• 전자공학회논문지B
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• 제30B권11호
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• pp.84-92
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• 1993

Calibration of Engine models is a painstaking process but very important for successful application to automotive industry problems. A combined heuristic and machine learning approach has therefore been adopted to improve the efficiency of model calibration. We developed an intelligent calibration program called ICALIB. It has been used on a daily basis for engine model applications, and has reduced the time required for model calibrations from many hours to a few minutes on average. In this paper, we describe the heuristic control strategies employed in ICALIB such as a hill-climbing search based on a state distance estimation function, incremental problem solution refinement by using a dynamic tolerance window, and calibration target parameter ordering for guiding the search. In addition, we present the application of amachine learning program called GID3*for automatic acquisition of heuristic rules for ordering target parameters.

• International Journal of Precision Engineering and Manufacturing
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• 제9권3호
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• pp.46-50
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• 2008

The present status and future prospects of the levitation mass method (LMM), a technique for precision mass and force measurement, are reviewed. In the LMM, the inertial force of a mass levitated using a pneumatic linear bearing is used as the reference force applied to the objects being tested, such as force transducers, materials, or structures. The inertial force of the levitated mass is measured using an optical interferometer. We have modified this technique for dynamic force calibration of impact, oscillation, and step loads. We have also applied the LMM to material testing, providing methods for evaluating material viscoelasticity under an oscillating or impact load, evaluating material friction, evaluating the biomechanics of a human hand, and generating and measuring micro-Newton-level forces.

• 국제초고층학회논문집
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• 제3권4호
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• pp.305-310
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• 2014

Wind-induced responses of a structure are often evaluated through dynamic analysis, where measured wind forces obtained from a wind-tunnel test and dynamic properties obtained from a FE (Finite Element) model are utilized. However, the FE model generally shows considerable discrepancies in the estimation of natural frequencies compared to field measurements due to some assumptions and simplifications. In this paper, a calibration method that can improve the estimation of natural frequencies in the FE model is proposed, and specific cases are studied for its validity with comparison to the field measurement results.

• 대한원격탐사학회지
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• 제35권5_1호
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• pp.665-679
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• 2019

면 단위의 고해상도 토양 수분 측정이 가능한 Cosmic-Ray Neutron Probe(CRNP)를 이용한 토양수분 관측 데이터는 위성기반의 큰 공간해상도를 지닌 토양 수분 자료와 지점 관측 토양 수분 자료를 연결하는 통로의 역할을 수행할 것으로 기대된다. 이러한 CRNP 센서를 이용하여 토양 수분을 산출하기 위해서는 측정된 중성자 강도의 교정이 필요한데 기존의 교정 방법은 관측 기간의 단일 교정 중성자 강도($N_0$)를 이용하여 장기간의 토양 수분 관측에 어려움이 있다. 또한 기존 방법을 이용한 $N_0$는 시간에 따라 변동하는 인자들에 의해 영향을 고려하지 못하며 이로 인해 CRNP 센서를 이용한 토양 수분 관측 값에 불확실성을 초래한다. 이를 극복하기 위해 새로운 교정 방법(Dynamic-$N_0$ 교정 방법)을 제시한다. Dynamic-$N_0$ 교정 방법은 시간에 따른 $N_0$의 변동을 고려함으로써 토양 수분 관측 값을 개선하는 방법으로 비선형 회귀 모델을 이용하여 $N_0$의 시계열 자료를 구하여 토양 수분 산출에 이용한다. 본 연구에서는 Dynamic-$N_0$ 교정 방법을 이용하여 산출된 토양 수분을 지점 기반 토양 수분 및 기존의 교정방법을 이용한 토양 수분 산출 값과 비교하였으며 결과적으로 상관계수를 0.7에서 0.72로 개선하였다. RMSE와 Bias는 각각 $0.036m^3m^{-3}$에서 $-0.026m^3m^{-3}$으로, $-0.006m^3m^{-3}$에서 $-0.001m^3m^{-3}$으로 개선되었다. Dynamic-$N_0$ 교정 방법의 기존의 방법 대비 탁월한 성능은 CRNP 센서 주변의 수소 공급원에 의하여 $N_0$의 변동이 발생했음을 시사한다. 그러나 몇몇 중성자 강도에 영향을 미치는 수소 공급원들에 대한 고려가 구체적으로 이뤄지지 않았는데 이는 향후 연구를 통해 Cosmic-Ray를 이용한 토양 수분 관측이 보다 개선될 수 있음을 보여준다.

• Journal of Astronomy and Space Sciences
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• 제40권4호
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• pp.173-197
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• 2023

ShadowCam is a high-sensitivity, high-resolution imager provided by NASA for the Danuri (KPLO) lunar mission. ShadowCam calibration shows that it is well suited for its purpose, to image permanently shadowed regions (PSRs) that occur near the lunar poles. It is 205 times as sensitive as the Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC). The signal to noise ratio (SNR) is greater than 100 over a large part of the dynamic range, and the top of the dynamic range is high enough to accommodate most brighter PSR pixels. The optical performance is good enough to take full advantage of the 1.7 meter/pixel image scale, and calibrated images have uniform response. We describe some instrument artifacts that are amenable to future corrections, making it possible to improve performance further. Stray light control is very challenging for this mission. In many cases, ShadowCam can image shadowed areas with directly illuminated terrain in or near the field of view (FOV). We include thorough qualitative descriptions of circumstances under which lunar brightness levels far higher than the top of the dynamic range cause detector or stray light artifacts and the size and extent of the artifact signal under those circumstances.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.390-393
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• 2007

KOMPSAT-2, the first Korean high resolution earth observing satellite, continuously acquires high resolution images since July 2006. The quality of satellite images should be geometrically and radiometrically ensured before distribution to users. This study focused on absolute radiometric calibration which is a prerequisite procedure to ensure the radiometric quality of optical satellite images. In this study, we performed reflectance-based vicarious calibration methods on several uniform targets collected through several field campaigns in 2007. The radiative transfer model, MODTRAN, was used to estimate the amount of energy received at the sensor. The energy reached at the sensor are affected by several factors such as reflectance of targets, atmospheric condition, geometry condition between Sun and the sensor, etc. This study proposes the absolute radiometric calibration coefficients of KOMPSAT-2 MSC images combining several types of collected data through field works and tried to compare dynamic range of sensor-detected energy with other commercial high resolution sensors.

• Geomechanics and Engineering
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• 제2권3호
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• pp.177-190
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• 2010

This paper presents the details of indigenous development of the piezovibrocone and calibration chamber. The developed cone has a cylindrical friction sleeve of $150cm^2$ surface area, capped with a $60^{\circ}$ apex angle conical tip of $15cm^2$ cross sectional area. It has a hydraulic shaker, coupled to the cone penetrometer with a linear displacement unit. The hydraulic shaker can produce cyclic load in different types of wave forms (sine, Hover sine, triangular, rectangular and external wave) at a range of frequency 1-10 Hz with maximum amplitude of 10 cm. The piezovibrocone can be driven at the standard rate of 2 cm/sec using a loading unit of 10 ton capacity. The calibration chamber is of size $2m{\times}2m{\times}2m$. The sides of the chamber and the top as well as the bottom portions are rigid. It has a provision to apply confining pressure (to a maximum value of $4kg/cm^2$) through the flexible rubber membrane inlined with the side walls of the calibration chamber. The preliminary static as well as dynamic cone penetration tests have been done sand in the calibration chamber. From the experimental results, an attempt has been made to classify the soil based on friction ratio ($f_R$) and the cone tip resistance ($q_c$).

• 한국공작기계학회논문집
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• 제17권3호
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• pp.47-52
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• 2008

The force transducer in the acceleration plant due to dynamic fracture is calibrated by dynamically using the stress pulses from a longitudinal bar. The bar is supported by two strings attached to the ceiling. The bar velocities before and after impact are measured and a full bridge at bar and transducer is formed by the four strain gauges. A transient recorder is used to store the stress pulse signals of force transducer and bar. For the first test series, three point bend test specimens can be chosen by means of test rig design and the inspection as sample experiment in this presented paper is sufficient for proving with the numerical simulation of the specimen model.

• 대한원격탐사학회지
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• 제16권2호
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• pp.135-143
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• 2000

Ocean Scanning Multispectral Imager (OSMI) is a payload on the Korean Multi-Purpose SATellite (KOMPSAT) to perform global ocean color monitoring for the study of biological oceanography. HOMPSAT was launched 21 December 1999. The radiometric performance of OSMI is analyzed for various gain settings in the viewpoint of the instrument developer for OSMI calibration and application based on its ground performance data measured before launch. The radiometric response linearity and dynamic range are analyzed and the dynamic range is compared with the nominal input radiance for the ocean and the land. The noise equivalent radiance (NER) corresponding to the instrument radiometric noise is compared with the radiometric resolution of signal digitization (1-count equivalent radiance). The best gain setting of OSMI for ocean monitoring is recommended. This analysis is considered to be useful for the OSMI mission and operation planning, the OSMI image data calibration, and users' understanding about OSMI image quality.

• 반도체디스플레이기술학회지
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• 제23권1호
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• pp.56-60
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• 2024

In this paper, we propose a SIFT feature-based dynamic stitching algorithm for image calibration and correction of a 360-degree surround view system. The existing surround view system requires a lot of processing time and money because in the process of image calibration and correction. The traditional marker patterns are placed around the vehicle and correction is performed manually. Therefore, in this study, images captured with four fisheye cameras mounted on the surround view system were distorted and then matched with the same feature points in adjacent images through SIFT-based feature point extraction to enable image stitching without a fixed marker pattern.