The accumulation of He on a W surface during keV-He ion irradiation has been simulated using cluster dynamics modeling. This is based mainly on rate theory and improved by involving different types of objects, adoptin...The accumulation of He on a W surface during keV-He ion irradiation has been simulated using cluster dynamics modeling. This is based mainly on rate theory and improved by involving different types of objects, adopting up-to-date parameters and complex reaction processes, as well as considering the diffusion process along with depth. These new features make the simulated results compare very well with the experimental ones. The accumulation and diffusion processes are analyzed, and the depth and size dependence of the He concentrations contributed by different types of He clusters is also discussed. The exploration of the trapping and diffusion effects of the He atoms is helpful in understanding the evolution of the damages in the near-surface of plasma-facing materials under He ion irradiation.展开更多
To extract more in-depth information of acoustic emission(AE)signal-cloud in rock failure under triaxial compression,the spatial correlation of scattering AE events in a granite sample is effectively described by the ...To extract more in-depth information of acoustic emission(AE)signal-cloud in rock failure under triaxial compression,the spatial correlation of scattering AE events in a granite sample is effectively described by the cube-cluster model.First,the complete connection of the fracture network is regarded as a critical state.Then,according to the Hoshen-Kopelman(HK)algorithm,the real-time estimation of fracture con-nection is effectively made and a dichotomy between cube size and pore fraction is suggested to solve such a challenge of the one-to-one match between complete connection and cluster size.After,the 3D cube clusters are decomposed into orthogonal layer clusters,which are then transformed into the ellip-soid models.Correspondingly,the anisotropy evolution of fracture network could be visualized by three orthogonal ellipsoids and quantitatively described by aspect ratio.Besides,the other three quantities of centroid axis length,porosity,and fracture angle are analyzed to evaluate the evolution of cube cluster.The result shows the sample dilatancy is strongly correlated to four quantities of aspect ratio,centroid axis length,and porosity as well as fracture angle.Besides,the cube cluster model shows a potential pos-sibility to predict the evolution of fracture angle.So,the cube cluster model provides an in-depth view of spatial correlation to describe the AE signal-cloud.展开更多
In order to learn more about the physical phenomena occurring in cloud cavitation,the nonlinear dynamics of a spherical cluster of cavitation bubbles and cavitation bubbles in cluster in an acoustic field excited by a...In order to learn more about the physical phenomena occurring in cloud cavitation,the nonlinear dynamics of a spherical cluster of cavitation bubbles and cavitation bubbles in cluster in an acoustic field excited by a square pressure wave are numerically investigated by considering viscosity,surface tension,and the weak compressibility of the liquid.The theoretical prediction of the yield of oxidants produced inside bubbles during the strong collapse stage of cavitation bubbles is also investigated.The effects of acoustic frequency,acoustic pressure amplitude,and the number of bubbles in cluster on bubble temperature and the quantity of oxidants produced inside bubbles are analyzed.The results show that the change of acoustic frequency,acoustic pressure amplitude,and the number of bubbles in cluster have an effect not only on temperature and the quantity of oxidants inside the bubble,but also on the degradation types of pollutants,which provides a guidance in improving the sonochemical degradation of organic pollutants.展开更多
In wireless sensor networks,node localization is a fundamental middleware service.In this paper,a robust and accurate localization algorithm is proposed,which uses a novel iterative clustering model to obtain the most...In wireless sensor networks,node localization is a fundamental middleware service.In this paper,a robust and accurate localization algorithm is proposed,which uses a novel iterative clustering model to obtain the most representative intersection points between every two circles and use them to estimate the position of unknown nodes.Simulation results demonstrate that the proposed algorithm outperforms other localization schemes (such as Min-Max,etc.) in accuracy,scalability and gross error tolerance.展开更多
The geometry and electronic topology properties of Mg/Al hydrotalcite cluster models were comparatively investigated by means of density functional theory at GGA/DND levels.The results suggested that cluster model con...The geometry and electronic topology properties of Mg/Al hydrotalcite cluster models were comparatively investigated by means of density functional theory at GGA/DND levels.The results suggested that cluster model containing seven octahedral cations was the smallest size to be employed to simulate other properties.The fact that the n＋ charge of cluster models containing n aluminum atoms can reflect electronic properties of anionic clay layer sheet.The bond lengths of clusters can be modified by terminating with or without OH-/H2O groups in terms of principle of bond order conservation.展开更多
The density functional theory and the cluster model methods have been employed to investigate the interactions between thiophene and the HZSM-5 zeolites. The molecular complexes formed by the adsorption of thiophene o...The density functional theory and the cluster model methods have been employed to investigate the interactions between thiophene and the HZSM-5 zeolites. The molecular complexes formed by the adsorption of thiophene on silanol H3SiOH with two coordination forms, and the model Brrnsted acid sites of zeolite cluster H3Si（OH）AI（OH）2SiH3 upon the interaction with thiophene have been comparatively studied. Full optimization and frequency analysis of all cluster models have been carried out using the B3LYP hybrid method at 6-31G basis level for hydrogen atoms and 6-31＋G（d） basis set level for silicon, aluminum, oxygen, carbon, and sulfur atoms. The calculated results showed that the nature of interactions leading to the formation of the zeolite cluster-thiophene and silanol-thiophene complexes was associated with the van der Waals force confirmed by a slight change of geometric structures and properties. Thiophene is adsorbed on bridging hydroxyl group prior to silanol OH group judging from the magnitude of adsorption heat. The cluster model calculation reproducing the experimental prediction to form the experimental adsorption spectra of thiophene in HZSM-5 zeolite has illustrated the validity of the proposed adsorption models.展开更多
We study the percolation transition in a one-species cluster aggregation network model, in which the parameter α describes the suppression on the cluster sizes. It is found that the model can exhibit four types of pe...We study the percolation transition in a one-species cluster aggregation network model, in which the parameter α describes the suppression on the cluster sizes. It is found that the model can exhibit four types of percolation transitions, two continuous percolation transitions and two discontinuous ones. Continuous and discontinuous percolation transitions can be distinguished from each other by the largest single jump. Two types of continuous percolation transitions show different behaviors in the time gap. Two types of discontinuous percolation transitions are different in the time evolution of the cluster size distribution. Moreover, we also find that the time gap may also be a measure to distinguish different discontinuous percolations in this model.展开更多
As a kind of statistical method, the technique of Hidden Markov Model （HMM） is widely used for speech recognition. In order to train the HMM to be more effective with much less amount of data, the Subspace Distribut...As a kind of statistical method, the technique of Hidden Markov Model （HMM） is widely used for speech recognition. In order to train the HMM to be more effective with much less amount of data, the Subspace Distribution Clustering Hidden Markov Model （SDCHMM）, derived from the Continuous Density Hidden Markov Model （CDHMM）, is introduced. With parameter tying, a new method to train SDCHMMs is described. Compared with the conventional training method, an SDCHMM recognizer trained by means of the new method achieves higher accuracy and speed. Experiment results show that the SDCHMM recognizer outperforms the CDHMM recognizer on speech recognition of Chinese digits.展开更多
As a cluster overlap amplitude,the reduced-width amplitude is an important physical quantity for analyzing clustering in the nucleus depending on specified channels and has been calculated and widely applied in nuclea...As a cluster overlap amplitude,the reduced-width amplitude is an important physical quantity for analyzing clustering in the nucleus depending on specified channels and has been calculated and widely applied in nuclear cluster physics.In this review,we briefly revisit the theoretical framework for calculating the reduced-width amplitude,as well as the outlines of cluster models to obtain microscopic or semi-microscopic cluster wave functions.We also introduce the recent progress related to cluster overlap amplitudes,including the implementation of cross-section estimation and extension to three-body clustering analysis.Comprehensive examples are provided to demonstrate the application of the reduced-width amplitude in analyzing clustering structures.展开更多
The symmetric spin-orbit interactions of one-gluon-exchange and confinement are included in the nucleon-nucleon phase shift calculation in the framework of quark delocalization eolour screening model. The spin-orbit i...The symmetric spin-orbit interactions of one-gluon-exchange and confinement are included in the nucleon-nucleon phase shift calculation in the framework of quark delocalization eolour screening model. The spin-orbit interaction has little influence on D wave phase shift. For the triplet P waves, aPT is in good agreement with the experimental data and 3pLs is attractive but not strong enough, whereas 3 Pc is too strongly repulsive. Our results indicate that the symmetric spin-orbit interaction of one-gluon-exchange and confinement potential cannot give a good description of the triplet P wave phase shifts. More sophisticated considerations, the delocalization depending on the relative orientation between two cluster, might be needed to improve the description of P-wave NN interaction.展开更多
The modification of HZSM-5 zeolite with phosphorus and steam has been studied. Results show that 1% phosphorus and steam modified HZSM-5 has the highest catalytic activity for n-heptane. Physicochemical and catalytic ...The modification of HZSM-5 zeolite with phosphorus and steam has been studied. Results show that 1% phosphorus and steam modified HZSM-5 has the highest catalytic activity for n-heptane. Physicochemical and catalytic properties of 1% phosphorus and steam modified HZSM-5 zeolites have been investigated. The X-ray diffraction （XRD） results exhibit that there is considerable variation in the relative intensity of the individual diffraction peaks. The acidity of the samples decreases with an increase in the steaming temperature, which is determined by the IR of adsorbed pyridine and temperature programmed desorption （TPD） of ammonia. The oxidation state of phosphorus shown by XPS is ＋5, and a model for surface structure modification is proposed. The nitrogen adsorption isotherm for all samples is a combination of type I and type IV, all hysteresis loops resemble the H4-type. The density functional and cluster model methods have been invoked to select the phosphorus grafting model, and it was found that the phosphorus grafting model were more probable in the form of the terminal oxygen coordinating with aluminum.展开更多
The density functional theory and cluster model methods have been employed to investigate the interactions between methanethiol, dimethyl sulfide and zeolites. The molecular complexes formed by adsorption of methaneth...The density functional theory and cluster model methods have been employed to investigate the interactions between methanethiol, dimethyl sulfide and zeolites. The molecular complexes formed by adsorption of methanethiol or dimethyl sulfide on silanol H3SiOSi（OH）2OSiH3 with five coordination forms or four coordination forms, and complexes formed by interactions of BrSnsted acid sites of bridging hydroxyl H3Si（OH）AI（OH）2OSiH3 with methanethiol or dimethyl sulfide have been investigated. Full optimization and frequency analysis of all cluster models have been carried out using the B3LYP hybrid method at 6-31＋G （d,p） basis set level for hydrogen, silicon, aluminum, oxygen, carbon, and sulfur atoms. The structures and energy changes of different coordination forms between methanethiol and H3Si（OH）Al（OH）2OSiH3, dimethyl sulfide and H3Si（OH）Al（OH）2OSiH3, methanethiol and H3SiOSi（OH）2OSiH3, dimethyl sulfide and H3SiOSi（OH）2OSiH3 complexes have been comparatively studied. The calculated results showed the nature of interactions that led to the formation of all complexes was van der Waals force confirmed by an insignificant change of geometric structures and properties. The conclusions that methanethiol and dimethyl sulfide molecules were adsorbed on bridging hydroxyl group prior to silanol group were obtained on the basis of adsorption heat, the most stable adsorption models of a 6 ring structure for interaction between bridging hydroxyl and methanethiol, and a 7 ring structure for interaction between bridging hydroxyl and dimethyl sulfide.展开更多
A new version of the generalized density-dependent cluster model （GDDCM） is developed to describe an α particle tunneling through a deformed potential barrier. The microscopic deformed potential is numerically cons...A new version of the generalized density-dependent cluster model （GDDCM） is developed to describe an α particle tunneling through a deformed potential barrier. The microscopic deformed potential is numerically constructed in the double-folding model using the multipole ex- pansion method. The decay width of an α-cluster state is evaluated using the integral of the quasi-bound state wave function, the scattering state wave function, and the difference of poten- tials. We perform a systematic calculation of α-decay half-lives for favored transitions in even-even nuclei ranging from Z=52 to Z=104. The calculated half-lives are in good agreement with the experimental values. The relation between nuclear deformations and α-decay half-lives is also discussed in details.展开更多
Nowadays, a considerably large number of documents are available over many online news sites (e.g., CNN and NYT). Therefore, the utilization of these online documents, for example, the discovery of a burst topic and i...Nowadays, a considerably large number of documents are available over many online news sites (e.g., CNN and NYT). Therefore, the utilization of these online documents, for example, the discovery of a burst topic and its evolution, is a significant challenge. In this paper, a novel topic model, called intermittent Evolution LDA (iELDA) is proposed. In iELDA, the time-evolving documents are divided into many small epochs. iELDA utilizes the detected global topics as priors to guide the detection of an emerging topic and keep track of its evolution over different epochs. As a natural extension of the traditional Latent Dirichlet Allocation (LDA) and Dynamic Topic Model (DTM), iELDA has an advantage: it can discover the intermittent recurring pattern of a burst topic. We apply iELDA to real-world data from NYT; the results demonstrate that the proposed iELDA can appropriately capture a burst topic and track its intermittent evolution as well as produce a better predictive ability than other related topic models.展开更多
The density functional theory and the cluster model methods have been employed to investigate the interactions between ethanethiol and HZSM-5 zeolites. Molecular complexes formed by the adsorption of ethanethiol on si...The density functional theory and the cluster model methods have been employed to investigate the interactions between ethanethiol and HZSM-5 zeolites. Molecular complexes formed by the adsorption of ethanethiol on silanol H3SiOH with two coordination forms, model Bronsted acid sites of zeolite cluster H3Si(OH)Al(OH)2SiH3 interaction with ethanethiol, aluminum species adsorbed ethanethiol have been comparatively studied. Full optimization and frequency analysis of all cluster models have been carried out using B3LYP hybrid method at 3-21G basis level for hydrogen atoms and 6-31G(d) basis set level for silicon, aluminum, oxygen, carbon, and sulfur atoms. The structures and energy changes of different coordination forms of H3Si(OH)Al(OH)2SiH3-ethanethiol, silanol-ethanethiol and Al(OH)3-ethanethiol have been studied. The calculated results showed the nature of interactions was van der Waals force as exhibited by not much change in geometric structures and properties. The preference order of ethanethiol adsorbed on HZSM-5 zeolite may be residual aluminum species, bridging hydroxyl groups and silanol OH groups from the adsorption heat. The adsorbed models of protonized ethanethiol on bridging hydroxyl OH groups and linear hydrogen bonded ethanethiol on bridging OH groups suggested in literature might not exist as revealed by this theoretical calculation. Possible adsorption models were obtained for the first time.展开更多
The Hartree-Fock and cluster model methods have been employed to investigate interactions of methanthiol or dimethyl sulfide on zeolites. Molecular complexes formed by adsorption of methanthiol on silanol H3SiOSi（OH...The Hartree-Fock and cluster model methods have been employed to investigate interactions of methanthiol or dimethyl sulfide on zeolites. Molecular complexes formed by adsorption of methanthiol on silanol H3SiOSi（OH）2OSiH3 with five coordination forms and dimethyl sulfide on silanol H3SiOSi（OH）2OSiH3 with four coordination forms, and Bronsted acid sites of bridging hydroxyl H3Si（OH）Al（OH）2OSiH3 entering into interactions with methanthiol or dimethyl sulfide have been investigated. Full optimization and frequency analysis of all cluster models have been carded out using the Hartree-Fock method at 6-31＋G＊＊ basis set level for hydrogen, silicon, aluminum, oxygen, carbon, and sulfur atoms. The structures and energy changes of different coordination forms derived from methanthiol and H3Si（OH）Al（OH）2OSiH3, dimethyl sulfide and H3Si（OH）Al（OH）2OSiH3, methanthiol and H3SiOSi（OH）2OSiH3, dimethyl sulfide and H3SiOSi（OH）2OSiH3 complexes have been comparatively studied. The calculated results showed that the nature of interactions leading to the formation of the bridging hydroxyl-methanthiol, silanol-methanthiol, bridging hydroxyl-dimethyl sulfide, silanol-dimethyl sulfide complexes was governed by the Van der Waals force as confirmed by a small change in geometric structures and properties. Methanthiol and dimethyl sulfide molecules were adsorbed on bridging hydroxyl group prior to silanol group as evidenced by the heat of adsorption, and the protonization of methanthiol adsorption on bridging hydroxyl model, which was supposed in the literature, was not found.展开更多
The catalytic activity of trimethyl phosphite modified HZSM-5 zeolite and un-modified HZSM-5zeolite treated with 100% steam at 673,773,873,973 and 1073K, respectively, were investigated using heptanecracking as a prob...The catalytic activity of trimethyl phosphite modified HZSM-5 zeolite and un-modified HZSM-5zeolite treated with 100% steam at 673,773,873,973 and 1073K, respectively, were investigated using heptanecracking as a probe reaction. The results showed that the heptane conversion of both trimethyl phosphitetreated samples and un-phosphated samples decreased with an increase in treating temperature, but trimethylphosphite modified samples showed higher activity in comparison with the un-modified samples, which weresteam-treated at a higher temperature. The results were firstly elucidated by the model cluster method andcomputational quantum chemistry method. Full optimization and frequency analysis of all cluster model havebeen carried out using the Gaussian 94 software-package with the PM 3 semi-empirical method performed onsmall cluster models. The computational results showed that the dealumination of trimethyl phosphite modi-fied zeolite model cluster was more difficult than that of un-modified zeolite model cluster when they weretreated with steam while investigating the heat of reaction.展开更多
基金supported by the Special Funds for Major State Basic Research Project of China(973)(Nos.2007CB925004 and 2008CB717802)the Knowledge Innovation Program of the Chinese Academy of Sciences(No.KJCX2-YW-N35)+2 种基金National Natural Science Foundation of China(No.11005124)the China Postdoctoral Science Foundation Funded Project(No.20100470863)Director Grants of CASHIPS.Part of the calculations were performed in the Center for Computational Science of CASHIPS
文摘The accumulation of He on a W surface during keV-He ion irradiation has been simulated using cluster dynamics modeling. This is based mainly on rate theory and improved by involving different types of objects, adopting up-to-date parameters and complex reaction processes, as well as considering the diffusion process along with depth. These new features make the simulated results compare very well with the experimental ones. The accumulation and diffusion processes are analyzed, and the depth and size dependence of the He concentrations contributed by different types of He clusters is also discussed. The exploration of the trapping and diffusion effects of the He atoms is helpful in understanding the evolution of the damages in the near-surface of plasma-facing materials under He ion irradiation.
基金This study was sponsored by the National Natural Science Foundation of China(No.51504257)the State Key Research Development Program of China(No.2016YFC0600704)+1 种基金the Fundamental Research Funds for the Central Universities(Yueqi Outstanding Scholars)(No.2018B051616,2021JCCXLJ01,2021YJSLJ06)the Open Fund of the State Key Laboratory of Coal Mine Disaster Dynamics and Control(No.2011DA105287-FW201604).
文摘To extract more in-depth information of acoustic emission(AE)signal-cloud in rock failure under triaxial compression,the spatial correlation of scattering AE events in a granite sample is effectively described by the cube-cluster model.First,the complete connection of the fracture network is regarded as a critical state.Then,according to the Hoshen-Kopelman(HK)algorithm,the real-time estimation of fracture con-nection is effectively made and a dichotomy between cube size and pore fraction is suggested to solve such a challenge of the one-to-one match between complete connection and cluster size.After,the 3D cube clusters are decomposed into orthogonal layer clusters,which are then transformed into the ellip-soid models.Correspondingly,the anisotropy evolution of fracture network could be visualized by three orthogonal ellipsoids and quantitatively described by aspect ratio.Besides,the other three quantities of centroid axis length,porosity,and fracture angle are analyzed to evaluate the evolution of cube cluster.The result shows the sample dilatancy is strongly correlated to four quantities of aspect ratio,centroid axis length,and porosity as well as fracture angle.Besides,the cube cluster model shows a potential pos-sibility to predict the evolution of fracture angle.So,the cube cluster model provides an in-depth view of spatial correlation to describe the AE signal-cloud.
基金Project supported by the National Natural Science Foundation of China(Grant No.11674207)
文摘In order to learn more about the physical phenomena occurring in cloud cavitation,the nonlinear dynamics of a spherical cluster of cavitation bubbles and cavitation bubbles in cluster in an acoustic field excited by a square pressure wave are numerically investigated by considering viscosity,surface tension,and the weak compressibility of the liquid.The theoretical prediction of the yield of oxidants produced inside bubbles during the strong collapse stage of cavitation bubbles is also investigated.The effects of acoustic frequency,acoustic pressure amplitude,and the number of bubbles in cluster on bubble temperature and the quantity of oxidants produced inside bubbles are analyzed.The results show that the change of acoustic frequency,acoustic pressure amplitude,and the number of bubbles in cluster have an effect not only on temperature and the quantity of oxidants inside the bubble,but also on the degradation types of pollutants,which provides a guidance in improving the sonochemical degradation of organic pollutants.
基金supported in part by the Key Program of National Natural Science Foundation of China(Grant No.60873244,60973110,61003307)the Beijing Municipal Natural Science Foundation(Grant No.4102059)
文摘In wireless sensor networks,node localization is a fundamental middleware service.In this paper,a robust and accurate localization algorithm is proposed,which uses a novel iterative clustering model to obtain the most representative intersection points between every two circles and use them to estimate the position of unknown nodes.Simulation results demonstrate that the proposed algorithm outperforms other localization schemes (such as Min-Max,etc.) in accuracy,scalability and gross error tolerance.
基金supported by China University of Petroleum (East China) (grant 09CX04045A)
文摘The geometry and electronic topology properties of Mg/Al hydrotalcite cluster models were comparatively investigated by means of density functional theory at GGA/DND levels.The results suggested that cluster model containing seven octahedral cations was the smallest size to be employed to simulate other properties.The fact that the n＋ charge of cluster models containing n aluminum atoms can reflect electronic properties of anionic clay layer sheet.The bond lengths of clusters can be modified by terminating with or without OH-/H2O groups in terms of principle of bond order conservation.
文摘The density functional theory and the cluster model methods have been employed to investigate the interactions between thiophene and the HZSM-5 zeolites. The molecular complexes formed by the adsorption of thiophene on silanol H3SiOH with two coordination forms, and the model Brrnsted acid sites of zeolite cluster H3Si（OH）AI（OH）2SiH3 upon the interaction with thiophene have been comparatively studied. Full optimization and frequency analysis of all cluster models have been carried out using the B3LYP hybrid method at 6-31G basis level for hydrogen atoms and 6-31＋G（d） basis set level for silicon, aluminum, oxygen, carbon, and sulfur atoms. The calculated results showed that the nature of interactions leading to the formation of the zeolite cluster-thiophene and silanol-thiophene complexes was associated with the van der Waals force confirmed by a slight change of geometric structures and properties. Thiophene is adsorbed on bridging hydroxyl group prior to silanol OH group judging from the magnitude of adsorption heat. The cluster model calculation reproducing the experimental prediction to form the experimental adsorption spectra of thiophene in HZSM-5 zeolite has illustrated the validity of the proposed adsorption models.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11575036 and 11505016
文摘We study the percolation transition in a one-species cluster aggregation network model, in which the parameter α describes the suppression on the cluster sizes. It is found that the model can exhibit four types of percolation transitions, two continuous percolation transitions and two discontinuous ones. Continuous and discontinuous percolation transitions can be distinguished from each other by the largest single jump. Two types of continuous percolation transitions show different behaviors in the time gap. Two types of discontinuous percolation transitions are different in the time evolution of the cluster size distribution. Moreover, we also find that the time gap may also be a measure to distinguish different discontinuous percolations in this model.
基金Supported by the National Natural Science Foundation of China (No.60172048)
文摘As a kind of statistical method, the technique of Hidden Markov Model （HMM） is widely used for speech recognition. In order to train the HMM to be more effective with much less amount of data, the Subspace Distribution Clustering Hidden Markov Model （SDCHMM）, derived from the Continuous Density Hidden Markov Model （CDHMM）, is introduced. With parameter tying, a new method to train SDCHMMs is described. Compared with the conventional training method, an SDCHMM recognizer trained by means of the new method achieves higher accuracy and speed. Experiment results show that the SDCHMM recognizer outperforms the CDHMM recognizer on speech recognition of Chinese digits.
基金supported by the National Key R&D Program of China(No.2023YFA1606701)the National Natural Science Foundation of China(Nos.12175042 and 12147101)。
文摘As a cluster overlap amplitude,the reduced-width amplitude is an important physical quantity for analyzing clustering in the nucleus depending on specified channels and has been calculated and widely applied in nuclear cluster physics.In this review,we briefly revisit the theoretical framework for calculating the reduced-width amplitude,as well as the outlines of cluster models to obtain microscopic or semi-microscopic cluster wave functions.We also introduce the recent progress related to cluster overlap amplitudes,including the implementation of cross-section estimation and extension to three-body clustering analysis.Comprehensive examples are provided to demonstrate the application of the reduced-width amplitude in analyzing clustering structures.
基金Supported by the National Science Foundation of China under Grant Nos 90503011, 10775072, 10375030 and 10505006.
文摘The symmetric spin-orbit interactions of one-gluon-exchange and confinement are included in the nucleon-nucleon phase shift calculation in the framework of quark delocalization eolour screening model. The spin-orbit interaction has little influence on D wave phase shift. For the triplet P waves, aPT is in good agreement with the experimental data and 3pLs is attractive but not strong enough, whereas 3 Pc is too strongly repulsive. Our results indicate that the symmetric spin-orbit interaction of one-gluon-exchange and confinement potential cannot give a good description of the triplet P wave phase shifts. More sophisticated considerations, the delocalization depending on the relative orientation between two cluster, might be needed to improve the description of P-wave NN interaction.
文摘The modification of HZSM-5 zeolite with phosphorus and steam has been studied. Results show that 1% phosphorus and steam modified HZSM-5 has the highest catalytic activity for n-heptane. Physicochemical and catalytic properties of 1% phosphorus and steam modified HZSM-5 zeolites have been investigated. The X-ray diffraction （XRD） results exhibit that there is considerable variation in the relative intensity of the individual diffraction peaks. The acidity of the samples decreases with an increase in the steaming temperature, which is determined by the IR of adsorbed pyridine and temperature programmed desorption （TPD） of ammonia. The oxidation state of phosphorus shown by XPS is ＋5, and a model for surface structure modification is proposed. The nitrogen adsorption isotherm for all samples is a combination of type I and type IV, all hysteresis loops resemble the H4-type. The density functional and cluster model methods have been invoked to select the phosphorus grafting model, and it was found that the phosphorus grafting model were more probable in the form of the terminal oxygen coordinating with aluminum.
文摘The density functional theory and cluster model methods have been employed to investigate the interactions between methanethiol, dimethyl sulfide and zeolites. The molecular complexes formed by adsorption of methanethiol or dimethyl sulfide on silanol H3SiOSi（OH）2OSiH3 with five coordination forms or four coordination forms, and complexes formed by interactions of BrSnsted acid sites of bridging hydroxyl H3Si（OH）AI（OH）2OSiH3 with methanethiol or dimethyl sulfide have been investigated. Full optimization and frequency analysis of all cluster models have been carried out using the B3LYP hybrid method at 6-31＋G （d,p） basis set level for hydrogen, silicon, aluminum, oxygen, carbon, and sulfur atoms. The structures and energy changes of different coordination forms between methanethiol and H3Si（OH）Al（OH）2OSiH3, dimethyl sulfide and H3Si（OH）Al（OH）2OSiH3, methanethiol and H3SiOSi（OH）2OSiH3, dimethyl sulfide and H3SiOSi（OH）2OSiH3 complexes have been comparatively studied. The calculated results showed the nature of interactions that led to the formation of all complexes was van der Waals force confirmed by an insignificant change of geometric structures and properties. The conclusions that methanethiol and dimethyl sulfide molecules were adsorbed on bridging hydroxyl group prior to silanol group were obtained on the basis of adsorption heat, the most stable adsorption models of a 6 ring structure for interaction between bridging hydroxyl and methanethiol, and a 7 ring structure for interaction between bridging hydroxyl and dimethyl sulfide.
基金supported by National Natural Science Foundation of China(Nos.10535010,10675090,10775068,10735010,10975072,11035001)973 National Major State Basic Research and Development of China(Nos.2007CB815004,2010CB327803)+1 种基金CAS Knowledge Innovation Project(No.KJCX2-SW-N02)Research Fund of Doctoral Point(RFDP) of China(Nos.20070284016,20100091110028)
文摘A new version of the generalized density-dependent cluster model （GDDCM） is developed to describe an α particle tunneling through a deformed potential barrier. The microscopic deformed potential is numerically constructed in the double-folding model using the multipole ex- pansion method. The decay width of an α-cluster state is evaluated using the integral of the quasi-bound state wave function, the scattering state wave function, and the difference of poten- tials. We perform a systematic calculation of α-decay half-lives for favored transitions in even-even nuclei ranging from Z=52 to Z=104. The calculated half-lives are in good agreement with the experimental values. The relation between nuclear deformations and α-decay half-lives is also discussed in details.
基金supported by the National Basic Research Program of China under Grant No. 2012CB316400the National High Technology Research and Development Program of China under Grant No. 2012AA012505the Fundamental Research Funds for the Central Universities
文摘Nowadays, a considerably large number of documents are available over many online news sites (e.g., CNN and NYT). Therefore, the utilization of these online documents, for example, the discovery of a burst topic and its evolution, is a significant challenge. In this paper, a novel topic model, called intermittent Evolution LDA (iELDA) is proposed. In iELDA, the time-evolving documents are divided into many small epochs. iELDA utilizes the detected global topics as priors to guide the detection of an emerging topic and keep track of its evolution over different epochs. As a natural extension of the traditional Latent Dirichlet Allocation (LDA) and Dynamic Topic Model (DTM), iELDA has an advantage: it can discover the intermittent recurring pattern of a burst topic. We apply iELDA to real-world data from NYT; the results demonstrate that the proposed iELDA can appropriately capture a burst topic and track its intermittent evolution as well as produce a better predictive ability than other related topic models.
文摘The density functional theory and the cluster model methods have been employed to investigate the interactions between ethanethiol and HZSM-5 zeolites. Molecular complexes formed by the adsorption of ethanethiol on silanol H3SiOH with two coordination forms, model Bronsted acid sites of zeolite cluster H3Si(OH)Al(OH)2SiH3 interaction with ethanethiol, aluminum species adsorbed ethanethiol have been comparatively studied. Full optimization and frequency analysis of all cluster models have been carried out using B3LYP hybrid method at 3-21G basis level for hydrogen atoms and 6-31G(d) basis set level for silicon, aluminum, oxygen, carbon, and sulfur atoms. The structures and energy changes of different coordination forms of H3Si(OH)Al(OH)2SiH3-ethanethiol, silanol-ethanethiol and Al(OH)3-ethanethiol have been studied. The calculated results showed the nature of interactions was van der Waals force as exhibited by not much change in geometric structures and properties. The preference order of ethanethiol adsorbed on HZSM-5 zeolite may be residual aluminum species, bridging hydroxyl groups and silanol OH groups from the adsorption heat. The adsorbed models of protonized ethanethiol on bridging hydroxyl OH groups and linear hydrogen bonded ethanethiol on bridging OH groups suggested in literature might not exist as revealed by this theoretical calculation. Possible adsorption models were obtained for the first time.
文摘The Hartree-Fock and cluster model methods have been employed to investigate interactions of methanthiol or dimethyl sulfide on zeolites. Molecular complexes formed by adsorption of methanthiol on silanol H3SiOSi（OH）2OSiH3 with five coordination forms and dimethyl sulfide on silanol H3SiOSi（OH）2OSiH3 with four coordination forms, and Bronsted acid sites of bridging hydroxyl H3Si（OH）Al（OH）2OSiH3 entering into interactions with methanthiol or dimethyl sulfide have been investigated. Full optimization and frequency analysis of all cluster models have been carded out using the Hartree-Fock method at 6-31＋G＊＊ basis set level for hydrogen, silicon, aluminum, oxygen, carbon, and sulfur atoms. The structures and energy changes of different coordination forms derived from methanthiol and H3Si（OH）Al（OH）2OSiH3, dimethyl sulfide and H3Si（OH）Al（OH）2OSiH3, methanthiol and H3SiOSi（OH）2OSiH3, dimethyl sulfide and H3SiOSi（OH）2OSiH3 complexes have been comparatively studied. The calculated results showed that the nature of interactions leading to the formation of the bridging hydroxyl-methanthiol, silanol-methanthiol, bridging hydroxyl-dimethyl sulfide, silanol-dimethyl sulfide complexes was governed by the Van der Waals force as confirmed by a small change in geometric structures and properties. Methanthiol and dimethyl sulfide molecules were adsorbed on bridging hydroxyl group prior to silanol group as evidenced by the heat of adsorption, and the protonization of methanthiol adsorption on bridging hydroxyl model, which was supposed in the literature, was not found.
文摘The catalytic activity of trimethyl phosphite modified HZSM-5 zeolite and un-modified HZSM-5zeolite treated with 100% steam at 673,773,873,973 and 1073K, respectively, were investigated using heptanecracking as a probe reaction. The results showed that the heptane conversion of both trimethyl phosphitetreated samples and un-phosphated samples decreased with an increase in treating temperature, but trimethylphosphite modified samples showed higher activity in comparison with the un-modified samples, which weresteam-treated at a higher temperature. The results were firstly elucidated by the model cluster method andcomputational quantum chemistry method. Full optimization and frequency analysis of all cluster model havebeen carried out using the Gaussian 94 software-package with the PM 3 semi-empirical method performed onsmall cluster models. The computational results showed that the dealumination of trimethyl phosphite modi-fied zeolite model cluster was more difficult than that of un-modified zeolite model cluster when they weretreated with steam while investigating the heat of reaction.
