design parameters, including the heat capacity rate and the convective heat transfer coefficients.