bluuebunny/crossref_metadata_2025 huggingface dataset:
A finite volume scheme for two‐dimensional chemically reactive hypersonic flow
Authors: Bertolazzi Enrico
Published: July 2002

A finite volume, semi‐implicit scheme, is proposed and discussed, which solves the two‐dimensional Euler equations for the hypersonic flow of a mixture of chemically reactive specie. The present scheme can be applied on a general, unstructured grid. The first order version guarantees non negativity of the densities and of the vibrational energies for arbitrarily large time steps. The semi‐implicit time discretization of advective terms and the fully implicit discretization of the highly nonlinear terms yield a simple and efficient computer algorithm. Numerical tests show that shocks are well captured and the correct profiles for the chemical specie are reproduced at low computational cost.
Knowledge and ethical responsibility in industrial disasters
Authors: Schneider Robert O.
Published: July 2002

The complexity of surprise industrial disasters, the high probability of their occurrence, their protracted effects, and the risks they impose on humanity make empirical research and international exchanges of information essential. Industrial disasters also give rise to significant ethical uncertainty which requires emergency managers, industrial leaders, and political decision makers to reformulate the manner in which expert knowledge is developed and applied to the tasks of risk reduction and public safety. In assessing the challenges posed by surprise or unexpected industrial disasters, it is the purpose of this essay to heighten awareness of the ethical dimensions of all knowledge in this field. Additionally, the concept of prohibited risk is suggested as a crucial normative variable to be analyzed in the application of this knowledge to the essential tasks of emergency management in relation to industrial disasters.
Information security management (3): the Code of Practice for Information Security Management (BS 7799)
Authors: von Solms Rossouw
Published: July 2002

Information security has become very important in most organizations. An acceptable level of information security can only be introduced and maintained if the correct set of security controls, both procedural and technical, is identified, implemented and maintained. The process of identifying the most effective set of security controls can be a very complicated, resource‐intensive process. A number of large British companies have joined forces to establish a Code of Practice for Information Security Management. This document provides guidelines to any organization to identify and introduce a set of controls that will provide an acceptable level of protection to the information resources. This paper briefly discusses the BS 7799 British standard.
The influence of the American Library Association on modern Chinese librarianship, 1924 to 1949
Authors: Tsay Ming‐yueh
Published: July 2002

The purpose of this study is to describe the causes, nature, extent and effect of the influence of the American Library Association (ALA) on the development of modern Chinese librarianship from 1924 to 1949. This study was based primarily on documents located in the ALA archives, which houses the documents of the International Relations Committee of ALA. It was found that library development changed in China during the period by borrowing from American librarianship as conveyed by the ALA, largely as a consequence of the following: American library advisors or educators, such as Arthur E. Bostwick, Charles H. Brown and Charles B. Shaw, conducting surveys of libraries in China; an American library and/or a library school in China; projects for the encouragement of public libraries; fellowships granted to Chinese librarians for study in the USA; the establishment and operation of the CLA; and the Book Program to strengthen library collections during the time of the China‐Japan War.
SIPP ACCESS, an information system for complex data: a case
study in creating a collaboratory for the social sciences
Authors: Robbin Alice
Published: July 2002

The “collaboratory” concept has recently entered the
vernacular of the scientific community to reflect new modes of
scientific communication, cooperation and collaboration made possible by
information technology. The collaboratory represents a scientific
research center “without walls” for accessing and sharing
data, information, instrumentation and computational resources. The
principal applications of the collaboratory concept have been in the
physical and biological sciences, including space physics, oceanography
and molecular biology. Discusses the attributes of the collaboratory,
and applies the concept developed by computer and physical scientists to
the design and operation of the SIPPACCESS prototype information
system for complex data to be used through the Internet by sociologists,
demographers and economists. Examines obstacles to collaboratory
development for the social sciences. Concludes that four major obstacles
will inhibit the development of collaboratories in the social sciences.
Differential chemical labeling of the AlcR DNA‐binding domain from Aspergillas nidulans versus its complex with a 16‐mer DNA target: Identification of an essential tryptophan involved in the recognition and the interaction with the nucleic acid
Authors: Marie Gérald , Serani Laurent , Laprévote Olivier , Cahuzac Bertrand , Guittet Eric , Felenbok Béatrice
Published: July 2002

DNA binding of the ethanol regulon transcription factor AlcR from Aspergillus nidulans was shown to involve a consensus basic region as in the other zinc cluster proteins. However, additional interactions between some residues and DNA were suspected, among which were a hypothetic hydrophobic interaction between Trp45 and the T residue of the consensus TGCGG sequence. In the present study, the differential chemical labeling of both the free protein and the protein/DNA complex showed significantly different behaviors of the three tryptophan residues comprised in the AlcR sequence toward the Koshland reagent. The spectacular decreased reaction rate for Trp45 within the complex confirmed the location of this residue at the protein/DNA interface. A similar result obtained with Trp53, an amino acid present at the C‐terminal side of AlcR, also indicated its involvement in the DNA recognition. In contrast, the formation of the complex accompanied by an allosteric rearrangement allowed the Trp36 to be much more exposed to the solvent than in the free protein. These data provide additional evidence that the unique specificity of AlcR among the zinc binuclear cluster family results in new types of interactions between AlcR and its cognate targets. From a methodological point of view, the approach of differential chemical labeling combined with mass spectrometric analyses proved to be an interesting tool for the recognition of hydrophobic interactions between the tryptophan residues of a protein and its macromolecular target.
Experimental determination and calculations of redox potential descriptors of compounds directed against retroviral zinc fingers: Implications for rational drug design
Authors: Topol Igor A. , McGrath Connor , Chertova Elena , Dasenbrock Catherine , Lacourse William R. , Eissenstat Michael A. , Burt Stanley K. , Henderson Louis E. , Casas‐Finet José R.
Published: July 2002

A diverse set of electrophilic compounds that react with cysteine thiolates in retroviral nucleocapsid (NC) proteins and abolish virus infectivity has been identified. Although different in chemical composition, these compounds are all oxidizing agents that lead to the ejection of Zn(II) ions bound to conserved structural motifs (zinc fingers) present in retroviral NC proteins. The reactivity of a congeneric series of aromatic disulfides toward the NC protein of the human immunodeficiency virus type 1 (HIV‐1), NCp7, has been characterized by HPLC separation of starting reagents from reaction products. We calculated the absolute redox potentials of these compounds in the gas phase and in aqueous solvent, using a density functional theory method and a continuum solvation model. Pulsed polarography experiments were performed and showed a direct correlation between calculated and experimentally determined redox propensities. A dependence between protein reactivity and redox potential for a specific compound was shown: Reaction with NCp7 did not take place below a threshold value of redox potential. This relationship permits the distinction between active and nonactive compounds targeted against NCp7, and provides a theoretical basis for a scale of reactivity with retroviral zinc fingers. Our results indicate that electrophilic agents with adequate thiophilicity to react with retroviral NC fingers can now be designed using known or calculated electrochemical properties. This may assist in the design of antiretroviral compounds with greater specificity for NC protein. Such electrophilic agents can be used in retrovirus inactivation with the intent of preparing a whole‐killed virus vaccine formulation that exhibits unaffected surface antigenic properties.
Evidence that the human cutaneous venoarteriolar response is not mediated by adrenergic mechanisms
Authors: Crandall C. G. , Shibasaki M. , Yen T. C.
Published: July 2002

The venoarteriolar response causes vasoconstriction to skin and muscle via local mechanisms secondary to venous congestion. The purpose of this project was to investigate whether this response occurs through α‐adrenergic mechanisms. In supine individuals, forearm skin blood flow was monitored via laser‐Doppler flowmetry over sites following local administration of terazosin (α1‐antagonist), yohimbine (α2‐antagonist), phentolamine (non‐selective α‐antagonist) and bretylium tosylate (inhibits neurotransmission of adrenergic nerves) via intradermal microdialysis or intradermal injection. In addition, skin blood flow was monitored over an area of forearm skin that was locally anaesthetized via application of EMLA (2.5 % lidocaine (lignocaine) and 2.5 % prilocaine) cream. Skin blood flow was also monitored over adjacent sites that received the vehicle for the specified drug. Each trial was performed on a minimum of seven subjects and on separate days. The venoarteriolar response was engaged by lowering the subject's arm from heart level such that the sites of skin blood flow measurement were 34 ± 1 cm below the heart. The arm remained in this position for 2 min. Selective and non‐selective α‐adrenoceptor antagonism and presynaptic inhibition of adrenergic neurotransmission did not abolish the venoarteriolar response. However, local anaesthesia blocked the venoarteriolar response without altering α‐adrenergic mediated vasoconstriction. These data suggest that the venoarteriolar response does not occur through adrenergic mechanisms as previously reported. Rather, the venoarteriolar response may due to myogenic mechanisms associated with changes in vascular pressure or is mediated by a non‐adrenergic, but neurally mediated, local mechanism.
Mg2+‐sensitive non‐capacitative basolateral Ca2+ entry secondary to cell swelling in the polarized renal A6 epithelium
Authors: Jans Danny , De Weer Paul , Srinivas S. P. , Larivière Els , Simaels Jeannine , Van Driessche Willy
Published: July 2002

Polarized renal A6 epithelia respond to hyposmotic shock with an increase in transepithelial capacitance (CT) that is inhibited by extracellular Mg2+. Elevation of free cytosolic [Ca2+] ([Ca2+]i) is known to increase CT. Therefore, we examined [Ca2+]i dynamics and their sensitivity to extracellular Mg2+ during hyposmotic conditions. Fura‐2‐loaded A6 monolayers, cultured on permeable supports were subjected to a sudden reduction in osmolality at both the basolateral and apical membranes from 260 to 140 mosmol (kg H2O)−1. Reduction of apical osmolality alone did not affect [Ca2+]i. In the absence of extracellular Mg2+, the hyposmotic shock induced a biphasic rise in [Ca2+]i. The first phase peaked within 40 s and [Ca2+]i increased from 245 ± 12 to 606 ± 24 nm. This phase was unaffected by removal of extracellular Ca2+, but was abolished by activating P2Y receptors with basolateral ATP or by exposing the cells to the phospholipase C (PLC) inhibitor U73122 prior to the osmotic shock. Suramin also severely attenuated this first phase, suggesting that the first phase of the [Ca2+]i rise followed swelling‐induced ATP release. The PLC inhibitor, the ATP treatment or suramin did not affect a second rise of [Ca2+]i to a maximum of 628 ± 31 nm. The second phase depended on Ca2+ in the basolateral perfusate and was largely suppressed by 2 mm basolateral Mg2+. Acute exposure of the basolateral membrane to Mg2+ during the upstroke of the second phase caused a rapid decline in [Ca2+]i. Basolateral Mg2+ inhibited Ca2+ entry in a dose‐dependent manner with an inhibition constant (Ki) of 0.60 mm. These results show that polarized A6 epithelia respond to hyposmotic shock by Ca2+ release from inositol trisphosphate‐sensitive stores, followed by basolateral Ca2+ influx through a Mg2+‐sensitive pathway. The second phase of the [Ca2+]i response is independent of the initial intracellular Ca2+ release and therefore constitutes non‐capacitative Ca2+ entry.
Interactive effect of chondroitin sulphate C and hyaluronan on fluid movement across rabbit synovium
Authors: Sabaratnam S. , Coleman P. J. , Badrick E. , Mason R. M. , Levick J. R.
Published: July 2002

The polysaccharide hyaluronan (HA) conserves synovial fluid by keeping outflow low and almost constant over a wide pressure range (‘‘buffering’), but only at concentrations associated with polymer domain overlap. We therefore tested whether polymer interactions can cause buffering, using HA‐chondroitin sulphate C (CSC) mixtures. Also, since it has been found that capillary filtration is insensitive to the Starling force interstitial osmotic pressure in frog mesenteries, this was assessed in synovium. Hyaluronan at non‐buffering concentrations (0.50–0.75 mg ml−1) and/or 25 mg ml−1 CSC (osmotic pressure 68 cmH2O) was infused into knees of anaesthetised rabbits in vivo. Viscometry and chromatography confirmed that HA interacts with CSC. Pressure (Pj) versus trans‐synovial flow (˙Qs) relations were measured. ˙Qs was outwards for HA alone (1.2 ± 0.9 μl min−1 at 3 cmH2O, mean ±s.e.m.; n= 6). CSC diffused into synovium and changed ˙Qs to filtration at low Pj (−4.1 μl min−1, 3 cmH2O, n= 5, P < 0.02, t test). Filtration ceased upon circulatory arrest (n= 3). At higher Pj, 0.75 mg ml−1 HA plus CSC buffered ˙Qs to ∼3 μl min−1 over a wide range of Pj, with an outflow increase of only 0.04 ± 0.02 μl min−1 cmH2O−1 (n= 4). With HA or CSC alone, buffering was absent (slopes 0.57 ± 0.04 μl min−1 cmH2O−1 (n= 4) and 0.86 ± 0.05 μl min−1 cmH2O−1 (n= 5), respectively). Therefore, polymer interactions can cause outflow buffering in joints. Also, interstitial osmotic pressure promoted filtration in fenestrated synovial capillaries, so the results for frog mesentery capillaries cannot be generalised. The difference is attributed to differences in pore ultrastructure.
Mechanical function of intermediate filaments in arteries of different size examined using desmin deficient mice
Authors: Wede Oskar Karlsson , Löfgren Mia , Li Zhenlin , Paulin Denise , Arner Anders
Published: July 2002

Protein composition and mechanical function of intermediate filaments were examined in arteries of different sizes using desmin deficient mice (Des−/−) and their wild‐type controls (Des+/+). Using SDS‐PAGE gels and Western blots we found a gradient in desmin expression in the arterial tree; the desmin content increased from the elastic artery aorta, via the muscular mesenteric artery to the resistance‐sized mesenteric microarteries ∼150 μm in diameter in Des+/+ mice. Mechanical experiments were performed on the aorta, the mesenteric artery and resistance‐sized arteries using wire myographs. For aorta and mesenteric artery, no differences in passive or active circumference‐ stress relations were found between Des−/− and Des+/+ mice. In microarteries, both passive and active stress were lower in the Des−/− group. In conclusion, large elastic and muscular arteries contain a relatively low amount of desmin, and the desmin intermediate filaments do not seem to play a major role in the mechanical properties of these larger arterial vessels. In the microarteries, where expression of desmin is high, desmin plays a role in supporting both passive and active tension.
High-Performance Radial AMTEC Cell Design for Ultra-High-Power Solar AMTEC Systems
Authors: Hendricks Terry J. , Huang Chendong
Published: July 2002

Solar thermal Alkali-Metal-Thermal-to-Electric-Conversion (AMTEC) power systems potentially have several important advantages over current solar photovoltaic power systems in ultra-high-power spacecraft applications for medium-earth orbit (MEO) and geosynchronous orbit (GEO) missions. This work presents key aspects of radial AMTEC cell design to achieve high cell performance in solar AMTEC systems delivering larger than 50 kW(e) with AMTEC cell conversion efficiency larger than 22 percent. A new design parameter methodology is demonstrated establishing optimum design parameters in radial cell design to satisfy high-power mission requirements. Specific temperature- and pressure-dependent relationships define critical dependencies between key cell design parameters, particularly the impact of parasitic thermal losses on Beta Alumina Solid Electrolyte (BASE) area requirements, voltage, BASE tube number, and system power production for maximum power-per-BASE-area and optimum efficiency conditions. High-level system tradeoffs are demonstrated using the design parameter methodology to establish high-power radial cell design requirements and determine optimum radial AMTEC designs. [S0199-6231(00)00102-7]
Optical Properties in the Visible of Overfire Soot in Large Buoyant Turbulent Diffusion Flames
Authors: Krishnan S. S. , Lin K.-C. , Faeth G. M.
Published: July 2002

Nonintrusive measurements of the optical properties of soot at visible wavelengths (351.2–800.0 nm) were completed for soot in the overfire region of large (2–7 kW) buoyant turbulent diffusion flames burning in still air at standard temperature and pressure, where soot properties are independent of position and characteristic flame residence time for a particular fuel. Soot from flames fueled with gaseous (acetylene, ethylene, propylene, and butadiene) and liquid (benzene, cyclohexane, toluene, and n-heptane) hydrocarbon fuels were studied. Scattering and extinction measurements were interpreted to find soot optical properties using the Rayleigh-Debye-Gans/polydisperse-fractal-aggregate theory after establishing that this theory provided good predictions of scattering patterns over the present test range. Effects of fuel type on soot optical properties were comparable to experimental uncertainties. Dimensionless extinction coefficients were relatively independent of wavelength for wavelengths of 400–800 nm and yielded a mean value of 8.4 in good agreement with earlier measurements. Present measurements of the refractive index function for absorption, Em, were in good agreement with earlier independent measurements of Dalzell and Sarofim and Stagg and Charalampopoulos. Present values of the refractive index function for scattering, Fm, however, only agreed with these earlier measurements for wavelengths of 400–550 nm but otherwise increased with increasing wavelength more rapidly than the rest. The comparison between present and earlier measurements of the real and imaginary parts of the complex refractive index was similar to Em and Fm.[S0022-1481(00)02203-9]
LearnIT: An Instance-Based Approach to Learning and Reusing Design Strategies
Authors: Stahovich Thomas F.
Published: July 2002

We describe LearnIT, a computer program that can observe an iterative solution to a parametric design problem and learn the design strategy employed. When the design requirements change, the program uses the learned strategy to automatically generate a new solution in the “style” of the original. The program uses a specialized instance-based learning method based on the observation that iterative design is often a form of debugging—each iteration is an attempt to repair a particular flaw in the design. Thus, the program learns the design strategy by observing what actions are taken in response to each kind of flaw. [S1050-0472(00)01203-4]
Effect of Fluid Inertia on Stability of Oil Journal Bearings
Authors: Kakoty S. K. , Majumdar B. C.
Published: July 2002

In the analysis of hydrodynamic journal bearings the effect of fluid inertia is generally neglected in view of its negligible contribution compared to viscous forces. However, the fluid inertia effect is to be taken in the analysis when modified Reynolds number is around one. Though there are a few attempts to analyze steady-state and dynamic characteristics of finite journal bearings, stability of the journal under the effect of fluid inertia is yet to be investigated. An attempt has been made to evaluate the mass parameter (a measure of stability) besides finding out the steady-state characteristics of finite journal bearings considering the effects of fluid inertia. The analysis is carried out for modified Reynolds number ∼O(1.), which is assumed to be laminar. A nonlinear time transient analysis is carried out for the stability analysis. [S0742-4787(00)00204-6]
A Constitutive Model for Distributed Microcracking In Titanium Matrix Composite Laminae
Authors: Ball D. L. , Chan W. S.
Published: July 2002

The ply constitutive relations of an energy-based model for distributed microcracking in continuous fiber reinforced metal matrix composites are presented. Simple models for damage progression are used in conjunction with these damage dependent constitutive relations to allow the prediction of fatigue life under constant amplitude, isothermal conditions. The microcracking model is discussed in the context of fatigue analysis of unnotched titanium matrix composite laminates. Analytical results generated by using this model in a unidirectional laminate analysis algorithm are presented and compared with experimental results. [S0094-4289(00)03104-2]
Kinematic Accuracy of Three Surface Registration Methods in a Three-Dimensional Wrist Bone Study
Authors: Neu C. P. , McGovern R. D. , Crisco J. J.
Published: July 2002

The use of registration techniques to determine motion transformations noninvasively has become more widespread with the increased availability of the necessary software. In this study, three surface registration techniques were used to generate carpal bone kinematic results from a single cadaveric wrist specimen. Surface contours were extracted from specimen computed tomography volume images of the forearm, carpal, and metacarpal bones in four arbitrary positions. Kinematic results from each of three registration techniques were compared with results derived from multiple spherical markers fixed to the specimen. Kinematic accuracy was found to depend on the registration method and bone size and shape. In general, rotation errors of the capitate and scaphoid were less than 0.5 deg for all three techniques. Rotation errors for the other bones were generally less than 2 deg, although error for the trapezoid was greater than 2 deg in one technique. Translation errors of the bones were generally less than 1 mm, although errors of the trapezoid and trapezium were greater than 1 mm for two techniques. Tradeoffs existed in each registration method between image processing time and overall kinematic accuracy. Markerless bone registration (MBR) can provide accurate measurements of carpal kinematics and can be used to study the noninvasive, three-dimensional in vivo kinematics of the wrist and other skeletal joints. [S0148-0731(00)01105-5]
A Cellular Solid Model for Modulus Reduction Due to Resorption of Trabeculae in Bone
Authors: Vajjhala S. , Kraynik A. M. , Gibson L. J.
Published: July 2002

In osteoporotic trabecular bone, bone loss occurs by thinning and subsequent resorption of the trabeculae. In this study, we compare the effects of density reductions from uniform thinning of struts or from removal of struts in a random, open-cell, three-dimensional Voronoi structure. The results of this study, combined with those previous studies on other regular and random structures, suggest that the modulus and strength of trabecular bone are reduced more dramatically by density losses from resorption of trabeculae than by those from uniform thinning of trabeculae. [S0148-0731(00)00805-0]
The Carothers Paradox in the Case of a Nonclassical Couple
Authors: Paukshto M. , Pitkin A.
Published: July 2002

The Carothers solution for a wedge loaded by a concentrated couple at its vertex is known to be valid for the wedge angles 2α<2α*≈257 deg only. Moreover, for π<2α<2α* it exists for antisymmetric loading only. The more realistic model of the concentrated couple of the arbitrary orientation is examined by the approach of Dundurs-Markenscoff. It is shown that the Carothers type solution holds for the edge angles 2α<π.[S0021-8936(00)00402-5]
Direct and Inverse Solutions for Elastohydrodynamic Lubrication of Finite Porous Journal Bearings
Authors: Elsharkawy Abdallah A. , Guedouar Lotfi H.
Published: July 2002

In this paper a numerical solution for the elastohydrodynamic lubrication of a finite porous journal bearing is presented. The Brinkman–extended Darcy model was applied within the porous layer to incorporate the viscous shear stresses into the analysis. A simple elastic model is used to describe the elastic deformation of the liner. An inverse model is introduced to estimate the permeability parameter and/or the eccentricity ratio from experimentally obtained pressure data. As experimental measurements were not conducted, these data were simulated numerically. It consists of a direct solution for the pressure, for given parameters (permeability parameter and/or the eccentricity ratio), to which a normally distributed random error is added. The least-squares optimization technique is used to solve the proposed inverse problem. A unique solution was obtained for one-parameter estimation. The two-parameter estimation case, however, leads to multiple solutions lying on a constant load line.
Numerical Computation of Differential-Algebraic Equations for the Approximation of Artificial Satellite Trajectories and Planetary Ephemerides
Authors: Fox B. , Jennings L. S. , Zomaya A. Y.
Published: July 2002

The principle of virtual work and Lagrange’s equations of motion are used to construct a system of differential equations for constrained spatial multibody system modeling. The differential equations are augmented with algebraic constraints representing the system being modeled. The resulting system is a high index differential-algebraic equation (DAE) which is cast as an ordinary differential equation (ODE) by differentiating the constraint equations twice. The initial conditions are the heliocentric rectangular equatorial generalized coordinates and their first time derivatives of the planets of the solar system and an artificial satellite. The ODE is computed using the integration subroutine LSODAR to generate the body generalized coordinates and time derivatives and hence produce the planetary ephemerides and satellite trajectories for a time interval. Computer simulation and graphical output indicate the satellite and planetary positions and the latter may be compared with those provided in the Astronomical Almanac. Constraint compliance is investigated to establish the accuracy of the computation. [S0021-8936(00)03403-6]
On Gaseous Free-Convection Heat Transfer With Well-Defined Boundary Conditions
Authors: Davies M. R. D. , Newport D. T. , Dalton T. M.
Published: July 2002

The scaling of free convection heat transfer is investigated. The nondimensional groups for Boussinesq and fully compressible variable property free convection, driven by isothermal surfaces, are derived using a previously published novel method of dimensional analysis. Both flows are described by a different set of groups. The applicability of each flow description is experimentally investigated for the case of the isothermal horizontal cylinder in an air-filled isothermal enclosure. The approach taken to the boundary conditions differs from that of previous investigations. Here, it is argued that the best definition of the boundary conditions is achieved for heat exchange between the cylinder and the enclosure rather than the cylinder and an arbitrarily chosen fluid region. The enclosure temperature is shown both analytically and experimentally to affect the Nusselt number. The previously published view that the Boussinesq approximation has only a limited range of application is confirmed, and the groups derived for variable property compressible free convection are demonstrated to be correct experimentally. A new correlation for horizontal cylinder Nusselt number prediction is presented. [S0022-1481(00)01604-2]
Numerical Simulation of Mechanical Effects in Composite Structures by the Finite Element Method
Authors: Mu¨ller C. , Bohmann A.
Published: July 2002

In electromagnetic railgun experiments at ISL, the composite projectiles are accelerated up to 2000 m/s with a maximal acceleration of 7×106 m/s2. The maximum forces typically will have been achieved after 200 μs. One consequence of this dynamic load is a strain rate in the order of ε˙=2000 s−1, a rate at which metals are also giving up their static properties. The aim of research at ISL is the construction of a fiber-reinforced sabot adapted for dynamic bearing. FE simulations support the construction process as well as allowing a detailed study of the mechanical effects occurring during the acceleration of the sabot. The most important problem of dynamical simulation of composites is an adequate material model. We show in this paper, that the classical homogenized laminate models are insufficient to be used in dynamics. To develop an appropriate material model, we investigated selected materials statically as well as dynamically and we compared the experimental results with those of their numerical simulation. For a first material model approach, we made quasi-static experiments with a special sabot geometry. The quasi-static investigations have revealed that different conditions, e.g., lateral support, involve a completely different system answer. We found that a specimen without radial strain has more than the double strength of a specimen that allows radial strain, whereby the system answer still remains linear elastic and only very little internal delamination occurs. A second step toward a material model consists of dynamic experiments with specimens in a simple cylinder geometry on a Split Hopkinson Pressure Bar test facility. The specimens are made of fiber-reinforced epoxy, as well as metal-matrix composites. The dynamic experiments proved the strain as principal failure criterion for dynamic bearing, whereby the failure strain depends upon the momentary strain rate. Failure strain is also a historical function, so that the deformation history is important. We can show that the viscous polymer matrix plays a very important role for the dynamic toughness of reinforced materials. When the material fails, the stress is far beyond that of static failure: up to two times the static strength has been measured. Experiments with real sabots in railguns have shown that the failure occurs a relatively long time after the stress has achieved its maximum.
Asymptotic Stability Analysis for Sheet Metal Forming—Part II: Application
Authors: Scherzinger W. , Chu E. , Triantafyllidis N.
Published: July 2002

The general asymptotic method proposed in Part I is applied to the investigation of the puckering instability in the hemispherical cup test. Both a membrane and a shell stress state for the principal axisymmetric solution have been considered. Due to the possibility of strong deviations from proportional loading in some cases, a corner theory of plasticity is also employed, in addition to the standard J2 deformation theory which is often used in plastic buckling calculations. Results are compared to a previous experimental investigation for brass specimens. [S0021-8936(00)00904-1]
Nonlinear Dynamics of a Taut String with Material Nonlinearities
Authors: Leamy M. J. , Gottlieb O.
Published: July 2002

A spatial string model incorporating a nonlinear (and nonconservative) material law is proposed using finite deformation continuum mechanics. The resulting model is shown to reduce to the classical nonlinear string when a linear material law is used. The influence of material nonlinearities on the string’s dynamic response to excitation near a transverse natural frequency is shown to be small due to their appearance at high orders only. Material nonlinearities appear at low order in the equations for excitation near a longitudinal natural frequency, and a solution for this case is developed by applying a second order multiple scales method directly to the partial differential equations. The material nonlinearities are found to influence both the degree of nonlinearity in the response and its softening or hardening nature.
A Stress and Relative Density-Dependent Dynamic Compliance Spectra Model of the Creep Response of Microcellular Polycarbonate
Authors: Armstrong W. D. , Kumar V.
Published: July 2002

The present paper reports a new discrete complex compliance spectra method in which each frequency component is a direct function of stress and relative density. Comparisons between model calculations and experimental measurements show that the model exhibits excellent quantitative agreement at all experimental stress-relative density states and significantly smoothes the experimental input data. It is anticipated that design engineers will use the present method to accurately predict the creep strain histories resulting from a broad range of specific stress-relative density combinations. [S0021-8936(00)01804-3]
Heat Transfer Enhancements in Rotating Two-Pass Coolant Channels With Profiled Ribs: Part 1–Average Results
Authors: Acharya S. , Eliades V. , Nikitopoulos D. E.
Published: July 2002

The effects of ribs with different cross-stream profiles are investigated through detailed, surface mass (heat) transfer distributions along four active walls of a square duct containing a sharp 180 deg bend. The duct simulates two passes of an internal coolant channel in a gas turbine engine with ribs mounted on two opposite walls. Mass (heat) transfer measurements, taken using the naphthalene sublimation technique, are presented for a Reynolds number of 30,000, and rotation number of 0.3. Comparisons are made with conventional ribs having a rectangular cross section. It is shown that the use of certain profiled ribs provides considerable heat transfer enhancements over conventional ribs with the same blockage ratio in the duct. These enhancements are attributed to the generation of longitudinal vorticity (or secondary flows) by the profiled ribs in the channel.
Topology Synthesis of Compliant Mechanisms for Nonlinear Force-Deflection and Curved Path Specifications
Authors: Saxena A. , Ananthasuresh G. K.
Published: July 2002

Optimal design methods that use continuum mechanics models are capable of generating suitable topology, shape, and dimensions of compliant mechanisms for desired specifications. Synthesis procedures that use linear elastic finite element models are not quantitatively accurate for large displacement situations. Also, design specifications involving nonlinear force-deflection characteristics and generation of a curved path for the output port cannot be realized with linear models. In this paper, the synthesis of compliant mechanisms is performed using geometrically nonlinear finite element models that appropriately account for large displacements. Frame elements are chosen because of ease of implementation of the general approach and their ability to capture bending deformations. A method for nonlinear design sensitivity analysis is described. Examples are included to illustrate the usefulness of the synthesis method.
Near Wall Measurements for a Turbulent Impinging Slot Jet (Data Bank Contribution)1
Authors: Zhe Jiang , Modi Vijay
Published: July 2002

The velocity field in the vicinity of a target surface with a turbulent slot jet impinging normally on it is examined. The impingement region is confined by means of a confinement plate that is flush with the slot and parallel to the impingement plate. The distance H of the impingement wall from the slot is varied from 2 to 9.2 slot widths. Jet Reynolds numbers (based on slot width B) of 10,000–30,000 are considered. Mean velocity and root mean square velocity measurements are carried out using hot-wire anemometry. A boundary layer probe is utilized in order to obtain measurements at a wall distance as close as 110 microns 0.0028B. This corresponds to a distance of approximately y+∼2-4 in wall units and is found to be adequate in order to permit an estimate of wall shear under most conditions. The problems of hot wire interference with the wall and calibration at low velocities are solved by calibrating the probe in a known Blasius flow. With the exception of the stagnation region where shear could not be evaluated, it is found that velocity profiles follow a linear behavior in the viscous sublayer everywhere along the wall. Results indicate that the peak in normal stress occurs at y/B∼0.025 to 0.04 at a distance six to eight jet widths away from the jet-axis.
Higher Order Perturbation Analysis of Stochastic Thermal Systems With Correlated Uncertain Properties
Authors: Emery A. F.
Published: July 2002

How the behavior of thermal systems depends on uncertainties in properties and boundary conditions is an important aspect of simulation. This dependence is usually judged by the statistics of the response, i.e., the mean response and its standard deviation which are often determined by perturbation methods, ranging from 1st to 3rd order. The aim of this paper is to be a tutorial for those interested in estimating uncertainties by summarizing the author’s experience in using higher order perturbation analysis for thermal problems, detailing the underlying assumptions, and presenting several examples. Problems involving correlated parameters, which occur in almost all thermal experiments, are also treated. It is shown that the scale of correlation has a strong effect upon the statistics of the response and that such correlation should not be ignored. It is recommended that the 1st order estimates of the standard deviation and 2nd order estimates of the mean response be used when characterizing thermal systems with random variables, regardless of the degree of correlation.
Infinitesimal-Area Radiative Analysis Using Parametric Surface Representation, Through NURBS
Authors: Daun K. J. , Hollands K. G. T.
Published: July 2002

The use of form factors in the treatment of radiant enclosures requires the radiosity be approximated as uniform over finite areas, and so when higher accuracy is required, an infinitesimal-area analysis should be applied. This paper describes a generic infinitesimal-area formulation suited in principle for any enclosure containing a transparent medium. The surfaces are first represented parametrically, through “non-uniform rational B-spline” (NURBS) functions, the industry standard in CAD-CAM codes. The kernel of the integral equation is obtained without user intervention, using NURBS algorithms, and then the integral equation is solved numerically. The resulting general-purpose code, which proceeds directly from surface specification to solution, is tested on problems taken from the literature.
Integration of Advanced Gas Turbines in Pulp and Paper Mills for Increased Power Generation
Authors: Maunsbach K. , Isaksson A. , Yan J. , Svedberg G. , Eidensten L.
Published: July 2002

The pulp and paper industry handles large amounts of energy and today produces the steam needed for the process and some of the required electricity. Several studies have shown that black liquor gasification and combined cycles increase the power production significantly compared to the traditional processes used today. It is of interest to investigate the performance when advanced gas turbines are integrated with next-generation pulp and paper mills. The present study focused on comparing the combined cycle with the integration of advanced gas turbines such as steam injected gas turbine (STIG) and evaporative gas turbine (EvGT) in pulp and paper mills. Two categories of simulations have been performed: (1) comparison of gasification of both black liquor and biomass connected to either a combined cycle or steam injected gas turbine with a heat recovery steam generator; (2) externally fired gas turbine in combination with the traditional recovery boiler. The energy demand of the pulp and paper mills is satisfied in all cases and the possibility to deliver a power surplus for external use is verified. The study investigates new system combinations of applications for advanced gas turbines.
Alternative Design of Flexible Jumpers for Deepwater Hybrid Riser Configurations
Authors: Fernandes Antonio C. , Jacob Breno P. , Silva Renato M. C. , Carvalho Roge´rio A. , Lemos Carlos A. D.
Published: July 2002

Recent studies on the behavior of the simple free-hanging configuration for flexible risers have shown that, for very deepwater levels, they are reaching their technical and economic limits. Other alternative configurations are currently being investigated, including hybrid riser configurations based on flexible jumpers connected to an intermediate point closer to the free surface (usually a submerged buoy). This work focuses on the jumper issue, considering that, since it is completely suspended, its behavior may differ significantly from the behavior of a riser resting on the seabed. Therefore, the usual design procedure employed for conventional applications may not be completely adequate, and should be complemented by alternative approaches. This work considers analytical, numerical, and experimental approaches for the design of flexible jumpers. First, a comprehensive static analysis using consistent catenary concepts is developed; this results in criteria that are essential for safe design. Subsequently, a modal analysis procedure is described; this procedure considers the nonlinear behavior of the jumpers under the static component of the environmental loads, and may show the existence of resonant modes that require careful consideration. This defines the importance of damping mechanisms, and orients parametric time-domain nonlinear verifications. Finally, reduced model tests are considered, devised specifically to investigate the jumper behavior under centenary conditions. The design of the physical model and the similarity analysis of the experimental results are also presented.
Process Window Derivation With an Application to Optical Media Manufacturing
Authors: Kazmer David , Zhu Liang , Hatch David
Published: July 2002

This paper derives the process window from quantitative process models. Multi-dimensional clipping algorithms are developed that operate on half-spaces defined from the quality specifications. The resulting polytope is difficult to directly interpret. To support interactive tuning and optimization of manufacturing processes, three types of graphical matrices are presented to the decision maker: (1) the function matrix describes the relations between the process parameters and the manufactured part quality attributes; (2) the process space illustrates the feasible processing space constrained by the product quality specifications; (3) the performance space provides the feasible region of the part quality attributes and the Pareto Optimal set corresponding to the processing space. Optimization of optical media manufacturing is presented to demonstrate the use of the process window to locate a feasible solution and proceed to a desired trade-off of multiple quality attributes.
Slow Crack Growth Analysis of Advanced Structural Ceramics Under Combined Loading Conditions: Damage Assessment in Life Prediction Testing
Authors: Choi S. R. , Gyekenyesi J. P.
Published: July 2002

Slow crack growth analysis was performed with three different loading histories including constant stress-rate/constant stress-rate testing (Case I loading), constant stress/constant stress-rate testing (Case II loading), and cyclic stress/constant stress-rate testing (Case III loading). Strength degradation due to slow crack growth and/or damage accumulation was determined numerically as a function of percentage of interruption time between the two loading sequences for a given loading history. The numerical solutions were examined with the experimental data determined at elevated temperatures using four different advanced ceramic materials, two silicon nitrides, one silicon carbide and one alumina for the Case I loading history, and alumina for the Case II loading history. The numerical solutions were in reasonable agreement with the experimental data, indicating that notwithstanding some degree of creep deformation presented for some test materials slow crack growth was a governing mechanism associated with failure for all the test materials.
Some Aspects of Wake-Wake Interactions Regarding Turbine Stator Clocking
Authors: Tiedemann Maik , Kost Friedrich
Published: July 2002

This investigation is aimed at an experimental determination of the unsteady flowfield downstream of a transonic high pressure turbine stage. The single stage measurements, which were part of a joined European project, were conducted in the windtunnel for rotating cascades of the DLR Go¨ttingen. Laser-2-focus (L2F) measurements were carried out in order to determine the Mach number, flow angle, and turbulence distributions. Furthermore, a fast response pitot probe was utilized to determine the total pressure distribution. The measurement position for both systems was 0.5 axial rotor chord downstream of the rotor trailing edge at midspan. While the measurement position remained fixed, the nozzle guide vane (NGV) was “clocked” to 12 positions covering one NGV pitch. The periodic fluctuations of the total pressure downstream of the turbine stage indicate that the NGV wake damps the total pressure fluctuations caused by the rotor wakes. Furthermore, the random fluctuations are significantly lower in the NGV wake affected region. Similar conclusions were drawn from the L2F turbulence data. Since the location of the interaction between NGV wake and rotor wake is determined by the NGV position, the described effects are potential causes for the benefits of “stator clocking” which have been observed by many researchers.
Multi-Modal Analysis of Human Motion From External Measurements
Authors: Dariush Behzad , Hemami Hooshang , Parnianpour Mohamad
Published: July 2002

The “analysis” or “inverse dynamics” problem in human motion studies assumes knowledge of the motion of the dynamical system in various forms and/or measurements of ground reaction forces to determine the applied forces and moments at the joints. Conceptually, methods of attacking such problems are well developed and satisfactory solutions have been obtained if the input signals are noise free and the dynamic model is perfect. In this ideal case, an inverse solution exists, is unique, and depends continuously on the initial data. However, the inverse solution may require the calculation of higher order derivatives of experimental observations contaminated by noise—a notoriously difficult problem. The byproduct of errors due to numerical differentiation is grossly erroneous joint force and moment calculations. This paper provides a framework for analyzing human motion for different sensing conditions in a manner that avoids or minimizes the number of derivative computations. In particular, two sensing modalities are considered: 1) image based and 2) multi-modal sensing: combining imaging, force plate, and accelerometery.