• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2004년도 한국우주과학회보 제13권2호
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• pp.296-299
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• 2004

KARI precision attitude determination system has been developed for high accurate geo-coding of KOMPSAT-2 image. Sensor data from two star trackers and a IRU are used as measurement and dynamic data. Sensor data from star tracker are composed of QUEST and unit vector filter. Filter algorithms consists of extended Kalman filter, unscented Kalman filter, and least square batch filter. The type of sensor data and filter algorithm can be chosen by user options. Estimated parameters are Euler angle from 12000 frame to optical bench frame, gyro drift rate bias, gyro scale factor, misalignment angle of star tracker coordinate frame with respect to optical bench frame, and misalignment angle of gyro coordinate frame with respect to optical bench frame. In particular, ground control point data can be applied for estimating misalignment angle of star tracker coordinate frame. Through the simulation, KPADS is able to satisfy the KOMPSAT-2 mission requirement in which geo-location accuracy of image is 80 m (CE90) without ground control point.

• 한국통신학회논문지
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• 제24권7B호
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• pp.1252-1260
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• 1999

HFC(Hybrid Fiber Coaxial) 망의 구조는 광케이블 구간과 동축케이블 구간으로 구분되는데 핸드엔드에서 광 노드까지의 주요 트렁크 부분은 광케이블로 설치되고 광 노드에서 가입자까지의 부분은 동출케이블로 구성된다. HFC 망의 형태는 광케이블 전송구간은 성형(Star)구조를 갖으며 동축 전송구간의 수지분기형(Tree and Branch)구조로 되어 있다. HFC 망의 상향 채널에는 구조적인 특성에 따라, 유입잡음, 공통모드 왜곡, 임펄스 노이즈, 백색잡음 등 여러 가지 노이즈가 존재한다. 다양한 서비스의 QoS(Quality of Service)를 만족시키기 위해서는 서비스 특성에 따른 우선순위를 제공할 필요가 있다. 예를들면 화상전화나 VOD와 같은 지연시간에 민감한 서비스에는 높은 우선순위를 제공한다. 본 논문에서는 다수의 가입자가 HFC 망의 상향채널을 공유하기 위한 MAC 프로토콜의 구성 요소들 중 여러 주거형 가입자들이 상향채널을 액세스하고 가입자간에 충돌이 발생하였을 경우 이를 해경하기 위한 서비스별 우선 순위를 고려한 충돌 해소 알고리즘을 제안한다. 제안된 충돌 해소 알고리즘은 데이터 슬롯 할당 요구 메시지의 특성에 따른 우선순위를 고려한 江磁\ulcorner遲막關\ulcorner구현이 용이하고 채널 사용이 효율적이며 기존 알고리즘의 문제점으로 제기된 HFC 전송망의 상향 채널에 존재하는 유입잡음, 공통모드 왜곡, 임펄스 노이즈 등 여러 가지 잡음으로 발생하는 헤드엔드의 충돌 검출 오류로 인한 상향 채널의 낭비를 줄이며 다중 충돌을 억제하는데 최적화된 알고리즘이다.

• Journal of Information Processing Systems
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• 제16권6호
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• pp.1324-1342
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• 2020

Various modified algorithms of rapidly-exploring random tree (RRT) have been previously proposed. However, compared to the RRT algorithm for collision avoidance with global and static obstacles, it is not easy to find a collision avoidance and local path re-planning algorithm for dynamic obstacles based on the RRT algorithm. In this study, we propose boundary-RRT*, a novel-algorithm that can be applied to aerial vehicles for collision avoidance and path re-planning in a three-dimensional environment. The algorithm not only bounds the configuration space, but it also includes an implicit bias for the bounded configuration space. Therefore, it can create a path with a natural curvature without defining a bias function. Furthermore, the exploring space is reduced to a half-torus by combining it with simple right-of-way rules. When defining the distance as a cost, the proposed algorithm through numerical analysis shows that the standard deviation (σ) approaches 0 as the number of samples per unit time increases and the length of epsilon ε (maximum length of an edge in the tree) decreases. This means that a stable waypoint list can be generated using the proposed algorithm. Therefore, by increasing real-time performance through simple calculation and the boundary of the configuration space, the algorithm proved to be suitable for collision avoidance of aerial vehicles and replanning of local paths.

• 한국IT서비스학회지
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• 제10권4호
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• pp.259-268
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• 2011

A robot education system by emulation based on Web can be efficiently used for understanding concept of robot assembly practice and control mechanism of robot by control programming. It is important to predict the path of the line tracer robot which has to be decided by the robot. Shortest Path Algorithm is a well known algorithm which searches the most efficient path between the start node and the end node. There are two related typical algorithms. Dijkstra Algorithm searches the shortest path tree from a node to the rest of the other nodes. $A^*$ Algorithm searches the shortest paths among all nodes. The delay time caused by turning the direction of navigation for the line tracer robot at the crossroads can give big differences to the travel time of the robot. So we need an efficient path determine algorithm which can solve this problem. Thus, It is necessary to analyze the overhead of changing direction of robot at multi-linked node to determine the next direction for efficient routings. In this paper, we reflect the real delay time of directional changing from the real robot. A speed based Dijkstra algorithm is proposed and compared with the previous ones to analyze the performance.

• 천문학논총
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• 제25권4호
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• pp.177-186
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• 2010

We developed an efficient Monte-Carlo algorithm to solve dust-scattering radiative transfer problems for continuum radiation. The method calculates the scattered intensities for various anisotropic factors ($g_i$) all at once, while actual photon packets are tracked following a scattering phase function given by a single anisotropic factor ($g_0$). The algorithm was tested by applying the method to a dust cloud embedding a star at the cloud center and found to provide accurate results within the statistical fluctuation that is intrinsic in Monte-Carlo simulations. It was found that adopting $g_0$ = 0.4 - 0.5 in the algorithm is most efficient. The method would be efficient in estimating the anisotropic factor of the interstellar dust by comparing the observed data with radiative transfer models.

• 천문학회보
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• 제43권1호
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• pp.43.1-43.1
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• 2018

Star formation in galaxies predominantly takes place in giant molecular clouds (GMCs). While it is widely believed that UV radiation feedback from young massive stars can destroy natal GMCs by exciting HII regions and driving their expansion, our understanding on how this actually occurs remains incomplete. To quantitatively assess the effect of UV radiation feedback on cloud disruption, we conduct a series of theoretical studies on the dynamics of HII regions and its role in controlling the star formation efficiency (SFE) and lifetime of GMCs in a wide range of star-forming environments. We first develop a semi-analytic model for the expansion of spherical dusty HII regions driven by the combination of gas and radiation pressures, finding that GMCs in normal disk galaxies are destroyed by gas-pressure driven expansion with SFE < 10%, while more dense and massive clouds with higher SFE are disrupted primarily by radiation pressure. Next, we turn to radiation hydrodynamic simulations of GMC dispersal to allow for self-consistent star formation as well as inhomogeneous density and velocity structures arising from supersonic turbulence. For this, we develop an efficient parallel algorithm for ray tracing method, which enables us to probe a range of cloud masses and sizes. Our parameter study shows that the net SFE, lifetime (measured in units of free-fall time), and the importance of radiation pressure (relative to photoionization) increase primarily with the initial surface density of the cloud. Unlike in the idealized spherical model, we find that the dominant mass loss mechanism is photoevaporation rather than dynamical ejection and that a significant fraction of radiation escapes through low optical-depth channels. We will discuss the astronomical.

• 로봇학회논문지
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• 제6권3호
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• pp.255-262
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• 2011

Many intelligent robots have to be given environmental information to perform tasks. In this paper an intelligent robot, that is, a cleaning robot used a sensor fusing method of two sensors: LRF and StarGazer, and then was able to obtain the information. Throughout wall following using laser displacement sensor, LRF, the working area is built during the robot turn one cycle around the area. After the process of wall following, a path planning which is able to execute the work effectively is established using flow network algorithm. This paper describes an algorithm for minimal turning complete coverage path planning for intelligent robots. This algorithm divides the whole working area by cellular decomposition, and then provides the path planning among the cells employing flow networks. It also provides specific path planning inside each cell guaranteeing the minimal turning of the robots. The proposed algorithm is applied to two different working areas, and verified that it is an optimal path planning method.

• 한국정보과학회논문지:소프트웨어및응용
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• 제36권10호
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• pp.836-850
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• 2009

포즈인식은 최근에 유비쿼터스 환경, 행위 예술, 로봇 제어 등에서 그 필요성이 증가되고 있는 분야로써, 컴퓨터비전, 패턴인식 등에서 활발히 연구되고 있다. 하지만 기존의 포즈인식 연구들은 사람의 회전이나 이동에 따라서 불안정한 인식률을 보인다는 단점을 갖고 있다. 이는 포즈 인식을 위해 추출한 특징이 사람의 회전, 이동 등의 다양한 변수에 영향을 크게 받기 때문이다. 이를 극복하기 위하여 본 논문에서는, 다 시점(multi-view) 환경에서의 3D Star Skeleton과 주성분 분석(principal component analysis: PCA)에 기반한 사람의 회전에 강건한 특징 추출을 제안한다. 제안된 시스템은 포즈의 특징 추출을 위해 다 시점 환경 기반의 visual hull을 생성하는 과정에서 획득 가능한 깊이 정보를 표현하는 8개의 projection map을 입력데이터로 사용한다. 이를 통해 포즈의 3D 정보를 반영하는 3D Star Skeleton을 구성하고 주성분 분석 기반의 회전에 강건한 특징을 추출한다. 실험결과에서는 다양하게 회전된 사람으로부터 생성된 3D Star Skeleton에서 특징을 추출하고 다양한 인식기를 통해 포즈인식을 해보았으며, 제안된 특징 추출 방법이 사람의 회전에 강건함을 알 수 있었다.

• 한국컴퓨터정보학회논문지
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• 제10권5호
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• pp.77-86
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• 2005

본 논문에서는 분류오차를 추출하고 학습하여 분류성능을 개선하는 LVQ 학습 알고리즘을 설계하였다. 제안된 LVQ학습 알고리즘은 초기기준백터의 학습을 위해 SOM을 이용하고, LVQ 출력뉴런의 부류지정을 위하여 out-star 학습법을 사용하는 학습네트워크이다. 분류오차가 발생되는 패턴백터로 추출하기 위하여 오차유발조건을 제안하였고, 이 조건을 이용하여 분류오차를 유발시키는 입력패턴벡터로 구성되는 패턴백터공간을 구성하여 분류오차가 발생되는 패턴백터를 학습시키므로 분류오차수를 감소시키고, 패턴분류성능을 개선하였다. 제안된 학습알고리즘의 성능을 검증하기 위하여 Fisher의 Iris 데이터와 EMG 데이터를 학습백터 및 시험 백터로 사용하여 시뮬레이션 하였고, 제안된 학습방식의 분류 성능은 기존의 LVQ와 비교되어 기존의 학습방식보다 우수한 분류성공률을 확인하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 제13회 신호처리 합동 학술대회 논문집
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• pp.471-474
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• 2000

In this paper, we present multisample DSP coding technique for StarCore, SC 140 DSP. The multisample programming is a pipelining technique that exploits operand reuse both coefficients and variables within kernel. A coefficient or operand is loaded once from memory and then the value may be used by multiple ALUs. It is possible to evaluate one intermediate product from each of four output sample calculations in parallel . Therefore, parallelization has been achieved by processing multiple samples in parallel rather than multiple intermediate products belonging to only one sample. The benefits of decreasing the number of memory moves per sample is to increase the algorithm perforomance. In this paper, the multisample technique has been implemented in FIR filter calculation using Motorola StarCore DSP development tool.