为研究加卸载对盾构隧道结构受力和材料损伤状态的影响,基于混凝土塑性损伤本构、非线性接触理论和Python二次开发,用全周单向受压弹簧模拟地层反力,建立二维管片-接缝不连续模型和三维精细化管片-接缝不连续模型,模拟不同土质中(固结...为研究加卸载对盾构隧道结构受力和材料损伤状态的影响,基于混凝土塑性损伤本构、非线性接触理论和Python二次开发,用全周单向受压弹簧模拟地层反力,建立二维管片-接缝不连续模型和三维精细化管片-接缝不连续模型,模拟不同土质中(固结黏性土、硬质黏性土、中等程度黏性)盾构隧道上方不同加卸载水平下的结构变形、材料内力以及材料损伤变化规律,并讨论了螺栓异常工作对结构的影响,得到了不同土质中径向相对位移、接头张开量、材料应力和混凝土损伤因子关于加卸载量的关系曲线,及接头张开量、螺栓应力水平分别在预紧力损失和锈蚀深度两种异常状态的变化曲线.研究结果表明:从结构变形宏观指标给出了3种土质条件下加卸载的荷载安全值分别为510、340 k Pa和170 k Pa;从材料应力水平及损伤程度给出了加卸载的荷载安全值分别为340、170 k Pa和170 k Pa;螺栓预紧力损失对结构的影响主要受拱顶接头张开量控制,螺栓锈蚀对结构的影响主要受螺栓应力水平控制,且锈蚀深度的安全限值为6 mm.展开更多
In this study,thermo-fluid characteristics of elliptical annular finned tube heat exchanger were numerically studied in detail.Transition SST model was utilized to simulate turbulent flow.Effects of air velocities,hor...In this study,thermo-fluid characteristics of elliptical annular finned tube heat exchanger were numerically studied in detail.Transition SST model was utilized to simulate turbulent flow.Effects of air velocities,horizontal to vertical fin diameter ratios,and fin densities were examined in detail.The simulations indicate superior performance of elliptical fin layout.It was shown that pressure drop of annular elliptical fin can be only one half of that of a circular annular fin while containing comparable heat transfer performance.The vertical elliptical annular fin may even contain a higher heat transfer performance over circular fin.Correlations are proposed to estimate the Nu number and pressure drop based on the annular circular fin.The maximum deviations between the proposed correlations and simulations regarding pressure drop and heat transfer coefficient are 5.6%and 3.2%,respectively.For further elaboration of the superiority of the elliptical layout from the second law perspective,normalized entropy generation was also studied.In all cases,the entropy generation rate in circular fin was higher than that of an elliptical fin.展开更多
This article introduces the analysis of strategic management of film production companies. The first part presents processes and models of strategic management and introduces a new and unified model of strategic manag...This article introduces the analysis of strategic management of film production companies. The first part presents processes and models of strategic management and introduces a new and unified model of strategic management. It is noteworthy that the film/film industry value chain helps to understand the notion that the links between separate stages have an impact on the company＇s competitive advantage and reveal how the main product in the film industry, the feature film, is developed. Therefore, the following part analyses models and composition of film industry value models. The final part of this article analyses the main features of a film production company and the sources of funding thereof. The strategic model of independent film production companies is based on the characteristics of strategic management and the value chain models of independent film projects.展开更多
文摘为研究加卸载对盾构隧道结构受力和材料损伤状态的影响,基于混凝土塑性损伤本构、非线性接触理论和Python二次开发,用全周单向受压弹簧模拟地层反力,建立二维管片-接缝不连续模型和三维精细化管片-接缝不连续模型,模拟不同土质中(固结黏性土、硬质黏性土、中等程度黏性)盾构隧道上方不同加卸载水平下的结构变形、材料内力以及材料损伤变化规律,并讨论了螺栓异常工作对结构的影响,得到了不同土质中径向相对位移、接头张开量、材料应力和混凝土损伤因子关于加卸载量的关系曲线,及接头张开量、螺栓应力水平分别在预紧力损失和锈蚀深度两种异常状态的变化曲线.研究结果表明:从结构变形宏观指标给出了3种土质条件下加卸载的荷载安全值分别为510、340 k Pa和170 k Pa;从材料应力水平及损伤程度给出了加卸载的荷载安全值分别为340、170 k Pa和170 k Pa;螺栓预紧力损失对结构的影响主要受拱顶接头张开量控制,螺栓锈蚀对结构的影响主要受螺栓应力水平控制,且锈蚀深度的安全限值为6 mm.
文摘In this study,thermo-fluid characteristics of elliptical annular finned tube heat exchanger were numerically studied in detail.Transition SST model was utilized to simulate turbulent flow.Effects of air velocities,horizontal to vertical fin diameter ratios,and fin densities were examined in detail.The simulations indicate superior performance of elliptical fin layout.It was shown that pressure drop of annular elliptical fin can be only one half of that of a circular annular fin while containing comparable heat transfer performance.The vertical elliptical annular fin may even contain a higher heat transfer performance over circular fin.Correlations are proposed to estimate the Nu number and pressure drop based on the annular circular fin.The maximum deviations between the proposed correlations and simulations regarding pressure drop and heat transfer coefficient are 5.6%and 3.2%,respectively.For further elaboration of the superiority of the elliptical layout from the second law perspective,normalized entropy generation was also studied.In all cases,the entropy generation rate in circular fin was higher than that of an elliptical fin.
文摘This article introduces the analysis of strategic management of film production companies. The first part presents processes and models of strategic management and introduces a new and unified model of strategic management. It is noteworthy that the film/film industry value chain helps to understand the notion that the links between separate stages have an impact on the company＇s competitive advantage and reveal how the main product in the film industry, the feature film, is developed. Therefore, the following part analyses models and composition of film industry value models. The final part of this article analyses the main features of a film production company and the sources of funding thereof. The strategic model of independent film production companies is based on the characteristics of strategic management and the value chain models of independent film projects.
