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The application of the dual-mode time-sharing technique in a novel transformerless photovoltaic (PV) inverters is proposed and investigated. The simultaneous high step-down or high step-up conversion with 97.6 % peak efficiency and injected current with THD < 2% is achieved. The leakage current problem, which is a main concern with the transformerless PV inverters, is around 20 mA. The indirect current control, especially at transition modes of operation is highly improved by utilizing a fast dead-beat control scheme. The working principles of the proposed converter show that the step-down and the step-up voltage gains are (D/(1-D)) 2 and D/(1-D) 2 , respectively. Furthermore, a 1 kW, 220 VAC and 200 VDC experimental prototype is implemented to confirm the theoretical achievements.Index terms-Dual-mode time-sharing, leakage current, on-grid inverter, transformerless.

Today entrepreneurship is considered as the economic driving engine for developed and developing countries and most countries have invested considerably on entrepreneurship development. The entrepreneurship development in a community could provide sustainable employment and economic development. It should be noted that entrepreneurship development has always been encountered different challenges and barriers. The present article is aimed to detect and classify the barriers of entrepreneurship development in Iranian SMEs and determine the importance of each barrier. Analyzing 28 detected barriers in the present study show that lack of sufficient knowledge in management skills, business management, lack of adequate investment to start and retain a business, difficulty in finding information about markets, products and prices, troublesome rules obtaining bank loans, and the difficulty in recruiting good and reliable staff are the most important barriers and challenges of corporate entrepreneurship development in Iranian SMEs.

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