Fluctuation and Noise Letters

In Zeng et al. [Fluct. Noise Lett. 7 (2007) L439–L447] the analysis of the lowest unique positive integer game is simplified by some reasonable assumptions that make the problem tractable for arbitrary numbers of players. However, here we show that the solution obtained for rational players is not a Nash equilibrium and that a rational utility maximizer with full computational capability would arrive at a solution with a superior expected payoff. An exact solution is presented for the three- and four-player cases and an approximate solution for an arbitrary number of players.

The cooperation of noise and the delayed coupling is investigated in a calcium model. Simulation results show that the constructive noise effect, like the coherence resonance (CR) and the optimization of signal regularity, can be significantly adjusted by the delayed coupling. Besides, the coupling may also play the constructive role to strengthen the signal by producing CR-like phenomenon under weak noise influence. When the noise is strong, the increase of coupling strength can decrease the adverse noise effect on the signal regularity.

A Monte Carlo study of hot-electron intrinsic noise in a n-type GaAs bulk driven by one or two mixed cyclostationary electric fields is presented. The noise properties are investigated by computing the spectral density of velocity fluctuations. An analysis of the noise features as a function of the amplitudes and frequencies of two applied fields is presented. Numerical results show that it is possible to reduce the intrinsic noise. The best conditions to realize this effect are discussed.

We analyse Selten' concept of trembling hand perfect equilibria in the context of quantum game theory. We define trembles as mixed quantum strategies by replacing discrete probabilities with probability distribution functions. Explicit examples of analysis are given.

In this study, we have presented a new approach to separate noisy components and to characterize frequency-energy variability for local real-time noisy earthquakes where epicentral distance is 0–10°. This approach is based on wavelet transform and deals with energy variations in different frequency bands. All records have been decomposed to approximation and detail components with using overlapping window design and wavelet transform. Energy components of each window were determined and highest energy component has been selected in all windows. When selected energy values have been associated in a vector, two different types of frequency-energy characteristics which include critical points to detect P (longitudinal) and S (transverse) waves have been obtained.

We present a laser delay control system based on adaptive averaging which utilises the jitter noise of the laser to stabilise the delay more precisely. The system contains delay lines to measure and control the laser delay and a microcontroller that runs our control algorithm. The algorithm regulates the laser delay on the basis of the average of detected delay values, where the steps with which the delay is varied and the averaging length are chosen adaptively, depending on the distance from the target delay. Our complementary numerical simulations show that the jitter of the laser may play a beneficial role here: the error of the delay has a distinct minimum at a non-zero noise level. In a way similar to the dithering principle applied in analogue-to-digital conversion, averaging the noise-modulated detection instances yields a precision in setting the delay that is well beyond the resolution provided by detection time windows, and is close to the theoretical limit determined by the step size of the delay line we applied.

One of the main important aspects in designing an active control system is the optimization of position and number of sensors and actuators. In this paper this problem is addressed for the implementation of a multi-channel active noise control (ANC) system with the aim of global reduction of broadband noise in a telephone kiosk. This includes optimizing the locations for loudspeakers and microphones, finding proper size of the control system, i.e. the number of loudspeakers and microphones, and optimization of the control signals. The mean of acoustic potential energy in the enclosure in a frequency range of 50 Hz to 300 Hz is selected as the performance index for optimization purpose. Several genetic algorithms are proposed and compared to find the global minimum of this performance index. In order to have a better performance in reaching the global minimum, the parameters of these genetic algorithms are tuned, and the best genetic algorithm is selected among them. The main difference between the proposed algorithms is the used coding scheme. Numerical simulations of the acoustical potential energy and also sound pressure at the height where the head of a person may be located, confirms the optimality of the locations proposed by the genetic algorithm.

The present paper proposes a discrete cosine transform (DCT) domain watermarking scheme by exploiting nonlinear dynamical saturating detectors in the design of a watermark detection process. A binary copyright character, i.e. watermark to be hidden into an image, is firstly reordered into a binary zig-zag sequence, and then mapped onto the pulse amplitude modulated signal. A certain desynchronization time delay can be deliberately placed into one code of the modulated signal, and is tolerated due to the superior robustness of nonlinear detectors over matched filters. A selected set of DCT coefficients of a host image in a mid frequency range is shuffled by the Arnold transform, which makes it look more like background noise with respect to the watermark signal. Then, the watermark signal is embedded in the set of shuffled DCT coefficients. The copyright character can be extracted by a nonlinear saturating detector without prior knowledge of the original image and watermark, i.e. blind watermark detection. Interestingly, a higher match between the original watermark character and the extracted one can be further achieved by a parallel array of nonlinear detectors via the mechanism of array stochastic resonance. Robustness of the proposed watermarking scheme is shown in the presence of noise, filtering, cropping, and compression.

A sensitive technique to measure the relative intensity noise of a laser is described. Such experiment is a useful tool for laser characterizations, allowing direct measurement of physical parameters like relaxation oscillation frequencies and damping factor. Examples of determination of such parameters are given.

Low frequency noise modeling and numerical simulation have been carried out to study the influence of the back interface quality and the silicon film thickness in Fully Depleted SOI MOSFETs, with special emphasis on the coupling effect. In devices with a standard film thickness, the noise level is higher than for an equivalent interface in bulk device, which could be a great concern for analog applications. On the other hand, it has been shown that in very thin SOI devices with a symmetrical structure (Double Gate architecture), the reduction of electric field in the silicon film, induces a conduction channel in the middle of the film, away from both interfaces which in turn reduces the scattering rate of carriers, decreasing the noise level.

The noise behavior of a two-port is usually described through the conventional set of noise parameters F_min, R_n, and the complex Y_opt. However, noise parameters developed using wave-based techniques also have their merit as they could offer different insights to a two-port's noise behavior. Unlike the conventional noise parameters, these wave-based noise parameters could be terminal-invariant and describe only the intrinsic noise behavior of a two-port. In this paper, several important noise parameters derived from wave-based approaches are reviewed. The derivation of each set of parameters is discussed and illustrated. The measurement approach of each set of parameters is also briefly covered.