Based on preliminary theoretical analysis and numerical experiment, it is found that land surface heterogeneity plays an important role in the models turbulent flux calculation. In nearly neutral atmosphere conditions...Based on preliminary theoretical analysis and numerical experiment, it is found that land surface heterogeneity plays an important role in the models turbulent flux calculation. In nearly neutral atmosphere conditions, variation coefficient of sub-scale roughness length, cell-average roughness, and reference height are main factors affecting the calculation of grid turbulent fluxes. The first factor has a determinant role on calculation deviation. The relative error generated by roughness heterogeneity could be more than 40% in some cases in certain areas (e.g., in vegetation-climate transition belt). Selecting a specific reference height may improve the calculation of turbulent flux. In stable or unstable atmosphere conditions, with sensible heat flux as an example, analysis shows that the discrepancy is correlated to the sub-grid distributions of mean wind velocity, potential temperature gradient between land surface and reference levels, and atmosphere stability near surface layer caused by the heterogeneity of land surface roughness. The calculation of turbulent flux is the most sensitive to stability in the above three factors. The above analysis shows that it is necessary to make a further consideration for the calculation deviation of the turbulent fluxes brought from land surface heterogeneity in the present numerical models.展开更多
The current coronavirus disease 2019(COVID-19)pandemic caused by severe acute respiratory syndrome coronavirus(SARS-CoV-2)remains a threat to pregnant women.However,the impact of early pregnancy SARS-CoV-2 infection o...The current coronavirus disease 2019(COVID-19)pandemic caused by severe acute respiratory syndrome coronavirus(SARS-CoV-2)remains a threat to pregnant women.However,the impact of early pregnancy SARS-CoV-2 infection on the maternal-fetal interface remains poorly understood.Here,we present a comprehensive analysis of single-cell transcriptomics and metabolomics in placental samples infected with SARS-CoV-2 during early pregnancy.Compared to control placentas,SARS-CoV-2 infection elicited immune responses at the maternal-fetal interface and induced metabolic alterations in amino acid and phospholipid profiles during the initial weeks post-infection.However,subsequent immune cell activation and heightened immune tolerance in trophoblast cells established a novel dynamic equilibrium that mitigated the impact on the maternal-fetal interface.Notably,the immune response and metabolic alterations at the maternal-fetal interface exhibited a gradual decline during the second trimester.Our study underscores the adaptive immune tolerance mechanisms and establishment of immunological balance during the first two trimesters following maternal SARS-CoV-2 infection.展开更多
The Daba Shan orocline is located at the northeastern margin of the Sichuan Basin and has been inferred as a foreland thrust-fold belt of the Qinling Orogen since the Late Triassic.A complete understanding of rock exh...The Daba Shan orocline is located at the northeastern margin of the Sichuan Basin and has been inferred as a foreland thrust-fold belt of the Qinling Orogen since the Late Triassic.A complete understanding of rock exhumation history is critical to elucidate how and when this typical orocline structure is developed.Detrital apatite fission-track dating of modern river sands is employed to reveal the regional exhumation history of the Daba Shan orocline.Four age peaks are identified and interpreted as the results of tectonic exhumation.Two older age peaks at ~150–140 and ~116–86 Ma are agreement with two main shortening deformation episodes of the Yanshanian Movement in the eastern China.The other two younger age peaks at ~69 and ~37 Ma support that the Daba Shan was reactivated by the Late Cretaceous to Cenozoic deformation which were likely related to the subduction of the Pacific Ocean and eastward growth of the Tibetan Plateau,respectively.It is worth noting that in contrast to the ~150–140 Ma rapid rock uplift and exhumation,the Middle Cretaceous exhumation(~116–86 Ma) shifted southward and continued to spread to southern tips of the Daba Shan.These exhumation variations in temporal and spatial allow a southward thrust deformation with piggyback style during the Yanshanian.展开更多
We present an experimental demonstration of ghost imaging of reflective objects with different surface roughness.The influence of the surface roughness, the transverse size of the test detector, and the reflective ang...We present an experimental demonstration of ghost imaging of reflective objects with different surface roughness.The influence of the surface roughness, the transverse size of the test detector, and the reflective angle on the signal-to-noise ratio(SNR) is analyzed by measuring the second-order correlation of the light field based on classical statistical optics. It is shown that the SNR decreases with an increment of the surface roughness and the detector's transverse size or a decrease of the reflective angle. Additionally, the comparative studies between the rough object and the smooth one under the same conditions are also discussed.展开更多
The contact stiffness of the joint surface directly affects the static and dynamic mechanical behavior,and accuracy of the machine tool.A new elastoplastic contact stiffness model is proposed by considering continuous...The contact stiffness of the joint surface directly affects the static and dynamic mechanical behavior,and accuracy of the machine tool.A new elastoplastic contact stiffness model is proposed by considering continuous and smooth contact characteristics and substrate deformation.First,the interpolation interval of cubic Hermite polynomials is improved to meet the continuous and smooth change of contact parameters during asperity deformation.Then,the micro-contact mechanism considering substrate deformation is explored by establishing an asperity-substrate system model.Furthermore,combined with statistical principles,a new contact stiffness model of the joint surface is established.Finally,the correctness of the built model is verified by comparing with experimental data and different contact models.The simulation results show that the model changes continuously and smoothly in the three deformation regions.The substrate deformation mainly affects the asperities in the elastic contact stage.The smoother is the surface,the more significant is the influence of substrate deformation.展开更多
To explain the intrinsic mechanism of the yield plateau phenomenon in commercially pure titanium,the tensile behaviors of commercially pure titanium specimens after 91.6%cryorolling and subsequent annealing at 280℃,...To explain the intrinsic mechanism of the yield plateau phenomenon in commercially pure titanium,the tensile behaviors of commercially pure titanium specimens after 91.6%cryorolling and subsequent annealing at 280℃,335℃,450℃and 600℃have been studied.The results show that the yield plateau phenomenon is a result of dislocation behaviors controlled by grain size and thus only exists within a given range of mean grain size.αgrain boundaries are the main dislocation multiplication sources of commercially pure titanium.Fine-grained microstructure could offer numerous dislocation multiplication locations during deformation.Once the applied stress is above the yielding strength,dislocations multiply rapidly and the mobile dislocation density is high.To retrieve the imposed strain rate,the mean dislocation velocity is bound to be low.Therefore,it takes time for them to interact with each other.As a result,the movement of dislocations is hardly blocked and the deformation could continue at a nearly constant applied stress.Consequently,the so-called yield plateau behavior presents in the tensile curves.The disappearance of yield plateau phenomenon in coarse-grained and ultrafi ne-grained microstructures is attributed to the quick realization of the mutual interactions among dislocations at the initial stage of tensile test.展开更多
The texture evolution behavior and its triggered mechanical anisotropy of commercially pure titanium(CP Ti) during severe cold rolling and subsequent annealing are discussed based on the optical microscopy and the ele...The texture evolution behavior and its triggered mechanical anisotropy of commercially pure titanium(CP Ti) during severe cold rolling and subsequent annealing are discussed based on the optical microscopy and the electron backscattered diffraction analyses. Some enlightening results are found. It is shown that planar textures exist under all treatments, namely the {11–29}<10–10> under rolling state, the {11–27}<10–10> under 300 °C annealing state and the {11–24}<10–10> under 500 °C annealing state. This indicates that the crystal plane indices of planar texture change toward {-12–10} with increasing annealing temperature, which is a result of crystal lattice rotation. Planar texture triggers anisotropy of the mechanical properties for CP Ti sheets under all treatments. In particular, CP Ti sheets exhibit severe and similar anisotropy behavior under rolling and 300 °C annealing states. Generally speaking, the rolling direction(RD) specimens get relatively low yield strength, high ultimate tensile strength and good plasticity, and RD + 45° specimens show relatively high yield strength, low ultimate tensile strength and good plasticity. The transverse direction specimens, however, usually exhibit high yield strength and low plasticity. It is proved that the above anisotropy behavior is mainly determined by the Schmid factor distribution of the(10–10)[11–20] prismatic slip system in different directions. Due to the non-negligible influence exerted by the(0001)[11–20] basal slip system after 500 °C annealing, the anisotropy behavior under this state is obviously different.展开更多
基金Cooperative Project (2007DFB20210) funded by the Ministry of Science and Technology of the People's Republic of Chinathe Key Project of Basic Scientific Research +1 种基金Operation fund of Chinese Academy of Meteorological Sciences (2008Z006)the Independent Research Project of LaSW (2008LASWZI04,2009LASWZF02)
文摘Based on preliminary theoretical analysis and numerical experiment, it is found that land surface heterogeneity plays an important role in the models turbulent flux calculation. In nearly neutral atmosphere conditions, variation coefficient of sub-scale roughness length, cell-average roughness, and reference height are main factors affecting the calculation of grid turbulent fluxes. The first factor has a determinant role on calculation deviation. The relative error generated by roughness heterogeneity could be more than 40% in some cases in certain areas (e.g., in vegetation-climate transition belt). Selecting a specific reference height may improve the calculation of turbulent flux. In stable or unstable atmosphere conditions, with sensible heat flux as an example, analysis shows that the discrepancy is correlated to the sub-grid distributions of mean wind velocity, potential temperature gradient between land surface and reference levels, and atmosphere stability near surface layer caused by the heterogeneity of land surface roughness. The calculation of turbulent flux is the most sensitive to stability in the above three factors. The above analysis shows that it is necessary to make a further consideration for the calculation deviation of the turbulent fluxes brought from land surface heterogeneity in the present numerical models.
基金supported by the Ministry of Science and Technology of China(2022YFC2702200,2021YFA1102900)the National Natural Science Foundation of China(Grant Nos.82022027,32270909,31721003,92168205,31871448,31820103009,and 32300684)+5 种基金supported by the key project of the Science and Technology of Shanghai Municipality(19JC1415300 and 21JC1405500)the Shanghai Municipal Medical and Health Discipline Construction Projects(2017ZZ02015)China Postdoctoral Science Foundation(2023M732660)the Postdoctoral Fellowship Program of CPSF(GZB20230523)Shanghai Municipal Health(Grant No.20214Y0254)Shanghai Pilot Program for Basic Research,Shanghai“Medical Academy Rising Star”Young Medical Talents Program,Shanghai First Maternity and Infant Hospital“Talent Reservoir”Sailing Program and the Fundamental Research Funds for the Central Universities.
文摘The current coronavirus disease 2019(COVID-19)pandemic caused by severe acute respiratory syndrome coronavirus(SARS-CoV-2)remains a threat to pregnant women.However,the impact of early pregnancy SARS-CoV-2 infection on the maternal-fetal interface remains poorly understood.Here,we present a comprehensive analysis of single-cell transcriptomics and metabolomics in placental samples infected with SARS-CoV-2 during early pregnancy.Compared to control placentas,SARS-CoV-2 infection elicited immune responses at the maternal-fetal interface and induced metabolic alterations in amino acid and phospholipid profiles during the initial weeks post-infection.However,subsequent immune cell activation and heightened immune tolerance in trophoblast cells established a novel dynamic equilibrium that mitigated the impact on the maternal-fetal interface.Notably,the immune response and metabolic alterations at the maternal-fetal interface exhibited a gradual decline during the second trimester.Our study underscores the adaptive immune tolerance mechanisms and establishment of immunological balance during the first two trimesters following maternal SARS-CoV-2 infection.
基金funded by the National Natural Science Foundation of China (Nos.42172257,41672199,41421002)MOST Special Fund from the State Key Laboratory of Continental Dynamics,Northwest Universitythe Foundation of Shaanxi Educational Committee (No.16JK1753)。
文摘The Daba Shan orocline is located at the northeastern margin of the Sichuan Basin and has been inferred as a foreland thrust-fold belt of the Qinling Orogen since the Late Triassic.A complete understanding of rock exhumation history is critical to elucidate how and when this typical orocline structure is developed.Detrital apatite fission-track dating of modern river sands is employed to reveal the regional exhumation history of the Daba Shan orocline.Four age peaks are identified and interpreted as the results of tectonic exhumation.Two older age peaks at ~150–140 and ~116–86 Ma are agreement with two main shortening deformation episodes of the Yanshanian Movement in the eastern China.The other two younger age peaks at ~69 and ~37 Ma support that the Daba Shan was reactivated by the Late Cretaceous to Cenozoic deformation which were likely related to the subduction of the Pacific Ocean and eastward growth of the Tibetan Plateau,respectively.It is worth noting that in contrast to the ~150–140 Ma rapid rock uplift and exhumation,the Middle Cretaceous exhumation(~116–86 Ma) shifted southward and continued to spread to southern tips of the Daba Shan.These exhumation variations in temporal and spatial allow a southward thrust deformation with piggyback style during the Yanshanian.
基金National Natural Science Foundation of China(NSFC)(61372102,61571183)Natural Science Foundation of Hunan Province(2017JJ1014)
文摘We present an experimental demonstration of ghost imaging of reflective objects with different surface roughness.The influence of the surface roughness, the transverse size of the test detector, and the reflective angle on the signal-to-noise ratio(SNR) is analyzed by measuring the second-order correlation of the light field based on classical statistical optics. It is shown that the SNR decreases with an increment of the surface roughness and the detector's transverse size or a decrease of the reflective angle. Additionally, the comparative studies between the rough object and the smooth one under the same conditions are also discussed.
基金This work was supported by the National Natural Science Foundation of China(Grant Number 51975449)the Key Research and Development Program of Shaanxi(Number 2021GY-309)。
文摘The contact stiffness of the joint surface directly affects the static and dynamic mechanical behavior,and accuracy of the machine tool.A new elastoplastic contact stiffness model is proposed by considering continuous and smooth contact characteristics and substrate deformation.First,the interpolation interval of cubic Hermite polynomials is improved to meet the continuous and smooth change of contact parameters during asperity deformation.Then,the micro-contact mechanism considering substrate deformation is explored by establishing an asperity-substrate system model.Furthermore,combined with statistical principles,a new contact stiffness model of the joint surface is established.Finally,the correctness of the built model is verified by comparing with experimental data and different contact models.The simulation results show that the model changes continuously and smoothly in the three deformation regions.The substrate deformation mainly affects the asperities in the elastic contact stage.The smoother is the surface,the more significant is the influence of substrate deformation.
基金financial support from the National Natural Science Foundation of China(Grant No.51801132)the China scholarship council(CSC NO.201906935013)for X.H.Shi.Specially。
文摘To explain the intrinsic mechanism of the yield plateau phenomenon in commercially pure titanium,the tensile behaviors of commercially pure titanium specimens after 91.6%cryorolling and subsequent annealing at 280℃,335℃,450℃and 600℃have been studied.The results show that the yield plateau phenomenon is a result of dislocation behaviors controlled by grain size and thus only exists within a given range of mean grain size.αgrain boundaries are the main dislocation multiplication sources of commercially pure titanium.Fine-grained microstructure could offer numerous dislocation multiplication locations during deformation.Once the applied stress is above the yielding strength,dislocations multiply rapidly and the mobile dislocation density is high.To retrieve the imposed strain rate,the mean dislocation velocity is bound to be low.Therefore,it takes time for them to interact with each other.As a result,the movement of dislocations is hardly blocked and the deformation could continue at a nearly constant applied stress.Consequently,the so-called yield plateau behavior presents in the tensile curves.The disappearance of yield plateau phenomenon in coarse-grained and ultrafi ne-grained microstructures is attributed to the quick realization of the mutual interactions among dislocations at the initial stage of tensile test.
基金the National Natural Science Foundation of China(Grant No.51801132)the China Scholarship Council(CSC NO.201906935013)for X.H.Shi+1 种基金the School Foundation of Taiyuan University of Technology(Grant No.2017QN02)the National Key Laboratory for Remanufacturing,Academy of Armored Forces Engineering(No.61420050204)。
文摘The texture evolution behavior and its triggered mechanical anisotropy of commercially pure titanium(CP Ti) during severe cold rolling and subsequent annealing are discussed based on the optical microscopy and the electron backscattered diffraction analyses. Some enlightening results are found. It is shown that planar textures exist under all treatments, namely the {11–29}<10–10> under rolling state, the {11–27}<10–10> under 300 °C annealing state and the {11–24}<10–10> under 500 °C annealing state. This indicates that the crystal plane indices of planar texture change toward {-12–10} with increasing annealing temperature, which is a result of crystal lattice rotation. Planar texture triggers anisotropy of the mechanical properties for CP Ti sheets under all treatments. In particular, CP Ti sheets exhibit severe and similar anisotropy behavior under rolling and 300 °C annealing states. Generally speaking, the rolling direction(RD) specimens get relatively low yield strength, high ultimate tensile strength and good plasticity, and RD + 45° specimens show relatively high yield strength, low ultimate tensile strength and good plasticity. The transverse direction specimens, however, usually exhibit high yield strength and low plasticity. It is proved that the above anisotropy behavior is mainly determined by the Schmid factor distribution of the(10–10)[11–20] prismatic slip system in different directions. Due to the non-negligible influence exerted by the(0001)[11–20] basal slip system after 500 °C annealing, the anisotropy behavior under this state is obviously different.