• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2008년도 춘계 종합학술대회 논문집
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• pp.892-896
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• 2008

도로, 철도 및 운하 등을 비롯한 각종 건설공사를 위해서는 건설공사의 기본설계과정에서 건설예정지에 대한 지형측량을 실시하고 이를 기초로 종 횡단면도의 제작이 필수적인 요소이다. 본 연구에서는 건설예정지에 대한 프로파일 제작에 있어 NGIS구축사업에 의해 제작된 수치지형도의 지형정보를 이용하여 정밀 3차원지형모델을 구축하고, 이로부터 자동 프로파일을 생성하여 종 횡단면도로 활용할 수 있는 방안을 제안하고자 하였다. 이를 위해 수치지형도로부터 표고 및 주요시설물의 레이어를 각각 추출하고 이를 이용하여 정밀 3차원 지형모델을 구축하는 한편, 3차원 지형모델로부터 자동 프로파일을 생성하여 종횡단면도를 제작하였다. 그리고 생성된 프로파일의 경로에 대하여 지형측량을 실시하여 상호 분석함으로써 자동 생성된 프로파일의 정확도가 현지측량 정확도와 허용정확도를 만족시킬 수 있는지의 여부를 검토하였다. 본 연구의 결과는 건설공사를 위해 실시되는 기본설계과정에서 설계기간의 단축, 설계비용의 감소와 설계업무의 효율화를 꾀할 수 있는 새로운 개념의 프로파일 생성기법으로 제안할 수 있을 것으로 사료된다.

• 한국정밀공학회지
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• 제19권6호
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• pp.62-69
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• 2002

For improving the motion accuracy of hydrostatic table, corrective machining algorithm is proposed in this paper. The algorithm consists of three main processes. reverse analysis is performed firstly to estimate rail profile from measured linear and angular motion error, in the algorithm. For the next step, corrective machining information is decided as referring to the estimating rail profile. Finally, motion errors on correctively machined rail are analized by using motion error analysis method proposed in the previous paper. These processes can be iterated until the analized motion errors are satisfied with target accuracy. In order to verify the validity of the algorithm theoretically, motion errors by the estimated rail, after corrective machining, are compared with motion errors by true rail assumed as the measured value. Estimated motion errors show good agreement with assumed values, and it is confirmed that the algorithm is effective to acquire the corrective machining information to improve the accuracy of hydrostatic table.

• 응용통계연구
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• 제22권5호
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• pp.911-921
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• 2009

신용평가 연구에서 부도와 정상차주에 대한 판별력을 평가하는 방법으로 Receiver Operating Characteristic(ROC)와 Cumulative Accuracy Profile(CAP) 곡선을 사용한다. ROC 곡선에서 최적의 분류정확도를 갖는 분류점과 CAP 곡선에서 최대의 이익을 나타내는 분류점은 일반적인 정확도의 개념으로 정의된 동일한 성과를 가진 접선을 사용하여 구한다. 본 연구에서는 정확도의 대안적인 측도로 진실율을 제안하고, 이 진실율을 이용하여 ROC와 CAP 곡선에서 대안적인 최적의 분류점을 구한다. 대부분 실제 차주의 모집단에서 부도차주는 정상차주보다 훨씬 수가 적다. 이러한 경우에 진실율은 정확도보다 비용함수의 측면에서 더욱 효율적일 수 있다. 진실율을 이용하여 최적의 분류정확도를 나타내는 분류점과 최대의 이익을 의미하는 분류점에 대응하는 스코어는 동일하다는 것을 보였으며, 이 스코어는 부도와 정상 차주의 분포함수의 동일성을 검정하는 Kolmogorov-Smirnov 통계량에 대응하는 스코어와도 일치하는 것을 발견하였다.

• 대기
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• 제32권2호
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• pp.163-178
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• 2022

This study aims to evaluate the accuracy of retrieved horizontal winds with different quality control methods from three Doppler lidars deployed over the complex terrain during the PyeongChang 2018 Olympic and Paralympic games. To retrieve the accurate wind profile, this study also proposes two quality control methods to distinguish between meteorological signals and noises in the Doppler velocity field, which can be broadly applied to different Doppler lidars. We evaluated the accuracy of retrieved winds with the wind measurements from the nearby or collocated rawinsondes. The retrieved wind speed and direction show a good agreement with rawinsonde with a correlation coefficient larger than 0.9. This study minimized the sampling error in the wind evaluation and estimation, and found that the accuracy of retrieved winds can reach ~0.6 m s^-1 and 3° in the quasi-homogeneous wind condition. We expect that the retrieved horizontal winds can be used in the high-resolution analysis of the horizontal winds and provide an accurate wind profile for model evaluation or data assimilation purposes.

• 대한기계학회논문집B
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• 제23권2호
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• pp.243-253
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• 1999

The dual reciprocity boundary element method (DRBEM) is used to solve the Graetz problem of laminar flow inside circular duct. In this method the domain integral tenn of boundary integral equation resulting from source term of governing equation is transformed into equivalent boundary-only integrals by using the radial basis interpolation function, and therefore complicate domain discretization procedure Is completely removed. Velocity profile is obtained by solving the momentum equation first and then, using this velocities as Input data, energy equation Is solved to get the temperature profile by advancing from duct entrance through the axial direction marching scheme. DRBEM solution is tested for the uniform temperature and heat flux boundary condition cases. Local Nusselt number, mixed mean temperature and temperature profile inside duct at each dimensionless axial location are obtained and compared with exact solutions for the accuracy test Solutions arc in good agreement at the entry region as well as fully developed region of circular duct, and their accuracy are verified from error analysis.

• 한국CDE학회논문집
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• 제17권3호
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• pp.156-163
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• 2012

Real-time three-dimensional shape measurement is becoming increasingly important in various fields, including medical sciences, high-technology industry, and microscale measurements. However, there are not so many 3D profile tools specially designed for specifically narrow space, for example, to scan the tooth shape of a human jaw. In this paper, a real-time 3D intraoral scanner is proposed for the measurement of tooth profile in the mouth cavity. The proposed system comprises a laser diode beam, a micro charge-coupled device, a graticule, a piezoelectric transducer, a set of optical lenses, and a polhemus device sensor. The phase-shifting technique is used along with an accurate calibration method for the measurement of the tooth profile. Experimental and theoretical inspection of the phase-to-coordinate relation is presented. In addition, a nonlinear system model is developed for collimating illumination that gives the more accurate mathematical representation of the system, thus improves the shape measurement accuracy. Experiment results are presented to verify the feasibility and performance of the developed system. The experimental results indicate that overall measurement error accuracy can be controlled within 0.4 mm with a variability of ${\pm}0.01$.

• 대한기계학회논문집A
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• 제26권1호
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• pp.15-22
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• 2002

This paper introduces a compensating system for machining error, which is resulted from chucking with separated jaws. In machining the chucked cylindrical workpiece, the deterioration of machining accuracy, such as out-of-roundness is inevitable due to the variation of the radial compliance of the chuck workpiece system which is caused by the position of jaws with respect to the direction of the applied force. To compensate the chucking compliance induced error, firstly roundness profile of workpiece due to chucking compliance after machining needs to be predicted. Then using this predicted profile, the compensated tool feed trajectory can be generated. And by synchronizing the cutting tool feed system with workpiece rotation, the chucking compliance induced error can be compensated. To satisfy the condition that the cutting tool feed system must provide high speed and high position accuracy, brushless linear DC motor is used. In this study, firstly through the force-deflection experiment in workpiece chucked lathe, the variation of radial compliance of chuck workpiece system is obtained. Secondly using the mathematical equation and cutting experiment result, the predicted profile of workpiece and its compensation tool trajectory are generated. Thirdly the configuration of compensation system using linear motor is introduced, and to improve the system performance, PID controller is designed. Finally the tracking performance of system is examined by experiment. Through the real cutting experiment, roundness is significantly improved.

• Tribology and Lubricants
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• 제39권3호
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• pp.118-122
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• 2023

In our study, we develop a finite element model based on Archard's wear law to predict the cumulative wear and the evolution of the tool profile in friction stir welding (FSW) applications. Our model considers the rotational and translational behaviors of the tool, providing a comprehensive description of the wear process. We validate the accuracy of our model by comparing it against experimental results, examining both the predicted cumulative wear and the resulting changes to the tool profile caused by wear. We perform a detailed comparison between the predictions of the model and experimental data by manipulating non-dimensional coefficients comprising model parameters, such as element sizes and time increments. This comparison facilitates the identification of a specific non-dimensional coefficient condition that best replicates the experimentally observed cumulative wear. We also directly compare the worn tool profiles predicted by the model using this specific non-dimensional coefficient condition with the profiles obtained from wear experiments. Through this process, we identify the model settings that yield a tool wear profile closely aligning with the experimental results. Our research demonstrates that carefully selecting non-dimensional coefficients can significantly enhance the predictive accuracy of finite element models for tool wear in FSW processes. The results from our study hold potential implications for enhancing tool longevity and welding quality in industrial applications.

• 대한기계학회논문집B
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• 제27권10호
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• pp.1450-1456
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• 2003

Three-dimensional pipe flows with elbows, tees and headers in three different pipe systems are calculated to estimate the effect of asymmetry of axial velocity profile and swirl on measuring accuracy of an orifice flowmeter. It is evaluated how the pressure difference across the orifice is dependent on the upstream straight pipe length and how swirl intensity, swirl angle, and axial velocity distribution affect the measuring error of the orifice flowmeter. From the results, it is found that variation of the pressure difference across the orifice is negligible in case that maximum swirl angle is less than 2$^{\circ}$, and also that the pressure difference across the orifice is more sensitive to the asymmetry of axial velocity profile rather than the swirl intensity.

• 한국정밀공학회지
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• 제17권6호
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• pp.83-88
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• 2000

In machining large screws such as those of extruders, it takes long time to machine them on conventional machines which usually use single-tipped fixed tools. And it is also difficult to use an existing CAD/CAM coftware when trying to get over the problems of conventional machines and making use of CNC machines. In this paper, generation of machining program using rotational tools for large screws defined by longitudinal-section profile is descrebed. Use of rotational tools in machining plays an important role in saving machining time. In the sort of extruder screws, it is easy to define a screw shape by longitudinal-section profile, and by which improvement of dimensional accuracy can be expected. The CAM software developed in this paper is based on user's and designer's friendliness.