• Korean Journal of Optics and Photonics
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• v.32 no.6
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• pp.296-305
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• 2021

This paper reports a study on the long axis performance of the line beam optics used in laser lift-off equipment for the OLED manufacturing process. The centration errors of the cylindrical lens are classified and defined in seven categories, and the measurement methods are presented. The cylindrical fly-eye lens is analyzed theoretically and experimentally to find the influence of the surface shape error and decentering error on the long axis performance of the line beam optics system. A future research direction is also presented to improve the long axis performance.

• Journal of Dental Rehabilitation and Applied Science
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• v.36 no.2
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• pp.95-103
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• 2020

Purpose: The purpose of this study was to compare the axial displacement of the hexagonal and conical abutment in internal conical connection implant after screw tightening and cyclic loading. Materials and Methods: Internal conical connection implants were divided into two groups (n = 10): group HEX, hexagonal abutment; and group CON, conical 2-piece abutments. The axial displacement and removal torque values were measured after 30 Ncm torque tightening and 250N loading test of 100,000 cycles. The Student t test with 5% significance level was used to evaluate the data. Results: HEX group demonstrated significantly higher axial displacement values after 30 Ncm tightening in comparison to the CON group (P < 0.05). No significant difference was found in axial displacement after cyclic loading (P = 0.052). Removal torque loss before and after the cyclic loading both revealed no significant difference between groups (P = 0.057 and P = 0.138). Removal torque value decreased after cyclic loading in both groups (P < 0.05). Conclusion: Overall, both abutment with or without hexagon index presented similar biomechanical performance except HEX group demonstrated significantly more axial displacement after applying tightening torque.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.24 no.2
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• pp.317-326
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• 1994

Panoramic radiographs of a dry skull were used to evaluate the accuracy of four panoramic dental X-ray systems in determining tooth angulations in the buccal segments. The four machines evaluated were the Philips Oralix Pan DC, the GE panelipse, the SS White panorex 1, and the SS White Panorex 2. Panoramic radiographs were taken at six different patient positions for each machine to evaluate the effects of patient positioning on determining tooth angulations in the buccal segments. All of the machines studied showed a significant correlation between the mean radiographic estimates and the actual measurements regardless of positioning(p<0.05). With correct placement of the skull, the results were analyzed for an error tolerance of +/-3/sup 0/ between the actual measurements and the radiographic estimates for tooth angulation. The SS White Panorex 1 was accurate 74% of the time, the GE Panelipse was accurate 67% of the time, the Philips Oralix Pan DC and the SS White Panorex 2 were accurate 64% of the time. When an error tolerance of +/-5/sup 0/ was permitted, the accuracy was 89% for the SS White Panorex 1 and the GE Panelipse, 85% for the Philips Oralix Pan DC, and 81% for the SS White Panorex 2.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.22 no.1
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• pp.109-116
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• 1992

To determine the horizontal inclination of the condylar long axis without taking the submentovertex radiograph, the author studied the interrelation between the angle formed by the midsagittal plane and the mandibular angle and the horizontal inclination of the condylar long axis. In 56 subjects, the author measured the angle formed by the midsagittal plane and both mandibular angle using the modified Twirl Bow and the horizontal inclination of the both condylar long axis from submentovertex radiographs. The result were as follows: The mean value of the angle formed by the midsagittal plane and the mandibular angle was l8.50±1.48° in right side and 19.30±1.55° in left side. The mean value of the horizontal inclination of the condylar long axis was 19.25±7.56° in right side and 20.27±7.050 in left side. The interrelation of the two angles was represented as follows: y = 20.31-0.0094× (r = -0.482, p<0.01) in right side and y = 20.64-0.066×(r =-0.301, p<0.05) in left side (y; the horizontal inclination of the condylar long axis, x; the angle formed by the midsagittal plane and the mandibular angle).

• Journal of Korea Water Resources Association
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• v.50 no.6
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• pp.419-427
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• 2017

In mountainous rivers, the drag force acting on cobbles abundant in the riverbed surface is important in predicting behavior and response of the river. However there is little research for the drag coefficients of cobbles. This paper is to carry out the experiments for drag force of cobble and analyze the relation between the cobble shape and the drag coefficient. The effects of the shape factor on the drag coefficients $C_D$ when the long axis or the short axis of the cobbles are parallel to the direction of flow velocity were analyzed. The coefficient of drag force increased with the nominal diameter Reynolds number $R_{ep}$. The drag coefficients are greater in short axis than long axis. The coefficient of determination of the relation between $C_D$ and $R_{ep}$ is greater in long axis than short axis. This means that the drag forces acting on the irregularly-shaped cobbles depend on the axis. A change of the drag force distribution has brought about the alternative swing of cobbles. For $R_{ep}$ > 12,000, the amplitude of the swing has been increased sharply and especially was greater in short axis than long axis.

• Journal of Convergence for Information Technology
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• v.10 no.5
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• pp.216-223
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• 2020

We investigated the morphology of the scalp hair shaft from the base to the distal end of the newborn hair and the ratio of the longitudinal axis diameter of the scale exposed to the surface of the hair to the diameter of the hair by scanning electron microscopy(SEM). Neonatal hair was observed to taper from the area adjacent to the scalp toward the end of the hair. In this study, as the thickness of the hair increases, the ratio of the long axis diameter of the exposed scale becomes relatively small, but the long axis diameter of the exposed scale on the surface of the hair is similar in length regardless of the thickness of the hair. In conclusion, it was confirmed that the major axis diameter of the scales exposed to the surface of fine or thick hair does not change significantly.

• The korean journal of orthodontics
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• v.25 no.4
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• pp.453-463
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• 1995

Most commonly used axis for central incisors in lateral cephalometric radiographs is the line connecting root apex and incisor edge. However, crown axis and root axis do not always coincide in cases of malocclusion patients. The angle created by these axis are called the collum angle, which should be considered in orthodontic diagnosis and treatment. In this study, 31 Class I malocclusion, 30 Class II division 1 malocclusion, 31 Class II division 2 malocclusion, and 31 Class m malocclusion patients were selected and their collum angles were measured. Correlation between these angles and malocclusions was investigated, and the correlation analysis with other parameters in cephalometrics was done. The results were as follows ; 1. The mean collum angles according to the types of malocclusions are ; $3.11^{\circ}{\pm}3.54^{\circ}$ for Class I, $1.23^{\circ}{\pm}2.41^{\circ}$ for Class II division 1, $3.77^{\circ}{\pm}4.39^{\circ}$ for Class II division 2, and $3.90^{\circ}{\pm}4.08^{\circ}$ for Class III malocclusion. 2. Statistically significant differences in collum angles were noted between Class II division 1 group and Class II division 2 and Class III group. 3. Significant correlations were found between collum angles and other parameters used in cephalometrics, namely IMPA for Class I, Wits for Class II division 1, Overbite for Class II division 2 and for ClassIII.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.199-201
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• 2006

풍력발전기에 있어서 블레이드의 Yaw방향 제어는 끊임없이 변화하는 풍향에 대해 효율의 극대화와 블레이드의 강도 및 진동측면에서 대단히 중요하다. 기존의 블레이드 Yaw 방향 측정은 접촉 및 비접촉 센서가 이용되어왔다. 본 논문에서는 풍력발전기의 원격모니터링 시스템에서 기본적으로 설치되는 카메라를 이용하여 블레이드의 Yaw방향을 측정하는 방법을 제안한다. 블레이드가 풍향에 따라 회전할 때 영상 누적을 행하고, 누적영상에 대해 경계점을 추정하여 타원의 궤적을 추정한다. 추정된 경계점들을 이용하고 최소자승법을 적용하여 타원방정식을 추정하고, 장축과 단축을 연산한다. 장축과 단축의 변화를 이용하여 카메라의 촬영방향의 기준점으로부터 Yaw방향의 변화를 정량적인 값으로 산출하여 이를 바탕으로 Yaw회전각을 추정한다. Yaw 방향 추정의 검증을 위해 블레이드 속도와 Yaw 방향의 제어가 가능한 모형풍력발전기를 제작하고 실험을 통하여 제안한 추정알고리즘의 유효성을 검증한다.

• Tribology and Lubricants
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• v.25 no.3
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• pp.171-175
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• 2009

One of the critical issues associated with the 40mm long hollow cylinder's development and maintenance is the prediction of cylinder erosion. The actual firing test is the most accurate method to measure the cylinder erosion rate. But it costs a great deal and requires a long measurement time. Hence many empirical methods have been proposed to predict the erosion rate and life span of long hollow cylinders. An EFC formula is calculated. An approximate erosion formula for the ammunition type A is derived to interpolate 16 observation values up to 4,000 rounds. A new erosion equation and muzzle velocity formula are also suggested. Several numerical results are presented.

• The Korean Journal of Zoology
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• v.35 no.1
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• pp.70-79
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• 1992

미국흰불나방(Hyphontria cunea Drury) 종령유충과 나, 그리고 성충을 재료로하여 정세포가 정자로 변형되는 과정에서 나타나는 미토콘드리아의 분화과정을 전자현미경으로 관찰하였다. 다핵체를 이루고 있는 초기 정세포의 미토콘드리아는 축사가 형성되는 부위를 중심으로 집적된 후, 서로 유합되어 대형의 미토콘드리아 복합체인 부핵(Nebenkern)을 형성하였다. 부핵은 첨체형성 시기를 전후하여 세포의 장축을 따라서 길게 신장되며, 편모가 형성됨에 따라 축사를 중심으로 두께와 전자밀도가 서로 다른 두개의 미토콘드리아로 분리되었다. 분화가 계속됨에 따라서 서로 동일한 모양으로 변형된 미토콘드리아의 주변에서는 장축방향을 따라 다수의 미세소관이 분포하였고, 기질에서는 intramitochondrial crystalloid의 축적이 관찰되었다. 정자변형이 끝난 성숙정자의 미토콘드리아는 기질내부에 전자밀도가 높은 준결정물질이 함유된 미토콘드리아 유도체로 변형되었는데, 정자의 중편에서는 하나로 융합되어 있는 반면, 미부에서는 크기가 같은 두개의 유도체로 분리된 매우 독특한 형태로 관찰되었다.