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Rotor design to improve dynamic performance of axial flux hysteresis motors
Modarres, Mohammad,Byung-Il Kwon IET 2015 IET electric power applications Vol.9 No.1
<P>In high-speed axial flux hysteresis motors (AFHMs), the hysteresis ring and the hysteresis ring holder have the main roles of producing hysteresis torque in steady state and eddy current torque at sub-synchronous speed, respectively. In conventional AFHM, and especially in the high-speed AFHM types, the hysteresis ring holder is placed between the hysteresis ring and stator to produce more eddy current torque at the time of starting. Since the minimum magnetic air gap can cause better motor performance, the previous research exchanges the hysteresis ring place and its holder. However, it has worst motor dynamic response as a result. To cope with these issues, a new model is proposed in this study. A thin copper piece is attached at the bottom of the hysteresis ring to improve the eddy current torque and consequently motor dynamic response. Then finite element analysis is done in order to acquire the accurate copper thickness and investigate the new proposed AFHM. Furthermore, experimental setups are provided and AFHM results in all cases are measured. The obtained test and simulation results show that the new proposed model make a better dynamic performance for the AFHM.</P>
MODARRES MOHAMMAD Korean Nuclear Society 2005 Nuclear Engineering and Technology Vol.37 No.3
This paper reviews the pivotal phases of the evolution of the current technology-dependent nuclear power safety regulation in the United States. Understanding of this evolution is essential to the development of any future regulatory paradigm, including the technology-neutral regulatory approach that the U.S. Nuclear Regulatory Commission (NRC) has recently embarked on to develop. The paper proposes and examines the implications of a predominately rationalist and best-estimate probabilistic regulatory framework called safety goals-driven performance-based regulation. This framework relies on continuous assessment of performance of a set of time-dependent safety-critical systems, structures and components that assure attainment of a broad set of technology-neutral protective, mitigative, and preventive goals. Finally, the paper discusses the steps needed to develop a corresponding technology-neutral regulatory system from the proposed framework.
Design of Novel Axial-Flux Dual Stator Doubly Fed Reluctance Machine
Khaliq, Salman,Modarres, Mohammad,Lipo, Thomas A.,Kwon, Byung-Il IEEE 2015 IEEE transactions on magnetics Vol.51 No.11
<P>This paper proposes a novel machine termed the axial-flux brushless doubly fed reluctance machine (AF-BDFRM) suitable for high-torque, low-speed direct drive applications. The main potential advantages of AF-BDFRM are its higher torque and power density compared with the radial-flux BDFRM. In addition, the proposed machine utilizes a bidirectional power converter of much lower rating as compared with the machine rating depending on the range of speed variation. The proposed machine axial-flux topology is composed of two stators and a reluctance iron rotor. The upper stator winding which is connected directly to the power grid, transfers active power to the grid and lower stator winding creates excitation for the machine and connects to the grid through a partially rated converter. The design principles of the proposed AF-BDFRM are studied in this paper. Furthermore, the transient 3-D finite-element analysis result of the improved design is presented.</P>
Reyhane DARSOUEI,Javad Karimi,Mehdi Modarres Awal 한국곤충학회 2011 Entomological Research Vol.41 No.5
The occurrence of Aphelinus paramali (Zehavi & Rosen) (Hym., Aphelinidae) was evidenced from North east Iran, in association with Aphis pomi (de Geer). This species is reported from Iran for the first time, and A. pomi is introduced as a new host for this parasitoid. Detailed morphological characters were studied with scanning electron microscopy (SEM) photographs. Also, sequences of ribosomal internal transcribed spacer 2 (ITS2) and cytochrome oxidase subunit I (COI) genes were used for determining species boundaries and comparing with other Aphelinus species. Different results were obtained in phylogenetic analysis of these two regions. Analysis of COI gene supported the closer relationship of this species with Aphelinus abdominalis. This is the first data about comprehensive characterization of a parasitic wasp using morphological characters, SEM and two-locus information from Iran.
Exponentially tilted empirical distribution function for ranked set samples
Saeid Amiri,Mohammad Jafari Jozani,Reza Modarres 한국통계학회 2016 Journal of the Korean Statistical Society Vol.45 No.2
We study nonparametric estimation of the distribution function (DF) of a continuous random variable based on a ranked set sampling design using the exponentially tilted (ET) empirical likelihood method. We propose ET estimators of the DF and use them to construct new resampling algorithms for unbalanced ranked set samples. We explore the properties of the proposed algorithms. For a hypothesis testing problem about the underlying population mean, we show that the bootstrap tests based on the ET estimators of the DF are asymptotically normal and exhibit a small bias of order O(n−1). We illustrate the methods and evaluate the finite sample performance of the algorithms under both perfect and imperfect ranking schemes using a real data set and several Monte Carlo simulation studies. We compare the performance of the test statistics based on the ET estimators with those based on the empirical likelihood estimators.