介观双粗糙弹塑性流体动力润滑界面法向接触刚度模型

弹性流体动力润滑状态通常出现在机械高副零部件的点/线接触部位,如齿轮、轴承和蜗轮蜗杆等.宏观上点/线接触在介观层面表现为两粗糙表面的接触,在微观层面上则又表现为微凸体间的接触.由于在中/重载荷作用下,粗糙表面上的微凸体发生接触后会产生弹塑性/塑性变形,从而使得两粗糙表面的弹流润滑接触转变为弹塑性流体动力润滑接触.此外,界面的接触刚度决定了机械装备的整机刚度.为了精确获得弹性流体动力润滑状态下界面法向接触刚度及其主要影响因素,基于界面的法向接触刚度由固体接触刚度和润滑油膜刚度两部分构成的思想,根据固体弹塑性理论和流体动力学理论,分别对界面间微凸体侧接触及部分膜流体动力润滑进行分析,从微观入手揭示双粗糙表面弹塑性流体动力润滑接触机理,进而建立考虑微凸体侧接触弹塑性变形的流体动力润滑界面法向接触刚度模型.通过仿真分析,揭示了法向载荷、卷吸速度、表面粗糙度及润滑介质特性等因素对润滑界面法向接触刚度的影响规律.研究表明:在相同速度、粗糙度及润滑油黏度的工况下,固体接触刚度和油膜接触刚度均随着法向接触载荷的增加呈非线性增大;在相同载荷、速度及润滑油黏度的工况下,接触表面粗糙度越大,表面形貌对于润滑状态的影响较强,固体接触刚度占界面总刚度的主要部分,界面主要由固体承载;在相同载荷、粗糙度及润滑油黏度工况下,随着卷吸速度的增大,固体接触刚度逐渐减小,油膜刚度占界面总刚度的主要部分;在相同载荷、粗糙度及速度工况下,随着润滑油黏度的增大,油膜刚度基本保持不变,固体接触刚度基本不受润滑油黏度的影响.通过理论建模准确获得单位面积弹塑性流体动力润滑结合面法向接触刚度,对改善机械装备动态性能、提高机械装备的可靠性具有重要的理论和实际意义.

大学生就业难原因分析与职业生涯规划

目前大学生就业难问题已经普遍存在,并已经成为社会、高校、家庭及大学生个人关注的最主要问题之一。所以开展大学生就业指导势在必行,通过这篇文章,希望对于大学生就业难和职业生涯规划有一个初步的介绍,大学生应通过努力提升自己的综合素质,加强社会实践,正确的就业定位来完善职业生涯规划。

立足税收 走出税收——兼谈三个层面的“税收观”

本文认为应在把握"立足税收、走出税收"的辩证关系中研究税制改革,并从经济财政、社会环境与内外统筹三个方面来理解可能影响税制改革的制约因素。倡导"不就税收论税收,走出税收看税收"的思路,通过对各种影响制约因素的分析来促进我们对税制改革目标与内容的把握。

语义运行的空间构想——《中国文化读本》阿译感悟

语言是一种符号或信号运行体系,其所承载的语义应语境的变换而变换.基于这一认识,并通过对《中国文化读本》阿拉伯文译本进行实例分析,本文提出：一、语义运作到位必要时需超越表层制约,进入深层空间去确定与表层相关的新义位,从而呈现词语表达的异化;二、驾驭语言应简化语体结构认知,前提是把握不同民族的思维方式,为之建立相应的语义框架和句体模式;三、翻译运作应有语言的美学追求,目的语应尽力表现源语言感情节奏.本文进而指出：语义空间大中有小,小中有大,但都相互穿插、套叠共存,是为一大特有的运动复合体.

A new electromagnetic functional material composed of metallic hollow micro-spheres

This paper presents a new electromagnetic functional material developed byelectron-less nickel deposition technique, with a single hollow micro-sphere as the core templateand a thin nickel layer as the shell. The micrograph taken by a scanning electron microscope showsthe microstructures of the materials in detail. Scattering parameters of the waveguide sample holderfilled with the materials have been obtained over X band. The electromagnetic parameters computedfrom the measured S parameters show that the material with metallic hollow spheres has as highrelative permeability μ'_r as 19.0 with about 0.6 magnetic loss tangent over the whole bandwidth.Compared to the material with non-metallic spheres, the permeability μ'_r and the magnetic losstangent μ'_r increase greatly, while the permittivity remains lower than 1.8.

The Micro-level Distributional Effects of Horticultural Export Value Chains Among Smallholders in Southern Ghana

Increasing foreign exchange problems and deteriorating prices of traditional exports have led policy makers and donor agencies to seek diversification in export crop production. In Ghana, crops such as pineapples and mangoes appear promising because of their high labour intensity and expanding demand for fruits in Europe. Notwithstanding, there is a possible trade-off between export and food crop production because of the possibility of resource re-allocation. So far the major concern of government has been the growth in export earnings while the micro-level distributional effects remain under-investigated. The study focused on a household survey undertaken in the forest and coastal-savannah transition zones, where the farming system has undergone transition from an established food-crop farming for urban markets to an intensive production of horticultural products for export. Logistic regression and Gini coefficient approaches were used to estimate the determinants of household food availability and income distribution respectively. Though, households engaged in export horticulture appear better-off than those that do not, the sole adoption of either staple or export crop is not sufficient for improving food availability. Consequently, linkages which allow simultaneous and reliably access to equitable distribution of resources and services are critical for household survival in competitive global food markets

Beyond the Ontology of“Dance” as an Art： An Anthropological Analysis of Female Stage Performers

The proposed paper focuses on art as a form of cultural expression and it presents data based on ethnographic information of famous Pakistani musical theatres in Lahore, Province of Punjab. Most description of the performing arts is written by men with an exclusive male perspective. Little or no attempt has been made to explore women lives in performing theatre apart from their assigned role as physical crowd-pullers. This study presents how symbols are used to communicate, as each member of theatre community uses entire repertoire to convey messages, manual gesticulations, body gestures, facial expressions, dance patterns, a particular dress etc. at the cultural level. The central idea of this study is how artists use the body in performance to imagine and enact culture, values, humor, selfhood, and the complex relations among them. It discusses their real backstage life experiences and problems faced as well how and what type of contact they maintain with their audience and admirers. What are their moral values and what kind of social dilemmas they face, how the sexuality of theatre women is being controlled, their fears emotions, distress of theatre women etc. are the major research questions. In short, this anthropological inquiry takes into account all relevant social, cultural, political, economic, and religious dimensions of performing art.

Ultrasonic testing and microscopic analysis on concrete under sulfate attack and cyclic environment

The damage process of concrete exposed to sodium sulfate attack and drying-wetting cycles was investigated. The water to binder(W/B) ratio and the concentration of sulfate solution were taken as variable parameters. Through the experiment, visual change, relative dynamic modulus of elasticity(RDME) and the surface damage layer thickness of concrete were measured.Furthermore, SEM and thermal analysis were used to investigate the changing of microstructure and corrosion products of concrete.The test results show that the ultrasonic velocity is related to the damage layer of concrete. It approves that an increase in damage layer thickness reduces the compactness and the ultrasonic velocity. The deterioration degree of concrete could be estimated effectively by measuring the surface damage layer and the RDME of concrete. It is also found that the content of gypsum in concrete is less than that of ettringite in test, and some gypsum is checked only after a certain corrosion extent. When the concrete is with high W/B ratio or exposed to high concentration of sulfate solution, the content of ettringite first increases and then decreases with corrosion time. However, the content of gypsum increases at a steady rate. The content of corrosion products does not correspond well with the observations of RDME change, and extensive amount of corrosion products can be formed before obvious damage occurs.

介观商务模式:管理领域的“纳米”研究

本文通过将企业经营内外环境细分为平台环境、客户环境、伙伴环境、顶板环境和内部环境,根据各个细分环境之间的资源和信息交互特点引入了平台界面、客户界面、伙伴界面、顶板界面和内部构造以及各个细分环境之间的互动关联,提出以客户界面、伙伴界面和内部构造中要素形态的有意义组合作为商务模式的定义。由此,商务模式的研究开始进入全新的介观层面,从而具有了如同自然科学中介观物理和纳米材料那样的科学探索意义。

Formation of efficient dye-sensitized solar cells by introducing an interfacial layer of hierarchically ordered macro-mesoporous TiO_2 film

Hierarchically ordered macro-mesoporous TiO2 films (Ti-Ma-Me) were fabricated on fluorine-doped tin oxide (FTO) substrates through the confinement self-assembly method. The prepared Ti-Ma-Me possesses periodically ordered structure and a large specific surface area, which was applied as an interfacial layer between the nanocrystalline TiO2 film (P25-TiO2) and FTO electrode in the dye-sensitized solar cell (DSSC). The introduction of a Ti-Ma-Me interfacial layer increased the shortcircuit current density (Jsc) from 7.49 to 10.65 mA/cm2 and the open-circuit voltage (Voc) from 0.65 to 0.70 V as the result of its improved light harvesting efficiency by allowing for the high roughness factor and enhanced multiple internal reflection or scattering as well as reducing the back-transport reaction by blocking direct contact between the electrolyte and FTO electrode. Therefore, the photovoltaic conversion efficiency (η) was improved by 83% from 3.04% to 5.55%, as compared to a device using a bare P25 TiO2 photoanode.

n-Octadecanethiol Self-Assembled Monolayer Coating with Microscopic Roughness for Dropwise Condensation of Steam

Here we presented a novel technology to achieve a Super-hydrophobic coating with microscopic roughness on copper surface. First, make a layer of verdigris grow on the fresh pure copper surface. Gain it by exposing the copper to air and the mist of acetic acid solution. The green coating is a mixture of basic copper（II） carbonate and copper（II） acetate. Second heat the coating and make it decompose to CuO. Lastly, form an n-octadecanethiol self-assembled monolayers coating on the outermost surface. Contact angle test, scanning electron microscope analysis and electrochemical testing were carded out to characterize the surface, and a heat transfer experiment for dropwise condensation of steam was performed also. Results show that the modified surface bears a few Super-hydrophobic features, the static contact angle is higher than that in literatures, reaching 153.1±1.7°. The microscopic roughness can be seen in SEM images, differing much from H2O2 etched surface and bare copper surface. The condensation of steam on the surface is a typical form of dropwise condensation, in the measured range of temperature difference, under 0.1 MPa, the average convection heat transfer coefficients of the vertical surface are 1.7-2.1 times for those of film condensation. At the same time, the inhibition efficiency of surface is improved to some extent comparing with the same kind of SAMs, which suggests that the lifetime of maintenance dropwise condensation would have the possibility to surpass the existing record.

Water droplet impact on superhydrophobic surfaces with microstructures and hierarchical roughness

Quantitative correlation between the critical impact velocity of droplet and geometry of superhydrophobic surfaces with microstructures is systematically studied.Experimental data shows that the critical impact velocity induced wetting transition of droplet on the superhydrophobic surfaces is strongly determined by the perimeter of single micropillar,the space between the repeat pillars and the advancing contact angle of the sidewall of the micropillars.The proposed model agrees well with the experimental results,and clarifies that the underlying mechanism which is responsible for the superhydrophobic surface with hierarchical roughness could sustain a higher liquid pressure than the surfaces with microstructures.

Analysis of internal tidal characteristics in the layer above 450 m from acoustic Doppler current profiler observations in the Luzon Strait

The characteristics of internal tides in the upper layer of the Luzon Strait are investigated on the basis of direct-observation current data recorded on April 25 and September 26, 2008 by an acoustic Doppler current profiler. Spectral analysis and energy estimation show that the diurnals and semidiurnals carry most of the energy of internal tides. Values of the depth-integrated total energy E for the three frequency bands of diurnal, semidiurnal, and high frequencies are 31, 6.9, and 3.4 kJ. m, respectively. Near-inertial peaks are only present in the baroclinic component. The behavior of typical tidal frequencies （i.e., O1, K1, M2, MK3, and M4） and the near-inertial frequency is basically consistent with linear internal wave theory, which predicts E＋（ω）/E_（ω）=（ω-f）2/（ω＋f）2 at depths above 66 m, while not all prominent tidal components coincide well with the relation of the linear internal wave field at other depths. Examinations of depth structures of the baroclinic tides and temporal variations show that the surface tides and internal tides are both of mixed type, having diurnal inequality and spring-neap fortnight periods. The K1 and O1 tides have comparable cross- and along-shelf components, while the M2 and S2 tides propagate toward the shelf in the northern South China Sea as wave beams. The amplitude and phase of internal tides vary with time, but M2 and S2 tides appear to have structures dominated by the first mode, while the K1 and O1 tides resemble second-mode structures. The minor to major axis ratios are close to expected values of flω in the thermocline.