• 한국물환경학회지
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• 제29권3호
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• pp.354-364
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• 2013

The performance of the stormwater wetlands can be significantly influenced by antecedent stormwater in storage at the commencement of a stormevent. As inflows are intermittent and stochastic in nature, the evaluation of the treatment efficiency of a stormwater wetland should be considered by runoff capture and water treatment characteristics during interevent periods. In this study, analytical probabilistic model is applied to identity runoff capture rate and treatment efficiency of the stormwater wetland. To achieve this, continuous rainfall data recorded in Busan for 31 years has been analyzed to derive the runoff capture rate, and 1st order kinetic decay constants ($k_V$, 1/d) are calculated from regression analysis to identify pollutants removal during interevent periods. The results show that about 60.9% of annual average runoff is captured through the stormwater wetland. The annual average treatment efficiencies of SS, BOD, COD, TN and TP is about 11.4, 8.9, 9.8, 4.3 and 9.6%, respectively. The analytical model has been compared with the numerical model and it shows that analytical model is valid. Performance evaluation methods developed in this study has the advantages of considering characteristics of rainfall-runoff, facility type and pollutant removal.

• 한국물환경학회지
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• 제34권6호
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• pp.569-578
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• 2018

To minimize the negative alterations in hydrologic and water quality environment in urban areas due to urbanization, Low Impact Development (LID) techniques are actively applied. In Korea, LID facilities are classified as Non-point Pollution Reduction Facilities (NPRFs), and therefore they are evaluated using the performance evaluation method for NPRFs. However, while LID facilities are generally installed in small, distributed configuration and mainly work with the infiltration process, the existing NPRFs are installed on a large scale and mainly work with the reservoir process. Therefore, some limitations are expected in assessing both facilities using the same method as they differ in properties. To solve these problems, in this study, a new method for performance evaluation was proposed with focus on bio-retention LID facilities. EPA SWMM was used to reproduce the hydrologic and water quality phenomena in study area, and SWMM-LID module used to simulate TP interception performance by installing a bio-retention cell under various conditions through long-term simulations. Finally, an empirical formula for Load Capture Ratio (LCR) was derived based on storm water interception ratio in the same form as the existing method. Using the existing formula in estimating the LCR is likely to overestimate the performance of interception for non-point pollutants in the extremely low design capacity, and also underestimate it in the moderate and high design capacity.

• Korean Chemical Engineering Research
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• 제48권2호
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• pp.140-146
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• 2010

이산화탄소 포집기술 중 건식흡수제를 이용한 연소 후 이산화탄소 포집기술에 대하여 최신기술개발 현황에 대하여 자세히 기술하였다. $CO_2$ 포집에 있어서 건식흡수제 이용 기술의 장점으로는 조업온도의 폭이 크고, 에너지손실이 적으며, 폐수발생이 없고, 부식성이 적으며, 고체폐기물의 상대적인 천연성을 들 수 있다. 현재 한국과 미국에서는 건식흡수제의 성능 개선과 더불어 실제 연소배가스로부터 $CO_2$ 포집을 위한 공정 개발을 통해 포집비용을 줄이려는 연구가 지속적으로 이루어지고 있다. 건식흡수제는 가격이 싼 알칼리금속 계열의 화학흡수제, 아민을 실리카 지지체에 고정시킨 흡수제, 아민을 실리카 지지체에 공유결합시킨 흡수제, 기공성의 탄소에 아민의 기능성을 첨가시킨 흡수제, 아민고정 고분자지지체 흡수제, 금속유기구조체등의 연구가 이루어지고 있다. 포집비용을 대폭 줄이기 위하여 소재에 있어서도 혁신적인 성능 개선이 필요한 시점이다.

• Nuclear Engineering and Technology
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• 제52권9호
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• pp.2072-2077
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• 2020

The purpose of this study was to demonstrate the feasibility of sensing changes in a tumor during boron neutron capture therapy (BNCT) using a Monte Carlo simulation tool. In the simulation, an epi-thermal neutron source and a water phantom including boron uptake regions (BURs) were simulated. Moreover, this simulation also included a detector for positron emission tomography (PET) scanning and an adaptively-designed collimator (ADC) for PET. After the PET scanning of the water phantom, including the 511 keV source in the BUR, the ADC was positioned in the PET's gantry. Single prompt gamma rays were collected through the ADC during neutron irradiation. Then, single prompt gamma ray-based tomography images of different sized tumors were acquired by a four-step process. Both the signal-to-noise ratio (SNR) and tumor size were analyzed from each step image. From this analysis, we identified a decreasing trend of both the SNR and signal intensity as the tumor size decreased, which was confirmed in all images. In conclusion, we confirmed the feasibility of sensing changes in a tumor during BNCT using PET and an ADC through Monte Carlo simulation.

• 한국물환경학회지
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• 제27권6호
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• pp.896-904
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• 2011

The features of the capture reaction of $CO_2$ by ammonia solution have been investigated along with the effect of temperature on the reaction based upon computer program-utilizing calculation and thermodynamic estimation. The stable region of $CO{_3}^{2-}$ was observed to increase with temperature and the change of the stable region of $CO{_3}^{2-}$ with temperature was greater than the temperature variation of the stable region of other carbonate species. The distribution diagram for $NH_4{^+}-NH_3$ system was constructed and the rise of temperature resulted in the decrease of the stability of $NH_4{^+}$ ion, which was thought to be due to the endothermic nature of its acidic dissociation. Considering the introduction of $Ca^{2+}$ ion in the carbon capture reaction by $NH_4{^+}$, the temperature was observed to be important in the determination of the order of reaction between carbonate ion and these cations. The removal process of $CO_2$ gas by ammonia solution was presumed to occur in open system and the temperature variations of the concentration of carbonate system species along with their total concentration were calculated for the proper control and design of the real process.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.257-257
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• 2015

Carbon Capture and Storage with ocean sequestration is being considered as one of the most effective option for reducing the $CO_2$ net flux from atmosphere nowadays. But it is still possible for $CO_2$ substance to leaks out from transport pipeline or from the under seabed storage sites and causing damage to ambient environment. The behavior of liquid $CO_2$ under droplet shape would be strongly affected by the presence of other contaminants such as $SO_2$ comes from processing processes. This presentation shows the behavior in the sea water of pure liquid $CO_2$ droplets as well as droplets that consist of $SO_2$ substances. The study uses computational fluid dynamic models in comparison with experimental data from other previous researchers. Droplet of liquid $CO_2$ is assumed to be released at several depths in deep ocean, with other environmental conditions are set up respectively. All calculations are conducted with many different ratio of contaminant $SO_2$ to provide fundamental data of those particles rising characteristics. The effect of contaminants on the behavior of $CO_2$ droplets would be clearly shown through the results of particle deformation, terminal rising velocity happen due to buoyancy force driving from the difference in density of $CO_2$ substance and ocean water around.

• 한국해양공학회지
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• 제35권3호
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• pp.216-228
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• 2021

In the present study, the performance of a floating oscillating water column (OWC) device has been studied in regular waves. The OWC model has the shape of a hollow cylinder. The linear potential theory is assumed, and a matched eigenfunction expansion method(MEEM) is applied for solving the diffraction and radiation problems. The radiation problem involves the radiation of waves by the heaving motion of a floating OWC device and the oscillating pressure in the air chamber. The characteristics of the exciting forces, hydrodynamic forces, flow rate, air pressure in the chamber, and heave motion response are investigated with various system parameters, such as the inner radius, draft of an OWC, and turbine constant. The efficiency of a floating OWC device is estimated in connection with the extracted wave power and capture width. Specifically, the piston-mode resonance in an internal fluid region plays an important role in the performance of a floating OWC device, along with the heave motion resonance. The developed prediction tool will help determine the various design parameters affecting the performance of a floating OWC device in waves.

• Fisheries and Aquatic Sciences
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• 제11권2호
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• pp.113-123
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• 2008

We modeled fish school movements as a capture process in relation to the purse seine method using the three steps of the stimulus-response process (i.e., input stimuli, central decision-making and output reaction). Input stimuli of the model were categorized as either physical stimuli such as visual stimulus, sound stimulus, water flow, and weather or as biological stimuli such as species and size, swimming performance, sensual sensitivity, and presence of prey or predators. The output process determining the spatial orientation of the fish school for 3-D movements was based on swimming speed and angular change in the fish response, and these movements were animated as the relative geometry between the fish school and the purse seine. Simulations were carried out for skipjack tuna (Katsuwonus pelamis) schools reacting to a pelagic purse seine in the southwest Pacific Ocean. Simulation results showed that escape ratios varied from 20 to 70% by the relevant ranges in the stimulus-response thresholds, swimming speeds, and angular changes of fish schools were similar to those observed in the field. Therefore, with knowledge of relevant parameters, this model can be used to predict capture and escape probabilities of purse seine operations for different fish species or conditions.

• 대한환경공학회지
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• 제35권5호
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• pp.340-349
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• 2013

본 연구에서는 해수를 이용하여 석탄 화력발전소에서 발생하는 $CO_2$를 포집하기 위해 발전소에서 수급이 용이한 비산재, NaOH, $Ca(OH)_2$를 해수에 첨가하여 제조된 흡수제의 $CO_2$ 포집 성능을 고찰하였다. 비산재가 첨가된 해수의 $CO_2$ 포집성능은 순 해수에 비해 높아 비산재의 $CO_2$ 포집 효과는 유효하다. 그러나 해수 내 다양한 이온들에 의해 증류수에서 보다 비산재 내 유효 성분들의 침출량과 침출속도가 제한적이다. NaOH가 첨가된 해수는 $OH^-$ 손실이 일어나 증류수에 비해 $CO_2$ 포집량이 낮았고 다양한 이온의 상호 작용에 의해 포집 속도가 낮았다. $Ca(OH)_2$를 첨가한 경우, 해수에서의 $CO_2$ 포집 성능은 증류수 보다 높았는데 이는 해수 내 이미 존재하고 있던 $Ca^{2+}$ 중 일부가 탄산화 반응에 참여했기 때문으로 판단된다.

• 한국수소및신에너지학회논문집
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• 제23권3호
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• pp.285-292
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• 2012

The integrated gasification combined cycle (IGCC) system is well known for its high efficiency compared with that of other coal fueled power generation system. IGCC offers substantial advantages over pulverized coal combustion when carbon capture and storage (CCS) is required. Commercial plants employ different types of quenching system to meet the purpose of the system. Depending on that, the downstream units of IGCC can be modeled using different operating conditions and units. In case with $CO_2$ separation and capture, the gasifier product must be converted to hydrogen-rich syngas using Water Gas Shift (WGS) reaction. In most WGS processes, the water gas shift reactor is the biggest and heaviest component because the reaction is relatively slow compared to the other reactions and is inhibited at higher temperatures by thermodynamics. In this study, tehchno-econimic assessments were found according to the quench types and operating conditions in the WGS system. These results can improve the efficiency and reduce the cost of coal gasification.