• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.9 no.7
• /
• pp.2354-2370
• /
• 2015

The advantages of employing SCTP-based Concurrent Multipath Transfer (CMT) have been demonstrated to be very useful for data delivery over multi-homed wireless networks. However, there is still significant ongoing work addressing some remaining limitations and challenges. The most important concern when applying CMT to data delivery is related to handling packet reordering and buffer blocking. Another concern on this topic is that current sender-based CMT solutions seldom consider balancing the overhead and sharing the load between the sender and receiver. This paper proposes a novel Receiver-driven Cooperation-based Concurrent Multipath Transfer solution (CMT-Rev) with the following aims: (i) to balance overhead and share load between the sender and receiver, by moving some functions including congestion and flow control from the sender onto receiver; (ii) to mitigate the data reordering and buffer blocking problems, by using an adaptive receiver-cooperative path aggregation model, (iii) to adaptively transmit packets over multiple paths according to their receiver-inspired sending rate values, by employing a new receiver-aware data distribution scheduler. Simulation results show that CMT-Rev outperforms the existing CMT solutions in terms of data delivery performance.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.26 no.9
• /
• pp.64-72
• /
• 2012

The interest in wind power generation area such as developing and operating wind-diesel pilot complex in remote and island regions that have difficulty in having power plant and connecting to power system is growing rapidly in the world. We have installed and researched the hybrid system in Sekgok Pilot Complex to meet the new generation system. From the monitored data of the system, the performance of each diesel power plant is outstanding. However, step out problem was detected with respect to load sharing and synchronization with decentralized power supply. An advanced controller design having better response time and stability is needed to solve such problem. In this paper, we proposed the algorithm, through digital controller of Governor, which is applied to hybrid system. As a result, we obtained the stable frequency value in variable loading conditions. Also, we proved the advanced response time and stability through the simulation and experiment by applying additional current signal to the control algorithm.

• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.1351-1354
• /
• 2005

Recently, as the feasibility study shows that trans-Korea railway and trans-continental railway are advantageous, interest in high speed railway system is increasing. Because railway vehicle is environment-friendly and safe compared with airplane and ship, its market-sharing increases gradually. Korean High Speed Train has been developed by KRRI for last 7 years to satisfy the need. Korean High Speed Train (350km/h), composed of 2 power cars, 2 motorized car and 3 trailer cars, has been developed and is under trial test. To verify the design requirements for the functions and traction performances of the train, KRRI (Korea Railroad Research Institute) decided to evaluate traction performances of the train during trial test. For this purpose, torque, velocity, voltage and current must be measured. KRRI has developed a measurement system that can measure vast and various signals effectively. In this paper, we introduce traction performances of Korean High Speed Train. The traction measurement items are focused on the verification of motor block performances. Motor block consists of 2 motors. By this test, we verified traction performances of Korean High Speed Train

• Korean Journal of Health Education and Promotion
• /
• v.30 no.4
• /
• pp.41-56
• /
• 2013

Objectives: This article reviewed researches on intersectoral partnership of school health programs to suggest importance, current status and development plan of those. Methods: Domestic research papers were screened though Research Information Sharing Service (RISS), Koreanstudies Information Service System (KISS), Medical Library Information System (MEDLIS), Korean Medical Database (KMbase), and digital national assembly library. International papers were searched mainly via Pubmed. Results: Since intersectoral partnership is effective, comprehensive and universal approach for school health programs, many collaborative programs are universally progressing in various domain including smoking, alcohol, mental health and sexual behavior. On the other hand, intersectoral partnership of school health programs in Korea is still in the beginning stage, and there are few intersectoral partnerships. Moreover, there are several limitations including top-down approach, passive participation and lack of studies on the effect of intersectoral partnership. However, intersectoral partnerships in school health program including tuberculosis control system in school or WEE project are in progress, so it is worth looking forward in the future. Conclusions: To achieve successful intersectoral partnership in school health programs, appropriate partnership guideline for Korean society, policy support, active participation and improvement of consciousness in community stakeholders are needed.

• The Journal of Korean Association of Computer Education
• /
• v.7 no.5
• /
• pp.71-82
• /
• 2004

The purpose of the study was to suggest policy implications to support K-12 education, especially weak areas, through e-Learning, With the literature review and discussions among experts in the field of K-12 education, we identified three areas - support for neglected students, preference-based curriculum, and gifted education - as the ones e-Learning may contribute much, and discussed current situations and problems for the each area followed by policy implications accordingly. In addition, we suggest strategic bases for the policy implications, which were reform of the law and polices, contents sharing, and quality control of e-Learning.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.58 no.1
• /
• pp.86-92
• /
• 2009

This paper presents development of 6kw ZVS(Zero Voltage Switching) boost converter by 4-parallel operation. To realize a high capacity converter with 6 kw, 4-parallel operation of 1.5kW unit module is proposed in this paper. To meet high ratio input to output voltage, isolated type booster converter is designed. To achieve ZVS operation of 4-switches of full bridge and protect a voltage overshoot caused by switch turn-off, simple active-clamp circuit is applied to the primary side. For parallel operation of 4-modules, master-slave control method is proposed to achieve input current sharing of 4-unit converter modules accurately. For performance tests, simulation is carried out. Also, load and experimental tests of the developed booster converter, 230Vdc/6kW, are carried out under various conditions. For field tests, the developed converter is applied for boosting a battery power to high DC_link voltage for a VSI inverter which starts a micro-turbine(MT) installed in vehicle and it's performance is verified through high speed motoring a MT up to tens of thousands of rpm.

• Journal of Electrical Engineering and Technology
• /
• v.8 no.1
• /
• pp.137-143
• /
• 2013

This paper presents development of variable speed generation (VSG) system with energy saving function. The rubber tyred gantry crane (RTGC) requires the power from diesel-engine. Significant fuel savings by reducing the engine speed can be achieved, because all of operation modes except hoisting are required lower power than rated value of engine. When low speed operation output voltage of generator is decrease until acceptable range of motor driver inverters and auxiliary load supplier. According to power demand engine speed is varying from 20 to 60Hz, and voltage is varying between 210Vac and 480Vac. When idle mode or low power operation dc/dc converter operates by constant output voltage control and inverters dc site voltage is compensated by it. This paper proposed 3-phase interleaved boost converter which has the same structure as the commercially available 3-phase inverter and current sharing capability. 400kW interleaved converter is designed and a performance of converter is evaluated through several experiments with a RTGC system. Energy saving VSG system can cut down fuel consumption by 36% and 21.3% at idle and unidirectional load operations.

• Proceedings of the KIPE Conference
• /
• 2003.07b
• /
• pp.872-875
• /
• 2003

This paper introduces the propulsion system for Korean High Speed Railway(HSR). The developed propulsion system consists of PWM AC/DC converter and inverter. Compared with TGV-K, converters can improve input harmonics characteristics by the interlaced PW switching methods. And several merits such as unity power factor and simple regenerative operations can be also made. As a main power component, IGCT stack with suitable structure for high speed train and environmentally friendly cooling heat pipe is designed. In this paper, overall configuration of controller and control scheme is briefly described. Finally running tests are made to verify the developed propulsion system. The presented test results shows fast torque response, balanced converter current sharing, and appropriate running sequence.

• Asia pacific journal of information systems
• /
• v.8 no.3
• /
• pp.37-49
• /
• 1998

The basic goal of CALS is to improve transactions and relationships among organizations through information sharing and integration. CALS is an information strategy which needs strong cooperation between organizations or between users and developers in design step. However, current design methodologies using IDEF models, that are considered to be standard for CALS system development, has some limitations. For example, it is difficult for system developers to communicate with counterparts by IDEF model since IDEF models are difficult for counterparts to understand. In this paper, we suggest a development methodology for GALS systems by complementing IDEF model with Document Trace Diagram, which we developed as a communication tool, The concept of Document Trace Diagram stems from the fact that most information exchanged within or between organizations is in the form of documents and most standard operating procedures of organizations are about processing the documents. It helps system developers identify functions and their ICOMs (Input, Control, Output, Mechanism) with ease and little communication cost. With this methodology, we have constructed the GALS prototype system for construction industry.

• Korean Management Science Review
• /
• v.30 no.2
• /
• pp.11-30
• /
• 2013

Small and medium-sized enterprises (SMEs) constitute an important part of current industrial economies. Information technologies can be useful strategic weapons for SMEs by enhancing their competitiveness. Categorized as one kind of cloud computing, SaaS is a computing resource and software sharing model which can be accessed via the Internet. Based on virtualization technology, SaaS is expected to improve the efficiency and quality of the IT service level in SMEs. This study attempts to identify the determinants of SaaS adoption intention among Korean SMEs. Through the lens of the theory of planned behavior, this study adopts technological, organizational, environmental factors to explore the determinants of cloud computing adoption intention. The research population is the SMEs that have been funded by the Korean government. Partial least square method was used for empirical analysis of 190 samples collected through on-line survey. The results show that the positive attitude is influenced by business process improvements. Vender support and top management support are positively associated with subjective norm. Vendor support, top management support can relieve perceived behavior control factors. Government support directly influences adoption intention of cloud computing. These findings can provide useful strategy for both SMEs and vendors of SaaS.