bluuebunny/crossref_metadata_2025 huggingface dataset:
A review of the consistency of breast cancer screening pamphlets produced by health authorities in Australia
Authors: Jones Sandra C.
Published: April 2003

Pamphlets are widely used by health authorities to inform the public about diseases, and it is essential that the information therein is accurate. This study reviewed the consistency of information on breast cancer screening in materials produced and distributed by Australian health authorities. The study found that there was a clear lack of consensus in terms of the stated lifetime risk of breast cancer; while most agreed that being a woman and increasing age were the major risk factors, there was far less agreement about other risk factors, and the specific representation of symptoms was one of the areas of greatest inconsistency. It appears that this lack of consensus is not unique to Australia, but exists in other countries. Material produced by health authorities is seen by the general public as “expert” opinion, and should be able to correct inaccurate perceptions generated by exposure to other sources. There is a need to develop and disseminate messages that provide women with an accurate understanding of breast cancer and breast cancer screening.
Bridging the gap between knowledge and action on the societal determinants of cardiovascular disease: how one Canadian community effort hit – and hurdled – the lifestyle wall
Authors: Raphael Dennis
Published: April 2003

An expanding conceptual and research literature identifies cardiovascular disease (CVD) as the disease whose incidence varies most, according to income level. To date however, there has been virtually no public consideration in Canada of the role that societal factors play in its incidence. In an attempt to redress this gap, a community coalition brought together the latest research on the societal determinants of CVD. Barriers to public awareness and public policy action to address these societal determinants of health included the unwillingness of health care associations to consider societal determinants of health as relevant to their activities; general resistance by the media; and active attempts by governments of the day to shift focus away from societal determinants of health. Considering these barriers, university personnel involvement appears essential to any attempt to identify and address the societal determinants of CVD and other diseases.
Flexible problem solving in construction projects on the National Museum of Australia project
Authors: Walker Derek H.T. , Loosemore Martin
Published: April 2003

In responding to unanticipated challenges during the course of a project, lessons from crisis management research can be valuable. Effective project management requires both a proactive and reactive strategy in dealing with unanticipated and challenging events. A key element of success is developing a learning culture, which permits flexibility within a systematic problem‐solving approach. We indicate how this can be achieved using a crisis management model and use data gathered from the National Museum of Australia project to demonstrate the potential benefits of a learning which encourages solution‐building by teams.
We think we can, we think we can, we think we can: the impact of thinking patterns and self‐efficacy on work team sustainability
Authors: Houghton Jeffery D. , Neck Christopher P. , Manz Charles C.
Published: April 2003

In terms of the body of knowledge examining work teams, several books and articles have attempted to address the underlying causes of why work teams fail. However, a scarcity of writings has focused on the issue of work team sustainability. The dictionary defines “sustain” as “to prevent from falling, collapsing, or giving way,” and “to endure.” This definition gives rise to the following question: “What are the factors that contribute to those work teams that ‘endure’ and that do not ‘fall, collapse, or give way’ during challenging organizational experiences?” In this paper, we will take an initial step toward answering this question by presenting a cognitive model of work team sustainability based upon established cognitive principles of individual‐level effort and performance sustainability. This model is designed to provide some practical insights into the long‐term team performance sustainability issue while also serving as a possible foundation for future research efforts.
A model for the valuation of farmland in Spain
Authors: Garcia Teresa , Grande Ildefonso
Published: April 2003

The main task when valuing land is to identify the variables affecting its value. This is critical when a large number of variables is involved. Furthermore, collinearity and other econometric disturbances frequently occur in this type of research. Against this background, and in an effort to surmount these difficulties, this paper proposes and then tests some statistical techniques based on multivariate analysis. Multiple correspondence analysis helps to ensure rigour, simplicity and accuracy in the process of identifying the variables involved in the valuation of farmland. Finally, once the relevant variables have been identified, a model for the valuation of farmland plots is then specified.
Kinetic Determinants of Agonist Action at the Recombinant Human Glycine Receptor
Authors: Lewis Trevor M. , Schofield Peter R. , McClellan Annette M. L.
Published: April 2003

The amino acids glycine, β‐alanine and taurine are all endogenous agonists of the glycine receptor. In this study, a combination of rapid agonist application onto macropatches and steady‐state single‐channel recordings was used to compare the actions of glycine, β‐alanine and taurine upon homomeric α1 human glycine receptors transiently expressed in human embryonic kidney (HEK 293) cells. The 10–90 % rise times determined from rapid application of 100 μm of each agonist were indistinguishable, indicating each agonist has a similar association rate. At saturating concentrations (30 mm) the rise time for glycine (0.26 ms) was 1.8‐fold faster than that for β‐alanine (0.47 ms) and 3.9‐fold faster than that for taurine (1.01 ms), indicating clear differences in the maximum opening rate between agonists. The relaxation following rapid removal of agonist was fitted with a single exponential for β‐alanine (3.0 ms) and taurine (2.2 ms), and two exponential components for glycine with a weighted mean time constant of 27.1 ms. This was consistent with differences in dissociation rates estimated from analysis of bursts, with taurine > β‐alanine > glycine. Exponential fits to the open period distributions gave time constants that did not differ between agonists and the geometric distribution for the number of openings per burst indicated that all three agonists had a significant component of single‐opening bursts. Based upon these data, we propose a kinetic scheme with three independent open states, where the opening rates are dependent upon the activating agonist, while the closing rates are an intrinsic characteristic of the receptor.
Coupled Movement of Permeant and Blocking Ions in the CFTR Chloride Channel Pore
Authors: Gong Xiandi , Linsdell Paul
Published: April 2003

The cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channel pore is blocked in a voltage‐dependent manner by a broad range of anionic substances added to the cytoplasmic side of the membrane. Here we investigate the origin of the voltage dependence of block by intracellular Au(CN)2−, a highly permeant lyotropic anion which also acts as a high‐affinity blocker of Cl− permeation. Not only the affinity, but also the voltage dependence of block by intracellular Au(CN)2− ions is strongly dependent on extracellular Cl− concentration; following replacement of most extracellular Cl− by glucose or by impermeant anions, block by Au(CN)2− shows greatly weakened voltage dependence. This suggests that coupled movement of Au(CN)2− and Cl− ions within the pore contributes to the voltage dependence of block. This explanation requires that interactions between different anions take place within the pore, implying simultaneous binding of multiple anions to intrapore sites. Other anions are able to substitute for extracellular Cl− and interact with intracellular Au(CN)2− ions. Analysis of the effects of different extracellular anions on the apparent affinity and voltage dependence of block by intracellular Au(CN)2− ions suggests that extracellular anions do not need to permeate through the channel in order to destabilize Au(CN)2− binding within the pore, implying that this destabilizing effect results from binding to an externally accessible site in the permeation pathway. We propose that multiple anions can bind simultaneously within the CFTR channel pore, and that repulsive interactions between bound anions speeds anion exit from the pore.
Molecular Determinants and Role of An Anion Binding Site in the External Mouth of the CFTR Chloride Channel Pore
Authors: Gong Xiandi , Linsdell Paul
Published: April 2003

Chloride permeation through the cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channel is blocked by highly lyotropic permeant anions which bind tightly within the pore. Here we show that several different substitutions of a positively charged amino acid residue, arginine R334, in the putative outer mouth of the CFTR pore, greatly reduce the block caused by lyotropic Au(CN)2− ions applied to the intracellular side of the channel. Fixed positive charge at this site appears to play a role in Au(CN)2− binding, as judged by multiple substitutions of differently charged amino acid side chains and also by the pH dependence of block conferred by the R334H mutant. However, non‐charge‐dependent effects also appear to contribute to Au(CN)2− binding. Mutation of R334 also disrupts the apparent electrostatic interaction between intracellular Au(CN)2− ions and extracellular permeant anions, an interaction which normally acts to relieve channel block. All six mutations studied at R334 significantly weakened this interaction, suggesting that arginine possesses a unique ability to coordinate ion‐ion interactions at this site in the pore. Our results suggest that lyotropic anions bind tightly to a site in the outer mouth of the CFTR pore that involves interaction with a fixed positive charge. Binding to this site is also involved in coordination of multiple permeant anions within the pore, suggesting that anion binding in the outer mouth of the pore is an important aspect in the normal anion permeation mechanism.
Ecto‐AMP Deaminase Blunts the ATP‐Derived Adenosine A2A Receptor Facilitation of Acetylcholine Release at Rat Motor Nerve Endings
Authors: Magalhães‐Cardoso M. Teresa , Pereira M. Fátima , Oliveira Laura , Ribeiro J. A. , Cunha Rodrigo A. , Correia‐de‐Sá Paulo
Published: April 2003

At synapses, ATP is released and metabolised through ecto‐nucleotidases forming adenosine, which modulates neurotransmitter release through inhibitory A1 or facilitatory A2A receptors, according to the amounts of extracellular adenosine. Neuromuscular junctions possess an ecto‐AMP deaminase that can dissociate extracellular ATP catabolism from adenosine formation. In this study we have investigated the pattern of ATP release and its conversion into adenosine, to probe the role of ecto‐AMP deaminase in controlling acetylcholine release from rat phrenic nerve terminals. Nerve‐evoked ATP release was 28 ± 12 pmol (mg tissue)−1 at 1 Hz, 54 ± 3 pmol (mg tissue)−1 at 5 Hz and disproportionally higher at 50 Hz (324 ± 23 pmol (mg tissue)−1). Extracellular ATP (30 μm) was metabolised with a half time of 8 ± 2 min, being converted into ADP then into AMP. AMP was either dephosphorylated into adenosine by ecto‐5′‐nucleotidase (inhibited by ATP and blocked by 200 μmα,β‐methylene ADP) or deaminated into IMP by ecto‐AMP deaminase (inhibited by 200 μm deoxycoformycin, which increased adenosine formation). Dephosphorylation and deamination pathways also catabolised endogenously released adenine nucleotides, since the nerve‐evoked extracellular AMP accumulation was increased by either α,β‐methylene ADP (200 μm) or deoxycoformycin (200 μm). In the presence of nitrobenzylthioinosine (30 μm) to inhibit adenosine transport, deoxycoformycin (200 μm) facilitated nerve‐evoked [3H]acetylcholine release by 77 ± 9 %, an effect prevented by the A2A receptor antagonist, ZM 241385 (10 nm). It is concluded that, while ecto‐5′‐nucleotidase is inhibited by released ATP, ecto‐AMP deaminase activity transiently blunts adenosine formation, which would otherwise reach levels high enough to activate facilitatory A2A receptors on motor nerve terminals.
Sleep Deprivation Reduces Proliferation of Cells in the Dentate Gyrus of the Hippocampus in Rats
Authors: Guzmán‐Marín Ruben , Suntsova Natalia , Stewart Darya R. , Gong Hui , Szymusiak Ronald , McGinty Dennis
Published: April 2003

The dentate gyrus (DG) of the adult hippocampus gives rise to progenitor cells, which have the potential to differentiate into neurons. To date it is not known whether sleep or sleep loss has any effect on proliferation of cells in the DG. Male rats were implanted for polysomnographic recording, and divided into treadmill sleep‐deprived (SD), treadmill control (TC) and cage control (CC) groups. SD and TC rats were kept for 96 h on a treadmill that moved either for 3 s on/12 s off (SD group) or for 15 min on/60 min off (TC group) to equate total movement but permit sustained rest periods in TC animals. To label proliferating cells the thymidine analogue 5‐bromo‐2′‐deoxyuridine (BrdU) was injected after the first 48 h of the experimental procedure in all groups (50 mg kg−1, i.p.). The percentage of time awake per day was 93.2 % in the SD group vs. 59.6 % in the TC group and 49.9 % in the CC group (P < 0.001). Stereological analysis showed that the number of BrdU‐positive cells in the DG of the dorsal hippocampus was reduced by 54 % in the SD group in comparison with the TC and by 68 % in comparison with the CC group. These results suggest that sleep deprivation reduces proliferation of cells in the DG of the dorsal hippocampus.
Glycogen Regulation and Functional Role in Mouse White Matter
Authors: Brown Angus M. , Tekkök Selva Baltan , Ransom Bruce R.
Published: April 2003

CNS glycogen, contained predominantly in astrocytes, can be converted to a monocarboxylate and transported to axons as an energy source during aglycaemia. We analysed glycogen regulation and the role of glycogen in supporting neural activity in adult mouse optic nerve, a favourable white matter preparation. Axon function was quantified by measuring the compound action potential (CAP) area. During aglycaemia, axon function persisted for 20 min, then declined in conjunction with glycogen content. Lactate fully supported CAPs in the absence of glucose, but was unable to sustain glycogen content; thus, axon failure occurred rapidly when lactate was withdrawn. Glycogen content in the steady state was directly proportional to bath glucose concentration. Increasing [K+]o to 10 mm caused a rapid decrease in glycogen content. Latency to onset of CAP failure during aglycaemia was directly proportional to glycogen content and varied from about 2 to 30 min. Intense neural activity reduced glycogen content in the presence of 10 mm bath glucose and CAP area gradually declined. CAP area declined more rapidly during high frequency stimulation if monocarboxylate transport was inhibited. This suggested that astrocytic glycogen was broken down to a monocarboxylate(s) that was used by rapidly discharging axons. Likewise, depleting glycogen by brief periods of high frequency axon stimulation accelerated onset of CAP decline during aglycaemia. In summary, these experiments indicated that glycogen content was under dynamic control and that glycogen was used to support the energy needs of CNS axons during both physiological as well as pathological processes.
Constitutive Modeling of Cold Compaction and Sintering of Hardmetal
Authors: Ma¨hler Lennart , Runesson Kenneth
Published: April 2003

Constitutive modeling and related numerical issues in conjunction with the macroscopic analysis and simulation of cold compaction and subsequent solid phase sintering of hard-metal are discussed. A key ingredient is the concept of sintering stress, which is derived as a thermodynamically consistent dissipative stress, based on a simplified microstructural arrangement with spherical pores. In order to account for the temperature effect on the rate-dependent response during the sintering phase, the concept of viscoplastic admissibility is employed as part of the model framework. A generic class of pressure-sensitive models is considered, and the particular model chosen for calibration is based on quasistatic and dynamic yield surfaces that are elliptic in the meridian planes of the stress space. Implicit integration is used for the pertinent evolution equations. The paper is concluded by a numerical investigation of the compaction and sintering of a specimen, whereby the model is calibrated using experimental data from free and uniaxially loaded sintering experiments (within a joint research project).
A Closure Model to Crack Growth Under Large-Scale Yielding and Through Residual Stress Fields
Authors: Wang C. H. , Barter S. A. , Liu Q.
Published: April 2003

This paper presents a closure model for predicting the growth behavior of short cracks in the presence of large-scale yielding and residual compressive stresses, representative of structures that have been shot-peened. The plasticity-induced crack closure model developed by Newman is first extended by using the cyclic crack-tip opening displacement as the correlating parameter for fatigue crack growth rates. This new approach also enables a better characterization of the effect of large-scale yielding on short crack growth. The effect of residual stress on crack closure is then analyzed by adding to the loading spectrum an equivalent stress, which varies with the applied load level and the crack size. It is shown that predictions of the extended closure model are within a factor of two of the experimental results of etched specimens tested under spectrum loading, highlighting the capability of the predictive model along with some important issues for future research in this area.
Analysis of Hemodynamic Fluid Phase Mass Transport in a Separated Flow Region
Authors: Lutostansky Elizabeth M. , Karner Gerhard , Rappitsch Gerhard , Ku David N. , Perktold Karl
Published: April 2003

The mass transfer behavior in the recirculation region downstream of an axisymmetric sudden expansion was examined. The Reynolds number, 500, and Schmidt number, 3200, were selected to model the mass transfer of molecules, such as ADP, in the arterial system. In a first step the transient mass transport applying zero diffusive flux at the wall was analyzed using experiments and two computational codes. The two codes were FLUENT, a commercially available finite volume method, and FTSP, a finite element code developed at Graz University of Technology. The comparison of the transient wall concentration values determined by the three methods was excellent and provides a measure of confidence for computational mass transfer calculations in convection dominated, separated flows. In a second step the effect of the flow separation on the stationary mass transport applying a permeability boundary condition at the water-permeable wall was analyzed using the finite element code FTSP. The results show an increase of luminal ADP surface concentration in the upstream and in the downstream tube of the sudden expansion geometry in the range of six and twelve percent of the bulk flow concentration. The effect of flow separation in the downstream tube on the wall concentration is a decrease of about ten percent of the difference between wall concentration and bulk concentration occurring at nearly fully developed flow at the downstream region at a distance of 66 downstream tube diameters from the expansion. The decrease of ADP flux into the wall is in the range of three percent of the flux at the downstream region.
Targeted Drug Aeroso Deposition Analysis for a Four-Generation Lung Airway Model With Hemispherical Tumors
Authors: Kleinstreuer C. , Zhang Z.
Published: April 2003

One important research area of broad interest is the development of highly efficient drug delivery systems for desired site deposition and uptake. For example, controlled drug aerosol release and targeting to specific regions of the lung is a novel way to combat lung diseases, diabetes, virus infections, cancers, etc. Determination of feasible air-particle streams is a prerequisite for the development of such delivery devices, say, smart inhalers. The concept of “controlled particle release and targeting” is introduced and results are discussed for a representative model of bronchial lung airways afflicted with hemispherical tumors of different sizes and locations. It is shown that under normal particle inlet conditions a particle mass fraction of only up to 11% may deposit on the surface of a specific tumor with critical radius r/R≈1.25, while a controlled particle release achieves deposition fractions of 35 to 92% for a realistic combination of inlet Stokes and Reynolds numbers, depending mainly on tumor size. Furthermore, with the controlled release and targeting approach nearby healthy tissue is hardly impacted by the typically aggressive drug aerosols. Assuming laminar, quasi-steady, three-dimensional air flow and spherical non-interacting micron-particles in sequentially bifurcating rigid airways, the results were obtained using a validated commercial finite-volume code with user-enhanced programs on a high-end engineering workstation. The new concept is generic and hence should be applicable to other regions of the respiratory system as well.
Investigation of Nanomechanical Properties of the Interphase in a Glass Fiber Reinforced Polyester Composite Using Nanoindentation
Authors: Khanna Sanjeev K. , Ranganathan P. , Yedla S. B. , Winter R. M. , Paruchuri K.
Published: April 2003

Glass fiber reinforced polymer composites are widely used as structural materials. These two-component materials can be tailored to suit a large variety of applications. A better understanding of the properties of the fiber-matrix “interphase” can facilitate optimum design of the composite structure. The interphase is a microscopic region around the fiber and hence nano-scale investigation using nano-indentation techniques is appropriate to determine mechanical property variations within this region. In this study the atomic force microscope adapted with a commercial nanoindenter has been used to determine the variation of the elastic modulus across the interphase for different silane coated glass fiber reinforced polyester matrix composites. A comparative study of the elastic modulus variation in the various interphases is reported. The results are discussed in the light of the current limitations of the instrumentation and analysis.
Modeling of Fatigue Crack Propagation During Sliding Wear of Polymers
Authors: Sadeghipour Keyanoush , Baran George , Zhang Hanqing , Wu Wei
Published: April 2003

The propagation of a crack initiating at the surface was analyzed to simulate the fatigue wear behavior of glassy polymer materials. A crack in a material half plane was assumed to propagate along a predefined path as a result of contact loading by a cylinder sliding on the polymer surface. The crack path consisted of a vertical straight-line segment and a declined straight line originating at a branch point on the vertical crack segment. The stress intensity factors KI and KII along the crack path were computed by using finite element methods, and their values utilized in the Paris law to determine crack propagation rates. Because this process simulates surface pitting, component fatigue life is assumed to be proportional to the time needed for the propagating declined crack to intersect a neighboring vertical crack, a condition known to lead to pitting. This fatigue life is estimated by integrating the Paris law. Numerical results show that the branch point where the declined crack path originates can effectively hinder crack propagation, and that the rate limiting step in fatigue is crack propagation along a small segment of the declined crack near the branch point. Some important factors that affect the reliability of numerically predicted fatigue life cycles are discussed. Experimental crack propagation paths and lifetimes are shown.
Numerical Simulation of Residual Stresses in a Spot Welded Joint
Authors: Long Xin , Khanna Sanjeev K.
Published: April 2003

An incremental and thermal-electro-mechanical coupled finite element model has been presented in this study for predicting residual stress distribution in a spot welded steel joint. Approximate temperature dependent material properties, including physical and mechanical properties, have been considered. The spot nugget shape and the residual stress distribution were obtained by simulation. The results obtained have been compared with experimental measurements, and good agreement is observed. The highest tensile residual stress occurs at the center of the nugget and the residual stress decreases towards the edge of the nugget.
Dynamic Fracture Toughness and Charpy Transition Properties of a Service-Exposed 2.25Cr-1Mo Reheater Header Pipe
Authors: Sreenivasan P. R. , Shastry C. G. , Mathew M. D. , Rao K. Bhanu Sankara , Mannan S. L. , Bandyopadhyay G.
Published: April 2003

Residual life analysis of power plant components like boiler tubes, superheater outlet headers, reheater headers, steam pipes, etc., is important for life extension and avoidance of catastrophic failure. In this context, fracture toughness is very important. The fracture characteristics after prolonged exposure to high temperatures and pressures are likely to be different from that of the virgin material. 2.25Cr-1Mo reheater header pipe exposed at 813 K for 120,000 h was studied by instrumented impact tests (IIT) to evaluate dynamic fracture toughness and Charpy transition properties. The methods presented in this paper for estimating dynamic fracture toughness from IIT of Charpy specimens give reliably conservative results without the need for precracking. For estimating fracture appearance transition temperature (FATT) from IIT load-time traces, the equation for percent shear fracture, PSF3, gives the best 1:1 correlation with measured values from fracture surfaces. The lower bound equation for variation of fracture toughness with temperature derived in the present study is higher than that obtained from the FATT master curve (FATT-MC) approach. Comparison of Charpy indices like FATT and upper-shelf energy for the service exposed steel to results for the virgin material reported in the literature and the compositional J-Factor estimates for temper-embrittlement susceptibility indicate that the present steel, even after 120,000 h exposure to high temperature service, has probably undergone only very little or nil degradation in toughness properties.
Plastic Collapse of Cylinders Under Constrained Conditions
Authors: Abdul-Latif A. , Nesnas K.
Published: April 2003

This paper deals with an experimental methodology of the large deformation of cylinders under constrained sides and end conditions. A specific arrangement of two geometrically identical cylinders compressed laterally is studied under different quasi-static strain rates. Several tests are performed using two different structural situations. In the first case, the two cylinders are made from superplastic tin-lead alloy, while in the second case, one cylinder is made from superplastic and the other from steel. Different cylindrical geometries are investigated having the same cross sectional area with different ratios of inner to outer diameter (di/do). The load-deflection curves are recorded and then the energy absorbed per unit volume is determined. The experiments show obviously the remarkable sensitivity of the utilized superplastic to the strain rate in the range of 10−5/s-10−3/s. A two-dimensional finite element simulation is also conducted describing the collapse behavior of these cylindrical geometries in both structural cases under different strain rates. A confrontation with experimental observation shows that the predictions describe fairly well the experiments.
On the Improvement of Calibration Coefficients for Hole-Drilling Integral Method: Part II—Experimental Validation of Calibration Coefficients
Authors: Aoh Jong-Ning , Wei Chung-Sheng
Published: April 2003

Experimental validation of the calibration coefficients for integral hole-drilling method obtained from an improved three-dimensional FEM model was achieved using bending test of a cantilever beam. The experimental setup is a simple yet accurate method to validate the calibration coefficients obtained by a three-dimensional FEM model. With this experiment, we also validate the adequacy of the criterion applied for thin or thick plates in a previous work. The relieved stresses calculated from the calibration coefficients of the three-dimensional FEM model were compared with those calculated from two-dimensional model calibration coefficients. The results show that the accuracy of relieved stress calculation has been greatly improved as the calibration coefficients based on a three-dimensional model are used for integral hole-drilling method. Significant error in the residual stress measurement and calculation could be arisen if calibration coefficients for integral hole-drilling method were not chosen correctly for corresponding thin plate or thick plate cases according the results of the bending test of cantilever beam. A transitional dimensionless thickness was proposed by examining the calculated relieved stresses obtained from the calibration coefficients for different plate thickness. The probability bounds of relieved stress corresponding to both cases were also calculated to further reveal the improvement of the calibration coefficients obtained from the three-dimensional model.
Simulating Distortion and Residual Stresses in Carburized Thin Strips
Authors: Prantil V. C. , Callabresi M. L. , Lathrop J. F. , Ramaswamy G. S. , Lusk M. T.
Published: April 2003

This paper illustrates the application of a new multiphase material model for simulating distortion and residual stresses in carburized and quenched gear steels. Simulation is focused on thin, metallic strips that are heat treated to introduce a through-thickness carbon gradient. Because the material properties are strongly dependent on the carbon content, quenching causes significant transverse out-of-plane distortion. The material model accounts for a multiphase alloy structure where inelasticity in the individual phases is temperature and rate dependent. The model is fit to an extensive matrix of experimental data for low carbon steels (0.2–0.8 percent) whose transformation kinetics and mechanical response are similar to 4023 and 4620 alloys used in experiments. While residual stress data are limited, reasonable agreement with X-ray diffraction measurements was obtained. Comparisons of transverse deflections predicted numerically showed excellent agreement with those measured experimentally for all five thicknesses reported. Accurate transformation and lattice carburization strains are critical to correctly predict the sense and magnitude of these transverse distortions and in-plane residual stresses.
The Effect of Asymmetry in Abdominal Aortic Aneurysms Under Physiologically Realistic Pulsatile Flow Conditions
Authors: Finol E. A. , Keyhani K. , Amon C. H.
Published: April 2003

In the abdominal segment of the human aorta under a patient’s average resting conditions, pulsatile blood flow exhibits complex laminar patterns with secondary flows induced by adjacent branches and irregular vessel geometries. The flow dynamics becomes more complex when there is a pathological condition that causes changes in the normal structural composition of the vessel wall, for example, in the presence of an aneurysm. This work examines the hemodynamics of pulsatile blood flow in hypothetical three-dimensional models of abdominal aortic aneurysms (AAAs). Numerical predictions of blood flow patterns and hemodynamic stresses in AAAs are performed in single-aneurysm, asymmetric, rigid wall models using the finite element method. We characterize pulsatile flow dynamics in AAAs for average resting conditions by means of identifying regions of disturbed flow and quantifying the disturbance by evaluating flow-induced stresses at the aneurysm wall, specifically wall pressure and wall shear stress. Physiologically realistic abdominal aortic blood flow is simulated under pulsatile conditions for the range of time-average Reynolds numbers 50⩽Rem⩽300, corresponding to a range of peak Reynolds numbers 262.5⩽Repeak⩽1575. The vortex dynamics induced by pulsatile flow in AAAs is depicted by a sequence of four different flow phases in one period of the cardiac pulse. Peak wall shear stress and peak wall pressure are reported as a function of the time-average Reynolds number and aneurysm asymmetry. The effect of asymmetry in hypothetically shaped AAAs is to increase the maximum wall shear stress at peak flow and to induce the appearance of secondary flows in late diastole.
Incorporation of Experimentally-Derived Fiber Orientation into a Structural Constitutive Model for Planar Collagenous Tissues
Authors: Sacks Michael S.
Published: April 2003

Structural constitutive models integrate information on tissue composition and structure, avoiding ambiguities in material characterization. However, critical structural information (such as fiber orientation) must be modeled using assumed statistical distributions, with the distribution parameters estimated from fits to the mechanical test data. Thus, full realization of structural approaches continues to be limited without direct quantitative structural information for direct implementation or to validate model predictions. In the present study, fiber orientation information obtained using small angle light scattering (SALS) was directly incorporated into a structural constitutive model based on work by Lanir (J. Biomech., v.16, pp. 1–12, 1983). Demonstration of the model was performed using existing biaxial mechanical and fiber orientation data for native bovine pericardium (Sacks and Chuong, ABME, v.26, pp. 892–902, 1998). The structural constitutive model accurately predicted the complete measured biaxial mechanical response. An important aspect of this approach is that only a single equibiaxial test to determine the effective fiber stress-strain response and the SALS-derived fiber orientation distribution were required to determine the complete planar biaxial mechanical response. Changes in collagen fiber crimp under equibiaxial strain suggest that, at the meso-scale, fiber deformations follow the global tissue strains. This result supports the assumption of affine strain to estimate the fiber strains. However, future evaluations will have to be performed for tissue subjected to a wider range of strain to more fully validate the current approach.
Accuracy and Reproducibility of CFD Predicted Wall Shear Stress Using 3D Ultrasound Images
Authors: Augst A. D. , Barratt D. C. , Hughes A. D. , Glor F. P. , Thom S. A. McG. , Xu X. Y.
Published: April 2003

Computational fluid dynamics (CFD) flow simulation techniques have the potential to enhance our understanding of how haemodynamic factors are involved in atherosclerosis. Recently, 3D ultrasound has emerged as an alternative to other 3D imaging techniques, such as magnetic resonance angiography (MRA). The method can be used to generate realistic vascular geometry suitable for CFD simulations. In order to assess accuracy and reproducibility of the procedure from image acquisition to reconstruction to CFD simulation, a human carotid artery bifurcation phantom was scanned three times using 3D ultrasound. The geometry was reconstructed and flow simulations were carried out on the three sets as well as on a model generated using computer aided design (CAD) from the geometric information given by the manufacturer. It was found that the three reconstructed sets showed good reproducibility as well as satisfactory quantitative agreement with the CAD model. Analyzing two selected locations probably representing the ‘worst cases,’ accuracy comparing ultrasound and CAD reconstructed models was estimated to be between 7.2% and 7.7% of the maximum instantaneous WSS and reproducibility comparing the three scans to be between 8.2% and 10.7% of their average maximum.
Determination of Optimal Graft Lengths for Posterior Cruciate Ligament Reconstruction—A Theoretical Analysis
Authors: Li Guoan , DeFrate Louis , Suggs Jeremy , Gill Thomas
Published: April 2003

Various graft materials have been used in posterior cruciate ligament (PCL) reconstruction. However, it is unclear if these grafts can reproduce the structural behavior of the PCL. This paper analyzed the effect of graft length on the structural behavior of the graft using a minimal deformation energy method. An analytical solution was obtained to determine the optimal effective graft length that can best reproduce the structural behavior of the PCL. This optimal graft length was determined as a function of the axial rigidity of the graft. Two typical grafts, bone-patella tendon-bone (BPTB) and Achilles tendon, were analyzed. The data demonstrated that in order to reproduce the PCL behavior, the effective length of a BPTB graft (10 mm width) should be 34 mm, while the Achilles tendon graft (with a cross sectional area of 55 mm2) needs to be 48 mm in length. Longer grafts result in less resistance and shorter graft increased the graft resistance. An initial graft tension cannot help recreate the overall structural behavior of the PCL. These results suggest that graft length is an important surgical variable in PCL reconstruction. An optimal reconstruction of the PCL should reproduce the structural properties of the PCL by using a graft with an optimal length.
Axial Mechanical Properties of Fresh Human Cerebral Blood Vessels
Authors: Monson Kenneth L. , Goldsmith Werner , Barbaro Nicholas M. , Manley Geoffrey T.
Published: April 2003

Human cerebral blood vessels are frequently damaged in head impact, whether accidental or deliberate, resulting in intracranial bleeding. Additionally, the vasculature constitutes the support structure for the brain and, hence, plays a key role in the cranial load response. Quantification of its mechanical behavior, including limiting loads, is thus required for a proper understanding and modeling of traumatic brain injury—as well as providing substantial assistance in the development and application of preventive measures. It is believed that axial stretching is the dominant loading mode for the blood vessels, regardless of the nature of the insult. Eighteen arteries and fourteen veins were obtained from the cortical surface of the cerebral temporal lobe of patients undergoing surgery. These vessels were stretched to failure in the longitudinal direction, either quasi-statically or dynamically. The significance of specimen and experiment parameters was determined using multivariate analysis of variance (MANOVA) testing. Results demonstrate that the arteries were considerably stiffer than the veins, carrying approximately twice as much stress at failure but withstanding only half as much stretch. No significant rate dependence was measured over a strain rate range of more than four orders of magnitude (0.01 to 500 s−1).
Ultimate Strength and Failure Mechanism of Resistance Spot Weld Subjected to Tensile, Shear, or Combined Tensile/Shear Loads
Authors: Chao Yuh J.
Published: April 2003

Strength tests were performed to reveal the failure mechanisms of spot weld in lap-shear and cross tension test samples. It is shown the while the lap-shear (cross tension) sample is subjected to shear (normal) load at the structural level the failure mechanism at the spot weld is tensile (shear) mode at the materials level. Based on the observed failure mechanism, stress distribution is assumed and related to the far field load for the lap-shear and cross tension test samples. It appears that the failure load of the cross tension sample is 74 percent of the lap-shear sample based on the classical von Mises failure theory. The theoretical model is further extended to the mixed normal/shear loading condition. Data from strength tests as well as finite element numerical method are used to validate the model. Finally, the utility of the model in accessing the failure strength of spot welds is discussed.
Analysis of Tube Free Hydroforming Using an Inverse Approach With FLD-Based Adjustment of Process Parameters1
Authors: Nguyen Ba Nghiep , Johnson Kenneth I. , Khaleel Mohammad A.
Published: April 2003

This paper describes an inverse approach (IA) formulation for the analysis of tubes under free hydroforming conditions. The IA formulation is derived from that of Guo et al. established for flat sheet hydroforming analysis using constant strain triangular membrane elements. First, an incremental analysis of free hydroforming for a hot-dip galvanized (HG/Z140) DP600 tube is performed using the Marc finite element code. The deformed geometry obtained at the last converged increment is then used as the final configuration in the inverse analysis. This comparative study allows an assessment of the predictive capability of the inverse analysis. The results are compared with the experimental values determined by Asnafi and Skogsga¨rdh. After that, a procedure based on a forming limit diagram (FLD) is described as a means to adjust the process parameters such as the axial feed and internal pressure. Finally, the adjustment process is illustrated through a re-analysis of the same tube using the inverse approach.
Experimental Implementation of Neural Network Springback Control for Sheet Metal Forming
Authors: Viswanathan Vikram , Kinsey Brad , Cao Jian
Published: April 2003

The forming of sheet metal into a desired and functional shape is a process, which requires an understanding of materials, mechanics, and manufacturing principles. Furthermore, producing consistent sheet metal components is challenging due to the non-linear interactions of various material and process parameters. One of the major causes for the fabrication of inconsistent sheet metal parts is springback, the elastic strain recovery in the material after the tooling is removed. In this paper, springback of a steel channel forming process is controlled using an artificial neural network and a stepped binder force trajectory. Punch trajectory, which reflects variations in material properties, thickness and friction condition, was used as the key control parameter in the neural network. Consistent springback angles were obtained in experiments using this control scheme.
Optimization of Directionally Attached Piezoelectric Actuators
Authors: Wetherhold Robert , Messer Markus , Patra Abani
Published: April 2003

A directionally attached piezoelectric (DAP) actuator is one method to control the twisting vibration of a plate with high authority. Although insuring proper performance for DAP actuators has been discussed in terms of the control law used, the optimization of the mechanical details of the actuator itself has received little attention. There is an interaction between the actuator and the controlled structure because more actuator material on the structure adds actuation power but also stiffens the structure. The effects of DAP actuator geometric parameters and material properties are explored in a systematic way for the case of a cantilever beam and it is shown that significant improvements in performance are possible. The material property study indicates that an optimum point exists whereby the weight and thus cost can be lowered while improving structure response by using a composite actuator. The actuator thickness, width, orientation angle, and offset from the clamped end have significant effects on structure response. In order of importance, the geometric parameters are: actuator thickness, orientation angle, width and offset. A study of the modal distribution for the structure shows that if the input disturbance that is to be suppressed is modally well characterized, the structure can be efficiently controlled by using more than one independent actuation voltage.
Measurement of In-Plane Residual Stresses Varying With Depth by the Interferometric Strain/Slope Rosette and Incremental Hole-Drilling
Authors: Tjhung Tana , Li Keyu
Published: April 2003

A new experimental method utilizing the Interferometric Strain/Slope Rosette (ISSR) and incremental hole-drilling is applied to measure in-plane residual stresses which vary with depth. For each depth increment, the ISSR measures three relieved strain components and two relieved slopes at point near the hole edge. Adapting the classical Integral Method to the ISSR, and incorporating a Tikhonov regularization scheme, stabilized residual stress solutions are back-calculated from the measured deformations. This paper describes the measurement principle of the ISSR, the derivation and numerical calculation of the ISSR hole-drilling coefficients, and the methodology used to back-calculate and regularize the residual stress solution. A verification test on a thin-plate with a through-hole, and residual stress measurements performed on a shot-peened Titanium-alloy block, are presented and discussed.
Surface Enhancement of Al2O3 Fiber With Nanosized Al2O3 Particles Using A Dry Mechanical Coating Process
Authors: Coowanitwong Nowarat , Wu Chang-Yu , Nguyen Judy , Cai Mei , Ruthkosky Martin , Rogers Jerry , Feng Lee , Watano Satoru , Yoshida Taizo
Published: April 2003

Currently, fabrication of composite materials is of great interest in industry. By combining materials of different properties, we can produce new composite materials with synergetic functionality that individual materials do not possess. In this study, Al2O3 nanosized particles were coated on Al2O3 fiber substrates using a dry mechanical coating technique employing high shear and compression forces. The materials thus synthesized had high surface area with good dispersion for enhanced reactivity and were strong to sustain rigorous operation. Operating parameters, including rotor speed, processing time and initial loading percentage were varied to study their effects on the coating condition. The experimental results showed that the product surface area increased as the nanoparticle loading increased. The dispersion of nanoparticles improved as the processing time increased. A higher rotor speed resulted in a shorter product length while the nanoparticle loading had no effect on the product length. The durability test, conducted in a fluidized bed, indicated no significant change of the coating layer after 7 days of continuous testing.