• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.2 s.54
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• pp.181-188
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• 2009

Measuring the tensile strength of steel cables used to support bridges is a critical inspection item in terms of the safety of a bridge. Today, cable tension is measured with the vibration method and loadcell. Recently, some advanced countries have conducted studies on measuring tension with magnetic method and are suggesting prospective results. Since there were no such studies ongoing in Korea, we began a study on measuring tension with magnetic method as we are undergoing researches to improve the precision of measurements. It is necessary to consider the influence for the magnetic field and the temperature of steel cables in tension measurement of magnetic method. In this paper, we tested an output characteristic of tension sensor according to temperature and deduced temperature compensation coefficient in the given magnetic field and applied the compensation coefficient to the tension measurement system in the lab. We analyzed and evaluated testing results for the output voltages of the tension sensor according to cable tensions.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.3
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• pp.283-288
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• 2010

Mobile harbor is characterized by the lightweight compact structure when compared to the conventional above-ground port container crane. A new concept RORI crane system, which was devised for mobile harbor to satisfy the compactness and light weightness, not only can load/unload containers with high speed on sea but can be completely folded at maneuvering mode. This study is concerned with the tip deflection of the horizontal boom of mobile harbor at container loading operation. Both the theoretical method utilizing the Castigliano's theorem and the numerical approach by finite element method are employed, and the reliability of the latter approach is verified through the comparison with the theoretical results. And then, the effect of the initial cable tension on the tip deflection is parametrically examined by the finite element analysis.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.589-589
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• 2013

열전재료는 제백효과(Seebeck effect)에 의해 폐열을 전기에너지로 변환시킬 수 있는 소재로서, 기존의 열전재료가 나노수준으로 크기가 줄어들 경우 양자제한효과에 의한 제백계수의 증가와 표면산란에 의한 열전도도 감소로 인해 벌크재료에 비해 높은 에너지변환효율을 가질 수 있을 것으로 기대되고 있다. 에너지 변환효율은 열전성능계수인 $ZT=S2{\sigma}T/k$로 정의되며 따라서 우수한 열전재료는 높은 제백계수 S와, 높은 전기전도도 ${\sigma}$ 및 낮은 열전도도 k를 갖는 재료여야 한다. 그러나 나노소재는 낮은 측정 신호와 측정소자준비가 어려워 기존 측정시스템으로는 원활한 측정이 어렵다. 특히 열전도도의 경우 나노소재 자체의 열전도 보다 나노소재 주변 구조에 의한 열전도가 큰 경우 정확한 열전도도 평가가 어렵다. 본 연구에서는 나노선의 열전물성을 평가하기 위해 MEMS기반 기술을 이용하여 열전물성 측정플랫폼(MEMS-based thermoelectric measurement platform, MTMP)을 개발하였다. 개발 된 MTMP는 얇은 Si nitride 브릿지들이 허공에 떠 있는 두 개의 아일랜드 형태의 멤브레인 구조를 지지하는 형태로 제작되었으며, 한 쪽 아일랜드구조 위에는 나노히터가 있어 두 아일랜드 구조 사이에 온도구배를 만들 수 있도록 제작되었다. 제작된 멤브레인을 이용하여 전기화학적인 방법으로 합성한 Bi-Te계 나노선의 S, ${\sigma}$ 그리고 k를 측정하였다. 측정결과 화학양론적 미세구조를 갖는 단결정 Bi2Te3 나노선은 300 K의 측정온도에서 $S=-57{\mu}V/K$, ${\sigma}=3.9{\times}10^5S/m$, k=2.0 W/m-K의 측정 값으로 ZT=0.19였다. 본 연구에서 개발한 MTMP는 나노선 뿐만 아니라 나노플레이트의 열전 측정에도 활용할 수 있는 구조로서 나노열전소재 측정에 널리 활용될 수 있다.

• Membrane Journal
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• v.24 no.6
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• pp.417-422
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• 2014

The poly(ethylene oxide) (PEO)/Ag Nanoparticles (NPs)/7,7,8,8-Tetracyanoquinodimethane (TCNQ) membrane was fabricated to obtain highly permeable facilitated olefin transport nanocomposite membrane, compared with PEO/Ag NPs/p-Benzoquinone (p-BQ) membrane. Polymer matrix, PEO and silver nanoparticle precursor $AgBF_4$ were fixed at 1 : 0.4 mole ratio and electron acceptor TCNQ content was controlled variously. And the best olefin separation performance was obtained at 1/0.4/0.004 mole ratio, and long-term separation performance was measured at this ratio. As a result, mixed-gas permeance decreased from 23 to 6 GPU, and selectivity decreased from 6 to 2 (propylene/propane) after 32 hours.

• Journal of Korean Society for Geospatial Information Science
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• v.22 no.1
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• pp.55-62
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• 2014

Diverse improvement projects such as replacing street lamps with LED, street trees, etc are currently in progress in Korea to reduce greenhouse gas so as to cope with change in climate. However, the effect of climate change policy is not exactly analyzed, because exhaust quantity and absorption quantity of greenhouse gas of the target street lamp and street trees are not arranged as information. Thus, this study studied the method to systematically manage low carbon related information of urban facilities by using GIS. It was found that low carbon information of the urban facilities is necessary to exactly analyze effect of climate change policy and the method to calculate carbon exhaust quantity and absorption quantity of each facilities should be established to build exact low carbon information of urban facilities. Further, it was found that the visualization of information related to low carbon of street lamp and street trees by using GIS easily and visually grasps and systematically controls the effect of policy coping with change in climate than the existing numeral data of exhaust quantity and absorption quantity of greenhouse gas.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.3
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• pp.259-267
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• 2005

The effects of hull flexibility on shaft alignment are growing as ship sizes are increased mainly for container carrier and LNG carrier. In order to consider hull flexibility on a propulsion shafting system, standardization of ship service conditions is necessary because hull deformation is continuously variable according to ship service conditions. How to summarize ship service conditions is suggested based on practically applicable four viewpoints : hull, engine, loading and sea status. Effects of the external forces acting on a ship propulsion shafting system are generally commented. Several design criteria regulated by classification societies are pointed at issue which seems to have Insufficient technical background. A qualitative verification is carried out to point out the invalidity of the assumption of effective supporting position. In this work, an elastic nonlinear multi-supporting bearing system is introduced as a key concept of the elastic shaft alignment. Hertz contact theory is proved to be more proper one than projected area method in calculation of the nonlinear elastic stiffness of the bearing, The squeezing and oil film pressure calculations in the long journal bearing like an after stern tube bearing are recognized as a necessary process for elastic shaft alignment design.

• Journal of Digital Convergence
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• v.14 no.12
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• pp.111-120
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• 2016

PCAOB conducts the direct supervision for the PCAOB registered accounting firm. Therefore, if an accounting firm is registered with the PCAOB, it will thoroughly manage for their quality management systems. The registered auditor can be expected to have better quality of the audit. This study carried out the analysis using the audit fee which proxies for audit quality. The results of analysis are as follows. After controlling for foreign accounting firms affiliated status, company size, risky assets, leverage, ROA, and market-related variables, PCAOB is a significant explanatory variable for the audit fees. The results of this study support the hypothesis that PCAOB-registered auditors will provide a good audit quality.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.52 no.7
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• pp.393-400
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• 2003

In this paper we deal with the virtually zero power control for the rigid rotor with radial suspension by the permanent magnetic bearing and axial suspension by electromagnetic bearing. The purpose of the virtually zero power control is to reduce the power consumption of the electromagnetic bearings. The axial active force is expressed by the normal second order equation which has only one degree-of-freedom. The virtually zero power control structure has two schemes. One is the coil control current integrator which is used to make the convergence of the control current to a range which is very close to zero. By using the current integrator the DC component which is included in the control current is eliminated, thus the control current converges to a range which is close to zero. The other is normal PD control loop which is used to make the rotor reach to stable equilibrium point and to maintain air gap so that the axial force produced by radial permanent magnet always balances the total weight of the rotor and its load. First we show a simple mathematical plant model and the virtually zero power (VZP) control blocks. Second, we investigate the theoretical feasibility and the stability of the proposed virtually zero Power control levitation system with PD feedback loop by using linear control theory Finally we show the effectiveness of the proposed control method to reduce the power consumption by simulations.

• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.983-987
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• 2008

Computational simulation has been performed to design optimally the filtration system for IGCC pilot plant. It was analyzed how the different inflow pattern influences the flow field and the particle behavior in a filter vessel. The particle loading onto the filter surface lowers significantly and decreases dramatically with particle size when the dusty gas flows into the filter vessel with a shroud tube through a tangential inlet setup tangentially on the vessel outer wall. However, the particle loading is considerably high when the dusty gas enters the filter vessel through a normal inlet setup vertically on the vessel top wall, and the decrease of the particle loading with particle size is not steeper compared with the tangential inflow pattern.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.4
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• pp.343-350
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• 2017

The RC flat plate system has benefits such as a short construction time, an improvement of workability and a floor height reduction. In the case of long span slab, cracking damages and large deflections tend to occur due to the low flexural stiffness of flat plates. Specially, over-loading by self-weight of slab during construction increases short and long-term deflections. These problems may be solved by the use of void slab that has benefits of the reduced self-weight. In this study, to analyze an effect of self-weight reduction of void slab on slab deflections, the parametric study is performed. Including variable conditions such as a concrete strength, a slab construction cycle, the number of shored floors, a compressive reinforcement ratio and a tensile reinforcement ratio, slab construction loads and deflections are calculated by considering the construction stages, concrete cracking, and long-term effects. The short-term deflections during construction and the long-term deflections after construction of both of normal and void slabs are compared and the effects of void slab on the reduction of slab deflections are analyzed.