• Korean Journal of Organic Agriculture
• /
• v.11 no.4
• /
• pp.103-115
• /
• 2003

In order to investigate the possibility for use to control environmental pollution, Kenaf(Hibiscus cannabinus L.) was used to obtain information of their growth and $CO_2$ response under different temperatures and $CO_2$ concentration. The highest percentage of germination and aboveground dry mass of Kenaf were found at 30$^{\circ}C$ and 35$^{\circ}C$ by 89.0% and 3.2g, respectively under different temperatures. The amount of $CO_2$ absorption and aboveground dry mass production of Kenaf were higher than those of maize during the whole growing period and the last sampling of aboveground dry mass of Kenaf and maize were 252.9g and 200.8g, respectively. The highest plant height was found at 400ppm by 131.0cm and the next was in the order of 600ppm by 1293cm, and 800ppm by 108.8cm. Leaf area was higher in the order of 400ppm > 600ppm > 800ppm, whereas leaf dry mass was in the order of 800ppm > 600ppm > 400ppm under different $CO_2$ concentration, showing that leaf became thicker as $CO_2$ concentration was increased. Days from seeding to flowering became shorter by 13 days in 35/25$^{\circ}C$ compared with 25/15$^{\circ}C$ between two temperature regimes and they also became shorter as $CO_2$ concentration was increased. Aboveground dry mass was higher in 35/25$^{\circ}C$ than that of 25/15$^{\circ}C$ between two temperature regimes. while it was increased in the order of 800ppm > 600ppm > 400ppm as CO2 concentration was increased. Temporal changes of leaf dry mass during growth period showed no difference between $CO_2$ concentration in 25/15$^{\circ}C$ , but the highest of it was found at 800ppm in 35/25$^{\circ}C$. The highest temporaI increase of root dry mass was found at 800ppm in 25/15$^{\circ}C$, but 35/25$^{\circ}C$ showed no difference between different $CO_2$ concentration.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.31 no.6 s.261
• /
• pp.514-521
• /
• 2007

This study focused on the effects of the $CO_2$ gas concentration in fresh charge and induction air temperature on the combustion characteristics of homogeneous charge compression ignition with dimethyl ether (DME) fuel, which was injected at the intake port. Because of adding $CO_2$ in fresh charge, start of auto-ignition was retarded and bum duration became longer. Indicated combustion efficiency and exhaust gas emission were found to be worse due to the incomplete combustion. Partial burn was observed at the high concentration of $CO_2$ in fresh charge with low temperature of induction air. However, indicated thermal efficiency was improved due to increased expansion work by late ignition and prolonged bum duration. Start of auto-ignition timing was advanced with negligible change of burn duration, as induction air temperature increased. Burn duration was mainly affected by oxygen mole concentration in induction mixture. Bum duration was increased, as oxygen mole concentration was decreased.

• Proceedings of the Korean Environmental Sciences Society Conference
• /
• 2003.11a
• /
• pp.47-50
• /
• 2003

$CO_2$ concentration profile was measured to investigate whether $CO_2$ concentration at one level (i.e., eddy covariance measurement level) can be used to estimate storage term without significant uncertainty at broadleaf deciduous forest at Kwangneung experiment forest in Korea. Based on t-test with significance level of 5％, there was no statistical difference between storage term from one-level $CO_2$ concentration and one from $CO_2$ profile measurement. Storage term constitutes on average 5％ of half hourly net ecosystem exchange (NEE) even at unstable stability (i.e., well mixed condition), indicating that storage term should be considered even at daytime, which is sometimes neglected.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.17 no.8
• /
• pp.736-745
• /
• 2005

This study is undertaken to evaluate the relationship between the indoor $CO_2$ concentration and the local mean air-age in the lecture room with the occupants. We conducted the experiments to examine the indoor $CO_2$ concentration and the local mean air-age with respect to the supply airflow of the ventilation system and the discharge angle and air-flow of the system air conditioner. Through the experiments, we found out that indoor $CO_2$ concentrations calculated by the prediction equation of Seidel are about 350 ppm lower than those measured by the experiments. The indoor $CO_2$ concentration is not related with the air-flow and the discharge angle of the system air-conditioner, but with the ventilation airflow. From the numerical calculation, the indoor $CO_2$ concentration is not related with the ventilation effectiveness, but strongly with the local mean air-age. In case of our model, the indoor $CO_2$ concentration is likely to fall within the acceptable air quality when the local mean air-age is averagely predicted under 400 seconds.

• Journal of Environmental Science International
• /
• v.3 no.4
• /
• pp.357-365
• /
• 1994

Air pollution characteristics and the influence of sea breeze on air pollution concentration were studied using the data measured at 7 air quality continuous monitoring stations in Pusan, 1993. Maximum air pollution concentration in Pusan was Gamjeondong for $SO_2$, Sinpyeongdong for TSP, Daeyeondong for $O_3, Kwangbokdong for $NO_2$, Beomcheondong for CO and all substances were under annual ambient air quality standards. Increased rate of concentration for sea breeze was 24.4% for 502, 31.5% for TSP, 8.0% fort $O_3, 26.7% for $NO_2$, 15.7% for CO. Frequencies distribution of $SO_2$, TSP, $O_3$, $NO_2$, and CO concentration for sea breeze moved toward high concentration class.

• Membrane Journal
• /
• v.4 no.4
• /
• pp.197-204
• /
• 1994

In this study, permeation characteristics of pure $CH_4,\;CO_2$ and $CH_4/CO_2$ gas mixture were examined by permeation experiments through hollow fiber membrane module and experimental results were compared with simulation results. Permeation rate of pure gas increased with increaseing temperature in Arrhenius type. Activation energy was 6.61 kJ/mol for $CO_2$ and 25.26 kJ/mol for $CH_4$. In the permeation experiment of gas mixture, permeate flow rate and $CO_2$ concentration in permeate decreased and $CH_4$ concentration in reject increased with the increase of cut. Separation factor was in the range of 20~40 at 5~20 atm and 20% cut and it increased with pressure and against temperature Experimental values corresponded to numerical values with the deviation of 8% in permeate flow rate and $CO_2$ concentration in permeate and 15% in $CO_2$ concentration in reject.

• Journal of Bio-Environment Control
• /
• v.18 no.2
• /
• pp.148-152
• /
• 2009

Numerous studies have presented evidence that global atmospheric carbon dioxide ($CO_{2}$ ) concentration and temperature is increasing every year. Both of the $CO_{2}$ and temperature are important components for photosynthesis activity of plants and thusgrowth and yield. However, little information is available in terms of the reaction of vegetable plants to increased $CO_{2}$ concentration and temperature, and also the reaction to a complex condition of both increased $CO_{2}$ concentration and temperature. The aim of this research was therefore to investigate changes in growth, photosynthetic activity and ultra-cellular structure of leaf tissue of Chinese cabbage. Plants were grown under either of elevated $CO_{2}$ concentration (elevated $CO_{2}$, 2-fold higher than atmospheric $CO_{2}$ ) or elevated temperature (elevated temp, 4$^{\circ}C$ higher than atmospheric temperature), under both of elevated $CO_{2}$ concentration and elevated temperature (elevated temp+$CO_{2}$), and under atmospheric $CO_{2}$ concentration and temperature (control). The treatment of 'elevated temp' negatively affected leaf area, fresh weight, chlorophyll and starch content. However, when the treatment of 'elevated temp' was applied coincidently with the treatment of 'elevated $CO_{2}$', growth and photosynthetic performance of plants were as good as those in the treatment of 'elevated $CO_{2}$', Microscopic study resulted that the highest starch content and density of cells were observed in the leaf tissue grown at the treatment of 'elevated $CO_{2}$', whereas the lowest ones were observed in the leaf tissue grown at the treatment of 'elevated temp'. These results suggest that when Chinese cabbage grows under a high-temperature condition, supplement of $CO_{2}$ would improve the growth and yield. In our knowledge, it is the first time to determine the effect of a complex relationship between the increased $CO_{2}$ concentration and temperature on the growth of Chinese cabbage.

• Korean Journal of Food Science and Technology
• /
• v.32 no.6
• /
• pp.1326-1330
• /
• 2000

Kimchi, made from seasonal baechu (Chinese cabbage), was sealed in PP trays with a Nylon/CPP lid film and stored at various temperatures (0, 10, $20^{\circ}C$) to investigate the feasibility of detecting its fermentation degree by measuring gas composition inside the packages. The gas composition inside the kimchi package continuously changed due to $CO_2$ evolution during fermentation. Regardless of temperature, the fermentative gas accumulation in the package caused $CO_2$ concentration to increase by two-stepwise pattern, but $O_2$ concentration to decrease exponentially. As $CO_2$ concentration increased secondarily, the pH values of kimchi decreased proportionally (r>0.968). The production of $CO_2$ during kimchi fermentation was stimulated at higher temperatures and affected by seasonal factor. Kimchi made from winter baechu produced more fermentative gas than that from summer baechu. It was suggested that the changes in $CO_2$ concentration could be used as a characteristic index for indicating the fermentation course of packaged kimchi products.

• Journal of the Korean institute of surface engineering
• /
• v.49 no.4
• /
• pp.331-338
• /
• 2016

In this work, anodic oxidation behavior of AZ31 Mg alloy was studied as a function of $Na_2CO_3$ concentration in electrolyte by voltage-time curves and observation of surface appearances and morphologies after the anodic treatments, using optical microscopy and confocal scanning laser microscopy (CSLM). The voltage-time curves of AZ31 Mg alloy surface and surface appearances after the anodic treatments showed three different regions with $Na_2CO_3$ concentration : region I, below 0.2 M $Na_2CO_3$ where shiny surface with a number of small size pits; region II, between 0.4 M and 0.6 M $Na_2CO_3$ where dark surface with relatively low number of large size burned or dark spots; region III, more than 0.8 M $Na_2CO_3$ where bright surface with or without large size dark spots were obtained. The anodically treated AZ31 Mg alloy surface became significantly brightened with increasing $Na_2CO_3$ concentration from 0.5 M to 0.8 M which was attribute to the formation of denser and smoother surface films. Pits and porous protruding reaction products were found at relatively large size and small size spots, respectively, on the AZ31 Mg alloy surface in low concentration of $Na_2CO_3$ less than 0.2 M. The formation of pits is attributed to the result of repetition of the formation and detachment of porous anodic reaction products. Based on the experimental results obtained in this work, it is concluded that more uniform, denser and smoother surface of AZ31 Mg alloy could be obtained at more than 0.8 M $Na_2CO_3$ concentration if there is no other oxide forming agent.

• Journal of Sensor Science and Technology
• /
• v.22 no.3
• /
• pp.197-201
• /
• 2013

This paper describes the fabrication and characterization of graphene based carbon dioxide ($CO_2$) gas sensors. Graphene was synthesized by thermal decomposition of SiC. The resistivity $CO_2$ gas sensors were fabricated by pure graphene and graphene decorated Au nanoparticles (NPs). The Au NPs with size of 10 nm were decorated on graphene. Au electrode deposited on the graphene showed Ohmic contact and the sensors resistance changed following to various $CO_2$ concentrations. Resulting in resistance sensor using pure graphene can detect minimum of 100 ppm $CO_2$ concentration at $50^{\circ}C$, whereas Au/graphene can detect minimum 2 ppm $CO_2$ concentration at same at $50^{\circ}C$. Moreover, Au NPs catalyst improved the sensitivity of the graphene based $CO_2$ sensors. The responses of pure graphene and Au/graphene are 0.04% and 0.24%, respectively, at $50^{\circ}C$ with 500 ppm $CO_2$ concentration. The optimum working temperature of $CO_2$ sensors is at $75^{\circ}C$.