A Monte Carlo estimation of the marginal distributions in a problem of probabilistic dynamics

Modelling the effect of the dynamic behaviour of a system on its PSA study leads, in a Markovian framework, to a development at first order of the Chapman-Kolmogorov equation, whose solutions are the probability densities of the problem. Because of its size, there is no hope of solving directly these equations in realistic circumstances. We present in this paper a biased simulation giving the marginals and compare different ways of speeding up the integration of the equations of the dynamics.     

A channel differential EZW coding scheme for EEG data compression

In this paper, a method is proposed to compress multichannel electroencephalographic (EEG) signals in a scalable fashion. Correlation between EEG channels is exploited through clustering using a k-means method. Representative channels for each of the clusters are encoded individually while other channels are encoded differentially, i.e., with respect to their respective cluster representatives. The compression is performed using the embedded zero-tree wavelet encoding adapted to 1-D signals. Simulations show that the scalable features of the scheme lead to a flexible quality/rate tradeoff, without requiring detailed EEG signal modeling.     

Reference frame modification techniques for temporal and spatial scalability

Compressed video is usually transmitted over channels which are not necessarily error free. Channel errors can result in a mismatch between the encoder and the decoder, and because of the predictive structures used in video coding, the errors will propagate both temporally and spatially. Consequently, the quality of the received video at the decoder may degrade significantly. In order to improve the quality of the received video, several error resilient methods have been proposed. In this paper, the introduced mismatch is reduced by modifying the prediction structure and forming a more robust reference frame. The proposed technique combines error robustness of previous Intra coded blocks, better prediction achieved using the previous reference frame, and exponential decay of error propagation caused by the leaky prediction. This technique was examined with the scalable extension of H.264/AVC. Furthermore, the technique was also used in combination with random Intra refresh and error resilience mode decision techniques to achieve better robustness. Simulation results show the effectiveness of our scheme, especially for medium and high motion sequences.     

Sol–gel processing and UVA patterning of epoxy-based hybrid organic–inorganic thin films

Sol–gel processed photosensitive hybrid organic–inorganic films, deposited from 2-(3,4-epoxycyclohexylethyltrimethoxysilane) (EETMOS), have been studied. EETMOS sols have been optimized with respect to several criteria that guarantee a good quality, photosensitivity, and reproducibility of derived films. Photo-sensitivity of EETMOS-based films has been assessed by UVA exposure experiments. Optimized films have been photo-patterned using a mercury lamp or a He–Cd laser source, both emitting in the UVA spectral range. Promising micronic size motives have been laser patterned. The quality of derived motives is discussed with respect to photopolymerization mechanisms and photo-patterning parameters.     

The electrical conductivity of polycrystalline SnO2(Cu) films and their sensitivity to hydrogen sulfide

The effect of doping with copper on the sensor properties and the electrical conductivity of polycrystalline SnO₂(Cu) films has been investigated. It has been found that at room temperature the residual conductivity is observed after the films are exposed to H₂S. This made it possible to determine the character of the low-temperature conductivity of the films for different degrees of saturation with hydrogen sulfide. A comparison of the obtained data with the results of layerwise elemental analysis suggested a model that explains the mechanism of the gas sensitivity of SnO₂(Cu) to hydrogen sulfide. In contrast to the mechanisms, which are associated with the work done by the surface and which are standard for gas sensors, in the present case the change in the conductivity is due to the chemical reaction of the electrically active copper with sulfur in the entire volume of the film. This reaction determines the selectivity and high sensitivity of SnO₂(Cu) to H₂S. Fiz. Tekh. Poluprovodn. 31, 400–404 (April 1997)     

Maintenance and replacement policies under technological obsolescence

The technological obsolescence of a unit is characterized by the existence of challenger units displaying identical functionalities, but with higher performances. This paper aims to define and model in a realistic way, possible maintenance policies of a system including replacement strategies when one type of challenger unit is available. The comparison of these possible strategies is performed based on a Monte Carlo estimation of the costs they incur.     

Complexity Reduction in SISO Decoding of Block Codes

SISO decoding for block codes can be carried out based on a trellis representation of the code. However, the complexity entailed by such decoding is most often prohibitive and thus prevents practical implementation. This paper examines a new decoding scheme based on the soft-output Viterbi algorithm (SOVA) applied to a sectionalized trellis for linear block codes. The computational complexities of the new SOVA decoder and of the conventional SOVA decoder, based on a bit-level trellis, are theoretically analyzed and derived for different linear block codes. These results are used to obtain optimum sectionalizations of a trellis for SOVA. For comparisons, the optimum sectionalizations for Maximum A Posteriori (MAP) and Maximum Logarithm MAP (Max-Log-MAP) algorithms, and their corresponding computational complexities are included. The results confirm that the new SOVA decoder is the most computationally efficient SISO decoder, in comparisons to MAP and Max-Log-MAP algorithms. The simulation results of the bit error rate (BER) performance, assuming binary phase -- shift keying (BPSK) and additive white Gaussian noise (AWGN) channel, demonstrate that the performance of the new decoding scheme is not degraded. The BER performance of iterative SOVA decoding of serially concatenated block codes shows no difference in the quality of the soft outputs of the new decoding scheme and of the conventional SOVA.