An oil-in-water (O/W) solvent evaporation method was used to prepare biodegradable microspheresbased on poly(D,L-lactic acid) (PLA). Nifedipine, a hydrophobic drug, was chosen as a model molecule in the studyof drug e...An oil-in-water (O/W) solvent evaporation method was used to prepare biodegradable microspheresbased on poly(D,L-lactic acid) (PLA). Nifedipine, a hydrophobic drug, was chosen as a model molecule in the studyof drug entrapment and release. Effect of preparation conditions on the size, morphology, drug loading, and releaseprofiles of micropheres was investigated. Based on in vitro release experimental findings, a diffusion/dissolutionmodel was presented for quantitative description of the resulting release behaviors and drug release kinetics fromPLA microspheres analyzed. The mathematical models were used to predict the effect of microstructure on theresulting drug release. It provided an approach to determine the suitable structure parameters for microspheres toachieve desired drug release behaviors.展开更多
According to the consequences of software failures, software faults remaining in safety-critical systems can be classified into two sets： common faults and fatal faults. Common faults cause slight loss when they are ...According to the consequences of software failures, software faults remaining in safety-critical systems can be classified into two sets： common faults and fatal faults. Common faults cause slight loss when they are activated. A fatal fault can lead to significant loss, and even damage the safety-crltical system entirely when it is activated. A software reliability growth model for safety-critical systems is developed based on G - 0 model. And a software cost model is proposed too. The cost model considers maintenance and risk costs due to software failures. The optimal release policies are discussed to minimize the total software cost. A numerical exampie is provided to illustrate how to use the results we obtained.展开更多
In recent decades,it presents a more obvious temperature rise in urban area along with the global warming.City is generally the center of human society,so the study on urban temperature variation will be helpful to ou...In recent decades,it presents a more obvious temperature rise in urban area along with the global warming.City is generally the center of human society,so the study on urban temperature variation will be helpful to our city development planning that is to reduce urban warming.The study is also helpful to a more comprehensive understanding of the causes of climate warming,which could provide a theoretical support to the government to make more reasonable international energy policies.Local temperature rise has different mechanisms with the global warming:large quantities of artificial heat release from the energy consumption will stay in urban areas for a period of time,which will inevitably influence the short-term trend of the local temperature change.Based on that view,a structural thermodynamic model was established in this paper to investigate the effect of the artificial heat release on the urban local temperatures.In the model,the city environment was divided into Human,Local,Outer three blocks,and then the heat and temperatures of the blocks were analyzed based on the laws of thermodynamics.After that,the effect of artificial heat release in Human block on the local temperatures was clarified.The model shows that the artificial heat release has an approximately linearly promoting effect on the local temperature rise,and the more the heat release is,the stronger the effect is.In addition,a validation of that model was carried out based on some national statistical data.The data of temperatures and artificial heat release of some provincial capitals of China were analyzed with linear regression extrapolation method and Pearson correlation statistical method.The results show that in most capital cities,the temperature variations basically depend on the artificial heat release in a linear relationship,which usually becomes more apparent with the increase of the artificial heat release in both spatial and temporal dimensions.The conclusions of the statistics have good conformity with the model and the rationality of the model is verified.展开更多
文摘An oil-in-water (O/W) solvent evaporation method was used to prepare biodegradable microspheresbased on poly(D,L-lactic acid) (PLA). Nifedipine, a hydrophobic drug, was chosen as a model molecule in the studyof drug entrapment and release. Effect of preparation conditions on the size, morphology, drug loading, and releaseprofiles of micropheres was investigated. Based on in vitro release experimental findings, a diffusion/dissolutionmodel was presented for quantitative description of the resulting release behaviors and drug release kinetics fromPLA microspheres analyzed. The mathematical models were used to predict the effect of microstructure on theresulting drug release. It provided an approach to determine the suitable structure parameters for microspheres toachieve desired drug release behaviors.
基金Sponsored by the Ph.D. Programs Foundation of Ministry of Education of China (Grant No. 20020213017).
文摘According to the consequences of software failures, software faults remaining in safety-critical systems can be classified into two sets： common faults and fatal faults. Common faults cause slight loss when they are activated. A fatal fault can lead to significant loss, and even damage the safety-crltical system entirely when it is activated. A software reliability growth model for safety-critical systems is developed based on G - 0 model. And a software cost model is proposed too. The cost model considers maintenance and risk costs due to software failures. The optimal release policies are discussed to minimize the total software cost. A numerical exampie is provided to illustrate how to use the results we obtained.
基金supported by the Knowledge Innovation Project of The Chinese Academy of Sciences(Grant No. KGCX2-YW-356)
文摘In recent decades,it presents a more obvious temperature rise in urban area along with the global warming.City is generally the center of human society,so the study on urban temperature variation will be helpful to our city development planning that is to reduce urban warming.The study is also helpful to a more comprehensive understanding of the causes of climate warming,which could provide a theoretical support to the government to make more reasonable international energy policies.Local temperature rise has different mechanisms with the global warming:large quantities of artificial heat release from the energy consumption will stay in urban areas for a period of time,which will inevitably influence the short-term trend of the local temperature change.Based on that view,a structural thermodynamic model was established in this paper to investigate the effect of the artificial heat release on the urban local temperatures.In the model,the city environment was divided into Human,Local,Outer three blocks,and then the heat and temperatures of the blocks were analyzed based on the laws of thermodynamics.After that,the effect of artificial heat release in Human block on the local temperatures was clarified.The model shows that the artificial heat release has an approximately linearly promoting effect on the local temperature rise,and the more the heat release is,the stronger the effect is.In addition,a validation of that model was carried out based on some national statistical data.The data of temperatures and artificial heat release of some provincial capitals of China were analyzed with linear regression extrapolation method and Pearson correlation statistical method.The results show that in most capital cities,the temperature variations basically depend on the artificial heat release in a linear relationship,which usually becomes more apparent with the increase of the artificial heat release in both spatial and temporal dimensions.The conclusions of the statistics have good conformity with the model and the rationality of the model is verified.
