• 아동학회지
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• 제22권3호
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• pp.211-227
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• 2001

Using literary and educational points of view, this study examined the prizewinning poems for children in the Annual Literary Contest sponsored by the Dongah-ilbo and the Chosun-ilbo between the 1970s and 2001. The average age of both male and female writers increased over time, 82% were college graduates, and 54% were educators. All of the poems referred to nature in some ways, either as the major theme(42%) or in passing reference to some aspect of nature(58%). Onomato-poetic words were used in 71% of the poems; similes and metaphors were expressed in 13% and 51%, respectively; 58% were written from a mediator's point of view; 59% were in the present tense; 78% of the space elements were fixed; and 98% were written in free verse. In conclusion, the poems for children of the Annual Literary Contest should be used in literary education with guidelines for the appreciation, creation, and criticism of poems for children.

• Journal of electromagnetic engineering and science
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• 제3권1호
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• pp.62-66
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• 2003

Novel coupled line phase shifters and its equivalent phase delay line for compact broadband phased array antennas are proposed. These phase control circuits are designed to be less complex, small size and to use a less number of active devices. The phase shifter is able to control a 120$^{\circ}$ phase shift continuously, and the phase delay line for a reference phase has a fixed 60$^{\circ}$ shifted phase. Both have the low phase error of less than $\pm$3.5$^{\circ}$ and the low gain variations of less than 1 ㏈ within the 300 MHz bandwidth. These proposed circuits are adequate to form the efficient beam-forming networks with compactness, broadband, less complexity, and low cost.

• International Journal of Aeronautical and Space Sciences
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• 제11권3호
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• pp.240-245
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• 2010

The controller of a model reference adaptive control monitors the plant's inputs and outputs to acknowledge its characteristics. It then adapts itself to the characteristics it encounters instead of behaving in a fixed manner. An important part of every adaptive scheme is the adaptive law for estimating the unknown parameters on line. A more precise model is required to improve performance and to stabilize a given dynamic system, such as a satellite in which performance varies over time and the coefficients change due to disturbances, etc. After model identification, the robust controller ($H{\infty}$) is designed to stabilize the rigid body and flexible body of a satellite, which can be perturbed due to disturbance. The result obtained by the $H{\infty}$ controller is compared with that of the proportional and integration controller which is commonly used for stabilizing a satellite.

• 한국군사과학기술학회지
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• 제4권1호
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• pp.177-187
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• 2001

It is important to test and evaluate the variation degree of ship-mounted antenna radiated power with respect to all directions in order to use more effectively antennas that installed on naval ships. The naval ship has various sensors for navigation, communication and electronic warfare, etc. And the performance of these sensors extremely depends on the various characteristics of antenna system to transmit and receive electromagnetic wave. The radiated power pattern of the antenna differs from all aspect angles of the ship because of complex superstructures. It is important to know the weak point(direction) of antenna radiation for appropriate operation. Therefore, the ARP(Antenna Radiation Pattern) of shipboard antennas is measured for the all aspect angles. The results of ARP measurement are utilized as reference for antenna arrangement of newly-built same class warship. This study also describes the development results for the ARP measurement technique, software design and test procedures to measure the radiation pattern of communication equipment antennas using the fixed test site.

• 한국멀티미디어학회논문지
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• 제12권6호
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• pp.785-793
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• 2009

This paper proposes a signature using dominant singular values for video sequence matching. By considering the input image as matrix A, a partition procedure is first performed to separate the matrix into non-overlapping sub-images of a fixed size. The SVD(Singular Value Decomposition) process decomposes matrix A into a singular value-singular vector factorization. As a result, singular values are obtained for each sub-image, then k dominant singular values which are sufficient to discriminate between different images and are robust to image size variation, are chosen and normalized as the signature for each block in an image frame for matching between the reference video clip and the query one. Experimental results show that the proposed video signature has a better performance than ordinal signature in ROC curve.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 추계학술대회 논문집
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• pp.15-18
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• 2001

This paper describes a control scheme for direct torque and flux control of induction machines. The proposed predictive flux control scheme has directly calculated the reference voltage space vector based on flux errors in order to control the torque and flux. This proposed control scheme has not the requirement of a separate current regulator and proportional-integral (PI) control of the flux, torque, and/or current error, thereby improving transient performance and also has the advantage of less torque ripple in steady state with a fixed switching period. The effect of proposed method has been proven by simulations and experiments.

• 한국조명전기설비학회지:조명전기설비
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• 제1권2호
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• pp.70-73
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• 1987

본 연구에서는 의사사인(Sine) 방식을 사용한 간단한 계단파 PWN을 소개하였다. 제어기의 구성은 기본파 성분인 Sine값을 계단 레벨로 분할하고 각각의 값을 디지탈 합성하여 3상 PWN 인버터를 구성하였다. 3상 출력 펄스는 캐리어 주파수를 일정하게하고 기본파만 변화시켜 낮은 주파수에서 고조파 감소 효과를 얻어냈다. 실험으로는 스위칭 주파수가 20[KHz]일때 0.5마력 유도 전동기 구동을 실행하였다.

• 비파괴검사학회지
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• 제29권4호
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• pp.283-292
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• 2009

Laser-based ultrasonic sensing requires the probe with fixed fecal length, but this requirement is not essential in laser-based ultrasonic generation. Based on this fact, we designed a pulsed laser-based ultrasonic wave propagation imaging (UWPI) system with a tilting mirror system for rapid scanning of target, and an in-line band-pass filtering capable of ultrasoaic mode selection. 1D-temporal averaging, 2D-spatial averaging, and 3D-data structure building algorithms were developed far clearer results allowing fur higher damage detectability. The imaging results on a flat stainless steel plate were presented in movie and snapshot formats which showed the propagation of ultrasound visible as a concentric wavefield emerging from the location of an ultrasonic sensor. A hole in the plate with a diameter of 1 mm was indicated by the scattering wavefields. The results showed that this robust UWPI system is independent of focal length and reference data requirements.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2004년도 춘계학술대회 논문집
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• pp.117-120
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• 2004

이 논문은 프리 자이로스코프의 방향의존성을 이용하여 위치를 결정하는 방댑을 이론적으로 검토한 것이다. 임의 기준 위치 혹은 출발 위치에 대하여 두 개 이상의 프리 자이로스코프의 자이로축의 경사각을 측정하고 아울러 기준 위치에서 시작한 시간의 경과를 측정한 다음, 이 두 가지의 기본 요소를 이용하여 위치를 구하는 것이다.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.367-367
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• 2006

With poly (ethylene-co-methacrylic acid) ionomer (i.e. Surlyn) as a compatibilizer, PP/organoclay (Cloisite(R)20A) nanocomposites were prepared via melt compounding in a co-rotating twin-screw extruder. For comparison, the widely used PP-g-MA was also used as a reference. The content of organoclay was fixed at 5phr based on the total weight of polymer resins. The structures of nanocomposites were characterized by XRD, rheometry in small amplitude oscillatory shear, SEM, and TEM, respectively. It was found that PP/Surlyn/OMMT nanocomposites displayed higher intercalation degree and better dispersion effect than the corresponding PP/PP-g-MA/OMMT counterpart. Additionally, their mechanical properties and wettability were measured.