• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.69-70
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• 2008

Automatic control systems(AVR, Governor, Synchronizer) installed $1970{\sim}1980$ in K-water were considered to be rehabilitated around 2000. Moreover, Korea Power Exchange market system was changed from PPA (Power Purchase Agreement) to a bidding system. Therefore, depending on the power quality, the power provider could achieve additional profits. It is the excitation system and governor that have the functions of enhancing power necessities. During the 20 to 30 years of generator operation, there were many major and minor problems. Examples are SCR burnout (Andong: Excitation system), hunting (Imha: governor), field circuit breaker failure (Chungju 1st: excitation system), the rise of leakage current (Chungju 2nd: excitation system), power supply burnout (Chungju 2nd: governor). These are the typical examples of malfunction which hindered the generator operation and, consequently, diminished the profit of power business. In order to satisfy the needs of the power market and prevent malfunctions mentioned above, the rehabilitation of AVRs and governors were executed. A new system was made to have the flexibility of ancillary service (GF, AGC, etc.), PSS function. With user friendly HMI software, it is more convenient for the operator to fulfill suitable maintenance. It was possible to connect SCADA system by opening protocol of AVR, governor for the efficiency of operation and maintenance.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.2
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• pp.106-113
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• 2002

Stencil is used normally as a mask for seeder pasting on pad of PCB. The objective of this study is to develop stencil cutting system and determine optimal conditions which make good-quality stencil by using a Nd:YAG laser. The effects of process parameters such as laser power, type of mask, gas pressure, cutting speed and pulse width old the cut edge quality were investigated. In order to analyse fille cut surface characteristics(roughness, kerf width, dross) optical microscopy, SEM photography and roughness test were used. As a result, the optimal conditions of process parameters were determined, and the practical feasibility of the proposed system is also examined by using a commercial Gerber file for PCB stencil manufacturing.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.10
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• pp.5062-5079
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• 2017

Malicious insider threats have increased recently, and methods of the threats are diversifying every day. These insider threats are becoming a significant problem in corporations and governments today. From a technology standpoint, detecting potential insider threats is difficult in early stage because it is unpredictable. In order to prevent insider threats in early stage, it is necessary to collect all of insiders' data which flow in network systems, and then analyze whether the data are potential threat or not. However, analyzing all of data makes us spend too much time and cost. In addition, we need a large repository in order to collect and manage these data. To resolve this problem, we develop an indicator-based behavior ontology (IB2O) that allows us to understand and interpret insiders' data packets, and then to detect potential threats in early stage in network systems including social networks and company networks. To show feasibility of the behavior ontology, we developed a prototype platform called Insider Threat Detecting Extractor (ITDE) for detecting potential insider threats in early stage based on the behavior ontology. Finally, we showed how the behavior ontology would help detect potential inside threats in network system. We expect that the behavior ontology will be able to contribute to detecting malicious insider threats in early stage.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.6
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• pp.192-201
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• 1997

The feedback control scheme of the pressure control system of the rear wheel steering gear which has relatively large volume and sprung load was built up in order to improve th response characteristic of the system. The control algorithm chosen was a feedback compensator joined by a feedfoward compensator and the model matching method was used in the process of control system design. The structures and properties of the reference models were inspected and the parameters of the controller were decided. The improvement of the response characteristic of the pressure control valve by means of the feedback control is affirmed. Particularly, when the order of the system model is higher than the 2nd order, the effectiveness of the feedback control on the improvement of the response characteristic of the valve is distinct. And the convenience of the model matching method is the process of control system design is confirmed as well.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.8
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• pp.1407-1411
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• 2008

In material processing, a laser system with optimal laser parameters has been considered to be significant. Especially, the laser scribing technology is thought to be very important for fabricating DSSC(Dye sensitized solar eel!) modules with good quality. Moreover, the $TEM_{00}$ mode laser beam is the most dominant factor to decide the IPCE(Incident photon to current conversion efficiency) characteristics. In order to get the $TEM_{00}$ mode, a pin-hole is inserted within a simple pulsed Nd:YAG laser resonator. And the spatial field distribution is measured by using three size pin-hole diameters of 2.0, 6.0mm respectively. At that moment, each case has the same laser beam energy by adjusting the discharge voltage and pps(pulse per second). From those results, it is known that the pin-hole size of 2.0mm has the perfect $TEM_{00}$ mode. In addition, at the charging voltage of 1000V, 10pps and the feeding speed of 1.11mm/sec, the SEM photo of FTO(Fluorine-doped tin oxide) thin film layers shows the best scribing trace.

• Journal of the Korean Applied Science and Technology
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• v.19 no.3
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• pp.174-180
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• 2002

In recent days, the study of a new phosphorescent phosphor has been performed in order to overcome the defect of sulfide phosphor and increase the brightness and long after-glow characteristic of phosphorescent phosphor. Particularly, sulfide phosphor usually used is so chemically unstable that the study of oxide phosphors are processing. $Eu^{2+}$, $Nd^{3+}$ doped Ba-Al-O phosphors sintered at $600{\sim}1500^{\circ}C$ for 2hours had the PL emission spectrum and after-glow over $1200^{\circ}C$. In this system, as the mole concentration of alumina increases, emission bands of phosphors moved from 500nm to 380nm. The optimum concentration of flux was 5wt% and after-glow characteristics of phosphors were found at the host material molar ratio ($BaCO_{3}:Al_{2}O_{3}$), 1:1 and 1:3.

• Journal of the Korean Geographical Society
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• v.46 no.2
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• pp.115-133
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• 2011

Yamada's mountain ordering is to be said as an upward system, because the area and volume of the mountains become the larger as more than two lower order mountains constitute the higher order mountain. However, his mountain ordering shows some limitations to totally understand the mountain systems and to systematically manage the various kinds of mountainous informations. Because the independent third, fourth and so on, as well as the second lower order mountains are included in the higher order mountain. In order to solve the problem above, the downward system is suggested as the alternative of his upward system. The downward system means that the higher order mountain is classified into the second lower order mountains, and the second lower order mountain is classified into the third lower order mountains and finally the 2nd order mountain classified into the 1st order mountains. The method to classify a certain mountain systematically into all mountainous elements and the new nomenclature to be used for the classified elements are developed, using the downward system above. And the structure of database could be also suggested for the integrated and systematic management of mountain informations.

• Proceedings of the KIEE Conference
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• 1998.11b
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• pp.429-431
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• 1998

In this paper, the sun-seeker control system that is driven by DC motor is modeled on linear 2nd order time invariant system under some assumptions. For the analysis of output characteristics, theory is developed using digital control methods. Computer simulation and numerical analysis has been performed.

• Korea Journal of Hospital Management
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• v.21 no.3
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• pp.65-70
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• 2016

The Long-Term Care Hospital (LTCH) accreditation system was initiated in 2013 in the form of mandatory accreditation system in order to improve patient safety and the quality of medical service at LTCHs. By June 2016, the accredited LTCHs were 76.2%. This research was conducted to review the implementation process in the first cycle and to promote development of the second cycle of LTCH accreditation system. There are some changes which reinforced the accreditation standards, accreditation survey, and public access to accreditation results in order to strengthen patient safety in the first cycle LTCH accreditation system. LTCHs which participated in the accreditation system achieved certain outcomes in respect to patient safety and employee satisfaction. However, there are several urgent problems in placement criteria of night duty health care providers, reinforcement plans in the accreditation system, and incentives for accredited hospitals. In order to solve these problems, the most important thing is to clearly recognize the fact that the healthcare accreditation system is not the means for control and regulate hospitals but a system to induce hospitals to continue to strive for improvements in patient safety and medical service quality. In addition, it is required that LTCHs, accrediting agency and the Ministry of Health and Welfare compromise and cooperate to seek solutions every time issues related to the accreditation system arise.

• International Journal of Ocean System Engineering
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• v.2 no.1
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• pp.8-15
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• 2012

An experimental study was carried out in order to understand the kinematics of bichromatic waves. Bichromatic waves are generated in a two-dimensional wave tank, and measured by panorama PIV technique, which allows the flow fields to be captured with respect to a spatial coordinate system. We compared wave profiles and velocities of wave particles obtained by experiment with theoretical results using Stokes 1st and 2nd order waves. The velocity distribution at wave crest and trough of the highest and lowest point of a bichromatic wave are investigated in this study.