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LYSO 섬광체를 이용한 감마선 분광용 광섬유 방사선 센서의 개발
한기택 ( Ki Tek Han ),유욱재 ( Wook Jae Yoo ),신상훈 ( Sang Hun Shin ),전다영 ( Da Yeong Jeon ),박장연 ( Jang Yeon Park ),박병기 ( Byung Gi Park ),이봉수 ( Bong Soo Lee ) 한국센서학회 2012 센서학회지 Vol.21 No.4
A fiber-optic radiation sensor was fabricated using a sensing probe, a plastic optical fiber, a photomultiplier tube, and a multichannel analyzer for gamma-ray spectroscopy. As an inorganic scintillator of the sensing probe, a LYSO crystal was used. In this study, we obtained the relationship between the photon counts of the fiber-optic radiation sensor and the activity of the radioactive isotope. In addition, the gamma-ray energy spectra were also measured using a fiber-optic radiation sensor to discriminate species of gamma-ray emitters.
Detection And Countermeasure Scheme For Call-Disruption Attacks On SIP-Based Voip Services
( Jea Tek Ryu ),( Byeong-hee Roh ),( Ki Yeol Ryu ),( Myungchul Yoon ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.7
Owing to its simplicity and flexibility, the session initiation protocol (SIP) has been widely adopted as a major session-management protocol for Internet telephony or Voice-over IP (VoIP) services. However, SIP has faced various types of security threats. Call-disruption attacks are some of the most severe threats they face, and can greatly inconvenience consumers. In this paper, we analyze such SIP call-disruption attacks, and propose a method for detecting and counteracting them by extending the SIP INFO method with authentication. Using the proposed method, both the target user and the SIP server can detect the existence of a call-disruption attack on a user and counteract the attack. We demonstrate the effectiveness of the proposed method from the viewpoint of computational complexity by configuring a test-bed with an Asterisk SIP proxy server and an SIP performance (SIPp) emulator.
Detection of SIP Flooding Attacks based on the Upper Bound of the Possible Number of SIP Messages
( Jea-tek Ryu ),( Byeong-hee Roh ),( Ki-yeol Ryu ) 한국인터넷정보학회 2009 KSII Transactions on Internet and Information Syst Vol.3 No.5
Since SIP uses a text-based message format and is open to the public Internet, it provides a number of potential opportunities for Denial of Service (DoS) attacks in a similar manner to most Internet applications. In this paper, we propose an effective detection method for SIP flooding attacks in order to deal with the problems of conventional schemes. We derive the upper bound of the possible number of SIP messages, considering not only the network congestion status but also the different properties of individual SIP messages such as INVITE, BYE and CANCEL. The proposed method can be easily extended to detect flooding attacks by other SIP messages.
The Differential Immunomodulating Effects of Levan and DFA-Ⅳ on Macrophage Function
Sulkyoung Park,Ki-Hyo Jang,Mi-Hyun Kim,Jung Dae Lim,Eun Tek Han,Seon-A Jang,Kyungho Kim,Suhkneung Pyo,Eun-Hwa Sohn 한국식품영양과학회 2008 Preventive Nutrition and Food Science Vol.13 No.1
Di-D-fructose-2,6':6,2'-dianhydride (DFA-Ⅳ) is a disaccharide consisting of two fructose residues that are prepared from levan by levan fructotransferase. Levan is a homopolysaccharide composed of D-fructofuranosyl residues joined by β-(2,6) and β-(2,1) linkages. We compared the immunomodulatory effects of levan with DFA-Ⅳ. Tumoricidal activity, phagocytosis and nitric oxide (NO) production were examined in levan- and DFA-Ⅳ-treated RAW264.7 cells. The NO production, tumoricidal and phagocytic activities were significantly increased in both treated cells. The results indicate that levan has significantly greater effects on tumoricidal activity than DFA-Ⅳ at low concentrations (1 ㎍/mL) and its effect on NO production shows a similar pattern. These results suggest that tumoricidal activity induced by both samples is mediated by NO production.