• Journal of Microbiology and Biotechnology
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• v.13 no.5
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• pp.717-724
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• 2003

A newly isolated Citrobacter sp. Y19 catalyzes the CO-dependent $H_2$ production (biological water-gas shift reaction) by the actions of CO dehydrogenase (CODH) and hydrogenase. Y 19 requires $O_2$ for fast growth, but its $H_2$ production activity is significantly inhibited by $O_2$. In the present study, the effect of $O_2$ on the activities of CODH ard hydrogenase was investigated quantitatively in both whole cells and broken cells, based on CO-dependent or methyl viologen (MV)-dependent $H_2$ production in addition to CO-dependent MV reduction. In crude cell extracts, CODH activity was mostly found in the soluble fraction. Inactivation of CODH and hydrogenase activities by $O_2$ followed the first-order decay kinetics, and the dependence of the rate constants on $O_2$ partial pressure could be expressed by the Michaelis-Menten equation. In whole cells, the maximum deactivation rate constants ($k_{d,max}$ of hydrogenase and CODH were quite similar: $0.07{\pm}0.03 min^{-1}\;and\;0.10{\pm}0.04 min^{-1}$, respectively. However, the first-order rate constant ($k_{d,max}/K_s$) of CODH ($0.25\;min^{-1}\;atm^{-1}$) at low $O_2$ partial pressures was about 3-fold higher than that of the hydrogenase, since the half-saturation constant ($K_s$) of CODH was about half of that of hydrogenase. In broken cells, both enzymes became significantly more sensitive to $O_2$ compared to the unbroken cells, while $k_{d,max}/K_s$ increased 37-fold for hydrogenase and 6.7-fold for CODH. When whole cells were incubated under anaerobic conditions after being exposed to air for 1 h, hydrogenase activity was recovered more than 90% in 2 h suggesting that the deactivation of hydrogenase by $O_2$ was reversible. On the contrary, CODH activity was not recovered once deactivated by $O_2$ and the only way to recover the activity was to synthesize new CODH. This study indicates that $O_2$ sensitivity of $H_2$ production activity of Citrobacter sp. Y19 is an important drawback as in other $H_2-producing$ bactria.

• Clean Technology
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• v.23 no.1
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• pp.104-112
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• 2017

Hydrogen production via steam reforming of liquefaction liquid from marine algae over hydrothermal liquefaction was carried out at 873 ~ 1073 K with a commercial catalyst and Ni based $K_2Ti_xO_y$ added catalysts. Liquefaction liquid obtained by hydrothermal liquefaction (503 K, 2 h) was used as a reactant and comparison studies for catalytic activity over different catalysts (FCR-4-02, $Ni/K_2Ti_xO_y-Al_2O_3$, $Ni/K_2Ti_xO_y-SiO_2$, $Ni/K_2Ti_xO_y-ZrO_2/CeO_2$ and Ni/$K_2Ti_xO_y$-MgO), reaction temperature were performed. Experimental results showed Ni/$K_2Ti_xO_y$ based catalysts ($Ni/K_2Ti_xO_y-Al_2O_3$, $Ni/K_2Ti_xO_y-SiO_2$, Ni/$K_2Ti_xO_y-ZrO_2$/ $CeO_2$ and Ni/$K_2Ti_xO_y$-MgO) have a higher activity than commercial catalyst (FCR-4-02) and In particular, a product composition was different depending on support materials. An acidic support ($Al_2O_3$) and a basic support (MgO) led to a higher selectivity for CO while a neutral support ($SiO_2$) and a reducing support ($ZrO_2/CeO_2$) resulted in a higher $CO_2$ selectivity due to water gas shift reaction.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.3
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• pp.173-179
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• 2016

This is a numerical study on the curved channel type of hydrogen reformer using the commercial code of fluid dynamics. We numerically compared the numerical model in a previous study model and the modelling of a tube type curved channel. In the result of numerical analysis on 4 types of curved channel reformers, the methanol conversion efficiency of type 1~4 were 45.0%, 45.3%, 45.6%, 45.6% respectively, and there was hardly any difference by ${\pm}0.6%$. In light of flow characteristics, the rectangle type tube and the type 2 with $45^{\circ}$ turn showed most uniform flow characteristics and concentration distribution of methanol, and the circular type tube and the type 3 with $90^{\circ}$ turn had most un-uniform flow characteristics and concentration distribution of methanol. We concluded that the design for curved channel reformer has to have rectangle type tube with curve of almost $45^{\circ}$ as in the type of curved pipe with $45^{\circ}$ turn.

• Journal of Energy Engineering
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• v.19 no.4
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• pp.215-220
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• 2010

Hydrogen is a clean and efficient energy source and is expected to take an important role in future energy demand. A possibly good route to produce hydrogen is by using biomass and organic wastes as a source through thermo-chemical conversion technology. In this study, pyrolysis of wood Pellet(Oregon pine) has been carried out in batch type fixed-bed reactor in $N_2$ atmosphere during 20 minutes to determine the optimum hydrogen generating conditions. At the influence of temperature, hydrogen yield was increased with increasing temperature. For the influence of Steam/Biomass Ratio(SBR), hydrogen yield was increased by steam addition at low temperature condition. However, effect of steam addition was insignificant over at SBR = 1. The hydrogen yield was increased with increasing SBR at high temperature condition. From result of $H_2$/CO and $H_2/CH_4$ ratio, dominant reaction was steam reforming in this experimental condition. The optimum condition for hydrogen production was determined as follows: $H_2$ yield = 38.3 vol.% (56.01 L/min kg) at $900^{\circ}C$, SBR=3.

• Journal of Food Hygiene and Safety
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• v.21 no.4
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• pp.231-237
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• 2006

Nowadays the teabag is worldwide used for various products including green tea, tea, coffee, etc. since it is convenient for use. In case of outer packaging printed, however, there is a possibility that the plasticizers which is used for improvement in adhesiveness of printing ink may shift to inner tea bag. In this study, in order to monitor residual levels of plasticizers in teabags, we have established the simultaneous analysis method of 9 phthalates and 7 adipates plasticizers using gas chromatography (GC). These compounds were also confirmed using gas chromatography-mass spectrometry (GC-MSD). The recoveries of plasticizers analyzed by GC ranged from 82.7% to 104.6% with coefficient of variation of $0.6\sim2.7%$ and the correlation coefficients of each plasticizer was $0.9991\sim0.9999$. Therefore this simultaneous analysis method was showed excellent reproducibility and linearity. And limit of detection (LOD) and limit of quantitation (LOQ) on individual plasticizer were $0.1\sim3.5\;ppm\;and\;0.3\sim11.5\;ppm$ respectively. When 143 commercial products of teabag were monitored, no plasticizers analysed were detected in filter of teabag products. The migration into $95^{\circ}C$ water as food was also examined and the 16 plasticizers are not detected. In addition we carried out analysis of heavy metals, lead (Pb), cadmium (Cd), arsenic (As) and aluminum (Al) in teabag filters using ICP/AES. $Trace\sim23{\mu}g$ Pb per teabag and $0.6\sim1718{\mu}g$ Al per teabag were detected in materials of samples and Cd and As are detected less than LOQ (0.05 ppm). The migration levels of Pb and Al from teabag filter to $95^{\circ}C$ water were upto $11.5{\mu}g\;and\;20.8{\mu}g$ per teabag, respectively and Cd and As were not detected in exudate water of all samples. Collectively, these results suggest that there is no safety concern from using teabag filter.

• The Journal of Engineering Geology
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• v.31 no.4
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• pp.603-620
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• 2021

A land nodal seismic system was employed to acquire seismic reflection data using stand-alone cable-free receivers in a land-river area. Acquiring reliable data using this technology is very cost effective, as it avoids topographic problems in the deployment and collection of receivers. The land nodal airgun system deployed on the mouth of the Hyungsan River (in Pohang, Gyeongsangbuk Province) used airgun sources in the river and receivers on the riverbank, with subparallel source and receiver lines, approximately 120 m-spaced. Seismic data collected on the riverbank are characterized by a low signal-to-noise (S/N) and inconsistent reflection events. Most of the events are represented by hyperbola in the field records, including direct waves, guided waves, air waves, and Scholte surface waves, in contrast to the straight lines in the data collected conventionally where source and receiver lines are coincident. The processing strategy included enhancing the signal behind the low-frequency large-amplitude noise with a cascaded application of bandpass and f-k filters for the attenuation of air waves. Static time delays caused by the cross-offset distance between sources and receivers are corrected, with a focus on mapping the shallow reflections obscured by guided wave and air wave noise. A new time-distance equation and curve for direct and air waves are suggested for the correction of the static time delay caused by the cross-offset between source and receiver. Investigation of the minimum cross-offset gathers shows well-aligned shallow reflections around 200 ms after time-shift correction. This time-delay static correction based on the direct wave is found essential to improving the data from parallel source and receiver lines. Data acquisition and processing strategies developed in this study for land nodal airgun seismic systems will be readily applicable to seismic data from land-sea areas when high-resolution signal data becomes available in the future for investigation of shallow gas reservoirs, faults, and engineering designs for the development of coastal areas.

• Journal of vocational education research
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• v.36 no.1
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• pp.47-75
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• 2017

The purpose of this study was to provide basic data for policy making for secondary vocational education in each region and transformation in vocational high schools. To achieve this, the regional strategic industries in Daejeon and Jeonnam were selected, new demand for vocational high school graduates was forecasted in each industry and occupation. The results of the study are as follows. First, locational quotient analysis and regional shift-share analysis revealed that Daejon and Jeonnam have different strategic industries. Daejon, unlike Jeonnam strategically develops 'manufacturing food, beverage and tobacco', 'manufacturing timber and paper, printing and copying', 'public service and administration of national defense and social security' and 'manufacturing electrical devices, electronics and precision devices'. Jeonnam has specialized industries distinguished from Daejon's, which are 'manufacturing of machinery transportation equipments and etc', 'manufacturing of non-metallic minerals and metal products', 'electric, gas, steam and water supply systems/industries', 'manufacturing coal and chemical products, refining petroleum', 'mining' and 'agriculture, forestry and fishery'. Second, new demand for vocational high school graduates by occupations and industries showed regional differences(in Daejon and Jeonnam). According the forecast, Daejon will have many workforce demands based on manufacturing industries, on the other hand Jeonnam's focused on service industries. Analysis by occupations was also different, Daejon showed high demands on professional and related workers, while Jeonnam requested many new office and service workers. Third, new workforce demand by occupations in regional strategic industries is big part of overall new workforce demand both in Daejon and Jeonnam. Forth, according to the results of analyzing the new demand for vocational high school graduates in Daejeon and Jeonnam in terms of industry location quotient and change effect, there was high demand in industries with positive total change effects. In terms of location quotient, Daejeon and Jeonnam showed different results.

• Journal of Venture Innovation
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• v.5 no.3
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• pp.57-70
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• 2022

In modern industrial capitalism, the relationship between the provision of work and the receipt of wages has become an important principle governing society. According to the labor contract, the wages provided by entrusting the right to dispose of one's labor to the employer are directly compensated, and human life should be guaranteed and reproduced with proper rest. The establishment of labor relations under free contracts represents a problem in protecting workers, and accordingly, the maximum of working hours is set as a minimum right for workers, and the standard for minimum rest is set and assigned. The reduction of working hours is very important in terms of the quality of life of workers, but it is also an important issue in efficient corporate activities. As of 2020, Korea has 1,908 hours of annual working hours, the third lowest among OECD 37 countries in the happiness index surveyed by the Sustainable Development Solution Network(SDSN), an agency under the United Nations. Accordingly, the necessity of reducing working hours has been recognized, and the maximum working hours per week has been limited to 52 hours since 2018. In this situation, various working hours are legally excluded as a way to maintain the company's value-added creation and meet the diverse needs of workers, and Korea's Labor Standards Act restricts flexible working hours within three months, flexible working hours exceeding three months, selective working hours, and extended working hours. However, in the discussion on the application of the revised flexible working hours system in 2021 and the expansion of the settlement unit period recently discussed, there is a problem with the flexible working hours system, which needs to be improved. Therefore, this paper aims to examine the problems of the flexible working hours system and improvement measures. The flexible working hours system is a system that does not violate working hours even if the legal working hours are exceeded on a specific day or week according to a predetermined standard, and does not have to pay additional wages for excessive overtime work. It is mainly useful as a form of shift work in manufacturing, sales service, continuous business or electricity, gas, water, and transportation for long-term operations. It is also used as a way to shorten working hours, such as expanding holidays through short working days. However, if the settlement unit period is expanded, it is disadvantageous to workers as the additional wages that workers can receive will not be received. Therefore, First, in order to expand the settlement unit period currently under discussion, additional wages should be paid for the period expanded from the current standard. Second, it is necessary to improve the application of the flexible working hours system to individual workers to have sufficient consultation with individual workers in a written agreement with the worker representative, Third, clarify the allowable time for extended work during the settlement unit period, and Fourth, limit the daily working hours or apply to continuous rest. In addition, since the written agreement of the worker representative is an important issue in the application of the flexible working hours system, it is necessary to secure the representation of the worker representative.