A novel variable baseline visibility detection system and its measurement method

As an important meteorological observation instrument, the visibility meter can ensure the safety of traffic operation. However, due to the optical system contamination as well as sample error, the accuracy and stability of the equipment are difficult to meet the requirement in the low-visibility environment. To settle this matter, a novel measurement equipment was designed based upon multiple baseline, which essentially acts as an atmospheric transmission meter with movable optical receiver, applying weighted least square method to process signal. Theoretical analysis and experiments in real atmosphere environment support this technique.     

A new method for stable numerical differentiation

In this paper, we proposed a new algorithm for stable numerical differentiation by optimizing node intervals. With the algorithm, noise-free differentiated values can be extracted within one-percent error. By overcoming noise problem due to numerical differentiation process, our algorithm can easily extract the differentiated values. Also, it can be extended to high order differentiation. To confirm the proposed algorithm, we applied it to the analysis of MOSFET electrical characteristics. It will provide us with a useful analysis tool in the field of parameter extraction from numerical data such as device characterization.     

基于三元伪随机序列集的多声源房间脉冲响应测量方法*

在多输入多输出系统中,诸多情况下需并行测量任意输入输出之间的脉冲响应。虽然利用以Kasami序列集为代表的二元伪随机序列集良好的相关特性可以实现多声源并行测量,但是囿于其编解码信号相同且为二元信号的特点,使得其相关特性仍存在较大的可优化空间。该文提供了一种基于三元伪随机序列集的多声源房间脉冲响应测量方法,具有更好的相关特性,提高了测量准确度。仿真和实验验证了该测量方法的可行性和准确性。在封闭空间几何模型构建等领域中,可使用该方法提高测量效率并降低由于各通道不同步导致的误差。     

长距离长期稳定的量子密钥分发系统

介绍了最近完成的长距离长期稳定的量子密钥分发系统.该系统利用往返光路补偿光纤偏振 抖动和相位漂移的原理,采用结电容平衡魔T网络耦合的单光子探测技术,在506km单模 光纤中实现了长时间（大于12h）稳定的量子密钥分发实验.单脉冲平均光子数为007, 误码率为4%,其中单光子探测器的探测效率大于5%,单脉冲暗计数低于29×10^{-6. 关键词： 量子保密通信 量子密钥分发 单光子探测}     

用FIR数字滤波器实现高精度时延的一种新方法

本文提供了一种实现高精度、连续可变数字时延的新方法。该方法利用FIR数字滤波器的线性相位特性,通过调节权向量,可连续改变信号时延。具有时延精度高、运算量小、可实现宽带时延等显著特点。该方法可用于宽带数字波束形成、自适应时延估计以及目标回波的时域分析等技术领域。本文对该方法的基本原理、设计方法及仿真结果进行了阐述,并给出了有关应用实例。     

Frequency response measurement of high-speed photodetectors using the spectrum power method in a delay self-heterodyne system

We report on a photoionization scheme for controlled loading of ⁸⁸Sr⁺ ions into a radio-frequency (rf) ion trap. The two-step doubly-resonant process drives the ⁸⁸Sr atom on the 5s^{2 1} S ₀ – 5s5p¹ P ₁ transition at 461 nm using a frequency-doubled diode laser, and then excites the atom to the autoionizing (4d²+5p²) ¹ D ₂ state with 405 nm light from a free-running diode laser. This method of trap loading is quantitatively compared to electron bombardment loading, and shown to reduce the Sr vapour pressure required to load by four orders of magnitude. It also provides more than an order of magnitude reduction in the day-to-day variation of the voltages required to compensate micromotion. We additionally introduce a two-step atomic source consisting of an oven and hotplate, which reduces the number of impurities evaporated towards the trap. This is shown to significantly reduce fluctuations in required micromotion compensation voltages. The demonstrated reduction in flux and increased source purity are expected to improve the reliability of trap operation for precision ion-trap experiments. PACS 32.80.Fb; 32.80.Pj; 39.10.+j     

Asymmetric delay feedback stochastic resonance detection method based on prior knowledge particle swarm optimization

For the adjustable parameters stochastic resonance system, the selection of the structural parameters plays a decisive role in the performance of the detection method. The vibration signal of rotating machinery is non-linear and unstable, and its weak fault characteristics are easily concealed by noise. Under strong background noise interference, the detection of fault features is particularly challenging. Therefore, a type of weak fault feature extraction method, named knowledge-based particle swarm optimization algorithm for asymptotic delayed feedback stochastic resonance (abbreviated as KPSO-ADFSR) is proposed. Through deduction under adiabatic approximation, we observe that both the asymmetric parameters, the length of delay and the feedback strength, impact the potential function. After adjusting the asymmetric parameters of the system, the output signal-to-noise ratio (SNR) is used as the fitness function, and the setting of the relationship between the noise intensity and barrier height is used as the prior knowledge of the particle swarm algorithm. Through this algorithm, the delay length and the feedback strength are optimized. This method achieves global optimization of system parameters in a short time; it overcomes the shortcomings of the traditional stochastic resonance method, which has a long convergence time and tends to easily fall into local optimization. It can effectively improve the detection of weak fault features. In the bearing rolling body pitting corrosion failure experiment and steel field engineering experiment, the proposed method could extract the characteristics of a weak fault more effectively than the traditional stochastic resonance method based on the standard particle swarm algorithm.     

车载鱼眼成像系统的运动矢量检测方法

在复合成像侦测系统中,鱼眼成像系统的超大视场突破了"旋转扫描"和"多镜头拼接"的设计常规,采用固定凝视的方式对整个半球空域的目标进行搜索.然而在车载环境下,车体运动将导致输出的图像序列不稳定,影响观察效果,甚至会引起黄斑成像系统跟踪偏差.根据鱼眼成像系统的工作特点,通过利用熵值理论确定出图像信息最为丰富的区域,探讨了一...     

偶极子声波测井仪发射声系性能快速检测方法*

该文提出了一种针对偶极子声波测井仪发射声系性能进行快速检测的方法。通过实验测量方法,采用专门设计的简易装置测量偶极子声波测井仪发射声系激发的声场波形,并提取声场强度、声源主频以及空间分布对称性等特征参数。如果准确掌握了仪器处于完好状态时的这些特征参数,以此为参考依据与实验测量结果进行对比,通过设定可接受的相对偏差,就可完成对偶极子声波测井仪发射声系性能的快速评价。相对于现有的声波测井仪器检测方法,该方法具有高效、便捷的优势,便于在测井前线基地应用。     

Structure and properties of condensates of a ternary system Cd-Sb-Zn

The alloy system cadmium-antimony-zinc was investigated using specimens of variable composition obtained by vacuum deposition of alloy components. The formation of a continuous series of solid solutions in the pseudobinary section ZnSb-CdSb was verified, and it was established that in the pseudobinary section Zn₃SB₂-Cd₃Sb₂ there is a wide range of solid solutions with a structure similar to that of metastable compound -Zn₃Sb₂. Type Sb₂Zn_3xCd_3(1-x) alloys prepared in the usual way have a thermal emf of up to 450 V/deg and a type -Zn₃Sb₂ lattice.Translated from Izvestiya VUZ. Fizika, Vol. 11, No. 11, pp. 48–54, November, 1968.     

A method for solving the functional equation with variable delay

Mathematical simulation of physical conditions at a moving boundary in problems of wave reflection leads to a finite-difference equation with variable delay. If the reflector velocity is smaller than the wave-propagation velocity, the existence and uniqueness of the equation solution is proved using the principle of contraction maps and the method of successive approximations. It is shown that the solution can be expressed as a function of the composite argument that depends on one variable. The required accuracy of numerical calculations is ensured by partial sums when the argument is represented by an infinite converging series. N. I. Lobachevsky State University, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 9, pp. 900–905, September, 1999     

A delay financial model with stochastic volatility; martingale method

In this paper, we extend a delayed geometric Brownian model by adding a stochastic volatility term, which is driven by a hidden process of fast mean reverting diffusion, to the delayed model. Combining a martingale approach and an asymptotic method, we develop a theory for option pricing under this hybrid model. The core result obtained by our work is a proof that a discounted approximate option price can be decomposed as a martingale part plus a small term. Subsequently, a correction effect on the European option price is demonstrated both theoretically and numerically for a good agreement with practical results.     

Controlling a time-delay system using multiple delay feedback control

In this paper multiple delay feedback control (MDFC) with different and independent delay times is shown to be an efficient method for stabilizing fixed points in finite-dimensional dynamical systems. Whether MDFC can be applied to infinite-dimensional systems has been an open question. In this paper we find that for infinite-dimensional systems modelled by delay differential equations, MDFC works well for stabilizing (unstable) steady states in long-, moderate- and short-time delay regions, in particular for the hyperchaotic case.     

Stochastic perturbation of a stable deterministic plasma system

A canonical model is proposed for a plasma system under the influence of stationary random fluctuations and its implication on the Liapunov stability of the stationary equilibria is studied.     

光电成像探测中目标方位测量方法

为了在光电成像探测目标的同时给出目标相对探测器的方位信息,探讨了一种基于单目视觉的运动目标方位测量方法。根据投射成像原理,推算出二维目标像点坐标与目标的空间三维位置之间的映射关系,建立了单目视觉测量目标方位的数学模型。结合帧间差分法和KLT方法检测静止背景下和变化背景下的运动目标,并对目标特征点进行亚像素定位。试验和仿真结果分析表明,该方法能够有效提取目标的特征点,可对目标较为准确地定位,并通过单目视觉测量出目标方位信息,误差控制在8%的范围内。     

光电成像探测中目标方位测量方法

为了在光电成像探测目标的同时给出目标相对探测器的方位信息,探讨了一种基于单目视觉的运动目标方位测量方法。根据投射成像原理,推算出二维目标像点坐标与目标的空间三维位置之间的映射关系,建立了单目视觉测量目标方位的数学模型。结合帧间差分法和KLT方法检测静止背景下和变化背景下的运动目标,并对目标特征点进行亚像素定位。试验和仿真结果分析表明,该方法能够有效提取目标的特征点,可对目标较为准确地定位,并通过单目视觉测量出目标方位信息,误差控制在8%的范围内。     

A non-iterative partial discharge source location method for transformers employing acoustic emission techniques

Partial discharge (PD) causes premature insulation failure of transformers. It is essential to detect PD to avoid unwanted failure of transformers. Only detection of PD is not sufficient for a transformer of huge size, unless it is possible to locate. Acoustic partial discharge measurement is advantageous for PD source location. There are different algorithms for PD source location. These are iterative and require large number of acoustic emission (AE) sensors. This paper presents a non-iterative source location algorithm employing four AE sensors. This algorithm is applied to experimental data. Proposed algorithm is also applied to published data and compared with existing iterative methods. Main error for source location is due to arrival time calculation. In order to reduce the error in AE signal arrival time calculation, different arrival time calculation methods are discussed and a comprehensive method is proposed. By applying these methods, arrival time is calculated from measured signal.