Here we present a novel approach of intercritical heat treatment for microstructure tailoring,in which intercritical annealing is introduced between conventional quenching and tempering.This induced a heterogeneous mi...Here we present a novel approach of intercritical heat treatment for microstructure tailoring,in which intercritical annealing is introduced between conventional quenching and tempering.This induced a heterogeneous microstructure consisting of soft intercritical ferrite and hard tempered martensite,resulting in a low yield ratio(YR)and high impact toughness in a high-strength low-alloy steel.The initial yielding and subsequent work hardening behavior of the steel during tensile deformation were modified by the presence of soft intercritical ferrite after intercritical annealing,in comparison to the steel with full martensitic microstructure.The increase in YR was related to the reduction in hardness difference between the soft and hard phases due to the precipitation of nano-carbides and the recovery of dislocations during tempering.The excellent low-temperature toughness was ascribed not only to the decrease in probability of microcrack initiation for the reduction of hardness difference between two phases,but also to the increase in resistance of microcrack propagation caused by the high density of high angle grain boundaries.展开更多
Large-scale and heavily jointed rocks have inherent planes of anisotropy and secondary structural planes,such as dominant joint sets and random fractures,which result in significant differences in their failure mechan...Large-scale and heavily jointed rocks have inherent planes of anisotropy and secondary structural planes,such as dominant joint sets and random fractures,which result in significant differences in their failure mechanism and deformation behavior compared to other rock types.To address this issue,inherent anisotropic rocks with large-scale and dense joints are considered to be composed of the rock matrix,inherent planes of anisotropy,and secondary structural planes.Then a new implicit continuum model called LayerDFN is developed based on the crack tensor and damage tensor theories to characterize the mechanical properties of inherent anisotropic rocks.Furthermore,the LayerDFN model is implemented in the FLAC3D software,and a series of numerical results for typical example problems is compared with those obtained from the 3DEC,the analytical solutions,similar classical models,laboratory uniaxial compression tests,and field rigid bearing plate tests.The results demonstrate that the LayerDFN model can effectively capture the anisotropic mechanical properties of inherent anisotropic rocks,and can quantitatively characterize the damaging effect of the secondary structural planes.Overall,the numerical method based on the LayerDFN model provides a comprehensive and reliable approach for describing and analyzing the behavior of inherent anisotropic rocks,which will provide valuable insights for engineering design and decision-making processes.展开更多
Background:Osteosarcoma is the most common bone malignancy in children and adolescents,and 20%-30%of the patients suffer from poor prognosis because of individual chemoresistance.The Hippo/yes-associated protein(YAP) ...Background:Osteosarcoma is the most common bone malignancy in children and adolescents,and 20%-30%of the patients suffer from poor prognosis because of individual chemoresistance.The Hippo/yes-associated protein(YAP) signaling pathway has been shown to play a role in tumor chemoresistance,but no previous report has focused on its involvement in osteosarcoma chemoresistance.This study aimed to investigate the role of the Hippo/YAP signaling pathway in osteosarcoma chemoresistance and to determine potential treatment targets.Methods:Using the Cell Titer-Glo Luminescent cell viability assay and flow cytometry analysis,we determined the proliferation and chemosensitivity of YAP-overexpressing and YAP-knockdown osteosarcoma cells.In addition,using western blotting and the real-time polymerase chain reaction technique,we investigated the alteration of the Hippo/YAP signaling pathway in osteosarcoma cells treated with chemotherapeutic agents.Results:Mammalian sterile 20-like kinase 1(MST1) degradation was increased,and large tumor suppressor kinase1/2(LAT51/2) total protein levels were decreased by methotrexate and doxorubicin,which increased activation and nuclear translocation of YAP.Moreover,YAP increased the proliferation and chemoresistance of MG63 cells.Conclusions:The Hippo/YAP signaling pathway plays a role in osteosarcoma chemoresistance,and YAP is a potential target for reducing chemoresistance.展开更多
30-m Global Land Cover(GLC)data products permit the detection of land cover changes at the scale of most human land activities,and are therefore used as fundamental information for sustainable development,environmenta...30-m Global Land Cover(GLC)data products permit the detection of land cover changes at the scale of most human land activities,and are therefore used as fundamental information for sustainable development,environmental change studies,and many other societal benefit areas.In the past few years,increasing efforts have been devoted to the accuracy assessment of GlobeLand30 and other finer-resolution GLC data products.However,most of them were conducted either within a limited percentage of map sheets selected from a global scale or in some individual countries(areas),and there are still many areas where the uncertainty of 30-m resolution GLC data products remains to be validated and documented.In order to promote a comprehensive and collaborative validation of 30-m GLC data products,the GEO Global Land Cover Community Activity had organized a project from 2015 to 2017,to examine and explore its major problems,including the lack of international agreed validation guidelines and on-line tools for facilitating collaborative validation activities.With the joint effort of experts and users from 30 GEO member countries or participating organizations,a technical specification for 30-m GLC validation was developed based on the findings and experiences.An on-line validation tool,GLCVal,was developed by integrating land cover validation procedures with the service computing technologies.About 20 countries(regions)have completed the accuracy assessment of GlobeLand30 for their territories with the guidance of the technical specification and the support of GLCVal.展开更多
This paper presents a novel guidance law to intercept non-maneuvering targets with impact angle and lateral acceleration command constraints. Firstly, we formulate the impact angle control to track the desired line-of...This paper presents a novel guidance law to intercept non-maneuvering targets with impact angle and lateral acceleration command constraints. Firstly, we formulate the impact angle control to track the desired line-of-sight(LOS) angle, which is achieved by selecting the missile s lateral acceleration to enforce the sliding mode on a sliding surface at impact time. Secondly, we use the Lyapunov stability theory to prove the stability and finite time convergence of the proposed nonlinear sliding surface. Thirdly, we introduce the wavelet neural network(WNN) to adaptively update the additional control command and reduce the high-frequency chattering of sliding mode control(SMC). The proposed guidance law, denoted WNNSMC guidance law with impact angle constraint,combines the SMC methodology with WNN to improve the robustness and reduce the chattering of the system. Finally, numerical simulations are performed to demonstrate the validity and effectiveness of the WNNSMC guidance law.展开更多
During the past thirty years, two generations of low alloy steels(ferrite/pearlite followed by bainite/martensite) have been developed and widely used in structural applications. The third-generation of low alloy stee...During the past thirty years, two generations of low alloy steels(ferrite/pearlite followed by bainite/martensite) have been developed and widely used in structural applications. The third-generation of low alloy steels is expected to achieve high strength and improved ductility and toughness, while satisfying the new demands for weight reduction, greenness, and safety. This paper reviews recent progress in the development of third-generation low alloy steels with an M^3 microstructure, namely, microstructures with multi-phase, meta-stable austenite, and multi-scale precipitates. The review summarizes the alloy designs and processing routes of microstructure control, and the mechanical properties of the alloys.The stabilization of retained austenite in low alloy steels is especially emphasized. Multi-scale nano-precipitates, including carbides of microalloying elements and Cu-rich precipitates obtained in third-generation low alloy steels, are then introduced. The structure–property relationships of third-generation alloys are also discussed. Finally, the promises and challenges to future applications are explored.展开更多
According to the classic doctrine of angiosperm evolution,the archetype carpel in angiosperms is of plicate form.However,this concept is facing increasing challenges from the systematics based on molecular data,which ...According to the classic doctrine of angiosperm evolution,the archetype carpel in angiosperms is of plicate form.However,this concept is facing increasing challenges from the systematics based on molecular data,which now takes ascidiate carpel as ancestral.This reorientation in evolutionary thinking cannot be fully achieved unless there is supporting fossil evidence.Here a fruit, named Liaoningfructus,is reported from the famous Yixian Formation(Early Cretaceous,125 Ma), which yielded several pioneer angiosperms in the past decades.The configuration of the fruit suggests that the carpel giving rise to the fruit is most likely ascidiate,favoring the above reorientation.There are two seeds in the fruit,and at least one of them is served by a vascular bundle arising from the bottom of the fruit,implying a basal placentation in the former carpel,which again is different from the classic thinking.This discovery not only enhances the diversity of angiosperms in the Yixian Formation,but also accelerates the on-going switching of thinking on angiosperm evolution.展开更多
In this paper, a novel fuzzy sliding mode control（FSMC） guidance law with terminal constraints of miss distance, impact angle and acceleration is presented for a constant speed missile against the stationary or slow...In this paper, a novel fuzzy sliding mode control（FSMC） guidance law with terminal constraints of miss distance, impact angle and acceleration is presented for a constant speed missile against the stationary or slowly moving target. The proposed guidance law combines the sliding mode control algorithm with a fuzzy logic control scheme for the lag-free system and the first-order lag system. Through using Lyapunov stability theory, we prove the sliding surface converges to zero in finite time. Furthermore, considering the uncertain information and system disturbances, the guidance gains are on-line optimized by fuzzy logic technique. Numerical simulations are performed to demonstrate the performance of the FSMC guidance law and the results illustrate the validity and effectiveness of the proposed guidance law.展开更多
Objective:To observe the regulatory impact of immune inhibitors on T cells in rats.Method:Forty SD rats were selected and randomly divided into experimental group and control group.Rapamycin(SRL)0.4 mg/d to fill the s...Objective:To observe the regulatory impact of immune inhibitors on T cells in rats.Method:Forty SD rats were selected and randomly divided into experimental group and control group.Rapamycin(SRL)0.4 mg/d to fill the stomach of the former one,saline lavage was used with the latter one for two weeks.Using flow cytometry to detect the two groups of rats with spleen and thymus level of CD4+CD25+T cells;and the spleen cells FoxP3 mRNA expression;Using ELISA method to detect TGF-β,IL-10 levels.Results:The peripheral blood,spleen and thymus of CD4+CD25+T cells accounted for the proportion of mononuclear cells were significantly higher than that of control group(P<0.05);FoxP3 mRNA expression quantity also significantly higher than the control group(P<0.05);Experimental TGF-βin rats,IL-10 levels are significantly higher than control group(P<0.05).Conclusions:Immune inhibitors can regulatory CD4+CD25+foxp3+T cells in rats,a single nuclear cell proportion increase,shows that it can induce rat CD4+CD25+foxp3+regulatory T cells proliferation.展开更多
The shear behavior of large-scale weak intercalation shear zones(WISZs)often governs the stability of foundations,rock slopes,and underground structures.However,due to their wide distribution,undulating morphology,com...The shear behavior of large-scale weak intercalation shear zones(WISZs)often governs the stability of foundations,rock slopes,and underground structures.However,due to their wide distribution,undulating morphology,complex fabrics,and varying degrees of contact states,characterizing the shear behavior of natural and complex large-scale WISZs precisely is challenging.This study proposes an analytical method to address this issue,based on geological fieldwork and relevant experimental results.The analytical method utilizes the random field theory and Kriging interpolation technique to simplify the spatial uncertainties of the structural and fabric features for WISZs into the spatial correlation and variability of their mechanical parameters.The Kriging conditional random field of the friction angle of WISZs is embedded in the discrete element software 3DEC,enabling activation analysis of WISZ C2 in the underground caverns of the Baihetan hydropower station.The results indicate that the activation scope of WISZ C2 induced by the excavation of underground caverns is approximately 0.5e1 times the main powerhouse span,showing local activation.Furthermore,the overall safety factor of WISZ C2 follows a normal distribution with an average value of 3.697.展开更多
Non-noble bimetals have attracted extensive attention for their natural aboundance and low cost,but it remains a big challenge to design and synthesize novel supported non-noble bimetal nanocatalyst in a controllable ...Non-noble bimetals have attracted extensive attention for their natural aboundance and low cost,but it remains a big challenge to design and synthesize novel supported non-noble bimetal nanocatalyst in a controllable and high-efficient manner.Herein,a novel hollow spherical supported non-noble bimetal nanocatalyst with porous carbon shell as the continuous matrix and Cu/Co bimetal nanoparticles as the dispersion phase is successfully fabricated by a convenient strategy involving spray drying and subsequent heat treatment.The morphology and microstructure depend catalyst activity of the hollow spherical supported catalyst has been studied systematically.It is found that the heating temperature plays a critical role in determining the microstructure and catalytic performance of the products.With an optimal heating temperature of 600°C,the corresponding product exhibits the highest normalized reaction rate constant(k_(n))of 25.4 s^(-1)g^(-1)for catalytic reduction of 4-notrophenol,which can be attributed to the suitable synergism of the well-defined bimetal structure,combined effect of the two metallic phases and the metal-support interaction.This work provides an additional strategy for the simultaneous formation of both the support and the active loading phase of supported non-noble bimetal nanocatalyst,and may shed some light on the high-efficiency synthesis of other supported heterostructure with various compositions and properties.展开更多
This study presents a simple technique for strengthening the adhesive-bond strength between aluminium(Al)substrate and carbon fibre reinforced polymer(CFRP) utilising resin pre-coating(RPC) with carbon nanotubes(CNTs)...This study presents a simple technique for strengthening the adhesive-bond strength between aluminium(Al)substrate and carbon fibre reinforced polymer(CFRP) utilising resin pre-coating(RPC) with carbon nanotubes(CNTs). The CNT-containing RPC solution with 90 wt% acetone and 10 wt% resin(without hardener) was applied onto Al substrates, where micro-/nano-vertical channels had been created by chemical or mechanical surface treatments to accommodate CNTs. RPC was able to fill all micro-/nano-cavities over the Al substrate surface, then CNTs were pulled into those vertical micro-channels by the capillary action generated from acetone evaporation.Normal epoxy adhesive(resin + hardener) was applied after the CNT-containing RPC treatment. CNTs bridging across the interface between the adhesive joint and Al substrate and sealing of micro-/nano-cavities by RPC effectively enhanced the interfacial shear bond strength between the Al substrate and CFRP by 30–100%depending on the Al substrate surface profiles. Al substrates with two different chemical treatments were compared in this study for the effectiveness of CNT interfacial reinforcement. Results from a steel substrate after sandblasting were also included for comparison.展开更多
Layered rock mass is a type of engineering rock mass with sound mechanical anisotropy,which is generally unfavorable to the stability of underground works.To investigate the strength anisotropy of layered rock,the Moh...Layered rock mass is a type of engineering rock mass with sound mechanical anisotropy,which is generally unfavorable to the stability of underground works.To investigate the strength anisotropy of layered rock,the Mohr-Coulomb and Hoek-Brown criteria are introduced to establish the two transverse isotropic strength criteria based on Jaeger's single weak plane theory and maximum axial strain theory,and parameter determination methods.Furthermore,the sensitivity of strength parameters(K 1,K 2,and K 3)that are used to characterize the anisotropy strength of non-sliding failure involved in the strength criteria and confining pressure are investigated.The results demonstrate that strength parameters K 1 and K 2 affect the strength of layered rock samples at all bedding angles except for the bedding angle of 90°and the angle range that can cause the shear sliding failure along the bedding plane.The strength of samples at any bedding angle decreases with increasing K 1,whereas the opposite is for K 2.Except for bedding angles of 0°and 90°and the bedding angle range that can cause the shear sliding along the bedding plane,K 3 has an impact on the strength of rock samples with other bedding angles that the specimens'strength increases with increase of K 3.In addition,the strength of the rock sample increases as confining pressure rises.Furthermore,the uniaxial and triaxial tests of chlorite schist samples were carried out to verify and evaluate the strength criteria proposed in the paper.It shows that the predicted strength is in good agreement with the experimental results.To test the applicability of the strength criterion,the strength data of several types of rock in the literature are compared.Finally,a comparison is made between the fitting effects of the two strength criteria and other available criteria for layered rocks.展开更多
Three-dimensional(3 D)topological insulators(TIs)are candidate materials for various electronic and spintronic devices due to their strong spin-orbit coupling and unique surface electronic structure.Rapid,low-cost pre...Three-dimensional(3 D)topological insulators(TIs)are candidate materials for various electronic and spintronic devices due to their strong spin-orbit coupling and unique surface electronic structure.Rapid,low-cost preparation of large-area TI thin films compatible with conventional semiconductor technology is the key to the practical applications of TIs.Here we show that wafer-sized Bi2Te3 family TI and magnetic TI films with decent quality and well-controlled composition and properties can be prepared on amorphous SiO2/Si substrates by magnetron cosputtering.The SiO2/Si substrates enable us to electrically tune(Bi1-xSbx)2Te3 and Cr-doped(Bi1-xSbx)2 Te3 TI films between p-type and n-type behavior and thus study the phenomena associated with topological surface states,such as the quantum anomalous Hall effect(QAHE).This work significantly facilitates the fabrication of TI-based devices for electronic and spintronic applications.展开更多
The magnetic force microscopy and a sample vibrating magnetometer have been used to investigate the domain structure in two antiferromagnetically coupled Co/Pt multilayers.In the antiferromagnetic coupled[Pt（0.5 nm）...The magnetic force microscopy and a sample vibrating magnetometer have been used to investigate the domain structure in two antiferromagnetically coupled Co/Pt multilayers.In the antiferromagnetic coupled[Pt（0.5 nm）/Co（0.4 nm）]n/NiO（1.1 nm）/[Co（0.4 nm）/Pt（0.5 nm）]n multilayers with perpendicular anisotropy,the antiferromagnetic interlayer coupling strength increases linearly with the repetition number n in Co/Pt multilayers.In demagnetized states,relatively shifted domain walls in the two Co/Pt multilayers are observed,with net ferromagnetic stripes formed between them for the repetition number n less than 5,and the stripe width decreases with the increase of n.The occurrence of these features can be attributed to the competition between the interlayer coupling and magnetostatic energies.展开更多
Cobalt thin films were deposited on silicon substrates by magnetron sputtering two commercial cobalt targets with different pass-through fluxes(PTFs).The influences of PTF on the magnetic properties of sputtered thin ...Cobalt thin films were deposited on silicon substrates by magnetron sputtering two commercial cobalt targets with different pass-through fluxes(PTFs).The influences of PTF on the magnetic properties of sputtered thin films were investigated.The results indicate that under the same sputtering conditions,cobalt thin film deposited by Co target with high PTF(84.21%) has lower remanence ratio(0.65),while cobalt thin film prepared by Co target with low PTF(69.13%) has higher remanence ratio(0.87).Through introducing an external magnetic field parallel to the film surface during sputtering processes,both the remanence ratios of cobalt thin films prepared by the two targets can be enhanced to approach 1.High-resolution transmission electron microscopy(HRTEM) images show that in the absence of the external magnetic field during sputtering,cobalt thin film deposited by the target with high PTF is randomly oriented in crystallographic orientations,which is due to that Co atoms have no enough time to migrate and diffuse on substrate and the atomic stacking is disordered.It is worth mentioning that crystallographic orientations of cobalt thin film deposited by target with low PTF are relatively consistent,resulting in relatively higher remanence ratio.In addition,HRTEM analysis indicates that the external magnetic field during sputtering drives the Co grains to arrange in a regular order with(002) orientation,leading to the improvement in remanence ratios.展开更多
基金This work was financially supported by the National Key Research and Development Program of China(No.2017YFB 0304800)One of the authors,H.Guo,would like to express her gratitude for the financial support of China Scholarship Council(award for one year visiting at Northwestern University in the USA,No.201706465056).
文摘Here we present a novel approach of intercritical heat treatment for microstructure tailoring,in which intercritical annealing is introduced between conventional quenching and tempering.This induced a heterogeneous microstructure consisting of soft intercritical ferrite and hard tempered martensite,resulting in a low yield ratio(YR)and high impact toughness in a high-strength low-alloy steel.The initial yielding and subsequent work hardening behavior of the steel during tensile deformation were modified by the presence of soft intercritical ferrite after intercritical annealing,in comparison to the steel with full martensitic microstructure.The increase in YR was related to the reduction in hardness difference between the soft and hard phases due to the precipitation of nano-carbides and the recovery of dislocations during tempering.The excellent low-temperature toughness was ascribed not only to the decrease in probability of microcrack initiation for the reduction of hardness difference between two phases,but also to the increase in resistance of microcrack propagation caused by the high density of high angle grain boundaries.
基金supported by financial support from the National Natural Science Foundation of China(Grant Nos.52309122 and U2340229)the Innovation Team of Changjiang River Scientific Research Institute(Grant No.CKSF2024329/YT).
文摘Large-scale and heavily jointed rocks have inherent planes of anisotropy and secondary structural planes,such as dominant joint sets and random fractures,which result in significant differences in their failure mechanism and deformation behavior compared to other rock types.To address this issue,inherent anisotropic rocks with large-scale and dense joints are considered to be composed of the rock matrix,inherent planes of anisotropy,and secondary structural planes.Then a new implicit continuum model called LayerDFN is developed based on the crack tensor and damage tensor theories to characterize the mechanical properties of inherent anisotropic rocks.Furthermore,the LayerDFN model is implemented in the FLAC3D software,and a series of numerical results for typical example problems is compared with those obtained from the 3DEC,the analytical solutions,similar classical models,laboratory uniaxial compression tests,and field rigid bearing plate tests.The results demonstrate that the LayerDFN model can effectively capture the anisotropic mechanical properties of inherent anisotropic rocks,and can quantitatively characterize the damaging effect of the secondary structural planes.Overall,the numerical method based on the LayerDFN model provides a comprehensive and reliable approach for describing and analyzing the behavior of inherent anisotropic rocks,which will provide valuable insights for engineering design and decision-making processes.
基金supported by the National Natural Science Foundation of China(No.81172553 and 81472513 to WB)
文摘Background:Osteosarcoma is the most common bone malignancy in children and adolescents,and 20%-30%of the patients suffer from poor prognosis because of individual chemoresistance.The Hippo/yes-associated protein(YAP) signaling pathway has been shown to play a role in tumor chemoresistance,but no previous report has focused on its involvement in osteosarcoma chemoresistance.This study aimed to investigate the role of the Hippo/YAP signaling pathway in osteosarcoma chemoresistance and to determine potential treatment targets.Methods:Using the Cell Titer-Glo Luminescent cell viability assay and flow cytometry analysis,we determined the proliferation and chemosensitivity of YAP-overexpressing and YAP-knockdown osteosarcoma cells.In addition,using western blotting and the real-time polymerase chain reaction technique,we investigated the alteration of the Hippo/YAP signaling pathway in osteosarcoma cells treated with chemotherapeutic agents.Results:Mammalian sterile 20-like kinase 1(MST1) degradation was increased,and large tumor suppressor kinase1/2(LAT51/2) total protein levels were decreased by methotrexate and doxorubicin,which increased activation and nuclear translocation of YAP.Moreover,YAP increased the proliferation and chemoresistance of MG63 cells.Conclusions:The Hippo/YAP signaling pathway plays a role in osteosarcoma chemoresistance,and YAP is a potential target for reducing chemoresistance.
基金This work is funded by the National Natural Science Foundation of China[Grant Nos.41930650,41631178]the Program of International S&T Cooperation,the Ministry of Science and Technology of China[Grant No.2015DFA11360]。
文摘30-m Global Land Cover(GLC)data products permit the detection of land cover changes at the scale of most human land activities,and are therefore used as fundamental information for sustainable development,environmental change studies,and many other societal benefit areas.In the past few years,increasing efforts have been devoted to the accuracy assessment of GlobeLand30 and other finer-resolution GLC data products.However,most of them were conducted either within a limited percentage of map sheets selected from a global scale or in some individual countries(areas),and there are still many areas where the uncertainty of 30-m resolution GLC data products remains to be validated and documented.In order to promote a comprehensive and collaborative validation of 30-m GLC data products,the GEO Global Land Cover Community Activity had organized a project from 2015 to 2017,to examine and explore its major problems,including the lack of international agreed validation guidelines and on-line tools for facilitating collaborative validation activities.With the joint effort of experts and users from 30 GEO member countries or participating organizations,a technical specification for 30-m GLC validation was developed based on the findings and experiences.An on-line validation tool,GLCVal,was developed by integrating land cover validation procedures with the service computing technologies.About 20 countries(regions)have completed the accuracy assessment of GlobeLand30 for their territories with the guidance of the technical specification and the support of GLCVal.
基金supported by National Natural Science Foundation of China(Nos.U1135005 and 61304224)General Equipment Department Advanced Research Project of China(No.51301010206)
文摘This paper presents a novel guidance law to intercept non-maneuvering targets with impact angle and lateral acceleration command constraints. Firstly, we formulate the impact angle control to track the desired line-of-sight(LOS) angle, which is achieved by selecting the missile s lateral acceleration to enforce the sliding mode on a sliding surface at impact time. Secondly, we use the Lyapunov stability theory to prove the stability and finite time convergence of the proposed nonlinear sliding surface. Thirdly, we introduce the wavelet neural network(WNN) to adaptively update the additional control command and reduce the high-frequency chattering of sliding mode control(SMC). The proposed guidance law, denoted WNNSMC guidance law with impact angle constraint,combines the SMC methodology with WNN to improve the robustness and reduce the chattering of the system. Finally, numerical simulations are performed to demonstrate the validity and effectiveness of the WNNSMC guidance law.
基金financially supported by the National Natural Science Foundation of China (No. 51701012)the National Basic Research Program of China (973 Program: No. 2010CB630801)the Fundamental Research Funds for the Central Universities (No. FRF-TP-17-004A1)
文摘During the past thirty years, two generations of low alloy steels(ferrite/pearlite followed by bainite/martensite) have been developed and widely used in structural applications. The third-generation of low alloy steels is expected to achieve high strength and improved ductility and toughness, while satisfying the new demands for weight reduction, greenness, and safety. This paper reviews recent progress in the development of third-generation low alloy steels with an M^3 microstructure, namely, microstructures with multi-phase, meta-stable austenite, and multi-scale precipitates. The review summarizes the alloy designs and processing routes of microstructure control, and the mechanical properties of the alloys.The stabilization of retained austenite in low alloy steels is especially emphasized. Multi-scale nano-precipitates, including carbides of microalloying elements and Cu-rich precipitates obtained in third-generation low alloy steels, are then introduced. The structure–property relationships of third-generation alloys are also discussed. Finally, the promises and challenges to future applications are explored.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(KZCX2-YW-154)the National Natural Science Foundation of China(40772006, 40625006,40632010 and J0630967)+1 种基金the State Key Laboratory of Palaeobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology Programs (20102108,20101104)the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry
文摘According to the classic doctrine of angiosperm evolution,the archetype carpel in angiosperms is of plicate form.However,this concept is facing increasing challenges from the systematics based on molecular data,which now takes ascidiate carpel as ancestral.This reorientation in evolutionary thinking cannot be fully achieved unless there is supporting fossil evidence.Here a fruit, named Liaoningfructus,is reported from the famous Yixian Formation(Early Cretaceous,125 Ma), which yielded several pioneer angiosperms in the past decades.The configuration of the fruit suggests that the carpel giving rise to the fruit is most likely ascidiate,favoring the above reorientation.There are two seeds in the fruit,and at least one of them is served by a vascular bundle arising from the bottom of the fruit,implying a basal placentation in the former carpel,which again is different from the classic thinking.This discovery not only enhances the diversity of angiosperms in the Yixian Formation,but also accelerates the on-going switching of thinking on angiosperm evolution.
基金supported by the National Natural Science Foundation of China(6130422461305018+1 种基金61472423)the National Advanced Research Project of China(51301010206)
文摘In this paper, a novel fuzzy sliding mode control（FSMC） guidance law with terminal constraints of miss distance, impact angle and acceleration is presented for a constant speed missile against the stationary or slowly moving target. The proposed guidance law combines the sliding mode control algorithm with a fuzzy logic control scheme for the lag-free system and the first-order lag system. Through using Lyapunov stability theory, we prove the sliding surface converges to zero in finite time. Furthermore, considering the uncertain information and system disturbances, the guidance gains are on-line optimized by fuzzy logic technique. Numerical simulations are performed to demonstrate the performance of the FSMC guidance law and the results illustrate the validity and effectiveness of the proposed guidance law.
基金supported by Hebei Province Baoding City Science and Technology Project(No:13ZF074)
文摘Objective:To observe the regulatory impact of immune inhibitors on T cells in rats.Method:Forty SD rats were selected and randomly divided into experimental group and control group.Rapamycin(SRL)0.4 mg/d to fill the stomach of the former one,saline lavage was used with the latter one for two weeks.Using flow cytometry to detect the two groups of rats with spleen and thymus level of CD4+CD25+T cells;and the spleen cells FoxP3 mRNA expression;Using ELISA method to detect TGF-β,IL-10 levels.Results:The peripheral blood,spleen and thymus of CD4+CD25+T cells accounted for the proportion of mononuclear cells were significantly higher than that of control group(P<0.05);FoxP3 mRNA expression quantity also significantly higher than the control group(P<0.05);Experimental TGF-βin rats,IL-10 levels are significantly higher than control group(P<0.05).Conclusions:Immune inhibitors can regulatory CD4+CD25+foxp3+T cells in rats,a single nuclear cell proportion increase,shows that it can induce rat CD4+CD25+foxp3+regulatory T cells proliferation.
基金support from the Key Projects of the Yalong River Joint Fund of the National Natural Science Foundation of China(Grant No.U1865203)the Innovation Team of Changjiang River Scientific Research Institute(Grant Nos.CKSF2021715/YT and CKSF2023305/YT)。
文摘The shear behavior of large-scale weak intercalation shear zones(WISZs)often governs the stability of foundations,rock slopes,and underground structures.However,due to their wide distribution,undulating morphology,complex fabrics,and varying degrees of contact states,characterizing the shear behavior of natural and complex large-scale WISZs precisely is challenging.This study proposes an analytical method to address this issue,based on geological fieldwork and relevant experimental results.The analytical method utilizes the random field theory and Kriging interpolation technique to simplify the spatial uncertainties of the structural and fabric features for WISZs into the spatial correlation and variability of their mechanical parameters.The Kriging conditional random field of the friction angle of WISZs is embedded in the discrete element software 3DEC,enabling activation analysis of WISZ C2 in the underground caverns of the Baihetan hydropower station.The results indicate that the activation scope of WISZ C2 induced by the excavation of underground caverns is approximately 0.5e1 times the main powerhouse span,showing local activation.Furthermore,the overall safety factor of WISZ C2 follows a normal distribution with an average value of 3.697.
基金financially supported by the National Natural Science Foundation of China(No.51872298)the National Key R&D Program of China(No.2016YFC0304505 and 2019YFC0311401)the Strategic Priority Research Program of Chinese Academy of Science(No.XDA22010202)。
文摘Non-noble bimetals have attracted extensive attention for their natural aboundance and low cost,but it remains a big challenge to design and synthesize novel supported non-noble bimetal nanocatalyst in a controllable and high-efficient manner.Herein,a novel hollow spherical supported non-noble bimetal nanocatalyst with porous carbon shell as the continuous matrix and Cu/Co bimetal nanoparticles as the dispersion phase is successfully fabricated by a convenient strategy involving spray drying and subsequent heat treatment.The morphology and microstructure depend catalyst activity of the hollow spherical supported catalyst has been studied systematically.It is found that the heating temperature plays a critical role in determining the microstructure and catalytic performance of the products.With an optimal heating temperature of 600°C,the corresponding product exhibits the highest normalized reaction rate constant(k_(n))of 25.4 s^(-1)g^(-1)for catalytic reduction of 4-notrophenol,which can be attributed to the suitable synergism of the well-defined bimetal structure,combined effect of the two metallic phases and the metal-support interaction.This work provides an additional strategy for the simultaneous formation of both the support and the active loading phase of supported non-noble bimetal nanocatalyst,and may shed some light on the high-efficiency synthesis of other supported heterostructure with various compositions and properties.
基金Chang’an University of China for a visiting professor grant (2018-2020) for research collaboration between Chang’an University and University of Western Australia。
文摘This study presents a simple technique for strengthening the adhesive-bond strength between aluminium(Al)substrate and carbon fibre reinforced polymer(CFRP) utilising resin pre-coating(RPC) with carbon nanotubes(CNTs). The CNT-containing RPC solution with 90 wt% acetone and 10 wt% resin(without hardener) was applied onto Al substrates, where micro-/nano-vertical channels had been created by chemical or mechanical surface treatments to accommodate CNTs. RPC was able to fill all micro-/nano-cavities over the Al substrate surface, then CNTs were pulled into those vertical micro-channels by the capillary action generated from acetone evaporation.Normal epoxy adhesive(resin + hardener) was applied after the CNT-containing RPC treatment. CNTs bridging across the interface between the adhesive joint and Al substrate and sealing of micro-/nano-cavities by RPC effectively enhanced the interfacial shear bond strength between the Al substrate and CFRP by 30–100%depending on the Al substrate surface profiles. Al substrates with two different chemical treatments were compared in this study for the effectiveness of CNT interfacial reinforcement. Results from a steel substrate after sandblasting were also included for comparison.
基金the financial support from the National Natural Science Foundation of China(Grant No.51979008)the National Natural Science Foundation of China(Grant No.51779018)the Innovation team of Changjiang River Scientific Research Institute(Grant No.CKSF2021715/YT).
文摘Layered rock mass is a type of engineering rock mass with sound mechanical anisotropy,which is generally unfavorable to the stability of underground works.To investigate the strength anisotropy of layered rock,the Mohr-Coulomb and Hoek-Brown criteria are introduced to establish the two transverse isotropic strength criteria based on Jaeger's single weak plane theory and maximum axial strain theory,and parameter determination methods.Furthermore,the sensitivity of strength parameters(K 1,K 2,and K 3)that are used to characterize the anisotropy strength of non-sliding failure involved in the strength criteria and confining pressure are investigated.The results demonstrate that strength parameters K 1 and K 2 affect the strength of layered rock samples at all bedding angles except for the bedding angle of 90°and the angle range that can cause the shear sliding failure along the bedding plane.The strength of samples at any bedding angle decreases with increasing K 1,whereas the opposite is for K 2.Except for bedding angles of 0°and 90°and the bedding angle range that can cause the shear sliding along the bedding plane,K 3 has an impact on the strength of rock samples with other bedding angles that the specimens'strength increases with increase of K 3.In addition,the strength of the rock sample increases as confining pressure rises.Furthermore,the uniaxial and triaxial tests of chlorite schist samples were carried out to verify and evaluate the strength criteria proposed in the paper.It shows that the predicted strength is in good agreement with the experimental results.To test the applicability of the strength criterion,the strength data of several types of rock in the literature are compared.Finally,a comparison is made between the fitting effects of the two strength criteria and other available criteria for layered rocks.
基金National Key R&D Plan Program of China(Grant No.2017YFF0206104)National Key Scien-tific Research Projects of China(Grant No.2015CB921502)+3 种基金National Natural Science Foundation of China(Grant Nos.61574169 and 51871018)Beijing Laboratory of Metallic Materials and Processing for Modern Transportation,the Opening Project of Key Laboratory of Microelectronics Devices&Integrated Technology,Institute of Microelectronics of Chinese Academy of SciencesBeijing Natural Science Foundation(Grant No.Z180014)Beijing Outstanding Young Scientists Projects(Grant No.BJJWZYJH01201910005018)。
文摘Three-dimensional(3 D)topological insulators(TIs)are candidate materials for various electronic and spintronic devices due to their strong spin-orbit coupling and unique surface electronic structure.Rapid,low-cost preparation of large-area TI thin films compatible with conventional semiconductor technology is the key to the practical applications of TIs.Here we show that wafer-sized Bi2Te3 family TI and magnetic TI films with decent quality and well-controlled composition and properties can be prepared on amorphous SiO2/Si substrates by magnetron cosputtering.The SiO2/Si substrates enable us to electrically tune(Bi1-xSbx)2Te3 and Cr-doped(Bi1-xSbx)2 Te3 TI films between p-type and n-type behavior and thus study the phenomena associated with topological surface states,such as the quantum anomalous Hall effect(QAHE).This work significantly facilitates the fabrication of TI-based devices for electronic and spintronic applications.
文摘The magnetic force microscopy and a sample vibrating magnetometer have been used to investigate the domain structure in two antiferromagnetically coupled Co/Pt multilayers.In the antiferromagnetic coupled[Pt（0.5 nm）/Co（0.4 nm）]n/NiO（1.1 nm）/[Co（0.4 nm）/Pt（0.5 nm）]n multilayers with perpendicular anisotropy,the antiferromagnetic interlayer coupling strength increases linearly with the repetition number n in Co/Pt multilayers.In demagnetized states,relatively shifted domain walls in the two Co/Pt multilayers are observed,with net ferromagnetic stripes formed between them for the repetition number n less than 5,and the stripe width decreases with the increase of n.The occurrence of these features can be attributed to the competition between the interlayer coupling and magnetostatic energies.
基金financially supported by the National Key R&D Program of China(No.2017YFB0305502)the National Natural Science Foundation of China(Nos.51571017,51671023,and 51871018)+2 种基金the Beijing Natural Science Foundation(No.2192031)the Key Science and Technology Projects of Beijing Education Committee(No.KZ201810011013)the Fundamental Research Funds for the Central Universities(No.FRF-TP-19-011B1)。
文摘Cobalt thin films were deposited on silicon substrates by magnetron sputtering two commercial cobalt targets with different pass-through fluxes(PTFs).The influences of PTF on the magnetic properties of sputtered thin films were investigated.The results indicate that under the same sputtering conditions,cobalt thin film deposited by Co target with high PTF(84.21%) has lower remanence ratio(0.65),while cobalt thin film prepared by Co target with low PTF(69.13%) has higher remanence ratio(0.87).Through introducing an external magnetic field parallel to the film surface during sputtering processes,both the remanence ratios of cobalt thin films prepared by the two targets can be enhanced to approach 1.High-resolution transmission electron microscopy(HRTEM) images show that in the absence of the external magnetic field during sputtering,cobalt thin film deposited by the target with high PTF is randomly oriented in crystallographic orientations,which is due to that Co atoms have no enough time to migrate and diffuse on substrate and the atomic stacking is disordered.It is worth mentioning that crystallographic orientations of cobalt thin film deposited by target with low PTF are relatively consistent,resulting in relatively higher remanence ratio.In addition,HRTEM analysis indicates that the external magnetic field during sputtering drives the Co grains to arrange in a regular order with(002) orientation,leading to the improvement in remanence ratios.
