Numerical investigation has been made on a linear array of surface wave driven plasma monopole antenna using finite difference time domain simulation. Variations of the excitation power can be used for construction of a dynamically reconfigurable antenna. Plasma elements in the nominal pressure of 0.4 mb are fed through an RF power at 500 MHz using an equal power divider. The results show that while the variations of the excitation power shift the array resonant frequency between 50 MHz to 120 MHz, the array gain and directivity remain approximately unchanged in the new resonant frequency. Since efficiency is critical to communication systems, the total efficiencies of the reconfigurable array were analyzed from the least to the highest excitation power. The highest efficiency belongs to the array which the separation between elements is a quarter of wavelength. Using this cutting edge technology in space application, it will be possible to transmit through an antenna in a multiple frequency avoiding interference between adjacent antennas.

In this paper a new topology based on “Z source inverters” is introduced. In the proposed structure, two inductors of the IMPEDANCE network in conventional Z Source Inverter are replaced by two transformers with three windings. Voltage gain of the new inverter is higher than other Z Source networks with any duty cycle. In order to access high output power quality, the proposed inverter operates at a higher modulation index (near 1). Thereby, stress of switching devices is reduced. The performance of the proposed inverter is verified using the MATLAB/SIMULlNK software.

MUTUAL funds were first established in Iran in 2007 under Securities Market Act 2005 and have since grown significantly to one of the most important capital market intermediaries. Hence understanding and evaluating the performance of these funds are critical to both investors and fund managers. This research aims to examine the effects of various MUTUAL fund attributes and characteristics, namely past performance, size, expenses ratio, turnover ratio, number of funds under fund manager’s management, and type of institution of fund founder, on their current performance. For this purpose, a sample of 43 equity MUTUAL fund was chosen and relevant weekly data for the period of 22th June to 22th September 2013 was collected. The results show that only past performance and the type of institution of founder have an impact on the MUTUAL fund's performance.

In this paper, a new feeding structure is applied in the patch antenna design to overcome undesirable features of the earlier multilayer feeding structures while maintaining their interesting features.To more readily understand the operation mechanism of proposed feeding structure, an efficient circuit model has been also presented.It is known that proximity and aperture coupled feeding structures are sensitive to the transverse feed point location. In contrast, the proposed feeding architecture is very easy to fabricate and it overcomes the alignment difficulties arising from the proximity and aperture coupled feeding structures. The CST simulation results, analytic results and measurement ones show good agreement with each other. Moreover, a new miniaturization technique which is based on using High IMPEDANCE Wire (HIW) structures has been introduced. Due to their artificial high permeability properties, using proposed method, someone may miniaturize conventional patch antenna without bandwidth and efficiency corruption. Applying suggested method to the proposed antenna structure, two different feeding structures have been designed and compared. Finally, by using AMC structures to load HIW, more miniaturization factor has been achieved.

The extensive penetration of microgrids in the distribution network poses challenges to the control system, coordination with the network, and especially the traditional current-based protection systems despite many advantages such as reducing power outages, increasing reliability and resiliency, enhancing the flexibility of the power system in supplying loads, and improving the power quality. The main reason for the incorrect performance of current protection schemes is the change in the network fault level due to the connection and disconnection of the distributed generator or the microgrid operating mode change from the grid connected to the islanded and vice versa. To improve the performance of the protection system in the presence of microgrids, some schemes have been presented in two general categories: schemes based on modifying the network behavior and schemes based on modifying the protection system. In the first category, the network behavior during the faults is modified by external equipment to operate the conventional protection schemes properly. In the second category, the protection schemes are modified to correct performance according to the network behavior change during the short circuit faults. Due to the limitations of the schemes in the first category, the schemes of the second ones are more practical. Among the second category schemes, the IMPEDANCE-based ones can operate in both grid-connected and islanded modes of the microgrid due to their directional nature and independence of the fault level of the network. This article rearranges and reforms the conventional sequence equivalent circuits of the lines during the short circuit faults and presents new equivalent circuits. Also, a protection scheme is proposed using these circuits for low-voltage and medium-voltage overhead and cable lines in smart AC microgrids. The basis of the proposed scheme is the large change in IMPEDANCE in the proposed delta sequence equivalent circuit. This scheme employs the voltage and current data at the relay location and the magnitude of the positive sequence voltage at the other line end. Therefore, minimum data exchange between two ends of the line and low sampling rate are the features of the proposed scheme. This scheme is independent of the configuration of the microgrid, its operating mode, and uncertainties in the microgrid. Also, it can detect high resistance and high IMPEDANCE short circuit faults in the grid-connected and islanded mode with a detection time of fewer than two cycles in low voltage lines and about three cycles in medium voltage lines. A case study microgrid is simulated in PSCAD software, and the proposed scheme is implemented on it by MATLAB software. The results show the accurate performance of the proposed protection scheme in detecting short circuit fault types in different conditions.

The extensive penetration of microgrids in the distribution network poses challenges to the control system, coordination with the network, and especially the traditional current-based protection systems despite many advantages such as reducing power outages, increasing reliability and resiliency, enhancing the flexibility of the power system in supplying loads, and improving the power quality. The main reason for the incorrect performance of current protection schemes is the change in the network fault level due to the connection and disconnection of the distributed generator or the microgrid operating mode change from the grid connected to the islanded and vice versa. To improve the performance of the protection system in the presence of microgrids, some schemes have been presented in two general categories: schemes based on modifying the network behavior and schemes based on modifying the protection system. In the first category, the network behavior during the faults is modified by external equipment to operate the conventional protection schemes properly. In the second category, the protection schemes are modified to correct performance according to the network behavior change during the short circuit faults. Due to the limitations of the schemes in the first category, the schemes of the second ones are more practical. Among the second category schemes, the IMPEDANCE-based ones can operate in both grid-connected and islanded modes of the microgrid due to their directional nature and independence of the fault level of the network. This article rearranges and reforms the conventional sequence equivalent circuits of the lines during the short circuit faults and presents new equivalent circuits. Also, a protection scheme is proposed using these circuits for low-voltage and medium-voltage overhead and cable lines in smart AC microgrids. The basis of the proposed scheme is the large change in IMPEDANCE in the proposed delta sequence equivalent circuit. This scheme employs the voltage and current data at the relay location and the magnitude of the positive sequence voltage at the other line end. Therefore, minimum data exchange between two ends of the line and low sampling rate are the features of the proposed scheme. This scheme is independent of the configuration of the microgrid, its operating mode, and uncertainties in the microgrid. Also, it can detect high resistance and high IMPEDANCE short circuit faults in the grid-connected and islanded mode with a detection time of fewer than two cycles in low voltage lines and about three cycles in medium voltage lines. A case study microgrid is simulated in PSCAD software, and the proposed scheme is implemented on it by MATLAB software. The results show the accurate performance of the proposed protection scheme in detecting short circuit fault types in different conditions.