• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.720-722
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• 2009

This work is mainly focused at developing the hydrogen production unit with the capacity of 20 $Nm^3/h$ of high purity hydrogen. At present steam reforming of natural gas is the preferable method to produce hydrogen at the point of production cost. The developed hydrogen production unit composed of natural gas reformer and pressure swing adsorption system. To improve the thermal efficiency of steam reforming reactor, the internal heat recuperating structure was adopted. The heat contained in reformed gas which comes out of the catalytic beds recovered by reaction feed stream. These features of design reduce the fuel consumption into burner and the heat duty of external heat exchangers, such as feed pre-heater and steam generator. The production rate of natural gas reformer was 41.7 $Nm^3/h$ as a dryreformate basis. The composition of PSA feed gas was $H_2$ 78.26%, $CO_2$ 18.49%, CO 1.43% and $CH_4$ 1.85%. The integrated production unit can produce 21.1 $Nm^3/h$ of high-purity hydrogen (99.997%). The hydrogen production efficiency of the developed unit was more than 58% as an LHV basis.

• Electrical & Electronic Materials
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• v.28 no.2
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• pp.25-33
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• 2015

Ruthenium (Ru) thin films were grown on thermally-grown $SiO_2$ substrates by atomic layer deposition (ALD) using a sequential supply of four kinds of novel zero-valent Ru precursors, isopropyl-methylbenzene-cyclohexadiene Ru(0) (IMBCHDRu, $C_{16}H_{22}Ru$), ethylbenzen-cyclohexadiene Ru(0) (EBCHDRu, $C_{14}H_{18}Ru$), ethylbenzen-ethyl-cyclohexadiene Ru(0) (EBECHDRu, $C_{16}H_{22}Ru$), and (ethylbenzene)(1,3-butadiene)Ru(0) (EBBDRu, $C_{12}H_{16}Ru$) and molecular oxygen (O2) as a reactant at substrate temperatures ranging from 140 to $350^{\circ}C$. It was shown that little incubation cycles were observed for ALD-Ru processes using these new novel zero-valent Ru precursors, indicating of the improved nucleation as compared to the use of typical higher-valent Ru precursors such as cyclopentadienyl-based Ru (II) or ${\beta}$-diketonate Ru (III) metallorganic precursors. It was also shown that Ru nuclei were formed after very short cycles (only 3 ALD cycles) and the maximum nuclei densities were almost 2 order of magnitude higher than that obtained using higher-valent Ru precursors. The step coverage of ALD-Ru was excellent, around 100% at on a hole-type contact with an ultra-high aspect ratio (~32) and ultra-small trench with an aspect ratio of ~ 4.5 (top-opening diameter: ~ 25 nm). The developed ALD-Ru film was successfully used as a seed layer for Cu electroplating.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.33.2-33.2
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• 2009

Diffuse ionized gas (DIG or warm ionized medium, WIM) outside traditional regions is a major component of the interstellar medium (ISM) not only in our Galaxy, but also in other galaxies. It is generally believed that major fraction of the Halpha emission in the DIG is provided by OB stars. In the "standard" photoionization models, the Lyman continuum photons escaping from bright H II regions is the dominant source responsible for ionizing the DIG. Then, a complex density structure must provide the low-density paths that allow the photons to traverse kiloparsec scales and ionize the gas far from the OB stars not only at large heights above the midplane, but also within a galactic plane. Here, I present Monte-Carlo models to examine the propagation of the ionizing radiation leaked out of traditional H II regions into the diffuse ISM applied to two face-on spirals M 51 and NGC 7424. We find that the "standard" scenario requires absorption too unrealistically small to be believed, but the obtained scale-height of the galactic disk is consistent with those of edge-on galaxies. We also report that the probability density functions of the Halpha intensities of the DIG and H II regions in the galaxies are log-normal, indicating the turbulence property of the ISM.

• Journal of muscle and joint health
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• v.28 no.1
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• pp.18-29
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• 2021

Purpose: This study examined the knowledge and education needs of nurses in charge of adequacy evaluation in small and medium-sized hospitals. Methods: Study participants included 198 nurses in charge of adequacy evaluation in small and medium-sized hospitals. Data were collected from November 19 to 28, 2020 through an online survey. The data were analyzed by independent t-test and one way ANOVA analysis using the SPSS. Results: The knowledge score for the adequacy evaluation of small and medium-sized hospitals was 11.61±4.10 (total of 20 points), and the educational demand was 3.87±0.88 points on a 5-point scale. Regarding the necessity of education for adequacy evaluation of small and medium-sized hospitals, 80.3% of the participants claimed education as being necessary. "Online video lectures" were the most preferred (22.7%) education method, and "2 times" was the most frequent education (47.0%); "1 hour" was the usual duration of class (48.5%). Conclusion: It is necessary to develop and apply an educational program reflecting the measure of educational needs to improve the knowledge level of nurses in charge of adequacy evaluation in small and medium-sized hospitals.

• Korean Journal of Materials Research
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• v.23 no.3
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• pp.190-193
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• 2013

Spatial distributions of alloying elements of an Fe-based amorphous ribbon with a nominal composition of $Fe_{75}C_{11}Si_2B_8Cr_4$ were analyzed through the atom probe tomography method. The amorphous ribbon was prepared through the melt spinning method. The macroscopic amorphous natures were confirmed using an X-ray diffractometer (XRD) and a differential scanning calorimeter (DSC). Atom Probe (Cameca LEAP 3000X HR) analyses were carried out in pulsed voltage mode at a specimen base temperature of about 60 K, a pulse to base voltage ratio of 15 %, and a pulse frequency of 200 kHz. The target detection rate was set to 5 ions per 1000 pulses. Based on a statistical analyses of the data obtained from the volume of $59{\times}59{\times}33nm^3$, homogeneous distributions of alloying elements in nano-scales were concluded. Even with high carbon and strong carbide forming element contents, nano-scale segregation zones of alloying elements were not detected within the Fe-based amorphous ribbon. However, the existence of small sub-nanometer scale clusters due to short range ordering cannot be completely excluded.

• Bulletin of the Korean Chemical Society
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• v.23 no.2
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• pp.205-214
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• 2002

The reaction of gas-phase atomic hydrogen with hydrogen atoms chemisorbed on a silicon surface is studied by use of the classical trajectory approach. Especially, we have focused on the mechanism changes with the hydrogen surface coverage difference. On the sparsely covered surface, the gas atom interacts with the preadsorbed hydrogen atom and adjacent bare surface sites. In this case, it is shown that the chemisorption of H(g) is of major importance. Nearly all of the chemisorption events accompany the desorption of H(ad), i.e., adisplacement reaction. Although much less important than the displacement reaction, the formation of $H_2(g)$ is the second most significant reaction pathway. At gas temperature of 1800 K and surface temperature of 300 K, the probabilities of these two reactions are 0.750 and 0.065, respectively. The adsorption of H(g) without dissociating H(ad) is found to be negligible. In the reaction pathway forming $H_2$, most of the reaction energy is carried by $H_2(g)$. Although the majority of $H_2(g)$ molecules are produced in sub-picosecond, direct-mode collisions, there is a small amount of $H_2(g)$ produced in multiple impact collisions, which is characteristic of complex-mode collisions. On the fully covered surface, it has been shown that the formation of $H_2(g)$ is of major importance. All reactive events occur on a subpicosecond scale, following the Eley-Rideal mechanism. At gas temperature of 1800 K and surface temperature of 300 K, the probability of the $H_2(g)$ formation reaction is 0.082. In this case, neither the gas atom trapping nor the displacement reaction has been found.

• Reproductive and Developmental Biology
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• v.30 no.4
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• pp.287-291
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• 2006

We have developed a new passaging technique for the expansion of human embryonic stem cells (hESCs) that involves simply pipetting portions of hESCs acquired from colonies, reducing the laborious and time-consuming steps in the expansion of hESCs. Compared to general mechanical methods of passaging, our pipetting method allowed hESCs colonies to be broken into small fragments, which showed significantly higher attachment rates onto feeder cell layers. This technique produced three times the number of hESCs colonies than conventional mechanical methods. In addition, this pipetting method allowed us to distinguish differentiated hESCs from undifferentiated hESCs during hESCs colony pipetting. The hESCs cultured by pipetting method displayed normal human chromosomes for over 60 passages. According to RT-PCR and immunohistochemical analysis, the hESCs successfully maintained their undifferentiated state and pluripotency which was also confirmed by teratoma formation in viva Therefore, the pipetting method described in this study is a useful tool to efficiently and quickly expand hESCs on a large scale without enzyme treatment.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.6
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• pp.1023-1035
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• 2016

Suspended sediment concentration (SSC) is a crucial riverine parameter in terms that it can be utilized for analyzing sediment transport, stability assessment of river and structure and so on. However, in case of domestic, sediment discharge data are not enough because of using conventional sediment samplers. This study aimed at developing a practical technique for estimating suspended sediment concentration in high spatial and temporal resolution by building relationship between acoustic backscatter (or SNR) from H-ADCP with actually observed data using LISST-100X. In this regard, a dedicated correction algorithm was proposed particularly for the adapted H-ADCP (SonTek SL-3000). Then, a SNR-SSC relation was built based upon a real-scale field experiment, where both H-ADCP and LISST-100X were concurrently operated to observe SNR and SSC, respectively. The coefficient of determination for the developed regression equation of SNR-SSC relation was around 0.85~0.88, thereby the relation could be evaluated to be highly correlated. The result of this study might be potentially applied for real-time and simultaneous observation of SSC when H-ADCP could be applied.

• Journal of the Korean Chemical Society
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• v.60 no.1
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• pp.16-20
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• 2016

The solvolysis rate constants of biphenyl-4-carbonyl chloride (C₆H₅C₆H₅COCl, 1) in 19 different solvents are well correlated with the extended Grunwald-Winstein equation, using the N_T solvent nucleophilicity scale, Y_Cl solvent ionizing scale, and I aromatic ring parameter with sensitivity values of 0.31±0.10, 0.46±0.05, and 0.96±0.20 for l, m, and h, respectively. These l, m, and h values can be considered to support a dissciative S_N2 reaction pathway. This interpretation is further supported by the activation parameters, i.e., relatively small positive ΔH^‡ (15.3~16.1 kcal/mol) values and large negative ΔS^‡ (−17.2~−20.0 cal/mol·K) values.

• Journal of Environmental Health Sciences
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• v.28 no.1
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• pp.51-65
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• 2002

This study was carried out to apply some basic physical and chemical treatment options including Fenton's oxidation, and to evaluate the performances and the characteristics of organic and nitrogen removal using lab-scale biological treatment system such as complete-mixing activated sludge and sequencing batch reactor(SBR) processes for the treatment of leachate from a municipal waste landfill in Gyeongnam province. The results were as follows: Chemical coagulation experiments using aluminium sulfate, ferrous sulfate and ferric chloride resulted in leachate CO $D_{Cr}$ removal of 32%, 23% and 21 % with optimum reaction dose ranges of 10,000～15,000 mg/$\ell$, 1,000 mg/$\ell$ and 500～2,000 mg/$\ell$, respectively. Fenton's oxidation required the optimum conditions including pH 3.5, 6 hours of reaction time, and hydrogen peroxide and ferrous sulfate concentrations of 2,000 ～ 3,000 mg/$\ell$ each with 1:1 weight ratio to remove more than 50% of COD in the leachate containing CO $D_{Cr}$ between 2,000 ～ 3,000 mg/$\ell$. Air-stripping achieved to remove more than 97% of N $H_3$-N in the leachate in spite of requiring high cost of chemicals and extensive stripping time, and, however, zeolite treatment removing 94% of N $H_3$-N showed high selectivity to N $H^{+}$ ion and much faster removal rate than air-stripping. The result from lab-scale experiment using a complete-mixing activated sludge process showed that biological treatability tended to increase more or less as HRT increased or F/M ratio decreased, and, however, COD removal efficiency was very poor by showing only 36% at HRT of 29 days. While COD removal was achieved more during Fenton's oxidation as compared to alum treatment for the landfill leachate, the ratio of BOD/COD after Fenton's oxidation considerably increased, and the consecutive activated sludge process significantly reduced organic strength to remove 50% of CO $D_{Cr}$ and 95% of BO $D_{5}$ . The SBR process was generally more capable of removing organics and nitrogen in the leachate than complete-mixing activated sludge process to achieve 74% removal of influent CO $D_{Cr}$ , 98% of BO $D_{5}$ and especially 99% of N $H_3$-N. However, organic removal rates of the SBR processes pre-treated with air-stripping and with zeolite were not much different with those without pre-treatment, and the SBR process treated with powdered activated carbon showed a little higher rate of CO $D_{Cr}$ removal than the process without any treatment. In conclusion, the biological treatment process using SBR proved to be the most applicable for the treatment of organic contents and nitrogen simultaneously and effectively in the landfill leachate.e.