• International Journal of Aeronautical and Space Sciences
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• v.9 no.2
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• pp.1-8
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• 2008

This paper presents a real-time algorithm for collision detection, collision avoidance and guidance. Three-dimensional point-mass aircraft models are used. For collision detection, conflict probability is calculated by using the Monte-Carlo Simulation. Time at the closest point of approach(CPA) and distance at CPA are needed to determine the collision probability, being compared to certain threshold values. For collision avoidance, one of possible maneuver options is chosen to minimize the collision probability. For guidance to a designated way-point, proportional navigation guidance law is used. Two scenarios on encounter situation are studied to demonstrate the performance of proposed algorithm.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.11
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• pp.883-887
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• 2016

Navigating an unknown environment is a challenging task for a robot, especially when a large number of obstacles exist and the odometry lacks reliability. Pose tracking allows the robot to determine its location relative to its previous location. The ICP (iterative closest point) has been a powerful method for matching two point clouds and determining the transformation matrix between the maps. However, in a situation where odometry is not available and the robot moves far from its original location, the ICP fails to calculate the exact displacement. In this paper, we suggest a method that is able to match two different point clouds taken a long distance apart. Without using any odometry information, it only exploits the features of corner points containing information on the surroundings. The algorithm is fast enough to run in real time.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.83-88
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• 2006

Evaluation of collision risk plays a key role in developing the expert system of navigation and collision avoidance. This paper presents a new collision risk model formula that is one modification model on the basis of one approach to the evaluation of collision risk using sech function produced by Prof. Jeong in his relevant $articles^{[2][3][4][5]}$. And as a grope in collision risk evaluation field, this paper applied the new model in appraising the collision risk, suggested how to decide the safe range of own ship’'s action. Moreover this paper also analyzed theoretically how to determine the coefficients as describes in the new modification model formula, and suggested the appropriate values as applicable.

• Journal of Navigation and Port Research
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• v.31 no.2
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• pp.121-126
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• 2007

Evaluation of collision risk plays a key role in developing the expert system of navigation and collision avoidance. This paper presents a new collision risk model formula that is one modification model on the basis of one approach to the evaluation of collision risk using sech function produced in earlier studies. And as a tool of the evaluation field of ship collision, this paper applied the new model in appraising the collision risk and represented how to decide the safe range of own ship's action. Moreover this paper also analyzed theoretically how to determine the coefficients as described in the new modification model, and suggested the appropriate values as applicable.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2021.11a
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• pp.181-182
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• 2021

본 연구에서는 자율운항선박의 원격 관제 및 제어하는 과정에서 원격 운항자에게 사전 충돌 위험 정보를 제공하기 위해 선박자동식별시스템(AIS, Automatic Identification System)의 항적 정보를 토대로 자율운항선박의 운항 경로 상에 잠재된 충돌 위험 영역을 예측하기 위한 기초 연구를 수행하였다. 자율운항선박의 운항 경로 상에 근접한 타선의 AIS 정보에는 기본적으로 선박의 위치, 속도, 침로에 대한 정보가 반영되어 있으므로, 이러한 정보를 토대로 일정 시간 동안 운항 경로를 예측할 수 있다. 그리고 예측한 정보를 기반으로 대표적 충돌 위험 지수인 최근접점(CPA, Closest Point of Approach)과 최근접점 거리(DCPA, Distance to CPA) 정보를 활용하여 충돌 위험 영역을 2차원 공간상에서 예측하였다. 제안된 방법은 실제 AIS 항적 데이터를 활용한 수치 시뮬레이션을 수행하여 초기 결과를 검증하였다.

• Journal of the Korean Institute of Rural Architecture
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• v.17 no.1
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• pp.73-81
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• 2015

The purpose of this study is to analyze the approach characteristics, relation to other facilities, and current status focusing on 28 total of exhibition-culture facilities in Gangneung. The results are following as. First, 19 facilities are located in urban area and nine are located in country side. With locational characteristics of Gangneung which is mountains in west and sea to east, three are located in high hill side and four are in sea shore among nine facilities. Facilities in urban area converge to Gungpodae and Ojukhuk which are symbol space in Gangneung. Those facilities started to have been increased from 1990s and rapidly increased from 2000s. The reason is that people have been interested in culture and art in society in general. In building structure, buildings related with traditional contents were constructed with wooden structure while buildings have been mainly constructed with modern ways such as steel and reinforced concrete structure. Second, the 28 facilities are classified into three types by function of other space or facilities within same a site or a building. The three types are themselves usage only, multi-function, and park type. The multi-function type is re-classified into two; public type and commercial type. Those functions have changed according to changes of society and times. Finally, for approaching to the exhibition-culture facilities with general transportation, the mean distance from the closest bus stop to those facilities each is 280m and 27 facilities are located within 670m from the closest bus stop. For approaching way using by car creates movement along road-building site-parking space-main entrance of building. When based on main entrance by the movement, parking space located in front side of main entrance is the largest, next is in the side, and the least is in back side. Various factors such as approaching form from road to parking space and space size between main entrance and parking space influence to approaching ways of exhibition-culture facilities in Gangneung.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.2
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• pp.188-198
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• 2013

In constructing a collision avoidance system, it is important to determine the time for starting collision avoidance maneuver. Many researchers have attempted to formulate various indices by applying a range of techniques. Among these indices, collision risk obtained by combining Distance to the Closest Point of Approach (DCPA) and Time to the Closest Point of Approach (TCPA) information with fuzzy theory is mostly used. However, the collision risk has a limit, in that membership functions of DCPA and TCPA are empirically determined. In addition, the collision risk is not able to consider several critical collision conditions where the target ship fails to take appropriate actions. It is therefore necessary to design a new concept based on logical approaches. In this paper, a collision ratio is proposed, which is the expected ratio of unavoidable paths to total paths under suitably characterized operation conditions. Total paths are determined by considering categories such as action space and methodology of avoidance. The International Regulations for Preventing Collisions at Sea (1972) and collision avoidance rules (2001) are considered to solve the slower ship's dilemma. Different methods which are based on a constant speed model and simulated speed model are used to calculate the relative positions between own ship and target ship. In the simulated speed model, fuzzy control is applied to determination of command rudder angle. At various encounter situations, the time histories of the collision ratio based on the simulated speed model are compared with those based on the constant speed model.

• The Journal of the Acoustical Society of Korea
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• v.21 no.5
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• pp.446-454
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• 2002

This paper presents the Doppler Scanning technique which enables us to detect the relative positions of moving distributed sources using Doppler frequency shift estimate when the moving source consists of distributed sources with different signature frequencies. Doppler frequency shifts of characteristic frequencies of machinery noise sources such as ship's generator and propeller, with tine along CPA (Closest Point of Approach of moving source) are unique, and can be functioned with respect to each source position. Therefore, this technique can be applied to estimate the relative geometrical positions between machinery noise sources. The Extended Kalman Filter (EKF) which has a high frequency resolution with high time resolution, is adopted for improving accuracy of Doppler frequency shift estimate geometric resolution of machinery positions since machinery noise sources show in general low frequency band characteristics with limited spacial distance. The performance of the technique is examined by the numerical simulations and is verified by the experiment using loudspeaker sources on the roof of the car.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.7
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• pp.1518-1524
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• 2014

In this paper, a new method of spatial query, which is called Surround Search (SuSe) is suggested. This method makes it possible to search for the closest spatial object of interest to the user from a query point. SuSe is differentiated from the existing spatial object query schemes, because it locates the closest spatial object of interest around the query point. While SuSe searches the surroundings, the spatial object is saved on an R-tree, and MINDIST, the distance between the query location and objects, is measured by considering an angle that the existing spatial object query methods have not previously considered. The angle between targeted-search objects is found from a query point that is hidden behind another object in order to distinguish hidden objects from them. The distinct feature of this proposed scheme is that it can search the faraway or hidden objects, in contrast to the existing method. SuSe is able to search for spatial objects more precisely, and users can be confident that this scheme will have superior performance to its predecessor.

• Korean Journal of Digital Imaging in Medicine
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• v.12 no.2
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• pp.119-125
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• 2010

In order to demonstrate the value of long-distance radiography, we have studied how distance affects images in chest frontal radiography and compared short-distance and long-distance images in chest lateral radiography. Cardiothoracic ratio(CTR %) of 50 patients with no disease in the chest(10 each at the age of 20~60) were evaluated in Supine AP(100 cm), Sitting AP(100 cm), Sitting AP(180 cm), and Erect PA(180 cm). In lateral radiography, we evaluated and compared left lateral radiography(100 cm and 180 cm) of the patients based on the horizontal maximum of the heart. The average value of CTR(%) were 0.48 in Erect PA(180 cm), 0.52 in Supine AP(100 cm), 0.50 in Sitting AP(100 cm), 0.49 in Sitting AP(180 cm), which were Supine AP(100 cm) > Sitting AP(100 cm) > Sitting AP(180 cm) > Erect PA(180 cm). The average value of Maximum transverse diameter of left of the cardiac(MLD), which showed how much axis of spine was slanted to the left, was 90.67 mm in Erect PA(180 cm), 103.92 mm in Supine AP(100 cm), 93.54 mm in Sitting(100 cm), 89.84 mm in Sitting AP(180 cm), 58.11 mm in the minimum value and 118.79 mm in the maximum value. The average value of Maximum transverse diameter of right side of the cardiac(MRD), which suggested how much axis of spine was slanted to the right, was 47.18 mm in Erect PA(180 cm), 48.12 mm in Supine AP(100 cm), 44.98 mm in Sitting AP(180 cm), and the minimum value 26.84 mm and the maximum value 65.30 mm. There was no standard method to calculate; therefore, the horizontal maximum of the heart was used for lateral radiography. The average value was 121.07 mm in 100 cm and 109.76 mm in 180 cm. Sitting AP(180 cm) among the types was closest to C-PA(180 cm). As a result, during C-AP radiography, long-distance radiography lessened shadow of the heart more than that of short distance, Sitting position more than Supine position.