西北大温差地区钢管混凝土构件温度场及脱粘分析

为研究西北大温差条件下钢管混凝土构件截面温度场变化规律及钢管与核心混凝土界面脱粘情况,选取新疆乌鲁木齐市和青海西宁市典型日平均大气温度,通过温度冲击循环环境模拟试验方法分为12个时间段在大气模拟箱分别进行素混凝土、钢管混凝土构件温度场和钢管混凝土构件脱粘测试试验,分析西北大温差环境钢管混凝土温度场变化和界面结合状态。结果表明：钢管混凝土构件在大温差反复作用下,因材料差异产生的不同步热胀会使钢管与核心混凝土发生界面脱粘现象,温差越大越明显;同一个系列上径向温度变化中,随直径缩小,温度变化越滞后;当大气温度骤降时,钢管对核心混凝土会产生套箍作用,且温度越低,钢管的套箍作用越强。     

泵送混凝土温度裂缝的成因和防治

一、温度裂缝产生的原因和特征 温度裂缝多发生在大体积混凝土表面或温差变化较大地区的混凝土结构中。混凝土浇筑后，在硬化过程中，水泥水化产生大量的水化热，导致内部温度急剧上升，而混凝土表面散热较快，就形成内外的较大温差，较大的温差造成内部与外部热胀冷缩的程度不同，使混凝土表面产生一定的拉应力，     

自然冷能及其应用

一、概述 常规采用提高热源温度(例如燃烧煤炭或石油)的方法获得热能,并且将自然环境作为冷凝器,使各种热机运行。因此,提高热源温度与降低冷凝器温度同样都能获得有效能量。根据这个原理,以自然环境为冷凝器而产生的工业余(废)热属于低温差低温热能,可以回收利用。我国大部分地区夏季炎热,冬季寒冷,昼夜与季节气温变化明显。气候环境温度变化所产生的自然温差,蕴涵着的低温热能,数量为无限大,同样能够作为一种廉价洁净能源加以利用。     

浅谈造成水泥混凝土路面破坏的原因及防治措施

造成水泥混凝土路面破坏的原因很多,可能是由于路基施工、路面施工、荷载产生的应力引起的裂缝和由变形变化引起的裂缝等方面。分析造成的原因,可以通过加强软基处理、路基填筑,强化基层施工质量和水泥混凝土的接缝处理进行防治。预防混凝土路面破坏要从每个环节、每道工序着手。     

浅谈大体积混凝土裂缝防治措施

大体积混凝土在硬化过程中,会释放出大量的水化热,由于积聚在内部的水化热不易发散,内外温度差引起的应力易使混凝土产生裂缝。因此控制混凝土内外温差及减小降温速率是控制裂缝产生的有效方法。     

水泥混凝土路面裂缝成因及对策分析

一、裂缝产生的原因分析 1．温度变化引起裂缝。 由于混凝土具有热胀冷缩的性质,混凝土硬化初期,水泥水化放出较多的热量,而混凝土又是热的不良导体、散热缓慢,混凝土内部的温度较外部高,有时温差可达50℃～70℃,这将使内部混凝土产生显著的体积膨胀,     

浅谈牧区公路翻浆处治

青海牧区海拔高,四季分明,冬季时间长,冬春及早晚温差大,这就造成公路路基翻浆严重,特别是伴随近几年的全球气温升高变暖,使得一些修筑在冻土层上的道路由于冻土消融而使路基发生翻浆的地段急剧增加.     

矿渣粉掺量及养护条件对地聚合物混凝土的影响

以粉煤灰和矿渣粉为原材料制备地聚合物混凝土,研究矿渣粉掺量和不同配比碱激发剂对于地聚合物混凝土坍落度、凝结时间及抗压强度的影响;并且通过3种不同的养护方式,探究养护温度及湿度对于地聚合物混凝土表观性状和力学性能的影响。研究结果表明：随矿渣粉掺量的提高,地聚合物混凝土强度增加,而凝结时间大幅度缩短;提高碱激发剂中水玻璃的掺量将降低混凝土的坍落度和凝结时间,而抗压强度呈先增大后减小的趋势;提高养护的湿度可有效地抑制地聚合物的泛碱现象,并取得较高的后期强度;提高养护温度可使地聚合物取得较高的早期强度,但后期强度增长缓慢。研究表明当矿渣粉掺量为胶材的30%,碱激发剂中水玻璃与氢氧化钠溶液的比值为1.5：1时,可制备在常温下即可硬化并取得较高强度的地聚合物混凝土。     

变厚度复合材料冲击后压缩试验研究

变厚度碳纤维复合材料在民机主承力结构上已得到应用,冲击后压缩强度(CAI)是复合材料结构设计时的一个重要参数。文章通过试验研究了过渡段厚度差、过渡段斜率、薄区厚度等影响因素对变厚度复合材料冲击后压缩强度的影响。结果表明:铺层递减厚度对冲击后压缩强度影响不明显;减小铺层递减区斜率可以有效提高冲击后压缩强度;加厚薄区有利于提高冲击后压缩强度和设计许用值。     

广州南沙某桥头路基处理方案对比及其工后沉降分析

桥头路基差异沉降是导致跳车的主要原因，严重影响行车舒适度和安全性。通过规范法和数值分析两种计算手段，对等载预压+塑料排水板+管桩、直接管桩两种桥头路基处理方案及其工后沉降进行对比分析。结果表明：规范法未能考虑路堤再加载时间的影响，且计算得到的工后沉降均为0，这与实际不符，说明规范法在进行分步工况及工后沉降计算时存在缺陷；数值分析能够同时考虑分层堆载时间、等载预压时间及路堤再加载时间的影响，也能够较好地解决分步计算工况问题；方案2的工后沉降要更大，表明经过堆载预压后，土层的固结度显著增加，有效减小了土层的后续沉降。对于方案1，随②5淤泥质粉质黏土的黏聚力或压缩模量增加，工后沉降均逐渐增加，而内摩擦的影响与之相反；对于方案2，随黏聚力、内摩擦角或压缩模量增加，工后沉降均逐渐减小，但减小幅度较小。     

泡沫玻璃的研究进展

概述了泡沫玻璃的发展及研究现状,介绍了制备泡沫玻璃的原材料的种类和工艺,同时介绍了辅助添加剂对泡沫玻璃的烧成反应和性能有重要影响,按照作用机理的不同,将添加剂划分为发泡剂、稳泡剂、促进剂、表面活性剂、着色剂、脱模剂等几类进行分析讨论。分析了制备过程中产生泡沫玻璃缺陷的原因及解决方法,从结构方面讨论了泡沫玻璃的性能及应用,同时概述了我国泡沫玻璃生产存在的主要问题和发展前景。     

浸水对硅质聚苯板保温性能的影响及解决方案探讨

研究了一种新型的外墙保温材料——硅质聚苯板在实际应用中保温性能的变化,发现该材料在浸水后保温性能急剧下降,导致整体外墙保温性能下降。通过改良试验,找出如何减少硅质聚苯板浸水效应的方法,结果表明：在硅质聚苯板外面增加防水涂层可大大降低浸水的影响。     

On the Major Transformation of the Asia-Pacific Regional Structure北大核心CSSCISSCI

Recent years have witnessedsignificant changes in the Asia-Pacific regionalstructure featuring the shift in power balance among related countries as well as adjust-ments in their respective regional strategies. So what is the prevailing trend in thistransformation and what kind of regional order will likely emerge in the future？ To an-swer these questions, the paper tries to explore the following dimensions： the evolvingregional context, shift in power balance and power conversion, geo-political and geo-e-conomic developments and interactions between them, and evolving regional order. Asthe study shows, the broadening of regional geographical scope, the rise in the numberof actors involved, as well as changesin the relations among them, have combined tocast a pluralistic and complex flavor to the regional structure. While the power balanceamong China, the United States and Japan shifts, and power conversion is also occur-ring. China and Japan are paying increasing attention to their security roles, whereasthe United States under the Obama administration laid more stress on expanding itsgeo-economic clout. In spite of the intensifying geopolitical competition among China,the United States and Japan in recent years, a Sino-US strategic compromise-whichholds the key to regional geopolitics-isother front, some kind of geo-economicmore likely to take place in the future. On thecooperation will probably emerge. In the longerterm, it will be the geo-economic trend thatwill prevail over the geopolitical trend inthe region. Finally, the future evolution of regional order wiI1 mainly follow the eco-nomic logic, accompanied by the dilutionof its hegemonic and hierarchical nature.Hence, a pluralistic and complex regional community will emerge.     

The German Hanse and Bergen – new perspectives on an old subject

Abstract

The Hanseatic League and her kontors (trading posts) were an integral part of the medieval trade system in Northern Europe. Hanse merchants dominated many markets in this region and managed to maintain a monopoly-like role in towns like Novgorod and Bergen for many centuries. Consequently, one focus of historical research about the Hanseatic League lay on the mechanisms that enabled the Hanse merchants to keep that strong of a position for such a long time.

This article is part of the discussion about this topic. Based on Lübeck merchants with business interest in the Norwegian town of Bergen, the so-called Bergenfahrers (Bergen travellers), it will give new insights into the Hansards' economical and social organization. The three main points are (a) the integration of the Bergen market in the Hanseatic trade network as an intermediary trading place on the vivid East–West route of Hanse trade; (b) the importance of the Bergenfahrers within the Hanse merchants' economical, social and political networks; and (c) the structure of the Bergenfahrers network patterns in the late Middle Ages.

In addition to new insights into the important role of Bergen and the Bergenfahrers within Lübeck's and the other Wendish Hanse towns' trading system, this articles provides further proof for the usefulness of the methods of Social Network Analysis in medieval economic research.     

Organization and incentives in the age of sail

The British Navy in the age of sail was the most successful bureaucracy of its time. Its organization and incentive structures differed importantly from contemporaneous private sailing ventures, but closely resembled those of today’s large corporations. To induce efficient effort, the navy used a hierarchical tournament, in which sailors competed for higher pay that came with promotions based on relative performance. Promotion probabilities, the option value of future promotions, and the higher effort required of men in higher ranks and on larger vessels, combined to yield a highly skewed pay structure.     

Financial Reporting and Trade Credit: Evidence from Mandatory IFRS Adoption*

We investigate the effect of mandatory IFRS adoption on trade credit. We document that firms in countries that adopt IFRS receive more trade credit from their suppliers, consistent with improved financial reporting quality and comparability playing a role in facilitating informal financing. This increase is larger for countries with a low level of societal trust, a poor pre‐IFRS‐adoption information environment, and stronger legal enforcement. These cross‐sectional results suggest that the conditions under which higher‐quality information is made publicly available affect suppliers' decisions to provide trade credit. This increase is also larger for firms with greater exposure to foreign markets, a finding that highlights the importance of more comparable international financial reporting standards in facilitating cross‐country trade credit. We also find that IFRS adoption has a stronger positive effect on trade credit for firms with greater liquidity needs. Finally, we find that firms in countries that adopt IFRS also extend more trade credit to their customers. Overall, our results support the notion that financial reporting can have a causal effect on trade credit.     

中俄经济技术合作面临新机遇

中俄在十年内把各自的GDP翻一番的目标,为发展中俄经济技术合作提供了机遇.仅仅依靠商品贸易的增长很难大幅度提升中俄经贸关系,需要全面开展经济技术合作,特别是加强在自然资源开发、跨国投资、军工技术和产品贸易领域的合作.     

INFRASTRUCTURE POLICY IN INDONESIA, 1965–2015: A SURVEY

This survey, first, provides an overview of the main developments in the infrastructure sector in Indonesia during the past five decades and, second, considers what the main policy and management bottlenecks in infrastructure appear to be. The overview of main developments indicates that, in broad terms, most parts of the sector have expanded considerably but that the needs remain acute for further expansion and for attention to the maintenance of existing facilities. Demand for infrastructure is high, especially since the regulated prices set for infrastructure services are often low. Access is often difficult, however, because of shortages of infrastructure, and quality is often unsatisfactory because of poor maintenance and indifferent management. These problems of access are exacerbated by the regulation of prices. This overview also points to the markedly different performances of industries in which pro-competitive policies have been applied and those in which more traditional policies of close regulation have restricted the operation of markets.