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Design Purposes (design + purpose)
Selected AbstractsMultiscale approach to geo-composite cellular structures subjected to rock impactsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 13 2007François Nicot Abstract Geo-composite cellular structures are an efficient technological solution for various applications in civil engineering. This type of structure is particularly well adapted to resisting rockfalls and can act as a defensive structure. However, the design of such structures is for the most part empirically based; this lack of research-based design stagnates optimization and advanced development. In this paper, the mechanical behaviour of a geo-composite cellular structure is investigated using a multi-scale approach, from the individual cell made up of an assembly of rocky particles contained in a wire netting cage to the entire structure composed of a regular array of cells. Based on discrete modelling of both the cell and structure scales, a computational tool has been developed for design purposes. Copyright © 2007 John Wiley & Sons, Ltd. [source] Spatially varied flow in non-prismatic channels.IRRIGATION AND DRAINAGE, Issue 1 2002II: numerical solution, experimental verification canal d'irrigation; modélisation; écoulement spatialement varié; équation de transfert; analyse numérique; expérimentation Abstract A new governing equation was proposed for the spatially varied flows with increasing discharge, which affects the position and the depth of the control section as well as the entire water surface profile within the channel. This paper presents the use of the Newton-Raphson method in the solution process. The results of the computational model were compared with experimental data and with the output of the traditional equation. It was indicated that because of incorporating the expansion factor of the non-prismatic channels, the proposed equation is able to represent the experimental data very well and hence is superior to the traditional equation for design purposes. Copyright © 2002 John Wiley & Sons, Ltd. RÉSUMÉ Une nouvelle éeuation a été purposée pour l'écoulement varié spatialement sous la condition de l'augmentation du débit. Cette équation considére la situation et la profondeue de coupe de contrôle et aussi calcule le profil de niveau de l'eau. La solution numérique utilise la méthode de Newton-Raphson. On a comparé les résultata obtenus par ce modéle avec les données expérimentales et la méthode traditionnelle. Cette comparison montre que grâce à l'incorporation du facteur d'expansion d'un cour d'eau irrégulier, la méthode proposée est capable de représenter trés bien les données expérimentales et peut être beaucoup plus efficace pour le motif de dessin par rapport à la méthode traditionnele Copyright © 2002 John Wiley & Sons, Ltd. [source] Optical and physicochemical properties of silica-supported TiO2 photocatalystsAICHE JOURNAL, Issue 8 2006Javier Marugán Abstract Commercial applications of photocatalysis in slurry reactors employing titanium dioxide particles present the disadvantage of the additional cost associated with the downstream catalyst separation. In past years a significant effort has been made to develop supported titania photocatalysts on particles of larger size in order to facilitate the sedimentation recovery process. In this work, two different silica materials have been used for preparing immobilized catalysts. Their physicochemical characteristics have been compared with those corresponding to two commercially available unsupported titanium dioxide catalysts. However, for reaction kinetics and reactor design purposes, three additional properties must be known: (i) the spectral specific radiation absorption coefficient, (ii) the spectral specific radiation scattering coefficient, and (iii) the asymmetry factor of a model for the angular distribution of the scattered photons (the phase function). They have been determined with specially designed spectrophotometer transmission, diffuse transmittance, and diffuse reflectance experiments and constitute the most significant addition to this contribution. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Minimal-power control of hydrogen evolution reactionsOPTIMAL CONTROL APPLICATIONS AND METHODS, Issue 2 2010Vicente Costanza Abstract An integral approach to solve finite-horizon optimal control problems posed by set-point changes in electrochemical hydrogen reactions is developed. The methodology extends to nonlinear problems with regular, convex Hamiltonians that cannot be explicitly minimized, i.e. where the functional dependence of the H -minimal control on the state and costate variables is not known. The Lagrangian functions determining trajectory costs will not have special restrictions other than positiveness, but for simplicity the final penalty will be assumed quadratic. The answer to the problem is constructed through the solution to a coupled system of three first-order quasi-linear partial differential equations (PDEs) for the missing boundary conditions x(T), ,(0) of the Hamiltonian equations, and for the final value of the control variable u(T). The independent variables of these PDEs are the time-duration T of the process and the characteristic parameter S of the final penalty. The solution provides information on the whole (T, S)-family of control problems, which can be used not only to construct the individual optimal control strategies online, but also for global design purposes. Copyright © 2009 John Wiley & Sons, Ltd. [source] Finding initial costates in finite-horizon nonlinear-quadratic optimal control problemsOPTIMAL CONTROL APPLICATIONS AND METHODS, Issue 3 2008Vicente Costanza Abstract A procedure for obtaining the initial value of the costate in a regular, finite-horizon, nonlinear-quadratic problem is devised in dimension one. The optimal control can then be constructed from the solution to the Hamiltonian equations, integrated on-line. The initial costate is found by successively solving two first-order, quasi-linear, partial differential equations (PDEs), whose independent variables are the time-horizon duration T and the final-penalty coefficient S. These PDEs need to be integrated off-line, the solution rendering not only the initial condition for the costate sought in the particular (T, S)-situation but also additional information on the boundary values of the whole two-parameter family of control problems, that can be used for design purposes. Results are tested against exact solutions of the PDEs for linear systems and also compared with numerical solutions of the bilinear-quadratic problem obtained through a power-series' expansion approach. Bilinear systems are specially treated in their character of universal approximations of nonlinear systems with bounded controls during finite time-periods. Copyright © 2007 John Wiley & Sons, Ltd. [source] Impact behavior of a short glass fiber reinforced thermoplastic polyurethanePOLYMER COMPOSITES, Issue 3 2000J. Jancar The temperature dependence of critical strain energy release rate (Gc,) and standardized Charpy notched impact strength (CNIS) were measured for a thermoplastic polyurethane (TPUR) reinforced with 30 wt% of short glass fibers (SGF) over a temperature interval ranging from ,150°C 23°C (RT) at two strain rates, 70 and 150 s,1, respectively. Fractographic observation of fracture planes was used to qualitatively assess the fracture modes and mechanisms. Adhesion between the reinforcement and the matrix was excellent and the integrity of the fiber-matrix interfacial contact was relatively insensitive to exposure to hydrolysis during the immersion in boiling water for 100 hours. At temperatures above ,30°C, there was a large extent of plastic deformation in the vicinity of crack planes while at temperatures below ,50°C, the extent of plastic deformation was substantially reduced. This resulted in a change in the major energy dissipation mechanism and led to a decrease of both CNIS and Gc, values for SGF/TPUR composites. It was suggested that the plastic deformation of TPUR matrix in the immediate vicinity of glass fibers was the primary source of energy dissipation at temperatures above ,30°C, while the friction and fiber pull-out was the main dissipative process below ,50°C. Over the whole temperature interval investigated, greater Gc, values were obtained at higher strain rate of 150 s,1, without any significant change in the fractographic patterns observed on the fracture planes. The CNIS/Gc, ratio, used to assess suitability of CNIS for comparison of materials, changed with temperature substantially suggesting that the functional dependences of CNIS and Gc, on temperature differ substantially. Hence, CNIS data do not provide a reliable base for material selection and for design purposes in this case. [source] A computer experiment application to the design and optimization of a capacitive accelerometerAPPLIED STOCHASTIC MODELS IN BUSINESS AND INDUSTRY, Issue 2 2009M. J. Alvarez Abstract An accelerometer is a transducer that allows measuring the acceleration acting on a structure. Physically, an accelerometer consists of a central mass suspended by thin and flexible arms and its performance is highly dependent on the dimensions of both the mass and the arms. The two most important parameters when evaluating the performance of these devices are the sensitivity and the operating frequency range (or bandwidth), the latter one being limited to of the resonance frequency. Therefore, it is very convenient to gain knowledge on how changes in the dimensions of the mass and arms affect the value of the natural frequency of the accelerometer, as it will provide guidelines to design accelerometers that fulfil frequency requirements of a specific application. A quadratic polynomial function of the natural logarithm of the frequency versus geometrical factors has been obtained using response surface methodology approach. A faced-centered cube design was used in the experimentation. The data were obtained conducting computer simulations using finite element design techniques. A better understanding of how these variables affect the value of frequency has been reached, which will be very useful for the device design purposes. Copyright © 2009 John Wiley & Sons, Ltd. [source] Application of statistical potentials to protein structure refinement from low resolution ab initio modelsBIOPOLYMERS, Issue 4 2003Hui Lu Abstract Recently ab initio protein structure prediction methods have advanced sufficiently so that they often assemble the correct low resolution structure of the protein. To enhance the speed of conformational search, many ab initio prediction programs adopt a reduced protein representation. However, for drug design purposes, better quality structures are probably needed. To achieve this refinement, it is natural to use a more detailed heavy atom representation. Here, as opposed to costly implicit or explicit solvent molecular dynamics simulations, knowledge-based heavy atom pair potentials were employed. By way of illustration, we tried to improve the quality of the predicted structures obtained from the ab initio prediction program TOUCHSTONE by three methods: local constraint refinement, reduced predicted tertiary contact refinement, and statistical pair potential guided molecular dynamics. Sixty-seven predicted structures from 30 small proteins (less than 150 residues in length) representing different structural classes (,, ,, ,,/,) were examined. In 33 cases, the root mean square deviation (RMSD) from native structures improved by more than 0.3 Å; in 19 cases, the improvement was more than 0.5 Å, and sometimes as large as 1 Å. In only seven (four) cases did the refinement procedure increase the RMSD by more than 0.3 (0.5) Å. For the remaining structures, the refinement procedures changed the structures by less than 0.3 Å. While modest, the performance of the current refinement methods is better than the published refinement results obtained using standard molecular dynamics. © 2003 Wiley Periodicals, Inc. Biopolymers 70: 575,584, 2003 [source] New Predictive Correlations for the Drop Size in a Rotating Disc Contactor Liquid-Liquid Extraction ColumnCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 2 2007M. Ismail Al-Rahawi Abstract Sauter mean drop sizes (d32) generated from a hole distributor in liquid extraction RDC columns were studied under various conditions. Experiments were designed to generate data required to determine the main variables that control the drop sizes in RDCs. Two precise correlations were proposed for predicting d32 in a RDC extraction column. The first was based on operating variables, hole-distributor diameter, disc speed, column geometry, and system physical properties. The second one considered the same variables, except the column geometry. This model can be used for design purposes. The two correlations are the first of their type to consider the distributor hole inlet diameter in a RDC column. This diameter has been neglected by previous investigators. The maximum standard deviation for all data is 0.75,%, with a maximum absolute error of 6.8,%. [source] | |||||||||||||