• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.385-386
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• 2006

A brake disk in railway vehicle is safety part. Requirements not only in performance but also in comfort, serviceability and working lifetime are high and rising. In this study, we carried out fatigue test and thermal stress analysis. To determine a pressure distribution, contact pressure analysis precede thermal stress analysis. Especially, characteristics of the brake disk were analyzed in considering intial velocity, and thickness of a frictional plate. Form the comparing the results of experiment and FEM analysis, fatigue characteristic and fatigue life assessment ok a brake disk of railway vehicle were performed.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.497-502
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• 2004

In this study, we compared the strength of a material used in the A-type disk brake with that in the B-type. From tensile test results, it has been found that the strength of the B-type disk brake is higher than that of the A-type. The microstructure observation and chemical analysis were conducted to determine the cause of the difference between the strength of A and B types of disk brake materials. From the experimental results, it has been confirmed that the difference in the strength between the two types of disk brake is due to the difference in the shape of graphite.

• The korean journal of orthodontics
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• v.35 no.5 s.112
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• pp.398-407
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• 2005

The present study was conducted to examine the morphometrics and function of the disk on both sides among patients with facial asymmetry (FA) and to elucidate plausible correlations between internal derangement (ID) and FA. The sample was composed of 10 males and 27 females with FA. The disk status of all subjects was evaluated by bilateral high resolution magnetic resonance scans in the sagittal (closed and open) and coronal (closed) planes. Five types of disk displacement were identified accordingly. The disk function was diagnosed as normal disk function, disk displacement with reduction, and disk displacement without reduction. The disk shape on sagittal MRI in closed position was classified as bi-concave, biplanar, funnel/hemiconvex, and deformed. The disk position, translation and rotation were also measured. The difference between the shifted side and non-shifted side was analyzed by statistical analysis. Approximately $70\%$ of the patients in the present study showed unilateral or bilateral ID. It was found that anterior disk displacements (ADD), especially rotational ADD, occurred more frequently in the shifted side, while normal disk position was observed mainly in the non-shifted side (p<0.01). The disk of the shifted side showed significantly deformed configuration and inferior-anterior disk position. However, the disk of the non-deviated side showed hyper-mobility during jaw opening movement. These results demonstrate that in FA patients, the disks status of the shifted side is different from that of the non-shifted side, a phenomenon that could be correlated to facial asymmetry.

• Structural Engineering and Mechanics
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• v.50 no.6
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• pp.723-740
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• 2014

A fracture criterion based on the strain energy density (SED) over a control volume, which embraces the notch edge, is employed in the present paper to assess the fracture loads of some U-notched Brazilian disk (UNBD) specimens. The specimens are made of commercial graphite and have been tested under pure mode I, pure mode II and mixed mode I/II loading. The results show that the SED criterion allows to successfully assess the fracture loads of graphite specimens for different notch tip radii and various mode mixity conditions with discrepancies that fall inside the scatter band of ${\pm}20%$.

• Transactions of Materials Processing
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• v.6 no.3
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• pp.250-256
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• 1997

Hammer forging was employed for Alloy 718 disk. The change in grain size during hot forging depends very much on dynamic recrystallization. The final grain size depends especially on the critical strain$($\varepsilon$_C)$/TEX> for dynamic recrystallization and Zener-Holloman parameter(Z). In this study, the critical strain$($\varepsilon$_C)$, the strain for 50 pct. recrystallization$($\varepsilon$_{0.5})$ and fraction of dynamic recrystallization(Xdyn) were measured by compression tests. FE simulation was also carried out ot predict the evolution of microstructure. The strain, strain rate and temperature distribution predicted by forging simulation can be effectively used to predict the distribution of grain sizes in the forged workpiece. The present model predictions showed an excellent agreement with the microstructural evolution of hammer-forged Alloy 718 disks.

• Structural Engineering and Mechanics
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• v.82 no.5
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• pp.679-690
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• 2022

This research effort examines the flow behavior and heat transfer assessment of water carrying iron (iii) oxide magnetic fluid due to a rotating and moving plane lamina under the influence of magnetic dipole. The effect of rotational viscosity and magnetic body force is taken into consideration in the present study. The involvement of the moving disk makes a significant contribution to the velocity distribution and heat transfer in rotational flow. Vertical movement of the disk keeps the flow unsteady and the similarity transformation converts the governing equation of unsteady flow into nonlinear coupled differential equations. The non-dimensional equation in the present system is solved through the finite element procedure. Optimizing the use of physical parameters described in this flow, such results can be useful in the rotating machinery industries for heat transfer enhancement.

• Journal of Applied Reliability
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• v.9 no.1
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• pp.1-12
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• 2009

BLDC motors are stored in the devices such as CD-RW, COMBO, DVD-ROM and CD-ROM. It is indispensable to establish reliability assessment criteria for BLDC motors, especially in the world where IT grows rapidly. In this article, reliability certification procedure is given. The reliability certification procedure consists of two separate tests such as quality certification test and lifetime test. The former quality certification test comprises general performance test and environmental test. Items which pass the test undergo lifetime test which guarantees the extent of mean lifetime with certain confidence.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.1 no.1
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• pp.105-112
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• 1995

This study was designed to investigate the efficiency of subjective assessment that exams the subjective symptom of patients with back pain at the department of physical therapy. To assess the subjective symptom, we used the pain questionnaire using visual analogue scale (VAS) that was developed by Wang on 1995. Questionnaires were administered to 31 adult patients(male : 11, female : 20) with herniated lumbar disk(13), low back pain(8), myofascial pain syndrom(5), lumbar strain(4), ankylosing spondylitis(1). Mean age was 36.3 ranged from 20 to 65. The results of this study were as follows : 1) In each of 15 subjects, there was a significant decrease in VAS between pre- and post-treatment(p<0.05). 2) Mean VAS of total subjects was $6.26{\pm}2.55$ in pre-treatment, $4.50{\pm}2.47$ in post-treatment (p<0.001). Result of this study was shown efficiency of pain management by subjective assessment. The continuous study is needed for many interesting illue of pain management using VAS.

• Journal of Korean Physical Therapy Science
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• v.2 no.3
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• pp.679-689
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• 1995

This study was designed to investigate the efficiency of subjective assessment that exams the subjective symptom of patients with back pain at the department of physical therapy. To assess the subjective symptom, we used the pain questionnaire using visual analogue scale(VAS) that was developed by Wang on 1995. Questionnaires were administered to 31 adult patients(male : 11, female: 20) with herniated lumbar disk(13), low back pain(8), myofascial pain syndrom(5), lumbar strain(4), ankylosing spondylitis(1). Mean age was 36.3 ranged from 28 to 65. The results of this study were as follows: 1) In each of 15 subjects, there was a significant decrease in VAS between pre-and post-treatment(p < 0.05 -p<0.001). 2) Mean VAS of total subjects was $6.26{\pm}2.55$ in pre-treatment, $4.50{\pm}2.47$ in post-treatment(p < 0.001). The result of this study was shown efficiency of pain management by subjective assessment. The continuous study is needed for many interesting issue of pain management using VAS.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.3
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• pp.36-43
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• 2016

Carbon fiber-reinforced silicon carbide (Cf-SiC) and SiC / SiC composites have high thermal conductivity, and excellent corrosion and wear resistance, a low coefficient for thermal expansion and are lightweight. This is why they are commonly used in parts of the aerospace industry to develop an aircraft thrust deflector, jet vane, combustion chamber, elevens, body flap, and a shingle. So, understanding how this state-of-the-art Cf-SiC affects both internal and external crack detection and determining issues during the manufacturing process of composite materials, should be evaluated according to valuation techniques in the external environment. In this paper, we apply a non-contact air ultrasonic technique of non-destructive testing techniques to perform a study on internal defect detection identification and assessment of carbon-fiber reinforced silicon carbide composites to perform basic research and applied research.