• 한국수소및신에너지학회논문집
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• 제21권5호
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• pp.390-397
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• 2010

0.5wt% Ru/$\alpha-Al_2O_3$ catalysts are prepared by deposition-precipitation method for the preferential CO oxidation In order to investigate the effect of pH on the Ru dispersion and particle size, the pH of precursor solution is adjusted to between 5.5 and 9.5. 0.5wt% Ru/$\alpha-Al_2O_3$ catalyst prepared at the pH of 6.5 has high Ru dispersion of 17.9% and small particle size of 7.7nm. In addition, 0.5wt% Ru/$\alpha-Al_2O_3$ catalyst prepared at the pH 6.5 is easily reduced at low temperatures below $150^{\circ}C$ due to high dispersion of $RuO_2$ particle and shows high CO conversion over 90% in the wide temperature range between $100^{\circ}C$ and $160^{\circ}C$. Moreover, the deposition-precipitation is a feasible method to improve the Ru dispersion as compared to the impregnation method. The 0.5wt% Ru/$\alpha-Al_2O_3$ catalyst prepared by deposition-precipitation exhibits higher CO conversion than 0.5wt% Ru/$\alpha-Al_2O_3$ catalysts prepared by impregnation due to higher metal dispersion and better reducibility at low temperature.

• 한국환경과학회지
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• 제15권11호
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• pp.1061-1067
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• 2006

Photodegradation of endosulfan alpha, beta, and sulfate known as the most toxic substance among organochlorine pesticides by UV irradiation was studied at experimental conditions such as different pH aqueous solution and reaction time. The initial concentration of endosulfan alpha, beta, and sulfate in aqueous solution was 500 ppb, respectively. The experiment of photodegradation was conducted in a quartz reactor equipped with a low pressure mercury lamp (100 W, 240 nm). The samples were withdrawn from the photo reactor at intervals of 0, 10 min, 30 min, 1 hr, 2 hr, and 4 hr. Endosulfan sulfate was never hydrolyzed and photodegraded in wide range of pH. At pH 5 and reaction time (240 min), endosulfan alpha was photodegraded up to 67%. Both endosulfan alpha and beta were started to photodegrade at pH 6.5 with the lapse of time, resulting in approximately 99.9% and 87.2% of photodegradation efficiency, respectively. Furthermore, at pH 9, endosulfan alpha and beta was partially hydrolyzed and photodegraded to 99.5% at 120 min of reaction time. During the photolysis, any photo-products of endosulfan alpha, beta, and sulfate were not observed.

• 한국가축번식학회지
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• 제25권2호
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• pp.155-162
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• 2001

본 실험은 한국재래산양에 있어서 분만 후 초기에 prostaglandin $F_{2{\alpha}}$(PG $F_{2{alpha}$)의 투여가 호르몬 농도 및 난포발육에 미치는 효과를 검토하기 위하여 수행되었던 바 그 결과는 다음과 같다. 1. 분만한 한국재래산양에 혈장중 PG $F_{2{\alpha}}$의 농도는 PG $F_{2{\alpha}}$처리 후 2일에 PG $F_{2{\alpha}}$처리군 (GR-1 및 GR-2)에서 각각 6.35$\pm$0.5 및 0.22$\pm$0.2pg/$m\ell$로서 저하한 후 점차 증가하여 4일 후 21.18$\pm$1.6 및 4.21$\pm$0.4 pg/$m\ell$로서 절정에 도달하였다. 2. 혈장중 PG $F_{2{\alpha}}$의 농도는 PG $F_{2{\alpha}}$ 처리 전 9.08$\pm$1.2 및 5.44$\pm$1.8 pg/$m\ell$였으며 처리후 농도는 다소 저하하였으나 처리 군간에 유의차는 없었다. 3. 혈장중 estradiol-l7$\beta$( $E_2$)농도는 PG $F_{2{\alpha}}$ 처리 후 2일까지 점차 감소한 후 3일에 증가하여 4일에 최대치에 도달하였다. 4. 혈장중 luteinizing hormone (나T)의 농도는 PG $F_{2{\alpha}}$ 처리 후 약간의 증가가 있었으나 유의한 차이는 없었다. 5. 혈장중 prolactin (PRL)의 농도는 PG $F_{2{\alpha}}$처리후 감소되었으나 저농도의 수준으로 남아 있었다. 6. PG $F_{2{\alpha}}$의 처리 후 소형 및 중형의 난포의 수는 거의 유사하였으나 4mm 이상 대형 난포의 수는 숫적로 증가하는 경향을 보였다. 이상의 결과로 보아 PG $F_{2{\alpha}}$ 및 estradiol-17$\beta$는 난포의 직경과 관계가 있다고 암시되며 PG $F_{2{\alpha}}$는 난포발육을 촉진하였다고 생각된다.

• 동력기계공학회지
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• 제4권4호
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• pp.41-47
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• 2000

Fatigue crack propagation rate and threshold characteristics of the SA516/70 steel which is used for the low temperature pressure vessels, were studied in the room temperature of $25^{\circ}C$ and low temperature ranges of $-10^{\circ}C,\;-30^{\circ}C,\;-60^{\circ}C\;and\;-80^{\circ}C$ with stress ratio of R=0.1. In the logarithmic relationship between the fatigue crack propagation rate($d{\alpha}/dN$) and stress intensity factor range ${\Delta}K$, the linear relationship was obtained up to $d{\alpha}/dN=4.425{\times}10^4mm/cycle$ in the same of room temperature, but in low temperature case, the relationship was extended to the range of low crack propagation rate. The fractured specimens were examined by SEM. Tested results showed that specimen failed at low temperature exhibit the quasi-cleavage fracture formation however considerable ductility proceed final fracture.

• 한국세라믹학회지
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• 제31권11호
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• pp.1307-1314
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• 1994

The aim of this work is to show the way of manufacturing the SiC mechanical seal at the low temperature of 130$0^{\circ}C$ using clay and frit as source of secondary phase. $\alpha$-SiC and $\beta$-SiC powder which showed different distribution of particle were used as starting materials, i.e. average particle size of $\alpha$-SiC was larger than that of $\beta$-SiC. The mechanical and tribological properties of two groups of specimen, i.e. one contained mainly larger $\alpha$-SiC powder and the other mainly fine particle $\beta$-SiC, were measured. The specimen consisted of larger $\alpha$-SiC exhibited lower density flexural strength and wear resistance is comparison with these of sample containning mainly $\beta$-SiC . This difference could be originated from the dependence of capillary force on the particle size. For the larger SiC particle, the liquid phase may not fill the whole pores during sintering, due to low capillary force, whereas the liquid phase can infiltrate into the small ores surrounded small $\beta$-SiC particle. Thus, the course of high flexural strength and high wear resistance of specimen prepared using small particles can be explaced from the easy infiltration of liquid phase.

• 대한치과기공학회지
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• 제27권1호
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• pp.65-71
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• 2005

Experimental Ti-13%Zr and Ti-13%Zr-5%Cu alloys were made in an argon-arc melting furnace. The grade 2 CP Ti was used to control. The alloys were cast into phosphate bonded $SiO_2$ investment molds using an argon-arc casting machine, and The hardness and microstructures of the castings were investigated in order to reveal their possible use for new dental casting materials and to collect useful data for alloy design. The hardness of the Ti-13%Zr-5%Cu alloy(379Hv) became higher than that of Ti-13%Zr(317Hv) alloy, and the hardness of this alloys became higher than that of CP Ti(247Hv). Increasing in the hardness of the Ti-13%Zr-5%Cu alloy was considered to be solid solution hardening as the Ti-Zr system shows a completely solid solution for both high temperature $\beta$phase and low temperature $\alpha$ phase and also the inclusion of the eutectoid structure($\alpha Ti+Ti_{2}Cu$). No martensitic structures are observed in the specimen made of CP Ti, but Ti-13%Zr and Ti-13%Zr-5%Cu alloys show a kind of martensitic structure. Ti-13%Zr-5%Cu shows the finest microstructure. From these results, it was concluded that new alloys for dental casting materials should be designed as Ti-Zr-Cu based alloys.

• 대한물리치료과학회지
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• 제19권1호
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• pp.17-25
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• 2012

Purpose : The aim of this study was from data collection to item development in the first study before developing a valid and reliable instrument reflecting Korean's own language expression and culture. Methods : The fist survey was 140 osteoarthritis(OA) patients in 2 Cites was studied from November to December 2009. Open-ended questionnaire was decided 39 items from the first open survey. Questionnaire on the Korean Osteoarthritis Impact Measurement Scale(KAIMS) was recruited 2 professors and 5 physical therapists. Second survey was applied to 133 OA patients. Results : OA patients's average age${\pm}$standard deviation was $66.08{\pm}11.10$ years. The internal consistency reliability of 3 items. As estimated by Cronbach's alpha coefficient(${\alpha}$), was high(range, 0.86~0.96). 0.43~0.91 ${\alpha}$ coefficient for the internal consistency reliability of item-each scale was also high. However, item-discriminant validity on 3 items was low(${\alpha}$, 0.92~0.97). The construct validity by factor analysis was a little low. Conclusion : This study revealed that we confirmed a generation for 39 items on KAIMS reflecting Korean's own language expression and culture. Also, those of reliability were a little high. And, we will have to study the last instrument development (3rd study) by more subjects in the future.

• 한국가시화정보학회지
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• 제4권2호
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• pp.44-50
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• 2006

A visualization study on the boundary layer and near-wake of an NACA 0012 airfoil was con-ducted in order to investigate the influence of boundary layer behavior on the near-wake at low Reynolds numbers. The present study is investigated at static angles of attack ${\alpha}=0^{\circ},\;3^{\circ},\;6^{\circ}$ and $Re=2.3{\times}10^4,\;3.3{\times}10^4,\;4.8{\times}10^4$ by using a smoke-wire technique. The results of this study show that the laminar boundary layer on the airfoil surface is attached to the surface at ${\alpha}=0^{\circ}$, and that laminar separation of boundary layer on the airfoil surface occurs at ${\alpha}=3^{\circ}$. Furthermore, reattachment of the boundary layer occurs in the case of ${\alpha}=6^{\circ}$. In the current study, the location of the laminar separation point moves upstream as the Reynolds number and the angle of attack increase.

• 동아시아식생활학회:학술대회논문집
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• 동아시아식생활학회 2004년도 참깨과학 국제학술대회 발표 논문집
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• pp.13-30
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• 2004

There are two groups of significant functional constituents in sesame seeds on the whole; one is the vegetable oils and another is the anti-oxidative compounds. However, although high amounts of major fatty acids are synthesized in sesame seeds, their composition is unfavorable because the contents of alpha- and gamma-linolenic acid, the essential fatty acids, are very low or do not produced in sesame seeds. So, to increase these fatty acids in sesame seeds, one strategy is to overexpress their genes, ${\omega}$-3 fatty acid desaturase for alpha-linolenic acid and delta-6 fatty acid desaturase for gamma-linolenid acid, in them. Another molecular target is to enhance alpha-tocopherol, vitamin E, because its content is very low in sesame seeds. The enzyme, gamma-tocopherol methyltransferase, catalyzes the conversion of gamma-tocophero to alpha-tocopherol. Overexpression of this enzyme in sesame seeds could be also a good molecular breeding target. Reduction of phytic acid is also another molecular target in sesame seeds because phosphorus pollution may be caused by its high content in sesame seeds. Accordingly, to do so, one of target enzymes could be myo-inositol 1-phosphate synthase which is a key regulatory enzyme in the pathway of phytic aicd biosyntheses. In this lecture, a molecular strategy for development of value-added sesame crop is described in association with some results of our experiments involved in the molecular characterizations of the genes mentioned above.

• 천문학회보
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• 제37권2호
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• pp.71.1-71.1
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• 2012

We have identified local analogs of strong $H{\alpha}$ Emitters (HAEs) that dominate the z~4 Lyman-break galaxy population using the Sloan Digital Sky Survey (SDSS). At z<0.4, only 0.04% of galaxies are classified as HAEs with $H{\alpha}$ equivalent width larger than $500{\AA}$, comparable to that of z~4 HAEs. The $H{\alpha}$-to-UV luminosity ratio of local HAEs is consistent with that of z~4 HAEs, indicating relatively large specific star formation rate in these galaxies compared to traditionally studied UV-selected Lyman break analogs. Local HAEs are young, less evolved galaxies with low metallicity. It is still difficult to constrain whether the star formation in local HAEs is powered by minor mergers or by cosmological cold gas accretion. However, the stacked optical spectrum of local HAEs shows several strong ionization lines, for example HeII 4686 emission line, which are shown in Wolf-Rayet galaxies. Thus it is highly likely that local HAEs are galaxies with an elevated ionization parameter, either due to a high electron density or large escape fraction of hydrogen ionizing photons.