• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.6
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• pp.1-15
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• 2009

In this paper, we have proposed an automated system that accurately measures the thickness and unbalanced wear of brake shoes, and the distance between brake shoes and wheels for travelling rolling stock. The images of brake shoes are captured automatically while rolling stock is passing by an inspection station. And in order to measure the thickness, etc. the locations of brake shoes are first determined because the locations are not the same in the captured image. Toward this goal, shadow regions between the brake shoes and wheels are utilized that are common in all captured images. The boundary of the shadow regions is modeled by an second order polynomial, and constrained curve fitting method is adopted to detect a curve (the initial curve) that passes through the regions. Then, three curves that correspond to the front, back of brake shoes and wheels, and a line that passes through the vertical surface of brake shoes are detected using the initial curve and intensity change information. Finally, the thickness, etc. are calculated using the detected curves and line, and experimental results showed that the brake shoe thickness was measured with an accuracy of 0.654mm.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.419-426
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• 1986

In an attempt to develop a method for the design of the aerial rope way, the traditional theories of rope way were examined and compared. The resulting formulas of the traditional and approximate parabolic curve theory were summarized and those of the catenary curve theory as an exact ones were summarized and newly developed when necessary. In particular, it was found that the resulting formulas from both of these theories can fully be expressed with only three dimensionless parameters $U^{*}$, $V^{*}$, and $W^{*}$, improving compactness and generality of these formulas. Comparision of the theories were done through error analysis, and it was shown that the error of the approximate parabolic curve is of order $U^{*2}$ and $V^{*}$. From this, it was concluded that the traditional parabolic curve theory has its limitation when the rope way becomes larger or steeper, leading to the necessity of the use of catenary curve theory.ve theory.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.1
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• pp.26-35
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• 1987

As an attempt to make the multi-objection for the line design of the rope way, the resulted formulas from the catenary curve as exact ones were summarized, and it was found out that the Kuhn-Tucker's optimality conditions and regions of the objective functions can analytically be expressed with dimensionless parameters. The Pareto's optimum solution set was analytically obtained through the objective function-the minimum relation of $W^{*}$, and $W^{*}$ is a trade-off relation. From this, The dimension of a rope and the value of an initial tension that are the standard in design of the rope way were determined. It was concluded that $V^{*}$ should become minimum, and that the ratio of the dimension of rope to the value of and initial tension become larger than superposition factor corresponding to curve AB.to curve AB.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.1
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• pp.53-63
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• 1988

Using COD-R curves, instability of crack growth in ductile material is studied here. Tearing modulus $T_{\delta}$, based on the COA concept is defined and the instability criterion $T_{{\delta}{\app}}$> $T_{{\delta}{\mat}}$ is compared with experiments. Variations of the COD-R curve and the location of rotation center are experimentally investigated as the initial crack ratio varies. Three-point bend specimens of alloy steel SCM4 are used here and two clip-on gauges are installed in order to obtain the COD-R curve. The results show that the tearing modulus $T_{\delta}$ is a good measure to characterize the instability of crack growth. Also it is found that the location of rotation center is almost constant regardless of the initial crack ratio and the amount of the crack growth.

• Journal of the Korea Computer Graphics Society
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• v.17 no.3
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• pp.33-42
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• 2011

We present a new technique for removing interior knots of parametric B-spline curves. An initial curve is constructed by continuous $L_{\infty}$ approximation proposed by Eck and Hadenfeld. We employ Hausdorff distance to measure the shape difference between the original curve and the initial one. The final curve is obtained by minimizing their Hausdorff distance. We demonstrate the effectiveness of our technique with experimental results on various types of planar and spatial curves.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.4
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• pp.803-808
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• 2010

We propose a smooth path planning method for autonomous mobile robots. Due to nonholonomic constraints by obstacle avoidance, the smooth path planning is a complicated one. We generate smooth path that is considered orientation of robot under nonholonomic constraints. The proposed smooth planning method consists of two steps. Firstly, the initial path composed of straight lines is obtained from V-graph by Dijkstra's algorithm. Then the initial path is transformed by changing the curve. We apply the cardinal spline into the stage of curve generation. Simulation results show a performance of proposed smooth path planning method.

• 한국방재학회:학술대회논문집
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• 2010.02a
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• pp.60.1-60.1
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• 2010

본 연구에서는 년 최대 홍수량의 발생에 대한 대안으로 사용하는 PMF 추정에 관한 내용을 중심으로 분석하고자 한다. PMF를 산정하는 매개변수 도달시간(Time of concentration, TC)과 저류상수(Storage constant, K), 유출곡선번호(Runoff curve number, CN), 감수상수(Recession constant, RC), 초기손실(Initial loss, IL), 초기기저유량(Initial base flow, IBF), Threshold(TQ)들 중 CN값을 고정 하였을 때와 고정하지 않았을 때로 나눠 산정된 각각의 PMF와 기 발표된 PMF와 상호비교 분석을 통해 신뢰성 있는 분석방법을 제시하였다.

• Journal of Magnetics
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• v.2 no.3
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• pp.105-109
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• 1997

The Preisach model neds a density function or Everett function for the hysterisis operator to simulate the hysteresis phenomena. To obtain the function, many experimental data for the first order transition curves are required. However, it needs so much efforts to measure the curves, especially for the hard magnetic materials. By the way, it is well known that the density function has the Gaussian distribution for the interaction axis on the Preisach plane. In this paper, we propose a simple technique to determine the distribution function or Everett function analytically. The initial magnetization curve is used for the distribution of the Everett function for the coercivity axis. A major, minor loop and the initial curve are used to get the Everett function for the interaction axis using the Gaussian distribution function and acceptable results were obtained.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.8
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• pp.4025-4042
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• 2017

Session initiation protocol (SIP) is a kind of powerful and common protocols applied for the voice over internet protocol. The security and efficiency are two urgent requirements and admired properties of SIP. Recently, Hamed et al. proposed an efficient authentication and key agreement scheme for SIP. However, we demonstrate that Hamed et al.'s scheme is vulnerable to de-synchronization attack and cannot provide anonymity for users. Furthermore, we propose an improved and efficient authentication and key agreement scheme by using elliptic curve cryptosystem. Besides, we prove that the proposed scheme is provably secure by using secure formal proof based on Burrows-Abadi-Needham logic. The comparison with the relevant schemes shows that our proposed scheme has lower computation costs and can provide stronger security.

• Journal of Ocean Engineering and Technology
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• v.22 no.1
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• pp.70-74
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• 2008

It is important to reduce the vibration and noise of submarines and ships. For the purpose of noise reduction, various researches are actively being conducted on the employment of complex structures. However, in the case of numerical analysis for complex structures with damping materials, substantial errors can be generated by the absence of an exact damping model. Thus experimental model analysis is necessary for the verification of a numerical analysis for complex structures. In this research, vibration experiments are conducted in order to ascertain the vibration properties of cantilever beam attached damping materials. First, an initial value is obtained by using a direct linear method. Next, based on this initial value, the exact modal parameters of the cantilever beam are obtained by using the Newton-Raphson method.