• Membrane Journal
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• v.23 no.5
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• pp.352-359
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• 2013

In the present study, $CO_2$ permeation through a hydrophilic NaY zeolite membrane was studied under permeate evacuation mode for $CO_2$ single gas, $CO_2-N_2$ and $CO_2-O_2$ binary mixtures, and $CO_2-N_2-O_2$ ternary mixture. It was reconfirmed that the $CO_2$ permeation was governed by surface diffusion and the $CO_2$ selectivity was induced from blocking effect of adsorbed $CO_2$ molecules. The $CO_2$ permeance measured in permeate evacuation mode was much lower than that done in He sweeping mode, but was comparable to that obtained under feed pressurization mode. The NaY zeolite membrane showed a considerable $CO_2$ separation for $14%CO_2-80%N_2-6%O_2$ mixture : $CO_2$ permeance was about $1{\times}10^{-7}mol/m^2secPa$ and $CO_2$ selectivity was more than 10. Therefore, it was concluded that NaY zeolite membrane was one of promising membranes for post-combustion CCS process.

• Journal of Life Science
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• v.26 no.7
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• pp.812-818
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• 2016

The aim of this study was to investigate the anti-amnesic effect of Stachys sieboldii MIQ. according to the mixing ratio of calcium on scopolamine-induced learning and memory impairment, in vivo. At the end of the adaptation period, SD rats were divided into a normal group (N), a control group (C: scopolamine), a positive control group (PC: scopolamine + tacrine), and a sample group (S: scopolamine + Stachys sieboldii MIQ., 1CS: scopolamine + low calcium-mixed Stachys sieboldii MIQ., 5CS: scopolamine + high calcium-mixed Stachys sieboldii MIQ.), and were tested with learning and memory tests. The C and CS groups were found to have a decreased scopolamine-induced memory deficit in the Y-maze and water maze tests. Brain tissue analysis showed that the CS group decreased acetylcholinesterase (AChE) activity and increased acetylcholine (Ach) content, both of which are indicative of neuronal cell activity. From a light microscopy study, the nucleus of neurons in the hippocampus of the brain was more shrunken or condensed in the C group compared to the CS group. In the CS group, the damage to the neurons in the hippocampus of the brain was suppressed. These results suggest that Stachys sieboldii MIQ. according to the mixing ratio of calcium provides a significant anti-amnesic effect against scopolamine-induced cholinergic system deficits and cognitive impairment.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.31 no.3
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• pp.256-263
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• 1995

This paper presents the evidence on the considerably strong stratification - destratification(SD) phenomena during spring - neap tidal cycle in summer of 1992 based on the observed temperature, salinity and density data. To find out the main factors causing SD in the bay, we computed the rate of potential energy balance of the surface heat flux, tidal and wind stirring proposed by Simpson and Hunter (1974) and Simpson and Bowders (1981) using observed data. It was found that the energy of the wind stirring was one - order smaller than those of the heat flux and the tidal stirring. It means that the variation of stratification phenomena in the bay mainly depend on tidal stirring and sea surface heating in summer if there was no exceptionally strong wind event like a typhoon. Finally, we tested the effects of typhoon on the mixing characteristics of the bay using the example of a empirical typhoon model. It was found that when wind speed is larger than 15m/sec in Deukryang Bay, the wind energy was always larger than the average heating energy based on empirical typhoon model test. Particularly, typhoon passed on the left side of the bay, strong wind energy happened, which is almost the same as tidal energy of spring tide.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.11
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• pp.4656-4663
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• 2010

In this study, the 3D computational fluid dynamics (CFD) was performed in relation to the internal fluid characteristics, flow distribution, air mean ages, and residence time for the development of the most optimal model in the complex post-disposal device. As it is expected that a channeling (drift) would be made by the semi-dry reactor due to the large difference in the flow distribution by the compartment in the bag filter, a structural improvement should be urgently made for more uniformed flow distribution in the bag filter. In addition, it showed the possibility that the velocity field and distribution characteristics of the residence time could be improved through a modification to inlet structure of the spray dryer reactor. The complex post-disposal device, modified and supplemented with this analysis, integrated the semi-dry reactor and the bag filter in a single body, so it follows that the improvement can make the device compact, the installation area, the operation fee, and management more convenient.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.618-627
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• 2016

This study numerically analyzes the characteristics of the velocity distribution for each location of a square-sectional $180^{\circ}$ bent duct using a Reynolds Stress Turbulent model. The flow parameters were varied, including the working fluids, inlet velocity, surface roughness, radius of curvature, and hydraulic diameter. The boundary conditions for computational fluid dynamics analysis were inlet temperatures of air and water of 288 K and 293 K, inlet air velocity of 3-15 m/s, inner surface roughness of 0-0.001 mm, radius of curvature of 2.5-4.5 D, and hydraulic diameter of 70-100 mm. The working fluid characteristics were highly affected by changes in the viscous force. The maximum velocity profiles in the bent duct were indicated when the $90^{\circ}$ section was in the region of X/D=0.8 and the $180^{\circ}$ section was in the region of Y/D=0.8. Lower surface roughness and higher radius of curvature resulted in a higher rate of velocity change. Also, an efficient measuring location downstream of the bent duct is suggested since the flow deviations were the most stable when the straight duct length was in the region of L/D=30. The minimum deviations at the same velocity conditions according to the hydraulic diameter were mostly indicated in the range of L/D=15-30 based on the standard deviation characteristics.

• Journal of KIISE:Software and Applications
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• v.32 no.7
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• pp.581-591
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• 2005

Collaborative filtering systems have problems involving sparsity and the provision of recommendations by making correlations between only two users' preferences. These systems recommend items based only on the preferences without taking in to account the contents of the items. As a result, the accuracy of recommendations depends on the data from user-rated items. When users rate items, it can be expected that not all users ran do so earnestly. This brings down the accuracy of recommendations. This paper proposes a collaborative recommendation method for extracting typical group preferences using user-item matrix optimization and user profiles in collaborative tittering systems. The method excludes unproven users by using entropy based on data from user-rated items and groups users into clusters after generating user profiles, and then extracts typical group preferences. The proposed method generates collaborative user profiles by using association word mining to reflect contents as well as preferences of items and groups users into clusters based on the profiles by using the vector space model and the K-means algorithm. To compensate for the shortcoming of providing recommendations using correlations between only two user preferences, the proposed method extracts typical preferences of groups using the entropy theory The typical preferences are extracted by combining user entropies with item preferences. The recommender system using typical group preferences solves the problem caused by recommendations based on preferences rated incorrectly by users and reduces time for retrieving the most similar users in groups.

• Journal of KIISE:Information Networking
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• v.29 no.2
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• pp.117-128
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• 2002

Virtual LAN (VLAN) is an architecture to enable communication between end stations as if they were on the same LAN regardless of their physical locations. VLAN defines a limited broadcast domain to reduce the bandwidth waste. The Newbridge Inc. developed a layer 3 VLAN product called VIVID, which configures a VLAN based on W subnet addresses. In a VIVID system, a single route server is deployed for address resolution, VLAN configuration, and data broadcasting to a VLAN. If the size of the network, over which the VLANS supported by the VIVID system spans, becomes larger, this single route server could become a bottleneck point of the system performance. One possible approach to cope with this problem is to deploy multiple route servers. We propose two architectures, organic and independent, to expand the original VIVID system to deploy multiple route servers. A course of simulations are done to analyze the performance of each architecture that we propose. The simulation results show that the performances of the proposed architectures depend on the lengths of VLAN broadcasting sessions and the number of broadcast data frames generated by a session. It has also been shown that there are tradeoffs between the scalability of the architecture and their efficiency in data transmissions.

• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.6
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• pp.716-720
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• 2006

Fuzzy sets are good for abstracting and unifying information using natural language like terms. However, fuzzy sets embody vagueness and users may have different attitude to the vagueness, each user may choose difference one as the best among several fuzzy values. In this paper, we develop a method teaming a user's, preference on fuzzy values and select one which fits to his preference. Users' preferences are modeled with artificial neural networks. We gather learning data from users by asking to choose the best from two fuzzy values in several representative cases of comparing two fuzzy sets. In order to establish tile representative comparing cases, we enumerate more than 600 cases and cluster them into several groups. Neural networks ate trained with the users' answer and the given two fuzzy values in each case. Experiments show that the proposed method produces outputs closet to users' preference than other methods.

• Korean Journal of Social Welfare Studies
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• v.45 no.3
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• pp.127-150
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• 2014

The purpose of this study was to evaluate the effect of parenting stress on marital conflict in dual earner couples with children in early childhood. Actor and Partner Interdependence Model (APIM) was conducted in order to identify how parenting stress affect husband and wife, respectively and how this make the actor effect as well as the partner effect regarding the marital conflict. The research was conducted with 629 married couples from the forth wave of the Panel Study of Korean Children (PSKC) data. In order to examine the relationships between the variables and to evaluate the appropriateness of the research model, structural equation model was used. The results showed that the parenting stress had significant positive effect on the marital conflict. The partner effect of parenting stress was significantly positive. This result implies that the mutual dependence in dual earner couple's marital conflict and parenting stress should be considered in the process of intervention. In other words, to improve the effectiveness of intervention, practitioners should treat couples together rather than being focused on individuals.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.14 no.5
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• pp.43-59
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• 2019

The promotion of social economy is one of the Korean government's top 100 initiatives. As of August 2019, there are 2,249 certified social enterprises in Korea, showing explosive growth with a 41-fold increase from 2007 when the Social Enterprise Promotion Act was first enacted. Currently, the discussion of the sustainability of social-economic organizations is lively, including the issue of changing the certification system to the registration system. Noting the unusual management structure of social enterprise - seeking both social and economic value, this study identifies factors affecting the performance of social enterprises. The study focuses on an empirical investigation of the relationships between characteristics of entrepreneurs' experiences in social economy, strategic competency, the extent to which they seek social value, and their performance. This study is unique in social enterprise research due to its approach to the hybrid management structure of social enterprise with a focus on entrepreneurs' characteristics. Accordingly, this empirical investigation focuses on how social-value seeking mediates the relationships between strategic competency emphasized in typical for-profit enterprises, the characteristics of experiences stressed in social-economic organizations, and the performance of social enterprises. The study findings suggest that, firstly, social entrepreneurs must seek social value as a top priority and improve economic performance using strategic competency to keep pursuing social value, and secondly, social-value seeking must be founded upon entrepreneurs' understanding and experiences in social economy. Practical implications of the study findings include concrete directions for training in social enterprises offered by relevant agencies and the establishment of competency models for current and future entrepreneurs.