• The Journal of Korean Academy of Prosthodontics
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• v.57 no.4
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• pp.335-341
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• 2019

Purpose: Chemically strong-acids (HF and $HCl/H_2SO_4$) dual etching implant surfaces have higher strengths of osseointegration than machined implant surfaces. However, the dual acid treatment deteriorates the physical properties of the titanium by weakening the fatigue resistance of the implant and causing microcracks. The removal torque comparison between the dual-acid etched (hydrochloric acid, sulfuric acid, HS) and single-acid etched implants (hydrochloric acid, H) could reveal the efficiency of implant surface acid treatment. Materials and methods: Nine $3.75{\times}4mm$ dual-acid etched SLA implants and nine single-acid etched SLA implants were inserted into New Zealand rabbit tibias. After 10 days, removal torque, roughness, and wetting angle were measured. Results: Mean removal torque values were as follows: Mean removal torque were 9.94 Ncm for HS group and 9.96 Ncm for H group (P=.995). Mean surface roughness value were $0.93{\mu}m$ for HS group and $0.84{\mu}m$ for H group (P=.170). Root mean square roughness (RSq) values were $1.21{\mu}m$ for HS group and $1.08{\mu}m$ for H group (P=.294), and mean wetting angle values were $99^{\circ}$ for HS group and $98^{\circ}$ for H group (P=.829). Statistical analysis showed no significant difference between the removal torques, roughness, or wetting angles of the two groups. Conclusion: In this experiment, we found no significant difference in removal torque, roughness, or wetting angle between dual-acid etched and single-acid etched implants.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.6
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• pp.293-299
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• 2018

Steel truss outriggers can be replaced by reinforced concrete walls to control the lateral drift of tall buildings. When reinforced concrete outrigger walls are connected to perimeter columns, not only axial forces but also shear forces and moments can be induced on the perimeter columns. In this study, the shear force of the perimeter column due to the rotation of the outer edge of the outrigger wall is derived as analytic equations and the result is compared with the finite element analysis result. In the finite element analysis, the effects of connecting beams at each floor and the effect of modeling shear walls and outriggers with beam element and plane stress element was analyzed. The effect of the connecting beam was almost negligible and the plane stress element was determined to have greater stiffness than the beam element. The inter-story rotation and the shear force of the perimeter column due to the rotation of the outer edge of the outrigger wall was considerably smaller than the allowable value. Therefore, even if the outrigger wall made of reinforced concrete is applied to a tall building, it is considered that there is no need to study the shear force and moment induced in the perimeter columns.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.2D
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• pp.209-215
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• 2011

Roundabout has circular traffic island in the intersection center and is kind of intersection where the automobile bypass circular traffic island. In Korea, the provisional Roundabouts Design Guidelines were published in 2004 by MLTM (Ministry of Land, Transport and Maritime Affairs). This guideline did not discussed domestic traffic circumstance. It just only introduced foreign instances and their guidelines. In addition, the recent National Competitiveness roundabouts as part of the green growth has been concentrated on the interest. In this paper, 90 degree of the 4-legged roundabout was compared with 72 degree, 45 degree, and 30 degree 5-legged roundabouts by micro simulation VISSIM. As a result of analysis, average travel time is decreased when the inscribed circle diameter become bigger the roundabout. 5-legged roundabout until 2,000 volume per hour evaluated to be similar effect at 90 degree of 4-legged roundabout.

• 대한치과보철학회:학술대회논문집
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• 1999.11a
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• pp.55-55
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• 1999

• Journal of Adhesion and Interface
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• v.16 no.1
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• pp.1-5
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• 2015

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.3
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• pp.246-252
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• 2004

This paper presents a position sensorless control system of Switched Reluctance Motor (SRM) using neural network. The control of SRM depends on the commutation of the stator phases in synchronism with the rotor position. The position sensing requirement increases the overall cost and complexity. In this paper, the current-flux-rotor position lookup table based position sensorless operation of SRM is presented. Neural network is used to construct the current-flux-rotor position lookup table, and is trained by sufficient experimental data. Experimental results for a 1-hp SRM is presented for the verification of the proposed sensorless algorithm.

• Journal of the Korean Magnetics Society
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• v.10 no.4
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• pp.178-182
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• 2000

We have constructed a rotational loss measuring system which consists of two yoke system for rotational magnetization and 4-channel transient recording system for Hx, Hy, Bx and By measurements. Using the constructed measuring system, we have mesaured rotational energy loss for non-oriented electrical steel sheets. Rotational energy loss was depending on the angle between B-search coil and H-search coil, and the direction of rotation (clockwise and counter clockwise). The average of the rotational energy losses under clockwise and counter clockwise was independent of the angle between B-search coil and H-search coil, and we could improve measuring uncertainty using the averaged rotational energy losses.

• Journal of Korean Society of Steel Construction
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• v.28 no.2
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• pp.85-96
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• 2016

Double split tee connection has various strength, stiffness, and energy dissipation capacity according to changes of thickness of T-stub flange and gauge distance, number, and diameter of high-strength bolt. If the double split tee connection is applied to a low- or medium-rise steel structure, a shear tab can't be applied for supporting shear force because of geometrical limitation. So it is required to propose details of improved double split tee connection to support shear force as well as flexural force. This research was performed to see if enough rotational stiffness is found when the double split tee connection without shear tab which was obtained through analytic and experimental researches by Yang et al. is applied to a low- or medium-rise steel structure. Also, it was seen if the low- or medium-rise steel structure having double split tee connection without shear tab has safe structural behavior, as well as material saving effect.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.881-882
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• 2006

선형전동기(linear motor)는 일반 회전형 모터에 비해 직선 구동력을 직접 발생시키는 특유의 장점이 있으므로 직선 구동력이 필요한 시스템에서 회전형에 비해 절대적으로 우세하다. 선형전동기의 성능인 추력을 스테이터, 코어, 영구자석 등의 구성요소의 형상과 치수, 코어와 영구자석의 극간격, 공극, 코일의 권수에 따라서 결정된다. 본 논문에서 제안한 2kW급 단상 구동형 횡자속 선형전동기는 압축기 제작에 필요한 직경 50mm, 구동 스트로크 18mm로 설계하였다. 또한 pole pitch가 20mm로 설계하였으며 요구되는 평균추력은 940N이다. 제작된 압축기의 특징은 고정자와 이동자가 맞닿는 flux path를 넓히기 위해서 최대한 경사진 각도의 형상으로 제작하였으며 경사의 각도가 커지면 커질수록 압축기로 구동하는 이동자와 고정된 부위사이에서 발생하는 흡인력이 상쇄되는 구조이기 때문에 진동의 원인으로 가장 크게 작용한다는 디텐트력이 작다는 것이 특징이며, 진동특성 등에 유리한 것으로 판단된다.

• Journal of the Korean earth science society
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• v.30 no.6
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• pp.787-798
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• 2009

A new apparatus was presented in order to help understand the concept of the Coriolis force which is essential in understanding the trajectories of the atmospheric current and the tide of seawater. In the apparatus proposed in high-school textbooks, since the slide from which the ball is released is set outside the rotating disk, it was not possible to interpret, with the trajectory of the ball on the disk, the motion of the atmosphere and the current of seawater occurring as a result of the Coriolis force. In order to resolve such problem, a new apparatus was developed in which the slide was set on the disk and rotated with the disk. Experiments were carried out using both the existing apparatus and the new apparatus, and the results were compared. While, in the experiment performed with the existing apparatus, it was difficult to analyze the trajectory of ball because the motion of the ball was not smooth when it hit the disk, in the experiment with the new apparatus it was much easier to analyze the trajectories. It was also possible to compare the trajectories when the initial velocity of the ball was varied.