西北太平洋温带气旋爆发性发展的热力-动力学分析

利用天气、位涡分析和导出的Lagrangian型广义Z－O发展方程的诊断分析,考查了两个西北太平洋温带气旋爆发件发展的主要强迫机制和热力一动力空;司结构。结果表明,热力强迫对爆发性气旋发展起主要控制作用,当反映大气斜乐性的Laplacian温度平流、积云对流和湍流加热为主的热力强迫共同作用使地转相对涡度急剧增长时,气旋便出现了爆发性发展,其中积二尺度的对流加热贡献更大。Laplacian绝热冷却、大气向海洋的感热输送和摩擦效应起阻滞发展的作用,也是控制气旋衰亡的主要过程。爆发性发展启动同子因例而异,涡度平流、Laplacian温度平流和Laplacian大尺度加热均可成为主要启动因子。垂直积分平均分布和垂直结构考查进一步佐证了诊断分析的结果,并揭示了气旋爆发性发展过程中一些重要的热力-动力学分布特征。     

一种时域复阻尼本构方程

为了将复阻尼理论应用于时步积分计算,本文根据文献［１］提供的建立时域复阻尼本构的思路,首先讨论了通过组合标准线性体构成与复阻尼理论在具有工程意义的频段内等效的时域本构方程的方法,即通过适当选取本构参数使滞回阻尼比和弹性模量与复阻尼理论相应值基本保持一致。然后,用一维波动数值模拟实例,对比了本文建议的本构方程、频域复阻尼理论及粘性阻尼本构对计算结果的影响,论证了本文建议的本构方程应用于地震工程的可行     

Numerical Simulation of Wave Field at the Kemena River Mouth in Kalimantan Island

-By use of the parabolic equation of numerical simulation of wave which is suitable forlarge-angle propagation and Crank-Nicolson differential method,the wave field at the Kemema Rivermouth has been studied for analysis of sediment movement in the area.In order to reflect wave energy lossaccurately,the Bretchneider-Reid formula is quoted and the friction coefficient in the formula is discussedin this paper.The calculation results indicate that the wave becomes a little damped at the mouth ofKemena River influenced by the topography and bottom friction,and the wave at the east beach is higherthan that at the west beach,because the east beach extends out.     

Sensitivity Analysis on GIS Procedures for the Estimate of Soil Erosion Risk

Land degradation by water erosion is one of the majorissues in the field of environmental planning. Soilerosion and sediment transport are spatiallydistributed processes, and their evaluation can beeasily realised by means of the use of GeographicInformation Systems. The greater availability ofdigital and geo-lithological data managed and storedinside GIS has implied the development of techniquesand procedures aimed at the definition of the spatialprediction of erosion and deposition rates across acatchment. In this paper using terrain data measuredon an experimental basin in southern Italy, asensitivity analysis on different GIS-basedmethodologies for the estimate of a Length-Slope factorhas been developed with the aim of determining whichof these is more reliable for spatial erosion riskassessment. Specifically, by using the unit stream powertheory, different estimates are shown, depending on thescheme adopted to represent the hydrological andtopographic three-dimensional effects inside theLength-Slope factor. The performances of theprocedures analysed have been evaluated through theinformation content of the corresponding spatialdistributions, estimated as an entropy measure. Theresults obtained have shown that among the approachesutilised to describe the routing of the surface runoffalong the hillslope profiles, the two-dimensionalscheme appeared to be more realistic both on divergingand converging surfaces. Such a scheme, during thecomputational phases also aimed at distinguishing the areasof the basin experiencing net erosion from those areasexperiencing net deposition, resulted, being inaccordance with on-site investigations.     

人影高炮作业落区的一种判定方法

提出了人影高炮弹丸轨迹的运动方程,根据方程计算理论弹丸落点并得出安全区外扩的误差范围。针对人影高炮作业射界设定安全区的情况,提出落点位于安全区内外的判定方法,从而在理论上给出判断人影高炮作业安全性的问题。     

Gully morphological characteristics in the loess hilly‐gully region based on 3D laser scanning technique

Gully morphology characteristics can be used effectively to describe the status of gully development. The Chabagou watershed, located in the hilly‐gully region of the Loess Plateau in China, was selected to investigate gully morphological characteristics using a 3D laser scanning technique (LIDAR). Thirty‐one representative gullies located at different watershed locations and gully orders were chosen to quantitatively describe gully morphology and establish empirical equations for estimating gully volume based on gully length and gully surface area. Images and point cloud data for the 31 gullies were collected, and digital elevation models (DEMs) with 10‐cm resolution were generated. ArcGIS 10.1 was then used to extract fundamental gully morphological parameters covering gully length (L), gully width (W_T) and gully depth (D), and some derivative morphological parameters, including gully head curvature (C), gully width–depth ratio (w/d), gully bottom‐to‐top width ratio (W_B/W_T), gully surface area (A_g) and gully volume (V_g). The results indicated that gullies in the upper watershed and the second order were more developed based on their high values of gully head curvature. The potential for gully development increased from the second order to the fourth order. Within the same gully orders, gullies in the lower watershed were more active with more development potential. A method for differentiating between gully head and gully sidewalls based on the gully head curvature value was proposed with a mean relative error of 8.77%. U‐shaped cross‐sections were widely distributed in the upper watershed and upper positions of a gully, while V‐shaped cross‐sections were widely distributed in the lower watershed and lower positions of a gully. V–L and V–A_g empirical equations with acceptable accuracy were established and can be used to estimate gully erosion in the Loess hilly‐gully region. Copyright © 2017 John Wiley & Sons, Ltd.     

集成波能转换功能的方箱—挡浪板式浮式防波堤水动力特性研究

浮式防波堤与振荡浮子式波浪能转换装置集成是一种较为合理的波浪能开发利用方式,基于方箱式浮式防波堤—波浪能转换集成系统和幕帘式防波堤的研究成果,提出了一种新型方箱—垂直挡浪板式浮式防波堤—波浪能转换集成系统,建立数学模型对该集成系统的水动力特性和能量输出特性进行研究。模型基于N-S方程,采用紧致插值曲线(CIP)方法结合浸没边界法(IBM)求解。运用数值模型探究在一定波浪条件下,动力输出系统(PTO)阻尼力的大小以及挡浪板对集成系统的水动力特性和能量转换特性的影响,得到如下结论:集成系统的俘获宽度比随PTO阻尼力的增大呈现先增大后减小的趋势,在阻尼力F_(PTO)=150 N时达到最大;相对于方箱型集成系统,增设0.1 m挡浪板后可使其最大俘获宽度比η_e提高33%左右;此外,集成系统的俘获宽度比随挡浪板长度增加而增大,增长趋势逐渐变缓,在挡浪板长度S_p=0.5 m时达到最大,此时俘获宽度比η_e=0.563 1。     

Relationships between physical‐geochemical soil properties and erodibility of streambanks among different physiographic provinces of Tennessee,USA

Erosion of cohesive soils in fluvial environments is dependent on physical, geochemical and biological properties, which govern inter‐particle attraction forces and control detachment rates from stream beds and banks. Most erosion rate models are based on the excess shear stress equation where the soil erodibility coefficient (k_d) is multiplied by the difference between the boundary hydraulic shear stress (τ_b) and the soil critical shear stress (τ_c). Both k_d and τ_c are a function of soil properties and must be obtained through in situ field or laboratory testing. Many studies have generated predictive relationships for k_d and τ_c derived from various soil properties. These studies typically were conducted in watersheds within a single physiographic region with a common surficial geology and/or investigated a limited number of soil properties, particularly geochemical properties. With widely reported differences in relationships between τ_c and soil properties, this study investigated differences in predictive relationships for τ_c among different physiographic provinces in Tennessee, USA. Erodibility parameters were determined in the field using a mini‐jet test device. Among these provinces, statistically four unique clusters were identified from a dataset of 128 observations and these data clusters were used to develop predictive models for τ_c to identify dominant properties governing erosion. In these clusters, 16 significant physical and geochemical soil properties were identified for τ_c prediction. Among these soil properties, water content and passing #200 sieve (percentage soil less than 75 μm) were the dominant controlling parameters to predict τ_c in addition to clay percentage (< 2 μm), bulk density, and soil pore water chemistry. This study suggests that unique relationships exist for physiographic provinces that are likely due to soil physical‐geochemical processes associated with surficial geology that determine minerology of the cohesive soil. Copyright © 2017 John Wiley & Sons, Ltd.     

Image-domain wavefield tomography for tilted transversely isotropic media

Transversely isotropic models with a tilted symmetry axis have become standard for imaging beneath dipping shale formations and in active tectonic areas. Here, we develop a methodology of wave-equation-based image-domain tomography for acoustic tilted transversely isotropic media. We obtain the gradients of the objective function using an integral wave-equation operator based on a separable dispersion relation that takes the symmetry-axis tilt into account. In contrast to the more conventional differential solutions, the integral operator produces only the P-wavefield without shear-wave artefacts, which facilitates both imaging and velocity analysis. The model is parameterized by the P-wave zero-dip normal-moveout velocity, the Thomsen parameter δ, anellipticity coefficient η and the symmetry-axis tilt θ. Assuming that the symmetry axis is orthogonal to reflectors, we study the influence of parameter errors on energy focusing in extended (space-lag) common-image gathers. Distortions in the anellipticity coefficient η introduce weak linear defocusing regardless of reflector dip, whereas δ influences both the energy focusing and depth scale of the migrated section. These results, which are consistent with the properties of the P-wave time-domain reflection moveout in tilted transversely isotropic media, provide important insights for implementation of velocity model-building in the image-domain. Then the algorithm is tested on a modified anticline section of the BP 2007 benchmark model.     

用稳定同位素方法估算大型浅水湖泊蒸发量——以太湖为例

湖泊蒸发量的准确估算对于水文学、气象学和湖泊学等研究有重要的意义.基于2013-2015年太湖水量收支资料、气象观测数据和稳定同位素观测资料,采用稳定同位素质量守恒模型、水量平衡法和Priestley-Taylor模型估算太湖蒸发量,分析太湖蒸发量的季节变化和年际变化特征,并以Priestley-Taylor模型结果为参考值,评价水量平衡法和同位素质量守恒方程的计算精度.结果表明:5-9月太湖蒸发量较高,冬季最低.2013-2015年太湖年总蒸发量分别为1069、894和935 mm,蒸发量的年际变化受到天气条件的影响.2013年12月2014年11月期间,用Priestley-Taylor模型计算的湖泊蒸发量为885 mm;同位素质量守恒模型的估算结果较一致,为893 mm;而水量平衡方程的估算结果明显偏高,为1247 mm.