• Investigative Magnetic Resonance Imaging
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• v.21 no.1
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• pp.28-33
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• 2017

Purpose: To investigate and compensate the effects of respiration-induced B0 variations on fat quantification of the bone marrow in the lumbar spine. Materials and Methods: Multi-echo gradient echo images with navigator echoes were obtained from eight healthy volunteers at 3T clinical scanner. Using navigator echo data, respiration-induced B0 variations were measured and compensated. Fat fraction maps were estimated using $T2^*$-IDEAL algorithm from the uncompensated and compensated images. For manually drawn bone marrow regions, the estimated B0 variations and the calculated fat fractions (before and after compensations) were analyzed. Results: An increase of temporal B0 variations from inferior level to superior levels was observed for all subjects. After compensation using navigator echo data, the effects of the B0 variations were reduced in gradient echo images. The calculated fat fractions show significant differences (P < 0.05) in L1 and L3 between the uncompensated and the compensated. Conclusion: The results of this study raise the need for considering respiration-induced B0 variations for accurate fat quantification using gradient echo images in the lumbar spine. The use of navigator echo data can be an effective way for the reduction of the effects of respiratory motion on the quantification.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.39 no.6
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• pp.575-584
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• 2002

This paper presents a novel DCT-based embedded zero-tree coding and optimal bit allocation algorithm for image sequence coding. In order to fully utilize the structure of the conventional standard coding algorithm and improve the coding efficiency, motion estimation and compensation(ME/MC)-DCT hybrid coding structure and a modified zero-tree coding algorithm are applied. After the rearrangement DCT coefficients into pyramidal structure according to their significance on the decoded image quality, the modified embedded zero-tree coding is performed on layered coefficients. Moreover, for a given overall bit rates, a new optimal bit control scheme is proposed to achieve the best decoded image quality in the consecutive frames. The rate control scheme can also provide the equal quality of decoded image with the control of bit rate and distortion for each frame. The various simulation results are provided to evaluate the coding performance of the proposed scheme.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.2
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• pp.438-446
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• 2013

Generally, a camera isn't located at the center of display in a tele-presence system and it causes an incorrect eye contact between speakers which reduce the realistic feeling during the conversation. To solve this incorrect eye contact problem, we newly propose an intermediate view reconstruction algorithm using both a color camera and a depth camera and applying for the depth image based rendering (DIBR) algorithm. In the proposed algorithm, an efficient hole filling method using the arithmetic mean value of neighbor pixels and an efficient boundary noise removal method by expanding the edge region of depth image are included. We show that the generated eye-contacted image has good quality through experiments.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.8 no.3
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• pp.187-196
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• 2014

This paper suggests linearity enhancement algorithm to Ensure safety of Mobile Walker on Slope. Mobile Walker happens to get off track due to external forces from Walker's weight and the degree of the slope while slope driving. In order to compensate this, this research used the controller that estimates the external forces according to the slope of road surface and adjusts it to the motor output. Also, through comparisons between targeted rotational angular velocity which the user inputs and its velocity of the robot, algorithm was applied which applies a weight to each shaft. As a result of applying the proposed correction controller, it diverges in case of non-compensation experiments that deviates when moving, but it case of applying the ramp calibration algorithm, the deviation distance at max was within 10cm that it keeps safe driving, and change rate of deviation distance was also stabilized after 1m where no more changes occurred.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.3C
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• pp.247-254
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• 2008

H.264 provides a good coding efficiency compared with existing video coding standards, H.263, MPEG-4, based on the use of multiple reference frame for variable block size motion estimation, quarter-pixel motion estimation and compensation, $4{\times}4$ integer DCT, rate-distortion optimization, and etc. However, many modules used to increase its performance also require H.264 to have increased complexity so that fast algorithms are to be implemented as practical approach. In this paper, among many approaches, fast mode decision algorithm by skipping variable block size motion estimation and spatial-predictive coding, which occupies most encoder complexity, is proposed. This approach takes advantages of temporal and spatial properties of fast mode selection techniques. Experimental results demonstrate that the proposed approach can save encoding time up to 65% compared with the H.264 standard while maintaining the visual perspectives.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.2
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• pp.826-840
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• 2020

Vertigo is one of the most common complaints encountered by physicians and the patients are steadily increasing. These patients are exposed to the risk of secondary accidents such as falls due to vertigo. There are two ways to improve this symptom: medication and rehabilitation. Although temporary symptomatic improvement may be expected in patients treated with medication, vertigo may recur and medication can delay central compensation. In contrast vestibular rehabilitation exploits central mechanisms of neuroplasticity to increase postural stability and enhance visual-vestibular interactions in situations that generate conflicting sensory information. However, vestibular rehabilitation may be compromised by incorrect performance of exercises, and there is a need for active effort and interest from the patient during rehabilitation. To solve these problems, we decided to apply FOVE HMD for eye-tracking and Unity3D to create virtual reality. The proposed eye-tracking based algorithm calculates the concentration of users with eye tracking data and calculates the motion width of the patient with nystagmus, thus the severity of the patient according to the score can be determined. According to our experimental test against healty group and patients group, this result showed the meaningful data to use define the contents result.

• The Journal of Korea Robotics Society
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• v.11 no.4
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• pp.285-292
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• 2016

For articulated swimming robots, there have been no researches about controlling the motion or trajectory following. A control method for articulated swimming robot is suggested by extending a previous algorithm, ESPG (Extended Swimming Pattern Generator). The control method focuses on the situation that continuous pre-determined swimming pattern is applied for long range travelling. In previous studies, there has not been a way to control the propulsive force when a swimming pattern created by ESPG was in progress. Hence, no control could be made unless the swimming pattern was completed even though an error occurred while the swimming pattern was in progress. In order to solve this problem, this study analyzes swimming patterns and suggests a method to control the propulsive force even while the swimming pattern was in progress. The angular velocity of each link is influenced and this eventually modifies the propulsive force. However, The angular velocity is changed, a number of problems can occur. In order to resolve this issue, phase compensation method and synchronization method were suggested. A simple controller was designed to confirm whether the suggested methods are able to control and a simulation has affirmed it. Moreover, it was applied to CALEB 10 (a biomimetic underwater articulated robot) and the result was verified.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.5
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• pp.465-470
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• 2010

This paper proposes an adaptive video watermarking algorithm according to bit detection rate of watermark in MPEG2 system. The watermark strength is adaptively applied as BER(bit error rate) of watermark extracted from decoded frame for motion compensation. Watermark insertion uses a frequency spread spectrum method. A realtime watermark extraction is done directly in the DCT domain during MPEG decoding. The experimental simulations show that PSNR(peak signal to noise ratio) results 31.5dB for a fixed watermark strength and 33.dB for an adaptive watermark strength. Also average BER is 0.126 and less than 0.2 avaliable value.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.11a
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• pp.193-198
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• 1999

In the 21th century, everyone feels that the multimedia system is close at hand in real life due to the rapid advance of the computer processing ability and high speed and high guality of communication services. Also the limited frequencies resource will be optimized due to rapid advances in digital video technology which is believed superior to analogue technology in information engineering. MEPG-2 has been introduced for broadcasting use such as digital TV Thus it features the high-definition and hyper-low bit rate. But, because of much throughput it has been implemented by high-priced private ASIC chip and is not in general use yet. But in this research, noticing the rapid enhancement of PC processor performance comparing with the price. MPEG-2 was developed by real time software MPEG-2 had been known impossible to implement with S/W, but the research proved the possibility of the S/W implementation and below are the pictures also in the research was improved 'Motion Vector and Compensation' Algorithm which requires the most operations and UT was made possible real time process. Multimedia Info Society has settled and accompanied by the rapid advance of image-processing technology and lots of standards.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.2
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• pp.185-194
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• 2002

To extract relative ranges from LOS(line of sight) information, we propose a passive ranging filter which is suitable for anti-ship missiles in HOJ(home on jam) mode. The proposed filter is devised to cope with the case that a passive ranging filter may include a large initial range estimation error since modem jammers are capable of very long range jamming. In addition, under the assumption that the missile motion is dominant over the HOJ engagement situation, the engagement geometry is modeled by a second order system. A new passive ranging filter is proposed by constructing an extended Kalman filter(EKF) based on the model. And then a least square initial state error estimation algorithm is attached to the EKF. Simulation results show that the proposed filter has a good range estimation performance with small computational load.