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Based on a simplified predator-prey model,the influence of noise on the ecosystem has been studied.The results show the following facts.(i)For all parameter values,the existence of noise maintains the oscillatory state of the ecosystem,and enough strong noise can destroy the ecosystem,which means the annihilation of the species.(ii)Comparing to oscillation with small amplitude,while the ecosystem oscillates explosively with large amplitude,it is more likely to lose balance.In addition,the small-amplitude oscillation takes on higher level of regularity.All the numerical results are reasonable comparing to the general knowledge about ecosystem. 相似文献
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Based on a simplified predator-prey model, the influence of noise on the ecosystem has been studied. The results show the following facts. (i) For all parameter values, the existence of noise maintains the oscillatory state of the ecosystem, and enough strong noise can destroy the ecosystem, which means the annihilation of the species. (ii) Comparing to oscillation with small amplitude, while the ecosystem oscillates explosively with large amplitude, it is more likely to lose balance. In addition, the small-amplitude oscillation takes on higher level of regularity. All the numerical results are reasonable comparing to the general knowledge about ecosystem. 相似文献
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采用对比测量方法研究了微通道板结构参数,即开口比、板厚、电极深度、离子阻挡膜、输入增强膜对其噪声因子的影响。结果表明,开口比增大,噪声因子减小;板厚增加,噪声因子增加;输入电极深度增加,噪声因子增加;离子阻挡膜会增加噪声因子;输入增强膜会降低噪声因子。其中,离子阻挡膜对噪声因子的影响最大,板厚对噪声因子的影响最小。微通道板的结构参数不仅对噪声因子产生影响,而且对其他参数,如增益、均匀性等性能均会产生影响。要降低微通道板噪声因子,比较可行的方法是将微通道板的开口比提高到68%,在此基础上,再在微通道板的输入端制作一层高二次电子发射系数的MgO2输入增强膜,使微通道板的噪声因子接近1,从而达到理想微通道板的水平。 相似文献
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The standard method for computing noise contours around civil airports is SAE-AIR-1845 (FAA Integrated Noise Model, European ECAC-CEAC Doc. 29). It is subject to the inaccuracies implicit in the model as well as those caused by erroneous or imprecise input data. Regarding the latter, the existing errors and/or uncertainties, may be amplified in the output results, to a greater or lower extent, in some cases offering unreliable predictions.In order to study this phenomenon, the Institute of Sound and Vibration Research (ISVR - Southampton) carried out a theoretical sensitivity analysis based on the segmentation technique, regarding the input parameters of the SAE-AIR-1845, and obtaining the input variables of the model, the variation of which implied greater changes in the output variables. The results were validated by using the FAA Integrated Noise Model Version 6.0 software, based on the aforementioned document. It has been revealed that the model has a greater sensitivity to factors that modify the flight path, and a lower sensitivity to the other parameters. Thus, an error greater than 10% in the variable “gross weight” offers an additional error of between 3 and 7 dB. However, parameters such as the ID of the flaps hardly modify the results obtained for the least favourable case by 1 dB.As a result of this research, the sensitivity of the model was quantified for each of the input parameters (taken alone and also in interaction with other parameters), and criteria for the minimisation of global error, resulting from uncertainties in the input parameters, were stated. 相似文献
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基于改进的漂移-扩散模型研究了光伏型光电探测器的材料参数对其光电特性的影响.计算结果表明载流子迁移率、材料组分、掺杂密度对探测器输出特性的影响大;载流子寿命越长、迁移率越大、杂质密度越小,则探测器输出信号越大,但各材料参数与探测器输出信号间并不构成线性关系;当入射光波长一定时材料组分不同探测器输出信号大小不同. 相似文献
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讨论带参数的自适应时域方法计算极光系统的参数,以一个有理形式函数模型来代表系统函数,采用可以在线实时应用的递推自适应算法来确定该模型的参数。利用这种方法处理测量所得的极光亮度数据,现用互谱方法计算的氧原子「OI32」跃迁时O(^1S)态的平均有效寿命符合得很好。 相似文献
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We discuss how the effective parameters characterising averaged motion in nonlinear systems are affected by noise (random fluctuations). In this approach to stochastic dynamics, the stochastic system is replaced by its deterministic equivalent but with noise-dependent parameters. We show that it can help to resolve certain paradoxes and that it has a utility extending far beyond its usual application in passing from the microscopic equations of motion to the macroscopic ones. As illustrative examples, we consider the diode-capacitor circuit, a Brownian ratchet, and a generic stochastic resonance system. In the latter two cases we calculate for the first time their effective parameters of averaged motion as functions of noise intensity. We speculate that many other stochastic problems can be treated in a similar way.
PACS: 05.10.Gg, 05.40.-a, 05.40.Jc 相似文献
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CHENG Qing-Hua CAO Li XU Da Hai WU Da-Jin 《理论物理通讯》2005,44(5):867-872
Using the linear approximation method, we have studied how the correlation function C(t) of the laser intensity changes with time in the loss-noise model of the single-mode laser driven by the colored pump noise with signal modulation and the quantum noise with cross-correlation between the real and imaginary parts. We have found that when the pump noise self-correlation time T changes, (i) in the case of r 〈〈 1, the C(t) vs. t curve experiences a changing process from the monotonous descending to monotonous rise, and finally to the appearance of a maximum; (ii) in the case of r 〉〉 1, the curve only exhibits periodically surging with descending envelope. When r 〈〈 i and T does not change, with the increase of the pump noise intensity P, the curve experiences a repeated changing process, that is, from the monotonous descending to the appearance of a maximum, then to monotonous rise, and finally to the appearance of a maximum again. With the increase of the quantum noise intensity O,, the curve experiences a changing process from the monotonous rise to the appearance of a maximum, and finally to the monotonous descending. The increase of the quantum noise with cross-correlation between the real and imaginary parts will lead to the fall of the whole curve, but not affect the form of the time evolution of C(t). 相似文献
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基于FPGA的红外焦平面成像条纹噪声逐帧抑制算法的研究 总被引:1,自引:0,他引:1
红外焦平面阵列是当今红外成像技术发展的主要方向,随着器件工艺的进步,红外焦平面阵列探测器有了长足的发展,然而红外图像普遍具有信噪比低的缺点,这大大限制了红外焦平面的应用。与固定图案噪声(FPN)相比,随机噪声的最大特点是每帧均不同,因此去除该类型噪声的算法必须在一帧之内完成。提出了一种新型的单帧去除此类条纹噪声的算法并加以硬件实现,在单帧内设置适合的校正参数和阈值,达到在单帧图像内有效去除条纹噪声的目的。通过算法处理前后的图像对比以及客观的MSE、PSNR测试数据对比,证明了该算法能够有效地改善焦平面器件成像质量。 相似文献
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本文结合1/f噪声信号功率谱随频率成反比变化的关系, 以及稀疏分解可以根据信号灵活构造原子库的特点, 提出一种基于稀疏分解估计大功率半导体激光器1/f噪声的新方法, 构造了具备1/f噪声特点的过完备库. 在该过完备库中通过Matching Pursuit(MP)算法完成了白噪声与1/f噪声混叠信号的稀疏分解. 实验结果显示:该方法估计出淹没在白噪声环境中1/f噪声的γ 参数, 与频谱分析仪的测量结果有较好的一致性, 通过对比不同的过完备库证明了所构造的过完备库的优越性. 相似文献
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应用由111个传声器组成的平面传声器阵列对当前流行的民用客机进场着陆过程中的机体噪声源进行了实验测量,本对七架窄体客机和七架宽体客机的起落架噪声进行了分析,得到了起落架噪声的频谱特性、指向特性和声级变化。研究发现,起落架噪声的频谱是由宽频随机噪声与一些较为明显的单噪声源组成,起落架噪声的指向性类似于一个水平放置的偶极子。不同飞机起落架噪声的声级相差较大,这说明可以通过重新结构设计降低起落架噪声。 相似文献
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Effects of nonlinear gain and nonradiative recombination on characteristics of intensity and phase noises of InGaAsP lasers emitting in a wavelength of 1.55 Μm are investigated. The investigations are performed based on a self consistent numerical approach that takes into account the cross correlation of fluctuations among the injected electron number, photon number and the optical phase. Time variations of the fluctuations of the intensity and the shift of the lasing frequency are statistically analyzed. The corresponding frequency dependencies of intensity and frequency noises are characterized. The results show that both intensity and frequency noises around the relaxation frequency are suppressed when counting the nonlinear gain in the rate equations. The intensity noise is enhanced in the low frequency regime by increasing the nonradiative recombination. The results fit well with those predicted by the small-signal analysis. 相似文献
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DLS粒度测量实验中噪声的影响与克服 总被引:1,自引:0,他引:1
噪声是始终存在于动态光散射实验的整个测量过程中,噪声的大小直接影响测量系统的信噪比大小与测量结果的准确性。根据噪声产生的物理原因,将动态光散射实验中的噪声分为外部环境噪声和设备内部噪声两大类。为了最大限度的降低噪声提高测量的准确性,在详细探讨影响动态光散射粒度测量实验中各种噪声的来源的基础上,分析了噪声对实验结果的影响,并提出相应解决的办法。 相似文献
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随机噪声对激光陀螺输出特性的影响 总被引:6,自引:0,他引:6
分析了纯随机噪声输入和周期性抖动信号叠加随机噪声的复合抖动输入两种激励下,激光陀螺输出信号均值偏差和分散系数与随机噪声强度之间的数学关系,基于该关系公式,综合读出角速度标准差、输出信号均值偏差和分散系数,提出随机噪声强度的选择方法。研究表明,纯随机噪声减小频率闭锁影响没有应用价值,因为随机噪声的引入将导致激光陀螺测量范围的减小或输出方差的增大,这都不是理想的结果。而在周期性抖动信号基础上叠加随机噪声,并不影响激光陀螺的测量范围,却可大幅度地提高激光陀螺的读出精度,输出方差的增大可以通过延长采样周期予以减小,满足应用要求。 相似文献