以液压挖掘机的工作区域为对象,针对工作机构尺寸变化对挖掘范围及作业性能指标的影响进行研究,依据性能要求逆向为工作机构尺寸优化设计提供方向策略。分别考虑挖掘作业中的斗杆挖掘和铲斗挖掘典型工况,利用开发的工作装置运动分析软...以液压挖掘机的工作区域为对象,针对工作机构尺寸变化对挖掘范围及作业性能指标的影响进行研究,依据性能要求逆向为工作机构尺寸优化设计提供方向策略。分别考虑挖掘作业中的斗杆挖掘和铲斗挖掘典型工况,利用开发的工作装置运动分析软件绘制了相应的挖掘轨迹的包络曲线。分析工作机构中动臂、斗杆、铲斗尺寸变化对整机挖掘作业性能指标的影响规律,同时对工作机构进行动力学分析,并优化复合挖掘力。结果表明:动臂尺寸增加时,最大挖掘深度、挖掘半径分别增幅达5.56%、13.31%,最大挖掘高度、卸载高度增幅分别达51.36%、53.87%。斗杆尺寸增加使其4种主要工作尺寸总体变化率在5%以内,增加幅度较低,其中挖掘高度的相对增幅率是下降的。铲斗尺寸增加,最大挖掘深度增幅最大为2.7%,且相对增幅变化率均匀;最大挖掘高度、挖掘半径总体变化率在1.3%左右,最大卸载高度呈下降趋势。优化后获得较大的挖掘力为532.16 k N较斗杆挖掘和铲斗挖掘有较大的提升,并给出在主要工况下的挖掘路径。展开更多
To acquire a knowledge of the stress-strain state in the process of mining beforehand, a numerical method was used to simulate the stoping process of access mechanized panel mining in No. 3 ore-body of Tonglushan mine...To acquire a knowledge of the stress-strain state in the process of mining beforehand, a numerical method was used to simulate the stoping process of access mechanized panel mining in No. 3 ore-body of Tonglushan mine; and for the sake of obtaining better stability, the optimal panel dimension and access stoping sequence were researched. The results show that the integral stability of the mechanized panel of No. 3 ore-body is passable in the process of winning at full level height; the stability of panel tends to be worse gradually with continuous increasing of panel width; and the better width of access panel in No.3 ore-body is less than 52 m. It is indicated that 3D elasto-plastic finite element method can make a satisfactory study of numerical simulation on the panel stability and its structural dimension in the test for the upward access mechanized-panel mining. The results of the theoretical calculation and analysis accord with the actual situation from the field ground pressure monitoring.展开更多
Industries that suitable for cluster innovation are often intensive in knowledge and technology, with high capital agglomeration; closely interact and corporate with each other through resources sharing. Its developme...Industries that suitable for cluster innovation are often intensive in knowledge and technology, with high capital agglomeration; closely interact and corporate with each other through resources sharing. Its development is depend on many factors, such as technical reliability, human resources, its own growth potential, competition, market prospects, and the government policies, etc.. Aimed at clarifying the path selection mechanism of cluster innovation, this paper first analyze the connotation of cluster innovation and its inside factors＇ bonding relationship, then exploring the triggers and path forming dimensions of cluster innovation. Finally, it builds a path-selection model on cluster innovation, and discusses the characteristics of each side.展开更多
Small size axial flow fans are used as a cooling component for computers,electronic equipment and other electronic components.With the increasing power of electrical equipment,the demand for lower noise and higher ven...Small size axial flow fans are used as a cooling component for computers,electronic equipment and other electronic components.With the increasing power of electrical equipment,the demand for lower noise and higher ventilation of cooling fan is also increasing.Traditional methods of improving ventilation by raising the fan's rotation speed causes a decrease in efficiency and an increase in noise.In this paper,different structures of fans were simulated,and as a result,the counter-rotating fan can achieve higher pressure,efficiency and facilitate ventilation in a smaller space.Furthermore,some other conclusions are as follows:(1) Higher pressure rise can be obtained by a counter-rotating fan than by the two-stage rotor fan in the same axial length.Meanwhile,the counter-rotating fan has a broader work scope.(2) The main noise type of the counter-rotating fan is rotating noise;the small peak pulse caused by vortex noise mainly due to the eddy current produced by small eddies.(3) When the distance of counter-rotating fans is smaller than 2 times the chord,the greater distance the greater total pressure of the circum-averages and along the axial direction,the total pressure begin to decline until the distance is three times the chord,so there is an optimal distance between rotors.The simulation results are of important significance to the quantitative analysis and optimization design of the counter-rotating fan.展开更多
Uniform core-shell SiO2@Fe_3O_4@C microspheres were prepared by a one-step hydrothermal method with SiO_2 microspheres as the template, and the hollow Fe_3O_4@C(HFC) microspheres were achieved via etching SiO_2 templa...Uniform core-shell SiO2@Fe_3O_4@C microspheres were prepared by a one-step hydrothermal method with SiO_2 microspheres as the template, and the hollow Fe_3O_4@C(HFC) microspheres were achieved via etching SiO_2 template. By changing the sizes of SiO_2 microspheres, a series of HFC microspheres with variable cavity sizes were obtained to study the relationship between cavity size and microwave absorbing(MA) performance for the first time. The morphology and structure of samples were characterized in detail. The results showed that the MA performance of HFC sample depended on its cavity size. In particular, the hollow structure was good for improving MA performance and could make MA move to the high-frequency region. More importantly, as the cavity size increases, the resonance frequency of HFC-i(i=1,2, 3, 4) samples moved to a low frequency, and the optimal matching thickness of HFC-i samples was increasing. Among all HFC-i samples, HFC-3 showed the most excellent MA performance,which could be mainly explained by the quarter-wavelength matching model, intrinsical magnetic and dielectric loss. Furthermore,the MA performance of HFC mixture blended by the equal mass fraction of HFC-2, HFC-3 and HFC-4 was the comprehensive results of three HFC-i samples. All the above suggested that the cavity size in HFC sample had a great influence on the MA performance.展开更多
文摘以液压挖掘机的工作区域为对象,针对工作机构尺寸变化对挖掘范围及作业性能指标的影响进行研究,依据性能要求逆向为工作机构尺寸优化设计提供方向策略。分别考虑挖掘作业中的斗杆挖掘和铲斗挖掘典型工况,利用开发的工作装置运动分析软件绘制了相应的挖掘轨迹的包络曲线。分析工作机构中动臂、斗杆、铲斗尺寸变化对整机挖掘作业性能指标的影响规律,同时对工作机构进行动力学分析,并优化复合挖掘力。结果表明:动臂尺寸增加时,最大挖掘深度、挖掘半径分别增幅达5.56%、13.31%,最大挖掘高度、卸载高度增幅分别达51.36%、53.87%。斗杆尺寸增加使其4种主要工作尺寸总体变化率在5%以内,增加幅度较低,其中挖掘高度的相对增幅率是下降的。铲斗尺寸增加,最大挖掘深度增幅最大为2.7%,且相对增幅变化率均匀;最大挖掘高度、挖掘半径总体变化率在1.3%左右,最大卸载高度呈下降趋势。优化后获得较大的挖掘力为532.16 k N较斗杆挖掘和铲斗挖掘有较大的提升,并给出在主要工况下的挖掘路径。
基金Project(2001BA901A09) supported by the Key Program of the 10th Five year Plan of China
文摘To acquire a knowledge of the stress-strain state in the process of mining beforehand, a numerical method was used to simulate the stoping process of access mechanized panel mining in No. 3 ore-body of Tonglushan mine; and for the sake of obtaining better stability, the optimal panel dimension and access stoping sequence were researched. The results show that the integral stability of the mechanized panel of No. 3 ore-body is passable in the process of winning at full level height; the stability of panel tends to be worse gradually with continuous increasing of panel width; and the better width of access panel in No.3 ore-body is less than 52 m. It is indicated that 3D elasto-plastic finite element method can make a satisfactory study of numerical simulation on the panel stability and its structural dimension in the test for the upward access mechanized-panel mining. The results of the theoretical calculation and analysis accord with the actual situation from the field ground pressure monitoring.
文摘Industries that suitable for cluster innovation are often intensive in knowledge and technology, with high capital agglomeration; closely interact and corporate with each other through resources sharing. Its development is depend on many factors, such as technical reliability, human resources, its own growth potential, competition, market prospects, and the government policies, etc.. Aimed at clarifying the path selection mechanism of cluster innovation, this paper first analyze the connotation of cluster innovation and its inside factors＇ bonding relationship, then exploring the triggers and path forming dimensions of cluster innovation. Finally, it builds a path-selection model on cluster innovation, and discusses the characteristics of each side.
基金The author acknowledges the support of Zhejiang Provincial Natural Science Foundation (No.R107635)Zhejiang Provincial Key Science Foundation (2008 C11027)National Natural Science Foundation of China (No.50735004)
文摘Small size axial flow fans are used as a cooling component for computers,electronic equipment and other electronic components.With the increasing power of electrical equipment,the demand for lower noise and higher ventilation of cooling fan is also increasing.Traditional methods of improving ventilation by raising the fan's rotation speed causes a decrease in efficiency and an increase in noise.In this paper,different structures of fans were simulated,and as a result,the counter-rotating fan can achieve higher pressure,efficiency and facilitate ventilation in a smaller space.Furthermore,some other conclusions are as follows:(1) Higher pressure rise can be obtained by a counter-rotating fan than by the two-stage rotor fan in the same axial length.Meanwhile,the counter-rotating fan has a broader work scope.(2) The main noise type of the counter-rotating fan is rotating noise;the small peak pulse caused by vortex noise mainly due to the eddy current produced by small eddies.(3) When the distance of counter-rotating fans is smaller than 2 times the chord,the greater distance the greater total pressure of the circum-averages and along the axial direction,the total pressure begin to decline until the distance is three times the chord,so there is an optimal distance between rotors.The simulation results are of important significance to the quantitative analysis and optimization design of the counter-rotating fan.
基金supported by the National Natural Science Foundation of China (20104017)the College Students’ Science and Technology Innovation Activities Plan of Zhejiang (2014R404056)
文摘Uniform core-shell SiO2@Fe_3O_4@C microspheres were prepared by a one-step hydrothermal method with SiO_2 microspheres as the template, and the hollow Fe_3O_4@C(HFC) microspheres were achieved via etching SiO_2 template. By changing the sizes of SiO_2 microspheres, a series of HFC microspheres with variable cavity sizes were obtained to study the relationship between cavity size and microwave absorbing(MA) performance for the first time. The morphology and structure of samples were characterized in detail. The results showed that the MA performance of HFC sample depended on its cavity size. In particular, the hollow structure was good for improving MA performance and could make MA move to the high-frequency region. More importantly, as the cavity size increases, the resonance frequency of HFC-i(i=1,2, 3, 4) samples moved to a low frequency, and the optimal matching thickness of HFC-i samples was increasing. Among all HFC-i samples, HFC-3 showed the most excellent MA performance,which could be mainly explained by the quarter-wavelength matching model, intrinsical magnetic and dielectric loss. Furthermore,the MA performance of HFC mixture blended by the equal mass fraction of HFC-2, HFC-3 and HFC-4 was the comprehensive results of three HFC-i samples. All the above suggested that the cavity size in HFC sample had a great influence on the MA performance.
