• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.7
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• pp.1127-1134
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• 1994

The analytical model for the induced Hall field in the magnetotransistor considering the diffusion of carriers has been proposed and verified by experiment and simulation. Previous models for the induced Hall field in the magnetotransistor do not consider the influence of the diffusion carrier transport. However, the carrier diffusion in the base region of magnetotransistors cannot be neglected and should be considered to evaluated the Hall field in the magnetotransistors accurately. We have measured the Hall voltage in the base region of the fabricated magnetotransistors. The measured values have been compared with the numerical results evaluated from our diffusion model as well as the calculated results from the conventional model. The evaluated Hall voltage from the diffusion model agrees well with the measured values while the sign of the Hall voltage calculated by the conventional model is opposite to that of the measured values in the saturation region. This discrepancy is due to the fact that the diffusion model considers the carrier diffusion while the conventional one does not. The Hall field model including the influence of carrier diffusion may be an important tool to optimize the device structure and to understand the operating principle of the magnetotransistor.

• Journal of Powder Materials
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• v.12 no.2 s.49
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• pp.131-135
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• 2005

7xxx series Al alloy has the most attractive properties including its excellent high specific strength, stress corrosion cracking and corrosion-resistance. However, in case of the Al-Zn system, the liquid phase has a transient aspect because of the high solid solubility of Zn in Al. Therefore, transient liquid phase sintering behavior was observed during the sintering process. And the amount of liquid and its duration were influenced by the process variables including heating rate and final sintering temperature. At high heating rates($100^{\circ}C/min$), the liquid fraction increased during sintering because diffusion was minimized and therefore local saturation could easily occur. The sintered density increased with increasing heating rate.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05a
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• pp.38-42
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• 2004

A pilot-scale experiment for the treatment of red tide in the enclosure was done in sea area of Shandong Province, P. R. China on Aug. 25, 2002. With the method of strong dielectric barrier discharge in microgap, $O_2$in air and $H_2O$ in seawater are ionized and dissociated into large numbers of OHㆍradicals, and then dissolved into a part of seawater to form OHㆍsolution of high concentration. With OH' concentration of 0.68mg/L, the kill efficiencies of 29 kinds of red tide organisms such as Chaetoceros lorenzianus and so on reached 99.89%, in which the kill efficiencies of bacterium and vibrio were 100%, and that of Gonyaulax cysts and Prei. Cysts were up to 100%. At the same time, the content of chlorophyll-a was decreased into the lowest limit of test. DO saturation of seawater was greatly increased to 100% because the residual OHㆍradical was decomposed into $H_2O$ and $O_2$after 20 minutes, Therefore the treatment of red tide using OHㆍradicals is a kind of advanced oxidation technology, which realizes zero pollution, zero emission and zero residual in the process of the production of OHㆍradicals and the treatment of red tide.

• Journal of Information Processing Systems
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• v.10 no.4
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• pp.589-601
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• 2014

The performance of edge detection often relies on its ability to correctly determine the dissimilarities of connected pixels. For grayscale images, the dissimilarity of two pixels is estimated by a scalar difference of their intensities and for color images, this is done by using the vector difference (color distance) of the three-color components. The Euclidean distance in the RGB color space typically measures a color distance. However, the RGB space is not suitable for edge detection since its color components do not coincide with the information human perception uses to separate objects from backgrounds. In this paper, we propose a novel method for color edge detection by taking advantage of the HSV color space and the Mahalanobis distance. The HSV space models colors in a manner similar to human perception. The Mahalanobis distance independently considers the hue, saturation, and lightness and gives them different degrees of contribution for the measurement of color distances. Therefore, our method is robust against the change of lightness as compared to previous approaches. Furthermore, we will introduce a noise-resistant technique for determining image gradients. Various experiments on simulated and real-world images show that our approach outperforms several existing methods, especially when the images vary in lightness or are corrupted by noise.

• Journal of the Korean GEO-environmental Society
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• v.17 no.5
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• pp.5-16
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• 2016

A rainfall induced slope failure is a common natural hazard in mountainous areas worldwide. Sudden and rapid failures which have a high possibility of occurrence in a steep slope are always the most dangerous due to their suddenness and high velocities. Based on a series of experiments this study aimed to determine a critical angle which could be considered as an approximate threshold for a sudden failure. The experiments were performed using 0.42 mm mean grain size sand in a 200 cm long, 60 cm wide and 50 cm deep rectangular flume. A numerical model was created by integrating a 2D seepage flow model and a 2D slope stability analysis model to predict the failure surface and the time of occurrence. The results showed that, the failure mode for the entire material will be sudden for slopes greater than $67^{\circ}$; in contrast the failure mode becomes retrogressive. There is no clear link between the degree of saturation and the mode of failure. The simulation results in considering matric suction showed good matching with the results obtained from experiment. A subsequent discarding of the matric suction effect in calculating safety factors will result in a deeper predicted failure surface and an incorrect predicted time of occurrence.

• International Journal of Air-Conditioning and Refrigeration
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• v.17 no.3
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• pp.81-87
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• 2009

The effect of oil on convective boiling of R-123 in an enhanced tube bundle is experimentally investigated at $26.7^{\circ}C$ saturation temperature. The enhanced tube had pores (0.23 mm diameter) and connecting gaps (0.07 mm width), which had been optimized using pure R-123. The effects of oil concentration (0 to 5%), heat flux (10 to $40\;kW/m^2$), mass velocity (8 to $26\;kg/m2^s$) and vapor quality are investigated. The oil significantly reduces the bundle boiling heat transfer coefficient. With 1% oil, the reduction is approximately 35%. Further addition of oil further reduces the heat transfer coefficient. The data are also compared with the pool boiling counterpart. The reduction in the heat transfer coefficient is smaller in a bundle (convective boiling) than in a pool (single-tube pool boiling), with larger difference at a smaller heat flux. Similar to pure R-123 case, the effects of mass velocity and vapor quality are negligible for the convective boiling of R-123/oil mixture.

• Food Science and Industry
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• v.49 no.4
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• pp.19-30
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• 2016

Food industry in Korea is one of the most important manufacturing field since the history of this country. Recent days all industries in the world move to $4^{th}$ industrial revolution beginning from 1st revolution. This means that connections between human to human, human to things and things to things should be settled down. food industry in this country should escape from the conventional manufacturing fields until now and accept new or cutting edge technology NT including artificial intelligence robot system and platform system using Internet of Thing. To overcome the saturation condition of domestic food market, it should be extended our market to overseas. To do this Korean food industry should be reformed the processing system to convergence and fusion inner or multi-disciplinary research in not only research field but also manufacturing field. The food industry must introduce new technology and concept of controlling all manufacturing systems. This paper present the fields should be convergence and the field study together and the new techniques, methods and new products be developed in the future.

• KSBB Journal
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• v.14 no.3
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• pp.284-290
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• 1999

Glucose fed-batch culture was studied to improve cellulose productivity by Acetobacter xylinum BRC5. When initial glucose concentrations in batch cultures were less than 20 g/L, yield coefficients of cellulose (Yp/s) remained a constant value of 0.21 g cellulose/g glucose. But a low yield coefficient, Yp/s=0.13 was obtained from an initial glucose concentration of 40 g/L. Since initial high glucose concentrations in batch culture resulted in low yields of cellulose, constant fed-batch cultures were carried out. The optimal feed rate for fed-batch culture was 2.22 g glucose/L.h. In constant fed-batch culture without DO control, 10 g/L of cellulose was obtained from 40 g/L of glucose with this feed rate, which was approximately two fold higher than that of the batch culture with the same initial glucose concentration. In DO stat plus fed-batch culture, the highest cellulose productivity could be obtained when dissolved oxygen level was controlled at 10% of air saturation, and cellulose productivity increased about 1.5 times compared with that of the culture without DO control.

• Journal of Environmental Impact Assessment
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• v.28 no.1
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• pp.49-62
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• 2019

Environmental changes can affect life-history traits, such as growth rate and reproduction, and organisms adapt on a given environmental condition to maximize ecological fitness. This study shows the effects of water temperature and dissolved oxygen level on early growth and accumulated damage in fish using a dynamic-state-dependent model. I have hypothesized that the level of foraging activity is related to growth and stress and so the optimal level can maximize reproductive success - ultimately, fitness. The critical temperature and dissolved oxygen (DO) is also defined as inducing the maximum growth rate at the level. So, the model predicts the highest growth rate at oxygen saturation and lower growth rate at lower or higher level of DO in water. Lower DO (i.e., hypoxia) causes slower growth rate through higher amount of accumulated stress whereas higher DO (i.e., hyperoxia) induces faster growth rate, but smaller body size. In addition, I show that there is lower impact when considering simple or independent environmental factors on environmental assessment. My findings suggest that multiple environmental factors as physiological ecology approach should be considered to improve impact assessment in environmental changes and a further study is needed to develop advanced assessment tools considering multiple environmental factors.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2381-2391
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• 2013

In general, ground's thermal properties, types of heat exchanger, operational method, thermal interference between piles can be considered as key factors which affect the thermal performance of energy pile. This study focused on the effect of these factors on the performance by a numerical model reflecting a real ground condition. Depending on the degree of saturation of ground, pile's heat transfer rate showed a maximum difference of three times, and the thermal resistance of pile made a maximum difference of 8.7%. As for the type of heat exchanger effects on thermal performance, thermal efficiency of 3U type energy pile had a higher value than those of W and U types. The periodic operation (8 hours operation, 16 hours pause) can preserve about 20% of heat efficiency compared to continuous operation, and hence it has an advantage of preventing the thermal accumulation phenomenon. Thermal interference effect in group piles may vary depending on the ground condition because the extent decreases as the ground condition varies from saturated to dry. The optimal separation distance that maintains the decreasing rate of heat efficiency less than 1% was suggested as 3.2D in U type, 3.6D in W type, and 3.7D in 3U type in a general ground condition.