• 한국분무공학회지
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• 제10권1호
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• pp.24-34
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• 2005

Injection technology is one of the important technologies in a diesel engine. Many studies have done on the injection system. In this study, the fuel chamber geometry, the orifice ratio and the needle lift of the injection valve for a marine diesel engine are varied, and simulated. The result shows that the nozzle hole size has influence on the rail pressure and injection duration sensitively. The decrease of the static pressure at the nozzle hole entrance and the increase of the dynamic pressure on the outlet surface are occurred with the increase of the nozzle hole diameter. The highest dynamic pressure of the outlet was occurred at the needle lift of 0.4mm and the nozzle hole diameter of 0.328mm in this test nozzle.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.333-338
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• 2001

Fractal geometry is a non-Euclidean geometry which has been developed to quantitative analysis irregular or fractional shapes. Fractal dimension of irregular surface has fractal values ranging from 2 to 3 and of irregular line profile has fractal values ranging from 1 to 2. In this paper, quantitative analysis of crack growth patterns during the fracture processing of fiber-reinforced cement composites based on fractal geometry. The fracture behaviors of fiber reinforced mortar beams subjected to three-point loading in flexure. The beams all had a single notch depth, but varing volume fractions of polypropylene, cellulose fibers. The crack growth behaviors, as observed through the image processing system, and the box counting method was used to determine the fractal dimension, Df. The results showed that the linear correlation exists between fractal dimension and fracture energy of the fiber reinforced cement mortar.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.267-271
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• 2000

A part definition must not only provide shape information of a nominal part but also contain non-shape information such as tolerances, surface roughness and material attributes. Although machining features are useful for suitable shape information for process reasoning in the CAPP, they need to be integrated with tolerance information for effective process planning. We develop the tolerance modeler that efficiently integrates machining features with tolerance information for feature-based CAPP It is based on the association of machining features, tolerance features. and tolerances Tolerance features, where tolerances are assigned, are classified into two types; one is the face that is a topological entity on a solid model and the other is the functional geometry that is not referenced to topological entities. The functional geometry is represented by using machining features All the data for representing tolerance information with machining features are stored completely and unambiguously in the independent tolerance structure. The developed tolerance modeler is implemented as a module of a comprehensive feature-based CAPP system.

• 한국정밀공학회지
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• 제20권8호
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• pp.39-46
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• 2003

Productivity and machining performance can be improved by cutting analysis including cutting force prediction, surface error prediction and machining stability evaluation. In order to perform cutting analysis, cutting force coefficients database have to be constructed. Since cutting force coefficients are dependent on cutting condition in the existing research, a large number of calibration tests are needed to obtain cutting force coefficients, which makes it difficult to build the cutting force coefficients database. This paper proposes a generalized method for constructing the cutting force coefficients database us ins cutting-condition-independent coefficients. The tool geometry and workpiece material were considered as important components for database construction. Cutting force coefficients were calculated and analyzed for various helix and rake angles as well as for several workpiece. Furthermore, the variation of cutting force coefficients according to tool wear was analyzed. Tool wear was found to affect tool geometry, which results in the change of cutting force coefficients.

• 산업기술연구
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• 제15권
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• pp.153-168
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• 1995

The purpose of this study is to develop a method for predicting the aerodynamic performance of the subsonic airfoils in the 2-dimensional, steady and viscous flow. For this study, the airfoil geometry is specified by adopting the longest chord line system and by considering local surface curvature. In case of the inviscid-incompressible flow, the analysis is accomplished by the linearly varying strength vortex panel method and the Karman-Tsien correction law is applied for the inviscid-compressible flow analysis. The Goradia's integral method and the Truckenbrodt integral method are adopted for the boundary layer analysis of the laminar flow and the turbulent flow respectively. Viscous and inviscid solutions are converged by the Lockheed iterative calculating method using the equivalent airfoil geometry. And the analysis of the seperated flow is performed using the Dvorak and Maskew's method as the basic method. The wake effect is also considered and its geometry expressed by the formula of Summey & Smith when no seperation occurs. A computational efficiency is verified by the comparison of the computational results with experimental data and by the shorter execution time.

• 한국가시화정보학회지
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• 제5권2호
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• pp.20-25
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• 2007

The geometry of a commercial passenger airplane is realized based on a Boeing 747-400 model through the photographic scanning and reverse engineering. The each element consisting of the plane such as fuselage, wing, vertical fin, stabilizer and engines, is individually generated and then the whole body is assembled by the photomodeler. The maximum error in the realized airplane is about 1.4% comparing with the real one. The three-dimensional inviscid steady compressible governing equations are solved in the unstructured tetrahedron grid system, and in a finite volume method using STAR-CD when the airplane flies at the cruise condition. The pressure distribution on the surface and the wing-tip vortices are visualized, and in addition to the aerodynamics coefficients, lift and drag are estimated.

• The Journal of Advanced Prosthodontics
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• 제6권6호
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• pp.547-554
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• 2014

Implant success is achieved by the synergistic combination of numerous biomechanical factors. This report examines the mechanical aspect of implants. In particular, it is focused on macrodesign such as thread shape, pitch, width and depth, and crestal module of implants. This study reviews the literature regarding the effect of implant thread geometry on primary stability and osseointegration under immediate loading. The search strategy included both in vitro and in vivo studies published in the MEDLINE database from January 2000 to June 2014. Various geometrical parameters are analyzed to evaluate their significance for optimal stress distribution, implant surface area, and bone remodeling responses during the process of osseointegration.

• Bulletin of the Korean Chemical Society
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• 제25권9호
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• pp.1392-1396
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• 2004

The micellization of dodecylpyridinum chloride (DPC) assembled on aqueous gold nanoparticles has been studied as a function of concentration using Surface-Enhanced Raman Scattering (SERS). At the low concentration, the strong SERS band of the benzene ring moiety was observed at 1025 $cm^{-1}$, and assigned to “trigonal ring breathing”. According to high concentration of DPC, a new strong band was also appeared at 1012 $cm^{-1}$, which was assigned to “totally symmetry ring breathing”. The difference of two spectra seems to ascribe to the geometry of polar head group, i.e., pyridinium cation. These geometry exist flat-down at low concentration, whereas standing-up or tilted geometry at high concentration. The critical micelle concentration (CMC) was first obtained from the ratio of intensities of the two bands related to the benzene ring moiety by vibrational spectroscopy, and was about 28 mM. After the CMC, the benzene ring moiety in the micelle state was more restricted than in monomer state because there is no more change of intensities at 1012 $cm^{-1}$. In addition, the size of gold-assembled micelle was estimated using light scattering and it was about 328.3 nm.

• 한국정밀공학회지
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• 제20권6호
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• pp.81-87
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• 2003

Triangulation method, conoscopic holography method and interferometry method are analyzed for effective measurement of micro burr geometry, which is formed in micro drilling. To select proper sensor, the cross section of a cylinder with 0.5mm diameter is measured and the result shows that conoscopic holography method is effective for measuring highly inclined surface in cylinder. Burrs with 1.0mm and 30${\mu}{\textrm}{m}$ height are measured by three suggested methods. As a result, the conoscopic holography method is proved to be most proper in measuring burr geometry. Burr measurement system is developed, which consists of conoscopic laser sensor, X-Y table, controller and burr measurement program. Burrs can be measured automatically and the result is displayed in 3D shape

• 소성∙가공
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• 제9권5호
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• pp.526-532
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• 2000

Springback simulation is receiving increasing attention throughout the automotive industry and the academic world. The knowledge of the real springback of stamped parts can help the stamping technicians to modify the process parameters or die geometry in order to reduce the shape defect. This paper presents the results of springback simulation after aluminium square cup deep drawing and trimming simulation, and results of springback optimization using response surface method.