Repositório Comunidade:
http://hdl.handle.net/10400.21/8
2018-03-24T06:09:26ZRigorous numerical method for irrigation canal system dynamics and control
http://hdl.handle.net/10400.21/8284
Título: Rigorous numerical method for irrigation canal system dynamics and control
Autor: Igreja, J. M.
Resumo: Water canals for water delivery or irrigation provide a challenging system dynamics and control problem for distributed parameter plants. Canals are formed by a sequence of pools separated by gates. Output variables are the pool level at certain points, manipulated variables are the position of the gates and disturbances are the outlet water flows for agricultural use. Water pool dynamics are derived from the shallow water equations (also called Saint-Venant equations in its one-dimensional form) that are a set of hyperbolic partial differential nonlinear equations. Gate opening produces a water wave that travels through the pool which is partially reflected back in the next gate, the remainder crosses the gate and propagates to the next pool. Rigorous numerical methods that are able to capture water wave Dynamics in canals are difficult to achieve. In this case a numerical routine was designed from a finite volume method for hyperbolic systems of conservation laws with source terms using a semi-discrete MUSCL flux reconstruction linear well-balanced scheme (Kurganov and Tadmor central scheme with superbee limiter). Time integration was done with a Runge-Kutta method. The numerical method was used to simulate water dynamics in the first two pools with with-draws of an existing irrigation canal in Vila Nova de Mil-Fontes, Portugal, including PI controlled gates movement to compensate for wave disturbances.2015-07-01T00:00:00ZHighly active and selective supported rhenium catalysts for aerobic oxidation of n-Hexane and n-Heptane
http://hdl.handle.net/10400.21/8278
Título: Highly active and selective supported rhenium catalysts for aerobic oxidation of n-Hexane and n-Heptane
Autor: Mishra, Gopal S.; Alegria, Elisabete C. B. A.; Pombeiro, Armando J. L.; Martins, Luísa M. D. R. S.
Resumo: A series of derivative C-scorpionate rhenium complexes, i.e., [ReCl2{NNC(O)C6H5} (Hpz)(PPh3)2] (A) (where Hpz is pyrazole), [ReCl2{NNC(O)C6H5}(Hpz)2(PPh3)] (B), [ReClF {NNC(O)C6H5}(Hpz)2(PPh3)] (C), and their precursor [ReOCl3(PPh3)2] (D), immobilized on 3-aminopropyl-functionalized silica have been prepared and used for neat O2 oxidation of n-hexane and n-heptane mainly to the corresponding alcohols and, in lower amounts, ketones. The supported catalyst C, with fluoro- and diazenido-ligands, exhibits the highest activity for both alkanes (overall turnover numbers (TONs) up to 3.8 _ 103 and 2.5 _ 103, for n-hexane and n-heptane, respectively) and can be reused in consecutive catalytic cycles. Improved conversion was observed after addition of hetero-carboxylate co-catalysts. A free-radical-based mechanism is proposed to explain the product formation.2018-03-15T00:00:00ZDetect and pointing algorithm’s performance for a planar smart antenna array: a review
http://hdl.handle.net/10400.21/8275
Título: Detect and pointing algorithm’s performance for a planar smart antenna array: a review
Autor: Varum, Tiago; Matos, João N.; Pinho, Pedro
Resumo: An adaptive antenna array combines the signal of each element, using some constraints to produce the radiation pattern of the antenna, while maximizing the performance of the system. Direction of arrival (DOA) algorithms are applied to determine the directions of impinging signals, whereas beamforming techniques are employed to determine the appropriate weights for the array elements, to create the desired pattern. In this paper, a detailed analysis of both categories of algorithms is made, when a planar antenna array is used. Several simulation results show that it is possible to point an antenna array in a desired direction based on the DOA estimation and on the beamforming algorithms. A comparison of the performance in terms of runtime and accuracy of the used algorithms is made. These characteristics are dependent on the SNR of the incoming signal.2015-08-01T00:00:00ZSimple general purpose ion beam deceleration system using a single electrode lens
http://hdl.handle.net/10400.21/8270
Título: Simple general purpose ion beam deceleration system using a single electrode lens
Autor: Lopes, J.; Rocha, J.
Resumo: Ion beam deceleration properties of a newly developed low-energy ion beam implantation system were studied. The objective of this system was to produce general purpose low-energy (5 to 15 keV) implantations with high current beam of hundreds of μA level, providing the most wide implantation area possible and allowing continuously magnetic scanning of the beam over the sample(s). This paper describes the developed system installed in the high-current ion implanter at the Laboratory of Accelerators and Radiation Technologies of the Nuclear and Technological Campus, Sacavém, Portugal (CTN).2015-01-01T00:00:00Z