外文翻译
本科毕业论文外文翻译【范本模板】
本科毕业论文外文翻译外文译文题目:不确定条件下生产线平衡：鲁棒优化模型和最优解解法学院：机械自动化专业：工业工程学号: 201003166045学生姓名: 宋倩指导教师：潘莉日期: 二○一四年五月Assembly line balancing under uncertainty: Robust optimization modelsand exact solution methodÖncü Hazır , Alexandre DolguiComputers ＆Industrial Engineering，2013,65：261–267不确定条件下生产线平衡：鲁棒优化模型和最优解解法安库·汉泽，亚历山大·多桂计算机与工业工程，2013，65：261–267摘要这项研究涉及在不确定条件下的生产线平衡，并提出两个鲁棒优化模型。
假设了不确定性区间运行的时间。
该方法提出了生成线设计方法,使其免受混乱的破坏。
基于分解的算法开发出来并与增强策略结合起来解决大规模优化实例.该算法的效率已被测试,实验结果也已经发表。
本文的理论贡献在于文中提出的模型和基于分解的精确算法的开发.另外，基于我们的算法设计出的基于不确定性整合的生产线的产出率会更高，因此也更具有实际意义。
此外,这是一个在装配线平衡问题上的开创性工作,并应该作为一个决策支持系统的基础。
关键字：装配线平衡；不确定性; 鲁棒优化；组合优化；精确算法1.简介装配线就是包括一系列在车间中进行连续操作的生产系统。
零部件依次向下移动直到完工。
它们通常被使用在高效地生产大量地标准件的工业行业之中。
在这方面，建模和解决生产线平衡问题也鉴于工业对于效率的追求变得日益重要。
生产线平衡处理的是分配作业到工作站来优化一些预定义的目标函数。
那些定义操作顺序的优先关系都是要被考虑的,同时也要对能力或基于成本的目标函数进行优化。
就生产（绍尔，1999）产品型号的数量来说，装配线可分为三类：单一模型（SALBP）,混合模型(MALBP）和多模式（MMALBP）。
外文翻译
毕业设计(论文)外文资料翻译学院(系)：计算机科学与工程专业：计算机科学与技术姓名：杨玉婷学号：120602127外文出处：[1]Jérôme Vouillon,Vincent Balat.From bytecode to JavaScript: the Js_of_ocaml compiler[J].Softw.Pract.Exper.,2014,44（8）:Pages 951-955附件：1.外文资料翻译译文；2.外文原文。
1.外文翻译译文：总结：我们目前从OCaml字节码编译器的设计与实现JavaScript。
编译器首先将字节码转换为静态单赋值的中间表示上进行优化，在生成的JavaScript。
我们相信，以字节而不是一个高层次的语言输入是一个明智的选择。
虚拟机提供了一个非常稳定的原料药。
这样的编译器是很容易维护的。
它也方便使用，它可以添加到现有的开发工具的安装。
已经编译好的库可以直接使用，无需重新安装任何东西，最后，一些虚拟机是几种语言的目标。
字节码编译为JavaScript可以重新审视所有这些语言的Web浏览器一次。
1。
简介我们提出了一个编译器将字节码转换为JavaScript OCaml[1][2]。
这个编译器可以交互式Web应用程序客户端在ocaml.javascript是唯一的语言，很容易在大多数Web浏览器和浏览器的API提供了直接访问。
（其他平台，如Flash 和Silverlight，并没有广泛使用和集成。
）因此，强制性语言开发Web应用程序，它将能够使用各种Web浏览器上的JavaScript语言有趣：可适用于某些任务，但可以在其他语言其他情况下更合适。
特别是，能够使用相同的语言，无论是在浏览器和服务器，使它可以共享代码，并降低了语言之间的阻抗不匹配的两个层次。
例如，表单验证必须在服务器上进行，以提供安全的原因，并且在客户端上进行，以向用户提供早期反馈。
外文翻译中英文对照
Strengths优势All these private sector banks hold strong position on CRM part, they have professional, dedicated and well-trained employees.所以这些私人银行在客户管理部分都持支持态度，他们拥有专业的、细致的、训练有素的员工。
Private sector banks offer a wide range of banking and financial products and financial services to corporate and retail customers through a variety of delivery channels such as ATMs, Internet-banking, mobile-banking, etc. 私有银行通过许多传递通道（如自动取款机、网上银行、手机银行等）提供大范围的银行和金融产品、金融服务进行合作并向客户零售。
The area could be Investment management banking, life and non-life insurance, venture capital and asset management, retail loans such as home loans, personal loans, educational loans, car loans, consumer durable loans, credit cards, etc. 涉及的领域包括投资管理银行、生命和非生命保险、风险投资与资产管理、零售贷款（如家庭贷款、个人贷款、教育贷款、汽车贷款、耐用消费品贷款、信用卡等）。
Private sector banks focus on customization of products that are designed to meet the specific needs of customers. 私人银行主要致力于为一些特殊需求的客户进行设计和产品定制。
毕业论文外文翻译格式【范本模板】
因为学校对毕业论文中的外文翻译并无规定，为统一起见,特做以下要求：1、每篇字数为1500字左右，共两篇；2、每篇由两部分组成:译文+原文.3 附件中是一篇范本，具体字号、字体已标注。
外文翻译（包含原文)(宋体四号加粗）外文翻译一（宋体四号加粗）作者：(宋体小四号加粗）Kim Mee Hyun Director, Policy Research & Development Team，Korean Film Council（小四号）出处：(宋体小四号加粗)Korean Cinema from Origins to Renaissance(P358～P340) 韩国电影的发展及前景（标题：宋体四号加粗）1996～现在数量上的增长(正文:宋体小四）在过去的十年间，韩国电影经历了难以置信的增长。
上个世纪60年代，韩国电影迅速崛起，然而很快便陷入停滞状态,直到90年代以后，韩国电影又重新进入繁盛时期。
在这个时期，韩国电影在数量上并没有大幅的增长，但多部电影的观影人数达到了上千万人次。
1996年，韩国本土电影的市场占有量只有23.1%。
但是到了1998年，市场占有量增长到35。
8%，到2001年更是达到了50%。
虽然从1996年开始，韩国电影一直处在不断上升的过程中，但是直到1999年姜帝圭导演的《生死谍变》的成功才诞生了韩国电影的又一个高峰。
虽然《生死谍变》创造了韩国电影史上的最高电影票房纪录，但是1999年以后最高票房纪录几乎每年都会被刷新。
当人们都在津津乐道所谓的“韩国大片”时，2000年朴赞郁导演的《共同警备区JSA》和2001年郭暻泽导演的《朋友》均成功刷新了韩国电影最高票房纪录.2003年康佑硕导演的《实尾岛》和2004年姜帝圭导演的又一部力作《太极旗飘扬》开创了观影人数上千万人次的时代。
姜帝圭和康佑硕导演在韩国电影票房史上扮演了十分重要的角色。
从1993年的《特警冤家》到2003年的《实尾岛》，康佑硕导演了多部成功的电影。
毕业论文 外文翻译格式
毕业论文外文翻译格式毕业论文外文翻译格式在撰写毕业论文时，外文翻译是一个重要的环节。
无论是引用外文文献还是翻译相关内容，都需要遵循一定的格式和规范。
本文将介绍一些常见的外文翻译格式，并探讨其重要性和应用。
首先，对于引用外文文献的格式，最常见的是使用APA（American Psychological Association）格式。
这种格式要求在引用外文文献时，先列出作者的姓氏和名字的首字母，然后是出版年份、文章标题、期刊名称、卷号和页码。
例如：Smith, J. D. (2010). The impact of climate change on biodiversity. Environmental Science, 15(2), 145-156.在翻译外文文献时，需要注意保持原文的准确性和完整性。
尽量避免意译或添加自己的解释，以免歪曲原文的意思。
同时，还需要在翻译后的文献后面加上“译者”和“翻译日期”的信息，以便读者可以追溯翻译的来源和时间。
其次，对于翻译相关内容的格式，可以参考国际标准组织ISO（International Organization for Standardization）的格式。
这种格式要求在翻译相关内容时，先列出原文，然后是翻译后的文本。
例如：原文：The importance of effective communication in the workplace cannot be overstated.翻译：工作场所有效沟通的重要性不容忽视。
在翻译相关内容时，需要注意保持原文的意思和语气。
尽量使用准确的词汇和语法结构，以便读者能够理解和接受翻译后的内容。
同时，还需要在翻译后的文本后面加上“翻译者”和“翻译日期”的信息，以便读者可以追溯翻译的来源和时间。
此外，对于长篇外文文献的翻译，可以考虑将其分成若干章节，并在每个章节前面加上章节标题。
这样可以使读者更容易理解和阅读翻译后的内容。
外文翻译及原文
Pyrolysis of oil sludge first by thermogravimetry/mass spectroscopy (TG/MS) and then in a horizontal quartz reactor with an electrical laboratory furnace under different pyrolysis conditions was carried out. The influence of heating rate from 5 to 20 °Camin-1, final pyrolysis temperature from 400 to 700 °C, various interval holding stage, and catalyst on the products were investigated in detail. The TG/MS results show that pyrolysis reaction of oil sludge starts at a low temperature of about 200 °C, and the maximum evolution rate is observed between the temperatures of 350-500 °C. A higher final pyrolysis temperature, an interval holding stage, and adding catalyst can promote the pyrolysis conversion (in terms of less solid residue production). In all parameters, an interval holding stage for 20 min near the peak temperature of 400 °C can enhance the yield of oil and improve its quality. Three additives used in this work as catalysts do not improve oil product quality markedly in spite of increasing pyrolysis conversion greatly.油泥的裂解首先通过热重/质谱分析（TG / MS），然后在水平石英反应器中具有不同热解条件下的电气实验室炉进行。
外文翻译及中文译文
车床用于车外圆、端面和镗孔等加工的机床称作车床。
车削很少在其他种类的机床上进行，因为其他机床都不能像车床那样方便地进行车削加工。
由于车床除了用于车外圆还能用于镗孔、车端面、钻孔和铰孔，车床的多功能性可以使工件在一次定位安装中完成多种加工。
这就是在生产中普遍使用各种车床比其他种类的机床都要多的原因。
两千多年前就已经有了车床。
现代车床可以追溯到大约1797年，那时亨利•莫德斯利发明了一种具有把主轴和丝杆的车床。
这种车床可以控制工具的机械进给。
这位聪明的英国人还发明了一种把主轴和丝杆相连接的变速装置，这样就可以切削螺纹。
车床的主要部件：床身、主轴箱组件、尾架组件、拖板组、变速齿轮箱、丝杆和光杆。
床身是车床的基础件。
它通常是由经过充分正火或时效处理的灰铸铁或者球墨铸铁制成，它是一个坚固的刚性框架，所有其他主要部件都安装在床身上。
通常在球墨铸铁制成，它是一个坚固的刚性框架，所有其他主要部件都安装在床身上。
通常在床身上面有内外两组平行的导轨。
一些制造厂生产的四个导轨都采用倒“V”，而另一些制造厂则将倒“V”形导轨和平面导轨结合。
由于其他的部件要安装在导轨上并（或）在导轨上移动，导轨要经过精密加工，以保证其装配精度。
同样地，在操作中应该小心，以避免损伤导轨。
导轨上的任何误差，常常会使整个机床的精度遭到破坏。
大多数现代车床的导轨要进行表面淬火处理。
以减少磨损和擦伤，具有更大的耐磨性。
主轴箱安装在床身一端内导轨的固定位置上。
它提供动力。
使工件在各种速度下旋转。
它基本上由一个安装在精密轴承中的空心轴和一系列变速齿轮---类似于卡车变速箱所组成，通过变速齿轮，主轴可以在许多中转速的旋转。
大多数车床有8～18中转速，一般按等比级数排列。
在现代车床上只需扳动2～4个手柄，就能得到全部挡位的转速。
目前发展的趋势是通过电气的或机械的装置进行无级变速。
由于车床的精度在很大程度上取决于主轴，因此主轴的结构尺寸较大，通常安装在紧密配合的重型圆锤滚子轴承或球轴承中。
外文翻译原文
IntroductionLatvian legislation for forest protection belts Latvian legislation demands that forest protection belts are established around all cities and towns. The concept of protection belts originates from the Soviet Era and is maintained in Latvian legislation despite the radical changes to the political system after regaining indepen-dence in 1991. The legal background for the establish-ment of protection belts is as follows:•Law on Protection Belts (1997, 2002)•Forest Law (2000)•Law on Planning of Territorial Development (1998).Designating a greenbelt around the city of Riga, LatviaJanis DonisLatvian State Forestry Research Institute ‘Silava’, Salaspils, LatviaAbstract: Latvian legislation demands that forest protection belts are established around all cities and towns. The main goal of a protection belt is to provide suitable opportuni-ties for recreation to urban dwellers and to minimise any negative impacts caused by urban areas on the surrounding environment. Legislation states the main principles to be adopted, which include the maximum area of protection belts, their integration in terri-torial development plans and restrictions placed on forest management activities. The largest part of the forest area around Riga is owned by the municipality of Riga, which, as a result, has two competing interests: to satisfy the recreational needs of the inhabitants of Riga, and to maximise the income from its property. In order to compile sufficient background information to solve this problem, the Board of Forests of Riga Municipality initiated the preparation of a proposal for the designation of a new protection belt.The proposal was based on the development and application of a theoretical framework developed during the 1980s. The analysis of the recreational value of the forest (5 class-es of attractiveness) was carried out based on categories of forest type, dominant tree species, dominant age, stand density, distance from urban areas and the presence of at-tractive objects. Information was derived from forest inventory databases, digital forest maps and topographic maps. Additional information was digitised and processed using ArcView GIS 3.2. Local foresters were asked about the recreation factors unique to differ-ent locations, such as the number of visitors and the main recreation activities. From a recreational point of view and taking into account legal restrictions and development plans for the Riga region, it was proposed to create three types of zones in the forest: a protection belt, visually sensitive areas and non-restricted areas.Key words:greenbelt forest, recreational value, GIS, zoningThe Law on Protection Belts states that protection belts around cities (with forests as part of a green zone)have to be established (a) to provide suitable conditions for recreation and the improvement of the health of urban dwellers, and (b) to minimise the negative im-pact of urban areas on the surrounding environment.Urban For.Urban Green.2 (2003):031–0391618-8667/03/02/01-031 $ 15.00/0Address for correspondence:Latvian State Forestry Re-search Institute ‘Silava’, Rı¯gas iela 111, Salaspils, LV-2169,Latvia. E-mail: donis@silava.lv© Urban & Fischer Verlaghttp://www.urbanfischer.de/journals/ufugRegulation nr 263 (19.06.2001) on the ‘Methodology for the establishment of forest protection belts around towns’issued by the Cabinet of Ministers (CM) states: (a) The area of a protection belt depends on the numberof inhabitants in the town: towns with up to 10,000 inhabitants should have a maximum of 100 ha of protection belt, those with between 10,000 and 100,000 inhabitants a maximum of 1,500 ha, and towns with more than 100,000 inhabitants a maxi-mum of 15,000 ha;(b) the borders of protection belts have to be able to beidentifiable on the ground, using features such as roads, ditches, power lines, and so forth;(c) protection belts have to be recorded in the territorialplans of regions adjacent to the town or city; and (d) establishment of protection belts has to be agreedupon by local municipalities.According to law, protection belts should be man-aged using adapted silvicultural measures. Clear-cut-ting, for example, is prohibited in a protection belt to mitigate any negative impacts of the city on the sur-rounding environment. The Forest Law of 2000 and subsequent regulations including the Regulation on Cutting of Trees, and the Regulation on Nature Conser-vation in Forestry define clear-cuts as felled areas larg-er than 0.1 ha where the basal area is reduced below a critical level in one year. These regulations also state the permitted intensity and periodicity of selective cut-ting (30–50%, at least 5 years between entries).The third element of the legal framework relevant for protection belts in Latvia is the Law on Planning of Territorial Development (1998). It defines:(a) Principles and responsibilities of the different or-ganisations involved;(b) the contents of territorial plans;(c) the procedures for public hearing; and(d) the procedures for the acceptance of plans.The law also states that protection belts around towns have to be designated in territorial plans. Thus, the legislation gives very detailed descriptions of the restrictions to maximum area, activities and guidelines for delineation and so forth, while there are no ‘rules’for the choice of what areas are to be included in pro-tection belts. It is up to territorial planners to propose what areas to include and for negotiation among mu-nicipalities to approve the selection.Protection belt for the city of RigaRiga and the Riga region are situated in the Coastal Lowland of Latvia within the Gulf of Riga. The main landform types are the Baltic Ice Lake plain, the Litto-rina Sea plain and the Limnoglacial plain and bog plain. The total area of the administrative area of the City of Riga covers 307.2 km2, and that of the Riga re-gion 3,059 km2. In 2000 the city of Riga had 815,000 inhabitants, while an additional 145,000 people resided in the greater Riga region. During the last decade the number of inhabitants in Riga decreased by 10.5%and in Riga region by 5.3%. In the mid-1990s the main types of industry in Riga were food processing, timber and wood processing, metal fabricating and engineer-ing, while in the region agriculture and forestry, wood processing, pharmaceuticals, and the power industry were the main activities. Due to reduced industrial ac-tivities today, the main sources of pollution in Riga re-gion are road transport and households.The greater part of the Riga region is covered by for-est, i.e. 1,642 km2or 53%. About 26% of the land is used for agriculture, 4% is covered by bogs, and 4% by water. The Riga region also has a coastal dune zone of some 30 km along the Gulf of Riga. The main tree species to be found in the Riga region are Scots pine (Pinus sylvestris L.),birch (Betula spp.) and Norway spruce (Picea abies (L.) Karsten) (see Table 1). In the administrative area of the city of Riga, 57 km2 or about 19% of the land area is forest. Scots pine is the domi-nant species, covering approx. 46.9 km2(i.e. 88% of the total forest area).According to the legislation described before, a pro-tection belt around Riga city, with a maximum size of 15,000 ha, could be designated. Moreover, any propos-al has to be agreed upon among 24 local municipalities. The Riga region is divided into 24 administrative units: 7 towns and 17 pagasts or ‘parishes’.Riga municipality currently owns more than 55,600 ha of forests. Most are situated in the vicinity of Riga. Four forest administrative districts lie completely with-in Riga region and close to Riga city (see Fig. 1). The total area of these districts is 44,158 ha out of which forest stands cover 36,064 ha (82%). Thus the Riga municipality forests of those 4 districts cover only 17% of the total forest area of the Region. The dominant tree species in the municipally owned forests are Scots32J.Donis:Designating a greenbelt around the city of Riga,LatviaUrban For.Urban Green.2 (2003)Table 1.Tree species composition in the Riga region Dominant tree Area covered, ha Average age, years species––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––Total Municipa-Total Municipa-lity*lity* Scots pine95,27627,3718581 Norway spruce20,8493,0175139Birch30,5585,1246056 Other10,438552––Total157,12136,0647369*Data only for the 4 forest districts of the Riga city munici-pality that are entirely situated within the Riga region.pine, birch and Norway spruce. These cover 76%, re-spectively 14% and 8% of the forest area. Other species cover less than 2% of the area.Until the re-establishment of Latvian independence almost all forestland was owned by the state but since then many areas have been returned to their former owners and are now privately owned. Current regula-tions state that until the designation of new boundaries for protection belts has been agreed upon, all forests of the previously existing and protected green zone have to remain protected whatever their functional role or ownership status. Consequently almost all forests of the Riga municipality located in the Riga region have management restrictions placed on them, and the same can be said for forests of other owners within the previ-ously existing green zone. Currently, therefore, on the one hand significant recreation opportunities for urban dwellers are provided, while on the other hand forest owners’rights to obtain income from timber harvest in the suburban areas continue to be restricted. Suburban municipalities also lose income because of reduced land taxes from land with management restrictions.The board of Forests of the Municipality of Riga there-fore initiated the preparation of a proposal to designate a new protection belt.Study to support protection belt designation The main objective of the study presented here has been to obtain background information in preparation for further discussions with local municipalities. Stud-ies in Latvia as well as elsewhere have revealed that recreational values of forests depend mainly on forest characteristics, location and level of pollution (Emsis et al. 1979; Emsis 1989; Holgen et al. 2000; Lindhagen & Hörnsten 2000; Rieps ˇas 1994; Su ¯na 1973, 1979). A very important aspect is the distance to the forest from places where people live (e.g. Rieps ˇas 1994). The abil-ity of a forest stand to purify the air by filtering or ab-sorbing dust, micro-organisms, and noxious gases de-pends on tree and shrub species composition, age, tree size and stand density (Emsis 1989). Stands purify the air most effectively at the time of maximum current an-nual volume increment, usually between 30 to 60 years of age in Latvian conditions, depending on species.Recreational value, on the other hand, increases with age (and tree size) and reaches its maximum consider-ably later. Taking into account the peculiarities of the dispersal of pollution as described by Laivin ‚s ˇ et al.(1993) and Za ¯lı¯tis (1993), selective cutting is prefer-able in the vicinity of a pollution source, especially ifJ.Donis:Designating a greenbelt around the city of Riga,Latvia 33Urban For.Urban Green.2 (2003)Fig. 1.Location ofthe Riga municipali-ty forests in the Riga region.the forest consists of a narrow strip between the pollu-tion source and housing. If the distance between a pol-lution source and housing exceeds several kilometres, a patch clear-cut system with stands of different ages is sufficient to provide a reduction in the negative impact of urban areas. Taking into account the fact that closer to residential areas it is more important to consider the visual qualities of the forest (e.g. Tyrväinen et al. 2003), this purification ability can generally be ignored when planning protection belts.MethodsThis study to support the designating of the Riga pro-tection belt used the following data sources for analysis (see Fig. 2): forest inventory databases, digital forest maps of the Riga municipal forests which are situated outside the administrative borders of the city (55,600 ha of which 44,158 ha located in the Riga region) (see Fig. 1), and corresponding topographic maps.The study and its developed proposal are based on an application of a theoretical approach developed during the 1980s by the Latvian State Forestry Research Insti-tute ‘Silava’(Emsis 1989) and the Lithuanian Forestry Research Institute (Riepsˇas 1994). According to the methodology developed by Emsis (1989), the first step in the process is to evaluate the recreational potential of the forest stands. This is carried out by analysing the following factors:• The tolerance of the forest ecosystem to different lev-els of anthropogenic (recreation) loading;• the status of forest ecosystems in terms of the damage or degradation as a result of recreational use;•the suitability of the landscape for non-utilitarian recreation (recreational value); and• the existing and potential levels of recreational loads.The second step involves evaluating the existing andexpected functional roles of the forest.The tolerance of the forest ecosystem to different levels of anthropogenic impact or loading is evaluated using a framework based on a combination of forest type, dominant tree species, dominant age group, soil type and relief, according to the stability of ecosystem. All stands are classified into one of five tolerance classes. The highest score is given to mature deciduous forests on mesotrophic and mesic soils on flat topogra-phy, while the lowest score is given to young pine stands on oligotrophic soils on steep slopes (forests on dunes).In this study ecosystem tolerance could not be evalu-ated, as it was primarily a desk using existing databas-es, and topographic relief maps were not available in digital form. The status of the forest ecosystem in rela-tion to damage or degradation was evaluated in terms of the degree of change in vegetation cover, under-growth, tree root exposure of the and level of littering, classified into three classes.Assessment of the recreational value of the forest stands was calculated using a formula developed by Riepsˇas (1994):Recreational value VR= (VS*kW*kS+VA)*kPWhere VSis stand suitability based on key internal at-tributes of the stand, such as species, age, stand densityand forest type. VSvalues range from 0 for young, high-density grey alder (Alnus incana L.) on wet peat soils, to 100 for average density mature pine stands ondry mineral soils. kwis a coefficient depending on the distance of the stand from watercourses, ranging from0.1 for stands further than 2 km from watercourses to1.0 for stands up to 500 m from watercourses. kSis a coefficient depending on the distance of the stand from urban areas, ranging from 0.1 for stands further than34J.Donis:Designating a greenbelt around the city of Riga,LatviaUrban For.Urban Green.2 (2003)Fig. 2.Structure of data sources used in data ana-lysis.80 km from Riga to 1.0 for stands within 30 km ofRiga. VA is an additional value depending on the pres-ence of attractive features, for example, 25 for forest stands up to 500 m from settlements, including summer cottages, or for areas intensively used for recreation ac-cording to information of local foresters. kP is a coeffi-cient depending on the level of environmental pollu-tion. Its value is 0 if the actual pollution level exceeds limit values, 0.5 if the level of environment pollution is between 50% and 100% of limit values, and 1 if the level of actual pollution is less than 50% of the limit values. In this study a coefficient of 1.0 was used, be-cause SO2and O3concentrations measured by Rigabackground measuring stations did not exceed 50% of the limit values (Fammler et al. 2000).The division of stands into classes of stand suitabili-ty is based on studies of visitors’preferences. Coeffi-cients kw, ksand VAare based on visitors’spatial distri-bution and show the ratio of the number of visitors in different zones. The evaluation of existing and expect-ed recreational loads was carried out by local foresters. They marked existing and potential recreation places on forest maps, including:•Small areas or sites for activities such as swimming, barbecuing, and so forth.•Recreation territories, defined as areas of 20 ha or more where people stay longer periods for walking, jogging, skiing or other forms of both active and pas-sive recreation.•Traditionally popular places for the collection of berries and mushrooms.•Recreational routes, including routes from public transport stops to recreation sites or recreation terri-tories, and between recreation sites and territories. For each recreation site and recreation territory data on the main seasons of use, the periods of use (week-days, weekends), and the average number of people in ‘rush-hours’during good weather conditions was col-lected or estimated.Data processing was carried out using ArcView GIS3.2a, Visual Fox pro and Microsoft Excel. VS values foreach stand were calculated from information in the for-est database using Visual Fox pro. Information collect-ed at a later stage from local foresters was digitised using separate themes (layers) in ArcView GIS 3.2a. Buffer zones along watercourses and water bodies, as well as residential areas, recreation sites and territoriesand recreation routes were created to get kW ,kSand VAvalues for each stand. Then VR values were calculatedfor each stand.A selection of recreation sites and territories was vis-ited by members of the project team in order to evalu-ate the state of the ecosystem with respect to wear and tear arising from different levels of recreational use. An evaluation of the existing functional role of each forest stand was carried out using the existing categories offorest protection. The anticipated future functional role was evaluated by annalysing the recreational value of stands, known expectations in terms of territorial de-velopment, and existing legal restrictions in order to find a compromise between recreation possibilities and other services of the forest. Next, a first draft of the protection belt was drawn according to experts’judge-ment. This draft included forests with high recreational value adjacent to residential areas and summer cot-tages, and larger tracts intensively used for recreation with medium to high recreational value.ResultsAccording to the original forest classification 65% of the total forest land area was designated as a commer-cial greenbelt forest, for which the main management goals are timber production and environmental consid-erations. The remaining 35% were designated as pro-tected (see Table 2). With regards to protected areas in Latvia: the main management goals of nature parks are nature conservation and recreation, including some ed-ucation. The goal for nature reserves is nature conser-vation, while that of the protected greenbelt forests is recreation.While interviewing local foresters it was revealed that they find it difficult to evaluate dispersed recreation loads (for example collection of berries, mushrooms). The assessments of foresters varied greatly and were considered to be unreliable. It was therefore decided to map only the places important for recreation, but not to use the inaccurate estimates of visitor numbers.In Latvia, special investigations have to be carried out in order to develop management objectives and principles for protected forests as part of the preparation of management plans. Pilot studies and visits to some of the recreation areas have revealed that the evaluation of the state of the forest ecosystem is useful only when de-veloping the detailed management plan. Even then, this is only the case for places identified by local foresters as recreation sites or territories, because otherwise it is too time consuming to carry out fieldwork which provides little useful additional information.Calculated VSvalues show that on average the forests studied have a medium suitability value for recreation (average score 47) (see Table 2). There are considerable differences between districts, with aver-age value ranging from 32 points in Olaine to 66 points in the Garkalne district. This indicates that the average stands in the Garkalne district are more suitable for recreation than those in other districts. If other aspects are taken into account, such as distance from wherepeople live, and VRvalues are calculated it can be seenJ.Donis:Designating a greenbelt around the city of Riga,Latvia35Urban For.Urban Green.2 (2003)that the districts are still ranked as follows: Garkalne,Jugla, Tireli and Olaine.Only 10% of the forest owned by Riga municipality within the Riga region were evaluated as having a high or very high recreational value. 12% had medium recreational value, while large areas used for the col-lection of berries and mushrooms were evaluated as having low or very low recreational value (60% of the total forest area) (see Table 3).More than 16% of the area is covered by bogs, for which according to the used methodology, recreational value was not evaluated at all. Some areas were recorded by the local foresters as important places for the collec-tion of berries. However, more valuable from a recre-ational point of view were those forests situated east and north-east of the city (Garkalne and Jugla districts),while the forests to the south (Olaine and Tireli districts)were found to have a lower recreational value (V R ).36J.Donis:Designating a greenbelt around the city of Riga,LatviaUrban For.Urban Green.2 (2003)Table 2.Distribution of forest by forest categories according to the original functional role Forest districtDataFormer forest category Total–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––Commercial Nature Nature Protected greenbelt forests parks reserves greenbelt forestsGarkalneArea, ha521.27,698.78,219.9Average of V S *61.966.566.2Average of V R **59.350.751.4JuglaArea, ha 8,376.74,098.812,475.4Average of V S 45.656.949.1Average of V R 22.034.025.7OlaineArea, ha 11,765.4707.512,473.0Average of V S 31.941.032.6Average of V R 8.527.410.0TireliArea, ha 8,689.5257.91,025.01,016.910,989.3Average of V S 40.666.710.059.342.3Average of V R 17.055.3 1.044.920.6TotalArea, ha 28,831.6779.11,025.013,522.044,157.6Average of V S 39.863.510.061.647.1Average of V R16.357.91.043.725.9* V S Suitability value – based on stand parameters (0–100 points).** V R Recreation value (0–125 points) based on stand parameters, distance to the residential areas, water and other attractive objects.Table 3.Distribution of forest areas by classes of attractiveness and by designated functional role Designated zoneDataClass of attractiveness Total –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––n.a.Very low Low Medium High Very high 0<2525,1–5051–7575–100100<Protection belt Area, ha76.7560.12,266.42,222.7850.5743.66719.9Average of V R *0.012.036.063.390.0125.053.4Visually sensitive Area, ha 447.64,150.54,157.7853.4847.1179.810636.1Average of V R 0.07.837.460.996.7125.028.5Non-restricted Area, ha 6,664.715,389.12,548.61,090.5874.8234.026801.7Average of V R 0.0 5.234.761.197.2125.015.8TotalArea, ha 7,189.020,099.88,972.74,166.52,572.31,157.344157.6Average of V R0.06.236.362.294.6125.025.9*V R Recreation value (0–125 points) based on stand parameters, distance to the residential areas, water and other attractive objects.Areas along main roads and railways are known to be visually sensitive, because of the large number of peo-ple who can see them during travel. The same is true for forest in the vicinity of small villages. Taking into ac-count the fact that legislation prohibits clear-cuts in pro-tection belts – which is not always necessary in order to maintain the visual quality of the landscape – it was proposed, as part of the zoning strategy, to create so called visually sensitive areas. In these areas the forest owner (Riga municipality) is recommended to use more detailed landscape-planning techniques and to pay more attention to visual aspects during management.As a result of the study, seen from a recreational point of view and taking into account legal restrictions and so forth, it has been proposed to create three zoning categories: (1) protection belts, (2) visually-sensitive areas, and (3) non-restricted areas (see Fig. 3). The protection belt should include:• Forest with high recreational value adjacent to residen-tial areas and summer cottages, to form a 200–500 m wide belt.• Larger tracts of forestland intensively used for recre-ation.The zone of visually-sensitive areas should include:• Forests within the administrative borders of Riga mu-nicipality and in the vicinity of villages (up to 200–500 m distance).• Forests along roads of national and regional impor-tance, railways, watercourses and streams as a protec-tion belt of 100–300 m wide.• Places used for mushroom and berry collection in the original restricted protection belt.• Places that could become important for recreation in the near future.J.Donis:Designating a greenbelt around the city of Riga,Latvia 37Urban For.Urban Green.2 (2003)Table 4.Proposed distribution of forest categories in designated zones (in hectares)Designated zoneFormer forest category Grand Total––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––Commercial Nature Nature Protected greenbelt forests parks reserves greenbelt forests Protection belt355.2779.15,585.76,719.9Visually sensitive areas 3,503.97,132.110,636.1Non-restricted areas 24,972.51,025.0*804.226,801.7Total 28,831.6779.11,025.013,522.044,157.6*Forests within nature reserves are not intended for recreation; their primary management goal is nature conservation.Fig. 3.Proposal for zon-ing of the Riga municipalforests in Riga region.The remaining areas should consequently be classi-fied as non-restricted areas.A revision of the first draft plan was made taking into account the known prospective development plans of Riga and Riga region. As a result, for forests owned by Riga municipality and located in Riga region the pro-posal is to include 6,720 ha in the protection belt (see Table 3). Moreover, it has been suggested to designate 10,636 ha as visually-sensitive areas, but to omit the re-maining 26,802 ha from zoning, as these do not need special management from a recreation point of view. Average recreational values of stands in this area range from 53 (medium), through 28 (low) to 15 points (very low) respectively.As a result, the major part of the forest remains in the same functional category as in the original allocation (see Table 4). As was mentioned above, the classifica-tion described here is only based on recreational as-pects, thus forests in nature reserves are misleadingly shown as non-restricted forests. Only 5,586 ha out of the 13,500 thousand ha of the originally protected greenbelt forests are proposed to be included in the protection belt, while 355 ha of the previous commer-cial greenbelt forests are proposed to be placed under stronger protection.DiscussionForests owned by Riga municipality within the Riga re-gion are divided over 13 rural municipalities. Accord-ing to legislation, revised draft proposals for zoning Riga city forests have to be accepted by Riga munici-pality, while the final decision is up to Riga and the sur-rounding municipalities. The study presented here has provided a tentative estimate of the recreational value and suitability of the forests for recreation and can be used as a starting point for political discussions. At the very beginning the intention was to divide the forests in two categories: the protection belt and the remainder of the forest. During the study it was concluded, however, that a third category would be needed, that of visually sensitive areas. Within this category more attention would have to be paid to the amenity of the landscape, but there would be no need to drastically restrict com-mercial forest management. As nature parks are also designated for recreation, it has been proposed to in-clude all forests of nature parks in the protection belt. It has to be noted that all the forests within the adminis-trative borders of cities, and as such not included in this study, are designated as protected. As a consequence, the forest area available for recreation to the inhabi-tants of Riga would increase to 12,500 ha.Unlike many other European cities, where timber ex-traction is of small importance (Konijnendijk 1999),Riga municipal forests have a considerable economic role. It is estimated that the allowable annual cut in suburban forests amounts to 169,800 m3or 81% of the annual increment (Dubrovskis et al. 2002). It should be kept in mind that income from logging is used for for-est regeneration and tending, forest fire protection and maintenance of recreation facilities.The objective of this study was not to evaluate the precision of the method nor possible errors occurring when applying it. This study revealed, however, the in-completeness of the methodology used. Bogs, which are very sensitive to recreation loads, are ascribed quite a high level of attractiveness from a recreation point of view (for the collection of wild berries), but according to the methodology they are not evaluated at all. All watercourses were assumed to be attractive sites, while the preliminary evaluation of recreation loads showed this not to be true. The use of watercourses is very vari-able and obviously depends on water quality and vege-tation structure of the edges or banks. Another aspect which was not taken into account was that amenity of a forest is not simply the sum of the amenity values of forest stands (Pukkala et al. 1995).It seems that the evaluation based on dominant species is appropriate for screening areas, but for more detailed management plans, species mixture, the number of forest layers, and principles of landscape architecture also have to be taken into account (Bell 1999; Bell & Nikodemus 2000). Various studies have shown that people prefer uneven-aged forests (e.g. Melluma et al. 1982) and uneven-aged stands (e.g. Riepsˇas 1994). The impacts of the screening effect show that there are, even in the visually-sensitive and commercial zones, considerable areas with high and very high recreational value. This is mainly because delineation of zonal boundaries is carried out using easily distinguishable natural lines, and often it is not worth including single stands of high recreational value in the protection belt if, as a consequence, re-strictions on management would be placed over whole compartments of 50 ha.For the preparation of specific management guide-lines detailed field inventories have to be carried out. This has not been done in this study, where more re-liance was placed on the experience of local foresters and existing databases. Detailed economical calcula-tions have yet to be carried out in order to evaluate the direct and indirect value of the forest. These will also assist in obtaining more background information to be used as part of a holistic approach and for development of a decision support system to resolve contradictions between different interest groups.After acceptance of the draft plan by the municipali-ty of Riga, the process of negotiation between Riga and its surrounding municipalities is currently ongoing.38J.Donis:Designating a greenbelt around the city of Riga,Latvia Urban For.Urban Green.2 (2003)。
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Load and Ultimate Moment of Prestressed ConcreteAction Under Overload-Cracking LoadIt has been shown that a variation in the external load acting on a prestressed beam results in a change in the location of the pressure line for beams in the elastic range.This is a fundamental principle of prestressed construction.In a normal prestressed beam,this shift in the location of the pressure line continues at a relatively uniform rate,as the external load is increased,to the point where cracks develop in the tension fiber.After the cracking load has been exceeded,the rate of movement in the pressure line decreases as additional load is applied,and a significant increase in the stress in the prestressing tendon and the resultant concrete force begins to take place.This change in the action of the internal moment continues until all movement of the pressure line ceases.The moment caused by loads that are applied thereafter is offset entirely by a corresponding and proportional change in the internal forces,just as in reinforced-concrete construction.This fact,that the load in the elastic range and the plastic range is carried by actions that are fundamentally different,is very significant and renders strength computations essential for all designs in order to ensure that adequate safety factors exist.This is true even though the stresses in the elastic range may conform to a recognized elastic design criterion.It should be noted that the load deflection curve is close to a straight line up to the cracking load and that the curve becomes progressively more curved as the load is increased above the cracking load.The curvature of the load-deflection curve for loads over the cracking load is due to the change in the basic internal resisting moment action that counteracts the applied loads,as described above,as well as to plastic strains that begin to take place in the steel and the concrete when stressed to high levels.In some structures it may be essential that the flexural members remain crack free even under significant overloads.This may be due to the structures’being exposed to exceptionally corrosive atmospheres during their useful life.In designing prestressed members to be used in special structures of this type,it may be necessary to compute the load that causes cracking of the tensile flange,in order to ensure that adequate safety against cracking is provided by the design.The computation of the moment that will cause cracking is also necessary to ensure compliance with some design criteria.Many tests have demonstrated that the load-deflection curves of prestressed beams are approximately linear up to and slightly in excess of the load that causes the first cracks in the tensile flange.(The linearity is a function of the rate at which the load is applied.)For this reason,normal elastic-design relationships can be used in computing the cracking load by simply determining the load that results in a net tensile stress in the tensile flange(prestress minus the effects of the applied loads)that is equal to the tensile strength of the concrete.It is customary to assume that the flexural tensile strength of the concrete is equal to the modulus of rupture of thewhen computing the cracking load.In should be recognized that the performance of bonded prestressed member is actually a function of the transformed section rather than the gross concrete section.If it is desirable to make a precise estimate of the cracking load,such as is required in some research work,this effect should be considered.Principles of Ultimate Moments Capacity for Bonded membersWhen prestressed flexural members that are stronger in shear and bond than in bending are loaded to failure,they fail in one of the following modes:Failure at cracking load In very lightly prestressed members,the cracking moment may be greater than the moment the member can withstand in the cracked condition and,hence,the cracking moment is the ultimate moment.This condition is rare and is most likely to occur in members that are prestressed concentrically with small amounts of steel.It can also occur in hollow or solid prestressed concrete members that have relatively low levels of reinforcing.Determination of the possibility of this type of failure is accomplished by comparing the estimated moment that would cause cracking to the estimated ultimate moment,computed as described below.When the estimated cracking load is larger than the computed ultimate load, this type of failure would take place if the member were subjected to the required loads.Because this type of failure is brittle failure,it occurs without warning–designs that would yield this mode of failure should be avoided.Failure due to rupture of steel In lightly reinforced members subjected to ultimate load,the ultimate strength of the steel may be attained before the concrete has reached a highly plastic state.This type of failure is occasionally encountered in the design of structures with very large compression flanges in comparison to the amount of prestressing steel,such as a composite bridge putation of the ultimate moment of a member subject to this type of failure can be done with a high precision. The method of computation,as well as the determination of which members are subject to this mode of failure,is described below.Failure due to strain The usual underreinforced,prestressed structure that are encountered in practice are of such proportions that,if loaded to ultimate,the steel would be stressed well into the plastic range and the member would evidence large deflection.Failure of the member will occur when the concrete attains the maximum strain that it is capable of withstanding.It is important to understand that research into the ultimate bending strength of reinforced and prestressed concrete has led most investigators to the conclusion that concrete,of the quality normally encountered in prestressed work fails when the limiting strain of0.003is attained in the concrete. Since the ultimate bending capacity is limited by strain rather than stress in the concrete,it is a function of the elastic moduli of the concrete and steel.The magnitude of the ultimate moment for members of this category can also be predicted,as a rule, within the normal tolerance expected in structural design.The ultimate moment of underreinforced sections cannot be predicted with the same precision as the lightly reinforced members described above,since the ultimate moments of underreinforcedare a function of the elastic properties of the steel and the effective stresses in the prestressing steel,whereas the ultimate moment capacities of lightly reinforced members are not.Failure due to crushing of the concrete Flexural members that have relatively large amounts of prestressing steel or relatively small compressive flanges are referred to as being overreinforced.Overreinforced members,when loaded to destruction,do not attain the large deflections associated with underreinforced members–the steel stresses do not exceed the yield point and failure is the result of the concrete being putation of the ultimate moments of overreinforced members is done by a trial and error procedure，involving assumed strain patterns,as well as by empirical relationships.It must be emphasized that there is no clear distinction between the different classifications of failure listed above.For convenience of design,certain parameters, which are a function of the percentage of steel,are used by different authorities to distinguish between the different types of failure that would be anticipated.In order to simplify the explanation of the theory related to the computation of the ultimate moments,a rectangular section will be assumed throughout the derivation, in order to eliminate the variable of flange width which is frequently encountered with I or T sections.In addition,the following assumptions,some of which differ slightly from those contained in ACI-318,are made:1)Plane sections are assumed to remain plane.2)The stress-strain properties of the steel are smooth curves without a definiteyield point.3)The limiting strain of the concrete is equal to0.0034,regardless of the strengthof the concrete.4)The steel and concrete are completely bonded.5)The sress diagram of the concrete at failure is such that the aveage concretestress is0.80ƒ΄c and the resultant of the stress in the concrete acts at a distance from the extreme fiber equal to0.42of the depth of the compression block.6)The strain in the top fiber under prestress alone is equal to zero.7)The section is subject to pure bending.8)The analysis is for the condition of static loads of short duration.As was stated above,the relationships that were developed are applicable to rectangular sections.These relationships are equally accurate for flanged sections, provided the neutral axis of the section at ultimate is within the limits of the flange.If the neutral axis falls outside of the flange area,the same strain distribution applies as in the case of rectangular sections,but due to the variable width of the section,the distance to the resultant of the compressive block must be calculated.To facilitate the calculation of the location of the resultant,the compression block can be assumed to be rectangular rather than curved without introducing significant error.When small quantities of non-prestressed reinforcement are used in combination with small quantities of prestressed reinforcement,the additional ultimate moment due to the non-prestressed reinforcement can be calculated.For larger amounts of non-prestressed reinforcement or for members with high steel indices,the moment shoulddetermined by trial and error from the basic strain patterns.Examination will show that small variations in the effective presstress have no significant effect on the ultimate strength of prestressed members.It is important to note that even if errors are made in estimating the losses of prestress,in estimating the stressing friction,or even if the stressing is not carried out to a high precision in the field due to poor workmanship,the effect on the ultimate moment is generally small for flexural members with bonded tendons.Principles of Ultimate Moment Capacity for Unbonded MembersBecause the prestressing tendons can slip(with respect to the concrete)during loading of an unbonded member,the relationships for ultimate moment capacity do not apply to unbonded beams.Because the tendons can slip with respect to the concrete,other variables affect the ultimate moment capacity of unbonded prestressed concrete members.Variables that affect the ultimate moment capacity of an unbonded beam,but which do not affect bonded beams in the same manner or not at all,include the following:1)Magnitude of the effective stress in the tendons.2)Span to depth ratio.3)Characteristics of the materials.4)Form of loading(shape of the bending moment diagram).5)Profile of the prestressing tendon.6)Friction coefficient between the prestressing steel and duct.7)Amount of bonded non-prestressed reinforcing.A method of computing the ultimate strength of prestressed members(with unbonded tendons)that takes into account the variables listed above has been proposed by Pannell.This method is based upon experimental data and is considered slightly conservative.It should be recognized that the ultimate moment capacity of a member stressed with unbonded tendons,unlike members with bonded tendons,may be adversely affected by unintentional variations in the effective prestress.Hence,it is considered prudent to exert more care in estimating the losses of prestress and in supervising the stressing of unbonded members than would be considered necessary for bonded members,in order to assure the desired results are obtained.。