• Journal of Ocean Engineering and Technology
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• v.13 no.1 s.31
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• pp.121-129
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• 1999

Double-diffusive convection with verical temperature and concentration gradients in thermally stratified fluids has been investigated experimentally using an electrochemical technique. Cupric sulfuric-sulffuric acid solution confined between two horizontal copper electrodes was used. The change of thermal and solutal buoyance has no influence on the range of voltage for the limiting current. Due to Soret effect, the onset time of natural convection is delayed as the stabilizing thermal buoyancy decreases. Also it is found that the shrinkage of the unstabilizing solutal buoyancy makes the onset of natural convection retard. Multi-layered convective phenomena do not appear because cupric sulfate-sulfuric acid solution is thermally stratified, and heat diffuses faster than cupric sulfate solfate solution.

• The Journal of Natural Sciences
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• v.12 no.1
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• pp.23-30
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• 2002

Atomic coherences induced by the interaction with light provide new physical properties and optical phenomena. Even though two-photon resonances play important roles in build-up of atomic coherences, only approximate formula for two-photon resonance condition has often been used. In this paper, we present the more accurate two-photon resonance condition and confirm it using numerical simulation. We also studied the effects of laser frequency detuning and intensity on the two-photon resonance .

• Food Science and Industry
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• v.49 no.3
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• pp.40-54
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• 2016

The recent much attention has been given to weight gain of the population and its consequences on the occurrence of diet-related diseases in developed countries. Sugar is considered to be the main culprit of these phenomena. Food manufacturers attempt to provide the consumer with reduced energy products with non-nutritional sugars. Some studies also showed that consumers preferred foods prepared with natural additives rather than chemical ones, due to health reasons. This article reviews issues related to sugar alternatives, as well as their use, health benefits and risks.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.16 no.2
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• pp.166-175
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• 1987

The heat loss of a building within a wind flow field results from convection and natural ventilation. Loss from natural ventilation is much more than one from convection, and the former depends mostly on the pressure distribution at the building surface. Therefore, the objective of the present study is to calculate the pressure distribution and investigate flow phenomena, around the building with a rectangular shape in a two-dimensional turbulent flow field. The finite difference method, modelled upon the turbulence $k-\epsilon$ model, has been applied to the analysis. The results, followed by the changes of Reynolds numbers, inlet flow conditions, and building shapes, have been also obtained, respectively. Various results of the present numerical analysis coincide qualitatively well with earlier reported empirical results.

• Steel and Composite Structures
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• v.48 no.5
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• pp.499-505
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• 2023

Geological hazards in landslide is one of the most extensive and destructive phenomena are among natural disasters. According to the topography high mountains, tectonic activity, high seismicity, diverse conditions Geology and climate, basically China to create a wide spectrum of landslides have natural conditions and these landslides are annual. They cause a lot of financial losses to the country. It is very difficult to predict the time of the landslide, hence the identification landslide sensitive areas and zoning of these areas based on the potential risk is very important. Therefore, it should be susceptible areas landslides should be identified in order to reduce damages caused by landslides find. the main purpose of landslide sensitivity analysis is identification high-risk areas and as a result, reducing damages caused by landslides It is the way of appropriate actions.

• Journal of Fisheries and Marine Sciences Education
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• v.29 no.3
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• pp.702-710
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• 2017

Recently, in many reptiles (14 genera of turtles in five families), common characteristics of incubation temperatures are known to determine the sexes of hatchlings in many species of turtles, including the map turtles, painted turtles and snapping turtles, emys turtle, etc. According to many researcher's reports, in general, incubation at $25^{\circ}C$ (cooler temperatures) produces all or mostly males, however, incubation at $31^{\circ}C$ (higher temperatures) or higher produces all or mostly females. Exceptionally, even cooler temperature ($20^{\circ}C$) produce females, they produced all or mostly females. Accordingly, it is well-known that incubation temperature is the sex determining agent in these turtles. However, this paper presents study of the sex ratio and nest ecology in natural spawning nest: Observations on hatching sex ratios of eggs collected from natural nests of T. sinensis are similar to a previous report of the same genus Trionyx in the soft-shelled turtles. However, this genus (or species) showed some different phenomena to other kinds of turtles such as various kinds turtles mentioned above. After collection of naturally spawned eggs (17 eggs of T. sisnensis) on the natural nests, a laboratory experiment by the constant incubation temperatures was conducted with natural fluctuating soil temperatures in the natural nest with the soft-shelled turtle, T. sinensis. And also laboratory experiments were conducted using constant incubation temperatures of $25^{\circ}C$ (cooler temp.) and $30^{\circ}C$ (higher temp.) with the turtle, T. sinensis. Exceptionally, it was confirmed that the first and second incubation temperatures can't control sex-determination in the freshwater soft-shelled turtle, T. sinensis. The sex ratio approximated 1:1 (${\chi}^2=0.06$, P>0.05 (the Ist experiment). And the sex ratio approximated 1:1 independently of incubation temperature (${\chi}^2=0.33$, P>0.05 (the 2nd experiment). Consequently, temperature has no effect on sex determination in the genus Trionyx in a soft-shelled turtle.

• Journal of the Korean Society of Safety
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• v.36 no.1
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• pp.86-94
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• 2021

Lecture rooms are crowded with many attendees. Moreover, they rely significantly on the natural ventilation through windows for removing and controlling indoor contaminants such as CO₂. With the aim of broadening the understanding of the characteristics of natural ventilation phenomena in lecture rooms, the average individual CO₂ release rates of attendees were measured during the course of a lecture and compared with previously reported CO₂ release rates. In addition, the effects of natural ventilation through windows on the time-variant CO₂ concentrations in the center of the lecture room were measured and analyzed. Moreover, details about the overall and regional CO₂ concentrations, as well as the air flows in the lecture room, were simulated and analyzed with computational fluid dynamics software, Fluent 2020 R2. It was found that the average individual CO₂ release rates were slightly slower than previously reported rates. The local CO₂ concentrations in the lecture room for regions with a high density of attendees increased over a short period of time, although the natural ventilation was already started by opening the windows. The overall CO₂ concentration in the lecture room rapidly decreased in the early stage of ventilation, but declined very slowly after a longer period of ventilation time. Therefore, in order to enhance the efficiency of a lecture room's natural ventilation, it is recommended to homogeneously distribute the attendees in the lecture room, and to frequently open the windows for short periods of time.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.2
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• pp.385-399
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• 2000

Groundwater contamination caused by landfill leachate leads to various changes in aquifer environment according to the characteristics of incoming contaminants and aquifer geochemistry. These changes in aquifer environment are known to contribute to the natural attenuation phenomena of contaminants. The knowledge on changes in aquifer environment is necessary to determine the extent of groundwater pollution, to assess risk of the pollution, and to develop an appropriate remediation technologies. In this paper, the changes in aquifer environment caused by landfill leachate development of various redox zones-and the natural attenuation phenomena occurred in each redox zone are reviewed. From this review, an appropriate research direction and control action is presented for the groundwater pollutions caused by unsanitary landfills scattered across the nation.

• Journal of Korean Society of Water and Wastewater
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• v.10 no.1
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• pp.96-111
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• 1996

The failure of water pipelines is progressed by several compound factors and the collection and analysis of data about pipeline failure are inevitable for effective pipeline rehabilitation. Data analysis of pipeline failure was already performed in USA and Europe. Based on such phenomena, failure characteristics about metropolitan pipelines in Korea were analyzed: The conclusions of this study are as followings. 1. The failure cause of pipelines can be classified into natural cause and artificial cause. Artificial cause is 32% of total causes, so artificial failure as several constructions happens frequently in Korea. Although the failure by old pipe is greatest of any other causes m classtfied cause, failure cause is not classified in detail now. 2. The damaged part of pipelines is affected by cities, distribution system inventory, bedding conditions, and so on. In this study, the failure of pipeline body(67%) is greater than the failure of pipeline joint(33%) in natural failure. 3. In regard to pipe materials, failure rate of DCIP(0.8456), PEP(0.7288), and GSP(0.6643) is greater than that of CIP(0.3985) and CWSP(0.2348). 4. Usually, faIlure rate is increased in proportion to diameter of pipeline. In this study, CIP, DCIP, and CWSP have clear trends. But the trends of PEP is reverse, the case of GSP, HP is obscure due to data shortage. 5. There are no direct relationships between burial age and failure rate of pipelines. 6. Annual breaks and winter(Nov.~Feb.) breaks of pipelines are investigated. As a result, WInter breaks to annual breaks of CIP is 51.3%(Seoul), 51.1%(Taegu),38.7%(Pusan). This phenomena have direct correlation with average winter temp. of cities.

• Journal of Science Education
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• v.39 no.2
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• pp.209-220
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• 2015

Science has an essentially integrated character as a discipline that explores the natural phenomena. And the integrated science education is required to achieve the goals of science education to forster scientific literacy of all students. In this respect, we defined the basic concepts and principles that can penetrate the natural phenomena as an integrated concepts in this study, and organized the contents of integrated science curriculum around them. Integrated concept centered curriculum was intended for the 10th grade students and the breadth and depth of learning concepts were represented by presenting the achievement level of the learning concepts. Contents organization of integrated science curriculum presented in this study was meant to provide a new perspectives to the revision of the national integrated science curriculum that is currently in progress.