Background:Foot kinematics,such as excessive eversion and malalignment of the hindfoot,are believed to be associated with running-related injuries.The maj ority of studies to date show that different foot strike patte...Background:Foot kinematics,such as excessive eversion and malalignment of the hindfoot,are believed to be associated with running-related injuries.The maj ority of studies to date show that different foot strike patterns influence these specific foot and ankle kinematics.However,technical deficiencies in traditional motion capture approaches limit knowledge of in vivo joint kinematics with respect to rearfoot and forefoot strike patterns(RFS and FFS,respectively).This study uses a high-speed dual fluoroscopic imaging system(DFIS)to determine the effects of different foot strike patterns on 3D in vivo tibiotalar and subtalar joints kinematics.Methods:Fifteen healthy male recreational runners underwent foot computed tomography scanning for the construction of 3-dimensional models.A high-speed DFIS(100 Hz)was used to collect 6 degrees of freedom kinematics for participants’tibiotalar and subtalar joints when they adopted RFS and FFS in barefoot condition.Results:Compared with RFS,FFS exhibited greater internal rotation at 0%-20%of the stance phase in the tibiotalar joint.The peak internal rotation angle of the tibiotalar joint under FFS was greater than under RFS(p<0.001,Cohen’s d=0.92).RFS showed more dorsiflexion at 0%-20%of the stance phase in the tibiotalar joint than FFS.RFS also presented a larger anterior translation(p<0.001,Cohen’s d=1.28)in the subtalar joint at i nitial contact than FFS.Conclusion:Running with acute barefoot FFS increases the internal rotation of the tibiotalar joint in the early stance.The use of high-speed DFIS to quantify the movement of the tibiotalar and subtalar joint was critical to revealing the effects of RF S and FFS during running.展开更多
Since ancient times,lightning disasters have undoubtedly been an unstoppable threat to humanity.During thunderstorms,lightning often damages objects on the ground,such as buildings and structures.Since Franklin invent...Since ancient times,lightning disasters have undoubtedly been an unstoppable threat to humanity.During thunderstorms,lightning often damages objects on the ground,such as buildings and structures.Since Franklin invented the lightning rod in 1752,lightning rods have been used worldwide to prevent direct lightning strikes in various fields such as high-voltage power transmission lines,outdoor chemical sites,highways,land and sea wind farms,and forest lightning fire protection.It has been proven that lightning accidents still occur frequently in places where lightning rods are installed and the protective angle method is used.In order to further study the protective effect of lightning rods and identify the shortcomings of lightning rod protection,negative lightning strikes are taken as the research object,to analyze the limitations of lightning rods in preventing direct lightning strikes from the working principle of lightning rods.展开更多
The nearly E-W-trending Aqqikkudug-Weiya zone, more than 1000 km long and about 30 km wide, is an important segment in the Central Asian tectonic framework. It is distributed along the northern margin of the Central T...The nearly E-W-trending Aqqikkudug-Weiya zone, more than 1000 km long and about 30 km wide, is an important segment in the Central Asian tectonic framework. It is distributed along the northern margin of the Central Tianshan belt in Xinjiang, NW China and is composed of mylonitized Early Palaeozoic greywacke, volcanic rocks, ophiolitic blocks as a melange complex, HP/LT-type bleuschist blocks and mylonitized Neoproterozoic schist, gneiss and orthogneiss. Nearly vertical mylonitic foliation and sub-horizontal stretching lineation define its strike-slip feature; various kinematic indicators, such as asymmetric folds, non-coaxial asymmetric macro- to micro-structures and C-axis fabrics of quartz grains of mylonites, suggest that it is a dextral strike-slip ductile shear zone oriented in a nearly E-W direction characterized by 'flower' strusture with thrusting or extruding across the zone toward the two sides and upright folds with gently plunging hinges. The Aqqikkudug-Weiya zone experienced at least two展开更多
Background: Lack of an observable vertical impact peak in fore/mid-foot running has been suggested as a means of reducing lower extremity impact forces, although it is unclear if impact characteristics exist in other ...Background: Lack of an observable vertical impact peak in fore/mid-foot running has been suggested as a means of reducing lower extremity impact forces, although it is unclear if impact characteristics exist in other axes. The purpose of the investigation was to compare three-dimensional(3 D) impact kinetics among foot-strike conditions in over-ground running using instantaneous loading rate–time profiles.Methods: Impact characteristics were assessed by identifying peak loading rates in each direction(medial–lateral(ML), anterior–posterior(AP),vertical, and 3 D resultant) following foot-strike instructions(fore-foot, mid-foot, subtle heel, and obvious heel strike). Kinematic and kinetic data were analyzed among 9 male participants in each foot-strike condition.Results: Loading rate peaks were observed in each direction and foot-strike condition, differing in magnitude by direction(3 D resultant and vertical > AP > ML, p ≤ 0.031) and foot-strike: ML(fore-foot and mid-foot strike > obvious heel strike, p ≤ 0.032), AP(fore-foot and mid-foot strikes > subtle-heel and obvious heel strikes, p ≤ 0.023). In each direction, the first loading rate peak occurred later during heel strike running relative to fore-foot(p ≤ 0.019), with vertical and 3 D resultant impact durations exceeding shear(ML and AP, p ≤ 0.007) in each condition.Conclusion: Loading rate–time assessment identified contrasting impact characteristics in each direction and the 3 D resultant following foot-strike manipulations, with potential implications for lower extremity structures in running.展开更多
In order to establish deformation history for the Cenozoic development of the Tibetan Plateau, we conducted geologic mapping along a 120km traverse between Nangqian and Yushu in the northeastern Qiangtang terrane. Thi...In order to establish deformation history for the Cenozoic development of the Tibetan Plateau, we conducted geologic mapping along a 120km traverse between Nangqian and Yushu in the northeastern Qiangtang terrane. This work reveals a complex interaction among Tertiary thrusting, strike\|slip faulting, sedimentation, and igneous activity. Two phases of deformation are recognized. The older northeast—southwest shortening, expressed by thrusting and folding, is followed by left\|slip faulting along northwest\|trending faults. Tertiary thrusts, predominantly southwest\|dipping, are distributed throughout the traverse, and typically juxtapose Mesozoic strata over Paleogene strata. The latter were deposited in several separated basins during folding and thrusting, as indicated by well\|developed growth strata. A preliminary construction of balanced cross\|sections suggests a minimum estimate of 45km of crustal shortening along the traverse. Numerous hypabyssal intrusions were mapped in the southern part of the traverse near Nangqian. They were emplaced into the Paleogene sediments and are dated between 36 and 33Ma by 40 Ar/ 39 Ar and U\|Pb methods. Paleogene sediments are also interbedded with volcanics in both the southern and northern parts of the study area. In the northernmost part of the traverse, a volcanic unit overlies a Tertiary thrust. This unit itself is broadly folded. This relationship suggests that Tertiary igneous activity was coeval with contractional deformation in the region, implying strongly the causal relationship between the two processes. The youngest event in the area is the development of northwest\|trending left\|slip faults. They cut Tertiary thrusts, folds, and about 35Ma igneous intrusions. In contrast to widely distributed Tertiary folds and thrusts, strike\|slip faulting is restricted only to the southern portion of our mapped area near Nangqian. The strike\|slip faults apparently control the distribution of modern drainage systems, suggesting that they may have been active recently. As the younger strike\|slip faults are subparallel to the older folds and thrusts, we have not been able to determine the magnitude of left\|slip on these faults. We interpret the termination of contractional deformation and the subsequent replacement by strike\|slip faulting as a result of both clockwise rotation of the region and westward propagation of strike\|slip deformation in eastern Tibet.展开更多
In order to research segmented diverters for aircraft lightning protection, a transient 2 D multiphysics model based on magnetohydrodynamics theory is proposed to predict the location of the arc plasma discharge and l...In order to research segmented diverters for aircraft lightning protection, a transient 2 D multiphysics model based on magnetohydrodynamics theory is proposed to predict the location of the arc plasma discharge and lightning channel, and to simulate the electrothermal behavior.Based on numerical calculation and preliminary analysis, factors that affect the breakdown voltage of the segmented diverter are discussed. The results show that the voltage increase rate of the voltage source, the width of the air gap between metal segments and the geometry of these segments influence the breakdown voltage of the strip. High-voltage tests of the segmented diverter are performed to reveal air breakdown of the strip and redirect the lightning current.Experimental and numerical results are compared to verify the correctness of the numerical model. The ionization of the air gap between metal segments and the breakdown voltage of the strip calculated by the model are qualitatively consistent with experimental results. The breakdown voltage of the segmented diverter is far lower than the lightning voltage. When a lightning strike occurs, the segmented diverter can be quickly ionized to form a plasma channel which can guide the lightning current well.展开更多
Background: Excessive vertical impacts at landing are associated with common running injuries. Two primary gait-retraining interventions aimed at reducing impact forces are transition to forefoot strike and increasing...Background: Excessive vertical impacts at landing are associated with common running injuries. Two primary gait-retraining interventions aimed at reducing impact forces are transition to forefoot strike and increasing cadence. The objective of this study was to compare the shortand long-term effects of 2 gait-retraining interventions aimed at reducing landing impacts.Methods: A total of 39 healthy recreational runners using a rearfoot strike and a cadence of 170 steps/min were randomized into cadence(CAD) or forefoot strike(FFS) groups. All participants performed 4 weeks of strengthening followed by 8 sessions of gait-retraining using auditory feedback. Vertical average load rates(VALR) and vertical instantaneous load rates(VILR) were calculated from the vertical ground reaction force curve. Both cadence and foot strike angle were measured using 3D motion analysis and an instrumented treadmill at baseline and at 1 week,1 month, and 6 months post retraining.Results: ANOVA revealed that the FFS group had significant reductions in VALR(49.7%) and VILR(41.7%), and changes were maintained long term. Foot strike angle in the FFS group changed from 14.2° dorsiflexion at baseline to 3.4° plantarflexion, with changes maintained long term. The CAD group exhibited significant reduction only in VALR(16%) and only at 6 months. Both groups had significant and similar increases in cadence at all follow-ups(CAD, +7.2% to 173 steps/min;and FFS, +6.1% to 172 steps/min).Conclusion: Forefoot strike gait-retraining resulted in significantly greater reductions in VALR and similar increases in cadence compared to cadence gait-retraining in the short and long term. Cadence gait-retraining resulted in small reductions in VALR at only the 6-month follow-up.展开更多
The structural analysis based on the explanation of seismic profiles indicates that a lot of thrust faults and strike-slip faults of Late Cenozoic occur in western Hexi Corridor and its nearby regions. They can be div...The structural analysis based on the explanation of seismic profiles indicates that a lot of thrust faults and strike-slip faults of Late Cenozoic occur in western Hexi Corridor and its nearby regions. They can be divided into two types. One is thrust faults dipping southwards and extending NWwards, which was mainly correlated with the thrusting of northern Qilianshan and located at the NE margin of Qilianshan and the southwestern Hexi Corridor, the other is thrust faults and strike-slip faults that were related to the strike-slipping of Altun fault and located mainly at the regions of Hongliuxia, Kuantaishan, and Helishan that are close to the Altun fault. All these faults, which were related to the remote effects of collision between the two continents of India and Tibet during the Late Eocene and later, started to develop since the Late Tertiary and presented the features of violent thrust or strike-slip movement in Quaternary. Many of them are still active up to now and thus belong to the active faults that are the potential inducement of earthquakes in the Hexi Corridor. Moreover, a lot of intense structural deformation and many morphology phenomena such as tectonic terrace and river offset were formed under the control of these faults in Quaternary.展开更多
A lightning strike accident of a residential house in the rural areas of Neijiang is analyzed through on-site investigation,and the causes are discussed. Defensive measures of lightning disasters are proposed to provi...A lightning strike accident of a residential house in the rural areas of Neijiang is analyzed through on-site investigation,and the causes are discussed. Defensive measures of lightning disasters are proposed to provide reference for the prevention of lightning disasters in the construction of new countryside.展开更多
Deca</span><span style="font-family:Verdana;">dal forerunning seismic activity is examined for very large, shall</span><span style="font-family:Verdana;">ow earthquakes alon...Deca</span><span style="font-family:Verdana;">dal forerunning seismic activity is examined for very large, shall</span><span style="font-family:Verdana;">ow earthquakes along strike-slip and intraplate faults of the world. It includes forerunning shocks of magnitude Mw ≥ 5.0 for 21 mainshocks of Mw 7.5 to 8.6 from 1989 to 2020. Much forerunning activity occurred at what are interpreted to be smaller asperities along the peripheries of the rupture zones of great mainshocks at transform faults and subduction zones. Several great asperities as ascertained from forerunning activity agree with the areas of high seism</span><span style="font-family:Verdana;">ic slip as determined by others using geodetic, mapping of surf</span><span style="font-family:Verdana;">ace faulting, and finite-source seismic modeling. The zones of high slip in many great earthquakes were nearly quiescent beforehand and are identified as the sites of great asperities. Asperities are strong, well-coupled portions of plate interfaces. Different patterns of forerunning activity on time scales of up to 45 years are attributed to the sizes and spacing of asperities (or lack of). This permits at least some great asperities along transform faults to be mapped decades before they rupture in great shocks. Rupture zones of many great mainshocks along transform faults are bordered either along strike, at depth or regionally by zones of lower plate coupling including either fault creep</span></span><span style="font-family:""> </span><span style="font-family:Verdana;"> forerunning activity, aftershocks and/or slow-slip events. Forerunning activity to transforms in continental areas is more widespread spatially than that adjacent to oceanic transforms. The parts of the San Andreas fault themselves that ruptured in great California earthquakes during 1812, 1857 and 1906 have been very quiet since 1920;moderate to large shocks have been concentrated on their peripheries. The intraplate shocks studied, however, exhibited few if any forerunning events, which is attributed to the short period of time studied compared to their repeat times. The detection of forerunning and precursory activities for various time scales should be sought on the peripheries of great asperities and not just along the major faults themselves. This paper compliments that on decadal forerunning activity to great and giant earthquakes along subduction zones.展开更多
Eastern Hunan-western Jiangxi, the main distribution domain of the Luoxiao MountainRange, is one of the key districts of the Circum-Pacific tectonically active belt in China, in whichNNE-trending en echelon strike-sli...Eastern Hunan-western Jiangxi, the main distribution domain of the Luoxiao MountainRange, is one of the key districts of the Circum-Pacific tectonically active belt in China, in whichNNE-trending en echelon strike-slip faulting since Cenozoic time has obviously controlled thefundamental framework of the modern land forms. Based on the study of tectonic evolution and ac-tive strike-slip faults, this paper discusses the forms, types and combinations of the modern tec-tonic land forms in this region.展开更多
Two sets of active faults,northwest-and northeast-trending faults,are developed in the Chao-shan Plain of East Guangdong.After detailed interpretation of aerophotos,we have found outthat there is the clear phenomenon ...Two sets of active faults,northwest-and northeast-trending faults,are developed in the Chao-shan Plain of East Guangdong.After detailed interpretation of aerophotos,we have found outthat there is the clear phenomenon of sinistral dislocation of drainage system on the Huang-gang-shui fault and part of Fengshun-Shantou fault.Field investigation confirmed that the geo-morphic bodies along the two faults have undergone displacement.Large-scale topographicmapping was made at three displaced sites and samples for age dating were collected from thegeomorphic booies.Calculation indicates that the average rate of sinistral strike-slip movementin the Holocene time amounts to 1.11±0.09～2.69±0.24mm/a along the Huanggangshuifault and 3.26±0.26mm/a along the Fengshun-Shantou fault.These two more active NW-trending faults extend into sea area,where they intersect the NE-trending strongly active Nius-han Island-Xiongdi Isle-Nanpeng Isles fault at a depth of 40～50m in water.The intersection isa location favorable展开更多
Based on the 3 D seismic structure interpretation of Bohai Sea, combined with physical modeling of structure, structural style analysis and apatite fission track simulation, the structural characteristics and genetic ...Based on the 3 D seismic structure interpretation of Bohai Sea, combined with physical modeling of structure, structural style analysis and apatite fission track simulation, the structural characteristics and genetic mechanism of the Cenozoic strike-slip faults in Bohai Sea were investigated. The results show that Tanlu strike-slip fault experienced three stages of strike-slip activities in the Cenozoic,and the transition from left-lateral strike to right-lateral strike-slip was completed at the end of the fourth member of the Shahejie Formation. The strike-slip faults in the Bohai Sea have the characteristics of multi-stage and multi-strength stress superposition. According to the superimposed forms of different strengths, different properties and different ratios, they can be divided into three major genetic types,extension and strike-slip superimposition, extension and extrusion superimposition, extrusion and strike-slip superimposition, and fifteen typical structure patterns. Affected by multiple changes in the direction and rate of subduction of the Cenozoic Pacific plate, the difference between the Cenozoic extension and the strike-slip in the Bohai Sea area leads to the diversity of the fault system and the zoning of the depression structure. According to superimposition features of faults, the Bohai Sea area can be divided into the Liaoxi S-type weak strike-slip zone, Liaodong braided strong strike-slip zone, Boxi conjugated medium strike-slip zone, Bodong brush structure medium strike-slip zone and Bonan parallel strong strike-slip zone. These zones differ in oil and gas accumulation features.展开更多
Meso\| and microstructural characteristics of cataclastic fault rocks developed in the Xialu chert are described. The Xialu chert represents pelagic and deep marine sediments (Middle Jurassic—Lower Cretaceous), and o...Meso\| and microstructural characteristics of cataclastic fault rocks developed in the Xialu chert are described. The Xialu chert represents pelagic and deep marine sediments (Middle Jurassic—Lower Cretaceous), and occupies the southern marginal part of the E—W trending Yarlung Zangbo suture zone. The apparent total thickness of siliceous deposits exceeds 1km. The current study is concentrated along the two measured sections, Xialu\|E and Xialu\|W. The Xialu\|E section is composed mainly of red chert associated with reddish purple siliceous mudstone and greenish gray mudstone. The beds steeply dip north or south. The 45m section studied is divided into three units (chert unit, chert\|siliceous mudstone unit, and melange unit from north to south). They are in fault contact with each other. In the southern half of the chert unit and the northernmost of the chert\|siliceous mudstone unit, a 15m thick cohesive cataclasite zone can be defined. The cataclasites are composed of chert fragments in a fine grained matrix, and deformed with jigsaw puzzle structures. The chert\|siliceous mudstone unit is made up of four slabs of chert\|siliceous mudstone sequence. Mesoscopic duplex zones in thickness from 1 to 3m are recognized at slab boundaries. Flat and ramp structure and associated P foliations, R1 shears, Y surfaces are developed. Shear spacing range from 1 to 10cm. The slip senses are dextral strike\|slip movement along these duplex zones. The cataclasite zone is cut by the duplex zone along the southern boundary.展开更多
During the collision between India and Eurasia, the continental compression and shorten is thought to be absorbed by the way of thickening of the Tibetan plateau crust and strike\|slip extrusion outwardly of blocks su...During the collision between India and Eurasia, the continental compression and shorten is thought to be absorbed by the way of thickening of the Tibetan plateau crust and strike\|slip extrusion outwardly of blocks surrounding the Tibetan plateau. A series of models have been proposed recently, of which the most typical one is continental blocks extrusion by Tapponnier et al.. Virtually previous studies show that the Red River—Ailaoshan fault is the eastern boundary of extrusion Indochina displaced southward relative to South China about 23 Ma ago, and more, the western boundary of extrusion blocks is inferred to be Sijie fault in the eastern Burma. But the movement age of Sijie fault is around 13 Ma inferred from the age of Andeman Sea formation and different from that of the Red River—Ailaoshan fault. It is an important scientific problem where the western boundary of extrusion blocks is.展开更多
The Western Yunnan located at the southeast margin of east Himalaya\|Burman syntaxis. A great number of small basins filled with lacustrine developed in the Indochina block during the Paleocene\|middle Eocene. Occurre...The Western Yunnan located at the southeast margin of east Himalaya\|Burman syntaxis. A great number of small basins filled with lacustrine developed in the Indochina block during the Paleocene\|middle Eocene. Occurrence of basins as en chelon arrangement suggests that they were formed under tectonic setting of right\|lateral strike\|slip. The north termination of main faults controlling basins deposition and evolution, meet the Red River fault as an acute angle. The Lanping basin, one representative of all basins, is chosen to study its formation mechanism. Facts of rapid lateral phase change, sediment offset from their source and lateral migration of alluvial fan, indicate that the Lanping basin is a strike\|slip basin and its boundary main fault is syndepositional left\|lateral strike\|slip normal fault. Basin formation was controlled by mechanism of strike\|slip and pull\|apart, the Lanping basin belongs to extension strike\|slip basin. The nature of the Lanping basin and infill suggest that the boundary fault controlling basin deposit was formed during right\|lateral strike\|slip deformation of the Red River fault. Whether formation mechanism of single basin or occurrence of basins supported that the Red River fault was a right\|lateral strike\|slip fault during the Paleocene\|middle Eocene.展开更多
Objective To investigate th e changes to the strike extent of piston to cylinder after engine supercharge de sign. Methods The lubrication model between the skirt of piston and liner is established by means of piston ...Objective To investigate th e changes to the strike extent of piston to cylinder after engine supercharge de sign. Methods The lubrication model between the skirt of piston and liner is established by means of piston dynamics, combined with the hydrody namic lubrication equation. Optimized numerical analysis method is employed in s olving the dynamics and lubrication equations. The analyses about piston strike under two combustion gas pressures are performed. Results The p eak values of maximum eccentricity under supercharge condition are much greater than under non-supercharge condition, which means a stronger impulsion of pisto n to cylinder wall and a greater possibility of scuffing. The horizontal velocit ies of piston in supercharge condition are larger, which illuminate the more uns table motion state. Conclusion The analysis gives a new conclus ion. Combustion gas pressure plays an important role in the piston strike motion . Influences of supercharge should be taken into account so that the traditional product test items can be improved.展开更多
基金provided by the National Natural Science Foundation of China(Grants No.12272238 and No.11932013)the"Outstanding Young Scholar"Program of Shanghai Municipalthe"Dawn"Program of Shanghai Education Commission(Grant No.19SG47)。
文摘Background:Foot kinematics,such as excessive eversion and malalignment of the hindfoot,are believed to be associated with running-related injuries.The maj ority of studies to date show that different foot strike patterns influence these specific foot and ankle kinematics.However,technical deficiencies in traditional motion capture approaches limit knowledge of in vivo joint kinematics with respect to rearfoot and forefoot strike patterns(RFS and FFS,respectively).This study uses a high-speed dual fluoroscopic imaging system(DFIS)to determine the effects of different foot strike patterns on 3D in vivo tibiotalar and subtalar joints kinematics.Methods:Fifteen healthy male recreational runners underwent foot computed tomography scanning for the construction of 3-dimensional models.A high-speed DFIS(100 Hz)was used to collect 6 degrees of freedom kinematics for participants’tibiotalar and subtalar joints when they adopted RFS and FFS in barefoot condition.Results:Compared with RFS,FFS exhibited greater internal rotation at 0%-20%of the stance phase in the tibiotalar joint.The peak internal rotation angle of the tibiotalar joint under FFS was greater than under RFS(p<0.001,Cohen’s d=0.92).RFS showed more dorsiflexion at 0%-20%of the stance phase in the tibiotalar joint than FFS.RFS also presented a larger anterior translation(p<0.001,Cohen’s d=1.28)in the subtalar joint at i nitial contact than FFS.Conclusion:Running with acute barefoot FFS increases the internal rotation of the tibiotalar joint in the early stance.The use of high-speed DFIS to quantify the movement of the tibiotalar and subtalar joint was critical to revealing the effects of RF S and FFS during running.
基金Supported by Lightning Multi-pulse Intelligent Monitoring System Optimization Technology Project of Guangdong Yuedian Dianbai Hot Water Wind Farm(SFC/DBW-Z-FW-23-006).
文摘Since ancient times,lightning disasters have undoubtedly been an unstoppable threat to humanity.During thunderstorms,lightning often damages objects on the ground,such as buildings and structures.Since Franklin invented the lightning rod in 1752,lightning rods have been used worldwide to prevent direct lightning strikes in various fields such as high-voltage power transmission lines,outdoor chemical sites,highways,land and sea wind farms,and forest lightning fire protection.It has been proven that lightning accidents still occur frequently in places where lightning rods are installed and the protective angle method is used.In order to further study the protective effect of lightning rods and identify the shortcomings of lightning rod protection,negative lightning strikes are taken as the research object,to analyze the limitations of lightning rods in preventing direct lightning strikes from the working principle of lightning rods.
文摘The nearly E-W-trending Aqqikkudug-Weiya zone, more than 1000 km long and about 30 km wide, is an important segment in the Central Asian tectonic framework. It is distributed along the northern margin of the Central Tianshan belt in Xinjiang, NW China and is composed of mylonitized Early Palaeozoic greywacke, volcanic rocks, ophiolitic blocks as a melange complex, HP/LT-type bleuschist blocks and mylonitized Neoproterozoic schist, gneiss and orthogneiss. Nearly vertical mylonitic foliation and sub-horizontal stretching lineation define its strike-slip feature; various kinematic indicators, such as asymmetric folds, non-coaxial asymmetric macro- to micro-structures and C-axis fabrics of quartz grains of mylonites, suggest that it is a dextral strike-slip ductile shear zone oriented in a nearly E-W direction characterized by 'flower' strusture with thrusting or extruding across the zone toward the two sides and upright folds with gently plunging hinges. The Aqqikkudug-Weiya zone experienced at least two
基金funded by the Institutional Development Award Network of Biomedical Research Excellence through the National Institute of General Medical Sciences (8 20 GM103440-11)
文摘Background: Lack of an observable vertical impact peak in fore/mid-foot running has been suggested as a means of reducing lower extremity impact forces, although it is unclear if impact characteristics exist in other axes. The purpose of the investigation was to compare three-dimensional(3 D) impact kinetics among foot-strike conditions in over-ground running using instantaneous loading rate–time profiles.Methods: Impact characteristics were assessed by identifying peak loading rates in each direction(medial–lateral(ML), anterior–posterior(AP),vertical, and 3 D resultant) following foot-strike instructions(fore-foot, mid-foot, subtle heel, and obvious heel strike). Kinematic and kinetic data were analyzed among 9 male participants in each foot-strike condition.Results: Loading rate peaks were observed in each direction and foot-strike condition, differing in magnitude by direction(3 D resultant and vertical > AP > ML, p ≤ 0.031) and foot-strike: ML(fore-foot and mid-foot strike > obvious heel strike, p ≤ 0.032), AP(fore-foot and mid-foot strikes > subtle-heel and obvious heel strikes, p ≤ 0.023). In each direction, the first loading rate peak occurred later during heel strike running relative to fore-foot(p ≤ 0.019), with vertical and 3 D resultant impact durations exceeding shear(ML and AP, p ≤ 0.007) in each condition.Conclusion: Loading rate–time assessment identified contrasting impact characteristics in each direction and the 3 D resultant following foot-strike manipulations, with potential implications for lower extremity structures in running.
文摘In order to establish deformation history for the Cenozoic development of the Tibetan Plateau, we conducted geologic mapping along a 120km traverse between Nangqian and Yushu in the northeastern Qiangtang terrane. This work reveals a complex interaction among Tertiary thrusting, strike\|slip faulting, sedimentation, and igneous activity. Two phases of deformation are recognized. The older northeast—southwest shortening, expressed by thrusting and folding, is followed by left\|slip faulting along northwest\|trending faults. Tertiary thrusts, predominantly southwest\|dipping, are distributed throughout the traverse, and typically juxtapose Mesozoic strata over Paleogene strata. The latter were deposited in several separated basins during folding and thrusting, as indicated by well\|developed growth strata. A preliminary construction of balanced cross\|sections suggests a minimum estimate of 45km of crustal shortening along the traverse. Numerous hypabyssal intrusions were mapped in the southern part of the traverse near Nangqian. They were emplaced into the Paleogene sediments and are dated between 36 and 33Ma by 40 Ar/ 39 Ar and U\|Pb methods. Paleogene sediments are also interbedded with volcanics in both the southern and northern parts of the study area. In the northernmost part of the traverse, a volcanic unit overlies a Tertiary thrust. This unit itself is broadly folded. This relationship suggests that Tertiary igneous activity was coeval with contractional deformation in the region, implying strongly the causal relationship between the two processes. The youngest event in the area is the development of northwest\|trending left\|slip faults. They cut Tertiary thrusts, folds, and about 35Ma igneous intrusions. In contrast to widely distributed Tertiary folds and thrusts, strike\|slip faulting is restricted only to the southern portion of our mapped area near Nangqian. The strike\|slip faults apparently control the distribution of modern drainage systems, suggesting that they may have been active recently. As the younger strike\|slip faults are subparallel to the older folds and thrusts, we have not been able to determine the magnitude of left\|slip on these faults. We interpret the termination of contractional deformation and the subsequent replacement by strike\|slip faulting as a result of both clockwise rotation of the region and westward propagation of strike\|slip deformation in eastern Tibet.
基金supported by National Natural Science Foundation of China (No. 51475369)the Natural Science Basic Research Plan in Shaanxi Province of China (No. 2018JM1001)
文摘In order to research segmented diverters for aircraft lightning protection, a transient 2 D multiphysics model based on magnetohydrodynamics theory is proposed to predict the location of the arc plasma discharge and lightning channel, and to simulate the electrothermal behavior.Based on numerical calculation and preliminary analysis, factors that affect the breakdown voltage of the segmented diverter are discussed. The results show that the voltage increase rate of the voltage source, the width of the air gap between metal segments and the geometry of these segments influence the breakdown voltage of the strip. High-voltage tests of the segmented diverter are performed to reveal air breakdown of the strip and redirect the lightning current.Experimental and numerical results are compared to verify the correctness of the numerical model. The ionization of the air gap between metal segments and the breakdown voltage of the strip calculated by the model are qualitatively consistent with experimental results. The breakdown voltage of the segmented diverter is far lower than the lightning voltage. When a lightning strike occurs, the segmented diverter can be quickly ionized to form a plasma channel which can guide the lightning current well.
基金funded by a student scholarship from the Force and Motion Foundation(501(c)(3))。
文摘Background: Excessive vertical impacts at landing are associated with common running injuries. Two primary gait-retraining interventions aimed at reducing impact forces are transition to forefoot strike and increasing cadence. The objective of this study was to compare the shortand long-term effects of 2 gait-retraining interventions aimed at reducing landing impacts.Methods: A total of 39 healthy recreational runners using a rearfoot strike and a cadence of 170 steps/min were randomized into cadence(CAD) or forefoot strike(FFS) groups. All participants performed 4 weeks of strengthening followed by 8 sessions of gait-retraining using auditory feedback. Vertical average load rates(VALR) and vertical instantaneous load rates(VILR) were calculated from the vertical ground reaction force curve. Both cadence and foot strike angle were measured using 3D motion analysis and an instrumented treadmill at baseline and at 1 week,1 month, and 6 months post retraining.Results: ANOVA revealed that the FFS group had significant reductions in VALR(49.7%) and VILR(41.7%), and changes were maintained long term. Foot strike angle in the FFS group changed from 14.2° dorsiflexion at baseline to 3.4° plantarflexion, with changes maintained long term. The CAD group exhibited significant reduction only in VALR(16%) and only at 6 months. Both groups had significant and similar increases in cadence at all follow-ups(CAD, +7.2% to 173 steps/min;and FFS, +6.1% to 172 steps/min).Conclusion: Forefoot strike gait-retraining resulted in significantly greater reductions in VALR and similar increases in cadence compared to cadence gait-retraining in the short and long term. Cadence gait-retraining resulted in small reductions in VALR at only the 6-month follow-up.
文摘The structural analysis based on the explanation of seismic profiles indicates that a lot of thrust faults and strike-slip faults of Late Cenozoic occur in western Hexi Corridor and its nearby regions. They can be divided into two types. One is thrust faults dipping southwards and extending NWwards, which was mainly correlated with the thrusting of northern Qilianshan and located at the NE margin of Qilianshan and the southwestern Hexi Corridor, the other is thrust faults and strike-slip faults that were related to the strike-slipping of Altun fault and located mainly at the regions of Hongliuxia, Kuantaishan, and Helishan that are close to the Altun fault. All these faults, which were related to the remote effects of collision between the two continents of India and Tibet during the Late Eocene and later, started to develop since the Late Tertiary and presented the features of violent thrust or strike-slip movement in Quaternary. Many of them are still active up to now and thus belong to the active faults that are the potential inducement of earthquakes in the Hexi Corridor. Moreover, a lot of intense structural deformation and many morphology phenomena such as tectonic terrace and river offset were formed under the control of these faults in Quaternary.
文摘A lightning strike accident of a residential house in the rural areas of Neijiang is analyzed through on-site investigation,and the causes are discussed. Defensive measures of lightning disasters are proposed to provide reference for the prevention of lightning disasters in the construction of new countryside.
文摘Deca</span><span style="font-family:Verdana;">dal forerunning seismic activity is examined for very large, shall</span><span style="font-family:Verdana;">ow earthquakes along strike-slip and intraplate faults of the world. It includes forerunning shocks of magnitude Mw ≥ 5.0 for 21 mainshocks of Mw 7.5 to 8.6 from 1989 to 2020. Much forerunning activity occurred at what are interpreted to be smaller asperities along the peripheries of the rupture zones of great mainshocks at transform faults and subduction zones. Several great asperities as ascertained from forerunning activity agree with the areas of high seism</span><span style="font-family:Verdana;">ic slip as determined by others using geodetic, mapping of surf</span><span style="font-family:Verdana;">ace faulting, and finite-source seismic modeling. The zones of high slip in many great earthquakes were nearly quiescent beforehand and are identified as the sites of great asperities. Asperities are strong, well-coupled portions of plate interfaces. Different patterns of forerunning activity on time scales of up to 45 years are attributed to the sizes and spacing of asperities (or lack of). This permits at least some great asperities along transform faults to be mapped decades before they rupture in great shocks. Rupture zones of many great mainshocks along transform faults are bordered either along strike, at depth or regionally by zones of lower plate coupling including either fault creep</span></span><span style="font-family:""> </span><span style="font-family:Verdana;"> forerunning activity, aftershocks and/or slow-slip events. Forerunning activity to transforms in continental areas is more widespread spatially than that adjacent to oceanic transforms. The parts of the San Andreas fault themselves that ruptured in great California earthquakes during 1812, 1857 and 1906 have been very quiet since 1920;moderate to large shocks have been concentrated on their peripheries. The intraplate shocks studied, however, exhibited few if any forerunning events, which is attributed to the short period of time studied compared to their repeat times. The detection of forerunning and precursory activities for various time scales should be sought on the peripheries of great asperities and not just along the major faults themselves. This paper compliments that on decadal forerunning activity to great and giant earthquakes along subduction zones.
文摘Eastern Hunan-western Jiangxi, the main distribution domain of the Luoxiao MountainRange, is one of the key districts of the Circum-Pacific tectonically active belt in China, in whichNNE-trending en echelon strike-slip faulting since Cenozoic time has obviously controlled thefundamental framework of the modern land forms. Based on the study of tectonic evolution and ac-tive strike-slip faults, this paper discusses the forms, types and combinations of the modern tec-tonic land forms in this region.
基金This paper presents one of the research results of a key project in Ninth Five-Year Program was supported by China Seismological Bureau grant (95-04-10-04). Institute of Geology, CSB, contribution No.2000B0034.
文摘Two sets of active faults,northwest-and northeast-trending faults,are developed in the Chao-shan Plain of East Guangdong.After detailed interpretation of aerophotos,we have found outthat there is the clear phenomenon of sinistral dislocation of drainage system on the Huang-gang-shui fault and part of Fengshun-Shantou fault.Field investigation confirmed that the geo-morphic bodies along the two faults have undergone displacement.Large-scale topographicmapping was made at three displaced sites and samples for age dating were collected from thegeomorphic booies.Calculation indicates that the average rate of sinistral strike-slip movementin the Holocene time amounts to 1.11±0.09～2.69±0.24mm/a along the Huanggangshuifault and 3.26±0.26mm/a along the Fengshun-Shantou fault.These two more active NW-trending faults extend into sea area,where they intersect the NE-trending strongly active Nius-han Island-Xiongdi Isle-Nanpeng Isles fault at a depth of 40～50m in water.The intersection isa location favorable
基金Supported by the China National Science and Technology Major Project(2016ZX05024-002,2016ZX05024-003)
文摘Based on the 3 D seismic structure interpretation of Bohai Sea, combined with physical modeling of structure, structural style analysis and apatite fission track simulation, the structural characteristics and genetic mechanism of the Cenozoic strike-slip faults in Bohai Sea were investigated. The results show that Tanlu strike-slip fault experienced three stages of strike-slip activities in the Cenozoic,and the transition from left-lateral strike to right-lateral strike-slip was completed at the end of the fourth member of the Shahejie Formation. The strike-slip faults in the Bohai Sea have the characteristics of multi-stage and multi-strength stress superposition. According to the superimposed forms of different strengths, different properties and different ratios, they can be divided into three major genetic types,extension and strike-slip superimposition, extension and extrusion superimposition, extrusion and strike-slip superimposition, and fifteen typical structure patterns. Affected by multiple changes in the direction and rate of subduction of the Cenozoic Pacific plate, the difference between the Cenozoic extension and the strike-slip in the Bohai Sea area leads to the diversity of the fault system and the zoning of the depression structure. According to superimposition features of faults, the Bohai Sea area can be divided into the Liaoxi S-type weak strike-slip zone, Liaodong braided strong strike-slip zone, Boxi conjugated medium strike-slip zone, Bodong brush structure medium strike-slip zone and Bonan parallel strong strike-slip zone. These zones differ in oil and gas accumulation features.
文摘Meso\| and microstructural characteristics of cataclastic fault rocks developed in the Xialu chert are described. The Xialu chert represents pelagic and deep marine sediments (Middle Jurassic—Lower Cretaceous), and occupies the southern marginal part of the E—W trending Yarlung Zangbo suture zone. The apparent total thickness of siliceous deposits exceeds 1km. The current study is concentrated along the two measured sections, Xialu\|E and Xialu\|W. The Xialu\|E section is composed mainly of red chert associated with reddish purple siliceous mudstone and greenish gray mudstone. The beds steeply dip north or south. The 45m section studied is divided into three units (chert unit, chert\|siliceous mudstone unit, and melange unit from north to south). They are in fault contact with each other. In the southern half of the chert unit and the northernmost of the chert\|siliceous mudstone unit, a 15m thick cohesive cataclasite zone can be defined. The cataclasites are composed of chert fragments in a fine grained matrix, and deformed with jigsaw puzzle structures. The chert\|siliceous mudstone unit is made up of four slabs of chert\|siliceous mudstone sequence. Mesoscopic duplex zones in thickness from 1 to 3m are recognized at slab boundaries. Flat and ramp structure and associated P foliations, R1 shears, Y surfaces are developed. Shear spacing range from 1 to 10cm. The slip senses are dextral strike\|slip movement along these duplex zones. The cataclasite zone is cut by the duplex zone along the southern boundary.
文摘During the collision between India and Eurasia, the continental compression and shorten is thought to be absorbed by the way of thickening of the Tibetan plateau crust and strike\|slip extrusion outwardly of blocks surrounding the Tibetan plateau. A series of models have been proposed recently, of which the most typical one is continental blocks extrusion by Tapponnier et al.. Virtually previous studies show that the Red River—Ailaoshan fault is the eastern boundary of extrusion Indochina displaced southward relative to South China about 23 Ma ago, and more, the western boundary of extrusion blocks is inferred to be Sijie fault in the eastern Burma. But the movement age of Sijie fault is around 13 Ma inferred from the age of Andeman Sea formation and different from that of the Red River—Ailaoshan fault. It is an important scientific problem where the western boundary of extrusion blocks is.
文摘The Western Yunnan located at the southeast margin of east Himalaya\|Burman syntaxis. A great number of small basins filled with lacustrine developed in the Indochina block during the Paleocene\|middle Eocene. Occurrence of basins as en chelon arrangement suggests that they were formed under tectonic setting of right\|lateral strike\|slip. The north termination of main faults controlling basins deposition and evolution, meet the Red River fault as an acute angle. The Lanping basin, one representative of all basins, is chosen to study its formation mechanism. Facts of rapid lateral phase change, sediment offset from their source and lateral migration of alluvial fan, indicate that the Lanping basin is a strike\|slip basin and its boundary main fault is syndepositional left\|lateral strike\|slip normal fault. Basin formation was controlled by mechanism of strike\|slip and pull\|apart, the Lanping basin belongs to extension strike\|slip basin. The nature of the Lanping basin and infill suggest that the boundary fault controlling basin deposit was formed during right\|lateral strike\|slip deformation of the Red River fault. Whether formation mechanism of single basin or occurrence of basins supported that the Red River fault was a right\|lateral strike\|slip fault during the Paleocene\|middle Eocene.
文摘Objective To investigate th e changes to the strike extent of piston to cylinder after engine supercharge de sign. Methods The lubrication model between the skirt of piston and liner is established by means of piston dynamics, combined with the hydrody namic lubrication equation. Optimized numerical analysis method is employed in s olving the dynamics and lubrication equations. The analyses about piston strike under two combustion gas pressures are performed. Results The p eak values of maximum eccentricity under supercharge condition are much greater than under non-supercharge condition, which means a stronger impulsion of pisto n to cylinder wall and a greater possibility of scuffing. The horizontal velocit ies of piston in supercharge condition are larger, which illuminate the more uns table motion state. Conclusion The analysis gives a new conclus ion. Combustion gas pressure plays an important role in the piston strike motion . Influences of supercharge should be taken into account so that the traditional product test items can be improved.
