Dear editor,Transcatheter aortic valve replacement (TAVR) is a safe and effective treatment for severe aortic valve stenosis and aortic regurgitation. Multiple randomized trials have proved its therapeutic advantages ...Dear editor,Transcatheter aortic valve replacement (TAVR) is a safe and effective treatment for severe aortic valve stenosis and aortic regurgitation. Multiple randomized trials have proved its therapeutic advantages in patients at any level of surgical risks.展开更多
Simple encapsulation of 3 nm gold nanoparticles in ordered mesoporous carbon with large pores of 17 nm and thick pore walls of 16 nm was achieved by a metal–ligand coordination assisted-selfassembly approach.Polystyr...Simple encapsulation of 3 nm gold nanoparticles in ordered mesoporous carbon with large pores of 17 nm and thick pore walls of 16 nm was achieved by a metal–ligand coordination assisted-selfassembly approach.Polystyrene-block-polyethylene-oxide(PS-b-PEO)diblock copolymer with a large molecular weight of the PS chain and mercaptopropyltrimethoxysilane were used as the template and the metal ligand,respectively.Small-angle X-ray scattering,X-ray diffraction,transmission electron microscopy,and X-ray photoelectron spectroscopy showed that monodispersed aggregation-free gold nanoparticles approximately 3 nm in size were partially embedded in the large open pore structure of the ordered mesoporous carbon.The strong coordination between the gold species and the mercapto groups and the thick porous walls increased the dispersion of the gold nanoparticles and essentially inhibited particle aggregation at 600℃.The gold nanoparticles in the ordered mesoporous carbon are active and stable in the reduction of nitroarenes involving bulky molecules using sodium borohydride as a reducing agent under ambient conditions(30℃)in water.The large interconnected pore structure facilitates the mass transfer of bulky molecules.展开更多
Accurate prediction of drilling efficiency is critical for developing the earth-rock excavation schedule.The single machine learning(ML)prediction models usually suffer from problems including parameter sensitivity an...Accurate prediction of drilling efficiency is critical for developing the earth-rock excavation schedule.The single machine learning(ML)prediction models usually suffer from problems including parameter sensitivity and overfitting.In addition,the influence of environmental and operational factors is often ignored.In response,a novel stacking-based ensemble learning method taking into account the combined effects of those factors is proposed.Through multiple comparison tests,four models,e Xtreme gradient boosting(XGBoost),random forest(RF),back propagation neural network(BPNN)as the base learners,and support vector regression(SVR)as the meta-learner,are selected for stacking.Furthermore,an improved cuckoo search optimization(ICSO)algorithm is developed for hyper-parameter optimization of the ensemble model.The application to a real-world project demonstrates that the proposed method outperforms the popular single ML method XGBoost and the ensemble model optimized by particle swarm optimization(PSO),with 16.43%and 4.88%improvements of mean absolute percentage error(MAPE),respectively.展开更多
To investigate the influence of island scanning on the microstructures and mechanical properties of direct laser-deposited Ti–6 Al–4 V structures,two samples are prepared using island scanning and orthogonal success...To investigate the influence of island scanning on the microstructures and mechanical properties of direct laser-deposited Ti–6 Al–4 V structures,two samples are prepared using island scanning and orthogonal successive scanning,respectively.The microstructures,relative density,and mechanical properties of the samples prepared using these two scanning strategies are compared.Each sample exhibits columnarβ-grain morphology and basket-weave microstructure characterization.The grains of the sample prepared using island scanning are significantly finer than that prepared by orthogonal successive scanning due to faster cooling during deposition.However,the relative density of the sample prepared using island scanning was slightly smaller due to the concentration of lack-of-fusion pores at the overlap zone of the island.Tensile testing at room temperature indicates that the ultimate tensile strength and yield strength of the sample prepared using island scanning is enhanced due to finer grains,while the ductility of the sample is weakened due to defects.展开更多
Additive manufacturing(AM)has gained extensive attention and tremendous research due to its advantages of fabricating complex-shaped parts without the need of casting mold.However,distortion is a known issue for many ...Additive manufacturing(AM)has gained extensive attention and tremendous research due to its advantages of fabricating complex-shaped parts without the need of casting mold.However,distortion is a known issue for many AM technologies,which decreases the precision of as-built parts.Like fusion welding,the local high-energy input generates residual stresses,which can adversely affect the fatigue performance of AM parts.To the best of the authors’knowledge,a comprehensive review does not exist regarding the distortion and residual stresses dedicated for AM,despite some work has explored the interrelationship between the two.The present review is aimed to fill in the identified knowledge gap,by first describing the evolution of distortion and residual stresses for a range of AM processes,and second assessing their influencing factors.This allows us to elucidate their formation mechanisms from both the micro-and macro-scales.Moreover,approaches which have been successfully adopted to mitigate both the distortion and residual stresses are reviewed.It is anticipated that this review paper opens many opportunities to increase the success rate of AM parts by improving the dimension precision and fatigue life.展开更多
Polymerization-induced cooperative assembly(PICA)is reported to efficiently access inverse bicontinuous mesophases within particles consisting of amphiphilic block copolymers(BCPs)and solvophobic copolymers.Reversible...Polymerization-induced cooperative assembly(PICA)is reported to efficiently access inverse bicontinuous mesophases within particles consisting of amphiphilic block copolymers(BCPs)and solvophobic copolymers.Reversible addition-fragmentation chain transfer(RAFT)dispersion alternating copolymerization of styrene and pentafluorostyrene is conducted in 2%v/v toluene/ethanol by simultaneously using poly(N,N-dimethylacrylamide)(PDMA29)as a macromolecular chain transfer agent(macro-CTA)and small molecule CTA.展开更多
A synchronization control scheme is proposed for uncertain coronary artery system (CAS) with input saturation. In order to deal with the input saturation, linear matrix inequalities (LMIS), adequate conditions are obt...A synchronization control scheme is proposed for uncertain coronary artery system (CAS) with input saturation. In order to deal with the input saturation, linear matrix inequalities (LMIS), adequate conditions are obtained based on the local sector condition. Furthermore, by constructing Lyapunov-Krasovskii functional (LKF), we design a state feedback controller to achieve synchronization for chaos system with input saturation. Moreover, the improved Jensen inequality, convex analysis, delay-partitioning approach and Moon et al.’s inequality are utilized to get the less conservative. Finally, the simulation result is given to explain the effectiveness of the proposed synchronization control scheme.展开更多
Biphenyl moiety represents a unique structural motif of many natural and unnatural products with biological interests, and dehydrogenative couplings of two aryl C–H bonds under oxidative conditions is unambiguously t...Biphenyl moiety represents a unique structural motif of many natural and unnatural products with biological interests, and dehydrogenative couplings of two aryl C–H bonds under oxidative conditions is unambiguously the most efficient and direct preparation of these compounds. However, higher oxidation potential of benzene derivatives makes such oxidative couplings much more difficult than other arenes. Only very limited advances have been achieved on direct formation of the crucial C–C bond between two phenyl derivatives by dehydrogenative phenyl coupling in the last two decades. This article briefly summarized and commented a number of representative recent achievements in this attractive field, including homo-, cross-and intramolecular rearrangement and couplings, as well as their applications in organic synthesis.展开更多
文摘Dear editor,Transcatheter aortic valve replacement (TAVR) is a safe and effective treatment for severe aortic valve stenosis and aortic regurgitation. Multiple randomized trials have proved its therapeutic advantages in patients at any level of surgical risks.
基金supported by the National Natural Science Foun-dation of China(22025204,92034301,21773156,and 51932005)the Shanghai Sci.&Tech.and Edu.Committee(19070502700)the Innovation Program of the Shanghai Municipal Education Com-mission(2021-01-07-00-02-E00119).
文摘Simple encapsulation of 3 nm gold nanoparticles in ordered mesoporous carbon with large pores of 17 nm and thick pore walls of 16 nm was achieved by a metal–ligand coordination assisted-selfassembly approach.Polystyrene-block-polyethylene-oxide(PS-b-PEO)diblock copolymer with a large molecular weight of the PS chain and mercaptopropyltrimethoxysilane were used as the template and the metal ligand,respectively.Small-angle X-ray scattering,X-ray diffraction,transmission electron microscopy,and X-ray photoelectron spectroscopy showed that monodispersed aggregation-free gold nanoparticles approximately 3 nm in size were partially embedded in the large open pore structure of the ordered mesoporous carbon.The strong coordination between the gold species and the mercapto groups and the thick porous walls increased the dispersion of the gold nanoparticles and essentially inhibited particle aggregation at 600℃.The gold nanoparticles in the ordered mesoporous carbon are active and stable in the reduction of nitroarenes involving bulky molecules using sodium borohydride as a reducing agent under ambient conditions(30℃)in water.The large interconnected pore structure facilitates the mass transfer of bulky molecules.
基金supported by the Yalong River Joint Funds of the National Natural Science Foundation of China(No.U1965207)the National Natural Science Foundation of China(Nos.51839007,51779169,and 52009090)。
文摘Accurate prediction of drilling efficiency is critical for developing the earth-rock excavation schedule.The single machine learning(ML)prediction models usually suffer from problems including parameter sensitivity and overfitting.In addition,the influence of environmental and operational factors is often ignored.In response,a novel stacking-based ensemble learning method taking into account the combined effects of those factors is proposed.Through multiple comparison tests,four models,e Xtreme gradient boosting(XGBoost),random forest(RF),back propagation neural network(BPNN)as the base learners,and support vector regression(SVR)as the meta-learner,are selected for stacking.Furthermore,an improved cuckoo search optimization(ICSO)algorithm is developed for hyper-parameter optimization of the ensemble model.The application to a real-world project demonstrates that the proposed method outperforms the popular single ML method XGBoost and the ensemble model optimized by particle swarm optimization(PSO),with 16.43%and 4.88%improvements of mean absolute percentage error(MAPE),respectively.
基金supported by the Science and Technology Support Program of Jiangsu (Nos. BE2014009-1 and BE2014009-2)the Key Research and Development Program of Jiangsu (No. BE2015161)
文摘To investigate the influence of island scanning on the microstructures and mechanical properties of direct laser-deposited Ti–6 Al–4 V structures,two samples are prepared using island scanning and orthogonal successive scanning,respectively.The microstructures,relative density,and mechanical properties of the samples prepared using these two scanning strategies are compared.Each sample exhibits columnarβ-grain morphology and basket-weave microstructure characterization.The grains of the sample prepared using island scanning are significantly finer than that prepared by orthogonal successive scanning due to faster cooling during deposition.However,the relative density of the sample prepared using island scanning was slightly smaller due to the concentration of lack-of-fusion pores at the overlap zone of the island.Tensile testing at room temperature indicates that the ultimate tensile strength and yield strength of the sample prepared using island scanning is enhanced due to finer grains,while the ductility of the sample is weakened due to defects.
基金National Key Research and Development Program of China(Grant No.2018YFB1105400)National Natural Science Foundation of China(Grant No.51475238)+2 种基金Key Research and Development Program of Jiangsu Provincial Department of Science and Technology of China(Grant No.BE2019002)China Post-Doctoral Fund(Grant No.2020M671475)UK's Engineering and Physical Sciences Research Council,and EPSRC Early Career Fellowship Scheme[EP/R043973/1].
文摘Additive manufacturing(AM)has gained extensive attention and tremendous research due to its advantages of fabricating complex-shaped parts without the need of casting mold.However,distortion is a known issue for many AM technologies,which decreases the precision of as-built parts.Like fusion welding,the local high-energy input generates residual stresses,which can adversely affect the fatigue performance of AM parts.To the best of the authors’knowledge,a comprehensive review does not exist regarding the distortion and residual stresses dedicated for AM,despite some work has explored the interrelationship between the two.The present review is aimed to fill in the identified knowledge gap,by first describing the evolution of distortion and residual stresses for a range of AM processes,and second assessing their influencing factors.This allows us to elucidate their formation mechanisms from both the micro-and macro-scales.Moreover,approaches which have been successfully adopted to mitigate both the distortion and residual stresses are reviewed.It is anticipated that this review paper opens many opportunities to increase the success rate of AM parts by improving the dimension precision and fatigue life.
基金support by the National Natural Science Foundation of China(nos.51733003 and 21674059)the Fundamental Research Funds for the Central Universities are thanked.
文摘Polymerization-induced cooperative assembly(PICA)is reported to efficiently access inverse bicontinuous mesophases within particles consisting of amphiphilic block copolymers(BCPs)and solvophobic copolymers.Reversible addition-fragmentation chain transfer(RAFT)dispersion alternating copolymerization of styrene and pentafluorostyrene is conducted in 2%v/v toluene/ethanol by simultaneously using poly(N,N-dimethylacrylamide)(PDMA29)as a macromolecular chain transfer agent(macro-CTA)and small molecule CTA.
基金the Technology Commission of Tianjin Municipality (Grants Nos. 18JCYBJC88100 and 15JCYBJC16100)the National Natural Science Foundation of China (Grant No. 61503280).
文摘A synchronization control scheme is proposed for uncertain coronary artery system (CAS) with input saturation. In order to deal with the input saturation, linear matrix inequalities (LMIS), adequate conditions are obtained based on the local sector condition. Furthermore, by constructing Lyapunov-Krasovskii functional (LKF), we design a state feedback controller to achieve synchronization for chaos system with input saturation. Moreover, the improved Jensen inequality, convex analysis, delay-partitioning approach and Moon et al.’s inequality are utilized to get the less conservative. Finally, the simulation result is given to explain the effectiveness of the proposed synchronization control scheme.
基金supported by the National Natural Science Foundation of China(21472087)
文摘Biphenyl moiety represents a unique structural motif of many natural and unnatural products with biological interests, and dehydrogenative couplings of two aryl C–H bonds under oxidative conditions is unambiguously the most efficient and direct preparation of these compounds. However, higher oxidation potential of benzene derivatives makes such oxidative couplings much more difficult than other arenes. Only very limited advances have been achieved on direct formation of the crucial C–C bond between two phenyl derivatives by dehydrogenative phenyl coupling in the last two decades. This article briefly summarized and commented a number of representative recent achievements in this attractive field, including homo-, cross-and intramolecular rearrangement and couplings, as well as their applications in organic synthesis.
