• 한국추진공학회지
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• 제15권4호
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• pp.41-47
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• 2011

75톤급 개방형 액체로켓 엔진에 장착되는 터보펌프의 터빈은 초음속 충동형 방식이다. 본 연구에서는 터빈 로터 앞전 두께가 성능에 미치는 영향을 실험을 통해 살펴보았다. 터빈 시험에서는 2가지 다른 앞전 두께를 가진 로터를 이용해 실험하였으며, 각 로터는 앞전 두께 대 피치비가 30톤 로터 대비 각각 1.9배와 1.4배이다. 시험 결과 로터 두께가 1.4배인 로터의 설계 상사점 효율이 1.5% 상승하였고, 동일 회전수에서 최대 효율이 나타나는 압력비도 완전팽창비 쪽으로 증가하였다.

• Bulletin of the Korean Chemical Society
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• 제31권11호
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• pp.3252-3258
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• 2010

In this study, the effects of the various parameters of spinning and drawing processes on the properties of polyester full drawn yarn (FDY) prepared by steam processing during high-speed spinning were investigated using several techniques. The wet shrinkage ratio of the FDY was able to be manipulated by controlling the temperature and draw ratio. The FDY made using the steam high speed spinning technique exhibited identical properties (such as tenacity, elongation, and wet shrinkage ratio) to that of regular FDY, made using the spin-draw process. FDY prepared using the steam process during high-speed spinning showed excellent dyeability. The dye pick-up of the polyester yarn spun at high-speed spinning was found to be improved when dyed under an atmospheric pressure of $100^{\circ}C$. This result was the same as regular FDY dyed under a high pressure of $130^{\circ}C$.

• Advances in concrete construction
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• 제10권2호
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• pp.93-104
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• 2020

Basalt fiber is an eco-friendly fiber and comparatively newer to the world of fiber-reinforced polymer (FRP) composites. A limited number of studies have been reported in the literature on the strengthening of reinforced concrete (RC) beams with basalt fiber reinforced polymer (BFRP). The present experimental work explores the feasibility of using the BFRP strips for shear strengthening of the RC beams. The strengthening schemes include full wrap and U-wrap. A simple mechanical anchorage scheme has been introduced to prevent the debonding of U-wrap as well as to utilize the full capacity of the BFRP composite. The effect of varying shear span-to-effective depth (a/d) ratio on the behavior of shear deficient RC beams strengthened with BFRP strips under different schemes is examined. The RC beams were tested under a four-point loading system. The study finds that the beams strengthened with and without BFRP strips fails in shear for a/d ratio 2.5 and the enhancement of the shear capacity of strengthened beams ranges from 5% to 20%. However, the strengthened beams fail in flexure, and the control beam fails in shear for a higher a/d ratio, i.e., 3.5. The experimental results of the present study have been compared with the analytical study and found that the latter gives conservative results.

• Structural Monitoring and Maintenance
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• 제5권4호
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• pp.489-506
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• 2018

This paper reported test of full-scale cables attached with four types of dampers: viscous damper, passive Magneto-Rheological (MR) damper, friction damper and High Damping Rubber (HDR) damper. The logarithmic decrements of the cable with attached dampers were calculated from free vibration time history. The efficiency ratios of the mean damping ratios of the tested four dampers to theoretical maximum damping ratio were derived, which was very important for practical damper design and parameter optimization. Non-ideal factors affecting damper performance were discussed based on the test results. The effects of concentrated mass and negative stiffness were discussed in detail and compared theoretically. Approximate formulations were derived and verified using numerical solutions. The critical values for non-dimensional concentrated mass coefficient and negative stiffness were identified. Efficiency ratios were approximately 0.6, 0.6, and 0.3 for the viscous damper, passive MR damper and HDR damper, respectively. The efficiency ratio for the friction damper was between 0-1.0. The effects of concentrated mass and negative stiffness on cable damping were positive as both could increase damping ratio; the concentrated mass was more effective than negative stiffness for higher vibration modes.

• 임산에너지
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• 제21권3호
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• pp.46-53
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• 2002

본 연구에서는 인공피음에 의해서 광조건을 3단계로 달리하여 생육시킨 펜둘라자작나무, 층층나무, 물푸레나무를 대상으로 생장량과 물질생산량 등 특성을 조사하여 생리ㆍ생태적 특성을 밝히고자 연구를 실시하였다. 인공피음처리에 따른 조사 대상 수종의 묘고생장 차이는 거의 없었으며, 근원직경의 생장은 전광처리구가 투광율 7-10%의 피음처리구보다 상대생장율이 29-32% 이상 우수한 생장율을 나타냈다. 하지만 층층나무의 근원직경생장은 투광율 26-34% 처리구에서 높은 생장율을 나타냈다. 대부분의 수종에서 피음처리 수준에 따른 광량감소와 함께 총 물질생산량도 감소하였고, 잎과 줄기의 비율이 뿌리에 비해 증가하는 경향을 보였다. 유묘의 T/R율은 대부분의 수종이 피음의 강도가 강할수록 T/R율이 높아지는 경향으로 전광처리구의 0.51∼l.13보다 투광율 7-10%의 강피음처리구가 1.00∼2.27로 높게 나타냈다. 전체적으로 비교할 때 인공피음처리에 의한 광량이 감소할수록 SLA, LAR, LWR은 광환경의 변화에 따른 피음의 강도가 강할수록 통계적으로 유의적인 차이를 보이며 증가하였다.

• 가족자원경영과 정책
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• 제23권3호
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• pp.89-107
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• 2019

This study aimed to examine the impact of academic background on full-time employment and on other important issues concerning job security and care faced by single-parent youths. The study alse aimed to verify the effect of related support on full-time employment. The analysis targeted 262 single parents under 24 years of age who were raising their children, and the main results were as follows: First, the ratio of adulthood was high for those who were employed, and the academic achievement of full-time workers was also significantly high. However, the rate of discontinuities in school was also high among those who were employed, especially those seeking full-time employment, whose desire to stay in school was higher than that of other difficulties of single, teenage parents. Second, the vocational education experience of single, teenage parents was 32 percent overall, and the rate of those seeking full-time employment was also relatively high, reaching 44 percent. However, the results of this study did not verify the direct effect of vocational education experience on full-time employment nor the interaction effect of the academic background. Therefore, a thorough review of the effectiveness of a vocational education program for young, single parents wishing to gain employment is necessary. Third, the overall rate of those who received a public nanny service was 31 percent, while the rate of full-time workers who experienced this service was significantly higher reaching 59 percent. In the research model verification, single parents who received a public nanny service were 3.8 times more likely to get a full-time job than those who did not, and receiving a public nanny service showed a regulatory effect between academic studies and full-time employment. The higher the academic level of the parents, the higher their possibility of full-time employment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.295-297
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• 2007

We design a new rate-3/2 full-diversity orthogonal space-time block code (STBC) for QPSK and 2 transmit antennas (TX) and 4 transmit antennas (TX) by enlarging the signalling set from the set of quaternions used in the Alamouti[I] and extendedcode and using additional members of the set of orthogonal matrices or Quasi-orthogonal matrices and higher than rate-5/4. Selective power scaling of information symbols is used to guarantee full-diversity while maximizing the coding gain (CG) and minimizing the transmitted signal peak-to-minimum power ratio (PMPR). The optimum power scaling factor is derived analytically and shown to outpetform schemes based only on constellation rotation while still enjoying a low-complexity maximum likelihood (ML) decoding algorithm.

• 한국통신학회논문지
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• 제41권3호
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• pp.298-300
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• 2016

본고에서는 중계 공격 성공확률을 낮추기 위해 RFID 리더가 무요청(void challenge)을 보내더라도 태그가 응답하는 거리 제한 프로토콜을 제안한다. Full challenge 비율에 따른 공격 성공 확률을 분석하고, 기존의 프로토콜과 비교 분석하여 제안 프로토콜의 공격 성공 확률이 낮음을 보인다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 전력전자학술대회 논문집
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• pp.403-404
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• 2013

In this paper, a PCS which consists of high boost interleaved full-bridge converter and single phase half-bridge inverter is proposed. Proposed PCS is using two full bridge converter modules. PCS consists of parallel input / serial output. It can reduce turn ratio of high frequency transformer. In this paper, PCS which is using 1.5[kW] interleaved full-bridge converter and single phase half bridge inverter is designed and verified stability of system through experiment.

• 전력전자학회논문지
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• 제18권5호
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• pp.501-506
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• 2013

A hold-up time compensation circuit is proposed to get high efficiency of the front-end phase-shifted full bridge DC/DC converter. The proposed circuit can make the phase-shifted full bridge front-end DC/DC converter built with 0.5 duty ratio so that the conduction loss of the primary side and voltage stress across rectifier in the secondary side are reduced and the higher efficiency can be obtained. Furthermore, the requirement of an output filter significantly can diminish due to the perfect filtered waveform. A 12V/100A prototype has been made and experimental results are given to verify the theoretic analysis and detailed features.