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81.
Gallay T Wayne CE 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2002,360(1799):2155-2188
We use the vorticity formulation to study the long-time behaviour of solutions to the Navier-Stokes equation on R(3). We assume that the initial vorticity is small and decays algebraically at infinity. After introducing self-similar variables, we compute the long-time asymptotics of the rescaled vorticity equation up to second order. Each term in the asymptotics is a self-similar divergence-free vector field with Gaussian decay at infinity, and the coefficients in the expansion can be determined by solving a finite system of ordinary differential equations. As a consequence of our results, we are able to characterize the set of solutions for which the velocity field satisfies ||u(.,t)||(L(2)) = o(t(-5/4)) as t-->+ infinity. In particular, we show that these solutions lie on a smooth invariant submanifold of codimension 11 in our function space. 相似文献
82.
We compare the spectral sky radiance measured by three ground-based optical radiometers during the second Aerosol Characterization Experiment (ACE-2) to estimate the total uncertainty of the radiance in field experimental conditions. The propagation of this uncertainty on the column-integrated aerosol single-scattering albedo omega0 at 868 nm is investigated. The radiance measurements are affected by a systematic gain uncertainty of less than 2% in the visible spectral region and within 6% in the near-IR region. Correcting the measured radiance by a systematic uncertainty reduces the dispersion of the omega0 from 0.07 to 0.03. Besides, the total relative uncertainty of the radiance measurements in field experimental conditions is within 4% at any wavelength. The corresponding uncertainty delta omega0 is 4% for an aerosol optical thickness of 0.2. 相似文献
83.
Lenoble J Martin T Blumthaler M Philipona R Albold A Cabot T de La Casinière A Gröbner J Masserot D Müller M Pichler T Seckmeyer G Schmucki D Touré ML Yvon A 《Applied optics》2002,41(9):1629-1639
A measurement campaign was organized in March 1999 in the Bavarian Alps as part of the European project, Characteristics of the UV Radiation Field in the Alps (CUVRA), to analyze the effect of altitude, aerosols, and snow cover on ground-level UV spectral irradiance. We present the results of simultaneous measurements of aerosol optical depth (AOD) made at various sites on two cloudless days in March 1999. The two days exhibited different aerosol conditions. Results derived from spectral measurements of UV irradiance are compared with data from filter radiometer measurements made at discrete wavelengths extending from the UV to the near IR. The different methods generated values for the AOD that were in good agreement. This result confirms that one can use either method to retrieve the AOD with an uncertainty of approximately 0.03-0.05. On 18 March, high turbidity was observed at low altitude (400-nm AOD approximately 0.5 at 700 m above sea level), and the AOD decreased regularly with altitude; on 24 March, the turbidity was much less (0.11 at 700 m above sea level). On both days very low AODs (0.05-0.09) were measured at 3000 m above sea level. The spectral dependence of the AOD is often parameterized by the angstrom relationship; the alpha parameter is generally difficult or impossible to retrieve from spectral measurements because of the relatively narrow wavelength range (320-400 nm), and only one of the spectro-radiometers used during the campaign permits this retrieval. In most cases, during this field campaign, alpha was found by filter sunphotometers to be 1.1-1.5. 相似文献
84.
Thierry Denoeux Philippe Smets 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》2006,36(6):1395-1406
The transferable belief model (TBM) is a model to represent quantified uncertainties based on belief functions, unrelated to any underlying probability model. In this framework, two main approaches to pattern classification have been developed: the TBM model-based classifier, relying on the general Bayesian theorem (GBT), and the TBM case-based classifier, built on the concept of similarity of a pattern to be classified with training patterns. Until now, these two methods seemed unrelated, and their connection with standard classification methods was unclear. This paper shows that both methods actually proceed from the same underlying principle, i.e., the GBT, and that they essentially differ by the nature of the assumed available information. This paper also shows that both methods collapse to a kernel rule in the case of precise and categorical learning data and for certain initial assumptions, and a simple relationship between basic belief assignments produced by the two methods is exhibited in a special case. These results shed new light on the issues of classification and supervised learning in the TBM. They also suggest new research directions and may help users in selecting the most appropriate method for each particular application, depending on the nature of the information at hand. 相似文献
85.
TGV: theory, principles and algorithms 总被引:3,自引:0,他引:3
Claude Jard Thierry Jéron 《International Journal on Software Tools for Technology Transfer (STTT)》2005,7(4):297-315
This paper presents the TGV tool, which allows for the automatic synthesis of conformance test cases from a formal specification of a (non-deterministic) reactive system. TGV was developed by Irisa Rennes and Verimag Grenoble, with the support of the Vasy team of Inria Rhônes-Alpes. The paper describes the main elements of the underlying testing theory, which is based on a model of transitions system which distinguishes inputs, outputs and internal actions, and is based on the concept of conformance relation. The principles of the test synthesis process, as well as the main algorithms, are explained. We then describe the main characteristics of the TGV tool and refer to some industrial experiments that have been conducted to validate the approach. As a conclusion, we describe some ongoing work on test synthesis. 相似文献
86.
Sorghum bicolor is an allelopathic crop that reduces the yield of succeeding crops. We have assessed its effect on the germination, emergence, and seedling growth of Arachis hypogea sown in soil that had had a prior sorghum cropping. A. hypogea was sown on rows and interrows of a previous sorghum crop in 1997 and 1998 in Senegal. Seedling establishment (germination rate and seedling weight) was better between rows than on rows of the previous crop. The highest concentrations of phenolic compounds occurred in the rows in 1998, while contents of row and interrow soils were similar in 1997. Vanillic acid was the main component of the six chemicals found in 1997 soils, whereas the 1998 soil samples contained mainly p-hydroxybenzoic acid, p-hydroxybenzaldehyde, vanillic, and p-coumaric acids (10 phenolics identified). The germination of peanut seeds in water (control), soil water extracts, and mixtures of pure phenolics (equivalent to those in 1997 and 1998 soil samples) was tested. All extracts inhibited germination compared to controls, but there was no significant difference among treatments, i.e., the inhibition was the same for seeds in soil solutions and those in the respective phenolic mixtures. Similarly, there were no significant differences among the germination rates in soil water extracts of rows and interrows or in the pure phenolic mixtures of rows and interrows. We propose a geometrical sowing pattern for peanuts between the rows of the previous sorghum crop to escape the latter's "allelopathic heritage." 相似文献
87.
Thierry Klein Isabelle Joumard Jacques Marcus Robert Cubitt 《Journal of Low Temperature Physics》1999,117(5-6):1353-1357
Small Angle Neutron Scattering has been used to observe diffraction from the flux line lattice in the fully isotropic (K, Ba)BiO
3
high T
c
superconductor. We show that the flux lines are ordered into a hexagonal lattice at low field (H < H
e
0.6T H
g (0) where H
g
is the second order vortex glass transition field). The diffracted intensity continuously drops to zero as the field is increased towards H
e
. Those observations are in good agreement with recent theoritical works which suggested that the formation of dislocations becomes favorable above H
e
leading to a glassy structure. The field H
e
lies close to the onset of the second peak in magnetization measurements indicating that this peak is related to the change in the vortex structure. 相似文献
88.
A new method to obtain the gate coupling ratio (αg) and oxide trapped charge (Qox) as a result of cycling in flash memory cells is described here. Three cells with an equivalent physical structure but different erase characteristics are measured. The threshold changes versus erase times are fitted to the charge removal rate calculated based on Fowler-Nordheim (FN) tunneling and the capacitive relations among all nodes. The extracted αg is independent of technologies and this method is particular useful when the profile of the floating gate is not traditionally rectangular owing to advanced processes such as trapezoidal poly etch or a poly-spacer addition on the floating gate sidewall. The Qox can also be determined once αg is extracted. 相似文献
89.
This paper first presents a groupware service and an associated protocol that manage the dynamic membership of agents inside cooperative groups and second gives the design methodology that has been used for defining the service and the protocol. The model used to represent cooperative groups is based on graphs that give the knowledge relationships between agents and define the dynamics of the group. The protocol providing the membership service is specified using the VAL formal specification environment based on a Petri net formalism. The VAL specification is verified using observational and safety projections derived from the reachability graph. Then the VAL specification is translated and adapted to an Estelle specification. The Estelle specification has been used for a final implementation of the protocol on top of a distributed platform. 相似文献
90.
The regulatory role of soluble cytokines in innate cellular immune responses induced by Pneumocystis carinii was assessed in vitro in direct comparison to induction by Listeria monocytogenes. This report shows that P. carinii organisms, as well as L. monocytogenes, stimulated in whole spleen cell cultures of SCID mice the release of IFN-gamma, TNF-alpha/beta, IL-10, IL-12, and iNO. This response was independent of functional T cells. Both macrophages (M phi) and natural killer (NK) cells were necessary for either microorganism to induce release of these cytokines. Cocultures of purified M phi--including alveolar M phi--and purified NK cells indicated that no other cell population was necessarily involved. Microbial induction of NK cell-derived IFN-gamma has been reported to be mediated by the combined effects of TNF-alpha and IL-12 released by M phi upon adequate microbial stimulation. Interestingly, only L. monocytogenes, but not P. carinii organisms could directly induce detectable amounts of TNF-alpha/beta, IL-12, or iNO in purified M phi cultures. In dose-response experiments, release of IFN-gamma, TNF-alpha/beta, and iNO was reduced at high relative concentrations of either microorganism. This high-dose suppression was at least partially controlled by M phi-produced IL-10. Our data show that, P. carinii potently induces activating and inhibitory innate cellular immune response mechanisms and indicate that the initial step of macrophage-mediated NK cell activation might also involve other pathways than those described to date. 相似文献