Sequential properties of function spaces with the compact-open topology

The main results of the paper are:

(1)

If X is metrizable but not locally compact topological space, then Ck(X) contains a closed copy of S₂, and hence does not have the property AP;

(2)

For any zero-dimensional Polish X, the space Ck(X,2) is sequential if and only if X is either locally compact or the derived set X^′ is compact; and

(3)

All spaces of the form Ck(X,2), where X is a non-locally compact Polish space whose derived set is compact, are homeomorphic, and have the topology determined by an increasing sequence of Cantor subspaces, the nth one nowhere dense in the (n+1)st.

     

C_m·F_n和C_m·Cn的邻点可区别VE-全色数

根据冠图C_m·F_n和C_m·C_n的结构性质,用穷染,递推的方法,讨论了两类冠图C_m·F_n和C_m·C_n的邻点可区别VE-全染色,得到了相应的色数,当m≥3,n≥3时,x′_(at)~(ve)(C_m·F_n)=4,x′_(at)~(ve)(C_m·C_n)=(?),并给出了一种染色方案.     

Experimental and Numerical Study of Film Cooling with Internal Coolant Cross-Flow Effects

This study experimentally and numerically analyzes the effect of the coolant cross-flow on film-cooling effectiveness. The three kinds of film holes considered are cylindrical, fan-shaped, and trenched holes. The results show that the internal coolant flow has a large effect on film cooling. The film-cooling effectiveness of the cross-flow coolant model is larger than that of the plenum model for the cylindrical and trenched holes, but it is less for the fan-shaped hole. A comparison of the experimental and numerical results shows that the Reynolds averaged Navier–Stokes model exaggerated the coolant diffusion downstream but underestimates the lateral distribution.     

Three-dimensional computation for flow-induced vibrations of an upstream circular cylinder in two tandem circular cylinders

It is well known from a lot of experimental data that fluid forces acting on two tandem circular cylinders are quite different from those acting on a single circular cylinder. Therefore, we first present numerical results for fluid forces acting on two tandem circular cylinders, which are mounted at various spacings in a smooth flow, and second we present numerical results for flow-induced vibrations of the upstream circular cylinder in the tandem arrangement. The two circular cylinders are arranged at close spacing in a flow field. The upstream circular cylinder is elastically placed by damper-spring systems and moves in both the in-line and cross-flow directions. In such models, each circular cylinder is assumed as a rigid body. On the other hand, we do not introduce a turbulent model such as the Large Eddy Simulation (LES) or Reynolds Averaged Navier-Stokes (RANS) models into the numerical scheme to compute the fluid flow. Our numerical procedure to capture the flow-induced vibration phenomena of the upstream circular cylinder is treated as a fluid-structure interaction problem in which the ideas of weak coupling is taken into consideration.     

煤矿大型风机设备磨损监控系统设计

针对煤矿大型风机设备主轴磨损而影响风机工作效率的问题,在对大型风机设备磨损故障的生成原因分析后,根据系统需求设计实现了系统的硬件模块和软件模块,通过传感器电路对大型风机设备的输入输出功率、出风量、主轴转速等参数进行采集,系统软件在对数据进行综合分析后将检测结果显示在液晶屏上,实时输出大型风机设备的运行状态以及主轴磨损状况,从而保证了风机的运行效率,避免设备故障的发生。通过系统测试表明本系统可以实时输出风机设备的主轴磨损程度监测结果,且风机设备的风量、风压、功率和效率等主要参数的测量精度高。     

模糊控制技术在隧道射流风机中的应用

不管是在铁路还是公路隧道中射流风机都属于隧道内的大功率运行设备,其能否合理、有效的运行直接影响着隧道内的环境状态和运营成本;文章以公路隧道为例,在分析现有隧道射流风机控制方法的基础上,提出运用模糊控制技术对射流风机进行控制的设计方案;首先用MATLAB模糊逻辑工具箱设计模糊控制器并创建了模糊控制规则表,然后对利用iFIX下的VBA开发环境在后台自动运行模糊控制程序完成仿真;根据CO的浓度变化以及在实验过程中风机利用的数量和时间证明该系统具有良好的控制性能,实时性强,隧道运行环境改善明显。     

新媒体环境中品牌粉丝效应形成机理研究

随着新媒体技术的不断发展以及消费模式的变迁,电子商务呈现出新型业态,对品牌新媒体营销提出了新的挑战。消费者的品牌消费已经从传统的功能性需求转移到更多的价值需求,营销领域的“粉丝效应”应运而生。本文即研究新媒体环境中粉丝效应的形成机理。结合新媒体环境,文中描述了粉丝效应的概念及内涵,探讨了新媒体环境中新型电商的业态及价值产出模式的变革,提出了粉丝效应的实现过程并实证分析了粉丝效应的形成机理。文中提出粉丝效应实现的三种影响因素,包括品牌体验、品牌认同、品牌形象。研究结果表明,品牌体验对品牌认同有正向影响;品牌认同分为个人品牌认同及社会品牌认同,个人品牌认同对社会品牌认同有正向影响;品牌认同对品牌形象有正向影响;品牌认同和品牌形象均对品牌粉丝效应有正向影响。     

外平面图的弱完备染色

假设G=（V,E,F）是一个平面图。如果e₁和e₂是G中两条相邻边且在关联的面的边界上连续出现,那么称e₁和e₂面相邻。图G的一个弱完备k-染色是指存在一个从V ∪ E ∪ F到k色集合{1, …, K}的映射,使得任意两个相邻点,两个相邻面,两条面相邻的边,以及V ∪ E ∪ F中任意两个相关联的元素都染不同的颜色。若图G有一个弱完备k-染色,则称G是弱完备k-可染的。平面图G的弱完备色数是指G是弱完备k-可染的正整数k的最小值,记成χ_vef（G）。2016年,Fabrici等人猜想：每个无环且无割边的连通平面图是弱完备7-可染的。证明外平面图满足猜想,即外平面图是弱完备7-可染的。     

An improved genetic algorithm and its applications to the optimisation design of an aspirated compressor profile

Genetic algorithm (GA) is a widely used method for numerical optimisation owing to their good global search ability; however, their local search ability has an obvious shortcoming. To improve local search ability, this paper introduces a simplex method and combines it with a GA to form an improved genetic algorithm (IGA). In the IGA, at each generation of the original GA, high‐fitness individuals are selected as vertices of a simplex, and then a one‐dimensional search within the simplex is conducted to obtain the most‐fit individuals while replacing the inferior ones. Typical test functions show that the IGA can effectively improve the optimisation effect over that of the original GA. To further verify the IGA's practicability, an aspirated compressor profile is optimised with profile, suction flow rate and suction flow location as coupled design parameters. The results again show that the IGA has a better optimising effect than the GA. In addition, it is also verified that coupling the profile and suction flow parameters results in a design that outperforms the uncoupled design; therefore, designing an aspirated compressor blade by arranging suction flow on a conventional blade without considering suction flow is not a good method. Copyright © 2015 John Wiley & Sons, Ltd.     

气液叉流条件下受热液膜传热特性

在气液叉流条件下,就不同气相雷诺数和液膜雷诺数对液膜传热特性影响进行了实验研究.结果表明：对于确定的被冷却水水温,在液膜雷诺数增加的过程中,液膜厚度逐渐增加,热阻增加,削弱液膜换热,但雷诺数上升使得液膜湍动强度增强,强化了液膜换热;在这两个因素的协同作用下,存在最佳液膜流动雷诺数,使得液膜的换热热阻最小,换热系数最大.层流时,热量传递受温度的影响较大;湍流时,热量传递对液膜进口温度的反应不如层流敏感.