Short-term expansion planning of radial electrical distribution systems using mixed-integer linear programming

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Biological aspects of the immature stages of Ceraeochrysa everes (Banks) (Neuroptera: Chrysopidae)

Para o estabelecimento de um programa de controle biológico, o conhecimento de alguns aspectos biológicos e de comportamento dos inimigos naturais é de extrema importância. Os aspectos biológicos do desenvolvimento larval e pupal do predador Ceraeochrysa everes (Banks) foram estudados. Larvas oriundas de adultos da geração F1 foram mantidas em laboratório a 25 ± 21°C, 70 ± 10 % UR e fotofase 14 horas, sendo alimentadas com ovos de Sitotroga cerealella (Olivier). A duração e viabilidade do período embrionário, estágios imaturos de desenvolvimento e o período de ovo a adulto foram avaliados. O período embrionário foi em média de 5,0 dias, enquanto que as durações médias para o primeiro, segundo e terceiro instares foram de 5,1 ± 0,03; 4,3 ± 0,05 e 4,5 ± 0,05 dias, respectivamente, com viabilidade superior a 90 %. Os estágios larval, pré-pupal e pupal apresentaram duração média de 13,9 ± 0,07; 5,7 ± 0,07 e 9,6 ± 0,12 dias, respectivamente. A duração do ciclo biológico foi de 34 ± 0,11 dias em média. Ovos de S. cerelella não foram adequados para a manutenção de C. everes em laboratório, por interferir no desenvolvimento do predador.

Efficient heuristic algorithm used for optimal capacitor placement in distribution systems

An efficient heuristic algorithm is presented in this work in order to solve the optimal capacitor placement problem in radial distribution systems. The proposal uses the solution from the mathematical model after relaxing the integrality of the discrete variables as a strategy to identify the most attractive bus to add capacitors to each step of the heuristic algorithm. The relaxed mathematical model is a nonlinear programming problem and is solved using a specialized interior point method, The algorithm still incorporates an additional strategy of local search that enables the finding of a group of quality solutions after small alterations in the optimization strategy. Proposed solution methodology has been implemented and tested in known electric systems getting a satisfactory outcome compared with metaheuristic methods.The tests carried out in electric systems known in specialized literature reveal the satisfactory outcome of the proposed algorithm compared with metaheuristic methods. (C) 2009 Elsevier Ltd. All rights reserved.

Strategic capacitor placement in distribution systems by minimisation of harmonics amplification because of resonance

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Melhora da estabilidade dinâmica de sistemas elétricos de potência multimáquinas usando o dispositivo facts thyristor-controlled series capacitor - TCSC

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Psychotria hoffmansegiana (Willd ex Roem. & Schult.) Mull. Arg. and Palicourea marcagravii st. Hil. (Rubiaceae): potential for forming soil seed banks in a brazilian Cerrado

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Capacitor Cilíndrico Excêntrico

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Biologia de Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae) em limão siciliano (Citrus limon Burm)

No estudo da biologia de Polyphagotarsonemus latus em limão Siciliano, foram utilizados potes plásticos circulares com capacidade de 250 ml, contendo areia esterilizada como suporte para dois frutos novos com aproximadamente 2,0 cm de diâmetro. O ensaio foi conduzido a 27,1 ± 0,5°C, umidade relativa de 67,6 ± 1,3% e fotofase contínua. O período de ovo a adulto durou 3,7 ± 0,1 dias para fêmeas e 3,6 ± 0,1 dias para machos, com sobrevivência de 100%. Após um período de pré-oviposição de 1,0 ± 0,2 dias, as fêmeas depositaram 5,6 ± 0,5 ovos por dia durante 10,5 ± 0,9 dias, totalizando 58,9 ± 6,7 ovos por fêmea. A longevidade foi de 13,4 ± 1,0 dias para fêmeas e 12,0 ± 2,4 dias para machos. A razão intrínseca de aumento (rm) foi de 0,359, a razão finita de aumento (l) de 1,43 indivíduos por fêmea por dia, o tempo médio de uma geração (T) de 10,34 dias e a taxa líquida de reprodução (Ro) de 41,0.

Optimal capacitor placement in radial distribution networks

The capacitor placement (replacement) problem for radial distribution networks determines capacitor types, sizes, locations and control schemes. Optimal capacitor placement is a hard combinatorial problem that can be formulated as a mixed integer nonlinear program. Since this is a NP complete problem (Non Polynomial time) the solution approach uses a combinatorial search algorithm. The paper proposes a hybrid method drawn upon the Tabu Search approach, extended with features taken from other combinatorial approaches such as genetic algorithms and simulated annealing, and from practical heuristic approaches. The proposed method has been tested in a range of networks available in the literature with superior results regarding both quality and cost of solutions.

Biologia de Polyphagotarsonemus latus (Banks, 1904) (Acari: Tarsonemidae) em algodoeiro

Leaf discs obtained from the first or second non-cotyledonal leaf of cotton (Gossypium hirsutum L.) seedlings were used for the study of the biology of Polyphagotarsonemus latus on cotton IAC-20 cultivar. Seedlings were grown in pots and placed on a layer of cotton moistened with distilled water. The assays were carried out at 28.5 ± 0.3°C, relative humidity of 71.0 ± 2.6% and a 14 h photophase. The duration of immature phases was 4.1 ± 0.1 days for females and 4.1 ± 0.3 days for males, with a survival of 91.2%. After a pre-oviposition period of 1.1 ± 0.2 days, the females deposited 4.5 ± 0.9 eggs per day during 6.8 ± 1.3 days, i.e., 29.6 ± 7.3 eggs per female. The longevity was 10.0 ± 1.5 days for females and 8.8 ± 1.1 days for males. The intrinsic rate of increase (rm) was 0.323; finite rate of increase (λ) 1.38 individual per female per day; mean generation time (T) 9.54 days and net reproductive rate (Ro) 21.73.

Effects of the thyristor controlled serie capacitor on the electric power system

This work deals with the effects of the series compensation on the electric power system for small-signal stability studies. Therefore, the system is modeled admitting the existence of the compensation and then, the equations are linearized and a linear model is obtained for a single machine-infinite bus power system with a compensator installed. The resulting model with nine defined constants is very similar to the Heffron & Phillips linear model widely used on the existent literature. Finally, simulations are executed for an example system, to analyze the behavior of these constants when loading the system. © 2004 IEEE.

Artificial immune systems applied to optimal capacitor placement in radial distribution networks

The capacitor placement problem for radial distribution networks aims to determine capacitor types, sizes, locations and control scheme. This is a combinatorial problem that can be formulated as a mixed integer nonlinear program. The paper presents an algorithm inspired in artificial immune systems and developed for this specific problem. A good performance was obtained through experimental tests applied to known systems. © 2006 IEEE.

Soil seed banks in tropical forest fragments with different disturbance histories in southeastern Brazil

Soil seed banks are considered an important mechanism for natural regeneration in tropical forest ecosystems. This paper investigated the soil seed bank in two semideciduous seasonal tropical forest fragments with different disturbance histories in Botucatu, southeastern Brazil. In each study site, 40 superficial soil samples (30 cm × 30 cm × 5 cm) were taken at the end of both the dry and rainy seasons. The seeds were estimated by the germination method. Average soil seed density was 588.6 and 800.3 seeds m-2, respectively, for site 1 (less disturbed) and site 2 (more disturbed). Seed density and diversity (H′) were significantly higher in site 2 in both seasons. Non-woody taxa predominated in both fragments, but pioneer tree species were better represented in the less disturbed forest. Both ecosystems have a potential for regeneration from soil seed banks, but this potential is higher in the less disturbed site. Low richness and density of pioneer tree species in the seed bank indicate that the ecosystem has lost its resilience. The seed bank is not as important in these ecosystems as in other forests. Results indicate that management strategies to restore these forests should take into account the possibility of recovering soil seed bank processes and dynamics. © 2007 Elsevier B.V. All rights reserved.

Heuristic algorithm to solve the short term transmission network expansion planning

In this paper, a method for solving the short term transmission network expansion planning problem is presented. This is a very complex mixed integer nonlinear programming problem that presents a combinatorial explosion in the search space. In order to And a solution of excellent quality for this problem, a constructive heuristic algorithm is presented in this paper. In each step of the algorithm, a sensitivity index is used to add a circuit (transmission line or transformer) or a capacitor bank (fixed or variable) to the system. This sensitivity index is obtained solving the problem considering the numbers of circuits and capacitors banks to be added (relaxed problem), as continuous variables. The relaxed problem is a large and complex nonlinear programming and was solved through a higher order interior point method. The paper shows results of several tests that were performed using three well-known electric energy systems in order to show the possibility and the advantages of using the AC model. ©2007 IEEE.