• Korean Journal of Optics and Photonics
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• v.8 no.4
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• pp.340-344
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• 1997

We proposed and demonstrated a tunable wavelength optical add/drop multiplexer(OADM) employing piezoactuated fiber grating pairs and polarization beam splitters. We used piezostack act as a fiber stretcher, using the fact that the resonant wavelength of the grating can be controlled by the axial strain along the fiber grating. The polarization controlled configuration showed high stability because the reflected signals from the two identical gratings are dropped or added not by interference but by polarizations of the beams. We could add and drop not noly 1549.3nm signal channel(original gratings), but also 1550.1nm(tuned gratings) with PZT actuators and in both cases, we found that the rejection of adjacent channels was more than -26dB, and signal leakage at the gratings was less than -34dB.

• Journal of Food Hygiene and Safety
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• v.36 no.4
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• pp.324-330
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• 2021

In this study, the microbial levels on mixed vegetable salads, fresh fruits, and frozen fruits distributed in Korea were comparatively analyzed by food group, region, and quarter. Samples were collected from big markets in large cities from 2018 to 2019 and used for microbiological analysis. The levels of aerobic bacteria for mixed vegetable salads, fresh fruits, and frozen fruits were 6.48, 5.07, and 3.78 log CFU/g, respectively. As a result of analyzing the quarterly contamination levels of aerobic bacteria, the first quarter contamination level was 5.12 log CFU/g while the second quarter showed 6.26 log CFU/g, the third quarter 5.73 log CFU/g, and the fourth quarter 4.42 log CFU/g. A higher number of aerobic bacteria was observed in the second and third quarters when the temperature was higher. There was no difference in the number of bacteria by region. The levels of the coliform group were 1.98 - 3.93 log CFU/g in all samples, and Escherichia coli was detected at 1.38 log CFU/g in 3 out of 27 mixed vegetable salads. Since the mixed vegetable salad and fresh fruit used in this study exceeded the standard (3 log CFU/g) for unheated foods and E. coli was detected in three fresh fruits, stricter hygiene management in the manufacturing stage of salads and fresh fruit is required.

• The Korea Swine Journal
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• v.12 no.7 s.131
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• pp.100-101
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• 1990

우선 3/4분기 돼지값은 2/4분기에 비해 약보합세가 될 것으로 예상된다. 그 주요 이유는 1년중 여름 및 장마로 돼지고기 소비가 크게 감소될 것으로 보이며,특히 돼지고기 수입에 따라 돼지사육농가들의 출하가 늘고 장기적으로 사육을 기피할 것으로 보이기 때문이다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.4 s.119
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• pp.416-422
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• 2007

In this paper, a broadband 2-way power divider which can be used from 20 MHz to 500 MHz in the V/UHF band is designed using transmission-line transformer and ferrite toroid. A 2:1 impedance transformer instead of the conventional 4:1 impedance transformer is realized and this 2:1 transformer is connected with the conventional bridge-type 2-way divider to form a 2-way power divider. Insertion loss of about 3.5 dB, isolation of less than -10 dB, and return loss of less than -10 dB in most band of interest are measured.

• Journal of the Korean Society for Railway
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• v.18 no.3
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• pp.175-185
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• 2015

Generally, in the train area, switch tracks have required high reliability because this system is directly associated with derailment. Especially, switch tracks of Maglev vehicles must be moved in terms of the whole geometric characteristics, in which the bogies are encased in the switch track. For this reason, switch track was constructed with steel lighter than concrete girders. But, the steel switch track was weak because of structural vibration as well as structural deformation. Therefore, it is important to predict the levitation stability when a vehicle passes over flexible switch track. The aims of this paper are to develop a coupled dynamic model to describe the relationship between a Maglev vehicle and switch track and to predict the levitation stability. In order to develop the coupled dynamic model, a three dimensional vehicle model was developed based on multibody dynamics; a switch model was made using the modal superposition method. And, the developed model was verified using comparison measured data.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.3
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• pp.433-440
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• 2002

A branched crack in a semi-infinite plate under uniform tension and bending moment is considered in this study By using the superposition, the stress and moment intensity factors for the branched crack subjected to uniform tension and bending moment we evaluated. The stress intensity factors we obtained by using the finite element method and the J-based mutual integral. The moment intensity factors are calculated by extrapolating the values of the moment new the crack tip. Numerical results lot the normalized stress and moment Intensity factors we shown as functions of the ratio of branched crack length to main crack length and the branching angle.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.3
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• pp.399-409
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• 1998

In this paper, the broad-band design theory for weakly-coupled Tap-Off for CATV systems has been described and the transmission line impedance matching method has been proposed. The fabricated weakly-coupled Tap-Offs based on the above theory and method have been much improved in the frequency characteristics compared with conventional ones. Thus, the useful bandwidth of weakly-coupled Tap-Offs have been extended from 5 to 2000 MHz. It is also recognized that turn numbers of the coils composing the transformer are not integers but 0.9, 1, 1.9, 2, 2.9, etc., in the actual circuits. Further, the practical measurements of the frequency characteristics for a fabricated weakly-coupled Tap-Off show very good agreements with theoretical results, and hence, the validity of the proposed design theory and transmission line impedance matching method have been confirmed.

• KAPE Magazine
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• s.163
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• pp.4-5
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• 2010

한국농촌경제연구원이 지난 2월 25일에 발표한 2010년 2/4분기 축산관측에 따르면 '10년 3~5월 수소 한우 평균은 530~550만원으로 전망됐다. 돼지의 '10년 3~4월 성돈 가격은 110kg 기준으로 32~33만원, 4월 육계 산지가격은 2,000~2,200원으로 전망했다. 본지는 축종별 전망 내용을 요약 게재한다.

• Digital Contents
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• no.8 s.147
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• pp.114-116
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• 2005

지식정보사회에서 정보의 효율적인 관리와 활용은 국가 경쟁력을 이끄는 주요한 축이다. 따라서 정보의 저장·관리·가공·유통 전반에 걸친 데이터베이스 산업은 명실공히 지식정보사회의 기간산업으로 주목받고 있다. 최근 한국데이터베이스진흥센터에서 실시한‘3분기 데이터베이스 산업 기업경기실사지수(DB-BSI) 및 이용환경지수(DB-CSI) 조사’결과를 통해 이러한 데이터베이스 산업의 현주소를 살펴본다.

• Digital Contents
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• no.8 s.159
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• pp.92-95
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• 2006

국내 산업 경기가 고전을 면치 못하고 하향세를 지속하고 있는 가운데서도 데이터베이스 산업은 3분기에 도호전세를 이어갈 전망이다. 한국데이터베이스진흥센터는 지난 6월5일부터 6월 28일까지 데이터베이스산업체 305개 및 데이터베이스정보서비스이용자 220명을 대상으로‘ 데이터베이스산업기업경기실사지수(DB-BSI) 및 이용환경지수(DB-CSI)’를 조사했다. 이번 조사 결과를 토대로 국내 데이터베이스 산업의 2006년 2~3분기 현황을 짚어봤다.