• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.208-222
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• 2021

Managing with the presence of sea ice is the primary challenge in the operation of floating platforms in the Arctic region. It is widely accepted that offshore structures operating in Arctic conditions need station-keeping methods as well as ice management by icebreakers. Dynamic Positioning (DP) is one of the station-keeping methods that can provide mobility and flexibility in marine operations. The presence of sea ice generates complex external forces and moments acting on the vessel, which need to be counteracted by the DP system. In this paper, an icevaning control algorithm is proposed that enables Arctic offshore vessels to perform DP operations. The proposed icevaning control enables each vessel to be oriented toward the direction of the mean environmental force induced by ice drifting so as to improve the operational safety and reduce the overall thruster power consumption by having minimum external disturbances naturally. A mathematical model of an Arctic offshore vessel is summarized for the development of the new icevaning control algorithm. To determine the icevaning action of the Arctic offshore vessel without any measurements and estimation of ice conditions including ice drift, task and null space are defined in the vessel model, and the control law is formulated in the task space. A backstepping technique is utilized to handle the nonlinearity of the Arctic offshore vessel's dynamic model, and the Lyapunov stability theory is applied to guarantee the stability of the proposed icevaning control algorithm. Experiments are conducted in the ice tank of the Korea Research Institute of Ships and Ocean Engineering to demonstrate the feasibility of the proposed approach.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.229-230
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• 2006

해상플랫폼설치가 불가능한 심해지역이나 파도가 심한 해상에서 원유를 발굴하는 선박형태의 시추설비인데, 심해에서의 시추능력은 물론 기동성까지 겸비한 고부가치선으로서 최근 고(高)유가에 따라 발주가 늘어나고 있는 해양분야의 대표적인 성장엔진으로, 파도와 바람이 심한 해상에서도 안정적 시추가 가능한 최첨단 자동위치 제어시스템, 드릴링장비, 통합제어시스템 등, 드릴쉽이 갖추고 있는 시스템에 대해 간단히 설명한다.

• Journal of Navigation and Port Research
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• v.30 no.9
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• pp.773-777
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• 2006

Significant increase of container flows in the marine terminals requires more efficient port equipments such as logistic and transfer systems. This paper presents collision avoidance and routing approach based on dynamic programming (DP) algorithm for a linear motor based shuttle car which is considered as a new transfer system in the port terminals. Most of routing problems are focused on automatic guided vehicle (AGV) systems, but its solutions are hardly utilized for LM based shuttle cars since both are mechanically different. Our proposed DP is implemented for real-time searching of an optimal path for each shuttle car in the Agile port terminal located at California in USA.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.586-592
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• 2000

터보머신 태부에 존재하는 정익 - 동익의 상호작용 유동현상을 수치모사 하는 코드를 병렬화 하였다 정익 - 동익의 상호작용을 해석하는 데에 편리하도륵 Multi-Block Grid System을 도입하여 계산영역을 형성하였고, 동익의 움직임으로 인해 발생하는 Sliding Interface부분은 Patched 알고리즘을 적용하여 해석하였다. 정익과 동익의 수를 1대 1로 단순화시켜 수치모사한 결과와 정익과 동익의 수를 실제 조건과 더 비슷하게 설정한 3대 4의 비율로 맞추어 수치모사한 결과를 비교하였다. 또한, 병렬컴퓨팅으로 인해 단축된 계산시간을 다른 연구에서의 계산시간들과 서로 비교하였다. 2차원 비정상 압축성 Navier-Stokes 방정식이 이용되었고, 난류모델링에는 K-w SST 모델링이 적응되었다. Roe의 FDS 기법을 사용하여 플럭스를 계산하였고, MUSCL 기법을 적용하여 3차의 공간정확도를 갖도록 하였다. 시간적분에는 이보성의 DP-SGS를 사용하였다. 해석결과의 분석에는 Time-averaged pressure distribution과 Pressure amplitude distribution 데이터를 사용했다.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.311-311
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• 2000

We propose a DP-based formulation for matching line patterns by defining a robust and stable geometric representation that is based on the conceptual organizations. Usually, the endpoint proximity and collinearity of image lines, as two main conceptual organization groups, are useful cues to match the model shape in the scene. As the endpoint proximity, we detect junctions from image lines. We then search for junction groups by using geometric constraint between the junctions. A junction chain similar to the model chain is searched in the scene, based on a local comparison. A Dynamic Programming-based search algorithm reduces the time complexity for the search of the model chain in the scene. Our system can find a reasonable matching, although there exist severely distorted objects in the scene. We demonstrate the feasibility of the DP-based matching method using both synthetic and real images.

• The Journal of Korea Robotics Society
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• v.11 no.4
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• pp.217-225
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• 2016

Dynamic Positioning (DP) is used to automatically maintain the position and heading of a floating structure subjected to environmental disturbances. A DP control system is composed of a motion controller to compute the desired force and moment and a thrust allocator to distribute the computed force and moment to multiple thrusters considering mechanical and operational constraints. Among various thruster configurations, azimuth thrusters or propeller/rudder pairs tend to make the allocation problem difficult to solve, because these types of propulsion systems include nonlinear constraints. In this paper, a dynamic positioning strategy for a twin-thruster ship that is propelled by two azimuthing thrusters is addressed, and a thrust allocation method which does not require a numerical optimization solver is proposed. The applicability of the proposed method is demonstrated with an experiment using an autonomous boat.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.4-7
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• 2013

In recent downtown high land due to an increase in the utilization of land from the property line to maximize the proximity of the construction and use of underground structures has increased. The nature of urban underground retaining structure construction safety, environmental management, and civil contrast situations, construction periodt perspective, this method is widely used in the backhand. Recent Patents DP method and the method of the DBS method than in the SPS process is deleted according to the PRD process cost savings are generated. The workability and safety study of two kinds of method, such as air speed, and considering the reduction of indirect costs in terms of economic efficiency is considered to be a superior method.

• The Journal of Internal Korean Medicine
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• v.33 no.3
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• pp.284-297
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• 2012

Objectives : This study was performed to investigate characteristic indice of heart rate variability (HRV) according to presence of metabolic syndrome (MS), pattern identification. Methods : We analyzed 167 subjects who participated in a stroke check-up. We classified the subjects into two groups as MS (n=48) and non-MS (n=119) based on NCEP ATP III. First, we investigated pattern identification of all subjects based on Korean Standard Pattern Identifications for Stroke-III. Second, we surveyed significance of HRV indices between MS and non-MS groups. Third, we investigated significance of HRV indices between classified DP of MS and classified DP of non-MS. Fourth, we investigated significance of HRV indices between classified DP of MS and non-MS. Fifth, we investigated significance between components of MS and HRV indices. Results : 1. SDNN, RMS-SD, HF, Ln(HF), and HF (NORM) were significantly lower in the MS than non-MS group. LN (TP), LF/HF were significantly higher in the MS than non-MS. 2. Ln (HF), Ln (TP), and LF/HF were statistically significant in the classified DP of MS group. 3. RMS-SD, and Ln (HF) were significantly lower in the abdominal obesity group than in the non-abdominal obesity group. SDNN, RMS-SD, TP, Ln (TP), VLF, Ln (VLF), and Ln (LF) were significantly lower in the hypertension group than in the non-hypertension group. RMS-SD was significantly lower in the diabetes group than in the non-diabetes group. Mean HRT,LF/HF were significantly higher in the hypertriglyceridemia than non-hypertriglyceridemia group, but Ln (HF), RMS-SD, and HF (NORM) were significantly lower in the hypertriglyceridemia than non-hypertriglyceridemia group. Conclusions : We found a few significant relationships between classified DP of MS and HRV indices. The resluts demonstrate that MS has potentially negative effects on the cardiovascular system, and these effects could be detected by HRV.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.7
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• pp.33-38
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• 2008

• ETRI Journal
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• v.6 no.4
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• pp.3-8
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• 1984

Frequency division multiplexed 3ch. Color TV signals have been transmitted via optical fiber by employing $1. 3\mum$ InGaAsP DH-laser diode, graded index optical fiber and Ge-APD as optical components. Overall system margin of 20 dB was realized at weighted SNR of more than 49 dB. With this system margin, measured DG and DP were less than 10% and $5^{\circ}$respectively. Throughout this experiment, it was confirmed that multichannel TV signals could be economically transmitted over optical fiber in short haul networks. This paper describes system outlines and hardware implementation results.