• 한국항해학회지
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• 제19권4호
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• pp.93-102
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• 1995

A design method of an electromagnetic wave absorber with ferrite fins in the second layer, which has very wide band frequency characteristics, is proposed and discussed. A theoretical model using the equivalent material constants method is adopted, assessed for its accuracy by comparision with the Hashin-Shtrikman formulas and compared with the conventional absorbers. Based on the model, a wide band electromagnetic wave absorber with excellent reflectivity frequency characteristics in frequency range of 30MHZ to 3530MHZ has been designed.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 1996년도 The Korean Institute of Navigation 1996년도 한·중 국제학술 심포지움 및 추계학술발표회 논문집
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• pp.125-134
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• 1996

A design method of double layered electromagnetic wave absorbers with cross-shaped ferrite prominence in the second layer which has broad band frequency characteristics was proposed. The broad band electromagnetic wave absorber can be designed under some approximations by the theoretical model using the equivalent material constants method for the second layer. Based on the developed model broad band electromagnetic wave absorbers with excellent reflectivity frequency characteristics in the frequency range of 30MHz to 3,990MHz were designed.

• 전기학회논문지
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• 제63권5호
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• pp.676-682
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• 2014

In this paper, precipitation echo(PRE) and non-precipitaion echo(N-PRE)(including ground echo and clear echo) through weather radar data are identified with the aid of neuro-fuzzy algorithm. The accuracy of the radar information is lowered because meteorological radar data is mixed with the PRE and N-PRE. So this problem is resolved by using RBFNN and judgement module. Structure expression of weather radar data are analyzed in order to classify PRE and N-PRE. Input variables such as Standard deviation of reflectivity(SDZ), Vertical gradient of reflectivity(VGZ), Spin change(SPN), Frequency(FR), cumulation reflectivity during 1 hour(1hDZ), and cumulation reflectivity during 2 hour(2hDZ) are made by using weather radar data and then each characteristic of input variable is analyzed. Input data is built up from the selected input variables among these input variables, which have a critical effect on the classification between PRE and N-PRE. Echo judgment module is developed to do echo classification between PRE and N-PRE by using testing dataset. Polynomial-based radial basis function neural networks(RBFNNs) are used as neuro-fuzzy algorithm, and the proposed neuro-fuzzy echo pattern classifier is designed by combining RBFNN with echo judgement module. Finally, the results of the proposed classifier are compared with both CZ and DZ, as well as QC data, and analyzed from the view point of output performance.

• 한국산학기술학회논문지
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• 제9권1호
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• pp.29-34
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• 2008

대전입자형 디스플레이 소자의 구동을 위하여 주파수, 펄스폭, 진폭, 경사 등을 구현하기 위한 4채널 파형발생기를 제작하였으며, 이 파형발생기로 노란색과 검정색으로 제작한 패널의 선택적 셀구동 신호를 확인하였다. $1^{\circ}$ 간격으로 동작하는 광방출부와 수광부, 광방출부의 분광기 연결이 구비된 집적화된 실험장치로부터 CIE 특성, 반사율, 대조비, 시야각을 측정하였으며 1 layer 입자충전일 경우 노란색은 $35{\sim}40%$, 검정색인 경우 $15{\sim}20%$의 반사율을 가지며, 노란색의 색좌표를 확인하였고 파장은 571.2nm였다. 3 layer 입자충전의 경우 광학특성은 향상됨을 확인하였다.

• 전자공학회논문지D
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• 제34D권4호
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• pp.8-16
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• 1997

A wide band design method of an electromagnetic wave absorber with using exponentially tapered ferritic is proposed and discussed. A theoretical model using the equivalent material constants method is also proposed to analyze the regions varying sptially in the shape of ferrite. Based on the developed model, wide band electromagnetic wave absorbers with excellent reflectivity frequency charaateristics in the freqency rang eof 30MHz to 2,150MHz or 2,430MHz were designed.

• 한국군사과학기술학회지
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• 제9권2호
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• pp.87-95
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• 2006

The performance of a microwave missile seeker and radar operating in an air-to-air look-down mode is strongly influenced by the presence of ground clutter In order to correctly account for the effects of ground clutter, it is required to develop a model capable of representing clutter characteristics as a function of range and/or frequency. In this paper, a program to estimate the clutter reflectivity for various ground conditions is developed, using the actually measured data and the data available from open literatures. In addition, clutter characteristics measured for various ground conditions such as sea, agricultural area, urban city and industrial area through the captive flight tests are presented.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.729-732
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• 2005

This paper describes a time-spatial domain model for simulating raw data acquisition of space-borne SAR system. The position, velocity and attitude information of the platform at a certain time instance is used for deriving sensor-target model. Ground target is modelled by a set of point scatters with reflectivity and two-dimensional ground coordinates. The signal received by SAR is calculated for each slow and fast time instance by integrating the reflectivity and phase values from all target point scatters. Different from frequency domain simulation algorithms, the proposed time domain algorithm can provide fully physical modelling of SAR raw data simulation without any assumptions or approximations.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2004년도 춘계학술대회 논문집
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• pp.23-27
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• 2004

GHz 대역용 전파흡수체의 개발에 있어 Cast Alnico magnets을 자성손실재로 이용하여 우수한 전파흡수특성을 나타내는 새로운 전파흡수체를 개발하였다. 특히 본 연구에서 개발한 전파흡수체는 폐처리된 Cast Alnico magnets을 이용한 것으로 이는 환경문제와 자원절약의 문제를 고려할 때 중요한 의미를 갖는다. 본 연구에서 개발한 Cast Aliico magnets을 이용한 전파흡수체는 X-band와 C-band를 고려한 전파흡수체로서 우수한 전파흡수특성 나타낸다.

• Current Optics and Photonics
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• 제2권5호
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• pp.443-447
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• 2018

We propose a diode-pumped cesium laser using frequency locking of a pump laser that can effectively increase the maximum output power of the cesium laser. We simultaneously monitored the absorption spectrum of cesium and the laser output power, and the frequency of pump laser was locked at the center of the $D_2$ absorption line of the cesium atom to obtain an effective gain enhancement. Using this scheme, we have achieved output power increase of ~0.1 W compared to when frequency locking was not applied. Furthermore, by optimizing the temperature of the cesium cell and the reflectivity of the output coupler, we successfully achieved an output power of 1.4 W using the pump power of 2.9 W, providing a slope efficiency of 61.5% and optical-to-optical efficiency of 49%.

• 지구물리와물리탐사
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• 제1권3호
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• pp.183-187
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• 1998

탄성파 파형은 탄성파트레이스가 탄성파의 고유파형과 매질의 반사계수시계열과의 1차 콘볼루션이라는 가정 아래 위너적합필터(Wiener match filter)에 의하여 산출될 수 있다. 이때 매질의 반사계수 시계열은 음파 및 밀도검층 기록으로부터 도출한다. 본 논문에서는 파형 산출의 한 방법으로 탄성파 트레이스 및 반사계수 시계열을 보정하는 전처리과정의 효과를 검증하는 실험을 실시하였다. 이 전처리과정은 시간 측정은 탄성파 트레이스로부터, 그리고 반사계수는 검층 기록으로부터 잘 측정될 수 있다는 가정에 근거한다. 따라서 전처리과정은 1) 음파검층 기록의 깊이로부터 시간으로의 변환을 탄성파 트레이스에 잘 적합하도록 시작시각과 구간별 시간 길이를 조절하고, 2)탄성파 트레이스의 진폭을 검층기록에서 도출된 반사계수와 잘 적합하도록 조절하는데 이때 탄성파와 검층의 저주파 성분만을 비교한다.