• Electronics and Telecommunications Trends
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• v.32 no.3
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• pp.56-67
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• 2017

오랫동안 미개척 주파수 대역이었던 테라헤르츠 대역은 소자 및 시스템 기술 연구성과의 축적과 기술 성숙 과정을 거쳐, 최근 다수의 상용화 시스템이 출시되는 등 산업 분야에의 응용이 확산되었다. 특히, 투과 이미징이 가능한 테라헤르츠 이미징 시스템은 산업 분야에서 비접촉 비파괴 품질검사 분야 등에 많은 응용이 기대되고 있다. 이밖에 분광 기술에 기반을 둔 막 두께 측정 시스템, 초고속 통신 시스템 등도 향후 중요한 테라헤르츠 기술 응용 분야로 여겨지고 있다. 본고에서는 테라헤르츠 응용 기술에 관한 최근의 연구 동향을 간략히 살펴보고, 한국전자통신연구원 전파위성연구본부 테라헤르츠 창의원천연구실에서 주력해 온 포토닉스 기반 테라헤르츠 소자 및 시스템에 관해 상세히 소개한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.303-306
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• 2001

Using THz time-domain spectroscopy (THz-TDS), the power absorption and the real conductivity of silica sand are measured terahertz frequency range. It is impossible to measure the characterization of the silica sand by simple electrical measurements using mechanical contacts, e.g., Hail effect or four-point probe measurements. However, the THz-TDS technique can measure not only electrical but also optical characterization of the sample. Also this technique can measure frequency dependent results. Especially, the real conductivity was increased according to THz frequency this is unusual material compare with metal and semiconductor materials; the measured real conductivity are not followed by the simple Drude theory.

• Korean Journal of Optics and Photonics
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• v.12 no.1
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• pp.1-4
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• 2001

Via terahertz (THz) reflection radar, the characterizations of reflected THz electromagnetic pulses are reported. Quasi-optical techniques are used to efficiently reflect pulses of THz electromagnetic radiation from an aluminum mirror and several conducting and nonconducting materials. An incident THz pulse is reflected up to 9 times to know the magnitude change of a reflected pulse from the aluminum mirror. Using this method, aluminum board, undoped silicon, quartz, and LDPE samples' reflection coefficient and index of refraction can be measured. These results suggest a possible application of transient THz reflection spectroscopy without surface contact.ontact.

• Electronics and Telecommunications Trends
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• v.27 no.6
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• pp.114-123
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• 2012

밀리미터파 및 테라헤르츠파는 미래 과학 기술의 보고로서 초고속 통신, 보안 검색 등 다양한 분야에 응용/연구되고 있으나, 밀리미터파 및 테라헤르츠파 영상 기술은 고출력 반도체 신호원이나 배열형 검출기와 같은 핵심 부품 기술의 부재로 연구개발 초기 단계에 있다. 밀리미터파 대역에서 100GHz 이상은 테라헤르츠파 대역과 겹쳐지는 부분으로 300GHz 대역의 밀리미터파 및 테라헤르츠파가 갖는 특성인 종이, 섬유 등의 비이온화 물질에 대한 투과성과 금속에 대한 높은 반사도를 이용하면 인구의 집중도가 높은 공공 장소에서의 은닉된 흉기나 폭발물 등의 위험물 영상을 비접촉식으로 획득할 수 있으며, 식품의 가공 또는 유통 과정 중에 발생할 수 있는 식품 이물질을 제품의 손상 없이 구별해 낼 수 있다.

• Tribology and Lubricants
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• v.31 no.5
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• pp.189-194
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• 2015

This paper focuses on the conformal contact problem. A typical example of conformal contact is the contact between a pin and hole. In particular, this paper focuses on the condition for assuming a contact stress field to be a Hertzian pressure profile by using well-known classical solutions associated with Hertzian contact. Persson first developed the conformal contact analysis method around half a century ago, but there have been no significant improvements since then. The present research also adopted this method, but developed new solutions from the viewpoint of application to structural design. The analysis began with a comparison between Persson°Øs conformal contact stress and the Hertzian stress fields. The next step was to check the differences in the normalized stress values of both. This study used the tolerance for the difference in the peak stresses of Persson°Øs solution and the Hertz solution to validate the Hertzian assumption. This gave the range for the difference in radii of the pin and hole when the contact force and mechanical properties of the material are specified. The results showed that, at a tolerance of 5%, the Hertzian assumption is valid if half of the contact angle is less than 35°ý. In addition, the Hertzian assumption holds even for a relatively long contact length, in contrast to the general incomplete contact problem. This paper discusses these results along with other aspects of the application to the design.

• Journal of the Korean Society for Nondestructive Testing
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• v.34 no.1
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• pp.68-76
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• 2014

최근 들어 급격히 발전한 테라헤르츠파 발생/검출 기술에 힘입어 생명, 화학, 기계, 통신 등의 다양한 분야에서 THz 관련 응용 연구가 진행되고 있다. 본 강좌에서는 최신 THz 발생/검출 기술을 분야별로 살펴보고 바이오, 재료, 기계 분야의 비접촉식 비파괴검사 분야에 적용 개발되고 있는 THz 기술에 대하여 기술하고자 한다. 특히, 구조물의 THz 비파괴검사 평가 분야 세부 기술에 대하여 자세하게 소개한다.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.30-37
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• 1999

헤르츠 접촉하에 있는 반무한체에서의 표면균열을 살펴보았다. 시편의 응력확대계수 K를 구하기 위해 사용되는 간단화된 방법을 이 논문에 쓰여진 모델에 적용시켰다. 기존에 알려진 결과에 비해 상당히 만족스런 결과를 얻었으며 다른 방법보다 이 방법이 훨씬 더 편리함이 입증되었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2008.08a
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• pp.171-171
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• 2008

• Journal of Conservation Science
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• v.32 no.2
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• pp.235-247
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• 2016

Conventional imaging techniques such as ultraviolet, infrared, and X-ray are used mainly to diagnose the damaged parts of the painted cultural assets in Korea. These techniques, however, have limits in diagnosing damages of interlayer parts. We have performed and extensive study on the applicability of Terahertz(THz) analysis technique, introduced recently to this field of study on cultural properties in Korea, to diagnose painted cultural assets. The specimens, produced to imitate the damage types of Korean painted properties, were analyzed over their painting, supporting, and backing layers by terahertz pulse imaging technique. The analyzed results provided information about the cracks, the separated areas, and the separated distances between layers on the specimens. Our research, then, was extended to real painted cultural remains, Birojana Sam-shin Gwebul-do at Bongseon Temple in Namyang-ju, Korea National Treasure Number 1792, through which we have obtained 3D information about the extent and pattern of damages to the asset. These results demonstrate that terahertz 3D imaging technique has the capability of noncontact 3D diagnosis on painted cultural properties.

• Journal of Conservation Science
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• v.35 no.3
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• pp.237-244
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• 2019

In this study, we applied terahertz imaging technology to three Korean modern oil paintings ('Boy,' 'Girl,' and 'Hyehwadong Landscape'); investigated the types of inner layer information in the pictures that can be extracted with terahertz imaging technology; and analyzed the conditions for extracting them. The biggest problem in the terahertz imaging analysis we encountered was the image distortion caused by the change of the distance between the target surface and the terahertz detector, depending on the surface curvature of the target paintings. We then developed a 'working distance maintaining device' to solve this problem. As a result, the terahertz imaging technique was used to identify the base material characteristics and any patterns of damage inside, and presented the optimal conditions for identifying each characteristic. In addition, it was useful to employ the terahertz frequency-division image to check the characteristics of the background materials. To confirm coloring techniques such as brush strokes, it is effective to compare the maximum reflection peak image with the cross-section image; and to detect damage information inside the paintings that cannot be observed on the surface, to compare the cross-section image with the frequency-division image. On the other hand, according to the terahertz imaging analysis of the oil paintings, the internal structural damage marks of 'Boy' and 'Girl' were confirmed, and the artist's painting style was confirmed in 'Hyehwadong Landscape.' The above results are expected to be useful for the analysis and diagnosis of Korean modern oil paintings for their preservation.