基于镜像变换的GPS坐标变换方法研究

解算GPS坐标系和国家坐标系间的转换参数,传统方法是最小二乘法和高斯约化相结合,通过解算由误差方程组推导出的法方程组,间接求出结果。该方法有两个缺陷:一是精度不高;二是“病态”矩阵带来的不稳定问题。采用最小二乘法和镜像变换相结合的方式直接解算误差方程组,不需解算法方程组,不但提高了解算精度,而且避免了“病态”法方程组问题。     

Quadrangle-grid velocity–stress finite difference method for poroelastic wave equations

A quadrangle-grid velocity–stress finite difference method, based on a first-order hyperbolic system that is equivalent to Biot's equations, is developed for the simulation of wave propagation in 2-D heterogeneous porous media. In this method the velocity components of the solid material and of the pore fluid relative to that of the solid, and the stress components of three solid stresses and one fluid pressure are defined at different nodes for a staggered non-rectangular grid. The scheme uses non-orthogonal grids, allowing surface topography and curved interfaces to be easily modelled in the numerical simulation of seismic responses of poroelastic reservoirs. The free-surface conditions of complex geometry are achieved by using integral equilibrium equations on the surface, and the source implementations are simple. The algorithm is an extension of the quadrangle-grid finite difference method used for elastic wave equations.     

CONSTABLE: A SIMPLE ONE-DIMENSIONAL CLIMATE MODEL FOR CLIMATOLOGISTS IN GEOGRAPHY

A one-dimensional global climate model is constructed from both the basic energy balance equation for the earth-atmosphere system and the planetary boundary layer equations of motion. The theoretically based model accurately simulates many features of the present climate system and appears useful in evaluating various climatic change mechanisms. The simplicity of this process-response model increases its educational and research applicability for climatologists in geography.     

粘性泥石流阻力和运动方程验证分析

现有的粘性泥石流阻力方程可以大致归纳为三类：一类是将泥石流视为固液两相流,通过理论分析建立的泥石流阻力运动方程;二类是认为粘性泥石流符合宾汉姆流体阻力方程;三类是依据泥石流体具有基本符合库伦公式的剪切强度,将泥石流视为固体颗粒散体重力流,在理论分析基础上建立的阻力和运动方程。用粘性泥石流动力学实验数据对三类阻力运动方程进行了验证,结果表明第三类阻力和运动方程与实际接近。     

Fast transform eigenfunction methods for boundary value problems

An extension of the classic eigenfunction expansion method is presented for solving boundary value problems on boundaries of essentially arbitrary shape in R ³. the algorithm yields approximate solutions in terms of simple eigenfunctions of the underlying differential operator. the coefficients of these eigenfunctions are calculated with two-dimensional FFTs. the algorithm has many applications in geophysics, such as potential theory, scattering theory, earthquake source dynamics, and wave propagation, where non-separable boundaries are common.     

LINEAR STRUCTURAL RELATIONSHIPS WITH LATENT VARIABLES: THE LISREL MODEL*

The LISREL model analyzes complex interrelationships involving latent variables, effectively integrating the widely used factor analysis and regression procedures. A residential mobility example, calibrated for Portland, OR, suggests that turnover rates are both directly and indirectly influenced by latent variables representing housing type, housing quality, family status, and socioeconomic status.     

Seismic rays in an ellipsoidal earth model: theoretical analysis and estimation of deviations due to the ellipticity

Summary. A first-order form of the Euler's equations for rays in an ellipsoidal model of the Earth is obtained. The conditions affecting the velocity law for a monotonic increase, with respect to the arc length, in the angular distance to the epicentre, and in the angle of incidence, are the same in the ellipsoidal and spherical models. It is therefore possible to trace rays and to compute travel times directly in an ellipsoidal earth as in the spherical model. Thus comparison with the rays of the same coordinates in a spherical earth provides an estimate of the various deviations of these rays due to the Earth's flattening, and the corresponding travel-time differences, for mantle P -waves and for shallow earthquakes. All these deviations are functions both of the latitude and of the epicentral distance. The difference in the distance to the Earth's centre at points with the same geocentric latitude on rays in the ellipsoidal and in the spherical model may reach several kilometres. Directly related to the deformation of the isovelocity surfaces, this difference is the only cause of significant perturbation in travel times. Other differences, such as that corresponding to the ray torsion, are of the first order in ellipticity, and may exceed 1 km. They induce only small differences in travel time, less than 0.01s. Thus, we show that the ellipticity correction obtained by Jeffreys (1935) and Bullen (1937) by a perturbational method can be recovered by a direct evaluation of the travel times in an ellipsoidal model of the Earth. Moreover, as stated by Dziewonski & Gilbert (1976), we verify the non-dependence of this correction on the choice of the velocity law.     

城市化进程中技术创新对环境污染的影响研究——基于动态联立方程模型

以2005-2015年省际面板数据,通过灰色关联度分析、联立方程及情景模拟等研究方法实证研究城市化、技术创新、环境污染的双向作用机制。结果表明：（1）灰色关联度分析显示,我国城市化与产业结构比例和研发经费投入强度存在较强的耦合性;环境污染物排放与GDP、人力资本存量存在较强的关联;对于科技创新水平,中部、西部是与物质资本存量及GDP存在较强关联度,东部是与城市化率、产业结构有较强的关联。（2）联立方程表明,城市化与科技创新有双向反馈作用,科技创新提高1个百分点,城市化提高2.07%,城市化提高1百分点,科技创新水平提高0.14%。西部省份城市化与科技创新出现非匹配,城市化对科技创新助推作用不明显。经济不发达区域物质资本存量对城市化的助推作用比经济发达区域作用更明显。特定区域的污染物而言,EKC曲线不一定成为必然。城市化率提高,环境污染物先增长后降低对特定污染物而言不一定存在,转折点高低与区域的经济发展水平并无必然联系。（3）情景分析的冲击模拟表明,提高研发投入强度对东部、中部污染物减排成效显著,对中部科技创新产出提升作用显著,对中部的城市化促进作用最明显。当前我国在技术创新同时更加关注绿色技术。针对区域发展实际,有针对性地实施差别化的城市化驱动路径。     

Regional aboveground biomass equations for North American arid and semi-arid forests

Calculations of dry tree, plot and regional aboveground biomass, M, and assessments of complex diverse forests remain key challenges in the implementation of conventional and sustainable projects. This study reports a set of robust regional equations and the application of several allometric tree and plot M equations in Mexican arid and semi-arid forest communities. The data were collected from 1084 tree M fitting models, and 195 arid and semi-arid and 206 mesquite trees and 55 plot datasets were used to validate the models. Theoretical, semi-empirical and empirical models with exogenous variables, as well as wood specific gravity, diameter, top height, and form-factor values, were used to evaluate aboveground biomass. Empirical computer-based equations projected more consistently similar tree M assessments than did semi-empirical or theoretical models. Therefore, empirical models are recommended for assessments of tree and plot M, and future allometry research should properly address independent variables in more theoretical models. The large sample size, model richness, economic and ecological importance, and wide coverage of this dataset make it useful for estimating several biogeochemical and bioenergy density parameters and contribute to the body of knowledge regarding heterogeneity in dry forest stand structures.     

Wave propagation characteristics in frozen saturated soil

Ultrasonic detection technology is of great significance in the detection and evaluation of physical and mechanical properties of frozen soil, but wave propagation characteristics in frozen soil are unclear. Based on the three-phase composition of frozen saturated soil and the mixture theory, considering Bishop's effective stress formula, the wave propagation equations are establish for frozen saturated soil. In wave propagation, an entropy inequality was introduced to describe the coupling of different phases. The analytic expressions of propagation velocity and attenuation law of waves in frozen soil are obtained, and wave propagation characteristics in frozen saturated soil are discussed. Results show that four types of waves(i.e., P1, P2, P3 and S) are found in frozen saturated soil and all four wave types are dissipative waves, in which the attenuation of P3 is the maximum. The velocity of four waves increases sharply at the excitation frequency range of 10~3–10~9 Hz,but the wave velocity at high-frequency and low-frequency is almost constant. When volume ice content increases, the wave propagation velocity of P1 and S decreases dramatically, and the velocity of P2 increases gradually, but P3 velocity increases first and then decreases to zero with increasing saturation. The attenuation coefficients of P1 and S waves begins to increase gradually when the volume ice content is about 0.4, P2 increases first and then decreases with an increase of volume ice content and P3 increases with the volume ice content and decreases rapidly from extreme to zero.     

A geometrical approach to time evolving wave fronts

The parameter that defines the ray tracing equations in the direct geometrical approach is the product of the radius of curvature of the wave front by the velocity on the wave front ( RV ). To show this, we derive motion equations for the centre and the radius of curvature of an expanding wave front. The continuity of RV along rays implies Snell's Law. For constant velocities the equation for the radius of curvature reduces to the original Huygens' Principle. The variable RV can be computed during ray tracing and used to determine the local radius of curvature, which in turn can be used in geometrical spreading, amplitude corrections and structure interpretation.     

Moraine-dammed glacial lake changes during the recent 40 years in the Poiqu River Basin, Himalayas

Glacier retreat is not only a symbol of temperature and precipitation change, but a dominating factor of glacial lake changes in alpine regions, which are of wide concern for high risk of potential outburst floods. Of all types of glacial lakes, moraine-dammed lakes may be the most dangerous to local residents in mountain regions. Thus, we monitored the dynamics of 12 moraine-dammed glacial lakes from 1974 to 2014 in the Poiqu River Basin of central west Himalayas, as well as their associated glaciers with a combination of remote sensing, topographic maps and digital elevation models (DEMs). Our results indicate that all monitored moraine-dammed glacial lakes have expanded by 7.46 km² in total while the glaciers retreated by a total of 15.29 km² correspondingly. Meteorological analysis indicates a warming and drying trend in the Nyalam region from 1974 to 2014, which accelerated glacier retreat and then augmented the supply of moraine-dammed glacial lakes from glacier melt. Lake volume and water depth changed from 1974 to 2014 which indicates that lakes Kangxico, Galongco, and Youmojanco have a high potential for outburst floods and in urgent need for continuous monitoring or artificial excavation to release water due to the quick increase in water depths and storage capacities. Lakes Jialongco and Cirenmaco, with outburst floods in 1981 and 2002, have a high potential risk for outburst floods because of rapid lake growth and steep slope gradients surrounding them.