Showing papers by "State University of Campinas published in 1987"
TL;DR: In this paper, a mathematical framework for the solution of the economic dispatch problem with security constraints is presented, which can take into account the system corrective capabilities after the outage has occurred, and the solution algorithm is based on mathematical programming decomposition techniques that allow the iterative solution of a "base-case" economic dispatch and separate contingency analysis with generation rescheduling to eliminate constraint violations.
Abstract: This paper describes a mathematical framework for the solution of the economic dispatch problem with security constraints, which can take into account the system corrective capabilities after the outage has occurred. The solution algorithm is based on mathematical programming decomposition techniques that allow the iterative solution of a "base-case" economic dispatch and separate contingency analysis with generation rescheduling to eliminate constraint violations. The resulting dispatch has the same security level as the usual security-constrained dispatch, but with lower operating costs. Case studies with the IEEE 118-bus are presented. The extension of the methodology to the probabilistic case will be discussed in a forthcoming paper.
621 citations
TL;DR: Structural studies of the as-deposited layers showed them to be composed of microcrystalline, cubic CdSe, and electron microscopy resolved them into individual crystallites of typically 40\char21{}80-A\r{} diameter, depending on deposition temperature, the first example reported of a three-dimensional quantum-size effect in a film.
Abstract: Optical band gaps, ${E}_{g}$, up to 0.5 eV higher than in single-crystal samples, are observed for chemically deposited films of CdSe and explained in terms of a quantum-size effect, whereby the electrons are localized in individual crystallites. The increase in ${E}_{g}$ depends strongly on deposition temperature, with the greatest increase obtained at the lowest temperature. Annealing at temperatures above the deposition temperature causes a decrease in ${E}_{g}$; this decrease is stronger at higher annealing temperature. Structural studies of the as-deposited layers showed them to be composed of microcrystalline, cubic CdSe, and electron microscopy resolved them into individual crystallites of typically 40--80-A\r{} diameter, depending on deposition temperature. This is the first example reported of a three-dimensional quantum-size effect in a film.
283 citations
01 Mar 1987
TL;DR: The distribution of post-Palaeozoic igneous rocks in Brazil and its continental margin is summarized in this paper, where it is suggested that those rocks are closely related to the structure and age of the basement and also to epeirogenic movements.
Abstract: The distribution of post-Palaeozoic igneous rocks in Brazil and its continental margin is summarized. It is suggested that those rocks are closely related to the structure and age of the basement and also to epeirogenic movements. The reactivated areas comprise many preexisting precambrian zones of structural weakness and some previous palaeozoic covers affected by younger tectonic movement s (such as tectonic arches, geosutures, flexures etc.). The activization occurred since the late Permian in the Amazon Craton and since the Triassic in other reglons. Basalt flows, sills and dykes tend to be concentrated in intracratonic sedimentary basins. The maximum total thicknesses of flows and sills in Parana and Parnaiba basins coincide with areas of maximum subsidence during the Palaeozoic. Dykes occur all over the precambrian shields, specially in areas of late stabilization. Alkaline rocks, including carbonatites and kimberlites, are concent rated in arches and flexures around the Parana Basin, but they also occur locally in the Amazon Craton and in the arched south margin of the Parnaiba Basin. They appear to be related to preexisting zones of weakness reactivated by the mesozoic continental fragmentation. Such zones are placed not far from precambrian cratonic borders. It is not certain that transform oceanic faults are placed in the prolongation of continental orogenic belts, fault zones, aulacogens or other clearly recognized tectonic features. However, the alkaline Mecejana volcanism in Ceara State is located in the coastal region near the end of an oceanic transform zone. Alligned centers of igneous activity ordered according to age, which could have been caused by the displacement of the South American Plate over hot spots, have not yet been observed in Brazil. Some models proposed by recent papers are discussed in order to explain the distribution of the brazilian mesozoic-cenozoic magmatism.
155 citations
TL;DR: In the semiclassical limit, the sum S(E, Delta E)= Sigma nm mod Anm mod 2 delta (E-1/2(En+Em)) delta ( Delta E-(En-Em)) of matrix elements of an arbitrary operator -A can be related to the classical correlation function of the Weyl symbol A(q, p) of -A: CA(e, t).
Abstract: In the semiclassical limit, the sum S(E, Delta E)= Sigma nm mod Anm mod 2 delta (E-1/2(En+Em)) delta ( Delta E-(En-Em)) of matrix elements of an arbitrary operator -A can be related to the classical correlation function of the Weyl symbol A(q, p) of -A: CA(E, t)= integral d alpha delta (E-H( alpha ))A( alpha )A( alpha t). S(E, Delta E) is proportional to the Fourier transform of CA(E, t) over t, plus a set of correction terms associated with periodic trajectories in phase space. If the system has a chaotic classical limit, the matrix elements are independently Gaussian distributed with mean value zero, and S(E, Delta E) gives the variance of this distribution.
123 citations
TL;DR: Results show that possession of EFNs increases ant density on Q. grandiflora shrubs over that of neighbouring non-nectariferous plants, and that Camponotus ants together attacked significantly more termites than nine other ant species grouped.
Abstract: Qualea grandiflora is a typical tree of Brazilian cerrados (savanna-like vegetation) that bears paired extrafloral nectaries (EFNs) along its stems. Results show that possession of EFNs increases ant density on Q. grandiflora shrubs over that of neighbouring non-nectariferous plants. Frequency of ant occupancy and mean number of ants per plant were much higher on Qualea than on plants lacking EFNs. These differences resulted in many more live termitebaits being attacked by foraging ants on Qualea than on neighbours without EFNs. Termites were attacked in equal numbers and with equal speeds on different-aged leaves of Qualea. The greatest potential for herbivore deterrence was presented by Camponotus ants (C. crassus, C. rufipes and C. aff. blandus), which together attacked significantly more termites than nine other ant species grouped. EFNs are regarded as important promoters of ant activity on cerado plants.
94 citations
TL;DR: In this paper, a combined theoretical and numerical study of the mass transfer effected by high Rayleigh number Benard convection in a two-dimensional saturated porous layer heated from below is presented.
89 citations
TL;DR: As cobras corais sao os representantes da familia Elapidae nas Americas, causando perda da forca muscular e morte por paralisia respiratoria e todas as que causam acidentes no homem Podem-se fazer as seguintes generalizacoes quanto aos efeitos produzidos por suas peconhas e a algumas propriedades destas.
Abstract: Coral snakes, the New World Elapidae, are included in the genera Micniroides and Micrurus. The genus Mlcrurus comprises nearly all coral snake species and those which are responsible for human snake-bite accidents. The following generalizations concerning the effects induced by their venoms, and their venom-properties can be made. Coral snake venoms are neurotoxic, producing loss of muscle strenght and death by respiratory paralysis. Local edema and necrosis are not induced nor blood coagulation or hemorrhages. Proteolysis activity is absent or of very low grade. They display phospholipase A2 activity. Nephrotoxic effects are not evoked. The main toxins from elapid venoms are postsynaptic and presynaptic neurotoxins and cardiotoxins. Phospholipases A2 endowed with myonecrotic or cardiotoxin-like properties are important toxic components from some elapid venoms. The mode of action of Micrurus frontalis, M. lemniscatus, M. corallinus and M. fulvius venoms has been investigated in isolated muscle preparations and is here discussed. It is shown that while M. frontalis and M. lemniscatus venoms must contain only neurotoxins that act at the cholinergic end-plate receptor (postsynaptic neurotoxins), M. corallinus venom also inhibits evoked acetylcholine release by the motor nerve endings (presynaptic neurotoxin-like effect) and M. fulvius induces muscle fiber membrane depolarization (cardiotoxin-like effect). The effects produced by M. corallinus and M. fulvius venoms in vivo in dogs and M. frontalis venom in dogs and monkeys are also reported.
80 citations
TL;DR: The main feature of the HSA code is a dynamic base choice that enables the decision maker to improve the convergence of the optimization procedure by the use of his practical experience.
Abstract: In this paper a Hydrothermal Scheduling Algorithm (HSA) for deterministic inflows is presented. A nonlinear network flow model representing the hydrothermal scheduling problem is used. By exploiting the special network structure, a temporally expanded arborescence [1], the HSA code attains important computational savings in processing time and memory requirements allowing the use of microcomputers even for large scale problems. The main feature of the HSA code is a dynamic base choice that enables the decision maker to improve the convergence of the optimization procedure by the use of his practical experience. The performance of the algorithm is tested on the Southeast Brazilian Power System.
73 citations
TL;DR: In this article, the volume fraction, X, of the conducting phase in a granular structure defined in the carbon matrix and applicable to heat treated biomass carbons is calculated as a function of structural parameters obtained from X-ray diffraction and small-angle Xray scattering measurements.
65 citations
TL;DR: A metodo de quadrantes (63 pontos) was used by Sorensen et al. as discussed by the authors to find 107 especies, sendo 80 exclusivas.
Abstract: Aplicou-se o metodo de quadrantes (63 pontos) na Reserva Estadual de Porto Ferreira (21o49'S e 47o25'W), numa area (l,08ha) a margem direita do rio Moji Guacu, amostrando dois individuos lenhosos em cada quadrante: um com fuste minimo de 130cm e DAP 10cm. Os resultados obtidos foram comparados com os publicados por outros autores para uma area de mata riparia na Estacao Ecologica de Moji Guacu (Mata da Figueira), cerca de 100 km a montante daquele rio. Em Porto Ferreira, encontraram-se 107 especies, sendo 80 exclusivas. Das 59 especies listadas por outros autores para a Mata da Figueira, 31 foram exclusivas. As duas areas tiveram 27 especies comuns, com uma similaridade de Sorensen de 48,6%, considerada baixa. A grande heterogeneidade ambiental das varzeas e os diferentes graus de perturbacao antropica poderiam contribuir para essa variacao floristica. Os maiores numeros de especies ocorreram em Leguminosae (20), Myrtaceae (17), Rutaceae (9), Euphorbiaceae (7) e Lauraceae, Meliaceae, Moraceae e Rubiaceae (6 especies cada). Ao nivel de familia, parece haver poucas diferencas'com as florestas paulistas nao inundaveis, mas as especies mostram diferentes graus de preferencia pelo habitat. As duas areas apresentaram uma mistura de especies tipicas com outras de florestas nâo inundaveis. Estas ocorreriam na varzea em decorrencia de, principalmente: a) adaptacoes do sistema radicular a periodos relativamente curtos de inundacao; b) menor tempo de inundacao nos pontos mais elevados do microrrelevo da varzea; c) maior aeracao provocada pela agua corrente.
63 citations
TL;DR: The effect of inelastic interactions on Zener transitions is studied in the context of externally driven systems (flux-driven normal metallic rings, current-biased tunnel junctions, etc.) using a time-dependent Hamiltonian and a two-level approximation.
Abstract: The effect of inelastic interactions on Zener transitions is studied in the context of externally driven systems (flux-driven normal metallic rings, current-biased tunnel junctions, etc.). We employ a time-dependent Hamiltonian and use a two-level approximation to study these systems. We consider a coupling (not necessarily weak) of the system to a phonon bath and allow for a large class of phonon spectra. The coupling tends to reduce the Zener tunneling. The Zener transitions are enhanced at finite temperatures. We also consider the effect of a phenomenological relaxation time \ensuremath{\tau} on the behavior of the system, and express the (nonlinear) resistance R in terms of \ensuremath{\tau} and the other important physical parameters. When the bias goes to zero, R vanishes.
TL;DR: The pyridine nucleotide specificity, the participation of delta psi, and the energy-linked transhydrogenase in the process of Ca2+ efflux stimulated by the oxidized state of NAD(P) were examined in rat liver mitochondria energized by ascorbate + TMPD.
TL;DR: In this paper, a flow injection/conductometric method is proposed for determing ammonia in solutions obtained from Kjeldahl digestion, based on diffusion of ammonia through a PTFE membrane from an alkaline (NaOH/EDTA) medium to a deionized water stream.
TL;DR: Nickel hydroxide films were electrochemically precipitated onto transparent conducting substrates in this paper, where the phase changes and loss of charge with potential cycling were discussed, as well as intermediate transmittance states are also possible.
TL;DR: In this article, the subcellular mechanism of alkenyl halide S-conjugate-induced nephrotoxicity was studied in mitochondria isolated from rat kidney cortex in vitro using the cysteine conjugate of hexachlorobutadienyl- l -cysteine (PCBC) as a model substrate.
TL;DR: Great aggressiveness and alertness to foreign objects, better eyesight, larger size, and an individual foraging technique appear to be responsible for the greater foraging success of Pseudomyrmex when compared with Crematogaster.
Abstract: Foraging parameters of two ant species, Pseudomyrmex triplarinus and Cremato- gaster sp., on P. triplarinus-occupied shrubs of Triplaris surinamensis were evaluated in a semi- deciduous forest of Mato Grosso, western Brazil. Live workers of the termite Microcerotermes strunckii, used as baits for ants, were placed on leaves in the lower, medium and upper thirds of the crown of thirty experimental Triplaris (nine baits/plant). Besides attacking more than twice as many baits as Crematogaster (131 against 59), Pseudomyrmex also attacked them signifi- cantly faster. Pseudomyrmex patrolled the plant uniformly, while Crematogaster patrolled more intensively the lower portion of the crown of Triplaris. Baits retrieved by Pseudomyrmex were taken to their nests in the stem galleries of Triplaris; those retrieved by Crematogaster were carried to nearby nests in the forest understory. Greater aggressiveness and alertness to foreign objects (i.e. baits), better eyesight, larger size, and an individual foraging technique appear to be responsible for the greater foraging success of Pseudomyrmex when compared with Crematogaster.
TL;DR: The so-called Feynman-Vernon influence functional theory has been generalized in order to include the possibility of dealing with initial conditions of the system plus environment other than the factorizable one.
Abstract: In this paper the so-called Feynman-Vernon influence functional theory has been generalized in order to include the possibility of dealing with initial conditions of the system plus environment other than the factorizable one. It has been shown that the new influence functional can now be written in terms of paths which represent the coupling of quantum-statistical to quantum-dynamical effects. Once the thermal paths are integrated out of this new influence functional, a generalization of the original Feynman-Vernon expression is obtained.
TL;DR: In this article, a microwave oven (2450 MHz) was used as heating source to inactivate soybean lipoxygenase, and the initial moisture level of the soybean and time of heating were studied.
Abstract: A microwave oven (2450 MHz) was used as heating source to inactivate soybean lipoxygenase. Variables studied were initial moisture level of the soybean and time of heating. After exposure to microwave, the temperature, the moisture loss, the residual lipoxygcnase activity and the nitrogen solubility index (NSI) of the soybeans were determined. No linear relationship was observed between lipoxygenase activity and NSI. Complete inactivation of lipoxygenase in soybeans with moisture content between 26.9 and 56.8% was reached after 210 sec of microwave heating, corresponding to NSI between 49.4 and 39.2%, respectively. The beans with their innate moisture (8.7%) had approximately 98% inactivation of lipoxygenase and 56.1% of NSI after 240 sec of exposure.
TL;DR: In this paper, the selectivity constants of silica gel functionalized with pyridinium ion were studied in exchange reactions with IO 3 −, ClO 4 −, Br −, I −, SCN −, CLO 3 −, BrO − and IO 4 −.
01 Jan 1987
TL;DR: Discussion de la possibilite d'utiliser le dephasage du signal photoacoustique de differents constituants d'un echantillon composite pour resoudre les spectres des constituants, a frequence de modulation fixe.
Abstract: Discussion de la possibilite d'utiliser le dephasage du signal photoacoustique de differents constituants d'un echantillon composite pour resoudre les spectres des constituants, a frequence de modulation fixe. Test experimental de la methode proposee en utilisant des verres avec des melanges binaires d'oxydes
TL;DR: In this article, the robustness of nonlinear discrete-time systems is analyzed based on the existence of a stationary solution of the dynamic programming equation (DPE), which provides directly a Lyapunov function associated to the closed-loop system.
Abstract: In this paper the robustness of nonlinear discrete-time systems is analyzed. The nominal plant is supposed to be controlled by means of a feedback control law which is optimal with respect to some given criterion. The robustness of the closed-loop system is studied for two different classes of perturbations in the control law, which are called gain and additive nonlinear perturbations. The results are entirely based on the existence of a stationary solution of the dynamic programming equation (DPE), which provides directly a Lyapunov function associated to the closed-loop system. The convexity of that solution and the use of the Taylor formula appear to be the key to establish the robustness properties of the nominal plant. Two examples are solved in order to show an interesting fact: the existence of a compromise between the robustness of the system subjected to the two different classes of perturbations.
TL;DR: The Birkhoff normal form for the neighbourhood of an unstable fixed point of an analytical area preserving map was proved by Moser to converge in this article, and the region of convergence in fact stretches along a narrow strip surrounding the stable and the unstable manifolds, which can be used to compute homoclinic points and unstable periodic orbit families that accumulate on them.
01 Jan 1987
TL;DR: In the last ten years, the recognition of several circular structures in the Brazilian territory which have, as common characteristics, the presence of similarities with well-known structures in other countries and planets attributed to impact with celestial bodies, and the absence of evidence for a terrestrial endogeneous origin, has been carried out as discussed by the authors.
Abstract: Studies carried out in the last ten years resulted in the recognition of several circular structures in the Brazilian territory which have, as common characteristics, the presence of similarities with well-known structures in other countries and planets attributed to impact with celestial bodies, and the absence of evidence for a terrestrial endogeneous origin. Those structures presently number six, ranging in diameter from three to 40kilometers. Two of them, Araguainha and Serra da Cangalha, were studied in some detail and presented enough evidence for their impact origin, including impact metamorphism features and morphologic/structural styles. The other four, Colonia, Sao Miguel do Tapuio, Vargeao and Riachao, are still poorly known, but the available data are very suggestive for their impact origin.
01 Jan 1987
TL;DR: The froth of spittlebugs in its whole structure and composition is not properly comparable to salivary and Malpighian tubule silks of other insect groups, but certainly provides it with special properties adequate to the performance of its functions.
TL;DR: In this article, the reduced density operator of a particle coupled to a fermionic environment (metal electrons) is written in terms of a Feynman-Vernon influence functional.
Abstract: The reduced density operator of a particle coupled to a fermionic environment (metal electrons) is written in terms of a Feynman-Vernon influence functional. Two different approaches are used in order to achieve this goal. Firstly, the environmental interacting electron gas is treated in RPA and the coupling is correctly accounted for up to second order in perturbation theory. Then the local and tight-binding models are studied. For the latter a second approach for obtaining the influence functional is used in the narrow-band limit. It is found that the popular representation of the environment in terms of a single set of harmonic oscillators is not feasible unless the particle is confined to move in a local region of radial extension r kF-1.