• Journal of Environmental Health Sciences
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• v.39 no.3
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• pp.289-299
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• 2013

Objectives: For the field application of the dielectric barrier discharge plasma reactor, scale-up of the plasma reactor is needed. This study investigated the possibility of inactivation of microorganisms in sewage using pilot multi-plasma reactor. We also considered the possibility of degradation of total organic carbon (TOC) and nonbiodegradable matter ($UV_{254}$) in sewage. Methods: The pilot plasma reactor consists of plasma reactor with three plasma modules (discharge electrode and quartz dielectric tube), liquid-gas mixer, high voltage transformers, gas supply equipment and a liquid circulation system. In order to determine the operating conditions of the pilot plasma reactor, we performed experiments on the operation parameters such as gas and liquid flow rate and electric discharge voltage. Results: The experimental results showed that optimum operation conditions for the pilot plasma reactor in batch experiments were 1 L/min air flow rate), 4 L/min liquid circulation rate, and 13 kV electric discharge voltage, respectively. The main operation factor of the pilot plasma process was the high voltage. In continuous operation of the air plasma process, residual microorganisms, $UV_{254}$ absorbance and TOC removal rate at optimal condition of 13 kV were $10^{2.24}$ CFU/mL, 56.5% and 8.6%, respectively, while in oxygen plasma process at 10 kV, residual microorganisms, $UV_{254}$ absorbance and TOC removal rate at optimal conditions were $10^{1.0}$ CFU/mL, 73.3% and 24.4%, respectively. Electric power was increased exponentially with the increase in high voltage ($R^2$ = 0.9964). Electric power = $0.0492{\times}\exp^{(0.6027{\times}lectric\;discharge\;voltage)}$ Conclusions: Inactivation of microorganisms in sewage effluent using the pilot plasma process was done. The performance of oxygen plasma process was superior to air plasma process. The power consumption of oxygen plasma process was less than that of air plasma process. However, it was considered that the final evaluation of air and oxygen plasma must be evaluated by considering low power consumption, high process performance, operating costs and facility expenses of an oxygen generator.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.44 no.5
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• pp.63-71
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• 2012

This study was carried out to investigate pulping properties of the forest biomass arising from the national forest management operation. The forest biomass was collected and classified into many groups according to their species and age. After the chips were made from the forest biomass, the measurement of chip size and chemical analysis were performed. To make the pulps from the forest biomass, the kraft pulping was applied and thereafter the physical and optical properties of kraft pulps were measured. The pulp fibers from the forest biomass had the similar mean fiber length, but their properties became different according to wood species and ages. Differently from the other species, kraft pulps from chestnut wood had the highest kappa number. Acacia, paulownia and chestnut woods made kraft pulps with lower tensile strength and brightness than the others. It could be concluded that acacia, paulownia and chestnut woods must be screened out in order to make a good quality of kraft pulps while being collected during Forest Management Operation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.258-264
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• 2018

This paper presents application of a differential search (DS) meta-heuristic optimization algorithm for optimal operation of a micro grid system. The DS algorithm simulates the Brownian-like random-walk movement used by an organism to migrate. The micro grid system consists of a wind turbine, a diesel generator, a fuel cell, and a photovoltaic system. The wind turbine generator is modeled by considering the characteristics of variable output. Optimization is aimed at minimizing the cost function of the system, including fuel costs and maximizing fuel efficiency to generate electric power. The simulation was applied to a micro grid system only. This study applies the DS algorithm with excellence and efficiency in terms of coding simplicity, fast convergence speed, and accuracy in the optimal operation of micro grids based on renewable energy resources, and we compared its optimum value to other algorithms to prove its superiority.

• Journal of Navigation and Port Research
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• v.40 no.4
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• pp.165-171
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• 2016

SEEMP (Ship Energy Efficiency Management Plan) has entered into force since 2013 for the reduction of GHG emission of operating ships. SEEMP guidelines include the hardware modification or installation of energy-saving device on ship. It also includes software based energy-saving technology such as optimum routing, speed optimization, etc. Hardware based technologies are not easy to apply to ongoing vessel due to the operational restriction. Therefore, IT based energy-saving technology was applied and its energy efficiency was evaluated using before and after energy-saving system applied voyage data. SEEMP advises a voluntary participation of EEOI (Ship Energy Efficiency Operation Indicator) use as an indicator of ship energy efficiency operation, and those results were also shown to evaluate the improvement efficiency of energy-saving system.

• Journal of Korea Water Resources Association
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• v.38 no.9 s.158
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• pp.737-746
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• 2005

Optimization is a process that searches an optimal solution to obtain maximum or minimum value of an objective function. Many researchers have focused on effective search algorithms for the optimum but few researches were interested in establishing the objective function. This study compares two approaches for the objective function: one allows a tradeoff among the objectives and the other does not allow a tradeoff by assigning weights for the absolute priority between the objectives. An optimization model using sampling stochastic dynamic programming was applied to these two objective functions and the resulting optimal policies were compared. As a result, the objective function with no tradeoff provides a decision making process that matches practical reservoir operations than that with a tradeoff allowed. Therefore, it is more reasonable to establish the objective function with no a tradeoff among the objectives for multi-purpose dam operation plan in Korea.

• Journal of Navigation and Port Research
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• v.35 no.8
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• pp.657-665
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• 2011

This study deals with an integrated problem for deciding sequencing and storage location of export containers together at its receiving operation in the container terminal with a perpendicular layout. The preferred storage location of an export container varies with the priority of the corresponding loading operation and the waiting time of an external truck depends on its storage time. This paper proposes the mixed integer programming model considering the expected arrival time and expected finish time of an external truck and the preferred storage location for its loading operation. And we suggest the heuristic algorithm based on a simulated annealing algorithm for real world adaption. We compare the heuristic algorithm with the optimum model in terms of the computation times and total cost and the performance of the heuristic algorithm is analyzed through a numerical experiment.

• Journal of Animal Science and Technology
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• v.48 no.2
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• pp.315-324
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• 2006

This research was conducted to clarify the characteristics of electrochemical decolorization of effluent discharged from a biological animal wastewater treatment process and to finally establish parameters or mode for optimum operation of electrolysis system. Average color unit of wastewater was about 1,200 and DSA(Dimensionally Stable Anode) was used as electrode. Experiments were performed with two different operation conditions or modes, fixed voltage-free current(Run A) and free voltage-fixed current(Run B). Color removal rate was proportional to the electrode area and electrical conductivity, and an equation subject to them at a condition of fixed voltage was derived as follows; Ct=C0ekt, k=[{0.0121×ａ(dm2)× c(mS/cm)}+0.0288], [where, C0: initial color, Ct: color unit after treatment for t, k: reaction coefficient, t: time(min.), ａ: electrode area, c: conductivity]. From the study on the effects of current density on color removal, it was revealed that the removal efficiency of color was function of the current density, showing direct proportion. However, when considered energy consumption rate, maintenance of low current density was an economical way. Based on the obtained results, it was concluded that supplementation of electrolyte is not necessary for the removal of color from the effluent of secondary treatment process and operation with the mode of free voltage-fixed current, rather than operation with fixed voltage-free current mode, would be an efficient way to increase the removal performance and capacity per consumed energy.

• KSBB Journal
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• v.23 no.1
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• pp.83-89
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• 2008

Food wastewater derived from the three-stage methane fermentation system developed in this lab contained high concentration organic substances. The organic wastewater should be treated through advanced wastewater treatment system to satisfy the "Permissible Pollutant Discharge Standard of Korea". In order to treat the organic wastewater efficiently, several optimum operation conditions of a modified $UV/TiO_{2}$ photocatalytic system have been investigated. In the first process, wastewater was pre-treated with $FeCl_{3}$. The optimum pH and coagulant concentration were 4.0 and 2000mg/L, respectively. Through this process, 52.6% of CODcr was removed. The second process was $UV-TiO_{2}$ photocatalytic reaction. The optimum operation conditions for the system were as follows: UV lamp wavelength, 254 nm; wastewater temperature, $40^{\circ}C$; pH 8.0; and air flow rate, 40L/min, respectively. Through the above two combined processes, 69.7% of T-N and 70.9% of CODcr contained in the wastewater were removed.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.9
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• pp.624-629
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• 2013

The relation between performance maintenance conditions and those cost efficiency was studied to choose an optimum operating condition in the seawater desalination pretreatment system. A hollow fiber microfiltration module, which was developed with domestic technology, was tested with the various operating conditions such as chemically enhanced backwash cycles and design dosages of a cleaning chemical. Transmembrane pressure was measured to investigate membrane fouling status and cleaning degree. In addition, economic analysis was performed to compare water production costs by the operation condition. As a result, The operation mode III, chemically enhanced backwash at once a day with 100 mg/L of sodium hypochlorite (NaOCl) was selected. The concurrent evaluation between membrane filtration performance and its economic analysis will be suitable to choose an efficient optimum condition.

• Journal of Biosystems Engineering
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• v.3 no.2
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• pp.114-125
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• 1978

The use of petroleum fuels in grain drying causes problems of high cost and management. To solve these problems, it is required to study on soLar energy as an alternative to petroleum fuels for grain drying. The purposes of this study were to find out the optimum received area and air flow rate of a flat-plate solar air collector for grain drying and to assess its effects on grain drying with a small grain bin. The results of this study are summarized as follows ; 1. The calculated optimum tilt angles of the collector in the summer and autumn drying seasons were 20 and 50 degress, respectively, in suwon area. 2. The outlet temperature of the collector was $36^\circ C$ on the daily average with the maximum of $36^\circ C$ at 12:00 o clock. Solar radiation on the collector surface was 1.04 ly( 1 langley = 1 cal/$cm^2$) per minute on the daily average and 1.30 ly per minute on the maximum at 11:00am. The thermal efficiency of the collector was 62.4 percent on the daily average, and the air flow-rate per unit receiving are was 1.03 $m^3$/min/$m^2$.4. The calculated optimum receiving area and the air flow-rate per unit cubic volume for paddy in autumn drying season was 2 $m^2$ and 2$m^3$/min , respectively. 5. not significantly difference in the collector efficiency was appeared between the rotating and fixed type of solar collector. 6. For drying of wheat with 0.6 meter of the depth in the bin, approximately 9 hours were required to reduce the moisture content from 21.6% to 13% with air follow rate of 5 $m^3$/min an initial moisture per cubic meter of wheat and with air temperature of $52^\circ C$. 7. In the drying test of rough rice with a turning operation in a grain bin approximately 21 hours were required to reduced the moisture from 21% to 14.5% with airflow rate of 2 $m^3$/min per cubic meter of rice and the air temperature of $43.5^\circ C$. 8. Over-drying at the bottom and less -drying at the top of the grain mass was resulted from the high -temperature of drying air which was obtained from the flat-plate solar collector in this test. An appropriate operation should be prepared for the uniform moisture of the grain in the bin.