bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation on Thermal Performance of a Simple Electronic Board Using Different Phase Change Material Packaging Types
Authors: Özkökdemir Emir , Usul Yener 
Published: February 2021

Abstract
Phase change materials (PCMs) are some kind of energy storage systems which have widely been used in many industries such as electronic equipment, heat pumps, buildings, solar panels and spacecraft thermal control applications. Two main outstanding features of PCMs are having large amount of energy storage capacity at low temperature difference between heat source-sink pair and being remained at almost constant temperature during phase change process. In this study, thermal performance of PCMs for passive cooling of electronic modules with heating components is investigated numerically. A commercially available solid-solid PCM is employed. Effects of different packaging types for PCM on thermal performance of the electronics board are examined. Three different packaging types are considered; bulk PCM inside a rectangular enclosure, a rectangular enclosure having rectangular fins with PCM inside and a rectangular foam structure. All of the enclosures containing the PCM are made up of aluminum. All of the PCM packages are placed over the heating component of the electronics board in the same environmental condition. Computations are performed in three dimensions using a conduction based finite element method. Computational method is verified by time-dependent temperature measurements of the PCM modules. Results for different cases are presented comparatively.
Acceleration of Grain Boundary Cracking in Ni-Base Alloy 617 Under Creep-Fatigue Loading at 800°C
Authors: Ishihara Kenta , Luo Yifan , Miura Hideo 
Published: February 2021

Abstract
In recent years, in order to solve the global warming issue, the operating temperature of advanced thermal power plants has attempted to improve thermal efficiency and reduce CO2 emissions. Under the creep and creep-fatigue conditions at elevated temperature, however, the effective lifetime of heat-resistant alloys such as Ni-base Alloy 617, which has high strength and good corrosion resistance at about 750°C, was found to decrease drastically. Main reason for this short lifetime was attributed to the change in the crack initiation and propagation paths from transgranular one to intergranular one. Therefore, it is important to understand and express the criteria for grain boundary cracking. In this study, electron back-scatter diffraction (EBSD) analysis was applied to the visualization of the degradation process of the quality of grain boundaries in the alloy. The change in the crystallinity of grains and grain boundaries were continuously monitored during creep and creep-fatigue tests. It was found that accumulation of vacancies and dislocations degraded the crystallinity of grain boundaries and thus, their strength. The accumulation occurred around the specific grain boundaries which consisted of grains with large difference of Schmid factor during creep test. On the other hand, it occurred around all grain boundaries under the creep-fatigue loading. Thus, the accumulation of defects was clearly accelerated under the creep-fatigue loading. The critical image quality (IQ) value of intergranular cracking was almost the same regardless of the loading mode. Once the IQ value of the damaged grain boundaries decreased to a critical value, intergranular cracking started to occur at the grain boundaries.
Tuning a New ECG and Breath Monitoring System Through Cardiopulmonary Exercise Test Comparison: The Case of IUTA Athletes
Authors: Fontanili Luca , Milani Massimo , Montorsi Luca , Scurani Letizia , Citarella Roberto 
Published: February 2021

Abstract
Heart Rate (HR) and Breath Rate (BR) are important parameters that define the physiological state of the athlete and evaluate his training the performances during a race or a match. In particular for runners, these are two indexes that can be easily monitored during the performance for the athlete to understand their physical state as well as for the trainer or the coach to improve the athlete deep knowledge and better design the subject specific training.
The HR can be typically acquired by lots of different technologies.
In this paper, a simple and fast fitting new device for ECG and BR acquisition is presented. This device is a first optimized prototype that use a reduced number of electrodes on the torso to acquire both the ECG waveform and a BR signal.
In order to evaluate the reliability and precision of this device we have defined an experimental campaign. Two IUTA athletes (a man and a woman) have been selected to wear the device during a Cardio Pulmonary Exercise Test (CPET).
The BR track and ECG waveform acquired by the CPET are compared to the ones acquired with the new device to confirm the reliability and precision of the system.
Evaluation of Fatigue Crack Growth Characteristics on Stainless Steel SS 316 LN Using Acoustic Emission Technique
Authors: Prakash Raghu V. , Thomas Manuel 
Published: February 2021

Abstract
Results of online acoustic emission (AE) monitoring during fatigue crack growth rate (FCGR) experiments on a stainless steel SS 316 LN are presented in this paper. Two specimen geometries — viz., standard compact tension (C(T)) specimens as well as side-grooved C(T) specimens were considered for experiments at ambient temperature and at 600°C (873K). There is a good correspondence between crack length increment and the increase in AE cumulative count and cumulative energy during the experiments. The side grove introduced on the thickness direction of the test specimen constrains the plastic zone ahead of the crack tip, thereby enforcing plane strain conditions at the crack. Reduced AE activity at initial stages of crack growth was observed for side grooved samples. The transition to Stage-II crack growth was observed using acoustic emission (AE) technique which otherwise was not visible from the fatigue crack growth plot.
The work further attempts to correlate the AE parameters obtained during elevated temperature (873K) fatigue crack growth in stainless steel. For the purpose of acquiring AE signals outside the heated zone, a waveguide was used to transmit the acoustic waves from the specimen at high temperature. A correlation between crack advance and AE parameters was obtained from the elevated temperature tests.
Theoretical Study of Heterojunction-Like Electronic Properties Between a Semiconductive Graphene Nanoribbon and a Metallic Graphene for Highly Sensitive Strain Sensors
Authors: Zhang Qinqiang , Qiao Xiangyu , Kobayashi Masasuke , Suzuki Ken 
Published: February 2021

Abstract
Graphene shows unique super-conductive properties and graphene nanoribbons (GNRs) with band gaps are the candidates for a sensing component of highly sensitive strain sensors. Usually, there is a large energy barrier between electrodes and semiconductors which is not suitable for electron transfer. Therefore, ohmic contact between them is indispensable for fabricating electronic applications. In order to achieve the ohmic contact between external electrodes and detective elements in the devices, the dumbbell-shaped structure of GNRs was proposed for the basic structure of the GNR-based strain sensors, dubbed as dumbbell-shape GNR (DS-GNR). It consists of a long narrow GNR at the center of the structure as the sensing element coalesced with two wider GNRs at both ends of the narrow GNR as the contact components to external electrodes. Both narrow and wide segments of DS-GNR consist of only carbon atoms. The effect of the interaction in the vicinity of the junction area between wide metallic and narrow semiconductive GNRs, however, has not been clearly demonstrated. In this study, first-principles calculations were implemented to the analysis of the electronic band structure of the DS-GNR. It was found that the localized distribution of the energy states of electrons exists in the wide segment of DS-GNR. The changes varied from wide to narrow segment is smooth and observable as strong functions of the length and the width of DS-GNRs. The current-voltage characteristics showed curved semiconductive-like electronic properties with a smooth-electron flow in DS-GNR. Therefore, the DS-GNR has great potential for the use of next-generation highly sensitive and deformable strain sensors.
Performance of a Generic 4-Step Global Reaction Mechanism With Equilibrium Effects for Detonation Applications
Authors: Peswani Mohnish , Maxwell Brian McN. 
Published: February 2021

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.