• Journal of the Society of Naval Architects of Korea
• /
• v.31 no.3
• /
• pp.31-37
• /
• 1994

When a lot of input data are not distributed uniformly n a chord-span direction or when the given shape is complicated, it is very difficult to obtain an inverse matrix which represents the smooth Bi-cubic B-spline surface of the initial shape. To overcome this problem, we suggest image Surface Expansion Method(ISE Method) which is suggested for vertex creation of B-spline curves and surfaces. Its basic concept, convergency and verification are shown. Also B-spline curves and Surfaces represented by ISE Method were compared with those represented by the existing method which is based on the inverse matrix method, the pseudoinverse matrix method and the chord length approximation method for vertex yielding. Ship Hull Forms which have Knuckle, Bulbous Bow, Transom and Stern frame were represented by the ISE Method.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.19 no.10
• /
• pp.1910-1924
• /
• 1994

Curved 3D objects represented by range data contain large amounts of information compared with planar objects, but do not have distinct features for matching to those of object models. This makes it difficult to represent and identify a general 3D curved object. This paper introduces a new view-point independent approach to recognizing general 3D curved objects using range data. Our approach makes use of the relative geometric differences between particular points on the object surface and some model points. The model points are prespecified arbitrarily and keeping the task in mind so that the following task can be easily described using the model points. Our approach has several advantages. Since model points are specified arbitrarily and task dependently, further processing can be reduced in application by locating the model points at places which are useful for further operations in the task. The knowledge base is simple with less storage requirement. And, it is easy to compensate the uncertainties of positions estimation caused by noise and quantization error.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.7
• /
• pp.4381-4387
• /
• 2015

Ship hull is a compound curved shape and most of shipyards have been using gas heating method for the surface forming of steel plate. This traditional forming process have problems such as difficulties in heat input control and poor working conditions due to loud noise and air contamination. Recently, researches on automatic hull forming system have been conducted using high frequency induction heating method which have good control ability and favorable working environment. In this study, the induction heating simulation system for curved surface forming of steel plate was developed and induction heating experiments were performed. Based on the results of this study, efficient induction heating coil design and optimal heating conditions for the automatic hull forming system can be obtained.

• Journal of the Society of Naval Architects of Korea
• /
• v.38 no.3
• /
• pp.31-40
• /
• 2001

Low-order panel methods are being used to design marine propellers. Since the potential value over each panel for these methods is assumed to be a constant, the accuracy of prediction is known to be limited. Therefore, a higher order boundary element method(HOBEM) has been studied to enhance the accuracy of prediction. In this paper, a HOBEM representing the body boundary surfaces and physical quantities by a 9-node Lagrangian shape function is employed to analyse the flow around marine propellers in steady potential flow. First, the numerical results for a circular wing with thickness variations are compared with Jordan's linear solution. Then, the computational results of two propellers(DTRC 4119 & DTRC 4842 propeller) are compared with the experimental and numerical results published. The pressure distribution on the surface of the propeller is also compared with experimental data.

• Korean Journal of Optics and Photonics
• /
• v.16 no.4
• /
• pp.304-312
• /
• 2005

Field performance of several different types of diffractive optical elements(DOEs) has been carried out. Using Zemax model, we have designed five different types of DOEs, such as transmissive flat-DOE, transmissive curved-DOE, reflective flat-DOE, reflective curved-DOE and parabolic mirror, We have applied two different wavelengths, i.e., 13 m(EUV) and 632.8 nm(visible) to above DOEs. Off_axis dominate aberrations and the diffraction limiting (Rayleigh limit) field angles have been investigated and compared at both wavelengths for each DOE. At diffraction limit, field angle of curved-DOEs was much greater than that of flat-DOEs for both transmission and reflective types. We also showed that dominated off_axis aberration of flat-DOEs was coma, but that of curved-DOEs was mixture of astigmatism and curvature of field. The measured field angle and expected OPD aberrations were well coincided with theoretical ones. Increasing the ratio of field angle with wavelength was more effective in curved-DOEs than flat-DOEs.

• Journal of KIISE:Computer Systems and Theory
• /
• v.26 no.8
• /
• pp.875-883
• /
• 1999

서로 다른 기하학적 모델링 시스템에 사용되는 곡선 및 곡면의 자료 교환에서, 시스템이 지원하는 그 곡선 및 곡면의 최대 차수에 제한이 있을 때, 낮은 차수로의 차수 감소가 필요하다. 본 논문에서는 근사 변환에 의한 B-spline 곡선의 차수 감소 방법을 제시한다. 기존의 Bzier 곡선의 차수감소 방법들을 적용하고, 그 방법들을 비교 분석한다. B-spline 곡선의 knot 제거 알고리즘이 자료 감소를 위해 차수 감소 과정에 적용된다.Abstract The degree reduction of B-splines is required in exchanging parametric curves and surfaces of the different geometric modeling systems because some systems limit the supported maximal degree. We propose an approximate degree reduction method of B-spline curves using the existing Bzier degree reduction methods. Knot removal algorithm is used to reduce data in the degree reduction process.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.4 no.5
• /
• pp.931-936
• /
• 2000

A novel CPFDTD algorithm for modeling the smooth curved surfaces is presented. This scheme subdivides electric fields on the distorted grid into the extended contour field, the non-distorted field, and the quasi-available field to avoid the collinear borrowing approximation. Several preceding methods are applied to the I-plane sectoral horn antenna to get far-field patterns. The accuracy of the presented method is demonstrated by comparison with measured values.

• Journal of the Society of Naval Architects of Korea
• /
• v.52 no.6
• /
• pp.501-508
• /
• 2015

Lately, much research on hull plate forming has been successful in improving productivity of the forming process. Those researches include forming methods, forming information, and automation. After forming each plate, the fabricated surface is compared with the corresponding designed surface. Two sets of data from the designed and fabricated surfaces are matched in order to complete the forming process. However, only a few papers deals with comparison of two surfaces. This paper presents a new matching method based on the bounding volume hierarchy (BVH). By comparing the conventional method, this new approach using BVH shows not only good agreement but also better advantages.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
• /
• 2000.10a
• /
• pp.40-50
• /
• 2000

본 연구에서는 Rolleiflex 6006 측정용 카메라로 촬영된 사진과 DCS 420 디지털 카메라로부터 촬영된 화상을 이용, 수치근접사진측량을 실시한 후, 조경석의 표면 거칠기 측정 정확도 향상을 위하여 최소제곱법으로 기준평면 또는 기준곡면을 찾아 사용하는 방법을 연구하였으며, 조경석 표면의 연마 이전과 연마 이후의 표면 거칠기를 측정, 비교하여 연마후의 거칠기 감소크기를 산출하고, 측정 정확도를 알아보기 위하여 거칠기가 거의 없는 평면인 돌과 곡면인 돌의 표면 거칠기를 측정한 결과, 그 거칠기를 기대정확도 이상인 각각 $\pm$0.lmm 및 $\pm$0.2mm의 정확도로 측정할 수 있었다. 또한 측정용 카메라인 경우 렌즈왜곡 보정에 있어서 검정자료를 토대로 기준점을 사용하지 않는 직접보정방법인 Newton-Raphson법을 적용하여 기하학적 정확도가 향상된 수치사진화상을 얻을 수 있었으며, DCS 420 디지털 카메라와 윈도우 운영체계인 Visual basic 6.0을 이용하여, 표면 거칠기 측정시스템을 구축함으로써 연마이전 조경석과 연마이후 조경석에 대한 표면 거칠기 및 형상을 정밀 측정할 수 있는 수치근접사진측량기법을 제시할 수 있었다.

• Journal of the Korea Society of Computer and Information
• /
• v.10 no.1 s.33
• /
• pp.35-44
• /
• 2005

The degree reduction of B-splines is necessary in exchanging parametric curves and surfaces of the different geometric modeling systems because some systems limit the supported maximal degree. In this paper, We provide an our experimental results in approximate conversion for B-splines apply to degree reduction. We utilize the existing Bezier degree reduction methods, and analyze the methods. Also, knot removal algorithm is used to reduce data in the degree reduction Process.