To rapidly generate a reentry trajectory for hypersonic vehicle satisfying waypoint and no-fly zone constraints, a novel optimization method, which combines the improved particle swarm optimization （PSO） algorithm w...To rapidly generate a reentry trajectory for hypersonic vehicle satisfying waypoint and no-fly zone constraints, a novel optimization method, which combines the improved particle swarm optimization （PSO） algorithm with the improved Gauss pseudospectral method （GPM）, is proposed. The improved PSO algorithm is used to generate a good initial value in a short time, and the mission of the improved GPM is to find the final solution with a high precision. In the improved PSO algorithm, by controlling the entropy of the swarm in each dimension, the typical PSO algorithm＇s weakness of being easy to fall into a local optimum can be overcome. In the improved GPM, two kinds of breaks are introduced to divide the trajectory into multiple segments, and the distribution of the Legendre-Gauss （LG） nodes can be altered, so that all the constraints can be satisfied strictly. Thereby the advan- tages of both the intelligent optimization algorithm and the direct method are combined. Simulation results demonstrate that the proposed method is insensitive to initial values, and it has more rapid convergence and higher precision than traditional ones.展开更多
The Susong complex zone is a relatively low-grade metamorphic unit located in the southern part of the Dabie orogen and preserves a variety of metasedimentary rocks,mostly with epidote-amphibolite facies.However,their...The Susong complex zone is a relatively low-grade metamorphic unit located in the southern part of the Dabie orogen and preserves a variety of metasedimentary rocks,mostly with epidote-amphibolite facies.However,their depositional age,provenance and tectonic setting of sedimentary protolith remain controversial due to the lack of fossils,precise dating and integrated geochemical investigation.This study has conducted whole-rock elemental,and zircon U-Pb SHRIMP dating and Lu-Hf isotope analyses on three types of representative metasedimentary rocks including garnetbearing mica-quartz schist,graphite-muscovite-quartz schist and dolomitic marble from the Susong complex zone.The UPb SHRIMP dating data indicate that the sedimentary protolith of these rocks have the maximum depositional ages of less than 840-750 Ma and have various sedimentary provenances.In combination with zircon Lu-Hf isotope compositions,the provenance of the metasedimentary rocks in the region is for the first time documented to be mainly derived from four groups of magmatic rocks formed at~2.5 Ga,~2.0 Ga,~1.4 Ga and~0.8 Ga in response to four episodes of igneous activity in the northeastern margin of the Yangtze Block.The conventional geothermobarometry combined with rare metamorphic zircon ages indicate that the studied rocks underwent the Late Triassic continental subduction-related metamorphism with peak epidote-amphibolite facies conditions at P=0.34-0.91 GPa and T=427-532°C.In addition,results of the elemental contents(i.e.,La,Ce,Th andΣREE)and ratios(i.e.,Eu/Eu^(*)and La_(N)/Yb_(N))suggest that the protoliths of the metasedimentary rocks were mainly shales,wackes and limestones,most probably related to the Rodinia supercontinent rifting along the northern margin of the Yangtze Block during the Neoproterozoic.展开更多
Objective The Susong complex zone（SCZ）is a relatively lowgrade metamorphic unit mostly with an epidoteamphibolite facies,located in the southernmost part of the Dabie orogen.However,its rock compositions,ages,
The quantitatively/semi-quantitatively formation conditions of vertical dominant hydrocarbon migration pathways were analyzed based on the big data analysis of petroleum geological parameters of complex fault Zone zon...The quantitatively/semi-quantitatively formation conditions of vertical dominant hydrocarbon migration pathways were analyzed based on the big data analysis of petroleum geological parameters of complex fault Zone zone in the central-south Bohai Bay. According to this condition, the vertical dominant migration pathway and its charge points/segments are searched through structural modeling assistant analysis in the East Sag of Huanghekou. Under the constraints of charge points/segments, numerical simulation of hydrocarbon charge and migration is carried out to successfully predict hydrocarbon migration pathways and hydrocarbon enrichment blocks in shallow layers of complex fault zone. The main results are as follows:(1) The hydrocarbon charge in shallow layers of the active fault zone is differential, the charge points/sections of vertical dominant migration pathways are the starting points of shallow hydrocarbon migration and are very important for the hydrocarbon migration and accumulation in the shallow layers.(2) Among the shallow faults, those cutting the deep transfer bins or deep major migration pathways, with fault throw of more than 80 m in the accumulation period and the juxtaposition thickness between fault and caprock of the deep layers of less than 400 m are likely to be vertical dominant migration pathways in the sag area.(3) By controlling the vertical dominant migration pathways and charging points/segments in carrier layer, Neo-tectonic movement caused the differential hydrocarbon accumulation in the complex fault zone. The research results are of great significance for the fine exploration of the complex fault zone.展开更多
The Jitang metamorphic complex is key to studying the tectonic evolution of the Northern Lancangjiang zone.Through structural-lithological mapping,structural analysis and laboratory testing,the composition of the Jita...The Jitang metamorphic complex is key to studying the tectonic evolution of the Northern Lancangjiang zone.Through structural-lithological mapping,structural analysis and laboratory testing,the composition of the Jitang metamorphic complex was determined.The macro-and microstructural analyses of the ductile detachment shear zone(Guoxuepu ductile shear zone,2–4 km wide)between the metamorphic complex and the overlying sedimentary cap show that the shear sense of the ductile shear zones is top-to-the-southeast.The presence of various deformation features and quartz C-axis electron backscatter diffraction(EBSD)fabric analysis suggests multiple deformation events occurring at different temperatures.The average stress is 25.68 MPa,with the strain rates(έ)ranging from 9.77×10^(−14)s^(−1)to 6.52×10^(−16)s^(−1).The finite strain of the Guoxuepu ductile shear zone indicates an elongated strain pattern.The average kinematic vorticity of the Guoxuepu ductile shear zone is 0.88,implying that the shear zone is dominated by simple shear.The muscovite selected from the protomylonite samples in the Guoxuepu ductile shear zone yields a 40Ar-39Ar age of 60.09±0.38 Ma.It is suggested that,coeval with the initial Indo–Eurasian collision,the development of strike-slip faults led to a weak and unstable crust,upwelling of lower crust magma,then induced the detachment of the Jitang metamorphic complex in the Eocene.展开更多
A No-Fly Zone (NFZ) is a unique mode of humanitarian intervention that is understudied in international relations. This article focuses on the politics of NFZs in international relations, and investigates their nature...A No-Fly Zone (NFZ) is a unique mode of humanitarian intervention that is understudied in international relations. This article focuses on the politics of NFZs in international relations, and investigates their nature by empirically reviewing all three cases of NFZs to date. NFZs represent a middle ground for international intervention which, both legally and legitimately, may be aimed at either protecting populations or promoting regime change in weak states, depending on the circumstances. There may be efforts by intervening states to highlight humanitarian crises among certain targets in order to secure UN authorization for the NFZs;but the implementation of NFZs is also largely driven by the security interests of the enforcing states. As a result, there is the potential for those states implementing NFZs to transcend legal authorization and to at times use excessive force, with the potential for calamitous results for local people, or, in extreme cases, to accomplish regime change by supporting opposition parties in target states.展开更多
Special economic zones(SEZs)help provide the momentum for China’s economic growth.This paper studies the influence of SEZs on enterprise’s export structures from the perspective of production complexity using data f...Special economic zones(SEZs)help provide the momentum for China’s economic growth.This paper studies the influence of SEZs on enterprise’s export structures from the perspective of production complexity using data from the China Industry Business Performance Database(CIBPD)collected between 2000 and 2007.We found that enterprises in SEZs have a higher export propensity and volume due to more complexity.Also,enterprises with more complexity outside SEZs show a higher export propensity and volume depending on the number of SEZs near them and the radiation effect of the SEZs.Similarly,high and new-tech industrial development zones perform more prominently in this regard.展开更多
A No-Fly Zone(NFZ)is a unique mode of humanitarian intervention which is understudied in international relations.This article focuses on the political dimension of NFZs in international relations and investigates thei...A No-Fly Zone(NFZ)is a unique mode of humanitarian intervention which is understudied in international relations.This article focuses on the political dimension of NFZs in international relations and investigates their implementations by empirically reviewing all three cases of NFZs to date.There may be efforts by intervening states to highlight humanitarian crises among certain targets to secure UN authorization for the NFZs;yet the implementation of NFZs is also driven largely by the security interests of enforcing states.As a result,there is the potential for those states implementing NFZs to transcend legal authorization and sometimes use excessive force,with likely calamitous results for local populations,or in extreme cases,accomplishing regime change by supporting opposition parties in target states.展开更多
The Shangla Complex ophiolite represents a relic of the Neo-Tethyan oceanic lithosphere along the Indus Suture Zone(also known as the Main Mantle Thrust)in northern Pakistan.This section,thrust onto the continental ma...The Shangla Complex ophiolite represents a relic of the Neo-Tethyan oceanic lithosphere along the Indus Suture Zone(also known as the Main Mantle Thrust)in northern Pakistan.This section,thrust onto the continental margin between the Indian and Karakoram(Asian)plates,is predominantly composed of depleted harzburgites,dunites and chromitites.In this study,we conducted a thorough analysis of mineralogy,whole-rock geochemistry(major oxides,trace elements,PGE),and integrated Re-Os isotopic data from mantle-derived peridotites to understand their petrogenesis and melt evolution.These peridotites exhibit a depleted nature,characterized by a low modal composition of clinopyroxene,a wide forsterite content range in olivine(86.5 to 95.2),and a large variation in Cr#values(25.1–91.4).Their diverse whole-rock geochemistry further suggests varying degrees of partial melting.The Cpx-harzburgites show high average Al_(2)O_(3)(1.83 wt.%),CaO(2.27 wt.%),ΣREE(12.9 ppb),and^(187)Os/^(188)Os values between 0.13095 and 0.12571.On the other hand,the depleted harzburgites and dunites exhibit lower average Al_(2)O_(3)(0.57 wt.%and 0.14 wt.%,respectively),CaO concentration(0.59 wt.%and 0.21 wt.%,respectively),and∑REE concentrations,measured at 12.7 ppb and 8.9 ppb,respectively.The^(187)Os/^(188)Os ratios in the depleted harzburgites and dunites range from 0.12643 to 0.11777,indicating they are less radiogenic compared to the Cpx-harzburgites.The spoon-shaped rare earth elements(REE)patterns suggest that the Cpx-harzburgites underwent low degrees of partial melting(∼10%–15%),whereas the depleted harzburgites and dunites indicate somewhat higher degrees of partial melting(additional melting of the Cpx-harzburgites).The PGE abundances in these depleted harzburgites and dunites are linked to the partial melting of Cpx-harzburgites,resulting in a boninitic-like melt.Their low degree of melting and melt extraction suggests that Cpx-harzburgites initially formed at a mid-ocean ridge(MOR)spreading center or a distal fore-arc basin.In contrast,the depleted harzburgites and dunites were formed during a second phase of melting,followed by refertilization,closely associated with a supra-subduction zone(SSZ)setting.The Re-Os isotopic systematics of the Shangla Complex peridotites reveal model age clusters of ca.250 Ma and ca.450 Ma,potentially corresponding to significant tectonic events in the geodynamic evolution of the Neo-Tethyan,Rheic,and Proto-Tethyan oceans.展开更多
Large-scale magmatism affected the Tongbai-Dabie orogenic belt during post-collisional lateral tectonic extension in the Cretaceous, which was suggested to account for the widespread deformation and migmatization in t...Large-scale magmatism affected the Tongbai-Dabie orogenic belt during post-collisional lateral tectonic extension in the Cretaceous, which was suggested to account for the widespread deformation and migmatization in the Tongbai-Dabie complexes. However, it cannot explain the most deformations in the shear zones. The northwest-southeast shear zones are developed around or wrapped the Tongbai-Dabie complexes. They play an important role for the interpretation of the tectonic evolution of the Tongbai-Dabie orogenic belt. By a systematically observation and description of the geometry and kinematics of these shear zones, we found that the shear zones to the north dip NE and have a uniform sinistral shear sense, the shear zone to the south dips SW and has a uniform dextral shear sense, and the shear zones at the core are sub-horizontal and have a uniform top-to-NW sense of shear. Combining with the comparison of previous and our geochronological studies, we interpret these associations as indicating that these shear zones were originally a single, more flat-lying and sub- horizontal shear zone with a uniform top-to-NW shear sense before the folding-doming of the Tongbai- Dabie complexes and suggest that the Tongbai-Dabie orogenic belt experienced a uniform top-to-NW orogen-paraUel extension in the ductile lithosphere before the widespread magmatism in the Cretaceous.展开更多
A discontinuous line of ophiolitic bodies occurs along the Yarlung Zangbo Suture Zone (YTSZ), which stretches across southern Tibet and beyond. This zone marks the locus of collision between Eurasia and India in the E...A discontinuous line of ophiolitic bodies occurs along the Yarlung Zangbo Suture Zone (YTSZ), which stretches across southern Tibet and beyond. This zone marks the locus of collision between Eurasia and India in the Early Cenozoic. Should we assume that the entire Tethyan Ocean basin that lay between these two continental blocks was oceanic or might it have been more complex? Fragments of any terranes that developed within this once extensive ocean potentially lie within the YTSZ. Detailed investigations over the past three field seasons reveal the presence of several terranes distributed along this zone. Work is currently underway to analyze the nature of individual terranes and the timing of any inter\|relationships.展开更多
The reentry trajectory optimization for hypersonic vehicle（HV）is a current problem of great interest.Some complex constraints,such as waypoints for reconnaissance and no-fly zones for threat avoidance,are inevitably...The reentry trajectory optimization for hypersonic vehicle（HV）is a current problem of great interest.Some complex constraints,such as waypoints for reconnaissance and no-fly zones for threat avoidance,are inevitably involved in a global strike mission.Of the many direct methods,Gauss pseudospectral method（GPM）has been demonstrated as an effective tool to solve the trajectory optimization problem with typical constraints.However,a series of diffculties arises for complex constraints,such as the uncertainty of passage time for waypoints and the inaccuracy of approximate trajectory near no-fly zones.The research herein proposes a multi-phase technique based on the GPM to generate an optimal reentry trajectory for HV satisfying waypoint and nofly zone constraints.Three kinds of specifc breaks are introduced to divide the full trajectory into multiple phases.The continuity conditions are presented to ensure a smooth connection between each pair of phases.Numerical examples for reentry trajectory optimization in free-space flight and with complex constraints are used to demonstrate the proposed technique.Simulation results show the feasible application of multi-phase technique in reentry trajectory optimization with waypoint and no-fly zone constraints.展开更多
Neoarchean metamorphic mafic rocks in the lower and the middle Wutai Complex mainly comprise metamorphic gabbros, amphibolites and chlorite schists. They can be subdivided into three groups according to chondrite norm...Neoarchean metamorphic mafic rocks in the lower and the middle Wutai Complex mainly comprise metamorphic gabbros, amphibolites and chlorite schists. They can be subdivided into three groups according to chondrite normalized REE patterns. Rocks in Group #1 are characterized by nearly flat REE patterns （Lan/Ybn=0.86-1.3）, the lowest total REEs （29-52 ppm）, and weak negative to positive Eu anomalies （Eun/Eun=0.84-1.02）, nearly flat primitive mantle normalized patterns and strong negative Zr（Hf） anomalies. Their geochemical characteristics in REEs and trace elements are similar to those of ocean plateau tholeiite, which imply that this group of rocks can represent remnants of Archean oceanic crust derived from a mantle plume. Rocks in Group #2 are characterized by moderate total REEs （34-116 ppm）, LREE-enriched （Lan/Ybn=1.76-4.34） chondrite normalized REE patterns with weak Eu anomalies （Eun/Eun=0.76-1.16）, and negative Nb, Ta, Zr（Hf）, Ti anomalies in the primitive mantle normalized spider diagram. The REE and trace element characteristics indicate that they represent arc magmas originating from a sub-arc mantle wedge metasomatized by slab-derived fluids. Rocks in Group #3 are characterized by the highest total REEs （61-192 ppm）, the strongest LREEs enrichment （Lan/Ybn=7.12-16） with slightly negative Eu anomalies （Eun/Eun=0.81-0.95） in the chondrite normalized diagram. In the primitive mantle normalized diagram, these rocks are characterized by large negative anomalies in Nb, Ta, Ti, negative to no Zr anomalies. They represent arc magmas originating from a sub-arc mantle wedge enriched in slab-derived melts. The three groups of rocks imply that the formation of the Neoarchean Wutai Complex is related to mantle plumes and island-arc interaction.展开更多
Numerical modelling is a common routine for slope stability analysis in the complex terrain,and the accuracy of topographic survey has a great impact on the results.In this study,a combination of unmanned aerial vehic...Numerical modelling is a common routine for slope stability analysis in the complex terrain,and the accuracy of topographic survey has a great impact on the results.In this study,a combination of unmanned aerial vehicle(UAV)photogrammetry and 3D laser scanning technique was first proposed to establish a high-precision digital elevation model(DEM),which could be accurate to 0.2 m,fulfilling the engineering requirements.Then,a series of 3D/2D finite element models(FEM)were constituted on the basis of DEM to investigate the slope stability in the complex terrain.The results indicate that the deformation of complex terrain slope is chiefly triggered by compression-shear failure and the failure zones are mostly distributed on the middle-upper part and the scarp.Furthermore,the complex terrain slope is divided into concave,convex,concave-convex and convex-concave slope according to the topographical curvature,and the factor of safety(FOS)is as follows:the maximum value 1.8504 for the concave-convex slope,the minimum value 1.1129 for the convexconcave slope,and the median for either concave or convex slope.The inflection points and curvature of the slope jointly determine the shape of nonlinear slope,dominating the morphological effect on the slope stability,so the rational use of section morphological effect will be conducive to the overall stability of the slope.For four representative slopes,the plastic deformation first emerges into the middle,then progressively develops to the upper,and finally forms the connected failure zones.展开更多
The Beishan rift zone in Xinjiang Uygur Autonomous Region was formed due to strong activities of faults on the basement of the Tarim continental crust.Despite the fact that many geological research results of the rift...The Beishan rift zone in Xinjiang Uygur Autonomous Region was formed due to strong activities of faults on the basement of the Tarim continental crust.Despite the fact that many geological research results of the rift zone have been achieved,only a few studies have been conducted on its regional geophysical characteristics.In this paper,the gravity and magnetic anomalies of the rift zone were highlighted through specific data processing of 1∶50000 high-precision aeromagnetic data and gravity data with a grid spacing of 2 km×2 km.Based on this,the geophysical evidence for the scope and internal structures of the Beishan rift zone was obtained for the first time.The distinct characteristics of magnetic and gravity fields in the areas to the north and south of the Beishan rift zone reveal that deep faults exist between the Beishan rift zone and the geological units on the southern and northern sides.Furthermore,the faults on the two areas contain the bidirectional thrusts and have flower-shaped structures according to the characteristics of the magnetic and gravity fields.The Beishan rift zone can be divided into two tectonomagmatic zones,namely the Zhongposhan-Bijiashan-Cihai-Baishanliang zone(the northern zone)and the Bayiquan-Qixin-Baishan zone(the southern zone).The northern zone can be further subdivided into three comet-shaped anomaly groups(tectonomagmatic areas),while the southern zone can be further subdivided into two tectonomagmatic areas.According to the characteristics of aeromagnetic anomalies and gravity field,19 mafic-ultramafic complexes were delineated.The known Pobei,Hongshishan,and Qixin complexes are all located within the inferred complexes,with estimates of total explored resources of Ni,Cu,and Au of 3×10^(6) t,10×10^(3) t and 10 t,respectively.The prospecting of high-grade copper-nickel deposits should focus on the periphery and deep parts of the known and inferred mafic-ultramafic complexes.Among them,the peripheral strata of the complexes specifically have great prospecting potential of large-scale high-grade copper-nickel deposits of magma injection type.Finally,this paper analyzed the application effects of the rapid airborne-ground-drilling synergetic exploration method in the prospecting of copper-nickel deposits in Qixin,Beishan,Xinjiang,which will provide references for further exploration of copper-nickel deposits in Beishan area,Xinjiang.展开更多
In virtue of effect of N-S intensive ground stress and mining disturbance to +579E2EB_(1+2) mining site at Weihuliang Mine,the dip angle and section height is 65° and 52 m,respectively,the collapses happed freque...In virtue of effect of N-S intensive ground stress and mining disturbance to +579E2EB_(1+2) mining site at Weihuliang Mine,the dip angle and section height is 65° and 52 m,respectively,the collapses happed frequently during mining.Firstly,mining condi- tions,spatial structure and parameters were investigated.Then physical simulation and dynamic numerical tracing and elaborate simulation relating roof and top-coal were ap- plied based on 2D-Block Program and quantitative regularity of stress at variable depths had been estimated.Furthermore,it was manifested that effective measures,i.e.,fast mining,control symmetrical top-coal-caving at dip and strike directions,optimizing ventila- tion system,active-stereo preventing gas were performed successfully in mining practice. Ultimately,the derived dynamic hazard were prevented so as to safety mining.展开更多
The Chayu area is located at the southeastern margin of the Qinghai-Tibet Plateau.This region was considered to be in the southeastward extension of the Lhasa Block,bounded by Nujiang suture zone in the north and Yarl...The Chayu area is located at the southeastern margin of the Qinghai-Tibet Plateau.This region was considered to be in the southeastward extension of the Lhasa Block,bounded by Nujiang suture zone in the north and Yarlung Zangbo suture zone in the south.The Demala Group complex,a set of high-grade metamorphic gneisses widely distributed in the Chayu area,is known as the Precambrian metamorphic basement of the Lhasa Block in the area.According to field-based investigations and microstructure analysis,the Demala Group complex is considered to mainly consist of banded biotite plagiogneisses,biotite quartzofeldspathic gneiss,granitic gneiss,amphibolite,mica schist,and quartz schist,with many leucogranite veins.The zircon U-Pb ages of two granitic gneiss samples are 205±1 Ma and 218±1 Ma,respectively,representing the ages of their protoliths.The zircons from two biotite plagiogneisses samples show core-rim structures.The U-Pb ages of the cores are mainly 644–446 Ma,1213–865 Ma,and 1780–1400 Ma,reflecting the age characteristics of clastic zircons during sedimentation of the original rocks.The U-Pb ages of the rims are from 203±2 Ma to 190±1 Ma,which represent the age of metamorphism.The zircon U-Pb ages of one sample taken from the leucogranite veins that cut through granitic gneiss foliation range from 24 Ma to 22 Ma,interpreted as the age of the anatexis in the Demala Group complex.Biotite and muscovite separates were selected from the granitic gneiss,banded gneiss,and leucogranite veins for 40Ar/39Ar dating.The plateau ages of three muscovite samples are 16.56±0.21 Ma,16.90±0.21 Ma,and 23.40±0.31 Ma,and the plateau ages of four biotite samples are 16.70±0.24 Ma,16.14±0.19 Ma,15.88±0.20 Ma,and 14.39±0.20 Ma.The mica Ar-Ar ages can reveal the exhumation and cooling history of the Demala Group complex.Combined with the previous research results of the Demala Group complex,the authors refer that the Demala Group complex should be a set of metamorphic complex.The complex includes not only Precambrian basement metamorphic rock series,but also Paleozoic sedimentary rock and Mesozoic granitic rock.Based on the deformation characteristics,the authors concluded that two stages of the metamorphism and deformation can be revealed in the Demala Group complex since the Mesozoic,namely Late Triassic-Early Jurassic(203–190 Ma)and Oligocene–Miocene(24–14 Ma).The early stage of metamorphism(ranging from 203–190 Ma)was related to the Late Triassic tectono-magmatism in the area.The anatexis and uplifting-exhumation of the later stage(24–14 Ma)were related to the shearing of the Jiali strike-slip fault zone.The Miocene structures are response to the large-scale southeastward escape of crustal materials and block rotation in Southeast Tibet after India-Eurasia collision.展开更多
Two equal collinear cracks with coalesced interior electric saturation zones are analytically studied for two-dimensional (2D) arbitrary polarized semipermeable piezo- electric media based on a modified strip saturate...Two equal collinear cracks with coalesced interior electric saturation zones are analytically studied for two-dimensional (2D) arbitrary polarized semipermeable piezo- electric media based on a modified strip saturated model. The strip saturated model is modified here by varying the strip saturated constant electric displacement condition to the polynomially varying electric displacement conditions. Based on the linear, quadratic, and cubic electric displacement conditions on the inner and outer saturated zones, dif- ferent modified strip saturated models are proposed and studied for two equal collinear cracks. With the Stroh formalism and the complex variable technique, these fracture problems are reduced into different types of non-homogeneous Riemann Hilbert problems in unknown generalized complex potential functions. These mathematical problems are then solved with the Riemann-Hilbert approach to obtain the stress and electric displace- ment components at any point of the domain. The explicit expressions for the outer saturated zone length, the crack opening potential (COP), the crack opening displace- ment (COD), and the local intensity factors (LIFs) are derived. A numerical study is presented for the modified strip saturated model in 2D arbitrary polarized semiperme- able PZT-4 material. The obtained results are compared with those of the strip saturated model, and the effects of the polynomially varying saturation condition on the saturated zones and the applied electrical loadings are presented.展开更多
Evonian massive limestones in the Northeastern Brilon reef complex comprise many marine calcareous algae. 10 genera all 12 species could be identified .They are Keega australe,Solenopora geikiei,Solenopora sp. (red al...Evonian massive limestones in the Northeastern Brilon reef complex comprise many marine calcareous algae. 10 genera all 12 species could be identified .They are Keega australe,Solenopora geikiei,Solenopora sp. (red algae ), Litanaia cf. perisseia,Ortonella sp.,Vermiporella sp. (green algae ); Epiphyton sp., Girvanella ducii, Girvanella problematica,?Sphaerocodium sp.,Renalcis sp. (blue green algae )and Kamaena sp.. The distribution and relative abundance of these algae are conjoined to specific factes types and therefore they are very in the interpretation of paleoenvironments. In addition, calcareous algae can be used for the geologic dating.展开更多
In the 1920s, a closed-form solution of the moving Criffith crack was first obtained by Yoffe. Based on Yoffe＇s solution, the Dugdale model for the moving crack case gives a good result. However, the Dugddle model fa...In the 1920s, a closed-form solution of the moving Criffith crack was first obtained by Yoffe. Based on Yoffe＇s solution, the Dugdale model for the moving crack case gives a good result. However, the Dugddle model fails when the crack speed is closed to the Rayleigh wave speed because of the discontinuity occurred in the crack opening displacement （COD）. The problem is solved in this paper by introducing a restraining stress zone ahead of the crack tip and two velocity functions. The restraining stresses are linearly distributed and related to the velocity of the moving crack. An analytical solution of the problem is obtained by use of the superposition principle and a complex function method. The final result of the COD is continuous while the crack moves at a Rayleigh wave speed. The characteristics of the strain energy density （SED） and numerical results are discussed, and conclusions are given.展开更多
基金supported by the National Natural Science Foundation of China(61272011)
文摘To rapidly generate a reentry trajectory for hypersonic vehicle satisfying waypoint and no-fly zone constraints, a novel optimization method, which combines the improved particle swarm optimization （PSO） algorithm with the improved Gauss pseudospectral method （GPM）, is proposed. The improved PSO algorithm is used to generate a good initial value in a short time, and the mission of the improved GPM is to find the final solution with a high precision. In the improved PSO algorithm, by controlling the entropy of the swarm in each dimension, the typical PSO algorithm＇s weakness of being easy to fall into a local optimum can be overcome. In the improved GPM, two kinds of breaks are introduced to divide the trajectory into multiple segments, and the distribution of the Legendre-Gauss （LG） nodes can be altered, so that all the constraints can be satisfied strictly. Thereby the advan- tages of both the intelligent optimization algorithm and the direct method are combined. Simulation results demonstrate that the proposed method is insensitive to initial values, and it has more rapid convergence and higher precision than traditional ones.
基金financially supported by the National Natural Science Foundation of China(Grant No.42072059)。
文摘The Susong complex zone is a relatively low-grade metamorphic unit located in the southern part of the Dabie orogen and preserves a variety of metasedimentary rocks,mostly with epidote-amphibolite facies.However,their depositional age,provenance and tectonic setting of sedimentary protolith remain controversial due to the lack of fossils,precise dating and integrated geochemical investigation.This study has conducted whole-rock elemental,and zircon U-Pb SHRIMP dating and Lu-Hf isotope analyses on three types of representative metasedimentary rocks including garnetbearing mica-quartz schist,graphite-muscovite-quartz schist and dolomitic marble from the Susong complex zone.The UPb SHRIMP dating data indicate that the sedimentary protolith of these rocks have the maximum depositional ages of less than 840-750 Ma and have various sedimentary provenances.In combination with zircon Lu-Hf isotope compositions,the provenance of the metasedimentary rocks in the region is for the first time documented to be mainly derived from four groups of magmatic rocks formed at~2.5 Ga,~2.0 Ga,~1.4 Ga and~0.8 Ga in response to four episodes of igneous activity in the northeastern margin of the Yangtze Block.The conventional geothermobarometry combined with rare metamorphic zircon ages indicate that the studied rocks underwent the Late Triassic continental subduction-related metamorphism with peak epidote-amphibolite facies conditions at P=0.34-0.91 GPa and T=427-532°C.In addition,results of the elemental contents(i.e.,La,Ce,Th andΣREE)and ratios(i.e.,Eu/Eu^(*)and La_(N)/Yb_(N))suggest that the protoliths of the metasedimentary rocks were mainly shales,wackes and limestones,most probably related to the Rodinia supercontinent rifting along the northern margin of the Yangtze Block during the Neoproterozoic.
基金financially supported by the National Basic Research Program of China(grant No.2015CB856104)the National Natural Science Foundation of China(grant No.41773020)
文摘Objective The Susong complex zone（SCZ）is a relatively lowgrade metamorphic unit mostly with an epidoteamphibolite facies,located in the southernmost part of the Dabie orogen.However,its rock compositions,ages,
基金Supported by the National Science and Technology Major Project(2016ZX05024-003)
文摘The quantitatively/semi-quantitatively formation conditions of vertical dominant hydrocarbon migration pathways were analyzed based on the big data analysis of petroleum geological parameters of complex fault Zone zone in the central-south Bohai Bay. According to this condition, the vertical dominant migration pathway and its charge points/segments are searched through structural modeling assistant analysis in the East Sag of Huanghekou. Under the constraints of charge points/segments, numerical simulation of hydrocarbon charge and migration is carried out to successfully predict hydrocarbon migration pathways and hydrocarbon enrichment blocks in shallow layers of complex fault zone. The main results are as follows:(1) The hydrocarbon charge in shallow layers of the active fault zone is differential, the charge points/sections of vertical dominant migration pathways are the starting points of shallow hydrocarbon migration and are very important for the hydrocarbon migration and accumulation in the shallow layers.(2) Among the shallow faults, those cutting the deep transfer bins or deep major migration pathways, with fault throw of more than 80 m in the accumulation period and the juxtaposition thickness between fault and caprock of the deep layers of less than 400 m are likely to be vertical dominant migration pathways in the sag area.(3) By controlling the vertical dominant migration pathways and charging points/segments in carrier layer, Neo-tectonic movement caused the differential hydrocarbon accumulation in the complex fault zone. The research results are of great significance for the fine exploration of the complex fault zone.
基金financially supported by the China Geological Survey Scientific Research Project(Grant Nos.DD20190167 and DD20190053)the National Natural Science Foundation of China(Grant No.42172259).
文摘The Jitang metamorphic complex is key to studying the tectonic evolution of the Northern Lancangjiang zone.Through structural-lithological mapping,structural analysis and laboratory testing,the composition of the Jitang metamorphic complex was determined.The macro-and microstructural analyses of the ductile detachment shear zone(Guoxuepu ductile shear zone,2–4 km wide)between the metamorphic complex and the overlying sedimentary cap show that the shear sense of the ductile shear zones is top-to-the-southeast.The presence of various deformation features and quartz C-axis electron backscatter diffraction(EBSD)fabric analysis suggests multiple deformation events occurring at different temperatures.The average stress is 25.68 MPa,with the strain rates(έ)ranging from 9.77×10^(−14)s^(−1)to 6.52×10^(−16)s^(−1).The finite strain of the Guoxuepu ductile shear zone indicates an elongated strain pattern.The average kinematic vorticity of the Guoxuepu ductile shear zone is 0.88,implying that the shear zone is dominated by simple shear.The muscovite selected from the protomylonite samples in the Guoxuepu ductile shear zone yields a 40Ar-39Ar age of 60.09±0.38 Ma.It is suggested that,coeval with the initial Indo–Eurasian collision,the development of strike-slip faults led to a weak and unstable crust,upwelling of lower crust magma,then induced the detachment of the Jitang metamorphic complex in the Eocene.
基金sponsored by the Key Research Base Project “The Comparative Study of the States outside the NPT Regime”(project number: 11JZ004)from the Education Department of Shaanxi Provincial Government
文摘A No-Fly Zone (NFZ) is a unique mode of humanitarian intervention that is understudied in international relations. This article focuses on the politics of NFZs in international relations, and investigates their nature by empirically reviewing all three cases of NFZs to date. NFZs represent a middle ground for international intervention which, both legally and legitimately, may be aimed at either protecting populations or promoting regime change in weak states, depending on the circumstances. There may be efforts by intervening states to highlight humanitarian crises among certain targets in order to secure UN authorization for the NFZs;but the implementation of NFZs is also largely driven by the security interests of the enforcing states. As a result, there is the potential for those states implementing NFZs to transcend legal authorization and to at times use excessive force, with the potential for calamitous results for local people, or, in extreme cases, to accomplish regime change by supporting opposition parties in target states.
基金a staged result of “Statistical Monitoring and Evaluation Research on China’s New Economy and Growth Drivers in the Context of Big Data”(Approved under No.18ZDA124),a key program sponsored by the National Social Science Fund of China
文摘Special economic zones(SEZs)help provide the momentum for China’s economic growth.This paper studies the influence of SEZs on enterprise’s export structures from the perspective of production complexity using data from the China Industry Business Performance Database(CIBPD)collected between 2000 and 2007.We found that enterprises in SEZs have a higher export propensity and volume due to more complexity.Also,enterprises with more complexity outside SEZs show a higher export propensity and volume depending on the number of SEZs near them and the radiation effect of the SEZs.Similarly,high and new-tech industrial development zones perform more prominently in this regard.
基金This article has been sponsored by the Core Research Base Project“The Comparative Study of the States outside the NPT Regime”(project number:11jz004)from Education Department of Shaanxi Provincial Government and two-class General Financial Grant for the China Postdoctoral Science Foundation(Grant No.:2012M521660).
文摘A No-Fly Zone(NFZ)is a unique mode of humanitarian intervention which is understudied in international relations.This article focuses on the political dimension of NFZs in international relations and investigates their implementations by empirically reviewing all three cases of NFZs to date.There may be efforts by intervening states to highlight humanitarian crises among certain targets to secure UN authorization for the NFZs;yet the implementation of NFZs is also driven largely by the security interests of enforcing states.As a result,there is the potential for those states implementing NFZs to transcend legal authorization and sometimes use excessive force,with likely calamitous results for local populations,or in extreme cases,accomplishing regime change by supporting opposition parties in target states.
基金supported by a grant from the Science and Technology Innovation Program of Hunan Province(Grant No.2021RC4055)Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring,during the Postdoctoral research of the first author(Zaheen Ullah,Assistant Professor,University of Swat,Pakistan)at the Central South University,Changsha,China.
文摘The Shangla Complex ophiolite represents a relic of the Neo-Tethyan oceanic lithosphere along the Indus Suture Zone(also known as the Main Mantle Thrust)in northern Pakistan.This section,thrust onto the continental margin between the Indian and Karakoram(Asian)plates,is predominantly composed of depleted harzburgites,dunites and chromitites.In this study,we conducted a thorough analysis of mineralogy,whole-rock geochemistry(major oxides,trace elements,PGE),and integrated Re-Os isotopic data from mantle-derived peridotites to understand their petrogenesis and melt evolution.These peridotites exhibit a depleted nature,characterized by a low modal composition of clinopyroxene,a wide forsterite content range in olivine(86.5 to 95.2),and a large variation in Cr#values(25.1–91.4).Their diverse whole-rock geochemistry further suggests varying degrees of partial melting.The Cpx-harzburgites show high average Al_(2)O_(3)(1.83 wt.%),CaO(2.27 wt.%),ΣREE(12.9 ppb),and^(187)Os/^(188)Os values between 0.13095 and 0.12571.On the other hand,the depleted harzburgites and dunites exhibit lower average Al_(2)O_(3)(0.57 wt.%and 0.14 wt.%,respectively),CaO concentration(0.59 wt.%and 0.21 wt.%,respectively),and∑REE concentrations,measured at 12.7 ppb and 8.9 ppb,respectively.The^(187)Os/^(188)Os ratios in the depleted harzburgites and dunites range from 0.12643 to 0.11777,indicating they are less radiogenic compared to the Cpx-harzburgites.The spoon-shaped rare earth elements(REE)patterns suggest that the Cpx-harzburgites underwent low degrees of partial melting(∼10%–15%),whereas the depleted harzburgites and dunites indicate somewhat higher degrees of partial melting(additional melting of the Cpx-harzburgites).The PGE abundances in these depleted harzburgites and dunites are linked to the partial melting of Cpx-harzburgites,resulting in a boninitic-like melt.Their low degree of melting and melt extraction suggests that Cpx-harzburgites initially formed at a mid-ocean ridge(MOR)spreading center or a distal fore-arc basin.In contrast,the depleted harzburgites and dunites were formed during a second phase of melting,followed by refertilization,closely associated with a supra-subduction zone(SSZ)setting.The Re-Os isotopic systematics of the Shangla Complex peridotites reveal model age clusters of ca.250 Ma and ca.450 Ma,potentially corresponding to significant tectonic events in the geodynamic evolution of the Neo-Tethyan,Rheic,and Proto-Tethyan oceans.
基金funded by the National Natural Science Foundation of China(Grants.41272222 to C.Z.Song and 41472166 to S.Lin)China Geological Survey(Grants.1212011121116 to S.Lin)a China Scholarship Council scholarship to H.Liu
文摘Large-scale magmatism affected the Tongbai-Dabie orogenic belt during post-collisional lateral tectonic extension in the Cretaceous, which was suggested to account for the widespread deformation and migmatization in the Tongbai-Dabie complexes. However, it cannot explain the most deformations in the shear zones. The northwest-southeast shear zones are developed around or wrapped the Tongbai-Dabie complexes. They play an important role for the interpretation of the tectonic evolution of the Tongbai-Dabie orogenic belt. By a systematically observation and description of the geometry and kinematics of these shear zones, we found that the shear zones to the north dip NE and have a uniform sinistral shear sense, the shear zone to the south dips SW and has a uniform dextral shear sense, and the shear zones at the core are sub-horizontal and have a uniform top-to-NW sense of shear. Combining with the comparison of previous and our geochronological studies, we interpret these associations as indicating that these shear zones were originally a single, more flat-lying and sub- horizontal shear zone with a uniform top-to-NW shear sense before the folding-doming of the Tongbai- Dabie complexes and suggest that the Tongbai-Dabie orogenic belt experienced a uniform top-to-NW orogen-paraUel extension in the ductile lithosphere before the widespread magmatism in the Cretaceous.
文摘A discontinuous line of ophiolitic bodies occurs along the Yarlung Zangbo Suture Zone (YTSZ), which stretches across southern Tibet and beyond. This zone marks the locus of collision between Eurasia and India in the Early Cenozoic. Should we assume that the entire Tethyan Ocean basin that lay between these two continental blocks was oceanic or might it have been more complex? Fragments of any terranes that developed within this once extensive ocean potentially lie within the YTSZ. Detailed investigations over the past three field seasons reveal the presence of several terranes distributed along this zone. Work is currently underway to analyze the nature of individual terranes and the timing of any inter\|relationships.
基金supported by Aviation Science Foundation of China(No.2011ZC13001 and 2013ZA18001)National Natural Science Foundation of China(Nos:60975073,61273349,61175109 and 61203223)Innovation Foundation of BUAA for PhD Graduates
文摘The reentry trajectory optimization for hypersonic vehicle（HV）is a current problem of great interest.Some complex constraints,such as waypoints for reconnaissance and no-fly zones for threat avoidance,are inevitably involved in a global strike mission.Of the many direct methods,Gauss pseudospectral method（GPM）has been demonstrated as an effective tool to solve the trajectory optimization problem with typical constraints.However,a series of diffculties arises for complex constraints,such as the uncertainty of passage time for waypoints and the inaccuracy of approximate trajectory near no-fly zones.The research herein proposes a multi-phase technique based on the GPM to generate an optimal reentry trajectory for HV satisfying waypoint and nofly zone constraints.Three kinds of specifc breaks are introduced to divide the full trajectory into multiple phases.The continuity conditions are presented to ensure a smooth connection between each pair of phases.Numerical examples for reentry trajectory optimization in free-space flight and with complex constraints are used to demonstrate the proposed technique.Simulation results show the feasible application of multi-phase technique in reentry trajectory optimization with waypoint and no-fly zone constraints.
基金The National Natural Science Foundation of. China （Grant No.40420120135 and 40472096） are thankefl for the fthancial support.
文摘Neoarchean metamorphic mafic rocks in the lower and the middle Wutai Complex mainly comprise metamorphic gabbros, amphibolites and chlorite schists. They can be subdivided into three groups according to chondrite normalized REE patterns. Rocks in Group #1 are characterized by nearly flat REE patterns （Lan/Ybn=0.86-1.3）, the lowest total REEs （29-52 ppm）, and weak negative to positive Eu anomalies （Eun/Eun=0.84-1.02）, nearly flat primitive mantle normalized patterns and strong negative Zr（Hf） anomalies. Their geochemical characteristics in REEs and trace elements are similar to those of ocean plateau tholeiite, which imply that this group of rocks can represent remnants of Archean oceanic crust derived from a mantle plume. Rocks in Group #2 are characterized by moderate total REEs （34-116 ppm）, LREE-enriched （Lan/Ybn=1.76-4.34） chondrite normalized REE patterns with weak Eu anomalies （Eun/Eun=0.76-1.16）, and negative Nb, Ta, Zr（Hf）, Ti anomalies in the primitive mantle normalized spider diagram. The REE and trace element characteristics indicate that they represent arc magmas originating from a sub-arc mantle wedge metasomatized by slab-derived fluids. Rocks in Group #3 are characterized by the highest total REEs （61-192 ppm）, the strongest LREEs enrichment （Lan/Ybn=7.12-16） with slightly negative Eu anomalies （Eun/Eun=0.81-0.95） in the chondrite normalized diagram. In the primitive mantle normalized diagram, these rocks are characterized by large negative anomalies in Nb, Ta, Ti, negative to no Zr anomalies. They represent arc magmas originating from a sub-arc mantle wedge enriched in slab-derived melts. The three groups of rocks imply that the formation of the Neoarchean Wutai Complex is related to mantle plumes and island-arc interaction.
基金supported by the National Key Research and Development Program of China(Grant No.2018YFC0808706)the Projects of Shaanxi Province Education Department Science and Technology Research Plan(Grant No.20JK0501,21JK0502)。
文摘Numerical modelling is a common routine for slope stability analysis in the complex terrain,and the accuracy of topographic survey has a great impact on the results.In this study,a combination of unmanned aerial vehicle(UAV)photogrammetry and 3D laser scanning technique was first proposed to establish a high-precision digital elevation model(DEM),which could be accurate to 0.2 m,fulfilling the engineering requirements.Then,a series of 3D/2D finite element models(FEM)were constituted on the basis of DEM to investigate the slope stability in the complex terrain.The results indicate that the deformation of complex terrain slope is chiefly triggered by compression-shear failure and the failure zones are mostly distributed on the middle-upper part and the scarp.Furthermore,the complex terrain slope is divided into concave,convex,concave-convex and convex-concave slope according to the topographical curvature,and the factor of safety(FOS)is as follows:the maximum value 1.8504 for the concave-convex slope,the minimum value 1.1129 for the convexconcave slope,and the median for either concave or convex slope.The inflection points and curvature of the slope jointly determine the shape of nonlinear slope,dominating the morphological effect on the slope stability,so the rational use of section morphological effect will be conducive to the overall stability of the slope.For four representative slopes,the plastic deformation first emerges into the middle,then progressively develops to the upper,and finally forms the connected failure zones.
基金supported by the National Key Research and Development Program of China(2017YFC0602206)the projects of the China Geological Survey(DD20160066,DD20190551).
文摘The Beishan rift zone in Xinjiang Uygur Autonomous Region was formed due to strong activities of faults on the basement of the Tarim continental crust.Despite the fact that many geological research results of the rift zone have been achieved,only a few studies have been conducted on its regional geophysical characteristics.In this paper,the gravity and magnetic anomalies of the rift zone were highlighted through specific data processing of 1∶50000 high-precision aeromagnetic data and gravity data with a grid spacing of 2 km×2 km.Based on this,the geophysical evidence for the scope and internal structures of the Beishan rift zone was obtained for the first time.The distinct characteristics of magnetic and gravity fields in the areas to the north and south of the Beishan rift zone reveal that deep faults exist between the Beishan rift zone and the geological units on the southern and northern sides.Furthermore,the faults on the two areas contain the bidirectional thrusts and have flower-shaped structures according to the characteristics of the magnetic and gravity fields.The Beishan rift zone can be divided into two tectonomagmatic zones,namely the Zhongposhan-Bijiashan-Cihai-Baishanliang zone(the northern zone)and the Bayiquan-Qixin-Baishan zone(the southern zone).The northern zone can be further subdivided into three comet-shaped anomaly groups(tectonomagmatic areas),while the southern zone can be further subdivided into two tectonomagmatic areas.According to the characteristics of aeromagnetic anomalies and gravity field,19 mafic-ultramafic complexes were delineated.The known Pobei,Hongshishan,and Qixin complexes are all located within the inferred complexes,with estimates of total explored resources of Ni,Cu,and Au of 3×10^(6) t,10×10^(3) t and 10 t,respectively.The prospecting of high-grade copper-nickel deposits should focus on the periphery and deep parts of the known and inferred mafic-ultramafic complexes.Among them,the peripheral strata of the complexes specifically have great prospecting potential of large-scale high-grade copper-nickel deposits of magma injection type.Finally,this paper analyzed the application effects of the rapid airborne-ground-drilling synergetic exploration method in the prospecting of copper-nickel deposits in Qixin,Beishan,Xinjiang,which will provide references for further exploration of copper-nickel deposits in Beishan area,Xinjiang.
基金the National Natural Science Foundation of China(10402033,10772144)
文摘In virtue of effect of N-S intensive ground stress and mining disturbance to +579E2EB_(1+2) mining site at Weihuliang Mine,the dip angle and section height is 65° and 52 m,respectively,the collapses happed frequently during mining.Firstly,mining condi- tions,spatial structure and parameters were investigated.Then physical simulation and dynamic numerical tracing and elaborate simulation relating roof and top-coal were ap- plied based on 2D-Block Program and quantitative regularity of stress at variable depths had been estimated.Furthermore,it was manifested that effective measures,i.e.,fast mining,control symmetrical top-coal-caving at dip and strike directions,optimizing ventila- tion system,active-stereo preventing gas were performed successfully in mining practice. Ultimately,the derived dynamic hazard were prevented so as to safety mining.
基金a project of National Natural Science Foundation of China(41773026)two geological survey projects initiated by the China Geological Survey(DD20190053,DD20160021).
文摘The Chayu area is located at the southeastern margin of the Qinghai-Tibet Plateau.This region was considered to be in the southeastward extension of the Lhasa Block,bounded by Nujiang suture zone in the north and Yarlung Zangbo suture zone in the south.The Demala Group complex,a set of high-grade metamorphic gneisses widely distributed in the Chayu area,is known as the Precambrian metamorphic basement of the Lhasa Block in the area.According to field-based investigations and microstructure analysis,the Demala Group complex is considered to mainly consist of banded biotite plagiogneisses,biotite quartzofeldspathic gneiss,granitic gneiss,amphibolite,mica schist,and quartz schist,with many leucogranite veins.The zircon U-Pb ages of two granitic gneiss samples are 205±1 Ma and 218±1 Ma,respectively,representing the ages of their protoliths.The zircons from two biotite plagiogneisses samples show core-rim structures.The U-Pb ages of the cores are mainly 644–446 Ma,1213–865 Ma,and 1780–1400 Ma,reflecting the age characteristics of clastic zircons during sedimentation of the original rocks.The U-Pb ages of the rims are from 203±2 Ma to 190±1 Ma,which represent the age of metamorphism.The zircon U-Pb ages of one sample taken from the leucogranite veins that cut through granitic gneiss foliation range from 24 Ma to 22 Ma,interpreted as the age of the anatexis in the Demala Group complex.Biotite and muscovite separates were selected from the granitic gneiss,banded gneiss,and leucogranite veins for 40Ar/39Ar dating.The plateau ages of three muscovite samples are 16.56±0.21 Ma,16.90±0.21 Ma,and 23.40±0.31 Ma,and the plateau ages of four biotite samples are 16.70±0.24 Ma,16.14±0.19 Ma,15.88±0.20 Ma,and 14.39±0.20 Ma.The mica Ar-Ar ages can reveal the exhumation and cooling history of the Demala Group complex.Combined with the previous research results of the Demala Group complex,the authors refer that the Demala Group complex should be a set of metamorphic complex.The complex includes not only Precambrian basement metamorphic rock series,but also Paleozoic sedimentary rock and Mesozoic granitic rock.Based on the deformation characteristics,the authors concluded that two stages of the metamorphism and deformation can be revealed in the Demala Group complex since the Mesozoic,namely Late Triassic-Early Jurassic(203–190 Ma)and Oligocene–Miocene(24–14 Ma).The early stage of metamorphism(ranging from 203–190 Ma)was related to the Late Triassic tectono-magmatism in the area.The anatexis and uplifting-exhumation of the later stage(24–14 Ma)were related to the shearing of the Jiali strike-slip fault zone.The Miocene structures are response to the large-scale southeastward escape of crustal materials and block rotation in Southeast Tibet after India-Eurasia collision.
文摘Two equal collinear cracks with coalesced interior electric saturation zones are analytically studied for two-dimensional (2D) arbitrary polarized semipermeable piezo- electric media based on a modified strip saturated model. The strip saturated model is modified here by varying the strip saturated constant electric displacement condition to the polynomially varying electric displacement conditions. Based on the linear, quadratic, and cubic electric displacement conditions on the inner and outer saturated zones, dif- ferent modified strip saturated models are proposed and studied for two equal collinear cracks. With the Stroh formalism and the complex variable technique, these fracture problems are reduced into different types of non-homogeneous Riemann Hilbert problems in unknown generalized complex potential functions. These mathematical problems are then solved with the Riemann-Hilbert approach to obtain the stress and electric displace- ment components at any point of the domain. The explicit expressions for the outer saturated zone length, the crack opening potential (COP), the crack opening displace- ment (COD), and the local intensity factors (LIFs) are derived. A numerical study is presented for the modified strip saturated model in 2D arbitrary polarized semiperme- able PZT-4 material. The obtained results are compared with those of the strip saturated model, and the effects of the polynomially varying saturation condition on the saturated zones and the applied electrical loadings are presented.
文摘Evonian massive limestones in the Northeastern Brilon reef complex comprise many marine calcareous algae. 10 genera all 12 species could be identified .They are Keega australe,Solenopora geikiei,Solenopora sp. (red algae ), Litanaia cf. perisseia,Ortonella sp.,Vermiporella sp. (green algae ); Epiphyton sp., Girvanella ducii, Girvanella problematica,?Sphaerocodium sp.,Renalcis sp. (blue green algae )and Kamaena sp.. The distribution and relative abundance of these algae are conjoined to specific factes types and therefore they are very in the interpretation of paleoenvironments. In addition, calcareous algae can be used for the geologic dating.
基金Project supported by the National Natural Science Foundation of China(No.51175404)
文摘In the 1920s, a closed-form solution of the moving Criffith crack was first obtained by Yoffe. Based on Yoffe＇s solution, the Dugdale model for the moving crack case gives a good result. However, the Dugddle model fails when the crack speed is closed to the Rayleigh wave speed because of the discontinuity occurred in the crack opening displacement （COD）. The problem is solved in this paper by introducing a restraining stress zone ahead of the crack tip and two velocity functions. The restraining stresses are linearly distributed and related to the velocity of the moving crack. An analytical solution of the problem is obtained by use of the superposition principle and a complex function method. The final result of the COD is continuous while the crack moves at a Rayleigh wave speed. The characteristics of the strain energy density （SED） and numerical results are discussed, and conclusions are given.
