• Journal of the Korean Society of Combustion
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• v.15 no.2
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• pp.1-11
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• 2010

Power generation systems based on the oxy-coal combustion with carbon dioxide capture and storage (CCS) capability are being proposed and discussed lately. Although a large number of lab scale studies for oxy-coal power plant have been made, studies of pilot scale or commercial scale power plant are not enough. Only a few demonstration projects for oxy-coal power plant are publicized recently. The proposed systems are evolving and various alternatives are to be comparatively evaluated. This paper presents a proposed approach for performance evaluation of a commercial 100 MWe class power plant, which is currently being considered for 'retrofitting' for the demonstration of the concept. The system is configurated based on design and operating conditions with proper assumptions. System components to be included in the discussion are listed. Evaluation criteria in terms of performance are summarized based on the system heat and mass balance and simple performance parameters, such as the fuel to power efficiency and brief introduction of the second law analysis. Also, gas composition is identified for additional analysis to impurities in the system including the purity of oxygen and unwanted gaseous components of nitrogen, argon and oxygen in air separation unit and $CO_2$ processing unit.

• Archives of Pharmacal Research
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• v.18 no.6
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• pp.427-433
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• 1995

A microscopic mass balance approach has hsown that the initial saturation (Is), absorption number (An), dose number (Do), and dissolution number (Dn) are four fundamental dimensionless parameters that can be used to estimate the fraction dose absorbed (F)l of suspensions of poorly soluble drugs in humans. The dissolution number of a drug increases with decreasing its particle size. The effect of micronization on F for suspensions was investigated in terms of Dn. About 90% of maximal F can be achieved at $Dn{\approx}2$. Increasing the solubility of a drug results in better oral absorption through increasing Dn and decreasing the solubility of a drug results in better oral absorption through increasing Dn and decreasing Do. The fractions dose absorbed of digoxin, griseofulvin, and benoxaprofen agree with predicted F values sorbed by reducing particle size, while absorption of drugs with high Do and low Dn is limited by solubility and requires higher solubility to enhance the fraction dose absorbed in addition to micronization. Solubility at the physiological pH should be used for the estimation of the fraction dose absorbed.

• Proceedings of the Membrane Society of Korea Conference
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• 2004.05a
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• pp.19-24
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• 2004

ED method is employed to effectively remove the organic acid salts in actual PDO fermentation broth. The lower electrical potential is selected to avoid the serious membrane fouling so as to ensure a stable and durative desalination process. Under the selected operation conditions, about 90% of organic acids salts are removed from PDO fermentation broth successfully by ED process. To reduce the loss of PDO product due to the diffusion, the operation time should be considered carefully. And based on mass balance equation and irreversible thermodynamics approach, a mathematical model is developed to describe the desalination process of an aqueous solution containing neutral solute by ED method. While the influence of concentration polarization is reflected by decreasing the conductivity of membrane, the model is verified well to describe the ED processes under varied operation conditions. Through the model, ED process of actual PDO fermentation broth is simulated to get a suitable scope of initial concentration in concentrated compartment.

• 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.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.232-232
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• 2019

The persistence of drought periods and water scarcity is a growing public concern, as climate change projections indicate a more critical scenario in the future. The sustainability of water resources for the increasing population, and to ensuring crop production will unarguably be a daunting task for the water resources managers, with a projected 9.8 billion people by 2050 as well as the need to increase food production by 70 to 100%. Consequently, there is a need for significant irrigation water use for more crop production in the face of stiff competition among water users. However, the available natural resources are already over-constrained, and the allocation of more resources for food production is not feasible. Currently, about two-thirds of global water withdrawer is used by the agricultural sector while 48% of water resources in Korea is used for agricultural production. Despite the apparent ecological deficit and unfavorable conditions of resources utilization, a staggering amount of food waste occurs in the country. Moreover, wastage of food translates to waste of all the resources involved in the food production including water resources. Food waste can also be considered a serious potential for economic and environmental problems. Hence, exploring an alternative approach to efficient resources utilization in a more sustainable way can ensure considerable resources conservation. We hypothesized that reducing food waste will decline the demand for food production and consequently reduce the pressure on water resources. We investigated the food wastage across the food supply chain using the top-down datasets based on the FAO mass balance model. Furthermore, the water footprint of the estimated food wastage was assessed using the representative of selected food crops. The study revealed that the average annual food wastage across the food supply chain is 9.05 million tonnes, signifying 0.51 kg/capita/day and 48% of domestic food production. Similarly, an average of 6.29 Gm3 per annum of water resources was lost to food wastage, which translates to 40% of the total allotted water resources for agriculture in the country. These considerable resources could have been conserved or efficiently used for other purposes. This study demonstrated that zero food waste generation would significantly reduce the impact on freshwater resources and ensure its conservation. There is a need for further investigation on the food waste study using the bottom-up approach, specifically at the consumer food waste, since the top-down approach is based on estimations and many assumptions were made.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.408-408
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• 2019

The persistence of drought periods and water scarcity is a growing public concern, as climate change projections indicate a more critical scenario in the future. The sustainability of water resources for the increasing population, and to ensuring crop production will unarguably be a daunting task for the water resources managers, with a projected 9.8 billion people by 2050 as well as the need to increase food production by 70 to 100%. Consequently, there is a need for significant irrigation water use for more crop production in the face of stiff competition among water users. However, the available natural resources are already over-constrained, and the allocation of more resources for food production is not feasible. Currently, about two-thirds of global water withdrawer is used by the agricultural sector while 48% of water resources in Korea is used for agricultural production. Despite the apparent ecological deficit and unfavorable conditions of resources utilization, a staggering amount of food waste occurs in the country. Moreover, wastage of food translates to waste of all the resources involved in the food production including water resources. Food waste can also be considered a serious potential for economic and environmental problems. Hence, exploring an alternative approach to efficient resources utilization in a more sustainable way can ensure considerable resources conservation. We hypothesized that reducing food waste will decline the demand for food production and consequently reduce the pressure on water resources. We investigated the food wastage across the food supply chain using the top-down datasets based on the FAO mass balance model. Furthermore, the water footprint of the estimated food wastage was assessed using the representative of selected food crops. The study revealed that the average annual food wastage across the food supply chain is 9.05 million tonnes, signifying 0.51 kg/capita/day and 48% of domestic food production. Similarly, an average of $6.29Gm^3$ per annum of water resources was lost to food wastage, which translates to 40% of the total allotted water resources for agriculture in the country. These considerable resources could have been conserved or efficiently used for other purposes. This study demonstrated that zero food waste generation would significantly reduce the impact on freshwater resources and ensure its conservation. There is a need for further investigation on the food waste study using the bottom-up approach, specifically at the consumer food waste, since the top-down approach is based on estimations and many assumptions were made.

• Animal cells and systems
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• v.3 no.2
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• pp.143-147
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• 1999

Annual production and redistribution of leaf litter were compared among three distinct understory patches in a temperate hardwood forest dominated by Quercus mongolica, Kalopanax pictus, Acer pseudo-sieboldianum, and Carpinus cordata. Two patches were located on a southwest-facing slope: one with an understory dominated by herbaceous plants (Patch S), and the other covered with evergreen dwarf bamboo, Sasa borealis (patch SS). The third patch was on the opposite slope with an understory dominated by herbaceous plants (Patch N). Annual leaf litterfall was averaged 330 g m$^{-2} yr$^{-2}$ in the three patches from 1994 to 1998. From mid-September 1996 to mid-September 1997, net transport of leaf litter over patch bound-aries was 1,824g m$^{-1}$ from Patch S to SS, 1,465g m$^{-1}$ from Patch S to N, and 886 g m$^{-1}$ from Patch SS to N. The amounts moving downslope out of Patch S, SS, and N were 2,548, 471, and 588g m$^{-1}$, respectively. When a mass balance approach was employed for the data of leaf litter transport, the results were relatively consistent with 216, 631, and 724g m$^{-2}$ of leaf litter stores in Patch S, SS, and N, respectively, in April 1997. This study suggests that leaf litter redistribution is largely regulated by aspect and understory type and exerts a significant effect on carbon processes in the forest ecosystem.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.4 no.3
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• pp.139-148
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• 2000

A mass balance/photochemical modeling approach was used to evaluate the sea-to-air dimethyl sulfide (DMS) fluxes in tropical regions and part of the Southern Ocean. The flux determinations were based on 10 airborne observations by ACE 1 transit flights (i.e., Flights 4-9 and 29-32). The DMS flux values for the tropical regions ranged from 1.0 to 7.4 $\mu$mole/$m^2$/day with an average estimate of 4.2$\pm$2.3 $\mu$mole/$m^2$/day. The seasonal variations in the DMS flux predicted for the equatorial Pacific Ocean based on atmospheric DMS measurements were not entirely consistent with those derived from seawater DMS measurements were not entirely consistent with those derived from seawater DMS measurements reported in previous literature. Inhomogeneities in the DMS flux field were found to cause significant shifts in the atmospheric DMS levels even in the same sampling location. Accordingly, no definitive statement can be made at this stage regarding systematic differences or agreements in the DMS flux estimates from the two approaches. Moreover, this study strongly suggests that DMS oxidation is the most likely dominant source of SO$_2$in tropical regions, which is also supported by another set of compiled observations. Finally, these SO$_2$observations indicate that, when significant data was available for both the boundary and buffer layers, the vertical SO$_2$gradient between these two zones was primarily negative.

• Journal of the Korean Geotechnical Society
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• v.27 no.3
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• pp.75-83
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• 2011

Emerging issues related with fully coupled Thermo-Hydro-Mechanical (THM) behavior of unsaturated soil demand the development of a numerical tool in diverse geo-mechanical and geo-environmental areas. This paper presents general governing equations for coupled THM processes in unsaturated porous media. Coupled partial differential equations are derived from three mass balances equations (solid, water, and air), energy balance equation, and force equilibrium equation. With Galerkin formulation and time integration of these governing equations, finite element code is developed to find nonlinear solution of four main variables (displacement-u, gas pressure-$P_g$), liquid pressure-$P_1$), and temperature-T) using Newton's iterative scheme. Three cases of numerical simulations are conducted and discussed: one-dimensional drainage experiments (u-$P_g-P_1$), thermal consolidation (u-$P_1$-T), and effect of pile on surrounding soil due to surface temperature variation (u-$P_1$-T).

• Nuclear Engineering and Technology
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• v.41 no.6
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• pp.831-840
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• 2009

In order to evaluate the start-up behavior and to identify, through abnormal operation occurrences, the transient behaviors of the Sulfur Iodine(SI) process, which is a nuclear hydrogen process that is coupled to a Very High Temperature Gas Cooled Reactor (VHTR) through an Intermediate Heat Exchanger (IHX), a dynamic simulation of the process is necessary. Perturbation of the flow rate or temperature in the inlet streams may result in various transient states. An understanding of the dynamic behavior due to these factors is able to support the conceptual design of the secondary helium loop system associated with a hydrogen production plant. Based on the mass and energy balance sheets of an electrodialysis-embedded SI process equivalent to a 200 $MW_{th}$ VHTR and a considerable thermal pathway between the SI process and the VHTR system, a dynamic simulation of the SI process was carried out for a sulfuric acid decomposition process (Second Section) that is composed of a sulfuric acid vaporizer, a sulfuric acid decomposer, and a sulfur trioxide decomposer. The dynamic behaviors of these integrated reactors according to several anticipated scenarios are evaluated and the dominant and mild factors are observed. As for the results of the simulation, all the reactors in the sulfuric acid decomposition process approach a steady state at the same time. Temperature control of the inlet helium is strictly required rather than the flow rate control of the inlet helium to keep the steady state condition in the Second Section. On the other hand, it was revealed that the changes of the inlet helium operation conditions make a great impact on the performances of $SO_3$ and $H_2SO_4$ decomposers, but no effect on the performance of the $H_2SO_4$ vaporizer.