• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.9
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• pp.47-52
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• 2020

With the 4th industrial revolution, condition monitoring using machine learning techniques has become popular among researchers. An overload due to complex operations causes several irregularities in MOSFETs. This study investigated the acquired voltage to analyze the overcurrent effects on MOSFETs using a failure mode effect analysis (FMEA). The results indicated that the voltage pattern changes greatly when the current is beyond the threshold value. Several features were extracted from the collected voltage signals that indicate the health state of a switched-mode power supply (SMPS). Then, the data were reduced to a smaller sample space by using a principal component analysis (PCA). A robust machine learning algorithm, the support vector machine (SVM), was used to classify different health states of an SMPS, and the classification results are presented for different parameters. An SVM approach assisted by a PCA algorithm provides a strong fault diagnosis framework for an SMPS.

• Nuclear Engineering and Technology
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• v.43 no.5
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• pp.413-420
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• 2011

In Korea, although the concept of dry storage system for PWR spent fuels first emerged in the early 1990s, wet storage inside nuclear reactor buildings remains the dominant storage paradigm. Furthermore, as the amount of discharged fuel from nuclear power plants increases, nuclear power plants are confronted with the problem of meeting storage capacity demand. Various measures have been taken to resolve this problem. Dry storage systems along with transportation of spent fuel either on-site or off-site are regarded as the most feasible measure. In order to develop dry storage and transportation system safety analyses, development of design techniques, full scale performance tests, and research on key material degradation should be conducted. This paper deals with two topics, structural analysis methodology to assess cumulative damage to transportation packages and the effects of an aircraft engine crash on a dual purpose cask. These newly emerging issues are selected from among the many technical issues related to the development of transportation and storage systems of spent fuels. In the design process, appropriate analytical methods, procedures, and tools are used in conjunction with a suitably selected test procedure and assumptions such as jet engine simulation for postulated design events and a beyond design basis accident.

• Journal of Digital Convergence
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• v.13 no.9
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• pp.251-257
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• 2015

Recently, techniques for detecting the movement of the object of energy saving, impact prevention, such as automatic door opening and closing has been applied to various fields. Doppler sensor does not receive a large impact on the environment, such as conventional infrared ray sensor, a problem with an ultrasonic sensor as a sensor which can compensate the temperature, noise, dust and so on. In this paper, when the object to be detected, the LED lamp is turned on 24 hours a Doppler sensor ON, if not switch to the OFF state, the illumination of the LED lamp has been developed for controlling the two-stage converter. Doppler sensor developed by applying the converter module and the power-saving control section leader and demonstrated the power savings.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.1814-1820
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• 2018

State estimation of power systems has become vital in recent days of power operation and control. SCADA and EMS are intended for the state estimation and to communicate and monitor the systems which are operated at specified time. Although various methods are used we can achieve the better results by using PMU technique. On placing the PMU, operating time is reduced and making the performance reliable. In this paper, PMU placement is done in two ways. Those are 'optimal technique with pruning operation' and 'depth of unobservability' considering incomplete and complete observability of a network. By Depth of Unobservability Number of PMUs are reduced to attain Observability of the network. Proposed methods are tested on IEEE 14, 30, 57, SR-system and Sub systems (1, 2) with bus size of 270 and 444 buses. Along with achieving complete observability analysis, single PMU loss condition is also achieved.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.699-701
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• 2011

The Next-generation IT technology has been evolving from single technique to another which has merged, converging characteristics. The government categorized the 5 essential technologies to secure competitiveness in designing system semiconductors as smart motor vehicle info-tainment platform, smart TV multimedia system, smart phone analog interface technique, smart convergence digital communication and RF techniques, and advanced power management for smart devices. Also, it designated smart phone, smart TV, smart motor vehicle, and smart pad as the key industries. Such core techniques will become the key technologies of semiconductor design to secure the competitiveness of the next generation smart devices and the techniques can be transferred to fab-less design companies. In this contribution, we analyze the issues and the problems of the SoC design trends for smart motor vehicle info-tainment platforms.

• 한국정보통신설비학회:학술대회논문집
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• 2006.08a
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• pp.35-38
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• 2006

Using the repeaters is indispensable to WiBro services. Repeater types are distinguished by usage, output power and required performance. In the paper, we have studied on the WiBro digital optic repeater design which has excellent performance characteristic than any other repeaters. WiBro has specific characteristic on modulation method TDD(Time Division Duplex)/OFDMA(Orthogonal Frequency Division Multiple Access) so that it demands specified H/W to design WiBro repeater. Switching technique has been introduced because of TDD characteristic in each amplifier on the repeater. Time Advance technique has been considered because of OFDM characteristic among RAS(Radio Access Station) and repeater. In this paper, we have studied on these techniques to increase repeater cell coverage and distance between RAS and repeater.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.325-329
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• 1998

This paper describes the controller for the improving speed control of the AC servo motor. The microprocessor provides an output to the difference in command. the servo system improves the characteristics of speed control. When the motor is running at the same speed as set by the reference signal, the speed encoder also provides a signal of the same frequency. Thus, the microprocessor controlled digital techniques enable to realize the flexible performance and control which was possible with time constant of linear acceleration/deceleration. We can know that optimal speed of machining center is 75msec in 30000mm/min and actually, 75msec is using on machining center. Finally experimental results prove excellent performance of this control system. This can be reduced error with more exact measure of actual speed. The system can be adaptable to CNC machine.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.292-295
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• 2001

This paper describes the implementation of UPS system controlled by the DSP. The digital techniques have been used tn overcome the problems of UPS system controlled by analog control circuits. By developing these systems using the digital technique we could increase the reliability and improve the electrical characteristics. And we designed and developed the system which is able to control UPSs and to monitor errors, statuses and actual values transmitted from UPS through internet. The UPSs also impose high demands on battery life time, reliability and energy-efficiency. These requirements can only be met by employing sophisticated battery management system(BMS). Therefore, a highly accurate, universal and inexpensive measuring system for BMS was developed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.2
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• pp.354-356
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• 2017

We focused on light management technology in amorphous silicon solar cells to suppress increase in absorber thickness for improving power conversion efficiency (PCE). $MgF_2$ and $TiO_2$ anti-reflection layers were coated on both sides of Asahi VU ($glass/SnO_2:F$) substrates, which contributed to increase in PCE from 9.16% to 9.81% at absorber thickness of only 150 nm. Also, we applied very thin $MgF_2$ as a rear reflector at n-type nanocrystalline silicon oxide/Ag interface to boost photocurrent. By reinforcing rear reflection, we could find the PCE increase from 10.08% up to 10.34% based on thin absorber about 200 nm.

• Journal of Advanced Navigation Technology
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• v.27 no.4
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• pp.469-472
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• 2023

If temperature management is required in factory or environmental monitoring, temperature can be measured by connecting various sensors wired or wirelessly. Surface acoustic wave sensors measure temperature using changes in acoustic waves on the sensor surface according to temperature, and are useful for wireless networks. In this paper, in order to build a wireless temperature measurement system in the 900 MHz frequency band, the temperature characteristics of the passive SAW sensor were measured, and the analysis and removal of multipath reflection wave effect inside the high temperature chamber were conducted. The resonant frequency of the SAW sensor was measured, and radio transmission/reception and multipath reflected wave removal techniques were proposed in the shielded chamber.