Specialised branch-and-bound algorithm for transmission network expansion planning

An algorithm is presented that finds the optimal plan long-term transmission for till cases studied, including relatively large and complex networks. The knowledge of optimal plans is becoming more important in the emerging competitive environment, to which the correct economic signals have to be sent to all participants. The paper presents a new specialised branch-and-bound algorithm for transmission network expansion planning. Optimality is obtained at a cost, however: that is the use of a transportation model for representing the transmission network, in this model only the Kirchhoff current law is taken into account (the second law being relaxed). The expansion problem then becomes an integer linear program (ILP) which is solved by the proposed branch-and-bound method without any further approximations. To control combinatorial explosion the branch- and bound algorithm is specialised using specific knowledge about the problem for both the selection of candidate problems and the selection of the next variable to be used for branching. Special constraints are also used to reduce the gap between the optimal integer solution (ILP program) and the solution obtained by relaxing the integrality constraints (LP program). Tests have been performed with small, medium and large networks available in the literature.

Reactive power dispatch and planning using a non-linear branch-and-bound algorithm

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Sperm storage structures in the ovary of Helicolenus dactylopterus dactylopterus (Teleostei : Scorpaenidae): An ultrastructural study

The ultrastructure of ovarian sperm storage of Helicolenus dactylopterus dactylopterus is described, before and after the spawning period. The spermatozoa remain inside cryptal structures that are situated in the interlamellar gaps and are connected to the ovarian lumen by a duct. This complex forms a highly specialised structure. During the long storage period, crypts are richly vascularised. Their surrounding simple epithelia have intercellular junctions that may serve to protect the spermatozoa from the female immune system. At the moment during which insemination of mature oocytes occurs, the sperm may be expelled from cryptal structures by means of a spasmodic contraction. During the post spawning period, residual spermatozoa that remain in the crypts are eliminated by cryptal phagocytes. At the end of the process the crypts contain only an amorphous material.

Post-larval morphology, growth, and development of Uca cumulanta Crane, 1943 (Crustacea, Decapoda, Ocypodidae) under laboratory conditions

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

Effects of flooding regime and woody bamboos on tree community dynamics in a section of tropical semideciduous forest in South-Eastern Brazil

The influence of a population of the understorey woody bamboo Merostachys riedeliana and different flooding regimes on tree community dynamics in a section of tropical semideciduous forest in South-Eastern Brazil was examined. A forest section with an area of 1.6 ha composed of 71 adjacent plots was located on a slope ending at the river margin. The section was divided into five topographical sectors according to the mean duration of river floods. In 1991 and 1998 all trees with a diameter at the base of the trunk greater than or equal to 5 cm were measured, identified and tagged, and all live bamboo culms were counted. Annualised estimates of the rates of tree mortality and recruitment, gain and loss of tree basal area, and change in bamboo density were calculated for each of the 71 plots and five topographical sectors as well as for diameter classes and tree species. To segregate patterns arising from spatially autocorrelated events, geostatistical analyses were used prior to statistical comparisons and correlations. In general, mortality rates were not compensated by recruitment rates but there was a net increase in basal area in all sectors, suggesting that the tree community as a whole was in a building phase. Tree community dynamics of the point bar forest (Depression and Levee sectors) differed from that of the upland forest (Ridgetop, Middle Slope and Lower Slope sectors) in the extremely high rates of gain in basal area. The predominant and specialised species, Inga vera and Salix humboldtiana, are probably favoured by relaxed competition in an environment stressed by long-lasting floods. In the upland forest, mortality rates were highest at the Middle Slope, particularly for smaller trees, while recruitment rates were lowest. As bamboo clumps were concentrated in this sector, the locally higher instability in the tree community probably resulted from the direct interference of bamboos. The density of bamboo culms in the upland forest was negatively correlated with the rates of tree recruitment and gain in basal area, and positively correlated with tree mortality rates. Bamboos therefore seemed to restrict the recruitment, growth and survival of trees.

Daily cleaning activity and diversity of clients of the barber goby, Elacatinus figaro, on rocky reefs in southeastern Brazil

Gobies of the genus Elacatinus are regarded as the most specialised cleaner fishes in the western tropical Atlantic, yet there are no studies on these cleaners in the southern portion of West Atlantic. We studied the diversity of clients and the daily cleaning activity of the barber goby, Elacatinus figaro, on rocky reefs in southeastern Brazil (23-24 degrees S). A total of 34 fish client species in 16 families were recorded over 484 cleaning events. The most frequent clients were damselfishes, Pomacentridae (37.9% of cleaning events) and grunts, Haemulidae (16.9%). Planktivores were the most frequently attended trophic category, and two species in that category accounted for about a half (44%) of the total cleaning events. Size of clients ranged 4.5-55 cm and most individuals were medium-sized (12-30 cm); as the barber goby ranged 2-4.5 cm, clients were 1.5 to 15 times larger than the cleaner was. Cleaning activity started at dawn and ended shortly before nightfall, the highest frequency of interactions occurring at early morning (nocturnal clients) and mid-afternoon (diurnal clients). By midday the frequency of cleaning events decreased and their duration increased. A total of 109 +/- 3 cleaning events and 30 +/- 1 min of cleaning activity were estimated per cleaning station per day, both figures low when compared to those recorded for cleaner fishes in tropical areas of the western Atlantic and Indo-Pacific.

Branch and bound algorithm for transmission system expansion planning using a transportation model

A method for optimal transmission network expansion planning is presented. The transmission network is modelled as a transportation network. The problem is solved using hierarchical Benders decomposition in which the problem is decomposed into master and slave subproblems. The master subproblem models the investment decisions and is solved using a branch-and-bound algorithm. The slave subproblem models the network operation and is solved using a specialised linear program. Several alternative implementations of the branch-and-bound algorithm have been rested. Special characteristics of the transmission expansion problem have been taken into consideration in these implementations. The methods have been tested on various test systems available in the literature.

Analysis of heuristic algorithms for the transportation model in static and multistage planning in network expansion systems

The usefulness of the application of heuristic algorithms in the transportation model, first proposed by Garver, is analysed in relation to planning for the expansion of transmission systems. The formulation of the mathematical model and the solution techniques proposed in the specialised literature are analysed in detail. Starting with the constructive heuristic algorithm proposed by Garver, an extension is made to the problem of multistage planning for transmission systems. The quality of the solutions found by heuristic algorithms for the transportation model is analysed, as are applications in problems of planning transmission systems.

The ecological causes of individual specialisation

University of Tennessee, KnoxvilleNational Science Foundation (NSF)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Algorithms for network piecewise-linear programs: A comparative study

Piecewise-Linear Programming (PLP) is an important area of Mathematical Programming and concerns the minimisation of a convex separable piecewise-linear objective function, subject to linear constraints. In this paper a subarea of PLP called Network Piecewise-Linear Programming (NPLP) is explored. The paper presents four specialised algorithms for NPLP: (Strongly Feasible) Primal Simplex, Dual Method, Out-of-Kilter and (Strongly Polynomial) Cost-Scaling and their relative efficiency is studied. A statistically designed experiment is used to perform a computational comparison of the algorithms. The response variable observed in the experiment is the CPU time to solve randomly generated network piecewise-linear problems classified according to problem class (Transportation, Transshipment and Circulation), problem size, extent of capacitation, and number of breakpoints per arc. Results and conclusions on performance of the algorithms are reported.

Dicionário onomasiológico de expressões cromáticas da fauna e flora:

Pós-graduação em Estudos Linguísticos - IBILCE

Território e indústria: as empresas metalomecânicas em Sertãozinho

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Colocação de endoprótese vascular versus cirurgia para coarctação de aorta: revisão sistemática

Pós-graduação em Bases Gerais da Cirurgia - FMB

Das ciências do léxico ao léxico nas ciências: uma proposta de dicionário português-espanhol de economia monetária

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Biologia, morfologia e bioquímica de veneno da formiga lava-pés Solenopsis saevissima Smith (Insecta, Hymenoptera, Formicidae)

Pós-graduação em Ciências Biológicas (Zoologia) - IBRC