• 토지주택연구
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• 제10권1호
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• pp.25-32
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• 2019

In this study, the case analysis data on underground temperature are presented. In addition, numerical analysis of the ventilation load reduction plan was derived according to the residence schedule change for the building with cool tube. The research scope and method are as follows. The overall system principle was examined through reviewing the theory of the Cool tube system. Case study and analysis were conducted. Numerical simulation was used to examine the change in energy usage. Also, the change of load energy in case of varying amount of ventilation was derived based on actual building room schedule. When the Cool tube system was applied to the residential buildings, the cooling load was reduced from 3,331 kW to 193 kW, which showed a reduction effect of about 90%.The heating load was reduced from 42,276kW to 32,575kW by 23%.Also, result shows that the cooling load decreased by 24% and the heating load decreased by 66% when the number of ventilation according to the occupancy schedule was applied.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.616-621
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• 2003

Fluid-elastic instability is believed to be a cause of the large-amplitude vibration and resulting rapid wear of heat exchanger tubes when the flow velocity exceeds a critical value. For sub-critical flow velocities, the random turbulence excitation is the main mechanism to be considered in predicting the long-term wear of steam generator tubes. Since flow-induced interactions of the tubes with tube supports in the sub-critical flow velocity can cause a localized tube wear, tube movement in the clearance between the tube and tube support as well as the normal contact force on the tubes by fluid should be maintained as low as possible. A simplified method is used for predicting fretting-wear damage of the double $90^{\circ}$U-bend tubes. The approach employed is based on the straight single-span tube analytical model proposed by Connors, the linear structural dynamic theory of Appendix N-1300 to ASME Section III and the Archard's equation for adhesive wear. Results from the presented method show a similar trend compared with the field data. This method can be utilized to predict the fretting-wear of the double $90^{\circ}$U-bend tubes in steam generators.

• 대한기계학회논문집
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• 제18권5호
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• pp.1218-1226
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• 1994

The shock tube is a useful device for investigating shock phenomena, spray combustion, unsteady gas dynamics, etc. Therefore, it is necessary to analyze exactly the flow phenomena in shock tube. In this study, the mechanics of its reflected shock zone has been investigated by using of the one-dimensional gas dynamic theory in order to estimate the transition from initial reflection of shock wave region. Calulation for four kinds of reflected shock tube temperature (i.e. (a) 1388 K (b) 1276 K (c) 1168 K (d) 1073 K) corresponding to the experimental conditions have been carried out sumarized as follows. (1) The qualitative tendency is almost the same as in that conditions in region of reflected wave region. (2) High temperature period (reflected shock wave temperature) $T_{5}$, exists 0-2.65 ms. (3) Transition period from temperature of reflection shock wave is far longer than the calculated one. This principally attributed to the fact that the contact surface is accelerated, also, due to the release of energy by viscoity effect. This apparatus can advance the ignition process of a spray in a ideal condition that involved neither atomization nor turbulent mixing process, where, using a shock tube, a column of droplets freely from atomizer was ignited behind a reflected shock.

• 한국수학사학회지
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• 제21권3호
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• pp.1-30
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• 2008

뉴턴의 중력이론의 성공은 수학물리학을 태동시키는 바, 최초로 19세기 초의 분자력의 모델성립에 중요한 요소로 등장하였다. 라플라스는 여기서 회전타원체의 작용이라는 모델을 이용하였고 회전타원체의 작용은 이계편미분방정식으로 표현이 되었다. 이것을 풀어서 유체를 담은 용기의 기하학적 모습과 와 유체와 고체의 접촉각에 대응시켰다. 알 수 없는 분자간거리는 추상적이고 미지의 힘 함수 $\varphi(f)$를 써서 표현하여, 분자 작용반경이라는 개념을 도입하여 이론적인 포텐셜 함수의 이론적인 토대를 구축하였다. 뉴턴의 중력이론은 라플라스이론에서 완성을 이루었고, 이후 분자력의 모델로서 작용을 하였다. 라플라스-영의 모세관이론은 수학적으로는 극소 곡면론에서 물리학적으로는 표면장력현상으로 설명이 된다.

• Structural Engineering and Mechanics
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• 제69권2호
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• pp.205-219
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• 2019

This paper analyzes nonlinear free vibration of the circular nano-tubes made of functionally graded materials in the framework of nonlocal strain gradient theory in conjunction with a refined higher order shear deformation beam model. The effective material properties of the tube related to the change of temperature are assumed to vary along the radius of tube based on the power law. The refined beam model is introduced which not only contains transverse shear deformation but also satisfies the stress boundary conditions where shear stress cancels each other out on the inner and outer surfaces. Moreover, it can degenerate the Euler beam model, the Timoshenko beam model and the Reddy beam model. By incorporating this model with Hamilton's principle, the nonlinear vibration equations are established. The equations, including a material length scale parameter as well as a nonlocal parameter, can describe the size-dependent in linear and nonlinear vibration of FGM nanotubes. Analytical solution is obtained by using a two-steps perturbation method. Several comparisons are performed to validate the present analysis. Eventually, the effects of various physical parameters on nonlinear and linear natural frequencies of FGM nanotubes are analyzed, such as inner radius, temperature, nonlocal parameter, strain gradient parameter, scale parameter ratio, slenderness ratio, volume indexes, different beam models.

• 한국산업정보학회논문지
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• 제28권2호
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• pp.31-45
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• 2023

본 연구는 유튜브 이용자의 사용 시간이 양적으로 증대하면서 나타나는 질적 단계와 경로에 주목하였다. 그리고 심리학과 신경과학의 이론을 적용하여 추천시스템의 개인화 알고리즘과 적극이용의 구간을 세분화하였고, 이론연구와 실증연구를 병행하였다. 이론연구에서 심리학과 신경과학의 관점으로 포그의 행동모델(FBM), 가변적 보상, 도파민 중독을 적용하였다. 포그의 행동모델(FBM)은 연관 콘텐츠 제시 기능인 개인화 추천 알고리즘이 트리거(계기)로서 쉬운 클릭을 유발하고, 가변적 보상은 검색하는 콘텐츠에 대한 예측불가능성으로 동기부여의 효과성을 높이며, 도파민 중독은 도파민 신경을 자극하면 지속적 적극적으로 콘텐츠를 소비하게 하는 것으로 요약된다. 본 연구는 개인화 추천 알고리즘과 적극이용 구간에서 콘텐츠의 이용 목적을 심리적 측면에서 처음이용, 재이용, 지속이용, 적극이용의 4단계로 구분하고, 경로를 분석하였다는 점에서 학문적 실무적 기여를 할 것으로 기대한다.

• 한국도서관정보학회지
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• 제52권4호
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• pp.277-307
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• 2021

본 연구의 목적은 정부출연연구기관에서 제공하는 과학 유튜브 채널 현황을 파악하고 이용자들의 이용 행태에 대해 조사, 분석하는 것이다. 26개 정부출연연구기관의 유튜브 채널 구독자수, 조회수, 콘텐츠 수를 수집하였고, 이용과 충족 이론을 바탕으로 이용자 연구를 설계하고, 반구조화 면담조사를 진행하였다. 연구 결과에 따르면, 정부출연연구기관 유튜브 채널은 홍보형, 강의형, 오락형, Vlog형, Q&A형 등 다양한 방식의 콘텐츠를 제공하고 있으나, 기관이나 연구소에 대한 홍보형 콘텐츠가 주를 이루고 있었다. 이용자들의 주요 이용 동기는 과학 정보획득이었으며 정부출연연구기관 유튜브가 과학 정보에 대한 지적 호기심을 충족시켜주며 신뢰성 있는 정보를 제공한다는 점에서 긍정적으로 인식하고 있었다. 그러나 이용자들은 콘텐츠 대부분이 오락적인 요소가 부족하고 재미가 없다고 언급했으며, 과학 유튜브 채널 자체의 홍보가 부족하여 많은 사람들에게 알려지지 못하고 있다고 지적했다. 본 연구 결과는 정부출연연구기관 유튜브 채널의 현황을 전체적으로 파악했다는 점에서 의의가 있으며, 과학대중화를 위한 다양한 유튜브 콘텐츠 개발에 기초자료로 활용될 수 있을 것으로 기대한다.

• 한국농공학회지
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• 제18권4호
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• pp.4209-4217
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• 1976

The purpose of this thesis is to search for the determination method of pumping rates in the existing tube wells for irrigation. Pumping tests were carried out for the twelve test tube wells which were selected in the provinces of Kyounggi, Kangwon, Chungbuk and Chungnam. The depths, static water levels, pumping levels, drawdowns and yields of tube wells were measured in the pumping tests, and a centrifugal pump with 3 inches diameter, a 5 HP motor and a 90$^{\circ}$ V-notch were used in the pumping tests. The average coefficient of transmissibility calculated by Chow's and Jacob's methods is 0.0336 square meter per second, and the average pumping rate calculated by Thiem's, Smreker's, Brinkhaus' and Theis' formulae, is 919 cubic meter per day, Therefore, the ground water storage in the test areas is comparatively abundant. Correlation between pumping rates and depths of tube wells is not in existence. Also, correlation between pumping rates and the thickness of aquifer is not found in this experiment. This shows that the depths of some tube wells are deep and their thicknesses of aquifer are thick, but their ground water storages are poor, and that the depths of some tube wells are shallow and their thicknesses of aquifer are thin, but their ground water storages are abundant. It seems that the test tube wells are influenced by the peculiar characteristics that the ground water in the test areas is free ground water in alluvium layer closely related with surface water. As drawdown increases, pumping rate decreases, and as the coefficient of transmissibility increases, pumping rate also increases. Namely, there are negative correlation between pumping rate and drawdown, and positive correlation between pumping rate and the coefficient of transmissibility. Judging from the results of the pumping tests in these tests areas, the pumping rate calculated by the formula, {{{{ { Q}_{m } =Q { ( { { S}_{ m} } over { TRIANGLE S } )}^{ { 2} over {3 } } }}}} used traditionally, is likely to be higher than real pumping rates. The formula, {{{{ { Q}_{m } =Q { { H}^{ 2} } over { (2H- TRIANGLE S) TRIANGLE S} }}}} derived from Thiem's theory, is looked upon as the reasonable one to detemine pumping rates in the existing tube wells for irrigation.

• 디지털산업정보학회논문지
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• 제17권3호
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• pp.39-61
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• 2021

This study aims to examine the effect of the Mindfulness for YouTube users. Recently, video sharing platforms have grown rapidly with YouTube, and YouTube has grown rapidly despite the emergence of various video sharing platforms. Which YouTube represents these changes, provides an environment where anyone can make and distribute videos. And through these advantages, many viewers are coming in and more creators are making videos. The purpose of this study is to understand the influence factors of YouTube service in Korea and to clarify the causal relationship between the factors that affect the continued use intention through usefulness, confirmation, and satisfaction. For this reason, presented a research model that applied key variables of the Mindfulness theory, which emphasized that users should be aware of their emotions. In order to empirical verification the research model of this study, a questionnaire was conducted for university students and general office workers who had experience using YouTube. As a result, first decentered attention has been shown that has no positive effect on perceived usefulness and confirmation. Second, non-judgmental acceptance has benn shown that has a postitive effect on perceived usefulness and confirmation. Third, current self-perception has been shown that has no positive effect on perceived usefulness and confirmation. Fourth, concentration has been shown that has no positive effect on perceived usefulness and confirmation. And Mindfulness has been shown that has a positive effect on satisfaction and perceived usefulness. Through this, it is important to use YouTube to use what users feel is important, and it is important to determine whether the video is helpful to them when accepting content and make them expect the next video.

• Applied Microscopy
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• 제12권1호
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• pp.1-10
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• 1982

Serous otitis media is closely related with auditory tube function, but its etiology and pathogenesis are not clearly defined yet. So we tried to prove the theory of hydrops ex vacuo via the experimental study with cats by means of obstructing the pharyngeal orfice of the auditory tube and observe the serial changes in tympanic mucosa through light and electron microscopy. The results are as follows; 1. We confirmed the production of serous otitis media with auditory tube obstruction and have a new understanding of auditory tube function in middle ear aeration. 2. The effusion in serous otitis media was produced from the next day of experiment and increased till the fourteenth day, but decreased after the spontaneous perforation of ear drum. 3. Through the light microscopy, we observed the increasement of the sercretory cells including goblet cells, epithelial hyperplasia, capillary proliferation and invasion of inflammatory cells. 4. Through the elctron microscopy, we observed the protrusion of secretory cells, blobs in cilia, loss of cilia, increasement of vesicles, vacuoles and dense bodies in ciliated cells and Invasion of inflammatory cells. With above results, we concluded that aeration through auditory tube is the most important factor in serous otitis media and presumed the effusion was secreted by secretory cells.