• Steel and Composite Structures
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• 제18권6호
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• pp.1465-1478
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• 2015

The effect of cutting off fibers on transient load in a polymeric matrix composite lamina was studied in this paper. The behavior of fibers was considered to be linear elastic and the matrix behavior was considered to be linear viscoelastic. To model the viscoelastic behavior of matrix, a three parameter solid model was employed. To conduct this research, finite difference method was used. The governing equations were obtained using Shear-lag theory and were solved using boundary and initial conditions before and after the development of break. Using finite difference method, the governing integro-differential equations were developed and normal stress in the fibers is obtained. Particular attention is paid the dynamic overshoot resulting when the fibers are suddenly broken. Results show that considering viscoelastic properties of matrix causes a decrease in dynamic load concentration factor and an increase in static load concentration factor. Also with increases the number of broken fibers, trend of increasing load concentration factor decreases gradually. Furthermore, the overshoot of load in fibers adjacent to the break in a polymeric matrix with high transient time is lower than a matrix with lower transient time, but the load concentration factor in the matrix with high transient time is lower.

• 한국항행학회논문지
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• 제19권3호
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• pp.244-249
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• 2015

본 연구는 지구의 높은 고도에서 핵폭발로 발생된 HEMP (high-altitude electromagnetic pulse)가 발생 즉시 지면에 도달하면서 OFDM (orthogonal frequency division multiplexing) 시스템에 미치는 영향을 분석한다. HEMP가 미치는 영향은 BER (bit error rate) 특성으로 확인한다. 시스템의 Q-factor로 인해 간섭 영향의 지속시간이 변화가 발생한다. Q값이 작으면, 간섭으로부터의 회복이 빠르고, Q값이 크면 영향을 받는 지속시간이 길어져 회복이 300~600%까지 늦어짐을 확인하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제20권5호
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• pp.58-67
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• 1996

In the present study, the pressure distribution, wall shear stress distribution and friction factor of developing turbulent pulsating flows are investigated theoretically and experimentally in the entrance region of a square duct. The pressure distribution for turbulent pulsating flows are in good agreement with the theoretical values. The time-averaged pressure gradients of the turbulent pulsating flows show the same tendency as those of turbulent steady flows as the time-averged Reynolds number $(Re_{ta})$ increase. Mean shear stresses in the turbulent pulsating flow increase more in the inlet flow region than in the fully developed flow region and approach to almost constant value in the fully developed flow region. In the turbulent pulsating flow, the friction factor of the quasi-steady state flow $({\lambda}_{q, tu})$ follow friction factor's law in turbulent steady flow. The entrance length of the turbulent pulsating flow is not influenced by the time-averaged Reynolds number $(Re_{ta})$ and it is about 40 times as large as the hydraulic diameter.

• Journal of Mechanical Science and Technology
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• 제17권2호
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• pp.197-206
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• 2003

It is intended to retrieve the time history of displacement from measured acceleration signal. In this study, the word retrieving means reconstructing the time history of original displacement signal from already measured acceleration signal not just extracting various information using relevant signal processing techniques. Unlike extracting required information from the signal, there are not many options to apply to retrieve the time history of displacement signal, once the acceleration signal is measured and recorded with given sampling rate. There are two methods, in general, to convert measured acceleration signal into displacement signal. One is directly integrating the acceleration signal in time domain. The other is dividing the Fourier transformed acceleration signal by the scale factor of - $\omega$$^2$and taking the inverse Fourier transform of it. It turned out both the methods produced a significant amount of errors depending on the sampling resolution in time and frequency domain when digitizing the acceleration signals. A simple and effective way to convert the time history of acceleration signal into the time history of displacement signal without significant errors is studied here with the analysis on the errors involved in the conversion process.

• 한국운동역학회지
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• 제25권1호
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• pp.11-19
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• 2015

Objective : The purpose of this study was to analyze the correlation between physical factors (X-factor, X-factor stretch) and club factors (club speed, ball speed, club path, smash factor, vertical launch angle, spin rate, flight time, total length) during impact and it affect on the total distance of the ball during a golf driver swing. Background : There were not enough studies that analyzed the correlation between physical factors(X-factor, X-factor stretch) and club factors(club speed, ball speed, club path, smash factor, launch angle, spin rate, flight time, total length) during a purpose swing to increase total distance. Method : For this study, 9 right handed professional male golfers (KPGA) were chosen. The test subject group used their own drivers and each took a total of 10 swings. These swings consisted of 5 purpose swings to increase total distance and 5 normal swings. Results : The purpose swing to increase total distance showed larger physical factors(X-factor, X-factor stretch) compared to a normal swing however the results were not statistically significant. Total distance increased during a purpose swing as a result of ball and club speed. Conclusion : The results showed that club factors, ball speed and club speed contributed the most in affecting the total distance of the ball during a purpose swing.

• 한국실내디자인학회논문집
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• 제22권3호
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• pp.195-204
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• 2013

Today, the children's museum evolved from place of exhibition for seeing and feeling, to that of exhibition for searching and touching, or so-called the hands-on exhibition. This will allow for grabbing the interest from children and provide an opportunity for learning by an actual experience at this intellectual and benign environment. But in this modern society that constantly undergoes evolution even as we speak, it is not an easy task to bring our children to museums, because they are vastly exposed to various media. Moreover, if the children who visited museums carelessly bypass the specific areas intended for exhibition, the educational purpose of "enhanced learning effect with hands-on experience" is easily underachieved. According to children's visual stimuli, their behavioral charactoristics are appeared to freewill curiosity but they show shorter elapsed time(impermanence), intensity(stubbornness), frequent occurrence(frequentness) and changeable (translatability). So, We need Improvement of visual image affordance through the measurement of stay time. Firstly, five factors are extracted by factor analysis on twenty questions based on visual image factors; Color accessability and Satistaction(factor1), brightness and color harmony(factor2), feeling on harmonization of color and stay time(factor3), simplex & complex of space(factor4), feeling on scale(factor5) Secondly, the following result are derived through a distribution chart on an exhibition room of K-museum. As shown above, this study based on various analyzed aspects proposes the directions of a color image plan to improve stay time in exhibition space of children museums with a hope to support educational goals of experience education-focused children museums.

• 육아정책연구
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• 제12권3호
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• pp.55-76
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• 2018

본 연구는 2012년 전국 규모로 실시된 5차 한국아동패널의 자료를 활용하여 만 4세 유아의 개인적 특성요인(기질), 가족특성변인(모 취업여부), 생활시간변인(육아지원기관 이용시간, 기관에서의 낮잠시간, 전자매체 사용시간)이 유아의 야간수면시간에 어떠한 영향을 미치는지와 가장 높은 설명력을 가지는 변인이 무엇인지 살펴보고자 하였다. 그 결과, 유아의 개인적 특성변인, 가족특성변인, 생활시간변인이 야간수면시간과 부적 상관관계가 있는 것으로 나타났다. 상대적 설명력은 생활시간변인, 가족특성변인 순으로 높았으며 개인적 특성변인은 유의하지 않았다. 이에 따라 유아가 가정에서 충분한 야간수면을 취할 수 있도록 부모는 적절한 생활환경을 제공해 주어야하며 자녀의 양육을 지원하기 위해 가정과 기관의 연계 강화, 부모의 근무시간 유연제 등의 제도 확산과 시행의 필요성이 제기된다.

• 한국안전학회지
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• 제8권3호
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• pp.78-82
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• 1993

The object of research is detecting and eliminating the unsafty factor in shortest time through a decision making simulation under uncertainty using simulation method The decision making simulation using C language Is used to analyze data from several factors which affects the crane breakdown under unsafe situation. Through this research, the following conclusions are obtained. first, the safety manager or the person can estimate the time required to handle the unsafe factors. Secondly, The decision making can be accomplished by minimizing the time required under uncertainty by analyzing them.

• 한국인터넷방송통신학회논문지
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• 제10권4호
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• pp.137-143
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• 2010

본 논문은 채널에서 발생되는 진폭과 위상 찌그러짐을 보상하기위한 MCMA (Modified Constant Modulus Algorithm)의 비용 함수에서 weighting factor에 의한 자기 적응 등화의 성능을 비교한 것이다. MCMA 는 기존 방식인 CMA 의 비용 함수를 개선하여 등화기의 출력에서 진폭과 위상에 대한 오차 함수를 최소화할 수 있으며, 이때 weighting factor 의 값이 이용된다. 등화기의 성능을 비교할 때 initial state와 steady state로 분류하고 미리 정해진 레벨까지의 수렴 시간과 수렴 속도 및 안정된 등화 상태를 나타내며, 이들은 weighting factor에 의해 결정된다. 컴퓨터 시뮬레이션을 통하여 weighting factor에 따라 이들 2 가지 state 에 대한 각각 상이한 결과를 확인할 수 있었다. 본 결과를 이용하여 사용되는 통신 채널의 환경에 따라 weighting factor 값을 적절히 선택한다면 고품질의 디지털 정보 전송이 가능하게 될 것으로 기대된다.

• 가정과삶의질연구
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• 제21권2호
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• pp.213-220
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• 2003

In this study, I analyzed dual-career commuting couples time use. Concretely, this study compared the husband with the wife on the becoming a commuter family, the living apart on weekdays. And it examined time use on weekdays and weekends by the time amount of each activities and the ratio of actor on each hour. The survey participants included 131 married people who were dual-career commuting couple and who were maintained separate residence and work place. The major findings are as follows: First, weekday separation of the dual-career commuting couples is largely due to career. This kind separation is mostly due to sociostructural labor market factor and individual factor to increasing working women. Second, 94.6%(53) of male participants were resident living apart from their family on weekdays. Third, the most wives mentioned some kind of emotional liberation such as freedom on weekdays. Finally, there was gender difference in the time spent on each activities when dual-career commuting couples are living together and they are apart. Especially the most gender difference on weekdays is household work time and leisure time.