稀土元素示踪法从上世纪90年代开始逐渐被相关学者重视,并在坡面土壤侵蚀的研究中得到越来越广泛的应用。笔者采用CiteSpace软件和文献计量学方法,以Web of Science数据库核心合集和中国知网(CNKI)数据库核心期刊为数据源,分析了近30年...稀土元素示踪法从上世纪90年代开始逐渐被相关学者重视,并在坡面土壤侵蚀的研究中得到越来越广泛的应用。笔者采用CiteSpace软件和文献计量学方法,以Web of Science数据库核心合集和中国知网(CNKI)数据库核心期刊为数据源,分析了近30年国内外稀土元素示踪法在坡面侵蚀研究的发展历程。研究发现:①总体而言,国内稀土元素示踪法在坡面侵蚀中的应用在理论和实践层面已经从初步探索走向了成熟;②随着研究的深入,稀土元素示踪法的研究与相关学科交叉更加密切,并在微观探索和宏观调控方面取得一定进展;③未来发展趋势来看,宏观方面趋向和生态系统、气候变化等互相作用机理的研究,微观方向趋向对团聚体等微观颗粒的迁移研究;④在国际相关研究方面,对于稀土元素示踪法在坡面侵蚀的应用从多个方面和角度做了大量的研究,我国的相关研究相较于国外顶尖水平的研究仍存在一定差距。展开更多
A two-dimensional computational fluid dynamics model was established to simulate the friction stir butt-welding of 6061 aluminum alloy. The dynamic mesh method was applied in this model to make the tool move forward a...A two-dimensional computational fluid dynamics model was established to simulate the friction stir butt-welding of 6061 aluminum alloy. The dynamic mesh method was applied in this model to make the tool move forward and rotate in a manner similar to a real tool, and the calculated volumetric source of energy was loaded to establish a similar thermal environment to that used in the experiment. Besides, a small piece of zinc stock was embedded into the workpiece as a trace element. Temperature fields and vector plots were determined using a finite volume method, which was indirectly verified by traditional metallography. The simulation result indicated that the temperature distribution was asymmetric but had a similar tendency on the two sides of the welding line. The maximum temperature on the advancing side was approximately 10 K higher than that on the retreating side. Furthermore, the precise process of material flow behavior in combination with streamtraces was demonstrated by contour maps of the phases. Under the shearing force and forward extrusion pressure, material located in front of the tool tended to move along the tangent direction of the rotating tool. Notably, three whirlpools formed under a special pressure environment around the tool, resulting in a uniform composition distribution.展开更多
文摘稀土元素示踪法从上世纪90年代开始逐渐被相关学者重视,并在坡面土壤侵蚀的研究中得到越来越广泛的应用。笔者采用CiteSpace软件和文献计量学方法,以Web of Science数据库核心合集和中国知网(CNKI)数据库核心期刊为数据源,分析了近30年国内外稀土元素示踪法在坡面侵蚀研究的发展历程。研究发现:①总体而言,国内稀土元素示踪法在坡面侵蚀中的应用在理论和实践层面已经从初步探索走向了成熟;②随着研究的深入,稀土元素示踪法的研究与相关学科交叉更加密切,并在微观探索和宏观调控方面取得一定进展;③未来发展趋势来看,宏观方面趋向和生态系统、气候变化等互相作用机理的研究,微观方向趋向对团聚体等微观颗粒的迁移研究;④在国际相关研究方面,对于稀土元素示踪法在坡面侵蚀的应用从多个方面和角度做了大量的研究,我国的相关研究相较于国外顶尖水平的研究仍存在一定差距。
基金Project(51475232)supported by the National Natural Science Foundation of China
文摘A two-dimensional computational fluid dynamics model was established to simulate the friction stir butt-welding of 6061 aluminum alloy. The dynamic mesh method was applied in this model to make the tool move forward and rotate in a manner similar to a real tool, and the calculated volumetric source of energy was loaded to establish a similar thermal environment to that used in the experiment. Besides, a small piece of zinc stock was embedded into the workpiece as a trace element. Temperature fields and vector plots were determined using a finite volume method, which was indirectly verified by traditional metallography. The simulation result indicated that the temperature distribution was asymmetric but had a similar tendency on the two sides of the welding line. The maximum temperature on the advancing side was approximately 10 K higher than that on the retreating side. Furthermore, the precise process of material flow behavior in combination with streamtraces was demonstrated by contour maps of the phases. Under the shearing force and forward extrusion pressure, material located in front of the tool tended to move along the tangent direction of the rotating tool. Notably, three whirlpools formed under a special pressure environment around the tool, resulting in a uniform composition distribution.
