• Journal of KIISE:Computing Practices and Letters
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• v.9 no.2
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• pp.182-190
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• 2003

For temporal relations of interactive media such as MPEG-4, it is necessary for a temporal model that can update dynamically presentation time and temporal relations among objects by user events occurring during playback. Also, 811hough the temporal attributes are changed by user events, the validity of scene must be maintained. In this paper, we propose a temporal model that supports user interaction and developed an MPES-4 contents authoring system applying this model. We define the temporal relations of MPEG-4 that tan be authored and user interactions that can change the temporal properties. This authoring system defines the constraints on temporal relations and events and can generate the scene without error by checking the constraints. Also it provides the authoring environment to author visual]y temporal relations and events in MPEG-4 scene and generates the MPEG-4 stream by encoding the authored scene.

• Journal of Korea Multimedia Society
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• v.15 no.1
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• pp.1-8
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• 2012

In this paper, we propose the digital video frame obfuscation method for intellectual property protection using the DC component of the intra frame and the motion vector of the inter frame at digital video encoding. The proposed method considers characteristics of the HVS (human visual system) which is sensitive at the low frequency and the middle frequency. This method makes the signal distorted as operating XOR between authentication signal and the DC coefficient of the intra frame including main information and the sign of the motion vector including edge motion, so that the video is normally displayed only when suitable authentication signal is applied.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.49 no.1
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• pp.29-38
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• 2012

Due to the rapid development of network environment and wireless communication technology, the distribution of digital video has made easily and the importance of the protection for digital video has been increased. This paper proposes the digital video encryption system based on multiple chaos maps for MPEG-2 video encoding process. The proposed method generates secret hash key of having 128-bit characteristics from hash chain using Tent map as a basic block and generates $8{\times}8$ lattice cipher by applying this hash key to Logistic map and Henon map. The method can reduce the encryption overhead by doing selective XOR operations between $8{\times}8$ lattice cipher and some coefficient of low frequency in DCT block and it provides simple and randomness characteristic because it uses the architecture of combining chaos maps. Experimental results show that PSNR of the proposed method is less than or equal to 12 dB with respect to encrypted video, the time change ratio, compression ratio of the proposed method are 2%, 0.4%, respectively so that it provides good performance in visual security and can be applied in real time.

• Progress in Medical Physics
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• v.21 no.2
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• pp.209-217
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• 2010

Retinal prostheses are being developed to restore vision for the blind with retinal diseases such as retinitis pigmentosa (RP) or age-related macular degeneration (AMD). Since retinal prostheses depend upon electrical stimulation to control neural activity, optimal stimulation parameters for successful encoding of visual information are one of the most important requirements to enable visual perception. Therefore, in this paper, we focused on retinal ganglion cell (RGC) responses to different voltage stimulation parameters and compared threshold charge densities in normal and rd1 mice. For this purpose, we used in vitro preparation for the retina of normal and rd1 mice on micro-electrode arrays. When the neural network of rd1 mouse retinas is stimulated with voltage-controlled pulses, RGCs in degenerated retina also respond to voltage amplitude or voltage duration modulation as well in wild-type RGCs. But the temporal pattern of RGCs response is very different; in wild-type RGCs, single peak within 100 ms appears while in RGCs in degenerated retina multiple peaks (~4 peaks) with ~10 Hz rhythm within 400 ms appear. The thresholds for electrical activation of RGCs are overall more elevated in rd1 mouse retinas compared to wild-type mouse retinas: The thresholds for activation of RGCs in rd1 mouse retinas were on average two times higher ($70.50{\sim}99.87\;{\mu}C/cm^2$ vs. $37.23{\sim}61.65\;{\mu}C/cm^2$) in the experiment of voltage amplitude modulation and five times higher ($120.5{\sim}170.6\;{\mu}C/cm^2$ vs. $22.69{\sim}37.57\;{\mu}C/cm^2$) in the experiment of voltage duration modulation than those in wild-type mouse retinas. This is compatible with the findings from human studies that the currents required for evoking visual percepts in RP patients is much higher than those needed in healthy individuals. These results will be used as a guideline for optimal stimulation parameters for upcoming Korean-type retinal prosthesis.