Principal Compressive Strain Research Articles

Simulation of hip fracture in sideways fall using a 3D finite element model of pelvis–femur–soft tissue complex with simplified representation of whole body

Hip fractures due to sideways falls are a worldwide health problem, especially among the elderly population. The objective of this study was to simulate a real life sideways fall leading to hip fracture. To achieve this a computed tomography (CT) scan based three-dimensional (3D) finite element (FE) model of the pelvis–femur complex was developed using a wide range of mechanical properties in the bone of the complex. For impact absorption through large deformation, surrounding soft tissue was also included in the FE model from CT scan data. To incorporate the inertia effect, the whole body was represented by a spring-mass-dashpot system. For trochanteric soft tissue thickness of 14 mm, body weight of 77.47 kg and average hip impact velocity of 3.17 m/s, this detailed FE model could approximately simulate a sideways fall configuration and examine femoral fracture situation. At the contact surface, the peak impact load was 8331 N. In spite of the presence of 14 mm thick trochanteric soft tissue, within the trochanteric zone the most compressive peak principal strain was 3.5% which exceeds ultimate compressive strain. The modeled trochanteric fracture was consistent with clinical findings and with the findings of previous studies. Further, this detailed FE model may be used to find the effect of trochanteric soft tissue thickness variations on peak impact force, peak strain in sideways fall, and to simulate automobile side impact and backward fall situations.

Horizontal movement and strain characteristics in Tianshan and its adjacent region with GPS deformation data

Based on the multiple-term horizontal velocity solutions of 230 GPS monitoring sites in Tianshan and its adjacent region, the GPS site velocity fields and crustal horizontal strain fields in the area have been obtained. The results show that the crustal shortening rate of Tianshan, with the longitude (77°±1°)E as the boundary, gradually decreased towards two sides, from the south to the north, indicating that the pushing force of plate becomes weaker along with the fold deformation decreasing of the Tianshan. The direction of principal compressive strain of Tianshan and its adjacent area, nearly NNW, is basically perpendicular to the Tianshan cordillera trend, suggesting the distribution and variation of maximum principal compressive stress in Tianshan and its adjacent region resulted from collision and extrusion of Indian Plate. This paper indicates that the maximum shear strain field mainly concentrates on two areas, one is Isyk lake of North Tianshan, Kyrgyzstan, and the other is the juncture of Jiashi (South Tianshan) and Pamir arc faults. In the above areas, it can be shown from the epicentral distribution that the strong earthquakes mostly occurs at the high shearing strain accumulation field or its edge.

Seismic anisotropy of the crust in Yunnan, China: Polarizations of fast shear-waves

Using seismic data recorded by Yunnan Telemetry Seismic Network from January 1, 2000 to December 31, 2003, the dominant polarization directions of fast shear-waves are obtained at 10 digital seismic stations by SAM technique, a systematic analysis method on shear-wave splitting, in this study. The results show that dominant directions of polarizations of fast shear-waves at most stations are mainly at nearly N-S or NNW direction in Yunnan. The dominant polarization directions of fast shear-waves at stations located on the active faults are consistent with the strike of active faults, directions of regional principal compressive strains measured from GPS data, and basically consistent with regional principal compressive stress. Only a few of stations show complicated polarization pattern of fast shear-waves, or are not consistent with the strike of active faults and the directions of principal GPS compressive strains, which are always located at junction of several faults. The result reflects complicated fault distribution and stress field. The dominant polarization direction of fast shear-wave indicates the direction of the in-situ maximum principal compressive stress is controlled by multiple tectonic aspects such as the regional stress field and faults.

Anisotropy of Fibrous Tissues in Relation to the Distribution of Tensed and Buckled Fibers

Fibrous tissues are characterized by a much higher stiffness in tension than compression. This study uses microstructural modeling to analyze the material symmetry of fibrous tissues undergoing tension and compression, to better understand how material symmetry relates to the distribution of tensed and buckled fibers. The analysis is also used to determine whether the behavior predicted from a microstructural model can be identically described by phenomenological continuum models. The analysis confirms that in the case when all the fibers are in tension in the current configuration, the material symmetry of a fibrous tissue in the corresponding reference configuration is dictated by the symmetry of its fiber angular distribution in that configuration. However, if the strain field exhibits a mix of tensile and compressive principal normal strains, the fibrous tissue is represented by a material body which consists only of those fibers which are in tension; the material symmetry of this body may be deduced from the superposition of the planes of symmetry of the strain and the planes of symmetry of the angular fiber distribution. Thus the material symmetry is dictated by the symmetry of the angular distribution of only those fibers which are in tension. Examples are provided for various fiber angular distribution symmetries. In particular, it is found that a fibrous tissue with isotropic fiber angular distribution exhibits orthotropic symmetry when subjected to a mix of tensile and compressive principal normal strains, with the planes of symmetry normal to the principal directions of the strain. This anisotropy occurs even under infinitesimal strains and is distinct from the anisotropy induced from the finite rotation of fibers. It is also noted that fibrous materials are not stable under all strain states due to the inability of fibers to sustain compression along their axis; this instability can be overcome by the incorporation of a ground matrix. It is concluded that the material response predicted using a microstructural model of the fibers cannot be described exactly by phenomenological continuum models. These results are also applicable to nonbiological fiber-composite materials.

Integral‐Rotation Linear‐Strain Model and Intraplate Deformation‐Strain Field of the Philippine Sea Plate

AbstractIn this paper, we create an integral‐rotation linear‐strain model (IRLSM) for the Philippine Sea plate (PHIL) on the basis of the ITRF2000 velocities of 7 sites on the PHIL. Our study indicates that the current‐day tectonic motion of PHIL is a clockwise rotation, which is consistent with the rotational direction estimated by NNR‐NUVEL‐1A, but largely different from the rotational pole position and angle velocity of NNR‐NUVEL‐1A. Our model can uniformly and accurately describe the current tectonic movement and interior deformation of PHIL as compared with Sella's rigid motion model (RMM). There is an intensive deformation‐strain field within the PHIL and there is consistent eastward deformation on the plate. The deformation rate is small near the central tectonic line and large near the eastern and western boundaries, small at the southern and northern ends and large in the central part. The eastward deformation rate on the Mariana Arc is as large as 48.4mm/a. The NS‐trending deformation on the plate differs evidently in the eastern and western parts with a very small rate in the eastern part and a larger rate near the Manila Trench in the western part. The northward deformation rate at the north end is 11.3mm/a and the southward deformation rate at the south end is 29.3mm/a. The principal strain field is divided into the eastern and western areas from the central tectonic line. In the eastern area, the tensile strain is very intensive, while the compressive strain is very weak. The principal tensile strain is in near‐EW direction, the principal tensile and compressive strain rates increase gradually from the central tectonic line to the east, and the principal tensile strain rate reaches the highest value of 8.58×10−8/a near the southeast boundary (148°E, 15°N). In the western area, the principal compressive strain is very strong in a direction of NW‐SE, while the principal tensile strain is rather weak. From the central tectonic line to the west, the principal compressive and tensile strain rates increase gradually and the principal compressive strain rate reaches the maximum value of 5.71×10−8/a near the northwest boundary (122°E, 23°N). Closely related to the intraplate and surrounding tectonic settings, the spatial variation of deformation‐strain field of PHIL can be considered as a reflection of tectonic stress field.

Evaluation of micro-behavior of strain field in Chinese mainland with the GPS time series

Based on the time series of GPS station coordinate in the intemational Earth reference frame (ITRF), we evaluate annual micro-behavior of strain field in Chinese mainland with the triangle method. The results show that the annual micro-behavior of strain field is divided into two parts by the north-south earthquake belt in the research region. The prevailing direction of compressive principal strain field is nearly consistent in the western region. From west to east, the direction varies from NS to NE. It is in accordance with the direction of the modern compressive principal strain field. This suggests that geologic deformation in western region was mainly caused by that India tectonic plate pushes the research region northward and the Siberia plate pushes it southward relatively. It is an inheritance of new tectonic motion. The prevailing direction of the compressive principal strain field does not exist in the eastern region. The annual biggest shear strain is different greatly in every grid-cell. The values varies from 4.13×10−8 to 7.0×10−10. By and large the annual biggest shear strain in the western region is bigger than that in the eastern region. And so is the variation between any two consecutive biggest annual shear strains in the same grid-cell. The annual surface dilatation show that in most grid-cells of the research region the surface dilatation is in compressibility, and the variation between any two consecutive annual surface dilatation in the same grid-cell is small.

상계치 이론을 이용한 개구부를 갖는 철근콘크리트 단순.연속 깊은 보 내력의 수치해석 모델

Models to predict the ultimate strength of simply supported or continuous deep beams with web openings are proposed. The derived equations are based on upper-bound theorem. The concrete is assumed as a perfectly plastic material obeying the modified Coulomb failure criteria with zero tension cutoff. Reinforcing bar is considered as elastic-perfectly plastic material and its stress is calculated from the limiting principal compressive strain of concrete. The governing failure mechanisms based on test results are idealized as rigid moving blocks separated by a hyperbolic yield line. The effective compressive strength of concrete is calculated from the formula proposed by Vecchio and Collins. Comparisons with existing test results are performed, and they show good agreement.

Assessment of mechanical conditions in sub-dermal tissues during sitting: A combined experimental-MRI and finite element approach

A common but potentially severe malady afflicting permanent wheelchair users is pressure sores caused by elevated soft tissue strains and stresses over a critical prolonged period of time. Presently, there is paucity of information regarding deep soft tissue strains and stresses in the buttocks of humans during sitting. Strain and stress distributions in deep muscle and fat tissues were therefore calculated in six healthy subjects during sitting, in a double-donut Open-MR system, using a “reverse engineering” approach. Specifically, finite element (FE) models of the undeformed buttock were built for each subject using MR images taken at the coronal plane in a non-weight-bearing sitting posture. Using a second MR image taken from each subject during weight-bearing sitting we characterized the ischial tuberosity sagging toward the sitting surface in weight-bearing, and used these data as displacement boundary conditions for the FE models. These subject-specific FE analyses showed that maximal tissue strains and stresses occur in the gluteal muscles, not in fat or at the skin near the body–seat interface. Peak principal compressive strain and stress in the gluteus muscle were 74±7% and 32±9 kPa (mean±standard deviation), respectively. Peak principal compressive strain and stress in enveloping fat tissue were 46±7% and 18±4 kPa, respectively. Models were validated by comparing measured peak interface pressures under the ischial tuberosities (17±4 kPa) with those calculated by means of FE (18±3 kPa), for each subject. This is the first study to quantify sub-dermal tissue strain and stress distributions in sitting humans, in vivo. These data are essential for understanding the aetiology of pressure sores, particularly those that were recently termed “deep tissue injury” at the US National Pressure Ulcer Advisory Panel (NPUAP) 2005 Consensus Conference.

Shear deformation in reinforced concrete beams with thin web

In this paper the main results of an experimental campaign, carried out to analyse the shear deformation and interaction between moment and shear on the global and local deformations of reinforced concrete (RC) ‘I’ section simply supported beams with thin web, are discussed. A new theoretical model, which considers the lattice-like behaviour and applies the constitutive laws of the modified compressive field theory, is also proposed. The ‘concrete contribution’ of shear strength resistance is theoretically calculated. Experimental and theoretical results are then compared, showing the rotation of the principal compressive strain axis in the web. The influence of shear deformation on the deflection of the tested beams with thin web reaches 25% of the total deflection.

Interaction of turbulence and scalar fields in premixed flames

The interaction of turbulence with progress variable, c, field in a premixed flame is studied. This interaction is characterized by the correlation c,ieijc,j¯, where the overbar denotes an appropriate averaging process, c,i is the gradient of c in spatial direction i and eij is the turbulence strain rate. The importance of this term is recognized via a transport equation for the square of the magnitude of the scalar gradient in turbulent premixed flames. It is also shown that the above correlation forms a natural part of the tangential strain rate which appears in the flame surface density, Σ, equation. It is well known that this correlation is negative signifying the scalar gradient production by incompressible turbulence via the preferential alignment of the scalar gradient with the most compressive principal strain rate. This physical picture is commonly adopted for turbulent premixed flames also. Contrary to this, analyses of direct numerical simulation data for a turbulent premixed flame having flamelet combustion characteristics show the preferential alignment of the scalar gradient with the most extensive principal strain rate. This preferential alignment is because of flame influence on the flow via dilation. The above alignment pulls the isoscalar surfaces from each other yielding positive values for the above correlation inside the flame brush. Thus the turbulence, in addition to the molecular dissipation process, dissipates the scalar gradients in premixed flames when the Damköhler number (Da) is large. These dissipation processes are counteracted by chemical reactions which produce the scalar gradients. A simple RANS model for the above correlation is obtained by decomposing it into contributions from flame front and nonflame front regions of the flow as suggested by the DNS results. The model obtained here involves Da and represents the dissipation of the scalar gradients by the turbulence when Da is larger than unity. This model also recovers the production of the scalar gradient by the turbulence when Da is less than unity. Comparison of this model prediction with the DNS data of large Da flame is reasonable. The turbulence-scalar interaction in low and moderate Damköhler number flames still needs to be explored.

Progress in the development of a system for early detection of deep pressure sores associated with sitting: Results from control subjects

4061 Citation: Journal of Biomechanics 2006; Vol. 39 Suppl. 1, page S50 Progress in the development of a system for early detection of deep pressure sores associated with sitting: Results from control subjects E. Linder-Ganz1, Z. Yizhar2, A. Gefen1 Departments of 1 Biomedical Engineering and 2 Physical Therapy, Tel Aviv University, Tel Aviv, Israel Wheelchair bound paralyzed patients are susceptible to deep pressure sores (DPS) which typically affect the gluteus muscles under the ischial tuberosities (IT). In these patients, elevated mechanical strains and stresses form around the IT, and are not relieved through motion. However, no attempts were made to develop patient-specific models with clinical orientation of providing early detection of sub-dermal mechanical conditions that potentially lead to DPS. Here, we aim at developing a subject-specific finite element (FE) model of the buttock that allows visualization and analysis of sub-dermal tissue strains and stresses during wheelchair sitting, in real-time, based on continuously measured interface forces. The hardware and software components of our subject-specific real-time FE system are described in reference [1]. As a first stage of the present research, internal gluteal strains and stresses were obtained from 4 control subjects monitored by this prototype for 90 minutes of continuous sitting. For each subject, a FE model of the IT and enveloping soft tissues was developed based on his/her MRI of the buttocks. Sitting contact forces were fed into the subject-specific models as real-time boundary conditions. The healthy subject studies showed maximal principal compressive strains of 72±5% and 68±7% in the right and left gluteus, respectively. Principal compressive, shear and von Mises stresses were 34±3 kPa, 14±1 kPa and 31±4 kPa under the right IT, and 32±4 kPa, 13±2 kPa and 30±2 kPa under the left IT, respectively. Maximal continuous exposure to internal gluteal stress was 24±17 minutes and 13±8 minutes for right and left buttock sides, respectively. We expect that this method will make a substantial contribution to efforts made to prevent DPS among permanent wheelchair users. Reference: 1. Yarnitzky G., Yizhar Z., Gefen A. Real-time subject-specific monitoring of internal deformations and stresses in the soft tissues of the foot: A new approach in gait analysis. J Biomech 2005; in press. doi: 10.1016/j.jbiomech.2005.08.021.

Effects of unsteady strain rate on scalar dissipation structures in turbulent planar jets

An analysis of previously acquired experimental data is performed with the objective of investigating the relationship between strain rate and scalar dissipation rate structures in gas-phase turbulent planar jet flows at local Reynolds numbers ranging from 1000 to 6100. The data analyzed were simultaneously acquired two-dimensional (2D) velocity and 2D conserved scalar fields. The measurements show that, in agreement with previous work, the scalar dissipation structures tend to align orthogonally to the axis of the principal compressive strain rate, and the magnitude of the strain rates acting on the dissipation layers is consistent with theoretical turbulent inner-scale values. Furthermore, the spatially resolved data show that profiles of scalar dissipation, taken across the sheet-like scalar dissipation structures, are approximately Gaussian, whereas the strain rate profiles across the same structures exhibit no characteristic shape, and rarely reach a maximum at the same location as the scalar dissipation. When the scalar dissipation layer thicknesses are cast in nondimensional form and plotted as a function of the instantaneous relative strain rate, the data at all Reynolds numbers exhibit similar characteristics. The measurements from the turbulent flow were compared to a simple one-dimensional (1D) unsteady strained laminar diffusion-layer model, where the imposed strain rate varied harmonically. The simplified model shows remarkable agreement with the experimental data as it predicts the correct trend of layer thickness with strain rate and captures the range of scalar dissipation layer thicknesses that are present in the turbulent flows. The model and experiments show that the layers with greater-than-average strain rate tend to be thicker than expected by steady-state theory, whereas at low strain rates the layers are significantly thinner than at steady state. The 1D model shows best agreement with the measurements when the imposed strain rates are allowed to be positive in the direction of the scalar gradient over some part of the oscillation cycle. This suggests that dissipation layers in turbulent flows experience significant positive strain over their lifetimes.

Computation of Present Strain Rate Field of Qinghai-Tibetan Plateau and Its Geodynamic Implications

Many researchers calculated strain rate of significant differences from the same GPS measurement data. In this paper, we use the Kriging method in geostatistics to GPS velocity field. Interpolating the scattered GPS velocity data of Qinghai-Tibetan plateau and its adjacent areas to grid point values by Kriging, we calculate the strain rates from these nodal values in each grid cell similar to derivative of shape functions (essentially Lagrange interpolation function) in finite element algorithm, and obtain the stable distribution of strain rate field in Qinghai-Tibetan plateau. The results show that the main part of Qinghai-Tibetan plateau is in the state of compression in north-south direction, and extension in west-east direction. On the contrary, in the eastern part of Tibet, the strain rate is compressive in west-east and extensional in north-south direction. The orientations of principal strain rates are consistent with those of the P axis and T axis in focal mechanism. The high values of maximum compressive principal strain rates are located in the Himalayan main boundary thrust zone (MBT) and the surrounded regions. The maximum extensive principal strain rates are higher than those of the compressive ones in the main part of the interior of Qinghai-Tibetan plateau. Also, the surface dilation strain rate shows that it is in the state of surface compression in Himalayan and its surrounded areas, and in the state of surface extension in the interior of Qinghai-Tibetan plateau. The distribution of maximum shear strain rate clearly displays the outlines of some main active fault zones. The result of the strain rate in this study suggests that the contemporary tectonic strain of Tibet inherits the long term geological deformation.

A three-dimensional finite element stress analysis for tunnel placement and buttons in anterior cruciate ligament reconstructions

This communication reports the results of a three-dimensional finite element (FE) model of stresses in a surgically altered femur and tibia. The model incorporated a novel approach in implementing orthotropic and inhomogeneous bone properties and non-uniform distributed loading. Cortical, cancellous, and subchondral bone of the femur and the tibia were modeled. Mechanical properties for the cortical and cancellous bone were mapped from published data characterizing the anisotropy and inhomogeneity of the bone properties. Mesh adequacy was determined using stress convergence and strain energy error convergence. Qualitatively, the results of the study compare well with experimental principal compressive strains from the literature. With respect to tunnel placement in anterior cruciate ligament reconstruction, the model predicted stress-shielding at the postero-lateral region of the tunnel wall, and increased stress at the postero-medial region of the tunnel wall. The stresses in the cancellous bone beneath the tunnel were, in general, lower than those above the tunnel. Prolonged stress shielding leads to bone resorption of the posterior tunnel wall leading to tunnel enlargement, and possible compromise of the ACL reconstruction. The stresses on the femoral cortex produced from a button-type fixation were noticeable for low levels of loading; the stress levels were very similar in models incorporating bone properties of patients aged 45 and 65. Repeated compression of the femoral cortex at these stress levels may cause microdamage to the cortex eventually resulting in fatigue failure.

Horizontal Strain Field in Chinese Mainland and the Surrounding Areas

AbstractIn the paper, two kinds of equations of block elastic motion are established: the equation with rotation in the entire block and homogeneous strain and the equation with rotation in the entire block and linear strain. Using the velocities of GPS sites located in the Western Region, Qinghai‐Xizang and North China blocks, both the elastic motion equations and the rigid motion equation are tested statistically for their unbiasedness and validity to simulate the site velocity of the block. The tested results indicate that the equation with rotation in the entire block and linear strain is the optimal model to describe the block motion; the equation with rotation in the entire block and homogeneous strain ranks the second; and the model of the block rigid rotation is the third. Dividing the Chinese mainland into 10 blocks, the rotation and strain parameters of each block are estimated using the equation with rotation in the entire block and linear strain and the velocities of GPS sites on the blocks. Then, the strain parameters of 1005 points in Chinese mainland and the surrounding areas are calculated with the spacing of 1° × 1°, and the strain field in Chinese mainland and the surrounding areas has been obtained. The basic characteristics of strain field in Chinese mainland and the surrounding areas are also analyzed in the paper. The direction of the principal compressive strain obtained by the method in the paper is well consistent with the principal compressive stress axes derived by the geological and seismological methods (except for South China block). The strain field has a very close relation with the main fault zones, and all the main fault zones of the block boundaries are the gradient zones with high‐level first shear strain rate. The fault zone is the result from the adjustment of strain‐stress field.

A comparison of bone strain measurements at anatomically relevant sites using surface gauges versus strain gauged bone staples

Instrumented bone staples were first introduced as an alternative to surface-mounted strain gauges for use in human in vivo bone strain measurements because their fixation to bone is secure and requires not only minimally invasive surgery. Bench-top bone bending models have shown that the output from strain gauged bone staples compares favorably to that of traditional mounted gauges. However their within- and across-subject performance at sites typically instrumented in vivo has never been examined. This study used seven human cadaver lower extremities with an age range of 23–81 years old and a dynamic gait simulator to examine and compare axial strains in the mid tibial diaphysis and on the dorsal surface of the second metatarsal as measured simultaneously with strain gauged bone staples and with traditional surface-mounted gauges. Rosette configurations were used at the tibial site for deriving principal compression and tension, and shear strains. Axial outputs from the two gauge types demonstrated strong linear relationships for the tibia ( r 2=0.78–0.94) and the second metatarsal ( r 2=0.96–0.99), but coefficients (slopes) for the relationship were variable (range 7–20), across subjects and across sites. The apparent low reliability of strain gauged staples may be explained by the fact that both strain gauged staples and surface strain gauges are inexact to some degree, do not measure strains from exactly the same areas and strain gauged staples reflect surface strains as well as deformations within the cortex. There were no relationships for the principal tibia compression, tension or shear strain measurements derived from the two rosette gauge types, reflecting the very different anatomical areas measured by each of the constructs in this study. Strain gauged bone staples may be most useful in comparing relative axial intra-subject differences between activities, but inter-subject variability may require larger sample sizes to detect differences between populations.

Movement and strain conditions of active blocks in the Chinese mainland

The definition of active block is given from the angles of crustal deformation and strain. The movement and strain parameters of active blocks are estimated according to the unified velocity field composed of the velocities at 1598 GPS stations obtained from GPS measurements carried out in the past years in the Chinese mainland and the surrounding areas. The movement and strain conditions of the blocks are analyzed. The active blocks in the Chinese mainland have a consistent E-trending movement component, but its N and S components are not consistent. The blocks in the western part have a consistent N-trending movement and the blocks in the eastern part have a consistent S-trending movement. In the area to the east of 90°E, that is the area from Himalayas block towards NE, the movement direction of the blocks rotates clockwisely and the movement rates of the blocks are different. Generally, the movement rate is large in the west and south and small in the east and north with a difference of 3 to 4 times between the rates in the west and east. The distributions of principal compressive strain directions of the blocks are also different. The principal strain of the blocks located to the west of 90°E is basically in the SN direction, the principal compressive strain of the blocks in the northeastern part of Qingzang plateau is roughly in the NE direction and the direction of principal compressive strain of the blocks in the southeastern part of Qingzang plateau rounds clockwisely the east end of Himalayas structure. In addition, the principal strain and shear strain rates of the blocks are also different. The Himalayas and Tianshan blocks have the largest principal compressive strain and the maximum shear strain rate. Then, Lhasa, Qiangtang, Southwest Yunnan (SW Yunnan), Qilian and Sichuan-Yunan (Chuan-Dian) blocks followed. The strain rate of the blocks in the eastern part is smaller. The estimation based on the stain condition indicates that Himalayas block is still the area with the most intensive tectonic activity and it shortens in the NS direction at the rate of 15.2 ± 1.5 mm/a. Tianshan block ranks the second and it shortens in the NS direction at the rate of 10.1 ± 0.9 mm/a. At present, the two blocks are still uprising. It can be seen from superficial strain that the Chinese mainland is predominated by superficial expansion. Almost the total area in the eastern part of the Chinese mainland is expanded, while in the western part, the superficial compression and expansion are alternatively distributed from the south to the north. In the Chinese mainland, most EW-trending or proximate EW-trending faults have the left-lateral or left-lateral strike-slip relative movements along both sides, and most NS-trending faults have the right-lateral or right-lateral strike-slip relative movements along both sides. According to the data from GPS measurements the left-lateral strike-slip rate is 4.8 ± 1.3 mm/a in the central part of Altun fault and 9.8 ± 2.2 mm/a on Xianshuihe fault. The movement of the fault along the block boundary has provided the condition for block movement, so the movements of the block and its boundary are consistent, but the movement levels of the blocks are different. The statistic results indicate that the relative movement between most blocks is quite significant, which proves that active blocks exist. Himalayas, Tianshan, Qiangtang and SW Yunnan blocks have the most intensive movement; China-Mongolia, China-Korea (China-Korea), Alxa and South China blocks are rather stable. The mutual action of India, Pacific and Philippine Sea plates versus Eurasia plate is the principal driving force to the block movement in the Chinese mainland. Under the NNE-trending intensive press from India plate, the crustal matter of Qingzang plateau moves to the NNE and NE directions, then is hindered by the blocks located in the northern, northeastern and eastern parts. The crustal matter moves towards the Indian Ocean by the southeastern part of the plateau.

Simultaneous measurements of velocity and CH distributions. Part 1: jet flames in co-flow

Velocity field and CH distribution are measured simultaneously using particle-image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) of CH in piloted, turbulent, jet flames in coflow. The CH distribution is found to correspond well with the location of the stoichiometric velocity, U S , both instantaneously and on average. In addition, the CH distribution is observed to align with high-strain rate regions; however, significantly higher values of the maximum strain rates, compared to the mean value, are frequently observed. The residence time in the flame surface as represented by CH, τ F , remains nearly constant with axial distance downstream and is found to scale as τ F ∼ d/ U b , where d and U b are nozzle exit diameter and bulk nozzle-exit velocity, respectively. The mean value of the compressive principal strain rate is observed to decrease along the axial direction and shows a good correlation to a S ∼ ( x/ d) −0.7 relation for a wide range of jet Reynolds numbers. Finally, the two-dimensional dilatation is not seen to be a good marker of the flame position, unlike the case for premixed flames.

Crustal movement and deformation in Taiwan and its coastal area

Based on the station velocity data obtained from Fujian coastal GPS network and Taiwan-Luzon GPS network and the data obtained from IGS permanent stations commonly used in the data processing of both networks, the uniformity of reference frames and velocity fields of both GPS networks is realized. It has been discovered from the analysis on the velocity field in Taiwan and its coastal areas that the horizontal crustal movements in the coastal area of Fujian, Taiwan Strait and the northern part of Taiwan Island are fully consistent. The movement direction is around 26.0°E by S and the rate is about 39 mm/a. The opposite variation occurs in the coastal mountain area in the eastern part of Taiwan Island with the movement direction of 30.0°N by W and the movement rate of about 33.3 mm/a. In the southern end of Taiwan Island, the movement direction is 50.0°S by W and the movement rate is about 13 mm/a. If the geometric center of Fujian coast is used as the reference datum, Taiwan Island has a consistent (except its north end) NW-trending movement with the direction of around 50.0°N by W. The maximum rate of 61 mm/a occurs along the eastern coast and decreases gradually towards west. The analysis of strain field indicates that Taiwan and its coastal area have a uniform strain field with the principal compressive strain direction of N48.0°W and the principal tensile strain direction of N42.0°E. The principal compressive strain rate along the eastern coast of Taiwan Island is 3.436×10−7/a, which decreases gradually towards west and reaches 1.861×10−8/a to Fujian coast. The collision and underthrust of Philippine Sea plate with Eurasian plate in the eastern part of Taiwan Island can be considered as the principal force for the crustal movement, deformation and great earthquake occurred in Taiwan and its coastal area. The direction of principal compressive stress in the area is about N55.0°W.

Current horizontal strain field in Chinese mainland derived from GPS data

The current crustal horizontal strain field is given in the paper based on the horizontal movement rates obtained from about 400 GPS stations located in Chinese mainland and its surrounding areas. The results show: a) The horizontal strain in Chinese mainland is “strong in the west and weak in the east” and the shear strain is larger than the normal strain (absolute magnitude). The general strain magnitude is 10−8/a and in local regions is 10−7/a, but the strain distribution is not homogeneous; b) The regions with the most significant NS-trending strains are the Himalayas belt along the western segment of Chinese southern boundary, the segment of 36°N–42°N along the western boundary and the northern margin of Qaidam block; c) The EW-trending strain variation along the western margin is the maximum and it is characterized by the alternatively positive and negative variations from the west to the east; d) The regions with larger magnitudes of R EN (NE-trending shear strain) and R max (maximum shear strain) are Himalayas belt, the segment of 36°N–42°N along the western boundary, the western part of Qaidam block, Sichuan-Yunnan (Chuan-Dian) rhombic block and the border area of Alxa, Qilian and Tarim blocks; e) The surrounding area of Qinghai-Xizang (Qingzang) block is mainly superfacial contraction and its interior is basically superfacial expansion. The area to its north is mainly superfacial contraction with the maximum magnitude along the western boundary and the minimum magnitude in the eastern part (except Yanshan tectonic zone); f) In the west of the western part, the principal compressive strain is in the SN direction and the principal tensile strain is in the EW direction, while in the eastern margin area of the western part, the principal compressive strain is proximate EW and the principal tensile strain is about SN. The principal strain direction of Chuan-Dian rhombic block has changed greatly. In the northern part, it is compression in the EW and tension in the SN, while in the southern part, it is just the opposite; g) The strain pattern in Chinese mainland might be the integration of “block mode” and “successive deformation mode”. In addition, the shear strain might be the small-scale dominant strain. Such a result might be resulted from the collision of Indian plate and the boundaries coupling, and it is also closely related to the motion of deep-seated matters and the physical nature of crustal medium. Therefore, it should be noted that since the GPS stations are not homogenous in spatial distribution, the obtained strain fields and the scales of the strain should be different.