• Journal of Broadcast Engineering
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• v.24 no.7
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• pp.1246-1258
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• 2019

Since light field (LF) image has huge data volume, it requires high-performance compression technique for efficient transmission and storage of its data. Camera users may like to represent parts of image at different levels of focus at their choice anytime. To address this refocusing functionality, in this paper, we first render a focal stack consisting of multi-focus images, then compress it instead of original LF data. The proposed method has advantage of minimizing the amount of LF data to realize the targeted refocusing applications. Our experiment results show that the proposed method outperforms the state-of-the-art for LF image compression method.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2019.06a
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• pp.216-217
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• 2019

Light Field (LF) image can be understood as a set of images captured by a multi-view camera array at the same time. The changes among views can be modeled by a general motion model such as affine motion model. In this paper, we study the impact of affine coding tool of Versatile Video Coding (VVC) on LF image compression. Our experimental results show a small contribution by affine coding tool in overall LF image compression of roughly 0.2% - 0.4%.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.114.1-114.1
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• 2012

To measure the magnetic field strength in the solar corona, we examined 10 fast (>1000 km/s) limb coronal mass ejections (CMEs) that show clear shock structures in Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph images. By applying the piston-shock relationship to the observed CME's standoff distance and electron density compression ratio, we estimated the Mach number, Alfven speed, and magnetic field strength in the height range 3-15 solar radii (Rs). The main results from this study are as follows: (1) the standoff distance observed in the solar corona is consistent with those from a magnetohydrodynamic model and near-Earth observations; (2) the Mach number as a shock strength is in the range 1.49-3.43 from the standoff distance ratio, but when we use the density compression ratio, the Mach number is in the range 1.47-1.90, implying that the measured density compression ratio is likely to be underestimated owing to observational limits; (3) the Alfven speed ranges from 259 to 982 km/s and the magnetic field strength is in the range 6-105 mG when the standoff distance is used; (4) if we multiply the density compression ratio by a factor of two, the Alfven speeds and the magnetic field strengths are consistent in both methods; and (5) the magnetic field strengths derived from the shock parameters are similar to those of empirical models and previous estimates.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2019.11a
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• pp.228-229
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• 2019

Digital refocusing and perspective change are the most expected applications of light field (LF) images. As LF image has a large amount of data, its compression is very essential. The fidelity of LF image after compression needs to be evaluated differently depending on a specific application such as perspective change or refocusing. In this paper, we investigate the fidelity of images after perspective change and refocusing. Several state-of-the-art objective quality metrics are compared. Our experiment shows that IWPSNR is the most reliable metric for both perspective and focus changes, but it does not outperform the popular metrics such as PSNR and SSIM.

• Magazine of the Korean Society of Agricultural Engineers
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• v.15 no.2
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• pp.2968-2979
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• 1973

The aim of this study was to bring light on the effect of permeability to yield weight of paddy rice on the compressed soil. a) The percolation volume during the growth of paddy rice reduced, while the degree of compression on soil column increased and varied by the evaporation and absorption volumn. b) The percolation volume in the natural soil column was notably low compared with that of in the artificial and had little influence to the variation of permeabilty by compression. c) The results in growth of paddy rice were best on the section of low compression and the yield weight reduced, while the degree of compression on the soil column increased. d) The relationship between the yield weight and percolation volumn, under the condition when percolation volume is 1mm/day, had little difference in the yield weight but immediately reduced under $0.5{\sim}1.0mm/day$. The consequences of investigation are not so perfect, but have done my best to get some new data for effect on additional yield by inquiring into influences of permeability to the yield weight of paddy rice on compressed paddy field. I will have a great pleasure if treatise helps investigaters or the men of affairs in this field.

• Electronics and Telecommunications Trends
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• v.34 no.6
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• pp.145-155
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• 2019

Holography is a technique that can acquire and reproduce 3D objects nearly perfectly by representing both the amplitude and phase of light. Recently, digital holography has received considerable attention because it is simpler than analog holography from acquisition to reproduction. The data size of the digital hologram increases tremendously as the quality of digital holograms depends on their pixel pitch and resolution. Hence, efficient compression is necessary to realize holographic imaging services. In this report, we introduce recent digital hologram compression techniques and JPEG Pleno holography, which is the first international standardization activity for digital hologram compression. Furthermore, we discuss the future of this field.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2019.06a
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• pp.222-224
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• 2019

Light Field (LF) camera captures not only the light intensity but also the light direction coming to camera. While the rich information captured by LF camera enables many interesting applications such as digital refocusing, viewpoint changing, and 3D reconstruction, but it also requires powerful coding tools to reduce its large volume of data. In this paper, we investigate using the intra prediction scheme of the versatile video coding (VVC), which is the most recent video coding technology currently under developing, to compress the LF image. The Intra Block Copy (IBC) technique in VVC is exploited considering special LF image structure. The experimental result shows that VVC intra predict ion outperforms the H.265/HEVC intra coding technique in encoding LF data irrespective of using the IBC mode or not.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.11a
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• pp.49-52
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• 2020

MPEG-I(Immersive) 그룹에서는 몰입형 미디어 영상처리 표준화의 일환으로 마이크로렌즈를 통한 다시점 영상 처리 기술인 Dense Light Field에 대한 성능 탐색을 진행하고 있다. 본 논문에서는 MPEG-I에서 정의된 라이트 필드 시퀀스에 대해 versatile video codec(VVC)에 대한 압축 성능 분석을 시행하였으며, 또한 렌즈렛(Lenslet) 형태의 특정적인 이미지 정보를 효율적으로 압축하기 위한 스크린 콘텐츠 코딩 툴의 효율 비교를 진행하였다. 또한 렌즈렛 영상에서의 화면 내 블록 카피(intra block copy) 기법이 선택되는 비율을 확인하고, 화면 내 블록 카피 기법을 통해 렌즈렛 영상이 효율적으로 압축될 수 있음을 보였다.

• Journal of Electrical Engineering and information Science
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• v.2 no.6
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• pp.106-110
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• 1997

The binding energies of the ground state of both the heavy-hole and light-hole excitons in a GaAs(In\ulcornerGa\ulcornerAs) quantum well sandwiched between two semi-infinite Al\ulcornerGa\ulcornerAs(InP) layers are calculated as a function of well width in the presence of an arbitray magnetic field. A variational approach is followed using very simple trial wave function. The applied magnetic field is assumed to be parallel to the axis of growth and the binding energies are calculated for a finite value of the height of the potential barrier. The exciton binding energies for a given value of the magnetic field are found to be increased than their values in a zero magnetic field due to the compression of their wave functions within the well with the applied magnetic field.

• Journal of the Korean Wood Science and Technology
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• v.33 no.1 s.129
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• pp.38-47
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• 2005

Compression, lateral, and opposite woods in a branch of Pinus parviflora S. et Z. were described and compared in the qualitative anatomical aspects through light and scanning electron microscopy. Tracheid transition from earlywood to latewood in the compression wood appeared to be relatively more gradual than in the opposite or lateral wood. Growth ring width and proportion of latewood were thought to be greater in the compression wood than in the lateral or opposite wood. The latewood tracheids of compression wood in transverse surface were mostly round, differently from those of lateral and opposite woods with square to angular shapes. Also, intercellular spaces, helical cavities and checks, and slit-like pit apertures were observed only in the compression wood tracheids. Cross-field pitting in the compression wood appeared not to be used as diagnostic guide because of their severe alteration from normal fenestriform or window-like type to cupressoid to taxodioid types. In tangential surface, fusiform rays in the compression wood were wider but lower than those in the lateral wood or opposite wood. In conclusion, compression wood was different from lateral and opposite woods but lateral and opposite woods were almost identical in qualitative anatomical features.