Optimisation of Magnetic Circuit for Brushless Doubly Fed Machines

This paper presents an optimized design method for the magnetic circuit of brushless doubly fed machines (BDFMs). The BDFM is an attractive electrical machine, particularly for wind power applications, as a replacement for doubly fed slip-ring generators. This study shows that the conventional design methods for the BDFM stator and rotor back iron can be modified, leading to a lighter and smaller machine. The proposed design concepts are supported by analytical methods, and their practicality is verified using two-dimensional finite-element modeling and analysis. Two BDFMs with frame sizes D180 and D400 are considered in this study

Equivalent Circuit Parameters for Large Brushless Doubly Fed Machines (BDFM)

This paper presents analytical methods to calculate the equivalent circuit parameters for large-scale brushless doubly fed machines (BDFMs) with magnetic wedges utilized for closing stator open slots. The use of magnetic wedges reduces the magnetizing currents in the machine, reflected in the values of magnetizing inductances, but also increases leakage fluxes affecting the value of series inductances in the equivalent circuit. Though such effects can be modeled by numerical models, the proposed analytical methods are particularly helpful in optimizing machine design, inverter rating, reactive power management, and grid low-voltage ride-through performance. The conventional analytical methods cannot be readily applied to the BDFM due to its complex magnetic field distribution; this paper presents analytical methods to calculate the magnetizing and leakage inductances for the BDFM with magnetic wedges used in the stator slots. The proposed methods are assessed by experimentally verified finite-element models for a 250 kW BDFM

Investigation of magnetic wedge effects in large-scale BDFMs

This paper studies the effects of magnetic wedges on the equivalent circuit parameters of the Brushless Doubly-Fed Machine (BDFM). Magnetic wedges are used in slot openings of large electrical machines to reduce magnetizing currents, but the study of their effects on the BDFM performance is not straightforward due to the complex magnetic fields in the BDFM. Equivalent circuit and FE models have been developed for a 250 kW BDFM taking into account the effects of wedges and verified experimentally

Rotor parameter determination for the brushless doubly fed (induction) machine

A procedure has been established for obtaining equivalent circuit parameters for the Brushless Doubly Fed Machine (BDFM), also known as the Brushless Doubly Fed Induction Machine (DFIM), by transforming a reduced coupled-circuit model into a sequence component form. This approach takes advantage of the model reduction procedure’s ability to reduce a complex rotor structure to a single equivalent loop without significant loss of accuracy. An alternative method based on winding factors has also been developed and includes coupling via harmonic fields. Parameters determined in both ways are in close agreement with those determined from Finite Element Analysis (FEA) and experimentally. The advantages of each method is discussed in the conclusion section.This work was supported by the European Union's Seventh Framework Programme managed by REA – Research Executive Agency (FP7/2007_2013) under Grant Agreement N.315485.This is the author accepted manuscript. The final version is available from IEEE via http://dx.doi.org/10.1049/iet-epa.2015.002

A New Calcareous Nannofossil Record from the Lower Jurassic of Kermanshah, Western Iran: Implications for Biostratigraphy and Evolutionary Reconstructions

Calcareous nannofossils are used here for the first time in order to establish a precise biostratigraphic framework for the Kermanshah Radiolarite Formation, an outcropping in Western Iran. The new data presented here challenge the previous tentative age interpretations (Pliensbachian to early Toarcian) based upon radiolarians. Calcareous nannofossil assemblages and events unequivocally indicated that the pelagic limestones and marls are late Sinemurian in age (NJT 3b nannofossil subzone), and that these are thrusted over shales and cherts dated as uppermost Sinemurian (NJT 3b-c nannofossil subzone) and lowermost Pliensbachian (NJT 4 nannofossil zone). This result leads not only to reconsideration of the age of the radiolarite formations, which are widespread in the Zagros orogenic system, but also a better understanding of the stratigraphic relationships between the various lithological units known in the area. Besides these new stratigraphic inferences, the calcareous nannofossil assemblages of the uppermost Sinemurian– lowermost Pliensbachian successions revealed the common presence of new morphologies of the Mitrolithus genus, never described before. These findings allow for the description of three new species, M. montgolfieri, M. pseudonannoconus, and M. tethysiensis, and reveal the existence of homeomorphy between the spine structure of conical Lower Jurassic coccoliths and the widespread Cretaceous nannoconids. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

Eningkatan Motivasi dan Hasil Belajar melalui Pembelajaran Team Assisted Individualization pada Kalor di SMP

TheAims of this research is to improve the motivation and study outcomes of VII G students of Junior High School 9 Pontianak on kalor topic with cooperative learning model Team Asissted Individualization (TAI) type. Student of class VII G Junior High School9 Pontianak as participants in this study consisted of 22 girls and 16 boys. This study consisted of 2 cycles with an indicator of success was 65% student got a score of 75 in the study outcomes test and for students study motivation the indicator was 65%. The increase of the cycle I was 68,42% with an average value of 72,2 while the percentage of cycle II was 84,21% with an average value of 78,3. The average of students study motivation was 84,64%. Cooperative learnig model Team Assisted Individualization (TAI) type was expected to be used as an alternative to improve students motivation and study outcomes. TAI is can be used as an alternative to improve motivation and result of student

Metformin for prevention of hypertensive disorders of pregnancy in women with gestational diabetes or obesity: systematic review and meta‐analysis of randomized trials

Objective Metformin has been reported to reduce the risk of pre‐eclampsia. It is also known to influence soluble fms‐like tyrosine kinase‐1 level, which correlates significantly with the gestational age at onset and severity of pre‐eclampsia. The main aim of this systematic review and meta‐analysis of randomized trials was to determine whether metformin use is associated with the incidence of hypertensive disorders of pregnancy (HDP). Methods MEDLINE (1947 to September 2017), Scopus (1970 to September 2017) and the Cochrane Library (inception to September 2017) were searched for relevant citations in the English language. Only randomized controlled trials on metformin use, reporting the incidence of pre‐eclampsia or pregnancy‐induced hypertension, were included. Studies on populations with a high probability of metformin use prior to randomization (those with type II diabetes or polycystic ovary syndrome) were excluded. Random‐effects models with the Mantel–Haenszel method were used for subgroup analyses. Bayesian random‐effects meta‐regression was used to summarize the evidence. Results In total, 3337 citations matched the search criteria. After evaluating 2536 abstracts and performing full‐text review of 52 studies, 15 were included in the review. In women with gestational diabetes, metformin use was associated with a reduced risk of pregnancy‐induced hypertension when compared with insulin (relative risk (RR), 0.56; 95% CI, 0.37–0.85; I2 = 0%; 1260 women) and a non‐significantly reduced risk of pre‐eclampsia (RR, 0.83; 95% CI, 0.60–1.14; I2 = 0%; 1724 women). In obese women, when compared with placebo, metformin use was associated with a non‐significant reduction in risk of pre‐eclampsia (RR, 0.74; 95% CI, 0.09–6.28; I2 = 86%; 840 women). In women with gestational diabetes, metformin use was also associated with a non‐significant reduction in risk of any HDP (RR, 0.71; 95% CI, 0.41–1.25; I2 = 0%; 556 women) when compared with glyburide. When studies were combined using Bayesian random‐effects meta‐regression, with treatment type as a covariate, the posterior probabilities of metformin having a beneficial effect on the prevention of pre‐eclampsia, pregnancy‐induced hypertension and any HDP were 92.7%, 92.8% and 99.2%, respectively, when compared with any other treatment or placebo. Conclusions There is a high probability that metformin use is associated with reduced HDP incidence when compared with other treatments or placebo. The small number of studies included in the analysis, the low quality of evidence and the clinical heterogeneity preclude generalization of these results to broader populations. Given the clinical importance of this topic and the magnitude of effect observed in this meta‐analysis, further prospective trials are urgently needed

Efikasi Beberapa Herbisida Secara Tunggal Dan Campuran Terhadap Clidemia Hirta (L.) D. Don. Di Perkebunan Kelapa Sawit

A field experiment was carried out in oil palm plantation to determine the efficacy of selectedherbicides to control Clidemia hirta (L.) D. Don. in oil palm plantations. Treatments were trichlopyr+ aminopylarid 333 + 17 g. ai/ha, trichlopyr + aminopylarid 416,25+21,25 g. ai/ha, trichlopyr +aminopylarid 499,5 + 25,5 g. ai/ha, trichlopyr 536 g. ai/ha, trichlopyr 536 g. ai/ha, paraquat 400 g.ai/ha + methyl metsulfuron 15 g. ai/ha, glyphosate 960 g. ai/ha + trichlopyr 251,25 g. ai/ha,glyphosate + trichlopyr 620 + 98 g. ai/ha and without treatment. The results showed that theefficacy of both single and mixed herbicides significantly affected mortality and percentage of plantdry weight 16 WAT. Herbicide trichlopyr with dose of 536 g. ai/ha was the most effective treatmentto control C. hirta (L.) D. Don. with mortality rate of 97,73%

Gambaran Kenakalan Berlalu Lintas pada Remaja dan Faktor – Faktor Penyebab

Road traffic delinquency is one form of juvenile delinquency. The purpose of this study was to describe the road traffic delinquency behavior in adolescents in Batulicin and the contributing factors. Subjects in this study were three teenagers who were the perpetrators of road traffic delinquency in Batulicin. Data were gathered through semi-structured in-depth interviews and observation of passive participation. It can be concluded from the results of the analysis that there were some various types of road traffic delinquency, namely not having a driver\u27s license, not carrying vehicle registration when driving, not using the license plate numbers, not wearing helmets while driving, not wearing the right and left rear-view mirrors, applying loud-voiced exhaust, not activating the Speedo meter, doing dangerous maneuvers, delivering verbal harassment or vulgarity on the other riders, wild racing, speeding, running a red light, and driving in a drunken state. There were some factors found in the three subjects that affected the road traffic delinquency. The first was the internal factors that included negative self-identity, low self-control, mischief in early age, male gender, low self-esteem, less emotional stability, hampered self-actualization, lack of good models, less social adjustment, less social development, and lack of attachment to parents. The second was the external factors including negative peer influences, low school performance, middle and lower socioeconomic status, poor parental role and poor quality of the surrounding environment