• 한국과학교육학회지
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• 제30권7호
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• pp.901-907
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• 2010

The purpose of this study is to analyze methods for measuring the size of the Earth, put forth in 6 different Korean 8th grade science textbooks. The research questions are as follows: 1) Do they adequately map out the experiments for measuring the size of the earth by using the concept of the sun's altitude? 2) Do they reduce the size of the sun like as the Earth is similarly downsized to the globe? 3) Do they suggest the precise experimental conditions for selecting two equal longitudinal spots for measuring the size of the earth? 4) Do they design adequate experiments for exact measurement? 5) Do they offer a proportional expression for seeking the size of globe which is easily understood by students? 6) Do they develop experiments to measure actual size of the earth? Four graduate students and one researcher took part in this study. All conditions were unanimously agreed upon by the participants. The results are as follows. First, one publishing company must include the concept of the sun's altitude to accurately measure the size of the Earth. However, some textbooks fail to mention this. As such, the concept of the sun's altitude must be introduced to accurately measure the size of the Earth. Second, a reduced size globe is used as the actual earth so; the sun should be factored in with a reduced light value. Third, you have to lay a stress on two points at the same longitude. In other words, a shadow located at the same longitude from two randomly selected points. Most textbooks mention two points at the same longitude but two of them design the experiment with a shadow at the same longitude. Fourth, we need a method to precisely measure the angle between a stick and its shadow. The angle between the stick and the tip of its shadow is the sun's altitude difference. Fifth, we need to present more specific proportional expressions for calculating the size of the globe. Only 3 out of the 6 texts employed a proportional expression. Sixth, we need to calculate the size of the earth by accurately presenting the scale of the globe to attain the goal of the experiment. Two of the texts analyzed, designed the experiment for the purpose of calculating the size of the globe. Three of the texts designed their experiments to calculate the radius of globe which is not even relevant to the purpose of experiment.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.280-283
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• 2004

This paper discribes the design concept, fabrication process and measuring result of 2.5kV Gate Commutated Thyristor devices. Integrated gate commutated thyristors(IGCTs) is the new power semiconductor device used for high power inverter, converter, static var compensator(SVC) etc. Most of the ordinary GTOs(gate turn-off thyristors) are designed as non-punch-through(NPT) concept; i.e. the electric field is reduced to zero within the N-base region. In this paper, we propose transparent anode structure for fast turn-off characteristics. And also, to reach high breakdown voltage, we used 2-stage bevel structure. Bevel angle is very important for high power devices, such as thyristor structure devices. For cathode topology, we designed 430 cathode fingers. Each finger has designed $200{\mu}m$ width and $2600{\mu}m$ length. The breakdown voltage between cathode and anode contact of this fabricated GCT device is 2,715V.

• 한국수자원학회논문집
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• 제44권4호
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• pp.327-338
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• 2011

본 연구에서는 등가타원을 이용하여 호우사상의 공간분포를 정량화 하는 문제를 살펴보았다. 주어진 호우사상의 등가 타원을 매 시간별 한계강우강도에 따라 추정하고, 이 등가타원의 개수와 규모의 변화를 살펴보았다. 또한 한계강우강도 별로 평균 등가타원을 결정하고, 이 평균 등가타원이 주어진 호우사상을 대표할 수 있는지 판단하기 위해 평균 등가타원의 장축과 단축, 그리고 회전각에 대한 신뢰구간을 산정하여 평가하였다. 연구결과, 한계강우강도가 커짐에 따라 등가타원의 개수와 크기는 감소하고 등가타원이 나타나는 시간도 늦어지는 것을 확인하였다. 또한 등가타원의 장축과 단축의 비는 2 : 1이 적절한 것으로 나타났으며, 한계강우강도별로 추정된 등가타원의 평균 회전각은 모든 등가타원의평균 회전각과 통계학적으로 유사함을 확인하였다.

• Tribology and Lubricants
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• 제34권4호
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• pp.146-159
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• 2018

This paper presents a wear analysis procedure for calculating the wear of journal bearings of a four-strokes and four-cylinder engine operating at a constant angular crank shaft speed during firing conditions. To decide whether the lubrication state of a journal bearing is in the possible region of wear scar, we utilize the concept of the centerline average surface roughness to define the most oil film thickness scarring wear (MOFTSW) on two rough surfaces. The wear volume is calculated from the wear depth and wear angle, determined by the magnitude of each film thickness on a set of oil films with thicknesses lower than the MOFTSW at every crank angle. To calculate the wear volume at one contact, the wear range ratio during one cycle is used. The total wear volume is then determined by accumulating the wear volume at every contact. The fractional film defect coefficient, asperity load sharing factor, and modified specific wear rate for the application of the mixed-elasto-hydrodynamic lubrication regime are used. The results of this study show that wear occurs only at the connecting-rod big-end bearing. Thus, simulation results of only the big-end bearing are illustrated and analyzed. It is shown that the wear volume of each wear scar group occurs consecutively as the crank angle changes, resulting in the total accumulated wear volume.

• Journal of Mechanical Science and Technology
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• 제17권6호
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• pp.825-835
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• 2003

Previous studies have demonstrated the importance of joint angle errors mainly due to skin artifact and measurement errors during gait analysis. Joint angle errors lead to unreliable kinematics and kinetic analyses in the investigation of human motion. The purpose of this paper is to present the Joint Averaging Coordinate System (JACS) method for human gait analysis. The JACS method is based on the concept of statistical data reduction of anatomically referenced marker data. Since markers are not attached to rigid bodies, different marker combinations lead to slightly different predictions of joint angles. These different combinations can be averaged in order to provide a "best" estimate of joint angle. Results of a gait analysis are presented using clinically meaningful terminology to provide better communication with clinical personal. In order to verify the developed JACS method, a simple three-dimensional knee joint contact model was developed, employing an absolute coordinate system without using any kinematics constraint in which thigh and shank segments can be derived independently. In the experimental data recovery, the separation and penetration distance of the knee joint is supposed to be zero during one gait cycle if there are no errors in the experimental data. Using the JACS method, the separation and penetration error was reduced compared to well-developed existing methods such as ACRS and Spoor & Veldpaus method. The separation and penetration distance ranged up to 15 mm and 12 mm using the Spoor & Veldpaus and ACRS method, respectively, compared to 9 mm using JACS method. Statistical methods like the JACS can be applied in conjunction with existing techniques that reduce systematic errors in marker location, leading to an improved assessment of human gait.

• 비파괴검사학회지
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• 제22권4호
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• pp.422-429
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• 2002

용접부 초음파 사각탐상은 용접 루트부나 counter bore와 같은 결함과 관련 없는 신호를 발생하는 기하학적 반사체로 인하여 신호의 식별이 매우 어렵다. 본 논문에서는 이와 같은 상황에서 결함 신호를 식별하는 새로운 기법을 제안하였다. 디컨볼루션(deconvolution)을 사용한 유사성함수의 개념을 도입한 새로운 기법에서는 먼저 결합과 기하학적 반사체에 대하여 기준신호와 대상신호를 획득하였으며 이들을 정규화 하였다. 대상신호를 기준신호로 디컨볼루션하여 얻은 유사성함수의 패턴으로부터 기하학적 반사 신호와 결함신호를 구분할 수 있었다. 그 결과로, 제안하고 있는 기법이 기하학적 반사체와 노치 모서리부에서 반사되는 신호를 분리하는데에 유용함을 알 수 있었다.

• 문화기술의 융합
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• 제8권5호
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• pp.591-596
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• 2022

다양한 산업분야에서 사용되는 4절 링크기구는 링크 길이가 고정되어 있으므로 기구의 움직임을 변경하기 위해서는 독립적인 링크기구나 제어장치를 추가해야 하는 불편함이 있다. 따라서 본 논문에서는 상황에 따라 링크기구의 운동을 선택적으로 제어할 수 있도록 링크 길이가 조절되는 가변형 4절 링크기구를 설계하였으며 링크기구에 의해 구동되는 제품인 선풍기에 적용하여 그 타당성을 검증하였다. 바람 범위의 효율성을 고려하여 선풍기 회전각도를3단계로 분할하였으며 각 구간에 필요한 링크 길이를 계산하였다. 또한, 원통캠을 이용하여 링크 길이를 조절하였으며 선풍기의 회전각도 조절 작동 여부를 실제 제작 및 측정을 통해 확인하였다. 본 논문에서 제시한 가변형 링크기구는 산업용 로봇이나 연료 밸브 시스템 등과 같은 4절링크 적용 제품의 효율성을 향상시킬 수 있을 것으로 기대된다.

• 대한치과교정학회지
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• 제43권1호
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• pp.42-52
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• 2013

The aim of this paper was to propose a new method of bimaxillary orthognathic surgery planning and model surgery based on the concept of 6 degrees of freedom (DOF). A 22-year-old man with Class III malocclusion was referred to our clinic with complaints of facial deformity and chewing difficulty. To correct a prognathic mandible, facial asymmetry, flat occlusal plane angle, labioversion of the maxillary central incisors, and concavity of the facial profile, bimaxillary orthognathic surgery was planned. After preoperative orthodontic treatment, surgical planning based on the concept of 6 DOF was performed on a surgical treatment objective drawing, and a Jeon's model surgery chart (JMSC) was prepared. Model surgery was performed with Jeon's orthognathic surgery simulator (JOSS) using the JMSC, and an interim wafer was fabricated. Le Fort I osteotomy, bilateral sagittal split ramus osteotomy, and malar augmentation were performed. The patient received lateral cephalometric and posteroanterior cephalometric analysis in postretention for 1 year. The follow-up results were determined to be satisfactory, and skeletal relapse did not occur after 1.5 years of surgery. When maxillary and mandibular models are considered as rigid bodies, and their state of motion is described in a quantitative manner based on 6 DOF, sharing of exact information on locational movement in 3-dimensional space is possible. The use of JMSC and JOSS will actualize accurate communication and performance of model surgery among clinicians based on objective measurements.

• 한국지반신소재학회논문집
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• 제6권1호
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• pp.1-7
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• 2007

연약지반처리를 위해 바로 장비가 진입하기 어려운 경우에, 적절한 강도를 갖는 토목섬유를 부설하고 그 위에 샌드매트층(Sand Mat)을 형성시켜 기초지반의 지지력을 증가시킨다. 이러한 보강메카니즘에 대한 지지력을 평가하는 식을 Yamanouchi(1985)가 제안을 하였다. 우리나라의 경우 주로 Yamanouchi가 제안한 식을 사용하여 설계를 행하고 있다. 그러나, 제안식에서 접지압을 감소시킬 목적으로 접지폭원을 증대시키면 오히려 지지력은 감소하고 소정의 안전율을 얻기 위해서는 성토두께를 증가해야 하는 등 지지력 산정에 있어서 논리적인 모순점을 내포하고 있다. 이러한 논리적인 모순점을 검토하기 위해서 모형토조에 연약지반을 조성하여 지지력실험을 실시하였다. 연약지반자체, 연약지반위에 보강재를 포설했을 때, 포설된 보강재에 인위적으로 인장력을 가했을 경우, 샌드매트층을 포설했을 때, 다른 조건을 일치시키며 단지 재하판의 폭을 달리 했을 때 등으로 나누어 모형재하시험을 행하였다. 실험결과를 다양하게 분석하였으며 특히 Yamanouchi가 제안한 식이 갖는 모순점을 설명하는 새로운 지지력식을 제안하였다.

• Journal of Korean Neurosurgical Society
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• 제62권4호
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• pp.376-381
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• 2019

Objective : To define optimal method that calculate the safe direction of cervical pedicle screw placement using computed tomography (CT) image based three dimensional (3D) cortical shell model of human cervical spine. Methods : Cortical shell model of cervical spine from C3 to C6 was made after segmentation of in vivo CT image data of 44 volunteers. Three dimensional Cartesian coordinate of all points constituting surface of whole vertebra, bilateral pedicle and posterior wall were acquired. The ideal trajectory of pedicle screw insertion was defined as viewing direction at which the inner area of pedicle become largest when we see through the biconcave tubular pedicle. The ideal trajectory of 352 pedicles (eight pedicles for each of 44 subjects) were calculated using custom made program and were changed from global coordinate to local coordinate according to the three dimensional position of posterior wall of each vertebral body. The transverse and sagittal angle of trajectory were defined as the angle between ideal trajectory line and perpendicular line of posterior wall in the horizontal and sagittal plane. The averages and standard deviations of all measurements were calculated. Results : The average transverse angles were $50.60^{\circ}{\pm}6.22^{\circ}$ at C3, $51.42^{\circ}{\pm}7.44^{\circ}$ at C4, $47.79^{\circ}{\pm}7.61^{\circ}$ at C5, and $41.24^{\circ}{\pm}7.76^{\circ}$ at C6. The transverse angle becomes more steep from C3 to C6. The mean sagittal angles were $9.72^{\circ}{\pm}6.73^{\circ}$ downward at C3, $5.09^{\circ}{\pm}6.39^{\circ}$ downward at C4, $0.08^{\circ}{\pm}6.06^{\circ}$ downward at C5, and $1.67^{\circ}{\pm}6.06^{\circ}$ upward at C6. The sagittal angle changes from caudad to cephalad from C3 to C6. Conclusion : The absolute values of transverse and sagittal angle in our study were not same but the trend of changes were similar to previous studies. Because we know 3D address of all points constituting cortical shell of cervical vertebrae. we can easily reconstruct 3D model and manage it freely using computer program. More creative measurement of morphological characteristics could be carried out than direct inspection of raw bone. Furthermore this concept of measurement could be used for the computing program of automated robotic screw insertion.