bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct Current/Alternating Current Magnetohydrodynamic Micropump of a Hybrid Nanofluid Through a Vertical Annulus With Heat Transfer
Authors: El-Masry Y. A. S. , Abd Elmaboud Y. , Abdel-Sattar M. A. 
Published: January 2020

Abstract
Gold nanoparticles (AuNPs) are increasingly being widely used in several biomedical applications for their compatibility of synthesis and less toxicity. The mixture of gold and titanium oxide nanoparticles is suspended in water to make a new class of nanofluid, which is called a hybrid nanofluid. The problem of direct current (DC)/alternating current (AC) magnetohydrodynamic (MHD) micropump of the hybrid nanofluid through a porous medium in the gap between vertical coaxial microtubes with heat transfer has been discussed. The mathematical model is established and then solved with the help of the Laplace transform. The inversion of the transformed functions is calculated numerically. The velocity, the flowrate, the pressure, and the heat transfer are discussed graphically. The higher concentration of the mixture of particles enhances the stream so that the required pressure is small. Moreover, it is found that the variation of the Nusselt number is noticeable by increasing the concentrations of nanoparticles, but this variation vanishes near the outer tube.
Constructing Oscillating Function-Based Covariance Matrix to Allow Negative Correlations in Gaussian Random Field Models for Uncertainty Quantification
Authors: Xu Hongyi 
Published: January 2020

Abstract
Gaussian random field has been widely applied to quantify high-dimensional uncertainties in the spatial or temporal domain. A common practice in Gaussian random field modeling is to use the exponential function to represent the covariance matrix. However, the exponential function-based covariance formulation does not allow negative values, thus it cannot capture the negative correlation between two locations in the input domain. To resolve this issue, this work reports new formulations of the covariance matrix based on oscillating functions, and a process of reconstructing Gaussian random field models from observation data. The proposed covariance functions are compared with the traditional exponential covariance functions on two test cases, where the datasets show negative correlations. The results of comparative studies demonstrate that the proposed formulations improve the accuracy of Gaussian random field models effectively.
Lateral Load Transfer due to Sloshing Cargo in Partially Filled Containers
Authors: Otremba Frank , Romero Navarrete José A. 
Published: January 2020

Abstract
The interaction of the liquid cargo and its carrying vehicle has been a common research subject, aiming at clarifying the potential effects of the mobility characteristics of such type of cargo, on the overall safety performance of the vehicle. While there has been extensive research on this topic, including both experimental and theoretical approaches, the comparative experimental testing of sloshing and non-sloshing cargoes has been only limited. In this paper, a scaled-down testing device that operates under the principles of a tilt table, is described and used to comparatively assess the effects, of a sloshing and non-sloshing cargo, on the lateral load transfer in the vehicle, as a function of the fill level and of the rate at which the lateral acceleration input is exerted on the vehicle-cargo system. Results suggest that the sloshing cargo generates greater load transfers, regardless of the fill level and acceleration rate input. As an average, the sloshing cargo generates a 14.75% greater load transfer.
Thermodynamic Modelling of Superfluid Stirling Cryocoolers
Authors: Domenikos G.-R. , Bitsikas P. , Rogdakis E. 
Published: January 2020

Abstract
The aim of this paper is to describe and thermodynamically model cryogenic Stirling refrigerators, using Helium in its different forms as the working medium. Helium has unique properties at cryogenic temperatures forming a superfluid. The cryogenic Stirling refrigerators with Helium at such low temperatures make use of the properties of this superfluid nature of Helium, thus they are referred to as Superfluid Stirling Refrigerators (SSR). To make use of these remarkable properties of superfluid helium a different version of Stirling refrigerator is used where superleaks are introduced in the pistons in order to let the superfluid part flow freely but constrain the normal fluid. This cooling procedure has an upper temperature limit as it is based on the superfluidity of helium, hence all the workings of this cycle must be well below the Lambda line. In addition, different models are needed and are used for the different isotopes of helium as their atomic spin nature is different and therefore their behavior at temperatures near absolute zero. In this study of SSR cryocoolers great care is being given towards the thermodynamic behavior of the entire system and working media, as well as different designs of the apparatus.
Power Electronics Sliding Mode Control Design for Photovoltaic Energy Conversion Systems
Authors: Gursoy Mehmetcan , Lozowski Andy G. , Wang Xin 
Published: January 2020

Abstract
The manuscript presents a novel power electronics sliding mode control design for photovoltaic energy conversion systems. In order to maximize the power generation from solar panels, P&O maximum power point tracking algorithm is applied. The purposed first and high-order sliding mode control techniques are developed to overcome the irradiance and load fluctuation challenge, and to optimize the power conversion efficiency. Compared with the first-order method, the higher-order sliding mode approach can significantly reduce the chattering effect in the Buck-Boost converter. The output of the DC-DC converter is then fed into a voltage-oriented control based SVPWM inverter for three-phase AC power generation. Computer simulation studies have shown the effectiveness and robustness of the proposed power electronics control approach for solar energy systems.
Effect of Shear Overloads on Crack Propagation in Al-7075 Under In-Plane Biaxial Fatigue Loading
Authors: Singh Abhay K. , Datta Siddhant , Chattopadhyay Aditi , Phan Nam 
Published: January 2020

Abstract
A cruciform specimen of Al 7075-T651 is used to study crack propagation behavior in an in-plane biaxial fatigue loading subjected to shear overloads of different magnitudes, which were applied at different crack lengths. The microscale fracture features of the specimen were identified and compared for the pre-overload region, overload region, and post-overload region at two different values of crack lengths, using scanning electron microscopy (SEM). It was observed that the transient region, created by the application of the shear overload, improved the fatigue life of the specimen. The overload also displayed an instant upsurge in the fatigue crack growth rate, which was immediately followed by a sharp crack retardation. The crack growth rate was restored once it came out of the transient zone and traveled a distance equal to the value of recovery distance. Both, the magnitude of the applied shear overload and the location of overload with respect to crack length seemed to affect the size of the transient zone, fatigue life, crack growth rate, and recovery distance. Investigations made on the fracture surfaces revealed that there is no significant change in the microscale fracture features when the overload was applied at different values of crack lengths; however, a clear and significant difference in the fracture features appear when the surfaces of the pre-overload region, overload region, and post-overload region are compared.
Improving Power and Frequency Bandwidth of a Magnetic Spring Based Vibration Energy Harvester Using FR4 Spring-Guided Magnet
Authors: Aldawood Ghufran , Nguyen Hieu Tri , Bardaweel Hamzeh 
Published: January 2020

Abstract
This article introduces an enhanced magnetic spring based energy harvester design suitable for harvesting kinetic energy from vibrations that are characterized by low acceleration levels. The presented design consists of a levitated magnet, an FR4 spring-guided magnet and coils. Prototypes of the enhanced harvester design are fabricated and characterized experimentally. For comparison, a traditional magnetic spring based vibration energy harvester is fabricated and characterized experimentally. Results from experiments confirm the superiority of the proposed enhanced harvester design over the traditional harvester design. At 0.1g [m/s2], the peak power of the enhanced harvester reaches approximately 40 times the peak power generated by the traditional harvester. At this acceleration level both enhanced and traditional harvesters exhibit approximately 0.4 [Hz] frequency bandwidth. At 0.3g [m/s2] the improvement in power generated by the enhanced harvester is approximately 400% compared to the power generated by the traditional harvester while the frequency bandwidth increases by 80%.
Miniature Humanoid Upgrade for Material Handling Tasks in Humanoid Challenge
Authors: Sohn Kiwon , Lee Jeongkyu , Huang Kevin 
Published: January 2020

Abstract
This paper presents the development of a miniature humanoid platform for various material-handling tasks. Since 2018, three universities in Connecticut (University of Hartford, University of Bridgeport and Trinity College) have made continuous efforts on building and organizing the annual robotics competition which is titled as Humanoid Challenge (HC). While most robotics competitions are concentrating on mobile robot and its navigation, HC focuses on the small-sized bipedal robot platform (miniature humanoid) and its task-execution in human-centered-environments. Inspired from DRC Trials 2013 and Finals 2015, the participants in the competition are asked to complete six different tasks in a mock-up of a disaster. To assist students and teams who are interested in participating in the competition, the authors in three universities share the progresses with both hardware and software components of each teams robot platform through this paper.
Measured Performance of a Variable Transmission Glazing System
Authors: Al-Dossary Ali , Dillon Heather , Farina Jordan 
Published: January 2020

Abstract
Variable Transmission Glazing (VTG) windows are an energy efficiency measures that have relatively high first cost. This paper describes the in-situ performance of VTG installed in an atrium space at the University of Portland. An experiment was conducted using thermocouples and photosensors to examine temperature gradients and solar gains across electrochromic glazing windows to quantify the performance of the installed system in terms of energy and cost saving. The system performance was measured with an average efficiency of 98.73% when the VTG was operating. The annual savings of the glazing system installed was estimated to be $7,683.
A Probabilistic Fatigue Damage Model for Describing the Entire Set of Fatigue Test Data of the Same Material
Authors: Le Xiaobin 
Published: January 2020

Abstract
One typical widely-accepted approach for describing the fatigue test data is the P-S-N curve approach. However, the P-S-N curve approach has some issues such as: (1) If there are only a few fatigue test data at a fatigue test stress level, the P-S-N curve approach is not valid due to the small sample size; (2) When the total number of fatigue tests under different stress levels might be larger such as more than 30 even though the number of fatigue tests at the same stress level is small, the P-S-N curve cannot be used to analyze such set of fatigue data; (3) It is difficult to calculate the reliability of a component under a cyclic stress level when the probabilistic distribution function under this stress level is not available in the P-S-N curves. The author has proposed the K-D probabilistic fatigue damage model (K-D model) to overcome those issues. The 6061-T6 10-gauge sheet-type flat fatigue specimen was designed, manufactured, and tested on the Instron 8081 fatigue test machine to verify this K-D model. The fatigue tests were under five different cyclic axial loadings with a total of 195 tests. In this paper, the fatigue test data will be analyzed by the P-S-N curve approach and the K-D model. The systematic comparisons between the P-S-N curve approach and the K-D model have approved and verified that the K-D model can be used to analyze and to describe the fatigue test data under all different fatigue stress levels and can be used to calculate the reliability of a component under any type of cyclic fatigue loading.
Hydrodynamic Coefficients for an Extraterrestrial Submarine
Authors: AlHasni Hani , Thornquist Ona , Islam Shafquat , Garrison Peter , Sahin Iskender 
Published: January 2020

Abstract
An autonomous submarine design was proposed as part of NASA’s NIAC program to explore the hydrocarbon seas of Titan, the Saturnian moon, and study its hydrological cycle. The submarine is to be capable of operating at both the surface and in a deeply-submerged mode. This study aims to complement and compare previous CFD simulations with results obtained using the panel code CMARC. The comparison is of interest as the previous studies included a grid-based viscous code and a particle method using smoothed-particle hydrodynamics. The previous approaches encountered difficulties in obtaining agreeable results as each method has flow regimes suitable for a specific formulation, specifically free-surface flow versus a deeply submerged case. The panel formulation presented here is for the deeply submerged configuration and results match well with other approaches and parametric analyses, particularly when appendages are included in the modeling.
Simulation and Validation of a Two-Phase Pumped Loop Cooling System
Authors: Magee Thomas C. , Hines Kristen M. , Dumesh Mike A. , Meekins Andrew D. , Bridges Michael M. 
Published: January 2020

Abstract
Two-phase refrigerant pumped loop cooling systems have seen wider use in recent years because of higher power density electronics and the need for increased heat transfer capability. However, two-phase systems are difficult to model because they operate in a closed-loop and both liquid and vapor phases exist and change with time throughout the system.
A two-phase “test-bed” system was constructed in order to explore the various operating regimes and limitations of this technology. Additionally, physical results from this test-bed were used to determine if the system performance could be accurately modeled using a commercially available software package such as SINDA/FLUINT. The refrigerant circuit uses R134a as the cooling fluid that is pumped around a complete loop using a positive displacement pump. Heat is added at the evaporator using ceramic heaters on the outside of the housing that boils the fluid, resulting in a liquid/vapor mix in the transport tube. Heat is removed at the condenser which is a commercial flat plate heat exchanger that uses building water for cooling. A closed-loop fluid-thermal model of the test-bed was created in Thermal Desktop®, which is the pre and post-processor for the SINDA/FLUINT analyzer, and compared to several tests conducted on the physical system at varying heat loads. The model successfully predicted the system performance after adjustments to the model for refrigerant mass charge and condenser performance. The maximum difference between the measured evaporator temperature and the modeled temperature was only 6.1°F; which occurred at the highest heat input level (1400 Watts). Explanations for differences between model and test results will be discussed. In particular, modeled system temperatures were found to have a very non-linear sensitivity to the total refrigerant mass charge.
Best Structural Theories for Free Vibrations of Sandwich Composites via Machine Learning
Authors: Petrolo Marco , Carrera Erasmo 
Published: January 2020

Abstract
This work presents a novel methodology for the development of refined structural theories for the modal analysis of sandwich composites. Such a methodology combines three well-established techniques, namely, the Carrera Unified Formulation (CUF), the Axiomatic/Asymptotic Method (AAM), and Artificial Neural Networks (NN). CUF generates structural theories and finite element arrays hierarchically. CUF provides the training set for the NN in which the structural theories are inputs and the natural frequencies targets. AAM evaluates the influence of each generalized displacement variable, and NN provides Best Theory Diagrams (BTD), i.e., curves providing the minimum number of nodal degrees of freedom required to satisfy a given accuracy requirement. The aim is to build BTD with far less computational cost than in previous works. The numerical results consider sandwich spherical shells with soft cores and different features, such as thickness and curvature to investigate their influence on the choice of generalized displacement variables. The numerical results show the importance of third-order generalized displacement variables and prove that the present framework can be of interest to evaluate the performance of any structural theory as typical design parameters change and provide guidelines to the analysts on the most convenient computational model to save computational cost without accuracy penalties.
Investigation of Flashing Flow in a Siphon to Extract Condensate in Paper Dryer Application
Authors: Majeed Hamed Abdul , Wang Ting 
Published: January 2020

Abstract
The paper industry uses steam to dry paper web through cylinder dryers. As steam condenses inside the cylinder dryer, the condensate is removed by means of either a stationary or a rotary siphon. However, during the siphoning process for transporting the condensate, flashing of the condensate occurs, which could cause backflow or discontinuity in the siphoning process. To resolve this flashing issue, two approaches have been employed: (a) increasing the amount of steam supplied to the cylinder to “blow-through” the stalled condensate-steam mixture and (b) reducing the back pressure by inducing “suction” through a thermocompressor from downstream. This practice of employing push from the upstream and suction from the downstream requires excessively large amounts of high-grade steam, resulting in an estimated 10 to 15 %, 15 to 25%, and 40 to 90 % of blow-through steam for stationary siphons, rotary siphons, and Yankee dryers respectively. The objective of this study is to investigate and improve understanding of the flashing phenomena during condensate transport through the siphon and piping system in order to develop means to reduce this excessive steam consumption during the paper drying process. A computational fluid dynamics (CFD) simulation is performed that uses the Eulerian-Eulerian multiphase method. The steady-state case is first solved to obtain the flow field without flashing. Then the transient method is initiated by employing flashing and condensation models. The results show that reduction of local pressure triggers flashing, however, flashing in turn reduces local temperature, and subsequently induces condensation, resulting in an alternating flashing and condensation behavior. To maintain continuity of the siphon flow, the inlet pressure fluctuates corresponding to the variation of total vapor volume ratio inside the siphon. The results will be used to modify the current siphon system design and operating practices to reduce steam consumption.
Experiments on Vortex Shedding From Reconfigured Flexible Filaments Vibrating in Flow
Authors: Silva-Leon Jorge , Cioncolini Andrea 
Published: January 2020

Abstract
This paper describes an experimental study of the spanwise vortex shedding frequencies from cantilever flexible filaments which are bent (reconfigured) when exposed to air crossflow. At a reduced velocity of approximately U* = 1500 (based on filament diameter) the filaments started to vibrate in the inline direction. Hot-wire anemometry was thus employed to investigate the wake flow of filaments of three aspect ratios (L/D = 38, 80, and 113) at Reynolds numbers Re &lt; 300. Despite the large relative inclination angles between the filament and the flow direction, the vortex shedding frequency measured along the span of the filaments remained close to those of a cylinder in pure crossflow. Moreover, it was found that as the aspect ratio (axial length) of the filaments was increased, vortex shedding lost coherence towards the free end of the filaments, whereas this was not the case for the shortest aspect ratio filament currently tested. This is thought to be due to the interaction between the crossflow vortex shedding and the axial flow component developing along the wake of the inclined filaments. Through comparisons with stiff inclined wires it was confirmed that the spanwise vortex shedding behaviors observed (frequency and coherence) were not modulated by the motions of the filaments.
Design of a Deformable Smart Tire Using Soft Actuator
Authors: Nandikolla Vidya K. , Costa Michael , Boyd Nathan , Rosales Gilberto 
Published: January 2020

Abstract
The unique functional properties of nickel-titanium Shape Memory Alloys (SMA) enable them to be used as actuators. This research paper demonstrates theoretically and experimentally the feasibility of using SMA in smart tires for a mobile robot. The design procedure for SMA as a coil spring actuator for a soft deformable wheel is described. The primary focus is the mechanical modeling, manufacturing, and system dynamics of a soft deformable wheel. The 3D printed soft tire exploits the capabilities of the SMA actuation using a voltage signal. The printed components are activated and integrated with electromechanical circuit for wireless communication system. The performance of the force feedback control system is evaluated at different operating conditions to demonstrate the shape-changing characteristic of the smart tire. The developed prototype is designed to propel forward and backward on flat and uneven surface. The experimental results obtained demonstrate the potential of SMA as soft actuators, its benefits and limitations as flexible systems.
A Method for Approximating the Mechanical Section Properties of Structural Members With Highly Complex Cross-Sections
Authors: Munsell W. P. 
Published: January 2020

Abstract
While mechanical section properties (such as the centroidal moment of inertia) of simple cross sections are easily calculated, those of highly complex structures (including organically-generated structures) defy such analyses. In this paper a method is described for approximating the mechanical section properties of highly complex cross-sections, and the factors affecting its accuracy are tested and its error rate is quantified. The method relies on the analysis of digital images of the subject cross-section and does not require extensive user expertise or investment in expensive FEA programs to implement. The limited file space necessary to install the required code means that standard smart phones could be used to directly evaluate the most complex cross-sections in the field.