墩体下承台厚度有限元分析

为分析墩体桩基承台厚度与应力分布的规律,文章结合鄂北地区水资源配置工程孟楼渡槽承台设计建立三维有限元模型,对不同厚度承台进行应力分析。结果表明,墩体下承台底面正应力为拉应力;在合理的承台厚度范围内,桩间承台截面上的最大正应力随着承台厚度的增加而减小,增加承台厚度能有效减小截面上的最大正应力;随着承台厚度的增加,承台双向受力的特征越发明显;承台底面桩顶部位处的剪应力极值显著大于正应力,承台的抗剪作用明显;设计中对墩体下承台进行抗弯曲、抗剪切验算是必要的。     

含水率对重塑黏土力学特性的影响研究

为探讨含水率对重塑黏土力学特性的影响,对不同含水率的重塑黏土进行直接剪切试验。结果表明:重塑黏土抗剪强度受含水率和竖向压力作用影响明显,随含水率增大,其抗剪强度逐渐减低,随垂直压力逐渐增大,其抗剪强度逐渐增大;随含水率增大,重塑黏土黏聚力逐渐减小而内摩擦角先增大后减小,在最优含水率附近时达到最大。     

某工程渠首增设排沙闸后水沙演变特征分析

为研究引黄济青工程渠首增设排沙闸后水沙演变特征,设计开展引水期水渠泥沙模型试验.研究了随水深增大,测点流速增大;测点间流速差幅随相对水深增大而减小.闸前悬板泥沙沉降受限较大;随闸前距离愈远,含沙量愈大,但增长速率为先慢后快.论文认为增设排沙闸有助于降淤,且多孔式排沙模型工作效率高于单孔.     

预应力锚索锚固效果的试验分析研究

通过理论分析锚固段应力分布弹性解和数值模拟计算,表明预紧力、孔径、锚固剂弹性模量和岩石弹性模量等影响因子对锚固段受力影响程度和方面各不相同,例如预紧力和锚固剂弹性模量的影响程度大于其他因子;锚索孔径对其剪应力分布产生影响而对轴力无影响等。锚索轴力和剪应力分布均呈指数关系从锚固端向内逐渐递减,峰值点位于锚固起始端,而锚固段周边剪应力的分布是不均匀的,峰值位于锚固端约0.25m深度内。     

基于有限元法的V型缺口平板应力集中系数研究

针对双边V型缺口有限宽平板的应力集中问题,采用有限元软件ANSYS对缺口尖端区域应力场进行了分析。采用数值积分方法对平均应力及不同开口角度2α、不同尖端半径ρ条件下的应力集中系数进行了计算,并将有限元分析结果与Filippi缺口应力场方程的结果进行了对比验证。结果表明,有限元分析方法得到的结果与Filippi方程的计算结果最大误差为3.77%;在缺口尖端处存在明显的应力集中,但随着到缺口尖端距离的增加应力集中系数降低很快;缺口处最大应力集中系数随缺口尖端半径的增大而明显减小,且减小速率逐渐降低;随着缺口角度的增加,应力集中系数缓慢减小。因此,采用有限元方法可以有效开展含缺口结构的应力集中分析,研究方法对于其他复杂含缺口结构的安全分析具有一定的参考价值。     

加筋聚苯乙烯轻质膨胀土室内试验研究

为了研究加筋聚苯乙烯轻质膨胀土的膨胀与强度特性,将聚苯乙烯颗粒与膨胀土混合,聚丙烯纤维作为加筋材料,开展了包括密度、无荷膨胀率、膨胀力以及饱和快剪等室内试验。结果表明,聚苯乙烯颗粒和聚丙烯纤维的掺入可有效抑制膨胀土的膨胀特性,表现为无荷膨胀率与膨胀力的显著减小;聚苯乙烯颗粒主要起到体积置换作用,土样密度以及膨胀力随聚苯乙烯颗粒掺量增加线性减小;随着聚苯乙烯颗粒的增加,混合土内摩擦角持续增大,黏聚力先增加后降低;随着纤维掺量的增加,混合土的黏聚力得到有效增长。因此,加筋聚苯乙烯轻质土在改良膨胀土方面具有良好的应用价值。     

硫磺用量对生物基杜仲胶性能的影响

探究在加入不同用量的硫磺对白炭黑补强后的生物基杜仲胶硫化特性、硬度、拉伸性能及交联密度等性质的测试。结果表明:随着硫磺用量的增加,胶料的T90先减小后增加,ML增大;MH增大;定伸应力先减小后增加,拉伸强度先减小后增大,断裂伸长率增加;邵氏硬度降低;交联密度逐渐增大。     

加强型KT型管节点几何参数对承载力的影响

为了最大限度提高节点的承载能力,提高海工结构及钢结构稳定性,提出了一种基于弧长法对KT型管节点的承载力进行有限元分析的方法。基于β,τ,γ,θ等4个几何参数对节点承载力的影响规律,最终确定了参数的合理取值:τ取0.75,γ取20,θ取30°～45°,β取0.6～0.8。同时引入参数材料强度比δ,研究支管与主管强度的不匹配对节点承载力的影响,结果显示:随着δ值的增大,节点的承载力先增大后减小再趋于某一值,节点的破坏模式由支管破坏过渡到主管破坏,但承载力的极值点和破坏模式过渡点的δ值的大小会随着τ,γ,β的取值的变化而变化,最终趋于某一个定值。研究结果可为工程上确定加强板的参数取值提供参考。     

膨胀管可靠性评价方法研究

膨胀率是描述膨胀管尺寸变化的重要参数,对胀后膨胀管力学性能以及可靠性有重要影响。分析了不同膨胀率条件下膨胀管残余应力以及抗外挤强度的变化规律,利用可靠性理论建立了膨胀管失效评价模型。结果表明:膨胀管胀后力学性能受到冷作硬化以及壁厚变化量双重影响,屈服强度随着膨胀率增加达到峰值后基本保持不变;不同膨胀率的膨胀管在膨胀过程中残余应力随轴向的分布情况大体相同,数值随膨胀率增加而变大,增长量逐渐减小;受到椭圆度、壁厚不均匀度以及残余应力等不确定因素影响,膨胀管抗外挤与抗内压强度服从正态分布规律,不同膨胀率条件的膨胀管失效概率不同。该研究为膨胀管强度安全系数的科学设计提供依据。     

干湿循环对山区水库库岸边坡稳定性影响

为探讨干湿循环对红砂岩库岸边坡影响,对不同干湿循环次数典型红砂岩试样进行三轴压缩试验,并分析干湿循环作用下,红砂岩强度衰减规律,此外基于Geostudio对某红砂岩库岸边坡干湿循环作用下稳定性进行分析。结果表明,随干湿循环次数增多,红砂岩吸水率和质量损失率逐渐增大而内摩擦角和黏聚力均逐渐减小,库岸边坡安全系数逐渐减小。     

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.     

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.     

蒸汽热量计量应用的探析

研究了石油化工企业的燕汽计量情况,着重对蒸汽热量计量的合理性进行了分析,阐述了蒸汽热量计量的依据及计算方法,以及蒸气热量计量对节能降耗的重要意义.     

论传统旗袍文化与现代时装

中国的旗袍文化蕴含着非常丰富的文化内涵和设计思想,如今旗袍的普及受到一定的限制,只有经过改良,才可变局限性为可行性,才可使旗袍焕发青春,走向新时代。     

望峰岗矿井贯通测量技术分析

在深部开采矿井两井间贯通测量时,利用加测陀螺定向边和用四架法代替传统的三架法测量,分析了由起始边的方位角误差引起的支导线终点误差及由测角量边引起的导线终点的点位误差.     

工程施工质量控制和管理要点

提高施工中质量管理工作水平，为公司今后发展打下良好基础。     

高油价影响我国经济

从2004年初以来，国际油价急剧攀升，文章分析了原油价格居高不下的原因，对未来油价的走势及其对我国经济的影响和冲击进行了预测，面对这种情况我国必须采取应对措施：树立节能消费理念；促进技术创新，推动产业升级；建立石油战略储备、推出原油期货、推动多元化战略等。     

亲油性纤维材料性能及应用

纤维素纤维是自然界广泛分布的天然纤维,像法桐球果纤维、木棉纤维、杨花纤维、蒲公英绒纤维,都是纤维素纤维,纤维具有吸油快、吸油量大、拒水的性能特点,纤维不易进行纺织生产加工,但可以作为海面吸油材料使用,并且加工方法简单,吸油效果好。     

Optimizing receiver performance using harm claim thresholds

More and more systems need to be squeezed together in frequency, space and time in order to satisfy the growth in demand for radio services. However, greater proximity increases the risk of service breakdowns caused both by poor interference tolerance in receivers and by inappropriate signals radiated by transmitters.     

Broadband expectations and the convergence of ranks

Broadband Internet service to widely held to be a significant contributor to economic development and global competitiveness, and comparison of adoption rates across countries are common. This paper presents evidence that the relative broadband Internet adoption ranks across the Organisation for Economic Co-Operation and Development (“OECD”) countries are converging to the wireline telephone adoption ranks in the mid 1990s. This was a time when wireline telephone service had reached maturity, but before consumers began to abandon traditional telephone services for mobile services and Internet telephone technologies. As such, in the absence of better data on household adoption, wireline telephone rank is a useful proxy for a country's ultimate fixed-line broadband penetration rank. Having such an educated guess available regarding broadband rank should reduce the amount of anxiety over rankings, since similar rankings across the two services implies suitable broadband performance. Large departures, alternately, may be a cause for concern or delight. Like prior analyses, the findings suggest that the adoption of communications services is largely an economic and demographic issue.