• 한국전산유체공학회지
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• 제11권2호
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• pp.49-55
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• 2006

This study investigates the oscillatory thermal convection of a fluid with Pr=0.02 in a wide-gap horizontal annulus with constant heat flux inner wall. When Pr=0.02, dual steady-state flows are not found. After the first Hopf bifurcation from a steady to a time-periodic flow, five successive period-doubling bifurcations are recorded before chaos. The power spectrum shows the $period-2^4\;and\;2^5$ flows clearly, and a window of period $3{\times}2^3$ flow is found in the chaotic regime. The approximate value of the Feigenbaum number for the last three period-doubling bifurcations is 4.76. The transition route to chaos of the present simulations is consistent with the period-doubling route of Feigenbaum.

• 교육시설 논문지
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• 제27권2호
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• pp.79-86
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• 2020

Since the introduction of the new Variation Type school, few studies have focused on students' adaptation to the changes in their learning environments at school. This paper is based on the Stage-Environment Fit theory, which asserts that a successful school life(in terms of motivation to learn) is ensured only when the school environment meets the social and emotional needs of students. Focusing on the third-grade student's adaptation to a new Variation Type school during their middle school period, the following conclusions were drawn. First, the transition to a new Variation Type school during middle school is much more difficult than adjusting to a new Variatio Type school upon admission to middle school. Second, this difficulty in adaptation is caused by socio-emotional dissatisfaction in adolescent students, for whom deconstruction of previous friendships can hinder motivation to learn. Third, third-grade students who experienced stress due to spatial changes tended to have a negative attitude towards the new Variation Type itself as they feel more tired from failing to use the space properly. Fourth, to transition successfully to a new Variation Type school, socio-emotional problems must be solved through the reduction of scale of the homebase, and the provision of various choices increasing the number of homebase.

• 전력전자학회논문지
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• 제4권6호
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• pp.561-569
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• 1999

최근에 유도 전동기의 고효율 구동을 위하여 ZVT(Zero Voltage Transition) 언버터에 대한 연구가 활발히 진행되고 있으며 또한 많은 토폴로지가 제안되었다. 하지만 기존의 ZVT 인버터는 보조공진 회로부분에 과도한 컴포년트의 추가사용으로 인하여 가격상승 및 제어회로가 복잡해지는 문제점이 있다. 이의 문제점을 해결하기 위하여 본 연구에서는 보조 공진 수위치 하나만을 사용하는 다이오드 브릿지-타입 ZVT 인버터를 제안하고, 이의 동작을 이론적으로 해석하였으며, ZVT용 보조공진회로의 설계 방법에 대하여 논하였다. 또한 제안된 ZVT 인버터가 최적의 조건으로 구동하기 위한 공진기간 가변제어에 대해 논의하고 이의 유용성을 시뮬레이션 및 실험을 통하여 입증하였다.

• 한국음향학회지
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• 제28권3호
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• pp.273-278
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• 2009

주파수 분석을 통해 음성과 음악의 특성을 살펴보면, 대부분 악기는 특정 주파수 소리를 지속적으로 내도록 고안되어 있다는 것을 알 수 있고, 음성은 조음 현상에 의해서 점차적인 주파수 변화가 발생하는 것을 알 수 있다. 본 논문에서는 이러한 음성과 음악이 갖고 있는 주파수 변화 특성을 이용하여 음성과 음악을 구별하는 방법을 제안한다. 즉, 음성과 음악을 구분해 주는 특성 값으로서 주파수 변화율을 사용하고자 한다. 제안한 주파수 변화율인 STR (spectral transition rate) 기반의 SMD (speech music discrimination) 실험 결과, 기존의 알고리즘보다 빠른 응답 속도에서 상대적으로 높은 성능을 보임을 알 수 있었다.

• 대한교통학회지
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• 제23권7호
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• pp.43-52
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• 2005

실시간 신호제어군의 결합 및 분리를 통한 실시간 연동신호교차로군 조절은 최근에 강조되고 있는 첨단교통신호제어시스템의 기능 중 하나이다. 필요에 따라 연동축 및 연동방향을 능동적으로 조절하는 과정에서 신호제어군의 실시간 분리 결합 상황이 발생하며, 이때 필수적으로 옵셋을 재조정을 위한 '옵셋전이시간'이 소요된다. 이 때 '옵셋전이시간'이 필요이상 긴 경우 비효율적인 신호운영변수가 장시간 적용됨으로 인하여, 필요이상 짧은 경우 갑작스런 신호시간 변화에 따른 교통흐름 장애 (turbulence)로 인하여 해당 구간 신호제어 운영 효율성이 저하될 수 있다. 현재의 국내 실시간 신호제어시스템은 3주기에서 5주기에 걸쳐 '옵셋전이시간'을 적용할 것을 개략적으로 권고하고 있으나 해당분야에서의 공학적 연구가 미비하다. 본 연구에서는 네 가지 다른 옵셋전이시간(한 주기길이, 두 주기길이, 세 주기길이, 네 주기길이)를 활용하는 네 가지 다른 옵셋전이방법의 성능을 CORSIM 모의실험 환경에서 CORSIM RTE 기능을 이용하여 분석하고 비교하였다. 설정된 총 15가지 상이한 교통소통 상황을 토대로 다양한 무작위난수를 적용하는 모의실험을 수행하며 수집된 평균 차량지체자료를 통계 분석한 결과 한 주기 길이 옵셋전이시간이 본 연구에서 설정된 모든 교통상황에서 기타 옵셋전이시간보다 우수하거나(낮은 지체도) 적어도 동일한 것으로 분석되었다. 본 연구는 한 주기 '옵셋전이길이' 적용을 옵셋전이 적용지침으로 사용할 것을 제안한다.

• 복식
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• 제1권
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• pp.131-150
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• 1977

The new sense of costume is controlled by silhouette. The sense of the times is sensitively reflected in silhouette. For we can perceive the transition of the times through silhouette it is significant to know what course of changes the western costume, which almost became the international costume today, had been going through. I began with the definition and condition of silhouette in this study of silhouette. I took a general survey of silhouette study-ing various kinds of silhouette and the relation between the material and silhouette. I sought the factors which causec the changes in costume and also studies the process of the changes The process of the costume changes is studied by the order of ancient times, mediaeval times, mordern ages and present days. I selected one representative silhouette of women's costume of each period. The darpery form of the ancient time's costume became the tunic form and the tunic form became the tight tunic form today. From this we can perceive that the Gothic period was the limitation of westrn costume. It means that the ancient times was the period of drapery, the midiaeval times was the period of transition from tunic into tight tunic and the modern ages is the period of development of tight tunic. In Egyptian period thin materials were used for costume which was worn in exposed style. In Greek period the costume had the drapery style. The Roman's magnificent costume resembled the Greek's. The mediaeval costume was formed in Byzantium where the northern Europe style of costume was mixed with the gay oriental costume. The Romanesque and Gothic period followed the Byzantine period completing the midiaeval costume. Tight tunic is developed in modern ages. Italian fashion of tight tunic was the first fashion of the modern ages. Germanic and spanish fashion came after it. As Baroque period opened the French royal costume became magnificent and added Brition fashish to it. With the commencement of the modern ages the royal fashion came to an end. Modernages became peaple's period and the costume was simplified. After the First world wav designers and fashion books appeared with the development of technology. Thus the period of fashion industry came. For the designers in 20th country competed to create new designs, the fashion was changed year by year. The simplicity and practicality are not ignored in design, arid the designers added more atristic sense to dresses.

• Fibers and Polymers
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• 제2권2호
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• pp.98-107
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• 2001

The phase transition behavior isothermal micro-phase separation kinetics of polyester-based thermoplastic elastomer were studied using the synchrotron X-ray scattering(SAXS) method. The structural changes occurring during heating period were investigated by determining the changes of the one-dimensional correlation function, interfacial thickness and Porod constant. Based on the abrupt increases of the domain spacing and interfacial thickness, a major structural change occurring well below the melting transition temperature is suggested. Those changes are explained in terms of melting of the thermodynamically unstable hard domains or/and the interdiffusion of the hard and soft segments in the interfacial regions. SAXS profile changes during the micro-phase separation process were also clearly observed at various temperatures and the separation rate was found to be sensitively affected by the temperature. The peak position of maximum scattering intensity stayed constant during the entire course of the phase separation process. The scattering data during the isothermal phase separation process was interpreted with the Cahn-Hilliard diffusion equation. The experimental data obtained during the early stage of the phase separation seems to satisfy the Cahn-Hilliard spinodal mechanism. The transition temperature obtained from the extrapolation of the diffusion coefficient to zero value turned out to be about 147$\pm$$2^{\circ}$, which is close to the order-disorder transition temperature obtained from the Porod analysis. The transition temperature was also estimated from the inveriant growth rate. By extrapolating the inveriant growth rate to zero, a transition temperature of about 145$\pm$$\pm$$2^{\circ}$ was obtained.

• 대한한방부인과학회지
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• 제23권2호
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• pp.154-160
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• 2010

Purpose: This study was done to report the progress of treatment with oriental medicine on a woman who complained of irregular menstruation in menopausal transition. Methods: The patient in this case was treated with Chokyungjongoktanggamibang, acupuncture and moxibustion. And to assess the effectiveness of this treatment, we evaluated the ovarian function by using hormone assay. Results: During treatment period the patient had three times of uterine bleeding, two of the three seemed like normal menstrual bleeding. And analyzing the hormone assay, estraiol level was increased and FSH, LH levels were decreased significantly. However a month after treatment end, estradiol level was decreased and FSH, LH levels were incresead as the levels in menopausal transition or menopause state. And the patient had no more uterine bleeding since last one according to follow up by phone-call. Conclusion: In this study, the progress of ovarian function was specified with hormonal changes after treatment of oriental medicine during menopausal transition. And further studies are needed to find the more appropriate clinical approach for women in menopausal transition.

• 임상간호연구
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• 제25권3호
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• pp.237-250
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• 2019

Purpose: The aim of this study was to investigate the satisfaction of newly graduated nurses with educational programs and their experiences in role transition. Methods: Data were collected from November 1 to December 15, 2018 and 483 new graduate nurses working at 15 tertiary hospitals and 10 general hospitals participated. For data collection, self-report questionnaires including the Casey-Fink Graduate Nurse Experience Survey tool and satisfaction with education were used. Data were analyzed using descriptive statistics, t-test, and one-way analysis of variance. Results: Satisfaction with education ranged from 3.09 to 3.27, and satisfaction with preceptors was 3.45(maximum 4). The skill that new nurses ranked as most difficult during the first 3 months was charting/documentation, and throughout a whole year, the top 4 difficult skills were cardiopulmonary resuscitation/emergency response, ventilator care, end-of-life care, and prioritization/time management. In comfort/confidence, new graduates felt most comfortable with support and least comfortable with patient safety. More than 50 percent of new graduates experienced stress during role transition, and the most frequently experienced stressors were related to job performance and personal life. Levels of satisfaction with education and comfort/confidence differed according to the hospital type and number of preceptors for new nurses. Conclusion: In order to facilitate the transition of new graduate nurses to professional nurse, an extended period of education, systematic and standardized transition programs, and continuous support during the first year of practice are required.

• 정보보호학회논문지
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• 제17권6호
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• pp.77-87
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• 2007

IPv6가 현재의 IPv4 프로토콜을 완전히 대치하기 위해서는 상당한 시일이 소요될 것으로 예상된다. 이 기간 동안 인터넷은 두 개의 IP 프로토콜이 함께 사용될 것이다. 이 두 프로토콜의 공존을 위해 IETF에서는 여러 가지 IPv4/IPv6 전이기법을 표준화하였다. 하지만 전이 기법에 주로 사용되는 터널링 때문에, IPsec 적용과 IPv6 패킷 필터링에 관한 보안 문제가 발생할 수 있다. 본 논문에서는 이러한 보안 문제 해결을 위해, 내부 헤더 필터링과 전이 기법 전용 필터링의 두 가지 패킷 필터링 개선 기법을 제안하였다. 또한 제안한 기법을 리눅스 넷필터(Netfilter) 프레임워크에서 구현하였으며, IPv4/IPv6 전이 기법 테스트 환경에서 구현 기능을 테스트하고, 시험적인 성능 평가를 수행하였다. 이러한 기능 시험과 성능 평가를 통해, 주 논문의 패킷 필터링 개선 기능이 시스템의 큰 성능 저하 없이, IPv4/IPv6 전이 기법의 패킷 필터링 문제들을 해결할 수 있음을 보였다.