含水率对水工混凝土修补材料工程性能影响研究

为研究水利工程抗冲磨修补材料的工程性能,室内对不同含水率的修补后混凝土展开了c试验,并基于电镜扫描试验分析了微观机理.研究发现,水分对试样的力学性质有明显的劣化效应,试样的劈拉强度、抗剪强度均逐渐减小;微观结果显示水分阻碍了环氧树脂与混凝土之间的黏附.研究成果为我国水利工程修复提供了借鉴作用.     

泡沫沥青冷再生混合料材料设计及其抗车辙性能评价

为研究如何合理利用沥青路面回收材料,通过一系列室内试验设计了泡沫沥青冷再生混合料并评价了其路用性能(抗车辙性能)。混合料设计阶段确定了最佳发泡条件:发泡温度为150~155℃,发泡用水量为3%,膨胀比为16,半衰期为9 s,最佳沥青用量为2.8%,混合料最佳含水量为3.81%。车辙试验数据显示:当空隙率为4.3%时车辙深度为1.63 mm,空隙率为5.0%时车辙深度为2.43 mm,空隙率为6.1%时车辙深度为3.45 mm,即随混合料空隙率的增大,车辙深度逐渐增加且增加趋势显著,表明混合料抗车辙性能逐渐减弱,因此建议泡沫沥青冷再生混合料空隙率设计不超过5.0%,且泡沫沥青冷再生混合料适用于沥青面层结构中的中下面层使用,不适用于上面层使用。研究结果为泡沫沥青冷再生混合料进行路段试验提供了理论参考。     

纤维编织网增强砂浆加固泵站梁抗剪性能的数值研究

纤维编织网增强砂浆是一种由纤维固定在无机粘合剂上的复合材料,常用于结构加固。以纤维编织网增强砂浆加固后的泵站结构钢筋混凝土梁为对象,利用ANSYS软件程序生成有限元分析模型,分析对抗剪切性能的影响。结果表明：纤维编织网增强砂浆可提高梁的抗剪强度,但随着梁有效高度的增加,纤维编织网增强砂浆对抗剪力的贡献会逐渐减少。纤维编织网增强砂浆在结构加固中具有应用前景。     

含Cr合金化钢组织及性能分析

为了研究超高硬度及强度的高速重轨钢，在U75V钢成分基础上进行了调整和优化，向其中添加一定量的Cr合金元素，并与原钢种进行了力学性能对比分析，以便得到成本与性能配合最佳的含Cr合金化重轨钢，使其力学性能优于现有的U75V重轨钢的性能指标，并且在内、外部质量方面能够满足高速铁路重轨钢的使用要求。同时利用Thermocalc热力学软件分析了Cr元素的加入对试验钢夹杂析出物的影响，利用金相显微镜和扫描电镜对试验钢微观组织、晶粒度进行观察分析，探究Cr合金元素对试验钢组织性能影响因素。结果表明：当合金化元素Cr的含量为0.45%时，重轨试验钢的强度、硬度性能达到最大值；珠光体片层间距最小，晶粒度等级提高，晶粒变得细小。研究结果对于开发超高强度和硬度级别重轨钢的应用具有一定的参考价值。     

超载对钢-混凝土组合梁桥疲劳力学性能影响分析

为了进一步揭示车辆超载对组合结构桥梁疲劳力学性能的影响规律,并减小车辆超载对桥梁疲劳刚度和剩余承载力等性能所产生的不利影响,对现有钢-混凝土组合梁疲劳刚度的理论计算方法加以改进。基于疲劳荷载计算模型量化分析超载车辆的荷载放大效应,并以某实桥为例分析了不同超载程度下该桥疲劳刚度、抗剪连接度与剩余承载力的退化规律。结果表明：随着超载程度的增加,组合梁桥疲劳刚度与剩余承载力的退化速率和退化量均有增大趋势,最大退化量分别为42%和32%,呈现出明显的非线性;抗剪连接度下降,但均保持在完全抗剪连接范围内。所得出的超载对疲劳刚度与剩余承载力的影响规律可为进一步完善钢-混凝土组合梁桥的疲劳损伤理论提供借鉴。     

SRC柱和CFST柱在车辆撞击下的动力响应分析

为了研究框架柱在冲击荷载作用下的抗撞击性能,基于非线性有限元软件LS-DYNA建立了精细化车辆-框架柱碰撞模型。首先,根据轴压承载力相同的原则设计2类框架柱：钢骨混凝土(SRC)柱和钢管混凝土(CFST)柱;其次,对轴压比、撞击角度、撞击速度和车型等影响方形框架柱抗撞击性能有关因素进行参数化分析,探讨框架柱在汽车撞击下的塑性损伤以及破坏模式;最后,比较SRC柱和CFST柱的抗撞击性。结果表明,SRC柱在柱顶受到斜向剪切破坏,在柱底受到弯剪破坏,而CFST柱的破坏模式是弯曲破坏。在车辆侧向撞击下,角度为15°撞击SRC柱时更危险,而CFST柱在正面撞击时更危险。车辆速度和车辆质量的增大,使得框架柱受到的碰撞损伤增大。CFST柱的抗撞击性能优于SRC柱。研究结果证明SRC柱和CFST柱具有优越的抗撞击性能,可为国家相关标准的修订提供参考。     

基于材料性能劣化的RC框架结构抗震性能评估及易损性分析

为了提高钢筋混凝土(reinforced concrete, RC)框架结构的使用寿命,明晰长期服役后的材料劣化对结构抗震性能和易损性的影响程度,建立了考虑材料性能劣化的RC框架结构的有限元分析模型。选取材料性能未劣化(100%)以及分别劣化至90%,80%和70%时的4种工况(依次表示为flsc-100,flsc-90,flsc-80和flsc-70)进行抗震性能评估,同时绘制地震易损性曲线,并分析其在不同地震强度作用下的易损性。结果表明：1)随着材料劣化程度的加剧,RC框架结构在不同地震波下的抗震性能明显降低。罕遇地震作用下,flsc-70的层间位移角比flsc-100增大了80%;2)随着结构刚度及承载力的降低,RC框架结构在不同破坏状态下的超越概率均有显著提升。罕遇地震作用下,flsc-90,flsc-80和flsc-70发生严重破坏的超越概率比flsc-100分别增大了75%,300%和975%。因此,在既有结构抗震性能评估中考虑材料性能劣化的影响十分必要。研究结果可以帮助预测材料性能劣化的RC框架结构在地震发生时的损伤程度,为结构的加固及修复提供参考依据。     

等面积异形柱与矩形柱多层框架的结构性能对比分析

为研究当框架柱截面面积相等时,采用异形柱和矩形柱对结构性能的影响,结合某6层框架住宅建筑,在保证同一位置处的异形柱与矩形柱截面面积相等的条件下,运用结构设计软件SATWE分别进行矩形柱框架和异形柱框架的结构设计,对这2种结构进行了地震作用下的层间位移角、楼层最大位移、楼层剪力、剪重比以及结构自振周期、振型等抗震性能的对比分析;根据规范选取了3条地震波,分别运用SATWE和EPDA软件对这2种结构进行弹性和弹塑性时程分析;从钢筋用量的角度进行了经济性的对比分析。结果表明,当框架柱截面面积相等时,和矩形柱框架相比,异形柱框架的抗震性能较好,但经济性稍差一些。研究结果为不同条件下异形柱与矩形柱的选用提供了理论参考。     

增强Linux系统安全性的措施

L inux系统的安全取决于系统管理员如何来管理它。本文探讨了一系列可以增强安全性的技巧与策略 ,包括 :系统安装原则、BIOS安全、口令安全策略、设计帐户自动注销功能、文件系统和日志安全策略、使用 SSH及 TCP-WRAPPERS,隐藏系统信息、删除所有特殊帐户、关闭控制台程序、限制系统中的 SUID/ SGID程序等。本文最后向 L inux系统管理员提出了一些安全管理方面的建议     

CIS与现代企业管理美学

概括性介绍了 ＣＩＳ（Ｃｏｒｐｏｒａｔｅ Ｉｄｅｎｔｉｔｙ Ｓｙｓｔｅｍ）的三大基本组成，并阐述了它与现代企业管理密不可分的相互联系及所处的举足轻重的地位，指出导入ＣＩＳ是现代企业谋求发展的重要手段。     

Divergent patterns of engagement in Internet standardization: Japan,Korea and China

This article analyzes the engagement of Japanese, Korean and Chinese participants in the development of Internet standards at IETF on the basis of four quantitative metrics: attendance, patenting, authorship and leadership. The results are strikingly divergent. Japanese involvement in Internet standardization began early and Japan was, for many years, second only to the U.S. in terms of IETF participation. Though Japanese participation has declined since the early 2000s, Japan remains a major contributor to IETF standardization. Korean involvement in IETF has always been significant, but below the levels of Japan and major European countries. Korean participation in IETF has also declined over the past decade, and has been dominated by one firm, Samsung. Though meaningful Chinese involvement in IETF did not begin until the mid-2000s, it has rapidly expanded in recent years. Today, China is a major player in numerous areas of Internet standardization in terms of three metrics (participation, patenting and leadership), and is rapidly gaining in terms of document authorship as well. Most of China׳s recent IETF involvement can be attributed to Huawei, though other Chinese firms have recently begun to increase their participation in the organization. Thus, contrary to some views that China׳s engagement with standardization is primarily one of indigenous innovation and “catching up”, China׳s experience with IETF demonstrates deliberate and effective engagement with a major Western standards-development organization on its own terms.     

Comparing FTTH access networks based on P2P and PMP fibre topologies

There is an ongoing discussion in the market which Next Generation Access (NGA) architecture best suits future needs and which investment and cost differences exist. The discussion can be subsumed as P2P vs. GPON, which is somewhat misleading as this article reveals. The discussion is driven by the fact that the high capital cost and the long asset life time of fibre mean that the technology choices made today will dominate the opportunities for telecommunication business of all market players, incumbents, competitors, content providers and business and residential users for many years in the future.The paper analyzes the cost and other differences between Fibre-to-the-Home (FTTH) access network architectures and their related different wholesale approaches by using the well-known and understood steady state approach applied in other NGA analyses in the past. In addition to the steady state analysis a dynamic cost evaluation is included taking into account the different investment behaviour of the FTTH architectures over time. The results describe investment and cost differences between architectures, incumbents and wholesale based competitive operators. The analysis has been performed for different geotypes (clusters) of decreasing population density in a representative European settlement structure.     

Whose Image is it Anyway?: Some Considerations of the Curricular Importance of Subject Image in Secondary School Design and Technology Education

This paper explores the idea that a sense of school subject image is a necessary feature of curriculum management and a potent force for change. The discussion centres on the view that all school subjects have an image and that if those intimately involved with the subject do not control the image then someone else does! In such circumstances the image is the product of past encounters and old euphemisms and is unlikely to hold the changed realities.The UK developments in Design and Technology education (the term Design and Technology is used to denote the school subject defined under this heading by the UK National Curriculum, 1995) have created something of an image problem which has interesting international parallels. Some of these problems are due to clearly discernible internal tensions and an ambiguous relationship with other subject areas.Through greater attention to subject image internal controversies might be acknowledged and resolved, relationships with other subject areas can be more meaningfully understood and practitioners can be helped to make sense of curriculum change.     

Diffusion and usage of public e-services in Europe: An assessment of country level indicators and drivers

We analyze the state of the art of indicators on e-government, e-health, e-procurement and e-participation. We survey the main methodological properties of these indicators, and highlight their heuristic potential. Further, we address empirically the issue of the explanation of the availability scores, i.e. how the supply of the various e-services in each country is affected by political, institutional and socio-economic differences, and is followed by actual usage. The econometric analysis uncovers the importance of broadband penetration and higher education as drivers for most of the types of e-services and users (citizens and businesses). Moreover, a corruption-free and agile public sector proves to be an important pre-condition for more effective supply and usage. Despite data limitations and the complexity of the underlying diffusion phenomena, our study is the first truly longitudinal contribution aimed at disentangling the common drivers of such an important phenomenon – the e-services availability and usage across European countries. As such, this work appears useful to inform the policy debate and practice, in a phase characterized by a prospective reorientation of the public e-services provision and policy agenda.     

一种高精度的频率标准比对系统

频率标准源可以提供精确的标准频率,在测定频率标准源的各项性能指标时,要求测试系统必须具有很高的比对精度。所设计的频率标准比对系统采取多级倍频 混频方式使频率偏差逐级扩大后再测量,从而避免了直接进行高次倍频的困难,提高了测量精度,可以对高精度的频率标准的准确度、长短期频率稳定度进行快速测量,是一种高精度时畴参数测量系统。     

Indigenous peoples’ nutrition transition in a right to food perspective

In indigenous communities the nutrition transition characterized by a rapid westernization of diet and lifestyle is associated with rising prevalence of chronic disease. Field work and literature reviews from two different policy environments, Argentina (Jujuy) and Canada (Nunavut), identified factors that add to indigenous peoples’ disease risk. The analytical framework was the emerging human right to adequate food approach to policies and programmes. Indigenous peoples’ chronic disease risk tends to increase as a result of government policies that infringe on indigenous peoples’ livelihoods and territories, undermining their economic system, values and solidarity networks. Policies intended to increase food security, including food aid, may also fuel the nutrition transition. There is a need to explore further the connection between well-intended policies towards indigenous peoples and the development of chronic diseases, and to broaden the understanding of the role that different forms of discrimination play in the westernization of their lifestyles, values and food habits. Food policies that take due account of indigenous peoples’ human rights, including their right to enjoy their culture, may counteract the growth of chronic disease in these communities.     

The role of government in broadband access

This paper discusses the role of governments in broadband. It is divided into five sections. Following an introduction in section one, section two discusses the diffusion of broadband Internet. Section three deals with competition-based and public-goods views on regulation and the corresponding roles and issues for governments. To gain deeper insights into the role of government in broadband, section four analyses market regulation and public activities in furthering broadband deployment in the US, Korea and Europe. These insights are evaluated in relation to the theoretical considerations established in section three. Section five closes with a discussion of our results and some conclusions. It becomes obvious that national broadband strategies benefit from considering both public good and competition-related aspects.     

A strategic skill based model of supplier integration and its effect on supply management performance

Supplier integration is a tool to help organizations gain competitive advantage. Strategic supply management skills and the supply management function's perceived status are hypothesized as antecedents to supplier integration leading to supply management performance. The sample for this study includes 152 executive level supply management professionals. The empirical results suggest that strategic skills and perceived status are essential antecedents to supplier integration and subsequent performance. Further, the relationship between strategic skills and performance is mediated by supplier integration. Results of a dominance analysis also suggest which strategic skills are most likely to explain status integration, and performance. These findings have significant implications for supply management theory and practice.