bluuebunny/crossref_metadata_2025_split huggingface dataset:
A New Look at Natural Convection From Isothermal, Vertical Parallel Plates
Authors: Li H. H. , Chung B. T. F. 
Published: July 2023

Abstract
Natural convection between isothermal plates is solved numerically by applying the full Navier-Stokes equations. The elliptic formulation allows separating the effect of the Rayleigh number, Ra, and the aspect ratio, L/B. Calculations are made on a wide range of the Rayleigh number and the aspect ratio, and the Nusselt number is provided as a function of both Ra and B/L. The conventional correlations in the literature presenting the Nusselt number in terms of a single parameter, RaB/L, have been found inaccurate. At a small value of RaB/L, multiple values of Nusselt number are obtained for different combinations of Ra and B/L. Previous results are found to be the special cases of the present study. A minimum Rayleigh number is also obtained above which a fully-developed flow is possible.
To simulate the natural convective flow, the ambient pressure is given at the exit while the pressure at the entrance is related to the ambient pressure by the Bernoulli equation. Velocities at the entrance and exit are also solved from the Navier-Stokes equations.
Natural Convection of a Liquid Metal in Vertical Circular Cylinders Heated Locally From Side
Authors: Selver R. , Kamotani Y. , Ostrach S. 
Published: July 2023

Abstract
An experimental study is made of natural convection in gallium melts enclosed by vertical circular cylinders with localized heating from the circumference. The heating is done at the mid-height, and the both ends of the cylinder are cooled. The cylinder aspect (Ar = height/diameter) ratio ranges from 2 to 10, and the Rayleigh number (Ra) ranges from 9.0 × 104 to 3.0 × 107. The Prandtl number is 0.021. Temperature measurements are made at six levels along the circumference of the cylinder to study the thermal convection in the melt. Numerical analysis is also conducted to supplement the experimental information. When Ra is small, the melt is in steady toroidal motion. Above a certain Ra the flow becomes non-axisymmetric as a result of a thermal instability in the case of Ar larger than 3. With increasing Ra the motion becomes oscillatory mainly in the upper-half. When Ar is smaller than 3, the toroidal flow becomes non-axisymmetric and oscillatory at the same time beyond a certain Ra. The conditions for the appearance of oscillations and the oscillation frequencies are investigated in detail.
Hydrodynamic Instabilities in Gas-Liquid Monolithic Reactors
Authors: Grolman Eric , Edvinsson Rolf K. , Stankiewicz Andrzej , Moulijn Jacob A. 
Published: July 2023

Abstract
Liquid holdup and pressure drop were measured during the co-current down flow of air and water through a monolith in the Taylor flow regime. The model presented accounts for the significant, up to three fold, increase in frictional pressure drop that is caused by the presence of gas bubbles. It is accurate to within 20%. In addition, the model presented is used to predict hydrodynamic stability, which is defined as the situation where all channels transport gas and liquid in the direction of mass flow. Essential for stability is a sufficiently good initial liquid distribution, which was achieved with a shower-type distributor. Furthermore, distribution was significantly enhanced by the natural occurrence of a well-mixed foam (aerated liquid) layer on top of the monolith at liquid holdup values above 0.5. The quality of the liquid distribution across the monolith follows directly from on-line, integral liquid holdup measurements.
Measurement of Local Mass Flux in a Circulating Fluidized Bed Using a Phase Doppler Particle Analyzer: A New Post-Processing Data Algorithm
Authors: Van Den Moortel T. , Santini R. , Tadrist L. 
Published: July 2023

Abstract
This study focused on the measurement of solid mass flux in the riser of a CFB cold pilot. The investigations were carried out using a Phase Doppler Particle Analyzer (PDPA). Inconsistencies in PDPA results were observed when investigating flows with high particle densities. It appears that the performance of the measuring technique was affected by the optical thickness of the measured medium, thus producing substantial overestimation of the global solid phase quantity (e.g., solid mass flux). To determine the origin of these inconsistencies, the measuring system was subjected to complete recalibration. It was found that in flows with high particle densities, noisy doppler signals tend to be split into several parts by the burst detector system, thus producing inconsistencies in the number of particles counted. The parameters associated with the splitting events were analyzed, and a post-processing algorithm was developed to limit PDPA measuring errors. The aim of the post-processing algorithm was to rebuild the data and to recover the original measurements. The reconstitution process was applied to solid mass flux measurements in a CFB cold pilot.
Heat Transfer Analysis and Evaluation for Two-Phase Flow in Porous-Channel Heat Sinks
Authors: Peterson G. P. , Chang C. S. 
Published: July 2023

Abstract
Presented here are the results of a heat transfer analysis of two-phase heat dissipation utilizing high-conductivity porous channels as a heat sink. A consistent set of conservation equations based on phase-averaged properties of the fluid are derived from the conventional ones and solved numerically by the finite volume method. The results indicate that the high conductivity and large solid-fluid contact surface of the porous channel result in a high heat transfer coefficient. In addition, the surface temperature was shown to remain quite uniform. Overall, the results confirm the expectation that the use of two-phase heat dissipation in high conductivity porous channels may be an acceptable cooling technique for future electronic devices where much higher heat fluxes than the present levels need to be removed effectively.
A Numerical Investigation of the 3-D Flow in Shell and Tube Heat Exchangers
Authors: Prithiviraj M. , Andrews M. J. 
Published: July 2023

Abstract
A three-dimensional computer program for simulation of the flow and heat transfer inside Shell and Tube Heat Exchangers has been developed. The simulation of shell and tube heat exchangers is based on a distributed resistance method that uses a modified two equation k-ε turbulence model along with non-equilibrium wall functions. Volume porosities and non-homogeneous surface permeabilities account for the obstructions due to the tubes and arbitrary arrangement of baffles. Sub-models are described for baffle-shell and baffle-tube leakage, shellside and tubeside heat transfer, with geometry generators for tubes, baffles, and nozzle inlets and outlets. The sub-models in HEATX use parameters that have not been altered from their published values.
Computed heat transfer and pressure drop are compared with experimental data from the Delaware project (Bell, 1963). Numerically computed pressure drops are also compared for different baffle cuts, and different number of baffles with the experiments of Halle et al. (1984) which were performed in an industrial sized heat exchanger at Argonne National Labs. Discussion of the results is given with particular reference to global and local properties such as pressure drop, temperature variation, and heat transfer coefficients. Good agreement is obtained between the experiments and HEATX computations for the shellside pressure drop and outlet temperatures for the shellside and tubeside streams.
An Experimental Study of Premixed Flame Impingement Heat Transfer
Authors: Mizuno K. , Mital R. , Viskanta R. 
Published: July 2023

Abstract
This paper reports results of an experimental study to determine the flame structure and heat transfer characteristics of a premixed methane-air flame impinging on a calorimeter. The flame structure is studied photographically and through temperature measurements. The convection and radiation heat transfer contributions of the flame are separated using a black and a highly reflecting water cooled calorimeter. The effects of nozzle-to-plate spacing, firing rate and equivalence ratio on the flame structure and average heat flux are reported. The axial temperature profiles are found to be a strong function of the gap between burner and calorimeter. The radial temperature profiles show a sharp decline near the burner edge. The photographs reveal that multiple jets, arranged in a circular configuration, exit between the cup-shaped ceramic burner and the calorimeter plate. The length of the flame increases with both the firing rate and the equivalence ratio. The heat flux is highest when the burner is closest to the calorimeter, except for the high firing rates when quenching occurs. Even though the heat flux increases, the heat transfer efficiency decreases with increasing firing rate. Heat flux is also found to increase as the flame becomes air rich in the range of parameters investigated.
Optimal Design of Constrained Plate Damping Layers Using Continuum Finite Elements
Authors: Lumsdaine Arnold , Scott Richard A. 
Published: July 2023

Abstract
The aim of this paper is to determine the optimal shape of a viscoelastic damping layer within a constrained layer plate that is undergoing harmonic excitation at its midpoint. The optimization objective is to minimize the peak displacement of the plate at the first resonant frequency. The material loss factor is monitored as well to determine the improvement in performance between an initial, uniform layer shape and the optimized shape. A fine mesh validation model is also created to verify the optimized shape. As manufacturing costs would be reduced for a uniform shape, the optimized shape is used as a guide to create a new, uniform damping layer, which is compared with the previous results. Several geometries and boundary conditions are examined. The ABAQUS finite element code is used to model the structures. Elasticity theory based continuum elements are used so that all stress effects are taken into account in the models. The optimization code uses a Sequential Quadratic Programming algorithm. Results show significant improvement in the loss factor for optimized shapes. For most models, the optimal shape tends towards being a thin, uniform damping layer, which indicates shearing effects dominate in producing the optimal shape. In one case, however, it appears that some normal stress effects also have some influence.
An Optimal Design Method to Control the Vibrations of Suspensions for Passenger Cars
Authors: Bouazara M. , Richard M. J. 
Published: July 2023

Abstract
In recent years, many studies treated the importance of suspension design. The problem is essentially one of a trade-off between many dynamic parameters. In this study, we consider many parameters such as an acceptable comfort level, suspensions deflection and good road handling behavior. It is well know that a soft suspension is inherently more capable of isolating the vehicle body from the effects of road disturbances compared with a firm suspension. However, the effects of accelerations, braking and cornering maneuvers are generally more severe with a softer suspension. Hence in this work, the response of a 2d vehicle equipped with passive, active or semi-active suspension to a road surface undulation interrelated with the vibrations of the human body is studied.
Estimation of Engine Performance Parameters via Time-Frequency Signal Processing of the Acoustic Emission Signal
Authors: Azzoni P. , Moro D. , Rizzoni G. 
Published: July 2023

Abstract
The aim of this paper is to estimate some engine performance parameters in anon intrusive way, processing the engine acoustic emissions signal by means of the application of joint time-frequency domain signal analysis method. The time-frequency analysis methodology represents a very interesting analysis approach with potential applicability to several specific engine diagnostics problems, such as knock detection, or detection of valve flutter in high performance engines. The paper begins with a brief presentation of time-frequency signal analysis; next the application problem is introduced; and finally experimental results are presented. The results of this study indicate that joint time-frequency signal analysis can be a powerful tool in the analysis of nonstationary signals, and can provide effective tools in the analysis of pass-by engine noise.
A Modeling Technique for Fuel Cell Stack Systems
Authors: Lee J. H. , Lalk T. R. 
Published: July 2023

Abstract
A technique for modeling a fuel cell stack is presented. The technique was specifically designed so that the models developed using it could be used to determine the fundamental thermal-physical behavior of a fuel cell stack for any operating and design configuration. Such models would be useful tools for investigating fuel cell power system parameters. The modeling technique can to be applied to any type of fuel cell stack for which performance data is available for a laboratory scale single cell. Use of the technique is demonstrated by generating sample results for a model of a Proton Exchange Membrane Fuel Cell (PEMFC) stack consisting of 125 cells each with an active area of 150 cm2. A PEMFC stack was chosen to demonstrate the technique because many researchers believe it is the type of fuel cell best suited for transportation applications.
Chatter Analysis of Machining Systems With Nonlinear Force Processes
Authors: Landers Robert G. , Ulsoy A. Galip 
Published: July 2023

Abstract
Regenerative chatter is a major limitation to the productivity and quality of machining operations owing to the poor surface finish, excessive tool wear, and reduced dimensional accuracy which are produced. Machining chatter analysis techniques examine the stability of the closed-loop model of the machining operation. This model is the combination of a force process model and a tool-workpiece structure model. Almost all chatter analysis techniques assume a linear force process although machining force processes inherently contain nonlinearities with respect to the cutting parameters (i.e., feed, depth-of-cut, and cutting speed). A novel machining chatter analysis approach is introduced for the stability analysis of machining systems with nonlinear force processes. The accuracy of this methodology is validated via comparisons to time domain simulations and experiments. The stability lobe diagrams (i.e., plots of the stable and unstable regions in the cutting parameter space) generated using linear and nonlinear force process models are compared and the machining force process nonlinearities are shown to significantly impact the resulting diagrams.
Closed-Loop Control of Sheet Metal Forming Using an Active Drawbead
Authors: Hao Shanlin , Klamecki Barney E. , Ramalingam Subbiah , Du Haiwei 
Published: July 2023

Abstract
The intent of this work was to develop the drawbead as an active element in the closed-loop control of sheet metal forming operations. An instrumented, computer controlled drawing press was built on which blank holddown force and drawbead penetration can be varied during drawing. Closed-loop strip drawing process control was demonstrated by in-process measurement of punch force and adjustment of drawbead penetration so as to follow a specified punch force trajectory. In addition, sensors and transducers were developed to measure local forces for process monitoring.
A Linear Observer Based Approach for Estimating Spindle Bearing Loads
Authors: Gibson Alex O. , Stein Jeffrey L. 
Published: July 2023

Abstract
Thermally induced bearing loads have long been recognized as a key factor limiting the performance of machine tool spindle systems. Previous researchers have developed a model based bearing load estimation system using a nonlinear heat transfer/thermal expansion model and nonlinear observer. While this system is capable of estimating the bearing loads, the difficulty of determining the parameters of the nonlinear model represent a significant barrier to transferring this technology to industry. This paper presents two linear design approaches, based upon disturbance rejection control (DRC) theory. The two approaches use an extended linear observer to estimate the nonlinear bearing friction torque heat input. This allows the division of the bearing load estimation problem into a linear temperature state estimation problem and a nonlinear bearing load calculation. The first approach calculates the bearing load by combining estimates of the bearing’s temperature states in a thermal expansion/bearing load calculation. The second approach uses the estimate of the nonlinear friction heat input to calculate the bearing load This approach allows a reduction in the temperature state model from third to first order, further reducing the model’s complexity. Time responses based upon experimental measurements are used to compare and contrast the above methods with the previously published nonlinear estimation approach. The bearing load estimate results demonstrate that DRC theory can be used to minimize the complexity of the bearing load estimation algorithm while maintaining the accuracy of the estimate.
Quantitative Experimental Analysis of Transparency and Stability in Haptic Interfaces
Authors: Lawrence Dale A. , Pao Lucy Y. , Salada Mark A. , Dougherty Anne M. 
Published: July 2023

Abstract
The notion of haptic transparency is used to quantify the fidelity with which virtual object properties are presented to, and perceived by, the human operator. Experimental results are presented quantifying the ability of humans to detect differences in mechanical impedances representing typical types of impedance corruption (loss of transparency) encountered in haptic interfaces due to stability-enhancing dynamic compensation. In particular, a poor connection is found between the stiffness of virtual walls and their perceptual “hardness”, prompting a new definition of hardness which is often dominated by the high frequency dynamics of the rendered impedance.
A New Mult-Finger Tactual Display
Authors: Tan Hong Z. , Rabinowitz William M. 
Published: July 2023

Abstract
A multi-finger positional display (the TACTUATOR) was developed to study communication through the kinesthetic and vibrotactile aspects of the tactual sensory system of the hand. The display consists of three independent single contact-point actuators interfaced (individually) with the fingerpads of the thumb, the index finger, and the middle finger. Each actuator utilizes a disk-drive head-positioning motor augmented with angular position feedback from a precision rotary variable differential transformer (RVDT). A floatingpoint DSP system provides real-time positional control using a digital PID controller. Stimuli from threshold to about 50 dB SL can be delivered throughout the frequency range from near DC to above 300 Hz, thereby encompassing the perceptual range from gross motion to vibration. Actuator frequency and step responses are well modeled as a second-order linear system. Distortion is low allowing delivery of arbitrary stimulus waveforms, e.g., 25 mm low-frequency motion with superimposed high-frequency vibration. System noise and inter-channel crosstalk are also small. As one example of behavioral performance verification, absolute thresholds measured with the stimulator are in general agreement with values in the literature. Overall, the TACTUATOR accurately follows its drive waveforms and is well suited for a variety of multi-finger tactual perceptual studies.
Performance Measurements for Robotic Actuators
Authors: Morrell John B. , Salisbury J. Kenneth 
Published: July 2023

Abstract
The first part of this paper present an argument on the importance of quantitative methods in robotic research. The remaining sections propose detailed performance metrics for actuator evaluation and example specifications. Several measurements which are new to actuator research are proposed: Impedance (“Backdrivability”), Force Dynamic Range and Force Fidelity. These specifications have emerged from research in robotics and haptics and address the need to obtain a more thorough understanding of machine performance.
Kinematic Design of a Three Degree of Freedom Parallel Hand Controller Mechanism
Authors: Adelstein Bernard D. , Ho Peter , Kazerooni H. 
Published: July 2023

Abstract
This paper presents the kinematic design of a 10 link “in-parallel” mechanism for use in a three degree of freedom force-reflecting haptic interface. The mechanism linkage couples three coplanar rotary electric motor shafts to the endpoint grasped by the human operator. The linkage permits all motor housings to be supported on a common base, thereby reducing the inertia and weight that the interface actuators and human operator must support and move. Furthermore, because only rigid links and rotary ball bearings are used, the linkage avoids the compliance, friction, and/or backlash associated with other types of transmission elements. The linkage workspace is bounded by the singular sphere of maximum reach and separated into two hemispheres by singularities in the plane of the motor shafts.
A Spatial Compliance Controller for Serial Manipulators
Authors: Fasse Ernest D. 
Published: July 2023

Abstract
The utility of robotic interactive control schemes such as stiffness control, admittance control and impedance control has been limited in part by the impedance selection problem. It is difficult to select appropriate impedance parameters to execute useful tasks. A spatial compliance controller is presented that simplifies compliance selection. The family of compliances is introduced with spatial transformation properties that simplify compliance parameter selection. A corresponding control law is derived assuming that the robot consists of a serial linkage of rigid links actuated by variable effort actuators. These results are a significant extension of previous results reported by Fasse (1995) and Fasse and Broenink (1995).
Transition Curves in the Quasiperiodic Mathieu Equation
Authors: Zounes Randolph S. , Rand Richard H. 
Published: July 2023

Abstract
In this work we investigate the following quasiperiodic Mathieu equation:x¨+(δ+ϵcos⁡t+ϵcos⁡ωt)x=0 We use numerical integration and Lyapunov exponents to determine transition curves bounding regions of stability in the δ–ω plane for fixed ϵ. In addition, we obtain approximate analytic expressions for these transition curves using two distinct methods: regular perturbations and harmonic balance. Comparison of the results of these methods with those of numerical integration shows that the perturbation method fails to converge in the neighborhood of resonant values of ω. The results obtained by harmonic balance do not display this undesirable feature.
System Dependent Stability of Direct Acting Relief Valves
Authors: Margolis Donald 
Published: July 2023

Abstract
Hydraulic pressure relief valves are known to become unstable at some operating conditions. A model is developed here that exposes instabilities in a fundamental way. It is shown that a valve can be unstable independent of the system to which it is attached. It is also shown that a stable valve can become unstable when it is placed in operation in some system. Some design relationships are developed that can help avoid potential problems during the system design process.
A Computational Tool for Failure Modes and Effects Analysis of Hydraulic Systems
Authors: Bull D. R. , Burrows C. R. , Edge K. A. , Hawkins P. G. , Woollons D. J. 
Published: July 2023

Abstract
Failure Modes and Effects Analysis is widely used in engineering for the assessment of reliability. With the current practice, the length of time involved in the analysis is prohibitive and therefore its full potential cannot be used in the design process. This paper proposes a computational tool, GNOME, which, when fully implemented, will provide a faster method. This paper will discuss its application to an FMEA of a simple hydrostatic transmission.