• Title/Summary/Keyword: $CO_2$농도

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A Study on Characteristics of column fails in DDI DRAM (DDI DRAM에서의 Column 불량 특성에 관한 연구)

  • Chang, Sung-Keun;Kim, Youn-Jang
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.9 no.6
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    • pp.1581-1584
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    • 2008
  • In dual-polycide-gate structure with butting contact, net doping concentration of polysilicon was decreased due to overlap between $n^+$ and $p^+$ and lateral dopant diffusion in silicide/polysilicon layers. The generation of parasitic Schottky diode in butting contact region is attributed both to the $CoSi_2$-loss due to $CoSi_2$ agglomeration and to the decrease in net doping concentration of polysilicon layer. Parasitic Schottky diode reduces noise margin of sense amplifier in DDI DRAM, which causes column fail. The column fail could be reduced by physical isolation of $n^+/p^+$ polysilicon junction or suppressing $CoSi_2$ agglomeration by using nitrogen implantation into $p^+$ polysilicon before $CoSi_2$ formation.

Effect of $CO_2$ Concentration of CA Conditions on Quality of Kiwifruit (Actinidia chinensis Planch.) during Storage (한국산 양다래(Actinidia chinensis Planch.)의 CA 저장성에 관한 연구)

  • Lee, Sei-Eun;Kim, Dong-Man;Kim, Kil-Hwan;Rhee, Chul
    • Korean Journal of Food Science and Technology
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    • v.21 no.6
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    • pp.869-875
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    • 1989
  • For the evaluation of storage stability of kiwifruit, the conditions of CA storage were based on the following gas compositions; 2% oxygen and 2, 4, 6% carbon dioxide, respectively. The results obtained from the experiment were as follows; The flesh softening was considerably reduced at the storage atmospheres of 4% $CO_2$ plus 2% $O_2$, and fruit firmness of 3.0kg was marked in this CA condition after storage for 180 days. The concentration of $CO_2$ affected clearly on the respiration rate and organic acid compositions of kiwifruit during CA storage. The respiration rate at the storage condition of 6% $CO_2$ was lower than those at 2 and 4% $CO_2$. Quinic and succinic acid contents were obviously increased in the kiwifruit stored at all the CA conditions studied. In comparision of the developed amounts of off-flavor substances, ethanol and acetaldehyde, depended upon the concentration of $CO_2$ in the CA conditions, the larger amount were produced in the storage condition of higher concentration of $CO_3$. From the results mentioned above, it could be concluded that the optimum atmosphere combination for CA storage of kiwifruit was 4% $CO_2$ plus 2% $O_2$.

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The Effect of CO2 Fixation for Microalgae based on CO2 Concentration and Flow Rate (이산화탄소 농도 및 유속에 따른 하천 내 미세조류의 이산화탄소 고정 효과)

  • Park, Hyomin;Lee, Sangdon
    • Journal of Wetlands Research
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    • v.20 no.4
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    • pp.363-369
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    • 2018
  • One of the recent environmental problems is climate change due to the increase of atmospheric $CO_2$, which causes ecological changes and various environmental problems. Therefore, various studies are being carried out to reduce $CO_2$ in the world in order to solve various environmental problems caused by increase of $CO_2$. The $CO_2$ reduction using microalgae is an environmentally friendly method by using photosynthesis reaction of microalgae. However, most studies using single species. There is no study on the $CO_2$ fixing efficiency of microalgae in natural rivers. Therefore, this study was to identify the microalgae in the Sum river and to analyze the growth characteristics of microalgae in the river to obtain optimal culture conditions. And the changes of biomass and chlorophyll-a of microalgae were analyzed according to $CO_2$ concentration and injection rate. The purpose of this study was to investigate the fixing efficiency of carbon dioxide in microalgae in natural rivers. Six kinds of dominant species were observed as a result of the identification of microalgae in Sum river(Ankistrodesmus falcatus, Scenedesmus intermedius, Selenodictyum sp., Xanthidium apiculatum var. laeve, Cosmarium pseudoquinarium, Dictyosphaerium pulchellum). All of these species were green algae. Biomass and chlorophyll-a increased with the increase of $CO_2$ concentration and biomass and chlorophyll-a increased faster flow rate at the same $CO_2$ concentration. Also, the quantity of $CO_2$ fixation on the microalgae tended to be higher when the flow rate of injected gas was faster. This study can be referred as being significant in the micro-algae in river. In addition, the optimal conditions for $CO_2$ fixation of microalgae in rivers and the quantification of the quantity of $CO_2$ fixation from microalgae in rivers can be used as basic data for future policy of $CO_2$ reduction.

A Study on the Concentration of CO(Carbon Monoxide) by the Length of the Curved Exhaust Tube for Household Gas Boiler (가정용 가스보일러 곡관 배기통의 길이 변화에 따른 CO농도 고찰)

  • Leem, Sa-Hwan;Huh, Yong-Jeong;Ma, Sung-Jun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.8 no.5
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    • pp.1220-1226
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    • 2007
  • As the industry of 21C has been developed, the gas industry has grown and it has not only the convenience but also the riskiness fer using. Especially, the energy and environment problems have been getting serious after the modern industry revolution. Therefore, the demand of gas as an eco-friendly energy source is getting increased. With the demand of gas, the installation and use of gas boiler is also increased, so human life injury by the waste gas(CO) of boiler goes on increasing every year. Therefore, we want to find out the harm to human body through the study on the concentration of CO by the length of the curved exhaust tube of boiler. The allowable concentration of CO is 50ppm. The length of the one-meter-three-curved tube after three minutes is applicable to 50ppm of the threshold limit values of CO. Also, five meters exceed the threshold limit values of CO after five minutes. Strangely, the concentration of CO is under the threshold limit values from two to four meters.

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Soil CO2 Monitoring Around Wells Discharging Methane (메탄 유출 관정 주변의 토양 CO2 모니터링)

  • Chae, Gitak;Kim, Chan Yeong;Ju, Gahyeun;Park, Kwon Gyu;Roh, Yul;Lee, Changhyun;Yum, Byoung-Woo;Kim, Gi-Bae
    • Economic and Environmental Geology
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    • v.55 no.4
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    • pp.407-419
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    • 2022
  • Soil(vadose zone) gas compositions were measured for about 3 days to suggest a method for monitoring and interpreting soil gas data collected around wells from which methane(CH4) is outflowing. The vadose zone gas samples were collected within 1 m around two test wells(TB2 and TB3) at Pohang and analyzed for CO2, CH4, N2 and O2 concentrations in situ. CO2 flux was measured beside TB2. In addition, gas samples from well head in TB2 and atmospheric air samples were collected for comparison. Carbon isotopes of CO213CCO2) of samples collected on the last day of the study period were analyzed in the laboratory. The two test wells (TB2 and 3) were 12.7 m apart and only TB3 was cemented to the surface. According to the bio-geochemical process-based interpretation, the relationships between CO2 and O2, N2, and N2/O2 of vadose zone gas were plotted between the lines of CH4 oxidation and CO2 dissolution. In addition, the CH4 concentrations of gas samples from the wellhead of the uncemented well (TB2) were 5.2 times higher than the atmospheric CH4 concentration. High CO2 concentrations (average 1.148%) of vadose zone gas around TB2 seemed to be attributed to the oxidation of CH4. On the other hand, the vadose zone CO2 around the cemented well(TB3) showed a relatively low concentration(0.136%). This difference indicates that the vadose zone gas(including CO2) around the CH4 outflowing well were strongly affected by well completion(cementing). This study result can be used to establish strategies for environmental monitoring of soil around natural gas sites, and can be used to monitor leakage around injection and observation wells for CO2 geological storage. In addition, the method of this study is useful for soil monitoring in natural gas storage and oil-contaminated sites.

Evaluation of the Prediction Performance of FDS Combustion Models for the CO Concentration of Gas Fires in a Compartment (구획실 내 가스연료 화재의 CO 농도에 대한 FDS 연소모델의 예측성능 평가)

  • Baek, Bitna;Oh, Chang Bo;Hwang, Chel-Hong;Yun, Hong-Seok
    • Fire Science and Engineering
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    • v.32 no.1
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    • pp.7-15
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    • 2018
  • The prediction performance of combustion models in the Fire Dynamics Simulator (FDS) were evaluated by comparing with experiment for compartment propane gas fires. The mixture fraction model in the FDS v5.5.3 and Eddy Dissipation Concept (EDC) model in the FDS v6.6.3 were adopted in the simulations. Four chemical reaction mechanisms, such as 1-step Mixing Controlled, 2-step Mixing Controlled, 3-step Mixing Controlled and 3-step Mixed (Mixing Controlled + finite chemical reactions) reactions, were implemented in the EDC model. The simulation results with each combustion model showed similar level for the temperature inside the compartment. The prediction performance of FDS with each combustion model showed significant differences for the CO concentration while no distinguished differences were identified for the $O_2$ and $CO_2$ concentrations. The EDC 3-step Mixing Controlled largely over-predicted the CO concentration obtained by experiment and the mixture fraction model under-predicted the experiment slightly. The EDC 3-step Mixed showed the best prediction performance for the CO concentration and the EDC 2-step Mixing Controlled also predicted the CO concentration reasonably. The EDC 1-step Mixing Controlled significantly under-predict the experimental CO concentration when the previously suggested CO yield was adopted. The FDS simulation with the EDC 1-step Mixing Controlled showed difficulties in predicting the $CO_2$ concentration when the CO yield was modified to predict the CO concentration reasonably.

Effect of Short-term High $CO_2$ on Growth of Botrytis cinerea (고농도 이산화탄소의 단기 처리가 Botrytis cinerea 생장에 미치는 영향)

  • 최정희;정문철;임정호
    • Food Science and Preservation
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    • v.11 no.2
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    • pp.246-249
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    • 2004
  • This study was conducted to evaluate the inhibition efficacy of high CO$_2$ atmosphere (35, 60, and 100% ${\times}$ 24, 48, and 72 h) on growth of Botrytis cinerea in vitro in order to offer sterilizing method of horticultural crops including peach fruits. Botrytis cinerea was isolated from a naturally infected peach fruits. Growth of the fungus at 25$^{\circ}C$ declined with increased CO$_2$ concentration and treatment duration. Especially, 100% CO$_2$ provided completely inhibition effect of growth of the fungus for 72 h. After removal of high CO$_2$ condition, however, the fungus showed normal growth speed. The growth of fungus at low temperature was completely inhibited temporarily by short-term 100% CO$_2$ treatment, but resumed right after transferring to normal atmosphere at 25$^{\circ}C$.

Biological Fixation of Carbon Dioxide by Synechocystis PCC 6803 (Synechocystis PCC 6803에 의한 이산화탄소의 생물학적 고정화)

  • 김장규;원성호;김남기
    • KSBB Journal
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    • v.13 no.1
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    • pp.101-107
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    • 1998
  • Carbon dioxide is estimated to be responsible for 60% of the global warming effect, and this percentage is tending upward. Studies on removal and fixation of $CO_2$ in the flue gas are recognized as one of the important roles of the future biotechnology. Photobiological systems have considerably higher photosynthetic efficiency than conventional biomass system. The experiment for the photosynthetic fixation of $CO_2$ and the biomass production was performed with various initial cell concentration in a tubular photobioreactor and a bubble column $CO_2$ contactor with a gas sparger of $CO_2$ -enriched air(0.03~20%). Synechocystis PCC 6803 could grow at 10~20% $CO_2$ content under pH control. The highest specific growth rate, 0.0258 $h^{-1}$ , was obtained at 5% $CO_2$-air mixture. The maximum cell production rate, 0.2784 g/L.day, was obtained when the initial cell concentration was 0.45 g/L at 5% $CO_2$ -air mixture. The maximum cell concentration was 2.03 g/L in the tubular photobioreactor when the light intensity was $45.5{\mu}$ $E/m^2$ . s. This system showed 0.482 g $CO_2$ /L . day of the $CO_2$ fixation.

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Correlations of Oil Concentration Prediction during In-line Flow of $CO_2/Oil$ Mixtures (유동중인 $CO_2$냉매와 오일 혼합물의 농도 예측을 위한 상관식)

  • Park, Keun-Seo;Kang, Byung-Ha;Park, Kyoung-Kuhn;Kim, Suk-Hyun
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.19 no.10
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    • pp.718-725
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    • 2007
  • In the general vapor-compression refrigeration system, refrigeration lubricant circulates in refrigeration system with refrigerant. Knowledge of the amount of circulating lubricant is very important to exactly calculate capacity of the refrigeration system. An experimental study was conducted to estimate the oil concentration of a flowing $CO_2/Oil$ mixtures. POE and PAG oil are considered as test lubricants in this study. Performance tests were conducted under simulated liquid conditions for $CO_2/POE$ oil mixture in oil concentration of 0 to 10 weight-percent and $CO_2/PAG$ oil mixture in oil concentration of 0 to 6 weight-percent in the temperature ranges of $-5^{\circ}C\;to\;15^{\circ}C$. The results obtained indicate specific gravity of $CO_2/Oil$ mixture is increased as oil concentration is increased and as temperature of mixture is decreased. Oil concentration correlation of $CO_2/POE$ oil mixture and $CO_2/PAG$ oil mixture is suggested, based on the measurement of specific gravity and temperature. This correlation enable to predict the oil concentration without extraction of the mixture and can be applied for $CO_2/POE$ mixtures and $CO_2/PAG$ mixtures.