• Journal of the Korean Wood Science and Technology
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• 제49권1호
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• pp.82-92
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• 2021

Nakdong technique is an unfamiliar scorching treatment using an iron heated in a kiln over 1000℃. It is a typical convention in Asian countries to treat Nakdong on the surface of paulownia species. The scorching treatment changes the surface characteristics as well as the color of the wood. This study focused on the effects of functional features such as water resistance, anti-mold, anti-termite, and sound improvement because this treatment is usually used on paulownia wood-bodied musical instruments surface. It took 28'57" for Nakdong-iron treated surface to absorb a droplet of water. The absorbance time of iron treated surface was longer than that of torch treated one. There was no noticeable effect on the anti-mold test. On the anti-termite test, there was nearly 3% more mean mass loss on the torch samples than controlled and iron treated ones. In examining the sound radiation coefficient before and after Nakdong treatment, the Nakdong-iron treated surface showed an increase in the average value of 1.2 m4/kg s, which means that it has sound quality improvement. Through this research, the Nakdong technique results are expected to be used as basic-data for further research and give a practical idea for using the traditional treatment method on the wood surface.

• 한국BIM학회 논문집
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• 제11권4호
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• pp.42-52
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• 2021

Paneling building facades is one of the essential procedures in building construction. Traditionally, it has been an easy task of simply projecting paneling patterns drawn in drawing boards onto 3d building facades. However, as many organic or curved building shapes are designed and constructed in modern architectural practices, the traditional one-to-one projection is becoming obsolete for the building types of the kind. That is primarily because of the geometrical discrepancies between 2d drawing boards and 3d curved building surfaces. In addition, curved compound surfaces are often utilized to accommodate the complicated spatial programs, building codes, and zoning regulations or to achieve harmonious geometrical relationships with neighboring buildings in highly developed urban contexts. The use of the compound surface apparently makes the traditional paneling pattern projection more challenging. Various mapping technics have been introduced to deal with the inabilities of the projection methods for curved facades. The mapping methods translate geometries on a 2d surface into a 3d building façade at the same topological locations rather than relying on Euclidean or Affine projection. However, due to the intrinsic differences of the planar 2d and curved 3d surfaces, the mapping often comes with noticeable distortions of the paneling patterns. Thus, this paper proposes a practical method of drawing paneling patterns directly on a curved compound surface utilizing Geodesic, which is faithful to any curved surface, to minimize unnecessary distortions.

• 실천공학교육논문지
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• 제10권2호
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• pp.89-94
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• 2018

사출 성형에서 금형 온도는 성형품의 품질에 큰 영향을 준다. 어느 정도의 온도가 적정한가는 성형 재료, 성형품에서 요구되는 품질에 의해서 결정되고 중요한 것은 그 온도가 안정적이어야 한다. 먼저 그 수지에 적합한 금형 온도 조건 범위 내에서 성형품이 요구하는 품질에 맞는 금형 온도를 설정해야 한다. 즉, 성형품의 표면 광택, 성형 사이클의 단축, 변형 방지, 수축 및 수지 흐름의 용이성 등의 중요성에 의해서 금형 온도는 변화한다. 실질적인 금형 기술 향상을 위해서 사출 금형을 설계하고 제작하는 산업체에서 적용할 수 있는 온도 제어에 대한 애로 기술 과정의 훈련 모형을 제시하고자 한다.

• 한국컴퓨터그래픽스학회논문지
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• 제8권3호
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• pp.1-7
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• 2002

This paper presents a practical technique for approximating the boundary surface of the volume swept out by three-dimensional objects using the depth-buffer. Objects may change their geometries and orientations while sweeping. The sweep volume is approximated as a union of volume elements, which are just rendered inside appropriate viewing frusta of virtual cameras and mapped into screen viewports with depth-buffer. From the depth of each pixel in the screen space of each rendering, the corresponding point in the original world space can be computed. Appropriately connecting these points yields polygonal faces forming polygonal surface patches approximately covering some portion of the sweep volume. Each view frustum adds one or more surface patches in this way, and these presumably overlapped polygonal surface patches approximately enclose the whole sweep volume. These patches may further be processed to yield non-overlapped polygonal surfaces as an approximation to the boundary of the original 3D sweep volume.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.214-219
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• 2004

Crack tip behavior of single mode loading condition(mode I)depend on tensile loading component but one of mixed mode loading condition(mode I+II) have influenced on shear loading component like the practical structure. Because crack closure is caused by shear loading component under mixed-mode loading a research on the behavior in the stage of crack initiation and propagation require to be evaluate about crack closure effect by fatigue crack surface friction. For that reasion we examined the behavior at the crack tip by direct measuring method. Measured behavior at the crack tip was analyzed through vector crack tip displacement. As a result, crack propafation equation was corrected by considering with crack closure effect. In addition we compared fatigue fracture crack surface and crack closure level.

• 펄프종이기술
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• 제33권1호
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• pp.1-7
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• 2001

The immediate purposes of this study is to establish the surface chemical principles associated with the flotation process of waste papers and to verify them by practical flotation experiments. To achieve this AKD sized hydrophobic microcrystallince cellulose (MCC) with different levels of hydrophobicity, and hydrophilic MCC dyed with black were prepared as model substances. The effects of surface characteristics on flotation efficiency were evaluated by measuing the brightness of the flotation rejects obtained after the flotation experiments carried out using MCC mixtures prepared with different ratios of hydrophobic and hydrophilic MCCs. Results showed that more than 90% of the flotation rejects consisted of hydrophobic MCC indicating the critical importance of the hydrophobicity of the materials in the flotation process. The proportions of hydrophobic materials in the reject remained constant when highly sized MCC was used as a model of hydrophobic substance.

• 한국정밀공학회지
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• 제16권7호
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• pp.94-100
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• 1999

This study adopted the ultra precision machining system which was composed of an air bearing spindle, a granite bed, air pad and a linear feeding mechanism. It also applied the cutting experiment on the aluminum alloy. To evaluate the safety of high speed machining, we examined the surface roughness according to the changes of cutting speed and obtained the speed limit. This paper also studied the effect of cutting condition such as feed rates and depths of cut on the surface roughness within the speed limit. This provided practical information regarding ultra precision machining.

• Geomechanics and Engineering
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• 제15권4호
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• pp.937-945
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• 2018

A probabilistic study of a reinforced earth wall in a frictional soil using the surface response methodology (RSM) is presented. A deterministic model based on numerical simulations is used (Abdelouhab et al. 2011, 2012b) and the serviceability limit state (SLS) is considered in the analysis. The model computes the maximum horizontal displacement of the wall. The response surface methodology is utilized for the assessment of the Hasofer-Lind reliability index and is optimized by the use of a genetic algorithm. The soil friction angle and the unit weight are considered as random variables while studying the SLS. The assumption of non-normal distribution for the random variables has an important effect on the reliability index for the practical range of values of the wall horizontal displacement.

• 한국CDE학회논문집
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• 제4권1호
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• pp.32-42
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• 1999

Approximate lofting or skinning is one of practical surface modeling techniques well used in CAD and reverse engineering applications. Presented in this paper is a method for approximately lofting a given set of curves wihin a specified tolereance. It is based on refitting input curves simultaneously on a common knot vector and interpolating them to get a resultant NURBS surface. A concept of reducing the number of interior knots of the common knot vector is well adopted to acquire more compact representation for the resultant surface. Energy minimization is newly introduced in curve refitting process to stabilize the solution of the fitting problem and get more fair curve. The proposed approximate lofting provides more smooth surface models and realizes more efficient data reduction expecially when the parameterization and compatibility of input curves are not good enough. The method has been successfully implemented in a new CAD/CAM product VX Vision? of Varimetrix Corporation.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제2권3호
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• pp.198-203
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• 2002

In this paper, a 3D model of the surface deformation is created in virtual environment. A proposed method is based on the fuzzy model and it is enough that only one rule set is added to the fuzzy model to model a surface deformation. Furthermore, the designer can easily determine which parameters should be used and how they should be changed in order to obtain the shapes as required. The proposed method is, thus, a simple, but effective technique that can also be used in practical applications. The results of the computer simulation are also given to demonstrate the validity of the proposed algorithm.