• 한국항공운항학회지
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• 제29권2호
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• pp.47-54
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• 2021

Recently, the issue of maintaining pilot competency has emerged as one of the major challenges in the aviation industry due to irregular schedules and flight intervals caused by the global COVID-19. Therefore, a survey was conducted on airline pilots to determine how stressed they would be when returning to their flights after experiencing irregular schedules or long-term furloughs. The level of stress that pilots receive due to flight intervals was divided into periods, and correlation with general characteristics was identified to see what emotional burdens exist as the lengths of flight interval increased. As a result, burdened flight intervals and the Pilot Flying(PF) intervals were identified as a statistically significant variables. In the case of the Pilot Flying interval, the level of stress was confirmed to be worse as the flying interval was elongated, and in the case of the burdened flying interval, the tendency of the stress index were lower as the period increased. Through this study, pilots who experienced reduced flight times were found to be accompanied by considerable amount of emotional burden proportionate to the length of the interval period.

• 한국통신학회논문지
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• 제32권5A호
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• pp.417-425
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• 2007

하향링크 OFDMA(Orthogonal Frequency Division Multiple Access) 시스템의 경우 순환전치 구간은 지연확산만을 고려하면 되지만 상향링크 OFDMA 시스템에서는 지연확산과 함께 상향링크 신호의 타이밍 오차를 고려한 보호구간이 필요하다. 특히 셀 반경이 큰 셀에서 초기 액세스를 하는 경우, 핸드오버를 하는 경우, 오래 동안 단말이 기지국과 데이터를 주고받지 않은 경우에는 타이밍 오차가 매우 클 수 있으며 매우 큰 보호구간이 요구될 수 있다. 상향링크 OFDMA 시스템에서 작은 크기의 순환전치 구간을 유지하기 위해서는 시스템의 순환전치 구간은 그대로 둔 체 큰 타이밍 오차가 발생할 수 있는 단말의 보호구간만 증대시키는 방법이 필요하다. 이 논문에서는 상항링크 OFDMA 시스템의 보호구간을 사용자 개별적으로 확장하는 방법을 제안한다.

• 한국콘텐츠학회논문지
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• 제10권1호
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• pp.103-113
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• 2010

RM이나 EDF에 기반을 둔 실시간 스케줄링 알고리즘들은 태스크들이 선점 가능함을 가정하고 있지만 현실적으로는 선점 불가능한 부분이 존재할 수도 있다. 또한 프로세서의 전력 소모를 줄이기 위한 기존의 스케줄링 알고리즘은 태스크 이용률을 기반으로 하여 블로킹 구간이 있는 경우와 없는 경우를 기준으로 두 가지 프로세서 속도($S_H$, $S_L$)를 결정한다. 이 알고리즘에서 높은 속도로 동작하는 $S_H$ 구간은 블로킹에 의한 우선순위 역전이 발생하는 구간이며 이 구간의 길이는 블로킹 구간을 포함한 태스크 종료시한까지로 설정된다. 본 논문에서는 $S_H$ 구간의 길이를 기존의 알고리즘보다 더 짧게 하여 전력소모율을 낮추는 방법을 제안하였다. 모의실험을 통해, 제안된 알고리즘의 전력소모율이 기존 알고리즘에 비하여 최대 13%만큼 감소되었음을 볼 수 있었다.

• 한국산학기술학회논문지
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• 제11권9호
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• pp.3563-3570
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• 2010

무선 센서 네트워크에서 에너지 소비를 줄이기 위한 MAC 프로토콜의 연구가 진행되어 왔다. 비동기 MAC Protocol에서 Preamble의 Overhearing과 Idle listening으로 인해 불필요한 에너지가 소모 된다. 본 논문에서는 Preamble 구조에서 목적지 주소와 Preamble의 종료 시간, 전송될 데이터 길이 정보를 포함하여 Preamble Overhearing과 Data Overhearing을 감소시키고 Data의 발생 유무에 따라 Dynamic 값을 변경하여 Check Interval의 길이를 조절하는 DPL(Dynamic Preamble Length)-MAC 프로토콜을 제안하였다. 그리고 기존의 비동기 방식의 무선 센서 네트워크 MAC 프로토콜들과 본 논문에서 제안한 DPL-MAC 프로토콜을 시뮬레이션 하여 에너지 소모를 비교 분석하였다.

• 한국축산시설환경학회지
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• 제8권3호
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• pp.171-176
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• 2002

Physical parameters of milk cow were measured to design and build RMS(Robotic Milking System) with a tape-measurer and body parameter measurer. The parameters are very important variables to design an RMS. For the working zone space of an RMS manipulator and the movement blunting of milk cow, an interval frame was installed on the stall bottom, and then cow's behavioral reactions were tested. The results from this study is summarized as follow. 1. On the general physical condition measurement, the maximum, minimum and average body length of cow which is related to the space that the manipulator could work into the RMS were 175cm, 144cm, and 163cm respectively. It appeared that the average distance between bottom and chest was 60cm. 2. The average length between fore teats, fore and hind teats and hind teats were 178mm, 150mm and 95mm respectively. It appeared that the average length between bottom and teat attachments was 544mm, and the average length between fore teats and tail-end was 331mm. 3. Although a cow kept a some extent length between hind legs for milking, it looked a stable pose. However, the cow kept a some extent distance between front legs for milking, it looked a unstable pose. Based on results of this test, an interval frame of stall bottom should be installed around the position which was located at its hind legs.

• Journal of Korean Neurosurgical Society
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• 제60권4호
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• pp.441-447
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• 2017

Objective : Computed tomography (CT)-based method of three dimensional (3D) analysis ($MIMICS^{(R)}$, Materialise, Leuven, Belgium) is reported as very useful software for evaluation of OPLL, but its reliability and reproducibility are obscure. This study was conducted to evaluate the accuracy of $MIMICS^{(R)}$ system, and inter- and intra-observer reliability in the measurement of OPLL. Methods : Three neurosurgeons independently analyzed the randomly selected 10 OPLL cases with medical image processing software ($MIMICS^{(R)}$) which create 3D model with Digital Imaging and Communication in Medicine (DICOM) data from CT images after brief explanation was given to examiners before the image construction steps. To assess the reliability of inter- and intra-examiner intraclass correlation coefficient (ICC), 3 examiners measured 4 parameters (volume, length, width, and length) in 10 cases 2 times with 1-week interval. Results : The inter-examiner ICCs among 3 examiners were 0.996 (95% confidence interval [CI], 0.987-0.999) for volume measurement, 0.973 (95% CI, 0.907-0.978) for thickness, 0.969 (95% CI, 0.895-0.993) for width, and 0.995 (95% CI, 0.983-0.999) for length. The intra-examiner ICCs were 0.994 (range, 0.991-0.996) for volume, 0.996 (range, 0.944-0.998) for length, 0.930 (range, 0.873-0.947) for width, and 0.987 (range, 0.985-0.995) for length. Conclusion : The medical image processing software ($MIMICS^{(R)}$) provided detailed quantification OPLL volume with minimal error of inter- and intra-observer reliability in the measurement of OPLL.

• 대한기계학회논문집
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• 제17권10호
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• pp.2391-2397
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• 1993

The distribution of fatigue crack growth rate is influenced by the measuring interval and methods of calculation of crack growth rate. The purpose of this paper is to suggest a method for the evaluation of crack growth rate distribution without the influence. The constant ${\Delta}P$ test and the constant .DELTA.K test are executed by using the CT specimen. The measuring interval of (${\Delta}a$/W=0.0067~0.014) crack length is not affected by methods of the calculation of the fatigue crack growth rate is suggested.

• 한국통신학회논문지
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• 제21권11호
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• pp.2923-2931
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• 1996

In this paper, the symbol error probability for orthogonal frequency division multiplexing (OFDM) in the multipath fading environment is obtained analytically. In the analysis, OFDM signals with and without the guard interval are considered, and the two-ray fading model is used for the multi-path fading channel. From the analysis results, it is found that the adjacent subchannel interfernce increases the symbol error rate when the guard interval is not employed or shorter than the length of the delay. It is also shown that the adjacent subchannel interference is a Gaussian random variable and its variance depends on the subchannel location and the number of subchannels. Finally, it is found that the variance of the subchannel interference also increases as the power of the signal increases for the OFDM with insufficient guard interval, yieldin an irreducible error at high signal to noise ratio.

• Journal of the Korean Data and Information Science Society
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• 제8권1호
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• pp.41-48
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• 1997

We construct the empirical Bayes(EB) confidence intervals that attain a specified level of EB coverage for the unknown scale parameter in the Weibull distribution with the known shape parameter under the type II censored data. Our general approach is to use an EB bootstrap samples introduced by Larid and Louis(1987). Also, we compare the coverage probability and the expected interval length for these bootstrap intervals with those of the naive intervals through Monte Carlo simulation.

• 대한수학회논문집
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• 제33권1호
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• pp.237-245
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• 2018

For every interval [a, b], we denote by $({\bar{x}}_A,{\bar{y}}_A)$ and $({\bar{x}}_L,{\bar{y}}_L)$ the geometric centroid of the area under a catenary curve y = k cosh((x-c)/k) defined on this interval and the centroid of the curve itself, respectively. Then, it is well-known that ${\bar{x}}_L={\bar{x}}_A$ and ${\bar{y}}_L=2{\bar{y}}_A$. In this paper, we fix an end point, say 0, and we show that one of ${\bar{x}}_L={\bar{x}}_A$ and ${\bar{y}}_L=2{\bar{y}}_A$ for every interval with an end point 0 characterizes the family of catenaries among nonconstant $C^2$ functions.