• Bulletin of the Korean Chemical Society
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• v.7 no.2
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• pp.102-105
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• 1986

Samples with the nominal composition of $Co_{9-x}M_xS_8$(M = Ni, Rh, Ru, and Fe) were prepared, and their magnetic properties were measured. X-ray diffraction analysis showed that small amount of the elements Ni, Rh, and Fe could be incorporated into $Co_9S_8$ forming a homogeneous ${\pi}$-phase, whereas the Ru-incorporated sample could not be prepared in a single phase. The lattice parameter was observed to increase as other elements were incorporated into $Co_9S_8$. Samples incorporated with the elements of Ni, Rh, and Ru showed Pauli-paramagnetism while the Fe-incorporated sample exhibited weak ferromagnetism. The values of magnetic susceptibility for the Ni, Rh, Ru-incorporated samples were nearly the same as that of pure $Co_9S_8$.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.10a
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• pp.65-67
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• 2008

Kyoto Protocol against global warming came into effect in Feb 2005. This paper presents a calculation $CO_2$ emission of D power plant for combusting LNG and heavy oil using the a, b, c coefficients obtained by the performance test. The authors also calculate the breakeven point of the fuel transfer from LNG to Oil considering recent $CO_2$ emission cost.

• Journal of Powder Materials
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• v.12 no.2 s.49
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• pp.112-116
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• 2005

In the present study, the focus is on the analysis of carbothermal reduction of oxide powder prepared from waste WC/Co hardmetal by solid carbon under a stream of argon for the recycling of the WC/Co hard-metal. The oxide powder was prepared by the combination of the oxidation and crushing processes using the waste $WC-8 wt.\%Co$ hardmetal as the raw material. This oxide powder was mixed with carbon black, and then this mixture was carbothermally reduced under a flowing argon atmosphere. The changes in the phase structure and gases discharge of the mixture during carbothermal reduction was analysed using XRD and gas analyzer. The oxide powder prepared from waste $WC-8wt.\%Co$ hardmetal has a mixture of $WO_{3} and CoWO_{4}$. This oxide powder reduced at about $850^{\circ}C$, formed tungsten carbides at about $950^{\circ}C$, and then fully transformed to a mixed state of tungsten carbide (WC) and cobalt at about $1100^{\circ}C$ by solid carbon under a stream of argon. The WC/Co composite powder synthesized at $1000^{\circ}C$ for 6 hours from oxide powder of waste $WC-8wt.\%Co$ hardmetal has an average particle size of $0.3 {\mu}m$.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.1
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• pp.17-22
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• 2013

In this study, a pH control method by carbon dioxide ($CO_2$) was applied to coagulation process in water treatment plant (WTP) to investigate the coagulation efficiency and residual dissolved aluminum when high pH raw water is flowing into the plant during algal blooming. Existing coagulant dose (1 mg/L in raw water) resulted in the pH reduction of 0.0384 by LAS, 0.0254 by PAC, 0.0201 by A-PAC, and 0.0135 by PACS2, respectively. And then the concentration of dissolved aluminum was 0.02 mg/L at pH 7.44, 0.07 mg/L at pH 7.96, 0.12 mg/L at pH 8.16, 0.39 mg/L at pH 8.38 showing the concentration increase with pH in the coagulation process. It was noteworthy that rapid increase was observed at pH above 8.0 next the rapid mixing. Therefore it is necessarily required to control pH below 7.8 in the coagulation process in order to meet drinking water quality standard of aluminum for high pH raw water into WTP, $CO_2$ injection could control pH successfully at about 7.3 even for the raw water of high pH above 8.0. In addition it was found that the pH control by $CO_2$ injection was significantly effective for coagulation in terms of turbidity removal, coagulant dosage, and residual dissolved aluminum concentration.

• Journal of the Korea Concrete Institute
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• v.28 no.3
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• pp.349-356
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• 2016

This report presents the results of an investigation on the early strength development of pastes high volume slag cement (HVSC) activated with different concentration of sodium carbonate ($Na_2CO_3$). The ordinary Portland cement (OPC) was replaced by ground granulated blast furnace slag (GGBFS) from 50% to 90% by mass, the dry powders were blended before the paste mixing. The $Na_2CO_3$ was added at 0, 2, 4, 6, 8 and 10% by total binder (OPC+GGBFS) weight. A constant water-to-binder ratio (w/b)=0.45 was used for all mixtures. The research carried out the compressive strength, ultrasonic pulse velocity (UPV), water absorption and X-ray diffraction (XRD) analysis at early ages(1 and 3 days). The incase of mixtures, V5 (50% OPC + 50% GGBFS), V6 (40% OPC + 60% GGBFS) and V7 (30% OPC + 70% GGBFS) specimens with 6% $Na_2CO_3$, V8 (20% OPC + 80% GGBFS) and V9 (10% OPC + 90% GGBFS) specimens with 10% $Na_2CO_3$ showed the maximum strength development. The results of UPV and water absorption showed a similar tendency to the strength properties. The XRD analysis of specimens indicated that the hydration products formed in samples were CSH and calcite phases.

• Korean Journal of Materials Research
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• v.15 no.10
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• pp.657-661
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• 2005

[ $ZnHgGa_4Se_8\;and\;ZnHgGa_4Se_8::Co^{2+}$ ] single crystals were grown by the Bridgman-Stockbarger method. The single crystals crystallized into a defect chalcopyrite structure. The optical energy band gap of the single crystals was investigated in the temperature range 11-300K. The optical energy band gap of the $ZnHgGa_4Se_8:Co^{2+}$ single crystal was smaller than that of the $ZnHgGa_4Se_8$ single crystal. The temperature dependence of the optical energy band gap of the single crystals was well fitted by the Varshni equqtion. The impurity optical absorption spectrum of the $ZnHgGa_4Se_8:Co^{2+}$ single crystal was measured in the wavelength region 300-2300 m at 80 K. Impurity absorption peaks in the spectrum were analyzed within the framework of the crystal field theory and were attributed to the electron transitions between the energy levels of $Co^{2+}$ sited in the Td symmetry point.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.2
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• pp.94-101
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• 2015

To mitigate the greenhouse gas emission, many carbon capture and storage projects are underway all over the world. In Korea, many studies focus on the storage of $CO_2$ in the offshore sediment. Assurance of safety is one of the most important issues in the geological storage of $CO_2$. Especially, the assessment of possibility of leakage and amount of leaked $CO_2$ is very crucial to analyze the safety of marine geological storage of $CO_2$. In this study, the leakage of injected $CO_2$ through fault was numerically studied. TOUGH2-MP ECO2N was used to simulate the subsurface behavior of injected $CO_2$. The storage site was 150 m thick saline aquifer located 825 m under the continental shelf. It was assumed that $CO_2$ leak was happened through the fault located 1,000 m away from the injection well. The injected $CO_2$ could migrate through the aquifer by both pressure difference driven by injection and buoyancy force. The enough pressure differences made it possible the $CO_2$ to migrate to the bottom of the fault. The $CO_2$ could be leaked to seabed through the fault due to the buoyancy force. Prior to leakage of the injected $CO_2$, the formation water leaked to seabed. When $CO_2$ reached the seabed, leakage of formation water stopped but the same amount of sea water starts to flow into the underground as the amount of leaked $CO_2$. To analyze the effect of injection rate on the leakage behavior, the injection rate of $CO_2$ was varied as 0.5, 0.75, and $1MtCO_2/year$. The starting times of leakage at 1, 0.75 and $0.5MtCO_2/year$ injection rates are 11.3, 15.6 and 23.2 years after the injection, respectively. The leakage of $CO_2$ to the seabed continued for a period time after the end of $CO_2$ injection. The ratios of total leaked $CO_2$ to total injected $CO_2$ at 1, 0.75 and $0.5MtCO_2/year$ injection rates are 19.5%, 11.5% and 2.8%, respectively.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.10
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• pp.67-72
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• 2010

G8 summit meeting held in July 2008 decided to set up a long-term goal, by 2050, reducing the world greenhouse emissions by half of those emitted in 1990. In November 2009, the Government announced to reduce the national $CO_2$ emission by 30[%] of BAU by 2020. Electric power industries in Korea produce most of their electricity by burning fossil fuels, and emit approximately 28[%] of national $CO_2$ emissions. Monitoring the $CO_2$ emissions. Monitoring the $CO_2$ emission of electric power plants is very important. This paper presents a method to calculate the hourly $CO_2$ emission for a thermal power plant burning mixture of coal and oil using the performance test data and coal-oil mix rate. An example of $CO_2$ emission calculation is also demonstrated.

• Journal of Environmental Science International
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• v.26 no.6
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• pp.741-750
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• 2017

A model coupling a meteorological predictive model and a vegetation photosynthesis and respiration model was used to simulate $CO_2$ concentrations over coastal basin areas, and modeling results were estimated with aircraft observations during a massive sampling campaign. Along with the flight tracks, the model captured the meteorological variables of potential temperature and wind speed with mean bias results of $0.8^{\circ}C$, and 0.2 m/s, respectively. These results were statistically robust, which allowed for further estimation of the model's performance for $CO_2$ simulations. Two high-resolution emission data sets were adopted to determine $CO_2$ concentrations, and the results show that the model underestimated by 1.8 ppm and 0.9 ppm at higher altitude over the study areas during daytime and nighttime, respectively, on average. Overall, it was concluded that the model's $CO_2$ performance was fairly good at higher altitude over the study areas during the study period.

• Advances in Computational Design
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• v.8 no.4
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• pp.295-307
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• 2023

This paper presents an optimization of the reinforced concrete ribbed slab in terms of minimum CO₂ emissions and an economic justification of the final optimal design. The design variables are six geometry variables including the slab thickness, the ribs spacing, the rib width at the lower and toper end, the depth of the rib and the bar diameter of the reinforcement, and the seventh variable defines the concrete strength. The objective function is considered to be the minimum amount of carbon dioxide gas (CO₂) emission and at the same time, the optimal design is economical. Seven significant design constraints of American Concrete Institute's Standard were considered. A robust metaheuristic optimization method called improved dolphin echolocation and ant colony optimization (IDEACO) has been used to obtain the best possible answer. At optimal design, the three most important sources of CO₂ emissions include concrete, steel reinforcement, and formwork that the contribution of them are 63.72, 32.17, and 4.11 percent respectively. Formwork, concrete, steel reinforcement, and CO₂ are the four most important sources of cost with contributions of 67.56, 19.49, 12.44, and 0.51 percent respectively. Results obtained by IDEACO show that cost and CO₂ emissions are closely related, so the presented method is a practical solution that was able to reduce the cost and CO₂ emissions simultaneously.