• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1999.10a
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• pp.33-33
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• 1999

The Coanda effect is the tendency for a fluid jet to atach itself to an adjacent surface and follow its contour without causing an appreciable flow separation. The jet is pulled onto the surface by the low pressure region which develops as entrainment pumps fluid from the region between the jet and the surface. Then the jet is held to the wall surface by the resulting radial pressure gradient which balance the inertial resistance of the jet to turning. The jet may attach to the surface and may be deflected through more than 180 dog, when the radius of the Coanda surface is sufficiently large compared to the height of the exhaust nozzle. However, if the radius of curvature is small, the jet turns through a smaller angle, or may not attach to the surface at all. In general, the limitations in size and weight of a device will limit the radius of the deflection surface. Thus much effort has been paid to improve the jet deflection in a variety of engineering fields. The Coanda effect has long been applied to improve aerodynamic characteristics, such as the drag/lift ratio of flight body, the engine exhaust plume thrust vectoring, and the aerofoil/wing circulation control. During the energy crisis of the seventies, the Coanda jet was applied to reduce vehicle drag and led to drag reductions of as much as about 30% for a trailer configuration. Recently a variety of industrial applications are exploiting another characteristics of the Coanda jets, mainly the enhanced turbulence levels and entrainment compared with conventional jet flows. Various industrial burners and combustors are based upon this principle. If the curvature of the Coanda surface is too great or the operating pressure too high, the jet flow will break away completely from the surface. This could have catastrophic consequences for a burner or combustor. Detailed understanding of the Coanda jet flow is essential to refine the design to maximize the enhanced entrainment in these applications.

• Journal of the Korean Institute of Gas
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• v.8 no.3 s.24
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• pp.16-23
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• 2004

A membrane reactor concept, which combines the typical characteristics of chemical reaction with separation process, has been analyzed and simulated in this study. The advantages of the use of a membrane reactor include chemical equilibrium shift towards higher reactant conversion and purer product than the traditional reactors. A membrane reactor model which incorporates a catalytic reaction zone and a separation membrane is proposed. The water-gas shift reaction to produce hydrogen was chosen as a model reaction to be investigated. The membrane reactor is divided into smaller parts by number of n and each part (named cell), which contains both reaction and product separation function is modeled. One of the membrane outlet streams is connected to the next cell, which is repeated up to the last cell. The simulation results can be used for various purposes including decision of optimum operating condition and membrane reactor design.

• Plant Journal
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• v.8 no.4
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• pp.34-39
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• 2012

This study presents how low quality coal combustion affects the desulfurizer draft system by correlating of draft loss in a coal-fired thermal power plant and predicts the stall occurrence time of a booster fan. In case of low quality coal, a lot of coal is needed to generate equivalent output power, thereby the rating of increasing draft loss was faster than designed amount of coal. We surely confirmed that draft loss affects the specific energy of a booster fan strongly. On this basis, it is possible to predict the occurring time of stall for a booster fan from current operation specific energy to stall limit specific energy. This study suggests increasing speed of draft loss in each caloric value and the impact of specific energy at a booster fan, it expects to help safe operating in a thermal power plant.

• Journal of Environmental Health Sciences
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• v.19 no.3
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• pp.1-16
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• 1993

This paper describes an investigation to determine whether the activated sludge (AS) process could be used for the treatment of wastewater at the Union Carbide Coporation (UCC) plant in Seadrift, Texas. This plant presently utilizes a waste stabilization pond (WSP) system for treatment of the wastewater. The treatment system consists of an in-plant primary WSP and two off-plant WSPs (secondary and tertiary WSPs), run in series. The total hydraulic detention time of the WSP system is approximately 150 days. Several laboratory-based treatability studies have been conducted to evaluate the performace of the WSP system and the degradability of specific chemical compounds. From an additional study, it was determined that the WSP system was stressed and occasionally operating near the limit of its treatment capacity. The existing primary WSP plays an important role in the overall treatmemt system, because it not only functions as a pH and organic-strength equalization basin, but also serves as a "preconditioning" basin by fermenting high strength organic wastes to volatile organic acids for subsequent degradation in the escondary WSP. However, in view of pending RCRA legislatin conerning the "proposed organic toxicity characteristics limits" (40 CFR Part261: Federal Register, July, 1988), it is possible that the primary WSP will have to be abandoned in favor of alternative treatment options. Therefore the main purpose of this study was to perform activated sludge treatability evaluations for the development of an alternative to the existing primary WSP treatment ststem. In addition, another purpose was to determine the degradability of bis(2-chloroethyl)ether (Chlorex or CX) and benzene(BZ) in the activated sludge process. The presence of these two chemicals in the wastewater of the plant prompted the question of whatedether they could be degraded in an activated sludge system.

• Journal of the Korean Society of Safety
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• v.29 no.4
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• pp.110-115
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• 2014

It is crucial for important facilities to withstand strong earthquakes because their damage may cause undesirable socio-economic effect. A liquefied natural gas (LNG) receiving terminal is one of the lifeline facilities whose seismic safety needs to be guaranteed. Even though all operating LNG receiving terminals in Korea were seismically designed, old design codes do not guarantee to comply with the current seismic design codes. In addition, if the constructional materials have been deteriorated, the seismic capacity of facilities may be also deteriorated. Therefore, it is necessary that the seismic performance of LNG receiving terminals is evaluated and the facilities that lack of seismic capacity have to be rehabilitated. In this paper, a procedure of seismic performance evaluation of such facilities is developed such that the procedure consists of three phases, namely pre-analysis, analysis, and evaluation phases. In the pre-analysis phase, design documents are reviewed and walk-on inspection is performed to determine the current state of the material properties. In the analysis phase, a structural analysis under a given earthquake or a seismic effect is performed to determine the seismic response of the structure. In the evaluation phase, seismic performance of the structure is evaluated based on limit states. Two of the important facilities, i.e. the submerged combustion vaporizer (SMV) and pipe racks of one of the Korean LNG receiving terminals are selected and evaluated according to the developed procedure. Both of the facilities are safe under the design level earthquake.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.5
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• pp.596-604
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• 2016

In this study, we used a stochastic approach for guaranteeing the reliability and robustness of the performance with regard to the design of polymer components, while taking into consideration the degradation properties and operating conditions in automobiles. Creep and tensile tests were performed for obtaining degradation properties. The Prony series, which described the viscoelastic models, were calculated to use the creep data by the Maxwell fluid model. We obtained the stress data from the frequency response analysis of the polymer components while considering the degradation properties. Limit state functions are generated by using these data. Reliability assessments are conducted under the variation of the degradation properties and area of frequency at peak response. For this study, the input parameters are assumed to be a normal distribution, and the reliability under the yield stress criteria is evaluated by using the Monte Carlo Simulation. As a result, the reliabilities, according to the three types of polymer materials in automotive components, are compared to each other and suggested the applicable possibility of polymeric materials in automobiles.

• Analytical Science and Technology
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• v.10 no.1
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• pp.43-52
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• 1997

The application of high performance liquid chromatogaphy(HPLC) with fluorimetric detection for the measurement of histamine in biological fluids has been developed recently. Because of time consumption during measurement and difficulties in controling optimum operating condition for HPLC system, spectrofluorimetry was adopted to detect histamine. Detection limit by spectrofluorimetry was $3.0{\times}10^{-2}{\mu}g/mL$ wi th R. S. D. 3.74%~16.2% on standard solution. The relative ratio of histmine levels between the result from HPLC-fluorimetry and that from spectrofluorimetry ranged from 1.5 to 3.5. The recoveries of each samples obtained from standard addition method by spctrofluorimetry have shown 100%~125%.

• Journal of Satellite, Information and Communications
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• v.7 no.2
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• pp.42-46
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• 2012

This paper analyses technical and economical conditions which activate the use of mobile communication spectrum not to limit the growth of mobile broadband service because of mobile big data traffic and proposes the method which activate the use of mobile communication spectrum. To activate new mobile communication spectrum the expenditure and income of investment should be balanced. The activation of new mobile communication spectrum to process mobile big data traffic depends on technical and economical conditions, internal and external factors of service provider. The investment expenditure is relate to CAPEX, OPEX which is internal factors of service provider and to spectrum price which is external factor of service. The investment income is relate to tariff system which is internal factors of service provider and to spectrum neutrality which is external factor of service provider. The activation of new mobile communication spectrum can be implemented when the investment expenditure and investment income meet the balance including the spectrum price in the investment expenditure and the tariff system which is able to extend network and the income based on traffic increase by external contents in the investment income.

• Journal of The Korean Society of Agricultural Engineers
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• v.53 no.1
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• pp.17-28
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• 2011

This study was performed to ascertain the possibility of securing inflows to reservoir with low ratio of watershed to paddy field areas by outside diversion weir. The case of Maengdong reservoir and Samryong diversion weir was selected. Most of inflows to Maengdong reservoir with watershed area of $7.06\;km^2$ and total storage capacity of $1,269{\times}10^4\;m^3$ are filled with intake water from outside Samryong diversion weir. Only using water storage data in Maengdong reservoir from 1991 to 2009, the range of water intake in Samryong diversion weir to Maengdong reservoir was optimized to 0.135~30 mm/d, from which water intake to Maengdong reservoir was $1,672.9{\times}10^4\;m^3$ (70.1 %) and downstream outflow to Weonnam reservoir was $714.4{\times}10^4\;m^3$ (29.9 %). The parameters of DAWAST model for reservoir inflow were determined to UMAX of 313.8 mm, LMAX 20.3 mm, FC 136.8 mm, CP 0.018, and CE 0.007. Inflows to Maengdong reservoir were $427.1{\times}10^4\;m^3$ (20.3 %) from inside watershed, and $1,672.9{\times}10^4\;m^3$ (79.7 %) from outside. Paddy irrigation water requirements were estimated to $1,549{\times}10^4\;m^3$ on annual average. Operation rule curve was drawn by using daily inflow and irrigation requirement data. By securing the amount of inflow to Maengdong reservoir to about 80 % from outside Samryong diversion weir, water supply capacity for irrigation of $1,549{\times}10^4\;m^3/yr$ was analyzed to be enough. Additional water supplies for instream flow were analyzed to $1,412\;m^3/d$ in normal reservoir operation, $36,000\;m^3/d$ in withdrawal limit operation by operation rule curve from October to March of non irrigation period.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.461-465
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• 2006

Recently, the operator modules to control external devices are concerned about automatic management system to process continuously changed signals. They need a efficient data management with high reliability and real time processing. The characteristics of these data are a large volume, a short report interval and asynchronous report time. The typical queries of these systems consist of the current query to search the latest signal value, the snapshot query to search the signal value of a past time, the historical query to search the signal value of a past tine to current. In this paper, we propose the efficient method to manage the above signals by using a file structured database in QNX operating systems. The data communications among the devices are done by Profibus-FMS protocol and the file databases are used for adjusting monitoring frequency and storing signals. The file database adopts a delta version and a periodical back up in due consideration of the resource limit of a small storage and a low computing power in QNX COM(Cabinet Operator Module).