bluuebunny/crossref_metadata_2025_split huggingface dataset:
Short Apron Drop Tests in Support of Automotive Composites Consortium Focal Project I
Authors: Browne Alan L. , Johnson Nancy L. 
Published: December 2021

Abstract
This paper documents the short apron drop tests that were conducted in support of ACC Focal Project I. The objective of Focal Project I, which has been successfully completed, was to develop a composite front apron that demonstrated acceptable structural and energy management characteristics while using a manufacturable preform configuration. The purpose of the short apron drop tests described in this paper was to validate various composite apron fabric/reinforcement designs and crush initiation methods in terms of their ability to produce stable progressive crush at acceptable force levels in frontal axial impacts prior to full scale sled, cart, and barrier tests. Most of the design approaches evaluated in these short apron tests were selected on the basis of promising performance in crush tube tests, of both hourglass (apron lower rail) and square-to-rectangular (apron upper rail) cross-section crush tubes. The subject short apron drop tests allowed a full scale check of these concepts on the apron level prior to significantly more expensive and time consuming full scale sled and barrier testing. A total of 17 such drop tests were conducted during the several year duration of Focal Project I, testing in general being in more of an iterative mode where we kept trying to move closer to the desired goal. The fact that these tests proved to be an important contributor to the success of Focal Project I is based on two observations, first the fact that more than one test was necessary, meaning that the first design (and several subsequent iterations) didn’t result in the desired response and second that the final short apron test, which was an unqualified success, gave support for the final successful full scale barrier test.
Transition From a Frontal Impact to a Redirection Impact on a New Bullnose Guardrail System Design
Authors: Reid John D. 
Published: December 2021

Abstract
Bullnose guardrail systems are used to protect vehicles from hazards in the median of divided highways. The Midwest Roadside Safety Facility is currently designing and testing a new bullnose system that will meet relatively new Federal safety performance specifications. After developing a system that successfully handled frontal impacts, attention was then focused on the redirection impacts required of such systems. Similar to vehicle design for frontal and side impact, there are many differences in the modeling and simulation requirements between frontal and redirection impacts for bullnose systems. Several complicated modeling problems were solved that only became evident when contacts became unstable during the simulations. The problems were mainly related to modeling issues such as course mesh sizes, contact penalty factors, contact thicknesses, edge-to-edge penetrations not being addressed in the model, and unstable element formulations after significant hourglassing had been induced. The resulting model can now be used to help re-design the bullnose system to meet the redirection requirements of such systems.
An Investigation of Thermal Enhancement on Flip Chip Plastic BGA Packages Using CFD Tool
Authors: Lee Tien-Yu Tom 
Published: December 2021

Abstract
This paper demonstrates the advantage of applying Predictive Engineering in thermal assessment of a 279 I/Os, 6-layer, depopulated array flip chip PBGA package. Thermal simulation was conducted using a Computational Fluid Dynamics (CFD) tool to analyze the heat transfer and fluid flow in a free air environment. This study first described the modeling techniques on multilayer substrate, thermal vias, C5 ball, and PCB. For a flip chip package without any thermal enhancement, more than 90% of the total power was conducted from the front surface of the die through the solder ball interconnects to the substrate, then to the board. To enhance the thermal performance of the package, the heat transfer area from the backside of the die needs to increase dramatically. Several thermal enhancing techniques were examined. These methods included copper heat spreader with various thicknesses and with thermal pads, metallic lid, overmolded with and without heat spreader, and with heat sink. With an aluminum lid and a heat sink, it gave the best improvement; followed by a heat spreader with thermal pads. Both methods reduced thermal resistance by an average of 50%. Detailed analyses on heat flow projections are discussed.
Computation of Transient and Steady Turbulent Isothermal Flows With an Impinging Rectangular Jet
Authors: Tucker P. G. , Pan Z. 
Published: December 2021

Abstract
The computation of both transient and steady turbulent incompressible isothermal flows is studied. The flow is very complex, having streamline curvature, large vortex structures and stagnation resulting from an impinging rectangular jet. For transient computations, the standard k-ε model is adopted. For steady flows, the k-ε, high and low Reynolds number k-l and mixing length models are tried. Zonal approaches combining the above turbulence models are also investigated. None of the models are found to give satisfactory agreement with velocity measurements.
Predictive Techniques for Turbulent Oscillatory Flows
Authors: Tucker P. G. 
Published: December 2021

Abstract
The prediction of turbulent oscillatory flow at around transitional Reynolds numbers is considered for an idealized electronics system. To assess the accuracy of turbulence models, comparison is made with measurements. A stochastic procedure is used to recover instantaneous velocity time traces from predictions. This procedure enables more direct comparison with turbulence intensity measurements which have not been filtered to remove the oscillatory flow component. Normal wall distances, required in some turbulence models, are evaluated using a modified Poisson equation based technique. A range of zero, one and two equation turbulence models are tested, including zonal and a non-linear eddy viscosity models. The non-linear and zonal models showed potential for accuracy improvements.
Effect of Humidity on PEM Fuel Cell Performance: Part I — Experiments
Authors: Lee W. K. , Van Zee J. W. , Shimpalee S. , Dutta S. 
Published: December 2021

Abstract
It is well known that proper water management inside a polymer electrolyte membrane (PEM) fuel cell is essential for obtaining high performance. Insufficient water lowers the conductivity of the membrane and yields low currents at a fixed voltage whereas excess water leads to flooding of the electrode and low currents at a fixed voltage due to a decreased reaction area. Typically the internal hydration is adjusted by the inlet humidity of the feed streams however the optimum depends on the given membrane and electrode assembly. As a first step in predicting this optimum a priori, data are presented for a 10-cm2 test cell with serpentine flow channels. Currents were measured for various unsaturated inlet humidity conditions, at different cell voltages, and for various operating cell temperatures. Data on the closure of water balances are presented and used to quantify the humidity effects on the current. These experimental data provide a basis for the numerical simulations presented in part II of this paper.
Slug Flow Model for Infiltration Into Fractured Porous Media
Authors: Martinez M. J. 
Published: December 2021

Abstract
A model for transient infiltration into a periodically fractured porous layer is presented. The fracture is treated as a permeable-walled slot and the moisture distribution is in the form of a slug behind an advancing meniscus. The wicking of moisture from the fracture to the unsaturated porous matrix is a nonlinear diffusion process and is approximated by self-similar solutions. The resulting model is a nonlinear Volterra integral equation with a weakly singular kernel. Numerical analysis provides solutions over a wide range of the parameter space and reveals the asymptotic forms of the penetration of this slug in terms of dimensionless variables arising in the model. The numerical solutions corroborate asymptotic results given earlier by Nitao and Buscheck (1991), and by Martinez (1988). Some implications for the transport of liquid in fractured rock are discussed.
Local Furnace Data and Modeling Comparison for a 600MWe Coal-Fired Utility Boiler
Authors: Hwang Yuh-Long , Howell John R. 
Published: December 2021

Abstract
Reductions in Furnace Exit Gas Temperature (FEGT) by changing boiler operating variables and/or adding wall soot blowers and/or lowering burner elevations are investigated. Evaluation of these approaches requires experimental furnace testing and computational furnace modeling. The experimental facility is a Combustion Engineering corner-fired pulverized-coal boiler with a capacity of 606 MWe. Local gas temperature distributions, local radiative and total wall heat flux distributions, and stack NOx were measured during constant-load furnace tests under various combinations of burner configuration, burner tilt angles, excess-O2 setpoints and overfire airflow rate. These measurements are used for tuning and calibrating a furnace model based on the PCGC-3 code developed by Brigham Young University. The experimental data gathered in this work comprises a comprehensive set under controlled conditions on a very-large-scale coal-fired plant, and provides information for use in comparing the predictions of furnace-design codes.
The Influence of Oxygen Injection Configuration in the Performance of an Aluminum Melting Furnace
Authors: Nieckele Angela O. , Naccache Mônica F. , Gomes Marcos S. P. , Kobayashi William T. 
Published: December 2021

Abstract
In the present work, a numerical simulation of the 100% oxy-firing combustion process inside an industrial Aluminum Remelting Reverb Furnace is presented. A staged combustion oxy-fuel burner is being simulated. The natural gas and oxygen were injected toward the aluminum bath, which was considered as an isotherm wall at melt temperature. Two types of burners are compared. For the first case, the oxygen and natural gas jets at the burner exit are parallel to each other, while for the second burner, a divergent oxygen jet is employed. The furnace heat loss to the ambient is neglected since it is small in relation to the heat liberated by the combustion process.
The k-ε model of turbulence was selected to represent the turbulent flow field. The combustion process was determined based on the Arrhenius and Magnussen Laws, and the discrete transfer radiation model was employed to predict the radiation heat transfer. The numerical procedure was based on the Finite Volume Method.
This numerical model is utilized to determine the flame pattern, species concentration distribution, and the velocity field. The temperature distribution is very useful in the evaluation of the furnace performance. Further, critical regions associated with high temperature spots at the refractory surface were discovered. The effect of the divergent jet in the heat flux distribution at the aluminum bath is also investigated.
Effect of Thin Films on Radiative Transport in Chemical Vapor Deposition Systems
Authors: Mazumder Sandip , Kersch Alfred 
Published: December 2021

Abstract
The thermal behavior of a wafer during a Rapid Thermal Chemical Vapor Deposition (RTCVD) process depends on its spectral radiative properties, along with other factors. One of the major contributing factors is the thin film that is deposited on the wafer substrate. The presence of a thin film (of thickness anywhere above 0.1 nm) can drastically alter the radiative properties of the wafer surface, thereby leading to significantly different wafer temperatures. This article presents a model to simulate thin film effects in RTCVD processes. Radiative transfer is modeled using a Monte-Carlo ray-tracing technique. Radiative properties are calculated using fundamental Electromagnetic Wave Theory. Simulation results match remarkably well with experimental data, demonstrating the importance of thin film effects.
Nanosecond Laser Experiments of Microstructure Adhesion Reduction
Authors: Rogers James W. , Phinney Leslie M. 
Published: December 2021

Abstract
Due to the small size of structures in modern microdevices, surface forces can create undesirable adhesion between microstructures, which is referred to as stiction. Prior investigations have used ultrashort-pulse lasers to recover stiction-failed microcantilevers. The current experiments study the use of a 400 ns, 1064 nm, Nd:YAG laser to free polycrystalline silicon microcantilevers stuck to the underlying substrate. The results show that a Nd:YAG, 1064 nm laser is capable of recovering failed microstructures with yields exceeding those reported in earlier studies. Yields of 100 percent for cantilevers up to 1 mm in length were demonstrated for several laser operating conditions. The yields are strongly dependent on laser fluence and slightly dependent on exposure time, with a single-shot at 160 mJ/cm2 resulting in yields around 60 percent.
Local Pressure Measurement of Gaseous Flow Through Microchannels
Authors: Turner Stephen E. , Sun Hongwei , Faghri Mohammad , Gregory Otto J. 
Published: December 2021

Abstract
This paper presents an experimental investigation on nitrogen and helium flow in microchannels etched in silicon with hydraulic diameters of 9.7, 19.6, and 46.6 μm, and Reynolds numbers ranging from 0. 2 to 1000. The objectives of this research are (1) to measure the pressure distribution along the length of a microchannel; and (2) to determine the friction factor within the fully developed region of the microchannel. The pressure distribution is presented as absolute local pressure plotted against the distance from the microchannel inlet. The friction factor results are presented as the product of friction factor and Reynolds number plotted against Reynolds number with the outlet Knudsen number, Kn, as a curve parameter. The following conclusions have been reached in the present investigation: (1) Pressure losses at the microchannel entrance can be significant; (2) the product, f*Re, when measured sufficiently far away from the entrance and exit is a constant in the laminar flow region; and (3) the friction factor decreases as the Knudsen number increases.
Microscale Heat Conduction in Dielectric Thin Tubes
Authors: Sheu Long-Jye , Lin Jenn-Der , Chou Fu-Chu 
Published: December 2021

Abstract
The radial heat conduction in the tube wall of dielectric thin tubes is studied in this work. An equation of phonon radiative transfer (EPRT) is used in association with nodal approximation technique for examining the heat transport in the thin tubes. The effective thermal conductivity of thin tubes is calculated based on the heat flux in the middle surface of the tubes. Results indicate that the energy distribution in the annulus is dominated by phonons excited by outer surface. Consequently, the temperature distribution is considerably affected by the temperature of outer surface. In addition to tube wall thickness, R2-R1, which was usually considered as the size effect on heat conduction, the curvature effect would significantly change the heat flux across the tube wall and consequently affect the effective thermal conductivity.
Analysis of Heat Transfer During Quenching of a Gear Blank
Authors: Sahai Vivek , Aceves Salvador M. 
Published: December 2021

Abstract
This paper presents experimental and numerical results for the quench of a gear blank in agitated and stagnant oil. Temperatures within the gear blank are determined with a whole domain-optimizer technique inverse solution method, to calculate the time history at every point in the gear blank. The development of this procedure represents the first stage in an overall analysis of the quench process that will later include material phase transformations and deformation.
The paper presents ten variations in setting up the inverse problem, to analyze which combination of independent variables and decision variables results in the best match between experimental and numerical results. The results indicate that dividing the boundary of the gear blank into four zones and assigning a fixed heat transfer coefficient or heat flux to each zone yields an average RMS error (average difference between experimental and numerical results) of the order of 40 K. This error can be reduced by either increasing the number of zones, by reducing the number of thermocouples being matched, or by allowing the heat transfer or heat flux to vary within the zones. Of these possibilities, variation of heat transfer within the zones gives the best improvement in the quality of the match for the amount of extra computational effort required to run the problem.
Visualization and Measurements of Picoliter-Size Molten Droplet Impact Dynamics and Solidification on a Surface
Authors: Attinger D. , Zhao Z. , Poulikakos D. 
Published: December 2021

Abstract
The basic problem of the impact and solidification of molten solder droplets on a flat substrate is of central importance to the novel micromanufacturing process of solder jetting, in which microscopic size solder droplets are dispensed for the attachment of microelectronic components. Under certain conditions, “frozen ripples” appear on the surface of solidified solder microbumps deposited using the solder jetting technology (Waldvogel et al. 1996). The mechanism for the formation of these “frozen ripples” was later explained and quantified in a theoretical study by Waldvogel and Poulikakos (1997) as a consequence of the dynamic competition between flow oscillations and rapid solidification. However, no analogous experimental results for the transient impact process have been reported to date to the best of our knowledge. Such a study is reported in this paper. Eutectic solder (63Sn37Pb) was melted to a preset superheat and used in a specially designed droplet generator to produce droplets with diameters in the range 50–100 μm. The size, temperature, and impacting speed of the molten droplets were maintained constant. The primary variable is the temperature of the substrate that was controlled in the range from 48 °C to 135 °C. The dynamics of molten solder microdroplet impact and solidification on the substrate was investigated using a flash microscopy technique. The duration of flash used in the study was 1 μs. The time for the completion of solidification from the moment of a solder droplet impact on the substrate varies between 150 μs and 350 μs. The dynamic interaction between the oscillation in the liquid region and the rapid advance of solidification front was visualized, quantified and presented in this paper. To the best of our knowledge, this study presents the first published experimental results on the transient fluid dynamics and solidification of molten microdroplets impacting on a substrate at the above mentioned time and length scales that are directly relevant to the novel solder jetting technology. Existing results on this problem pertain to time and length scales at least one order of magnitude higher (Jonas et al. 1997; Pasandideh-Fard et al. 1998; Zhao et al. 1996). The visualization results on the oscillatory motion and rapid solidification shed light on a host of interesting phenomena and also support the frozen ripple formation theory presented by Waldvogel and Poulikakos (1997).
Investigation of Thermal Conductivity of a Polymer Solution as Function of Shearing Rate
Authors: Kostic Milivoje , Tong Haibo 
Published: December 2021

Abstract
A novel research apparatus is developed to measure the fluid thermal conductivity while in shearing flow, and to determine its dependence on the shearing itself, contrary to the current state-of-the-art of measuring thermal conductivity under the condition of motionless fluid.
A concentric cylinders’ apparatus was developed to provide controlled heat transfer in the radial direction, orthogonal to the circumferential fluid velocity, thus virtually preserving pure conductive heat transfer mode. The measurement and control are accomplished and integrated by using a computerized data acquisition system and a comprehensive virtual instrument, developed using the LabVIEW application software.
It was found that the thermal conductivity of a Newtonian fluid, such as distilled water, was virtually independent of the fluid motion, as expected. However, for non-Newtonian fluids such as 1000 and 2000 wppm aqueous polyacrylamide (Praestol) solutions, there was up to 10–20% increase of thermal conductivity in the operating shear rate range (40 ≤ γ ≤ 510 sec−1) at 27°C average fluid temperature.
Performance and Modeling of Heat Flux Sensors in Different Environments
Authors: Holmberg D. G. , Womeldorf C. A. 
Published: December 2021

Abstract
Heat flux measurement is not simple; care is required in selecting a suitable sensor for a given application. Surface substrate properties and the convective and radiative environment determine the choice of sensors. Mounting of the sensor, especially in calibration versus application, influences accuracy of measurement. The purpose of the present study is to increase awareness of potential errors in heat flux sensor use. This paper compares sensor performance in general by examining results of testing three commercially available sensors and by numerical modeling of these sensors. Comparisons of sensor calibrations in the NIST convective heat flux calibration facility are made with manufacturer calibrations and give evidence of potential pitfalls when using a sensor in a different environment than the calibration environment. Modeling results help explain observed data, demonstrating specific sensor parameters that can lead to significantly different calibrations in different environments.
Influence of Non-Isothermal Button Gage Surface Temperature in Heat Flux Measurement Applications
Authors: Zilles David A. , Abhari Reza S. 
Published: December 2021

Abstract
Button gages have been extensively used to measure convective heat transfer coefficients in a number of short duration experiments. A button gage consists of a small insert made from an insulator material, typically Pyrex, with a thin film of Platinum active element painted on its surface. In a typical short duration experiment, gages are initially at the same temperature as the test article. As the flow is established, convective heat flux results in the surface temperature of the gage to rise much more rapidly than the surrounding metal walls. The influence of this non-isothermal wall condition on the local thermal boundary layer and hence the measured data is the focus of the present program.
A detailed experimental study of the influence of local non-isothermal conditions on the inferred heat flux from button heat-flux gages is performed. An existing wind tunnel capable of generating subsonic through transonic flow conditions has been modified to include an isothermal flat plate test section with a row of surface flush-mounted button heat-flux gages. In addition to the button gages, a uniform sheet of two-layered Kapton heat-flux gages, operating under isothermal conditions, are also applied to the flat plate surface. A detailed study of the uncertainties of experimental results is performed. As part of this study, flow Mach number and Reynolds number are varied and their relative significance upon the deviation in the response of the gages is quantified. The measured heat flux did show a deviation from the isothermal measured values. It is further shown that a correction term based on classical heat transfer theory will adjust the measured heat flux on the flat plate to match isothermal values for a range of Reynolds numbers and temperature ratios.