Design and analysis on reduced switching frequency current mode control isolated power converters for light load efficiency

This paper focus on improving light load efficiency of isolated DC/DC converters. A mixed signal control platform is proposed to implement multiple-mode variable frequency control. An 8-bit Micro Controller Unit MCU is used in the platform to provide adaptive control schemes and cost effectiveness digital solutions. Small signal analysis is covered to explain frequency modulation effects. Control of isolation transformer flux swing to avoid saturation is also implemented, to provide safe operation both in steady and transient states. A 300 Watt prototype Two-FET forward converter is built up to verify the proposed mixed signal control platform. © 2009 IEEE.published_or_final_versionThe Inaugural IEEE Energy Conversion Congress and Exposition (ECCE 2009), San Jose, CA., 20-24 September 2009. In Proceedings of the IEEE Energy Conversion Congress and Exposition, 2009, p. 3268-327

Current driven synchronous rectifier with saturable current transformer and dynamic gate voltage control for LLC resonant converter

This paper proposes an improved current driven synchronous rectifier with saturable current transformer and dynamic gate voltage control feature for LLC resonant converter efficiency improvement. A model of saturable current transformer is proposed. Compared with other voltage driven and current-driven synchronous rectifier, this current driven synchronous rectifier has several outstanding characteristics. This synchronous rectifier is completely self-contained. It needs no external signal or power supply. It is also insensitive to parasitic inductance. Inherent dynamic gate voltage control reduces gate loss in the MOSFET by saturable current transformer. A 300W 400V-12V converter is built to demonstrate the advantages of the proposed current driven synchronous rectifier. High efficiency at 98% can be achieved. There is more than 4% efficiency improvement compared with schottky diode.published_or_final_versio

Optimization methodology for efficient LLC resonant converter with power factor correction circuit

High efficiency is required in power conversion circuits. A systematic optimization procedure is presented in this paper to optimize LLC series resonant converter efficiency where the effect of LLC input voltage variation cased by power factor correction circuit is considered. A mode solver technique is proposed to handle LLC converter steady-state solutions under different input voltage conditions. Loss models are provided to calculate total component losses using the current and voltage information derived from the mode solver. A prototype 300W 12V output LLC converter is built using the optimization results. Experimental results are presented.postprintThe 6th IET International Conference on Power Electronics, Machines and Drives (PEMD 2012), University of Bristol, UK., 27-29 March 2012. In The I E T Conference Publication Series, 2012, Conference no. CP592, p. 1-

Influence of Altered Serum Cholesterol Levels and Fasting on Cutaneous Cholesterol Synthesis

Barrier perturbation stimulates epidermal cholesterol synthesis, which plays an important role in restoring barrier function. In the present study, we examined whether changes in serum cholesterol levels or nutrition regulate epidermal cholesterol synthesis in hairless mice. Serum cholesterol levels were lowered by 50% after injection with 4- aminopyrazolo (3,4-d) pyrimidine and were increased by 51% by feeding an atherogenic diet. In contrast to most other tissues, cholesterol synthesis in the epidermis and dermis was not inhibited by elevations or stimulated by decreases in serum cholesterol levels. Additionally, feeding a high-cholesterol diet did not decrease epidermal or dermal cholesterol synthesis. However, fasting significantly decreased both epidermal (38%) and dermal (34%) cholesterologenesis. Furthermore, barrier recovery after acetone disruption of the barrier was impaired in fasted animals. However, treatment with topical lipids did not restore barrier repair rate to normal, indicating that factors in addition to lipids are necessary to overcome the effects of fasting. These results demonstrate that cholesterol synthesis in the epidermis and dermis is regulated independently of changes in serum cholesterol levels

Effects of Mistletoe and Other Defects on Lumber Quality in White Fir

The presence or absence of defects, including dwarf and true mistletoes, was determined for logs from twenty white fir trees. Grade and volume were determined for all boards sawed from these logs. Differences between defect categories and logs without defect, with regard to degrade and overrun, were not statistically significant. With the exception of shop grades derived from logs containing dwarf mistletoe, differences between logs without defect and those with defect were not statistically significant after the effect of diameter was accounted for; even in this single exception, the volume derived from dwarf mistletoe logs was greater than that derived from no-defect logs. This suggests that the presence in logs of dwarf mistletoe, true mistletoe, and the other defects considered in this study either does not adversely affect lumber grade or that present quality control procedures are ineffective in detecting the changes. The latter possibility appears most likely

Computer-aided design and optimization of high-efficiency LLC series resonant converter

High conversion efficiency is desired in switch mode power supply converters. Computer-aided design optimization is emerging as a promising way to design power converters. In this work a systematic optimization procedure is proposed to optimize LLC series resonant converter full load efficiency. A mode solver technique is proposed to handle LLC converter steady-state solutions. The mode solver utilizes numerical nonlinear programming techniques to solve LLC-state equations and determine operation mode. Loss models are provided to calculate total component losses using the current and voltage information derived from the mode solver. The calculated efficiency serves as the objective function to optimize the converter efficiency. A prototype 300-W 400-V to 12-V LLC converter is built using the optimization results. Details of design variables, boundaries, equality/inequality constraints, and loss distributions are given. An experimental full-load efficiency of 97.07 is achieved compared to a calculated 97.4 efficiency. The proposed optimization procedure is an effective way to design high-efficiency LLC converters. © 1986-2012 IEEE.published_or_final_versio

Community-acquired pneumonia in children: cell-free plasma sequencing for diagnosis and management.

Community-acquired pneumonia (CAP) is a common cause of pediatric hospital admission. Empiric antibiotic therapy for hospitalized children with serious CAP now targets the most likely pathogen(s), including those that may demonstrate significant antibiotic resistance. Cell-free plasma next-generation sequencing (CFPNGS) was first made available for Pediatric Infectious Diseases physicians in June 1, 2017, to supplement standard-of-care diagnostic techniques. A retrospective chart review was performed for children hospitalized with CAP between June 1, 2017, and January 22, 2018, to evaluate the impact of CFPNGS. We identified 15 hospitalized children with CAP without other underlying medical conditions for whom CFPNGS was performed. CFPNGS identified a pathogen in 13 of 15 (86%) children compared with 47% for those using standard culture and PCR-based methods alone. Changes in antibiotic management were made in 7 of 15 (47%) of children as a result of CFPNGS

PENGARUH APLIKASI ENDOSULFAN TERHADAP KERAGAAN PRODUKSI UDANG WINDU (penaeus monodon) DAN BANDENG (Chanos chanos) DI TAMBAK

Penelitian bertujuan mengetahui pengaruh aplikasi tingkat dosis endosulfan terhadapproduksi dan residu dalam tubuh udang windu dan bandeng di tambak Penelitian dilakukan selama tiga bulan dari bulan Mei sampai Juli 1996 di lnstalasi Tambak Percobaan Maranak, Balai Penelitian Perikanan Pantai, Maros. Percobaan diawali dengan persiapan tambak, kemudian tiodan diaplikasikan dengan dosis 0,5 L/ha, 1 L/ha, dan 2 Llha rnasing-masing dengan dua kali ulangan, kemudian dilakukan pencucian kembali terhadap tiodan yang telah diaplikasikan