bluuebunny/crossref_metadata_2025 huggingface dataset:
The Place of Catholic Historians and Catholic Historiography in Nazi Germany
Authors: Heilbronner Oded
Published: May 2003

This article examines the neglected subject of the place and role of Catholic historians in Nazi Germany. It argues that the Third Reich provided an opportunity for Catholic historians: first, to express their vision of the Reich within the legitimacy provided by the Nazi state; secondly, to represent themselves as the only experienced force in Germany that could effectively convey the idea of the Reich to the German people; and thirdly, to leave the intellectual ‘ghetto’ in which they had been placed following the creation of the Bismarckian Reich of 1871.
Elastic Stresses in Elbows Submitted to In-Plane Bending Moment
Authors: Marie S. , Ne´de´lec M.
Published: May 2003

New analytical equations are developed to calculate stresses in an elbow submitted to an in-plane bending moment. If a detailed stress analysis is asked (for example, for the elastic stress intensity factor calculation KI), available code equations are not accurate enough because their determination is based on an axi-symmetric analysis, where the elbow is compared to a torus, and therefore the end effects are not taken into account. This work relies on elastic finite element calculations using shell elements. Longitudinal and circumferential stresses are calculated in the median section and in the junction section between the elbow and the straight pipe. Elbows considered here have a bend angle αc=45, 90, and 180 deg and show a ratio rm/t between 5 and 20 and a parameter λ up to 1. Analytical expressions are proposed to fit the membrane and bending components of each stress. Coefficients of these equations are tabulated and expressed only as a function of the ratio rm/t and the parameter λ for the median section and the junction section. An interpolation methodology is also given for intermediate elbow angles: these analytical relations give a simple solution to have an accurate estimate of the elastic stress distribution in the median section and the junction section in a elbow submitted to an in-plane bending moment, for a wide range of elbow angles, ratios rm/t and parameters λ.
Study of Nonuniform In-Plane and In-Depth Residual Stress of Friction Stir Welding
Authors: Ya Min , Dai Fulong , Lu Jian
Published: May 2003

Friction stir welding (FSW) is a newly developed welding technique that can join aluminum alloys of low fusion weldability. The conventional hole-drilling method does not consider the nonuniform in-plane stress around the drilled hole, it is no longer valid for the residual stress of FSW which has high stress gradient. However, assuming the relaxation of in-plane nonuniform residual stress to be uniform on a small increment of the boundary of the hole, the recently developed Moire´ interferometry incremental hole-drilling (MIIHD) method can be used. Residual stress of a thin plate of friction stir welded aluminum alloy was studied by MIIHD. The longitudinal residual stress distribution in the transversal direction and through the thickness was obtained and compared with results by strain gage method.
Survey of nonlinear vibration of gear transmission systems
Authors: Wang Jianjun , Li and Runfang , Peng Xianghe
Published: May 2003

In this paper, the progress in nonlinear dynamics of gear driven systems in the past twenty years is reviewed, especially the gear dynamic behavior, by considering the backlash and time-varying mesh stiffness of teeth. The basic concepts, the mathematical models and the solving methods for the non-linear dynamics of geared systems are then reviewed. The critical issues for further research on the nonlinear vibration in gear transmission systems are also discussed. There are 204 references cited in this review article.
A Probabilistic Assessment of the Design S-N Curves for 1Cr18Ni9Ti Pipe-Welded Joint
Authors: Zhao Y. X.
Published: May 2003

A probabilistic assessment is made of the design S-N curves for 1Cr18Ni9Ti pipe-welded joint. The material exhibits a character of random cyclic stress-strain and fatigue life responses. Then, both the S and N in the virtual stress amplitude-fatigue crack initiation life (S-N) data are random variables. A general maximum likelihood method, which considers the randomness of the test S-N data, is developed to model the probabilistic S-N relations of material. The design S-N curves with reduction factors of 20 on cycles, 2 on stress and 2.5 on stress applied to the best-fit S-N curve of test data as used in the ASME code and general practice, are assessed in a probabilistic sense. The results reveal that in the lower S regime the 20 and 2.5 reduction factor curves may be appropriate, while the reduction factor of 2 is slightly nonconservative. But in the higher S regime these curves are all much more conservative. The intrinsic cause is that the standard deviation of logN exhibits an increase with the S decreasing, while the constant reduction factors do not consider this increase. It is shown that from the general statistical scatter of S-N data the design S-N curves should be appropriately determined by a probabilistic approach.
Intensive Quenching Theory and Application for Imparting High Residual Surface Compressive Stresses in Pressure Vessel Components
Authors: Freborg Andrew M. , Ferguson B. Lynn , Aronov Michael A. , Kobasko Nikolai I. , Powell Joseph A.
Published: May 2003

An alternative method for the hardening of steel parts has been developed as a means of providing steel products with superior mechanical properties through development of high residual compressive stresses on the part surface, and involves the application of intensive quenching during heat treatment. This processing method, termed “Intensive Quenching,” imparts high residual compressive stresses on the steel surface, thus allowing for the use of lower alloy steels, reduction or elimination of the need for carburization and shot peening, and providing for more cost-effective heat treating. Intensive quenching also provides additional environmental benefits, as the process uses plain water as the quenching media in contrast to traditional heat treatment practices which typically employ hazardous and environmentally unfriendly quenching oil. This paper presents an overview of the theory and application of intensive quenching, as well as provides experimental and computational data obtained for a variety of steel products. Also presented will be results of computer simulations of temperature, structural and stress/strain conditions for a typical pressure vessel during intensive quenching.
Historical review of Zig-Zag theories for multilayered plates and shells
Authors: Carrera Erasmo
Published: May 2003

This paper gives a historical review of the theories that have been developed for the analysis of multilayered structures. Attention has been restricted to the so-called Zig-Zag theories, which describe a piecewise continuous displacement field in the plate thickness direction and fulfill interlaminar continuity of transverse stresses at each layer interface. Basically, plate and shell geometries are addressed, even though beams are also considered in some cases. Models in which the number of displacement variables is kept independent of the number of constitutive layers are discussed to the greatest extent. Attention has been restricted to those plate and shell theories which are based on the so-called method of hypotheses or axiomatic approach in which assumptions are introduced for displacements and/or transverse stresses. Mostly, the work published in the English language is reviewed. However, an account of a few articles originally written in Russian is also given. The historical review conducted has led to the following main conclusions. 1) Lekhnitskii (1935) was the first to propose a Zig-Zag theory, which was obtained by solving an elasticity problem involving a layered beam. 2) Two other different and independent Zig-Zag theories have been singled out. One was developed by Ambartsumian (1958), who extended the well-known Reissner-Mindlin theory to layered, anisotropic plates and shells; the other approach was introduced by Reissner (1984), who proposed a variational theorem that permits both displacements and transverse stress assumptions. 3) On the basis of historical considerations, which are detailed in the paper, it is proposed to refer to these three theories by using the following three names: Lekhnitskii Multilayered Theory, (LMT), Ambartsumian Multilayered Theory (AMT), and Reissner Multilayered Theory (RMT). As far as subsequent contributions to these three theories are concerned, it can be remarked that: 4) LMT although very promising, has almost been ignored in the open literature. 5) Dozens of papers have instead been presented which consist of direct applications or particular cases of the original AMT. The contents of the original works have very often been ignored, not recognized, or not mentioned in the large number of articles that were published in journals written in the English language. Such historical unfairness is detailed in Section 3.2. 6) RMT seems to be the most natural and powerful method to analyze multilayered structures. Compared to other theories, the RMT approach has allowed from the beginning development of models which retain the fundamental effect related to transverse normal stresses and strains. This review article cites 138 references.
Vibration Control of Toroidal Shells With Parallel and Diagonal Piezoelectric Actuators
Authors: Tzou H. S. , Wang D. W.
Published: May 2003

Effective control of toroidal shells, e.g., cooling tubes, space colonies, inflatable space structures, etc., enhances their operational precision, accuracy, and reliability. Dynamics and control effectiveness of toroidal shell panels laminated with distributed piezoelectric sensor/actuator layers are investigated in this study. Mathematical model and finite element formulations of piezo(electric)-elastic shell structures are presented. Element and system matrix equations of the piezoelastic shell structronic (sensor/actuator/structure/control) system are defined and the system equations reveal the coupling of mechanical and electric (or control) fields. Free vibration analyses of two toroidal shells are investigated and compared favorably with published data. Two sensor/actuator configurations based on identical sensor/actuator sizes, namely the parallel configuration and the diagonal configuration, laminated on the toroidal shell are investigated and analysis data suggest that the diagonal configuration provides better control effects, as compared with the parallel configuration. The parallel configuration is ineffective to anti-symmetrical modes; the diagonal configuration is effective to most natural modes and ineffective to quad-anti-symmetrical modes with respect to the panel center.
Active Vibration Control for the Measurement of Fluidelastic Effects
Authors: Caillaud Se´bastien , de Langre Emmanuel , Baj Franck
Published: May 2003

A new method based on active vibration control is proposed to investigate fluidelastic coupling effects beyond fluidelastic instability. This active control method allows to extend the range of flow velocity explored for single input-single output control systems. The method is applied on a flexible tube inserted in a rigid bundle in water and air-water cross-flows. This structure becomes unstable for high flow velocities, fluidelastic forces then causing the damping of the fluid-structure system to fall towards zero. The active control method allows to carry out tests beyond the fluidelastic instability. The flow velocity range explored is doubled in two-phase flow.
Dish-Stirling Systems: An Overview of Development and Status
Authors: Mancini Thomas , Heller Peter , Butler Barry , Osborn Bruce , Schiel Wolfgang , Goldberg Vernon , Buck Reiner , Diver Richard , Andraka Charles , Moreno James
Published: May 2003

Dish-Stirling systems have demonstrated the highest efficiency of any solar power generation system by converting nearly 30% of direct-normal incident solar radiation into electricity after accounting for parasitic power losses[1]. These high-performance, solar power systems have been in development for two decades with the primary focus in recent years on reducing the capital and operating costs of systems. Even though the systems currently cost about $10,000 US/kW installed, major cost reduction will occur with mass production and further development of the systems. Substantial progress has been made to improve reliability thereby reducing the operating and maintenance costs of the systems. As capital costs drop to about $3000 US/kW, promising market opportunities appear to be developing in green power and distributed generation markets in the southwestern United States and in Europe. In this paper, we review the current status of four Dish-Stirling systems that are being developed for commercial markets and present system specifications and review system performance and cost data. We also review the economics, capital cost, operating and maintenance costs, and the emerging markets for Dish-Stirling systems.
Experiences With Using Solar Photovoltaics to Heat Domestic Water
Authors: Dougherty Brian P. , Fanney A. Hunter
Published: May 2003

The solar photovoltaic (PV) industry continues to make progress in increasing the efficiency while reducing the manufacturing costs of PV cells. Economies of scale are being realized as manufacturers expand their production capabilities. Products are commercially available that integrate photovoltaic cells within building fac¸ade, fenestration, and roofing components. Legislation and incentive programs by government and commercial entities are supporting both reduced first costs and greater rates of return. The combination of factors support improved cost-effectiveness. As this trend continues, more options for using PV become possible. One such application is a stand-alone, PV-direct, solar water heating application. Solar water heating can be effectively accomplished by directly using the DC power production from solar photovoltaic modules. A simple controller having multiple power relays connects the PV modules with different combinations of in-tank resistive elements. The controller actively changes the resistive combination so that the photovoltaic modules generate power at or near their maximum output. The technology, which has been patented, is applicable to configurations that use a single water heater and to two water heaters that are piped in series. Prototypes using both tank configurations were monitored at four field sites. This paper emphasizes the single-tank application and the field results from installations in Maryland and Florida.
Measurement of High Temperatures in the DLR Solar Furnace by UV-B Detection
Authors: Rohner Nicola , Neumann Andreas
Published: May 2003

The correct selection of the operating wavelength is essential for a precise pyrometric temperature measurement on solar irradiated samples, as the measurement may be disturbed by reflected solar radiation. Atmospheric conditions and particularly the material emissivity have an impact on these measurements. As an approach to solve this problem, we developed a new system that uses the UV-B wavelength range for pyrometry. Simulations and measurements on blackbodies and on real hot bodies heated in the DLR Solar Furnace specified the final measurement wavelength to be in the range of 280–292 nm. A sensitive monochromator system for this UV-B pyrometry was developed and experimentally tested. Measurements in the range of 1320-1500°C on a blackbody without solar irradiation and measurements from 1500°C to about 2400°C on a real solar heated sample are presented and discussed. Final calibration was performed by using blackbody radiation of 1500°C. Two calculation methods are compared. The influence of the calibration temperature on the quality of the measurement is shown. In this first approach, the resolution of the system turned out to be in the order of magnitude of 1 K and the accuracy in the order of magnitude of 10 K.
Optimization of a Novel Combined Power/Refrigeration Thermodynamic Cycle
Authors: Lu Shaoguang , Goswami D. Yogi
Published: May 2003

A novel combined power/refrigeration thermodynamic cycle is optimized for thermal performance in this paper. The cycle uses ammonia-water binary mixture as a working fluid and can be driven by various heat sources, such as solar, geothermal, and low temperature waste heat. The optimization program, which is based on the Generalized Reduced Gradient algorithm, can be used to optimize for different objective functions. In addition, cycle performance over a range of ambient temperatures was investigated.
Field Tests of a PV-Powered Air Monitoring System
Authors: Sanidad L. , Baghzouz Y. , Boehm R. , Hodge E.
Published: May 2003

A compact stand-alone PV power system was recently designed and built to run an air sampler for environmental monitoring at the Nevada Test Site. This paper presents an overview of the system design and analysis of some of the recorded daily cycles of various power flows during the summer period. The system long-term performance during both high and low solar resource periods is simulated with the computer code PVFORM using historical weather data.
Immersed boundary technique for turbulent flow simulations
Authors: Iaccarino Gianluca , Verzicco Roberto
Published: May 2003

The application of the Immersed Boundary (IB) method to simulate incompressible, turbulent flows around complex configurations is illustrated; the IB is based on the use of non-body conformal grids, and the effect of the presence of a body in the flow is accounted for by modifying the governing equations. Turbulence is modeled using standard Reynolds-Averaged Navier-Stokes models or the more sophisticated Large Eddy Simulation approach. The main features of the IB technique are described with emphasis on the treatment of boundary conditions at an immersed surface. Examples of flows around a cylinder, in a wavy channel, inside a stirred tank and a piston/cylinder assembly, and around a road vehicle are presented. Comparison with experimental data shows the accuracy of the present technique. This review article cites 70 references.
Fatigue Crack Propagation Properties of Welded Joints at 300°C
Authors: Ohta Akihiko , Suzuki Naoyuki , Maeda Yoshio
Published: May 2003

Fatigue crack propagation properties of welded joints were investigated on steel plate for boilers and other pressure vessels. The fatigue crack propagation properties at 300°C became similar to those at room temperature when the thermal stress could be reduced down to −1 MPa by using center cracked type specimen with longitudinal slits and a specially designed furnace. The tensile residual stress was +152 MPa in the as-welded joint, and +12 MPa after PWHT. The fatigue threshold was about 2.7, 5.1 and 7.3 MN/m3/2 for weld metal in the as-welded condition, after PWHT and the base metal, respectively.
Influence of Pad Reinforcement on the Limit and Burst Pressures of a Cylinder-Cylinder Intersection
Authors: Xue L. , Widera G. E. O. , Sang Z. F.
Published: May 2003

The purpose of the paper is to provide experimental results for the limit pressure of a vessel-nozzle intersection under internal pressure with and without an intermediate pad-reinforced opening d/D=0.526. Two different methods, double elastic-slope and tangent intersection, are employed to determine the experimental limit pressure. A comparison of the limit and burst pressures with and without pad reinforcement is carried out. The present test results indicate that the pad reinforcement significantly improves the limit and the bust pressures. It can thus be concluded that pad reinforcement is an effective reinforcement method.
Variation of Insolation Transmission With Glazing Plane Position and Sky Conditions
Authors: Waide Paul A. , Norton Brian
Published: May 2003

A model to determine the instantaneous transmittance of glazing for specific direct and diffuse solar radiation conditions is developed. Plots illustrative of the generic behavior of the mean monthly hourly transmittance of glazings in different planes are presented. Using test reference year meteorological data for 29 western European locations, limiting values are determined for clearness indices, orientations, and slopes for which an isotropic diffuse assumption is valid for calculating mean daily transmittance.
Solar Powered Module for Portable Computers
Authors: Serrano David
Published: May 2003

A laptop by its virtue is a mobile apparatus, therefore, a power outlet may not necessarily be available to charge its batteries. Typical laptops have a range of up to 2.5 hr. of battery life under normal operation and some have as little as 1.5 hr. For the computer user on the move, it is important to have enough power available for more extended periods of time. Today’s technology provides a large number of other mobile appliances, instruments, and tools that will also greatly benefit from extended power. Existing solar panels operate under direct sunlight conditions and are deployed only when the equipment is in use or stationary. The solar-powered module developed at the Department of Mechanical Engineering, University of Puerto Rico-Mayaguez, has the advantage that it recharges the laptop in transit even when it is not in operation. By charging the battery when it is stored allows the battery to be recharged during a larger period of time thereby increasing the amount of energy stored. Different types of solar cells were tested under “real world” lighting situations in order to assess their potential for the intended application. The solar array was optimized for use under a larger range of illumination conditions such that it may operate when direct sunlight is not available. The ergonomic design is integrated into the laptop’s carrying case, but it may also be detached and/or repositioned if desired. The solar panel is based on the latest technology of triple junction spectrum-splitting amorphous silicon solar cells. The equipment allows the use of a laptop or other portable equipment in situations when power is not available, providing a needed service in remote locations to professionals in the field and provides a backup power source in the event of an emergency or lack of adequate infrastructure. This paper describes the design process in the selection of the solar cell technology used in the module.
Determination of Constraint-Modified J-R Curves for Carbon Steel Storage Tanks
Authors: Lam P.-S. , Chao Y. J. , Zhu X.-K. , Kim Y. , Sindelar R. L.
Published: May 2003

Mechanical testing of A285 carbon steel, a storage tank material, was performed to develop fracture properties based on the constraint theory of fracture mechanics. A series of single edge-notched bend (SENB) specimen designs with various levels of crack tip constraint were used. The variation of crack tip constraint was achieved by changing the ratio of the initial crack length to the specimen depth. The test data show that the J-R curves are specimen-design-dependent, which is known as the constraint effect. A two-parameter fracture methodology is adopted to construct a constraint-modified J-R curve, which is a function of the constraint parameter, A2, while J remains the loading parameter. This additional fracture parameter is derived from a closed form solution and can be extracted from the finite element analysis for a specific crack configuration. Using this set of SENB test data, a mathematical expression representing a family of the J-R curves for A285 carbon steel can be developed. It is shown that the predicted J-Rcurves match well with the SENB data over an extensive amount of crack growth. In addition, this expression is used to predict the J-R curve of a compact tension specimen (CT), and reasonable agreement to the actual test data is achieved. To demonstrate its application in a flaw stability evaluation, the configuration of a generic A285 storage tank with a postulated axial flaw is used. For a flaw length of 10% of the tank height, the predicted J-R curve is found to be similar to that for a SENB specimen with a short notch, which is in a state of low constraint. This implies that the use of a J-R curve from the ASTM (American Society for Testing and Materials) standard designs, which typically are high-constraint specimens, may be overly conservative for analysis of fracture resistance of large structures.
3-D Finite Element Modeling of the Welding Process Using Element Birth and Element Movement Techniques
Authors: Fanous Ihab F. Z. , Younan Maher Y. A. , Wifi Abdalla S.
Published: May 2003

The modeling and simulation of the welding process has been of main concern for different fields of applications. Most of the modeling of such a problem has been mainly in 2-D forms that may also include many sorts of approximation and assumptions. This is due to limitations in the computational facilities as the analysis of 3-D problems consumes a lot of time. With the evolution of new finite element tools and fast computer systems, the analysis of such problems is becoming in hand. In this research, a simulation of the welding process with and without metal deposition is developed. A new technique for metal deposition using element movement is introduced. It helps in performing full 3-D analysis in a shorter time than other previously developed techniques such as the element birth.
Axial Leakage Flow-Induced Vibration of a Thin Cylindrical Shell With Respect to Axisymmetric Vibration
Authors: Fujita Katsuhisa , Shintani Atsuhiko , Ono Masakazu
Published: May 2003

In this paper, the stability of a thin cylindrical shell subjected to axial leakage flow is discussed. In this paper, the first part of a study of the axial leakage flow-induced vibration of a thin cylindrical shell, we focus on axisymmetric vibration, that is, the ringlike vibration of a shell. The coupled equations between a shell and a fluid are obtained by using the Donnell’s shell theory and the Navier-Stokes equation. The added mass, added damping and added stiffness matrices in the coupled equations are described by utilizing unsteady fluid forces on a shell. The influence of the axial flow velocity on the unstable phenomena is clarified concerning axisymmetric vibration mode of shell. The numerical calculations are performed taking the dimensions of shell and fluid as parameters.
Pressure Drop in Solar Power Plant Chimneys
Authors: von Backstro¨m Theodor W. , Bernhardt Andreas , Gannon Anthony J.
Published: May 2003

The paper investigates flow through a representative tall solar chimney with internal bracing wheels. It presents experimental data measured in a 0.63-m-dia model chimney with and without seven bracing wheels. The bracing wheels each had a rim protruding into the chimney and 12 spokes, each spoke consisting of a pair of rectangular section bars. The investigation determined coefficients of wall friction, bracing wheel loss, and exit kinetic energy in a model chimney, for both ideal non-swirling uniform flow and for swirling distorted flow. A fan at one end of the chimney model either sucked or blew the flow through it. The flow entering the chimney through the fan and its diffuser simulated the flow leaving the turbine at the bottom of the chimney. The swirling distorted flow increased the total pressure drop by about 28%, representing 4.7% of the turbine pressure drop. The pressure drop across the bracing wheels exceeded the frictional pressure drop by far. Designers of tall, thin-walled chimneys should take care to minimize the number of bracing wheels, reduce their rim width as much as possible, and investigate the feasibility of streamlining their spoke sections. If at all structurally possible, the top bracing wheel should be far enough from the chimney exit to allow the spoke wakes to decay and the separated flow to re-attach to the chimney wall downstream of the rims before the flow leaves the chimney, to reduce the exit kinetic energy loss.
Temperature Distribution in a Porous Medium Subjected to Solar Radiative Incidence and Downward Flow: Convective Boundaries
Authors: Liu Pai-Chuan
Published: May 2003

The knowledge of steady-state temperature distribution is known a priori for natural convection stability analysis. The present study determines the temperature profiles in an infinite horizontal layer of fluid filled with saturated porous medium confined between two convective surfaces subjected to external radiative incidence and imposed downward convection. The investigation concentrates on the influences of the thermal boundary condition (Biot number), internal and external Rayleigh numbers, Peclet number, optical thickness, and surface reflectivities. The implications of these factors on fluid stability are addressed in detail.
Photocatalytic Oxidation of Toluene in Water From an Algae Pond With High Dissolved Oxygen Content
Authors: Vijayaraghavan Sanjay , Goswami D. Y.
Published: May 2003

Water in well-mixed ponds containing photosynthetic algae has been observed to have an extremely high Dissolved Oxygen (DO) content. Up to four times saturation levels of DO have been recorded. Since DO is known to have an important role in the photocatalytic oxidation of organic contaminants in water, it was hypothesized that a faster rate of contaminant destruction would be observed in water drawn from algae ponds supersaturated with DO. In order to verify this hypothesis, a bench scale, batch-type photoreactor was constructed. Some baseline tests were performed to investigate the influence of UV intensity, water pH, and DO content on the photocatalytic destruction of toluene in water. An array of ultraviolet blacklight lamps in a lamp box was used to simulate solar ultraviolet radiation. First-order reaction rate constants were calculated from the destruction data, using a kinetic model proposed earlier. The reaction was found to proceed forward equally fast at pH 4 and 10. A power law relation was derived for the reaction rate dependence on UV intensity. Presence of DO in the water was found to be required for the reaction to go forward. Water from an algae pond, supersaturated with dissolved oxygen was spiked with toluene and destruction tests were then conducted in the same reactor. These tests did not show the expected improvement in destruction rates.
Novel Combined Power and Cooling Thermodynamic Cycle for Low Temperature Heat Sources, Part II: Experimental Investigation
Authors: Tamm Gunnar , Goswami D. Yogi
Published: May 2003

A combined thermal power and cooling cycle proposed by Goswami is under intensive investigation, both theoretically and experimentally. The proposed cycle combines the Rankine and absorption refrigeration cycles, producing refrigeration while power is the primary goal. A binary ammonia-water mixture is used as the working fluid. This cycle can be used as a bottoming cycle using waste heat from a conventional power cycle or as an independent cycle using low temperature sources such as geothermal and solar energy. An experimental system was constructed to demonstrate the feasibility of the cycle and to compare the experimental results with the theoretical simulation. Results showed that the vapor generation and absorption condensation processes work experimentally, exhibiting expected trends, but with deviations from ideal and equilibrium modeling. The potential for combined turbine work and refrigeration output was evidenced in operating the system. Analysis of losses showed where improvements could be made, in preparation for further testing over a broader range of operating conditions.
Maximum Temperature Rise in the Reacted Zone of Electrochemical Devices for Space Applications
Authors: Hall, Carsie A. , Russo Edwin P. , Mackie Calvin
Published: May 2003

A model to predict the temperature rise in the reacted zone of discharging electrochemical devices has been developed. The model assumes that electrode kinetics are fast and concentration gradients are negligible. In the reacted zone, a thermal boundary layer grows, and its thickness is proportional to the reacted zone thickness. In the model, the temperature rise is predicted using the one-dimensional heat diffusion equation for a porous medium. The effective heat capacity per unit volume and effective thermal conductivity are defined as a function of electrode porosity. The instantaneous power per unit area dissipated in the reacted zone is used as a source term in the heat diffusion equation. With fixed parameters such as discharge current density, charge capacity per unit volume, electrode electrical conductivity, electrode porosity, and thermophysical properties of the pore-space fluid and electrode, the transient temperature distribution in the reacted zone is derived in closed-form. Subsequently, the maximum electrode temperature is readily obtained, and the maximum electrode temperature at complete discharge is derived. A new dimensionless parameter, the electro-thermal number, emerges as one of the most important parameters controlling the discharge time and maximum temperature rise.
Novel Combined Power and Cooling Thermodynamic Cycle for Low Temperature Heat Sources, Part I: Theoretical Investigation
Authors: Tamm Gunnar , Goswami D. Yogi , Lu Shaoguang , Hasan Afif A.
Published: May 2003

A combined thermal power and cooling cycle proposed by Goswami is under intensive investigation, both theoretically and experimentally. The proposed cycle combines the Rankine and absorption refrigeration cycles, producing refrigeration while power is the primary goal. A binary ammonia-water mixture is used as the working fluid. This cycle can be used as a bottoming cycle using waste heat from a conventional power cycle or as an independent cycle using low temperature sources such as geothermal and solar energy. Initial parametric studies of the cycle showed the potential for the cycle to be optimized for first or second law efficiency, as well as work or cooling output. For a solar heat source, optimization of the second law efficiency is most appropriate, since the spent heat source fluid is recycled through the solar collectors. The optimization results verified that the cycle could be optimized. Theoretical results were extended to include realistic irreversibilities in the cycle, in preparation for the experimental study.
Measurement of Pressure Drop in a Full-Scale Fuel Assembly of a Liquid Metal Reactor
Authors: Choi Seok Ki , Choi Il Kon , Nam Ho Yun , Choi Jong Hyeun , Choi Hoon Ki
Published: May 2003

An experimental study has been carried out to measure the pressure drop in a 271-pin fuel assembly of a liquid metal reactor. The rod pitch to rod diameter ratio P/D of the fuel assembly is 1.2 and the wire lead length to rod diameter ratio H/D is 24.84. Measurements are made for five different sections in a fuel assembly; inlet orifice, fuel assembly inlet, wire-wrapped fuel assembly, fuel assembly outlet and fuel assembly upper region. A series of water experiments have been conducted changing flow rate and water temperature. It is shown that the pressure drops in the inlet orifice and in the wire-wrapped fuel assembly are much larger than those in other regions. The measured pressure drop data in a wire-wrapped fuel assembly region is compared with the existing four correlations. It is shown that the correlation proposed by Cheng and Todreas fits best with the present experimental data among the four correlations considered.
Axial Leakage Flow-Induced Vibration of a Thin Cylindrical Shell With Respect to Lateral Vibration
Authors: Fujita Katsuhisa , Shintani Atsuhiko , Ono Masakazu
Published: May 2003

In this paper, the stability of a thin cylindrical shell subjected to axial leakage flow is discussed. In this paper, the second part of a study of the axial leakage flow-induced vibration of a thin cylindrical shell, we focus on lateral vibration, that is, the beamlike vibration of a shell. The coupled equations between a shell and a fluid are obtained by using the Donnell’s shell theory and the Navier-Stokes equation as same as the former paper. The influence of the axial velocity on the unstable vibration phenomena is clarified concerning the beamlike vibration mode of a shell. The numerical results on shell theory are compared with the ones on beam theory which have been already reported by the authors; and the numerical parameter studies are done for various dimensions of a shell and a fluid.
The Use of “Fitness for Service” Assessment Procedures to Establish Critical Flaw Sizes in High-Pressure Gas Cylinders
Authors: Smith John H. , Rana Mahendra D. , Hall Clark
Published: May 2003

Typical flaws that can occur in high-pressure seamless gas cylinders during service are: corrosion pits, line corrosion, gouges, local thin areas of corrosion, and cracks. The required periodic inspection of seamless cylinders requires that “critical flaw sizes” be established. To establish “critical flaw sizes” an assessment of typical flaws that occur in seamless cylinders was carried out using the analytical procedures described in the API Recommended Practice 579 “Fitness-for-Service.” To verify the API 579 analysis procedures, a number of hydrostatic tests were conducted on selected cylinders with various sizes of flaws to determine the burst pressure of cylinder containing flaws. These results showed that the analysis conducted according to API 579 reliably estimated the actual measured burst pressure of the cylinders for all flaw sizes and types. After the API 579 analysis procedures were verified by these experiments to reliably estimate the burst pressure of cylinders with various types of flaws, the “critical flaw sizes” to cause failure of the cylinders at selected pressures were determined by analysis. This paper presents the results of the analytical and experimental work that was performed on the assessment procedures to establish the “critical flaw sizes” in high-pressure gas cylinders.
Suppression of Acoustic Waves in Steam Generator and Heat Exchanger Tube Banks
Authors: Eisinger F. L. , Sullivan R. E.
Published: May 2003

Tube banks located in flow channels and exposed to crossflow have a low resistance to acoustic resonance and vibration in general. Such resistance can be increased substantially by placing acoustic baffles inside the tube banks. The locations and the number of baffles play an important role in the degree of their effectiveness of suppressing acoustic waves. One or two baffles placed within a tube bank will raise the threshold to acoustic vibration significantly. Optimum baffle locations suppressing acoustic resonance and vibration or reducing noise levels at resonance can be determined. A general procedure based on acoustic particle velocity mode shape functions is presented for the evaluation of the acoustic baffle effects.
Acoustic Vibration in a Stack Induced by Pipe Bends
Authors: Eisinger F. L. , Sullivan R. E. , Feenstra P. , Weaver D. S.
Published: May 2003

Acoustic vibration in two stack liners located inside a stack downstream of two induced draft fans occurred at high loads. Measurements confirmed that an acoustic wave developed in the fundamental diametral mode of the cylindrical stack liners. It manifested itself as a pure tone traveling through the stack to surrounding residential areas. It was suspected that turbulent flow in the pipe bends upstream of the stack and downstream of the fans was the source of the excitation. Laboratory scale model tests confirmed that the bends indeed acted as the source. Two guide vane configurations placed inside the bends were tested experimentally. The tests showed that properly placed guide vanes would reduce the acoustic levels in the stack. The paper gives a description and evaluation of the problem.
Microsecond temporal resolution in monaural hearing without spectral cues?
Authors: Krumbholz Katrin , Patterson Roy D. , Nobbe Andrea , Fastl Hugo
Published: May 2003

The auditory system encodes the timing of peaks in basilar-membrane motion with exquisite precision, and perceptual models of binaural processing indicate that the limit of temporal resolution in humans is as little as 10–20 microseconds. In these binaural studies, pairs of continuous sounds with microsecond differences are presented simultaneously, one sound to each ear. In this paper, a monaural masking experiment is described in which pairs of continuous sounds with microsecond time differences were combined and presented to both ears. The stimuli were matched in terms of the excitation patterns they produced, and a perceptual model of monaural processing indicates that the limit of temporal resolution in this case is similar to that in the binaural system.
Responses of squirrel monkeys to their experimentally modified mobbing calls
Authors: Fichtel Claudia , Hammerschmidt Kurt
Published: May 2003

Previous acoustic analyses suggested emotion-correlated changes in the acoustic structure of squirrel monkey (Saimiri sciureus) vocalizations. Specifically, calls given in aversive contexts were characterized by an upward shift in frequencies, often accompanied by an increase in amplitude. In order to test whether changes in frequencies or amplitude are indeed relevant for conspecific listeners, playback experiments were conducted in which either frequencies or amplitude of mobbing calls were modified. Latency and first orienting response were measured in playback experiments with six adult squirrel monkeys. After broadcasting yaps with increased frequencies or amplitude, squirrel monkeys showed a longer orienting response towards the speaker than after the corresponding control stimuli. Furthermore, after broadcasting yaps with decreased frequencies or amplitude, squirrel monkeys showed a shorter orienting response towards the speaker than after the corresponding manipulated calls with higher frequencies or amplitude. These results suggest that changes in frequencies or amplitude were perceived by squirrel monkeys, indicating that the relationship between call structure and the underlying affective state of the caller agreed with the listener’s assessment of the calls. However, a simultaneous increase in frequencies and amplitude did not lead to an enhanced response, compared to each single parameter. Thus, from the receiver’s perspective, both call parameters may mutually replace each other.
Performance bounds for passive sensor arrays operating in a turbulent medium: Plane-wave analysis
Authors: Collier S. L. , Wilson D. K.
Published: May 2003

The performance bounds of a passive acoustic array operating in a turbulent medium with fluctuations described by a von Kármán spectrum are investigated. This treatment considers a single, monochromatic, plane-wave source at near-normal incidence. A line-of-sight propagation path is assumed. The primary interests are in calculating the Cramer–Rao lower bounds of the azimuthal and elevational angles of arrival and in observing how these bounds change with the introduction of additional unknowns, such as the propagation distance, turbulence parameters, and signal-to-noise ratio. In both two and three dimensions, it is found that for large values of the index-of-refraction variance, the Cramer–Rao lower bounds of the angles of arrival increase significantly at large values of the normalized propagation distance. For small values of the index-of-refraction variance and normalized propagation distance, the signal-to-noise ratio is found to be the limiting factor. In the two-dimensional treatment, it is found that the estimate of the angle of arrival will decouple from the estimates of the other parameters with the appropriate choice of array geometry. In three dimensions, again with an appropriate choice of array geometry, the estimates of the azimuth and elevation will decouple from the estimates of the other parameters, but due to the constraints of the model, will remain coupled to one another.
Multiple scattering in a trabecular bone: Influence of the marrow viscosity on the effective properties
Authors: Luppé Francine , Conoir Jean-Marc , Franklin Hervé
Published: May 2003

The Foldy and the Waterman and Truell approximations are used to determine the effective properties of the coherent wave that emerges after multiple scattering of a plane longitudinal fast wave by the largest pores in a trabecular bone. The unit scattering cell considered is either a single pore or two close cylindrical pores (cluster), at a fixed overall bone porosity. In the cluster case, the effective attenuation is about twice that obtained with one single pore per scatterer. It is shown that taking into account the marrow viscosity leads only to minor differences on the effective dispersion and attenuation.
Stimulus-frequency-emission group delay: A test of coherent reflection filtering and a window on cochlear tuning
Authors: Shera Christopher A. , Guinan John J.
Published: May 2003

This paper tests and applies a key prediction of the theory of coherent reflection filtering for the generation of reflection-source otoacoustic emissions. The theory predicts that reflectionsource-emission group delay is determined by the group delay of the basilar-membrane (BM) transfer function at its peak. This prediction is tested over a seven-octave frequency range in cats and guinea pigs using measurements of stimulus-frequency-emission (SFOAE) group delay. A comparison with group delays calculated from published measurements of BM mechanical transfer functions supports the theory at the basal end of the cochlea. A comparison across the whole frequency range based on variations in the sharpness of neural tuning with characteristic frequency (CF) suggests that the predicted relation holds in the basal-most 60% of the cochlea. At the apical end of the cochlea, however, the measurements disagree with neural and mechanical group delays. This disagreement suggests that there are important differences in cochlear mechanics and/or mechanisms of emission generation between the base and apex of the cochlea. Measurements in humans over a four-octave range indicate that human SFOAE group delays are roughly a factor of 3 longer than their counterparts in cat and guinea pig but manifest similar trends across CF. The measurements thus reveal global deviations from scaling whose form appears quantitatively similar in all three species. Interpreted using the theory of coherent reflection filtering, the group delay measurements indicate that the wavelength at the peak of the traveling wave decreases with increasing CF at a rate of roughly 25% per octave in the base of the cochlea. The measurements and analysis reported here illustrate the rich potential inherent in OAE measurements for obtaining valuable information about basic cochlear properties such as tuning.
Backscatter from a limestone seafloor at 2–3.5 kHz: Measurements and modeling
Authors: Soukup Raymond J. , Gragg Robert F.
Published: May 2003

Physics-based interface scattering models for the seafloor [H.-H. Essen, J. Acoust. Soc. Am. 95, 1299–1310 (1994); Gragg et al., ibid. 110, 2878–2901 (2001)] exhibit features in their predicted grazing angle dependence. These features have a strong dependence on the assumed composition and roughness of the bottom. Verifying such predictions requires data that cover a wide range of grazing angles and involve minimal sub-bottom penetration. Such measurements were performed in the frequency band 2–3.5 kHz over an exposed limestone bottom off the Carolina coast during the second Littoral Warfare Advanced Development Focused Technology Experiment of 1996 (LWAD FTE 96-2). Direct-path bottom scattering strengths were obtained in shallow water (198–310 m deep) for grazing angles from 8° to 75° using data fusion from multiple experimental geometries coupled with careful signal processing. The processing included corrections for the surface-reflected path, other multipaths, and characteristics of the reverberation decay observed over the pulse duration at higher grazing angles. The resulting frequency and grazing-angle dependences exhibit trends consistent with theoretical predictions, and geoacoustic parameters obtained by inversion are consistent with values expected for limestone.