Effect of Bubble Contact Diameter on Bubble Departure Size in Flow Boiling

The growth and departure of bubbles on a vertical heated wall of an annular channel in flow boiling were observed by a high-speed camera, and the bubble contact diameter and bubble departure diameter were measured. It was found that bubble departure diameters were different among different nucleation sites in the same boiling area (same test condition, same surface roughness). Force balance on a single bubble attached to the heated surface was also analyzed to explain this phenomenon. The theoretical research results show that bubble contact diameter has a significant influence on bubble departure diameter, and the corresponding departure diameter is larger as the bubble contact diameter is larger. This agrees with the visual experimental results.     

太赫兹mesh带通滤波器的设计与仿真

基于太赫兹波的大气吸收窗口,设计了一款四级级联的太赫兹mesh带通滤波器。此滤波器的中心频率为0.25 THz,在3 dB处带宽为0.1 THz,在通带内的插入损耗为1.5 dB,纹波系数小于0.5 dB,在室温下通带内的透过率能达80%以上,且此滤波器的中心工作频率和带宽可以通过缩放mesh槽孔的尺寸来调节。利用电磁仿真软件HFSS,结合周期边界条件及理想匹配层吸收边界条件模拟了太赫兹mesh带通滤波器的mesh排列方式、介质衬底及不同入射角度的入射波、不同极化方式等因素对滤波器透过率、插入损耗的影响。     

A reduced form model for ESO valuation

In this paper we extend a reduced form model for the valuation of employee share options (ESOs) to incorporate employee departure, and company takeover. We also allow for performance linked vesting and other exotic features specific to ESOs. We clarify the assumptions underlying the reduced form model, and discuss their implications. We analyze the probabilistic structure of the model which includes an explicit characterization of the set of equivalent martingale measures, as well as the computation of the variance optimal martingale measure and the minimal martingale measure. Moreover, we deduce an additive decomposition of the relative entropy. Particular ESO specifications are studied emphasizing different aspects of the proposed framework. In this context, we also provide strict no-arbitrage bounds for ESO prices by applying optimal stopping. Furthermore, possible limitations of the proposed model are explored by examining departures from the crucial assumptions of no-arbitrage, i.e. by considering the effects of the employee having inside information.     

Crystal and molecular structure of [i-Pr2Si]4 and [(Me3SICH2)2Si]4 and some structural properties of cyclopolysilanes, [R1R2Si]n (n = 3-6)

The crystal structures of octaisopropylcyclotetrasilane [i-Pr₂Si]₄ (1) and octakis(trimethylsilylmethyl)cyclotetrasilane [(Me₃SiCH₂)₂Si]₄ (2) have been determined by means of X-ray diffraction analysis. Various crystallographic and structural data for the two compounds were recorded. The Si₄ rings of the compounds are nonplanar with quite large dihedral angles of 37.1° in (1) and 36.6° in (2), being comparable to that (36.8)° for [t-BuMeSi]₄ reported previously and other characteristic features in the structures of (1) and (2) were described. Some structural properties of the cyclic catenation systems, [R¹R²Si]_n (n = 3–6), including (1) and (2) were also discussed from a comparative viewpoint with respect to the ring shape and the relationship between ring size and Si-Si bond length.     

一种新型组合单元频率选择表面

为了实现频率选择表面(FSS)的平顶传输特性.选取矩形栅格和传统圆环的组合图形为基本单元,设计了一种新型组合图形单元的FSS.利用谱域法对这种新型FSS的单屏结构进行理论计算和分析.计算结果表明,这种新型的FSS单屏结构能够给出陡峭边缘和平顶的宽频带传输特性,平顶带宽可达8 GHz;同时能够把相邻很近的信号带分离开从而实现双重通信,例如在X波段和Ku波段的信号,并且对不同入射角度的电磁波保持稳定的双带特性.     

夹持方式对频率转换KDP晶体面形的影响

 针对惯性约束聚变（ICF）系统中大口径超薄KDP晶体在不同夹持和不同姿态下的面形变化,采用有限元分析软件ANSYS,建立了大口径超薄KDP晶体在不同夹持和不同姿态下的应变模型及其边界条件的确定方法,计算了四周简支正面点力、四周固支正面压条、四周简支侧面点力、四周固支侧面压条4种夹持方式在30°和垂直姿态下大口径超薄KDP晶体的面形变化,并给出了面形变化的P-V值和RMS值。在此基础上,通过对不同夹持和不同姿态下KDP晶体面形变化的分析和比较,给出了四周固支正面压条是引起晶体面形变化相对较小的夹持方式的结论。     

表面特性对矩形小流道内液滴脱离现象的影响

本文设计了一个可视化微小平直流道,利用摄影装置观察记录了液态水通过平板内部直径70μm的微孔在水平平板表面上形成液滴并成长直至脱离的过程,分析了不同流道高度条件下接触角之差与液滴高度和通道内流动空气的雷诺数的关系,并且进一步讨论了平板表面特性对液滴脱离高度和接触角之差的影响.     

Influence of ionic composition in aqueous solution on wettability of rock surface-experiment and economics evaluation

In this study, the influence of different ionic composition in aqueous solution on the minerals surface wettability was studied. The differences effect of monovalent ion and divalent ions onto the wettability alteration were studied. The anions were Cl^- and SO₄^2-. The SO₄^2- could make the minerals surface more hydrophilic. Besides, the influence of NaCl, MgCl₂, CaCl₂, Na₂SO₄, K₂SO₄ and MgSO₄ on the mineral wettability alteration were studied. The results indicated that divalent ions showed significant impact on the minerals wettability alteration, compared with monovalent ion. The reasons were due to the fact that divalent ions showed higher ions adsorption than monovalent ion, and divalent ions have higher effect on compressing the electric double layer. The static contact angle and dynamic contact angle were measured. Different heavy oils were studied, including heavy oil with 100 ppm, heavy oil, heavy oil without resins, heavy oil without asphaltenes. The results showed that the asphaltenes would make it difficult for the heavy oils to liberate from minerals, thus decreasing the oil drops contact angle. Then the resins would decrease the heavy oil contact angles. CaCl₂/MgCl₂ and K₂SO₄ have synergistic effect on the change of the minerals surface wettability. Atomic force microscope (AFM) measurement indicated that the ions would effectively decrease the interaction force on the surface of heavy oil-minerals, which was beneficial to the heavy oil liberation. The roughness measurement indicated that the different ions would effectively increase the minerals surface wettability.     

Reduction of bacterial adhesion on modified DLC coatings

The high incidence of infections caused by the use of implanted biomedical devices, including catheters, bone fracture fixation pins and heart valves, etc. has a severe impact on human health and health care costs. Diamond-like carbon (DLC) films as biomaterial for medical devices have been attracting great interest due to their excellent properties such as low friction and chemical inertness. It has been demonstrated that the properties of DLC films can be further improved by the addition of selective elements into DLC films. In this paper Si- and N-doped DLC coatings with various silicon and nitrogen contents on 316 stainless steel substrates were prepared by a magnetron sputtering technique. Bacterial adhesion to the modified DLC coatings was evaluated with Pseudomonas aeruginosa (ATCC 33347) which frequently cause medical device infections. The results showed that the addition of N or Si in DLC coatings had a significant influence on bacterial adhesion. In general the modified DLC coatings with N or Si performed better than the pure DLC coatings in inhibiting bacterial adhesion. The bacterial adhesion mechanism on the modified DLC coatings was explained with thermodynamic theory.     

Theoretical study of the molecular properties of benzyl azide, 2-, 3- and 4-methyl benzyl azide

Ab initio and density functional calculations have been performed to study the benzyl azide, 2-, 3- and 4-methyl benzyl azides. Several molecular properties, such as conformational equilibrium, optimal geometry, and vibrational frequencies, have been computed for these molecules. Ionisation energies were also computed.