综合降水技术在临江基坑中的施工应用

本工程通过轻型井点和真空深井相结合的降水方案,取得了良好的效果。     

无线信道上能量约束条件下可伸缩视频的自适应传输

为提高无线信道上可伸缩视频码流的传输效率,提出了一种新的能量约束条件下可伸缩视频码流自适应传输算法。基于无线信道的Markov模型假设,在满足延时约束条件下,对各可伸缩视频编码帧的增强层数目以及信道发送速率进行联合优化,并给出了动态规划算法求解该约束优化问题。实验结果表明,相对于采用固定信道传输速率的可伸缩视频码流传输方案,该方案在达到相同平均视频质量时平均可节省44.95%~52.86%的能量,显著提高了无线信道上可伸缩视频传输的能量利用效率。     

Water isotope variations in the snow pack and summer precipitation at July 1 Glacier, Qilian Mountains in northwest China

This paper presents the stable isotope data of the snow pack and summer precipitation collected at the July 1 Glacier, Qilian Mountains in northwest China and analyses their relationships with meteorologi- cal factors. On an event scale, there is no temperature effect on the δ 18O values in the summer pre- cipitation, whereas the amount effect is shown to be clear. By tracing the moisture transport history and comparing the precipitation with its isotopic composition, it is shown that this amount effect not only reflects the change in moisture trajectory, which is related to the monsoon activities, but is also associated with the cooling degree of vapor in the cloud, the evaporation of falling raindrops and the isotopic exchange between the falling drops and the atmospheric vapor. As very little precipitation occurs in winter, the snow pack profile mainly represents the precipitation in the other three seasons. There are low precipitation δ 18O ratios in summer and high ratios in spring and autumn. The Meteoric Water Line (MLW) for the summer precipitation is δ D = 7.6 δ 18O 13.3, which is similar to that at Delingha, located in the south rim of the Qilian Mountains. The MWL for the snow pack is δ D = 10.4 δ 18O 41.4, showing a large slope and intercept. The deuterium excess (d) of the snow pack is positively correlated with δ 18O, indicating that both d and δ 18O decrease from spring to summer and increase from early autumn to early spring. This then results in the high slope and intercept of the MWL. Sea- sonal fluctuations of d in the snow pack indicate the change of moisture source and trajectory. During spring and autumn, the moisture originates from continental recycling or rapid evaporation over rela- tively warm water bodies like Black, Caspian and Aral Seas when the dry westerly air masses pass over them, hence very high d values in precipitation are formed. During summer, the monsoon is responsi- ble for the low d values. This indicates that the monsoon can reach the western part of the Qilian Mountains.     

“新能源热”下的忧思

风能、太阳能和其他非化石能源虽然重要,但就中国的节能减排工作而言,更重要和更紧迫的是做好大力发展水电、继续大幅度提高常规能源利用效率。     

ELNio事件与我国月降水和温度的关系

用对比度分析方法,研究了ELNino事件对我国月降水和温度的影响,并进行了信度检验.结果表明:ELNino年,全国降水1～9月偏少,10～12月偏多.当5月降水异常少时,ELNino发生的概率达50%以上.当4月温度异常高时,ELNino发生的概率为零,而4月气温异常低时,ELNino发生的概率达50%～83%.这对ELNino的预测,提出了一个重要的信号依据.     

贵州省植被NDVI与气象因子的相关性分析

本文选取贵州省2001～2018年MOD13A1数据和贵州省31个气象站点气象数据，逐像元分析不同时间尺度下植被NDVI与降水和气温的相关性，同时探讨贵州省NDVI对降水和气温的响应特征。结果表明：（1）贵州省植被NDVI与气温的相关性明显大于植被NDVI与降水的关系，即植被生长对气温变化的响应比降水更敏感。（2）贵州省植被NDVI对降水变化的响应存在明显的滞后性，尤其表现出毕节市的植被NDVI对降水和气温的敏感性高于贵州省其他地区。     

道路板涵基础施工轻型井点降水工法与实施

阐述了由于道路板涵基础施工时地下水位过高影响施工进城及施工质量的措施方法,给出了其降水条件,对轻型井点降水管的数量及相关数据进行了计算,利用井点降水使得板涵基础在施工过程中得到有利的施工条件,保证了板涵基础施工质量,实践表明,该工艺具有操作简便,效率高,成本低等特点。     

井点降水对周围环境的危害及预防措施

随着高层建筑的不断增加，在工程施工中多采用井点降水，引起邻近建筑、管线、路面开裂下沉的现象屡见不鲜。因此，采用井点降水要特别慎重井采取相应对策。本文详细分析了井点降水对附近环境产生危害的原因，井提出了可行的预防措施。     

纳木错流域扎当冰川径流对气温和降水形态变化的响应

报道西藏纳木错湖南岸念青唐古拉山脉北坡扎当冰川2007/2008年的径流年际大变化并分析其成因. 与2007年夏半年相比, 2008年同期降水量增加了17.9%, 流域径流量却减少了33.3%, 由此得出冰川消融量减少了53.8%. 利用通常的度日模型分析发现, 大气正积温的变化只能解释约一半的冰川消融量年际差, 说明该冰川对气温变化异常敏感. 能量平衡分析显示, 冰川表面反照率的改变造成了冰川消融量的年际重大差异. 而反照率的改变主要是由降水形态的差异造成的. 统计得出, 2007年夏半年冰川末端以降雨为主, 降雨量占降水总量的71.5%; 相反, 2008年以降雪为主, 降雨量仅占30.7%. 说明在对某些冰川进行气候变化的敏感性分析或径流预测时, 降水形态是需要单独考虑的一个因素.