• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.10
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• pp.1703-1707
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• 2008

Low frequency oscillation of inter-area system is important problem in power system areas because the operation conditions of power system depend on it. Generally, the analysis of the problem is used by small signal stability. Especially, the analysis results are affected by decision of load models. In this paper, the effect of the analysis results was studied according to load component characteristics. ZIP model, popular in large-scaled power system analysis, was used as the load model. Many cases were studied according to the combination of ZIP model in inter-area system.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2004.04a
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• pp.523-527
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• 2004

This paper presents a new design methods of the short-term load forecasting system (STLFS) using the data mining. The proposed predictor takes form of the convex combination of the linear time series predictors for each inputs. The problem of estimating the consequent parameters is formulated by the convex optimization problem, which is to minimize the norm distance between the real load and the output of the linear time series estimator, The problem of estimating the premise parameters is to find the parameter value minimizing the error between the real load and the overall output. Finally, to show the feasibility of the proposed method, this paper provides the short-term load forecasting example.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.9
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• pp.869-874
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• 2015

We developed an LSDC (Load Shift and Load Distribution Control) technology in order to improve coil quality and productivity by reducing tension fluctuation especially for the tail of the strip in the down coiler in hot strip mills. To adapt the new controller, the torque and speed distribution between the zero pinch roll, pinch roll, and mandrel are needed. The proposed controller is a combination of an LSC to share the tension between the mill stand and the mandrel, and an LDC to shift the torque load from the zero pinch roll to the pinch roll. From the simulation, the proposed controller is verified under the torque disturbance. Using a field test, the torque deviation decreased by nearly 50% through utilization of the LSDC control.

• Wind and Structures
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• v.3 no.4
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• pp.279-289
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• 2000

The main purpose of this paper is to demonstrate the necessity of considering wind load combinations even for low-rise buildings. It first discusses the overall quasi-static wind load effects and their combinations to be considered in structural design of low-rise buildings. It was found that the maximum torsional moment closely correlates with the maximum along-wind base shear. It was also found that the instantaneous pressure distribution causing the maximum along-wind base shear was quite similar to that causing the maximum torsional moment, and that this asymmetric pressure pattern simultaneously accompanies considerable across-wind and torsional components. Secondly, the actual wind pressure distributions causing maximum quasi-static internal forces in the structural frames are conditionally sampled and their typical pressure patterns are presented.

• Wind and Structures
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• v.31 no.6
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• pp.523-532
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• 2020

As the height and flexibility of high-rise buildings increase, the wind loads become more dominant and the combination coefficient of Equivalent Static Wind Loads (ESWLs) should be considered when they are used in the structural design. In the first phase of the study, a brief introduction to the theory on the combination coefficient for high-rise buildings was given and then the time history of wind-induced responses of a 208-meter high-rise building with an elliptical cross-section was presented based on the wind tunnel test results for pressure measurement. The correlation between wind-induced responses was analyzed and the combination coefficients of ESWLs of the high-rise buildings using Turkstra's rule, and Asami's method, were calculated and compared with related design codes, e.g., AIJ-RLB, ASCE 7-10, and China Load Code for structural design. The results of the study showed that the combination coefficients from Asami's method are conservative compared with the other three methods. The results of this paper would be helpful to the wind-resistant design of high-rise buildings with elliptical cross-section.

• Journal of Biosystems Engineering
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• v.16 no.1
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• pp.83-89
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• 1991

One of the most serious problems in Korean sericulture farms is to improve the adiabatic conditions for the simple silkworm rearing houses which has been widely adapted since early 1980'. Thus, this study is aimed to solve the problems by selecting the thermal screen material and by finding the method of its instalation. For the study, 4 kinds of materials which are (1) TE005,(2) NW60, (3) NW300 and (4) AL110 are selected and 4 different types of methods which are surrounding boundary of rearing bed(type A), surrounding inside of wall and ceiling (type B), installing on inside of wal ony (type C) and installing on ceiling Inly (type D) are installed. Decision criteria of the best combination of screen material and installation methods is made by calculating the heating load coefficients and by testing the application at the simple silkworm rearing houses. The obtained results are summarized as follows ; 1. The effect of thermal screen on reducing the thermal energy is remarkable. It saves energy more 50% than unscreened simple silkworm rearing houses. 2. From a stand point of a good screed material on thermal energy reduction, the NW300, AL110 and PE005 are recommanded materials. However, NW60 and PE005 are regarded as desirable materials from the practical point view. 3. Also, the effect on thermal energy reduction is largely affected by the method of thermal screen installation. The surrounding boundary of the silkworm rearing bed(type A) is the most desirable method to reduce the energy, which saves 56.6% of it. 4. In the practical application, NW60 and type A is considered to be the best combination of material and installation method. By this combination, the level of maximum heating load can be reduced at the rate of 43% for spring season and 40% for autumn season. 5. Another heating method, comparted heating, can be recommended to save the energy.

• Steel and Composite Structures
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• v.12 no.4
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• pp.353-379
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• 2012

The accuracy of the 30% and SRSS rules, commonly used to estimate the combined response of structures, and some related issues, are studied. For complex systems and earthquake loading, the principal components give the maximum seismic response. Both rules underestimate the axial load by about 10% and the COV of the underestimation is about 20%. Both rules overestimate the base shear by about 10%. The uncertainty in the estimation is much larger for axial load than for base shear, and, for axial load, it is much larger for inelastic than for elastic behavior. The effect of individual components may be highly correlated, not only for normal components, but also for totally uncorrelated components. The rules are not always inaccurate for large values of correlation coefficients of the individual effects, and small values of such coefficients are not always related to an accurate estimation of the response. Only for perfectly uncorrelated harmonic excitations and elastic analysis of SDOF systems, the individual effects of the components are uncorrelated and the rules accurately estimate the combined response. In the general case, the level of underestimation or overestimation depends on the degree of correlation of the components, the type of structural system, the response parameter, the location of the structural member and the level of structural deformation. The codes should be more specific regarding the application of these rules. If the percentage rule is used for MDOF systems and earthquake loading, at least a value of 45% should be used for the combination factor.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.6
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• pp.589-597
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• 2015

In this paper, the live load model for the design of high-speed railway bridge is analyzed by statistic and probabilistic methods and the safety level that is given by the load factors of the load combination is analyzed. This study is a part of the development of the limit state design method for the railway bridge, and the train data collected from the Gyeongbu high-speed railway for about one month are utilized. The four different statistical methods are applied to estimate the design load to match the bridge design life and the results are compared. In order to examine the safety level that the design load combination of the railway bridge gives, the reliability indexes are determined and the results are analyzed. The load effect from the current design live load for the high-speed rail bridge which is 0.75 times of the standard train load is came out greater than at least 30-22% that from the estimated load from the measured data. If it is judged based on the ultimate limit state, there is a possibility of additional reduction of the safety factors through the reliability analysis.

• Korean Journal of Agricultural Science
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• v.46 no.3
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• pp.613-627
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• 2019

The purpose of this study was to design a powertrain for a 78 kW AWD (all wheel drive) electric tractor by analyzing the combination of various reduction gear ratios on a commercial motor using data from actual agricultural work and driving conditions. A load measurement system was constructed to collect data using wheel torque meters, proximity sensors, and a data acquisition system. Field experiments for measuring load data were performed for two environmental driving conditions (on asphalt and soil) and four agricultural operations (plow tillage, rotary tillage, loader operation, and baler operation). The attached implements and gear stages were selected through farmer surveys. The range of the reduction ratio was determined by selecting the minimum reduction ratio needed to satisfy the torque condition required for agricultural operations and the maximum reduction gear ratio to satisfy the maximum travel speed. The minimum reduction gear ratio selected was 57 in consideration of the working load condition and the maximum reduction gear ratio selected was 62 considering the maximum running speed. In the range of the reduction gear ratio 57 - 62, the selected motor satisfied all working torque conditions. As a result, the combination of the selected motor and reduction gear ratio was applicable for satisfying the loads required during agricultural operation and driving operation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.8
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• pp.1291-1296
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• 2017

Single-phase and three-phase load can be used together in 3-phase 4-wire system. Single-phase and three-phase loads can be classified as linear loads without harmonics and nonlinear with harmonics. Single-phase linear loads are linear loads such as lamps and heat, and single-phase nonlinear loads are power converters such as rectifiers. It is recommended that the distribution of loads in the 3-phase, 4-wire distribution lines be evenly distributed within a certain range. However, harmonic currents generated in a nonlinear load flow on the neutral line and affect the phase current magnitude. The difference in the magnitude of the individual phase current due to the influence of the harmonic current present in the neutral line can produce a difference in current and load unbalance. In this study, current unbalance ratio and load unbalance ratio which can occur when a combination of linear and nonlinear loads are applied to 3-phase 4-wire distribution line are calculated.