遗传算法在非线性地下水经济管理模型中的应用

通常采用基于梯度的数学规划方法求解地下水管理模型,如线性规划和非线性规划。但对于高度非线性、非凸的优化问题,尤其是涉及到经济或环境的地下水管理模型,传统方法难以有效地寻找全局最优解。本文介绍了一种求解非线性地下水资源管理模型的遗传算法,并以山东羊庄盆地分布参数地下水系统非线性管理模型为例,给出了用遗传算法在求解这类问题的一般步骤。结果表明该方法能快速有效地找到全局最优解。     

“数字地球”科学工程

“数字地球”是集科学、技术和工程于一体的一项宏伟的科学体系。“数字地球”由基础研究、技术支撑和科学工程三部分组成,其中科学工程是“数字地球”的核心和目标。文章在我国“数字地球”科学工程现状分析的基础上,结合国情,对我国“数字地球”科学工程的发展提出了建议。     

地震信息融媒体公共服务研究

地震信息传播已进入实时、全面、多维的公共服务时代，单一媒体地震信息服务已无法满足政府、社会公众和地震行业需求，地震信息向融媒体公共服务模式发展。本文对地震信息内容服务需求及特点、地震媒体平台功能特色、融合式媒体信息服务模式等进行分析，对地震信息融媒体公共服务进行研究，旨在提高地震信息服务效率与用户满意度，促进地震信息化建设科学、健康发展。     

On combined operational method for transfer problems in homogeneous,spherical media

In this paper, the Combined Operational Method developed by Busbridge (1961) in connection with the radiative transfer problems in plane-parallel atmospheres has been extended to similar problems in isotropic scattering, homogeneous spherical media. The relevant auxiliary equation has been formulated, the scattering function defined and the integro-differential equation for such function deduced. For a medium having radial distribution of source in addition to the incident flux at the outer surface, the integro-differential equations for source function and emergent intensity have been established.     

Effects of E-region electric fields on F-region parameters at the magnetic equator

The effects of E-region electric fields on F-region parameters like height of constant electron density contours (h_N) and semi-thickness, at an equatorial station, Trivandrum, are investigated. The E-region east-west electric field (E_y) has been deduced using the horizontal magnetic field values from the ground magnetograms. It is found that the semi-thickness parameter and h_N follow closely the E-region electric field (E_y) variations in the forenoon and noon periods. In the afternoon, it is shown that there is close association between h_N and E_y, when the electric field variations are large. On a day-to-day basis also, h_N and the E-region electric field show very good correlation in the forenoon and noon hours. It is also shown that higher levels are affected more than the lower levels in the F-region by E_y.     

GIS-based hazard mapping and zonation of debris flows in Xiaojiang Basin,southwestern China

Debris flow sites were identified at 140 locations in the Xiaojiang Basin in Yunnan province, southwestern China. Their spatial distribution and catchment characteristics are described in detail on the basis of previous research, air photo interpretation, field investigation and mapping using Geographical Information Systems (GIS). Using a statistical approach, a quantitative model of hazards assessment and zonation was developed through synthesis analysis of basin areas, gradients, and the relative reliefs of these debris flow sites. In terms of debris flow hazard assessment, areas within the Xiaojiang Basin can be classified as severe, heavy and light hazard regions.     

A water quality model for the Patuxent estuary: Current conditions and predictions under changing land-use scenarios

A water quality model was developed for the Patuxent estuary using the modeling framework CE-QUAL-W2 (called W2) to address the impact of current and projected land-use changes (stress) on the water quality. The W2 code, supported by the Army Corps of Engineers Waterways Experiment Station, is a two-dimensional (longitudinalvertical) model designed for hydrodynamic and water quality simulations of reservoirs and estuaries. The code was configured for the Patuxent estuary using a finite-difference grid for the water column. Also incorporated into the model calculations are flow and nutrient load results from a watershed model. The integrated model was calibrated with data of 1 yr from 1997 to 1998 by matching results with measured temperature, dissolved oxygen, chlorophylla, and nutrient levels in the water column. The calibrated model was used to predict the water quality effects of different watershed land-use scenarios. Model projection results suggest that reductions of nutrient loads would lead to improvement of anoxic conditions in the bottom waters of the lower Patuxent estuary.     

On the Disappearance of Kilohertz Quasi-periodic Oscillations at a High Mass Accretion Rate in Low-Mass X-Ray Binaries

We here investigate the possibility that the ultra-high-energy cosmic-ray (UHECR) events observed above the Greisen-Zatsepin-Kuzmin (GZK) limit are mostly protons accelerated in reconnection sites just above the magnetosphere of newborn millisecond pulsars that are originated by accretion-induced collapse (AIC). We formulate the requirements for the acceleration mechanism and show that AIC pulsars with surface magnetic fields 1012 G/=10(20) eV. Because the expected rate of AIC sources in our Galaxy is very small ( approximately 10(-5) yr(-1)), the corresponding contribution to the flux of UHECRs is negligible and the total flux is given by the integrated contribution from AIC sources produced by the distribution of galaxies located within the distance that is unaffected by the GZK cutoff ( approximately 50 Mpc). We find that reconnection should convert a fraction xi greater, similar0.1 of magnetic energy into UHECRs in order to reproduce the observed flux.     

Enforcing smoothness and assessing uncertainty in non-linear one-dimensional prestack seismic inversion

Estimation of elastic properties of rock formations from surface seismic amplitude measurements remains a subject of interest for the exploration and development of hydrocarbon reservoirs. This paper develops a global inversion technique to estimate and appraise 1D distributions of compressional‐wave velocity, shear‐wave velocity and bulk density, from normal‐moveout‐corrected PP prestack surface seismic amplitude measurements. Specific objectives are: (a) to evaluate the efficiency of the minimization algorithm (b) to appraise the impact of various data misfit functions, and (c) to assess the effect of the degree and type of smoothness criterion enforced by the inversion. Numerical experiments show that very fast simulated annealing is the most efficient minimization technique among alternative approaches considered for global inversion. It is also found that an adequate choice of data misfit function is necessary for a reliable and efficient match of noisy and sparse seismic amplitude measurements. Several procedures are considered to enforce smoothness of the estimated 1D distributions of elastic parameters, including predefined quadratic measures of length, flatness and roughness. Based on the general analysis of global inversion techniques, we introduce a new stochastic inversion algorithm that initializes the search for the minimum with constrained random distributions of elastic parameters and enforces predefined autocorrelation functions (semivariograms). This strategy readily lends itself to the assessment of model uncertainty. The new global inversion algorithm is successfully tested on noisy synthetic amplitude data. Moreover, we present a feasibility analysis of the resolution and uncertainty of prestack seismic amplitude data to infer 1D distributions of elastic parameters measured with wireline logs in the deepwater Gulf of Mexico. The new global inversion algorithm is computationally more efficient than the alternative global inversion procedures considered here.