• Environmental Engineering Research
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• v.17 no.3
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• pp.151-156
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• 2012

This research described the magnetic method for the rapid removal of green algae in water. We modified the pH, cation concentration, and magnetic powder concentration to discover the best removal performance. In order to rapidly remove green algae from water, we added magnetic powder and chitosan into algae water to make a magnetic substance and this was extracted by a strong neodymium magnet. The optimized conditions were pH of 6.5-7.5, chitosan concentration of 10 mg/L, and magnetite powder concentration of less than 0.05%. A higher removing rate was observed when a higher amount of magnetite or chitosan was used, but the total amounts of phosphorus or nitrogen were not decreased.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1993.05a
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• pp.64-69
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• 1993

The solar energy collection of a passive solar system depends on the finish of collecting surfaces. In this study, the test models of T.W system with different wall surface finishes were constructed, and the temperature distribution through the models was monitored. At the same time, a computer program based on F.D.M was developed in order to simulate various surface finishes. The difference of indoor temperature between the model with white color finish ($\alpha$=0.25) and the one with black color finish ($\alpha$=0.95) was about 1$0^{\circ}C$. For the wall with selective coating, the indoor temperature was 4-5$^{\circ}C$ higher than that of red brick wall, and 3-4$^{\circ}C$ higher than that of wall with black paint.

• Journal of Nutrition and Health
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• v.19 no.3
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• pp.190-198
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• 1986

The result of the analytical experimental by HPLC on amino acid which is contained in such samples as white-raw-sesame, white-roast -seasame, black -raw -sesame, black-roast-sesame, raw-perilla seed and roast-perilla seed is as follows ; In the six smaples, the amino acid contents in raw seeds were all higher than those in roasted seeds, and the contents of alutamic acid and lysine were more reduced in roasted seeds than in raw seeds. All the amino acid contents except threoninewere highest in raw perilla seed. The amino acids which the six samples contain to a higher degree were in order of glutamic acid (18 %-21%), threonine(16%-19%), glycine (8%-9%), leucine(77.5%), aspartic acid (7%-7.4%), while methinine (1-2%) was contained least in all six samples followed by Isoleucine(3%).

• 연구논문집
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• s.26
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• pp.33-42
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• 1996

The transmission system of a washing machine which is called by the clutch is one of the most important components to preserve the performance. The clutch housing has a role to guard and mount the transmission system on the frame of the machine. The load which is applied on the clutch housing depends on the operating conditions. Nowadays the dehydration speed is higher and higher in order to improve the efficiency. In this study, the strains on the predicted weak positions were measured using the strain gage and its measuring equipment. The relationships between the dehydration speeds and the maximum principal strains were obtained. Finite element analysis is executed to acquire the effect of the dehydration speed on the stress of the clutch housing. The distributions of the equivalent stress and the maximum stresses under the various speeds, the various loading directions and the various thickness of the clutch housing were obtained.

• International Journal of Fluid Machinery and Systems
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• v.2 no.4
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• pp.426-430
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• 2009

In order to investigate the design method for a micro centrifugal compressor, which is the most important component of an ultra micro gas turbine, an impeller having the outer diameter of 20mm was designed, manufactured and tested. The designed rotational speed is 500,000 rpm and the impeller has a fully 3-dimensional shape. The impeller was rotated at 250,000 rpm in the present study. The experimental results of the tested compressor with the vaned and the vaneless diffusers were compared. It was found that the vaned diffuser attained the higher flow rate than the vaneless diffuser at the maximum pressure ratio. In addition the maximum pressure ratio was higher for the diffuser having a larger diffuser divergence angle at the high flow rate. These results were compared with those obtained by the prediction method used at the design stage.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.3
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• pp.1-7
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• 2009

Ethanol has properties of a lower setting point, higher oxygen contents, lower cetane numbers, and also higher volatility compared to biodiesel. Thus, biodiesel fuel can be improved in the fluidity of and exhaust emissions by blended ethanol fuel. This research aims to understand combustion characteristics of biodiesel-ethanol blending fuel inside a constant volume chamber by obtaining some fundamental data in order to improve combustion atmosphere. To understand the physics of combustion, high speed camera was applied to visualize the development of combustion processes, and combustion pressure and exhaust emission were measured at several blending ratios of ethanol and biodiesel fuel. This information may contribute to improve the performance of biodiesel engine and reduce emissions in future.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.49-49
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• 2009

Phosphors with oxide host material, YAG:$Ce^{3+}$ and $(Ca,Sr,Ba)_2SiO_4:Eu^{2+}$ yellow phosphor, has been used for LED applications. The WLEDs using these phosphors are widely used for LCD backlighting, automobile, and general lighting applications since they have high conversion efficiency and good thermal and chemical stability which can meet necessary life time of LED products up to now. With advances of LED chip technology, the external quantum efficiency and driving current in chip get higher so that the phosphors for high power chip are required to maintain high conversion efficiency and stability at high temperature due to the heat dissipated from LED chips. In addition, higher color rendering index of LED lighting and color reproducibility of LCD than those of LEDs with single yellow phosphors are required. In order to overcome these technical issues rising from evolution of LED technology, new phosphors are in demand and nitride phosphors, one of the promising new candidate materials, will be discussed here.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.2
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• pp.79-89
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• 2016

If scour is occurred at shallow foundation of bridge, seismic performance of the bridge will be reduced. In order to evaluate accurate seismic response of bridge according to scour depths, modeling of foundation reflecting scour effect is important. In this study, taking into account the effect of the reduction in embedment depth of the shallow foundation by scouring, the soil around the foundation is modelled as an equivalent soil spring with various stiffness. Seismic fragility analyses for 3 types of bridges subjected to 4 types of ground motions classified into Site Class A, B, C, D are evaluated according to several scour depths. From the fragility analysis results, it can be observed that the deeper the scour depth, the higher probability of exceeding damage states. Also, seismic failure probability of asymmetric bridge is higher than that of symmetric bridge.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.273-278
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• 2006

In order to use a GPS antenna for launch vehicles, it should be installed on the skin of the vehicle and be able to normally receive the live GPS signals during the vehicle's full flight mission. The GPS antenna on the surface of the launch vehicle is, however, exposed to higher temperature than inner equipments of the vehicle due to aerodynamic heating generated during the flight. Test specification of the GPS antenna for qualification of hot-temperature is determined to $+95^{\circ}C$ that is higher than inner components by $25^{\circ}C$. Test results in this paper show that the GPS antenna normally operates under the above environment.

• East Asian Economic Review
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• v.23 no.1
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• pp.89-107
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• 2019

This paper ranks higher education in Korea based upon research productivity in business and economics disciplines. The number of SCI-level journal articles are tabulated using the Web of Science search engine, over the sample period from 1990 to 2016. The league table shows that many private universities dominate top-tier ranks, which is consistent with the school reputations most commonly cited by the general public in Korea. In contrast, many national universities appear in the second-tier, and their scanty performance in business and economics is in sharp contrast with our earlier findings in which national universities performed well in science and engineering fields (Jin and Kim, 2018). In addition, the ranking order in lower-ranked schools is found to be sensitive to a small change in publications, whereas the publication gap among top-tier schools is relatively large. Finally, unlike our general perception, the size of school does not matter for collaborative research. Some policy implications are discussed as a conclusion.