• 펄프종이기술
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• 제47권4호
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• pp.177-186
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• 2015

Until Mandelbrot introduced the concept of fractal geometry and fractal dimension in early 1970s, it has been generally considered that the geometry of nature should be too complex and irregular to describe analytically or mathematically. Here fractal dimension indicates a non-integer number such as 0.5, 1.5, or 2.5 instead of only integers used in the traditional Euclidean geometry, i.e., 0 for point, 1 for line, 2 for area, and 3 for volume. Since his pioneering work on fractal geometry, the geometry of nature has been found fractal. Mandelbrot introduced the concept of fractal geometry. For example, fractal geometry has been found in mountains, coastlines, clouds, lightning, earthquakes, turbulence, trees and plants. Even human organs are found to be fractal. This suggests that the fractal geometry should be the law for Nature rather than the exception. Fractal geometry has a hierarchical structure consisting of the elements having the same shape, but the different sizes from the largest to the smallest. Thus, fractal geometry can be characterized by the similarity and hierarchical structure. A process requires driving energy to proceed. Otherwise, the process would stop. A hierarchical structure is considered ideal to generate such driving force. This explains why natural process or phenomena such as lightning, thunderstorm, earth quakes, and turbulence has fractal geometry. It would not be surprising to find that even the human organs such as the brain, the lung, and the circulatory system have fractal geometry. Until now, a normal frequency distribution (or Gaussian frequency distribution) has been commonly used to describe frequencies of an object. However, a log-normal frequency distribution has been most frequently found in natural phenomena and chemical processes such as corrosion and coagulation. It can be mathematically shown that if an object has a log-normal frequency distribution, it has fractal geometry. In other words, these two go hand in hand. Lastly, applying fractal principles is discussed, focusing on pulp and paper industry. The principles should be applicable to characterizing surface roughness, particle size distributions, and formation. They should be also applicable to wet-end chemistry for ideal mixing, felt and fabric design for papermaking process, dewatering, drying, creping, and post-converting such as laminating, embossing, and printing.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(2)
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• pp.266-269
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• 2000

As the device geometry continuously shrink down less than sub-quarter micrometer, DRAM makers are going to replace conventional tungsten-polycide with tungsten bit-line structure in order to reduce the chip size and use it as a local interconnection. In this paper we showed low resistance and leakage tungsten bit-line process with various RTP(Rapid Thermal Process) temperature. As a result we obtained that major parameters impact on tungsten bit-line process are RTP Anneal temperature and BF2 ion implantation dopant. These tungsten bit-line process are promising to fabricate high density chip technology.

• Journal of Electrical Engineering and Technology
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• 제11권2호
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• pp.463-469
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• 2016

In this paper, the use of a dual composite right/left-handed coplanar waveguide (CPW) transmission line is proposed for the design of a band rejection filter. The notch property of the filter is achieved by combining the convex signal line with the shorted concave meander line, and the equivalent circuit model is extracted from the geometry of the unit cell for organizing the band rejection property. Then the equivalent parameters of the unit cell are analyzed to identify those behaviors. And the dispersion characteristics and energy distributions are simulated. In the end, the band rejection filter is manufactured by cascading two proposed unit cells. We show that the measurement result for the resonant frequency demonstrates good agreement with the simulation result and the band rejection filter provides a rejection performance of 17.5 dB at the stopband frequency ranging from 869 MHz to 894 MHz.

• 대한수학회지
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• 제56권2호
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• pp.387-419
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• 2019

A fullness conjecture of Kuznetsov says that if a smooth projective variety X admits a full exceptional collection of line bundles of length l, then any exceptional collection of line bundles of length l is full. In this paper, we show that this conjecture holds for X as the blow-up of ${\mathbb{P}}^3$ at a point, a line, or a twisted cubic curve, i.e., any exceptional collection of line bundles of length 6 on X is full. Moreover, we obtain an explicit classification of full exceptional collections of line bundles on such X.

• 한국수학교육학회지시리즈D:수학교육연구
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• 제26권4호
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• pp.271-289
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• 2023

This research investigates the development of elementary students' concepts of line segments, straight lines, and rays, employing metaphor analysis as a research methodology. By analyzing metaphorical expressions, the research aims to explore how elementary students form these geometric concepts line segments, straight lines, and lays and evolve their understanding of them across different grades. Surveys were conducted with elementary school students in grades three to six, focusing on metaphorical expressions and corresponding their reasons associated with line segments, straight lines, and rays. The data were analyzed through coding and categorization to identify the types in students' metaphorical expressions. The analysis of metaphorical expressions identified five types: straightness, infinity or direction, connections of another geometric concepts, shape and symbols, and terminology.

• International Journal of Korean Welding Society
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• 제4권1호
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• pp.30-37
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• 2004

There have been continuous efforts on automating welding processes. This automation process could be said to fall into two categories, weld seam tracking and weld quality evaluation. Recently, the attempts to achieve these two functions simultaneously are on the increase. For the study presented in this paper, a vision sensor is made, a vision system is constructed and using this, the 3 dimensional geometry of the bead is measured on-line. For the application as in welding, which is the characteristic of nonlinear process, a fuzzy controller is designed. And with this, an adaptive control system is proposed which acquires the bead height and the coordinates of the point on the bead along the horizontal fillet joint, performs seam tracking with those data, and also at the same time, controls the bead geometry to a uniform shape. A communication system, which enables the communication with the industrial robot, is designed to control the bead geometry and to track the weld seam. Experiments are made with varied offset angles from the pre-taught weld path, and they showed the adaptive system works favorable results.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.333-338
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• 2001

Fractal geometry is a non-Euclidean geometry which has been developed to quantitative analysis irregular or fractional shapes. Fractal dimension of irregular surface has fractal values ranging from 2 to 3 and of irregular line profile has fractal values ranging from 1 to 2. In this paper, quantitative analysis of crack growth patterns during the fracture processing of fiber-reinforced cement composites based on fractal geometry. The fracture behaviors of fiber reinforced mortar beams subjected to three-point loading in flexure. The beams all had a single notch depth, but varing volume fractions of polypropylene, cellulose fibers. The crack growth behaviors, as observed through the image processing system, and the box counting method was used to determine the fractal dimension, Df. The results showed that the linear correlation exists between fractal dimension and fracture energy of the fiber reinforced cement mortar.

• Journal of Mechanical Science and Technology
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• 제17권4호
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• pp.617-625
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• 2003

Effects of Injector nozzle geometry and operating pressure conditions such as opening pressure, ambient pressure. and injection pressure on the transient fuel spray behavior have been examined by experiments. In order to clarify the effect of internal flow inside nozzle on the external spray, flow details Inside model nozzle and real nozzle were alto investigated both experimentally and numerically. for the effect of injection pressures, droplet sizes and velocities were obtained at maximum line pressure of 21 MPa and 105 MPa. Droplet sizes produced from the round inlet nozzle were larger than those from the sharp inlet nozzle and the spray angle of the round inlet nozzle was narrower than that from the sharp inlet nozzle. With the increase of opening pressure, spray tip penetration and spray angle were increased at both lower ambient pressure and higher ambient pressure. The velocity and size profiles maintained similarity despite of the substantial change in injection pressure, however, the increased injection pressure produced a higher percentage of droplet that are likely to breakup.

• 콘크리트학회지
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• 제10권1호
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• pp.161-169
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• 1998

프리스트레스트 콘크리트 교량의 건설공법인 프리캐스트 세그멘탈 공법에서선형관리 기술은 핵심기술 중 하나이다. 그럼에도 불구하고 , 우리나라에서는 몇몇 교량기술자들에게 경험적으로 이해되고 있는 수준을 넘지 못하고 있다. 특히, 세그멘트의 제작에서부터 반드시 필요한 선형관리용 S/W 및 그 운용기술은 아직까지도 선진기술에 의존하고 있는 실정이다. 본 연구에서는 프리캐스트 세그멘탈 공법의 선형관리 기술에 대한 연구를 통하여 3차원적인 세그멘트 제작관리와 가설시 선형관리를 위한 제작선형을 자동적으로 계산할 수 있는 GEOCON을 개발하였다. 본 논문에서는 GEOCON의 알고리즘에 대하여 논하였으며, 특히 수치예제로서 제작오차의 발생위치에 따라 교량선형에 미치는 영향을 분석하였다.

• 한국수학교육학회지시리즈A:수학교육
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• 제45권3호
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• pp.367-373
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• 2006

This study suggests that it is necessary to prove that the values of three areas of a triangle, which are obtained by the multiplication of the respective base and its corresponding height, are the same. It also seeks to deeply understand the meaning of Area formula of triangles by exploring some questions raised in the analysis of the proof. Area formula of triangles expresses the invariance of congruence and additivity on one hand, and the uniqueness of parallel line, one of the characteristics of Euclidean geometry, on the other. This discussion can be applied to introducing and developing exploratory learning on area in that it revisits the ordinary thinking on area.