• Journal of Environmental Science International
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• v.20 no.2
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• pp.251-260
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• 2011

$TiO_2$- and $SiO_2$-supported $Co_3O_4$, Pt and $Co_3O_4$-Pt catalysts have been studied for CO and $C_3H_8$ oxidations at temperatures less than $250^{\circ}C$ which is a lower limit of light-off temperatures to oxidize them during emission test cycles of gasoline-fueled automotives with TWCs (three-way catalytic converters) consisting mainly of Pt, Pd and Rh. All the catalysts after appropriate activation such as calcination at $350^{\circ}C$ and reduction at $400^{\circ}C$ exhibited significant dependence on both their preparation techniques and supports upon CO oxidation at chosen temperatures. A Pt/$TiO_2$ catalyst prepared by using an ion-exchange method (IE) has much better activity for such CO oxidation because of smaller Pt nanoparticles, compared to a supported Pt obtained via an incipient wetness (IW). Supported $Co_3O_4$-only catalysts are very active for CO oxidation even at $100^{\circ}C$, but the use of $TiO_2$ as a support and the IW technique give the best performances. These effects on supports and preparation methods were indicated for $Co_3O_4$-Pt catalysts. Based on activity profiles of CO oxidation at $100^{\circ}C$ over a physical mixture of supported Pt and $Co_3O_4$ after activation under different conditions, and typical light-off temperatures of CO and unburned hydrocarbons in common TWCs as tested for $C_3H_8$ oxidation at $250^{\circ}C$ with a Pt-exchanged $SiO_2$ catalyst, this study may offer an useful approach to substitute $Co_3O_4$ for a part of platinum group metals, particularly Pt, thereby lowering the usage of the precious metals.

• Korean Journal of Biological Psychiatry
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• v.17 no.1
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• pp.37-43
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• 2010

Objectives : The $2^{nd}$ to $4^{th}$ digit length ratio(2D : 4D) is a sexually dimorphic trait regardless of ethnicity and shows sex differences. According to previous research, men usually have a relatively shorter $2^{nd}$ digit than $4^{th}$ digit. There is tendency that men with lower 2D : 4D are perceived as being more masculine and tend to perform better in some physical sports. Furthermore, 2D : 4D is negatively associated with trait aggression. In this study, we examine gender difference of 2D : 4D and compare 2D:4D of female Korean national team members to 2D : 4D of control subjects. Besides that, we also compare 2D : 4D of female Korean national team members according to their sports entries. Methods : The sample of this study is 396 people, 67 female Korean national team member, 216 control women and 113 control men. We measured $2^{nd}$ to $4^{th}$ digit length of their right hand. In addition, we collected demographic information of female Korean national team members using a self-report questionnaire. Results : The mean 2D : 4D of female Korean national team members is 0.96(SD=0.04), smaller than control women's 2D : 4D(0.97, SD=0.03) and significantly higher than control men's 2D : 4D(0.95, SD=0.03). We also found differences between control men and women. Non-martial arts related sports athletes have significant difference with control men in 2D : 4D. However, martial arts related sports athletes' 2D : 4D is not significantly different from other groups, including control men. Conclusion : These results are consistent with the findings of previous research that there is a significant difference between men and women in their 2D : 4D. Furthermore, 2D : 4D of martial arts related sports athletes have not shown any difference from the 2D : 4D of control men that 2D : 4D of non-martial arts related athletes have shown. This fact is important in consideration of masculine characteristics. For further research, it is necessary to examine 2D : 4D difference according to sport ability and gender differences.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.3
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• pp.566-576
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• 2017

Key-value stores proved its superiority by being applied to various NoSQL databases such as Redis, Memcached. Lookup performance is important because key-value store applications performs more lookup than insert operations in most environments. However, in traditional applications, lookup may be slow because hash tables are constructed out of linked-list. Therefore, cuckoo hashing has been getting attention from the academia for constant lookup time, and bucketized cuckoo hashing (BCH) has been proposed since it can achieve high load factor. In this paper, we introduce Sorting Cuckoo which inserts data using insertion sort in BCH structure. Sorting Cuckoo determines the existence of a key with a relatively small memory access because data are sorted in each buckets. In particular, the higher memory load factor, the better lookup performance than BCH's. Experimental results show that Sorting Cuckoo has smaller memory access than BCH's as many as about 19 million (25%) in 10 million negative lookup operations (key is not in the table), about 4 million times (10%) in 10 million positive lookup operations (where it is) with load factor 95%.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.1
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• pp.121-129
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• 2008

Major factors affecting water quality in rivers are transportation, input of pollutant loads and kinetic transformation of pollutants. Government level decision makings on water quality management are based on steady state water quality modeling. However, it is more than often that such a steady state assumption is far from real situations in rivers. Therefore, it is unavoidable to have modeling errors in water quality modeling especially for steady state modeling for longer period of time. Authors attempted to identify sources of errors in results of steady state models and thus tried to find out ways to minimize those errors. Three water quality models, QUAL2E (Brown et al., 1983), QUAL2K (Chapra et al., 2006) and CAP (Seo and Lee, 2000) were applied to the lower stream of the Geum River. $BOD_5$ and COD tend to underestimate observed data while TN and TP showed relatively smaller errors. QUAL2E model provided best calibration results for BOD5 and TP and QUAL2K model showed best calibration results for TN. Since these errors are only relative values, it was difficult to conclude which model is better performing in certain situations. The most probable reasons for errors in water quality modeling are; 1) inappropriate consideration on flow characteristics, 2) lack of information on incoming pollutant load and 3) inappropriate location of sampling for water quality analysis.

• Journal of Labour Economics
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• v.28 no.2
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• pp.1-27
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• 2005

This study intends to analyze outcomes in labor market of students who graduated from provincial colleges. And For this aim, this study used 'Youth Panel Data' (2001, 2002) of HRD Korea Work Information Center. The reference groups are students who graduated from capital region colleges. The main results of this study are as follows. Students who graduated from provincial colleges have difficulty in acquiring job information than capital region college graduates. And students who graduated from provincial colleges get first job in smaller firm than capital region college graduates. The monthly wage level of students who graduated from provincial colleges is less than that of capital region college graduates. And the outcomes in labor market of students who graduated from Chungcheong region colleges are better than those of students who graduated from Yeongnam region and Honam region colleges. As results of this study show, there are differences between provincial college graduates and capital region college graduates. And there are differences between Chungcheong region college graduates and another region (namely, Yeongnam region and Honam region) college graduates.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.6
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• pp.581-589
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• 2005

Recently, membrane processes have been replacing the conventional processes for waste water treatment to produce better quality of effluent and to meet more stringent regulations because of water shortage. However, using membrane processes for water treatment has confronted with fouling and difficulty in treating dissolved organic pollutants. In this study, membrane process equipped with crossflow microfiltration is combined with coagulation process using alum and PAC to improve permeability and treatment efficiency. The effects of coagulant dosage and optimum membrane operating conditions were investigated from measurement of permeate flow, cumulative volume, total resistance, particle size, dissolved organic pollutant, dissolved aluminium and quality of effluent. Characteristic of PAC coagulation was compared with that of alum coagulation. PAC coagulation reduced membrane fouling because of forming larger particle size and increased permeate velocity and cumulative volume. Less dissolved organic pollutants and dissolved aluminum made decreasing-rate of permeate velocity being lowered. At using $0.2\;{\mu}m$ membrane, cake filtration observed. At using $0.45\;{\mu}m$ membrane, there was floc breakage due to shear stress occurred born circulating operation. It made floc size smaller than membrane pore size, which subsequently to decrease permeate velocity and to increase total resistance. The optimum coagulation dosage was $300{\pm}50\;mg/L$ for both alum and PAC. PAC coagulation was more efficiently used with $0.2\;{\mu}m$ membrane, and the highest permeate flux was in using $0.45\;{\mu}m$membrane. The greatest efficiency of treatment was as follows; turbidity 99.8%, SS 99.9%, $BOD_5$ 94.4%, $COD_{Cr}$ 95.4%, T-N 54.3%, T-P 99.8%.

• Sleep Medicine and Psychophysiology
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• v.1 no.2
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• pp.163-171
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• 1994

Objectives: Symptoms of sleep apnea consisted of insomnia, excessive sleepiness during daytime, impaired cognitive functions and emotional disturbances. It was not so well known how these symptoms are correlated with various parameters of sleep and respiration, and what kind of psychophysiological processes are involved in development of these symptoms. Methods: In sixty patients with sleep apnea, sleep and respiration were studied by polysomnography of one night, also symptoms of sleep apnea were evaluated with the scales of insomnia, daytime sleepiness, emotional disturbance and cognitive impairment We studied correlations between apnea symptoms, and various parameters of sleep and respiration such as sleep efficiency, number severity of apnea, $O_2$ desaturation and number of snoring. Results: The result showing significant correlations are as follows. The patients with better sleep in insomnia scale showed more number of apnea, particularly more central type, and much more snoring in stage 3 sleep and mild desaturation of $O_2$. Excessive sleepiness during daytime correlated significantly with stage 1 sleep and its snoring, but correlated negatively with stage 2 sleep. However, no significant correlation was found with degree of $O_2$ desaturation. Emotional disturbance was more apparent in the patients with severe $O_2$ desaturation and smaller amounts of stage 4 sleep. Cognitive function was more impaired in cases of more REM sleep and less apnea. Conclusions: Symptoms of sleep apnea may occur through different causes and processes. The evaluation of apnea symptoms may be helpful to understand in some degree the condition of sleep and respiration during sleep in clinical setting.

• Korean Chemical Engineering Research
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• v.44 no.6
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• pp.669-675
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• 2006

Toluene of aromatic compounds, MEK of ketones and IPA of alcohols were extremely used as VOCs (Volatile Organic Compounds) on the getting into step with industrial process. The adsorption characteristics of three component solvent vapors (Toluene-MEK-IPA) on the activated carbonaceous adsorbents such as AC, ACF and AC+ACF were investigated in a stainless steel fixed bed adsorption experimental apparatus in order to identify those carbons for eliminating and recovering solvent vapors from industrial emission sources. The used activated carbonaceous adsorbents were pelletized commercial activated carbon and activated carbon fiber. The breakthrough curves and adsorption capacity have been obtained at atmospheric pressure in a adsorption fixed bed. It has been found that non-polar and larger molecules have been adsorbed better than polar and smaller molecules. Especially, alcohols and ketones were poorly adsorbed due to competitive adsorbability in ternary mixture system. However, it could be overcome by employment of activated carbonaceous adsorbent which have different porosity distribution appropriately.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.28 no.2
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• pp.173-183
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• 1983

To evaluate growing degree days(GDD) as an index of growth duration of rice plants, 30 days old seedlings of 16 japonica and 14 indica/japonica varieties were transplanted six times from May 10 at the 10-day intervals at Gyeongsan in 1982. The number of days from transplanting to heading decreased as transplanting dates delayed in all japonica varietie and 4 indica/japonica varieties but that of 10 indica/japonica varieties decreased up to June 9 or June 19 transplantings and then it levelled off or increased with further delay of transplanting. However, GDD requirement was similar among transplanting dates at appropriate base temperatures; GDD could be better than calendar day system to classify maturity of varieties especially grown in a wide range of climatic conditions. Required GDD from transplanting to heading of all indica/japonica and early japonica varieties showened a smaller coefficient of variation (CV) compared to longer season japonica varieties. Among GDD methods, an accumulation of daily Max + Min temp./2 -$l0^{\circ}C$ showed the smallest CV for the duration from transplanting to heading, but for ripening period GDD calculated with adjusted maximum temperature when it was higher than $30^{\circ}C$ showed the best results. Heading date did not affect required GDD for maturity of japonica varieties, but in indica/japonica varieties GDD decreased as heading date delayed; at late transplantings ripening period of indica/japonica varieties was less extended compared to japonica varietes due to a decrease in grain weight.

• Polymer(Korea)
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• v.39 no.3
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• pp.433-440
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• 2015

Aluminum trihydroxide (ATH) has been commonly employed as a flame retardant for ethylene vinyl acetate (EVA) copolymers. In the present work, ATH was obtained from a recycling process of multi-layer packaging film wastes. EVA/ATH composite samples were prepared using a two roll-mill and flame retardancy of EVA/ATH composites were examined using limiting oxygen index (LOI) and flame retardancy test (UL94). We observed excellent flame retardancy in case of adding 150 phr or more of recycled ATH to EVA. Particle size and specific surface area play crucial roles in LOI value and UL-94 classification of the EVA/ATH composites. Smaller particle size and higher specific surface area of ATH was found out to improve the flame retardancy. Regarding tensile properties, crosslinked EVA/ATH compounds which is practically used for electric cables had similar to or even better tensile property values than the ones without ATH.