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排序方式: 共有89条查询结果,搜索用时 62 毫秒
1.
Reducing the complexity of distance measurement methods for circular turbo codes that use structured interleavers
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Youssouf Ould‐Cheikh‐Mouhamedou 《International Journal of Communication Systems》2015,28(9):1572-1579
The knowledge of turbo code's minimum Hamming distance (dmin) and its corresponding codeword multiplicity (Amin) is of a great importance because the error correction capability of a code is strongly tied to the values of dmin and Amin. Unfortunately, the computational complexity associated with the search for dmin and Amin can be very high, especially for a turbo code that has high dmin value. This paper introduces some useful properties of turbo codes that use structured interleavers together with circular encoding. These properties allow for a significant reduction of search space and thus reduce significantly the computational complexity associated with the determination of dmin and Amin values. © 2014 The Authors. International Journal of Communication Systems published by John Wiley & Sons, Ltd. 相似文献
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Mostafa Moussaid Stphane Caillet Josphine Nketsia‐Tabiri Cheikh Boubekri Monique Lacroix 《Journal of the science of food and agriculture》2004,84(13):1657-1662
The study evaluated the effects of waxing, irradiation dose and post‐irradiation storage time on the essential oils in orange peel. Mature oranges (Maroc late) waxed or unwaxed were treated with 1 or 2 kGy radiation and stored for 9 weeks at 20 °C and 40–50% RH. Essential oils from the peel were extracted and analysed by GC. Results showed that D ‐limonene was significantly lower in waxed oranges; levels in samples treated with 2 kGy were higher than those in non‐irradiated or treated with 1 kGy. Linalool, methyl anthranilate and 3,7‐dimethyl‐2,6‐octadienal decreased as the dose increased. Levels of linalool increased with storage time but D ‐limonene was unaffected. These results may aid in guaranteeing the quality of orange essential oils during storage time. Copyright © 2004 Society of Chemical Industry 相似文献
5.
Influence of thermal boundary conditions on natural convection in a square enclosure partially heated from below 总被引:1,自引:0,他引:1
Nader Ben Cheikh Brahim Ben BeyaTaieb Lili 《International Communications in Heat and Mass Transfer》2007
Natural convection in air-filled 2D square enclosure heated with a constant source from below and cooled from above is studied numerically for a variety of thermal boundary conditions at the top and sidewalls. Simulations are performed for two kinds of lengths of the heated source, i.e., a small and a large source corresponding to 20% and 80% of the total length of the bottom wall, respectively. The Rayleigh number varied from 103 to 107. Results are presented in the form of streamline and isotherm plots as well as the variation of the Nusselt number and maximum temperature at the heat source surface. Comparisons among the different thermal configurations considered are reported. 相似文献
6.
The kinetics of non-congruent dissolution of long E-glass fiber in saturated calcium hydroxide solution has been investigated at 25°C in a closed reactor adopting the rotating disc method for the sample holder. The fiber dissolution rate (), measured from the relative loss weight of the fiber after selective dissolution of the attack layer in acetic acid, is a linear function of time, what implies an interfacial dissolution process. However, the kinetics does not stay regular for a long time due to local detachment of the attack layer. The comparison between = f (t) and ′ = f (t) curves, where ′ is the formation rate of the attack layer, shows that the formation of the layer does not only imply the deposit of a bad-crystalline hydrated calcium silicate but the nucleation and growth of solid calcium hydroxide and calcium carbonate resulting from the transfert, to the interface, of ions coming from the liquid phase. This phenomenon was precedently observed by some other authors in the case of glass-fiber reinforced cement matrix. 相似文献
7.
H. Ben Ameur G. Chavent F. Cheikh V. Martin J. E. Roberts 《Inverse Problems in Science & Engineering》2018,26(1):1-32
Faults and geological barriers can drastically affect the flow patterns in porous media. Such fractures can be modelled as interfaces that interact with the surrounding matrix. We propose a new technique for the estimation of the location and hydrogeological properties of a small number of large fractures in a porous medium from given distributed pressure or flow data. At each iteration, the algorithm builds a short list of candidates by comparing fracture indicators. These indicators quantify at the first order the decrease of a data misfit function; they are cheap to compute. Then, the best candidate is picked up by minimization of the objective function for each candidate. Optimally driven by the fit to the data, the approach has the great advantage of not requiring remeshing, nor shape derivation. The stability of the algorithm is shown on a series of numerical examples representative of typical situations. 相似文献
8.
Bart Goethals Dominique Laurent Wim Le Page Cheikh Tidiane Dieng 《Knowledge and Information Systems》2012,33(3):655-684
We present an approach for mining frequent conjunctive in arbitrary relational databases. Our pattern class is the simple, but appealing subclass of simple conjunctive queries. Our algorithm, called Conqueror $^+$ , is capable of detecting previously unknown functional and inclusion dependencies that hold on the database relations as well as on joins of relations. These newly detected dependencies are then used to prune redundant queries. We propose an efficient database-oriented implementation of our algorithm using SQL and provide several promising experimental results. 相似文献
9.
This paper presents an intelligent control method for the maximum power point tracking (MPPT) of a photovoltaic system under variable temperature and irradiance conditions. First, for the purpose of comparison and because of its proven and good performances, the perturbation and observation (P&O) technique is briefly introduced. A fuzzy logic controller based MPPT (FLC) is then proposed which has shown better performances compared to the P&O MPPT based approach. The proposed FLC has been also improved using genetic algorithms (GA) for optimisation. Different development stages are presented and the optimized fuzzy logic MPPT controller (OFLC) is then simulated and evaluated, which has shown better performances. 相似文献
10.
M. Ben Abderrahmane R. Ben Cheikh 《Surface Engineering and Applied Electrochemistry》2008,44(6):484-488
Cyanoethylation of long alfa fibers was studied, and these chemically modified fibers were used to manufacture alfa-polyester
composites. The dynamic mechanical thermal properties of an unsaturated polyester resin (cured) and of composites of unmodified
and chemically modified alfa-polyester were studied using a dynamic mechanical analyzer over a wide temperature range. The
data suggest that in spite of the fragility of the cyanoethylated alfa fibers compared to the unmodified ones, both unmodified
and modified alfa-polyester composites manifest the same order of mechanical properties: Tg, tan δ and E′ values are very near in the two cases. Fragility of fibers is compensated by the better interfacial bond between
the fibers and the matrix. The scanning electron micrographs of the fracture surface of the samples reveal the improved bonding
at the interface between the cyanoethylated fiber and the polyester resin.
The article is published in the original. 相似文献