考虑土体非均质传热的河岸带水热耦合模型

为弥补当前河岸带水热交换模拟对土体非均质传热考虑不足的缺陷,在饱和-非饱和渗流及多孔介质传热理论基础上,引入土体有效导热系数模型,构建考虑土体非均质传热的河岸带水热耦合模型。结合COMSOL软件的特点,给出河岸带水热耦合模型的实现方法及求解流程,并通过河岸带温度和水位原型观测资料验证和对比分析不同有效导热系数模型下河岸带水热耦合模型的模拟效果。结果表明：与传统不考虑土体非均质传热方法相比,该模型能够较好地反映河岸带水热交换过程。此外,基于Johansen有效导热系数模型的河岸带水热耦合模型模拟效果表现最佳,模拟结果与前人试验结果一致。研究成果可为河岸带水热交换及污染物迁移过程的深入研究提供技术支撑。     

Sea Surface Heights Retrieval from Ship-Based Measurements Assisted by GNSS Signal Reflections

Measurements of the sea surface height (SSH) can be carried out with GNSS aboard ships, but data about the static draft and the hydrodynamic squat effect are necessary. This information is often not available or has an insufficient accuracy. In this study, an alternative method based on the GNSS signal-to-noise ratio observations is presented. Using this method, the distance between the water surface and a GNSS antenna can be estimated directly, if corrections of the heave and the ship’s attitude are considered properly. Suitable segments of a 3-month dataset, gathered aboard a ferry ship operating in the German Bight, were analysed. A global optimization approach based on interval analysis was used and all available observations from a segment were analysed in a common adjustment calculation. The resulting SSH was validated with data from a tide gauge station at Heligoland. The mean difference is 4?mm and a standard deviation of the differences of 5.3?cm was found. The SSH for the same GNSS dataset was also derived from a well-established processing based on the comprehensive consideration of ship dynamics. The mean difference with respect to the tide gauge was 2?mm with a slightly smaller standard deviation of 4.0?cm.     

土壤有效硫批量检测方法改进

土壤有效硫检测的常规方法是利用硫酸钡比浊法,鉴于规范推荐的测试步骤在批量土壤样品测试时效率较低,因此对常规方法进行了改进。加入2.0g氯化钡晶粒改为加入浓度为200g/L氯化钡溶液10mL;加稳固剂阿拉伯胶水溶液4mL改为加入浓度为6%甘油-乙醇(1+2)溶液5mL。通过对比实验,改进后检测方法比常规方法操作简便快捷,省时、省力、数据准确可靠,标准曲线线性相关系数达到0.9982。对土壤有效态成分分析标准物质土样GBW07459(ASA-8)、GBW07460(ASA-9) GBW07461(ASA-10)进行多次平行测试,测试结果全部在标准值范围内,且平行相对相差≤10%,证明改进后的检测方法可用于土壤有效硫的检测。     

��̬Ӧ��������Ӱ�����Ӧ���仯�IJ��������Է���

???????λ????????????????????????ж?????Ч???????????????????????????????С???????????????????????仯????????????????????????????о??У???Щ????????????????仯????????????????繹?????????????????????????????????????????棬??????????????????????????仯??????????????????????????仯???С?????????????????仯???????????????????     

A modification to the Munk wind-driven ocean circulation theory

In order to fulfill the no-slip condition at the western and eastern boundaries of the ocean basin, introduced ＂effective wind stress＂, which has much larger spatial variations towards the boundaries than in the ocean interior. The effective wind stress can thus be decomposed into spatially slow-varying and fast varying components. Careful scale analysis on the classical Munk winddriven ocean circulation theory, which consists of the interior Sverdrup flow and the western boundary current but of no eastern boundary current, shows that the wind stress curl appearing in the Sverdrup equation must have negligible spatial variations. In the present model the spatially slow-varying component of the wind stress appears in the Sverdrup equation, and the spatially fastvarying component becomes the forcing term of the boundary equations. As a result, in addition to the classical Munk solution the present model has an extra term at the western boundary which （Northern Hemisphere） increases the northward transport as well as the southward return transport, and has a term at the eastern boundary corresponding to the eastern boundary current.     

Work input for unsaturated soils considering interfacial effects

In this research, the interfacial energy is taken into account in the deformation work for unsaturated soils. Based on porous media theory, the thermodynamic balance equations for each phase and the interface are used to derive the work input for unsaturated soils. The work input equation serves as the basis and starting point for the choice of stress state variables, based on which the conjugate stresses and strain increments are derived. The influences of the interfaces on the effective stress and the constitutive law for the liquid phase are then discussed based on the work input equation. The effective stress can be expressed as Bishop's type, and the effective stress parameter is shown to be a function of both the degree of saturation and the interfacial area. The constitutive law for the liquid phase under dynamic condition is also presented. The relationship among interfacial area, saturation, and capillary pressure is proposed to calculate the value of the effective stress. Experimental data obtained from literature are used to validate the proposed model equations. Results show that our findings are in accordance with the existing research. Unlike the phenomenal study, our research has a rigorous theoretical basis, which lays a foundation for further research of unsaturated soils considering the interfacial effects.     

A linear constitutive model for unsaturated poroelasticity by micromechanical analysis

This paper extends the Biot theory of poroelasticity from the saturated to unsaturated case. The Biot phenomenological model uses parameters that are easily observable, such as the deformation of porous frame, total stress, pore pressure, and fluid specific discharge. Such model is preferred for engineering applications. At this macroscopic level, the extension of Biot theory from saturated to unsaturated is straightforward. The constitutive constants, however, are combined properties of solid, pore space, and fluids. In the unsaturated case, the constants are functions of the degree of saturation. Their measurements and tabulation over a range of saturation is generally not feasible for practical applications. In this work, a Biot-Willis type analysis is performed for the unsaturated case to provide a theory that the bulk material constants can be evaluated using laboratory measurable micromechanical constants under saturated condition, plus a capillary pressure curve (saturation versus suction pressure) typically available for unsaturated porous medium, without the need of measurement at each state of saturation. In particular, it is demonstrated that the surface energy contained in the meniscus interface manifests as a “capillary modulus,” given by the negative inverse slope of the capillary pressure curve. A rigorous analysis based on the thermodynamic variational energy approach is also conducted to lend theoretical support to the phenomenological approach. The presented model can bring a closure to the practical engineering modeling of the deformation of partially saturated porous medium that lacks the information of material constants over the range of saturation.     

A fully coupled simple model for unsaturated soils

Different phenomena influence the strength and volumetric behavior of unsaturated soils. Among the most important are suction hardening, hydraulic hysteresis, and the influence of volumetric strain on the soil-water retention curves. Fully coupled hydro-mechanical models require including all three phenomena in their constitutive relationships. Among these phenomena, suction hardening is the most influencing as it determines the apparent preconsolidation stress, the position of the loading-collapse yield surface, and the shift of both the isotropic consolidation and the critical state lines. In this paper, a fully coupled hydro mechanical model is presented. It is based on the modified Cam-Clay model but includes a yield surface with anisotropic hardening that takes account of the shift of the critical state line with suction. For highly overconsolidated materials, the sub-loading surface concept has been included in order to increase the precision of the model for these materials. The shift of the retention curves produced by volumetric strains is simulated using a hydraulic model based on the grain and current pore size distribution of the soil.     

双基地天气雷达系统的有效照射体积

根据"有效照射体"的基本概念,采用微分理论来回避椭球面近似为平面的假设,推导了双基地雷达系统有效照射体积表达式,证明双基地雷达系统有效照射体积与单基地雷达有效照射体积之比值V_b/V_m,在数值上等于双基地系统主站极轴长度R_t相对于半长轴长度a的导数.有效照射体积数值计算结果与以往相同,放宽了推导过程中的假设条件,显得更加严谨、易懂.还给出了双基地雷达系统各几何量(如V_b/V_m、R_t、主站共面方位Φ、辅站极轴长度Rr、辅站共面方位Φ_r、双基地角β)之间的一些关系式,分析了在双基地雷达系统探测过程中有效照射体积随有关量变化的特征,为双基地偏振雷达系统天线控制、资料处理、旁瓣影响分析、探测精度提高等提供理论依据.     

基于三角网光滑规则的LiDAR点云噪声剔除算法

通过对传统移动均值法、频率域信号分析等离散点云噪声剔除算法局限性的分析,结合LiDAR点云离散空间分布特性,本文提出一种基于三角网光滑规则的点云噪声剔除算法。该算法先快速生成离散点云的二维Delaunay三角网,并构建任意点的邻接拓扑关系,然后依据设定的光滑规则进行噪声信号点检测,并输出非噪声点信号。针对条带数据进行实验,结论表明本文算法适合离散点状噪声剔除,可较大程度提高点云数据的信噪比。