bluuebunny/crossref_metadata_2025 huggingface dataset:
Nestedness and β‐diversity in ectoparasite assemblages of small mammalian hosts: effects of parasite affinity, host biology and scale
Authors: Krasnov Boris R. , Stanko Michal , Khokhlova Irina S. , Shenbrot Georgy I. , Morand Serge , Korallo‐Vinarskaya Natalia P. , Vinarski Maxim. V.
Published: November 2010

We asked whether (a) variation in species composition of parasite assemblages on the same host species follows a non‐random pattern and (b) if so, manifestation of this non‐randomness across space and time differs among parasites, hosts and scales. We assessed nestedness and its contribution to β‐diversity of fleas and gamasid mite assemblages exploiting small mammals across three scales: (a) within the same region across different locations; (b) within the same location across different times and (c) across distinct geographic regions. We estimated (a) the degree of nestedness (NCOL) and (b) the proportional contribution of nestedness to the total amount of β‐diversity across locations, times and regions (βNESP). In the majority of host species, parasite assemblages were nested significantly across all three scales. In mites, but not fleas, NCOL correlated with the contribution of nestedness to the total amount of β‐diversity. In fleas, NCOL did not differ among assemblages at the two local scales, but was significantly lower at regional scale. In mites, NCOL was the highest in assemblages at local spatial scale. βNESP was significantly higher (a) in flea than in mite assemblages at both local scales and (b) in mite than in flea assemblages at regional scale. In fleas, βNESP was higher at both local scales, whereas in mites it was higher at both local temporal and regional scales. Sheltering habits and geographic range of a host species did not affect either NCOL or βNESP in flea assemblages, but both metrics significantly decreased with an increase of geographic range of a host species in mite assemblages. We conclude that flea and mite assemblages across host populations at smaller and larger spatial scales and at temporal scale were characterized by nestedness which, in turn, contributed to an important degree to the total amount of β‐diversity of these assemblages.
Who's the Boss? Patterns of Control in Adolescents' Sibling Relationships
Authors: Tucker Corinna Jenkins , Updegraff Kim , Baril Megan E.
Published: November 2010

The goals of this study were to examine longitudinal changes in perceived control in adolescents' sibling relationships and to describe the nature and correlates of three distinct control patterns: firstborn dominant, equal, and secondborn dominant. Firstborn and secondborn adolescents in 184 predominately European‐American families participated in home interviews and a series of phone interviews as part of a longitudinal a study of family relationships and adolescent development. Findings revealed changes in control over 3 years as well as sibling differences. In addition, different patterns of control were linked to qualities of the sibling relationship and to adolescent adjustment. The different roles that firstborn and secondborn siblings assume and why these roles are linked to relationship experiences and adjustment are discussed.
The Characteristics and Well‐Being of Adopted Stepchildren
Authors: Stewart Susan D.
Published: November 2010

This study draws upon 22,680 children from the 2002 National Survey of America's Families to investigate the demographic and family characteristics and well‐being of stepchildren who have been adopted by a stepparent (n = 140) relative to children with 2 biological parents, children with 2 adoptive parents, and children with 1 biological parent and 1 nonadoptive stepparent. Five percent of all stepchildren and one quarter of all adopted children have been adopted by a stepparent. How the characteristics of adopted stepchildren compare to those of other children depends on the child's age—whereas younger adopted stepchildren are most similar to children with 2 biological parents, older adopted stepchildren are most similar to nonadopted stepchildren. Adopted stepchildren of all ages have significantly more behavior and emotional problems than children with 2 biological parents, but have similar levels of school engagement. There were no significant differences between children with 2 adoptive parents, nonadopted stepchildren, and adopted stepchildren on any measure of well‐being regardless of the child's age. Implications for practice and policy include increasing awareness of adopted stepchildren and paying greater attention to the legal context under which stepchildren are adopted.
The Female Genital Self-Image Scale (FGSIS): Results from a Nationally Representative Probability Sample of Women in the United States
Authors: Herbenick Debra , Schick Vanessa , Reece Michael , Sanders Stephanie , Dodge Brian , Fortenberry J. Dennis
Published: November 2010

Introduction

Over the past two decades, an expanding body of research has examined women’s and men’s genital self-image. Support for the reliability and validity of the 7-item Female Genital Self-Image Scale (FGSIS) has been found in a convenience sample of women.

Aims

The purpose of this study was to assess the reliability and validity of the FGSIS, its model of fit, and its association with women’s scores on the Female Sexual Function Index (FSFI) in a nationally representative probability sample of women in the United States ages 18 to 60. A second purpose was to assess the temporal stability of the scale in a subset of this sample.

Methods

A nationally representative sample of 3,800 women ages 18 to 60 were invited to participate in a cross-sectional Internet-based survey; 2,056 (54.1%) participated.

Main Outcome Measures

Demographic items (e.g., age, race/ethnicity, marital status, sexual orientation, geographic region), having had a gynecological examination in the past year, having performed a genital self-examination in the past month, frequency of masturbation in the past month, vibrator use in the past month, the FGSIS, and the FSFI.

Results

An abbreviated 4-item version of the scale, the FGSIS-4, was a better fit to the data than the original 7-item scale. Women’s scores on the FGSIS-4 were significantly related to vibrator use, frequency of masturbation, having had a gynecological exam in the past year, having performed genital self examination in the past month, and all FSFI subscales.

Conclusion

Most of the participants felt generally positively about their genitals and female genital self-image was significantly related to female sexual function, women’s sexual behavior and their sexual and genital healthcare behaviors. In addition, the FGSIS-4 has evidence of reliability, validity, and temporal stability in a nationally representative probability sample of women in the United States.
A rhodanese‐like protein is highly overrepresented in the mutant S. clavuligerus oppA2::aph: effect on holomycin and other secondary metabolites production
Authors: Nárdiz Nuria , Santamarta Irene , Lorenzana Luis M. , Martín Juan F. , Liras Paloma
Published: November 2010

A protein highly overrepresented in the proteome of Streptomyces clavuligerus oppA2::aph was characterized by MS/MS as a rhodanese‐like enzyme. The rhlA gene, encoding this protein, was deleted from strains S. clavuligerus ATCC 27064 and S. clavuligerus oppA2::aph to characterized the RhlA enzyme activity, growth on different sulfur sources and antibiotic production by the mutants. Whereas total thiosulfate sulfurtransferase activity in cell extracts was not affected by the rhlA deletion, growth, cephamycin C and clavulanic acid production were impaired in the rhlA mutants. Holomycin production was drastically reduced (66–90%) in the rhlA mutants even when using S. clavuligerusΔrhlA pregrown cells, suggesting that this enzyme might be involved in the formation of the cysteine precursor for this sulfur‐containing antibiotic. While growth on thiosulfate as the sole sulfur source was particularly low the volumetric and specific antibiotic production of the three antibiotics increased in all the strains in the presence of thiosulfate. This stimulatory effect of thiosulfate on antibiotic production was confirmed by addition of thiosulfate to pre‐grown cells and appears to be a general effect of thiosulfate on oxidative stress as was also evident in the production of staurosporin by S. clavuligerus.
Self-Reported Comorbidity Affects Health-Related Quality of Life and Perception of Shoulder Function in Patients with Rotator Cuff Disease
Authors: Wolf Brian R. , Britton Carla L. , Gao Yubo , Johnston Richard C.
Published: November 2010

Background

The present study aimed to describe the comorbidity burden of a rotator cuff disease cohort and to examine the effects of patient comorbidities on general health and shoulder-specific outcome measures.

Methods

A retrospective cohort of patients with rotator cuff disease was identified using the coding of the International Classification of Diseases, Ninth Revision, Clinical Modification. Demographic variables and numbers of systemic and musculoskeletal comorbid conditions were collected. General health and shoulder-specific tools were used to assess disability. Analyses using regression, correlation and analysis of variance were performed to assess the impact of comorbidity upon outcome measures.

Results

Three hundred and seventy-three patients with rotator cuff disease were identified. Two-thirds of the group reported at least one systemic comorbidity. Non-shoulder musculoskeletal comorbidities were reported by 80% of the cohort. Women reported a significantly greater number of comorbid conditions than men ( p < 0.02). Baseline health-related quality of life and self-reported shoulder function were impacted significantly by comorbidity when controlling for patient demographic characteristics.

Discussion

Comorbidities are common in this population and significantly affect health-related quality of life and self-reported shoulder pain and disability in patients presenting with rotator cuff-related symptoms. Comorbidities should be considered when shoulder disability measures are utilized in clinical practice and when studying outcomes.
Effect of silicon on trace element partitioning in iron‐bearing metallic melts
Authors: CHABOT Nancy L. , SAFKO Trevor M. , McDONOUGH William F.
Published: November 2010

Abstract– Despite the fact that Si is considered a potentially important metalloid in planetary systems, little is known about the effect of Si in metallic melts on trace element partitioning behavior. Previous studies have established the effects of S, C, and P, nonmetals, through solid metal/liquid metal experiments in the corresponding Fe binary systems, but the Fe‐Si system is not appropriate for similar experiments because of the high solubility of Si in solid metal. In this work, we present the results from 0.1 MPa experiments with two coexisting immiscible metallic liquids in the Fe‐S‐Si system. By leveraging the extensive available knowledge about the effect of S on trace element partitioning behavior, we explore the effect of Si. Results for 22 trace elements are presented. Strong Si avoidance behavior is demonstrated by As, Au, Ga, Ge, Sb, Sn, and Zn. Iridium, Os, Pt, Re, Ru, and W exhibit weak Si avoidance tendencies. Silicon appears to have no significant effect on the partitioning behaviors of Ag, Co, Cu, Cr, Ni, Pd, and V, all of which had similar partition coefficients over a wide range of Si liquid concentrations from Si‐free to 13 wt%. The only elements in our experiments to show evidence of a potentially weak attraction to Si were Mo and Rh. Applications of the newly determined effects of Si to problems in planetary science indicate that (1) The elements Ni, Co, Mo, and W, which are commonly used in planetary differentiation models, are minimally affected by the presence of Si in the metal, especially in comparison to other effects such as from oxygen fugacity. 2) Reduced enstatite‐rich meteorites may record a chemical signature due to Si in the metallic melts during partial melting, and if so, elements identified by this study as having strong Si avoidance may offer unique insight into unraveling the history of these meteorites.
On the Stability Analysis of Imperfect Spherical Shells
Authors: Kalnins A. , Biricikoglu V.
Published: November 2010

A procedure is given for the analysis of axisymmetrically imperfect spherical shells which is not limited by the magnitude of the imperfections. The geometric parameters of the imperfect shell are expressed in terms of those of the perfect shell and known imperfection distribution, and the imperfect shell is solved directly by means of a nonlinear theory. As an application of the proposed procedure, the critical pressures for an axisymmetrically imperfect complete spherical shell are calculated. The results are compared with those predicted by Koiter’s general theory of initial postbuckling behavior, and their asymptotic character is verified.
The Application of Energy Theorems to Bodies Which Creep in the Plastic Range
Authors: Ponter A. R. S. , Leckie F. A.
Published: November 2010

In a previous paper [4] displacement and deformation bounds were derived for a body composed of a creeping/plastic material. In this paper, plastic limit state solutions are used in conjunction with these theorems to compute displacement and deformation bounds for some simple redundant structures. In this way, plastic design calculations may be used directly to estimate creep deformations.
Dynamic Behavior of Metals Under Tensile Impact—Part 1: Elevated Temperature Tests
Authors: Schultz A. B.
Published: November 2010

The mechanical behavior of metals subjected to uniaxial tensile impact at elevated temperatures is reported. Tests were conducted on annealed 1100 aluminum at 200, 350, 550, and 800 deg F; annealed 2024 aluminum at 200, 450, and 600 deg; and annealed C1010 steel at 430, 700, 1050, and 1400 deg F. The materials exhibit a wide range of dynamic behavior, including some in which the stress required to produce a given level of strain is significantly lowered by dynamic loading. The ratios of the dynamic ultimate stresses to the static are found to range from 0.71–6.0.
The Hydroelastic Stability of a Flat Plate
Authors: Weaver D. S. , Unny T. E.
Published: November 2010

This paper examines the hydroelastic stability of a flat plate, one side of which is exposed to a high velocity flow of a heavy fluid such as water. The plate is found to become unstable statically at first, but flutter is predicted for higher velocities.
Natural Convection Above Fires—An Analytical Solution
Authors: Varma R. K. , Murgai M. P.
Published: November 2010

In this paper an analytical solution of the problem of turbulent buoyant plume, in a dry and calm atmosphere with an arbitrary lapse rate variation, is attempted. The results are compared with those given in an earlier publication based on the solution obtained by a Pace analog computer.
An Energy Approach to the Dynamic Stability of Arches
Authors: Cheung M. C. , Babcock C. D.
Published: November 2010

Concentrated static and step loading were applied to circular arches with geometric parameters 7 < γ < 20. The static equilibrium path and the dynamic response at the loading position were recorded. Dynamic buckling is distinct. Supercritical and subcritical response were separated by 0.5 percent of the total load. The sensitivity of the arch to off set loading was studied. The effect was pronounced in the static tests but moderate in the dynamic case. An energy approach was used to determine the lower, and upper bound for the critical step load. The lower bound agrees well with the experimental results.
Stress Analysis for a Nonlinear Viscoelastic Compressible Cylinder
Authors: Ting E. C.
Published: November 2010

Real solids are not incompressible, although many viscoelastic materials which undergo large deformations show only small changes in volume under ordinary loading conditions. This paper is concerned with a pressurized isotropic viscoelastic hollow cylinder bonded to an elastic casing in which, during a finite deformation, the dilatational change in any element of the cylinder is a small quantity. The analysis is based in part upon the theory of small deformations superposed on finite deformations. Numerical calculations are evaluated by using finite-difference techniques and assuming particular forms of kernel functions in the stress-strain relation. The results for compressible and incompressible materials are compared.
Numerical Analysis of Creep of an Indeterminate Composite Beam
Authors: Bazˇant Z. P.
Published: November 2010

Approximating the hereditary integrals by finite sums, a creep problem may be reduced to a succession of elasticity problems with initial strains. It is shown how the well-known general relationship between initial strains and equivalent loads may be applied to a composite beam on statically indeterminate supports. A highly accurate numerical method for memory-type creep problems is demonstrated and its convergence studied by means of examples.
Coupler Cognate of Geared Five-Link Mechanism
Authors: Soni A. H. , Pamidi P. R.
Published: November 2010

Using Cayley’s construction of parallelograms and similar triangles, the existence of the coupler cognate of the geared five-link mechanism is established for the general case in which the coupler point is arbitrarily located in the plane of one of the coupler links. The Cayley diagram for the geared five-link mechanism is proposed. Its extension leads to the coupler cognates of plane, single-loop, geared, multilink mechanisms.
Peristaltic Transport in a Circular Cylindrical Pipe
Authors: Chow T. S.
Published: November 2010

The flow of an incompressible viscous fluid through a circular pipe is studied for the case of an axisymmetric wave traveling along the wall when the initial motion is assumed to be a Hagen-Poiseuille flow. The solution is represented by a power series expansion to the second order of amplitude-to-radius ratio, ε2, which is assumed to be much less than unity. Two domains of the flow, with convective term not negligible compared to the viscous term, are of main concern. The first is the case of low Reynolds number (R = wave speed × radius/kinematic viscosity). The second is for small radius-to-wave-amplitude ratio (α = 2π radius/wavelength). Analytical calculations are carried out to the second order of R and α, respectively. The result obtained indicates that the series expansion in powers of α is applicable up to R-values of order 10.
Pressure Boundary Layer in a Transient or Steady Gas Film and Mass Interaction
Authors: Hsing F. C. , Cheng H. S.
Published: November 2010

This paper presents a numerical scheme capable of yielding accurate pressure profile for the transient and steady hydrodynamic gas film generated by high-speed relative motion of two nonparallel surfaces. The numerical difficulties associated with high compressibility numbers for the gas film Reynolds equation were overcome by employing a set of systematically generated irregular grid spacings based on a coordinate transformation. By coupling the fluid-film solution with the equations of motion of a tilting pad, the dynamics of the mass film interaction were treated. Results are presented for both steady-state and dynamical solutions. Static solutions for a 120-deg partial-arc gas bearing have been used for comparison.
Behavior of a Steep Prestressed Arch Made From a Buckled Strut
Authors: Huddleston J. V.
Published: November 2010

The buckling and snap-through behavior of a steep prestressed arch (or shell) obtained by first buckling a thin elastic strut (or plate) into a deformed shape and then attaching it to its supports is studied by solving a set of nonlinear boundary-value problems on a digital computer. Finite displacements of the arch as produced by vertical concentrated load and uniform load are determined for several cases, including both symmetric and unsymmetric modes of buckling. Bifurcation points that give the snap-through load are located in each case. Comparisons are made with the behavior of conventional steep arches and between the theoretical results and experimental data obtained from model tests.
Distribution of Mass, Velocity, and Intensity of Turbulence in a Two-Phase Turbulent Jet
Authors: Hetsroni G. , Sokolov M.
Published: November 2010

The effect of small liquid droplets on the flow structure of an axially symmetrical turbulent air jet was studied. The flux of the droplets was measured and correlated by a normal-distribution curve with a spreading coefficient of 0.05. Distributions of time-average and fluctuating longitudinal velocities were measured and correlated. In general the two-phase jet is narrower than the single-phase one, with smaller normalized velocity fluctuations. Studies of the spectra and probability density functions indicated that the discontinuous phase causes suppression of turbulence in the dissipation range, namely at high wave numbers. This effect is proportional to the droplets’ concentration in the investigated range.
Two Edge-Bonded Elastic Wedges of Different Materials and Wedge Angles Under Surface Tractions
Authors: Bogy D. B.
Published: November 2010

The elastostatic problem of two materially dissimilar wedges of arbitrary angles that are bonded together along a common edge and subjected to surface tractions on the boundary of the configuration is treated. Emphasis is placed on the investigation of the dependence of the order of the singularity in the stress field at the apex on the wedge angles and material constants. Numerical results for several special wedge geometries are included for all physically relevant material combinations. In particular the families of (a) equal angle wedges, (b) composite half planes, (c) composite full-planes, as well as the single geometry of a (d) half-plane bonded to a quarter-plane, are studied in detail.
Laminated Transversely Isotropic Cylindrical Shells
Authors: Zukas J. A. , Vinson J. R.
Published: November 2010

A theory for the analysis of stresses in laminated circular cylindrical shells subjected to arbitrary axisymmetric mechanical and thermal loadings has been developed. This theory, specifically for use with pyrolytic-graphite-type materials, differs from the classical thin shell theory in that it includes the effects of transverse shear deformation and transverse isotropy, as well as thermal expansion through the shell thickness. Solutions in several forms are developed for the governing equations. The form taken by the solution function is governed by geometric considerations. A range in which the various solution forms occur was determined numerically. As a sample problem, the slow cooling of pyrolytic graphite deposited onto a commercial graphite mandrel was considered. Investigation of normal and shear stress behavior at the pyrolytic graphite-mandrel interface showed that these stresses decrease in magnitude with increasing E/Gc ratio and increasing deposit to mandrel thickness (ha/hb) ratio. This implies that a thin mandrel and a material weak in shear are desirable to minimize the possibilities of flaking and delamination of the pyrolytic graphite.
An Improved Numerical Calculation Technique for Large Elastic-Plastic Transient Deformations of Thin Shells: Part 1—Background and Theoretical Formulation
Authors: Morino L. , Leech J. W. , Witmer E. A.
Published: November 2010

Recent improvements are reported in both the theoretical formulation and in the finite-difference treatment of the relations governing the large-deflection elastic-plastic dynamic responses of thin shells of arbitrary shape to transient loading.
Free Vibrations of a Linear Structure With Arbitrary Support Conditions
Authors: Dowell E. H.
Published: November 2010

A method for the analysis of the free vibrations of a linear structure supported in an arbitrary way is presented based upon the use of the normal modes of the unsupported or unconstrained structure in a Rayleigh-Ritz analysis with the support or constraint conditions enforced by means of Lagrange multipliers. The advantages of such a procedure over more conventional methods are discussed.
Plane Deformations of Incompressible Fiber-Reinforced Materials
Authors: Pipkin A. C. , Rogers T. G.
Published: November 2010

A continuum theory of finite, plane deformations of composites consisting of materials reinforced by strong fibers is discussed. The composite is assumed to be incompressible, and the fibers are treated as inextensible and continuously distributed. The analysis is not restricted to any particular material behavior such as elasticity, plasticity, or visco-elasticity. Plane deformations are kinematically determinate, in that the deformation can be found by using the constraint conditions and suitable displacement boundary conditions. The reactions to the constraints produce stress equilibrium in any kinematically admissible deformation. The theory admits stress singularities of an unusual kind: a single fiber or normal line can carry a finite load. Simple examples illustrating this and other points of the theory are given.
Complex Envelopes for Oscillations in Slightly Nonlinear Systems
Authors: Pierce W. H.
Published: November 2010

A complex envelope f(t) is used to replace the traditional sine and cosine envelopes of the response of a sinusoidally forced, slightly nonlinear system, so that the response is y(t) = Re [f(t)ejw0t]. By setting Im [f(t)ejw0t] equal to the Hilbert transform of y(t), simple equations for the derivative of f(t) are easily obtained by the method of averaging. The approximations implicit in the method of averaging are shown to introduce broad-band filtering, whose effects can be eliminated by use of all harmonics. An example of an off-center rotary load shaken by a general elliptical motion shows how resonant modes of the device’s mount can be selectively energized at different frequencies, provided the modes have high Q and adequate separation of resonant frequency.
On the First Excursion Probability in Stationary Narrow-Band Random Vibration
Authors: Yang J.-N. , Shinozuka M.
Published: November 2010

Dealing with a stationary narrow-band Gaussian process X(t) with mean zero, this paper derives a number of approximate solutions on the basis of the point-process approach. In particular, upper and lower bounds sharper than those presently available are established, an approximation based on the Markov point process is obtained, and the clump size approach is also used for approximation. These approximations are checked with the result of the semisimulation performed by Crandall, et al. [11]. Some remarks are also made on the use of the principle of maximum entropy.
Nonstationary Quasi-Static Thermal Displacements and Thermal Stresses in a Cylindrical Body of Finite Height Subject to Convective Heat Losses
Authors: Karlekar B. V.
Published: November 2010

The quasi-static thermoelastic differential equations for a cylindrical body of finite height, subject to convective heat losses from all the three faces, have been solved analytically assuming that the film coefficients for the three faces are different. Expressions for displacements and stresses are obtained in the dimensionless form and curves showing dimensionless displacements and stresses are presented.
A Plasticity Model for Cyclic Strain Accumulation
Authors: Mulcahy T. M.
Published: November 2010

A general plasticity model is developed which is able to predict a cyclic strain accumulation phenomenon, sometimes called cyclic creep. To assess the consequences of the phenomenon for nonhomogeneous stress states, simple forms of the model are used in the analysis of two idealized structural elements. Very large stresses are found to develop for continued load cycling.
A Minimum Principle for the Law of Dry Friction—Part 2: Application to Nonsteadily Rolling Elastic Cylinders
Authors: Kalker J. J.
Published: November 2010

A minimum principle for the law of dry friction was established in Part 1 of this paper. Here, in Part 2, the principle is applied to the nonsteady contact problem in which the traction evolves under the influence of a gross motion and loading program, and the principle appears to lead to a time sequence of linear programming problems. Such contact problems under several restrictions have been treated before by Kalker [3–5] without the aid of minimization techniques. In the present paper these restrictions are all removed. Numerical results are presented.
Application of Ritz’s Method to Thin Elastic Shell Analysis
Authors: Dupuis G.
Published: November 2010

This paper is concerned with finite-element analysis of thin elastic shells described by the Koiter-Sanders mathematical model. The middle surface of the shell is decomposed into curved finite triangular elements, which are mapped onto straight triangles in the plane of parameters of the surface. We show that with an appropriate approximation of the given surface, rigid-body motions may be represented exactly. Nine degrees of freedom are associated with each nodal point (the vertices of the elements) and the displacement functions fulfill the conditions of regularity required by Ritz’s method and assure convergence in energy. The derivation is quite general with respect to the geometry of the shell. A cylindrical shell analysis is presented as an illustrative numerical example.
Stress-Intensity Factors for a Surface Crack in a Finite Solid
Authors: Thresher R. W. , Smith F. W.
Published: November 2010

A solution to the problem of a circular crack partially embedded in a solid of finite thickness is presented. A superposition and iteration technique is used to determine the stress-intensity factor numerically. The stress-intensity factor is determined as a function of position around the crack front for a variety of crack depths. The results of this study are compared with experimental data for a semielliptical surface flaw in a brittle material.
Bounds on Motions of Some Lumped and Continuous Dynamic Systems
Authors: Plaut R. H. , Infante E. F.
Published: November 2010

Lumped and continuous systems subjected to general dynamic loads or perturbations are considered. The motions of these systems are assumed to be described by ordinary or partial differential equations with time-varying forcing terms. Upper bounds on the motions are derived with a Liapunov type of approach. The results are applied to some structural dynamics problems. Displacement bounds are determined for elastic columns, plates, and arches, and sufficient conditions for stability of arches against dynamic “snap-through” are obtained.
The Merit of Different Error Minimization Criteria in Approximate Analysis
Authors: Iwan W. D. , Patula E. J.
Published: November 2010

The generation of approximate periodic solutions for certain ordinary nonlinear differential equations is considered. Three different minimization criteria are discussed within the context of a generalized equivalent equation type of analysis. The three minimization criteria are mean square, mean modulus, and extreme modulus minimization. Examples are used to investigate the relative merit of these minimization criteria.
Some Classical Elastic Sphere Problems Solved Numerically by Integral Equations
Authors: Cruse Thomas A.
Published: November 2010

Use is made of the boundary-integral equation to obtain numerical comparison to a family of classical problems. The numerical procedure replaces the actual surface by flat segments and numerically calculates all unknown boundary data. The entirety of boundary data is queried for the internal stresses. Excellent agreement is found between numerical and exact results.
Fracture of Lucite Cones by Shock Waves
Authors: Sharpe W. N.
Published: November 2010

A compressive pulse applied to the base of a cone develops a tensile tail as it propagates toward the cone apex. This tension can cause fracture of the cone perpendicular to the cone axis before the leading edge of the pulse reaches the tip. It is shown that the elementary one-dimensional wave-propagation theory for cones and a time-independent critical tensile stress fracture criterion adequately describe the fracture of lucite cones subjected to narrow rectangular compressive pulses between 1 and 7 kilobars in magnitude.
Impulsive Parametric Excitation: Theory
Authors: Hsu C. S.
Published: November 2010

Given in this paper is the development of a theory for dynamical systems subjected to periodic impulsive parametric excitations. By periodic impulsive parametric excitation we mean those excitations representable by periodic coefficients which consist of sequences of Dirac delta functions. It turns out that for this class of periodic systems the stability analysis can be carried out in a remarkably simple and general manner without approximation. In the paper, after giving the general theory, many special cases are examined. In many instances simple and closed-form analytic stability criteria can be easily established.
The Generation of Stress Pulses at the Junction of Two Noncollinear Rods
Authors: Lee J. P. , Kolsky H.
Published: November 2010

The reflection of a stress pulse at the junction of two elastic rods which are not collinear, results, in general, in the generation of four separate pulses. A longitudinal pulse and a flexural pulse are reflected back along the first rod, and a pulse of each type is also transmitted into the second rod. For a given incident wave shape Fourier techniques may be employed to predict the shapes of these four pulses. In this paper the analytic relations between the incident pulse and the four generated pulses are derived both for an incident longitudinal pulse and an incident fluxural pulse. The simple one-dimensional theory is used to describe the propagation of longitudinal waves, and the Timoshenko equation is used for flexural propagation. The equations derived were solved numerically for a rectangular longitudinal pulse propagated along a system consisting of two rods of the same material (carbon steel) at an angle to each other, and these results were tested experimentally by impact experiments. The agreement was found to be very satisfactory for all the angles that were tried.
Nonlinear Shell Theory With Finite Rotation and Stress-Function Vectors
Authors: Simmonds J. G. , Danielson D. A.
Published: November 2010

A general nonlinear theory for thin shells of arbitrary midsurface geometry is formulated in terms of a finite rotation vector and a stress-function vector. Compatibility equations, equilibrium equations, and boundary conditions are derived which are valid for shells undergoing arbitrarily large rotations and strains. For problems admitting a potential energy functional, a variational principle is formulated. The simplifications implied by small extensional strains are discussed. The theory contains, as special cases, Reissner’s equations for the axisymmetric deformation of shells of revolution, and the Sanders-Koiter linear shell theory.
On the Vibration of a Rotating Disk
Authors: Barasch S. , Chen Y.
Published: November 2010

The equation of motion of a rotating disk, clamped at the inner radius and free at the outer radius, is solved by reducing the fourth-order equation of motion to a set of four first-order equations subject to arbitrary initial conditions. A modified Adams’ method is used to numerically integrate the system of differential equations. Results show that Lamb-Southwell’s approximate calculation of the frequency is justified.
An Upper Bound on the Small Displacements of Elastic, Perfectly Plastic Structures
Authors: Ponter A. R. S.
Published: November 2010

An inequality is described which allows the evaluation of upper bounds to the displacement of an elastic/perfectly plastic structure subject to variable loading. Simple examples indicate that although the bound may not be very accurate, it may well provide a useful additional calculation to the limit state and shakedown solutions.
A Lattice Model for Stress Wave Propagation in Composite Materials
Authors: Drumheller D. S. , Sutherland H. J.
Published: November 2010

Geometric dispersion, observed in a wide variety of composite materials, is believed to result mainly from the relatively periodic arrangement of the reinforcing elements in the matrix rather than from the precise shape of each reinforcing element. On the basis of this observation, a lattice model for composite materials which ignores the shape of the reinforcing elements but preserves their periodicity has been developed. For a wide range of engineering applications, this model can be used to predict the behavior of actual engineering composites. In the application of the lattice model to a specific material, consideration of the dispersive characteristics of the composite are set aside, initially, and the composite is treated as a nondispersive homogeneous mixture. The effective or average properties of the mixture are determined either by steady-wave analysis or appropriate experiments. A lattice is then formed by redistributing the mass within the mixture to form a periodic structure of laminated plates. This mass redistribution is carried out in a manner which yields a lattice with theoretical dispersive characteristics that match the measured dispersive characteristics of the composite. The model was applied to composites consisting of a regular array of tungsten fibers in an aluminum matrix and composed of 2.2 and 22.1 percent by volume of tungsten. Two flyer-plate experiments were performed in the plastic range of the composite. The agreement between experiment and calculation for the arrival time and rise time of the wave front and for the frequency of the ringing behind the wave front is good.
The Bursting of Pointed Drops in Slow Viscous Flow
Authors: Buckmaster J.
Published: November 2010

Viscous drops, confined by the slow axisymmetric straining motion of a viscous fluid, are considered when the surface tension is weak. The shape of the drops is determined using slender-body theory, and it is found that steady solutions only exist for sufficiently small drop viscosities. Nonuniqueness exists, with bifurcation from a simple quadratic solution. At high drop viscosities, when there are no steady solutions, a description of the unsteady elongation of shape-preserving drops is obtained. This is the bursting phenomenon described experimentally by Taylor [1].
Conservation Laws and Energy-Release Rates
Authors: Budiansky B. , Rice J. R.
Published: November 2010

New path-independent integrals recently discovered by Knowles and Sternberg are related to energy-release rates associated with cavity or crack rotation and expansion. Complex-variable forms are presented for the conservation laws in the cases of linear, isotropic, plane elasticity. A special point concerning plastic stress distributions around cracks is discussed briefly.
On the Contact Problem of an Inflated Spherical Nonlinear Membrane
Authors: Feng W. W. , Yang W.-H.
Published: November 2010

The contact problem of an inflated spherical nonlinear elastic membrane between two large rigid plates is formulated in terms of three first-order ordinary differential equations for the region where the spherical membrane is not in contact with the rigid plates. The constraint condition introduced by the rigid plate on part of the spherical membrane reduces the number of governing equations to two for the contact region. A general stress-strain relation for the spherical membrane is used in the formulation. The results presented in this paper assume that the material behavior of the spherical membrane is that described by the Mooney model. Nonlinear spring characteristics and the instability phenomena of the inflated membrane are discussed.
On the Stability of Linear Stochastic Differential Equations
Authors: Kozin F. , Wu C.-M.
Published: November 2010

In this paper we present a study of the almost-sure sample stability properties of second-order linear systems with stochastic coefficients. Using knowledge of the first density functions of the coefficient processes, stability conditions are obtained. Based upon recent necessary and sufficient conditions for white-noise coefficient systems, the conditions obtained may yield a close approximation of the exact stability region for the Gaussian coefficient case.
Stability of Circular Couette Flow With Constant Finite Acceleration
Authors: Chen C. F. , Liu D. C. S. , Skok M. W.
Published: November 2010

The stability of flow in a Couette flow apparatus induced by the motion of the inner cylinder brought to its final speed through a constant finite acceleration is investigated both experimentally and theoretically. The instability of the flow manifests itself in the simultaneous occurrence of Taylor vortices more or less evenly spaced along the inner cylinder. A linear stability analysis using the initial-value problem approach is applied to this flow situation. Its prediction on the delay of the onset time of secondary flow and the increase in critical wavelength when the acceleration is reduced from infinite to finite values is generally confirmed by the experimental results.
Flow in a Tube With a Circumferential Wall Cavity
Authors: Stevenson J. F.
Published: November 2010

Streamlines, velocity profiles, and wall shear stress profiles are presented for a numerical solution of the Navier-Stokes equations for steady flow through a tube (radius = 1) with a circumferential wall cavity (depth = 1.33, length = 1.33). For tube Reynolds numbers equal to 0, 50, and 200, the numerical calculations show that a region of separated flow with closed streamlines exists in the cavity and that the attachment points for the separating streamline are located along the cavity wall. An assessment is made of the dependence of the numerical results on mesh size and the type of vorticity boundary condition applied at the protruding corners.
Dynamic Buckling of Shallow Spherical Shells
Authors: Ball R. E. , Burt J. A.
Published: November 2010

The dynamic behavior of clamped shallow spherical shells subjected to axisymmetric and nearly axisymmetric step-pressure loads is examined using a digital computer program for the geometrically nonlinear static and dynamic analysis of arbitrarily loaded shells of revolution. A criterion for dynamic buckling under the nearly axisymmetric load is proposed and critical buckling pressures are determined for a large range of shell sizes.
The Response of an Elastic Disk With a Moving Mass System
Authors: Iwan W. D. , Stahl K. J.
Published: November 2010

An investigation of the dynamic response of a circular elastic disk excited by a moving mass-spring-dashpot system is presented. Three distinct types of unstable response are observed. A stiffness instability region occurs immediately above each critical speed of the disk. Other regions of instability arise as a consequence of modal interaction. A terminal instability region exists for all load speeds above a certain limiting value. The presence of viscous dissipation in the loading system may destabilize the total system.
Torsional Impact of a Stepped Shaft With a Rigid Body at One End
Authors: Dalessandro J. A.
Published: November 2010

A numerical solution of the wave equation for torsional impact of a shaft which contains a single step and a rigid body at one end is found using the method of characteristics. The results are based on discontinuous stresses and elementary wave theory at the step. An experiment verified the predicted results, but showed that the actual impact stresses will always be slightly less since they are not discontinuous, as assumed. Some qualitative and quantitative generalizations are made concerning the expected maximum impact stress.
Elastic Response of a Thin Conical Shell to an Oblique Impact
Authors: Albrecht B. , Baker W. E. , Valathur M.
Published: November 2010

Strain waves in a truncated conical shell generated by oblique impact of the small end of the shell are discussed. The analysis is based on the general first-order linear shell theory of Sanders with all pertinent variables expanded into Fourier series in circumferential direction, resulting in decoupled sets of ordinary differential equations. Finite-difference approximations to these differential equations are then solved by matrix techniques. Theoretical values compare well with experimental results for the angle of oblicity β = 0, 5, 10, and 15 deg, the range of the experimental work.
Vibrations of a Two Cantilever Beam System
Authors: Sharma S. P. , Goel R. P.
Published: November 2010

A composite system of two cantilever beams subjected suddenly to a vibrating environment has been studied. The effect of various parameters defining the system on its chatter characteristics has been investigated. With a proper choice of the values of these parameters, it is possible to design a system with a minimum of chatter.
Laminar Flow and Blood Oxygenation in Channels With Boundary Irregularities
Authors: Chow J. C. F. , Soda K.
Published: November 2010

To understand the abnormal flow conditions caused by the boundary irregularities in diseased vessels, an analytical solution is obtained for the steady laminar flow of an incompressible Newtonian fluid in a channel with irregular surfaces where the spread of the surface roughness is large compared to the mean width of the channel. The hydrodynamic solution is then used to obtain the effects of wall roughness upon the blood oxygenation in a membrane oxygenator. The effects of various pertinent parameters upon the flow field, energy loss, and oxygen concentration, and possible occurrence of separation and reattachment are examined for symmetric and nonsymmetric channels with sinusoidal variation. It is found that when the blood is assumed to behave like a homogeneous fluid the wall irregularity has a strong effect on local oxygen concentration distribution, but has little effect on the saturation length. The saturation length is found to be of the order of 3/2 (1 + FS0/P0)ReScd for a channel with, or without, wall irregularity. Therefore, the secondary flows induced by the cell-plasma and cell-cell interaction is more likely the primary mechanism for a vast increase in oxygenation efficiency using wavy channels reported by Kolobow, et al.
An Information Theory Approach to Nonequilibrium Thermodynamics
Authors: El-Sayed Y. M.
Published: November 2010

This is an attempt to establish a simple approach to nonequilibrium thermodynamics. A generalized entropy is formulated from an information theory viewpoint and from a thermodynamic viewpoint. Rate laws, coupling phenomena, equality of cross coefficients, and a criterion for the changes of the steady state, all emerge when the maximum entropy of information is linearly related to the thermodynamic entropy. The results are not strictly new but their integration in one simple approach is believed to be novel.
Stability of Hydromagnetic Thermoconvective Flow Through Porous Medium
Authors: Patil Prabhamani R. , Rudraiah N.
Published: November 2010

The stability of the onset of thermal convection of a conducting viscous fluid in a porous medium has been investigated using the linear (normal mode technique) and the non-linear (energy) stability theories. Both the theories show that the stability region is increased to the maximum extent when the usual viscous dissipation is also present in addition to the dissipation due to Darcy’s resistance and Joule heating.
A Method for Estimating Creep Deformation of Structures Subjected to Cyclic Loading
Authors: Williams J. J. , Leckie F. A.
Published: November 2010

A method is proposed for estimating structural creep deformation due to histories of cyclic proportional loading. The method applies to structures composed of materials whose creep strain due to constant uniaxial stress is given by an equation of the form ε(t)/ε0={σ/σ0}n{t/t0}m Knowledge of the form of the creep law for time-varying stress is not required, as use is made of an effective stress obtained from a single cyclic creep test.
Optimal Topography of Force Transmission by Flexure
Authors: Rozvany G. I. N.
Published: November 2010

Optimality conditions for grillages of maximum strength and maximum stiffness and fiber-reinforced plates of maximum strength are discussed in the light of Prager’s theories of optimal design and a comprehensive description of the topographical properties of optimal solutions for clamped boundaries is given. General rules are derived for obtaining optimal solutions for a wide range of boundary and loading conditions.