• Journal of Positioning, Navigation, and Timing
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• 제7권1호
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• pp.25-35
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• 2018

This paper describes the measurement of pulse positioning (input time) to calculate a time of arrival (TOA) that takes from transmitting a signal from the target of multilateration (MLAT) system to receiving the signal at the receiver. In this regard, this paper analyzes performances of simple threshold method and level adjust system (LAS) method, which is one of the adaptive threshold detector (ATD) methods, among many methods to calculate pulse positioning of signal received at the receiver. To this end, Cramer-rao lower bound (CRLB) with regard to pulse positioning, which was measured when signals transmitted from a transponder mounted at the target were received at the receiver, was induced and then deviation sizes with regard to pulse positioning, which was measured with simple threshold and LAS methods through MATLAB simulations, were compared. Next, problems occurring according to a difference in amplitude of signals inputted to each receiver are described when pulse positioning is measured at multiple receivers located at a different distance from the target as is the case in the MLAT system. Furthermore, LAS method to resolve the problems is explained. Lastly, this study analyzes whether a pulse positioning error occurring due to the signal noise satisfies the requirement (6 nsec. or lower) recommended for the MLAT system when using these two methods.

• 한국군사과학기술학회지
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• 제20권3호
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• pp.369-375
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• 2017

One of good DF(Direction Finding) methods is based on TDOA(Time Difference of Arrival) estimation when finding underwater moving target. For small DF error, high time resolution A/D(Analog-to-digital) conversion board and long baseline are needed. But the result of sea trial about close-range and high speed moving target, spatial correlation coefficient and appeared poor properties below 0.3 when hydrophone arrangement are separated over 6 ${\lambda}$ because of underwater fading channel. And we also find out that the distance between hydrophone should be under 4 ${\lambda}$ apart to take advantage of spatial correlation coefficient gain and performance of DF in underwater moving channel environments.

• 전자공학회논문지
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• 제51권10호
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• pp.137-144
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• 2014

전자전지원시스템은 실시간 전자 공격에 대처하기 위해 레이더 신호를 수집하고 분석한다. 레이더 펄스 클러스터링 시스템은 단일 소스에 방사되는 것으로 예상되는 레이더 신호를 분류한다. 본 논문에서는 도착방향, 주파수, 펄스 폭, 연속된 펄스의 도착시간의 차이 4가지 특징을 기반으로 한 클러스터링 알고리즘을 제안하였고 실험을 통하여 제안한 알고리즘이 이동방사체의 추적과 시간적으로 분리된 신호를 다른 군집으로 분리함을 보였다.

• 한국통신학회논문지
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• 제40권2호
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• pp.334-348
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• 2015

최근 스마트기기가 널리 보급되면서 무선망이 가능한 AP(Access Point)의 사용 또한 증가하였다. AP를 사용하여 무선망에 접속할 때, 적절한 보안이 제공되지 않는다면, 로그 AP(Rogue AP)에 의해 다양한 보안 문제가 발생될 수 있다. 이 연구에서는 로그 AP의 유형 중 하나인 이블 트윈(Evil Twin)에 대한 위협에 대해서 살펴본다. 최근 대부분의 이블 트윈을 탐지하기 위한 연구에서는 RTT(Round Trip Time)와 같이 인가된 AP와 이블 트윈 사이에서 측정될 수 있는 시간 차이를 이용하는 방법이 주로 이용되고 있다. 그러나 이와 같이 이블 트윈을 탐지하는 방법은 채널이 혼잡한 상태일 때 탐지율이 떨어지는 단점이 있다. 이러한 이유에서 이 연구에서는 이블 트윈을 탐지하는 기준으로 RTT와 함께 추가로 PIAT(Packet Inter-Arrival Time)을 측정한다. 또한 측정된 값을 SVM(Support Vector Machine)의 학습 요소로 사용함으로써, 이블 트윈 분류를 위한 비선형적 기준을 정한다. 결과적으로 채널이 혼잡한 상황에서도 최대 96.5% 최소 89.75%의 높은 확률로 이블 트윈을 성공적으로 탐지하였다.

• 성인간호학회지
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• 제19권2호
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• pp.167-177
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• 2007

Purpose: This cross-sectional survey research was undertaken to identify the factors influencing time from onset to hospital arrival of stroke patients and to provide basic information for the development of intervention programs for stroke patients. Methods: The data were collected using a convenient sampling method from three hospitals in Inchon. The subjects were 78 patients who were diagnosed as stroke by doctor and they voluntarily participated in the study. Results: On the average, subjects arrived at the hospitals by 16.72 hours after the onset of stroke events with the range from 0.17 hours to 72 hours. Thirty-four(43.6%) subjects arrived within 3 hours which can maximize treatment effects. There was significant difference in hospital presentation time according to the level of knowledge(${\chi}^2=18.629$, p=.0003). A negative correlation was found between the hospital presentation time and self-efficacy (r= -.320, p=.004). Stepwise multiple regression analysis revealed that the most powerful predictor was self-efficacy. Self-efficacy, the level of knowledge and physical symptoms were significant factors and accounted for 21.7% of the variance of hospital presentation time in stroke patients. Conclusion: According to the results, self-efficacy is a useful concept for reducing the hospital presentation time from onset of attack in stroke patients. Therefore, nurses should consider educational programs which include not only a knowledge of stroke and recurrence prevention but also the concept of self-efficacy.

• 한국통신학회논문지
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• 제38A권12호
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• pp.1069-1078
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• 2013

본 논문에서는 최근 차세대 무선 통신네트워크 기술로 주목받고 있는 OFDMA 무선 메쉬통신시스템에서의 분산 시간동기화 기법을 제안한다. 제안방식은 물리계층 기반에서 이루어지는 생체모방 알고리즘을 활용한 자가 분산 시간동기화 기법으로, 인접 이웃노드로부터 수신된 신호의 TDoA(Time Difference of Arrival) 정보를 이용하여 다음 주기의 전송주기와 FFT 시작점을 업데이트한다. 분산처리가 가능한 생체모방 알고리즘의 장점이 반영되어, 제안된 동기화 기법에서도 중앙제어 없이 주위 정보(local Information)와 각 노드에 의한 분산처리만으로 빠르고 간단하게 노드 간 시간 동기 획득이 가능하다. 제안된 분산 시간 동기화 기법은 모의실험을 통하여 시간동기화 수렴 확률 및 정확도 등의 측면에서 성능을 분석한다.

• 한국항행학회논문지
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• 제16권2호
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• pp.297-306
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• 2012

본 논문에서는 NLOS(non-line-of-sight) 환경에서 신뢰성 있는 LBS(location based service)를 제공하기 위해, TDOA(time difference of arrival) 위치 추정 성능 향상을 위한 시간 지연 역추적 기법을 제안하고, 다양한 사용조건에서 성능을 분석하였다. 제안하는 위치 추정 기법은 탐색영역 주변에 복수의 리더를 배치하여 송신된 신호를 리더 조합(reader combination) 수만큼 재활용 하는 방안을 적용하였다. 또한, NLOS에 의한 성능 열화를 개선하기 위해 리더가 수신한 시간에서 일정한 시간 간격을 빼주면서 위치를 재추정하는 기법을 적용하였다. 실험 결과 제안하는 시간 지연 역추적 기법을 적용하였을 때, NLOS 시간 지연 70 m에서 NLOS 리더를 3개로 가정하고 Sub-blink 수를 3회로 하였을 때 약 16 m의 RMSE 개선을 확인 할 수 있었다. 이와 같은 결과를 통해 NLOS 환경에서 LBS 서비스 제공을 위해 요구되는 위치 추정 기법으로 본 논문에서 제안하는 시간 지연 역추적 기법이 적합함을 확인하였다.

• Journal of Trauma and Injury
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• 제22권1호
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• pp.71-76
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• 2009

Purpose: The goal of this study was to compare the outcome of the after trauma team (AfterTT) group to the before trauma team (BeforeTT) group. Methods: All trauma patients who visited to emergency room (ER) between July 1, 2006 and February 29,2008 based on trauma registry, with systolic blood pressure (SBP) < 90 mmHg or GCS < 9 were included in this study. We compared the amount of packed RBC transfusion, the ER stay time, the ER visit to CT evaluation time, the ER visit to operation time, the length of ICU stay, the length of hospital admission and the survival discharge rate between the AfterTT group and the BeforeTT group. Patients with brain injuries had little chance of survival. Burn patients, who visited the ER 24 hours after injury and patients who were dead on arrival (DOA) were excluded from this study. Results: Total of 93 patients were included in this study: 42 in the AfterTT group and 51 in the BeforeTT group. The AfterTT group and the Before TT group showed no differences in Revised Trauma Score (RTS) and mean age. The amount of packed RBC transfusion was lower in the AfterTT group, but no statistically significant difference was noted (AfterTT 11${\pm}$11units, BeforeTT 16${\pm}$15units, p=0.136). The ER visit to operation time was shorter in the AfterTT group, but there were no statistically significant difference between the groups (AfterTT 251${\pm}$223 minutes, BeforeTT 486${\pm}$460 minutes, p=0.082). The length of ICU stay was shorter in the AfterTT group, but the difference was not statistically significant (AfterTT 11${\pm}$12 days, Before TT 15${\pm}$30 days, p=0.438). The length of Hospital admission was shorter in the AfterTT group (AfterTT 43${\pm}$37 days, BeforeTT 68${\pm}$70 days, p=0.032), but this difference was not statistically significant. Conclusion: Simple Trauma team activation criteria decreased the amount of packed RBC transfusion and the hospital admission duration. Hemodynamic instability (SBP < 90 mmHg) and decreased mental state (GCS<9) are good indices for activating the trauma team.

• 한국응급구조학회지
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• 제1권1호
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• pp.42-53
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• 1997

To offer basic data about the influential factors on patient's Satisfaction level for emergency medical services the authors were performed this study in 60 patients visited to emergency room of third stage general hospital in Taejeon city. Data were collected through interview with patients by using a 15 items' questionaire according to care subscale, teaching subscale of Likert's five stage quantitative scale and the tools developed by Barbara Davis. The data were analyzed by using the SPSS/PC computerized program for mean, standard deviation, percentage, ANOVA, t-test, and pearson correlation. The results are as followings ; 1. Satisfaction of emergency medical service were showed in care area, but not showed in teaching and total area 2. Satisfaction of sociodemographic characteristics were a statistically significant difference only marriage, that were the higher in marriaged than single(P<.0.05). 3. In the emergency situation characteristics the satisfaction accordings to the visit cause were lower in accident than disease group, the reason of hospital selection were in order trust, introduction group, distance, traffic, kinds, and score of satisfaction were showed each of 43.47, 51.27(P<.001), the transportation vehicle was the 119, hospital ambulance group. but were not a satistically significant difference. 4. The negative correlation was observed between satisfaction and the length of stay at ER and the longer length of stay at ER was showed the lower satisfaction. But the positive correlation was observed between satisfacton and the arrival time, patients who arrived ER from 6:00P.M. to midnight were more satisfied than patients who arrived other time. 5. The length of stay at ER was significantly different according to the reason of hospital selection, the reason of ER selection, the visitant cause and hopital decisioner. Especially the length of stay was much longer in accident group and unconscious group.

• 한국ITS학회 논문지
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• 제20권3호
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• pp.74-85
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• 2021

전파를 수신하여 측위를 수행하는 GNSS 수신기는 본질적으로 재밍에 취약하다. 재밍 발생 검출, 재밍 신호 종류 판별, 재밍원 위치추정 기능을 갖는 GNSS 재밍 모니터링 시스템은 안전한 자율주행 환경구축에 도움을 준다. 이를 위하여 다수의 저가 GNSS 수신기들의 배치로 구성된 GNSS 모니터링 네트워크 구축이 필요하며, 앞서 언급한 3가지 기능 구현을 위하여 네트워크 내 독립된 저가 GNSS 수신기 간 정밀 시각 동기가 요구된다. 본 논문은 신호영역 TDOA 기술 직접 사용방식의 수신기 간 시각 동기화 기법을 제안한다. 계산 효율성을 위하여 상대적으로 낮은 샘플링 주파수에도 시각 동기 정밀도를 유지하고자 블록 보간법을 추가로 활용한다. 수치적 시뮬레이션을 통하여 제안한 GNSS 수신기 간 시각 동기화 기법의 가용성을 입증한다.