共查询到20条相似文献，搜索用时 15 毫秒
1.
为了防止桥头跳车的出现,在桥头路基的设计中,确定加固段长度时,一般只考虑各种处理方法对台后填土的加固作用,而未考虑到加固段在道路正常使用时还起到了对正常路基与桥台差异沉降的过渡作用。通过分析加固段在道路使用中的作用和汽车的行驶轨迹,对不同设计车速的道路桥头加固段长度给出了建议值。从算例比较可以看出,在考虑了加固段在道路正常使用时对正常路基与桥台差异沉降的过渡作用所得的结果更为合理。 相似文献
2.
肖扬 《山西师大学报(社会科学版)》2007,34(5):78-82,126
进入21世纪的中国妇女运动史研究在研究视域、研究方法和叙事方式上呈现出新的取向,不同形态的妇女运动被置于中国现代化的历史脉络中加以考察,新概念、新范畴的介入引发了对妇女运动事件与人物的重新审视,凸显了运动主体的成长轨迹,使新世纪的妇女运动史研究更加生动鲜活。但综观五年来的妇运史研究仍存在着基础理论研究薄弱,自我更新能力不足,在用外来概念重新建构历史时,忽视对史料的梳理分析等问题。为此,妇运史研究者应钩沉探微,处理好理论与实证、叙述与阐释、传统与创新、外来与本土的关系,以整合复杂多样的历史经验,增强妇运史的研究活力。 相似文献
3.
Peter Keith Woodward Abdellah El Kacimi Omar Laghrouche Gabriela Medero Meysam Banimahd 《浙江大学学报(A卷英文版)》2012,13(11):836-849
There are many issues surrounding the performance of critical assets on high-speed ballasted railway lines. At assets like switch & crossings and bridge transitions high track forces can be produced resulting in higher ballast settlements and hence track misalignments. The latter result in higher track forces and hence more settlement, leading to the need for increased track maintenance to ensure comfort and safety. Current technologies for solving issues like ballast movement under high-speed loading regimes are limited. However, a technique that has been well used across the UK and now increasingly overseas to stabilise and reinforce ballasted railway tracks is the application of in-situ polyurethane polymers, termed XiTRACK. This paper discusses how this technique can be used to solve these types of long-standing issues and presents actual polymer application profiles at two typical critical sites, namely a junction and a transition onto concrete slab-track. 相似文献
4.
SADEGHI J AKBARI B. 《浙江大学学报(A卷英文版)》2006,7(11):1846-1855
INTRODUCTION Among the numerous components used in the railway industry for high axle load operations, wheels and rails comprise a major source of running expen- diture. The wheel/rail interaction is the main technical factor determining design procedures and mainte- nance and replacement schedules for both vehicle and track. The rail wear is one of the most important factors causing reduction of the railway track life cycle. The re-profiling and replacement of worn wheels and rails is re… 相似文献
5.
Doctoral programs have high dropout rates of 43% representing the highest among all post-baccalaureate programs. Cross sectional studies of doctoral students?? retention have showed the importance of financial aid in predicting degree completion. These studies however, do not estimate the labor market??s effect on doctoral student retention and neglect the longitudinal nature of doctoral study and the multiple requirements that make doctoral education a three-stage process. This research study examines the effect of various factors, including financial aid and labor market conditions, on the likelihood that doctoral students will complete the three stages of doctoral education: transition, development, and research. The results show that although financial aid as a whole is important, the type of financial aid received is even more significant and has differential impacts on doctoral students?? retention at each stage. The study concludes that research assistantships have the highest likelihood of degree completion compared to students with other forms of financial support. Labor market conditions are also an important factor affecting doctoral student retention with higher expected earnings motivating doctoral students in the later part of their programs to complete their degrees. 相似文献
6.
沉降缝、后浇带和整体连接是控制建筑物各部分之间发生差异沉降的主要做法。参照工程实例,总结了三种现行方法的构造、特点及其应用。分析表明：沉降缝安全合理,但后续施工中对缝隙的盖缝处理较难;后浇带是建筑与结构设计中针对差异沉降采用的折中方案,在一定范围内能起到较好的效果;整体连接方式通过基础及结构的刚度来调整不均匀沉降,施工方便,但对基础的要求较高,有待进一步的理论研究分析和工程实践检验。伴随着计算机数值分析技术的发展,整体连接方式必将得到广泛应用。 相似文献
7.
边士龙 《石家庄铁路职业技术学院学报》2021,(1):57-61
高铁无砟轨道在长轨铺设完后需要对线路进行全面静态调整,将轨道几何尺寸调整到允许误差范围内,使线路轨道平顺性充分满足高铁联调联试前提要求.由于过程中消除轨道病害时间短、任务重,快速查找病害位置和消除方法便成为关键.位于高寒、高海拔、风沙环境下的兰新铁路LXS-2标段及时研究并采用绝对和相对小车结合法轨道调整技术,不仅提高... 相似文献
8.
本文从高铁服务管理与教学研究和发展现状着手,结合高铁服务意识培养的影响因素,提出加强高校在动乘专业学生的服务意识的培养途径。 相似文献
9.
A high-speed train-track coupling dynamic model is used to investigate the dynamic behavior of a high-speed train operating on a curved track with failed fasteners. The model considers a high-speed train consisting of eight vehicles coupled with a ballasted track. The vehicle is modeled as a multi-body system, and the rail is modeled with a Timoshenko beam resting on the discrete sleepers. The vehicle model considers the effect of the end connections of the neighboring vehicles on the dynamic behavior. The track model takes into account the lateral, vertical, and torsional deformations of the rails and the effect of the discrete sleeper support on the coupling dynamics of the vehicles and the track. The sleepers are assumed to move backward at a constant speed to simulate the vehicle running along the track at the same speed. The train model couples with the track model by using a Hertzian contact model for the wheel/rail normal force calculation, and the nonlinear creep theory by Shen et al. (1984) is used for wheel/rail tangent force calculation. In the analysis, a curved track of 7000-m radius with failed fasteners is selected, and the effects of train operational speed and the number of failed fasteners on the dynamic behaviors of the train and the track are investigated in detail. Furthermore, the wheel/rail forces and derailment coefficient and the wheelset loading reduction are analyzed when the high-speed train passes over the curved track with the different number of continuously failed fasteners at different operational speeds. Through the detailed numerical analysis, it is found that the high-speed train can operate normally on the curved track of 7000-m radius at the speeds of 200 km/h to 350 km/h. 相似文献
10.
This study analyzed a stratified random sample of 1,707 senior students at 60 four-year universities in South Korea to explore the gender-specific pathways to Korean students?? development of generic skills??analytical thinking and problem-solving skills. Multiple regression analyses were performed to investigate the involvement factors differential effects on the development of students?? generic skills. The findings suggest that college student involvement plays a critical role in developing the important generic skills. Furthermore, male and female students do have different routes to the development of such skills. In the case of Korean students, at 4-year institutions of higher education, male students tend to develop generic skills more through formal and independent activities in and out of the classroom, whereas female students do so typically in an informal and interdependent way. These results call for additional scholarly investigation into gender influence on college impact and gender-dependent activities during college; moreover, they encourage institutions of higher education to adopt more gender-specific approaches to relevant institutional policies and practices. 相似文献
11.
One basis of good teaching is to know about your students?? preconceptions. Studies about typical ideas that students bring to the science classroom have been and continue to be a major field in science education research. This study aims to explore associations and ideas that students have regarding ??radiation??, a term widely used in various fields and necessary to understand fundamental ideas in science. In an explorative study, the perceptions of 50 high school students were examined using semi-structured interviews. The students were 14?C16?years old and were chosen from 7 different high schools in an urban area in Austria. Following an interview guideline, students were asked about their general associations with the term ??radiation?? as well as about their general understanding of different types of radiation. A qualitative analysis of these interviews following the method of Flick (2009) revealed that the students?? associations were, to a great extent, very different from the scientific use of the term. Several conceptions that could inhibit students?? learning processes could be identified. Consequences for the teaching of the topic ??radiation?? in science lessons, which are based on these preconceptions, are presented in the conclusion. 相似文献
12.
高速铁路运营过程中的关键问题：轮轨磨耗等 总被引：1，自引：0，他引：1
Xue-song JIN 《浙江大学学报(A卷英文版)》2014,(12):936-945
随着高速铁路运营里程和列车运营速度的不断增长,出现了一些和列车轨道耦合大系统密切相关的关键科学和技术问题。这些问题不仅影响到列车的运行品质,甚至威胁到安全运行,是当前高速铁路运用和发展中急需解决的问题。本文系统描述了高速铁路在运营过程中所出现的一些关键科学和技术问题,并述评了全世界有关这些问题的研究进展、现状和不足之处,提出了今后有利于认识和解决这些问题的发展方向。在长期高速运营的铁路大系统环境中,这些问题的形成的机理、发生、发展过程和预防措施的研究,需要从列车／轨道耦合大系统运营环境（速度、路况、气候和运用维修）、系统的自身参数匹配、材料选用和运营成本等全面系统考虑,并从理论、技术、工艺、监控和维修等方面解决。 相似文献
13.
《浙江大学学报(A卷英文版)》2021,(1)
The dynamic behaviour of slab and ballast tracks was investigated using measurements and calculations. Hammer impacts and train passages were analysed and measurements were made using geophones(velocity transducers) which had been time-integrated to displacements. The calculations were carried out in the frequency-wavenumber domain for multi-beamon-continuous soil models. The characteristics of the different tracks and track elements were established in theory and by experiment. The frequency-dependent compliances(displacement transfer functions) showed clear rail-on-railpad resonances or highly damped track-soil resonances. Compared to the rail and sleeper, the track slab had much lower amplitudes. The slab track usually had the highest rail amplitudes due to soft railpads. Train passage yielded track displacements which were a superposition of the axle loads from the two neighbouring axles of a bogie and from the two bogies of two neighbouring carriages. This global behaviour was characteristic of the track slab of the slab track, whereas the rails of the slab and the ballast tracks behaved more locally with only one bogie of influence. The measurements agreed very well with the theory of continuous soil in the case of the six measured slab tracks and acceptably well for the six measured ballast tracks. The measurements allowed us to find appropriate model parameters and to check the models. For example, the Winkler model of the soil was found to be less appropriate because it reacted more locally. 相似文献
14.
Dr. Ruprecht Mattig 《Zeitschrift für Erziehungswissenschaft》2012,15(4):807-827
This paper interprets Wilhelm von Humboldt??s travelogue of his voyage to the Basque country (??Die Vasken??) as an empirical study on human development (??Bildung??) that applies an ethnographic research approach. Against the background of Humboldt??s comparative anthropological considerations the paper focuses on the underlying theory and methodology as well as on the results in Humboldt??s study of the Basques. It will be shown that in ??Die Vasken?? Humboldt directs his attention at anthropological questions on character building (??Charakterbildung??) through applying his anthropological method which combines empirical research with philosophical speculation. The analysis of the results of Humboldt??s study of the Basques demonstrates that Humboldt succeeds in developing his anthropological theory of ??Bildung?? in such a way that he can apply his new insights later in practice in the reform of the Prussian educational system. Finally, a critical reflection about the results of ??Die Vasken?? points out a central methodological and at the same time educational problem in ethnographic research on ??Bildung??. With this interpretation of Humboldt??s study of the Basques the paper provides a historical reflection about theory and methodology in educational anthropology that offers still important insights for actual ethnographic research in the field of education. 相似文献
15.
Robin Millar 《课程研究杂志》2013,45(4):369-382
This paper identifies, depicts and sets out to interpret the common ground between the Australian radical education movement of the late 1960s and early 1970s and the present pre‐occupation with competency‐based reform in school education, the ‘new vocationalism’. The paper contends that both of these developments should be understood as historically novel, Janus‐faced radical movements. The helpfulness of the political‐economic concept of settlement for dealing with the nature and consequences of this congruence is explored. It is argued that the Janus‐faced radicalism of both movements locates them at the interface of modernity and postmodernity, and a particular interpretive response based on this perspective is proposed. 相似文献
16.
陈文哲 《绵阳师范学院学报》2007,26(5):95-99
首先采用大量实例论述城乡界限淡化现象的普遍性,继而指出城市化研究的传统城乡二元分析框架的现实背景已经改变,迫切需要对城乡界限淡化条件下的聚落模式进行研究。文章重点分析了国际上三种主要的城乡界限淡化条件下的聚落模式,并利用对比研究的方法探讨了三种聚落模式之间的区别与联系,认为三种聚落模式可以看作人类聚落发展的三个不同阶段,低一级的聚落模式在一定条件下可能向高一级的聚落模式发生转变。 相似文献
17.
Carlos Alberto Torres 《International Review of Education/Internationale Zeitschrift für Erziehungswissenschaft/Revue internationale l'éducation》2011,57(1-2):39-55
This article begins with a discussion of the implications of CONFINTEA VI having been organised in Brazil ?C the author uses the term ??Brazilian effect?? ?C and the role of social movements challenging neoliberalism. Next, drawing from the experience of Latin America, this paper analyses the counter-hegemonic practice of the new social movements. The concluding section highlights the dilemmas faced by UNESCO in trying to create a democratic and efficient process of policy-making and institutional service in adult education in the nation-states. Furthermore, the proposal of popular education portrayed by the new social movements is described as a tool for empowerment. CONFINTEA VI??s recommendation of moving from rhetoric to action in adult education programmes, practices and policies demands that we take the agendas of the new social movements in the post-neoliberalism era seriously. 相似文献
18.
Cheryl Charles 《Journal of Science Education and Technology》2009,18(6):467-475
Cheryl Charles, Ph.D gave the 2009 Paul F-Brandwein Lecture. The lecture addresses the impact of children’s disconnect from the natural world in their everyday lives. Co-founder of the Children & Nature Network (C&NN) with Richard Louv, author of Last Child in the Woods: Saving Our Children from Nature-Deficit Disorder (2005/2008), the author describes C&NN’s approach to building a movement to reconnect children and nature for their health and well-being. She puts the growth of the movement in recent historical perspective, chronicling relevant contributing factors. Drawing on research as well as common sense, she summarizes evidence that indicates some of the negative impacts on children’s health from their lack of contact with nature and other characteristics of contemporary lifestyles, as well as positive benefits to children’s cognitive, emotional, social and physical development from direct learning and play in nature-based settings. She describes what she calls “natural guides” to building the children and nature movement as a part of the process of achieving sufficient critical mass to facilitate positive social change. Finally, she offers recommendations for actions. 相似文献
19.
工程建设在经济高速发展的推动下取得了重大的突破,尤其是高层建筑物的密集程度日益提高,建筑物不均匀沉降成为地基面临的主要问题之一。在介绍建筑物地基不均匀沉降带来的危害的基础上,从不同方面分析和总结了其产生的原因,深入研究防治措施并且阐述了针对软弱地基与不良地基的处理方法,以求达到有效预防、控制建筑物不均匀沉降的产生,最终消除事故根源的目的。 相似文献
20.
Low frequency vibrations induced by underground railways have attracted increasing attention in recent years. To obtain the
characteristics of low frequency vibrations and the low frequency performance of a floating slab track (FST), low frequency
vibration tests on an FST in an underground laboratory at Beijing Jiaotong University were carried out. The FST and an unbalanced
shaker SBZ30 for dynamic simulation were designed for use in low frequency vibration experiments. Vibration measurements were
performed on the bogie of the unbalanced shaker, the rail, the slab, the tunnel invert, the tunnel wall, the tunnel apex,
and on the ground surface at distances varying from 0 to 80 m from the track. Measurements were also made on several floors
of an adjacent building. Detailed results of low frequency vibration tests were reported. The attenuation of low frequency
vibrations with the distance from the track was presented, as well as the responses of different floors of the building. The
experimental results could be regarded as a reference for developing methods to control low frequency vibrations and for adopting
countermeasures. 相似文献