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111.
Braconnier A Broussolle V Dargaignaratz C Nguyen-The C Carlin F 《Journal of food protection》2003,66(5):833-839
The growth of proteolytic Clostridium botulinum from spore inocula and changes in spore counts in mushroom, broccoli, and potato purées were monitored. Four strains of proteolytic C. botulinum types A and B were inoculated separately at approximately 10(4) spores per ml in nutrient broth and vegetable purées incubated at 15, 20, and 30 degrees C for up to 52 days. The times for the cell populations to increase 1,000-fold (T1,000) in the tested vegetables (1 to 5 days at 30 degrees C, 3 to 16 days at 20 degrees C, 7 to > 52 days at 15 degrees C) were similar to those for meat or fish. Only temperature significantly influenced growth rate. In contrast, the lag phase depended on the strains and media tested, in addition to temperature. Lag times and T1,000S for proteolytic C. botulinum were longer for potato and broccoli purées than for mushroom purée. These differences were not related to different pHs or redox potentials. The germination level, evaluated as the decrease in the spore count, was low. The addition of a germinant mixture (L-cysteine, L-alanine, and sodium lactate) to some strains inoculated in vegetable purées resulted in an increase in germination, suggesting a lack of germination-triggering agents in the vegetable purées. 相似文献
112.
Human exposure to electromagnetic fields emitted by mobile phones is characterised by the Specific Absorption Rate (sar). This value corresponds to therf power absorbed by unitary mass of the equivalent tissue. It represents the basic restriction used to define limit of human exposure torf electromagnetic fields. Academic and industrial labs have contributed through thecomobio project to define international standards for mobile phones certification. 相似文献
113.
Free-Sets: A Condensed Representation of Boolean Data for the Approximation of Frequency Queries 总被引:5,自引:4,他引:1
Jean-François Boulicaut Artur Bykowski Christophe Rigotti 《Data mining and knowledge discovery》2003,7(1):5-22
Given a large collection of transactions containing items, a basic common data mining problem is to extract the so-called frequent itemsets (i.e., sets of items appearing in at least a given number of transactions). In this paper, we propose a structure called free-sets, from which we can approximate any itemset support (i.e., the number of transactions containing the itemset) and we formalize this notion in the framework of -adequate representations (H. Mannila and H. Toivonen, 1996. In Proc. of the Second International Conference on Knowledge Discovery and Data Mining (KDD'96), pp. 189–194). We show that frequent free-sets can be efficiently extracted using pruning strategies developed for frequent itemset discovery, and that they can be used to approximate the support of any frequent itemset. Experiments on real dense data sets show a significant reduction of the size of the output when compared with standard frequent itemset extraction. Furthermore, the experiments show that the extraction of frequent free-sets is still possible when the extraction of frequent itemsets becomes intractable, and that the supports of the frequent free-sets can be used to approximate very closely the supports of the frequent itemsets. Finally, we consider the effect of this approximation on association rules (a popular kind of patterns that can be derived from frequent itemsets) and show that the corresponding errors remain very low in practice. 相似文献
114.
Christophe Berthon Pierre Charrier Bruno Dubroca 《Journal of scientific computing》2007,31(3):347-389
The M
1 radiative transfer model is considered in the present work in order to simulate the radiative fields and their interactions
with the matter. The model is governed by an hyperbolic system of conservation laws supplemented by relaxation source terms.
Several difficulties arise when approximating the solutions of the model; namely the positiveness of the energy, the flux
limitation and and the limit diffusion behavior have to be satisfied. An HLLC scheme is exhibited and it is shown to satisfy
all the required properties. A particular attention is payed concerning the approximate extreme waves. These approximations
are crucial to obtain an accurate scheme. The extension to the full 2D problem is proposed. It satisfies, once again, all
the expected properties. Numerical experiments are proposed. They show that the considered scheme is actually less diffusive
than the currently used numerical methods.
相似文献
115.
Christophe Serra Guy Schlatter Nicolas Sary Friedhelm Schönfeld Georges Hadziioannou 《Microfluidics and nanofluidics》2007,3(4):451-461
This paper investigates the modeling of styrene free radical polymerization in two different types of microreactor. A multiphysics
model which simultaneously takes into account the hydrodynamics, thermal and mass transfer (convection, diffusion and chemical
reaction) is proposed. The set of partial differential equations resulting from the model is solved with the help of the finite
elements method either in a 2D or a 3D approach. The different modeled microreactors are on one hand an interdigital multilamination
microreactor with a large focusing section, and on the other hand a simple T-junction followed by a straight tube with three
different radii. The results are expressed in terms of reactor temperature, polydispersity index, number-average degree of
polymerization and monomer conversion for different values of the chemical species diffusion coefficient. It was found that
the 2D approach gives the same results as the 3D approach but allows to dramatically reduce the computing time. Despite the
heat released by the polymerization reaction, it was found that the thermal transfer in such microfluidic devices is high
enough to ensure isothermal conditions. Concerning the polydispersity index, the range of diffusion coefficients over which
the polydispersity index can be maintained close to the theoretical value for ideal conditions increases as the tube reactor
radius decreases. The interdigital multilamination microreactor was found to act as a tubular reactor of 0.78 mm ID but with
a shorter length. This underlines that the use of microfluidic devices can lead to a better control of polymerization reactions. 相似文献
116.
Trimmed bagging 总被引:1,自引:0,他引:1
Bagging has been found to be successful in increasing the predictive performance of unstable classifiers. Bagging draws bootstrap samples from the training sample, applies the classifier to each bootstrap sample, and then averages over all obtained classification rules. The idea of trimmed bagging is to exclude the bootstrapped classification rules that yield the highest error rates, as estimated by the out-of-bag error rate, and to aggregate over the remaining ones. In this note we explore the potential benefits of trimmed bagging. On the basis of numerical experiments, we conclude that trimmed bagging performs comparably to standard bagging when applied to unstable classifiers as decision trees, but yields better results when applied to more stable base classifiers, like support vector machines. 相似文献
117.
Opto-electronic properties of rough LP-CVD ZnO:B for use as TCO in thin-film silicon solar cells 总被引:1,自引:0,他引:1
Sylvie Faÿ Jérôme Steinhauser Nuno Oliveira Evelyne Vallat-Sauvain Christophe Ballif 《Thin solid films》2007,515(24):8558-8561
Polycrystalline Boron-doped ZnO films deposited by low pressure chemical vapor deposition technique are developed for their use as transparent contacts for thin-film silicon solar cells. The size of the columnar grains that constitute the ZnO films is related to their light scattering capability, which has a direct influence on the current generation in thin-film silicon solar cells. Furthermore, if the doping level of the ZnO films is kept below 1 × 1020 cm− 3, the electron mobility can be drastically enhanced by growing large grains, and the free carrier absorption is reduced. All these considerations have been taken in account to develop ZnO films finely optimized for the fabrication of microcrystalline thin-film silicon solar cells. These TCO allow the achievement of solar cell conversion efficiencies close to 10%. 相似文献
118.
This paper presents a new circuit architecture for turbo decoding, which achieves ultra high data rates when using product codes as error correcting codes. This architecture is able to decode product codes using binary BCH or m-ary Reed Solomon component codes. The major advantage of our full-parallel architecture is that it enables the memory block between each half-iteration to be removed. In fact, the proposed architecture opens the way to numerous applications such as optical transmission. In particular, our block turbo decoding architecture can support optical transmission at data rates above Gbit/s 相似文献
119.
Pierre Dupont Bernard Lambeau Christophe Damas Axel van Lamsweerde 《Applied Artificial Intelligence》2013,27(1-2):77-115
This article presents a novel application of grammatical inference techniques to the synthesis of behavior models of software systems. This synthesis is used for the elicitation of software requirements. This problem is formulated as a deterministic finite-state automaton induction problem from positive and negative scenarios provided by an end user of the software-to-be. A query-driven state merging (QSM) algorithm is proposed. It extends the Regular Positive and Negative Inference (RPNI) and blue-fringe algorithms by allowing membership queries to be submitted to the end user. State merging operations can be further constrained by some prior domain knowledge formulated as fluents, goals, domain properties, and models of external software components. The incorporation of domain knowledge both reduces the number of queries and guarantees that the induced model is consistent with such knowledge. The proposed techniques are implemented in the ISIS tool and practical evaluations on standard requirements engineering test cases and synthetic data illustrate the interest of this approach. 相似文献
120.
Asma Adnane Christophe Bidan Rafael Timóteo de Sousa Júnior 《Computer Communications》2013,36(10-11):1159-1171
The trust is always present implicitly in the protocols based on cooperation, in particular, between the entities involved in routing operations in Ad hoc networks. Indeed, as the wireless range of such nodes is limited, the nodes mutually cooperate with their neighbors in order to extend the remote nodes and the entire network. In our work, we are interested by trust as security solution for OLSR protocol. This approach fits particularly with characteristics of ad hoc networks. Moreover, the explicit trust management allows entities to reason with and about trust, and to take decisions regarding other entities.In this paper, we detail the techniques and the contributions in trust-based security in OLSR. We present trust-based analysis of the OLSR protocol using trust specification language, and we show how trust-based reasoning can allow each node to evaluate the behavior of the other nodes. After the detection of misbehaving nodes, we propose solutions of prevention and countermeasures to resolve the situations of inconsistency, and counter the malicious nodes. We demonstrate the effectiveness of our solution taking different simulated attacks scenarios. Our approach brings few modifications and is still compatible with the bare OLSR. 相似文献