bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design Evolution of a Novel Tilting Three-Wheeled Motorcycle for City Environments
Authors: Darling Jos , Harrison Adrian , Shalders Ben 
Published: November 2021

Abstract
The average speed of European City traffic is less than 12 miles per hour and the vast majority of journeys are less than two miles. It seems reasonable therefore to devise an environmentally friendly vehicle with low or zero emissions to serve a market that requires safe but manoeuvrable transport with a small road footprint. Working with European colleagues in industry and academia a narrow track three-wheeled vehicle with crash protection, partial enclosure, electric drive and lightweight construction has been developed to the prototype stage.
In this paper the design evolution of a tilting mechanism for this narrow track vehicle which provides locking of the tilt axis at low speed and variable damping at high speed is presented. Active and passive alternatives are discussed and a passive alternative is chosen on the basis of cost and safety. A range of actuation and speed sensing mechanisms are compared and a solution identified which is simple, low power, low cost and controllable. The system uses appropriate technology with a low maintenance requirement that is both compact and lightweight. Despite the potential for good reliability the system is designed to be fail safe; it is of paramount importance that the vehicle be allowed to tilt freely rather than become locked once the speed has risen above that required to balance. The driving style required at low speed, when the tilt axis is locked, will be different to that required at higher speeds, when the handling will be similar to that of a standard motorcycle. However the low lateral accelerations associated with low speed manoeuvres should make the change in driving style imperceptible and a degree of rear wheel steering, introduced as a result of the tilt axis, should improve mid-speed manoeuvrability. Having an estimated sale cost of $7000 the vehicle would be suitable for personal transport or a carrier of light loads in city environments.
A New Technique for Characterizing the Transient Rheological Response of Polymer Melt at High Shear Rates
Authors: Feng R. , Hu Y. 
Published: November 2021

Abstract
Characterization of the transient rheological response of polymer melts is important for computerized modeling and optimization of the manufacturing processes involving fast polymer melt flow such as injection molding and extrusion. In this paper, a new cone-and-plate rheometer utilizing the Kolsky torsion bar technique is reported. This rheometer can be accelerated to an angular velocity of 1600 rad/s within 100 μs. It enables characterization of the transient response of polymer melts for shear rates up to 104 1/s, temperatures up to 300°C, pressures up to 10 MPa, and shear strains up to 1000%. Experimental data are presented for a low-density polyethylene melt at shear rates between 780 1/s and 6840 1/s. The results show that the shear stress in the material increases not only with the shear rate but also more significantly with the shear strain. The significance of this finding is also discussed.
A Numerical Solution of the Inverse Problem for Thermoforming Processes Using Finite Element Analysis
Authors: Wang Chao-Hsin , Nied Herman F. 
Published: November 2021

Abstract
Finite element analysis of thermoforming simulation based on isothermal as well as non-isothermal initial conditions has been applied successfully for predicating final thickness distributions. For these simulations, it is assumed that the initial sheet temperature is known and does not change significantly during forming at a rapid stretch rate. For a non-isothermal analysis, the temperature dependent material properties are necessary. In this paper sample results are presented for the so-called inverse thermoforming problem, where an initial temperature distribution is sought numerically that will result in a specific final thickness distribution. Thus, a finite element simulation is combined with an iterative algorithm to obtain inverse solutions for a thermoformed part. In this example, the required initial temperature distributions that result in a uniform final thickness are determined for a thermoformed part. It is shown that the calculated results are quite sensitive to perturbations in the specified initial temperature profile and thus the practical application of optimal temperature distributions may require high precision thermal sensors and controls. This initial temperature distribution can then be used for the determination of desired heating patterns on zone-controlled heaters of a thermoforming machine using transient heat transfer analysis.
Runner System Design Optimization for Multigated and Multicavity Injection Molds
Authors: Jin Xiaoshi 
Published: November 2021

Abstract
Runner system design for injection molds with multiple gates or multiple cavities often requires iterative analyses for optimized results, because the gate locations or cavity shapes may not be naturally balanced. In addition, in molds with symmetrical layouts, the required injection pressure may be unnecessarily high if the runners are poorly sized. In this paper, a scheme for quickly optimizing runner system design is presented. The objective of design optimization is to minimize the required injection pressure within the design space defined by a given total runner volume. Each runner segment can be given an upper limit and lower limit to define the range of runner cross sectional dimensional size. Application examples are included to demonstrate the effectiveness of the scheme.
An Optimized Specimen for Crack Growth Studies in a Constant K Environment
Authors: Cammino R. , Gosz M. , Mostovoy S. 
Published: November 2021

Abstract
Techniques in computational fracture mechanics were employed to optimize the performance of a fracture specimen for use in crack growth studies in a constant K environment. The finite element method was used to model the specimen. In the numerical calculations, the mode I stress intensity factors were obtained using a domain integral approach. The specimen was optimized by systematically changing its geometry and performing finite element calculations in an iterative fashion. The procedure was carried out until a variation in the mode I stress intensity factor of less than three percent within the desired range of crack propagation was achieved.
Sizing and Topology Optimization of a Chassis Frame
Authors: Krishna Murali M. R. , Simboli Andrew 
Published: November 2021

Abstract
The application of sizing and topology optimization to a complete chassis frame has been undertaken to improve its performance within mass/weight constraints. The static frame stiffness (vertical bending and torsion), the first four modal frequencies and point mobility numbers were targeted for improvement. First, sizing optimization was undertaken to meet frame targets. The gage thicknesses of a number of different components, were allowed to be varied. This resulted in an increase in frame weight. Later topology optimization was undertaken to recommend the area where weight can be taken off without affecting the performance. An MSC NASTRAN optimizer was used for all the analyses.
Optimization of Mission Critical Joints in Bolted Machine Tool Structures
Authors: Kushnir Emmanuil , Patel Mahendra R. , Sheehan Terrence M. 
Published: November 2021

Abstract
In general, precision machine tools consist of a number of structural components, usually castings machined and bolted together to very tight and precise tolerances. Machine bolts are used to prevent the contact surfaces from separating or sliding relative to each other. The issues critical in the design of these precision bolted joints include tensile, compressive, and lateral stiffness, and stability of the joint under different types of load.
In machine tool design, the shape and tightening force in these joints are usually evaluated based on two counteracting requirements: (1) maintain sufficient stiffness provided by the joint at the cutting (load) point, and (2) allow the joint to slip (breakaway) in the event of a machine crash; in this case, the bolted joint works as a fuse preventing damage and, thus, protect critical/expensive components in the machine and/or avoid extensive repairs.
Field data from machines running production have shown that satisfaction of the two criteria, presented above, using conventional methods of bolted joint design does not always assure that the stability requirements are met. This data shows that in the range of loads that do not exceed the maximum force allowed in the machine, there might occur permanent lateral displacements in the joint. These displacements accumulate during normal operations under repeated loads and the machine looses alignment without obvious instantaneous slippage in the joint.
This paper discusses an approach that gives a qualitative and numerical evaluation of the joint shape, position of the bolts, tightening force, and load that it can withstand without compromising the joint integrity while still providing an effective breakaway for the protection of critical components.
Effects of Distribution in Headers of Microchannel Evaporators on Transcritical CO2 Heat Pump Performance
Authors: Beaver Andrew C. , Hrnjak Predrag S. , Yin Jian M. , Bullard Clark W. 
Published: November 2021

Abstract
This article presents experimental results on the effect of refrigerant distribution in microchannel a parallel flow evaporator that is part of an air conditioner/heat pump system that operates with CO2 in transcritical cycle. The improvements of COP achieved are as high as 20%. Three different refrigerant feeding strategies are discussed.
Performance Evaluation of a Window Room Air Conditioner With Micro-Channel Condensers
Authors: Kim Man-Hoe , Bullard Clark W. 
Published: November 2021

Abstract
The performance evaluation for a residential window air conditioning system with micro-channel condensers has been performed. First, a series of wind-tunnel calorimeter tests are conducted for two different prototype micro-channel heat exchangers. The measured heat transfer and pressure drop characteristics for the heat exchangers are then compared to four conventional finned round tube designs, which were obtained using a validated simulation model for identical air and refrigerant inlet conditions. Finally, two prototype micro-channel condensers are installed in the system and system performance tests are conducted. System characteristics such as capacity, energy efficiency ratio, and suction and discharge pressures and temperatures are presented, compared to those for the conventional system. Refrigerant charge amount for a window air conditioner with a micro-channel condenser is decreased by 35%, and the condenser core volume and weight can be reduced by 55% and 35%, respectively, compared to the conventional baseline system.
Regenerative PEM Fuel Cell Systems for Low Earth Orbit Satellites
Authors: Savin Olivier , Weng Dacong , Rehg Tim 
Published: November 2021

Abstract
Thanks to recent considerable progress in proton exchange membrane (PEM) technology, fuel cells and electrolyzers are on the verge of widespread commercialization. When a fuel cell and an electrolyzer are combined, a regenerative fuel cell (RFC) system is formed. By using an auxiliary power supply, such as solar power, for recharging, an RFC provides a complete power system for niche markets such as low-earth-orbit (LEO) satellites.
The thermodynamics of RFC systems are presented, and design tradeoffs are investigated: a unitized system, where the fuel cell and the electrolyzer are combined into a single electrochemical device, is compared to a discrete system, where the fuel cell and the electrolyzer are discrete components. The analyses show that the RFC is well suited for LEO space applications, due to an appropriate charge/discharge cycle, and represents a high-energy-density, high-efficiency power solution.
The Thermodynamics of Air-Water Vapor Mixtures
Authors: Adebiyi George A. 
Published: November 2021

Abstract
Traditional approaches to the thermodynamic analysis of processes involving air-water vapor mixtures are often limited to a psychrometric analysis and a first-law analysis. The substances involved are moist air (a mixture of dry air and moisture), and water (either as vapor, or as a liquid). A complete thermodynamic analysis must, however, include a second-law analysis.
This article presents a complete outline for the thermodynamic analysis and evaluation of processes involving air-water vapor mixtures. With regards to exergy analysis, in particular, it is noted that the published and widely accepted equation for the exergy of moist air is indeterminate when the humidity ratio of the ambient air is zero. This raises questions about the appropriate reference environment for water or water vapor when the atmospheric air does not contain moisture. The alternative of an expanded reference environment, which includes a large pool of water co-existing with ambient air is proposed in this article. The resulting equations for the exergy of moist air are determinate regardless of the humidity ratio of the atmospheric air in the reference environment.
The Scope of Application of Continuum Thermodynamics
Authors: Geskin Ernest S. 
Published: November 2021

Abstract
The objective of this study is to address the ambiguities concerning the application of continuum thermodynamics. In particular, we consider the limitation imposed on this application by the values of the time and space derivatives of the process variables as well as the degree of process irreversibility. We discuss the distribution and the properties of the shock waves in a compressible fluid. Shock waves are one of the fastest phenomena, which occur in continuous systems. It is shown that the analysis of this phenomenon is based completely on the apparatus of continuum thermodynamics. At the same time, the characteristic equations, which determine the distribution of the shock waves, do not depend on process irreversibility. We also show that any modification of the Gibbs (fundamental) equation due the rate of the process, for example, violate the First and the Second Laws of thermodynamics. The analysis presented demonstrates that the only condition for the application of continuum thermodynamics is compliance with the continuum hypothesis.
Three-Dimensional Thermocapillary Convection in Open Cylindrical Annuli
Authors: Sim Bok-Cheol , Zebib Abdelfattah 
Published: November 2021

Abstract
Three-dimensional, time-dependent thermocapillary convection in open cylindrical containers is investigated numerically. Results for aspect ratios (Ar) of 1, 2.5, 8, and 16 and a Prandtl number of 6.84 are obtained to compare the results of numerical simulations with ongoing experiments. Convection is steady and axisymmetric at sufficiently low values of the Reynolds number (Re). Transition to oscillatory states occurs at critical values of Re which depend on Ar. With Ar = 1.0 and 2.5, we observe, respectively, 5 and 9 azimuthal wavetrains travelling clockwise at the free surface near the critical Re. With Ar = 8.0 and 16.0, there are substantially more, but pulsating waves near the critical Re. In the case of Ar = 16.0, which approaches the conditions in an infinite layer, our results are in good agreement with linear theory. While the critical Reynolds number decreases with increasing aspect ratio in the case of azimuthal rotating waves, it increases with increasing aspect ratio in the case of azimuthal pulsating waves. The critical frequency of temperature oscillations is found to decrease linearly with increasing Ar. We have also computed supercritical time-dependent states and find that while the frequency increases with increasing Re near the critical region, the frequency of supercritical convection decreases with Re.
Measurements of the Effect of Pressure on the Thermal Conductivity of Silica Aerogel Particles
Authors: Vakil Sachin S. , Hosticka Bouvard , Norris Pamela M. 
Published: November 2021

Abstract
Aerogels are highly porous solids that are made out of a variety of materials such as silica, alumina, or zirconia. Silica aerogel, under a modest vacuum, has the lowest thermal conductivity of any known solid. Values as low as 0.008 W/mK have been reported. While monolithic aerogel is fragile, expensive, and difficult to work with, silica aerogel particles may pose a viable, cost-effective alternative as a thermal insulator. This study details thermal conductivity tests on silica aerogel particles at various pressures. An apparatus that enables cost effective and simple measurements of the total thermal conductivity of aerogel particles at a range of pressures is described. The apparatus employs a platinum resistor placed in the center of a glass spherical bomb filled with aerogel particles. The resistor is the heat source, whose direction of heat flow can easily be traced. Drawing on basic principles of heat transfer, the thermal conductivity of the aerogel particles is found by developing a heat balance to model the data gathered from the apparatus. Furthermore, to test the effects of pressure, a vacuum is used to reduce the pressure and to thus decrease the effective thermal conductivity. Crushed aerogel particles with diameters no greater than 300 μm were found to have thermal conductivities which fell within the same order of magnitude as bulk silica aerogel and the overall thermal conductivity decreased with decreasing pressure, as has been reported with monolithic aerogel.
Thermal-Fluid Transport Phenomena in Concentric Annulus With Inner Core Rotation Under Strong Heating
Authors: Torii Shuichi , Yang Wen-Jei 
Published: November 2021

Abstract
A numerical study is performed to investigate thermal-fluid transport phenomena in a concentric annulus, in which an axially rotating inner cylinder and stationary outer cylinder are strongly heated under the same heat flux. The anisotropic t 2 ¯ -εt heat-transfer model is employed to determine thermal eddy diffusivity. When the inner cylinder is at rest, the turbulent kinetic energy and temperature variance over the whole cross-section in the flow and thermal fields substantially diminish along the flow, resulting in laminartization, i.e., a deterioration in heat transfer performance at the inner and outer cylinder walls. By contrast, a substantial reduction in the turbulent kinetic energy and temperature variance in the laminarzing flow are suppressed in the presence of inner core rotation. In other words, an inner core rotation contributes to a suppression of laminarization of the strongly heated gas flow.
An Interdisciplinary Approach to Brain Tumor Growth Dynamics
Authors: Torquato Salvatore , Deisboeck Thomas S. 
Published: November 2021

Abstract
Intensive medical research over the last fifty years has left the prognosis for patients diagnosed with malignant brain tumors nearly unchanged. This suggests that a new perspective on the problem may offer important insight. We have undertaken an interdisciplinary research program, seeking to study brain tumors as complex systems. This research aims to develop computational models coupled with experimental assays to investigate the hypothesis of self-organizing behavior in tumor systems. Preliminary assays have revealed behavior consistent with this hypothesis. A cellular-automaton model to study the growth of the tumor core has been developed. This model has proven successful in reproducing macroscopic tumor growth from a limited parameter set. Further, it has been applied to investigate the importance of heterogeneity to determination of a clinical prognosis and has demonstrated the importance of understanding clonal composition in making an accurate prognosis.
Arthropod Motion-Sensing Hairs: Biological Models for Micro-Electro-Mechanical Systems
Authors: Humphrey Joseph A. C. , Barth Friedrich G. 
Published: November 2021

Abstract
The filiform hairs of terrestrial and aquatic arthropods are uniquely sensitive medium motion sensors, refined by natural selection pressures over hundreds of millions of years. These sensors provide biological models for the design and fabrication of corresponding artificial sensors that could be used for fundamental research as well as practical applications. However, the measurement and modeling of filiform hairs poses a highly complex interdisciplinary problem involving various facets of biology, mechanics and mathematics. Specifically, it is of special interest to uncover the basic “design” principles affecting the maximum angular deflection and maximum angular velocity, and their respective resonance frequencies, of the hairs as a function of the physical parameters that affect these four quantities. To this end, the physically-approximate theoretical analysis of Humphrey et al. (2000) is used to predict and understand the performance characteristics of single hairs. Calculated results obtained using the approximate analysis compare well with corresponding results from a more exact physical analysis and with previous measurements and calculations, showing that all qualitative aspects of hair behavior are correctly captured by the simplified theory. The theory is then used to explain the dependence of hair motion on the physical parameters that affect it. The findings of this study suggest that an artificial motion-sensing micro-electro-mechanical system (MEMS), patterned along the lines of an array of hairs, could be designed to detect and resolve the temporal and spatial characteristics of unsteady flow structures in the near-wall region of boundary layer flows.
Design, Fabrication and Heat Transfer Analysis of a Mesoscopic Pulse Tube as an Integrated Micro-Refrigeration System
Authors: Shinde Ninad , Bashir Rashid , Groll Eckhard , Chiu George 
Published: November 2021

Abstract
The phenomenon of surface heat pumping has been widely used to accomplish refrigeration in macro-scale devices such as pulse-tubes and thermo-acoustic devices. Pulse tube refrigerators are typically used to lift heat at cryogenic temperatures. The advantage of a pulse tube as a no moving part device makes it amenable to miniaturization at dimensional scales where areal effects, such as friction and viscosity, dominate. In this paper, the design and preliminary fabrication results of such a device to investigate the effect of surface heat pumping in mesoscopic glass channels are presented.
Scanning Thermal Wave Microscopy
Authors: Kwon O. , Shi L. , Miner A. , Majumdar A. 
Published: November 2021

Abstract
This paper reports the development of a new technique for nanometer-scale thermal imaging and thermal property measurement — scanning thermal wave microscope (STWM). By raster scanning a sharp temperature-sensing probe the STWM measures the distribution of the phase lag and the amplitude of a thermal wave on the sample surface at a certain distance away from the heat source. As a benchmark experiment for this technique, the phase lag distribution of a thermal wave generated by a line heat source on a Pyrex glass sample was measured and compared with analytical solution. The effect of liquid film at the tip-sample contact on the measured phase lag was also studied. The ability of STWM to locate sub-surface heat source in a ULSI circuit was experimentally demonstrated.