Avaliação de metodologias de transferência de vazões de referência em bacias hidrográficas: sua aplicação na bacia do rio Japaratuba - Sergipe - Brasil

Para avaliar a disponibilidade de água e definir as áreas de inundação nas bacias hidrográficas, é necessário considerar a vazão mínima, média e máxima, denominadas de vazões de referência, e isto requer dados observados de vazão, que são bem escassos em bacias brasileiras, principalmente as pequenas e médias bacias. Para superar esta falta, utiliza-se dados de bacias contribuintes com comportamento hidrológico similar, que são transferidos por meio de operações matemáticas, utilizando variáveis físicas e climáticas. Tais procedimentos, geralmente, são mal avaliados quanto à sua precisão. Assim, objetivou avaliar a acurácia da estimação de cinco vazões de referência em quatro estações de medição dos dois principais afluentes do rio Japaratuba (Sergipe, Brasil), os rios Japaratuba-Mirim e Siriri. Os resultados mostraram diferentes comportamentos para as duas sub-bacia, quer seja pelas variáveis influentes, quer seja pelos efeitos antrópicos como a mudança no uso do solo que precisam ser melhor avaliados. Para a bacia do rio Japaratuba-Mirim a transferência de vazões mínimas e médias deve ser realizada considerando-se o produto área x precipitação média anual e para as vazões máximas deve-se considerar o comprimento do rio até a seção. Para a bacia do Siriri, os melhores resultados de transferência de vazões médias e máximas foram obtidos com o produto "área x precipitação média anual” e a variável "precipitação média anual" gerou um erro menor para as vazões mínimas. Assessing the reference flow transfer methodologies in watersheds: their application at Japaratuba River Basin – Sergipe State – BrazilA B S T R A C TIn order to evaluate the water availability and define the flood areas in the river basins, it is necessary to consider minimum, medium and maximum discharge, called reference flows requiring records on flow data, quite scarce in Brazilian river basin, mainly those of small and medium scale. To overcome this gap, data from nearby basins with similar hydrological behavior are used, based on mathematical operations involving physical and climatic variables of the contributing basins. However, these procedures are poorly evaluated for their accuracy. Thus, this study aimed to evaluate the accuracy of the estimation of five reference flows through the transfer of information, using physical and climatic variables in four gage stations of the main tributaries of the Japaratuba river basin (Japaratuba-Mirim and Siriri river) - Sergipe State, Brazil. The results showed different behaviors for the two sub-basins as for either by influential variables or by anthropic effects such as land use and land cover changes that need to be better evaluated. The flow transfer to the subbasin of the Japaratuba-Mirim river should be performed considering the product "Area x Mean annual rainfall" for minimum and medium flows. For maximum flows the "Length" of the basin should be considered. For the Siriri river basin, the "Mean annual rainfall" variable generated a smaller error in the minimum flows and the product "Area x Mean annual rainfall” led to better results for medium and maximum flows.Keywords: Water resource management; statistical hydrology; geographic information systems.

Sub-Tree-Based Approach for Reconfiguration of Light-Tree Pair without Flow Interruption in Sparse Wavelength Converter Network

Network reconfiguration is an important mechanism for network operators to optimize network performance and optical flow transfer. It concerns unicast and multicast connections. Multicast connections are required to meet the bandwidth requirements of multicast applications, such as Internet Protocol-based TeleVision (IPTV), distance learning, and telemedicine. In optical networks, a multicast connection is made possible by the creation of an optical tree-shaped path called a light-tree. The problem of light-tree pair reconfiguration is addressed in this study. Given an initial light-tree used to transfer an optical flow and a final light-tree that is computed by the network operator to optimize network performance, the goal is to migrate the optical flow from the initial light-tree to the final light-tree without flow interruption. Flow interruption is not desirable for network operators because it forces them to pay financial penalties to their customers. To solve this problem, existing methods use a branch approach that is inefficient if some network nodes do not have wavelength conversion capability. Therefore, we proposed in this study a sub-tree-based method. This approach selects and configures sub-tree pairs from the light-tree pair (initial light-tree, final light-tree) to be reconfigured. Then, we produce a sequence of configurations. The performance study confirms that our method is efficient in solving the problem of light-tree pair reconfiguration because our method does not cause flow interruption.

Transparent Control Flow Transfer between CPU and Accelerators for HPC

Heterogeneous platforms with FPGAs have started to be employed in the High-Performance Computing (HPC) field to improve performance and overall efficiency. These platforms allow the use of specialized hardware to accelerate software applications, but require the software to be adapted in what can be a prolonged and complex process. The main goal of this work is to describe and evaluate mechanisms that can transparently transfer the control flow between CPU and FPGA within the scope of HPC. Combining such a mechanism with transparent software profiling and accelerator configuration could lead to an automatic way of accelerating regular applications. In this work, a mechanism based on the ptrace system call is proposed, and its performance on the Intel Xeon+FPGA platform is evaluated. The feasibility of the proposed approach is demonstrated by a working prototype that performs the transparent control flow transfer of any function call to a matching hardware accelerator. This approach is more general than shared library interposition at the cost of a small time overhead in each accelerator use (about 1.3 ms in the prototype implementation).

Security Margin Assessment Method of Centralized Spot Market Based on Information Entropy

In the centralized spot market, each participant pursues the maximization of economic benefits, which leads to the operation condition of the power grid closer to the security boundary. Thus, in this paper, a novel approach to security margin assessment of the centralized spot market is proposed. By proceeding from the mechanism of influence of load variation on power flow, the relationship between power flow transfer characteristics and the security margin of the power grid is explored. Then, on the basis of information entropy theory, the power flow transfer balancing evaluation index of the power grid is established. And this index is applied for security margin assessment of the power grid in the environment of the centralized spot market. Results of an IEEE 14-bus system case study have validated the effectiveness and quickness of the proposed method. Meanwhile, in accordance with the analysis results, it is proved that the proposed method is capable of accurately identifying the critical power transmission and transformation equipment affecting the security margin of the power grid, which is helpful to identify the potential risks of the operation of the power grid in advance.