• The Journal of the Acoustical Society of Korea
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• v.21 no.8
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• pp.766-771
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• 2002

In this study, we have developed a 3-dimensional diagnostic ultrasonic sector probe using a convex type ultrasonic probe with 128 active elements. The probe was made to operate at the center frequency of 4.5㎒ with the bandwidth of 66%. The driving part was designed to rotate the axis of the convex probe by means of a step motor equipped with reduction gears and spur gears attached to the motor so that the probe could enable us to acquire a series of 2-dimensional images to construct a 3-dimensional image. Acoustic cover of the probe was made of polymers to have the same radius of rotation as that of the convex probe. The controllability of the rotation angle and the structural stability of the probe were confirmed through experimental 3-dimensional images obtained using the developed 3-dimensional sector probe.

• Journal of Advanced Navigation Technology
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• v.15 no.1
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• pp.83-90
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• 2011

The technique of localization is the core technology for information exchange or environment monitering to measure the position of an object or person. Today, the techniques of localization have been studied extensively and it can be applied to logistics, medical, robotics, etc. But, a lot of money to apply technique of localization is needed. Hence in this paper, we proposed AoA localization system based on Zigbee at low cost. The System measured the RSSI value by rotating the directional antenna using a step motor and Zigbee module. When the measured RSSI is the largest, the receiver measures the angles from beacons which are located at the corners with the rotating angle of a stepping motor and the position of the receiver will be calculated by appling AoA localization method. The measured results show an error about 35~36 cm.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.3
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• pp.283-289
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• 2010

Owing to the increasing worldwide interest in green technology and renewable energy sources, flywheel energy storage systems (FESSs) are gaining importance as a viable alternative to traditional battery systems. Since the energy storage capacity of an FESS is proportional to the principal mass-moment of inertia and the square of the running speed, a design that maximizes the principal inertia while operatingrunning at the highest possible speed is important. However, the requirements for the stability of the system may impose a constraint on the optimal design. In this paper, an optimal design of an FESS that not only maximizes the energy capacity but also satisfies the requirements for system stability and reduces the sensitivity to external disturbances is proposed. Cross feedback control in combination with a conventional proportional-derivative (PD) controller is essential to reduce the effect of gyroscopic coupling and to increase the stored energy and the specific energy density.

• Korean Journal of Crystallography
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• v.9 no.1
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• pp.30-38
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• 1998

A new frequency weighing sensor was applied to grow Bi12GeO20 crystals in the auto-di-ameter control system of Czochralski method. The rotation rate was varied in the range of 23 to 21 rpm to preserve flat interface in a given heat configuration. To prevent the constitutional super-cooling from the evaporation loss, 105% stoichiometric amount of Bi2O3 was employed, equivalent to 6.18 molar ratio of Bi2O3 to GeO2. Transparent and light brown Bi12GeO20 single crystal in uniform diameter was grown. The dislocation density was determined to be 103/cm2 corresponding to the optical quality in commercial applications. The grown crystal measured diameter 25 mm and length 70 mm and the preferred growth direction was confirmed to be <110>.

• Journal of the Korean Institute of Gas
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• v.15 no.3
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• pp.47-52
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• 2011

The purpose of this paper analyzes and studies to seek the failure examples of electronic control actuators for engine in liquified petroleum gas vehicle. The first, it was verified phenomenon for intial starting damage and no-acceleration of engine because of occasionally fuel feeding interception by clogged of emergency cutting solenoid valve filter. The second, the contact resistance produced in the connecting part of engine control relay because of no fully surface contacting by processes and assembly badness. It was displayed phenomenon of re-starting badness. The actuator that idle speed control system was sticked inside because of intake-air decreasing by carbon deposit. As a result, it was verified the phenomenon of disharmony that repeated up and down the engine revolution.

• Korean Journal of Remote Sensing
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• v.25 no.2
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• pp.133-143
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• 2009

This paper describes differences of performance when the orbit attitude model is applied to the respective images obtained from two different types of satellite. The one is Spot that rotates its pointing mirror and the other is Kompsat-2 that rotates its whole body when they obtain imagery for target. Our research scope is limited to the orbit-attitude model only as its good performance was proved in prior investigation. Model performances between two images were compared with sensor model accuracy and 3D coordinates calculation. The results show performances of the orbit-attitude model for each image type were different. For Spot imagery, the model required attitude angle to be included as adjustment parameters. For Kompsat-2 imagery, the model required high-order parameter for adjustment. This implies that satellite sensor model may be applied differently in accordance with platform's attitude control scheme and accuracy. Understanding of this information can be a base for improvement and development of model and application for new satellite images.

• Journal of the Korean Magnetics Society
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• v.13 no.1
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• pp.41-46
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• 2003

This study deals with the Benard flow of magnetic fluids in a rectangular cavity. The ratio of height to length of the cavity is 1 : 4 and the bottom of the cavity is assumed to be a heating face while the other sides are to be cooling faces. When magnetic field was equally impressed, considering the internal rotation of the elementary ferromagnetic particle, we found the following result from the numerical analysis of the GSMAC algorithm applied to the equations for the magnetic fluid. Benard flow was controled by the intensity and the direction of magnetic fields, and a critical point was appeared when the magnetic field near H=-7000 was applied.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.69.2-69.2
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• 2015

세종시대의 장영실(蔣英實)은 두 가지의 자동 물시계를 제작했다. 이미 잘 알려진 보루각루(報漏閣漏, '자격루'로 불림)는 1434년에 완성되어 국가 표준시계로서의 역할을 수행했고, 이어서 만들어진 흠경각루(欽敬閣漏, 1438년 제작)는 세종을 위한 특별한 시계였다. 이 연구는 흠경각(欽敬閣)에 설치한 물시계에 대한 것이다. 당시 흠경각은 세종의 정치적 구상을 위한 장소로 사용됐다. 이는 흠경각루를 이루고 있는 외형 부분인 가산(假山)에 빈풍사시(豳風四時)의 풍경을 그린 점과 의기(倚器)를 설치한 정황에서 알 수 있다. 빈풍사시의 그림은 당시에 유행하던 그림 화법으로 계절에 따른 농사일이 그려져 있어 농사짓는 백성들의 어려움을 살필 수 있었다. 또한 물시계와 함께 작동되는 의기(倚器)는 누수(漏水)에 의해서 그릇에 물이 담겨져 균형을 이루거나 기울어지는 것을 권력의 모습으로 비유하여 보여주었다. 우리는 흠경각루의 문헌내용을 분석하여 먼저 외형모습, 내부의 구성요소에 대한 것을 연구했다. 이러한 연구 성과를 확장하여 내부의 작동메커니즘의 기초설계를 실시했다. 흠경각루의 시간을 유지하는 중요한 요소는 물시계, 수차, 천형시스템의 유기적인 운영이다. 물시계의 유량실험을 통해 수압과 유량의 관계를 분석하고, 수차의 회전과 제어를 담당하는 천형시스템의 모델을 제시했다. 또한 연구과정에서 얻어진 자료의 일부를 전통천문학 교육에 활용하기 위한 웹페이지(history.kasi.re.kr)를 한국천문연구원 서버를 통해 구축중에 있다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.3
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• pp.591-598
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• 2016

The final step of driving a car is parking, which is the most difficult part for people learning to drive. Parking in narrow parking spaces is difficult for both ordinary drivers and beginners. To solve this problem, the development of SPAS (Smart Parking Assist System), ACC (Automatic Control System) improves the convenience of drivers. In addition, parking assistance systems have been developed to recognize more accurately the surrounding environment to the driver using the ultrasound, camera, thermal camera, and radar. This paper proposes the reverse turning radius to process images as if the camera is located in the center of the vehicle regardless of the actual camera position. In addition, it generates the parking guidelines through verification using the vehicle.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.461-464
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• 2001

본 연구에서는 생체 임피던스를 이용하여 3채널 상지(upper arm) 운동 분석 시스템을 제작하였다. 각 채널은 상지의 외전(supination)과 내전(pronation), 팔꿈치(elbow)의 폄과 굽힘, 손목(wrist)의 평과 굽힘에 따른 각 관절의 임피던스 변화를 얻을 수 있도록 설계되었다. 상체 임피던스는 전극의 부착위치에 의존하므로 정밀한 감지를 위해 상지 운동에 대한 임피던스의 변화와 각도계(goniometer)의 각도 변화와의 상관관계를 통하여 상관 관계가 높고, 변화량이 가장 크고 다른 관절의 움직임에 따른 영향이 최소인 곳을 찾아 이를 최적의 전극 위치로 정하였다. 그리고, 선정된 최적의 전극 위치에서 임피던스 변화를 얻어 상지 운동을 분석해 보았다. 최적의 전극 위치에서 손목과 팔꿈치의 각도 변화와 임피던스 변화의 상관 계수는 각각 0.94, -0.97로 아주 높은 상관 관계를 보였다. 또한 이전의 다른 연구에서 임피던스 방법으로 구현해 본적이 없는 팔의 회전(rotation)도 분석이 가능하였다. 이 시스템은 피검자의 동작에 거의 제한을 주지 않고, 가벼우며, 장시간 측정이 용이할 뿐만 아니라 시스템 구성이 영상 분석기에 비해서 단순하다는 장점을 가지고 있다. 본 연구에서 제안하는 방법은 재활과 생체역학, 로봇의 원격 제어, 그리고 가상 현실에서의 동작 구현 등에 활용 할 수 있을 것으로 사료된다.