• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.5 no.2
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• pp.56-64
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• 1987

The concept of standard error ellipse and confidence ellipse is vtilized in the detection of displaced station which are uncluded in the observational network. In this paper, the influences on the accuracy of unknown stations according to the varied selection and geometrical conditions of fixed stations were evaluated. And then the displaced stations were detected by error ellipse concept, and the amounts of displacement were determined by coordinate differences between epochs which were calculated by fixed point adjustment and free network adjustment. As a result, it is found that the free network adjustment is more efficient in the detection and displacement calculation of displaced stations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.10
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• pp.3983-4001
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• 2015

Exact average bit error probability (BEP) expressions for mobile-relay-based mobile-to-mobile (M2M) cooperative networks with incremental decode-and-forward (IDF) relaying over N-Nakagami fading channels are derived in this paper. The average BEP performance under different conditions is evaluated numerically to confirm the accuracy of the analysis. Results are presented which show that the fading coefficient, the number of cascaded components, the relative geometrical gain, and the power allocation parameter have a significant influence on the average BEP performance.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.2
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• pp.338-346
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• 1987

This paper describes a method for verifying whether a given geometrical layout correcdtly reflects the original logic level description. The logic description extracted from layout data was directly compadred with the original logic diagram generated at logic level design stage where the logic diagram is represented as a weighted multi-place graph. The comparison is based on graph isomorphism and error messages(error categories and locations)are invoked if any difference is found between the two logic descriptions. An efficient partitioning algorithm which consists of two steps, candidate selection and equal weight partitioning procedure, enables the entire verification process to occur in O(n log n) time.

• Fire Science and Engineering
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• v.27 no.6
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• pp.38-43
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• 2013

As a preliminary study to evaluate the reliability of the calculation method of fire load for residential furniture combustibles, the present study estimates the fire load considering the volume data obtained by the 3D geometrical information of combustibles and material properties based on the literature survey and sample burning test. A kitchen sink cabinet, couch and workstation were investigated for estimating its fire load and real fire test have been performed to measure total energy released from the combustibles. Based on total energy measured from real fire test, the relative error of the estimated fire load due to literature survey and measured material properties showed 6~120% and less than 20%, respectively. It shows that the estimation error of fire load are greatly affected by its material properties as well as geometrical information of combustibles and the present study will be able to contribute to accurate estimation of fire load.

• The Journal of Korean Physical Therapy
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• v.24 no.2
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• pp.66-72
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• 2012

Purpose: The purpose of this study is to explore the importance of the image distortion correction in the cross sectional area measurement for the iliopsas muscle, tensor fasciae latae muscle, gluteus maximus muscle and the knee extensor muscles, by using (magnetic resonance imaging) MRI. Methods: This study was performed using an open 0.32T MRI system. To estimate the image distortion, T1 images for an AAPM homogeneity/linearity phantom were acquired, and the region in which the maximum geometric distortion was less than or equal to the pixel size (1.6 mm) of the images, it was defined as the distortion correction-free region. The T2 images for a human subject's pelvis and thigh in normal positions were obtained. Then, after the regions of interest in the pelvis and thigh were moved into the distortion correction-free region, T2 images for the pelvis and thigh were scanned with the same imaging parameters used in the previous T2 imaging. The cross-sectional areas were measured in the two T2 images that were obtained in the normal position, and the distortion correction-free region, as well as the area error caused by geometric image distortion was calculated. Results: The geometrical distortion is gradually increased, from the magnet center to the outer region, in axial and coronal plane. The cross-sectional area error of gluteus maximus muscle and the knee extensors was as high as 9.27% and 3.16% in before and after distortion correction, respectively. Conclusion: The cross-sectional area of the muscles that suffered from the geometrical distortion is necessary to correct for the estimation of the intervention.

• The Journal of the Acoustical Society of Korea
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• v.27 no.1
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• pp.1-11
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• 2008

To overcome the mid frequency limitation of geometrical acoustic techniques, the phased geometrical method was suggested by introducing the phase information into the sound propagation from the source. By virtue of phase information, the phased tracing method has a definite benefit in taking the interference phenomenon at mid frequencies into account. Still, this analysis technique has suffered from difficulties in dealing with low frequency phenomena, so called, wave nature of sound. At low frequencies, diffraction at corners, edges, and obstacles can cause errors in simulating the transfer function and the impulse response. Due to the use of real valued absorption coefficient, simulated results have shown a discrepancy with measured data. Thus, incorrect phase of the reflection characteristic of a wall should be corrected. In this work, the uniform theory of diffraction was integrated into the phased beam tracing method (PBTM) and the result was compared to the ordinary PBTM. By changing the phase of the reflection coefficient, effects of phase information were investigated. Incorporating such error compensation methods, the acoustic prediction by PBTM can be further extended to low frequency range with improved accuracy in the room acoustic field.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.5 s.170
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• pp.63-71
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• 2005

When an almost flat surface under test is measured by an interferometer, the measurement result is largely influenced by systematic errors that include geometrical errors of a reference flat surface. To determine the systematic errors of the interferometer by the conventional method that is called the three flat method, we must take the reference flat surface out from the interferometer and measure it. Because of difficulties to set the reference flat surface to the interferometer exactly and quickly, this method is not practical. On the other hand, the method that measures a surface under test with some shifts in the direction being perpendicular to the optical axis of the interferometer is studied. However, the parasitic pitching, rolling and up-down movement caused by the above shifts brings serious error to the measurement result, and the algorithm by which the influences can be eliminated is not still established. In this paper, we propose the self-calibration algorithm for determining the systematic errors that include geometrical errors of a reference flat surface by several rotation shifts and a linear shift of general surface under test, and verify by a numerical experiment that this algorithm is useful for determining the systematic errors.

• Smart Structures and Systems
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• v.26 no.6
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• pp.735-751
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• 2020

Identification of structure parameters is crucial in Structural Health Monitoring (SHM) context for activities such as model validation, damage assessment and signal processing of structure response. In this paper, guided waves generated by piezoelectric transducers are used for in-situ and non-destructive structural parameter estimation based on Bayesian approach. As Bayesian approach needs iterative process, which is computationally expensive, this paper proposes a method in which an analytical model is selected and developed in order to decrease computational time and complexity of modeling. An experimental set-up is implemented to estimate three target elastic and geometrical parameters: Young's modulus, Poisson ratio and thickness of aluminum and steel plates. Experimental and simulated data are combined in a Bayesian framework for parameter identification. A significant accuracy is achieved regarding estimation of target parameters with maximum error of 8, 11 and 17 percent respectively. Moreover, the limitation of analytical model concerning boundary reflections is addressed and managed experimentally. Pulse excitation is selected as it can excite the structure in a wide frequency range contrary to conventional tone burst excitation. The results show that the proposed non-destructive method can be used in service for estimation of material and geometrical properties of structure in industrial applications.

• Nuclear Engineering and Technology
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• v.55 no.4
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• pp.1400-1409
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• 2023

In this study, three condensation models of the CUPID code, i.e., the resolved boundary layer approach (RBLA), heat and mass transfer analogy (HMTA) model, and an empirical correlation, were tested and validated against the COPAIN and CAU tests. An improvement on HMTA model was also made to use well-known heat transfer correlations and to take geometrical effect into consideration. The RBLA was a best option for simulating the COPAIN test, having mean relative error (MRE) about 0.072, followed by the modified HMTA model (MRE about 0.18). On the other hand, benchmark against CAU test (under natural convection and occurred on a slender tube) indicated that the modified HMTA model had better accuracy (MRE about 0.149) than the RBLA (MRE about 0.314). The HMTA model with wall function and the empirical correlation underestimated significantly, having MRE about 0.787 and 0.55 respectively. When using the HMTA model, consideration of geometrical effect such as tube curvature was essential; ignoring such effect leads to significant underestimation. The HMTA and the empirical correlation required significantly less computational resources than the RBLA model. Considering that the HMTA model was reasonable accurate, it may be preferable for large-scale simulations of containment.

• Journal of the Korea Convergence Society
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• v.9 no.11
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• pp.277-284
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• 2018

Recently, the demand for precision machining through multi-axis machining has been greatly increased. However, it is difficult to evaluate the geometrical accuracy of the machine tool because of its complicated geometric relationship. In this study, we organized the KS/ISO specifications which are distributed in various regulations, and re-organized the geometrical precision evaluation items of multi-axis machine tools. In addition, a test workpiece was proposed to evaluate and analyze the accuracy of a multi-axis machine tool, and a test workpiece was machined according to predetermined methods and procedures, and then the machined surfaces were measured using CMM. As a result, it was verified that the machining results of the standard workpiece and the precision of the machine tool were very similar qualitatively and quantitatively. From these results, it can be confirmed that the precision analysis of the multi-axis machine tool is possible only by machining the test workpiece.