• International Journal of Highway Engineering
• /
• v.13 no.3
• /
• pp.177-184
• /
• 2011

There are several differences between freeways and general national roads in terms of structures, conditions and limited speeds. Likewise, the characteristics of $CO_2$ emission in these roads differ depending on the road types. For these reasons, it is necessary to compare the two types of roads in terms of $CO_2$ emissions. The study was performed targeting Gyeongbu Expressway and National Highway 1. Firstly, the amount of $CO_2$ emission each car was compared in the whole sections of the both. Secondly, top 10 sections were picked out, and then $CO_2$ emission each section were compared. Lastly, two sections which were with the highest and lowest amount of $CO_2$ emission per car, were compared. As results, it were found that there were less amount of $CO_2$ emission on freeways. because cars are running on uniform velocity at relatively high speed, and that there were more amount of $CO_2$ emission on the national highway. because of frequent intersections and associated congestion. It may be concluded that the amount of $CO_2$ emission at the national highway could be reduced if signal coordination and intersection intervals are improved there.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2022.11a
• /
• pp.187-188
• /
• 2022

In this study, the compressive strength and carbonation properties of geopolymer paste according to the amount of alkali admixture added were evaluated for the development of geopolymer concrete that recycles industrial waste. A geopolymer paste specimen was prepared using Ca(OH)2 as an admixture, and the prepared specimen was standard cured for 28 days. After curing, the compressive strength of the specimen was measured. As the amount of alkali admixture increased, the compressive strength increased. After curing, carbonation was carried out for 7 days in a CO2 5% environment. As a result of comparative evaluation of the amount of CaCO3 produced according to carbonation, the amount of CaCO3 produced increased as the amount of Ca(OH)2 added increased. However, when the amount of admixture added exceeds 5%, the increase rate decreases, so the optimum addition rate is considered to be 5%.

• Journal of Korean Society for Atmospheric Environment
• /
• v.30 no.1
• /
• pp.68-76
• /
• 2014

The present study has evaluated the $CO_2$ adsorption amount of activated carbon pellets (AC). Coconut shell based test AC were modified with surface impregnation of glycine, glycine metal salts and monoethanolamine for low level $CO_2$ (3000 ppm) adsorption. Physical and chemical properties of prepared adsorbents were analyzed and the adsorbed amount of $CO_2$ was investigated by using pure and 3,000 ppm $CO_2$ levels. The impregnation of nitrogen functionalities was verified by XPS analysis. The adsorption capacity for pure $CO_2$ gas was found to reach upto 3.08 mmol/g by AC-LiG (Activated carbon-Lithium glycinate), which has the largest specific surface area ($1026.9m^2/g$). As for low level $CO_2$ flow the primary amine impregnated adsorbent showed 0.26 mmol/g of adsorption amount, indicating the highest selectivity. An adsorbent with potassium-glycine salts (AC-KG, Activated carbon-Potassium glycinate) instead of amine presented with 0.12 mmol/g of adsorption capacity, which was higher than that of raw activated carbon granules (0.016 mmol/g).

• Journal of Advanced Marine Engineering and Technology
• /
• v.31 no.5
• /
• pp.558-566
• /
• 2007

The performance characteristics of water-chilling heat pump using $CO_2$ with respect to variation of refrigerant charge amount was investigated experimentally. An experimental apparatus is consisted of a compressor, a gas cooler, an expansion valve, an evaporator and a liquid receiver. All heat exchangers used in the test rig are counter-flow-type heat exchangers with concentric dual tubes, which are made of copper. The gas cooler and the evaporator consist of 6 and 4 straight sections respectively arranged in parallel, each has 2400 mm length. The experimental results summarize as the followings : As the refrigerant charge ratio of $CO_2$ heat pump system increases, the discharge pressure and compressor ratio increases, but mass flow rate of refrigerant decreases. Also the compressor work increases with the increase of refrigerant charge ratio. However, the heating and cooling capacity of $CO_2$ heat pump decreases as the refrigerant charge ratio increases. The maximum heating COP of $CO_2$ heat pump system presented at 0.25 refrigerant charge ratio. It is possible to confirm the optimum charge ratio of $CO_2$ heat pump system by the viewpoint of heating COP.

• Nutrition Research and Practice
• /
• v.17 no.5
• /
• pp.1028-1041
• /
• 2023

BACKGROUND/OBJECTIVES: This study aimed to analyze the potential of school meals in South Korea as a sustainable tool to reduce carbon emissions by focusing on animal- vs. plant-based protein foods. MATERIALS/METHODS: By using a stratified proportional allocation method, 536 out of the 11,082 schools nationwide were selected including 21 kindergartens, 287 elementary-, 120 middle- and 108 high schools. A total of 2,680 meals served for 5 consecutive days (June 21-25, 2021) were collected. We analyzed the average serving amounts of protein foods (animal- vs. plant-based) per meal and then, calculated the estimated average amounts of carbon emission equivalents per meal by applying the conversion coefficients. The t-test and analysis of variance were used for statistical analyses (α = 0.05). RESULTS: The average serving amount of animal-based protein foods per meal was 12.5 g, which was approximately 3 times higher than that of plant-based ones (3.8 g) (P < 0.001); the Meat-group had the highest average amount of 17.0 g, followed by Egg-group (9.6 g), Fish-group (7.6 g), and Beans-and-Nuts-group (3.8 g) (P < 0.05). Specifically, pork (25.1 g) was ranked first, followed by poultry (19.6 g), processed meat products (18.0 g). The estimated average amount of carbon emission equivalents of animal-based protein foods per meal was 80.1 g CO₂e, which was approximately 31 times higher than that of plant-based ones (2.6 g CO₂e) (P < 0.001); the Meat-group had the highest average amount of 120.3 g CO₂e, followed by Fish-group (44.5 g CO₂e), Egg-group (25.9 g CO₂e), and Beans-and-Nuts-group (2.6 g CO₂e) (P < 0.05). Specifically, processed meat products (270.8 g CO₂e) were ranked first, followed by pork (91.7 g CO₂e), and processed fish products (86.6 g CO₂e). CONCLUSIONS: The results implied that school meals with plant-based alternatives could be a sustainable tool to improve carbon footprint.

• Journal of Welding and Joining
• /
• v.12 no.1
• /
• pp.51-58
• /
• 1994

Amount of spatter, welding conditions and welding costs were investigated for MAG welding. $CO_2$, Ar+18%;$CO_2$ and Ar+8%$O_2$ were used for shielding gases. As results, arc characteristics and appropriate range for welding were obtained. Amount of spatter in Ar+18%$CO_2$ gas welding was 20% of that of $CO_2$ welding, and Ar+8%$O_2$ was 10% of that of $CO_2$ welding. Therefore by using Ar+18%$CO_2$and Ar+8%$O_2$ gases, welding costs could be reduced compared with $CO_2$ welding due to avoiding spatter.

• Journal of Powder Materials
• /
• v.3 no.2
• /
• pp.97-103
• /
• 1996

The densification of the compacts of pure Co, Fe+50%.Co and Fe+25% Co sintered under H$_2$ gas or in vacuum was investigated. The effects of AL, Nb, Ti, and V additions on the densification were also studied. The sintered compact of Co was fully-dense when the density of the compact was lower than $Dg^c$. However, above $Dg^{c}$, it was never fully-dense regardless of sintering atmosphere, temperature, and time. The densification of sintered compacts of Fe-50% Co and Fe-25% Co were always incomplete. While the addition of AL made all compacts fully-dense, the addition of Ti was effective for the compacts of Co and Fe-25% Co. V was effective only for the Fe-25% Co. These results tell us that the particle size of Co powder, the amount of Fe, and the amount of additives forming stable oxides play on important role for the complete densification. Therefore it is desirable to reduce or eliminate the equilibrium pressure of H$_{2}$O or CO in isolated pores to obtain a fully-dense sintered compact.

• Bulletin of the Korean Chemical Society
• /
• v.15 no.1
• /
• pp.23-25
• /
• 1994

A simple analytical method that allows direct monitoring of small amount of CO$_2$ in a CO$_2$ discharge tube which utilizes the optoacoustic detection technique is described. The dependence of the optoacoustic signal on the mole fraction of CO$_2$ was shown that the system responded linearly to the amount of CO$_2$ present in the miniature discharge cavity equipped with Cu electrodes. It was also found that fraction of dissociated CO$_2$ varied from 14 to 37% of the initial concentration which depended on the current and the pressure in the tube. This simple and easy detection method has proven to possess the practical advantages over the conventional systems for the study of CO$_2$ laser electrodes.

• Journal of the Korean Society of Safety
• /
• v.19 no.4 s.68
• /
• pp.74-79
• /
• 2004

[ $CO_3O_4/{\gamma}-Al_2O_3$ ] catalysts were reported high activity on the low temperature CO oxidation. The effects of the calcination temperature, the loaded amount of cobalt and the oxygen concentration on the characteristics of CO oxidation have been investigated for a emergency escape mask cartridge. $Co(NO_3)_2\cdot6H_2O$ was used as cobalt precursor and the catalysts were prepared by incipient wetness impregnation. TGA shows that enough calcination is accomplished at $450^{\circ}C$ and cobalt phase is $Co_3O_4$ after calcination in the temperature range of $300\ ~500^{\circ}C$. The specific surface area and pore volume of catalysts are decreased with increasing of loaded amount of cobalt. And with the increase of loaded amount of cobalt and the oxygen concentration, the catalytic activity is increased.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.18 no.11
• /
• pp.851-858
• /
• 2006

[ $CO_2$ ] and propane mixtures, which are environmentally benign, nontoxic, low in price, and compatible with materials and lubricants, were considered as promising alternative refrigerants. A fully instrumented air-conditioning system was developed for a precise performance evaluation of pure $CO_2$ and $CO_2/propane$ mixtures. In this paper, the effect of the charging amount and circulation concentration on the cooling performance of the system using $CO_2$ and propane mixtures was tested and discussed. Pure $CO_2$ and 85/15, 75/25 and 60/40 binary blends by the charged mass percentage of $CO_2/propane$ were selected as working fluids. An optimum charging amount was proposed as a parameter instead of the degree of subcooling, which can not be well defined in the transcritical cycle, to properly compare the performance between the transcritical and subcritical cycles.