bluuebunny/crossref_metadata_2025 huggingface dataset:
Design of a Multifunctional Porous Coaxial Electrospun Mesh Using Polycaprolactone (PCL) and Poly Butylene Adipate-CO-Terephthalate (PBAT)
Authors: Rizvi Hussain R. , D'Souza Nandika
Published: February 2017

In this paper, we formulate a method to create a potential drug delivery vehicle and scaffold architecture of coaxial electrospun fibers. Having the capability to introduce porosity either in core or sheath of the fiber using supercritical CO2 as a foaming agent is utilized. Polycaprolactone (PCL) and Poly butylene adipate-co-terephthalate (PBAT) were used because of their biodegradable and biocompatible nature. Physical morphology of the porous coaxial fibers was studied using Scanning Electron Microscopy (SEM), Image J software was used to quantify the pore size and fiber diameter. Dynamic Mechanical Analysis (DMA) and Tensile Testing of the three-dimensional fibrous mesh was done to determine the mechanical properties of the porous structure. Differential Scanning Calorimeter (DSC) was used to study the thermal characteristics of the mesh.
Haptic and Visual Feedback Technology for Upper-Limb Disability Assessment
Authors: Pernalete Norali , Raheja Amar , Carey Stephanie
Published: February 2017

In this paper, we discuss the possibility to determine assessment metrics for eye-hand coordination and upper-limb disability therapy, using a mapping between a robotic haptic device to a virtual environment and a training algorithm based on Complex Valued Neural Networks that will calculate how close a set movement pattern is in relationship with that traced by a healthy individual.

Most of the current robotic systems’ therapy relies on the patient’s performance on standardized clinical tests such as the functional independence measure (FIM), and the upper limb subsection of the Fugl-Meyer (FM) scales. These systems don’t have other standardized metrics for assessment purposes. There is a need to establish a more intelligent and tailored therapy that could be implemented for patients to use at home in between therapy sessions, or in the long term. This therapy should be based on performance data gathered by the robotic/computer system that will provide an assessment procedure with improved objectivity and precision.

A set of complex and movement demanding virtual environments, representing various levels of difficulty labyrinths was developed in a virtual environment. The participants were instructed to use a haptic device (Omni) to follow the trajectories. This was completed while video data were collected using a Vicon motion capture system. Readings of traced trajectories, time, and upper limb motions are recorded for further analysis.
Scale Effect in FEM Simulation of Axisymmetric Hot Micro-Extrusion of Aluminum Alloys
Authors: Costa André L. M. , Valberg Henry S. , Misiolek Wojciech Z.
Published: February 2017

Hot micro-extrusion is a good candidate for manufacturing metallic micro-components with complex shapes and good mechanical properties. This work investigates the metal flow in direct hot mini- and micro-extrusion of aluminum rods by means of FEM simulations. The presented study was performed with the numerical code DEFORM 2D in axisymmetric mode using experimental material flow curves for AA 7108 alloy. The mini-to-micro dimensional scale factor was 10:1, the extrusion ratios were 16 and 100, and the ram speed ranged from 0.5 to 20 mm/s. The initial temperature of the billet and tooling was 400°C. It was found that the temperature distribution within the profile changed from mini-to micro-extrusion and the effect was more significant for higher reductions and higher extrusion velocities. The micro-scale effect increased the stress field just behind the die orifice and the material deformed more intensely to achieve the equilibrium velocity. It was shown that the scale effect can be evaluated by the relative strain rates associated with the corresponding deformation. Numerical results indicate that the scale effect does increase exponentially with the velocity and it becomes significant for final exit velocities of the extrudate above the level of 100 mm/s.
Numerical Simulation of Jamming Transition in Granular System Under Cyclic Compression Using Smooth Particle Hydrodynamics
Authors: Tayeb Raihan , Mao Yijin , Zhang Yuwen
Published: February 2017

The jamming of granular materials, which indicates how disordered particle systems change from mechanically unstable to stable states, has attracted significant recent interest due, but not limited, to the appearance of jamming transition or similar behavior in a broad variety of systems. Recent experiments on jamming transition have revealed the relationship between mean coordination number and packing fraction for different jammed states. In this paper the jamming states of two dimensional granular materials under cyclic compression using Smooth Particle Hydrodynamics (SPH) approach is numerically investigated. The SPH method allows one to study the stress developed within individual granular particles of arbitrary shape. In this study the granular system is cyclically and isotropically compressed or expanded. The system undergoes a range of jamming states over a large number of cycles. We measure the evolution of global pressure, mean coordination number, and packing fraction. The force chains and probability density function of force for different compression cycles are also investigated.
Tailoring Cellular Auxetics for Wearable Applications With Multimaterial 3D Printing
Authors: Saxena Krishna Kumar , Calius Emilio P. , Das Raj
Published: February 2017

The properties of cellular materials depend as much on their architecture as on their composition. Auxetic materials are a novel class of mechanical metamaterials which exhibit an interesting property of negative Poisson’s ratio by virtue of their architecture rather than composition. One of their most interesting aspects is their improved indentation resistance, impact resistance and fracture toughness. Thus, they have potential applications in wearable impact protection. The classical re-entrant structure has been a focus of research for many years because of its well established auxetic behaviour. However, the stiff re-entrant corners, buckling of struts, less strain sensitivity and limited cellular stiffness limit its applications in wearable impact protection devices. In this work, multi-material cellular designs are proposed which have the capability to fulfill the requirements for wearable impact protection devices. With the advancements in 3D printing, multi-material cellular designs can be realized in practice. Using Finite Elements approach, two-material and multi-material cellular designs are investigated. It was observed that introduction of material gradient/distribution in the cell provides a means to tailor auxetic behaviour, cellular stiffness and strain-sensitivity as per the specific requirement. The results will lead to a better understanding of tailoring auxeticity in cellular materials and will aid in the design of auxetic wearable impact protection devices which rely on auxeticity gradients and variable auxeticity as well.
Variation of the Strength of Grains and Grain Boundaries Caused by the Fluctuation of Their Crystallinity
Authors: Nakanishi Takahiro , Suzuki Ken , Miura Hideo
Published: February 2017

The variation of the strength of a grain and a grain boundary was measured by a micro tensile test system fabricated in an electron microscope. A micro-scale beam structure was fabricated from a single-crystalline silicon wafer and a fine nano-scale sample cut from a thin film using a focused ion beam was attached to the center of the beam by deposition of tungsten in the microscope. The other end was attached to a micro probe similarly. Finally, the micro probe was activated to pull the sample and the deformation of the sample was observed by a scanning electron microscope. The fracture strength of a bicrystal sample was measured by detecting the deflection of the beam at the breakage of the sample. The crystallinity of both a grain and a grain boundary was quantitatively evaluated by using electron back-scatter diffraction analysis from the viewpoint of the change of the order of atom arrangement in them. It was found that the strength of a grain and a grain boundary varied clearly depending on their crystallinity. In addition, there was a critical value of the crystallinity at which the fracture mode of a polycrystalline material changed from intergranular fracture to transgranular fracture.
Theoretical and Experimental Study on Large Amplitude Vibrations of Clamped Viscoelastic Plates
Authors: Balasubramanian Prabakaran , Ferrari Giovanni , Guzman N. del Prado Zenon J. , Amabili Marco
Published: February 2017

In this paper, the large amplitude vibrations of clamped-clamped thin viscoelastic rectangular plates due to a concentrated transversal harmonic load are investigated both theoretically and experimentally. Clamped boundary condition on all edges and von Kármán nonlinear strain-displacement relationships are considered while rotary inertia, geometric imperfections, and shear deformation are neglected. In the theoretical study, the viscoelastic behaviour of the material is modelled using the Kelvin-Voigt model. In-plane loads applied during the assembly of the plate are taken into account and clamped boundary conditions are modelled using artificial rotational springs. The nonlinear ordinary differential equations for the considered Kelvin-Voigt model are obtained using the generalized energy approach. These equations contain quadratic and cubic nonlinear viscoelasticity terms in addition to quadratic and cubic stiffness terms. Non-dimensionalization of variables is carried out and each second order equation is converted into two first order equations. The resulting system of equations is solved using AUTO (software based on the arclength continuation method that allows bifurcation analysis), to get the frequency-response curves at various force levels. Moreover numerical time integration of equations was also performed using the fourth-order Runge-Kutta method to understand the time response of the structure. In the experimental study, two rubber plates with different material and thicknesses were considered; a silicone plate with 0.0015 m thickness and a neoprene plate with 0.003 m thickness. The plates were fixed on a heavy rectangular metal frame thereby ensuring the clamped boundary condition on all edges. Linear experimental modal analysis was carried out as a first step to estimate the mode shapes and natural frequencies. In the second step, the nonlinear vibration response of the plate around its first resonance was measured at various harmonic force levels. At each force level, the amplitude of the harmonic excitation was kept constant by LMS Data Acquisition System and Test.Lab Stepped Sine software module while slowly varying the frequency of excitation to get the frequency-response curves. Laser Doppler Vibrometry was used to measure the response from the plate as it eliminates the possible mass loading effect introduced by any contact type sensors. A maximum amplitude of more than three times the thickness of the plate was achieved. The nonlinear response curves showed a typical hardening type nonlinearity along with sudden jumps as expected for plates. Experimental frequency-response curves were compared with theoretical results and a good agreement was found. The influence of nonlinear viscoelastic damping terms was clearly noticed on the response curves of the plate. The retardation time, measured in seconds decreases with increasing excitation force and larger amplitude vibrations.
Numerical Study of a Hybrid Thermal Insulation With Phase Change Material for Subsea Pipelines
Authors: Parsazadeh Mohammad , Duan Xili
Published: February 2017

Flow assurance is critical in offshore oil and gas production. Thermal insulation is an effective way to reduce heat loss from subsea pipelines and avoid the formation of hydrates or wax deposits that could block the flowlines. This paper presents a hybrid thermal insulation model with a combination of phase change material (PCM) and conventional insulating layers. The idea is to use PCM to store thermal energy with normal oil and gas production and release heat back to the fluids during a shut-in operation. Melting and solidification of the PCM layer is analyzed for different thicknesses at both working and shut-in conditions. The model is developed numerically using a Finite Volume Method (FVM) and an enthalpy porosity technique. It accounts for heat conduction with liquid-solid phase changes, as well as natural convection in the PCM. In this study, paraffin is implemented as PCM with temperature dependent properties while Aerogel is used as the conventional insulation layer. The results show that ticker PCM layer than conventional insulating layer can significantly improve thermal insulation performance, with extended cool-down time during flow line shut in.
Modeling of the Gas-Controlled Crack Growth: Non-Ideal vs Ideal Sink
Authors: Balueva Alla V. , Dashevskiy Ilia N.
Published: February 2017

We consider delamination crack growth controlled by gas diffusion into crack. Initially, with small pressure, the crack can be considered as an ideal sink. However, as crack grows, the pressure becomes greater, and therefore the crack cannot be considered an ideal sink anymore. In this research for both ideal- and real-sink conditions, closed-form solutions for the dependence of the radius of the growing delamination on time are obtained.
Analytical Model for the Deformation of Viscoelastic Non-Newtonian Drops Undergoing Secondary Atomization
Authors: Snyder Sharon E. , Kulkarni Varun , Sojka Paul E.
Published: February 2017

While there is no single analytical model that accurately predicts all stages and modes of secondary atomization, many groups have developed models that predict deformation and oscillation of a single, isolated drop. The TAB (Taylor Analogy Breakup) model was chosen for this investigation, mainly due to its widespread use by Liu and Reitz [1], Hwang et al. [2], Tanner [3], and Lee and Reitz [4], among others. Since the TAB model is also the foundation for many other analytical models, it will also be used here as a starting point for the development of a viscoelastic non-Newtonian model to predict droplet deformed radii, droplet deformation time, and velocity at deformation time for viscoelastic xanthan gum - DI water solutions.

Three additional improvements are made to this viscoelastic TAB model: the first is a change to a TAB coefficient; the second to the equation for the drag coefficient, and the third modification is to the breakup criterion. This model uses Carreau rheology and Zimm relaxation time. Non-dimensional drop diameter and initiation times are plotted against We; model results are compared to experimental results for a range of xanthan gum solution concentrations. Results show fair agreement between experimental results and model results for non-dimensional drop diameter, with the best match at low XG concentration and low-to-medium We (10–30). It was also noted that increased viscoelasticity seems to increase this drop diameter. Good agreement between experimental data and model results has been seen for initiation time, with increased viscoelasticity increasing this parameter as well.
Evaluation of Auxetic Polymeric Structures for Use in Protective Pads
Authors: Yang Chulho , Vora Hitesh D. , Chang Young Bae
Published: February 2017

Auxetic materials, known as materials with negative Poisson’s ratio (NPR), have many promising application areas. However, there are only few natural and man-made materials such as certain living bone tissues, certain rocks and minerals, polymeric honeycombs, microporous polytetrafluoroethylene (PTFE), foams, and carbon-fiber-reinforced epoxy composite laminate panels that possess this property.

In recent years, various auxetic material structures have been designed and fabricated for diverse applications that utilized normal materials which follow Hooke’s law but still show the NPR properties. One of the applications is body protection pads that are comfortable to wear and effective in protecting body parts by reducing impact force and preventing injuries in high-risk individuals such as elderly people, industry workers, law enforcement and military personnel, and sports players. It is important to develop new body protectors that best combine each individual’s requirements for wearing comfort (flexible, light-weight), ease of fitting (customized), ensured protection, and cost-effectiveness. The protection pad would be made from multilayer materials and adaptive structures to achieve unique multifunctional properties such as high hardness, impact toughness, light weight, and excellent shock absorption suitable for the needs.

This paper reports an integrated theoretical, computational (finite element analysis), and experimental investigation conducted for typical auxetic polymeric materials that exhibit negative Poisson’s ratio (NPR) effect. Parametric 3D CAD models of auxetic polymeric structures such as re-entrant hexagonal cells and arrowhead were developed. Then, key structural characteristics of protectors were evaluated through static analyses of FEA models. In addition, impact/shock analyses were conducted through dynamic analyses of FEA models to validate the results obtained from the static analyses. Particularly, an advanced additive manufacturing (3D printing) technique was used to build prototypes of the auxetic polymeric structures. Specifically, three different materials typically used for FDM (Fused Deposition Modeling) technology such as Polylactic acid (PLA) and thermoplastic polyurethane (TPU) material (NinjaFlex® and SemiFlex®) were used for different stiffness and shock-absorption performances. The 3D printed prototypes were then tested and the results were compared with the computational prediction. The results showed that the auxetic material can be effective for body protection pads. Each structure and material had unique structural properties such as stiffness, Poisson’s ratio, and efficiency in shock absorption. Particularly, auxtetic structures showed better shock absorption performance than non-auxetic ones. The mechanism for ideal input force distribution or shunting could be suggested for designing protectors using various shapes, thicknesses, and materials of auxetic materials to reduce the risk of injury.
Microscopic Analysis of the Initiation of High-Temperature Damage of Ni-Based Heat-Resistant Alloy
Authors: Murakoshi Takuya , Suzuki Ken , Nonaka Isamu , Miura Hideo
Published: February 2017

It is imperative to reduce greenhouse-effect gas such as CO2. Since the emission of CO2 from fossil fuel combustion to generate electricity is a critical quantity, accounting for 42% of global CO2 emissions in 2013 [1], high efficiency of thermal power plants is indispensable for reducing the CO2 emissions. In order to further improve thermal efficiency of thermal power plants, various R&D projects have been conducted (such as Thermie 700 in the EU and DOE-Vision 21 in the US) to develop A-USC (advanced ultra-supercritical) power plants of the 700°C-class.

Alloy 617 is a candidate alloy for boiler tubes and pipes. Since it has higher coefficient of thermal expansion than conventional ferritic steels, however, the increase in the thermal stress is of concern in the power plant components. In addition, it is important to consider the effect of creep-fatigue loading on the lifetime of the components in the design and maintenance of the components. This is because frequent output change is inevitable for assuring the stable and reliable supply of electricity under the combination with renewable energies.

Conventionally, the creep-fatigue damage has been evaluated by linear cumulative damage rule. However, it has been found that there are a lot of loading conditions and materials to which the rule can’t be applied [2–3]. Therefore, it is indispensable to establish the method for evaluating the total damage of materials under creep-fatigue loading conditions. Thus, the authors conducted fatigue and creep-fatigue tests and observed the change of the micro texture to elucidate the damage evolution of the alloy from the viewpoint of the change of the order of atom arrangement using EBSD (Electron Back-Scatter Diffraction) analysis. As a result, it was found that the difference of damage accumulation under fatigue and creep-fatigue loadings appeared in the change of the GROD (Grain Reference Orientation Deviation) value in the inelastic strain range. Therefore, the difference in the damage mode between fatigue and creep loads can be analyzed by using these KAM and GROD values.
Modelling and Simulation of a Solar Single Effect Absorption Cooling System in Aspen Hysys®
Authors: Ramos Erni S. , Valencia Guillermo E. , Jiménez Adriana M. , Osorio Marisol , Vanegas Marley C.
Published: February 2017

As an alternative to conventional vapor compression cooling systems, a thermodynamic analysis with the integration of Aspen Hysys® and MatLab® to a solar driven single effect LiBr - Water absorption cooling is conducted in this paper under meteorological conditions for Barranquilla in Colombia supplied with a solar captive system integrated by 15 flat plat solar collectors Barilla F22AR. First law and second law of thermodynamic are applied to system in order to calculate the thermodynamic states and exergy of each stream of the system, in addition to the Coefficient of performance and second law exergy efficiency of the chiller, and exergy loss rate for every component and the whole system. The influence of monthly variation of total solar irradiance on COP, exergy efficiency and exergy loss rate is evaluated in this study under steady state condition for each month of the year. The results of this study show a proportional relationship between heat loads calculated in each component and the heat flow supplied by the solar captive system to the generator, moreover the total solar radiation is directly related to the COP and inversely proportional exergy efficiency.
Highly-Sensitive Graphene Nano-Ribbon-Base Strain Sensor
Authors: Sasaki Shinichirou , Yang Meng , Suzuki Ken , Miura Hideo
Published: February 2017

Large-area and high-quality monolayer graphene was synthesized in order to fabricate a graphene-base highly sensitive strain sensor. A rapid LPCVD (Low Pressure Chemical vaper deposition) synthesis process of monolayer graphene was developed by using acetylene as a resource gas. To synthesize high-quality single-crystal graphene, the surface of copper substrate was strongly orientated to (111) crystallographic plane. By optimizing the concentration of acetylene gas by diluting hydrogen, the high quality of monolayer single-crystalline graphene film was successfully grown on the copper substrate. A strain sensor was fabricated using the graphene-coated Cu foils by applying the MEMS process and reactive ion etching (RIE). Then, the sensor was transferred onto a polydimethysiloxane (PDMS) substrate. Tree-dimensional bending test was performed to investigate the piezoresistive property of the patterned graphene nano-ribbon. It was confirmed that the highly sensitive strain sensor was obtained when the width of the nano-ribbon was thinner than 70 nm.
Carbon Nanofiber and PDMS Based Nanocomposite With Sensing Functions
Authors: Chowdhury Shoieb , Olima Mark , Liu Yingtao , Saha Mrinal
Published: February 2017

In this paper a nanocomposite system is proposed to accurately measure pressure generated by normal force. The strain sensing function is achieved by correlating the piezoresistance variations to the normal force applied on the sensing area. Due to the conductive network formed by carbon nanofibers (CNFs) and the tunneling resistance change between neighboring CNFs the electrical resistance measured using the four-probe method shows a clear correlation with the load conditions. In order to improve the piezoresistivity, CNF are uniformly dispersed in PDMS using a solvent assisted ultra-sonication method. The proposed nanocomposite based strain sensor is experimentally characterized under both quasi-static and cyclic load conditions.
Effects of the Installation of Driven Motor at the Impeller Eye on Performance of Volute-Free Centrifugal Fan
Authors: Cui Haoyu , Xiong Jin , Chen Congcong , Li Jingyin
Published: February 2017

Volute-free centrifugal fans can find wide applications in ventilation systems. To make the volute-free centrifugal fan more compact in size, such as in the locomotive cooling system, the driven motor is often installed at the impeller eye. The installation of the motor blocks the flow passage to the impeller severely and may affect the fan’s aerodynamic performance evidently. However, such a blockage effect is often ignored in the design of the common centrifugal impeller. In this paper, numerical simulations are carried out to study the effect of the existence of the motor at the impeller eye. The results show that the choking effect of the motor has an obvious influence on the fan’s performance and must be taken into account in designing the impeller. The effects of the axial installation position and the supporting configuration of the motor on the characteristics of the fan are numerically investigated in detail. It is found that a shorter axial gap between the motor and the hub or the back plate of the impeller gives a better aerodynamic performance of the fan. In contrast, the cooling gap between the motor’s supporting barrel and the motor, and the struts for the barrel have little influence on the volute-free centrifugal fan’s aerodynamic performance. The results of numerical simulation agree well with the test results, which verified the rationality of considering the blockage effect of the pre-posed motor.
Analysis of Energy Loss Mechanism at the Speed Ratio of Design Operating Condition in Hydrodynamic Torque Converters
Authors: Yan Qingdong , Huang Mingxing , Wei Wei
Published: February 2017

Low transmission efficiency of hydrodynamic torque converters limits their wider application, so it is necessary to observe the microstructures of internal flow in depth and to analyze the mechanism of energy loss for reducing the energy loss in flow field. Computational Fluid Dynamics (CFD) is a common way to model and simulate the flow field and Proper Orthogonal Decomposition (POD) is also a good method to do some simplified calculation. Combined CFD and POD, internal flow field in a hydrodynamic torque converter was analyzed to study the relationships among energy percentage of the first mode, vortex structure and the mechanism of energy loss on design operating condition (speed ratio of 0.7). Compared with the energy percentage amount of the first mode, the phenomenon was found that the vortex structure of the internal flow field became clearer with larger percentage amount. Therefore, the existence of regular vortex structure is the major reason for energy loss inside hydrodynamic torque converters. The position of vortex core went hand in hand with internal structures not only with the existence of low pressure area, but also the different locations with various features, which should be adopted to improve the performance in hydrodynamic torque converters.
Crystallinity-Induced Degradation of the Lifetime of Advanced Interconnections
Authors: Kato Takeru , Suzuki Ken , Miura Hideo
Published: February 2017

The electromigration (EM) resistance of interconnections manufactured by electroplating was investigated from the viewpoint of temperature and diffusion paths in the polycrystalline materials. The crystallinity of the interconnections was evaluated by image quality (IQ) value obtained from electron back-scatter diffraction analysis. The degradation process under the EM test was observed by using the IQ value. The degradation of the interconnections was dominated by the diffusion of component atoms along random grain boundaries with low crystallinity. It was also found that the electrical resistance of the interconnections varied drastically depending on the crystallinity of the material, and thus, the maximum temperature in the interconnections caused by Joule heating during the EM loading also varied drastically because of the change of the resistance. Since the diffusion constant of the component atoms is accelerated by not only the current density but also temperature, the lifetime of the interconnections under the EM loading is a strong function of the crystallinity of the interconnections. It is necessary, therefore, to evaluate and control the crystallinity of the interconnections quantitatively using IQ value to assure their long-term reliability.
Electrolyte-Free Nano-Electronic Sensor for the Rapid Quantification of DNA
Authors: Saadat-Moghaddam Darius , Kim Jong-Hoon
Published: February 2017

Electric detection using a nanocomponent could lead to platforms for rapid and simple biosensing. Sensors composed of nanostructures have been described for applications requiring high sensitivity on account of their confined geometries. However, both fabrication and use of nanostructured sensors remain challenging. Here, we present a nano-electronic sensor, used as an amperometric biosensor, for the highly sensitive quantification of DNA. The proposed nano-electronic sensor is fabricated by a two-step process; 1) fabricate microscale-cantilever structure using ultraviolet (UV) lithography and anisotropic etching for reliable electrical measurement, and 2) immobilize single-walled carbon nanotubes (SWNCTs) onto the structure for generation of a high electric field. The electrical characteristics of nano-electronic sensor upon binding DNA are studied by I-V measurement in deionized (DI) water. When the DNA is dielectrophoretically captured onto the sensor, the electric current through DI water decreases. The sensitivity test shows that the signal is discernable from the noise level down to 100 attomolar (aM). Measurement results are consistent with fluorescence microscopy. Unlike other optical-based quantification methods, a nano-electronic sensor is capable of rapidly concentrating and detecting small amounts of DNA.
Energy Simulations of Data Centers With Hybrid Liquid/Air Cooling and Waste Heat Re-Use
Authors: Mok Seungho , Joshi Yogendra K. , Kumar Satish , Hutchins Ronald R.
Published: February 2017

This study focuses on developing computational models for hybrid or liquid cooled data centers that may reutilize waste heat. A data center with 17 fully populated racks with IBM LS20 blade servers, which consumes 408 kW at the maximum load, is considered. The hybrid cooling system uses a liquid to remove the heat produced by high power components, while the remaining low power components are cooled by air. The paper presents three hybrid cooling scenarios. For the first two cases, air is cooled by direct expansion (DX) cooling system with air-side economizer. Unlike the cooling air, two different approaches for cooling water are investigated: air-cooled chiller and ground water through liquid-to-liquid heat exchanger. Waste heat re-use for pre-heating building water in co-located facilities is also investigated for the second scenario. In addition to the hybrid cooling models, a fully liquid cooling system is modeled as the third scenario for comparison with hybrid cooling systems. By linking the computational models, power usage effectiveness (PUE) for all scenarios can be calculated for selected geographical locations and data center parameters. The paper also presents detailed analyses of the cooling components considered and comparisons of the PUE results.
Transient Analysis of Non-Uniform Heat Input Propagation Through a Heat Sink Base
Authors: Sudhakar Srivathsan , Weibel Justin A.
Published: February 2017

For thermal management architectures wherein the heat sink is embedded close to a dynamic heat source, non-uniformities may propagate through the heat sink base to the coolant. Available transient models predict the effective heat spreading resistance to calculate chip temperature rise, or simplify to a representative axisymmetric geometry. The coolant-side temperature response is seldom considered, despite the potential influence on flow distribution and stability in two-phase microchannel heat sinks. This study uses multi-dimensional transient and steady-periodic models to predict spatial and temporal variations of temperature within the heat sink base. The response to arbitrary transient heat inputs is obtained using Duhamel’s method. For time-periodic heat inputs, the steady-periodic solution is calculated using the method of complex temperature. Solution of the coolant-side temperature response in the presence of multiple different transient heat inputs is demonstrated. The degree of spatial and temporal non-uniformity in the coolant-side temperature profiles are mapped as a function of nondimensional geometric parameters and boundary conditions. Several case studies are presented to demonstrate the utility of such maps.
Detecting Malicious Defects in 3D Printing Process Using Machine Learning and Image Classification
Authors: Wu Mingtao , Phoha Vir V. , Moon Young B. , Belman Amith K.
Published: February 2017

3D printing, or additive manufacturing, is a key technology for future manufacturing systems. However, 3D printing systems have unique vulnerabilities presented by the ability to affect the infill without affecting the exterior.

In order to detect malicious infill defects in 3D printing process, this paper proposes the following: 1) investigate malicious defects in the 3D printing process, 2) extract features based on simulated 3D printing process images, and 3) an experiment of image classification with one group of non-defect infill image and the other group of defect infill training image from 3D printing process. The images are captured layer by layer from the top view of software simulation preview.

The data extracted from images is input to two machine learning algorithms, Naive Bayes Classifier and J48 Decision Trees. The result shows Naive Bayes Classifier has an accuracy of 85.26% and J48 Decision Trees has an accuracy of 95.51% for classification.
Void Nucleation and Growth at Grain Boundaries in Copper Bicrystals With Surface Perturbations
Authors: Fortin Elizabeth V. , Opie Saul , Brown Andrew D. , Lynch Jenna M. , Loomis Eric , Peralta Pedro D.
Published: February 2017

Material failure on the microstructural level is important in determining macroscale behavior. When a material is subjected to dynamic (shock) loading conditions, damage and deformation patterns due to spall failure can provide a basis for connecting micro- to macroscale behavior. By analyzing deformation patterns at and around interfaces and boundaries that are representative of those found in engineering materials at high strain rates, we can develop stronger structures that can withstand impact collisions and rapid crack propagation. The addition of surface perturbations to one side of the samples provides insight on how strain localization occurs during the shock loading process and how the rippled release wave interacts with the boundary. Copper bicrystal samples were grown from two single crystal seeds using the vertical Bridgeman technique. A photolithography process was developed to create periodic surface perturbations on one side of the samples. The square wave ripples had a 150 μm wavelength and 5 μm amplitude. The bicrystals were shocked using laser ablation on the perturbation side at the Trident laser at Los Alamos National Laboratory and monitored using a VISAR (velocity interferometer systems for any reflector) and TIDI (transient imaging displacement interferometry) system. Shock pressures used were around 8–10 GPa. Targets measured 5 mm in diameter and 100 microns thick. The orientations of the grains were [001] and [111] along the shock direction with a 50° misorientation angle for the boundary, which was aligned parallel to the shock direction. Samples were soft recovered and cross-sectioned to perform quantitative characterization of damage using electron backscattering diffraction (EBSD) and Scanning Electron Microscopy (SEM) to gather information on the characteristics of the grain boundary and its surroundings, with emphasis on how the rippled surfaces and material anisotropy affected strain localization and spallation, initial results show that damage indeed localized at the grain boundary and that surface perturbations led to heterogeneity of spall damage distribution in the grain bulks.
Influences of Target Surface Cylindrical Roughness on Impingement Jet Array Heat Transfer: Effects of Roughness Height, Roughness Shape, and Reynolds Number
Authors: Ren Z. , Buzzard W. , Ligrani P. M.
Published: February 2017

The present investigation considers the effects of special roughness patterns on impingement target surfaces to improve the effectiveness and surface heat transfer augmentation levels of impingement jet array cooling. This investigation utilizes various sizes, distributions, shapes, and patterns of surface roughness elements for impingement cooling augmentation. In total, fifteen different test surfaces are considered, either with cylinder small roughness, triangle small roughness, or rectangle small roughness element shapes. Six of these test surfaces also employ large roughness elements with rectangular shapes (along with either triangle or rectangle small roughness elements). Tests are performed at impingement jet Reynolds numbers of 900 and 11000. Nusselt number variations for the small cylinder roughness show different trends with streamwise development and changing roughness height, compared to target plates with small rectangle roughness and small triangle roughness. In general, this is because roughness elements which contain surface shapes with sharp edges generate increased magnitudes of vorticity with length scales of the order of the roughness element diameter. Such generation is not always present in an abundant fashion with the small cylinder roughness because of the smooth contours around each roughness element periphery. Such effects are illustrated by several data sets, including Nusselt numbers associated with the small cylinder roughness with a height of 0.250D at a turbulent Reynolds number of 11000.
Novel Evaporator Geometries Based on Entrance-Length Flow-Paths for Geothermal Binary Power Plants
Authors: Sabau Adrian S. , Nejad Ali H. , Klett James W. , Bejan Adrian , Ekici Kivanc
Published: February 2017

In this paper, a novel geometry is proposed for evaporators that are used in Organic Rankine Cycles. The proposed geometry consists of employing successive plenums at several length-scale levels, creating a multi-scale heat exchanger. The channels at the lowest length-scale levels were considered to have their length given by the thermal entrance-length. Numerical simulations based on turbulent flow correlations for supercritical R134a and water were used to obtain performance indicators for new heat exchangers and baseline heat exchangers. The relationship between the size of the channels at one level, k, with respect to the size of the channels at the next level, k + 1, is based on generalization of the “Murray’s law.” In order to account for the variation of the temperature and heat transfer coefficient in the entrance region, a heat transfer model was developed. The variation of the brine and refrigerant temperatures along each pipe was considered. Using the data on pumping power and weight of metal structures, including that of all the plenums and piping, the total present cost was evaluated using a cost model for shell-and-tube heat exchangers. In addition to the total present cost, the data on overall thermal resistance is also used in identifying optimal heat exchanger configurations. The main design variables include: tube arrangement, number of channels fed from plenum, and number of rows in the tube bank seen by the outside fluid. In order to assess the potential improvement of the new evaporator designs, baseline evaporators were designed. The baseline evaporator designs include long tubes of the same diameter as those of the lowest length-scale levels, placed between one inlet and one outlet. The baseline evaporator designs were created from the new evaporator designs by simply removing most of the internal plenums employing tubes much longer than their entrance length, as they would currently be used. Consistent with geothermal applications, the performance of new heat exchanger designs was compared to that of baseline heat exchanger designs at the same flow rates. For some operating conditions it was found that the new heat exchangers outperform their corresponding baseline heat exchangers.
Temporal Variation Characteristics of Analysis Accuracy in Two-Dimensional Ultrasonic-Measurement-Integrated Blood Flow Analysis
Authors: Kadowaki Hiroko
Published: February 2017

A two-dimensional ultrasonic-measurement-integrated (2D-UMI) blood flow analysis system was developed for easy acquisition of an intravascular hemodynamics, which feeds back Doppler velocity obtained by an ultrasonic measurement to a numerical blood flow simulation for clinical application. In previous study, ultrasonic measurement and 2D-UMI simulation were performed to clarify the analysis accuracy for real flow field. Additionally, spatial variation characteristics of analysis accuracy was clarified by comparison of velocity vectors between 2D-UMI and 3D-CFD analysis results corresponding to an experimental flow. However, temporal variation of analysis accuracy of 2D-UMI analysis result has not been examined in spite of essential information for reduction of experimental measurement error due to speckle noise.

The aim of this study was to clarify temporal variation characteristics of analysis accuracy of each velocity component obtained in 2D-UMI blood flow analysis. Comparisons of Doppler velocity V and (u, v) velocity profiles between measurement data, 2D-UMI, and 3D-CFD analysis results were performed, and their time variations were discussed. As a result, it was clarified that temporal variation of Doppler velocity error for measurement data became larger with increasing feedback gain. Temporal variations of u and v velocity component errors for 3D-CFD analysis result showed the same tendency as that of Doppler velocity in feedback gain.
Vibration Assisted Hot-Wire Gas-Tungsten Arc Welding of Duplex Stainless Steel 2205
Authors: Silwal Bishal , Santangelo Michael
Published: February 2017

Duplex stainless steel are excellent corrosion resistance two-phase alloy as compared to stainless steel. The corrosion resistance of duplex stainless steel depends upon the balance phase of ferrite and austenite. During non-equilibrium processes such as welding, the fast cooling rate (as compared to the controlled environment where it is produced) suppresses the austenite to ferrite transformation. A low frequency vibration assisted hot-wire Gas-Tungsten Arc Welding (GTAW) has been used to weld commercial duplex stainless steel alloy 2205. The results are compared with cold-wire GTAW weldments. The micro-hardness and microstructure of the weldments and heat-affected zones are characterized. A pitting corrosion test was performed on the weldments to measure the weight loss. A lower weight loss was achieved by using the low frequency vibration assisted hot-wire GTAW, however small pit was observed on the weld cap.
A Base Study to Investigate MASH Conservativeness of Occupant Risk Evaluation
Authors: Silvestri Dobrovolny Chiara , Prodduturu Harika Reddy , Arrington Dusty R. , Schulz Nathan , Hurlebaus Stefan , Rupp Jonathan D.
Published: February 2017

The Manual for Assessing Safety Hardware (MASH) defines crash tests to assess the impact performance of highway safety features in frontal and oblique impact events. Within MASH, the risk of injury to the occupant is assessed based on a “flail-space” model that estimates the average deceleration that an unrestrained occupant would experience when contacting the vehicle interior in a MASH crash test and uses the parameter as a surrogate for injury risk. MASH occupant risk criteria, however, are considered conservative in their nature, due to the fact that they are based on unrestrained occupant accelerations. Therefore, there is potential for increasing the maximum limits dictated in MASH for occupant risk evaluation.

A frontal full-scale vehicle impact was performed with inclusion of an instrumented anthropomorphic test device (ATD). The scope of this study was to investigate the performance of the Flail Space Model in a full scale crash test compared to the instrumented ATD recorded forces which can more accurately predict the occupant response during a collision event.

Results obtained through this research will be considered for better correlation between vehicle accelerations and occupant injury. This becomes extremely important for designing and evaluating barrier systems that must fit within geometrical site constraints, which do not provide adequate length to redirect test vehicles according to MASH conservative evaluation criteria.
A Bionic Test-Bed for Sensing and Balance Augmentation in Biological Applications
Authors: Taghavi Nazita , Luecke Greg R. , Jeffery Nicholas D.
Published: February 2017

In this research, we are working to develop a wearable device for stabilizing walking in dachshunds with spinal cord injuries. Our approach is to use sensors on the dog to measure the angle of the torso and stimulate leg motion to balance the animal during standing and walking. The first step in this work is to develop a mechanical test-bed in order to replicate the motion and muscle response during the gait of the dog. This testbed will be used for exploring sensor device operation and for developing appropriate leg stimulation to achieve stability. This robotic testbed is a replica of dog’s rear limbs and is programmed to mimic the gait of the dog. Our initial experiments test the automatic stabilization of the robot by mimicking the walking gait of a healthy dog. We use test data from an actual dog walking on a treadmill to develop representative walking gait characteristics for use on our experimental test bed. Our results show that our bionic dog is an acceptable replica for use in testing the stabilization and control algorithms.
Coupling Sound Absorbing Materials With an Air Cavity Using Frequency Dependent Bulk Material Properties
Authors: Sung Shung H. , Nefske Donald J.
Published: February 2017

This paper presents the acoustic finite element method and the modal solution method for coupling sound absorbing materials with an air cavity to predict the sound pressure frequency response. The sound absorbing materials are represented with complex, frequency-dependent, effective mass-density and bulk-modulus properties obtained from the acoustic impedance of material samples. To couple the sound absorber cavity and air cavity, the boundary conditions at the interface between the cavities requires equality of pressure and equality of acoustic volume flow. Two modal solution methods are developed to compute the frequency response of the coupled system with frequency dependent material properties: the component mode method and the coupled mode method. The finite element and modal solution methodology is developed in a form readily adaptable for implementation in commercially available codes. The accuracy of the modal solution methodology is assessed for modeling a one-dimensional air tube terminated with absorbent material and the seats in an automobile passenger compartment.