文档库 最新最全的文档下载
当前位置:文档库 › 外文翻译---综述菠萝叶纤维,剑麻纤维及其生物复合材料

外文翻译---综述菠萝叶纤维,剑麻纤维及其生物复合材料

外文翻译---综述菠萝叶纤维,剑麻纤维及其生物复合材料
外文翻译---综述菠萝叶纤维,剑麻纤维及其生物复合材料

外文翻译(一)

综述菠萝叶纤维,剑麻纤维及其生物复合材料1

1.简介

当今对聚合物的科技领域的研究已经集中在发展中的塑胶,纸张,粘着剂,织物纤维,复合物,混合物及其他许多来自可持续发展资源的工业品。大多数为可再生农业污染和木质纤维材料。新一代的既经济又环保的材料和复合物正在被考虑应用到汽车行业,建筑,家具以及包装业。随着越来越强的环境保护意识,新规则和遍及全球的生物生产经济的调节正在挑战相关产业,学术环境,政府和农业。在过去的几年之间,天然化合物纤维有了一个戏剧性般的增长。天然纤维的最新进展,遗传工程及复合物科学为来自可再生资源的改良材料提供了意义重大的机会并且为全球可持续发展提供了强大的支持[1,2]。

使用了纤维素,木材,麻纤维,洋麻,大麻纤维,椰皮纤维,波罗麻,凤梨纤维等等的天然纤维材料的复合物的潜能,比如能加强纤维们的热塑性并且热塑性塑料树脂由于去自身的极好的特殊性能引起了世界各地的科学家极大的注意。一些调查者[3-9]已经为天然纤维素复合物的多元应用整理并统计了它的性能。聚合复合材料已经被发展成使用为长短纤维,碎片,薄片,线状,木浆纤维和木粉等等。Mohanty和Misra[10]已经再一次审查了黄麻热固性材料,热成塑性体和橡胶复合物同时Bledzki和Gassan再一次审查了聚合物加强细胞膜质纤维素[11]的性

1作者:Supriya Mi shra ,Amar K. Mohan ty,La wrence T. Drza l,Manjusr i Mi sra,Georg Hinri chsen.来源:Macromol. Mater. Eng. 2004, 289,955 – 974

能。最近,菠萝麻纤维素及其复合物已被Lietal[12]再一次审阅。

通过嵌入天然强化纤维列如亚麻,大麻,苎麻,黄麻等等到来自细胞膜质,淀粉,乳酸等等的生物聚合物母体材质的衍生物中。被称为生物复合材料的新强化纤维材料已被制造出来且待改良[13-20]。包含了天然纤维素和生物降解材质生物复合材料已在建筑材料应用方面获得专利[21]。那些材料包含天然天然纤维包含例如亚麻,大麻,苎麻,菠萝麻或黄麻,例如细胞膜质二醋酸盐的生物分解母体,或者某个淀粉衍生物。Mohantyetal[22-23]等人已经报告了各种表面修饰对黄麻复合纤维性能的影响。Avella 和dell’Erba[24]在报告中指出木质秸秆纤维素渐渐地让人们对这些复合物期望良好的机械性能。来自黄麻的生物复合材料和合成生物可降解塑料以及聚酯酰胺也同样被报告了[25]。一种三角测量法——高效的生物纤维表面处理,基本改良,以及选择加工技术已被锁定[26-36]在设计生物复合材料更优良的物理力学性能中。

提供廉价的天然木质纤维素,列如在热带国家的菠萝叶纤维和剑麻为探索利用廉价的生物合成降解材料复合物的多元应用的肯能性提供了一个独一无二的机会。使用这些强化纤维聚合复合材料的优点列举如下:低密度,低成本,天然无摩擦,高填补性能,低能耗,高性能,生物降解性,和以新一代的农村/农业为基础的经济。这些天然纤维的结构和性能取决于几个因素,如年龄,来源,微纤维,直线度,直径和化学成分。由于该纤维的截面太小且不能直接应用在工程应用中,他们被嵌入在基质材料中从而形成纤维复合材料。矩阵作为粘结剂将纤维素们结合在一起并转移负荷给纤维素们。为了发展和促进这些天然纤维及其复合材料,有必要了解他们的物理-力学性能。关于这些天然纤维结构和性能的一些报告已发表,但在这一领域大量的研究仍然需要。

天然纤维素的主要成分是纤维素,半纤维素,木质素。纤维素高分子的基础单元是葡萄糖酐,其中包含三个羟基。这些羟基在高分子内形成氢键同时在其他纤维素高分子间也形成羟基。因此,菠萝叶纤维和剑麻,像所有植物纤维一样是亲水性的且他们的含水量达到11%。[37]这些纤维可以作为有效的增强聚合物,橡胶,石膏,水泥矩阵。然而,菠萝叶纤维/剑麻纤维增强复合材料通常有不良的界面和抗湿性能。复合材料的性能取决于这些的个别成分和界面的粘附性。纤维和基质之间的粘附是通过纤维表面两端进入基质这种机械固定而获得的。未经处理的纤维润湿性差,聚合物基体和纤维素之间不充分的粘附导致其随着时间而剥离[38-40]。如果纤维没有有效的润湿,导致内部压力的强附着力是不可能存在的[41],孔隙度和环境恶化[42,43]。因此,改性纤维是目前一个关键的研究领域从而获得最佳纤维性能。加固纤维的性能可以通过一些化学物理方法修改且追踪到不同的方式和程度。

2.天然纤维的可用性,组成,结构与性能

天然纤维的来源,起源,性质,以及不同的物理和化学组成已被审查[44,45]。天然纤维是在起源的基础上细分的,来自植物,动物或矿物。一般来说,植物或植物纤维被用来增强塑料。植物纤维可包括:剑麻叶,菠萝叶纤维,和剑麻;韧皮纤维亚麻,苎麻,红麻/大麻,黄麻和棉花;种子;果:椰子壳,气候条件,年龄和消化过程不仅影响纤维结构也影响化学组成。部分天然纤维是纤维素,半纤维素,木质素,果胶,蜡,和水溶性物质,纤维素半纤维素和木质素的基本组成部分,是关于纤维的物理特性。化学组成和结构参数的应用和剑麻是代表表1表2包括重要特征的纤维。单纤维的植物为基础的天然纤维组成的几个细胞。这些细胞形成了结晶过程微纤维的纤维素,这是连接到一个完整的层,由无定形的木素和半纤维素。例如多层纤维素木质素/半纤维素在一个主要和三个次要细胞壁粘在一起形成一个复合层。这些细胞壁有不同的组成(纤维素和木质素/半纤维素之间的比例)。

表格1菠萝叶纤维和剑麻的化学组成和结构参数。

菠萝叶纤维剑麻

纤维素/重量-% 70-82 67-78

木质素/重量-% 5-12 8-12

半纤维素/重量-% - 10-14.2

果胶/重量-% - 10

脂肪油/度数- 2

微小纤维状螺旋角14 20

含水率/重量-% 11.8 11

表格2 菠萝叶纤维和剑麻的物理和力学性能。

属性菠萝叶纤维剑麻

密度 1.44 1.45

直径/毫米20-80 50-200

抗拉强度/兆帕413-1627 468-640

杨氏模量/千兆34.5-82.51 9.4-22.0

断裂延伸率/ % 1.6 3-7

(螺旋角)的纤维素微纤丝。这些结构参数的特征值从一个天然纤维到另一个以

及物理化学纤维治疗。螺旋角的纤维和纤维素含量一般能确定以纤维素为基础的天然纤维力学性能。例如,模型开发商Hearle[46]认为这些结构参数能计算纤维素的杨氏模量。模型的基本思想已被Hearle和Sparrow[46]描述。模型已被Mukherjee 和satyanarayana[47]应用到各种天然纤维中。

参考文献

[1] R.P.Wool,CHEMTECH1999, 29, 44..

[2] A.K.Mohanty,M.Misra,G.Hinrichsen,Macromol.Mater.Eng.2000 276/277,1.

[3] [3a] Indian 28281 (1926), invs.:S.S.Bhatnaggar, G. A. R.Khan, L. C. Virman; [3b]

Indian 28427 (1926), invs.: S. S.Bhatnaggar, G. A. R. Khan, L. C. Virman.

[4] P. K. Pal, Plast. Rubber Process. Appl. 1984, 3,4.

[5] A. R. Philip, Reinf. Plast. (London) 1964, 306.

[6] A. R. Philip, Eng. Mater. 1965, 8, 475.

[7] A.K.Mohanty,M.Misra, L. T. Drazal, ‘‘The Influence of Surface Modifications on

Performance of Short HenequenFiber Polypropylene Composite’’, in:SAMPE, Advanced Composite Technology for 21st Century Transportation,Midwest Advanced Materials and Processing Conference Proceedings , Dearborn, Michigan, Sept. 12 – 14, 2000,pp. 299 – 310.

[8] S. Sahoo, M. Misra, D. Pati, S. K. Nayak, A. K. Mohanty,‘‘Effects of Different

Types of Chemical Modifications ofJute on Performance of Polyester Resin Based Composites:A Comparative Study’’, in:National Seminar on Polymer Research in Academy, Industry and R & D Organization,Calcutta, India, June 26 – 27, 1998.

[9] J. Rout, M. Misra, A. K. Mohanty, S. K. Nayak, ‘‘Studies on Aqueous

Co-Polymerization of MMA onto Chemically Modified Coir Fiber and its Effect on Mechanical Performance of Fiber’’, in: National Seminar on Polymer Research in Academy, Industry and R & D Organization, Calcutta, India, June 26 –27, 1998.

[10] A. K. Mohanty, M. Misra, Polym. Plast. Technol. Eng. 1995, 34, 729.

[11] A. K. Bledzki, J. Gassan, Prog. Polym. Sci. 1999, 24, 221.

[12] Y. Li, Y.-W. Mai, L. Ye, Compos. Sci. Technol.2000, 60, 2037.

[13] Z. A. Rogovin, L. S. Galbraykh, ‘‘ Chemical Conversions and Modification of

Cellulose’’, Khimiy a Publ., Moscow 1979, p. 205.

[14] S. Goa, Y. Zeng, J. Appl. Polym. Sci. 1993, 47, 2065.

[15] A. K. Bledzki, S. Reihmane, J. Gassan, J. Appl. Polym. Sci. 1996, 59, 1329.

[16] R. Karnani, M. Krishnan, R. Narayan, Polym. Eng. Sci. 1997, 37, 476.

[17] A. S. H errmann, H. Hanselka, J. Nickel, U. Riedel,‘‘Biodegradable Fiber

Reinforced Plastics Based upon Renewable Resources’’, in:TECNITEX , Torino-Lingotto, Nov. 1996.

[18] H. Hanselka, A. S. Herrmann, ‘‘BioVerbund: Biologisch Abbaubare

Konstruktionswerkstoffe au f der Basis Nachwachsender Rohstoffe’’, in: Techtextil Symposium 94 , Frankfurt, Germany, June 1994.

[19]A.S.Herrmann,H.Hanselka,”Biologisch Abbaubare Konstruktionswerkstoffe

Auf der Basis Nachwachsender Rohstoffe”,in:26 Int.AVK-Tagung,Sept.1994. [20] M. M isra, A. K. Mohanty, L. T. Drzal, ‘‘Environmentally-Friendly

复合材料与工程专业毕业设计外文文献翻译

毕业设计外文资料翻译 题目POLISHING OF CERAMIC TILES 抛光瓷砖 学院材料科学与工程 专业复合材料与工程 班级复材0802 学生 学号20080103114 指导教师 二〇一二年三月二十八日

MATERIALS AND MANUFACTURING PROCESSES, 17(3), 401–413 (2002) POLISHING OF CERAMIC TILES C. Y. Wang,* X. Wei, and H. Yuan Institute of Manufacturing Technology, Guangdong University ofTechnology, Guangzhou 510090, P.R. China ABSTRACT Grinding and polishing are important steps in the production of decorative vitreous ceramic tiles. Different combinations of finishing wheels and polishing wheels are tested to optimize their selection. The results show that the surface glossiness depends not only on the surface quality before machining, but also on the characteristics of the ceramic tiles as well as the performance of grinding and polishing wheels. The performance of the polishing wheel is the key for a good final surface quality. The surface glossiness after finishing must be above 208 in order to get higher polishing quality because finishing will limit the maximum surface glossiness by polishing. The optimized combination of grinding and polishing wheels for all the steps will achieve shorter machining times and better surface quality. No obvious relationships are found between the hardness of ceramic tiles and surface quality or the wear of grinding wheels; therefore, the hardness of the ceramic tile cannot be used for evaluating its machinability. Key Words: Ceramic tiles; Grinding wheel; Polishing wheel

英文文献翻译

中等分辨率制备分离的 快速色谱技术 W. Clark Still,* Michael K a h n , and Abhijit Mitra Departm(7nt o/ Chemistry, Columbia Uniuersity,1Veu York, Neu; York 10027 ReceiLied January 26, 1978 我们希望找到一种简单的吸附色谱技术用于有机化合物的常规净化。这种技术是适于传统的有机物大规模制备分离,该技术需使用长柱色谱法。尽管这种技术得到的效果非常好,但是其需要消耗大量的时间,并且由于频带拖尾经常出现低复原率。当分离的样本剂量大于1或者2g时,这些问题显得更加突出。近年来,几种制备系统已经进行了改进,能将分离时间减少到1-3h,并允许各成分的分辨率ΔR f≥(使用薄层色谱分析进行分析)。在这些方法中,在我们的实验室中,媒介压力色谱法1和短柱色谱法2是最成功的。最近,我们发现一种可以将分离速度大幅度提升的技术,可用于反应产物的常规提纯,我们将这种技术称为急骤色谱法。虽然这种技术的分辨率只是中等(ΔR f≥),而且构建这个系统花费非常低,并且能在10-15min内分离重量在的样本。4 急骤色谱法是以空气压力驱动的混合介质压力以及短柱色谱法为基础,专门针对快速分离,介质压力以及短柱色谱已经进行了优化。优化实验是在一组标准条件5下进行的,优化实验使用苯甲醇作为样本,放在一个20mm*5in.的硅胶柱60内,使用Tracor 970紫外检测器监测圆柱的输出。分辨率通过持续时间(r)和峰宽(w,w/2)的比率进行测定的(Figure 1),结果如图2-4所示,图2-4分别放映分辨率随着硅胶颗粒大小、洗脱液流速和样本大小的变化。

建筑结构设计中英文对照外文翻译文献

中英文对照外文翻译 (文档含英文原文和中文翻译) Create and comprehensive technology in the structure global design of the building The 21st century will be the era that many kinds of disciplines technology coexists , it will form the enormous motive force of promoting the development of building , the building is more and more important too in global design, the architect must seize the opportunity , give full play to the architect's leading role, preside over every building engineering design well. Building there is the global design concept not new of architectural design,characteristic of it for in an all-round way each element not correlated with building- there aren't external environment condition, building , technical equipment,etc. work in coordination with, and create the premium building with the comprehensive new technology to combine together. The premium building is created, must consider sustainable development , namely future requirement , in other words, how save natural resources as much as possible, how about protect the environment that the mankind depends on for existence, how construct through high-quality between architectural design and building, in order to reduce building equipment use quantity and

外文翻译--农村金融主流的非正规金融机构

附录1 RURAL FINANCE: MAINSTREAMING INFORMAL FINANCIAL INSTITUTIONS By Hans Dieter Seibel Abstract Informal financial institutions (IFIs), among them the ubiquitous rotating savings and credit associations, are of ancient origin. Owned and self-managed by local people, poor and non-poor, they are self-help organizations which mobilize their own resources, cover their costs and finance their growth from their profits. With the expansion of the money economy, they have spread into new areas and grown in numbers, size and diversity; but ultimately, most have remained restricted in size, outreach and duration. Are they best left alone, or should they be helped to upgrade their operations and be integrated into the wider financial market? Under conducive policy conditions, some have spontaneously taken the opportunity of evolving into semiformal or formal microfinance institutions (MFIs). This has usually yielded great benefits in terms of financial deepening, sustainability and outreach. Donors may build on these indigenous foundations and provide support for various options of institutional development, among them: incentives-driven mainstreaming through networking; encouraging the establishment of new IFIs in areas devoid of financial services; linking IFIs/MFIs to banks; strengthening Non-Governmental Organizations (NGOs) as promoters of good practices; and, in a nonrepressive policy environment, promoting appropriate legal forms, prudential regulation and delegated supervision. Key words: Microfinance, microcredit, microsavings。 1. informal finance, self-help groups In March 1967, on one of my first field trips in Liberia, I had the opportunity to observe a group of a dozen Mano peasants cutting trees in a field belonging to one of them. Before they started their work, they placed hoe-shaped masks in a small circle, chanted words and turned into animals. One turned into a lion, another one into a bush hog, and so on, and they continued to imitate those animals throughout the whole day, as they worked hard on their land. I realized I was onto something serious, and at the end of the day, when they had put the masks into a bag and changed back into humans,

文献综述,外文翻译,论文网站

文献综述怎么写 1) 什么是文献综述? 文献综述是研究者在其提前阅读过某一主题的文献后,经过理解、整理、融会贯通,综合分析和评价而组成的一种不同于研究论文的文体。 2) 文献综述的写作要求 1、文献综述的格式 文献综述的格式与一般研究性论文的格式有所不同。这是因为研究性的论文注重研究的方法和结果,而文献综述介绍与主题有关的详细资料、动态、进展、展望以及对以上方面的评述。因此文献综述的格式相对多样,但总的来说,一般都包含以下四部分:即前言、主题、总结和参考文献。撰写文献综述时可按这四部分拟写提纲,再根据提纲进行撰写工作。 前言,要用简明扼要的文字说明写作的目的、必要性、有关概念的定义,综述的范围,阐述有关问题的现状和动态,以及目前对主要问题争论的焦点等。前言一般200-300字为宜,不宜超过500字。 正文,是综述的重点,写法上没有固定的格式,只要能较好地表达综合的内容,作者可创造性采用诸多形式。正文主要包括论据和论证两个部分,通过提出问题、分析问题和解决问题,比较不同学者对同一问题的看法及其理论依据,进一步阐明问题的来龙去脉和作者自己的见解。当然,作者也可从问题发生的历史背景、目前现状、发展方向等提出文献的不同观点。正文部分可根据内容的多少可分为若干个小标题分别论述。 小结,是结综述正文部分作扼要的总结,作者应对各种观点进行综合评价,提出自己的看法,指出存在的问题及今后发展的方向和展望。内容单纯的综述也可不写小结。 参考文献,是综述的重要组成部分。一般参考文献的多少可体现作者阅读文献的广度和深度。对综述类论文参考文献的数量不同杂志有不同的要求,一般以30条以内为宜,以最近3-5年内的最新文献为主。 2、文献综述规定 1. 为了使选题报告有较充分的依据,要求硕士研究生在论文开题之前作文献综述。 2. 在文献综述时,研究生应系统地查阅与自己的研究方向有关的国内外文献。通常阅读文献不少于30篇,且文献搜集要客观全面 3. 在文献综述中,研究生应说明自己研究方向的发展历史,前人的主要研究成果,存在的问题及发展趋势等。 4. 文献综述要条理清晰,文字通顺简练。 5. 资料运用恰当、合理。文献引用用方括号[ ]括起来置于引用词的右上角。 6. 文献综述中要有自己的观点和见解。不能混淆作者与文献的观点。鼓励研究生多发现问题、多提出问题、并指出分析、解决问题的可能途径,针对性强。 7. 文献综述不少于3000字。 3、注意事项 ⒈搜集文献应尽量全。掌握全面、大量的文献资料是写好综述的前提,否则,随便搜集一点资料就动手撰写是不可能写出好的综述。 ⒉注意引用文献的代表性、可靠性和科学性。在搜集到的文献中可能出现观点雷同,有的文献在可靠性及科学性方面存在着差异,因此在引用文献时应注意选用代表性、可靠性和科学性较好的文献。 ⒊引用文献要忠实文献内容。由于文献综述有作者自己的评论分析,因此在撰写时应分清作者的观点和文献的内容,不能篡改文献的内容。引用文献不过多。文献综述的作者引用间接文献的现象时有所见。如果综述作者从他人引用的参考文献转引过来,这些文献在他人

外文翻译

改善木粉/聚丙烯(PP)复合材料中木粉和聚丙烯间的界面支持CHENG ZHANG, KAICHANG LI 和JOHN SIMONSEN 美国俄勒冈州大学木材自然科学工程系Corvallis 2004年九月一日发表. 摘要 乙烯基N-甲酰胺接枝聚丙烯(VFPP)通过自由基接枝反应已经成功合成了。聚合物亚甲基联苯二异氰酸酯(PMDI)和VFPP都能够通过有效地相容来促进木粉/聚丙烯复合物的强度和硬度。当PMDI和VFPP一起作为一个完整的相容剂系统时,更能增强木粉/聚丙烯复合物的断裂模量和弹性模量。这种新的PMDI-VFPP相容剂系统在增强木粉/聚丙烯复合物强度和硬度方面可以比得上顺丁烯酐接枝聚丙烯。用电子显微方法研究木粉/聚丙烯复合物的表面断裂情况显示这种新型的P12MDI-VFPP相容剂系统能更好地改良木粉和聚丙烯间的界面支持。这种PMDI-VFPP相容剂系统同样可以很大程度地降低木粉/聚丙烯复合物的吸水率。在这个PMDI-VFPP相容剂系统中,PMDI的作用被认为是木粉粘合剂范畴而VFPP的作用则是在PP粘合剂的范畴。PMDI跟VFPP里的氨基团反应,因此在PMDI和VFPP之间形成了共价键。 关键词:界面支持,木粉,聚丙烯,木/塑复合物,相容剂

目录 1.绪论 (1) 2.实验 (2) 2.1.原料和分析工具 (2) 2.2乙烯基N-甲酰胺接枝聚丙烯的合成 (2) 2.3 木/PP复合材料混和过程 (2) 2.4 木粉/PP制品的模压 (3) 2.5 木粉/PP复合材料的弯曲测试 (3) 2.6 木粉/PP复合材料的吸水率 (4) 3. 结论 (5) 4. 讨论 (10) 5.小结 (11) 致谢 (12) 参考文献 (13)

计算机网络-外文文献-外文翻译-英文文献-新技术的计算机网络

New technique of the computer network Abstract The 21 century is an ages of the information economy, being the computer network technique of representative techniques this ages, will be at very fast speed develop soon in continuously creatively, and will go deep into the people's work, life and study. Therefore, control this technique and then seem to be more to deliver the importance. Now I mainly introduce the new technique of a few networks in actuality live of application. keywords Internet Network System Digital Certificates Grid Storage 1. Foreword Internet turns 36, still a work in progress Thirty-six years after computer scientists at UCLA linked two bulky computers using a 15-foot gray cable, testing a new way for exchanging data over networks, what would ultimately become the Internet remains a work in progress. University researchers are experimenting with ways to increase its capacity and speed. Programmers are trying to imbue Web pages with intelligence. And work is underway to re-engineer the network to reduce Spam (junk mail) and security troubles. All the while threats loom: Critics warn that commercial, legal and political pressures could hinder the types of innovations that made the Internet what it is today. Stephen Crocker and Vinton Cerf were among the graduate students who joined UCLA professor Len Klein rock in an engineering lab on Sept. 2, 1969, as bits of meaningless test data flowed silently between the two computers. By January, three other "nodes" joined the fledgling network.

土木工程外文文献翻译

专业资料 学院: 专业:土木工程 姓名: 学号: 外文出处:Structural Systems to resist (用外文写) Lateral loads 附件:1.外文资料翻译译文;2.外文原文。

附件1:外文资料翻译译文 抗侧向荷载的结构体系 常用的结构体系 若已测出荷载量达数千万磅重,那么在高层建筑设计中就没有多少可以进行极其复杂的构思余地了。确实,较好的高层建筑普遍具有构思简单、表现明晰的特点。 这并不是说没有进行宏观构思的余地。实际上,正是因为有了这种宏观的构思,新奇的高层建筑体系才得以发展,可能更重要的是:几年以前才出现的一些新概念在今天的技术中已经变得平常了。 如果忽略一些与建筑材料密切相关的概念不谈,高层建筑里最为常用的结构体系便可分为如下几类: 1.抗弯矩框架。 2.支撑框架,包括偏心支撑框架。 3.剪力墙,包括钢板剪力墙。 4.筒中框架。 5.筒中筒结构。 6.核心交互结构。 7. 框格体系或束筒体系。 特别是由于最近趋向于更复杂的建筑形式,同时也需要增加刚度以抵抗几力和地震力,大多数高层建筑都具有由框架、支撑构架、剪力墙和相关体系相结合而构成的体系。而且,就较高的建筑物而言,大多数都是由交互式构件组成三维陈列。 将这些构件结合起来的方法正是高层建筑设计方法的本质。其结合方式需要在考虑环境、功能和费用后再发展,以便提供促使建筑发展达到新高度的有效结构。这并

不是说富于想象力的结构设计就能够创造出伟大建筑。正相反,有许多例优美的建筑仅得到结构工程师适当的支持就被创造出来了,然而,如果没有天赋甚厚的建筑师的创造力的指导,那么,得以发展的就只能是好的结构,并非是伟大的建筑。无论如何,要想创造出高层建筑真正非凡的设计,两者都需要最好的。 虽然在文献中通常可以见到有关这七种体系的全面性讨论,但是在这里还值得进一步讨论。设计方法的本质贯穿于整个讨论。设计方法的本质贯穿于整个讨论中。 抗弯矩框架 抗弯矩框架也许是低,中高度的建筑中常用的体系,它具有线性水平构件和垂直构件在接头处基本刚接之特点。这种框架用作独立的体系,或者和其他体系结合起来使用,以便提供所需要水平荷载抵抗力。对于较高的高层建筑,可能会发现该本系不宜作为独立体系,这是因为在侧向力的作用下难以调动足够的刚度。 我们可以利用STRESS,STRUDL 或者其他大量合适的计算机程序进行结构分析。所谓的门架法分析或悬臂法分析在当今的技术中无一席之地,由于柱梁节点固有柔性,并且由于初步设计应该力求突出体系的弱点,所以在初析中使用框架的中心距尺寸设计是司空惯的。当然,在设计的后期阶段,实际地评价结点的变形很有必要。 支撑框架 支撑框架实际上刚度比抗弯矩框架强,在高层建筑中也得到更广泛的应用。这种体系以其结点处铰接或则接的线性水平构件、垂直构件和斜撑构件而具特色,它通常与其他体系共同用于较高的建筑,并且作为一种独立的体系用在低、中高度的建筑中。

碳纤维复合材料英文文献

Journal of Materials Processing Technology168(2005) 262–269 Process optimisation for a squeeze cast magnesium alloy metal matrix composite M.S.Yong a,?,A.J.Clegg b a Singapore Institute of Manufacturing Technology,71Nanyang Drive,Singapore638075,Singapore b Wolfson School of Mechanical and Manufacturing Engineering,Loughborough University,Loughborough,Leicestershire LE113TU,UK Received5January2004;received in revised form5January2004;accepted27January2005 Abstract The paper reports the in?uence of process variables on a zirconium-free(RZ5DF)magnesium alloy metal matrix composite(MMC) containing14vol.%Saf?l?bres.The squeeze casting process was used to produce the composites and the process variables evaluated were applied pressure,from0.1MPa to120MPa,and preform temperature from250?C to750?C.The principal?ndings from this research were that a minimum applied pressure of60MPa is necessary to eliminate porosity and that applied pressures greater than100MPa cause?bre clustering and breakage.The optimum applied pressure was established to be80MPa.It was also established that to ensure successful preform in?ltration a preform temperature of600?C or above was necessary.For the optimum combination of a preform preheat temperature of600?C and an applied pressure of80MPa,an UTS of259MPa was obtained for the composite.This represented an increase of30%compared to the UTS for the squeeze cast base alloy. ?2005Elsevier B.V.All rights reserved. Keywords:Magnesium alloys;Squeeze casting;Metal matrix composites;Mechanical properties 1.Introduction Metal matrix composite(MMC)components can be man-ufactured by several methods.The metal casting route is espe-cially attractive in terms of its ability to produce complex near net shapes.However,castings produced by conventional cast-ing processes may contain gas and/or shrinkage porosity.The tendency for porosity formation will be exacerbated when?-bres are introduced because they tend to restrict the?ow of molten metal and cause even greater gas entrapment within the casting.It is pointless to use?bres to reinforce a casting if defects are present,since the addition of?bres will not com-pensate for poor metallurgical integrity.In order to ful?l the potential of?bre reinforcement and produce pore free cast-ings the squeeze casting process can be selected.The unique feature of this process is that metal is pressurised throughout solidi?cation.This prevents the formation of gas and shrink-age porosity and produces a metallurgically sound casting.?Corresponding author. E-mail address:msyong@https://www.wendangku.net/doc/ac14240144.html,.sg(M.S.Yong).Selection of this process is also based on its suitability for mass production,ease of fabrication and its consistency in producing high quality composite parts. With the development of MMCs,magnesium alloys can better meet the various demands of diverse applications.The addition of reinforcement to magnesium alloy produces su-perior mechanical properties[1–3]and good thermal stability [4,5].Of the various composite types,the discontinuous and randomly oriented?bre-reinforced composites provide the best“value to strength ratio”. Despite the potential advantage of using magnesium MMC for lightweight and high strength applications,little is known about the in?uence of squeeze in?ltration parame-ters.Key parameters,such as applied pressure and preform temperature must be optimised,especially for the squeeze in?ltration of a magnesium–zinc MMC.These process pa-rameters were researched and the results are presented in this paper.However,it was?rst necessary to select appropriate ?bres and binders since their selection is fundamental to the success of the MMC.The main criterion determining the se-lection of?bre type is compatibility with the matrix.Two 0924-0136/$–see front matter?2005Elsevier B.V.All rights reserved. doi:10.1016/j.jmatprotec.2005.01.012

变电站_外文翻译_外文文献_英文文献_变电站的综合概述

英文翻译 A comprehensive overview of substations Along with the economic development and the modern industry developments of quick rising, the design of the power supply system become more and more completely and system. Because the quickly increase electricity of factories, it also increases seriously to the dependable index of the economic condition, power supply in quantity. Therefore they need the higher and more perfect request to the power supply. Whether Design reasonable, not only affect directly the base investment and circulate the expenses with have the metal depletion in colour metal, but also will reflect the dependable in power supply and the safe in many facts. In a word, it is close with the economic performance and the safety of the people. The substation is an importance part of the electric power system, it is consisted of the electric appliances equipments and the Transmission and the Distribution. It obtains the electric power from the electric power system, through its function of transformation and assign, transport and safety. Then transport the power to every place with safe, dependable, and economical. As an important part of power’s transport and control, the transformer substation must change the mode of the traditional design and control, then can adapt to the modern electric power system, the development of modern industry and the of trend of the society life. Electric power industry is one of the foundations of national industry and national economic development to industry, it is a coal, oil, natural gas, hydropower, nuclear power, wind power and other energy conversion into electrical energy of the secondary energy industry, it for the other departments of the national economy fast and stable development of the provision of adequate power, and its level of development is a reflection of the country's economic development an important indicator of the level. As the power in the industry and the importance of the national economy, electricity transmission and distribution of electric energy used in these areas is an indispensable component.。Therefore, power transmission and distribution is critical. Substation is to enable superior power plant power plants or power after adjustments to the lower load of books is an important part of power transmission. Operation of its functions, the capacity of a direct impact on the size of the lower load power, thereby affecting the industrial production and power consumption.Substation system if a link failure, the system will protect the part of action. May result in power outages and so on, to the production and living a great disadvantage. Therefore, the substation in the electric power system for the protection of electricity reliability,

框架结构设计外文翻译

毕业设计(论文)外文资料翻译 系:机械工程系 专业:土木工程 姓名: 学号: 外文出处:Design of prestressed (用外文写) concrete structures 附件: 1.外文资料翻译译文;2.外文原文。

附件1:外文资料翻译译文 8-2简支梁布局 一个简单的预应力混凝土梁由两个危险截面控制:最大弯矩截面和端截面。这两部分设计好之后,中间截面一定要单独检查,必要时其他部位也要单独调查。最大弯矩截面在以下两种荷载阶段为控制情况,即传递时梁受最小弯矩M G的初始阶段和最大设计弯矩M T时的工作荷载阶段。而端截面则由抗剪强度、支承垫板、锚头间距和千斤顶净空所需要的面积来决定。所有的中间截面是由一个或多个上述要求,根它们与上述两种危险截面的距离来控制。对于后张构件的一种常见的布置方式是在最大弯矩截面采用诸如I形或T形的截面,而在接近梁端处逐渐过渡到简单的矩形截面。这就是人们通常所说的后张构件的端块。对于用长线法生产的先张构件,为了便于生产,全部只用一种等截面,其截面形状则可以为I形、双T形或空心的。在第5 、 6 和7章节中已经阐明了个别截面的设计,下面论述简支梁钢索的总布置。 梁的布置可以用变化混凝土和钢筋的办法来调整。混凝土的截面在高度、宽度、形状和梁底面或者顶面的曲率方面都可以有变化。而钢筋只在面积方面有所变化,不过在相对于混凝土重心轴线的位置方面却多半可以有变化。通过调整这些变化因素,布置方案可能有许多组合,以适应不同的荷载情况。这一点是与钢筋混凝土梁是完全不同的,在钢筋混凝土梁的通常布置中,不是一个统一的矩形截面便是一个统一的T形,而钢筋的位置总是布置得尽量靠底面纤维。 首先考虑先张梁,如图 8-7,这里最好采用直线钢索,因为它们在两个台座之间加力比较容易。我们先从图(a)的等截面直梁的直线钢索开始讨论。这样的布置都很简单,但这样一来,就不是很经济的设计了,因为跨中和梁端的要求会产生冲突。通常发生在跨度中央的最大弯矩截面中的钢索,最好尽量放低,以便尽可能提供最大力臂而提供最大的内部抵制力矩。当跨度中央的梁自重弯矩M G相当大时,就可以把c.g.s布置在截面核心范围以下很远的地方,而不致在传递时在顶部纤维中引起拉应力。然而对于梁端截面却有一套完全不同的要求。由于在梁端没有外力矩,因为在最后的时刻,安排钢索要以c.g.s与 c.g.c在结束区段一致,如此同样地获得克服压力分配的方法。无论如何,如果张应力在最后不能承受,放置 c.g.s.

农村金融小额信贷中英文对照外文翻译文献

农村金融小额信贷中英文对照外文翻译文献(文档含英文原文和中文翻译) RURAL FINANCE: MAINSTREAMING INFORMAL FINANCIAL INSTITUTIONS By Hans Dieter Seibel Abstract Informal financial institutions (IFIs), among them the ubiquitous rotating savings and credit associations, are of ancient origin. Owned and self-managed by local people, poor and non-poor, they are self-help organizations which mobilize their own resources, cover their costs and finance their growth from their profits. With the expansion of the money economy, they have spread into new areas and grown in numbers, size and diversity; but ultimately, most have remained restricted in size, outreach and duration. Are they best left alone, or should they be helped to upgrade

相关文档
相关文档 最新文档