In the advanced pre ssurized water reactor nuclearpowerplant design,the pas sive res idual heat removals ystem is adopted.This system is composed of the secondary side ofsteam generator,air coo ler and air loop whichc...In the advanced pre ssurized water reactor nuclearpowerplant design,the pas sive res idual heat removals ystem is adopted.This system is composed of the secondary side ofsteam generator,air coo ler and air loop whichconsis ts of the air cooling tower and atmosphere environment.Wall-air heat exchanging corre lation equation is added tothe RELAP5 Code.The modified code is used to s imulate the AC600 PWR nuclearpower plant trans ient behavior withPas sive Res idualHeat RemovalSystem(PRHR)in micro-circulation start-up mode after the bla ckout accident occurs.The calculation res ults show that the higher the chimney or the larger the air cooler heattransfêr area,the more the heatremoval capacity of PRHR sys tem.The computationalresults are cons istent with the theoreticalanalyses.展开更多
A novel hydrogel composite was prepared via inverse suspension polymerization using starch, acrylic acid and organo-mordenite micropowder with the cross- linker, N,N＇-methylenebisacrylamide and the initiator, potassi...A novel hydrogel composite was prepared via inverse suspension polymerization using starch, acrylic acid and organo-mordenite micropowder with the cross- linker, N,N＇-methylenebisacrylamide and the initiator, potassium persulfate. Fourier transform infrared spectro- scopy, X-ray diffraction spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy confirmed that the acrylic acid was grafted onto the backbone of the corn starch, that the organo-mordenite participated in the polymerization, and that the addition of organo-mordenite improved the surface morphology of the hydrogel composite. The swelling capacity of the hydrogel compo- site was evaluated in distilled water, and solutions with different pH values, and various salt solutions. It was found that the incorporation of 10wt-% organo-mordenite enhanced the water absorbency by 144% （from 268 to 655 g-gl） and swelling was extremely sensitive to the pH values, the concentration of the salt solution and cation type. Swelling kinetics and water diffusion mechanism of the hydrogel composite in distilled water were also discussed. Moreover, the hydrogel composite showed excellent reversibility of water absorption even after five repetitive cycles and the hydrogel composite exhibited significant environmental-responsiveness by changing the swelling medium from distilled water to 0.1 mol. L-1 NaC1 solution. In addition, the loading and release of urea by the hydrogel composite were tested and the nutrient-slow- release capability of this material was found to be suitable for many potential applications.展开更多
Predatory lady beetles (Coccinellidae)contribute to biological control of agri- cultural pests,however,multiple species frequently compete for similar resources in the same environment.Numerous studies have examined e...Predatory lady beetles (Coccinellidae)contribute to biological control of agri- cultural pests,however,multiple species frequently compete for similar resources in the same environment.Numerous studies have examined ecological interactions among the native North American convergent lady beetle (Hippodamia convergens)and two intro- duced species,the seven-spotted lady beetle (Coccinella septempunctata)and the Asian lady beetle (Harmonia axyridis),in agricultural fields and described multiyear population dynamics.However,the evolutionary dynamics of these interacting species of predatory beetles are uncharacterized.We utilize publicly available multilocus genotype data from geographically disjunct populations of these three species to estimate demography across North American populations.Coalescent analyses reveal (1)a recent (4-5years)decline (>12 fold)in microsatellite effective population size ofH.convergens,while expanding (mutation scaled growth rate in 1/u generations =2910,SD =362)over evolutionary time scales,(2)a massive (>150 fold),and very recent,effective population size decline in Ha. axyridis,and (3)population size growth (mutation scaled growth rate =997,SD =60)over recent and evolutionary time scales in C.septempunctata.Although these estimates are based on genetic data with different mutation rates and patterns of inheritance (mitochondrial versus nuclear),these dynamic and differing population size histories are striking. Further studies of the interactions of these predatory lady beetles in the field are thus warranted to explore the consequences of population size change and biological control activities for evolutionary trajectories in North America.展开更多
In this paper, we investigated an impulsive predator-prey model with mu- tual interference and Crowley-Martin response function. By the comparison theorem and the analysis technique of [12,14], sufficient conditions f...In this paper, we investigated an impulsive predator-prey model with mu- tual interference and Crowley-Martin response function. By the comparison theorem and the analysis technique of [12,14], sufficient conditions for the per-manence of the impulsive model are obtained, which generalizes one of main results of [4].展开更多
文摘In the advanced pre ssurized water reactor nuclearpowerplant design,the pas sive res idual heat removals ystem is adopted.This system is composed of the secondary side ofsteam generator,air coo ler and air loop whichconsis ts of the air cooling tower and atmosphere environment.Wall-air heat exchanging corre lation equation is added tothe RELAP5 Code.The modified code is used to s imulate the AC600 PWR nuclearpower plant trans ient behavior withPas sive Res idualHeat RemovalSystem(PRHR)in micro-circulation start-up mode after the bla ckout accident occurs.The calculation res ults show that the higher the chimney or the larger the air cooler heattransfêr area,the more the heatremoval capacity of PRHR sys tem.The computationalresults are cons istent with the theoreticalanalyses.
文摘A novel hydrogel composite was prepared via inverse suspension polymerization using starch, acrylic acid and organo-mordenite micropowder with the cross- linker, N,N＇-methylenebisacrylamide and the initiator, potassium persulfate. Fourier transform infrared spectro- scopy, X-ray diffraction spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy confirmed that the acrylic acid was grafted onto the backbone of the corn starch, that the organo-mordenite participated in the polymerization, and that the addition of organo-mordenite improved the surface morphology of the hydrogel composite. The swelling capacity of the hydrogel compo- site was evaluated in distilled water, and solutions with different pH values, and various salt solutions. It was found that the incorporation of 10wt-% organo-mordenite enhanced the water absorbency by 144% （from 268 to 655 g-gl） and swelling was extremely sensitive to the pH values, the concentration of the salt solution and cation type. Swelling kinetics and water diffusion mechanism of the hydrogel composite in distilled water were also discussed. Moreover, the hydrogel composite showed excellent reversibility of water absorption even after five repetitive cycles and the hydrogel composite exhibited significant environmental-responsiveness by changing the swelling medium from distilled water to 0.1 mol. L-1 NaC1 solution. In addition, the loading and release of urea by the hydrogel composite were tested and the nutrient-slow- release capability of this material was found to be suitable for many potential applications.
文摘Predatory lady beetles (Coccinellidae)contribute to biological control of agri- cultural pests,however,multiple species frequently compete for similar resources in the same environment.Numerous studies have examined ecological interactions among the native North American convergent lady beetle (Hippodamia convergens)and two intro- duced species,the seven-spotted lady beetle (Coccinella septempunctata)and the Asian lady beetle (Harmonia axyridis),in agricultural fields and described multiyear population dynamics.However,the evolutionary dynamics of these interacting species of predatory beetles are uncharacterized.We utilize publicly available multilocus genotype data from geographically disjunct populations of these three species to estimate demography across North American populations.Coalescent analyses reveal (1)a recent (4-5years)decline (>12 fold)in microsatellite effective population size ofH.convergens,while expanding (mutation scaled growth rate in 1/u generations =2910,SD =362)over evolutionary time scales,(2)a massive (>150 fold),and very recent,effective population size decline in Ha. axyridis,and (3)population size growth (mutation scaled growth rate =997,SD =60)over recent and evolutionary time scales in C.septempunctata.Although these estimates are based on genetic data with different mutation rates and patterns of inheritance (mitochondrial versus nuclear),these dynamic and differing population size histories are striking. Further studies of the interactions of these predatory lady beetles in the field are thus warranted to explore the consequences of population size change and biological control activities for evolutionary trajectories in North America.
基金supported by the Natural Science Foundation of Fujian Province(2015J01012,2015J01019,2015J05006)the Scientific Research Foundation of Fuzhou University(XRC-1438)
文摘In this paper, we investigated an impulsive predator-prey model with mu- tual interference and Crowley-Martin response function. By the comparison theorem and the analysis technique of [12,14], sufficient conditions for the per-manence of the impulsive model are obtained, which generalizes one of main results of [4].
