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【Objective】 Crop growth and ecological functions in arid and semi-arid loess regions in northwestern China are limited not only by topsoil water directly available to crop but by deep soil water which functions as a reservoir. Slopes and lands formed by artificial retaining are two typical geographical units in small watersheds in the loess plateau. This paper presents a method to estimate soil water distribution in them up to 12.5 m deep. 【Method】 The method was based on electrical resistivity tomography (ERT). We measured electrical resistivity of the soil in typical slope and retained land in the small Liudaogou watershed in northern Shaanxi province. Using the measured soil volumetric water content, a power function relating the resistivity to soil water content was established, from which we calculated water distribution and water storage in the 0~12.5 m profile in both the slope and the retained land. 【Result】 The distribution of electrical resistivity over the slope was significantly affected by slope position, with the resistivity decreasing gradually from the slope top to the slope toe. Such changes were associated with vegetation consumption of the topsoil water and redistribution of the infiltrated precipitation over the slope. The vertical distribution of the resistivity in the retained land showed a high-low-high variation; this was also related to root water uptake from the topsoil and precipitation recharge to the subsoil. ERT inversion showed co-existence of a saturated zone and an unsaturated zone in the retained land, while the slope was partly saturated. In a 1.8×104 m2 of retained land, there was 1.49×104 m3 of water in the 0~6.5 m unsaturated layer, and 5.10×104 m3 of water in the saturated layer. In a same area but on the slope, there was only 2.59×104 m3 of water in the 0~12.5 m soil layer. 【Conclusion】 Retained land contains more water than slope, and the deep soil in it functions as a reservoir banking infiltration water in wet seasons. ERT is suitable for measuring spatiotemporal variation in soil moisture in both slopes and flatten plains in the loess plateau.

In order to solve the reverse distribution of energy and demand in China, ultra high voltage direct current transmission (UHVDC), which has significant advantages such as large transmission capacity, low line loss and long transmission distance, has become an important scheme. However, due to its long transmission distance, complex terrain and climate across the region, the distribution of soil resistivity along the line is uneven. Based on Zhundong-Wannan ± 1 100 kV UHVDC transmission project, the overvoltage mechanism of DC line was analyzed. The electromagnetic transient calculation software PSCAD was used to simulate and analyze the overvoltage of DC line with different average soil resistivity and actual soil resistivity in four seasons. The results show that the soil resistivity will affect the reflection of the converter station, and the actual soil resistivity will make the maximum overvoltage position shift towards the transmitting side. It is concluded that the overvoltage suppression effect is better by optimizing the installation position of line arrester, which provides an important reference for the development of UHVDC transmission project. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to overcome the shortcomings of fuzziness, randomness and interaction between the soil corrosion factors of buried pipeline, as well as the low accuracy of prediction with the traditional methods, a prediction model of external corrosion rate was established with 10 influencing factors as the input, and the external corrosion rate as the output based on the field data of corrosion coupons of a buried pipeline. Thereby, the data samples were trained, verified and tested using the Radial Basis Function (RBF) neural network mode, and the key parameters affecting the corrosion were identified through Sobol sensitivity analysis. The results show that the mean square error is 0.000 99 when 10-35-1 type RBF model is iterated to step 2 273, and the correlation coefficients of the training, validation and testing stages are 0.970 7, 0.981 3 and 0.990 1 respectively. Compared with BP, MLR and SVM models, the average relative error of RBF neural network model is 2.07%, indicating that RBF neural network model has some advantages in terms of the external corrosion rate prediction of buried pipeline. The soil resistivity has the maximum effect on the external corrosion rate. Moreover, the soil resistivity, pH value, and Cl- content significantly interact with other factors, which should be paid much more attention. Generally, the established model can be effectively applied to the external corrosion rate prediction of pipeline, and the results could provide theoretical basis and reference for pipeline integrity management.

Soil resistivity is an important soil property that affects the selection of grounding electrode sites for HVDC transmission. How to quickly obtain the spatial distribution of soil resistivity and provide reference for the selection of grounding electrode sites is an important issue in HVDC transmission. This paper takes part of Shanxi Province and Fugu County, Yulin City, Shaanxi Province as the study area. The Sentinel-1, Sentinel-2 and SMAP satellite data are used to retrieve the soil volumetric water content in the study area, and the spatial distribution of soil gravimetric water content is obtained by combining the soil bulk density with volumetric water content. Finally, the estimation model is established by the field measurements of soil resistivity and soil gravimetric water content estimated based on remote sensing. Through the estimation model, the fitting relationship between soil resistivity and soil gravimetric water content in the form of power function is obtained, and the distribution of soil resistivity at the grounding electrode sites to be selected and its surrounding areas is obtained. The results show that remote sensing can assist in the selection of grounding electrode sites, which provides a new idea for the selection of grounding electrode sites in a large range of areas. [ABSTRACT FROM AUTHOR]

In view of problems of limited terrain, short effective dispersion length, and low resistance reduction efficiency in the extensional resistance reduction of the grounding grid of incoming line section of mine substation, a resistance reduction method using long -distance extension lead for auxiliary grounding of incoming line tower was proposed. The grounding calculation software CDEGS is used to establish simulation model of 'Τ' type, 'Γ' type, box type, vertical type unidirectional auxiliary grounding network, and study stray current characteristics of unidirectional auxiliary grounding grid of steel tube tower and corresponding influencing factors. The research results show that the longer the extension lead, the higher the resistance reduction efficiency; when the extension lead length exceeds 60 m, the resistance reduction efficiency is stable at about 80% under the action of high -frequency current; the 'Γ' type unidirectional auxiliary grounding grid has stable stray current characteristics, strong shunting ability, and its resistance reduction effect is the best; resistance reduction efficiency of the unidirectional auxiliary grounding grid is more than 70% under different soil conditions. In practical engineering applications, it is recommended to determine the extension lead length and terminal structure of the auxiliary grounding grid according to the actual soil conditions, and to lay the auxiliary grounding grid to areas with low soil resistivity or to take local soil replacement measures for areas with high soil resistivity to improve the resistance reduction efficiency of unidirectional auxiliary grounding grid of the incoming line tower.

Copyright of Journal of Mine Automation is the property of Industry & Mine Automation Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Natural Gas & Oil is the property of Editorial Department of Natural Gas & Oil and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The lighting accident within or nearby the substation will make the ground potential rise (GPR) rise sharply, which may be easy to bum the control cable due to the potential difference between a conductor and skin. Aiming at the problem, this paper makes the theoretical analysis and data calculation. Combining with the theory of electromagnetic, it establishes the relevant mathematical model, and programs through MATLAB. The result shows that under the action of transient lightning curren, not only the soil resistivity should be considered, but also the optimization of the network and the choice of reasonable ground material and double - side - grounding control cable shielding layer. At the same time, the paper measures out the maximum withstand voltage for the control cable is 2 kV and calculate the limit value of GPR is 5 kV. [ABSTRACT FROM AUTHOR]