As data security has become one of the most crucial issues in modern storage system/application designs, the data sanitization techniques are regarded as the promising solution on 3D NAND flash-memory-based devices. Many excellent works had been proposed to exploit the in-place reprogramming, erasure and encryption techniques to achieve and implement the sanitization functionalities. However, existing sanitization approaches could lead to performance, disturbance overheads or even deciphered issues. Different from existing works, this work aims at exploring an instantaneous data sanitization scheme by taking advantage of programming disturbance properties. Our proposed design can not only achieve the instantaneous data sanitization by exploiting programming disturbance and error correction code properly, but also enhance the performance with the recycling programming design. The feasibility and capability of our proposed design are evaluated by a series of experiments on 3D NAND flash memory chips, for which we have very encouraging results. The experiment results show that the proposed design could achieve the instantaneous data sanitization with low overhead; besides, it improves the average response time and reduces the number of block erase count by up to 86.8% and 88.8%, respectively.

As data security has become the major concern in modern storage systems with low-cost multi-level-cell (MLC) flash memories, it is not trivial to realize data sanitization in such a system. Even though some existing works employ the encryption or the built-in erase to achieve this requirement, they still suffer the risk of being deciphered or the issue of performance degradation. In contrast to the existing work, a fast sanitization scheme is proposed to provide the highest degree of security for data sanitization; that is, every old version of data could be immediately sanitized with zero live-data-copy overhead once the new version of data is created/written. In particular, this scheme further considers the reliability issue of MLC flash memories; the proposed scheme includes a one-shot sanitization design to minimize the disturbance during data sanitization. The feasibility and the capability of the proposed scheme were evaluated through extensive experiments based on real flash chips. The results demonstrate that this scheme can achieve the data sanitization with zero live-data-copy, where performance overhead is less than 1%.

Due to the increasing security concerns, the conventional deletion operations in NAND flash memory can no longer afford the requirement of secure deletion. Although existing works exploit secure deletion and scrubbing operations to achieve the security requirement, they also result in performance and disturbance problems. The predicament becomes more severe as the growing of page numbers caused by the aggressive use of 3-D NAND flash-memory chips which stack flash cells into multiple layers in a chip. Different from existing works, this paper aims at exploring a scrubbing-aware secure deletion design so as to improve the efficiency of secure deletion by exploiting properties of disturbance. The proposed design could minimize secure deletion/scrubbing overheads by organizing sensitive data to create the scrubbing-friendly patterns, and further choose a proper operation by the proposed evaluation equations for each secure deletion command. The capability of our proposed design is evaluated by a series of experiments, for which we have very encouraging results. In a 128 Gbits 3-D NAND flash-memory device, the simulation results show that the proposed design could achieve 82% average response time reduction of each secure deletion command.

Abstract In computer graphics, mesh decomposition is a fundamental problem and it can benefit many applications. In this paper, we propose a novel mesh decomposition algorithm using motion information derived from a given animation sequence. The proposed algorithm first use principal component analysis (PCA) to construct a compact representation of a given animation sequence. Next, from this representation, we derive several motion parameters including motion complexity and similarity. Finally, we decompose a given mesh into sub‐meshes using derived motion information and subdivide the triangles along the cutting paths for the smoother borders between the mesh parts. Our experimental results show that this new decomposition scheme can bring the benefit of good compression ratios on animation sequences. Copyright © 2005 John Wiley & Sons, Ltd.

In this paper, we propose a novel vector field, called a camera-sampling field, to represent the sampling density distribution of a pinhole camera. We give the derivation and discuss some essential properties of the camera-sampling field, including flux, divergence, curl, gradient, level surface, and sampling patterns. This vector field reveals camera-sampling concisely and facilitates camera sampling analysis. The usage for this vector field in several computer graphics applications is introduced, such as determining the splat kernel for image-based rendering, texture filtering, mipmap level selection, level transition criteria for LOD, and LDI-construction.

We describe a low-cost three-dimensional (3-D) virtual colonoscopy system that is a noninvasive technique for examining the entire colon and can assist physicians in detecting polyps inside the colon. Using the helical CT data and proposed techniques, we can three-dimensionally reconstruct and visualize the inner surface of the colon. We generate high resolution of video views of the colon interior structures as if the viewer's eyes were inside the colon. The physicians can virtually navigate inside the colon in two different modes: interactive and automatic navigation, respectively. For automatic navigation, the flythrough path is determined a priori using the 3-D thinning and two-pass tracking schemes. The whole colon is spatially subdivided into several cells, and only potentially visible cells are taken into account during rendering. To further improve rendering efficiency, potentially visible cells are rendered at different levels of detail. Additionally, a chain of bounding volume in each cell is used to avoid penetrating through the colon during navigation. In comparison with previous work, the proposed system can efficiently accomplish required preprocessing tasks and afford adequate rendering speeds on a low-cost PC system.