• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.7
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• pp.1-7
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• 2015

In this paper, we demonstrated a polarimetric fiber pressure sensor using a polarization-diversity-loop-based Sagnac interferometer(PDLSI) composed of polarization-maintaining fiber(PMF) and a fiber Bragg grating(FBG). In order to compare the pressure sensitivity for various kinds of PMF, three kinds of bow-tie PMF were employed as sensor heads. The maximum pressure sensitivity was measured as approximately -15.07nm/MPa, and an R2 value to represent sensor linearity was measured as ~0.992 at the sensor system using corresponding PMF over a pressure range of 0-0.3MPa. An FBG was utilized and located adjacent to the PMF segment for compensating temperature-induced errors in the measurement of pressure. The pressure sensitivity of the proposed sensor was improved by approximately four times compared with the previously reported pressure sensor based on polarization-maintaining photonic crystal fiber.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.11
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• pp.43-52
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• 1997

Ultrasonic sensors are widely employed in detecting range to a target by the virtue of their low cost and simplicity. However, the sensor's measurements are corrupted by systematic errors due mainly to the dependency of sound speed upon surrounding conditions and random errors of uncertain origin. In this paper, we present the results of research carried out to reduce these errors for increasing the reliability of an untrasonic sensor system to be used in orbotic or other automated system's range finding. The sensor system designed herein is in a peuliar structure having a reference target and two receivers. Echoes from a small reference target placed at a known distance are used for compensating the variations of sound speed according to the changes of sensing conditions. Unlike existing ones, the technique proposed can compensate the effects of temperature or any other physical parameters without an additional sensor dedicated to the compensation. The measurements by two redundantly employed receivers are fused to reduce random errors in a statistical sense. The correlation of the signals from the receivers sharing a hardware in part is considered in the fusion process. The methodology desicribed in this paepr is conceptually simple, easy to be implemented, and effetive to increase the accuracy of the sensor measurements as experimental results confirm.

• Journal of the Korean Ceramic Society
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• v.47 no.1
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• pp.19-25
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• 2010

Traditional Kr$\ddot{o}$ger-Vink (K-V) notation defines sites in ionic crystals as interstitial or belonging to host ions. It enables description and calculations of combinations of native and foreign defects, including dopants and substituents. However, some materials exhibit inherently disordered partial occupancy of ions and vacancies, or partial occupancy of two types of ions. For instance, the high temperature disordered phases of $Bi_2O_3$, $Ba_2In_2O_5$, $La_2Mo_2O_9$, mayenite $Ca_{12}Al_{14}O_{33}$, AgI, and $CsHSO_4$ are all good ionic conductors and thus obviously contain charged point defects. But traditional K-V notation cannot account for a charge compensating defect in each case, without resorting to terms like "100% substitution" or "Frenkel disorder". the former arbitrary and awkward and the latter inappropriate. Instead, a K-V compatible nomenclature in which the partially occupied site is defined as the perfect site, has been proposed. I here introduce it thoroughly and provide a number of examples.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.65-68
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• 2001

In the vector control methods of induction motor, the stator current is divided into the flux and torque component current. By controlling these components respectively, the methods control independently flux and torque as in the DC motor and improve the control effects. To apply the vector control methods, the position of the rotor current is identified. The indirect vector control use the parameters of the machine to identify the position of rotor flux. But due to the temperature rise during machine operation, the variation of rotor resistance degrades the vector control. To solve the problem, the q-axis is aligned to reference frame without phase difference by comparing the real flux component with the reference flux component. Then to compensate the slip, PI controller is used. The proposed method keeps a constant slip by compensating the gain of direct slip frequency when the rotor resistance of induction motor varies. To prove the validations of the proposed algorithm in the paper, computer simulations is executed.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.11
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• pp.654-659
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• 2005

An improved power supply for APD(Avalanche Photo Diode) with a received optical power monitoring circuit allows the received optical power increase temporary without of the degradation of the electrical signal. For the cost reduction and simple fabrication, an improved power supply has been proposed that it was designed for driving a APD as a receiving device of a wireless optical transmission system. It was demonstrated that it was possible to improve a dynamic range by compensating the temperature coefficient of the APD up to 1.0 V/$^{\circ}C$ through the power supply. Also, for an efficient transmission at the receiver end, a simple structure of a single cylindrical micro-lens configuration was used in conjunction with the laser diode to partially compensate a laser beam ellipticity. For this purpose, an astigmatism introduced by the micro-lens is utilized for the additional compensation of the beam ellipticity at the receiver end. In this paper, it is demonstrated that an efficient beam shaping is realized by using the proposed configuration consisting of the single lens attached to the laser diode.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.285-287
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• 2001

To obtain a high performance in a vector controlled induction machine, it is essential to know the instantaneous position of the rotor flux which depends on the rotor time constant. But the rotor time constant mainly varies due to the temperature rise in the motor winding, so real time compensating algorithm is necessary. This paper proposes that it uses short duration pulses added to the constant flux command current and then resultant torque command current produced by speed controller is utilized for the rotor resistance estimation. This method has advantages with a low computational requirement and does not require voltage sensors. The proposed method is proved by simulations.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.4
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• pp.401-409
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• 2007

Because of the various excellent characteristics of cast basalt materials. such as, anti-corrosion, anti-wearing, good hardness. high chemical stability, of which steel may not possess, the steel-basalt composite pipes are used in severe environments for compensating the defects of steel. However. without sufficient mechanical investigation prior to application. the basalt liners in steel-basalt composite pipes may be cracked and broken or the basalt liners are omitted from steel pipes in applications. In these cases, the merits of basalt materials may disappear and the basalt liners may not play their good roles as expected. Therefore, it is required that mechanical behavior of steel-basalt composite pipes and surrounding environments be fully examined before installation. The limit of bending moment with which steel-basalt composite pipe may safely endure is calculated and the limit curvature of the composite pipe in the safe range is presented in this paper. The temperature distributions and the thermal stresses are also computed and the limit difference of temperatures between inner and outer side of composite pipe is given together.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.2
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• pp.69-76
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• 2002

To obtain a high performance in a vector controlled induction motor, it is essential to know the instantaneous position of the rotor flux which depends on the rotor time constant. But the rotor time constant mainly varies due to the temperature rise in the motor winding, so real time compensating algorithm is necessary. This paper proposes that it uses short duration pulses added to the constant flux command current and then resultant torque command current produced by speed controller is utilized for the rotor resistance estimation. This method has advantage with a low computational requirement and does not require voltage sensors. The proposed method is proved by simulations and experimentals.

• Journal of IKEEE
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• v.26 no.4
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• pp.653-658
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• 2022

This paper presents a Maximum Torque per Ampere (MTPA) control algorithm for an interior permanent magnet synchronous motor (IPMSM) drive considering the permanent magnet (PM) flux linkage variations due to PM temperature variation. PM flux linkage are estimated in real time via a Gopinath style stator flux linkage observer and a torque error correction factor is calculated from the estimated PM flux linkage. A 2-dimensional (2D) MTPA look-up table (LUT) is developed to achieve the MTPA trajectory reflecting PM flux linkage variation for compensating torque error occurred by parameter variation. The proposed IPMSM control algorithm is verified through simulations.

• Korean Journal of Materials Research
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• v.14 no.3
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• pp.203-210
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• 2004

Effects of various pretreatments on the adhesion of copper-coated polymer films were investigated. Copper-coated polymer films were prepared by an electron cyclotron resonance-metal organic chemical vapor deposition (ECR-MOCVD) coupled with a DC bias system at room temperature. PET(polyethylene terephthalate) film was employed as a substrate material and it was pretreated by industrially feasible methods such as chromic acid, sand-blasting, oxygen plasma and ion-implantation treatment. Surface characterization of the copper-coated polymer film was carried out by AFM(Atomic Force Microscopy) and FESEM(Field Emission Scanning Electron Microscopy). Surface energy was calculated by based on the value of the contact angle measured. The adhesion of copper/PET films was determined by a pull-off test according to ASTM D-5179. It was found that suitable pretreatment of the PET substrate was required for obtaining good adhesion property between copper films and the substrate. In this study the highest adhesion was observed in sand-blasting, and then followed by those of acid and oxygen plasma treatment. However, the effect of surface energy was insignificant in our experimental range. This is probably due to compensating the difference in surface energy from various pretreatments by exposing substrate to ECR plasma for 5 min or longer at the early stage of the copper deposition. Therefore, it can be concluded that surface roughness of the polymer substrate plays an important role to determine the adhesion of copper-coated polymer for the deposition of copper by ECR-MOCVD.