• Culinary science and hospitality research
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• v.20 no.6
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• pp.200-210
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• 2014

The purpose of this study was to investigate the quality changes and contamination of microorganisms such as Escherichia coli, mold and yeast in cherry tomatoes during storage at different temperatures, gas composition and periods(7 and 14 days). This study determined pH, color change and the growth pattern of microorganisms in cherry tomato during storage at $5^{\circ}C$, $10^{\circ}C$ and $15^{\circ}C$. According to the results, pH level was a little raised with storage period. On average, $L^*$, $a^*$ and $b^*$ value of cherry tomato were irregular value of increase and decrease of all gas packaging with storage period. In regard of the types of microorganism, aerobic count plate, coliform count, mold and yeast were detected when cherry tomatoes were stored at $5^{\circ}C$, $10^{\circ}C$ and $15^{\circ}C$ during storage for 14 days. Equally, all microorganisms of cherry tomato were irregular with storage period and complex gas packaging. However, this study determined that packaging with a higher $CO_2$ concentration than $O_2$ concentration can reduce growth of microorganism. These studies can be used as primary data for determining the optimal complex gas to storage enlargement.

• Journal of Animal Environmental Science
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• v.12 no.3
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• pp.133-140
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• 2006

The climate of stall significantly influences on animal production ability. High concentration of ammonia gas, $CO_2$ and lots of dust are found in modern densely raising stall system, as results, they provide a negative influence on animal and farmer health, and production ability. Therefore, it is necessary to keep clean the inside air of stall to increase the productivity. An air cleaner of wet type, consisting of a fan, a motor, rotating discs, a dust collector, a water bowl, an ozone generator etc, has been developed to clean the stall air. The work principle is that the inside air is sucked through the fan, and the rotating discs make water into fineness spray and blow into the stall. The rest water flows down to the dust collector. In the present study, we measured the dust, ammonia gas, odor, temperature and humidity in a swine stall that were installed two wet air cleaners with 700 fattening swine with On-mode and Off-mode of wet air cleaners. The dust measure was divided into 3 categories, TSP, $PM_{10}$, and $PM_{2.5}$. In summer, the TSP in on-mode were maximum $0.259mg/m^3$ and minimum $0.128mg/m^3$, and the average was $0.195mg/m^3$. These are comparable to the data from Off-mode stall that maximum $0.308mg/m^3$, minimum $0.139mg/m^3$, and average $0.277mg/m^3$. However, $PM_{10}$ and $PM_{2.5}$ showed any significant differences between the tests. The concentrations of ammonia gas in Off-mode stall were maximum 13.8 ppm and minimum 5.9 ppm, and the average was 8.47 ppm. However in On-mode stall the ammonia gas concentrations were maximum 10.5 ppm and minimum 5.5 ppm, and the average was 7.63 ppm. The concentration of ammonia gas in On-mode was 10% in average lower than off-mode stall. Odor was measured by olfactometer. In the Off-mode stall, the odor unit were maximum 420 $Ou/m^3$ and minimum $300\;OU/m^3$, and the average was $367\;OU/m^3$, but in the On-mode stall the odor unit were maximum $330\;OU/m^3$ and minimum $210\;OU/m^3$, and the average was $253\;OU/m^3$. Odor removal efficiency was about 31% in On-mode stall.

• Membrane Journal
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• v.4 no.1
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• pp.1-8
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• 1994

There are growing needs to produce relatively high purity(99.0% or higher) oxygen at low cost. For small scale production, both pressure swing adsorption(PSA) and membrane process are competitive and less expensive or more convenient than well known cryogenic fractionation technology. A continuous membrane column(CMC) combined with a PSA oxygen generator can be employed to produce high purity oxygen continuously. The oxygen enriched gas generated by a PSA unit, with a concentration of 93~94%, is fed to the CMC that consism of three modules of poly(imide) hollow fibers. Several experiments were conducted by varying parameters, such as feed flow rate, transmembrane pressure drop, stage cut, and feed location in order to obtain a high oxygen concentration above 99.0%. A two-series unit mode was also employed with CMC operation to optimize the given membrane area.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1781-1783
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• 2004

Flue gas from fossil fuel combustion is the main source of air pollution. It is recognized that $SO_2$ and $NO_x$, (sum of NO and $NO_2$) react with $H_2O$ and $O_2$ in atmosphere and convert precursors of acid rain. Streamer corona process using pulse power is one of the effective methods to remove these gases from stack. For this, pulse generator with 160 kV of output peak voltage, 0.3 ${\mu}s$ of pulse width and 120Hz of pulse repetition rate is developed. This paper shows the pulse compression characteristics to obtain optimum parameters for basic system design.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.4
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• pp.561-568
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• 2018

Passivity theory is significantly applied to analyze stability of nonlinear dynamic systems and construct its stable control systems. This paper presents a passivity based control design approach for exciters and governors which are employed to regulate the terminal voltage and the rotor velocity of synchronous generator systems in industry fields. We consider the IEEE type 1 exciter and the gas turbine (GT) governor models respectively in this paper. We first carry out a passivity analysis for exciter and governor control systems, which are numerically obtained from its mathematical models. And then its control parameters are selected to assure passivity conditions in a design procedure. Lastly, we investigate numerical simulations to demonstrate reliability of the proposed control approach against large-scale generators with parameter changes.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.35 no.12
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• pp.560-566
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• 1986

In the design of an RF discharge system, the electrical equivalence of the gas discharge must be known. With this knowledge, one can design a suitable matching network for a maximum power transfer from the RF generator into the discharge. For this purpose, an experiment has been conducted in which the electrical impedance (conductance and capacitance) was determined as a function of power. In parallel with this, a detailed theoretical analysis has been done and the results are in accord with those of our experiment. Design equations are also given for a simple matching network, and a design example is presented to demonstrate its application. During the actual operation of an RF discharge system, however, it has been often observed that the reflected power tends to vary in small values due to the changes in the impedance of the system. This problem can be relieved by adding an automatic impedance matching circuit to the system and this paper presents such an automatic impedance matching network.

• 전기의세계
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• v.25 no.5
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• pp.79-87
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• 1976

This paper is to investigate the A.C generation of MHD engine, converting directly the kinetic energy of conductive gas in high temperature to electric power by the effect of magnetic field. It is known that there are at least two kinds of method in A.C MHD power generation; one, by sending stationary plasma flow in an alternating or rotating magnetic field and the other, by transmission of pulse type plasma flow in uniform and constant magnetic field, former method is adopted here. In order to raise the total efficiency of close cycle in combination with nuclear power and MHD genertaion, an argon plasma jet is utilized as heat source, which is not mixed with the seed material, and the design data are obtained for A.C MHD generation in small capacity, but induced voltage and power output have the maximum values, 15 voltages and 7.5W respectively due to plasma flow with low conductivity and weak magnetic field.

• Aerospace Engineering and Technology
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• v.7 no.2
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• pp.157-161
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• 2008

This study introduce a newly developed program to calculate the combustion process of combustion chamber and gas generator of liquid rocket engine by use of Gibbs free energy minimization method based on chemical equilibrium. The simulation results of the new program and CEA code of NASA were compared and showed good agreement, thus proving the validity of the newly developed in-house program for combustion analysis.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.251-255
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• 2008

Biogas plant was started in 2007 for the purpose of treatment of $20m^3$/d of wastewater from piggery farm, biogas-production and electricity generation during treatment of the wastewater. The biogas plant is consists of two anaerobic digesters, gas holder and 60 kWe generator. $62,287m^3$ of biogas was produced and 74,745kWh electricity was generated by using the biogas after commencing the biogas plant.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.4
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• pp.700-707
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• 2009

The application of renewable energy in electric power systems is growing rapidly in order to make provision for the inequality of the climate, the dwindling supplies of coal, oil and natural gas and a further rise in oil prices. Solar cell generators(SCG) is one of the fastest growing renewable energy. This paper presents a methodology on probabilistic production cost simulation of a power system including SCGs. The generated power by SCGs is variable due to the random variation of solar radiation. In order to solve this problem, the SCGs is modeled as multi-state operational model in this paper. Probabilistic production cost of a power system can be calculated by proposed method considering SCGs with multi-state. The results show that the impacts of SCGs added to a power system can be analyzed in view point of production cost using the proposed method.