• Journal of Bio-Environment Control
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• v.30 no.4
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• pp.383-392
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• 2021

It has been known that oyster mushrooms cultivated in facilities with thermal insulation have been strongly affected by inner environments. Forced air-circulation fans exert much direct influence on disturbing air inside the facility so the matter is of particular interest. This study is carried out to investigate the measured levels of air uniformity in a cultivation facility for oyster mushroom in the various cases that reversibly controlled air-circulation fans which drove the flow in the upward and reverse direction by turn and unidirectional fans by which the wind blew upwards only were operated from July 1 to 10. The actual survey for the selection of ongoing operation cases presented that farmers, even though there were some discrepancies, have made use of fans in a way that it paused for 5-30min after running for 5-15min by turn. The level of air uniformity in the case of adopting reversible fans revealed a slight difference of 1.4-1.8℃ (Temp.) and 7.8-8.7% (R.H.) under the condition of not using a cooler during the investigation period. By contrast, unidirectional fans showed a noticeable difference of 3.2-3.7℃ and 14.0-15.4%, which meant that air uniformity driven by reversible fans much more increased compared to that for unidirectional fans. Among the twenty operational applications considered for reversible fans, the circumstance that the wind blew upwards for 10-15min and ceased for 5-10min and blew again in the reverse direction for 10-15min in succession gave minor improvements at the level of air uniformity, but at present there was somewhat difficult to make decision on which cases were optimally best. It seems necessary that the effects of reversible fans on air uniformity as well as qualities of oyster mushrooms have to be appraised in the cultivation period and the flow visualization needs to be done to ascertain the performance of air mixture.

• Journal of Bio-Environment Control
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• v.27 no.2
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• pp.147-157
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• 2018

With the rapid development of the 4th industrial revolution, the large-sized facilities of agriculture have been developed with high-technologies. However, it is difficult to maintain the optimum environment in large-sized facilities. Although it is essential to control micro-climate properly in large-sized facilities, there are a lot of problems to utilize high-technologies and equipment because of insufficient education for farmers. Most farms have limitations to access to their farm because of prevention of epidemics, exposure of management know-how, and so on. Especially, it is difficult to understand internal environmental factors (airflow, temperature, humidity, etc.) for farmers because these factors are invisible. Recently, Virtual reality technology which allows users to experience various phenomena directly is attracting attention. Virtual reality is very useful technology to visualize airflow and temperature distribution and so on. However, there is no cases applied this technology to agricultural facilities. In this study, research trends of virtual reality in various fields were investigated. In particular, the limitation and possibility of virtual reality technology were analyzed for educating farmers. Finally, the development of virtual reality contents for smart-farm facility were suggested.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.12
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• pp.1-8
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• 2006

An experimental study was carried out in order to investigate the influence of Reynolds number on the near-wake of an oscillating airfoil. An NACA 0012 airfoil was sinusoidally pitched at the quarter chord point, and is oscillated over a range of instantaneous angles of attack of $\pm$6$^{\circ}$. An X-type hot-wire probe was employed to measure the near-wake of an oscillating airfoil, and the smoke-wire visualization technique was used to examine the flow properties of the boundary layer. The free-stream velocities were 1.98, 2.83 and 4.03 m/s and the corresponding chord Reynolds numbers were 2.3${\times}10^4$, 3.3$\times$104 and 4.8${\times}10^4$, respectively. The frequency of airfoil oscillation was adjusted to fix a reduced frequency of K=0.1. The results show that the properties of the boundary layer and the near-wake can dramatically be distinguished in the range of Reynolds numbers between 2.3${\times}10^4$ and 3.3${\times}10^4$, on the other hand, it is similar in the cases of Re=3.3$\times$104 and 4.8$\times$104. This is caused by that the unsteady separation point is dramatically delayed in case of Re= 2.3${\times}10^4$.

• 한국해양학회지
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• v.25 no.2
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• pp.62-73
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• 1990

An experimental study is performed in order to catch the characteristics of the flow field at arrested salt wedge, using a rectangular open channel. Arrested salt wedge is generally so stable that the observations are easy, but velocities and interfacial waves are measured with the aid of visualization method, by injection of fluorescent dyes. The density interface, which is defined as the zone of maximum density variation with depth, exists in about 0.5 cm below the visual interface, and vertical density profile is quite well satisfied with Homeborn model. Interfacial layer has high turbulent intensity and its thickness decreases as the overall Richardson number increases and has magnitude of roughly 17% of upper layer. Cross-sectional velocity distribution just shows the influence of a side-wall friction and in the upper layer vertical velocity profile also becomes uniformly as Reynolds number increases, but in the lower layer it shows nearly parabolic type. Supposes that we divide salt wedge into three domains, that is, river mouth, intermediate and tip zone, entertainment coefficient is small at the intermediate zone and large at the river mouth and the tip zone. River mouth or intermediate zone has comparatively stable interface and capillary wave therefore s produced and propagated downstream. On the other hand, tip zone is very unstable, cusping ripple or bursting ripple is then produced incessantly. Arrested salt wedge form is nearly linear and has no relation to densimetric Froude number and Reynolds number.

• Proceedings of the Korean Society of Community Living Science Conference
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• 2009.09a
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• pp.98-98
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• 2009

농촌 지역의 인구 감소 및 그에 따른 지자체의 위기의식이 심화됨에 따라 국내에서도 지역마다 각종 인구 늘리기 시책을 실행하고, 중앙에서 도시민 농촌유치 프로그램 지원 시범사업을 기획하는 등 지역 발전의 기본 요건이 되는 인구 감소의 해결을 위한 노력이 가시화되고 있다. 이에 따라 본 연구는 일본의 정주촉진 정책 사례에 대한 고찰을 통해 국내 정책에의 시사점을 도출하고자 한다. 시마네현은 일본 혼슈의 동해 연안에 위치하고 있으며, $6707.26km^2$의 면적에 약 74만 2천 명의 인구(2005)가 살고 있는 지역이다. 시마네현의 총 토지면적 중 약 80%가 산림면적이며, 경지면적은 41,000ha로 약 6%를 차지하고 있다. 이 중 논이 80%를 차지하여 논농사 중심의 농업이 이루어지고 있으며, 풍요로운 수산자원을 보유하고 있어 어업활동도 활발하다. 이러한 시마네현에서는 UI턴의 촉진을 위해 '산업체험사업'을 1996년부터 시행하고 있는데, 농림어업에 관한 산업체험을 실시하고, 체험 후의 거주지로 빈집을 활용하는 사업이다. 현 외 거주자가 시마네현 내에서 일정시기 산업체험을 하고자 할 경우, 월 50,000엔이 지급되며, 거주지 확보가 어려울 경우 트레일러하우스나 빈집활용주택, 공영주택 등을 임대해주고 있다. 또 시마네 현 내에서 30세 미만의 청년 미취업자가 일정기간 산업체험을 실시할 경우, 체험에 필요한 경비의 일부를 제공해주고 있다. 그간의 실적을 보면 연간 평균 105명이 체험에 참가하고 있으며, 2000년 이후 정착률은 50%를 넘고 있다. 총 259개의 체험 장소에서 월 평균 4명이 참가하고 있으며, 업종별 참가자수는 농업 및 기타(관광, 전통공예), 어업, 임업, 축산업의 순서로 많은 것으로 나타나고 있다. 또한 시마네현의 고츠시에서는 '도시와의 공생 교류' 실현을 위한 9가지 중점시책을 설정하고 그에 따른 사업을 실행하고 있다. 농산어촌의 취락을 유지하는 것이 첫 번째 중점시책으로서 이를 위해 빈집을 활용한 정주와 교류가 활발히 이루어질 수 있도록 주거 정보를 수집, 관리, 웹을 통해 제공하고 있으며, 농지 유동화 및 농림수산물의 직거래 시스템 확립에 주력하고 있다. 이 밖에도 UI턴자 확보를 위해 지역에서 살고, 일하고, 즐기는데 대한 일체적인 정보 제공 시스템을 마련하고 있으며, '고향교육'을 통해 지역에 대한 애착심을 기르는 동시에 지역에서의 취업 지향을 높이는데 힘쓰고 있다. 농촌 정주촉진을 위한 사업 내용면에서는 일본과 우리나라 간 큰 차이가 없다. 그러나 사업에의 의지와 방향 설정, 사업 추진체계 및 운영방식 등에서 발견되는 차이를 주시함으로써 농촌 지역 인구 증가에 보다 실질적으로 기여할 수 있는 정책으로 만들어가야 할 것이다.

• Journal of Biomedical Engineering Research
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• v.23 no.6
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• pp.467-475
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• 2002

Hyperthermia using transrectal thermal probes has been used for a noninvasive treatment of prostate diseases. However it is known that heating the rectal wall at excessively high temperature can lead to destruction of the rectal mucous membrane. and it is difficult to maintain an optimum temperature over the entire prostate. Thus, a more accurate understanding of the heat transfer mechanism between prostate and hyperthermia system is needed Numerical analysis was performed to investigate how the cold/warm stimulations on the prostate surface affect the temperature distribution in the prostate model. The general purpose software "FLUENT" was used for obtaining a finite volume solution to the unsteady conduction equation and to calculate the time-varying temperature in the prostate. Effects of the warm/cold stimulations and the stimulation frequency on the temperature distribution were simulated. and we visualized how hyperthermia affected the inside of the prostate. It was found that the effect of hyperthermia by using a typical heating method is limited due to the low thermal conductivity of the prostate. Consecutive repetitions of warm and cold stimulations were considered to provide the thermal irritations inside a prostate. The effects of temperature difference and duration of warm/cold stimulations were investigated, and basic data for the optimum period and effective patterns of stimulations were obtained. A simplified bioheat equation was also solved to describe effects of the blood flow on the blood-tissue heat transfer. The effect of blood flow was not dominant compared to that of warm/cold stimulations. These results might be used as data for design of prostate treating probe, prostatic therapy and thermal stimulation effects on the prostate.

• Fire Science and Engineering
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• v.33 no.5
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• pp.37-47
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• 2019

In the present study, the influences of the fire curtain and natural vent in a theater fire were investigated through the numerical simulation of a reduced-scale model of a theater fire using the Fire Dynamics Simulator (FDS). Based on a previous experimental study using the reduced-scale model, the 1/14 reduced-scale model and its conditions were constructed according to the law of similarity with a real-scale theater. Through a series of numerical simulations, the smoke movements were visualized, and the temperatures in the stage and auditorium, mass flow rate of the outflow through natural vent, and time at which smoke started moving toward the auditorium were measured and analyzed. The general trends on the effects of the fire curtain and natural vent during the theater fire predicted by the present numerical simulation were similar to the previous experimental results. For quantitative comparison of the present numerical simulation and previous experimental results, the mean percentage errors of temperatures in the stage and auditorium, and the mass flow rate of outflow through the natural vent were calculated. The present numerical simulation results showed good agreement with previous experimental results with reasonable accuracy.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.1
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• pp.27-39
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• 1996

The effects of free surface and a strut on the lifting characteristics on a fin attached at the mid-chord of the strut are investigated experimentally in a circulating water channel. Variation of lift force on the fin is investigated with respect to free stream velocity(V), angle of attack of the fin(${\alpha}$) and ratio of the submergence depth of the fin to the chord of the fin(H/C). Attentions are focused on the lifting characteristics of the fin at shallow depths of submergence. Visualization of the free surface deformation along the strut and of the streamline about the fin is made in order to examine the inflow angle to the fin. Lift force on the fin alone i.e. in absence of the strut is also measured to investigate the difference in lifting characteristics of the fin caused by the strut. The results show that lift forces over the fin are largely affected by a free surface in the case of small submergence ratios(HiC<3.0). For HiC>5.0, the effects of the free surface are negligibly small. The inflow angle to the fin is significantly influenced by the strut and flow speed at the shallow depths of submergence. The deformation of the free surface is largely governed by the waves generated by the strut. However, for small submergence depths, the effects of the fin are found also significant.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.4
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• pp.364-372
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• 2012

Transient mixing states of two different fuel oils, dimethylformamide (DMF) oil and JetA1 oil, were investigated by using a color image processing and a neural network. A tank ($D{\times}H$, $310{\times}370mm$) was filled with JetA1 oil. The DMF oil was filled at a top tank, and was mixed with the JetA1 oil in the tank mixing tank via a sudden opening which was performed by nitrogen gas with 1.9 bar. An impeller was rotated with 700 rpm for mixing enhancements of the two fuel oils. To visualize the mixing state of the DMF oil with the JetA1 oil, the DMF oil was coated with Rhodamine B whose color was red. A LCD monitor was used for uniform illumination. The color changes of the DMF oil were captured by a camcoder and the images were transferred to a host computer for quantifying the information of color changes. The color images of two mixed oils were captured with the camcoder. The R, G, B color information of the captured images was used to quantify the concentration of the DMF oil. To quantify the concentration of the DMF oil in the JetA1 oil, a calibration of color-to-concentration was carried out before the main experiment was done. Transient mixing states of DMF oil with the JetA1 oil since after the sudden infiltration were quantified and characterized with the constructed visualization technique.

• Fire Science and Engineering
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• v.24 no.1
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• pp.90-94
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• 2010

In this study it is intended to review the moving characteristics of smoke by performing visualization simulation for the calculation of the optimal smoke exhaust air volume in case a fire occurs in tunnels where transverse ventilation is applied, and to obtain basic data necessary for the design of smoke exhaust systems by deriving optimal smoke exhaust operational conditions under various conditions. As a result of this study, if it was assumed 0 critical velocity in the tunnel, the smoke exhaust air volume was limited within 250 meter in the road-tunnel disaster prevention indicator and the exhaust efficiency was from 55.1% to 95.8% in the result of this study. If the wind velocity is in the tunnel, the exhaust rate intends to increase rapidly and the exhaust efficiency is decreased. In addition, if the wind velocity is increased, the exhaust rate should be increased in compared with the generation rate of smoke in maximum 1.8 or 1.04 times. In this study, when the wind velocity is in the tunnel, the limited exhaust rate is $84m^3/s{\cdot}250m$. And if it was assumed 1.75 m/s critical velocity in the tunnel, the exhaust rate would be defined $393m^3/s{\cdot}250m$($Q_E$ = 80 + 5Ar).