Sharif Digital Repository

Boost converter operating in critical conduction mode is widely used in low-power power factor corrector because of its simplicity and low switching losses. The switching loss due to parasitic capacitor discharge at the on-time instant can also be reduced by a valley switching technique. In this paper, we introduce a new driver topology for the high-side switch in a synchronous boost converter operating in the critical conduction mode to obtain full zero-voltage switching. Using the proposed high-side driver topology, the conventional control circuit is sufficient to control the low-side switch, and no additional control circuit is required to adjust the timing of the switches. Finally, the... 

Self-oscillating converters operating in the critical conduction mode are popular in low power applications because of their simplicity and low cost. However, these converters are not suited for Power Factor Correction (PFC) because the peak switch current is controlled to regulate the output voltage and does not follow the shape of the line voltage waveform. A new control circuit implementation is proposed for a self-oscillating boost converter to achieve power factor correction. A full featured design example is provided which can be simplified for use in various cost sensitive applications such as electronic lighting, etc. This wide input voltage range self-oscillating PFC prototype... 

The COVID-19 pandemic cast doubts on governments' traditional crisis responses and sparked a surge in citizen-led, participatory, bottom-up responses. Iran's experience is worth investigating because it relied significantly on citizen groups to manage the crisis despite long-term sanctions and extremely restricted resources. The authors undertook an exploratory case study using the grounded theory (GT) method and an online survey to explore Iran's confrontation. The central notion discovered was referred to as 'faith-driven civic engagement.’ The response was characterized by adaptability, promptness, and comprehensiveness. The causes and strategic orientations included intrinsic motives,... 

Background: The typical features of eccentric exercise-induced muscle damage are delayed-onset muscle soreness (DOMS) and prolonged loss of muscle strength. It has been shown that passive warmth is effective in reducing muscle injury. Due to the interaction of different systems in vivo, we used isolated perfused medial gastrocnemius skeletal muscle to study the direct effect of temperature on the eccentric contraction-induced force loss. Methods: After femoral artery cannulation of a rat, the left medial gastrocnemius muscle was separated and then the entire lower limb was transferred into a prewarmed (35oC) chamber. With the chamber temperature at 31, 35 and 39oC before and during eccentric... 

In this study isolated perfused rat muscle was used to examine the direct effect of temperature changes on the eccentric contraction-induced force and desmin loss. The left medial gastrocnemius muscle was separated and the entire lower limb was transferred into a prewarmed (35°C) organ bath. Temperature was adjusted to 31 or 39°C before and during eccentric contractions. Maximal isometric force and desmin loss were measured after 15 isometric or eccentric contractions. According to our data, organ bath temperature changes before or during eccentric contractions had no significant effect on force loss. However, a strong correlation between desmin loss and temperature changes before (r = 0.93,...