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.     

Evaluation method of the gait motion based on self-organizing map using the gravity center fluctuation on the sole

This paper describes the evaluation method of the gait motion in walk rehabilitation. We assume that the evaluation consists of the classification of the measured data and the prediction of the feature of the gait motion. The method may enable a doctor and a physical therapist to recognize the condition of the patients more easily, and increase the motivation of patient further for rehabilitation. However, it is difficult to divide the gait motion into discrete categories, since the gait motion continuously changes and does not have the clear boundaries. Therefore, the self-organizing map (SOM) that is able to arrange the continuous data on the almost continuous map is employed in order to classify them. And, the feature of the gait motion is predicted by the classification. In this study, we adopt the gravity-center fluctuation (GCF) on the sole as the measured data. First, it is shown that the pattern of the GCF that is obtained by our developed measurement system includes the feature of the gait motion. Secondly, the relation between the pattern of the GCF and the feature of the gait motion that the doctor and the physical therapist evaluate by visual inspection is considered using the SOM. Next, we describe the prediction of following features measured by numerical values: the length of stride, the velocity of walk and the difference of steps that are important for the doctor and the physical therapist to make a diagnosis of the condition of the gait motion in walk rehabilitation. Finally, it is investigated that the position of a new test data that is arranged on the map accords with the prediction. As a consequence, we confirm that the method using the SOM is often useful to classify and predict the condition of the patient.     

电话自动监控瓦斯报警器研究与开发

新型电话自动监控瓦斯报警器是在固定式瓦斯报警器的基础上开发研制出来的。它具有在瓦斯浓度超限时进行声光报警功能，同时还具有电话自动监控功能。使煤矿安全官员对基层煤矿负责人、安监员、矿主等人员的失职行为进行监管，避免人为因素造成的瓦斯爆炸事故发生。该文介绍了新型电话自动监控瓦斯报警器的组成结构，对其工作原理进行了详细的分析。     

Maximum probable life time analysis under the required time-dependent failure probability constraint and its meta-model estimation

Time-dependent reliability (failure probability) aims at measuring the probability of the normal (abnormal) operation for structure/mechanism within the given time interval. To analyze the maximum probable life time under a required time-dependent failure probability (TDFP) constraint, an inverse process corresponding to the time-dependent reliability is proposed by taking the randomness of the input variables into consideration. The proposed inverse process employs the monotonicity between the TDFP and the upper boundary of the given time interval which reflects the life time, and an adaptive single-loop sampling meta-model for the time-dependent limit state function is presented to estimate the TDFP at the given time interval flexibly. Since the TDFP is generally monotonic to the upper boundary of the given time interval, thus by adjusting the probable upper and lower boundaries of the time interval in which the corresponding TDFPs include the required TDFP constraint, the proposed approach can always search the maximum probable life time at the required TDFP by the dichotomy. By introducing the time variable as an input which is the same level as the input random variables and constructing the adaptive single-loop sampling meta-model for the time-dependent limit state function in a longer time interval with the TDFP bigger than the required TDFP, the TDFP in any subintervals of the time interval involved in the constructed meta-model can be estimated as a byproduct of the constructed meta-model without any additional actual limit state evaluations. Then the efficiency for analyzing the maximum probable life time is improved by the dichotomy and the unified meta-model of the time-dependent limit state function. Two examples are employed to illustrate the accuracy and the efficiency of the proposed approach.     

一种保护青少年脊柱健康的减重背包设计与研究

目前市面上的青少年背包主要通过肩部来进行载荷,而忽略了腰部载荷的作用。背包长期负重 不当会影响脊柱生长。为了平衡肩部、腰部和臀部的载荷,设计一种通过臀部带和弹性杆结构改变重力传递方 式的减重背包。首先对人体背包进行生物力学分析,提出设计方案;然后借助 ADAMS 对传统背包与减重背包 在平地、上坡、下坡 3 种路况下进行人体肩部、腰部和臀部载荷的动力学仿真,并利用 MATLAB 对 2 种背包 的肩部、腰部和臀部的力矩进行分析。结果表明减重背包减轻了肩部 6.1%和腰部 5.4%力矩;减重背包肩部力 矩与腰臀部合力矩的比值是 4.17,而传统背包的比值是 6.58。减重背包减少了肩部和腰部的载荷,同时发现肩 部力矩与腰、臀部合力矩的比值越小,转移到臀部的力矩越大,背包的平衡性越好,表明了减重背包优于传统 背包。     

基于SMS的旅游咨询信息系统的设计与实现

通过介绍国内旅游业的背景引出旅游咨询信息系统，基于SMS模式阐述系统设计原则。以云南省丽江市的旅游现状为列，说明系统总体设计、网关逻辑结构设计及系统模块设计。在系统开发过程中，主要应用数据挖掘技术和短信网关技术。     

内置转子强化管抗污垢性能数值模拟

采用数值模拟方法研究光管及内置螺旋叶片转子强化管的抗污垢性能,得到换热管颗粒污垢体积分数分布,研究流体流速对强化管抗污垢性能的影响.结果表明:与在相同条件下的光管相比,强化管管内沉积的污垢明显减少;由于颗粒自身重力影响,底部沉积的污垢体积分数高于换热管顶部;随着流体流速的增加,强化管底部的颗粒污垢体积分数有所减小,顶部的颗粒污垢体积分数有所增大,并且强化管的颗粒污垢体积分数不断趋近于入口处设置的颗粒污垢体积分数.     

On the execution of the secondary task of redundant manipulators

In the paper, we compare two different approaches to accelerate the execution of the secondary task of redundant manipulators when a standard task-priority control scheme is utilised. In the task-priority approach, the vector of the desired increment in the secondary task space is projected in the null space of the primary task. This projection may distort the projected vector and the secondary task may not adequately be executed. One approach to avoid the difficulty is to optimise the weight of the pseudoinverse matrix. The problem is that the change of the weight simultaneously influences the execution of the primary task. In the second approach, we directly optimise the null space projection matrix by minimising the difference between the projected and the desired vector of the secondary task increment. In the latter approach, we have the freedom to choose the weight of the pseudoinverse matrix.     

具有输入增量分辨率的多变量预测控制策略

工业现场中不可避免地会出现噪声和不可测扰动等不利因素,造成控制器的控制变量波动,不利于加以控制和实现设备的长期使用.同时,对于现场中需要控制动作较大的阀门,在面对较小的控制动作时,无法准确跟踪控制.针对上述两种问题,结合当前工业控制目标为设定点和区间混合类型,引入动态增量阈值和静态增量阈值作为输入分辨率.当约束多变量系统通过QP规划算法求解出最优控制律后,对于动态阈值,若控制律超过阈值,则将此控制律添加到输入上,反之则忽视此控制律;对于静态阈值,若控制律超过阈值,则将此控制律添加到输入上,反之将控制律累加,直到累加值超出阈值后采用累加的控制律.仿真结果验证了所提策略能够有效保证控制变量的稳定,解决大控制动作阀门的跟踪控制问题.     

基于导叶位置数据分析的刘家峡水电厂导叶立面间隙调整方法改进

在水电厂水轮机检修过程中,水轮机导叶立面间隙调整是一项重要而精细的工作,其主要目的是将水轮机24片矩形导叶两两相靠,调整为一个密不透水的圆筒状。传统导叶立面间隙调整方法虽然能满足调整完成后两两导叶立面间隙为零的技术要求,但因缺乏精确的反馈量和监视量,调整过程费时费力,同时可能造成导叶之间压紧程度不一的现象,对后续调整产生一定影响。通过采集机组检修前导水机构各项数据,导入三维建模软件进行精确建模,在模型中进行多项初始条件下进行水轮机导叶立面间隙模拟调整,并与检修前数据比较,得出该检修状态下导叶的标准位置。在现场实际调整过程中,根据不同水轮机导叶立面间隙分布情况、机组检修级别,结合导叶标准位置提出差异化水轮机导叶立面间隙调整策略,极大提高了水轮机导叶立面间隙[3]调整效率和精度,保证了机组运行安全性。     

基于机器视觉的口岸车道闸机故障远程检测方法

针对口岸车道闸机运行时间的延长，噪声信号会逐渐掩盖真实信号，从而造成信号混合行为的出现，导致口岸车道闸机抬杆机械动作故障检测精度较低的问题，提出基于机器视觉的口岸车道闸机故障远程检测方法。利用CCD传感器，最大化扫描复原口岸车道闸机抬杆机械动作故障信号，并对关键应用镜头设备进行选型处理，完成机器视觉检测的硬件结构设计。输入口岸车道闸机的远程故障图像，按照图像配准原则，得到具体的直方图修正处理结果，拼接与预处理远程故障图像。在此基础上，分析口岸车道闸机抬杆机械动作实际故障特征，通过信号参量非均匀采样的方式，对检测盲源进行分离，再联合故障信号输出信噪比数值，实现口岸车道闸机抬杆机械动作故障远程检测。实验结果表明，基于机器视觉的检测方法的口岸车道闸机抬杆机械动作故障检测准确率可达90.4%，IMF分量值较大，可有效抑制噪声信号对真实信号的覆盖影响，提高口岸车道闸机抬杆机械动作故障检测精度