扩频技术及其在GPS相位模糊度解算中的应用

ＧＰＳ高精度定位采用的是载波相位观测量，快速而准确地求解相位整周模糊度是提高ＧＰＳ定位效率的关键。本文从理论上对扩频技术在模糊度解算中的应用进行了系统的研究。     

GPS动态定位的初始化

ＧＰＳ动态定位的研究始于１９８３￣１９８５年。利用相位观测量进行相对动态定位目前可达到厘米级精度，但其前提是要解决三大问题，即周跳、初始化和改正数据的实时传输。本文着重研究动态定位的初始化问题。     

GPS数据周跳探测的预处理

周跳探测是ＧＰＳ数据处理的重要课题。根据所得数据的类型，例如码伪距和相位伪距等，已有多种方法。总的说来，每种方法都各有其优缺点。本文提出两步探测法，用来探测周跳，在建立起检验量后，从平滑角度对其探测功能进行，检定，一旦出现间断，就说明存在周跳。     

大蒿的波谱反射率响应用于怀俄明州Bighorn盆地中由烃类引起的病变

在怀俄明州Ｂｉｇｈｏｒｎ盆地中的５个地区进行了地植物反射率研究，波谱测试用的是ＳＥ—５９０手提式波谱仪，采集可见光及近红外区的数据（０．４５～１．１μｍ）。这项调查结果表明，绿峰（０．５６μｍ）和红谷（０．６７μｍ）位置的大幅度蓝移（向较短波长移动）是蒿类植物中由烃引起的病变的最可靠标志。只有在蒿长在大量地表看得见或近地下烃类的地区，这种蓝移才能检测到。研究发现波谱反射率强度数据与地在或地下烃类的出现无大的相关性。     

Biomarker responses and genotoxicity in the mud snail (Bullacta exarata) as indicators of coastal contamination

In the present study different biomarker responses and genotoxicity were determined in wild mud snails (Bullacta exarata) collected from 3 sampling sites in Bohai Bay in northeastern China, which is a region that is under considerable anthropogenic influence. Significant spatial variability of superoxide dismutase (SOD) and metallothionein (MT)-like proteins were recorded, while glutathione transferase (GST), catalase (CAT), and vitellin-like proteins (Vn's) were not observed. Furthermore, genomic DNA that was amplified with 4 fluorescence-labeled primer pairs showed variable genetic distances among the 3 wild mud snail populations found in Bohai Bay, which may be correlated with differences in the types of environmental genotoxicants, such as heavy metals and polycyclic aromatic hydrocarbons. This multi-biomarker approach provided an improved understanding of the potential toxicological impact of contaminated sediments on benthic organisms.     

成都粘土孔隙性的微观研究

孔隙是土结构的重要标志之一,其特征对土的工程地质性质有很大影响。本文介绍了应用结构图象定量分析系统对成都粘土孔隙性的微观研究成果并对孔隙的大小、数量、形状、类型和定向程度等形态和几何特征进行了讨论。     

Matrix diffusion-derived plume attenuation in fractured bedrock

Matrix diffusion can attenuate the rate of plume migration in fractured bedrock relative to the rate of ground water flow for both conservative and nonconservative solutes of interest. In a system of parallel, equally spaced constant aperture fractures subject to steady-state ground water flow and an infinite source width, the degree of plume attenuation increases with time and travel distance, eventually reaching an asymptotic level. The asymptotic degree of plume attenuation in the absence of degradation can be predicted by a plume attenuation factor, beta, which is readily estimated as R' (phi(m)/phi(f)), where R' is the retardation factor in the matrix, phi(m) is the matrix porosity, and phi(f) is the fracture porosity. This dual-porosity relationship can also be thought of as the ratio of primary to secondary porosity. Beta represents the rate of ground water flow in fractures relative to the rate of plume advance. For the conditions examined in this study, beta increases with greater matrix porosity, greater matrix fraction organic carbon, larger fracture spacing, and smaller fracture aperture. These concepts are illustrated using a case study where dense nonaqueous phase liquid in fractured sandstone produced a dissolved-phase trichloroethylene (TCE) plume approximately 300 m in length. Transport parameters such as matrix porosity, fracture porosity, hydraulic gradient, and the matrix retardation factor were characterized at the site through field investigations. In the fractured sandstone bedrock examined in this study, the asymptotic plume attenuation factors (beta values) for conservative and nonconservative solutes (i.e., chloride and TCE) were predicted to be approximately 800 and 12,210, respectively. Quantitative analyses demonstrate that a porous media (single-porosity) solute transport model is not appropriate for simulating contaminant transport in fractured sandstone where matrix diffusion occurs. Rather, simulations need to be conducted with either a discrete fracture model that explicitly incorporates matrix diffusion, or a dual-continuum model that accounts for mass transfer between mobile and immobile zones. Simulations also demonstrate that back diffusion from the matrix to fractures will likely be the time-limiting factor in reaching ground water cleanup goals in some fractured bedrock environments.     

Spatial scales and evolution of stormwater plumes in Santa Monica Bay

Rainfall during winter storms produces extensive turbid, freshwater plumes in the coastal waters of the Southern California Bight. When the plumes result from urban runoff they contain toxic pollutants along with pathogenic bacteria and viruses, often resulting in closure of public beaches. We examined the spatial structure and evolution of stormwater plumes in Santa Monica Bay in 1996. The plumes resulted from freshwater discharge from the Ballona Creek and Malibu Creek watersheds which supply approximately 60% of the freshwater runoff to Santa Monica Bay. The spatial scales of the plumes were determined using shipboard measurements of water properties obtained from towyo transects and surface underway sampling. Salinity maps showed that the plumes typically extended 4-7 km offshore, consistent with scaling by the internal Rossby radius of deformation. Plumes extended along shore 10 km or more. Generally the plumes occupied the upper 10 m of the water column. The persistence time of a plume offshore of Ballona Creek was about three days based on a sequence of surveys in March 1996 following rainfall of about 21 mm. Limited comparison of plumes from Ballona Creek, which drains a developed watershed, and Malibu Creek, which drains a rural watershed, suggested that Malibu Creek required greater rainfall to produce an offshore plume. A stormwater plume offshore of Malibu Creek was observed on both sides of the creek mouth, possibly due to freshwater discharge from smaller surrounding watersheds or advection of freshwater discharges from the east and south. Plumes offshore of Ballona Creek mainly resulted from the creek itself and usually extended northward from the creek mouth, consistent with the wind forcing and the Coriolis acceleration.