bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance of a Generic 4-Step Global Reaction Mechanism With Equilibrium Effects for Detonation Applications
Authors: Peswani Mohnish , Maxwell Brian McN.
Published: February 2021

A reduced 4-species, 4-step Global Reaction Mechanism (GRM) [1], derived from detailed chemistry using a thermochemical approach, is investigated for three different reactive mixtures. The trade-off between preciseness of Elementary Reaction Mechanisms (ERMs), and low computational overhead requirements of GRMs remains a dilemma in the application of chemical kinetic models to detonation problems. Reducing a reaction mechanism often compromises the chemical details, and reduces the scope of applicability of the derived model. This is largely due to the mixture chemistry having a vital influence on several key aspects of the detonation phenomenon like initiation, quenching, and the dynamics of the wave front and hydrodynamic structure during propagation. For detonation problems in particular, there has been an insufficient replication of the complex reality of the phenomenon through numerical simulations which has lead to a constant demand for more accurate and affordable models. Three separate stoichiometric combustion mixtures are investigated, each involving acetylene, methane, or propane mixed with oxygen. Each mixture exhibits very different global activation energies, heat release, and ignition characteristics.
Vibration Analysis in Multiple Close Proximity Flow Restrictions
Authors: Verma Rahul , Horiates George , Kanellis Nicholas
Published: February 2021

In this study, a segment of water conveyance system at a chemical manufacturing facility is under investigation. The pipe segment under investigation conveys a daily average flow of five million gallons of water per day (MGD) from the river to a water treatment plant. The exact age of the pipe system is unknown as limited construction or maintenance information exists. The study area is a pipe segment near the treatment plant where three flow restrictions exist within a 30-foot distance bounded by a T-junction and a water filtration plant. These restrictions include two self-actuated butterfly valves and an orifice plate on a 16-inch diameter steel pipe, buried approximately three feet below ground surface. When standing in the study area, heavy vibrations are felt at the ground surface. The valves and orifice plate are to control flowrate and reduce pressure from 80 PSI to 45PSI as the flow enters the water treatment plant.

Flow restrictions in close proximity can cause cavitation, water hammer and other flow phenomena within a pipe system. This can result in excessive wear of the pipe’s inner walls and valves which may compromise the structural integrity and/or function of the system. Computational fluid dynamics (CFD) software is a useful tool for determining if the conditions for the various flow phenomena are present in a system.

The flow characteristics were numerically calculated in MATLAB then computationally modeled in AFT Fathom. The purpose of the numerical analysis was to describe the stability of the fluid flow at discrete points in the pipe network and identify the network segments with significantly unstable flow profiles. The purpose of the AFT Fathom CFD model purpose was to provide a continuous simulation of the flow stability in the pipe segment and provide a more robust description of the flow profiles in the network. While Fathom cannot explicitly predict cavitation or water hammer, the kinematic parameters produced by the Fathom model and the physical conditions observed in the study indicate that water hammer is likely occurring.
Stiffness Analysis of a Simplified Ankle-Foot Orthosis
Authors: Swierski Ethan , Burke Molly , Arenas Maria , Bernat Jessica , Manzer James , Piovesan Davide
Published: February 2021

Due to the impact gait impairments have on afflicted individuals’ lives, there are many efforts to find effective remedies. One example is drop foot, a condition in which the dorsiflexion in the leg falters, and the forefront of the foot drags during walking. One of these is the use of an Ankle Foot Orthosis (AFO), a device worn on the lower extremity of the leg to improve walking ability. Although these orthoses have been improved over time to address a user’s physical needs, material and financial restrictions are still an obstacle. To find the lowest cost AFO design of high performance, a study was conducted to investigate the applications of a simplified design process for an AFO. The design process is a fast, low cost, easy technique of laser cutting thermoplastic resin and bending a drawing into a 3-dimensional AFO. Finding the best AFO possible using this design process was easy, involving making a 2-dimensional CAD model for laser cutting, performing Finite Element Analysis (FEA) simulations and comparing a variety of designs, materials, and configurations for their ability to improve a user’s gait kinematics while also meeting optimal cost and comfort needs.
Stress Corrosion Cracking of Graphene
Authors: Elapolu Mohan S. R. , Tabarraei Alireza
Published: February 2021

We use molecular dynamics (MD) simulations to study the stress corrosion cracking (SCC) of monolayer graphene sheets with an initial edge cracks. Two types of edge cracks are considered in the simulations; one with armchair edges and another one with zigzag edges. All the simulations are conducted at 300 K and the corrosive environment is O2 molecules. Tensile stresses are induced in the graphene sheet by applying mode–I loading. To understand the mechanism of the sub–critical crack growth during SCC, we expose the graphene sheets to O2 molecules at strains of 0.047 and 0.076. Our MD simulations capture the chemisorption process between the O2 molecules and pre–stressed graphene sheet. Oxygen molecules react with carbon radicals at the edges of the crack tip and gets adsorbed to the graphene surface. The atomic stresses in the vicinity of crack tip relaxes due to the adsorption of O2 molecule. Our results show that the reaction of O2 molecules with the carbon radicals at the crack tip can cause the failure of C–C bonds which leads to the sub critical cracking.
Delaying the Chaotic Onset in the Flow-Field of Flapping Foil With Flexible Aft Tail
Authors: Shah Chhote Lal , Majumdar Dipanjan , Sarkar Sunetra
Published: February 2021

The present study is focused on examining the flow-field dynamics of a flapping foil with a flexible aft tail as compared to a rigid configuration where tail flexibility is infinite. The flow around the oscillating body is governed by the incompressible Navier-Stokes equations. An in-house Fluid-Structure Interaction solver has been developed following a discrete forcing type Immersed Boundary Method coupled with an inextensible filament structural model. The flapping amplitude is considered as a bifurcation parameter, and as the bifurcation parameter is increased, the periodic wake transitions into the chaotic patterns. The periodic to chaotic transition happens through an intermittency route. However, the elliptic foil with flexible aft tail exhibits chaotic onsets much later compared to the foil with a rigid tail. Time series analysis techniques, such as frequency spectra and recurrence plots, have been used to establish the intermittency and the chaotic dynamics conclusively.
Least Cost Microgrid Resource Planning for the Natural Energy Laboratory of Hawaii Authority Research Park
Authors: Headley Alexander , Schenkman Benjamin , Olson Keith , Sombardier Laurence
Published: February 2021

The Natural Energy Laboratory of Hawaii Authority’s (NELHA) campus on The Island of Hawai’i supplies resources for a number of renewable energy and aquaculture research projects. There is a growing interest at NELHA to convert the research campus to a 100% renewable, islanded microgrid to improve the resiliency of the campus for critical ocean water pumping loads and to limit the increase in the long-term cost of operations. Currently, the campus has solar array to cover some electricity needs but scaling up this system to fully meet the needs of the entire research campus will require significant changes and careful planning to minimize costs. This study will investigate least-cost solar and energy storage system sizes capable of meeting the needs of the campus.

The campus is split into two major load centers that are electrically isolated and have different amounts of available land for solar installations. The value of adding an electrical transmission line if NELHA converts to a self-contained microgrid is explored by estimating the cost of resources for each load center individually and combined. Energy storage using lithium-ion and hydrogen-based technologies is investigated. For the hydrogen-based storage system, a variable efficiency and fixed efficiency representation of the electrolysis and fuel cell systems are used. Results using these two models show the importance of considering the changing performance of hydrogen systems for sizing algorithms.
Physiological Validation of the 360° Panorama in HMD, for Research and Design of Engineering Classrooms
Authors: Higuera-Trujillo Juan Luis , Llinares Carmen , Rojas Juan-Carlos , Muniz Gerardo
Published: February 2021

Classroom design has a significant impact on curriculum development and student motivation. To study the impact of classroom space on students, environmental simulations are often. Due to its relative accessibility, the set-up of 360° panoramas formats shown through head-mounted displays (HMD) stands out. However, this set-up does not have a physiological validation (a physical-simulated comparison) for the specific case of educational spaces. A laboratory fieldwork was developed to address this lack. Participants performed tasks in a classroom or in its virtual replica, in a counterbalanced way. The sample was made up of 40 university students. While the participants performed these tasks, their heart rate variability (HRV) and electrodermal activity (EDA) were recorded. Four physiological metrics were extracted from these records, which quantified the participants’ experience in both the virtual and physical classrooms. Complementarily, the sense of presence was quantified, according to the SUS questionnaire. Regarding the level of presence, the average level generated by the virtual simulation of the classroom was relatively high. Regarding the physiological response, no differences were found in any of the metrics studied. In conclusion, this supports the findings obtained through studies that use this set-up and the development of educational applications based on these technologies.
Combined Effect of Loading and Interference Level on Stress Intensity Factor for a Pin Loaded Joint
Authors: Prakash Raghu V. , K Hithendra
Published: February 2021

Lugs and pins, rivets, bolts are the most essential joints used in structural components apart from the welds. These elements experience dynamic loading during their life, leading to failure by fatigue. Many studies have been performed to estimate stress intensity factors (SIFs) and fatigue life for these joints. Although the effect of geometric configuration, loading methodology and interference levels on SIFs have been studied independently, very few have studies the combined effect; this may be either due to non-availability of closed form solutions or difficulty in experimentation. The current study uses Finite Element Analysis to evaluate the SIF for cracks emanating from a circular hole in a finite width rectangular plate under different loading conditions such as open hole load, bearing load, pin load (with and without interference) and the effect of introducing a bush. This study brings out the crack lengths beyond which the type of loading is not significant on the stress intensity factor, as well as interference levels beyond which there is no beneficial impact on the SIF and hence the life of component.
Testing the Validity of the NIJ Clay Standard for Approving Body Armor With a Preliminary Insight Into Injury Correlation
Authors: Eaton Madelyn A. K. , Henderson Kyvory A. , McMahon Justin A. , Salzar Robert S.
Published: February 2021

Body armor is tested for efficacy using the NIJ’s clay standard. This standard is based on a 44 mm upper limit of back face deformation into the clay to prevent severe cases of behind armor blunt trauma (BABT). The NIJ clay standard has never been directly correlated with human injury, and it is previously unknown how 44 mm into clay translates to the response of a human torso. This study developed a method for reproducing BABT in a laboratory setting, and performed matched pair testing on the ballistics clay and a cadaveric specimen. Tests at a low, non-injurious speed and a high, injurious speed were performed at the NIJ specified clay temperature, along with two tests at a lower temperature representing exposure to a room temperature setting. It was found that for both speeds the displacement into the human thorax was greater than the displacement into the clay. The greatest displacement into the clay was only 5mm above the standard’s limit, and the same speed into the human model caused failure of the ribcage. Lowering the clay temperature by two degrees Celsius resulted in a passing clay displacement for the extremely injurious high speed test. This experimentation is sufficient in showing that the NIJ standard may not be valid for preventing serious BABT injuries in the wearers of body armor. Further testing is required to correlate clay displacements with human injury risk.
Development of Aperture Total Internal Reflection (A-TIR) for Droplet Profiles With 3-D Ray Tracing and Modified Fresnel Equation
Authors: Kim Iltai Isaac , Lie Yang , Park Jaesung
Published: February 2021

This study proposes and demonstrates a new approach using aperture total internal reflection (A-TIR) by means of various apertures in front of a detector to characterize micro/macro droplet. Pure liquid is used to make micro and macro scale droplets. An aperture in front of a detector in TIR configuration generates unique reflectance curve by filtering the amount of aberrated beams from the top curved profiles of droplets. A scheme of three-dimensional (3-D) ray tracing is developed for the reflected beam profile from the curved surface of the droplet with the modified Fresnel modeling to show a good agreement with the measurement. The modified Fresnel modeling is proposed to consider the morphological features of the droplet such as the thickness, the surface coverage fraction, the effective flatness ratio, and the quantum phenomenon of Goos-Hänchen (G-H) shift effect. Various sizes of apertures are employed to demonstrate the A-TIR reflectance depending on the aperture sizes for the macro and micro-sized droplets with a good agreement between the experiment and the simulation. Furthermore, it is demonstrated that important morphological features of the droplet such as the thickness (micrometer-range) and the ultra small contact angle less than 6 degree can be successfully determined with a reasonable agreement with the measurement. This outcome can be used to measure the morphological features of droplets and to characterize uneven surface features like human fingerprinting.
Heat Exchanger Design, Analysis and Evaluation by Data-Driven Computational Fluid Dynamics
Authors: Zhang Zhifeng , Chen Yilun , Ma Jiefu
Published: February 2021

Heat exchanger design, analysis and evaluation are traditionally based on experimental data, empirical relationships and theoretical equations. Recently, due to the recent development of data-driven computational fluid dynamics, we are able to conduct “smart” analysis based on a large amount of data. In the present research, we developed a fast CFD data generation method. Based on the large amount of data, we developed two data-driven models: 1) a machine learning model that can predict the heat transfer behavior, and 2) a tree-based model that can capture the feature importance. This methodology can potentially be applied to future high-efficiency heat exchanger designs.
Effect of Additional Weight on Lyapunov Exponents for Human Squat Exercise
Authors: Galarza Jose , Caruntu Dumitru I.
Published: February 2021

This work deals with the stability of the dynamics of human squat exercise. This is a common exercise. The focus of this investigation is to analyze the knee angle time series and calculate the divergence for different weight added in the exercise. Experiments are conducted and motion capture used for each of the cases. Then the Lyapunov exponents of the time series of the knee joint angle are determined. Matlab software package is used for all calculations. Results are compared with data available in the literature. This work provides insight on the level of stability for added weight on the human squat exercise. This gives an insight on the level of safety of this exercise as weight is added to the human subject.
Clustering Algorithm Based Straight and Curved Crop Row Detection Using Color Based Segmentation
Authors: Khan Nazmuzzaman , Rajendran Veera P. , Al Hasan Mohammad , Anwar Sohel
Published: February 2021

Autonomous navigation of agricultural robot is an essential task in precision agriculture, and success of this task critically depends on accurate detection of crop rows using computer vision methodologies. This is a challenging task due to substantial natural variations in crop row images due to various factors, including, missing crops in parts of a row, high and irregular weed growth between rows, different crop growth stages, different inter-crop spacing, variation in weather condition, and lighting. The processing time of the detection algorithm also needs to be small so that the desired number of image frames from continuous video can be processed in real-time. To cope with all the above mentioned requirements, we propose a crop row detection algorithm consisting of the following three linked stages: (1) color based segmentation for differentiating crop and weed from background, (2) differentiating crop and weed pixels using clustering algorithm and (3) robust line fitting to detect crop rows. We test the proposed algorithm over a wide variety of scenarios and compare its performance against four different types of existing strategies for crop row detection. Experimental results show that the proposed algorithm perform better than the competing algorithms with reasonable accuracy. We also perform additional experiment to test the robustness of the proposed algorithm over different values of the tuning parameters and over different clustering methods, such as, KMeans, MeanShift, Agglomerative, and HDBSCAN.
Trajectory Control of Robotic Manipulators: A Comparison Study
Authors: Lee Ho-Hoon
Published: February 2021

In this paper, two different types of model-based trajectory control schemes are designed and compared for the control of robotic manipulators. First, two PD-based control schemes and one sliding-mode control scheme are designed, where Lyapunov stability theorem is used as a mathematical design tool. Then, the performances of the PD-based control schemes are compared to those of the sliding-mode control schemes with realistic computer simulations. The global asymptotic stability and the boundedness of all internal signals of the designed control schemes are shown with Lyapunov stability theorem.
Performance Analysis of Wind Tower Greenhouse Integration Using CFD
Authors: Sajjad Muhammad , Islam MD , Janajreh Isam
Published: February 2021

The current study investigates the effect of wind catcher-greenhouse integration on the micro-climatic conditions inside the green house. The potential application of wind tower in greenhouse systems for hot climatic conditions with water mist injection was carefully evaluated. The effect of various parameters such as air flow velocity, relative humidity, injector mass flow rate and injector position in the wind tower was studied. The variations in the temperature and relative humidity was observed in the greenhouse. The computational fluid dynamic analysis was carried out using Fluent and k-ε turbulence model was adopted for the analysis. A non-isothermal, multiple species, viscous and turbulent flow is pursued. It was observed that the addition of water injectors inside the wind catcher significantly reduced the temperature and enhanced the relative humidity of the air.
Data-Based Modeling for Reactive Ion Etching: Effectiveness of an Artificial Neural Network Model for Estimating Tungsten Silicon Nitride Etch Rate
Authors: Walters Madeline A. , Fan Zhaoyan , Sencer Burak
Published: February 2021

This paper presents a data-based approach for modeling a plasma etch process by estimating etch rate based on controlled input parameters. This work seeks to use an Artificial Neural Network (ANN) model to correlate controlled tool parameters with etch rate and uniformity for a blanket 1100 Å WSiN thin film using Cl2 and BCl3 chemistry. Experimental data was collected using a Lam 9600 PTX plasma metal etch chamber in an industrial cleanroom. The WSiN film was deposited over 3000 Å TEOS to ensure adhesion, with an 8-inch bare silicon wafer as the base layer. Controlled tool parameters were radio frequency (RF) upper electrode power, RF lower electrode power, Cl2 gas flowrate, BCl3 gas flowrate, and chamber pressure. The full factorial design of experiment method was used to select the combinations of experimental configurations. The ANN model was validated using a subset of the training data.
Vibration-Based Early Crack Diagnosis With Machine Learning for Spur Gears
Authors: Karpat Fatih , Dirik Ahmet Emir , Kalay Onur Can , Doğan Oğuz , Korcuklu Burak
Published: February 2021

Gear mechanisms are one of the most significant components of the power transmission systems. Due to increasing emphasis on the high-speed, longer working life, high torques, etc. cracks may be observed on the gear surface. Recently, Machine Learning (ML) algorithms have started to be used frequently in fault diagnosis with developing technology. The aim of this study is to determine the gear root crack and its degree with vibration-based diagnostics approach using ML algorithms.

To perform early crack detection, the single tooth stiffness and the mesh stiffness calculated via ANSYS for both healthy and faulty (25-50-75-100%) teeth. The calculated data transferred to the 6-DOF dynamic model of a one-stage gearbox, and vibration responses was collected. The data gathered for healthy and faulty cases were evaluated for the feature extraction with five statistical indicators. Besides, white Gaussian noise was added to the data obtained from the 6-DOF model, and it was aimed at early fault diagnosis and condition monitoring with ML algorithms.

In this study, the gear root crack and its degree analyzed for both healthy and four different crack sizes (25%-50%-75%-100%) for the gear crack detection. Thereby, a method was presented for early fault diagnosis without the need for a big experimental dataset. The proposed vibration-based approach can eliminate the high test rig construction costs and can potentially be used for the evaluation of different working conditions and gear design parameters. Therefore, catastrophic failures can be prevented, and maintenance costs can be optimized by early crack detection.
A Hybrid Supervised Deep Learning and Nonlinear Finite Element Framework for Efficient Fatigue Life Predictions of Rotary Shouldered Threaded Connections
Authors: Song Fei , Li Ke
Published: February 2021

In this paper, a hybrid computational framework that combines the state-of-the art machine learning algorithm (i.e., deep neural network) and nonlinear finite element analysis for efficient and accurate fatigue life prediction of rotary shouldered threaded connections is presented. Specifically, a large set of simulation data from nonlinear FEA, along with a small set of experimental data from full-scale fatigue tests, constitutes the dataset required for training and testing of a fast-loop predictive model that could cover most commonly used rotary shouldered connections. Feature engineering was first performed to explore the compressed feature space to be used to represent the data. An ensemble deep learning algorithm was then developed to learn the underlying pattern, and hyperparameter tuning techniques were employed to select the learning model that provides the best mapping, between the features and the fatigue strength of the connections. The resulting fatigue life predictions were found to agree favorably well with the experimental results from full-scale bending fatigue tests and field operational data. This newly developed hybrid modeling framework paves a new way to realtime predicting the remaining useful life of rotary shouldered threaded connections for prognostic health management of the drilling equipment.
Simulation of Large-Scale Magnetic Manipulation of Micro/Nano-Material Based on Monte Carlo Method
Authors: Su Che-Fu , Xiang Xinrui , Wang Jirui , Fratto Edward , Charmchi Majid , Gu Zhiyong , Sun Hongwei
Published: February 2021

Magnetic assembly of micro/nano materials are of great interest due to their unique properties. These nano-scale materials can be ensemble with other matrixes to prepare for new functional micro/nano composites with enhanced specific properties such as, thermal conductivity. In this study, we demonstrated the distribution and magnetic alignment of nickel (Ni) nanoparticle/nanowires inside of a non-magnetic matrix, (e.g., water or a molten wax), experimentally and computationally. A two-dimensional Monte Carlo simulation model is employed to investigate the aggregate structures of Ni nanoparticle/nanowires subjected to a one-directional static magnetic field. It is anticipated that the applied magnetic strength will influence the attractive forces between nanoparticle/nanowires that will produce chain-like cluster structures parallel to magnetic direction where the aligned chains will be separated by a range of distances that are also function of magnetic field strength.
Development of Manufacturing and Characterization Methods for Carbon Black-Based Conductive Polymer Composite Sensors
Authors: Albright Tyler B. , Hobeck Jared D.
Published: February 2021

This research details the process and methodology deployed to better understand the arrangement of colloidal carbon black (CB) nanoparticles in a spray-layer-by-layer (SLBL) manufactured conductive polymer composite (CPC). The effects of various SLBL parameters on the qualitative consistency and electromechanical performance of the resulting sensors are experimentally examined. Microscopy techniques are used to investigate the distribution and resulting CB structures of CPC films deposited on different types of substrates. Various substrate preparation methods and effects are discussed. Electrical characteristics of CPC films are investigated via deposition between copper electrode pairs on printed circuit boards. Practical applications of the characterized films are discussed along with future works regarding such sensors.
Naturalistic Male Skateboard User Speed Study
Authors: Buczek Sean , Eichaker Lauren , Graham Troy , Maull Thomas
Published: February 2021

Skateboards have been used as a means of transportation and extreme sport participation for decades. However, the prevalence of skateboards as a source of transportation is increasing. The laws that permit skateboard users to travel in roadways and in pedestrian walkways can vary by state, city, or county, allowing for a large variance in travel speed and user behavior. The amount of data available for the average speed of skateboard users during travel and trick initiation is limited. This study will preliminarily describe the natural travel and trick initiation speeds of skateboard users. The data that is presented in this study is beneficial to a vast audience including, but not limited to: traffic safety, road and intersection design, accident reconstruction, skateboard design, bearing design and useful life, and wheel design and useful life. This is an observational study of users on public spaces; no personal identification or biometric data was collected.
The Acquisition and Management of Healthcare Data, Within a Hospital Infrastructure
Authors: Darby-Taylor James , Luís-Ferreira Fernando , Sarraipa João , Jardim-Goncalves Ricardo
Published: February 2021

The quality of care provided to citizens by professionals and institutions depends on the quality and availability of information. Early commencement of treatment and medication, and the decisions on how to proceed, depend a lot on patients’ data in the different modalities available. It is also important to notice that large pools of data help inform health and wellbeing parameters for the largest possible community. To make that possible it is necessary both to have the best hospital practices but also to get consent and collaboration from patients. In order to accomplish such a goal, it is necessary to use practices, which adhere to legal constraints and are transparent while handling data and also to transmit those practices and protocols to professionals and patients. The present document aims to provide a framework envisaging the seamless application of the clinical procedures, following legal guidance and making the process known, secure and trustworthy. It aims to contribute to clinical practice, and clinical research, thereby contributing to big data analysis by ensuring trust and best clinical data handling.
Capacity Fade Estimation of a Lithium-Ion Battery Through an Integrated Electrochemical Battery Model and Empirical Cycle Aging Model
Authors: Anwar Sohel
Published: February 2021

An electrochemical model based capacity fade estimation method for a Li-Ion battery is investigated in this paper. An empirical capacity fade model for estimating the state of health of a LiFePO4 electric vehicle battery was integrated with electrochemical battery model in Matlab/Simulink platform. This combined model was then validated against experimental data reported in the literature for constant current charge / discharge cycling. An HPPC current profile was then applied to the validated electrochemical-empirical battery prognosis model which reflected a real-time operating condition for charge and discharge current fluctuations in an electric vehicle battery. The combined model was simulated under the two different HPPC current inputs for three different cycle times. Additionally temperature was taken in account in estimating the cycle aging under the applied current profile to assess the present capacity remaining in the battery. The simulation results provided the state of health (SOH) of the battery for these cycling times which were comparable to the published experimental SOH values for constant current charge/discharge profiles. Thus this model can potentially be used to predict the capacity fade status of an electric vehicle battery.
A Comparison Between Numerical and Experimental High Reynolds Number Supersonic Jets Generated by Millimeter Scale Converging-Diverging Nozzles
Authors: Conahan Joseph M. , Ozdemir Ozan C. , Taslim Mohammad E. , Muftu Sinan
Published: February 2021

In thermal spray applications, such as cold spray, an inert gas jet (typically helium or nitrogen) is used to accelerate micron scale particles to supersonic velocities. The complex gas dynamics of these supersonic jets are critical to understand via computational methods for the control of the spray. This work compares supersonic jet waveforms visualized by schlieren imaging with those predicted by computational fluid dynamics (CFD) simulations. A supersonic nitrogen jet is produced by a millimeter scale converging-diverging nozzle with inlet pressures as high as 50 bars. The jet Reynolds numbers based on the nozzle exit diameter and stagnation gas properties range between 60,000 to 325,000. A schlieren visualization setup has been built which shows the first spatial derivative of densities within the flow field. The strong density gradients across the oblique shock waves in the jets allow for clear photographs of the flow pattern of the jets using this schlieren visualization setup. Comparisons between the experiments and the CFD results act as a validation technique for the accuracy of the simulations in terms of the positions and orientations of the oblique shock waves. Through this study, the nozzle internal surface roughness is determined to be a critical parameter in millimeter scale nozzles for the development of the boundary layer. The CFD surface roughness parameters inside the nozzle are incremented until the geometry of the oblique shock waves matches the schlieren images. This work validates the simulation techniques which will be used for future jet simulations, in which shock wave locations and orientations are important, such as jet impingement on a flat plate and particle-shock interactions.
Experimental Investigation and Data Analytics of Annular Cutting Velocity in Inclined and Horizontal Pipes
Authors: Seibi Abdennour C. , Salazar Brandon , Ben Hmida Jalel , Guillory Gordon
Published: February 2021

The lack of cutting transportation during drilling operations especially in horizontal and inclined wells can lead to large amounts of non-productive time and costly solutions. This problem has been encountered very often in the field due mostly to settlement of the cuttings at the bottom side of the hole and especially around pipe joints. Moreover, adopted rheological models are limited to 60 deg. inclination angle to predict the flow behavior of cuttings transport in directional wells. Therefore, the objective of this paper is to investigate the effect of various parameters related to the well configuration (inclined vs. horizontal), operating conditions, pipe/tool joints configurations, and flow conditions on the cutting velocity through an extensive experimental study with data analytics. The experimental approach was analyzed through film software, which allowed for the cutting velocities to be estimated. Regression models of cutting velocity with respect to each dimensionless group were formed and validated through a statistical analysis. A new empirical model for the cutting velocity was developed using multiple linear regression analyses. A sensitivity analysis was conducted to highlight the contribution of each dimensionless group on the variation of the cutting velocity. The newly proposed model for cutting velocity was tested and the calculated cutting velocity of 0.532 ft/s (.162 m/s) fell within the range of study between 0.188 ft/s (.057 m/s) and 0.690 ft/s (.210 m/s).
Conductive Polymer-Based Sensor for Soil Nutrient Detection
Authors: He Yue , Zhang Shenglong , Dong Ziqian , Li Fang
Published: February 2021

To increase the production of crops, chemical fertilizers are used in crop fields. However, underuse or overuse cannot increase crop yields but even decrease them and cause severe environmental problems. Thus, the detection and monitoring of chemical concentration are increasingly important. To build up and monitor a data-based system for a large area, such a method is costly and time-consuming. In this research, we developed a conductive polymer-based sensor to detect nitrate concentrations in soil water. Conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) was used as our sensing material. To increase its conductivity, we used the vacuum phase polymerization method to achieve a high conductive and stable polymer film. The conductivity of the polymer film is 500 S/cm. Our results have demonstrated that the conductive polymer-based sensors have high sensitivity to nitrate solution. The response to 1000 ppm nitrate solution is 47.2% (Response = (Initrate - IDIwate) / IDIwater). The sensors can detect nitrate range from 1ppm to 1000 ppm. The response time is less than 1 minute. This impedance-based sensor will eventually be integrated with the surface acoustic wave sensors, combined with an antenna and a GPR unit for low maintenance, autonomous, and in-situ soil nutrient sensing.
Pre-Feasibility Study and Unit Sizing of Hybrid Renewable Energy System for a Global System for Mobile Communications (GSM) Station in Tabriz, Iran
Authors: Amini Reza , Pourgol Mohammad Mohammad
Published: February 2021

This research, a part of more extensive research, presents pre-feasibility and unit sizing analysis of a hybrid system equipped with renewable energy resources in Tabriz, Iran (46°26/E, 38°06/N). This case study examines a GSM telecommunication station as a stand-alone load system. Renewable energy resources include photovoltaic (PV), a wind turbine as primary resources and fuel cell, and a battery stack as backup and energy storage systems, while an electrolyzer is used to provide the required hydrogen in the fuel cell system. Feasibility analysis and unit sizing are conducted based on climatic data such as solar irradiance and wind speed to derive an optimal model during the study. HOMER software is used to simulate the feasibility analysis, measure the size, and optimize the system. The results showed that the hybrid system performs cost-effectively. According to wind energy data and fuel-cell costs, sensitivity analysis is conducted. The load is a stand-alone GSM station that consumes 60kW per day with a maximum of 3.8kW per hour. This analysis showed that wind, PV, electrolyzer, battery, and fuel cells are not currently the best solutions. Shortly, according to improved prediction in fuel-cell technology, it is expected that this source as a backup will be the best option because it has decreased fuel-cell costs up to 65 percent. Some criteria such as size, application, and cost, have been mainly examined. These results provide excellent opportunities for this hybrid system. The result shows using fuel cells in a hybrid system is not affordable by considering current fuel cell price, and the main suggestion hybrid system configuration is PV, wind turbine, and battery, while for the nearby location of Tabriz by decreasing wind speed, using wind turbines is not feasible and more PV array should be added to the system.
A Linear Acoustic Phased Array for Nonreciprocal Transmission and Reception
Authors: Adlakha R. , Moghaddaszadeh M. , Attarzadeh M. A. , Aref A. , Nouh M.
Published: February 2021

Acoustic phased arrays are capable of steering and focusing a beam of sound via selective coordination of the spatial distribution of phase angles between multiple sound emitters. Here, we propose a controllable acoustic phased array with space-time modulation that breaks time-reversal symmetry, and enables phononic transition in both momentum and energy spaces. By leveraging the dynamic phase modulation, the proposed linear phased array is no longer bound by the reciprocity principle, and supports asymmetric transmission and reception patterns that can be tuned independently. Through theoretical and numerical investigations, we develop and verify a mathematical framework to characterize the nonreciprocal phenomena, and analyze the frequency conversion between the wave fields. The space-time acoustic phased array facilitates unprecedented control over sound waves in a variety of applications including underwater telecommunication.
Effect of Sensor Failure on Dynamometry Calibration
Authors: Vlajic Nicholas , Jonson Michael , Guers Manton
Published: February 2021

Dynamometers are used to measure integrated fluid dynamic loads such as thrust, torque or side forces. To resolve all of three force and three moment components, multiple embedded force gages are often used. Due to arrangement, static loads, and redundancy, the number of sensor channels can exceed the six degrees of freedom needed to resolve the generalized rigid body forces. This paper considers modeling of the force gages as simple springs to develop an elastic model of the dynamometer. The method was applied to a dynamometer consisting of six three-component force gages arranged in an axisymmetric ring. A calibration matrix based on the elastic model with individual force gage sensitivities was shown to match a full calibration matrix where properly summed force gage voltages were obtained under global load application. The elastic model was then extended to consider calibration matrices where sensors were assumed to fail. In this scenario, several virtual loads were applied to the dynamometer and the calibration matrix was obtained by minimizing the least square error. It was found that nearly half of the sensors could be lost and still a virtual calibration could be applied to the measurements. Extending the least square idea, an actual in-situ calibration matrix was formed by striking the dynamometer with a diverse set of instrumented hammer strikes. This calibration matrix also agreed with the other calibrations at frequencies below where system dynamics become important.
Velocity Frequency Analysis for a Transverse Half-Car Model With Third Damper Using Bond Graph Approach
Authors: Darius Jared , Medina Hector
Published: February 2021

We present a bond graph analysis of a three-damper suspension system in a transverse half-car model. This is compared against the conventional two-damper system used in most commercial and racing vehicles. The transverse third damper system pioneered by the Koenigsegg Triplex suspension system is an innovative design said to improve straight-line tire contact during single-sided disturbance and help mitigate the adverse effects of squat and dive, while not inhibiting the function of the anti-roll bar’s lateral load transfer in cornering capability. No published literature exists exploring a transverse half-car model with effects of a third damper. We focused specifically on mathematical modeling of energy element relationships exploring vehicle dynamics frequency response behavior compared between transverse half-car models with and without the third damper. Calculated transfer functions explore first-order time derivative relationships of wheel-mass velocity to the harmonic input velocity of the road surface. The mathematical model demonstrated some ranges of resonance within typical driving and racing frequencies. Implementing the model to a Formula SAE race car, we explored the effects of manipulating spring stiffness, anti-roll bar stiffness, damping ratio, and mass in both two- and three-damper systems. Ultimately, it was observed that the addition of the third damper resulted in objective improvements in vehicle dynamics, shown by a reduction in amplitude ratio of both the left and right wheels compared to a conventional system. Interestingly, the left wheel (input side) experienced a greater reduction in amplitude ratio when it was hypothesized that the right wheel would be more affected.
Full Steam Ahead: Hands-on Elementary Education and Persistence During COVID-19
Authors: Das Madhurima
Published: February 2021

It is well recognized that the world needs to develop interdisciplinary problem solvers and creative thinkers to address the problems of the future. Training in the fields of Science, Technology, Engineering, Art, and Math (STEAM) is essential for understanding the complexity of the world around us and for identifying and tackling critical technical and social issues. To that end, many programs have been launched all around the world to expose students to STEAM fields and to encourage them to pursue STEAM careers. Hands-on, project-based learning has been shown to get more students engaged with STEAM and help them learn key skills for the future. However, most STEAM education programs target students in upper-middle or high school. If students are nurtured at earlier ages to love thinking critically, solving problems, and building, they are more likely to pursue STEAM fields.

This paper describes the implementation of project-based STEAM curriculum with elementary school students from ages 6–13. It includes a detailed discussion of curriculum design, case studies of specific student work, subjective analysis of engagement level with various projects, and discussion of lessons learned. The paper also discusses how the makerspace environment where the students execute their projects has been set up to be accessible for students in this age range.

Additionally, the paper describes how a hands-on STEAM curriculum that traditionally relies on in-person feedback, materials, and access to peers as teammates can be maintained while having students learning remotely. Educational techniques for hands-on learning while physical distancing due to the COVID-19 pandemic are discussed.
Nonlinear Dynamics of Human Aortas for Viscoelastic Mechanical Characterization
Authors: Amabili Marco , Balasubramanian Prabakaran , Bozzo Isabella , Breslavsky Ivan D. , Ferrari Giovanni , Franchini Giulio
Published: February 2021

The results of this work present eleven human thoracic aortas tested on a mock circulatory loop (MCL) that was developed to simulate physiological pulsatile flow conditions. Results showed cyclic axisymmetric diameter changes, which were compatible with in-vivo cyclic diameter changes at resting heart rate. The dynamic stiffness increased with age, but the cyclic axisymmetric diameter variation decreased with age when at a resting pulse rate. The energy dissipation was also noted to decrease with increased age. The synergistic effects of the fluid-structure interaction and the viscoelasticity led to larger damping at higher pulse rates. The projected outcome of this work is creating innovative biomaterials that better reproduce the aortic dynamic behavior. The findings complement expanding avenues in advanced materials, with the aim of creating improved and mechanically compatible cardiovascular devices, like grafts and stents.
Thermo-Oxidation Analysis of Structural Adhesives: An Experimental Study
Authors: Alazhary Sharif , Mohammadi Hamid , Dargazany Roozbeh
Published: February 2021

Cross-linked polymers play an important role in structural applications as adhesives. In this article, we performed an experimental study to understand the effects of high temperature i.e. thermo-oxidative aging on the mechanical behavior of polymers. Subsequently, the constitutive behavior, i.e. stress-strain relation of these adhesives before and after the accelerated aging tests were studied on samples aged at different temperature and different time durations at zero humidity. The aging conditions and periods selected for the tests have been specifically designed to simulate the effects of aging under the working conditions that the materials will be subjected to in their standard applications. The focus of this study is on the investigation of the effects of aging on the polymeric adhesives used in automotive applications. Consequently, four different polymeric adhesives (one silicone-based, two polyurethane-based, and one acrylic type), which are being used extensively in these applications, have been chosen. The quasi-static tensile loading was used on these four adhesives and the changes in the constitutive behavior were measured. The failure tensile tests as well as the cyclic tensile tests were performed in our lab using a Test-Resources tensile testing machine. The temperatures that were used in this work are 60, 80 and 95°C for varying aging periods of 24hrs, 240hrs, and 720hrs. Then, all the data was collected and consequently analyzed, and the resulting behavior was compared to that of the unaged material, showing varying results depending on the material, temperature, and aging period. Different behaviors have been observed after aging. The polymers’ behavior was expanding from no effect to significant damage caused by aging conditions. This work provides the core understanding required for modeling the material behavior during aging and lays down the groundwork for further data-infused model-free approaches.