• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.4B no.2
• /
• pp.65-72
• /
• 2004

Switching power supply systems are widely used in many industrial fields. Power factor correction (PFC) circuits have a tendency to be applied in new power supply designs. The input active power factor correction (APFC) circuits can be implemented in either the two-stage approach or the single-stage approach. The two-stage approach can be classified into boost type PFC circuit and dc/dc converter. The power factor correction circuit with a boost converter used as an input power source is studied in this paper. In a boost power factor correction circuit there are two feedback control loops, which are a current feedback loop and a voltage feedback loop. In this paper, the regulation performance of output voltage and compensator to improve the transient response presented at the continuous conduction mode (CCM) of the boost PFC circuit is analyzed. The validity of designed boost PFC circuit is confirmed by MATLAB simulation and experimental results.

• Journal of Korean Institute of Industrial Engineers
• /
• v.26 no.2
• /
• pp.146-154
• /
• 2000

This study showed a way to develop web site of shopping mall through systematic identification of the interface elements affecting user's performance and subjective sensibility for Internet shopping mall. To quantify the effects of factors, simulators were designed and used in experiments. It was shown that location of 'Table of Contents'(left > right = up = down) and 'Menu' type(non_Drop down and page Movement = Drop down and page Movement > Drop down and non_age Movement) were the significant factors. However, whether 'Frame' was used or not, there was no significant difference. Also, in the evaluation of subjective sensibility, 'Background color' was a significant factor. And for 'Header & Scanning Column color', yellow color had a tendency to enhance satisfaction for 'simplicity', while green or blue color strengthened 'balance' feeling. But 'text style' was not significant.

• Journal of Computing Science and Engineering
• /
• v.5 no.1
• /
• pp.51-70
• /
• 2011

This paper introduces a new credit card payment scheme called No Number Credit Card that can significantly reduce the possibility of credit card fraud. The proposed payment system is loosely based on Kerberos, a cryptographic framework that has stood the test of time. In No Number Credit Card, instead of card numbers, only payment tokens are exchanged between the customers and merchants. The tokens are generated based on the payment amount, payment type, client information, and merchant information. However, it does not contain the credit card number, so the merchant or a database hacker cannot acquire and illegally use any credit card numbers. The No Number Credit Card system is ideal for online e-commerce transactions and can be used with any credit card that users possess. It can be used with minor modifications to the current card payment system. We provide the principles of its operation through scenario analysis, a sample implementation, and a security analysis

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.5B no.4
• /
• pp.324-330
• /
• 2005

The complex sensorless control scheme is not practical for use in the field of home appliance systems because it is not economical. Therefore, it is necessary to introduce a simplified sensorless control scheme that is composed of least calculation to estimate the rotor position. This paper presents the principle of the rotor position estimation with comparison of the estimated flux linkage and reference flux linkage. In order to verify the feasibility of the control scheme, ACSL is used for the simulation and TI DSP TMS320F240 is used for the experiment.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.3B no.2
• /
• pp.84-89
• /
• 2003

The finite element method (FEM) is typically used in the process of motor design. However, the FEM requires computation time, Therefore, decreasing the number of FEM simulations may also decrease the simulation cost. Several optimal design methods overcoming this problem have been recently studied. This paper investigates the optimal design of the magnet pole of a BLDC motor through reducing simulation cost. The optimization minimizes the magnet volume and limits the average and cogging torques to certain values. In this paper, the response surface methodology and Taguchi's table for reducing the number of FEM simulations are used to approximate two constraints. The optimization result shows that the presented strategy is satisfactorily performed.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.11B no.2
• /
• pp.22-27
• /
• 2001

Salient pole rotor type single phase switched reluctance motor is of simple and rigid structure, short shaft and simple driving circuit. Especially, the output power per unit volume of salient pole rotor structure is comparatively high because the magnetic fluxes of axial and radial direction are simultaneously used. Therefore, this motor will be used at small space and difficult maintenance situations. In this paper, the selecting method of proper pole arc, stator, and rotor dimension of salient pole rotor type single phase SRM is proposed.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.11B no.2
• /
• pp.15-21
• /
• 2001

This paper presents an improved characteristic analysis methodology for a 5-phase hybrid stepping motor. The basic approach is based on the use of equivalent magnetic circuit taking into account the localized saturation throughout the hybrid stepping motor. The finite element method(FEM) is used to generate the magnetic circuit parameters for the complex stator and rotor teeth and airgap considering the saturation effects in tooth and poles. In addition, the neural network is used to map a change of parameters and predicts their approximation. Therefore, the proposed method efficiently improves the accuracy of analysis by using the parameter characterizing localized saturation effects and reduces the computational time by using the neural network. An improved circuit model of 5-phase hybrid stepping motor is presented and its application is provided to demonstrate the effectiveness of the proposed method.

• East Asian Economic Review
• /
• v.21 no.1
• /
• pp.81-100
• /
• 2017

This study measures the degree of dollarization in North Korea using results from a survey of 231 North Korean refugees. Specifically, we compare foreign currency use of households as both store-of-value substitutes (i.e., asset substitution) and transaction substitutes (i.e., currency substitution) before and after the confiscatory currency reform of 2009. The degree of dollarization has advanced since the currency reform in terms of both asset and currency substitutions. Survey results also indicate that the Chinese yuan is frequently used in the Sino-North Korean border area, whereas the US dollar is predominantly used in non-border areas. Furthermore, foreign currency increasingly serves as a medium of exchange not only for large transactions but also for smaller transactions, such as food purchases.

• Journal of Distribution Science
• /
• v.8 no.1
• /
• pp.13-19
• /
• 2010

Segmentation, targeting, and positioning are marketing tools used by a company to gain competitive advantage in the market. For an accurate segmentation, various statistics models or datamining techniques are used. Especially, datamining techniques are introduced in the beginning of the 1980s and solved several marketing problems effectively. In this paper, we research about datamining technique for segmentation and analyze customer's transaction data of Department Store using Decision Tree Analysis, one of the dataming technique. After that, we discuss effects and advantages of segmentation using Decision Tree.

• KIPS Transactions on Computer and Communication Systems
• /
• v.10 no.2
• /
• pp.47-52
• /
• 2021

As blockchain technology develops, encryption for blockchain blocks is also becoming more important. Encryption in the blockchain is used to secure the identity of the person who created the transaction and to prevent manipulation of information in the past block. However, increasing the security of encryption decreases the speed of block creation, one of the biggest drawbacks of the blockchain. Therefore, in this paper, we propose a method to minimize the performance of the current OTP and the degradation of the blockchain by comparing the status and performance of OTP used in the blockchain.