bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Cryogenic Temperature Rolling on High Speed Impact Behavior of AA 6082 Thin Targets
Authors: Dubey Rahul , Allavikutty Raja , Velmurugan R. , Jayaganthan R.
Published: January 2020

Aluminium alloy AA 6082-T6 was rolled at cryogenic and room temperatures to final thickness of 0.5 mm after 75% thickness reduction and subjected to high speed impact. The deformed alloy was investigated for its ballistic properties due to potential applications in aerospace and automotive sectors. The cryogenic and room temperature rolled samples were subjected to normal high-speed impact using a gas gun arrangement to shoot nosed projectiles at velocities higher than the ballistic limits. Phantom ‘V611’ high-speed camera was used to measure the initial and residual velocities of the projectile. Nano-indentation was performed to relate hardness of the initial sample with the observed impact behaviour. Detailed fractographic studies were conducted using Scanning Electron Microscopy (SEM) to substantiate the possible failure mechanisms upon impact. Electron Backscatter Diffraction (EBSD) and Energy Dispersive X-ray Spectroscopy (EDS) were used to characterize the microstructure of the deformed samples.

The high speed impact data is correlated with the metallographic observations in this study.
Optimization of Machining Parameters During Turning of Tungsten Heavy Alloys Using Taguchi Analysis
Authors: Kiran Sagar Chithajalu , Priyadarshini Amrita , Gupta Amit Kumar
Published: January 2020

Tungsten heavy alloys (WHAs) are ideally suited to a wide range of density applications such as counterweights, inertial masses, radiation shielding, sporting goods and ordnance products. Manufacturing of these components essentially require machining to achieve desired finish, dimensions and tolerances However, machining of WHAs are extremely challenging because of higher values of elastic stiffness and hardness. Hence, there is a need to find the right combination of cutting parameters to carry out the machining operations efficiently. In the present work, turning tests are conducted on three different grades of WHAs, namely, 90WHA, 95WHA and 97WHA. Taguchi analysis is carried out to find out the most contributing factor as well as optimum cutting parameters that can give higher metal removal rate (MRR), lower surface roughness and lower cutting forces. It is observed that feed rate is the most prominent factor with percentage contribution varying in the range of 46–61%; whereas cutting speed has least effect on cutting forces, especially for 95WHA and 97WHA. Optimum values of forces, surface roughness and MRR and the corresponding machining parameters to be taken are presented. It is observed that 95W WHA has slightly better machinability as compared to other two grades since it gives highest MRR with lowest cutting forces and surface roughness values. The optimum machining parameter settings, so predicted, can be utilized to machine WHAs efficiently for manufacture of counter weights and inertial masses used in aerospace applications.
Analysis of Labyrinth Seal Flow Patterns to Improve Bulk Flow Code Predictions
Authors: Gibbons Nathaniel , Watson-Kassa Cori , Goyne Christopher , Wood Houston
Published: January 2020

Non-contacting annular seals are frequently used in turbomachinery to reduce leakage of a fluid through a section with a large pressure differential. A typical type of non-contacting seal is the labyrinth seal, where circumferential grooves are cut into the rotor, stator or both. Using a tortuous path, labyrinth seals reduce leakage by dissipating the fluid’s kinetic energy through viscous forces caused by the formation of vortices in each seal groove.

Due to a lower cost when compared to experimental measurements, bulk flow codes are frequently used for predicting seal contributions to rotordynamic performance. Existing seal codes use constant or linear values for the fluid film thickness at different seal sections and display inaccuracies in their prediction of velocity and pressure profiles and rotordynamic coefficients for labyrinth seals when compared to experimental data. The primary objective of this study is to determine the effect of implementing an effective film thickness into the governing bulk flow equations on the code prediction of axial velocity and pressure profiles.

Simulations were run using ANSYS CFX with cross-sectional models of individual seal grooves. Seal parameters, including inlet circumferential velocity and rotor speed, were varied to better understand the behavior of the film thickness under various operating conditions. Streamlines were used to determine the maximum film thickness and an effective film thickness profile that can be used in the modified bulk flow code. Modified governing equations were developed, and predictions for the axial profiles resulting from the modified code solutions for the zeroth order governing equations are compared to CFD results and previous code predictions for improved accuracy. Preliminary results for a set of cases indicate far higher accuracy when an effective film thickness is used and represent the first results from a seal bulk flow code that implements a nonlinear effective film thickness. Improvement in code prediction of flow behavior across the seal, and subsequently in the seal codes accurate prediction of rotordynamic coefficients, allows for the design of more efficient and effective seals and machine systems.
3D Finite Element Assisted Numerical Simulation of Orbital Drilling Process of Ti6Al4V
Authors: Pervaiz Salman , Daneji Ali , Kannan Sathish
Published: January 2020

Drilling is one of most executed manufacturing operations to assist the assembling of different engineering components. In orbital drilling process, a milling tool is rotating along its own axis in combination with the spiral rotational movement. The rotation of tool about its own axis is with high rotational speed, but the spiral movement of tool is at low rotational speed. These rotational movements generate a hollow geometry when moved in combination. Orbital drilling process is emerging as a viable drilling process when burr formation has to be reduced from the metallic workpiece. It is gaining more popularity in the aerospace industry due to its ability to machine holes in difficult to cut alloys, composites and composite stacks. Major advantages of orbital drilling are linked with efficient chip evacuation, reduction in heat build-up and low thrust forces due to its intermittent cutting nature.

The cutting forces generated during the process can be taken as a significant output parameter that play a vital role towards the overall performance of the cutting process. Controlling the cutting forces under threshold value can improve the overall machining efficiency by limiting associated deflections, tool wear and energy consumption. The current paper aims to study the orbital drilling process using finite element (FE) assisted numerical methodology. The study will utilize different orbital drilling parameters such as spindle speed, orbit speed and axial feed rate, and explore their influence on the over all machining process.
Spatial Variations in Achilles Tendon Shear Wave Speed Using a Cost-Effective Method of Accelerometers
Authors: Salman Muhammad , Ge Conghui , Morris Clint
Published: January 2020

Currently there are no cost-effective ways to quantitatively measure the in-vivo mechanical properties of the Achilles tendon. Stiffness can be used as a measure of tone and mechanical integrity of both muscles and tendons. Stiffness of the Achilles tendon (AT) can be quantified by the speed of shear wave propagation. The speed of propagation can then be used to find the instantaneous shear modulus. Currently there are other methods such as Ultrasound (US) imaging and Magnetic Resonance Imaging (MRI) which are used clinically to determine the variations in stiffness of the AT. However, these methods require complex signal processing and experienced technicians. Moreover, US imaging technique is limited in measuring high shear wave speed values which are greater than 17 m/s. In this research, one-dimensional accelerometers were used to measure acceleration through the AT. Then a cross-correlation signal processing technique was used to convert acceleration to the velocity of shear wave propagation across the AT. This method could potentially evaluate the mechanical properties of both normal and damaged tendons. This process has proven to be a cost-effective and simple way to assess the stiffness of the AT. The modulus of elasticity (E) was found using the following relation: E = 3ρV2.
Investigating Density Functional Theory’s Effectiveness in Studying Metal-Organic Frameworks Structures
Authors: Roberts Kendric , Han Yen-Lin
Published: January 2020

In combatting human induced climate change, carbon capture provides the potential to more slowly ease away from the dependence on hydrocarbon fuel sources, while mitigating the amount of CO2 released into the atmosphere. One promising material to use is metal-organic frameworks (MOF’s). MOF’s offer an immense variety in potential exceptionally porous structures, a property important in separation. As a result of practical experimental measurements being expensive and time consuming, interest in accomplishing the same goal through modeling has also increased. Using density functional theory to optimize the approximate experimentally measured atomic geometries has been shown to have sufficient accuracy. A previous study by Nazarian et al. was performed to optimize structures on the CoRE MOF Database using a supercomputer. The purpose of this study was to attempt to replicate their work done with a single MOF using computational resources more commonly available. Furthermore, as time tends to be the limiting factor in conducting these studies, the use of a smearing function was adjusted for two optimizations to see if any considerable improvement on the efficiency of the optimizations could be made. Our results show both optimizations improved the bond length accuracy relative to the raw data compared with the optimization from Nazarian, et al. The optimization with a more present smearing effect was able to converge the electron field in roughly half the time, while still showing nearly the same results, except for slightly more variability in the bond lengths involving transition metals. Unfortunately, the improvement in bond length, did not correspond in consistent improvement of the larger cell defining metrics. This shows that either a different energy minimum was found or the relationship between the larger cell parameters, with the more local parameters such as bond length is too complex for the method to effectively solve.
The Potential of Solar Cooling Using a Medium Concentration Photovoltaic-Thermal System
Authors: Abdel-Mesih Bahy
Published: January 2020

Using solar energy for space cooling is a very interesting concept that relies on several facts. First, both the solar gains and cooling loads or demand coincide with each other. The high insolation levels in summer increase indoor temperatures and accordingly increase the necessity for cooling to fulfill the comfort requirements of occupants. Second, in summer, the electric peak loads occur due to excess usage of electrically-driven air-conditioning systems. Third, there is a surplus of solar gains in solar systems designed for heating applications during the summer season. In this work, the author investigates the usage of the heat produced by a concentrated photovoltaic-thermal (CPVT) system for running an absorption chiller for cooling applications. The CPVT generator is a 22-suns linear Fresnel reflecting system. Water pipes run beneath the PV cells to cool them down, improving their efficiency, and thus simultaneously producing hot water. Different areas of the concentrator and configurations of storage tanks are looked at. TRNSYS simulation platform is used in this study. Results show great potential for a system that produces electricity, hot domestic water, and cooling effect.
Digital Twin in a Manufacturing Integrated System: Siemens TIA and PLM Case Study
Authors: Guerra-Zubiaga David A. , Bondar Alex , Escobedo Gilberto , Schumacher Arthur
Published: January 2020

The new industrial revolution called Industry 4.0 embraces diverse Digital Manufacturing Tools (DMT). Trying to improve Product Life-cycle Management (PLM), some companies are trying to implement DMT to create Digital Twins (DT). New Product Introduction (NPI) demands large effort in digitalization and virtual simulation through the PLM process. Sometimes a new product could be only the development of a single component and/or an entire manufacturing process including complex instruments and controls. In this direction, it is important to accelerate Manufacturing Integrated Systems (MIS) by improving the automation not only in the NPI, but also in the PLM. This paper integrates Siemens PLM software as DMT called Tecnomatix Process Simulate (TPS), Totally Integrated Automation (TIA) and PLCSIM advanced. The scope in the NPI is showing how a Digital Twin could help the MIS. The aim of this paper is to evaluate the interconnectivity of a small physical prototype with its virtually simulated clone to support the virtual commissioning for a NPI.
Two Methods for the Constitutive Modeling of TiB2/7050 Al Composites
Authors: Lin Kunyang , Wang Wenhu , Jiang Ruisong , Liu Xiaofen , Zhu Xiaoxiang , Zhang Zhanfei
Published: January 2020

In this paper, the Johnson-Cook constitutive model of in situ TiB2/7050 Al metal matrix composites determined by two different methods are compared. The commonly used quasi-static and dynamic compressive experiments are firstly conducted under the strain rate range of 10−3∼5000s−1 and temperature range of 20∼200 °C. The orthogonal cutting experiments are also used to calculate the JC model. The description ability of two models are evaluated by two statistical parameters: correlation coefficient and average absolute error. The results show that the JC model determined by the compression experiments performs better to describe the stress-strain behavior of in situ TiB2/7050 Al composites. Although the JC model from orthogonal cutting experiments can be used to simulate the cutting process, it cannot describe the flow stress behavior exactly during material deformation processes. For an accurate constitutive model of a material, the basic tensile or compression test is deemed necessary.
Synthesis and Deposition of Rutile TiO2 for Dye-Sensitized Solar Cell Applications
Authors: Teferi Blen , Schnupf Udo , Manseki Kazuhiro , Sugiura Takashi , Vafaei Saeid
Published: January 2020

The purpose of this research was to produce semiconductor Rutile TiO2 films using a new deposition method on F-doped SnO2 (FTO) glasses i.e. nanofluid boiling method, using TiO2 nanoparticles. A low-temperature synthesis without using conventional hydrothermal methods was established to obtain the Rutile TiO2 nanoparticles with different size and shape under different temperatures. The crystalline TiO2 was separated from the reaction liquid by centrifugation and dried under ambient condition. The current boiling deposition of the TiO2 nanofluid was found to form porous semiconductor TiO2 nanoparticle films without cracks in the deposited TiO2 film. The obtained TiO2 films will be utilized as TiO2 photoanodes in dye-sensitized solar cells.
Anisotropic Deformation Behavior of Porous Polymeric Membranes Under Uni-Axial and Bi-Axial Loadings
Authors: Emori Kanako , Yonezu Akio , Nagakura Takumi , Miura Tatsuma
Published: January 2020

This study systematically investigates the uniaxial and biaxial tensile deformation behavior of polytetrafluoroethylene (PTFE) membranes which are used for water purification. The present PTFE membrane has micron size pores with open cell structure, and the pore is anisotropic shape. During the uniaxial tensile test, the membranes undergo elastic deformation and plastic deformation with strain rate sensitivity (i.e. time-dependent deformation behavior). In addition, it strongly demonstrates anisotropic deformation, i.e. deformation behavior is different along longitudinal direction and transverse ones. To clarify the microscopic deformation mechanism, in-situ SEM observation is carried out during tensile loading. It is found that the anisotropic deformation behavior appears due to the inherent pore structure. Next, to investigate deformation behavior under biaxial loading condition, small punch test using a spherical indenter is carried out. The membrane undergoes elastic and plastic deformations. Finally, crack nucleates around the indenter contact and indenter completely penetrates through the membrane. It is also found that the membrane demonstrates anisotropic out-of-plane deformation behavior. To clarify these mechanisms, FEM computation is carried out, such that experimental results of force-displacement curve and out-of-plane deformation behavior are compared with the computational ones. The present FEM model enables the prediction of the membrane’s deformation behavior under biaxial loading.
Study on Turning of Non-Axisymmetric Three-Dimensional Curved Surfaces
Authors: Nakagawa Kensuke , Mori Taichi , Morimoto Yoshitaka , Hayashi Akio , Kaneko Yoshiyuki , Suzuki Naohiko , Hirono Ryo
Published: January 2020

Conventional machining of complex parts having three-dimensional curved surfaces is done by two processes using a five-axis machining center and a grinding machine. Although these tools make it possible to machine a product with complicated profiles, the tool path is complex and the process is time consuming. Also, because the amount of movement accompanying the control of the tool position increases, the productivity decreases. Therefore, we developed a CNC lathe for high-speed and high-efficiency machining in a previous study. The NC positioning table on which the tool is mounted is synchronized with the rotation angle of the main spindle; thus, the developed CNC lathe can form a three-dimensional curved surface on a workpiece. However, the previous study did not evaluate the surface profile of a product created with the developed CNC lathe.

In this study, for the purpose of improving the contour accuracy of the machined workpiece, we propose a method for on-machine measurement and compensated machine tool position using the measurement result. The proposed on-machine measurement method is a non-contact method that employs a line laser displacement sensor. In the proposed method, the workpiece attached to the spindle of the CNC lathe is moved to a sensor reference position and measured. The measurement position is recorded in the NC machining program; thus, it is possible to adjust the tool position during machining to reduce the machining error by feeding the measurement results back to the machining program. Because machining is started in a state offset from the machining origin, the compensated machining can deal with both overcutting and undercutting of the workpiece. Testing of the proposed compensated method confirmed improvement in the desired profile accuracy.
Inverse Optimization of Design Parameters in a Hybrid Solar Pond System With External Heat Addition
Authors: Kumar Abhishek , Das Ranjan
Published: January 2020

External heat supply to solar ponds from various types of solar collectors is a feasible alternative that significantly enhances its performance. In this work, various design parameters in a hybrid solar pond with external heat addition from Evacuated Tube Solar Collector (ETSC) are evaluated using an inverse approach. A forward model based on heat balance equations is solved for various zones of the solar pond to predict temperatures attained by its storage zone under a given climatic condition. Bryant and Colbeck’s relation is used to account for the diminution of the solar radiation as it travels from upper layers of the solar pond to its bottom layers. The relevant differential equations are solved using a Runge-Kutta fourth order scheme. The component of heat addition from ETSC is added to the forward model in the storage zone’s equation. Heat added from ETSC is considered proportional to the fraction of the aperture area to the pond’s base area, the thermal efficiency of ETSC and global solar radiation incident on ETSC. Both the forward model of the solar pond and combined solar pond and ETSC model were validated with previous experimental and numerical studies available in the literature for El Paso, USA, and Melbourne, Australia. An inverse model based on genetic algorithm is proposed for evaluating the set of geometrical parameters of ETSC and solar pond in order to derive a required performance from the combined solar pond-ETSC system.
Influence of Input Image Configurations on Output of a Convolutional Neural Network to Detect Cerebral Aneurysms
Authors: Watanabe Kazuhiro , Anzai Hitomi , Juchler Norman , Hirsch Sven , Bijlenga Philippe , Ohta Makoto
Published: January 2020

Rupture of cerebral aneurysms is the main cause of subarachnoid hemorrhage, which can have devastating effects on quality of life. The identification and assessment of unruptured aneurysms from medical images is therefore of significant clinical relevance.

In recent years, the availability of clinical imaging data has rapidly increased, which calls for computer assisted detection (CAD) systems. Previous studies have shown that CAD systems based on convolutional neural networks (CNN) can help to detect cerebral aneurysms from magnetic resonance angiographies (MRAs). However, these CAD systems require large datasets of annotated medical images. Thus, more efficient tools for processing and categorizing medical imaging data are required.

Previous studies of CNN-based classification for medical images used various patch configurations of input data. These studies showed that classification accuracy was affected by the patch size or image representation. Thus, we hypothesize that the accuracy of CADs to detect cerebral aneurysms can be improved by adjusting the configuration of the input patches.

In the present study, we performed CNN-based medical imaging classification for varying input data configurations to examine the relationship between classification accuracy and data configuration.
3D Assembly Model Matching Based on Motion Features and Shape Distribution
Authors: Baoning Ji , Yuan Li , Jie Zhang , Jianfeng Yu
Published: January 2020

Assembly retrieval is a significant technology to reuse the abundant design knowledge embedded in the products. However, the existing assembly retrieval methods are still lacking and the research on this topic is needed. It is found that the motion features of the internal mechanism in the assembly model are closely related to its mechanical function, which is significant for mechanism motion design, assembly simulation, etc. So we propose an approach for assembly matching by motion and shape features. First, assembly model are decomposed into separate kinematic components according to analyzing its motion structure. Then, we take geometric information of kinematic component as a vertex, and kinematic pair between components is taken as an edge to construct graph-based assembly descriptor, which contains motion features of the assembly. Afterwards, Ullmann algorithm is introduced to match the input descriptor with the assemblies in the library, and the maximum subgraph of them is solved so as to estimate the similarity. In case study, some experiments have been carried out, and the results have shown the feasibility of the method proposed in this paper and demonstrated the practical value in engineering.
Real-Time Assembly Recognition Based on the Similarity Between Spatial Increment and Part Model
Authors: Pang Jiazhen , Li Yuan , Zhang Jie , Yu Jianfeng
Published: January 2020

Manual work is a weak link within the intelligent manufacturing, however, it plays an important role in the highly customized and multi-variety assembling. Assisted by intelligent assembling technology such as augmented reality, a manual worker can integrate into the cyber-physics system to improve efficiency and reduce errors, which is of great engineering significance in the assembling field of industry 4.0. Assembly recognition is the initial part of progress analysis and it has predictable changing progress stages which can be matched with the digital model for recognition constraints. Therefore, based on the similarity between spatial increment information and part model, a real-time assembly recognition method is proposed in this paper. Firstly, the depth images from the multi-camera system were used to capture the assembling scene. Then, compared with the previous assembling scene, the spatial incremental information was used to quantitatively represent the assembled part. The spatial increment information and digital model are described with distance distribution. Finally, based on Earth mover’s distance algorithm, the matching between the spatial increment information and the part model indicates the part which had been assembled to realize the real-time assembly recognition. In the case study, an assembling process for 3D printing assembly which corresponded with the digital model was used to approve the feasibility of the real-time assembly recognition method.
Coordinated Motion Planning of Legged Mobile Manipulator for Tracking the Given End-Effector’s Trajectory
Authors: Bhavanibhatla Kondalarao , Suresh-Fazeela Sulthan , Pratihar Dilip Kumar
Published: January 2020

In this paper, a novel algorithm is presented to achieve the coordinated motion planning of a Legged Mobile Manipulator (LMM) for tracking the given end-effector’s trajectory. LMM robotic system can be obtained by mounting a manipulator on the top of a multi-legged platform for achieving the capabilities of both manipulation and mobility. To exploit the advantages of these capabilities, the manipulator should be able to accomplish the task, while the hexapod platform moves simultaneously. In the presented approach, the whole-body motion planning is achieved in two steps. In the first step, the robotic system is assumed to be a mobile manipulator, in which the manipulator has two additional translational degrees of freedom at the base. The redundancy of this robotic system is solved by treating it as an optimization problem. Then, in the second step, the omnidirectional motion of the legged platform is achieved with a combination of straight forward and crab motions. The proposed algorithm is tested through a numerical simulation in MATLAB and then, validated on a virtual model of the robot using multibody dynamic simulation software, MSC ADAMS. Multiple trajectories of the end-effector have been tested and the results show that the proposed algorithm accomplishes the given task successfully by providing a singularity-free whole-body motion.
Elimination of Sommerfeld Effect in Non-Ideal Systems Using Dry Friction
Authors: Chakraborty Pratyaya , Chakraborty Goutam , Bhattacharyya Ranjan
Published: January 2020

Most of the power sources of mechanical systems can only deliver limited amount of power. Due to this insufficiency of power, often the system fails to achieve a smooth passage through resonance. For example, a non-ideal DC motor driven vibrating system with viscous damping often gets stuck near resonance speed of the system as a large amount of supplied power is utilized to oscillate the system which causes a scarcity of power for the motor speed to go past the resonance condition. However, most of the available power can be used to rotate the motor shaft if somehow the oscillating motion is arrested or minimized. In this paper, a study of a non-ideal DC motor driven mechanical system with dry friction is presented. The response of the system under stick phase, as given by the Karnopp model of friction is found and subsequently, a nonslip operating condition is obtained analytically. With the help of numerical results, the obtained nonslip condition is verified for different voltage inputs. A smooth variation of rotational speed of the motor shaft is numerically achieved without being affected by the Sommerfeld Effect.
Influence of Timestep and Mesh Sizes on Numerical Simulations of Boundary Value Problem Model of Electrostatically Actuated MEMS Resonators
Authors: Beatriz Julio , Caruntu Dumitru I.
Published: January 2020

This paper deals with the effects of mesh size and time step on the numerical simulations using bvp4c, a Matlab Boundary Value Problem solver, on the time response of electrostatically actuated MEMS resonators. These results are compared to the reduced order model as well as the method of multiple scales to test how accurate these results are at lower amplitudes. The refinement of mesh size leads to more accurate results to a certain extent, as it eventually reaches a convergence. It should be said that the larger the mesh size, the longer the calculations take. A similar result occurs with timestep size. The smaller the timestep the more accurate the results. However, the CPU time increases significantly. However, beyond a certain timestep, any smaller time step would not yield any noticeable differences. Thus it can be said convergence has been reached.
Contact Stress Analysis During Fretting of a Surface Modified Flat-on-Flat With Round Edge
Authors: Dhaka Pankaj , Prakash Raghu V.
Published: January 2020

In the present work, a two-dimensional finite element analysis is carried out to understand the influence of contact geometry and surface treatment on the fretting behavior of a flat with round edge-on-flat plate contact. The fretting pad and plate are modeled using isotropic elastic material properties of Ti-6Al-4V. The mating pair was subjected to a constant normal load followed by a tangential displacement. The effect of contact geometry was studied by independently varying length of the central flat region and radii of corners. Parameters important from the context of fretting viz. contact pressure and normal stress (in tangential direction) were extracted.

The effect of surface treatment was studied by modeling two layers of different elastic modulus and yield strength on the mating surfaces. It is found that addition of intermediate layers of lower elastic modulus and yield strength than the parent material leads to a reduction in both contact pressure and peak tensile stress; the influence was more on the peak tensile stress than contact pressure. Further, the addition of softer and less stiff layers on the pad is noted to be less advantageous than adding it on both pad and substrate or substrate only case. The study suggests that contact geometry should be taken into account while carrying out surface modifications of contact pairs.
Effect of Obesity on Human Squat Exercise
Authors: Caruntu Dumitru I. , Galarza Jose , Vasquez Simon , Ramos Jennifer , Sander Michael
Published: January 2020

This paper deals with the effect of obesity on human squat exercise. The aforementioned clinical condition affects gait (and other daily common activities) in a sense that alterations are made to gait patterns and speed in order to accommodate the patient when participating in physical activities such as walking, making a turn, etc. This work consists of experimental data collected from a subject during moderate squat exercise. Two cases were considered, first, subject with no additional mass, and second, subject with additional mass. The experimental data is collected in the Biomechanics Laboratory at the University of Texas Rio Grande Valley. The squat depth for each trial was kept at a constant height 1 foot from the ground, which corresponds to moderate squat exercise. Phase planes, tools used in nonlinear dynamics, were used to investigate the significant differences between the two cases, no additional weight vs. additional weight. Also, Lyapunov exponents are calculated to assess the stability of the knee joint. There are significant differences in the lateral direction of the centers of mass of both femur and tibia. Moreover the stability of the knee flexion angle decreases with additional mass.
Design and Experimental Study of Radial Piston Pump With Valve Plate Distribution
Authors: Dong Peng , Zhao Shengdun , Wang Yongfei , Zhang Peng , Han Xiaolan , Liu Chen , Meng Dean , Dong Yuanzhe
Published: January 2020

In the field of forging machinery and construction machinery, the hydraulic transmission has become the preferred transmission mode for its high efficiency. The hydraulic pump is the core component of the transmission system as the power component. It is also the main research focus in the field of hydraulic transmission in recent years. According to the axis direction of the piston and the drive shaft, the piston pump can be grouped into radial piston pump and axial piston pump. There are two shafts in the conventional radial piston pumps, which are distribution shaft and drive shaft to complete distribution the pump and transmission work, and the friction between the shoes and the stator is high for its high load and relative sliding speed. In order to reduce the impact of these drawbacks on pump performance, a valve plate is designed to distribute the oil to avoid the stress of the conventional distribution shaft in this paper. The working principle of the radial piston pump is discussed. An electro-hydraulic proportional servo control system was adopted to control the displacement of the pump. The design and manufacturing of the radial piston pump were completed. A test platform is carried out to test the performance and the variable displacement control system of the radial piston pump with a good test result. The radial piston pump has a certain novelty in structure and has practical value.
Soot Mass Estimation From Electrical Capacitance Tomography Imaging for a Diesel Particulate Filter
Authors: Hassan Salah , Anwar Sohel
Published: January 2020

The Electrical capacitance tomography (ECT) method has recently been adapted to obtain tomographic images of the cross section of a diesel particulate filter (DPF). However, a soot mass estimation algorithm is still needed to translate the ECT image pixel data to obtain soot load in the DPF. In this paper, we propose an estimation method to quantify the soot load in a DPF through an inverse algorithm that uses the ECT images commonly generated by a back-projection algorithm. The grayscale pixel data generated from ECT is used in a matrix equation to estimate the permittivity distribution of the cross section of the DPF. Since these permittivity data has direct correlation with the soot mass present inside the DPF, a permittivity to soot mass distribution relationship is established first. A numerical estimation algorithm is then developed to compute the soot mass accounting for the mass distribution across the cross-section of the DPF as well as the dimension of the DPF along the exhaust flow direction. Experimental data has been used to validate the proposed soot estimation algorithm which compared the estimated values with the actual measured soot mass. The estimated soot mass for various soot load amounts were found to correlate reasonably well with the measured soot masses in those cases.
Modeling and Analysis of Noise Barrier Shape Effects on Highway Automobiles Emission Dispersion
Authors: Wang Shaoguang , Wang Xiuling
Published: January 2020

Noise barriers are common configurations along highways. They are originally designed to impede and absorb the noise from vehicles on highways. Recent research has suggested that noise barriers have significant impacts on near-road automobile emissions. Highway noise barriers can make a great difference on the dispersion of air pollutants on and downstream of highway than those with non-barriers features. Certain shaped noise barriers have better performance on reduction noise than others, but the noise barrier shape effects on emission dispersion are still not clear.

In this paper a 3-dimensional computational fluid dynamics (CFD) model has been developed to simulate the shape effects on highway downstream and nearby region emission dispersion. The realizable k-ε turbulence model was adopted to simulate the turbulent flow caused by fast moving vehicles on highway. A non-reaction species transport model was applied to simulate emission dispersion. The model was first used to simulate rectangular shaped noise barriers effect on highway emission dispersion. Results were compared with the data from literature, and good agreements were observed. Further, simulations were conducted to reveal the noise barrier shape as well as various height effects on emission dispersion on highway and nearby regions.
Improving Students’ Learning and Performance Using Mock Tests in Engineering Classes
Authors: Hossan Mohammad Robiul , Islam Nazmul
Published: January 2020

Class performance and classroom environment have a direct impact on students’ learning and long-term retention of key engineering concepts. In addition, class performance is critical for preserving students’ interest and continuous engagement. However, engineering classes are widely rated as boring and monotonous by students due to one-way lectures and lack of application of active learning techniques. In this study, we employed mock tests as an active learning technique to empower students on their own learning through identification of conceptual weakness, reinforcement of understanding and hence, to improve their overall learning and class performance in two different engineering classes at two different universities. Mock tests were conducted on the exam materials before the occurrence of the actual exams. The mock test key with grading rubric was provided to the students. Students were required to grade their mock test based on the rubric. The impact of this technique is evaluated using questionnaires where students were asked to provide their feedback on the enhancement of their understanding of the material, understanding of grading criteria, improvement on their study habits, and identifying conceptual weakness about a topic. The assessment and student feedback shows that the use of the mock test improves the understanding of basic concepts and topics through perspective transformation. It also shows that it improves the average grade of the class, motivates students to study hard, promotes peer discussion, reduces exam related stresses, and strengthens fellowship among students. Thus, mock tests can be used in other disciplines and classes with similar positive effect.
On the Development of a Thermal Comfort Control for Classrooms Conditioned by Split-Type Systems
Authors: Silva Junior Anastacio , Mendes Nathan , Vilain Rogério , Pereira Marcelo , Mendonça Katia Cordeiro
Published: January 2020

Thermal comfort conditions may vary substantially within an air-conditioned room equipped by split-type systems. In this work, the comfort conditions in a classroom were evaluated experimentally based on the PMV index, according to ISO 7730 Standard that defines the thermal satisfaction in occupied environments. The experiment was carried out at three different supply airflows (high, medium and low) and three set-point temperatures (23, 24 and 25°C). The results showed that there is a considerable variation in the air velocity field in the room as well as in the PMV values for three different supply airflows, consequently significant changes of thermal comfort indices can be noticed. Several curves were adjusted aiming to express the values of PMV, deriving a simplified comfort index for rooms conditioned by split-type systems based on dry-bulb air temperature and air speed. The purpose of this adjustment is to obtain an equation that provides the value of the comfort index for cooling purposes. Thus, for a certain condition of use, one can predict what will be the value of PMV in an occupied environment, enabling the implementation of a control system of the comfort according to this new index (ICS). The variables considered in obtaining the curve were the air temperature (Tar) and the air velocity (Var), since these two variables can be controlled directly by the split-type system. The general purpose of this work is to provide experimental data for the development of a low-cost device to automatically control ICS-based thermal comfort in a space conditioned by a split-type system through a single and representative point within the classroom.
Multi-Objective Optimization of Parameters for Milling Using Evolutionary Algorithms and Artificial Neural Networks
Authors: Banerjee Amit , Abu-Mahfouz Issam , Rahman AHM Esfakur
Published: January 2020

Model-based design of manufacturing processes have been gaining popularity since the advent of machine learning algorithms such as evolutionary algorithms and artificial neural networks (ANN). The problem of selecting the best machining parameters can be cast an optimization problem given a cost function and by utilizing an input-output connectionist framework using as ANNs. In this paper, we present a comparison of various evolutionary algorithms for parameter optimization of an end-milling operation based on a well-known cost function from literature. We propose a modification to the cost function for milling and include an additional objective of minimizing surface roughness and by using NSGA-II, a multi-objective optimization algorithm. We also present comparison of several population-based evolutionary search algorithms such as variants of particle swarm optimization, differential evolution and NSGA-II.
Microfluidic Temperature Behavior in a Multi-Material 3D Printed Chip
Authors: Sanchez Derek , Nordin Greg , Munro Troy
Published: January 2020

As analysis systems shrink in size to microfluidic scales and devices, there is a need to improve temperature control in the microscale for temperature-sensitive processes. Technology that combines accurate temperature measurement and 3D spatial control of the temperature distribution is limited by common 2D layer-based microfluidic fabrication techniques but can be realized with 3D printed microfluidic chips. This work presents an iterative process to create a microfluidic chip using multi-material 3D printing to improve temperature sensing and create an even temperature around a target volume. Through an iterative process, verification is presented of fluorophore viability (specifically CdTe quantum dots) after being secured in place by cured PR48 3D printing resin, thus confirming the possibility of fluorescent thermometry as an accurate non-contact temperature sensing method. Numerical analyses of various geometries of chip design iterations are also presented verifying spatially even heating due to the placement of heating sources in the microfluidic chip. Combining the fluorescent thermometry and improved heating will lead to improved temperature control in microfluidic devices.
Measuring the Effect of Local Commercial Roofing Samples on the Thermal Behavior of a Social Interest Dwelling Located in Different Climates in Ecuador
Authors: Litardo Jaqueline , Macías José , Hidalgo-León Rubén , Cando Maria Gabriela , Soriano Guillermo
Published: January 2020

This paper presents an assessment of the effect of the solar reflectance of roofing assemblies on the thermal behavior of a social interest dwelling model located in six representative cities in Ecuador. The model house complies the Ecuadorian building standard. The solar reflectances of 23 local commercial roofing samples were measured following the E1918A Procedure. The thermal behavior of the dwelling was simulated in EnergyPlus. The models use input data, such as: loads and schedules, provided by previous studies on social dwellings. The hours of thermal discomfort based on ASHRAE Standard 55-2013 adaptive model were obtained for each case by varying the experimental solar reflectance of the roofing sample and meteorological data for each hourly time step calculation. Results indicated that the 1808001-50 sample provided between 3240 to 5524 discomfort hours in all cases, being the most suitable roofing assembly for all studied cities due to its higher solar reflectance.
Analysis of a Double Inlet Gerotor Pump: A Dynamic Multi-Phase CFD Approach Accounting for the Fluid Compressibility and Temperature Dependent Properties
Authors: Milani Massimo , Montorsi Luca , Terzi Stefano , Storchi Gabriele , Lucchi Andrea
Published: January 2020

The paper analyzes the fluid dynamic performance of a double inlet Gerotor pump by means of a multi-phase and multicomponent CFD approach. The numerical simulation includes the full 3D geometry of the pump as well as the real physics of the compressible hydraulic fluid and the rotating dynamic motion. The aeration and cavitation phenomena are included in the analysis adopting the Rayleight-Plesset equation and inertia controlled growth model for bubble formation. Cavitation and aeration phenomena are detected, especially when intake pressure is lower than atmospheric pressure. The influence of the fluid temperature variation on the component performance is also numerically predicted. The accuracy of a detailed modelling of the fluid properties variation with respect to the temperature and pressure is addressed and the effects on the numerical results is investigated.

The rotational speeds of the internal and the external gears of the pump and the engagement between the teeth are addressed by means of an overset mesh approach. Constant leak height is considered between the gears and the case, while the overset mesh approach is adopted in order to accurately predict the leakage due to the teeth engagement.

This numerical approach enables to investigate the dynamic performance of Gerotor gear pumps in terms of flow rate and pressure ripples and volumetric efficiency under standard and critical (actual) operating conditions. Good agreement between numerical and experimental results was found for specific operating conditions.
Effects of Drive Side Pressure Angle on Gear Fatigue Crack Propagation Life for Spur Gears With Symmetric and Asymmetric Teeth
Authors: Karpat Fatih , Dogan Oguz , Yilmaz Tufan , Yuce Celalettin , Kalay Onur Can , Karpat Esin , Kopmaz Osman
Published: January 2020

Today gears are one of the most crucial machine elements in the industry. They are used in every area of the industry. Due to the high performances of the gears, they are also used in aerospace and wind applications. In these areas due to the high torques, unstable conditions, high impact forces, etc. cracks can be seen on the gear surface. During the service life, these cracks can be propagated and gear damages can be seen due to the initial cracks. The aim of this study is to increase the fatigue crack propagation life of the spur gears by using asymmetric tooth profile.

Nowadays asymmetric gears have a very important and huge usage area in the industry. In this study, the effects of drive side pressure angle on the fatigue crack propagation life are studied by using the finite element method. The initial starting points of the cracks are defined by static stress analysis. The starting angles of the cracks are defined constant at 45°. The crack propagation analyses are performed in ANSYS SMART Crack-Growth module by using Paris Law. Four different drive side pressure angles (20°-20°, 20°-25°, 20°-30° and 20°-35°) are investigated in this study. As a result of the study the fatigue crack propagation life of the gears is increased dramatically when the drive side pressure angle increase. This results show that the asymmetric tooth profile not only decrease the bending stress but also increase the fatigue crack propagation life strongly.