Search

The junction temperature of power semiconductors is a critical parameter during reliability evaluation. The incorporation of long-term mission profiles, such as power loadings and ambient temperature, into lifetime and reliability evaluations of power semiconductors increases the computational burden. Thus, there is an urgent need for a more accurate method for junction temperature acquisition. Current methods for junction temperature calculation are computationally inefficient and do not comprehensively incorporate long-term factors into junction temperature calculation and power semiconductor reliability evaluation. Here, a junction temperature calculation method is proposed that enables reliability evaluation for insulated gate bipolar transistor (IGBT) power semiconductors. This approach calculates the IGBT module junction temperature on the basis of an electro-thermal analogy using Gauss–Seidel iteration. When compared with electrical–thermal simulation and other numerical calculation methods, the proposed method guarantees accuracy, while greatly reducing the computational time and load. A performance comparison between the proposed method, electro-thermal simulation based on a Fuji IGBT simulator, and experimental results was carried out using a three-phase DC/AC inverter as a case study. [ABSTRACT FROM AUTHOR]

Improvement of cotton fibre yield and quality is challenging due to the narrow genetic base of modern cotton cultivars, which emphasizes the great need to effectively explore the existing germplasm resources. With major objective to assess the genetic diversity and population structure at DNA level, 302 elite upland cotton germplasm accessions (253 Chinese and 49 different exotic origins), were genotyped using 198 simple sequence repeats (SSRs) markers. Each of the 198 markers differed greatly in its ability to detect variations in the panel of cotton germplasm. The SSRs amplified 897 alleles, of which 77.7% were polymorphic. The number of alleles varied from 2 to 12 (mean 4.53). Gene diversity ranged from 0.020 to 0.492 with a mean of 0.279. The polymorphic information content (PIC) values ranged from 0.371 to 0.019 (mean 0.225). Genetic distances in the whole cotton germplasm ranged from 0.451 to 0.052 (mean 0.270), demonstrating relatively wider genetic diversity range. Chinese-origin cotton germplasm showed the highest level of SSR polymorphisms (gene diversity = 0.268, PIC = 0.218), whereas American-origin revealed the highest mean genetic distance (0.274). Model-based Bayesian analysis clustered the whole cotton germplasm into three subpopulations, and the highest molecular variation ws revealed between subpopulations (4%, P<0.001). The SSRs revealed moderate level of genetic diversity at DNA level, identified three structured subpopulations, suggesting a potential use of these markers for genomewide association mapping studies and for identifying and conserving useful alleles in upland cotton germplasm. [ABSTRACT FROM AUTHOR]

Multiple output LED drivers are necessary to achieve better performance and higher reliability in street lighting, tunnel lighting and LCD background lighting applications. Based on LCL-T constant-current characteristics, a modular multiple output LED driver is proposed in this paper. The LCL-T rectifiers are connected to the same voltage bus and work like current sources. However, since there are much higher voltage harmonics in the AC square bus voltage, it is very important to quantitatively analyze how these harmonics influence the precision of the output currents. In addition, all of the switches can achieve Zero Voltage Switching (ZVS) by proper design of the LCL-T network. Finally, a 200-W prototype with five channels is established with an efficiency of 92.25%. [ABSTRACT FROM AUTHOR]

The impact of alien DNA fragments on plant genome has been studied in many species. However, little is known about the introgression lines of Gossypium. To study the consequences of introgression in Gossypium, we investigated ∼2000 genomic and ∼800 epigenetic sites in three typical cotton introgression lines, as well as their cultivar ( Gossypium hirsutum) and wild parents ( Gossypium bickii), by amplified fragment length polymorphism (AFLP) and methylation-sensitive amplified polymorphism (MSAP). The results demonstrate that an average of 0.5% of exotic DNA segments from wild cotton is transmitted into the genome of each introgression line, with the addition of other forms of genetic variation. In total, an average of 0.7% of genetic variation sites is identified in introgression lines. Simultaneously, the overall cytosine methylation level in each introgression line is very close to that of the upland cotton parent (an average of 22.6%). Further dividing patterns reveal that both hypomethylation and hypermethylation occurred in introgression lines in comparison with the upland cotton parent. Sequencing of nine methylation polymorphism fragments showed that most (7 of 9) of the methylation alternations occurred in the noncoding sequences. The molecular evidence of introgression from wild cotton into introgression lines in our study is identified by AFLP. Moreover, the causes of petal variation in introgression lines are discussed. [ABSTRACT FROM AUTHOR]