• Publications of The Korean Astronomical Society
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• v.20 no.1 s.24
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• pp.125-134
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• 2005

In this paper, we propose a small-scale Gigabit VLBI observing system for the Korean VLBI Network (KVN) under construction. The system consists of high-speed sampler, IP-VLBI board, PC-VSI board, and software correlator. Radio signal received by receiver is sampled by high-speed sample. at 1 Gsps (Gigabit sample per second) rate with 2 bits quantization. The digitized signal is recorded in PC and the software correlator does the cross correlation. IP-VLBI board will be used for the geodesy VLBI observation, while PC-VSI board is for the astronomical VLBI observation. The PC-VSI board adopts the VSI-H (VLBI Standard Interface Hardware). The proposed system is based on commercial PCs and therefore can be built inexpensively.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.319-321
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• 2005

한국천문연구원에서는 한국우주전파관측망(Korean VLBI Network; KVN)에서 사용할 관측 시스템 중에서 소규모 자료획득시스템(DAS) 구축을 위하여 기가비트 고속샘플러, PC-VSI 보드, 소프트웨어 상관기를 도입하였다. 고속샘플러는 기가비트급 ADS1000, PC-VSI 보드는 VSI-H(VLBI Standard Interface Hardware) 표준을 따른 PCI 버스를 채택하고 있어 일반 컴퓨터에 설치하여 동작되며, 이 규격을 갖춘 시스템과의 데이터 입출력이 가능하다. 소프트웨어 상관기는 일본 NILT와의 연구협력을 통하여 본 연구원에서도 사용할 수 있게 되었으며, FX와 XF 형 2가지를 모두 갖추고 있다. 하지만 현재 구현된 소프트웨어 상관기는 측지 VLBI 관측을 위해 설계되어 있어, 향후 KVN의 하드웨어 상관기와 함께 천문 VLBI 관측을 위한 3기선 분의 소프트웨어 상관기로 개량하려고 한다. 이상에서 소개한 시스템을 좁은 의미로 K5 시스템이라고도 한다. 본 논문에서는 PC-VSI 보드에 대해 간략히 소개하고, K5 시스템을 이용하여 관측한 결과를 빨리 관측자가 원하는 정보를 얻을 수 있는 소프트웨어 상관기의 구조에 대해서도 소개하고자 한다.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.28B no.12
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• pp.38-50
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• 1991

A current-controlled scheme of pulse width modulation voltage source inverter (PWM VSI) has attracted considerable attention due to its fast response with current limit and especially suitable for potentially high performance applications such as AC motor drives and UPS systems. These features yield near-sinusoidal currents in the load with reduced current peaks, lower inverter switching frequency and reduce inverter and load stresses. A high performance current-controlled inverter must have a quick response in transient state and low harmonic current in steady state. This paper compares and shows the controlled-characteristics with hysteresis controller(HC), ramp comparison controller(RCC) and predictive controller(PC) of PWM inverter to control actual current of VSI-IM.

• The Journal of Korean Society for School & Community Health Education
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• v.10 no.2
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• pp.1-13
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• 2009

Objectives: This study is a quasi-experimental research with nonequivalent control group pretest-posttest design study to compare and verify the educational effects between CPR Song.Video Self-Instruction and CPR VSI. Method: We selected total 58 subjects who were freshmen at the Dept of Emergency Medical technology, G College in G Metropolitan City and 28 of them were experimental group which had no experience to have CPR instruction and consented to take part in this research and 30 students were control group. Data were collected from Apr. 27 to 29, 2009. Data were analyzed with SPSS/PC+(version 14.0). and all significance level was set as p<0.05. Results: 1. In the knowledge of CPR, the knowledge level before CPR instruction was 2.17 out of 10 in experimental group and 1.86 in control group. After CPR instruction, experimental group got 9.07 and it meant the increase of 6.89 and control group showed increase to 7.16(p=0.000). 2. Self-efficacy of CPR showed 2.61 out of 10 in both experimental and control groups, and after CPR instruction, experimental group showed increase of 3.93 as 6.55 and control group showed increase of 3.91 as 6.52(p=0.000). 3. Accuracy of CPR performance was 0.32 out of 10 in experimental group and 0.40 in control group. After CPR instruction, experimental group got 9.25 and showed increase of 8.92 and control group got 9.20 and showed increase of 8.80(p=0.000). 4. Study satisfaction was 4.22 out of 5 in experimental group and 3.04 in control group, and experimental group was higher than control group. there was no statistically significant difference. Conclusions: This study found that CPR Song；Video Self-Instruction achieved better results than CPR VSI. With these results, it is considered that CPR instruction for college students through mass communication or video will be very helpful.

• Publications of The Korean Astronomical Society
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• v.19 no.1
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• pp.83-92
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• 2004

In this paper, we introduce the development of the large storage system in order to record the observed space radio signal in the Korean VLBI Network(KVN) with high-speed. The KVN is the Very Long Baseline Interferometery(VLBI) to observe the birth of star, the structure of space by constructing radio telescope with diameter 21m at the Seoul, Ulsan, Jeju from 2001 to 2007 years. To do this, Korea Astronomy Observatory joined the international consortium for developing the high-speed large storage system(Mark 5), which is developed by MIT Haystack observatory. The Mark 5 system based on hard disk has to record up to 1 Gbps the observed space radio signal. The main features of Mark 5 system are as follows; First it is able to directly record the input data to the hard disk without PC1(Peripheral Component Interconnect) internal bus, and the second, it has two hard disk banks, which are able to hot-swap ATA/IDE type very cheap up to 1 Gbps recording and playback. The third is that it follows the international VLBI standard interface hardware(VSI-H). Therefore it can be connect directly the VSI-H type system at the input/output. Finally it also supports e- VLBI(Electronic-VLBI) through the standard Gigabits Ethernet connection.

• Journal of Power Electronics
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• v.12 no.2
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• pp.305-316
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• 2012

The paper presents an accurate loss model based controller of an induction motor to calculate the optimal air gap flux. The model includes copper losses, iron losses, harmonic losses, friction and windage losses, and stray losses. These losses are represented as a function of the air gap flux. By using the calculated optimal air gap flux compared with rated flux for speed sensorless indirect vector controlled induction motor, an improvement in motor efficiency is achieved. The motor speed performance is improved using a fuzzy logic speed controller instead of a PI controller. The fuzzy logic speed controller was simulated using the fuzzy control interface block of MATLAB/SIMULINK program. The control algorithm is experimentally tested within a PC under RTAI-Linux. The simulation and experimental results show the improvement in motor efficiency and speed performance.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.2
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• pp.164-174
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• 1990

The improvement of linearized characteistics of induction motor control system with field oriented method is presented in this paper. A fully digitally controlled induction motor driver system based on the proposed linear control condition is described. The control system consists of IBM-PC/AT microcomputer, VSI PWM Inverter, and PI controller with softwave. By controlling the torque component, the rated flux component can be kept constant, even in the transient state. It is clearly confirmed by experiment that the improvement of the vector control condition is satisfactory. A simplified control model of an induction motor similar to the model for a separately excited DC motor drive system is obtained.

• Publications of The Korean Astronomical Society
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• v.20 no.1 s.24
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• pp.63-71
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• 2005

e-VLBI was invented to enhance the efficiency of VLBI (Very-Long-Baseline Interferometry) system by transmitting the data via high speed network. Korean VLBI Network (KVN) has a plan to construct e-VLBI system named e-KVN. High speed backbone network and efficient network model are essential to implement successful e-VLBI system. This paper introduces a network model based on PC cluster technology. The present status of high speed backbone network in Korea is overviewed. We suggest that the network link via Korea Advanced Research Network (KOREN) is one of feasible way for e-KVN. We also describe the principles of e-VLBI and protocol for network transmission such as VSI-E (VLBI Standard Interface - Electronic), RTP (Real-Time Transport Protocol) and RTCP (Real-Time Transport Control protocol).

• The Korean Journal of Emergency Medical Services
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• v.13 no.2
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• pp.87-98
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• 2009

Purpose : This study set out to compare the educational effects of a video self-instruction program for child CPR education on childcare teachers by applying the 2006 KACPR Guideline. By adopting the nonequivalent control group posttest quasi-experimental design, the study examined the educational effects on a group that did not receive instructions from the instructor, another group that received his instructions, and the other group that received an extra three-minute practice training session in addition to instructions. Methods : Data were gathered from August 6 to 18, 2008. As for research tools, the Knowledge Instrument of CPR by Connolly (2006) was used along with the National Practice Test Protocol for C1ass 1 Emergency Medical Technicians (2007) and Common Protocol for CPR (2006) to examine the performance of child CPR. By shooting the guide screen of $Resusci^{(R)}$ Junior CPR Manikin of Leardal with a video camera and using the Skill Guide Checklist of the Common Protocol for CPR (2006), the subjects' technical accuracy of chi1d CPR was evaluated. There were three subject groups: 29 childcare teachers randomly assigned to received the video self-instruction program training for chi1d CPR and no instructions from the instructor made up the control group; 22 childcare teachers randomly assigned to received the program training and instructions from the instructor made up experiment group I; 23 childcare teachers randomly assigned to received an extra three-minute practice training session in addition to the program training and the instructions made up experiment group II. The gathered data were analyzed with SPSS/PC+ (Version 14.0) in frequency, percentage, $X^2$-test, ANOVA, Scheffe test. Results : 1) There were no statistically significant differences (F=1.030, p=.362) among the groups in terms of knowledge scores after the child CPR education. 2) There were statistically significant differences (F=13.625, p=.000) among the groups in terms of performance abilities after the child CPR education. 3) There were no statistically significant differences (F=1.610, p=.207) among the groups in terms of technical accuracy of mouth-to-mouth resuscitation after the child CPR education 4) There were no statistically significant differences (F=1.484, p=.234) among the groups in terms of technical accuracy of chest compression after the child CPR education. Conclusion : The results indicate that childcare teachers can improve their performance abilities in child CPR when the instructors are active with their instructions and extra practice hours are secured through a VSI program. It's also needed to provide education with increasing concentration ratio about the items of lower knowledge points in order to help the teachers learn the accurate theory of child CPR. And there should be VSI programs of diverse conditions to increase the effects of child CPR training among childcare teachers.