The equation of polarization transfer in an inhomogeneous magnetized plasma     

F. T. Cheng  P. C. W. Fung 《Astrophysics and Space Science》1979,63(1):177-183

Recently we have derived the equation of polarization transfer in an inhomogeneous magnetized plasma in the case where absorption is so weak that the characteristic modes can be considered to be orthogonal. We extend this investigation to the study of polarization transfer in a plasma where the characteristic polarizations need not be orthogonal. We obtain explicit expressions for the Faraday rotation tensor, the absorption tensor, the mode-coupling tensor and the tensor describing the explicit spatial variation of characteristic polarizations due to plasma inhomogeneity.  相似文献   

Hydrochemistry of formation water with implication to diagenetic reactions in Sanzhao depression and Qijia-gulong depression of Songliao Basin, China     

Jianmei Cheng  Jennifer C. McIntosh  Xinong Xie  Jiu Jimmy Jiao 《Journal of Geochemical Exploration》2006,88(1-3):86

The Sanzhao depression and Qijia-gulong depression are two of the most important hydrocarbon-bearing sub-depressions in the Songliao basin, dominated by Cretaceous fluvial and lacustrine strata with volcanic and volcaniclastic rocks. In this paper, the pressure distributions and hydrochemistry variations in those two depressions are investigated. It is found that the Qijia-gulong depression is dominated by overpressure, but the Sanzhao depression is dominated by underpressure, especially in the Quantou formation. The salinity of formation water ranges from 1.0 g/L to 20 g/L, with a mean of 4 g/L in most formations. Water composition is dominated by NaHCO₃ water type but varies greatly in salinity and ionic ratios in the different depressions. The results of mass balance calculation reveal that, fluid chemistry in the Qijia-gulong depression is dominated by dissolution of silicate minerals and halite, whereas in the Sanzhao depression it is dominated by silicate mineral dissolution, evaporite dissolution (halite and gypsum), carbonate mineral dissolution/precipitation, and cation exchange.  相似文献   

Structure of the chromosphere-corona transition region     

R. L. Moore  P. C. W. Fung 《Solar physics》1972,23(1):78-102

The structure and energy balance of the chromosphere-corona transition region is investigated by means of a static, planar model which is compared with the results of XUV-resonance-line observations. In this model, the transition region is heated by thermal conduction from the corona and cooled by radiative losses. Comparison of the model with observational results implies that this is the dominant process in the energy balance of the transition region, and that the base of the transition region is inherently non-static and/or non-planar. The model explains the observational finding of Noyes et al. (1970) that the number density and the downward heat flux both increase by the same factor from quiet regions to active regions. The implications of these results are discussed with regard to spicules.  相似文献   

Reply to comments on ‘the equation of polarization transfer in an inhomogeneous magnetized plasma. I. Formalism’     

F. T. Cheng  P. C. W. Fung 《Astrophysics and Space Science》1979,64(1):49-51

Recently D. B. Melrose (1978) has raised some points in the above mentioned paper (referred to as Paper I) concerning the meaning of some terms in our equation of polarization transfer. These points are very interesting and we would like to analyze his comments in our reply.  相似文献   

SOIL FINGERPRINTING IN THE PALOUSE BASIN, USA USING STABLE CARBON AND NITROGEN ISOTOPES     

Athanasios N. PAPANICOLAOU  Jimmy.F. FOX  John MARSHALL 《国际泥沙研究》2003,(2)

1 INTRODUCTION Watershed restoration efforts have been accelerated in recent years by mandates in the Clean Water Act, the Endangered Species Act, and increasing pressure from environmental groups (Wagner and Roberts, 1998). To address these mandates, water-quality management plans and Total Maximum Daily Loads (TMDLs) have been developed for surface waters, such as streams placed on the 303(d) list because of beneficial use impairment. Commonly, much of the degradation of surface…  相似文献   

Improved treatments for evaluating horizontal magnetic components through the 3-D FDM in E-polarization induction problems     

陈伯舫 《地震学报(英文版)》2002,15(5)

Introduction The algorithm of the finite difference method (FDM) for solving the 3-D induction problem used by CHEN (1985) is based on the concept suggested by Brewitt-Taylor and Weaver (1976), which assumes the conductivity to be a smoothly-varying function of position. After the comparisons between many model calculations carried out by the author and other methods showed that the vertical components estimated by our method are acceptable in general cases. However, the reliability of the…  相似文献   

Particulate-associated potentially harmful elements in urban road dusts in Xi’an,China     

Yongming Han  Junji Cao  Eric S. Posmentier  Kochy Fung  Hui Tian  Zhisheng An 《Applied Geochemistry》2008

Sixty five urban road dust samples were collected from different land use areas of ∼240 km² in Xi’an, China. The concentrations of Ag, As, Cr, Cu, Hg, Pb, Sb and Zn were determined to investigate potentially harmful element (PHE) contamination, distribution and possible sources. In addition, the concentrations in different size fractions were measured to assess their potential impact on human health. The highest concentrations were found in the fraction with particle diameters between 80 μm and 101 μm, the finest particles (<63 μm) were not the most important carriers for Ag, As, Cd, Cr, Cu, Hg, Pb and Zn. The percentages of these elements in particles with diameters less than 63 μm (PM₆₃) and less than 101 μm (PM₁₀₁) were in the range of 7–15%, and 30–55%, respectively. Three main factors influencing element distributions have been identified: (a) industrial activities; (b) prior agricultural land use; and (c) other activities commonly found in urban areas, such as traffic, coal combustion, waste dumping, and building construction/renovation. The highest concentrations were found in industrial areas for As (20 mg kg⁻¹), Cr (853 mg kg⁻¹), Cu (1071 mg kg⁻¹), Pb (3060 mg kg⁻¹) and Zn (2112 mg kg⁻¹), and in previous agricultural areas for Ag and Hg, indicating significant contributions from industrial activities and prior agricultural activities.  相似文献   

Changes to the groundwater system, from 1888 to present, in a highly-urbanized coastal area in Hong Kong, China   总被引：3，自引：1，他引：2  

Jiu Jimmy Jiao  Chi-man Leung  Guoping Ding 《Hydrogeology Journal》2008,16(8):1527-1539

Historical groundwater levels in a coastal region of Hong Kong Island (China) were reviewed and compared with data collected recently to reveal changes to the groundwater regime over the last century. The coastal springs and seeps have disappeared and the lower boundary of the seepage zone has moved uphill. Groundwater was found to be flowing upward along the boundary of natural slopes and urbanized areas. Artesian flows were commonly noted in the deep piezometers in the lower urbanized areas. Moreover, an overall rise in water levels in a 10-year period was observed in the urbanized areas, except in areas with good drainage. Extensive urbanization since the 1950s has included large-scale land reclamation, deep foundations of high-rise buildings, an underground transport system, water mains and horizontal drains in slopes; the effect has been a slow but gradual increase in the water level of the hillslope groundwater system. Further urbanization activities such as the westward extension of the underground transport system and new major drainage systems in the slopes, should be assessed for possible further changes to the groundwater system. The results presented here may serve as reference for other highly-urbanized coastal areas in the world.  相似文献   

Regional modeling of climate change impacts on smallholder agriculture and ecosystems in Central America     

Lee Hannah  Camila I. Donatti  Celia A. Harvey  Eric Alfaro  Daniel Andres Rodriguez  Claudia Bouroncle  Edwin Castellanos  Freddy Diaz  Emily Fung  Hugo G. Hidalgo  Pablo Imbach  Peter Läderach  Jason P. Landrum  Ana Lucía Solano 《Climatic change》2017,141(1):29-45

Climate change will have serious repercussions for agriculture, ecosystems, and farmer livelihoods in Central America. Smallholder farmers are particularly vulnerable due to their reliance on agriculture and ecosystem services for their livelihoods. There is an urgent need to develop national and local adaptation responses to reduce these impacts, yet evidence from historical climate change is fragmentary. Modeling efforts help bridge this gap. Here, we review the past decade of research on agricultural and ecological climate change impact models for Central America. The results of this review provide insights into the expected impacts of climate change and suggest policy actions that can help minimize these impacts. Modeling indicates future climate-driven changes, often declines, in suitability for Central American crops. Declines in suitability for coffee, a central crop in the regional economy, are noteworthy. Ecosystem models suggest that climate-driven changes are likely at low- and high-elevation montane forest transitions. Modeling of vulnerability suggests that smallholders in many parts of the region have one or more vulnerability factors that put them at risk. Initial adaptation policies can be guided by these existing modeling results. At the same time, improved modeling is being developed that will allow policy action specifically targeted to vulnerable groups, crops, and locations. We suggest that more robust modeling of ecological responses to climate change, improved representation of the region in climate models, and simulation of climate influences on crop yields and diseases (especially coffee leaf rust) are key priorities for future research.  相似文献   

Soliton solutions to the Einstein gravitational field equations in the presence of a spherically-symmetric static background field     

P. C. W. Fung  F. Z. Tao 《Astrophysics and Space Science》1987,139(2):311-320

Using a differential geometry approach, we have found two sets of new solutions to Einstein's equation of gravity in the presence of a spherically-symmetrical gravitational background, like the Earth. The transverse and longitudinal components of the metric tensor representing the gravity waves are all soliton solutions, propagating towards the origin of the Earth. If we consider the situation where the static background field is absent, the solutions still remain soliton-like in nature. The difference between our result and Einstein's is attributed to the two approximations taken previously — weak field and harmonic condition.On study leave of absence from Zhong Shan University, China  相似文献