序列图像帧间预测技术的研究

在视频压缩领域,帧间预测技术占有十分重要的地位。在简要介绍两种帧间运动估计/补偿模式基础上,该文重点讨论了局部运动估计中块匹配算法的应用和Sprite编码中的全局运动估计算法,提出一种"改进的分级块匹配法",并结合Sprite编码实现序列图像帧间压缩。大量实验表明,采用这种局部和全局相结合的预测算法,可以减少搜索时间,提高图像压缩质量和压缩比,是视频压缩可以输出甚低码流的有效手段之一。     

Issues and prospects of belowground ecology with special reference to global climate change

The theory of ecology is based on over 100 a of research and investigation, all centered on aboveground patterns and processes. However, as contemporary ecologists are increasingly acknowledging, belowground structures, functions, and processes are some of the most poorly understood areas in ecology. This lack of understanding of belowground ecological processes seriously restricts the advance of global change research. The interdisciplinary field of belowground ecology began to flourish in the 1990s, along with the expansion of global change research, and quickly gained momentum. Belowground ecology aims to investigate belowground structures, functions, and processes, as well as their relationships with corresponding aboveground features, emphasizing the responses of belowground systems under global change conditions. Key research areas include root ecology, belowground animals, and soil microorganisms. This review summarizes and analyzes the relationships between aboveand belowground ecosystems, root ecology, root biogeography, belowground biodiversity, as well as research areas with particular challenges and progress. This commentary emphasizes certain theoretical issues concerning the responses of belowground processes to global change, and concludes that belowground ecology is a critical research priority in the 21st century.     

一类广义kdv的整体吸引子

通过对广义kdv方程的初值问题的整体解关于时间t作一致估计,得到了解的整体吸收集,从而证明了其整体吸引子的存在性.     

大坝背管混凝土裂缝全局优化网络的预测研究

基于人工神经网络的全局优化方法的基本理论,对钢衬钢筋混凝土压力管道外包混凝土结构裂缝预测进行了研究,提出了基于神经网络的管道混凝土裂缝预测模型.并重点研究了水头的变化对压力管道混凝土最大裂缝宽度的影响,最后对三峡电站压力管道混凝土结构裂缝进行了预测.     

一类具有连续时滞和HollingⅣ功能反应的非自治扩散系统

对一类具有HollingⅣ功能反应和连续时滞的非自治扩散系统进行了研究，得到了系统一致持久生存，正周期解存在和全局稳定的充分判据．     

具有反馈控制的捕食-竞争系统的全局性态

利用Lyapunov函数方法得到了具有反馈控制的捕食一竞争系统正平衡点的全局渐近稳定的充分条件；分别用构造递归序列的方法和构造Lyapunov泛函的方法得到了具有反馈控制与时滞的捕食一竞争系统正平衡点全局吸引和全局渐近稳定的充分条件．     

无界区域Rn上GBBM方程的整体吸引子

研究了无界区域R^n上GBBM方程的长时间动力学行为，利用算子分解技巧和构造加权空间上紧算子等方法，通过对方程的解作先验范数估计，证明了无界区域R^n上GBBM方程整体吸引子的存在性。     

具周期系数时滞差分方程的全局渐近稳定性

考虑具周期系数非线性时滞差分方程xn 1-xn pnxn-k=pnf(x[n/τ]τ-l），n=0，1，2，…，其中{pn}为T周期正数列，即Pn τ=pn，k=sT，k，s，T为自然数，通过讨论对应的齐次线性差分方程的性质，获得了关于零解全局渐近稳定的充分必要条件。     

Weak response of the Atlantic thermohaline circulation to an increase of atmospheric carbon dioxide in IAP／LASG Climate System Model

Response of the Atlantic thermohaline circulation (THC) to global warming is examined by using the climate system model developed at IAP/LASG. The evidence indicates that the gradually warming climate associated with the increased atmospheric carbon dioxide leads to a warmer and fresher sea surface water at the high latitudes of the North Atlantic Ocean, which prevents the down-welling of the surface water. The succedent reduction of the pole-toequator meridional potential density gradient finally results in the decrease of the THC in intensity. When the atmospheric carbon dioxide is doubled, the maximum value of the Atlantic THC decreases approximately by 8%. The associated poleward oceanic heat transport also becomes weaker. This kind of THC weakening centralizes mainly in the northern part of the North Atlantic basin, indicating briefly a local scale adjustment rather than a loop oscillation with the whole Atlantic “conveyor belt” decelerating.     

Natural interdecadal weakening of East Asian summer monsoon in the late 20th century

Based on the reanalysis data throughout 1948-2002 as derived from the United States National Centers for Environmental Prediction and National Center for Atmospheric Research, it is revealed that East Asian summer monsoon （EASM） intensity weakens on an interdecadal timescale since the mid-1960s, and twice interdecadal jumps are recorded in the EASM intensity index series in the late 20th century, respectively occurring in the mid-1960s and mid- to late 1970s. Six globally coupled atmosphere-ocean models＇ outputs under the SRES A2 greenhouse gas and aerosol emission scenario, provided by the IPCC Data Distribution Center and the Hadley Center for Climate Prediction and Research, are then systematically examined. It follows that the above EASM weakening is not closely related to synchro- nizing anthropogenic global warming, and, therefore, it should be qualitatively natural change process. Over the 21st century, the EASM intensity is likely increased slightly by continually intensified greenhouse effect relative to the late 20th century.