The COVID-19 is a major global health event that has changed people’s lives and behaviors. As a fragile and sensitive area with high population density and poor living conditions in the city, collective housing is al...The COVID-19 is a major global health event that has changed people’s lives and behaviors. As a fragile and sensitive area with high population density and poor living conditions in the city, collective housing is also an important construction area for future urban renewal. In the process of the spread of the new crown epidemic, the collective housing has exposed a series of weaknesses such as difficult community management, inconvenience of life, and insufficient outdoor space. Therefore, the update and transformation of the outdoor environment of the collective housing combined with the concept of public health is a problem that must be considered at present. This article combines the practice of renewal and transformation of the X community in Chaoyang District, Beijing, combined with survey methods such as questionnaires, interviews, and observations, combined with the needs of residents and the practical experience of the grassroots management unit, and carried out an overall renewal design of the external space environment of the collective housing. The epidemic is combined with the division of functional layout, refined design of outdoor activity space to ensure safe distance, and increased shared smart facilities to improve the quality of the outdoor environment of collective residences and strengthen community resilience;to achieve communication and sharing, epidemic prevention and control on the basis of ensuring safe social distance outdoor sports and other functions. In this way, the ability of collective housing to prevent, identify, and dispose of urban risks will be improved, and will provide residents with a better and livable community life.展开更多
We consider an age-dependent branching process in random environments. The environments are represented by a stationary and ergodic sequence ξ = (ξ 0, ξ 1,…) of random variables. Given an environment ξ, the proce...We consider an age-dependent branching process in random environments. The environments are represented by a stationary and ergodic sequence ξ = (ξ 0, ξ 1,…) of random variables. Given an environment ξ, the process is a non-homogenous Galton-Watson process, whose particles in n-th generation have a life length distribution G(ξ n ) on ?+, and reproduce independently new particles according to a probability law p(ξ n ) on ?. Let Z(t) be the number of particles alive at time t. We first find a characterization of the conditional probability generating function of Z(t) (given the environment ξ) via a functional equation, and obtain a criterion for almost certain extinction of the process by comparing it with an embedded Galton-Watson process. We then get expressions of the conditional mean E ξ Z(t) and the global mean EZ(t), and show their exponential growth rates by studying a renewal equation in random environments.展开更多
文摘The COVID-19 is a major global health event that has changed people’s lives and behaviors. As a fragile and sensitive area with high population density and poor living conditions in the city, collective housing is also an important construction area for future urban renewal. In the process of the spread of the new crown epidemic, the collective housing has exposed a series of weaknesses such as difficult community management, inconvenience of life, and insufficient outdoor space. Therefore, the update and transformation of the outdoor environment of the collective housing combined with the concept of public health is a problem that must be considered at present. This article combines the practice of renewal and transformation of the X community in Chaoyang District, Beijing, combined with survey methods such as questionnaires, interviews, and observations, combined with the needs of residents and the practical experience of the grassroots management unit, and carried out an overall renewal design of the external space environment of the collective housing. The epidemic is combined with the division of functional layout, refined design of outdoor activity space to ensure safe distance, and increased shared smart facilities to improve the quality of the outdoor environment of collective residences and strengthen community resilience;to achieve communication and sharing, epidemic prevention and control on the basis of ensuring safe social distance outdoor sports and other functions. In this way, the ability of collective housing to prevent, identify, and dispose of urban risks will be improved, and will provide residents with a better and livable community life.
基金the National Natural Sciente Foundation of China (Grant Nos. 10771021, 10471012)Scientific Research Foundation for Returned Scholars, Ministry of Education of China (Grant No. [2005]564)
文摘We consider an age-dependent branching process in random environments. The environments are represented by a stationary and ergodic sequence ξ = (ξ 0, ξ 1,…) of random variables. Given an environment ξ, the process is a non-homogenous Galton-Watson process, whose particles in n-th generation have a life length distribution G(ξ n ) on ?+, and reproduce independently new particles according to a probability law p(ξ n ) on ?. Let Z(t) be the number of particles alive at time t. We first find a characterization of the conditional probability generating function of Z(t) (given the environment ξ) via a functional equation, and obtain a criterion for almost certain extinction of the process by comparing it with an embedded Galton-Watson process. We then get expressions of the conditional mean E ξ Z(t) and the global mean EZ(t), and show their exponential growth rates by studying a renewal equation in random environments.