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1.
We consider retrial queueing systems, in which an arriving customer finding the server busy, may repeat his call after a random duration. The consideration of repeated calls introduces great analytical difficulties. In fact, detailed analytical results exist for some special retrial queueing systems, while for many others, the performance evaluation is limited to numerical algorithms, approximation methods and simulation. Retrial queues have been widely used to model many problems in telephone switching systems, telecommunication and computer networks. In this paper, we show a method of modelling and analysing retrial queueing systems, using the Generalized Stochastic Petri nets (GSPNs). 相似文献
2.
Chadeau-Hyam M Tard A Bird S Le Guennec S Bemrah N Volatier JL Alpérovitch A 《Statistical methods in medical research》2003,12(3):247-260
Assuming that human exposure to BSE was through beef mechanically recovered meat (MRM) consumed as burgers and other meat products, we estimated the French consumption of different food items containing beef MRM, and compared these consumptions for French and British populations. To estimate consumption of meat products containing bovine MRM, we used dietary data from national individual and household food surveys conducted between 1980 and 1995. After reconciliation of consumption data between the available surveys and calendar year adjustments, we simulated consumption of one-thousandth of the French population. Consumption was estimated by birth cohort and gender, and for the periods 1980-89 and 1990-95 separately. Data showed that burgers (including manufactured minced meat) represented around 75-80% of the individual consumption of meat products containing MRM, and that consumption of burgers increased by 40% over the 1980-95 period. In all age groups, consumption was higher in males than in females. In both genders, the 1940-69 birth cohort had the highest mean consumption of burgers and other beef products containing MRM. Similar findings have been reported for the UK population. Estimated consumption of bovine MRM per calendar year increased markedly over the study period, concomitantly with an increase of bovine carcasses imported from the UK. Comparison of the 1980-1995 pattern of bovine MRM consumption in the UK and France indicated thatthis consumption peaked later in France than in the UK. This difference might result in different temporal pattern of vCJD incidence. 相似文献
3.
Nawel Achir Verohanitra A. Randrianatoandro Philippe Bohuon Andréina Laffargue Sylvie Avallone 《European Journal of Lipid Science and Technology》2010,112(3):349-361
The kinetics of trans‐β‐carotene and trans‐lutein degradation were individually investigated in palm olein and Vegetaline®, at four temperatures ranging from 120 to 180 °C. HPLC‐DAD analysis was carried out to monitor trans and cis carotenoid variations over the heating time at each temperature. In both oils, initial trans‐β‐carotene and trans‐lutein degradation rates increased with temperature. Trans‐lutein was found to degrade at a slower rate than trans‐β‐carotene, suggesting a higher thermal resistance. The isomers identified were 13‐cis‐ and 9‐cis‐β‐carotene, and 13‐cis‐, 9‐cis‐, 13'‐cis‐, and 9'‐cis‐lutein. In spite of the higher number of lutein cis isomers, their total amount was lower than that of β‐carotene cis isomers. Trans and cis carotenoids were involved in degradation reactions at rates that increased with temperature. All degradation rates were generally found to be lower in Vegetaline® than in palm olein. These results were explained by the initial composition of the two oils and especially their peroxide and vitamin E contents. 相似文献
4.
Guzmán E Ortega F Baghdadli N Cazeneuve C Luengo GS Rubio RG 《ACS applied materials & interfaces》2011,3(8):3181-3188
The adsorption processes of polymers that belong to two different families (neutral hydrophilic polymers and cationic polysaccharide polymers) onto solid surfaces with different charge density have been studied using dissipative quartz crystal microbalance (D-QCM) and ellipsometry. The polymers studied are very frequently used in the cosmetic industry as conditioning agents. The adsorption kinetics of the polymers involves at least two steps. The total adsorbed amount depends on the charge density of the surface for both types of polymers. The comparison of the adsorbed mass on each layer obtained from D-QCM and from ellipsometry has allowed calculating the water content of the layers that reaches high values for the polymers studied. The analysis of D-QCM results also provided information about the shear modulus of the layers, whose values have been found to be typical of a rubber-like polymer system. The main driving force of the adsorption was found to be the energy of the interactions between chains and surface. 相似文献
5.
Novel hybrid DNN approaches for speaker verification in emotional and stressful talking environments
Shahin Ismail Nassif Ali Bou Nemmour Nawel Elnagar Ashraf Alhudhaif Adi Polat Kemal 《Neural computing & applications》2021,33(23):16033-16055
Neural Computing and Applications - In this work, we conducted an empirical comparative study of the performance of text-independent speaker verification in emotional and stressful environments.... 相似文献
6.
Boufenneche Yassine Zitouni Rafik George Laurent Gharbi Nawel 《Wireless Networks》2021,27(6):3927-3946
Wireless Networks - Performance and communication security in the Internet of Things (IoT) area draw a major concern for both academic and industrial communities. Indeed, an emerging number of IoT... 相似文献
7.
Barry Stidder Jean‐Pierre Alcaraz Lavinia Liguori Nawel Khalef Aziz Bakri Erik B. Watkins Philippe Cinquin Donald K. Martin 《Advanced functional materials》2012,22(20):4259-4267
A simple way to form an interpenetrating hydrogel (IPH) by combining a layer‐by‐layer polyelectrolyte membrane with agarose is reported. The formed IPH membrane is more robust and easily manipulated compared to a polyelectrolyte membrane with the same number of layers. The IPH has good diffusion characteristics and retains the advantageous surface charge from the polyectrolyte composition that facilitates the adsorption of a stable lipid bilayer. The stable adsorption of a lipid bilayer on the IPH creates a biomimetic membrane system that is optimized for utilization in a diffusion chamber. 相似文献
8.
Nawel Achir Caroline Pénicaud Aurélie Bechoff Renaud Boulanger Manuel Dornier Claudie Dhuique-Mayer 《Food and Bioprocess Technology》2014,7(6):1656-1669
In order to give insight into β-carotene degradation mechanism during the storage of dried orange-fleshed sweet potato, and particularly into the role of isomers and norisoprenoids formation, multi-response kinetic modelling was applied. Determination of degradation compounds were carried out by HPLD-DAD and SPME-GC-MS as a function of time between 10 and 40 °C and at four water activities from 0.13 to 0.76. Kinetic modelling was developed assuming first-order reactions and by using mass balance. Eight compounds, namely, two isomers (9-cis- and 13-cis-β-carotene), two β-carotene epoxides (β-carotene 5,6 and 5,8 epoxide) and four volatile compounds (β-cyclocitral, β-ionone, 5,6-epoxy-β-ionone and dihydroactinidiolide), were integrated into two theoretical reaction schemes. The different models were discriminated according to goodness of fit to experimental data. This work showed that: (1) the formation of cis-isomers from β-carotene preceded oxidation, (2) β-cyclocitral arose directly from β-carotene scission while the other norisoprenoids resulted from β-carotene epoxide degradation, (3) cis-isomers were high reactive compounds. Temperature had a major influence on reaction rates k while water activities only impacted k at values under 0.51. Therefore, multi-response modelling is not only a tool to predict β-carotene degradation but a interesting way to select the appropriate degradation scheme based on the different options presented in literature. 相似文献
9.
Nawel Achir Caroline Pénicaud Sylvie Avallone Philippe Bohuon 《Journal of the American Oil Chemists' Society》2011,88(12):2035-2045
The aim of this study was to gain further insight into β-carotene thermal degradation in oils. Multiresponse modeling was
applied to experimental high-performance liquid chromatography–diode array detection (HPLC–DAD) data (trans-, 13-cis-, and 9-cis-β-carotene concentrations) during the heat treatments (120–180 °C) of two β-carotene-enriched oils, i.e., palm olein and
copra. The test of different reaction schemes showed that β-carotene isomerization reactions were dominant and reversible.
The resulting cis isomers and trans-β-carotene simultaneously underwent oxidation and cleavage reactions at the same rate constant. From the kinetic analysis,
it appeared that—contrary to oxidation and cleavage reactions—isomerization rate constants did not follow the Arrhenius law.
However, the isomerization equilibrium constant increased with temperature, favoring isomer production, particularly 9-cis-β-carotene. Its production was shown to be concomitant with oxidation and cleavage reactions, indicating that 9-cis-β-carotene could be a good degradation indicator during oil storage or processing. 相似文献
10.
We propose a game-theoretic model involving the manufacturer of a national brand and a retailer selling her private label
along with the national brand. The retailer can use either a differentiation strategy or an imitation strategy for offering
her store brand. We consider two cases: the benchmark case, where both players have symmetric information and play a Nash
game, and the incentive case, where the national brand’s manufacturer, acting as a leader, offers an incentive to the retailer
in order to benefit from a larger proportion of the shelf space, which ultimately increases her own profit. By comparing both
situations, we attempt to derive the conditions under which it is profitable for the manufacturer to implement such an incentive
strategy and investigate if the results are idiosyncratic to the PL concept. These conditions are fourfold, and include the
private label’s image, the price competition between the national brand and the private label, the transfer price level and
the shelf-space allocated to the national brand in the benchmark case. 相似文献