• 대한조선학회논문집
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• 제54권4호
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• pp.329-334
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• 2017

As the motion response of heave for floating bodies on the water surface is relatively large near the natural frequency, it is necessary to predict its value accurately from the stage of initial design. Bodies accelerating in fluid experience force acted upon by the fluid, and this force is quantified by using the concept of added mass. For predicting the natural frequency of heave we need to know the added mass, which is given as a function of frequency, and hence the natural frequency can be obtained through only by iteration process, as was pointed out by Lee (2008). His method was applied to circular cylinders, and two dimensional cylinders of Lewis form by making use of the Ursell-Tasai method in the previous works, Lee and Lee (2013), Kim and Lee (2013), and Song and Lee (2015). In this work, a similar algorithm employing the concept of strip method is adopted for predicting the heave natural frequency of KCS(KRISO Container Ship), and the obtained computational result was compared with other existing experimental data, and the agreement seems reasonable. Furthermore, through the error analysis, it is shown that why the frequency corresponding to the local minimum of the added mass and the natural frequency are very close. And it seems probable that we can predict the heave natural frequency if we know only the local minimum of added mass and the corresponding frequency under a condition, which holds for ship-like bodies in general.

• 한국철도학회논문집
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• 제16권3호
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• pp.163-168
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• 2013

장기간 수명주기(Life Cycle)을 갖는 도시철도차량은 초기 도입비용보다 유지보수비용이 많은 비중(60%~70%)을 점유하고 있으므로 효율적인 유지보수 연구를 통하여 유지보수 비용의 절감과 대형시스템의 수명연장을 추구하는 일이 무엇보다 시급하다. 이를 위해 신뢰성기반의 유지보수체계에 대해 여러 산업분야의 국내 외 사례 조사 분석을 통해 도시철도차량 신뢰도/가용도 관리시스템을 구성하였다. 본 연구에서는 이 시스템이 가져야 할 주요 기능을 상세히 정하고 성공적인 시스템 개발이 될 수 있도록 관련 시스템을 개발하였다. 본 논문은 성공적으로 개발이 완료된 도시철도차량 신뢰도/가용도 관리시스템에 관한 내용을 기술한 것이다.

• 반도체디스플레이기술학회지
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• 제9권3호
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• pp.53-58
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• 2010

In this study, we have investigated the effect of the ambient gases on the characteristics of IZO thin films for the OLED (organic light emitting diodes) devices. For this purpose, IZO thin films were deposited by RF magnetron sputtering under various ambient gases (Ar, $Ar+O_2$ and $Ar+H_2$) at $150^{\circ}C$. In order to investigate the influences of the oxygen and hydrogen, the flow rate of oxygen and hydrogen in argon mixing gas has been changed from 0.1sccm to 0.5sccm, respectively. All the samples show amorphous structure regardless of ambient gases. The electrical resistivity of IZO film increased with increasing flow rate of $O_2$ under $Ar+O_2$ while under $Ar+H_2$ atmosphere the electrical resistivity showed minimum value near 0.5sccm of $H_2$. All the films showed the average transmittance over 85% in the visible range. The OLED device was fabricated with different IZO substrates made by configuration of IZO/${\alpha}$-NPD/DPVB/$Alq_3$/LiF/Al to elucidate the performance of IZO substrate. OLED devices with the amorphous-IZO (a-IZO) anode film show better current densityvoltage-luminance characteristics than that of OLED devices with the commercial crystalline-ITO (c-ITO) anode film. It can be explained that very flat surface roughness and high work function of a-IZO anode film lead to more efficient hole injection by reduction of interface barrier height between anode and organic layers. This suggests that a-IZO film is a promising anode materials substituting conventional c-ITO anode in OLED devices.

• 한국컴퓨터정보학회논문지
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• 제18권11호
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• pp.13-21
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• 2013

본 논문은 다양한 분야에서 활용되고 있는 초기의 위성 데이터가 자체적으로 내포하고 있는 많은 왜곡 요소(구름, 광휘 등)에 대한 보정 작업을 클러스터에서 분산 처리함으로써 성능 향상 및 안정성을 제공해 주는 것이 목적이다. 이를 위해 로컬 스토리지와 상태 테이블을 이용한SGE(Sun Grid Engine) 기반 분산 처리 방식을 제안하였고, 시스템으로 구현하였다. 이를 검증하기 위해 7개의 실행노드를 이용한 실험 결과에서는 기존 시스템보다 138.81%의 성능 향상을 가져옴을 알 수 있었으며, 분산 처리 작업에 대한 안정성 또한 확보됨을 보여주었다. 이는 위성 데이터에 대한 분산 처리 작업이 I/O바운드 작업보다는 CPU 바운드 작업에 보다 더 적합하다는 것을 보여주며, 이러한 SGE 기반 분산 처리 방식은 위성영상 데이터를 처리해야하는 다양한 분야에서의 데이터 처리 및 분석 속도 향상을 가져올 수 있고, 더 나아가 근실시간적 서비스를 가능하게 할 것으로 기대한다.

• Journal of the Optical Society of Korea
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• 제18권3호
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• pp.274-282
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• 2014

In this study, closely spaced Au nanoparticles which are arranged in nanocluster (heptamer) configurations have been employed to design efficient plasmonic subwavelength devices to function at the telecommunication spectrum (${\lambda}$~1550 nm). Utilizing two kinds of nanoparticles, the optical properties of heptamer clusters composed of Au rod and shell particles that are oriented in triphenylene molecular fashion have been investigated numerically, and the cross-sectional profiles of the scattering and absorption of the optical power have been calculated based on a finite-difference time-domain (FDTD) method. Plasmon hybridization theory has been utilized as a theoretical approach to characterize the features and properties of the adjacent and mutual heptamer clusters. Using these given nanostructures, we designed a complex four-branch ($1{\times}4$) Y-shape splitter that is able to work at the near infrared region (NIR). This splitter divides and transmits the magnetic plasmon mode along the mutual heptamers arrays. Besides, as an important and crucial parameter, we studied the impact of arm spacing (offset distance) on the guiding and dividing of the magnetic plasmon resonance propagation and by calculating the ratio of transported power in both nanorod and nanoshell-based structures. Finally, we have presented the optimal structure, that is the four-branch Y-splitter based on shell heptamers which yields the power ratio of 23.9% at each branch, 4.4 ${\mu}m$ decaying length, and 1450 nm offset distance. These results pave the way toward the use of nanoparticles clusters in molecular fashions in designing various efficient devices that are able to be efficient at NIR.

• 여성건강간호학회지
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• 제27권3호
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• pp.220-229
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• 2021

Purpose: The world saw a shift into a new society consequent to the coronavirus disease 2019 (COVID-19), which made home quarantine mandatory for a person in close contact with those who tested positive. For children, however, home quarantine was not limited only to themselves but parents, especially mothers were involved and required to quarantine. This qualitative study aims to explore and understand mothers' experience and their related psychosocial issues while caring for their school-aged children in Korea, who had to home quarantine after coming in close contact with COVID-19 positive individuals. Methods: Data were collected from October 2020 to January 2021 via in-depth, semi-structured interviews with nine mothers of children who had to home quarantine. Interviews were conducted face-to-face in an independent space near the participant's home or workplace (n=5) or via online platforms or telephone (n=4). The data were analyzed using thematic analysis through several iterative team meetings. Results: Thematic analysis revealed the following four themes: "Unable to be relieved due to uncertain situations surrounding me," "Blame and hurt toward me, others, and one another," "Pulling myself together for my children in my broken daily life," and "Changes in the meaning of life amid COVID-19." Conclusion: The narratives show that mothers experienced psychosocial difficulties while caring for their children during home quarantine. It is necessary to reduce the social stigma toward individuals in home quarantine and establish policies to ensure work-family compatibility for such mothers.

• 문화기술의 융합
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• 제5권3호
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• pp.191-195
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• 2019

우리나라는 정전으로 남북관계가 대치됨에 따라 남북의 MDL(군사분계선)을 기준으로 남북 간의 전쟁이 언제라도 촉발될 수 있는 위험한 상황에 처해 있다. 또한, 타 국가의 국경과는 달리 남북의 접경지역은 전쟁으로 촉발될 수 있는 생명의 위협을 느낄 수 있는 곳이 최전방 접적지역이다. 접적지역과 같은 특수한 지역에서 근무하는 병사들은 지역적 여건상 접근성이 용이하지 못하여 외출, 외박, 면회가 적은 실정이고, 근무 환경은 야밤에 넓은 숲과 적막함이 넘치고 적과 근접하여 언제 어떤 상황이 일어날지 모르기에 불안함과 외로움 그리고 불안함이 과중 되는 지역이다. 따라서 이곳에서 목숨을 내놓고 국방의 의무를 수행하는 병사들에게 관심을 갖고 병영생활을 안전하고 충실히 마칠 수 있도록 많은 도움이 필요할 것이며, 접적지역 복무병사들의 심리적 적응을 위한 지원이 필요하다.

• 한국해양공학회지
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• 제33권3호
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• pp.300-311
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• 2019

An ROV trencher is a type of heavy-duty work class ROV equipped with high-pressure water jet tools for cutting into the sea floor and burying cables. This kind of trencher is mostly used for PLIB operations. This paper introduces the development of this kind of ROV trencher, which has a 698 kW power system, with a 250 kW hydraulic system and two 224 kW water jet systems. The project was launched in January 2014. After four years of design, manufacturing, and system integration, we carried out two sea trials near the Yeongilman port (about 20-30 m in depth) in Pohang to evaluate the system performance in November 2017 and August 2018. Through tests, we found that most of specifications were satisfied, including a maximum bury depth of 3 m, maximum bury speed of 2 km/h, and maximum forward speed of 1.54 m/s.

• Journal of Astronomy and Space Sciences
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• 제36권1호
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• pp.35-43
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• 2019

The Optical Wide-field patroL-Network (OWL-Net) is a global optical network for Space Situational Awareness in Korea. The primary operational goal of the OWL-Net is to track Low Earth Orbit (LEO) satellites operated by Korea and to monitor the Geostationary Earth Orbit (GEO) region near the Korean peninsula. To obtain dense measurements on LEO tracking, the chopper system was adopted in the OWL-Net's back-end system. Dozens of angle-only measurements can be obtained for a single shot with the observation mode for LEO tracking. In previous work, the reduction process of the LEO tracking data was presented, along with the mechanical specification of the back-end system of the OWL-Net. In this research, we describe an integrity assessment method of time-position matching and verification of results from real observations of LEO satellites. The change rate of the angle of each streak in the shot was checked to assess the results of the matching process. The time error due to the chopper rotation motion was corrected after re-matching of time and position. The corrected measurements were compared with the simulated observation data, which were taken from the Consolidated Prediction File from the International Laser Ranging Service. The comparison results are presented in the In-track and Cross-track frame.

• 한국융합학회논문지
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• 제12권2호
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• pp.221-231
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• 2021

본 논문은 인구이동의 이론에 따라 혁신도시 이전기관 종사자 구성세대의 이동 요인을 추출하고 요인들의 상대적 영향을 설명하고자 하였다. 개인 및 가구변수와 거리와 인구의 중력모델, 네트워크변수, 지방재정·지역경제·교육·문화·주택 등 전입지와 전출지의 상대적 유용성판단의 지역변수를 선정하였다. 종속변수의 이산성과 데이터의 구조를 감안하여 다층로짓모형 구축하였고 최종모형은 확률절편모델을 선택하였다. 실증분석 결과 개인·가구변수에서는 남성보다 여성이, 30대 미만보다는 30-40대가, 대졸이하보다는 박사학위취득자가, 취업한 배우자보다는 미취업배우자의 이전종사자가 주민등록을 더하였다. 지역변수에서는 중력모델과 관련하여 기관까지 거리가 멀수록 주민등록을 더 한 반면, 이전 시기(t-1)의 일반 유입이 클수록 주민등록 이전을 덜 하였다. 지역간 상대적 유용성과 관련하여 전입지의 지역경제, 교육환경, 주거환경이 클수록 이전을 더하였고 지방재정의 경우는 반대였다.