Islamic Azad University

About: Islamic Azad University is a education organization based out in Tehran, Iran. It is known for research contribution in the topics: Population & Catalysis. The organization has 83635 authors who have published 113437 publications receiving 1275049 citations. The organization is also known as: Azad University.

Design-Oriented Study of Advanced Synchronous Reference Frame Phase-Locked Loops

Abstract: In grid-connected applications, the synchronous reference frame phase-locked loop (SRF-PLL) is a commonly used synchronization technique due to the advantages it offers such as ease of implementation and robust performance Under ideal grid conditions, the SRF-PLL enables a fast and accurate phase/frequency detection; however, unbalanced and distorted grid conditions highly degrade its performance To overcome this drawback, several advanced PLLs have been proposed, such as the multiple reference frame-based PLL, the dual second-order generalized integrator-based PLL, and the multiple complex coefficient filter-based PLL In this paper, a comprehensive design-oriented study of these advanced PLLs is presented The starting point of this study is to derive the small-signal model of the aforementioned PLLs, which simplifies the parameter design and the stability analysis Then, a systematic design procedure to fine tune the PLLs parameters is presented The stability margin, the transient response, and the disturbance rejection capability are the key factors that are considered in the design procedure Finally, the experimental results are presented to support the theoretical analysis

Critical review of automotive steels spot welding: process, structure and properties

Abstract: Spot welding, particularly resistance spot welding (RSW), is a critical joining process in automotive industry. The development of advanced high strength steels for applications in automotive industry is accompanied with a challenge to better understand the physical and mechanical metallurgy of these materials during RSW. The present paper critically reviews the fundamental understanding of structure–properties relationship in automotive steels resistance spot welds. The focus is on the metallurgical characteristics, hardness–microstructure correlation, interfacial to pullout failure mode transition and mechanical performance of steel resistance spot welds under quasi-static, fatigue and impact loading conditions. A brief review of friction stir spot welding, as an alternative to RSW, is also included.

Mineral trioxide aggregate (MTA) and calcium hydroxide as pulp-capping agents in human teeth: a preliminary report.

Abstract: Aim To compare mineral trioxide aggregate (MTA) with calcium hydroxide when used as pulp-capping materials in human teeth. Methodology Eleven pairs of maxillary third molars in subjects between 20 and 25 years of age were subjected to mechanical pulp exposure. The exposed pulps were capped with MTA or calcium hydroxide, covered with ZOE and restored with amalgam. A total of 14 teeth were extracted after periods of 1 week (two molars) 2 months (three molars), 3 months (five molars), 4 months (two molars) and 6 months (two molars). Results Histological evaluation demonstrated less inflammation, hyperaemia and necrosis plus thicker dentinal bridge and more frequent odontoblastic layer formation with MTA than calcium hydroxide. Conclusions Although the results favour the use of MTA, more studies with larger samples and a longer follow up are suggested.

Relations between transformational leadership, organizational learning, knowledge management, organizational innovation, and organizational performance: an empirical investigation of manufacturing firms

Abstract: The aim of this study is to determine relations between transformational leadership, organizational learning, knowledge management, organizational innovation, and organizational performance among Iranian manufacturing companies through structural equation modeling. Two hundred eighty senior, executive, administrative, and other-level managers are selected from among 106 companies having more than 50 employees. Data are analyzed using structural equation modeling. The following findings are found: transformational leadership directly influenced organizational learning and knowledge management. Organizational learning directly and positively influenced knowledge management of manufacturing firms. Transformational leadership positively influenced organizational innovation and organizational performance of manufacturing firms. Organizational learning and knowledge management directly influenced organizational innovation; whereas organizational learning and organizational innovation directly influenced organizational performance among manufacturing firms. Meanwhile, transformational leadership positively and indirectly influenced organizational innovation through organizational learning and knowledge management. Knowledge management and organizational learning effected organizational performance indirectly by organizational innovation. The fit indices shows that the proposed model have an appropriate fit (χ2/df = 2.33, RMSEA = 0.069, NFI = 0.95, NNFI = 0.95, CFI = 97). If leaders of manufacturing firms undertake a transformational role and use organizational learning and knowledge management, this will facilitate organizational innovation and will consequently improve organizational performance to a great extent in manufacturing firms.