Impacts of land-use change on ecosystem service value in Changsha,China

Changsha,a typical city in central China,was selected as the study area to assess the variations of ecosystem service value on the basis of land-use change. The analysis not only included the whole city but also the urban district where the landscape changed more rapidly in the center of the city. Two LANDSAT TM data sets in 1986 and 2000 and land use data of five urban districts from 1995 to 2005 were used to estimate the changes in the size of six land use categories. Meanwhile,previously published value coefficients were used to detect the changes in the value of ecosystem services delivered by each land category. The result shows that the total value of ecosystem services in Changsha declines from $1 009.28 million per year in 1986 to $938.11 million per year in 2000. This decline is largely attributable to the increase of construction land,and the conversion from woodland and water body to cropland to keep the crop production. In the five districts,there is $6.19 million decline in ecosystem service value between 1995 and 2005. Yuelu District has the highest unit ecosystem service value while Yuhua District has the lowest one. This may be attributed to the greater conversion from cropland and grassland to woodland and water body with the increase of construction land in Yuelu District. It is suggested that the increase rate of construction land should be controlled rigorously and the area of woodland and water body should be increased or at least retained in the study area.

Optimizing the Resource Utilization of Datacenter Networks with OpenFlow

Decreasing the flow completion time(FCT) and increasing the throughput are two fundamental targets in datacenter networks(DCNs), but current mechanisms mostly focus on one of the problems. In this paper, we propose OFMPC, an Open Flow based Multi Path Cooperation framework, to decrease FCT and increase the network throughput. OFMPC partitions the end-to-end transmission paths into two classes, which are low delay paths(LDPs) and high throughput paths(HTPs), respectively. Short flows are assigned to LDPs to avoid long queueing delay, while long flows are assigned to HTPs to guarantee their throughput. Meanwhile, a dynamic scheduling mechanism is presented to improve network efficiency. We evaluate OFMPC in Mininet emulator and a testbed, and the experimental results show that OFMPC can effectively decrease FCT. Besides, OFMPC also increases the throughput up to more than 84% of bisection bandwidth.

The Evolution Pattern and Simulation of Land Use in the Beijing Municipal Administrative Center(Tongzhou District)

Beijing Municipal Administrative Center(Beijing MC)in Tongzhou District has inherited the non-capital core functions of Beijing’s central urban area,and its rapid construction and development urgently require a scientific understanding of the pattern of land use evolution in the region.This paper analyzes the pattern of land use evolution in Tongzhou District over the past 40 years,from 1980 to 2020.According to the historical evolutionary characteristics of land use and urban development planning goals,combined with the driving factors of cultural tourism development,the Future Land-use Simulation(FLUS)model is used to simulate the spatial distribution of land use in Beijing MC(Tongzhou District)in 2035 under three scenarios of urbanization acceleration,deceleration and sustainable development.The results show three major trends.(1)Beijing MC(Tongzhou District)is dominated by urban development and construction.During the high-speed urbanization stage from 1980 to 2010,the urban expansion pattern of“along the Sixth Ring Road and along the Grand Canal”was formed.During the low-speed urbanization stage from 2010 to 2020,the land distribution was stable,and Tongzhou District formed a pattern of urban-rural differentiation and land intensification from northwest to southeast.As a typical area of Tongzhou District’s urbanization,Beijing MC has the same characteristics of the temporal and spatial evolution as Tongzhou as a whole.(2)By 2035,there are significant differences in land use among the three scenarios with respect to the magnitude of change and spatial distribution.The area and distribution of ecological land under the urban sustainable development scenario are optimal,which is conducive to the realization of sustainable urban development.In analyzing the degree of conformity with the three Beijing MC zoning plans,the prediction simulation under the sustainable development scenario is highly consistent with the land use of the“Beijing Municipal Administrative Center Regulatory Detailed Planning(Block Level)(2016–2035)”(hereinafter referred to as“Planning”)issued by the municipal government.However,there are certain deviations between the simulation predictions in the cultural tourism function area and the livable living scenery area and the corresponding“Planning”expectations.During the urban construction process,the internal ecological land area still needs to be increased.(3)Tongzhou District may lack a close connection between the urban and rural areas in the southeast.Potential risks such as the imbalance in the development of northern and southern townships require further attention in the development process.The prediction and simulation results of the model can provide certain data and methodological support for the construction of a harmonious and livable city in Beijing MC(Tongzhou District).