bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stability of Sandwich Cylindrical Shells and Panels With Rib-Reinforced Facings
Authors: Birman Victor , Simitses George J. , Shen Liang 
Published: November 2021

Abstract
A new concept in sandwich structures, considered in the paper, employs composite facings with internal ribs. The advantage of this approach is related to enhanced local stiffness and strength of the facings. In particular, the material of facings can be redistributed making the facings thinner, while using the released material for internal ribs. Obviously, this means that the weight of the structure remains without change, while local strength and stiffness increase. The penalty for using this approach is a potential decrease of global stability and global strength as well as lower natural frequencies. The present paper addresses the stability problem for cylindrical shells and panels subjected to axial compression. Buckling loads are calculated for short, complete, cylindrical shells. Based on the numerical results discussed below, it is obvious that ribs should be symmetrically located with respect to the middle surface of the shell. Then a decrease of global stability is relatively small and the proposed design is justified and feasible in practical applications.
Failure Behavior of Closed Cell Foams
Authors: Christensen Richard M. , DeTeresa Steven J. 
Published: November 2021

Abstract
A two-parameter theory of failure is developed for materials for which the uniaxial compressive stress failure magnitude is less than that for uniaxial tension. The theory is compared with data for a closed cell foam material under combined shear and normal stresses. Although the theory shows the correct general behavior, it probably omits certain finer scale features seen in the data. A more refined theory is now being developed, along with further experimental data.
Behavior of Unidirectional Sandwich Panels With a Bi-Linear “Soft” Core: High Order Approach
Authors: Schwarts-Givli Hilla , Frostig Yeoshua 
Published: November 2021

Abstract
A closed-form high-order theory for the analysis of a sandwich panel with a core made of a material characterized by a bi-linear constitutive relation is presented. The non-linearities in the core are a result of bi-linear constitutive relations of the shear and vertical normal stresses. The governing equations are non-linear in the longitudinal and in the vertical coordinates in general. The solution procedure adopted is an iterative one along with convergence criteria. The numerical examples include two types of core material behaviors; where the first one deals with a bi-linear constitutive relation for the shear stress only; and the second one with a bi-linear constitutive relation for vertical normal stresses only. The results demonstrate the relaxation of the stress concentration involves as the load level increase beyond the yielding level as the secant modulus decrease. In the sequel, a summary and conclusions are presented.
On the Choice of Shear Correction Factor in Sandwich Structures
Authors: Birman Victor , Bert Charles W. 
Published: November 2021

Abstract
The first-order shear deformation theory (FSDT) is a relatively simple tool that has been found to yield accurate results in the non-local problems of sandwich structures, such as buckling and free vibration. However, a key factor in practical application of the theory is determination of the transverse shear correction factor (K), which appears as a coefficient in the expression for the transverse shear stress resultant. The physical basis for this factor is that it is supposed to compensate for the FSDT assumption that the shear strain is uniform through the depth of the cross section. In the present paper, the philosophies and results of K determination for homogeneous rectangular cross sections are first reviewed, followed by a review and discussion for the case of sandwich structures.
Drag Coefficients of Viscous Drops
Authors: Feng Zhigang , Michaelides Efstathios E. 
Published: November 2021

Abstract
We have used a finite-difference scheme to solve the Navier-Stokes equations for the steady flow inside and outside viscous spheres in a fluid of different properties. Hence, we obtained the hydrodynamic forces and the steady-state drag coefficient of the spheres. The computational technique we have used enables us to extend the results to Reynolds numbers between 0 and 1,000. The viscosity ratio of the computations ranges between 0 (inviscid bubble) and infinity (solid particle). The method presented here makes use of a two-layer concept for the computational domain outside the sphere. The first layer is a very thin one [O(Re−1/2)] and is positioned at the interface of the sphere. The second layer is based on an exponential function and covers the rest of the domain. The computations yield the friction and the form drag of the sphere. It is observed that both the Reynolds number and the viscosity ratio play a major role on the value of the hydrodynamic force and the drag coefficient. If all other conditions are the same, there is a negligible effect of the density ratio on the drag coefficient of viscous spheres.
Transient Heat Transfer in the Case of Fast Starting Process for Small Steam-Generator
Authors: Bai Bofeng , Guo Liejin 
Published: November 2021

Abstract
The present paper deals with the results of an experimental investigation on transient heat transfer of helical coil steam generator during transient caused by two types of starting processes, which were named lag-start-up and synchro-start-up. The lag-start-up in this paper was referred to as that the working fluid keeps actionless in the initial stages and the pump is started after the heat loading. The synchro-start-up was referred to as that the pump and the heat load were started synchronously from zero to one certain high level. The investigation was conducted to provide one optimal operation. Some correlation to calculate the transient forced convective heat transfer coefficients of single-phase water flow and boiling flow were proposed, and a criterion of critical heat flux for the safety evaluations of starting processes were also obtained. The influence on the starting time was investigated as well.
Cycle-Induced Flow and Transport in a Model of Alveolar Liquid Lining
Authors: Benintendi Steven W. , Grotberg James B. , Halpern David 
Published: November 2021

Abstract
A simplified model of alveolar liquid lining dynamics is developed using a stretchable two-dimensional slot and an insoluble surfactant. Using lubrication theory, a coupled set of evolution equations is derived that describes the film height and interfacial surfactant distribution during the oscillation cycle. This system is solved asymptotically in the limit of small stretching amplitudes. The unsteady flow field is characterized by vortices at the end positions of the oscillation cycle. The cycle-averaged flow field also contains vortical structures, whose number and size vary over parameter space. For large molecular species, like proteins and surfactants, the bulk Peclet numbers can be large, indicating the importance of this liquid layer in the transport process. This may have an impact on the effectiveness and optimization of several medical treatment modalities. Also, since the liquid lining covers many cells within an alveolus, the predicted flow/transport patterns can allow a communication pathway among cells of the same alveolus.
Cavitation Bubble Field at Low Frequency: Simulations and Experiments
Authors: Laborde J.-L. , Servant G. , Hita A. , Caltagirone J.-P. , Gerard A. 
Published: November 2021

Abstract
Power ultrasound is becoming a generally recognized tool in small-scale laboratory. It has considerable potential for industrial use. Actually, propagation of ultrasound wave (from 20 to 800 kHz) through a liquid inside a cylindrical reactor initiates acoustic cavitation and fluid dynamics phenomena. Acoustic cavitation is the formation and activity of bubbles in a liquid due local negative pressures. Spectacular effects including: erosion, sonoluminescence, molecular damage and chemical effects occur. Traveling power ultrasound also initiates fluid dynamics phenomena such as free surface deformations (aerosol formation), convection (macro-mixing), acoustic streaming (micro-mixing), … Characterization of the wave field formation is of significant importance for understanding phenomena and designing and optimizing industrial reactors. Mathematical modeling is here of a great interest, because the scale-up difficulties of ultrasound-based processes. Then, two-phase models (bubbles in liquid) are shown necessary, because bubble clouds interact directly with ultrasound propagation and modify the pressure field establishment. The cavitation field is so dense that it could play the role of an acoustic screen. Bubbles dynamic is considered and simple models are derived. Results show the influence of a homogeneous density distribution of bubbles on the wave attenuation and the agreement between the transient bubble motion induced by pressure gradients and visualizations.
Application of Wavelet Packet to Particle Image Velocimetry Technique
Authors: Li Hui , Takei Masahiro , Saito Yoshifuru , Horii Kiyoshi 
Published: November 2021

Abstract
Our motive of this study is to develop an application of the wavelet packet to PIV image compression processing in order to improve the spatial resolution and reliability furthermore. It was found that the reconstructed PIV image with a lower compression ratio may emphasize particle edges at a relatively high spatial resolution, and the reconstructed PIV image with a higher compression ratio may display the large-scale motion of particles and may deduce noisy. In this study, the relative error of the wavelet packet image compression technique was lower than that of the standard wavelet image compression technique. The higher compression ratio of 64:1 can be realized without losing significant flow information in PIV processing. It could say that the wavelet packet could provide a better compression performance than the standard wavelet image compression technique when compressing PIV images.
Computation of the Vortical Flow in Human Aorta
Authors: Liu Hao 
Published: November 2021

Abstract
Blood flow in aorta cannot spiral as a single helical flow according to conventional fluid dynamic theories. Most in vivo studies, however, show a helical flow in the aorta and such a rotational flow is seen even in the descending aorta. Through a series of stepwise parametrical computational fluid dynamic studies we here show that a swirl secondary flow imposed at inlet can create the helical flow in the aorta. We built an aortic arch model which has realistic geometry of the aorta being reconstructed based on MRI images and a computer-aided method. Our results demonstrate that, rather than geometric influence of the curvature and torsion of the aorta, the swirl inflow condition at inlet plays a key role in the generation of the helical flow. This also implies that the secondary inflow conditions can affect the flows downstream significantly at high Reynolds numbers and we may need to reinvestigate and restudy some fluid dynamic phenomena with application to the physiological fluid dynamics.
Scheduling Algorithms With Application to Parallel Computing of Aeroacoustics
Authors: Povitsky Alex 
Published: November 2021

Abstract
In this study we consider one method of parallelization of implicit numerical schemes on multiprocessor systems. Then, the parallel high-order compact numerical algorithm is applied to physics of amplification of sound waves in a non-uniform mean flow. Due to the pipelined nature of this algorithm, its efficient parallelization is based on scheduling of processors for other computational tasks while otherwise the processors stay idle. In turn, the proposed scheduling algorithm is taken as a special case of the general shop scheduling problem and possible extentions and generalizations of the proposed scheduling methodology are discussed.
Numerical results are discussed in terms of baroclinic generation of wave-associated vorticity that appear to be a key process in energy transfer between a non-uniform mean flow and a propagating disturbance. The discovered phenomenon leads to significant amplification of sound waves and controls the direction of sound propagation.
Analysis of a Novel DCB Specimen for Stitched Texile Composites
Authors: Chen Leishan , Sankar Bhavani V. , Ifju Peter G. 
Published: November 2021

Abstract
Laminated composites, such as graphite-epoxy, are vulnerable to delamination. Through-the-thickness stitching can dramatically improve the interlaminar strength and fracture toughness of laminated composites. In some instances the fracture toughness is so high that conventional DCB tests cannot propagate the crack, instead the specimen fails in flexure. Recently a novel fixture has been developed and used successfully to measure Mode I fracture toughness of such stitched composites. Due to the stable propagation, the location of the crack front and the corresponding load can be precisely measured. The nonlinear differential equations of equilibrium of the new specimen were solved using an iterative procedure to obtain the strain energy release rate as a function of load and crack length. Results include, bending moment, transverse deflection and slope as a function of crack length. The analytical method in conjunction with experimental measurements has been successfully used to determine the instantaneous GIC of the specimen. It was found that the apparent fracture toughness of the specimens tested was roughly constant along the stitched zone, and was about sixty times that of unstitched specimen.
Evaluation of Progressive Failure Simulation Based on Continuum Damage Approximations
Authors: Whitcomb John , Noh Jae , Chapman Clint 
Published: November 2021

Abstract
Discrete modeling of individual damage sites in composites is generally impractical using finite element analysis. A popular alternative is reduction of material properties at those integration points where the stress state exceeds the allowable. This selective reduction of properties results in inhomogeneous properties within an element. Using ordinary finite element interpolation results in severe violation of equilibrium. This paper examines the behavior of the the simplest element, a uniaxial rod element, when selective property reduction is used. Both exact and numerically integrated forms were examined. The results show that errors can be reduced significanly if a robust technique can be developed for representing the damage with a smooth function.
Decoupling the Design Sampling Region From the Trust Region in Approximate Optimization
Authors: Pérez Victor M. , Renaud John E. 
Published: November 2021

Abstract
Response Surface Approximations (RSA’s) are widely used in the design community to provide designers with an approximate representation of a system. The use of RSA’s allow designers to query the system while avoiding the high computational costs associated with today’s advanced simulation codes. Sequential Approximate Optimization (SAO) methodologies have proved to be effective in managing the optimization of multi-disciplinary design problems. In SAO the sampling required to build the RSA’s often takes place within the same bounds as imposed on the current optimization iterate. This assures a good representation of the system in the region where it will be optimized. However it may restrict the approximation from extrapolating beyond the design space, and therefore improve the convergence rate of the algorithm. In this research a decoupling of the sampling region from the trust region is proposed.
Multi-Junction, Multi-Branch Torsional Vibration in a Geared Rotating System
Authors: Yuan Qing Ke , Yao David Y. 
Published: November 2021

Abstract
A multi-junction, multi-branch torsional vibration system is often found in a geared rotating system. This is an important part in many types of machinery, such as mining machinery, petroleum machinery, steel rolling machinery and automobiles. If the design parameters of the system are improper, there will be serious torsional vibration, which will cause noticeable sound disturbances, severe shakings, and component fatigue problems. Analyzing and pre-estimating critical speeds or torsional natural frequencies and mode shapes of the vibration systems in the design stage is very important to avoid future disastrous and costly repairs of the machinery. In this paper, a radical and effective method for calculating natural frequencies and mode shapes of multi-junction, multi-branch torsional vibration systems, has been put forward, a program named MJBTVAP (Multi-Junction, multi-Branch Torsional Vibration Analysis Program) based on this method has been developed, actual problems have been solved.
Dynamics of Two Time-Delay Coupled Relaxation Oscillators of the van der Pol Type
Authors: Sen Asok K. , Rand Richard H. 
Published: November 2021

Abstract
In this paper we examine the dynamics of two time-delay coupled relaxation oscillators of the van der Pol type. By integrating the governing differential-delay equations numerically, we find the various phase-locked motions including the in-phase and out-of-phase modes. Our computations reveal that depending on the strength of coupling (α) and the amount of time delay (τ), the in-phase (out-of-phase) mode may be stable or unstable. There are also values of α and τ for which the in-phase and out-of-phase modes are both stable leading to birhythmicity. The results are illustrated in the α-τ parameter plane. Near the boundaries of stability and instability of the in-phase (out-of-phase) mode, many other types of phase-locked motions can occur. Several examples of these phase-locked states are presented.
Design Optimization of a Special Mounting System: Floating Raft for Ship Power Equipment Vibration Isolation
Authors: Wang Yu , Hua HongXing , Shen Rongying 
Published: November 2021

Abstract
Design optimization of ship power equipment mount system for vibration isolation is presented. The power equipment is modeled as nearly rigid body supported by a set of rubber mounts, called upper level mounts. The upper level mounts are mounted on a middle flexible structure, which is supported by another set of rubber mounts, the lower level mounts. This whole mount system is called floating raft system, which is mounted on elastic bases. This paper, at first explained that the transmissibility, which is defined as the ratio of power equipment vibration response to the transmitted vibration response of the base, can be expressed by frequency response functions. Then based on the frequency response sensitivity analysis, a new design optimization scheme is presented in which the transmissibility is the optimization objective. Finally, an example is used to demonstrate its feasibility.
Dynamics of a Nonlinear System Under Combined Parametric and Quasiperiodic Excitation
Authors: Tan Chin An , Kang Bongsu 
Published: November 2021

Abstract
The forced response of a Duffing oscillator under combined parametric and quasiperiodic excitation with two frequencies is studied. Numerical results are obtained by the spectral balance method. Characteristics of the motion as a frequency parameter is tuned are investigated in terms of the response time histories, frequency spectra, Poincaré sections and Lyapuov exponents. It is found that routes to chaotic motions are different at the primary and parametric resonances.
Analytical Models for Time-Resolved Fluorescence Spectroscopy in Tissues
Authors: Sadoqi Mostafa , Riseborough Peter , Kumar Sunil 
Published: November 2021

Abstract
Laser induced fluorescence is a rapidly growing technique for the characterization of scattering material, most notably in in-vivo biomedical testing. Most previous applications have relied on the measurements of the steady-state emission spectrum, with subsequent analysis of the spectrum for relative concentrations of potential fluorophores. Only recently a few investigators have explored the use of the fluorescence lifetimes as a diagnostic tool by taking advantage of the perturbation of the lifetime by multiple scattering of the excitation and emission light in the tissue.
We have developed a model to study the fluorescence signal generated by a fluorophore distributed in a scattering medium. This model is based on two coupled transient transfer phenomena: the transport of the pulsed source laser, and the induced transient fluorescence excited by the laser. The two are coupled through the source term for the induced fluorescence field. Whereas previous research focused mainly on the fluorescence properties of various dyes, compounds, and materials, only recently have such transport questions been addressed by researchers. In addition, the studies that have been done in the literature have taken the optical properties of the tissue to be the same at the excitation and emission wavelengths. We have presented analytical and numerical solutions for finite, infinite, cylindrical and spherical geometries.
Source Terms in Thermal Therapy: A Parametric Study
Authors: Bhowmick Sankha , Bischof John C. 
Published: November 2021

Abstract
Interstitial thermal therapy heats tissues to temperatures exceeding 50°C for a period of seconds to minutes. This technique is currently being investigated as an autonomous therapeutic option for the treatment of benign and malignant diseases at different sites in the body including the prostate, uterine fibroid, kidney and liver (Diller and Ryan, 1998). Some of the interstitial heating techniques that are being studied are microwave, ultrasound (US) and laser. The predominant mechanism of heating associated with each of these techniques appears to be different, i.e. microwave heating is dielectric, US is by mechanical vibration and lasers through photon absorption. Clearly, the thermal distribution in the heated tissue is intrinsically dependent on the mechanism of heating. Since accurate characterization of heat deposition in the tissue is imperative for successful thermal therapy treatments, a broader understanding of the parameters governing the heating or source term(s) is needed.
Nonlinear Thermal and Mechanical Analysis in the Vibration of a Printed Wiring Board
Authors: He Xiaoling , Fulton Robert 
Published: November 2021

Abstract
Nonlinear laminate theory is applied and extended for the printed wiring board dynamic analysis. Equations of motion for the isotropic laminates are derived for vibration response analysis of the simply supported printed wiring board under mechanical and thermal loads. Temperature variation in spatial domain is taken into consideration. The effect of the temperature variation on the response character is analyzed and demonstrated by means of numerical results. Modal analysis is made to predict the vibration behavior in terms of deflection and stresses. Lamina stresses are used for failure prediction.