Low Cost AC/DC converter with Power Factor Correction

A high performance single stage Power Factor Correction (PFC) converter with tight output voltage regulation and a very simple circuit to carry out those functions, which means its cost is lower than its counterparts. Two basic flyback circuits include a simple control circuit. For the hard switching circuit, only one switch is used to achieve low cost; for the soft switching scheme, one auxiliary switch is added to get higher efficiency and smaller size. There are two power flow paths, resulting in part power processed by an active switch only once to reduce the current stress and improve the efficiency. A direct current (DC) bus voltage will be limited to the peak value of input voltage. The maximum DC bus voltage will be less than 400 and a single commercial capacitor can be used for universal voltage stress under light load condition

Biodegradation of Dimethyl Phthalate by Freshwater Unicellular Cyanobacteria

The biodegradation characteristics of dimethyl phthalate (DMP) by three freshwater unicellular organisms were investigated in this study. The findings revealed that all the organisms were capable of metabolizing DMP; among them, Cyanothece sp. PCC7822 achieved the highest degradation efficiency. Lower concentration of DMP supported the growth of the Cyanobacteria; however, with the increase of DMP concentration growth of Cyanobacteria was inhibited remarkably. Phthalic acid (PA) was detected to be an intermediate degradation product of DMP and accumulated in the culture solution. The optimal initial pH value for the degradation was detected to be 9.0, which mitigated the decrease of pH resulting from the production of PA. The optimum temperature for DMP degradation of the three species of organisms is 30 ∘ C. After 72 hours' incubation, no more than 11.8% of the residual of DMP aggregated in Cyanobacteria cells while majority of DMP remained in the medium. Moreover, esterase was induced by DMP and the activity kept increasing during the degradation process. This suggested that esterase could assist in the degradation of DMP

Assemblathon 2: evaluating de novo methods of genome assembly in three vertebrate species

Background: The process of generating raw genome sequence data continues to become cheaper, faster, and more accurate. However, assembly of such data into high-quality, finished genome sequences remains challenging. Many genome assembly tools are available, but they differ greatly in terms of their performance (speed, scalability, hardware requirements, acceptance of newer read technologies) and in their final output (composition of assembled sequence). More importantly, it remains largely unclear how to best assess the quality of assembled genome sequences. The Assemblathon competitions are intended to assess current state-of-the-art methods in genome assembly. Results: In Assemblathon 2, we provided a variety of sequence data to be assembled for three vertebrate species (a bird, a fish, and snake). This resulted in a total of 43 submitted assemblies from 21 participating teams. We evaluated these assemblies using a combination of optical map data, Fosmid sequences, and several statistical methods. From over 100 different metrics, we chose ten key measures by which to assess the overall quality of the assemblies. Conclusions: Many current genome assemblers produced useful assemblies, containing a significant representation of their genes and overall genome structure. However, the high degree of variability between the entries suggests that there is still much room for improvement in the field of genome assembly and that approaches which work well in assembling the genome of one species may not necessarily work well for another

A heterozygous moth genome provides insights into herbivory and detoxification

How an insect evolves to become a successful herbivore is of profound biological and practical importance. Herbivores are often adapted to feed on a specific group of evolutionarily and biochemically related host plants1, but the genetic and molecular bases for adaptation to plant defense compounds remain poorly understood2. We report the first whole-genome sequence of a basal lepidopteran species, Plutella xylostella, which contains 18,071 protein-coding and 1,412 unique genes with an expansion of gene families associated with perception and the detoxification of plant defense compounds. A recent expansion of retrotransposons near detoxification-related genes and a wider system used in the metabolism of plant defense compounds are shown to also be involved in the development of insecticide resistance. This work shows the genetic and molecular bases for the evolutionary success of this worldwide herbivore and offers wider insights into insect adaptation to plant feeding, as well as opening avenues for more sustainable pest management.Minsheng You … Simon W Baxter … et al

A Review Of Distributed Power Systems Part Ii: High Frequency Ac Distributed Power Systems

The present development state in high frequency (HF) ac distributed power systems (DPS) is reviewed. First, background and motivations of developing HF AC-DPS are addressed. Two types of basic HF AC-DPSs based on sine wave and square/PWM (pulsewidth modulated) wave bus are described, and the system level design considerations are discussed. Further, the issues and challenges in this research area are identified. These issues include high electromagnetic interference (EMI) level, difficulty to back up power, nonredundant system structure and limited post-regulation capability, etc. Finally, a viable HF AC-DPS is proposed, which is expected to yield effective EMI trade-off and system redundancy. © 2006 IEEE

A Review Of Distributed Power Systems Part I: Dc Distributed Power System

The present development state in dc distributed power systems (DPS) is comprehensively reviewed in this tutorial. Basic distributed structures and their characteristics are described. The system level design considerations are discussed. The profile of current technologies is drawn. Finally, the issues and challenges in this research area are identified. These issues include not only improving efficiency, but also increased concerns regarding the cost and complexity of power supplying systems. © 2005 IEEE

Modeling Of Conduction Losses In Pwm Converters Operating In Discontinuous Conduction Mode

In this paper, a non-ideal PWM switch model considering conduction losses is developed. This issue was considered in the past only with the assumption that the inductor current ripple is negligible compared with its average value. Derivation of the new model is based on the energy loss invariant principle. The resulting model can be applied to simulating large inductor current ripple conditions. Accuracy of the proposed model is verified through Pspice simulation using the buck and boost converters

Full Bridge Zcs Pwm Converter For High-Voltage High-Power Applications

This paper presents a comprehensive study of a full bridge (FB) zero-current switched (ZCS) PWM converter which is suitable for high-voltage and high-power de application that achieves ZCS for all active switches, and zero-voltage-switched (ZVS) operation for all diodes on the high voltage side. The given converter utilizes component parasitic parameters, particularly for the high-voltage transformer, and employs fixed-frequency phase-shift control to implement soft-switching commutations. Detailed steady state analysis of the converter power stage is presented for the first time and the major features of the converter\u27s power stage are discussed. Small-signal characteristics are also presented and accompanied by a discussion of the controller design and implementation. A design example is also presented based on the steady state analysis and is validated by simulation. Theoretical and simulated results are in good agreement