新型交叉孔道式平板热管的性能研究

提出了一种设计交叉孔道式平板热管的新思路,按照这种方法设计加工的新型结构的平板热管均热器具有较强的轴向和径向导热能力,能明显减小导热热阻;特殊的孔道结构增强了毛细作用力,能有效强化相变换热。实验测试了不同热流密度和不同充液率下该热管正常工作时的稳态温度分布,给出了不同充液率和不同热流下的热阻,得到了热管的最佳充液率,证...     

Smallest Vertex‐Transitive Graphs of Given Degree and Diameter

For every d and k, we determine the smallest order of a vertex‐transitive graph of degree d and diameter k, and in each such case we show that this order is achieved by a Cayley graph.     

Unitary Graphs

Unitary graphs are arc‐transitive graphs with vertices the flags of Hermitian unitals and edges defined by certain elements of the underlying finite fields. They played a significant role in a recent classification of a class of arc‐transitive graphs that admit an automorphism group acting imprimitively on the vertices. In this article, we prove that all unitary graphs are connected of diameter two and girth three. Based on this, we obtain, for any prime power , a lower bound of order on the maximum number of vertices in an arc‐transitive graph of degree and diameter two.     

On connected dominating sets of restricted diameter

A connected dominating set (CDS) is commonly used to model a virtual backbone of a wireless network. To bound the distance that information must travel through the network, we explicitly restrict the diameter of a CDS to be no more than s leading to the concept of a dominating s-club. We prove that for any fixed positive integer s it is NP-complete to determine if a graph has a dominating s  -club, even when the graph has diameter s+1$s+1$. As a special case it is NP-complete to determine if a graph of diameter two has a dominating clique. We then propose a compact integer programming formulation for the related minimization problem, enhance the approach with variable fixing rules and valid inequalities, and present computational results.     

The thresholds for diameter 2 in random Cayley graphs

Given a group G, the model denotes the probability space of all Cayley graphs of G where each element of the generating set is chosen independently at random with probability p. In this article we show that for any and any family of groups G_k of order n_k for which , a graph with high probability has diameter at most 2 if and with high probability has diameter greater than 2 if . We also provide examples of families of graphs which show that both of these results are best possible. Of particular interest is that for some families of groups, the corresponding random Cayley graphs achieve Diameter 2 significantly faster than the Erd?s‐Renyi random graphs. © 2014 Wiley Periodicals, Inc. Random Struct. Alg., 45, 218–235, 2014     

关于三分Cantor集的构造的一个基本性质及其应用

本文提出了三分 Cantor集的构造的一个基本性质 .作为应用 ,给出了计算三分 Cantor集的简明的初等的计算方法 ,另外还得到了一列有趣的对数不等式     

Investigation of droplet size distribution for liquid-liquid emulsions in Taylor-Couette flows

In this paper, we investigate oil-in-water emulsions in a Taylor-Couette flow. A high-speed camera was employed to record the formation of those emulsions, and image processing was used to obtain the diameter of the droplets. No surfactants were added in order to study the pure effect of the fluid dynamical forces on the droplets. The results for three different oil-in-water emulsions show that the Sauter mean diameter considerably depends on the local shear rate and the material properties and that the droplet size distribution follows a log-normal distribution. We, therefore, propose to express the Sauter mean diameter normalized by Prandtl mixing length in terms of a correlation, which is based on the Kolmogorov turbulence theory. This correlation subsequently depends on the local shear rate and the material properties such as viscosity, density, and interfacial tension. The predictions of the correlation show fairly good agreement with the experimental measurement the Sauter mean diameter. Finally, comparing the predictions of the correlation to the data presented by Eskin et al. [Chem. Eng. Sci. 161 36–47; 2017] shows excellent agreement in the case, where the droplets are larger than the Kolmogorov length scale.     

半导体冰箱冷热端散热条件实验研究

半导体制冷器件是一种高热流密度元件,在红外测量、低温超导、生物医学、空间技术等领域有重要的应用,还可开发成专用制冷装置,适用于野外施工、勘探,考古以及郊游等户外活动食品饮料的保鲜,也可用于食品、饮料及医用疫苗等的冷藏。在给定工况下,通过改善半导体器件的冷热端散热条件,可使系统制冷量和制冷性能系数大幅提高。本文设计了实验装置,特别设计了8种实验工况对采用强迫对流换热和热端采用热管换热器散热的实际半导体制冷装置进行了实验分析,提出了改善半导体制冷元件散热条件的具体措施。     

Temperature control of electrohydrodynamic micro heat pipes

Active thermal control was achieved by using an electrohydrodynamically (EHD) assisted micro heat pipe array. A simulation model of temperature control of EHD micro heat pipes was established in a Matlab Sinulink environment. An experimental model was designed and fabricated to verify the model and identify the factors most influential to the thermal control via EHD micro heat pipe array. Good correspondence between simulations and experiments was achieved. Electric field intensity, set-point temperature and the gap between the upper and lower set-point temperatures were shown to have a dramatic influence on the temperature control.