FLAC 3D 强度折减理论在边坡稳定分析中的应用

FLAC3D 是岩土工程中广泛应用的软件。本文主要介绍强度折减理论的基本原理,利用基于强度折减法的FLAC3D 软件,对某高速公路K377 + 230 ～ K377 + 520 段滑坡体进行数值模拟。计算边坡在自重作用达到初始化平衡状态时,边坡的横向与竖直方向的应力与位移,分析出边坡的破坏机制为牵引式滑坡,通过强度折减理论计算出边坡的稳定系数为0. 97,由剪切应变增量云图确定边坡的滑动面。     

陕西一次强沙尘暴过程诊断与分析

2006年陕西共发生沙尘天气13次,其中4月11日的沙尘天气最为严重,危害最大,这也是陕西近10 a来最为严重的一次沙尘暴天气过程。这次沙尘天气带来一系列的天气演变过程,它持续时间虽然只有8~9 h,但覆盖面积大,影响范围广,全省70%~80%左右的区域都受到了影响。运用FY-2卫星红外云图及MICAPS2.0模式中的数值预报进行分析,发现红外云图呈现出异常状态,高低空形势配合较好,气压梯度、温度梯度密集,狂风突起等状况,试图揭示与解读沙尘天气在发生过程中某些气象因子的特征及其对沙尘天气的影响机理,为今后预报沙尘暴强度和发生区域提供一定的理论依据。     

黄河大堤非饱和土的三轴试验研究

利用特制的非饱和土三轴仪器,模拟实际工程中土体的受力条件,对黄河大堤非饱和土在不同围压条件下的土水特性以及非饱和土的强度进行了试验研究。试验表明：非饱和土基质吸力随着土体周围压力的增大而减小,随着含水率的增大而减小;非饱和土的有效摩擦角 值受含水量的影响不大。但总凝聚力 受含水率的影响较大,含水率越小,基质吸力就越大,总凝聚力亦越大。根据试验结果,提出了非饱和土的抗剪强度的拟合模型,该模型参数易于确定,与实测结果：拟合误差较小,满足非饱和土的强度计算精度要求。     

RBFNN模型在渗透系数反演中的应用

针对经典的BP网络存在的一些缺陷,采用了径向基函数神经网络（RBFNN）。在相同的收敛条件下,用RBFNN和经典算法的BP网络进行了比较,表明前者具有优越性。在工程实例中,基于人工神经网络的非线性特点,在三维渗流有限元的基础上,利用RBFNN反演了大坝的渗透系数。并利用反演结果进行渗流场分析,水头预报值也有很高的精度,说明反演结果是正确的,从而,验证了RBFNN应用于反演分析中的可靠性。     

长江三角洲地区农业可持续发展的问题与对策

随着农地制度的改革、农业投入以及技术创新活动的加强,长江三角洲地区的农业现代化建设取得了较快发展,但从长远来看,影响和制约农业发展的问题非常严骏。文章主要从土地资源合理利用角度分析对农业可持续发展的影响。基于日趋严峻的人地矛盾和快速发展的市场经济条件,阐述了农业可持续发展对策;加强宏观调控和对资源开发利用保护的监督,坚持优质高效,从市场需求出发开发利用资源,建立高效地利用土地资源机制,面向国内国际     

本溪县汤池沟热田热储特征及资源量评价

汤池沟热田大地构造位置处于辽阳－本溪凹陷与凤城凸起的交接部位,属浅埋藏水热对流型热田。热储由中生代燕山期花岗斑岩、凝灰岩组成。热源为岩浆活动的余热。热流体主要靠侧向基岩裂隙水及断裂充水带的水补给,自北东向南西方向以脉状裂隙水运动为主,热流体直接受北东、北北东及北西向断裂控制。该热田储存有较丰富的地热资源,热能总量计算为 58.05 TJ,目前的热水开采量每年为 414 000 t,相当于消耗燃烧值为 29.3 MJ的标准煤每年 1 833.43 t,如果按此潜力开发,其开采年限预计可持续 80年以上。     

基于循环神经网络的重力异常数据推估研究

利用鄂尔多斯西南缘的重力观测数据对长短期记忆循环神经网络(long short-term memory,LSTM)进行训练,结果表明,该神经网络可基于有限的数据获取较好的推估结果.基于自由空气重力异常数据,对比分析长短期记忆循环神经网络和传统克里金方法的推估结果发现,神经网络的推估能力优于传统克里金方法,但运算效率低于...     

Identification of Suitable Hydrologic Response Unit Thresholds for Soil and Water Assessment Tool Streamflow Modelling

Use of a non-zero hydrologic response unit(HRU) threshold is an effective way of reducing unmanageable HRU numbers and simplifying computational cost in the Soil and Water Assessment Tool(SWAT) hydrologic modelling. However, being less representative of watershed heterogeneity and increasing the level of model output uncertainty are inevitable when minor HRU combinations are disproportionately eliminated. This study examined 20 scenarios by running the model with various HRU threshold settings to understand the mechanism of HRU threshold effects on watershed representation as well as streamflow predictions and identify the appropriate HRU thresholds. Findings show that HRU numbers decrease sharply with increasing HRU thresholds. Among different HRU threshold scenarios, the composition of land-use, soil, and slope all contribute to notable variations which are directly related to the model input parameters and consequently affect the streamflow predictions. Results indicate that saturated hydraulic conductivity, average slope of the HRU, and curve number are the three key factors affecting stream discharge when changing the HRU thresholds. It is also found that HRU thresholds have little effect on monthly model performance, while evaluation statistics for daily discharges are more sensitive than monthly results. For daily streamflow predictions, thresholds of 5%/5%/5%(land-use/soil/slope) are the optimum HRU threshold level for the watershed to allow full consideration of model accuracy and efficiency in the present work. Besides, the results provide strategies for selecting appropriate HRU thresholds based on the modelling goal.     

互联网信息特征研究综述

随着互联网的高速发展,网络上信息呈爆炸性增长.理解互联网上信息的特征对信息的快速获取具有重要意义.本文首先介绍了互联网信息载体的特征,然后分别按照互联网信息在时间上的演化特征、信息的大小特征、信息的内容特征以及信息的类型特征从不同的角度对互联网信息的特征进行了分析、归纳和总结,最后,对互联网信息特征潜在的应用给出了一个可能的实际例子.     

Spatio-temporal differences in cloud cover of Landsat-8 OLI observations across China during 2013–2016

Currently, the historical archive images of Landsat family sensors are probably the most effective data products for tracking global longitudinal changes since the 1970s. However, the issue of the degree and extent of cloud coverage is always a challenge and varies distinctively worldwide. So far, acquisition probability (AP) analyses of cloud cover (CC) of Landsat observations have been conducted with different sensors at regional scale. To our knowledge, CC probability analysis for the newly-launched Landsat-8 Operational Land Imager (OLI) across China is not reported. In this paper, monthly, seasonal, and annual APs for Landsat OLI (44,228 in total) images over China acquired from April 2013 to October 2016 with various CC thresholds were analyzed. The results showed that: first, the cumulative average APs of all OLI data over China at the CC thresholds ≤30% was about 49.6% which illustrated the availability of OLI imagery across China. Second, the spatial patterns of 10%, 20%, and 30% CC thresholds of OLI observations, coincided well with the precipitation distributions separated by the respective 200 mm, 400 mm, and 800 mm isohyetal lines. Third, the APs of images with the 30% CC threshold are the highest in autumn and winter especially in October of 58.7%, while the corresponding lowest probability occurred in June of 41.0%. Finally, the spatial differences in APs of targeted images with ≤30% CC thresholds were quite significant. At regional scales, the arid and semi-arid areas, Inland River and Songliao River basins, and northwestern side of the Hu Huanyong population line had the larger probabilities of obtaining high-quality images. Our study suggested that OLI imagery satisfy the data requirements needed for land surface monitoring, although there existed obvious spatio-temporal differences in APs over China at the 30% CC threshold.