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Fast Randomized Singular Value Thresholding for Low-Rank Optimization
Oh, Tae-Hyun,Matsushita, Yasuyuki,Tai, Yu-Wing,Kweon, In So IEEE 2018 IEEE transactions on pattern analysis and machine Vol.40 No.2
<P>Rank minimization can be converted into tractable surrogate problems, such as Nuclear Norm Minimization (NNM) and Weighted NNM (WNNM). The problems related to NNM, or WNNM, can be solved iteratively by applying a closed-form proximal operator, called Singular Value Thresholding (SVT), or Weighted SVT, but they suffer from high computational cost of Singular Value Decomposition (SVD) at each iteration. We propose a fast and accurate approximation method for SVT, that we call fast randomized SVT (FRSVT), with which we avoid direct computation of SVD. The key idea is to extract an approximate basis for the range of the matrix from its compressed matrix. Given the basis, we compute partial singular values of the original matrix from the small factored matrix. In addition, by developping a range propagation method, our method further speeds up the extraction of approximate basis at each iteration. Our theoretical analysis shows the relationship between the approximation bound of SVD and its effect to NNM via SVT. Along with the analysis, our empirical results quantitatively and qualitatively show that our approximation rarely harms the convergence of the host algorithms. We assess the efficiency and accuracy of the proposed method on various computer vision problems, e.g., subspace clustering, weather artifact removal, and simultaneous multi-image alignment and rectification.</P>
조성현(Sunghyun Cho),Yasuyuki Matsushita,이승용(Seungyong Lee) 한국정보과학회 2008 한국정보과학회 학술발표논문집 Vol.35 No.1
본 논문에서는 영상의 중요한 정보를 유지하는 동시에 영상의 왜곡을 막으며, 영상의 크기를 줄이는 방법을 제시한다. 영상의 각 픽셀의 중요도를 측정 후, 가장 중요하지 않은 픽셀들을 제거하는데, 이 때 단순히 중요하지 않은 픽셀들을 제거하면, 이로 인해 영상의 왜곡이 생길 뿐 아니라 중요하지 않은 픽셀들이 가지고 있던 정황에 대한 정보도 잃게 된다. 이를 막기 위해 제시된 방법은 중요하지 않은 픽셀들을 제거한 후에, 그 픽셀들의 중요도를 주변으로 확산시키는 방법을 이용하여 영상의 왜곡을 막고, 영상의 정황을 보다 효과적으로 전달하며 영상 리타겟팅을 수행한다. 실험 결과는 제시된 방법의 효율성을 보여준다.
Robust Multiview Photometric Stereo Using Planar Mesh Parameterization
Jaesik Park,Sinha, Sudipta N.,Matsushita, Yasuyuki,Yu-Wing Tai,In So Kweon IEEE 2017 IEEE transactions on pattern analysis and machine Vol.39 No.8
<P>We propose a robust uncalibrated multiview photometric stereo method for high quality 3D shape reconstruction. In our method, a coarse initial 3D mesh obtained using a multiview stereo method is projected onto a 2D planar domain using a planar mesh parameterization technique. We describe methods for surface normal estimation that work in the parameterized 2D space that jointly incorporates all geometric and photometric cues from multiple viewpoints. Using an estimated surface normal map, a refined 3D mesh is then recovered by computing an optimal displacement map in the same 2D planar domain. Our method avoids the need of merging view-dependent surface normal maps that is often required in conventional methods. We conduct evaluation on various real-world objects containing surfaces with specular reflections, multiple albedos, and complex topologies in both controlled and uncontrolled settings and demonstrate that accurate 3D meshes with fine geometric details can be recovered by our method.</P>
Nakagawa, Takayuki,Kudoh, Keiko,Fukuda, Naoyuki,Kasugai, Shohei,Tachikawa, Noriko,Koyano, Kiyoshi,Matsushita, Yasuyuki,Sasaki, Masanori,Ishikawa, Kunio,Miyamoto, Youji Korean Academy of Periodontology 2019 Journal of Periodontal & Implant Science Vol.49 No.6
Purpose: The purpose of this study was to elucidate the efficacy and safety of carbonate apatite (CO<sub>3</sub>Ap) granules in 2-stage sinus floor augmentation through the radiographic and histomorphometric assessment of bone biopsy specimens. Methods: Two-stage sinus floor augmentation was performed on 13 patients with a total of 17 implants. Radiographic assessment using panoramic radiographs was performed immediately after augmentation and was also performed 2 additional times, at 7±2 months and 18±2 months post-augmentation, respectively. Bone biopsy specimens taken from planned implant placement sites underwent micro-computed tomography, after which histological sections were prepared. Results: Postoperative healing of the sinus floor augmentation was uneventful in all cases. The mean preoperative residual bone height was 3.5±1.3 mm, and this was increased to 13.3±1.7 mm by augmentation with the CO<sub>3</sub>Ap granules. The mean height of the augmented site had decreased to 10.7±1.9 mm by 7±2 months after augmentation; however, implants with lengths in the range of 6.5 to 11.5 mm could still be placed. The mean height of the augmented site had decreased to 9.6±1.4 mm by 18±2 months post-augmentation. No implant failure or complications were observed. Few inflammatory cells or foreign body giant cells were observed in the bone biopsy specimens. Although there were individual differences in the amount of new bone detected, new bone was observed to be in direct contact with the CO<sub>3</sub>Ap granules in all cases, without an intermediate layer of fibrous tissue. The amounts of bone and residual CO<sub>3</sub>Ap were 33.8%±15.1% and 15.3%±11.9%, respectively. Conclusions: In this first demonstration, low-crystalline CO<sub>3</sub>Ap granules showed excellent biocompatibility, and bone biopsy showed them to be replaced with bone in humans. CO<sub>3</sub>Ap granules are a useful and safe bone substitute for two-stage sinus floor augmentation.
Takayuki Nakagawa,Keiko Kudoh,Naoyuki Fukuda,Shohei Kasugai,Noriko Tachikawa,Kiyoshi Koyano,Yasuyuki Matsushita,Masanori Sasaki,Kunio Ishikawa,Youji Miyamoto 대한치주과학회 2019 Journal of Periodontal & Implant Science Vol.49 No.6
Purpose: The purpose of this study was to elucidate the efficacy and safety of carbonate apatite (CO3Ap) granules in 2-stage sinus floor augmentation through the radiographic and histomorphometric assessment of bone biopsy specimens. Methods: Two-stage sinus floor augmentation was performed on 13 patients with a total of 17 implants. Radiographic assessment using panoramic radiographs was performed immediately after augmentation and was also performed 2 additional times, at 7±2 months and 18±2 months post-augmentation, respectively. Bone biopsy specimens taken from planned implant placement sites underwent micro-computed tomography, after which histological sections were prepared. Results: Postoperative healing of the sinus floor augmentation was uneventful in all cases. The mean preoperative residual bone height was 3.5±1.3 mm, and this was increased to 13.3±1.7 mm by augmentation with the CO3Ap granules. The mean height of the augmented site had decreased to 10.7±1.9 mm by 7±2 months after augmentation; however, implants with lengths in the range of 6.5 to 11.5 mm could still be placed. The mean height of the augmented site had decreased to 9.6±1.4 mm by 18±2 months post-augmentation. No implant failure or complications were observed. Few inflammatory cells or foreign body giant cells were observed in the bone biopsy specimens. Although there were individual differences in the amount of new bone detected, new bone was observed to be in direct contact with the CO3Ap granules in all cases, without an intermediate layer of fibrous tissue. The amounts of bone and residual CO3Ap were 33.8%±15.1% and 15.3%±11.9%, respectively. Conclusions: In this first demonstration, low-crystalline CO3Ap granules showed excellent biocompatibility, and bone biopsy showed them to be replaced with bone in humans. CO3Ap granules are a useful and safe bone substitute for two-stage sinus floor augmentation.