• The Korean Journal of Vision Science
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• v.20 no.4
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• pp.531-541
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• 2018

Purpose : To evaluate the acute cytotoxic effect of polyhexamethylene biguanide (PHMB), epigallocatechin gallate (EGCG) and PHMB/EGCG mixture on the cultured human corneal epithelial cell (HCEpiC). Methods : HCEpiCs were cultured in the media of HCEpiC containing 0.00001~0.005% PHMB, 0.001~5% EGCG and 0.00005% PHMB/0.05% EGCG mixture respectively for 30, 60, 120 and 240 min. Cultured HCEpiCs were fixed and stained with Draq5 and cell viability and apoptosis were evaluated using confocal microscope and ImageXpress $Ultra^{TM}$. Results : Cultured HCEpiC did not show cytotoxic effect at below 0.00005% PHMB and below 0.05% EGCG concentration. In the media containing 0.00005% PHMB/0.05% EGCG, acute cytototoxic effect was not found, whereas damaged HCEpiCS were increased and survival cells were decreased in the media incubated for 240 min. Conclusion : The mixture of 0.00005% PHMB/0.05% EGCG showed non acute cytotoxic effect on the cultured HCEpiCs, however it is needed to investigate its chronic cytotoxic effect.

• Journal of fish pathology
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• v.32 no.1
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• pp.9-20
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• 2019

The study investigated the dietary effects of medicinal herbs extract and multiple probiotics mixture on the growth performance, innate immune response and antibacterial activity of nile tilapia Oreochromis niloticus. Tilapia were divided in four groups. The first is a fish group fed a basal diet added with 40% medicinal herbs extract (MHE). The second is a fish group fed a basal diet supplied with $2{\times}10^8CFU/g$ of 2 Bacillus sp, 2 Lactobacillus sp and 2 Yeast sp, respectively (PB). The third group was fed with a mixture of probiotics (2 Bacillus sp, 2 Lactobacillus sp and 2 Yeast sp) with the medicinal herbs extract added in basal diet (MHE+PB). The fourth group was fed only a basal diet (C). In a non-specific immune parameters analysis, respiratory burst activity, lysozyme activity, phagocytic activity (PA), alternative complement pathway activity ($ACH_{50}$) and superoxide dismutase (SOD) activity were significantly (p<0.05) increased in the group MHE+PB compared to other groups. Both PB and MHE groups showed a significant (p<0.05) increase in respiratory burst activity, lysozyme activity compared to the control C group, whereas no significant differences were observed in PA, $ACH_{50}$ and SOD activity compared to the control group. In challenging test, fish were administered with Edwardsiella tarda (E. tarda) on 30 days after feeding with each experimental diet and viable E. tarda cell reduction was checked over 21 days post injection. MHE+PB group showed a significantly (p<0.05) reduced E. tarda cells compared to other groups. No significant antibacterial difference (p>0.05) was observed between PB and MHE only treated group. Compared to the control, a significant antibacterial difference (p<0.05) appeared in PB but not in MHE (p>0.05). The results suggest that the probiotics and MHE mixture could be utilized as an alternative to antibiotics in the control of fish diseases caused by E. tarda.

• Journal of ILASS-Korea
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• v.1 no.2
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• pp.16-23
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• 1996

In case of a high-speed D.I. diesel engine. the injected fuel spray is unavoidable that the impinging on the wall of piston cavity and in this case the geometry of piston cavity has a great influence on the atomization structure and air flow fields. In the field of combustion and in many other spray applications, there are clear evidence of correlation between spray structure and emission of pollutants. Ordinary, the combustion chamber of driving engine have unsteady turbulent flow be attendant on such as the change of temperature, velocity and pressure. So the analysis of spray behavior is difficult. In this study, a single spray was impinged on each cavity wall at indicated angle in a quiescent atmosphere at room temperature and pressure, as being the simplest case, and 3 types of piston cavity such as Dish, Toroidal and Re-entrant type was tested for analyzing the influence of cavity geometry. And hot wire probe was used for analyze non-steady flow characteristics of impinging spray, and to investigate the behavior of spray, the aspects of concentration c(t), standard deviation $\sigma(t)$ and variation factor (v.f.) was measured with the lapse of time.

• Journal of The Korean Association For Science Education
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• v.33 no.3
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• pp.650-663
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• 2013

Multidimensional scaling can be used to identify relationships among concepts, revealing the structure of the cognitive framework by measuring distances within perceptual maps. The current study sought to examine the relationships among concepts related to photosynthesis in 2,844 $3^{rd}-11^{th}$ grade science students. The questionnaire included items on 'location,' 'products,' 'reactants,' and 'environmental factors', presenting images related to each theme. Students provided responses corresponding to particular topics, and reported the extent to which the concept was related to the topic on a scale from 1 to 30. The survey results were as follows: first, students were not able to clearly distinguish between or understand the four main topics. Second, students organized their cognitive structures by closely associating related concepts after learning. Third, the presented concepts revealed a mixture of scientific and non-scientific concepts, suggesting that students needed to clearly distinguish the preconceptions through which they organized concepts, so that they are suitable for cognitive structures based on learning. Furthermore, non-scientific concepts within perceptions were consistently maintained throughout learning, affecting the proximity of scientific concepts.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.2
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• pp.227-235
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• 2003

The WSGG-based narrow band model was employed to solve the radiative transfer equations along isothermal and non-isothermal paths through $CO_2-H_2O-N_2$ gas mixtures at 1 atm. When the WSGGM is applied for arbitrary gas mixtures by considering the multiplication property of transmissivity in overlapping bands, the number of gray gases is significantly increased. To reduce the computation time, three different regrouping methods for the gray gases are tested in obtaining the mean absorption coefficient for each gray gas group. Among them, the regrouping method by minimizing the regrouping error shows the best results. For the isothermal media, 10 gray gases show fairly good agreement with the results by statistical narrow band(SNB) model which are regarded as reference solutions. For non-isothermal media, 20 gray gases show good agreement with reference solutions.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.300-303
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• 1991

Sulphur-hexafluoride has extensively been used as an insulating gas of electric power equipment in substation for its high dielectric strength, non-toixity and non-flammable properties. But it is very expensive and is liquidizable under the condition of low temperature and high pressure. And it is very sensible to the locally high electric field strength. To resolve these problems, we studied 50% FOV and V-t characteristics of $SF_6-N_2$ mixtures under positive and negative lightning impulses using a 25mm rod-plane gap. 50% FOV of $SF_6-N_2$ 50% mixture was about 85% of pure $SF_6$ and it was known that $SF_6-N_2$ mixtures can be used as an economic substitution insulating gas for $SF_6$.

• Nuclear Engineering and Technology
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• v.29 no.2
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• pp.110-126
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• 1997

A two-dimensional continuum model for the hydrogen mining phenomena in the containment subcompartment under severe accident conditions has been developed to predict the spatial distribution of the hydrogen concentration. The model can predict the distribution of time-dependent hydrogen concentration for HEDL experiments well. For the simulation of these experiments, the hydrogen is mixed uniform within the test compartment. To predict the extent of non-uniform distribution, the dominant factors such as the geometrical shape of obstacle and velocity of source injection in mixing phenomena are investigated. If the obstacle disturbing the flow of gas mixture exists in the compartment, the uniform distribution of hydrogen might be not guaranteed. The convective circulation of gas flow is separately formed up and down of the obstacle position, which makes a difference of hydrogen concentration between the upper and lower region of the compartment. The recirculation flow must have a considerable mass flow rate relative to velocity of the source injection to sustain the well-mixed conditions of hydrogen. Finally, in order to account for non-uniform distribution of the hydrogen due to the geometrical configuration the maximum-to-average ratio is functionalized.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.339-340
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• 2006

AC spark discharge voltage of SF6/CO2and SF6/N2 containing various mixed rate in volume percent (1, 5 and 10%) of SF6 in non-uniform fields are investigated. The needle to plane electrode gap spacing was 5 and 10 mm, and the gas pressure was varied within the range of 0.1~0.7 MPa. We have observed a N-characteristic typical for the electronegative gases even in gas mixtures of 1% SF6 with CO2 and N2 as buffer gases. Especially, the materials of the needle electrode affect the insulation properties of the gas mixtures drastically. On the contrary to the case of needle electrodes made by mild steel or high carbon steel, the N-characteristics are hardly perceived in the case of stainless steel needle in this experiment.

• Journal of Technologic Dentistry
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• v.30 no.1
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• pp.131-139
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• 2008

It's very important to find the most appropriate adhesion technique available, taking into consideration factors such as biocompatibility, non-corrosiveness, mechanical stability, etc. Laser welding is the best choice you can make because from a mechanical viewpoint, a laser welded surface has better particle structure than does a casted particle structure. Furthermore, it requires no additional material and the same metal alloy which is used when casting can be used. Therefore, the resulting mixture will consist of a single alloy, instead of utilizing different alloy combinations. Another benefit is the low economic cost. The most beneficial aspects of laser welding is that it is biologicallly friendlly, doesn't require soldering, can fuse different metal alloys together, and can weld on heat-sensitive spots(E.g. around resin or ceramic). A consistent strong pulse is possible. This technique is capable of welding on master models and creates accurate welds. It is capable of due to its stronger, non-corrosive microscope, which allows 25times magnification during the soldering process. This is possible because of its high stability from the tiny particle structure.

• ETRI Journal
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• v.38 no.3
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• pp.579-588
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• 2016

To improve the ability to determine a vehicle's movement information even in a challenging environment, a hybrid approach called non-Gaussian square rootunscented particle filtering (nGSR-UPF) is presented. This approach combines a square root-unscented Kalman filter (SR-UKF) and a particle filter (PF) to determinate the vehicle state where measurement noises are taken as a finite Gaussian kernel mixture and are approximated using a sparse Gaussian kernel density estimation method. During an outage-free GPS period, the updated mean and covariance, computed using SR-UKF, are estimated based on a GPS observation update. During a complete GPS outage, nGSR-UPF operates in prediction mode. Indeed, because the inertial sensors used suffer from a large drift in this case, SR-UKF-based importance density is then responsible for shifting the weighted particles toward the high-likelihood regions to improve the accuracy of the vehicle state. The proposed method is compared with some existing estimation methods and the experiment results prove that nGSR-UPF is the most accurate during both outage-free and complete-outage GPS periods.