Induction of auroral zone electric currents within the Alaska pipeline     

Wallace H. Campbell 《Pure and Applied Geophysics》1978,116(6):1143-1173

The Alaskar pipeline is a highly conducting anomaly extending 800 miles (1300 km) from about 62° to 69° geomagnetic latitude beneath the most active regions of the ionospheric electrojet current. The spectral behavior of the magnetic field from this current was analyzed using data from standard geomagnetic observatories to establish the predictable patterns of temporal and spatial changes for field pulsation periods between 5 min and 4 hr. Such behavior is presented in a series of tables, graphs and formulae. Using 2- and 3-layer models of the conducting earth, the induced electric fields associated with the geomagnetic changes were established. From the direct relationship of the current to the geomagnetic field variation patterns one can infer counterpart temporal and spatial characteristics of the pipeline current. The relationship of the field amplitudes to geomagnetic activity indices,A _p, and the established occurrence of various levels ofA _p over several solar cycles were employed to show that about half of the time the induced currents in the pipe would be under 1 A for the maximum response oscillatory periods near 1 hr. Such currents should be of minimal consequence in corrosion effects for even a section of the pipeline unprotected by sacrificial electrodes. Of greater interest was the result that the extreme surges of current should reach over one-hundred amperes in the pipeline during high activity.  相似文献   

THE FORMATION AND THE DEVELOPMENT OF CAMS TWO-DIMENSIONAL DYNAMICAL-PHYSICAL CLIMATE MODEL          下载免费PDF全文

Li Weiliang  Gong Wei  Wang Wei-Chyung 《Acta Meteorologica Sinica》1993,7(2):129-146

In the paper,we have developed a 2-D physical-dynamical coupled climate model.Some sensitive experiments have been done by use of this model.First of all,we have studied the effects of different results by two radiational calculation schemes on circulation variation.The calculated results have shown that the different radiation parameterization schemes give different results,therefore the variational effects of wind,temperature,and humidity field are presented on the medium-range circulation variation.Besides,we have also studied the role of the meridional eddy momentum fluxes in formation of the monsoon over East Asia.The results of study have shown that on the average,the roles of meridional eddy flux of momentum formative processes of monsoon which is added to momentum equations by using the scheme of moist process parameterization with plateau are manifest.  相似文献   

The development of stochastic space transformation and diagrammatic perturbation techniques in subsurface hydrology     

G. Christakos  C. T. Miller  D. Oliver 《Stochastic Environmental Research and Risk Assessment (SERRA)》1993,7(1):14-32

This paper develops concepts and methods to study stochastic hydrologic models. Problems regarding the application of the existing stochastic approaches in the study of groundwater flow are acknowledged, and an attempt is made to develop efficient means for their solution. These problems include: the spatial multi-dimensionality of the differential equation models governing transport-type phenomena; physically unrealistic assumptions and approximations and the inadequacy of the ordinary perturbation techniques. Multi-dimensionality creates serious mathematical and technical difficulties in the stochastic analysis of groundwater flow, due to the need for large mesh sizes and the poorly conditioned matrices arising from numerical approximations. An alternative to the purely computational approach is to simplify the complex partial differential equations analytically. This can be achieved efficiently by means of a space transformation approach, which transforms the original multi-dimensional problem to a much simpler unidimensional space. The space transformation method is applied to stochastic partial differential equations whose coefficients are random functions of space and/or time. Such equations constitute an integral part of groundwater flow and solute transport. Ordinary perturbation methods for studying stochastic flow equations are in many cases physically inadequate and may lead to questionable approximations of the actual flow. To address these problems, a perturbation analysis based on Feynman-diagram expansions is proposed in this paper. This approach incorporates important information on spatial variability and fulfills essential physical requirements, both important advantages over ordinary hydrologic perturbation techniques. Moreover, the diagram-expansion approach reduces the original stochastic flow problem to a closed set of equations for the mean and the covariance function.  相似文献   

Granitoids around the Malanjkhand copper deposit: Types and age relationship   总被引：1，自引：0，他引：1  

M K Panigrahi  A Mookherjee  G V C Pantulu  K Gopalan 《Journal of Earth System Science》1993,102(2):399-413

On the basis of field relations, petrography and chemistry, three types of granitoids are recognized at Malanjkhand in and around the copper deposit over an area of about 200 km². These are (i) a fine grained ‘leucogranite’ of restricted occurrence in the surrounding area (Gr-I); (ii) coarse-grained, grey in most parts, gneissose granitoid of regional extension (Gr-II); and (iii) the pink-feldspar bearing massive type hosting the mineralization with occasional representatives in the surrounding country (Gr-III). Gr-I comes out as a distinct entity on the basis of cross-cutting relation and mineralogical and chemical composition, the Rb-Sr whole rock isochron also giving a younger age than the other two groups irrespective of the regression model used. Gr-II comes out as the oldest unit but its age relationship with Gr-III cannot be established unequivocally. An uncorrelated error regression model establishes the age relationship as Gr-I<Gr-III<Gr-II, whereas a two-error regression model establishes temporal closeness between Gr-II and III. The term ‘granitoids’ is being used broadly to include rocks ranging in composition from alkali-granite to tonalite.  相似文献   

THE SENSITIVITY INFLUENCE OF NUMERICAL MODEL INITIAL VALUES ON FOUR-DIMENSIONAL ASSIMILATION-STUDY BASED ON LORENZ SYSTEM^*          下载免费PDF全文

Gao Jidong  Qiu Chongjian  Chou Jifan 《Acta Meteorologica Sinica》1995,9(3):278-287

Numerical experiments of adjoint variational assimilation have been performed using the known Lorenz system.With the increase of sensitivity of model's initial values,it is more and more difficult to use the adjoint method to get the initial values which are consistent with the dynamics of the forecast model.Under some circumstances the algorithm completely fails.This shows that four-dimensional assimilation is related to the limit of predictability.On the other hand.with the increase of model equation's error,the result of variational assimilation may become worse and worse so that the prediction has no meaning.But if the model parameters are corrected when variational assimilation is made,the forecast results can be greatly improved based on Lorenz model.  相似文献   

非线性伪双曲方程的第二初边值问题     

任留成 《测绘学院学报》1995,(4)

本文利用Ｌｅｒａｙ－Ｓｃｈａｕｄｅｒ不动点原理和Ｓｏｂｏｌｅｖ估计，证明了非线性伪双曲方程的第二初边值问题整体弱解的存在唯一性，其中ｍ≥１，ａｉ＞０（ｉ＝１，２，３）都是常数。  相似文献   

Influence　caused　by　initial　tectonic　stress　on　relative　measurement　of　borehole　groundstresinviscoelasticmedia     

赵鹏君  沈建文 《地震学报(英文版)》1996,9(3):389-398

ＩｎｆｌｕｅｎｃｅｃａｕｓｅｄｂｙｉｎｉｔｉａｌｔｅｃｔｏｎｉｃｓｔｒｅｓｏｎｒｅｌａｔｉｖｅｍｅａｓｕｒｅｍｅｎｔｏｆｂｏｒｅｈｏｌｅｇｒｏｕｎｄｓｔｒｅｓｉｎｖｉｓｃｏｅｌａｓｔｉｃｍｅｄｉａＰＥＮＧ－ＪＵＮＺＨＡＯ１）（赵鹏君），ＪＩＡＮ－Ｗ...  相似文献   

Statistical Research on the Seismic Quiescence Before the 1988 Lancang-Gengma Earthquakes with M=7.6 and 7.2 in Yunnan Province,China     

Liu ZuyinSeismological Bureau of Yunnan Province  Kunming  China 《中国地震研究》1996,(3)

In this paper,the temporal and spatial variation process of seismicity in areas from Lancang to Tengchong before the 1988 Lancang-Gengma earthquakes(M=7.6,7.2),January 1980 to October 1988,is studied in detail according to the theory that the whole process of earthquake sequence in the time stage of anomalous seismicity before a strong event may be considered as the non-homogeneous Poisson process.The results demonstrate that(1)from April 1985 to April 1988,there existed an obvious difference of seismicity in spatial distribution in the whole region; to the north of Lancang,there occurred two seismic quiescent belts:one is 210 km long for M≥3.5 events and anotheris 160 km long for M≥3.0 events; therefore,this may be classified into four sub-regions from south to north,that is,the south region,the mid-region,the mid'-region,and the north region.(2)Before the mainshocks,there existed anomalous seismic quiescence for as Song as 42 months in the mid-region(M≥3.5)and 32.5 months in the mid'-region(M≥3.0)  相似文献   

HYDRO_GEN: A spatially distributed random field generator for correlated properties   总被引：1，自引：0，他引：1  

Alberto Bellin  Yoram Rubin 《Stochastic Environmental Research and Risk Assessment (SERRA)》1996,10(4):253-278

This paper describes a new method for generating spatially-correlated random fields. Such fields are often encountered in hydrology and hydrogeology and in the earth sciences. The method is based on two observations: (i) spatially distributed attributes usually display a stationary correlation structure, and (ii) the screening effect of measurements leads to the sufficiency of a small search neighborhood when it comes to projecting measurements and data in space. The algorithm which was developed based on these principles is called HYDRO_GEN, and its features and properties are discussed in depth. HYDRO_GEN is found to be accurate and extremely fast. It is also versatile: it can simulate fields of different nature, starting from weakly stationary fields with a prescribed covariance and ending with fractal fields. The simulated fields can display statistical isotropy or anisotropy.  相似文献   

THE STUDY OF THE CHARACTERISTICS OF BOUNDARY LAYER OVER HILL TERRAIN     

郝为锋  刘凯  王庆安 《热带气象学报(英文版)》1996,2(2):203-215

Taking advantage of the actual continuous materials of hilly area, we analyse the structures of the wind and temperature fields of planetary bounday layer over hill terrain under different weather conditions. As the results show that being similar to the situation in flat area, the planetary boundary layer has striking characteristics of daily variation and distinct regularity. We also find that in certain weather situation or under certain weather condition, these characteristics are principally determined by complex effect of such factors as the features of specific radiation field and intensity of turbulent exchange, and the advection of wind, and the thermodynamic effect of valley or lake-land, and the extending direction of valley, as well as difference between states of sunlessness and sunshine of the surface. Therein, the local environmental situation, where the reference station stands, is of considerable importance to the formation of the characteristics of planetary boundary over hill terrain (shortened as HTBL). These results not only help us to disclose the characteristics of planetary boundary layer over hill terrain in theory, but also are of great value in practice, like developing hilly area, and implementing environment conservation etc.  相似文献