bluuebunny/crossref_metadata_2025_split huggingface dataset:
Three-Dimensional Concentration and Velocity Measurements of a Pulsatile Contaminant Release in a Model of Oklahoma City
Authors: Benson Michael , Chung Daniel , Fuhrman Gabriel , Helmer David , Homan Ty , Mooradian Lynne , Rhee Joshua , Elkins Christopher , Banko Andrew 
Published: February 2021

Abstract
Motivated by the Joint Urban 2003 field project and subsequent studies, magnetic resonance imaging (MRI) techniques were used to collect full-field measurements of three-dimensional fluid velocity and concentration across a scaled model of 2003 Oklahoma City. The study was intended to develop, test, and demonstrate a repeatable puff release with MRI compatible equipment. In order to accomplish this, a contaminant was injected through the floor of a city model in discrete puffs using a solenoid valve. Sealed to fit inside a water channel, the 1:2,206 scale city model covered the central business district of the city as it was in 2003. The main flow was fully turbulent with a Reynolds number of 36,000, while vertical puff injection occurred at a Reynolds number of 2,642. Using MRV and MRC methods, the three components of velocity and concentration were measured at more than 2 million locations for each of the 12 phases of the injection period. MRV measurements examined the fluid flow with respect to building geometry. Collected at heights corresponding to this MRV data, MRC measurements enabled the analysis of the vertical and lateral dispersion of the contaminant. Ultimately, the study demonstrated a novel MRI technique through contaminant puff release and can be used for the validation of urban contaminant dispersion models.
Numerical and Experimental Analysis of a Novel Concept for Axels Dry Braking System in Off-Road Vehicles
Authors: Milani Massimo , Montorsi Luca , Muzzioli Gabriele , Storchi Gabriele , Terzi Stefano , Rinaldi Pier Paolo , Stefani Matteo 
Published: February 2021

Abstract
The paper proposes a novel concept for axels dry braking system in off-road vehicles by implementing an oil recovery system in the friction plates chamber. The new system is able to remove the oil in the discs’ chamber when they are not engaged and to replenish it when the braking system is activated and the heat generated has to be dissipated. Thus, the energy losses due to the oil splashing will be significantly reduced with remarkable effects on the fuel consumption of the vehicle. Since experimental measurements are very difficult to carry out on a real system, a simplified geometry is designed and an ad-hoc test rig realized. Fast imaging techniques are used to capture the multiphase flow pattern within the friction plates chamber at different rotational speeds of the axel. The experimental results are used to validate a full 3D multi-phase CFD approach. A good agreement between the measurements and the calculations is found.
The numerical modeling is therefore employed to predict the flow distribution in the real geometry and under actual operating conditions. A modular approach is adopted for the domain subdivision in order to represent accurately the three dimensional geometrical features, while the volume of fluid approach is used to model the multi-phase flow that characterizes the component. A conjugate heat transfer model is also adopted to predict the heat transferred from the discs to the working fluid and how the fluid is dissipating the heat within the component. By means of the numerical analysis the geometry of the real system is designed in order to improve the performance of the dry braking systems both in terms of energy saving and oil cooling.
Wire Arc Additive Manufacturing (WAAM): Reviewing Technology, Mechanical Properties, Applications and Challenges
Authors: Zahid Moosa , Hai Khizar , Khan Mujtaba , Shekha Ahmed , Pervaiz Salman , Moneeb Ali Syed , Abdul-Latif Omar , Salman Muhammad 
Published: February 2021

Abstract
Because of the flexible nature of 3D printing and additive manufacturing technology, manufacturing sector has been revolutionized. There is a possibility to manufacture different intricate geometrics that cannot be produced through conventional processes previously. The conventional design concepts such as design for manufacture (DFM) and design for assembly (DFA) have been modified and simplified. Wire arc additive manufacturing (WAAM) has emerged as one of the leading additive manufacturing (AM) processes due to its high deposition rate and economic feasibility. A lot of progress has been made to understand and improve this process and the mechanical properties associated with the fabricated parts. It is specifically cheaper to print large-scale metallic components using WAAM. This paper gives a thorough review of the work that has been done on WAAM by comparing different technological variants of WAAM, which include Metal Inert Gas (MIG), Tungsten Inert Gas (TIG) and Plasma Arc Welding (PAW). The study also discusses the mechanical properties of the fabricated components using different metals, the defects and challenges the process faces today and how they can be reduced. In the end the study also provides overview of WAAM applications in some of the industrial sectors such as construction, automotive, and structural etc.
Development of Fiber Structures for High Performance Heat Resistant Curtains
Authors: Araujo Paulo , Teixeira José Carlos , Silveira Dionisio , Silva Elisabete , Soares Delfim , Fangueiro Raul , Vilarinho Maria Cândida 
Published: February 2021

Abstract
The protection of human life and goods assumes a growing concern in all forms of activities. The fire and smoke curtains have as main role to act as a physical barrier to prevent the fire from spreading between spaces as well as to staunch the smoke and heat transfer to adjacent areas. They can also be easily operated (opening and closing) causing a minimal interference with the flow of materials and humans within confines spaces, such as warehouses and industries, while providing adequate protection. Thus, there are a set of characteristics that these products must exhibit high fire protection, thermal resistance and gas impermeability.
The classification of the heat resistance, described in the European Standard BS EN 1634-1: Fire resistance and smoke control tests for door, shutter and, openable window assemblies and elements of building hardware — fire resistance tests for doors, shutters and openable windows, is the procedure that allows determining the response of a product in contributing by its decomposition to a fire to which it is exposed, being according to three criteria: (i) integrity, (ii) insulation and (iii) radiation.
Usually curtains are based on fiber-based structures which can be coated to enhance their protective capabilities. In addition, the fibrous structure can be tailored to optimize its behaviour using 2D and 3D complex architectures, with single or multiple materials.
The performance assessment of the curtains regarding the aforementioned parameters is performed resorting to several experimental procedures that are detailed in the specific standards.
The present paper reports the development of novel fibrous structures used for heat protection curtains. They are based on the various combinations of hybrid structures combining 2 or 3 different yarn materials. The tests are carried out in a purpose built oven that induces a steep temperature rate (approximately 600 °C in 5 min) on one side of the sample followed by a slower rate up to 950 °C in 60 min. The sample is placed under stress during the test in order to mimic that caused by its own weight. Thermocouples monitor the temperature on both sides of the sample and its integrity is assessed by both the occurrence of fabric rupture and smoke release due to ignition. Both the fabric integrity and the temperature on the back side of the sample are an indicator of its performance which follows the European Standard BS EN 13501-2: Fire classification of construction products and building elements. Classification using data from fire resistance tests, excluding ventilation services.
From the results one can conclude that hybrid structures, including either basalt and glass fibers, are the most suitable.
Design and Build a T-Shirt Cannon Firing Mechanism
Authors: Norvell Kyle , McClelland Michael , Ratajczak Ethan , Dong Janet 
Published: February 2021

Abstract
The work in this paper is a part of the T-shirt cannon automation project. The objective of the project is to develop an autonomous robot carrying cannons to automatically shoot T-shirts during the sports events at the University of Cincinnati (UC). More specifically, the T-shirt cannon will be used and driven by the UC cheerleading team and be able to automatically shoot T-shirts at the audience in the Nippert Stadium and the 5/3 Arena for football and basketball games, respectively. The design and automation of the T-shirt cannon require a significant effort and a multi-disciplinary team to complete. This paper will focus on the process of designing, building, and testing the firing mechanism for the cannon, including the determination of cannon’s firing method, barrel design and assembly, base design and barrel mounting method, pneumatic analysis, and automation and control of the firing of T-shirts. The goal of the firing mechanism is that the cannon would fire off as many T-shirts as possible with the window of a single timeout at the game.
The project starts with the preliminary research and the initial testing. During the preliminary research, the relevant safety standards/codes and previous T-shirt cannon designs were reviewed and studied. Especially the possible working with pressurized air, the material used in the design must be rated above the target firing pressure to ensure the cannon itself not explode and the air supply tank and fittings must be in good condition. During the initial testing, the site visits were conducted, the cheerleaders were interviewed, the dimensions of the stadium and the 5/3 arena were measured, and therefore the shooting distance and shooting angles were estimated. After the initial testing and preliminary research, a set of engineering characteristics were established, following by the concept design, in which the barrel assembly, the pneumatics, the firing mechanism, and the mounting method were discussed, analyzed, and determined. The barrels had two major designs, one is using a railing support system with an external tank of air to power and fire the cannon, and another one is using a chamber of air to power and fire the cannon with the barrels surrounding the air chamber itself. Two methods are analyzed and compared. The optimum one, therefore, was determined and developed. For the firing mechanism, two main designs are a spring-loaded firing mechanism that could increase the sealing capabilities of the barrels, and a tight tolerance fit that has less weight. Two designs were tested and analyzed, the optimum one was determined and built, followed by the firing mechanism testing.
This paper will describe the process of design, building, and testing the firing mechanisms of this T-shirt cannon at UC. The paper will also discuss the testing results on shooting performance.
Investigation of the Effects of Design and Process Parameters on the Mechanical Properties of Biodegradable Bone Scaffolds, Fabricated Using Pneumatic Microextrusion Process
Authors: Yu Mohan , Yeow Ye Jien , Lawrence Logan , Claudio Pier Paolo , Day James B. , Salary Roozbeh (Ross) 
Published: February 2021

Abstract
Pneumatic micro-extrusion (PME) is a direct-write additive manufacturing process, which has emerged as a robust, high-resolution method for the fabrication of a broad spectrum of biological tissues and organs. In the PME process, a high-pressure flow is injected into a cartridge, which contains a bioink material, resulting in pressure-driven material deposition on a free surface via a converging conical micro-capillary. In this study, PCL powder was loaded into the cartridge, maintained at 120 °C. The flow pressure was set to 550 kPa. Laminar molten PCL flow was deposited on a glass surface (steadily and uniformly kept at 45 °C), using a 200 μm nozzle. A porous, cylindrical scaffold was designed (honeycomb-filled), having a diameter and height of 10 mm and 3 mm, respectively.
To investigate the effects of the design and process parameters, a series of experiments were designed and conducted where print speed was varied at four levels in the range of 0.30–0.45 mm/s with 0.05 mm/s increments. In addition, similarly, layer height and layer width were changed at four levels in the range of 125–200 μm with 25μm increments. Finally, infill density was set at four levels in the range of 0.20–0.35 with 5% increments. As a result, 16 experimental runs were characterized, each replicated four times. Of each of the PME-fabricated samples, an image was acquired (both horizontally and vertically) using a high-resolution CCD camera. Illumination was provided by an LED ring light (being of a brightness in the range of 30,000–40,000 Lux as well as a color temperature of 6000 K). Subsequently, the acquired images were analyzed using in-house digital image processing algorithms, forwarded with the aim to characterize both the diameter and the height of the fabricated bone scaffolds. The veracity of the image-based measurements was corroborated, using offline caliper measurements. Furthermore, the compression properties of the fabricated bone scaffolds were measured using a compression testing machine; the samples were subjected to a compression load, applied with a velocity of 0.08 mm/s. Overall, the results of this study pave the way for future investigation of PME-deposited PCL scaffolds with optimal mechanical and morphological properties for incorporation of hBMSCs toward the treatment of osseous fractures and defects.
Nonlinear Vibrations of Model PWR Fuel Assemblies: Part 2 — Interpretation of Results Using Bilinear Stiffness Model
Authors: Balasubramanian Prabakaran , Ferrari Giovanni , Franchini Giulio M. , Amabili Marco , Karazis Kostas , Painter Brian 
Published: February 2021

Abstract
The experimental response of fuel rods with spacer grids was interpreted using a bilinear hysteresis model. Nonlinear experimental responses of two configurations of rods made out of Zirconium alloy tubes were considered in this paper: one configuration with a single beam and the second configuration with a cluster of beams (stacked in a 3 × 3 matrix formulation). These two configurations were designed to emulate part of the nuclear fuel assembly in Pressurized Water Reactors (PWR). Both configurations were supported by spacer girds at their extremities and were immersed in still water. Spacer grids are grid-like structures made out of thin Zirconium alloy sheets with 17 × 17 cells arranged in a square pattern. Spacer grids provide mechanical support and reduce flow-induced vibration of nuclear fuel rods. They also improve the heat transfer between nuclear fuel rods and the surrounding coolant. The spacer grids impose nonlinear boundary conditions to the beams at the contact points/surface. Specifically, spacer grids present bilinear hysteresis due to their inherent complexity. The bilinear hysteresis shown by spacer grids was measured in terms of force-displacement loops by testing rigid rod inserted in one of its cells. The rigid rod was then excited by external harmonic excitation with excitation frequencies ranging from 5 Hz to 50 Hz in steps of 5 Hz.
The bilinear hysteresis model, first studied by Caughey, was modified to include viscous damping and was used to interpret the experimental results. The method of slowly varying parameters was used to solve the equation of motion. First, the measured force-displacement loops of spacer grids were fitted with the numerical model described in the current analysis. Good agreement between the model response and measured loops was found, and the identified parameters allowed the characterization of the nonlinear boundary conditions imposed by spacer grids. Finally, the nonlinear responses of the two configurations under study were interpreted using the bilinear hysteresis model. Excellent agreement between numerical and experimental results was obtained for both configurations.
Experimental Investigation on the Performance Loss of Cross-Linked Polymers During Photo-Oxidative Aging
Authors: Korayem Abd-Elrahman , Mohammadi Hamid , Dargazany Roozbeh 
Published: February 2021

Abstract
Polymeric substances have seen an unprecedented integration in countless applications and fields of life, subjecting them to a broad range of environmental conditions, which can cause a form of damage to the structural and mechanical properties of these components known as aging. In this study we investigate the effects of the degradation of polymeric materials due to the extended exposure to sunlight, which can be simulated through controlled photo-oxidative aging using ultraviolet (UV) radiation as the main catalyst of this phenomenon. The effects on mechanical behavior and chemical properties of four polymeric materials with different mechanical characteristics was accordingly monitored throughout the study. The materials range in hardness with the polyurethane adhesive being the hardest and acting plastically, followed by an acrylic which exhibits greater hardening with time, a polyurethane sealant, which behaves in an elastomeric manner, and a silicon sealant, which is the softest of the set. Samples were prepared and subjected to UV radiation at three different temperatures namely 45, 60 and 80°C, for different aging periods ranging from 1 day for higher temperatures to 150 days for lower ones. The samples were then subjected to the Fourier transform Infrared spectroscopy (FTIR) test to monitor the change in the chemical composition of the materials along the aging durations and conditions. The materials were then subjected to mechanical testing along two modes of mechanical loading, which are a simple tension until failure and a double-cyclic test with progressively increasing strain limits after every two successful cycles until the sample reaches failure. The samples are loaded at constant strain rates throughout both tests. These tests revealed the change of behavior of our materials along the aging periods and conditions. The changes in mechanical behavior vary across each individual material depending on the aging temperature and period, with the changes ranging from hardening to softening, embrittlement or an increase in the maximum strain the material can endure before failure. A general trend would be that most materials become harder after photo-oxidation, however due to the range of temperatures in the aging conditions, thermo-oxidation, which causes softening in some of the polymers, has an increasingly notable effect at higher temperatures. A visible correlation can be noted between the change in mechanical behavior and a change in absorbance of Infrared Radiation (IR) in the FTIR spectrum, as the greater the crosslinking throughout the polymer matrix, the lower the absorbance of IR radiation due to the increased stiffness of the overall macro-molecular structure.
A Computational Fluid Dynamics (CFD) Study of Material Flow in Pneumatic Microextrusion (PME) Additive Manufacturing Process
Authors: Yeow Ye Jien , Yu Mohan , Day James B. , Salary Roozbeh (Ross) 
Published: February 2021

Abstract
The objective of this study is to investigate the underlying physical phenomena behind material transport in pneumatic micro-extrusion (PME) process, using a computational fluid dynamics (CFD) model. The geometry of the PME deposition head assembly (including a micro-capillary having a diameter of 200 μm) was set up in the ANSYS-Fluent environment, based on a patented design in addition to direct measurements of the dimensions of the assembly. Subsequently, the geometry was meshed using tetrahedron cells. Besides, five layers of inflation were defined with the aim to obtain an accurate solution near all wall boundaries. The transient, pressure-based Navier-Stokes algorithm (based on absolute velocity formulation) was the mathematical model of choice, used to obtain transient solutions. To account for the effects of compressibility as well as viscose heating, the energy equation (in addition to the continuity and momentum equations) was utilized in the CFD model. Furthermore, the explicit volume of fluid model (composed of two Eulerian phases) and the laminar viscose model were used to collectively establish a viscose two-phase flow model for the molten polymer (PCL) deposition in the PME process. Pressure-velocity coupling was implemented using the semi-implicit method for pressure linked equations (SIMPLE). Finally, experimental sensor data was used with the aim to: (i) define the boundary conditions (as follows), and (ii) validate the CFD model.
In this study, PCL powder was loaded into the cartridge, maintained at 120 °C, defined as the temperature of all stationery walls (with no slip condition). Pressure inlet was the type of boundary defined for the high-pressure gas flow in the PME process, set at 550 kPa. The laminar molten PCL flow was deposited on a glass substrate, steadily and uniformly kept at 45 °C, defined as the temperature of the substrate wall, moving with a speed of 0.35 mm/s. Overall, the results of this study pave the way for better understanding of the causal phenomena behind material transport and deposition in the PME process toward fabrication of bone tissue scaffolds with optimal functional properties.
3D Printed MEMS-Scale Vibration Isolators
Authors: Bond Arthur , Bottenfield Brent D. , Dean Robert N. , Adams Mark L. , Zhao Jing , Li XiaoFu , Flowers George T. , Perkins Edmon 
Published: February 2021

Abstract
Mechanical vibration isolation is an important element for many traditional MEMS devices, (e.g., MEMS inertial sensors and micro-optics) that are deployed in harsh environments (e.g., aerospace applications or automotive applications). Without suitable vibration isolation, environmental vibrations can potentially damage these devices. Micro-scale mechanical vibration isolators usually consist of a center proof mass pad, a suspension system, and a surrounding frame. The isolator functions as a mechanical low-pass filter that provides useful attenuation of high frequency environmental vibrations between the frame and the proof mass pad, to which the vibration sensitive device is attached. These vibration isolators are usually fabricated with either laser processing or silicon micromachining techniques. Although these traditional techniques produce high quality vibration isolators, these methods take time to develop for specific sensor applications, and the batch size is typically large. This paper has two key highlights. First, the efficacy of 3D printing as a prototyping tool for small batch MEMS sensor vibration isolation applications is considered. Twenty-five mechanical vibration isolators were tested for this investigation, using both SLA and FDM printers. The resulting test data demonstrated that the MEMS-scale 3D printed mechanical vibration isolators can be a valid option for real-world vibration isolation applications. Second, it is unclear whether the bulk material properties are valid for MEMS-scale 3D printed structures, since these bulk material properties are typically calculated using tensile tests on macro-scale dog-bone specimens. Considerable variation in vibratory system parameters was found, even when the same printer, print orientation, material, and post-processing were used.