• Journal of Korean Society on Water Environment
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• v.38 no.4
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• pp.171-176
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• 2022

Recently, an autotrophic single-stage nitrogen removal (ASSNR) process based on the anaerobic ammonium oxidation (ANAMMOX) reaction has been proven as an economical ammonia treatment. It is highly evident that double-layered gel beads are a promising alternative to the natural biofilm for ASSNR because of the high mechanical strength of poly(vinyl alcohol) (PVA)/alginate structure and efficient protection of ANAMMOX bacteria from dissolved oxygen (DO) due to the thick outer layer. However, the thick outer layer results in severe mass transport limitation and consequent lowered bacterial activity. Therefore, the effects of the thickness of the outer layer on the overall reaction rate were tested in the biofilm model using AQUASIM for ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB) and ANAMMOX bacteria. A thickness of 0.5~1.0 mm is preferred for the maximum total nitrogen (TN) removal. In addition, a DO of 0.5 mg/L resulted in the best total nitrogen removal. A higher DO induces NOB activity and consequent lower TN removal efficiency. The optimal density of AO B and NO B density was 1~10% for a 10% ANAMMOX bacterial in the double-layered PVA/alginate gel beads. The real effects of operating parameters of the thickness of the outer layer, DO and concentrations of biomass balance should be intensively investigated in the controlled experiments in batch and continuous modes.

• Journal of Korean Society on Water Environment
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• v.31 no.5
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• pp.507-522
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• 2015

In this study, some of the model verification results of STREAM (Spatio-Temporal River-basin Ecohydrology Analysis Model), a newly-developed hybrid watershed model, are presented for the runoff processes of nonpoint source pollution. For verification study of STREAM, the model was applied to a test watershed and a sensitivity analysis was also carried out for selected parameters. STREAM was applied to the Mankyung River Watershed to review the applicability of the model in the course of model calibration and validation against the stream flow discharge, suspended sediment discharge and some water quality items (TOC, TN, TP) measured at the watershed outlet. The model setup, simulation and data I/O modules worked as designed and both of the calibration and validation results showed good agreement between the simulated and the measured data sets: NSE over 0.7 and $R^2$ greater than 0.8. The simulation results also include the spatial distribution of runoff processes and watershed mass balance at the watershed scale. Additionally, the irrigation process of the model was examined in detail at reservoirs and paddy fields.

• Korean Institute of Interior Design Journal
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• v.25 no.2
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• pp.3-12
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• 2016

Aires Mateus Architects is one of the most well-known Portuguese architects after $\acute{A}lvaro$ Siza and Eduardo Souto de Moura. The studio shows clear design methods in which the relationship between solid mass and void space are creatively inter-connected. Subtractive transformation of form is the fundamental aspect of this relationship. Most of Aires Mateus' projects were designed based on the subtractive method. Although subtraction can be seen as architectural formal presentation, in Aires Mateus' cases, there are deeper logics, strategies, and meanings. Not only to create a form, subtractive method has been flexibly used to organize and compose different programs and spatial atmosphere. To examine this hidden dimension of Aires Mateus' unique design process, 5 case projects were selected and analyzed in detail based on program, light & visual-perception, and site's placeness. From the case study results, it is found that there are much deeper role of subtraction: relationship between solid-void are constantly changing to generate serviced and servant spaces, there are central spaces that are contrast against the complexity of exterior forms, aiming to build an archetypal form that transcends ever-changing time, ambivalent balance between universality and peculiarity in the genealogy of contemporary architecture. The study concluded that the unique characteristics of subtraction method as design organization have various possibilities that can apply on other architectural and interior projects which would have similar ideas and circumstances.

• Journal of the Korea Safety Management & Science
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• v.17 no.1
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• pp.271-279
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• 2015

Global warming has pressured companies to put a greater emphasis on environment management which allows them to reduce environmental impact and costs of their operations. In Korea, the coal-fired power plants take a large account of electricity generation at 31.7% of the total electricity usage in 2014. Thus, environmental impact of coal-fired power plants is significant. This paper illustrated how to compute environmental impact and costs in electricity generation at a coal-fired power plant using MFCA methodology. Compared to the traditional accounting, an advantage of MFCA is to provide information on electricity generation costs and environmental wastes incurring throughout the production process of electricity. Based on MFCA, the coal-fired power plant was able to reduce production cost of electricity by 52.3%, and environmental wastes by 47.7%. As a result, MFCA seemed to be an effective tool in environmental management for power plants.

• The KSFM Journal of Fluid Machinery
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• v.2 no.2 s.3
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• pp.19-26
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• 1999

Thermal output in a nuclear power plant is verified with calorimetric heat balance on the secondary plant. The calorimetry involves the precise measurement of the feedwater flow rate. However, the correct indication of feedwater flow rate obtained by a pressure-difference measurement across a venturi can be affected by instrument errors, fouling or a poorly developed velocity profile. This can result in an inaccurate mass flow rate and consequently an inaccurate estimate of power. The purpose of this study is to develop verification methods with accuracy better than $0.5\%$ for high precision flow measurement to be used for measuring feedwater flow rate. This chemical tracer method is a testing process that uses tracers which can be applied to quantify losses in electrical output due to the incorrect measurements of feedwater flow rate. And this system has good response to the variation of the flow rate. Accuracy of better than 0.5 percent can be expected for feedwater flow measurement, providing that the system can be stabilized during the test. This methodology is applicable to other flow systems well.

• Proceedings of the KAIS Fall Conference
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• 2009.05a
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• pp.848-850
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• 2009

화석에너지 고갈로 인한 유가 상승으로 폐기물 에너지화가 이슈화 되고 있다. 폐기물 고형 연료 RDF는 에너지 문제를 해결하기위한 대안 중 하나로 수송성, 저장성, 연소안정성이 우수하나 환경오염 물질의 발생이 문제가 된다. 이러한 오염물질을 처리하기 위한 배가스 오염 물질처리를 위한 plant 설비 비용과 시간이 많이 투자된다. Aspen plus는 mass energy balance와 화학적평형, 열역학을 이용하여 공정 모사를 할 수 있는 프로그램으로 검증되었다. RDF의 삼성분, 원소분석, 발열량을 입력을 통해 HCl, SOx, NOx, CO의 배출량을 예측하고 이에 맞는 SNCR, SDA 등과 같은 반응기를 적용 하므로써 다양한 배가스 처리를 모사 할 수 있다. NOx를 제어하기위에 urea주입과 SOx와 HCl을 제거하기 위한 CaO를 주입을 모사 하므로써 실제 운영 적용 전 단계에 역할로 유용한 도구로 판단된다.

• Journal of Korean Society on Water Environment
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• v.24 no.1
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• pp.30-35
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• 2008

In this study, we investigated the nitrification/denitrification rate and classification of output nitrogen of a sequencing batch reactor (SBR) system with the variation of COD loads ; COD loads of 0.3, 0.4, 0.6, 0.7, 0.8, 1.0 and $1.2kgCOD/m^3{\cdot}d$ were tested to determine the optimum conditions for the operation of the SBR and increase its nitrogen removal efficiency. As the COD loads increased, the nitrification rate at aerobic(I) period and the denitrification rate at anoxic(I) period were decreased. With the variation of COD loads, the amounts of nitrogen removed in the clarified water effluent were 63.9, 54.2, 34.7, 22.5, 13.7, 12.5 and 26.5 mg/cycle, respectively. The amounts of nitrogen removed during the sludge waste process were 19.5, 26.6, 41.0, 47.3, 58.1, 72.4 and 88.1 mg/cycle, respectively. The amounts of nitrogen removed by denitrification were 66.8, 69.3, 68.9, 56.5, 39.5, 7.3 and 0.0 mg/cycle, respectively, indicating that COD load more than $0.7kgCOD/m^3{\cdot}d$ decreases the amounts of denitrified nitrogen. The nitrogen mass balances were calculated as the percentages of nitrogen removed in the clarified water effluent or by denitrification and sludge waste processing in each cycle of SBR operation and were 99.0, 98.5, 95.4, 82.1, 73.0, 60.5 and 74.8% for COD loads of 0.3, 0.4, 0.6, 0.7, 0.8, 1.0 and $1.2kgCOD/m^3{\cdot}d$, respectively.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.2
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• pp.201-207
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• 2004

Dissolved air flotation (DAF) is a solid-liquid separation process that uses fine rising bubbles to remove particles in water. Most of particle-bubble collision occurs in the DAF contact zone. This initial contact considered by the researchers to play a important role for DAF performance. It is hard to make up conceptual model through simple mass balance for estimating collision efficiency in the contact zone because coupled behavior of the solid-liquid-gas phase in DAF system is 90 complicate. In this study, 2-phase(gas-liquid) flow equations for the conservation of mass, momentum and turbulence quantities were solved using an Eulerian-Eulerian approach based on the assumption that very small particle is applied in the DAF system. For the modeling of turbulent 2-phase flow in the reactor, the standard $k-{\varepsilon}$ mode I(liquid phase) and zero-equation(gas phase) were used in CFD code because it is widely accepted and the coefficients for the model are well established. Particle-bubble collision efficiency was calculated using predicted turbulent energy dissipation rate and gas volume fraction. As the result of this study, the authors concluded that bubble size and recycle ratio play important role for flow pattern change in the reactor. Predicted collision efficiency using CFD showed good agreement with measured removal efficiency in the contact zone. Also, simulation results indicated that collision efficiency at 15% recycle ratio is higher than that of 10% and showed increasing tendency of the collision efficiency according to the decrease of the bubble size.

• Journal of the Korea Organic Resources Recycling Association
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• v.20 no.3
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• pp.34-40
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• 2012

This research has looked into the treatment process of wood waste generated from industrial waste within the region and in order to modify the problem that may occurred during the mass balance were analyzed for development of suitable solid waste recycling network regionally. As as result, quite amount of wood waste are being transferred to another region, even though a treatment facility's capacity could bear the total amount of waste generated within the area. Although the wood waste could be treated locally, it is analyzed that amount of wood waste are being transferred due to inefficient and irrational processing system between regions. It is assumed that $CO_2$ generated and loss of unnecessary fuel cost from these inefficient system is quite a lot and in order to modify this disorganized system, it will not inevitable to treat the waste based on the characteristics of each regions. Also, the wood waste recycling system should be studied with the efficient, environmental friendly processing and delivering network by minimized transfer distance and local systemizing the waste treatment system.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.3
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• pp.277-282
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• 2007

For more accurate and practical design of the residual treatment train at water treatment plants(WTPs), a computational program based on the commercial spreadsheet, Microsoft Excel, was developed. The computational program for the design of a residual treatment train(DRTT) works in three steps which estimate the residual production to be treated, analyze the mass balance, and determine the size of each unit process. Of particular interest in the DRTT program, is provision for a filter backwash recycle system consisting of surge tank and sedimentation basin for more efficient recycling of backwash water. When the DRTT program was applied to the Chungju WTP, the program was very beneficial in avoiding errors which might have occurred during arithmetic calculations and in reducing the time needed to get the output. It is anticipated that the DRTT program could be used for design of new WTPs as well as the rehabilitation of existing ones.