1. Introduction In quantum optics, optical frequency conversion is a typical nonlinear process and is worth studying, for example, a second harmonic frequency generation will generate a squeezed state.[1＇2l In this ...1. Introduction In quantum optics, optical frequency conversion is a typical nonlinear process and is worth studying, for example, a second harmonic frequency generation will generate a squeezed state.[1＇2l In this work, we tackle the evolution of an initial coherent state in a Raman dispersion process which is also a nonlinear process. The process involves the inelastic scattering of a pho- ton when it is incident on a molecule. The photon loses some of its energy to the molecule or gains some from it, and so leaves the molecule with a lower or a higher frequency. The lower frequency components of the scattered radiation are called the Stokes lines and the higher frequency components are called the anti- Stokes lines. The Hamiltonian governing its dynamics is[3]展开更多
Remaining Useful Life(RUL)is one of the most important indicators to detect a component failure.RUL can be predicted by historical data by adopting a model-based method.The stochastic process models have become the mo...Remaining Useful Life(RUL)is one of the most important indicators to detect a component failure.RUL can be predicted by historical data by adopting a model-based method.The stochastic process models have become the most popular way to model degradation data for high-quality products,such as the Wiener process,gamma process and inverse Gaussian process.However,this leads to poor reliability assessment if the model is misspecified.Application of the Tweedie exponential dispersion(TED)process,including the above-mentioned classical stochastic processes as special cases,transforms the model selection problem into a parameter estimation problem dexterously.In this paper,we propose a TED process with random drifts for degradation data and a TeD process with random drifts and covariates for accelerated degradation data.A hierarchical Bayesian method is adopted to estimate the parameters of the proposed models.We also derive the failure-time distribution and the remaining useful life distribution for the proposed models.The simulation study shows that the proposed model outperforms the wrongly specified models.Two illustrative examples demonstrate the performance of the proposed TED process with random drifts and the TED process with random drifts and covariates.展开更多
Missiles provide long-range precision strike capabilities and have become a cornerstone of modern warfare.The contrail clouds formed by missile during their active flight phase present significant chal-lenges to high-...Missiles provide long-range precision strike capabilities and have become a cornerstone of modern warfare.The contrail clouds formed by missile during their active flight phase present significant chal-lenges to high-altitude environmental observation and target detection and tracking.Existing studies primarily focus on specific airspace regions,leaving critical gaps in understanding the effects of long dispersion times,wide altitude ranges,and variable atmospheric conditions on missile contrail clouds.To address these gaps,this article develops a numerical method based on the Lagrangian random walk model,which incorporates various velocity variation terms,including particle velocity caused by the difference of wind field,by the thermal motion of local gas molecules and by random collisions between contrail cloud particles to capture the influence of environmental wind fields,atmospheric conditions,and particle concentrations on the motion of contrail cloud particles.A general coordinate system aligned with the missile's flight trajectory is employed to represent particle distribution characteristics.The proposed method is in good agreement with the conducted experiments as well as with the available numerical simulations.The results demonstrate that the proposed model effectively simulates the dispersion state of contrail clouds,accurately reflecting the impact of large-scale wind field variations and altitude changes with high computational efficiency.Additionally,simulation results indicate that the increased distance between gas molecules in rarefied environments facilitates enhanced particle dispersion,while larger particles exhibit a faster dispersion rate due to their greater mass.展开更多
The regime of disturbance with natural or anthropogenic origin can lead to the destabilization or even to a mass mortality of benthic communities. Due to the heterogeneity of the disturbance there is a formation of pa...The regime of disturbance with natural or anthropogenic origin can lead to the destabilization or even to a mass mortality of benthic communities. Due to the heterogeneity of the disturbance there is a formation of patches in different stages of ecological succession. The aim of this study is to follow and describe the resilience in artificial disturbed sediment in a polluted bay in Rio de Janeiro. The sediment was collected, sterilized and placed inside corers (10 cmdiameter ×15 cmheight) in the same place where it was collected. We allocated the samples in two structures, the difference between them was that one was placed closed to the bottom and the other was placed50 cmheight. We found 2352 organisms distributed in 14 taxons. The class Polychaeta and the order Amphipoda showed the highest density in all the survey and treatments. We identified the factors influencing the scenarium: different mechanisms of dispersal, the position of the structures and life history of each group. Disturbance can be the main cause of the patch’s diversity found in estuaries and coastal areas. Because of this, monitoring of selected areas becomes an important tool to understand the regime of disturbance as a key factor structuring benthic communities in soft sediment, also suggesting a metapopulation dynamics.展开更多
Aim To study fuel dispersion in fuel air explosive(FAE) and computational ways of fuel dispersion velocity in the near area. Methods\ The dispersion process of fuel in FAE was analyzed by the use of results measured ...Aim To study fuel dispersion in fuel air explosive(FAE) and computational ways of fuel dispersion velocity in the near area. Methods\ The dispersion process of fuel in FAE was analyzed by the use of results measured with KODAK EKTAPRO EM Motion Analyzer and setting up mechanical models. Results\ Computational methods for fuel dispersion velocity in the acceleration stage is given and taken as a base for the study of fuel dispersion in the intermediate and the far area. Conclusion\ When the fuel flow velocity is higher than that of the explosion gas in the center cavity, the fuel divides with the explosion gas and its velocity of flow reaches a maximum. The acceleration stage ends at that time. The fuel dispersion velocity at this time is the initial conditions for numeral analyses of dispersion process in the intermediate and far areas.展开更多
Aggregation is suggested beneficial with foraging,defense,and other fitness for the group members.While long distance dispersal with kinship has been found in several marine fishes,similar cases have not been reported...Aggregation is suggested beneficial with foraging,defense,and other fitness for the group members.While long distance dispersal with kinship has been found in several marine fishes,similar cases have not been reported in inland waters.We utilized microsatellite genotype data of 397 eggs or juvenile silver carp(Hypophthalmichthys molitrix)born in 2017 from the middle and lower reaches of the Yangtze River in China to analyze their relatedness and infer the dispersal patterns during their early life stages and whether they dispersed with their kinship.There were 11–58 pairs of full siblings or half siblings between samples from the spawning ground(Yichang section)and other sites(34.1–1047.2 km)which showed the dispersal path.Particularly,the proportion of maternal siblings(mean:47.9%)was higher than random,indicating kinship aggregation,or that the fish traveled with their kinship during their early life stages.Such kin aggregation has profound implications for our understanding of early life stage dispersal in inland water fish populations.Our findings suggest that the preservation of habitats along the middle Yangtze River should be increased.In particular,the channelized river bank should be rebuilt with more heterogeneous habitat,and the lake-river connections should be restored to expand the amount of appropriate habitat.展开更多
Following the quantitative determination of dust cloud parameters, this study investigated the flame propagation through cornstarch dust clouds in a vertical duct of 780 mm height and 160×160 mm square cross sect...Following the quantitative determination of dust cloud parameters, this study investigated the flame propagation through cornstarch dust clouds in a vertical duct of 780 mm height and 160×160 mm square cross section, and gave particular attention to the effect of turbulence on flame characteristics. The turbulence induced by dust dispersion process was measured using a particle image velocimetry （PIV） system. Upward propagating dust flames were visualized with direct fight and shadow photography. The results show that a critical value of the turbulence intensity can be specified below which laminar flame propagation would be established. This transition condition is about 10 cm/s. The measured propagation speed of laminar flames appears to be in the range of 0.45-0.56 m/s, consistent with the measurements reported in the literature. For the present experimental conditions, the flame speed is little sensitive to the variations in dust concentration. Some information on the flame structure was revealed from the shadow records, showing the typical heterogeneous feature of dust combustion process.展开更多
Nanosized dispersive hexagonal magnesium hydroxide （Mg（OH）2） has been prepared using an ammonia- hydrothermal method. Citric acid and monoethanolamine （MEA） were added to the reaction system during the ammonia p...Nanosized dispersive hexagonal magnesium hydroxide （Mg（OH）2） has been prepared using an ammonia- hydrothermal method. Citric acid and monoethanolamine （MEA） were added to the reaction system during the ammonia precipitation and hydrothermal processes, respectively, to improve the crystallinity and dispersion of the （Mg（OH）2） particles. The resulting Mg（OH）2 samples obtained under the opti- mum preparation conditions were characterized by scanning electron microscopy, X-ray diffraction and thermal gravity analysis, which showed that this newly developed procedure afforded well-dispersed hexagonal nanoolates of Mg（OH）2 with a mean diameter of 246 nm.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos.10775097 and 10475056)
文摘1. Introduction In quantum optics, optical frequency conversion is a typical nonlinear process and is worth studying, for example, a second harmonic frequency generation will generate a squeezed state.[1＇2l In this work, we tackle the evolution of an initial coherent state in a Raman dispersion process which is also a nonlinear process. The process involves the inelastic scattering of a pho- ton when it is incident on a molecule. The photon loses some of its energy to the molecule or gains some from it, and so leaves the molecule with a lower or a higher frequency. The lower frequency components of the scattered radiation are called the Stokes lines and the higher frequency components are called the anti- Stokes lines. The Hamiltonian governing its dynamics is[3]
基金supported by the National Natural Science Foundation of China[grant number 12001266]Natural Science Foundation of Jiangsu Province of China[grant number BK20180813]supported by the National Natural Science Foundation of China[grant number 12271168,12531013]and the 111 Project of China[grant number B14019].
文摘Remaining Useful Life(RUL)is one of the most important indicators to detect a component failure.RUL can be predicted by historical data by adopting a model-based method.The stochastic process models have become the most popular way to model degradation data for high-quality products,such as the Wiener process,gamma process and inverse Gaussian process.However,this leads to poor reliability assessment if the model is misspecified.Application of the Tweedie exponential dispersion(TED)process,including the above-mentioned classical stochastic processes as special cases,transforms the model selection problem into a parameter estimation problem dexterously.In this paper,we propose a TED process with random drifts for degradation data and a TeD process with random drifts and covariates for accelerated degradation data.A hierarchical Bayesian method is adopted to estimate the parameters of the proposed models.We also derive the failure-time distribution and the remaining useful life distribution for the proposed models.The simulation study shows that the proposed model outperforms the wrongly specified models.Two illustrative examples demonstrate the performance of the proposed TED process with random drifts and the TED process with random drifts and covariates.
文摘Missiles provide long-range precision strike capabilities and have become a cornerstone of modern warfare.The contrail clouds formed by missile during their active flight phase present significant chal-lenges to high-altitude environmental observation and target detection and tracking.Existing studies primarily focus on specific airspace regions,leaving critical gaps in understanding the effects of long dispersion times,wide altitude ranges,and variable atmospheric conditions on missile contrail clouds.To address these gaps,this article develops a numerical method based on the Lagrangian random walk model,which incorporates various velocity variation terms,including particle velocity caused by the difference of wind field,by the thermal motion of local gas molecules and by random collisions between contrail cloud particles to capture the influence of environmental wind fields,atmospheric conditions,and particle concentrations on the motion of contrail cloud particles.A general coordinate system aligned with the missile's flight trajectory is employed to represent particle distribution characteristics.The proposed method is in good agreement with the conducted experiments as well as with the available numerical simulations.The results demonstrate that the proposed model effectively simulates the dispersion state of contrail clouds,accurately reflecting the impact of large-scale wind field variations and altitude changes with high computational efficiency.Additionally,simulation results indicate that the increased distance between gas molecules in rarefied environments facilitates enhanced particle dispersion,while larger particles exhibit a faster dispersion rate due to their greater mass.
文摘The regime of disturbance with natural or anthropogenic origin can lead to the destabilization or even to a mass mortality of benthic communities. Due to the heterogeneity of the disturbance there is a formation of patches in different stages of ecological succession. The aim of this study is to follow and describe the resilience in artificial disturbed sediment in a polluted bay in Rio de Janeiro. The sediment was collected, sterilized and placed inside corers (10 cmdiameter ×15 cmheight) in the same place where it was collected. We allocated the samples in two structures, the difference between them was that one was placed closed to the bottom and the other was placed50 cmheight. We found 2352 organisms distributed in 14 taxons. The class Polychaeta and the order Amphipoda showed the highest density in all the survey and treatments. We identified the factors influencing the scenarium: different mechanisms of dispersal, the position of the structures and life history of each group. Disturbance can be the main cause of the patch’s diversity found in estuaries and coastal areas. Because of this, monitoring of selected areas becomes an important tool to understand the regime of disturbance as a key factor structuring benthic communities in soft sediment, also suggesting a metapopulation dynamics.
文摘Aim To study fuel dispersion in fuel air explosive(FAE) and computational ways of fuel dispersion velocity in the near area. Methods\ The dispersion process of fuel in FAE was analyzed by the use of results measured with KODAK EKTAPRO EM Motion Analyzer and setting up mechanical models. Results\ Computational methods for fuel dispersion velocity in the acceleration stage is given and taken as a base for the study of fuel dispersion in the intermediate and the far area. Conclusion\ When the fuel flow velocity is higher than that of the explosion gas in the center cavity, the fuel divides with the explosion gas and its velocity of flow reaches a maximum. The acceleration stage ends at that time. The fuel dispersion velocity at this time is the initial conditions for numeral analyses of dispersion process in the intermediate and far areas.
基金supported by Key R&D plan of Hubei Province[grant number 2023BCB039]the Strategic Priority Research Program of the Chinese Academy of Sciences[grant number XDB31000000]Science&Technology Fundamental Resources Investigation Program[grant number 2022FY100400].
文摘Aggregation is suggested beneficial with foraging,defense,and other fitness for the group members.While long distance dispersal with kinship has been found in several marine fishes,similar cases have not been reported in inland waters.We utilized microsatellite genotype data of 397 eggs or juvenile silver carp(Hypophthalmichthys molitrix)born in 2017 from the middle and lower reaches of the Yangtze River in China to analyze their relatedness and infer the dispersal patterns during their early life stages and whether they dispersed with their kinship.There were 11–58 pairs of full siblings or half siblings between samples from the spawning ground(Yichang section)and other sites(34.1–1047.2 km)which showed the dispersal path.Particularly,the proportion of maternal siblings(mean:47.9%)was higher than random,indicating kinship aggregation,or that the fish traveled with their kinship during their early life stages.Such kin aggregation has profound implications for our understanding of early life stage dispersal in inland water fish populations.Our findings suggest that the preservation of habitats along the middle Yangtze River should be increased.In particular,the channelized river bank should be rebuilt with more heterogeneous habitat,and the lake-river connections should be restored to expand the amount of appropriate habitat.
文摘Following the quantitative determination of dust cloud parameters, this study investigated the flame propagation through cornstarch dust clouds in a vertical duct of 780 mm height and 160×160 mm square cross section, and gave particular attention to the effect of turbulence on flame characteristics. The turbulence induced by dust dispersion process was measured using a particle image velocimetry （PIV） system. Upward propagating dust flames were visualized with direct fight and shadow photography. The results show that a critical value of the turbulence intensity can be specified below which laminar flame propagation would be established. This transition condition is about 10 cm/s. The measured propagation speed of laminar flames appears to be in the range of 0.45-0.56 m/s, consistent with the measurements reported in the literature. For the present experimental conditions, the flame speed is little sensitive to the variations in dust concentration. Some information on the flame structure was revealed from the shadow records, showing the typical heterogeneous feature of dust combustion process.
文摘Nanosized dispersive hexagonal magnesium hydroxide （Mg（OH）2） has been prepared using an ammonia- hydrothermal method. Citric acid and monoethanolamine （MEA） were added to the reaction system during the ammonia precipitation and hydrothermal processes, respectively, to improve the crystallinity and dispersion of the （Mg（OH）2） particles. The resulting Mg（OH）2 samples obtained under the opti- mum preparation conditions were characterized by scanning electron microscopy, X-ray diffraction and thermal gravity analysis, which showed that this newly developed procedure afforded well-dispersed hexagonal nanoolates of Mg（OH）2 with a mean diameter of 246 nm.
