6,340 research outputs found
Influence of ac ageing on space charge dynamics in LDPE
No full textPolymeric materials have been widely used as insulation in power industry due to their excellent electrical properties. However, these properties deteriorate in time irreversibly when the material is subjected to electric stress. Although space charge is believed to play an important role in ac ageing, exact mechanisms are poorly understood due to very limited experimental data. In the present work efforts have been made to investigate the influence of ac ageing on space charge dynamics in low-density polyethylene (LDPE). LDPE films with 200mm were aged at 50 kV/mm at 50 Hz for various times at ambient temperature. Space charge dynamics in the samples prior to and after ageing were monitored using the pulsed electroacoustic (PEA) technique under dc electric stress. The results indicate that there is a significant amount of homocharge accumulation in the unaged sample due to charge injection. These injected charges are the captured by the deep traps originated from the interface between crystalline and amorphous regions in LDPE. Ageing under ac condition does not necessarily lead to an increase in amount of charge in the bulk but leads to an increase in mobility of charge carriers. Chemical analysis by infrared spectroscope (FTIR) reveals there are chemical changes taken place in the bulk of the material after ac ageing. It is believed that the chemical changes introduce shallow traps which promote the movement of charge carriers in the bulk. Consequently, the injected charges spread across the sample
A power sharing series power BJT array with isolated low voltage control for AC power control applications
No full textA technique for a continuously variable AC resistance using a series BJT array is presented. This array provides high power dissipation capability and uniform voltage and power distribution across the individual transistors. The array, controlled using a set of optoisolators to maintain the electrical isolation between the control circuits and the power stage, could be used as the basis to develop several useful techniques including a solid state AC regulator with comparable performance to the commonly used ferro-resonant systems; a linear AC electronic load suitable for testing UPS and other power conditioners; and, in other AC power control applications such as switching capacitors in AC resonant circuits
Inheritance of resistance to oat stem rust in the cultivars Ronald and AC Gwen
No full text Mitchell Fetch, J. and Fetch Jr., T. 2011. Inheritance of resistance to oat stem rust in the cultivars Ronald and AC Gwen. Can. J. Plant Sci. 91: 419–423. Oat stem rust, caused by Puccinia graminis Pers. f. sp. avenae Eriks. and E. Henn., causes sporadic epidemics and yield losses in Manitoba and eastern Saskatchewan. Oat (Avena sativa L.) cultivars registered for production in this area possess resistance to stem rust, but their genetic composition is unknown. Race TJJ (NA67), first detected in 1998, is virulent on most Pg genes; thus, it is desirable to know the gene(s) that are present in currently grown oat varieties. The hulled cultivar Ronald and the hulless cultivar AC Gwen were selected for characterization of inheritance of stem rust resistance, and crossed to the susceptible cultivar Triple Crown. Race BLD (NA1) was used to evaluate F1 plants and F2 populations. All F1 plants were resistant, indicating the presence of at least one dominant gene. Pooled F2 populations fit a 13:3 (resistant:susceptible) ratio for both Ronald (χ2 =0.31, P =0.58) and AC Gwen (χ2 =3.32 and P =0.07), indicating the presence of one dominant and one recessive gene. Segregation ratios in pooled F3 families fit a 7:8:1 (homozygous resistant:segregating:homozygous susceptible) ratio with race BLD (χ2 =0.84, P =0.66 for Ronald; χ2 =1.99, P =0.37 for AC Gwen), a 1:2:1 ratio (segregating families with 1:3 ratio) with race TJD (χ2 =2.87, P =0.24 for Ronald; χ2 =3.45, P =0.18 for AC Gwen), and a 1:2:1 ratio (segregating families with 3:1 ratio) with race FDJ (χ2 =1.33, P =0.51 for Ronald; χ2 =2.04, P =0.36 for AC Gwen). These results and reactions to known races of Puccinia graminis f. sp. avenae indicate that both Ronald and AC Gwen possess the dominant gene Pg2 and recessive gene Pg13. This genetic study characterized the stem rust resistance in Ronald and AC Gwen, and confirmed the limited base of stem rust resistance in Canadian oat cultivars. </jats:p
Genetic analysis of leaf and stripe rust resistance in the spring wheat (Triticum aestivum L.) cross RL4452/AC Domain
No full textLeaf rust and stripe rust of wheat (Triticum aestivum L.) are caused by the fungal pathogens Puccinia triticina, and Puccinia striiformis f.sp. tritici, respectively. In North America, the incorporation of adult-plant resistance (APR) genes into breeding lines has been an important strategy to achieve durable resistance to both diseases. Previously, the spring wheat cultivar AC Domain was reported to express an effective level of adult-plant resistance (APR) to leaf rust under field conditions. Early gene postulation work had suggested AC Domain might carry the APR gene Lr34 due to its phenotypic similarity to other Lr34 carrying lines. However, new gene specific markers have shown that AC Domain is not a carrier of Lr34. The objective of this research was to genetically localize the resistance in AC Domain, which is important because the cultivar has frequently been used as a parent in Canadian breeding programs, primarily for its value as a source of pre-harvest sprouting resistance. A mapping population of 185 doubled haploid (DH) lines derived from the cross ‘RL4452’ by ‘AC Domain’ was used for this study. RL4452 is a known carrier of Lr34. During 2011-2012, the DH population was evaluated in field leaf rust nurseries at Saskatoon, SK and Portage, MB and at a stripe rust nursery at Lethbridge, AB. Field results indicated that rust resistance in the mapping population was variable, with lines ranging from highly resistant, to highly susceptible. DH lines carrying Lr34 showed a high level of resistance to both diseases. Thus, the non-Lr34 carriers were genotyped using select SSR markers, and by an Illumina 9k Infinium iSelect SNP assay for subsequent quantitative trait loci (QTL) analysis. QTL analysis revealed that AC Domain donated a major resistance QTL located on chromosome 2BS, that mapped 46 cM proximal to markers linked to Lr16, and explained a significant portion of the leaf and stripe rust phenotypic variance in all test environments. In addition, this QTL was significantly associated with the expression leaf tip necrosis (LTN), reduction in area under the disease progress curve (AUDPC), and coefficient of infection (CI). In certain environments the interaction between the 2B QTL and Lr34 was additive resulting in a superior level of rust resistance. Indoor rust testing showed AC Domain was susceptible to both diseases at the seedling stage. Taken together these results suggest that the identified resistance in AC Domain is likely due to the presence of an APR gene, on chromosome 2BS
AC Rebel oat
No full text AC Rebel is a high-yielding, high-protein, white hulled oat cultivar possessing the crown rust resistance genes Pc38 and Pc39. It has good resistance to loose and covered smut, good resistance to stem rust, and moderate tolerance to Barley Yellow Dwarf Virus (BYDV). AC Rebel has good kernel characteristics including commercially acceptable hull and oil content. AC Rebel is well suited for the oat growing areas of western Canada where crown rust is not a problem, in particular to the Brown soil zone of Saskatchewan and Alberta. Key words: Oat, Avena sativa L., cultivar description </jats:p
AC Assiniboia oat
No full text AC Assiniboia is a high-yielding, tan hulled oat cultivar possessing the crown rust resistance gene combination Pc38, Pc39, and Pc68, which is highly effective against the crown rust population on the Canadian prairies at the time of registration. It has very good resistance to loose and covered smut, good resistance to stem rust, and excellent tolerance to Barley Yellow Dwarf Virus (BYDV). AC Assiniboia has good kernel characteristics, including good protein and oil content. AC Assiniboia is well suited for the oat-growing areas of western Canada and in particular the Black soil zone of Manitoba and Saskatchewan. Key words: Oat, Avena sativa L., cultivar description </jats:p
AC Ultima spring triticale
No full text AC Ultima, a spring triticale cultivar (X Triticosecale Wittmack), is widely adapted to the Canadian Prairies. AC Ultima represents an improvement in Hagberg Falling Number, which is usually associated with improved harvest-time sprouting resistance. AC Ultima expressed high grain yield, early maturity, heavy kernels and excellent lodging resistance compared to the check cultivars. AC Ultima is very resistant to the prevalent races of leaf rust, stem rust, and common bunt and resistant to common root rot. AC Ultima is eligible for the grades of Canada Triticale. Key words: Cultivar description, triticale (spring, X Triticosecale Wittmack), Hagberg Falling Number, yield, maturity, disease resistance, seed size </jats:p
AC Gwen hulless oat
No full text AC Gwen is a hulless oat (Avena sativa L.) cultivar postulated to carry the crown rust resistance combination Pc38, Pc39 and Pc68, which is highly effective against most of the present crown rust races on the Canadian prairies. It has very good resistance to loose and covered smut and good resistance to most of the prevalent races of stem rust, due to the likely presence of Pg2 and Pg13, and moderate tolerance to barley yellow dwarf virus. AC Gwen has characteristics that confer good milling quality, such as high test weight, kernel weight, and percent plump kernels. The cultivar has suitable levels of protein and oil for food products or for animal feed. It has good resistance to lodging. AC Gwen is well suited for production in the oat growing areas of western Canada and in particular the Black Soil Zone of Manitoba and Saskatchewan where crown rust is prevalent. Key words: Oat, Avena sativa L., cultivar description, hulless oat, disease resistance </jats:p
Experimental High-Frequency Parameter Identification of AC Electrical Motors
No full textIn order to predict conducted electromagnetic interference in inverter-motor drive systems, high-frequency (HF) motor models are requested and the involved parameters have to be available. In previous studies, the authors have presented an accurate HF model for induction motors and they have defined the procedures to identify the model parameters. In this paper, these results are extended to several types and sizes of industrial ac motors such as induction, synchronous reluctance (without interior permanent magnets), and brushless motors. The model parameter-identification procedure has been improved, and it is based on a least-squares data fitting applied to the measured magnitude and phase-frequency-response curves of the phase-to-ground and the phase-to-neutral impedances. The aim of this paper is to provide quick indications to select the suitable values of the HF model parameters, with reference to the size and type of the ac motor, to evaluate the HF voltage and current components in inverted-fed ac motor system
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