• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.6
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• pp.72-80
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• 2004

In this paper, the design procedure of a guidance algorithm in the boosting phase of missiles with free-flight after thrust cut-off is introduced. The purpose of the guidance is to achieve a required velocity vector at the thrust cut-off. Trajectory optimizations for four cost functions are performed to investigate implementable trajectories in the pitch plane. It is observed from the optimization results that high angle of attack maneuver in the beginning of the flight are required to satisfy the constraints. The proposed guidance algorithm consists of the pitch program to produce open-loop pitch attitude command and the yaw attitude command generator to nullify the velocity to go. The pitch program utilizes the pitch attitude histories obtained from the trajectory optimization.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.411-413
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• 2009

This paper deals with supersonic vehicle. A supersonic vehicle has very complicated and high nonlinear thrust characteristics with respect to outer and inner environment during operation. For this reason, supersonic vehicle has many maneuver constraints and allows to operate within more narrow flight envelope. In this paper, trajectory optimization of supersonic vehicle is accomplished. The trajectory optimization problem is formulated by a discrete parameter optimization problem and the operation constraints are considered during trajectory optimization. It is shown that results of trajectory optimization give senses to fuel supply and nozzle throttle area control into effectiveness. Furthermore, general operation direction and its application for supersonic vehicles are discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.7
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• pp.767-772
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• 2011

Trajectory generation is important because it determines the walking stability, continuity, and performance of a body in motion. Generally, the Linear Inverted Pendulum Mode is used for trajectory generation; however, for the sake of simplicity, the trajectory in this mode does not allow vertical motions and pitching motions of the body. This paper proposes a new trajectory generation method called Extended Linear Inverted Pendulum Mode (ELIPM) that allows vertical motion as well as pitching motion. This method can also improve the performance of locomotion by controlling the stride and locomotion frequency of a body.

• The Journal of the Acoustical Society of Korea
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• v.18 no.8
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• pp.75-83
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• 1999

This paper proposes a new F0 contour model for intonation control in speech synthesis. We assume that the F0 contour of an utterance can be described using a sequence of time-overlapping events, which determine the fluctuation of a given F0 contour, described by asymmetric Gaussian functions. In addition, We propose a parameter estimation algorithm for the proposed model. The proposed model is not developed with a particular phonological theory in mind, and can be used in both F0 contour analysis and synthesis. For testing our F0 model, we collected 500 sentences from various genres and built a corresponding speech corpus uttered by a professional female announcer. As n result of F0 resynthesis experiment using the proposed model, the RMSE was 7.87Hz for given speech corpus.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.4
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• pp.360-365
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• 2013

The paper introduces dynamic generation technique of foot trajectories using CPG(Central Pattern Generator). In this approach, the generated foot trajectories can be changeable according to variable outputs of CPG in various environments, because they are given as mapping functions of the output signals of the CPG oscillators. It enables to provide an adaptable foot trajectory for environmental change. To demonstrate the effectiveness of the proposed approach, experiments on humanoid robot Nao is executed in the Webot simulation. The performance and motion features of CPG based approach is analyzed.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11b
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• pp.22-24
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• 2005

RFID 시스템은 전자태그를 상품에 부착하여 리더를 통해 태그를 인식함으로써 상품의 정보 및 위치정보를 추적할 수 있다. 태그 객체의 위치정보는 시간에 따라 궤적 정보가 누적되는 이동체와 유사한 특성을 가지지만 이동체의 위치와 달리 태그의 위치는 리더의 위치로 인식되며 위치보고가 리더의 인식영역 안에서만 이루어지므로 시간축에 평행한 interval의 형태를 나타난다. 태그가 리더의 인식영역에 들어와 나가지 않으면 궤적이 완성되지 않아 리더에 머물고 있는 태그의 궤적을 표현할 수 없으므로 질의 시 이러한 태그를 검색할 수 없다. 시공간 이동체 색인에서는 이러한 태그의 특성을 표현하기 힘들기 때문에 태그의 특성을 고려한 색인이 필요하게 되었다. TPIR-Tree(Time Parameterized Interval R-tree)는 시간 매개변수 간격으로 태그의 interval을 정의하여 리더안에 머무는 태그의 interval을 표현할 수 있다. 그러나 각 interval이 시공간적으로 연결되어 있지 않아 색인 상에서 태그의 궤적을 검색하는 것은 매우 높은 검색 비용을 가지는 단점이 있다. 이 논문에서는 태그 궤적 검색 시 TPIR-Tree의 높은 검색 비용문제를 해결한 $TPIR^{*}$-Tree를 제안한다. 제안된 $TPIR^{*}$-Tree는 색인에서 태그의 궤적 정보를 유지할 수 있도록 하기 위해서 시간적으로 연결되지 않은 각 interval을 연결하기 위한 기법을 제시하고 있다. 또한. interval을 색인에 삽입할 때 연결정보를 유지하기 위해 이전 interval을 효율적으로 검색할 수 있는 방법을 제시하고 있다.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06c
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• pp.36-38
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• 2012

최근 사용자들의 궤적 분석을 통해 사용자의 성향에 적합한 정보를 추천해주는 연구들이 진행되고 있다. 이러한 연구들은 여행지 추천, 친구 추천 등과 같은 응용 서비스를 위해서 클러스터링 기법과 패턴 매칭 기법을 많이 사용하고 있다. 그러나 클러스터링 기법은 추천 받는 사용자의 선호도가 반영되지 않고, 다른 사용자들의 선호도에 따라 추천을 해주는 단점이 존재한다. 또한, 패턴 매칭 기법은 다른 사용자와의 POI(Point of Interest)의 유형과 거리를 비교하여 추천을 수행하기 때문에 사용자의 세부적인 선호도를 반영할 수 없는 단점이 존재한다. 이러한 기존 연구들을 보완하기 위해 본 논문에서는 POI의 속성 정보와 사용자의 이동 패턴을 고려한 POI을 추천 기법을 제안한다. 제안하는 기법은 크게 사용자의 속성 정보를 이용해서 선호도를 계산하고 선호도가 다른 궤적을 필터링하는 부분과 패턴 매칭 기법을 사용하여 근접한 궤적을 찾는 부분으로 구성된다. 제안하는 기법의 우수성을 입증하기 위해서 추천된 POI 궤적과 사용자 POI 궤적을 비교하여 두 궤적의 이동 패턴이 유사함을 확인하였다.

• Resources Recycling
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• v.28 no.6
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• pp.96-105
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• 2019

Automobile shredder residue (ASR) is the final waste produced when end-of-life vehicles (ELVs) are shredded. ASR can be separated using mineral-processing operations such as comminution, air classification, magnetic separation, and/or electrostatic separation. In this work, trajectory analyses of conductors (copper) and non-conductors (glass) in the ASR have been carried out using induction electrostatic separator for predicting or improving the ASR-separation efficiency. From results of trajectory analysis for conductors, the trajectories of copper wire by observation versus simulation for coarse particles of 0.5 and 0.25 mm showed consistent congruity. The observed 0.06 mm fine-particles trajectory was deflected toward the (-) attractive electrode owing to the charge-density effects due to the particle characteristics and relative humidity. In the case of non-conductors, the actual trajectory of dielectric glass deflected toward the (-) electrode, showing characteristics similar to those of conductive particles. The analyses of stereoscopic microscope and SEM & EDS found heterologous materials (fine ferrous particles and conductive organics) on the glass surface. This demonstrates the glass decreasing separation efficiency for non-ferrous metals during electrostatic separation for the recycling of ASR. Future work will require a pretreatment process for eliminating impurities from the glass and advanced trajectory-simulation processes.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.1
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• pp.41-51
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• 2018

Downwash from helicopter rotor blades and external winds from various maneuvering make an unguided rocket change its trajectory and range. For the prediction of the trajectory and range, it is essential to consider the downwash effect. In this study, an algorithm was developed to calculate 6-Degree-Of-Freedom(6 DOF) forces and moments exerting on the rocket, and total flight trajectory of a 2.75-inch unguided rocket in a helicopter downwash flow field. Using Actuator Disk Model(ADM) analysis result, the algorithm could analyze the entire trajectory in various initial launch condition such as launch angle, launch velocity, and external wind. The algorithm that considered the interference between a fuselage and external winds could predict the trajectory change more precisely than inflow model analysis. Using the developed algorithm, the attitude and trajectory change mechanism by the downwash effect were investigated analyzing the effective angle of attack change and characteristics of pitching stability of the unguided rocket. Also, the trajectory and range changes were analyzed by considering the downwash effect with external winds. As a result, it was concluded that the key factors of the rocket range change were downwash area and magnitude which effect on the rocket, and the secondary factors were the dynamic pressure of the rocket and the interference between a fuselage and external winds. In tailwind case which was much influential on the range characteristics than other wind cases, the range of the rocket rose as increasing the tailwind velocity. However, there was a limit that the range of the rocket did not increase more than the specific tailwind velocity.

• Journal of Korea Spatial Information System Society
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• v.9 no.1
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• pp.1-13
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• 2007

The necessity of future index is increasing to predict the future location of moving objects promptly for various location-based services. A representative research topic related to future index is the probability trajectory prediction technique that improves reliability using the past trajectory information of moving objects in the road network environment. However, the prediction performance of this technique is lowered by the heavy load of extensive future trajectory search in long-range future queries, and its index maintenance cost is high due to the frequent update of future trajectory. Thus, this paper proposes the Probability Cell Trajectory-Tree (PCT-Tree), a cell-based future indexing technique for efficient long-range future location prediction. The PCT-Tree reduces the size of index by rebuilding the probability of extensive past trajectories in the unit of cell, and improves the prediction performance of long-range future queries. In addition, it predicts reliable future trajectories using information on past trajectories and, by doing so, minimizes the cost of communication resulting from errors in future trajectory prediction and the cost of index rebuilding for updating future trajectories. Through experiment, we proved the superiority of the PCT-Tree over existing indexing techniques in the performance of long-range future queries.