• 한국정보통신학회논문지
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• 제7권5호
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• pp.907-915
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• 2003

유선 통신환경과 비교해서 무선 자원이 부족한 무선 환경에서는 매우 효율적인 패킷 전송 방식이 필요하다. 일반적으로는 이중 모드 패킷 전송 방식이 널리 사용된다. 스위칭 기준에 따라서, 패킷은 전용채널이 할당되거나 또는 공통의 채널을 통해서 전송된다. 일반적인 기준은 패킷의 길이와 생성 주파수이다. 즉 크고 발생 빈도가 높은 패킷은 전용 채널을 통해서 전송되고 작고 발생빈도가 낮은 패킷은 공통 채널을 통해서 전송된다. 이중 모드 패킷 전송 방식의 성능은 스위칭 기준과 밀접한 관련이 있다. 그렇지만 최적의 스위칭 포인트를 찾는 것은 매우 힘드는데 스위칭 포인트가 고정되어 있는 것이 아니라 트래픽 부하와 생성된 패킷의 길이와 채널의 수와 같은 환경에 따라 변동하기 때문이다. 본 논문에서는 동적 스위칭 임계점(dynamic switching threshold)을 이용하는 이중 모드 패킷 전송 방식을 위한 새로운 기법을 제안한다. 이 방식에서는 스위칭 임계값이 네트워크 환경에 따라서 변동한다. 제안한 방식의 성능은 시뮬레이션을 통해 분석하였다. 시뮬레이션 결과는 기존의 이중 모드 패킷 전송 방식과는 달리 제안한 방식의 성능이 네트워크 환경의 영향을 그다지 받지 않음을 보여준다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2013년도 제46회 KOSCO SYMPOSIUM 초록집
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• pp.21-23
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• 2013

Various solid particle materials are treated in the industrial processes including fixed-beds or moving grate beds, and modeling approaches have been widely applied to the processes to predict and evaluate their performance. For this study, the modeling approach was applied to iron ore sintering process with various improvement measures. Based on the previous modeling approach, the changes and effects of the improvement measures were discussed at the point of controlling the combustion environment in the bed.

• 한국가스학회:학술대회논문집
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• 한국가스학회 2005년도 춘계학술대회 및 특별심포지움
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• pp.206-206
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• 2005

• 대한환경공학회지
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• 제22권2호
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• pp.217-229
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• 2000

입상 및 분말 활성탄에 대한 페놀의 흡착평형실험을 $25{\pm}1^{\circ}C$에서 행하였으며 그 결과를 Freundlich isotherm으로 나타내었다. 흡착속도 실험은 회분식 흡착법으로 입자외부 물질이동저항이 무시되는 조건하에서 행하였으며, 실험결과는 LDF 흡착속도상수를 구하기 위하여 Miller의 방법으로 해석하였다. 고정층 흡착칼럼에서 페놀-활성탄계의 흡착실험을 행하였다. 흡착칼럼실험은 온도를 $25{\pm}1^{\circ}C$로 일정하게 유지하면서, 흡착대의 길이는 추산한 흡착대 길이보다 크게 하여 정형농도분포가 이루어지도록 하였다. 그리고 각기 다른 두 가지 공탑유속의 경우에 대해 실험하였다. LDF 모델식의 흡착속도계수는 흡착율에 따라 변화되며, 이 가변성 흡착속도계수를 사용하여 정형 농도변화곡선을 추정한 결과 일정 평균치를 사용한 경우보다 실험결과와 더 일치하였다.

• 제어로봇시스템학회논문지
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• 제20권12호
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• pp.1272-1277
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• 2014

This article describes a path planning algorithm for fixed-wing UAVs when a real terrain should be considered. Nowadays, many UAVs are required to perform mission flights near given terrain for surveillance, reconnaissance, and infiltration, as well as flight altitude of many UAVs are relatively lower than typical manned aerial vehicles. Therefore, real terrain should be considered in path planning algorithms of fixed-wing UAVs. In this research, we have extended a spline-$RRT^*$ algorithm to three-dimensional planner. The spline-$RRT^*$ algorithm is a $RRT^*$ based algorithm, and it takes spline method to extend the tree structure over the workspace to generate smooth paths without any post-processing. Direction continuity of the resulting path is guaranteed via this spline technique, and it is essential factor for the paths of fixed-wing UAVs. The proposed algorithm confirm collision check during the tree structure extension, so that generated path is both geometrically and dynamically feasible in addition to direction continuity. To decrease degrees of freedom of a random configuration, we designed a function assigning directions to nodes of the graph. As a result, it increases the execution speed of the algorithm efficiently. In order to investigate the performance of the proposed planning algorithm, several simulations are performed under real terrain environment. Simulation results show that this proposed algorithm can be utilized effectively to path planning applications considering real terrain.

• 임상간호연구
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• 제18권1호
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• pp.63-73
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• 2012

Purpose: The purpose of this study was to compare job satisfaction and nursing performance of nurses on fixed night shifts (FNS) and nurses working three shifts (W3S), to identify the environment of night work and recognition of the viability of the FNS system. Methods: The research was conducted with 106 nurses on FNS and 257 on W3S. The nurses had worked for 1 to 11 years at A hospital, Seoul. Results: Job satisfaction was significantly higher (t=-3.51, p< .001) for nurses on FNS. However, no significant difference was found for nursing performance (t=-1.019, p=.309) between the two groups. Both groups of nurses were mostly satisfied. Subjective fatigue scores (0 to 10 points) during the night for nurses on FNS (6.02) were lower than for W3S nurses (7.28) A high percentage (88.7%) of nurses on FNS indicated a willingness to further participate in FNS. Conclusion: Results indicate that the demonstration FNS system showed its effectiveness. Therefore, efforts are needed to enhance and revitalize FNS and to upgrade the system to control patient transfer time from emergency departments to wards, and to provide nurses needed resources for emergency or intensive care.

• 실천공학교육논문지
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• 제14권2호
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• pp.295-303
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• 2022

본 연구는 고등 공학교육에 플립러닝을 Active Learning Classroom(ALC)에 적용한 사례와 고정식 강의실에 적용한 사례를 비교하는 것을 목적으로 하였다. 이를 위하여 ALC 플립러닝과 고정식 강의실 플립러닝 사례 간에 사전학습, 학업성취, 수업만족도가 어떻게 다른지 비교하였다. 연구결과, ALC 플립러닝이 고정식 강의실 플립러닝에 비해 사전학습 영상강의 시청을 더 많이 하였고, 중간시험 점수는 낮으나 기말시험 점수는 더 높았다. 또한 수업 요인, 교수자 요인, 전반적 만족도 문항으로 수업만족도를 확인한 결과, ALC 플립러닝이 고정식 강의실 플립러닝에 비해 모든 요인에서 높은 만족도를 보였다. 본 사례연구는 플립러닝 강의실 환경으로서 학습자중심의 수업에 용이하도록 구축한 학습공간인 ALC 환경이 강의실에서 학생 중심의 활발한 상호작용을 필요로 하는 플립러닝에 더 효과적임을 시사한다.

• 한국환경과학회지
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• 제17권4호
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• pp.461-468
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• 2008

Competitive power of pelagic fishery in Korea has been weakened by the domestic and international problems such as wage increase and exclusive economic zone. To make it worse, fishing fleet spends more than 80% of fishing time on searching fishing grounds. Real-time information on oceanographic data, temperature in particular, are likely to contribute to raise efficiency of fishing. However, available data obtained by satellite remote sensing, fixed buoy and drifting buoy, limited to sea surface or fixed positions. ARGO (Array for Real-time Geostrophic Oceanography), an international program, has delivered vertical profiles of temperature and salinity in the upper 2000m of the world ocean every 10 days using freely moving floats. We have developed real-time oceanographic information system for pelagic fishery based on the Argo data which has the contents of vertical profile, horizontal distribution and vertical section of temperature around fishing grounds and searched data can be download unrestrictedly. Comparison of skipjack catch with sea surface temperature and depth of $20^{\circ}C$ derived from Argo data in the West Equatorial Pacific revealed that Argo data are able to help fishing fleet to find fishing grounds and to increase catch.

• 한국대기환경학회지
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• 제17권5호
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• pp.375-384
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• 2001

Optical remote sensing techniques are particularly advantageous over the conventional fixed point methods because with these methods large-area monitoring can be possible and sample preparation difficulties are avoidable. Instruments based on the differential optical absorption spectroscopy (DOAS) technique are widely used for monitoring air pollutants in urban areas in recent years. In this study, $O_3$, SO$_2$, NO$_2$, and VOCs (benzene, toluene, xylene, and styrene) are measured continuously at Sihwa industrial area using a DOAS from February to November. 1999. Intercomparison between the DOAS method and the conventional methods (filed point samplers for $O_3$, NO$_2$, and SO$_2$, and adsorbent sampling methods and gas chromatography for VOCs) are performed simultaneously at the same site. The time series of the DOAS data and that of fixed point method show good match at the view point of the tendency, but the absolute concentration values of these two methods differ quite a lot from each other; correlation coefficients shows 0.78 for $O_3$and 0.97 for SO$_2$. However, the results of VOCs measurements are not quite satisfactory ; the spectral interference with $O_2$and $O_3$appears to be the major cause of the errors for VOCs .

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2001년도 추계학술발표회
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• pp.23-26
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• 2001

Batch test and column test were performed to develop the design factors for PRBs against the contaminated groundwater by ammonium and lead. Clinoptilolite, one of the natural zeolites having excellent cation exchange capacity(CEC), was chosen as the reactive material through the ion-exchange mechanism. In the batch test, the reactivity of Clinoptilolite to ammonium and lead was examined with varying the particle size of Clinoptilolite. The nit weight of Clinoptilolite showed removal efficiencies of 65 % against the ammonium and 98% against lead. The effect of particle size of Clinoptilolite was not noticeable. In the column test, the permeability was examined using flexible-wall permeameters with varying the particle size of Clinoptilolite. When the washed Clinoptilolite having the diameter of 0.42-0.85 nm was mixed with Jumunjin sands in 20:80 ratio (w/w), the highest permeability of 2$\times$10$^{-3}$ -7 x 10$^{-4}$ cm/s was achieved. The reactivity and the strength property of the mixed material were investigated using fixed wall column having 8 sampling ports on the wall and the direct shear test, respectively. Clinoptilolite was found to be a suitable material for PRBs against the contaminated groundwater with ammonium and/or heavy metals.