基于磁异常信号的油田地下管线探测方法

在油田开发过程中,为准确检测输油、输气、输水管线及光缆、电缆的分布、走向及埋藏深度,提出基于磁异常信号的地下管线探测系统:首先,根据磁异常信号探测原理,建立地球磁场模型,进行管线探测系统的软、硬件设计;其次,通过改变扫描时间间隔和探测方向,利用管线探测系统探测地下管线并分析探测结果;最后,分析地球磁场探测数据成像结果,...     

一度电能做些什么

日常生活中,节能环保意识不能少。但说到节能,大多数人只有一个模糊概念,好比大家都知道夏天空调开低1度能节省不少电,但节省下来的这些“微能量”能做些什么？专家告诉我们,日常居家生活,1度电能做的事情还真不少。     

Assessment of point and nonpoint sources pollution in Songhua River Basin,Northeast China by using revised water quality model

Individual participation of pollutants in the pollution load should be estimated even if roughly for the appropriate environmental management of a river basin. It is difficult to identify the sources and to quantify the load, especially in modeling nonpoint source. In this study a revised model was established by integrating point and nonpoint sources into one-dimensional Streeter-Phelps (S-P) model on the basis of real-time hydrologic data and surface water quality monitoring data in the Jilin Reach of the Songhua River Basin. Chemical oxygen demand (COD) and ammonia nitrogen (NH_3-N) loads were estimated. Results showed that COD loads of point source and nonpoint source were 134 958 t/yr and 86 209 t/yr, accounting for 61.02% and 38.98% of total loads, respectively. NH_3-N loads of point source and nonpoint source were 16 739 t/yr and 14 272 t/yr, accounting for 53.98% and 46.02%, respectively. Point source pollution was stronger than nonpoint source pollution in the study area at present. The water quality of upstream was better than that of downstream of the rivers and cities. It is indispensable to treat industrial wastewater and municipal sewage out of point sources, to adopt the best management practices to control diffuse pollutants from agricultural land and urban surface runoff in improving water quality of the Songhua River Basin. The revised S-P model can be successfully used to identify pollution source and quantify point source and nonpoint source loads by calibrating and validating.     

Crest-height distribution of nonlinear random waves

The wave crest is an important factor for the design of both fixed and floating marine structures. Wave crest height is a dominant parameter in assessing the likelihood of wave-in-deck impact and resultant severe damage. Many empirical and theoretical distribution functions for wave crest heights have been proposed, but there is a lack of agreement between them. It is of significance to develop a better new nonlinear wave crest height distribution model. The progress in the research of wave crest heights is reviewed in this paper. Based on Stokes’ wave theory, an approximate nonlinear wave crest-height distribution formula with simple parameters is derived. Two sets of measured data are presented and compared with various theoretical distributions of wave crests obtained from nonlinear wave models and analysis of the comparison is given in detail. The new crest-height distribution model agrees well with observations. Also, the new theoretical distribution is more accurate than the other methods cited in this paper and has a greater range of applications.     

Managing Soil Erosion Potential by Integrating Digital Elevation Models with the Southern China＇s Revised Universal Soil Loss Equation——A Case Study for the West Lake Scenic Spots Area of Hangzhou, China

In China, many scenic and tourism areas are suffering from the urbanization that results from physical development of tourism projects, leading to the removal of the vegetative cover, the creation of areas impermeable to water, in-stream modifications, and other problems. In this paper, the risk of soil erosion and its ecological risks in the West Lake Scenic Spots （WLSS） area were quantitatively evaluated by integrating the revised universal soil loss equation （RUSLE） with a digital elevation model （DEM） and geographical information system （GIS） software. The standard RUSLE factors were modified to account for local climatic and topographic characteristics reflected in the DEM maps, and for the soil types and vegetation cover types. An interface was created between the Areinfo software and RUSLE so that the level of soil erosion and its ecological risk in the WLSS area could be mapped immediately once the model factors were defined for the area. The results from an analysis using the Areinfo-RUSLE interface showed that the risk value in 93 % of the expanding western part of the WLSS area was moderate or more severe and the soil erosion risk in this area was thus large compared with that in the rest of the area. This paper mainly aimed to increase the awareness of the soil erosion risk in urbanizing areas and suggest that the local governments should consider the probable ecological risk resulting from soil erosion when enlarging and developing tourism areas.     

f-3项与投影函数对电离层延迟的影响

依据Chapman正常电离层理论,构造Chapman剖面函数加权投影函数,给出VTEC三角多项式模型,并以武汉站2005年1月1日观测数据进行实例解算,分析电离层延迟f-3项、电离层单层高度、电离层投影函数形式等对电离层延迟的影响.     

Assimilation of ASAR data with a hydrologic and semi-empirical backscattering coupled model to estimate soil moisture

The most promising approach for studying soil moisture is the assimilation of observation data and computational modeling.However,there is much uncertainty in the assimilation process,which affects the assimilation results.This research developed a one-dimensional soil moisture assimilation scheme based on the Ensemble Kalman Filter(EnKF)and Genetic Algorithm(GA).A two-dimensional hydrologic model-Distributed Hydrology-Soil-Vegetation Model(DHSVM)was coupled with a semi-empirical backscattering model(Oh).The Advanced Synthetic Apertture Radar(ASAR)data were assimilated with this coupled model and the field observation data were used to validate this scheme in the soil moisture assimilation experiment.In order to improve the assimilation results,a cost function was set up based on the distance between the simulated backscattering coefficient from the coupled model and the observed backscattering coefficient from ASAR.The EnKF and GA were used to re-initialize and re-parameterize the simulation process,respectively.The assimilation results were compared with the free-run simulations from hydrologic model and the field observation data.The results obtained indicate that this assimilation scheme is practical and it can improve the accuracy of soil moisture estimation significantly.     

天线相位中心偏差变化及改正模型对精密单点定位精度的影响

利用精密单点定位程序对IGS站的实测数据进行计算,结果表明:平面方向,天线相位中心偏差和变化对精密单点定位精度影响较小;高程方向,天线相位中心偏差可造成厘米级的影响,天线相位中心变化的影响约5 mm;相比相对天线相位中心改正模型,使用绝对相位改正模型具有更多优点,尤其用于高精度GPS授时其精度明显提高.