Transformer and LCL Filter Design for DPFCs

Flexible AC Transmission Systems (FACTS) can be used for power flow control in AC transmission grids, allowing simultaneous control of the bus voltage and line active and reactive power. However, due to high costs and reliability concerns, the application of this technology has been limited in such applications. Recently, the concept of Distributed FACTS (DFACTS) and Distributed Power Flow Controller (DPFC) has been introduced as a low cost high reliability alternative for power flow control. This paper presents the design of a coupling transformer and a LCL filter for DPFC devices. To extract the electromagnetic energy from the transmission line a transformer with a single turn primary is designed and optimized. A third-order LCL filter is used to guarantee high order harmonics filtering. Simulations results are presented and discussed

Control of distributed power flow controllers using active power from homopolar line currents

Flexible AC Transmission Systems (FACTS) devices can be used for power flow control in AC transmission grids, improving power line utilization and performance. Nowadays, Unified Power Flow Controllers (UPFC) are one of the most useful FACTS, allowing the simultaneous control of the bus voltage and line active and reactive power. However, due to high costs and reliability concerns, the utilization of this technology has been limited in such applications. The concept of Distributed FACTS (DFACTS) and Distributed Power Flow Controller (DPFC) was recently introduced as a low coast alternative for power flow control. This paper presents a distributed power flow controller that uses third-harmonic frequency currents transmitted through the line to independently control active and reactive power flow at fundamental frequency. Simulations were carried in the Matlab/Simulink environment. © 2012 IEEE

Study of welding strengh in PVC profiles

Polyvinyl chloride, PVC, is one of the most widely produced and used plastic, being commonly used in civil industry due to its wide range of mechanical properties (from rigid to flexible), low cost, durability, and easy to assemble. Due to its good mechanical and thermal properties, PVC can be used to produce window and door frames, protecting the interior from the external actions, such as noise and temperature gradients. In order to achieve the final dimensions and geometry, previously extruded profiles must be cut and assembled, being the butt welding one of the most efficient techniques. This plastic welding method involves three main steps: i) pressing the parts to be joined against either side of a heated plate; ii) removing the plate when the parts are sufficiently molten and iii) pressing the components together and holding them until they are cooled. The amount of molten material, generated during the heating stage at an adequate heating time and the plate temperature, as well as the amount of material forced out from the joint during the pressing stage (joining displacement), have major influence in the final welding properties. Although the lack of information about the butt welding of PVC, previous studies with for others materials [1-3] showed that the welding strength can be optimized changing the plate temperature and/or joining displacement. The aim of this work was to study the influence of the plate temperature and the heating time in the welding strength of PVC profiles used in windows frames. The profiles were welded in an industrial butt welder machine, setting the plate temperature at 245ºC, 260ºC and 275ºC and the heating time at 15 and 20s. The mechanical properties were evaluated by mechanical bending tests, according to UNE-EN 514 standard and the welding strength was correlated with the morphology of the welded parts observed by optical microscopy. The results are showing that the increase of plate temperature and heating time increase the welding strength. However, the presence of impurities in the joint, such as trapped air or degraded material, as well as the joint alignment, can have a detrimental effect on the welding strength, as observed by the morphological analyses

Molecular Insights into Appetite Control and Neuroendocrine Disease as Risk Factors for Chronic Diseases in Western Countries

Environmental factors such as stress, anxiety and depression are important to consider with the global increase in chronic diseases such as cardiovascular diseases, cancer, stroke, obesity, diabetes and neurodegenerative diseases. Brain metabolic diseases associated with conditions such as obesity and diabetes require early intervention with diet, lifestyle and drug therapy to prevent diseases to various organs such as the liver with non alcoholic fatty liver disease (NAFLD) and other organs such as the heart, lungs thyroid, pancreas, brain, kidneys and reproductive systems. Behavioural stress and the molecular mechanisms that are involved in neuroendocrine diseases such as insulin resistance in obesity require attention since associated inflammatory processes early in the disease process have been associated with neurodegenerative diseases. Molecular neuroendocrine disturbances that cause appetite dysregulation and hyperphagia are closely linked to hyperinsulinemia, dyslipidaemia and reduced lifespan. The origins of metabolic diseases that afflict various organs possibly arise from hypothalamic disturbances with loss of control of peripheral endocrine hormones and neuropeptides released from the brain. Diet and drug therapies that are directed to the autonomic nervous system, neuroendocrine and limbic systems may help regulate and integrate leptin and insulin signals involving various neuropeptides associated with chronic diseases such as obesity and diabetes. The understanding of brain circuits and stabilization of neuroanatomical structures in the brain is currently under investigation. Research that is involved in the understanding of diet and drugs in the stabilization of brain structures such as frontostriatal limbic circuits, hypothalamus brainstem circuits and parasympathetic nervous system is required. Information related to neuropeptides and neurotransmitters that are released from the brain and their regulation by therapeutic drugs requires further assessment. The promise of appropriate diets, lifestyle and drugs that target the CNS and peripheral tissues such as the adipose tissue, liver and pancreas may improve the prognosis of chronic diseases such as obesity and diabetes that are also closely associated with neurodegeneration

Fetal Growth Restriction - a 4-Year Case Series

Overview and aims: Fetal growth restriction (FGR) affects 15% of pregnancies and is associated with both increased perinatal and neonatal morbidity and mortality and long-term effects in adult life. Our aim was to describe cases and outcomes of FGR from a tertiary perinatal care centre and identify the predictors of neonatal morbidity and mortality. Study design: retrospective cohort. Population: pregnancies with early or late FGR caused by placental factors followed from 2006 to 2009 in a tertiary perinatal care centre. Methods: we collected data from clinical records on demographics, clinical history and fetal ultrasound parameters. Perinatal and neonatal outcomes were stratiied according to gestational age (above or below 28 weeks) and we used bivariate analysis to identify any associations with clinical and imaging indings. Results: we included 246 pregnancies; hypertension was the most prevalent maternal risk factor (16%). There were 15 cases of early FGR, 11 of which had cesarean delivery due to deterioration of fetal Doppler parameters. Outcomes in this group included one fetal and three neonatal deaths. Of 231 cases of late FGR, 64% were delivered early given a non-reassuring fetal status i.e. due to changes in Doppler evaluation or altered Manning biophysical proile. There were four cases of perinatal death in this group, three of which delivered at 28 weeks. Neonatal morbidity was associated with lower gestational age, lower birthweight and progressive placental dysfunction (p<0.01). Conclusion: there was an association between neonatal morbidity and gestational age, birthweight and Doppler deterioration, particularly for deliveries below 28 weeks. The assessment of vascular changes through Doppler analysis allows anticipation of fetal deterioration and is a helpful tool in deciding the optimum timing of delivery

Of?p stars: a class of slowly rotating magnetic massive stars

Only 5 Of?p stars have been identified in the Galaxy. Of these, 3 have been studied in detail, and within the past 5 years magnetic fields have been detected in each of them. The observed magnetic and spectral characteristics are indicative of organised magnetic fields, likely of fossil origin, confining their supersonic stellar winds into dense, structured magnetospheres. The systematic detection of magnetic fields in these stars strongly suggests that the Of?p stars represent a general class of magnetic O-type stars.Comment: Proceedings of IAUS 272: Active OB star

Implant Site Nexplanon Reaction?

Nexplanon (Schering-Plough Limited/Merck Sharp & Dohme Limited (MSD)) is a long active reversible contraceptive method that provides effective contraception for 3 years. It consists of a single, flexible, rod-shaped implant, containing 68 mg etonogestrel. It is 4 cm long, consists of an ethylene vinyl acetate copolymer, a non-absorbable material, and also contains 15 mg of barium sulfate, which makes it visible by X-ray. We describe a case of a 39-year-old woman who experienced a local reaction to the barium sulfate in Nexplanon. She was given medical treatment, but only the removal of the implant resolved the symptoms. After removal there was gradual improvement and 72 h later the patient was asymptomatic. Allergic reaction to barium sulfate is extremely rare: until now, there have only been two cases associated with Nexplanon described in the literature

New results for the t-J model in ladders: Changes in the spin liquid state with applied magnetic field. Implications for the cuprates

Exact Diagonalization calculations are presented for the t-J model in the presence of a uniform magnetic field. Results for 2xL ladders (L=8,10,12) and 4x4 square clusters with 1 and 2 holes indicate that the diamagnetic response to a perpendicular magnetic field tends to induce a spin liquid state in the spin background. The zero-field spin liquid state of a two-leg ladder is reinforced by the magnetic field: a considerable increase of rung antiferromagnetic correlations is observed for J/t up to 0.6, for 1 and 2 holes. Pair-breaking is also clearly observed in the ladders and seems to be associated in part with changes promoted by the field in the spin correlations around the zero-field pair. In the 4x4 cluster, the numerical results seem to indicate that the field-induced spin liquid state competes with the zero-field antiferromagnetic short-range-order, the spin liquid state being favored by higher doping and smaller values of J/t. It is interesting to note that the field-effect can also be observed in a 2x2 plaquette with 1 and 2 holes. This opens up the possibility of gaining a qualitative understanding of the effect.Comment: 16 pages, 7 figures, latex New results adde

Surface abundances of ON stars

Massive stars burn hydrogen through the CNO cycle during most of their evolution. When mixing is efficient, or when mass transfer in binary systems happens, chemically processed material is observed at the surface of O and B stars. ON stars show stronger lines of nitrogen than morphologically normal counterparts. Whether this corresponds to the presence of material processed through the CNO cycle or not is not known. Our goal is to answer this question. We perform a spectroscopic analysis of a sample of ON stars with atmosphere models. We determine the fundamental parameters as well as the He, C, N, and O surface abundances. We also measure the projected rotational velocities. We compare the properties of the ON stars to those of normal O stars. We show that ON stars are usually helium-rich. Their CNO surface abundances are fully consistent with predictions of nucleosynthesis. ON stars are more chemically evolved and rotate - on average - faster than normal O stars. Evolutionary models including rotation cannot account for the extreme enrichment observed among ON main sequence stars. Some ON stars are members of binary systems, but others are single stars as indicated by stable radial velocities. Hence, mass transfer is not a simple explanation for the observed chemical properties. We conclude that ON stars show extreme chemical enrichment at their surface, consistent with nucleosynthesis through the CNO cycle. Its origin is not clear at present.Comment: 18 pages, 10 figures (+ appendix). A&A accepte