Home About us Contact
|
Home About us Contact | ||
|
|
||
Stress Measurements (stress + measurement)
Kinds of Stress Measurements Selected AbstractsRESIDUAL STRESS MEASUREMENT USING THE HOLE DRILLING METHOD AND LASER SPECKLE INTERFEROMETRYEXPERIMENTAL TECHNIQUES, Issue 4 2003E. Ponslet First page of article [source] A New Method to Identify Quaternary Moraine: Acoustic Emission Stress MeasurementACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 5 2006ZHAO Zhizhong Abstract: How to effectively identify glacial sediments, especially Quaternary moraine, has been in dispute for decades. The traditional methods, e.g., sedimentary and geomorphologic ones, are facing challenge in eastern China where controversial moraine deposits are dominatingly distributed. Here, for the first time, we introduce the acoustic emission (AE) stress measurement, a kind of historical stress measurement, to identify Quaternary moraine. The results demonstrate that it can be employed to reconstruct stress information of glaciation remaining in gravels, and may shed light on the identification of Quaternary moraine in eastern China. First, we measured the AE stress of gravels of glacial origin that are underlying the Xidatan Glacier, eastern Kunlun Mountains in western China. Second, we calculated the stress according to the actual thickness of the glacier. The almost identical stress values suggest that the glacial gravels can memorize and preserve the overlying glacier-derived aplomb stress. And then we introduce this new approach to the controversial moraine in Mount Lushan, eastern China. The results indicate that the stress is attributed to the Quaternary glacier, and the muddy gravels in the controversial moraine in Mount Lushan are moraine deposits but not others. [source] New Research Results on Mechanism, Surface Rupture, Deep Controlling Factors and Stress Measurements of the Wenchuan Earthquake,Earth Scientists' Post-quake ActionsACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 4 2009Shuwen DONG First page of article [source] Preliminary Results of In-situ Stress Measurements along the Longmenshan Fault Zone after the Wenchuan Ms 8.0 EarthquakeACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 4 2009Manlu WU Abstract: Four months after the Wenchuan Ms 8 earthquake in western Sichuan, China, in situ stress measurements were carried out along the Longmenshan fault zone with the purpose of obtaining stress parameters for earthquake hazard assessment. In-situ stresses were measured in three new boreholes by using overcoring with the piezomagnetic stress gauges for shallow depths and hydraulic fracturing for lower depths. The maximum horizontal stress in shallow depths (,20 m) is about 4.3 MPa, oriented N19°E, in the epicenter area at Yingxiu Town, about 9.7 MPa, oriented N51°W, at Baoxing County in the southwestern Longmenshan range, and about 2.6 MPa, oriented N39°E, near Kangding in the southernmost zone of the Longmenshan range. Hydraulic fracturing at borehole depths from 100 to 400 m shows a tendency towards increasing stress with depth. A comparison with the results measured before the Wenchuan earthquake along the Longmenshan zone and in the Tibetan Plateau demonstrates that the stress level remains relatively high in the southwestern segment of the Longmenshan range, and is still moderate in the epicenter zone. These results provide a key appraisal for future assessment of earthquake hazards of the Longmenshan fault zone and the aftershock occurrences of the Wenchuan earthquake. [source] Clarification of regional and local in situ stresses using the compact conical-ended borehole overcoring technique and numerical analysisISLAND ARC, Issue 3 2003Seong-Seung Kang Abstract Stress measurement is performed to estimate the states of in situ rock stress at the Torigata open-pit limestone mine in Japan using the compact conical-ended borehole overcoring (CCBO) technique. A set of back and forward analyses are then carried out to evaluate the states of regional and local in situ rock stresses and the mine-induced rock slope stability using a 3-D finite element model. The maximum horizontal local in situ rock stress measured by the CCBO technique acts in the northeast,southwest direction. The horizontal regional tectonic stresses obtained by the back analysis are in good agreement with those of the horizontal local in situ rock stress measured by the CCBO technique. However, the horizontal regional tectonic stress is more compressive than the horizontal local in situ rock stress. This is because the horizontal regional stress due to gravity is not considered in the back-analyzed horizontal regional tectonic stress, but it is included in the local in situ rock stress measured by the CCBO technique. The local stress obtained by the forward analysis, especially its horizontal components, is in good agreement with the horizontal local in situ rock stress measured by the CCBO technique, and the magnitude of the vertical normal stress increases more rapidly than those of the horizontal normal stresses with depth. As a result, the ratio of the horizontal normal stress to the vertical normal stress is largest at the nearest excavation level and decreases with depth. This means that the stress field within the mine-induced rock slope is affected by the horizontal components of the local in situ rock stress. [source] Mapping of unstressed lattice parameters using pulsed neutron transmission diffractionJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2002Javier Roberto Santisteban Stress measurement by neutron diffraction depends critically on knowledge of the unstressed lattice parameter (a0) of the specimen under study. As a result, measurement of stress profiles in components where a0 is not homogeneous throughout the sample, such as welds or carburized surfaces, can be particularly difficult. An efficient solution to this problem is proposed based on the pulsed neutron transmission diffraction technique. This technique exploits the sharp steps in intensity, the so-called Bragg edges, appearing in the transmitted neutron spectra of polycrystalline materials, such steps being produced by coherent scattering from lattice planes. The position of these Bragg edges as defined by the time-of-flight technique is used to determine precisely local interplanar distances. In this work it is shown that the unstressed lattice parameter of thin specimens subjected to plane stress fields can be defined by recording transmission spectra at different sample inclinations, in complete analogy with the sin2, technique used in X-ray diffraction. Moreover, by using an array of detectors it is possible to produce a radiographic `image' of a0 for plane specimens or thin sections out of three-dimensional ones. The capability of the technique is exemplified by mapping the changes in a0 for a ferritic weld that was used as a round robin sample in an international program for standardization of stress measurements by neutron diffraction. [source] Effect of Microstructure on Residual Stresses in Sintered Diamond,Metal Composites,ADVANCED ENGINEERING MATERIALS, Issue 6 2009U. Selvadurai-Laßl As residual stresses can reduce the lifetime of diamond-cobalt composite cutting tools, the composite stress state needs to be understood very well. Thus, the effect of microstructure on the residual stresses was investigated here. Stress measurements were carried out in the cobalt matrix by X-ray diffraction (XRD) and Synchrotron-XRD (SXRD). In addition to global stress measurements, investigations of stresses in small cobalt areas near the diamonds were performed by high brilliant synchrotron radiation using different apertures. [source] Influence of anti-washout agents on the rheological properties and injectability of a calcium phosphate cementJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2007Xiupeng Wang Abstract Anti-washout-type calcium phosphate cement (aw-CPC) was prepared by introducing chitosan, sodium alginate, or modified starch into the powder phase of CPC, respectively. The results showed that these cements cannot be washed out and set within approximately 10,30 min even if the pastes were immersed in distilled water immediately and were shaken in a shaker after mixing and moulding. To our knowledge, it is the first report about the influence of the content of these anti-washout additives on the rheological properties and injectability of the cement. Moreover, novel approach of yield stress measurement was used to evaluate the injectability of the pastes. A modified starch was originally used as anti-washout agent for CPC. This study provided a convenient way to use the injectable CPC with good anti-washout performance when the paste was exposed to blood. The aw-CPC had potential prospects for the wider applications in surgery such as orthopaedics, oral, and maxillofacial surgery. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source] INTERNATIONAL INTER-LABORATORY TRIALS TO DETERMINE THE FACTORS AFFECTING THE MEASUREMENT OF CHOCOLATE VISCOSITYJOURNAL OF TEXTURE STUDIES, Issue 5 2000J.-M. AESCHLIMANN The working group of the International Office of Cocoa, Chocolate and Sugar Confectionery (IOCCC) performed a sequence of five ring tests to improve the agreement of the standard method for measuring viscosity of chocolate between laboratories. Reporting shear stress measurements instead of using the Casson equation improved the agreement, as did standardising the method of cleaning the concentric cylinder and calibrating the viscometers. In the revised method, the standard deviation for shear stress measurement at shear rates greater than 5 s,1 from 23 laboratories was less than 8%. However, the Casson yield values had a seven-fold range and the Casson plastic viscosity a two-fold range, which was unacceptably high. A new method (IOCCC 2000) has been published as a result of this work and is available from CAOBISCO in Bruxelles, Belgium. [source] Stress Development Due to Capillary Condensation in Powder Compacts: A Two-Dimensional Model StudyJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2000Stefan Lampenscherf A model experiment is presented to investigate the relationship between the humidity-dependent liquid distribution and the macroscopic stress in a partially wet powder compact. Therefore, films of monosized spherical particles were cast on silicon substrates. Using environmental SEM the geometry of the liquid necks trapped between particles was imaged as a function of relative humidity. Simultaneously the macroscopic stress in the substrate adhered particle film was measured by capacitive deflection measurement. The experimentally found humidity dependence of the liquid neck size and the macroscopic film stress are compared with model predictions. The circle,circle approximation is used to predict the size of the liquid necks between touching particles as a function of the capillary pressure. Using the modified Kelvin relation between capillary pressure and relative humidity, we consider the effect of an additional solute which may be present in the capillary liquid. The results of the stress measurement are compared with the model predictions for a film of touching particles in hexagonal symmetry. The contribution of the capillary interaction to the adhesion force between neighboring particles is calculated using the integrated Laplace equation. The resulting film stress can be approximated relating this capillary force to an effective cross section per particle. The experimentally found humidity dependence of the liquid neck size is in good agreement with the model predictions for finite solute concentration. The film stress corresponds to the model predictions only for large relative humidities and shows an unexpected increase at small values. As is shown with an atomic force microscope, the real structure of the particle,particle contact area changes during the wet/dry cycle. A solution/reprecipitation process causes surface heterogeneities and solid bridging between the particles. It is claimed that the existence of a finite contact zone between the particles gives rise to the unexpected increase of the stress at small relative humidities. [source] A New Method to Identify Quaternary Moraine: Acoustic Emission Stress MeasurementACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 5 2006ZHAO Zhizhong Abstract: How to effectively identify glacial sediments, especially Quaternary moraine, has been in dispute for decades. The traditional methods, e.g., sedimentary and geomorphologic ones, are facing challenge in eastern China where controversial moraine deposits are dominatingly distributed. Here, for the first time, we introduce the acoustic emission (AE) stress measurement, a kind of historical stress measurement, to identify Quaternary moraine. The results demonstrate that it can be employed to reconstruct stress information of glaciation remaining in gravels, and may shed light on the identification of Quaternary moraine in eastern China. First, we measured the AE stress of gravels of glacial origin that are underlying the Xidatan Glacier, eastern Kunlun Mountains in western China. Second, we calculated the stress according to the actual thickness of the glacier. The almost identical stress values suggest that the glacial gravels can memorize and preserve the overlying glacier-derived aplomb stress. And then we introduce this new approach to the controversial moraine in Mount Lushan, eastern China. The results indicate that the stress is attributed to the Quaternary glacier, and the muddy gravels in the controversial moraine in Mount Lushan are moraine deposits but not others. [source] Raman spectroscopic and X-ray investigation of stressed states in diamond-like carbon filmsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 1-2 2005R. Krawietz Abstract The non-destructive characterization of intrinsic stress is very important to evaluate the reliability of devices based on diamond-like carbon (DLC) films. Whereas the only requirement for the X-ray diffraction method is a crystalline state of specimen, Raman spectroscopic stress analysis is restricted to materials showing intensive and sharp Raman peaks. On the other hand, Raman spectroscopy offers the possibility to measure stress profiles with lateral resolution of about 1 micron. The results of stress measurements in DLC films using both X-ray diffraction and Raman spectroscopy are found in very good correspondence. Mean stress in carbon films consisting of very small crystallites on silicon substrates has been determined by measuring and fitting the stress profiles in the substrate near artificial vertical film edges. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of Microstructure on Residual Stresses in Sintered Diamond,Metal Composites,ADVANCED ENGINEERING MATERIALS, Issue 6 2009U. Selvadurai-Laßl As residual stresses can reduce the lifetime of diamond-cobalt composite cutting tools, the composite stress state needs to be understood very well. Thus, the effect of microstructure on the residual stresses was investigated here. Stress measurements were carried out in the cobalt matrix by X-ray diffraction (XRD) and Synchrotron-XRD (SXRD). In addition to global stress measurements, investigations of stresses in small cobalt areas near the diamonds were performed by high brilliant synchrotron radiation using different apertures. [source] Fatigue crack initiation life estimation in a steel welded joint by the use of a two-scale damage modelFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 5 2009N. LAUTROU ABSTRACT This work deals with the fatigue behaviour of S355NL steel welded joints classically used in naval structures. The approach suggested here, in order to estimate the fatigue crack initiation life, can be split into two stages. First, stabilized stress,strain cycles are obtained in all points of the welded joint by a finite element analysis, taking constant or variable amplitude loadings into account. This calculation takes account of: base metal elastic,plastic behaviour, variable yield stress based on hardness measurements in various zones of the weld, local geometry at the weld toe and residual stresses if any. Second, if a fast elastic shakedown occurs, a two-scale damage model based on Lemaitre et al.'s work is used as a post-processor in order to estimate the fatigue crack initiation life. Material parameters for this model were identified from two Wöhler curves established for base metal. As a validation, four-point bending fatigue tests were carried out on welded specimens supplied by ,DCNS company'. Two load ratios were considered: 0.1 and 0.3. Residual stress measurements by X-ray diffraction completed this analysis. Comparisons between experimental and calculated fatigue lives are promising for the considered loadings. An exploitation of this method is planned for another welding process. [source] Fretting fatigue behaviour of shot-peened Ti-6Al-4V at room and elevated temperaturesFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 9 2003H. LEE ABSTRACT Fretting fatigue behaviour of shot-peened titanium alloy, Ti-6Al-4V was investigated at room and elevated temperatures. Constant amplitude fretting fatigue tests were conducted over a wide range of maximum stresses, ,max= 333 to 666 MPa with a stress ratio of R= 0.1. Two infrared heaters, placed at the front and back of specimen, were used to heat and maintain temperature of the gage section of specimen at 260 °C. Residual stress measurements by X-ray diffraction method before and after fretting test showed that residual compressive stress was relaxed during fretting fatigue. Elevated temperature induced more residual stress relaxation, which, in turn, decreased fretting fatigue life significantly at 260 °C. Finite element analysis (FEA) showed that the longitudinal tensile stress, ,xx varied with the depth inside the specimen from contact surface during fretting fatigue and the largest ,xx could exist away from the contact surface in a certain situation. A critical plane based fatigue crack initiation model, modified shear stress range parameter (MSSR), was computed from FEA results to characterize fretting fatigue crack initiation behaviour. It showed that stress relaxation during test affected fretting fatigue life and location of crack initiation significantly. MSSR parameter also predicted crack initiation location, which matched with experimental observations and the number of cycles for crack initiation, which showed the appropriate trend with the experimental observations at both temperatures. [source] In situ stress measurements in a borehole close to the Nojima FaultISLAND ARC, Issue 3-4 2001Hiroaki Tsukahara AbstractIn situ stress was measured close to the fault associated with the 1995 Kobe Earthquake (Hyogo-ken Nanbu earthquake; January 1995; M7.2) using the hydraulic fracturing method. The measurements were made approximately 2 years after the earthquake. The measured points were approximately 40 m from the fault plane at depths of about 1500 m. The maximum and the minimum horizontal compressive stresses were 45 MPa and 31 MPa, respectively. The maximum compressive stress and the maximum shear stress are very small in comparison with those of other seismically active areas. The azimuth of the maximum horizontal compressive stress was estimated from the observed azimuths of well bore breakouts at depths between 1400 m and 1600 m and was found to be N135° (clockwise). The maximum stress axis is perpendicular to the fault strike, N45°. These features are interpreted in terms of a small frictional coefficient of the fault. The shear stress on the fault was released and dropped almost to zero during the earthquake and it has not yet recovered. Zero shear stress on the fault plane resulted from the perpendicular orientation of one of the principal stress to the fault plane. [source] A method for the non-destructive analysis of gradients of mechanical stresses by X-ray diffraction measurements at fixed penetration/information depthsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2006A. Kumar A rigorous measurement strategy for (X-ray) diffraction stress measurements at fixed penetration/information depths has been developed. Thereby errors caused by lack of penetration-depth control in traditional (X-ray) diffraction (sin2,) measurements have been annulled. The range of accessible penetration/information depths and experimental aspects have been discussed. As a practical example, the depth gradient of the state of residual stress in a sputter-deposited nickel layer of 2,µm thickness has been investigated by diffraction stress measurements with uncontrolled penetration/information depth and two controlled penetration/information depths corresponding to about one quarter and one tenth of the layer thickness, respectively. The decrease of the planar tensile stress in the direction towards the surface could be well established quantitatively. [source] Mapping of unstressed lattice parameters using pulsed neutron transmission diffractionJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2002Javier Roberto Santisteban Stress measurement by neutron diffraction depends critically on knowledge of the unstressed lattice parameter (a0) of the specimen under study. As a result, measurement of stress profiles in components where a0 is not homogeneous throughout the sample, such as welds or carburized surfaces, can be particularly difficult. An efficient solution to this problem is proposed based on the pulsed neutron transmission diffraction technique. This technique exploits the sharp steps in intensity, the so-called Bragg edges, appearing in the transmitted neutron spectra of polycrystalline materials, such steps being produced by coherent scattering from lattice planes. The position of these Bragg edges as defined by the time-of-flight technique is used to determine precisely local interplanar distances. In this work it is shown that the unstressed lattice parameter of thin specimens subjected to plane stress fields can be defined by recording transmission spectra at different sample inclinations, in complete analogy with the sin2, technique used in X-ray diffraction. Moreover, by using an array of detectors it is possible to produce a radiographic `image' of a0 for plane specimens or thin sections out of three-dimensional ones. The capability of the technique is exemplified by mapping the changes in a0 for a ferritic weld that was used as a round robin sample in an international program for standardization of stress measurements by neutron diffraction. [source] INTERNATIONAL INTER-LABORATORY TRIALS TO DETERMINE THE FACTORS AFFECTING THE MEASUREMENT OF CHOCOLATE VISCOSITYJOURNAL OF TEXTURE STUDIES, Issue 5 2000J.-M. AESCHLIMANN The working group of the International Office of Cocoa, Chocolate and Sugar Confectionery (IOCCC) performed a sequence of five ring tests to improve the agreement of the standard method for measuring viscosity of chocolate between laboratories. Reporting shear stress measurements instead of using the Casson equation improved the agreement, as did standardising the method of cleaning the concentric cylinder and calibrating the viscometers. In the revised method, the standard deviation for shear stress measurement at shear rates greater than 5 s,1 from 23 laboratories was less than 8%. However, the Casson yield values had a seven-fold range and the Casson plastic viscosity a two-fold range, which was unacceptably high. A new method (IOCCC 2000) has been published as a result of this work and is available from CAOBISCO in Bruxelles, Belgium. [source] Laser-Assisted Machining of Damage-Free Silicon Nitride Parts with Complex Geometric Features via In-Process Control of Laser PowerJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2006Yinggang Tian A methodology to achieve optimal operating conditions for laser-assisted machining (LAM) is developed for silicon nitride parts with complex geometric features by applying a three-dimensional, transient thermal model and in-process laser power control. Complex silicon nitride parts are successfully produced by the LAM operation, where the maximum and material removal temperatures are carefully designed and controlled to achieve good machining results and avoid thermal damage on the final part. On-line temperature and laser power measurements are conducted and compared with prescribed values to show the effectiveness of the power control scheme. Scanning electron microscopy examination reveals virtually no subsurface microcrack or thermal damage on the silicon nitride parts. The X-ray diffraction (XRD) study shows the preservation of the silicon nitride microstructure and no phase transformation of ,-Si3N4 during the LAM experiments. XRD residual stress measurements show moderate compressive residual stresses on the silicon nitride workpieces produced by the LAM operation. [source] Laminar Ceramics Utilizing the Zirconia Tetragonal-to-Monoclinic Phase Transformation to Obtain a Threshold StrengthJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2002Michael G. Pontin Ceramic laminates have been fabricated with thin layers, containing a mixture of unstabilized zirconia (MZ-ZrO2) and alumina (Al2O3), sandwiched between thicker layers of alumina that contain a small fraction of Y2O3 -stabilized tetragonal ZrO2 to inhibit grain growth. The MZ-ZrO2 undergoes a tetragonal-to-monoclinic phase transformation during cooling to produce biaxial compressive stresses in the thin layers. Cracks that extend within the thicker alumina layers can be arrested by the compressive layers to produce a threshold strength, i.e., a strength below which the probability of failure is zero. Laminates composed of Al2O3 layers 315 ± 15 ,m thick and Al2O3/MZ-ZrO2 layers 29 ± 3 ,m thick exhibit a threshold strength of 507 ± 36 MPa, regardless of the MZ-ZrO2 content, for volume fractions ,0.35. These results, piezospectroscopic stress measurements, and microstructural observations suggest that microcracking produced during the transformation reduces the magnitude of the compressive stresses achieved, which in turn limits the magnitude of the threshold strength. [source] Performance of thin-film transistors fabricated by sequential lateral solidification crystallization techniquesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2008M. A. Exarchos Abstract The performance of Excimer Laser Annealed (ELA) Thin-Film Transistors (TFTs), in terms of drain current behaviour in unstressed as well as in DC stressed devices, is presented. The transistors studied were fabricated under different irradiation schemes of a novel Sequential Lateral Solidification (SLS) process. As far as unstressed transistors concerned, drain current transients relaxed through stretched exponential law. Fitting results disclosed that both gate dielectric polarization and carrier recombination mechanisms occurred through transient relaxation. Deep Level Transient Spectroscopy (DLTS) technique was called forth in order to investi- gate the origin of carrier recombination mechanisms. DC hot carrier stress measurements, under "worst ageing condition" regime, were conducted in order to probe degradation mechanisms and device reliability standards. Crystal domain size significantly affects threshold voltage degradation. The latter increases with decreasing crystal domain size, due to increased concentration of protrusions in the polysilicon film. Transconductance degradation also depends on crystal domain size, attributed mainly to bulk polysilicon trap generation. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Preliminary Results of In-situ Stress Measurements along the Longmenshan Fault Zone after the Wenchuan Ms 8.0 EarthquakeACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 4 2009Manlu WU Abstract: Four months after the Wenchuan Ms 8 earthquake in western Sichuan, China, in situ stress measurements were carried out along the Longmenshan fault zone with the purpose of obtaining stress parameters for earthquake hazard assessment. In-situ stresses were measured in three new boreholes by using overcoring with the piezomagnetic stress gauges for shallow depths and hydraulic fracturing for lower depths. The maximum horizontal stress in shallow depths (,20 m) is about 4.3 MPa, oriented N19°E, in the epicenter area at Yingxiu Town, about 9.7 MPa, oriented N51°W, at Baoxing County in the southwestern Longmenshan range, and about 2.6 MPa, oriented N39°E, near Kangding in the southernmost zone of the Longmenshan range. Hydraulic fracturing at borehole depths from 100 to 400 m shows a tendency towards increasing stress with depth. A comparison with the results measured before the Wenchuan earthquake along the Longmenshan zone and in the Tibetan Plateau demonstrates that the stress level remains relatively high in the southwestern segment of the Longmenshan range, and is still moderate in the epicenter zone. These results provide a key appraisal for future assessment of earthquake hazards of the Longmenshan fault zone and the aftershock occurrences of the Wenchuan earthquake. [source] Reproducibility of coronary lumen, plaque, and vessel wall reconstruction and of endothelial shear stress measurements in vivo in humansCATHETERIZATION AND CARDIOVASCULAR INTERVENTIONS, Issue 1 2003Ahmet U. Coskun PhD Abstract The purpose of this study was to assess the reproducibility of an in vivo methodology to reconstruct the lumen, plaque, and external elastic membrane (EEM) of coronary arteries and estimate endothelial shear stress (ESS). Ten coronary arteries without significant stenoses (five native and five stented arteries) were investigated. The 3D lumen and EEM boundaries of each coronary artery were determined by fusing end-diastolic intravascular ultrasound images with biplane coronary angiograms. Coronary flow was measured. Computational fluid dynamics was used to calculate local ESS. Complete data acquisition was then repeated. Analysis was performed on each data set in a blinded manner. The intertest correlation coefficients for all arteries for the two measurements of lumen radius, EEM radius, plaque thickness, and ESS were r = 0.96, 0.96, 0.94, 0.91, respectively (all P values < 0.0001). The 3D anatomy and ESS of human coronary arteries can be reproducibly estimated in vivo. This methodology provides a tool to examine the effect of ESS on atherogenesis, remodeling, and restenosis; the contribution of arterial remodeling and plaque growth to changes in the lumen; and the impact of new therapies. Catheter Cardiovasc Interv 2003;60:67,78. © 2003 Wiley,Liss, Inc. [source] | ||||||||||||||||||||||