Geographical Accessibility to Basic Infrastructures and Services in Rural Senegal: The Case of the Niakhar Area

Access to basic infrastructure and services is a factor in economic development and an important aspect in combatting social and spatial disparities. But this access is often subject to several constraints, including geographical accessibility. In this article, we aim to analyze the geographical accessibility to basic infrastructure and services in the Niakhar area, using the improved two step floating catchment area method and local spatial association indicators. The results reveal that the areas with high accessibility to health and education infrastructures and services are mainly located along the south-east and north-west gradient, while those with low accessibility are found in the south-west and north-east center. They also show high accessibility to trade services in the center of the study area.

Particle-in-Cell Simulation Study on the Floating Potential of Spacecraft in the Low Earth Orbit

In order to further understand the characteristics of the floating potential of low earth orbit spacecraft,the effects of the electron current collection area,background electron temperature,photocurrent emission,spacecraft wake,and the shape of spacecraft on spacecraft floating potential were studied here by particle-in-cell simulation in the low earth orbit.The simulation results show that the electron current collection area and background electron temperature impact on the floating potential by changing the electron current collection of spacecraft.By increasing the electron current collection area or background electron temperature,the spacecraft will float at a lower electric potential with respect to the surrounding plasma.However,the spacecraft wake affects the floating potential by increasing the ion current collected by spacecraft.The emission of the photocurrent from the spacecraft surface,which compensates for the electrons collected from background plasma,causes the floating potential to increase.The shape of the spacecraft is also an important factor influencing the floating potential.

我国产前诊断机构空间可及性与公平性

目的评价我国产前诊断机构的空间可及性与公平性,以期为优化此类机构的空间规划布局提供参考。方法用两步移动搜索法和空间基尼系数对我国产前诊断机构的空间可及性和公平性进行评价。结果我国中东部地区和各省(自治区、直辖市)中心城市产前诊断服务的空间可及性与公平性均优于西部地区和偏远地区。结论建议适当增加西部地区和偏远地区的产前诊断机构与卫生技术人员数量,以优化我国产前诊断机构的规划布局。

Suitability Evaluation of Rural Settlements Based on Accessibility of Production and Living： A Case Study of Tingzu Town in Hubei Prov- ince of China

Rural settlements are the main carriers of agriculture, rural areas and farmers; thus, optimizing the production and living space of rural settlements is highly significant to rural development. Taking the effective allocation of resources as the starting point, a suitability evaluation system of rural settlements, based on accessibility of production and living, was proposed in this study to provide scientific basis for the optimization of production and living space. The accessibility of production and living was measured by an im- proved two-step floating catchment area method, which considered proximity and availability based on the inclination of rural residents. The suitability evaluation system consisted of traditional suitability evaluation and newly proposed limiting factor identification based on the loss score proportion of suitability. Tingzu Town of Hubei Province, China, was chosen as the case study area. Based on the re- suits of the suitability evaluation system, corresponding suggestions on rural land consolidation, industry division, as well as the layout of health care and education facilities were proposed to optimize the production and living space of rural settlements in Tingzu Town. It is found that the suitability evaluation based on accessibility of production and living is more scientific and accurate than the traditional ones which significantly overestimate production and living convenience. Moreover, the limiting factor identification can help us put forward suggestions according to local conditions and bring about the highly targeted optimization of production and living space of rural settlements.

Evaluation and Promotion of the Service Capacity of Urban Public Open Spaces Based on Improving Accessibility:A Case Study of Shenyang City,China

The service capacity of urban public open spaces is an important indicator of the justness and soundness of the allocation of public space resources,such as parks and green spaces,in the process of urban development.Improving the service capacity of urban public open spaces is conductive to healthy,sustainable urban development.In this study,taking Shengyang City,China as a case study,a Gaussian-based two-step floating catchment area method(2 SFCA)is used to calculate an accessibility index and identify residential areas with a poor accessibility to urban public open spaces.Then,a particle swarm algorithm(PSA)is used to optimize the locations of new open space developments.Finally,the optimization results are verified using the analytic network process(ANP).The results show that the service capacity of public open spaces in the center of Shenyang City(covering six districts)is relatively low and exhibits an uneven spatial distribution.In the service scope of the existing urban public open spaces,the accessibility for 48.6%of the residential estates is moderately poor or poor.The layout is optimized when the number of optimization points is set to 8.These points are mainly located in old town areas such as the Tiexi,Huanggu,and Dadong districts.The optimization increases the green space area accessible by motor vehicles(60 min),bicycles(60 min),and walking(30 min)by 4.67%,5.38%,and 8.03%of the study area,respectively.Finally,green space planning recommendations are offered from two perspectives:spatial layout and transport system optimization.