• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.3
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• pp.190-194
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• 2003

Dielectric thin films of (P $b_{0.72}$,L $a_{0.28}$) $Ti_{0.93}$ $O_3$ (PLT(28)) have been deposited on Pt(111)/Ti/ $SiO_2$/Si(100) substrates in-situ by pulsed laser deposition using different annealing and deposition Processes. We have investigated the effect of hydrogen annealing on the ferroelectric properties of PLT thin films and found that the annealing process causes the diffusion of hydrogen into the ferroelectric film resulting in the destruction of polarization. We have tried to form the film by a two-step deposition process In order to improve electrical property. Two-step process to grow PLT films was adopted and verified to be useful to enlarge the grain size of the film and to reduce the leakage current characteristics. Structural properties and electrical properties including dielectric constant, ferroelectric characteristics, and leakage current of PLT thin films were shown to be strongly influenced by grain size. The film deposited by using two-step Process including pre-annealing treatment has a strongly(111) orientation. However, the films deposited by using single -step process with hydrogen annealing process show the smallest grain size. The film deposited by using two-step process including pre-annealing treatment shows the leakage current density of below 10$^{-7}$ A/c $m^2$ for the field of smaller than 100 kV/cm. However, the films deposited by using single-step process with hydrogen annealing process and pre-annealing process show worse leakage current density than the film deposited by using two-step process including pre-annealing treatment.tment.

• Journal of Power Electronics
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• v.17 no.1
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• pp.127-135
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• 2017

Recently the researches on modular multi-level converter (MMC) are being highlighted because high quality and efficient power transmission have become key issues in high voltage direct current (HVDC) systems. This paper proposes an improved pre-charging method for the sub-module (SM) capacitor of MMC-based HVDC systems, which operates in the nearest level control (NLC) modulation and does not need additional circuits or pulse width modulation (PWM) techniques. The feasibility of the proposed method was verified through computer simulations for a scaled 3-phase 10kVA MMC with 12 SMs per each arm. Hardware experiments with a scaled prototype have also been performed in the lab to confirm the simulation results.

• English Language & Literature Teaching
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• v.17 no.4
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• pp.339-356
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• 2011

This study explored pre-service English teachers' participation in the development of a rubric and examined evaluation of their own English poetry. The current study would investigate: 1) the pre-service English teachers' perception as a rubric developer and self-evaluator, 2) the number of analytic area that the participants included in their rubrics and the scoring scheme that they designed in their rubrics, and 3) the inter-rater differences between self-assessemnt and expert-assessment across analytic areas. Twenty-four EFL learners participated in the current study. The researchers analyzed the learners' own English poetry, their field notes which contained the process of their writing, their rubrics, scores of self-assessment, and expert raters' scores. The results revealed that learners showed positive responses on learner-directed assessment, that 'content' is the most important area, and that inter-rater difference is small across all analytic areas.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• autumn
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• pp.481-484
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• 2003

Recently, the importance of Pre-construction is gradually increasing in construction business. In addition to increasing greatness, Pre-construction affect to success or failure of projects. However, current domestic construction business doesn't constitute exact concepts and systems, and there are a lot of problems such as disorganize management of construction because most of Pre-construction depends on supervisors' experiences. Therefore, according as doing this study, We are going to analyze the tendency of Pre-construction step and bring up designed operation systems between departments in construction company. So we can expect to develop efficiency by excluding unnecessary operation and formulating more improved operation process.

• Wind and Structures
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• v.29 no.5
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• pp.339-359
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• 2019

Pre-stressed concrete poles are among the supporting systems used to support transmission lines. It is essential to protect transmission line systems from harsh environmental attacks such as downburst wind events. Typically, these poles are designed to resist synoptic wind loading as current codes do not address high wind events in the form of downbursts. In the current study, the behavior of guyed pre-stressed concrete Transmission lines is studied under downburst loads. To the best of the authors' knowledge, this study is the first investigation to assess the behaviour of guyed pre-stressed concrete poles under downburst events. Due to the localized nature of those events, identifying the critical locations and parameters leading to peak forces on the poles is a challenging task. To overcome this challenge, an in-house built numerical model is developed incorporating the following: (1) a three-dimensional downburst wind field previously developed and validated using computational fluid dynamics simulations; (2) a computationally efficient analytical technique previously developed and validated to predict the non-linear behaviour of the conductors including the effects of the pretension force, sagging, insulator's stiffness and the non-uniform distribution of wind loads, and (3) a non-linear finite element model utilized to simulate the structural behaviour of the guyed pre-stressed concrete pole considering material nonlinearity. A parametric study is conducted by varying the downbursts locations relative to the guyed pole while considering three different span values. The results of this parametric study are utilized to identify critical downburst configurations leading to peak straining actions on the pole and the guys. This is followed by comparing the obtained critical load cases to new load cases proposed to ASCE-74 loading committee. A non-linear failure analysis is then conducted for the three considered guyed pre-stressed concrete transmission line systems to determine the downburst jet velocity at which the pole systems fail.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.36 no.3
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• pp.91-102
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• 2020

This study examined the apartment sale in lots system from 1960s to 1970s in Seoul from a historical perspective, with the focus on the concept and changes of pre-sale in lots system. By tracing back historical context and application of the system in that period through the analysis of the advertisements for apartment sale, we found out the hidden side of the apartment pre-sale in lots system from the public's point of view, and its impact and meaning on the formation of our current residential culture. In the 1960s and 1970s, the apartment sale in lots system based on the pre-sale in lots system formed strong seller's market and it has been the main reason for imposing the wrong residential awareness that led the public to recognize housing as a means of property growth. Even now, the current apartment sale in lots system remains to be a supplier-oriented one, and lots of people tend to regard housing as investment method. That is, this mechanism is not only still working but one of the fundamental causes of impoverishing our residential culture. It is necessary to reconsider the pre-sale in lots system and the apartment sale in lots system in relation to the public of housing.

• ETRI Journal
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• v.37 no.6
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• pp.1154-1164
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• 2015

This paper proposes a fully sensorless driver for a permanent magnet synchronous motor (PMSM) integrated with a digital motor controller and an analog pre-driver, including sensing circuits and estimators. In the motor controller, a position estimator estimates the back electromotive force and rotor position using a sliding-mode observer. In the pre-driver, drivers for the power devices are designed with a level shifter and isolation technique. In addition, a current sensing circuit measures a three-phase current. All of these circuits are integrated in a single chip such that the driver achieves control of the speed with high accuracy. Using an IC fabricated using a $0.18{\mu}m$ BCDMOS process, the performance was verified experimentally. The driver showed stable operation in spite of the variation in speed and load, a similar efficiency near 1% compared to a commercial driver, a low speed error of about 0.1%, and therefore good performance for the PMSM drive.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1676-1678
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• 2000

The electrical characteristics of $Pre_{6}O_{11}$-based ZnO varistors doped with $Y_{2}O_3$ in the range 0.0-4.0 mol% sintered at 1350$^{\circ}C$ were investigated. The varistor without $Y_{2}O_3$ exhibited very low nonlinearity, which the nonlinear exponent is 4.54 and leakage current is 87.91${\mu}A$. However the varistors with $Y_{2}O_3$ exhibited in the range of 30.00-51.19 in the nonlinear exponent and 0.52-3.89${\mu}A$ in the leakage current. Especially, the varistor with $Y_{2}O_3$ of 0.5 mol% exhibited the nonlinear exponent of 51.19 and the leakage current of 1.32${\mu}A$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.1
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• pp.142-147
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• 2018

Private electrical facilities are judged whether it is suitable for the insulation aging condition of their incoming underground cables using DC leakage current test method. In the case where the service point of utility is the secondary side of cut out switch installed in the electric pole, there is a problem that it is difficult to separate the lightning arresters(LA) because of their high position of the pole. Therefore, the field test voltage is applied at value lower than DC 30 kV, which are stated in the inspection guideline. However, this test could reduced the insulation performance of the LA by accelerating the electrical stress of the metal oxide varistor element in the pre-breakdown region. In this study, we analyzed the relationship between the DC test voltage and the leakage current using the non-destructive DC high voltage equipment with leakage current measurement function. The results show that the leakage current increases sharply above the specified test voltage. As a consequence, it could be contributed to improve insulation aging inspection method by selecting the possible test area on the VI characteristic curve of the pre-breakdown area of the LA.

• Journal of Intelligence and Information Systems
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• v.9 no.2
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• pp.171-184
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• 2003

A project planning is one of the most important processes that determines success and failure of the project. A pre-project planning is also essential job for information system implementations at the early stage of project planning, especially for management information system like ERP. However, pre-project planning is very difficult, because lots of factors and their relationships should be considered. Pre-project planning of ERP implementation has been done by project manager's own knowledge and experiences. In this article, we propose a system that help project manager to make a pre-project plan of ERP project with case-based reasoning(CBR) framework. The proposed CBR system saves previous cases of ERP pre-project planning in the case base. Then, the system finds the most similar case with the current pre-project planning problem. Project manager can make a pre-project plan by adjusting the most similar case. From the interview with project managers, we collect some field cases of ERP implementation. We organized these cases by using XML(Extensible Markup Language), which is good for representing hierarchical information. XML gives us some flexibilities to correct and maintain cases. We make a prototype system, PPSS(Project Planning Support System) that help project manager to make a pre-project plan of ERP implementations. The object of the system is to support project manager to make a pre-project plan of ERP. We hope the result of the study can be applied to other information systems. Our research would be extended to cover other stages of project planning.