Hou A.,Tsinghua University |
Ni G.,Tsinghua University |
Lei Z.,Tsinghua University |
Jing S.,Hydrochina Beijing Engineering Corporation
Shuili Fadian Xuebao/Journal of Hydroelectric Engineering | Year: 2013
Change in impervious ratio of ground surface is an important index of urbanization. This paper presents a direct estimation of impervious surface distribution in the plain area of Beijing from landsat thematic mapper (ET) data of 1995 and 2007 with a fully constrained linear spectral mixture model of four endmembers, i. e. high albedo, low albedo, vegetation, and soil. The estimation accuracy of this ratio in 2007 was evaluated by using a high-precision geographic vector map of 2006~2007, and an overall RMS error of 17.3% was obtained. Comparison of the impervious surface distributions in 1995 and 2007 shows the main regions of urbanization in Beijing and their scales. Results show that in this period the urbanization were prominent in Shunyi, Tongzhou, Fangshan, Daxing, Chaoyang and Changping. This direct estimation method from Landsat TM images provides important information to the studies of urbanization, urban hydrological and energy cycle. © Copyright.
Wang W.,Beijing Institute of Technology |
Ma X.,HydroChina Beijing Engineering Corporation
2012 2nd International Conference on Remote Sensing, Environment and Transportation Engineering, RSETE 2012 - Proceedings | Year: 2012
This paper presents a novel data preprocessing method for resolving Doppler ambiguity of spaceborne spotlight synthetic aperture radar. The new method enhances the azimuth sampling rate of received data by taking dechirping operation and increasing chirp rate operation combined with Fast Fourier Transform (FFT) and Inverse FFT (IFFT). On premise of maintaining imaging quality, Pulse Repetition Frequency can be decreased to the lowest value by this method, which avoids the subapertures recombination difficulty of traditional Subaperture Processing Technique. Finally, simulation results demonstrate the validity of this method. © 2012 IEEE.
Wang W.,Beijing Institute of Technology |
Liu Z.,Beijing Institute of Technology |
Song X.,Beijing Institute of Technology |
Ma X.,HydroChina Beijing Engineering Corporation
International Conference on Signal Processing Proceedings, ICSP | Year: 2012
This paper introduces a hybrid imaging mode of spaceborne SAR, which holds the particular advantages of high-resolution and large imaging swath, and it has been uniquely applied to the TECSAR Satellite of Israel successfully in 2008. According to the azimuthal time-frequency analysis of mosaic mode, imaging method is presented and ECS algorithm is selected for processing a single mosaic data. In order to resolve the inevitable Doppler ambiguity, a data preprocessing algorithm is utilized to improve the traditional ECS algorithm. Finally, simulation results demonstrate the validity of the proposed imaging method. © 2012 IEEE.
Zhao H.J.,Hydrochina Beijing Engineering Corporation |
Jin Y.D.,Hydrochina Beijing Engineering Corporation |
Liu J.,No. 6 Project Section of Shengli Oil Field Shengli Engineering Construction Co.
Applied Mechanics and Materials | Year: 2013
Restricted by such factors as the size of test area, amount of work and water depth of model, hydraulic models are often made into distorted patterns, whereas the distorted models demand for roughening usually. The hydraulic model of comprehensive harness of Qian'an Reach of Luan River requires big roughness that general roughening technologies can't meet, so the plastic grass cushions were introduced. The preliminary experiment in flume, the preliminary experiment of the comprehensive model and the verification experiment of the comprehensive model proved the feasibility of the technology of roughening with the grass cushions in hydraulic model tests. © (2013) Trans Tech Publications, Switzerland.
Li G.B.,China Agricultural University |
Li G.B.,HYDROCHINA Beijing Engineering Corporation |
Li Y.K.,China Agricultural University |
Li Y.K.,CAS Research Center for Eco Environmental Sciences |
And 7 more authors.
Irrigation Science | Year: 2012
Emitter clogging, a phenomenon commonly seen in reclaimed wastewater drip irrigation systems, is a severe obstacle to the wide applications and popularization of the irrigation technology. Some experiments showed that the emitter clogging was tightly related to biofilms formation attached to the irrigation system. In this paper, two types of wastewaters reclaimed respectively by fluidized-bed reactor (FBR) process and biological aerated filter (BAF) process were chosen as the experiment objects and then the effects of the average velocity on the growth and topography of biofilms attached to the irrigation laterals were studied. The parameters of biofilms reached their maximal values at a critical velocity of 0.45 m/s. The formation of biofilms was primarily controlled by the transport of the nutrients and suspended particles within the laterals when the average velocity is below the critical velocity, whereas it was primarily controlled by the hydraulic shear force when above the critical velocity. The main mechanism for emitter clogging was that the biofilms detached from laterals accumulated and grew at the inlets and outlets of emitters. A similar variation pattern was observed for both reclaimed wastewaters. However, the growth of biofilms for BAF process was more affected by the shear force than that for FBR process, since the nutrients and suspended particles for BAF were larger than those for FBR. © 2011 Springer-Verlag.
Kong C.,Hydrochina Beijing Engineering Corporation |
Wu H.,Hydrochina Beijing Engineering Corporation
Shuili Fadian Xuebao/Journal of Hydroelectric Engineering | Year: 2010
The dam of Songta hydroplant is located in a canyon at the foot of a high mountain, where a supper-high arch and a huge reservoir are to be constructed, but the topographic and geological conditions are complicated. The key to the general plan of this project is the arrangement of the dam, the diversion and power generation structures and the discharging structures. Configurations of the structures are first selected in consideration of the distinctive features of this project and the experiences of similar projects, and then by a preliminary analysis and comparison, three layout schemes are studied. Finally, the recommended general plan is chosen by means of technical and economic comparison of the alternatives. © Tsinghua University Press.
Jing X.Y.,Hubei Engineering University |
Liu X.H.,Hubei Engineering University |
Zhang X.,HydroChina Beijing Engineering Corporation
Advanced Materials Research | Year: 2014
When mixed with the admixture MgO, the volume contraction deformation of mass concrete could be compensated, which is an effective way to solve the temperature cracking problems in construction of concrete projects. Taking an arch dam in China as an example, the thermal stress compensation characteristics of MgO concrete in cold areas are studied using the finite element method. Results indicate that the stress compensation of MgO concrete is significant inside the dam, and with a better effect along with a larger mixing amount of MgO in a certain range. But on the surface of the dam, the stress compensation of MgO concrete is not significant. © (2014) Trans Tech Publications, Switzerland.
Zhao X.,Hydrochina Beijing Engineering Corporation |
Qi J.,Hydrochina Beijing Engineering Corporation
Global View of Engineering Geology and the Environment - Proceedings of the International Symposium and 9th Asian Regional Conference of IAEG | Year: 2013
Permeability and seepage deformation are important parameters for design and construction of earth and rockfill dam, dam base and foundation pit, which shall be prepared for both large- and medium-sized hydropower projects. Based on the measured data of 155 samples taken from 18 hydropower projects, the statistic analyses are made on the regularity of permeability coefficient, critical gradient and failure gradient of the crushed gravel soil. Studies are conducted on the effects of grain gradation (content of grains smaller than 2 mm), compactness, weathering degree and silty clay content of the crushed gravel soil on the permeability and seepage deformation performance (critical gradient and failure gradient). The results indicate that above four factors all have obvious effects on the permeability and seepage deformation performance, in which, the effect of grain gradation (content of grains smaller than 2 mm) is the most significant. © 2013 Taylor & Francis Group, London.
Wu L.,China Three Gorges University |
Guo X.,Hydrochina Beijing Engineering Corporation
Applied Mechanics and Materials | Year: 2012
On discussing the value of inundated land the paper points out the problems of existing land evaluation methods and analyses the factors affecting land evaluation as well as discusses the principle of land value assessment. On this basis, the paper put forwards a model based on income approach -- residual method to reflect the true market value of the inundated land. © (2012) Trans Tech Publications, Switzerland.
Zhao X.,HydroChina Beijing Engineering Corporation |
Qi J.,HydroChina Beijing Engineering Corporation |
Zheng H.,HydroChina Beijing Engineering Corporation
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2014
The shear strength parameters of rockfill material are the main factors in calculation of dam stability against sliding, thus shear tests of rockfill materials should be conducted for all the rockfill dam projects. In order to further obtain the exact parameter values, regularity and main effective factors of shear strength, according to the classification of weathering degrees of the rockfill materials and with the method of data statistical analysis, this paper provides a statistical analysis on the shear strength parameters and regularities of rocks, crushed gravel soil and sandy pebble soil taken as main rockfill, secondary rockfill, cushion, and transition materials based on the test data of 101 specimen groups from 7 projects designed by HydroChina Beijing Engineering Corporation. Further analysis is made on the effects of immersion saturation, compaction, grain gradation(<5 mm content), roundness, weathering degree, and lithology to the shear strength parameters of rockfill materials. The result shows that the effect of weathering degree of rockfill material on the shear strength parameters is the most obvious, other effects are in different degrees.