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排序方式: 共有400条查询结果,搜索用时 15 毫秒
1.
An original procedure has been established for estimating the overall volumetric mass transfer coefficient using the oxygen concentration curves resulting from the usual gassing-in and gassing-out method. This procedure was applied to experimental data obtained in a small scale bubble column using both tap water and a coalescence-inhibiting liquid mixture that represents the coalescence behavior of biological media. It is based on the analysis of the characteristics times of the system, including those of the hydrodynamics of the two phases, the sensor dynamics and the system inertia when the gas composition is modified. A numerical procedure was developed to estimate the characteristic time of the system inertia ti, using the assumption that this inertia is nearly independent of superficial gas velocity UG. The calculations confirmed that the optimized ti value was nearly independent of UG and of the coalescence behavior of the liquid phase. Additionally, the resulting KLaL values for tap water were closer to the correlation of Shah et al. [1982. Design parameters estimations for bubble column reactors. A.I.Ch.E. Journal 28, 353-379] than those of other conventional models. Finally, the original procedure was also reported to reduce significantly the square sum deviation between the predicted and the measured oxygen response curves. 相似文献
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This study aimed at identifying the roll motion parameters of a motorcycle simulator prototype. Experienced motorcyclists tuned the angular physical movement of the mock-up and that of the visual scene to achieve an optimal riding experience during curves. The participants exceeded the rolling angles that would be required in real-world riding, while avoiding leaning the mock-up beyond 10°. In addition, they were more influenced by the speed of the virtual motorcycle than by road curvature, especially in a wide field of view. Heterogeneity was found in the roll applied to the visual scene. The overall patterns suggest that at least when washout is not applied to remove the side forces that in real-world riding are compensated by a centrifugal force, greater roll of the visual at the expense of the mock-up is mandatory to avoid performance biases that might be enhanced due to fear of falling off the simulator. Future roll motion models must take into consideration factors such as riding postures, which might not only influence the forces operating on the rider-motorcycle system, but also how motorcyclists perceive the visual world. 相似文献
4.
Global hydrodynamic characteristics, liquid mixing and gas‐liquid mass transfer for a 63 L split‐rectangular airlift reactor were studied. Correlations for gas holdup and overall liquid circulation velocity were derived for the air‐water system as a function of the specific power input; these were compared to data and correlations for reactor volumes between 4.7 L and 4600 L. A partial recirculation of small bubbles in the riser was observed when Ugr > 0.03 m/s, which was attributed to the use of a single‐orifice nozzle as the gas phase distributor. The dimensionless mixing time and the overall axial dispersion coefficient were nearly constant for the range of gas flow rates studied. However, values of KL/dB were greater than those reported in previous studies and this is caused by the partial recirculation of the gas phase in the riser. While scale effects remain slight, the use of a gas distributor favouring this partial recirculation seems adequate for mass transfer in split‐rectangular airlift reactors. 相似文献
5.
Dai J Park G Perry JL Il'ichev YV Bow DA Pritchard JB Faucet V Pfohl-Leszkowicz A Manderville RA Simon JD 《Accounts of chemical research》2004,37(11):874-881
Ochratoxins are a class of naturally occurring compounds produced by several fungi. The most toxic is ochratoxin A (OTA), and occurrence of some human nephropathies and tumors correlate with enhanced OTA exposure. In this Account, the following areas are examined: molecular details of the binding of OTA to human serum albumin (HSA), the influences of binding to HSA on the trans-port of OTA across epithelial cell membranes by organic anion transport proteins, the oxidative activation of OTA, and the formation of OTA adducts with biological molecules. These studies are beginning to provide a detailed chemical model for the trans-port, accumulation, and genotoxic and carcinogenic effects of OTA. 相似文献
6.
Virginie Boy Wajdi Ben Khalifa Lucie Drvillon Yves Leme Thomas Lendormi Jean‐Louis Lanoisell 《加拿大化工杂志》2021,99(1):120-134
An original drying process combining air impingement and intermittent drying was studied on apple slices and mango cubes. The influence of four operating parameters (air velocity, drying/tempering periods, upper height, and air temperature) on the drying time and on the drying rate was evaluated. Continuous and intermittent drying were compared. The intermittency α = 1/7 (τon = 10 seconds and τoff = 60 seconds) gave the best results. A time savings of 54% for apple and 67% for mango was reached. In continuous drying, a time savings of 4620 seconds was observed by increasing the air velocity from 6 to 40 m s?1 for apple. Air temperatures of 328 K for apple and of 328 K or 338 K for mango were determined as optimum to prevent case‐hardening. Experimental results were fitted with the analytical solution of Fick's second law and the modified Page equation (average values R2 = 0.985 and 0.961, for apple and mango, respectively). For both products, the apparent moisture diffusivity Dapp, the drying constant k, the drying coefficient n, and the activation energy Ea, were identified. Activation energies calculated from the analytical solution were 30.3 and 36.8 kJ mol?1 and were 25.4 and 30.0 kJ mol?1 using the modified Page equation for apple and mango, respectively. Mango has an increased temperature sensitivity and thus will need less energy for drying than apple. 相似文献
7.
G. Garib C. Vial F. Negroni E. G. Thomsen 《Journal of Materials Shaping Technology》1988,5(3):191-195
A hollow punch-torque method was used to measure friction between tough pitch copper and three different lubricants. The tests indicated that the coefficient μ is not a function of the applied pressure, while the friction factorm is. Both μ andm depend only slightly on the degree of prior deformation. The range of pressure investigated was that encountered in drawing operations and is below that for lubricated sliding surfaces where sublayer plastic flow occurs. 相似文献
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Yamine Ait Ameur Frédéric Boniol Virginie Wiels 《International Journal on Software Tools for Technology Transfer (STTT)》2010,12(1):1-7
Nowadays, it is well accepted that the development of critical systems involves the use of formal methods. One of the major
fields where these methods made a lot of progress are the avionics, aerospace and more generally transport areas. Several
methods, tools and techniques have been applied for the development of such systems in different parts of the world, and they
have been actually put into practice during the development of specific aircraft programs. The aim of this introductory article
and of this STTT special issue is to propose a brief overview of the state-of-the-art of current researches in formal methods
applied to the development of avionics and aerospace systems and more broadly to take stock of the integration of formal methods
in the aerospace industry. 相似文献
10.
Samuel Aupetit Virginie Gallier Jacques Riff Stéphane Espié Flavien Delgehier 《Ergonomics》2016,59(8):1109-1120
This article sets out to identify the typical risky situations experienced by novice motorcyclists in the real world just after licensing. The procedure consists of a follow-up of six novices during their first two months of riding with their own motorbike instrumented with cameras. The novices completed logbooks on a daily basis in order to identify the risky situations they encountered, and were given face-to-face interviews to identify the context and their shortcomings during the reported events. Data show a large number of road configurations considered as risky by the riders (248 occurrences), especially during the first two weeks. The results revealed that a lack of hazard perception skills contributed to the majority of these incidents. These situations were grouped together to form clusters of typical incident scenarios on the basis of their similarities. The most frequent scenario corresponds to a lane change in dense traffic (15% of all incidents). The discussion shows how this has enhanced our understanding of novice riders’ behaviour and how the findings can improve training and licensing. Lastly, the main methodological limitations of the study and some guidelines for improving future naturalistic riding studies are presented.
Practitioner Summary:
This article aims to identify the risky situations of novice motorcyclists in real roads. Two hundred forty-eight events were recorded and 13 incident scenarios identified. Results revealed that a lack of hazard perception contributed to the majority of these events. The most frequent scenario corresponds to a lane change in dense traffic. 相似文献