Generalization of the Y-differential autotransformer for 12- and 18-pulse converters

This work proposes a methodology to generalize the Y-connections for 12- and 18-pulse autotransformers. A single mathematical expression, obtained through simple trigonometric operations, represents all the connections. The proposed methodology allows choosing any ratio between the input and the output voltages. The converters can operate either as step-up or as step-down voltage. To simplify the design of the windings, graphics are generated to calculate the turn-ratio and the polarity of each secondary winding, with respect to the primary winding. A design example, followed by digital simulations, illustrates the presented steps. Experimental results of two prototypes (12 and 18 pulses) are presented. The results also show that high power factor is an inherent characteristic of multi-pulse converters, without any active or passive power factor pre-regulators needs. (c) 2005 Elsevier B.V. All rights reserved.

Generalization of the delta-differential autotransformer for 12 and 18-pulse converters

This work proposes a methodology to generalize the A-connections for 12 and 18-pulse autotransformers. A single mathematical expression, obtained through simple trigonometric operations, represents all the connections. The proposed methodology allows choosing any ratio between the input and the output voltages. The converters can operate either as step-up or as step-down voltage. To simplify the design of the windings, graphics are generated to calculate the turn-ratio and the polarity of each secondary winding, with respect to the primary winding. A design example, followed by digital simulations, and experimental results illustrate the presented steps. The results also show that high power factor is an inherent characteristic of multi-pulse converters, without any active or passive power factor pre-regulators needs.

Zirconia needles synthesized inside hexagonal swollen liquid crystals

We report the synthesis of zirconia microneedles by the direct nucleation of particles inside a hexagonal swollen liquid crystal (SLC) (cell parameter a = 27 nm) prepared by mixing with the proper ratio, an aqueous solution of sulfated zirconium colloids, a cationic surfactant (cetylpyridinium chloride), cychlohexane as swelling agent with an oil over water ratio of 2.5 (vol.), and 1-pentanol as cosurfactant. After a slow crystallogenesis that can be enhanced by an initial induction step under moderate temperature, particles in the centimeter range can be obtained, with a very high shape ratio (over 100). These particles are made of crystalline octahydrate zirconium oxychloride containing pores of 20 nm diameter, aligned along the main axis of the liquid crystal, as the fingerprint of the oil cylinders present in the hexagonal phase. The morphology of these particles confirms that the shaping mechanism is based on true liquid crystal templating (TLCT). Further thermal treatment of these particles, after extraction from the SLC, leads to the crystallization of zirconia with the same needlelike morphology as the zirconium oxychloride.

A Family of Autoconnected Transformers for 12-and 18-Pulse Converters-Generalization for Delta and Wye Topologies

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Millennium development goals: advances in environmentally sustainable development in Latin America and the Caribbean

Includes bibliography

Generalization of Wye and Delta auto-connections: Analysis of voltages and currents

Multipulse rectifier topologies based on autoconnections, or differential connections, are more and more applied as interface stages between the mains and power converters. These topologies mitigate many low-order current harmonics in the utility, reducing the THD (total harmonic distortion) and increasing the power factor. This paper presents a mathematical model based on phasor diagrams, that results in a single expression able to unify all differential topologies connections (Delta and Wye), for both step-up or step-down autotransformers, for 12 and 18-pulse AC-DC converters. The proposed family of converters can be designed for any relationship between the input voltage and the load voltage. An immediate application would be the retrofit, i.e. to replace a conventional rectifier with poor quality of the processed energy by the 12 or 18 pulses rectifier with Wye or Delta-differential connection. The design procedure, simple and fast, is developed and tested for a prototype rating 6 kW and 250 V on the DC load © 2010 IEEE.

Uma nova metodologia de projeto e controle para o inversor Boost (CSI) monofásico, para o aproveitamento de fontes alternativas e renováveis de energia elétrica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise e modelação de perdas em conversores CC-CC do tipo Boost entrelaçados

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Comportamento ingestivo de bovinos Nelore confinados adaptados com diferentes protocolos à dieta de alto concentrado

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Protocolos de adaptação a rações de alto teor de concentrados para bovinos nelore confinados

Pós-graduação em Zootecnia - FMVZ

Latin America and the Caribbean in the World Economy: 2005 Trends

The study recently published by the Division of International Trade and Integration of ECLAC considers that 2005 will be a good year for trade in the countries of the region. Despite a favourable international context, there are still serious problems of competitiveness. The region needs to increase productivity, promote technological innovation and take a proactive part in worldwide networks. The conclusions of the study include the need to update integration; to take a strategic view of the links to be constructed with China and the countries of the Pacific; to manage free-trade agreements so as to increase and diversify exports; to step up the pace of work and improve coordination with the developing countries on the Doha Round, and to gradually incorporate the demands of security into competitiveness policies, ensuring that they do not become protectionist barriers (traceability, food safety and maritime and port security).

Capital Flows to Latin America and the Caribbean: Recent Developments

For six years, the global economy has been driven by the U.S. Federal Reserve’s policies of easy money. Liquidity has flowed from developed to developing economies, financing infrastructure and corporate investment and allowing consumers to indulge in credit-fuelled retail spending. Thus the effective ending of the Fed’s third round of asset purchases (QE3) at the end of October represents both a watershed and the beginning of a new stage in the world economy. The end of asset-purchases comes at a challenging time for emerging markets, with China’s economy slowing, the Euro zone struggling to avoid a recession and the Japanese economy already in recession. The unwinding of the U.S. monetary stimulus, while the European Central Bank and the Bank of Japan step up their monetary stimulus, has underpinned an appreciation by the U.S. dollar, in which most commodities are priced. An appreciated dollar makes dollar-denominated commodities more expensive to buyers, thereby creating pressure for sellers to lower their prices. Latin American markets ended the third quarter of 2014 under pressure from a stronger U.S. dollar. In this changing external context, there are many signs that a slowdown in Latin American and Caribbean (LAC) financial markets, particularly debt markets, which have been breaking issuance records for the past six years, may slowdown from now on. Commodity prices – including those of oil, base metals and some goods – are in a prolonged slump. The Bloomberg commodity price index, a benchmark of commodity investments, has fallen to a five-year low as China’s economy slows down, and with it the demand for commodities. Investment into the LAC region has decelerated, in large part because of a deceleration of mining investments. Latin American currencies have suffered depreciations, as current account deficits have widening for a number of countries. And LAC companies, having issued record amounts of foreign currency bonds may now struggle to service their debt. In October, credit-rating agency Moody’s downgraded the bonds of Brazil’s Petrobras to tow notches above speculative grade because of the impact of falling oil prices and the weaker real on its debt. Growth prospects look brighter in 2015 relative to 2014, but a strengthening U.S. dollar, uneven global growth and weakness in commodity prices are skewing the risk toward the downside for the 2015 forecasts across the region. The Institute of International Finance expects the strengthening of the dollar to have a divergent impact across the region, however, depending on trade and financial linkages. The Institute of International Finance, Capital Flows to Emerging Markets, October 2, 2014. A stronger dollar lifts U.S. purchasing power, supporting exports, growth and capital inflows in countries with close trade links to the U.S. economy. However, rising dollar financing costs will increase pressure on countries with weak external positions. Given the effects of falling oil prices and a stronger dollar, some companies in the region, having issued record amounts of foreign currency bonds, may now struggle to service their debts. Prospects of Fed rate hikes resulting in tighter global liquidity amid the rapid rise in the corporate external bond stock has indeed raised concerns over some companies. However, there is still a shortage of bonds at a global level and the region still enjoys good economic policy management for the most part, so LAC debt markets may continue to enjoy momentum despite occasional bursts of high volatility – even if not at the record levels of recent years.

Capital Flows to Latin America and the Caribbean: 2014 Overview

Divergence in macro trends and in monetary policy in advanced economies was a dominant driver of rates and currencies in emerging markets in 2014. Diverging macroeconomic developments were reflected in different monetary policy actions in 2014, with the European Central Bank (ECB) and the Bank of Japan (BOJ) moving in the opposite direction of the U.S. Federal Reserve. The unwinding of the U.S. monetary stimulus, while the ECB and the BOJ step up their monetary stimulus, has underpinned an appreciation by the U.S. dollar, in which most commodities are priced. Latin American markets, which started the year under pressure from fears of the U.S. Federal Reserve tapering off its quantitative easing program and concerns over stability, ended 2014 under pressure from a stronger U.S. dollar. However, there are many signs that a slowdown in LAC financial markets – particularly debt markets, which have been breaking records in debt issuance for the past six years – is under way. The region’s growth prospects look somewhat brighter in 2015 relative to 2014, but a strengthening U.S. dollar, uneven global growth and weakness in commodity prices are skewing the risk toward the downside for the 2015 forecasts across the region.

Macroeconomic trade-offs and external vulnerabilities of human development in Nicaragua

Nicaragua is making progress towards the Millennium Development Goals, but is set to miss a number of targets in 2015. This paper’s general equilibrium analysis shows that it is unfeasible for the government to step up spending in order to meet these targets by the 2015 deadline. Any boost to public spending and financing would have to be front-loaded, which would entail pernicious macroeconomic trade-offs. A more realistic scenario would be to postpone meeting the goals until 2020. In that case, the allocation of public spending would spur economic growth without causing macroeconomic hardships, although the country would nevertheless remain highly vulnerable to external shocks.

Inactivating Mutations of the Human Luteinizing Hormone Receptor in Both Sexes

The human luteinizing hormone/chorionic gonadotropin receptor (LHCGR) plays a fundamental role in male and female reproductive physiology. Over the past 15 years, several homozygous or compound heterozygous loss-of-function mutations in the LHCGR gene have been described in males and females. In genetic males, mutations in LHCGR were associated with distinct degrees of impairment in pre- and postnatal testosterone secretion resulting in a phenotypic spectrum. Patients with the severe form of LH resistance have predominantly female external genitalia and absence of secondary sex differentiation at puberty. Patients with milder forms have predominantly male external genitalia with micropenis and/or hypospadias or only infertility without ambiguity. The undermasculization is associated with low basal, as well as human CG-stimulated, testosterone levels and elevated LH levels after pubertal age, without abnormal step-up in testosterone biosynthesis precursors. The testes have only slightly reduced size but mature Leydig cells are absent or scarce (Leydig cell hypoplasia). Genetic females with inactivating LHCGR mutations have female external genitalia, spontaneous breast and pubic hair development at puberty, and normal or late menarche followed by oligoamenorrhea and infertility. Estradiol and progesterone levels are normal for the early to midfollicular phase, but do not reach ovulatory or luteal phase levels. Serum LH levels are high whereas follicle-stimulating hormone levels are normal or only slightly increased. Pelvic ultrasound has demonstrated a small or normal uterus and normal or enlarged ovaries with cysts. The inactivating mutations of the LHCGR have provided important insights into distinct physiological roles of LH in reproduction of both sexes.