• Structural Engineering and Mechanics
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• v.29 no.6
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• pp.643-658
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• 2008

In this paper, we present a quadratic element model based on non-conforming displacement modes and modified shape functions. This new and refined 8-node hybrid stress plane element consists of two additional non-conforming modes that are added to the translational degree of freedom to improve the behavior of a membrane component. Further, the modification of the shape functions through quadratic polynomials in x-y coordinates enables retaining reasonable accuracy even when the element becomes considerably distorted. To establish its accuracy and efficiency, the element is compared with existing elements and - over a wide range of mesh distortions - it is demonstrated to be exceptionally accurate in predicting displacements and stresses.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.110-112
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• 2007

Output voltage waves of a DC/AC inverter system are likely to be distorted if variable loads e.g. motors or rectifiers exist in the output terminal. This paper designs a disturbance observer-based PI controller for a single-phase inverter system that is robust against load changes. In this paper, we regard the output voltage changes due to various loads as disturbances of the control system, Then we design a disturbance observer for estimation of the disturbances caused by the load current and any other error sources (such as parameter uncertainties and model mismatches etc.). In order to test the performance of the proposed control law, simulation studies are carried out for a single-phase inverter system using SimPowerSystems of Matlab Simulink. Compared to a simple PI control, the disturbance observer-based controller shows enhanced performance in transient responses for step load changes.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.596-600
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• 2011

In this numerical analysis, the distortion of flow measurement by inlet velocity profile of orifice flowmeter was investigated. To validate the numerical method, the convergence was monitored and the grid dependency was also checked. realizable k-e model was selected and y+ was about 50 in this calculation. the results shows that the pressure at the pressure tab near pipe wall was changed by inclined inlet velocity profile and it leads to distorted a measurement values of flow through the orifice plate from -3.8% to 9%. Therefore, the fully developed inlet flow was required for accurate flow measurement by orifice flowmeter. If not, the orifice plate installed at wrong location should be re-installed or additional actions should be taken.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.84-89
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• 2001

Ultrasonic pulse echo method comes to be difficult to apply to the multi-layered structure with very thin layer, because the echoes from the top and the bottom of the layer are overlapped. Conventionally method, deconvolution technique has been used for the decomposition of overlapped UT signals, however it has disabilities when the waveform of the transmitted signal is distorted according to the propagation. In this paper, the wavelet transform based deconvolution (WTBD) technique is proposed as a new signal processing method that can decompose the overlapped echo signals in A-Scan signal with superior performances compared to the conventional deconvolution technique. Performances of the proposed method are shown by through computer simulations using model signal with noise and are demonstrated by through experiments for the fabricated acryl rod with a thin steel plate bonded to it.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1998.06b
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• pp.16.2-21
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• 1998

Old movies are often corrupted by randomly located blotches and scratches. In this paper were present an efficient method for detection and removal of these distortions. The presented method is composed of two separate steps: the detection process and the restoration process. In the detection process, blotch locations are detected through global motion segmentation, the sequential approach to motion segmentation, a robust model-fit criterion and so on, we form the algorithm for the algorithm for the global motion segmentation tuned to the blotch detection problem. In the restoration process, the missing data of the detected blotch areas are temporally extrapolated from the corresponding image areas at the preceding or the succeeding image frame with considering the global motion segmentation results. We apply the presented method to moving image sequences distorted by artificial blotches. The method works very well and provides a subjective improvement of picture quality.

• Special Issue of the Society of Naval Architects of Korea
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• 2011.09a
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• pp.106-111
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• 2011

The use of thin plate increases due to the need for light weight in large ship. Thin plate is easily distorted and has residual stress by welding heat. Therefore, the thin plates should be carefully joined to minimize the welding deformation. In this study, the welding deformation of PCTC which use a thin plate is investigated by using equivalent load method. The analysis model of 10, 11, 12, upper and garage deck is composed of thin plate of 6mm which is susceptible to welding heat. For two different welding sequences, the welding deformation is calculated and its trend is investigated. The influence of gravity on welding deformation is studied.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.226-227
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• 2019

The basic type construction cost which is the base of the building cost estimation is being adjusted according to the price changes by utilizing the apartment construction cost index in order to flexibly operate it. In this study, we analyzed the change trends and characteristics of the housing cost index for the basic type building cost model project operated from September, 2012 to March, 2018. As a result, the increase in material costs is slight while the share of the labor cost increased in the construction cost due to the rise of labor unit price, leading to a perceived increase in sensitivity of labor costs. We should be careful to keep the sensitivity of the material cost and the labor cost to an appropriate level so that the index may not be distorted.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.8
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• pp.1412-1417
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• 2007

Magnetic anomaly generated around a ship is mainly due to the permanent magnetization(PM) and induced magnetization (IM) remaining on the hull. It is very difficult to predict the direction and its magnitude of the permanent magnetization distributed over the hull, that is caused by mechanical or thermal stress. In this paper, an effective method is proposed to separate two components, the one produced by PM and the other by IM, from the underwater earth field signal distorted by the ferromagnetic material of the ship. The method can easily provide the two kinds of magnetic anomaly through exploiting experimental results and 3D electromagnetic field analyses even though the PM distribution on the hull is not known. To validate the proposed method, a model ship is manufactured and tested. The results would be of much help to basis research for securing safe navigation of a ship against dangerous factors in underwater.

• Journal of Korea Multimedia Society
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• v.18 no.1
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• pp.9-16
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• 2015

Various approaches to process active sonar signals are under study, but there are many problems to be considered. The sonar signals are distorted by the underwater environment, and the spatio-temporal and spectral characteristics of active sonar signals change in accordance with the aspect of the target even though they come from the same one. And it has difficulties in collecting actual underwater data. In this paper, we synthesized active target echoes based on ray tracing algorithm using target model having 3-dimensional highlight distribution. Then, Fractional Fourier transform was applied to synthesized target echoes to extract feature vector. Recognition experiment was performed using probabilistic neural network classifier.

• New Physics: Sae Mulli
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• v.68 no.11
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• pp.1275-1280
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• 2018

We demonstrated transmission direct phase-measuring deflectometry (DPMD) with a specular phase object having discontinuous surfaces by using two displays and a two-dimensional array detector for display and by recording the distorted fringe patterns. Three-dimensional (3D) information was obtained by calculating the height map directly from the phase information. We developed a mathematical model of the phase-height relationship in transmission DPMD. Unlike normal transmission deflectometry, this method supports height measurement directly from the phase. Compared with other 3D measurement techniques such as interferometry, this method has the advantages of being inexpensive and easy to implement.