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41.
Efrén Aguilar-Garnica Denis Dochain Víctor Alcaraz-González Víctor González-Álvarez 《Journal of Process Control》2009,19(8):1324-1332
This paper deals with the design and application of a nonlinear multivariable controller in an anaerobic digestion system (AD) carried out in two interconnected fixed bed bioreactors. The proposed control scheme is derived from a mathematical model of the AD system described by a set of partial differential equations and consists of an estimator and two nonlinear control laws. The first law is developed to regulate the volatile fatty acids in the first bioreactor while the second aims at maintaining the chemical oxygen demand at predetermined set-points in the second bioreactor. The performance of the control algorithm is evaluated via numerical simulations in the face of load disturbances, parameter kinetic uncertainties and set-point changes. Stability and convergence properties of the proposed control scheme are also addressed in this paper. 相似文献
42.
Rita Cunha Carlos Silvestre João Hespanha A. Pedro AguiarAuthor vitae 《Automatica》2011,(5):1020-1027
This paper addresses the problem of stabilizing to a desired equilibrium point an eye-in-hand system, which consists of a single camera mounted on a rigid body free to move on . It is assumed that there is a collection of landmarks fixed in the environment and that the image coordinates of those landmarks are provided to the system by an on-board CCD camera. The proposed method addresses not only the problem of stabilization but also that of maintaining feature visibility along the system’s trajectory. The resulting solution consists of a feedback control law based on the current and desired image coordinates and reconstructed attitude and depth ratio information, which guarantees that (i) the desired equilibrium point is an almost global attractor; (ii) a set of necessary conditions for feature visibility holds throughout the system’s trajectories; and (iii) the image of a predefined feature point is kept inside the camera’s field of view. 相似文献
43.
Francisco García‐Sánchez Luís Álvarez Sabucedo Rodrigo Martínez‐Béjar Luís Anido Rifón Rafael Valencia‐García Juan Miguel Gómez 《Expert Systems》2011,28(5):416-436
The increasing volume of eGovernment‐related services is demanding new approaches for service integration and interoperability in this domain. Semantic web (SW) technologies and applications can leverage the potential of eGovernment service integration and discovery, thus tackling the problems of semantic heterogeneity characterizing eGovernment information sources and the different levels of interoperability. eGovernment services will therefore be semantically described in the foreseeable future. In an environment with semantically annotated services, software agents are essential as the entities responsible for exploiting the semantic content in order to automate some tasks, and so enhance the user's experience. In this paper, we present a framework that provides a seamless integration of semantic web services and intelligent agents technologies by making use of ontologies to facilitate their interoperation. The proposed framework can assist in the development of powerful and flexible distributed systems in complex, dynamic, heterogeneous, unpredictable and open environments. Our approach is backed up by a proof‐of‐concept implementation, where the breakthrough of integrating disparate eGovernment services has been tested. 相似文献
44.
Paulo Augusto Cunha Libanio 《国际水》2013,38(3):513-533
This article examines the use of output-based aid and payment for environmental services to reduce water pollution in Brazil. Two nationwide initiatives are reviewed. First, the output-based aid concept of the River Basin Clean-up Programme (PRODES) to tackle the problem of sanitation deficit in urban areas is presented. Second, the payment for environmental services scheme supported by Brazil’s National Water Agency (ANA) through the Water Producer Programme to promote water conservation on rural properties is discussed. Both programmes are evaluated not only as financing mechanisms for water conservation but also as strategies for implementing Brazil’s water policy. 相似文献
45.
Attila T. Áfra 《Computer Graphics Forum》2012,31(1):75-88
We propose an efficient approach for interactive visualization of massive models with CPU ray tracing. A voxel‐based hierarchical level‐of‐detail (LOD) framework is employed to minimize rendering time and required system memory. In a pre‐processing phase, a compressed out‐of‐core data structure is constructed, which contains the original primitives of the model and the LOD voxels, organized into a kd‐tree. During rendering, data is loaded asynchronously to ensure a smooth inspection of the model regardless of the available I/O bandwidth. With our technique, we are able to explore data sets consisting of hundreds of millions of triangles in real‐time on a desktop PC with a quad‐core CPU. 相似文献
46.
Wide parabolic wells can be created by properly controlling the Al content during the growth of successive Ga1–xAlxAs thin layers. Under a tilted magnetic field these systems present interesting transport properties, which are associated to their composition dependent g-factor. We present an exact solution for the eigenstates of an electron gas inside such a quantum well. We calculate the renormalized cyclotron frequencies as functions of the angle of tilt, as well as the density of states, and the Fermi level. We discuss the conditions for the existence of spin-polarized charge. 相似文献
47.
J. A. O. Barros V. M. C. F. Cunha A. F. Ribeiro J. A. B. Antunes 《Materials and Structures》2005,38(1):47-56
Recently, RILEM TC 162-TDF has proposed equivalent,f
eq
, and residual,f
R
, flexural tensile strength parameters to characterize and simulate the post-cracking behaviour of steel fibre reinforced
concrete (SFRC) structures. In the current work, more than two hundred flexural tests are carried out according to the RILEM
TC 162-TDF recommendations and the corresponding values off
eq
andf
R
parameters are evaluated. In series of specimens reinforced with fibres of a distinct length/diameter ratio, similar values
off
eq
andf
R
parameters were obtained in these series. Although a strong correlation betweenf
eq
andf
R
was determined, a larger scatter off
R
values was observed thereby revealingf
eq
to be more appropriate for design purposes. A numerical strategy involving a cross sectional layered model and an inverse
analysis was developed to evaluate the post-cracking stress-strain and the stress-crack opening diagrams for the tested SFRC.
This strategy was also used to determine a relation between the post-cracking strain, ɛ
pcr
, and the crack opening displacement,w, (ɛ
pcr
=w/L
p
) which is useful for evaluating the crack opening when numerical strategies based on a stress-strain approach are used. The
obtainedL
p
values range from half the specimen cross section height to half the distance between the tip of the notch and the top of
the cross section.
Résumé Récemment, pour caractériser et simuler le comportement post-fissuration en traction du béton renforcé des fibres d'acier, la Commission Technique 162-TDF de la RILEM a proposé des paramètres désignés par résistance équivalente, feq, et résistance résiduelle, fR, à la contrainte en flexion. Dans le travail présent, des valeurs de ces paramètres sont obtenues sur plus de deux cents essais de flexion effectués en accord avec les recommandations du TC 162-TDF de la RILEM. Des valeurs semblables de feq et fR ont été obtenues dans des séries d'éprouvettes renforcées avec des fibres d'un rapport longueur/diamètre distinct. Bien qu'une forte corrélation entre feq et fR ait été déterminée, une plus grande dispersion de valeurs du fR a été observée, en démontrant que feq est plus approprié pour les buts du projet. Pour évaluer les diagrammes contrainte-déformation et contrainte-ouverture après fissuration, une stratégie numérique a été développée, en utilisant un modèle de section et en effectuant une analyse inverse. Cette stratégie a aussi été utilisée pour déterminer une relation entre la contrainte après fissuration, ɛ pcr , et l'ouverture de fissure, w, (ɛ pcr =w/L p ) utile pour évaluer l'ouverture de la fissure quand les stratégies numériques sont basées sur une approche contrainte-déformation. Les valeurs de Lp obtenues ont varié entre la demi-hauteur de la section de l'éprouvette et la demi-distance entre l'extrémité de l'entaille et le sommet de la section.相似文献
48.
A general equation has been derived for the threshold pressure of infiltration of liquids into porous solids. From this equation all the known equations for the threshold pressure can be obtained, using different assumptions on the morphology of the porous solid and on the way how the liquid infiltrates the solid. Particularly, the Young-Laplace equation, the Carman-equation, and the modification of the Carman equation, suggested by White and later by Mortensen and Cornie have been reproduced as particular cases of the general equation. A new particular solution of this general equation is also suggested, taking into account that the original solid/gas interface inside the porous body is not fully replaced by the solid/liquid interface during infiltration, especially for the case of non-wetting liquids. The new, general equation consists of three semi-empirical parameters, which should be found experimentally for a given type of morphology of the porous solid and for the given ratio of the surface tension to the density of the infiltrating liquid metal. The new equation provides a value of the threshold contact angle to be between 65.5° and 90°, depending on the morphology of the porous solid. Consequently, the threshold pressure appears to be an asymmetrical function of the contact angle. Based on the new equation, the practical constancy of the threshold pressure is predicted in the interval of the contact angles between 120° and 180°. 相似文献
49.
Although the principles behind generic programming are already well understood, this style of programming is not widespread and examples of applications are rarely found in the literature. This paper addresses this shortage by presenting a new method, based on generic programming, to automatically visualize recursion trees of functions written in Haskell. Crucial to our solution is the fact that almost any function definition can be automatically factorized into the composition of a fold after an unfold of some intermediate data structure that models its recursion tree. By combining this technique with an existing tool for graphical debugging, and by extensively using Generic Haskell, we achieve a rather concise and elegant solution to this problem. 相似文献
50.
Caio Bezerra Machado Leidivan Sousa da Cunha Jersey Heitor da Silva Maus Flvia Melo Cunha de Pinho Pessoa Marcelo Braga de Oliveira Rodrigo Monteiro Ribeiro Germison Silva Lopes Manoel Odorico de Moraes Filho Maria Elisabete Amaral de Moraes Andr Salim Khayat Caroline Aquino Moreira-Nunes 《International journal of molecular sciences》2022,23(10)
Human T cell leukemia virus type 1 (HTLV-1) was identified as the first pathogenic human retrovirus and is estimated to infect 5 to 10 million individuals worldwide. Unlike other retroviruses, there is no effective therapy to prevent the onset of the most alarming diseases caused by HTLV-1, and the more severe cases manifest as the malignant phenotype of adult T cell leukemia (ATL). MicroRNA (miRNA) dysfunction is a common feature of leukemogenesis, and it is no different in ATL cases. Therefore, we sought to analyze studies that reported deregulated miRNA expression in HTLV-1 infected cells and patients’ samples to understand how this deregulation could induce malignancy. Through in silico analysis, we identified 12 miRNAs that stood out in the prediction of targets, and we performed functional annotation of the genes linked to these 12 miRNAs that appeared to have a major biological interaction. A total of 90 genes were enriched in 14 KEGG pathways with significant values, including TP53, WNT, MAPK, TGF-β, and Ras signaling pathways. These miRNAs and gene interactions are discussed in further detail for elucidation of how they may act as probable drivers for ATL onset, and while our data provide solid starting points for comprehension of miRNAs’ roles in HTLV-1 infection, continuous effort in oncologic research is still needed to improve our understanding of HTLV-1 induced leukemia. 相似文献