bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stress and Mesh Stiffness Evaluation of Bimaterial Spur Gears
Authors: Karpat Fatih , Yılmaz Tufan Gürkan , Doğan Oğuz , Kalay Onur Can 
Published: January 2020

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.