bluuebunny/crossref_metadata_2025 huggingface dataset:
Phylogenetic beta diversity of native and alien species in European urban floras
Authors: Ricotta Carlo , La Sorte Frank A. , Pyšek Petr , Rapson Gillian L. , Celesti‐Grapow Laura , Thompson Ken
Published: October 2011

Aim  Human activities have weakened biogeographical barriers to dispersal, increasing the rate of introduction of alien plants. However, their impact on beta diversity and floristic homogenization is poorly understood. Our goal is to compare the phylogenetic beta diversity of native species with that of two groups of alien species, archaeophytes and neophytes (introduced before and after ad 1500, respectively), across European urban floras to explore how biological invasions affect phylogenetic turnover at a continental scale.

Location  Twenty European cities located in six countries between 49 and 53° N latitude in continental Europe and the British Isles.

Methods  To compare the phylogenetic beta diversity of native and alien species we use the average phylogenetic dissimilarity of individual floras from their group centroid in multivariate space. Differences in phylogenetic beta diversity among different species groups are then assessed using a randomization test for homogeneity of multivariate dispersions.

Results  Across European urban floras, and when contrasted with natives, archaeophytes are usually associated with lower levels of phylogenetic beta diversity while neophytes tend to increase phylogenetic differentiation.

Main conclusions  While archaeophytes tend to promote limited homogenization in phylogenetic beta diversity, because of their diverse geographical origin together with short residence times in the invaded regions, neophytes are not promoting biotic homogenization of urban floras across Europe. Therefore, in spite of the increasing rate of alien invasion, an intense phylogenetic homogenization of urban cities is not to be expected soon.
Exploring Real‐Time Geoprocessing in Cloud Computing: Navigation Services Case Study
Authors: Karimi Hassan Ali , Roongpiboonsopit Duangduen , Wang Haopeng
Published: October 2011

Today, many real‐time geospatial applications (e.g. navigation and location‐based services) involve data‐ and/or compute‐intensive geoprocessing tasks where performance is of great importance. Cloud computing, a promising platform with a large pool of storage and computing resources, could be a practical solution for hosting vast amounts of data and for real‐time processing. In this article, we explored the feasibility of using Google App Engine (GAE), the cloud computing technology by Google, for a module in navigation services, called Integrated GNSS (iGNSS) QoS prediction. The objective of this module is to predict quality of iGNSS positioning solutions for prospective routes in advance. iGNSS QoS prediction involves the real‐time computation of large Triangulated Irregular Networks (TINs) generated from LiDAR data. We experimented with the Google App Engine (GAE) and stored a large TIN for two geoprocessing operations (proximity and bounding box) required for iGNSS QoS prediction. The experimental results revealed that while cloud computing can potentially be used for development and deployment of data‐ and/or compute‐intensive geospatial applications, current cloud platforms require improvements and special tools for handling real‐time geoprocessing, such as iGNSS QoS prediction, efficiently. The article also provides a set of general guidelines for future development of real‐time geoprocessing in clouds.
Local adaptation: simultaneously considering herbivores and their host plants
Authors: Garrido Etzel , Andraca‐Gómez Guadalupe , Fornoni Juan
Published: October 2011

Although a major expectation of coevolutionary theory between plants and herbivores is the occurrence of reciprocal local adaptation, this has remained almost untested. Thus, we evaluated the presence and variation in the patterns of reciprocal local adaptation between an herbivorous insect and its host plant.

Two four‐by‐four cross‐infestation experiments were performed under similar abiotic conditions. The first one was done under laboratory conditions to estimate herbivore individual performance while the second one was performed in a common garden to simultaneously estimate herbivore population growth rate as well as seed production and plant defenses (resistance and tolerance to herbivory).

The patterns of population differentiation for the herbivore and the plant were not independent of each other, showing all the possible outcomes from locally adapted to maladapted populations. These results indicate differences in the magnitude of local adaptation. While an association between resistance and herbivore performance was observed, there was no clear pattern between tolerance and herbivore local adaptation.

Our results demonstrated the occurrence of reciprocal local adaptation following the pattern expected by theory: when the herbivores or the plants were adapted, the other species was non‐adapted or even maladapted.
Comparison of actions of systemically and locally administrated local anaesthetics in diabetic rats with painful neuropathy
Authors: Mert Tufan , Gunes Yasemin , Gunay Ismail
Published: October 2011

Nothing is known about actions of levobupivacaine, a long‐acting local anaesthetic belonging to the amino amide group, in diabetes‐induced neuropathic pain conditions. In this study, we therefore investigated the possible antihyperalgesic and antiallodynic effects of levobupivacaine in diabetic animal model. Actions of systemically (intraperitoneal) or locally (intraplantar) administrated levobupivacaine on streptozotocin‐induced diabetic rats with painful neuropathy were examined using a thermal plantar test and a dynamic plantar aesthesiometer. Effects of levobupivacaine were compared with those of a well‐known amide local anaesthetic lidocaine. Levobupivacaine was more potent than lidocaine in all tests employed on diabetic rats. After intraperitoneal injections to diabetic rats, levobupivacaine, but not lidocaine, produced pronounced antihyperalgesic and antiallodynic effects. However, intraplantar administration of both levobupivacaine and lidocaine produced antihyperalgesic and antiallodynic action in diabetic rats. In contrast to the transient effects of lidocaine (30 min), antihyperalgesic and antiallodynic actions of levobupivacaine gradually disappeared within 120 min after intraplantar injections. Intraperitoneal or intraplantar administrations of levobupivacaine or lidocaine at the effective dose had no effect on any parameters in intact rats. Findings revealed that antiallodynic and antihyperalgesic potency of levobupivacaine was higher in comparison with that of lidocaine after their intraperitoneal or intraplantar administration to diabetic animals. Furthermore, locally administrated levobupivacaine has the greatest antihyperalgesic and antiallodynic actions in diabetic rats.
Parameter Stability and the Valuation of Mortgages and Mortgage‐Backed Securities
Authors: LaCour‐Little Michael , Park Yun W. , Green Richard K.
Published: October 2011

The recent financial crisis was triggered by large and unexpected losses on mortgages and mortgage‐related securities. Here we examine model risk arising from innovations in mortgage markets and the effect on asset values. In particular, we examine the effect of parameter instability in the prepayment function. Using carefully constructed microdata, we find that the refinancing propensity was greater in 1998 for a 1997 issue given the same incentives, compared to the 1993 performance of a 1992 issue. The associated change in cash flow patterns produces economically significant changes in asset prices. Results are robust to alternative term structure models.
Exploring variations in employment practices in the emerging economies of Europe: assessing the impact of foreign ownership and European integration
Authors: Sahadev Sunil , Demirbag Mehmet
Published: October 2011

Few studies have assessed the impact of European Union (EU) integration on the emerging economies of Europe, especially with regard to employment practices. In this study, we focus on three aspects of employment practices and assess whether EU integration has lead to any differences between the emerging economies aligned to the EU and those that remain out of the EU fold. This comparison is quite valid because the emerging economies that we compare have all had a similar background in terms of their economic systems. We use a large World Bank database to compare domestically owned and foreign‐owned firms separately. The results show that, while there is some level of divergence between the two blocs of countries in terms of the percentage of temporary employees and education level of employees, in terms of the percentage of skilled workers employed, however, there is no divergence between firms in the two blocs of countries.
Advanced glycation end‐products inhibition improves endothelial dysfunction in rheumatoid arthritis
Authors: SYNGLE Ashit , VOHRA Kanchan , GARG Nidhi , KAUR Ladbans , CHAND Prem
Published: October 2011

Aim:  Chronic inflammation in rheumatoid arthritis is associated with vascular endothelial dysfunction. The objective was to study the efficacy and safety of advanced glycation end products (AGEs) inhibitor (benfotiamine 50 mg + pyridoxamine 50 mg + methylcobalamin 500 μg, Vonder® (ACME Lifescience, Baddi, Himachal Pradesh, India)) on endothelial function in rheumatoid arthritis (RA).

Methods:  Twenty‐four patients with established active RA with high disease activity (Disease Activity Score of 28 joints [DAS28 score] > 5.1) despite treatment with stable doses of conventional disease‐modifying antirheumatic drugs were investigated. Inflammatory disease activity (DAS28 and Health Assessment Questionnaire‐Disability Index [HAQ‐DI] scores, erythrocyte sedimentation rate [ESR] and C‐reactive protein [CRP]), markers of endothelial dysfunction, serum nitrite concentration and endothelium‐dependent and ‐independent vasodilation of the brachial artery were measured before and after 12 weeks therapy with twice a day oral AGEs inhibitor.

Results:  After treatment, flow‐mediated vasodilation improved from 9.64 ± 0.65% to 15.82 ± 1.02% (P < 0.01), whereas there was no significant change in endothelium‐independent vasodilation with nitroglycerin and baseline diameter; serum nitrite concentration significantly reduced from 5.6 ± 0.13 to 5.1 ± 0.14 μmol/L (P = 0.004), ESR from 63.00 ± 3.5 to 28.08 ± 1.5 mm in the first h (P < 0.01) and CRP levels from 16.7 ± 4.1 to 10.74 ± 2.9 mg/dL (P < 0.01). DAS28 and HAQ‐DI scores were significantly reduced, from 5.9 ± 0.17 to 3.9 ± 0.17 (P < 0.01) and 4.6 ± 0.17 to 1.7 ± 0.22 (P < 0.01), respectively.

Conclusions:  Advanced glycation end products inhibitor improves endothelial dysfunction and inflammatory disease activity in RA. In RA, endothelial dysfunction is part of the disease process and is mediated by AGEs‐induced inflammation.
Free, Periodic, Nonlinear Oscillation of an Axially Moving Strip
Authors: Thurman A. L. , Mote C. D.
Published: October 2011

The free, nonlinear, fundamental period of transverse oscillation of axially moving strips (e.g., tapes, fibers, belts, and band saws) is determined by the approximate solution of two, coupled, nonlinear, partial differential equations. One equation describes longitudinal motion and the other transverse motion. A solution method is developed that permits accurate and efficient period calculations. The results indicate that the existence of the axial transport velocity reduces the fundamental period of oscillation and increases the relative importance of the nonlinear terms in the equations of motion. In many cases of practical interest the linear analysis is shown to be seriously in error and one may be led to erroneous conclusions because of its limited range of applicability. Curves are presented that assist one to estimate the accuracy of the linear period calculation.
Measurements of Velocity and Droplets Concentration in Two-Phase Flows
Authors: Hetsroni G. , Cuttler J. M. , Sokolov M.
Published: October 2011

A simple method is presented for measuring time-average velocity, turbulence intensity, and concentration of droplets in two-phase (air-liquid) turbulent flows.
On the Spacing of Karman Vortices
Authors: Sallet D. W.
Published: October 2011

Equations for the absolute dimensions of the Karman vortex street are developed in terms of the coefficient of drag and the Strouhal number of the vortex shedding bluff body. The body is assumed to be of large slenderness ratio and of uniform cross section. The predicted vortex spacings are compared with the experimental results of other investigators for circular cylinders, flat plates, and a wedge.
Optimization of a Viscoelastic Structure: The Seat-Belt Problem
Authors: Nachbar W. , Schipmo¨lder J. B.
Published: October 2011

Optimization of the parameters of elementary linear viscoelastic models is considered for the design of a lap seat belt in automobiles. The vehicle is assumed to stop abruptly on impact. The parameters are optimized to allow the speed of the vehicle before impact to have the largest permissible value consistent with constraints imposed for the safety of the user of the belt. The constraints chosen here are: (a) the maximum displacement of the body after impact is equal to or less than a prescribed critical displacement; (b) the forward speed of the body at the critical displacement does not exceed a prescribed maximum value; (c) the force exerted by the belt on the body during the motion following impact does not exceed a prescribed maximum value. It is found that the optimized Kelvin-Voigt viscoelastic model is nearly 40 percent more effective than the purely elastic material. It is nearly as effective as constant deceleration. An additional and advantageous property is proposed, moreover, for belts of viscoelastic materials. This is that the material should have a relatively low spring rate at relatively small strain rates. The optimized belts for the elementary viscoelastic models are shown to be quite stiff at low strain rates, however.
On the Determination of Stress, Strain, Strain-Rate Relations From Dynamic Beam Tests
Authors: Gillis P. P. , Kelly J. M.
Published: October 2011

A direct method is proposed for the determination of stress, strain, strain-rate relations from dynamic flexural tests in which bending moment is given in terms of curvature and curvature rate, or any other suitable deformation parameter and deformation rate parameter. The method is demonstrated by application to published experimental results. It is found that the stress, strain, strain-rate relations that are derived from the flexural test data are in significantly better accord with uniaxial data on the same material, than moment, curvature, curvature-rate relations predicted from the uniaxial data correspond with the experimental results. It appears that the process of reducing flexural data to uniaxial relations by the method proposed is much less sensitive than that of predicting flexural response from uniaxial data. Since flexural tests have many experimental advantages over uniaxial tests this analytical technique seems to open up possibilities for improved dynamic testing methods.
On Integral Methods for Predicting Shear Layer Behavior
Authors: Shamroth S. J.
Published: October 2011

The origin and consequences of a nonphysical constraint which may arise when boundary-layer momentum integral equations are used to predict the behavior of shear layers are examined. It is pointed out that should the constraint occur within the domain of integration of the momentum integral equations, the effect may either be catastrophic or significantly constrain the solution. Several methods of solution having the usual advantages associated with boundary-layer momentum integral equations, but free from this constraint, are proposed for the specific problem of the plane turbulent near wake. One method developed to avoid this constraint in the case of a plane turbulent near wake appears to be perfectly general, and therefore, it may be possible to apply this method to both boundary layers and wakes.
Free Molecule Flow Through Slit and Annular Orifices in the Presence of Participating Bounding Walls
Authors: Sparrow E. M. , Yu H. S. , Lundgren T. S.
Published: October 2011

The effect of actively participating bounding surfaces on the free molecule flow through a slit or an annular orifice situated in a wall separating two regions of different pressure is analyzed. The flow through the slit or orifice depends on the distributions of the flux of mass leaving the bounding surfaces. These distributions are found by formulating and solving pairs of integral equations. In the case of the slit, the integral equations are formulated by employing kinetic theory methods, while for the annular orifice it was found advantageous to use the techniques of radiative transfer. In addition to exact solutions, closed-form solutions based on an approximate model are derived. Results are presented for a wide range of values of the relevant geometrical parameters.
Thermal Buckling of Shallow Bimetallic Two-Hinged Arches
Authors: Vahidi B. , Huang N. C.
Published: October 2011

The snap-through phenomenon of shallow bimetallic two-hinged arches due to temperature rise is analyzed. Two types of arch geometry are included. The effect of the position of supporting hinges on the critical temperature rise for snap-through is discussed. Comparisons are made between the present more accurate solution of the critical temperature rise and the approximate solution obtained by Timoshenko. Striking discrepancies are found between these two solutions.
The Flow of Conducting Fluids in Circular Pipes With Finite Conductivity Under Uniform Transverse Magnetic Fields
Authors: Ihara Sadatoshi , Tajima Kiyohiro , Matsushima Akira
Published: October 2011

The flow of incompressible, viscous, electrically conducting fluids in circular pipes in the presence of an applied transverse magnetic field is analyzed theoretically and experimentally. The relations among the Hartmann number, the Poiseuille number, skin friction coefficient, the Reynolds number, sensitivity, and wall conductivity are discussed. The experimental results using carbon pipe, stainless-steel pipe, and glass pipe are in good agreement with theoretical calculations.
Invariant Stress and Deformation Functions for Doubly Curved Shells
Authors: Libai A.
Published: October 2011

Exact invariant stress and deformation functions for doubly curved (nondevelopable) shells are derived. The invariant stress function reduces the six shell equilibrium equations into a single equation in the stress function and moment resultants. The deformation function reduces the three surface strain-displacement relations into a single compatibility equation in the strains and deformation function, in terms of which the changes of curvature are also expressed. Application of these functions in the formulation of an approximate bending theory for shells is presented.
On Dynamic Stress Concentration Around a Discontinuity
Authors: Cheng S. L. , Jahanshahi A.
Published: October 2011

The redistribution of dynamic stresses due to the presence of a circular cylindrical discontinuity in an unbounded isotropic homogeneous elastic plate is studied. The source of excitation is a time-harmonic line force located at a finite distance from the discontinuity. In particular, the effects of source location on the concentration of energy around a rigid insert or a cavity is explored.
Stress Concentrations in Three-Dimensional Electrostriction
Authors: Smith T. E.
Published: October 2011

Using the techniques employed in developing a Papkovich-Neuber representation for the displacement vector in classical elasticity, a particular integral of the kinematical equations of equilibrium for the uncoupled theory of electrostriction is developed. The particular integral is utilized in conjunction with the displacement potential function approach to problems of the theory of elasticity to obtain closed-form solutions of several stress concentration problems for elastic dielectrics. Under a prescribed uniform electric field at infinity, the problems of an infinite elastic dielectric having first a spherical cavity and then a rigid spherical inclusion are solved. The rigid spheroidal inclusion problem and the penny-shaped crack problem are also solved for the case where the prescribed field is parallel to their axes of revolution.
Transfer of Load From an Edge-Stiffener to a Sheet—A Reconsideration of Melan’s Problem
Authors: Muki Rokuro , Sternberg Eli
Published: October 2011

The problem posed by the diffusion of load from an infinite edge-stiffener into a semi-infinite elastic sheet is reconsidered under two alternative refinements of the underlying stiffener model. First, the stiffener is regarded as an elastic strip of finite width, and the theory of generalized plane stress is applied rigorously to the sheet and stiffener alike. Next, Melan’s one-dimensional treatment of the stiffener is amended to account for its bending rigidity. The “exact” and the intermediate approximate solution thus obtained are compared to Melan’s results with particular attention to the relevant asymptotic behavior in the vicinity of the applied load and at large distances from the load. Comparative numerical results, showing the variation of the sheet stresses at the interface and the distribution of the axial stiffener force, are included.
Laminar, Gravitational Film Flow of Liquid on Vertical, Circular, Cylindrical Surfaces
Authors: Chien Sze-Foo
Published: October 2011

Analytic solutions of the laminar, gravitational film flow of liquid on vertical, circular, cylindrical surfaces were obtained. These solutions lead to the introduction of a new dimensionless number which characterizes the flow and is a function of the dimensionless film thickness. The results were compared with that of Nusselt’s film flow equation and show that the Nusselt’s equation gives a good approximation when the dimensionless film thickness is small.
On Fundamental Solutions and Green’s Functions in the Theory of Elastic Plates
Authors: Kalnins A.
Published: October 2011

This paper is concerned with fundamental solutions of static and dynamic linear inextensional theories of thin elastic plates. It is shown that the appropriate conditions which a fundamental singularity must satisfy at the pole follow from the requirement that the reciprocal theorem is satisfied everywhere in the region occupied by the plate. Furthermore, dynamic Green’s function for a plate bounded by two concentric circular boundaries is derived by means of the addition theorem of Bessel functions. The derived Green’s function represents the response of the plate to a harmonically oscillating normal concentrated load situated at an arbitrary point on the plate.
Elastic-Plastic Solutions for Notched Shafts in Torsion
Authors: Davis E. A. , Tuba I. S.
Published: October 2011

An elastic-plastic analysis of the stress and strain distribution in a solid or hollow shaft containing external or internal hyperbolic notches is presented. The solution can be applied for any stress-strain relationship and for various specified amounts of plastic-zone penetration.
Stress Concentration in Nonlinear Creep of a Simple Shell
Authors: Calladine C. R.
Published: October 2011

A long, thin circular cylindrical shell is loaded at one edge by symmetrical radial shear Qx and bending moment Mx. (No interior pressure.) The shell is made of material which under applied stress creeps with a strain rate which is proportional to the rth power of the stress. Previous results are used to derive, approximately, the greatest stress in the shell for any Qx, Mx, and r. It is shown that for any load the greatest stress decreases as r increases, and is approximately a linear function of 1/r. The case r = 1 is exactly analogous to a linear elastic problem, and the case r → = ∞ corresponds exactly to a perfectly plastic problem. Results for any exponent r may thus be found approximately by simple interpolation between results obtained in linearelastic analysis and perfectly plastic analysis.
Compliance Under a Small Torsional Couple of an Elastic Plate Pressed Between Two Identical Elastic Spheres
Authors: O’Connor J. J.
Published: October 2011

The object of the analysis is to calculate the surface shear traction and the torsional compliance of an elastic system comprising a plate pressed between identical spheres. The problem is formulated in terms of an integral equation which is solved numerically. The parameters are the plate thickness and ratio of shear moduli. Solutions are obtained for all except extremely thin plates, for which a previous approximate solution is shown to be valid. The contact stress distribution is always close to the well-known distribution appropriate to the half-space, with a singularity at the edge of the contact circle, unless the plate is simultaneously thin and flexible. A thin flexible plate confines the singularity to a very small region at the edge of the contact circle, the stress elsewhere being essentially proportional to radius. The torsional compliance predicted by the analysis agrees well with experiment.
Inelastic Buckling of Rib-Cored Sandwich Cylinders Under External Hydrostatic Pressure
Authors: Theocaris P. S. , Hill P. W.
Published: October 2011

The extension of the equations of Stein and Mayers to include application to inelastic buckling of orthotopic sandwich shells for those classes of loading for which torsion does not act in combination with axial or lateral forces is presented. A deformation theory of plasticity is used to evaluate the 12 remaining orthotropic rigidities for rib-cored sandwiches. The solution for the critical buckling pressure is given for loading by external hydrostatic pressure. The effect of Poisson’s ratio is discussed, and corrections for the elastic compressibility are presented. These corrections permit a smooth transition from elastic to inelastic solutions.
On a Class of Exact Solutions of the Navier-Stokes Equations
Authors: Wang Chang-Yi
Published: October 2011

A class of exact solutions of the Navier-Stokes equations has been generalized. This class of solutions has the property that the non-linear terms of the Navier-Stokes equations are self-canceling such that the resultant equations are linear and solvable. Examples in Cartesian coordinates and their applications are also illustrated.
Concentrated Force Near a Smooth Circular Inclusion
Authors: Dundurs J. , Fukui K. , Fukui T.
Published: October 2011

A concentrated force applied to an infinite matrix near a smooth circular inclusion is discussed. The smooth interface is defined as one that allows slip, but does not transmit shearing tractions. The solution is partially in terms of series, but for certain combinations of materials the series sum to elementary functions. The solution which is of significance for applications in micromechanics exhibits interesting behavior also from the point of view of classical elastostatics. When the force is allowed to approach the interface, the singularity for the force shows dependence on the curvature of the interface. In this respect the smooth interface between two materials in two dimensions resembles a curved boundary in three dimensions.
Invariant Imbedding Applied to Eigenvalue Problems in Mechanics
Authors: Shoemaker E. M.
Published: October 2011

A formal method is presented for obtaining eigenvalues of ordinary differential equations associated with problems of buckling and vibration. The method utilizes the idea of invariant imbedding which has previously been applied to two point boundary value problems in transport theory and wave propagation. The present method reduces the eigenvalue problem to an initial value problem for a matrix of Riccati equations. The numerical solution of such formulations has proved to be generally more efficient than known methods.
Thermomechanical Behavior of Viscoelastic Media With Variable Properties Subjected to Cyclic Loading
Authors: Schapery R. A.
Published: October 2011

The interaction between heat and dynamic response of viscoelastic bodies with temperature-dependent properties is studied. First, equations governing the small deformation thermomechanical response to sinusoidal loading are shown to be equivalent to a set of two variational principles. Viscoelastic properties of a solid propellant are characterized and then used in numerical examples dealing with sinusoidal shear loading of slabs and cylinders. As the first problem, an approximate variational method is used to calculate one-dimensional transient and steady-state temperature distributions in a massless slab. An exact steady-state solution is obtained for the thermomechanical behavior of a slab with concentrated mass and is then used to deduce the solution for a similarly loaded cylinder. Finally, the influence of distributed mass in a cylinder is studied using a variational method. It is found that without inertia a large temperature rise may occur when the applied stress amplitude is above a certain critical value which depends on thermal and mechanical properties, geometry, and frequency. Moreover, the combination of temperature-dependent properties and inertia leads to temperature and displacement jump instabilities that are similar to those existing in a nonlinear spring-mass system with a spring that softens with increasing displacement.
Experimental and Analytical Investigation of the Film-Conductance-Coefficient Boundary Condition for Thermal Shock of a Conical Shell
Authors: Carr R. B. , Smith J. O.
Published: October 2011

This investigation considered the problem of submerging a hot conical shell into a stream of cold water flowing axially up the outer surface of the shell. The thermal boundary condition on the outer surface was formulated in terms of a film-conductance coefficient that was considered to be of constant value for any one instant of time. A 15-in-long by 8 in. in largest diameter by 0.21 in. in thickness cone constructed of 2017-T4 aluminum was used in the experimental portion of this investigation. By recording strains and temperatures on the inner surface of the shell, the variation in film-conductance coefficient with temperature on the outer surface of the shell was determined for water velocities of 1.37, 2.32, 3.20 fps. The assumption of a constant value of film-conductance coefficient over the outer surface of the shell is capable of yielding stresses accurate to ± 12 percent for the range of temperature to 100–300 F. The maximum stress resulting on the outer surface of the shell for the highest water velocity of 3.2 fps and a shell temperature of 300 F such that nucleate boiling was taking place on the surface resulted in a value of stress 25 percent of the maximum theoretical possible stress of EαΔT/(1 − ν).
A Method of Solving Supersonic Laminar Boundary-Layer Separation and Its Application to Wedges and Curved Surfaces
Authors: Pinkus Oscar
Published: October 2011

By use of a quartic velocity profile with one of its coefficients varying along the boundary layer, a technique is developed to calculate the general characteristics of adiabatic separated flows. The technique is based on the integral solution of the differential equations of laminar compressible boundary layers utilizing the energy-momentum concept and on expressions derived from the notion of a dividing streamline in the separated region. Detaching, central, and reattaching regions are defined which, by their combination, embrace most known forms of flow separation. The derived equations are here applied to the case of separated laminar boundary layers on compression corners and curved surfaces.
Thin Plates and Shallow Cylindrical Shells Subjected to Hot Spots
Authors: Jahanshahi A.
Published: October 2011

Using Lagrange’s equation of motion for thin plates, the equations of plane stress, and the equations for shallow cylindrical shells, the deformations of thin plates and cylindrical shells subjected to bending and plane hot spots are studied. The interrelation between different singular functions associated with these problems has been indicated also.
On Asymptotic Expansions for Circular Cylindrical Shells
Authors: Reissner Eric
Published: October 2011

The paper presents an asymptotic expansion procedure (with reference to decreasing values of wall-thickness shell-radius ratio) for the solutions of the linear theory of the three simultaneous equations for displacements in isotropic circular cylindrical shells. The resultant expansions are applied to a number of fundamental boundary-value problems for a semi-infinite shell. The analysis shows the importance of the joint consideration of differential equations and boundary conditions for a clarification of the asymptotic nature of the solution to be determined.
Elastoplastic Stress and Strain Distribution in a Finite Plate With a Circular Hole Subjected to Unidimensional Load
Authors: Durelli A. J. , Sciammarella C. A.
Published: October 2011

This paper deals with the experimental determination of the elastoplastic stress and strain distribution around an empty circular hole in a finite aluminum plate subjected to a unidimensional load as the deformation increases from the elastic far into the plastic field. The strains were measured using the moire method. The stresses were computed by means of the Prandtl-Reuss stress-strain relationships presented in a convenient form for the case of a strain-hardening material.
Vortex Formation and Resistance in Unsteady Flow
Authors: Sarpkaya Turgut , Garrison C. J.
Published: October 2011

The strength, growth, and motion of vortices behind a circular cylinder immersed in a two-dimensional uniform flow with constant acceleration are analyzed. Equations for lift and drag forces are obtained from potential theory in terms of the flow and vortex characteristics. By combining the theoretical equations with the experimental results, drag and inertia coefficients are separated and shown to be a function of the relative displacement of the fluid. The results are striking evidence of the existence of a unique relationship between the drag and inertia coefficients.
An Approximate Analysis of Laminar Magnetohydrodynamic Flow in the Entrance Region of a Flat Duct
Authors: Roidt M. , Cess R. D.
Published: October 2011

Laminar flow of a conducting fluid with constant properties entering a semi-infinite flat duct with a transverse applied magnetic field is considered. The fluid is assumed to enter the duct with a uniform velocity profile. The duct walls are nonconducting and a variable external resistance connects the two end plates which are displaced to infinity. The velocity and pressure distributions are then determined for the region between the inlet and fully developed flow. A method developed by Schlichting is used wherein the flow field is divided into two sections and an appropriate analysis utilized in each. In the section near the inlet a boundary-layer formulation of equations is used and a solution developed in a series stream function with Blasius functions as coefficients. When this solution becomes unwieldy, an exponential velocity deviation from the fully developed flow is assumed and joined to the boundary-layer solution to complete the description of the flow.
Some Measurements of a Wake Boundary-Layer Interaction
Authors: Eichhorn R. , Eddy T. L.
Published: October 2011

When a strut or other object is attached to a surface along which a fluid flows, the strut disturbs the boundary-layer flow and the wake region of the strut interacts with the boundary layer along the surface giving rise to complicated three-dimensional effects. In the present paper these effects were investigated for a geometry consisting of a 2-in-diam cylinder in uniform axial flow to which was attached normally a 3/16-in-diam dowel forming a strut. The measurements reported include both static and total-pressure surveys in the wake-boundary layer region behind the strut. The resulting wake velocity profiles far from the interaction region behave normally but those within this region do not. The existence of vortexes is in some cases clearly seen.
On the Meaning of Isoclinic Parameters in the Plastic State in Cellulose Nitrate
Authors: Frocht M. M. , Cheng Y. F.
Published: October 2011

In applying the shear-difference method to the determination of stress distributions in photo plasticity, a basic question arises whether, under plastic flow, the isoclinic parameters represent the directions of the secondary principal stresses. Special equipment, new techniques, and a series of experiments are described to study this problem. Tests were made with stress systems which varied in magnitude and direction at normal and oblique incidence, and at strains for which a one-to-one stress-optic relation exists as well as at strains for which it breaks down. Typical results are given. These findings together with the method of scattered light and an appropriate stress-optic law may provide a foundation for three-dimensional photoplasticity. The effects described are limited to loading. Cases of loading plus unloading are not considered in the present paper.
Further Consideration of the Thick-Plate Problem With Axially Symmetric Loading
Authors: Nelson C. W.
Published: October 2011

The Fourier-Bessel integral approach was first applied to thick-plate problems of elasticity by Lamb and later by Dougall. Still later, the method, now known as the Hankel transform method, was applied to several cases of the thick-plate problem by Sneddon who, apparently, was the first to obtain numerical results for the stresses in thick plates by this method. Sneddon devised an approximate method for evaluating the integrals; i.e., inverting the transforms, which he encountered. The main contribution of the present paper consists in the more precise numerical evaluation of the integrals involved for a special case previously considered by Sneddon, but for values of parameters outside the range studied by Sneddon. In particular, it is hoped that the formulation of integration procedures presented will be found useful in other thick-plate problems.
The Bending Stress in a Cracked Plate on an Elastic Foundation
Authors: Ang D. D. , Folias E. S. , Williams M. L.
Published: October 2011

Classical Kirchhoff bending solutions for a normally loaded elastically supported flat plate containing a semi-infinite straight crack are obtained using an integral equation formulation. Because the effects of initial spherical plate curvature are related to those of an elastic foundation, the solution can be applied to the problem of a crack in an initially curved unsupported plate as well. The explicit nature of the stresses near the crack point is found to depend upon the inverse half power of the nondimensional distance from the point, r/(D/k)1/4, where D is the flexural rigidity of the plate and k the foundation modulus. The particular case of an infinite strip containing the crack along the negative x-axis and loaded by constant moments M* along y = ±y* is presented. The inverse half-power decay of stress is additionally damped by an exponential factor of the form exp(−λy*/2).
The Removal of the Boundary Layer of a Supersonic Flow by Means of a Slot
Authors: Cloutier M.
Published: October 2011

The influence of slot opening and of suction pressure upon the mass flow through the slot and the subsequent development of the boundary layer has been studied for the case of a single transverse slot opening into a boundary layer with a displacement thickness of 0.168 in. at a free-stream Mach number of 2.92. The results show that as much as 85 percent of the mass flow in the boundary layer between the wall and the position of the slot lip enters the slot, and that this result is independent of the slot reservoir pressure, providing the latter is less than approximately twice the tunnel static pressure.
Gravity-Gradient Excitation of a Rotating Cable-Counterweight Space Station in Orbit
Authors: Chobotov V.
Published: October 2011

The gravity-gradient excitation of a whirling cable-counterweight space station in orbit is investigated. The Lagrange’s equations of motion for transverse oscillations of the system are derived and shown to be of the Mathieu type. A few representative cases are investigated analytically and on an IBM 7090 computer. The stability criteria for the axial vibrations are also considered and shown to be of the same kind as those for the transver se vibrations of the cable. Viscous damping is included in the analyses and found to be effective and essential for prevention of parametric excitation instability of the system.
Stress Distribution in a Rotating Spherical Shell of Arbitrary Thickness
Authors: Goldberg M. A. , Salerno V. L. , Sadowsky M. A.
Published: October 2011

This paper contains an exact solution for the stress distribution in an elastic spherical shell rotating about a diametral axis. The surfaces of the shell are free of boundary tractions. The coefficients necessary to determine the stresses at any point have been calculated for eight values of a thickness parameter, α. Graphs of the maximum stress intensity as a function of α are presented.
Stability of the Hinge Formed in an Ideal Rigid-Plastic Beam
Authors: Hillier M. J.
Published: October 2011

The hinge formed at yield in an ideal rigid-plastic beam is considered plastically stable if the moment of resistance increases after a small deformation, and unstable if the moment decreases. An initially curved beam of strain-hardening material and rectangular section is considered, and the change in moment of resistance due to a small change in curvature calculated. It is shown that, for a material which does not strain harden, the yield hinge is unstable if the initial curvature and the change in curvature are of the same sign. However, the initial rate of change of moment of resistance is small. The change of yield moment of a straight beam is initially zero. The minimum initial hardening rate required for stability of a curved beam is calculated.
Nonsymmetric Deformation of Dome-Shaped Shells of Revolution
Authors: Steele C. R.
Published: October 2011

Bending solutions that are uniformly valid in both shallow and nonshallow regions of a dome with arbitrary meridian are determined for edge loads that vary sinusoidally in the circumferential direction. The membrane and inextensional deformation solutions are obtained in terms of a function which satisfies a simple integral equation which eliminates the usual trial-and-error method of isolating the solutions that are regular at the apex. For a specific application, curves and formulas are obtained for the stresses and deformations of a dome with rigid rings clamped to the edges under the action of axial force, side force, and tilting moment.
Transient Thermoelastic Problem for an Infinite Medium With a Spherical Cavity Exhibiting Temperature-Dependent Properties
Authors: Nowinski Jerzy
Published: October 2011

This paper is concerned with a polarly symmetric transient thermoelastic problem for an infinite medium with a spherical cavity, the boundary of the cavity being subjected to a sudden temperature rise. Thermal and elastic properties of the medium are assumed to be temperature dependent. Using the perturbation method general equations for the displacements and stresses corresponding to particular boundary-value problems have been found. An illustrative example, involving linear variation of conductivity and thermal expansion as well as quadratic variation of shear modulus with temperature, has been discussed in detail.
Response of a Loaded Nonlinear String to Random Excitation
Authors: Ariaratnam S. T.
Published: October 2011

The response to white noise excitation of a light elastic string loaded at equal intervals by a number of equal masses is examined using the theory of the Markov random process and the associated Fokker-Planck equation. Taking nonlinear effects due to variation in string tension into account, an exact solution of the Fokker-Planck equation is obtained and used in an approximate analytical evaluation of the mean squared response of the system.
On the Flow in the Vaneless Diffuser of a Centrifugal Compressor
Authors: Schreier Stefan
Published: October 2011

The flow in the vaneless diffuser of a centrifugal compressor is found by means of a series of conformal transformations which map the uniform parallel flow over a semi-infinite flat plate into the flow in a scroll-type diffuser. The method is based on the assumptions that the flow is inviscid, incompressible, and two-dimensional and that the impeller may be replaced by a source vortex for purposes of calculation. The walls of the diffuser are assumed to have the shape of logarithmic spirals, but their divergence may be adjusted arbitrarily within limits. The method is applied to finding the expressions for the velocity and pressure distributions along the upper and lower walls of the diffuser, showing the points of maximum velocity and minimum pressure and making it possible to calculate the thrust on the diffuser due to the flow.
Shells of Revolution With Edge Loads of Rapid Circumferential Variation
Authors: Steele C. R.
Published: October 2011

After an investigation of membrane theory, solutions to the general equations for a thin shell of revolution of arbitrary meridian are obtained for rapidly varying sinusoidal edge loading. The solutions from membrane theory are shown to be valid for shells near spherical shape but can give quite misleading results, particularly for shells of negative curvature. The “edge-effect” solutions also are shown to become significantly modified for the high harmonics.
Experiments on the Postbuckling Behavior of Square Plates Loaded in Edge Compression
Authors: Yamaki Noboru
Published: October 2011

In previous papers [1, 2], the postbuckling behavior of rectangular plates under edge compression has been studied theoretically under eight different boundary conditions, and numerical solutions are presented for square plates with and without initial deflection. To compare with these results, experiments were carried out by using aluminum square plates, and the relations of the maximum deflection, stresses, and strains at typical points in the plate with applied loads were determined under four different boundary conditions. It is found that the experimental results are in reasonable agreement with those theoretically predicted.