• 지구물리와물리탐사
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• 제26권4호
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• pp.185-198
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• 2023

해양 탄성파 탐사 수행 시 송·수신 케이블의 구조적인 거리차에 의해서 필연적으로 발생하는 가까운 벌림(near offset)의 트레이스(trace)빠짐은 뒤따르는 탄성파 자료처리의 결과 및 영상화에 악영향을 끼치게 된다. 특히 가까운 벌림의 자료의 부재는 정확한 탄성파 영상화를 저해하는 다중반사파의 제거에 주요한 인자로 작용하므로 다중반사파의 영향력이 강해지는 천해 및 연안 탐사의 경우 빠짐을 효과적으로 해결해야 한다. 전통적으로 다양한 라돈 변환(Radon transform) 기반의 내삽 방법들이 가까운 벌림 빠짐의 해결책으로 제시되어왔으나 여러 한계점을 보여, 최근 이를 보완하기 위한 딥러닝(deep learning) 기반의 방법들이 제시되고 있다. 이 논문에서는 기존에 제시된 두 가지의 대표적인 딥러닝 기반의 접근법에 대해 면밀히 분석하여 앞으로 가까운 벌림 내삽 연구가 해결해야 하는 문제점들에 대해 깊이 있게 논의한다. 또한 기존의 딥러닝 기반의 트레이스 내삽 기술을 가까운 벌림 상황에 적용할 때 나타나는 한계점을 현장자료 실험을 통해 명확히 분석하여 향후 가까운 벌림 자료 빠짐의 문제는 내삽이 아닌 외삽으로 접근해야 한다는 것을 보여준다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1031-1032
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• 2011

This paper deals with the characteristics analysis of Interior Permanent Magnet Type Motor varying with magnetization curve of electrical steel interpolated with several method in the high field region. The data of magnetization curve of electrical steel given by the steel maker is not enough in order to analysis the characteristics by menas of FEM. Especially, the core in the bridge part have a severe saturation because the bridge width is narrow to reduce the flux leakage produced by the permanent magnet. This paper make the three kinds of magnetization curve by extrapolation and then the motor is analyzed by using these magnetization curve. The motor parameters are compared to explain the effects of magnetization curve.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1996년도 춘계공동학술대회논문집; 공군사관학교, 청주; 26-27 Apr. 1996
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• pp.262-265
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• 1996

An ALT(accelerated life testing) method is to test a product in over-stressed conditions, and then the test result is extrapolated to an usual (normal stressed) condition. It is the major disadvantage of ALT method that the more extrapolation to an usual condition applies the bigger error is indispensable. Therefore a reliability model combining field failure data and laboratory test data is required in pratice. We propose several methods of estimating the failure rate of a product life which is assumed to follow an exponential distribution. Structural similarity and technological advances are also cosidered. Finally, We derive the acceleratio factor which can be used to predict the failure rate for a new product.

• 한국자동차공학회논문집
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• 제11권3호
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• pp.209-213
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• 2003

It is advantage of accelerated vibration testing to compress service exposures to operating vibration into a reduced laboratory test by increasing the amplitude or frequency of the applied input excitations. This paper proposes an accelerated test method to estimate the high-cycle fatigue life under random excitation. The method consists of conducting a test with amplified input excitation and extrapolating linearly the lift in the accelerated condition into the real lift in field condition. The extrapolation is carried out applying the high-cycle irregular excitation fatigue theory including the rainflow counting, Miner’s damage accumulation rule, and Goodman’s mean stress correction. As a verification, those estimated lift is compared with that acquired by experiment f3r the simple case of spot welding specimen with good agreement. This testing procedure will provide an useful scheme that can reduce testing period associated with developing time schedule of new product.

• Journal of Advanced Marine Engineering and Technology
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• 제22권6호
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• pp.935-941
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• 1998

Experiments were carried out for a cubic cavity flow. Contrinuous shear stress is supplied by driven flow for high Reynolds number and three kinds of aspect ratios. Velocity vectors are obtained by PIV and they are used as velocity components for Poisson equation for pressure, Related boundary conditions and no-slip condition at solid wall and the linear velocity extrapolation on the upper side of cavity are well examined for the present study. For calculation of pressure resolution of grid is basically $40{\times}40$ and 2-dimensional uniform mesh using MSC staggered grid is adopted. The flow field within the cavity maintains a forced-vortex formation and almost of the shear stress from the driving inflow is transformed into rotating flow energy and the size of the distorted forced-vortex increases with increment of Reynolds number

• 상하수도학회지
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• 제17권4호
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• pp.495-502
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• 2003

In order to modify incorrect flow data in the sewage system, the method using the stage-discharge relation and hydraulic characteristic curve of sewer pipe are applied. The modified data were verified with field measured data and the infiltration analysis using the modified data was carried out. When flowrate were measured using the flow-meter in fair weather, the stage data were comparatively consistent but velocity data were very poor for the most part. Therefore, it was recommended that sewage flowrate variation characteristic curve and infiltration were computed using the modified data on the basis of stage data. Especially, in the case of using the hydraulic characteristic curve, extrapolation results of the rainy season flowrate using regression curve on the basis of the data in fair weather were also reasonable.

• 천문학회보
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• 제46권1호
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• pp.59.3-60
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• 2021

An investigation of flare-producing magnetic structure is important for studying an initiation of eruptive events. In this study we select two different eruptive events, M5.3 and X1.2 flares in active region (AR) 11283. Both events occur in the same AR, but brightenings of flare ribbons, seen in EUV images, are different shapes. In order to understand triggering process of eruptive flares, we reconstruct coronal magnetic fields using two observation-based models: a nonlinear force-free field (NLFFF) extrapolation model and a magnetohydodynamic (MHD) one. The NLFFFs show that sheared arcades and overlying fan-spine configurations are found in both cases, but the distributions of magnetic twist are weaker before the M5.3 flare than before the X1.2 flare. The MHD model is to explore the temporal evolution of coronal magnetic structures by considering the NLFFF with an anomalous resistivity as an initial condition. We discuss possible processes of two eruptive events using the MHD as well as the NLFFF model results.

• 한국초전도ㆍ저온공학회논문지
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• 제18권1호
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• pp.1-5
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• 2016

Field and temperature dependence of the critical current density, Jc, were measured for both un-doped and carbon doped $MgB_2/Nb/Monel$ wires manufactured by Hyper Tech Research, Inc. In particular, carbon incorporation into the $MgB_2$ structure using malic acid additive and a chemical solution method can be advantageous because of the highly uniform mixing between the carbon and boron powders. At 4.2 K and 10 T, Jc was estimated to be $25,000-25,300Acm^{-2}$ for the wire sintered at $600^{\circ}C$ for 4 hours. The irreversibility field, $B_{irr}$, of the malic acid doped wire was approximately 21.0 - 21.8 T, as obtained from a linear extrapolation of the J-B characteristic. Interestingly enough, the Jc of the malic acid doped sample exceeds $10^5Acm^{-2}$ at 6 T and 4.2 K, which is comparable to that of commercial Nb-Ti wires.

• 천문학회보
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• 제45권1호
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• pp.29.5-30
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• 2020

We present an improved weak-lensing (WL) study of the high-z (z=0.87) merging galaxy cluster ACT-CL J0102-4915 ("El Gordo"), the most massive system known to date at z > 0.6. El Gordo has been known to be an exceptionally massive and rare cluster for its redshift in the current ΛCDM cosmology. Previous multi-wavelength studies have also found that the cluster might be undergoing a merging event showing two distinctive mass clumps and radio relics. The previous WL study revealed a clear bimodal mass structure and found that the entire system is indeed massive (M200a = (3.13 ± 0.56) × 1015 Msun). This mass estimate, however, was obtained by extrapolation because the previous HST observation did not extend out to the virial radius of the cluster. In this work, we determine a more accurate mass estimate of the cluster using WL analysis utilizing a new set of WFC3/IR and wide-field ACS observations. While confirming the previous bimodal mass structure, we find that the new data yield a ~20% lower mass for the entire system (M200a = (2.37 ± 0.28) × 1015 Msun). We also discuss the rarity of the cluster in the ΛCDM paradigm and suggest an updated merging scenario based on our new measurement.

• 한국과학교육학회지
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• 제15권1호
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• pp.92-103
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• 1995

Since the late of 1960,s, the improvement of science inquiry skills has been one of the most important goals in secondary science education. To achieve this goal, it is essential to develop a valid and reliable instrument for evaluating science inquiry skills. The purpose of this study is to develop a valid and reliable instrument for evaluating science inquiry skills for high school students. The instrument is developed through R & D procedure, which includes two field trials of the instrument. This study has formed a clear definition of the elements of science inquiry skills (formulating a hypothesis, controlling variables, designing an experiment, numeric calculation, graphing experimental data, inference, determining relationship, determining causalities, predicting experimental results , drawing a conclusion, formulating a generalization or model), and established the goals of assessment and developed the items of assessment. The instrument, Test of Earth Science Inquiry Skills, consists of 33 items which measure 11 science inquiry skills. There are content-free items for each science inquiry skills. This study has selected 11 science inquiry skills which are considered appropriate for being evaluated by paper-and-pencil test with SIEI (Hur,1984). The content validity of items, objectivity of the scoring keys and clarity of the items were checked by six experienced specialists in science education. At the same time, the two field trials has been executed and produced the reliability of the instrument, item difficulty index, and the effectiveness of distracters. The first field trial was performed using a sample of 304 high school students, and the second one using a sample of 872 high school students. Because the content validity is 84 % and the reliability (K-R 20) is 0.84, the developed instrument in this study is considered valid and reliable. The difficulty index is 49.4 %, answer ratio 59.1 %, the discrimination index 0.47 and the effectiveness of distracters evenly distributed, which also suffice the criteria of good instrument. The developed instrument in this study can diagnosis the well-developed science inquiry skills and the ill-developed science inquiry skills of the students, and trace the degree of the improvement of science inquiry skills.