Search

In the increasingly intense high-intensity mining process of coal mines, many factors comprehensively influence the spatial distribution characteristics of overburden fissure. The characteristics of overburden fissure distribution have important guiding significance for gas control in mining. Explored the distribution characteristics of overburden fissure networks and the boundary characteristics of gas channels under multi-factor mining conditions (mining height, advancing speed, coal seam dip angle) through conducting two-dimensional physical similarity simulation experiments. Simultaneously analysed the changing trends of the development of "two longitudinal zones" and "five horizontal zones" of overburden fissures and their influencing factors and determined the boundary characterization parameters of gas storage and migration channels based on the comprehensive criteria of "Hf," "S," and "ρ". And evaluated the determination process of gas channels, established, and optimized the theoretical model considering multi-factor mining conditions. The results indicate that gas storage and migration channels mainly develop in the fracture migration zone. The range of development continuously increases with mining height and dip angle and decreases gradually as the working face advance speed increases. It elucidated the temporal variations of gas channels and provides theoretical support for optimizing the layout parameters of gas extraction boreholes and improving gas extraction efficiency. [ABSTRACT FROM AUTHOR]

Copyright of Electric Power Automation Equipment / Dianli Zidonghua Shebei is the property of Electric Power Automation Equipment Press 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.)

Abstract For AC transmission lines connected to an LCC-HVDC inverter station, commutation failure can lead to the wrong operation of traditional protection. To solve the problem, this paper proposes a fast protection scheme using transient information from one end of the AC line. The boundary frequency characteristics of the AC line connected to LCC-HVDC inverter are analyzed first. This reveals the existence of significant attenuation on both high frequency signals and some specific frequency signals. Based on the boundary characteristics, a novel boundary protection principle utilizing a backward traveling wave is then proposed. A PSCAD/EMTDC simulation model of a ± 800 kV LCC-HVDC and 500 kV AC transmission system is established, and different fault cases are simulated. The simulation results prove that the novel protection principle is immune to commutation failure, fault resistance and fault type.

On the basis of the consideration of the boundary-value problem for the generalized equation of heat conduction in bounded nonuniform spaces with Dirichlet, Neumann, and Robin boundary conditions, corresponding sequences of boundary characteristics have been obtained. For each of these sequences, definite integro-differential representations (relations) have been constructed. It has been shown that approximate analytical solutions can be obtained for bounded nonuniform regions with variable transfer coefficients in the Cartesian, cylindrical, and spherical coordinate systems. On the basis of systems of algebraic equations, approximate analytical solutions have been constructed with approximately equal accuracies independently of the calculation scheme used (with the introduction of the temperature-disturbance front or without it, i.e., by multiple integration of the heat-conduction equation over the whole computational region). These solutions have a negligibly small error and, therefore, can be considered as conditionally exact. [ABSTRACT FROM AUTHOR]

Ｂａｓｅｄ ｏｎ ｔｈｅ ａｎａｌｙｓｉｓ ｏｆ ｔｈｅ ｐｌａｎｅ ｂｏｕｎｄａｒｙ ａｎｄ ｖｅｒｔｉｃａｌ ｂｏｕｎｄａｒｙ ｏｆ ｔｈｅ Ｋａｒｓｔ ｗａｔｅｒ ｓｙｓｔｅｍ ｉｎ Ｍｉａｎｃｈｉ Ｂａｓｉｎ， ｔｈｉｓ ｐａｐｅｒ ｃａｌｃｕｌａｔｅｄ ｔｈｅ ｇｒｏｕｎｄｗａｔｅｒ ｒｅｓｏｕｒｃｅｓ ｏｆ ｔｈｅ ｋａｒｓｔ ｗａｔｅｒ ｓｙｓｔｅｍ ｂｙ ｕｓｉｎｇ ｅｑｕｉｌｉｂｒｉｕｍ⁃ａｐｐｒｏａｃｈ． Ｔｈｅ ｏｕｔｃｏｍｅｓ ｓｈｏｗ ｔｈａｔ ｔｈｅ ａｎｎｕａｌ ｇｒｏｕｎｄｗａｔｅｒ ｌｅｖｅｌ ｉｓ ｄｅｃｒｅａｓｅｄ ｂｙ １．７９ ｍ ｄｕｒｉｎｇ ｔｈｅ ｂａｌａｎｃｅ ｐｅｒｉｏｄ， ｉｔ ｉｓ ｉｎ ｔｈｅ ｓｔａｔｅ ｏｆ ｐｏｓｉｔｉｖｅ ｂａｌａｎｃｅ ｉｎ ｗｅｔ ｙｅａｒｓ ｗｉｔｈ ｗａｔｅｒ ｌｅｖｅｌ ｉｎｃｒｅａｓｉｎｇ ｂｙ ０．０１ ｍ， ｗｈｉｌｅ ｉｔ ｉｓ ｉｎ ｔｈｅ ｓｔａｔｅ ｏｆ ｎｅｇａｔｉｖｅ ｂａｌａｎｃｅ ｉｎ ｎｏｒｍａｌ ａｎｄ ｄｒｙ ｙｅａｒｓ， ｔｈｅ ｇｒｏｕｎｄｗａｔｅｒ ｌｅｖｅｌ ｄｏｗｎｒａｎｇｅ ｉｓ ４．６０ ｍ ｉｎ ｎｏｒｍａｌ ｙｅａｒｓ ａｎｄ １６．８９ ｍ ｉｎ ｄｒｙ ｙｅａｒｓ． Ｔｈｅ ｇｒｏｕｎｄｗａｔｅｒ ｌｅｖｅｌ ｉｓ ｉｎ ａ ｃｏｎｔｉｎｕｏｕｓ ｄｅｃｌｉｎｅ ａｃｃｏｒｄｉｎｇ ｔｏ ｔｈｅ ａｎａｌｙｓｉｓ ｄａｔａ ｏｆ ｔｈｅ ｇｒｏｕｎｄｗａｔｅｒ ｌｅｖｅｌ ｏｆ ｂｏｒｅｈｏｌｅｓ ｗｉｔｈｉｎ ｔｈｅ ｒｅｇｉｏｎ； ｔｈｅ ｇｒｏｕｎｄｗａｔｅｒ ｌｅｖｅｌ ｈａｓ ｂｅｅｎ ｄｅｃｒｅａｓｅｄ ｂｙ ４０－１４０ ｍ ｄｕｒｉｎｇ ｔｈｅ ｐｅｒｉｏｄ ｏｆ １９８４－２００８， ｔｈｅ ａｎｎｕａｌ ｄｅｃｌｉｎｅ ｏｆ ｔｈｅ ａｖｅｒａｇｅ ｇｒｏｕｎｄｗａｔｅｒ ｌｅｖｅｌ ｏｆ ｂｏｒｅｈｏｌｅｓ ｉｓ ５．６８ ｍ， ｔｈｅ ｃａｌｃｕｌａｔｉｏｎ ｒｅｓｕｌｔｓ ｆｉｔ ｗｅｌｌ ｗｉｔｈ ｔｈｅ ａｃｔｕａｌ ｄａｔａ ｏｆ ｏｂｓｅｒｖａｔｉｏｎ ｂｏｒｅｈｏｌｅｓ． Ｔｈｅ ｇｒｏｕｎｄｗａｔｅｒ ｒｅｃｈａｒｇｅ ｍａｉｎｌｙ ｃｏｍｅｓ ｆｒｏｍ ｉｎｆｉｌｔｒａｔｉｏｎ ｏｆ ｐｒｅｃｉｐｉｔａｔｉｏｎ， ｍａｋｉｎｇ ｕｐ ７４．０％， ｗｈｉｌｅ ｔｈｅ ｄｉｓｃｈａｒｇｅ ｃｏｍｅｓ ｆｒｏｍ ｅｘｐｌｏｉｔａｔｉｏｎ ｏｆ ｗａｔｅｒ ｓｏｕｒｃｅ， ｃｏｖｅｒｉｎｇ ａｂｏｕｔ ９７．５％. [ABSTRACT FROM AUTHOR]

A new integral method based on the system of identical equalities of 2 n-multiple integrals of the desired temperature function and the corresponding boundary characteristics is presented. This method was used for the approximate solution of problems of a semi-bounded space and a lengthy plate with first-kind boundary conditions. The results obtained show that the integral method of boundary characteristics surpasses the analogous integral methods by several orders of magnitude in accuracy and convergence of approximate solutions. The solutions constructed with this method are exact in essence because the errors in determining parameters in a wide range of their values comprise hundredths and ten-thousands of a percent. [ABSTRACT FROM AUTHOR]

Using remote sensing and geographic information system technologies, we analyzed changes in ecosystem boundary conditions in the Yellow River Delta. We investigated variations in soil water, bulk density, total nitrogen, total phosphorus, and organic matter, as well as concentrations of soluble Ca2+, Mg2+, and Na+, under different ecosystem conversions. Results indicated that from 1992 to 2006, boundary characteristics became more complicated and ecosystem conversion was mainly from farmland to a mixed ecosystem supporting Tamarix chinensis-Phragmites communis. These ecosystem conversions may be attributed to a combination of urban expansion, oil exploration and extraction, water interception, and soil salinization. Ecosystem conversion also affected soil properties. Organic matter differed among the ecosystems, as did the concentrations of the soil base cations. Ca2+ concentration was higher than concentrations of other cations, and significant differences existed in Ca2+ and Mg2+ concentrations among ecosystems. While the concentration of K+ and Mg2+ showed similar concentrations, mostly increasing, among different ecosystem conversions, Na+ concentrations decreased. In summary, the concentrations of soluble minerals were significantly influenced by ecosystem conversions. [ABSTRACT FROM AUTHOR]

Abstract: Osteoarthritis (OA), the most prevalent form of arthritis, is a degenerative joint disease affecting millions of people worldwide. The overall aims of the project were: (i) to gain a better understanding of the wear processes occurring in human joints during a walking process, particularly in relation to osteoarthritic degeneration and (ii) to develop effective, minimally intrusive tools to assess OA activity and progression. Based on existing developments, this project, using three-dimensional numerical descriptors, further investigated correlation between the cartilage surface subjected and particle generated in the walking process. This is a critical step in developing and utilizing wear particle analysis techniques for OA assessment. With further study and development along with this study, it is possible to develop better diagnostic and prognostic procedures for clinic OA assessment using wear debris analysis techniques. [Copyright &y& Elsevier]

Contractualism is one of the most promising centers of gravity in business ethics. In this guest editorial we provide a concise roadmap to the field, sketching contractualisms historic and disciplinary antecedents, the basic argumentative structure of the contract model, and its boundary conditions. We also sketch two main dimensions along which contributions to the contractualist tradition can be positioned. The first dimension entails positive versus normative theorizing; does a given contribution analyze the world as it is or how it ought to be? The second dimension involves four different levels of analysis that are commonly employed in contractualist business ethics: the nano, micro, meso, and macro levels. We then proceed to position the articles comprising this special issue along these two dimensions. [ABSTRACT FROM AUTHOR]

In high-permeability grain-oriented silicon steel, island grains are often observed in the final sheets. In this work, the formation of island grains was studied in high-permeability grain-oriented silicon steel manufactured by the acquired inhibitor method. It was found that the {210}<001> and {110}<112> orientations dominated in the island grains. To understand the formation mechanisms of island grains, the grain boundary characteristics were investigated. Abnormal growth of island grains occurs because their orientations have a higher frequency of high-energy boundaries in the primary recrystallization texture. The {210}<001> grains could be left behind as island grains because they had a low misorientation angle with a Goss orientation (about 20°), whereas the {110}<112> island grains formed because of the size advantage of abnormally growing grains. The conclusions were also supported by the results of the interruption experiment. The {210}<001> grains were observed in the subsurface sheared area of the hot band and mainly nucleated at the subsurface layer during primary recrystallization. In addition, it was confirmed that the island grains (except for the exact {210}<001> orientation) had a negative influence on the magnetic properties because of the large deviation angle of the <001> axis from the rolling direction. • A statistically representative analysis of island grains in commercial HGO silicon steel has been conducted. • {210}<001> and {110}<112> orientations dominate in the island grains. • The abnormal growth of island grains is attributed to the high frequency of HE boundaries. • {210}<001> and {110}<112> island grains are formed due to grain boundary and size factors respectively. • The island grains (except for the exact {210}<001> orientation) have a negative effect on the magnetic properties. [ABSTRACT FROM AUTHOR]