The longwall mining method is often affected by the out-of-seam dilution （OSD）. Therefore, predicting and controlling of dilution are important factors for reducing mining costs. In this study, the fuzzy set theory ...The longwall mining method is often affected by the out-of-seam dilution （OSD）. Therefore, predicting and controlling of dilution are important factors for reducing mining costs. In this study, the fuzzy set theory and multiple regression models with parameters, including variation in seam thickness, dip of seam, seam thickness, depth of seam, and hydraulic radius as inputs to the models were applied to pre- dict the OSD in the longwall coal panels. Field data obtained from Kerman and Tabas coal mines, lran were used to develop and validate the models. Three indices including coefficient of determination （R2）, root mean square error （RMSE） and variance account for （VAF） were used to evaluate the perfor- mance of the models. With 10 randomly selected datasets, for the linear, polynomial, power, exponential, and fuzzy logic models, R2, RSME and VAF are equal to （0.85, 4.4, 84.4）, （0.61, 7.5, 59.6）, （0.84, 4.5, 72.7）, （0.80, 4.1, 79.6）, and （0.97, 2.1, 95.7）, respectively. The obtained results indicate that the fuzzy logic model predictor with R2 = 0.97, RMSE = 2.1, and VAF = 95.7 performs better than the other models.展开更多
A slip critical connection has various values to adopt the proper slip coefficient in various conditions of faying surfaces in AISC, AIJ and Eurocode3. The Korean Building Code regulates the unique slip coefficient, f...A slip critical connection has various values to adopt the proper slip coefficient in various conditions of faying surfaces in AISC, AIJ and Eurocode3. The Korean Building Code regulates the unique slip coefficient, from 0.45 to 0.5 without consideration of the diverse faying conditions in 2009. In this study, the slip resistance test, including five kinds of surface treatments were conducted to obtain the proper slip coefficients available to steel plate KS SM490A. The slip coefficient of specimens over zinc primer thickness of 128 lam exhibit was 0.42. The clean mill treated surface had prominently lower values as slip coefficient, 0.27. For red lead painted treatment, it is suggested to setup a minimum slip coefficient, 0,21, below a coating thickness of 65 μam. The slip coefficient of one faced lap connection was higher 1.4 times than the slip coefficient of two faced lap connection.展开更多
Anodic coatings were prepared by micro-arc oxidation on AZ91HP magnesium alloys in a base solution containing 10 g/L NaOH and 12 g/L phytic acid with addition of 0-8 g/L sodium tungstate.The effects of sodium tungstat...Anodic coatings were prepared by micro-arc oxidation on AZ91HP magnesium alloys in a base solution containing 10 g/L NaOH and 12 g/L phytic acid with addition of 0-8 g/L sodium tungstate.The effects of sodium tungstate on the coating thickness, mass gain,surface morphology and corrosion resistance were studied by eddy current instrument,electronic scales,scanning electron microscope and immersion tester.With the addition of sodium tungstate,the electrolytic conductivity increases and the final voltage decreases.The sodium tungstate has a minor effect on the coating thickness,but lightens the coating color.With increasing sodium tungstate concentration,the size of micropores on the coatings is enlarged and the corrosion resistance of the anodized samples decreases.展开更多
In order to study the water-inrush mechanism of concealed collapse pillars from the mechanical view, a mechanical model for water-inrush of collapse pillars has been established based on thick plate theory of elastic ...In order to study the water-inrush mechanism of concealed collapse pillars from the mechanical view, a mechanical model for water-inrush of collapse pillars has been established based on thick plate theory of elastic mechanics in this paper.By solving this model the deformation of water-resistant rock strata under the action of water pressure and the expression of critical water pressure for collapse pillar waterinrush have been obtained The research results indicate that：the boundary conditions and strength of water-resistant strata play important roles in influencing water-inrush of collapse pillars.The critical water-inrush pressure is determined by both relative thickness and absolute thickness of water-resistant strata.展开更多
Heat transport phenomenon of two-dimensional magnetohydrodynamie Casson fluid flow by employing Cattaneo-Christov heat diffusion theory is described in this work. The term of heat absorption/generation is incorporated...Heat transport phenomenon of two-dimensional magnetohydrodynamie Casson fluid flow by employing Cattaneo-Christov heat diffusion theory is described in this work. The term of heat absorption/generation is incorporated in the mathematical modeling of present flow problem. The governing mathematical expressions are solved for velocity and temperature profiles using RKF 45 method along with shooting technique. The importance of arising nonlinear quantities namely velocity, temperature, skin-friction and temperature gradient are elaborated via plots. It is explored that the Casson parameter retarded the liquid velocity while it enhances the fluid temperature. Fhrther, we noted that temperature and thickness of temperature boundary layer are weaker in case of Cattaneo-Christov heat diffusion model when matched with the profiles obtained for Fourier＇s theory of heat flux.展开更多
文摘The longwall mining method is often affected by the out-of-seam dilution （OSD）. Therefore, predicting and controlling of dilution are important factors for reducing mining costs. In this study, the fuzzy set theory and multiple regression models with parameters, including variation in seam thickness, dip of seam, seam thickness, depth of seam, and hydraulic radius as inputs to the models were applied to pre- dict the OSD in the longwall coal panels. Field data obtained from Kerman and Tabas coal mines, lran were used to develop and validate the models. Three indices including coefficient of determination （R2）, root mean square error （RMSE） and variance account for （VAF） were used to evaluate the perfor- mance of the models. With 10 randomly selected datasets, for the linear, polynomial, power, exponential, and fuzzy logic models, R2, RSME and VAF are equal to （0.85, 4.4, 84.4）, （0.61, 7.5, 59.6）, （0.84, 4.5, 72.7）, （0.80, 4.1, 79.6）, and （0.97, 2.1, 95.7）, respectively. The obtained results indicate that the fuzzy logic model predictor with R2 = 0.97, RMSE = 2.1, and VAF = 95.7 performs better than the other models.
文摘A slip critical connection has various values to adopt the proper slip coefficient in various conditions of faying surfaces in AISC, AIJ and Eurocode3. The Korean Building Code regulates the unique slip coefficient, from 0.45 to 0.5 without consideration of the diverse faying conditions in 2009. In this study, the slip resistance test, including five kinds of surface treatments were conducted to obtain the proper slip coefficients available to steel plate KS SM490A. The slip coefficient of specimens over zinc primer thickness of 128 lam exhibit was 0.42. The clean mill treated surface had prominently lower values as slip coefficient, 0.27. For red lead painted treatment, it is suggested to setup a minimum slip coefficient, 0,21, below a coating thickness of 65 μam. The slip coefficient of one faced lap connection was higher 1.4 times than the slip coefficient of two faced lap connection.
基金Projects(GJJ08363,GJJ09573)supported by the Scientific Research Fund of Jiangxi Provincial Education Department,China
文摘Anodic coatings were prepared by micro-arc oxidation on AZ91HP magnesium alloys in a base solution containing 10 g/L NaOH and 12 g/L phytic acid with addition of 0-8 g/L sodium tungstate.The effects of sodium tungstate on the coating thickness, mass gain,surface morphology and corrosion resistance were studied by eddy current instrument,electronic scales,scanning electron microscope and immersion tester.With the addition of sodium tungstate,the electrolytic conductivity increases and the final voltage decreases.The sodium tungstate has a minor effect on the coating thickness,but lightens the coating color.With increasing sodium tungstate concentration,the size of micropores on the coatings is enlarged and the corrosion resistance of the anodized samples decreases.
基金Projects are supported by the National Basic Research Program of China(No.2007CB209400)the National Natural Science Foundation of China(Nos.50974115,50904065 and 50974107)the 111 Project(No.B07028).
文摘In order to study the water-inrush mechanism of concealed collapse pillars from the mechanical view, a mechanical model for water-inrush of collapse pillars has been established based on thick plate theory of elastic mechanics in this paper.By solving this model the deformation of water-resistant rock strata under the action of water pressure and the expression of critical water pressure for collapse pillar waterinrush have been obtained The research results indicate that：the boundary conditions and strength of water-resistant strata play important roles in influencing water-inrush of collapse pillars.The critical water-inrush pressure is determined by both relative thickness and absolute thickness of water-resistant strata.
文摘Heat transport phenomenon of two-dimensional magnetohydrodynamie Casson fluid flow by employing Cattaneo-Christov heat diffusion theory is described in this work. The term of heat absorption/generation is incorporated in the mathematical modeling of present flow problem. The governing mathematical expressions are solved for velocity and temperature profiles using RKF 45 method along with shooting technique. The importance of arising nonlinear quantities namely velocity, temperature, skin-friction and temperature gradient are elaborated via plots. It is explored that the Casson parameter retarded the liquid velocity while it enhances the fluid temperature. Fhrther, we noted that temperature and thickness of temperature boundary layer are weaker in case of Cattaneo-Christov heat diffusion model when matched with the profiles obtained for Fourier＇s theory of heat flux.
