电气回路存在谐波电流时导体截面的选择

阐述了电气回路中谐波电流产生的原因及其引起中性线和相线过载的危险。指出在建筑电气设计中为防谐波电流引起的回路过载应相应增大中性线和相线的截面。文中还根据国际电工标准的规定，列举了按回路谐波含量发数选择导体截面的例子。     

The construction productivity debate and the measurement of service qualities

Since the 1960s, researchers have provided short-term and long-term explanations for low productivity growth in the construction industry. In retrospect, the main challenge appears to be the measurement of changes in heterogeneous input and output qualities. The aim here is to review earlier construction productivity research and to compare it with more recent approaches to quality measurement used when analysing services productivity, ultimately intending to provide guidance for using performance data from construction projects. Relying on the EU KLEMS database, industries with similar patterns of productivity growth are identified, primarily the business services industry. In services productivity analyses, the attempts to introduce output quality measures reflecting customer satisfaction are particularly interesting, as this creates a link to productivity effects on clients. A conclusion is that it should be possible to use the increasing volume of performance indicator data collected for construction project benchmarking for extending the range of output quality variables. However, resource constraints imply that it is infeasible to base industry productivity statistics on project level data reflecting customer satisfaction and customer productivity effects.     

钢轨气压焊接头的超声相控阵检测技术研究

常规超声脉冲反射法检测钢轨气压焊接头时,需要更换不同K值探头检测钢轨气压焊接头的不同区域,探伤过程耗时长,效率低。超声相控阵技术可以灵活调节扫描角度,能有效提高检测效率。主要采用超声相控阵方法对钢轨气压焊焊缝进行探伤效果分析研究,实验中采用CTS-602型相控阵仪器、含机械加工缺陷的钢轨气压焊焊缝试样,通过确定合理的实验参数和检测方案,进行超声相控阵探伤检测。实验结果表明超声相控阵对气压焊接头检测效果好,检测效率高。     

改造辊子轴承冷却水管路及延长扇形段使用寿命

太钢二钢南区2#连铸机在线扇形段,经常出现辊子复合回路旋转接头处有漏水现象,造成辊子轴承因冷却不好发生轴承抱死,导致铸坯表面出现划伤现象。主要原因是辊子轴承冷却水冷却管路不合理,同时二冷水清洁度不够,复合回路孔仅3mm,易被堵塞,进水和回水管路造成压力差。通过对辊子轴承冷却水采用单回路旋转接头的改造,有效提高了轴承冷却效果,延长了扇形段在线使用寿命。     

The role of European forests in the global carbon cycle-A review

The first part of this paper presents an overview of national forest carbon balance studies that have been carried out in Europe. Based on these national assessments, an estimate is made of the present role of European forests in the global carbon cycle. Differences in the methodologies applied are discussed. At present, 15 European countries have assessed a national forest and/or forest sector carbon balance. Together, these studies cover 104 million ha and present the average situation in the mid-1980s. Most of the studies have used a static methodology to convert forest inventory data into carbon. Extrapolating those studies to the total forest area of Europe (149 million ha) (excluding the FSU), yields a whole tree carbon sink of 101.3 Tg C y⁻¹ (9.5% of the European emissions) and a whole tree carbon stock of 7929 Tg C. Although in general the applied methodologies are comparable, they differ considerably in the way net fluxes are assessed and in the applied conversion coefficients. The role of forest fires in the European forest C balance might be larger than generally expected. A disadvantage of the static methodologies used is that they often regard only the forest ecosystem part of the carbon cycle which may result in misleading results concerning the role of the total forest sector; another disadvantage is that results are only valid for the year(s) on which the data are based. The second part of the paper discusses a methodology that could be applied to all national forests and forest sectors yielding more consistent results. The possibilities of using a large-scale forestry scenario model for a study on the present and future European forest sector carbon balance are presented.     

Divide and rule. The economic and legal implications of the proposed ownership unbundling of distribution and supply companies in the Dutch electricity sector

In Machiavelli's theory of power, the concept of ‘divide and rule’ forms the main theme: the ruler has absolute power and to maintain and increase such power all means are justified. When viewed against the background of this theory, the current debate in the Netherlands on the unbundling of energy (electricity, gas) companies can be observed as an example of ‘divide and rule’, in which the Dutch Minister of Economic Affairs plays a central role. Yet, contrary to Machiavelli in his time, the Dutch government does, in fact, aim principally at the greater welfare of the Dutch people. It is therefore noteworthy that, while important steps in the decision to unbundled have been taken, there is no evidence that the Dutch people will indeed benefit from the envisaged unbundling.     

Potential contribution of the forest sector to carbon sequestration in Finland

Although Finland's forest resources have been utilized intensively, the size of the total volume of the growing stock has increased since the mid-1960s, and hence increasing amounts of carbon have been sequestered by forests. The net sequestration by forests has also been substantial when compared with the CO₂ emissions resulting from energy generation and consumption based on fossil fuels and peat. It is also important, from the point of view of mitigating the effects of climate change, to assess how the sequestration capacity of forests may change under changing climatic conditions. This paper presents the results of a study assessing the development of the forest and wood-product carbon budget for Finland, based on regionally measured data, detailed dynamic models, and recent predictions concerning the changing climate. At the starting point for the simulation (1990), nearly 90% of the forest sector's carbon storage was found in the forest. Regular management transferred carbon from forests to wood products. Under the current climatic conditions, the simulated forest carbon storage increased 45% by the year 2100, and the wood-product storage by 320%, as a consequence of continuous production. Under changing climate conditions, the forest carbon storage increased, but started to decline when the temperature increase exceeded 2.5°C within 40 years.     

扇区水泥胶结测井仪实验研究

扇区水泥胶结图像是通过扇区水泥胶结测井仪器（Scan Bound Tool,SBT）获得的。仪器的底端是发射探头,在距离发射探头0.6m处安装了一个接收探头。接收探头用一个压电圆管,分成8个等间隔的扇区极化,每个扇区接收到一个波形,一共8个波形。用实验的方法研究了激发脉冲宽度和幅度对波形幅度和频率的影响。取出每个波形的首波幅度得到8条曲线,描述圆周8个扇区的水泥胶结情况。将每个深度点对应的8个幅值用颜色表示出来,得到整个圆周的水泥胶结图像。由于圆周方向只有8个扇区,分辨率比较低,图像边缘不清晰。对观测到的8个扇区的幅度值用高斯函数进行插值处理后,图像边缘得到了一定改善。分别用线性插值,二次插值处理后,图像连续、边缘清晰,对比度明显增强,整个圆周不同扇区水泥胶结的差异显示明显,为进一步分析扇区水泥胶结提供了基础。     

热电冷三联产技术在第三产业中的应用

热电冷三联产能源利用率高,能节省燃料并有效减少大气污染物的排放。近年来第三产业能源消费量迅速增加,大型超市、医院、酒店等为三联产的应用提供了广阔的空间。     

Wind power in Brazil—transition using German experience

The development of the installed capacity of wind energy converters in Germany shows that a significant increase of its contribution to the energy supply is possible, depending on the measures introduced by the state. In contrast to Germany, Brazil has not been very concerned about its greenhouse gas emissions yet, as more than 90% of the electricity is generated by hydropower. However, due to the current energy crisis Brazil has to search for alternatives in order to stabilize the energy matrix and diminish the dependence on precipitation, especially as a new capacity of about 4 GW has to be installed each year. The intention of the authors is to present the German conditions that led to the current favorable situation for wind energy and to compare these to the Brazilian circumstances that exist for an extended application of this energy source. At the same time special attention is paid to the newest legal developments in Brazil.