The Experts below are selected from a list of 92250 Experts worldwide ranked by ideXlab platform
Ningbo Wang - One of the best experts on this subject based on the ideXlab platform.
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igs real time service for global ionospheric total electron Content Modeling
2020Co-Authors: Ningbo Wang, M Hernandezpajares, Yunbin Yuan, Andrzej Krankowski, Ang Liu, Jiuping Zha, Alberto Garciarigo, David Romadollase, Heng YangAbstract:Benefiting from global multi-frequency and multi-constellation GNSS measurements provided by the experimental International GNSS real-time service (IGS RTS), a predicting-plus-Modeling approach employed by Chinese Academy of Sciences (CAS) for the routine generation of real-time global ionospheric maps (RT-GIM) is first reported. Along with RT-GIMs generated by Universitat Politecnica de Catalunya (UPC), the quality of CAS and UPC RT-GIMs in IONEX format is assessed during a low soar activity period from September 2017 to December 2019. The differential slant total electron Contents (dSTEC) derived from 50 GPS stations of the IGS and Jason-3 vertical TECs (VTEC) over the ocean are used as references. In comparison with different reference TECs, CAS and UPC RT-GIMs are approximately 1.7–4.9% and 8.6–12.5% worse than the respective post-processed GIMs CASG and UQRG, respectively. Using RTCM ionospheric data streams from CAS, Centre National d’Etudes Spatiales (CNES) and UPC, the first experimental IGS combined RT-GIM is generated and validated in actual real-time conditions. Compared to Jason-3 VTEC measurements available during the period of common availability, from October 2018 to April 2019, RT-GIM discrepancies present similar relative RMS errors, which are 33, 36, 36 and 38% for CNES, combined one, UPC and CAS, respectively. Aside from a better understanding of the influence of working in the original IONEX versus RTCM ionospheric formats, the update to a new experimental adaptation of RT strategy is highlighted by UPC, and the computation of multi-layer RT-GIM is emphasized by CAS in view of the inadequacy of single-layer ionospheric assumption in the presence of large latitudinal gradients.
Heng Yang - One of the best experts on this subject based on the ideXlab platform.
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igs real time service for global ionospheric total electron Content Modeling
2020Co-Authors: Ningbo Wang, M Hernandezpajares, Yunbin Yuan, Andrzej Krankowski, Ang Liu, Jiuping Zha, Alberto Garciarigo, David Romadollase, Heng YangAbstract:Benefiting from global multi-frequency and multi-constellation GNSS measurements provided by the experimental International GNSS real-time service (IGS RTS), a predicting-plus-Modeling approach employed by Chinese Academy of Sciences (CAS) for the routine generation of real-time global ionospheric maps (RT-GIM) is first reported. Along with RT-GIMs generated by Universitat Politecnica de Catalunya (UPC), the quality of CAS and UPC RT-GIMs in IONEX format is assessed during a low soar activity period from September 2017 to December 2019. The differential slant total electron Contents (dSTEC) derived from 50 GPS stations of the IGS and Jason-3 vertical TECs (VTEC) over the ocean are used as references. In comparison with different reference TECs, CAS and UPC RT-GIMs are approximately 1.7–4.9% and 8.6–12.5% worse than the respective post-processed GIMs CASG and UQRG, respectively. Using RTCM ionospheric data streams from CAS, Centre National d’Etudes Spatiales (CNES) and UPC, the first experimental IGS combined RT-GIM is generated and validated in actual real-time conditions. Compared to Jason-3 VTEC measurements available during the period of common availability, from October 2018 to April 2019, RT-GIM discrepancies present similar relative RMS errors, which are 33, 36, 36 and 38% for CNES, combined one, UPC and CAS, respectively. Aside from a better understanding of the influence of working in the original IONEX versus RTCM ionospheric formats, the update to a new experimental adaptation of RT strategy is highlighted by UPC, and the computation of multi-layer RT-GIM is emphasized by CAS in view of the inadequacy of single-layer ionospheric assumption in the presence of large latitudinal gradients.
Anastasios Doulamis - One of the best experts on this subject based on the ideXlab platform.
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evaluation of relevance feedback schemes in Content based in retrieval systems
2006Co-Authors: Nikolaos Doulamis, Anastasios DoulamisAbstract:Abstract Multimedia Content Modeling, i.e., identification of semantically meaningful entities, is an arduous task mainly due to the fact that (a) humans perceive the Content using high-level concepts and (b) the subjectivity of human perception, which often interprets the same Content in a different way at different times. For this reason, an efficient Content management system has to be adapted to current user's information needs and preferences through an on-line learning strategy based on users’ interaction. One adaptive learning strategy is relevance feedback, originally developed in traditional text-based information retrieval systems. In this way, the user interacts with the system to provide information about the relevance of the Content, which is then fed back to the system to update its performance. In this paper, we evaluate and investigate three main types of relevance feedback algorithms; the Euclidean, the query point movements and the correlation-based approaches. In the first case, we examine heuristic and optimal techniques which are based either on the weighted or the generalized Euclidean distance. In the second case, we survey single and multipoint query movement schemes. As far as the third type is concerned, two different ways for parametrizing the normalized cross-correlation similarity metric are proposed. The first scales only the elements of the query feature vector and called query-scaling strategy, while the second scales both the query and the selected samples (query-sample scaling strategy). All the examined algorithms are evaluated using both subjective and objective criteria. Subjective evaluation is performed by depicting the best retrieved images as response of the system to a user's query. Instead, objective evaluation is obtained using standard criteria, such as the precision–recall curve and the average normalized modified retrieval rank (ANMRR). Furthermore, a newly objective criterion, called average normalized similarity metric distance is introduced which exploits the difference among the actual and ideal similarity measure among all best retrievals. Discussions and comparisons of all the aforementioned relevance feedback algorithms are presented.
Rahul Krishnan - One of the best experts on this subject based on the ideXlab platform.
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A Model Centric Framework and Approach for Complex Systems Policy
2026Co-Authors: Shamsnaz Virani Bhada, Rahul KrishnanAbstract:Twenty-first century systems engineering is no longerdocument-centric; instead, it is model-centric. Model-centric systems engineering helps reduce ambiguity, increase clarity, and increase the analytics of the resulting complex systems. However, complex systems are governed by organizational policies that are still document-centric. Such policies are difficult to analyze, and gaps in policy can lead to major deficiencies in the resulting complex systems. This article introduces a framework for policy Content Modeling (PCM) and analysis. The framework represents the conceptual view and is supported by a step-by-step approach to achieve complete policy Modeling and analysis. This approach was used with the intention of identifying and analyzing gaps in policy Content and calculating policy toxicity, which negatively affects the resulting system. This framework and approach was also applied to Veterans Affairs (VA) and university policies. The VA PCM is conducted to discover toxicity in the policies and University policies Modeling is done to graphically represent an undocumented policy and toxicity in the policy implementation.
Yunbin Yuan - One of the best experts on this subject based on the ideXlab platform.
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igs real time service for global ionospheric total electron Content Modeling
2020Co-Authors: Ningbo Wang, M Hernandezpajares, Yunbin Yuan, Andrzej Krankowski, Ang Liu, Jiuping Zha, Alberto Garciarigo, David Romadollase, Heng YangAbstract:Benefiting from global multi-frequency and multi-constellation GNSS measurements provided by the experimental International GNSS real-time service (IGS RTS), a predicting-plus-Modeling approach employed by Chinese Academy of Sciences (CAS) for the routine generation of real-time global ionospheric maps (RT-GIM) is first reported. Along with RT-GIMs generated by Universitat Politecnica de Catalunya (UPC), the quality of CAS and UPC RT-GIMs in IONEX format is assessed during a low soar activity period from September 2017 to December 2019. The differential slant total electron Contents (dSTEC) derived from 50 GPS stations of the IGS and Jason-3 vertical TECs (VTEC) over the ocean are used as references. In comparison with different reference TECs, CAS and UPC RT-GIMs are approximately 1.7–4.9% and 8.6–12.5% worse than the respective post-processed GIMs CASG and UQRG, respectively. Using RTCM ionospheric data streams from CAS, Centre National d’Etudes Spatiales (CNES) and UPC, the first experimental IGS combined RT-GIM is generated and validated in actual real-time conditions. Compared to Jason-3 VTEC measurements available during the period of common availability, from October 2018 to April 2019, RT-GIM discrepancies present similar relative RMS errors, which are 33, 36, 36 and 38% for CNES, combined one, UPC and CAS, respectively. Aside from a better understanding of the influence of working in the original IONEX versus RTCM ionospheric formats, the update to a new experimental adaptation of RT strategy is highlighted by UPC, and the computation of multi-layer RT-GIM is emphasized by CAS in view of the inadequacy of single-layer ionospheric assumption in the presence of large latitudinal gradients.