|
Depth-aided inpainting for disocclusion restoration of multi-view images using depth-image-based rendering
Kai LUO, Dong-xiao LI, Ya-mei FENG, Ming ZHANG
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(12): 1738-1749.
https://doi.org/10.1631/jzus.A0820806
A new algorithm is proposed for restoring disocclusion regions in depth-image-based rendering (DIBR) warped images. Current solutions include layered depth image (LDI), pre-filtering methods, and post-processing methods. The LDI is complicated, and pre-filtering of depth images causes noticeable geometrical distortions in cases of large baseline warping. This paper presents a depth-aided inpainting method which inherits merits from Criminisi’s inpainting algorithm. The proposed method features incorporation of a depth cue into texture estimation. The algorithm efficiently handles depth ambiguity by penalizing larger Lagrange multipliers of filling points closer to the warping position compared with the surrounding existing points. We perform morphological operations on depth images to accelerate the algorithm convergence, and adopt a luma-first strategy to adapt to various color sampling formats. Experiments on test multi-view sequence showed that our method has superiority in depth differentiation and geometrical loyalty in the restoration of warped images. Also, peak signal-to-noise ratio (PSNR) statistics on non-hole regions and whole image comparisons both compare favorably to those obtained by state of the art techniques.
|
|
Efficient processing of ordered XML twig pattern matching based on extended Dewey
Jin-hua JIANG, Ke CHEN, Xiao-yan LI, Gang CHEN, Li-dan SHOU
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(12): 1769-1783.
https://doi.org/10.1631/jzus.A0920006
Finding all occurrences of a twig pattern is a core operation of extensible markup language (XML) query processing. Holistic twig join algorithms, which avoid a large number of intermediate results, represent the state-of-the-art algorithms. However, ordered XML twig join is mentioned rarely in the literature and previous algorithms developed in attempts to solve the problem of ordered twig pattern (OTP) matching have poor performance. In this paper, we first propose a novel children linked stacks encoding scheme to represent compactly the partial ordered twig join results. Based on this encoding scheme and extended Dewey, we design a novel holistic OTP matching algorithm, called OTJFast, which needs only to access the labels of the leaf query nodes. Furthermore, we propose a new algorithm, named OTJFaster, incorporating three effective optimization rules to avoid unnecessary computations. This works well on available indices (such as B+-tree), skipping useless elements. Thus, not only is disk access reduced greatly, but also many unnecessary computations are avoided. Finally, our extensive experiments over both real and synthetic datasets indicate that our algorithms are superior to previous approaches.
|
|
Certificateless key-insulated signature without random oracles
Zhong-mei WAN, Xue-jia LAI, Jian WENG, Sheng-li LIU, Yu LONG, Xuan HONG
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(12): 1790-1800.
https://doi.org/10.1631/jzus.A0820714
Leakage of the private key has become a serious problem of menacing the cryptosystem security. To reduce the underlying danger induced by private key leakage, Dodis et al.(2003) proposed the first key-insulated signature scheme. To handle issues concerning the private key leakage in certificateless signature schemes, we devise the first certificateless key-insulated signature scheme. Our scheme applies the key-insulated mechanism to certificateless cryptography, one with neither certificate nor key escrow. We incorporate Waters (2005)’s signature scheme, Paterson and Schuldt (2006)’s identity-based signature scheme, and Liu et al.(2007)’s certificateless signature scheme to obtain a certificateless key-insulated signature scheme. Our scheme has two desirable properties. First, its security can be proved under the non-pairing-based generalized bilinear Diffie-Hellman (NGBDH) conjecture, without utilizing the random oracle model; second, it solves the key escrow problem in identity-based key-insulated signatures.
|
|
Reliability assessment of networks-on-chip based on analytical models
Mojtaba VALINATAJ, Siamak MOHAMMADI, Saeed SAFARI
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(12): 1801-1814.
https://doi.org/10.1631/jzus.A0820853
As technology scales down, the reliability issues are becoming more crucial, especially for networks-on-chip (NoCs) that provide the communication requirements of multi-processor systems-on-chip. Reliability evaluation based on analytical models is a precise method for dependability analysis before and after designing the fault-tolerant systems. In this paper, we accurately formulate the inherent reliability and vulnerability of some popular NoC architectures against permanent faults, also depending on the employed routing algorithm and traffic model. Based on this analysis, effects of failures in the links, switches and network interfaces on the packet delivery of NoCs are determined. Besides, some extensions to evaluate a fault-tolerant method and some routing algorithms are described. The analyses are validated through appropriate simulations. The results thus obtained are exactly the same as or very close to the analytical ones.
|
|
A sensorless and simple controller for VSC based HVDC systems
E. ABIRI, A. RAHMATI, A. ABRISHAMIFAR
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(12): 1824-1834.
https://doi.org/10.1631/jzus.A0820504
Voltage source converter high-voltage direct current (VSC-HVDC) is a new power transmission technology preferable in small or medium power transmission. In this paper we discuss a new control system based on space vector modulation (SVM) without any voltage line sensors. Using direct power control (DPC) SVM and a new double synchronous reference frame phase-locked loop (DSRF-PLL) approach, the control system is resistant to the majority of line voltage disturbances. Also, the system response has accelerated by using a feed forward power decoupled loop. The operation of this control strategy was verified in a SIMULINK/MATLAB simulation environment. To validate this control system, a 5 kV·A prototype system was constructed. Compared to the original controllers, the current total harmonic distortion (THD), the active and reactive deviations and the DC voltage overshoot were lowered by 2.5%, 6.2% and 8%, respectively. The rectifier power factor in the worst condition was 0.93 and the DC voltage settling time was 0.2 s.
|
16 articles
|