• 수산해양기술연구
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• 제16권1호
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• pp.37-42
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• 1980

The purpose of the present study is to find the color induced maximum gathering rate and to observed'the trend of the - gathering rate by using two species of commercial fishes: rock bream, Oplegnathus fasciatus (Temminet et Schlegel) and 'grass puffer, Fugu niphobles (Jordan et Snyder). An experimental tank($360L{\times}50W{\times}55H cm$) was set up in a dark room. An illumination system was attached to the two end of tank to fix horizontal light intensity by co~bination c' one light bulb(20W) and four filters (red, blue, yellow, white) and the five regulating filters in order to fix light intensity. During the experiment water depth was maintained 50 cm lever in the tank. The tank was marked into six longitudinal sections each being 60 em long to observe the distribution of fish. The fish were acclimatized in dark condition for 40 minutes prior to the main experiment. Upon turning on the light, the number of fish in each section was counted 40 times every 30 seconds, and the gathering rates ,were obtain from the average number of fish in each secion. The color induced maximum gathering rate of rock bream appeared to be red, blue yellow and white color orderly.However, that of grass puffer appeared to be blue, white, yellow and red color orderly. Trend of the gathering rate in illumination time showed the remarkable fluctuation in the rock bream and little difference at the two color light sources. However, trend of the gathering rate in illumination time showed the little fluctuation in grass puffer and much difference at the two color light sources.

• 한국노년학
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• 제38권4호
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• pp.1083-1105
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• 2018

본 연구에서는 서울 및 수도권에 거주하는 65세 이상의 노인이 매일 느끼는 일상적 행복감(daily happiness)이 일주일 동안 변동하는지, 매일의 사회적 교류와 신체활동이 개인 내 일상적 행복감의 변동과 어떤 관련성을 갖는지 탐색한다. 다음으로, 노인의 성별, 연령, 학력, 건강에 따라 사회적 교류 및 신체활동과 일상적 행복감 사이의 관련성이 달라지는지 살펴본다. 마지막으로 일상적 행복감의 수준과 변동이 전반적 행복감(global happiness) 수준과 어떻게 관계되는지 확인한다. 이를 위하여 일주일 동안 수집한 생활일지(daily diary) 자료(n=175명${\times}$7일=1225응답)와 동일 기간 동안 활동량계로 수집한 신체활동 자료(n=16명${\times}$7일=112응답)를 활용하여 위계적 회귀분석과 위계적 선형모형(HLM)으로 분석하였다. 분석결과 첫째, 노인의 일상적 행복감 수준은 일주일 동안 변동하고 노인의 젠더와 건강에 따라 일상적 행복감의 수준과 변동 정도에 차이가 있었다. 둘째, 자녀와 대화한 날과 친구와 만난 날 노인의 일상적 행복감이 더 높아졌고, 형제자매와의 만남은 일상적 행복감 수준에 유의한 영향을 미치지 않았다. 하지만 건강상태와의 상호작용항을 투입 결과, 건강하지 않은 노인은 건강한 노인에 비해 형제자매와 만난 날 일상적 행복감이 더 큰 폭으로 높아지는 것이 발견되었다. 셋째, 많이 걸은 날은 일상적 행복감 수준이 높았으며, 저강도 활동시간이 긴 날은 일상적 행복감의 수준이 낮아졌다. 넷째, 일상적 행복감 수준과 전반적 행복감 수준 사이에는 긍정적 관계가 관찰되었으나, 일상적 행복감의 변동 정도는 전반적 행복과 유의미한 관련성을 보이지 않았다. 이상의 결과가 갖는 함의와 후속연구에 대한 제언을 제시하였다.

• 수산해양기술연구
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• 제54권3호
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• pp.217-223
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• 2018

Overfishing capacity has become a global issue due to over-exploitation of fisheries resources, which result from excessive fishing intensity since the 1980s. In the case of Korea, the fishing effort has been quantified and used as an quantified index of fishing intensity. Fisheries resources of coastal fisheries in the Korean waters of the East Sea tend to decrease productivity due to deterioration in the quality of ecosystem, which result from the excessive overfishing activities according to the development of fishing gear and engine performance of vessels. In order to manage sustainable and reasonable fisheries resources, it is important to understand the fluctuation of biomass and predict the future biomass. Therefore, in this study, we forecasted biomass in the Korean waters of the East Sea for the next two decades (2017~2036) according to the changes in fishing intensity using four fishing effort scenarios; $f_{current}$, $f_{PY}$, $0.5{\times}f_{current}$ and $1.5{\times}f_{current}$. For forecasting biomass in the Korean waters of the East Sea, parameters such as exploitable carrying capacity (ECC), intrinsic rate of natural increase (r) and catchability (q) estimated by maximum entropy (ME) model was utilized and logistic function was used. In addition, coefficient of variation (CV) by the Jackknife re-sampling method was used for estimation of coefficient of variation about exploitable carrying capacity ($CV_{ECC}$). As a result, future biomass can be fluctuated below the $B_{PY}$ level when the current level of fishing effort in 2016 maintains. The results of this study are expected to be utilized as useful data to suggest direction of establishment of fisheries resources management plan for sustainable use of fisheries resources in the future.

• 대한기계학회논문집B
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• 제21권2호
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• pp.213-223
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• 1997

Premixed flame is better than diffusion flame to accomplish a high loading combustion. Since the turbulent characteristics of unburned mixture has a great influence on the flame structure, it is general that many researchers realize a high loading combustion with strengthening turbulent intensity of unburned mixture. Because turbulent premixed flame reacts efficiently on the condition of distributed reaction region, we made high turbulent premixed flame in the doubled impingement field. We investigated turbulent characteristics of unburned mixture with increasing shear force and visualized flames with direct and Schlieren photographs. And the combustion characteristics of flame was elucidated by instantaneous temperature measurement with a thermocouple, by ion currents with a micro electrostatic probe, by radical luminescence intensity and local equivalence ratio. Extremely strong turbulent of small scale is generated by impingement of mixture, and turbulent intensity of unburned mixture increased with the mean velocity. As a result of direct photographs, visible region of flame became longer due to increasing central direction flux. But as strengthed turbulent intensity, visible region of flame turned to shorter and reaction occurred efficiently. As strengthened turbulent intensity of mixture with increasing flux of central direction, maximum fluctuating temperature region moved to radial direction and fluctuation of temperature became lower. The reason is influx of central direction which caused flame zone to move toward radial direction, to maintain flame zone stable and to make flame scale smaller.

• 대한기계학회논문집A
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• 제23권7호
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• pp.1139-1146
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• 1999

Reliability analysis of structures based on fracture mechanics requires knowledge on statistical characteristics of the parameter C and m in the fatigue crack growth law, $da/dN=C({\Delta}K)^m$. The purpose of the present study is to investigate if it is possible to predict fatigue crack growth rate by only the fluctuation of the parameter C. In this study, Paris-Erdogan law is adopted, where the author treat the parameter C as random and m as constant. The fluctuation of crack growth rate is assumed only due to the parameter C. The growth resistance coefficient of material to fatigue crack growth (Z=1/C) was treated as a spatial stochastic process, which varies randomly on the crack path. The theoretical crack growth rates at various stress intensity factor range are discussed. Constant ${\Delta}K$ fatigue crack growth tests were performed on the structural steel, SM45C. The experimental data were analyzed to determine the autocorrelation function and Weibull distributions of the fatigue crack growth resistance. And also, the effect of the parameter m of Paris' law due to variation of fatigue crack growth resistance was discussed.

• 대한기계학회논문집B
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• 제27권5호
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• pp.561-568
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• 2003

An experiment using high preheated air in a turbulent non-premixed flame was performed to investigate the effects of high preheated air on the combustion characteristics. Combustion using high preheated and diluted air with flue gas is a new technology which enables NO emission to be reduced. In this study, Na was used as diluent and propane as fuel. Combustion characteristics, especially the distributions of the flame temperature, NO concentration and OH radical intensity were examined under the condition of 300 K, 600 K, 1000 K in terms of the combustion air temperature, and also under the condition of the dilution level from 21% to 13% in terms of oxygen concentration. As the preheated air temperature increased, it appeared that the flame length became shorter, maximum flame temperature increased, the reaction region moved to upstream, and NO concentration increased, but the flame temperature's fluctuation was reduced. In opposite, it was shown with decrement of oxygen concentration at the maximum temperature that both maximum value and the gradient of the flame temperature decreased, and NO emission also decreased considerably, but its fluctuation became larger, being inclined to be unstable.

• International Journal of Automotive Technology
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• 제6권5호
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• pp.453-460
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• 2005

The tumble or swirl flow is used to promote mixing of air and fuel in the cylinder and to enlarge turbulent intensity in the end of the compression stroke. Since the in-cylinder flow is a kind of transient state with rapid flow variation, which is non-steady state flow, the tumble or swirl flow has not been analyzed sufficiently whether they are applicable to combustion theoretically. In the investigation of intake turbulent characteristics using PIV method, typical flow characteristics were figured out by SCV configurations. An engine installed SCV had higher vorticity and turbulent strength by fluctuation and turbulent kinetic energy than a baseline engine, especially near the cylinder wall and lower part of the cylinder. Above all, the engine with SCV 8 was superior to the others in aspect of vorticity and turbulent strength. For energy dissipation, a baseline engine had much higher energy loss than the engine installed SCV because flow impinged on the cylinder wall. Consequently, as swirl flow was added to existing tumble flow, it was found that fluctuation increased and flow energy was conserved effectively through the experiment.

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.79-92
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• 2021

Venturi tube is based on turbulent flow, whereby the microbubbles can be generated by the turbulent fragmentation. This phenomenon is common in several venturi bubblers used by the nuclear, aerospace and chemical industries. The first objective of this paper is to study the liquid-phase velocity field experimentally and develop correlations for the turbulent quantities. The second objective is to research velocity field characteristics theoretically. Stereoscopic PIV measurements for the velocity field have been analyzed and utilized to develop the turbulent kinetic energy in the venturi tube. The tracking properties of the tracer particles have been verified enough for us to analyze the turbulence field. The turbulence kinetic energy has a bimodal distribution trend. Also, the results of turbulence intensity along the horizontal direction is gradually uniform along the downstream. Both the mean velocity and the fluctuation velocity are proportional to the Reynolds number. Besides, the distribution trend of the mean velocity and the velocity fluctuation can be determined by the geometric parameters of the venturi tube. An analytical function model for the flow field has been developed to obtain the approximate analytical solutions. Good agreement is observed between the model predictions and experimental data.

• Nuclear Engineering and Technology
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• 제54권1호
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• pp.207-219
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• 2022

The suppression of high-intensity blob structures in the scrape-off layer (SOL) by ion-cyclotron range of frequencies (ICRF) power, leading to a decrease in the turbulent fluctuation level, is observed first in the Experimental Advanced Superconducting Tokamak (EAST) experiment. This suppression effect from ICRF power injection is global in the whole SOL at EAST, i.e. blob structures both in the regions that are magnetically connected to the active ICRF launcher and in the regions that are not connected to the active ICRF launcher could be suppressed by ICRF power. However, more ICRF power is required to reach the full blob structure suppression effect in the regions that are magnetically unconnected to the active launcher than in the regions that are magnetically connected to the active launcher. Studies show that a possible reason for the blob suppression could be the enhanced E_r × B shear flow in the SOL, which is supported by the shaper radial gradient in the floating potential profiles sensed by the divertor probe arrays with increasing ICRF power. The local RF wave power unabsorbed by the core plasma is responsible for the modification of potential profiles in the SOL regions.

• Journal of Oral Medicine and Pain
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• 제20권2호
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• pp.327-334
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• 1995

In order to observe the influence of pulsed Nd:YAG laser at its out-of-contact with dentin on tooth temperature, we have applied pulsed Nd:YAG laser to 2mm thick dentin sample at a point of contact and from a distance of 1mm, 2mm, 3mm and 4mm with an energy of 0.3W, 0.5W, 0.8W, 1.5W and 2.0W. They were exposed to periods of 3 seconds, 6 seconds, 9 seconds and 15 seconds respectively and measured temperature changes. The results as follows : 1. When the time ad intensity of power were constant, the temperature changes on dentin of tooth depended on the distance. The temperature increased when the laser intensity increased bu two other conditions were contact. 2. At the point of contact, the temperature has risen over $5^{\circ}C$ regrdless of intensity of the power or the time. However, there was $5^{\circ}C$ fluctuation with 0.3 W for 3 seconds treatment. 3. The temperature change was less than $5^{\circ}C$ thermal change at the distance of 1mm and 2mm respectively when lased for 3 seconds, 6 seconds, 12 seconds and 15 seconds with 0.3 W. Similar results were observed at 3 and 6 seconds treatment with 0.5 W and at 3 seconds treatment with 0.8 and 1.0W respectively. 4. It showed less than 5(C thermal change when lased for 3 seconds, 6 seconds, 9 seconds, 12 seconds and 15 seconds with 0.3W at the distance of 3mm and 4mm. The same results were seen in 3 seconds, 6 seconds and 9 seconds treatment with 0.5W and in 3 seconds with 0.8W and 1.0W respectively. As we have seen the above, the results has indicated that pulsed Nd:YAG lasing at its off contact on dentin of 2mm thickness will not cause irreversible changes if lasing intensity, lasing distance and lasing time are appropriate.