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AIP Conference Proceedings [Author(s) SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems - Santiago, Chile (26–29 September 2017)] - Measurement of total electronic cross-section, total atomic cross-section, effective atomic numbers and effective electron densities for some Sm compounds
摘要： Total electronic cross-section, total atomic cross-section, effective atomic number, and effective electron density were determined experimentally and theoretically for Sm2O3, SmI2, and SmCl3 compounds. The mass attenuation coefficient and total atomic cross section were calculated experimental values for Sm2O3, SmI2, and SmCl3 compounds. Theoretical mass attenuation coefficient values were computed from the XCOM data program. Exciting Sm compounds were measured using a Si(Li) detector with γ photons at 59.543 keV from 241 Am annular source. We have performed the measurements for the calculations of these values in attenuation and direct excitation experimental geometry. The effective atomic number and electron density for Sm compounds are being reported here for the first time.
关键词： effective atomic number,X-ray fluorescence,electron density,mass attenuation coefficient
更新于2025-09-04 15:30:14
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Symmetric surface complex waves in Goubau Line
摘要： Existence of symmetric surface complex waves in a Goubau line—a perfectly conducting cylinder of circular cross-section covered by a concentric dielectric layer—is proved by constructing perturbation of the spectrum of symmetric real waves with respect to the imaginary part of the permittivity of the dielectric cover. Closed-form iteration procedures for calculating the roots of the dispersion equation (DE) in the complex domain supplied with efficient choice of initial approximation are developed. Numerical modeling is performed with the help of a parameter-differentiation method applied to the analytical and numerical solution of DEs.
关键词： dispersion equation,attenuation,losses,Goubau line,complex surface wave
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Comparison of Measured and Theoretically Predicted Rain Attenuation at 32 GHz and 38 GHz
摘要： Rain attenuation of terrestrial microwave links is addressed here. Statistics of attenuation from 17 short range links at frequency of 32 GHz and 38 GHz spanning over period of more than two years are shown. Statistics of measured attenuation is compared with theoretically calculated statistics of rain loss. Rainfall data used in theoretical calculations come from a network of rain gauges. It is found that theoretically calculated rain attenuation systematically underestimates measured loss by several dB.
关键词： attenuation statistics,microwave links,propagation
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Dense Multipath Component Polarization and Wall Attenuation at 1.35 GHz in an Office Environment
摘要： This paper presents an analysis of dense multipath components in office meeting rooms. Radio channel sounding measurements at 1.35 GHz were performed with transmitter and receiver in the same room (intra-room) and in adjacent rooms (inter-room). Specular and dense multipath components were estimated with the RiMAX maximum-likelihood algorithm. The dense multipath reverberation characteristics were found to be not significantly different between polarization subchannels for both the intra-room and the inter-room channels, supporting the validity of a scalar dense multipath model. The specular and dense multipath wall attenuation losses were found to be 12.0 and 5.4 dB, respectively.
关键词： wall attenuation,office,specular multipath,channel sounding,dense multipath,polarization,RiMAX
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Reliability of Disdrometer-derived W-Band Attenuation Predictions
摘要： applications W-band frequencies are used for radar observations of clouds. In a undergo underneath potential significant attenuation. Also in satellite telecommunications the use of W-band frequencies is planned, to transfer the ever increasing amount of data. Rain attenuation is one of the most significant atmospheric effects influencing propagation, and precise knowledge is important for system design. signals the Often the specific rain attenuation is given as a function of rain rate, but at higher frequencies, such as W-band, the sensitivity to the shape of the drop size distribution (DSD) increases. Incorporating DSD measurements in the prediction process is recommended. In this study the reliability of the on DSD attenuation measurements is confirmed through comparison with radiometric attenuation data, acquired from an Atmospheric Propagation and Profiling System (ATPROP). 90 GHz, 2D-Video-Disdrometer predictions (2DVD), based of at a
关键词： W-band frequencies,electromagentic wave propagation,specific rain attenuation
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Numerical Weather Prediction Models for the Estimate of Clear-Sky Attenuation Level in Alphasat Beacon Measurement
摘要： With the move of satellite systems towards Ka and QIV bands, the Alphasat TDPS Aldo Paraboni scientific experiment aims to characterize atmospheric attenuation in those bands. However, during the retrieval of the attenuation from the measured beacon signal, the clear-sky contribution to attenuation is lost. Microwave radiometers give the clear sky absolute reference level, but these are costly and not always available. This paper proposes Numerical Weather Prediction models as an alternative source of clear-sky attenuation. Three months of beacon and radiometric data from Spino d' Adda the Alphasat receiving station are used as benchmark for validation of the method. A preliminary conclusion is that gaseous attenuation is well predicted, but cloud attenuation is underestimated.
关键词： microwave radiometer,Numerical Weather Prediction model,radiowave propagation,clear-sky attenuation,Alphasat
更新于2025-09-04 15:30:14
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Constructing excellent electromagnetic wave absorber with dielectric-dielectric media based on 3D reduced graphene and Ag(I)-Schiff base coordination compounds
摘要： The dielectric-dielectric composite (SRGA) for electromagnetic absorber was fabricated via integrating Ag(I)-Schiff base coordination compounds (SSBCC) with three-dimensional reduced graphene aerogel (3D-rGA) powders. SRGA showed excellent electromagnetic wave absorption properties in terms of re?ection loss, absorption band width and absorber thickness. Specially, when the mass ratio of SSBC to 3D-rGA powders was 1:3 (SRGA-25), the maximum value of re?ection loss at 2 mm was up to (cid:1)63.82 dB and the effective frequency bandwidth of 6.28 GHz (10.16e16.44 GHz) at 2.5 mm can be obtained. The mechanism investigation of electromagnetic wave absorption for SRGA showed that the enhanced electromagnetic wave absorption was ascribed to enhanced polarization loss derived from good 3D-conductive-network units of 3D-rGA, abundant interfaces caused by the media heterostructure due to the introduction of SSBCC and the good impedance matching condition. And 3D-rGA based materials might be put into practical application only in powder state due to the very low strength of the buck state. Therefore, the investigation on SRGA in our contribution is considered to be an actual performance evaluation of the materials based on three-dimensional graphene for microwave attenuation. This work also provided a method for fabricating excellent graphene-based electromagnetic wave absorbers by simply mixing a suitable dielectric lossy material, e.g. SSBCC.
关键词： Electromagnetic wave absorber,Schiff base,Composite,Microwave attenuation,Graphene aerogel
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Statistics of Rain Attenuation in Prague, Empirical Data and Numerical Predictions
摘要： Attenuation of electromagnetic waves in microwave bands is determined experimentally via measurement of received signal variations on terrestrial radio links operating in three frequency bands around 58, 94 and 122 GHz. The measured time series of attenuation are processed to obtain long-term cumulative distributions of attenuation due to hydrometeors. The obtained empirical distributions are compared with the ones predicted using the model of the Recommendation ITU-R P.530. For a given time percentages, the predicted attenuation levels exceeded are apparently lower than the levels of empirical distributions. A power-law relationship between attenuation and rain intensity is obtained by a least square approximation of measured simultaneous rain intensity and rain attenuation. The results are discussed and compared with the numerical predictions.
关键词： electromagnetic wave propagation,atmospheric hydrometeors,rain attenuation
更新于2025-09-04 15:30:14
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A DISTINCTIVE METHOD OF ELIMINATING OUT-BAND INSTABILITY IN CASCADED ACTIVE DEVICE SYSTEM BASED ON NARROW-BAND ATTENUATION
摘要： A distinctive connection method in cascaded RF/MW active device system achieving both stability and low gain loss is presented. Unlike traditional methods (isolator and attenuator), the proposed solution introduces an appropriate length of transmission line to change the input impedance at the out-band instable frequency point and uses a narrow-band termination to absorb the instable power without deteriorating in-band signal. Moreover, the reason that instability often occurs in the cascaded system is analysed with S-parameters, and it turns out to be a kind of out-band instability. The solution is veri?ed by an adjustable circuit example whose insertion loss is below 0.3 dB.
关键词： stability,RF/MW active devices,narrow-band attenuation,out-band instability,cascaded system
更新于2025-09-04 15:30:14