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무선랜 환경에서 AP간 상호인증을 통한 핸드오프 방식연구
임승철(SeungCheol Lim) 한국정보기술학회 2010 한국정보기술학회논문지 Vol.8 No.9
One of mobile terminals characteristics is that moves frequently in wireless environments. Therefore between mobile terminals and APs is caused many handoffs. Everytime when handoffs are created, there are lots of overheads that are repeatedly authentications between APs. So in this paper, for fast handoff latency that comes out handoffs apply to serve as elements to short time for authentication, mutual authentication, soft handoff scheme between AP handoffs. Through comparing between the proposed algorithm methods and existing methods, the results is proposed handoff algorithm gets a better performance at average handoff time than existing algorithm.
차량자세제어시스템 적용을 위한 가속도 Sensor의 MEMS구조체 특성에 관한 연구
이승철(SeungCheol Lee),임정택(Jungtaek Lim),김성수(Seongsoo Kim) 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
This paper describes our verification work for multi-axes sensing MEMS accelerometers of comb structure for electronic stability control (ESC) system. The results of basic, environmental performance test and durability test using simulation, it proved that comb structure has same performance and durability with cantilever structure. And we can also find there is no difference between single axis and multi-axes sensing cantilever-structured accelerometer's performance. The multi-axes sensing MEMS accelerometers of comb structure can reduce costs and increase the space efficiency of the advanced ESC system.
A Real-Time Intrusion Detection Using Monitoring in Computer Network Security
San Eamsot,Lim SeungCheol 한국정보기술학회 2012 Proceedings of KIIT Conference Vol.2012 No.5
Recently, Intrusion detection system is an important technology in computer network system because of has seen a dramatic increase in the number of attacks. The most of intrusion detection methods do not detect intrusion on real-time because difficult to analyze an auditing data for intrusions. A network intrusion detection system is used to monitors the activities of individual users, groups, remote hosts and entire systems, and detects suspected security violations, by both insider and outsiders, as they occur. It is learns user’s behavior patterns over time and detects behavior that deviates from these patterns. In this paper has rule-based component that can be used to encode information about known system vulnerabilities and intrusion scenarios. Integrating the two approaches makes Intrusion Detection System a comprehensive system for detecting intrusions as well as misuse by authorized users or Anomaly users (unauthorized users) using RFM analysis methodology and monitoring collect data from sensor Intrusion Detection System(IDS).
Bone Marrow-derived Side Population Cells are Capable of Functional Cardiomyogenic Differentiation
Yoon, Jihyun,Choi, Seungcheol,Park, Chiyeon,Choi, Jihyun,Kim, Yangin,Shim, Wanjoo,Lim, Dosun Korean Society for Molecular Biology 2008 Molecules and cells Vol.25 No.2
It has been reported that bone marrow (BM)-side population (SP) cells, with hematopoietic stem cell activity, can transdifferentiate into cardiomyocytes and contribute to myocardial repair. However, this has been questioned by recent studies showing that hematopoietic stem cells (HSCs) adopt a hematopoietic cell lineage in the ischemic myocardium. The present study was designed to investigate whether BM-SP cells can in fact transdifferentiate into functional cardiomyocytes. Phenotypically, BM-SP cells were 19.59%±9.00 CD14+, 8.22%±2.72 CD34+, 92.93%±2.68 CD44+, 91.86%±4.07 CD45+, 28.48%±2.24 c-kit+, 71.09%±3.67 Sca-1+. Expression of endothelial cell markers (CD31, Flk-1, Tie-2 and VEGF-A) was higher in BM-SP cells than whole BM cells. After five days of co-culture with neonatal cardiomyocytes, 7.2%±1.2 of the BM-SP cells expressed sarcomeric α-actinin as measured by flow cytometry. Moreover, BM-SP cells co-cultured on neonatal cardiomyocytes fixed to inhibit cell fusion also expressed sarcomeric α-actinin. The co-cultured BM-SP cells showed neonatal cardiomyocyte-like action potentials of relatively long duration and shallow resting membrane potential. They also generated calcium transients with amplitude and duration similar to those of neonatal cardiomyocytes. These results show that BM-SP cells are capable of functional cardiomyogenic differentiation when co-cultured with neonatal cardiomyocytes.
The Effectiveness of a Predictor-corrector Technique in European Currency Option Valuation
Sangwoo Heo,Jinsuk Yang,SeungCheol Lim,Peter Cashel-Cordo 사람과세계경영학회 2019 Global Business and Finance Review Vol.24 No.4
In this work, we adopt a predictor-corrector technique to examine the accuracy of the Fractional Black-Scholes (FBS) model. Compared to the standard Black-Scholes (B-S) model, FBS model involves one additional parameter, a Hurst value (H) providing information whether the time series exhibits persistent or anti-persistent behavior. The FBS model, as a result, has been shown to provide more accurate predictions of option price [Heo et al. (2017) and reference therein]. Estimation accuracy of volatility and H values are key to better option price estimates. However, volatility and Hurst values are unknown prior to the closing time; consequently, the estimation of option prices relies heavily on the accuracy of volatilities and Hurst parameter estimation. In this study we compare option price estimation accuracy using three variations of calculating H values, and two volatility measures. We estimate two H values using historic data using one-month data (21 trading days) and three-month data (63 trading days), respectively, and by using predicted volatility estimates obtained using a binomial method, as a predictor and then used them to estimate implied H values. We subsequently correct the predicted volatility measure using the implied H value, the predictor-corrector technique. We investigate the accuracy of these FBS models and examine effectiveness of this predictor-corrector technique using Euro currency option (XDE) data traded in NASDAQ from November 2007 to June 2016.
Does the regulation change play a role in the dividend policy?: Empirical study of REITs
Jinsuk Yang,Manfen Chen,SeungCheol Lim 사람과세계경영학회 2019 Global Business and Finance Review Vol.24 No.4
According to Modernization Act (RMA) of 1999, real estate investment trusts (REITs) must distribute at least 90% of their taxable income to be exempt from tax at the corporate level, less than the percentage required prior to 2001 (95%), implying more funds from operation (FFO) are kept by REITs for growth and profitability. This study examines whether REITs disburse more cash by means of dividends after the tax regulation changes in 2001 to reduce agency problems. Our study reveals that excessive dividends paid by REITs increase with the excess funds from the operation. Furthermore, we document that managers pay excessive dividends after the change in required distribution from 95% to 90% of taxable income, implying that the tax regulation changes in REITs industry do impact excess dividends paid to reduce agency issues. These findings support the agency cost theory. In addition, our findings also imply that policy makers should consider not only stakeholders subject to regulations but also market reactions.
정영진(Young-Jin Jeong),임승철(SeungCheol Lim) 한국정보기술학회 2010 Proceedings of KIIT Conference Vol.2010 No.-
무선랜은 단말의 특성상 이동이 빈번하게 발생하며, 핸드오프시마다 반복되는 인증으로 많은 무선영역 및 단말기에 많은 오버헤드를 발생한다. 따라서 본 논문에서는 빠른 핸드오프를 위해 핸드오프 시 지연 시간 요소로 작용하는 인증 시간을 단축하기 위한 AP간의 상호 인증 방안을 이용한 핸드오프을 방식을 제안하고 제안된 방식과 기존의 방식을 시뮬레이션을 통하여 핸드오프 수행 평균 시간이 개선되는 것을 확인할 수 있었다. One of major characteristics in wireless LAN is frequent terminal mobility, so it makes many overheads in the process of authentications repeatedly at each handoffs. In this paper, for fast handoff latency handoff happens to serve as elements to short the time for authentication, mutual authentication between AP handoff using the method proposed plan and the proposed method and existing methods. Proposed handoff algorithm is get a good performance tham existing algorithm.
과붕산나트륨 양극 활물질 첨가에 따른 차량용 납산배터리 성능 특성
임태섭,김성준,김상동,양승철,정연길,Lim, Tae Seop,Kim, Sung Jun,Kim, Sang Dong,Yang, SeungCheol,Jung, Yeon-Gil 한국재료학회 2020 한국재료학회지 Vol.30 No.8
The performance characteristics of a lead acid battery are investigated with the content of Sodium Perborate Tetrahydrate (SPT, NaBO<sub>3</sub>·4H<sub>2</sub>O) in a positive plate active material. SPT, which reacts with water to form hydrogen peroxide, is applied as an additive in the positive plate active material to increase adhesion between the substrate (positive plate) and the active material; this phenomenon is caused by a chemical reaction on the surface of substrate. A positive plate with the increasing content of SPT is prepared to compare its properties. It is confirmed that the oxide layer increases at the interface between the substrate and the active material with increasing content of SPT; this is proven to be an oxide layer through EDS analysis. Battery performance is confirmed: when SPT content is 2.0 wt%, the charging acceptance and high rate discharge properties are improved. In addition, the lifetime performance according to the Standard of Battery Association of Japan (SBA) S0101 test is improved with increasing content of SPT.
Tracing Resistances of Anion Exchange Membrane Water Electrolyzer during Long-term Stability Tests
Niaz, Atif Khan,Lee, Woong,Yang, SeungCheol,Lim, Hyung-Tae The Korean Electrochemical Society 2021 Journal of electrochemical science and technology Vol.12 No.3
In this study, an anion exchange membrane water electrolysis (AEMWE) cell was operated for ~1000 h at a voltage bias of 1.95 V. Impedance spectra were regularly measured every ~ 100 h, and changes in the ohmic and non-ohmic resistance were traced as a function of time. While there was relatively little change in the I-V curves and the total cell resistance during the long-term test, we observed various electrochemical phenomena in the cell: 1) initial activation with a decrease in both ohmic and non-ohmic resistance; 2) momentary and non-permanent bubble resistance (non-ohmic resistance) depending on the voltage bias, and 3) membrane degradation with a slight increase in the ohmic resistance. Thus, the regular test protocol used in this study provided clear insights into the performance degradation (or improvement) mechanism of AEMWE cells.