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Microwave Subsurface Imaging: Methodologies and Applications 微波地下成像:方法和应用
2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) Pub Date : 2019-03-01 DOI: 10.23919/URSIAP-RASC.2019.8738221
M. Akhtar, Greeshmaja Govind, Z. Akhter
{"title":"Microwave Subsurface Imaging: Methodologies and Applications","authors":"M. Akhtar, Greeshmaja Govind, Z. Akhter","doi":"10.23919/URSIAP-RASC.2019.8738221","DOIUrl":"https://doi.org/10.23919/URSIAP-RASC.2019.8738221","url":null,"abstract":"Over the years, microwave subsurface imaging has gained widespread attention in many fields such as concealed weapon detection at security checkpoints, landmine detection, biomedical imaging, structural health monitoring, quality inspection of composite structures etc. The strategy of microwave imaging is to illuminate the object under investigation using a known electromagnetic source, and from the reflection and transmission parameters received in response, information regarding the electromagnetic signature of the target is derived using suitable inverse process. Of the various measurement techniques available, the criteria for selecting a particular scheme for microwave imaging would be primarily based on factors such as the ease of imaging, frequency of operation, imaging accuracy etc. In recent years, real-time imaging of objects has garnered interest where the imaging scheme does not involve complex iterative inverse solutions or time-consuming calibration procedures [1]. Accordingly, the focus has been shifted from theoretical studies to the development of sophisticated practical arrangements where one can acquire information about objects in real time.","PeriodicalId":344386,"journal":{"name":"2019 URSI Asia-Pacific Radio Science Conference (AP-RASC)","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116977644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Origin and Nature of Electromagnetic Interference in X-band Weather Radars x波段气象雷达电磁干扰的来源和性质
2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) Pub Date : 2019-03-01 DOI: 10.23919/URSIAP-RASC.2019.8738610
M. Vaccarono, V. Chandrasekar, R. Bechini, R. Cremonini
{"title":"Origin and Nature of Electromagnetic Interference in X-band Weather Radars","authors":"M. Vaccarono, V. Chandrasekar, R. Bechini, R. Cremonini","doi":"10.23919/URSIAP-RASC.2019.8738610","DOIUrl":"https://doi.org/10.23919/URSIAP-RASC.2019.8738610","url":null,"abstract":"Weather radars are experiencing an increasing amount of strong interferences caused by artificial radio sources, such as telecommunications systems, with a negative impact on radar quantitative measurements. In most European countries, operational weather radars operate at the C-band, in the 5.6 GHz frequency band, which is shared with Radio Local Area Networks (RLAN) and Wireless Local Area Networks. The impact of these telecommunications systems in weather radar measurements has been already discussed in literature.","PeriodicalId":344386,"journal":{"name":"2019 URSI Asia-Pacific Radio Science Conference (AP-RASC)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117037847","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
A study of solar-cycle variation of coronal rotation using the SDO/AIA 211 Å observations 利用SDO/AIA 211 Å观测资料研究日冕旋转的太阳周期变化
2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) Pub Date : 2019-03-01 DOI: 10.23919/URSIAP-RASC.2019.8738564
Jaidev Sharma, B. Kumar, Anil K.Malik, S. Chandra, H. Vats
{"title":"A study of solar-cycle variation of coronal rotation using the SDO/AIA 211 Å observations","authors":"Jaidev Sharma, B. Kumar, Anil K.Malik, S. Chandra, H. Vats","doi":"10.23919/URSIAP-RASC.2019.8738564","DOIUrl":"https://doi.org/10.23919/URSIAP-RASC.2019.8738564","url":null,"abstract":"We present the results of variation in the rotational profile of solar corona for the period from 2012 to 2017, covering the peak and descending phases of the Solar Cycle 24. There is a clear evidence of North-South asymmetry in the solar coronal rotation. For this work, we used flux modulation method analysis for the solar full disk images (SFD) obtained at 211 Å by the Atmospheric Imaging Assembly (AIA) telescope on board Solar Dynamics Observatory (SDO) space mission. The SDO has three scientific instruments namely, the Extreme Ultraviolet Variability Experiment (EVE), the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA). SDO mission was launched by NASA on 11 February 2010 aimed to study the dynamics of Sun's surface and its atmosphere. AIA filters cover 10 different wavelength bands, chosen to reveal key aspects of solar activity at different heights in the solar atmosphere. Solar full disc (SFD) images obtained at the extreme ultraviolet wavelength (EUV) 211 Å by AIA are available in different sizes: $512 times 512, 1024 times 1024$ and others with a very less data gap.","PeriodicalId":344386,"journal":{"name":"2019 URSI Asia-Pacific Radio Science Conference (AP-RASC)","volume":"96 4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117297508","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Committee on Radio Astronomy Frequencies of the European Science Foundation (CRAF) - Quo Vadis? 欧洲科学基金会(CRAF)射电天文频率委员会- Quo Vadis?
2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) Pub Date : 2019-03-01 DOI: 10.23919/URSIAP-RASC.2019.8738200
M. Lindqvist
{"title":"Committee on Radio Astronomy Frequencies of the European Science Foundation (CRAF) - Quo Vadis?","authors":"M. Lindqvist","doi":"10.23919/URSIAP-RASC.2019.8738200","DOIUrl":"https://doi.org/10.23919/URSIAP-RASC.2019.8738200","url":null,"abstract":"Radio astronomy plays a vital role in the understanding of the universe. However, it is becoming increasingly difficult to protect radio astronomy from radio interference as use of the spectrum increases for both terrestrial and space-borne communications. On behalf of European radio astronomers, the Committee on Radio Astronomy Frequencies of the European Science Foundation (CRAF) coordinates activities to keep the frequency bands used by radio astronomy and space sciences free from interference. In this talk we will give an overview of CRAF and its work with an emphasis on the preparation for the World Radio Conference 2019.","PeriodicalId":344386,"journal":{"name":"2019 URSI Asia-Pacific Radio Science Conference (AP-RASC)","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115993291","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
On the Accuracy of Simplified Models for Water Vapor Attenuation Prediction at Ka band and Q band Ka波段和Q波段水汽衰减预报简化模式的精度研究
2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) Pub Date : 2019-03-01 DOI: 10.23919/URSIAP-RASC.2019.8738387
L. Luini, C. Riva, C. Capsoni
{"title":"On the Accuracy of Simplified Models for Water Vapor Attenuation Prediction at Ka band and Q band","authors":"L. Luini, C. Riva, C. Capsoni","doi":"10.23919/URSIAP-RASC.2019.8738387","DOIUrl":"https://doi.org/10.23919/URSIAP-RASC.2019.8738387","url":null,"abstract":"The accuracy of the approximate prediction models included in recommendation ITU-R P.676 aimed at estimating the attenuation due to gases (water vapor and oxygen) from ground meteorological inputs is assessed. To this aim, the gaseous attenuation derived from a multichannel radiometer installed at the experimental station of Spino d’Adda is used as reference. Two versions of the same recommendation are considered, defining different simplified expressions for the gaseous specific attenuation, but both taking advantage of the same equivalent height concept. Results, evaluated over a full year of data, indicate that the most recent model (version 11 of P.676) significantly underestimate the attenuation due to gases; on the contrary, the previous version of the recommendation turns out to be accurate enough to be used reliably in supporting the derivation of total tropospheric attenuation from the received beacon signal in electromagnetic wave propagation experiments, especially when no radiometric data are available at the site.","PeriodicalId":344386,"journal":{"name":"2019 URSI Asia-Pacific Radio Science Conference (AP-RASC)","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125850433","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
X-Band Metamaterial Wideband Polarization Insensitive Thin Absorber using Lumped Resistors 集总电阻的x波段超材料宽带极化不敏感薄吸收体
2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) Pub Date : 2019-03-01 DOI: 10.23919/URSIAP-RASC.2019.8738201
S. Sambhav
{"title":"X-Band Metamaterial Wideband Polarization Insensitive Thin Absorber using Lumped Resistors","authors":"S. Sambhav","doi":"10.23919/URSIAP-RASC.2019.8738201","DOIUrl":"https://doi.org/10.23919/URSIAP-RASC.2019.8738201","url":null,"abstract":"A novel frequency selective surface (FSS) based absorber with broadband characteristics is presented in this paper. The absorber is designed for X band applications. The absorber presented here is thin broadband and polarization insensitive owing to its four fold symmetric nature. The simple design of the structure makes it more realizable and hence practically feasible.","PeriodicalId":344386,"journal":{"name":"2019 URSI Asia-Pacific Radio Science Conference (AP-RASC)","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125976657","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Reconstruction of Relative Permittivity and Thickness Profiles of Different Dielectric Samples Using Time Domain Multiple Reflection Method 用时域多重反射法重建不同介质样品的相对介电常数和厚度分布
2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) Pub Date : 2019-03-01 DOI: 10.23919/URSIAP-RASC.2019.8738348
Aman, V. Singh, Somak Bhattacharyya
{"title":"Reconstruction of Relative Permittivity and Thickness Profiles of Different Dielectric Samples Using Time Domain Multiple Reflection Method","authors":"Aman, V. Singh, Somak Bhattacharyya","doi":"10.23919/URSIAP-RASC.2019.8738348","DOIUrl":"https://doi.org/10.23919/URSIAP-RASC.2019.8738348","url":null,"abstract":"In this paper, a novel method involving multiple reflections has been proposed for the reconstruction of the relative permittivity and thickness pertaining to different dielectric samples from the measurement of the reflection coefficients only. The unique advantage of this method is no requirement of measurement of any additional parameter to determine relative permittivity and thickness profile of the sample. Thus, it provides a cost-effective solution. The accuracy of this method for reconstructing the permittivity and thickness of the dielectric wall is very high and the measured error is less than 0.26% for permittivity values and 1.4% for thickness values for the most optimized reconst1ructed values. This method has been verified for different samples having different thickness and hence the optimum thickness for each sample has been determined.","PeriodicalId":344386,"journal":{"name":"2019 URSI Asia-Pacific Radio Science Conference (AP-RASC)","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124731202","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Features of low level winds over Cochin during the deluge of Monsoon-2018 using 205 MHz wind Profiler Radar 205mhz风廓线雷达对2018年季风大洪水期间科钦低空风特征的观测
2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) Pub Date : 2019-03-01 DOI: 10.23919/URSIAP-RASC.2019.8738657
M. G. Manoj, Mohankumar, V. Rakesh, Rejoy Rebello
{"title":"Features of low level winds over Cochin during the deluge of Monsoon-2018 using 205 MHz wind Profiler Radar","authors":"M. G. Manoj, Mohankumar, V. Rakesh, Rejoy Rebello","doi":"10.23919/URSIAP-RASC.2019.8738657","DOIUrl":"https://doi.org/10.23919/URSIAP-RASC.2019.8738657","url":null,"abstract":"This study focusses on the application of remotely sensed wind data from a VHF wind profiler to understand the features of the monsoon low level jet during the great deluge happened in the monsoon months of 2018. A major flood-induced disaster occurred during the period 07-16 August 2018. The sophisticated radar installed at the Advanced Centre for Atmospheric Radar Research (ACARR), Cochin University of Science and Technology, Kerala, and operating at 205 MHz, provides high spatial (45 m) and temporal ($sim$10 minutes) data of all the three wind components. Deep convective clouds which moved in south-east direction over the State led to the unprecedented flood situation, which was obvious from the wind profiler data. The radar data was screened for data quality and examined for its daily variation during the flood event. It is observed that the monsoon low level jet showed an increasing tendency during the major event, and crossed a threshold value of around 18 ms$^{-1}$ on many days.","PeriodicalId":344386,"journal":{"name":"2019 URSI Asia-Pacific Radio Science Conference (AP-RASC)","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129404049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Phased array of 619-element Yagi-Uda antenna for Wind Profiler Radar at Cochin University of Science and Technology 科钦科技大学风廓线雷达619元Yagi-Uda天线相控阵
2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) Pub Date : 2019-03-01 DOI: 10.23919/URSIAP-RASC.2019.8738742
Titu K. Samson, B. Babu, V. Anandan, R. V., Rejoy Rebello, K. Mohanakumar, P. Mohanan
{"title":"Phased array of 619-element Yagi-Uda antenna for Wind Profiler Radar at Cochin University of Science and Technology","authors":"Titu K. Samson, B. Babu, V. Anandan, R. V., Rejoy Rebello, K. Mohanakumar, P. Mohanan","doi":"10.23919/URSIAP-RASC.2019.8738742","DOIUrl":"https://doi.org/10.23919/URSIAP-RASC.2019.8738742","url":null,"abstract":"During the last 3 to 4 decades radar technology has grown into an indispensable technology for weather phenomenon detection, prediction and tracking. There are mainly two types of atmospheric radar, Doppler weather radar to detect clouds, thunder storms, cyclone etc and Wind Profiler Radars (WPR) used to detect the speed and direction of wind above the radar. In this paper we are discussing the design of 619 element Yagi-Uda antenna array for Stratosphere Troposphere Wind profiler radar(ST Radar) operating at 205MHz. Frequency was selected considering the objective of height coverage of 500m to 20Km above earth. Design is done based on the volume reflectivity and refractive index structure coefficient of atmosphere. Minimum detectable signal(MDS -150dBm) of the system is considered as design criteria.","PeriodicalId":344386,"journal":{"name":"2019 URSI Asia-Pacific Radio Science Conference (AP-RASC)","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129853506","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Single Trapped 171Yb+ for Optical Frequency Standards 光频率标准单阱171Yb+
2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) Pub Date : 2019-03-01 DOI: 10.23919/URSIAP-RASC.2019.8738233
A. Roy, L. Sharma, H. Rathore, J. Saroha, Neelam, K. Kumari, S. De, S. Panja
{"title":"Single Trapped 171Yb+ for Optical Frequency Standards","authors":"A. Roy, L. Sharma, H. Rathore, J. Saroha, Neelam, K. Kumari, S. De, S. Panja","doi":"10.23919/URSIAP-RASC.2019.8738233","DOIUrl":"https://doi.org/10.23919/URSIAP-RASC.2019.8738233","url":null,"abstract":"An optical clock or frequency standard based on the interrogation of an atomic transition in the optical domain, operates at-1014 Hz is capable of providing orders of magnitude better accuracy than the present primary standard of frequency or time operating in the microwave range. Optical transitions of an ions, confined within a radio frequency ion trap and laser cooled to $sim mathrm {m}mathrm {K}$temperature, provides better long term stability since they are free from Coulomb and intra-atomic interactions. Optical frequency standards have been realized with several ions, e.g., <sup>199</sup>Hg<sup>+</sup>, <sup>171</sup>Yb<sup>+</sup>, <sup>115</sup>In<sup>+</sup>, <sup>88</sup>Sr<sup>+</sup>, <sup>40</sup>Ca<sup>+</sup>, <sup>27</sup>Al<sup>+</sup> and among those <sup>171</sup>Y<sup>+</sup> has multiple ultra-narrow optical transitions suitable for serving as frequency standards [1–2]","PeriodicalId":344386,"journal":{"name":"2019 URSI Asia-Pacific Radio Science Conference (AP-RASC)","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128747467","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
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