• Communications of Mathematical Education
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• v.18 no.2 s.19
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• pp.93-108
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• 2004

Wassily Leontief가 미국 경제의 모델에 선형 대수를 적용한 이론으로 1973년에 노벨 경제학상을 받은 후로는 인문${\cdot}$사회 과학(특히 상경(商經) 분야)을 전공하는 사람에게도 선형 대수는 큰 관심 분야가 되었다. 그래서 1980년대 부터는 대학의 기초 과목으로써 선형 대수를 가르치는 것은 유행처럼 퍼졌고 또 가르침에 관한 연구도 활발하여졌다. 현행 우리나라의 초${\cdot}$중${\cdot}$고등 학교의 수학과 교육과정(이른바 “제 7차 개정”) 속에는 선형대수의 내용이 어느 정도 있으나 학생들에게 확실한 개념을 갖도록 가르치고 있지 않다. 수직선, 순서 쌍, n-겹수, 직교 좌표, 벡터 등 해석기하적인 내용과 선형 방정식계의 풀이법(가우스${\cdot}$조르단 소거법을 쓰지 않는 풀이법) 등 일반 대수적인 내용은 다루지만 선형 변환, 벡터 공간의 구조 등은 다루지 않는다. m${\sim}$n 행렬은 수학II에 나와 있긴 하나 소개하는 정도에 그친다. 한편 과학 계열 고등학교 학생을 위한 "고급 수학"에는 비교적 많은 양의 선형 대수의 내용이 있다. 일반 계열 고등학교의 수학에서도 선형 대수의 내용을 확장하고 학생들에게 확실한 개념을 갖도록 가르쳐서 이들이 대학에 진학하여 전공 분야에서 아무 어려움이 없도록 하는 것이 바람직하다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.336-339
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• 2005

동영상에서의 움직임 검출에 대한 기술은 다양한 응용분야를 가지고 있다. 특히 고정된 카메라에서 움직임 검출과 움직이는 카메라에 대응하여 움직임 검출하고 추적하는 기법들은 현재까지 많은 연구들이 진행되고 있고, 또 응용 제품들의 출시되어지고 있다. 그렇지만 일반적이고 보다 완전한 제품의 개발은 아직 한계가 있다. 본 논문에서는 움직임 벡터를 이용하여 카메라가 패닝(Panning) 여부를 판단하여 패닝 시에는 움직임 검출을 하지 않는 기법을 제안한다. 이 기법은 카메라 패닝 시 즉, 카메라 팬/틸트 드라이버의 고장이나 바람등의 상황에는 움직임 검출을 하지 않음으로써 보다 효과적인 움직임 검출을 할 수 있다. 또한 두 개의 임계치를 적응적으로 조절할 수 있어 기존의 고정된 카메라에서 사용하는 움직임 검출 기법들보다 효율적이라고 할 수 있다.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.3
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• pp.475-483
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• 2012

The characteristic features of speech signal do not vary significantly from frame to frame. Therefore, it is advisable to reduce the redundancy involved in the similar feature vectors. The objective of this paper is to search for the optimal condition of minimum redundancy and maximum relevancy of the speech feature vectors in speech recognition. For this purpose, we realize redundancy reduction by way of a vigilance parameter and investigate the resultant effect on the speaker-independent speech recognition of isolated words by using FVQ/HMM. Experimental results showed that the number of feature vectors might be reduced by 30% without deteriorating the speech recognition accuracy.

• Journal of Environmental Science International
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• v.25 no.2
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• pp.267-280
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• 2016

Ground echo is radar return from stationary targets such as buildings and trees. Wind vectors from the wind profile radar in Gangneung are affected by ground echoes due to the complex mountainous terrain located to the west and the south. These ground echoes make a spurious peak close to the direct current (DC) line signal in Doppler spectra. Wind vectors polluted by ground clutters were determined from spectra of oblique beams. After eliminated the terrain echoes, the accuracy of wind vector compared with radiosonde was improved about 68.4% and its relative coefficient was increased from 0.58 to 0.97.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.10
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• pp.833-841
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• 2014

This paper proposes an algorithm to estimate the wind velocity by tracking free flying balloons. Balloons used in this method are expendable but inexpensive, which increases the usefulness of the method. Also we can obtain accurate 3D information by using multiple cameras and estimate the wind velocity of the local field. The proposed system consists of aerodynamic modeling of the balloon, a tracking algorithm using image processing, and the velocity estimation algorithm. We performed unit tests of each algorithm for the verification. The method is validated using a system simulation and sources of error case identified.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.3
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• pp.393-398
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• 2022

During the test operation period of the wind profiler prototype, radio frequency interference (RFI) contamination occurred in the spectrum. The reference of the RFI that removed the algorithm appearing in the wind profiler spectrum were investigated, and a new algorithm was developed to remove the RFI. First, it was filtered with a threshold value of 0.1 m/s of the spectral width, and the range of the number of gates with the same radial velocity was determined according to whether the beam was a vertical beam or an oblique beam. RFI contamination was removed through filtering and scanning of non-weather signals, and the continuity of wind vectors calculated from the improved spectral radial velocity was verified.

• Journal of the Korean association of regional geographers
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• v.22 no.4
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• pp.887-911
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• 2016

The empirical law that transverse dunes migrate inversely with their heights leads logically to the prediction that multiple dune ridges will converse to a single huge dune by merging. This contradicts the existence of the steady state dune fields on the Earth. The recent studies have emphasized dune collisions as a key mechanism to the stability of dunefield. The roles of wind shadow aspect ratio, however, have yet to be fully explored. This research aims to investigate the potential roles of wind shadow aspect ratio in the dynamical behaviors of transverse dune field. The simplified model is established for this, based upon allometric properties of transverse dunes, wind speedup on the stoss slope and sand trapping efficiency. The derived governing equations can be transformed to the zoning criteria and vector field for dune evolution. The dynamics analysis indicates that wind shadow aspect ratios do not produce convergent areas on the behavior space; rather, they just act as one of the factors that affect the trajectories of dune evolution. Though the model cannot represent the stability of dune field, but seem to produce a reasonable exponent for dune spacing-height relations.

• Journal of Conservation Science
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• v.37 no.3
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• pp.209-219
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• 2021

In this study, the wind environment in an urban area near Sungneymun gate was numerically investigated in the cases of inflow directions. The wind fields for the target area were simulated using Geographic Information System data and Computational Fluid Dynamics model. Results, including vector fields, three-dimensional wind velocity components, and wind speeds, were analyzed to examine flow characteristics. Wind direction variability affected by buildings was shown in the target area. The complex flows around Sungneymun did not depend on the inflow direction as a boundary condition. The wind speed around Sungneymun was generally 3 times stronger at 14 m above ground level (AGL) compared to the surface wind at 2 m AGL and relatively high in the case of easterly inflow. The effect of wind was also analyzed to be relatively significant at the southeast side of Sungneymun. Thus, it was suggested that the assessment of wind environment affected by high-rise and high-density buildings should be necessary for the architectural heritage in urban areas.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.1
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• pp.75-82
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• 1999

일반 해양 구조물이나 해저면에 설치되는 해저 관로는 외력에 의한 변형이 발생된다. 구조물 형상이 복잡하거나, 구성 요소의 개수가 많을 경우 응력해석 시 많은 초기값이 필요하고 해석 시간 또는 장 시간 소요된다. 해양 구조물에 작용하는 대표적인 외력은 파도, 조류, 바람이고 이런 외력은 구조물의 사용 기간(operation life)동안 계속적으로 작용하기 때문에 구조물의 변형율은 항상 허용치 안에서 발생되도록 설계되어야 한다. 허용 변형은 탄성범위 내에 존재해야 하며, 비교적 큰 변형을 일으키는 구조물이나 해저파이프라인의 응력해석을 수치적으로 접근하는 방법을 고찰하였다. 평행상태의 하중 벡터값만 직각 좌표계에서 인트린직(intrinsic) 좌료로 변환시킬 때 변형이 발생함으로, 본 논문에서 소개하는 이차 요소(quadratic element)방법을 사용할 경우 수치해석 시 많은 장점이 있다는 것을 보여준다. 본 방법을 도입함으로써 비교적 큰 변형이 발생되는 구조물 해석 시 일반 수치해석 방법과 그 결과는 같으나 해석 시간을 단축시킬 수 있다는 장점이 있다. 응력 해석 시 국부 강도 행열(element stiffness matrix)은 방향과 무관하며 이차요소 방법을 사용하여 각 요소 벡터를 발생시켰다. 해저관로 일점 상승 시 관로에 작용하는 변형과 상승력에 따른 휨 모멘트를 산출하여 일반적으로 사용되는 선형이론과 비교하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.5
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• pp.376-382
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• 2014

This paper presents a method to enable a UAV in autonomous flight along a desired path to follow it backwards when a strong headwind prevents the vehicle from proceeding forward. The main purpose of the reverse path following in this study is to return to a mission quickly when the wind becomes weaker. When the nonlinear path following guidance law is used, there are two reference points available in the path following. One of the two points is selected considering a flight direction for calculating a straight-line distance(L) from the vehicle to the point for the path following. An initial heading angle with respect to the wind direction determines whether the reverse path following is feasible or not at the time of the wind is generated. The result of the proposed method based on kinematic model in this study is verified through simulations implemented in Matlab.