• Journal of Power Electronics
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• v.12 no.3
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• pp.410-417
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• 2012

In this paper, a direct current control method based on a one-cycle controller (DCOCC) for double frequency buck converters (DF buck) is proposed. This control method can make the average current through the high frequency and low frequency inductors of a DF buck converter equal. This is similar to the average current control method. However, the design of the loop compensator is much easier when compared with the average current control. Since the average current though the high frequency and low frequency inductors is equivalent, the current stress of the high frequency switches and the switch losses are minimized. Therefore, the efficiency of the DF buck converter is improved. Firstly, the operation principle of DCOCC is described, then the small signal models of a one cycle controller and a DF buck converter are presented based on the state space average method. Eventually, a system block diagram of the DCOCC controlled DF buck is established and the compensator is designed. Finally, simulation and experiment results are given to verify the correction of the theory analysis.

• Journal of electromagnetic engineering and science
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• v.11 no.3
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• pp.220-226
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• 2011

We have proposed a new method to accurately predict the resonance of Fabry-Perot Cavity (FPC) antennas enclosed with conducting side walls. When lateral directions of an FPC antenna are not blocked with metallic walls, the conventional technique is accurate enough to predict the resonance of the FPC antenna. However, when the FPC antenna has side walls, especially for case with only a short distance between the walls, the conventional prediction method yields an inaccurate result, inevitably requiring a tedious, time-consuming tuning process to determine the correct resonant height to provide the maximum antenna gain in a target frequency band using three-dimensional full-wave computer simulations. To solve that problem, we have proposed a new resonance prediction method to provide a more accurate resonant height calculation of FPC antennas by using the well-known resonance behavior of a rectangular resonant cavity. For a more physically insightful explanation of the new prediction formula, we have reinvestigated our proposal using a wave propagation characteristic in a hollow rectangular waveguide, which clearly confirms our approach. By applying the proposed technique to an FPC antenna covered with a partially reflecting superstrate consisting of continuously tapered meander loops, we have proved that our method is very accurate and readily applicable to various types of FPC antennas with lateral walls. Experimental result confirms the validness of our approach.

• Journal of Ocean Engineering and Technology
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• v.27 no.2
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• pp.1-7
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• 2013

This paper aims at contributing to the field of ship design by introducing new systematic variation methods for ship hull forms. Hull form design is generally carried out in two stages. The first is the global variation considering the sectional area curve. Because the geometric properties of a sectional area curve have a decisive effect on the global hydrodynamic properties of ships, the design of a sectional area curve that satisfies various global design conditions, e.g., the displacement, longitudinal center of buoyancy, etc., is important in the initial hull form design stage. The second stage involves the local design of section forms. Section forms affect the local hydrodynamic properties, e.g., the local pressure in the fore- and aftbody. This paper deals with a new method for the systematic variation of sectional area curves. The longitudinal volume distribution of a ship depends on the sectional area curve, which can geometrically be controlled using parametric variation and a variation that uses the modification function. Based on these methods, we suggest a more generalized method in connection with the derivation of the lines for a new design compared to those for similar ships. This is the so-called the volumetric balanced variation (VOB) method for ship forms using a B-spline modification function and an optimization technique. In this paper the global geometric properties of hull forms are totally controlled by the form parameters. We describe the new method and some application examples in detail.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09c
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• pp.18-23
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• 2010

The estimation of the undrained shear strength $s_u$ for clays using CPT results has been mainly based on the cone factor $N_k$. In this study, a new CPT-based method for the estimation of the undrained shear strength $s_u$ is presented. This aims at reducing uncertainties for the estimation of $s_u$ and enhancing the application of CPT results in more effective manner. For this purpose, a site located at a marine clay deposit is selected and test results from extensive experimental testing program are adopted. The new method defines a direct correlation between the undrained shear strength $s_u$ and the cone resistance $q_t$, excluding the procedure of the overburden pressure correction and therefore undisturbed soil sampling process. In order to verify the new CPT-based method, additional test sites and example sites from literature, which consist of a variety of soil conditions, are selected and examined. It is observed that values of su obtained from the proposed method are in good agreements with measured values of $s_u$ for all the selected verification cases.

• Industrial Engineering and Management Systems
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• v.1 no.1
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• pp.64-72
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• 2002

In the field of plant maintenance, data that are gathered by sensors on multiple machines are handled and analyzed. Online or pseudo online data handling is required on such fields. When the data occurrence speed exceeds the data handling speed, multiple data should be handled at a time (batch data handling or pseudo online data handling). If l amount of data are received at one time following N amount of data, how to estimate the new parameters effectively is a great concern. A new simplified calculation method, which calculates the N data's weights, is introduced. Numerical examples show that this new method has a fairly god estimation accuracy and the calculation time is less than 1/10 compared with the case when the whole data are re-calculated. Even under the restriction calculation ability in the apparatus is limited, this proposed method makes the failure detection of equipments possible in early stages with a few new coming data. This method would be applicable in many data handling fields.

• Journal of the military operations research society of Korea
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• v.33 no.1
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• pp.31-42
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• 2007

While Defense Agency fur Technology and Quality(DTaQ) has been utilized a risk assessment method as a quality assurance activity for defense goods since 1999, a risk assessment method is known to be ineffective to identify defective items. The objective of this study is to propose the new evaluation method, that adjusts a relative priority of evaluation elements using AHP(Analytic Hierarchy Process). Newly evaluated scores have been applied to the risk assessment result of 2005 defective items to test a validity of the new evaluation model. The new model is capable to identify more high and medium risk-level items than the current method. The company risk-level gets more scores than the item risk-level in the new model.

• Journal of Korea Multimedia Society
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• v.5 no.1
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• pp.120-127
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• 2002

The common problems found in the data mining methods current in use have following problems. First: It is ineffective in searching for frequent items due to changing of minimal support values. Second: It is not adaptable to occurring of unuseful relation rules. Third: It is very difficult to re-use preceding results while adding new transactions. In this paper, we introduce a new method named as SPM-IRG(Selective Patters Mining using item Relation Graph), that is designed to solve above listed problems. SPM-IRG method creates a frequent items using minimal support values obtained by investigating direct or indirect relation of all items in transaction. Moreover, the new method can minimize inefficiency of existing method by constructing frequent items using only the items that we are interested.

• Journal of applied mathematics & informatics
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• v.42 no.5
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• pp.1195-1210
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• 2024

This research aims to determine an optimal (best) solution for transporting the logistics at a minimum cost from various sources to various destinations. We proposed a new algorithm for the initial basic feasible solution (IBFS). Developing a new IBFS is the first step towards finding the optimal solution. A new approach for the initial basic feasible solution that reduces iterations and produces the best answer in the initial process of the transportation issue. Different IBFS approaches have been generated in the literature review. Some statistical fundamentals, such as normal distribution and the root mean square technique, are employed to find new IBFS. A TP is transformed into a normal distribution, and penalties are determined using the root mean square method. Excel Solver is used to calculate normal distribution values. The second step involves using a stepping-stone approach to compute the optimum solution. The results of our study were calculated using numerical examples and contrasted with a few other methodologies, such as Vogel's approximation, the Continuous Allocation Method (CAM), the Supply Demand Repair Method (SDRM), and the Karagul-Sahin Approximation Method (KSAM). The conclusion of our proposed method gives more accurate results than the existing approach.

• Nuclear Engineering and Technology
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• v.56 no.10
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• pp.4042-4049
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• 2024

A new automatic group structure optimization method based on the perturbation theory was proposed for the few-group structure in two-step nuclear design procedure for VHTR. It applies the sensitivity coefficient of the perturbation theory which includes not only the effect of the cross section on the multiplication factor but also the adjoint weighted reaction rate. The sensitivity coefficient of the fine group for the multiplication factor was calculated and the group boundary for a few-group can be determined so that the summation of the fine group sensitivity for a few-group should be evenly distributed over every few-group. This method was successfully implemented in the ABGO code. VHTR-350 and MiHTR 2D core were used to investigate the performance and applicability of the proposed method. The code generated the new group structures for two cores and the error of the multiplication and reaction rate by the new group structure was compared with the result by the fine group structure. The comparisons indicate that the new group structure by the proposed method can provide the multiplication factor and reaction rates comparable to the existing group structure and more accurate results than the group structure obtained using the Contributon theory.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.591-598
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• 2018

Short term load forecasts complexly affected by socioeconomic factors and weather variables have non-linear characteristics. Thus far, researchers have improved load forecast technologies through diverse techniques such as artificial neural networks, fuzzy theories, and statistical methods in order to enhance the accuracy of load forecasts. Short term load forecast errors for special days are relatively much higher than that of weekdays. The errors are mainly caused by the irregularity of social activities and insufficient similar past data required for constructing load forecast models. In this study, the load characteristics of Lunar New Year's Day holidays well known for the highest error occurrence holiday period are analyzed to propose a load forecast technique for Lunar New Year's Day holidays. To solve the insufficient input data problem, the similarity of the load patterns of past Lunar New Year's Day holidays having similar patterns was judged by Euclid distance. Lunar New Year's Day holidays periods for 2011-2012 were forecasted by the proposed method which shows that the proposed algorithm yields better results than the comprehensive analysis method or the knowledge-based method.