单索面矮塔斜拉桥的动力特征参数研究

结合小西湖双塔三跨单索面矮塔斜拉桥地震荷载作用下的结构动力反应,引入“斜拉索动力荷警效应暨响度”的概念定量分析了矮塔斜拉桥斜拉索在地震荷载下的实质作用,并据此提炼出能综合反映矮塔斜拉桥结尊翌考譬征的参数——“矮塔斜拉桥动力特征参数”;用“斜拉索动力荷载效应影响度”与“矮塔斜拉桥动力特征参数”的相关性定量描述矮塔斜拉桥的动力特点,对进一步认识矮塔斜拉桥的动力性能有一定的参考意义。     

大跨度混凝土斜拉桥抗爆分析

为研究大跨度混凝土斜拉桥在爆炸荷载下的动力响应和损伤模式。建立全桥实体模型和跨中主梁局部模型,并开展不同炸药条件下的斜拉索应力分析和结构动力响应分析。结果表明:(1)斜拉索在爆炸荷载下直接破坏的风险较低,只有偏载作用时近爆点斜拉索有断索风险;(2)斜拉桥混凝土主梁的局部破坏模式与爆炸位置和TNT当量均有关系;爆炸位置相同时,随着TNT当量增大,破坏模式由弯曲破坏转变为直剪破坏;(3)梁体纵向加劲肋在中小爆炸荷载作用下能有效提高梁体的抗爆能力,其与箱梁顶板形成具有相对强弱刚度的熔断体系,有效限制梁体横向破坏面的扩展,降低破坏程度,甚至可改变梁体的破坏模式;(4)箱梁结构破坏时冲击波在箱室内传播存在明显的约束效应并引起更严重破坏。     

基于并行算法的船桥碰撞数值模拟分析

船撞桥是在巨大冲击动能作用下的复杂的非线性动态响应过程.为模拟船桥碰撞过程,建立了桥梁和船舶碰撞的三维有限元模型.采用了基于接触均衡的并行计算技术,利用上海超级计算机曙光4000A,对桥梁在船舶撞击荷载作用下的动态响应进行仿真计算.主要分析了船艏结构的损坏、碰撞力演变、能量转化以及斜拉桥主塔和桥面的动态响应.将整桥整船的船桥碰撞模型与不考虑主梁和斜拉索的船桥碰撞模型进行了比较,结果表明,后者将使计算结果偏大.     

冷却塔定向爆破拆除及爆破效果有限元数值模拟

介绍了3000m2冷却塔的爆破拆除实例,采用动力有限元分析软件ANSYS/LS-DYNA建立了冷却塔爆破拆除三维有限元模型,对爆破倒塌效果进行了模拟.模拟结果与真实情形在倾倒过程与倒塌效果方面有很大相似性.冷却塔结构上窄下宽,重心较低,失稳后重心不容易移出,但由于本身体积和重量都比较大,而塔壁较薄,爆破缺口形成后发生塑...     

索力调整在斜拉桥施工中的影响

分阶段施工实际上是斜拉桥结构体系与作用于结构上的荷载不断变化的过程。施工工序的变化引起荷载的变化,结构上荷载的变化改变着斜拉索的索力,斜拉索的主动调索表面上是改变着斜拉索的索力,而本质上是改变了斜拉索的无应力长度。按照无应力状态控制法最终结构的内力和线形与施工过程无关的基本原理,可以实现斜拉桥施工中斜拉索调索与其他工序同步并行作业。     

框架结构爆破拆除分离式模拟研究

随着爆破拆除结构及其所处环境日趋复杂,爆破拆除理应向拆除过程可控制、爆破效果可预测的方向发展.采用共用节点分离式建立模型,运用ANSYS/LS-DYNA软件模拟框架结构定向爆破拆除的倒塌过程.通过改变材料的失效应力分析了不同材料强度对结构倒塌效果的影响,数值模拟结果表明材料强度与倒塌位移成正相关.通过对混凝土和钢筋单元...     

桥礅柱定向倒塌拆除爆破后坐分析

根据建筑物拆除爆破失稳原理，对桥礅柱定向倒塌控制爆破拆除试爆时产生后坐进行力学分析，得出试爆产生后坐的主要原因是保留支撑截面瞬间强度不够，调整主爆相关参数，使主爆达到预期效果。     

大跨度钢索和CFRP索斜拉桥车桥耦合振动研究

以跨度600m～1400m的大跨度斜拉桥为对象,应用考虑拉索侧向振动影响的车桥耦合振动分析方法研究了钢索和CFRP索斜拉桥的交通振动响应,比较了车辆计算模型、行车速度对计算结果的影响,并分析了斜拉桥的动力冲击系数。研究结果表明,大跨度斜拉桥主梁的振动响应以静位移和长周期振动成分为主,拉索局部侧向振动不明显,车辆计算模型对结构振动响应的影响十分有限,行车速度的提高增加了结构的动力系数,两种拉索材料对斜拉桥在车辆荷载下的振动响应影响很小,斜拉桥的动力系数离散性大且与构件类型有关。     

预拆除对薄壁双曲型冷却塔爆破拆除的影响

针对贵阳发电厂内冷却塔是由钢筋混凝土构成的薄壁双曲型圆筒,具有底部直径大,垂直高度高,塔壁外部没有施工条件且周边环境较为复杂的特点,采用预拆除技术,以确保冷却塔爆破拆除顺利实施并取得良好的效果。预拆除技术主要由3个部分组成:冷却塔内部支撑、倒塌方向薄壁的减荷槽以及倒塌反向的泄压窗。通过理论计算设计出正梯形爆破切口的参数,在人字形柱上同时采用开设减荷槽(13个)的方法,来保证冷却塔筒壁在倒塌过程中的屈服破碎效果,为了进一步减小爆炸冲击波对冷却塔筒壁的破坏作用,在倒塌方向的反方向开出一个2m×4m的矩形泄压窗。根据现场实验结果和冷却塔整体爆破效果,预拆除技术对薄壁双曲型冷却塔爆破起到了良好的作用,达到了冷却塔整体失稳倒塌,精确定向以及整体不下坐的效果。     

联体砖混结构圆筒仓的控制爆破拆除

介绍了设有提升机房的联体砖混圆筒仓的控制爆破拆除。对圆筒仓间仓壁重叠部前端的"x"型部分进行了爆破预拆除,充分考虑爆破切口形状的影响合理选择爆破参数,利用中间通道作定向窗,设置减荷窗及合理的延时时间,保证了联体结构的整体失稳,避免了筒仓整体下坐而产生后坐或倒塌不充分。可为同类工程提供借鉴。     

Growth and Study of Borocarbide Single Crystals

Superconducting yttrium borocarbides were synthesized by different methods. A two-step method was found to be advantageous. Influence of the annealing time on superconducting properties is investigated. The superconducting temperature of YNi ₂ B ₂ C single crystal is 15 K.     

Single parameter indices and bibliometric outliers

In this paper, we look at the issue of the high-end of research performance which is captured in the tail of a citation distribution. As the mean is insufficient to capture the skewness of such distributions, a consistency or concentration measure is the additional parameter needed. We show that the h-index is only approximately a heuristic mock of a composite indicator built from three primary indicators which are the number, mean and consistency term. The z-index is able to sense the change in consistency in the distribution due to the outliers in the tail of the distribution.     

Charge Transfer at Junctions of a Single Layer of Graphene and a Metallic Single Walled Carbon Nanotube

Junctions between a single walled carbon nanotube (SWNT) and a monolayer of graphene are fabricated and studied for the first time. A single layer graphene (SLG) sheet grown by chemical vapor deposition (CVD) is transferred onto a SiO₂/Si wafer with aligned CVD‐grown SWNTs. Raman spectroscopy is used to identify metallic‐SWNT/SLG junctions, and a method for spectroscopic deconvolution of the overlapping G peaks of the SWNT and the SLG is reported, making use of the polarization dependence of the SWNT. A comparison of the Raman peak positions and intensities of the individual SWNT and graphene to those of the SWNT‐graphene junction indicates an electron transfer of 1.12 × 10¹³ cm^?2 from the SWNT to the graphene. This direction of charge transfer is in agreement with the work functions of the SWNT and graphene. The compression of the SWNT by the graphene increases the broadening of the radial breathing mode (RBM) peak from 3.6 ± 0.3 to 4.6 ± 0.5 cm^?1 and of the G peak from 13 ± 1 to 18 ± 1 cm^?1, in reasonable agreement with molecular dynamics simulations. However, the RBM and G peak position shifts are primarily due to charge transfer with minimal contributions from strain. With this method, the ability to dope graphene with nanometer resolution is demonstrated.     

螺纹的综合测量和单项测量

简要介绍了螺纹测量的现状和目前存在的问题,讨论了螺纹测量需要研究的几个问题,分析了螺纹单项参数测量和综合测量的关系以及螺纹量值传递技术.具体介绍了实现内螺纹中径参数测量的测量原理、测量方法和测量中的问题.     

Single Side Imaging of Corrosion Under Insulation Using Single Photon Gamma Backscattering

In this work, a gamma ray Compton backscatter technique is used for imaging defects and thickness variations in insulated pipes and metal plates containing depressions of various diameters and at various depths from one side of the object. The scattered radiation was measured by a scintillation detector that scans the object using a two-dimensional mechanical scanning system. The gamma spectrum was displayed with a multichannel analyzer (MCA), and the energy window width was selected so that only Compton single scatter counts were measured. Images were constructed using the LabVIEW computer program. Successful images of defects on the outer surface of the object under the insulation were obtained, and the system was found to be able to detect wall thickness changes in large pipes with walls more than 15 mm thick. Low activity sources of 10⁸ Bq (a few mCi) were used, and the dose rate near the surface is four orders of magnitude lower than conventional industrial radiography sources, permitting it to be much safer.     

Single bubble sonoluminescence and stable cavitation

A single bubble trapped at an antinode of an acoustic standing wave field in water can emit 50ps-140ps light pulses, called "single bubble sonoluminescence" (SBSL). It arouses much interest in physical acoustics because of its highly non-linear characteristics, high concentration of energy, and stable cavitation behavior. In this paper, bubble stability, the dynamic behavior of bubbles, non-invasive measurement of driving acoustic pressure and Mie scattering method are introduced.     

Single electron encoded latches and flip-flops

Single electron tunneling (SET) technology offers the ability to control the transport of individual electrons. In this paper, we investigate single electron encoded logic (SEEL) memory circuits, in which the Boolean logic values are encoded as zero or one electron charges. More specifically, we focus on the implementation of SEEL latches and flip-flops. All proposed circuits are verified by means of simulation using the SIMulation Of Nanostructures package. We first present a generic SEEL linear threshold gate implementation, from which we derive a family of Boolean logic gates. Second, we propose Boolean gate-based implementations of the RS latch, the D latch, and D flip-flop. Third, we propose threshold gate-based implementations of the same memory elements. Finally, we discuss the estimated area, delay, and power consumption of the Boolean gate-based and threshold gate-based implementations, and compare them with other SET-based memory elements.