• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.10
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• pp.1370-1377
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• 2002

This study analyzed the design performance of the bottoming system of combined cycle power plants using a once-through heat recovery steam generator. For a parallel arrangement of the main heater and reheater, parametric analyses were carried out to present the criteria for determining the reheater pressure and the location of the starting point of the reheater in the HRSG. The performance of the bottoming system was presented fer a range from high subcritical to supercritical pressure. The steam turbine power is as high as that of conventional triple-pressure bottoming systems. The serial arrangement of heat exchangers with division of each heater into several segments can achieve similar power level.

• Journal of Positioning, Navigation, and Timing
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• v.7 no.3
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• pp.175-181
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• 2018

The use of dual-frequency measurements from the Global Navigation Satellite System (GNSS) enables us to observe precise ionospheric total electron content (TEC). Currently, many GNSS reference stations in South Korea provide both GPS and GLONASS data. In the present study, we estimated the grid-based TEC values and relative receiver differential code biases (DCB) from a GNSS network operated by the Korea Astronomy and Space Science Institute. In addition, we compared the diurnal variations in a TEC time series from solutions of the GPS only, the GLONASS only, and combined GPS/GLONASS processing. A significant difference between the GPS only TEC and combined GPS/GLONASS TEC at a specific grid point over South Korea appeared near the solar terminator. It is noted that GLONASS measurements can contribute to observing a variation in ionospheric TEC over high latitude regions.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.782-787
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• 2001

An optimum thermal design analysis of the combined cycle power plant with triple pressure heat recovery steam generator was performed by the numerical simulation. The optimum design module used in the paper is DNCONF, a function of IMSL Library, which is widly known as a method to search for the local optimum. The objective function to be minimized is the cost of total power plant including the steam turbine power enhancement premium. The result of this paper shows that the cost reduces if the design point of power plant becomes the local optimum, and many calculations at various initial conditions should be carried out to get the value near the global optimum.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.29 no.2
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• pp.58-66
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• 2006

This paper addresses the analysis of the travel distance and the number of storage location for storage location allocation methods in a warehouse system. The dedicated, randomized, combined and limited storage methods are considered. The combined and the limited storage methods are suggested here, which the combined storage method is to divide the storage locations into the dedicated storage area and the randomized storage area, and the limited storage method is to restrict the storage area of each product. Through a numerical example, the average travel distance between input/output point and the storage locations, and the number of storage location needed in the warehouse are compared between storage location allocation methods. The nearest randomized storage method is shown as the reasonable one in the travel distance and the number of storage location.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.11
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• pp.1949-1955
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• 2010

This paper describes the characteristic and effectiveness of combined GIL transmission line through lightning surge analysis. In addition the XLPE cable is analyzed in the same condition to compare with GIL. Lighting surge analysis is carried out by EMTP/ATP-Draw to obtain overvoltage of GIL and XLPE cable at service-point and load-out area of underground line. Propagation velocity is calculated in combined transmission lines with GIL and XLPE cable. The overvoltage is also analyzed on GIL and XLPE cable with or without arrester operation. The Analysis results show that overvoltage of GIL is occurred higher than XLPE cable at the same condition. Therefore it is evaluated that the application of GIL at the field should be considered cautiously when more detailed transient analysis, another electrical testes and economic evaluations are implemented.

• Journal of Ocean Engineering and Technology
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• v.35 no.2
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• pp.113-120
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• 2021

In order to perform a precise wave tank experiment, it is necessary to maintain the incident wave generated by the wavemaker in a steady state and to effectively remove the reflected waves. In this paper, a combined sloping-wall-type punching plate wave absorber was proposed to attenuate reflected waves effectively in a two-dimensional mini wave tank. Using the four-point reflection separation method, the reflected waves were measured to determine the reflection coefficients. Experiments were conducted under various punching plate porosities, sloping plate angles, and incident wave conditions to evaluate the performance of the combined punching plate wave absorber. The most effective wave absorbing performance was achieved when the porosity was 10% and the inclination angle of the punching plate was 18.6° under the present condition. It was also found that the installation of the sloping plate could improve the wave attenuation performance by generating the shoaling effect of the incident wave.

• Journal of Ocean Engineering and Technology
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• v.22 no.5
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• pp.39-43
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• 2008

For a partially filled and deeply submersed membrane container, an analytic solution for similarity shape was studied. The static shape of a membrane container can be expressed as a set of nonlinear ordinary differential equations. These equations are combined into an integrable equation. The solution of the equation is derived in terms of elliptic integrals, the arguments of which contain an unknown at the point of inflection. The point of inflection is determined by using the boundary condition at a separating point. Some characteristic values of the similarity shape were evaluated and the shapes are illustrated.

• Journal of Korean Society on Water Environment
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• v.22 no.6
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• pp.1075-1081
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• 2006

In this research, mortality rates of pathogen indicator microorganisms discharged from various point sources and diffuse sources in urban area were measured. Water samples were taken at domestic sewer, combined sewer overflow, effluent from a wastewater treatment plant, urban river, and sediment of an urban river. Mortality rates of indicator microorganisms in domestic sewer estimated by assuming the first order kinetics at $20^{\circ}C$ were as follows: total coliform = 0.092/day, fecal coliform = 0.185/day, E. coli = 0.252/day, and fecal streptococci = 0.281/day. Sensitivity of mortality rates of total coliform on temperature was estimated as $K_{temp}=K_{20}{\times}1.162^{(temp-20)}$ for the range of $10-20^{\circ}C$. Mortality rates due to sunlight were measured as 1.22-1.59/day while mortality rate due to settling for 40 min were estimated as $9.21{\times}10^3-20.0{\times}10^3/day$.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.6
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• pp.959-970
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• 2011

The frequent occurrence of sewer flooding and the intermittent discharge of non-point pollutions into the receiving water body are emerging issues recently due to the climate change and urbanization. These problems might be solved by introducing a multifunctional storage facility. Unlike a single-purpose storage facility, a multi-purpose storage facility should be operated at an instant to meet for flood prevention, reduction of non-point pollution and/or rainwater reuse. Considering various operational combinations it is suggested that prevention of sewer flooding coupled with reduction of non-point pollution is the most effective operational strategy for a multi-functional storage facility.

• Journal of the Korean Data and Information Science Society
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• v.26 no.2
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• pp.525-533
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• 2015

Modern production process is a very complex structure combined observations which are correlated with several factors. When the error signal occurs in the process, it is very difficult to know the root causes of an out-of-control signal because of insufficient information. However, if we know the time of the change, the system can be controlled more easily. To know it, we derive a maximum likelihood estimator (MLE) of the change point in a process when observations are from a multivariate IMA(1,1) process by monitoring residual vectors of the model. In this paper, numerical results show that the MLE of change point is effective in detecting changes in a process.