• Structural Engineering and Mechanics
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• 제20권3호
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• pp.313-334
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• 2005

The paper presents a new approach for the analysis of slope stability that is based on the numerical solution of a differential equation, which describes the thrust force distribution within the potential sliding mass. It is based on the evaluation of the thrust force value at the endpoint of the slip line. A coupled approximation of the slip and thrust lines is applied. The model is based on subdivision of the sliding mass into slices that are normal to the slip line and the equilibrium differential equation is obtained as the slice width approaches zero. Opposed to common iterative limit equilibrium procedures the present method is straightforward and gives an estimate of slope stability at the value of the safety factor prescribed in advance by standard requirements. Considering the location of the thrust line within the soil mass above the trial slip line eliminates the possible development of a tensile thrust force in the stable and critical states of the slope. The location of the upper boundary point of the thrust line is determined by the equilibrium of the upper triangular slice. The method can be applied to any smooth shape of a slip line, i.e., to a slip line without break points. An approximation of the slip and thrust lines by quadratic parabolas is used in the numerical examples for a series of slopes.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 압출 및 인발 심포지엄
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• pp.47-55
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• 1999

The microstructure of Al 6061 powder milled from rapidly solidified flake and it's extrudate were investigated. The grain size of flake was about $0.8-1.5{\mu}m$ and the powder shape was spherical due to the milling condition. In the microstructure of extrudate, the unbinded powder boundary was found the front part of extrudate and all the macroscopic defects such as boundary defect, holes or cracks was not observed except the front part. It was found that the extrudate except 60cm of front part was useful part.

• 대한치과보철학회지
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• 제38권1호
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• pp.108-115
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• 2000

This study was designed to compare the effect of polishing on surface roughness of composite resin. We used Z100(3M) composite resin and placed the composite resin in the hole (4mm thick and 4mm in diameter) of vinyl plate and polymerized it under manufacturer's instructions. Samples were divided into 5 groups by polishing methods. Group 1 was control: resin was polymerized under glass plate, Group 2: resin was polymerized without any polishing procedure, Group 3: resin was polymerized with a polishing procedure of abrasive disc, Group 4: bonding agent was applyed in thin layer and polymerized on the polished polymerized resin surface. Group 5: resin was polymerized under transparent celluloid strip. The surface roughness of each specimen was measured with Sufacoder SEF-30D (Kosaka lab. Ltd) under 0.08mm cut off, 0.05mm/s stylus speed, ${\times}40$ horizontal magnification, ${\times}5000$ vertical magnification. The results were as follows : 1. Group 1 showed the most smooth surface in this study. 2. Group 3 showed more rough surface than Group 2. Considering the surface roughness, it would be better to make the shape completely before polymerize the resin. To finish and polish after the polymerization of resin makes less smooth surface. 3. When we use the transparent celluloid strip, minimum finishing procedures are recommended. Any polishing procedure could not recover the smooth resin surface of celluloid strip. 4. Application and polymerization of the thin layer of bonding agent on the polished surface showed the minimum surface smoothing effect.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.633-640
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• 2005

Most existing methods for the footing settlement estimation are for either isolated or strip footings. No sufficient details are available for settlement calculation of footings with different shapes and multiple footing conditions, which are commonly adopted in actual construction projects. In this paper, estimation of footing settlements for various footing conditions of different shapes and multiple conditions is investigated based on Schmertmann's method with focus on values of the strain influence factor $I_z$. In order to examine the effect of multiple footing conditions, field plate load tests are performed in sands using single and double plates. 3D non-linear finite element analyses are also performed for various footing conditions with different footing shape and distance ratios. Results obtained in this study indicate that there are two significant components in the strain influence diagram that need to be taken into account for settlement estimation of rectangular and multiple footings: depth of $I_{zp}$ and depth of strain influence zone. Based on results from experimental and 3D non-linear finite element analyses, improved strain influence diagrams available for various footing conditions are proposed.

• Journal of Mechanical Science and Technology
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• 제15권7호
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• pp.906-920
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• 2001

This paper presents three-dimensional mean velocities, turbulent intensities and Reynolds shear stresses measured in the Y-Z plane of the gas swirl burner with a cone type baffle plate by using an X-type hot-wire probe. This experiments is carried out at the flow rate of 450ℓ/min which is equivalent to the combustion air flow rate necessary to heat release 15,000 kcal/hr in a gas furnace. Mean velocities and turbulent intensities etc. show that their maximum values exist around the narrow slits situated radially on the edge of and in front of a burner. According to downstream regions, they have a peculiar shape like a starfish because the flows going out of the narrow slits and the swirl vanes of an inclined baffle plate diffuse and develop into inward and outward of a burner. The rotational flow due to the inclined flow velocity going out of swirl vanes of a cone type baffle plate seems to decrease the magnitudes of mean velocities V and W respectively by about 30% smaller than those of mean velocity U. The turbulent intensities have large values of 50%∼210% within the range of 0.5

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.668-673
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• 2000

Spud angle( ${\alpha}$ ) and fuel injection angle ( ${\beta}$ ) have strong influence on spud type gas burner combustion. A wide range of flame stability is shown at ${\alpha}=60^{\circ}$, but at ${\alpha}=30^{\circ}$ is narrow. Optimum condition of flame stability swirl angle( ${\gamma}$ ) is $40^{\circ}$. At condition of ${\alpha}=30^{\circ}$ flame shape is relatively narrow and long, on the other hand, at ${\alpha}=60^{\circ}$ flame is wide and short. Regardless of spud angle, maximum flame temperature shows in the range of Z=200mm and R=0mm. Flame temperature, on the whole, is high at ${\alpha}=45^{\circ}$. At ${\alpha}=45^{\circ}$, NOx emission is higher than other conditions that may be concerned with flame temperature. At ${\beta}=60^{\circ}$ and ${\gamma}=40^{\circ}$, NOx emission is reduced due to fuel injection angle.

• Advances in materials Research
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• 제1권4호
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• pp.285-297
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• 2012

The present study addresses the problem of quantitative prediction of effective complex relative permittivity of Barium Titanate/Polyvenylidene Fluoride (PVDF) and $(Bi_{0.5}Na_{0.5})_{0.94}Ba_{0.06}TiO_3$/Poly(VDF-TrFE) biphasic ceramic-polymer composites. Theoretical results for effective relative permittivity derived from several dielectric mixture equations were fitted to the experimental data taken from the works of Prasad et al. (2010), Wang et al. (2004), Takenaka et al. (1991) and Yamada et al. (1982). The study revealed that out of the different test equations, only a few equations like modified Rother-Lichtenecker equation, Dias-Dasgupta equation or Rao equation for the real part and Bruggeman equation for the imaginary part of complex permittivity well fitted the corresponding experimental results. In the present study, some of the equations were used in their original forms, while some others were modified by choosing suitable shape-dependent parameters in order to get reasonably good agreement with experimental results. Besides, the experimental results have been proposed in the form of a mathematical model using first order exponential growth, which provided excellent fits.

• 한국CDE학회논문집
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• 제5권4호
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• pp.347-358
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• 2000

The view dependency of typical spatial-partitioning based NC simulation methods is overcome by polygon rendering technique that generates polygons to represent the workpiece, thus enabling dynamic viewing transformations without reconstruction of the entire data structure. However, the polygon rendering technique still has difficulty in realizing real-time simulation due to unsatisfactory performance of current graphics devices. Therefore, it is necessary to develop a mesh decimation method that enables rapid rendering without loss of display quality. In this paper. we proposed a new mesh decimation algorithm thor a workpiece whose shape varies dynamically. In this algorithm, the 2-map data thor a given workpiece is divided into several regions, and a triangular mesh is constructed for each region first. Then, if any region it cut by the tool, its mesh is regenerated and decimated again. Since the range of mesh decimation is confined to a few regions, the reduced polygons for rendering can be obtained rapidly. Our method enables the polygon-rendering based NC simulation to be applied to the computers equipped with a wider range of graphics cards.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권7호
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• pp.3112-3127
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• 2018

Since time series clustering is performed without prior information, it is used for exploratory data analysis. In particular, clusters of time series with similar shapes can be used in various fields, such as business, medicine, finance, and communications. However, existing time series clustering algorithms have a problem in that time series with different shapes are included in the clusters. The reason for such a problem is that the existing algorithms do not consider the limitations on the size of the generated clusters, and use a dimension reduction method in which the information loss is large. In this paper, we propose a method to alleviate the disadvantages of existing methods and to find a better quality of cluster containing similarly shaped time series. In the data preprocessing step, we normalize the time series using z-transformation. Then, we use piecewise aggregate approximation (PAA) to reduce the dimension of the time series. In the clustering step, we use density-based spatial clustering of applications with noise (DBSCAN) to create a precluster. We then use a modified K-means algorithm to refine the preclusters containing differently shaped time series into subclusters containing only similarly shaped time series. In our experiments, our method showed better results than the existing method.

• 한국정밀공학회지
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• 제19권10호
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• pp.195-201
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• 2002

This paper deals with the precision grinding for aspherical surface of optical parts. A parallel grinding method using the spherical wheel was suggested as a new grinding method. In this method, the wheel axis is positioned at a $\pi$/4 from the Z-axis in the direction of the X-axis. An advantage of this grinding method is that the wheel used in grinding achieves its maximum area, reducing wheel wear and improving the accuracy of the ground mirror surface. In addition, a truing by the CG (curve generating) method was proposed. After truing, the shape of spherical wheel transcribed on the carbon is measured by the Form-Talysurf-120L. The error of the form in the spherical wheel which is the value ${\Delta}x$ and $R{^2}{_y}$ inferred from the measured profile data is compensated by the re-truing. Finally, in the aspherical grinding experiment, the WC of the molding die was examined by the parallel grinding method using the resin bonded diamond wheel with a grain size of ＃3000. A form accuracy of 0.16${\mu}m$ P-V and a surface roughness of 0.0067${\mu}m$ Ra have been resulted.