bluuebunny/crossref_metadata_2025_split huggingface dataset:
The influence of the depth of the ground water table on free field road traffic‐induced vibrations
Authors: Schevenels M. , Degrandec G. , Lombaert G. 
Published: April 2004

AbstractThis paper describes the influence of seasonal variations of the ground water table on free field traffic‐induced vibrations. The passage of a truck on two types of road unevenness is considered: a joint in a road pavement consisting of concrete plates and a speed bump with a sinusoidal profile. Free field vibrations are computed with a two‐step solution procedure, where the computation of the vehicle axle loads is decoupled from the solution of the road–soil interaction problem. The impedance of the soil is calculated using a boundary element method, based on the Green's functions for a dry layer on top of a saturated half‐space. It is demonstrated that, in the low‐frequency range of interest, wave propagation in the saturated half‐space can be modelled with an equivalent single phase medium as an alternative to Biot's poroelastic theory for saturated porous media. The relation between the free field velocity and the depth of the ground water table is dominated by three phenomena: (1) the compressibility of the soil decreases due to the presence of the pore water, (2) the ground water table introduces a layering of the soil which may cause resonance of the dry layer and (3) refracted P‐waves in the dry layer interfere with surface waves. If the depth of the ground water table is large with respect to the wavelength of the vibrations in the soil, the response tends to the response of a dry half‐space. The average free field velocity is equal to the velocity in the absence of ground water. If the depth of the ground water table is small with respect to the wavelength of the vibrations in the soil, the response tends to the response of a saturated half‐space and resonance of the dry layer does not occur. The average free field velocity is smaller than the velocity in the absence of ground water. The interference of refracted P‐waves and surface waves causes an additional oscillation of the response as a function of the excitation frequency and the distance between the road and the receiver. Copyright © 2004 John Wiley & Sons, Ltd.
Crack propagation analysis with Galerkin boundary element method
Authors: Xu K. , Lie S. T. , Cen Z. 
Published: April 2004

AbstractThis paper describes the application of symmetric Galerkin boundary element methods (SGBEM) for the analysis of a 2D crack propagation problem. The sub‐domain SGBEM for crack problem is derived. The coefficient matrix is completely symmetric. Cohesive crack model is used to simulate crack propagation. The increment control method for crack propagation and the method for unknown crack propagation path have been derived for high‐order element. Two‐stage interpolation method called the ‘quasi‐higher order element method’ (QHOEM) is then proposed to solve the double integrals. In the initial stage, it uses higher order elements to interpolate the field variables, and for the numerical integration involved, it further uses interpolation functions to decompose the higher order elements into lower order elements so that the existing analytical integration can be applied. A finite rectangular plate containing a centre crack growth and four‐points bending beam problem have been analysed to check the accuracy of the proposed method. For actual application, a dam buttress with an edge crack has been analysed and the results are found to be in agreement with the other numerical and experimental results. Copyright © 2004 John Wiley & Sons, Ltd.
Deformations resulting from the movements of a shear or tensile fault in an anisotropic half space
Authors: Sheu Guang Y. 
Published: April 2004

AbstractEarlier solutions (Bull. Seismol. Soc. Amer. 1985; 75:1135–1154; Bull. Seismol. Soc. Amer. 1992; 82:1018–1040) of deformations caused by the movements of a shear or tensile fault in an isotropic half‐space for finite rectangular sources of strain nucleus have been extended for a transversely isotropic half‐space. Results of integrating previous solutions (Int. J. Numer. Anal. Meth. Geomech. 2001; 25(10): 1175–1193) of deformations due to a shear or tensile fault in a transversely isotropic half‐space for point sources of strain nucleus over the fault plane are presented. In addition, a boundary element (BEM) model (POLY3D:A three‐dimensional, polygonal element, displacement discontinuity boundary element computer program with applications to fractures, faults, and cavities in the Earth's crust. M.S. Thesis, Stanford University, Department of Geology, 1993; 62) is given. Different from similar researches (e.g. Thomas), the Akaike's view on Bayesian statistics (Akaike Information Criterion Statistics. D. Reidel Publication: Dordrecht, 1986) is applied for inverting deformations due to a fault to obtain displacement discontinuities on the fault plane.An example is given for checking displacements predicted by proposed analytical expressions. Another example is generated for the use of proposed BEM model. It demonstrates the effectiveness of this model in exploring displacement behaviours of a fault. Copyright © 2004 John Wiley & Sons, Ltd.
Excretion of collagen derived peptides is increased in women with stress urinary incontinence
Authors: Kushner Leslie , Mathrubutham Mahesh , Burney Tracey , Greenwald Robert , Badlani Gopal 
Published: April 2004

AbstractAimsThe objective of this study was to demonstrate that weakened pelvic floor support of the lower genitourinary tract in women with stress urinary incontinence (SUI) is due to increased collagenolysis. When fibrillar collagen is degraded, pyridinium (PYD) crosslinks are released and excreted in the urine. Degradation of collagen also results in peptide fragments of various lengths which are excreted in the urine. Degradation of mature fibrillar collagen and collagen which has not been crosslinked can be assessed independently by measurement of both PYD and collagen‐derived peptides in the urine.MethodsTwenty‐four hour urine collections were obtained from women with SUI (n = 23) and women without urinary incontinence (n = 39). Urinary PYD concentration was assayed by ELISA. The urinary concentration of helical peptide α1 (I) 620–633 fragments derived from collagen was assayed by competitive enzyme immunoassay. Values were normalized to creatinine.ResultsThe mean urine PYD concentration for women with SUI (110.8 ± 19.7 nM/mM creatinine) was not significantly different than that for women without SUI (85.2 ± 13.7 nM/mM creatinine). The mean urine concentration of helical peptide α1 (I) 620–633 for women with SUI (0.80 ± 0.13 μg/mg creatinine) was significantly (P < 0.02) higher than that for women without SUI (0.49 ± 0.06 μg/mg creatinine).ConclusionsThese data suggest that collagenolytic activity in women with SUI is elevated compared to continent controls, as measured by urinary helical peptide α1 (I) 620–633 excretion. The lack of difference in urinary PYD excretion between the two populations suggests that the increased collagenolytic activity in women with SUI, compared to continent controls, is restricted to uncrosslinked collagen. Neurourol. Urodynam. 23:198–203, 2004. © 2004 Wiley‐Liss, Inc.
Reliability, validity, and gender differences in the quality of life index of the SEAPI‐QMM incontinence classification system
Authors: Stothers Lynn 
Published: April 2004

AbstractPurposeTo evaluate reliability and validity of the SEAPI‐QMM 15‐item quality of life index and assess differences between male and female patients with urinary incontinence.Materials and MethodsTwice pre‐ and once post‐treatment, 315 patients (102 men, 213 women) with incontinence and 35 without incontinence completed the self‐directed SEAPI‐QMM quality of life index. A voiding diary reported frequency of incontinence episodes with number of pads or type of protection used daily for incontinence. In 30%, the Nottingham Health Profile (NHP) was administered to further validate the measure.ResultsCronbach's alpha coefficient for the index was 0.91. Domain‐specific alpha coefficients ranged from 0.88 to 0.73. Test‐retest reliability scores at 5 days gave a reliability coefficient of 0.93. Split half reliability was 0.89. Correlation of the index with the NHP was 0.78 for women, 0.72 for men. Mean scores before and after treatment with medical or surgical management were significantly different in both genders and were sensitive to the presence or absence of use of protection and the type of protection chosen in men. Men with incontinence (61%) reported a high level of impact in the sexuality domain compared to 7% of women.ConclusionsThe SEAPI quality of life index has a high degree of reliability relating to stability and internal consistency across a wide age range in both genders. There are differences between men and women in life domains most frequently affected by urinary incontinence. Neurourol. Urodynam. 23:223–228, 2004. © 2004 Wiley‐Liss, Inc.
Course and clinical impact of magnetic resonance imaging findings in diabetes insipidus associated with Langerhans cell histiocytosis
Authors: Grois Nicole , Prayer Daniela , Prosch Helmut , Minkov Milen , Pötschger Ulrike , Gadner Helmut 
Published: April 2004

AbstractBackgroundDiabetes insipidus (DI) is the most frequent sequela in Langerhans cell histiocytosis (LCH). The clinical relevance and therapeutic impact of brain magnetic resonance imaging (MRI) findings in LCH patients with LCH during the disease course is unclear.ProcedureIn this retrospective study, we reviewed 113 brain MRIs from 59 DI patients, in 17 of these serial follow up MR‐examination findings were correlated to the clinical course and therapy.ResultsAt DI diagnosis, 71% patients showed a thickened stalk, in 24% the stalk was still thickened on MRIs done more than 5 years after DI onset, and in two patients the stalk was already thickened several months before DI onset. The changes of the pituitary stalk thickness were highly variable and did not clearly correlate with the treatment. Regression of pituitary thickness on MRI did not concur with clinical recovery of DI, which persisted in all but one patient with initially partial DI. The occurrence of anterior pituitary hormone deficiencies appeared to be linked to a thickening of the stalk at DI diagnosis. LCH‐lesions in the craniofacial bones were seen in 75% DI patients, and 76% of DI patients with follow up MRIs done 5 years or longer after DI diagnosis had parenchymal neurodegenerative brain changes.ConclusionsOur study indicates that repeated MR‐examinations in DI patients are of limited value for assessing a response to therapy in the pituitary stalk, but are important for the monitoring of craniofacial bone lesions and for the detection of parenchymal CNS disease. © 2004 Wiley‐Liss, Inc.
Stiffness and toughness of polypropylene/glass bead composites
Authors: Kwok K. W. , Gao Z. M. , Choy C. L. , Zhu X. G. 
Published: April 2004

AbstractThe effects of coupling effect, particle diameter (d), volume fraction (Vb) and size distribution (σ) of glass beads on the impact strength and tensile modulus of polypropylene (PP)/glass bead composites have been investigated. The toughness and stiffness of the composite can be simultanously enhanced by using a titanate coupling agent, which gives rise to a moderate interfacial adhesion (characterized by an interaction parameter B ∼ 1) between the glass beads and the matrix. With the addition of this coupling agent, the impact strength of the PP/glass bead composite with d = 2.7 μm and σ = 1.85 increases about 4.5 times as Vb increases from 0 to 0.25, while the tensile modulus remains roughly unchanged. For the composites with larger d and narrower size distribution, the impact strength increases only slightly with increasing Vb. The combined effect of d, Vb and size distribution of the glass beads are described by using a single parameter, the average matrix ligament thickness T. Unlike rubber‐modified polymers, the impact strength of PP/glass bead composites does not follow a master curve when plotted against T.
A model for the transverse permeability of bi‐material layered fibrous preforms
Authors: Markicevic B. , Papathanasiou T. D. 
Published: April 2004

AbstractWe consider viscous flow across unidirectional hexagonal arrays of porous tows of elliptical cross section. Using the lubrication approximation we develop an analytical model for the hydraulic permeability of layered systems, in which the permeability of the porous tows making up each alternating layer is allowed to differ. Extensive validation of this model is carried out through numerical computations using the Computational Fluid Dynamics package FIDAP. Good agreement between model predictions and numerically calculated permeabilities is found in the interesting region of small porosity (ϕ = 0.20 or ϕ = 0.30). Using this model we also address the issue of the inaccuracies that may be introduced if the overall permeability of a fibrous preform is calculated using an arithmetic average permeability instead of the actual permeability of each layer. We find that use of an average permeability will result in overestimation of the overall permeability of the system. This overestimation will increase as the porosity is reduced and/or as the difference in permeabilities increases.
Studies in interchain crosslinking and heat shrinkability of polymer blends consisting of grafted low‐density polyethylene and ethylene‐acrylic rubber
Authors: Mishra J. K. , Das C. K. 
Published: April 2004

AbstractBlends prepared by the melt mixing of thermoplastic and elastomer have gained considerable attention in recent years. Heat shrinkability, which is dependent on elastic memory, can be introduced into the system in the form of an elastomeric phase. The present study deals with the measurement of heat shrinkability of the blends of grafted polyethylene and an ethylene acrylic elastomer. Interchain crosslinking between grafted polyethylene and elastomer improves the shrinkability. High temperature performance of the samples depends on interchain crosslinking. From torque rheometry it was observed that the maximum amount of interchain crosslinking was obtained in the sample containing acrylamide grafted LDPE. The probable interaction between the rubber and the plastic phase is confirmed by IR spectroscopy.
Static deformation of low structure HAF black‐loaded (SBR+NR) rubber blend
Authors: El‐Lawindy A. M. Y. 
Published: April 2004

AbstractThe stress‐strain behavior of different concentrations of low‐structure high abrasion furnace black (HAF‐LS, N326)‐loaded rubber blend of styrene butadiene rubber and natural rubber (SBR+NR) of equal parts was measured. Moduli of elasticity and the n‐measure of such blends were calculated using different approaches. An anomaly, of modulus of elasticity, found at 50 phr may be attributed to carbon black reinforcement and to an early crystallization of stretched natural rubber (NR) in the blend. These assumptions are confirmed through the measurement of the swelling factor as a function of time of swelling in kerosene.
The influence of matrix chemical structure on the mode I and II interlaminar fracture toughness of glass‐fiber/epoxy composites
Authors: Álvarez Vera , Bernal Celina R. , Frontini Patricia M. , Vázquez Analia 
Published: April 2004

AbstractThe present paper is concerned with Mode I and Mode II delamination tests performed on three different glass fiber reinforced epoxy composites, chosen to obtain different final structures. The effect of crosshead speed on the fracture resistance of the composites was also analyzed. It was found that Mode I propagation values (GIC) increase as the crosshead speed decreases, probably because of the increase of brittleness in the studied range. An Arrhenius type relation between GIC and the glass transition temperature of the epoxy resin/amine system (Tg) was found. Mode II initiation values (GIICinit) and apparent shear strength (SH) were found to increase with the decrease of Tg. The relation between matrix toughness and composite interlaminar fracture toughness was also considered. Finally, the GIC propagation values were compared to the data available in literature for similar materials.
Simultaneous optimization of die‐heating and pull‐speed in pultrusion of thermosetting composites
Authors: Jianhua Li Y. C. Lam , Joshi Sunil C. 
Published: April 2004

AbstractDie‐temperature and pull‐speed are the key parameters in pultrusion that affect the degree and uniformity of the curing of thermosetting composites, which in turn influence their mechanical properties and in‐service performance. This paper presents the development, implementation, and validation of a numerical procedure for arriving at an optimum combination of die‐heater temperatures and pull‐speed for producing a uniformly cured composite pultrudate. An objective function representing the effects of both parameters on the distribution of degree‐of‐cure across the cross section of a pultruded part at the die exit was established. The function was used to develop an algorithm for calculating the required changes in die‐heater temperatures and pull‐speed to achieve a desirable degree‐of‐cure with maximum possible uniformity. The algorithm was implemented using the three‐dimensional. Finite Element/Nodal Control Volume (FE/NCV) approach for process simlation, in which a general‐purpose FE package was used to perform heat transfer analysis, together with other routines developed to perform cure modeling and the optimization. The application of the developed procedure was demonstrated by simulating pultrusion of a graphite/epoxy C‐section. The results of the studies show that the procedure is numerically stable and works well for a die with multiple heaters.
Pore network modeling of permeability for textile reinforcements
Authors: Delerue J.‐F. , Lomov S. V. , Parnas R. S. , Verpoest I. , Wevers M. 
Published: April 2004

AbstractThe homogenized permeability of textile reinforcement is computed using pore network modeling. The model takes as input a 3D image of the reinforcement, reduced to an array of points, each of them having a binary value designating whether the point lies inside a yarn or in a pore. The array can be acquired by X‐ray micro‐computerized tomography. The calculations proceed in two steps. First, the 3D image is analyzed to create a representation of the pores in the reinforcement by a system of interconnected pipes. Each pipe is characterized by its hydraulic resistance. Then the hydraulic resistance of the system of pipes is computed using the Kirchoff theory to yield a value for homogenized permeability of the reinforcement. The model is applied to a glass woven laminate, producing results in good agreement with experimentally measured values.
The role of the interaction coefficient in the prediction of the fiber orientation in planar injection moldings
Authors: Pontes A. J. , Neves N. M. , Pouzada A. S. 
Published: April 2004

AbstractThe mechanical properties of injection molded parts in glass reinforced materials are sensitive to processing. A successful design requires a good estimate of the product performance before production. Its performance is strongly affected by the fiber orientation field set up during processing. The fiber orientation pattern is complex and varies three‐dimensionally in the moldings. Some commercial simulation programs already allow the prediction of the fiber orientation induced during the flow by the associated stress field. The results from the simulations are dependent on a parameter accounting for the interactions between fibers during the flow, known as the fiber interaction coefficient. In this paper the effectiveness of the interaction parameter on controlling the predicted patterns of the fiber orientation is studied. This is done by comparing and analyzing the experimental data and the corresponding predictions.
Identification of fiber misalignment in continuous fiber composites
Authors: Barwick S. C. , Papathanasiou T. D. 
Published: April 2004

AbstractMisaligned fibers are invariably present in nominally unidirectional high‐performance composites. Such misaligned fibers are known to affect key mechanical properties of the composite, such as the longitudinal compressive strength, longitudinal tensile modulus, fatigue endurance, shear strength, and delamination resistance (1). In this paper we present a method for the automated detection of large angle fiber misalignment (θ > 40°) in continuous fiber‐reinforced composite materials. The method relies on the application of a series of geometrical criteria based upon measurements routinely obtained during optical scanning of polished sample cross‐sections. As such, the technique is ideal for the automated identification of highly misaligned fibers in large‐area (∼ cm2) specimens that may contain several millions of individual fiber images. The criteria applied take into account the fact that prepared cross‐sections of such materials contain many damaged fibers as a result of attrition during polishing. Data obtained from three pultruded unidirectional rods reinforced with continuous carbon filaments are used to illustrate the effectiveness of this method in identifying regions where large angle misalignment occurs.
The effect of maleated compatibilizers on the structure and properties of EVOH/clay nanocomposites
Authors: Artzi N. , Nir Y. , Narkis M. , Siegmann A. 
Published: April 2004

AbstractThe effect of compatibilizers on the blending torque, crystallization behavior, intercalation level, thermal stability and morphology of EVOH/treated clay systems was investigated. Maleic anhydride‐grafted ethylene vinyl acetate (EVA‐g‐MA) or maleic anhydride‐grafted linear low density polyethylene (LLDPE‐g‐MA) were used as compatibilizers of EVOH with clay, in various concentrations (1, 5 and 10 wt%). The blends were processed using Brabender Plastograph and characterized by XRD, SEM, DSC, DMTA and TGA. X‐ray diffraction shows advanced intercalation within the galleries when the compatibilizers were added. Unique results were obtained for the EVOH/clay/compatibilizer systems, owing to a high level of interaction developed in these systems, which plays a major role. Thermal analysis showed that with increasing compatibilizer content, lower crystallinity levels result, until at a certain content no crystallization has taken place. Significantly higher viscosity levels were obtained for the EVOH/clay blends compared to the neat polymer, as seen by a dramatic torque increase when processed in the Brabender machine. The DMTA spectra showed lower Tg values for the compatibilized nanocomposites compared to the neat EVOH and the uncompatibilized composites. Storage modulus was higher compared to the uncompatibilized EVOH/clay blend when EVA‐g‐MA compatibilizer was added (at all concentrations), and only at low contents of LLDPE‐g‐MA. TGA results show significant improvement of the blends thermal stability compared to the neat EVOH, and to the uncompatibilized blend, indicating an advanced intercalation.