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사륜 독립구동 차량시스템의 제어입력 조정을 통한 결함진단
박성호(Sungho Park),박영진(Youngjin Park),박윤식(Youn-sik Park) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11
In this research, quantitative measurement of fault isolation is defined to evaluate fault isolate performance in parity equation. If it is hard or impossible to isolate fault components with parity equation, fault diagnosis method by adjustment of input distribution is applied to overcome the limitation of parity equation method. Noticeable characteristic in four wheels independently driven vehicle system is that there are lots of input distribution to achieve equivalent control performance. In normal case, controller makes optimal input distribution. But if there exist probability to have fault components, fault diagnosis system makes input perturbation and analyze system response to isolate fault components.
Electrochemical Synthesis of Dumbbell-like Au-Ni-Au Nanorods and Their Surface Plasmon Resonance
Park, Yeon Ju,Liu, Lichun,Yoo, Sang-Hoon,Park, Sungho The Korean Electrochemical Society 2012 Journal of electrochemical science and technology Vol.3 No.2
In this report, we demonstrate that the longitudinal localized surface plasmon resonance mode can be suppressed when the nanorods were in dumbbell shape. The seed nanorods were synthesized by electrochemical deposition of metals into the pores of anodic aluminum oxide templates. The dumbbell-like nanorods were grown from seed Au-Ni-Au nanorods by a rate-controlled seed-mediated growth strategy. The selective deposition of Au atoms onto Au blocks of Au-Ni-Au nanorods produced larger diameter of Au nanorods with bumpy surface resulting in dumbbell-like nanorods. The morphology of nanorods depended on the reduction rate of $AuCl_4^-$, slow rate producing smooth surface of Au nanorods, but high reduction rate producing bumpy surface morphology. Through systematic investigation into the UV-Vis-NIR spectroscopy, we found that the multiple localized surface plasmon resonance (LSPR) modes were available from single-component Au nanorods. And, their LSPR modes of Au NRs with bumpy surface, compared to the smooth seed Au NRs, were red-shifted, which was obviously attributed to the increased electron oscillation pathways. While the longitudinal LSPR modes of smoothly grown Au NRs were blue-shifted except for a dipole transverse LSPR mode, which can be interpreted by decreased aspect ratio. In addition, dumbbell-like nanorods showed an almost disappeared longitudinal LSPR mode. It reflects that the plasmonic properties can be engineered using complex nanorods structure.
Study on Sliding Wear Characteristics and Processing of MoSi
Park, Sungho,Park, Wonjo,Huh, Sunchul Korean Society of Ocean Engineers 2012 International journal of ocean system engineering Vol.2 No.4
In this study, a monolithic MoSi2 matrix reinforced with 20 vol% SiC particles, a SiC/MoSi2 composite matrix reinforced with 20 vol% ZrO2 particles, and a ZrO2/MoSi2 composite were fabricated using hot press sintering at $1350^{\circ}C$ for 1 h under a pressure of 30 MPa. The Vickers hardness and sliding wear resistance of the monolithic MoSi2, ZrO2/MoSi2, and SiC/MoSi2 composite were investigated at room temperature. A wear behavior test was carried out using a disk-type wear tester with a silicon nitride ball. The ZrO2/MoSi2 composite showed an average Vickers hardness value and excellent wear resistance compared with the monolithic MoSi2 and SiC/MoSi2 composite at room temperature.
Whole Life Performance Bid Evaluation in the Korean Public Sector
Park, Kenneth Sungho,임형철 한국건축시공학회 2012 한국건축시공학회지 Vol.12 No.6
Over the last several years, Korea has increasingly adopted design-build for public construction projects. There is a much greater awareness of the need to change to a system based on ‘Value for Money’, which is high on the government's agenda. A whole life performance bid evaluation model is proposed to aid decision makers in the selection of a design-builder. This is based on the integration of a framework using an analytic hierarchy process, as the bid awarding system is being changed from one based on the lowest price to one based on best value over the life-cycle. Key criteria such as whole life cost, service life planning and design quality are important through the key stages of the evaluation process. The model uses a systematic and holistic approach, which enables the public sector client to make better decisions in design-builder selection, which will deliver whole life benefits based on long-term cost-effectiveness.
Gear fault diagnosis using transmission error and ensemble empirical mode decomposition
Park, Sungho,Kim, Seokgoo,Choi, Joo-Ho Elsevier 2018 Mechanical systems and signal processing Vol.108 No.-
<P><B>Abstract</B></P> <P>Classification of spall and crack faults of gear teeth is studied by applying the ensemble empirical mode decomposition (EEMD) to the transmission error (TE) measured by the encoders of the input and output shafts. Finite element models of the gears with the two faults are built, and TE’s are obtained by simulation of the faulty gears under loaded contact to identify the different characteristics. A simple test bed for a pair of spur gears is prepared to illustrate the approach, in which the TE’s are measured for the gears with seeded spall and crack, respectively. EEMD is applied to extract fault features under the noise from the measured TE. The differences of the spall and crack are clearly identified by the selected features of the intrinsic mode functions based on the class separability criterion. The k-nearest neighbor method is applied for the classification of the faults and normal gears using the features. The proposed method is advantageous over the existing practices in the sense that the TE signal measures the gear faults more directly with less noise, enabling successful diagnosis.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A new approach is proposed to identify the two faults: spall and crack. </LI> <LI> The method is based on the transmission error measurement. </LI> <LI> Ensemble empirical mode decomposition is applied to extract features from the measured signals. </LI> <LI> Fault type is identified via the FEA and virtual signal processing. </LI> <LI> The method is useful since the TE gives faulty signal more directly and FEA is used for the fault identification. </LI> </UL> </P>
Block-wise Correction of Vignetting Distortion
Sungho Park,Yongseok Jin,Hyuk-Jae Lee 대한전자공학회 2009 ITC-CSCC :International Technical Conference on Ci Vol.2009 No.7
Vignetting refers to a distortion of an image near the periphery caused by loss of light. To compensate for the vignetting distortion, previous schemes use lookup table to store the distribution of light intensity and use this distribution to correct the distortion. Another previous scheme uses a functional model for the vignetting distortion and correct the distortion based on the model. This model-based correction reduces the memory space to store the lookup table, but it suffers from the reduction of the correction accuracy. This paper combines the previous two approaches by decomposing an image into small blocks, obtaining the functional models for every block, correcting vignetting distortion block by block based on the function models. Experimental results show that a functional model based on the 2<SUP>nd</SUP> order equation with the block size of 64×64 gives a reasonably good trade-off between the required memory space and the correction accuracy.