Abstract:The improper layout of urban public parks leads to the difference between citizens sharing or not sharing this kind of public resource, particularly in the historical districts of mountainous cities in China. The purpose of this study is to explore the spatial equity and quantitative measures of urban public parks' layouts by building a demand index of socially vulnerable groups sharing public parks based on the accessibility evaluation model. In this paper, Changting-a famous national historical and cultural city-is taken as the empirical object, then the accessibility and social equity of public parks is quantitatively measured with the aid of the field investigation method, the spatial analysis model of geographic information system (GIS) and the SPSS statistical analysis method. The results indicate that it is feasible to measure the spatial equity of urban public parks with the accessibility and demand index of socially vulnerable groups, and it can effectively characterize the rationality and social equity of urban ecological space. It shows that a degree of spatial mismatch exists between the distribution of urban public parks and that of residents, that is to say the spatial distribution of public parks is not equitable in terms of accessibility or residents' demands. Therefore, the data suggest that the spatial patterns and accessibility levels of parks in Changting County-especially the historical districts-should be further improved and perfected to achieve high levels of accessibility and equity through urban green space system planning. The paper may be used as a scientific reference for the planning and construction of ecological urban spaces. It can also provide useful decision-making guidance for urban planners in investigating, analyzing, and adjusting the distribution of public service facilities to achieve equitable outcomes, while promoting the harmonious and sustainable development of mountainous cities.

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The most widely studied linear models of the suspension forces in AC-DC three-degree of freedom hybrid magnetic bearings (AC-DC 3-DOF HMB) may not be practical for application to the precision control of bearings with larger air-gaps for larger suspension forces. In addition, the simplified linear and the real nonlinear models in linear zone of current and displacements have not been compared before. In the present study, the two most commonly used nonlinear models are analyzed comprehensively to address the lack of nonlinear model analysis in previous research and to seek the most appropriate model for both nonlinear and linear zones (full zone). The results show that no single model completely approximates the test results over the entire zone. A composite model, such as the "switching model", is more accurate. To illustrate the applicability of the results to both nonlinear model analysis and the proposed "switching model," nonlinear stiffness and performance test experiments were conducted. It is concluded that the model analysis and the proposed "switching model" can provide a control system with the most suitable mathematical models of the suspension force.

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The position of rotor and stator in switched reluctance motor is exchanged to obtain the single winding bearingless flywheel motor (SWBFM), which is more useful for flywheel energy storage with outer rotor. Compared with the switched reluctance motor, bearingless flywheel motor has obvious advantages in cost savings and consumption reducing. The radial force and torque are produced by single windings and the outer rotor could directly drive the flywheel with less mechanical transmission. In this study, a mathematical model of SWBFM is established based on Maxwell tensor method, in addition, the correction factor is present to obtain an accurate mathematical model based on finite element. In energy storage keeping state, the flywheel energy storage system could run on rated speed without the power input. Considering the relationship between the angle and the radial force coefficient, and the difference of radial force coefficient with each tooth pole, radial force dynamic current compensation methods of without β direction constraint and β direction constraint are present to ensure the SWBFM stable suspension under the condition of winding open-circuit fault. The results show that the proposed compensation methods are feasible and have high precision.