南方丘陵区植被覆盖度遥感估算与时空变化研究——以福建省永定县为例

植被覆盖度是生态环境监测的重要指标,而复杂地形因素影响对山地植被遥感信息准确提取。基于Landsat-8OLI遥感数据,分别采用像元二分模型和线性混合光谱分解法,在对比分析植被覆盖度的地形敏感性基础上,选择山地植被指数(NDMVI)估算了1992、2002和2014年永定县的植被覆盖度,并分析其变化。结果表明:1基于山地植被指数(NDMVI)的覆盖度估算模型的地形敏感性最弱,更适合于南方丘陵山地的植被覆盖度遥感反演;2永定县总体植被覆盖度较高,平均植被覆盖度达77.99%以上,高覆盖度区占59.73%以上,22年内植被覆盖度经历了先提高再下降的过程;3在空间上,高坎抚、金丰和西部片区的植被覆盖度较低,动态变化较明显。永定县金丰片区植被覆盖度明显提高;而近12年内高坎抚片区因矿业开采活动对生态环境的破坏,植被覆盖度降低幅度大,且变化面积较大。     

海冰与海洋平台碰撞分析中的可视化方法

针对基于离散元方法的海冰与海洋平台结构碰撞分析系统,对运行于CPU GPU异构高性能计算平台上的大规模粒子模拟进行可视化方法的研究.使用OpenGL完成不同规模的平整冰、浮冰、冰脊和不规则形态海冰的呈现,不同形状海洋平台结构与受力网格的绘制,海冰粒子的运动轨迹与速度的表达,海浪效果的模拟以及碰撞过程的动画演示等.通过定义合理的交互模式与接口,在一定程度上融合GPU加速的离散元计算与后处理显示,基于多进程管道通信、多线程并行输出等实现在GPU加速计算的同时实时显示粒子模拟计算结果.该方法在帮助研究者随时掌握程序执行状况的同时,大幅减少后续传输、处理和存储的数据.     

A computational approach to measuring the correlation between expertise and social media influence for celebrities on microblogs

Social media influence analysis, sometimes also called authority detection, aims to rank users based on their influence scores in social media. Existing approaches of social influence analysis usually focus on how to develop effective algorithms to quantize users’ influence scores. They rarely consider a person’s expertise levels which are arguably important to influence measures. In this paper, we propose a computational approach to measuring the correlation between expertise and social media influence, and we take a new perspective to understand social media influence by incorporating expertise into influence analysis. We carefully constructed a large dataset of 13,684 Chinese celebrities from Sina Weibo (literally ”Sina microblogging”). We found that there is a strong correlation between expertise levels and social media influence scores. Our analysis gave a good explanation of the phenomenon of “top across-domain influencers”. In addition, different expertise levels showed influence variation patterns: e.g., (1) high-expertise celebrities have stronger influence on the “audience” in their expertise domains; (2) expertise seems to be more important than relevance and participation for social media influence; (3) the audiences of top expertise celebrities are more likely to forward tweets on topics outside the expertise domains from high-expertise celebrities.     

Generation of GHZ states with invariant-based shortcuts

A scheme is proposed to generate three-atom GHZ states by applying the inversely engineered control method on the basis of Lewis–Riesenfeld invariants. In the proposal, three atoms that have different configurations are trapped in a bimodal cavity. Numerical simulations indicate that our protocol has an obvious improvement of speed for the generation of GHZ states. Moreover, the present scheme is robust against both parameter fluctuations and dissipation.     

Generation of singlet states with Rydberg blockade mechanism and driven by adiabatic passage

A single state is a special state that entangles multi-state quantum systems and plays a significant role in the field of quantum computation. In this paper, we propose a scheme to realize the generation of single states for Rydberg atoms, where one Rydberg atom is trapped in an optical potential and the others are trapped in an adjacent optical potential. Moreover, combining Rydberg blockade and adiabatic-passage technologies, an N-atom singlet state can be generated with the interaction of an N-dimensional Rydberg atom and an (\(N-1\))-atom singlet state. Compared to previous schemes, the advantage of our proposal is that an N-particle N-level singlet state with \(N\ge 3\) may be realized more simply.     

基于LabVIEW的显微镜自动控制设计

为方便CCD相机采集显微镜下的图像,对显微镜的控制进行了研究;设计了一种实现显微镜自动控制的方法;利用THB6128芯片驱动步进电机实现焦距的电控调节,利用PT4115芯片控制LED灯实现照明灯光亮暗的调节,基于LabVIEW虚拟仪器平台开发主控制程序搭建外围硬件,实现显微镜的自动控制;实验证明,上位机运用程序通过串口进行数据通信向下位机发送指令,通过调节LED灯的亮暗以及步进电机转动带动载物台的上下移动,实现了在一个合适的光照和焦距下获取清晰的图像;使显微镜控制更加的简化与精确,便于图像的采集。     

基于摆扫反射镜的大视场成像像移模型

为实现大视场技术指标,建立了一种基于摆镜转动的摆扫成像模型;通过对摆扫成像与推扫成像模式的比较,分析得出当横滚角等于摆镜转角的2倍时,摆扫成像能够实现与推扫成像小姿态时相同的视场;经过实验验证,在横滚角为2°、4°、6°、8°、10°时,文章的方法与推扫成像模型像移相对误差在1%以内,偏流角大小相对误差在0.001%以内,两种方法保持了较好的一致性,保证了模型的合理性与正确性;此外,该模型还可以通过实时地控制摆镜的转动来实现穿航方向上的对地的扫描成像,进而实现大视场、宽幅盖对地成像,减小回访周期,提高空间相机对地成像的工作效率。