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871.
In this work we consider the problem of detecting the irregularities of univariate functions from noisy data and its extension
to bivariate functions which present lines of points of irregularity.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
872.
Tom Scarvie Nord Andresen Ken Baptiste John Byrd Mike Chin Michael C. Martin Wayne R. McKinney Christoph Steier 《Infrared Physics & Technology》2004,45(5-6):403-408
The quality of infrared microscopy and spectroscopy data collected at synchrotron based sources is strongly dependent on signal-to-noise. We have successfully identified and suppressed several noise sources affecting beamlines 1.4.2, 1.4.3, and 1.4.4 at the advanced light source (ALS), resulting in a significant increase in the quality of FTIR spectra obtained. In this paper, we present our methods of noise source analysis, the negative effect of noise on the infrared beam quality, and the techniques used to reduce the noise. These include reducing the phase noise in the storage ring radio-frequency (RF) system, installing an active mirror feedback system, analyzing and changing physical mounts to better isolate portions of the beamline optics from low-frequency environmental noise, and modifying the input signals to the main ALS RF system. We also discuss the relationship between electron beam energy oscillations at a point of dispersion and infrared beamline noise. 相似文献
873.
A spectral decomposition of the Frobenius–Perron operator is constructed for one-dimensional maps with intermittent chaos, using the method of coherent states. A technique using the spectral density function is applied to the the well-known cusp map, which generates weak type-II intermittency. Higher-order corrections are obtained to the leading 1/t long-time behavior of the x–x autocorrelation. 相似文献
874.
At the Pattern Recognition group at the Delft University of Technology, we are working on new ways to measure fluorescence
lifetimes. There are two well-known ways to measure lifetimes; the phase method and the pulse method. In the phase method
fluorescent material is stimulated by sinusoidally modulated light. The emitted fluorescent light will have the same modulation
frequency, but there will be a phase shift between the excitation and the emission light. Measuring this phase shift will,
after some simple calculation, give the lifetime of the fluorescent material. The second method is the pulse method. Short
pulses of light are used to excite the material. The emitted light is detected, and from these measurements the decay curve
of fluorescent light is determined. In our research we want to use a new method that may allow us to measure a mixture of
lifetimes. We want to use excitation light that is modulated by a white noise signal. We are currently building an experimental
setup for these measurements. We have been working on numerical and electrical simulations to investigate the properties of
noise signals. Some results of these simulations are presented in this paper. 相似文献
875.
A. V. Reshetnikov V. I. Sannikov V. N. Skokov V. P. Koverda 《Journal of Applied Mechanics and Technical Physics》2007,48(1):7-10
Arc current fluctuations between a solid metal electrode and a liquid melt of alkaline carbonates at atmospheric pressure
are measured. Arc current fluctuation power spectra are determined from the measurement data. It is shown that the fluctuation
power is inversely proportional to the frequency (1/f-fluctuations). The fluctuations have a normal Gaussian distribution.
The observed 1/f fluctuations exhibit scale invariance.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 1, pp. 11–15, January–February, 2007. 相似文献
876.
基于B样条迭代法的激光光条噪声去除技术研究 总被引:5,自引:0,他引:5
在基于线结构光的视觉测量系统中,激光光条中心的提取精度是影响系统最后精度的关键因素。目前常用的光条中心提取方法都没有去除光条上的干扰噪声,在分析现有方法的基础上提出了一种利用B样条迭代去除光条噪声的方法。以光条上的点作为控制顶点拟合B样条曲线,在同一位置下用B样条曲线上的点取代噪声点,这样反复修改噪声点的位置使其逐渐逼近实际曲线,从而达到去除噪声的目的。利用重心法提取去噪后光条的中心,着重分析了参与运算的像素的取值范围。通过对比实验证明该方法的提取精度远高于其它方法,从而验证了去除噪声的有效性。 相似文献
877.
结构噪声是超声脉冲在介质结构上激发产生的一种特殊噪声,它严重妨碍超声检测,是超声检测的基本限制因素之一;但也可被利用进行某些检测。本文综述了有关结构噪声的基本研究,抑制或降低结构噪声的方法,以及在结构噪声背景下进行超声检测和利用结构噪声进行超声检测的有关工作。 相似文献
878.
T. Sasagawa 《Journal of Optimization Theory and Applications》1989,61(3):451-471
For the deterministic case, a linear controlled system is alwayspth order stable as long as we use the control obtained as the solution of the so-called LQ-problem. For the stochastic case, however, a linear controlled system with multiplicative noise is not alwayspth mean stable for largep, even if we use the LQ-optimal control. Hence, it is meaningful to solve the LP-optimal control problem (i.e., linear system,pth order cost functional) for eachp. In this paper, we define the LP-optimal control problem and completely solve it for the scalar case. For the multidimensional case, we get some results, but the general solution of this problem seems to be impossible. So, we consider thepth mean stabilization problem more intensively and give a sufficient condition for the existence of apth mean stabilizing control by using the contraction mapping method in a Hilbert space. Some examples are also given.This research was conducted while the author was a visitor at the Forschungsschwerpunkt Dynamische Systeme, Universität Bremen, Bremen, West Germany. The author is grateful to Professor L. Arnold for providing interesting seminars and excellent working conditions during his stay. The financial assistance given by the Alexander von Humboldt Foundation during the author's stay is also gratefully acknowledged. 相似文献
879.
Within the framework of a specified acousto-biomechanical model, a possibility of explaining wheezes during forced expiration on the basis of a vortex separation mechanism is tested and the localization of the zones in the bronchial tree where forced expiratory wheezes are generated is refined. As an experimental model, a group of 18 healthy volunteers from 18 to 44 years old (median is equal 19) was used. On the basis of linear regression modeling the relationship between the principal spectral frequency of medium-frequency forced expiratory wheezes (400–600 Hz) recorded on the trachea and the standard volume flow-rates of expired air measured in computer spirometry is analyzed. The data obtained show that vortex separation in the air flow at the bronchial tree bifurcations (where a stepwise increase in the cross-section area takes place) is a probable mechanism of medium-frequency forced expiratory wheeze generation and that during the forced expiratory maneuver the vortex separation zone tends to be displaced deeper into the bronchial tree. 相似文献
880.
S. V. Koshevaya D. A. Solovyev M. Tecpoyotl-Torres J. Escobedo-Alatorre J. Sánchez-Mondragon V. V. Grimalsky M. Basurto-Pensado 《International Journal of Infrared and Millimeter Waves》2004,25(2):277-289
This paper is focused on the choice of the module for low noise receiver in millimeter (mm) and sub millimeter (submm) wave ranges used in geophysical remote sensing systems for measurement of geophysical parameters by means of radiobrightness temperatures (radiometer systems obtaining data by means of radiobrightness temperatures). The observed data analysis, used in order to obtain recommendations and forecasts based on the radio telescope measurements and geophysical phenomena in the events of earthquakes, volcano explosions and typhoons, are realized by means of specialized computer codes. 相似文献