• 소성∙가공
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• 제6권2호
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• pp.95-101
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• 1997

The thermal fatigue and wear properties of high speed steel roll which was recently developed were investigated by observing microstructure, by measuring mechanical and physical properties, by conducting thermal fatigue testing, and by measuring the amount of wear in actual mill. High speed steel roll had better thermal fatigue testing, and by measuring the amount of wear in actual mill. High speed steel roll had better thermal fatigue life than high chromium iron roll, which was due to lower carbide content, higher strength, and higher thermal conductivity. The amount of wear of high speed steel roll was nearly the same as that of high chromium iron roll in the first finishing stand, which was due to the oxide formation on the roll surface. However, in the third finishing stand, the wear resistance of high speed steel roll was 2~3 times as good as that of high chromium iron roll because the former had higher hardness at high temperature.

• 한국전자파학회논문지
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• 제8권2호
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• pp.161-172
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• 1997

본 논문에서는 다충 유전체 위의 주기적인 도체 스트립 구조에 의한 전자파산란 문제를 Fourier-Galerkin 모멘트법으로 수치해석하여 정규화된 반사 및 투과전력을 계산하였다. 도체띠에 유도되는 전류밀도는 적절한 모서리 경계조건을 만족하는 함수와 l종 Chebyshev 다항식의 곱의 급수로 전개하였으며, 각유전체층의 경계 면에 서는 전자계 연속조건을 적용하였다. 산란 전자파는 Floquet 모드 함수를 이용하여 무한개의 급수로 전개하였다. 본 논문에서 제안된 방법의 타당성을 입증하기 위하여 각 유전체층의 비유전율과 두께를 변화시켜 얻어진 정규화된 반사 및 투과전력은 기존의 수치방법 및 논문의 결과와 평가 및 비교하였으며, 이 때 본 논문의 수치결과들은 기존의 수치방볍 및 논문의 결과와 매우 잘 일치하였다. 기하광학적 정규화된 반사 및 투과전력의 급변점 의 위치는 입사각 및 격자 주기 그리고 유전체충의 비유전율 및 두께에 따라 주된 영향을 받음을 알수 있었고, Wood의 변칙이라고 불리우는 이러한 급변점은 고차 모드의 반사전력이 전파모드와 감쇠모드 사이에서 모드 전환이 주된 요인으로 관측되었으며, 국부적인 최소 위치들은 유전체층의 비 유전율이 증가함에 따라 격자주기가 작아지는 좌측방향으로 약간 이동함을 알 수 있었다.

• 한국임상보건과학회지
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• 제2권4호
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• pp.231-238
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• 2014

Purpose. This study examines the effects of improving students self-esteem and sociability by conducting a Group Art Therapy Program for students with learning disabilities. This study focused on three students with learning disabilities, attending B middle school special education class located in K county. The study was conducted for two hours once a week (Friday) at B middle school during special education class from May 2, 2014 to July 18, 2014. Methods. For the tools of studying, Self-esteem and social strip forms/rubrics were filled, by students', before and after and data processing was inspected, paired t-Test using the SPSS / WIN (Ver.18.0) for quantitative analysis. Also, on the basis of content, analyzed data of the individuals' self-esteem social changes are shown in graph format. In addition, this qualitative study shows before and after of dynamic house, tree, person (K-H, T, P), dynamic family (KFD), dynamic school life of search phase (4-6 sessions) significant improvement of self-esteem and sociability in adolescents' with learning disabilities influenced by conducting a Group Art Therapy Program. Results. The result of this study can be summarized as follows. First, Group Art Therapy Program shows a statistically significant difference (p<.05) showing that self esteem average is 2.04 before Group Art Therapy Intervention but self esteem average is 2.92 after Group Art Therapy Intervention. Second, as a result of social strip pre-post, there wasn't statistically significant difference compared to self esteem pre-post result, although, post examination's average level was enhanced after Group Art Therapy Program in difference examination.(p>.05). Third, as a result of analysis the indicated pre-post change of Students' pre-post dynamic house, tree, person (HTP), dynamic family (KFD), a dynamic school daily life (KSD), students' family and interpersonal relationships, self-concept shows statistical significant changes. Conclusion. As the result of this study, Group Art Therapy Program shows effective improvement in students' self-esteem and social skills learning disabilities. However, a future study on larger and more diverse group of students' with learning disabilities are advised to be conducted in order to better understand the significance of the Group Art Therapy Program.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2015년도 추계학술대회
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• pp.939-940
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• 2015

본 논문에서는 UHF 대역에 적합한 준-야기 안테나 설계방법에 대해 연구하였다. 코플래너 스트립으로 급전되는 평면 다이폴과 그에 근접하는 도체 스트립 도파기는 상호결합에 의해 광대역 다이폴 특성을 갖는다. 접지면 반사기는 저주파 대역의 이득을 개선할 수 있고, 반사기를 접어서 안테나 크기를 감소시킬 수 있다. 마이크로스트립과 코플래너 스트립 간 밸런은 마이크로스트립 선로 종단을 코플래너 스트립에 단락 핀으로 연결하여 구성하였으며, 코플래너 스트립 선로와 반사기를 원형 링도체로 연결하였다. 안테나의 여러 가지 파라미터들과 밸런이 안테나 특성에 미치는 영향을 관찰하였다. 제안된 구조의 안테나를 지상파 DTV 방송 주파수대역인 470-806 MHz 대역에서 동작하도록 설계하였다.

• 우주기술과 응용
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• 제1권1호
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• pp.33-40
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• 2021

본 논문에서는 총 무게 42 kg 이내의 요구사항을 토대로 차세대소형위성 2호 영상 레이다 시스템을 개발한 결과를 보고한다. 차세대소형위성 2호는 소형급 인공위성으로, 탑재체의 무게 비중이 전체 무게 대비 약 40% 정도를 차지하도록 설계하였다. 영상 레이다 시스템은 안테나, RF송수신기, 기저대역 신호처리기, 전력부 등으로 구성되며, 이 중에서 특히 무게 비중이 큰 부품은 영상 레이다의 핵심인 안테나이다. 안테나 설계시 이득, 효율 등을 고려한 다양한 선택이 가능하지만, 차세대소형위성 2호 사업에서 요구하는 무게, 전력 및 해상도 등을 반영하여 Micro-strip Patch Array 안테나를 채택하여 설계하였다. 차세대소형위성 2호의 임무 요구 조건에 부합하도록 안테나의 주파수는 9.65 GHz, 이득은 42.7 dBi 그리고 반사손실은 -15 dB로 규정하여 개발하였으며, 차량에 탑재한 현장시험을 통하여 요구 성능의 충족 여부를 검증하였다.

• 한국전기전자재료학회논문지
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• 제15권6호
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• pp.492-498
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• 2002

In this paper, we present the simulation results of multi-layer VCO(voltage controlled oscillator), which is composed of resonator, oscillator, and buffer circuit, using EM simulator and nonlinear RF circuit simulator. EM simulator is used for obtaining the EM(Electromagnetic) characteristics of conductor pattern as well as designing the multi-layer VCO. Obtained EM characteristics were used as real components in nonlinear RF circuit simulation. Finally the overall VCO was simulated by the nonlinear RF circuit simulator. The material for the circuit pattern was Ag and the dielectric was Dupont 951AT, which will be applied for LTCC process. The structure of multi-layer VCO is constructed with 4 conducting layer. Simulated results showed that the output level was about 4.5 [dBm], the phase noise was -104 [dBc/Hz] at 30 [kHz] offset frequency, the harmonics -8 dBc, and the control voltage sensitivity of 30 [MHz/V] with a DC current consumption of 9.5 [mA]. The size of VCO is $6{\times}9{\times}2 mm$(0.11 [cc]).

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2005년도 종합학술발표회 논문집 Vol.15 No.1
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• pp.371-374
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• 2005

This paper presents the design and fabrication of a cost effective and broad band 8$\times$8 stacked patch array antenna which are backed by a metal cavity operating at 400Hz based on 4 layers LTCC technology. Gain of antenna can be enhanced by using a metal cavity, which can be easily implemented by using LTCC substrates and vias. The broadband performance can be obtained by varying the dimension of patch and the number of layers. Furthermore, to keep the feeding network as smal1 as possible and reduce radiation from feeding network a mirrored patch orientation and embedded micro strip line are adopted, The fabricated antenna is $40\times45\times0.4$ $mm^3$in size. It shows gain 20.4dBi, beam width 10.7deg and impedance bandwidth of l0dE return loss 3.35GHz (40.9$\sim$44.25 GHz), which is about 8% of a center frequency.

• 박물관보존과학
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• 제9권
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• pp.67-83
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• 2008

국립중앙박물관이 소장하고 있는 청연군주 출토복식(신수751 의류 일괄) 중 織金 및 金箔이 있는 복식의 보존 처리 과정을 소개하고자 한다. 금사 및 금박의 비파괴분석(X-선형광분석:XRF)을 실시한 다음 표면의 금(Au)이 열화가 진행되면서 분상화된 금층에 아교 2%용액을 도포하여 접착력을 강화하였다. 표면의 먼지와 오염물제거를 위해 진공흡입을 통한 건식세척과 분사식 습식세척을 병행하였고 손상부분을 보수하여 유물의 원형을 회복하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.653-656
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• 2002

In this paper, we present the simulation results of multi-layer VCO(voltage controlled oscillator), which is composed of resonator, oscillator, and buffer circuit, using EM simulator and nonlinear RF circuit simulator. EM simulator is used for obtaining the EM(Electromagnetic) characteristics of conductor pattern as well as designing the multi-layer VCO. Obtained EM characteristics were used as real components in nonlinear RF circuit simulation. Finally the overall VCO was simulated by the nonlinear RF circuit simulator. The material for the circuit pattern was Ag and the dielectric was DuPont 951AT, which will be applied for LTCC process. The structure of multi-layer VCO is constructed with 4 conducting layer. Simulated results showed that the output level was about 4.5 [dBm], the phase noise was -104 [dBc/Hz] at 30 [kHz] offset frequency, the harmonics -8 dBc, and the control voltage sensitivity of 30 [MHz/V] with a DC current consumption of 9.5 [mA]. The size of VCO is $6{\times}9{\times}2$ mm(0.11[cc]).

• Wind and Structures
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• 제7권1호
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• pp.13-28
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• 2004

A method of numerical analysis without conducting 3D wind tunnel model tests was examined in our previous study for predicting vortex-induced oscillation of bridge girders with span-wise varying geometry. The aerodynamic damping forces measured for plural wind tunnel 2D models were used in the analysis. A further study was conducted to examine the precision of solution obtained by this method. First, the responses of vortex-induced oscillation of two rocking models and a taut-strip bridge girder model with span-wise varying geometry were measured. Next, the responses of these models were numerically analyzed by means of this method, and then a comparison was made between the obtained $Vr-A-{\delta}_a$ contour diagram of each 3D model in the wind tunnel test and the diagram in the numerical analysis. Since close correlations were observed between each two $Vr-A-{\delta}_a$diagrams obtained in the model test and in the analysis in cases where the 3D model did not have strong three-dimensionality, our findings revealed that the predicted solution proved to be reasonably accurate.