• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7941-7948
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• 2015

Rolling noises during train operation are caused by vibration excited from irregularities of surface roughness between wheel and rail. Therefore, a proper measurement and analysis techniques of acoustic roughness between wheel and rail surface are required for transmission, prediction, and analysis of the train rolling noise. However, since current measuring devices and methods use trolley-based manual handling devices, the measurements induce unstable measuring speed and vibrational interface that increases errors and disturbances. In this paper, a new automatic rail surface exploring platform with a speed controller has been developed for improving measurement accuracy and reducing inconsistency of measurements. In addition, we propose a data integration method of the rail surface roughness with multiple homogeneous displacement sensors and verified the accuracy of the integrated data through standard test-bed railway track investigation.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.794-801
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• 2006

The linkage framework of geometric modeling and analysis based on the NURBS technology is developed in this study. The NURBS surfaces are generated by interpolating the given set of data points or by extracting the necessary information to construct the NURBS surface from the IGES format file which is generated by the commercial CAD systems in the present study. Numerical examples shows the rate of displacement convergence according to the paramterization methods of the NURBS surface. NURBS can generate quadric surfaces in an exact manner. It is the one of the advantages of the NURBS. A trimmed NURBS surface that is often encountered in the modeling process of the CAD systems is also presented in the present study. The performance of the developed geometrically exact shell element integrated with the exact geometric representations by the NURBS equation is compared to those of the previous reported FE shell elements in the selected benchmark problems.

• Korean Journal of Materials Research
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• v.22 no.6
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• pp.292-297
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• 2012

In order to improve osseointegration of dental implants with bone we studied an implant with holes inside its body to deliver bioactive materials based on a proposed patent. Bioactive materials can be selectively applied through holes to a patient according to diagnosis and the integration progress. After the bioactive material is applied, bone can grow into the holes to increase implant bonding and also enhance surface integration. In order to improve the concept and study the effect of bioactive material injection on implant integration, design optimization and integration research were undertaken utilizing the finite element method. A 2-dimensional simulation study showed that when bone grew into the holes after the bioactive material was injected, stress vertically distributed in the upper part of the implant was relieved and mild stress appeared at the opening of the injection holes. This confirmed the effect of the bioactive material and the contribution of the injection holes, but the maximum stress increased ten-fold at the opening. In order to reduce the maximum stress, the size, location, and the number of holes were varied and the effects were studied. When bioactive materials formed an interface layer between the implant and the mandible and four holes were filled with cortical and cancellous bones all the stress concentrated opposite to the loading side without holes disappeared. The stresses at the four outlets of the holes was mildly elevated but the maximum stress value was ten-fold greater compared to the case without the bioactive material.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.5
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• pp.218-224
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• 2003

This paper describes a novel MEMS integration technique on a CMOS chip. MEMS integration on CMOS circuit has many advantages in view of manufacturing cost and reliability. The surface topography of a CMOS chip from a commercial foundry has 0.9 ${\mu}{\textrm}{m}$ bumps due to the conformal coating on aluminum interconnect patterns, which are used for addressing each MEMS element individually. Therefore, it is necessary to achieve a flat mirror-like CMOS chip fer the microelectromechanical system (MEMS) such as micro mirror array. Such CMOS chip needs an additional thickness of the dielectric passivation layer to ease the subsequent planarization process. To overcome a temperature limit from the aluminum thermal degradation, this study uses RF sputtering of silicon nitride at low temperature and then polishes the CMOS chip together with the surrounding dummy pieces to define a polishing plane. Planarization reduces 0.9 ${\mu}{\textrm}{m}$ of the bumps to less than 25 nm.

• Journal of Advanced Navigation Technology
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• v.7 no.2
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• pp.180-190
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• 2003

By using accurate closed-form Green's functions obtained from real-axis integration method, the full-wave analysis of CPW discontinuities are performed in space domain. In solving MPIE(Mixed Potential Integral Equation), Galerkin's scheme is employed with the linear basis functions on the triangular elements in air-dielectric boundary. In the singular integral arising when the observation point and source point coincides, the surface integral is transformed into the line integral and the integral is evaluated by regular integration. By using the Green's function from the real-axis integration method, the discontinuities are characterized accurately.

• Laser Solutions
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• v.18 no.1
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• pp.7-11
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• 2015

In this paper, micro trench structure is fabricated by femtosecond laser for inserting optical reflecting wavelength filter in planar waveguide. The width and depth of the trench is controlled by femtosecond laser machining condition. Also, large scale of single channel with 500um and 1000um on silica plate is fabricated by femtosecond laser, and roughness of the channel surface is polished by $CO_2$ laser for the insertion of the filter. Then, the characteristic of the planar waveguide inserted the filter is verified.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.1
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• pp.38-45
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• 1997

The steady drift forces on a barge in waves are investigated. The steady drift forces due to a near-field method which is based on direct integration of the pressure acting on the submerged surface of barge are compared with those due to far-field method which is based on the theory of momentum conservation. Numerical results of the linear motions are compared with the experimental and numercal ones which was submitted in the literature. A convergence of the steady drift forces according to the increase of the number of panels which represent the submerged surface are discussed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.5
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• pp.1243-1250
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• 1995

For the numerical solution of frictional dynamic contact problems, correct contact points and displacements are determined by iteratively reducing the displacement error vector monotonically toward zero And spurious oscillations are prevented from the solution by enforcing the velocity and acceleration compatibilities of the contact points with the corresponding error vectors. Numerical simulations are conducted to demonstrate the accuracy of the solution and the necessity of the velocity and acceleration compatibilities on the contact surface.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.203-203
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• 2015

반도체 제조 공정 중에 CMP(Chemical Mechanical Planarization)는 디바이스의 집적도(degree of integration)에 크게 영향을 미치고 있으므로, 20nm급 이하의 디바이스에서 CMP 공정 안정화는 양질의 소자 특성을 확보하기 위해서는 시급한 문제가 되고 있다. CMP 공정 안정화를 위해서는 여러 가지 해결되어야 할 문제가 있는데, 그 중에서도 W plug 연마 공정 중에 관찰되고 있는 W missing은 전기 배선의 신뢰성에 직접 영향을 주고 있으므로 공정 엔지니어에게는 도전적인 과제이다. 본 연구에서는 W missing 현상을 전기화학적인 입장에서 해석하고 몇 가지 해결책을 제기하고자 한다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.173-174
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• 2007

Through Silicon Via ( TSV)는 향후3D integration devices (CMOS image sensors) 와 보다 더 직접화되고 진보된 memory stack에 기여 할 것이다. 이는 한층 더 진보된 microprocessors system 을 구축 하리라 본다. 해서 본문은 TSV plasma etching processing 소개와 특히 Bosch process에 대한 개선 방법을 제시하고자 한다.