南海北部海域油气资源调查技术及其应用研究——震源子波检测及模拟分析          下载免费PDF全文

曾宪军  翟继锋  韦成龙 《海洋技术学报》2019,38(2)

在野外采集中考察气枪的稳定性以及室内进行确定性子波反褶积处理,都要求能够获得气枪阵列的实时远场子波。从震源子波检测方法出发,阐述了近场子波采集、幅值转换及记录流程,并列举出实测近场子波时需要考虑解决的问题;接着介绍了震源远场子波的获取方法和主要途径;震源近场子波及远场子波的实测方案,检测震源子波所需的仪器设备和采集技术方法。文中分析了气枪子波的气泡干扰问题,虚反射与后续气泡震荡间的关系以及吸收衰减对子波的影响,并根据实测远场子波,对齐氏和范氏两种气体模型进行了模拟效果对比,结果表明:采用范氏气体模型所模拟的子波与实际子波更为吻合,模拟出的气枪的子波波形、振幅大小、气泡周期上,与业界通用的Nucleus软件的模拟结果吻合较好,在后续的使用中将继续优化。  相似文献   

利用短期静态PPP结果反演海潮负荷位移     

魏国光  王琪洁  彭葳  郭良琦 《大地测量与地球动力学》2019,39(6):607-612

采用香港11个GPS测站的观测资料进行1 h、2 h、3 h和4h静态PPP解算，获得4组PPP坐标序列，利用调和分析求取11个测站处8个主要分潮的负荷位移参数（振幅和相位），将其与海潮模型计算的负荷位移参数进行对比，并比较分析PPP反演值与海潮模型值改正海潮负荷信号的效果。结果表明，垂直和水平方向上，不同PPP结果反演8个分潮的负荷位移分别具有约5 mm和7 mm的差异；PPP反演8个分潮垂向负荷位移优于全球海潮模型，但水平方向上的反演效果稍弱。  相似文献   

Socio-hydrological framework for investigating farmers’ activities affecting the shrinkage of Urmia Lake; hybrid data mining and agent-based modelling     

Parsa Pouladi  Amir Molajou  Mohammad Hadi Afshar 《水文科学杂志》2020,65(8):1249-1261

ABSTRACT

Developing a general framework to capture the complexities associated with the non-linear and adaptive nature of farmers facing water resources scarcity is a challenging problem. This paper integrates agent-based modelling (ABM) and a data mining method to develop a hybrid socio-hydrological framework to provide future insights for policy-makers. The data associated with the farmers’ main characteristics were collected through field surveys and interviews. Afterwards, the association rule was employed to discover the main patterns representing the farmers’ agricultural decisions. The discovered patterns were then used as the behavioural rules in ABM to simulate the agricultural activities. The proposed framework has been was applied to explore the interactions between agricultural activities and the main river feeding the Urmia-Lake, Iran. The outcomes indicate that farmers’ acquisitive traits and belongings have significant impacts on their socio-hydrological interactions. The reported values of the efficiency criteria may support the satisfactory performance of the proposed framework.  相似文献   

Event-based classification for global study of river flood generating processes     

Lina Stein  Francesca Pianosi  Ross Woods 《水文研究》2020,34(7):1514-1529

Better understanding of which processes generate floods in a catchment can improve flood frequency analysis and potentially climate change impacts assessment. However, current flood classification methods are either not transferable across locations or do not provide event-based information. We therefore developed a location-independent, event-based flood classification methodology that is applicable in different climates and returns a classification of all flood events, including extreme ones. We use precipitation time series and very simply modelled soil moisture and snowmelt as inputs for a decision tree. A total of 113,635 events in 4155 catchments worldwide were classified into one of five hydro-climatological flood generating processes: short rain, long rain, excess rainfall, snowmelt and a combination of rain and snow. The new classification was tested for its robustness and evaluated with available information; these two tests are often lacking in current flood classification approaches. According to the evaluation, the classification is mostly successful and indicates excess rainfall as the most common dominant process. However, the dominant process is not very informative in most catchments, as there is a high at-site variability in flood generating processes. This is particularly relevant for the estimation of extreme floods which diverge from their usual flood generation pattern, especially in the United Kingdom, Northern France, Southeastern United States, and India.  相似文献   

隔震曲线梁桥不同等级地震的振动特性模拟分析          下载免费PDF全文

高菁阳 《地震工程学报》2020,42(3):607-612

曲线桥梁抗震特性模拟分析对于曲线桥梁隔震、减震有着重要意义。基于隔震曲线桥梁设计过程中的特点,通过非线性水平弹簧单元对铅芯橡胶支座双向非线性的能力进行模拟,根据SAP2000科学选择强震观测地震波,并考量曲线桥梁本身存在的特性对桥梁振动特性产生的影响,针对隔震曲线桥梁在不同等级地震下振动特征进行模拟分析,其中,通过隔震曲线桥梁铅芯橡胶支座模型的构建和梁桥不同等级地震计算模型、输入地震波与传感器量测等步骤得到的模拟结果为:不同地震波与加速度峰值输入过程中,地震动较小下的支座水平刚度比较大,且结构相对稳定;地震幅值增大时,桥梁支座水平刚度减小,且支座的恢复力位移滞回变化曲线面积比较大,能够更多地将地震输入能量消散掉,减小能量不断向曲线桥梁上方传递的速度,可有效减轻地震反应,起到隔震的效果。  相似文献   

Relating the depth of the water table to the depth of weathering     

M.I. Lebedeva  S.L. Brantley 《地球表面变化过程与地形》2020,45(9):2167-2178

Weathering of bedrock creates and occludes permeability, affecting subsurface water flow. Often, weathering intensifies above the water table. On the contrary, weathering can also commence below the water table. To explore relationships between weathering and the water table, a simplified weathering model for an eroding hillslope was formulated that takes into account both saturated and unsaturated subsurface water flow (but does not fully account for changes in dissolved gas chemistry). The phreatic line was calculated using solutions to mathematical treatments for both zones. In the model, the infiltration rate at the hill surface sets both the original and the eventual steady-state position of the water table with respect to the weathering reaction front. Depending on parameters, the weathering front can locate either above or below the water table at steady state. Erosion also affects the water table position by changing porosity and permeability even when other hydrological conditions (e.g. hydraulic conductivity of parent material, infiltration rate at the surface) do not change. The total porosity in a hill (water storage capacity) was found to increase with infiltration rate (all else held constant). This effect was diminished by increasing the erosion rate. We also show examples of how the infiltration rate affects the position of the water table and how infiltration rate affects weathering advance. Published 2020. This article is a U.S. Government work and is in the public domain in the USA  相似文献   

Response of A Gravel - Bed River To Dam Closure: Insights From Sediment Transport Processes And Channel Morphodynamics     

A. Brenna  N. Surian  L. Mao 《地球表面变化过程与地形》2020,45(3):756-770

This work deals with the impacts of dams on large gravel -bed rivers in terms of altering coarse transport regimes and the relationship with river morphodynamics. Using data collected by a tracer -based monitoring programme carried out in a 4 -km -long study sector of the Parma River (Italy), located downstream from a relatively recently established dam, we applied a virtual velocity approach to estimate the coarse bed material load at four river cross -sections. Monitoring and calculation results provided new insights into the impacts of the dam on streambed material mobility and the sediment regime over the 17 -month calculation period. A longitudinal gradient of effects was observed along the study sector. Sections located closer to the dam are characterized by more evident impacts due to deficits in coarse sediment input from upstream. Sediment mobility here is strongly altered, especially in the highly armoured main channel, and the overall bed material load is extremely low. A partial recovery of sediment dynamics was observed at the sections located further from the dam, where estimates indicate higher sediment yield. The observed longitudinal trend in the coarse sediment transport regime matches the morphology, as the river shifts downstream from a sinuous configuration with alternate bars to a wandering one. The novel insights into alteration of coarse sediment dynamics and the relationship with river morphodynamics are potentially applicable to many other fluvial contexts affected by similar impoundments. © 2019 John Wiley & Sons, Ltd.  相似文献   

云平台下地震监测台网软件系统的应用方案研究     

李勇  段毅 《震灾防御技术》2018,13(1):245-253

针对数字化地震台网JOPENS软件系统的技术特点及功能需求，在对当前各种主流云计算平台进行比较的基础上，基于较为合适的阿里云计算平台，提出了在云环境下部署JOPENS系统的应用方案。测试结果表明JOPENS系统部署在云环境下能够提升测震台网中心运行的稳定性及可扩展性，并节约运行维护成本。该研究对于当前三网融合新形势下云南省地震台网的建设及运行工作具有借鉴意义。  相似文献   

Developing constitutive models from EPR‐based self‐learning finite element analysis          下载免费PDF全文

Ali Nassr  Akbar Javadi  Asaad Faramarzi 《国际地质力学数值与分析法杂志》2018,42(3):401-417

A constitutive model that captures the material behavior under a wide range of loading conditions is essential for simulating complex boundary value problems. In recent years, some attempts have been made to develop constitutive models for finite element analysis using self‐learning simulation (SelfSim). Self‐learning simulation is an inverse analysis technique that extracts material behavior from some boundary measurements (eg, load and displacement). In the heart of the self‐learning framework is a neural network which is used to train and develop a constitutive model that represents the material behavior. It is generally known that neural networks suffer from a number of drawbacks. This paper utilizes evolutionary polynomial regression (EPR) in the framework of SelfSim within an automation process which is coded in Matlab environment. EPR is a hybrid data mining technique that uses a combination of a genetic algorithm and the least square method to search for mathematical equations to represent the behavior of a system. Two strategies of material modeling have been considered in the SelfSim‐based finite element analysis. These include a total stress‐strain strategy applied to analysis of a truss structure using synthetic measurement data and an incremental stress‐strain strategy applied to simulation of triaxial tests using experimental data. The results show that effective and accurate constitutive models can be developed from the proposed EPR‐based self‐learning finite element method. The EPR‐based self‐learning FEM can provide accurate predictions to engineering problems. The main advantages of using EPR over neural network are highlighted.  相似文献   

基于修正SWAT模型的岩溶地区非点源污染模拟初探——以横港河流域为例   总被引：3，自引：0，他引：3  

赖格英  易姝琨  刘维  盛盈盈  彭小娟  熊家庆  潘思怡  吴青 《湖泊科学》2018,30(6):1560-1575

岩溶流域含水系统的主要特征之一是连通地表的落水洞等垂直管道将近水平的地下暗河联系起来，降水及其形成的地表径流可以通过这些管道迅速地灌入地下河系，从而改变了水及其所携带的非点源污染物质在垂直与水平方向的传输速度与数量，使岩溶流域内地表-地下之间的物质交换与传输过程变得比较复杂；应用广泛的SWAT模型在模拟岩溶地区的水文、水质时会存在一些不足与局限.为此，本文针对岩溶水系统特征，引入落水洞、伏流、暗河的水文过程以及主要营养盐的输移过程，修正SWAT模型原有的水文循环过程及相关算法，改变其只适用于松散均匀介质流域非点源污染模拟的单一特征，并研究建立适合于岩溶流域的非点源污染模型和相应的模拟方法.选取横港河流域岩溶地区作为非点源污染的对象，应用修正后的模型通过控制性的模拟方法和敏感性性分析，定量评估落水洞、伏流、暗河等岩溶特征对氮、磷等主要非点源污染物质输移的影响及其带来的时空效应，并进一步探讨落水洞、伏流、暗河等对地表-地下水文与营养盐的交互作用及转换机理.结果表明，岩溶特征对流域的氮、磷负荷有增加作用，其中总磷的增加明显大于总氮的增加，总磷和总氮的增量分别为0.86%和2.12%；植被岩溶指数的增加会导致流域可溶性磷、有机磷的产出量增加，有机氮、地表产流中硝酸氮和沉积磷的产出量则居其次，落水洞改变了降雨的产流方式，增加了落水洞所在流域的有机磷和有机氮的产出，其增量变化在0~0.7和0~0.3 kg/hm²之间.  相似文献