Based on the conclusions of domestic and foreign research, we have analyzed the collapse-fall characteristics of overlying strata and the mechanism of aquifer-protective mining in shallow coal seam working faces at th...Based on the conclusions of domestic and foreign research, we have analyzed the collapse-fall characteristics of overlying strata and the mechanism of aquifer-protective mining in shallow coal seam working faces at the Shendong Mine. We have selected the height of the water-conducting fracture zone in overlying strata as a composite index and established the applicable conditions of aquifer-protective mining in shallow coal seams with a multi-factor synthetic-index classification method. From our calculations and analyses of variance, we used factors such as the overlying strata strength, mining disturbing factors and rock integrity as related factors of the composite index. We have classified the applicable conditions of aquifer-protective mining in shallow coal seams into seven types by comparing the result of the height of water-conducting fractured zones of long-wall and short-wall working faces with the thickness of the bedrock, the thickness of the weathered zone and the size of safety coal-rock pillars. As a result, we propose the preliminary classification system of aquifer-protective mining in shallow coal seams. It can provide a theoretical guidance for safe applications of aquifer-protective mining technology in shallow coal seams under similar conditions.展开更多
A P-substituted sulfonyl-containing compound was synthesized in the lab. The structure of the compound was demonstrated by 1H and 31P NMR. The propylene polymerization catalysts were prepared by incorporating an inter...A P-substituted sulfonyl-containing compound was synthesized in the lab. The structure of the compound was demonstrated by 1H and 31P NMR. The propylene polymerization catalysts were prepared by incorporating an internal donor, and the content of Ti, H and C in the catalysts was also checked by elemental analysis. The effect of dosage of the donor, the Al/Ti ratio and the polymerization temperature on the catalyst activity were studied, the results suggested that the dosage of donor, the Al/Ti ratio and the polymerization temperature could affect not only the activity of catalyst but also the isotacticity index of the polymer. A catalyst with high activity was selected, and the polypropylene formed in the presence of this catalyst had high isotacticity index.展开更多
With the aging process, people been looked after properly in the old age has already become an important index to the national happiness index. Nowadays, government has a increasingly clear roadmap in promoting the de...With the aging process, people been looked after properly in the old age has already become an important index to the national happiness index. Nowadays, government has a increasingly clear roadmap in promoting the development of pension system. Pension system unification refers to the same pension system for workers in public institutions and enterprises. It is a relative concept to the dual pension system. It has positive effect on social equity. But it also has many problems. In this article, author explained the relation between pension system unification and social equity on the basic of analyzing viewpoints of several scholars. And make comments by extending it and analyzing it.展开更多
Opsaridium microlepis migrates for spawning during the rainy season （November to May） to major affluent rivers. Linthipe River is one of the major rivers, into which this species migrates. Determination of reproduct...Opsaridium microlepis migrates for spawning during the rainy season （November to May） to major affluent rivers. Linthipe River is one of the major rivers, into which this species migrates. Determination of reproductive seasonality of O. microlepis is paramount in the improved management of this endangered species. Reproductive seasonality ofO. microlepis in the Linthipe River in Central Malawi was estimated using 546 specimens for 12 months. The GSI （Gonadosomatic Index） ranged between 5.6% and 13% for females and between 0.3% and 1.4% for males, respectively. GSI variation between the months was significantly different （one-way ANOVA （analysis of variance）, P 〈 0.05）. The peak breeding activity was observed between January to April. This was at the onset of rainy season while the condition factor of O. microlepis was found to be variable with lowest value in the month of August. The study revealed that for O. microlepis fishery to be sustainably exploited, proper management regimes should be instituted along the migratory rivers during the peak breeding periods. These sustainable methods need to be managed in a participatory manner together with the majority of people living along these rivers.展开更多
A three-dimensional autonomous chaotic system is discussed in this paper. Some basic dynamical properties of the system, including phase portrait, Poincar′e map, power spectrum, Kaplan–Yorke dimension, Lyapunov expo...A three-dimensional autonomous chaotic system is discussed in this paper. Some basic dynamical properties of the system, including phase portrait, Poincar′e map, power spectrum, Kaplan–Yorke dimension, Lyapunov exponent spectra, signal amplitude and topological horseshoe are studied theoretically and numerically. The main finding by analysis is that the signal amplitude can be modulated via controlling the coefficients of the linear term, cross-product term and squared term simultaneously or respectively, and the phase of x3 can be modulated by the product of the coefficients of the linear term and cross-product term. Furthermore, scaling chaotic attractors of this system are achieved by modified projective synchronization with an optimization-based linear coupling method, which is safer for secure communications than the existed synchronization scheme since the scaling factors can be regarded as the security encoding key.展开更多
This paper introduces the finding of a unified Lorenz-like system.By gradually tuning the only parameter d,the reported system belongs to Lorenz-type system in the sense defined by Clikovsky.Meanwhile,this system belo...This paper introduces the finding of a unified Lorenz-like system.By gradually tuning the only parameter d,the reported system belongs to Lorenz-type system in the sense defined by Clikovsky.Meanwhile,this system belongs to Lorenz-type system,Lu-type system,Chen-type system with d less than,equivalent to and greater than 1.5,respectively,according to the classification defined by Yang.However,this system can only generate a succession of Lorenz-like attractors.Some basic dynamical properties of the system are investigated theoretically and numerically.Moreover,the tracking control of the system with exponential convergence rate is studied.Theoretical analysis and computer simulation show that the proposed scheme can allow us to drive the output variable x\ to arbitrary reference signals exponentially,and the guaranteed exponential convergence rate can be estimated accurately.展开更多
基金Financial support for this work, provided by the research fund of the North China Institute of Science and Technology (No.A09002)the National Natural Science Foundation of China (No.50834005)the National Basic Research Program of China (No.2007CB209402)
文摘Based on the conclusions of domestic and foreign research, we have analyzed the collapse-fall characteristics of overlying strata and the mechanism of aquifer-protective mining in shallow coal seam working faces at the Shendong Mine. We have selected the height of the water-conducting fracture zone in overlying strata as a composite index and established the applicable conditions of aquifer-protective mining in shallow coal seams with a multi-factor synthetic-index classification method. From our calculations and analyses of variance, we used factors such as the overlying strata strength, mining disturbing factors and rock integrity as related factors of the composite index. We have classified the applicable conditions of aquifer-protective mining in shallow coal seams into seven types by comparing the result of the height of water-conducting fractured zones of long-wall and short-wall working faces with the thickness of the bedrock, the thickness of the weathered zone and the size of safety coal-rock pillars. As a result, we propose the preliminary classification system of aquifer-protective mining in shallow coal seams. It can provide a theoretical guidance for safe applications of aquifer-protective mining technology in shallow coal seams under similar conditions.
基金the PetroChina Science & Technology Management Department for the financial support (No.2010F-19)
文摘A P-substituted sulfonyl-containing compound was synthesized in the lab. The structure of the compound was demonstrated by 1H and 31P NMR. The propylene polymerization catalysts were prepared by incorporating an internal donor, and the content of Ti, H and C in the catalysts was also checked by elemental analysis. The effect of dosage of the donor, the Al/Ti ratio and the polymerization temperature on the catalyst activity were studied, the results suggested that the dosage of donor, the Al/Ti ratio and the polymerization temperature could affect not only the activity of catalyst but also the isotacticity index of the polymer. A catalyst with high activity was selected, and the polypropylene formed in the presence of this catalyst had high isotacticity index.
文摘With the aging process, people been looked after properly in the old age has already become an important index to the national happiness index. Nowadays, government has a increasingly clear roadmap in promoting the development of pension system. Pension system unification refers to the same pension system for workers in public institutions and enterprises. It is a relative concept to the dual pension system. It has positive effect on social equity. But it also has many problems. In this article, author explained the relation between pension system unification and social equity on the basic of analyzing viewpoints of several scholars. And make comments by extending it and analyzing it.
文摘Opsaridium microlepis migrates for spawning during the rainy season （November to May） to major affluent rivers. Linthipe River is one of the major rivers, into which this species migrates. Determination of reproductive seasonality of O. microlepis is paramount in the improved management of this endangered species. Reproductive seasonality ofO. microlepis in the Linthipe River in Central Malawi was estimated using 546 specimens for 12 months. The GSI （Gonadosomatic Index） ranged between 5.6% and 13% for females and between 0.3% and 1.4% for males, respectively. GSI variation between the months was significantly different （one-way ANOVA （analysis of variance）, P 〈 0.05）. The peak breeding activity was observed between January to April. This was at the onset of rainy season while the condition factor of O. microlepis was found to be variable with lowest value in the month of August. The study revealed that for O. microlepis fishery to be sustainably exploited, proper management regimes should be instituted along the migratory rivers during the peak breeding periods. These sustainable methods need to be managed in a participatory manner together with the majority of people living along these rivers.
基金Supported by Hunan Provincial Natural Science Foundation of China under Grant No.2016JJ4036University Natural Science Foundation of Jiangsu Province under Grant No.14KJB120007the National Natural Science Foundation of China under Grant Nos.11504176and 11602084
文摘A three-dimensional autonomous chaotic system is discussed in this paper. Some basic dynamical properties of the system, including phase portrait, Poincar′e map, power spectrum, Kaplan–Yorke dimension, Lyapunov exponent spectra, signal amplitude and topological horseshoe are studied theoretically and numerically. The main finding by analysis is that the signal amplitude can be modulated via controlling the coefficients of the linear term, cross-product term and squared term simultaneously or respectively, and the phase of x3 can be modulated by the product of the coefficients of the linear term and cross-product term. Furthermore, scaling chaotic attractors of this system are achieved by modified projective synchronization with an optimization-based linear coupling method, which is safer for secure communications than the existed synchronization scheme since the scaling factors can be regarded as the security encoding key.
基金Supported by the Research Foundation of Education Bureau of Hunan Province of China under Grant No.13C372Jiangsu Provincial Natural Science Foundation of China under Grant No.14KJB120007the Outstanding Doctoral Dissertation Project of Special Funds under Grant No.27122
文摘This paper introduces the finding of a unified Lorenz-like system.By gradually tuning the only parameter d,the reported system belongs to Lorenz-type system in the sense defined by Clikovsky.Meanwhile,this system belongs to Lorenz-type system,Lu-type system,Chen-type system with d less than,equivalent to and greater than 1.5,respectively,according to the classification defined by Yang.However,this system can only generate a succession of Lorenz-like attractors.Some basic dynamical properties of the system are investigated theoretically and numerically.Moreover,the tracking control of the system with exponential convergence rate is studied.Theoretical analysis and computer simulation show that the proposed scheme can allow us to drive the output variable x\ to arbitrary reference signals exponentially,and the guaranteed exponential convergence rate can be estimated accurately.
