• Journal of IKEEE
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• v.19 no.2
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• pp.225-231
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• 2015

The parameter K which decides how much to convert wind energy to electric energy in MPPT(maximum power point tracking) control of wind turbine system using torque controller is changed because blade shape and air density change. If the parameter K is not optimal value, power lose occur. The changed parameter K is important issue in wind turbine system. In this paper, to solve this problem, considering wind turbine system using back-to-back converter control and torque control, we propose the adaptive MPPT algorithm which performs fast control by using initial K, estimates mechanical power using Kalman filter method, uses the estimated mechanical power as input for MPPT algorithm again, and consequently performs optimal MPPT control.

• Journal of IKEEE
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• v.21 no.3
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• pp.174-184
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• 2017

This paper proposes a torque predictive control for dynamic performance improvement of clamping force in electro-mechanical brake (EMB) for railroad cars. In general, pneumatic braking system (PBS) is used for railroad cars. It is sensitive depending on environmental changes and it has increasing idle running time because of slow dynamic response. Additionally, the PBS has low braking efficiency in case braking torque more than standard value is applied to the brake system such as emergency braking. In order to overcome these disadvantages of the PBS, the EMB is used for the railroad cars. The EMB for railroad cars has advantages that increasing the fuel efficiency and design flexibility because it is able to decrease vehicle weight of railroad cars and secure space for design. In this paper, control method for dynamic performance improvement of clamping force in EMB for railroad car is proposed. The effectiveness of the proposed control method is verified by the simulation results.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.4
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• pp.626-632
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• 2001

Ectodermal dysplasia is a hereditary disease characterized by congenital dysplasia of one or more ectodermal structures. Intraorally, common findings are anodontia or oligodontia, conical teeth, and, consequently, generalized spacing. This case presented the oral rehabilitation of a child with hypohidrotic ectodermal dysplasia. Oral rehabilitation is important from functional, esthetic, and psychologic perspectives. Due to the absence of teeth, the volume of alveolar bone and its growth are decreased, resulting in a loss of vertical dimension and protuberant lips. The treatment involved increasing the patient's vertical dimension of occlusion, fabricating a maxillary partial denture, and using magnets to help retain the mandibular partial denture. A 5-year 7-month old Korean boy was referred to the pediatric department for examination, evaluation and treatment of his disorder. we used magnets on '73 and '83 for enhanced retention of a mandibular overdenture. The magnet used in this case was the Magfit system(GC Co., Japan).

• Journal of the Korean Magnetics Society
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• v.8 no.5
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• pp.317-332
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• 1998

The adiabatic nuclear demagnetization cooling technique has reduced the lowest accessible temperature to the regime of microkelvin, and consequently led to a large expansion in microkelvin physics such as solid and liquid $^{3}He$, superconductivity of noble metals, spin glass transition, and nuclear magnetism. Our ability to reach temperature in microkelvin regime has greatly facilitated by the developments of dilution refrigerator and superconductivity magnet. It is appropriate to divide nuclear demagnetization cooling into two categories; those in which only the nuclear spin system is cooled down and those in which the lattice and conduction electrons in the refrigerant or the specimen are also cooled by the cooling power of nuclear spin system. The former cooling technique has utilized to investigate the nuclear magnetism at temperature in nanokelvin regime. The latter is widely used in studying the phenomena occurring in microkelvin regime. In this review paper, we will discuss the basic principles of nuclear demagnetization cooling and its applications. This work is supported by the Basic Science Research Institute Program under contract number BSRI-97-2404.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.212-212
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• 1999

Ar-O2 분위기의 Plasma 표면 처리된 OPP 의 polymer 위에 약 400$\AA$ 정도로 sputter 코팅된 Al의 부착력에 관하여 연구를 하였다. 금속과 polymer와 같이 성질이 서로 다른 물질이 서로 결합할 때 접착력은 제품의 성능과 신뢰도를 결정하는데 매우 중요한 인자이다. 최근 고분자재료의 표면을 플라즈마 처리 (plasma surface treatment)에 의해 고분자와 금속도포(coating) 층간의 접착력향상에 따라, 증착필름 및 인쇄용 필름 등의 기능도 향상시킬 수 있다. 저온 plasma를 이용한 표면처리는 plastic 재료가 가지고 있는 기본적인 특성을 저해하지 않고, 그 표면 층만을 개량하는 plasma 또는 sputter etching 갚은 electrical discharge 방법은 진공 증착 방식에서 많이 사용되고 있다. 7$\mu\textrm{m}$의 두께 OPP polymer를 10m/min의 속도로 OPP의 표면을 연속 plasma pretreatment를 하였다. 5$\times$10-2torr에서, PEM(Plasma Emission Monitor)를 이용하여 plasma intensity에 따른 Ar/O2비를 변화시키면서 test를 하였다. AFM과 XPS를 이용하여 OPP의 표면분석을 하였다. 이 plasma처리는 기존의 D.C plasma 처리 방식과는 달리 Midium frequency AC voltage hollow cathod 방식으로 plasma를 발생된 high energy plasma 분위기를 만들 수 있다. 이러한 방식은 -cycle일 때 plasma로부터 발생된 전자가 polymer 표면을 bombard 하게 되고, +cycle 일 때 polymer 표면이 cathod 가 되어 active ion에 의해 sputtering 이 된다. 이때 plasma 처리기의 polymer 기판 후면에 magnet를 설치하여 높은 ionization을 발생시켜 처리 효과를 한층 높여 주었다. 이 plasma 처리는 표면 청정화, 표면 etching 이 동시에 행하는 것과 함께 장시간 처리에 의해 표면에서는 미세한 과, C=C기, -C-O-의 극성기의 도입에 의한 표면 개량이 된다는 것을 관찰할 수 있다. OPP polymer 표면을 Ar 100%로 plasma 처리한 경우 C-O, C=O 등의 carbonyl가 발생됨을 알 수 있었다. C-O, C=O 등의 carbynyl polor group이 도입됨에 따라 sputter된 Al의 접착력이 향상됨을 알 수 있으며, TEM 관찰 결과 grain size도 상당히 작아짐을 알 수 있었다.

• Journal of the Korean Vacuum Society
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• v.7 no.4
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• pp.390-396
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• 1998

Neutral stream was generated from Helicon plasma source and was applied to etch silicon for the purpose of preventing physical and electrical damages from the bombardment of charged particles with high translation energy. By installing a permanent magnet and applying positive bias beneath the substrate, the cusp-magnetic and electric fiddles were generated in order to remove the charged particles from the downstream plasma. As a result, the electron density and ion density in the vicinity of the substrate were reduced by 1/1000 and 1/10, respectively. The directional etching of silicon was observed and the etch rate was found to be very low to below 100 $\AA$/min at a pressure of $8.5{\times}10^{-4}$ Torr, when $Cl_2$ and 10% $SF_{sigma}$ etchant gases were used.

• Journal of Hydrogen and New Energy
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• v.27 no.1
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• pp.114-120
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• 2016

This paper describes generating efficiency characteristics of the double acting Stirling engine/generator for domestic small-scale CHP (Combined Heat and Power) system. In small distributed generation applications, Stirling engine has competition from fuel cell, microturbine and etc. In order to be economical in the applications, a long life with minimum maintenance is generally required. Free piston Stirling engine (FPSE) has no crank and rotating parts to generate lateral forces and require lubrication. Double acting Stirling engine/generator has one displacer and two power piston which are supported by flexure springs. Two power pistons oscillate with symmetric displacement and are connected with moving magnet type linear generators for power generation from PV work. In experiments, 1 kW class double acting free piston Stirling engine/generator is fabricated and tested. Heat is supplied to hot end of engine by the combustion of natural gas and converted to electric power by linear generators which are assembled with power pistons. The electric parameters such as voltage, current and phase are measured with for variable flow rate of fuel gas. Especially, generating efficiency of FPSE is measured with three different measurement methods. Generating efficiency of the double acting Stirling engine/alternator is about 24%.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.11
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• pp.1675-1680
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• 2013

Recently, the permanent magnet linear synchronous motor as low noise, high speed and high thrust force transportation system has been proposed but this motor causes an increase of material cost because of its characteristic arranging the armature on the full length of transportation lines when this system is applied to the long distance transportation system. Therefore, we suggested discontinuous arrangement method of the armature to solve this problem. However, Detent force which causes thrust force ripple generating noise, vibration and decline of performance is generated when a mover pass between the armatures. Thus, in this paper, we examined characteristic of detent force to reduce the end edge effect according to the end edge teeth's height and auxiliary teeth and suggested the shape that can the most reduce the detent force.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.4
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• pp.757-764
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• 2018

This paper describes the design and implementation of a 1hp class two-phase type BLDC fan motor used in an air conditioning system. The BLDC motor, which is implemented in this study, is not a commutator motor type with excellent lifetime and durability and is driven by two phase power source. The most important target specification of a motor used in an air conditioning system is that it has a high efficiency at the rated operating point. For this purpose, we designed the stator shape of the BLDC motor, the design of the rotor magnet, and the control circuit for driving. The BLDC motor has a structure where the motor part, the control part, and the power part are integrated. The finite element analysis was used to calculate the characteristics of the BLDC motors, and the conformity of the design results was confirmed by fabricating and testing the prototype model.

• Environmental Mutagens and Carcinogens
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• v.25 no.1
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• pp.25-31
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• 2005

The objective was to use MR imaging to provide a template of posterior fossa development during the late stages in the chick embryos. The MR findings were then correlated with histological data. Fourteen normal formalin-fixed embryonic specimens with a gestational age of 14 to 20 days were examined with 1.5 Tesla unit MRl using a conventional clinical magnet and pulse sequences. The MR findings were correlated with the whole-mount histological specimens. Resolution of the morphological features of posterior fossa development in embryos greater than 14 days gestational age was possible. Development of cerebellum, brain stem, 4th ventricle and bony posterior fossa was documented. In the 14-day-old embryos, a premordial cerebellum was visualized in the enlarged bony posterior fossa, and it covered the the roof of the primitive fourth ventricle. The bony posterior fossa grows at the same rate along the supratentorial skull. The supratentorial skull and the rostral part of the brain grows at the same rate. The cerebellum begins to grow later than the rostral part of the brain. In the 19- to 20-day-old embryos, MRl revealed the rapid development of the cerebellar hemispheres, along with an increase in volume manifested by the more typical mushroom-shaped configuration observed in the newly hatched. At this stage, the cerebellum almost completely filled the posterior fossa and covered the entire fourth ventricle. The brain stem grew steadily, but the volume change was too subtle to evaluate. Features of cerebellar histogeneis were beyond the resolution of MRl. However, there were lots of artifacts in the features of the bony posterior fossa. An MR template of normal posterior fossa development would be useful to avoid confusion of normal development with abnormal development and to identify the expected developmental features when provided the estimated gestational age of a embryo.