Steel 20Mn23AlV is a type of high aluminum steel with a very low ladle free-opening rate. The aluminum composition of 20Mn23AlV ranges from 1.6% to 2.45% ,which is significantly higher than other types of steel. Accor...Steel 20Mn23AlV is a type of high aluminum steel with a very low ladle free-opening rate. The aluminum composition of 20Mn23AlV ranges from 1.6% to 2.45% ,which is significantly higher than other types of steel. According to the real condition of 40 t ladle in steel-making plant of Baosteel Special Steel Company, previous works show that the key factors affecting the ladle free-opening rate of high aluminum steel in continuous casting are：sand material, accessories baking, ladle nozzle cleaning, the process and amount of adding sand, and the rate of argon stirring during refining. Therefore, improving the ladle filler sand quality, baking all of the raw materials, controlling the addition of ladle filler sand, cleaning the ladle nozzle, and optimizing argon stirring during the refining process can resolve the problem of a low ladle free-opening rate of high aluminum steel caused by the long ladle time of liquid steel.展开更多
Tourism in developing countries are some means of solving their economic problems and improving live standards of people and creates job opportunity for the host people in getting additional income and improve the dev...Tourism in developing countries are some means of solving their economic problems and improving live standards of people and creates job opportunity for the host people in getting additional income and improve the developments of the country. The result of tourism in terms of environmental, cultural, economic and social aspects has a greater effect for Ethiopia. Gondar, the center of Ethiopian art and culture, is famous in its many Imperial castles and the design and decoration of its churches. This land of castles and churches was founded by Emperor Fasiladas in 1930s and served as tourist attraction sites all over the world. The main challenge to attract international tourists in the study area is Scarce and insufficient promotion of the tourist attraction sites, Lack of broad information based on the internet about tourism information, and lack of organized information about tourism facilities & destinations. This study tries to identify tourist attraction elements of Gondor town and its surrounding area & to identify non spatial data’s essential for touristic activities to develop & propose a web based GIS portal for the improvement of tourism activity in the town. The main target of developing a web based GIS interactive map is to promote and improve tourism industry of the area. It has been produced using free and open source software’s for fast processing, displaying, sharing, and distribution of tourism information using world wide web. For the web services PHP, HTML script language and QGIS2leaflet plugins are used in the development of web GIS portal.展开更多
The rapid development of the technology of the web systems and GIS, in conjunction with the world economic crisis, formed the content for the promotion and development of free systems and open-source technologies. At ...The rapid development of the technology of the web systems and GIS, in conjunction with the world economic crisis, formed the content for the promotion and development of free systems and open-source technologies. At the same time, the tendency toward the standardization of data, metadata and services, with the aim of creating common “Language” for the reading and the dissemination of information available, is a basic research area in the global scientific community in this field. The development of WebGIS systems, taking advantage of the free technology, also contributes to finding more economical solutions, where the use of such systems is more directly accessible. The aim of this research work is, through the analysis of technologies for the Internet, and also the architecture of the WebGIS systems, to investigate the possibilities and to develop the appropriate free technologies, so as to design and implement a spatial content management system for the web. Search with the use of the latter, is the best response to the needs and visualization application maps, with scope in rural areas. In addition, reference is made to the existing content management systems, which provide both processing spatial data, and easily create a WebGIS application.展开更多
Cyclic acrylates, 2,2- dimethyl-5-methylene-1 , 3-dioxolan-4 -one and 2- phenyl-5-methylene-1,3-dioxolan-4-one, were synthesized successfully. The monomers were characterized by ~1H NMR, ^(13)C NMR, IR and elemental a...Cyclic acrylates, 2,2- dimethyl-5-methylene-1 , 3-dioxolan-4 -one and 2- phenyl-5-methylene-1,3-dioxolan-4-one, were synthesized successfully. The monomers were characterized by ~1H NMR, ^(13)C NMR, IR and elemental analysis or HRMS. Polymerization of the monomers were carried out at 120℃ with di-t-butylperoxide as initiator. The polymers were studied by ~1H NMR, ^(13)C NMR, UV and hydrolysis. The molecular weights of the resulting polymers were estimated by viscosity measurement and the extent of ring opening was estimated also by ~1H NMR and hydrolysis of the polymers and further confirmed by UV spectra.展开更多
The problem of Magnetohydrodynamic (MHD) free convection heat transfer in a square open cavity containing a heated circular cylinder at the centre has been investigated in this work. As boundary conditions of the cavi...The problem of Magnetohydrodynamic (MHD) free convection heat transfer in a square open cavity containing a heated circular cylinder at the centre has been investigated in this work. As boundary conditions of the cavity, the left vertical wall is kept at a constant heat flux, bottom and top walls are kept at different high and low temperature respectively. The remaining side wall is open. Finite element analysis based on Galerkin weighted Residual approach is used to visualize the temperature distribution and fluid flow solving two-dimensional governing mass, momentum and energy equations for steady state, natural convection flow in presence of magnetic field in side an open square cavity. A uniformly heated circular cylinder is located at the centre of the cavity. The object of this study is to describe the effects of MHD on the thermal fields and flow in presence of such heated circular cylinder by visualization of graph. The investigations are conducted for different values of Rayleigh number (Ra) and Hartmann number (Ha). The results show that the temperature field and flow pattern are significantly dependent on the above mentioned parameters.展开更多
This paper describes the synthesis and free radical ring-opening polymerization of 2-methyl-and 2-methyl-9-n-butyl (-7-methylene-1, 4, 6-trioxaspiro (4, 4) nonane). The structures of the two polymers were verified by ...This paper describes the synthesis and free radical ring-opening polymerization of 2-methyl-and 2-methyl-9-n-butyl (-7-methylene-1, 4, 6-trioxaspiro (4, 4) nonane). The structures of the two polymers were verified by IR, 'H and ^(13)C NMR spectra. The substituent on 9-position of 7-methylene-trioxaspiro (4, 4) nonane affects the structure of polymer and polymerization activity. The polymerization mechanism is discussed.展开更多
能量路由器的核心元件为双有源桥(dual active bridge,DAB)直流变压器,针对其短路故障时电流上升速率快,峰值大,导致DAB内部电力电子器件闭锁的问题,该文提出一种具有限流型结构的直流变压器,限流装置结构为从DAB高压侧H桥连接单相整流...能量路由器的核心元件为双有源桥(dual active bridge,DAB)直流变压器,针对其短路故障时电流上升速率快,峰值大,导致DAB内部电力电子器件闭锁的问题,该文提出一种具有限流型结构的直流变压器,限流装置结构为从DAB高压侧H桥连接单相整流桥,再与输出端口的限流电感相连。当直流系统发生短路故障时,限流型直流变压器采用混合控制算法进行整流,为限流电感提供钳位电压,限制故障电流的峰值,并与断路器配合实现无弧开断,该方法避免DAB中电力电子器件发生闭锁,快速实现故障限流和隔离。在仿真系统中搭建了基于10kV/750V直流变压器的限流型直流变压器的模型,仿真结果表明限流型直流变压器与断路器配合实现故障限流和隔离的有效性和可行性。展开更多
文摘Steel 20Mn23AlV is a type of high aluminum steel with a very low ladle free-opening rate. The aluminum composition of 20Mn23AlV ranges from 1.6% to 2.45% ,which is significantly higher than other types of steel. According to the real condition of 40 t ladle in steel-making plant of Baosteel Special Steel Company, previous works show that the key factors affecting the ladle free-opening rate of high aluminum steel in continuous casting are：sand material, accessories baking, ladle nozzle cleaning, the process and amount of adding sand, and the rate of argon stirring during refining. Therefore, improving the ladle filler sand quality, baking all of the raw materials, controlling the addition of ladle filler sand, cleaning the ladle nozzle, and optimizing argon stirring during the refining process can resolve the problem of a low ladle free-opening rate of high aluminum steel caused by the long ladle time of liquid steel.
文摘Tourism in developing countries are some means of solving their economic problems and improving live standards of people and creates job opportunity for the host people in getting additional income and improve the developments of the country. The result of tourism in terms of environmental, cultural, economic and social aspects has a greater effect for Ethiopia. Gondar, the center of Ethiopian art and culture, is famous in its many Imperial castles and the design and decoration of its churches. This land of castles and churches was founded by Emperor Fasiladas in 1930s and served as tourist attraction sites all over the world. The main challenge to attract international tourists in the study area is Scarce and insufficient promotion of the tourist attraction sites, Lack of broad information based on the internet about tourism information, and lack of organized information about tourism facilities & destinations. This study tries to identify tourist attraction elements of Gondor town and its surrounding area & to identify non spatial data’s essential for touristic activities to develop & propose a web based GIS portal for the improvement of tourism activity in the town. The main target of developing a web based GIS interactive map is to promote and improve tourism industry of the area. It has been produced using free and open source software’s for fast processing, displaying, sharing, and distribution of tourism information using world wide web. For the web services PHP, HTML script language and QGIS2leaflet plugins are used in the development of web GIS portal.
文摘The rapid development of the technology of the web systems and GIS, in conjunction with the world economic crisis, formed the content for the promotion and development of free systems and open-source technologies. At the same time, the tendency toward the standardization of data, metadata and services, with the aim of creating common “Language” for the reading and the dissemination of information available, is a basic research area in the global scientific community in this field. The development of WebGIS systems, taking advantage of the free technology, also contributes to finding more economical solutions, where the use of such systems is more directly accessible. The aim of this research work is, through the analysis of technologies for the Internet, and also the architecture of the WebGIS systems, to investigate the possibilities and to develop the appropriate free technologies, so as to design and implement a spatial content management system for the web. Search with the use of the latter, is the best response to the needs and visualization application maps, with scope in rural areas. In addition, reference is made to the existing content management systems, which provide both processing spatial data, and easily create a WebGIS application.
文摘Cyclic acrylates, 2,2- dimethyl-5-methylene-1 , 3-dioxolan-4 -one and 2- phenyl-5-methylene-1,3-dioxolan-4-one, were synthesized successfully. The monomers were characterized by ~1H NMR, ^(13)C NMR, IR and elemental analysis or HRMS. Polymerization of the monomers were carried out at 120℃ with di-t-butylperoxide as initiator. The polymers were studied by ~1H NMR, ^(13)C NMR, UV and hydrolysis. The molecular weights of the resulting polymers were estimated by viscosity measurement and the extent of ring opening was estimated also by ~1H NMR and hydrolysis of the polymers and further confirmed by UV spectra.
文摘The problem of Magnetohydrodynamic (MHD) free convection heat transfer in a square open cavity containing a heated circular cylinder at the centre has been investigated in this work. As boundary conditions of the cavity, the left vertical wall is kept at a constant heat flux, bottom and top walls are kept at different high and low temperature respectively. The remaining side wall is open. Finite element analysis based on Galerkin weighted Residual approach is used to visualize the temperature distribution and fluid flow solving two-dimensional governing mass, momentum and energy equations for steady state, natural convection flow in presence of magnetic field in side an open square cavity. A uniformly heated circular cylinder is located at the centre of the cavity. The object of this study is to describe the effects of MHD on the thermal fields and flow in presence of such heated circular cylinder by visualization of graph. The investigations are conducted for different values of Rayleigh number (Ra) and Hartmann number (Ha). The results show that the temperature field and flow pattern are significantly dependent on the above mentioned parameters.
基金Supported by National Natural Science Foundation of China
文摘This paper describes the synthesis and free radical ring-opening polymerization of 2-methyl-and 2-methyl-9-n-butyl (-7-methylene-1, 4, 6-trioxaspiro (4, 4) nonane). The structures of the two polymers were verified by IR, 'H and ^(13)C NMR spectra. The substituent on 9-position of 7-methylene-trioxaspiro (4, 4) nonane affects the structure of polymer and polymerization activity. The polymerization mechanism is discussed.
文摘能量路由器的核心元件为双有源桥(dual active bridge,DAB)直流变压器,针对其短路故障时电流上升速率快,峰值大,导致DAB内部电力电子器件闭锁的问题,该文提出一种具有限流型结构的直流变压器,限流装置结构为从DAB高压侧H桥连接单相整流桥,再与输出端口的限流电感相连。当直流系统发生短路故障时,限流型直流变压器采用混合控制算法进行整流,为限流电感提供钳位电压,限制故障电流的峰值,并与断路器配合实现无弧开断,该方法避免DAB中电力电子器件发生闭锁,快速实现故障限流和隔离。在仿真系统中搭建了基于10kV/750V直流变压器的限流型直流变压器的模型,仿真结果表明限流型直流变压器与断路器配合实现故障限流和隔离的有效性和可行性。
