南京一次局地暴雨的风切变以及大气结构特征研究

突发性局地暴雨一直是灾害性天气预测的重点,对于城市的防洪排涝具有重要意义。利用2012年7月3日南京站的多普勒天气雷达的径向风场数据,并基于风场反演的方法对风切变的识别和大小进行了分析和计算;利用南京和安庆站的常规探空资料,对比分析了其局地大气结构特征。针对风切变区风场的不均匀特点,在风场反演中选用了均匀风场模型进行计算,用临近格点之间风矢差来表示风切变的大小。对2012年7月3日南京地区的一次强对流过程中风切变的识别结果表明,切变区主要集中在强对流区,以及移动路径的前侧;风切变的量级显示,此次暴雨过程在强对流与中尺度气旋区边缘的切变大小一般在4.0 m/(s.km)以上,并且切变发展的方向与天气过程的一致;对于潜在发展的对流,对比结果发现风切变的大小在3.0 m/(s.km)以上时容易发展成新的单体。分析结果表明,强切变出现的位置,指示了暴雨的强度和落区;而大气能量结构揭示了暴雨前的先兆信息,发现冷层云高度较低使大气层结更不稳定,它有聚合积雨云的作用,使降水量超常增加,是引起此次局地暴雨的重要因素。研究结果为改进临近预报和对流潜势预报提供了丰富的细节和新的思路。     

灰色神经网络组合模型在区域水质预测中的应用

针对神经网络用于水质预测时需要大量数据才能获得较为准确的预测结果的局限性,为降低预测时对数据的依赖引入灰色模型,从而建立两者最优组合模型,以用于数据贫瘠时的情况.将该模型用于珠江支流的水质预测,结果表明,该模型拟合误差小,预测精度高.     

Efficient selection of hyperparameters in large Bayesian VARs using automatic differentiation

Large Bayesian vector autoregressions with the natural conjugate prior are now routinely used for forecasting and structural analysis. It has been shown that selecting the prior hyperparameters in a data-driven manner can often substantially improve forecast performance. We propose a computationally efficient method to obtain the optimal hyperparameters based on automatic differentiation, which is an efficient way to compute derivatives. Using a large US data set, we show that using the optimal hyperparameter values leads to substantially better forecast performance. Moreover, the proposed method is much faster than the conventional grid-search approach, and is applicable in high-dimensional optimization problems. The new method thus provides a practical and systematic way to develop better shrinkage priors for forecasting in a data-rich environment.     

广义Lebesgue空间Lp(x)(Ω)中的非方常数

在广义Lebesgue空间Lp(x)(Ω)中推广了Clarkson不等式,并对非方常数进行了研究,得到了当p(x)满足p-≥2或1相似文献   

周期Anderson模型的Green函数方法处理

基于Ｇｒｅｅｎ函数技术,作者首先分析了切断近似对处理一维对称周期Ａｎｄｅｒｓｏｎ模型中电子间关联的影响,然后计算了该模型的局域磁矩,杂化能量元和基态能量,计算结果与Ｂｌａｎｋｅｎｋｅｃｌｅｒ等人的Ｍｏｎｔｅ Ｃａｒｌｏ模型一致,这表明Ｇｒｅｅｎ函数方法可以较好地处理周期Ａｎｄｅｒｓｏｎ模型的基态性质。     

Effect of nluminants on the Colour Appearance of Reactive - dyed Cotton

The colour appearance of dyed textile materials changes with the viewing condition, especially with a change in the light source or Illuminant. The attitude and magnitude of the change vary with the hue of the colour, the light absorbance nature of the dye and the colour depth to which it is dyed. This paper examines the change in colour appearance of reactive - dyed cotton when the light source is changed from CIE Uluminant D65 to CIE illuminant A. Reactive dyes of primary hues were selected and applied at various depths and the dyed colours were assessed with reference to changing the illuminant.     

Purge and trap method to determine alpha factors of VOC liquid-phase mass transfer coefficients

A theoretical approach and laboratory practice of determining the alpha factors of volatile organic compound (VOC) liquid-phase mass transfer coefficients are present in this study.Using Purge Trap Concentrator, VOC spiked water samples are purged by high-purity nitrogen in the laboratory, the VOC liquid-phase mass transfer rate constants under the laboratory conditions are then obtained by observing the variation of VOCs purged out of the water with the purge time.The alpha factors of VOC liquid-phase mass transfer coefficients are calculated as the ratios of the liquid-phase mass transfer rate constants in real water samples to their counterparts in pure water under the same experimental conditions. This direct and fast approach is easy to control in the laboratory, and would benefit mutual comparison among researchers, so might be useful for thestudy of VOC mass transfer across the liquid-gas interface.     

A novel member of the Rhomboid family, RHBDD1, regulates BIK-mediated apoptosis

Rhomboid family members are widely conserved and found in all three kingdoms of life. They are serine proteases and serve important regulatory functions. In the present study, a novel gene highly expressed in the testis, RHBDD1, is shown to be a new member of the Rhomboid family, participating in the cleavage of BIK, a proapoptotic member of the Bcl-2 family. The RHBDD1-involved proteolytic modification is upstream of the BIK protein degradation pathway. Mutagenesis studies show that the amino acid residues glycine142 and serine144 of RHBDD1 are crucial for its activity in cleaving BIK at a site located in the transmembrane region. Overexpression or knock-down of RHBDD1 in HEK 293T cells can reduce or enhance BIK-mediated apoptosis, respectively. The present findings suggest that, by acting as a serine protease, RHBDD1 modulates BIK-mediated apoptotic activity. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Received 31 July 2008; received after revision 16 September 2008; accepted 19 September 2008     

溶剂型冷补沥青混合料低温施工和易性定量评价方法

针对目前溶剂型冷补沥青混合料低温施工和易性定量评价方法欠缺的问题,设计了“等效圆法”,以散落面积S作为评价指标,对CA、LB、XR型冷补料及对照组进行低温施工和易性定量评价。研究结果表明散落面积S作为“等效圆法”的定量评价指标,不仅试验操作简单,而且与经验法所得出的低温施工和易性等级之间具有较好的相关性,显著提高了试验结果的客观性与可靠性;通过“等效圆法”得出,四种冷补料低温施工和易性依次为：对照组>CA>XR>LB;马歇尔稳定度试验表明,四种冷补料初始强度依次为：LB>CA>XR>对照组。结合试验结果,推荐冷补料性能评价指标为：散落面积S≥44πcm²,初始强度≥2.4 kN。