基于"饿了么"网站获取中国287个地级市的外卖O2O(online to offline)数据,通过构建外卖O2O扩散指数和渗透指数来表征中国地级市外卖O2O电子商务发展水平和发育程度,从宏观尺度探究外卖O2O电子商务的空间发展逻辑,并对技术扩...基于"饿了么"网站获取中国287个地级市的外卖O2O(online to offline)数据,通过构建外卖O2O扩散指数和渗透指数来表征中国地级市外卖O2O电子商务发展水平和发育程度,从宏观尺度探究外卖O2O电子商务的空间发展逻辑,并对技术扩散假说和效率假说的适用性进行验证。结果表明:(1)整体上中国外卖O2O电子商务扩散与渗透过程表现出东部→中部→西部区域梯度递减规律,大部分地区扩散指数处于中等水平,少数城市的扩散指数处于低等或高等水平,空间分布相对均衡;渗透指数空间单极化现象明显,大部分地区渗透指数处于中低等水平,仅有少数城市处于高等水平。(2)外卖O2O扩散和渗透过程区域分异特征明显,扩散指数热点区范围较广,主要分布于东、中部地区,表现为从平原热点区到高原冷点区逐渐过渡的空间格局;渗透指数热点区范围较小,主要分布于东南沿海城市,未在全国尺度形成大范围集聚。(3)外卖O2O高扩散-高渗透区主要集中于上海、北京、深圳等经济发达城市,低扩散-低渗透区覆盖范围相对较广,主要分布在西北和西南地区,高扩散-低渗透区较为分散,其外卖O2O电子商务在实体商业的普及度和覆盖率虽然较高,但外卖O2O业态发育尚不成熟,未来市场潜力巨大。(4)中国外卖O2O电子商务空间扩散与渗透过程更契合技术扩散假说,高收入、高学历以及年轻化成为推动电子商务空间扩散和渗透的重要因素,而实体商业的低可达性在一定程度上并未促进电子商务发展。展开更多
The preparation of functional material titanium carbide by the carbothermal reduction of Ti-bearing blast furnace slag with microwave heating is an effective method for valuable metals recovery;it can alleviate the en...The preparation of functional material titanium carbide by the carbothermal reduction of Ti-bearing blast furnace slag with microwave heating is an effective method for valuable metals recovery;it can alleviate the environmental pressure caused by slag stocking.The dynamic dielectric parameters of Ti-bearing blast furnace slag/pulverized coal mixture under high-temperature heating are measured by the cylindrical resonant cavity perturbation method.Combining the transient dipole and large π bond delocalization polarization phenomena, the interaction mechanism of the microwave macroscopic non-thermal effect on the titanium carbide synthesis reaction was revealed.The material thickness range during microwave heating was optimized by the joint analysis of penetration depth and reflection loss, which is of great significance to the design of the microwave reactor for the carbothermal reduction of Ti-bearing blast furnace slag.展开更多
The numerical thermal mechanical simulation of radial forging process of steel H13 stepped shaft with GFM(Gesellschaft fur Fertigungstechnik und Maschinenbau) forging machine was carried out by three-dimensional finit...The numerical thermal mechanical simulation of radial forging process of steel H13 stepped shaft with GFM(Gesellschaft fur Fertigungstechnik und Maschinenbau) forging machine was carried out by three-dimensional finite element code DEFORM 3D.According to the effective plastic strain,the mean stress and the mean plastic strain distribution of the radial forging,the forging penetration efficiency(FPE) was studied throughout each operation.The results show that the effective plastic strain in the center of the forging is always greater than zero for the desirable larger axial drawing velocity.The mean stress in the center of the workpiece is proposed to describe hydrostatic pressure in this paper.There is compressive strain layer beneath the surface of the workpiece to be found,while there is tensile strain core in the center of the workpiece.These results could be a valuable reference for designing the similar forging operations.展开更多
文摘基于"饿了么"网站获取中国287个地级市的外卖O2O(online to offline)数据,通过构建外卖O2O扩散指数和渗透指数来表征中国地级市外卖O2O电子商务发展水平和发育程度,从宏观尺度探究外卖O2O电子商务的空间发展逻辑,并对技术扩散假说和效率假说的适用性进行验证。结果表明:(1)整体上中国外卖O2O电子商务扩散与渗透过程表现出东部→中部→西部区域梯度递减规律,大部分地区扩散指数处于中等水平,少数城市的扩散指数处于低等或高等水平,空间分布相对均衡;渗透指数空间单极化现象明显,大部分地区渗透指数处于中低等水平,仅有少数城市处于高等水平。(2)外卖O2O扩散和渗透过程区域分异特征明显,扩散指数热点区范围较广,主要分布于东、中部地区,表现为从平原热点区到高原冷点区逐渐过渡的空间格局;渗透指数热点区范围较小,主要分布于东南沿海城市,未在全国尺度形成大范围集聚。(3)外卖O2O高扩散-高渗透区主要集中于上海、北京、深圳等经济发达城市,低扩散-低渗透区覆盖范围相对较广,主要分布在西北和西南地区,高扩散-低渗透区较为分散,其外卖O2O电子商务在实体商业的普及度和覆盖率虽然较高,但外卖O2O业态发育尚不成熟,未来市场潜力巨大。(4)中国外卖O2O电子商务空间扩散与渗透过程更契合技术扩散假说,高收入、高学历以及年轻化成为推动电子商务空间扩散和渗透的重要因素,而实体商业的低可达性在一定程度上并未促进电子商务发展。
基金financially supported by the National Key R&D Program of China (No.2018YFC1900500)the National Natural Science Foundation of China (No.51961020)+1 种基金the Key Technology Research and Industrialization Application Demonstration Project of the Renewable Multi-energy Complementary (No.2018IB020)the Academician Workstation of Kefa Cen (No.2018IC085)。
文摘The preparation of functional material titanium carbide by the carbothermal reduction of Ti-bearing blast furnace slag with microwave heating is an effective method for valuable metals recovery;it can alleviate the environmental pressure caused by slag stocking.The dynamic dielectric parameters of Ti-bearing blast furnace slag/pulverized coal mixture under high-temperature heating are measured by the cylindrical resonant cavity perturbation method.Combining the transient dipole and large π bond delocalization polarization phenomena, the interaction mechanism of the microwave macroscopic non-thermal effect on the titanium carbide synthesis reaction was revealed.The material thickness range during microwave heating was optimized by the joint analysis of penetration depth and reflection loss, which is of great significance to the design of the microwave reactor for the carbothermal reduction of Ti-bearing blast furnace slag.
文摘The numerical thermal mechanical simulation of radial forging process of steel H13 stepped shaft with GFM(Gesellschaft fur Fertigungstechnik und Maschinenbau) forging machine was carried out by three-dimensional finite element code DEFORM 3D.According to the effective plastic strain,the mean stress and the mean plastic strain distribution of the radial forging,the forging penetration efficiency(FPE) was studied throughout each operation.The results show that the effective plastic strain in the center of the forging is always greater than zero for the desirable larger axial drawing velocity.The mean stress in the center of the workpiece is proposed to describe hydrostatic pressure in this paper.There is compressive strain layer beneath the surface of the workpiece to be found,while there is tensile strain core in the center of the workpiece.These results could be a valuable reference for designing the similar forging operations.
