• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.478-483
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• 2005

This paper presents the comparison analysis of a Journal and thrust FDB (fluid dynamic bearing) and a conical FDB in a HDD spindle motor. The Reynolds equation is appropriately transformed to describe journal, thrust and conical bearing. Finite element method is applied to analyze the FDB by satisfying the continuity of mass and pressure at the interface between the hearings. The pressure field of the bearings is numerically approximated by applying the Reynolds boundary condition. The load and friction torque are obtained by integrating the pressure and the velocity gradient along the fluid film. The flying height of the spindle motor is measured to verify the proposed analytical result. This research shows that the conical bearing generates bigger load capacity and less friction torque than the journal and thrust bearing in a HDD spindle motor.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.4
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• pp.213-223
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• 2004

In the machine tool industry, direct drive linear motor technology is of increasing interest as a means to achieve high acceleration, and to increase reliability. The advantages of such a motor are that it has a good linearity and has no need of such mechanical energy conversion parts, which change rotary motion into linear motion, as screws, gears, chains etc In this paper, two structures of LOA are analyzed. One is the moving-coil type LOA and the other is moving-magnet type LOA. Two types of LOA are analyzed, with reference to the following parameters as variables: magnetic field, flux linkage, motor thrust and back emf. These variables are derived by the use of analytical method in terms of two-dimensional rectangular coordinate system. The maximum values of thrust according to such design parameters as air-gap length and magnet height for each model is also represented. The results are validated extensively by comparison with finite element method. In particular, we experiment moving-coil LOA which is already manufactured and confirm that the experimental results are shown in good agreement with analysis through the comparison of between analytical and experimental results

• The Journal of Korean Physical Therapy
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• v.33 no.6
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• pp.304-306
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• 2021

Objectives: We report on a patient who showed mild bradykinesia due to injury of the corticofugal tract (CFT) from the secondary motor area following direct head trauma, which was demonstrated on diffusion tensor tractography (DTT). Case summary: A 58-year-old male patient underwent conservative management for subarachnoid hemorrhages caused by direct head trauma resulting from a fall from six-meter height at the department of neurosurgery of a local hospital. His Glasgow Coma Scale score was 3. He developed mildly slow movements following the head trauma and visited the rehabilitation department of a university hospital at ten weeks after the fall. The patient exhibited mild bradykinesia during walking and arm movements with mild weakness in all four extremities (G/G^-). Results: On ten-week DTT, narrowing of the right CFT from the supplementary motor area (SMA-CFT), and partial tearing of the left SMA-CFT, left CFTs from the dorsal premotor cortex (dPMC-CFT) and both corticospinal tracts (CSTs) at the subcortical white matter were observed. Conclusion: This case demonstrated abnormalities in both CSTs (partial tearing at the subcortical white matter and narrowing), both SMA-CFTs (narrowing and partial tearing) and left dPMC-CFT. We believe our findings suggest the necessity of assessment of the CFTs from the secondary motor area for patients with unexplained bradykinesia following direct head trauma.

• Journal of the Ergonomics Society of Korea
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• v.36 no.2
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• pp.69-86
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• 2017

Objective: The present study is intended to develop an improved bus seat armrest design by evaluating various bus armrest designs from ergonomic aspects. Background: An ergonomic armrest design which considers the sitting postures and body shapes of passengers can improve the convenience and comfort of a bus seat. Method: Subjective satisfaction of each of five design dimensions (length, width, height from seatpan, shape, and angle) was evaluated for seven bus seat armrest designs in various sizes and shapes by 58 participants (28 males and 33 females) using a 7-point scale (1: very dissatisfied, 4: neutral, and 7: very satisfied). Improved bus seat armrest designs adjustable in length and rotatable to the left or right (sliding and rotating armrest, SRA) with a concave, flat, or convex shape of the upper part were developed by considering the preferred design features and the body size and shape in sitting posture and needs of passengers and then compared with a conventional armrest. Results: A bus seat armrest with a wide width (40~50mm), a long length (360mm), a lower height (213mm), and a curved shape was found significantly preferred in terms of comfort. The proposed armrest designs (SRA-convex, SRA-flat, and SRA-concave) improved satisfaction by 46~62% for length suitability, 184~216% for width suitability, 205~214% for angle suitability, 138~181% for contact area suitability, and 49~64% for height suitability, 138~174% for comfort, and 93~111% for overall satisfaction. Conclusion: The preferred design features and passengers' needs of bus seat armrest were identified and the SRA designs were recommended for better usability. Application: The ergonomic design process of bus seat armrest employed in the present study can be applied to designing armrests in various vehicles for better convenience and comfort.

• International journal of advanced smart convergence
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• v.9 no.2
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• pp.38-48
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• 2020

The shaking-off the dust from balustrade of higher stories may cause the higher risk of falling accident rate. Main purpose of this study was to quantify an effect of balustrade heights and blanket types on possibility of falling accident relative to one's motor controllability during shaking-off the dust of the blanket from balcony. Female participants, who consisted of total 10 under condition of balustrade height of 3 kinds (90 cm, 110 cm, 130 cm) and blanket types (0.4 kg, 1.6 kg, 3 kg, 200^⁎230 cm), performed repetitively the task of shaking-off the dust of the blanket. Vertical position and velocity of center of mass due to increase of blanket weigh in case of balustrade height of 90 cm was increased, but vertical ground reaction force was decreased swiftly. That is, the higher balustrade height was, the less distance difference between center of mass and center of pressure was.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.5 no.1
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• pp.13-18
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• 2006

The magnetic abrasive machining has been developed as a new finishing technology to obtain a fine surface of workpiece. In this paper, a static magnetic field method and a magnetic abrasive brush which has many technical advantages, are applied for the magnetic abrasive machining. In the experiment, some items such as finishing time, ratio of the magnetic abrasives to Fe-powder, motor revolutions per minute, and motor ratio revolutions per minute are tested. The results of this study have shown the fact that the burr height is mostly affected by the finishing time and the abrasive ratio. Also, it has been found that the magnetic abrasive machining is a possible new technology for the deburring.

• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.75-78
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• 2003

Mobile Robot climbing stairs needs high power and high efficiency. one of the high power type motor is Transverse Flux Motor (TFM). Moreover, TFM is a high force density per volume. We analyzed a characteristic for the TFM and simulated the parametric research of the TPM by using 3D FEM solutions. It presents to design the basis of the TPM. design parameters are Radius of outer rotor, pole height, pole depth, pole depth, airgap, and Magnetomotive force.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.854-855
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• 2011

In this paper, Interior permanent magnet synchronous motor(IPMSM) with concentrated winding for 110cc electric motorcycle is introduced. Optimum design is performed so as to satisfy wide speed operation range. And output characteristics is analyzed according to shoe height in many variables. Because partial magnetic saturation in shoe affects the harmonics, output characteristics of motor could be confirmed that a significant change. As a result, the new shape and the optimal design parameters considering the partial magnetic saturation is obtained. Compared with the base model, wide operating range was confirmed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.6
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• pp.1105-1109
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• 2009

This paper deals with a polynomial thrust equation of a permanent magnet linear synchronous motor that is considered by a skew and overhang effects of permanent magnet. The skew length, the overhang length, the width and height of permanent magnet, the teeth length and air-gap length which effect to the flux density of air-gap are selected as variables of the polynomial thrust equation. Polynomial thrust equation is elicited by the 6 parameters. The results are satisfied that the values by polynomial thrust equation are compared ones by using 3-dimensional finite element analysis and experiment.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.1
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• pp.27-33
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• 2005

The development of modern high-energy magnet materials has allowed the replacement of field coils in many different types of electromagnetic energy conversion machines. As well, the linear synchronous motor has recently been proposed for linear motion with high efficiency and thrust. Thus, this paper presents an analytical solution for the high thrust and cost reduction of the Iron-Cored Permanent Magnet Linear Synchronous Motor (PMLSM) considering magnetization arrays and geometry. Hence, the superior utilization points in each of the magnetization arrays are provided by the height ratio of the magnet/air-gap and magnet/winding coil, etc. In formulation, the space harmonic method in analytical solutions and the generalized 2-D tensor finite element analysis can be used to evaluate force components in magneto static devices including the magnetostrictive phenomenon.