• Solar Energy
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• v.15 no.2
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• pp.25-37
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• 1995

This paper presents an approximate analytical solution to one-dimensional model of the charging process for stratified thermal storage tanks, in which variation of the inlet temperature as well as the momemtum-induced mixing is taken into accout. The mixing is incorporated into the model as a constant-depth perfectly mixed layer above the plug flow region. Based on the superposition principle, the variable inlet temperature is approximated by a number of step functions. Temperature distributions for the thermocline corresponding to three types of interfacial condition arr successfully derived in terms of well-defined functions, so that a linear combination of them constitutes the final solution. Validity and utility of this work is examined through the comparison of the approximate solution with an exact solution available for the case of linearly increasing inlet temperature. With increasing the number of steps, the present solution asymptotically approaches to the exact one. Even with a limited number of steps, the present results favorably agree with those by the exact solution for a wide range of the mixing depth. Also, it is revealed that fewer steps are needed for meaningful predictions as the mixing. depth becomes larger.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.5
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• pp.429-434
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• 2007

This study was conducted to estimate site productivity of Quercus acutissima and Quercus mongolica by four forest climatic zones. We used site environmental variables (28 geographical and pedological factors) and site index as a site productivity indicator from nation-wide 23,315 stands. Based on multiple regression analysis between site index and major environmental variables, the best-fit multivaliate models were made by each species and forest climatic zone. Most of site index prediction models by species were regressed with seven to eight factors, including altitude, relief, soil depth, and soil moisture etc. For those models, three evaluation statistics such as mean difference, standard deviation of difference, and standard error of difference were applied to the test data set for the validation of the results. According to the evaluation statistics, it was found that the models by climatic zones and species fitted well to the test data set with relatively low bias and variation. Also having above middle of site index range, total area of productive sites for the two Quercus spp. estimated by those models would be about 6% of total forest area. Northern temperate forest zone and central temperate forest zone had more productive area than southern temperate forest zone and warm temperate forest zone. As a result, it was concluded that the regressive prediction with site environmental variables by climatic zones and species had enough estimation capability of forest site productivity.

• Composites Research
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• v.32 no.1
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• pp.71-77
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• 2019

In this study, the structural and rheological characterizations of polyacrylonitrile(PAN)/dimethyl sulfoxide(DMSO) solutions for PAN fiber were investigated according to the change of storage times and temperatures. As a result, PAN/DMSO solutions exhibited a very characteristic rheological behavior with variation of temperature. The solutions showed an increase of complex viscosity and a decrease of loss tangent($tan{\delta}$) as temperature was increased over the temperature range of 40 and $70^{\circ}C$ and it could be seen that the viscosity rapidly increased at low frequency. These results indicated that the gel polymer and denser gel structure were formed due to the intermolecular hydrogen bonding of water in the polymer solution depending on the storage time.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.106-106
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• 2015

The information of flow regimes continues to be norm in water resource and watershed management, in that stream flow regime is a crucial factor influencing water quality, geomorphology, and the community structure of stream biota. The objectives of this study were to estimate Korean stream flows from landscape variables, classify stream flow gages using hydraulic characteristics, and then apply these methods to ungaged biological monitoring sites for effective ecological assessment. Here I used a linear modeling approach (MLR, PCA, and PCR) to describe and predict seasonal flow statistics from landscape variables. MLR models were successfully built for a range of exceedance discharges and time frames (annual, January, May, July, and October), and these models explained a high degree of the observed variation with r squares ranging from 0.555 (Q95 in January) to 0.899 (Q05 in July). In validation testing, predicted and observed exceedance discharges were all significantly correlated (p<0.01) and for most models no significant difference was found between predicted and observed values (Paired samples T-test; p>0.05). I classified Korean stream flow regimes with respect to hydraulic and hydrologic regime into four categories: flashier and higher-powered (F-HP), flashier and lower-powered (F-LP), more stable and higher-powered (S-HP), and more stable and lower-powered (S-LP). These four categories of Korean streams were related to with the characteristics of environmental variables, such as catchment size, site slope, stream order, and land use patterns. I then applied the models at 684 ungaged biological sampling sites used in the National Aquatic Ecological Monitoring Program in order to classify them with respect to basic hydrologic characteristics and similarity to the government's array of hydrologic gauging stations. Flashier-lower powered sites appeared to be relatively over-represented and more stable-higher powered sites under-represented in the bioassessment data sets.

• Korean Journal of Metals and Materials
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• v.49 no.3
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• pp.221-230
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• 2011

The cold spray process is an emerging technology that utilizes high velocity metallic particles for surface coating. Metallic powder particles are injected into a converging-diverging de Laval nozzle and accelerated to a high velocity by a supersonic gas flow. The cold spray process normally uses a circular nozzle that has a rather narrow spraying range. To overcome this fault, a slit nozzle was considered in this study. The slit nozzle is anticipated to reduce the coating process time because it has a wider coating width than the circular nozzle. However, the slit nozzle can reduce the coating efficiency because it does not allow as much gas and particle velocity as the circular nozzle. To improve the coating efficiency of a slit nozzle, the shape of the slit nozzle was modified. And the results of gas flow and particle behaviour according to the nozzlers shape were compared by the a numerical analysis. As a results, as Expansion Ratio(ER) of 7.5 was found to be the most optimal condition for enhancing the spraying efficiency when the ER was changed by the variation of nozzle neck and exit size.

• Journal of Advanced Navigation Technology
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• v.27 no.2
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• pp.214-220
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• 2023

Because there exist a region in the rotational speed and torque map that the a particular combination of a motor and an ESC (Electronic Speed Control) can maintain its peak efficiency, identifying this region is important for designing an efficient system. Firstly the accuracy of the measurement device is verified using the published propeller measurement data. And then, the combined motor-ESC efficiencies of an individual propeller are measured at a wide range of rotational speeds. With measurements obtained from a large number of different propellers, efficiency contours are obtained. It is shown that there exist a significant difference between the measured combined efficiency and the motor efficiency computed using a simple model. In addition, with the same motor, the combined efficiency can have a meaningful variation depending on the model of the ESC. The efficiency contours derived from this study will be useful for the design and optimization of electric propulsion systems of an aircraft where propulsion efficiency is critical.

• Korean Journal of Culture and Social Issue
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• v.18 no.2
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• pp.215-234
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• 2012

The purpose of this study was to explore linkages between stress and a range of individual difference factors on children's memory for a potentially stressful event. Children (N=63) aged from 4 to 10 years, who undergone a minor dental operative procedure were evaluated. Overall, the results of this study replicated and extended previous findings of the related literature, providing some further evidence for a negative relation between stress and children's recall. More considerable variation in individual difference variables, in particular, children 's stress coping strategies, quality of previous experiences, amount of the advanced parental preparation were existed among the children, influencing the relation between the level of stress and children's remembering of a stressful event. Future inquiries for understanding theoretical, clinical, and forensic issues in children's remembering of a stressful event were discussed.

• Plant Journal
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• v.11 no.2
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• pp.32-38
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• 2015

This study was conducted on combined cycle power plant consisting of HRSG with integral deaerator type to avoid tube failures of low pressure evaporator tubes. Based on the observation of pH variation at the discharge of boiler feed water pump by continuous pH measurement for a period of time, it was identified that pH of feed water is getting reduced as ammonia is distributed into vapor and liquid depending on the distribution ratio of ammonia in the LP drum after the deaerator. To solve this problem, the counterplan was prepared by reexamination of ammonia injection point and quantity. In conclusion, it was accomplished that 9.2~9.6 is the optimized pH range for boiler feed water by arranging additional piping for ammonia to inject directly to LP drum.

• Animal cells and systems
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• v.15 no.4
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• pp.315-324
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• 2011

The actiniarian sea anemone, Entacmaea quadricolor, and the scleractinian coral, Alveopora japonica, host symbiotic dinoflagellates belonging to the genus Symbiodinium (Freudenthal). We studied the host-symbiont specificity of these two anthozoan hosts in the northwestern Pacific Ocean. Symbionts within the two hosts were identified using partial large subunit (LSU) ribosomal DNA (rDNA) and complete internal transcribed spacers (ITS) 1 rDNA regions. The host, E. quadricolor, was identified using the partial LSU rDNA molecular marker. Genetic analysis showed that E. quadricolor only harbors dinoflagellates belonging to subclade C1/3 of the genus Symbiodinium. Moreover, no genetic variation was detected among the symbionts of E. quadricolor within the study region (Korea and Japan), even though the two distant sites were separated by more than 1000 km, at collection depths of 1 m in shallow and 13-16 m in deep water. Whilst scleractinian corals host multiple Symbiodinium clades in tropical waters, A. japonica, sampled over a wide geographical range (800 km) within the study region, only hosts Symbiodinium sp. clade F3. The high specificity of endosymbionts in E. quadricolor and A. japonica within the northwestern Pacific Ocean could be accounted for because symbiotic dinoflagellates within the host anemones appear to be acquired maternally, and the Kuroshio Current might affect the marine biota of the northwestern Pacific. However, the consistency of the symbiotic relationships between these two anthozoan hosts and their endosymbionts could change after climate change, so this symbiotic specificity should be monitored.

• Korean Institute of Interior Design Journal
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• v.25 no.1
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• pp.163-171
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• 2016

The objectives of this study is to analyze the characteristics of Chinese traditionality expression at restaurants in Beijing area. 12 restaurants were selected and visited for the investigation research. The results were as follows. First, traditional reproduction was found mainly manifested through the reproduction of traditional ornaments, in particular, the facade and interior element ornaments. Second, Traditional transformation was mainly manifested in replacement material while changing the shape slightly, or to stretch or shorten prototype shape and other negative deformation methods which did not largely out of the scope of traditional reproduction. Third, Traditional reinterpretation was expressed by abstract, symbol or metaphor on designs, usually people can not directly recognize the traditional archetype. When compare with traditional reproduction or traditional transformation, traditional reinterpretation was relatively fewer, however, in this study the traditional reinterpretation and traditional transformation have same numerical result. Reinterpretation as a positive performance method of traditional modernized, it was encouraging the phenomenon, especially in the ceiling design. Chinese traditional cloud patterns have been three-dimensional and diversification of use. And in the wall design, traditional elements have been extremely simplistic or adopted a wide variety of traditional elements, it may be preferred in diversity. In addition, furniture was tinge traditional elements in modern form, lighting was added symbolize color or picture on the traditional lighting which shape was simplified to emphasize space's traditional. But the facade, sign board, floor, and window element seems the range of variation was not wild, promote more use the positive traditional reinterpretation method.