Maintaining range trees in secondary memory

Summary When storing and maintaining a data structure in secondary memory it is important to partition it into parts such that each query and update passes through a small number of parts. In this way the number of disk accesses and the amount of data transport required can be kept low. In Part I of this paper a number of partition schemes were given for partitioning range trees. In this paper we study lower bounds for partitions. In this way we prove that many of the partitions given in Part I are optimal.Supported by the Netherlands Organization for Scientific Research (NWO)     

热固耦合作用下9F级燃气轮机碰摩转子的振动分析

针对燃气轮机转子碰摩故障的振动特性,建立了包含温度因素的9F级燃气轮机碰摩转子的动力学方程.建立9F级燃气轮机转子的结构模型,对燃气轮机转子进行瞬态热应力分析,同时考虑到碰摩力的影响.研究了9F燃气轮机转子从正常运行到停机72小时不同时刻的温度场及热应力.分析结果表明：采用有限元分析方法对9F级燃气轮机碰摩转子的振动特性研究是可行的,同时考虑到转子热固耦合作用的影响,对于更准确地研究转子的碰摩故障的振动特性具有重要意义.     

基于二次参数化技术的风电机组序列化建模

针对常规建模方法在庞大复杂风电机组应用上的不足,在建立单台风电机 组全参数化模型的基础上,以风电机组序列整体为研究对象,根据同序列不同功率机组之间 各零部件设计参数变化规律,研究应用二次参数化技术和参数序列化方法实现了高效的风电 机组模型建立与管理;并结合三维模型参数驱动技术,研发了风电机组序列建模系统,可有 效减少建模和造型工作量、降低设计失误率、提高设计效率,验证了该建模方法的正确性与 合理性。     

Calculation of medium-frequency vibrations over a wide frequency range

An enhancement of the “variational theory of complex rays” (VTCR) is being developed in order to calculate the vibrations of slightly damped elastic structures in the medium-frequency range. Here, the emphasis is put on the extension of this theory to the analysis over a wide frequency range. The solution is sought in the form of an original decomposition: the mean value and its complementary part over the frequency range. Numerical examples show the capability of the VTCR to predict the vibrational response of a structure in a frequency range.     

Modeling and simulation of wind turbine Savonius rotors using artificial neural networks for estimation of the power ratio and torque

The power factor and torque of wind turbines are predicted using artificial neural networks (ANNs) based on experimental data which have been collected for seven prototype vertical Savonius rotors tested in a wind tunnel. In this research, the rotors with different configurations were located in the wind tunnel and the tests were repeated 4–6 times in order to reduce errors. Since the Reynolds number has a negligible effect on power ratio, therefore tip speed ratio (TSR) is the main input parameter to be predicted in neural network. Also, the rotor’s power factor and torque were simulated for different tip speed ratios and different blade angles. The simulated results show a strong capability for providing reasonable predictions and estimations of the maximum power of rotors and maximizing the efficiency of Savonius turbines. According to artificial neural nets simulations and the experimental results, increasing tip speed ratio leads to a higher power ratio and torque. For all the tested rotors, a maximum and minimum amount of torque has happened at angle of 60^o and 120^o, respectively.     

一维弹道修正弹射程扩展量计算及计算机仿真

为提高炮弹密集度,一维弹道修正弹采用增阻方式对射程进行修正,在射击距离的基础上增加射程扩展量确定瞄准射程,计算射击诸元,确定最佳射程扩展量对提高密集度具有重要意义。建立了射程扩展量计算模型,提出了当可靠性较低时对射程扩展量进行系数修正的观点,进行了仿真计算,得出了最多平均命中弹数与目标纵深、可靠度和修正系数的关系。研究成果可以为一维弹道修正弹射击诸元的计算提供参考。     

霍尔传感器在离心机转子识别中的应用

介绍了运用霍尔传感器A3144来实现离心机的转子编码识别。介绍了转子编码识别原理,并给出了硬件电路图和最终的测试结果。该技术只利用4只霍尔传感器A3144和4片磁钢,就可对16种转子进行识别,简单易行,安全可靠。     

Torsional vibrations of rotors with transverse surface cracks

The torsional vibrations of a rotor with a transverse crack are investigated. The crack is modelled by way of a local flexibility matrix which is calculated analytically and measured experimentally. Good agreement between the two methods is obtained. The free vibration problem is solved and the three first eigenvalues are plotted versus the crack location and depth. The finite element method is used for the solution of any shaft system with a crack, using a modified stiffness matrix for the cracked element.     

基于DSP的悬浮转子的控制

为满足陀螺转子自动控制的需求,设计了以DSP微处理器中的TMS320F2812为硬件核心的悬浮转子自动控制系统,完成了系统的自动控制及状态监测,与上位机的数据与控制信号通讯。采用CPLD作为扩展接口实现了DSP与数据输入输出等外围设备之间的联接,完成了对转子信号及运行参数的采集控制与存储,多串行口的扩展等功能。与传统转子控制系统相比,提高了系统的安全性和通信的高效性与抗干扰性能,实现了转子控制的自动化、智能化,为与其他系统的整体运作提供了可能性。     

Optimization of cylindrical composite flywheel rotors for energy storage

The use of flywheel rotors for energy storage presents several advantages, including fast response time, high efficiency and long cycle lifetime. Also, the fact that the technology poses few environmental risks makes it an attractive solution for energy storage. However, widespread application of tailorable circumferentially wound composite flywheel rotors is hampered by the relatively low energy density that these rotors have been able to achieve. This contributes to high capital cost, which currently makes the flywheels prohibitively expensive for many applications. With the materials that are currently available, there seems to be ample room for improvement in the energy density achieved by composite flywheel rotors. To this aim, some of the design methods that have previously been proposed are herein studied, and our findings suggest that the manner in which the optimization problem is formulated is crucial to the design of high energy density flywheels. A new problem formulation is proposed, which is shown to lead to notable improvements in certain cases. By making use of the proposed problem formulation, flywheel rotors can be designed to consistently achieve high energy density relative to the materials that are made available. This can contribute towards lowering the cost of flywheel systems, and making flywheel energy storage viable for a wider range of applications.     

Modeling and simulation of quadrotor UAV with tilting rotors

Quadrotors have recently been drawing greater research and commercial attention to the point that they have become one of the most popular types of unmanned aerial vehicles. Their applications vary from entertainment to transportation, commercial and even military applications. In this paper, a novel quadrotor design is proposed. The design decouples all motions by allowing each rotor to tilt in two directions about the quadrotor fixed frame. This modification improves the stability and safety of the quadrotor and gives it more manoeuvrability and robustness. The mathematical model of the proposed system is carried out using Newton-Euler technique. Several flight scenarios are also simulated under a simple PID controller to illustrate the superiority over conventional quadrotor designs.     

Cost optimization of hybrid composite flywheel rotors for energy storage

A novel approach to composite flywheel rotor design is proposed. Flywheel development has been dominated by mobile applications where minimizing mass is critical. This technology is also attractive for various industrial applications. For these stationary applications, the design is considerably cost-driven. Hence, the energy-per-cost ratio was used as the objective function. Based on an analytical approach for calculating stresses in multi-rim hybrid composite rotors, the nonlinear optimization problem was solved using a multi-strategy optimization scheme that combines an evolutionary algorithm with a nonlinear interior-point method. The problem was solved for a sample rotor with varying cost ratio of the rim materials. Instead of an optimal solution per cost ratio, only four optimal designs were obtained with a sharp transition between designs at specific cost ratios. This sharp transition is explained by the intricate interplay that exists between the objective function and the nonlinear constraints imposed by the applied failure criteria.     

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.     

Strong stabilisation of a wind turbine tower model in the plane of the turbine blades

We investigate the strong stabilisation of a wind turbine tower model in the plane of the turbine blades, which comprises a nonuniform NASA Spacecraft Control Laboratory Experiment (SCOLE) system and a two-mass drive-train model (with gearbox). The control input is the torque created by the electrical generator. Using a strong stabilisation theorem for a class of impedance passive linear systems with bounded control and observation operators, we show that the wind turbine tower model can be strongly stabilised. The control is by static output feedback from the angular velocities of the nacelle and the generator rotor.     

Numerical solution of creep problems

Numerical techniques which have been previously used in the solution of creep problems are reviewed. The different techniques are used to obtain solutions for the creep deformation and rupture of a steadily loaded three-bar structure. The results of numerical calculations are presented, and the most appropriate techniques are identified for the solution of creep problems in engineering structures.     

Synchronization of the four identical unbalanced rotors in a vibrating system of plane motion

A new mechanism is proposed to implement the synchronization of the four unbalanced rotors in a vibrating system, which consists of a main rigid frame (MRF) and two accessorial rigid frames (ARF). An analytical approach is developed to study the coupling dynamic characteristics of the four unbalanced rotors, which converts the problem of synchronization of the four unbalanced rotors into the existence and the stability of zero solutions for the non-dimensional differential equations of the angular velocity ...     

Voronoi-based range and continuous range query processing in mobile databases

With the wide availability of mobile devices (smart phones, iPhones, etc.), mobile location-based queries are increasingly in demand. One of the most frequent queries is range search which returns objects of interest within a pre-defined area. Most of the existing methods are based on the road network expansion method – expanding all nodes (intersections and objects) and computing the distance of each node to the query point. Since road networks are extremely complex, node expansion approaches are inefficient. In this paper, we propose a method, Voronoi Range Search (VRS) based on the Voronoi diagram, to process range search queries efficiently and accurately by partitioning the road networks to some special polygons. Then we further propose Voronoi Continuous Range (VCR) to satisfy the requirement for continuous range search queries (moving queries) based on VRS. Our empirical experiments show that VRS and VCR surpass all their rivals for both static and moving queries.     

Design and fabrication of microchannel test rig for ultra-micro wave rotors

Wave rotor technology has shown a significant potential for performance improvement of thermodynamic cycles. The wave rotor is an unsteady flow machine that utilizes shock waves to transfer energy from a high energy fluid to a low energy fluid, increasing both the temperature and the pressure of the low energy fluid. At microscale, shock wave compression was shown analytically to have higher efficiency than compression by mechanical devices such as impellers or pistons. A second step in proving this superiority of shock wave compression is to design and test a microscale shock tube, which is a perfect model for one of the wave rotor channels. Last step is fabrication of a full wave rotor manufactured using traditional MEMS technology. The paper summarizes the conclusions of the analytical study, describes the details of fabrication of micro shock tube test rig and the design of the ultra-micro wave rotor (UμWR). Florin Iancu is currently employed by Johnson Controls Inc., in York, PA, USA. Research was conducted while he was a Ph.D. candidate at Michigan State University.     

刚性转子动平衡现场检测系统的硬件设计

基于传感器.计算机的设计思想,通过系统硬件的选型和信号处理电路的设计,组成以PCL-818L数据采集卡为核心的刚性转子动平衡现场检测系统.检测系统软件使用Visual C 编写,可在Win32环境下运行.与传统检测方法相比较,该系统不仅人机交互性强、操作简便,而且具有工作效率高、生产成本低等优势,比较适用于单件转子拆装比较困难的场合.