bluuebunny/crossref_metadata_2025_split huggingface dataset:
Toughening, Strengthening and Densification Approaches Applied to Carbon/Carbon Composites
Authors: Gajiwala H. M. , Vaidya U. K. , Sodah S. , Jeelani S. 
Published: July 2023

Abstract
The current study is directed towards development of high performance, toughened, strengthened and easily processable carbon/carbon (C/C) composites. These composites were developed through a hybridized matrix approach involving conventional resole-type resin precursor used in conjunction with an in-house synthesized processable polyimide resin. Plain weave graphite fabric layers were impregnated with a resole-type phenolic resin and thermo-oxidatively stable, high carbon yield polyimide resin by the hand lay-up technique. The resultant composite was subjected to two successive cycles of carbonization followed by densification, to obtain a C/C composite. At each stage of the process, the composite was subjected to quantitative ultrasonic velocity measurements using longitudinal dry coupling transducers to characterize the elastic constants in three directions. Destructive interlaminar shear strength (ILSS) testing was done at various stages of processing to determine the failure modes and mechanisms that lead to toughening and strengthening.
Free Bending Vibrations of Partially Stiffened, Stepped-Thickness, Bonded Composite Plates and Panels
Authors: Yuceoglu U. , Özerciyes V. 
Published: July 2023

Abstract
The present study is primarily concerned with the free bending or transverse vibrations of a multi-layer, partially stiffened, bonded composite plate system. Here, the two-layer plate system is composed of two dissimilar, orthotropic plates of different lengths but of the same width and in-between very thin adhesive layer. Thus, a two-layer, partially stiffened, stepped-thickness, bonded composite plate system is created. In the dynamic equations, the influence of the thickness shear deformations and the rotatory moments of inertia of plates are taken into account in the sense of the Mindlin Plate Theory. The normal and shear strains and the corresponding stresses in the relatively very thin adhesive layer are included in the formulation. They are the coupling terms of the upper stiffening plate and the lower base plate. The composite plates are to be simply supported at two opposite edges. However, at the other two opposite edges, the boundary conditions may be arbitrary. The solution technique is a combination of a “Modified Version of the Transfer Matrix Method” and the classical “Levy’s Method“. The natural frequencies and the typical mode shapes of the stepped-thickness and partially stiffened, bonded composite plate system of dissimilar members are presented. It is shown that, in some cases, the deflection shapes of the upper stiffening plate and the lower base plate corresponding to the same mode of the composite system are significantly different. Also, the influence of some of the characteristic parameters on the natural frequencies are plotted and presented.
Laminar Convective Heat Transfer for a Bingham Plastic in a Circular Pipe: The Graetz Problem Extended
Authors: Min Taegee , Yoo Jung Y. , Choi Haecheon 
Published: July 2023

Abstract
Thermally fully developed and thermally developing laminar flows of a Bingham plastic in a circular pipe with uniform heat flux have been studied analytically. For thermally fully developed flow, the Nusselt numbers and temperature profiles are presented in terms of the yield stress and Brinkman number. The solution to the Graetz problem has been obtained by using the method of separation of variables, where the resulting eigenvalue problem is solved approximately by using the method of weighted residuals. The effects of the yield stress, Peclet and Brinkman numbers on the Nusselt number are discussed.
The Motion of Bubbles in Non-Newtonian Fluids
Authors: De Kee D. , Rodrigue D. , Fong C. F. Chan Man 
Published: July 2023

Abstract
The drag and the rise velocity of a spherical bubble rising freely and slowly in an inelastic Carreau fluid are calculated by a perturbation method. Measurements of the rise velocity of gas bubbles in several Newtonian and non-Newtonian fluids are reported. The transition from the Stokes to the Hadamard-Rybczynski regimes has been observed and in the case of viscoelastic fluids a jump discontinuity in the velocity has also been recorded. An equation is proposed to predict the volume at which the jump discontinuity occurs and the prediction is in good agreement with the experimental data.
Bubble-Collision Effects on Nonlinear Void Fraction Waves in Bubbly Liquids
Authors: Delassade Xavier A. 
Published: July 2023

Abstract
The concept of dispersed two-phase flow via the theory of micrmorphic fluids is briefly presented. Balance laws for each phase are given. For the isothermal case, a summary of the constitutive relations expressing the contribution of the collisional forces and other interactions concludes the derivation of the dynamic equations.
For finite amplitude disturbances, nonlinear effects are considered. A balance is made in order to determine the dominant effects of the many terms in the equations of motion. Over a long timescale, the collisional bubble-bubble couplings are shown to be purely dispersive. Weakly nonlinear waves propagate according to the Benney equation or the fifth order Korteweg-de Vries equation, both with perturbation terms which can be either amplifying or dissipative Burgers perturbation terms, depending on the level of description and the sign of a coefficient.
A brief discussion of some of the current issues and their implications is given.
Displacement of a Fluid by Another in Tubes
Authors: Siginer Dennis A. , Bakhtiyarov Sayavur 
Published: July 2023

Abstract
The displacement of Newtonian fluids by non-Newtonian fluids in a horizontal cylindrical tube has been investigated both theoretically and experimentally. Theoretical expressions for the breakthrough time, a function of the constitutive constants of the fluids and of the flow parameters and geometry, are derived when the displacing fluids are either of the inelastic viscous or viscoelastic type. The dynamics of the displacement process is studied experimentally using the photometry method and an oil field spacer fluid and glycerol/water mixtures as the displacing and displaced fluids, respectively. The ratio of the zero shear viscosities of the displacing and displaced fluids plays a crucial role both when the displacing fluid is characterized by a viscoelastic and viscoinelastic structure. The density ratio of the displacing and displaced fluids is close to one in our experiments as it may be in most field operations. We show that characterization of this type of spacer fluid by a viscoelastic model at moderate pressure gradients will not lead to good predictions of the breakthrough time when the viscosity of the displaced crude is much smaller than that of the displacing spacer fluid, that is, for high values of the zero shear viscosity ratios which may be desirable for high efficiency displacement processes.
Do Molten Polyolefins Reptate in Large Amplitude Oscillatory Shear?
Authors: Giacomin A. J. , Jeyaseelan R. S. 
Published: July 2023

Abstract
The linear relaxation spectrum predicted by reptation theory cannot accurately describe melt behavior in mild deformations. Replacing the linear spectrum with a generalized Maxwell model, one can assess how well reptation theory predicts large departures from linear viscoelasticity. In this way, three systems are studied in large amplitude oscillatory shear: a nearly monodisperse unbranched melt, a polydisperse unbranched melt, and a polydisperse branched system. Surprisingly, only the nonlinearities exhibited by the polydisperse branched system are reasonably predicted by reptation theory in oscillatory shear.
Acoustic Enhancement of the Rate of Heat Transfer Over a Flat Plate: An Experimental Investigation
Authors: Preston John M. , Johnson William S. 
Published: July 2023

Abstract
Increasing the rate of heat transfer can improve product quality and lower energy cost for many energy systems and pulsating fluid flow has been used to increase the rate of heat transfer in some situations. Specifically, sound waves below the audible limit, termed infrasound, have been used to increase the rate of heat transfer from small diameter, wire rods. This study examined the effects of infrasound on the rate of heat transfer from a flat plate.
A standing sound wave is formed in the neck of a Helmholtz resonator and may be enhanced by producing sound waves at the resonant frequency at or near the neck of the resonator. In this study a standing wave of infrasound was produced in a rectangular channel by two loudspeakers driven sinusoidally by a function generator at the resonant frequency of the system. The top of the channel was formed by a copper plate maintained at a constant temperature. Thermocouples placed along the center line of the channel measured the temperature of the air inside the channel and heat flux gauges mounted on the inside surface of the copper plate were used to measured the local rate of heat transfer from the plate to the air inside the channel Air flow inside the channel was produced by a centrifugal blower and varied by an inlet damper.
The use of infrasound increased the rate of heat transfer by approximately an order of magnitude when compared to natural convection Infrasonic enhancement of the rate of heat transfer over a two-dimensional region in forced convection was more effective in the laminar flow regime, for Reynolds numbers based on the hydraulic diameter between zero and 10,000. Typically for laminar flow, infrasound increased the rate of heat transfer up to five times the rate of heat transfer without infrasound. For turbulent air flow; however, the increase of the rate of heat transfer was almost negligible. The effect of infrasound on the rate of heat transfer was shown to depend on the air velocity inside the channel, the hydraulic diameter of the channel and the sound pressure level inside the channel. The temperature of the copper plate over the limited range tested did not significantly affect the heat transfer coefficient. It should be noted that the speakers were limited to a maximum sound pressure level of 121 dB, while infrasonic generators are capable of producing sound pressure levels over 170 dB.
Methods of Simulating Fouling Effect in Water-Cooled Condenser With a Sub-Cooler
Authors: Li Shan S. 
Published: July 2023

Abstract
The fouling on heat exchanger surfaces produces an additional thermal resistance Rf. It tends to reduce chiller capacity and increase power consumption. A method is needed to simulate the fouling phenomenon and to test new and fouling-free chillers for performance under simulated condition of the field fouling.
The fouling effect results in a penalty in the form of an additional temperature approach, ΔTa, between the hot and cool sides of a heat exchanger. If assuming single phase or simple two-phase (no sub-cooling) flow and some other conditions, this ΔTa can be rigorously derived by using LMTD method. ARI-550/92 Standard provides one form of the formulation.
When a sub-cooler is combined with a condenser, the temperature profile along the length of the heat exchanger becomes strongly non-linear. Simply using the above method will generate false information if the sub-cooling and the fouling are large. An analysis using piece-wise LMTD method should be utilized to calculate ΔTa. Because of the complexity of the pipe lines and couplings between water and refrigerant sides, this calculation requires iteration algorithm which is not convenient to use.
Present work proposes an approximate formulation. The flow circuit was simplified with the heat duties equivalent to the original circuit. This approximation provides very good accuracy in ΔTa calculation.
Parametric Study of Heat Transfer Enhancement in the Reciprocating Regenerative Magnetic Heat Pump
Authors: Chen D. T. , Murphy R. W. , Mei V. C. , Chen F. C. 
Published: July 2023

Abstract
The heat transfer enhancement parametric study of the gadolinium cores in reciprocating magnetic heat pumps has been studied numerically. The main objective of this study is to enhance the heat transfer rate from the gadolinium core to the regenerative fluid. The optimization of the core includes optimizing the volume of the core and the ratio of the effective heat transfer area to the volume. The total volume represents the total amount of heat generated from the core; the effective surface area to the volume ratio reflects the actual quantity of heat transferred from the core to the surrounding fluid. Both parameters have to be optimized to fit their particular applications. In general, the more core volume, the more heat will be generated; and the more surface area, the more heat will be transferred to the fluid. However, in reciprocating regenerative magnetic heat pumping applications, these two factors have to be adjusted well to allow the core to generate two extremely hot and cold regions in the top and bottom end of the regenerator fluid column, respectively. The result of this numerical study shows that porosity of the gadolinium core in the range 0.36–0.40 and area-to-volume ratio in the range 500–600 are two design criteria for designing a better gadolinium core for reciprocating heat pump application. In addition, the optimal operating conditions based on the regenerator tube’s moving speeds (or Reynolds numbers) have also been studied. According to the current investigation, Reynolds number 60–120 is the optimal operating range for running a well-designed gadolinium core. The flow’s thermal mixing has been controlled by using the technique of variable flow rate, which, according to the current study, can increase the maximum temperature span as much as 5 K.
Feasibility Analysis of a Vortex Generator for Absorption Heat Pumps
Authors: Fineblum Solomon S. 
Published: July 2023

Abstract
Significant thermal resources in the form of low temperature industrial waste heat, between 211 to 528 trillion kJ (200 and 500 trillion BTU’s) per annum, have the potential to drive absorption heat pumps. The proposed vortex generator permits a practical heat pump to operate efficiently with as much as 20 to 30°C below the boiling temperature of water (70–80°C (158–176°F)). Energy flows and auxiliary power requirements are computed. The system is shown to operate with relatively low temperature waste heat with higher specific capacity than conventional systems.
Exergy Analysis of Sodium Tripolyphosphate Manufacture
Authors: Atanasova Lubka G. , Rasheva Dimitrina A. 
Published: July 2023

Abstract
Sodium tripolyphosphate finds wide application in different branches of industry and medicine. It is used in big amounts for softening of water and as a component of different detergent compositions.
Using exergy method for thermodynamic analysis an evaluation of energy effectively of an installation for sodium tripolyphosphate production was done. Material, heat and exergy balances of the whole system and its separate parts were made. The exergy coefficients of efficiency, internal and external exergy losses are calculated.
It was found that-the exergy efficiency of the investigated system is low. The exergy efficiency coefficient is 6.75 %. The high exergy losses are due to poor utilization of heat of flue gas, obtained from natural gas.
Efficiency Analysis of a Process Design Integrating Cogeneration and District Energy
Authors: Rosen M. A. , Le M. N. 
Published: July 2023

Abstract
An efficiency analysis, accounting for both energy and exergy considerations, is reported of a design for cogeneration-based district energy proposed for the city of Edmonton, Canada, by the utility Edmonton Power. The original concept using central electric chillers, as well as two variations (one considering single-effect and the other double-effect absorption chillers), are examined. The energy- and exergy-based results differ markedly (e.g., overall energy efficiencies are shown to vary for the three configurations considered from 83 to 94%, and exergy efficiencies from 28 to 29%). For the overall processes, as well as individual subprocesses and selected combinations of subprocesses, the exergy efficiencies are generally found to be more meaningful and indicative of system behaviour than the energy efficiencies.
Influence of Trailer Tandem-Axle Versus Tridem-Axle on Pavement Damage and Dynamic Performance
Authors: Fekpe Edward S. K. , El-Gindy Moustafa 
Published: July 2023

Abstract
This paper reports a study on the effect of a semitrailer’s axle arrangements, tandem-axle versus tridem-axle, on dynamic performance and pavement damage potential of tractor semitrailers. Generally, dynamic performance properties of both tandem and tridem axles tend to deteriorate with increasing axle spread and maximum axle weight limit. Friction demand in particular is sensitive to tridem axle spread. There are maximum spreads and weight limits for both tridem and tandem axles to satisfy the dynamic performance measures. Tridem axle spreads between 2.4m and 3.6m and weight limits less than or equal to 27000kg satisfy the current dynamic performance criteria. Tandem axle spread less than 2.4m and weight less than 20000kg exhibit adequate dynamic performance properties. In the transportation of dense commodities, it is operationally more efficient to use semitrailers with a tridem axle than one with a tandem axle for gross vehicle weights less than 48,000 kg (i.e. tridem axle spread around 3.6m and maximum weight of about 25000 kg). Relative to the tandem axle, operational performance is greatly improved with the tridem trailer axle.
Stability of a Flexible Wheelset for High Speed Rail Vehicles With Constant and Varying Parameters
Authors: Lieh Junghsen , Yin Jie 
Published: July 2023

Abstract
The stability of an elastic wheelset coupled with a torsional spring and a torsional damper is presented in this paper. With flexible elements between two wheels, the advantages of both rigid and independently rotating wheel (IRW) systems may be obtained. Previous studies indicated that the flexible elements will affect the vehicle dynamic behavior and an optimal parameters may improve the system performance. However, those studies were limited to constant wheel/rail geometry as the wheelset rolls along the track. In this paper, it is intended to determine the critical speed regions thus to reduce the potential for hunting. The critical velocity of constant and time-varying models is presented. The variation in conicity is assumed to be periodic thus the Floquet stability concept may be employed. The computation of the state-transition matrix is based on a Runge-Kutta algorithm.
Wide-Range Surface Roughness Measuring System
Authors: Shiraishi M. , Aoshima S. 
Published: July 2023

Abstract
A wide-range surface roughness measuring system based on a laser beam has been developed. This method consists of two measuring approaches: a laser speckle method for smooth roughness and a light scattering method for rougher surfaces. When a measured roughness value exceeds about 1.0 μm Ra, the measuring principle automatically changes from the speckle approach to the light scattering approach. The experimental results with on-machine measurements indicate the accuracy of 0.04 μm to 0.5 μm for smooth surfaces and 2.0 μm to 5.0 μm for rougher surfaces.
H
∞ Based Robust Multivariable Linear Control of Weld Pool Shape
Authors: Zhang Y. M. , Yao Y. X. , Li L. , Kovacevic R. 
Published: July 2023

Abstract
In order to achieve the desired weld penetration and grain structure, the weld pool shape must be controlled. In this paper, the weld pool shape is specified by the length and width of the weld pool. Its feedback is provided by a realtime vision system. Due to unavoidable variations during welding, the process uncertainty is substantial. In order to develop a robust control system, the H∞ approach is used. Simulation and experimentation showed that the performance of the developed H∞ control system is quite satisfactory.
Performance Evaluation of Modular Real-Time Controllers
Authors: Zhou Lei , Washburn Michael J. , Shin Kang G. , Rundensteiner Elke A. 
Published: July 2023

Abstract
With the progress in the research and development of open-architecture control systems, traditionally-monolithic controllers need to be modularized. Modularization is necessary in order to take advantage of newly available hardware and software components and to reduce controller development and maintenance costs. The resulting modular controllers rely more on the underlying support services, such as the POSIX timer and operating system scheduler. The behavior of an underlying real-time operating system can have a significant impact on an open and modular controller. In this paper, we investigate such an impact by empirically evaluating the performance of our prototype modular controllers in the University of Michigan Open-Architecture Controller testbed. A modular software architecture allows for flexibility in running real-time control applications. For example, a controller may consist of several cooperative periodic real-time tasks, each of which runs as a separate computer process and controls a particular machine axis. However, we observe that real-time operating systems exhibit significant unpredictability. In particular, the timing uniformity of tasks suffers when multiple tasks run as separate computer processes. This indicates a need for approaches to improve controller performance. One strategy we propose is to minimize operating system activities, e.g., by disabling unnecessary peripheral devices. However, we find that some major sources of unpredictability are essential system software modules. Another strategy is to combine tasks with similar periods into a composite task. We conducted experiments to measure performance before and after restructuring software and found that combining tasks with similar periods is a more desirable approach.
Optimal Feedforward Control for High Speed and High Precision Digital Motion Systems
Authors: Guo Lin , Tomizuka Masayoshi 
Published: July 2023

Abstract
A feedforward controller which respects the underlying hybrid nature of digital control systems, i.e. continuous-time plant and discrete-time feedback loop, is proposed for high speed/high precision motion systems. The feedforward controller combines the shift(q) and the delta (δ) operators such that uncancellable discrete-time zeros caused by sampling the continuous-time plant at high rates, which make the mathematical inverse unstable, are handled in a natural way. The controller is optimized by tuning two parameters in a pre-filter of the feedforward controller. The optimization problem is generalized to an H∞ problem. Convex minimization techniques are used to find the solution to the optimization problem. Experiments are carried out on a Matsuura Vertical Machining Center. The performance of the proposed optimal hybrid feedforward controller is compared with that of the zero phase error tracking controller. Some improvements have been observed from the experimental results.