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Simulation and Examination for DFB Lasers with Grating Phase of π/2 on One Mirror Face (한쪽 거울면의 격자 위상이 π/2인 DFB 레이저의 시뮬레이션과 검정)

  • Kwon, Kee-Young
    • Journal of Software Assessment and Valuation
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    • v.15 no.2
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    • pp.101-109
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    • 2019
  • Lasers for optical broadband communication systems should have excellent frequency selectivity and modal stability. DFB(Distributed Feedback) lasers have low lasing frequency shift during high speed current modulation. In this paper, I have developed a simulation software and analysed threshold gain and lasing frequency of a lasing mode in longitudinal direction of an 1.55um DFB laser with two mirrors and without anti-reflection coatings, that have both an index- and gain-gratings. The grating phase on a left mirror face is fixed as π/2 and the grating phase on a right mirror face is varied. As the phases of the index and gain gratings on the right mirror facet are π and 0, κL should be in the range of 2~6 in order to enhance the frequency stability. In order to reduce the threshold current of a lasing mode, κL should be greater than 8, regardless of the grating phases on the mirror faces.

Robust Real-time Pose Estimation to Dynamic Environments for Modeling Mirror Neuron System (거울 신경 체계 모델링을 위한 동적 환경에 강인한 실시간 자세추정)

  • Jun-Ho Choi;Seung-Min Park
    • The Journal of the Korea institute of electronic communication sciences
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    • v.19 no.3
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    • pp.583-588
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    • 2024
  • With the emergence of Brain-Computer Interface (BCI) technology, analyzing mirror neurons has become more feasible. However, evaluating the accuracy of BCI systems that rely on human thoughts poses challenges due to their qualitative nature. To harness the potential of BCI, we propose a new approach to measure accuracy based on the characteristics of mirror neurons in the human brain that are influenced by speech speed, depending on the ultimate goal of movement. In Chapter 2 of this paper, we introduce mirror neurons and provide an explanation of human posture estimation for mirror neurons. In Chapter 3, we present a powerful pose estimation method suitable for real-time dynamic environments using the technique of human posture estimation. Furthermore, we propose a method to analyze the accuracy of BCI using this robotic environment.

A Study on Glass Mirror Trade and its Characteristics of Craft after Joseon Dynasty (조선 후기 유리거울의 수입과 공예품의 특징)

  • Park, Jinkyung
    • Korean Journal of Heritage: History & Science
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    • v.52 no.4
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    • pp.206-225
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    • 2019
  • This paper examines the trade and development aspects of glass mirrors through the literature records of the Joseon Dynasty, and studies the characteristics of existing glass mirror crafts by referring to the terms and types shown in the literature. The glass mirror in the records had called western mirrors(西洋鏡, 洋鏡), glass mirrors(玻璃鏡, 玻瓈鏡), stone mirrors(石鏡), etc. Glass mirrors were imported mainly through trade with Russia and the Qing Dynasty since the 17th century and were banned from importation in the late Joseon Dynasty. These mirrors were something new that caused a great stirring in Joseon society in the 18th century, and in the 19th century, it grew larger as a commodity needed for everyday life, especially with trade with Japan. At that time, glass mirrors were used for various purposes, such as installing large glass at a store, which were not the standard mirror usage of confirming one's appearance. These mirrors surprised Koreans in Joseon who experienced them at Yanjing Liulichang(燕京 琉璃廠) in the 18th and 19th centuries. As a result, the demand for glass mirrors rapidly increased and quickly surpassed that of bronze mirrors. Consequentially, new crafts using glass mirrors instead of bronze mirrors in Joseon began to be produced and used after the 18th century. In particular, integrated flat boards of glass mirrors were developed as crafts used indoors. It was convenient to use the hair comb box, a long-time presence in Joseon society, with the bronze mirror. This kind of mirror remained apparent in various genre paintings, including the Taepyeong Seongsido(太平城市圖, 'A Thriving City in a Peaceful Era') collected the National Museum of Korea which reflect its populism of the times. Also, the Mirror Stand(鏡臺) used in the Qing Period was produced in Joseon, but there was a difference in the way of making the drawers and box shapes between two nations. On the other hand, the Face Mirror(面鏡) was made to look at the face. Various crafts made with the aesthetic sense of Joseon, such as the ox horn inlaying craft technique, were produced with auspicious designs. In the 19th century, glass mirrors were imported from European countries, such as France, Denmark, the Netherlands, and the United Kingdom, however after the end of the 19th century Japanese crafts were popular. Glass mirrors, which were popular in the Meiji and Taisho eras of Japan, were imported and also the Mirror Screen(鏡屛) using large glass mirrors were used. In particular, the mirror screen had developed wood furniture since the previous time, which were used for banquets and large spaces, such as the drawing room, and were imported from China and Japan. In addition, the western architectural effect of attaching a mirror to the wall was also attempted to adjust the brightness of the space and introduce another image and scenery in the mirror. This was done at Deoksugung Palace's Seokjojeon.

Surface Treatments of Bronze Mirrors Excavated from Korean Peninsula (한반도 출토 청동거울의 표면처리 기법에 관한 연구)

  • Jeon, Ik-Hwan;Lee, Jae-Sung;Baek, Ji-Hye;Park, Jang-Sik
    • Journal of Conservation Science
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    • v.22
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    • pp.87-98
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    • 2008
  • Microstructures and chemical compositions of 24 bronze mirrors recovered from the Korean peninsula were examined using the scanning electron microscope equipped with the energy dispersive spectrometer in an effort to characterize the treatments applied on their surface. Their provenance and chronology are mostly unspecified except for two objects from a Koryo burial site. In antiquity the surface of bronze mirrors was frequently finished by mere polishing when their tin content was high enough to guarantee the required reflectivity. In many cases, however, their surface was given a special treatment. The most typical treatment was to coat the surface with tin in two different processes referred to as wipe-tinning and amalgam-tinning. In wipe-tinning only tin was used, but in amalgam-tinning tin and mercury were used together. The surface was often coated with mercury in a process known as mercury-polishing. The present mirrors showed that all these techniques were in fact practiced, not only on the reflective surface but, in some cases, on the decorative surface. The detection of mercury played a crucial role in the assessment of a specific technique applied in each mirror. Mercury often remained in the substrate in the form of sulfide and thereby allowed the method of surface treatment to be estimated even when the coated layer was completely lost. The future study is expected to uncover the regional and temporal variation of the surface treatments to the better understanding of bronze mirrors with respect to provenance and chronology.

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Studies on Conservation and Metallographic Manufacturing Technique of Iron Mirror in the Korean Christian Museum at Soongsil University Collections (숭실대학교 한국기독교박물관 소장 철제거울의 보존과 금속조직분석을 통한 제작기법 연구)

  • Kim, Haena;Lee, Hyojin;Kim, Sooki
    • Journal of Conservation Science
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    • v.28 no.3
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    • pp.257-264
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    • 2012
  • Ancient mirrors are generally made of bronze, and it is very rare to find cases of iron mirrors excavated domestically. In this study, the unidentified ferrous artifact was treated for conservation, and was identified as a mirror. In this process, the sample was taken and analyzed for microstructure, and the manufacturing technology was studied. Analysis involved optical microscope, micro-hardness tester, and SEM-EDS. As the result of analysis, iron mirror structure exist not almost non-metallic inclusions, and partially network cementite was observed. This appears to have been caused by reduced carbon content due to decarburizing the cast iron in the solid state mirror which was created by cast iron. The ledeburite structure of the casting has difficult to cut or polish because has great hardness by high carbon content. Thus, the cast iron mirror was decarburized at a temperature under $850^{\circ}C$ with CO or $CO_2$ blocked, which reduced the hardness of the iron mirror and made it possible to polish the mirror surface. This deformation of structure according to carbon content results from such manufacturing technology.

The Effect of Task-Oriented Mirror Therapy involve Visual Illusion on Upper Extremity Functions in Stroke Patients: Single Subject Study (착시현상이 반영된 과제지향적 거울치료가 뇌졸중 환자의 상지기능에 미치는 영향: 개별실험연구)

  • Choi, Seong-Youl;Kim, Su-Kyoung;Lee, Jae-Hong
    • The Journal of Korean society of community based occupational therapy
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    • v.3 no.2
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    • pp.13-23
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    • 2013
  • Objective : The purpose of this study is to evaluate the effect of task-oriented mirror therapy involve visual illusion on upper extremity functions in stroke patients. Method : We divided into two groups that task-oriented mirror therapeutic exercise program include visual illusion and not include. In order to determine the change in upper extremity function, Box & Block Test and Line-bisection Test was evaluated each time period. Result : The result of this study that we found out that all participation's upper extremity function had been improved during the intervention and sustained during baseline regression. Applying mirror therapy program include visual illusion group more improved trend line during the intervention, visual illusion group, it had been shown there are higher difference between visual illusion group and non-visual illusion group in upper extremity functions. Conclusion : It is thoughtful that task-oriented mirror therapy could help for stroke. It might be more effectiveness to apply who have exercise program include visual illusion.

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Acquisition of Monochromatic X-ray Using Multilayer Mirror (다층박막 거울을 이용한 단색 엑스선 획득)

  • Chon, Kwon-Su
    • Journal of radiological science and technology
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    • v.33 no.3
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    • pp.179-184
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    • 2010
  • A hard X-ray microscope system for obtaining images of nano-spatial resolution has been widely studied and requires monochromatic X-ray. A multilayer mirror of 84% reflectivity was designed to acquire tungsten characteristic X-ray of 8.4 keV from the white beam generated from an X-ray tube, and the C/W multilayer mirror of $50{\times}50\;mm$ size and 5.65 nm d-spacing was fabricated by the ion-beam sputtering system. The C/W multilayer had a uniformity of 99.5%, and the structure of the multilayer mirror was verified by a TEM image. The obtainable x-ray reflectivity for the C/W multilayer mirror at 8.4 keV was estimated from measuring the X-ray reflectivity using the copper characteristic X-ray of 8.05 keV. Monochromatic X-ray of 8.4 keV was generated by combining a X-ray tube, and the reflectivity and monochromaticity were 77.1% and 0.21 keV, respectively. Monochromatic X-ray generated from the combination of an X-ray tube and an C/W multilayer mirror has enough potential to use X-ray source for hard X-ray microscope system of laboratory size. If the C/W multilayer mirror of d-spacing of a few nanometers can be fabricated, monochromatic X-ray corresponded to 17.5 keV, molybdenum characteristic X-ray, can be obtained and applied to mammography in the medical application.

화제의 책속으로 - 매트 리들리의 '붉은 여왕' <남녀 차이에서 나타나는 성의 역할>

  • Korean Federation of Science and Technology Societies
    • The Science & Technology
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    • v.35 no.12 s.403
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    • pp.82-84
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    • 2002
  • 붉은여왕은 모든 진보가 상대적이라는 것을 말한다. 붉은여왕은 '거울나라의 엘리스'에서 엘리스가 거울을 통해 만난 체스판의 말로서 주변의 경치가 함께 움직이기 때문에 멀리 가지도 못하면서 끊임없이 뛰어야 하는 그 말의 이름에서 따온 것이다. 더 빨리 뛰면 뛸수록 세상 또한 빨리 움직이므로 점점 더 진보가 둔화된다는 것이다.

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역사속 과학인물 - 큰 거울로 배를 태운 그리스 과학자 '아르키메데스(287~212BC)

  • Park, Seong-Rae
    • The Science & Technology
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    • v.30 no.7 s.338
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    • pp.32-34
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    • 1997
  • 목욕하다 알몸으로 뛰어나와 "발견했다"를 외친 기원전 그리스 과학자 아르키메데스는 우리나라에도 일찍이 소개된 인물이다. 거울로 적의 배를 태우고 도르래를 이용해 큰 배를 이동시켰으며 천체를 관측한 혼천의를 발명해 명성을 떨친 과학문명의 개척자이다.

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