• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.7
• /
• pp.4665-4674
• /
• 2014

The aim of this study was to confirm the feasibility of the electro-coagulation process as a pre-treatment for the membrane separation of anaerobic digestion effluents to minimize membrane fouling. The reduction of membrane fouling was evaluated according to the number of electrodes (immersed surface area of electrodes), current density and contact time. In the case of the small surface area of electrodes, the increased electric field strength resulted in a soluble COD increase due to the destruction of the microbial flocs and/or cells, whereas large changes in the soluble COD were not observed in the case of the high surface area of electrodes. On the other hand, the T-P concentration decreased as a result of the precipitation of aluminum ions and phosphates. The membrane permeation flux increased and the fouling resistance (Rc+Rf) decreased with increasing electric current density. Although the particle size of the anaerobic digestion effluent increased slightly, it was not related directly to the reduced fouling phenomena. The main mechanism for the enhanced flux was attributed to the inorganic particulate produced during electrocoagulation, such as $AlPO_4$, which acted as a dynamic membrane deposited on the membrane surface.

• Journal of Korean Society of Environmental Engineers
• /
• v.31 no.4
• /
• pp.263-271
• /
• 2009

This study evaluated the flocs forming characteristics in the mixing zone to increase the coagulation effect in the drinking water plant. As a measuring tool of formed flocs, on-line particle dispersion analyzer (iPDA) was used in Y drinking water plant. To evaluate the forming flocs, many parameters such as poly amine, coagulant dosing amount, raw water turbidity, and pH was applied in this study. During the periods of field test, poly aluminium chloride (PACl) as a coagulant was used. With the increase of the raw water turbidities, poly amine was also added as one of aids for increasing in coagulation efficiency. The turbidity and pH of raw water was ranged from 7 to 9 and from 25 to 140 NTU, respectively. The increasing of raw water turbidity brought the bigger floc sizes accordingly. From a regression analysis, $R^2$ value was 0.8040 as a function of T, raw water turbidity. Floc size index (FSI) was obtained from a correlation equation as follows; FSI = 0.9388logT - 0.3214 Also, polyamine gave the bigger flocs the moment it is added to the coagulated water in the rapid mixing zone. One of parameters influencing the floc sizes was the addition of powdered active carbon(PAC) in the mixing zone. In case of higher turbidity of raw water, $R^2$ value was 0.9050 in the parameters of [PACl] and [PAC]; FSI = $0.0407[T]^{0.324}[PACI]^{0.769}[PAC]^{0.178}$ On-line floc monitor was beneficial to evaluate the flocs sizes depending on the many parameters consisting raw water properties, bring the profitable basic data to control the mixing zone more effectively.

• Journal of the Korea Convergence Society
• /
• v.10 no.12
• /
• pp.307-314
• /
• 2019

This paper was intended to identify the knowledge structure of youth-related research by looking at the research trends of research papers published in Korean Journal of Youth Studies from 2010 to 2018. Using keywords extracted from the papers, the Centrality and Cohesion analysis of the keyword network analysis of the NetMiner program were used. In the analysis of degree centrality, the "relationship" was the highest, followed by schools and youth, and high in the order of parents and violence. In the analysis of betweenness centrality, the "relationship" was also the highest, followed by youth, school, need, education, parents, children, abuse/emotion(the same level), institutions, regions, cell phones/prevention/welfare(the same level), elementary, attachment, suicide, addiction, society, violence, children, services, support, policy/teachers(the same level). According to the cohesion analysis, school life and policy, addiction, parent & peer relations, civic education & welfare support, sentiment and thinking, college, abuse & suicide were divided into a total of seven sub-topic subjects.

• Korean Journal of Food Science and Technology
• /
• v.28 no.1
• /
• pp.44-52
• /
• 1996

Sensory properties of cooked rice were affected by the varieties and growing environments of the rice. Moistness, cohesiveness, and adhesiveness of cooked rice were highly and positively correlated each other, whereas firmness was negatively correlated with these attributes. Sixty rice samples which differed in varieties and/or growing environments were divided into four groups based on their textural properties through principal component analysis and cluster analysis. Quality type I showed the highest values for moistness, cohesiveness, and adhesiveness, and the lowest values for firmness of cooked rice. On the other hand, quality type IV showed just the opposite values. There was no significant difference among rice starches in amylose content (P<0.05). A17 (type III) and A09 (type IV) had higher blue values for starch and amylopectin than the other samples (type I and II). On the amylogram, these samples showed lower values for breakdown and higher values for setback than the other samples. Average degree of polymerization, average chain length, and average number of chains for amylose and amylopectin were 597-878 and 2660-3140, 140-230 and 17-19, and 3.1-4.9 and 140-170, respectively.

• Korean Journal of Food Science and Technology
• /
• v.30 no.5
• /
• pp.1077-1084
• /
• 1998

The optimum conditions fer the measurement of texture profile of imitation crab-leg products were investigated by different conditions using Texture Analyser and the date were compared to those of sensory evaluations. The textural characteristics of surimi gels were compared with those of imitation crab-leg products. The TPA values of 5 different kinds of commercial imitation crab-leg product and 2 kinds of surimi gel products purchased in a market in Seoul were measured. In surimi gels, instrumental hardness and cohesiveness were higher than those of imitation crab-leg products, especially chewiness and gumminess were significantly higher than those of imitation crab-leg products. In imitation crab-leg products, hardness and cohesiveness increased and springiness decreased as the probe diameter increased from 12.5 mm to 24.6 mm. In the different compression ratio (60, 70, 80%), hardness increased and cohesiveness and springiness decreased as the compression ratio increased. The chewiness, gumminess, cohesiveness and hardness increased slightly as the cross-head speed increased from 0.8 to 2.4 mm/sec. Significant correlations between mechanical and sensory values were observed in gumminess, chewiness, cohesiveness and hardness. The optimum conditions for the TPA measurement of imitation crab-leg products were a cross-head speed of 2.4 mm/sec and 60% compression ratio with a flat probe having twice of the sample diameter (24.6 mm).

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.11a
• /
• pp.381-381
• /
• 2009

염료감응형 태양전지의 효율 향상을 위한 다양한 방법들 중 $TiO_2$ 나노 파우더의 표면 개질 및 페이스트의 분산성 향상을 위한 연구가 활발하게 진행되고 있다. 기존 나노 파우더의 표면 개질법으로는 액상 공정인 졸겔법이 있으나 표면 처리 공정에서의 응집현상은 아직 해결해야 할 과제 중 하나이다. 이에 본 연구에서는 진공증착방법인 ALD법을 이용하여 염료감응형 태양전지용 $TiO_2$ 나노 파우더의 $SiO_2$ 산화물 표면처리를 통한 분산특성을 파악하였다. 기존 ALD법의 경우 reactor의 온도가 $300{\sim}500^{\circ}C$ 정도의 고온에서 공정이 이루어졌지만 본 실험에서는 2차 아민계촉매(pyridine)을 사용하여 reactor의 온도를 $30^{\circ}C$정도의 저온공정에서 $SiO_2$ 산화물을 코팅을 하였다. MO source로는 액체상태의 TEOS$(Si(OC_2H_5)_4)$를, 반응가스로는 $H_2O$를 사용하였고, 불활성 기체인 Ar 가스는 purge 가스로 각각 사용 하였다. ALD 공정에 의해 표면처리 된 $TiO_2$ 나노 파우더의 분산특성은 각 공정 cycle에 따라 FESEM을 통하여 입자의 형상 및 분산성을 확인하였으며 입도 분석기를 통하여 부피의 변화 및 분산 특성을 확인하였다. 공정 cycle 이 증가함에 따라 입자간의 응집현상이 개선되는 것을 확인 할 수 있었으며, 100cycles에서 응집현상이 가장 많이 감소하는 것을 확인할 수 있었다. 또한 표면 처리된 $SiO_2$ 산화막은 XRD를 통한 결정 분석 및 EDX를 통한 정성 분석을 통하여 확인하였다.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
• /
• v.11 no.2
• /
• pp.101-111
• /
• 2016

Startup has lot of limitation such as time and budget shortage, and few human resources, and may be under the very stressful condition. Naturally in these context, there is always conflict among the startup team members, but the impact of conflict on teamwork or team performance has not been empirically tested. This study examines the relationship among the conflict, teamwork and team performance in startup context. Different two types of conflict and four factors of teamwork for team performance are identified from a literature review and tested; task conflict and relationship conflict as antecedents, teamwork was composed of communication, collaboration, coordination and cohesion, leading to team performance. 142 data points were collected from startup representatives to test these hypotheses. PLS data analysis indicated that the task conflict positively effects on all teamwork factors, but relationship conflict has statistically significant effect on only two teamwork factors, collaboration and coordination in negative relationship. Teamwork factors effects on team performance except communication. Based on the results, we proposed practically several team management skills for startup managers, leaders and even members, and explained theoretical contributions.

• Journal of the Korean Vacuum Society
• /
• v.14 no.3
• /
• pp.115-118
• /
• 2005

Structure analysis of model polymeric micelles, both for non-asosciative and associative cases is done by small angle neutron scattering method. Aggregation number of the hydrophobic cores and the lyotropic ordering transitions of aqueous solutions of poly(ethylene glycol)(PEG) (6 K or 10 K g/mol) end-capped with perfluoroalkyl groups $(-(CH_2)_2C_OnF_{2n+1}$ (n =6,8, or 10) are characterized. Aggregation number is mainly determined by the hydrophobe end group only, and is insensitive to polymer concentration or temperature. Also, there is no difference between non-associative micelles and associative micelles in terms of aggregation number. The model systems order into a BCC structure with increasing concentration.

• Journal of The Korean Association For Science Education
• /
• v.22 no.4
• /
• pp.717-724
• /
• 2002

In this study. the effects of grouping by students' agreeableness in cooperative learning strategy applied to middle school science classes on their achievement. confidence, satisfaction, attitude toward science class, and cohesion of group members were investigated. One hundred and fifty-eight students were assigned to control group, homogeneous group and heterogeneous group, and taught about separation of mixture for 7 class hours. The results revealed that there was no significant difference in the achievement test scores. However, significant interaction between the instruction and the level of agreeableness were found in the satisfaction and the cohesion of group members. Students of higher agreeableness level in the homogeneous group were more satisfied with science class and cohesive. Students' attitude toward science class in the homogeneous group was also significantly higher than those in the other groups.

• Korean Journal of Cognitive Science
• /
• v.19 no.3
• /
• pp.223-255
• /
• 2008

In this paper, we introduce an automatic system of scoring English essays. The system is comprised of three main components: a spelling checker, a grammar checker and a lexical cohesion checker. We have used such resources as WordNet, Link Grammar/parser and Roget's thesaurus for these components. The usefulness of an automatic scoring system depends on its reliability. To measure reliability, we compared the results of automatic scoring with those of manual scoring, on the basis of the Kappa statistics and the Multi-facet Rasch Model. The statistical data obtained from the comparison showed that the scoring system is as reliable as professional human graders. This system deals with textual units rather than sentential units and checks not only formal properties of a text but also its contents.