Transfer functions interpolating an ideal amplitude with arbitrary phase and delay

A method is presented to generate polynomials with phase values and delay (first derivative) specified at given frequencies. Then a closed form solution is described for the scattering transfer function S₁₂(p) of a resistively terminated lossless reciprocal two-port network with ideal amplitude and arbitrary phase and delay.     

Wave structure and flow amplitude-frequency characteristics in the turbine nozzle lattice in the presence of phase transition

This paper is devoted to the wave structure of a flow at its near- and supersonic velocities in a flat turbine cascade of profiles in the zone of phase transitions. The main task was investigation of the mechanics of interaction of the condensation jump with the adiabatic jumps of packing in a change of the initial condition of the flow. The obtained results are necessary for verification of the calculation models of the moisture-steam flow in the elements of lotic parts of the steam turbines. The experimental tests were made on a stand of the wet steam contour (WSC-2) in the Moscow Power Engineering Institute (MPEI, National Research University) at various initial states of steam in a wide range of Mach numbers. In the investigation of the wave structure, use was made of an instrument based on the Schlieren-method principle. The amplitude-frequency characteristics of the flow was found by measurement of static pressure pulsations by means of the piezo resistive sensors established on a bandage plate along the bevel cut of the cascade. It is shown that appearance of phase transitions in the bevel cut of the nozzle turbine cascade leads to a change in the wave structure of the flow. In case of condensation jump, the system of adiabatic jumps in the bevel cut of the cascade becomes nonstationary, and the amplitude-frequency characteristics of static pressure pulsations are restructured. In this, a change in the frequency pulsations of pressure and amplitude takes place. It is noted that, at near-sonic speeds of the flow and the state of saturation at the input, the low-frequency pulsations of static pressure appear that lead to periodic disappearance of the condensation jump and of the adiabatic jump. As a result, in this mode, the flow discharge variations take place.     

A damping of rotor natural vibration in three‐phase hybrid stepping motors

This paper proposes a damping method of rotor natural vibration in three‐phase hybrid stepping motors, in which optimal commutation signals are calculated from the period of the natural vibration measured by detecting the motor voltages. Moreover, an acceleration and deceleration pattern is derived from a simple model of the rotor vibration, to suppress undesirable transient oscillation in acceleration, deceleration, and positioning operations. An experimental drive system has been implemented and tested to confirm the effectiveness and versatility of the proposed method. Some experimental results show that the experimental system can damp the rotor natural vibration even if the rotor inertia varies. Compared with the conventional pattern, it is confirmed that the proposed pattern makes a great contribution to damping the undesirable transient oscillations. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(3): 69–77, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10153     

Lowpass approximations of a constant amplitude with arbitrary phase and delay

A review is made of recent developments to the simultaneous lowpass approximation problem of amplitude, phase and delay. the closed from solutions (reciprocal and non-reciprocal) are expressed in terms of the arbitrary phase and delay polynomials (APD).     

Asynchronous BCI and local neural classifiers: an overview of the adaptive brain interface project

In this communication, we give an overview of our work on an asynchronous brain-computer interface (where the subject makes self-paced decisions on when to switch from one mental task to the next) that responds every 0.5 s. A local neural classifier tries to recognize three different mental tasks; it may also respond "unknown" for uncertain samples as the classifier has incorporated statistical rejection criteria. We report our experience with 15 subjects. We also briefly describe two brain-actuated applications we have developed: a virtual keyboard and a mobile robot (emulating a motorized wheelchair).     

语音信号相空间重构中时间延迟的选择方法

本文阐述了时间延迟对重构相空间轨迹的影响,介绍了选择时间延迟的主要方法,详细分析了基于相空间扩展准则的平均位移法选择时间延迟的原理.通过分析相空间扩展的几何意义,针对平均位移法存在的缺点,计算相空间矢量偏离相空间主对角线和辅对角线的距离相结合的新位移度量,并以此位移度量为依据确定最佳延迟时间.应用于语音信号相空间重构的实验表明,改进的平均位移法具有更明确的物理意义,可以更好地选择时间延迟.     

Reduction of higher harmonic sequences in terminal voltage of an AC exciting synchronous generator using magnetically anisotropic slot wedges

This paper describes relationships between characteristics of a magnetically anisotropic slot wedge and voltage higher harmonics in an ac exciting synchronous generator terminal due to permeance ripple caused by an open-slot-type rotor. From the relationships obtained, practical guidelines were formulated for machine designs applying the magnetically anisotropic slot wedge. The results are as follows.

• 1 (1) Equivalent permeability of the magnetically anisotropic slot wedge became isotropic wedge permeability for air-gap flux ripple.
• 2 (2) Two ways were identified to reduce voltage-higher harmonics by using the slot wedges.
• 3 (3) The level of leakage flux passing through the anisotropic slot wedge was determined only by its permeability in the width direction.
• 4 (4) Effectiveness of the magnetic anisotropic slot wedges inserted into the stator slots was verified from experimental results using a model machine of the open- slot-type rotor.

     

Incorporation of an advanced evaluation criteria in an expertsystem for the creation and evaluation of planned switching sequences

An expanded criteria for the creation and evaluation of scheduled switching sequences is presented. This criteria incorporates both remote control and manual switching steps as well as steps or actions that require a human operator, such as attaching hold cards or removing fuses. The advanced evaluation criteria has been incorporated into an expert system and tested for the creation and evaluation of planned switching sequences for circuit breakers, busbars and transformers     

A minimal set of electrodes for motor imagery BCI to control an assistive device in chronic stroke subjects: a multi-session study

The brain-computer interface (BCI) system has been developed to assist people with motor disability. To make the system more user-friendly, it is a challenge to reduce the electrode preparation time and have a good reliability. This study aims to find a minimal set of electrodes for an individual stroke subject for motor imagery to control an assistive device using functional electrical stimulation for 20 sessions with accuracy higher than 90%. The characteristics of this minimal electrode set were evaluated with two popular algorithms: Fisher's criterion and support-vector machine recursive feature elimination (SVM-RFE). The number of calibration sessions for channel selection required for robust control of these 20 sessions was also investigated. Five chronic stroke patients were recruited for the study. Our results suggested that the number of calibration sessions for channel selection did not have a significant effect on the classification accuracy. A performance index devised in this study showed that one training day with 12 electrodes using the SVM-RFE method achieved the best balance between the number of electrodes and accuracy in the 20-session data. Generally, 8-36 channels were required to maintain accuracy higher than 90% in 20 BCI training sessions for chronic stroke patients.     

基于幅频特性的复值小波构造及其在电力系统信号分析中的应用

提出了基于幅频特性的复值小波函数构造方法及其相应的复值小波变换。该方法构造的复值小波具有频率局部化性能好、提取故障信号特征分量较准确的优点。复值小波变换能准确分辨出信号中所包含的幅值信息和相位信息 ,因而 ,适用于电力系统的故障信号的检测。利用基于幅频特性的复值小波变换 ,对发电机转子部分故障信号进行了分析 ,显示了基于幅频特性的复值小波变换的电力系统故障信号分析方法 ,是一种有效的方法。     

一种利用矢网测试接收机幅相特性的方法

幅相一致性和幅相线性是影响接收机性能提高的重要因素,也是精确测试的难题。本文在简要介绍矢网测试原理的基础上,给出了利用安捷伦公司矢网N5242A测试上述两项指标的方法,给出了测试结果。实际测试结果表明利用矢网测试接收机的幅相一致性和线性是高效可行的。此外,文中还提出了利用矢网测试应该注意的问题。     

基于幅频特性的复值小波构造及其在电力系统信号分析中的应用

提出了基于幅频特性的复值小波函数构造方法及其相应的复值小波变换。该方法构造的复值小波具有频率局部化性能好、提取故障信号特征分量较准确的优点。复值小波变换能准确分辨出信号中所包含的幅值信息和相位信息,因而,适用于电力系统的故障信号的检测。利用基于幅频特性的复值小波变换,对发电机转子部分故障信号进行了分析,显示了基于幅频特性的复值小波变换的电力系统故障信号分析方法,是一种有效的方法。     

变电站操作票专家系统的研究与应用

介绍了一种基于产生式知识表达方式的变电站操作票自动生成系统。该系统通过建立一种通用的电力系统设备认知模型－操作类，来简化相应的专家系统知识库。系统通过在线拓扑分析算法，推理出正确的操作路径，系统的解释机能对推理过程及推理中所应用的相关知识进行解释。开发出图形网络浏览系统，通过网络远程可视化监测变电站所有设备的状态。该系统已成功用于多个变电站。     

使用力科示波器测量信号相位变化的方法

在实际应用中,经常会遇到相位的测量,比如说两个信号之间的相位测量,或者同一个信号在不同时刻的相位变化(如相位调制信号).示波器是测量信号时域特征最常用的仪器,本文就基于力科示波器来介绍如何使用示波器来测量信号的相位变化.     

Adaptive control of feedforward nonlinear systems with uncertain time-varying parameters and an unknown time-varying delay in the input

In this paper, we consider a global regulation problem for a class of feedforward nonlinear systems. The key features of our considered system are identified by the presence of uncertain time-varying parameters associated with main diagonal states and input and an unknown time-varying delay in the input. Moreover, the growth rates of nonlinearity and the input-delay are only known to be finite. To solve our considered problem, we give a process to obtain a compact set that contains the allowed time-varying parameters. Then, we propose an adaptive controller which handles both unknown growth rate of nonlinearity and input-delay for system regulation. We carry out the rigorous system analysis and show the effectiveness of our proposed control scheme via an application example.     

Generation and correlation of orthogonal complementary pairs of sequences of lengths 2N10M26P based on an improved multilevel complementary sequences approach

Binary complementary pairs of sequences of lengths 2^N 10^M 26^P posses some interesting properties for their application in signal detection in noisy channels. Nonetheless, they have not been broadly used because of their greater processing requirements as compared with binary complementary sequences with L  = 2^N . The present work introduces a new approach for generation and correlation of binary complementary pairs of sequences of length 2^N 10^M 26^P that reduces the number of required operations. The proposed algorithm allows not only to optimize the number of arithmetic operations but also to correlate two orthogonal complementary pairs simultaneously with the use of a single architecture. Due to the fact that multilevel complementary sequences algorithms are used to generate and correlate binary complementary sequences of length 2^N 10^M 26^P , the aforementioned algorithms are also improved. The proposal is theoretically proved and its arithmetic efficiency is assessed by comparing the number of operations with that of previously published architectures. Copyright © 2017 John Wiley & Sons, Ltd.     

Development of a long‐life three‐phase flywheel UPS using an electrolytic capacitorless converter/inverter

A long‐life three‐phase flywheel (FW) uninterruptible power supply (UPS) using an electrolytic capacitorless converter/inverter and a transformerless isolating system rating of 200 V and 5 kW–1min is described. The UPS has the following characteristics: (1) electrolytic capacitorless converter/inverter configuration for long life and smaller size (2) transformerless isolating system to realize small size and correct weight (3) batteryless system for maintenance‐free long life of about 20 years The electrolytic capacitorless converter/inverter has a small‐film capacitor value of 1/50 times of a conventional one. The converter/inverter is controlled by a current and voltage follow‐up method using PWM control. Charging and discharging abilities of the FW energy is achieved only by controlling the instantaneous slip frequency of the induction machine. The UPS has obtained excellent test results, such as an input power factor of 99.8%, a small output voltage distortion of 1.03%, and 93.8% efficiency at full load. © 1999 Scripta Technica, Electr Eng Jpn, 127(3): 25–32, 1999     

Control and synchronization of the generalized Lorenz system with mismatched uncertainties using backstepping technique and time‐delay estimation

We propose a robust control technique for regulation and synchronization of the generalized Lorenz system (GLS) that covers the Lorenz system, Chen system and Lü system. The proposed control provides synergy through the combination of the backstepping control and time‐delay estimation (TDE) technique. TDE is used to estimate and cancel nonlinearities and uncertainties while the backstepping method is adopted to provide robustness against matched and mismatched uncertainties. As a result, we observe in numerical simulation that the proposed technique shows better performances in regulating and synchronizing the GLS with mismatched uncertainties, in comparison with existing schemes. The efficacy of the proposed technique is also validated with a circuit‐implemented chaotic system. Copyright © 2017 John Wiley & Sons, Ltd.     

k-t BLAST and SENSE accelerated time-resolved three-dimensional phase contrast MRI in an intracranial aneurysm

Objective

The objective of this study was to investigate the performance of k-t BLAST (Broad-use Linear Acquisition Speed-up Technique) accelerated time-resolved 3D PC-MRI compared to SENSE (SENSitivity Encoding) acceleration in an in vitro and in vivo intracranial aneurysm.

Materials and methods

Non-accelerated, SENSE and k-t BLAST accelerated time-resolved 3D PC-MRI measurements were performed in vivo and in vitro. We analysed the consequences of various temporal resolutions in vitro.

Results

Both in vitro and in vivo measurements showed that the main effect of k-t BLAST was underestimation of velocity during systole. In the phantom, temporal blurring decreased with increasing temporal resolution. Quantification of the differences between the non-accelerated and accelerated measurements confirmed that in systole SENSE performed better than k-t BLAST in terms of mean velocity magnitude. In both in vitro and in vivo measurements, k-t BLAST had higher SNR compared to SENSE. Qualitative comparison between measurements showed good similarity.

Conclusion

Comparison with SENSE revealed temporal blurring effects in k-t BLAST accelerated measurements.