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排序方式: 共有139条查询结果,搜索用时 15 毫秒
91.
92.
Rodolphe Sardeing 《Chemical engineering science》2006,61(19):6249-6260
This paper focuses on the effect of surfactants on the mass transfer parameters (volumetric mass transfer coefficient kLa and liquid-side mass transfer coefficient kL). Tap water and aqueous solutions with surfactants (anionic, cationic and non-ionic at concentrations up to are used as liquid phases. The bubbles are generated into a small-scale bubble column having an elastic membrane with a single orifice as gas sparger. To understand the effects of the surfactants on the mass transfer, not only the static surface tension is used, but also the characteristic adsorption parameters like the surface coverage ratio at equilibrium Se. The liquid-side mass transfer coefficient is obtained from the ratio of the volumetric mass transfer coefficient (measured by a chemical method) and the specific interfacial area. These two parameters are obtained simultaneously. The methods used to obtain these parameters are described in Painmanakul et al. [2005. Effects of surfactants on liquid-side mass transfer coefficients. Chemical Engineering Science 60, 6480-6491].Whatever the liquid phase, three zones are found on the liquid-side mass transfer coefficient variation with the bubble diameter. For bubble diameters less than 1.5 mm, whatever the liquid phases, the kL values are roughly constant at . For bubble diameters greater than 3.5 mm, the kL values do not vary much with the bubble diameter, but depend on the surfactant concentration. For bubble diameters between 1.5 and 3.5 mm, the kL values increase from to the value reached at 3.5 mm. This increase depends on the surfactants. Higbie's model does not represent the kL values for bubble diameters greater than 3.5 mm, even though there is a small amount of surfactant in the liquid phase. Thus, a model is proposed for each zone described above. Explanations are also proposed for the effect of the surfactant on the kL values for each of the above zones. 相似文献
93.
Garnier-Laplace J Della-Vedova C Gilbin R Copplestone D Hingston J Ciffroy P 《Environmental science & technology》2006,40(20):6498-6505
The FASSET Radiation Effects Database (FRED) constitutes a unique structured resource of the biological effects of ionizing radiation on non-human species mainly from temperate ecosystems, encompassing 26,000 primary data entries. Quality-assessed data were extracted from FRED and dose-effect relationships were constructed to provide estimates of ED50 and EDR10. These estimates are Doses (or Dose Rates) related to the percent change in the average level of the endpoint for a particular effect (50% or 10% for acute or chronic exposure regimes, respectively). Acute and chronic Species Sensitivity Distributions (SSDs) were built on the basis of these data sets, and the Assessment Factor Method (AFM) was applied when data were too scarce. The Hazardous Dose corresponding to 5% of species acutely affected at the 50% effect level varied from 1 to 5.5 Gy according to the ecosystem. For chronic gamma external irradiation exposure, no-effect values varied from 10 microGy/h for freshwaters through application of the AFM to 67 microGy/h for terrestrial ecosystems, corresponding to the 5th percentile of the non-weighted SSD (vs 229 microGy/h when trophic weights are applied). These values are higher by ca. x50 to x100 than the upper bound of natural background, and lower than dose rates triggering effects at individual levels on contaminated sites. 相似文献
94.
David Gaudrie Rodolphe Le Riche Victor Picheny Benot Enaux Vincent Herbert 《Structural and Multidisciplinary Optimization》2020,61(6):2343-2361
Parametric shape optimization aims at minimizing an objective function f(x) where x are CAD parameters. This task is difficult when f(⋅) is the outpu 相似文献
95.
Mohamed Ghattassi Jean Rodolphe Roche Didier Schmitt 《Computers & Mathematics with Applications》2018,75(11):3918-3928
This paper deals with existence and uniqueness results for a transient nonlinear radiative–conductive system in three-dimensional case. This system describes the heat transfer for a grey, semi-transparent and non-scattering medium with general boundary conditions. We reformulate the full transient state system as a fixed-point problem. The existence and uniqueness proof is based on Banach fixed point theorem. 相似文献
96.
Zhang W Xu Z Lours M Boudot R Kersalé Y Luiten AN Le Coq Y Santarelli G 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2011,58(5):900-908
We report what we believe to be the lowest phase noise optical-to-microwave frequency division using fiber-based femtosecond optical frequency combs: a residual phase noise of -120 dBc/Hz at 1 Hz offset from an 11.55 GHz carrier frequency. Furthermore, we report a detailed investigation into the fundamental noise sources which affect the division process itself. Two frequency combs with quasi-identical configurations are referenced to a common ultrastable cavity laser source. To identify each of the limiting effects, we implement an ultra-low noise carrier-suppression measurement system, which avoids the detection and amplification noise of more conventional techniques. This technique suppresses these unwanted sources of noise to very low levels. In the Fourier frequency range of ~200 Hz to 100 kHz, a feed-forward technique based on a voltage-controlled phase shifter delivers a further noise reduction of 10 dB. For lower Fourier frequencies, optical power stabilization is implemented to reduce the relative intensity noise which causes unwanted phase noise through power-to-phase conversion in the detector. We implement and compare two possible control schemes based on an acousto-optical modulator and comb pump current. We also present wideband measurements of the relative intensity noise of the fiber comb. 相似文献
97.
Dissolved and bioavailable contaminants in the Seine river basin 总被引:2,自引:0,他引:2
Tusseau-Vuillemin MH Gourlay C Lorgeoux C Mouchel JM Buzier R Gilbin R Seidel JL Elbaz-Poulichet F 《The Science of the total environment》2007,375(1-3):244-256
Diffusive Gradient in Thin Films (DGT) and Semi-Permeable Membrane Devices (SPMDs) were deployed in the Seine river basin in order to assess labile metals and truly dissolved Polycyclic Aromatic Hydrocarbons. We show that the tools are reliable in aquatic environments to assess the speciation of dissolved contaminants and hence provide a good insight into the potential bioavailability of contaminants. The deployment of the DGT and SPMDs in contrasting environments in the Seine river basin allowed distinction to be made of availability of contaminants between headwater streams and much more impacted river reaches and an assessment of bioavailability. At the stations under urban influence, the impact of dissolved organic matter on both copper and PAHs bioavailability is less pronounced than at upstream stations, where humic substances dominate. 相似文献
98.
Lin Zhu Nannan Zhang Baicheng Zhang Rodolphe Bolot Hanlin Liao Christian Coddet 《Journal of Thermal Spray Technology》2013,22(2-3):90-95
With the purpose of elaborating high-quality FeAl coatings, a so-called very low pressure reactive plasma spray technique that combines very low pressure plasma spray and self-propagation high-temperature synthesis processes was used in the present study. A dense and homogeneous FeAl coating was thus successfully in situ synthesized by reactive plasma spraying of an Al/Fe2O3 composite powder under 1 mbar. The phase composition and microstructural features of the coating were characterized by XRD and SEM. Results indicated that the B2 ordered FeAl phase was synthesized, and the coating featured a dense and defect-free microstructure. The fracture mechanism of the coating remains mainly a brittle failure but the appearance of some dimples in local zones suggested some unexpected toughness. 相似文献
99.
Saed Raji Yves Jannot Philippe Lagière Jean Rodolphe Puiggali 《Construction and Building Materials》2009,23(10):3189-3195
The experimental results obtained by the thermophysical characterization of a wall made of stacked laminated solid-wood planks are reported in this article. The interface between two logs is filled with a felt packing that is compressed under the weight of the upper plank. The characteristics which affect heat, air and water vapour transfers through the wall have been determined, i.e. the sorption isotherm, density, thermal conductivity and diffusivity, water vapour diffusion coefficient, and air permeability of the wall. The results achieved demonstrate the influence of the presence of the laminating adhesive on water vapour and air diffusion, and the influence of the presence of the felt packing on air permeability. The result is that the hygrothermal behaviour of the wall studied cannot be described properly by simply taking into account the properties of the solid wood, and it is thus necessary to determine the global properties of the composite wall. 相似文献
100.
Evripidis Bampis Rodolphe Giroudeau Jean-Claude Knig 《Theoretical computer science》2003,290(3):1883-1895
We study the problem of minimizing the makespan for the precedence multiprocessor constrained scheduling problem with hierarchical communications (Parallel Process. Lett. 10(1) (2000) 133). We propose an
-approximation algorithm for the Unit Communication Time hierarchical problem with arbitrary but integer processing times and an unbounded number of biprocessor machines. We extend this result in the case where each cluster has m processors (where m is a fixed constant) by presenting a (2−2/(2m+1))-approximation algorithm. 相似文献