• 한국공작기계학회논문집
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• 제11권6호
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• pp.1-9
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• 2002

This study describes the geometric characteristics and the 5-axis machining method in order to make end mill cutter coming with insert tips. End mill geometry is consisted of flute part and insert tip part. Flute part modeled by using ruled surfaces with constant helix angle, and insert tip part modeled by rectangular planes containing tapped hole of specified direction in its center. In this study, the modeled insert tip part considered both of a radial rake angle and a axial rake angle, because they were important cutting conditions. In order to machining the virtual end mill defined from geometric characteristics, we programmed a special software to machining the end mill considered in this study. This software can generate NC-codes about following processes, end milling or ball end milling of flute part end milling of rectangular plane, centering of hole, drilling of hole, and tapping of hole. Ant sampled end mills were modeled and machined on 5-axis CNC machining center with two index tables. Since machined end mills were very agreeable to designed end mills, we saw that the method proposed in this study can be very useful for manufacturing of end mill body with insert tip.

• Journal of Radiation Protection and Research
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• 제36권3호
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• pp.107-118
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• 2011

Conventional (SRS) and fractionated (FSRS) stereotactic radiosurgery necessarily require stringent overall target point accuracy and precision. We determine three-dimensional intracranial target point deviations (TPDs) in a whole treatment procedure using magnetic resonance image (MRI)-based polymer-gel dosimetry, and suggest a technique for overall system tests. TPDs were measured using a custom-made head phantom and gel dosimetry. We calculated TPDs using a treatment planning system. Then, we compared TPDs using mid bi-plane and three-dimensional volume methods with spherical and elliptical targets to determine their inherent analysis errors; finally, we analyzed regional TPDs using the latter method. Average and maximum additive errors for ellipses were 0.62 and 0.69 mm, respectively. Total displacements were 0.92 ${\pm}$ 0.25 and 0.77 ${\pm}$ 0.15 mm for virtual SRS and FSRS, respectively. Average TPDtotal at peripheral regions was greater than that at central regions for both. Overall system accuracy was similar to that reported previously. Our technique could be used as an overall system accuracy test that considers the real radiation field shape.

• 한국멀티미디어학회논문지
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• 제5권1호
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• pp.94-104
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• 2002

본 연구는 하나의 도메인을 기반으로 하여 모델링된 Genus N 객체에 새로운 텍스쳐 매핑방법을 제안한 연구이다. 기존의 2D 텍스쳐 매핑의 문제점은 텍스쳐 도메인의 경계선이 객체상에 현저하게 나타난다는 사실이다. 이 현상은 부자연스러울 뿐 아니라 객체의 부드러운 연속성의 효과를 감소시킨다. 특히 무한대의 연속성을 가진 Genus N 객체는 경계선이 생성되지 않는 텍스쳐 매핑이 필수적이다. 이러한 텍스쳐 매핑을 위하여 multiperiodic 함수 즉, 불연속의 함수를 연속함수로 변형시키는 함수를 제안하였다. 하지만 사례에 따라 경계선이 보이는 텍스쳐가 더 사실적으로 보일 수 있다. 따라서 본 연구에서는 가중치를 이용하여 불연속과 연속 함수를 상호적으로 제어하도록 하였다.

• 한국항해항만학회지
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• 제32권6호
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• pp.447-452
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• 2008

본 연구에서는 만타형 수중운동체의 수평 및 수직 방향에 대한 자동제어 및 충돌회피 시스템을 확립하였다. PID 제어이론, 퍼지 추론 등이 적용되었으며, 시뮬레이션에 사용된 6자유도 운동 방정식은 이론계산과 구속모형 시험에 의하여 확립하였다. PID제어에 의한 심도제어 결과가 제시되었으며, UUV의 충돌 위험도는 가상 소나 시스템을 이용한 퍼지 추론으로 추정하였다. 이를 이용하여 만타형 수중운동체의 심도제어 시스템 및 충돌회피 시뮬레이션 시스템이 개발되었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권6호
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• pp.3165-3181
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• 2019

Spherical videos, which are also called 360-degree videos, have become increasingly popular due to the rapid development of virtual reality technology. However, the large amount of data in such videos is a huge challenge for existing transmission system. To use the existing encode framework, it should be converted into a 2D image plane by using a specific projection format, e.g. the equi-rectangular projection (ERP) format. The existing high-efficiency video coding standard (HEVC) can effectively compress video content, but its enormous computational complexity makes the time spent on compressing high-frame-rate and high-resolution 360-degree videos disproportionate to the benefits of compression. Focusing on the ERP format characteristics of 360-degree videos, this work develops a fast decision algorithm for predicting the coding unit depth interval and adaptive mode decision for intra prediction mode. The algorithm makes full use of the video characteristics of the ERP format by dealing with pole and equatorial areas separately. It sets different reference blocks and determination conditions according to the degree of stretching, which can reduce the coding time while ensuring the quality. Compared with the original reference software HM-16.16, the proposed algorithm can reduce time consumption by 39.3% in the all-intra configuration, and the BD-rate increases by only 0.84%.

• Structural Engineering and Mechanics
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• 제70권3호
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• pp.325-337
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• 2019

In the present article, cross ply laminated composite plates are considered and a simple sinusoidal shear deformation model is tested for analyzing their flexural, stability and dynamic behaviors. The model contains only four unknown variables that are five in the first order shear deformation theory (FSDT) or other higher order models. The in-plane kinematic utilizes undetermined integral terms to quantitatively express the shear deformation influence. In the proposed theory, the conditions of zero shear stress are respected at bottom and top faces of plates without considering the shear correction coefficient. Equations of motion according to the proposed formulation are deduced by employing the virtual work principle in its dynamic version. The analytical solution is determined via double trigonometric series proposed by Navier. The stresses, displacements, natural frequencies and critical buckling forces computed using present method are compared with other published data where a good agreement between results is demonstrated.

• Current Optics and Photonics
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• 제7권3호
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• pp.263-272
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• 2023

A collimator refers to an optical system that images a collimated beam at a desired point. A resolution target located at a near distance can be converted into a virtual image located at a long distance. To test the resolution for mobile cameras, a large target is placed at a long distance. If a collimator system is used, the target can be placed at a near distance. The space required for a resolution inspection can thus be drastically reduced. However, to inspect a mobile camera, the exit pupil of the collimator system and the entrance pupil of the mobile camera must match, and the stop of the collimator system must be located on the last surface. Because a collimator system cannot be symmetrical with respect to the stop, the distortion becomes extremely large, which can be corrected by combining the collimator symmetrically with respect to the object plane. A novel system was designed to inspect an optical lens on a mobile phone. After arranging the refractive power, lenses were added using the equivalent lens design method. The distortion was reduced to less than 1%. This optical system satisfies a half-field angle of 45° and an optical performance sufficient for inspection.

• Geomechanics and Engineering
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• 제33권4호
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• pp.369-380
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• 2023

The aim of this paper is to investigate stress analysis of semi-infinite soils consisting of two layers with twin rectangular tunnels under static loads. The region close to the ground surface and tunnel modelled within finite elements. In order to use a more realistic model, the far region is modelled within infinite elements. The material model of the layered soil is considered as elastic and isotropic. In the finite element solution of the problem, two dimensional (2D) plane solid elements are used with sixteen-nodes rectangular finite and eight-nodes infinite shapes. Finite and infinite elements are ordered to be suitable for the tunnel and the soils. The governing equations of the problem are obtained by using the virtual work principle. In the numerical process, the five-point Gauss rule is used for the calculation of the integrations. In order to validate using methods, comparison studies are performed. In the numerical results, the stress distributions of the two layered soils containing twin rectangular tunnels presented. In the presented results, effects of the location of the tunnels on the stress distributions along soil depth are obtained and discussed in detail. The obtained results show that the locations of the tunnels are very effective on the stress distribution on the soils.

• Advances in aircraft and spacecraft science
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• 제10권3호
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• pp.281-302
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• 2023

In this paper, bending analysis of exponentially varying functionally graded (FG) plate is presented using trigonometric shear deformation theory (TSDT) considering both transverse shear and normal deformation effects. The in-plane displacement field consists of sinusoidal functions in thickness direction to include transverse shear strains and transverse displacement include the effect of transverse normal strain using the cosine function in thickness coordinate. The governing equations and boundary conditions of the theory are derived using the virtual work principle. System of governing equations, for simply supported conditions, Navier's solution technique is used to obtain results. Plate material properties vary across thickness direction according to exponential distribution law. In the current theory, transverse shear stresses are distributed accurately through the plate thickness, hence obviates the need for a shear correction factor. TSDT results are compared with those from other theories to ensure the accuracy and effectiveness of the present theory. The current theory is in excellent agreement with the semi-analytical theory.

• 대한치과보철학회지
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• 제53권2호
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• pp.105-110
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• 2015

목적: 새롭게 개발된 인상채득이 가능한 치유지대주를 이용한 인상채득과 기존의 임프레션 코핑을 이용한 인상채득을 3차원적으로 비교함으로써 개발된 시스템의 정확성을 평가하였다. 재료 및 방법: 10명의 환자에서 구치부에 임플란트(SuperLine; Dentium, Seoul, Korea)를 식립 후 치유지대주(MyHealing; Raphabio Co., Seoul, Korea)를 연결하였다. 식립 3개월 후 보철물 제작을 위한 인상채득시 인상채득이 가능한 치유지대주를 이용한 transfer 방식과 기존의 인상용 코핑을 이용한 pick-up 방식으로 두 번 인상채득 후 각각 주모형을 제작하였다. 맞춤형 보철 지대주(Myplant; Raphabio Co., Seoul, Korea)를 제작하고 각각의 주모형에 체결 후 치과용 스캐너(Scanner S600; Zirkonzahn, South Tyrol, Italy)로 가상의 모형을 형성하였다. 3차원 분석 프로그램(Geomagic Qualify 12; Geomagic, Morrisville, NC, USA)을 이용하여 두 개의 가상의 모형을 중첩하여 지대주의 위치와 기울기의 차이를 분석하였다. 측정값은 Kruskal Wallis과 Mann-Whitney U test 방법을 통해 분석하였고, 유의수준은 0.05 로 설정하였다. 결과: 두 가지 인상법에 따른 지대주의 위치는 근원심 방향에서 0.032 mm, 협설측 방향에서 0.029 mm, 상하 방향에서 0.023 mm의 차이를 보였다. 기울기는 근원심 방향에서 $0.755^{\circ}$, 협설측 방향에서 $1.275^{\circ}$, 상하 방향에서 $0.420^{\circ}$의 차이를 보였다. 결론: 인상채득이 가능한 치유지대주를 이용한 인상채득 방식은 기존의 전통적인 인상용 코핑을 이용한 방식과 비교 시 0.032 mm 이내의 차이를 보였고 기존 논문과의 비교 시 유사한 수치이다.