bluuebunny/crossref_metadata_2025 huggingface dataset:
Validation of the Combustion Space Simulation of a Glass Furnace Model
Authors: Golchert B. , Chang S. L. , Petrick M. , Zhou C. Q.
Published: November 2021

A completely coupled glass furnace simulation that combines calculations for the combustion space, glass melt, and radiative heat transfer throughout the furnace has been developed as part of a Department of Energy sponsored program. A major component of this program entailed the collection of an extensive set of data from an operating glass furnace for the purpose of validation. The data collected were compared with the results from computer simulations of the furnace based on the actual operating conditions. These comparisons indicated that the computated results were valid. This paper will present and discuss the gas velocity and gas temperature measurements/validation studies.
Modeling Large-Size Boilers As a Set of Heat Exchangers: Tips and Tricks
Authors: Cortés Cristóbal , Díez Luis I. , Campo Antonio
Published: November 2021

Practical calculation of the heat-recovery sections of large-size boilers is still based on approximate methods. On the one hand, CFD-based models cannot directly handle the geometric intricacy of tube bundles, and thus rely on volume-averaged source terms that demand empirical input. On the other hand, the standard, lumped heat exchanger calculation, which can be a far simpler and more robust alternative, fails in several important aspects, mainly related to the effects of thermal radiation and the coupling between several sections.

In this paper, we consider the diverse sections of a coal-fired utility boiler as a case study to show how to deal with these shortcomings. Under the objective of developing a simple monitoring method, we extend the traditional heat exchanger model to take into account most of the peculiarities of boiler superheaters, reheaters and economizers. Techniques range from the re-examination of analytical solutions to the auxiliary use of CFD calculations. The models are assembled to simulate the thermal performance of the boiler as a whole unit. Results are validated against actual measurements taken at a thermoelectric plant.
Influence of a Periodic Radiation Heat Source on Polymer Ignition
Authors: Zheng Guanyu , Bénard André , Wichman Indrek S.
Published: November 2021

The ignition process of a thermoplastic polymer is investigated numerically regarding to the influence of a periodic radiation source for a given range of frequency. The ignition process is initiated when a solid polymer receives a high radiation heat flux in convective flow environment. The solid polymer undergoes preheating, melting, and pyrolysis with the development of ignition. The combustible gases, as a result of condensed phase pyrolysis process, react with oxygen in the gas phase via combustion reaction. A two-dimensional multi-phase combustion model is utilized to predict the influence of periodic radiation on ignition. The ignition delay and combustion characteristics are examined with respect to the transient patterns of the external radiation sources.
Fire Behavior in a Poorly Ventilated Compartment
Authors: Wakatsuki K. , Ringwelski B. , Quintiere J. G.
Published: November 2021

The fire behavior of heptane burning in a poorly ventilated compartment was studied. The diameter of the heptane pan fires were varied and the ventilation opening size and location were adjusted. Two kinds of compartment fire experiment were conducted: (1) horizontal slits at the top and bottom of a wall, and (2) a single vent at the roof. Temperature, oxygen, fuel mass loss rate and differential pressure were measured. Extinction was studied with an oxygen meter to find the minimum oxygen concentration in the compartment achieved in ventilation-controlled fires. Extinguishments due to ventilation or complete fuel consumption was distinguished. Flow exchange was measured by differential pressure transducers. Particularly, flow exchange of ceiling vent was examined by calculation of flooding pressure difference, which will allow bi-directional flow. The wall vent case had oscillatory combustion (puffing), which sometimes leads to an increase in fire amplitude followed by extinction. This was not observed for the ceiling vent case. Video recording of the flame was conducted through a glass on sidewall. The fire behavior varied from conditions in which the flame extinguishes to cases of steady burning. In some cases, “ghosting flames” were observed.
Self-Preserving Properties of Unsteady Round Nonbuoyant Turbulent Starting Jets and Puffs in Still Fluids
Authors: Sangras R. , Kwon O. C. , Faeth G. M.
Published: November 2021

The self-preserving properties of round nonbuoyant turbulent starting jets, puffs and interrupted jets were studied experimentally and theoretically for flows in still and unstratified environments. The experiments involved dye-containing fresh water sources injected into still fresh water within a large fresh water tank with images of the flows obtained using a video camera. Near-source behavior varied significantly with source properties but self-preserving behavior was observed at distances greater than 20–30 source diameters from the source. Within the self-preserving region, normalized streamwise and radial penetration distances varied as functions of time, in accord with requirements for self-preservation, to the following powers: 1/2 for starting nonbuoyant jets and 1/4 for nonbuoyant puffs. Effects of injected fluid quantity for puffs were reflected by the location of the virtual origin which was independent of injected fluid volume for small volumes but became proportional to injected fluid volume for large volumes typical of interrupted jets.
Transport in Turbulent Jet Diffusion Flames With Annular Counterflow
Authors: Torii Shuichi , Chan Sze Man Simon , Yano Toshiaki
Published: November 2021

The present study deals with the augmentation of the turbulent shear effect on transport in turbulent jet diffusion flames due to the presence of air-suction flow and the possibility of extending the flame blow-off limits through augmentation. The experimental apparatus employed here comprises a fuel nozzle placed at the center of a concentric annulus with an outer cylinder encompassing the nozzle. The fuel jet is allowed to eject upwards and turbulent jet diffusion flames are formed by igniting the jet, then by increasing the volume flow rate of the fuel. The annular counterflow technique was employed to augment the turbulent shear effect. It is found that (1) the augmentation of turbulent shear effect exerted on the shear layer formed between the jet flames and the opposed flow of air causes an increase in temperature of the cold fuel gas at the flame center and an extension of flame blowoff limits; (2) flame lift-off heights are suppressed; (3) the lift-off propensity of the diffusion flame is alleviated by such augmentation.
A Procedure for View Factor Calculation Using the Finite-Volume Method
Authors: Chai John C. , Moder Jeffrey P. , Karki Kailash C.
Published: November 2021

This article presents a finite-volume method to calculate view factors between surfaces of control volumes. A simple approach, which does not lead to the increase in memory requirement with increasing angular grid, is used. The spatial and angular resolution errors are resolved by grid refinements. The procedure can handle straight-edged, inclined, and curved boundaries. Three problems are examined and the exact solutions are reproduced.
Apparent Radiative Properties and Radiation Scattering by a Semitransparent Hemispherical Shell
Authors: Fan Tai-Hsi , Fedorov Andrei G.
Published: November 2021

Knowledge of the apparent radiative properties of the semitransparent hemispherical shell placed on an opaque surface is of the fundamental interest and also important to a number of application in materials processing and manufacturing ranging from metallurgical slag foaming to batch foams in glass melting to hollow bead fabrication. This paper extends our recent work [7] on using the analytical and numerical ray tracing techniques to study radiative transfer in the system described. Specifically, the local volumetric heating rate and the scattering phase function of a thin hemispherical shell exposed to incident collimated radiation are calculated both analytically and numerically, and the results are discussed in detail. To further elucidate the results, the comparison is made of the total apparent transmittance of the hemispherical shell to a plane parallel layer of semitransparent material.
Consideration of the Scattering Effects in the Glass As a Participating Medium Using the Discrete Ordinates Method
Authors: Rodicio S. Coutin , Torres B. Restrepo
Published: November 2021

Three-dimensional radiative heat exchange in a commercial type of glass as a participating medium is predicted using the discrete ordinates method. The radiative transfer equation (RTE) is analyzed for an absorbing, re-emitting, and scattering medium enclosed by gray walls. The main objective of this work is to formulate the RTE in a three-dimensional enclosure represented by a rectangular glass furnace where scattering effects are considered in the prediction of the radiant intensity, temperature distribution, incident and emitted energy, and heat flux at the glass surface. A comparative study is performed for glass under scattering and non-scattering conditions. The influence of scattering effects in the radiant intensity will provide further understanding of their impact in the glass thermal behavior. Additionally, the results of a parametric study on the glass for different scattering coefficients, surface heat flux, wall emissivity, and the forward scattering are discussed. The S4 approximation of the discrete ordinates method is employed in this model.
Modeling of Transport Processes Within a Molten Carbonate Fuel Cell Stack
Authors: Ma Z. , Jeter S. M. , Abdel-Khalik S. I.
Published: November 2021

Concern over global warming due to emission of green house gases has generated considerable interests and intensive development of fuel cells. In order to reduce the fuel cell manufacturing costs and to improve its performance and reliability, a better understanding of the fuel and oxidant species transport processes within fuel cell stack is important for fuel cell design. Fuel and oxidant stream flow distributions within a stack have significant impact on fuel cell performance and efficiency. To this end, this investigation presents the effects of the fuel and oxidant flow distributions on fuel cell stack performance with a model of fluid flow, heat and mass transfer including the electrochemical reaction, within a molten carbonate fuel cell under different gas supply conditions.
Analysis for the Effect of Inverter Ripple Current on Fuel Cell Operating Condition
Authors: Gemmen Randall S.
Published: November 2021

The effect of inverter ripple current on fuel cell stack performance and stack lifetime remains uncertain. This paper provides a first attempt to examine the impact of inverter load dynamics on the fuel cell. Since reactant utilization is known to impact the mechanical state of a fuel cell, it is suggested that the varying reactant conditions surrounding the cell govern, at least in part, the lifetime of the cells. This paper investigates these conditions through the use of a dynamic model for the bulk conditions within the stack, as well as a one-dimensional model for the detailed mass transport occurring within the electrode of a cell. These two independent modeling approaches help to verify their respective numerical procedures. In this work, the inverter load is imposed as a boundary condition to the models. Results show the transient behavior of the reactant concentrations within the stack, and of the mass diffusion within the electrode under inverter loads with frequencies between 30 Hz and 1250 Hz.
Application of a New CFD Analysis Tool for SOFC Technology
Authors: Prinkey Michael T. , Gemmen Randall S. , Rogers William A.
Published: November 2021

FLUENT™, a commercial computational fluid dynamics (CFD) package, has been modified to include fuel cell electrochemistry. The model is being developed to account for three loss mechanisms present in fuel cells: ohmic overpotential, concentration overpotential, and electrochemical overpotential, each capable of temperature dependency. Because we envision this model to be applied to a wide range of geometries, the present model is also being developed to directly assess the electric potential field. This paper presents some preliminary results from the present model, and provides a summary status of our development.

The main results from the present study arise from an analysis of a single monolithic SOFC geometry. Several cases were analyzed in order to generate a typical steady-state V-I curve for the cell, which summarizes its performance. Results on the detailed distribution of various conserved quantities are also presented. The preliminary results are encouraging, and show that for the geometry under study, simple scale-up relations may hold. Additionally, the newly developed tool no longer requires the modeler to manually input approximate current flow information, which will be seen to be of great benefit in fuel cell analysis.
Modeling of Recuperative Heat Exchanger in a Joule-Thomson Cooler
Authors: Ng Kim Choon , Wang Jinbao , Xue Hong
Published: November 2021

To develop effective heat exchangers for miniature and micro Joule-Thomson (J-T) cooling system, the performance of a recuperative heat exchanger is analyzed and evaluated. The evaluation is based on a theoretical model of the Hampson-type counter-flow heat exchanger. The effect of the pressure and temperature-dependent properties and longitudinal heat conduction are considered. The results of the numerical simulation are validated with the corresponding experimental measurements. The performance of the heat exchanger on effectiveness, flow and various heat conduction losses as well as liquefied yield fraction are analyzed and discussed. The simulation model provides a useful tool for miniature J-T cooler design.
Tuning of Membership Functions in a Fuzzy Rule Set for Controlling Convergence of Laminar CFD Solutions
Authors: Dragojlovic Zoran , Kaminski Deborah A. , Ryoo Juntaek
Published: November 2021

Under-relaxation in an iterative CFD solver is guided by fuzzy logic to achieve automatic convergence with minimum CPU time. The fuzzy rule set uses information from a Fourier transform of a set of characteristic values. The control algorithm adjusts the relaxation factors for the system variables on each iteration and restarts the solver if divergence occurs.

Four problems of laminar fluid flow and heat transfer are solved. They include buoyancy driven flow in a square cavity, lid driven flow in a square enclosure, mixed convection over a backward facing step and Dean flow. The consideration of buoyancy driven flow in a square cavity took into account a case with isothermal vertical walls, as well as a case with heat conduction in the solid wall on the right hand side of the cavity. The incompressible Newtonian conservation equations are solved by the SIMPLER algorithm with simple substitution. In order to achieve the best performance of the fuzzy controller, a set of triangular membership functions was tuned by using a gradient method.

The fuzzy control algorithm with the optimal membership functions significantly reduced the CPU time needed for solving the problem, compared to performance of triangular membership functions before optimization. The improvement in speed of convergence varied from 10% in the case of Dean flow to 70% in the case of buoyancy driven flow in a square enclosure with isothermal walls. For all the problems considered, the fuzzy rule set provided convergence comparable in speed to that obtained with the best choice of constant relaxation factors. In the case of buoyancy driven cavity flow with conjugate heat transfer, the fuzzy controller outperformed any choice of constant relaxation factors.
Aerodynamics of Scallop Seal Flows in Turbomachinery
Authors: Chochua Gocha , Shyy Wei , Moore Jeffrey
Published: November 2021

Gas annular seals are commonly adopted for leakage control in turbomachinery applications. Scallop seal is an representative example of damper seals, and is attractive from rotordynamic stability viewpoint. To understand flow physics in such seals a computational analysis is developed to study compressible, turbulent flow in it. The following issues are addressed: (i) validation of results obtained using periodic boundary conditions accounting for turbulent and compressible flows, (ii) effect of the rotor rotation and inlet swirl ratio on flow development in the seal, (iii) extrapolation of the full-length results from limited periodic simulations, and (iv) breakdown of the friction factor on contributing pressure and shear stress components. The computational techniques presented can help address the design related issues more economically, and the findings offer insight into the fluid physics associated with a scallop seal.
Effects of Inlet Swirl Angle on Flow and Heat Transfer in Contoured Turbine Nozzle Guide Vanes
Authors: Lin Y.-L. , Schock H. J. , Shih T. I-P. , Bunker R. S.
Published: November 2021

Computations, based on the ensemble-averaged compressible Navier-Stokes equations closed by the shear-stress transport (SST) model of turbulence, were performed to investigate the effects of inlet swirl angle on the three-dimensional flow and heat transfer in two contoured endwall configurations. Swirl angles investigated include three constant angles (0°, 15°, 30°) and a linearly varying angle from +30° at one endwall to −30° at the other. For all swirl angles, the mass-flow rate through the nozzle was fixed so that the higher the swirl angle, the higher is the velocity magnitude. Of the two endwalls investigated, one has all of the contouring upstream of the airfoil (C1), and another has contouring that starts upstream of the airfoil and continues until the airfoil’s trailing edge (C2).

Computed results show that at all swirl angles investigated, the C2 configuration was able to reduce significantly secondary flows on the contoured endwall. Results also show that with reduced secondary flows, the heat-transfer coefficients are also reduced on the suction surface next to the juncture, where the airfoil meets the contoured endwall. On aerodynamics, the C2 configuration was found to produce essentially the same lift as the C1 configuration, but does so with less loss in stagnation pressure. For the C1 configuration, secondary flows are quite pronounced, and they increase slightly in size and in magnitude when swirl angle is increased. However, aerodynamic loss and surface heat transfer were found to decrease with increase in swirl angle. One explanation is that increasing the swirl angle shifted the stagnation zone downstream on the pressure surface to a flatter portion of the airfoil, producing a thicker boundary layer at the stagnation zone, and this changed considerably the evolution of the turbulent boundary layer. When the swirl angle varied linearly from +30° to −30°, increasing the velocity component towards the pressure surface was found to enhance instead of suppress the formation of secondary flows.
Experimental Investigation of Micro Heat Pipe Radiators in Radiation Environment
Authors: Wang Y. X. , Peterson G. P.
Published: November 2021

A flexible micro heat pipe radiator, fabricated by sintering an array of aluminum wires between two thin aluminum sheets, was developed as part of a program to conceptulize, develop, and test lightweight, flexible radiator fin structures for use on long-term spacecraft missions. A detailed experimental investigation was conducted to determine the temperature distribution, maximum heat transport capacity, and radiation efficiency of these micro heat pipe radiators in a radiation environment. Experimental results from three Aluminum-Acetone micro heat pipe radiators with wire diameters of 0.635 mm, 0.813 and 1.016 mm are presented, evaluated and discussed.

The results of the experimental program indicted that the maximum heat transport capacity and radiation efficiency, both increased with increasing wire diameter. The maximum heat transport capacity of the micro heat pipe radiator utilizing a wire diameter of 0.635 mm was 15.2 W. The radiators utilizing wire diameters of 0.813 mm and 1.016 mm never reached the maximum heat transport capacities for the given test conditions. In the tests, temperature distributions were recorded for several sink temperatures and indicated that as the sink temperature decreased the radiation efficiency decreased for a given heat input. The maximum heat transport capacity increased with increasing evaporating temperature for the micro heat pipe radiator utilizing a wire diameter of 0.635 mm. Comparison of micro heat pipe radiators with and without working fluid, indicated that significant improvements in temperature uniformity and radiation efficiencies could be obtained, especially at high heat fluxes. A maximum radiation efficiency of 0.95 was observed. In general, while some variation in performance was observed, all three micro heat pipe radiators were found to be capable of meeting the thermal requirements of long-term missions.
Numerical Simulation of a Dielectric Material Exposed to Short Pulsed Laser Radiation
Authors: Whalen Richard A. , Kowalski Gregory J.
Published: November 2021

A numerical simulation code is developed to study laser beam propagation and the significance of self-focussing or defocusing effects on a manufacturing process. The solution method includes the thermally stimulated nonlinear optical effects caused by the temperature and intensity dependent index of refraction. The results demonstrate that radial temperature gradient magnitudes of 0.06 to 0.6°C produce significant changes in the focal volume of the beam. The magnitudes of the temperature changes are directly related to differences in the absorption coefficient. The thermal transport of the absorbed radiation is modeled using Fourier heat conduction for long time scales and Hyperbolic heat conduction for short time scales. The focal volume of the beam is significantly altered by the differences between these thermal transport mechanisms. These results were determined using a simulation of a Z-scan measurement technique.
Heat Transfer and Phase Transformations in Laser Annealing of Thin a-Si Films
Authors: Moon Seung-Jae , Lee Minghong , Grigoropoulos Costas P.
Published: November 2021

The liquid-solid interface motion and the temperature history of thin Si films during excimer laser annealing are observed by in situ experiments combining time-resolved (∼lns) thermal emission measurements, optical reflectance and transmittance at near-IR wavelengths and electrical conductance measurements. The spontaneous nucleation temperature in the supercooled liquid melt is studied from the thermal emission measurement A new double laser recrystallization technique using a temporally modulated CW Ar+ laser in conjunction with a superposed nanosecond laser pulse produces lateral grain growth at the irradiated spot. The laser melting process is numerically simulated. High-resolution laser flash photography enabled in-situ direct visualization of the resolidification process. The images reveal lateral solidification velocity of about 10 m/s.
Use of Sensors and Actuators to Address Flow Disturbances During the Resin Transfer Molding Process
Authors: Lawrence Jeffrey M. , Advani Suresh G.
Published: November 2021

In Resin Transfer Molding a fiber preform is placed in a mold, the mold is closed and a thermoset polymeric resin is injected through gates into the mold to saturate the preform completely. The resin flow rate is controlled by actuators, which are usually injection machines. When one places the preform into the mold, the gap between the preform and the mold walls can create racetracking channels and provide the resin flow paths that can severely influence the flow patterns and drastically change the flow history. As this gap is unavoidable and not reproducible, one could have different strengths of this disturbance from one part to the next, some of which will cause incomplete saturation of the fibers by the resin. Hence, an active control of the filling stage is necessary which can detect and characterize the race tracking and provide the control action to re-direct the flow with the aim to saturate the preform without resin starved regions (macro voids or dry spots). A methodology is proposed that intelligently places sensors in the mold to detect the resin arrival times at these locations. This information is used to determine and quantify the strength of the disturbance and used as an input parameter for the actuators to redirect the flow. This paper demonstrates this methodology on a simple mold configuration, and outlines how this technique can be generalized to any mold geometry or disturbance set in an automated RTM environment. Numerical simulations are used to establish the control methodologies, and all of the efforts are confirmed in a laboratory setting. The proposed methodology should prove useful in increasing the yield of Resin Transfer Molded parts.
Steady and Transient Flow of a Non-Newtonian Chemically Reactive Fluid in a Twin-Screw Extruder
Authors: Zhu W. , Jaluria Y.
Published: November 2021

The flow of chemically reactive non-Newtonian materials, such as bio-polymers and aciylates, in a fully intermeshing, co-rotating twin-screw extruder is numerically investigated. A detailed study of the system transient behavior is carried out. The main transient aspects, including response time, variation of system variables, and instability of operation, are studied for both single- and twin-screw extruders. The effect of a time-dependent variation in the boundary conditions is studied. The coupling due to conduction heat transfer in the screw barrel is found to be very important and is taken into account for single-screw extruders. In the absence of this conjugate coupling, the response time is much shorter. Several other interesting trends are obtained with respect to the dependence of the transient response on the fluid, materials, and operating conditions. Steady state results are obtained at large time. The calculated velocity distributions in the screw channel are compared with experimental results in the literature for steady state flow and good agreement has been obtained. The numerical results show that not all desired operating conditions are feasible. The calculated results for transient transport agree with the few experimental observations available on this system. These results will be useful in the design, control and optimization of polymer extrusion processes.
Experimental and Numerical Investigation of Polymer Preform Heating
Authors: Reeve Hayden M. , Mescher Ann M. , Emery Ashley F.
Published: November 2021

The transient heating of a polymer preform within a cylindrical furnace is the initial step in the manufacture of polymer optical fiber. A numerical model was used to simulate the radiative and convective heat transfer within the furnace enclosure during this initial heating. Results illustrate a strong dependence of the preform’s heating rate on the radiative properties of the preform. Due to the prominence of radiative heat transfer at steady-state, the resulting axial temperature profile within the preform is strongly coupled to the corresponding axial temperature profile of the furnace wall. Numerical predictions were compared with experimental results for several preform surface emissivities, preform diameters, and thermal boundary conditions. The results compare well for preforms with well-characterized surface finishes (such as black paint and aluminum), with discrepancies between experimental and numerical results typically less than 1.3°C. Experiments indicate that the heating characteristics of poly(methyl methacrylate) preforms can be adequately simulated by assuming that the preform exhibits nearly blackbody behavior (ε = 0.96) when exposed to the low furnace temperatures (85°C) used in this study. Finally, the experiments revealed the tendency for unstable natural convection within tall furnace cavities, with experimental readings indicating oscillatory air temperatures as the system approached steady-state.
Thermal Spray: A Case History for the Integration of Materials Science and Thermo-Fluid Dynamics
Authors: Berndt Christopher C.
Published: November 2021

The thermal spray process involves the injection of particulates into a high flux environment so that momentum and heat transfer can take place. The particles are then accelerated within the gaseous effluent and within several milliseconds impact and splash against a suitably prepared substrate. In this fashion a coating rapidly grows over a time period that may range from minutes to hours.

The materials engineering concept comes into play when it is appreciated that the temperature, velocity, and chemical nature of the spray effluent controls the dispersion, impact phenomenon, and, therefore, the precise nature of the microstructure which is being formed in situ and in real time. Unsurprisingly, this is a somewhat random and chaotic process that is seeking practical and theoretical solutions so that some manner of engineering control can be employed.

This paper explores the scientific relationship between materials engineers and mechanical engineers so that a functional product can evolve. This relationship includes (i) the use of diagnostic equipment to monitor the spray process, (ii) the dynamic impact behavior of particulates, (iii) modeling of thermal fluxes and the resultant mechanical stress state, and (iv) the way in which the microstructure evolves. The eventual aim of this vast body of work is to enable real time feedback loops for the thermal spray process so that predictable and engineered structures can be manufactured.
Heat Transfer in Chemical Vapor Deposited Optical Fiber Coatings
Authors: Iwanik Patricia O. , Chiu Wilson K. S.
Published: November 2021

A fundamental understanding of how reactor parameters influence the fiber surface temperature is essential to manufacturing high quality optical fiber coatings by chemical vapor deposition (CVD). In an attempt to better understand this process, a finite volume model has been developed to study the gas flow and heat transfer of an optical fiber as it travels through a CVD reactor. This study showed that draw speed significantly affects fiber temperature inside the reactor, with temperature changes up to 45% observed under the conditions studied. Multiple heat transfer modes contribute to this phenomena, with convection heat transfer dominating the process.
Prediction of Thermal Contact Conductance by Surface Deformation Analysis
Authors: Singhal Vishal , Garimella Suresh V.
Published: November 2021

An improved method has been developed for the prediction of thermal contact conductance between two nominally flat metallic rough surfaces by analysis of the deformation of individual asperities in contact. The deformation of the asperities in contact has been taken into account by considering three different modes of deformation — elastic, elastic-plastic and plastic. The model uses an iterative procedure to determine the real area of contact between the deformed surfaces for a given load, nominal area of contact, surface profiles and material properties of the surfaces in contact. The contact conductance is then determined as a function of the ratio of the real area of contact to the apparent area of contact The predicted variation of contact conductance with load obtained from the model is compared to simplified analytical predictions in the literature as well as to experiments conducted as part of this work.
Small Heat Source Effects in Sub-Micron Heat Conduction
Authors: Narumanchi Sreekant V. J. , Murthy Jayathi Y. , Amon Cristina H.
Published: November 2021

Decreasing dimensions of integrated circuit devices is leading to increased importance of microscale heat transfer effects and the failure of Fourier’s law in predicting sub-micron heat conduction. In compact transistors, large electric fields near the drain side create hot spots whose dimensions are smaller than the phonon mean free path in the medium. Under these conditions, the phonon Boltzmann equation (BTE) needs to be solved in order to resolve the non-local thermal conduction phenomena. In this paper, the problem of an unsteady heat source of size comparable to or smaller than the phonon mean free path is considered. The unsteady 2-D phonon Boltzmann transport equation in the relaxation time approximation is solved using a finite volume method. The interaction of the heat-up time constant with the phonon residence time in the hotspot and also its interaction with the time scales associated with scattering processes are studied. The results are useful in assessing the peak temperatures during unsteady operation in microelectronic devices.
Ballistic-Diffusive Equations for Transient Heat Conduction From Nano- to Macroscales
Authors: Chen Gang
Published: November 2021

In this paper, we present the derivation of a new type of heat conduction equations, named as the ballistic-diffusive equations, that are suitable for describing transient heat conduction from nano- to macroscale. The equations are derived from the Boltzmann equation under the relaxation time approximation. The distribution function is divided into two parts. One represents the ballistic transport originating from the boundaries and the other is the transport of the scattered and excited carriers. The latter is further approximated as a diffusive process. The obtained ballistic-diffusive equations are applied to the problem of transient heat conduction across a thin film and the results are compared to the solutions for the same problem based on the Boltzmann equation, the Fourier law, and the Cattaneo equation. The comparison suggests that the ballistic-diffusive equations can be a useful tool in dealing with transient heat conduction problems from nano- to macroscales. Boundary conditions for the derived equations are also discussed. Special emphasis is placed on the consistency of temperature used in the boundary conditions and in the equations.
The Effect of Sink Temperature on a Capillary Pumped Loop Employing a Flat Evaporator and Shell and Tube Condenser
Authors: Cerza M. , Herron R. C. , Harper M. J.
Published: November 2021

An experimental facility for conducting research on capillary pumped loop (CPL) systems was developed. In order to simulate shipboard cooling water encountered at various locations of the ocean, the heat sink temperature of the facility could be varied. A flat plate, CPL evaporator was designed and tested under various heat sink temperatures. The sink temperature ranged from 274.3 to 305.2 K and the heat input varied from 250 to 800 W which corresponds to heat fluxes up to 1.8 W/cm2. The CPL flat plate evaporator performed very well under this range of heat input and sink temperatures. The main result obtained showed that a large degree of subcooling developed between the evaporator vapor outlet line and liquid return line. This condensate depression increased with increasing heat input.
Combination of Holographic Interferometry and Digital Speckle Tomography for Analysis of Three-Dimensional Density Distributions
Authors: Ko H. S. , Okamoto K. , Madarame H.
Published: November 2021

A digital speckle tomography has been combined with a holographic interferometry to improve the accuracy of reconstruction of density distributions. For the combined system, several beam splitters have been used to separate the laser beams from a continuous wave laser for the digital speckle tomography and the holographic interferometry so that measurements can be performed simultaneously by both of the experiments. The density distributions have been reconstructed by the tomography methods for both of the experiments. While the projection of the digital speckle tomography expresses the integration of the density gradients, those of the holographic interferometry can be obtained from the integration of the density itself. Thus, the steep region of the density distribution has been reconstructed by the use of the digital speckle tomography more accurately while the holographic interferometry has been used to calculate the density distributions for other regions from the simultaneous measurements of the combined system. Initially, the downward CO2 flow from one-nozzle and two-nozzle test sections have been investigated to confirm the accuracy. Then, the downward flow of CO2 from a circular small opening with a vertical partition (CO2-air exchange flow) has been analyzed for the transient three-dimensional density fields by the proposed combined system in this study.
Heat Generation in Bone Cutting-Implications for Thermal Necrosis
Authors: Millon Debra Chenet , Hitt Darren L. , LaPointe Stephan J.
Published: November 2021

A bunion is a common foot disorder caused by an abnormal outward projection of the joint and inward turning of the toe. Surgery to correct the malformation involves cutting the first metatarsal head, repositioning and setting it; the bone is then left to heal itself over time. A potentially serious by-product of the bone cutting is the frictional heat generated. While the heat susceptibility of individual bone cells varies throughout bone and is difficult to quantify, studies have shown that when injured, bone may not always heal as bone but rather as a fibrous tissue of varying degrees of differentiation. Prolonged heat exposure at or above critical temperatures may also lead to fat and bone cell resorption, a subsequent fat cell degeneration of the tissue, local swelling of cells as well as denaturation of the enzymatic and membrane proteins (Eriksson & Albrektsson, 1983, Li et al, 1999).
A Visual Basic Program to Calculate Gear Features
Authors: Vavrek Edward M.
Published: November 2021

This paper describes a spur gear design analysis program written in visual basic. The program is used to assist engineering students in the design of spur gears, which involves many calculations and decisions. This software program simplifies and streamlines the design and selection process. Since the visual basic program is event driven, the user can go through the program by inputting values into text boxes and then initiating events by clicking on command buttons. An important feature of this program is the ability to insert pictures, tables, graphs, drawings, and figures to enhance the program functionality. Most inputs are taken from graphs, charts, or tables so the user knows where and how the information is obtained and used. Outputs are shown with their appropriate figures, drawings, or calculation formulas to assist the user in understanding how the output was derived. The software has the advantage of making minor changes to the problem quickly and easily to see how the output is affected.
Blind Image Restoration for Ultrasonic C-Scan Using Constrained 4th Order Cumulants
Authors: Qidwai Uvais , Chen Chi-Hau
Published: November 2021

C-Scans are ways to visualize the sample under study by utilizing the reflections from various levels of non-homogenous wave transfer within the sample. Unlike other imaging techniques, C-scan are usually constructed from the pulse-echoed A-Scans by mapping the 1D windowed signal into a point corresponding to a pixel on the C-scan by calculating its energy within the window. Hence, although the A-scans are predominantly Gaussian in nature, the spatial 1D waveforms mapping into spatial energy values, results in completely unpredictable statistical characteristics. Also, the medium characteristics incorporate distortions that are essentially due to a non-minimum phase system response. Hence, the usual Second Order Statistics (SOS) based identification and deconvolution, i.e., correlation and covariance based techniques, may not work very well in this case.

In this paper, an approach is presented to use 4th order cumulants to deconvolve the effects of blurring in the C-Scans due to above-mentioned effects. The proposed approach is completely blind to the source or the type of distortion and the formulation is purely two-dimensional. When the blurring function is modeled as an Auto Regressive (AR) process, the image is restored recursively with the application of the inverse filter based on the AR estimate. A significant improvement in the image quality has been demonstrated. Especially, the edges are detected more prominently than present in the original image. Very little or no post processing is needed to obtain the final image.
Analysis of Curved Beams by the B-Spline Field Approximation Method
Authors: Vermeulen A. H. , Heppler G. R.
Published: November 2021

The B-spline field approximation method is applied to the static deflection analysis of curved Euler-Bernoulli and Timoshenko beams. A formal definition of membrane locking is presented along with a simple test that allows a priori determination of a models susceptibility to membrane locking. Formulations for both types of beam models, that under certain discretizations experience membrane locking, are presented and additional formulations that can never experience membrane locking are presented for both beam models. Examples that demonstrate the efficacy of the membrane locking test and illustrate the two means of avoiding membrane locking are presented.
Epidemiological estimates and early detection of polycystic kidney disease by ultrasonographic assessment in Japan
Authors: Kobayashi Minoru , Kamai Takao
Published: November 2021

Aims: To estimate the prevalence of autosomal dominant polycystic kidney disease (ADPKD) and provide the evaluation of new ultrasonographic criteria and clinical indicators to help its early detection.Materials and methods: A total of 30750 individuals for health check-up with abdominal ultrasonography (US) were included, in which 231 suspects of ADPKD based on the number of renal cysts were extracted. They were divided into 4 groups by the grade of suspicion (definitive, a strong suspect, a fair suspect and a weak suspect). Longitudinal data of US and renal function tests were compared between the groups.The estimated prevalence rate was 0.068% from the study subjects. The level of eGFR did not differ between the definitive and suspects, while the annual estimated glomerular filtration ratio (eGFR) decline was significantly larger in the former (p<0.001). The subjects with growing renal cysts showed a larger annual eGFR decline than those without growth (p=0.0324). The proposed cut-off set at the first quartile of the annualized eGFR change efficiently divided the subjects according to the presence of cyst growth (p= 0.027) and the grade of suspicion of ADPKD (p=0.028).Conclusion: The prevalence rate of ADPKD was higher than the corresponding rate previously reported in Japan (0.025%), suggesting that health check-ups may be an efficient opportunity to pick up undiagnosed ADPKD. The large annual eGFR decline and the presence of growing cysts may be feasible indicators to isolate ADPKD and should be introduced into US based screening to facilitate early detectionof ADPKD.
A light-weight periodic plate with embedded acoustic black holes and bandgaps for broadband sound radiation reduction
Authors: Tang Liling , Gao Nansha , Xu Jiali , Chen Kean , Cheng Li
Published: November 2021

Conceiving lightweight structures with low vibration and sound radiation properties is an important topic. The concept of Acoustic Black Hole (ABH) offers new impetus to tackle this problem. Most existing ABH structures are based on simple ABH cells. Apart from the reduced structural strength, systematic ABH effects occur typically above the cut-on frequency of the ABH element, which is perceived as a bottlenecking problem. To tackle the problem, this paper examines the sound radiation properties of a plate comprising periodically tangled ABH cells. Through combining ABH effects with sub-wavelength bandgaps (BGs), numerical and experimental studies show that the plate exhibits reduced sound radiation properties in an ultra-broad frequency range, far below the cut-on frequency of an ABH element. This is owing to the tangled nature of the ABH elements, which extends the actual dimension of the ABH, lowers its onset frequency and reduces the sound radiation efficiency through creating slow waves. Inside the BGs, the reduced sound radiation is mainly due to the redistribution of the vibration energy, basically confined to the excitation area. Capitalizing on the combined ABH and BG features alongside improved mechanical properties, the proposed structure shows promise as a light-weight solution for broadband noise reduction.
Pathways in Paralympic Sport: An In-Depth Analysis of Athletes’ Developmental Trajectories and Training Histories
Authors: Dehghansai Nima , Pinder Ross A. , Baker Joseph
Published: November 2021

This three-part investigation conducted a comprehensive analysis of 213 Australian and Canadian athletes’ developmental trajectories, training histories, and experiences in organized sports from 18 Paralympic sports (PS). While athletes with early-onset impairments (i.e., congenital, preadolescent) reached milestones and commenced various types of training at a significantly younger age than athletes with later-onset impairments (i.e., early adulthood, adulthood), the latter groups progressed through their careers and incorporated various trainings at a faster pace (i.e., fewer years). Preferences to certain training conditions varied between groups. Eighty-two percent of the athletes with acquired impairments had experience in able-bodied sports before the onset of their impairment, with 70% noting involvement in sports similar to their current PS. The participation rates (38%) and sport similarity (53%) were lower in PS. The amalgamation of findings from this series of studies highlights the complexity associated with PS athletes’ development and demonstrates the importance of taking an individualized approach.
Structure of the hexameric fungal plasma membrane proton pump in its autoinhibited state
Authors: Heit Sabine , Geurts Maxwell M. G. , Murphy Bonnie J. , Corey Robin A. , Mills Deryck J. , Kühlbrandt Werner , Bublitz Maike
Published: November 2021

The structure of the hexameric fungal proton pump Pma1 reveals its mechanism of autoinhibition and interactions with lipids.
A sound approach to improving exoskeletons and exosuits
Authors: Franz Jason R.
Published: November 2021

Integrating onboard ultrasound imaging to an exosuit enhances muscle-machine coordination to improve economy of locomotion.
Oncostatin M can sensitize sensory neurons in inflammatory pruritus
Authors: Tseng Pang-Yen , Hoon Mark A.
Published: November 2021

Itch sensory neurons can be sensitized by OSM released from dermal immune cells.
Rhizobacteria Impact Colonization of Listeria monocytogenes on Arabidopsis thaliana Roots
Authors: Schoenborn Alexi A. , Clapper Haley , Eckshtain-Levi Noam , Shank Elizabeth A.
Published: November 2021

Listeria monocytogenesis ubiquitous in the environment, being found in or on soil, water, plants, and wildlife. However, little is known about the requirements forL. monocytogenes’ existence in these settings.
Paenibacillussp. Strain UY79, Isolated from a Root Nodule ofArachis villosa, Displays a Broad Spectrum of Antifungal Activity
Authors: Costa Andrés , Corallo Belén , Amarelle Vanesa , Stewart Silvina , Pan Dinorah , Tiscornia Susana , Fabiano Elena
Published: November 2021

Phytopathogenic fungi and oomycetes are responsible for causing devastating losses in agricultural crops. Therefore, there is enormous interest in the development of effective and complementary strategies that allow the control of the phytopathogens, reducing the input of agrochemicals in croplands.
CRM1 Promotes Capsid Disassembly and Nuclear Envelope Translocation of Adenovirus Independently of Its Export Function
Authors: Lagadec Floriane , Carlon-Andres Irene , Ragues Jessica , Port Sarah , Wodrich Harald , Kehlenbach Ralph H.
Published: November 2021

A role of nucleoporins and of soluble transport factors in adenoviral genome import into the nucleus of infected cells in interphase has previously been established. The nuclear export receptor CRM1 promotes genome import, but its precise function is not known.