Wave group is important in ocean wave theory and applications. In the past, nonlinear interaction among wave groups has been studied on the basis of the nonlinear Sehrrdinger equation. Using this theoretical approach,...Wave group is important in ocean wave theory and applications. In the past, nonlinear interaction among wave groups has been studied on the basis of the nonlinear Sehrrdinger equation. Using this theoretical approach, we found that the nonlinear interaction among wave groups causes asymmetry in the shape of the wave envelope （steeper in the front of the curve of the envelope）. An important consequence of this asymmetry is that the highest wave in a wave group appears one individual wave length ahead of the center of the wave group. Further results show that the degree of envelope asymmetry increases with increasing spectral width and the wave steepness. This theoretical analysis has been supplemented by a systematic experimental study of wind waves. Laboratory and some open sea wave data were analyzed. The results show that the shape of the wind wave envelope of wind waves has the same asymmetry predicted by the theoretical approach. The observed degree of deformation of the envelope also increases with increasing spectral width and the wave steepness as predicted by theory. These conclusions have important ramifications for practical applications of ocean wave theory.展开更多
It is claimed that open spaces in cities, such as parks, have an urban cooling effect. However, the relationship between urban parks and adjacent districts is still not explicit. In order to clarify the interaction be...It is claimed that open spaces in cities, such as parks, have an urban cooling effect. However, the relationship between urban parks and adjacent districts is still not explicit. In order to clarify the interaction between urban parks and their urban surroundings, this paper takes the Temple of Heaven Park （THP） as an example of a park station and focuses on analyzing the differences with a nearby urban station.THP is located in the center of Beijing, and the nearest urban station is Tian An Men. It is interesting that the cooling effect of THP reaches a peak and remains stable when its city background urban heat island （UHI） varies within a given range, but becomes unstable when the UHI goes beyond the range. This is called an enhanced cooling effect in this paper. As a result, the UHi intensities （UHIIs） are calculated in order to comprehend the role of the park cooling effect in the urban heating characteristics of Beijing. By comparison with five other park-district pairs, this paper attempts to identify the causes of the enhanced cooling effect. It is found that six park-district pairs consistently demonstrate a persistently stronger cooling rate during the night, and that the water coverage might be a key factor in enhancing the park cooling effect. Based on further investigation of the influence of surrounding UHIs on the park cooling effect, it is found that the UHII differences in park-district pairs show quasi-linear changes within a given range as the UHli of the surrounding district increases.展开更多
Objective: To explore the possibility of repairi ng long segmental bone defects and preventing infection with cefazolin loaded bo ne matrix gelatin (C-BMG).Methods: C-BMG was made from putting cefazolin into BMG by va...Objective: To explore the possibility of repairi ng long segmental bone defects and preventing infection with cefazolin loaded bo ne matrix gelatin (C-BMG).Methods: C-BMG was made from putting cefazolin into BMG by vac uum absorption and lyophilization techniques. The sustaining period of effective drug concentration in vitro and in vivo was detected. The time of inhibiting ba cteria,and the drug concentration in local tissues (bone and muscle) and plasma after implantation of C-BMG were examined by high performance liquid chromatog raphy. Results: The effective inhibition time to staphylococcus aureus of C-BMG was 22 days in vitro; while 14 days in vivo. The cefazolin concentrat ion in local tissues was higher in early stage,and later it kept a stable and l ow drug release. C-BMG showed an excellent ability to repair segmental long bon e defects.Conclusions: C-BMG can gradually release cefazolin with effect ive drug concentration and has excellent ability to repair segmental bone defect s. It can be used to repair segmental long bone defects and prevent infection af ter operation.展开更多
Macao was one of the earliest port cities in China to be opened to foreigners; but how, under the institutions of Ming dynasty China, it should be opened to the Portuguese, and what its character and function should b...Macao was one of the earliest port cities in China to be opened to foreigners; but how, under the institutions of Ming dynasty China, it should be opened to the Portuguese, and what its character and function should be, were subjects that triggered controversy both at court and among non-officials. It was only after a lengthy process of evolution that Macao finally developed into a commercial city. The special political environment, administrative patterns and social experiences of early Macao created a unique character and tradition of ＂harmony amidst difference, and difference amidst harmony＂ that was maintained for centuries with undiminished vitality.展开更多
基金Supported by the National Science Foundation of China (No. 40576007)the New Century Excellent Talent Foundation from Education Ministry of China (No. NCET-08-0509)
文摘Wave group is important in ocean wave theory and applications. In the past, nonlinear interaction among wave groups has been studied on the basis of the nonlinear Sehrrdinger equation. Using this theoretical approach, we found that the nonlinear interaction among wave groups causes asymmetry in the shape of the wave envelope （steeper in the front of the curve of the envelope）. An important consequence of this asymmetry is that the highest wave in a wave group appears one individual wave length ahead of the center of the wave group. Further results show that the degree of envelope asymmetry increases with increasing spectral width and the wave steepness. This theoretical analysis has been supplemented by a systematic experimental study of wind waves. Laboratory and some open sea wave data were analyzed. The results show that the shape of the wind wave envelope of wind waves has the same asymmetry predicted by the theoretical approach. The observed degree of deformation of the envelope also increases with increasing spectral width and the wave steepness as predicted by theory. These conclusions have important ramifications for practical applications of ocean wave theory.
基金supported by the National Natural Science Foundation of China[grant number 41375069]National Basic Research Program of China[grant number 2012CB957804]Young Talent Programming of China Meteorological Administration
文摘It is claimed that open spaces in cities, such as parks, have an urban cooling effect. However, the relationship between urban parks and adjacent districts is still not explicit. In order to clarify the interaction between urban parks and their urban surroundings, this paper takes the Temple of Heaven Park （THP） as an example of a park station and focuses on analyzing the differences with a nearby urban station.THP is located in the center of Beijing, and the nearest urban station is Tian An Men. It is interesting that the cooling effect of THP reaches a peak and remains stable when its city background urban heat island （UHI） varies within a given range, but becomes unstable when the UHI goes beyond the range. This is called an enhanced cooling effect in this paper. As a result, the UHi intensities （UHIIs） are calculated in order to comprehend the role of the park cooling effect in the urban heating characteristics of Beijing. By comparison with five other park-district pairs, this paper attempts to identify the causes of the enhanced cooling effect. It is found that six park-district pairs consistently demonstrate a persistently stronger cooling rate during the night, and that the water coverage might be a key factor in enhancing the park cooling effect. Based on further investigation of the influence of surrounding UHIs on the park cooling effect, it is found that the UHII differences in park-district pairs show quasi-linear changes within a given range as the UHli of the surrounding district increases.
基金ThisprojectwassupportedbyagrantfromtheMinistryofHealth (No .96 1 14 5 )
文摘Objective: To explore the possibility of repairi ng long segmental bone defects and preventing infection with cefazolin loaded bo ne matrix gelatin (C-BMG).Methods: C-BMG was made from putting cefazolin into BMG by vac uum absorption and lyophilization techniques. The sustaining period of effective drug concentration in vitro and in vivo was detected. The time of inhibiting ba cteria,and the drug concentration in local tissues (bone and muscle) and plasma after implantation of C-BMG were examined by high performance liquid chromatog raphy. Results: The effective inhibition time to staphylococcus aureus of C-BMG was 22 days in vitro; while 14 days in vivo. The cefazolin concentrat ion in local tissues was higher in early stage,and later it kept a stable and l ow drug release. C-BMG showed an excellent ability to repair segmental long bon e defects.Conclusions: C-BMG can gradually release cefazolin with effect ive drug concentration and has excellent ability to repair segmental bone defect s. It can be used to repair segmental long bone defects and prevent infection af ter operation.
文摘Macao was one of the earliest port cities in China to be opened to foreigners; but how, under the institutions of Ming dynasty China, it should be opened to the Portuguese, and what its character and function should be, were subjects that triggered controversy both at court and among non-officials. It was only after a lengthy process of evolution that Macao finally developed into a commercial city. The special political environment, administrative patterns and social experiences of early Macao created a unique character and tradition of ＂harmony amidst difference, and difference amidst harmony＂ that was maintained for centuries with undiminished vitality.
