• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.2
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• pp.101-107
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• 2005

In this paper, optimized operating parameters were found using multi-dimensional engine simulation software (KIVA-3V) and micro-genetic algorithm for heavy duty diesel engine. The engine operating condition considered was at 1,737 rev/min and 57 % load. Engine simulation model was validated using an engine equipped with a high pressure electronic unit injector (HEUI) system. Three important parameters were used for the optimization - boost pressure, EGR rate and start of injection timing. Numerical optimization identified HCCI-like combustion characteristics showing significant improvements for the soot and $NO_X$ emissions. The optimized soot and $NO_X$ emissions were reduced to 0.005 g/kW-hr and 1.33 g/kW-hr, respectively. Moreover, the optimum results met EPA 2007 mandates at the operating point considered.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.1
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• pp.83-88
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• 2016

This paper describes the test results of plant minimum stable load (Pmin) for Ilijan Power Plant. The test was conducted on May 13 through 14, 2015 to investigate the plant operating and equipment condition in accordance with "Ilijan Plant Performance Test Procedure on Plant Minimum Stable Load" [1]. This paper also contains the assessment of the impact of Pmin to plant operating parameters and possible technical operating issues when operating at lower loads and to recommend the safe minimum load operation of Ilijan per block. In addition, this paper describes the performance calculation results of efficiency and heat rate depending on the load level.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.517-520
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• 2008

Recently, use of adhesive bonding technology is increased to achieve the multi-material design for lightweight structure in automobile industry. In this paper, the fracture strength of adhesive has been studied with the single lap shear test conducted at different temperatures. The joint specimens are made from Al 5052 and SPRC 440 bonded with structural epoxy adhesive. The operating temperature has been considered up to $150[^{\circ}C]$ and the single lap shear test has been conducted with 5mm/min tensile rate. Fracture strength of adhesive bonded joint has been decreased with increase of operating temperature. The fracture strength at the $100[^{\circ}C]$ was shown about half of that at room temperature.

• Korea Journal of Hospital Management
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• v.11 no.3
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• pp.73-93
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• 2006

This study aims at providing necessary informations for management decision-making to the hospital manager, such as ratios of fixed and variable cost to total operating expense, and variable cost ratio to operating revenues, and determinant factors affecting cost behavior. A study model and related hypotheses were established, data were collected from 41 private university hospitals for the 6years from 1998 to 2003, and regression analyses were performed to test the hypotheses. The results of the analyses and conclusions are as follows; First, labor cost and administration cost within the same number of beds have not only fixed quality of the cost, but variable quality of that. Also, the ratio of the variable costs to operating revenue of the metropolitan was estimated 76.9% and that of other area hospitals was 80.1%. Second, the major factors affecting the increase rate of the operating expense were the increase rates of the number of inpatients, the number of employee, and the number of hospital operating bed. This result implies that maintaining a optimal hospital bed size and efficient operation of the beds are important strategic factors of hospital management.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3013-3018
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• 2008

Supercharging system was adopted to investigate the influence of boost pressure on operating range, brake specific fuel consumption (BSFC) and exhaust emissions by using a supercharger at low temperature diesel combustion (LTC) condition in a 5-cylinder 2.7 L direct injection diesel engine. The experimental parameters such as injection quantity, injection timing, injection pressure and exhaust gas recirculation (EGR) rate were varied to find maximum operating range. The result showed that operating range with boost was expanded up to 41.9% compared to naturally aspirated LTC condition due to increased mixing intensity. The boosted LTC engine showed low BSFC value and dramatically reduced soot emission under all operating range compared with high speed direct injection (HSDI) mode. Finally, this paper presents the boosted LTC map of emission and the strategy of improved engine operating range.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.34 no.8
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• pp.43-50
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• 2018

The purpose of this study is to analyze the effect of architectural attributes on operating revenue by concentrating on the facility side and to investigate how much individual architectural factors can affect operating revenue. The time range of this study is limited to 2015, and the spatial range is limited to a tourist hotel in Seoul that can be easily surveyed and verified. The analysis method is to confirm the significance and influence of each attribute through regression analysis. According to the results, The room part such as number of rooms or area showed a relatively low correlation with "revenue per available room (Rev.PAR)" than "average daily rate (ADR)", but showed a high correlation with non - architectural attributes such as auxiliary facilities and chain. This shows that factors that influence the operating profit of hotel are not the part of the room but the other factors such as the auxiliary facilities work more. In addition, the presence of spa and the number of auxiliary facilities in the hotel have a positive effect on the operating profit of the hotel due to the non - architectural attributes. This is expected to provide a new direction for future research in studying hotel facilities.

• Environmental Engineering Research
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• v.25 no.2
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• pp.251-257
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• 2020

This study was performed to verify the possibility of nitrification and denitrification in a single reactor. In batch type experiment, optimal point of experimental conditions could be found by performing the experiments. When supply location of microbubbles was located at half of width of the aeration tank and operating pressure of 0.5 bar, it was possible for zones in the aeration tank to be separated into anoxic and aerobic by controlling air suction rate according to operating pressure of the generator. To be specific, the concentration of dissolved oxygen (DO) in zone 1 and 2 of the aeration tank could be maintained as less than 0.5 mg/L. Also, in the case of concentration of oxygen in zone 3 and 4, the concentration of DO was increased up to 1.7 mg/L due to effects of microbubbles. In continuous flow type experiment based on the results of batch type experiments, the removal efficiency of nitrogen based on T-N was observed as 39.83% at operating pressure of 0.5 bar and 46.51% at operating pressure of 1 bar so it was able to know that sufficient air suction rate should be required for nitrification. Also, denitrification process could be achieved in a single reactor by using ejector type microbubble generator and organic matter and suspended solid could be removed. Therefore, it was possible to verify that zones could be separated into anoxic and aerobic and nitrification and denitrification process could be performed in a single reactor.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.4
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• pp.357-361
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• 2018

Forward osmosis (FO) process has been attracting attention for its potential applications such as industrial wastewater treatment, wastewater reclamation and seawater desalination. Particularly, in terms of fouling reversibility and operating energy consumption, the FO process is assumed to be preferable to the reverse osmosis (RO) process. Despite these advantages, there is a difficulty in the empirical step due to the lack of separation and recovery techniques of the draw solution. Therefore, rather than using FO alone, recent developments of the FO process have adapted a hybrid system without draw solution separation/recovery systems, such as the FO-RO osmotic dilution system. In this study, we investigated the performance of the hollow fiber FO module according to various operating conditions. The change of permeate flow rate according to the flow rates of the draw and feed solutions in the process operation is a factor that increases the permeate flow rate, one of the performance factors in the positive osmosis process. Our results reveal that flow rates of draw and feed solutions affect the membrane performance, such as the water flux and the reverse solute flux. Moreover, use of hydraulic pressure on the feed side was shown to yield slightly higher flux than the case without applied pressure. Thus, optimizing the operating conditions is important in the hollow fiber FO system.

• Journal of Biosystems Engineering
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• v.25 no.6
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• pp.463-470
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• 2000

For maximum seeding efficiency of a nozzle type seeder, the performance of the nozzle should be considered sufficiently. This study was carried out to investigate the optimum operating conditions of a seeder attached the vacuum nozzle which was modified syringe needle acting on the plug seedling tray and the seed plate. Such operating factors as the hole diameter of the nozzle (d), the distance from the nozzle tip to the bottom plate of seed hopper(D) the absorbing air pressure of the nozzle tip(P) the bounding height of seed from the vibrated bottom plate of seed hopper and the seeding speed were selected based on the weight of a grain of seed(W). The treated materials were pepper seed as the flat type, cucumber seed as the oval type and radish seed as the spherical type. The optimum operating conditions of the experimental seeder were revealed as follows: 1. The height of the seed bounding from the bottom plate of seed hopper and the distance from nozzle tip to bounded seed were 5 mm and 0.5 mm at all seeds. The hole diameter of the nozzle and the absorbing pressure for pepper seed, cucumber seed and radish seed was 0.45 mm, 0.65 mm. 0.65mm and 39.2 kPa, 88.3 kPa, 58.8 kPa, respectively. 2. The absorbing pressure P was represented as P=η.4W/$\pi$d$^2$ where η was 100. The seeding speed using a 128 cell tray was 2.4 cm/s which was same transfer as 2.5 trays per minute. 3. The maximum seeding rate in case of the pepper seed was 97% the cucumber seed was 95% and the radish seed was 100% under the optimum operating conditions of the seeder.

• Journal of Microbiology and Biotechnology
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• v.23 no.10
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• pp.1445-1453
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• 2013

The scale-up criterion of constant oxygen mass transfer coefficient ($k_La$) was applied for the production of itaconic acid (IA) in a 50 L pilot-scale fermentor by the fungal cells of Aspergillus terreus. Various operating conditions were examined to collect as many $k_La$ data as possible by adjusting the stirring speed and aeration rate in both 5 L and 50 L fermentor systems. In the fermentations performed with the 5 L fermentor, the highest IA production was obtained under the operating conditions of 200 rpm and 1.5 vvm. Accordingly, we intended to find out parallel agitation and aeration rates in the 50 L fermentor system, under which the $k_La$ value measured was almost identical to that ($0.02sec^{-1}$) of the 5 L system. The conditions of 180 rpm and 0.5 vvm in the 50 L system turned out to be optimal for providing almost the same volumetric amount of dissolved oxygen (DO) into the fermentor, without causing shear damage to the producing cells due to excessive agitation. Practically identical fermentation physiologies were observed in both fermentations performed under those respective operating conditions, as demonstrated by nearly the same values of volumetric ($Q_p$) and specific ($q_p$) IA production rates, IA production yield ($Y_{p/s}$), and specific growth rate (${\mu}$). Specifically, the negligible difference of the specific growth rate (${\mu}$) between the two cultures (i.e., $0.029h^{-1}$ vs. $0.031h^{-1}$) was notable, considering the fact that ${\mu}$ normally has a significant influence on $q_p$ in the biosynthesis of secondary metabolites such as itaconic acid.