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- 저자 : Sungho Park (검색결과 896 건)
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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.
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Park, Sunkyung,Lee, Jeong-Eun,Kang, Wonseok,Lee, Sang-Gak,Chun, Moo-Young,Kim, Kang-Min,Yuk, In-Soo,Lee, Jae-Joon,Mace, Gregory N.,Kim, Hwihyun,Kaplan, Kyle F.,Park, Chan,Sok Oh, Jae,Lee, Sungho,Jaffe American Astronomical Society 2018 The Astrophysical journal Supplement series Vol.238 No.2
<P>We present a library of high-resolution (R lambda/Delta lambda similar to 45,000) and high signal-to-noise ratio (S/N >= 200) near-infrared spectra for stars of a wide range of spectral types and luminosity classes. The spectra were obtained with the Immersion GRating INfrared Spectrograph covering the full range of the H (1.496-1.780 mu m) and K (2.080-2.460 mu m) atmospheric windows. The targets were primarily selected for being MK standard stars covering a wide range of effective temperatures and surface gravities, with metallicities close to the solar value. Currently, the library includes flux-calibrated and telluric-absorption-corrected spectra of 84 stars, with prospects for expansion to provide denser coverage of the parametric space. Throughout the H and K atmospheric windows, we identified spectral lines that are sensitive to T-eff or log g and defined corresponding spectral indices. We also provide their equivalent widths (EWs). For those indices, we derive empirical relations between the measured EWs and the stellar atmospheric parameters. Therefore, the derived empirical equations can be used to calculate the T-eff and log g of a star without requiring stellar atmospheric models.</P>
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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>
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Park, Kwangwoo,Bak, Jino,Park, Sungho,Choi, Wonhoon,Park, Suk Won Institute of Physics in association with the Ameri 2016 Physics in medicine & biology Vol.61 No.3
<P>A semiempirical method based on the averaging effect of the sensitive volumes of different air-filled ionization chambers (ICs) was employed to approximate the correction factors for beam quality produced from the difference in the sizes of the reference field and small fields.</P> <P>We measured the output factors using several cylindrical ICs and calculated the correction factors using a mathematical method similar to deconvolution; in the method, we modeled the variable and inhomogeneous energy fluence function within the chamber cavity. The parameters of the modeled function and the correction factors were determined by solving a developed system of equations as well as on the basis of the measurement data and the geometry of the chambers. Further, Monte Carlo (MC) computations were performed using the Monaco<SUP>®</SUP> treatment planning system to validate the proposed method.</P> <P>The determined correction factors (<img ALIGN='MIDDLE' ALT='$k_{{{Q}_{\text{msr}}},Q}^{{{f}_{\text{smf}}},\,{{f}_{\text{ref}}}}$ ' SRC='http://ej.iop.org/images/0031-9155/61/3/1293/pmbaa0e14ieqn001.gif'/>) were comparable to the values derived from the MC computations performed using Monaco<SUP>®</SUP>. For example, for a 6 MV photon beam and a field size of 1 × 1 cm<SUP>2</SUP>, <img ALIGN='MIDDLE' ALT='$k_{{{Q}_{\text{msr}}},Q}^{{{f}_{\text{smf}}},\,{{f}_{\text{ref}}}}$ ' SRC='http://ej.iop.org/images/0031-9155/61/3/1293/pmbaa0e14ieqn002.gif'/> was calculated to be <img ALIGN='MIDDLE' ALT='$1.125$ ' SRC='http://ej.iop.org/images/0031-9155/61/3/1293/pmbaa0e14ieqn003.gif'/> for a PTW 31010 chamber and <img ALIGN='MIDDLE' ALT='$1.022$ ' SRC='http://ej.iop.org/images/0031-9155/61/3/1293/pmbaa0e14ieqn004.gif'/> for a PTW 31016 chamber. On the other hand, the <img ALIGN='MIDDLE' ALT='$k_{{{Q}_{\text{msr}}},Q}^{{{f}_{\text{smf}}},\,{{f}_{\text{ref}}}}$ ' SRC='http://ej.iop.org/images/0031-9155/61/3/1293/pmbaa0e14ieqn005.gif'/> values determined from the MC computations were 1.121 and 1.031, respectively; the difference between the proposed method and the MC computation is less than 2%. In addition, we determined the <img ALIGN='MIDDLE' ALT='$k_{{{Q}_{\text{msr}}},Q}^{{{f}_{\text{smf}}},\,{{f}_{\text{ref}}}}$ ' SRC='http://ej.iop.org/images/0031-9155/61/3/1293/pmbaa0e14ieqn006.gif'/> values for PTW 30013, PTW 31010, PTW 31016, IBA FC23-C, and IBA CC13 chambers as well.</P> <P>We devised a method for determining <img ALIGN='MIDDLE' ALT='$k_{{{Q}_{\text{msr}}},Q}^{{{f}_{\text{smf}}},\,{{f}_{\text{ref}}}}$ ' SRC='http://ej.iop.org/images/0031-9155/61/3/1293/pmbaa0e14ieqn007.gif'/> from both the measurement of the output factors and model-based mathematical computation. The proposed method can be useful in case the MC simulation would not be applicable for the clinical settings.</P>
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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.
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Park, Daehun,Na, Myeongsu,Kim, Jung Ah,Lee, Unghwi,Cho, Eunji,Jang, Mirye,Chang, Sunghoe AAAS 2017 Science signaling Vol.10 No.487
<P><B>Amyloid-β and intersynaptic trafficking</B></P><P>Synaptic loss and dysfunction as well as neuronal accumulation of amyloid-β (Aβ) are classic features of Alzheimer’s disease (AD). Synaptic components are transported along axons in actin- and synapsin-associated vesicles to adjust synaptic strength in response to activity and to promote the formation of new synapses. Using hippocampal neurons isolated from rats and mouse models of AD, Park <I>et al</I>. found that a soluble form of Aβ impedes Ca<SUP>2+</SUP> clearance from neurons, which led to activation of the kinase CaMKIV. CaMKIV-mediated phosphorylation of synapsin caused its dissociation from synaptic vesicles and actin, thereby impairing vesicular transport. Targeting this pathway might suppress the pathological effects of Aβ in patients with AD.</P><P>The prefibrillar form of soluble amyloid-β (sAβ<SUB>1–42</SUB>) impairs synaptic function and is associated with the early phase of Alzheimer’s disease (AD). We investigated how sAβ<SUB>1–42</SUB> led to presynaptic defects using a quantum dot–based, single particle–tracking method to monitor synaptic vesicle (SV) trafficking along axons. We found that sAβ<SUB>1–42</SUB> prevented new synapse formation induced by chemical long-term potentiation (cLTP). In cultured rat hippocampal neurons, nanomolar amounts of sAβ<SUB>1–42</SUB> impaired Ca<SUP>2+</SUP> clearance from presynaptic terminals and increased the basal Ca<SUP>2+</SUP> concentration. This caused an increase in the phosphorylation of Ca<SUP>2+</SUP>/calmodulin-dependent protein kinase IV (CaMKIV) and its substrate synapsin, which markedly inhibited SV trafficking along axons between synapses. Neurons derived from a transgenic AD mouse model had similar defects, which were prevented by an inhibitor of CaMK kinase (CaMKK; which activates CaMKIV), by antibodies against Aβ<SUB>1–42</SUB>, or by expression a phosphodeficient synapsin mutant. The CaMKK inhibitor also abolished the defects in activity-dependent synaptogenesis caused by sAβ<SUB>1–42</SUB>. Our results suggest that by disrupting SV reallocation between synapses, sAβ<SUB>1–42</SUB> prevents neurons from forming new synapses or adjusting strength and activity among neighboring synapses. Targeting this mechanism might prevent synaptic dysfunction in AD patients.</P>
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