Earthquakes result from continuous geodynamic processes.A topic of significant interest for the scientific community is to elaborate on the phenomena governing the faulting and fracturing of crustal rocks.Therefore,in...Earthquakes result from continuous geodynamic processes.A topic of significant interest for the scientific community is to elaborate on the phenomena governing the faulting and fracturing of crustal rocks.Therefore,in this study,uniaxial compressive shear failure experiments were conducted on Fangshan marble rock samples with a prefabricated slot to simulate thrust faulting.The center of each marble plate(105 mm × 80 mm × 5 mm) was engraved with a 30-mm long double-sided nonpenetrating slot(depth:2 mm,width:0.5 mm).The deformation and destruction processes of the rock surface were recorded using a high-speed camera.The digital image correlation method was used to calculate the displacement and strain distribution and variation at different loading stages.The accumulative and incremental displacement fields u and v,strain field exand e_(y),and shear strain e_(xy) were analyzed.When the loading level reached its ultimate value,the strain field was concentrated around the prefabricated slot.The concentration reached a maximum at the ends of the prefabricated slot.The magnitude of shear strain reached 0.1.This experiment contributes to our understanding of the dynamic process of active faulting.展开更多
<span style="font-family:;" "=""><span style="font-family:Verdana;">In this paper, it was introduced that </span><i><span style="font-family:Verdana;&...<span style="font-family:;" "=""><span style="font-family:Verdana;">In this paper, it was introduced that </span><i><span style="font-family:Verdana;">Coix lacryma-jobi</span></i><span style="font-family:Verdana;"> is a traditional dual-</span></span><span style="font-family:;" "=""><span style="font-family:Verdana;">use edible and medicine crops in China, and the nutritional components and medicinal value of </span><i><span style="font-family:Verdana;">Coix lacryma-jobi</span></i><span style="font-family:Verdana;"> were described. Based on the published literature at home and abroad, a variety of chemical components found in </span><i><span style="font-family:Verdana;">Coix lacryma jobi</span></i><span style="font-family:Verdana;"> and their medicinal effects were reviewed. At the same time,</span></span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">the problems existing in the production of </span><i><span style="font-family:Verdana;">Coix lacryma jobi</span></i><span style="font-family:Verdana;"> were put forward. With the improvement of people’s living standards, the nutritional and health care value of </span><i><span style="font-family:Verdana;">Coix lacryma-jobi</span></i><span style="font-family:Verdana;"> has been paid more and more attention.</span></span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">The problems of </span><i><span style="font-family:Verdana;">Coix lacryma-jobi</span></i><span style="font-family:Verdana;"> in production were analyzed.</span></span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">Some biological characteristics of </span><i><span style="font-family:Verdana;">Coix lacryma-jobi</span></i><span style="font-family:Verdana;">, especially its hygrophyte characteristics, were re-recognized, which is very important to increase the yield of </span><i><span style="font-family:Verdana;">Coix lacryma jobi</span></i><span style="font-family:Verdana;">. In the paper, the key cultivation techniques for high and stable yield of </span><i><span style="font-family:Verdana;">Coix lacryma-jobi</span></i><span style="font-family:Verdana;"> were also summarized. In order to obtain high quality, high and stable yield, we should adopt the new technical methods of “two wet, two dry and two water” in water management. At </span></span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">same time, if artificial pollination is applied in the peak of flowering period, the seed setting rate and the yield will be increased.</span>展开更多
On May 12,2008,an Mw7.9 earthquake occurred in Wenchuan County,Sichuan Province,China.Movement of Yingxiu–Beichuan Fault in the Longmenshan Fault Zone was considered to be the main cause of the earthquake.Earthquakes...On May 12,2008,an Mw7.9 earthquake occurred in Wenchuan County,Sichuan Province,China.Movement of Yingxiu–Beichuan Fault in the Longmenshan Fault Zone was considered to be the main cause of the earthquake.Earthquakes are closely related to fault activities.Therefore,studying the strain distribution and evolution process around active fault zones is important to the understanding of seismic activities.In this study,we conduct laboratory experiments with uniaxial compression applied to marble sheets with intentionally fabricated cracks.The speckle patterns of the rock samples under different loading conditions are recorded in real time by a digital camera.To calculate the deformation fields of the deliberately cracked marble sheets during different stages of the loading processes,the recorded images are processed by the digital image correlation method.The distribution and variation of the displacement and strain are further analyzed in order to understand the strain localization of and observed damage in the experimental fracture zones.Finally,we compare these laboratory results with the GPS-observed coseismic displacements during the 2008 Wenchuan earthquake,to assess the consistency between our laboratory observations and the field observations of the earthquake,but also to suggest how laboratory results can improve thinking about how earthquake patterns do and do not reflect fault patterns.展开更多
This article presents a systematic research methodology of modular design for conceptual auto body frame by hybrid optimization method.A modified graph-based decomposition optimization algorithm is utilized to generat...This article presents a systematic research methodology of modular design for conceptual auto body frame by hybrid optimization method.A modified graph-based decomposition optimization algorithm is utilized to generate an optimal BIW assembly topo model composed of“potential modules”.The consistency constraint function in collaborative optimization is extended to maximize the commonality of modules and minimize the performance loss of all car types in the same product family simultaneously.A novel screening method is employed to select both“basic structures”and“reinforcement”modules based on the dimension optimization of the manufacturing elements and the optimal assembly mode;this allows for a more exhaustive modular platform design in contrast with existing methods.The proposed methodology is applied to a case study for the modular design of three conceptual auto body types in the same platform to validate its feasibility and effectiveness.展开更多
Before the major earthquake or rock damage occurs,it is often accompanied by a sudden change in the degree of non-uniformity of the strain field.In order to find a stronger non-uniformity signal before the rock failur...Before the major earthquake or rock damage occurs,it is often accompanied by a sudden change in the degree of non-uniformity of the strain field.In order to find a stronger non-uniformity signal before the rock failure,the coefficient of variation(Cv)is examined and reformed in this study.We test the Cv calculation way of the"normal-abnormal"model proposed in the previous studies.Based on the analysis of the physical process of rock failure and its relationship to the shear strain field,we construct a new way to calculate the Cv value.The variation of shear strain field on rock sample with the increase of stress is obtained by the digital speckle correlation method(DSCM).The new Cv value calculation way is used to study the non-uniformity of the spatial distribution for the shear strain field.The results show that this Cv calculation way can get more obvious abnormal signals.When the number of observation points are limited,the specific distribution of points can increase the signal strength,which may provide reference for the research on precursor detection of earthquakes.展开更多
Seismic hazard analysis is gaining increased attention in the present era because of the catastrophic effects of earthquakes.Scientists always have as a goal to develop new techniques that will help forecast earthquak...Seismic hazard analysis is gaining increased attention in the present era because of the catastrophic effects of earthquakes.Scientists always have as a goal to develop new techniques that will help forecast earthquakes before their reoccurrence. In this research,we have performed a shear failure experiment on rock samples with prefabricated cracks to simulate the process of plate movement that forms strike-slip faults. We studied the evolution law of the deformation field to simulate the shear failure experiment, and these results gave us a comprehensive understanding of the elaborate strain distribution law and its formation process with which to identify actual fault zones. We performed uniaxial compression tests on marble slabs with prefabricated double shear cracks to study the distribution and evolution of the deformation field during shear failure. Analysis of the strain field at different loading stages showed that with an increase in the load, the shear strain field initially changed to a disordered-style distribution. Further, the strain field was partially concentrated and finally completely concentrated near the crack and then distributed in the shape of a strip along the crack. We also computed coefficients of variation(CVs) for the physical quantities u, v, and exy, which varied with the load. The CV curves were found to correspond to the different loading stages. We found that at the uniform deformation stage, the CV value was small and changed slowly,whereas at the later nonuniform deformation stage, the CV value increased sharply and changed abruptly. Therefore, the precursor to a rock sample breakdown can be predicted by observing the variation characteristics of CV statistics. The correlation we found between our experimental and theoretical results revealed that our crack evolution and sample deformation results showed good coupling with seismic distribution characteristics near the San Andreas Fault.展开更多
To investigate the role of grain boundary sliding during dislocation creep of dunite, a series of deformation experiments were carried out under anhydrous conditions on fine-grained (～15 μm) samples synthesized from...To investigate the role of grain boundary sliding during dislocation creep of dunite, a series of deformation experiments were carried out under anhydrous conditions on fine-grained (～15 μm) samples synthesized from powdered San Carlos olivine and powdered San Carlos olivine+1.5 vol.% MORB. Triaxial compressive creep tests were conducted at a temperature of 1 473 K and con-fining pressures of 200 and 400 MPa using a high-resolution, gas-medium deformation apparatus. Each sample was deformed at several levels of differential stress between 100 and 250 MPa to yield strain rates in the range of 10-6 to 10-4 s-1. Under these conditions, the dominant creep mechanism involves the motion of dislocations, largely on the easy slip system (010)[100], accommodated by grain boundary sliding (gbs). This grain size-sensitive creep regime is characterized by a stress ex-ponent of n=3.4±0.2 and a grain size exponent of p=2.0±0.2. The activation volume for this gbs-accommodated dislocation creep regime is V*=(26±3)×10-6 m2·mol-1. Comparison of our flow law for gbs-accommodated dislocation creep with those for diffusion creep and for dislocation creep reveals that the present flow law is important for the flow of mantle rocks with grain sizes of <100 μm at differential stresses >20 MPa. Hence, gbs-accommodated dislocation creep is likely to be an important deformation mechanism in deep-rooted, highly localized shear zones in the lithospheric upper mantle.展开更多
基金This research was supported by the National Key R&D Program of China(Nos.2018YFC1504203 and SQ2017YFSF040025).
文摘Earthquakes result from continuous geodynamic processes.A topic of significant interest for the scientific community is to elaborate on the phenomena governing the faulting and fracturing of crustal rocks.Therefore,in this study,uniaxial compressive shear failure experiments were conducted on Fangshan marble rock samples with a prefabricated slot to simulate thrust faulting.The center of each marble plate(105 mm × 80 mm × 5 mm) was engraved with a 30-mm long double-sided nonpenetrating slot(depth:2 mm,width:0.5 mm).The deformation and destruction processes of the rock surface were recorded using a high-speed camera.The digital image correlation method was used to calculate the displacement and strain distribution and variation at different loading stages.The accumulative and incremental displacement fields u and v,strain field exand e_(y),and shear strain e_(xy) were analyzed.When the loading level reached its ultimate value,the strain field was concentrated around the prefabricated slot.The concentration reached a maximum at the ends of the prefabricated slot.The magnitude of shear strain reached 0.1.This experiment contributes to our understanding of the dynamic process of active faulting.
文摘<span style="font-family:;" "=""><span style="font-family:Verdana;">In this paper, it was introduced that </span><i><span style="font-family:Verdana;">Coix lacryma-jobi</span></i><span style="font-family:Verdana;"> is a traditional dual-</span></span><span style="font-family:;" "=""><span style="font-family:Verdana;">use edible and medicine crops in China, and the nutritional components and medicinal value of </span><i><span style="font-family:Verdana;">Coix lacryma-jobi</span></i><span style="font-family:Verdana;"> were described. Based on the published literature at home and abroad, a variety of chemical components found in </span><i><span style="font-family:Verdana;">Coix lacryma jobi</span></i><span style="font-family:Verdana;"> and their medicinal effects were reviewed. At the same time,</span></span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">the problems existing in the production of </span><i><span style="font-family:Verdana;">Coix lacryma jobi</span></i><span style="font-family:Verdana;"> were put forward. With the improvement of people’s living standards, the nutritional and health care value of </span><i><span style="font-family:Verdana;">Coix lacryma-jobi</span></i><span style="font-family:Verdana;"> has been paid more and more attention.</span></span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">The problems of </span><i><span style="font-family:Verdana;">Coix lacryma-jobi</span></i><span style="font-family:Verdana;"> in production were analyzed.</span></span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">Some biological characteristics of </span><i><span style="font-family:Verdana;">Coix lacryma-jobi</span></i><span style="font-family:Verdana;">, especially its hygrophyte characteristics, were re-recognized, which is very important to increase the yield of </span><i><span style="font-family:Verdana;">Coix lacryma jobi</span></i><span style="font-family:Verdana;">. In the paper, the key cultivation techniques for high and stable yield of </span><i><span style="font-family:Verdana;">Coix lacryma-jobi</span></i><span style="font-family:Verdana;"> were also summarized. In order to obtain high quality, high and stable yield, we should adopt the new technical methods of “two wet, two dry and two water” in water management. At </span></span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">same time, if artificial pollination is applied in the peak of flowering period, the seed setting rate and the yield will be increased.</span>
文摘On May 12,2008,an Mw7.9 earthquake occurred in Wenchuan County,Sichuan Province,China.Movement of Yingxiu–Beichuan Fault in the Longmenshan Fault Zone was considered to be the main cause of the earthquake.Earthquakes are closely related to fault activities.Therefore,studying the strain distribution and evolution process around active fault zones is important to the understanding of seismic activities.In this study,we conduct laboratory experiments with uniaxial compression applied to marble sheets with intentionally fabricated cracks.The speckle patterns of the rock samples under different loading conditions are recorded in real time by a digital camera.To calculate the deformation fields of the deliberately cracked marble sheets during different stages of the loading processes,the recorded images are processed by the digital image correlation method.The distribution and variation of the displacement and strain are further analyzed in order to understand the strain localization of and observed damage in the experimental fracture zones.Finally,we compare these laboratory results with the GPS-observed coseismic displacements during the 2008 Wenchuan earthquake,to assess the consistency between our laboratory observations and the field observations of the earthquake,but also to suggest how laboratory results can improve thinking about how earthquake patterns do and do not reflect fault patterns.
基金This work was funded by the Innovation Foundation of GAC R&D Center.
文摘This article presents a systematic research methodology of modular design for conceptual auto body frame by hybrid optimization method.A modified graph-based decomposition optimization algorithm is utilized to generate an optimal BIW assembly topo model composed of“potential modules”.The consistency constraint function in collaborative optimization is extended to maximize the commonality of modules and minimize the performance loss of all car types in the same product family simultaneously.A novel screening method is employed to select both“basic structures”and“reinforcement”modules based on the dimension optimization of the manufacturing elements and the optimal assembly mode;this allows for a more exhaustive modular platform design in contrast with existing methods.The proposed methodology is applied to a case study for the modular design of three conceptual auto body types in the same platform to validate its feasibility and effectiveness.
基金jointly supported by the China Postdoctoral Science Foundation(No.2018M630028)the National Natural Science Foundation of China(Nos.41274094,40821062 and 40872133).
文摘Before the major earthquake or rock damage occurs,it is often accompanied by a sudden change in the degree of non-uniformity of the strain field.In order to find a stronger non-uniformity signal before the rock failure,the coefficient of variation(Cv)is examined and reformed in this study.We test the Cv calculation way of the"normal-abnormal"model proposed in the previous studies.Based on the analysis of the physical process of rock failure and its relationship to the shear strain field,we construct a new way to calculate the Cv value.The variation of shear strain field on rock sample with the increase of stress is obtained by the digital speckle correlation method(DSCM).The new Cv value calculation way is used to study the non-uniformity of the spatial distribution for the shear strain field.The results show that this Cv calculation way can get more obvious abnormal signals.When the number of observation points are limited,the specific distribution of points can increase the signal strength,which may provide reference for the research on precursor detection of earthquakes.
基金Support for this research was provided by the National Key R&D Program of China(grant numbers 2018YFC1504203 and SQ2017YFSF040025)
文摘Seismic hazard analysis is gaining increased attention in the present era because of the catastrophic effects of earthquakes.Scientists always have as a goal to develop new techniques that will help forecast earthquakes before their reoccurrence. In this research,we have performed a shear failure experiment on rock samples with prefabricated cracks to simulate the process of plate movement that forms strike-slip faults. We studied the evolution law of the deformation field to simulate the shear failure experiment, and these results gave us a comprehensive understanding of the elaborate strain distribution law and its formation process with which to identify actual fault zones. We performed uniaxial compression tests on marble slabs with prefabricated double shear cracks to study the distribution and evolution of the deformation field during shear failure. Analysis of the strain field at different loading stages showed that with an increase in the load, the shear strain field initially changed to a disordered-style distribution. Further, the strain field was partially concentrated and finally completely concentrated near the crack and then distributed in the shape of a strip along the crack. We also computed coefficients of variation(CVs) for the physical quantities u, v, and exy, which varied with the load. The CV curves were found to correspond to the different loading stages. We found that at the uniform deformation stage, the CV value was small and changed slowly,whereas at the later nonuniform deformation stage, the CV value increased sharply and changed abruptly. Therefore, the precursor to a rock sample breakdown can be predicted by observing the variation characteristics of CV statistics. The correlation we found between our experimental and theoretical results revealed that our crack evolution and sample deformation results showed good coupling with seismic distribution characteristics near the San Andreas Fault.
基金supported by the National Science Foundation of USA (No. EAR-0910687)the National Natural Science Foundation of China (No. 40874043)
文摘To investigate the role of grain boundary sliding during dislocation creep of dunite, a series of deformation experiments were carried out under anhydrous conditions on fine-grained (～15 μm) samples synthesized from powdered San Carlos olivine and powdered San Carlos olivine+1.5 vol.% MORB. Triaxial compressive creep tests were conducted at a temperature of 1 473 K and con-fining pressures of 200 and 400 MPa using a high-resolution, gas-medium deformation apparatus. Each sample was deformed at several levels of differential stress between 100 and 250 MPa to yield strain rates in the range of 10-6 to 10-4 s-1. Under these conditions, the dominant creep mechanism involves the motion of dislocations, largely on the easy slip system (010)[100], accommodated by grain boundary sliding (gbs). This grain size-sensitive creep regime is characterized by a stress ex-ponent of n=3.4±0.2 and a grain size exponent of p=2.0±0.2. The activation volume for this gbs-accommodated dislocation creep regime is V*=(26±3)×10-6 m2·mol-1. Comparison of our flow law for gbs-accommodated dislocation creep with those for diffusion creep and for dislocation creep reveals that the present flow law is important for the flow of mantle rocks with grain sizes of <100 μm at differential stresses >20 MPa. Hence, gbs-accommodated dislocation creep is likely to be an important deformation mechanism in deep-rooted, highly localized shear zones in the lithospheric upper mantle.
