不规则知识晶格视角下的数字图书馆资源聚合机理研究北大核心CSSCI

数字图书馆资源聚合理论体系不断丰富、实践应用不断拓展,但从微观内部层面对知识晶格结构和晶格聚合研究得较少,很有必要从微观内部结构和宏观组织方式对数字图书馆晶格聚合机理进行研究。为此,从不规则知识晶格视角出发,借助金属材料物理学,对不规则知识晶格微观结构和宏观组织方式进行分析,在此基础之上研究不规则知识晶格的聚合机制、聚合模型和聚合机理。通过不规则知识晶格的聚合属性和机理探讨以及实证研究,丰富了数字资源聚合的理论体系,为进一步研究奠定了基础。     

节能新技术在金属材料热处理中的应用

金属材料的性能与热处理工艺的制定在机械零件制造中占有十分重要的地位。在生产实际使用中，应准确把握二者之间的关系，有效地提高金属零件的制造水平。     

关于金属学文献分类的研究(续)

2．7 热处理。热处理是一种人们有意识地使固体态金属材料或合金材料工件的整部或局部采用适当的方式加热到一定的温度，并且保温，再冷却，以改变其原性能而获得所期盼的组织结构和性能的工艺。《中图法》在“TG15热处理”中首先根据研究的内容范围分为下列类目。     

铬酸镧晶体本征缺陷和迁移能模拟计算

本文基于原子间势、能量最小化以及量子力学方法,利用动力学软件GULP模拟计算了钙钛矿型立方结构LaCrO3晶体的本征缺陷形成能和氧空位迁移能,还计算了完整晶体的部分物理性质。利用原子间势计算得到的结果与实验值很接近。本征缺陷和迁移能的计算结果表明：氧空位和氧的夫伦克尔缺陷在LaCrO3晶体中占主导地位;计算出了比较低的氧空位迁移能,其值为1.2eV,这表明晶体中氧空位是容易迁移的。     

FeMn基粉末触媒的性能及在金刚石合成中的应用

文章利用气雾化方法制备了Fe100-Χ-YMnYNiΧ(Χ﹤Y,Y=Y1,Y2,Y3)三种触媒,利用金相显微镜、扫描电镜和X射线衍射仪对粉末的性能进行了检测,分析表明:制备的粉末均为面心立方结构单相固溶体,点阵常数约为0.36nm,接近于金刚石的晶格常数。与石墨不同配比的合成实验表明:Mn含量为Y3时,合成的金刚石呈团粒状结构(CSD),石墨转化率达到70%以上;此种金刚石堆积密度、静压强度、冲击强度和形貌与元素六的PDA产品相当;制备的树脂砂轮耐磨性比普通金刚石磨料砂轮提高了80%,加工光洁度Ra达到0.34μm以下;与当前合成CSD磨料常用的Ni基触媒相比,该触媒成本较低,有较好的应用前景。     

化学镀纳米铜膜的微观组织和摩擦学性能浅析

本文从纳米薄膜的制备方法入手,介绍了化学镀纳米铜膜的历史、原理和制备工艺,讨论了不同方法获得的纳米铜膜微观组织和摩擦学性能差异,并对其研究前景进行了展望。     

三角3m晶体等栅条反射系数的研究

SAW滤波器的反射栅条主要由晶体对称类型为立方3m、四方4／mmm、六角6／mmm和三角3m等几种。立方m3m栅条反射系数已有具体的计算公式,由于晶体材料特性不同,该公式不适用于四方4／mmm,六角6／mmm和三角3m等栅条反射系数的计算。文章对四方4／mmm,六角6／mmm和三角3m等栅条反射系数进行了详细理论推导,给出其具体的数学表达式。最后数值计算了几种栅条的反射系数。     

网络新闻传播结构的构建与分析(下)

三、网络新闻传播中的意见传播结构网络中意见的自由传播 ,不是简单的复制或增减过程 ,它比信息的传播要复杂得多 ,参与作用的要素也要多。因此 ,需要从不同层面来进行结构的解释。大体上我们可以将它分成三个层面 :意见形成结构 (个体、微观层面 )意见冲突结构 (社群、中观层面 )意见流动结构 (网络、宏观层面 )这几个结构之间的关系 ,不是简单的分层关系。从微观到中观 ,是一个汇聚的关系。个体的意见到达社群后汇聚 ,在此基础上进行意见斗争。从中观到宏观 ,则体现了意见流的影响从点到面 ,从短期向长期累积的过程。(一 )意见形成结构这…     

基于组织合法性与社会化行为的文件形成机制研究

组织文件在传统认知中被视为组织事务的客观记录,而近年来的研究却表明其形成涉及诸多社会因素,其本质是社会建构的产物。本文提出一个宏观与微观相结合的解释框架,对具有社会建构性本质的组织文件形成机制进行综合解释,宏观解释层次基于组织合法性视角,微观解释层次基于组织成员的社会化文件形成行为。宏观层次的解释路径包括组织文件是组织合法性的承载物、象征物与建构性资源。微观层次的解释路径则指出组织成员的社会化行为包含两个层次：一个层次是组织成员通过惩罚、模仿和规范学习机制对于社会化文件形成行为的习得过程;另一个层次是组织成员在文件形成过程中采取的迎合、回避、选择等具体策略。     

水基油墨配制中溶液和乳液聚合物使用上的若干重要问题(下)

除聚合物结构和聚合物在介质内的溶解性外,颜料的化学性和晶体形态对聚合物的吸附作用,也因此具有明显的影响,晶体表面会影响到须重视其形成厚度的界面部位的生成,底层聚合物层特定的和非特定的吸附作用,形成了颜料表面各种不同形貌,此后,这一层将会影响后面聚合物的吸附作用。       

THE USE OF THE AIRBRASIVE PROCESS FOR CLEANING ETHNOLOGICAL MATERIALS

Abstract

Ethnological specimens of many different materials can be dry cleaned mechanically by means of a grit-spraying unit. Plain and painted leather, corroded metal, beadwork, metallic embroidery, wood, ivory, bone, basketry, some paper, pottery, shell, some textiles and stone are items which can be cleaned with less disturbance to the surface than is often occasioned by the use of other methods. A specimen constructed of several materials may be cleaned by this one method rather than by several, thereby also avoiding the use of water, solvents or other chemicals. The powdered abrasives used are calcium magnesium carbonate, sodium bicarbonate, glass beads, and several grades of aluminium oxide. Silicone carbide powder is used occasionally for very hard corrosion products on metal.     

Study of Post-World War II French Aeronautical Aluminium Alloy and Coatings: Historical and Materials Science Approach

ABSTRACT

In many countries, collections of historic aircraft, conserved in Air and Space museums or local associations, reflect the importance of a national or local history. Mostly parked outdoors, aircraft suffer from significant corrosion requiring conservation operations. During renovation, metallic parts are often replaced by association members. This can lead to a major loss of information since industrial archives dealing with materials and processes do not always survive. However, if these elements can be considered, they could be a fundamental source of information on the materials originally used and of the technical history of aeronautics. This work reports a thorough study of aluminium-based alloy parts collected on a Breguet aeroplane dating from the 1950s, during its recent renovation. Thanks to an approach coupling multi-scale material characterisation and research in archives, information on the industrial knowledge is revealed. Several historic grades of aluminium-based alloys were found, namely A-U4G, A-U4G1, and A-U3G, depending on the role of the part. Similarly, different protective coatings were identified (anodic oxidation, primers, and paintings), depending on the role of the metallic part and its location in the plane. Knowledge of the materials from bulk metal to the coated surface is necessary for good conservation practices regarding aeronautical heritage artefacts. Related documents and archives also fundamentally help in understanding such complex artefacts.     

重视课堂结构研究 全面提高音乐教学效果

合理的课堂结构可以尽可能多的调功学生感官,增强学生的参与意识。我们从宏观和微观研究课堂结构,不是为把教学搞成程式化,而是要使不同类型的课都各自有所遵循,使教学更加科学化,用最短时间取得最佳效果。因此,我们要不断提高音乐教学水平,全面提高音乐教学效果。     

A note on the analysis of metal threads

Abstract

The present work demonstrates by means of two practical examples the extreme importance of examination of cross sections of metal threads to obtain an overview of their structure and of the different materials employed in their manufacture. Problems that might be caused by disturbance of surface features during polishing were prevented by covering the sample before embedding with a layer of nickel, using electroless deposition. Results from scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX) showed that, although the mean chemical composition of both metal wires is the same, their metallurgical structure is completely different: one consisting of pure silver with inclusions of copper particles and the other a silver–copper alloy.     

Lead soaps in paintings: Friends or foes?

The origin(s) and role(s) of metal soaps in paints are a worldwide concern today. These hybrid compounds, containing both fatty acid chains and metals associated with a carboxylate function, are increasingly identified in paints. As reviewed in the first part of this work, the presence of metal soaps in paints is differently interpreted in scientific publications: metal soaps are sometimes considered to play a positive role as anchor points, during paint drying processes; they can also be considered as responsible for many degradation processes (protrusions, efflorescences, darkening, etc.). Their origins are also interpreted in various ways. In some paintings (in particular from the twentieth century), they have sometimes introduced on purpose, as additives, to modify the physical properties of the painting materials. In older paintings, metal soaps are usually thought to result from an uncontrolled reaction of oil with lead-based pigments, in particular lead white, red lead, and lead tin yellow. In the second part of this work, the review of historical recipes of lead-based paint shows an important number of recipes based on controlled mixing of oil with lead driers. In the third part, the experimental reproduction of such traditional recipes using walnut oil and litharge (PbO) shows that lead soaps can be formed, both in about one hour at ～100°C, or in about one month at room temperature. It shows as well that after a few years, litharge is no longer detected in the paint medium, while different lead carbonates are. Finally, the micro-infrared spectroscopy and micro-X-ray diffraction re-analysis of protrusions from a nine-year model painting shows together with lead soaps, the presence of Pb₅(CO₃)₃(OH)₂O (‘synthetic plumbonacrite’), an unusual phase recently observed in a protrusion from a painting by Vincent Van Gogh. This work highlights (i) the multiple origins and roles of metal soaps in paints and (ii) the importance of combining the analysis of fragments from historical paintings with the analysis and reproduction of historical recipes. In particular, we show that the components detected today in historical paintings may severely differ from those originally used or prepared by the painter, complicating the assessment of the painter's intentions. More than the presence of metal soaps, the key questions to be tackled should be about their origins and (re)mobilization.     

The influence of temperature and humidity on swelling and surfactant migration in acrylic emulsion paint films

It has often been observed anecdotally and implied through experimentation that acrylic emulsion paintings accumulate and entrain soils over time due to the inherent mechanical softness in artist's acrylic paint films, through the presence of hydrophilic film components, and by virtue of the ubiquitous presence of surfactant moieties on these film surfaces once they dry. In the present study, it has been this last effect that we have sought to describe more fully in terms of surfactant responsiveness to both temperature and relative humidity (RH). Surfactant hydration and dehydration under varying temperature and RH conditions affects the ultimate partitioning of the surfactant at the paint–air interface, as well as the inherent size, aggregation tendencies, and solubility of surfactant in the bulk paint materials which contain components that are highly responsive to changes in temperature and RH (e.g. polyacrylic or polymaleic anhydride-type dispersal materials). In this work, analytical techniques including three-dimensional microscopy and quartz crystal microbalance with dissipation were used to add to and reinforce current understanding of the physical and mechanical changes to acrylic paint films with temperature and RH. The migration of surfactant at the film surface was studied using desorption electrospray ionization-mass spectrometry and attenuated total reflectance Fourier transform infrared microscopy.     

Surface Investigation of Metal Threads and Solid Metals of Ottoman Textiles in the Topkapi Palace Museum

ABSTRACT

We analyzed 53 historical textile samples from a collection of caftans and brocades dating between the sixteenth and nineteenth century in the Topkapi Palace Museum (TPM) by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). Data were collected on the type, dimensions, elemental composition, and level of corrosion. The technique is presented in this work as an efficient and micro-destructive tool for the characterization of the structure of historical metal threads. SEM-EDX analysis for different energies was performed on a selection of gold and silver threads belonging to the historical textiles. The results were interpreted via laboratory prepared samples of gilt Ag and sulfur reacted Ag at different thicknesses for Au and Ag₂S layers respectively. A series of Au–Ag alloys for different Au/Ag ratios were prepared for comparative analysis. The threads were made of metal strips wound around a silk core. Metal wires and flat strips were also used. The use of differential energies allowed for differentiating strips and wires made of homogeneous silver and gold alloys from the ones coated with a thin gold layer. Analysis of EDX data revealed that the Au film thickness was very thin (10–60?nm). Formation of Ag₂S layers over the thin Au film as thick as 1.5?µm was taking place. Formation of thinner Ag₂S layers over non-gilt Ag suggested different reaction mechanisms for gilt and non-gilt cases.     

Application of colour metallography in the examination of ancient metals

The use of colour in the metallographic examination of ancient metals is useful both for research and teaching purposes. Application of different optical methods of examination include: polarized light, with or without a first-order red compensator, and differential interference contrast microscopy (DIC). The use of DIC can be combined with the other techniques mentioned in the text for the examination of etched or unetched metal surfaces, which are best observed microscopically using a metallograph. Colour techniques are now used routinely in industrial metallography, and are available for a variety of metals and alloys. Colour tint etching can be used to enhance grain structure or different phases present in the metallic artefact which may not be visible in conventional etched samples, or which lack optical contrast. Many more applications of these techniques in the examination of ancient metals will be published in the literature as they become better known and second-hand equipment with DIC lenses enter the market at a price suitable for conservation laboratories to purchase them.     

Decay and treatment of Macael white marble

Abstract

This paper reports the process of deterioration of the white marble used in the Alhambra of Granada, and its consequences. Variations in mineralogical composition, microscopic topology, hardness, compressive strength, propagation of ultrasonic waves, absorptIon and diffusion of water and properties related to the pore structure were studied. The relationships between these factors, the visible deterioration and possible mechanisms are discussed. A preliminary evaluation of some protective treatments was carried out. The results can also be applied to white Macael marble used in other monuments in an environment with wide fluctuations in temperature and relative humidity.     

热化学反应动力学研究

NH4Cl和NaNO2在一定条件下反应产生大量的热和气体,利于蜡的熔化和剥离,只有掌握它的反应动力学特征,了解它的最佳反应条件及其影响因素,才能更好的利用其热量。本文通过测量不同条件下两者反应生成气体和温度的变化量,计算出各种相关的动力学参数,得到该反应的动力学方程。