Chirality hold broad applications in life sciences,quantum devices,and various other areas.Traditionally,molecular chirality can be characterized by using steady-state circular dichroism spectroscopy.However,the techn...Chirality hold broad applications in life sciences,quantum devices,and various other areas.Traditionally,molecular chirality can be characterized by using steady-state circular dichroism spectroscopy.However,the techniques that can characterize excited state chirality are progressively capturing the public interest as it can provide the dynamic information for chirality generation and transfer.In this review,we focus on the theoretical background and the developmental history of femtosecond time-resolved circular dichroism spectroscopy(TRCD)techniques around the world.Additionally,we provide examples to showcase the utility of these techniques in the analysis of the dynamical molecular chemical structures,the investigation of molecular chirality generation,and the detection of electron spin dynamics in semiconductor quantum dots.展开更多
The adsorption sites and diffusion mechanism of CO2 molecules in the flexible Zn（MeIM）2 （MeIM=2-methylimidazole） （ZIF-8） have been investigated by grand canonical Monte Carlo and molecular dynamics simulations. ...The adsorption sites and diffusion mechanism of CO2 molecules in the flexible Zn（MeIM）2 （MeIM=2-methylimidazole） （ZIF-8） have been investigated by grand canonical Monte Carlo and molecular dynamics simulations. A reasonable time correlation function is for the first time constructed to explore the mean residence time of CO2 molecules in the ZIF-8 cages, suggesting that C02 molecules can remain in the same cage for up to several tens of picoseconds. Furthermore, we find that the mean residence time almost linearly increases with the increasing pressure （or loading） at 273 and 298 K.展开更多
Statistics of exponentially decaying radiation of any nuclide always obeys the binomial stochastic distribution. The variance is derived for the number of atoms disintegrating in a time interval. The variance determin...Statistics of exponentially decaying radiation of any nuclide always obeys the binomial stochastic distribution. The variance is derived for the number of atoms disintegrating in a time interval. The variance determines the error of the disintegrations number. When the measuring time is short compared with the half life, then the Poisson stochastics is valid. Today, computers can be used to determine either distribution very easily. The dependence of absolute and relative error on the measuring time interval is examined, but here assuming the absence of the background contribution.展开更多
Dynamic numerical simulation of water conditions is useful for reservoir management. In remote semi-arid areas, however, meteorological and hydrological time-series data needed for computation are not frequently measu...Dynamic numerical simulation of water conditions is useful for reservoir management. In remote semi-arid areas, however, meteorological and hydrological time-series data needed for computation are not frequently measured and must be obtained using other information. This paper presents a case study of data generation for the computation of thermal conditions in the Joumine Reservoir, Tunisia. Data from the Wind Finder web site and daily sunshine duration at the nearest weather stations were utilized to generate cloud cover and solar radiation data based on meteorological correlations obtained in Japan, which is located at the same latitude as Tunisia. A time series of inflow water temperature was estimated from air temperature using a numerical filter expressed as a linear second-order differential equation. A numerical simulation using a vertical 2-D （two-dimensional） turbulent flow model for a stratified water body with generated data successfully reproduced seasonal thermal conditions in the reservoir, which were monitored using a thermistor chain.展开更多
We evaluate economic and environmental impacts of climate change mitigation in a country scale considering various time horizons in the analysis applying a single-country dynamic computable general equilibrium model w...We evaluate economic and environmental impacts of climate change mitigation in a country scale considering various time horizons in the analysis applying a single-country dynamic computable general equilibrium model with endogenous technological change. Although there is a possibility that Gross Domestic Product （GDP） becomes larger for the abatement cases than the baseline case in the earlier years, it tends to be lower than that in the later years. The longer the time horizon and/or the more severe the abatement, the larger the negative impacts will be. When subsidizing R＆D investment, increase in GDP compared to the baseline case is realized in the middle of the time horizon, and the larger increase tends to be observed for the longer-term cases. These results would be due to technological change induced by the subsidies and emission abatement. Environmental indicators are also improved. We showed that the results were influenced by the target time horizon when using an intertemporal dynamic model.展开更多
An orientation of a graph G with even number of vertices is Pfaffian if every even cycle C such that G-V(C) has a perfect matching has an odd number of edges directed in either direction of the cycle. The significance...An orientation of a graph G with even number of vertices is Pfaffian if every even cycle C such that G-V(C) has a perfect matching has an odd number of edges directed in either direction of the cycle. The significance of Pfaffian orientations stems from the fact that if a graph G has one, then the number of perfect matchings of G can be computed in polynomial time. There is a classical result of Kasteleyn that every planar graph has a Pfaffian orientation. Little proved an elegant characterization of bipartite graphs that admit a Pfaffian orientation. Robertson, Seymour and Thomas (1999) gave a polynomial-time recognition algorithm to test whether a bipartite graph is Pfaffian by a structural description of bipartite graphs. In this paper, we consider the Pfaffian property of graphs embedding on the orientable surface with genus one (i.e., the torus). Some sufficient conditions for Pfaffian graphs on the torus are obtained. Furthermore, we show that all quadrilateral tilings on the torus are Pfaffian if and only if they are not bipartite graphs.展开更多
With the development of the global economy, interaction among different economic entities from one region is intensifying, which makes it significant to consider such interaction when constructing composite index for ...With the development of the global economy, interaction among different economic entities from one region is intensifying, which makes it significant to consider such interaction when constructing composite index for each country from one region. Recent advances in signal extraction and time series analysis have made such consideration feasible and practical. Singular spectrum analysis （SSA） is a well-developed technique for time series analysis and proven to be a powerful tool for signal extraction. The present study aims to introduce the usage of the SSA technique for multi-country business cycle analysis. The multivariate SSA （MSSA） is employed to construct a model-based composite index and the two dimensional SSA （2D-SSA） is employed to establish the multi-country composite index. Empirical results performed on Chinese economy demonstrate the accuracy and stability of MSSA-based composite index, and the 2D-SSA based composite indices for Asian countries confirm the efficiency of the technique in capturing the interaction among different countries.展开更多
We improve the twin support vector machine(TWSVM)to be a novel nonparallel hyperplanes classifier,termed as ITSVM(improved twin support vector machine),for binary classification.By introducing the diferent Lagrangian ...We improve the twin support vector machine(TWSVM)to be a novel nonparallel hyperplanes classifier,termed as ITSVM(improved twin support vector machine),for binary classification.By introducing the diferent Lagrangian functions for the primal problems in the TWSVM,we get an improved dual formulation of TWSVM,then the resulted ITSVM algorithm overcomes the common drawbacks in the TWSVMs and inherits the essence of the standard SVMs.Firstly,ITSVM does not need to compute the large inverse matrices before training which is inevitable for the TWSVMs.Secondly,diferent from the TWSVMs,kernel trick can be applied directly to ITSVM for the nonlinear case,therefore nonlinear ITSVM is superior to nonlinear TWSVM theoretically.Thirdly,ITSVM can be solved efciently by the successive overrelaxation(SOR)technique or sequential minimization optimization(SMO)method,which makes it more suitable for large scale problems.We also prove that the standard SVM is the special case of ITSVM.Experimental results show the efciency of our method in both computation time and classification accuracy.展开更多
Targeting the mode-mixing problem of intrinsic time-scale decomposition （ITD） and the parameter optimization problem of least-square support vector machine （LSSVM）, we propose a novel approach based on complete en...Targeting the mode-mixing problem of intrinsic time-scale decomposition （ITD） and the parameter optimization problem of least-square support vector machine （LSSVM）, we propose a novel approach based on complete ensemble intrinsic time-scale decomposition （CEITD） and LSSVM optimized by the hybrid differential evolution and particle swarm optimization （HDEPSO） algorithm for the identification of the fault in a diesel engine. The approach consists mainly of three stages. First, to solve the mode-mixing problem of ITD, a novel CEITD method is proposed. Then the CEITD method is used to decompose the nonstationary vibration signal into a set of stationary proper rotation components （PRCs） and a residual signal. Second, three typical types of time-frequency features, namely singular values, PRCs energy and energy entropy, and AR model parameters, are extracted from the first several PRCs and used as the fault feature vectors. Finally, a HDEPSO algorithm is proposed for the parameter optimization of LSSVM, and the fault diagnosis results can be obtained by inputting the fault feature vectors into the HDEPSO-LSSVM classifier. Simulation and experimental results demonstrate that the proposed fault diagnosis approach can overcome the mode-mixing problem of ITD and accurately identify the fault patterns of diesel engines.展开更多
In this paper,the problem of time optimal feedrate generation under confined feedrate,axis accelerations,and axis tracking errors is considered.The main contribution is to reduce the tracking error constraint to const...In this paper,the problem of time optimal feedrate generation under confined feedrate,axis accelerations,and axis tracking errors is considered.The main contribution is to reduce the tracking error constraint to constraints about the axis velocities and accelerations,when the tracking error satisfies a second order linear ordinary differential equation.Based on this simplification on the tracking error,the original feedrate generation problem is reduced to a new form which can be efficiently solved with linear programming algorithms.Simulation results are used to validate the methods.展开更多
基金funded by the National Natural Science FoundationofChina(No.92156024and No.92356307 to Jinquan Chen)Menghui Jia thanks the Materials Characterization Center and the Office of Laboratory and Equipment of East China Normal University for funding support(ECNUETR2023-13).
文摘Chirality hold broad applications in life sciences,quantum devices,and various other areas.Traditionally,molecular chirality can be characterized by using steady-state circular dichroism spectroscopy.However,the techniques that can characterize excited state chirality are progressively capturing the public interest as it can provide the dynamic information for chirality generation and transfer.In this review,we focus on the theoretical background and the developmental history of femtosecond time-resolved circular dichroism spectroscopy(TRCD)techniques around the world.Additionally,we provide examples to showcase the utility of these techniques in the analysis of the dynamical molecular chemical structures,the investigation of molecular chirality generation,and the detection of electron spin dynamics in semiconductor quantum dots.
文摘The adsorption sites and diffusion mechanism of CO2 molecules in the flexible Zn（MeIM）2 （MeIM=2-methylimidazole） （ZIF-8） have been investigated by grand canonical Monte Carlo and molecular dynamics simulations. A reasonable time correlation function is for the first time constructed to explore the mean residence time of CO2 molecules in the ZIF-8 cages, suggesting that C02 molecules can remain in the same cage for up to several tens of picoseconds. Furthermore, we find that the mean residence time almost linearly increases with the increasing pressure （or loading） at 273 and 298 K.
文摘Statistics of exponentially decaying radiation of any nuclide always obeys the binomial stochastic distribution. The variance is derived for the number of atoms disintegrating in a time interval. The variance determines the error of the disintegrations number. When the measuring time is short compared with the half life, then the Poisson stochastics is valid. Today, computers can be used to determine either distribution very easily. The dependence of absolute and relative error on the measuring time interval is examined, but here assuming the absence of the background contribution.
文摘Dynamic numerical simulation of water conditions is useful for reservoir management. In remote semi-arid areas, however, meteorological and hydrological time-series data needed for computation are not frequently measured and must be obtained using other information. This paper presents a case study of data generation for the computation of thermal conditions in the Joumine Reservoir, Tunisia. Data from the Wind Finder web site and daily sunshine duration at the nearest weather stations were utilized to generate cloud cover and solar radiation data based on meteorological correlations obtained in Japan, which is located at the same latitude as Tunisia. A time series of inflow water temperature was estimated from air temperature using a numerical filter expressed as a linear second-order differential equation. A numerical simulation using a vertical 2-D （two-dimensional） turbulent flow model for a stratified water body with generated data successfully reproduced seasonal thermal conditions in the reservoir, which were monitored using a thermistor chain.
文摘We evaluate economic and environmental impacts of climate change mitigation in a country scale considering various time horizons in the analysis applying a single-country dynamic computable general equilibrium model with endogenous technological change. Although there is a possibility that Gross Domestic Product （GDP） becomes larger for the abatement cases than the baseline case in the earlier years, it tends to be lower than that in the later years. The longer the time horizon and/or the more severe the abatement, the larger the negative impacts will be. When subsidizing R＆D investment, increase in GDP compared to the baseline case is realized in the middle of the time horizon, and the larger increase tends to be observed for the longer-term cases. These results would be due to technological change induced by the subsidies and emission abatement. Environmental indicators are also improved. We showed that the results were influenced by the target time horizon when using an intertemporal dynamic model.
基金National Natural Science Foundation of China (Grant Nos. 10831001 and 11171279)the Scientific Research Foundation of Zhangzhou Normal University (Grant No. SX1002)
文摘An orientation of a graph G with even number of vertices is Pfaffian if every even cycle C such that G-V(C) has a perfect matching has an odd number of edges directed in either direction of the cycle. The significance of Pfaffian orientations stems from the fact that if a graph G has one, then the number of perfect matchings of G can be computed in polynomial time. There is a classical result of Kasteleyn that every planar graph has a Pfaffian orientation. Little proved an elegant characterization of bipartite graphs that admit a Pfaffian orientation. Robertson, Seymour and Thomas (1999) gave a polynomial-time recognition algorithm to test whether a bipartite graph is Pfaffian by a structural description of bipartite graphs. In this paper, we consider the Pfaffian property of graphs embedding on the orientable surface with genus one (i.e., the torus). Some sufficient conditions for Pfaffian graphs on the torus are obtained. Furthermore, we show that all quadrilateral tilings on the torus are Pfaffian if and only if they are not bipartite graphs.
基金supported by the National Science Foundation of China under Grant No.71101142Presidential Award of Chinese Academy of Sciences
文摘With the development of the global economy, interaction among different economic entities from one region is intensifying, which makes it significant to consider such interaction when constructing composite index for each country from one region. Recent advances in signal extraction and time series analysis have made such consideration feasible and practical. Singular spectrum analysis （SSA） is a well-developed technique for time series analysis and proven to be a powerful tool for signal extraction. The present study aims to introduce the usage of the SSA technique for multi-country business cycle analysis. The multivariate SSA （MSSA） is employed to construct a model-based composite index and the two dimensional SSA （2D-SSA） is employed to establish the multi-country composite index. Empirical results performed on Chinese economy demonstrate the accuracy and stability of MSSA-based composite index, and the 2D-SSA based composite indices for Asian countries confirm the efficiency of the technique in capturing the interaction among different countries.
基金supported by National Natural Science Foundation of China(Grant Nos.11271361 and 70921061)the CAS/SAFEA International Partnership Program for Creative Research Teams,Major International(Regional)Joint Research Project(Grant No.71110107026)+1 种基金the Ministry of Water Resources Special Funds for Scientific Research on Public Causes(Grant No.201301094)Hong Kong Polytechnic University(Grant No.B-Q10D)
文摘We improve the twin support vector machine(TWSVM)to be a novel nonparallel hyperplanes classifier,termed as ITSVM(improved twin support vector machine),for binary classification.By introducing the diferent Lagrangian functions for the primal problems in the TWSVM,we get an improved dual formulation of TWSVM,then the resulted ITSVM algorithm overcomes the common drawbacks in the TWSVMs and inherits the essence of the standard SVMs.Firstly,ITSVM does not need to compute the large inverse matrices before training which is inevitable for the TWSVMs.Secondly,diferent from the TWSVMs,kernel trick can be applied directly to ITSVM for the nonlinear case,therefore nonlinear ITSVM is superior to nonlinear TWSVM theoretically.Thirdly,ITSVM can be solved efciently by the successive overrelaxation(SOR)technique or sequential minimization optimization(SMO)method,which makes it more suitable for large scale problems.We also prove that the standard SVM is the special case of ITSVM.Experimental results show the efciency of our method in both computation time and classification accuracy.
基金Project supported by the National High-Tech R&D Program(863)of China(No.2014AA041501)
文摘Targeting the mode-mixing problem of intrinsic time-scale decomposition （ITD） and the parameter optimization problem of least-square support vector machine （LSSVM）, we propose a novel approach based on complete ensemble intrinsic time-scale decomposition （CEITD） and LSSVM optimized by the hybrid differential evolution and particle swarm optimization （HDEPSO） algorithm for the identification of the fault in a diesel engine. The approach consists mainly of three stages. First, to solve the mode-mixing problem of ITD, a novel CEITD method is proposed. Then the CEITD method is used to decompose the nonstationary vibration signal into a set of stationary proper rotation components （PRCs） and a residual signal. Second, three typical types of time-frequency features, namely singular values, PRCs energy and energy entropy, and AR model parameters, are extracted from the first several PRCs and used as the fault feature vectors. Finally, a HDEPSO algorithm is proposed for the parameter optimization of LSSVM, and the fault diagnosis results can be obtained by inputting the fault feature vectors into the HDEPSO-LSSVM classifier. Simulation and experimental results demonstrate that the proposed fault diagnosis approach can overcome the mode-mixing problem of ITD and accurately identify the fault patterns of diesel engines.
基金partially supported by a National Key Basic Research Project of China under Grant No.2011CB302400the Natural Science Foundation of China under Grant No.60821002
文摘In this paper,the problem of time optimal feedrate generation under confined feedrate,axis accelerations,and axis tracking errors is considered.The main contribution is to reduce the tracking error constraint to constraints about the axis velocities and accelerations,when the tracking error satisfies a second order linear ordinary differential equation.Based on this simplification on the tracking error,the original feedrate generation problem is reduced to a new form which can be efficiently solved with linear programming algorithms.Simulation results are used to validate the methods.
