A type of new conserved quantity deduced from Mei symmetry for Appell equations in a holonomic system with unilateral constraints     

贾利群  解银丽  张耀宇  杨新芳 《海洋学报(英文版)》2010,29(11)

A type of new conserved quantity deduced from Mei symmetry of Appell equations for a holonomic system with unilateral constraints is investigated. The expressions of new structural equation and new conserved quantity deduced from Mei symmetry of Appell equations for a holonomic system with unilateral constraints expressed by Appell functions are obtained. An example is given to illustrate the application of the results.  相似文献   

Static bay beach concept for scientists and engineers: A review     

John R.-C. Hsu  M.-J. Yu  F.-C. Lee  Lindino Benedet 《Coastal Engineering》2010

Headland-bay beach (HBB) is one of the most prominent physiographic features on the oceanic margin of many countries in the world. Under the influence of a predominant swell, its curved periphery in natural environment may reach static equilibrium and remains stable without sediment supply from updrift and/or a riverain source within its own embayment. Coastal scientists and engineers have attempted to develop mathematical expressions to quantify this ideal bay shape since the 1940s. As the scenario with depleting sediment supply has become a common reality on many parts of the world coastline in more recent time, some coastal engineers have advocated a rational approach to mimicking the static bay shape found in nature in order to mitigate beach erosion as well as for coastal management. Nowadays, many useful applications have emerged since the publication of the parabolic bay shape equation (PBSE) developed for static equilibrium planform (SEP) in late 1980s. The advance in modern computer technologies and international collaboration has further facilitated the exchange of knowledge and applications of this static bay beach concept (SBBC).  相似文献   

Remote detection of bare soil moisture using a surface-temperature-based soil evaporation transfer coefficient     

Shaohua Zhao  Yonghui Yang  Guoyu Qiu  Qiming Qin  Yunjun Yao  Yujiu Xiong  Chunqiang Li 《International Journal of Applied Earth Observation and Geoinformation》2010

An approach for estimating soil moisture is presented and tested by using surface-temperature-based soil evaporation transfer coefficient (h_a), a coefficient recently proposed through the equation h_a = (T_s − T_a)/(T_sd − T_a), where T_s, T_sd, and T_a are land surface temperature (LST), reference soil (dry soil without evaporation) surface temperature, and air temperature respectively. Our analysis and controllable experiment indicated that h_a closely related to soil moisture, and therefore, a relationship between field soil moisture and h_a could be developed for soil moisture estimation. Field experiments were carried out to test the relationship between h_a and soil moisture. Time series Aqua-MODIS images were acquired between 11 Sep. 2006 and 1 Nov. 2007. Then, MODIS derived h_a and simultaneous measured soil moisture for different soil depths were used to establish the relations between the two variables. Results showed that there was a logarithmic relationship between soil moisture and h_a (P < 0.01). These logarithmic models were further validated by introducing another ground-truth data gathered from 46 meteorological stations in Hebei Province. Good agreement was observed between the measured and estimated soil moisture with RMSE of 0.0374 cm³/cm³ and 0.0503 cm³/cm³ for surface energy balance method at two soil depths (10 cm and 20 cm), with RMSE of 0.0467 cm³/cm³ and 0.0581 cm³/cm³ for maximum temperature method at two soil depths. For vegetated surfaces, the ratio of h_a and NDVI suggested to be considered. The proposed approach has a great potential for soil moisture and drought evaluation by remote sensing.  相似文献   

准饱和多孔介质中圈闭气体对渗透系数的影响          下载免费PDF全文

程东会  李爽  于丹  王倩  杨银科 《水科学进展》2019,30(5):691-698

含圈闭气体的地下水流称为准饱和流,准饱和流中的圈闭气体对含水层渗透系数有重大影响。通过柱试验开展了粉砂、细砂、中砂和粗砂4种介质圈闭气体饱和度与准饱和渗透系数关系的研究。结果表明:圈闭气体饱和度明显受介质的粒径影响,在细粒介质中圈闭气体饱和度明显较大;4种介质圈闭气体饱和度在0~15%范围内,准饱和渗透系数与完全饱和相比减少了32.82%~56.38%,且准饱和渗透系数与圈闭气体饱和度之间可表达为一个负线性相关的经验公式;该公式与Faybishenko公式等效,但形式简单,参数较少,使用方便;准饱和渗透系数的变化规律可概化为圈闭气体占据了原有的有效孔隙,造成原有效孔隙度减少,从而使渗透系数减小。利用该理论,Kozeny-Carman方程能较准确地描述准饱和渗透系数的变化规律,而基于哈根-泊肃叶方程的渗透系数公式则存在较大误差,不适用于描述准饱和渗透系数;试验结果证明了室内测定饱和渗透系数时排除圈闭气体的必要性。  相似文献   

基于改进Bingham模型的软岩参数非定常三维非线性黏弹塑性蠕变本构研究     

刘开云  薛永涛  周辉 《岩土力学》2018,39(11):4157-4164

传统线性元件组合模型难以描述岩石非线性加速蠕变阶段特性,给工程应用带来了巨大困难。提出一种新的应变触发非线性黏壶元件,并将其与Bingham模型串联,建立了可以描述岩石等速和加速蠕变特性的一维本构模型,进而推导出相应的三维蠕变本构模型,再将三轴压缩过程中岩石弹性模量的衰减方程引入该三维蠕变本构方程,得到一个能反映岩石蠕变全过程特性的三维非线性黏弹塑蠕变本构模型,根据泥岩蠕变试验数据对该模型参数进行了辨识。模型理论计算值与泥岩蠕变试验数据的对比表明改进的Bingham模型不仅可以充分反映软岩的等速蠕变特性,还可以很好地描述软岩的衰减和加速蠕变规律,且模型元件少,组合形式简单,为软岩非线性蠕变本构模型研究提供了新的借鉴。  相似文献   

考虑Hansbo渗流的二维Biot固结有限元分析     

刘忠玉  张家超  郑占垒  关聪 《岩土力学》2018,39(12):4617-4626

为进一步深入研究弹性饱和黏性土地基的二维固结机制,引入Hansbo渗流方程描述固结过程中的非达西渗流,修正Biot二维固结方程。基于加权残数法,给出相应的有限元数值求解格式。通过和饱和黏性土一维非达西渗流固结理论有限体积法数值结果的对比,证明数值计算方法的有效性。在此基础上,探讨Hansbo渗流参数对二维地基固结进程的影响。计算结果表明,在固结初期,Hansbo渗流将增强Mandel-Cryer效应,增大孔压的峰值,并延长孔隙水压力达到峰值的时间;在固结中后期,整个土层存在孔隙水压力滞后现象。同时,Hansbo渗流将阻碍地基沉降的发展。而且,上述影响会随着Hansbo渗流参数的增大而更加明显。  相似文献   

非均匀介质地震AVO响应模拟及分析     

刘财  裴思嘉  郭智奇  符伟  张宇生  刘喜武 《吉林大学学报(地球科学版)》2018,48(5):1512-1521

地震AVO （amplitude versus offset）技术是一项利用振幅信息研究岩性、检测油气的地震勘探技术。常规方法基于Zoeppritz方程计算模型界面处的反射系数,而实际地下非均匀介质中地震反射特征不仅与入射角度、物性差异有关,还与入射波频率、地层厚度、薄互层结构等因素有关。为此,应用传播矩阵理论充分考虑与这些因素有关的调谐干涉等传播效应,针对实际数据计算非均匀地下介质的高精度合成地震记录,对比Zoeppritz方程、Shuey二项近似方程、Shuey三项近似方程以及传播矩阵算法的模拟效果。研究发现：在小角度入射时Zoeppritz方程、Shuey二项近似方程和Shuey三项近似方程的反射振幅和波形基本一致,大角度入射时Zoeppritz方程与Shuey三项近似方程接近;Zoeppritz算法的模拟结果在小角度入射和浅层情况下与传播矩阵算法差别较小,而在大角度入射和深层情况下与传播矩阵差别较大,说明层间多次波的调谐干涉等传播效应不可忽略。  相似文献   

陡倾层状斜向岩层视向溃屈机制力学分析——以陕西山阳滑坡为例   总被引：2，自引：1，他引：1  

王佳运  石小亚 《地质力学学报》2018,24(4):482-489

以陕西山阳滑坡为例,分析了陡倾层状斜向岩层岩质滑坡的视向滑动特征、滑移-溃屈破坏模式与机制。基于梁板理论、层状板裂结构岩体弯曲-溃屈破坏的力学模型在考虑自重、地下水静水压力作用及斜倾层状山体视向滑动侧向摩阻力作用的影响下,采用岩体结构力学分析的方法建立了相应的力学模型;经过力学分析,推导出基于斜坡自重、地下水静水压力与侧向摩阻力作用下的陡倾层状斜向岩层斜坡溃屈段长度条件方程。为验证条件方程的正确性,以山阳滑坡为例进行了验算,最后得出与实际调查较一致的结果,为防御陡倾层状斜向岩层斜坡产生视向溃屈破坏提供依据。   相似文献   

Transport simulation of sorptive contaminants considering sediment-associated processes     

李瑞杰  陆莎莎  郑俊 《中国海洋湖沼学报》2012,30(4):668-674

Sediment-associated processes, such as sediment erosion, deposition, and pore water diffusion/advection affect sorptive contaminant transport. By considering these processes, we developed an equation to simulate contaminant transport. Erosion and deposition processes are considered as erosion and deposition fluxes of sediment, and adsorption-desorption processes of contaminants by sediment are simulated using the Langmuir Equation. Pore water diffusion is calculated based on the contaminant concentration gradient across the sediment-water interface. Pore water advection is estimated using pore water contained in the sediments of erosion flux. The equation is validated to simulate total phosphorus concentrations in Guanhe estuary in the northern Jiangsu, China. The simulated total phosphorus concentrations show better agreement with field observations compared to estimations that do consider sediment-associated processes.  相似文献   

具有精确色散性的非线性波浪水平二维数学模型     

邹志利  金红 《海洋工程》2012,30(2):38-45

建立具有色散性的水平二维非线性波浪方程,方程的非线性近似到了三阶。方程以波面升高和自由表面速度势表达的微分-积分型数学方程,给出方程的数值求解方法和算例,对方程积分项的处理给出了计算方法。计算结果与Boussinesq方程模型和缓坡方程模型的对应计算结果进行了对比。  相似文献