• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.443-447
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• 1999

The AC drive systems of a voltage source inverter and an induction motor. The inverter non linearity caused by the turn on/off time dependency of the current level in the switching IGBT is described in the first part of this paper. To improve the low-speed drive characteristics, accurate applied voltage calculation is proposed under considerations of the compensations for the quantization error in the digital controller, the forward voltage drop of switching drives and the dead time of the inverter. The experimental studies show the improved drive characteristics.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.287-290
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• 1999

This paper describes an optimal design method of VSI output filter for CVCF system. The cost function is used for design, and all parameters are described in p.u(per unit) so that can be adapted to the change of CVCF rating. The capacitor current feedback scheme is proposed to control the damping ratio of the filter plant to meet the system more stable. This means that the LC resonance can be suppressed well in transient condition and can use the same control gains under the change of system capacity. The validity of the proposed method is well verified with the theoretical analysis and simulation results.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.17 no.30
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• pp.101-106
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• 1994

The basic of the VSI charts is that if the sample statistic computed after a sample is taken shows some indication of a process change than the sampling interval before the next sample should be short otherwise long. This paper was shown the VSS chart can be considerably more efficient than the FSS chart and the effectiveness of VSI R chart with S chart used for monitoring a process standard deviation.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.403-404
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• 2006

Sintered materials have been applied widely in Valve Seat Inserts (VSI). The demands for VSIs are not only good heat and wear resistance but also good machinability. The sintered materials, which are made of a mixture of manganese containing iron powder and certain types of sulfide powder, have superior machinability due to precipitation of the fine MnS particles in the matrix. This report introduces a new VSI material, which has both superior machinability, and wear resistance due to applies of this "MnS precipitation" technique.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.391-392
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• 2006

Sintered materials have been applied widely in Valve Seat Inserts (VSI). The amount of wear on VSIs increases when used in gas (LPG, CNG) engines because of their dry environments. In this paper, two newly developed high performance VSI materials for gas engines are introduced. These materials applied new techniques, which are both high performance hard particle and new distribution method of solid lubricant, to increase wear resistance.

• Journal of KIISE
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• v.44 no.9
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• pp.992-1004
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• 2017

To assess image quality accurately, an image quality assessment (IQA) metric is required to reflect the human visual system (HVS) properly. In other words, the structure, color, and contrast ratio of the image should be evaluated in consideration of various factors. In addition, as mobile embedded devices such as smartphone become popular, a fast computing speed is important. In this paper, the proposed IQA metric combines color similarity, gradient similarity, and phase similarity synergistically to satisfy the HVS and is designed by using optimized pooling and quantization for fast computation. The proposed IQA metric is compared against existing 13 methods using 4 kinds of evaluation methods. The experimental results show that the proposed IQA metric ranks the first on 3 evaluation methods and the first on the remaining method, next to VSI which is the most remarkable IQA metric. Its computing speed is on average about 20% faster than VSI's. In addition, we find that the proposed IQA metric has a bigger amount of correlation with the HVS than existing IQA metrics.

• The Plant Pathology Journal
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• v.36 no.5
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• pp.468-475
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• 2020

Malva vein clearing virus (MVCV) is a member of the Potyvirus species, and has a negative impact on the aesthetic development of Alcea rosea. It was first reported in Germany in 1957, but its complete genome sequence data are still scarce. In the present work, A. rosea leaves with vein-clearing and mosaic symptoms were sampled and analyzed with small RNA deep sequencing. By denovo assembly the raw sequences of virus-derived small interfering RNAs (vsiRs) and whole genome amplification of malva vein cleaning virus SX strain (MVCV-SX) by specific primers targeting identified contig gaps, the full-length genome sequences (9,645 nucleotides) of MVCV-SX were characterized, constituting of an open reading frame that is long enough to encode 3,096 amino acids. Phylogenetic analysis showed that MVCV-SX was clustered with euphorbia ringspot virus and yam mosaic virus. Further analyses of the vsiR profiles revealed that the most abundant MVCV-vsiRs were between 21 and 22 nucleotides in length and a strong bias was found for "A" and "U" at the 5′-terminal residue. The results of polarity assessment indicated that the amount of sense strand was almost equal to that of the antisense strand in MVCV-vsiRs, and the main hot-spot region in MVCV-SX genome was found at cylindrical inclusion. In conclusion, our findings could provide new insights into the RNA silencing-mediated host defence mechanism in A. rosea infected with MVCV-SX, and offer a basis for the prevention and treatment of this virus disease.

• Publications of The Korean Astronomical Society
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• v.22 no.3
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• pp.63-73
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• 2007

In this paper, we introduce the performance test results of digital data processing system for KVN (Korean VLBI Network). The digital data processing system for KVN consists of DAS (Data Acquisition System) and high-speed recorder which called Mark5B system. DAS system performs the digitalization of analog radio signal through ADS-1000 gigabit sampler with 1 Gsps/2-bit and process the digital filtering of digital signal. Mark5B system records the output data of DFB (Digital Filter Bank) with about 1 Gbps. In this paper, we carried out the preliminary evaluation experiments of the KVN digital data processing system connected between DAS system and Mark5B with VSI (VLBI Standard Interface) interface which is designed for compatible in each VLBI system. We first performed all of the KVN digital data processing system connected by VSI interface in the world. In factory inspection phase, we found that the DAS system has a memory read/write error in DSM (Digital Spectrometer) by analyzing the recorded data in Mark5B system. We confirmed that the DSM memory error has been correctly solved by comparing DSM results with Mark5B results. The effectiveness of KVN digital data processing system has been verified through the preliminary experiments such as data transmission, recording with VSI interface connection and data analysis between DSM and Mark5B system. In future work, we will perform the real astronomical observation by using the KVN 21m radio telescopes so as to verify its stability and performance.

• Journal of Digital Convergence
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• v.17 no.7
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• pp.207-214
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• 2019

This study was designed to find effective CPR education methods by comparing and analyzing the quality of Field-Focus Type (FFT) CPR using SimPad and the quality of Video Self-lnstruction(VSI) CPR for the learners. The data collection were conducted from November 28, 2018 to December 5, 2018, on 64 first graders who completed CPR lectures at universities located in G metropolitan city, and analyzed using the SPSS ver. 23.0. The results of the study, Field Focus Type (FFT) CPR showed higher quality of Video Self-lnstruction (VSI) CPR in areas such as CPR total score, chest compressions score, chest compressions dept, chest compressions rate, chest compression velocity, total ventilation score, and Total number of ventilation than that of the subjects. Therefore, using Field Focus Type CPR (FFT) education law was found to improve the quality of cardiopulmonary resuscitation compared to the existing Video Self-lnstruction CPR (VSI) education method, and it is believed that it can be used as a basic data for cardiopulmonary resuscitation education in the future.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.2
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• pp.190-199
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• 2014

In the last years, fault problem in power electronics has been more and more investigated both from theoretical and practical point of view. The fault problem can cause equipment failure, data and economical losses. And the analyze system require to ensure fault problem and also rectify failures. The current errors on these faults are applied for identified type of faults. This paper presents technique to detection and identification faults in three-phase voltage source inverter (VSI) by using time-frequency distribution (TFD). TFD capable represent time frequency representation (TFR) in temporal and spectral information. Based on TFR, signal parameters are calculated such as instantaneous average current, instantaneous root mean square current, instantaneous fundamental root mean square current and, instantaneous total current waveform distortion. From on results, the detection of VSI faults could be determined based on characteristic of parameter estimation. And also concluded that the fault detection is capable of identifying the type of inverter fault and can reduce cost maintenance.