bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Response of Cross Tube With Crushable Foam-Filled Cellular Core
Authors: Jenson Sean , Ali Muhammad
Published: January 2022

Thin-walled crush tubes and other axial members are often employed as energy absorbers in vehicle chassis to improve crashworthiness of front and side chassis members. Thin-walled axial crushing members are primarily used due to their high strength to weight ratios. Previous works cover extensively the study of thin-walled members under axial crushing loads. Additionally, work has been done exploring the effects of core addition to a standalone thin-walled structure. Functionally graded cellular structures are often employed to enhance energy absorption due to their high strength and stability with minimal added weight burden. Previously, investigation on the addition of composite functionally graded hexagonal extruded cores proved to increase energy absorption capacity and improve stability of the structure. The present study is a continuation of the previous work on functionally graded core material addition to thin-walled crush tubes. Additionally, this study investigated the addition of crushable foam material to the volume of the cellular structures. This study was conducted utilizing ABAQUS explicit dynamic modeling environment. The addition of graded cellular core material with crushable foam provided increased energy absorption capacity of the structure through increased structural stiffness and decreased crush stroke. The structure exhibited progressive folding/collapse mechanisms with a more global crushing response as compared to an empty tube structure. As compared to previous graded cellular core structures, the crushable foam addition promoted a more global structural response and allowed for total energy absorption before structure densification. The addition of core materials within thin-walled crush tubes have shown positive influences on energy absorbing capacity and overall performance of crush tube members.
Simulating Dynamic Tension Effects From an Out-of-Round Unwind Roll
Authors: Reish Benjamin
Published: January 2022

Web handling systems maintain a certain amount of tension in the web and a process speed. Non-circular rolls of material are not uncommon in the real world arising from storing the rolls or imprecise control of parameters. Non-circular rolls at the beginning of a web handling system cause tension spikes in the web as they are unwound. Simulating the tension effects of the non-circular unwind roll is the aim of this paper. A review of numerical models, called primitive elements, for web handling systems is included. The parameters required to describe a web handling system are reviewed. A primitive element for modeling a non-circular roll is introduced. The web handling system model, which uses linear and nonlinear elements in simulation, is compared with experimentally measured data.
Detachable Fine Bump Connection Using Multi-Walled Carbon-Nanotube Bundles for 3D Semiconductor Modules
Authors: Kobayashi Masasuke , Suzuki Ken , Miura Hideo
Published: January 2022

In the 3D chip stacking structure, fine TSV (Through Silicon Via) structures are used in the stacked chips and fine metallic bumps are jointed between the stacked chips for the 3D interconnection. It is not easy, however, to make perfect reliable joints of the huge number of fine bumps in micro scale due to the large bending deformation of each chip with different surface interconnection and dielectric structures and the height fluctuation among the bumps. It is, therefore, very important to establish the largely deformable bump joint system with easy detachability.

In order to solve these problems of fine metallic bump joint structures, multi-walled carbon nanotube (MWCNT) bundle structures were applied to the bump joint structure. To investigate the possibility of detachable fine bumps, high quality MWCNTs were grown by thermal CVD method using acetylene gas. The area-arrayed MWCNTs bundle structures were grown on a silicon substrate and the deformation behavior by compression was measured. The MWCNTs bundles exhibited elastic deformation in the range of strain addition up to 3%. The electrical properties were measured by jointing the MWCNTs films. In the range of compressive strain up to about 30%, the connection between MWCNTs films shows stable ohmic contacts due to the point and side-wall contacts by each MWCNTs. The contact resistance did not change so much even after the 10 cyclic mounting and dismounting.
Numerical Analysis of Flow and Heat Transfer for Supercritical CO2 and Liquid Sodium in Semicircular Mini-Channels
Authors: Qin Lei , Xie Gongnan , Li Shulei
Published: January 2022

The Brayton cycle of supercritical carbon dioxide (S-CO2), is an ideal choice to replace the outdated power cycle. In order to improve the heat transfer performance, the Print Circuit Heat Exchanger (PCHE) has been attracted more attention, since it has a larger specific heat transfer area, compact structure, high efficiency. Based on this inspiration, the flow and heat transfer mechanism of S-CO2 and liquid metal sodium in a straight horizontal semicircular channel were studied, and the flow and coupled heat transfer was numerically analyzed. The influences of flow direction, Reynolds number and channel diameter on heat transfer performance and pressure drop in the semicircular straight channel were further studied. The results demonstrate that the performance of countercurrent designs 8.5% higher than that of the downstream pattern. The total heat transfer coefficient and pressure drop of both cold and hot channels in PCHE increase linearly with the rise in Reynolds number. The buoyancy effect affects the heat transfer when the pipeline velocity is small. The effect of buoyancy on heat transfer basically disappears when the pipeline velocity is high. When the diameter of the hot side channel is fixed and the diameter of the cold side channel is increased from 0.8mm to 1.1mm, the total heat transfer coefficient in the cold channel is increased by 8%, while the total heat transfer coefficient in the hot channel is increased by 51.6%. Through the above research in this paper, some heat transfer characteristics of sodium and supercritical carbon dioxide in PCHE are obtained, which is contribute to the design and optimization of the heat exchanger in sodium cooled fast reactor.
Towards a Digital Twin Setup for Individualized Production of Fabricated Components
Authors: Hultman Hugo , Cedergren Stefan , Söderberg Rikard , Wärmefjord Kristina
Published: January 2022

As the aerospace industry continues its shift towards digital manufacturing, an increased use of inline sensors and data collection is creating an opportunity to further optimize the production process. Measurements from individual parts make it possible to adapt each process to current conditions rather than running all processes nominally. This is sometimes described as individualized production as opposed to traditional mass production. The concept of a digital twin for manufacturing has recently gained more attention as a promising method for individualized production. A digital twin collects data from a real environment to create a virtual copy of a physical phenomenon, which can be used to predict how its real counterpart is going to behave. The approach has been proposed for a manufacturing environment where it would be used to predict the outcome of a production process. This could prove particularly useful for fabrication processes, a method used for making aero engine parts by joining large assemblies of smaller parts through welding. This paper presents functionalities that can be used to implement a digital twin in a high precision fabrication process, outlining different approaches for data collection, data analysis, and adaptive process adjustments. An example is shown where physical measurements are used to improve the predictive capabilities of a welding simulation in order to enable more accurate process adjustments.
Validation of an Indian Rail Vehicle Model Using Ride Indices From Oscillation Test Trials
Authors: Singh Sultan , Kumar Anil
Published: January 2022

Safety and comfort are more critical factors prior to efficient and economical travel for any passenger train. Due to the wheel-rail interaction at high speed, high amplitude vibrations occur that deteriorate the ride comfort of the passengers. In this paper, a multi-body dynamic model is developed by using Adams/VI-Rail software. Actual parameters of track and LHB coach are considered to simulate the rail vehicle model. Sperling’s ride index (Wz) method determines the ride indices values at different speeds with random track irregularity. The proposed multi-body dynamic model is analysed, and the results are compared with oscillation test trials performed and reported by the Research Design and Standards Organisation (RDSO). Obtained results were in good agreement and within permission values. The validated model can be extended to study the improvements in ride quality and ride comfort by introducing a semi-active suspension system based on an MR damper.
Experimental Investigation of High-Speed Flows Past Pillow Plates
Authors: Sundermeier Stephan , aus der Wiesche Stefan
Published: January 2022

This paper presents an experimental investigation of highspeed flows past Pillow-Plate Heat Exchanger (PPHE) geometries by means of conventional and focussing schlieren optics. Past investigations have already shown that PPHE has positive flow behaviours compared to other heat exchangers. The static pressure drop along a pillow-plate surface is relatively low, but the profile offers a good mixing and heat transfer behaviour. These characteristics were not very well researched for higher Mach numbers until now.
Performance Characterization of Hollow Fiber Direct Contact Membrane Distillation Module
Authors: Asiri Jaber M. , Alasiri Abdulaziz M. , Caspar Justin , Xue Guanyang , Oztekin Alparslan
Published: January 2022

Computational fluid dynamics (CFD) simulations were carried out to study the performance of a single hollow fiber in a direct contact membrane distillation (HF-DCMD) module for a desalination process. The feed solution is seawater with a salt (NaCl) concentration of 35 g/L. The Navier-Stokes, mass and energy transport equations are considered, with a coupled boundary condition imposed by the membrane. The system is investigated to examine sensitivity toward the membrane thickness, pore size, and inner hollow fiber diameter based on existing commercial fibers. Two membrane thicknesses (300 μm, 500 μm), two membrane pores sizes (0.2 μm, 0.45 μm), and two inner diameters (1.2 mm, 1.8 mm) are studied in the laminar regime at fixed operating conditions. The presence of temperature polarization causes a significant drop in the water permeation in the DCMD system due to reduced driving force across the membrane. The characterization of polarization inside the hollow fiber will be the focus of this work. It was found that the vapor flux was most sensitive to the membrane thickness (a 30% flux increase) versus the inner diameter (2% flux increase). The pore size is also a very influential parameter (20% flux increase), moving from optimal to less-optimal properties.
Three-Dimensional Deviation Analysis of High-Speed Spindle Assembly Based on Skin Model Shapes
Authors: Tian Ang , Jin Sun , Chen Kun , Liu Shun , Li Hangyu , Niu Zhihua
Published: January 2022

The high-speed motorized spindle is the core component of the machine tool, and its assembly accuracy directly determines the quality of the processing product and the service life of the spindle itself. As a typical revolving components assembly, it is critical to ensure that the radial and axial runout performance of the assembly is extremely excellent to satisfy the requirements of high precision and rigidity. Meanwhile, geometric deviations are inevitably observable on manufactured components of spindle, especially the form deviations of revolving part have huge influences on the quality and function of spindle. However, geometric deviations are reduced to dimensional and orientation defects without considering form deviations in most previous models of deviation analysis. Skin Model Shape of a work piece is a discrete geometry representation of the physical interface between the work piece and its environment, which is based on a representation of non-ideal work pieces employing discrete geometry representation schemes. This paper presents a deviation analysis method for high-speed motorized spindle assembly using Skin Model Shapes, concerning all kinds of geometric deviations of the components. Deviations of the components are represented by the Skin Model Shapes, which is a point cloud-based discrete representative that is able to model the actual toleranced surfaces instead of the ideal or associated ones in an assembly. This paper solves the constrained objective function by means of the ideas of sequential quadratically constrained quadratic programming (SQCQP) method, which can solve problems with high degree of non-linearity and also has relatively small amount of calculation. The procedures outlined in the paper are quite general and can be used for tolerance analysis of any assembly process.
Dynamic Trajectory Planning of a 7-DOF Surgical Robot Based on HER-DDPG Algorithm
Authors: Hou Qitao , Gu Chenchen , Wang Xiaoyu , Zhang Yating , Zhao Ping
Published: January 2022

Traditional trajectory planning approaches are currently lacking in intelligence and autonomy. We used the reinforcement learning approach to solve the autonomous trajectory planning of the robot arm to avoid obstacles with uniform motion and hit the target point quickly with obstacle avoidance planning for surgical robots taken as the practical background. We used the algorithm of experience playback mechanism combined with off-policy DDPG based on reinforcement learning, and after several iterations, the robot completed trajectory planning with obstacle avoidance autonomously. Moving obstacles were added to roughly simulate the autonomous obstacle avoidance of a surgical robotic arm with moving medical personnel or mobile instruments in the operating room, based on the simple trajectory planning example of Open-AI Open-Source Project Baseline, combined with the research context. Sparse rewards were used for each iteration based on the HER algorithm, so that each attempt could gain experience. The HER-DDPG method can quickly complete the manipulator’s trajectory planning in a simulation environment, which is critical for the surgical robot’s autonomous positioning in the real world. Furthermore, the experience playback system has been tested to allow full use of sparse rewards and handle parallel tasks equally well.
Simulation and Accuracy Guarantee Technology of Fuselage Component Trial Assembly Based on Dynamic Process Model
Authors: Kang Yonggang , Chen Mingyuan , Chen Xiduo , Chen Zhihao , Xiao Huan
Published: January 2022

Modern aircraft fuselage size is large, structural rigidity is weak, the docking process is complex, accuracy guarantee is difficult and assembly efficiency is low. Especially in the plug-in butt joint assembly process of large fuselage parts, there is the inherent problem of invisible and unmeasurable docking end surfaces. It is more likely to lead to interference or uneven gaps in the docking process, and eventually lead to repeated trial assembly and decline in the consistency of the connection quality. That will affect the assembly efficiency and fatigue characteristics of the local structure. Aiming at the plug-in butt joint assembly of large fuselage parts, this paper integrates digital measurement technology, numerical control positioning technology and virtual simulation technology, through measurement modeling and trial assembly simulation to guide the digital positioning and docking process. It makes the invisible and unmeasurable process of insertion digitally visible. Through the integration of point cloud data acquisition and pre-processing, digital twin modeling and assembly simulation, a dynamic process model for trial assembly simulation is constructed. A complete test environment for the joint assembly of the fuselage barrel parts was built. Research was conducted on the reduced test pieces of MA700 front fuselage and middle fuselage. We developed a large space measurement module, a spatial attitude solution module, an integrated control module and a virtual simulation module. The effectiveness of the fuselage component trial assembly simulation based on dynamic process model and accuracy assurance technology was verified.
Mechanical Properties of Snap-Fits Fabricated by Selective Laser Sintering From Polyamide
Authors: Detzel Samuel , Sigling Annette C. , Lueth Tim C.
Published: January 2022

Snap-fits provide a quick, simple and reversible way to join larger additively manufactured parts. They take up little space and are flexible in their placement. The mechanical properties of snap-fits fabricated by selective laser sintering are not well explored. While the mechanical properties of the bulk material are available, these do not sufficiently describe the behavior of thin and flexible structures. The purpose of this research is the investigation of the mechanical properties of SLS-fabricated snap-fits. We explored the influence of geometric parameters, orientation during the manufacturing process and post-processing by chemical vapor smoothing as well as stress cycling. In a series of experiments, we measured the retaining force applied along the axis of the joint as well as the force necessary to open the snap-fit by pressing sideways. Based on literature, we formulated the relationship between geometry and mechanical properties. The resulting formulas were tested experimentally and corrected if necessary. The results show that the effective flexural modulus is 45% lower in cantilever snap-fits with width and thickness of less than 3 mm compared to bulk material. Smoothing reduced the flexural modulus as well as the friction even further.
Effect of Thermal Expansion Coefficient, Viscosity and Melting Range in Simulation of PCM Embedded Heat Exchangers With and Without Fins
Authors: Alam Tanjebul , Bacellar Daniel , Ling Jiazhen , Aute Vikrant
Published: January 2022

Phase change material heat exchangers (PCMHX) have animportant role in integrating renewable energy systems. PCMHX can offer high storage density at various temperatures of interest and can be used for grid load shifting purposes. Numerical models enable engineers to estimate PCMHX performance for different design parameters and operating conditions. Modeling phase change phenomena is challenging due to the complex time-dependent nature of the process. The accuracy of models is highly sensitive to PCM thermo-physical properties. Thermal expansion coefficient (β), viscosity (μ) and melting temperature range (MR) of a PCM are important properties, especially when natural convection is not negligible. In PCMHX modeling, using less than accurate values for these properties can have significant impact on the simulation outcomes. These propertiesand discussions thereof are not readily available in the literature. This paper presents a brief review of the literature and a numerical study investigating the model sensitivity to the above-mentioned properties for PCMHX with and without fins. CFD is used to evaluate the charging (melting) phenomena. The study quantifies the impact of uncertainty in these properties on the melting rate and temperature profile. Constant wall temperature was consideredas heat source with no heat loss to ambient. The results show that β and μ has significant effect on the melting rate andevolution of the melting front. For a non-finned domain when comparing results for different published values of β and μ, the deviation in melting time can be up to 12.9% and 57.6% respectively. For high wall temperatures, change in melting range did not impact melting time. But when the wall temperature is reduced, up to 9.8% deviation in melting time is observed.
Computational Model for an Electrochemical Hydrogen Compressor
Authors: Aziz Majid , Aryal Utsav Raj , Prasad Ajay K.
Published: January 2022

One of the main challenges in developing the hydrogen infrastructure is the distribution and storage of hydrogen. A common method to store hydrogen is as a compressed gas. Electrochemical compression (ECC) is a promising technology that can sidestep some of the disadvantages present in conventional mechanical compressors. ECC is an externally powered device that employs an electrochemical cell containing a polymer electrolyte membrane (PEM) to compress the gas. This work presents a detailed 2D ECC model developed using COMSOL Multiphysics 5.6, that considers the important phenomenon of back diffusion resulting from the high pressure differential between cathode and anode during compression. Results from the current simulations are validated against experimental results obtained previously in our lab. Simulations were first conducted for the unpressurized cathode and the performance was analyzed in terms of the polarization curve. Next, simulations were conducted for the pressurized cathode, with and without considering back diffusion. In the absence of back diffusion, the pressure ratio reaches the value predicted by the Nernst equation. However, the presence of back diffusion greatly reduces the pressure ratio similar to experimental observations.
Experimental and Computational Study of Direct Contact Membrane Distillation
Authors: Kim Deliya , Caspar Justin , Romero Carlos , Neti Sudhakar , Oztekin Alparslan
Published: January 2022

Experimental and computational studies of direct contact membrane distillation (DCMD) are conducted. The permeate flux is measured in a module containing a flat sheet membrane. Polytetrafluoroethylene (PTFE) hydrophobic membrane (Membrane Solutions, FPB045A16) with a nominal pore size of 0.45 μm, the thickness of 179∼239 μm, the porosity of 80% is used in the experiments. The feed solution is a binary mixture of water and NaCl. The inlet feed temperature is fixed at 70°C, and the feed Reynolds number is varied between 500 and 2000. Two inlet feed concentrations, 0 and 35g/L, are considered. The permeate flow rate was kept constant at Re of 1300 and temperature of 20°C. Three-dimensional steady-state computational fluid dynamics (CFD) simulations are performed using the laminar model. The Navier’s Stokes, energy, and mass transport equations in each channel coupled with flux boundary conditions imposed at the membrane surface are solved. The predicted module-averaged flux is compared to measured data for all operating conditions. Measured and predicted flux agrees well; validating both experiments and model, Temperature polarization in the feed and permeate channel and concentration polarization in the feed channel are characterized by validated CFD simulations.
Wind Tunnel Data Acquisition System
Authors: Bishop Riley , Fisher Wesley , Doom Alex , Hollingsworth Elena , Mazzoni Brian , Chidurala Manohar
Published: January 2022

A team of mechanical engineering students at Western Kentucky University designed a subsonic wind tunnel data acquisition system through LabVIEW to analyze the forces acting on an object in external air flow. The experimental setup provides future fluid mechanics laboratory students a hands-on procedure to study aerodynamic forces such as lift and drag. The physical models tested include two 3D-printed cylinders and a NACA 0012 airfoil placed in the wind tunnel test section. The cylinder shape was chosen, because it provides a simple flow field that can easily be used to verify the accuracy of the system, and the NACA 0012 was selected for the simplicity of symmetric airfoil theory calculations. Pressure transducers were used to measure pitot tube velocity readings as well as the pressure at 16 points around the upper 180 degrees of the objects. The resulting pressure distribution on the surface of the bodies was then applied to calculate lift and drag forces acting on the objects. A force balance was also designed to securely mount objects in the wind tunnel while directly measuring the total lift and drag forces, calculating the moment about the leading edge, and monitoring the angle of attack. The force balance results can be used to verify the experimental results from the pressure distribution data. A LabVIEW program was written to communicate directly with data acquisition hardware (NI CompactDAQ), set experimental parameters such as air flow speed and sample rate, record data, and interpret the results through a single user interface. Inviscid theory was used to theoretically predict the ideal drag acting on the cylinder, and symmetric thin airfoil theory was used to predict the ideal lift acting on the airfoil. Along with theoretical models, CFD analysis was performed to simulate a controlled experiment and validate the experimental results. Though experimental data has not yet been collected, the LabVIEW code has been tested using simulated data, and the accuracy of the pressure transducers has been confirmed by comparing pressure readings to controlled manometer readings. The system is expected to provide accurate data limited to the maximum speed of the subsonic wind tunnel currently owned by the Thermofluids Laboratory at Western Kentucky University. Future improvements of this project could include purchasing a more capable wind tunnel to run experiments in the turbulent flow regime, as well as a larger test section to avoid error from wall effects. This experimental set up has laid the groundwork for a multitude of future studies. It can be used to observe aerodynamic forces acting on more complex NACA airfoil shapes, rotating plates, cylinders and spheres, wind turbine blades, ground vehicles, airplanes and more.
Deformation Manifold Learning Model for Deformation of Multi-Walled Carbon Nano-Tubes: Exploring the Latent Space
Authors: Yadav Upendra , Pathrudkar Shashank , Ghosh Susanta
Published: January 2022

A novel machine learning model is presented in this work to obtain the complex high-dimensional deformation of Multi-Walled Carbon Nanotubes (MWCNTs) containing millions of atoms. To obtain the deformation of these high dimensional systems, existing models like Atomistic, Continuum or Atomistic-Continuum models are very accurate and reliable but are computationally prohibitive for these large systems. This high computational requirement slows down the exploration of physics of these materials. To alleviate this problem, we developed a machine learning model that contains a) a novel dimensionality reduction technique which is combined with b) deep neural network based learning in the reduced dimension. The proposed non-linear dimensionality reduction technique serves as an extension of functional principal component analysis. This extension ensures that the geometric constraints of deformation are satisfied exactly and hence we termed this extension as constrained functional principal component analysis. The novelty of this technique is its ability to design a function space where all the functions satisfy the constraints exactly, not approximately. The efficient dimensionality reduction along with the exact satisfaction of the constraint bolster the deep neural network to achieve remarkable accuracy. The proposed model predicts the deformation of MWCNTs very accurately when compared with the deformation obtained through atomistic-physics-based model. To simulate the complex high-dimensional deformation the atomistic-physics-based models takes weeks high performance computing facility, whereas the proposed machine learning model can predict the deformation in seconds. This technique also extracts the universally dominant pattern of deformation in an unsupervised manner. These patterns are comprehensible to us and provides us a better explanation on the working of the model. The comprehensibility of the dominant modes of deformation yields the interpretability of the model.
Tritium Absorption on Carbon Nanostructures
Authors: Atchley Bryce , Wu Erica , Park Jungkyu , Farfan Eduardo
Published: January 2022

In the present research study, we utilize a molecular dynamics simulation to investigate the possibility of using multiple graphene sheets for tritium control. The graphene sheets are equilibrated to temperatures of 10k, 100k, 300k, 600k, 900k, or 1200k in a simulation. After equilibration, the tritium atoms are made to travel toward the graphene sheet with uniform velocity. The velocities of tritium atoms are selected so that incident energies may be 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 eV. Reflection is shown to be the dominant interaction at low tritium incident energy, with a sharp decline in reflection rates as energy increases. For the case of a single layer of graphene, reflection rates reach a minimum around 5eV and steadily climbs as energy is increased to 10eV. Absorption rates are shown to increase with increasing tritium energy until energies are very high, around 5 eV. After 5 eV, absorption rates decrease as incident energy increases. Penetration rates of incident tritium atoms remain low until 5 eV, after which the rates increase steadily. Higher graphene equilibration temperatures yield higher absorption rates at low incident energies but lead to lower absorption rates at high incident energies. At low incident energies, reflection is favored more at lower temperatures, while graphene temperatures do not seem to affect reflection rates much at high incident energies. Lastly, penetration rates are consistently higher at higher graphene temperatures. The larger amount of energy present in the structure at higher temperatures allows for the C-C bonds in graphene to be more readily broken. The results obtained in this research study will be used to develop novel nanomaterials that can be employed for tritium control.
Aeromedical Evacuation Skeletal Traction
Authors: Rabb Ethan , Zifchock Rebecca , Nowicki Margaret , Paquin Jeremy , Posner Matthew
Published: January 2022

The purpose of this project is to design a device that provides skeletal traction to a patient with a fractured femur in an aeromedical evacuation environment. Skeletal traction is typically provided by using weights and cable to provide tension onto a fractured limb. However, in an aeromedical evacuation environment, the forces vary and the environment is not stable, so the traditional method to provide skeletal traction is not suitable. Therefore, we designed and tested a device that could provide skeletal traction to a femoral fracture in an aeromedical evacuation environment.
Targeted CAD/CAM Workshops for Freshmen to Improve Overall Performance
Authors: Kocharian Tikran , Manoharan Sanjivan
Published: January 2022

Introduction to Computer Aided Design (CAD)/Computer Aided Manufacturing (CAM) is typically covered at the freshman level. This course is especially crucial for institutes where students engage in cooperative education with employers in the manufacturing industry. In addition, given the demanding nature of the course, retention at the freshman level has been a persisting issue. The culminating experience for this particular course requires all students to take the Certified SolidWorks Associate (CSWA) exam. Unfortunately, 54.7% of the students failed the CSWA exam in the previous offering. A major issue has been the insufficient course contact hours for this content-heavy course. In addition to CAD/CAM introduction, there are several other courses in the freshman sequence resulting in a total class time of only 50 minutes per week. Taking this into consideration, targeted practical workshops were held every three weeks in the latter half of the semester to better prepare the students. The workshops were carefully designed to effectively cover the following areas: fluency in SolidWorks, critical thinking and decision making, design intent, CAD management, and software customization. A total of three workshops were held remotely for the students enrolled in a section taught by the primary author. The control group comprised of the remaining students enrolled in other sections. The student response for the workshops was overwhelmingly positive, and there was an evident improvement in the performance on the CSWA exam. All students who attended the workshop passed the certification exam thus improving the overall course failure rate by over 10%.
A Comparative Study on Feature Descriptors for Relative Pose Estimation in Connected Vehicles
Authors: Nayak Anshul , Eskandarian Azim , Ghorai Prasenjit , Doerzaph Zachary
Published: January 2022

In cooperative perception, reliable detection and localization of surrounding objects and communicating the information between vehicles is necessary for safety. However, V2V transmission of huge datasets or images can be computationally expensive and pose bandwidth issue often making real-time implementation non-feasible. An efficient and robust approach for ensuring such cooperation can be achieved by relative pose estimation between two vehicles sharing a common field of view. Especially when an object is not in the field of view of an ego vehicle, dynamically detecting the object and transferring its location in real-time to the ego vehicle is necessary. In such scenarios, reliable and robust pose recovery at each instant ensures accurate trajectory estimation by the ego vehicle. In our current study, pose recovery is achieved through common visual features present in a pair of images. Traditionally, algorithms like SIFT and KAZE have been used to detect and match features between an image pair from sensors looking from a different perspective. However, recently with the advent of binary detection and description algorithms like ORB and AKAZE, we have decided to analyze and show a comparative study on the efficacy and robustness of such methods for feature matching. The performance metrics for each method are decided based on total detected features, the number of good matches, and the computation time. The current study also tests the performance of each method under varying degrees of angular orientation and camera exposure setting, which can be helpful for motion estimation under dim light. Overall, AKAZE was computationally faster among all, while ORB and SIFT fared equally on other parameters. The corresponding research can be a precursor to future trajectory prediction of dynamic objects by the ego vehicle when there is a sudden loss of communication with the lead vehicle after the initial data transfer.
Peculiar Transmission Manipulation of Antisymmetric Lamb Waves via a Surface-Bonded Single-Layer Elastic Meta-Structure
Authors: Tian Yiran , Shen Yanfeng
Published: January 2022

Metasurfaces, treated as equivalent two-dimensional (2D) metamaterials, have the advantages of compactness and simplicity. In spite of the recent related booming researches, the non-perforated or surface-bonded ultrathin elastic metasurfaces have seldom been reported, since there exists a big challenge in designing such a single unit to satisfy the requirements of 2π phase span and simultaneous high transmission. In this paper, an elastic meta-structural functional unit is carefully designed, enabling an effective wave manipulation application for Structural Health Monitoring (SHM) and Non-destructive Evaluation (NDE) communities. Through conducting a series of parametric studies, the full 2π phase span and high transmittance can be achieved by a singl-elayer meta-structural unit. When proceeding to calculate the phase profile for realizing the full 2π phase span, the height of the unit cell stub is tuned by exploring a finite element model (FEM) using harmonic analysis. The nephograms of the phase shift varying with the stub height and excitation frequency exhibit the successful achievement of a full 2π span covering a wide frequency range. Further, to enable a high transmittance at the same time, two sets of parametric studies are complementally carried out through adjusting two additional structural parameters. Subsequently, various single-layer elastic meta-structures are designed with the proposed unit cell for the peculiar transmission manipulation of antisymmetric Lamb waves demonstrated by numerical simulations. The paper finishes with summary, concluding remarks, and suggestions for future work.
Numerical Study of the Effect of Burner Position and Reformer Tubes on the Design of an Annular Steam Methane-Reforming Reactor for Hydrogen Production
Authors: Rohini Ajith Krishnan , Lee Hee Joon
Published: January 2022

This work presents a computational fluid dynamic-based numerical study of the effect of burner position and number of reformer tubes on an annular steam methane-reforming (SMR) reactor for hydrogen (H2) production. Three different burner configurations such as single co-axial inside burner (SCIB), single top burner (STB), and multiple top burner (MTB) arrangements were considered. The number of reformer tubes inside the reactor was varied to four-, six-, and eight-tube arrangements. This study revealed that the STB configuration was preferable to the SCIB and MTB configurations owing to the effective utilization of heat from the combustion gas and uniform temperature distribution. The flue-gas inlet temperature, reformer inlet velocity, and number of reformer tubes were found to exert a significant effect on the SMR reactor. Additionally, the SMR design was modified by installing a sleeve around the outer reformer with a sleeve spacing of 15 mm and a burner at the bottom. The effect of the sleeve design on the H2 yield, temperature distribution, and wall heat-transfer coefficient was also presented.
Peridynamics for Quasistatic Fracture Modeling
Authors: Bhattacharya Debdeep , Diehl Patrick , Lipton Robert P.
Published: January 2022

Fracture involves interaction across large and small length scales. With the application of enough stress or strain to a brittle material, atomistic scale bonds will break, leading to fracture of the macroscopic specimen. From the perspective of mechanics fracture should appear as an emergent phenomena generated by a continuum field theory eliminating the need for a supplemental kinetic relation describing crack growth. We develop a new fast method for modeling quasi-static fracture using peridynamics. We apply fixed point theory and model stable crack evolution for hard and soft loading. For soft loading we recover unstable fracture. For hard loading we recover stable crack growth. We show existence of quasistatic fracture solutions in the neighborhood of stable critical points for appropriately defined energies. The numerical method uses an analytic stiffness matrix for fast numerical implementation. A rigorous mathematical analysis shows that the method converges for load paths associated with soft and hard loading. For soft loading the crack becomes unstable shortly after the stress at the tip of the pre-crack reaches the material strength.
Electrophysiology of Phosphatidylserine Bilayer Membranes Using Electrochemical Impedance Spectroscopy
Authors: Tantawi Khalid H. , Hunnicutt Hope
Published: January 2022

In this work the electrical properties (resistance and capacitance) of the phospholipid phosphatidylserine, which was recently found to be the major constituent of plasma membranes of cancer cells that undergo chemotherapy, were measured using electrochemical impedance spectroscopy (EIS) in the frequency range 0.01 Hz to 100 kHz. The measurements show that the resistance of phosphatidylserine is 800 kω and the capacitance is approximately 90 pF. These numbers are significantly less than the reported resistance and capacitance of a lipid bilayer membrane that is composed primarily of phosphatidylethanolamine, which is the major constituent in plasma membranes in normal cells. Consequently, the results show that the electrical conductivity of the membranes of cancer cells increase significantly following chemotherapy treatments.
Investigation of Pore Size Distribution and Mechanical Properties of Porous Polydimethylsiloxane (PDMS) Structures Using Solvent Evaporation Technique
Authors: Abshirini Mohammad , Altan M. Cengiz , Liu Yingtao , Saha Mrinal C.
Published: January 2022

This paper reports a fast and straightforward method for controlling the pore size distribution and mechanical properties of porous polydimethylsiloxane (PDMS) structures. The solvent evaporation-induced phase separation is implemented for the fabrication of absorbent PDMS sheets. The ternary polymer solution containing PDMS, water (nonsolvent), and three different solvents are prepared. Tetrahydrofuran, Heptane, and Toluene are the solvents explored in this study. The stepping heat treatment is applied to the sample to control the solvent evaporation and trigger the phase separation. The pore morphology and pore size distribution are explored using the scanning electron microscope images captured from the internal surface. The results demonstrate that the pore microstructure is sensitive to the solvent used in polymer solution preparation. Besides, the mechanical properties of the porous PDMS sheets are characterized by tensile testing of the dog bone-shaped specimens cut from the sheets. The results indicate that the elastic modulus of the porous PDMS is dependent on the pore size distribution of the structure. Moreover, the mechanical properties and pore microstructure are shown to be dependent on the solvent type used in the mixture.
Energetic Management of Power Plant Protection and Control Activities by Applying Maintenance Principles Based on Reliability
Authors: Radulescu Victorita
Published: January 2022

In recent decades in Romania, many power plants have been built using renewable resources. We are now facing new challenges related to electricity transmission lines, which need to be adapted to these new conditions. A complex and extensive solution associated with the rehabilitation of the existing network system, based on new reliability concepts, is analyzed. Energy management must be adapted to these new parameters imposed by electricity consumption. Some aspects of modernization activities that cover new technologies, equipment and installations, but also the maintenance and ongoing management of existing installations are illustrated. A multi-stage algorithm of this congestion management is proposed, starting from the available transport capacity between two nodes or between two interconnected areas. This algorithm also provides a method for classifying problems that go as far as disconnecting the generating units, starting with the worst case. A redistribution solution is proposed depending on the local power generated. As a case study, the situation at Lacu Sarat station is presented correlated with the main causes that generated incidents. A solution is recommended to minimize the load in the nodes by redistribution, due to the problems encountered by connecting the new wind farm built nearby.
Topological Optimization of Piezoelectric Materials for the Control of Wave Propagation in Periodic Structures
Authors: Shi Jiahui , Fan Yu , Li Lin
Published: January 2022

Piezoelectric materials can be introduced as the additional components into the periodic structures as they can couple the mechanical and electric fields. However, the added mass is always constrained in practical engineering. A method is needed to guide how to posit the piezoelectric materials on the host structure under the mass limit. In this work, we develop a numerical method to determine the best distribution of piezoelectric materials on the host structure in order to control the wave propagation in the periodic structures. This is based on the fact that the propagation properties of the waves in the mechanical field can be regulated by electric impedance shunted to the piezoelectric materials. The coupling strength between the mechanical field and the electric field is quantified by the wave electromechanical coupling factor (WEMCF). It is related to the geometric of the piezoelectric materials only. As the periodic structures are constructed by the identical unit cell, the aim is to design the distribution of the piezoelectric materials on the unit cell. There is no constrain on the shape of piezoelectric materials in the optimized method, only the overall mass is limited. A linear weighing of stress components is proposed as the criterion to determine the priority of locations for piezoelectric materials. In the proposed method, the piezoelectric materials are introduced to the FE model by adding the additional piezoelectric element layers on the host structure. Details for handling polarization direction, electrode connection and the electric circuit parameters selection are also presented. A 1D thin-wall box beam is taken as the application example. Results show that the Bragg band gap can be adjusted to cover the target frequency range under the optimization design with the 10% mass limitation.
Multiobjective Reliability-Based Design of an Aircraft Wing Using a Fuzzy-Based Metaheuristic
Authors: Sleesongsom Suwin , Winyangkul Saksan , Bureerat Sujin
Published: January 2022

This research presents a new multiobjective fuzzy-based metaheuristic (MOFBMH) for aircraft wing design, which considers the uncertain structural design based on a fuzzy set model. Usually, the objective of this kind of design problem is to minimize weight of the composite wing with failure possibility constraints rather than converting it to multiobjective optimization with a fuzzy variable vector for material properties and loading conditions. The proposed technique is established in the form of multiobjective optimization, which sets the possibilistic safety index (PSI) as an objective function along with structural weight. This technique can explore a possible reliability solution set in one optimization run, which is advantageous. The present technique is one of the posteriori-techniques that start with finding all solutions and choosing it later. Two design examples are used to demonstrate the present technique i.e.simple cantilever beam and composite aeroelastic wing design problems.The results show the proposed technique can explore all possible structures, which are more conservative, and realizable.
Development and Manufacturing of Cervical Stenosis Models for the Integration Into a Neurointerventional Simulation Model
Authors: Wortmann Nadine , Guerreiro Helena , Kyselyova Anna , Frölich Andreas M. , Fiehler Jens , Krause Dieter
Published: January 2022

Ischemic stroke is one of the main causes of death and disability worldwide. This can be caused directly by vessel occlusions or secondarily, through constrictions, so-called stenoses. It is therefore important to treat the stenosis as quickly as possible in order to minimize long term patient disability. Since endovascular stroke treatment is a complicated procedure, performed under high time pressure, the establishment of an appropriate training environment is of particular importance. The aim of this study is the development and manufacturing of cervical stenosis models to simulate the endovascular treatment in a physical stroke training and research model to replace training on animal models. Additive Manufacturing (AM) is used to produce the models, as its geometric freedom makes it possible to assemble complicated anatomical shapes. In a series of tests in a full physical simulation environment with medical professionals, the concept of an outer shell held together with two snap fasteners or by Dual Lock™ velcro was shown to be suitable. For the fabrication of the vascular models, the Formlabs material Flexible 80 A Resin proved to be more promising than the Elastic Resin, as the latter ruptured too easily due to the compression in the molded shell.