• 한국생산제조학회지
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• 제8권6호
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• pp.55-63
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• 1999

The acceleration of the performance of machine tools influences the development of the semi-conductor and optical technology as the development of NC and measurement technology. Because the measurement has been done to unload condition without considering of mechanical stiffness in the case of machining center as we measure the quasi-static error of machine tools on general study people who works on the spot has many problems on the data value. Also there are no satisfiable results until now in spite of many studys about this because the deflections of the table and the shaft supporting a workpiece influence, influence the accuracy of the table and shaft supporting a workpiece influence the accuracy of the workpiece. And there is doubt about the inspection method of measured error. In this paper Therefor we will help working more accurately on the spot by measuring analyzing displaying the defoec-tion of the table and support shaft when we load on the table and the support shaft of machining center using laser interfer-ometer. Also we try to settle new conception of the measurement method and more accurate grasp of the deflection tenden-cy by verifing the tendency of the error measured through the comparison of the simulated error measured through the comparison of the simulated error using ANSYS a common finite element analysis program which is able to measure heat deformation material deformation and error resulted from this study.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 사면안정 학술발표회
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• pp.155-180
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• 2000

The pattern of domestic slope construction has been steadily changed from the simpled and small-scale to the large-scale and complicated one, frequently near the existing structures, as the density of population and the traffic increases. In some cases, the slopes become steeper and larger due to the road improvement and construction. For the rock slope, the existence of discontinuity cannot be disregarded and acts as an important factor on the slope stability. Most of the existing methods for stabilizing the slope were focused on reducing the slope angle. Under the specific geographic condition, it is necessary to concentrate more efforts on the research and development of supporting system for the slope stability. As a supporting system, it is often very advantageous to use the FRP pipe grouting method that is similar to the existing soil nailing method or the rock bolting method but uses the high strength FRP pipe as a principal reinforcement in place of steel bar. Through the FRP pipe, the grout material can be injected into the rock mass to improve its shear strength to the required value. .In this study, the characteristics of FRP are investigated by the laboratory tests and the field tests. And, the practical aspects of FRP method are reviewed and analyzed.

• Steel and Composite Structures
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• 제17권6호
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• pp.803-824
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• 2014

The dynamic characterization is important in making accurate predictions of the seismic response of the hybrid structures dominated by different damping mechanisms. Different damping characteristics arise from the construction of the tower with different materials: steel for the upper part; reinforced concrete for the lower main part and interaction with supporting soil. The process of modeling damping matrices and experimental verification is challenging because damping cannot be determined via static tests as can mass and stiffness. The assumption of classical damping is not appropriate if the system to be analyzed consists of two or more parts with significantly different levels of damping, such as steel/concrete mixed structure - supporting soil coupled system. The dynamic response of structures is critically determined by the damping mechanisms, and its value is very important for the design and analysis of vibrating structures. An analytical approach capable of evaluating the equivalent modal damping ratio from structural components is desirable for improving seismic design. Two approaches are considered to define and investigate dynamic characteristics of hybrid tower of cable-stayed bridges: The first approach makes use of a simplified approximation of two lumped masses to investigate the structure irregularity effects including damping of different material, mass ratio, frequency ratio on dynamic characteristics and modal damping; the second approach employs a detailed numerical step-by step integration procedure in which the damping matrices of the upper and the lower substructures are modeled with the Rayleigh damping formulation.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.417-417
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• 2009

Although a transparent conductive film (TCF) belongs to essential supporting materials for many device applications such as touch screens, flat panel displays, and sensors, a conventional transparent conductive material, indium-tin oxide (ITO), suffers from considerable drawback because the price of indium has soared since 2001. Despite a recent falloff, a demand of ITO is expected to increase sharply in the future due to the trend of flat panel display technologies toward flexible, paper-like features. There have been recently extensive studies to replace ITO with new materials, in particular, carbon nanotubes (CNTs) since CNTs possess excellent properties such as flexibility, electrical conductivity, optical transparency, mechanical strength, etc., which are prerequisite to TCFs. This study fabricated TCFs with single-walled carbon nanotubes (SWCNTs) produced by arc discharge. The SWCNTs were dispersed in water with a surfactant of sodium dodecyl benzene sulfonate (NaDDBS) under sonication. Carbon black and fullerene nanoparticles were added to the SWCNT-dispersed solution to enhance contact resistance between CNTs. TCFs were manufactured by a filtration and transfer method. TCFs added with carbon black and fullerene nanoparticles were characterized by scanning electron microscopy (SEM), UV-vis spectroscopy (optical transmittance), and four-point probe measurement (sheet resistance).

• 한국정밀공학회지
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• 제23권1호
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• pp.145-151
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• 2006

Wheel bearing unit has been exclusively applied to car wheel supporting device. The seal for wheel bearing is required to have both high sealing effects and low reaction forces because wheel bearing are operated on adverse environmental conditions such as mud and splash water. High sealing effects are for the protection of bearing ball wear from dust influx. In order to ensure high sealing effects, it is a easiest way to increase contact force which are affected by geometric characteristics, material properties and interferences between seal and inner bearing but induces higher wear phenomena. Interferences in all variables are most important factor to determine the performance of wheel bearing. In this study, optimization of interference amount was performed with finite element analysis with commercial code ABAQUS. For the sake of finite element analysis, tensile tests of rubber material were conducted and governing equation of nonlinear behavior was achieved. Hock-up bearing was manufactured with optimized interference amount. Results of torque and mud spray tests using this bearing unit are performed. Less torque and moisture influx of bearing with optimized interference amount is evidence to validity of this study.

• 한국전기전자재료학회논문지
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• 제21권6호
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• pp.556-561
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• 2008

This paper reports the characteristics of piezoelectric microspeakers that are audible in open air with high quality piezoelectric AlN thin film according to the materials properties. When we use a tensile-stressed silicon nitride diaphragm as a supporting layer, the Sound Pressure Level (SPL) is relatively small and constant at low frequency region and shows about 70 dB at 10 kHz. However, in case of a compressively stressed composite diaphragm, the SPL of the fabricated microspeakers shows higher output pressure than those of a tensile-stressed diaphragm. It produces more than 66 dB from 100 Hz to 15 kHz and the highest SPL is about 100 dB at 9.3 kHz with $20V_{peak-to-peak}$, sinusoidal input biases and at 10 mm distances from the fabricated microspeakers to the reference microphone. From the experimental results, it is superior to have a compressively composite diaphragm in order to produce a high SPL in piezoelectric microspeaker.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2005년도 생물공학의 동향(XVII)
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• pp.456-462
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• 2005

The objective of this study was to develop a removal process by which $H_2S$ could be biologically removed from the odoriferous gases generated in the waste food recycling process. In order to develop this process we were first required to select a proper biofilter support protocol. When the selected biofilter equipment was then tested suing a synthetic odoriferous gas containing 600 ppm of $H_2S$, we noted a maximal removal rate of 658 $g-H_2S/m^3{\cdot}hr$, using polypropylene fibrils as supporting materials. Under identical experimental conditions, we obtained a value of 411.2 $g-H_2S/m^3{\cdot}hr$, using polyurethane as a support material. We also conducted a trial in which volcanic stone was utilized as a support material, and in this trial, we logged a maximal 105.1 $g-H_2S/m^3{\cdot}hr$ removal rate. As the result of our experiments, we concluded that polypropylene fibrils constituted the ideal material for the removal of $H_2S$ gas via biological treatment.

• 한국터널지하공간학회 논문집
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• 제3권1호
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• pp.11-19
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• 2001

이 연구는 강관 보강형 다단 그라우팅공법의 설치 및 절단 시 어려움, 부식에 취약한 문제점 등을 개선하는데 목적이 있으며, 강관 대신에 고강도 유리섬유(fiberglass)를 이용한 FRP(Fiberglass Reinforced Plastic)의 적용성에 대한 연구를 수행하였다. 연구결과는 강관에 비하여 FRP 보강재의 가격이 높긴 하지만 시공성 및 내구성 등에서 우수한 것으로 파악되었다. 그리고 FRP 보강재의 형상에 따른 수치해석 결과에서는 국외에서 상용화 된 판상형 보강재 보다 등각곡선형 보강재가 더 구조적 측면에서 효율적임을 알 수 있었고, 그라우트 복합체에 대한 굴곡강도시험 결과에서는 강관과 FRP 보강재의 지보효과가 유사한 것으로 평가되었다.

• Composites Research
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• 제14권2호
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• pp.43-49
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• 2001

무선 랜용 시스템에 응용할 수 있는 스마트 스킨의 좌굴에 따른 성능변화에 대하여 살펴보았다. 스마트 스킨 구조물은 샌드위치 구조물을 응용한 것으로써 3층의 면재가 있으며 각 면재 사이에는 하니콤 심재가 있다. 좌굴하중을 Rayleigh-Ritz방법에 의하여 예측하고 실험결과와 비교하였다. 압축시 심재를 둘러싸고 있는 면재만 하중을 지지한다고 가정하여 좌굴이 발생하지 않는 시편의 길이를 계산하였으며, 그 근방에서는 좌굴 현상이 명확이 발생하지 않음을 확인 할 수 있었다. 시편의 길이가 길어 좌굴이 명확하게 발생한 경우 예측식과 잘 일치하였다. 좌굴의 진행정도에 따른 반사 계수와 방사패턴을 측정하여 안테나의 성능변화에 대하여 살펴보았으며, 하중지지능력이 상실된 후에 안테나의 기능이 상실됨을 확인하였다.

• Korean Chemical Engineering Research
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• 제45권4호
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• pp.372-377
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• 2007

본 연구에서는 생물학적 공정을 사용하여 황화수소를 제거하는데 있어 망상구조의 폴리우레탄 담체의 바이오필터 충진물로서의 특성을 유입가스농도와 유입가스량의 두 변수를 대상으로 조사하였다. 실험결과 망상구조의 폴리우레탄 담체를 적용한 바이오필터의 황화수소 최대제거용량은 $488.3g-H_2S/m^3{\cdot}h$이었으며, 추정된 임계부하속도는 $330.1g-H_2S/m^3{\cdot}h$이었다. 본 연구의 결과 망상구조의 폴리우레탄 담체를 황화수소의 생물학적 처리를 위한 바이오필터의 담체로서 적용가능성을 확인하였다.