• Clean Technology
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• v.28 no.3
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• pp.218-226
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• 2022

As a result of the recent social transformation towards a hydrogen economy and carbon-neutrality, the demands for hydrogen energy have been increasing rapidly worldwide. As such, eco-friendly hydrogen production technologies that do not produce carbon dioxide (CO₂) emissions are being focused on. Among them, ammonia (NH₃) is an economical hydrogen carrier that can easily produce hydrogen (H₂). In this study, Ru/Al₂O₃ catalyst coated onmetallic monolith for hydrogen production from ammonia was prepared by a dip-coating method using a catalyst slurry mixture composed of Ru/Al₂O₃ catalyst, inorganic binder (alumina sol) and organic binder (methyl cellulose). At the optimized 1:1:0.1 weight ratio of catalyst/inorganic binder/organic binder, the amount of catalyst coated on the metallic monolith after one cycle coating was about 61.6 g L^-1. The uniform thickness (about 42 ㎛) and crystal structure of the catalyst coated on the metallic monolith surface were confirmed through scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. Also, a numerical optimization regression equation for NH3 conversion according to the independent variables of reaction temperature (400-600 ℃) and gas hourly space velocity (1,000-5,000 h^-1) was calculated by response surface methodology (RSM). This model indicated a determination coefficient (R²) of 0.991 and had statistically significant predictors. This regression model could contribute to the commercial process design of hydrogen production by ammonia decomposition.

• Journal of the Korea Organic Resources Recycling Association
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• v.31 no.1
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• pp.69-84
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• 2023

Despite the continuous installation and regular inspection of waste treatment facilities, complaints about excessive incineration and illegal dumping stench continue to occur at on-site treatment facilities. In addition, field surveys were conducted on the waste treatment facilities currently in operation (6 type) to understand the waste treatment process for each field, to grasp the main operating factors applied to the inspection. In addition, we calculated the material·energy balance for each main process and confirmed the proper operation of the waste disposal facility. As a result of the site survey, in the case of heat treatment facilities such as incineration, cement kilns, and incineration heat recovery facilities, the main factors are maintenance of the temperature of the incinerator required for incineration and treatment of the generated air pollutants, and in the case of landfill facilities Retaining wall stability, closed landfill leachate and emission control emerged as major factors. In the case of sterilization and crushing facilities, the most important factor is whether or not sterilization is possible (apobacterium inspection).In the case of food distribution waste treatment facilities, retention time and odor control during fermentation (digestion, decomposed) are major factors. Calculation results of material balance and energy resin for each waste treatment facility In the case of incineration facilities, it was confirmed that the amount of flooring materials generated is about 14 % and the amount of scattering materials is about 3 % of the amount of waste input, and that the facility is being operated properly. In addition, among foodwaste facilities, in the case of an anaerobic digestion facility, the amount of biogas generated relative to the amount of inflow is about 17 %, and the biogas conversion efficiency is about 81 %, in the case of composting facility, about 11 % composting of the inflow waste was produced, and it was comfirmend that all were properly operated. As a result, in order to improve the inspection method for waste treatment facilities, it is necessary not only to accumulate quantitative standards for detailed inspection methods, but also to collect operational data for one year at the time of regular inspections of each facility, Grasping the flow and judging whether or not the treatment facility is properly operated. It is then determined that the operation and management efficiency of the treatment facility will increase.

• Journal of the Korea Organic Resources Recycling Association
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• v.31 no.1
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• pp.85-100
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• 2023

In this study, in order to improve the installation periodical inspection method of waste treatment facilities, we conducted on-site surveys of waste treatment facilities classified into six fields, grasped the problems of inspection methods, and made improvements accordingly. And revised the inspection method for waste treatment facilities. As a result, in the field of incineration and incineration heat recovery, inspection methods such as total temperature measurement and one-year TMS data comparison using a thermal imaging camera were established. And for the safety of the inspected person, it was applied so that the waste can be replaced with a document without opening it. In the case of landfill facilities, the details regarding the use of video information processing equipment and the management of facilities covering the upper part of the landfill facility are presented in the law, but the items that do not have a inspection methods were applied to the inspection method. In the case of Food Waste Treatment Facility, inspection methods were put in place to ensure compliance with standards for foul-smelling fish in odor control, a major cause of complaints. As a result, 10 out of 18 improvement proposals were reflected in the incineration and sterilization grinding, cement kiln, and incineration heat recovery facilities, and 11 out of 12 improvement proposals were reflected in the landfill facility. In the case of food distribution waste treatment facilities, 10 out of 12 improvement proposals were reflected, and a total of 31 inspection methods were improved.

• Journal of Korea Water Resources Association
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• v.56 no.12
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• pp.993-1003
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• 2023

Due to the increasing greenhouse gas emissions, the global mean temperature has risen by 1.1℃ compared to pre-industrial levels, and significant changes are expected in functioning of water supply systems. In this study, we assessed impacts of climate change and instreamflow management on water supply reliability in the Geum River basin, Korea. We proposed univariate climate response functions, where mean precipitation and potential evaporation were coupled as an explanatory variable, to assess impacts of climate stress on multiple water supply reliabilities. To this end, natural streamflows were generated in the 19 sub-basins with the conceptual GR6J model. Then, the simulated streamflows were input into the Water Evaluation And Planning (WEAP) model. The dynamic optimization by WEAP allowed us to assess water supply reliability against the 2020 water demand projections. Results showed that when minimizing the water shortage of the entire river basin under the 1991-2020 climate, water supply reliability was lowest in the Bocheongcheon among the sub-basins. In a scenario where the priority of instreamflow maintenance is adjusted to be the same as municipal and industrial water use, water supply reliability in the Bocheongcheon, Chogang, and Nonsancheon sub-basins significantly decreased. The stress tests with 325 sets of climate perturbations showed that water supply reliability in the three sub-basins considerably decreased under all the climate stresses, while the sub-basins connected to large infrastructures did not change significantly. When using the 2021-2050 climate projections with the stress test results, water supply reliability in the Geum River basin was expected to generally improve, but if the priority of instreamflow maintenance is increased, water shortage is expected to worsen in geographically isolated sub-basins. Here, we suggest that the climate response function can be established by a single explanatory variable to assess climate change impacts of many sub-basin's performance simultaneously.

• Applied Chemistry for Engineering
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• v.35 no.1
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• pp.1-7
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• 2024

Mn-M/Al₂O₃ (M = Cu, Fe, Co, and Ce) catalysts were prepared for simultaneous oxidation of NO, CO, and CH₄, and their oxidation activities were compared. The Mn-Cu/ Al₂O₃ catalyst with the best simultaneous oxidation activity was characterized by XRD, Raman, XPS, and O₂-TPD analysis. The result of XRD indicated that Mn and Cu existed as complex oxides in the Mn-Cu/Al₂O₃ catalyst. Raman and XPS results showed that electron transfer between Mn ions and Cu ions occurred during the formation of the Mn-O-Cu bond in the Mn-Cu/Al₂O₃ catalyst. The XPS O 1s and O₂-TPD analyses showed that the Mn-Cu/Al₂O₃ catalyst has more adsorbed oxygen species with high mobility than the Mn/Al₂O₃ catalyst. The high simultaneous oxidation activity of the Mn-Cu/Al₂O₃ catalyst is attributed to these results. Gas-phase NO promotes the oxidation reactions of CO and CH₄ in the Mn-Cu/Al₂O₃ catalyst while suppressing the NO oxidation reaction. These results were presumed to be because the oxidized NO was used as an oxidizing agent for CO and CH₄. On the other hand, the oxidation reactions of CO and CH₄ competed on the Mn-Cu/Al₂O₃ catalyst, but the effect was not noticeable because the catalyst activation temperature was different.

• Journal of Korean Society of Disaster and Security
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• v.16 no.4
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• pp.45-59
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• 2023

The global focus on mitigating climate change has traditionally centered on carbon dioxide, but recent attention has shifted towards methane as a crucial factor in climate change adaptation. Natural settings, particularly aquatic environments such as wetlands, reservoirs, and lakes, play a significant role as sources of greenhouse gases. The accumulation of organic contaminants on the lake and reservoir beds can lead to the microbial decomposition of sedimentary material, generating greenhouse gases, notably methane, under anaerobic conditions. The escalation of methane emissions in freshwater is attributed to the growing impact of non-point sources, alterations in water bodies for diverse purposes, and the introduction of structures such as river crossings that disrupt natural flow patterns. Furthermore, the effects of climate change, including rising water temperatures and ensuing hydrological and water quality challenges, contribute to an acceleration in methane emissions into the atmosphere. Methane emissions occur through various pathways, with ebullition fluxes-where methane bubbles are formed and released from bed sediments-recognized as a major mechanism. This study employs Biochemical Methane Potential (BMP) tests to analyze and quantify the factors influencing methane gas emissions. Methane production rates are measured under diverse conditions, including temperature, substrate type (glucose), shear velocity, and sediment properties. Additionally, numerical simulations are conducted to analyze the relationship between fluid shear stress on the sand bed and methane ebullition rates. The findings reveal that biochemical factors significantly influence methane production, whereas shear velocity primarily affects methane ebullition. Sediment properties are identified as influential factors impacting both methane production and ebullition. Overall, this study establishes empirical relationships between bubble dynamics, the Weber number, and methane emissions, presenting a formula to estimate methane ebullition flux. Future research, incorporating specific conditions such as water depth, effective shear stress beneath the sediment's tensile strength, and organic matter, is expected to contribute to the development of biogeochemical and hydro-environmental impact assessment methods suitable for in-situ applications.

• Journal of Chest Surgery
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• v.35 no.10
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• pp.712-723
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• 2002

Substantial alterations in cerebral blood flow(CBF) are known to occur during cardiopulmonary bypass(CPB). Many investigators have speculated that these changes may be responsible for both minor and major cerebral damages after CPB. More recently, these changes in CBF have been observed to be intimately related to the arterial carbon dioxide tension(Pa$CO_2$) maintained during CPB. The present study was prospectively designed to investigate the clinical effects of normocapnic and hypercapnic CPB on the cerebral oxygen metabolism in cardiac surgery Material and Method: Thirty-six adult patients scheduled for elective cardiac surgery were randomized to either normocapnic group (Pa$CO_2$35~40 mmHg, n＝18) or hypercapnic group(Pa$CO_2$, 45~55 mmHg, n＝18) with moderately hypothermic nonpulsatile CPB(nasopharyngeal temperature of 29~3$0^{\circ}C$). In each patient, middle cerebral artery blood flow velocity( $V_{MCA}$), cerebral arteriovenous oxygen content difference (C(a-v) $O_2$), cerebral oxygen extraction(COE), cerebral metabolic rate for oxygen(CMR $O_2$), cerebral oxygen transport( $T_{E}$ $O_2$), $T_{E}$ $O_2$/CMR $O_2$ ratio, cerebral desaturation(internal jugular bulb blood oxygen saturation $\leq$ 50%), and arterial and jugular bulb blood gas were evaluated throughout the operation. Postoperative neuropsychologic complications were assessed in all patients. All variables were compared between the two groups. Result: VMCA(169.13 $\pm$ 8.32 vs 153.11 $\pm$8.98%), TE $O_2$(1,911.17$\pm$250.14 vs 1,757.40$\pm$249.56), $T_{E}$ $O_2$,/CMR $O_2$ ratio(287.38$\pm$28.051 vs 246.77$\pm$25.84), $O_2$ tension in internal jugular bulb (41.66$\pm$9.19 vs 31.50$\pm$6.09 mmHg), and $O_2$saturation in internal jugular bulb(68.97$\pm$10.96 vs 58.12$\pm$12.11%) during CPB were significantly lower in normocapnic group(p＝0.03), whereas hypercapnic group had lower C(a-v) $O_2$(3.9$\pm$0.3 vs 4.9$\pm$0.3 mL/dL), COE(0.3$\pm$0.03 vs 0.4$\pm$0.03), CMR $O_2$(5.8 $\pm$0.5 vs 6.8$\pm$0.6), and arterial blood pH(7.36$\pm$0.09 vs 7.46$\pm$0.07, p＝0.04) during CPB. Hypercapnic group had lower incidence of cerebral desaturation than normocapnic group(3 vs 9 patients, p=0.03). Duration of the neuropsychologic complication(delirium) were shorter in hypercapnic group than in normocapnic group(36 vs 60 hrs, p＝0.009). Conclusion: These findings suggest that hypercapnic CPB may have salutary effects on the cerebral oxygen metabolism and postoperative neurologic outcomes in cardiac surgery.surgery.

• Parasites, Hosts and Diseases
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• v.29 no.3
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• pp.235-244
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• 1991

An epidemiological study and mass treatments of Enterobius vermicularis infection among children near Wonju area of Kangwon province were carried out. The children were divided into 4 groups according to their residing localities; children in the mountainous area, rural area, urban area and in orphanage. They were examined by adhesive cellotape anal swab technique, and egg positive rates were obtained. The rates of egg reduction and re-infection rates after repeated mass treatments were also observed. The results obtained were as follows: 1. The overall egg Positive rate of E. vermicularis in the first screening was 19.9% (251 out of 1, 262 examinees; 19.7% in males and 20.1% in females). The positive rates were 13.0% in the mountainous area, 11 9% in the rural area, 15.1% in the urban (medium-sized) area and 61.9% in orphanages. 2. The highest positive rates were observed in the kindergarten children, and 1st and 2nd grade children of primary schools (26.2~32.2%), and the lowest rate (13.6%) in 6-year grade children of primary schools. 3. Cumulative detection rates from 3 repeated anal swabs at 4~5 days interval were higher (70.8%) than those from single anal swabs (50.0~59.2%). 4. Out of the examinees who showed the highest cumulative positive rate (70.8%), about 39.2% were consecutively positive in 3 anal swabs. Among different groups of children, the higher the total egg detection rates (87.5%), the higher the consecutive positive rates (71.9%) . 5. A total of 2, 609 (male : female=1 : 12.4) worms were collected from 17 egg-positive cases treated with anthelinintics. The mean number of worms per child was 153 (range: 4-824) . 6. The egg-positive cases in several studied groups (180 children) were treated with anthelmintics 6 times at 3-week intervals. In this case, the overall positive rate was decreased from 54.8% to 2.2% at 15 weeks after the treatments, but no complete negative conversion was experienced. However, in a group of children (154 children) including egg Positive and negative cases who were both treated with anthelmintics at 3-week interval, a complete egg-negative conversion was observed in the 9th week after treatments. 7. The egg-detection rate in the brothers or sisters of egg Positive children was 70.0% (28 out of 40 examined), and the egg-positive rate according to the family unit was 69.7%. In summarizing the above results, it is concluded that Enterobius vermicularis infection is still highly prevalent among children in Korea, and that repeated mass treatments of more than 3 times will be effective for control of this infection.