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91.
长江三角洲地区深基坑降水复杂,且极易引起地面沉降地质灾害问题,传统的基于地下水动力学原理的解析解模型(Theis公式或Dupuit公式)已难以满足降水设计模拟计算的需要,尤其是无法预测降水引起的地面沉降问题,深基坑降水与地面沉降耦合模型将地下水渗流模型和土体应力-应变模型耦合起来,可根据基坑地下水位的控制要求,同时模拟计算出降水井的布局、各井的开采量和地面沉降量。据此确定出的基坑降水方案既能满足地下水位的控制要求,又能对降水引起的地面沉降进行最优化控制。 相似文献
92.
This paper introduces a new method to estimate the long-term regional hurricane wind and storm surge hazard. The output is a relatively small set of hurricane scenarios that together represent the regional hazard. For each scenario, the method produces a hazard-consistent annual occurrence probability, and wind speeds and surge levels throughout the study area. These scenarios can be used for subsequent evacuation or loss estimation modeling. This optimization-based probabilistic scenario (OPS) method involves first simulating tens of thousands of candidate hurricane scenarios with wind speeds and approximate surge depths. A mixed-integer linear optimization is then used to select a subset of scenarios and assign hazard-consistent annual occurrence probabilities to each. Finally, a surge model is used to estimate accurate surge depths for the reduced set of events. The method considers the correlation between winds and surge depths and the spatial correlations of each; it is computationally efficient; and it makes explicit the tradeoff between the number of scenarios selected and the errors introduced by using a reduced set of events. A case study for Eastern North Carolina is presented in which a final set of 97 hurricanes provides unbiased results with errors small enough for many practical uses. 相似文献
93.
JOHN H.KALIVAS 《地理学报(英文版)》1991,(1)
ealibrared.The diseussion in this PaPer foeuses on near一infrared(NIR)sPeetroseoPy as the examPle instrument.However,the Proeedures Presented are aPPlieable tomost methods of instrumental analysis.Essentially,ealibration eonsists of assembling a seriesof samPles eontaining the analyte or analytes at 相似文献
94.
Excessive settlement caused by tunneling during construction often damages adjacent infrastructures and utilities. Such excessive settlement can also present a challenge in the maintenance of subways during their operation. Thus, it is important to be able to accurately predict tunneling-induced settlement. The uncertainties in geotechnical parameters, however, can lead to either an overestimation or an underestimation of the tunneling-induced settlement. Such uncertainties can arise from many sources such as spatial variability, measurement error, and model error; in this paper, the focus is on the geotechnical parameters characterization from site exploration. The goal here is to determine an optimal level of site exploration effort so that effective predictions of the tunneling-induced settlement in clays can be achieved. To this end, a Monte Carlo simulation-based numerical model of site exploration is first established to generate artificial test data. Then, a series of parametric analyses are performed to investigate the relationship between the level of site exploration effort and the accuracy of the tunneling-induced ground settlement prediction. Through the assumed different levels of site exploration effort, statistics of soil parameters are estimated using the maximum likelihood method and the tunneling-induced ground settlement is then analyzed using the probabilistic method, and finally the effect of site exploration effort is assessed. The knowledge generated from this series of analyses is then used to develop the proposed framework for selecting an optimal site exploration program for improved prediction of the tunneling-induced ground settlement in clays. Examples are presented to illustrate the proposed framework and demonstrate its effectiveness and significance. 相似文献
95.
The shape of an underground opening is a major factor influencing the stability of the underground excavation. Obtaining an optimized shape is significant in civil and mining engineering applications for increasing stability and reducing costs. This paper presents an updated method for finding the optimal shape of an underground excavation using the latest bi-directional evolutionary structural optimization (BESO) techniques considering material nonlinearities. Recent development in the BESO applications to underground excavation is discussed through illustrated examples. Details are given of the BESO method used to finding the optimal shape based on the global stiffness. The methodology of the stiffness based optimization techniques is described with examples of applications to underground excavation. Applications to underground void structures, such as cavern and tunnel, as well as underground solid structure such mine pillar are demonstrated. It is concluded that stiffness based optimization techniques are applicable to underground excavations and practical shape of an excavation can be generated as a result of the BESO application. 相似文献
96.
本文基于地层反射系数非高斯的统计特性,在反褶积输出单位方差约束下,将反褶积输出的负熵表示为非多项式函数,作为盲反褶积的目标函数,然后采用粒子群算法优化目标函数寻找最佳反褶积算子,实现地震信号的盲反褶积.数值模拟和实际资料处理结果表明,与传统反褶积方法相比,本文方法同时适应于最小相位子波及混合相位子波的反褶积,能够更好地从地震数据中估计反射系数,有效拓宽地震资料的频谱,得到高分辨率的地震资料. 相似文献
97.
98.
为探索三维掠动叶降低对转压气机二次流损失的潜力,进一步提高对转压气机气动性能,基于近似函数与遗传算法,针对某对转压气机双排转子在整机环境下进行三维掠动叶优化设计,并对优化前后流场进行对比分析。优化成功的得到了双排“S”形掠动叶,结果表明:三维掠动叶有效改善了双排动叶吸力面径向二次流,减小了吸力面低速区,提高了对转压气机性能,优化工况点整机效率提高0.6%,全工况范围内效率均有所提高;三维掠动叶提高对转压气机效率的根本原因是其对径向负荷分配的重新调整,将叶展下方流动较差区域负荷移至叶展上方,改善流场的同时保证对转压气机负荷不变。 相似文献
99.
100.
物理过程参数化方案的不确定性是目前气候系统模式不确定性的重要来源之一.随着模式内在复杂度攀升,模拟场景多样化,参数化方案中基于先验的和人工的物理参数选取方法已经逐步成为限制模式模拟能力的瓶颈之一.为此,本文设计并提出了初选与寻优相结合的两步法参数优化方案.初选阶段用全因子采样方法对不确定参数空间进行初始敏感性分析,估计最优解所在区域;寻优步采用单纯型下山法,基于初选阶段确定的参数组合快速寻优.将两步法应用于中国科学院大气物理研究所(英文缩写:IAP)大气科学和地球流体力学数值模拟国家重点实验室(英文缩写:LASG)格点大气模式第2版:GAMIL2,选取其深对流方案和云量方案中的3个重要参数开展寻优,优化以综合减小模式降水、风场、温度、湿度、位势高度以及辐射通量的误差为目标.这些变量用GAMIL2标准版本标准化后形成单一的目标.结果显示,优化后的目标函数值比GAMIL2标准版本改进了7.5%.机理分析表明,调优后的参数优化了大气中的水汽凝结作用,进而减少模式的湿度偏差,改进云量的模拟效果;同时水汽凝结作用的变化通过大气内部动力和热力相互作用及响应影响温度、位势高度和风场的模拟. 相似文献