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In this paper, a novel zero current switching (ZCS) flyback inverter in discontinuous conduction mode (DCM) is proposed. In the proposed flyback inverter, the ZCS for the primary switch is achieved by adding a simple auxiliary circuit to the conventional flyback inverter. Also, the auxiliary switch is turned on and turned off at ZCS condition. Therefore, the switching losses of the switches are negligible, which increases the efficiency and allows higher switching frequency and more compact design. The resonant auxiliary cell is activated only in short transition times that makes its conduction losses negligible. Furthermore, the voltage overshoot of the main switch is limited during the turn-off process, which allows utilization of lower voltage metal-oxide semiconductor field-effect transistors (MOSFETs) with low conduction losses and low cost. The detailed operation of the flyback inverter with auxiliary circuit and design considerations are presented. Simulation and experimental results are presented to verify the performance of the proposed inverter.

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We propose estimators for the tail index and the spectral measure of multivariate α-stable distributions and derive their asymptotic properties. Simulation studies reveal the appropriateness of the estimators. Applications to financial data are also considered.

The purpose of this study was to describe and analyze the prevalence and pattern of corneal astigmatism in cataract surgery candidates. In a prospective cross-sectional study, preoperative demographics, and keratometric and refractive values of cataract surgery candidates were collected from January 2013 to December 2014. Axial length (AL) and flat and steep keratometry measurements were optically measured by a partial coherence interferometry device (IOLMaster). This study consisted of 2156 eyes of 1317 patients with a mean age of 64.92 ± 11.48 (SD) (30-88 years). The mean of AL was 23.33 ± 1.37 mm, and the mean of corneal astigmatism was 1.12 ± 1.10 diopter (D) (range 0.0-7.00), in all patients. Furthermore, the mean of flat and steep keratometry were 43.70 ± 1.70 and 44.83 ± 1.79 D, respectively. Corneal astigmatism was 1.50 D or less in 1590 eyes (73.7 %), more than 1.50 D in 566 eyes (26.2 %), 3.00 D or more in 161 eyes (7.4 %), WTR in 796 eyes (36.9 %), ATR in 1010 eyes (46.8 %), and oblique in 350 eyes (16.2 %). ATR astigmatism axis significantly increased with the increase in age. Corneal astigmatism of most cataract surgery candidates fell between 0.50 and 1.50 D. The results of our study however is confined to our demographics might provide useful data for cataract patients, surgeons, and intraocular lens manufacturers for different purposes.