电线积冰及舞动高风险区域的数值模拟

导线覆冰舞动是一种影响电网正常运行的灾害性天气.通过对2018年1月25—29日长江中下游地区大范围导线覆冰舞动事故的天气形势、大气层结与云中水成物特征的分析,探讨了导线覆冰舞动的天气成因,进而利用耦合了电线覆冰增长模型的天气研究和预报模式,对导线覆冰厚度及舞动高风险区域的时空分布进行了模拟,结果表明:①冷空气与西南暖湿气流在长江中下游地区交汇,该区从地面到700 hPa的温度均低于0℃,冻雨为"过冷暖雨"机制;②模拟结果显示覆冰期间地面降水经历了"固态-混合态-固态"的相态转化过程,与观测结果较为一致;③耦合了积冰增长预报系统(IFAS)的WRF模式,模拟的各阶段电线积冰厚度的空间分布特征与监测到冻雨天气的气象站点分布较为吻合,覆冰厚度极值与观测结果接近;④利用耦合了美国空军气象局诊断方案的WRF模式,根据模拟的积冰厚度与瞬时最大风速,模拟出了导线覆冰舞动高风险区域分布,与电网的观测记录较为吻合.该研究表明模拟的导线覆冰厚度能够反映冻雨过程中电线积冰厚度的时空变化特征,特别是舞动高风险区域分布的成功模拟,对舞动进行提前预警进而降低舞动损失具有重要的实用价值.     

基于融合分割和LASSO回归的实时车道偏离预警

在有路面污染、标识干扰等复杂高速道路环境下,车道偏离预警系统的鲁棒性和实时性会变差。为此提出一种利用两种算法融合分割和LASSO回归模型进行车道线检测和偏离预警的新方法。首先,分别采用TopHat算法和OTSU算法分割出车道线背景并进行"与"运算融合,据此准确提取出车道信息;其次,分两步检测车道线,第一步基于概率Hough变换进行直线检测,将检测出的车道线位置设为动态ROI区域并进行卡尔曼滤波跟踪处理,第二步是基于LASSO多项式回归模型对车道线再次进行参数估计和拟合,以改善使用最小二乘法时的过拟合问题;最后,根据设置的虚拟车道线和角度模型进行车道偏离预警决策。实验结果表明,所提出的方法在复杂道路环境下的平均正检率为96.07%,检测速率可达到32 ms/帧,即具有良好的鲁棒性和实时性。     

Millennial-scale climate change since the last glaciation recorded by grain sizes of loess deposits on the northeastern Tibetan Plateau

Whether climatic changes in high latitudes of the Northern Hemisphere since the last glaciation have effects on the Tibetan Plateau monsoon, and the variation characteristics of the Plateau monsoon itself are still not solved but of great significance. The 22-m high-resolution Ioess-paleosol sequence in the Hezuo Basin on the northeastern Tibetan Plateau demonstrates that the Plateau winter monsoon experienced a millennial variation similar to high latitude Northern Hemisphere, with cold events clearly correlated with Heinrich events but less for the warm events (Dansgarrd-Oeschger events). It may indicate that the climate system at high latitudes in the Northern Hemisphere had played an important role in both the Plateau monsoon and the high-level westerlies. On 10^4 year scale, there are two distinct anomalous changes, which are not found in the records from high latitude northern hemisphere, revealed by the loess grain size in the Hezuo Basin. One is that there was a considerable grain size increase at -36 kaBP, suggesting an abrupt enhancement of the Plateau winter monsoon at that time; the other is that, during 43--36 kaBP, the grain size decreased distinctly, indicating a notable weakening of the Plateau winter monsoon around that period. Both of the two anomalies suggest that the Tibetan climate may have been controlled by some other factors, besides the high latitude climatic changes in the Northern Hemisphere.     

Address at the Opening Ceremony of the 22nd International Congress of History of Science

Honorable Council members of the DHS, Chairs of Delegations, Distinguished Guests, Lances and Gentlemen ： On behalf of the Chinese host, I sincerely and warmly welcome you to Beijing and the 22^nd International Congress of the History of Science. To my knowledge, in the 76 years of its history, this is only the second time that the Congress is being held in the Far East, and is also the second time the Congress is meeting in a developing country.     

10%灰霉清烟剂防治番茄和茄子灰霉病试验及示范

20 0 2—2 0 0 3年开展了10 %灰霉清烟剂防治番茄和茄子灰霉病的试验及示范工作。试验结果表明,10 %灰霉清烟剂6 0 0 0、75 0 0 g/hm2 对番茄灰霉病的防效分别为91.88%、94 .19% ,显著优于对照药剂10 %速克灵烟剂4 5 0 0 g/hm2 之防效(88.6 0 % ) ;对茄子灰霉病的防效分别为87.31%、92 .73% ,也显著优于速克灵烟剂(85 .86 % )。示范结果显示,10 %灰霉清烟剂对番茄灰霉病的平均防效为93.6 % ,对茄子灰霉病的平均防效为92 .8%。     

Contemporary velocity field of crustal movement of Chinese mainland from Global Positioning System measurements

Significant advancement for the monitoring of crustal deformation in the Chinese mainland was accomplished in 1998 when the Crustal Movement Observation Network of China (CMONOC) was established. This National Key Scientific Infrastructural Project provides important information on present-day crustal deformation that can be used for many aspects of earth sciences such as navigation,     

一个半线性抛物型初边值问题的正则性结果及其应用

R. Redlinger在文[1]中证明了半线性抛物型系统的每个有界解是C~2(?)-紧的.本文加强了这一结果,证明了在一定条件下,每个有界解是C~(2+μ,1+μ/2)(?×R~+)-正则的.应用这个结果讨论了线性非齐抛物型系统周期解的存在性.     

玻璃态聚合物的Grüneisen常数计算

本文用似谐振子模型得出了聚合物非线性振动的Gruneisen常数计算式,并用聚甲基丙烯酸甲酯的实验值加以比较,所得结果与文献报道一致。     

动态地表移动和变形预计方法

针对目前地下开采引起地表移动变形致使地表建筑物、构筑物及农田等遭受严重破坏的问题,以Knothe模型的函数为基础,探讨了时间影响系数的确定方法,建立了地下开采引起地表移动动态过程的计算模型,并采用阳泉二矿3201东工作面的实测岩移资料进行了验证.研究结果表明:该方法能够反映地表移动的动态特征,解释某些采动现象,对指导"三下"开采设计和选择地面建筑物保护措施具有较大的实用价值.     

滴流床反应器流区改变的稳定性分析

采用线性稳定性分析方法和分支理论，分析了滴流床反应器的流区改变与两相流的稳定性损失及动量方程稳态解的损失之间的内在关系。据此分别提出了两个相应的判别流区过渡的理论准则，并结合压力脉动在线测量实验对判别准则作了校正。得到了校正曲线与文献值一致。