半湿润地区风沙化土地改造利用的生态效益研究——以豫北延津县沙地农业综合开发试验示范区为例

观测、实验和样品分析结果表明,位于半湿润地区的豫北延津县,其沙地农业综合开发试验示范区的改造利用取得了良好的生态效益,具体表现为:①抑制了风沙活动,防止了风沙危害;②恢复和提高了沙地生产力;③改善了沙地小气候。最终实现了土地风沙化的逆转。     

台风移动规律的研究 Ⅰ.非绝热加热与水平温度分布的影响

根据大气运动原始方程组导出一个支配台风中心移动的基本方程。方程中包括了非绝热加热、温度场分布、地形与摩擦等各种可能影响台风移动的强迫因子。对非绝热加热与水平温度分布的作用所作分析表明,非轴对称的非绝热引导作用可使台风加速、减速或转向运动;温度场上的冷区对台风有吸引作用。      

菱刈矿床矿脉群形成的构造环境

本文主要介绍菱刈矿床矿脉的赋存状态、裂隙体系分析、矿脉群赋存的构造环境。菱刈矿床属脉状浅成热液型金银矿床。矿床成因与裂隙系统的形成关系密切。矿脉群大致位于基底岩石(四万十层群)隆起的中央部位。     

海洋平台隔水套管群桩性状的研究

海洋平台的隔水套管群桩与土共同作用研究是一个很复杂的课题,目前国内外研究资料甚少,因此在平台导管架设计中,一般不考虑隔水套管群桩承受水平力作用,这与实际不相符合。本文结合工程课题,在调查研究和模型试验的基础上,对隔水套管群桩在水平力作用下的工作性状与破坏机理、群桩的水平力及其主要影响因素、单桩与群桩情况下应力应变关系等方面进行较深入的研究;并提出砂土地基隔水套管群桩效应经验公式,弥补了现行计算方法的缺陷和不足。研究成果可供工程设计参考使用。     

Elastic response of catamaran wetdeck to liquid impact

The impact of an elastic plate onto the compressible fluid without free surface deformation is considered. The ability of the liquid volume to be deformed is geometrically limited which leads to severe impact conditions. The present analysis is focused on the stresses in the plate and the hydrodynamic loads under the impact. The motivation for this research comes from ship hydrodynamics, where the hulls of a catamaran restrict the liquid outflow and the water impacts onto the wetdeck. The influence of the air on the impact process is investigated. The analysis did not reveal any great advantage of utilizing the air-cushion effect or ejection of air into the water near the impact region to prevent high stresses in the elastic plate. It was found that in the problem considered, the stress peaks far from the plate centre and the one-mode approximation does not provide correct information about the stress level.     

镧-氨基酸络合物对球等鞭金藻的影响

本文首次研究了镧-脯氨酸和镧-苯丙氨酸络合物对球等鞭金藻(Isochrysis galbana)的影响,结果表明,两种络合物对球等鞭金藻细胞繁殖及叶绿素的合成有明显的促进作用,浓度范围为5-20mg/dm3时,至第6天细胞数分别提高10.8%～17.2%,11.5%-20.5%(P<0.05);叶绿素浓度分别提高31.7%-37.5%,44.7%～48.4%(P<0.05),其中以浓度为10mg/dm3的实验组最高。镧的氨基酸络合物对球等鞭金藻的作用效果与镧相比是等同的。     

Mechanisms of the southward translation of meddies

Meddies are warm and saline anticyclonic eddies found at the mid-depth of the Mediterranean Outflow in the Eastern North Atlantic. They are observed to move almost southward at average speeds as high as 1.3±0.2 cm s⁻¹. This paper examines a mechanism which accelerates this curious translation to a reasonable speed when combined with nonlinearity and a suitable vertical eddy structure. This mechanism is thepseudo-topographic β effect due to the westward decrease in the thickness of the mid-layer induced by the surface southward mean current. The linear dispersion relation including this effect is shown to account for a quarter of the surface southward mean current or a fifth of the observed southward translation of meddies. Three-layer quasi-geostrophic experiments reveal that the surface southward mean current certainly enhances the southward translation velocity of meddies to a speed in agreement with observation, if the meddy has a current structure of plausible intensity and vertical coherence. In the light of the current-induced pseudo-topographic β effect, previous hypotheses are also re-examined through dynamic arguments together with numerical experiments; they are suggested to have some difficulty either in dynamics or in correspondence with observation. Thus the nonlinear effect due to secondary eddies combined with thecurrent-induced pseudo-topographic β effect is the most likely mechanism responsible for the rapid southward translation of meddies among those examined in the paper.     

基于纤维模型的高墩连续刚构桥地震行波效应分析

本文基于在MSC.Marc中加入纤维模型编制的THUFIBER程序的基础上,分别采用纤维模型和三维实体单元模型模拟桥墩和上部结构,建立高墩大跨连续刚构桥有限元模型。同时,采用2008年汶川地震波,分析了行波效应对四川某高墩大跨连续刚构桥非线性地震反应的影响。结果表明：行波效应对高墩桥的墩顶位移和墩底剪力影响较大,墩顶位移减小了20%—50%;而墩底剪力增大了20%—30%。     

热红外遥感中大气下行辐射效应的一种近似计算与误差估计

在热红外遥感中,大气下行辐射效应很难处理,原因是地表双向反射分布函数很难精确描述。因此常见的处理方法是在如下２ 个假设前提下对该项作做简化计算： 一是假设地表反射为朗伯体特性,二是大气下行辐射在半球空间内取常数。该文提出了一种在地表为非朗伯体、大气下行辐射为非各向同性等一般条件下近似计算大气下行辐射效应的方法。通过数值模拟表明：（１） 所采用的方法可以在放弃２ 个假设的前提下,更精确地计算热红外大气下行辐射效应的数值,计算精度比２ 个假设前提下的计算方法至少提高２０ ．５３ ％ ;（２） 该方法所带来的误差是大气模式、遥感器视角和通道的函数。其中,通道４ 的相对误差比通道５大,同一通道中模式５ 的相对误差最大,但最大可能相对误差不到８ ％ ,且随扫描角的增大而减小;（３） 大气下行辐射效应项占总辐射亮度值之比例在±３０°视角范围内一般不超过４ ％ 。     

Markov Models for Cross-Covariances

Markov models based on various data screening hypotheses are often used because they reduce the statistical inference burden. In the case of co-located cokriging, the commonly used Markov model results in the cross-covariance being proportional to the primary covariance. Such model is inappropriate in the presence of a smoothly varying secondary variable defined on a much larger volume support than the primary variable. For such cases, an alternative Markov screening hypothesis is proposed that results in a more continuous cross-covariance proportional to the secondary covariance model. A parallel development of both Markov models is presented. A companion paper provides a comparative application to a real data set.