混凝土桥梁施工中裂缝产生原因浅析

混凝土因取材广泛,价格低廉,抗压强度高,可浇筑成各种形状,并且耐火性好,不易风化,养护费用低,成为桥梁结构中使用量最广泛的建筑材料。但是,混凝土最主要的缺点是抗拉能力差,容易开裂。混凝土开裂可以说是“常发病”、“多发病”,经常困绕着桥梁工程施工技术人员。其实,如果采取一定的设计和施工措施,在施工过程中产生的很多裂缝是可以克服和控制的。     

太原公交GPS运营调度系统的规划与功能探究

1系统概述 太原公交目前有营运车辆1800多台,营运线路110多条,始发站点80多个.预计5年后营运车辆将达到3000多辆,营运线路增加到150多条,始发站点100多个.     

量本利分析法在港口施工企业中的具体应用

在简要阐述量本利分析基本原理的基础上,运用该方法对某港口施工企业中商品砼业务进行具体分析,说明其在企业经营及决策中的作用。     

Air pollution from ships: Recent developments

All developments on air pollution by ships are fairly recent. Annex VI of the international Marpol-convention, regulating the emissions of CFCs, Halons, Volatile Organic Compounds (VOCs) from cargoes, emissions from incinerators and exhaust gas emissions from engines (NO_x and SO_x) entered into force in May 2005. The International Maritime Organization is currently discussing an upgrade of the air pollution issues covered by Annex VI and some that are not in Annex VI, such as greenhouse gas emissions. CO₂ is the most important greenhouse gas emitted by ship. Fuel consumption by the world merchant fleet is expected to grow to between 250–300 million tons per year with corresponding CO₂ emissions of 800–960 million tons per year. In Western Europe land based measures have reduced sulphur emissions substantially, leaving shipping as an important remaining source of these emissions. Average sulphur content of heavy fuel oils is 3%, with a limit of 4.5% imposed by Annex VI. Both the Baltic- and the North Sea have the status of SO_x emission control area, limiting sulphur content to 1.5%.     

Investment strategies in market uncertainty

The nature of the global economy is one of dynamic change. Shipping is a service industry with its demand related to changes in international trade levels and patterns. As a consequence shipping is subject to sometimes unpredictable swings in demand so that the operator is required to make strategic planning decisions while navigating through boom or bust environments. While boom economies generate rising freight rates which are welcomed and encourage investment, ship operators may also have to face falling freight demand and declining freight rates that may have significant impact on profitability, often falling to uneconomic levels for extended periods. In such a period of uncertainty and declining profitability management will make operational decisions to reduce costs. However, shipping lines operate in a market environment so any decisions made to rationalize the trade may have significant long-term competitive implications. For example, traditional micro economic theory might suggest that the prudent strategy to adopt would be to close down the operation and reopen when the market conditions improve. In a world of certainty or when costs of taking this action are zero, this would be a valid strategy. However, because of fear of competitors taking up a line's market share if the shipping company exits, even temporarily, this strategy cannot be valued simply in terms of shut-down and start-up costs. A further consideration is the fact that standard capital budgeting techniques, such as Net Present Value (NPV), cannot incorporate the flexibility to respond to new information and strategic responses explicitly into their investment analysis. This paper will demonstrate the use of Real Option Analysis (ROA) to provide guidelines for decisions about closing operations in adverse market conditions.     

The coastal edge of the Northeast Water polynya in spring 1993

Multidisciplinary, marine ecological observations were conducted at the shallow water edge of the Northeast Water in June, 1993. Although variable in size and shape, a small polynya was constantly present at Eskimonaes, at the fast-ice edge of Ingolfsfjord. A shallow stratified layer developed at the water sufface at negative water and air temperatures—an effect of sea ice melting in cold water early in the season. Nutrients were recorded in considerable quantities, although by mid July NO₃ had become depleted. The chlorophyll and phytoplankton maxima at 8–12 m depth had peak values of 2 mg chl a m⁻³, typical for Arctic algal blooms. The phytoplankton included over 90 species and was dominated by the Fragillariopsis group. Zooplankton was poor in biomass and density, but over 23 taxa were found, with the copepods Oithona similis and Pseudocalanus acuspes being numerically dominant. Sedimentation was approximately 0.2 g dry weight m⁻² d⁻¹ and suspended matter concentrations ranged from 4 to 19 mg l⁻¹. The benthos was represented by hard bottom forms only, with a surprisingly dense cover of macrophytes. Juvenile sea urchins (Strongylocentrotus droebachiensis), brittle stars (Ophiocten sericeum) and amphipods were dominant. Higher trophic levels were represented by benthic feeders, such as eiders and walruses. The area observed was more similar to high Arctic fjord ecosystems than to the offshore central Northeast Water polynya.     

物流外包战略分析——上海大众汽车有限公司物流战略

文章结合物流在汽车行业竞争中的重要地位,对上海大众汽车有限公司(SVW)入场零部件物流外包战略的实施背景、运作情况进行论述。     

视频双微分补偿电路的仿真研究

交通管理监视器的视频电路，受通频带限制导致图像轮廓模糊、清晰度下降，通常需要采用双微分视频补偿．以一种具体的双微分视频补偿电路为例，分析了两次微分的补偿过程，用电路理论对元件的取值进行了研究，并采用功能强大的Electronics Workbench软件进行了仿真实验论证．     

德国铁路电力机车动车概况

简要介绍德国铁路现有电力机车动车的各种系列、数量和主要改进.