• Journal of Power Electronics
• /
• v.16 no.5
• /
• pp.1904-1917
• /
• 2016

The moving average filter (MAF) is widely utilized to improve the disturbance rejection capability of phase-locked loops (PLLs). This is of vital significance for the grid-integration and stable operation of power electronic converters to electric power systems. However, the open-loop bandwidth is drastically reduced after incorporating a MAF into the PLL structure, which makes the dynamic response sluggish. To overcome this shortcoming, some new techniques have recently been proposed to improve the transient response of MAF-based PLLs. In this paper, a comprehensive performance comparison of advanced MAF-based PLL algorithms is presented. This comparison includes HPLL, MPLC-PLL, QT1-PLL, and DMAF-PLL. Various disturbances, such as grid voltage sag, voltage flicker, harmonics distortion, phase-angle and frequency jumps, DC offsets and noise, are considered to experimentally test the dynamic performances of these PLL algorithms. Finally, an improved positive sequence extraction method for a HPLL under the frequency jumps scenario is presented to compensate for the steady-state error caused by non-frequency adaptive DSC, and a satisfactory performance has been achieved.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.17 no.7
• /
• pp.1544-1550
• /
• 2013

In recent years, Container Security Device(CSD) using GPS & GLONASS to improve logistics efficiency are being extensively researched. The purpose of this paper is to examine the performance development antenna usable cargo container security transport. Antenna developed by study were optimized to match logistics environment apply to GPS/GLONASS dual frequency for monitering system. The measure of antenna have confirmation about frequency characteristics each 1575.42MHz, 1602MHz and VSWR is 2:1 measured in return loss -9.54dB. Reliability of this antenna has been verified about GPS/GLONASS through test-operation between the south korea and Russia.

• Journal of Information Technology Services
• /
• v.9 no.1
• /
• pp.27-42
• /
• 2010

Recently, many organizations are actively adopting Enterprise Architecture (EA) as a methodology to manage IT assets and build IT-based business system. However, most existing studies on EA have focused on the adoption stage of EA. Now the research concerning effective management and utilization of EA after adopting EA is keenly required. This study intended to empirically examine how the role of EA operating unit and the EA utilization capability of organizational members impact on EA performance at the post-adoption stage of EA. Based on Resource Based View (RBV), this study proposed the model and the hypotheses describing that the impact of the role of EA operating unit on EA performance is mediated by the EA utilization capability of organizational members. In order to test the hypotheses, the field survey whose respondents were seventy four Korean public agencies which have adopted EA was conducted by means of questionnaire. Data analysis was done with partial least square (PLS), which is a structural equation modeling (SEM) technique that uses a component-based approach to estimation. The results of the empirical analyses showed that the organizational operation ability of EA operating unit significantly influenced EA performance via the EA utilization capability of organizational members, but that EA education and training performed by EA operating unit did not. The results of this study provided a lot of theoretical and practical implications regarding EA management activities at the post-adoption stage of EA to enhance EA performance.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.10
• /
• pp.4354-4358
• /
• 2011

Many Korean construction companies have fallen on hard times because the construction business continues to stagnate. Therefore it is necessary to measure the management efficiency for efficient operation and strengthening competitiveness of them in order to survive a difficult situation. This paper proposes a combined ANP and DEA model to analyze the efficiency of the listed construction firms. In order to determine the input and output variables of DEA, the ANP model is applied to evaluate the importance of input and output variables. The benchmarking companies and efficiency value for the construction firms with inefficiency are also provided to improve the their efficiency. The 57 listed construction companies consisted of 36 listed on KOSPI and 21 listed on KOSDAQ are analyzed in this study. The analysis results show that 11 companies whose values of CCR are 1, and 14 firms whose values of BCC efficiency are 1. In additions, the 19 firms have the scalability efficiency. Finally, we test the correlation between efficiency and the stock price.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.17 no.2
• /
• pp.158-165
• /
• 2012

In this paper, the test bed using three-phase PWM converter connected with single phase inverter in series is set up to configure an active AC electric load. Since the two topologies, three-phase PWM converter and single-phase inverter, can be operated bidirectionally, the system not only re-generates surplus power to grid but also prevents power dissipation. However, the construction of system has a drawback. That is, ripple components two times of inverter operation frequency occur at DC-Link due to cascade connection, it can be cause of three phase unbalance Since the operational characteristic of the active AC electric load, the power frequency entered into the electric load can be varied, and the ripple of DC-Link is changed as well. In this paper, the three-phase PWM converter using a variable notch filter is proposed, and the reduction of three-phase current unbalance is presented. the validity of the proposed PWM converter using a variable notch filter is verified by the simulation and experimental results.

• The KIPS Transactions:PartB
• /
• v.16B no.3
• /
• pp.215-224
• /
• 2009

A film colored overlay has been used as an assistive device for dyslexics, Recently, several virtual colored overlays which can be used in computer were developed. But existing virtual overlays have some drawbacks which have limited colors and limited control capability over overlapped window by the overlays. Limited colors may prevent optimum color selection and limited control capability can obstruct to transfer keyboard and mouse operation to the overlapped window. In this paper, we implemented an overlay function which controls an overlapped window under the overlay window by using keyboard hooking and tray icon. We propose a method to determine the source color of a virtual overlays by estimating alpha value of alpha blending algorithm through measurement of the chromaticity and transmissivity of film overlays and implemented all colors which we can produce colors by using Intuitive Overlays. Test results of the developed virtual overlay show that all mentioned drawbacks of existing virtual overlays were eliminated. Therefore we can employ a result of WRRT to use the developed overlays.

• Journal of Korean Society for Geospatial Information Science
• /
• v.17 no.2
• /
• pp.133-143
• /
• 2009

Next Generation Digital Maps on demand Updating System is a system for setup of efficient on-demand updating system, keeping up-to-date data and conducting high-quality service and efficient management. The system is designed that object-based continuous Digital Maps may have on-demand updating available, as well as the exiting feature-based digital maps, and the relevant development is being done. This study presented some problems and improvement plans related to the system operation, by means of implementing object-based continuous Digital Maps and feature-based digital maps updating test, for the next generation digital maps on demand updating system, in order to contribute to present plans to apply next generation digital maps and to secure competitiveness. And, for the economical efficiency of the next generation digital maps on demand updating system, this study analyzed expenses and benefit resulted from introduction of on demand updating system for 1:5,000 digital maps, intended for National Geographic Information Institute. and the land category which have an effect on the officially assessed land price and it using GIS technology.

• The Korean Journal of Pain
• /
• v.19 no.2
• /
• pp.288-291
• /
• 2006

Epidural analgesia using an epidural catheter is an effective method to relieve the pain during the rehabilitating procedure for postoperative orthopedic patients. Total spinal anesthesia is one of the possible complications of epidural catheterization which can lead to a life-threatening condition. Achondroplasia is the most common form of short-limbed dwarfism resulting from a failure of endochondral bone formation. In patients suffering with short stature syndrome like achondroplasia, the incidence and risk of total spinal anesthesia during epidural anesthesia may increase because of the technical difficulty and structural anomaly of the spine. We report here on a 35-year old female patient with a height of a 115 cm. She was diagnosed as achondroplasia and she had a previous Ilizarov operation; both tibial lengthening and correction of valgus were done. No specific event occurred during epidural catheterization. Immediately after the injection of a test dose via epidural catheter, the patient became hypotensive, drowsy and showed weakness of both her upper and lower extremities. The symptoms were disappeared after 40 minutes. The catheter was removed on the next day. We concluded that the total spinal anesthesia was caused by intrathecal injection of local anesthetics through the epidural catheter, and the anesthesia then migrated into the subarachonoid space.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.27 no.5
• /
• pp.358-363
• /
• 2015

As a preparation process for successful establishment of demonstration offshore wind farm, analyses have been made for working time at the construction site where working time is defined as the time available for marine operation to take place under given weather conditions. Data used are hourly wave and wind data from met mast, HeMOSU-1, and 3 hour numerical model data from Korea Meteorological Administration (KMA). Seasonal results show the minimum working time during winter and moderate during autumn and spring. The most working time was seen during summer on average. Monthly analyses show the most working time in May, June, and August which was higher than the working time in July and September. Working time reaches at steady state and no significant change was seen above wave height of 1.5 m and wind speed of 8 m/s.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.11 no.4
• /
• pp.161-171
• /
• 2008

Nowdays the need of modeling a real world using computers leads to increase the importance of GIS. Moreover, the wide spread of the Internet service has brought about Web GIS Development. Especially, the tuning of Web GIS system has a crucial role in improving the performance of high resolution image Web GIS system. Thus, this study provides a variety of ways to improve the performance of high resolution image Web GIS system. We have tuned IBM AIX operation system, Oracle, ArcSDE in the database level and Tomcat, ArcIMS in the application level. What is more, we propose ways of coding which can have a positive impact on performance. As a result, the proposed methods guarantee high resolution image Web GIS system to improve performance.