• Journal of Advanced Marine Engineering and Technology
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• 제31권3호
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• pp.263-271
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• 2007

The heat transfer coefficient and pressure drop during 9as cooling process of $CO_2$ (R744) in a helically coiled copper tube with the inner diameter of 4.55 mm and outer diameter of 6.35 mm were investigated experimentally. The main components of the refrigerant loop are a receiver, a variable-speed pump. a mass flow meter a pre-heater and a helically coiled type gas cooler (test section). The refrigerant mass fluxes are varied from 200 to $800kg/m^2s$ and the inlet pressures of gas cooler are 7.5 to 10.0 MPa. The heat transfer coefficients of $CO_2$ in a helically coiled tube are higher than those in a horizontal tube. The Pressure drop of $CO_2$ in the gas cooler shows a relatively good agreement with those predicted by Ito's correlation developed for single-phase in a helically coiled tube. The local heat transfer coefficient of $CO_2$ agrees well with the correlation by Pitla et al. However. at the region near pseudo-critical temperature. the experiments indicate higher values than the Pitla et al correlation. Therefore, various experiments in helically coiled tubes have to be conducted and it is necessary to develop the reliable and accurate prediction determining the heat transfer and pressure drop of $CO_2$ in a helically coiled tube.

• Journal of Communications and Networks
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• 제18권5호
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• pp.744-761
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• 2016

For about the past decade and a half research efforts into cognitive radio networks (CRNs) have increased dramatically. This is because CRN is recognized as a technology that has the potential to squeeze the most out of the existing spectrum and hence virtually increase the effective capacity of a wireless communication system. The resulting increased capacity is still a limited resource and its optimal allocation is a critical requirement in order to realize its full benefits. Allocating these additional resources to the secondary users (SUs) in a CRN is an extremely challenging task and integer programming based optimization tools have to be employed to achieve the goals which include, among several aspects, increasing SUs throughput without interfering with the activities of primary users. The theory of the optimization tools that can be used for resource allocations (RA) in CRN have been well established in the literature; convex programming is one of them, in fact the major one. However when it comes to application and implementation, it is noticed that the practical problems do not fit exactly into the format of well established tools and researchers have to apply approximations of different forms to assist in the process. In this survey paper, the optimization tools that have been applied to RA in CRNs are reviewed. In some instances the limitations of techniques used are pointed out and creative tools developed by researchers to solve the problems are identified. Some ideas of tools to be considered by researchers are suggested, and direction for future research in this area in order to improve on the existing tools are presented.

• 동의생리병리학회지
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• 제16권4호
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• pp.734-744
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• 2002

The purpose of this study was to evaluate the protective effect of Kamicheonggan-tang(KCGT) on pre-hepatocarcinogenesis induced by N-nitrosomorpholine. The studied using blood chemistry, lipidperoxidation, antioxidant, immunohistochemistry and morphological change. The results were obtained as follows. In the pre-hepatocarcinogenesis induced by NMP, serum AST, ALT, ALP and total bilirubin were not changed in NMP and NK treated group after 1 st week, but desreased in NK treated group after 4th week as compared with NMP treated 4th week group. The content of GSH was similary to in NK treated groups as compares with data of normal group. The content of MDA was increased in NK treated group after 1st and 4th week, and more increased in the NMP treated group than those of their NK treated group. The immunohistochemically, stain of GST-p, positive lesions of KCGT were significantly decreased than those of NMP treated group. The histopathologically, fat changes, nucleotic changes, oval cell and inflammatory cells in periportal were observed in NMP treated fater 4th week, but those were significantly decreased from 4th week in the NK treated group. And the enlarged nucleus was not changed in KCGT treated group, but increased in NMP treated group after 1st and 4th week. The ultrastructurally, nucleotic changes, glycogen degeneration, lipid droplet and rER fragmentation were observed in NMP treated group after 4th week, but those changes were significantly decreased from 4th week in the NK treated group. These results suggested that KCGT extracts has protective effect on prehepatocarcinogenesis by NMP, might be usefully applied for clinical treatment of hapatic disease and also it was necessary to do more studies about its mechanisms.

• Journal of Advanced Marine Engineering and Technology
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• 제31권6호
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• pp.699-706
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• 2007

The cooling heat transfer coefficient and pressure drop of $CO_2$(R-744) in helical coil copper tubes were investigated experimentally The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter. a pre-heater and a inclined helical coil type gas cooler (test section). The test section consists of a smooth copper tube of 2.45 and 4.55mm inner diameter The refrigerant mass fluxes were varied from 200 to $600 [kg/m^2s]$ and the inlet pressures of 9as cooler were 7.5 to 10.0 [MPa]. The heat transfer coefficients of $CO_2$ in helical coil tubes increase with the increase of mass flux and gas cooling pressure of $CO_2$. The pressure drop of $CO_2$ in the gas cooler shows a relatively food agreement with those Predicted by Ito's correlation developed for single-phase in helical coil tubes. Though a few correlation available with the data. the local heat transfer coefficient of $CO_2$ agrees well with those presented by Pitla et al. among the predictions. However at the region near pseudo-critical temperature. the experiment data indicate higher values than the Pitla et al. correlation.

• Journal of Advanced Marine Engineering and Technology
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• 제31권6호
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• pp.707-714
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• 2007

The heat transfer coefficient and Pressure drop during gas cooling process of $CO_2$ (R-744) in inclined helical coil copper tubes were investigated experimentally. The main components of the refrigerant loop are a receiver. a variable-speed pump. a mass flow meter, a pre-heater and a inclined helical coil type gas cooler (test section). The test section consists of a smooth copper tube of 2.45mm inner diameter. The refrigerant mass fluxes were varied from 200 to $600[kg/m^2s]$ and the inlet Pressures of gas cooler were 7.5 to 10.0 [MPa]. The heat transfer coefficients of $CO_2$ in the inclined helical coil tubes increases with the increase of mass flux and gas cooling pressure of $CO_2$. The pressure drop of $CO_2$ in the gas cooler shows a relatively good agreement with those Predicted by Ito's correlation developed for single-phase in a helical coil tube. The local heat transfer coefficient of $CO_2$ agrees well with the correlation by Pitla et al. However, at the region near pseudo-critical temperature. the experiments indicate higher values than the Pitla et al. correlation. Therefore. various experiments in the inclined helical coil tubes have to be conducted and it is necessary to develop the reliable and accurate prediction determining the heat transfer and pressure drop of $CO_2$ in the inclined helical coil tubes.

• 한국식품영양과학회지
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• 제41권6호
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• pp.739-744
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• 2012

본 연구는 자생분포가 높은 4가지 지역(경기, 강원, 전남 및 제주)에서 채집한 엉겅퀴를 에탄올 추출하여 총 폴리페놀과 총 플라보노이드 함량, DPPH 및 ABTS radical 소거능, 2가지 방법에 의한 환원력을 분석하여 새로운 자생식물 유래의 항산화제 소재개발에 있어 원물 최적화를 위하여 시행하였다. 총 폴리페놀 및 플라보노이드를 많이 함유하고 있을수록 4가지 항산화능의 평가 역시 효과적인 것으로 나타났다. 이는 총 폴리페놀 및 플라보노이드 함량과 항산화 활성의 유의적인 상관성이 있음을 확인할 수 있는 결과라 사료된 다. 엉겅퀴는 현재 잘 소비되는 식물자원은 아니지만 다양한 효능이 확인되고 있는 엉겅퀴를 이용한 소재 및 제품 개발을 위해서는 본 연구결과를 활용한 최적의 재배지역을 선정하고, 향후 재배기술 및 원물의 규격화를 위한 연구는 반드시 수행되어야 할 것으로 판단된다.

• Asian Pacific Journal of Cancer Prevention
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• 제15권14호
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• pp.5883-5888
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• 2014

Background: Breast cancer is the most common cancers in female populations. The exact cause is not known, but is most likely to be a combination of genetic and environmental factors. Log-logistic model (LLM) is applied as a statistical method for predicting survival and it influencing factors. In recent decades, artificial neural network (ANN) models have been increasingly applied to predict survival data. The present research was conducted to compare log-logistic regression and artificial neural network models in prediction of breast cancer (BC) survival. Materials and Methods: A historical cohort study was established with 104 patients suffering from BC from 1997 to 2005. To compare the ANN and LLM in our setting, we used the estimated areas under the receiver-operating characteristic (ROC) curve (AUC) and integrated AUC (iAUC). The data were analyzed using R statistical software. Results: The AUC for the first, second and third years after diagnosis are 0.918, 0.780 and 0.800 in ANN, and 0.834, 0.733 and 0.616 in LLM, respectively. The mean AUC for ANN was statistically higher than that of the LLM (0.845 vs. 0.744). Hence, this study showed a significant difference between the performance in terms of prediction by ANN and LLM. Conclusions: This study demonstrated that the ability of prediction with ANN was higher than with the LLM model. Thus, the use of ANN method for prediction of survival in field of breast cancer is suggested.

• 한국식품조리과학회지
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• 제32권6호
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• pp.734-744
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• 2016

Purpose: This study investigated the preference and awareness of consumers residing in the capital area with respect to South and North Korean regional cuisine to provide baseline data for developing effective commercialization strategies. Methods: This survey was conducted among adults over the age of 19 years who were residing in Seoul and Gyeonggi province area, and data analysis was performed using SPSS WIN 18.0. Results: Analysis of the survey participants' preference for South and North Korean regional cuisine showed that Hwanghae province had the highest preference by $4.35{\pm}1.72$ points, whereas Gangwon province had the lowest preference by $3.75{\pm}0.66$ points. Factorial analysis on general characteristics of Korean regional cuisine resulted in 2 factors - 'locality' and 'health'. Cluster analysis showed that participants could be sorted into two clusters by their awareness of Korean regional cuisine - 'the lower cognitive group' and 'the higher cognitive group'. Cluster analysis on the tourism commercialization strategy for Korean regional cuisines showed that 'the higher cognitive group' had significantly higher awareness regarding the following 3 items: 'merchandising strategy', 'popularization strategy' and 'marketing strategy' (p<0.001). Cluster analysis of the world commercialization strategy showed that 'the higher cognitive group' had significantly higher awareness regarding all items of the 'R&D support strategy' and 'Food culture promotion strategy' categories than the 'the lower cognitive group' (p<0.01). Conclusion: Popularization strategies such as value perception based on the well-being concept, and standardization of recipes; merchandising strategies based on storytelling; and food and culture promotional strategies such as Korean cooking classes and food tasting events, were rated as effective commercialization strategies to increase the popularity of Korean regional cuisine.

• 설비공학논문집
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• 제19권9호
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• pp.640-646
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• 2007

The cooling heat transfer coefficient of $CO_2$ (R-744) for tube and coil diameter (CD), inclined angle of tube and coil pitch of inclined helical coil type copper tubes were investigated experimentally. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and a inclined helical coil type gas cooler (test section). The test section consists of a smooth copper tube of 2.45 and 4.55 mm inner diameter (ID). The refrigerant mass flukes were varied from 200 to 800 [$kg/m^2s$] and the inlet pressures of gas cooler were 7.5 to 10.0 [MPa]. The heat transfer coefficients of $CO_2$ in inclined helical coil tube with 2.45 mm ID are $5{\sim}10.3%$ higher than those of 4.55 mm. The heat transfer coefficients of 41.35 mm CD are $8{\sim}32.4%$ higher than those of 26.75 mm CD. Comparison between $45^{\circ}\;and\;90^{\circ}$ of coil angle, the heat transfer coefficients of $45^{\circ}$ are higher than those of $90^{\circ}$. For coil pitch of gas cooler, the heat transfer coefficients of inclined helical coil gas cooler with coil pitch of 5 mm are similar to those of 10 and 15 mm.

• 한국환경과학회지
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• 제25권5호
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• pp.737-744
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• 2016

For electrolysis process using an insoluble electrode, electrochemical performance was greatly affected by the manufacturing method and procedure, such as the firing temperature, pre-treatment, type of precursor solution, coating method, electrode material, etc. Components of the electrode therein is one of the most important factors in electrochemical reaction. To achieve such characteristics, a appropriate ratio of the electrode material should be carefully chosen. The aim of this research was to apply experimental design method in the optimization of electrode component for the maximum generation of oxidants in electrochemical oxidation process. Mixture design, especially expanded simplex lattice design, in DOME (design of mixture experiments) with Design Expert - commercial software - was used to analyze the data. Analysis of variance (ANOVA) showed a high coefficient of determination ($R^2$) value of 0.9470, thus ensuring a satisfactory adjustment of the $3^{rd}$ order special cubic regression model with the experimental data. The application of response surface methodology (RSM) yielded the following regression equation, which is an empirical relationship between the TRO generation concentration and independent variables(mol ratio of 3 electrode components) in a real unit: TRO generation concentration $(mg/L)=TRO\;conc.=98.25{\times}[Ir]+49.71{\times}[Sn]+95.29{\times}[Sb]-16.91{\times}[Ir]{\times}[Sn]-29.47{\times}[Ir]{\times}[Sb]-22.65{\times}[Sn]{\times}[Sb]+703.19{\times}[Ir]{\times}[Sn]{\times}[Sb]$. The optimized formulation of the 3 component electrode for an high TRO (total residual oxidants) generation was acquired at mol ratio of Ir 0.406, Sn 0.210, Sb 0.384 (desirability d value, 1).