• The KIPS Transactions:PartB
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• v.11B no.6
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• pp.661-666
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• 2004

In the wireless communication systems, transmission errors degrade the reconstructed image quality severely. Error concealment in video communication is becoming increasingly important because transmission errors can cause single or multiple loss of macroblocks in video delivery over unreliable channels such as wireless networks and internet. Among various techniques which can reduce the degradation of video quality, the error concealment techniques yield good performance without overheads and the modification of the encoder. In this paper, lost image blocks can be concealed with the OBMC(Overlapped Block Motion Compensation) after new motion vectors of the lost image blocks are allocated by median values using the adaptive selection with motion vectors of adjacent blocks. We know our algorithm is more effective in case of continuous GOB loss. The results show a significant improvement over the zero motion error concealment and other temporal concealment methods such as Motion Vector Rational Interpolation or Median＋OBMC by 3dB gain in PSNR.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.12 s.115
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• pp.1249-1258
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• 2006

Two-dimensional(2-D) radar images, namely, ISAR images from a maneuvering target include unwanted phase errors due to the target's motion. These phase errors make ISAR images to be blurred. The ISAR autofocus technique is required in order to remove these unwanted phase errors. Unless those unwanted phase errors produced by the target's motion are removed prior to target identification, we cannot expect a reliable target identification performance. In this paper, we use the entropy-based ISAR autofocus technique which consists of two steps: range alignment and phase adjustment. We analyze a relationship between the number of sampling point and a image quality in a range alignment algorithm and also analyze a technique for reducing computation time of the SSA(Stage-by-Stage Approachng) algorithm in a phase adjustment.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.2
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• pp.366-385
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• 2013

In this paper, we propose a compressed sensing (CS) based Wyner-Ziv (WZ) codec using motion-aligned auto regressive model (MAAR) based side information (SI) extrapolation to improve the compression performance of low-delay distributed video coding (DVC). In the CS based WZ codec, the WZ frame is divided into small blocks and CS measurements of each block are acquired at the encoder, and a specific CS reconstruction algorithm is proposed to correct errors in the SI using CS measurements at the decoder. In order to generate high quality SI, a MAAR model is introduced to improve the inaccurate motion field in auto regressive (AR) model, and the Tikhonov regularization on MAAR coefficients and overlapped block based interpolation are performed to reduce block effects and errors from over-fitting. Simulation experiments show that our proposed CS based WZ codec associated with MAAR based SI generation achieves better results compared to other SI extrapolation methods.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1438-1441
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• 2005

To establish of standard technique of nano-length measurement in 2D plane, new AFM system has been designed. In this system, measurement uncertainty is dominantly affected by the Abbe error of XY scanning stage. No linear stage is perfectly straight; in other words, every scanning stage is subject to tilting, pitch and yaw motion. In this paper, an AFM system with minimum offset of XY sensing is designed. And XY scanning stage is designed to minimize rotation angle because Abbe errors occur through the multiply of offset and rotation angle. To minimize the rotation angle optimal design has performed by maximizing the stiffness ratio of motion direction to the parasitic motion direction of each stage. This paper describes the design scheme of full AFM system, especially about XY stage. Full range of fabricated XY scanner is $100um\times{100um}$. And tilting, pitch and yaw motion are measured by autocollimator to evaluate the performance of XY stage. Using this AFM system, 3um pitch specimen was measured. As a result, the uncertainty of total system has been evaluated.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.3
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• pp.285-291
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• 2011

The error motion of a machine tool spindle directly affects the surface errors of machined parts. The error motions of the spindle are not desired errors in the three linear direction motions and two rotating motions. Those are usually due to the imperfect of bearings, stiffness of spindle, assembly errors, external force or unbalance of rotors. The error motions of the spindle have been needed to be decreased to desired goal of spindle's performance. The level of error motion is needed to be estimated during the design and assembly process of the spindle. In this paper, the estimation method for the five degree of freedom (5 D.O.F) error motions of the spindle is suggested. To estimate the error motions of the spindle, waviness of shaft and bearings, external force model was used as input data. And, the estimation models are considering geometric relationship and force equilibrium of the five degree of the freedom. To calculate error motions of the spindle, not only imperfection of the shaft, bearings, such as rolling element bearing, hydrostatic bearing, and aerostatic bearing, but also driving elements such as worm, pulley, and direct driving motor systems, were considered.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.6
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• pp.1-7
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• 2001

It is very important to test circular motion accuracy of NC machine tools as it affects all other machines machined by them in industries. In this paper, it has become possible to detect errors of linear displacement of radial directions for circle tar motion accuracy test using newly assembled magnetic type of linear scale so called Magnescale ball-bar system. It has also organized computer program systems using tick pulses come out from computer for getting error motion data at colt start time interval in circular motion test on NC lathe. Error data gotten from test is expressed to plots and analysed to numerics by various statistical treatments.

• Journal of Broadcast Engineering
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• v.12 no.6
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• pp.555-564
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• 2007

Discrete cosine transform (DCT) coefficient dropping is well recognized as an efficient rate adaptation transcoding in motion-compensated (MC)-DCT based MPEG-compressed videos. However, in this scheme, the errors incurred by the DCT coefficient-dropping are propagated and often result in significant visual quality degradation. This paper presents two propositions describing well the statistical properties of propagated errors. That is, we propose that the DCT error of the current frame is not correlated to the propagated errors of the previous frames. We also propose that the overall distortions in a given frame can be approximated as the sum of the DCT error of the current frame and the propagated errors from the previous frames. Then, it is shown that several computer simulations with different video sequences verify the effectiveness of the proposed statistical analyses.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.10B
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• pp.1803-1812
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• 2000

A new motion compensation method for ISAR is presented in this paper. It employs amplitude limiting and integration of consecutive range profiles to improve the range and phase alignment accuracy and to alter the propagation properties of compensation errors. These allow the image quality to be significantly improved. It is shown from the imaging results that the new motion compensation algorithm can get images of targets in field situations with much better quality than the traditional cross-correlation algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.9B
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• pp.1604-1608
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• 2000

The three-step search (TSS) algorithm for block motion estimation has been widely used in real-time video coding due to the simplicity of the algorithm significant reduction of computationl cost and good performance. In this paper an improved three-step search (ITS) algorithm is proposed to improve the performance of the TSS algorithm. Simulation results show that in terms of motion compensation errors the proposed ITSS outperforms some popular fast search algorithms while it has the lower computational complexity.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.681-684
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• 2008

Motion interpolation is adopted and has been spread widely into market since it is effective in reducing motion blur, which is considered as weak characteristic due to slow response time of liquid crystal and hold-type display. 120Hz driving using interpolated frames achieves better moving picture quality with less motion blur and less motion judder. However, errors in the interpolated frames can cause visual artifacts such as static text breakup, halos, and occlusions. This paper focuses on categorizing characteristics of visual artifacts and on reducing side-effects by using information from original frames in special cases.