共查询到20条相似文献,搜索用时 78 毫秒
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设计了一种参数观测器,对不确定Rossler系统中的未知参数进行了识别,采用backstepping方法实现了异结构不确定Rossler系统和Coullet系统之间的混沌同步.根据稳定性原理,确定了同步控制器的结构和控制增益的取值范围.仿真模拟结果表明,在参数观测器和backstepping控制器的共同作用下, Coullet系统所有的状态变量严格地跟踪了不确定Rossler系统的混沌轨迹,从而证明了该观测器和控制器的有效性. 相似文献
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本文总结和评论了立体声技术近年来的进展,包括声像定位理论和实验,传统的双通路立体声系统的改进,环绕产系统,高清晰度电视声系统,假头型立体声系统,数字声频技术在立体声的应用等.文中最后还叙述了对立体声今后发展的展望. 相似文献
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Noise mapping using measured noise and GPS data 总被引:1,自引:0,他引:1
In this paper, we introduce a system to easily produce a noise map using noise and GPS data measured simultaneously. The system consists of a sound level meter, a GPS receiver, a database program to manage the measured data, and a program to produce the noise map including a computer model of the target area. The GPS receiver interfaced to the sound level meter allows simultaneous measurement and storage of the noise level and the global position at a location. The database program directly imports one or more measured data stored in the sound level meter. Then, selected measurement results are exported to the noise mapping program for producing colour-coded or noise contour line maps using measured data at user-defined locations. The noise map produced can be exported to DXF and SHP files with other modeling items, for post-processing in GIS software. To demonstrate the capability of the developed system, we show a noise map for a university campus produced by the system. 相似文献
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Shootings at test shooting sites indoors can cause a risk of hearing loss for the workers at the site. The noise can also disturb other persons working in nearby rooms in the same building. A simple suppressor was constructed from a ventilation sound absorber. Sound level meters were installed near the shooter, to his side and in front of him, and in two nearby rooms. The suppressor solution attenuated the peak noise level to the side by 14–18 dB. Near the ear of the shooter, the amplification was 1–4 dB due to reflections. Therefore, a suppressor should have an adjustment mat between the muzzle of the weapon and the suppressor that would isolate sound from the muzzle backwards. In front of the shooter, the peak levels were attenuated by 0–3 dB due to the suppressor system. The suppressor system attenuated noise best to the side. The opening between the muzzle and the suppressor system caused the attenuation at the back of the weapon to be modest. In front, the bullet flight noise remained, and as a result there was no significant noise reduction in this direction. More noise control work is still needed, and one possibility for improvement would be a better enclosure of the imminent shooting area. 相似文献
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In economically developing countries such as Brazil, India and China, rising levels of noise pollution are associated with the accelerated growth of cities and the increasing circulation of automotive vehicles. This paper presents the results of an acoustic evaluation conducted in areas adjacent to federal highway BR-116, part of which lies within the urban limits of the city of Curitiba in southern Brazil. In situ measurements were taken of the noise levels, from which noise maps were drawn in different stages of the implementation of the road restructuring project called the Green Line. After calibration, a computational model was used to evaluate an operational scenario of the highway in the future. The results of the mappings were compared with reference noise emission values established by municipal legislation. The maps revealed the existence of noise pollution in the urban stretch of the federal highway in all the scenarios [LAeq > 65 dB(A)]. Efforts to control environmental noise in cities are aided by computational models for urban planning. These models are extremely helpful for environmental management and decision-making by public authorities for solutions to potential environmental risks, as is the case of urban noise. 相似文献
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This paper presents the difficulties found in trying to apply the “Balanced Approach” concept of ICAO (UN-International Civil Aviation Organization) on the noise pollution mitigation at urban Brazilian airports using, as a case study, the Congonhas Airport. It has been discussed by means of alternative operating scenarios, how to make the concept more flexible, aiming to bring the benefit of any additional acoustic comfort, without diminishing the installed capacity and already limited for environmental reasons. The results show that there are conditions for improvement, since there are both awareness of all players involved and permanent and real-time noise monitoring, even if those mitigating measures are not reflected on the noise annoyance models currently adopted for the land use planning. 相似文献
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L. Gammaitoni M. Martinelli L. Pardi S. Santucci 《Journal of statistical physics》1993,70(1-2):425-435
Experimental evidence of the stochastic resonance phenomenon in an electron paramagnetic resonance (EPR) system is reported. The amplitude and phase response of the EPR system operating in bistable conditions are measured for increasing values of the noise intensity. Theoretical predictions based on a simple dynamical model for the relevant system observables are shown to be in good agreement with experimental results. 相似文献
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This paper proposes an active partition that can be placed between a snorer and a non-snorer on a bed to reduce the snoring noise around the non-snorer ears by integrating a rigid finite size passive partition with a two channel active noise control system. The noise reduction performance of the passive partition on a bed with a headboard is studied first, where the effects of the height and the width of the partition are discussed. Due to the limited partition size, the attenuation for the low-frequency diffracted noise is not sufficient, so two loudspeakers are proposed to be installed on the partition as the secondary sources to increase the overall noise attenuation. Both numerical simulations and experiments are carried out to demonstrate the feasibility of the proposed integrated snoring noise control system, and the results show that the proposed active partition can achieve over 10 dB noise attenuation at non-snorer ears in the 1/3 octave bands from 80 to 1000 Hz. 相似文献
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A theoretical study of the temperature dependent noise effects of praseodymium-doped fiber amplifiers (PEDFAs) has been examined. The Pr3+-doped ZBLAN fiber amplifier pumped at 1017 nm and Pr3+-doped GeGa-sulfied fiber amplifier pumped at 1028 nm are chosen. The temperature-dependent rate and propagation equation related to four-level system consideration which is based on the population difference among amplification levels has been used. The population difference depends on pump and signal powers, Boltzman factor KB, cross-sections, noise figure (NF) and Pr3+ concentration. The numerical results obtained over the temperature range from −20 °C to + 60 °C are used to present an analytical expression for the signal gain and noise figure effects in PDFAs length and noise figure with input pump power. The amplified spontaneous emission (ASE) has been taken into account. 相似文献
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An examination of the effect of noise on a general system at a saddle-node bifurcation has revealed that, in the limit of weak noise, the probability density of the time to pass through the saddle-node has a universal shape, the specific kinetics of the particular system serving only to set the time scale. This probability density is displayed and its salient features are explicated. In the case of a saddle-node bifurcation leading to relaxation oscillations, this analysis leads to the prediction of the existence of noise-induced oscillations which appear much less random than might at first be expected. The period of these oscillations has a well-defined, nonzero most probable value, the inverse of which is a noise-induced frequency. This frequency can be detected as a peak in power spectra from numerical simulations of such a system. This is the first case of the prediction and detection of a noise-induced frequency of which the authors are aware. 相似文献