bluuebunny/crossref_metadata_2025 huggingface dataset:
Correcting for dispersion interaction and beyond in density functional theory through force matching
Authors: Song Yang , Akin-Ojo Omololu , Wang Feng
Published: November 2010

The force matching method is used to improve density functional theory (DFT) by designing a supplemental potential to capture the difference in atomic forces between a DFT functional and a high-quality post Hartree–Fock method. The supplemental potential has two-body terms designed to correct for dispersion and hydrogen bond interactions. The potential also has one-body terms to improve the description of the intramolecular potential energy surface. Our procedure is tested by providing corrections to the Becke–Lee–Yang–Parr exchange-correlation functional for water and is found to perform significantly better than the standard DFT-D approach, giving QCISD quality predictions for relative cluster energies, atomic forces, and molecular structures. It is found that a simple Lennard-Jones term does a good job at correcting for van der Waals interactions and possibly also providing corrections to exchange repulsion. The one-body corrections, while contributing only slightly to improving relative cluster energies, significantly reduce the errors in binding energies and atomic forces for the systems studied.
Urbach tail studies by luminescence filtering in moderately doped bulk InP
Authors: Subashiev Arsen V. , Semyonov Oleg , Chen Zhichao , Luryi Serge
Published: November 2010

The shape of the photoluminescence line registered from a side edge of InP wafer is studied as a function of the distance from the excitation spot. The observed redshift in the luminescence maximum is well described by radiation filtering and is consistent with the absorption spectra. Our method provides an independent and accurate determination of the Urbach tails in moderately doped semiconductors.
Stability of terbium scandate on Si(100)
Authors: Copel M. , Bojarczuk N. , Edge L. F. , Guha S.
Published: November 2010

We have examined the stability of TbScO3 on Si(100) using medium energy ion scattering. At high temperatures the dielectric decomposes into a Tb-rich silicate layer near the substrate, and a Sc-rich layer near the surface. Interfacial SiO2 is consumed in the reaction. We find that Sc2O3 by itself does not react with SiO2 while Tb2O3 readily forms a silicate. This difference in reactivity drives the vertical separation of metal ions. Consideration of the fundamental chemistry of rare-earth scandates suggests that rare-earth scandates are unstable in the presence of SiO2
Experimental library screening demonstrates the successful application of computational protein design to large structural ensembles
Authors: Allen Benjamin D. , Nisthal Alex , Mayo Stephen L.
Published: November 2010

The stability, activity, and solubility of a protein sequence are determined by a delicate balance of molecular interactions in a variety of conformational states. Even so, most computational protein design methods model sequences in the context of a single native conformation. Simulations that model the native state as an ensemble have been mostly neglected due to the lack of sufficiently powerful optimization algorithms for multistate design. Here, we have applied our multistate design algorithm to study the potential utility of various forms of input structural data for design. To facilitate a more thorough analysis, we developed new methods for the design and high-throughput stability determination of combinatorial mutation libraries based on protein design calculations. The application of these methods to the core design of a small model system produced many variants with improved thermodynamic stability and showed that multistate design methods can be readily applied to large structural ensembles. We found that exhaustive screening of our designed libraries helped to clarify several sources of simulation error that would have otherwise been difficult to ascertain. Interestingly, the lack of correlation between our simulated and experimentally measured stability values shows clearly that a design procedure need not reproduce experimental data exactly to achieve success. This surprising result suggests potentially fruitful directions for the improvement of computational protein design technology.
Polycystic ovarian syndrome and subclinical atherosclerosis among women of reproductive age in the Dallas heart study
Authors: Chang Alice Y. , Ayers Colby , Minhajuddin Abu , Jain Tulika , Nurenberg Pamela , de Lemos James A. , Wild Robert A. , Auchus Richard J.
Published: November 2010

Objective  Polycystic ovarian syndrome (PCOS), the most common endocrinopathy of young women, is characterized by androgen excess and is frequently associated with cardiovascular risk factors. However, it is unclear whether PCOS is a risk factor for atherosclerosis. We sought to determine in a multiethnic population‐based sample whether women with PCOS have greater measures of subclinical atherosclerosis than women without PCOS.

Design  Cross‐sectional study of a nested cohort from the Dallas Heart Study (2000–2002).

Participants  Women between the ages of 35 and 49 (n = 827). PCOS was defined by Rotterdam criteria. The normal control group had regular menses, total testosterone <2·78 nmol/l, no signs of hirsutism and no polycystic ovarian morphology by magnetic resonance imaging (MRI).

Measurements  Subclinical atherosclerosis defined as coronary artery calcium (CAC) by computed tomography and abdominal aortic plaque by MRI.

Results  The prevalence of PCOS in Dallas County was 19·6% (n = 144), and 8·0% (n = 56) had both oligomenorrhea and hyperandrogenism. Women with PCOS had higher body mass index, blood pressure, insulin and leptin than regularly cycling controls. Despite a greater prevalence of cardiovascular risk factors, women with PCOS did not have a greater prevalence of CAC > 10 Agatston units (PCOS 5%, controls 6·3%, P = 0·74) or abdominal aortic plaque (PCOS 25·8%, controls 34·4%, P = 0·13) than controls.

Conclusions  In a large, multiethnic, population‐based sample of premenopausal women, PCOS, defined by Rotterdam criteria, was not associated with a higher prevalence of coronary artery calcium or abdominal aortic plaque.
The effect of coronary angiography on renal function in preemptive renal transplant candidates
Authors: Lorenz Elizabeth C. , Stegall Mark D. , Cosio Fernando G. , Gloor James M. , Larson Timothy S. , Taler Sandra J.
Published: November 2010

Lorenz EC, Stegall MD, Cosio FG, Gloor JM, Larson TS, Taler SJ. The effect of coronary angiography on renal function in preemptive renal transplant candidates. Clin Transplant 2011: 25: 594–599. © 2010 John Wiley & Sons A/S.

Abstract:  Background:  Increasing numbers of patients undergo preemptive renal transplantation. Obtaining cardiac catheterizations prior to transplantation to screen for coronary artery disease is controversial because of the perceived risk of inducing contrast nephropathy and the need for dialysis in patients with marginal renal function. We sought to examine the true impact of cardiac catheterization on time to dialysis in a cohort of preemptive renal transplant candidates.

Methods:  From a cohort of 376 transplant candidates evaluated preemptively at our program between 2/2001 and 4/2005, 34 patients had positive dobutamine stress echocardiograms. We reviewed the subsequent need for dialysis in these patients.

Results:  Among candidates undergoing angiography, 8.7% required dialysis within 14 d of contrast administration and 26% eventually needed dialysis prior to transplantation at 5.3 ± 3.7 months after their pre‐transplant evaluation. Among patients who did not undergo angiography, 27% needed dialysis prior to transplantation at 2.4 ± 1.8 months after pre‐transplant evaluation.

Conclusions:  Our results demonstrate a low risk of hastening the need for dialysis after coronary angiography in preemptive renal transplant candidates. Undergoing angiography had no effect on the ultimate need for or timing of dialysis initiation. These findings support completion of full cardiac evaluation as indicated for high‐risk preemptive renal transplant candidates.
Trade‐off acquisition and allocation inGryllus firmus: a test of the Y model
Authors: KING E. G. , ROFF D. A. , FAIRBAIRN D. J.
Published: November 2010

Many models of life history evolution assume trade‐offs between major life history traits; however, these trade‐offs are often not found. The Y model predicts that variation in acquisition can mask underlying allocation trade‐offs and is a major hypothesis explaining why negative relationships are not always found between traits that are predicted to trade‐off with one another. Despite this model’s influence on the field of life history evolution, it has rarely been properly tested. We use a model system, the wing dimorphic cricket,Gryllus firmusas a case study to test the assumptions and predictions of the Y model. By experimentally altering the acquisition regime and by estimating energy acquisition and energy allocation directly in this species, we are able to explicitly test this important model. Overall, we find strong support for the predictions of the Y model.
Neuroprotective preconditioning of rat brain cultures with ethanol: potential transduction by PKC isoforms and focal adhesion kinase upstream of increases in effector heat shock proteins
Authors: Sivaswamy Sreevidya , Neafsey Edward J. , Collins Michael A.
Published: November 2010

Preconditioning rat hippocampal–entorhinocortical (HEC) slice or cerebellar cell cultures with moderate concentrations of ethanol (20–30 mm) neuroprotects against pro‐inflammatory proteins such as HIV‐1 glycoprotein 120 (gp120) or amyloid‐β. The neuroprotective mechanism of ethanol is unclear, but it conceivably involves sensors→transducers→effectors, analogous to other preconditioning modalities. We initially found that the preconditioning augmented two likely heat shock protein (HSP) ‘effectors’, HSP70 and HSP27, and that precluding HSP upregulation abolished neuroprotection. Here we examined whether pro‐survival kinases are transducers potentially leading to HSP effectors. In cerebellar cultures, protein kinase C (PKC) activity increased modestly after 2 days of 30 mm ethanol and was significantly induced after 6 days, when neuroprotection against gp120 becomes manifest. After 4 and particularly after 6 days of preconditioning, immunoblots showed highly elevated PKCε levels and moderately increased PKCα and PKCδ, accompanied by increased membrane translocation (activation) of these isoforms. Also, at the latter preconditioning duration, focal adhesion kinase (FAK), an important actin‐associated kinase, and its Y397‐phosphorylated form (p‐FAK) were elevated, along with parallel increases in HSP27, S85p‐HSP27 and HSP70. Furthermore, while confirming increased HSP27 and HSP70 in HEC slices ethanol‐preconditioned for 6 days, we detected elevations in PKC isoforms, FAK, p‐FAK and p‐HSP27 in these organotypic cultures. Importantly, PKC inhibition with GF109203X suppressed FAK, HSP70 and HSP27 amplification/activation in ethanol‐preconditioned cerebellar cultures, indicating that PKC is an upstream transducer of FAK and the HSP effectors. Neuroprotection associated with increases in HSP27/HSP70 from ethanol preconditioning entails upregulation/activation of PKC isoforms and FAK, the latter kinase implicating actin cytoskeletal prosurvival pathways in brain preconditioning.
Moistened Hands Do Not Necessarily Allude to High Quality Fingerprints: The Relationship Between Palmar Moisture and Fingerprint Donorship
Authors: Almog Joseph , Sheratzki Hadar , Elad‐Levin Michal , Sagiv Assaf E. , Singh Gagan Deep , Jasuja Om Prakash
Published: November 2010

Abstract:  We explored the quality distribution of ninhydrin‐developed prints on A4 bond paper in two groups of individuals, in Israel and in India. While the quality distributions of the developed marks in both countries had some dissimilarities, both groups showed the expected bell‐shape distribution, with the majority of the donors belonging to the central zone, defined as “average” or “good.” Attempt was made to correlate between a physiological feature, palmar moisture, and the fingerprint donorship. As a rule, high fingermark quality could be associated with sweating hands, but there were individuals with moist palms whose fingermarks had a low score and vice versa. This finding supports the logical but hitherto unproven assumption that besides the amount of palmar sweat, the other physiological factor governing the prints’ quality is the total amount of substrate, amino acids in this case, in the latent deposits, which depends on the substrate concentration in the sweat.
Treatment of diabetic retinopathy with anti‐VEGF drugs
Authors: Waisbourd Michael , Goldstein Michaella , Loewenstein Anat
Published: November 2010

The aim of this review is to summarize the latest developments in the treatment of diabetic retinopathy (DR) with anti‐vascular endothelial growth factor (VEGF) drugs. We reviewed recent studies that evaluated the role of the anti‐VEGF agents bevacizumab, ranibizumab and pegaptanib in the treatment of DR. There was only one large randomized controlled trial that evaluated the role of ranibizumab in diabetic macular oedema (DME). Other prospective and retrospective studies provided important insight into the role of anti‐VEGF drugs in DR, but most of them were not conducted in large scales. The growing evidence indicates that anti‐VEGF drugs are beneficial in DR, especially in DME. Further studies are needed to fully evaluate the role of these agents, especially in proliferative DR and in DR candidates for vitrectomy surgery.
Mechanics of the Flow in an Elastic Tube Extending From an Orifice Into a Pressure Vessel
Authors: Holmberg J. L. , Wilson T. A.
Published: November 2010

A model consisting of two elastic beams separated by hinged rods is used to analyze the axially nonuniform collapse of an elastic tube extending into a pressure vessel. The conditions for which the tube will close are determined experimentally. A self-excited oscillation of the deformation is observed over a range of a factor of 10 in reservoir pressure. The frequency of the oscillation is from 10–100 Hz when water is the fluid flowing out of thin-walled Penrose drainage tubing and approximately 2000 Hz when air is the fluid. A second model is analyzed to describe the important features of the oscillation.
On Turbulence-Induced Vibrations of a Thin Ribbon With Velocity-Dependent Damping
Authors: McCormick M. E. , Ripley T. C.
Published: November 2010

Results of an experimental study of the turbulence-induced random vibrations of a thin metal ribbon show that an interaction between the vibrating surface and the turbulence exists which results in an increase in the turbulent energy within the boundary layer. In addition, the system damping is shown to vary with the free-stream velocity and to be proportional to the amplitude response of the ribbon. The experimental data and an accompanying theoretical analysis give support to the belief that the damping is primarily a velocity-squared type which is characteristic of a flat plate vibrating normally in a fluid.
Axisymmetric One-Dimensional Compressible Flow—Theory and Applications
Authors: Anderson L. R. , Heiser W. H. , Jackson J. C.
Published: November 2010

Several generations of engineers have found that the one-dimensional approach to compressible fluid flows in ducts is extremely informative and effective. This paper extends these methods to axisymmetric flows so that they may be used to understand and estimate the behavior of azimuthally unrestrained, swirling flows. The already-established understanding of duct flows makes an elaborate investigation of the new results unnecessary. The paper contains the underlying assumptions and resulting equations, an outline of the solution technique, a comprehensive table of influence coefficients, and a variety of interesting examples peculiar to swirling flows drawn from the field of rotating machinery.
Indentation of an Elastic Layer by an Array of Punches Moving With Steady Velocity
Authors: Keer L. M. , Sve C.
Published: November 2010

A solution is presented for the problem of an elastic layer that is indented by an infinite array of punches moving with a steady velocity below the Rayleigh wave speed. The layer is assumed to be loaded symmetrically about its midplane. The equations of plane elasticity are used to develop dual series equations which are reduced to a single Fredholm integral equation. An asymptotic solution to the integral equation is developed for the case when the ratio of contact length to punch spacing is small, and it is compared with a numerical solution. Numerical calculations for the effective stiffness of the layer and the stresses along the midplane are included.
Series Solutions for Beams on Elastic Foundations
Authors: Hete´nyi M.
Published: November 2010

In this paper series solutions are derived for beams on elastic foundation, subjected to a variety of end and loading conditions. These series solutions have the following advantages over the “formal” solutions of the differential equations of the corresponding problems: 1. The parameters of the beams (EI and l) and the modulus of the foundation (k) appear in these formulas in an explicit form and are not incorporated in the arguments of trigonometric and hyperbolic functions, as it is in the case of the formal solutions of the corresponding differential equations. For this reason, the series formulas are very suitable for design purposes and can also be used to obtain any desired degree of accuracy. 2. These formulas are valid for the entire lengths of the beams, irrespective of the discontinuities in the derivatives of the elastic line caused by the loadings. Solutions, for hinged-hinged beams, which reduce to the form of simple sine series, are not discussed here because they can be found in the related literature in a large variety of loading conditions.
Singularities in Acoustic Pulse Scattering by Free-Surface Obstacles With Sharp Corners
Authors: Shaw R. P.
Published: November 2010

The order of singularity in velocity at the corner of an infinite free-surface wedge of arbitrary angle struck by a plane acoustic pulse is found by means of the Kirchhoff integral form of the wave equation.
Transient Solutions of a Longitudinally Impacted Conical Shell
Authors: Mortimer R. W. , Blum A.
Published: November 2010

A thin conical shell theory, which includes the effects of transverse and rotary inertias and transverse shear deformation, is used to analyze the response of a conical shell to longitudinal impact. The governing equations of this theory are solved by the method of characteristics and the results are compared to published experimental results.
Measurement of Energy Dissipation in a Liquid-Filled, Precessing, Spherical Cavity
Authors: Vanyo J. P. , Likins P. W.
Published: November 2010

Methods are described for the experimental measurement and analytical estimation of the losses of mechanical energy in a spinning and precessing spherical cavity filled with fluid. Test results are presented and correlated with analytical estimates based on two different mathematical models of the system. The experimental apparatus is a gimbaled mechanism which constrains a rigid body with a spherical cavity to spin about an axis through the cavity center at a constant rate ψ˙, while the spin axis cones about an inertially fixed axis at a constant rate φ˙ with a constant conical half angle θ. Measurements of current required by motors which maintain the constancy of ψ˙ and φ˙ provide a measure of the energy losses in the fluid in the steady state, after suitable dry test calibrations. Experimental results are presented for a 22-cm-dia cavity containing fluids of kinematic viscosities of 1 and 20 centistokes, with θ ranging from 5–30 deg, ψ˙ ranging from 60–1000 rpm, and φ˙ ranging from −400 to +600 rpm. Analytical approximations are developed on the basis of (a) a variation of the oscillating flat-plate solution, and (b) a rigid interior sphere of fluid idealization. The rigid sphere method gives energy dissipation rates that are generally valid over most of the important range of parameters, while the oscillating surface solution is generally an order of magnitude too low in its predictions of energy dissipation.
The Turbulent Boundary Layer With Mass Transfer and Pressure Gradient
Authors: Lubard S. C. , Fernandez F. L.
Published: November 2010

An analysis of the incompressible, turbulent boundary layer, including the combined effects of mass transfer and pressure gradient is presented in this paper. An integral method employing the integral mechanical energy equation forms the basis of the analysis. Stevenson’s velocity profiles are used to obtain the functional dependence of the integral properties and also obtain a skin-friction law. A definition of an equilibrium flow with mass transfer and pressure gradient is given in order to evaluate the dissipation integral (CD) which appears in the integral mechanical energy equation. This definition requires a pressure gradient parameter similar to Clauser’s βT with a modification to include the effect of mass transfer to be held constant. An expression for CD in the case of equilibrium turbulent flows is then obtained which depends directly on this new pressure gradient parameter (βT*). In order to treat the general case of nonequilibrium flows, this expression for CD is uncoupled from βT*, through the use of a single empirical curve fit of the existing no mass transfer equilibrium flow data relating βT to the Clauser shape parameter. In addition to unhooking CD from the pressure gradient parameter, several specified variations in mass transfer rate are assumed in order to obtain an expression for CD which is not a function of the mass transfer rate derivative. The numerical results are found to be weakly dependent on which of these variations is used. Comparisons of the numerical results with a wide variety of experimental data, including cases where the blowing rate and pressure are varying simultaneously, show good agreement. In addition, several problems with discontinuities in blowing or suction are solved and seem to be in good agreement with the data.
Flexure of Symmetrically Loaded Circular Plates Including the Effect of Transverse Shear
Authors: Perakatte G. J. , Lehnhoff T. F.
Published: November 2010

Mindlin’s linear shear-deformation theory of moderately thick elastic isotropic plates is applied to axially symmetric deformations of uniform circular plates with static loads. The flexural equilibrium equations are solved for 12 specific cases of loading and boundary conditions. The solutions and numerical results are presented in nondimensional form.
Concerning a Creep Surface for an Aluminum Alloy
Authors: Findley W. N. , Lai J. S. Y. , Nolte K. G.
Published: November 2010

Following creep under combined tension and torsion for 2 hr, probes of 5-min duration were made with different sequences along (a) a Mises ellipse through the loading point, and (b) along a possible creep surface suggested by the normality concept as applied to previous experiments. The results indicate that the sequence of probing makes considerable difference and the shape of a creep surface estimated from normality is not necessarily consistent with a definition of the creep surface as a surface of constant creep rate.
The Plastic Flow of Surface Metal Layers
Authors: The´ J. H. L. , Scrutton R. F.
Published: November 2010

Various aspects of the plastic deformation of metals adjacent to the surfaces of tools or dies are discussed. The influence of thermal conduction between the thin plastic layer and the hot or cold surface of the tool or die is considered, while an approximate analysis is presented of the variation in the overall thickness of the layer at the chip-tool interface in metal cutting.
Web-Stiffened Sandwich Structures
Authors: Chen Y. N. , Ranlet D. , Kempner J.
Published: November 2010

A model representation of a web-cored sandwich structure, which is based upon the energy principles of continuum theory while retaining the discrete nature of the webs, is studied. The determination of a second-order shear modulus, which measures local bending effects, accounts for the transverse shear deformation of the core. This notion is exemplified through consideration of the flexure and buckling of a web-stiffened sandwich beam, and by comparison of the results calculated from rigid frame analysis with those based on the sandwich solution. Additionally, the technique for employing classical Bernoulli-Euler modes in the eigenfunction expansion of displacement functions is extended and applied to the problems of free vibrations of a free-free web-stiffened sandwich beam.
A Direct Method for Analyzing Accelerations in Complex Mechanisms
Authors: Chiang C. H.
Published: November 2010

Complex mechanism containing four-bar loops may be treated as simpler compound mechanisms in acceleration analysis by introducing the relative center of curvature of the relative path of a certain point on one link with respect to the opposite link. By means of a new method of acceleration analysis recently suggested by the author, together with the relative center of curvature, it is possible to analyze accelerations of complex mechanisms in a simple and direct way. Results thus obtained are obviously more accurate than those found by using the conventional acceleration diagram method.
A Note on Carter-Hall Circle
Authors: Radjagopal A. S.
Published: November 2010

This paper deals with derivation of a formula for the diameter of Carter-Hall circle corresponding to a given position of a four-link mechanism and illustrates the formula by a numerical example.
Analysis of Wave Propagation in Elastic Cylindrical Shells by the Perturbation Method
Authors: Geers T. L.
Published: November 2010

Simple perturbation solutions are given for the propagation of stress waves in an elastic cylindrical shell subjected to transient, axisymmetric, longitudinal excitations. The solutions are shown to be accurate even at rather large distances from the boundary at which the excitation is applied. Convergence of the series solutions is examined and application of the technique to related problems is discussed.
Thermally Induced Stress Waves in an Elastic Layer
Authors: Sve C. , Miklowitz J.
Published: November 2010

A solution is presented for the stress-wave response of a partially transparent infinite elastic layer subjected to electromagnetic radiation. The radiation is assumed to be deposited with a radial Gaussian distribution in a time short compared with thermal diffusion times. The development is based on the equations of uncoupled dynamic thermoelasticity with heat conduction neglected. Laplace and Hankel transform techniques provide the formal solution and numerical integration of the resulting expressions yields the time-dependent stress distributions in the layer. Several examples are included that illustrate the significance of the dynamic effects and their dependence on the radial coordinate and heating time.
An Upper Bound on the Failure Probability for Linear Structures
Authors: Koopmans L. H. , Qualls C. , Yao J. T. P.
Published: November 2010

This paper establishes a new upper bound on the failure probability of linear structures excited by an earthquake. From Drenick’s inequality max|y(t)| ≤ MN, where N2 = ∫h2, M2, = ∫x2, x(t) is a nonstationary Gaussian stochastic process representing the excitation of the earthquake, and y(t) is the stochastic response of the structure with impulse response function h(τ), we obtain an exponential bound computable in terms of the mean and variance of the energy M2. A numerical example is given.
Error Bounds in an Optimization Problem Using the Finite-Element Method
Authors: McLay R. W. , Buturla E. M.
Published: November 2010

An optimization problem involving the thermal deflections of two parallel circular disks is examined. Error bounds are developed for both the finite-element solution and the optimization problem. The relationship between the errors is illustrated in a single bound.
A Method for Obtaining Stresses and Displacements in Thick Cylindrical Shells Under Arbitrary Boundary Conditions
Authors: Golub E. B. , Romano F.
Published: November 2010

This paper presents a means for obtaining both the stress and displacement states which appear in thick, circular, cylindrical shells under arbitrary load and boundary conditions. The governing differential equations and the associated boundary conditions are obtained by utilizing Reissner’s variational principle [6], the assumed form of the stress state containing, in addition to terms corresponding to conventional membrane and bending stress resultants, supplementary sets of self-equilibrating stress resultants. Comparison of results obtained from known elasticity solutions shows that the present theory accurately yields solutions for shells with radius-thickness ratios of the order of 3.0. Numerically computed here, for comparison purposes, is the axisymmetric, periodically spaced, band load problem of Klosner and Levine.
The Stress Field Due to a Line Load Acting on a Half Space of a Power-Law Hardening Material (A Comparison Between Plane Strain and Plane Stress)
Authors: Atkinson C.
Published: November 2010

The exact solution is given for a line load acting on a half space of a power-law elastic material under conditions of plane stress. This solution is compared with the corresponding solution under plane-strain conditions; see Aruliunian [1]. A marked difference is found between the plane-stress and plane-strain fields for different values of the hardening exponent.
Application of the Hydrogen-Bubble Technique for Velocity Measurements in Thin Liquid Films
Authors: Thomas W. C. , Rice J. C.
Published: November 2010

A unique adaptation of the hydrogen-bubble flow visualization method was applied to measure velocity profiles and film thicknesses of very thin films on an inclined plane wall. Data were obtained in the three flow regions for a developing falling film with an initially uniform velocity profile and thickness ≤0.1 in. The measured profiles compared more favorably with parabolic profiles in the intermediate fully developed region than in the initial developing region. However, measured film thicknesses compared favorably with a simplified solution of the integral momentum equation based on parabolic velocity profiles. The results confirm the theoretical prediction that a relatively long distance may be required even for a thin film before nonaccelerating flow with a constant film thickness is obtained and Nusselt’s classical analysis applies. The experimental technique was shown to be a practical experimental method for obtaining data for the two-dimensional laminar flow of thin liquid films.
Free Turbulent Mixing in Axial Pressure Gradients
Authors: Hokenson G. J. , Schetz J. A.
Published: November 2010

The results of an experimental investigation of the free turbulent mixing of wakes and jets in axial pressure gradients are presented. The data include static pressure and velocity profiles and the turbulent intensity which is presented in terms of the parameter u′cL2¯(Δu)max2. It is hypothesized that the representation of the Reynolds stress by a generalized Clauser eddy viscosity model is scaled by this parameter. The experimentally observed dependence of this turbulence quantity on flow field dimensionality and the imposed pressure gradient places more stringent demands on the form of the eddy viscosity than has been shown before. However, the experimental data reveal some fortuitous behavior which aids in the specification of the spatial dependence of the turbulence parameter, leaving the scaling to be determined primarily by the initial conditions, i.e., the state of the turbulence in the near field. Substantial lateral static pressure gradients were observed in all two-dimensional cases studied. It is shown that the boundary-layer form of the viscous flow equations are inadequate in such cases, and a numerical solution of a system of equations that includes an approximate form of the lateral momentum equation provides predictions in good agreement with the data for the mean flow field.
Effect of Orthotropy on Singular Stresses for a Finite Crack
Authors: Ohyoshi T.
Published: November 2010

The diffraction of P and SV-waves by a finite crack located on a symmetric surface of orthotropy is considered. By obtaining the singular stress distributions near the crack tip and dynamic stress-intensity factors, we show the influences of orthotropy on the stress distributions with orthotropic parameters, κα and κβ, and on the stress-intensity factors for P-waves in graph. The solution is presented in the form of integral equation having the kernel of a finite integration which is derived under some restrictions among the elastic constants. The conditions are satisfied for many orthotropic solids.
On a Continuum Theory for a Laminated Medium
Authors: Drumheller D. S. , Bedford A.
Published: November 2010

An extension of the effective stiffness theory developed for elastic laminates by Sun, Achenbach, and Herrmann [1] is presented in a form suitable for the solution of dynamical processes in composite materials including determination of stresses. A derivation of displacement and stress interface boundary conditions suitable for higher-order theories is presented. The theory is illustrated with dispersion and mode shape results for two examples of steady-state wave propagation.
Spherical Shells Like Hexagons: Cylinders Prefer Diamonds—Part 1
Authors: Lange C. G. , Newell A. C.
Published: November 2010

The purpose of this paper is to describe the initial postbuckling behavior of cylindrical shells under axial compression. Our thesis is that, out of a single infinity of possible buckling configurations which all correspond to diamond-shaped patterns, the square diamond pattern dominates. We do not claim that this pattern will be seen under all circumstances; we do claim, however, that if no substantial bias is present in either the initial imperfections or initial conditions, a natural selection mechanism exists which favors the square diamond configuration. In this paper we carry out the analytic work. A multiple scale technique is used to describe both the dynamic interaction and evolution of competing diamond patterns and the propagation of spatial inhomogeneities. Stability analysis on the resulting differential equation system lends support to our stated thesis. In addition, some initial numerical studies are presented which verify our conclusions. Part 2 will be devoted to more extensive numerical experiments.
Load Transfer in Torsion of Compound Cylinders With a Cylindrical Crack
Authors: Prasad S. N. , Chatterjee S. N.
Published: November 2010

A general formulation is given for the problem of torsion of a cylinder embedded in another cylinder in the presence of a cylindrical crack at the interface. The present formulation leads to a coupled pair of dual relations involving trigonometric series. By an extension of certain methods of solving dual series equations an integral equation is obtained which in general is singular. Stress singularities near the crack tip and at the juncture when there is no crack are discussed. Based upon a numerical solution of the integral equation, stress-intensity factor, torque, and several other quantities of interest are obtained for the homogeneous case when the radius of the outer cylinder is infinitely large.
Methods for Automated Dynamic Analysis of Discrete Mechanical Systems
Authors: Bayazitoglu Y. O. , Chace M. A.
Published: November 2010

The equations of motion for any discrete, lower pair mechanical system can be obtained by analyzing a branched, three-dimensional compound pendulum of indefinite length. In this paper, a set of expressions which provides the equations of motion of arbitrary mechanical dynamic systems directly as ordinary differential equations are presented. These expressions and the associated technique is applicable to linear and nonlinear unconstrained dynamic systems, kinematic systems and multidegree-of-freedom constrained systems.
Vibration of Plates Subject to Arbitrary In-Plane Loads—A Perturbation Approach
Authors: Bassily S. F. , Dickinson S. M.
Published: November 2010

Perturbation theory is used to obtain the natural frequencies and mode shapes of lateral vibration of rectangular plates under arbitrary in-plane loading in terms of a power series in a loading parameter, commencing from known approximate or “exact” solutions of the same plate under no in-plane loading. The range of loading over which the solution is applicable is shown to be extendible to practically any limit by the introduction of a stepwise perturbation technique. Numerical results demonstrating the applicability and accuracy of the analysis are presented for plates subject to uniform, linear, and parabolic in-plane stress distributions. Simple approximate frequency expressions are also given.
An Integral Equation Approach to the Semi-Infinite Strip Problem
Authors: Gupta G. D.
Published: November 2010

A semi-infinite strip held rigidly on its short end is considered. Loads in the strip at infinity (far away from the fixed end) are prescribed. Integral transform technique is used to provide an exact formulation of the problem in terms of a singular integral equation. Stress singularity at the strip corner is obtained from the singular integral equation which is then solved numerically. Stresses along the rigid end are determined and the effect of the material properties on the stress-intensity factor is presented. The method can also be applied to the problem of a laminate composite with a flat inclusion normal to the interfaces.
Stability of an Annular Plate Reinforced With a Surrounding Edge Beam
Authors: Phillips J. S. , Carney J. F.
Published: November 2010

In this paper, the buckling load for a radially compressed annular plate surrounded on its outer edge with an edge beam is determined. A uniform, ring-type load is applied to the edge beam along its entire length, and the inner edge of the annular plate is free from tractions. In the solution to this problem, all possible buckled shapes are considered to obtain the critical buckling load. Use of an edge beam provides a practical way to vary the fixity condition at the plate’s outer edge.
A First and Second-Order Theory on a Supercavitating Hydrofoil With a Jet Flap
Authors: Kida T. , Miyai Y.
Published: November 2010

The basic relations for an infinite steady flow around a thin hydrofoil with a jet flap are obtained as the solution of the Riemann-Hilbert-Poincare problem, and the first and second-order problem at small incidence and small deflection angle of the jet is analytically solved by means of the matched asymptotic expansions in the case of the jet-momentum coefficient small. Expressions for lift, drag, pitching-moment, and the cavity shape have been obtained as the asymptotic expansions in powers of the jet-momentum coefficient together with its logarithm. From the comparison of the lift with numerical results of Ho, the analytical method in this paper is seen to be very useful and reasonable.
The Effect of Radial Inertia on Combined Plastic Stress Wave Propagation in Thin-Walled Tubes
Authors: Myers C. D. , Eisenberg M. A.
Published: November 2010

This investigation is concerned with the analysis of combined longitudinal and torsional inelastic stress wave propagation in thin-walled tubes. The effects of radial inertia are included in the development of the governing hyperbolic differential equations which are solved by the method of characteristics. Numerical results are presented for combined stress wave propagation in statically preloaded tubes of material assumed to be described by rate-independent plasticity. The effects of finite rise time of the imposed dynamic load and of radial inertia are analyzed in detail.
Analysis of Twisting Stiffness for a Multifiber Composite Layer
Authors: Bert C. W. , Chang S.
Published: November 2010

The twisting stiffness of a rectangular cross section consisting of a single row of solid circular cross-section fibers embedded in a matrix is analyzed. The problem is formulated as a Dirichlet torsion problem of a multielement region and solved by the boundary-point least-squares method. Numerical results for a single-fiber square cross section compare favorably with previous relaxation-method results. New numerical results for three and five-fiber composites suggest that the torsional rigidity of a multifiber composite can be approximated from the torsional rigidities of single and three-fiber models.
Stresses in a Transversely Isotropic Half Space Having a Spherical Cavity
Authors: Atsumi A. , Itou S.
Published: November 2010

In this paper, a solution is given for the stresses and displacements around a spherical cavity in a transversely isotropic homogeneous elastic half space under all-around tension. The traction-free boundary conditions on the faces of the plane and on the cavity are satisfied with the aid of Hankel transforms and the Schmidt method, respectively. Numerical calculations are carried out for some practical materials.
Dispersion of Torsional Waves in Uniform Elastic Rods
Authors: Engstro¨m O. L.
Published: November 2010

Approximate equations of motion are derived by use of Hamilton’s variational principle. The warping function, which is part of the solution, depends on wavelength. Numerical results on dispersion for rectangular cross sections have been obtained by the finite-element method. A comparison with the experimentally verified Barr theory is given. The paper is a contribution to the low-order approximate theories of torsional waves. It shows how good the Saint Venant warping function assumption in the low-order theory is at long relative wavelengths and it provides a modification of the theory for use at shorter wavelengths.
Measurement of Surface-Displacements Normal to Line of Sight by Holo-Moire´ Interferometry
Authors: Hung Y. Y. , Taylor C. E.
Published: November 2010

This paper describes a new technique called “Holo-moire´ interferometry” which combines the moire´ and holographic techniques so that full-field measurement of the displacements normal to the line of sight is achieved. The method is particularly useful in measuring in-plane displacements; a type of measurement for which the conventional moire´ technique is too insensitive, and for which holographic interferometry requires pointwise separation of displacement components from a multiple-hologram scheme. Holo-moire´ interferometry overcomes the major limitations of both. An example which compares experimental with analytical predictions is presented. The limitations of the scheme are discussed.
Transient Vibration Experiments for Determination of Properties for Viscoelastic Structures
Authors: Forrestal M. J. , Sagartz M. J.
Published: November 2010

Two experimental techniques devised to determine the mechanical properties for viscoelastic structures are demonstrated with experiments on polymethyl methacrylate (PMMA). Circular rings are loaded with an axisymmetric impulse which excites the fundamental membrane mode and free-free beams are loaded with a spatially distributed impulse which excites the fundamental bending mode. Because only one mode of vibration is excited, these structures can be regarded as single-degree-of-freedom systems in free vibration. Loading is produced by magnetic pressure pulses and the response is measured with strain gages. The complex modulus is obtained from period of vibration and logarithmic decrement of the strain response. Geometry of the specimens is varied to obtain complex moduli over a wide range of frequencies.
Influence of the Viscosity on the Growth of Cavitation Bubbles
Authors: Persson B.
Published: November 2010

Numerical calculations have been carried out to investigate the influence of viscosity on the maximum attainable radius for a bubble exposed to a transient pressure pulse. Three types of pulses are considered, a step pulse, a triangular pulse, and a sine pulse. By using a suitable definition of a nondimensional viscosity parameter, it is found that the results for the triangular and the sine pulses can be determined from data for the step pulse.
The Motion of Aircraft Trailing Vortices
Authors: Maxworthy T.
Published: November 2010

We use our new knowledge of the motion of turbulent vortex rings [1] to speculate upon the dynamical characteristics of the trailing vortex pair which forms the wake of a lifting surface. We present an interpretation of common observations which suggests that the gross features of the two systems are similar, at least before the aircraft wake distorts due, among other things, to a self-induced instability. The theory presented in [1] is extended to the two-dimensional case and predictions of the shape of aircraft trails are displayed in nondimensional form. As a special case we present a preliminary prediction for the wake shape of a 747, in cruise condition, for a set of parameters that are only approximately correct. Only comparison with actual observations can further refine these guesses. Unfortunately the required observations are not available for any aircraft type. However, the present work suggests a program of measurements which would help in narrowing the possible parameter range. Comments on the motion of vortex rings and vortex pairs in a stratified atmosphere complete the presentation.
An Axisymmetric Separated and Reattached Flow on a Longitudinal Blunt Circular Cylinder
Authors: Ota T.
Published: November 2010

Low-speed experiments are made for an axisymmetric separated, reattached, and redeveloped flow over a longitudinal circular cylinder with blunt leading edge. The flow characteristics such as the reattachment length and the flow pattern in the separated region are measured. The redevelopment of the flow downstream of reattachment is also investigated through various experimental results.
Finite Elasticity Analysis of Unanesthetized and Anesthetized Aorta
Authors: Ayorinde O. A. , Kobayashi A. S. , Merati J. K.
Published: November 2010

A combined experimental-theoretical technique was developed to determine the elastic properties of in-vitro canine aorta with and without the influence of a clinical anesthetic, i.e., Halothane. The results of four canine aortas of unknown ages show that the aortic tissue was dilated and became more compliant in the presence of Halothane. Also the axial force on an aorta tethered at its in-situ length was significantly reduced by the anesthetics.
Reflection and Transmission of Elastic-Plastic Spherical Waves at a Spherical Interface
Authors: Srinivasan M. G.
Published: November 2010

When a spherical wave is incident on a spherical interface of two different elastic-plastic, rate-independent materials, which of the many different admissible cases of reflection and transmission will actually occur must be determined in order to extend any numerical solution for subsequent times. An analytical method for this determination in terms of the known solution for times just prior to the incidence of the wave is outlined. The wave considered may be either an acceleration wave or a shock wave. The discontinuity conditions across the wave fronts and the continuity of displacement at the interface form the basis of this method and examples are given for illustration.
Vibration Frequencies for a Uniform Beam With One End Elastically Supported and Carrying a Mass at the Other End
Authors: Grant D. A.
Published: November 2010

In this paper the author obtains the frequency equation for the normal modes of vibration of uniform beams with linear translational and rotational springs at one end and having a concentrated mass at the other free end. The eigenfrequencies for the fundamental mode are given for a wide range of values of mass ratio, mass moment of inertia ratios, and stiffness ratios.
The Influence of Constitutive Relationships on Stress-Redistribution Times in Creeping Structures
Authors: Williams J. J.
Published: November 2010

The influence of related constitutive equations upon the stress-redistribution times for a simple two-bar structure is such that the time-hardening model is unlikely to provide reliable estimates of the stress-redistribution time for structures composed of a wider class of materials.