bluuebunny/crossref_metadata_2025 huggingface dataset:
Steerable Unidirectional Wave Emission From a Single Piezoelectric Transducer Using a Shape Memory Alloy Composite Metasurface
Authors: Song Yihao , Shen Yanfeng
Published: February 2021

Structural Health Monitoring (SHM) and Nondestructive Evaluation (NDE) systems generally adopt piezoelectric transducers which emit omnidirectional wave fields. The achievement of directionality of guided wave generation will benefit the structural sensing purpose, which allows better detection and localization of the damage sites.

In this study, a type of metamaterial ultrasonic radar is proposed for the steerable unidirectional wave manipulation. It contains a circular array of unit cells stuck in an aluminum plate which are delicately arranged in a circular fashion. Each unit cell is composed of a shape memory alloy substrate and a lead stub. The controllable bandgap of such metamaterial system can be achieved due to the stiffness change of nitinol between its martensite phase and austenite phase under a thermal load. This research starts with a Finite Element Model (FEM) of the unit cell to compute its frequency-wavenumber domain dispersion characteristics, demonstrating the adjustable bandgap feature. Then, numerical modeling of the metamaterial radar is performed by shifting the bandgap of one sector of the metasurface away from the excitation frequency. The modeling results demonstrate that the martensite phase metasurface area forms a bandgap region where guided wave energy cannot penetrate, while the bandgap of the austenite sector shifts away from the excitation frequency, opening up a transmission path for the ultrasonic waves. By rotating the austenite sector, the metamaterial structure can work like a wave emission radar, realizing of the steerable unidirectional wave radiation with a single transducer. Such an active metasurface possesses great application potential in future SHM and NDE systems.
Dendrite Suppression and Energy Density in Metal Batteries With Electrolyte Flow Through Perforated Electrodes
Authors: Parekh Mihir , Rahn Christopher
Published: February 2021

Previous research shows that forced advection through porous lithium metal electrodes can eliminate dendrite growth in lithium metal batteries. In this paper, we study the effect of creeping electrolyte flow through perforated metal anodes on dendrite growth and energy density by using a 2D COMSOL Multiphysics model. The flowing electrolyte enhances plating inside the slot (2D model of pore) and reduces plating on the part of electrode directly facing the counter-electrode. This reduces the chances of short circuit via dendrite growth. Higher electrolyte velocity reduces the plating current density in the inter-slot gap and increases the amount of plating in the slot. Larger slot separation and thicker electrodes alleviate dendrite growth but lower the specific charge density. Wider slots enhance the possibility of short circuits and narrower slots may get plugged due to plating inside the hole. Thus, slot width, slot separation, and electrode thickness should be optimized to ensure high specific charge density and non-dendritic plating in the inter-slot gap.
Non-Volatile Fraction Effects in Dispersed Vacuum Spray Flash Evaporation
Authors: Guo Guangyu , Deng Hongling , Zhu Chao , Ji Zhiming
Published: February 2021

Spray flash evaporation has been widely used in spray cooling and thermal distillation as a technology of heat/mass transfer enhancement. In a vacuum spray flash process, the vapor is instantly extracted by vacuuming, while the supersaturated droplets are further cooled by the continued spray flash until becoming saturated or discharged. Hence, in the evaporator, non-equilibrium exists not only in the flash evaporation driven by the pressure difference between droplet and ambient but also in the temperatures of yields, namely, generated vapor and discharged liquid with or without precipitates.

To deeper understand such interesting thermal non-equilibrium between two phases in a spray flash evaporation of salty water, this paper establishes a multi-component spray flash evaporation model which coupled with diffusivity effect of non-volatile fraction, as well as the influence of spray polydispersion. An experimental system is also set up for evaporative coefficient determination, as well as model validation. The theoretical and experimental results meet a good agreement. It indicates the salinity and the superheat level of inlet feed have substantial impacts on such thermal non-equilibrium phenomenon of the temperature difference between the extracted vapor and the discharged liquid residue.
Design of a Dexterous Robotic Arm Manipulator Using Hybrid BCI
Authors: Medina Portilla Daniel A. , Nandikolla Vidya K.
Published: February 2021

The paper describes the design of a hybrid Brain Computer Interface (BCI) system that provides control commands to manipulate a robotic arm. The goal is to facilitate BCI controlled real-time robotic applications by using a semi-autonomous operation mode that accepts multiple commands. Simple tasks, like moving forward or turning, are executed based on a single BCI command while more complicated tasks, like grabbing or pushing an object are automated once the task is selected. The robotic arm vision system uses an Intel RealSense D435 camera for image and depth perception where a point cloud generates an interface for the user to select an object. The user selects an object to manipulate, which identifies the goal position and location. After the location and object is determined, the software interface moves the robotic arm to have the selected object in the robotic arms’ workspace. The current robotic arm design utilizes an open bionics Brunel dexterous hand as the end effector which allows for human-like hand actions. A simulation platform is developed to verify the effect of the entire system of a dexterous robotic arm on a mobile platform. The system design and results using a hybrid BCI system is demonstrated.
Damage Size Estimation for Composite Laminates Based on an Anisotropic Wavefront Expression
Authors: Hameed M. Saqib , Li Zheng , Zheng Kaihong
Published: February 2021

A Multistage Elliptical Parametric (MEP) method is developed in this research for damage size evaluation in anisotropic composite laminates. The Lamb waves are actuated and sensed using piezoelectric (lead zirconate titanate, PZT) transducers arranged as a network of square cells. The dynamic response signals are processed using a continuous wavelet transformation (CWT) based on the Gabor wavelet for accurate time of flight (ToF) measurements. A numerical method is developed for the construction of non-elliptic path loci for each actuator-sensor pair. The damage is localized first using the least squares method, and then the damage edge points are located on each non-elliptic path loci as points which have the minimum distance from the damage location. The MEP method based on the damage edge points is implemented in multiple stages for damage size evaluation in a cross-ply laminate. Each stage is designed on the basis on excitation of specific prearranged transducers inside the square cell. The results indicate that the MEP method can quantitatively estimate the size of an elliptical damage in cross-ply laminates.
Effect of Filter Type and Filter Size on Roundness/Circularity Measurement Using Different Mathematical Algorithms
Authors: Sahay Chittaranjan , Ghosh Suhash , Premkumar Joseph Daniel , Ramachandran Siva Pooja
Published: February 2021

In the manufacturing industry, it is almost inconceivable to produce a rotating component without a minimal amount of roundness tolerance. The importance of studying roundness form deviations of circular and cylindrical features is to avoid the excessive lateral or axial runout deviations of the rotating and reciprocating parts during dynamic operations. Considering the precision that industries require now and will require in the future, the authors of this article have chosen roundness (also called circularity per ASME Standards) as the measurable parameter. In order to arrive at precise results, the roundness of a near-to-perfect cylinder is measured on an accurate spindle and turn-table type measuring instrument. Roundness profile, when measured, can be filtered in various ways to reduce or eliminate unwanted details, with a cut-off value set in terms of undulations per revolution (UPR), which gives valuable information about how the component may function, under specific conditions. Looking at real-life roundness graphs it is clear that information exists in the data at different frequencies. A classic example is ovality, which indicates an irregularity that occurs two times in one complete revolution. The workpiece would be said to have two lobes or two UPR. Multiple lobes may be present on a component, a condition contributing to either problems of fit with mating components or part functionality. Additionally, usage of recommended or generalized filter, yields data that approximately lies in the range of acceptability. Thus, there is a strong need to thoroughly understand the effect of filter size and type on roundness (form error for fit) and part functionality. Many published articles have investigated novel filters to accurately and efficiently calculate roundness. However, no work was found in literature that would present the filter size and type selection criteria and correlate it with roundness depending on mathematical method of calculating roundness and further to part functionality. This paper focusses on the investigation of filter type and size effect on roundness based on different mathematical methods of roundness error calculations. By varying parameters like the filter type (Gaussian 50%, 75% and RC Filters), the filter sizes (1 through 500 UPR) and the methods of measuring the roundness — (Least Squares Circle (LSC), Minimum Circumscribed Circle (MCC), Maximum Inscribed Circle (MIC) and Minimum Zone Circles or Separation (MZC or MZS)), roundness at different heights of the workpiece is evaluated. A clear trend is observed from the results, which can further help one to choose filters and their respective sizes for the respective design intent or the application in question.
The Effect of Working Temperature on the Performance of Water Desalination Using Forward Osmosis: A CFD Study
Authors: Alshwairekh Ahmed M. , Alqsair Umar F. , Alwatban Anas M. , Caspar Justin , Oztekin Alparslan
Published: February 2021

Computational fluid dynamics simulations for water desalination using forward osmosis were conducted on a flat membrane module. In the simulations, the effect of the porous support layer is assumed negligible. The simulations were performed with two values of flow rate such that the Reynolds number equals 200 and 800 in each channel. The working temperatures of both the feed and the draw solutions were varied from 20°C to 40°C. The feed solution had a concentration of 0.00355 solute mass fraction while the draw concentration was set to 0.0355 solute mass fraction. In all simulations, the laminar model was utilized. The results of the simulations suggest that the osmotic pressure is not the only factor that affects the water flux in forward osmosis when there is a temperature difference between the two sides of the membrane. The solution properties have a significant effect on the separation process. As the solution temperature increases, the viscosity decreases, which in turn increases the water permeation through the membrane. The feed temperature had a more substantial influence on the water flux compared to the draw temperature. Also, the effect of changing the flow rate did not change the results substantially.
Effect of Geometric Shape of Periodic Cavities in Attenuating Baseframe Vibration
Authors: Das S. N. , Kohli Kachita , Kumar Ayush , Sabareesh G. R.
Published: February 2021

Vibration attenuation is an important factor while designing rotating machinery since frequency lying in the range corresponding to natural modes of structures can result in resonance and ultimately failure. Damping dissipates energy in the system, which reduces the vibration level. The mitigation of vibrations can be achieved by designing the base frame with periodic air holes. The periodicity in air holes result in vibration attenuation by providing a stop band. A finite element-based approach is developed to predict the modal and frequency response. The analysis is carried out with different shapes of periodic cavities in order to study the effectiveness of periodic stop bands in attenuating vibrations. The amount of mass removed due to the periodic cavities is kept constant. It is seen that better attenuation is obtained in case of periodic cavities compared to a uniform base frame. Among the different geometries tested, rectangular cavities showed better results than circular and square cavities. As a result, it is seen that waves propagate along periodic cells only within specific frequency bands called the “Pass bands”, while these waves are completely blocked within other frequency bands called the “Stopbands”. The air cavities filter structural vibrations in certain frequency bands resulting in effective attenuation.
Retracted: “Locomotion System Design of an Active Capsule Endoscopy” [ASME 2020 International Mechanical Engineering Congress and Exposition, Volume 7A: Dynamics, Vibration, and Control, Virtual, Online, November 16–19, 2020, Conference Sponsors: ASME, ISBN: 978-0-7918-8454-6, Copyright © 2020 by ASME. Paper No. IMECE2020-23598, V07AT07A012; 6 pages; doi: 10.1115/IMECE2020-23598]
Authors: ASME
Published: February 2021

This paper was removed from publication at the author’s request, February 26, 2021.

Copyright © 2021 by ASME
An Innovative Design for Drillstring Testbed for High Pressure High Temperature Drilling
Authors: Tucker Randall , Palazzolo Alan , Gharib Mohamed
Published: February 2021

In this paper, a novel design for a full-scale, industrial-size, and high pressure high temperature (HPHT) drillstring test rig is presented. The test more accurately replicates the downhole environment with regards to bit performance limiters. The facility has a high-power drill string with side loading, reasonably sized mud pumps, a HPHT sample that generates a hot pressurized rock-bit interface and the ability to easily replicate specific drilling scenarios. This provides a step change in drilling research. Replicating down-hole HPHT conditions in a surface level drilling test rig is challenging but will deliver significant benefits for downhole tool and instrument development. The proposed test rig will provide these test conditions for developing longer lasting and more efficient bits, more effective drilling fluids, and lower friction tool joints to increase weight on bit (WOB) and rate of penetration (ROP). A secondary benefit is for identification of bit-rock interaction laws that will assist in implementing successful automated drilling (AD) approaches to reduce drillstring and bit failures from stick-slip, bit-bounce and other drilling anomalies. AD has the potential for increasing efficiency as well as reliability of drilling. The force and torque laws will also be utilized in drillstring dynamics simulation software for operator training and hardware development. The proposed test rig gives the industry a unique opportunity to couple experimental work that is representative of downhole conditions with actual industry problems and concerns. By using data sets from actual drilling operations, we will be able to replicate what is occurring downhole but in a controlled, measurable environment on the surface. The system will be highly automated with a remotely operated control room, to increase safety in the high temperature, pressure, force and torque environment of the test rig. The system is to be fully enclosed with an API rated pressure containment system. The description of the test rig here is intended to convey the complexity of the hardware needed to meet functionality requirements and operating conditions. The design is purposely configured to accommodate the inevitable small requirement modifications, with minimal delays in rig completion.
Molecular Dynamics Simulation Based Cohesive Zone Representation of Intergranular Fracture Processes in Bicrystalline Graphene
Authors: Shishir MD Imrul Reza , Tabarraei Alireza
Published: February 2021

The fracture properties of various grain boundaries in graphene are investigated using the cohesive zone method (CZM). Molecular dynamics simulations are conducted using REBO2+S potential in order to develop a cohesive zone model for graphene grain boundaries using a double cantilever bicrystalline graphene sheet. The cohesive zone model is used to investigate the traction–separation law to understand the separation-work and strength of grain boundaries.
Smooth Time-Optimal Path Tracking for Robot Manipulators With Kinematic Constraints
Authors: Hu Kui , Dong Yunfei , Wu Dan
Published: February 2021

Previous works solve the time-optimal path tracking problems considering piece-wise constant parametrization for the control input, which may lead to the discontinuous control trajectory. In this paper, a practical smooth minimum time trajectory planning approach for robot manipulators is proposed, which considers complete kinematic constraints including velocity, acceleration and jerk limits. The main contribution of this paper is that the control input is represented as the square root of a polynomial function, which reformulates the velocity and acceleration constraints into linear form and transforms the jerk constraints into the difference of convex form so that the time-optimal problem can be solved through sequential convex programming (SCP). The numerical results of a real 7-DoF manipulator show that the proposed approach can obtain very smooth velocity, acceleration and jerk trajectories with high computation efficiency.
Retracted: “Sensorless Control of Tubular Permanent Magnet Synchronous Linear Motor Considering the End Effect” [ASME 2020 International Mechanical Engineering Congress and Exposition, Volume 2B: Advanced Manufacturing, Virtual, Online, November 16–19, 2020, Conference Sponsors: ASME, ISBN: 978-0-7918-8449-2, Copyright © 2020 by ASME. Paper No. IMECE2020-23676, V02BT02A042; 6 pages; doi: 10.1115/IMECE2020-23676]
Authors: ASME
Published: February 2021

This paper was removed from publication at the author’s request, March 8, 2021.

Copyright © 2021 by ASME
Investigation and Characterization of Clay Mixture Feedstock for Extrusion-Based Additive Manufacturing
Authors: Alkindi Tawaddod , Alyammahi Mozah , Susantyoko Rahmat Agung
Published: February 2021

The extrusion-based AM technique has been recently employed for rapid ceramic components fabrication due to scalability and cost-efficiency. This paper investigated aspects of the extrusion technique to print ceramic materials. Specifically, we assessed and developed a process recipe of the formulations (the composition of water and ethanol-based clay mixtures) and mixing processes. Different clay paste formulations were prepared by varying clay, water, ethanol ratios. The viscosity of clay paste was measured using a DV3T Viscometer. Afterward, the produced clay paste was used as a feedstock for WASP Delta 60100 3D printer for computer-controlled extrusion deposition. We evaluated the quality of the clay paste based on (i) pumpability, (ii) printability, and (iii) buildability. Pressure and flow rate were monitored to assess the pumpability. The nozzle was monitored for continuous material extrusion to assess printability. The maximum layer-without-collapse height was monitored to assess the buildability. This study correlated the mixture composition and process parameters, to the viscosity of the mixture, at the same printing speed. We found that 85 wt% clay, 5 wt% water, 10 wt% ethanol paste formulation, with the viscosity of 828000 cP, 202400 cP, 40400 cP at 1, 5, and 50 rpm, respectively, demonstrates good pumpability, as well as best printability and buildability.
Enhance PV Panel Detection Using Drone Equipped With RTK
Authors: Ismail Hesham , Alhussein Mohammed , Aljasmi Nawal , Almazrouei Saeed
Published: February 2021

Solar energy is getting a lot of traction due to the reduced cost and friendlier to the environment compared to fossil fuel. It is essential to inspect the PV farms to ensure that the correct capacity produced through early PV fault detection. We proposed a full autonomous solution, where the drone mission is programmed to follow a specific Global Positioning System (GPS) waypoints. The collected videos will undergo various image processing techniques to detect and track the PV panels.

In this paper, we tried two different PV panel detection approaches. Both detections gave acceptable results. The first detection relies on various image processing techniques. The second detection relies on deep learning architecture called mask Region-based Convolution Neural Network (R-CNN). After that, we track the PV panels in every frame using camera data alone. The advantage of tracking the PV panels is to ensure unrepeated PV panel through tagging even if the drone flies over the panel again since each PV panel will be associated with a tag. The next step will be to test the PV panel’s proposed detection and tracking algorithm on a larger solar farm.
Investigation of Spatial Variability on Strut Diameters of Additively Manufactured Lattice Structures
Authors: Gorguluarslan Recep M. , Gungor O. Utku
Published: February 2021

In this study, the influence of the spatial variability of geometric uncertainties on the strut members of the lattice structures fabricated by additive manufacturing is investigated. Individual struts are fabricated with various printing angles and diameters using a material extrusion process and PLA material. The diameter values of the fabricated samples are measured along the printing and radial directions at each layer under an optical microscope. Spatial correlations are characterized based on the measurements using the experimental autocorrelation function. Candidate autocorrelation functions are fitted to the measured data to identify the best fitted one for each diameter parameter and the corresponding correlation lengths are evaluated for random field. The applicability of the Karhunen-Loeve expansion (KLE) is investigated to reduce the dimensionality of the random field discretization. The results show that the diameters of the strut members at each layer are spatially dependent and the KLE method was found to give a good representation of the random field.
Analytical and Numerical Investigation of the Fluid Structure Interaction of an Elastic Beam in a Water Channel
Authors: Fritsche Manuel , Epple Philipp , Delgado Antonio
Published: February 2021

The interaction between fluids and solids is becoming increasingly important in the design and analysis of machines, buildings and systems. Due to the fluid-mechanical phenomenon of turbulence and the associated flow and vortex shedding, the fluid structure interaction must be considered, for example, in aircraft wings, civil engineering (e. g. television towers or bridges), the rotor blades of wind turbines or in the field of sensor technology. Due to the increasing computing power, increasingly complex tasks can be calculated with the help of numerical simulations.

In this paper, an elastic beam has been defined as test case and has been analyzed in different ways with the methods of the fluid structure interaction (FSI), i.e. with analytical and numerical approaches. For this purpose, the plastic beam has been fixed on one side in a water channel and the flow around it and the beam deflection have been measured. The deformation of the beam due to the flow load around it has been analyzed for varied flow velocities.

First, the beam deformation has been estimated based on the analytical equations from structural mechanics and an assumed stagnation pressure on the beam surface. Additionally, the drag coefficient from experimental data of the literature was used to estimate the force on and the bending of the beam. Then two numerical simulations with different FSI coupling methods have been performed with Ansys Workbench 2020 R1. On the one hand, a one-way coupling analysis has been performed in which the pressure field was calculated from the CFD simulation and then transferred to the mechanical analysis. On the other hand, a two-way coupling computation has been performed, which also takes transient effects into account. For this purpose, the flow field and the pressure field have been exchanged iteratively between the fluid and the mechanical solver. This coupling approach is general and corresponds to reality since large deformations and non-linearities are considered. However, this approach always requires a very computation intensive, non-stationary calculation.

The results obtained from these parameter studies have then been evaluated and compared in order to determine the accuracy of each analysis methodology. The elaborated results have been discussed and analyzed in detail.
Validation of Two Open Source Discrete Element Software Packages Against Theoretical Benchmarks
Authors: Rittenhouse Justin , Gustafson Peter
Published: February 2021

As computational expense decreases Discrete Element Method (DEM) has increased in popularity as a tool to model granular material. Unfortunately wide spread access to DEM software is still an issue, as many researchers in academia and industry simply do not have access to proprietary software packages, including the author of this paper. Thus the importance of verifying open-source packages for their legitimacy relative to their proprietary counterparts. Thus the scope of this paper is to further validate two open-source packages, Yet Another Dynamic Engine (Yade) and Project Chrono, are capable of generating reliable results.

Yade and Project Chrono were evaluated against a series of established particle level impact benchmark modeling cases (e.g., between two spheres or a sphere and rigid wall). These cases were designed to evaluate elastic normal impacts, energy dissipation for normal impacts, and energy dissipation due to oblique impacts. In addition each test case was investigated twice implementing a change in material properties on the second simulation. Many of the resulting forces, moments, and accelerations were found to agree with theoretical solutions and/or proprietary software model results published in the existing literature [1]. The discrepancies are still under investigation. These open source software packages are found to have advantages that are useful in an university research or an industrial environment.
Evaluation of Metal Lattice Structures With X-Ray Micro-Computed Tomography: Dimensional Accuracy and Manufacturability
Authors: Puttonen Tuomas
Published: February 2021

Additive manufacturing enables product designers to incorporate complexity onto their designs on multiple size scales. Computer-aided design methods, such as topology optimization and lattice design, have emerged as software tools for applications where part consolidation and weight reduction are desired. Still, a more delicate control of hierarchical complexity and submillimeter-sized features would unlock a widely unexplored frontier of new design possibilities.

However, the complexity of a design can respectively affect the manufacturing process. In powder bed fusion, the diameter, power and speed of the laser spot and the resulting size of the melt pool define the attainable feature resolution and accuracy in comparison with the original design intent. X-ray computed tomography can be a useful tool in validation and provide a detailed, volumetric representation of a part with internal features.

This paper examines the design accuracy of 316L metal lattice structures and density of solid cubes with industrial X-ray micro-computed tomography. Accessible tools with open source software are presented for CT data analysis. The nominal values are compared against the as-built and CT scanned samples for surface area, volume, and dimensional accuracy. A CT voxel size of 30–40 μm allows to identify printability issues and general trends in the part density in comparison to the geometry changes. However, a finer voxel size in the submicron range would be required to properly detect and localize internal porosity and evaluate surface topography.
On the Uses of Linear-Quadratic Methods in Solving Nonlinear Dynamic Optimization Problems With Direct Transcription
Authors: Herber Daniel R. , Sundarrajan Athul K.
Published: February 2021

Solving nonlinear dynamic optimization (NLDO) and optimal control problems can be quite challenging, but the need for effective methods is ever increasing as more engineered systems become more dynamic and integrated. In this article, we will explore the various uses of linear-quadratic dynamic optimization (LQDO) in the direct transcription-based solution strategies for NLDO. Three general LQDO-based strategies are discussed, including direct incorporation, two-level optimization, and quasi-linearization. Connections are made between a variety of existing approaches, including sequential quadratic programming. The case studies are solved with the various methods using a publicly available, MATLAB-based tool. Results indicate that the LQDO-based strategies can improve existing solvers and be effective solution strategies. However, there are robustness issues and problem derivative requirements that must be considered.
Rolling Resistance of a Skateboard
Authors: Maull Thomas , Eichaker Lauren , Buczek Sean , Graham Troy
Published: February 2021

Skateboards have been used as a means of transportation and extreme sports for decades. The forensic analysis of skateboard-related accidents requires knowledge of the kinematic characteristics of the skater-skateboard and skateboard-ground interactions to aid in the investigative process.

Much of the existing skateboard research has focused on the motion of the skater-skateboard system. Few studies have investigated the interactions of the skateboard and the ground surface. The velocities and accelerations of a skateboard/skater system is not well defined in literature. A skateboard’s rolling resistance has also not been defined. Therefore, this study was conducted to describe the effect of rider mass and wheel bearing resistance on the rolling resistance of a skateboard.

Understanding the dynamics of the skateboard and rider in relation to rolling resistance is critical to an investigator attempting to determine the behavior of a skateboard when reconstructing a skateboard related incident. In addition, the data that will be presented in this study is beneficial to a wide audience including, but not limited to; traffic safety, accident reconstruction, skateboard design, bearing design and useful life, and wheel design and useful life.
Numerical Analysis and Parametric Study of a Thermoelectric-Based Radiant Ceiling Panel for Building Cooling Applications
Authors: Seyednezhad Mohadeseh , Najafi Hamidreza
Published: February 2021

Buildings are known as one of the foremost energy consumer sectors in the world with a share of nearly 40% and hence the design and development of clean and energy efficient building energy systems is an important step towards a sustainable future. Cooling and air conditioning systems, as an essential component for occupants’ comfort, are among the largest energy end-users in buildings. Additionally, most air conditioning systems rely on using refrigerants that are harmful for the environment with considerable potential for ozone depletion and global warming. Solid-state cooling technologies that do not require refrigerant are therefore of interest to eliminate these environmental concerns. Thermoelectric (TE) modules, as a solid-state cooling technology, when supplied by DC electricity, produce a temperature gradient through the Peltier effect that can be used for cooling purposes. Due to the attractive characteristics that TE technology offers, mainly high controllability, lack of refrigerant and large moving parts, quiet operation, promising efficiency and requiring minimum maintenance required, TE-based systems are becoming an emerging technology for building cooling applications. TE-based cooling technologies have been developed and tested through integrated and non-integrated systems in the building envelope. In the present paper, the design of a TE-based radiant cooling ceiling panel is investigated through numerical modeling and parametric study. The system can be incorporated in the ceiling and will maintain a reduced ceiling temperature to provide cooling through radiation and convection for the occupants. COMSOL Multiphysics is used for modeling and simulation purposes and the performance of the system under various configurations is assessed. The effect of number and placement of TE modules for a given size of ceiling panel are investigated using several simulations in COMSOL to achieve a desired and uniform surface temperature in the minimum amount of time. The impact of incorporating various amounts of phase change material (PCM) in the ceiling panel is also assessed. PCM allows the ceiling panel to maintain the desired temperature for an extended amount of time, but it also increases the time that it takes for the panel to reach the desired temperature. Transient thermal simulations are performed for both start up and shut down scenarios and the amount of time that it takes for the ceiling temperature to cool down to the desired level (on-mode) or heat up (off-mode) to the temperature at which it has to turn back on again are calculated for various system configurations. The results from this study can be used for optimal design of TE-based radiant cooling ceiling panels to achieve high energy efficiency and low operating cost while maintaining occupants’ comfort in the buildings.
An Improved Risk Priority Measure for the Management of Project Risk
Authors: Unwin Stephen D. , Calderin Duriem , Simpson Brett C. , Spitz Casey J. , Veeramany Arun , Gastelum Jason A. , Maloney Craig T.
Published: February 2021

Monte Carlo-based project risk models are essential tools in project risk management, particularly for large, complex projects in which it is difficult to glean intuitively the importance of individual risks to the overall project. Conventional correlation-based methods for measuring the importance of contributing risks in such models are argued here to be both statistically flawed and unintuitive in the importance metrics they produce. Drawing on and adapting methods more traditionally associated with engineering risk models, Risk Reduction Worth (RRW) is introduced as an importance measure. RRW is shown to be statistically robust and provide an easily interpretable, quantitative measure of the importance of a risk to the overall performance of a project; specifically, measuring the extent to which removal of a risk would improve confidence in project outcomes. To ensure practicality of the method, an approach is described in which RRWs can be produced for all contributing risks based on a single Monte Carlo sample. This is demonstrated through application to a large, complex project risk model from which intuitive risk importance insights provide a robust, transparent basis for the allocation of risk management resources.
Machine Learning Assisted Design for Active Cathode Materials
Authors: Yong Sihan , Zheng Zhuoyuan , Wang Pingfeng , Li Yumeng
Published: February 2021

The traditional way of designing materials, including experimental measurement and computational simulation, are not efficient. Machine learning is considered a promising solution for material design in the recent years. By observing from previous data, machine learning finds patterns, learns from the patterns and predict the material properties. In this study, machine learning methods are used for discovering new cathode with better properties, includes crystal system learning and the property prediction. K-Folder cross-validation is used for finding the best training data with a limited dataset, nevertheless increasing the percentage of training data would ultimately result in better performance on prediction. It is found that, random forest gives the highest average accuracy in crystal system classification, meanwhile, extra randomized tree algorithm provides a higher averaged coefficient of determination and lower mean squared error in the regression model predicting electrical properties of cathodes. The random forest algorithm is chosen from a wide range of machine learning algorithms with the implementation of Monte Carlo validation. Based on the feature importance evaluation, oxygen contents are found to have the highest effects in determining capacity gravity and volume change in properties prediction.
Characterization of Fluid-Filled Interconnected Dual-Cells for Reduction of Force and Linear Acceleration due to Blunt Impact
Authors: Erel Veysel , Lindsay Alexandra R. , Singh Inderjeet , Wijesundara Muthu B. J.
Published: February 2021

Although modern body and head protective gears are well studied by experts, innovators, and manufacturers, incidence of sports-related injuries is still very high in the United States and all around the world. To reduce the negative effects from blunt impact, an impact reduction structure which contains a channel, shell, and dual-cells was designed and developed with the intention of improving existing helmet liners. This study utilized a previously proven interconnected-cells concept, where a primary cell compresses, then air inside the cell transfers to a secondary cell which expands accordingly, causing impact reduction. While the concept remained the same, a new dual-cells architecture was explored, with numerical and experimental studies for helmet liner impact reduction, and compared to a commercial Xenith helmet liner element. The simulation study began with exploring the effect of adding corrugation to the walls of both cells on impact behavior, then persisted with optimizing impact reduction structure design, and finalized with a comparison study. An experimental study was performed with the optimized structure, provided by simulation, and compared against commercial Xenith helmet liner element in terms of reaction force, linear acceleration, and impact duration. Experimental and simulation results showed that our impact reduction structure provides lower reaction force and linear acceleration.
Numerical Study of Airfoil Shape and Blade Pitching on Vertical Axis Wind Turbine Through CFD Simulations
Authors: Ali Ussama , Modrek Mhd , Islam Md , Janajreh Isam
Published: February 2021

Wind energy has proved to be a promising sustainable energy source; the energy of wind has been harvested not only for decades but for centuries. It was in the late 19th century that wind energy was used to directly obtain electrical power. Horizontal axis wind turbines (HAWTs) are widely used in commercial applications but recently a lot of research is being done on vertical axis wind turbines (VAWTs) to improve their operation and efficiency. Absence of yaw mechanism, low noise emission, and low manufacturing, installation and maintenance costs are some of the prominent advantages of VAWT over HAWT. The objective of this study is to evaluate the performance of different blade airfoils and the influence of blade pitching in the operation of VAWT. Blade pitching is widely used in HAWTs and has proven to be very advantageous in terms of output power, but the effect of blade pitching on VAWT has not been widely studied and much less practically implied due to complex functional mechanism. VAWTs with fixed pitch experience continuously varying angle of attack which reduces the power generation. Airfoils tested in this study, for their performance on a VAWT rotor, are Joukowski airfoil (J-15), NACA0012 and NACA4312, furthermore, passive blade pitching was applied to analyze the effect of inoffset and out-offset blade pitching on the performance of the turbine. High fidelity Navier-Stokes computational flow models were applied for the analysis. A 2D unsteady CFD model was constructed to perform the simulations. Power and torque coefficients were evaluated over a varying range of tip speed ratios and a strong correlation of these coefficients was seen with different input parameters, such as airfoil shape, turbine solidity and tip speed ratios. Out-offset blade pitch angles showed better results than in-offset blade pitch angles.
Study the Effect of Communication Delay for Perception and Collision Avoidance in Cooperative Autonomous Driving
Authors: Ghorai Prasenjit , Eskandarian Azim , Kim Young-Keun
Published: February 2021

Cooperative perception through connectivity offers additional safety to autonomous driving by extending the field of view of the vehicles beyond their sensors. Critical safety information is passed among vehicles via wireless communications; therefore, communication among the vehicles in the system should be perfect and delay-free. In this article, an analytical study is proposed to show the effect of communication delays in a critical and emergency situation, where relying on the lead vehicle is so much crucial for an ego vehicle to avoid danger without any delay in sharing the dynamic information of on-road pedestrian or any such vulnerable road users. A simple and effective control algorithm is utilized based on distance modeling in a cooperative driving environment to control the vehicle’s longitudinal dynamics. A detailed simulation study using a dynamic model for both ego and lead vehicles, as well as a pedestrian on a hazardous on-road scenario, is presented to illustrate the effect of communication delays in autonomous driving.
Variations of In-Plane Mechanical Properties of Cellular Structures With Different Hierarchical Organizations
Authors: Chakraborty Souvik , Hebert Dylan , Faisal Tanvir Rahman
Published: February 2021

Inspired by the nature, this study analyzes in-plane compressive responses of different modes of hierarchical architected structures with varying topologies. Architected cellular structures with two different unit cell topologies — square and kagome are considered, both having a relative density of 0.25. Each unit cell topology is designed with three different configurations. The base structure is the primitive one with solid homogeneous cell wall. The nested hierarchical structure is derived from the primitive one with cellular structuring in the cell wall. The third and final one is the fractal-like hierarchical structure, where same unit cells appear on different length scales. 3D printed structures were subjected to uniaxial compression to characterize their in-plane mechanical properties. The compressive stress-strain behaviors reveal that all the structures demonstrate the classical behavior of cellular structures followed by significant recovery of their initial shape upon load withdrawal. The energy absorptions demonstrated by the plateau regions before densification are not only governed by their structural topologies, but also largely governed by the configurations of hierarchical organizations. Hence, this study suggests the application specific design of hierarchical architected structures for defined loading conditions.
Design and Implementation of a Pulley-Based Movable LED System for Optimal Plant Growth
Authors: Ilhan Zeki Okan , Ok Jeong Tae , Eakins Brandon , Masters Clayton , Thompson Kelcee , Vital Tojya
Published: February 2021

A pulley-based movable LED light apparatus is designed and implemented based on a request from the Biology Department of the Midwestern State University to provide a controllable environment for plant research. The proposed apparatus consists of a large aluminum structure with added pulleys, the movable LED light platform, a DC-motor-driven gearbox, and electronics for sensing and control. The proposed conceptual design has been fabricated, tested, and successfully implemented in the MSU greenhouse. Performance of the initial design is also demonstrated through mechanical efficiency, light intensity profile, and the ultrasonic sensor sensitivity. Finally, some propositions are introduced to improve upon the hardware, sensors, and the control logic, that could allow for a better performance and an increased overall life span of the apparatus.
Experiential Learning in STEM for a Diverse Student Population at the University of the District of Columbia (UDC) Through the Implementation of the UDC Rover Project
Authors: D'Orazio Giancarlo , Xu Jiajun , Haghani Sasan
Published: February 2021

In 2018, the University of the District of Columbia (UDC) participated in the NASA Human Exploration Rover Challenge for the first time in the school’s history. An interdisciplinary team of students designed and fabricated a two-person, human-powered rover which competed against 100 other colleges and universities. Based on their success, in 2019 UDC again formed a team to participate in the challenge, improving on the 2018 rover design and performance. This paper reports the process of implementing this experiential learning activity and how this project has contributed to the STEM curriculum at UDC, and recruitment and participation of underrepresented STEM students. Lessons learned from implementing this project is also shared and discussed in this paper.
Combined Brayton, Inverse Brayton and Steam Cycles Power Plant
Authors: Carapellucci R. , Di Battista D.
Published: February 2021

Nowadays, more significant effort is needed to improve power generation efficiency to respond to environmental concerns. Several innovative technological options are under development and, among them, the integration of different energy systems is one remarkable opportunity.

In this work, a combination of three different thermodynamic cycles has been proposed and studied: an Inverted Brayton cycle (IBC) is used to exploit the exhaust gas enthalpy of a Brayton-Joule cycle and a Steam Power Plant is bottomed to the Inverted Brayton Cycle, in order to recover the high thermal power wasted in its cooling section. In other words, a quite conventional natural gas combined cycle power plant is repowered introducing the Inverted Brayton Cycle to exploit the gas thermal power between the gas turbine and the heat recovery steam generator.

In this integration, each parameter has a strong influence on the overall performance of the system: pressure ratio of the gas cycle, sub-atmospheric pressure of the inverted one, turbines inlet and outlet temperatures and heat recovery grade in the bottom steam section have been investigated in order to optimize the working conditions and find a best operating point. A post combustion opportunity was also considered, exploring for the best position to place it along the gases path and to get the maximum additional power through the repowering intervention.
Nonlinear Dynamics and Stability of Pressure-Loaded Shallow Spherical Caps
Authors: Iarriccio G. , Pellicano F.
Published: February 2021

In this work, the nonlinear dynamic response of a shallow spherical cap subjected to a time-dependent pressure load is analyzed. The Novozhilov’s nonlinear thin shell theory is used to express the strain-displacement relations, geometric imperfections are considered. Using the Rayleigh-Ritz method, the displacement fields are expanded using a mixed series: Legendre polynomials are considered in the azimuthal direction and harmonic functions in the circumferential one. The dynamic model is derived by using the Lagrange equations. The response of a homogeneous shell, made of isotropic material, clamped at its ends, and subjected to an external pressure load is investigated: using the continuation software AUTO, the bifurcation analysis of equilibrium points and periodic responses has been performed. The model is validated by means of comparison with the existing results in literature for spherical shells having a circular base, in particular with models developed through the Marguerre’s theory.