隧道微差爆破的延时计算及电子雷管减振应用

为实现复杂环境下隧道爆破减振,根据微差爆破延时计算理论,综合考虑围岩的物理力学参数及隧道爆破施工参数,提出采用电子雷管进行微差爆破的延时计算方法。研究起爆药量对爆破地震波振速和主频的影响,并将研究成果应用到成渝客专新红岩隧道爆破工程中。结果表明:1)微差爆破的合理延时需要考虑岩石破碎及沿裂缝扩展到掌子面并抛掷足够距离的时间; 2)采用微差爆破延时计算方法,可合理设置电子雷管延时,实现单孔间隔微差爆破,有效降低峰值振速、提高振动主频; 3)在新红岩隧道爆破工程中,采用电子雷管爆破相比毫秒非电雷管爆破振速减小60%以上,证明电子雷管微差爆破延时计算方法的准确性和合理性。

无线供能边缘计算时延优化卸载策略研究综述

无线供能及移动边缘计算技术的整合为下一代无线通信网的实现提供了技术支持。然而,用户数量的激增将对诸如系统响应时效性和超低延时等需求的实现提出了新的挑战。因此,如何设计迭代次数少、收敛速度快、灵活性强的实时计算卸载策略成了研究的新热点。文章梳理了无线供能移动边缘计算(Wireless Powered Mobile Edge Computing,WP-MEC)系统在实现超低延时需求上面临的问题与挑战;总结了WP-MEC系统的网络模型及其计算卸载策略的研究概况;详细阐述了4种不同接入方式下的WP-MEC系统的计算卸载策略研究现状;对比分析了各类传统的数值优化方法及深度强化学习优化方法在实时计算卸载决策方面的优劣;对低复杂度高效计算卸载策略的发展进行总结与展望,提出了延时最小化计算卸载策略的3个关键研究方向。

开环自调匀整控制器中延时在线计算方法

本文研究了并条机开环自调匀整控制器的延时计算方法,精确延时是决定输出纱条匀整效果的关键。现有确定延时的方法主要有几何法、实验法和相关法,都是离线测量方法。本文提出了一种基于相关分析的在线延时计算算法,该算法首先建立开环自调匀整的数学模型,然后进行喂入棉条定量检测点和输出棉条定量检测点的相关分析,根据相关函数的最大值和最小值可以一次性确定系统的延时时间。仿真结果显示该算法的正确性。与现有算法相比,该算法具有准确、在线自适应及易操作等优点。

计算机的计算延时对二次型性能指标的影响

本文针对具有计算延时的计算机控制系统,首先求出离散的闭环状态方程,然后将指标函数及其导数化为闭环状态的二次型函数,最后通过求解李雅普诺夫方程解出它们,从而可分析计算延时对系统性能的影响。

基于SMITH预估控制的计算延时补偿控制算法

基于对Ｓｍｉｔｈ控制结构的改造，提出了计算延时补偿的Ｓｍｉｔｈ预估控制算法；指出了在模型失配时Ｓｍｉｔｈ控制结构的缺陷，提出了提高Ｓｍｉｔｈ控制鲁棒性的新方案，并从频域对控制算法的鲁棒性给以定性分析。在ＭＡＴＬＡＢ上仿真结果表明：计算延时的Ｓｍｉｔｈ预估控制算法和提高其鲁棒性的新方案是十分有效的。

一类实时控制系统中计算延时的串联补偿研究

受ＰＩＤ控制和Ｄａｈｌｉｎｅ控制思想的启示，提出一种新的实时控制系统中计算延时的串联补偿控制算法。其补偿环节只与计算延时和对象的延时有关，而与对象的其他特性参数无关。仿真结果证明了该算法的有效性。

基于软件延时补偿的高速磁悬浮电机转子低频颤振抑制研究

针对磁悬浮电机高速时由于低频颤振导致转子失稳问题,由控制系统计算延时及对功放系统影响进行分析、建模,提出控制系统软件延时补偿算法消除控制系统计算延时,提高功放系统高频时电流跟踪能力,抑制磁悬浮电机转子高速时低频颤振,并在100 kW磁悬浮电机上进行实验验证。结果表明,通过软件延时补偿算法消除控制系统计算延时,磁悬浮电机转子低频增益可减小20 dB,转子在24000 r/min时跳动量减小36.8μm,控制精度提高63.89%。该方法不但能有效抑制磁悬浮转子高速时的低频颤振,且可提高磁悬浮电机高速时的稳定性。

基于新型权重因子校正和延时补偿的永磁同步电动机模型预测转矩控制

为解决永磁同步电动机(Permanent magnet synchronous motor,PMSM)模型预测直接转矩控制(Model predictive direct torque control,MPC-DTC)权重因子和计算延时问题,提出了新型权重因子校正和延时补偿策略,改善PMSM控制性能,完善模型预测转矩控制理论方法。为校核代价函数中的磁链和转矩权重因子,分析了权重因子的本质,利用标准化算法将磁链和转矩转换至无量纲、同幅值范围的变量,并根据转矩和磁链对控制电压波动的响应速度不同,理论地计算出MPC-DTC控制器中的权重因子。与传统的两步计算延时补偿策略不同,所提出的新型补偿方案基于"单周期双采样"算法,需要分三步执行:延时时间计算,补偿电流预测和补偿磁链及转矩预测。试验结果表明,提出的权重因子校核和延时补偿方法能够保证良好的系统性能。

基于时序路径的FPGA时序分析技术研究

针对于航天高可靠FPGA测试时时序分析技术的重要性,根据多年FPGA设计测试经验对时序分析技术进行深入剖析,提炼出一套切实可行的时序分析技术,阐明了时序分析的分析对象,时序分析技术的主要方法,给出了时序分析时接口信号时序计算法则,以及时序测试结果的分析准则;并把这套分析技术成功的应用到了多个航天高可靠软件的测试中,发现了很多由时序问题引起功能失效的重大问题,对其中常见的时序问题给予归类总结.

大功率并网逆变器多采样控制研究

分析了大功率光伏逆变器控制策略中开关频率和采样频率的矛盾,指出计算延时和PWM控制延时对系统性能的危害.分析并指出多采样PWM控制策略及其优势,指出该策略在PWM调制过程中的脉冲丢失和多次比较问题,给出多采样无阻尼控制解决方案.利用Matlab建立实验平台,并进行了仿真和实验验证.仿真和实验结果表明,该控制策略可有效减小PWM控制延时从而解决大功率并网逆变器低开关频率与采样频率的矛盾,提高系统的稳定域度和动态响应特性,实现无阻尼高性能控制.

Method of Time-Delay Calculating and Correcting to Control Spin-Stabilized Satellite Synchronously

The key to control Spin-Stabilized Satellites Synchronously is to determine the models for calculating and correcting of time-delay at the different situations. Based on the principle of Synchronous-Control mode, the methods of determining the models of calculating and correcting of time-delay are proposed. The methods have been proved to be effective in real satellite control engineering.

大功率并网逆变器多采样控制研究

分析了采样和开关频率在进行并网控制时的冲突,指出问题的根源是计算延时与PWM控制延时。分析了多采样PWM控制策略的优势,指出了多采样PWM调制过程中的PWM调制波与载波多次比较和垂直相交问题并给出了解决方案。利用Matlab建立实验平台,并进行了仿真和实验验证。结果表明,多采样有源阻尼PWM控制策略能有效减小计算延时和PWM控制延时,解决了在低开关频率与采样频率的矛盾;同时能有效抑制输出电流的谐振问题,提高了平台的稳定性和动态响应特性。

基于互联网大数据的自然场景的四季合成

针对传统的纹理合成与颜色迁移对自然场景的四季合成问题存在的失效问题,提出了基于大规模数据驱动的方法.首先,从互联网上获取关于场景地点的图像并且通过全局匹配性与局部一致性约束进行粗略筛选;其次,利用动态规划算法简化场景图像特征点匹配,并通过最小化约束函数确定场景参考帧以及相应场景帧;最后,将相应场景帧通过变换对齐到参考帧,并根据梯度域方法补全对齐场景从而形成场景四季序列.实验结果表明,该方法能够生成更加合理的关于场景的四季图像以及四季变化鲜明的延时摄影视频.

A Study of Acetylene Production by Methane Flaming in a Partial Oxidation Reactor

The partial oxidation of hydrocarbons is an important technical route to produce acetylene for chemical industry.The partial oxidation reactor is the key to high acetylene yields.This work is an experimental and numerical study on the use of a methane flame to produce acetylene.A lab scale partial oxidation reactor was used to produce ultra fuel-rich premixed jet flames.The axial temperature and species concentration profiles were measured for different equivalence ratios and preheating temperatures,and these were compared to numerical results from Computational Fluid Dynamics(CFD)simulations that used the Reynolds Averaged Navier-Stokes Probability Density Function(RANS-PDF)approach coupled with detailed chemical mechanisms.The Leeds 1.5,GRI 3.0 and San Diego mechanisms were used to investigate the effect of the detailed chemical mechanisms.The effects of equivalence ratio and preheating temperature on acetylene production were experimentally and numerically studied.The experimental validations indicated that the present numerical simulation provided reliable prediction on the partial oxidation of methane.Using this simulation method the optimal equivalence ratio for acetylene production was determined to be 3.6.Increasing preheating temperature improved acetylene production and shortened greatly the ignition delay time.So the increase of preheating temperature had to be limited to avoid uncontrolled ignition in the mixing chamber and the pyrolysis of methane in the preheater.

Delay-performance optimization resource scheduling in many-to-one multi-server cellular edge computing systems

To further reduce the delay in cellular edge computing systems, a new type of resource scheduling algorithm is proposed. Without assuming the knowledge of the statistics of user task arrival traffic, the analytical formulae of the communication and computing queueing delays in many-to-one multi-server cellular edge computing systems are derived by using the arriving curve and leaving curve. Based on the analytical formulae, an optimization problem of delay minimization is directly formulated, and then a novel scheduling algorithm is designed. The delay performance of the proposed algorithm is evaluated via simulation experiments. Under the considered simulation parameters, the proposed algorithm can achieve 12% less total delay, as compared to the traditional algorithms. System parameters including the weight, the amount of computing resources provided by servers, and the average user task arrival rate have impact on the percentage of delay reduction. Therefore, compared with the queue length optimization based traditional scheduling algorithms, the proposed delay optimization-based scheduling algorithm can further reduce delay.

A virtual delay queue-based backpressure scheduling for multi-cell cellular edge computing systems

To further improve delay performance in multi-cell cellular edge computing systems,a new delay-driven joint communication and computing resource BP(backpressure)scheduling algorithm is proposed.Firstly,the mathematical models of the communication delay and computing delay in multi-cell cellular edge computing systems are established and expressed as virtual delay queues.Then,based on the virtual delay models,a novel joint wireless subcarrier and virtual machine resource scheduling algorithm is proposed to stabilize the virtual delay queues in the framework of the BP scheduling principle.Finally,the delay performance of the proposed virtual queue-based BP scheduling algorithm is evaluated via simulation experiments and compared with the traditional queue length-based BP scheduling algorithm.Results show that under the considered simulation parameters,the total delay of the proposed BP scheduling algorithm is always lower than that of the traditional queue length-based BP scheduling algorithm.The percentage of the reduced total delay can be as high as 51.29%when the computing resources are heterogeneously configured.Therefore,compared with the traditional queue length-based BP scheduling algorithms,the proposed virtual delay queue-based BP scheduling algorithm can further reduce delay in multi-cell cellular edge computing systems.

Analysis of Systematic Error Influences on Accuracy of Airborne Laser Scanning Altimetry

The error sources related to the laser rangefinder, GPS and INS are analyzed in details. Several coordinates systems used in airborne laser scanning are set up, and then the basic formula of system is given. This paper emphasizes on discussing the kinematic offset correction between GPS antenna phase center and laser fired point. And kinematic time delay influence on laser footprint position, the ranging errors, positioning errors, attitude errors and integration errors of the system are also explored. Finally, the result shows that the kinematic time delay can be neglected as compared with other error sources. The accuracy of the coordinates is not only influenced by the amplitude of the error, but also controlled by the operation parameters such as flight height, scanning angle amplitude and attitude magnitude of the platform.

A reduced combustion kinetic model for the methanol-gasoline blended fuels on SI engines.

A reduced combustion kinetic model for the methanol-gasoline blended fuels for SI engines was developed. Sensitivity analysis and rate constant variation methods were used to optimize the kinetic model. Flame propagation, shock-tube and jet-stirred reactor systems were modeled in CHEMKIN. The laminar flame speed, ignition delay time and change in concentrations of species were simulated using the reduced kinetic model. The simulation results of reduced chemical mechanism agreed well with the relevant experimental data published in the literature. The experimental investigations on engine bench were also carried out. The in-cylinder pressure and exhaust emissions were obtained by using a combustion analyzer and an FTIR(Fourier transform infrared spectroscopy) spectrometer. Meanwhile, an engine in-cylinder CFD model was established in AVL FIRE and was coupled with the proposed reduced chemical mechanism to simulate the combustion process of methanol-gasoline blends. The simulated combustion process showed good agreement with the engine experimental results and the predicted emissions were found to be in accordance with the FTIR results.

Design of chirped fiber gratings for optical beamforming networks

The properties of the linear chirped fiber grating （CFG） which is used in the true time delay unit of the optical beamforming networks （OBFNs） are studied intensively through theoretical analyses and numerical calculations. It is concluded that the dispersion of the CFG is equal to 1/（3Gc）, where G is the chirp coefficient of CFG and c is the light speed. Based on this relationship, a simplified designing process of a CFG which satisfies the requirements of the O13 FN is given. The simula- tion results are coincident with the theoretical conclusions.