bluuebunny/crossref_metadata_2025_split huggingface dataset:
Real contact mechanisms and finite element formulation—a coupled thermomechanical approach
Authors: Zavarise G. , Wriggers P. , Stein E. , Schrefler B. A. 
Published: November 2005

AbstractThe solution of contact problems involves great numerical efforts to satisfy non‐penetration conditions. The search for numerical efficiency hence has limited the modelling of the real physical interface behaviour. Up to now mainly simple laws, usually formulated using constant coefficients, have been available to study contact problems in uncoupled from.Here a thermomechanically coupled contact element is presented which accounts for the real microscopic shape of the surfaces, the microscopic mechanism of force transmission and heat exchange. The contact element geometrical behaviour has been put together with experimental and theoretical well founded micro‐mechanical and micro‐thermal laws adapted to Finite Element Method (FEM) necessities. Based on these laws the macroscopic related stiffnesses are calculated and continuously updated taking into account changes in significant parameters. The linearization of the set of equations has been obtained using a consistent technique which implies computational efficiency.
An element formulation for the classical finite difference and finite volume method applied to arbitrarily shaped domains
Authors: Lahrmann Andreas 
Published: November 2005

AbstractPotential problems can be solved by analytical methods. However, for three‐dimensional structures of geometrically complex shape with non‐linear boundary conditions, numerical methods have to be applied. The most popular technique is the finite element method, which is used throughout the engineering community. The main advantage of this method lies in the application to arbitrarily shaped structures, which requires the use of non‐orthogonal meshes. More recently, the boundary element method has been proven to be a competitive tool in the field of potential problems.In other research areas different numerical methods are used, for example in fluid mechanics the finite volume or the finite difference methods. But the application to irregularly shaped domains is difficult compared to the finite element and boundary element methods. The big drawback of these methods is not a poor numerical quality, but the absence of an element concept. In some cases, the results are even better compared to the other methods. Therefore, the main subject of this paper is the introduction of the element concept not only for the popular finite element method, but also for the finite difference and finite volume methods, which provides a high degree of geometric flexibility.
A knowledge‐based A‐priori approach to mesh generation in thermal problems
Authors: Kang E. , Haghighi K. 
Published: November 2005

AbstractA new approach to the finite element mesh generation for two‐dimensional steady state thermal problems of conduction and convection is presented. Unlike other approaches, the proposed technique incorporates the information about the object geometry as well as the boundary and loading conditions to generate an a‐priori finite element mesh which is more refined around the critical regions of the problem domain. A blackboard architecture expert system is developed to intelligently identify critical regions and to choose the proper mesh size for them by performing an approximate heat flux calculation. From the results of the blackboard system, nodes are generated in the problem domain using the new concept of wave propagation. The wave propagation technique is fully automatic and does not require any user‐provided information except the data which define the object geometry and boundary conditions. After nodes are generated, well‐shaped triangular elements are formed ensuring the Delaunay property. During the triangulation process and to reduce the computation time for checking the overlapping problem, a new and efficient algorithm is proposed which defines a certain range only in which a potential triangular element might overlap the previously generated elements and boundary segments. Several examples are presented and discussed. When incorporated into and compared with the traditional approach to the adaptive finite element analysis, it is expected that the proposed approach, which starts the process with near‐optimal initial meshes, will result in lower levels of error and faster convergence of the solution to the desired accuracy in less time and at less cost.
Non‐linear finite strip analysis of rectangular laminates under end shortening, using classical plate theory
Authors: Dawe D. J. , Lam S. S. E. , Azizian Z. G. 
Published: November 2005

AbstractThe finite strip method is developed for predicting the geometrically non‐linear response of rectangular composite laminates with simply supported ends when subjected to uniform end shortening in their plane. At the loaded ends lateral in‐plane expansion may be allowed freely or may be prevented completely in different versions of the approach. The permitted laminate material properties are quite general, encompassing anisotropy and full coupling between in‐plane and out‐of‐plane behaviour. The analysis is based on the use of the classical plate theory and the non‐linearity is introduced in the strain‐displacement equations in the manner of the von Karman assumptions. Three different types of finite strip are presented with either linear, quadratic or cubic interpolation of the membrane displacement components across a strip: in each case the bending displacement component varies cubically across a strip. Results are presented for isotropic plates and for unsymmetric cross‐ply, angle‐ply and arbitrary laminates.
An explicit unconditionally stable variable time‐step method for one‐dimensional stefan problems
Authors: Zerroukat M. , Chatwin C. R. 
Published: November 2005

AbstractModelling of heat conduction processes with phase changes benefits from the application of variable time‐step methods when the behaviour of the moving boundary is not knowna prioiri. Due to convergence and stability constraints only implicit difference equations have been used with these methods. Implicit methods show a significant loss of accuracy and exhibit convergence difficulties when used for relatively slow or rapid moving‐boundary problems. To overcome these problems an improved explicit variable time‐step method which combines the explicit exponential difference equation and a variable time‐step grid network with virtual subspace increments around the moving boundary is presented and tested for both a solidification and a melting problem. A virtual subinterval time‐step elimination technique is incorporated to ensure that stability is automatically maintained for any mesh size. Unlike the implicit variable time‐step methods, the accuracy of the resulting method is not affected by the velocity of the moving boundary. For both test problems numerical results are in better agreement with known analytical solutions than results predicted by other numerical methods.
A multigrid method for the generalized symmetric eigenvalue problem: Part I—algorithm and implementation
Authors: Hwang T. , Parsons I. D. 
Published: November 2005

AbstractA multigrid method is described that can solve the generalized eigenvalue problem encountered in structural dynamics. The algorithm combines relaxation on a fine mesh with the solution of a singular equation on a coarse mesh. A sequence of coarser meshes may be used to quickly solve this singular equation using another multigrid method. The hierarchy of increasingly finer meshes can be further exploited using a nested iteration scheme, whereby initial approximations to the fine mesh eigenvectors are computed using interpolated coarse mesh eigenvectors. The solution of some simple plate problems on a Convex C240 demonstrates the efficiency of a vectorized version of the multigrid algorithm.
Implementation of mixed time integration techniques on a vectorized computer with shared memory
Authors: Belytschko Ted , Gilbertsen Noreen D. 
Published: November 2005

AbstractThe implementation of subcycling in an explicit finite element program executed on a concurrent computer with shared memory is described. The effects of vectorization and parallelization on the speed‐up and efficiency achieved with subcycling is discussed. Numerical studies are presented to illustrate the effects of the number of processors, the size of element blocks and problem size. Finally, an efficient allocation algorithm which minimizes the effects of processor idleness is presented.
Thermoelastic stability of trusses with temperature‐dependent constitutive relations
Authors: Wriggers P. , Reese S. 
Published: November 2005

AbstractThis paper is concerned with stability problems of spatial trusses due to thermal and mechanical loading. A fully coupled thermomechanical truss element is formulated which accounts also for the temperature dependence of the constitutive parameters. The formulation leads to a non‐linear problem which is solved by the finite element method. The computation of critical points is based on the linearization of the coupled weak form which yields a non‐symmetric tangent operator. The formulation and its associated algorithmic treatment is validated by means of examples.
Theoretical optimization by genetic algorithm of delayed extraction parameters for a matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometer
Authors: Tauro S. , Razvi M. A. N. 
Published: November 2005

AbstractThis paper presents the application of a genetic algorithm (GA) to optimize the operating parameters, namely pulse voltage and extraction delay time, when using matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS). Simulations predict the presence of several combinations of these parameters that give a local maximum. The aim is to locate the optimal combination (a global maximum) of pulse voltage and extraction time delay in order to focus the ions of a particular m/z value to achieve the best resolution in a given instrumental geometry. The GA locates the global maximum quickly. The results indicate that it may be possible to achieve very high resolving power by using delayed extraction (DE)‐MALDI‐TOFMS with parameters obtained from the GA. Copyright © 2005 John Wiley & Sons, Ltd.
Application of stable isotope labeled glutathione and rapid scanning mass spectrometers in detecting and characterizing reactive metabolites
Authors: Mutlib Abdul , Lam Wing , Atherton Jim , Chen Hao , Galatsis Paul , Stolle Wayne 
Published: November 2005

AbstractThe formation of reactive metabolites from a number of compounds was studied in vitro using a mixture of non‐labeled and stable isotope labeled glutathione (GSH) as a trapping agent. GSH was labeled by incorporating [1,2‐13C2,15N]glycine into the tripeptide to give an overall increase of 3 Da over the naturally occurring substance. Detection and characterization of reactive metabolites was greatly facilitated by using the data‐dependent scanning features of the linear ion trap mass spectrometers to give complimentary and confirmatory data in a single analytical run. A comparison was made by analyzing the samples simultaneously on a triple‐stage quadrupole mass spectrometer operated in the constant neutral loss mode. The compounds studied included 2‐acetamidophenol, 3‐acetamidophenol, 4‐acetamidophenol (acetaminophen), and flufenamic acid. GSH adducts for each of these compounds produced a characteristic pattern of ‘twin ions’ separated by 3 Da in the mass spectral data. This greatly facilitated the detection and characterization of any GSH‐related adducts present in the microsomal extracts. Furthermore, characterization of these adducts was greatly facilitated by the rapid scanning capability of linear ion trap instruments that provided full‐scan, MS/MS and MS3 data in one single analysis. This method of detecting and characterizing reactive metabolites generated in vitro was found to be far superior to any of the existing methods previously employed in this laboratory. The combination of two techniques, stable isotope labeled glutathione and linear ion traps, provided a very sensitive and specific method of identifying compounds capable of producing reactive metabolites in a discovery setting. The complimentary set of mass spectral data (including full‐scan, MS/MS and MS3 mass spectra), obtained rapidly in a single analysis with the linear ion trap instruments, greatly accelerated identification of metabolically bioactivated soft spots on the molecules. This in turn enabled chemists to rapidly design out the potential metabolic liability from the back‐up compounds by making appropriate structural modifications. Copyright © 2005 John Wiley & Sons, Ltd.
Psychophysical Tuning Curves in Subjects with Tinnitus Suggest Outer Hair Cell Lesions
Authors: Mitchell Curtin R. , Creedon Thomas A. 
Published: November 2005

A study by Penner (J Speech Hear Res 1980;23:779‐86) found evidence for Impaired lateral suppression in subjects with tinnitus and sensorineural hearing loss. If lateral suppression is related to tuning curve sharpness and lateral suppression is impaired, the shape of the tuning curve should be affected. The purpose of this study was to determine whether subjects with tinnitus have psychophysical tuning curves that are different from those of subjects without tinnitus. Psychophysical tuning curves and hearing thresholds were obtained from 18 subjects, 7 with tinnitus and 11 without tinnitus. Only subjects with normal audiograms (through 8 kHz) were selected for this study. In subjects with tinnitus psychophysical tuning curves were obtained in the region pitch‐matched to their tinnitus. In nontinnitus subjects psychophysical tuning curves were determined at the same frequencies as for the tinnitus subjects in a yoked‐control design. The slopes of the tails and tips and the Q10 and other measures were calculated for each tuning curve. The psychophysical tuning curves in subjects with tinnitus were significantly different (0.01 level) from those of control subjects and often had hypersensitive tails and some elevated tips. These shapes of tuning curves are consistent with cochlear lesions involving the loss of outer hair cells without damage to the Inner hair cells or nerve fibers.
Measurement of energy expenditure
Authors: Levine James A 
Published: November 2005

AbstractMeasurement of energy expenditure in humans is required to assess metabolic needs, fuel utilisation, and the relative thermic effect of different food, drink, drug and emotional components. Indirect and direct calorimetric and non-calorimetric methods for measuring energy expenditure are reviewed, and their relative value for measurement in the laboratory and field settings is assessed. Where high accuracy is required and sufficient resources are available, an open-circuit indirect calorimeter can be used. Open-circuit indirect calorimeters can employ a mask, hood, canopy or room/chamber for collection of expired air. For short-term measurements, mask, hood or canopy systems suffice. Chamber-based systems are more accurate for the long-term measurement of specified activity patterns but behaviour constraints mean they do not reflect real life. Where resources are limited and/or optimum precision can be sacrificed, flexible total collection systems and non-calorimetric methods are potentially useful if the limitations of these methods are appreciated. The use of the stable isotope technique, doubly labelled water, enables total daily energy expenditure to be measured accurately in free-living subjects. The factorial method for combining activity logs and data on the energy costs of activities can also provide detailed information on free-living subjects.
A compilation of energy costs of physical activities
Authors: Vaz Mario , Karaolis Nadine , Draper Alizon , Shetty Prakash 
Published: November 2005

AbstractObjectivesThere were two objectives: first, to review the existing data on energy costs of specified activities in the light of the recommendations made by the Joint Food and Agriculture Organization/World Health Organization/United Nations University (FAO/WHO/UNU) Expert Consultation of 1985. Second, to compile existing data on the energy costs of physical activities for an updated annexure of the current Expert Consultation on Energy and Protein Requirements.DesignElectronic and manual search of the literature (predominantly English) to obtain published data on the energy costs of physical activities. The majority of the data prior to 1955 were obtained using an earlier compilation of Passmore and Durnin. Energy costs were expressed as physical activity ratio (PAR); the energy cost of the activity divided by either the measured or predicted basal metabolic rate (BMR).ResultsThe compilation provides PARs for an expanded range of activities that include general personal activities, transport, domestic chores, occupational activities, sports and other recreational activities for men and women, separately, where available. The present compilation is largely in agreement with the 1985 compilation, for activities that are common to both compilations.ConclusionsThe present compilation has been based on the need to provide data on adults for a wide spectrum of human activity. There are, however, lacunae in the available data for many activities, between genders, across age groups and in various physiological states.
Low-dose and standard-dose unenhanced helical computed tomography for the assessment of acute renal colic: prospective comparative study
Authors: Kim Bong Soo , Hwang Im Kyung , Choi Yo Won , Namkung Sook , Kim Heung Cheol , Hwang Woo Cheol , Choi Kuk Myung , Park Ji Kang , Han Tae Il , Kang Weechang 
Published: November 2005

Purpose: To compare the efficacy of low-dose and standard-dose computed tomography (CT) for the diagnosis of ureteral stones. Material and Methods: Unenhanced helical CT was performed with both a standard dose (260 mAs, pitch 1.5) and a low dose (50 mAs, pitch 1.5) in 121 patients suspected of having acute renal colic. The two studies were prospectively and independently interpreted for the presence and location of ureteral stones, abnormalities unrelated to stone disease, identification of secondary signs, i.e. hydronephrosis and perinephric stranding, and tissue rim sign. The standard-dose CT images were interpreted by one reviewer and the low-dose CT images independently by two reviewers unaware of the standard-dose CT findings. The findings of the standard and low-dose CT scans were compared with the exact McNemar test. Interobserver agreements were assessed with kappa analysis. The effective radiation doses resulting from two different protocols were calculated by means of commercially available software to which the Monte-Carlo phantom model was given. Results: The sensitivity, specificity, and accuracy of standard-dose CT for detecting ureteral stones were 99%, 93%, and 98%, respectively, whereas for the two reviewers the sensitivity of low-dose CT was 93% and 95%, specificity 86%, and accuracy 92% and 94%. We found no significant differences between standard-dose and low-dose CT in the sensitivity and specificity for diagnosing ureter stones ( P>0.05 for both). However, the sensitivity of low-dose CT for detection of 19 stones less than or equal to 2 mm in diameter was 79% and 68%, respectively, for the two reviewers. Low-dose CT was comparable to standard-dose CT in visualizing hydronephrosis and the tissue rim sign. Perinephric stranding was far less clear on low-dose CT. Low-dose CT had the same diagnostic performance as standard-dose CT in diagnosing alternative diseases. Interobserver agreement between the two low-dose CT reviewers in the diagnosis of ureter stones and alternative diseases, the identification of secondary signs, and tissue rim sign were high, with kappa values ranging from 0.769 to 0.968. On standard-dose CT scans, the calculated mean effective radiation dose was 7.30 mSv for males and 10.00 mSv for females. On low-dose CT scans, the calculated mean effective radiation dose was 1.40 mSv for males and 1.97 mSv for females. Conclusion: Compared with standard scans using 260 mAs, low-dose unenhanced helical CT using a reduced tube current of 50 mAs results in a concomitant decrease in the radiation dose of 81%. Although low-dose CT was limited in its ability to depict small-sized calculi less than or equal to 2 mm, it is still comparable to standard-dose CT for the diagnosis of ureter stones and alternative disease.
Cellular inflammatory response to persistent localizedStaphylococcus aureusinfection: phenotypical and functional characterization of polymorphonuclear neutrophils (PMN)
Authors: Wagner C , Iking-Konert C , Hug F , Stegmaier S , Heppert V , Wentzensen A , Hänsch G M 
Published: November 2005

SummaryPersistent, localized Staphylococcus aureus infections, refractory to antibiotic treatment, can result in massive tissue destruction and surgical intervention is often the only therapeutic option. In that context, we investigated patients with S. aureus-induced infection at various sites, apparent as either olecranon bursitis, empyema of the knee joint or soft tissue abscess formation. As expected, a prominent leucocyte infiltrate was found, consisting predominantly of polymorphonuclear neutrophils (PMN) (up to 75%) and to a lesser extent of T lymphocytes and natural killer (NK) cells. In line with their bactericidal capacity, PMN expressed the high-affinity receptor for IgG, CD64 and the lipopolysaccharide (LPS) receptor CD14; moreover, the oxygen radical production in response to the bacterial peptide f-MLP was enhanced, while chemotactic activity was greatly reduced. The more intriguing finding, however, was that a portion of PMN had acquired major histocompatibility complex (MHC) class II antigens and CD83, indicative of a transdifferentiation of PMN to cells with dendritic-like characteristics. Of note is that a similar transdifferentiation can be induced in PMN in vitro, e.g. by gamma interferon or by tumour necrosis factor alpha. Co-cultivation of transdifferentiated PMN with autologous T lymphocytes resulted in prominent T cell proliferation, provided that S. aureus enterotoxin A was added. Taken together, persistent S. aureus infection induces PMN to acquire characteristics of dendritic cells, which in turn might promote the local immune response.