In order to improve the incipient fault sensitivity and stability of degradation index in the rolling bearing performance degradation evaluation process,an embedding selection-based neighborhood preserving embedding(E...In order to improve the incipient fault sensitivity and stability of degradation index in the rolling bearing performance degradation evaluation process,an embedding selection-based neighborhood preserving embedding(ESNPE)method is proposed.Firstly,the acquired vibration signals are decomposed by variational mode decomposition(VMD),and the singular value and relative energy of each intrinsic mode function(IMF)are extracted to form a high-dimensional feature set.Then,the NPE manifold learning method is used to extract the embedded features in the feature space.Considering the problem that useful embedding information is easily suppressed in NPE,an embedding selection strategy is built based on the Spearman correlation coefficient.The effectiveness of embeddings is measured by the coefficient absolute value,and useful embeddings are preserved in the early stage of bearing degradation by using the first-order difference method.Finally,the degradation index is established using the support vector data description(SVDD)model and bearing performance degradation evaluation is achieved.The proposed method was tested with the whole life experiment data of a rolling bearing,and the result was compared with the feature extraction methods of traditional principal component analysis(PCA)and NPE.The results show that the proposed method is superior in improving the incipient fault sensitivity and stability of the degradation index.展开更多
The thermo-oxidative aging behaviors of Nylon 1010 films were studied by various analytical methods,such as measuring the chromaticity,relative viscosity,carbonyl index,UV absorbance at 280 nm and elongation at break ...The thermo-oxidative aging behaviors of Nylon 1010 films were studied by various analytical methods,such as measuring the chromaticity,relative viscosity,carbonyl index,UV absorbance at 280 nm and elongation at break of the aged films.The thermo-oxidative aging plots of the results obtained via these various methods at different temperatures are subjected to the time-temperature superposition analysis,which are found to be well superposed.The b＊ values are used as X axis and the other results,i.e.,relative viscosity,carbonyl index,UV absorbance at 280 nm and elongation at break,are used as V axis,respectively.The relationship between the b values and the other results is obtained,from which we can derive the changes of physical and chemical properties at different b＊ values.Since the b＊ values can be quickly determined by using a portable spectrophotometer,the on-line evaluation of the thermo-oxidative aging of Nylon 1010 can be realized.展开更多
In this paper,the degradation related parameters of GaInP/GaAs/Ge triple-junction solar cell induced by electron irradiation are carried out by numerical simulation.The degradation results of short-circuit current,ope...In this paper,the degradation related parameters of GaInP/GaAs/Ge triple-junction solar cell induced by electron irradiation are carried out by numerical simulation.The degradation results of short-circuit current,open-circuit voltage,maximum power have been investigated,and the degradation mechanism is analyzed.Combining the degradation results,the degradation of normalized parameters versus displacement damage dose is obtained.The results show that the degradation increases with the increase of the electron fluence and electron irradiation energy.The degradation normalized related parameters versus displacement damage dose can be characterized by a special curve that is not affected by the type of irradiated particles.By calculating the annual displacement damage dose and the on-orbit operation time of special space orbit,the degradation of normalized parameters can be obtained with the fitting curve in the simulation.The study will provide an approach to estimate the radiation damage of triple-junction solar cell induced by space particle irradiation.展开更多
With the rapid economic development and continuous expansion of human activities,forest degradation—characterized by reduced forest stock within the forest including declining carbon storage—poses significant threat...With the rapid economic development and continuous expansion of human activities,forest degradation—characterized by reduced forest stock within the forest including declining carbon storage—poses significant threats to ecosystem stability.Understanding the current status of forest degradation and assessing potential carbon stocks in China are of strategic importance for making forest restoration efforts and enhancing carbon sequestration capacity.In this study,we used the national forest inventory data from 2009 to 2018 to develop a set of standard measures for assessing degraded forests across China,based on five key indicators:forest accumulation growth rate(FAGR),forest recruitment rate(FRR),tree species reduction rate(TSRR),forest canopy cover reduction rate(FCCRR),and forest disaster level(FDL).Additionally,we estimated standing carbon stock,potential carbon stock,and theoretical space to grow by developing a stand growth model,which accounts for stand density across different site classes,to evaluate the restoration potential of degraded forests.The results indicate that degraded forest area in China is 36.15 million hectares,accounting for 20.10% of a total forest area.Standing carbon stock and potential carbon stock of degraded forests in China are 23.93 million tons and 61.90 million tons,respectively.Overall,degraded forest varies significantly across different regions.The results highlight the important trade-offs among environmental factors,policy decisions,and forest conditions,providing a robust foundation for developing measures to enhance forest quality.展开更多
Vascular scaffolds are one of the important application fields of biodegradable Mg alloys, and related research has been carried out for more than 20 years. In recent years, the application expansion of Mg alloy vascu...Vascular scaffolds are one of the important application fields of biodegradable Mg alloys, and related research has been carried out for more than 20 years. In recent years, the application expansion of Mg alloy vascular scaffolds has brought new challenges to the research of related fields. This review focuses on the relevant advances in the field of Mg alloys for both cardio-/cerebrovascular scaffolds. The frequently investigated alloy series for vascular scaffolds were reviewed. The bottleneck of processing of Mg alloy minitubes was elucidated.The idea of functionalized surface modification was also pointed out in this review, and the authors put forward guidelines based on research experience in terms of scaffold structural design and degradation behavior evaluation. Finally, suggestions for further research directions of Mg alloy vascular scaffolds were provided.展开更多
According to the results of accelerated tests of acidification corrosion depth and compressive strength of concretes subjected to sulfuric acid environments,the acidification depth laws of concretes were predicted bas...According to the results of accelerated tests of acidification corrosion depth and compressive strength of concretes subjected to sulfuric acid environments,the acidification depth laws of concretes were predicted based on the grey system theory.Thus,the remaining compressive strength was calculated when the acidification depth reached the protection layer thickness of concrete structures,which indicates that the limit state of durability failure can be defined based on strength degradation,and the calculation process was illustrated by an example.The calculated results show that the remaining compressive strength values in the durability failure limit state for the concrete structures exposed to p H=2 and 3 sulfuric acid water environments and wet-dry cyclic sulfuric acid environment with p H=2 are 74%,72%,and 80% of initialstrength,respectively.The method provides references for the durability evaluation of concrete structure design under the acidic environments.展开更多
In the last decade,integrated computation of corrosion has made significant progress towards the atomic-scale clarification of corrosion mechanisms and computer-aided designing of advanced materials with excellent cor...In the last decade,integrated computation of corrosion has made significant progress towards the atomic-scale clarification of corrosion mechanisms and computer-aided designing of advanced materials with excellent corrosion resistance.This review focuses on the theoretical calculation methods and developing tendency in corrosion study,and three specific applications are presented.First-principle techniques combined with molecular dynamics method,peridynamic theory and finite element method provide multiscale models to investigate micromechanisms of stress corrosion cracking and hydrogen-induced cracking.Calculations of passivity and passive film breakdown are elaborated through point defects diffusion and its correlation of the energy level degeneracy.By surveying publications,the artificial intelligence technology is pointed out how the computer can pave the way of predicting corrosion degrees as well as designing new corrosion resistant materials.To get better and efficient development of integrated computation of corrosion,extensive cooperation and powerful data infrastructure are needed by stronger collaboration in the future.展开更多
基金The National Natural Science Foundation of Chin(No.51975117)
文摘In order to improve the incipient fault sensitivity and stability of degradation index in the rolling bearing performance degradation evaluation process,an embedding selection-based neighborhood preserving embedding(ESNPE)method is proposed.Firstly,the acquired vibration signals are decomposed by variational mode decomposition(VMD),and the singular value and relative energy of each intrinsic mode function(IMF)are extracted to form a high-dimensional feature set.Then,the NPE manifold learning method is used to extract the embedded features in the feature space.Considering the problem that useful embedding information is easily suppressed in NPE,an embedding selection strategy is built based on the Spearman correlation coefficient.The effectiveness of embeddings is measured by the coefficient absolute value,and useful embeddings are preserved in the early stage of bearing degradation by using the first-order difference method.Finally,the degradation index is established using the support vector data description(SVDD)model and bearing performance degradation evaluation is achieved.The proposed method was tested with the whole life experiment data of a rolling bearing,and the result was compared with the feature extraction methods of traditional principal component analysis(PCA)and NPE.The results show that the proposed method is superior in improving the incipient fault sensitivity and stability of the degradation index.
文摘The thermo-oxidative aging behaviors of Nylon 1010 films were studied by various analytical methods,such as measuring the chromaticity,relative viscosity,carbonyl index,UV absorbance at 280 nm and elongation at break of the aged films.The thermo-oxidative aging plots of the results obtained via these various methods at different temperatures are subjected to the time-temperature superposition analysis,which are found to be well superposed.The b＊ values are used as X axis and the other results,i.e.,relative viscosity,carbonyl index,UV absorbance at 280 nm and elongation at break,are used as V axis,respectively.The relationship between the b values and the other results is obtained,from which we can derive the changes of physical and chemical properties at different b＊ values.Since the b＊ values can be quickly determined by using a portable spectrophotometer,the on-line evaluation of the thermo-oxidative aging of Nylon 1010 can be realized.
基金supported by the National Natural Science Foundation of China(Nos.11875223 and 11805155)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA15015000)+1 种基金the Innovation Foundation of Radiation Application(No.KFZC2018040201)the Foundation of State Key Laboratory of China(No.SKLIPR1803,1903Z)。
文摘In this paper,the degradation related parameters of GaInP/GaAs/Ge triple-junction solar cell induced by electron irradiation are carried out by numerical simulation.The degradation results of short-circuit current,open-circuit voltage,maximum power have been investigated,and the degradation mechanism is analyzed.Combining the degradation results,the degradation of normalized parameters versus displacement damage dose is obtained.The results show that the degradation increases with the increase of the electron fluence and electron irradiation energy.The degradation normalized related parameters versus displacement damage dose can be characterized by a special curve that is not affected by the type of irradiated particles.By calculating the annual displacement damage dose and the on-orbit operation time of special space orbit,the degradation of normalized parameters can be obtained with the fitting curve in the simulation.The study will provide an approach to estimate the radiation damage of triple-junction solar cell induced by space particle irradiation.
基金supported by National Key Research and Development Program of China(No.2021YFD2200405(S.R.L.))Natural Science Foundation of China(Grant No.31971653).
文摘With the rapid economic development and continuous expansion of human activities,forest degradation—characterized by reduced forest stock within the forest including declining carbon storage—poses significant threats to ecosystem stability.Understanding the current status of forest degradation and assessing potential carbon stocks in China are of strategic importance for making forest restoration efforts and enhancing carbon sequestration capacity.In this study,we used the national forest inventory data from 2009 to 2018 to develop a set of standard measures for assessing degraded forests across China,based on five key indicators:forest accumulation growth rate(FAGR),forest recruitment rate(FRR),tree species reduction rate(TSRR),forest canopy cover reduction rate(FCCRR),and forest disaster level(FDL).Additionally,we estimated standing carbon stock,potential carbon stock,and theoretical space to grow by developing a stand growth model,which accounts for stand density across different site classes,to evaluate the restoration potential of degraded forests.The results indicate that degraded forest area in China is 36.15 million hectares,accounting for 20.10% of a total forest area.Standing carbon stock and potential carbon stock of degraded forests in China are 23.93 million tons and 61.90 million tons,respectively.Overall,degraded forest varies significantly across different regions.The results highlight the important trade-offs among environmental factors,policy decisions,and forest conditions,providing a robust foundation for developing measures to enhance forest quality.
基金the financial support from the National Key Research and Development Program of China (2021YFC2400703)the Key Projects of the Joint Fund of the National Natural Science Foundation of China (U1804251)。
文摘Vascular scaffolds are one of the important application fields of biodegradable Mg alloys, and related research has been carried out for more than 20 years. In recent years, the application expansion of Mg alloy vascular scaffolds has brought new challenges to the research of related fields. This review focuses on the relevant advances in the field of Mg alloys for both cardio-/cerebrovascular scaffolds. The frequently investigated alloy series for vascular scaffolds were reviewed. The bottleneck of processing of Mg alloy minitubes was elucidated.The idea of functionalized surface modification was also pointed out in this review, and the authors put forward guidelines based on research experience in terms of scaffold structural design and degradation behavior evaluation. Finally, suggestions for further research directions of Mg alloy vascular scaffolds were provided.
基金Funded by the Nnational Natural Science Foundation of China(51372185)
文摘According to the results of accelerated tests of acidification corrosion depth and compressive strength of concretes subjected to sulfuric acid environments,the acidification depth laws of concretes were predicted based on the grey system theory.Thus,the remaining compressive strength was calculated when the acidification depth reached the protection layer thickness of concrete structures,which indicates that the limit state of durability failure can be defined based on strength degradation,and the calculation process was illustrated by an example.The calculated results show that the remaining compressive strength values in the durability failure limit state for the concrete structures exposed to p H=2 and 3 sulfuric acid water environments and wet-dry cyclic sulfuric acid environment with p H=2 are 74%,72%,and 80% of initialstrength,respectively.The method provides references for the durability evaluation of concrete structure design under the acidic environments.
基金the financial support from the National Key Research and Development Program of China(No.2017YFB 0702300)the National Natural Science Foundation of China(No.51871028)the Fundamental Research Funds for the Central Universities(No.FRF-TP-19-003B2)
文摘In the last decade,integrated computation of corrosion has made significant progress towards the atomic-scale clarification of corrosion mechanisms and computer-aided designing of advanced materials with excellent corrosion resistance.This review focuses on the theoretical calculation methods and developing tendency in corrosion study,and three specific applications are presented.First-principle techniques combined with molecular dynamics method,peridynamic theory and finite element method provide multiscale models to investigate micromechanisms of stress corrosion cracking and hydrogen-induced cracking.Calculations of passivity and passive film breakdown are elaborated through point defects diffusion and its correlation of the energy level degeneracy.By surveying publications,the artificial intelligence technology is pointed out how the computer can pave the way of predicting corrosion degrees as well as designing new corrosion resistant materials.To get better and efficient development of integrated computation of corrosion,extensive cooperation and powerful data infrastructure are needed by stronger collaboration in the future.
