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QUADRUPLY-IMAGED QUASARS: SOME GENERAL FEATURES
Tuan-Anh, P.,Thai, T.T.,Tuan, N.A.,Darriulat, P.,Diep, P.N.,Hoai, D.T.,Ngoc, N.B.,Nhung, P.T.,Phuong, N.T. The Korean Astronomical Society 2020 Journal of The Korean Astronomical Society Vol.53 No.6
Gravitational lensing of point sources located inside the lens caustic is known to produce four images in a configuration closely related to the source position. We study this relation in the particular case of a sample of quadruply-imaged quasars observed by the Hubble Space Telescope. Strong correlations between the parameters defining the image configuration are revealed. The relation between the image configuration and the source position is studied. Some simple features of the selected data sample are exposed and commented upon. In particular, evidence is found for the selected sample to be biased in favor of large magnification systems. While having no direct impact on practical analyses of specific systems, our results have pedagogical value and deepen our understanding of the mechanism of gravitational lensing.
( Anh Tuan Tran ),( Jin Young Kim ),( Asmatullah Chaudhry ),( The Bao Pham ),( Hyoung-gook Kim ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.4
The GMM is a conventional approach which has been recently applied in many face recognition studies. However, the question about how to deal with illumination changes while ensuring high performance is still a challenge, especially with real-world databases. In this paper, we propose a Visual Observation Confidence (VOC) measure for robust face recognition for illumination changes. Our VOC value is a combined confidence value of three measurements: Flatness Measure (FM), Centrality Measure (CM), and Illumination Normality Measure (IM). While FM measures the discrimination ability of one face, IM represents the degree of illumination impact on that face. In addition, we introduce CM as a centrality measure to help FM to reduce some of the errors from unnecessary areas such as the hair, neck or background. The VOC then accompanies the feature vectors in the EM process to estimate the optimal models by modified-GMM training. In the experiments, we introduce a real-world database, called KoFace, besides applying some public databases such as the Yale and the ORL database. The KoFace database is composed of 106 face subjects under diverse illumination effects including shadows and highlights. The results show that our proposed approach gives a higher Face Recognition Rate (FRR) than the GMM baseline for indoor and outdoor datasets in the real-world KoFace database (94% and 85%, respectively) and in ORL, Yale databases (97% and 100% respectively).
The Impact of Heterogeneous Propagation Delays on Multipath TCP Performance
Tuan-Anh Le,Choong Seon Hong 한국정보과학회 2011 한국정보과학회 학술발표논문집 Vol.38 No.1A
In this paper we study the impact of heterogeneous round trip times on multipath TCP (MPTCP) performance via analysis the fluid model and simulation. Using parameter 'a' in MPTCP can alleviate poor performance due to divergent RTTs between paths. Moreover, divergent RTTs in MPTCP can affect response to changes in the network conditions.
Anh-Tuan Le,Ninh-Thuy Nguyen,Deawook Park,Hyunjong Lee 한국도로학회 2018 한국도로학회 학술대회 발표논문 초록집 Vol.2018 No.05
Fly ash is used as alumina-silicate resource material to reaction processing on geopolymer materials. The strength of material is belonging to alkaline liquid, fly ash, activity reaction of fly ash. Geopolymer concrete as non-toxic, bleed free and high strength material can be used for construction on rigid pavement. Study on influence of polypropylene fiber on performance characteristic of geopolymer concrete is considered. In this research, the mix proportion with fly ash and alkaline liquid is used to react on geopolymer concrete. The poly-propylene fiber in range from 0 to 0.5% by volume is added in mixture of geopolymer concrete. The ratio between length and diameter in range of 100-500 is investigated. The results are indicated that workability of fresh concrete is reduced by using poly-propylene fiber. The adding of poly-propylene fiber is significantly affected on characteristic of geopolymer concrete. Poly-propylene fiber can be distributed in fly ash matrix and reduced shrinkage of concrete during activation. After geopolymerization, compressive and the flexural strength of concrete produced with fibers are enhanced up to 10% and 20%, respectively. However, when the length to diameter ratio increases, compressive strength is tended to decrease with mixture using polypropylene fiber.