Monitoring of Tree Island Condition in the Southern Everglades: Hydrologic Driven Decadal Changes in Tree Island Woody Vegetation Structure and Composition: 2012 Annual Report

This report examines the interaction between hydrology and vegetation over a 10-year period, between 2001/02 and 2012 within six permanent tree island plots located on three tree islands, two plots each per tree island, established in 2001/02, along a hydrologic and productivity gradient. We hypothesize that: (H1) hydrologic differences within plots between census dates will result in marked differences in a) tree and sapling densities, b) tree basal area, and c) forest structure, i.e., canopy volume and height, and (H2) tree island growth, development, and succession is dependent on hydrologic fluxes, particularly during periods of prolonged droughts or below average hydroperiods.

A storage scheme for an automated archive

Presentation given at the Al-Azhar Engineering First Conference, AEC’89, Dec. 9-12 1989, Cairo, Egypt. The paper presented at AEC'89 suggests an infinite storage scheme divided into one volume which is online and an arbitrary number of off-line volumes arranged into a linear chain which hold records which haven't been accessed recently. The online volume holds the records in sorted order (e.g. as a B-tree) and contains shortest prefixes of keys of records already pushed offline. As new records enter, older ones are retired to the first volume which is going offline next. Statistical arguments are given for the rate at which an off-line volume needs to be fetched to reload a record which had been retired before. The rate depends on the distribution of access probabilities as a function of time. Applications are medical records, production records or other data which need to be kept for a long time for legal reasons.

Proposta de um framework conceitual para apoiar a criação de técnicas de indexação para banco de dados temporais

Bancos de Dados Temporais (BDTs) surgiram para tentar suprir a necessidade de se obter um melhor aproveitamento das informações que circulam atualmente. Porém, ao mesmo tempo em que é benéfico o seu uso, uma vez que armazenam o histórico das informações, existe um problema neste tipo de banco de dados, que é o desempenho. Além do grande volume de dados armazenados, este problema se agrava ainda mais devido à complexidade nas operações que governam os BDTs, como por exemplo, inclusão, remoção, alteração e consulta. Portanto, focalizando o problema, existe a necessidade de melhorar o desempenho dos BDTs frente às operações de manipulação de dados. Técnicas de indexação apropriadas para dados temporais podem amenizar este problema de desempenho. Técnicas consagradas de indexação são largamente usadas, amparadas no seu alto grau de desempenho e portabilidade. São exemplos B-Tree, B+-Tree e R-Tree, entre outras. Estas técnicas não suportam indexar os complexos BDTs, mas são fundamentais para que sirvam de base para novas estruturas que suportem esses tipos de dados. As técnicas de indexação para dados temporais existentes não conseguem suprir a semântica temporal na sua totalidade. Existem ainda algumas deficiências do tipo: poucas técnicas que abrangem ao mesmo tempo tempo de validade e tempo de transação; não existe uma técnica que oferece informações do seu desempenho; a maioria não distingue ponto no tempo de intervalo de tempo; entre outras. Entretanto, possuem características relevantes em cada uma delas. Assim, um estudo das características mais importantes se tornou um fator importante para que possa ser desenvolvido um modelo capaz de auxiliar na criação de novas técnicas de indexação para dados temporais, a fim de contemplar melhor estes tipos de dados. O objetivo deste trabalho é, com base nas características das técnicas estudadas, desenvolver um framework conceitual capaz de auxiliar na criação de novas técnicas de indexação para dados temporais. Esta estrutura apresenta as características mais relevantes das técnicas existentes, agregando novas idéias e conceitos para contemplar os dados temporais. O framework conceitual desenvolvido agrega características de diferentes técnicas de indexação, possibilitando de variar a arquitetura de um índice para dados temporais, ajustando-os para um melhor desempenho em diferentes sistemas. Para validar o framework proposto é apresentada uma especificação de índices para o modelo de dados TF-ORM (Temporal Functionality in Objects With Roles Model).

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

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Transmission system expansion planning by a branch-and-bound algorithm

A branch and bound (B& B) algorithm using the DC model, to solve the power system transmission expansion planning by incorporating the electrical losses in network modelling problem is presented. This is a mixed integer nonlinear programming (MINLP) problem, and in this approach, the so-called fathoming tests in the B&B algorithm were redefined and a nonlinear programming (NLP) problem is solved in each node of the B& B tree, using an interior-point method. Pseudocosts were used to manage the development of the B&B tree and to decrease its size and the processing time. There is no guarantee of convergence towards global optimisation for the MINLP problem. However, preliminary tests show that the algorithm easily converges towards the best-known solutions or to the optimal solutions for all the tested systems neglecting the electrical losses. When the electrical losses are taken into account, the solution obtained using the Garver system is better than the best one known in the literature.

Branch and bound algorithm for transmission network expansion planning using DC model

This paper presents an algorithm to solve the network transmission system expansion planning problem using the DC model which is a mixed non-linear integer programming problem. The major feature of this work is the use of a Branch-and-Bound (B&B) algorithm to directly solve mixed non-linear integer problems. An efficient interior point method is used to solve the non-linear programming problem at each node of the B&B tree. Tests with several known systems are presented to illustrate the performance of the proposed method. ©2007 IEEE.

A logical approach to the management of object identifiers in non-conventional database management systems

Non-conventional database management systems are used to achieve a better performance when dealing with complex data. One fundamental concept of these systems is object identity (OID), because each object in the database has a unique identifier that is used to access and reference it in relationships to other objects. Two approaches can be used for the implementation of OIDs: physical or logical OIDs. In order to manage complex data, was proposed the Multimedia Data Manager Kernel (NuGeM) that uses a logical technique, named Indirect Mapping. This paper proposes an improvement to the technique used by NuGeM, whose original contribution is management of OIDs with a fewer number of disc accesses and less processing, thus reducing management time from the pages and eliminating the problem with exhaustion of OIDs. Also, the technique presented here can be applied to others OODBMSs. © 2011 IEEE.

Managing object identity with less I/O operations

Non-conventional database management systems are used to achieve a better performance when dealing with complex data. One fundamental concept of these systems is object identity (OID). Two techniques can be used for the implementation of OIDs: physical or logical. A logical implementation of OIDs, based on an Indirection Table, is used by NuGeM, a multimedia data manager kernel which is described in this paper. NuGeM Indirection Table allows the relocation of all pages in a database. The proposed strategy modifies the workings of this table so that it is possible to reduce considerably the number of I/O operations during the request and release of pages containing objects and their OIDs. Tests show a reduction of 84% in reading operations and a 67% reduction in writing operations when pages are requested. Although no changes were observed in writing operations during the release of pages, a 100% of reduction in reading operations was obtained. © 2012 IEEE.

Uma abordagem lógica para o gerenciamento de identificadores de objetos em sistemas gerenciadores de banco de dados não convencionais

Pós-graduação em Ciência da Computação - IBILCE

A Modified Branch and Bound Algorithm to Solve the Transmission Expansion Planning Problem

In this paper a novel Branch and Bound (B&B) algorithm to solve the transmission expansion planning which is a non-convex mixed integer nonlinear programming problem (MINLP) is presented. Based on defining the options of the separating variables and makes a search in breadth, we call this algorithm a B&BML algorithm. The proposed algorithm is implemented in AMPL and an open source Ipopt solver is used to solve the nonlinear programming (NLP) problems of all candidates in the B&B tree. Strategies have been developed to address the problem of non-linearity and non-convexity of the search region. The proposed algorithm is applied to the problem of long-term transmission expansion planning modeled as an MINLP problem. The proposed algorithm has carried out on five commonly used test systems such as Garver 6-Bus, IEEE 24-Bus, 46-Bus South Brazilian test systems, Bolivian 57-Bus, and Colombian 93-Bus. Results show that the proposed methodology not only can find the best known solution but it also yields a large reduction between 24% to 77.6% in the number of NLP problems regarding to the size of the systems.

Available nitrogen and responses to nitrogen fertilizer in brazilian eucalypt plantations on soils of contrasting texture

Eucalyptus plantations have seldom responded to N fertilization in tropical and subtropical regions of Brazil. This implies that rates of N mineralization have been adequate to supply tree needs. However, subsequent crop rotations with low N fertilization may result in declining concentrations of organic and potentially mineralizable N (N-0), and consequent loss of wood productivity. This study investigated (a) in situ N mineralization and N-0 in soils of eucalypt plantations in Sao Paulo state, Brazil; (b) tree growth responses to N fertilizer applied 6-18 months after planting; and (c) the relationships between N-0,N- other soil attributes and tree growth. We established eleven N fertilizer trials (maximum 240 kg ha(-1) of N) in E. grandis and E. grandis x urophylla plantations. The soil types at most sites were Oxisols and Quartzipsamments, with a range of organic matter (18 to 55 g kg(-1)) and clay contents (8% to 67%) in the 0-20 cm layer. Concentrations of N-0 were measured using anaerobic incubation on soil samples collected every three months (different seasons). The samples collected in spring and summer had N-0 140-400 kg ha(-1) (10%-19% total soil N), which were best correlated with soil texture and organic matter content. Rates of in situ net N mineralization (0-20 cm) ranged from 100 to 200 kg ha(-1) year(-1) and were not correlated with clay, total N, or N-0. These high N mineralization rates resulted in a low response to N fertilizer application during the early ages of stand growth, which were highest on sandy soils. At the end of the crop rotation, the response to N fertilizer was negligible and non-significant at all sites.

An adaptive and dynamic dimensionality reduction method for high-dimensional indexing

The notorious "dimensionality curse" is a well-known phenomenon for any multi-dimensional indexes attempting to scale up to high dimensions. One well-known approach to overcome degradation in performance with respect to increasing dimensions is to reduce the dimensionality of the original dataset before constructing the index. However, identifying the correlation among the dimensions and effectively reducing them are challenging tasks. In this paper, we present an adaptive Multi-level Mahalanobis-based Dimensionality Reduction (MMDR) technique for high-dimensional indexing. Our MMDR technique has four notable features compared to existing methods. First, it discovers elliptical clusters for more effective dimensionality reduction by using only the low-dimensional subspaces. Second, data points in the different axis systems are indexed using a single B+-tree. Third, our technique is highly scalable in terms of data size and dimension. Finally, it is also dynamic and adaptive to insertions. An extensive performance study was conducted using both real and synthetic datasets, and the results show that our technique not only achieves higher precision, but also enables queries to be processed efficiently. Copyright Springer-Verlag 2005

Toward efficient multifeature query processing

In many advanced applications, data are described by multiple high-dimensional features. Moreover, different queries may weight these features differently; some may not even specify all the features. In this paper, we propose our solution to support efficient query processing in these applications. We devise a novel representation that compactly captures f features into two components: The first component is a 2D vector that reflects a distance range ( minimum and maximum values) of the f features with respect to a reference point ( the center of the space) in a metric space and the second component is a bit signature, with two bits per dimension, obtained by analyzing each feature's descending energy histogram. This representation enables two levels of filtering: The first component prunes away points that do not share similar distance ranges, while the bit signature filters away points based on the dimensions of the relevant features. Moreover, the representation facilitates the use of a single index structure to further speed up processing. We employ the classical B+-tree for this purpose. We also propose a KNN search algorithm that exploits the access orders of critical dimensions of highly selective features and partial distances to prune the search space more effectively. Our extensive experiments on both real-life and synthetic data sets show that the proposed solution offers significant performance advantages over sequential scan and retrieval methods using single and multiple VA-files.

A new indexing method for high dimensional dataset

Indexing high dimensional datasets has attracted extensive attention from many researchers in the last decade. Since R-tree type of index structures are known as suffering curse of dimensionality problems, Pyramid-tree type of index structures, which are based on the B-tree, have been proposed to break the curse of dimensionality. However, for high dimensional data, the number of pyramids is often insufficient to discriminate data points when the number of dimensions is high. Its effectiveness degrades dramatically with the increase of dimensionality. In this paper, we focus on one particular issue of curse of dimensionality; that is, the surface of a hypercube in a high dimensional space approaches 100% of the total hypercube volume when the number of dimensions approaches infinite. We propose a new indexing method based on the surface of dimensionality. We prove that the Pyramid tree technology is a special case of our method. The results of our experiments demonstrate clear priority of our novel method.