反排木鼓舞：从历史记忆到文化表征

反排木鼓舞作为文化的一种展示方式,随着时代的不同发生着文化的变迁和意义的生产,由一种族群源流与迁徙,祖先历史与记忆的隐喻和象征,逐渐转向反排文化,这种文化的展示与表征,一是通过苗族形象,二是展示和表征贵州少数民族和苗族的文化符号,从而实现文化的再生产。     

浅析苏州红木雕在中国木雕界的杰出地位

本文基于传统手工艺木雕的研究,展示了丰富多彩的木雕历史、工艺介绍。今天远离了手工艺的我们,在审视和研究手工艺时,对它的评价是不高的,可喜的是苏州木雕并没有被人们所遗忘,并没有被历史的尘沙所掩埋。越来越多的人开始关注它,因为这是历史留下来的瑰宝,是值得后代人去继承和探讨的。     

煤矿采掘面产尘模拟分析实践教学系统研发及应用

文章构建了具有自主知识产权的煤矿采掘面产尘模拟分析实践教学系统。该系统可使学生全面、直观地感受煤矿采掘面截割/钻进破煤产尘过程,并指导学生开展“截割/钻进参数调控-产尘特征监测-数据统计分析”的全过程自由探索型创新实验,量化分析截割/钻进参数对产尘特征(浓度、分散度等)的影响。对于提高学生的思考和实践能力,培养学生的创新思维,深化学生对采煤、掘进过程中粉尘灾害和产尘机理的理解,激发学生的科研兴趣,以及有针对性地提出截割/钻进减尘、优化粉尘工程控制措施和个体防尘技术具有重要意义。     

木结构施工课程教学方法探讨

在加拿大木业协会的帮助下,北京京北职业技术学院开展了木结构课程教学工作。介绍了木结构施工课程开设情况及其教学方法,对课程教学方法进行探索,提高学生的实践能力。     

魏晋官文书以纸代简及其启示

从公元105年东汉蔡伦发明纸张,到公元404年东晋桓玄以诏令的形式肯定纸张,沿袭上千年的简牍书写材料被纸张所代替。在这以纸代简的300年间,书信和书籍最先使用纸张,其完成时间在东汉末年。官文书以纸代简要迟缓一些,至东晋才告完成。其中案牍文书、簿籍文书分别在西晋和东晋实现了转变。一种新的官文书书写材料代替另一种官文书书写材料,需要新的书写材料性能良好、实际应用富有成效且时机成熟。这对于今天电子文件代替纸质文件也许有所启发。     

循环水泵叶轮车削在实际中的应用

循环水泵运行中发生超电流,导致电动机烧坏,影响正常供热.根据循环水泵不同的比转数和不同的结构,论述具体切割方法和效果.     

HyperSnap-DX软件在科技期刊图形与图像处理中的应用

北大方正书版排版系统支持的图形、图像格式有限,仅支持.tif等少数图形文件格式,因此,在很多情况下,如格式为.doc、,dwg等的图形一般采用扫描的方法,通过photoshop软件处理后,再存为.tif格式文件为北大方正书版所利用,但有时效果不佳.     

一种轴承内圈硬车削加工夹具

为研究滚动轴承套圈硬车削加工的特性,设计并研制了一种硬车削加工轴承内圈外圆表面、滚道、端面及倒角的夹具,文章介绍了该夹具的工作原理和结构特点。     

A nano to macroscale study on structure-mechanics relationships of archaeological oak

Mechanical properties of wood at different length scales of its hierarchical structure are governed by structural and compositional properties on smaller length scales. This opens up the possibility to use microstructural data for estimating mechanical properties, which are difficult to assess by conventional, destructive testing but are nevertheless of high relevance for conservation practice. Herein, we investigate such microstructure-mechanics relationships for a particular example, namely the load bearing archaeological oak of the Oseberg Viking ship, displayed at the Viking Ship Museum in Oslo, Norway. In order to identify the effects of degradation on the mechanical behavior and their relations to the microstructure, recent oak specimens of different geographical origin (Norway and Austria) are investigated as well. Wood exhibits a cellular structure. Its cell walls are composed of an amorphous polymer matrix consisting of lignin and hemicelluloses and embedded, stiff cellulose fibers. At the cell level, experimental studies comprised microscopic investigations of the cellular structure, chemical analyses of the composition of the cell walls, as well as nanoindentation tests on single cell walls. The same samples were also analyzed on the macroscopic level, where additionally mass density and annual ring data were measured together with ultrasonic stiffnesses. The chemical data clearly indicate deterioration in the archaeological oak, affecting mainly hemicelluloses and amorphous cellulose. At the cell wall scale, however, this does not necessarily lead to a weaker material behavior. The nanoindentation modulus, as a measure of the cell wall stiffness, was found to even increase. This is counterintuitive to our understanding of the effects of chemical degradation. It might be due to possible modification of lignin in the Oseberg oak, and thus have a stronger effect on the indentation modulus than the concurrent weakening of the interfaces between the load-carrying cellulose fibers and the connecting cell wall matrix when analyzing wood at the microscopic level. A similar effect is also observed for the transversal stiffness of macroscopic samples, which increases. In tension-dominated loading modes, however, the degradation of the interfaces is the dominant effect, resulting for example in a considerable reduction of the macroscopic stiffness in longitudinal direction. This underlines the utmost relevance of the loading condition on the remaining load-carrying capacity of degraded wood. On the macroscale, effects of the geographical origin (i.e. growth conditions) on ring characteristics of the oak tissues override the effects of degradation on the mechanical behavior. They have to be carefully extracted in order to come up with conclusions on the effect of degradation from macroscopic test results. The identified microstructure-mechanics relationships provide the basis for–in further research steps–building mathematical models describing the relations between microstructural characteristics and macroscopic mechanical properties and, thereon, for structural analyses of historical wooden objects.     

Chemical bleaching of wood: an investigation into the bleaching of mahogany,walnut, rosewood,padauk, and purpleheart

This paper investigates chemical bleaching of wood to make species-specific practical recommendations for colour adjustment of veneer in furniture conservation. In more detail, chemical bleaching of Honduras mahogany (Swietenia macrophylla), European walnut (Juglans regia), Rio rosewood (Dalbergia nigra), padauk (Pterocarpus spp.), and purpleheart (Peltogyne spp.) is investigated using 11 different bleach solutions. Both oxidative (e.g. hydrogen peroxide and potassium permanganate) and reductive (e.g. oxalic acid and sodium bisulphite) solutions were used. The results show that the wood species react differently with the investigated bleach solutions. It can also be noted that not all investigated solutions were suitable for all wood species. Based on the results, wood species-specific bleach solutions are recommended.