基于自补偿技术的时栅电流型激励信号源设计

三相激励信号源的相位对称性将直接影响时栅位移传感器性能,针对这一特点,设计了一种基于自补偿技术的电流型时栅三相激励信号源,该信号源采用直接数字频率合成技术产生三路正交的正弦信号,经相位自检和自修后,使三相激励信号源达到高稳定和高精度三相对称.实验表明该设计大大提高了时栅位移传感器的稳定性和测量精度.     

高精度标准源中低频信号源的设计与分析

针对直接数字合成的高精度信号源在低频段容易产生杂波干扰,难以适应我国公共电网频率的问题,采用锁相合成频率技术来产生范围在40 Hz~65 Hz、分辨率为0.01 Hz的低频信号作为高分辨率信号源合成的时钟频率。采用数模转换器外接基准可调电压技术产生了调节细度优于满量程的0.000 1%的可调幅值;同时利用相位计数器区分相位,设计出了频率、幅值、相位都可调的正弦波信号;建立了信号源失真度与数模转换器位数的关系和取样点数的关系,找到了影响信号源输出稳定性的原因;在理论分析和实践的基础上提出了减小信号源失真度的方法。研究结果表明,该低频信号源可以在误差接受范围内减小差频影响和公共阻抗的影响,输出40 Hz~65 Hz频率范围内标准正弦波信号的失真度小于0.03%。     

基于DDS技术的频率合成源设计

直接数字合成（DDS）是一种重要的频率合成技术，采用该技术产生的信号，具有频率转换速度快、频率分辨率高、频率稳定度高、相位变换连续、相位噪声低、集成度高、易于控制及性价比高等多种优点，可用于各种对信号频率的性能指标要求高的场合。详细介绍了高性能DDS芯片AD9858的基本原理和结构特点，以及单片机PICl8F442芯片的结构、性能特点和相关接口电路。描述了利用该芯片作为核心芯片组成频率源的全过程，包括设计原理、硬件电路和软件设计的主要流程图。     

数字式移相与频率合成的一种软件实现方法

介绍了使用软件方法,在虚拟仪器模式下,用任意波发生器产生精确相移与合成任意频率的周期信号.讨论了应用模型化测量方法,使用模型平移产生精确相移,使用波形重构技术精确合成周期信号的频率.给出了相移分辨力的实验判据、频率精确合成的条件和步骤.软件合成技术不存在漂移、稳定性等误差问题,是一种值得尝试的相位合成方法和频率合成方法.     

在DDS波形发生器中相位截尾噪声的分析和抑制

直接数字频率合成技术（DDS）是近年来发展迅速的一种新的频率合成技术。全数字化的结构赋予了它很多的优点：频率转换时间短，频率分辨率很高，输出相位连续，容易集成和易编程控制等，当然也就引进了数字化结构的缺点－－输出杂散在。本文对DDS波形发生器中由于相位截尾所产生的杂散进行分析，并提出抑制相位截尾噪声的方法，给出了实现方法和实验结果。     

多台原子钟性能在线监测方法研究

时频基准驱动的系统要求提供频率相位连续的时频信号,这对时频信号产生系统的可靠性提出要求,目前,冗余备份是提高设备可靠性的主要手段,可靠的时频信号产生系统通常由主备多台原子钟、在线监测设备、钟组合算法和控制设备组成,以原子钟的性能监测结果为基础,通过实施组合算法计算频率或相位调整量,驾驭各钟输出的时频信号.如何获得最优性能的时频信号,在线监测设备准确、实时评估原子钟性能是关键.在分析原子钟关键指标的基础上,提出了多台原子钟频率、相位性能并行比较的数字测量方法,研究了使用比对结果获得相位连续、频率稳定信号的方法.最后根据该方法研制了原理样机,样机的测试结果验证该方法满足铯或氢原子钟等高性能原子钟组在线实时监测需求,其中测试10 MHz信号源阿伦方差表征的设备本底噪声为3.4E-14/s,达到了世界先进水平.     

SQUID磁强计的低噪声设计—频率合成及锁相技术的应用

本文阐述了在ＳＱＵＩＤ磁强计的电子线路中采用的频率合成及锁要上技术用来恢复淹没在噪声中的信号相位和频率，从而可以对信号进行相干检测的技术。本振信号及载波信号相同频率和采用高精度的稳压电源提高压控振荡器的信号的频谱纯度，使其信号有较纯净的输出，以最大限度地减少相位噪声。     

基于全相位FFT的故障信号检测方法

针对机械系统中的机械故障信号检测,首次提出了一种通用的全相位FFT检测方法.全相位FFT就是自身的频谱分析功能来实现对信号相位、频率和振幅的判决,所得到的相位没有误差,振幅误差也远小于基于FFT的检测技术.通过理论分析和MATLAB仿真,全相位FFT检测得到的信号相位误差为0,频谱校正后的振幅和频率误差也非常低,表明了该方法在故障信号检测中的可行性和正确性.     

基于Walsh函数的多频率同步信号合成方法

多频率同步(MFS)激励信号源是实现生物电阻抗频谱多频率快速测量的关键,但目前尚无理想解决方案。通过研究提出了一种基于Walsh函数的MFS信号合成方法,论述了MFS信号的合成原理及合成步骤,并给出了5频率同步信号f(5,t)的合成实例及其FPGA实现方法。傅里叶级数分析表明,f(5,t)在其5个主谐波分量上的幅值较大,其功率之和占据信号平均总功率的73.91%,且具有相同的零初始相位。合成的MFS信号的主谐波个数可根据需要进行选择,且主谐波的频率也可以通过改变FPGA的工作时钟来调整,信号易于调节和实现,是一种理想的、可用于BIS快速测量的多频率同步激励信号源。     

一种高精度直接数字式频率源的设计

直接数字频率合成(DDS)是近年来发展非常迅速的一种新型频率合成技术,它具有频率分辨率高、相位噪声低、频率转换时间短等特点。首先简要介绍DDS的工作原理及其性能,然后主要阐述如何利用AD9851芯片设计一个高精度直接数字式合成频率源。     

双频激光干涉仪中的数字相位计设计

基于Altera公司FPGA芯片,提出了一种基于双频激光干涉仪系统中数字相位计的实现方法。该相位计用于测量系统中被测信号和参考信号之间的相位差角度,间接测量激光干涉仪的光程差信息。被测信号经过光电接收器以及A/D模数转换成数字信号送到FPGA芯片中,与FPGA内建的查找表参考信号做正交相关法解调运算,得到一组X-Y值,再利用CORDIC算法计算arctan函数获取相位差,最后计算出干涉仪的光程差,算法的全过程使用FPGA硬件实现。实验结果表明,该相位计使双频激光干涉仪的相位差测量精度在0.01°以内。     

电定标热释电辐射计系统的数字相位计

基于Altera公司cycloneⅢ系列EP3C5芯片,提出了一种基于电定标热释电辐射计（ECPR）系统中一种数字相位计的实现方法.该相位计的作用是调整系统中被测信号和参考信号之间的相位差,使得相敏检波的幅度达到最大,从而提高光功率的检测精度.将被测信号A/D转换成数字信号送到FPGA芯片中,与查找表中的参考信号做I-Q正交解调算法,得到一组I-Q值利用CORDIC算法计算arctan函数荻取相位差,最后做出相应的信号同步调整.实验结果表明,该相位计使辐射计系统的测量光功率值的精度得到了改善和提高,系统运行更加稳定,当测量精度为1mW,其不确定度为1％.     

Imaging the dynamics of intracellular protein translocation by photoconversion of phamret-cybr/ROM

Cybr/Reduced On-random Motile (ROM) is a scaffold protein, containing a postsynaptic density protein-95/discs-large/ZO-1 (PDZ) domain, a LEU region and a PDZ domain binding region at the C-terminus. In the immune system, Cybr/ROM was found to localize in vesicles and at the plasma membrane, through interactions with cytohesin-1. In this investigation, we reported Cybr/ROM as occurring in vesicles, the cytoplasm and at membrane ruffles of H1299 lung cancer cells. Its localization at the ruffles was dependent on intact actin structures as indicated by latrunculin A treatment, which abrogated ruffle formation and staining of Cybr/ROM at the cells' periphery. Transfection of truncation mutants consisting of either the PDZ or LEU domain showed that the LEU domain of ROM was localized to membrane ruffles, vesicles and the cytoplasm, whereas, the PDZ domain localized to the membrane ruffles and cytoplasm only. There was therefore, domain/molecular segregation of Cybr/ROM in different cellular compartments. Cybr/ROM was subcloned into a plasmid carrying the photoactivation-mediated resonance energy transfer (Phamret) protein. The photoconversion experiments demonstrated the diffusion of ROM from the cytoplasm to the membrane ruffling sites and conversely from membrane ruffles to the cytoplasm. Large variances in the transport velocity of Cybr/ROM in the cytoplasm suggested that its movements were facilitated by other mechanisms in addition to diffusion.     

伪随机码在绝对式光电轴角编码器中的应用

介绍了中国光电轴角编码器制造业中新出现的一种绝对式编码器,伪随机码绝对式光电轴角编码器.阐述了伪随机码绝对式光电轴角编码器的编码方法、技术要点及特点.伪随机码绝对式编码器采用M序列伪随机码作为编码方法,采用双狭缝技术进行分时位置读取,并采用ROM元件进行译码输出.伪随机码可以在一条码道上存储多位信息,多位码盘只需要一条码道,极大限度缩小了码盘直径,为国内生产小型化的多位绝对式编码器开辟了新途径.     

Development and validation of an electrogoniometric wrist alignment device

This paper reports the development of an instrumented flexible electrogoniometric hand posture corrective device designed specifically for monitoring and controlling the range of motion (ROM) at the hand and wrist. The device, known as the wrist alignment device (WAD), consists of flexible electrogoniometers attached to a Lycra glove and a control box housing the WAD circuitry. The WAD controls the wrist ROM within set limits by means of presetting the joint angle ranges prior to commencing measurements, thereby preventing or reducing extreme wrist ulnar deviation, wrist hyperflexion, and wrist hyperextension. Additionally, the device consists of a window comparator, which allows the joint movement always to remain within the set limits. Where the subject's wrist ROM is outside the presettings, a piezo-buzzer is triggered which alerts the subject to reduce the ROM, thereby ensuring that the joint angles are always kept within the preset angle range. All instrumentation associated with the development of the device underwent calibration. As a device, it has widespread applications within the office and clinical environment. Preliminary results indicate that reliable measurements based on ROM settings can be obtained when using the WAD.     

Enhancement of autoregressive model based gear tooth fault detection technique by the use of minimum entropy deconvolution filter

This paper proposes the use of the minimum entropy deconvolution (MED) technique to enhance the ability of the existing autoregressive (AR) model based filtering technique to detect localised faults in gears. The AR filter technique has been proven superior for detecting localised gear tooth faults than the traditionally used residual analysis technique. The AR filter technique is based on subtracting a regular gearmesh signal, as represented by the toothmesh harmonics and immediately adjacent sidebands, from the spectrum of a signal from one gear obtained by the synchronous signal averaging technique (SSAT). The existing AR filter technique performs well but is based on autocorrelation measurements and is thus insensitive to phase relationships which can be used to differentiate noise from impulses. The MED technique can make a use of the phase information by means of the higher-order statistical (HOS) characteristics of the signal, in particular the kurtosis, to enhance the ability to detect emerging gear tooth faults. The experimental results presented in this paper validate the superior performance of the combined AR and MED filtering techniques in detecting spalls and tooth fillet cracks in gears.     

Quantitative analytical electron microscopy of multiphase alloys

In this paper, we present a technique for analysis of composition gradients, using an analytical electron microscope, within the primary phase of a two-phase alloy for the case where the second-phase particle size is similar to the size of the irradiated volume. If the composition difference between the two phases is large, the detected compositional fluctuations associated with varying phase fractions may mask any underlying composition gradient of the primary phase. The analysis technique was used to determine grain boundary chromium concentration gradients in a nickel-base superalloy, alloy X-750. The technique may also be of use in other alloy systems.     

Wrist motion in computer keyboard typing

The purpose of this study is to define how wrist motion is affected by different postures and supporting devices and to discover functional range of wrist motion for keyboard typing. The range of wrist motion (ROM) needed for fourteen experienced typists to type on a computer keyboard was measured by flexible and biaxial electrogoniometers. The most frequent wrist motion during typing was in extended and ulnarly deviated positions in both wrists. Range of wrist motion was similar in both wrists. The average ROM for keyboard typing with the typists’ own posture was about 39° in flexion/extension (FEM) and 29° in radial/ulnar deviation (RUD) in both wrists. The range of wrist motion was significantly reduced to 30° in FEM and 27° in RUD with use of either wrist or forearm supporting devices, which suggests that these devices might help to relieve fatigue, discomfort, or pain during and/or after typing. Results of this study will be of interest to clinicians and helpful to those who are professionally or nonprofessionally involved in typing.     

基于分段多项式的直接数字频率合成器设计

为提高直接数字频率合成器（DDS）系统的性能,将分段多项式逼近算法应用于优化相幅转换电路中,实现了基于此结构的直接数字频率合成器设计。提出了适合在流行的现场可编程门阵列（FPGA）平台上实现的电路结构方案,进行了硬件实验,给出了在Altera Cyclone II器件中的实现结果,并在性能和资源消耗方面与基于ROM查找表的方案作了比较。研究结果表明,由于避免了庞大的查找表,这一方案大大减小了电路面积,提高了系统性能。     

Reduced order model of three-dimensional Euler equations using proper orthogonal decomposition basis

This study seeks to validate the accuracy and the efficiency of the aerodynamic reduced order model (ROM). In doing this, snapshot data are generated from the full system analysis of a fighter wing problem. From an eigensystem analysis of these snapshots, the basis vector reproducing the behavior of the full system is obtained. The span length, sweep angle, dihedral angle, and spar and rib thickness representing the wing configuration are determined as the input variables. The constructed ROM is applied to the fighter wing problem while varying the input conditions for validation. Subsequently, a comparison of the reduced system with the full system confirmed that the aerodynamic performance is within 4% error and that the L₂ norms are 10⁻⁶ order of the entire flow field. Therefore, the ROM is able to capture the variation of the aerodynamic performance with respect to the input variables. Though there are structural input variables which influence the aerodynamic performance indirectly, the ROM can reproduce the flow field of the full system. Additionally, even if the ROM incurs a high computational cost to generate snapshots, it can represent the behavior of the full system efficiently once the reduced order model is constructed.