• KSBB Journal
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• 제10권2호
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• pp.119-125
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• 1995

균류를 이용하는 생물공정의 생산성, 분리성, 유변 학적 성질에 영향을 미치는 중요한 변수인 균류의 형태를 fractal 차원을 사용하여 정량화하였다. 산업적으로 중요한 균류인 Aspegillus oryzae와 Aspergil Ius niger가 초기의 접종 포자량과 탄소원의 놓도를 변화시켜 액상배지에서 성장하는 경우 디지탈 영상 분석장치를 사용하여 fractal 차원을 계산하였다. 균 샤가 형성하는 구체의 특성과 fractal로 표현된 균사 의 형태와의 상관관계를 구하였다. 일반적으로 낮은 fractal 차원의 균사가 낮은 밀도(compactness)의 구체를 형 성하고 외부의 모양이 불규칙 척 이 었다.

• KSBB Journal
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• 제9권5호
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• pp.512-517
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• 1994

균류를 이용하는 생물공정의 생산성, 분리성, 유변 학적 성질에 영향을 주는 중요한 변수인 균류의 형 태를 fractal 차원을 사용하여 정량화하였다. 산업적 으로 중요한 균류인 Aspegillus oryzae와 Aspergil­l Ius niger가 초기의 접종 포자량과 탄소원의 농도를 변화시켜 액상배지에서 성장하는 경우, 디지탈 영상 분석장치를 사용하여 fractal 차원을 계산하였다. 균 사가 형성하는 구체의 특성과 fractal로 표현된 균사 의 형태와의 상관관계를 구하였다. 일반적으로 낮은 fractal 차원의 균사가 낮은 멜도(compactness)의 구체를 형성하고 외부의 모양이 불규칙적이었다.

• Imaging Science in Dentistry
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• 제52권1호
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• pp.33-41
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• 2022

Purpose: This study aimed to evaluate the structural complexity of craniofacial trabecular bone in multiple myeloma by fractal analysis of panoramic and lateral skull radiography, and to compare the fractal dimension values of healthy patients (HPs), pre-treatment patients (PTPs), and patients during bisphosphonate treatment (DTPs). Materials and Methods: Pairs of digital panoramic and lateral skull radiographs of 84 PTPs and 72 DTPs were selected. After application of exclusion criteria, 43 panoramic and 84 lateral skull radiographs of PTPs, 56 panoramic and 72 lateral skull radiographs of DTPs, and 99 panoramic radiographs of age- and sex-matched HPs were selected. The fractal dimension values from panoramic radiographs were compared among HPs, PTPs, and DTPs and between anatomical locations within patient groups using analysis of variance with the Tukey test. Fractal dimension values from lateral skull radiographs were compared between PTPs and DTPs using the Student t-test. Pearson correlation coefficients were used to assess the relationship between the mandible from panoramic radiographs and the skull from lateral skull radiographs. Intra-examiner agreement was assessed using intraclass correlation coefficients (α=0.05). Results: The fractal dimension values were not significantly different among HPs, PTPs, and DTPs on panoramic radiographs or between PTPs and DTPs on lateral skull radiographs (P>0.05). The mandibular body presented the highest fractal dimension values (P≤0.05). The fractal dimension values of the mandible and skull in PTPs and DTPs were not correlated. Conclusion: Fractal analysis was not sensitive for distinguishing craniofacial trabecular bone complexity in multiple myeloma patients using panoramic and lateral skull radiography.

• 한국지리정보학회지
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• 제8권3호
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• pp.1-10
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• 2005

본 연구의 목적은 프랙털(fractal)이론을 이용하여 도시공간을 구성하는 요소들의 특성을 반영하면서 도시형태를 정량적으로 측정하여 도시공간구조적 측면에서 그 의미를 알아보고자 하는 것이다. 프랙털이론은 단순히 사물이 공간상에서 차지하는 비율만을 대상으로 하는 밀도와 달리, 도시공간내부에 존재하는 사물들 간의 자기유사성(self-similarity )과 복잡함(complexity )을 양적으로 표현이 가능한 이론이다. 본 연구에서 도시의 형태는 프랙털차원(fractal dimension)으로 계산하여, 이론 적용의 타당성과 실제 도시형태를 비교분석해 보기 위해 도시화가 거의 완성된 북구주시(北九州市)와 지역 대부분이 농지로 구성되어 있는 신궁정(神宮町) 지역을 사례지역으로 하였다. 먼저 GIS 벡터데이터를 레스터데이터로 변환한 다음, 두 사례 지역의 프랙털차원을 계산하였다. 그 결과 북구주지역은 분석면적에 따라 프랙털차원 값에서 차이가 발생하지만, 시전체가 프랙털형상이라고 할 수 있었다. 그러나 신궁정 지역은 프랙털차원의 값이 작아 도시형상이 프랙털이라고 하기 어려운 결과가 도출되었다. 사례연구를 통해 프랙털이론이 도시형태를 정량적으로 측정 가능한 수단임을 알 수 있었으며 또한 구성요소간의 유사성을 반영할 수 있으므로 유사한 도시개발패턴이 이루어지는 경계(예를 들면 도시와 농촌의 경계)를 찾는 데에도 유효하게 사용될 수 있음을 알 수 있었다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.457-458
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• 2002

The fractal dimension is the characteristics that can quantitatively define the irregularity in natural. It is useful in describing the morphology or various rubbed surface for hydraulic piston motor instead of the stylus profiling method. But fractal parameters had not constructed on the morphological characteristic or rubbed surface because of the insufficient knowledge about a conception of fractal dimension. In this study, for the purpose or applying fractal I parameters practically, we have suggested way to establish the morphological characteristic of rubbed surface with fractal parameters, and we carried out an experiment on the lubricant friction and wear by using Ball-ON-Disk type tester. Materials were the brass and the bronze which are used to slipper-pad in the hydraulic piston motor. We searched for fractal parameters or surface structure with the digital image processing, Surface fractal dimension can be determined by sum of intensity difference of surface pixel. Using the image processing and fractal parameters for rubbed surface in the friction and wear test, morphology of rubbed sur race can be effectively obtained by fractal dimensions.

• Structural Engineering and Mechanics
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• 제23권2호
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• pp.147-161
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• 2006

Recent developments in fractal theory suggest that fractal may provide a more realistic representation of characteristics of cementitious materials. In this paper, the roughness of fracture surfaces in cementitious material has been characterized by fractal theory. A systematic experimental investigation was carried out to examine the dependency of fracture parameters on the aggregate sizes as well as the loading rates. Three maximum aggregate sizes (4.76 mm, 12.7 mm, and 19.1 mm) and two loading rates (slow and fast loading rate) were used. A total of 25 compression tests and 25 tension tests were performed. All fracture parameters exhibited an increase, to varying degrees, when aggregates were added to the mortar matrix. The fracture surfaces of the specimens were digitized and analyzed. Results of the fractal analysis suggested that concrete fracture surfaces exhibit fractal characteristics, and the fractal geometry provide a useful tool for characterizing nonlinear fracture behavior of concrete. Fractal dimension D was monotonically increased as maximum aggregate sizes increase. A new fractal fracture model was developed which considers the size and shape of aggregate, and the crack paths in the constituent phases. Detailed analyses were given for four different types of fracture paths. The fractal fracture model can estimate fractal dimension for multiphase composites.

• Journal of Periodontal and Implant Science
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• 제43권5호
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• pp.209-214
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• 2013

Purpose: To assess bony trabecular changes potentially caused by loading stress around dental implants using fractal dimension analysis. Methods: Fractal dimensions were measured in 48 subjects by comparing radiographs taken immediately after prosthesis delivery with those taken 1 year after functional loading. Regions of interest were isolated, and fractal analysis was performed using the box-counting method with Image J 1.42 software. Wilcoxon signed-rank test was used to analyze the difference in fractal dimension before and after implant loading. Results: The mean fractal dimension before loading ($1.4213{\pm}0.0525$) increased significantly to $1.4329{\pm}0.0479$ at 12 months after loading (P<0.05). Conclusions: Fractal dimension analysis might be helpful in detecting changes in peri-implant alveolar trabecular bone patterns in clinical situations.

• Structural Engineering and Mechanics
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• 제20권3호
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• pp.265-277
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• 2005

This paper is focused on fractal analysis of the surface cracking, a new tool for safety evaluation of corroded reinforced concrete (RC) beams. Comprehensive experimental investigations, including flexural tests, coupon tests on strength evaluation of corroded concrete and rusty rebar, and pullout tests to determine bond strength between concrete and rebar were carried out on nine Corroded Reinforced Concrete Beams (CRCB) exposed to an aggressive environment for more than 10 years. In combination with test results from a previous study on CRCBs fabricated in the laboratory from accelerated methods, it is found that, for both types of beams, the surface cracking distributions are fractal in character at loading and failure stages. Fractal dimension is calculated for all specimens at different corrosion states based on fractal analysis method. Relationships between the fractal dimension and mechanical properties of corroded concrete, rebar corrosion ratio, and ductility of CRCBs are discussed in detail. It is concluded that the fractal dimension can act as a damage index and can be efficiently used to describe the corrosion state of CRCBs.

• 대한기계학회논문집A
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• 제25권11호
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• pp.1737-1742
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• 2001

The fractal-based method for describing rubbed surface texture has aroused great interest. The determination of rubbed surface topography is believed to be extremely important in the areas of contact mechanics, adhesion and friction. In order to describe topography of the rubbed surface, the wear test was carried out with annular surfaces of wear testing specimens in dry friction. furthermore, the relation between the fractal dimensions and the frictional conditions are also investigated and fractal descriptors was applied to rubbed surface with image processing. Fractal dimension can be determined by sum of intensity difference of image surface pixel. Fractal dimension increased according as the applied load and sliding distance increase. Topography of the rubbed surface can be effectively obtained by fractal dimensions.

• 자원환경지질
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• 제27권1호
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• pp.81-91
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• 1994

There has been considerable research dealing with the influence of surface roughness along surfaces of rock discontinuities in relation to the peak shear strength of rock masses. Concepts accepted recently for measuring such strength include estimation of a roughness coefficient such as developed by Barton's studies. The method for estimation the Joint Roughness Coefficient (JRC) value of a measured roughness profile is subjective. The aim of this research is to estimate the JRC value of the roughness of a surface profile in a rock mass system using an objective method. The study of roughness of surfaces has included measurement of fractal geometric characteristics. Once the irregularity of the surface has been described by the fractal dimension, the spatial variation of the surface irregularities can be described using variogram and drift analysis. An empirical relationships between the roughness profiles of selected JRC ranges and their fractal dimension with variogram and drift were derived. The application of analyses of fractal dimension, variogram and drift was novel for the analysis of roughness profiles. Also, an empirical equation was applied to experimental data.