• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.10
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• pp.40-45
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• 2007

Lightning warning system plays an important role in protecting human life and other facilities from lightning return strokes. This paper dealt with lightning positioning algorithms and circuits as a main function of lightning warning system, which monitor movements and activities of thunderclouds. Electric field component produced by lightning discharge is detected by the configuration of a whip antenna and a narrow-band resonance amplifier with center frequency of 300[kHz]. Measurement circuit of magnetic field waveform consists of a crossed-loop coil and an integral amplifier, and its frequency bandwidth is ranges from 5[kHz] to 1.2[MHz]. The polarity of lightning discharge is discriminated by electric field component. After-fixing the polarity, we can calculate the direction and distance of lightning discharge by the peak and the zero-cross time of magnetic field waveform.

• Clinics in Shoulder and Elbow
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• v.21 no.4
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• pp.186-191
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• 2018

Background: To determine the normal range of humeral head positioning on magnetic resonance imaging (MRI). Methods: We selected normal subjects (64 patients; group A) to study the normal range of humeral head positioning on the glenoid by MRI measurements. To compare the MRI measurement method with the computed tomography (CT), we selected group B (70 patients) who underwent both MRI and CT. We measured the humeral-scapular alignment (HSA) and the humeral-glenoid alignment (HGA). Results: The HSA in the control group was $1.47{\pm}1.05mm$, and the HGA with and without reconstruction were $1.15{\pm}0.65mm$ and $1.03{\pm}0.59mm$, respectively, on MRI. In the test group, HSA was $2.67{\pm}1.47mm$ and HGA with and without reconstruction was $1.58{\pm}1.16mm$ and $1.49{\pm}1.08mm$, on MRI. On CT, the HSA was $1.72{\pm}1.01mm$, and HGA with and without reconstruction were $1.54{\pm}0.96mm$ and $1.59{\pm}0.93mm$, respectively. HSA was significantly different according to image modality (p=0.0006), but HGA was not significantly different regardless of reconstruction (p=0.8836 and 0.9234). Conclusions: Although additional CT scans can be taken to measure decentering in patients with rotator cuff tears, reliable measurements can be obtained with MRI alone. When using MRI, it is better to use HGA, which is a more reliable measurement value based on the comparison with CT measurement (study design: Study of Diagnostic Test; Level of evidence II).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.5
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• pp.779-787
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• 2001

The multi degree of freedom system using magnetic levitation has been implemented successfully. Differently from another noncontact systems, the developed system was focused on the maximization of the system stiffness under the constraint of a limited input. The variation of a relative adopting point between the magnetic pair, its location on the fixed base, and the selection of optimal specifications for the main active magnetic elements give us another chance to realize the increased robustness against external disturbances with the less control inputs. In this paper, the overall development procedures are given including the optimal design, the dynamic modeling, the various control tests, and the main issues to be solved.

• Journal of the Korean Society of Radiology
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• v.12 no.6
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• pp.793-799
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• 2018

As interest in artificial intelligence has increased, artificial intelligence has been actively studied in the medical field. In Korea, artificial intelligence has been applied to medical imaging devices such as X-ray imaging, Computer Tomography and Magnetic Resonance Imaging and artificial intelligence capable of acquiring radiation images of patients without radiologists in the future Medical devices are expected to be invented. This study was an initial study on the automation of patient positioning in X - ray imaging. We used x-ray equipment and human phantoms to evaluate the positioning. The program used Visual Studio 2010 MFC and the image was in the size $1450{\times}1814$. The pixel values were converted to contrasts with values of 0 to 255 that can be visually recognized and output to the monitor. We developed a procedure algorithm program that predicts the angle of the output image through three pixel coordinate values and induces the patient to perform correct positioning according to the voice guidance according to the angle. In the next study, we will study the artificial intelligence to grasp the structure itself and calculate the angle, rather than conveying the reference of coordinates to artificial intelligence. In the future, it is expected that it will be helpful in the study of artificial intelligence from shooting to positioning through the automation of positioning.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.6 s.249
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• pp.622-630
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• 2006

This paper is about the magnetic suspension stage based on the Switched Reluctance propulsion principle. Because the previous studies on contact-free stage adopted the Lorentz force for main force generation mechanism they have suffered from thermal problem deteriorating the precision. Thus, the magnetic suspension stage adopting SR principle which can achieve high force density is proposed. The main operating principle and structure for achieving high resolution and long travel range are represented. The magnetic force analysis of each actuator, providing back data for dynamic modeling and controller design are carried out. By conducting basic experiments, the feasibility of the proposed system is shown. In addition the problems which should be improved and their solutions are represented.

• Journal of KSNVE
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• v.5 no.1
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• pp.49-57
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• 1995

An electronic circuit device is developed such that the displacement between an electromagnet and a moving target can be estimated from the coil current measurement, and then applied to an active magnetic bearing system. In order to levitate the shaft without using displacement sensor the stable control gains are obtained from the linearized model which includes the gap estimation circuit. Experimental results show that the shaft, by the estimated gap feedback, can be levitated within $\pm$6 ${\mu}m$ positioning error.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.348-352
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• 2002

a basis such as IT(Information Technology), NT(Nano Technology) and BT(Bio Technology). Recently, NT is applied to various fields that are composed of science, industry, media and semiconductor-micro technology. It has need of IT that is ultra-precision positioning technology with strokes of many hundreds mm and maintenance of nm precision in fields of ultra micro process, ultra precision measurement, photo communication part and photo magnetic memory. This thesis represents optimal design on ultra-precision positioning with single plane X-Y stage and development of artificial control system for adequacy of industrial demand. Also, dynamic simulation on global stage is performed by using ADAMS (Automated Dynamic Analysis of Mechanical System) for the purpose of grasping dynamic characteristic on user designed X-Y global stage. The error between displacements from micro stage and from FEM(Finite Element Method) is 3.53% by verifications of stability on micro stage and control performance. As maximum Von-mises stress on hinge of micro stage is 5.981kg/mm$^2$ that is 1.5% of yield stress, stability on hinge is secured. Preparing previous results, optimal design of micro stage can be possible, and reliance of results with FEM can be secured.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1082-1087
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• 2003

In this paper, we address the development of magnetic levitation positioning system. This planar magnetic levitator employs four permanent magnet liner motors. Each motor generates vertical force for suspension against gravity, as well as horizontal force for drive levitation object called a platen This stage can generate six degrees of freedom motion by the vertical and horizontal force. We derived the mechanical dynamics equation using lagrangian method and used coenergy to express an electromagnetic force. We proposed control algorithm for the position and posture control from its initial value to its desired value using sliding mode control. Some simulation result is provided to verify the effectiveness of the proposed control scheme.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.6
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• pp.906-915
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• 2004

In this paper, we address the development of magnetic levitation positioning system. This planar magnetic levitator employs four permanent magnet liner motors. Each motor generates vertical force for suspension against gravity, as well as horizontal force for driving levitation object called a platen. This stage can generate six degrees of freedom motion by the vertical and horizontal force. We derived the mechanical dynamics equation using Lagrangian method and used coenergy to express an electromagnetic force. We proposed a control algorithm for the position and posture control from its initial value to its desired value using sliding mode control. Some simulation results are provided to verify the effectiveness of the proposed control scheme.

• Journal of Mechanical Science and Technology
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• v.17 no.5
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• pp.708-717
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• 2003

With the development of precision manufacturing technologies, the importance of precision positioning devices is increasing. Conventional actuators, dual stage or mechanically contacting type, have limitation in coping with performance demands. As a possible solution, magnetic suspension technology was studied. Such a contact-free system has advantages in terms of high accuracy, low production cost and easy adaptability to high precision manufacturing processes. This paper deals with magnetically suspended multi-degrees of freedom actuator which can realize large linear motion. In this paper, the operating principle is explained with the magnetic force analysis, and the equations of motion are derived. Experimental results of the implemented system are also given.