• Tribology and Lubricants
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• v.34 no.1
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• pp.1-8
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• 2018

This paper presents the analysis of friction master curves for a sliding elastomer on rough granite. The hysteresis friction is calculated using an analytical model that considers the energy spent during the local deformation of the rubber due to surface asperities. The adhesion friction is also considered for dry friction prediction. The viscoelastic modulus of the rubber compound and the large-strain effective modulus are obtained from dynamic mechanical analysis (DMA). We accurately demonstrate the large strain of rubber that contacts with road substrate using the GW theory. We found that the rubber block deforms approximately to 40% strain. In addition, the viscoelastic master curve considering nonlinearity (at 40% strain) is derived based on the above finding. As viscoelasticity strongly depends on temperature, it can be assumed that the influence of velocity on friction is connected to the viscoelastic shift factors gained from DMA using the time-temperature superposition. In this study, we apply these shift factors to measure friction on dry granite over a velocity range for various temperatures. The measurements are compared to simulated hysteresis and adhesion friction using the Kluppel friction theory. Although friction results in the low-speed band match well with the simulation results, there are differences in the predicted and experimental results as the velocity increases. Thus, additional research is required for a more precise explanation of the viscoelastic material properties for better prediction of rubber friction characteristics.

• Composites Research
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• v.36 no.3
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• pp.141-153
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• 2023

This review paper presents an introduction of contact mechanics and rubber friction theory for sliding friction of elastomer composites in contact with rough surfaces. Particularly, Klüppel & Heinrich theory considers the self-affine (or fractal) characteristic for rough surfaces to predict adhesion and hysteresis frictions of elastomers based on the contact mechanics of Greenwood & Williamson. Due to dynamic excitation process of elastomer composites while sliding in contact with multiscale surface roughness (or asperity), viscoelastic properties in a wide frequency range becomes major contributor to friction behaviors. A brief description and examples are provided to construct a viscoelastic master curve considering nonlinear viscoelasticity of elastomer composites. Finally, application of rubber friction theory to tire tread compounds in traction with road surfaces is discussed with several experimental and theoretical results.

• Water for future
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• v.28 no.4
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• pp.185-194
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• 1995

The objective of this study is to explore scale problem and to analyze the relations between scale and geomorphologic parameters of the rainfall-runoff model. Generally, measurement and calculation of geomorphologic parameters rely on and are sensitive to the resolution of source information available. Therefore, rainfall-runoff models using geomorphologic parameters should take account of the effects of the map scale used in their development. The derived rainfall-runoff model considering scale problem in this research is the GIUH type model, that is a basin IUH consisting of the channel network response and hillslope response. The cannel network response is computed by means of the diffusion analogy transformed from linearized St. Venant equation and hillslope response is calculated by 2-parameter gamma distribution function. Representing geomorphologic structure of the channel network and initial distribution of its response is width function. This width function is derived by fractal theory and Melton's law to consider scale problems and is weighted by the source location function (SLF) proposed in this research to increase the applicability.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.5
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• pp.110-116
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• 2008

This paper presents a new postprocessing method to eliminate the false minutiae, that caused by the skelectonization of fingerprint image, and an image compression method using Isometric Self Organizing Map(ISOSOM). Since the SOM has simple structure, fast encoding time, and relatively good classification characteristics, many image processing areas adopt this such as image compression and pattern classification, etc. But, the SOM shows limited performances in pattern classification because of it's single layer structure. To maximize the performance of the pattern classification with small code book, we a lied the Isometric SOM with the isometry of the fractal theory. The proposed Isometric SOM postprocessing and compression algorithm of fingerprint image showed good performances in the elimination of false minutiae and the image compression simultaneously.

• Water for future
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• v.27 no.3
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• pp.45-54
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• 1994

Basic theory of fractal dimension is introduced and performed for the generated time series using the water balance model. The water balance equation over a large area is analyzed at seasonal time scales. In the generation and modification of mesoscale circulation local recycling of precipitation and dynamic effects of soil moisture are explicitly included. Time delay is incorporated in the analysis. Depending on the parameter values, the system showed different senarios in the evolution such as fixed point, limit cycle, and chaotic types of behavior. The stochastic behavior of the generated time series is due to deterministic chaos which arises from a nonlinear dynamic system with a limited number of equations whose trajectories are highly sensitive to initial conditions. The presence of noise arose from the characterization of the incoming precipitation, destroys the organized structure of the attractor. The existence of the attractor although noise is present is very important to the short-term prediction of the evolution. The implications of this nonlinear dynamics are important for the interpretation and modeling of hydrologic records and phenomena.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.79-82
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• 2006

최근 사물에 태그를 부착하여 무선으로 사물과 주변의 정보를 감지하는 RFID 기술이 등장하여 IT시장을 선도할 기술로 주목받고 있다. 그 중 국내에서 아마추어용으로 사용되던 433MHz대역이 컨테이너용 RFID 대역으로 지정되면서 국내에서도 활발히 연구가 이루어지고 있으며, 부산항에서 시범 운영하고 있으며 향후 확대 운영할 계획에 있다. 이에 본 논문에서는 프랙탈 이론을 적용하여 433MHz대역의 RFID 태그 안테나를 설계 및 제작하였다. 프랙탈 이론 중 민코스키 곡선을 응용하였고, 중심에 미앤더를 둔 구조로 설계하였다. 또한 접지면을 안테나와 같은 면에 구조로 최종 설계하였다.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.11
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• pp.93-101
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• 1997

Ever since the nonlinearity of machine tool dynamics was established, researchers attempted to make use of this fact to devise better monitoring, diagnostics and control system, which were hitherto based on linear models. Theory of chaos which explains many nonlinear phenomena comes handy for furthering the analysis using nonlinear model. In this study, measuring system will be constructed using multi-sensor (Tool Dynamometer, Acoustic Emission) in end milling process. Then, it will be verified that cutting force is low-dimensional chaos by calculating Lyapunov exponents. Fractal dimension, embedding dimension. And it will be investigated that the relation between characteristic parameter calculated from sensor signal and tool wear.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2015.11a
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• pp.305-306
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• 2015

본 논문은 복잡다단한 환경변화에 효과적으로 대응하기 위하여 오늘날 여러 학문 분야에서 주로 이용되고 있는 복잡계 이론의 사고와 방법론을 기반으로 테러대응을 위한 분야별 제 접근에 대하여 논하는데 그 목적이 있다. 우리는 수많은 테러조직 및 테러환경 요인들과 연결된 복잡한 시스템 속에서 활동하고 있기 때문에 이 모든 것을 이해하고 통제하며 예측하면서 대응한다는 것은 사실상 애초부터 불가능한 일일지도 모른다. 테러대응 역시 테러대응 관계 기관간, 관계 기관 전담 부서 내의 구성원들의 상호작용뿐만 아니라 넓게는 정부, 민간단체, 산업체, 학계, 언론 등 나아가서는 국가간의 이해 관계자, 국제기구 등 테러대응 분야의 다양한 조직들의 참여하에 이들의 상호작용으로 공식적, 비공식적 의사 결정을 통한 방안들을 모색하는 것이 필요할 것이다. 이에 따라 초기조건의 민감성, 프랙탈과 자기유사성, 자기 조직화, 창발, 공진화, 혼돈의 가장자리의 복잡계 이론을 통하여 테러대응 분야의 적용가능성을 은유적으로 탐색할 수 있을 것이다.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.04a
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• pp.1441-1444
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• 2011

본 논문에서는 초등학교 교육과정에서 교육목표로 다루고 있는 창의성이라는 주제와 학교현장에서 초등학생들에게 쉽게 접목시킬 수 있는 교육용 프로그래밍 언어인 LOGO 프로그래밍과 프랙탈 기하이론을 초등학교 컴퓨터교육에 활용하기 위한 방안을 제시한다. 향후 컴퓨터교육과정은 알고리즘과 프로그래밍 영역이 포함될 예정이며, 이러한 알고리즘과 프로그래밍 교육에는 교육용 프로그래밍 언어 사용이 필수적이며 이의 활용에 대한 연구가 시급한 상황이다. LOGO 프로그래밍과 프랙탈을 함께 지도함으로서 규칙성, 반복성, 유사성, 닮음 등 수학적 개념을 쉽게 이해하는 것이 가능하므로, 이를 활용하여 초등학교 수학과 교육과정에서 반드시 학습해야 할 도형, 측정, 규칙성과 문제 해결 영역과 연계하여 지도하면 좋은 효과를 얻을 수 있을 것으로 기대된다.

• Journal of applied mathematics & informatics
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• v.42 no.3
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• pp.583-605
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• 2024

This paper discusses the properties of attractors of Type 1 IFS which construct self similar fractals on product spaces. General results like continuity theorem and Collage theorem for Type 1 IFS are established. An algebraic equivalent condition for the open set condition is studied to characterize the points outside a feasible open set. Connectedness properties of Type 1 IFS are mainly discussed. Equivalence condition for connectedness, arc wise connectedness and locally connectedness of a Type 1 IFS is established. A relation connecting separation properties and topological properties of Type 1 IFS attractors is studied using a generalized address system in product spaces. A construction of 3D fractal images is proposed as an application of the Type 1 IFS theory.