Transformers have recently lead to encouraging progress in computer vision.In this work,we present new baselines by improving the original Pyramid Vision Transformer(PVT v1)by adding three designs:(i)a linear complexi...Transformers have recently lead to encouraging progress in computer vision.In this work,we present new baselines by improving the original Pyramid Vision Transformer(PVT v1)by adding three designs:(i)a linear complexity attention layer,(ii)an overlapping patch embedding,and(iii)a convolutional feed-forward network.With these modifications,PVT v2 reduces the computational complexity of PVT v1 to linearity and provides significant improvements on fundamental vision tasks such as classification,detection,and segmentation.In particular,PVT v2 achieves comparable or better performance than recent work such as the Swin transformer.We hope this work will facilitate state-ofthe-art transformer research in computer vision.Code is available at https://github.com/whai362/PVT.展开更多
There is a massive amount of geomorphic evidence for active tectonics in the Longmen Shan at the eastern margin of the Tibetan plateau. We have surveyed some typical geomorphic markers including the Wenchuan-Maowen, B...There is a massive amount of geomorphic evidence for active tectonics in the Longmen Shan at the eastern margin of the Tibetan plateau. We have surveyed some typical geomorphic markers including the Wenchuan-Maowen, Beichuan-Yingxiu and Pengxian-Guanxian faults, terrace offsets, scarps, fault-controlled saddles, dextral shutter ridges, dextral channel offsets, graben, shatter belts, and pull-apart basins. Electron spin resonance （ESR） and thermoluminescence（TL） ages were obtained using silty sand taken from below the surface of the sediments. According to these data, we calculated the rates of thrusting and strike-slip, and the results indicate that Cenozoic tectonic shortening at the plateau margin is minor with the rate of thrusting less than 1.10 mm/a and the rate of strike-slipping less than 1.46 mm/a. The Longmen Shan is a zone of NNE-trending dextral shear with slip-dip ratio of 6：1-1.3：1. From NW to SE, the thrust component becomes smaller, whereas the strike-slip component becomes larger.展开更多
根据龙门山前陆盆地西缘沉降中心、冲积扇侧向迁移、活动构造地貌和古地磁等标志及龙门山在中生代以来的走滑作用和走滑方向的标定研究,结果表明:龙门山断裂带具有走滑性质,走滑方向曾发生过反转,在反转之前以左行走滑作用为特征,在反...根据龙门山前陆盆地西缘沉降中心、冲积扇侧向迁移、活动构造地貌和古地磁等标志及龙门山在中生代以来的走滑作用和走滑方向的标定研究,结果表明:龙门山断裂带具有走滑性质,走滑方向曾发生过反转,在反转之前以左行走滑作用为特征,在反转之后以右行走滑作用为特征。根据地层记录和古地磁证据,认为龙门山走滑方向反转的时间应介于43 M a^3.6 M a之间,即由中生代至早新生代时期的左行走滑作用反转为晚新生代时期的右行走滑作用。然对龙门山断裂带走滑方向反转的成因初步分析认为晚新生代龙门山右行走滑作用是印-亚碰撞后构造作用的产物,晚三叠世至早新生代左行走滑作用是青藏高原自晚三叠世以来大陆碰撞作用导致松潘-甘孜褶皱带北东-南西向缩短的产物。展开更多
The eastern margin of the Tibetan Plateau is marked by an extremely steep mountain front with relief of over 5 km. This topography,coupled with abundant Mesozoic thrusts within the margin,explains why tectonic maps of...The eastern margin of the Tibetan Plateau is marked by an extremely steep mountain front with relief of over 5 km. This topography,coupled with abundant Mesozoic thrusts within the margin,explains why tectonic maps of the India-Asia collision typically show the eastern margin as a major thrust zone. Actually,it does not like that. Field observations suggest that the margin is better characterized as a zone of NNE-directed dextral shear with extensive strike-slip faulting and secondary thrusting. The high relief and steep gradients are partially explained by erosional unloading of an elastic lithosphere;the pre-erosion inherited topography may be the inherited Mesozoic thrust belt landscape modified by a component of Cenozoic tectonic shortening.展开更多
We study a new algorithm for solvingparabolic partial differential equations(PDEs)and backward stochastic differential equations(BSDEs)in high dimension,which is based on an analogy between the BSDE and reinforcement ...We study a new algorithm for solvingparabolic partial differential equations(PDEs)and backward stochastic differential equations(BSDEs)in high dimension,which is based on an analogy between the BSDE and reinforcement learning with the gradient of the solution playing the role of the policy function,and the loss function given by the error between the prescribed terminal condition and the solution of the BSDE.The policy function is then approximated by a neural network,as is done in deep reinforcement learning.Numerical results using TensorFlow illustrate the efficiency and accuracy of the studied algorithm for several 100-dimensional nonlinear PDEs from physics and finance such as the Allen–Cahn equation,the Hamilton–Jacobi–Bellman equation,and a nonlinear pricing model for financial derivatives.展开更多
C-type adakites have been commonly considered as a result of partial melting of the mafic lower continental crust (LCC) at high pressure, as supported by high P-T experiments on hydrous basalts. However, because the m...C-type adakites have been commonly considered as a result of partial melting of the mafic lower continental crust (LCC) at high pressure, as supported by high P-T experiments on hydrous basalts. However, because the mafic eclogitic LCC is generally dry, experiments on water-bearing materials cannot be used to constrain the melting processes of the dry mafic LCC. Due to the lack of systematic melting experimental studies on dry mafic rocks at crustal pressures, MELTs software was applied to simulating melting of the dry mafic LCC at 1–2 GPa. Comparison of model results with experimental data indicates that, when melting de-gree is greater than 20%, melts from the dry mafic LCC at 1–3 GPa cannot produce the C-type adakitic melt with high SiO2 con-tent (～70%). Although the limited experimental results about dry mafic rock melting at 1–2 GPa in the literature suggest that low degree melting (<10%) cannot produce silicic melt either, MELTs software simulation shows that, at pressure >1.8 GPa, low-degree melting can produce dacitic melt with high K2O/Na2O (～1) if SiO2 content of the melt is controlled by residual garnet. Furthermore, the simulation also suggests that, if pressure is <1.8 GPa, abundant plagioclase (plg) in the residual phase may de-crease SiO2 content in the melt to below 62%, much lower than that of the C-type adakites observed in eastern China. Given the high P-T conditions required to produce melts with high SiO2 and extremely low HREE contents, such melts could easily be con-taminated by other crustal-derived melts, implying that the C-type adakites from eclogite melting could be less commonly ob-served in the outcrops than previously believed. Besides the interpretation that garnet fractionates Sr, Y, and REE, high Sr/Y and La/Yb could be also produced by multiple ways such as inheriting the source features and fractional crystallizing clinopyroxene (cpx). Therefore, it may be problematic using high Sr/Y and La/Yb as criteria to identify adakites. Instead, REE patterns with strong depleti展开更多
Lightweight,ultra-flexible,and robust crosslinked transition metal carbide(Ti3C2 MXene)coated polyimide(PI)(C-MXene@PI)porous composites are manufactured via a scalable dip-coating followed by chemical crosslinking ap...Lightweight,ultra-flexible,and robust crosslinked transition metal carbide(Ti3C2 MXene)coated polyimide(PI)(C-MXene@PI)porous composites are manufactured via a scalable dip-coating followed by chemical crosslinking approach.In addition to the hydrophobicity,anti-oxidation and extreme-temperature stability,efficient utilization of the intrinsic conductivity of MXene,the interfacial polarization between MXene and PI,and the micrometer-sized pores of the composite foams are achieved.Consequently,the composites show a satisfactory X-band electromagnetic interference(EMI)shielding effectiveness of 22.5 to 62.5 dB at a density of 28.7 to 48.7 mg cm−3,leading to an excellent surface-specific SE of 21,317 dB cm^(2)g^(−1).Moreover,the composite foams exhibit excellent electrothermal performance as flexible heaters in terms of a prominent,rapid reproducible,and stable electrothermal effect at low voltages and superior heat performance and more uniform heat distribution compared with the commercial heaters composed of alloy plates.Furthermore,the composite foams are well attached on a human body to check their electromechanical sensing performance,demonstrating the sensitive and reliable detection of human motions as wearable sensors.The excellent EMI shielding performance and multifunctionalities,along with the facile and easy-to-scalable manufacturing techniques,imply promising perspectives of the porous C-MXene@PI composites in next-generation flexible electronics,aerospace,and smart devices.展开更多
基金National Natural Science Foundation of China under Grant Nos.61672273 and 61832008Science Foundation for Distinguished Young Scholars of Jiangsu under Grant No.BK20160021+1 种基金Postdoctoral Innovative Talent Support Program of China under Grant Nos.BX20200168,2020M681608General Research Fund of Hong Kong under Grant No.27208720。
文摘Transformers have recently lead to encouraging progress in computer vision.In this work,we present new baselines by improving the original Pyramid Vision Transformer(PVT v1)by adding three designs:(i)a linear complexity attention layer,(ii)an overlapping patch embedding,and(iii)a convolutional feed-forward network.With these modifications,PVT v2 reduces the computational complexity of PVT v1 to linearity and provides significant improvements on fundamental vision tasks such as classification,detection,and segmentation.In particular,PVT v2 achieves comparable or better performance than recent work such as the Swin transformer.We hope this work will facilitate state-ofthe-art transformer research in computer vision.Code is available at https://github.com/whai362/PVT.
基金This research was supported by the National Nature Foundation of China （49803031, 40372084） the Seismic Scientific United Fund （95-07-0425）+3 种基金 US National Science Foundation grant EAR-0125565 ETH Forschungskommission grant TH-4/03-01 Key Subject Program of Sichuan province Grant No. SZD0408 and the Program for the Subject of Ph.D. in Higher Education Institute, Grant No.20050616004.
文摘There is a massive amount of geomorphic evidence for active tectonics in the Longmen Shan at the eastern margin of the Tibetan plateau. We have surveyed some typical geomorphic markers including the Wenchuan-Maowen, Beichuan-Yingxiu and Pengxian-Guanxian faults, terrace offsets, scarps, fault-controlled saddles, dextral shutter ridges, dextral channel offsets, graben, shatter belts, and pull-apart basins. Electron spin resonance （ESR） and thermoluminescence（TL） ages were obtained using silty sand taken from below the surface of the sediments. According to these data, we calculated the rates of thrusting and strike-slip, and the results indicate that Cenozoic tectonic shortening at the plateau margin is minor with the rate of thrusting less than 1.10 mm/a and the rate of strike-slipping less than 1.46 mm/a. The Longmen Shan is a zone of NNE-trending dextral shear with slip-dip ratio of 6：1-1.3：1. From NW to SE, the thrust component becomes smaller, whereas the strike-slip component becomes larger.
文摘根据龙门山前陆盆地西缘沉降中心、冲积扇侧向迁移、活动构造地貌和古地磁等标志及龙门山在中生代以来的走滑作用和走滑方向的标定研究,结果表明:龙门山断裂带具有走滑性质,走滑方向曾发生过反转,在反转之前以左行走滑作用为特征,在反转之后以右行走滑作用为特征。根据地层记录和古地磁证据,认为龙门山走滑方向反转的时间应介于43 M a^3.6 M a之间,即由中生代至早新生代时期的左行走滑作用反转为晚新生代时期的右行走滑作用。然对龙门山断裂带走滑方向反转的成因初步分析认为晚新生代龙门山右行走滑作用是印-亚碰撞后构造作用的产物,晚三叠世至早新生代左行走滑作用是青藏高原自晚三叠世以来大陆碰撞作用导致松潘-甘孜褶皱带北东-南西向缩短的产物。
基金supported by the NSF(EAR 9803484)to M.EllisA.Densmore,and NSFC(40372084)SZD0408 and EYTP to Li Yong
文摘The eastern margin of the Tibetan Plateau is marked by an extremely steep mountain front with relief of over 5 km. This topography,coupled with abundant Mesozoic thrusts within the margin,explains why tectonic maps of the India-Asia collision typically show the eastern margin as a major thrust zone. Actually,it does not like that. Field observations suggest that the margin is better characterized as a zone of NNE-directed dextral shear with extensive strike-slip faulting and secondary thrusting. The high relief and steep gradients are partially explained by erosional unloading of an elastic lithosphere;the pre-erosion inherited topography may be the inherited Mesozoic thrust belt landscape modified by a component of Cenozoic tectonic shortening.
文摘We study a new algorithm for solvingparabolic partial differential equations(PDEs)and backward stochastic differential equations(BSDEs)in high dimension,which is based on an analogy between the BSDE and reinforcement learning with the gradient of the solution playing the role of the policy function,and the loss function given by the error between the prescribed terminal condition and the solution of the BSDE.The policy function is then approximated by a neural network,as is done in deep reinforcement learning.Numerical results using TensorFlow illustrate the efficiency and accuracy of the studied algorithm for several 100-dimensional nonlinear PDEs from physics and finance such as the Allen–Cahn equation,the Hamilton–Jacobi–Bellman equation,and a nonlinear pricing model for financial derivatives.
基金supported by the National Natural Science Foundation of China (40773013)
文摘C-type adakites have been commonly considered as a result of partial melting of the mafic lower continental crust (LCC) at high pressure, as supported by high P-T experiments on hydrous basalts. However, because the mafic eclogitic LCC is generally dry, experiments on water-bearing materials cannot be used to constrain the melting processes of the dry mafic LCC. Due to the lack of systematic melting experimental studies on dry mafic rocks at crustal pressures, MELTs software was applied to simulating melting of the dry mafic LCC at 1–2 GPa. Comparison of model results with experimental data indicates that, when melting de-gree is greater than 20%, melts from the dry mafic LCC at 1–3 GPa cannot produce the C-type adakitic melt with high SiO2 con-tent (～70%). Although the limited experimental results about dry mafic rock melting at 1–2 GPa in the literature suggest that low degree melting (<10%) cannot produce silicic melt either, MELTs software simulation shows that, at pressure >1.8 GPa, low-degree melting can produce dacitic melt with high K2O/Na2O (～1) if SiO2 content of the melt is controlled by residual garnet. Furthermore, the simulation also suggests that, if pressure is <1.8 GPa, abundant plagioclase (plg) in the residual phase may de-crease SiO2 content in the melt to below 62%, much lower than that of the C-type adakites observed in eastern China. Given the high P-T conditions required to produce melts with high SiO2 and extremely low HREE contents, such melts could easily be con-taminated by other crustal-derived melts, implying that the C-type adakites from eclogite melting could be less commonly ob-served in the outcrops than previously believed. Besides the interpretation that garnet fractionates Sr, Y, and REE, high Sr/Y and La/Yb could be also produced by multiple ways such as inheriting the source features and fractional crystallizing clinopyroxene (cpx). Therefore, it may be problematic using high Sr/Y and La/Yb as criteria to identify adakites. Instead, REE patterns with strong depleti
基金support of the Qilu Young Scholar Program of Shandong University(No.31370082163127)the authors acknowledge funding from the support from the Chinese Scholarship Council(to NW,project#201709370040).
文摘Lightweight,ultra-flexible,and robust crosslinked transition metal carbide(Ti3C2 MXene)coated polyimide(PI)(C-MXene@PI)porous composites are manufactured via a scalable dip-coating followed by chemical crosslinking approach.In addition to the hydrophobicity,anti-oxidation and extreme-temperature stability,efficient utilization of the intrinsic conductivity of MXene,the interfacial polarization between MXene and PI,and the micrometer-sized pores of the composite foams are achieved.Consequently,the composites show a satisfactory X-band electromagnetic interference(EMI)shielding effectiveness of 22.5 to 62.5 dB at a density of 28.7 to 48.7 mg cm−3,leading to an excellent surface-specific SE of 21,317 dB cm^(2)g^(−1).Moreover,the composite foams exhibit excellent electrothermal performance as flexible heaters in terms of a prominent,rapid reproducible,and stable electrothermal effect at low voltages and superior heat performance and more uniform heat distribution compared with the commercial heaters composed of alloy plates.Furthermore,the composite foams are well attached on a human body to check their electromechanical sensing performance,demonstrating the sensitive and reliable detection of human motions as wearable sensors.The excellent EMI shielding performance and multifunctionalities,along with the facile and easy-to-scalable manufacturing techniques,imply promising perspectives of the porous C-MXene@PI composites in next-generation flexible electronics,aerospace,and smart devices.
