bluuebunny/crossref_metadata_2025 huggingface dataset:
Does Financial Intermediation Development Increase Per Capita Income in Rural China?
Authors: Pan Suwen , Rejesus Roderick M. , He Xiurong
Published: July 2009

This paper investigates the impacts of financial intermediary (or banking) development on village‐level per capita income using a Chinese dataset for selected years between 1993 and 2006. The empirical results from a random effect regression model indicate that mean per capita income in rural villages follows an inverted U‐shaped path as financial intermediation develops. However, using a pooled quantile regression approach, we find that median per capita income in rural villages follows a positive linear path, rather than an inverted U‐shaped path, as financial intermediation develops. The positive linear effect of financial intermediary development is observed at the lower and higher ends of the conditional per capita income distribution. This suggests that development of financial intermediation in China might not have statistically significant differential effects in low‐income or high‐income rural villages.
Independent regulation of hair and skin color by two G protein‐coupled pathways
Authors: Van Raamsdonk Catherine D. , Barsh Gregory S. , Wakamatsu Kazumasa , Ito Shosuke
Published: July 2009

Hair color and skin color are frequently coordinated in mammalian species. To explore this, we have studied mutations in two different G protein coupled pathways, each of which affects the darkness of both hair and skin color. In each mouse mutant (GnaqDsk1,Gna11Dsk7,andMc1re), we analyzed the melanocyte density and the concentrations of eumelanin (black pigment) and pheomelanin (yellow pigment) in the hair or skin to determine the mechanisms regulating pigmentation. Surprisingly, we discovered that each mutation affects hair and skin color differently. Furthermore, we have found that in the epidermis, the melanocortin signaling pathway does not couple the synthesis of eumelanin with pheomelanin, as it does in hair follicles. Even by shared signaling pathways, hair and skin melanocytes are regulated quite independently.
From epidemiology to lysyl oxidase like one (LOXL1) polymorphisms discovery: phenotyping and genotyping exfoliation syndrome and exfoliation glaucoma in Iceland
Authors: Jonasson Fridbert
Published: July 2009

The first Icelandic articles on exfoliation syndrome (XFS) and exfoliation glaucoma (XFG) appeared some 35 years ago in 1974. Articles since then have included epidemiology, pedigree‐based and twin‐studies as well as investigations into XFG response to medical therapy and XFS/XFG genetics. All studies found XFS/XFG to be common in Iceland and to be age‐related. The Reykjavik Eye Study (RES), a population‐based epidemiological study, was first conducted in 1996. The RES found that XFS and XFG prevalence in patients aged 50 years and older was 11% and that XFS/XFG was more common in women than in men. These results were confirmed in 5‐ and 12‐year incidence studies that also suggested that detailed characterization of the phenotype is important, including pupil dilation. In the RES, eyes with XFS were found to be clinically unilateral in about half of cases and to have higher mean intraocular pressure (IOP) than non‐XFS eyes. However, XFS was not found to be associated with central corneal thickness, corneal curvature, anterior chamber depth, lens thickness, lens opacification or optic disc morphology. About 15% of persons with XFS had XFG, and XFG eyes had higher risk of developing visual impairment and blindness than eyes with primary open‐angle glaucoma. The first genetic studies on Icelanders, conducted about 12 years ago, were linkage studies and were unsuccessful in discovering the genetics behind XFS/XFG. However, in 2007 a genome‐wide association study in Iceland using more than 300 000 markers [single nucleotide polymorphisms (SNPs)] on a relatively small number of patients did discover that lysyl oxidase like 1 (LOXL1) on chromosome 15q24 is a major gene for XFS/XFG. These results have now largely been replicated world‐wide.
Information and the hold‐up problem
Authors: Hermalin Benjamin E. , Katz Michael L.
Published: July 2009

We examine situations in which a party must make a sunk investment prior to contracting with a second party to purchase an essential complementary input. We study how the resulting hold‐up problem is affected by the seller's information about the investing party's likely returns from its investment. Our principal focus is on the effects of the investment's being observable by the noninvesting party. We establish conditions under which the seller's ability to observe the buyer's investment harms the seller, benefits the buyer, and reduces equilibrium investment and total surplus. We also note conditions under which investment and welfare rise when investment is observable.
Avoiding market dominance: product compatibility in markets with network effects
Authors: Chen Jiawei , Doraszelski Ulrich , Harrington, Jr. Joseph E.
Published: July 2009

As is well recognized, market dominance is a typical outcome in markets with network effects. A firm with a larger installed base offers a more attractive product which induces more consumers to buy its product which produces a yet bigger installed base advantage. Such a setting is investigated here but with the main difference that firms have the option of making their products compatible. When firms have similar installed bases, they make their products compatible in order to expand the market. Nevertheless, random forces could result in one firm having a bigger installed base, in which case the larger firm may make its product incompatible. We find that strategic pricing tends to prevent the installed base differential from expanding to the point that incompatibility occurs. This pricing dynamic is able to neutralize increasing returns and avoid the emergence of market dominance.
Multiobjective Robust Regulating and Protecting Control for Aeroengines
Authors: Yu Daren , Liu Xiaofeng , Bao Wen , Xu Zhiqiang
Published: July 2009

The multiobjective regulating and protecting control method presented here will enable improved control of multiloop switching control of an aeroengine. The approach is based on switching control theory, the switching performance objectives and the strategy are given, and a family of H∞ proportional-integral-derivative controllers was designed by using linear matrix inequality optimization algorithm. The simulation shows that using the switching control design method not only can improve the dynamic performance of the engine control system but also can guarantee the stability in some peculiar occasions.
Design Procedure of a Novel Microturbine Low NOx Conical Wire-Mesh Duct Burner
Authors: Ramadan Omar B. , Gauthier J. E. Donald , Hughes Patrick M. , Brandon Robert
Published: July 2009

Nowadays, air pollution and climate change have become a global environmental problem. As a result, government regulations worldwide are becoming increasingly stringent. This has led to an urgent need to develop new designs and methods for improving combustion systems to minimize the production of toxic emissions, such as nitrogen oxides. Microturbine based cogeneration units are one of the interesting alternatives for combined electrical power and heat generation (CHP). Microturbine CHP technology still needs to be developed to increase efficiency and heat-to-power ratio and to improve operating flexibility. This can all be obtained by adding a duct burner to the CHP unit. This paper documents the design process for a novel low NOx conical wire-mesh duct burner for the development of a more efficient microcogeneration unit. This burner provides the thermal energy necessary to raise the microturbine exhaust gas temperature to increase the heat recovery capability. The duct burner implements both lean premixed and surface combustion techniques to achieve low NOx and CO emission levels. The design process includes a set of preliminary design procedures relating the use of empirical and semiempirical models. The preliminary design procedures were verified and validated for key components, such as the duct burner premixer, using the laser sheet illumination (LSI) technique. The LSI was used to study the mixing process inside the premixer fitted with different swirlers. The designed duct burner successfully operated in a blue flame mode over a wide range of conditions with NOx emissions of less than 5 ppmv and CO emissions of less than 10 ppmv (corrected to 15% O2).
High-Temperature Properties of Nuclear Graphite 1
Authors: Albers Tracy L.
Published: July 2009

The unique combination of physical properties inherent to graphite makes it an attractive material for use as a moderator in high-temperature nuclear reactors. High-temperature physical properties of three nuclear-grade graphites manufactured by GrafTech International Holdings Inc. (GrafTech, Parma, OH), PCEA™, PCIB-SFG™, and PPEA™, have been determined experimentally and are presented here. Tensile strength, Young’s modulus, thermal conductivity, specific resistance, and coefficient of thermal expansion (CTE) data are collected at temperatures from 25°C to as high as 2000°C, and are found to be consistent with classical graphite behavior.
Mixing Conditions in the Lower Plenum and Core Inlet of a Boiling Water Reactor
Authors: Tinoco Hernan , Ahlinder Stefan
Published: July 2009

A thermal mixing analysis of the downcomer, main recirculation pumps (MRPs) and lower plenum of Forsmark’s Unit 3 has been carried out with three separate computational fluid dynamics models. Several difficulties with the boundary conditions have been encountered, particularly with the MRP model. The results obtained predict stable temperature differences of around 8 K at the core inlet. Such large temperature differences have never been observed at Forsmark nuclear power plant (NPP). Temperature measurements at four positions above the reactor pressure vessel (RPV) bottom give the mean value used as the core inlet temperature for core analyses. Even if the temperature transmitters used are rather slow and inaccurate, they should be able to detect such large temperature differences that may lead to fuel damage. The only damage reported at Forsmark NPP since the implementation of liner cladding in fuel design is that caused by mechanically induced debris fretting (threadlike particles). Also, the difficulties with the connection of the models throw some doubt on the accuracy of these predictions. A completely connected model of the same RPV volume covered by the separate models predicts temperature differences at core inlet that are almost one-fourth of those mentioned above, i.e., approximately 2.5 K. Most of the mixing occurs downstream of the MRP diffusers, at the lower plenum “inlet.” This prediction divergence seems to arise from an impossibility of a correct transfer of complete three-dimensional flow field properties by means of boundary conditions defined at a two-dimensional inlet section.
Investigation of High-Temperature Printed Circuit Heat Exchangers for Very High Temperature Reactors
Authors: Mylavarapu Sai , Sun Xiaodong , Figley Justin , Needler Noah , Christensen Richard
Published: July 2009

Very high-temperature reactors require high-temperature (900–950°C) and high-integrity heat exchangers with high effectiveness during normal and off-normal conditions. A class of compact heat exchangers, namely, the printed circuit heat exchangers (PCHEs), made of high-temperature materials and found to have these above characteristics, are being increasingly pursued for heavy duty applications. A high-temperature helium test facility, primarily aimed at investigating the heat transfer and pressure drop characteristics of the PCHEs, was designed and is being built at Ohio State University. The test facility was designed to facilitate operation at temperatures and pressures up to 900°C and 3 MPa, respectively. Owing to the high operating conditions, a detailed investigation on various high-temperature materials was carried out to aid in the design of the test facility and the heat exchangers. The study showed that alloys 617 and 230 are the leading candidate materials for high-temperature heat exchangers. Two PCHEs, each having 10 hot plates and 10 cold plates, with 12 channels in each plate, were fabricated from alloy 617 plates and will be tested once the test facility is constructed. Simultaneously, computational fluid dynamics calculations have been performed on a simplified PCHE model, and the results for three flow rate cases of 15, 40, and 80 kg/h at a system pressure of 3 MPa are discussed. In summary, this paper focuses on the study of the high-temperature materials, the design of the helium test facility, the design and fabrication of the PCHEs, and the computational modeling of a simplified PCHE model.
Optimum Planning of Electricity Production
Authors: Cerri Giovanni , Gazzino Marco , Iacobone Francesca Alessandra , Giovannelli Ambra
Published: July 2009

The problem of planning the production of a pool of power plants has been deeply investigated. Maintenance management and load allocation problems have been assumed as crucial aspects for achieving maximum plant profitability. A production-planning approach has been developed, and genetic algorithm techniques have been adopted to implement the developed approach. Life consumption of gas turbines’ hot-section components has been considered as a key element required in simulating plants’ behaviors. As a result, a deterioration model has been developed and included into the planning algorithm. The developed approach takes market scenarios, as well as actual statuses and performances of plant components into account. The plants’ physical models are developed on a modular approach basis and provide the operating parameters required by the planning algorithm. Neural network techniques have been applied to speed up the simulation. Economic implications related to maintenance strategies, including postponement or anticipation of maintenance interventions, are investigated and the results obtained by the numerical simulation are presented and widely discussed.
Softening Instability: Part I—Localization Into a Planar Band
Authors: Bazˇant Zdeneˇk P.
Published: July 2009

Distributed damage such as cracking in heterogeneous brittle materials may be approximately described by a strain-softening continuum. To make analytical solutions feasible, the continuum is assumed to be local but localization of softening strain into a region of vanishing volume is precluded by requiring that the softening region, assumed to be in a state of homogeneous strain, must have a certain minimum thickness which is a material property. Exact conditions of stability of an initially uniform strain field against strain localization are obtained for the case of an infinite layer in which the strain localizes into an infinite planar band. First, the problem is solved for small strain. Then a linearized incremental solution is obtained taking into account geometrical nonlinearity of strain. The stability condition is shown to depend on the ratio of the layer thickness to the softening band thickness. It is found that if this ratio is not too large compared to 1, the state of homogeneous strain may be stable well into the softening range. Part II of this study applies Eshelby’s theorem to determine the conditions of localization into ellipsoidal regions in infinite space, and also solves localization into circular or spherical regions in finite bodies.
Softening Instability: Part II—Localization Into Ellipsoidal Regions
Authors: Bazˇant Zdeneˇk P.
Published: July 2009

Extending the preceding study of exact solutions for finite-size strain-softening regions in layers and infinite space, exact solution of localization instability is obtained for the localization of strain into an ellipsoidal region in an infinite solid. The solution exploits Eshelby’s theorem for eigenstrains in elliptical inclusions in an infinite elastic solid. The special cases of localization of strain into a spherical region in three dimensions and into a circular region in two dimensions are further solved for finite solids — spheres in 3D and circles in 2D. The solutions show that even if the body is infinite the localization into finite regions of such shapes cannot take place at the start of strain-softening (a state corresponding to the peak of the stress-strain diagram) but at a finite strain-softening slope. If the size of the body relative to the size of the softening region is decreased and the boundary is restrained, homogeneous strain-softening remains stable into a larger strain. The results also can be used as checks for finite element programs for strain-softening. The present solutions determine only stability of equilibration states but not bifurcations of the equilibrium path.
On a Modified Hellinger/Reissner Variational Theorem for the Analysis of Elastoplastic Solids
Authors: Karamanlidis Dimitrios
Published: July 2009

A new general variational theorem is proposed for the analysis of elastoplastic solids. By utilizing the method of Lagrangian multipliers, a Hellinger/Reissner-type theorem is derived wherein the yield criterion along with the flow rule are satisfied a posteriori as Euler/Lagrange equations. The proposed formulation represents a rational generalization of the classical Hellinger/Reissner variational theorem for it treats all relevant field equations for an elastoplastic boundary-value problem as natural constraints.
The Interior Solution for Linear Problems of Elastic Plates
Authors: Gregory R. D. , Wan F. Y. M.
Published: July 2009

Necessary conditions have been established recently for the prescribed data along the cylindrical edge(s) of an elastic flat plate to induce only an exponentially decaying elastostatic state. The present paper describes how these conditions may be used to determine the interior solution (or its various thin and thick plate theory approximations) of plate problems. The results in turn show that the necessary conditions for a decaying state are also sufficient conditions. Boundary conditions for the interior solution of circular plate problems with edgewise nonuniform boundary data are discussed in detail and then applied to two specific problems. One of them is concerned with a circular plate compressed by two equal and opposite point forces at the plate rim. The solution process for this problem illustrates for the first time how the stretching action in the plate interior induced by transverse loads can be properly analyzed.
Debondings at a Semielliptic Rigid Inclusion on the Rim of a Half Plane
Authors: Hasebe N. , Tsutsui S. , Nakamura T.
Published: July 2009

An elastic half plane with a semielliptic rigid inclusion is analyzed as a mixed boundary value problem with a clamped edge. A rational mapping function of a sum of fractional expressions and the complex stress functions are used for the analysis. The debondings emanated from both ends of the semielliptic inclusion under uniform tension is examined and singular values of the stress at the debonded tips are obtained. By using these values, it is examined for some elliptical shapes how the debonding propagates. The stress values at the base of the semielliptic inclusion are also examined. Even if the loading is uniform compression, the debonding may occur at the base.
Damage Coupled With Heat Conduction in Uniaxially Reinforced Composites
Authors: Weitsman Y.
Published: July 2009

This paper presents a continuum damage model for a unidirectionally reinforced composite based upon fundamental concepts of continuum mechanics and irreversible thermodynamics. Damage is incorporated by two symmetric, second-rank, tensor-valued, internal state variables which represent the total areas of “active” and “passive” cracks contained within a representative material volume element. Constitutive relations are derived for both the mechanical response and heat flux in the presence of damage. It is shown that damage growth contributes to dissipation in the coupled heat conduction process. A specific fracture mechanics solution is employed to relate “microlevel” crack growth processes to “macrolevel” damage growth expressions. This approach lends itself to a probabilistic formulation of the continuum damage model.
A Statistical Study of Generalized Cell Mapping
Authors: Sun Jian-Qiao , Hsu C. S.
Published: July 2009

In this paper a statistical error analysis of the generalized cell mapping method for both deterministic and stochastic dynamical systems is examined, based upon the statistical analogy of the generalized cell mapping method to the density estimation. The convergence of the mean square error of the one step transition probability matrix of generalized cell mapping for deterministic and stochastic systems is studied. For stochastic systems, a well-known trade-off feature of the density estimation exists in the mean square error of the one step transition probability matrix, which leads to an optimal design of generalized cell mapping for stochastic systems. The conclusions of the study are illustrated with some examples.
A Recursive Householder Transformation for Complex Dynamical Systems With Constraints
Authors: Amirouche F. M. L. , Jia Tongyi , Ider Sitki K.
Published: July 2009

A new method is presented by which equations of motion of complex dynamical systems are reduced when subjected to some constraints. The method developed is used when the governing equations are derived using Kane’s equations with undetermined multipliers. The solution vectors of the constraint equations are determined utilizing the recursive Householder transformation to obtain a Pseudo-Uptriangular matrix. The most general solution in terms of new independent coordinates is then formulated. Methods previously used for handling such systems are discussed and the new method advantages are illustrated. The procedures developed are suitable for computer automation and especially in developing generic programs to study a large class of systems dynamics such as robotics, biosystems, and complex mechanisms.
On the Transverse Twisting of Shallow Spherical Ring Caps
Authors: Reissner E.
Published: July 2009

The problem of transverse twisting of a shallow spherical shell with a small circular hole is solved, in generalization of the corresponding problem of a flat plate. The solution is of interest as a closed-form solution of an unsymmetrical stress concentration problem, with quantitative features depending on its boundary-layer behavior for large values of a relevant parameter. The problem is also of interest as an example of applicability of a previously proposed asymptotic procedure where interior contributions and edge-zone contributions are determined in sequence rather than simultaneously.
Stability of a Beam on an Elastic Foundation Subjected to a Nonconservative Load
Authors: Celep Z.
Published: July 2009

In this investigation, the influence of a Winkler type of elastic foundation on the stability of the cantilever beam subjected to a nonconservative load which consists of a vertical and a follower components is studied. In addition to the common transverse foundation modulus, a rotatory foundation modulus is considered. Approximate solution is obtained by using Galerkin’s method. Numerical calculation are reported and displayed for various combinations of the nonconservativeness parameter, transverse and rotatory modulus of the foundation, distance of the point of application of the load and that of the transverse spring. As a result of the numerical study unexpected feature of stability of the cantilever beam in contrast to the behavior of the column is identified.
Pressure-Shear Impact of 6061-T6 Aluminum
Authors: Kim K. S. , Clifton R. J.
Published: July 2009

Experimental results are presented for impact of two parallel plates of 6061-T6 Aluminum, skewed at an angle of 26.6° from the axis of the projectile. A transverse displacement interferometer (TDI) [1] with a 200 lines/mm grating is used to monitor the transverse motion of the rear surface of the aluminum target plate. Two first-order diffracted laser beams are used for this TDI with a resulting sensitivity of 2.5 μm per fringe. In addition the normal motion of the rear surface is monitored simultaneously by means of a velocity interferometer [2] in which the zeroth-order diffracted beam is used as the beam reflected from a moving mirror. Comparison of the velocity-time profiles of the target rear surface with those predicted by the analysis given by Abou-Sayed and Clifton [17] indicates that the computed transverse velocity-time profiles have regions of steeper slope than observed in the experiments. This discrepancy appears to be mainly due to the inadequacy of the assumption of isotropic hardening and the Huber-Mises yield function in the analysis [17]. The sensitivity of the transverse velocity profiles to the plastic flow characteristics of the material suggests that the pressure-shear impact experiment, when used with a TDI, is a good technique for the study of material properties at very high strain rates (104 ∼ 105 sec−1) and under postshock conditions.
Effect of Transverse Shear and Rotatory Inertia on Large Amplitude Vibration of Anisotropic Skew Plates: Part 2—Numerical Results
Authors: Sathyamoorthy M. , Chia C. Y.
Published: July 2009

Based on the single-mode analysis, solutions to the governing equations developed in Part 1 of this paper are presented for various boundary conditions by use of Galerkin’s method and the Runge-Kutta numerical procedure. Excellent agreement is found between the present results and those available for nonlinear bending and large amplitude vibration of skew plates. The present results for moderately thick anisotropic skew plates indicate significant influences of the transverse shear deformation, orientation angle, skew angle, and side ratio on the large amplitude vibration behavior of certain fiber-reinforced composite skew plates.
Nonlinear Contact Geometry Effects on Wheelset Dynamics
Authors: Burton T. D. , Whitman A. M.
Published: July 2009

The nonlinear dynamic behavior of a simply restrained railway vehicle wheelset on tangent track is investigated. Nonlinearities due to the kinematics of wheel/rail contact (excluding flange contact) and creep force variation with creepage are considered for mildly noncircular wheel and rail profiles. The general equations of lateral and yawing motion of the wheelset are derived. These are then simplified by considering both normalized amplitude ε of the motion and angle of wheel/rail contact in the undisturbed position α0 as small parameters. Asymptotic solutions describing the influence of the nonlinearities on the stability and frequency of wheelset motion are obtained using the method of multiple time scales. The results are used to derive conditions for which a linear creep force model is valid.
The Dynamical Characteristics of a Gyroscope With a Tuned Elastic Suspension
Authors: Fox C. H. J. , Burdess J. S.
Published: July 2009

This study investigates the dynamics of a gyroscope rotor, supported on a “heavy” elastic suspension, using a mathematical model which allows the gyroscope to be treated as a two-degree-of-freedom rigid body on a light suspension. The natural frequencies are functions of spin rate and it is shown that the lower natural frequency can be reduced to zero by appropriate selection of suspension parameters. In this condition the gyroscope is “tuned” and could provide a useful inertial reference. Some problems associated with predicting the tuning speed of a practical gyroscope are highlighted.
Modal Identities for Elastic Bodies, With Application to Vehicle Dynamics and Control
Authors: Hughes P. C.
Published: July 2009

It is a standard procedure to analyze a flexible vehicle in terms of its vibration frequencies and mode shapes. However, the entire mode shape is not needed per se, but two integrals of the mode shape, pi and hi, which correspond to the momentum and angular momentum in Mode i. Together with the natural frequencies ωi, these modal parameters satisfy several important identities, 25 of which are derived in this paper. Expansions in terms of both “constrained” and “unconstrained” modes are considered. A simple illustrative example is included. The paper concludes with some remarks on the theoretical and practical utility of these results, and several potential extensions to the theory are suggested.
A Theory of Index for Point Mapping Dynamical Systems
Authors: Hsu C. S.
Published: July 2009

Dynamical systems governed by discrete time-difference equations are referred to as point mapping dynamical systems in this paper. Based upon the Poincare´ theory of index for vector fields, a theory of index is established for point mapping dynamical systems. Besides its intrinsic theoretic value, the theory can be used to help search and locate periodic solutions of strongly nonlinear systems.
An Analysis of Delamination in Angle-Ply Fiber-Reinforced Composites
Authors: Wang S. S.
Published: July 2009

A study of the mechanics and failure modes of delamination initiated from a surface flaw in angle-ply fiber-reinforced composites is presented. The analysis employs a hybrid-stress finite-element method including a crack-tip singular element with its field variables expressed by Muskhelishvili’s complex stress functions. Solutions are obtained for the delaminated composites with various laminate parameters. The results elucidate unique and important characteristics of delamination crack-tip response and interlaminar stress transfer mechanisms. Of particular interest are the mixed-mode stress-intensity factors associated with the delamination crack. The influence of ply orientation on KI and KII and their effects on subsequent crack extension are discussed.
Flow in Narrow Curved Channels
Authors: Wang C.-Y.
Published: July 2009

The flow through narrow, arbitrarily curved channels is formulated using intrinsic coordinates. An exact solution exists for constant curvature or circular arc boundaries. A perturbation scheme is used for the case of small, periodic curvature. The velocities and flow rates depend on both the curvature amplitude and the wave number. It is found that for a given pressure gradient per arc length, the flow may be larger for periodically curved channels than that of straight channels.
Rubber Covered Rolls—The Nonlinear Elastic Problem
Authors: Batra R. C.
Published: July 2009

The problem of the indentation of a rubberlike layer bonded to a rigid cylinder and indented by another rigid cylinder is analyzed. The rubberlike layer is assumed to be made of a homogeneous Mooney-Rivlin material. The materially and geometrically nonlinear problem is solved by using the finite-element code developed by the author. Results computed and presented graphically include the pressure profile at the contact surface, stress distribution at the bond surface and the deformed shape of the indented surface.
An Application of Mixture Theory to Particulate Sedimentation
Authors: Hill C. D. , Bedford A. , Drumheller D. S.
Published: July 2009

Equations for two-phase flow are used to analyze the one-dimensional sedimentation of solid particles in a stationary container of liquid. A derivation of the equations of motion is presented which is based upon Hamilton’s extended variational principle. The resulting equations contain diffusivity terms, which are linear in the gradient of the particle concentration. It is shown that the solution of the equations for steady sedimentation is stable under small perturbations. Finally, finite-difference solutions of the equations are compared to the data of Whelan, Huang, and Copley for blood sedimentation.
Nonuniqueness in Contained Plastic Deformation
Authors: Hodge P. G. , White D. L.
Published: July 2009

It is well known that in a well-defined load-controlled boundary-value problem for an elastic/perfectly-plastic structure the displacements are unique if the structure is everywhere elastic, and they are not unique at the yield-point load when the structure becomes a mechanism. The present paper is concerned with the range of contained plastic deformation between these two extremes. Several examples are given in which more than one displacement field exists for loads less than the yield-point load. The significance of this phenomenon is commented on from a physical, mathematical, and computational point of view.
A Useful Theorem for Constructing Convex Yield Functions
Authors: Yang W. H.
Published: July 2009

Known yield functions have been constructed in the three-dimensional space of principal stresses. Their convexity in the six-dimensional space of the stress components is only conjectured. Mathematical theorems of convexity are known for functions of Hermitian matrices but have not been applied to yield functions. In this paper, Drucker’s hypothesis is properly restated, leading to convexity requirement for yield functions of elastoplastic materials. Then a special version of a known convexity theorem is presented. The theorem can be applied to construct yield functions for isotropic materials. Examples of such applications are extended to some known yield functions and other theoretically acceptable new ones.
On the Internal Stresses in a Half Plane and a Layer Containing Localized Inelastic Strains or Inclusions
Authors: Chiu Y. P.
Published: July 2009

An Airy stress function has been used to formulate the internal stresses in an isotropic body in terms of the distribution of inelastic strains under the conditions of plane stress and plane strain. Formulation has been first obtained for the stresses in closed forms for an infinite plane containing a rectangular zone with uniform inelastic strains. Using method of Fourier transforms, analytic solutions have been obtained for the stresses due to the inclusion in a half plane with free, fixed and rigid, frictionless boundaries as well as in a layer lying on a rigid, frictionless foundation. Elastic strain energy has been formulated in closed form for the rectangular domain with uniform inelastic strain in an infinite plane and a half plane.
A No-Slip Interface Crack
Authors: Mak A. F. , Keer L. M. , Chen S. H. , Lewis J. L.
Published: July 2009

Adhesive fracture of an interdigitated or very rough interface is investigated by considering an interface crack with no-slip zones. Both the normal and the shear stresses are singular at the crack tip with the Mode II stress-intensity factor being generally smaller than that of the Mode I.
Diffraction of Antiplane Shear Waves by an Edge Crack
Authors: Stone S. F. , Ghosh M. L. , Mal A. K.
Published: July 2009

The diffraction of time harmonic antiplane shear waves by an edge crack normal to the free surface of a homogeneous half space is considered. The problem is formulated in terms of a singular integral equation with the unknown crack opening displacement as the density function. A numerical scheme is utilized to solve the integral equation at any given finite frequency. Asymptotic solutions valid at low and high frequencies are obtained. The accuracy of the numerical solution at high frequencies and of the high frequency asymptotic solution at intermediate frequencies are examined. Graphical results are presented for the crack opening displacement and the stress intensity factor as functions of frequency and the incident angle, Expressions for the far-field displacements at high and low frequencies are also presented.
Sanders’ Energy-Release Rate Integral for Arbitrarily Loaded Shallow Shells and Its Asymptotic Evaluation for a Cracked Cylinder
Authors: Nicholson J. W. , Simmonds J. G.
Published: July 2009

Sanders’ path-independent, energy-release rate integral I is specialized to an arbitrarily loaded shallow shell containing a stress-free void, assuming linear theory. Two forms of I are given. When the void is a crack, one form reduces to integrals over circles of vanishing radius centered at the tips and is expressible in terms of bending and stretching stressintensity factors. The other form reduces to an integral along the crack. For an elastically isotropic cylindrical shell containing a longitudinal crack and subject to a uniform bending stress at large distances from the crack, the dimensionless form of I depends on Poisson’s ratio v and a dimensionless crack length λ. When λ is small the shell is nearly flat; when λ is large the shell is very thin. An asymptotic formula is obtained for I as λ → ∞. This is done by reducing the boundary-value problem to a coupled set of singular integral equations, scaling, taking the limit as λ → ∞ to obtain inner and outer integral equations, solving the outer equations analytically, and, finally, evaluating I along the crack where the outer solutions dominate. As the evaluation of I does not require an explicit solution of the inner integral equations, an apparently intractible coupled Wiener-Hopf problem is evaded.
Shear-Lag Effect in Sandwich Panels With Stiffeners Under Three-Point Bending
Authors: Kemmochi K. , Akasaka T. , Hayashi R. , Ishiwata K.
Published: July 2009

In this paper, a modified theory based upon Reissner’s procedure for the shear-lag effect of the sandwich panel is presented, which includes the effects of the anisotropy of the faces and the shearing rigidity of the core. In order to verify this theory, bending experiments were performed with sandwich panels composed of a soft core, stiffeners, and orthotropic faces. It was found that the effective bending rigidity calculated from this theory was lower than that derived from the classical bending theory and that the theoretical strain distribution on the faces agreed well with the experimental results.
Torsion of Pretwisted Beams Due to Axial Loading
Authors: Hodges D. H.
Published: July 2009

The equations for static torsional deformation of a pretwisted beam under axial loading are obtained from the principle of virtual work. Theory appropriate for a curvilinear coordinate system is used, and warp is included in the analysis from the outset. The present formulation yields the expected result that a pretwisted beam of noncircular cross section will untwist under tensile loading. A slender-beam approximation of the present theory is offered, and the resulting torsion-extension coupling terms are similar but not identical to those in common use in analyses of rotating blades. Numerical results indicate that the effect is not negligible when the ratio of shear modulus to extension modulus is small.
In-Plane Vibration and Buckling of a Rotating Beam Clamped Off the Axis of Rotation
Authors: Peters D. A. , Hodges D. H.
Published: July 2009

Some work on the in-plane vibrations and buckling of rotating beams, clamped off the axis of rotation, is unclear as to behavior in the limit of small stiffness and small off-clamping. In this paper, asymptotic expansion formulas are developed for both small and large values of stiffness and off-clamping parameters. A composite expansion formula is also introduced as an engineering approximation to the buckling curve for all values of parameters. The present results agree quite well with an exact numerical solution and indicate that buckling can occur for arbitrarily small stiffness and off-clamping.
Hoff’s Problem in a Probabilistic Setting
Authors: Elishakoff Isaac
Published: July 2009

Hoff’s problem—that of investigation of the maximum load supported by an elastic column in a compression test—is considered in a probabilistic setting. The initial imperfections are assumed to be Gaussian random fields with given mean and autocorrelation functions, and the problem is solved by the Monte Carlo Method. The Fourier coefficients of the expansion for the initial imperfection function are simulated numerically; for each realization of the initial imperfection function, the maximum load supported by an elastic column in a compression test is found by the solution of a set of coupled nonlinear differential equations. For slightly imperfect columns, the closed solution is given in terms of Bessel and Lommel functions and turns out to compare well with the result of numerical integration. Results of the Monte Carlo solution are used in constructing the reliability function at a specified load. Reliability functions for different manufacturing processes (represented by different autocorrelation functions with equal variance) are calculated; design requirement suggests then that, other conditions being equal, the preference should be given to the manufacturing process resulting higher reliability.
Controllability and Observability of Linear Matrix-Second-Order Systems
Authors: Hughes P. C. , Skelton R. E.
Published: July 2009

This paper studies the controllability and observability of the system Mq¨ + Gq˙ + Kq = Bu, where M is symmetric and positive-definite, G is skew-symmetric and K is symmetric. In all cases, the output equation is y = Pq + Rq˙. This special structure is exploited to derive relatively simple controllability and observability conditions which are shown to provide important insights on the modal behavior of the system and to furnish information on the number and positioning of sensors and actuators.
Theory of Index for Dynamical Systems of Order Higher Than Two
Authors: Hsu C. S.
Published: July 2009

This paper is concerned with the generalization of Poincare´’s theory of index to systems of order higher than two. The basic tool used in the generalization is the concept of the degree of a map. In topology this concept has been used to discuss the index of a vector field. In this paper we shall use the degree of a map concept to present a theory of index for higher-order systems in a form which might make it more accessible to engineers for applications. The theory utilizes the notion of the index of a hypersurface with respect to a given vector field. After presenting the theory, it is applied to dynamical systems governed by ordinary differential equations and also to dynamical systems governed by point mappings. Finally, in order to show how the abstract concept of the degree of a map, hence the index of a surface, may actually be evaluated, illustrative procedures of evaluation for two kinds of hypersurfaces are discussed in detail and an example of application is given.
Asymmetric Boundary Layer on a Nonisothermally Heated Cone
Authors: Yao L.-S. , Catton I. , McDonough J. M.
Published: July 2009

The development of a three-dimensional boundary layer along a heated cone is analyzed. The surface of the cone is heated under the condition of constant wall heat flux. The perturbation solution is obtained for the flow close to the leading edge where the buoyancy force can be treated as a higher-order effect. A finite-difference solution is obtained for the flow far downstream from the leading edge where buoyancy is one of the cominant forces. The numerical results clearly describe the boundary-layer development along heated cones of different cone angles as well as the heat transfer rate. Boundary-layer stability is briefly discussed in terms of the boundary-layer shape factor.
The Flow of a Non-Newtonian Fluid Past Projections and Depressions
Authors: Mir-Mohamad-Sadegh A. , Rajagopal K. R.
Published: July 2009

The plane flow of a homogenous incompressible second-order fluid past projections or depressions of arbitrary shape is considered. A numerical technique based on a boundary integral equation is developed and the problem of the flow past a rectangular slot of depth d and width W is solved.
Harmonic Wave Propagation in a Periodically Layered, Infinite Elastic Body: Plane Strain, Numerical Results
Authors: Delph T. J. , Herrmann G. , Kaul R. K.
Published: July 2009

Numerical results are presented for the dispersion spectrum for harmonic wave propagation in an unbounded, periodically layered elastic body in a state of plane strain. Both real and complex branches are considered. The spectrum is shown to be multiple-valued and quite intricate in detail. Some analytical properties of the Floquet surface are also discussed.
Numerical Modeling of Dynamic Crack Propagation in Finite Bodies, by Moving Singular Elements—Part 2: Results
Authors: Nishioka T. , Atluri S. N.
Published: July 2009

Using the moving-singularity finite-element method described in Part 1 of this paper, several problems of dynamic crack propagation in finite bodies have been analyzed. Discussions of the effects of wave interactions on the dynamic stress-intensity factors are presented. The obtained numerical results are compared with the corresponding infinite domain solutions and other available numerical solutions for finite domains.
Elastic Instability of an Annular Plate Under Uniform Compression and Lateral Pressure
Authors: Tani J.
Published: July 2009

The elastic instability of a thin clamped annular plate which has suffered a finite axisymmetric deformation due to simultaneous loading of uniform compression and lateral pressure is studied by examining the asymmetric small free vibration in the neighborhood of the nonlinear axisymmetric equilibrium state. The problem is solved by applying a finite-difference method to the dynamic version of the nonlinear von Karman plate theory. The numerical results indicate that there are the ranges of the magnitude of combined loads under which the axisymmetric deformation of the plate becomes unstable.
The Effect of Damping on Dynamic Snap-Through
Authors: Johnson E. R.
Published: July 2009

Dynamic snap-through criteria are compared for an impulsively loaded shallow circular arch modeled as a Kelvin-Voigt material. The Budinasky-Roth criterion is used in conjunction with direct numerical integration of an approximate set of motion equations to obtain critical magnitudes of the load as a function of small viscous damping and the spatial distribution of the load. These critical magnitudes are compared to a lower bound estimate which is independent of the load distribution and damping. This lower bound is a stability-sufficiency condition formulated by Hsu. The presence of small damping significantly increases the critical magnitudes with respect to the undamped results for non-symmetric loading, and thus indicates the conservative nature of the lower bound.
Effect of Blunt Chamfers on Contact Pressure Distribution and Elastic Limit
Authors: Francis H. A.
Published: July 2009

The interfacial pressure profile is derived analytically, and the elastic load limit is evaluated numerically, for plane strain frictionless elastic contact between a flat surface and a symmetric trapezoidal body whose obtuse corners are replaced by tangent circular arcs. The shape of the pressure distribution depends only on plateau and arc widths. The results enable design of radiused chamfers to give peak-to-mean pressure ratios as low as 1.2 and elastic mean pressure limits up to 1.5 times the yield stress. Conversely, the pressure peak and elastic limit can be predicted for any microscopically blunt chamfer.
Laminar Boundary-Layer Flow Near the Entry of a Curved Circular Pipe
Authors: Yeung W. S.
Published: July 2009

The fluid mechanics of a viscous, incompressible fluid entering a circular curved pipe at large Reynolds number is investigated numerically. The flow field is divided into two regions, the boundary-layer region and the inviscid core region. The boundary layer is assumed to be laminar and the method of integral relations is used to solve the governing equations. The core region, on the other hand, is assumed irrotational and is solved by a modified version of Telenin’s method. The coupling of the two regions is accounted for through the imposition of the outer edge normal velocity as a boundary condition for the core region. Results are presented for a Reynolds number of 104 and a curvature ratio of 0.1. It has been shown that the cross flow in the core region is initially directed from the outer to the inner bend and reverses its direction downstream for the entry condition of uniform axial motion. The core velocity profiles are consistent with a recent experimental investigation, while the boundary-layer results are qualitatively similar to those of Yao and Berger, although a direct quantitative comparison is not applicable, due to the different range of Reynolds number considered.