• Korean Journal of Crystallography
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• v.16 no.1
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• pp.43-53
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• 2005

The dihydrido P-C-P pincer complex, $IrH_2{C_6H_3-2,6-(CH_2PBu_2^t)_2}$ (1), was successfully prepared from the reaction of the hydrochloride complex, $IrClH (C_6H_3-2,6-(CH_2PBu_2^t)_2}$, and super acid $(LiBEt_3H)$ under 1 atm of hydrogen in pentane solution at room temperature and followed by Heating at $130^{\circ}C$ in vacuo. Jensen recently found that the dihydrido P-C-P pincer complex 1 is a highly active homogeneous catalyst for the transfer dehydrogenation of alkanes with unusual longterm stability at temperatures as high as $200^{\circ}C$. The treatment of dihydrido complex 1 with nitrogen, water, carbon dioxide, and carbon monoxide in presence of tert-butylethylene (the) at room temperature in an appropriate solution gave the dinitrogen complex, $[Ir{C-6H_3-2,6-(CH_2PBu_2^t)_2}]_2({\mu}-N_2)$ (2), the hydrido hydroxyl complex, $IrH(OH){C_6H_3-2,6-(CH_2PBu_2^t)_2}$ (3), the carbon dioxide complex, $Ir({\eta}^2-CO_2) {C_6H_3-2,6-(CH_2PBu_2^t)_2}$ (including the bicarbonate complex, $IrH({\kappa}^2-O_2COH){C_6H_3-2,6-(CH_2PBu_2^t)_2}\;(4))$, and the carbonyl complex, $Ir(CO) {C_6H_3-2,6-(CH_2PBu_2^t)_2}\;(5)$ (including the carboxyl complex, $IrH(C(O)OH) {C_6H_3-2,6-(CH_2PBu_2^t)_2}\;(6))$, in good yield, respectively. These P-C-P iridium complexes were isolated and characterized by $^1H,\;^{13}C,\;^{31}P\; NMR$, and IR spectroscopy. In addition, the complexes (1-6) were characterized by a single crystal X-ray crystallography. These complexes account for these small molecules' inhibition of dehydrogenation of alkanes catalyzed by the dihydrido complex 1.

• Journal of the Korean Wood Science and Technology
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• v.38 no.6
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• pp.507-517
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• 2010

This study estimated the amount of carbon stocks in harvested wood products (HWP) using accounting approaches suggested by 2006 IPCC guidelines and analyzed the impacts of different approaches on national greenhouse gas inventory and the forest sector in Korea. The change in carbon stocks was calculated at the level of semi-finished wood products, which cover sawnwood, wood-based panels, other industrial wood, paper and paperboard. An estimation of the changes in carbon stocks in HWP in use for the period 1970~2008 varied between -9,023 Gg $CO_2$/yr and 4,052 Gg $CO_2$/yr depending on the accounting approach used. The stock-change approach provided the most favorable results because Korea was a net importer of wood products. However, each approach generates different impacts on harvest, trade, the use of wood for energy production and recycling. When deciding its position on accounting approach, thus, the Government should consider future direction of national forest policies as well as the effect on national greenhouse gas inventory for the minimization of negative impacts resulting from its selection.

• Journal of Life Science
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• v.20 no.11
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• pp.1691-1696
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• 2010

Neohesperidin is a natural new nutrition sweetener, widely existing in plants of dry citrus peel, which can be derived from extraction. Since the sweetness is 1,300-1,500 times greater than that of sugar, neohesperidin are widely used in fruit juices, wines, beverages, bakeries and pharmaceutical formulations, and are particularly suitable for consumption by diabetic patients. However, the yield of extraction from citrus peel waste is very low. In this study optimal yield conditions were determinedusing response surface methodology (RSM) in order to increase the neohesperidin extraction yield. The critical factors for maximum extraction yield were selected extraction pressure ($x_1$), extraction time ($x_2$), and concentration of ethanol ($x_3$). As a result, the extraction yield was improved when the extracting pressure increased. The extraction yield also increased in a time-dependent manner. When adding ethanol as an assistance solvent to the supercritical carbon dioxide, extraction yield was increased as more ethanol concentration was added. Finally, the extraction yield of neohesperidin was improved to about 162.22% compared to ethanol extraction as a conventional method.

• Journal of Energy Engineering
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• v.23 no.2
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• pp.62-73
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• 2014

This research was focused to apply response surface methodology for optimization of bio-methane production by biogas upgrading process. Methane concentration(Y1) and methane efficiency(Y2) on biogas upgrading process were mathematically described as being modeled by the use of the Box-Behnken design on response surface methodology. The results of ANOVA(analysis of variance) about models, the probability value of the methane concentration and methane recovery response surface model are 0.0001 and 0.0001, respectively and coefficient of determination($R^2$) are 0.9788 and 0.9710, respectively. The response surface model is proved of high reliability and suitability. The operation pressure had the greatest influence to methane concentration than other operation parameters and the PSA rotary valve velocity had the greatest influence to methane recovery than other operation parameters. Optimal condition of biogas upgrading process for production of $100Nm^3/hr$ bio-methane were operation pressure 8.0bar and outlet flow rate 31.55RPM, respectively. At that operation condition the methane concentration of bio-methane was 97.13% and methane recovery in biogas upgrading process was 75.89%.

• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.77-83
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• 2023

Energy consumption is increased by rapid industrialization. As a result, climate change is accelerating due to the increase in CO₂ concentration in the atmosphere. Therefore, a shift in the energy paradigm is required. Hydrogen is in the spotlight as a part of that. Currently 95% of hydrogen is fossil fuel-based reforming hydrogen which is accompanied by CO₂ emissions. This is called gray hydrogen, if the CO₂ is captured and emission of CO₂ is reduced, it can be converted into blue hydrogen. There are 3 technologies to capture CO₂: absorption, adsorption and membrane technology. In order to select CO₂ capture technology, the analysis of the exhaust gas should be carried out. The concentration of CO₂ in the flue gas from the hydrogen production process is higher than 20%if water is removed as well as the emission scale is classified as small and medium. So, the application of the membrane technology is more advantageous than the absorption. In addition, if LNG cold energy can be used for low temperature CO₂ capture system, the CO₂/N₂ selectivity of the membrane is higher than room temperature CO₂ capture and enabling an efficient CO₂ capture process. In this study, we will analyze the flue gas from hydrogen production process and discuss suitable CO₂ capture technology for it.

• Korean Chemical Engineering Research
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• v.62 no.4
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• pp.312-326
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• 2024

This review comprehensively reviews the latest research trends in nickel catalysts for low-temperature CO₂ methanation reactions, with special emphasis on catalyst synthesis and reactor design for low-temperature CO₂ methanation reactions. In addition to the previously reported catalyst synthesis method of impregnation, the effects of structural and chemical properties of catalysts synthesized by solvothermal synthesis and electrospinning on CO₂ methanation reactions were analyzed. We also discuss the potential for process cost reduction and scale-up based on 3D catalyst structures and catalyst stacked reactor designs to improve reaction efficiency. It is found that the efficiency of the CO₂ methanation reaction can be maximized by controlling the oxygen vacancies and crystal structure of the catalyst through an innovative catalyst synthesis method, and by increasing the active area of nickel through the 3D structure of the catalyst and the reactor design. It is expected that this review will serve as the basis for the field of converting natural gas into CH₄, which can be used as a substitute for natural gas while reducing CO₂, a major greenhouse gas.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.9
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• pp.961-972
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• 2008

In 2004, total emissions of Greenhouse Gases(GHGs) in Korea was estimated to be about 590 million metric tons, which is the world's 10th largest emissions. Considering the much amount of nation's GHG emissions and growing nation's position in the world, GHG emissions in Korea should be reduced in near future. The CO$_2$ emissions from two sub-sections of energy sector in Korea, such as thermal power plant and industry section(including manufacturing and construction industries), was about 300 million metric tons in 2004 and this is 53.3% of total GHG emissions in Korea. So, the mitigation of CO$_2$ emissions in these two section is more important and more effective to reduce the nation's total GHGs than any other fields. In addition, these two section have high potential to qualitatively and effectively apply the CCS(Carbon Capture and Storage) technologies due to the nature of their process. There are several CCS technologies applied to these two section. In short term, the chemical absorption technology using amine as a absorbent could be the most effectively used. In middle or long term, pre-combustion technology equipped with ATR(Autothermal reforming), or MSR-$H_2$(Methane steam reformer with hydrogen separation membrane reactor) unit and oxyfuel combustion such as SOFC+GT(Solid oxide fuel cell-Gas turbine) process would be the promising technologies to reduce the CO$_2$ emissions in two areas. It is expected that these advanced CCS technologies can reduce the CO$_2$ avoidance cost to $US 8.5-43.5/tCO$_2$. Using the CCS technologies, if the CO$_2$ emissions from two sub-sections of energy sector could be reduced to even 10% of total emissions, the amount of 30 million metric tons of CO$_2$ could be mitigated.

• Tuberculosis and Respiratory Diseases
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• v.46 no.5
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• pp.628-635
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• 1999

Background : Maximal expiratory flow rate is determined by the size of airway, elastic recoil pressure and the collapsibility of airway in the lung. The obstruction of expiratory flow is one of the major functional impairments of emphysema, which represents COPD. Nevertheless, expiratory narrowing of upper airway may be recruited as a mechanism for minimizing airway collapse, and maintaining lung volume and hyperinflation by an endogenous positive end-expiratory pressure in patients with airflow obstruction. We investigated the physiologic role of trachea in respiration in emphysema. Method : We included 20 patients diagnosed as emphysema by radiologic and physiologic criteria from January to August in 1997 at Seoul Municipal Boramae Hospital. Chest roentgenogram, high resolution computed tomography(HRCT), and pulmonary function tests including arterial blood gas analysis and body plethysmography were taken from each patient. Cross-sectional area of trachea was measured according to the respiratory cycle on the level of aortic arch by HRCT and calibrated with body surface area. We compared this corrected area with such parameters of pulmonary function tests as $PaCO_2$, $PaO_2$, airway resistance, lung compliance and so on. Results : Expiratory cross-sectional area of trachea had significant correlation with $PaCO_2$ (r=-0.61, p<0.05), $PaO_2$ (r=0.6, p<0.05), and minute ventilation (r=0.73, p<0.05), but inspiratory cross-sectional area did not (r=-0.22, p>0.05 with $PaCO_2$, r=0.26, p>0.05 with $PaO_2$, and r=0.44, p>0.05 with minute ventilation). Minute ventilation had significant correlation with tidal volume (r=0.45, p<0.05), but it had no significant correlation with respiratory frequency (r=-0.31, p>0.05). Cross-sectional area of trachea had no significant correlation with other parameters of pulmonary function including $FEV_1$, FVC, $FEV_1$/FVC, peak expiratory flow, residual volume, diffusing capacity, airway resistance, and lung compliance, whether the area was expiratory or inspiratory. Conclusion : Cross-sectional area of trachea narrowed during expiration in emphysema, and its expiratory area had significant correlation with $PaCO_2$, $PaO_2$, and minute ventilation.

• Membrane Journal
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• v.22 no.2
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• pp.128-134
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• 2012

In this study, hydroxy polyimide (HPI) was prepared for non-porous membrane by solvent evaporation method. As the result of gas permeance properties measurement, $CO_2$ permeability was 85 Barrer and the $CO_2/N_2$ selectivity was 23 at $30^{\circ}C$. Flat sheet membrane and hollow fiber membrane were prepared by using ternary system of polymer, solvent and non-solvent additive. Morphologies and gas permeance properties were measured by FE-SEM and bubble flow meter. Each $CO_2$ permeability of 18.28 GPU, 70 GPU and $CO_2/N_2$ selectivity of 6.72, 8.63 at $30^{\circ}C$ in the flat sheet membrane and hollow fiber membrane. Hollow fiber membrane has gas permeance property better than flat sheet membrane.

• Journal of Korea Multimedia Society
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• v.15 no.2
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• pp.234-241
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• 2012

The purpose of this study is to analyze the economic effects of telepresence system for public sector relocation. As a Green IT system, the importance of telepresence is being recognized increasingly as a means to replacing a majority of business trips and thereby reducing greenhouse gases emitted in the process. However, there are only a few related researches that analyze the economic effects of telepresence at the moment. This study conducts the cost-benefit analysis of 157 public sectors which are to relocate from 2012 based on the sample case of National Information Society Agency. The results obtained reveals that telepresence would save about 180 billion won and reduce about 580t $CO_2$ emission. This study are expected to provide the academic framework for organizations contemplating the adoption of Green IT system moving forward.