Relation between Earthward magnetotail flow and low-latitude Pi2 pulsations

권혁진,김관혁,이동훈,이은상,Kwon, Hyuck-Jin,Kim, Khan-Hyuk,Lee, Dong-Hun,Takahashi, Kazue,Lee, Ensang,Angelopoulos, Vassilis,Park, Young-Deuk 한국천문학회 2012 天文學會報 Vol.37 No.2

It has been suggested that oscillatory earthward bursty bulk flows (BBFs) in the magnetotail are driving Pi2 oscillations on the ground. However, only a few studies examined the BBF-driven Pi2 model. The goal of this study is to establish the relation between BBFs and Pi2s. In order to examine BBF-drive model, we will conduct the timing analysis between BBFs and Pi2s for the intervals during which both Pi2 and BBF are present. In our study BBFs are identified with earthward flow speeds up to 200 km/s from THEMIS probes with a geocentric distance between 7 and 12 RE in the nightside magnetosphere for the interval from January 2008 to March 2008. Pi2 pulsations are identified at three low/mid-latitude ground stations having different local times; Bohyun (L = 1.35, LT ~ UT +9 hr), Hermanus (L = 1.83, LT ~ UT +2 hr) and Carson city (L = 2.00, LT ~ UT -2 hr). It is found that ~28% of BBFs have onset timing nearly identical to Pi2 onset. To investigate whether there is high similarity in the waveform between BBF and Pi2 oscillations, the coherence analysis is applied to the time series of BBF and Pi2 events. We found that there is no high coherence between BBF and Pi2 oscillations. Thus our observations suggest that low-latitude Pi2 oscillations are not directly driven by earthward flow bursts.

공적연금의 최저생계 보장 효과에 대한 장기 전망

권혁진,류재린,Kwon, Hyukjin,Ryu, Jaerin 한국통계학회 2015 응용통계연구 Vol.28 No.4

본 연구는 동학적 미시모의실험(Micro-simulation) 모형인 MMESP(ver. 2.1)를 활용하여 절대빈곤선으로 간주되는 최저생계비를 기준으로 공적연금 수급액수준을 장기적으로 전망 평가한다. 즉, 본 논문에서 제시하는 노인빈곤율은 공적연금소득만을 고려한 전망치임을 주의할 필요가 있다. 그 주요 결과는 다음과 같다. 첫째, 공적연금액의 장기적 변화는 경제성장효과와 제도효과로 분해할 수 있다. 두 효과를 모두 고려하는 경우, 공적연금액이 최저생계비 이하인 노인가구는 2040년대에 20% 정도수준까지 감소한다. 그러나 경제성장효과를 제외한 제도효과만을 고려하는 경우 노인빈곤율은 장기적으로 90% 내외 수준에 이를 것으로 전망된다. 둘째, 기초연금을 A값의 10% 수준으로 고정한다고 할지라도 경제성장효과를 제외한 공적연금 제도 효과만을 보면, CPI에 연동하는 현행 제도에 비해 노인빈곤율을 10%p 정도 더 축소시킬 뿐이다. 셋째, 현행 국민연금의 급여산식에는 소득수준과 가입기간의 현실적인 상관관계가 고려되지 못함으로써 소득계층간 연금급여의 소득대체율이 역전될 가능성이 높다. 넷째, 2007년 개혁으로 소득대체율이 인하되지 않았다면 현행 체계(국민연금+기초연금)에 비해 과거 체계가 노인빈곤 완화 측면에서는 더 효과적일 수 있다. 즉, 개혁 이전의 제도 하에서는 국민연금만으로도 노인빈곤율은 약 70% 수준까지 축소되었을 것이다. 이것은 2007년 개혁을 통한 연금재정 상의 이득을 얻기 위해 지불한 비용이다. 연금개혁의 올바른 평가는 사회적 편익과 비용을 동시에 고려할 때 가능하다는 점에서 기존 논의에 대한 재검토와 향후 발전적인 논의가 필요하다. This study examines the long-term prospects for a minimum living guarantee by public pensions for the elderly using a dynamic micro-simulation model. "Elderly poverty" here is an estimate calculated by considering only the public pension income and it means how public pension affects the minimum living guarantee for the elderly. The main results are: First the impact of the public pension system on elderly poverty can be decomposed into economic growth and institutional effect. When considering both effects, the absolute poverty rate of the elderly will be reduced to 20% by the year 2040. But when considering the institutional effect(except economic growth effect), that rate is expected to be a long-term level of around 90%. Second, even if the Basic Pension is indexed to 10% of A-value, the elderly poverty rate is only about 10%p to be reduced further, compared to the current CPI-indexed system. Third, current benefit formula for National Pension does not consider the actual correlation of income level and insured period; consequently, the reversal possibility of the replacement rate appears likely. Fourth, the reform of 2007 improves the sustainability of the National Pension; however, it deteriorates the adequacy of the pension policy, i.e., the past system would be better than the current system in regards to a reduction in elderly poverty. Further discussion is needed on aspects of correct pension reform assessments which is difficult to achieve without understanding the comprehensive benefits and costs to society.

무선 랜 밀집 지역의 전송률 향상을 위한 시분할 매체 접근 제어 프로토콜

권혁진,황경호,Kwon, Hyeok-Jin,Hwang, Gyung-Ho 한국정보통신학회 2018 한국정보통신학회논문지 Vol.21 No.3

무선 랜 기기의 보급에 따라 같은 무선 채널에 존재하는 단말의 수가 증가하고 있다. 기존의 무선 랜 프로토콜인 CSMA/CA는 랜덤 백오프 방식을 사용한다. 랜덤 백오프 방식은 같은 채널에 존재하는 단말의 개수가 수십 개 이상되는 밀집 지역에서 단말간의 충돌이 잦아 표준 CSMA/CA 프로토콜의 성능 저하가 심각하게 발생한다. 이와 같은 프로토콜의 성능 저하를 막기 위해 IEEE 802.11ah 표준에서는 Restricted Access Window(RAW) 무선 접속 방식을 제안하였다. RAW는 단말을 여러 그룹으로 나눠 동시 접속 단말의 수를 제한하여 성능을 개선하였다. 본 논문에서는 기존의 RAW방식을 개선하여 트래픽 변화에 따른 새로운 그룹생성, 그룹 제거와 그룹 재배치 알고리즘을 사용하여 채널 접속에 관한 성능을 높일 수 있는 방안을 제시한다. The number of stations existing in the same wireless channel is increasing due to the spread of the wireless LAN devices. CSMA/CA, a conventional wireless LAN protocol, uses a random backoff method. In the random backoff scheme, collision between stations is frequent in a dense region where the number of stations existing in the same channel is several tens or more, and the performance of the performance degradation of such a protocol, the IEEE 802.11ah standard proposed a Restricted Access Window(RAW) wireless access method. RAW improves performance by limiting the number of concurrent access stations by dividing the stations into several groups. In this paper, we propose a method to improve the performance of channel connection by using new group creation, group removal and group relocation algorithm according to traffic change by improving existing RAW method.

항공관제 전문성 수준에 따른 시각정보 판독과 미래정보 예측 차이

권혁진,Kwon, Hyuk-Jin 한국항공운항학회 2015 한국항공운항학회지 Vol.23 No.3

Many studies have shown that having perception of spatial information is important for air traffic control officer (ATCO) since it helps them understand the current situation and predict the situation it leads to. However, little or no research has been done to investigate if there is any difference at the levels of expertise in perceiving spatial information and predicting a prospective situation. This study investigates the difference between expert and novice ATCO groups in how accurately each group of ATCO perceive spatial information such as position, altitude, speed, and flying direction, and predicting such information they will encounter shortly. In completing a task to watch the movement of airplanes displayed on the computer monitor as a blip, the participants were asked to predict the position, speed, and the altitude of the aircraft in a minute by marking on the sector map. The results show that the expert group performed better in accuracy and had tendency to overestimate on position and altitude; however, no significant difference was found between the two groups in terms of reading a flying direction. Therefore reading a flying direction may not be a reliable indicator to judge expertise of ATCO. But the expert group shows better predicting performance by perceiving spatial information such as airplane's position and altitude with feeling on time. The study suggests that it is important to enhance perceptive skills in ATCO training in improving their expertise in predicting accuracy traffic situation, preventing from air collision, and improving productivity for more efficient air traffic flow. A further study on the relationship between the perception of spatial information and the sense of time in predicting future information and effectiveness as an independent factor would contribute to providing more insights into expertise of ATCOs.

상황인식 및 의사결정지원을 위한 국방AI기술의 성숙도 수준비교

권혁진,주예나,김성태,Kwon, Hyuk Jin,Joo, Ye Na,Kim, Sung Tae 한국시스템엔지니어링학회 2022 시스템엔지니어링학술지 Vol.18 No.1

On February 12, 2019, the U.S. Department of Defense newly established and announced the "Defense AI Strategy" to accelerate the use of artificial intelligence (AI) technology for military purposes. As China and Russia invested heavily in AI for military purposes, the U.S. was concerned that it could eventually lose its advantage in AI technology to China and Russia. In response, China and Russia, which are hostile countries, and especially China, are speeding up the development of new military theories related to the overall construction and operation of the Chinese military based on AI. With the rapid development of AI technology, major advanced countries such as the U.S. and China are actively researching the application of AI technology, but most existing studies do not address the special topic of defense. Fortunately, the "Future Defense 2030 Technology Strategy" classified AI technology fields from a defense perspective and analyzed advanced overseas cases to present a roadmap in detail, but it has limitations in comparing private technology-oriented benchmarking and AI technology's maturity level. Therefore, this study tried to overcome the limitations of the "Future Defense 2030 Technology Strategy" by comparing and analyzing Chinese and U.S. military research cases and evaluating the maturity level of military use of AI technology, not AI technology itself.

가스사고 통계 및 분석에 관한 고찰

권혁진,박찬옥,박찬일,여창훈,이장우,홍지룡,Kwon, H.J.,Park, C.O.,Park, C.I.,Yeo, C.H.,Lee, J.W.,Hong, J.R. 한국화재조사학회 2008 한국화재조사학회 논문지 Vol.11 No.1

각종 화재사고 분류 중 대표적으로 나타나는 가스사고는 그 형태와 원인이 다양하다고 할 수 있다. 가스사용량은 사용가구수가 증가와 사용 장소 및 가스기기의 다양화로 증가하고 있으며, 2007년도 가스사용량은 35,078천톤으로서 연평균 9.4%증가하였다. 가스사고는 95년 557건을 최고로 하여 2007년도에는 123건 발생하여 연평균 11.5%감소되었다. 가스의 종류에 따른 사고건수는 LP가스의 경우 전체 가스사고중 약 80%를 차지하고, 도시가스와 고압가스가 약 20%를 차지하고 있다. LP가 많았고, 특히 공급자부주의에 의한 사고가 끊이지 않고 증가하고 있는 추세이다. 가스사고는 사용자취급부주의, 공급자 취급부주의, 시공불량 및 노후제품으로부터 사고가 발생하여 인명과 재산피해가 발생하고 있다. 본 논문에서는 가스사고의 분류와 형태별, 원인별, 지역별 등에 대한 사고분포를 통해 가스사고의 원인에 대한 이해를 하고 가스안전사고를 예방하는 자료로 활용되도록 하였다. Among the various cases of fire accident, gas accident which is roost essential have a lot of forms and causes. The quantity consumed of gas is increasing because of increment of gas-using families and variations of gas machinery. The quantity consumed of gas in 2007 was 35078 tons and the average rate of increasement was 9.4%. The amount of gas accident was on the peak at 1995 when 557 accidents occurred in a year. In 2007, 123 gas accidents was occurred and the average rate of diminution was 11.5%. Accidents by LP gas took 80% of the whole accident and city gas and high pressure gas took 20%. In case of LP gas, accidents were usually occurred because of lack of blocking after the removal of gas machinery and moveable butane burner. Especially, the accidents cause by carelessness of a provider is increasing. Gas accidents which generate damage of human life and property, are caused by users' carelessness, providers' carelessness, inferiority of structure and old products. In this thesis, We will classify the gas accidents. Furthermore through the classification of accidents by forms, causes and regions, this thesis going to be a reference to understand and prevent the accidents.

END법을 이용한 돼지콜레라바이러스 및 이에 대한 중화항체가 측정법 개량에 대한 시험

권혁진,윤석민,하용공,조성수,김교종,윤지병,Kwon Hyock-Jin,Yoon Seok-Min,Ha Rung-Kong,Cho Sung-Soo,Kim Kgo-Jong,Yoon Ji-Byung 대한수의사회 1991 대한수의사회지 Vol.27 No.12

The END method for titration of hog cholera virus and its serum neutralizing antibody was improved using ST cells grown and kept in modified media. ST cells were grown in Eagles media containing 0.5$\%$ lactalbumin hydrolysate, 10$\%$</TEX

항공부품 프레팅 손상 측정용 시험 장치 개발

권혁진,김경목,Kwon, Hyuk-Jin,Kim, Kyung-Mok 한국항공운항학회 2015 한국항공운항학회지 Vol.23 No.1

In this paper, a fretting testing machine is developed using ball-on-flat test apparatus. Precise micro-slip motion is produced by a linear stage. A relative displacement between a ball and a flat specimen is measured with a laser displacement sensor. Dry friction tests are conducted with AISI 52100 steel balls and cold-rolled high strength steel plates at room temperature and ambient humidity. The evolution of the kinetic friction coefficient is determined. Comparison between measured friction coefficients and those found in the literature is then carried out. Fretting tests with an electro-deposited coating are employed at an amplitude of 0.05 mm. Slip regime is identified with slip ratio. It is demonstrated that a developed testing machine allows determining the friction coefficient under fretting condition.

사각 덕트 내부 열전달 향상을 위한 요철의 단락 효과

권혁진,우성제,조형희,Kwon, Hyuk-Jin,Wu, Seong-Je,Cho, Hyung-Hee 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.5

The influence of arrangement and length of discrete ribs on heat/mass transfer and friction loss is investigated. Mass transfer experiments are conducted to obtain the detailed local heat/mass transfer information on the ribbed wall. The aspect ratio (width/height) of the duct is 2.04 and the rib height is one tenth of the duct height, such that the ratio of the rib height to hydraulic diameter is 0.0743. The ratio of rib-to-rib distance to rib height is 10. The discrete ribs were made by dividing each continuous rib into 2, 3 or 5 pieces and attached periodically to the top and the bottom walls of the duct with a parallel orientation The combined effects of rib angle and length of the discrete ribs on heat/mass transfer ae considered for the rib angles $({\alpha})\;of\;90^{\circ}\;and\;45^{\circ}$. As the number of the discrete ribs increases, the uniformity of the heat/mass transfer distributions increases. For $(\alpha})=90^{\circ}$, the heat/mass transfer enhancement with the discrete ribs is remarkable, while the heat/mass transfer performances are slightly higher than that of the transverse continuous ribs due to the accompanied high friction loss penalty. For $(\alpha})=90^{\circ}$, the average heat/mass transfer coefficients and the heat/mass transfer performances decrease slightly with the discrete ribs compared to the case of the angled continuous ribs.

고령화와 연금: 지속가능성과 적정성에 대하여

권혁진,박유성,Kwon, Hyukjin,Park, Yousung 한국통계학회 2015 응용통계연구 Vol.28 No.4

고령화, 연금, 그리고 관련된 이슈에 대해 총 12편의 엄선된 논문의 내용을 간략하게 정리하였다. 이 12편의 논문은 내용적으로 지속가능성, 연금의 적정성, 연금의 개혁방안으로 분류할 수 있다. 특히, 국민연금제도에 대한 심도 있고 광범위한 논의와 다양한 연금개혁방안은 정책입안자와 연금관련연구자에 많은 도움이 될 것으로 기대한다. We summarize the twelve papers carefully selected for aging, pensions, and related issues, The twelve novel papers are grouped into three categories: sustainability, adequacy, pension reforms. In particular, these twelve papers include depth and extensive discussions for national pension system and present the direction of the various pension reforms. It will be a great help to policy makers and researchers.