bluuebunny/crossref_metadata_2025 huggingface dataset:
Intracellular Degradation of Elastin by Cathepsin K in Skin Fibroblasts— A Possible Role in Photoaging
Authors: Codriansky Katerine A. , Quintanilla‐Dieck Maria J. , Gan Stephanie , Keady Michelle , Bhawan Jag , Rünger Thomas M.
Published: July 2009

Solar elastosis is observed in the dermis of photoaged skin and is characterized by an accumulation of abnormal elastin in the extracellular space. Several proteases that degrade elastin in the extracellular space have been implicated in its formation. The lysosomal protease cathepsin K (catK) has recently been described to be highly expressed in skin fibroblasts under certain pathologic conditions. As cat K is one of the most potent mammalian elastases, we hypothesized that catK‐mediated intracellular elastin degradation may play a role in the formation of solar elastosis. Immunostaining of cultured skin fibroblasts incubated with labeled elastin demonstrated internalization of extracellular elastin to lysosomes and its degradation by catK. Induction of catK expression in fibroblasts was observed both in vitro and in vivo after exposure to longwave UVA. In contrast to fibroblasts from young donors, cells from old donors failed to activate catK in response to UVA. These data suggest a role of intracellular elastin degradation by catK in the formation of solar elastosis. We propose that an age‐related decline in catK activity, in particular after UV exposure, may promote the formation of actinic elastosis through a decline of orderly intracellular elastin degradation and subsequent accumulation of elastin in the extracellular space.
Retracted:Genistein improves liver function and attenuates non‐alcoholic fatty liver disease in a rat model of insulin resistance
Authors: MOHAMED SALIH Sumiyabanu , NALLASAMY Palanisamy , MUNIYANDI Pooranaperundevi , PERIYASAMI Viswanathan , CARANI VENKATRAMAN Anuradha
Published: July 2009

Background: The high fructose‐fed rat is widely used as a model of insulin resistance. Genistein, a soy isoflavone, has been shown to improve insulin sensitivity in this model. The present study investigated whether genistein could prevent fatty liver disease in this model.

Methods: Male Wistar rats were fed a diet containing starch (control) or 60% fructose (insulin‐resistant model). Fifteen days later, rats in each dietary group were divided into two groups and were treated with either genistein (1 mg/kg per day) in dimethylsulfoxide (DMSO) or 30% DMSO alone. After 60 days, markers of liver injury, oxidative stress, interleukin (IL)‐6, tumor necrosis factor (TNF)‐α, lipids, lipoprotein profile, nitrite, and nitrosothiol in the plasma and liver were quantified. Liver sections were examined for 3‐nitrotyrosine (3‐NT) expression and pathological lesions.

Results: Fructose‐fed rats displayed hyperlipidemia, significant changes in plasma lipoprotein profile, and increases in IL‐6 and TNF‐α levels compared with control. In addition, the accumulation of lipids, liver injury, a decline in liver function, inactivation of the glyoxalase system, depletion of antioxidants, and increased 3‐NT expression were observed in the fructose‐fed group. Administration of genistein to fructose‐fed rats significantly reduced these biochemical and histological abnormalities.

Conclusions: Genistein activates the antioxidant profile, decreases IL‐6 and TNF‐α concentrations, prevents oxidative damage, and ameliorates fatty liver in insulin‐resistant rats.
Television watching and incident diabetes: Findings from the European Prospective Investigation into Cancer and Nutrition–Potsdam Study*
Authors: FORD Earl S. , SCHULZE Matthias B. , KRÖGER Janine , PISCHON Tobias , BERGMANN Manuela M. , BOEING Heiner
Published: July 2009

Background:  The aim of the present study was to examine whether the amount of time spent watching television is a potential risk factor for incident diabetes and to what extent this association may be explained by obesity.

Methods:  We used data for 23 855 men and women from the European Prospective Investigation into Cancer and Nutrition–Potsdam Study. During an average of 7.8 years of follow‐up, 927 participants developed diabetes. Incident diabetes was identified on the basis of self‐report and was verified by contacting the patient’s attending physician. The amount of time spent watching television was self‐reported.

Results:  The mean time that the participants who developed diabetes watched television was 2.4 h/week, compared with 2.0 h/week for those who did not develop diabetes (P < 0.001). After adjusting for age, sex, educational status, smoking status, alcohol use, occupational activity, physical activity, the intake of various foods, and systolic blood pressure, the adjusted hazard ratio for diabetes among participants who watched ≥4 h/day of television compared with those who watched <1 h/day was 1.63 [95% confidence interval (CI): 1.17–2.27]. After additional adjustment for waist circumference and body mass index, the hazard ratio was reduced to 1.14 (95% CI: 0.81–1.61).

Conclusions:  In the present study, the amount of time spent watching television was an independent predictor of incident diabetes only in models that adjusted for sociodemographic characteristics, lifestyle behaviors, and systolic blood pressure. The attenuation of the association after adjusting for anthropometric measures may represent an explanatory mechanism for our findings.
A welfare analysis of spectrum allocation policies
Authors: Hazlett Thomas W. , Muñoz Roberto E.
Published: July 2009

Economic analysis of spectrum policy focuses on government revenues derived via competitive bidding for licenses. Auctions generating high bids are identified as “successful” and those with lower receipts as “fiascoes.” Yet spectrum policies that create rents impose social costs. Most obviously, rules favoring monopoly predictably increase license values but reduce welfare. This article attempts to shift analytical focus to efficiency in output markets. In performance metrics derived by comparing 28 mobile telephone markets, countries allocating greater bandwidth to licensed operators and achieving more competitive market structures are estimated to realize efficiencies that generally dominate those associated with license sales. Policies intended to increase auction receipts (e.g., reserve prices and subsidies for weak bidders) should be evaluated in this light.
Liability insurance under the negligence rule
Authors: Fagart Marie‐Cécile , Fluet Claude
Published: July 2009

We incorporate the concept of evidentiary standard to the analysis of the negligence rule under liability insurance and court errors. When the postaccident evidence is privately contractible and not too noisy, efficiency is achieved by both strict liability and a negligence rule with appropriate due care and evidentiary standards. When the evidence is not directly contractible, trial outcomes represent useful contractible information for the risk‐incentives tradeoff in the liability insurance policy. Strict liability is then inefficient and dominated by the negligence rule. The negligence rule can itself be improved upon by decoupling damages from the harm suffered by the victim.
Horizontal transmission of Nosema ceranae (Microsporidia) from worker honeybees to queens (Apis mellifera)
Authors: Higes Mariano , Martín‐Hernández Raquel , García‐Palencia Pilar , Marín Pilar , Meana Aránzazu
Published: July 2009

Horizontal transmission from worker honeybees to queens is confirmed in a laboratory essay as a possible route of Nosema ceranae infection in field colonies and pathological repercussions on honeybee queens are described. Lesions are only detected in the epithelial ventricular layer of the infected queens and death occurs within 3 weeks when the nurse workers are experimentally and collectively infected with approximately 5000 viable spores per bee. These data suggest that the higher number of infected house bees, the higher risk of transmission to queens. The presented data may explain the role of house honeybees in natural queen infection, although it is probably that a high proportion of infected house bees must be required to infect the queen.
Current status and activity regarding natural orifice translumenal endoscopic surgery (NOTES) in Japan
Authors: Kitano Seigo , Tajiri Hisao , Yasuda Kazuhiro , Ikdeda Kiichi , Sumiyama Kazuki , Nakajima Kiyokazu , Saida Yoshihisa ,   Japan NOTES working group for white paper constitution
Published: July 2009

Natural orifice translumenal endoscopic surgery (NOTES) is a new, minimally invasive technique in the field of gastroenterological surgery. Research on NOTES has rapidly progressed all over the world. A joint committee on NOTES organized by the Japan Society for Endoscopic Surgery (JSES) and the Japan Gastroenterological Endoscopy Society (JGES) established Japan NOTES to encourage the responsible development and safe adoption of NOTES into clinical practice. This paper provides an overview of the current activity in regard to NOTES in Japan.
Laparoscopic Bariatric Surgery in Asia
Authors: Chowbey Pradeep
Published: July 2009

Often coexisting in developing countries with under‐nutrition, obesity is a complex condition, with serious medical, social, psychological and economic implications1. This has led to the dual burden of fighting against both under and over‐nutrition. It is widely recognized today that bariatric surgery is the only safe and effective approach to treatment of morbid obesity5. This article discusses the scope, evolution and current status of Bariatric Surgery in Asia
Experimental Study of Oblong Exhaust Ejectors With Multiring Oblong Entraining Diffusers
Authors: Chen Qi , Birk A. M.
Published: July 2009

This paper presents experimental data for the performance of two oblong, straight, air-air ejectors with four-ring oblong entraining diffusers. The effects of inlet swirl angle, nozzle diameter, and flow temperature on the ejector pumping, backpressure, wall pressure distribution, diffuser pressure recovery, and surface film cooling effectiveness were studied. The experiments were carried out on a hot gas wind tunnel that could provide primary mass flow rates up to 2.2kg∕s at ambient temperature and 1.8kg∕s at 500°C. Velocity, pressure, and temperature were measured in the annulus upstream of the primary nozzle, on the mixing tube and diffuser walls, at the diffuser gap inlets, and at the diffuser exit. A comparison between the performance of the oblong ejector and a round ejector indicated that for a short length ejector, the oblong ejector provided better overall performance in terms of pumping and velocity and temperature distributions.
Energy and Economic Analyses of Integrated Biogas-Fed Energy Systems
Authors: Bettocchi R. , Cadorin M. , Cenci G. , Morini M. , Pinelli M. , Spina P. R. , Venturini M.
Published: July 2009

The process, which includes production, collection, carriage, and transformation of biomass into renewable fuels and then into energy (both electrical and thermal), involves a large number of decisions to select the most efficient plant layout. In order to identify the optimal solutions, models, which simulate the whole process, represent a useful and practical tool. In this paper, the energy and economic analysis of the entire process from biomass to energy production is presented. Among the different transformation processes, the thermophilic batch anaerobic digestion is considered in this paper. The analyses performed allow the comparison of the results for different scenarios characterized by different types of biomass (ensiled corn and organic fraction of municipal solid wastes), yearly mass of biomass, anaerobic digestion process parameters (number of yearly batch cycles and number of batch digesters), and type of energy systems (micro gas turbine and internal combustion engine). The results are presented in terms of classical economic indices for the investment and of producible electric and thermal energy. With respect to the economic indices, micro gas turbines allow a higher profitability than internal combustion engines, mainly because internal combustion engines require a scrubbing system to remove hydrogen sulphide from biogas. The contrary occurs with the producible electric and thermal energy. With regard to the digested substance, even if the methane yield is lower for organic fraction of municipal solid wastes than for ensiled corn, the net present values for organic fraction of municipal solid wastes are always higher than those obtained by using ensiled corn, and they are always positive, since municipal waste digestion avoids their disposal costs. The efficiency of the cogeneration process, evaluated in terms of primary energy saving index, usually shows quite high values and confirm the good capability of these systems.
Low-Temperature Combustion Within a HSDI Diesel Engine Using Multiple-Injection Strategies
Authors: Fang Tiegang , Coverdill Robert E. , Lee Chia-Fon F. , White Robert A.
Published: July 2009

Low-temperature compression ignition combustion employing multiple-injection strategies in an optical high-speed direct injection diesel engine was investigated. Heat release characteristics were analyzed. The whole cycle combustion process was visualized by imaging the natural flame luminosity. The NOx emissions were measured in the exhaust pipe. The effects of the pilot injection timing, pilot fuel quantity, main injection timing, operating load, and injection pressure on the combustion and emissions were studied. Low-temperature combustion modes were achieved by using a small pilot injection with an injection timing much earlier than top dead center (TDC) followed by a main injection after TDC. The results were compared with conventional diesel (diffusion) combustion for comparison purposes. A premixed-combustion-dominated heat release rate pattern was seen for all the low-temperature combustion cases, while a typical diffusion flame combustion heat release rate was obtained for the conventional combustion case. A highly luminous flame was observed for the conventional combustion condition while a much less luminous flame was seen for the low-temperature combustion cases. For the higher-load and lower injection pressure cases, liquid fuel being injected into low-temperature premixed flame was observed for certain cases. Compared with the conventional diffusion combustion, simultaneous reductions in soot and NOx were obtained for the low-temperature combustion mode under similar operating loads. For high-load conditions, higher NOx emissions were obtained due to higher in-cylinder temperatures. However, compared with the conventional combustion case, a significant reduction in soot was achieved for the high-load conditions, which shows that increasing injection pressure greatly reduces soot emissions.
Large Eddy Simulation of Premixed Combustion With a Thickened-Flame Approach
Authors: De Ashoke , Acharya Sumanta
Published: July 2009

A thickened-flame (TF) modeling approach is combined with a large eddy simulation (LES) methodology to model premixed combustion, and the accuracy of these model predictions is evaluated by comparing with the piloted premixed stoichiometric methane-air flame data of Chen et al. (1996, “The Detailed Flame Structure of Highly Stretched Turbulent Premixed Methane-Air Flames,” Combust. Flame, 107, pp. 233–244) at a Reynolds number Re=24,000. In the TF model, the flame front is artificially thickened to resolve it on the computational LES grid and the reaction rates are specified using reduced chemistry. The response of the thickened-flame to turbulence is taken care of by incorporating an efficiency function in the governing equations. The efficiency function depends on the characteristics of the local turbulence and on the characteristics of the premixed flame such as laminar flame speed and thickness. Three variants of the TF model are examined: the original thickened-flame model, the power-law flame-wrinkling model, and the dynamically modified TF model. Reasonable agreement is found when comparing predictions with the experimental data and with computations reported using a probability distribution function modeling approach. The results of the TF model are in better agreement with data when compared with the predictions of the G-equation approach.
A Viscoplastic Modeling Approach for MCrAlY Protective Coatings for Gas Turbine Applications
Authors: Mücke Roland
Published: July 2009

MCrAlY coatings are applied in industrial gas turbines and aircraft engines to protect surfaces of hot gas exposed components from oxidation and corrosion at elevated temperature. Apart from oxidation resistance, coatings have to withstand cracking caused by cyclic deformation since coating cracks might propagate into the substrate material and thus limit the lifetime of the parts. In this context, the prediction of the coating maximum stress and the strain range during cyclic loading is important for the lifetime analysis of coated components. Analyzing the state of stress in the coating requires the application of viscoplastic material models. A coupled full-scale cyclic analysis of substrate and coating, however, is very expensive because of the different flow characteristics of both materials. Therefore, this paper proposes an uncoupled modeling approach, which consists of a full-scale cyclic analysis of the component without coating and a fast postprocessing procedure based on a node-by-node integration of the coating constitutive model. This paper presents different aspects of the coating viscoplastic behavior and their computational modeling. The uncoupled analysis is explained in detail and a validation of the procedure is addressed. Finally, the application of the uncoupled modeling approach to a coated turbine blade exposed to a complex engine start-up and shut-down procedure is shown. Throughout the paper bold symbols denote tensors and vectors, e.g., σ stands for the stress tensor with the components σij. The superscripts (.)S and (.)C symbolize the substrate and the coating, respectively, e.g., εthS stands for the tensor of substrate thermal strain. Further symbols are explained in the text.
Flow Visualization in the Scaled Up Pebble Bed of High Temperature Gas-Cooled Reactor Using Particle Image Velocimetry Method
Authors: Lee Jae-Young , Lee Sa-Ya
Published: July 2009

The flow visualization in the complicated flow geometry of the pebble bed of the high temperature gas-cooled reactor is investigated to identify the stagnation points at which internal hot spots are expected. A particle image velocimetry method was employed to visualize flow for the pebble bed in the structure of the face centered cubic. The wind tunnel was designed to provide the same Reynolds number of 2.1614×104 as the pebble bed nuclear reactor. Scaling law determined the diameter of the pebble as 120 mm, which is two times bigger than the reference when we use air as a coolant rather than helium. The present scaled up design reduces the load of high speed imaged acquisition and the flow field measured by 4000 frames/s. It was found that the present method identified flow field successfully, including the stagnation points suspected to produce hot spots on the surface of the pebble bed. The present data are useful in evaluating the three-dimensional computational fluid dynamics analysis.
Two-Dimensional Effects in the Necking of Elastic Bars
Authors: Silling S. A.
Published: July 2009

Numerical solutions for incompressible hyperelastic bars undergoing smooth necking in plane strain show complex phenomena in which two-dimensional effects are inherently important. In long bars, the two-dimensional effects are confined to a transition zone between the necked and non-necked phases. In spite of the two-dimensional effects, the nominal stress in necked long bars is close to the Maxwell stress under certain conditions. For very long bars there are necked equilibrium deformations in which the overall stretch is less than that of the maximum in the constitutive relation.
The Weight-Function Theory for Piecewise Homogeneous Isotropic Notches in Antiplane Strain
Authors: Sham T.-L. , Bueckner H. F.
Published: July 2009

An extension of the two-dimensional weight-function theory in linear elastic crack mechanics is introduced for piecewise homogeneous isotropic notched structures under antipiane strain conditions. Using the concepts of fundamental fields and elastic reciprocity, we show that the notch-interface stress-intensity factor for a notch with the tip situated at the material interface can be computed for any antiplane strain loading through the notch-interface weight function by quadrature. Closed-form notch-interface weight functions are given for some simple geometries.
Elastic Field Around A Circular Punch
Authors: Fabrikant V. I.
Published: July 2009

A solution is called complete when the explicit expressions are derived for the field of displacements as well as stresses in an elastic body. A new method is proposed here which allows us to obtain exact and complete solutions to various contact problems in elementary functions; no integral transforms or special function expansions are involved. The method is based on the new results in potential theory obtained earlier by the author. The main potential function and the relevant Green’s functions are derived explicitly. The interaction between an arbitrarily located concentrated load and a circular flat punch is considered. The use of the method is illustrated by examples.
Finite Element Modeling of the Punch Stretching of Square Plates
Authors: Nakamachi E. , Sowerby R.
Published: July 2009

The paper presents an updated Lagrangian-type finite element procedure, formulated with reference to a surface embedded coordinated system. Membrane shell theory is employed, and an attempt is made to calculate the strain distribution incurred by a peripherally clamped square plate, when impressed by a rigid punch. Three different punch geometries were considered. The material is treated as a rate insentive, elastic work-hardening solid, which obeys the J2 flow theory; both finite deformation and normal anisotropy can be considered. A linear relationship between the Jaumann rate of Cauchy stress and the Eulerian rate of Green’s strain tensor is derived. A slip-stick model was adopted for the interfacial frictional conditions. This was achieved by considering the equilibrium of a constant strain-element node in contact with the tools, and deciding whether such a node would stick or slip under Coulomb friction conditions. It is demonstrated that the punch geometry and frictional conditions exert a strong influence on the deformation mode, and hence, upon the overall strain distribution. The predictions were checked against experimental observations when stretch-forming square plates of pure aluminum, 0.5-mm thick. Contours of equal height on the deforming blanks were determined using a Moir´e fringe technique. The agreement between theory and experiment was favorable.
Pseudodissipative Systems I: Stability of Generalized Equilibria
Authors: Walker J. A.
Published: July 2009

A class of mechanical systems called “pseudodissipative” is defined in terms of the Lagrange formulation of dynamics. Generalized equilibria of such systems are studied with regard to their stability properties. Both broad results and simple results are obtained.
Exact Stationary Response Solution for Second Order Nonlinear Systems Under Parametric and External White Noise Excitations: Part II
Authors: Lin Y. K. , Cai Guoqiang
Published: July 2009

A systematic procedure is developed to obtain the stationary probability density for the response of a nonlinear system under parametric and external excitations of Gaussian white noises. The procedure is devised by separating the circulatory portion of the probability flow from the noncirculatory flow, thus obtaining two sets of equations that must be satisfied by the probability potential. It is shown that these equations are identical to two of the conditions established previously under the assumption of detailed balance; therefore, one remaining condition for detailed balance is superfluous. Three examples are given for illustration, one of which is capable of exhibiting limit cycle and bifurcation behaviors, while another is selected to show that two different systems under two differents sets of excitations may result in the same probability distribution for their responses.
Approximate Decoupling of the Equations of Motion of Linear Underdamped Systems
Authors: Shahruz S. M. , Ma F.
Published: July 2009

One common procedure in the solution of a normalized damped linear system with small off-diagonal damping elements is to replace the normalized damping matrix by a selected diagonal matrix. The extent of approximation introduced by this method of decoupling the system is evaluated, and tight error bounds are derived. Moreover, if the normalized damping matrix is diagonally dominant, it is shown that decoupling the system by neglecting the off-diagonal elements indeed minimizes the error bound.
Synchronized Periodic Solutions of a Class of Periodically Driven Nonlinear Oscillators
Authors: Mahmoud Gamal M. , Bountis Tassos
Published: July 2009

We consider a class of parametrically driven nonlinear oscillators: x¨ + k1x + k2f(x,x˙)P(Ωt) = 0, P(Ωt + 2π) = P(Ωt)(*) which can be used to describe, e.g., a pendulum with vibrating length, or the displacements of colliding particle beams in high energy accelerators. Here we study numerically and analytically the subharmonic periodic solutions of (*), with frequency 1/m ≅ √k1, m = 1, 2, 3,…. In the cases of f(x,x˙) = x3 and f(x,x˙) = x4, with P(Ωt) = cost, all of these so called synchronized periodic orbits are obtained numerically, by a new technique, which we refer to here as the indicatrix method. The theory of generalized averaging is then applied to derive highly accurate expressions for these orbits, valid to the second order in k2. Finally, these analytical results are used, together with the perturbation methods of multiple time scaling, to obtain second order expressions for regions of instability of synchronized periodic orbits in the k1, k2 plane, which agree very well with the results of numerical experiments.
Minimum-Weight Design of Thin-Walled Cylinders Subject to Flexural and Torsional Stiffness Constraints
Authors: Parbery R. D. , Karihaloo B. L.
Published: July 2009

We consider the problem of determining the cross-sectional shape of a thin-walled cylinder of constant (unknown) wall thickness and given contour length that uses the least possible material to achieve prescribed minimum stiffness in torsion and bending. The corresponding variational problem is shown to belong to a class with nonadditive functionals whose Euler equation is an integrodifferential equation. Cross-sectional shapes are presented for various stiffness ratios and compared with circular and elliptical cylinders.
The Dynamically Loaded Circular Beam on an Elastic Foundation
Authors: Panayotounakos D. E. , Theocaris P. S.
Published: July 2009

In this investigation an analytical treatment for the determination of the natural frequencies of a circular uniform beam on an elastic foundation, subjected to harmonic loads, is presented. This problem in the most general case of response is reduced to a system of six-coupled linear partial differential equations. The effects of rotatory inertia and transverse shear deformation are also included in the analysis. The problem is treated by considering the beam as a continuous system, as well as a discrete system. The aforementioned solution methodology is successfully demonstrated through several numerical examples.
Analytic Approximations for the Elastic Contact of Rough Spheres
Authors: Hughes B. D. , White L. R.
Published: July 2009

The basic equations of a model of Greenwood and Tripp for contact of rough elastic spheres are discussed using analysis approximation techniques.
Turbulence Measurements in an Axisymmetric Separated and Reattached Flow Over a Longitudinal Blunt Circular Cylinder
Authors: Ota T. , Motegi H.
Published: July 2009

Turbulence measurements were made in the separated, reattached, and redeveloped regions of an axisymmetric incompressible airflow over a longitudinal circular cylinder with blunt leading edge. Three components of turbulent fluctuating velocity and the turbulent shear stress are presented. In the boundary layer downstream of the reattachment point, Prandtl’s mixing length and turbulent kinetic energy length scale are estimated, and the correlation between the turbulent shear stress and the turbulent kinetic energy is described.
An Iterative Numerical Solution for the Elastica With Causally Mixed Inputs
Authors: Hubbard M.
Published: July 2009

An iterative numerical solution is given for the case of a thin elastic rod whose inputs are simultaneously the positions of the two ends and an applied moment at one end. The development begins by considering the real rod as an end section of a longer fictitious rod loaded with end forces only. Newton’s method is then used to obtain both the shape of the real road and its vector restoring force. The results show that both the magnitude and the direction of the restoring force are changed considerably from the zero-moment case, especially when the percent deflection of the elastica is small. Such a model is a useful alternative to a pure force-deflection one because it accounts not only for the direct effect of the applied moment on the reaction rigid body but the indirect contribution to the reaction force as well.
On Stress Boundary Conditions in Shell Theory
Authors: Sanders J. Lyell
Published: July 2009

Boundary conditions on the stress-functions of shell theory in terms of given boundary data are derived. The results are shown to be fully equivalent to the Kirchhoff boundary conditions and have the same form for all first-approximation theories of thin shells.
Brittle Fracture of Plates in Tension: Virgin Waves and Boundary Reflections
Authors: Kinra V. K. , Vu B. Q.
Published: July 2009

Virgin waves emitted during tensile fracture of edge-notched brittle plates have been measured at points on and away from the crack path. The results are in excellent agreement with the analysis of Freund. Boundary reflections were also determined. Both the rear and the front edge reflections are small but not negligibly small; the former are tensile, the latter compressive. Unloading waves are propagated behind the crack tip, and are small compared to the loading waves, which are propagated ahead of the tip. The front edge reflections were also examined near the edge; these are compressive and large. Finally, for an embedded crack, the field scattered by the stationary crack tip was found to be negligibly small.
Construction of a Dynamic Weight Function From a Finite-Element Solution for a Cracked Beam
Authors: Petroski H. J. , Glazik J. L. , Achenbach J. D.
Published: July 2009

An elastodynamic weight function for a cracked beam is shown to be determined by the elastodynamic stress intensity factor corresponding to a single crack-face loading of the beam. This weight function suffices to determine the time-dependent stress intensity factor corresponding to other dynamic loadings of the same cracked beam. The example of a center-cracked pinned-pinned beam serves to illustrate and verify the technique. The weight function is constructed from finite element results for the case of a step pressure distributed uniformly along the beam, and the case of a step load concentrated at the crack plane serves as an illustration of the efficacy of the weight function so constructed.
A Simple and Effective Pipe Elbow Element—Linear Analysis
Authors: Bathe K. J. , Almeida C. A.
Published: July 2009

The formulation of a new, simple, and effective displacement-based pipe bend element is presented. The displacement assumptions are axial, torsional, and bending displacements that vary cubically along the axis of the elbow with plane sections remaining plane, and a generalization of the von Karman pipe radial displacement patterns to include the ovalization effects. The amount of ovalization varies cubically along the elbow with full compatibility between elbows. The pipe bend element has been implemented, and the results of various sample analyses are presented, which illustrate the effectiveness of the element.
Unsteady Incompressible Three-Dimensional Asymmetric Stagnation-Point Boundary Layers
Authors: Kumari M. , Nath G.
Published: July 2009

The unsteady laminar incompressible boundary-layer flow near the three-dimensional asymmetric stagnation point has been studied under the assumptions that the free-stream velocity, wall temperature, and surface mass transfer vary arbitrarily with time. The partial differential equations governing the flow have been solved numerically using an implicit finite-difference scheme. It is found that in contrast with the symmetric flow, the maximum heat transfer occurs away from the stagnation point due to the decrease in the boundary-layer thickness. The effect of the variation of the wall temperature with time on heat transfer is strong. The skin friction and heat transfer due to asymmetric flow only are comparatively less affected by the mass transfer as compared to those of symmetric flow.
An Elastic-Plastic Stress Analysis of the Specimen Used in the Torsional Kolsky Bar
Authors: Leung Eric K. C.
Published: July 2009

This paper examines the stress concentration, the yielding process, and the growth of the elastic-plastic boundary as a function of applied torque in tubular specimens with a short thin-walled section. Although the analysis is entirely quasi-static, it can, under the proper circumstances, be applied to the deformation of short specimens as generally used for dynamic testing in the torsional Kolsky bar. In the analysis, the governing equations for both elastic and elastic-plastic analyses are presented, the latter taking into account work hardening. Numerical solutions of these equations employ the finite-element method. The elastic stress distribution in the specimen and the elastic-plastic enclaves are presented for various loading stages.
Instability of a Layer on a Half Space
Authors: Dorris J. F. , Nemat-Nasser S.
Published: July 2009

Unstable deformations of an elastic or elastoplastic layer on an elastic or elastoplastic half space, are studied under compressive forces. Various combinations of material properties are considered, e.g., an elastic layer on an elastoplastic half space, elastoplastic layer on an elastic half space, etc. Both the flow and the total deformation plasticity models are used and the corresponding results compared. The results seem to have relevance to the problem of folding of geological formations and crustal buckling under tectonic stresses.
Normal and Shear Impact of Layered Composite With a Crack: Dynamic Stress Intensification
Authors: Sih G. C. , Chen E. P.
Published: July 2009

The dynamic response of a layered composite under normal and shear impact is analyzed by assuming that the composite contains an initial flaw in the matrix material. Because of the complexities that arise from the interaction of waves scattered by the crack with those reflected by the interfaces within the composite, dynamic analyses of composites with cracks have been treated only for a few simple cases. One of the objectives of the present work is to develop an effective analytical method for determining dynamic stress solutions. This will not only lead to an in-depth understanding of the failure of composites due to impact but also provide reliable solutions that can guide the development of numerical methods. The analysis method utilizes Fourier transform for the space variable and Laplace transform for the time variable. The time-dependent angle loading is separated into two parts: one being symmetric and the other skew-symmetric with reference to the crack plane. By means of superposition, the transient boundary conditions consist of applying normal and shear tractions to a crack embedded in a layered composite. One phase of the composite could represent the fiber while the other could be the matrix. Mathematically, these conditions reduce the problem to a system of dual integral equations which are solved in the Laplace transform plane for the transform of the dynamic stress-intensity factor. The time inversion is carried out numerically for various combinations of the material properties of the composite and the results are displayed graphically.
Partitioned Transient Analysis Procedures for Coupled-Field Problems: Stability Analysis
Authors: Park K. C.
Published: July 2009

A general partitioned transient analysis procedure is proposed, which is amenable to a unified stability analysis technique. The procedure embodies two existing implicit-explicit procedures and one existing implicit-implicit procedure. A new implicit-explicit procedure is discovered, as a special case of the general procedure, that allows degree-by-degree implicit or explicit selections of the solution vector and can be implemented within the framework of the implicit integration packages. A new element-by-element implicit-implicit procedure is also presented which satisfies program modularity requirements and enables the use of single-field implicit integration packages to solve coupled-field problems.
Finite-Element Analysis of Magnetoelastic Buckling of Ferromagnetic Beam Plate
Authors: Miya K. , Takagi T. , Ando Y.
Published: July 2009

Some corrections have been made hitherto to explain the great discrepancy between experimental and theoretical values of the magnetoelastic buckling field of a ferromagnetic beam plate. To solve this problem, the finite-element method was applied. A magnetic field and buckling equations of the ferromagnetic beam plate finite in size were solved numerically assuming that the magnetic torque is proportional to the rotation of the plate and by using a disturbed magnetic torque deduced by Moon. Numerical and experimental results agree well with each other within 25 percent.
Nonlinear Resonances in a Column Subjected to a Constant End Force
Authors: Crespo da Silva M. R. M.
Published: July 2009

A canonical perturbation method based on Hamilton-Jacobi theory, used together with Galerkin’s method, is employed to analyze the nonlinearly coupled transverse free oscillations of columns subjected to a constant end force. Integrals of motion, readily obtained from this type of analysis, are used to allow the analytical determination of the main characteristics of the resonant motion and of the region of resonance of the system.
Fluid Motion Past a Porous Circular Cylinder With Initial Pressure Gradient
Authors: Gupta J. L.
Published: July 2009

The problem of two-dimensional flow, past a porous circular cylinder, with initial pressure gradient is solved using the method of matched asymptotic expansions. It is found that the drag force experienced by the cylinder is increased due to initial gradient although it remains smaller than the drag force experienced by an identical impervious body.
Static Equilibrium of a Fluid-Saturated Porous Solid
Authors: Jenkins J. T.
Published: July 2009

The equilibrium equations for a fluid-saturated, porous elastic solid are obtained by a variational method. The total energy of the body is assumed to be the sum of that of the fluid and that of the solid, and the free energy of the solid is taken to be sensitive to its porosity.
Elastostatic Far-Field Behavior in a Layered Half Space Under Surface Pressure
Authors: Muki R. , Dong S. B.
Published: July 2009

Elastostatic problem of a half space with a layer of possibly distinct mechanical properties under arbitrary normal tractions on the surface is reconsidered to establish far-field asymptotic expansions of the displacements. This work was motivated by application of such far field solutions to problems of the layered half space by Global-Local Finite-Element Method (GLFEM). When the traction is a unit concentrated force, the asymptotic expansion is found to coincide, up to the second term of its inverse power series expansion with respect to the distance from the point at interface below the point of load application, with that of the classical Boussinesq solution with a suitably chosen coordinate system. This agreement between the two solutions is also observed for normal tractions on a bounded surface region. Comparative numerical results are given to demonstrate the modeling capabilities of the far-field asymptotic expansions in a GLFEM example. It’s effectiveness is shown in terms of greater accuracy and computational efficiency over the conventional finite-element method.
The Elastostatic Axisymmetric Problem of a Cracked Sphere
Authors: Kant R. , Bogy D. B.
Published: July 2009

The problem of a cracked sphere is solved with the use of Boussinesq stress functions. Two coordinate systems—oblate spheroidal for representing the crack surface and spherical polars for the spherical surface—are used to satisfy boundary conditions. Integral representations and transformations of harmonic functions are used to relate stress functions in the two coordinate systems. This procedure leads to a system of algebraic equations which is solved, for axisymmetric tractions on both the surfaces. Graphical results are presented for one specific loading case.
Measurements of Mixed-Mode Crack Surface Displacements and Comparison With Theory
Authors: Sharpe W. N. , Altiero N. J. , Mirmohamadsadegh A.
Published: July 2009

The problem of a finite-width tension specimen containing a crack oriented at various angles to the load axis is attacked from experimental and theoretical viewpoints. Displacements of an electro-machined slot, 12.5 mm long and oriented at angles of 0°, 15°, 30°, 45°, 60°, and 75°, are measured using a laser-based in-plane measuring technique. Various width specimens, ranging from a crack-length/width ratio of 0.167 to 0.794, are tested. A boundary-integral equation method is extended to deal with the presence of a sharp crack. Agreement between the two approaches is generally good except near the tips of the cracks.
On the Influence of a Rigid Circular Inclusion on the Twisting and Shearing of a Shallow Spherical Shell
Authors: Reissner E.
Published: July 2009

Known results for plates with rigid inclusions are complemented by explicit asymptotic solutions of the corresponding problems for sufficiently thin spherical shells. An important element of the analysis is recognition of the fact that in addition to the distinction between interior and edge zone solution contributions there is a significant distinction between near-field and far-field behavior of the interior solution, with the nature of this distinction depending on the nature of the boundary conditions which are prescribed. In the event that near-field behavior is of the membrane type and far-field behavior of the inextensional bending type, or vice versa, much higher stress concentrations occur than without such change in interior solution behavior.
Critical Damping in Linear Discrete Dynamic Systems
Authors: Beskos D. E. , Boley B. A.
Published: July 2009

Free viscously damped vibrations of linear discrete systems are studied. The amount of damping varies among the various elements of the system resulting in several critical damping possibilities. A general method is developed for determining the “critical damping surfaces” of a system. These surfaces represent the loci of combinations of damping values corresponding to critically damped motions, and thus separate regions of partial or complete underdamping from those of overdamping. The dimension of a critical damping surface is equal to the number of independent amounts of damping present in the system. Three examples presented in detail illustrate the proposed technique and some of the important characteristics of critical damping surfaces.
A Family of Early-Time Approximations for Fluid-Structure Interaction
Authors: Felippa C. A.
Published: July 2009

A hierarchical family of early-time, high-frequency asymptotic, surface interaction approximations is derived for a structure submerged in an infinite acoustic fluid. Kirchhoff’s retarded-potential integro-differential formulation is used as exact source formula. The well-known plane-wave and curved-wave approximations result as the first two members of the hierarchy. Acoustic impedance characteristics of the first four members are exhibited for several sample geometries.
Reexamination of Unsteady Fluid Dynamic Forces on a Two-Dimensional Finite Plate at Small Mach Numbers
Authors: Matsuzaki Y. , Ueda T.
Published: July 2009

The Fourier transform theory is applied to the analytical determination of the disturbance velocity potential and pressure acting on a two-dimensional plate, in order to reexamine those of previous analyses by other investigators. Simplified expressions of the generalized forces are presented for incompressible and nearly incompressible flows. As the Mach number tends to zero, the virtual mass induced by an oscillating fluid becomes infinitely large for a natural mode symmetric with respect to the midchord point. It is recommended to take into account a symmetric mode which changes no fluid volume contained in a control surface, when a coupled flutter oscillation at very low Mach numbers is analyzed. Incorrectness in the generalized forces of the previous analyses is pointed out by comparing with the present analysis.
Drawing of Tubes
Authors: Durban D.
Published: July 2009

The process of the tube drawing between two rough conical walls is analyzed within the framework of continuum plasticity. Material behavior is modeled as rigid/linear-hardening along with the von-Mises flow rule. Assuming a radial flow pattern and steady state flow conditions it becomes possible to obtain an exact solution for the stresses and velocity. Useful relations are derived for practical cases where the nonuniformity induced by wall friction is small. A few restrictions on the validity of the results are discussed.
Approximate Laplace Transform Inversion in Dynamic Viscoelasticity
Authors: Swanson S. R.
Published: July 2009

Laplace transform techniques greatly simplify many problems in linear viscoelasticity. However, if realistic material property representations are used, inversion of the resulting transforms can be difficult. Although approximate transform inversion methods have been widely used in quasi-static viscoelastic problems, the application of these techniques to wave propagation problems has been less successful. Inaccuracy of the transform inversion has been noted previously in the literature. The present work shows that one of the numerical Laplace transform inversion techniques of Bellman can successfully be applied to dynamic viscoelasticity. Comparisons with literature solutions and exact functions indicate accuracies to within ±1 percent can be obtained.
Approximation of the Strain Field Associated With an Inhomogeneous Precipitate—Part 2: The Cuboidal Inhomogeneity
Authors: Johnson W. C. , Earmme Y. Y. , Lee J. K.
Published: July 2009

The modified equivalency and integral equation methods for determination of the constrained strain field associated with a precipitate that has undergone a dilatational stress-free transformation strain as developed in Part 1, are applied to the case of a cuboidal inhomogeneity within an isotropic matrix. Agreement between the two methods is good for small and moderate differences in the shear moduli between precipitate and matrix. For large differences in the shear moduli, some divergence is observed in that fluctuations in the constrained strain field become quite pronounced near the cube edge and corner when considering the integral equation method. Although some error is inevitable due to the cutoff of higher-order terms in the Taylor series expansion, the modified equivalency method yields fair results under such circumstances. With the latter method, the constrained strain field of a cuboid is analyzed as a function of position and orientation. Although the strain field behaves as expected in the central regions of the cube in that the harder the precipitate the larger the constrained strain, its behavior becomes complicated as the precipitate-matrix interface is approached, demonstrating a strong dependency on precipitate rigidity. As a result, the dilatation in the inhomogeneous cuboidal precipitate is found not to be a constant as contrasted with the homogeneous case.