• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.6
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• pp.585-589
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• 1999

In order to grow $Bi_4Ge_3O_{12}$ crystals by the Czochralski method equipped with the auto-diameter control system, we used the resistance heater of our own design. We measure the temperature gradients under-arious thermal configurations. The relation between the critical rotation rate corresponding to the flat interface and the temperature gadient was investigated, and the importance of the axial temperature gradient was pointed out. The results from this work were compared with those obtained by other authors when RF heating was used. The optimal conditions for the crystal growth were determined as follows; under $O_2$ atmosphere with the pulling rate fixed at 2 mm/hr, rotation rate changed from 30 to 23 rpm as the crystal growth proceeded, radial and axial temperature gradients were 50 and $40^{\circ}C$/cm near melts respectively, and the composition was chemically stoichiometric.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.4
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• pp.397-403
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• 2015

In this paper, a method of ISAR geometric calibration is represented by using impulse-radio UWB radar. The ir-UWB is good for using a signal processing in time domain, so, it does not occur a multi-path or coupling problem. If a signal that between antennas and target is assumed a plane wave, a center of rotation in ISAR geometry model can be estimated by using point target. Before image is reconstructed with sinogram, the center of rotation can be calculated by using least square fitting. This method can be obtained a more contrast image, and a maximum value of entropy of image. The method, that estimates a center of rotation in received data, will be used a initial setup of instruments or a periodic compensation to reconstruct image. It would be useful in medical, security and surveillance imaging equipments that have a fixed geometry.

• Korean Journal of Crystallography
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• v.6 no.2
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• pp.141-157
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• 1995

Single crystals of TeO2 with large diameter were grown by Czochralski technique with auto-diameter control system. The ratio of crystal to crucible was 60-70%. The effect of critical pulling and rotation rate on the crystal quality was studied. Optimum growth parameters for high quality crystal pulling rate was less than 1.2 mm/hr. The solid-liquid interface was convex at the rotation rate of 10-23 rpm and concave at the rotation rate of more than 25 rpm, depending on the size of crystal and crucible. The platinum concentration in the melts is one of the main factors of the constitutional supercooling and thus the bubble entrapment in the growing crystal. Growth axis was confirmed to {110} direction during the whole growth procedure. Infrared spectrometric study and dislocation density measurment by chemical etching method on the grown crystal were performed. Finally, the reasons of cooperation of striations, inclusions, and optical inhomogeneities were discussed.

• Journal of the Korean Orthopaedic Association
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• v.55 no.2
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• pp.135-142
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• 2020

Purpose: This paper presents the long term follow-up results of arthroscopic partial repair for massive irreparable rotator cuff tears using a biceps long head auto graft. Materials and Methods: Forty-one patients with massive irreparable rotator cuff tear, who underwent arthroscopic repair, were reviewed retrospectively. Patients who underwent arthroscopic partial repair using a biceps long head auto graft were assigned to group 1, and patients in group 2 underwent arthroscopic partial repair alone. Patients with a less than 50% partial tear of the long head biceps tendon were included in this study. The clinical scores were measured using a visual analogue pain scale (VAS) for pain, range of motion (ROM), The University of California, Los Angeles shoulder score (UCLA), American Shoulder and Elbow Surgeons Shoulder Score (ASES), and Korean Shoulder Scoring System (KSS) scores preoperatively and at the final follow-up. The acromiohumeral interval (AHI) was measured using plain radiographs taken preoperatively and at the final follow-up, and re-tear was evaluated using postoperative ultrasound or magnetic resonance imaging at the last follow-up. Results: The mean age of the patients was 62.1±12.7 years, and the mean follow-up period was 90.3±16.8 months. No significant differences in the VAS and ROM (forward flexion, external rotation, internal rotation) were found between the two groups (p=0.179, p=0.129, p=0.098, p=0.155, respectively). The UCLA (p=0.041), ASES (p=0.023), and KSS (p=0.019) scores showed functional improvements in group 1 compared to group 2. At the last follow-up, the measured AHI values were 9.46±0.41 mm and 6.86±0.64 mm in group 1 and 2, respectively (p=0.032). Re-tear was observed in six out of 21 cases (28.6%) in group 1 and nine out of 20 cases (45.0%) in group 2; the retear rate was significantly lower in group 1 than in group 2 (p=0.011). Conclusion: Arthroscopic partial repair for a massive irreparable rotator cuff tear using a biceps long head auto graft has significant clinical usefulness in functional recovery and decreases the re-tear rates after surgery than arthroscopic partial repair alone, showing favorable results after a long-term follow-up.

• Journal of the Optical Society of Korea
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• v.18 no.6
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• pp.746-752
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• 2014

In a multi-camera measurement system, the determination of the external parameters is one of the vital tasks, referred to as the calibration of the system. In this paper, a new geometrical calibration method, which is based on the theory of the vanishing line, is proposed. Using a planar target with three equally spaced parallel lines, the normal vector of the target plane can be confirmed easily in every camera coordinate system of the measurement system. By moving the target into more than two different positions, the rotation matrix can be determined from related theory, i.e., the expression of the same vector in different coordinate systems. Moreover, the translation matrix can be derived from the known distance between the adjacent parallel lines. In this paper, the main factors effecting the calibration are analyzed. Simulations show that the proposed method achieves robustness and accuracy. Experimental results show that the calibration can reach 1.25 mm with the range about 0.5m. Furthermore, this calibration method also can be used for auto-calibration of the multi-camera mefasurement system as the feature of parallels exists widely.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.11a
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• pp.289-295
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• 1999

A new conceptual wave rolling ball reducer was proposed and investigated. The main components of the reducer were a eccentric input shaft and bearings, followers with balls, a flange, and a outer ring with waved groove. Followers moved along the holes of the flange according to the rotation of the shaft. And the balls installed in tips of followers were rolled with the waved groove of outer ring. When the shaft was rotated as one revolution and the outer ring was fixed, the flange was rotated as one wave. The kinematic analysis of the reducer carried out. The forces of each components were estimated, and the main design parameters were investigated. The design program using Visual C++ and Auto Lisp to determine the design parameters and to generate the drawing sheet.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.44-46
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• 2001

This paper describes the use of the PHOENICS CFD package for the simulation of the high-current period of the arcing process in a hybrid rotating arc/auto expansion by interrupter. The operating principle of this device depends on rapid arc rotation due to the magnetic field created by the fault current through a coil which is mounted on contacts and also relies on the principle of thermal expansion created by arc energy in extinguishing chamber and finally causes pressure rise in expansion volume. This paper is divided into three main sections. The first gives a brief overview of the interrupter. The second section gives a full description of the methods used in the calculation. The final section presents some sample results for the hybrid interrupter.

• Aerospace Engineering and Technology
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• v.7 no.1
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• pp.254-262
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• 2008

Several decades have passed since tiltrotor technology became a hot issue of debates between aircraft majors, policy maker and mass-media. Although most of those subjects have been officially probed or answered in objective way, biased articles or argues related with the adequacy of this technology still prevail in the way of tilt-rotor development programs, which are totally irrelevant and out-dated. This paper aims to help understanding on those issues in technically balanced manner and the cases of flight test mishaps.

• Smart Structures and Systems
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• v.30 no.3
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• pp.263-271
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• 2022

In this paper we present an overview of damage diagnosis algorithms that have been developed over the past two decades using vibration signals obtained from structures. Then, the paper focuses primarily on algorithms that can be used following an extreme event such as a large earthquake to identify structural damage for responding in a timely manner. The algorithms presented in the paper use measurements obtained from accelerometers and gyroscope to identify the occurrence of damage and classify the damage. Example algorithms are presented include those based on autoregressive moving average (ARMA), wavelet energies from wavelet transform and rotation models. The algorithms are illustrated through application of data from test structures such as the ASCE Benchmark structure and laboratory tests of scaled bridge columns and steel frames. The paper concludes by identifying needs for research and development in order for such algorithms to become viable in practice.

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.1
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• pp.57-66
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• 2012

The purpose of this study was to evaluate the relation between intentionally induced internal stress and cyclic fatigue failure of ProTaper Universal. ProTaper Universal (Dentsply Maillefer) S1, S2, F1, F2, F3, F4 and F5 (25 mm length) were used in this study. To give the internal stress, the ProTaper Universal were put into the .02 taper Endo-Training-Bloc (Dentsply Maillefer) until auto-stop by torque controlled motor. The rotation speed was 300 rpm and torque value was 1.0 Ncm. ProTaper Universal were grouped by the induced number of internal stress and randomly distributed among one control group and three experimental groups (n=10). The four groups were Stress 0 (control), Stress 1, Stress 2 and Stress 3. These instruments were rotated until separation. For cyclic fatigue measurement, inclined plane was used and time for separation was recorded. It was statistically analyzed using two-way ANOVA and Duncan post-hoc test at 95% confidential level. In all ProTaper Universal, there was statistically significant decrease on time for separation in Stress 3. In F2 and F3, there were statistically significant difference between control group and all experimental groups. And in F4 and F5, Stress 2 and 3 groups showed significantly lower cyclic fatigue resistance from Stress 0 group. In the limitation of this study, cyclic fatigue failure of ProTaper Universal is influenced by accumulated internal stress.