插层纳米复合材料的制备和应用(英文)
Advances in Preparation and Application of
Intercalated Nanocomposites
Abstract: Because of the different properties from ordinary materials, the intercalated nanocomposites have a very broad application prospect. Phyllo-silicates are the most suitable materials to prepare intercalated nanocomposites because of its natural laminated structure. Intercalated nanocomposites have many advantages and can be used in many fields. The properties and structures of intercalated nanocomposites are introduced, the preparation methods and the intercalate mechanisms are described: there are three methods to prepare the intercalated nanocomposites: intercalation of polymer or pre-polymer from solution, in situ intercalative polymerization method, melt intercalation method; the thermodynamics and kinetics of intercalation process are analyzed. At last, the application prospect of intercalated nanocomposites is pointed out.
Key Words: intercalated nanocomposites; intercalation; phyllo-silicates
1Introduction
Traditionally, polymeric materials have been filled with synthetic or natural inorganic compounds in order to improve their properties, or simply to reduce cost. Nanocomposites, which can be also added into polymeric materials, are a new class of composites for which at least one dimension of the dispersed particles is in the nanometer range [1]. Compared to virgin polymers, corresponding nanocomposites can show particular improvements, including mechanical properties such as tension, compression, bending and fracture. Barrier properties like permeability and solvent resistance can also be improved, as well as optical properties. Ionic conductivity can also be improved. Among all the potential nanocomposite precursors, those based on clay and layered silicates have been most widely investigated, probably because the starting clay materials are easily gained and because their intercalation chemistry has been studied for a long time[2].
2Structure and characteristics
2.1layered silicates
The structures of different kinds of layered silicates are similar. The commonly used layered
silicates belong to the same general
family of 2:1 layered or
phyllo-silicates, consisting of very
thin layers that are usually bound
together with counter-ions. Their
basic building blocks are tetrahedral
sheets in which silicon is
surrounded by four oxygen atoms,
and octahedral sheets in which a
metal like aluminum is surrounded
by eight oxygen atoms [3]. The layer
thickness is around 1 nm, and the
lateral dimensions of these layers
may vary from 30 nm to several microns or larger, depending on the particular layered silicate. MMT, hectorite, and saponite are the most commonly used layered silicates. Their structure is given in Fig. 1[4].
2.2 Nanocomposite structures
There are three main types of composites may be obtained when a layered clay is associated with a polymer (Fig.2). They are: phase separated micro-composite, intercalated nanocomposite and exfoliated nanocomposite. When the polymer is unable to intercalate between the silicate sheets, a phase separated composite is obtained (Fig.2a), whose properties stay in the same range as traditional micro-composites. Intercalated structure (Fig.2b) in which a single (and sometimes more than one) extended polymer chain is intercalated between the silicate layers resulting in a well ordered multilayer morphology built up with alternating polymeric and inorganic layers. When the silicate layers are completely and uniformly dispersed in a continuous polymer matrix, an exfoliated or delaminated structure (Fig.2c) is obtained [5].
3 Nanocomposite preparation
The preparative methods are divided into three main groups according to the starting materials and reacting conditions: intercalation of polymer or pre-polymer from solution; in situ intercalative polymerization method; melt intercalation method [6~7].
3.1 Intercalation of polymer or pre-polymer from solution
If the polymer or pre-polymer is soluble and the silicate layers are expandable, this method is available. First, the layered silicate is swollen in a solvent, such as water, chloroform, or toluene. Then put the polymer into the layered silicate solutions, blend them together, the polymer chains will intercalate and displace the solvent within the interlayer of the silicate. While the solvent removing, the intercalated structure still remains, resulting in nanocomposite.
3.2 In situ intercalative polymerization method
In this method, the layered silicate is swollen within the liquid monomer or a monomer solution so the polymer can occur within the interlayer of the silicate. Polymerization can be initiated either by heat or radiation, by the diffusion of a suitable initiator, or by an organic initiator or catalyst. 3.3 Melt intercalation method
In this method, the layered silicate is first mixed with the polymer above the softening point of the polymer, then the polymer will intercalate into the silicate under shear or static stress. This method has great advantages over either in situ intercalative polymerization or polymer solution intercalation. First, this method is environmentally friendly due to the absence of organic solvents. Second, it is compatible with current industrial process, such as extrusion and injection molding. The melt intercalation method allows the use of polymers which were previously not suitable for in situ polymerization or solution intercalation.
4 Intercalation reaction mechanisms
There are two main explanations about how the intercalation occurs: thermodynamics theory and kinetics theory.
4.1Thermodynamics theory
Thermodynamics theory believes that whether the intercalation process can occur or not is determined by its free energy (ΔG). If ΔG is less than zero, the intercalation is available. Since the temperature is constant during intercalation, so ΔG=ΔH-TΔS, if ΔG<0, ΔH must less than TΔS, there are three situations that are possible to satisfy this condition:（a）ΔH<0 and ΔS>0；（b）ΔH The enthalpy and entropy change varies in different preparation methods. Take melt intercalation method for example to explain the thermodynamic change during intercalation. The syste m’s initial state is fused polymer and layer silicate minerals. Its final state is intercalated nanocomposite with polymer chains fixed within the interlayer of the silicate. The entropy during this process is less than zero. In this case, ΔH must be less than TΔS so that the intercalation process can happen. Therefore, the whole process is determined by the enthalpy change. The strength of the interaction between the polymer chains and the silicate layers is the key point to whether the intercalation can occur or not. From the formula: ΔG=ΔH-TΔS, the conclusion is got that high temperature is not beneficial to the reaction [8~9]. 4.2Kinetics theory In the kinetics theory, the intercalation process is divided into two processes: first, the polymer gets through the primary particles and reaches the edge of the grains, then spreads into the crystal lattice layers. If the speed of the first stage is larger than the second stage, the volume of the grain will influence the intercalation. A principle about how to select compatible polymer / layered silicate system is proposed based on the above discussion: the shorter of the functional groups of the layered silicate, the more conductive to the intercalation [10]. 5 Nanocomposite properties 5.1 Mechanical properties In general, the addition of an organically modified layered silicate in a polymer matrix results in significant improvements of Young’s modulus. For example, Gorrasi [11] reported an increase from 216 to 390MPa for a PCL nanocomposite containing 10 wt% ammonium-treated montmorillonite. Apart from the modulus, the addition of an organically modified layered silicate in a polymer matrix usually can also increase the tensile strength compared to that of polymer material. For example, Shelley [12]reported a 175% improvement in yield stress accompanied by a 200% increase in tensile modulus for a nylon 6 nanocomposite containing 5 wt% clay. 5.2 Barrier properties Generally, polymer/layered silicate nanocomposites are characterized by very strong enhancements of their barrier properties. Polymers ranging from epoxies and good sealants (like siloxanes) to semi-permeable (e.g. polyureas) and highly hydrophilic (e.g. PV A) are all improved up to an order of magnitude by low clay loadings [13]. The dramatic improvement of barrier properties can be explained by the concept of tortuous paths. That is, when impermeable nanoparticles are incorporated into a polymer, the permeating molecules are forced to wiggle around them in a random walk, and hence diffuse by a tortuous pathway, so its barrier properties are improved. 5.3 Thermal stability Generally, the incorporation of clay into the polymer matrix was found to enhance thermal stability by acting as a superior insulator and mass transport barrier to the volatile products generated during decomposition, as well as by assisting in the formation of char after thermal decomposition [14]. 6 Application As described above, polymer nanocomposite materials have many properties better than conventional composites, such as strength, stiffness, thermal and barrier properties, as well as flame retardant behavior. These improved properties are generally attained at lower filler content in comparison with conventionally filled systems. Therefore, polymer/layered silicate nanocomposites are far lighter in weight than a conventional composite, which makes them quite competitive for specific applications. Another unique aspect of nanocomposites is the lack of property trade-offs. Traditionally, blend or composite formulations require trade-offs between desired performance, mechanical properties or cost. However, polymer nanocomposite provides a route around these traditional limitations, and offers the opportunity to design materials without the compromises typically found in conventionally filled polymers. These advantages of polymer/layered silicate nanocomposites bring it a variety of possible industrial applications: barrier material, construction, aerospace, food packaging, textiles, etc [15]. 6.1 As barrier materials Polymer nanocomposites are expected to find wide applications as barrier materials. In fact, the excellent barrier properties of clay-based polymer nanocomposites could result in considerable enhancement of shelf-life for many types of packaged food. Therefore, the property advantages would make them widely acceptable in packaging industries as wrapping films and beverage containers. For example, Bayer has developed a new grade of plastic films for food packaging, which are made from PA6 exfoliated nanocomposites [16]. 6.2 In environmental protection It is worth noticing that the weight advantage of polymer nanocomposites could have a significant impact on environmental protection and material recycling. It is predicted that widespread use of polymer nanocomposites would save 1.5 billion liters of gasoline over the life of 1 year’s production of vehicles and reduce related CO2emissions by more than 5 billion kilograms [17]. 7 Summary Up to now, the research about intercalated nanocomposites is still at the exploration stage and there are many problems need to be solved. To figure out these problems, some suggestions are proposed: first of all, the dispersion of the nano-particles should be improved. Because of its small scale, nano-particles have a big surface area which increase the adsorption force between the particles, therefore, surface modification of nano-particles are very important. It is significant to choose a suitable surface modifier to reduce the force between the particles to guarantee the granules are effectively scattered in the polymerization process; further more, new highly effective intercalators should be sought. To some layered silicate minerals which has a strong interlayer force like kaolinite, inserting directly is very hard, and the preparation of the existing intercalators are tedious, the stability is bad, therefore, seeking new intercalators and expanding its range of choice can bring new developments to the synthesize of the silicate nanocomposites; w hat’s more, the intercalation technology should be improved and the reaction time should be reduced. The existing inserting reactions are very complex. It needs long time consuming and is inefficiency, so improving the inserting technology is very necessary. Intercalated nanocomposite is a highly promising new research field. It combines the rigidity, dimensional stability, thermal stability of the inorganic silicate and the tenacity of the polymer together and shows excellent performance in many fields. Until now, many nano-properties of the composite are unknown. Therefore, the functions of the nanocomposite should be developed so that its additional value can be greatly increased. References: [1] S. Pavlidoua, C.D. Papaspyridesb. A review on polymer–layered silicate nanocomposites. Progress in Polymer Science. 2008, 33: 1119–1198; [2] Gorrasi G, Tortora M, Vittoria V, Galli G, Chiellini E. Transport and mechanical properties of blends of poly caprolactone and a modified montmorillonite–poly caprolactone nanocomposite. J Polym Sci Polym Phys. 2005, 40: 1118–24; [3] Suprakas Sinha Ray, Masami Okamoto. Polymer/layered silicate nanocomposites: a review from preparation to processing. Prog. Polym. Sci. 2003, 28: 1539–1641; [4] Michael Alexandre, Philippe Dubois. Polymer-layered silicate nanocomposites: preparation, properties and uses of a new class of materials. Materials Science and Engineering, 2000,28: 1-63; [5] S.H. Anastasiadis, K. Chrissopouloua, B. Frick. Structure and dynamics in polymer/layered silicate nanocomposites. Materials Science and Engineering B. 2008, 152: 33–39; [6] Xiaoying Wang, Y umin Du, Jianhong Yang, Xiaohui Wang, Xiaowen Shi, Ying Hu. Preparation, characterization and antimicrobial activity of chitosan/layered silicate nanocomposites. Polymer. 2006, 47:6738-6744; [7] Hu Chong-han, Chen Xiao-chen. The Status and Suggestion of Legal Protection of the Right to Exclusive Use Registered Trademark in Foshan Ceramic Industry [J]. Fo Shan Ceramics. 2005, 18:139-142; [8] ZHAO Shun-ping, XIA Hua, ZHANG Sheng-hui. Reasearch Advances in Kaolinite/Organics Intercalated Complex [J]. Journal of Materials Science&Engineering, 2006, 21:58-62; [9] Lu Yinping, Zhang Y ude, Liu Qinfu, Li Jingru. Research progress in preparation and application of nanoclay[J]. New Chemical Materials, 2005, 37, 108-114; [10] Wang Linjiang. Kaolinite-Organic Intercalation reaction and In-Situ Synthesis of Sialon Materials. Ph. D. Dissertation of Chinese Academy of Sciences, 2002; [11] Gorrasi G, Tortora M, Vittoria V, Pollet E, Lepoittevin B, Alexandre M, et al. Vapor barrier properties of polycaprolactone montmorillonite nanocomposites: effect of clay dispersion. Polymer 2003, 44:2271-2279; [12] Shelley JS, Mather PT, DeVries KL. Reinforcement and environmental degradation of nylon 6/clay nanocomposites. Polymer 2002, 42:5849-5858; [13] Lee S-S, Ma YT, Rhee H-W, Kim J. Exfoliation of layered silicate by ring opening reaction of cyclic oligomers in PET–clay nanocomposites. Polymer 2005, 46:2201-2210; [14] Ray SS, Bousima M. Biodegradable polymers and their layered silicate nanocomposites: in greening the 21st century materials world. Prog Mater Sci 2005, 50:962–1079; [15] Chen Fu, Zhao Enlu. The preparation and application of nano-kaolinite [J]. Ceramics, 2007, 5:48-53; [16] Gacitua WE, Ballerini AA, Zhang J. Polymer nanocomposites: synthetic and natural fillers. Maderas Ciencia y tecnología. 2005, 7:159–78; [17]Zeng QH, Yu AB, Lu GQ, Paul DR. Clay-based polymer nanocomposites: research and commercial development. J Nanosci Nanotechnol. 2005, 5:1574–92. 有关建筑转换层结构设计中的关键性问题综述 本文首先介绍了建筑转换层的概念与特点，然后探讨了建筑转换层结构设计的原则和分类，最后提出了建筑转换层结构设计中的注意事项，本文提出了自己的一些观点和看法，望能为建筑转换层的结构设计提供参考。 标签建筑设计；转换层；结构设计；注意事项； 一、概念与特点分析研究 转换层是建筑施工领域常见的一种建筑结构，由于建筑物不同层面之间的使用功能和结构存在差异，因此需要通过设置转换层的方式作为过渡，对楼层的上下部的结构与设施进行转换。当前，我国的建筑设计、特别是高层建筑的设计，常常会采用商业功能与住宅功能结合的设计模式，在建筑物下部构建举架较高的大跨度商用建筑空间，而上层则采用更加紧密的设计，体现建筑的居住功能。为了对不同的实用功能和建筑结构进行划分，便需要在建筑内部设置转换层，以调整不同结构之间的受力情况，确保建筑物的使用安全。转换层主要功能包括：对建筑物内部的剪力墙结构或框架—剪力墙体系进行转换，实现剪力墙与框架之间的变换；改变建筑物上下受力柱的分布情况和分布密度；同时转变建筑层的结构形式和结构轴网，形成上下结构的不对齐布置三种。根据建筑物自身的特点和使用功能的需要，合理的选择转换层的设计模式，充分发挥出转换层在建筑领域所发挥的作用，能够进一步提高建筑物的稳定性，延长建筑物的使用寿命，对我国建筑行业的发展有着积极的促进作用。由于转换层的结构需要同时承受上部构造在重力的作用下产生的垂直荷载，以及悬挂下部结构产生的多层荷载，导致转换层结构内部长期存在有较大的内应力。此外，转换层的存在会对建筑物整体的受力状况造成较大的影响，在一程度上降低了建筑物的整体性，这就要求转换层的结构设计不能单纯遵循传统的建筑设计原则，而是要根据建筑物自身的特点进行灵活的设计，以满足转换层对刚度和强度的需求，确保建筑物的使用安全。 二、原则及分类分析研究 1、转换层的设计原则。首先，由于转换层的设置会造成建筑物纵向刚度的突变，使其成为建筑物的薄弱环节，因此，在进行转换层的结构设计时，应当尽可能减少需要结构转换的纵向构件，并相应的增加直接落地的纵向构件数量，从而降低建筑刚性突变的程度，提高结构的抗震能力。其次，当转换层高度较低时，对建筑物重心与受力状况的影响相对较小，建筑物也因此更加稳固。所以，在进行转换层结构设计时，应当尽量降低转换层所处的位置，保证建筑物结构的稳固。最后，转换层的结构设计应当采取强化下部结构，弱化上部结构的设计思路，并选择具有明确传力路径的设计模式，在保证工程质量的前提下，降低转成的施工难度，控制转换成的施工成本，更好的实现建筑物的经济效益社会效益。 2、转换层的结构设计的分类。一是梁式转换结构。梁式转换结构采用剪力墙、框支梁与框支柱相结合的结构布置方式来提高转换层的强度与刚度，具有结 + plus 加号；正号 - minus 减号；负号 ±plus or minus 正负号 ×is multiplied by 乘号 ÷is divided by 除号 ＝is equal to 等于号 ≠is not equal to 不等于号 ≡is equivalent to 全等于号 ≌is equal to or approximately equal to 等于或约等于号 ≈is approximately equal to 约等于号 ＜is less than 小于号 ＞is more than 大于号 ≮is not less than 不小于号 ≯is not more than 不大于号 ≤is less than or equal to 小于或等于号 ≥is more than or equal to 大于或等于号 % per cent 百分之… ‰per mill 千分之… ∞infinity 无限大号 ∝varies as 与…成比例 √(square) root 平方根 ∵since; because 因为 ∴hence 所以 ∷equals, as (proportion) 等于，成比例 ∠angle 角 ⌒semicircle 半圆 ⊙circle 圆 ○circumference 圆周 πpi 圆周率 △triangle 三角形 ⊥perpendicular to 垂直于 ∪union of 并，合集 ∩intersection of 交，通集 ∫the integral of …的积分 ∑(sigma) summation of 总和 °degree 度 ′minute 分 ″second 秒 ℃Celsius system 摄氏度 { open brace, open curly 左花括号 } close brace, close curly 右花括号 ( open parenthesis, open paren 左圆括号 ) close parenthesis, close paren 右圆括号() brakets/ parentheses 括号 [ open bracket 左方括号 ] close bracket 右方括号 [] square brackets 方括号 . period, dot 句号，点 | vertical bar, vertical virgule 竖线 & ampersand, and, reference, ref 和，引用 * asterisk, multiply, star, pointer 星号，乘号，星，指针 / slash, divide, oblique 斜线，斜杠，除号 // slash-slash, comment 双斜线，注释符 # pound 井号 \ backslash, sometimes escape 反斜线转义符，有时表示转义符或续行符 ~ tilde 波浪符 . full stop 句号 , comma 逗号 : colon 冒号 ; semicolon 分号 ? question mark 问号 ! exclamation mark (英式英语) exclamation point (美式英语) ' apostrophe 撇号 - hyphen 连字号 -- dash 破折号 ... dots/ ellipsis 省略号 " single quotation marks 单引号 "" double quotation marks 双引号 ‖ parallel 双线号 & ampersand = and ～swung dash 代字号 §section; division 分节号 →arrow 箭号；参见号 试论高层建筑工程的转换层结构设计 先进科技在建筑领域的应用为现代建筑行业的发展带来了强大的动力，在现代建筑技术的支持下，高层建筑工程的大量建设与实施得以实现，现代高层建筑不仅在高度上较以往有了很大的增加，同时在建筑外观及结构的复杂性上也与以往有了很大的不同，要充分保障高层建筑工程的结构受力的稳定性，保障高层建筑在建设与使用过程中的安全性，加强对转换层设计的研究是十分必要的，本文就将对此展开探讨。 标签：高层建筑工程；转换层；结构设计 现代城市人口增加以及城市功能的日益丰富和完善，对于城市建筑工程的建设也有着更高的需求，一方面，要求城市建筑工程要在有限的开发土地面积上，创造更多的居住、办公、休闲等功能空间，这可以通过高层建筑工程的建设予以满足，同时还要保障建筑工程的质量与可靠性，这就要求针对高层建筑的结构受力特性进行深入研究，并通过对转换层机构的优化设计予以保证。 一、高层建筑工程转换层结构的主要类型 1.梁式转换层 梁式转换层是现代高层建筑中应用非常广泛的一种转换层结构形式，尤其适用于底部大空间的框支剪力墙结构体系的高层建筑结构转换中，此类转换层结构形式的作用原理主要是通过将转换层上部的剪力墙落在框支梁上，而框支梁则是通过稳定的框支柱进行支撑，从而保证整体建筑结构的稳定性，形成较为稳固的转换结构体系，其在实际应用中的主要优势在于设计简单，便于施工操作，结构传力十分明确，且施工成本较低，具有着良好的经济性优势，因而受到许多建筑企业的青睐。 2.箱式转换层 箱式转换层结构形式相对适用范围要小于梁式转换层，其主要应用于转换梁截面超出一定范围，不能够通过一层楼板的设置来满足其需要的刚度要求情况下的转换层构建。为充分保证建筑结构的稳定性，箱式转换层结构形式通常是在转换梁的顶与底分别设置一层楼板，两层楼板和四周围护的墙壁结构之间形成一个箱式的空间，从而使转换层结构的形式整体呈现为箱式结构。这种结构形式在应用中能够有效的保障对转换梁的较强约束力，同时转换梁的刚度也相对较大，从上到下整体结构在传力效果方面相对更为均匀，同时箱式结构中间所形成的空间也可以满足建筑设备层设置的功能需求，具有着良好的应用效果。但相对的，此类转换层结构形式在建设过程中需要在转换梁中进行较多的开洞处理，相对施工操作的复杂性更高，其施工成本也相对较高，经济效益一般。 3.厚板式转换层 中英文标点符号地读法用法大全 ⒈汉语中地某些标点符号为英语所没有. ⑴顿号（、）：顿号在汉语中起分割句子中地并列成分地作用；英语中没有顿号，分割句中地并列成分多用逗号.如：, , . 注意：类似地情况下，最后一个逗号后可加，这个逗号也可省略, (,) . ⑵书名号（《》）：英文没有书名号，书名、报刊名用斜体或者下划线表示.如： 《哈姆雷特》' ' 《冬天地童话》《纽约时报》另外，英语中文章、诗歌、乐曲、电影、绘画等地名称和交通工具、航天器等地专有名词也常用斜体来表示. ⑶间隔号（?）：汉语有间隔号，用在月份和日期、音译地名和姓等需要隔开地词语地正中间，如"一二?九"、"奥黛丽?赫本（人名）"等.英语中没有汉语地间隔号，需要间隔时多用逗号. ⑷着重号：有时汉语用在文字下点实心圆点表示需要强调地词语，这些实心点就是着重号.而英语中没有这一符号，需强调某些成分时可借助文字斜体、某些强调性词汇、特殊句型、标点停顿等多种方法. ⒉英语中地某些标点符号为汉语所没有. ⑴撇号（'）：该符号主要表示①所有格，如' ' ；②数字、符号、字母或词形本身地复数，如' .; ③省略了字母、数字或单词，如'（）'（）. ⑵连字号（）：该符号主要用于以下几种情况.①复合词，如.②派生词地词缀与词根或词之间，如.③两个比分、比赛对手、地名、人名、数字之间，可视情况译为"比""对""至"等.④单词移行，把在一行写不开地单词按音节移到下一行，但必须注意：. 单音节词不移行. . 曲折变化后地词尾，如等一般不移行.. 数字、缩略词不宜移行.. 易引起歧义地词不移行，如不宜移行为.. 移行后行尾不宜只剩一个字母，如不宜移为. . 带词缀地词应在词缀和词根处移行，如移为.. 复合词在复合成分之间移行，如移为. ⑶斜线号或（）：该符号主要起分割作用，如. 也常用于标音，如. ⒊某些符号在汉英两种语言中地形式不同. ⑴中文地句号是空心圈（.），英文地句号是实心点（.）. ⑵英文地省略号是三个点（...），位置在行底；中文地为六个点（......），居于行中.在美国英语中，如果省略号恰好在句尾，就用四个点，如' ' .... ⑶英文地破折号是（），中文地是（）. 四、美国英语与英国英语在标点符号方面地细微差别 ．引号地用法：①属于引语地逗号、句号在美国英语中位于引号内，而在英国英语中多位于引号外；②引语内再套用引语时，美国英语中双引号在外单引号在内，而英国英语中地单引号在外、双引号在内. ．冒号地用法：①在小时与分钟之间，美国英语多用冒号，英国英语多用句号；②美国 浅析高层建筑桁架转换层结构设计 发表时间：2019-07-30T11:57:40.153Z 来源：《基层建设》2019年第14期作者：黄桂生 [导读] 摘要：复杂的建筑结构常常需要采用结构转换层来完成上、下层建筑物结构的转换，一般结构层相比，转换层结构具有结构重量大、结构层刚度大、几何尺寸超大、受力复杂等特点。 身份证：45252819750527XXXX 摘要：复杂的建筑结构常常需要采用结构转换层来完成上、下层建筑物结构的转换，一般结构层相比，转换层结构具有结构重量大、结构层刚度大、几何尺寸超大、受力复杂等特点。这意味着转换结构组成了建筑物的主要构件，它们的设计是否合理、安全、经济对整个结构的安全性、结构造价、施工费用等有着重要的影响。通过时钢桁架转换层高层建设结构体系的工程实例的分析，从结构选型的确定等方面进行系统的研究。以得到一些对设计有实际指导意义的结论。 关键词：建筑工程；结构设计；转换层构造 在当前建筑结构设计过程中，为了更好的适合建筑物的各部楼层所体现的安全使用功能的需求，往往需要在各楼层之间布置转换层以消除楼层中间的较大差异。转换层的设置起到传承上部结构荷载，保持结构稳定的作用，是建筑结构中的重要部位，也是建筑结构设计的重点和难点。因此，深入探讨高层建筑转换层结构设计问题，对于促进我国民用高层建筑的发展具有一定的现实意义。 1.转换层高层建筑结构的构造要求 结构设计不仅是对建筑物本身功能的设计，还关系到建筑物的建设成本，这就需要设计人员优化结构设计，降低建设成本。其优化目标就是实现建筑的本体功能性、安全性、经济性与环保性。为了实现这一目标，未来的从事结构设计者将遵循功能性、安全性、经济性、环保性四位一体的设计思路，真正实现未来建筑结构的优化升级，为人类提供一个更好的物质生存与发展环境。 转换层的结构应按“强化转换层及其下部、弱化转换层上部”的原则，使转换层上下主体结构的侧向刚度尽量接近，平滑过渡。抗震设计时。控制转换层上下主体的结构侧向刚度，当转换层设置在3层及3层以上时。其楼层侧向刚度尚不应小于相邻上部楼层侧向刚度的60％。将转换桁架置于整体空间结构中进行整体分析。此时，腹杆作为柱单元。上、下弦杆作为梁单元，按空间协同工作玻三维空间分析程序计算整体的内力和位移。计算时，转换桁架按实际杆件布置参与整体分析，但上、下弦杆的轴向刚度、弯曲刚度中应计入楼板的作用。整体结构计算需采用两个以上不同力学模型的程序进行抗震计算。还应进行弹性时程分析并宜采用弹塑性时程分析校核。转换层的结构设计中应按转换层“强斜腹杆，强节点”。桁架转换层上部框架结构接“强柱弱梁、强边柱弱中柱”的原则，以保证转换层的结构具有较好的延性，确保塑性饺在梁端出现，能够满足工程抗震的要求。转换桁架的相邻层楼板宜双向双层配筋，每个方向贯通钢筋的配筋率不宜小于0.25％，且在楼板边缘、孔洞边缘应结合边粱设置予以加强。转换桁架上、下弦杆的配筋应加上楼板平面内弯曲计算引起的附加钢筋。 2.转换层商层建筑结构实例分析 对于大跨度的钢桁架转换层结构的受力。各方面的影响因素较多，导致结构受力情况比较复杂，对它的受力影响因素进行探讨具有实际意义，可为实际工程的设计与施工提供理论依据。因此，通过对大跨度钢桁架转换层的受力影响因素进行分析，认识钢桁架转换层的受力特点。以期充分利用钢结构构件受力性能好的特点，使其承担较多的荷载作用。以调整端部混凝土结构的受力，减少混凝土结构的荷载作用，使整个结构体系的受力更为合理。下面结合工程实例分析高层转换桁架的受力影响因素及其受力特点，某高层建筑为地上24层，地下2层，总建筑面积72788m2，其中地上58300m2，地下14488m2。平面长92.1M，宽49M。结构檐口标高为108.80m，中间有电梯、楼梯、机房等的高层建筑。 2.1梁式转换与精架转换的比较确定 与最为常见的转换结构形式粱式转换相比，本例中转换粱的跨度很大而且上部荷载较大，采用梁式的转换结构，转换梁的截面必然很大，一方面导致转换梁下部空间无法再利用、自重大、配筋多、不经济等缺点；另一方面导致沿竖向结构质量和刚度分布在转换层的变化不连续。发生突变，对结构的整体抗震性能不利。因此，需要另一种形式的转换构件来解决这个问题，而转换桁架具有传力明确，传力途径清楚，虽构造和施工复杂，但转换桁架不仅为开洞和设置管道创造了条件，而且它们的位置与大小都有很大的灵活性，可以充分利用该转换层的建筑空间，而且桁架转换层的节间采用轻质建筑材料填充甚至可以外露不填充，有利于减轻结构的自重；转换桁架的抗侧力刚度比转换粱要小，也就是说。具有桁架转换层的高层建筑其质量和刚度的突变要比带转换粱的高层建筑缓和。因此带转换桁架的高层建筑其地震反应要比带转换梁的高层建筑小得多，由此可见，在本例工程的三层转换构件采用转换大粱的结构形式是不合适的，而采用转换桁架的结构形式将很好的避免了上述的多个问题且将节约混凝土用量近30％。将是一个较为合理正确的选择。 2.2转换桁架的具体形式的确定 在本例工程的三层转换构件采用确定桁架结构后，设计人员则需要进一步确定桁架的结构形式。根据前面的论述，转换桁架的结构形式有多种，但是根据本例工程的三层转换构件的具体情况，采用何种最合理的结构形式，则必须加以比较分析后方可确定。 2.2.1单层转换桁架与双层转换桁架的确定 采用精架结构作为高层建筑的转换构件时，一般情况是取出一层层高的高度作为转换桁架的高度。对于本项目，转换桁架位于结构的边缘，建筑师为了使转换桁架对于立面的影响降至最小，希望桁架仅在中庭设置，即取一层高度(4.00m)作为转换桁架的高度。在本例中各层的层高情况分别是：底层：6.44ml，二层：4.80m，三层以上：4.00mt，而结构的柱距为9.0m，若仅取4.00m为桁架高度时，在柱与柱之间必须另设一个桁架节点以保证桁架斜腹杆与水平弦杆的角度在合理的450~550之间。若取建筑的两层层高即8.00m为转换桁架的高度，则在柱与柱之间可以不必设置多余的桁架节点，使桁架的结构形式趋于简单。 2.2.2空腹桁架、斜杆桁架、无竖杆桁架的比较确定 作为高层建筑中的转换结构一桁架结构有如下的主要结构形式：空腹桁架、交叉斜杆桁架、无竖杆的交叉斜杆桁架。作为一种相对独立的结构形式，无论采用何种结构形式。应该说都是可以实现的。对于建筑师来说，空腹桁架如果在构件尺寸可以接受的条件下。当然是首选，当然，采用无竖杆的交叉斜杆桁架形式，结构上可以使桁架的构造节点趋于简单，在建筑师看来，也可以接受。 2.2.3单跨桁架与多跨桁架的确定 在确定了以交叉斜杆桁架作为本次项目的转换结构的结构形式后，结构工程师尚发现在这个计算模型中的框架柱的内力较大。作为抗震设计“强柱弱梁”的一般设计原则，框架柱中的内力相对越大，则在柱中率先出现塑性铰的可能性将越大。而在模型计算中同样可以发 英文标点符号翻译大全 + plus 加号；正号 - minus 减号；负号 ±plus or minus 正负号 ×is multiplied by 乘号 ÷is divided by 除号 ＝is equal to 等于号 ≠is not equal to 不等于号 ≡is equivalent to 全等于号 ≌is equal to or approximately equal to 等于或约等于号≈is approximately equal to 约等于号 ＜is less than 小于号 ＞is more than 大于号 ≤is not less than 不小于号 ≥is not more than 不大于号 ?is less than or equal to 小于或等于号 ?is more than or equal to 大于或等于号 % per cent 百分之… ‰per mill 千分之… ∞infinity 无限大号 ∝varies as 与…成比例 √(square) root 平方根 ∵since; because 因为 ∴hence 所以 ∷equals, as (proportion) 等于，成比例 ∟angle 角 ?semicircle 半圆 ≦circle 圆 ○circumference 圆周 πpi 圆周率 △triangle 三角形 ≧perpendicular to 垂直于 ∪union of 并，合集 ∩intersection of 交，通集 ∫the integral of …的积分 ∑(sigma) summation of 总和 °degree 度 ′minute 分 ″second 秒 ℃Celsius system 摄氏度 { open brace, open curly 左花括号 } close brace, close curly 右花括号 ( open parenthesis, open paren 左圆括号 ) close parenthesis, close paren 右圆括号 +plus加号；正号 -minus减号；负号 ±plus or minus正负号 ×is multiplied by乘号 ÷is divided by除号 ＝is equal to等于号 ≠is not equal to不等于号 ≡is equivalent to全等于号 ≌is equal to or approximately equal to等于或约等于号≈is approximately equal to约等于号 ＜is less than小于号 ＞is more than大于号 ≮is not less than不小于号 ≯is not more than不大于号 ≤is less than or equal to小于或等于号 ≥is more than or equal to大于或等于号 %per cent百分之… ‰per mill千分之… ∞infinity无限大号 ∝varies as与…成比例 √(square) root平方根 ∵since; because因为 ∴hence所以 ∷equals, as (proportion)等于，成比例 ∠angle角 ⌒semicircle半圆 ⊙circle圆 ○circumference圆周 πpi 圆周率 △triangle三角形 ⊥perpendicular to垂直于 ∪union of并，合集 ∩intersection of 交，通集 ∫the integral of …的积分 ∑(sigma) summation of总和 °degree度 ′minute分 ″second秒 ℃Celsius system摄氏度 { open brace, open curly 左花括号 } close brace, close curly 右花括号 ( open parenthesis, open paren 左圆括号 ) close parenthesis, close paren 右圆括号 () brakets/ parentheses 括号[ open bracket 左方括号 ] close bracket 右方括号 [] square brackets 方括号 . period, dot 句号，点 | vertical bar, vertical virgule 竖线 & ampersand, and, reference, ref 和，引用 * asterisk, multiply, star, pointer 星号，乘号，星，指针 / slash, divide, oblique 斜线，斜杠，除号 // slash-slash, comment 双斜线，注释符 # pound 井号 \ backslash, sometimes escape 反斜线转义符，有时表示转义符或续行符 ~ tilde 波浪符 . full stop 句号 , comma 逗号 : colon 冒号 ; semicolon 分号 ? question mark 问号 ! exclamation mark (英式英语) exclamation point (美式英语) ' apostrophe 撇号 - hyphen 连字号 -- dash 破折号 ... dots/ ellipsis 省略号 " single quotation marks 单引号 "" double quotation marks 双引号 ‖ parallel 双线号 & ampersand = and ～swung dash 代字号 §section; division 分节号 →arrow 箭号；参见号 Appreciating in English Movies The Everlasting Existence—Artificial Intelligence 罗欢 Class 7 Grade 3 Number：201105140715 China West Normal University 2014/5/4 The Everlasting Existence---A.I Abstract:Human create the robot and make them to love,but they are also scared by the robots if they do something out of control.The human are selfish,so is their love while the love from robots is everlasting. Key words: robot ; human ;existence&love Commentary text: After seeing the movie A.I by Steven Spielberg and Kubrick.I am lost in the deep thinking, there are too many things contained in it and makes me moved. In the film,there is a very special artificial intelligent robot named David, just as the movie said, David is 11 years old. He weighs 60 pounds. He is 4 feet and 6 inches tall. He has brown hair, his love is real but he is not. This is a story about the process that David seek for the love from his mother,Monica. He experiences the abandonment and persecution and at last he successes, just like the ending of Pinocchio and Blue Fairy, he becomes a real boy, though it compared with other robots and he gains the love from his mother though it only last for one day. It is not a very long story but it makes us think a lot. Because of the climate change, there exist enormous problems and crisis. In order to reduce the burden then the low-cost robot has been came into use in a large scale. To meet the vanity of human, these robots own the same appearance as human, even the feelings and memories.To some degree, this shows the loneliness of human and the robot just like David who can love is the extremely showing of this. About David, he is very unique for he is the first robot child and he was made by very special reasons. When he is started by Monica, David would love Monica forever and only love her in the world. When he first comes into Monica’s home, his bright smile brings the happiness to this home. But when Martin, the real child of Monica comes back, all are ruined. For Monica, this is the perfect thing in the world but for David, the tragedies just begins. When Martin asks David when is your birthday or what is the first thing that you can remember, all the questions emphasized that David is not a real boy but just a robot. In order to win more love from Monica, David does many things, some are even crazy. However, all things have to stop in the birthday party of Martin. For 标点符号英文翻译大全 + plus 加号；正号 - minus 减号；负号 ± plus or minus 正负号 × is multiplied by 乘号 ÷ is divided by 除号 ＝ is equal to 等于号 ≠ is not equal to 不等于号 ≡ is equivalent to 全等于号 ≌ is equal to or approximately equal to 等于或约等于号 ≈ is approximately equal to 约等于号 ＜ is less than 小于号 ＞ is more than 大于号 ≮ is not less than 不小于号 ≯ is not more than 不大于号 ≤ is less than or equal to 小于或等于号 ≥ is more than or equal to 大于或等于号 百分之 % per cent… 千分之 ‰ per mill… ∞ infinity 无限大号 与成比例 ∝ varies as… √ (square) root 平方根 ∵ since; because 因为 ∴ hence 所以 ∷ equals, as (proportion) 等于，成比例 ∠ angle 角 ⌒ semicircle 半圆 ⊙ circle 圆 ○ circumference 圆周 π pi 圆周率 △ triangle 三角形 ⊥ perpendicular to 垂直于 ∪ union of 并，合集 ∩ intersection of 交，通集 ∫ the integral of …的积分 ∑ (sigma) summation of 总和 ° degree 度 ′ minute 分 ″ second 秒 ℃ Celsius system 摄氏度 { open brace, open curly 左花括号 } close brace, close curly 右花括号 ( open parenthesis, open paren 左圆括号 ) close parenthesis, close paren 右圆括号 () brakets/ parentheses 括号 [ open bracket 左方括号 ] close bracket 右方括号 [] square brackets 方括号 . period, dot 句号，点 | vertical bar, vertical virgule 竖线 & ampersand, and, reference, ref 和，引用 * asterisk, multiply, star, pointer 星号，乘号，星，指针 / slash, divide, oblique 斜线，斜杠，除号 // slash-slash, comment 双斜线，注释符 # pound 井号 \ backslash, sometimes escape 反斜线转义符，有时表示转义符或续行符~ tilde 波浪符 . full stop 句号 , comma 逗号 : colon 冒号 ; semicolon 分号 ? question mark 问号 ! exclamation mark (英式英语) exclamation point (美式英语) ' apostrophe 撇号 - hyphen 连字号 -- dash 破折号 电影人工智能英文简介 电影人工智能英文简介 AI - Artificial Intelligence is the hardest kind of movie to review-but it s also the most enjoyable kind of movie to watch. It s been over three weeks since my screening of Steven Spielberg s emotionally harrowing epic about a robot boy. Before writing my review, I wanted to let its themes, content, and characters sink into my head and make a solid impact. The film was based on an idea by Stanley Kubrick, but when he died in 1999, Speilberg took charge of the project. I could spend pages discussing the techniques of Kubrick s intentions and Spielberg s decisions, but I will not. Stanley Kubrick and Steven Spielberg are two of the greatest directors American cinema has to offer; it s pure pleasure watching their ideas clash and flow. I am not going to examine each individual theme here, either. That would ruin the movie for you. AI - Artificial Intelligence presents many themes on screen, but it s important to take what you get out of it. Whenever I read a review of Kubrick s A Clockwork Orange or 2001: A Space Odyssey I feel influenced by the reviewer s interpretation of the movie s themes. Every time I watch either of those movies I get something new out of it. I hate it when other critics state the movie s themes on paper as if it s a fact. There is far too much room for interpretation to reveal this movie s message, or the message of any Kubrick film for that matter. Ask 100 people, and you might get 100 different answers. AI - Artificial Intelligence is that kind of movie-one of the year s best. Critics and audiences alike have torn apart this movie s ending-a clear miscalculation by Spielberg. If Kubrick were in charge, the movie would have called it quits about twenty minutes earlier in an unsettling sequence that takes place in the ocean. But Speilberg, who always seems entranced by science fiction, injects an additional segment into the mix that does not work quite as well, but isn t so completely awful that it deserves such harsh criticism. It still leaves us with an open, startled emotional disorientation. I left the theater with tears in my eyes. The movie before the conclusion is so 2020高考英语作文预测热点+范文——5G和人工智能 01 5G技术与人工智能 假定你是李华，你所在的山西国际学校要征集一封英文感谢信，以致意奋战在抗击新型冠状病毒肺炎第一线的医护人员，请你根据下列要点写一封信用于投稿。 【题目要求】 人工智能与5G时代已悄然来临，随着科技越来越与人类生活相结合，随处可见的人工智能，让生活越来越便利的同时也带来许多的困惑，按要求完成一篇作文。内容包括： 1. 描述或畅想未来人工智能的发展状况 2. 分析这种现象产生的原因 3. 陈述利弊以及表明个人态度 【优秀范文】 As we all know , the time of 5G technology is coming , it is called the fourth industrial revolution , future of computer science lies in the artificial intelligence，it is the research and artificial simulation of human thought and eventually be able to ma ke a human like to think the same machine , for human services and to help people solve problems. After all, people thought it was unique, there are feelings, there are a variety of character, this will be very difficult to achieve in the machine.In fact, to do the same as the human thinking machine, the only one of the artificial intelligence, is by no means all. Through the study of artificial intelligence, it can resolve all kinds of scientific problems, promote the development of other science will have a great impact on all people's lives . 对建筑转换层结构设计的探讨 摘要：结合多年工作经验，分析梁式转换层的主要结构形式及特点，阐述转换层设计中应该注意的原则性问题，并提出高层建筑梁式转换层结构设计的关键要点。关键词：高层建筑；梁式转换层；施工abstract: combined with years work experience, analysis of the main girder storey structure form and characteristics, this paper expounds the conversion layers should pay attention to in the design of principle problems, and put forward the high-rise buildings beam type conversion layers structure design of the key points.keywords: high building; beam type conversion layers; construction 中图分类号：tu97 文献标识码：a 文章编号：随着我国经济的持续快速发展，高层建筑一般上部需要较多的墙体来分隔空间以满足住宅户型的需要；而下部则希望有较大的自由灵活空间，大柱网、少墙体，以满足公共使用要求。这样的建筑上部楼层部分竖向构件（剪力墙、框架柱）不能直接连续贯通落地时，为了满足建筑要求就必须在上下不同结构体系转换的楼层设置转换层，在结构转换层布置转换结构构件。转换层结构形式有以下几种：梁式转换层、板式转换层、箱式转换层、桁架式转换层、空腹桁架式转换层等。 1 梁式转换层结构形式 1.1 梁式转换层结构形式实际工程中应用的梁式转换层结构有多 种形式，主要原理就是利用下部的转换大梁来支托上部结构。 第十章不容忽视的细节：标点、拼写、和格式 ?主要章节：10.1 细节的意义（P227） 10.2 标点符号（P227～241） 10.3 拼写（P241～243） 10.4 文件格式（P243～245） 10.5 其他细节（PP246） 10.6 练习答案（P246～249） 10.1 细节的意义（责任重大、微观要求） 10.2标点符号（目的：理清结构、划分意群、便于阅读） 10.2.1英汉标点符号和用法的主要差异 1）英文标点：①看起来较小； ②句号是圆点； ③破折号用两个连字符（--）表示； ④无顿号、书名号、间隔号（·）； 2）汉译英时：①顿号转化为逗号或“and”； ②去掉书名号，但英语中书名号实词首字母大写； ③整个书名斜体； 3）英文标点的前后空格问题 ①逗号、分好、句号、冒号、感叹号、问号→前无空格，后有空格 ②圆括号、方括号、引号→内无空格，外有空格 ③破折号、连字符→两端无空格 ④撇号（’）→前后均无间隔 10.2.2 英语标点用法要点 1)句号、分号、逗号、括号、破折号（正式问题中不用破折号）； 2)冒号→英语中的副标题不用破折号，用冒号 例如：《翻译学导论》——理论与实践 Introducing Translation Studies: Theories and Applications 3）连字符：①用于单词断行、构成复合词； ②避免意思含糊，出现误解； 例如：Mr. Green was a small-business man. 格林先生是位做小买卖的商人。 Mr. Green was a small business man 格林先生是一个身材矮小的商人。 4）省略号：①英语省略号一般是三个点，而且居下（…）； ②MLA规定，省略号都用方括号括住； ③英语省略号三个点和前面的内容之间留一个空格，最后一个 点和后面的内容之间留一个空格； ④英语省略号如果出现在段落的最后，即省略号之后没有其他 句子时，应该在省略号之后再加上其他的标点。 5）直接引语： ①直接引语两边用单引号（英式英语）或者双引号（美式英语）； ②“he said”之类的话： a.“he said”之类的话放在直接引语之后，在右引号之前加逗号、 问好、感叹号等，但不能加句号； 例如：“Let’s go,” I whispered. (例子：P236)有关建筑转换层结构设计中的关键性问题综述
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电影人工智能英文简介.doc
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word中的中英文标点、拼写和格式的使用(详细汇总)