• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 춘계학술대회 논문집
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• pp.123-127
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• 1999

This paper suggests the establishment of high-accuracy and high-efficiency machining method of scroll shape workpiece by using the feed control method. The cutting paths for machining the inside and outside surfaces of the scroll-shape workpiece are calculated, and the calculation method of the cutting chip areas based on the coordinate of the base circle is shown. A feed control method is proposed for a constant cutting area and cutting force. By machining test of scroll shape workpiece, The machined accuracy of wrap, tool wear, and surface roughness are evaluated. By this method, Reduction of the machining time and large increase of the efficiency can be expected.

• Structural Engineering and Mechanics
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• 제85권2호
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• pp.207-216
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• 2023

Three time-discontinuous Galerkin quadrature element methods (TDGQEMs) are developed for structural dynamic problems. The weak-form time-discontinuous Galerkin (TDG) statements, which are capable of capturing possible displacement and/or velocity discontinuities, are employed to formulate the three types of quadrature elements, i.e., single-field, single-field/least-squares and two-field. Gauss-Lobatto quadrature rule and the differential quadrature analog are used to turn the weak-form TDG statements into a system of algebraic equations. The stability, accuracy and numerical dissipation and dispersion properties of the formulated elements are examined. It is found that all the elements are unconditionally stable, the order of accuracy is equal to two times the element order minus one or two times the element order, and the high-order elements possess desired high numerical dissipation in the high-frequency domain and low numerical dissipation and dispersion in the low-frequency domain. Three fundamental numerical examples are investigated to demonstrate the effectiveness and high accuracy of the elements, as compared with the commonly used time integration schemes.

• 대기
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• 제33권5호
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• pp.549-560
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• 2023

This study evaluates three distinct observation methods, CRDS, OA-ICOS, and OF-CEAS, in greenhouse gas monitoring equipment for atmospheric CO₂ and CH₄ concentrations. The assessment encompasses fundamental performance, high-concentration measurement accuracy, calibration methods, and the impact of atmospheric humidity on measurement accuracy. Results indicate that within a range of approximately 500 ppm, all three devices demonstrate high accuracy and linearity. However, beyond 1000 ppm, CO₂ accuracy sharply declines (84%), emphasizing the need for caution when interpreting high-concentration CO₂ data. An analysis of calibration methods reveals that both CO₂ and CH₄ measurements achieve high accuracy and linearity through 1-point calibration, suggesting that multi-point calibration is not imperative for precision. In dynamic atmospheric conditions with significant CO₂ and CH₄ concentration variations, a 1-point calibration suffices for reliable data (99% accuracy). The evaluation of humidity impact demonstrates that humidity removal devices significantly reduce air moisture levels, yet this has a negligible effect on dry CO₂ concentrations (less than 0.5% relative error). All three observation method instruments, which have integrated humidity correction to calculate dry CO₂ concentrations, exhibit minor sensitivity to humidity removal devices, implying that additional removal devices may not be essential. Consequently, this study offers valuable insights for comparing data from different measurement devices and provides crucial information to consider in the operation of monitoring sites.

• 대한기계학회논문집A
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• 제32권10호
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• pp.823-830
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• 2008

We present a high-accuracy digital-to-analog (DA) actuator using a load spring, specially designed to compensate the output displacement errors caused by fabrication errors. The compensated linear DA actuator is capable to change the slope of input-output modulation line in order to compensate fabrication errors. We design, fabricate, and characterize three different prototypes: one uncompensated design and two compensated designs respectively for a specific value and for a given range of fabrication error. The compensated linear DA actuators show the output displacement errors of $-0.20{\pm}0.23{\mu}m\;and\;-0.13{\pm}0.18{\mu}m$, respectively, reduced by 64.3% and 76.8% of the output displacement error, $0.56{\pm}0.20{\mu}m$, produced by the conventional uncompensated linear DA actuator. We experimentally verify the fabrication error compensation capability of the present compensated linear DA actuators, thus demonstrating high-accuracy actuation performance immune to fabrication errors.

• 대한원격탐사학회지
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• 제38권4호
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• pp.395-409
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• 2022

The purpose of this study is to evaluate the classification performance and applicability when land cover datasets constructed for AI training are cross validation to other areas. For study areas, Gyeongsang-do and Jeolla-do in South Korea were selected as cross validation areas, and training datasets were obtained from AI-Hub. The obtained datasets were applied to the U-Net algorithm, a semantic segmentation algorithm, for each region, and the accuracy was evaluated by applying them to the same and other test areas. There was a difference of about 13-15% in overall classification accuracy between the same and other areas. For rice field, fields and buildings, higher accuracy was shown in the Jeolla-do test areas. For roads, higher accuracy was shown in the Gyeongsang-do test areas. In terms of the difference in accuracy by weight, the result of applying the weights of Gyeongsang-do showed high accuracy for forests, while that of applying the weights of Jeolla-do showed high accuracy for dry fields. The result of land cover classification, it was found that there is a difference in classification performance of existing datasets depending on area. When constructing land cover map for AI training, it is expected that higher quality datasets can be constructed by reflecting the characteristics of various areas. This study is highly scalable from two perspectives. First, it is to apply satellite images to AI study and to the field of land cover. Second, it is expanded based on satellite images and it is possible to use a large scale area and difficult to access.

• 대한토목학회논문집
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• 제29권1D호
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• pp.161-166
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• 2009

고해상도, 고정밀도의 초고차항 전 지구 중력장모델은 현대측지학, 지구물리학, 지구동력학 및 해양학 등 다양한 과학 분야의 발전에 있어서 매우 중요한 의미를 가지고 있다. 본 연구에서는 최근 미국 국가지형정보국(NGA)에서 발표한 초고차항 중력장모델 EGM2008을 소개하고, 초고차항 중력장모델 개발에 있어서의 문제점과 연구현황을 살펴보았으며, 남한지역에서 의 정확도를 분석하였다. 우선 EGM2008을 기존의 전 지구 중력장모델 EGM96 및 한국의 고정밀 합성 지오이드모델인 KGEOID08과 모델 간 정밀도를 비교하였고, 위성측지기준점의 타원체고와 정표고를 이용해 절대 정확도를 평가하였다. 전반적으로 EGM2008은 KGEOID08과 비슷한 높은 정확도를 보였으며, 이는 향후 지역적 지오이드의 개발 또는 전 지구적인 중력장 분석에 큰 도움을 줄 것으로 판단된다.

• 대한원격탐사학회지
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• 제40권1호
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• pp.103-114
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• 2024

The escalating demands for high-resolution satellite imagery necessitate the dissemination of geospatial data with superior accuracy.Achieving precise positioning is imperative for mitigating geometric distortions inherent in high-resolution satellite imagery. However, maintaining sub-pixel level accuracy poses significant challenges within the current technological landscape. This research introduces an approach wherein upsampling is employed on both the satellite image and ground control points (GCPs) chip, facilitating the establishment of a high-resolution satellite image precision sensor orientation. The ensuing analysis entails a comprehensive comparison of matching performance. To evaluate the proposed methodology, the Compact Advanced Satellite 500-1 (CAS500-1), boasting a resolution of 0.5 m, serves as the high-resolution satellite image. Correspondingly, GCP chips with resolutions of 0.25 m and 0.5 m are utilized for the South Korean and North Korean regions, respectively. Results from the experiment reveal that concurrent upsampling of satellite imagery and GCP chips enhances matching performance by up to 50% in comparison to the original resolution. Furthermore, the position error only improved with 2x upsampling. However,with 3x upsampling, the position error tended to increase. This study affirms that meticulous upsampling of high-resolution satellite imagery and GCP chips can yield sub-pixel-level positioning accuracy, thereby advancing the state-of-the-art in the field.

• International Journal of Precision Engineering and Manufacturing
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• 제1권1호
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• pp.111-117
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• 2000

One of the major limitations of productivity and quality in metal cutting is the machining accuracy of machine tools. The machining accuracy is affected by geometric errors, thermally-induced errors, and the deterioration of the machine tools. Geometric and thermal errors of machine tools should be measured and compensated to manufacture high quality products. In metal cutting, the machining accuracy is more affected by thermal errors than by geometric errors. This paper models the thermal errors for error analysis and develops an on-the-machine measurement system by which the volumetric errors are measured and compensated. The thermal error is modeled by means of angularity errors of a column and thermal drift error of the spindle unit which are measured by the touch probe unit with a star type styluses and a designed spherical ball artifact (SBA). Experiments show that the developed system provides a high measuring accuracy, with repeatability of $\pm$2$\mu\textrm{m}$ in X, Y and Z directions. It is believed that the developed measurement system can be also applied to the machine tools with CNC controller. In addition, machining accuracy and product quality can be also improved by using the developed measurement system when the spherical ball artifact is mounted on a modular fixture.

• 한국정보통신학회논문지
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• 제16권5호
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• pp.1083-1094
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• 2012

현재 상용화 되어 있는 위치 추정 시스템은 높은 정확도로 다양한 서비스에 폭넓게 사용되고 있다. 그러나 위치추정 시스템은 실내에서 완벽하게 설치하지 않을 경우 위치 추정 정확도가 매우 좋지 않은 경향을 보인다. 본 논문에서는 Location Fingerprint 기법을 활용하여 완벽하게 설치되지 않은 위치 추정 시스템으로부터 얻은 위치 정보를 보정하여 객체의 위치 정확도를 향상시켜 설치비용을 최소화할 수 있는 실내 위치 추정 알고리즘을 제안한다. 본 논문에서는 실내 환경에서 우수한 위치 정밀도를 제공하는 UWB 기반의 Ubisense 시스템을 활용하였다. 결론적으로, 본 논문에서는 위치 추정 시스템에서 측정한 객체의 위치 정보를 보정함으로써 위치 정확도를 향상시킬 수 있었다.

• Current Optics and Photonics
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• 제5권2호
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• pp.164-172
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• 2021

In this paper a catadioptric laser-irradiation-precision test system is designed, to achieve a high-precision laser-irradiation-accuracy test. In this system, we adopt the method of imaging the entire target surface at a certain distance to realize the measurement of laser-irradiation precision. The method possesses the advantages of convenient operation, high sensitivity, and good stability. To meet the test accuracy requirement of 100 mm/km (0.01%), the coma, field curvature, and distortion over the entire field of view should be eliminated from the optical system's design. Taking into account the whole length of the tube and the influence of stray light on the structure type, a catadioptric system with a hood added near the primary imaging surface is designed. After optimization using the ZEMAX software, the modulation transfer function (MTF) of the designed optical system is 0.6 at 30 lp/mm, the full-field-of-view distortion is better than 0.18%, and the energy concentration in the 10-㎛-radius surrounding circle reaches about 90%. The illumination-accuracy test results show that the measurement accuracy of the radiation hit rate is better than 50 mm when the test distance is 1 km, which is better than the requirement of 100 mm/km for the laser-irradiation-accuracy test.