A Class-E-Based Resonant AC-DC Converter With Inherent PFC Capability

This paper investigates the use of the class-E inverter for power factor correction (PFC) applications. Analytical and state-space models are derived showing the class-E inverter’s capability of achieving inherent PFC operation with a constant duty cycle. The inherent PFC operation limits the controller responsibility to the regulation of the output voltage, which is key for resonant converters with challenging control. A converter incorporating a diode bridge, a class-E inverter, and a class-D rectifier is presented for the PFC stage in single-phase offline converters. A prototype is designed to validate the analysis and presented design method. The prototype operates with zero-voltage switching (ZVS) across the load range and achieves up to 211 W of output power at an efficiency of 88%, with an inherent power factor of 0.99 and a total harmonic distortion (THD) of 8.8 %. Frequency modulation is used to achieve lower output power down to 25 W, with a power factor of 0.95, THD of 28 %, and an efficiency of 88 %

Laparoscopic versus open surgery for treatment of colorectal cancer

Background: Colorectal cancer (CRC) is the fourth most frequently diagnosed cancer in United States and has the second highest cancer related mortality rate after lung cancer. Cancer of the colon is equally frequent in men and women while cancer of the rectum occur 20-50% more frequently in men. This study aimed to compare the outcome of laparoscopic and open approach in surgical management of colorectal carcinoma and to better selection of the best procedure for treatment of colorectal cancer.Patients and Method: This prospective randomized study included 18 cases who underwent colorectal surgeries during the period October, 2019 till October, 2020 in the Surgery Unit at Zagazig Faculty of Medicine. These patients were subdivided into equal two groups: 9 cases underwent the open approach while the remaining 9 cases underwent the laparoscopic approach, with a period of one year follow up postoperative. Results: Intraoperatively, the laparoscopic group showed some cons like total operative time (p = 0.001) and time needed for dissection (p < 0.001), which were significantly higher when compared to the open group. In the postoperative period, close monitoring of all clinical and laboratory parameters was performed with bedside imaging by ultrasound in indicated cases. The laparoscopic group took the upper hand over open group regarding day of first motion, when to start oral intake and hospital stay (p = <0.001, <0.001 and 0.002 respectively).Conclusion: Analysis of the scientific literature confirmed that for the curative treatment of colon and rectal cancer, laparoscopy is not inferior to open surgery with respect to overall survival, disease-free survival and rate of recurrence