In recent years,chiral inorganic nanomaterials have become promising candidates for applications in sensing,catalysis,biomedicine,and photonics.Plasmonic nanomaterials with an intrinsic chiral structure exhibit intrig...In recent years,chiral inorganic nanomaterials have become promising candidates for applications in sensing,catalysis,biomedicine,and photonics.Plasmonic nanomaterials with an intrinsic chiral structure exhibit intriguing geometry‑dependent optical chirality,which benefits the combination of plasmonic characteristics with chirality.Recent advances in the biomolecule‑directed geometric control of intrinsically chiral plasmonic nanomaterials have further provided great opportunities for their widespread applications in many emerging technological areas.In this review,we present the recent progress in biosensing using chiral inorganic nanomaterials,with a particular focus on electrochemical and enzyme‑mimicking catalytic approaches.This paper commences with a review of the basic tenets underlying chiral nanocatalysts,incorporating the chiral ligand‑induced mechanism and the architectures of intrinsically chiral nanostructures.Additionally,it methodically expounds upon the applications of chiral nanocatalysts in the realms of electrochemical biosensing and enzyme‑mimicking catalytic biosensing respectively.Conclusively,it proffers a prospective view of the hurdles and prospects that accompany the deployment of chiral nanoprobes for nascent biosensing applications.By rational design of the chiral nanoprobes,it is envisioned that biosensing with increasing sensitivity and resolution toward the single‑molecule level can be achieved,which will substantially promote sensing applications in many emerging interdisciplinary areas.展开更多
The asymmetric creep aging behaviors of a pre-treated Al-Zn-Mg-Cu alloy under high and low stresses have been investigated for high precision creep age forming application of aluminum integral panels.With the increase...The asymmetric creep aging behaviors of a pre-treated Al-Zn-Mg-Cu alloy under high and low stresses have been investigated for high precision creep age forming application of aluminum integral panels.With the increase of applied stress,the creep strains under the tensile stresses are higher than those of compressive stresses and the asymmetry of creep strain is more obvious.However,the mechanical properties of tensile stress creep aged samples are lower than those of compressive stress creep aged samples.Dislocation density,dislocation moving velocity and the proportion of precipitates directly lead to the asymmetry of creep strain and mechanical properties after tensile-compressive creep aging process.In addition,the tensile and compressive stresses have little effect on the width of the precipitate-free zone(PFZ).It indicates that in the high stress creep age forming process of the pretreated Al-Zn-Mg-Cu alloy,the tensile stress promotes the dislocation motion to obtain a better creep strain but weakens its mechanical properties compared with the compressive stress.In the field of civil aviation aircraft component manufacturing,the introduction of tension and compression stress asymmetry into the creep constitutive model may improve the accuracy of creep age forming components.展开更多
α-Diimide catalysts have attracted widespread attention due to their unique chain walking characteristics.A series ofα-diimide nickel/palladium catalysts with different electronic effects and steric hindrances were ...α-Diimide catalysts have attracted widespread attention due to their unique chain walking characteristics.A series ofα-diimide nickel/palladium catalysts with different electronic effects and steric hindrances were designed and synthesized for olefin polymerization.In this work,we synthesized a series of asymmetricα-diimide nickel complexes with different steric hindrances and used them for ethylene polymerization.These nickel catalysts have high ethylene polymerization activity,up to 6.51×10^(6)g·mol^(−1)·h^(−1),and the prepared polyethylene has a moderate melting point and high molecular weight(up to 38.2×10^(4)g·mol^(−1)),with a branching density distribution between 7 and 94 branches per 1000 carbons.More importantly,the polyethylene prepared by these catalysts exhibits excellent tensile properties,with strain and stress reaching 800%and 30 MPa,respectively.展开更多
Attackers inject the designed adversarial sample into the target recommendation system to achieve illegal goals,seriously affecting the security and reliability of the recommendation system.It is difficult for attacke...Attackers inject the designed adversarial sample into the target recommendation system to achieve illegal goals,seriously affecting the security and reliability of the recommendation system.It is difficult for attackers to obtain detailed knowledge of the target model in actual scenarios,so using gradient optimization to generate adversarial samples in the local surrogate model has become an effective black‐box attack strategy.However,these methods suffer from gradients falling into local minima,limiting the transferability of the adversarial samples.This reduces the attack's effectiveness and often ignores the imperceptibility of the generated adversarial samples.To address these challenges,we propose a novel attack algorithm called PGMRS‐KL that combines pre‐gradient‐guided momentum gradient optimization strategy and fake user generation constrained by Kullback‐Leibler divergence.Specifically,the algorithm combines the accumulated gradient direction with the previous step's gradient direction to iteratively update the adversarial samples.It uses KL loss to minimize the distribution distance between fake and real user data,achieving high transferability and imperceptibility of the adversarial samples.Experimental results demonstrate the superiority of our approach over state‐of‐the‐art gradient‐based attack algorithms in terms of attack transferability and the generation of imperceptible fake user data.展开更多
According to the interaction of three shallow tunnels with large section, the analytical solution to rock pressure has been derived and discussed. The load model is given when the bilateral tunnels are excavated. Acco...According to the interaction of three shallow tunnels with large section, the analytical solution to rock pressure has been derived and discussed. The load model is given when the bilateral tunnels are excavated. According to the model, the stresses of three tunnels and single tunnel are calculated and compared to analyze the distribution characteristics, where the stresses are influenced by controlling factors of clear distance, covering depth and inclination angle of ground surface. The results show that, in general, the bias distribution is more serious. Therefore, it is significant to settle down the load model of three shallow tunnels so as to determine the measure of reinforcement and design the structure of support. The model and results can be used as a theoretical basis in designation and further research of the three shallow tunnels.展开更多
The structure and working principle of a two-cylinder four-stroke single-piston hydraulic free piston engine(HFPE) were introduced. The basic vibration equation of free piston assembly(FPA) was established based upon ...The structure and working principle of a two-cylinder four-stroke single-piston hydraulic free piston engine(HFPE) were introduced. The basic vibration equation of free piston assembly(FPA) was established based upon the energy conversion between the injected fuel and the friction together with the load. Both the theoretical and numerical results show that the vibration system of FPA is a nonlinear conservative autonomous system in one cycle. The FPA vibration is symmetric with constant amplitude when FPA is only driven by the compression pressure in the compression accumulator and that in the combustion chamber. When considering the friction and load, FPA could still achieve a stable vibration after a few cycles' adjustment whether the input energy is equal to the consumed energy or not. The vibration characteristics are different when FPA vibrates in the compression stroke and the expansion stroke, which is the unique feature of the single-piston HFPE.展开更多
To research the influence of asymmetric brake shoe forces(ABSF)induced by braking failure on the dynamic performance of six-axle locomotive,the static equilibrium model of three-axle bogie and dynamic model for locomo...To research the influence of asymmetric brake shoe forces(ABSF)induced by braking failure on the dynamic performance of six-axle locomotive,the static equilibrium model of three-axle bogie and dynamic model for locomotive are established.The coupling vibration equations of axle hung motor and wheelset are derived.For the air braking,the influence mechanism of ABSF on the wheel-rail asymmetric motion and force characteristics are discussed.It can be found that if the ABSF is applied in the front wheelset,all the wheelsets move laterally in the same direction.Once the ABSF occurs in the middle or rear one,other wheelsets may move laterally towards the opposite direction.The motion amplitude and direction of all wheelsets strictly depend on the resultant moment of suspension yawing moment and brake shoe asymmetric moment.For the asymmetric braking,the free lateral gap of axle-box could increase the wheelset motion amplitude,but could not change the moving direction.In both the straight line and curve,the ABSF may lead to wheelset misaligning motion,intensify the wheel-rail lateral dynamic interaction and deteriorate wheel-rail contact state.Especially for the steering wheelsets,the asymmetric braking increases the wheelset attack angle significantly,which forms the worst braking condition.展开更多
The present investigation addresses the simultaneous effects of heat and mass transfer in the mixed convection peristaltic flow of viscous fluid in an asymmetric channel. The channel walls exhibit the convective bound...The present investigation addresses the simultaneous effects of heat and mass transfer in the mixed convection peristaltic flow of viscous fluid in an asymmetric channel. The channel walls exhibit the convective boundary conditions. In addition, the effects due to Soret and Dufour are taken into consideration. Resulting problems are solved for the series solutions. Numerical values of heat and mass transfer rates are displayed and studied. Results indicate that the concentration and temperature of the fluid increase whereas the mass transfer rate at the wall decreases with increase of the mass transfer Biot number. Furthermore, it is observed that the temperature decreases with the increase of the heat transfer Biot number.展开更多
Based on a simplified 3-DOF model of twin-tower structure linked by a sky-bridge,the frequency response functions,the displacement power spectral density(PSD)functions,and the time-averaged total vibration energy were...Based on a simplified 3-DOF model of twin-tower structure linked by a sky-bridge,the frequency response functions,the displacement power spectral density(PSD)functions,and the time-averaged total vibration energy were derived,by assuming the white noise as the earthquake excitation.The effects of connecting parameters,such as linking stiffness ratio and linking damping ratio,on the structural vibration responses were then studied,and the optimal connecting parameters were obtained to minimize the vibration energy of either the independent monomer tower or the integral structure.The influences of sky-bridge elevation position on the optimal connecting parameters were also discussed.Finally,the distribution characteristics of the top displacement PSD and the structural responses,excited by El Centro,Taft and artificial waves,were compared in both frequency and time domain.It is found that the connecting parameters at either end of connection interactively affect the responses of the towers.The optimal connecting parameters can greatly improve the damping connections on their seismic reduction effectiveness,but are unable to reduce the seismic responses of the towers to the best extent simultaneously.It is also indicated that the optimal connecting parameters derived from the simplified 3-DOF model are applicable for two multi-story structures linked by a sky-bridge with dampers.The seismic reduction effectiveness obtained varies from 0.3 to 1.0 with different sky-bridge mass ratio.The displacement responses of the example structures are reduced by approximately 22% with sky-bridge connections.展开更多
Local inhomogeneity in totally asymmetric simple exclusion processes （TASEPs） with different hopping rates was studied. Many biological and chemical phenomena can be described by these non-equilibrium processes. A s...Local inhomogeneity in totally asymmetric simple exclusion processes （TASEPs） with different hopping rates was studied. Many biological and chemical phenomena can be described by these non-equilibrium processes. A simple approximate theory and extensive Monte Carlo computer simulations were used to calculate the steady-state phase diagrams and bulk densities. It is found that the phase diagram for local inhomogeneity in TASEP with different hopping rates p is qualitatively similar to homogeneous models. Interestingly, there is a saturation point pair （a＊, fl＊） for the system, which is decided by parameters p and q. There are three stationary phases in the system, when parameter p is fixed （i.e., p=0.8）, with the increase of the parameter q, the region of LD/LD and HD/HD phase increases and the HD/LD is the only phase which the region shrinks. The analytical results are in good agreement with simulations.展开更多
acetoxy-17,17-ethylendioxy-15β,16β-methylene-5-androsten-7β-ol（Ⅰ） was prepared by 3 steps from 3β-acetoxy-15β,16β-methylene-5-androsten-17-one （Ⅱ） with overall yield of 52.7%. Thus, interaction of ethylene...acetoxy-17,17-ethylendioxy-15β,16β-methylene-5-androsten-7β-ol（Ⅰ） was prepared by 3 steps from 3β-acetoxy-15β,16β-methylene-5-androsten-17-one （Ⅱ） with overall yield of 52.7%. Thus, interaction of ethylene glycol and material （Ⅱ） gave 3β-acetoxy- 17,17-ethylendioxy-15β,16β-methylene-5-androsten （Ⅲ） which was subsequently oxidated and stereoselectively reduced to produce compound（Ⅰ）. The normal influencing factors, such as the types of oxidants and reductives, the mole ratio of reactants, the reaction temperature, and the addition ways of reactants, in oxidation and reduction were discussed. The results show that the oxidation rate order is CrO3-C5H5N （1∶1, mole fraction）>CrO3-C5H5N（1∶2）>（C5H5NH）2Cr2O7 in terms of the oxidant, the yield of the oxidation becomes higher with increasing the oxidant stoichiometry and raising the reaction temperature. And the optimum condition is that the reaction temperature is at 30 ℃, and n （Ⅲ）/ n （CrO3-C5H5N（1∶2））=1∶20. The yield of the -7β alcohol order with Li[Al（OC（CH3）3）3H] （e.g.78.6%） is more than that with NaBH4 （e.g.14.5%） in terms of the reductive （agent） and the reduction rate decreases in the course of reaction. The compound （Ⅰ） is characterized by IR and MS.展开更多
The mechanical and microstructural properties as well as crystallographic textures of asymmetrically rolled low carbon steel were studied.The modelling of plastic deformation was carried out in two scales:in the macro...The mechanical and microstructural properties as well as crystallographic textures of asymmetrically rolled low carbon steel were studied.The modelling of plastic deformation was carried out in two scales:in the macro-scale,using the finite elements method,and in the crystallographic scale,using the polycrystalline deformation model.The internal stress distribution in the rolling gap was calculated using the finite elements method and these stresses were then applied to the polycrystalline elasto-plastic deformation model.Selected mechanical properties,namely residual stress distribution,deformation work,applied force and torques,and bend amplitude,were calculated.The diffraction measurements,X-ray and electron backscatter diffraction,enabled the examination of texture heterogeneity and selected microstructure characteristics.The predicted textures agree well with those determined experimentally.The plastic anisotropy of cold rolled ferritic steel samples,connected with texture,was expressed by Lankford coefficient.展开更多
文摘In recent years,chiral inorganic nanomaterials have become promising candidates for applications in sensing,catalysis,biomedicine,and photonics.Plasmonic nanomaterials with an intrinsic chiral structure exhibit intriguing geometry‑dependent optical chirality,which benefits the combination of plasmonic characteristics with chirality.Recent advances in the biomolecule‑directed geometric control of intrinsically chiral plasmonic nanomaterials have further provided great opportunities for their widespread applications in many emerging technological areas.In this review,we present the recent progress in biosensing using chiral inorganic nanomaterials,with a particular focus on electrochemical and enzyme‑mimicking catalytic approaches.This paper commences with a review of the basic tenets underlying chiral nanocatalysts,incorporating the chiral ligand‑induced mechanism and the architectures of intrinsically chiral nanostructures.Additionally,it methodically expounds upon the applications of chiral nanocatalysts in the realms of electrochemical biosensing and enzyme‑mimicking catalytic biosensing respectively.Conclusively,it proffers a prospective view of the hurdles and prospects that accompany the deployment of chiral nanoprobes for nascent biosensing applications.By rational design of the chiral nanoprobes,it is envisioned that biosensing with increasing sensitivity and resolution toward the single‑molecule level can be achieved,which will substantially promote sensing applications in many emerging interdisciplinary areas.
基金Project(2021YFB3400900)supported by the National Key R&D Program of ChinaProjects(51905551,52205435)supported by the National Natural Science Foundation of China Youth Foundation+1 种基金Project(2022ZZTS0196)supported by the Fundamental Research Founds for the Central Universities,ChinaProject(CX20220282)supported by the Hunan Provincial Innovation Foundation for Postgraduate,China。
文摘The asymmetric creep aging behaviors of a pre-treated Al-Zn-Mg-Cu alloy under high and low stresses have been investigated for high precision creep age forming application of aluminum integral panels.With the increase of applied stress,the creep strains under the tensile stresses are higher than those of compressive stresses and the asymmetry of creep strain is more obvious.However,the mechanical properties of tensile stress creep aged samples are lower than those of compressive stress creep aged samples.Dislocation density,dislocation moving velocity and the proportion of precipitates directly lead to the asymmetry of creep strain and mechanical properties after tensile-compressive creep aging process.In addition,the tensile and compressive stresses have little effect on the width of the precipitate-free zone(PFZ).It indicates that in the high stress creep age forming process of the pretreated Al-Zn-Mg-Cu alloy,the tensile stress promotes the dislocation motion to obtain a better creep strain but weakens its mechanical properties compared with the compressive stress.In the field of civil aviation aircraft component manufacturing,the introduction of tension and compression stress asymmetry into the creep constitutive model may improve the accuracy of creep age forming components.
基金supported by the National Natural Science Foundation of China(52203016)the USTC Research Funds of the Double First-Class Initiative(YD9990002018)+3 种基金the Overseas Students Innovation and Entrepreneurship Support Program Project of Anhui Province(2021LCX022)the Key R&D Projects in Anhui Province(2022i01020012)the Natural Science Foundation of Hefei(2022039)the Excellent Research and Innovation Team Project of Anhui Province(2022AH010001).
文摘α-Diimide catalysts have attracted widespread attention due to their unique chain walking characteristics.A series ofα-diimide nickel/palladium catalysts with different electronic effects and steric hindrances were designed and synthesized for olefin polymerization.In this work,we synthesized a series of asymmetricα-diimide nickel complexes with different steric hindrances and used them for ethylene polymerization.These nickel catalysts have high ethylene polymerization activity,up to 6.51×10^(6)g·mol^(−1)·h^(−1),and the prepared polyethylene has a moderate melting point and high molecular weight(up to 38.2×10^(4)g·mol^(−1)),with a branching density distribution between 7 and 94 branches per 1000 carbons.More importantly,the polyethylene prepared by these catalysts exhibits excellent tensile properties,with strain and stress reaching 800%and 30 MPa,respectively.
基金The National Natural Science Foundation of China (61876001)Opening Foundation of State Key Laboratory of Cognitive Intelligence,Opening Foundation of State Key Laboratory of Cognitive Intelligence(iED2022-006)Scientific Research Planning Project of Anhui Province (2022AH050072)
文摘Attackers inject the designed adversarial sample into the target recommendation system to achieve illegal goals,seriously affecting the security and reliability of the recommendation system.It is difficult for attackers to obtain detailed knowledge of the target model in actual scenarios,so using gradient optimization to generate adversarial samples in the local surrogate model has become an effective black‐box attack strategy.However,these methods suffer from gradients falling into local minima,limiting the transferability of the adversarial samples.This reduces the attack's effectiveness and often ignores the imperceptibility of the generated adversarial samples.To address these challenges,we propose a novel attack algorithm called PGMRS‐KL that combines pre‐gradient‐guided momentum gradient optimization strategy and fake user generation constrained by Kullback‐Leibler divergence.Specifically,the algorithm combines the accumulated gradient direction with the previous step's gradient direction to iteratively update the adversarial samples.It uses KL loss to minimize the distribution distance between fake and real user data,achieving high transferability and imperceptibility of the adversarial samples.Experimental results demonstrate the superiority of our approach over state‐of‐the‐art gradient‐based attack algorithms in terms of attack transferability and the generation of imperceptible fake user data.
基金Projects(2013CB036004, 2011CB013800) supported by the National Basic Research Program of ChinaProject(51178468, 50908234) supported by the National Natural Science Foundation of ChinaProject(2011G103-B) supported by the Science and Technology Development of Railway in China
文摘According to the interaction of three shallow tunnels with large section, the analytical solution to rock pressure has been derived and discussed. The load model is given when the bilateral tunnels are excavated. According to the model, the stresses of three tunnels and single tunnel are calculated and compared to analyze the distribution characteristics, where the stresses are influenced by controlling factors of clear distance, covering depth and inclination angle of ground surface. The results show that, in general, the bias distribution is more serious. Therefore, it is significant to settle down the load model of three shallow tunnels so as to determine the measure of reinforcement and design the structure of support. The model and results can be used as a theoretical basis in designation and further research of the three shallow tunnels.
基金Project(51275451)supported by the National Natural Science Foundation of ChinaProject(51221004)supported by the Science Fund for Creative Research Groups of National Natural Science Foundation of China+1 种基金Project(2013CB035400)supported by the National Basic Research Program of ChinaProject(2011BAK03B09)supported by the National Key Technology R&D Program of China
文摘The structure and working principle of a two-cylinder four-stroke single-piston hydraulic free piston engine(HFPE) were introduced. The basic vibration equation of free piston assembly(FPA) was established based upon the energy conversion between the injected fuel and the friction together with the load. Both the theoretical and numerical results show that the vibration system of FPA is a nonlinear conservative autonomous system in one cycle. The FPA vibration is symmetric with constant amplitude when FPA is only driven by the compression pressure in the compression accumulator and that in the combustion chamber. When considering the friction and load, FPA could still achieve a stable vibration after a few cycles' adjustment whether the input energy is equal to the consumed energy or not. The vibration characteristics are different when FPA vibrates in the compression stroke and the expansion stroke, which is the unique feature of the single-piston HFPE.
基金Projects(52072249,51605315)supported by the National Natural Science Foundation of ChinaProject(E2018210052)supported by the Natural Science Foundation of Hebei Province,ChinaProject(TPL1707)supported by the Open Funds for the State Key Laboratory of Traction Power,China。
文摘To research the influence of asymmetric brake shoe forces(ABSF)induced by braking failure on the dynamic performance of six-axle locomotive,the static equilibrium model of three-axle bogie and dynamic model for locomotive are established.The coupling vibration equations of axle hung motor and wheelset are derived.For the air braking,the influence mechanism of ABSF on the wheel-rail asymmetric motion and force characteristics are discussed.It can be found that if the ABSF is applied in the front wheelset,all the wheelsets move laterally in the same direction.Once the ABSF occurs in the middle or rear one,other wheelsets may move laterally towards the opposite direction.The motion amplitude and direction of all wheelsets strictly depend on the resultant moment of suspension yawing moment and brake shoe asymmetric moment.For the asymmetric braking,the free lateral gap of axle-box could increase the wheelset motion amplitude,but could not change the moving direction.In both the straight line and curve,the ABSF may lead to wheelset misaligning motion,intensify the wheel-rail lateral dynamic interaction and deteriorate wheel-rail contact state.Especially for the steering wheelsets,the asymmetric braking increases the wheelset attack angle significantly,which forms the worst braking condition.
基金the Higher Education Commission of Pakistan (HEC) for the financial support through Indigenous program
文摘The present investigation addresses the simultaneous effects of heat and mass transfer in the mixed convection peristaltic flow of viscous fluid in an asymmetric channel. The channel walls exhibit the convective boundary conditions. In addition, the effects due to Soret and Dufour are taken into consideration. Resulting problems are solved for the series solutions. Numerical values of heat and mass transfer rates are displayed and studied. Results indicate that the concentration and temperature of the fluid increase whereas the mass transfer rate at the wall decreases with increase of the mass transfer Biot number. Furthermore, it is observed that the temperature decreases with the increase of the heat transfer Biot number.
基金Project(51178203)supported by the National Natural Science Foundation of China
文摘Based on a simplified 3-DOF model of twin-tower structure linked by a sky-bridge,the frequency response functions,the displacement power spectral density(PSD)functions,and the time-averaged total vibration energy were derived,by assuming the white noise as the earthquake excitation.The effects of connecting parameters,such as linking stiffness ratio and linking damping ratio,on the structural vibration responses were then studied,and the optimal connecting parameters were obtained to minimize the vibration energy of either the independent monomer tower or the integral structure.The influences of sky-bridge elevation position on the optimal connecting parameters were also discussed.Finally,the distribution characteristics of the top displacement PSD and the structural responses,excited by El Centro,Taft and artificial waves,were compared in both frequency and time domain.It is found that the connecting parameters at either end of connection interactively affect the responses of the towers.The optimal connecting parameters can greatly improve the damping connections on their seismic reduction effectiveness,but are unable to reduce the seismic responses of the towers to the best extent simultaneously.It is also indicated that the optimal connecting parameters derived from the simplified 3-DOF model are applicable for two multi-story structures linked by a sky-bridge with dampers.The seismic reduction effectiveness obtained varies from 0.3 to 1.0 with different sky-bridge mass ratio.The displacement responses of the example structures are reduced by approximately 22% with sky-bridge connections.
基金Project(2011FZ050) supported by Applied Basic Research Program of Yunnan Provincial Science and Technology Department,ChinaProject(2011J084) supported by Master Program of Yunnan Province Education Department,China
文摘Local inhomogeneity in totally asymmetric simple exclusion processes （TASEPs） with different hopping rates was studied. Many biological and chemical phenomena can be described by these non-equilibrium processes. A simple approximate theory and extensive Monte Carlo computer simulations were used to calculate the steady-state phase diagrams and bulk densities. It is found that the phase diagram for local inhomogeneity in TASEP with different hopping rates p is qualitatively similar to homogeneous models. Interestingly, there is a saturation point pair （a＊, fl＊） for the system, which is decided by parameters p and q. There are three stationary phases in the system, when parameter p is fixed （i.e., p=0.8）, with the increase of the parameter q, the region of LD/LD and HD/HD phase increases and the HD/LD is the only phase which the region shrinks. The analytical results are in good agreement with simulations.
文摘acetoxy-17,17-ethylendioxy-15β,16β-methylene-5-androsten-7β-ol（Ⅰ） was prepared by 3 steps from 3β-acetoxy-15β,16β-methylene-5-androsten-17-one （Ⅱ） with overall yield of 52.7%. Thus, interaction of ethylene glycol and material （Ⅱ） gave 3β-acetoxy- 17,17-ethylendioxy-15β,16β-methylene-5-androsten （Ⅲ） which was subsequently oxidated and stereoselectively reduced to produce compound（Ⅰ）. The normal influencing factors, such as the types of oxidants and reductives, the mole ratio of reactants, the reaction temperature, and the addition ways of reactants, in oxidation and reduction were discussed. The results show that the oxidation rate order is CrO3-C5H5N （1∶1, mole fraction）>CrO3-C5H5N（1∶2）>（C5H5NH）2Cr2O7 in terms of the oxidant, the yield of the oxidation becomes higher with increasing the oxidant stoichiometry and raising the reaction temperature. And the optimum condition is that the reaction temperature is at 30 ℃, and n （Ⅲ）/ n （CrO3-C5H5N（1∶2））=1∶20. The yield of the -7β alcohol order with Li[Al（OC（CH3）3）3H] （e.g.78.6%） is more than that with NaBH4 （e.g.14.5%） in terms of the reductive （agent） and the reduction rate decreases in the course of reaction. The compound （Ⅰ） is characterized by IR and MS.
基金Projects(DEC-2011/01/B/ST8/07394,DEC-2011/01/D/ST8/07399)supported by the Polish National Centre for Science(NCN)The support of the Polish Ministry of Science and Higher Education and of the French ANR 05-BLAN-0383 project
文摘The mechanical and microstructural properties as well as crystallographic textures of asymmetrically rolled low carbon steel were studied.The modelling of plastic deformation was carried out in two scales:in the macro-scale,using the finite elements method,and in the crystallographic scale,using the polycrystalline deformation model.The internal stress distribution in the rolling gap was calculated using the finite elements method and these stresses were then applied to the polycrystalline elasto-plastic deformation model.Selected mechanical properties,namely residual stress distribution,deformation work,applied force and torques,and bend amplitude,were calculated.The diffraction measurements,X-ray and electron backscatter diffraction,enabled the examination of texture heterogeneity and selected microstructure characteristics.The predicted textures agree well with those determined experimentally.The plastic anisotropy of cold rolled ferritic steel samples,connected with texture,was expressed by Lankford coefficient.
