The year of 2000 is at the turn of the century as well as of the millennium. Themankind waves farewell to the 20th century as well as the second millenniumand welcomes the 21st century and the third millennium. At thi...The year of 2000 is at the turn of the century as well as of the millennium. Themankind waves farewell to the 20th century as well as the second millenniumand welcomes the 21st century and the third millennium. At this special juncture,looking closely at the future based on understanding which was obtained from re-viewing and summarizing the past and present world politics from historical andphilosophical standpoints, we can find that it has become an unavoidable subject onhow to regard the trend of the world pattern toward multi-polarization and respon-sibility adjustment arising from it.展开更多
Adequate freshwater supply has become an issue of increasing local and international concern. Reducing water use in agriculture, which is the largest water using sector of the economy, is both important and urgent. Th...Adequate freshwater supply has become an issue of increasing local and international concern. Reducing water use in agriculture, which is the largest water using sector of the economy, is both important and urgent. The aim of this paper was to quantify how recent cropping pattern changes have influenced water resources in the great Beijing metropolitan area, an expanding megacity which also includes rural counties. Crop production affects blue water use through water consumption and water pollution, the latter assessed here using a critical dilution method. From 1990 to 2010, the total blue water used by crop production declined due to a decrease in overall cropped area, initially in response to local government policies favouring urban development. However, the average blue water use per hectare increased from 2 112 m3 ha-~ yr-~ in 1990 to 2 764 m3 ha-1 yr-1 in 2003, largely as the result of a transition from cereal to vegetable crops, and in particular an increase in intensively managed plastic and glass covered vegetable production systems. Current policies aim to conserve agricultural land, in the interests of food security, and to stimulate cereal production systems with higher ecosystem services provision. As such, in 2010 the average blue water use was 2 425 m3 ha-~ yr-l. These results demonstrate that cropping pattern changes in peri-urban regions and rural communities surrounding the Beijing metropolitan area can have a substantial impact on water resources. They also highlight the tradeoffs between food production and urban and industrial water supply and the need for integrated policy development.展开更多
In this paper,we propose a novel adjustable multiple cross-hexagonal search(AMCHS) algorithm for fast block motion estimation. It employs adjustable multiple cross search patterns(AMCSP) in the first step and then use...In this paper,we propose a novel adjustable multiple cross-hexagonal search(AMCHS) algorithm for fast block motion estimation. It employs adjustable multiple cross search patterns(AMCSP) in the first step and then uses half-way-skip and half-way-stop technique to determine whether to employ two hexagonal search patterns(HSPs) subsequently. The AMCSP can be used to find small motion vectors efficiently while the HSPs can be used to find large ones accurately to ensure prediction quality. Simulation results showed that our proposed AMCHS achieves faster search speed,and provides better distortion performance than other popular fast search algorithms,such as CDS and CDHS.展开更多
文摘The year of 2000 is at the turn of the century as well as of the millennium. Themankind waves farewell to the 20th century as well as the second millenniumand welcomes the 21st century and the third millennium. At this special juncture,looking closely at the future based on understanding which was obtained from re-viewing and summarizing the past and present world politics from historical andphilosophical standpoints, we can find that it has become an unavoidable subject onhow to regard the trend of the world pattern toward multi-polarization and respon-sibility adjustment arising from it.
基金supported by the Special Fund for Agro-scientific Research in the Public Interest,China(201103001)the National Basic Research Program of China(2010CB951500)the CSIRO-Chinese Ministry of Education Ph D Research Fellowship Program
文摘Adequate freshwater supply has become an issue of increasing local and international concern. Reducing water use in agriculture, which is the largest water using sector of the economy, is both important and urgent. The aim of this paper was to quantify how recent cropping pattern changes have influenced water resources in the great Beijing metropolitan area, an expanding megacity which also includes rural counties. Crop production affects blue water use through water consumption and water pollution, the latter assessed here using a critical dilution method. From 1990 to 2010, the total blue water used by crop production declined due to a decrease in overall cropped area, initially in response to local government policies favouring urban development. However, the average blue water use per hectare increased from 2 112 m3 ha-~ yr-~ in 1990 to 2 764 m3 ha-1 yr-1 in 2003, largely as the result of a transition from cereal to vegetable crops, and in particular an increase in intensively managed plastic and glass covered vegetable production systems. Current policies aim to conserve agricultural land, in the interests of food security, and to stimulate cereal production systems with higher ecosystem services provision. As such, in 2010 the average blue water use was 2 425 m3 ha-~ yr-l. These results demonstrate that cropping pattern changes in peri-urban regions and rural communities surrounding the Beijing metropolitan area can have a substantial impact on water resources. They also highlight the tradeoffs between food production and urban and industrial water supply and the need for integrated policy development.
文摘In this paper,we propose a novel adjustable multiple cross-hexagonal search(AMCHS) algorithm for fast block motion estimation. It employs adjustable multiple cross search patterns(AMCSP) in the first step and then uses half-way-skip and half-way-stop technique to determine whether to employ two hexagonal search patterns(HSPs) subsequently. The AMCSP can be used to find small motion vectors efficiently while the HSPs can be used to find large ones accurately to ensure prediction quality. Simulation results showed that our proposed AMCHS achieves faster search speed,and provides better distortion performance than other popular fast search algorithms,such as CDS and CDHS.
