• Journal of the Korean Society of Safety
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• v.14 no.3
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• pp.84-92
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• 1999

The effects of air velocity and excess air on combustion characteristics were studied in a fluidized bed combustor. The domestic low-grade anthracite coal with heating value of 2010 kcal/kg and the imported bituminous coal from Australia with heating value of 6520 kcal/kg were used as coal samples. The combustion characteristics of mixed fuels in a fluidized bed combustor could be interpreted by pressure fluctuation properties, ash distribution and gas emission. The properties of the pressure fluctuations, such as the standard deviation, cross-correlation function, dominant frequency and the power spectral density function, were obtained from the statistical analysis. From this study, the combustion region increased with increasing air velocity but decreased with excess air due to combustion characteristics of anthracite and bituminous coal.

• The Transactions of the Korea Information Processing Society
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• v.7 no.6
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• pp.1988-1995
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• 2000

In this paper, we have proposed the contrast control method for improving image quality. The proposed method can be easily applied to the FPD (flat panel display) which requires real-time processing because of its lower hardware complexity that the conventional methods. In addition, it can flexibly control the contrast of input image by arraying the weight values that control the contrast range. Visual test and standard deviation of their histograms have been introduced to evaluate the results of proposed method and the original images. The functional operation of he proposed method has been verified using the SYNOPSYS VHDL tool and computer simulation. Its results show that he proposed method might be very suitable for real-time processing on the FPD.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.10
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• pp.1935-1940
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• 2011

The control logic of steam temperature was redesigned, tested and applied to the power plant after its steam temperature equipments had been revised. This power plant use the ancillary gas gotten in the process of making iron in the steel mill. The boiler of power plant has the superheater and reheater to make the superheated steam. The superheater and reheater have the spray valve to control their temperature. The reheater has the gas bypass damper additionally in this plant. The control logics were redesigned in cascade forms and the initial parameters of control logics were calculated from the several step tests. The final parameters could be obtained through the several repeated tests and the feedforward functions were added by temperature deviation and air flow. The power plant is being commercially-operated normally by improved control logics and It is expected that this improved controls help the efficiency improvement and safe operation of plant.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.9
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• pp.1223-1227
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• 2013

If the factory test efficiency and field operation efficiency of water turbine are different from each other, issues for efficiency warranty can be raised. So, This paper shows the result for comparative analysis of field operating efficiency vs plant testing efficiency of the water turbine generator installed in agricultural reservoir. The efficiency of the induction generator is analyzed by the change of rotational speed with the parameter obtained by test, the efficiency of water turbine is calculated by the change of head with the design flow. Efficiency deviation of induction generator is lower but the variation of developed power is pretty high near the rated speed and the efficiency variation of water turbine is high by the fluctuation of head for constant flow. It was found that factory test efficiency and total efficiency of water turbine generator calculated according to the rotational speed are very close.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.4
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• pp.117-122
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• 2000

This paper presents an indirect compensation of thermal errors during machining , in which thermal error is modelled as a linear regression of temperatures measured at 4 specified positions. In this regression model, weighting coefficients of the measured temperatures were estimated by using the least square method. The grinding test with compensation , after 4 -hour warning-up operation before the test, showed that the maximum machining error of the work pieces was reduced to 12${\mu}{\textrm}{m}$ while it measured by 28${\mu}{\textrm}{m}$ without compensation . Furthermore the standard deviation of machining errors was also reduced from 8${\mu}{\textrm}{m}$ to 2${\mu}{\textrm}{m}$.

• Journal of the Korean Operations Research and Management Science Society
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• v.23 no.4
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• pp.63-73
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• 1998

With the success of flexible manufacturing systems(FMSs), flexible assembly systems(FASs) have been developed to automatic factories further. As in a cellular FMS, a celluar FAS is considered as the most flexible and feasible assembly systems configuration. This paper presents a method for the integrated layout design in cellular FASs. Unlike the traditional paper, this paper deals with the formation of cells and the layout of cells for jobs with operation times on different machines. The procedure in this paper consists of two distinct phases. The first phase presents machine arrangement in a double rows flowline. cell formation not to allow intercellular movements, and integrated layout design in cellular FASs considering the characteristics of FAS, layout, and production factors This phase uses older optimal algorithm. The second phase proposes to balance the system with an objective of reducing the degree of workload deviation in the cells. Simulated annealing method is used to balance the system. This phase also shows the integrated layout design in cellular FASs with the cost less than total cost of the first phase.

• Journal of the Korean Operations Research and Management Science Society
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• v.11 no.1
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• pp.36-43
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• 1986

In this study, the fuzzy programming is extended to handle various types of membership functions by transformation of the complicated fuzzy programming problems into the equivalent crisp linear programming problems with single objective. It is well-known that the fuzzy programming problem with linear membership functions (i.e., ramp type) can be easily transformed into a linear programming problem by introducing one dummy variable to minimize the worst unwanted deviation. However, until recently not many researches have been done to handle various general types of complicated linear membership functions which might be more realistic than ramp-or triangular-type functions. In order to handle these complicated membership functions, the goal dividing concept, which is based on the fuzzy set operation (i. e., intersection and union operations), has been prepared. The linear model obtained using the goal dividing concept is more efficient and single than the previous models [4, 8]. In addition, this result can be easily applied to any nonlinear membership functions by piecewise approximation since the membership function is continuous and monotone increasing or decreasing.

• 전기의세계
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• v.25 no.6
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• pp.81-88
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• 1976

The present voltage-reactive power control aims at an overall coordination of reactive power sources and voltage regulation devices to keep the bus voltages within their allowable bounds on one hand and to reduce the transmission losses on the other. This paper presents an efficient computer control scheme for the real-time control of system voltage and reactive power on the basis of a simplified linear equation by using the system characteristic constant. Computational algorithm is used for the minimization of bus voltage deviation in the first phase of optimization and for the reduction of transmission losses under the constraint of vlotage settling condition in the second phase. The numerical example for sample practical system is also given. The present study on the computer control scheme will contribute to the automation of power system operation in the near future.

• 전기의세계
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• v.30 no.3
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• pp.167-171
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• 1981

In this paper, the mathematical model of influenza derived by the state space method induced a new model by using normal distribution curve of incubation period and researched the effect of vaccination. The important results are as follows. (1) A new model represents accurate spread curve. (2) The standard deviation period in Korea is about 1.5 degree. (3) The number of carries of influenza since put in practice to the vaccination 20% is reduced by average 9.8% degree, the period of spread increase 4 days degree. (4) The vaccination at early put in operation was far surperior and the period of spread grow longer more or less. (5) In the first stage of an attack of disease a case increase since reducing. (6) The number of carries at night is reduced by average 5.468% than in the daytime.

• International Journal of Air-Conditioning and Refrigeration
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• v.12 no.4
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• pp.192-197
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• 2004

A capillary tube, which is a common expansion device in small sized refrig-eration and air-conditioning systems, should be redesigned properly to establish an optimum operation cycle of a refrigerating system with alternative refrigerants. Based on experimental data for R-22, R-290, and R-407C, an empirical correlation is developed to predict mass flow rate through capillary tubes. Dimensionless parameters are derived from the Buckingham Pi theorem, considering the effects of operating conditions and capillary tube geometry on mass flow rate. Approximately $97\%$ of the present data are correlated within a relative deviation of $\pm\;10\%.$ The present correlation also predicts the data obtained from open literature within $\pm\;15\%.$ In addition, rating charts of refrigerant flow rate for R-12, R-22, R-134a, R-152a, R-407C, R-410A, R-290, and R-600a are developed.