• Journal of Information Processing Systems
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• v.4 no.4
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• pp.153-158
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• 2008

This paper deals with the geometric fitting algorithms for parametric curves and surfaces in 2-D/3-D space, which estimate the curve/surface parameters by minimizing the square sum of the shortest distances between the curve/surface and the given points. We identify three algorithmic approaches for solving the nonlinear problem of geometric fitting. As their general implementation we describe a new algorithm for geometric fitting of parametric curves and surfaces. The curve/surface parameters are estimated in terms of form, position, and rotation parameters. We test and evaluate the performances of the algorithms with fitting examples.

• Nuclear Engineering and Technology
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• v.42 no.6
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• pp.680-689
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• 2010

The crack-tip stress fields and fracture mechanics assessment parameters for a surface crack, such as the elastic stress intensity factor or the elastic-plastic J-integral, can be affected significantly by the adjacent cracks. Such a crack interaction effect due to multiple cracks can alter the fracture mechanics assessment parameters significantly. There are many factors to be considered, for instance the relative distance between adjacent cracks, the crack shape, and the loading condition, to quantify the crack interaction effect on the fracture mechanics assessment parameters. Thus, the current assessment codes on crack interaction effects (crack combination rules), including ASME Sec. XI, BS7910, British Energy R6 and API 579-1/ASME FFS-1, provide different rules for combining multiple surface cracks into a single surface crack. The present paper investigates crack interaction effects by evaluating the elastic stress intensity factor and the elastic-plastic J-integral of adjacent in-plane surface cracks in a plate through detailed 3-dimensional elastic and elastic-plastic finite element analyses. The effects on the fracture mechanics assessment parameters of the geometric parameters, the relative distance between two cracks, and the crack shape are investigated systematically. As for the loading condition, an axial tension is considered. Based on the finite element results, the acceptability of the crack combination rules provided in the existing guidance was investigated, and the relevant recommendations on a crack interaction for in-plane surface cracks are discussed. The present results can be used to develop more concrete guidance on crack interaction effects for crack shape characterization to evaluate the integrity of defective components.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.1
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• pp.54-61
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• 2011

Ball screw systems are largely used in industry for motion control and motor applications. But the problem of noise, which really perplexes us, is highly correlated with the quality in ball screw systems all the way. In this paper, machining process parameters were evaluated in respects of technique, business, produce and quality to verify which impact influences the noise most. In order to adjust and compare, two comparison groups were set with the present parameters bench mark. Different ball screws were produced as specimens for the noise tests. Through comparing the noise performance of different parameters in the machining process respectively, a group of optimized machining process parameters were obtained. Another noise test was proceeded to know how noise performance was improved by optimizing the machining process parameters. At last, surface roughness tests have been done to know how surface roughness improved by optimization. The improvement of surface roughness is the main factor influences the noise performances.

• 제어로봇시스템학회:학술대회논문집
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• 1999.10a
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• pp.41-44
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• 1999

Nonlinear sliding surface design in variable structure systems for spacecraft attitude control problems is studied. A robustness analysis is performed for regular form of system, and calculation of actuator bandwidth is presented by reviewing sliding surface dynamics. To achieve non-singular attitude description and minimal parameterization, spacecraft attitude control problems are considered based on modified Rodrigues parameters(MRP). It is shown that the derived controller ensures the sliding motion in pre-determined region irrespective of unmodeled effects and disturbances.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.11c
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• pp.57-68
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• 1999

This paper summarizes the results of a study which uses the recently developed Optical Profile Microscopy technique (Dove and Frost, 1996) as the basis for investigating the role of geomembrane surface roughness on the shear mechanism of geomembrane/geotextile interfaces. The alternative roughness parameters which consider the direction of shearing are described. These directional parameters are compared with the existing roughness parameters, and the relationship between these directional and non-directional parameters are investigated. Then, the relationship between interface shear strength and surface roughness quantified at the interface is investigated. The results show that interface friction can be quantitatively related to the surface roughness of the geomembrane. The peak and residual interface strengths increase dramatically through the use of textured geomembranes as opposed to smooth geomembranes. For the smooth geomembranes, the sliding of the geotextile is the main shear mechanism. For the textured geomembranes, the peak interface strength is mainly mobilized through the micro-texture of the geomembrane, however, the residual interface strength is primarily attributed to macro scale surface roughness which pulls out and breaks the filaments from the geotextile. The results of this study can be extended to the other interfaces such as joints in rock mass, and also can be used to provide a quantitative framework that can lead to a significantly improved basis for the selection and design of geotextiles and geomembranes in direct contact.

• Advances in nano research
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• v.14 no.1
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• pp.17-25
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• 2023

Gold nanoparticles have recognized a promising drug carriers in many diseases. These nanoparticles could carry anti-inflammatory drugs in the case of muscle injury and for fatigue relief. On the other hand, specific surface of this kind of nanoparticles could be critical in amount of drug they could carry. Therefore, in this study, we explore different methodology and influencing parameters on the specific surface of gold nanoparticles. After specifying the main parameters, different machine learning and artificial neural network are adopted to model the effects of different parameters. Furthermore, response surface methodology is utilized to obtain a quadrilateral relationship between different parameters and specific surface. The results indicate that concentration of the gold salt solution is the most important parameter in increasing the size of gold nanoparticle and, as a consequence, increasing specific surface. Moreover, the ability of gold nanoparticles in prolonging retention of the drugs is discussed in detail.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.11a
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• pp.136-145
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• 1999

This paper describes the surface roughness effect in parallel thrust bearing. In mixed lubrication, some contacts will take place between asperities, and partial lubrication will occur. An average Reynolds Equation is utilized to determine effects of surface roughness on partially lubricated contacts. By using an autocorrelation function for the surface profile, surface model is generated numerically Although the two surfaces are parallel in thrust bearing separated by thin film, the pressure peak is formed due to asperites. By means of surface profile parameters, it is shown that which surface is optimal for the parallel thrust bearing.

• Tribology and Lubricants
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• v.40 no.2
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• pp.47-53
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• 2024

Surface topography plays a decisive role in determining the performance of several precision components. In particular, the surface roughness of semiconductor devices affects the precision of the circuit. In this regard, the surface topography of a given surface needs to be appropriately assessed. Typically, the average roughness is used as one of the main indicators of surface finish quality because it is influenced by both dynamic and static parameters. Owing to the increasing demand for such accurate and reliable surface measurement systems, studies are continuously being conducted to understand the parameters of surface roughness and measure the average roughness with high reliability. However, the differences in the measurement methods of surface roughness are not clearly understood. Hence, in this study, the surface roughness of the back of a silicon wafer was measured using both contact and noncontact methods. Subsequently, a comparative analysis was conducted according to various surface roughness parameters to identify the differences in surface roughness depending on the measurement method. When using a 3D laser confocal microscope, even smaller surface asperities can be measured compared with the use of a 3D profiler. The results are expected to improve the understanding of the surface roughness characteristics of precision components and be used as a useful guideline for selecting the measurement method for surface topography assessment.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.286-291
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• 2004

The objective of this research work is to investigate the influence of process parameters, such as power of laser, travel speed of laser and material thickness, on roughness and striation of the cut surface for the case of cutting of CSP 1N sheet using high power Nd:YAG laser with continuous wave(CW). In order to find the practical cutting region and the relationship between process parameters on the roughness and the striation, several laser cutting experiments are carried out. From the results of experiments, the allowable cutting region and an optimal cutting speed for each cutting condition have been obtained to improve the quality of the cut surface. In addition, it has been shown that the surface roughness is related to the number of striation and depth of valley of the cut surface.

• Structural Engineering and Mechanics
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• v.61 no.4
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• pp.519-526
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• 2017

In the present paper, the effects of cutting parameters and coating material on the performances of cutting tools in turning of AISI 52100 steel are discussed experimentally. A comparative study was carried out between uncoated and coated (with TiCN-TiN coating layer) cermet tools. The substrate composition and the geometry of the inserts compared were the same. A mathematical model was developed based on the Response Surface Methodology (RSM). ANOVA method was used to quantify the effect of cutting parameters on the machining surface quality and the cutting forces. The results show that feed rate has the most effect on surface quality. However, cutting depth has the significant effect on the cutting force components. The effect of coating layers on the surface quality was also studied. A lower surface roughness was observed when using PVD (TiCN-TiN) coated insert. A second order regression model was developed and a good accuracy was obtained with correlation coefficients in the range of 95% to 97%.