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181.
Laurent Houssin Sébastien Lahaye Jean-Louis Boimond 《Discrete Event Dynamic Systems》2013,23(3):261-276
In this paper, we develop a new control technique for discrete event dynamic systems subject to synchronization phenomena. We propose a feedback controller for (max,?+?)-linear systems which delays input events as little as possible while constraints on internal or output events are satisfied. The synthesis is mainly based on new results about fixed points of antitone (i.e., order reversing) mappings. 相似文献
182.
Ayoub Moradi Laurent Metivier Olivier de Viron Stephane Calmant Catherine Mering 《International journal of remote sensing》2013,34(16):6060-6075
Moderate-Resolution Imaging Spectroradiometer (MODIS) optical and infrared data are used to monitor changes in the Caspian Sea coastline. The information extracted from MODIS images is converted into total water volume and mean lake level by combining a digital elevation model (DEM) with remote-sensing data. The elevation estimates were enhanced by reprocessing the MODIS data at the sub-pixel scale. The water volume variations estimated from MODIS data along with DEM are compared to other estimations derived from altimetry data sets, and show fair agreement. 相似文献
183.
The Pythagoras number of real sum of squares polynomials and sum of square magnitudes of polynomials
In this paper, we conjecture a formula for the value of the Pythagoras number for real multivariate sum of squares polynomials as a function of the (total or coordinate) degree and the number of variables. The conjecture is based on the comparison between the number of parameters and the number of conditions for a corresponding low-rank representation. This is then numerically verified for a number of examples. Additionally, we discuss the Pythagoras number of (complex) multivariate Laurent polynomials that are sum of square magnitudes of polynomials on the $n$ -torus. For both types of polynomials, we also propose an algorithm to numerically compute the Pythagoras number and give some numerical illustrations. 相似文献
184.
Eric Becker Véronique Favier Regis Bigot Pierre Cezard Laurent Langlois 《Journal of Materials Processing Technology》2010,210(11):1482-1492
Semi-solid forming is an effective near-net-shape forming process to produce components with complex geometry and in fewer forming steps. It benefits from the complex thixotropic behaviour of semi-solids. However, the consequences of such behaviour on the flow during thixoforming, is still neither completely characterized and nor fully understood, especially for high melting point alloys. The study described in this paper investigates thixoextrusion for C38 low carbon steel material using dies at temperatures much lower than the slug temperature. Four different process parameters were studied: the initial slug temperature, the die temperature, the ram speed and the presence of a ceramic layer at the tool/material interface. The extruded parts were found to have an exact shape and a good surface state only if the temperature was below a certain value. This critical temperature is not an intrinsic material property since its value depends on die temperature and the presence of the Ceraspray© layer. Two kinds of flow were highlighted: a homogeneous flow controlled by the behaviour of the solid skeleton characterized by a positive strain rate sensitivity, and a non homogeneous flow (macro liquid/solid phase separation) dominated by the flow of the free liquid. With decreasing ram speed, heat losses increase so that the overall consistency of the material improves, leading to apparent negative strain rate sensitivity. Finally, some ways to optimise thixoforming are proposed. 相似文献
185.
186.
Annabelle Joulin Zohir Younsi Laurent Zalewski Stéphane Lassue Daniel R. Rousse Jean-Paul Cavrot 《Applied Energy》2011
The application of phase change materials (PCMs) for solar thermal-energy storage capacities has received considerable attention in recent years due to their large storage capacity and isothermal nature of the storage process. This study deals with the comparison of numerical and experimental results for a PCM conditioned in a parallelepipedic polyefin envelope to be used in passive solar walls. The experimental results were obtained by use of a genuine set-up involving heat flux sensors and thermocouples mounted on two vertical aluminium exchanger plates squeezing the samples. Numerical predictions were obtained with a custom one-dimensional Fortran code and a two-dimensional use of Fluent. Both methods showed a very good agreement with experimental observations for the melting process (?5%). However during solidification, both numerical codes failed to predict the phase change process accurately, the maximal relative error was as high as 57% (with an average of 8%). 相似文献
187.
ABSTRACT Biofilms are edible films formed from biopolymers. In the casting process technique, the biofilm is obtained by the drying of a colloidal solution in the final process stage The aim of this work was to analyse the drying process of gelatin based biofilms, in room frontier conditions. The biofilms were prepared initially by dissolving gelatin in water and adding sorbitol as plasticizer. The filmogenic solution was dried in an automatic drier under various drying conditions, for 1mm film: air temperature (T= 35, 40 and 45 °C), relative humidity (?= 60 and 75 %) and air velocity (v= 3m/s). The drying kinetics was measured for 15, 30 and 45 % sorbitol concentrations. Sorption isotherms at 25, 35 and 45 °C were determined for the 15% sorbitol concentration films by the static gravimetric method. The glass transition and the melting temperature for various moisture contents were determined with a Differential Scanning Calorimeter TA 2010. The results showed an unusual behaviour for temperature dependence: decreasing drying kinetics with increasing air temperature. Also separation of gelatin and sorbitol were seen when the temperature increased. This phenomenon occurs when the film temperature during the drying process gets close to the melting temperature of the film. 相似文献
188.
Ziad Damaj Aude Naveau Laurent Dupont Eric Hénon Guillaume Rogez Emmanuel Guillon 《Inorganic chemistry communications》2009,12(1):17-20
A solid CoII complex with l-proline as ligand was synthesized and fully characterized using spectroscopic studies, magnetic data, and DFT calculations. Dioxygen scavenging properties were investigated by UV/Vis spectroscopy and oxymetry techniques. The Co-proline system presented very interesting properties in matter of oxygen absorption capacity both in solution and incorporated in a polymer matrix. 相似文献
189.
We conclude, in this third part, the presentation of an algorithm for computing an exact and proper parameterization of the intersection of two quadrics. The coordinate functions of the parameterizations in projective space are polynomial, whenever it is possible. They are also near-optimal in the sense that the number of distinct square roots appearing in the coefficients of these functions is minimal except in a small number of cases (characterized by the real type of the intersection) where there may be an extra square root. 相似文献
190.
Many approaches may lead to integrate security functions in the intranet/internet services. These functions may be placed at the application layer or at lower OSI layers. IPsec suite protocols were specified by IETF in order to integrate security functionality at network layer. This paper describes the features of IPESC protocols and identifies the aspects which are not standardized. The network translation address (nat) functionality used by routers and firewalls is not always compatible with IPESC. We describe and discuss some solutions for the compatibility of ipsec and nat. The last part of this paper describes a typical architecture for ip vpn based on IPSec technology. 相似文献