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Aperture Efficiency Study of Square Reflect Array Antennas

Wireless Engineering and Technology 2018年第3期9卷 66-78页

作者： Javad Nourinia Changiz Ghobadi bahman mohammadi Farzad Alizadeh Department of Electrical Engineering Urmia University Urmia Iran

This paper presents a detailed study of square reflect array (RA) antenna aperture efficiency (ηa). Effects of quantization-phase and limited phase-range errors on radiation pattern, half-power beam width (HPBW) and ηa for different feed locations are investigated. Results show an in-crease in side-lobe levels (SLLs) and a slightly reduction in ηa with quantization-phase augmentation or element phase-range reduction, however, the effects on HPBW are negligible. Nevertheless, the degradation in ηa is negligible when the quantization-phase is lower than 30° or phase-range is more than 300°. Parametric studies have been carried out to provide design guidelines to maximize ηa. It is perceived that the offset-angle plays an important role to determine ηa, especially for feed with narrow beam width.

关键词： Aperture Efficiency Limited Phase-Range Error Quantization-Phase Error Reflect array Antennas Square Aperture

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Use of fuzzy set theory for minimizing overbreak in underground blasting operations——A case study of Alborz Tunnel,Iran

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International Journal of Mining Science and Technology 2015年第3期25卷 439-445页

作者： mohammadi Mohammad Hossaini Mohammad Farouq Mirzapour bahman Hajiantilaki Nabiollah General Mechanic Co. Faculty of Mining Engineering Engineering University CollegeUniversity of Tehran

In order to increase the safety of working environment and decrease the unwanted costs related to overbreak in tunnel excavation projects, it is necessary to minimize overbreak percentage. Thus, based on regression analysis and fuzzy inference system, this paper tries to develop predictive models to estimate overbreak caused by blasting at the Alborz Tunnel. To develop the models, 202 datasets were utilized, out of which 182 were used for constructing the models. To validate and compare the obtained results,determination coefficient(R2) and root mean square error(RMSE) indexes were chosen. For the fuzzy model, R2 and RMSE are equal to 0.96 and 0.55 respectively, whereas for regression model, they are 0.41 and 1.75 respectively, proving that the fuzzy predictor performs, significantly, better than the statistical method. Using the developed fuzzy model, the percentage of overbreak was minimized in the Alborz Tunnel.

关键词： Fuzzy model Overbreak Regression analysis Underground blasting Alborz Tunnel

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