Soil-structure interaction and effect of axial force on the dynamics of offshore structures

The offshore structures are flexible systems subjected to various types of loadings. The heavy gravitational loads on the top decks, wind and water wave pressures acting on the platforms are transferred to the soil through the piles or mat foundations. Under the vibration, the variation in the pore pressures induces additional effects on the embedded part of the piles. The effect of the soil-structure interaction on the dynamics of the structure is taken into account as the deformations of the soil caused by the motion of the structure which in turn modify the response of the structure. The effect of the axial forces, within the individual members, on the vibration of the structure is included in the formulation. The dynamic stiffness matrix of the members are developed by considering the actual mass distribution and the effect of the axial force of the members. For the members embedded into soil, the soil reactions and the skin frictions are also considered as continuously varying over the members. Therefore, the equations of motion are satisfied along any infinitesimal element of the members. The new formulation is introduced in the general purpose computer code STDYNL, then the sensitivity of the overall dynamic response of the deep water platforms to the variation of the soil characteristics and to the effect of the axial forces of the members are investigated.     

齿轮箱吊杆节点刚度对轴箱内置式高速列车驱动系统动态特性影响研究

为探明齿轮箱吊杆节点刚度对驱动系统悬挂节点力和驱动系统振动加速度的影响规律,以某型轴箱内置式高速动车为研究对象,基于多体动力学理论,建立了考虑驱动系统和齿轮啮合的车辆系统动力学模型,研究了齿轮箱吊杆节点刚度对齿轮箱吊杆节点力、电机吊点力、齿轮箱车轴铰接力、车辆平稳性和驱动系统振动加速度的影响.研究结果表明：由于1、2位驱动系统的齿轮啮合力方向不同,1位驱动系统悬挂节点的垂向力比2位驱动系统悬挂节点的垂向力大.齿轮箱吊杆节点刚度在1～30 MN/m增大时,1位齿轮箱吊杆节点力增大,1位电机吊点力减小,1位齿轮箱车轴铰接纵向力增大、横向力减小;2位齿轮箱吊杆节点力增大,2位电机吊点垂向力增大,纵向力和横向力减小,2位齿轮箱车轴铰接纵向力减小,横向力增大.齿轮箱吊杆节点刚度在30～100MN/m增大时,各悬挂节点力变化不明显.此外,车体的平稳性指标、电机和齿轮箱的振动加速度受齿轮箱吊杆节点刚度变化的影响较小.     

基于能量和频谱共享的传感器网络时延性能分析

采用协同频谱共享和射频能量采集技术后,传感器网络的可用频谱资源和可用能量均受主用户行为约束。为了刻画主用户对传感器网络性能的影响,利用排队理论对基于能量和频谱共享的无线传感器网络时延性能进行建模和分析。首先,通过分析主用户的服务过程和传感器节点的服务过程,推导出了主用户的时延性能。然后,分析了主用户参数对传感器节点服务时间的影响,得到了传感器节点的时延性能,并推导出了Nakagami衰落信道下传感器节点平均时延与系统参数关系的表达式。最后,比较了仿真结果和理论结果,验证了理论分析的正确性,并揭示了网络时延性能与到达率、节点间距离等参数的关系。     

Engine for brain development: similarity between engine and brain

A theoretical model that simulates the developmental process of the human brain, including the blood vessels, is proposed. Observations of the development of the human brain with a high-speed camera show that the bones of the skull become increasingly large over the neck, and that a lot of soup-like fluid for generating brain cells enters the skull from the body. This process is essentially similar to the intake process of an internal combustion engine, because the volume of the engine cylinder, which increases according to the descent of the piston, corresponds geometrically to the development of the skull, and also because the human neck resembles the intake port that serves as the throat of the engine. A higher-order numerical computation of the Navier-Stokes equation reveals the similarity between the convexo-concave forms inside the brain and the flow structure in the internal combustion engine at very low Reynolds numbers. Further, we examine the similarity between the main blood vessels in the brain and the path lines in the engine.     

大型机械部件传动空心轴用液压联轴器内外套壁厚设计的研究

船用空心轴在保证传动不发生变化情况下,可以减轻传动轴重量及传动惯性,但在装配时空心轴会出现液压联轴器内套受力变化不均,在设计液压联轴器时无法准确设计内、外套的壁厚。论文研究液压联轴器内套内压力p沿轴向的变化规律,为以后设计设计内、外套的壁厚打下理论基础。用SAS软件来分析空心轴外侧所受液压联轴器的内套的压力回归曲线并进行数据采集处理,利用高斯曲线的数学模型,算出液压联轴器内套内压力p沿轴向的变化规律方程,理论值和实测压力比较,研究了空心轴外侧压力与径向变形位移比值的变化发展趋势。理论压力值与实际压力p值基本相同,空心轴外侧压力与径向变形位移比值的变化发展趋势回归方程实际效果良好可以用来指导生产,为液压联轴器的内、外套壁厚设计提供理论支撑。     

信息论课程在网络安全与执法专业建设中的重要性研究

网络安全与执法专业融合信息通信工程、信息安全和计算机科学与技术专业学科知识,旨在培养信息时代的优秀网络安全执法人员。信息论作为现代通信的理论基础,涵盖信源编码、信道传输和密码学等多学科理论。作为通信类专业的主干课程,信息论同样应该成为网络安全与执法专业的重要课程之一。在网络安全与执法专业开设信息论课程,通过教授基础信息理论、结合当前技术发展前沿,讲授信息网络通信理论体系,对完善网络安全与执法专业建设具有重要意义。文章论述信息论课程对网络安全与执法专业建设的重要性并得出结论：信息论课程建设是网络安全与执法专业建设的重要工作。因此,在网络安全与执法专业建设中,应当开始相应信息论课程。     

基于信任网络的C2C电子商务信任算法

C2C电子商务交易具有匿名性、随机性、动态性的特点,交易双方仅通过虚拟网络交换信息,缺乏基本的信任基础,交易存在较大的风险.构造科学的信任计算模型、客观度量卖家的可信度、辅助买家(消费者)做出正确的购买决策,是降低交易风险的有效手段之一.为此,从买家的角度出发,详细讨论了信任网络的基本概念及其相关属性,并以信任的时间敏感性、不对称性、可传递性和可选择性为基础,建立了C2C电子商务环境下的动态信任算法(C2C dynamic trust algorithm,简称CDTA).该算法首先通过买家自身的交易经验计算买家对卖家的直接信任度,然后计算来自信任网络中买家的朋友对卖家的推荐信任度,最后通过信任调节因子集成直接信任度和推荐信任度来获得买家对卖家的信任度.仿真实验分析结果表明:一方面,该算法考虑了交易的多属性及其相关性,信任评价的粒度更加细化,使得信任计算的结果更加客观;另一方面,评价相似度可以很好地筛选出符合买家“个性”的推荐节点,使推荐信任度更准确,可以进一步抑制恶意节点对信任算法的影响.     

基于感知源的数据驱动信任评测模型

为解决物联网数据源头的可靠问题,构建一种基于感知源的数据驱动信任评测模型.模型以监测模块为评测单元,由中继节点完成其所在监测模块内感知节点的信任评测,通过感知节点自身数据之间的关系实现直接信任的计算,利用监测模块内各邻居节点之间关系实现推荐信任的计算,再结合历史信任,输出感知节点的综合信任.同时与模型预设的可疑阈值和异常阈值进行对比,更新历史信任和信任列表,实现感知节点的异常检测,利用预警检测误差和失信检测误差对模型的检测效果进行评价,统计结果表明模型能够保持较低的平均误差.将信任机制引入到数据融合过程,用综合信任作为加权因子,从而提高了数据融合的准确度.最后,通过实验仿真对信任评测模型进行评价,结果表明引入信任评测模型后延长了节点开始死亡的时间,随着节点的更新迭代,失信节点越来越少,在一定程度上提高了节点的存活率,延长了网络的生命周期.     

Hierarchical dispatch using two-stage optimisation for electricity markets in smart grid

This paper proposes a hierarchical dispatch method for the electricity markets consisting of wholesale markets and retail markets. In the wholesale markets, the generators and the retailers decide the generation and the purchase according to the market-clearing price. In the retail markets, the retailers set the retail price to adjust the electricity consumption of the consumers. Due to the two-way communications in smart grid, the retailers can decide the electricity purchase from the wholesale markets based on the information on electricity usage of consumers in the retail markets. We establish the hierarchical dispatch model for the wholesale markets and the retail markets and develop distributed algorithms to search for the optimal generation, purchase, and consumption. Numerical results show the balance between the supply and demand, the profits of the retailers, and the convergence of the distributed algorithms.     

一种新型高旋弹体滚转角测量系统

利用常规方法直接测量高速旋转弹体的滚转角测量精度较低,针对该问题,提出了一种基于微惯性测量组合(MIMU)与光电编码器综合测试的弹体滚转角测量系统.通过MIMU实时测量半捷联惯性测量平台内筒的姿态信息,利用光电编码器测量半捷联惯性测量平台内筒与弹体之间的相对转角,采用FPGA作为主控芯片来实现弹载环境下光电编码器输出脉冲的抗抖动干扰设计,结合MIMU数据,实现了弹体滚转角的准确测量.经试验验证,该系统能够完整有效地记录弹体滚转角信息,测量精度稳定在3°以内.