• Korean Chemical Engineering Research
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• v.60 no.2
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• pp.237-242
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• 2022

In this study, a drying method that can effectively remove residual solvent from (+)-dihydromyricetin was developed. Residual acetone concentration was efficiently removed below ICH-specified value (5,000 ppm) by simple rotary evaporation with ethanol pretreatment. In addition, the residual ethanol met the ICH-specified value (5,000 ppm) by simple rotary evaporation through the addition of water, and the residual moisture also met the specified value (<4%) for active pharmaceutical ingredients. At all the drying temperature (35, 45, and 55 ℃), a large amount of the residual solvent was initially removed during the drying, and the drying efficiency increased when increasing the drying temperature. Removal of residual solvent by ethanol pretreatment was shown to be related to high vapor pressure of acetone-ethanol mixture and hydrogen bonding between acetone and ethanol.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.46 no.3
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• pp.20-27
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• 2014

Nowadays, the bleaching techniques of thermomechanical pulp(TMP) are fast developing on the strength of some benefits, mainly on low production cost and good fiber property. In this study, the optimum concentration of bleaching chemicals and the environmental load of bleaching wastes were considered to improve the bleaching efficiency of thermomechanical pulp using Korean redpine(Pinus densiflora) under the peroxide-based bleaching system. The optical property of TMP after bleaching was planned to use higher grade of paper, like printing & writting paper, not general newspaper. The concentration of bleaching chemicals, NaOH, $Na_2SiO_3$ and EDTA, in hydrogen peroxide bleaching system, on the basis of O.D. pulp was closely influenced on the improvement of TMP brightness. Final target of bleaching efficiency was set up to above 76%-ISO brightness. The optimal target brightness of Korean redpine TMP was reached to 76.45%-ISO under the conditions of $H_2O_2$ 7% with NaOH 2.20%, $Na_2SiO_3$ 0.63% and EDTA 0.02%. The concentration of NaOH, $Na_2SiO_3$ and EDTA was correlated functional to the residual peroxide content of wastewater, pH value and electric conductivity of TMP fibers after bleaching treatment. The optimal bleaching conditions by controlling the addition amount of chemicals were positively contributed to the brightness stabilization and environmental load of TMP.

• KSBB Journal
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• v.20 no.6
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• pp.401-407
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• 2005

Optimum culture conditions and medium composition for hydrogen production by Clostridium beijerinckii KCTC 1785 were investigated. Initial pH and temperature for growth were 7.0 and $35^{\circ}C$, respectively. Agitation accelerated the hydrogen production. Although C. beijerinckii KCTC 1785 could grow up to 6%(w/v) glucose in the medium, the optimum glucose concentration for hydrogen production was 4% and hydrogen content in the biogas was 37%(v/v). However, the economical glucose concentration for hydrogen production was 1% regarding to the residual glucose which was not used in the medium. During hydrogen fermentation, acetic and butyric acid were produced simultaneously. High concentrations of acetic(>5,000 mg/L) or butyric(>3,000 mg/L) acid inhibited hydrogen production. When pH was maintained at 5.5 in the batch fermentation, 1,728 mL of hydrogen was produced from 0.5% glucose within 15 hr. $H_2$ yield was estimated to be 1.23 mol $H_2/mol$ glucose. It was found that yeast extract or tryptose in the medium was essential for hydrogen production.

• Journal of Microbiology and Biotechnology
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• v.15 no.1
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• pp.131-135
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• 2005

Under sulfur deprived conditions, PS II and photosynthetic $O_2$ evolution by Chlamydomonas reinhardtii UTEX 90 are inactivated, resulting in shift from aerobic to anaerobic condition. This is followed by hydrogen production catalyzed by hydrogenase. We hypothesized that the photosynthetic capacity and the accumulation of endogenous substrates such as starch for hydrogen production might be different according to cell age. Accordingly, we investigated (a) the relationships between hydrogen production, induction time of sulfur deprivation, increase of chlorophyll after sulfur deprivation, and residual PS II activity, and (b) the effect of initial cell density upon sulfur deprivation. The maximum production volume of hydrogen was 151 ml $H_2$/l with 0.91 g/l of cell density in the late-exponential phase. We suggest that the effects of induction time and initial cell density at sulfur deprivation on hydrogen production, up to an optimal concentration, are due to an increase of chlorophyll under sulfur deprivation.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.114-119
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• 2007

Sulfide stress cracking (SSC) of materials exposed to oilfield environment containing hydrogen sulfide $(H_{2}S)$ has been recognized as a materials failure problem. Laboratory data and field experience have demonstrated that extremely low concentration of $H_{2}S$ may be sufficient to lead to SSC failure of susceptible materials. In some cases, $(H_{2}S)$ can act synergistically with chlorides to produce corrosion and cracking failures. SSC is a form of hydrogen embrittlement that occurs in high strength steels and in localized hard zones in weldment of susceptible materials. In the heat-affected zones adjacent to welds, there are often very narrow hard zones combined with regions of high residual stress that may become embrittled to such an extent by dissolved atomic hydrogen. On the base of understanding on sulfide stress cracking and its mechanism, SSC resistance for the several materials, those are ASTM A106 Gr B using in the oil industries, are evaluated.

• Journal of Soil and Groundwater Environment
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• v.11 no.6
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• pp.8-17
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• 2006

Laboratory scale experiments were performed to investigate the removal efficiency of the in-situ chemical oxidation method and the air-sparging method for diesel contaminated soil and groundwater. Two kinds of diesel contaminated soils (TPH concentration : 2,401 mg/kg and 9,551 mg/kg) and groundwater sampled at Busan railroad station were used for the experiments. For batch experiments of chemical oxidation by using 50% hydrogen peroxide solution, TPH concentration of soil decreased to 18% and 15% of initial TPH concentration. For continuous column experiments, more than 70% of initial TPH in soil was removed by using soil flushing with 20% hydrogen peroxide solution, suggesting that most of diesel in soil reacted with hydrogen peroxide and degraded into $CO_2$ or $H_2O$ gases. Batch experiment for the air-sparging method with artificially contaminated groundwater (TPH concentration : 810 mg/L) was performed to evaluate the removal efficiency of the air-sparging method and TPH concentration of groundwater decreased to lower than 5 mg/L (waste water discharge tolerance limit) within 72 hours of air-sparging. For box experiment with diesel contaminated real soil and groundwater, the removal efficiency of air-sparging was very low because of the residual diesel phase existed in soil medium, suggesting that the air-sparging method should be applied to remediate groundwater after the free phase of diesel in soil medium was removed. For the last time, the in-situ box experiment for a unit process mixed the chemical oxidation process with the air-sparging process was performed to remove diesel from soil and groundwater at a time. Soil flushing with 20% hydrogen peroxide solution was applied to diesel contaminated soils in box, and subsequently contaminated groundwater was purified by the air-sparging method. With 23 L of 20% hydrogen peroxide solution and 2,160 L of air-sparging, TPH concentration of soil decreased from 9,551 mg/kg to 390 mg/kg and TPH concentration of groundwater reduced to lower than 5 mg/L. Results suggested that the combination process of the in-situ hydrogen peroxide flushing and the air-sparging has a great possibility to simultaneously remediate fuel contaminated soil and groundwater.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.12
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• pp.889-896
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• 2013

Advanced Oxidation Processes (AOP) have been interested for removing micropollutants in water. Most of water treatment plants (WTPs) located along the lower part of Nakdong River have adopted the $O_3/BAC$ process and have interesting in peroxone process a kind of AOP. This study evaluated the removal characteristics of residual hydrogen peroxide ($H_2O_2$) combining with the biofiltration process in the next BAC process when the hydrogen peroxide is applied for the WTP operating $O_3/BAC$ process. In the experiment, changing the temperature and the concentration of $H_2O_2$ of influent, the biofiltration process showed rapidly dropped the biodegradability when the $H_2O_2$ concentration was increased and lowered water temperature while BAC process maintained relatively stable efficiency. The influent fixed at $20^{\circ}C$ and the concentration of $H_2O_2$ at 300 mg/L was continuously input for 78 hours. Most of the $H_2O_2$ in the influent did not remove at the biofiltration process controlled 5 to 15 minutes EBCT condition after 24~71 hours operating time while BAC process controlled 5 to 15 minutes EBCT showed 38~91% removal efficiency condition after 78 hours operating time. Besides, after 78 hours continuously input experiment, the biomass and activity of attached bacterial on the biofilter and BAC were $6.0{\times}10^4CFU/g$, $0.54mg{\cdot}C/m^3{\cdot}hr$ and $0.4{\times}10^8CFU/g$, $1.42mg{\cdot}C/m^3{\cdot}hr$ respectively. These biomass and activity values were decreased 99% and 72% in biofilter and 68% and 53% in BAC compared with initial condition. The biodegradation rate constant ($k_{bio}$) and half-life ($t_{1/2}$) in BAC were decreased from $1.173min^{-1}$ to $0.183min^{-1}$ and 0.591 min to 3.787 min respectively according to increasing the $H_2O_2$ concentration from 10 mg/L to 300 mg/L at $5^{\circ}C$ water temperature and the $k_{bio}$ and $t_{1/2}$ were $1.510min^{-1}$ to $0.498min^{-1}$ and 0.459 min to 1.392 min at $25^{\circ}C$ water temperature. By increasing the water temperature from $5^{\circ}C$ to $15^{\circ}C$ or $25^{\circ}C$, the $k_{bio}$ were increased 1.1~2.1 times and 1.3~4.4 times. If a water treatment plant operating $O_3/BAC$ process is considering the hydrogen peroxide for the peroxone process, post BAC could effectively decrease the residual $H_2O_2$, moreover, in case of spilling the $H_2O_2$ into the water process line, these spilled $H_2O_2$ concentration can be able to decrease by increasing the EBCT at the BAC process.

• Journal of the Korean Vacuum Society
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• v.8 no.2
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• pp.165-171
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• 1999

Diamond-like carbon(DLC) films were synthesized using the rf-plasma CVD technique with the addition of small amounts of nitrogen and oxygen to a gas mixture of $CH_4$ and $H_2$. The gas flow ratio of $CH_4$ to $H_2$ was 2.4:1, and 3% , 13.6% of nitrogen were added to the gas mixture of $CH_4$ and $H_2$ for the deposition of DLC films. The film stress tended to decrease as the nitrogen concentration increased from 3% to 13.6%, probably due to the decrease of the number of the interlink between carbon atoms. The residual stress tended to slightly decrease when 3% of oxygen was added. Scratch tests were performed to investigate the adhesion between the DLC films and the Ti intelayer after pretreating the TiN surface with direct hydrogen plasma. The adhesion was enhanced by adding nitrogen and oxygen to the $CH_4$ and $H_2$ gas mixture. The adhesion for the 3% nitrogen addition was better than that for the 13.6% nitrogen addition. The Vicker's hardness of the DLC films was measured to be 1100Hv.

• KSBB Journal
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• v.19 no.6 s.89
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• pp.446-450
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• 2004

We investigated the effective culture conditions of anaerobic bacteria, Enterobacter cloacae YJ-1 on hydrogen production. It was cultured with 60 mL of working volume at $35^{\circ}C$, 120 rpm for 40 h. With culture time, hydrogen production and cell growth increased, but residual glucose and pH decreased. When the $2\%$ of glucose was used as single carbon source, hydrogen production was 975.1 mL/L. To enhance hydrogen productivity, mixed carbon sources of glucose and sucrose were added. The maximum hydrogen production was earned at the mixing ratio of 25:75, and it was 1319.5 mL/L. When we added 50 mM of phosphate to protect the pH drop in culture broth, hydrogen production increased 1.3 times more than that of initial concentration. The organic nitrogen sources were more effective than inorganic nitrogen for hydrogen production. Among organic nitrogen, yeast extract was the most effective and its hydrogen production was 1691.3 mL/L. Among 9 of mineral sources, Ferric citrate and $NaMoO_4$ were especially effective, and their productions were 1782.3 mL/L and 1784.8 mL/L, respectively.

• Journal of Sensor Science and Technology
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• v.22 no.3
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• pp.175-180
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• 2013

This paper describes the characteristics of cubic silicon carbide (3C-SiC) films grown on a carbonized Si(100) substrate, using hexamethyldisilane (HMDS, $Si_2(CH_3)_6$) as a safe organosilane single precursor in a nonflammable $H_2$/Ar ($H_2$ in Ar) mixture carrier gas by atmospheric pressure chemical vapor deposition (APCVD) at $1280^{\circ}C$. The growth process was performed under various conditions to determine the optimized growth and carbonization condition. Under the optimized condition, grown film has a single crystalline 3C-SiC with well crystallinity, small voids, low residual stress, low carrier concentration, and low RMS. Therefore, the 3C-SiC film on the carbonized Si (100) substrate is suitable to power device and MEMS fields.