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1.
In this paper, the multiple refraction phenomenon is investigated on the boundary of a scalar impedance surface (SIS) and a tensor impedance surface (TIS). When a surface wave (SW) propagates on the SIS and radiates to the boundary of the TIS, the propagation direction of it is changed and the refraction phenomenon is accrued. The method that is proposed in this paper can predict the multiple refraction for the SW. Moreover, another analytical method is introduced for designing the proposed structure which the double refraction (DR) occurs at arbitrary angles on it. Using it, a sample of the structure is designed by printed circuits in 15.2GHz and the results are verified by the full‐wave simulation and measurement. The results are shown that in the structure, DR is occurred in 2° and 22° as predicted. The proposed method can provide many applications such as design of SW power dividers based on the TISs, impedance surface based waveguides, holographic antennas, and feeding of array antennas. 相似文献
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In this study, a microchannel reactor was designed, its catalytic performance in dry methane reforming (DRM) was assessed, and the results were compared with those observed in a conventional fixed bed reactor. The catalyst was prepared in two forms, including catalyst pellets and catalyst-coated plate. The microchannel reactor had thin films of Ni/Al2O3 coated on stainless steel substrate via radio frequency (RF) magnetron sputtering method in various sputtering times. The fall-off rate of the catalyst-coated plates can be neglected after putting the plates under the high-temperature DRM reaction, due to the formation of firm active catalyst coatings. The performance of the samples was evaluated at different temperatures from 700 to 800 °C, at P = 1 atm, with a CH4:CO2 ratio of 1. The results of XRD showed that with increasing the sputtering time, there was an increase in crystallinity. As observed in FESEM images, the sample prepared with 5 min of sputtering was dense and uniform. The results of EDX not only proved the dispersion of the samples observed in XRD and FESEM analysis, but also verified the presence of the utilized elements. The temperature of 800 °C and the sample with 5 min sputtering time were selected as the optimum condition that provided the best performance. Catalytic performance was investigated in fixed bed reactor at the same GHSV; based on the results there were no significant conversions in the fixed bed reactor. The results of the stability test in the microchannel reactor showed a good performance during 30 h on stream. Therefore, Ni/Al2O3 thin films had a satisfactory performance in the designed microchannel. Our study shows that this type of reactor has many advantages in terms of performance, compactness, and economic concerns. 相似文献
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Change in the color of heat‐treated,vacuum‐packed broccoli stems and florets during storage: effects of process conditions and modeling by an artificial neural network 下载免费PDF全文
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Microbiological and Chemical Properties of Siahmazgi Cheese,an Iranian Artisanal Cheese: Isolation and Identification of Dominant Lactic Acid Bacteria 下载免费PDF全文
8.
Mohsen Hosseinzadeh Soreshjani Navidreza Abjadi Gholamreza Arab Markadeh 《International Journal of Circuit Theory and Applications》2015,43(10):1491-1507
In this study, a Z‐source alternating current‐to‐alternating current (AC–AC) converter with a specific topology, which can provide both buck and boost modes, is investigated. This converter, which can be implemented easily, utilizes only two switches with complemented commands. A comparison between the Z‐source AC–AC converter and a conventional thyristor voltage controlled one is presented here, and it shows that in the most areas, the Z‐source converter provides a faster response and lower total harmonic distortion of the output currents than the conventional one. Moreover, the Z‐source converter is also extended to the multiphase systems. In addition, a new arrangement of this converter is proposed here to remove the isolated single‐phase sources. Furthermore, an open‐loop method is proposed for soft‐starting applications. Finally, a closed‐loop control system is also suggested for a three‐phase Z‐source converter to soft start and control the speed of an induction motor. Computer simulations show the validity and effectiveness of the proposed schemes. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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The objective of this work is to implement a
pseudo-forward equation which is called PFE to transform
data (similarity attribute) to model parameters (porosity) in
a gas reservoir in the F3 block of North Sea. This equation
which is an experimental model has unknown constants in
its structure; hence, a least square solution is applied to find
the best constants. The results derived from solved equations
show that the errors on measured data are mapped
into the errors of estimated constants; hence, Tikhonov
regularization is used to improve the estimated parameters.
The results are compared with a conventional method such
as cross plotting between acoustic impedance and porosity
values to validate the PFE model. When the testing dataset
in sand units was used, the correlation coefficient between
two variables (actual and predicted values) was obtained as
0.720 and 0.476 for PFE model and cross-plotting analysis,
respectively. Therefore, the testing dataset validates relatively
well the PFE optimized by Tikhonov regularization
in sand units of a gas reservoir. The obtained results indicate
that PFE could provide initial information about
sandstone reservoirs. It could estimate reservoir porosity
distribution approximately and it highlights bright spots
and fault structures such as gas chimneys and salt edges. 相似文献