This paper presents a mixed-integer second-order cone programing (MISOCP) model to solve the optimal operation problem of radial distribution networks (DNs) with energy storage. The control variables are the active and reactive generated power of dispatchable distributed generators (DGs), the number of switchable capacitor bank units in operation, the tap position of the voltage regulators and on-load tap-changers, and the operation state of the energy storage devices. The objective is to minimize the total cost of energy purchased from the distribution substation and the dispatchable DGs. The steady-state operation of the DN is modeled using linear and second-order cone programing. The use of an MISOCP model guarantees convergence to optimality using existing optimization software. A mixed-integer linear programing (MILP) formulation for the original model is also presented in order to show the accuracy of the proposed MISOCP model. An 11-node test system and a 42-node real system were used to demonstrate the effectiveness of the proposed MISOCP and MILP models. Index Terms-Distributed generation, energy storage, mixed-integer linear programing (MILP), mixed-integer second-order cone programing (MISOCP), optimal operation of radial distribution networks, smart grid. ACRONYMS The abbreviations of common terms used in this paper are presented below. CB Fixed capacitor bank. DG Distributed generator. DN Distribution network. DSS Distribution substation. ESD Energy storage device. MILP Mixed-integer linear programing. MINLP Mixed-integer nonlinear programing. MISOCP Mixed-integer second-order cone programing. OLTC On-load tap-changer. OODN Optimal operation of DNs. OPF Optimal power flow. RS Renewable source.
Nuclear-follower interaction is a particular kind of interspecific foraging association that includes a nuclear species, which dig in or inspect the bottom, and follower species, which access the food items made available by the nuclear. In this study we examined the effect of habitat structure on nuclear-follower relationship in a stream of Bodoquena Plateau, Central-West Brazil. Foraging associations were registered while snorkeling in 24 observation sessions, totaling six hours in unaltered and altered sites. Overall, 272 nuclear-follower associations were registered, having four species acting as nuclear and seven as followers. The dominant nuclear species were different in each site. Prochilodus lineatus was the main nuclear species in the altered site and Leporinus macrocephalus in the unaltered site. The richness of follower species was similar between sites, however, follower species abundance per interaction were significantly higher in the unaltered site than in the altered site. These differences seem to be a consequence of the alterations in assemblage composition and feeding behavior of the nuclear species that presumably are affected by different substrate composition and food availability between the structurally distinct areas.A interação nuclear-seguidor é um tipo particular de associação alimentar interespecífica que envolve uma espécie nuclear, que revolve ou vasculha o substrato, e espécies seguidoras, que acessam os itens alimentares disponibilizados pela atividade do nuclear. Neste estudo investigamos o efeito da estrutura do habitat sobre essa interação em um riacho no Planalto da Bodoquena, Centro-Oeste do Brasil. Foram registradas 272 interações durante 24 sessões de observação subaquática em áreas estruturalmente inalteradas e alteradas. A espécie nuclear dominante diferiu entre as áreas. Prochilodus lineatus foi a espécie nuclear dominante das áreas alteradas, enquanto que Leporinus macrocephalus foi a espécie nuclear dominante nas áreas inalteradas. A riqueza de espécies seguidoras por interação não diferiu entre as áreas, entretanto a abundância de seguidores foi maior nas áreas inalteradas do que nas alteradas. Essas diferenças parecem ser consequência das modificações na composição da comunidade e no comportamento alimentar das espécies nucleares que são, por sua vez, decorrentes das diferenças na composição do substrato e disponibilidade de alimento entre as áreas estruturalmente distintas.
Few studies have been carried out on nesting of sea turtles in the southern coast of Bahia, an area that is experiencing a fast process of tourist occupation what can increase levels of threat to these species. Thus, this study aimed to identify sea turtle species that nest in the area and to describe the main characteristics of their clutches. During four reproductive seasons, from 2004 to 2008, we identified and monitored nests found at beaches located between the municipalities of Uruçuca and Itacaré, in the southern coast of Bahia. The collected variables were: clutch size, incubation duration, hatching success and stages of embryonic mortality. We registered an average of 37 ± 6.2 nests per season, with nests of Caretta caretta and Eretmochelys imbricata being more frequent, along with sporadic nests of Chelonia mydas. Nesting season of C. caretta extends from October to January and that of E. imbricata from December to March. This temporary displacement of reproductive seasons might be related to a selective adjustment to minimize competition among species. Besides the time of nesting, the two species differed also in clutch size, but they did not differ in incubation duration and in hatching success. According to our results, we believe that areas with low concentration of nests should also be a target of conservation programs, due to their relevance to the increase of genotypic, and specially fenotypic, variation of sea turtle species, so that Brazilian populations can adapt and survive to the constant threats. Those conservation programs can be established by partnerships between non-governmental organizations and private institutions and the Brazilian government institution for the conservation of sea turtles (Centro TAMAR/ICMBio). Resumo: Poucos estudos foram realizados sobre a nidificação de tartarugas marinhas no litoral sul da Bahia, região que está passando por um processo rápido de ocupação turística que pode ameaçar ainda mais estas espécies. Por estes motivos, este estudo teve como objetivos identificar as espécies de tartarugas marinhas que desovam no local e descrever as principais características de suas ninhadas. Durante quatro temporadas reprodutivas, de 2004 a 2008, foram identificados e monitorados os ninhos encontrados nas praias localizadas entre Uruçuca e Itacaré no litoral sul da Bahia. As variáveis coletadas foram: tamanho de ninhada, duração da incubação, sucesso de eclosão e fases de mortalidade embrionária. Foi registrada uma média de 37 ± 6,2 ninhos por temporada, com maior freqüência de ninhos das espécies Caretta caretta e Eretmochelys imbricata, tendo sido registradas também desovas esporádicas de Chelonia mydas. A temporada de desova de C. caretta ocorre de outubro a janeiro e de E. imbricata de dezembro a março. Este deslocamento temporal das temporadas reprodutivas pode estar relacionado a uma adaptação para minimizar a competição interespecífica. Além da época de nidificação, as duas espécies diferiram no tamanho de suas ninhadas, mas não diferiram na duração da...
Trawling is the most common method of shrimp harvesting. This technique causes a negative impact on the fauna due to the high bycatch rates and to the animals that are accidentally caught and generally returned to the sea dead. The consequences of this technique and the biological aspects of the involved species are poorly studied, specially in the Brazilian northeast. The objective of this study was to show some aspects of the population biology of Isopisthus parvipinnis (Bigtooth corvina) captured as bycatch during sea-bob (Xiphopenaeus kroyeri) shrimp fishing in the region of Ilhéus, in the state of Bahia in Brazil. A total of 1290 individuals were caught in a monthly sampling at three different stations, from March, 2003 to February, 2005. The standardized Morisita index of dispersion suggests that this species has a clumped distribution in the studied area. The number of individuals showed a significant variation (p < 0.0001) between the seasons, being higher during the winter. The estimated first maturation length (L 50 ) was about 159 mm, and 95% of the captured individuals were below this value. The sexual ratio found was 1.5 males for each female. Concerning to diet, 10 feeding categories were identified, and Decapoda Dendobranchiata was the most important in numeric frequency and occurrence. This fact suggests that Isopisthus parvipinnis is a carnivorous species, with a tendency toward crustacean-eating at least in the younger individuals.A pesca de arrasto é o método mais comum de captura de camarão. Esta técnica causa impactos negativos na fauna demersal devido ao grande número de animais que são capturados acidentalmente e que geralmente são devolvidos mortos ao mar. As conseqüências desta metodologia de pesca e os aspectos biológicos das espécies envolvidas são pouco estudados, especialmente no Nordeste do Brasil. Este estudo tem como objetivo mostrar aspectos biológicos de Isopisthus parvipinnis (tortinha) capturada como fauna acompanhante da pesca do camarão sete barbas (Xiphopenaeus kroyeri) na região de Ilhéus, no estado da Bahia, Brasil. Um total de 1290 indivíduos foram capturados em coletas mensais, em três pontos de coleta distintos, de março de 2003 a fevereiro de 2005. O índice de dispersão de Morisita padronizado sugere que a espécie, na área analisada, apresenta uma distribuição agregada. O número de indivíduos variou significativamente entre as estações do ano (p < 0,0001), sendo maior durante o inverno. O comprimento estimado de primeira maturação (L 50 ) foi de 159 mm, sendo que 95% dos indivíduos capturados estavam abaixo deste valor. A razão sexual encontrada foi de 1,5 machos para cada fêmea. Quanto à dieta, foram identificadas 10 categorias alimentares, sendo que Decapoda Dendobranchiata foi a mais importante em freqüência numérica e de ocorrência. Este fato sugere que Isopisthus parvipinnis é uma espécie carnívora, com tendência a carcinofagia, ao menos nos indivíduos jovens.
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