利用GMS卫星资料进行强对流降水估计

对利用静止卫星云图资料进行降水的估计方法进行了回顾,在总结前人方法的基础上。针对GMS云图资料及华南地区的特点对强对流云团降水方法进行了研究,包括冷云区持续时间估计法、红外亮温法,并将梯度、发展率和常规探测资料加入其中进行分析。结果显示,综合几种资料,能较好地进行强降水的估计。     

Can forecasters forecast successfully? Evidence from UK betting markets

This paper investigates the performance of professional racetrack forecasting services in the UK. The racetrack market is chosen for investigation because it offers a clear and well‐defined set of costs and returns. As such, it provides a useful perspective from which to consider the efficiency of professional forecasting performance. Five services are selected based on their reported success in a period prior to the sample selection. The results of this study indicate that all the services showed evidence of net pre‐tax profits, notably for more strongly recommended tips, but this would have required quite high stakes to cover the costs of accessing the information. Statistical tests of significance were unable, however, to confirm the evidence of profitability at conventional levels of acceptance. Taking into account the transactions costs of using these services, it is even more difficult to confirm the existence of abnormal returns. Copyright © 2000 John Wiley & Sons, Ltd.     

防沙栅栏风洞实验的数值模拟

通过给出描述横条栅栏附近风场初边值问题基本方程,成功实现了对栅栏风洞实验结果的数值模拟.在此基础上,给出栅栏背风面的风场分布规律以及栅栏高度、孔隙度和空行数等对栅栏有效防护距离的影响.     

0.47J×100Hz高光束质量二极管泵浦脉冲固体激光器

采用二极管侧面泵浦结构和主振放大方案,设计和实验研究了大能量高光束质量脉冲固体Nd：YAG激光器.获得了单脉冲输出能量0.47J,重复频率100Hz,光束质量M2因子为4的高光束质量全固态脉冲激光输出.     

考虑解答者公平关切的众包竞赛知识共享激励

研究了解答者之间的横向公平关切特征对众包竞赛发包方知识共享激励的影响。在构建公平关切下解答者效用函数的基础上,建立并求解了无知识共享激励模型(NKS)和知识共享激励模型(KS),用理论分析和数值仿真方法研究了公平关切敏感度对发包方最优知识共享激励程度、解答者最优私有解答努力程度及知识共享努力程度、众包项目绩效以及双方期望经济收益的影响,并与无知识共享激励进行了对比。研究表明：解答者公平关切心理能降低实施共享知识激励机制的门槛,并提升发包方最优知识共享激励程度;解答方知识共享努力与公平关切正相关,但私有解答努力与之负相关;众包项目绩效、发包方绝对经济收益与公平关切的关系取决于解答努力绩效转化率和知识共享努力绩效转化率之间的比值;知识共享激励机制能实现发包方和解答者双方经济利益的共赢,且其经济价值随公平关切敏感度增大而提高,并受到参赛人数的调节作用。     

A copy number variation morbidity map of developmental delay

To understand the genetic heterogeneity underlying developmental delay, we compared copy number variants (CNVs) in 15,767 children with intellectual disability and various congenital defects (cases) to CNVs in 8,329 unaffected adult controls. We estimate that ～14.2% of disease in these children is caused by CNVs >400 kb. We observed a greater enrichment of CNVs in individuals with craniofacial anomalies and cardiovascular defects compared to those with epilepsy or autism. We identified 59 pathogenic CNVs, including 14 new or previously weakly supported candidates, refined the critical interval for several genomic disorders, such as the 17q21.31 microdeletion syndrome, and identified 940 candidate dosage-sensitive genes. We also developed methods to opportunistically discover small, disruptive CNVs within the large and growing diagnostic array datasets. This evolving CNV morbidity map, combined with exome and genome sequencing, will be critical for deciphering the genetic basis of developmental delay, intellectual disability and autism spectrum disorders.     

Carbon isotope discrimination and water relations of oak hybrid populations in southwestern Utah

The evergreen oak Quercus turbinella and the deciduous Q. gambelii form natural hybrids in southwestern Utah and northern Arizona. Hybrid individuals also are found in northern Utah in a region where only Q. gambelii currently exists, indicating that Q. turbinella has recently retreated southward. Our objectives were to (1) examine the ecophysiology of parental taxa and hybrids under natural conditions in southeastern Utah, and (2) investigate the level of integration between leaf carbon isotope discrimination (a synthetic gas exchange trait) and structural and chemical traits of leaves in morphologically variable hybrid populations. Leaf length, width, mass-to-area ratio (LMA, g m -2 ), and nitrogen concentration (N, g g -1 ) within 2 hybrid populations near New Harmony, Utah, were highly intercorrelated. Variation within the hybrid populations spanned mean values for these traits observed in parental taxa from adjacent ""pure"" populations of each species. Carbon isotope discrimination (Δ), an integrated measure of the ratio of intercellular to ambient CO 2 concentration, ranged from 16.1‰ to 19.6‰ within the 2 hybrid populations and was positively correlated with leaf nitrogen concentration and negatively correlated with LMA; individuals in hybrid populations with leaves resembling Q. gambelii had the highest leaf Δ and N concentrations and lowest LMA compared with leaves from plants that resembled Q. turbinella . CO 2 uptake is limited by stomatal conductance and possibly by mesophyll resistance to a greater extent in Q. turbinella phenotypes than in intermediate or Q. gambelii phenotypes. δD of stem xylem water (an indication of active rooting depth) and predawn water potential during the peak monsoon period in August were not correlated to leaf Δ values within the hybrid populations. Several individuals that were morphologically similar to Q. turbinella in the hybrid populations maintained high predawn water potentials and derived moisture from winter recharge that presumably was taken from deep soil layers. Apparently, a few adult individuals of the Q. turbinella phenotype in hybrid populations accessed water from deep in the soil profile, which enabled them to avoid summer drought. Reduced monsoonal activity may have been an important, but not the single, determinant of Q. turbinella s retreat from northern Utah during the recent Holocene.     

由稳定流型和不稳定流型证实氢原子的粘性效应

本文研究了氢原子哈密顿系统暴露在强激光场下的粘性效应，即使对于单电子系统，其庞加莱截面也显示出了由激光场引起的混沌部分和规则部分，并可以用KAM理论来解释.通过变分方法对混沌“海”中的不稳定周期轨道进行了寻找，并数值求解了相应的稳定流形和不稳定流形.研究结果表明，单电子系统电离的动力学性质由不稳定周期轨迹控制.一方面，不稳定周期轨迹的稳定流形很好地与递归图叠加在一起，表明稳定流形只与相空间中稳定的初始点重叠.另一方面，不稳定流形几乎与庞加莱表面上密集分布的点重合.这表明不稳定流形只是通过激光场驱动轨迹演化的电离通道.此外，在稳定流形与不稳定流形相互穿插的不稳定岛附近的不同区域的存活概率也被深入研究.它们服从代数衰减规律.相同的衰减趋势也出现在不稳定流形上，它们具有与不稳定周期轨迹附近区域相近的衰减参数.这些观察证实了不稳定周期轨迹的稳定性对在KAM稳定岛附近相空间的粘滞效应起着非常重要的作用.     

一阶半正常微分系统周期边值问题正解的存在性

本文研究了一阶半正常微分系统周期边值问题■正解的存在性，其中，参数λ>0,函数a,b∈C([0,1],[0,∞))且在[0,1]的任何子区间上不恒为0,f,g∈C([0,1]×?,?),f(x,0)<0,g(x,0)<0.基于拓扑度理论，本文证明：存在λ₀>0,使得当0<λ<λ₀时该问题至少有一个正解.