西部地区县乡公路设计参数敏感性分析及土基等级划分

分析西部地区县乡公路沥青路面典型结构设计参数的敏感性.通过对路基路面设计参数(结构层厚度和材料模量)的变化对路基路面工作状态影响的研究,得到路面结构强度随各结构层设计参数变化规律,确定路面结构的敏感性层位,推荐出设计参数的建议值,为县乡公路土基强度等级划分及路基路面的结构优化设计提供依据.     

阳极时效时间与电解质对Fe—31Mn—7Cr合金钝化膜的稳定性与耐腐蚀性能的影响

运用综合的电化学方法与原子吸收光谱技术，研究阳极时效时间及其电解液对Fe-31Mn-7Cr合金于50％HNO3或1molL^-1Na2SO4溶液中形成的钝化膜的稳定性与耐蚀性的影响。在阳极钝化电位中区，延长Fe-32Mn-7Cr合金在50％HNO3或1molL^-1Na2SO4水溶液中阳极时效时间能增加钝化膜的稳定性与防护性，随之进一步改善合金的耐腐蚀抗力。由1molL^-1Na2SO4水溶液中阳极极化曲线各参数所表征的Fe-31Mn-7Cr(经1molL^-1Na2SO4阳极时效5h后）的耐腐蚀性能接近于1Cr13不锈钢的水平。在强氧化性的50％HNO3溶液中阳极时效表面改性的效果明显优于在中性的1molL^-1Na2SO4溶液中改性。表面改性后，抗腐蚀性能的提高主要归因于钝化膜中Cr氧化物的富集与Fe和Mn氧化物的贫乏。     

双线隧道现场监控量测数据分析

武广客运专线金沙洲隧道属于浅埋双线隧道,围岩条件复杂,采用新奥法正台阶法施工。为了进一步修改和完善原设计,并有效地指导下阶段施工,对台阶法施工中现场监控量测的数据采取了分段处理分析,实践表明采用此法能更好的指导施工和准确预测极值。     

安装铅芯橡胶支座桥梁的抗震性能研究

在高地震烈度区的桥梁结构,设计时地震力起绝对控制作用,此时如果采取结构本身的"硬抗"不仅增加设计负担,并且大量浪费原材料,同时增加了经济负担。一般情况下,可采取"延性设计"和"减隔震设计"来达到减震耗能的目的。该文针对某8度区桥梁,采用国内外较常用的整体型减隔震装置——铅芯橡胶支座对其进行减隔震设计,计算结果表明铅芯橡胶支座既能延长结构的周期,又能耗散地震能量,具有良好的减隔震效果,是一种比较理想的减隔震装置。     

Magnetic resonance imaging of atherosclerotic lesion with new devised animal surface coil

The ability of dynamic contrast enhanced magnetic resonance imaging(DCE MRI) with a new devised animal surface coil was analyzed in identifying atherosclerotic plaques in the rabbit medium-sized iliac artery(IA).Then a comparative analysis of multi-detector computed tomography(MDCT) and DCE MRI was done in discerning morphology and components of 80 atherosclerotic plaques identified by histopathology.It shows that the DCE MRI may be an emerging noninvasive and economic way to characterize atherosclerotic plaques at present.What's more, a new devised animal surface coil would further improve the signal-to-noise ratio(SNR) and the quality of imaging.However, CT angiography(CTA) may be better than MR angiography(MRA) in detecting vessel stenosis.     

Demonstration of reduced airport congestion through pushback rate control

Airport surface congestion results in significant increases in taxi times, fuel burn and emissions at major airports. This paper describes the field tests of a congestion control strategy at Boston Logan International Airport. The approach determines a suggested rate to meter pushbacks from the gate, in order to prevent the airport surface from entering congested states and to reduce the time that flights spend with engines on while taxiing to the runway. The field trials demonstrated that significant benefits were achievable through such a strategy: during eight four-hour tests conducted during August and September 2010, fuel use was reduced by an estimated 12,250–14,500 kg (4000–4700 US gallons), while aircraft gate pushback times were increased by an average of only 4.4 min for the 247 flights that were held at the gate.     

使用30°楔形防松螺纹安装扭矩的建议

为明确30°楔形防松螺纹在同样的施加扭矩下所获得的轴力。试验了30°楔形防松螺纹和普通螺纹经振动防松试验轴力的衰减情况和同扭矩下扭矩系数及轴力的比对试验。从而获得在施加相同扭矩下,30°楔形防松螺纹所获得的轴力比普通螺纹所获得的轴力低。     

Study of the Settlement Control of Deformation Joints of Tunnels Passing Closely under the Existing Station北大核心CSCD

The newly-built tunnel passing closely under the existing station will inevitably lead to settlement of the existing station, and especially deformation joints are prone to differential settlement. Based on the Suzhoujie Station of Beijing Subway Line 16 passing closely under the existing Line 10, this paper analyzes the overall settlement of the existing station and the differential settlement at deformation joints through a combination of field measurement and numerical simulation. The study results show that installing jacks significantly prevents the settlement of the existing station, after installation of jacks the settlement of the existing station is reduced by about 58%, and the jacking force of the jack shall be controlled between 180-450 t; the impact of construction on the single-deck station structure side at deformation joints is greater than that on the double-deck station structure side, the stress on the socket is gradually increased with the excavation of the lower tunnel, and reduced after installation of jacks, indicating that the jack can effectively reduce the tensile stress of the existing station and maintain the safety of the existing station; with the action of the jacking force of jacks, the settlement curve of the existing station presents a stepwise change at the jack installation points, while the upper ground surface settlement is relatively uniform. © 2022, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

A planar quasi-static constraint mode tyre model

The fast-paced, iterative, vehicle design environment demands efficiency when simulating suspension loads. Towards that end, a computationally efficient, linear, planar, quasi-static tyre model is developed in this work that accurately predicts a tyre's lower frequency, reasonably large amplitude, nonlinear stiffness relationship. The axisymmetric, circumferentially isotropic, stiffness equation is discretised into segments, then parameterised by a single stiffness parameter and two shape parameters. The tyre's deformed shape is independent of the overall tyre stiffness and the forces acting on the tyre. Constraint modes capture enveloping and bridging properties and a recursive method yields the set of active constraints at the tyre–road interface. The nonlinear stiffness of a tyre is captured by enforcing unidirectional geometric boundary conditions. The model parameters are identified semi-empirically; simulated cleat test loads match experiments within 7% including nonlinear stiffness when simulating a flat plate test and a discontinuous stiffness when simulating a cleat test.     

传感型土工格栅加筋含轮胎片体填料挡墙性能模型试验

风化料-废旧轮胎片体（TDA）混合形成的轻质土具有重度小、透水性强等优点，可用于台背回填，能显著降低工后沉降。然而TDA在土中的质量比对加筋土挡土墙性能的影响尚不清楚。为此，针对以风化料和TDA混合料填筑挡土墙的性能开展了一系列比例为1：5的缩尺模型试验，研究风化料中的TDA质量比（20%、30%和40%）和条形荷载位置对挡土墙极限承载力和变形的影响。模型中的加筋材料为自主研发的传感型土工格栅（SEGG），SEGG兼具加固和变形自检测功能，可以通过测试其电阻变化的方法实现对筋材应变的分布式测量。试验结果表明：加筋土挡墙的极限承载力在条形荷载距离侧墙0.4H（H为侧墙高度）时达到最大，同时极限承载力随着TDA质量比增加而减小；破坏时侧墙变形随TDA质量比增加而显著增加，同时侧墙形状随条形荷载的位置不同而不同；通过试验观察可知，滑裂面通过了每层SEGG的最大应变区域；随着条形基础与墙面距离的增加，滑裂面向更深处发展；当条形荷载距离侧墙0.8H时，挡墙破坏模式接近平面基础剪切破坏模式；当TDA质量比达到40%时，TDA与风化料出现离析现象。对比发现，20% TDA质量比更适用于加筋土挡土墙工程；当条形荷载距离侧墙为0.4H时，极限承载力达到最大；锚固楔体法适用于加筋土挡墙滑裂面；SEGG应变的测量结果与滑裂面的试验观察结果吻合较好，同时也证明，TDA质量比和条形基础的位置均对挡墙破坏时的滑裂面有影响。