P granules are germ granules contained in Caenorhabditis elegans germ cells.The first germ cell is specified by the one-cell embryo in which P granules localize to the posterior.Previous studies suggested that the mec...P granules are germ granules contained in Caenorhabditis elegans germ cells.The first germ cell is specified by the one-cell embryo in which P granules localize to the posterior.Previous studies suggested that the mechanism of the localization phenomena is induced by liquid-liquid phase transition(LLPT),in which the polarity proteins control the saturation point of P granules.In the present study,we propose that the P granules phase transition can be triggered by the cytoplasmic streaming.A two-phase flow model is employed to simulate the localization of P granules,i.e.,the cytoplasm is considered as a liquid phase,and the droplet-like P granules are another liquid phase.With the presence of the cytoplasmic streaming,P granules,initially distributing uniformly in the entire one-cell embryo,eventually condense/dissolve in the cytoplasm phase,regulated by difference between the saturation pressure and the hydrodynamic pressure.The numerical results reveal that the cytoplasmic streaming has significant effects on the localization of P granules,as well as the embryo division.展开更多
By using the NCEP/NCAR pentad reanalysis data from 1968 to 2009, the variation characteristics of Middle East jet stream(MEJS) and its thermal mechanism during seasonal transition are studied. Results show that the in...By using the NCEP/NCAR pentad reanalysis data from 1968 to 2009, the variation characteristics of Middle East jet stream(MEJS) and its thermal mechanism during seasonal transition are studied. Results show that the intensity and south-north location of MEJS center exhibit obvious seasonal variation characteristics. When MEJS is strong, it is at 27.5°N from the 67 th pentad to the 24 th pentad the following year; when MEJS is weak, it is at 45°N from the 38 th pentad to the 44 th pentad. The first Empirical Orthogonal Function(EOF) mode of 200-hPa zonal wind field shows that MEJS is mainly over Egypt and Saudi Arabia in winter and over the eastern Black Sea and the eastern Aral Sea in summer. MEJS intensity markedly weakens in summer in comparison with that in winter. The 26th-31 st pentad is the spring-summer transition of MEJS, and the 54th-61 st pentad the autumn-winter transition. During the two seasonal transitions, the temporal variations of the 500-200 hPa south-north temperature difference(SNTD) well match with 200-hPa zonal wind velocity, indicating that the former leads to the latter following the principle of thermal wind. A case analysis shows that there is a close relation between the onset date of Indian summer monsoon and the transition date of MEJS seasonal transition. When the outbreak date of Indian summer monsoon is earlier than normal, MEJS moves northward earlier because the larger SNTD between 500-200 hPa moves northward earlier, with the westerly jet in the lower troposphere over 40°-90°E appearing earlier than normal, and vice versa.展开更多
The operation variables,including feed rate of ore slurry,caustic solution and live steams in the double-stream alumina digestion process,determine the product quality,process costs and the environment pollution.Previ...The operation variables,including feed rate of ore slurry,caustic solution and live steams in the double-stream alumina digestion process,determine the product quality,process costs and the environment pollution.Previously,they were set by the technical workers according to the offline analysis results and an empirical formula,which leads to unstable process indices and high consumption frequently.So,a multi-objective optimization model is built to maintain the balance between resource consumptions and process indices by taking technical indices and energy efficiency as objectives,where the key technical indices are predicted based on the digestion kinetics of diaspore.A multi-objective state transition algorithm(MOSTA)is improved to solve the problem,in which a self-adaptive strategy is applied to dynamically adjust the operator factors of the MOSTA and dynamic infeasible threshold is used to handle constraints to enhance searching efficiency and ability of the algorithm.Then a rule based strategy is designed to make the final decision from the Pareto frontiers.The method is integrated into an optimal control system for the industrial digestion process and tested in the actual production.Results show that the proposed method can achieve the technical target while reducing the energy consumption.展开更多
The phenomena associated with the entrainment of free-stream turbulence （FST） into boundary-layer flows are relevant for a number of subjects. It has been be- lieved that the continuous spectra of the Orr-Sommerfeld...The phenomena associated with the entrainment of free-stream turbulence （FST） into boundary-layer flows are relevant for a number of subjects. It has been be- lieved that the continuous spectra of the Orr-Sommerfeld （O-S）/Squire equations describe the entrainment process, and thus they are used to specify the inlet condition in simulation of bypass transition. However, Dong and Wu （Dong, M. and Wu, X. On continuous spectra of the Orr-Sommerfeld/Squire equations and entrainment of free-stream vortical disturbances. Journal of Fluid Mechanics, 732, 616-659 （2013）） pointed out that continuous spectra exhibit several non-physical features due to neglecting the non-parallelism. They further proposed a large-Reynolds-number asymptotic approach, and showed that the non-parallelism is a leading-order effect even for the short-wavelength disturbance, for which the response concentrates in the edge layer. In this paper, the asymptotic solution is verified numerically by studying its evolution in incompressible boundary layers. It is found that the numerical results can be accurately predicted by the asymptotic solution, implying that the latter is adequate for moderate Reynolds numbers. By introducing a series of such solutions as the inflow perturbations, the bypass transition is investigated via the direct numerical simulation （DNS）. The transition processes, including the evolution of streaks, the amplification of secondary-instability modes, and the emergence of turbulent spots, agree with the experimental observations.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11272197,and 11372175)the Innovation Program of Shanghai Municipality Education Commission,China(Grant No.14ZZ095)
文摘P granules are germ granules contained in Caenorhabditis elegans germ cells.The first germ cell is specified by the one-cell embryo in which P granules localize to the posterior.Previous studies suggested that the mechanism of the localization phenomena is induced by liquid-liquid phase transition(LLPT),in which the polarity proteins control the saturation point of P granules.In the present study,we propose that the P granules phase transition can be triggered by the cytoplasmic streaming.A two-phase flow model is employed to simulate the localization of P granules,i.e.,the cytoplasm is considered as a liquid phase,and the droplet-like P granules are another liquid phase.With the presence of the cytoplasmic streaming,P granules,initially distributing uniformly in the entire one-cell embryo,eventually condense/dissolve in the cytoplasm phase,regulated by difference between the saturation pressure and the hydrodynamic pressure.The numerical results reveal that the cytoplasmic streaming has significant effects on the localization of P granules,as well as the embryo division.
基金Project of Natural Science Foundation of China(41205035,40905045,40775059)National Basic Research and Development Program of China(2013CB430202)+3 种基金NSF of Jiangsu Higher Education Institutions(13KJB170013)Special Scientific Research Fund of Public Welfare Industries of China(GYHY201306028)Qing Lan ProjectProject Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘By using the NCEP/NCAR pentad reanalysis data from 1968 to 2009, the variation characteristics of Middle East jet stream(MEJS) and its thermal mechanism during seasonal transition are studied. Results show that the intensity and south-north location of MEJS center exhibit obvious seasonal variation characteristics. When MEJS is strong, it is at 27.5°N from the 67 th pentad to the 24 th pentad the following year; when MEJS is weak, it is at 45°N from the 38 th pentad to the 44 th pentad. The first Empirical Orthogonal Function(EOF) mode of 200-hPa zonal wind field shows that MEJS is mainly over Egypt and Saudi Arabia in winter and over the eastern Black Sea and the eastern Aral Sea in summer. MEJS intensity markedly weakens in summer in comparison with that in winter. The 26th-31 st pentad is the spring-summer transition of MEJS, and the 54th-61 st pentad the autumn-winter transition. During the two seasonal transitions, the temporal variations of the 500-200 hPa south-north temperature difference(SNTD) well match with 200-hPa zonal wind velocity, indicating that the former leads to the latter following the principle of thermal wind. A case analysis shows that there is a close relation between the onset date of Indian summer monsoon and the transition date of MEJS seasonal transition. When the outbreak date of Indian summer monsoon is earlier than normal, MEJS moves northward earlier because the larger SNTD between 500-200 hPa moves northward earlier, with the westerly jet in the lower troposphere over 40°-90°E appearing earlier than normal, and vice versa.
基金Project(62073342)supported by the National Natural Science Foundation of ChinaProject(2014 AA 041803)supported by the Hi-tech Research and Development Program of China。
文摘The operation variables,including feed rate of ore slurry,caustic solution and live steams in the double-stream alumina digestion process,determine the product quality,process costs and the environment pollution.Previously,they were set by the technical workers according to the offline analysis results and an empirical formula,which leads to unstable process indices and high consumption frequently.So,a multi-objective optimization model is built to maintain the balance between resource consumptions and process indices by taking technical indices and energy efficiency as objectives,where the key technical indices are predicted based on the digestion kinetics of diaspore.A multi-objective state transition algorithm(MOSTA)is improved to solve the problem,in which a self-adaptive strategy is applied to dynamically adjust the operator factors of the MOSTA and dynamic infeasible threshold is used to handle constraints to enhance searching efficiency and ability of the algorithm.Then a rule based strategy is designed to make the final decision from the Pareto frontiers.The method is integrated into an optimal control system for the industrial digestion process and tested in the actual production.Results show that the proposed method can achieve the technical target while reducing the energy consumption.
基金Project supported by the National Natural Science Foundation of China(Nos.11472189 and11332007)
文摘The phenomena associated with the entrainment of free-stream turbulence （FST） into boundary-layer flows are relevant for a number of subjects. It has been be- lieved that the continuous spectra of the Orr-Sommerfeld （O-S）/Squire equations describe the entrainment process, and thus they are used to specify the inlet condition in simulation of bypass transition. However, Dong and Wu （Dong, M. and Wu, X. On continuous spectra of the Orr-Sommerfeld/Squire equations and entrainment of free-stream vortical disturbances. Journal of Fluid Mechanics, 732, 616-659 （2013）） pointed out that continuous spectra exhibit several non-physical features due to neglecting the non-parallelism. They further proposed a large-Reynolds-number asymptotic approach, and showed that the non-parallelism is a leading-order effect even for the short-wavelength disturbance, for which the response concentrates in the edge layer. In this paper, the asymptotic solution is verified numerically by studying its evolution in incompressible boundary layers. It is found that the numerical results can be accurately predicted by the asymptotic solution, implying that the latter is adequate for moderate Reynolds numbers. By introducing a series of such solutions as the inflow perturbations, the bypass transition is investigated via the direct numerical simulation （DNS）. The transition processes, including the evolution of streaks, the amplification of secondary-instability modes, and the emergence of turbulent spots, agree with the experimental observations.
