No abstract

Green Gross Domestic Product (GDP) is an important indicator to reflect the trade-off between the ecosystem and economic system. Substantial research has mapped historical green GDP spatially. But few studies have concerned future variations of green GDP. In this study, we have calculated and mapped the spatial distribution of the green GDP by summing the ecosystem service value (ESV) and GDP for China from 1990 to 2015. The pattern of land use change simulated by a CA-Markov model was used in the process of ESV prediction (with an average accuracy of 86%). On the other hand, based on the increasing trend of GDP during the period of 1990 to 2015, a regression model was built up to present time-series increases in GDP at prefecture-level cities, having an average value of R square (R2) of approximately 0.85 and significance level less than 0.05. The results indicated that (1) from 1990 to 2015, green GDP was increased, with a huge growth rate of 78%. Specifically, the ESV value was decreased slightly, while the GDP value was increased substantially. (2) Forecasted green GDP would increase by 194978.29 billion yuan in 2050. Specifically, the future ESV will decline, while the rapidly increased GDP leads to the final increase in future green GDP. (3) According to our results, the spatial differences in green GDP for regions became more significant from 1990 to 2050.

Dynamic stiffness and damping of the headstock, which is a critical component of precision horizontal machining center, are two main factors that influence machining accuracy and surface finish quality. Constrained Layer Damping (CLD) structure is proved to be effective in raising damping capacity for the thin plate and shell structures. In this paper, one kind of high damping material is utilized on the headstock to improve damping capacity. The dynamic characteristic of the hybrid headstock is investigated analytically and experimentally. The results demonstrate that the resonant response amplitudes of the headstock with damping material can decrease significantly compared to original cast structure. To obtain the optimal configuration of damping material, a topology optimization method based on the Evolutionary Structural Optimization (ESO) is implemented. Modal Strain Energy (MSE) method is employed to analyze the damping and to derive the sensitivity of the modal loss factor. The optimization results indicate that the added weight of damping material decreases by 50%; meanwhile the first two orders of modal loss factor decrease by less than 23.5% compared to the original structure.

Urban green space (UGS) is important in urban systems, as it benefits economic development, ecological conservation, and living conditions. Many studies have evaluated the economic, ecological, and social value of UGS worldwide, and spatial optimization for UGS has been carried out to maximize its value. However, few studies have simultaneously examined these three values of UGS in one optimization system. To fill this gap, this study evaluated the economic value of UGS in terms of promoting housing prices, its ecological value through the relief of high land surface temperature (LST), and its social value through the provision of recreation spaces for residents within a 255 m distance. Subsequently, these three values were set as objectives in a genetic algorithm (GA)-based multi-objective optimization (MOP) system. Shenzhen was taken as the case study area. The results showed that the influencing distance of UGS in Shenzhen for house prices was 345 m, and the influencing distance of UGS for LST was 135 m. Using MOP, the Pareto solutions for increasing UGS were identified and presented. The results indicate that MOP can simultaneously optimize UGS's economic, ecological, and social value.Sustainability 2020, 12, 1844 2 of 18 effects [16,17], absorbing particle air pollutants, improving air quality, infiltrating storms [18][19][20], reducing noise levels [13], and sequestering carbon [21].The social and ecological value of UGS is widely accepted, while its economic value is not as immediately recognizable, because the services it provides are public goods without market prices [22]. However, real estate markets in developed countries and regions with good environmental quality indicate that many people are willing to pay more for urban properties that are close to UGS [23,24]. Many studies have estimated the economic value or amenity benefits of urban parks and public open spaces [22,25,26].In summary, UGS has high social, ecological, and economic value. A comparative plan for UGS is essential for increasing the ecological and socioeconomic benefits of urban development [27]. To date, many studies have examined the spatial optimization of UGS to maximize its value. Huang et al. [27] used a space optimization strategy to improve the quality and accessibility of green spaces and proposed that this optimization method should be used in UGS planning and management. Zhang et al. [28] developed a multi-objective model to evaluate the diurnal cooling of UGS and identify the best locations and configurations for new UGSs. Unal and Uslu [29] attempted to minimize the distances between people and UGS service areas to optimize UGS. Yoon [30] used a multi-objective model to maximize the cooling effect and connectivity of UGS.Even though the spatial optimization of UGS has often been considered in urban planning research, existing studies typically consider only one function of UGS in their spatial optimization processes, such as its social function (through maximizing accessibility) or ecological function (through maximizing...