The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Edward K. N. Yung - One of the best experts on this subject based on the ideXlab platform.
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Aperture coupled dielectric resonator antenna with a thick ground plane
IEEE Transactions on Antennas and Propagation, 1998Co-Authors: Kwok Wa Leung, Z.n. Chen, Kwai-man Luk, Edward K. N. YungAbstract:The aperture-coupled hemispherical dielectric resonator antenna with a thick ground plane is investigated theoretically and experimentally. The effects of the ground plane thickness on the input impedance, resonant frequency, and front-to-back Radiation Ratio are studied.
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On the aperture-coupled dielectric resonator antenna using a thick ground plane
IEEE Antennas and Propagation Society International Symposium. 1999 Digest. Held in conjunction with: USNC URSI National Radio Science Meeting (Cat. N, 1Co-Authors: Kwok Wa Leung, Z.n. Chen, Kwai-man Luk, Edward K. N. YungAbstract:The aperture-coupled hemispherical dielectric resonator antenna with a thick ground plane is studied. The effects of the ground plane thickness on the resonant frequency, impedance bandwidth, and front-to-back Radiation Ratio are presented.
A. Alnajjar - One of the best experts on this subject based on the ideXlab platform.
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Solar energy potential in the United Arab Emirates
1995Co-Authors: A. Khalil, A. AlnajjarAbstract:In the present study, the global, direct and diffuse components of solar Radiation as well as temperature, relative humidity and wind speed have been continuously monitored and analyzed on hourly, daily and monthly basis. Experimental data is compared to the predictions of different theoretical models as functions of declination and hour angles. Correlations are obtained describing the variation of hourly, daily and monthly averages of total and diffuse solar Radiation using polynomial expressions. Empirical correlations describing the dependence of the daily average diffuse to total Radiation Ratio on the clearness index are also obtained. Data of daily diffuse to total Radiation Ratio is compared to correlations obtained by other investigators. The comparison shows a reasonable agreement with some scatter due to the seasonal dependence of the correlation. Comparison of calculations with experimental measurements under clear sky conditions show excellent agreement with a maximum error of 8%. The measured Ratio of hourly to daily insolation is in excellent agreement with the model of Hottel which is expressed as a function of the clearness index, hour and the sunset hour angles.
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Experimental and theoretical investigation of global and diffuse solar Radiation in the United Arab Emirates
Renewable Energy, 1995Co-Authors: A. Khalil, A. AlnajjarAbstract:Abstract In the present study, the global, direct and diffuse components of solar Radiation as well as temperature, relative humidity and wind speed have been continuously monitored and analysed on an hourly, daily and monthly basis. The monthly average daily total solar Radiation varies from 2700 W h/m2 in December to 8000 W h/m2 in June with an average clearness index of 0.65. Experimental data are compared to the predictions of different theoretical models as functions of declination and hour angles. Correlations are obtained describing the variation of hourly, daily and monthly averages of total and diffuse solar Radiation using polynomial expressions. Empirical correlations describing the dependence of the daily average diffuse to total Radiation Ratio on the clearness index are also obtained. Data for the daily diffuse to total Radiation Ratio are compared to correlations obtained by other investigators. The comparison shows a reasonable agreement with some scatter due to the seasonal dependence of the correlation. Comparison of calculations with experimental measurements under clear sky conditions show excellent agreement with a maximum error of 8%.
Kwok Wa Leung - One of the best experts on this subject based on the ideXlab platform.
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Excitation of low-profile equilateral-triangular dielectric resonator antenna using a conducting conformal strip
Microwave and Optical Technology Letters, 2001Co-Authors: Kwok Wa LeungAbstract:A new configuRation that employs a conducting conformal strip to excite the low-profile equilaterial-triangular dielectric resonator antenna (DRA) of very high permittivity is proposed. As compared with the previous aperture-coupling configuRation, the new configuRation has a wider impedance bandwidth (∼5.5%) and a higher front-to-back Radiation Ratio. The return loss, Radiation patterns, and antenna gain are measured and discussed. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 317–319, 2001.
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Aperture coupled dielectric resonator antenna with a thick ground plane
IEEE Transactions on Antennas and Propagation, 1998Co-Authors: Kwok Wa Leung, Z.n. Chen, Kwai-man Luk, Edward K. N. YungAbstract:The aperture-coupled hemispherical dielectric resonator antenna with a thick ground plane is investigated theoretically and experimentally. The effects of the ground plane thickness on the input impedance, resonant frequency, and front-to-back Radiation Ratio are studied.
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On the aperture-coupled dielectric resonator antenna using a thick ground plane
IEEE Antennas and Propagation Society International Symposium. 1999 Digest. Held in conjunction with: USNC URSI National Radio Science Meeting (Cat. N, 1Co-Authors: Kwok Wa Leung, Z.n. Chen, Kwai-man Luk, Edward K. N. YungAbstract:The aperture-coupled hemispherical dielectric resonator antenna with a thick ground plane is studied. The effects of the ground plane thickness on the resonant frequency, impedance bandwidth, and front-to-back Radiation Ratio are presented.
A. Khalil - One of the best experts on this subject based on the ideXlab platform.
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Solar energy potential in the United Arab Emirates
1995Co-Authors: A. Khalil, A. AlnajjarAbstract:In the present study, the global, direct and diffuse components of solar Radiation as well as temperature, relative humidity and wind speed have been continuously monitored and analyzed on hourly, daily and monthly basis. Experimental data is compared to the predictions of different theoretical models as functions of declination and hour angles. Correlations are obtained describing the variation of hourly, daily and monthly averages of total and diffuse solar Radiation using polynomial expressions. Empirical correlations describing the dependence of the daily average diffuse to total Radiation Ratio on the clearness index are also obtained. Data of daily diffuse to total Radiation Ratio is compared to correlations obtained by other investigators. The comparison shows a reasonable agreement with some scatter due to the seasonal dependence of the correlation. Comparison of calculations with experimental measurements under clear sky conditions show excellent agreement with a maximum error of 8%. The measured Ratio of hourly to daily insolation is in excellent agreement with the model of Hottel which is expressed as a function of the clearness index, hour and the sunset hour angles.
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Experimental and theoretical investigation of global and diffuse solar Radiation in the United Arab Emirates
Renewable Energy, 1995Co-Authors: A. Khalil, A. AlnajjarAbstract:Abstract In the present study, the global, direct and diffuse components of solar Radiation as well as temperature, relative humidity and wind speed have been continuously monitored and analysed on an hourly, daily and monthly basis. The monthly average daily total solar Radiation varies from 2700 W h/m2 in December to 8000 W h/m2 in June with an average clearness index of 0.65. Experimental data are compared to the predictions of different theoretical models as functions of declination and hour angles. Correlations are obtained describing the variation of hourly, daily and monthly averages of total and diffuse solar Radiation using polynomial expressions. Empirical correlations describing the dependence of the daily average diffuse to total Radiation Ratio on the clearness index are also obtained. Data for the daily diffuse to total Radiation Ratio are compared to correlations obtained by other investigators. The comparison shows a reasonable agreement with some scatter due to the seasonal dependence of the correlation. Comparison of calculations with experimental measurements under clear sky conditions show excellent agreement with a maximum error of 8%.
Peter Van Oevelen - One of the best experts on this subject based on the ideXlab platform.
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analytical treatment of the relationships between soil heat flux net Radiation Ratio and vegetation indices
Remote Sensing of Environment, 1993Co-Authors: William P. Kustas, Craig S. T. Daughtry, Peter Van OevelenAbstract:Relationships between leaf area index (LAI) and midday soil heat flux/net Radiation Ratio (G/Rn) and two more commonly used vegetation indices (VIs) were used to analytically derive formulas describing the relationship between G/Rn and VI. Use of VI for estimating G/Rn may be useful in opeRational remote sensing models that evaluate the spatial variation in the surface energy balance over large areas. While previous experimental data have shown that linear equations can adequately describe the relationship between G/Rn and VI, this analytical treatment indicated that nonlinear relationships are more appropriate. Data over bare soil and soybeans under a range of canopy cover conditions from a humid climate and data collected over bare soil, alfalfa, and cotton fields in an arid climate were used to evaluate model formulations derived for LAI and G/Rn, LAI and VI, and VI and G/Rn. In general, equations describing LAI-G/Rn and LAI-VI relationships agreed with the data and supported the analytical result of a nonlinear relationship between VI and G/Rn. With the simple Ratio (NIR/Red) as the VI, the nonlinear relationship with G/Rn was confirmed qualitatively. But with the normalized difference vegetation index (NDVI), a nonlinear relationship did not appear to fit the data.
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Analytical treatment of the relationships between soil heat flux/net Radiation Ratio and vegetation indices
Remote Sensing of Environment, 1993Co-Authors: William P. Kustas, Craig S. T. Daughtry, Peter Van OevelenAbstract:Relationships between leaf area index (LAI) and midday soil heat flux/net Radiation Ratio (G/Rn) and two more commonly used vegetation indices (VIs) were used to analytically derive formulas describing the relationship between G/Rn and VI. Use of VI for estimating G/Rn may be useful in opeRational remote sensing models that evaluate the spatial variation in the surface energy balance over large areas. While previous experimental data have shown that linear equations can adequately describe the relationship between G/Rn and VI, this analytical treatment indicated that nonlinear relationships are more appropriate. Data over bare soil and soybeans under a range of canopy cover conditions from a humid climate and data collected over bare soil, alfalfa, and cotton fields in an arid climate were used to evaluate model formulations derived for LAI and G/Rn, LAI and VI, and VI and G/Rn. In general, equations describing LAI-G/Rn and LAI-VI relationships agreed with the data and supported the analytical result of a nonlinear relationship between VI and G/Rn. With the simple Ratio (NIR/Red) as the VI, the nonlinear relationship with G/Rn was confirmed qualitatively. But with the normalized difference vegetation index (NDVI), a nonlinear relationship did not appear to fit the data.
