Using hysteretic behaviour and hydrograph classification to identify hydrological function across the “hillslope–depression–stream” continuum in a karst catchment

In cockpit karst landscapes, fluxes from upland areas contribute large volumes of water to low-lying depressions and stream flow. Hydrograph hysteresis and similarity between monitoring sites is important for understanding the space–time variability of hydrologic responses across the “hillslope–depression–stream” continuum. In this study, the hysteretic feature of hydrographs was assessed by characterizing the loop-like relationships between responses at upstream sites relative to subsurface discharge at the outlet of a small karst catchment. A classification of hydrograph responses based on the multi-scale smoothing Kernel -derived distance classifies the hydrograph responses on the basis of similarities between hillslope and depression sites, and those at the catchment outlet. Results demonstrate that the temporal and spatial variability of hydrograph hysteresis and similarity between hillslope flow and outlet stream flow can be explained by the local heterogeneity of depression aquifer. Large depression storage deficits emerging in the highly heterogeneous aquifer produce strong hysteresis and multiple relationships of upstream hydrographs relative to the outlet subsurface discharge. In contrast, when depression storage deficits are filled during consecutive rainfall events, depression hydrographs at the high permeability sites are almost synchronous or exhibit a monotonous function with the hydrographs at the outlet. This reduced hydrograph hysteresis enhances preferential flow paths in fractured rocks and conduits that can accelerate the hillslope flow to the outlet. Therefore, classification of hydrograph similarities between any upstream sites and the catchment outlet can help to identify the dominant hydrological functions in the heterogeneous karst catchment.     

Site effects at Euroseistest—I. Determination of the valley structure and confrontation of observations with 1D analysis

This paper describes the process of construction of the 2D model of Volvi's geological structure and results of empirical and theoretical approaches to the evaluation of site response at Euroseistest. The construction of the 2D model is based on a re-interpretation of the available geophysical and geotechnical data in an effort to improve the definition of the subsoil structure at Euroseistest in terms of the most important parameters needed to model site response. The results of this re-interpretation are compared with a previous published 2D model of the same alluvial valley. Different analysis of the measurements and different criteria in the synthesis of data have led to a different model, even if both studies had access to the same field measurements. This underscores the fact that a model results of an interpretation and is not uniquely determined by the data, no matter how detailed they are. The well known subsoil structure opened the possibility to correlate the geometry and the dynamic properties of the 2D model with the results of site response determined from a detailed analysis of two events in frequency and time domains and 1D numerical modeling. The study of site response shows the important effect of the lateral variations on the ground motion and suggests that the contribution of locally generated surface waves to the resonant peak may be important. In the case of Volvi's graben, the limitations of the 1D approximation to simulate ground motion under complex soil conditions in both frequency and time domains are also shown. This paper lays the ground for a companion article dealing with 2D site effects in this basin.     

中国大陆M2波理论应变潮汐模型

本文主要研究和讨论了我国大陆固体潮和海潮负荷效应的M2波理论应变潮汐模型。推导了球扇波应变张量大地系数和计算公式,着重研究和计算了M2波海潮应变负荷效应,讨论了计算方法,计算中采用了到目前为止最新的Schwiderski（M2）全球海潮图和沈育疆近中国海潮汐图;给出了40个点的负荷效应结果,并绘制了中国大陆固体应变潮、海潮应变负荷效应同相位,相差π/2相位以及总效应的应变花。为理论研究,观测资料的分析和改正提供了理论参考模型。     

High parallelization efficiency in barotropic-mode computation of ocean models based on multi-grid boundary ghost area

In general, barotropic-mode computation requires the largest communication time in ocean models because of its iterative nature, when parallel computation is performed based on regional partitioning. In this study, reduction in the overhead time included in the communication in the parallel computation of the barotropic mode is considered to achieve a high parallelization efficiency of ocean models. We verify that the reduction in the communication frequency based on the multi-grid boundary ghost area reduces the total communication time. We find that this is because the sum of several kinds of overhead time for communication occupies a fairly large part of the total communication time. We discuss the trade-off between the decrease in communication time and the increase in computation time due to increased boundary area in such cases, leading to a determination of a suitable width of the multi-grid boundary that minimizes the total required time. We also discuss the efficiencies of the one- and two-dimensional partitioning of the model domain, when a multi-grid boundary is used. In general, two-dimensional partitioning is more efficient than one-dimensional for large partitioning numbers.     

The sheltering effect of the Balearic Islands in the hindcast wave field

The sheltering effect of the Balearic Islands in the hindcast wave field was studied for typical Mediterranean wave situations of Llevant, Tramuntana and Mestral and for mild conditions such as the Garbí and Ponent winds. For this purpose, a third generation wave model was applied to the Mediterranean Sea and different patterns of the sheltered areas were found for the various representative situations depending on the wind variability and on the magnitude of the wind speed. From the analysis it was concluded that the sheltered zones created during storms generally persist for short periods of time of the order of 6 h, possibly reaching a maximum of 12 h. In contrast with earlier results obtained for swell dominated ocean areas, it was observed that in this area, due to the short fetches the sea states are mainly local wind seas and thus the wave field behind the islands depends on the local wind.     

“一带一路”建设对沿线国家经济增长的影响效果与中介路径

科学评估“一带一路”建设对沿线国家经济增长的影响效果与中介路径,对理解国际合作模式、推动“一带一路”建设向高质量发展转变具有重要意义。基于2003—2017年“一带一路”沿线64个国家的相关数据,采用固定效应面板模型和中介效应检验程序,实证检验了“一带一路”建设对沿线国家经济增长的总体性影响效果,并分析对外直接投资、进出口贸易、交通运输、就业等中介因素之间的作用关系。研究结果表明：2013—2017年间“一带一路”建设能够显著地促进沿线国家的经济增长,但新建交通基础设施线路长度、中国对外直接投资等对沿线国家GDP增长的直接促进作用并不显著。它主要通过推动中国与沿线国家之间的贸易增长,对沿线国家内部的货物资源流动、人口就业率、就业结构等产生积极影响,进而促进沿线国家的GDP增长。     

Second-Order Wave Diffraction Around 3-D Bodies by A Time-Domain Method

A time-domain method is applied to simulate nonlinear wave diffraction around a surface piercing 3-D arbitrary body. The method involves the application of Taylor series expansions and the use of perturbation procedure to establish the corresponding boundary value problems with respect to a time-independent fluid domain. A boundary element method based on B-spline expansion is used to calculate the wave field at each time step, and the free surface boundary condition is satisfied to the second order of wave steepness by a numerical integration in time. An artificial damping layer is adopted on the free surface for the removal of wave reflection from the outer boundary. As an illustration, the method is used to compute the second-order wave forces and run-up on a surface-piercing circular cylinder. The present method is found to be accurate, computationally efficient, and numerically stable.     

北京地区一次特大强风过程边界层结构的研究

利用北京325 m气象塔资料对1993年4月9日北京地区出现的一次特大强风过程的边界层结构（风、温、风切变及阵风特征）进行了分析。随着该次大风的过境，边界层内风场出现数个风速高值中心，高度位于200～300 m，时间间隔1～3 h。伴随上层风速垂直切变和阵风特性。湍流能谱的计算结果表明了大尺度涡旋对边界层湍流微结构的影响。     

可调滞回模型的磁流变阻尼器及其试验

本文在现在磁流变阴尼器性能研究的基础上，提出了可调滞回模型的磁流变阻尼器及其试验方法，并进行理论、试验及算例分析。首先，根据恒定电流下磁流变阻尼器的阻尼力滞力特性，利用磁流变材料特性的电流（即磁场）可控特点，建立了变电流下的阻尼力滞回模型；其次，在中通过电路板控制外加电流与装置变形间的函数关系，实现了变电流调节的阻尼力滞回模型；最后，将磁流变阻尼器与橡胶隔震装置结合，形成智能磁流变隔夺装置，并对一个单自由度隔震结构进行了数值仿真分析。     

青藏高原云-辐射-加热效应和南亚夏季风--1985年与1987年对比分析

文中首先利用NCEP NCAR再分析的风场资料 ,分析了南亚夏季风的时空特征 ,选取了有代表性的典型强、弱夏季风年 ,继而利用ISCCP C2、ERBE S4卫星观测资料和NCEP NCAR再分析资料 ,对比分析了强、弱夏季风前期青藏高原地区的云—辐射—加热状况及其在海、陆差异中的作用。分析结果表明 ,南亚夏季风强或弱 ,其前期青藏高原地区的云—辐射—加热效应有明显的差异。在强 (弱 )南亚夏季风的前期 ,青藏高原大部分地区为相对少 (多 )云区 ,其云量变化不仅表明了此区的云—辐射—加热效应的不同 ,更重要的是与此同时出现的海、陆之间云量分布的“跷跷板”现象 ,进一步改变了海、陆之间的热力差异。而且 ,在强南亚夏季风年 ,这种热力差异不但开始得早 ,而且持续时间长、作用范围大 ,从而对南亚夏季风的形成和变化产生重要的影响