bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Impingement Surface Velocity on Slot Jet and Slot Jet Reattachment Nozzles’ Flow Field
Authors: Farzad M. , Yagoobi J.
Published: January 2020

Slot jet reattachment (SJR) nozzle is developed in an attempt to enhance heat and mass transfer characteristics while effectively controlling the impingement surface force exerted by the jet flow. In the SJR nozzle, the jet is directed outward from the nozzle exit and it then reattaches on an adjacent surface in its vicinity. The turbulent mixing occurs at the boundaries of the free stream induces secondary flow by mass entrainment and causes the flow to reattach the surface in the form of an oval reattachment at close nozzle to surface spacing [1].

All the previous studies had considered a stationary reattachment surface. This paper, for the first time, investigates the impact of reattachment surface movement on the flow structure of SJR nozzle with three different exit angles of +45°, +20°, and +10°. Specifically, this numerical study is carried out by varying the surface-to-jet velocity ratio (u* = up/ue) from 0 to 1.5 and comparing of flow reattachment flow fields to those of a regular slot jet (SJ) nozzle, where up is the speed of reattachment surface (moving plate) and ue is the jet exit velocity. In this study, jet exit temperature is kept constant at the room temperature of 20°C and all comparisons were performed at the same Reynolds number of 7,900. Additionally, the effect of SJR air exit angle on the peak surface pressure is investigated.
Experimental and Computational Study on the Failure Behavior of Vehicle Battery Modules Subject to Wedge Cutting
Authors: Zhu Feng , Bulla Marian , Lei Jianyin , Du Xianping , Currier Patrick , Sypeck David
Published: January 2020

Lithium-ion (or Li-ion) battery systems have been widely used as the main power source in new generation electric vehicles. Their mechanical performance is very important for vehicle crashworthiness design. In this research, a combined experimental and computational study has been performed to investigate the failure behavior of vehicle battery modules subject to high force wedge cutting. The tests were conducted on a commercial Li-ion battery module at very low speed using a high capacity material testing system. The force and voltage change as a function of cutting depth were measured, and the failure modes were analyzed. A finite element (FE) model based on an explicit FEA solver, was developed to simulate the wedge cutting process. The model predictions demonstrated reasonable agreement. In addition, the influence of several material constants in the failure model on the structural response was also discussed.
Risk Assessment of Escalator Sidewall Entrapment Between the Years 1990 and 2017
Authors: Bress Thomas , Kennedy Eugenia , Sullivan MariAnne , Guttag Mark
Published: January 2020

In previous work, hazards related to escalator sidewall entrapment were examined between the years 1998 and 2017 [1]. This prior analysis included entrapment of the escalator riders’ fingers, hands, toes, or feet. Data were analyzed from the U.S. Consumer Product Safety Commission National Electronic Injury Surveillance System (NEISS) to better understand the trends associated with escalator sidewall entrapment since the introduction of the step/skirt performance index in the 2000 edition of ASME A17.1 Safety Code for Elevators and Escalators. This current effort extends the analysis to include injury data as early as 1990 to discern the trends in sidewall entrapment hazards during the decade prior to the introduction of the step/skirt performance index. The 1990 to 1997 data set was statistically adjusted to account for changes in the sampling frame of the NEISS data set between that period and the 1998 to 2017 data that were analyzed in the previous work [2,3]. This new work analyzes data from the entire time period, 1990 to 2017, to better understand the injury data trends and risks associated with sidewall entrapment. The resulting trends are then compared to the Code modifications introduced to mitigate the hazards of sidewall entrapment.

The statistical grouping analysis used in the previous work is improved and extended in this work. This grouping analysis presents an estimate of the number of sidewall entrapment incidents per day and overall incident percentage for contiguous date ranges covering the years 1990–2017. In all, the work presented herein will allow for a comparison across date ranges for both hand/finger and foot/toe injuries as it relates to modifications to ASME A17.1 such as the addition of the step/skirt performance index.
Control Design Strategies for Semi-Active Suspension System
Authors: Maradey Lazaro Jessica Gissella , Esteban Villegas Helio , Ruiz Brajan , Aldana Andrés
Published: January 2020

Semi-Active Suspension Systems are very important to achieve comfort, ride handling, ground contact of the tyre, road-friendliness and works in a large range of operation. Its use an active dampers and the action of control is very good because of low energy consumption. The force of the damper is regulated according to the operating conditions. Magnetorheological Dampers are commonly used because of his yield resistance, low power, fast response and low cost of production. However, they behave in a non-linear way, following a dynamic of hysteresis so you should give a more sophisticated mathematical treatment. In this paper, we describe the modelling and design of two control strategies for Semi-Active Suspension System. Two control laws will be developed; classical PID and Fuzzy Logic controls law with the simulation and evaluate the stability and performance properties of our controllers in several different scenarios through analysis and simulation simultaneously. The performance of the system is determined by computer simulation in Matlab/ Simulink. The results obtained to compare and prove the effectiveness of these control approaches.
Numerical and Experimental Study of an FSAE Intake Manifold
Authors: Dunn Christian J. , Enriquez Luis G. , Godinez Joel , Moore Matthew T. , Wang Xiuling , Zhou Chenn
Published: January 2020

Formula SAE (FSAE) is an international student engineering competition that allows students to design, manufacture and race a formula-style race car to compete with other universities. This season the Purdue University Northwest (PNW) Formula SAE Team required a means of evaluating potential performance characteristics and optimizing future design concepts for the intake manifold system prior to manufacturing, to reduce the overall time and cost. The air intake system is a critical powertrain system component that requires numerical study and experimentation to validate any meaningful design. Without simulation and testing, an efficient intake may only be designed by chance.

This project focused on replicating the characteristic flow behavior witnessed in the 2017–2018 PNW FSAE intake system using the computational fluid dynamics (CFD) software named STAR-CCM+. A 3D printed test model was manufactured and tested on a flow bench to gather boundary conditions and pressure data from multiple locations within the intake manifold. The physical testing results of the 2017–2018 intake system were with the CFD results in order to validate the simulation models.
Optimization of 3D Printed Elastomeric Nanocomposites for Flexible Strain Sensing Applications
Authors: Abshirini Mohammad , Charara Mohammad , Saha Mrinal C. , Altan M. Cengiz , Liu Yingtao
Published: January 2020

Flexible and sensitive strain sensors can be utilized as wearable sensors and electronic devices in a wide range of applications, such as personal health monitoring, sports performance, and electronic skin. This paper presents the fabrication of a highly flexible and sensitive strain sensor by 3D printing an electrically conductive polydimethylsiloxane (PDMS)/multi-wall carbon nanotube (MWNT) nanocomposite on a PDMS substrate. To maximize the sensor’s gauge factor, the effects of MWNT concentration on the strain sensing function in nanocomposites are evaluated. Critical 3D printing and curing parameters, such as 3D printing nozzle diameter and nanocomposites curing temperature, are explored to achieve the highest piezoresistive response, showing that utilizing a smaller deposition nozzle size and higher curing temperature can result in a higher gauge factor. The optimized 3D printed nanocomposite sensor’s sensitivity is characterized under cyclic tensile loads at different maximum strains and loading rates. A linear piezoresistive response is observed up to 70% strain with an average gauge factor of 12, pointing to the sensor’s potential as a flexible strain sensor. In addition, the sensing function is almost independent of the applied load rate. The fabricated sensors are attached to a glove and used as a wearable sensor by detecting human finger and wrist motion. The results indicate that this 3D printed functional nanocomposite shows promise in a broad range of applications, including wearable and skin mounted sensors.
A Preliminary Study of Active Stabilization for Agricultural Machines Using a Movable Mass
Authors: Bietresato Marco , Belotti Roberto , von Ellenrieder Karl D. , Mazzetto Fabrizio
Published: January 2020

Side overturning is a potentially dangerous phenomenon that can easily happen to agricultural machines because they typically have a high center-of-gravity (CoG) and a very narrow track-width (e.g., tractors operating in orchards). Overturning occurs when the direction of the resultant of the forces acting on the vehicle CoG intercepts the support plane outside of the “support polygon”, defined by taking the footprints of the vehicle wheels as its vertices. Here, we propose the use of a stabilization system that shifts the CoG position to ensure that the resultant force stays within the support polygon. This active stabilization is accomplished by equipping the vehicle with an additional mass that can be moved using an actuator. Using numerical simulations of a four-wheeled narrow-track tractor moving along a trajectory at constant speed, we characterize how the position of the movable mass affects vehicle stability under a quasi-static assumption. The path is a horizontal Euler spiral, having a continuously varying turning radius. The simulations are used to: (i) analyze the sensitivity of four metrics related to the vehicle stability with respect to the additional weight of the moveable mass and the position of the stabilization system, and (ii) find an optimal configuration of the stabilization system that will improve the operational limits of the vehicle.
Modelling and Experimental Validation of a Controllable Energy Harvester for Pressure Regulation
Authors: Ko Youngmok , Yu Shi Miao , Bilton Amy M.
Published: January 2020

A pico-scale Francis turbine (or energy harvester) was designed, fabricated and tested for pressure regulation and power generation application. The prototype energy harvester contains pivotable guide vanes and a controllable load to change the runner speed. This allows the simultaneous variation of the pressure drop and the output power. A computational fluid dynamics (CFD) model of the turbine was developed in ANSYS CFX 18.1 to evaluate the turbine’s sensitivity to geometric parameters such as the clearance gap size of the guide vane and its modularity. In conjunction to the CFD model, the electric generator’s characteristics were used to predict the turbine performance at varying guide vane angles. The turbine was prototyped and tested using a custom-built experimental set-up. The pico-scale turbine, with a runner diameter of 1.42 inches, was able to output up to 100 W of electrical power at its rated flowrate of 29 GPM. By varying the guide vane angles, the pressure drop and the hydraulic efficiency varied between 3–22 psi and up to 60% respectively. When validated against the experimental results, the CFD model showed a good agreement despite its low computational cost. The energy harvester’s initial characteristics demonstrate its potential as a game changer in the control valve market.
Mechanical Response and Incomplete Filling in Compression Molding With Microscale Double-Punch Sets
Authors: Zhang Bin , Dodaran M. , Shao S. , Meng W. J.
Published: January 2020

Forming nano-/micro-scale surface patterns on metal surfaces by direct compression molding is an important means for achieving small scale surface features with potential usage in wide ranging technological applications. Geometric fidelity of molded features and the corresponding molding response are of critical importance in determining the usefulness of the molding replication technique. In this paper, two series of microscale punches made of tool steels were fabricated using Ga+ focused ion beam (FIB). In one series, the punch consists of a single protruding rectangular strip of different width, w (dubbed the “single punch”). In the other series, the punch consists of two rectangular strips of identical dimensions separated by a spacing in between, s (dubbed the “double punch”). These so-fabricated punches were used to mold elemental single crystal Al. The mechanical response during compression molding was measured and analyzed. For the double-punch experiments, measured characteristic molding pressure exhibited a significant dependence on the spacing to punch width ratio, λ = s/w, as well as a significant dependence on s when λ was fixed. The molded features were examined and the phenomenon of incomplete filling was observed to occur at λ < 0.5.
Microstructural Hyperelastic Characterization of Brain White Matter in Tension
Authors: Ramzanpour Mohammadreza , Hosseini-Farid Mohammad , Ziejewski Mariusz , Karami Ghodrat
Published: January 2020

Axons as microstructural constituent elements of brain white matter are highly oriented in extracellular matrix (ECM) in one direction. Therefore, it is possible to model the human brain white matter as a unidirectional fibrous composite material. A micromechanical finite element model of the brain white matter is developed to indirectly measure the brain white matter constituents’ properties including axon and ECM under tensile loading. Experimental tension test on corona radiata conducted by Budday et al. 2017 [1] is used in this study and one-term Ogden hyperelastic constitutive model is applied to characterize its behavior. By the application of genetic algorithm (GA) as a black box optimization method, the Ogden hyperelastic parameters of axon and ECM minimizing the error between numerical finite element simulation and experimental results are measured. Inverse analysis is conducted on the resultant optimized parameters shows high correlation of coefficient (>99%) between the numerical and experimental data which verifies the accuracy of the optimization procedure. The volume fraction of axons in porcine brain white matter is taken to be 52.7% and the stiffness ratio of axon to ECM is perceived to be 3.0. As these values are not accurately known for human brain white matter, we study the material properties of axon and ECM for different stiffness ratio and axon volume fraction values. The results of this study helps to better understand the micromechanical structure of the brain and micro-level injuries such as diffuse axonal injury.
Stress and Mesh Stiffness Evaluation of Bimaterial Spur Gears
Authors: Karpat Fatih , Yılmaz Tufan Gürkan , Doğan Oğuz , Kalay Onur Can
Published: January 2020

Lightweight spur gears have been a trending topic in aerospace and automotive applications recently. Traditionally, weight reduction could be ensured by using gear body with holes or thin rim design which result in to fluctuate mesh stiffness or it may increase stress and deformation levels. Indeed, high stresses occur in only contact and root region of gear tooth during the meshing process, so other regions are subjected to low stress. Based upon this point; various materials with low density and adequate strength could be used in low stress region while gear steel remains for high stress region. In this study, two different lightweight materials (Aluminum alloy and Carbon fiber reinforced polymer) were used for low stress region. The effect of these materials was investigated in view of stiffness and root stress for the same gear design parameters. Unidirectional CFRP laminas were used in a symmetric lay up to ensure quasi-isotropic laminate properties. Finite element analyses were conducted to obtain root stress and then total deformation of the tooth for stiffness calculation. Interface properties of ring and core regions were assumed as pure bonded. Meshing load was applied on the highest point single tooth contact (HPSTC) line. Weight reduction ratios were also compared. According to results, the steel/composite design is superior to steel/aluminum hybrid design in view of stress, stiffness and weight.
Design and Performance of a Directional Permeability Membrane
Authors: Bayat Hamidreza , Willis David A. , Krueger Paul S.
Published: January 2020

Directional permeability membranes were designed, fabricated, and tested with the potential application of facilitating drug delivery. Membranes were constructed from two porous polyimide sheets with offset pores and bonded with double sided tape with thickness values of 20 or 70 μm at the perimeter. The pores ranged in diameter from 0.25 to 1.0 mm and were cut using a laser micromachining apparatus. The pores were arranged in a square array with distance of 2 mm from center to center. The membranes were tested under pressure-driven water flow in the range of 0.01–0.10 m of H2O and flow rates were measured for two configurations: one with the thicker sheet upstream (forward direction) and one with the thinner sheet upstream (reverse direction) and the ratio of forward/reverse flow was calculated. In order to better understand membrane behavior, the maximum deflection of the thinner sheet was measured using an imaging system composed of a lens with small depth of field, digital camera, motorized linear translation stage, and a motion controller. Results show that in forward flow, by increasing hydrostatic pressure from 0.01 to 0.10 m H2O the mass flow rate increased by 40–55%. Conversely, increasing the hydrostatic pressure in the reverse direction from 0.01 to 0.10 m H2O considerably reduces the flow rate. The ratio of forward to reverse flow rate of the membrane varied in the range of 1.5 to 9529, depending on the pressure head.
Conceptual Cost Estimation of Multistage Axial Compressor Modules
Authors: Favi Claudio , Campi Federico , Mandolini Marco , Martinelli Irene , Germani Michele
Published: January 2020

Development of product architectures is a fundamental task in the conceptual design of complex products such as axial compressor of gas turbines. The definition of cost-effective architectures results from the introduction of conceptual cost estimation models aiming at the assessment of economical performances of different modules. Conceptual cost estimation means the product cost assessment in conceptual design phase. These models vary based on the technical and geometrical features of the defined product modules as well as to the specific manufacturing processes. The paper aims to describe the approach for early design cost estimation of Axial Compressor modules. The approach includes the design workflow and the required steps to build product architectures driven by cost indicator. The main limitation overtaken by the adoption of the proposed approach is the needs of a design tool able to characterize cost-effective design solution and to guide designer in product definition with the right level of confidence. The axial compressor product has been analyzed to retrieve different architectures and a case study of a rotor disc module is presented to demonstrate the feasibility of the proposed approach in the development of conceptual cost models starting from preliminary design information.
Effect of Metal Foam Thickness and Pore Density on Array Jet Impingement Heat Transfer
Authors: Singh Prashant , Zhang Mingyang , Mahajan Roop L.
Published: January 2020

High porosity metal foam is a popular option for high performance heat exchangers as it offers significantly larger area per unit volume for heat dissipation as compared to other cooling techniques by convection. Further, metal foams provide highly tortuous flow paths resulting in thermal dispersion assisted by enhanced mixing. This paper reports an experimental study on jet array impingement onto high-porosity (ε∼0.95) thin aluminum foams. Our goal was to study the effect of foam thickness on convective transport and determine the optimum combination of foam thickness and pore density for maximum gain in thermal-hydraulic performance. To this end, three different pore-density foams (5, 10 and 20 pores per inch, ppi) were tested with three different jet array (5 × 5) impingement configurations (x/dj = 2,3 and 5), where “x” is the distance between any two adjacent jets and “dj” is the jet diameter. For the three pore densities selected, six values of foam thickness — 6.35 mm, 12.7 mm and 19.05 mm for the 20 ppi foam, 12.7 mm and 19.05 mm for the 10 ppi foam, and 12.7 mm for the 5 ppi foam — were deployed. The minimum thickness for each of the ppi value was dictated by the vendor’s manufacturing constraint. The thermal performance of these foams was compared against the orthogonal jet impingement onto a smooth heated surface, for which the distance between the jet exit plane and the heated surface was maintained at the foam thickness level. The data indicates that for a given pore density, thin foams have higher heat transfer rates compared to those for thicker foams, especially with jet configurations with larger open area ratios. The gain is due to the increased jet penetration and foam volume usage in thin foams compared to those for thick foams. Of the different pore density and foam thickness combinations, a 12.70 mm/20 ppi combination was found to have the highest thermal hydraulic performance.
Structure-Property Relationships Between Morphological Anisotropy and Mechanical, Thermal, and Dielectric Behavior in Liquid Crystal Polymers
Authors: Sullivan Anthony , Saigal Anil , Zimmerman Michael A.
Published: January 2020

Liquid crystal polymers (LCPs) form a class of high-performance plastics that exhibit comparable mechanical, chemical, and electrical characteristics to engineering metals and ceramics arising from their mesoscopic ordering. The unique hierarchal LCP microstructure leads to anisotropic bulk behavior and an understanding of the development of this morphology during manufacturing, as well as the subsequent effect on polymer properties, is essential to the design of isotropic material manufacturing processes. In this investigation, the preferred orientation in injection molded LCP plaque samples was measured using wide-angle x-ray scattering (WAXS). The direction of preferred alignment was observed from the WAXS scattering patterns and the degree of orientation in the material was quantified using an anisotropy factor. In addition, the mechanical, thermal, and dielectric bulk behavior was measured with respect to the mold direction (MD) and transverse direction (TD). To investigate the effects of processing geometry on microstructural development, and the resulting macroscopic properties, plaques of three different thicknesses were analyzed. In addition, the influence of melt rheology was probed through the comparison of two different commercial LCP resins. It is shown that a strong correlation exists between material performance and both the bulk polymer texture and the individual regimes of the hierarchal structure. The effects of processing geometry and polymer rheology also demonstrate the structure-property-processing dynamics at work in injection molded LCPs.
Modeling of Pressure Exchanger for Energy Recovery on Trans Critical CO2 Refrigeration Cycle
Authors: Elatar Ahmed , Nawaz Kashif , Fricke Brian , Sharma Vishaldeep
Published: January 2020

Pressure exchanger is a device used to recover energy from high pressure working fluid in systems like Reverse Osmosis water desalination. The pressure exchanger enables the high-pressure fluid to transfer portion of its energy to the low-pressure fluid by transferring the fluid pressure. This working concept can be applied to systems where there is a significant pressure variation of the working fluid along the system. Trans critical CO2 refrigeration system is a good example for significant pressure variation during the flow path. The high-pressure CO2 exiting the condenser can be recovered by the low-pressure CO2 upstream of the compressor using a pressure exchanger to increase the system overall efficiency. The proposed research is to numerically simulate a prototype pressure exchanger for trans critical CO2 refrigeration system. The focus of this study is to understand the thermo-fluid behavior of the system when CO2 is used as the working fluid. Contour plots of velocity and pressure are presented for qualitative analysis.
An Experimental Study of the Combustion Process in a Natural-Gas Spark-Ignition Engine
Authors: Liu Jinlong , Dumitrescu Cosmin E. , Bommisetty Hemanth
Published: January 2020

The conversion of existing internal combustion engines to natural-gas operation can reduce U.S. dependence on petroleum imports and curtail engine-out emissions. In this study, a diesel engine with a 13.3 compression ratio was modified to natural-gas spark-ignited operation by replacing the original diesel injector with a high-energy spark plug and by fumigating fuel inside the intake manifold. The goal of this research was to investigate the combustion process inside the flat-head and bowl-in-piston chamber of such retrofitted engine when operated at different spark timings, mixture equivalence ratios, and engine speeds. The results indicated that advanced spark timing, a lower equivalence ratio, and a higher speed operation increased the ignition lag and made it more difficult to initiate the combustion process. Further, advanced spark timing, a larger equivalence ratio, and a lower speed operation accelerated the flame propagation process inside the piston bowl and advanced the start of the burn inside the squish. However, such conditions increased the burning duration inside the squish due to more fuel being trapped inside the squish volume and the smaller squish height during combustion. As a result, the end of combustion was almost the same despite the change in the operating conditions. In addition, the reliable ignition, stable combustion, and the lack of knocking showed promise for the application of natural-gas lean-burn spark-ignition operation in the heavy-duty transportation.
Model-Based EEG Analysis: Proposal and Verification of Mathematical Model for Application to Neurotechnology
Authors: Uehara Kenyu , Saito Takashi
Published: January 2020

We have modeled dynamics of EEG with one degree of freedom nonlinear oscillator and examined the relationship between mental state of humans and model parameters simulating behavior of EEG. At the IMECE conference last year, Our analysis method identified model parameters sequentially so as to match the waveform of experimental EEG data of the alpha band using one second running window. Results of temporal variation of model parameters suggested that the mental condition such as degree of concentration could be directly observed from the dynamics of EEG signal. The method of identifying the model parameters in accordance with the EEG waveform is effective in examining the dynamics of EEG strictly, but it is not suitable for practical use because the analysis (parameter identification) takes a long time. Therefore, the purpose of this study is to test the proposed model-based analysis method for general application as a neurotechnology. The mathematical model used in neuroscience was improved for practical use, and the test was conducted with the cooperation of four subjects. model parameters were experimentally identified approximately every one second by using least square method. We solved a binary classification problem of model parameters using Support Vector Machine. Results show that our proposed model-based EEG analysis is able to discriminate concentration states in various tasks with an accuracy of over 80%.
Defect Induced Variabilities in Thermal Conductivity of Nano Structures
Authors: Nakarmi Sushan , Unnikrishnan Vinu U.
Published: January 2020

The high thermal conductivity of carbon nanotubes makes them ideal candidates for use as nano-fins for thermal management in electronics and composites. At the nanoscale, the thermal conductivity of nanotubes are found to be dependent on size, strain states, temperature, and presence of defects and vacancy. The proper understanding of the effect of these parameters are important in constructing a nanotube system with desired thermal characteristics. Here, we pay special focus on the effect of different kinds of defects and vacancies on the thermal conductivities of nanotubes. Defects and vacancies are imperfections in an otherwise hexagonal structure of nanotube. Their presence have shown to impede the thermal transport in nano-structures which is attributed to the scattering of phonons that occurs in these imperfections. The thermal conductivities of (10,10) armchair nanotube with defects and vacancies are determined using the heat bath method, a non-equilibrium molecular dynamic simulation and are compared with that of pristine carbon nano-structures. This is followed by the comparative study of phonon density of states of nanotubes with and without the defects.
Anisotropic Phase-Field Modeling of Crack Growth in Shape Memory Ceramics: Application to Zirconia
Authors: Moshkelgosha Ehsan , Mamivand Mahmood
Published: January 2020

Shape memory ceramics (SMCs) are promising candidates for actuators in extreme environments such as high temperature and corrosive applications. Despite outstanding energy dissipation, compared to metallic shape memory materials, SMCs suffer from sudden brittle fracture. While the interaction of crack propagation and phase transformation in SMCs have been subject of several experimental and theoretical studies, mainly at macroscale, the fundamental understanding of the interaction of crack propagation dynamics with evolving martensitic transformation is poorly understood. In this work we use the phase field technique to fully couple the martensitic transformation to the variational formulation of brittle fracture. The model is parameterized for zirconia which experiences tetragonal to monoclinic transformation during crack propagation. For the mode I of fracture, opening mode, crack shows an unusual propagation path which indicates the effect of phase transformation on crack path. The model is efficiently capable of predicting the crack initiation as well as propagation. The results show the dramatic effect of phase transformation on fracture toughening and crack propagation path.
Design of a Composite Encapsulation for Concentrated Photovoltaic Systems With Improved Performance
Authors: Raza Kabeer , Akhtar Syed Sohail , Arif Abul Fazal M. , Hakeem Abbas Saeed
Published: January 2020

Most of the currently used encapsulants are inefficient for cooled concentrated photovoltaic (CPV) systems. The encapsulant of cells for CPV systems, must have an optimum combination of thermal conductivity, coefficient of thermal expansion and long term shear modulus. In this work an improved backside composite encapsulation is designed and developed that can provide increased power output and longer life by enhancing the effectiveness of cooling and reducing thermal stresses. The best combination of material properties is identified through parametric studies on finite element model of CPV laminate using ethylene vinyl acetate as datum line. It is found that increasing thermal conductivity from 0.311 to 0.75 W/mK can improve the cooling and hence the power production by 2%. While long term shear modulus and coefficient of thermal expansion needs to be reduced for a longer service life. Using in-house built material design codes, optimum combinations of matrix and filler were identified that could provide the set range of properties. In line with material design code, a total of only four samples using thermoplastic polyurethane as matrix and Al2O3 or AlN as fillers were synthesized to validate the design experimentally. The material properties were measured and used in the parent finite element model to evaluate the performance of the experimentally developed material and to validate the parametric studies. A good agreement is found between the experimental and computational results and hence the overall methodology is found effective for application focused design and development of composite materials. It is expected that this material design and development approach will provide a useful guideline to the CPV manufacturing industries.
Numerical Modelling of Impact Behavior of Composite Sandwich Panel With Honeycomb Core
Authors: Alam Shah , Bungatavula Aakash
Published: January 2020

The goal of this paper is to find the best impact response of the composite sandwich panels with honeycomb core. The focus of the study is to find the effects of changing the face sheet thickness and the core height of the sandwich panel subjected to variable velocities on impact performance. Initially, honeycomb core sandwich panel with 1mm thick face sheet is modelled in Abaqus/explicit to calculate the energy absorption, residual velocity, and deformation at four different velocities. Then, the process is repeated by changing the face sheets thickness to 2mm and 3mm to see the effects of changing the thickness on the impact performance of a composite sandwich panel. The honeycomb core height is also changed to see its effect on the performance. In all models, Al 7039 is used in the core and T1000G is used in the face sheets.
Implementation of an Integrated Sequential Procedure for Computer Simulation of Dynamics of Multibody Molecular Structures in Polymers and Biopolymers
Authors: Hay Akara , Duan Shanzhong (Shawn)
Published: January 2020

This paper presents the implementation results of an integrated sequential algorithm, which the second author developed mathematically in a pseudo code format previously to improve computational efficiency of computer simulation of the dynamical behaviors of multibody molecular structures in polymers and biopolymers. This new algorithm is a seamless integration between multibody molecular algorithm (MMA: a multibody-dynamics-based procedure for motion simulation of molecular structure) and fast multipole method (FMM). The fast multipole method is used to calculate interatomic forces from potentials, and the multibody molecular algorithm is used to generate equations of motion associated with molecular structures. The algorithm improves computational efficiency when comparing with its counterpart procedures.

A study case of an opened-chain molecular structure was used to demonstrate the algorithm works and to study improvement of computing efficiency of the algorithm. The algorithm is coded in MATLAB and run on both laptop and workstations computers with various numbers of molecules along the chain. FMM started with scaling all atoms into a box with coordinate ranges to ensure numerical stability of subsequent operations. The flow of calculations in FMM was carried out along the chain structure with five computational passes. MMA began with numbering subsets, forming bond graph, and developing three computing passes along the chain structure. Flows of both calculations and data in FMM and MMA were lined up recursively along the chain structure to obtain an O(N)1 computational efficiency. Simulation results were compared with results produced by MMA and traditional methods of FMM for interatomic force calculation procedure.

Implementation presented in this paper first proves that the integration between FMM and MMA works and the integrated algorithm improves computing efficiency associated with both calculation of interatomic forces from potentials and formation/solution of equations of motion. Implementation results also indicates that the integrated algorithm works more efficiently for a large-sized molecular chain than a small-sized molecular chain. Further work is needed to optimize the related FMM codes.
Integration Protocol of Different Measurement Methods for the Analysis of the Physiological and Biomechanical Efficiency of a Professional Athlete
Authors: Milani Massimo , Montorsi Luca , Fontanili Luca , Rossini Salvatore , Citarella Roberto
Published: January 2020

The paper focuses on the methodology for the analysis of the physiological and biomechanical efficiency of a professional athlete for integrating the standard preparation routine. The proposed methodology combines an in-house developed prototype of multiple uniaxial force plates for the measurement of the vertical component of ground reaction forces during movement and an infrared motion capture technique is adopted for measuring accurately the body motion.

The procedure is applied on a top level professional volley player and integrates the working routines used for the training over an entire season. The dynamic performance of the athlete is measured in terms of fatigue threshold and the aerobic workload. The proposed methodology demonstrates to be an accurate and reliable instrument for quantifying, for both slow and fast movements, the efficiency with which the athlete reaches the defined training targets and the precision achieved in developing an exercises’ routine. Furthermore, the dynamic response of the athlete is also measured by evaluating the position of the body during the workload as well as the speed of the movements and the corresponding interaction with the ground. This analysis verifies if an asymmetrical loading of the lower limbs and the power exerted during the impulsive contact phase with the ground. The measurements carried out during the analysis provide a map of the athlete performances during an entire season training and the mono- and bi-podalic movements could be associated with the time evolution of the athletic results, such as jumping length and height, speed, precision. Therefore, inefficiencies in the postural and technical aspects during the training can be measured and thus corrected leading to an improvement of the performance and to a reduction of the possibility for injuries onset.
A Compact Integrated Thermosyphon Heat Sink for Power Electronics Cooling
Authors: Elkholy Ahmed , Kempers Roger
Published: January 2020

The trend in miniaturization of power electronic components requires the development of new robust and passive cooling methods to meet increased heat flux demands. Conventional heat sinks encounter inherent shortcomings due to heat spreading resistance of the heat sink baseplate particularly in natural convection heat sinks used to cool small localized heat sources. Heat pipes embedded within the base of heat sinks can be used to improve spreading performance but are limited by the ability to conduct heat into and out of the heat pipes.

In the current study, a small, naturally aspirated two-phase thermosyphon heat sink was developed and characterized experimentally. The proposed architecture integrates all thermosyphon components into one compact device, where the evaporator, riser and the downcomer are incorporated at the heat sink base. The downcomer also serves as the condenser within the base of a vertical finned natural convection heat sink.

The side-heated evaporator consists of an array mini-channels configuration which can operate in either pool boiling or flow boiling configuration, which allows the thermosyphon heat sink to operate in either reflux mode or looped mode, respectively.

Experiments were carried out using HFE 7000 as the working fluid. The effect of the of input power on the thermal performance is examined for both modes for powers ranging from 10 to 80 W. Results demonstrate that this approach significantly reduces the spreading resistance resulting in a net improvement which can be traded-off for a decrease the overall size or weight of the heat sink.
A Dynamic Pipeline Network Health Assessment Software Platform for Optimal Risk-Based Prioritization of Inspection, Structural Health Monitoring, and Proactive Management
Authors: Chalgham Wadie , Diaconeasa Mihai , Wu Keo-Yuan , Mosleh Ali
Published: January 2020

The Pipeline Health Monitoring and Management web application is a risk-based pipeline integrity management support tool to support pipeline operators in decision-making and planning activities. The platform design is supported by a multi-disciplinary science and engineering approach for a comprehensive, state-of-the-art solution. The goal of the software platform is to integrate the data, methods, and technologies into a dynamic pipeline heath monitoring system supported by multiple probabilistic predictive models such as dynamic hybrid causal logic, corrosion prognosis, and sensor placement optimization models. This total system health management support tool provides online or offline updates on the reliability state of various segments of the pipeline system, and dynamically updates the recommendations on when and where to take mitigating actions, e.g., increase or decrease inspection frequency. The pipeline health monitoring system software platform under development provides the ability for (a) Integrity assessment based on comprehensive range of evidence from sensing, inspection, and real-time monitoring in addition to probabilistic integration of mechanistic models and data on failure mechanisms relating to various causal factors (e.g., uniform corrosion, pitting corrosion, etc.) for assessment of the pipe segment health (remaining life); (b) Dynamic pipeline network probabilistic health assessment model software for optimal risk-based prioritization of inspection and proactive management, and (c) Geographical mapping capabilities that will augment the interaction of the pipeline operators with the pipeline system such as viewing pipeline/sensor locations, and adding new pipelines if desired. The selected computational foundation for the assessment is the hybrid causal logic engine with a wide range of capabilities in terms of system model building and probabilistic analysis of various types of evidence for assessment of model parameters. On this foundation we are adding capabilities to integrate predictive corrosion models, sensor placement optimization, and computational modules to perform pipeline health assessment, and develop inspection and maintenance strategies. The resulting software will be deployed as a control room health dashboard and hand-held web-based field inspection support tool.
A Smart Pipeline Monitoring and Emergency Response System Using Web Services
Authors: Chalgham Wadie , Diaconeasa Mihai , Elgazzar Khalid , Seibi Abdennour
Published: January 2020

The Smart Pipeline Monitoring System introduced in this paper demonstrates a proof-of-concept for replicating a full-scale water pipeline system that is able to monitor the pipeline health and respond to hazard conditions through the use of multiple sensors and a statistical monitoring control strategy. The system aims at mitigating the effects of common sources of damage that occur in pipelines, such as leaks and overheating, by offering real time data visualization and autonomous actions in case of emergencies. The data visualization is provided by a desktop user interface and a mobile application. In the case of a detected anomaly, described by out-of-bounds/out-of-statistical control conditions detected by the sensors, the system is programmed to shut off its pump and alert the supervisors by SMS instantly. The proposed monitoring system will enhance remote pipeline monitoring and structural safety by offering real-time data and automatic emergency response capabilities. Our experimental results and prototype implementation show that the proposed system effectively detects anomaly conditions under various realistic scenarios and takes necessary safety measures to prevent further damages.
Rapid Motion Control and Design of a Tricopter Style Hovering Ground Robot
Authors: Simko Justin , Tatoglu Akin
Published: January 2020

An analysis of the design and manufacture of a tricopter style hovercraft is realized in detail, along with the parameters for determining the geometry due to power requirements. The aircraft is constructed with three ducted fans in the vertical orientation, denoting the layout of the classic tricopter frame. The purpose of this study is to establish a design of a ground vehicle capable of multi-terrain navigation. A simplified skirt solution is presented for the aircushion. The model is robust enough for rough terrain and sufficient for maintaining the cushion pressure that enables the ground effect to work towards a higher efficiency. The design process for the model consists of the use of CAD to layout and simulate all components. The efficiency and battery life of the vehicle is compared to the tricopter and a flight test verifies its capability to follow a given path.
Wind Effects on Power Generation of Solar Farm in California
Authors: Li Ni , Fatahi Arianna , Lee Dennis , Kuo Jim Y. , Shen He
Published: January 2020

In comparison to fossil fuels, solar energy is a more sustainable option due to its high availability and less environmental impact. Improving the efficiency of solar farms has been a primary concern of solar energy research. Many studies focus on the control of the tilt angle of solar modules to maximize their solar radiation reception and energy generation. However, an increase in solar radiation is accompanied by an increase in module temperature, which is known to be a significant parameter that reduces the power generation efficiency. Wind is another influential factor that helps Photovoltaic systems maintain a low operating temperature by enhancing the rate of heat transfer. Therefore, solar radiation and wind behavior are both critical parameters that must be considered to optimize solar panel performance. In this paper, the effect of wind conditions on solar panel performance will be examined. The solar panel energy output model will be built by empirically considering the irradiation, ambient temperature, wind speed, and wind direction. The published weather data and energy output data for the year 2017–2018 have been collected from Antelope Valley Solar Ranch, located in Lancaster, California. Four models have been proposed and the results indicate that the model which incorporates the wind conditions has the highest accuracy in approximating the energy production of solar farms. Among the factors that affect the temperature of solar panels and further the efficiency of solar panels including solar irradiation, convection, conduction, wind plays a major role in convective heat transfer. Based on this model, the potential improvement of energy generation via introducing a horizontal installation angle and adjusting this angle monthly according to the wind conditions is further analyzed. These results will help designers improve the design of solar farms by taking into consideration the local weather conditions.