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91.
Lajos Szalmas Jeerasak Pitakarnnop Sandrine Geoffroy Stephane Colin Dimitris Valougeorgis 《Microfluidics and nanofluidics》2010,9(6):1103-1114
A comparative study between computational and experimental results for pressure-driven binary gas flows through long microchannels is performed. The theoretical formulation is based on the McCormack kinetic model and the computational results are valid in the whole range of the Knudsen number. Diffusion effects are taken into consideration. The experimental work is based on the Constant Volume Method, and the results are in the slip and transition regime. Using both approaches, the molar flow rates of the He–Ar gas mixture flowing through a rectangular microchannel are estimated for a wide range of pressure drops between the upstream and downstream reservoirs and several mixture concentrations varying from pure He to pure Ar. In all cases, a very good agreement is found, within the margins of the introduced modeling and measurement uncertainties. In addition, computational results for the pressure and concentration distributions along the channel are provided. As far as the authors are aware of, this is the first detailed and complete comparative study between theory and experiment for gaseous flows through long microchannels in the case of binary mixtures. 相似文献
92.
Mhand Hifi Stephane NegreRachid Ouafi Toufik Saadi 《Computers & Industrial Engineering》2012,62(1):177-189
In this paper, we solve the two-staged two-dimensional cutting problem using a parallel algorithm. The proposed approach combines two main features: beam search (BS) and strip generation solution procedures (SGSP). BS employs a truncated tree-search, where a selected subset of generated nodes are retuned for further search. SGSP, a constructive procedure, combines a (sub)set of strips for providing both partial lower and complementary upper bounds. The algorithm explores in parallel a subset of selected nodes following the master-slave paradigm. The master processor serves to guide the search-resolution and each slave processor develops its proper way, trying a global convergence. The aim of such an approach is to show how the parallelism is able to efficiently solve large-scale instances, by providing new solutions within a consistently reduced runtime. Extensive computational testing on instances, taken from the literature, shows the effectiveness of the proposed approach. 相似文献
93.
This paper presents an automatic method of correcting non-uniform RF coil response for the classification of body composition
using MR imaging. By linear mosaic modelling, the smoothly but non-linearly varying bias field, which modulates tissue intensities
within the image, was corrected. The overlapping between adjacent mosaics ensured consistent segmentation of body fat content
and the effectiveness of the technique was validated by both phantom and in vivo experiments. Ten whole body composition data
sets, each with 39 trans-axial slices, were acquired. Automatic segmentation results using the proposed technique were compared
with those from manual delineations. The automatic segmentation method was found to be highly accurate and the mean percentage
error between the two methods was less than 1.5%. 相似文献
94.
95.
Anne-Catherine Brulez Cedric Boschard Mathieu Larochette Stephane Benayoun 《Polymer Engineering and Science》2020,60(12):3258-3269
Numerical simulation of classical dimension parts with micrometric textures on their surface is still difficult to master. The limit condition of the calculations, and in particular, the implemented values, characteristics of the polymer and thermal exchanges (polymer/mold) strongly impact the results. Starting from a model with a 370 μm wide rib, by means of a numerical simulation, a study was done on the evolution of the material flow front velocities and the flow lengths in both the macroscopic part and the microgroove. This innovative visualization mold design was used to determine the velocities from an experimental perspective and to discuss the calculation conditions. On the one hand, there are significant differences regarding the choice of the no flow temperature (~ 40 K) used in the calculation code, the analytical heat transfer equation as well as the experimental results. On the other hand, according to the no flow temperature, it may be necessary to consider, during the filling phase, a perfect mold/polymer thermal contact in the groove. Depending in particular on the injection velocity and the geometry of the micro textures, a characteristic time can be determined which defines an optimal operating point for the topographic texture of the part. 相似文献
96.
We propose several examples of robotics applications where interactions with the environment play an important role, and where no modelization of the robot or of the world is needed. We argue that, in general, this helps to simplify the complexity of the control system, and illustrate this claim through several examples. We propose different neural networks which allow clustering of scattered objects by several robots, learning of obstacle avoidance and learning of target retrieval. 相似文献
97.
Tracking Fronts in One and Two-phase Incompressible Flows Using an Adaptive Mesh Refinement Approach
Stephanie Delage-Santacreu Stephane Vincent Jean-Paul Caltagirone 《Journal of scientific computing》2009,41(2):221-237
Numerical computation is an essential tool for describing multi-phase and multi-scale flows accurately. One possibility consists
in using very fine monogrids to obtain accurate solutions. However, this approach is very costly in time and memory size.
As an alternative, an Adaptive Mesh Refinement method (AMR) has been developed in order to follow either interfaces in two-phase flows or concentration of a pollutant in one-phase
flows. This method has also been optimized to reduce time and memory costs. Several 2D cases have been studied to validate
and show the efficiency of the method. 相似文献
98.
Stephane Dauzere-Peres Jean-Bernard Lasserre 《Computers & Industrial Engineering》1993,25(1-4):231-234
The issue in Lot Streaming is to split lots into sublots in order to improve the makespan (or some other criterion). We present a model and an iterative procedure in a general job-shop environment. In a first step, optimal sublot-sizes are computed given a sequence of sublots on the machines. In a second step, a better sequence is computed by solving a standard job-shop scheduling problem with fixed sublot-sizes. Some computational results on a sample (including the famous 10-10) are reported. In case of no set-up, in few iterations, the makespan approaches a lower bound with few sublots. 相似文献
99.
Josep AltetSebastian Volz Jean-Michel RampnouxAntonio Rubio Stephane GraubyLuis David Patino Lopez Wilfrid ClaeysJean-Bernard Saulnier 《Microelectronics Journal》2002,33(9):689-696
Silicon die surface temperature can be used to monitor the health state of digital and analogue integrated circuits (IC). In the present paper, four different sensing techniques: scanning thermal microscope, laser reflectometer, laser interferometer and electronic built-in differential temperature sensors are used to measure the temperature at the surface of the same IC containing heat sources (hot spots) that behave as faulty digital gates. The goal of the paper is to describe the techniques as well as to present the performances of these sensing methods for the detection and localisation of hot spots in an IC. 相似文献
100.
In this paper we present new results on the performance of the Minimum Spanning Tree heuristic for the Minimum Energy Broadcast Routing (MEBR) problem. We first prove that, for any number of dimensions d≥2, the approximation ratio of the heuristic does not increase when the power attenuation coefficient α, that is the exponent to which the coverage distance must be raised to give the emission power, grows. Moreover, we show
that, for any fixed instance, as a limit for α going to infinity, the ratio tends to the lower bound of Clementi et al. (Proceedings of the 18th annual symposium on theoretical
aspects of computer science (STACS), pp. 121–131, 2001), Wan et al. (Wirel. Netw. 8(6):607–617, 2002) given by the d-dimensional kissing number, thus closing the existing gap between the upper and the lower bound. We then introduce a new
analysis allowing to establish a 7.45-approximation ratio for the 2-dimensional case, thus significantly decreasing the previously
known 12 upper bound (Wan et al. in Wirel. Netw. 8(6):607–617, 2002) (actually corrected to 12.15 in Klasing et al. (Proceedings of the 3rd IFIP-TC6 international networking conference, pp. 866–877,
2004)). Finally, we extend our analysis to any number of dimensions d≥2 and any α≥d, obtaining a general approximation ratio of 3
d
−1, again independent of α. The improvements of the approximation ratios are specifically significant in comparison with the lower bounds given by the
kissing numbers, as these grow at least exponentially with respect to d.
The research was partially funded by the European project COST Action 293, “Graphs and Algorithms in Communication Networks”
(GRAAL).
Preliminary version of this paper appeared in Flammini et al. (Proceedings of ACM joint workshop on foundations of mobile
computing (DIALM-POMC), pp. 85–91, 2004). 相似文献