A Bilevel Approach to Transmission Expansion Planning Within a Market Environment

We present a bilevel model for transmission expansion planning within a market environment, where producers and consumers trade freely electric energy through a pool. The target of the transmission planner, modeled through the upper-level problem, is to minimize network investment cost while facilitating energy trading. This upper-level problem is constrained by a collection of lower-level market clearing problems representing pool trading, and whose individual objective functions correspond to social welfare. Using the duality theory the proposed bilevel model is recast as a mixed-integer linear programming problem, which is solvable using branch-and-cut solvers. Detailed results from an illustrative example and a case study are presented and discussed. Finally, some relevant conclusions are drawn.

Single real transformation matrices applied to double three-phase transmission lines

Single real transformation matrices are tested as phase-mode transformation matrices of typical symmetrical systems with double three-phase and two parallel double three-phase transmission lines. These single real transformation matrices are achieved from eigenvector matrices of the mentioned systems and they are based on Clarke's matrix. Using linear combinations of the Clarke's matrix elements, the techniques applied to the single three-phase lines are extended to systems with 6 or 12 phase conductors. For transposed double three-phase lines, phase Z and Y matrices are changed into diagonal matrices in mode domain. Considering non-transposed cases of double three-phase lines, the results are not exact and the error analyses are performed using the exact eigenvalues. In case of two parallel double three-phase lines, the exact single real transformation matrix has not been obtained yet. Searching for this exact matrix, the analyses are based on a single homopolar reference. For all analyses in this paper, the homopolar mode is used as the only homopolar reference for all phase conductors of the studied system. (C) 2008 Elsevier B.V. All rights reserved.

Analysis of the Electrical Characteristics of an Alternative Solution for the Brazilian-Amazon Transmission System

This article analyzes the electrical parameters of a 3-phase transmission line using a 280-m-high steel tower that has been proposed for the Amazon transmission system in Brazil. The height of the line conductors and the distance between them are intrinsically related to the longitudinal and transverse parameters of the line. Hence, an accurate study is carried out in order to show the electrical variations between a transmission line using the new technology and a conventional 3-phase 440-kV line, considering a wide range of frequencies and variable soil resistivity. First, a brief review of the fundamental theory of line parameters is presented. In addition, by using a digital line model, simulations are carried out in the time domain to analyze possible and critical over-voltage transients on the proposed line representation.

Evaluation of hybrid models for static and multistage transmission system planning

Neste trabalho é analisada a aplicação de algoritmos heurísticos para o Modelo Híbrido Linear - Hybrid Linear Model (HLM) - no problema de planejamento da expansão de sistemas de transmissão. O HLM é um modelo relaxado que ainda não foi suficientemente explorado. Assim, é realizada uma análise das características do modelo matemático e das técnicas de solução que podem ser usadas para resolver este tipo de modelo. O trabalho analisa em detalhes um algoritmo heurístico construtivo para o HLM e faz uma extensão da modelagem e da técnica de solução para o planejamento multi-estágio da expansão de sistemas de transmissão. Dentro deste contexto, também é realizada uma avaliação da qualidade das soluções encontradas pelo HLM e as possibilidades de aplicação deste modelo em planejamento de sistemas de transmissão. Finalmente, são apresentados testes com sistemas conhecidos na literatura especializada.

Alternative proposal for Modal Representation of a Non-transposed Three-Phase Transmission Line with a Vertical Symmetry Plane

The objective of this paper is to show an alternative representation in time domain of a non-transposed three-phase transmission line decomposed in its exact modes by using two transformation matrices. The first matrix is Clarke's matrix that is real, frequency independent, easily represented in computational transient programs (EMTP) and separates the line into quasi-modes a, b and zero. After that, Quasi-modes a and zero are decomposed into their exact modes by using a modal transformation matrix whose elements can be synthesized in time domain through standard curve-fitting techniques. The main advantage of this alternative representation is to reduce the processing time because a frequency dependent modal transformation matrix of a three-phase line has nine elements to be represented in time domain while a modal transformation matrix of a two-phase line has only four elements. This paper shows modal decomposition process and eigenvectors of a non-transposed three-phase line with a vertical symmetry plane whose nominal voltage is 440 kV and line length is 500 km.

Knowledge and attitudes of health care workers from intensive care units regarding nosocomial transmission of influenza: a study on the immediate pre-pandemic period

The transmission of influenza in health care settings is a major threat to patients, especially those with severe diseases. The attitude of health care workers (HCWs) may influence the transmission of countless infections. The current study aimed to quantify knowledge and identify attitudes of HCWs involved in intensive care units (ICUs) regarding the risk of nosocomial influenza transmission. A questionnaire was applied through interviews to HCWs who worked in one of the five ICUs from a teaching hospital. Questions about influenza were deliberately dispersed among others that assessed several infectious agents. Forty-two HCWs were interviewed: nine physicians, ten nurses and 23 nursing technicians or auxiliaries. Among the 42 HCWs, 98% were aware of the potential transmission of influenza virus in the ICUs, but only 31% would indicate droplet precautions for patients with suspected infection. Moreover, only 31% of them had been vaccinated against influenza in the last campaign (2008). Nursing technicians or auxiliaries were more likely to have been vaccinated, both by univariate and multivariable analysis. When asked about absenteeism, only 10% of the study subjects stated that they would not go to work if they had an influenza-like illness. Those findings suggest that, in non-pandemic periods, influenza control in hospitals requires strategies that combine continuous education with changes in organizational culture.

Comparação entre dois testes de rastreamento do diabetes gestacional e o resultado perinatal

OBJETIVO: comparar dois testes de rastreamento para diabetes e seus resultados com o resultado da gestação. MÉTODOS: no total, 279 pacientes foram submetidas a dois testes de rastreamento do diabetes gestacional - associação glicemia de jejum e fatores de risco (GJ + FR) e o teste de tolerância à glicose simplificado (TTG50g). O rastreamento pela associação GJ + FR caracterizou-se pela dosagem da glicemia de jejum e anamnese para identificação dos fatores de risco na primeira consulta de pré-natal. O TTG50g foi realizado entre a 24ª e a 28ª semana de gestação e caracterizou-se pela dosagem das glicemias plasmáticas em jejum e uma hora após a sobrecarga oral com 50 g de glicose. Os resultados, positivo e negativo, foram relacionados ao resultado da gestação. Foram consideradas variáveis dependentes: via de parto, idade gestacional, peso e índice ponderal ao nascimento, índices de Apgar <7 no 1º e 5º minutos, necessidade de Unidade de Terapia Intensiva (UTI), tempo de permanência hospitalar e óbito neonatal. Empregou-se o teste t de Student, admitindo-se 5% como limite de significância para calcular a diferença de proporção de das médias. RESULTADOS: apenas dois resultados perinatais estudados foram diferenciados pelos testes. O TTG50g alterado esteve associado à maior proporção de cesárea (58,7 versus 34,3%) e a associação GJ + FR positiva, maior taxa de prematuridade (15,4 versus 5,4%). As demais variáveis não foram diferentes nas pacientes com testes de rastreamento positivo e negativo. CONCLUSÕES: Apesar da relação entre a prematuridade e associação GJ + FR positiva e aumento de cesárea e TTG50g alterado, seria falha crítica aceitá-los como definitivos. Entre outras explicações, múltiplos fatores intercorrentes e as características próprias dos testes de rastreamento devem ser consideradas.

Influence of Maternal Hyperglycemia on IL-10 and TNF-alpha Production: The Relationship with Perinatal Outcomes

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

Maternal and perinatal outcomes of first pregnancy after chemotherapy for gestational trophoblastic neoplasia in Brazilian women

Objective. To evaluate maternal and perinatal outcomes of first pregnancy after chemotherapy for gestational trophoblastic neoplasia (GTN) in Brazilian patients.Methods. This study included 252 subsequent pregnancies after chemotherapy for GTN treated between 1960-2005. Correlations of maternal and perinatal outcomes with chemotherapy regimen (single or multiagent) and the time interval between chemotherapy completion and first subsequent pregnancy were investigated.Results. There was a significant increase in adverse maternal outcomes in women who conceived <6 months than 6-12 months (76.2% and 19.6%; p<0.0001; OR=13.12; CI 95%=3.87-44.40) and >12 months (76.2% and 21.7%; P<0.0001; OR=11.56; CI 95%=3.98-33.55) after chemotherapy. Spontaneous abortion frequency was higher <6 months (71.4%) than 6-12 months (17.6%; p<0.0001: OR=11.66; CI 95%=3.55-38.22) and >12 months (9.4%; p<0.0001: OR=23.97: CI 95%=8.21-69.91) after chemotherapy. There was no difference in adverse perinatal outcomes (stillbirth, fetal malformation, and preterm birth) related to the interval after chemotherapy and Subsequent pregnancy. The overall occurrence of adverse maternal and perinatal outcomes did not significantly differ between patients on single or multiagent regimens.Conclusion. Adverse maternal outcomes and spontaneous abortion were more frequent among patients who conceived within 6 months of chemotherapy completion. In these cases, careful prenatal monitoring and hCG level measurement 6 weeks after the completion of any new pregnancy are recommended. (C) 2008 Elsevier B.V. All rights reserved.

Mild gestational hyperglycaemia as a risk factor for metabolic syndrome in pregnancy and adverse perinatal outcomes

Objective The aims of this study were to evaluate the prevalence of metabolic syndrome (MS) in a cohort of pregnant women with a wide range of glucose tolerance, pre-pregnancy risk factors for MS during pregnancy and the effects of MS in the occurrence of adverse perinatal outcomes.Research Design and Methods One hundred and thirty six women with positive screening for gestational diabetes (GDM) were classified by two diagnostic methods: glycaemic profile and 100 g oral glucose tolerance test (OGTT) as normoglycaemic, mild gestational hyperglycaemic, GDM, and overt GDM. Markers of insulin resistance were measured between 24-28 and 36th week of gestation, and 6 weeks after delivery.Results The prevalence of MS was 0; 20.0; 23.5 and 36.4% in normoglycaemic, mild hyperglycaemic, GDM and overt GDM groups, respectively. Previous history of GDM with or without insulin use, body mass index (BMI) >= 25, hypertension, family history of diabetes in first-degree relatives, non-Caucasian ethnicity, history of prematurity and polyhydramnios were statistically significant pre-pregnancy predictors for MS in the index pregnancy, that by its turn increased the occurrence of adverse perinatal outcomes (p = 0.01).Conclusions The prevalence of MS increases with the worsening of glucose tolerance and is an independent predictor of adverse perinatal outcomes; impaired glycaemic profile identifies pregnancies with important metabolic abnormalities that are linked to the occurrence of adverse perinatal outcomes even in the presence of a normal OGTT, in patients that are not currently classified as having GDM. Copyright (C) 2008 John Wiley & Sons, Ltd.

The safe motherhood referral system to reduce cesarean sections and perinatal mortality - a cross-sectional study [1995-2006]

Background: In 2000, the eight Millennium Development Goals (MDGs) set targets for reducing child mortality and improving maternal health by 2015.Objective: To evaluate the results of a new education and referral system for antenatal/intrapartum care as a strategy to reduce the rates of Cesarean sections (C-sections) and maternal/perinatal mortality.Methods: Design: Cross-sectional study. Setting: Department of Gynecology and Obstetrics, Botucatu Medical School, São Paulo State University/UNESP, Brazil. Population: 27,387 delivering women and 27,827 offspring. Data collection: maternal and perinatal data between 1995 and 2006 at the major level III and level II hospitals in Botucatu, Brazil following initiation of a safe motherhood education and referral system. Main outcome measures: Yearly rates of C-sections, maternal (/100,000 LB) and perinatal (/1000 births) mortality rates at both hospitals. Data analysis: Simple linear regression models were adjusted to estimate the referral system's annual effects on the total number of deliveries, C-section and perinatal mortality ratios in the two hospitals. The linear regression were assessed by residual analysis (Shapiro-Wilk test) and the influence of possible conflicting observations was evaluated by a diagnostic test (Leverage), with p < 0.05.Results: Over the time period evaluated, the overall C-section rate was 37.3%, there were 30 maternal deaths (maternal mortality ratio = 109.5/100,000 LB) and 660 perinatal deaths (perinatal mortality rate = 23.7/1000 births). The C-section rate decreased from 46.5% to 23.4% at the level II hospital while remaining unchanged at the level III hospital. The perinatal mortality rate decreased from 9.71 to 1.66/1000 births and from 60.8 to 39.6/1000 births at the level II and level III hospital, respectively. Maternal mortality ratios were 16.3/100,000 LB and 185.1/100,000 LB at the level II and level III hospitals. There was a shift from direct to indirect causes of maternal mortality.Conclusions: This safe motherhood referral system was a good strategy in reducing perinatal mortality and direct causes of maternal mortality and decreasing the overall rate of C-sections.

A multidisciplinary program of preparation for childbirth and motherhood: maternal anxiety and perinatal outcomes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)