A new code structure for spectral amplitude coding in optical code division multiple access (OCDMA) systems called Smart Direct Detection (SDD) code is proposed. SDD code is constructed using code segment and data segment. One of the important properties of this code is that the cross correlation at data segment is always zero, which means that Phase Intensity Induced Noise (PIIN) is reduced. The simulation results show that the performance of the proposed new code using direct detection technique perform significantly better than other codes employing same spectral amplitude coding technique and, hence, improve the overall system performance.
In this paper, we present a simple empirical model for calculating gain and excess noise in heterojunction GaAs/AlξGa1-ξAs APDs (0.3≤ξ≤0.6), without going through the relatively complicated and time consuming Monte Carlo simulation, commonly used for such devices. In this model, we present a set of empirical formula which can predict a distribution function for ionization path length for a given electric field throughout multiplication region. To determine the optimized values of the adjustable parameters used in our empirical model, we train a back-propagation neural network. The results are in excellent agreement with those obtained by the random path length (RPL) technique.
This paper presents an efficient extended linear convolution interpolation method for efficient scaling. The kernel of the extended linear convolution interpolation is built up of first-order polynomial and approximates the ideal sinc-function in interval [-2, 2]. The approach reduces the computational complexity of interpolation and the interpolation quality is compatible to that of bi-cubic convolution interpolations.
In an environment of fierce noise contamination, infected pixels tend to connect into noise blotches that could give the filtering algorithm an illusion of being part of the original image data. Therefore, many impulses would be difficult to detect, with the consequence of a less chance for proper detection and thus, filtering. Previously, median filters or its variant have been adopted to filter image corrupted with impulsive noise. Although advanced techniques have been added to these filters, many details such as thin lines and edges are either lost or blurred, especially at high noise situation. In this paper, a filtering method that consists of two stages, namely impulse noise detection and noise filtering is proposed, where the two stages are carried out separately and iteratively. Through computer simulation, the effectiveness of the suggested filter has been proven, especially at the high impulse noise levels.
The present study illustrates a new lossless data hiding method for digital images using image prediction technique. In the proposed method which is based on gradient-adjusted prediction (GAP), first prediction errors are computed and then the error values are slightly modified through shifting the prediction errors. The modified errors are used for embedding the data. Experimental results of present research have demonstrated that the proposed method called shifted gradient-adjusted prediction error (SGAPE) is capable of hiding more secret data with absolutely high PSNR.
A new methodology of searching for an effective triplet set for an arithmetic built-in self-test is proposed. The proposed methodology minimizes both the number of triplets and the total test length using an ant colony optimization heuristic that iteratively selects the best triplet according to the fault coverage of each solution. Experimental results on the ISCAS 85 and ISCAS 89 benchmark circuits resulted in a 66.6% average triplet size reduction and a 62.7% average test length reduction compared to previous methodologies.
In this paper, the genetic algorithm (GA) combined with ray tracing (RT) method is employed to simultaneously optimize the boresight error (BSE) and power transmittance of the 3D A-sandwich radome. The thicknesses of the skin and core layer of the radome wall are chosen as the optimal parameters, and minimizing the BSE and maximizing the power transmittance of the antenna-radome system are the objects. A new structure of local uniform thickness radome, which is more easily to be fabricated than the traditional variable thickness one, is proposed for the multi-objective optimization. The BSE of the optimal antenna-radome system is reduced significantly and the power transmittance of the radome is also improved.