Recording and analysis of fluctuating signals using a microcomputer

This paper describes the application of both the Acorn Atom microcomputer and the Apple II microcomputer to the recording and analysis of the fluctuating signals associated with turbulent flow. Sampling rates up to 20 kHz are achieved using fast analogue-to-digital converters and machine code programs, while sample periods approaching one second can be employed by using all the available memory of the 48K Apple II computer. Subsequent digital analysis of the data provides accurate and rapid evaluation of the mean and rms values, the autocorrelation function and, for transitional flow, the intermittency factor.In order to check the accuracy of these systems and the DISA Amplitude Probability Analysis System for the measurement of intermittency, an Intermittency Simulator was developed. This unit included an analogue gate controlled by two decade counters, so that precise 1% variations could be obtained in the intermittency of transmission of the adjustable sinusoidal waveform from a signal generator. The calibrations indicated that the computer systems were well within 1% accurate in evaluating the intermittency factor, while the Amplitude Probability Analysis System could be in error by 4% at the higher values of intermittency factor.Fast analogue-to-digital converters used with microcomputers can therefore provide a rapid, accurate and convenient method for the capture and analysis of fluctuating signals associated with turbulent flows. The Acorn system is also being used in waterwave experiments at very much lower frequencies.     

Recording and processing of partial discharge signals

Electromagnetic-activity signals that arise in an air discharge gap under the action of an alternating voltage at a frequency of 50 Hz were studied using an omnidirectional antenna, a measuring pulse transformer, and an oscilloscope. The frequency range with the maximum signal-to-noise ratio for partial discharge signals was determined. Partial discharges that cause a breakdown in the air discharge gap and that are identical in the apparent-discharge value to partial discharges in the polymer insulation were simulated using a system of surface-needle electrodes. Corona discharges were modeled. Amplitude-phase diagrams were constructed for distinguishing corona signals from partial-discharge signals. Model discharges made it possible to investigate the specific features of a polymer-insulation breakdown.     

斜摆头五坐标数控加工机床的后置处理算法研究

基于DMU80P五轴联动加工中心的结构特点,针对第五旋转轴的旋转中心线和三直线轴不重合的特殊回转轴机构,分析该结构类型机床的联动加工方式及角度坐标变换规律,依据机床采用的HEIDENHAIN系统设计了该机床的后置处理算法.加工实验表明,该后置处理方法能满足工程使用要求.     

磁性液体倾斜角传感器的有限元耦合分析

根据一种差动式变压器结构的磁性液体倾斜角传感器工作原理,推导出传感器输出电压与灵敏度公式,并利用ANSYS软件对这种结构的传感器进行电磁-电路的耦合场分析,通过对数值模拟结果进行深入分析以便能为传感器的设计提供指导,并将模拟结果与已公开发表的实验数据进行对比.得出当磁性液体倾斜角传感器的结构参数确定后,传感器的输出电压与转动角度成线性正比关系;且传感器的灵敏度与激励电压的振幅、磁性液体相对磁导率及激励电压频率成正比,但激励电压频率超过一定范围后,传感器灵敏度增加值会逐渐减小,建议激励电压频率最好不超过1.5 kHz.     

The development of Fresnel contrast analysis, and the interpretation of mean inner potential profiles at interfaces

This paper provides a summary of recent published and unpublished research on the development of Fresnel contrast analysis, a transmission electron microscopy technique for measuring the mean inner potential profile across an interface or a narrow layer. An algorithm for finding a best-fitting potential profile is described, energy-filtered experimental data are analyzed and contributions to Fresnel contrast from surface grooves and space charge are assessed. Many of the conclusions drawn are equally relevant for the interpretation of phases measured using off-axis electron holography.     

小型机载云台结构设计和分析

针对小型无人机的拍摄需求问题,设计了能实现两自由度转动的小型机载云台结构。首先,在CATIA中建立了结构的三维实体模型;接着,在ANSYS中建立了其有限元模型,对结构的关键零部件进行了静力学分析,及对整体结构进行了模态分析。研究结果表明,设计的结构满足使用功能性和可靠性要求,并为进一步的结构优化和隔振技术研究提供了基础。     

Recording of chromosome banding with the Vickers M85/M86 scanning microdensitometer

An electronic interface is described which permits the Vickers M85/M86 microdensitometer to be used with a chart recorder to plot linear distance along a chromosome against (1) the absorbance, (2) the product of the chromosome width and the mean absorbance transverse to the long axis of the chromosome, or (3) the integrated absorbance accumulating during a two-dimensional scan of the specimen.     

穿刺针尖光纤力传感信号的小波变换分析

经皮软组织穿刺过程中,穿刺针尖会历经不同材料特性的器官组织,受到复杂变化的作用力。为了测量针尖处的作用力并鉴定穿刺路径上不同层次的软组织,研制了一种光纤力传感器,并进行了力信号分析。首先,基于法-珀干涉介绍了光纤力传感器的测量原理、光链路设计、及其与针的集成和标定方法。在穿刺力信号分析的基础上,提出利用Mallat算法对力信号进行小波变换,提取信号的特征模式,界定软组织的各层边界。最后,在猪的肝脏和肋条组织样本上进行了针穿刺实验验证。结果显示:光纤力传感器的可测力为0至3.20N,测量精度可达0.01N。得到的穿刺试验结果表明Mallat算法能够有效地区分软组织的类型。研制的光纤传感器满足穿刺力的测量范围、精度和可靠性等要求,所提出的小波变换算法可用于软组织边界的界定,有望用于机器人穿刺控制。     

五轴五联动加工技术应用的分析与研究

五轴五联动加工中心，采用CAD／CAM技术予以设计、编程和数字化加工，在机械设计制造领域显示其强大的威力和发展前景，这里就该领域应用五轴联动加工中心加工工艺及实现过程加以分析论述，以利于数控化五轴五联动技术的广泛应用。     

Correlated ion analysis and the interpretation of atom probe mass spectra

Several techniques are presented for extracting information from atom probe mass spectra by investigating correlations within multiple-ion detector events. Analyses of this kind can provide insights into the origins of noise, the shape of mass peaks, or unexpected anomalies within the spectrum. Data can often be recovered from within the spectrum noise by considering the time-of-flight differences between ions within a multiple event. Correlated ion detection, particularly when associated with shifts in ion energies, may be used to probe the phenomenon of molecular ion dissociation, including the questions of data loss due to ion pile-up or the generation of neutrals in the dissociation process.     

Simulation and analysis of vibration signals generated by rolling element bearing with defects

Dynamic loading of a rolling element bearing structure is modeled by a computer program developed in Visual Basic programming language. The vibration response of the structure to the dynamic loading is obtained using a standard finite element package I-DEAS. A force model is proposed to model the localized rolling element bearing defects. Time and frequency domain analyses are performed for diagnostics of rolling element bearing structures. Statistical properties of the vibration signals for healthy and defected structures are compared. The envelope (HFRT) method is employed in the frequency domain analysis. The effect of the rotational speed on the diagnostics of rolling element bearing defects is investigated. An optimum sensor location on the structure is sought. Effect of the structure geometry on the monitoring techniques is studied. An optimum monitoring method can be employed by analyzing the rolling element bearing structure following the procedure proposed in this study. The present commercial computer aided engineering packages can be used in special engineering applications such as condition monitoring of rolling element bearings.     

采用ADAMS的五自由度抛光机械手仿真分析

用机器人运动学的知识求出机械手的雅可比矩阵,用UG软件对五自由度抛光机械手进行三维实体建模,通过UG和ADAMS接口直接导入到ADAMS软件中,在此基础上进行五自由度抛光机械手的运动仿真分析,得到五自由度抛光机械手手腕关节的位移变化曲线,为机械手设计的改进和完善提供依据。     

Three-dimensional analysis of high voltage electron microscope tilt images: Methods and problems

A quantification program for obtaining three-dimensional image information from high voltage electron microscope stereo pair pictures was developed for a Luzex 5000 image analyzer. A zero tilt image was used as a reference. A real-time image processor system was introduced to improve the image quality and to reduce the beam damage of the specimens. Some modifications of the optical system and the specimen stage were made to improve the accuracy and efficiency of stereoscopy. The accuracy of the measurement was considerably improved by these modifications. Some basic problems and limitations of the method are discussed.     

Generation of pure phase and amplitude-modulated signals at microwave frequencies

This work describes various techniques for generation of pure phase and amplitude-modulated signals at microwave frequencies. It presents experimental study of a microwave phase modulator with spurious amplitude modulation of the order of 1 ppm.     

Design and analysis of tilt integral derivative controller with filter for load frequency control of multi-area interconnected power systems

In this paper, a novel Tilt Integral Derivative controller with Filter (TIDF) is proposed for Load Frequency Control (LFC) of multi-area power systems. Initially, a two-area power system is considered and the parameters of the TIDF controller are optimized using Differential Evolution (DE) algorithm employing an Integral of Time multiplied Absolute Error (ITAE) criterion. The superiority of the proposed approach is demonstrated by comparing the results with some recently published heuristic approaches such as Firefly Algorithm (FA), Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) optimized PID controllers for the same interconnected power system. Investigations reveal that proposed TIDF controllers provide better dynamic response compared to PID controller in terms of minimum undershoots and settling times of frequency as well as tie-line power deviations following a disturbance. The proposed approach is also extended to two widely used three area test systems considering nonlinearities such as Generation Rate Constraint (GRC) and Governor Dead Band (GDB). To improve the performance of the system, a Thyristor Controlled Series Compensator (TCSC) is also considered and the performance of TIDF controller in presence of TCSC is investigated. It is observed that system performance improves with the inclusion of TCSC. Finally, sensitivity analysis is carried out to test the robustness of the proposed controller by varying the system parameters, operating condition and load pattern. It is observed that the proposed controllers are robust and perform satisfactorily with variations in operating condition, system parameters and load pattern.     

Theoretical analysis of the dynamic stiffness of conical hydrostatic thrust bearings under tilt,eccentricity and rotation

A theoretical study of the dynamic stiffness characteristics of capillary compensated annular recess conical hydrostatic thrust bearings under conditions of tilt, eccentricity and rotation is reported. The influences of aspect ratios, cone angles and resistance ratios on the dynamic stiffness are discussed.     

一种带预置存储功能的防爆电动云台镜头步进串行控制器设计

介绍了基于89S52单片机的云台镜头控制器的主要功能、结构、原理和控制协议,并给出了一种采用步进电机来实现云台的转动,及带预置存储功能的实现方法.     

磁记忆信号定量分析的电子交换模型及性能

磁记忆法可以有效地判断铁磁性金属构件的应力损伤区域。但是,磁记忆自发漏磁信号形成机理和影响因素复杂,不同应力集中程度的磁记忆信号特征很难得到定量化分析,严重影响了该项技术的实际应用。根据电子自旋理论,建立了s-d轨道电子交换模型,计算了晶体屈服前后电子自旋态密度、原子磁矩、晶格尺寸的变化规律,进而定量分析磁记忆信号与应力集中程度的对应关系。研究结果表明,磁记忆信号与应力成一一对应的线性变化关系。晶体在屈服前,磁记忆效应主要由d轨道电子自旋作用决定,磁记忆信号与应力的对应关系具有很好的可重复性;晶体发生屈服后,电子自旋交换作用增强,d轨道电子自旋作用减弱,s轨道电子自旋作用增强,磁记忆信号变化幅度减小,磁记忆效应整体减弱。     

氯气离心式压缩机振动信号监测与分析

针对国内氯碱企业关键设备氯气离心式压缩机的运行时振动状况，利用频谱检测装置即时采集振动信号进行监测与分析。     

非平稳信号巢式半马尔可夫探测过程描述和分析

本文探讨由下垫面和晴朗天空散射引起的以时间为标示过程的可能性,以及对流层的巢式半马尔可夫过程折射率的季节性变化。各阶段状态中的过程都可以用局部高斯模型描述。本文提出了描述海面反射统计数据的可能性,并且首次用克拉夫钦科有限函数给出了折射率。