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Three-dimensional conceptual model for service-oriented simulation
Wen-guang WANG, Wei-ping WANG, Justyna ZANDER, Yi-fan ZHU
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(8): 1075-1081.
https://doi.org/10.1631/jzus.A0920258
In this letter, we propose a novel three-dimensional conceptual model for an emerging service-oriented simulation paradigm. The model can be used as a guideline or an analytic means to find the potential and possible future directions of the current simulation frameworks. In particular, the model inspects the crossover between the disciplines of modeling and simulation, service-orientation, and software/systems engineering. Finally, two specific simulation frameworks are studied as examples.
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On-line topical importance estimation: an effective focused crawling algorithm combining link and content analysis
Can WANG, Zi-yu GUAN, Chun CHEN, Jia-jun BU, Jun-feng WANG, Huai-zhong LIN
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(8): 1114-1124.
https://doi.org/10.1631/jzus.A0820481
Focused crawling is an important technique for topical resource discovery on the Web. The key issue in focused crawling is to prioritize uncrawled uniform resource locators (URLs) in the frontier to focus the crawling on relevant pages. Traditional focused crawlers mainly rely on content analysis. Link-based techniques are not effectively exploited despite their usefulness. In this paper, we propose a new frontier prioritizing algorithm, namely the on-line topical importance estimation (OTIE) algorithm. OTIE combines link- and content-based analysis to evaluate the priority of an uncrawled URL in the frontier. We performed real crawling experiments over 30 topics selected from the Open Directory Project (ODP) and compared harvest rate and target recall of the four crawling algorithms: breadth-first, link-context-prediction, on-line page importance computation (OPIC) and our OTIE. Experimental results showed that OTIE significantly outperforms the other three algorithms on the average target recall while maintaining an acceptable harvest rate. Moreover, OTIE is much faster than the traditional focused crawling algorithm.
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Unwrapping and stereo rectification for omnidirectional images
Jie LEI, Xin DU, Yun-fang ZHU, Ji-lin LIU
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(8): 1125-1139.
https://doi.org/10.1631/jzus.A0820357
Omnidirectional imaging sensors have been used in more and more applications when a very large field of view is required. In this paper, we investigate the unwrapping, epipolar geometry and stereo rectification issues for omnidirectional vision when the particular mirror model and the camera parameters are unknown in priori. First, the omnidirectional camera is calibrated under the Taylor model, and the parameters related to this model are obtained. In order to make the classical computer vision algorithms of conventional perspective cameras applicable, the ring omnidirectional image is unwrapped into two kinds of panoramas: cylinder and cuboid. Then the epipolar geometry of arbitrary camera configuration is analyzed and the essential matrix is deduced with its properties being indicated for ring images. After that, a simple stereo rectification method based on the essential matrix and the conformal mapping is proposed. Simulations and real data experimental results illustrate that our methods are effective for the omnidirectional camera under the constraint of a single view point.
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Parallel processing architecture of H.264 adaptive deblocking filters
Hu WEI, Tao LIN, Zheng-hui LIN
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(8): 1160-1168.
https://doi.org/10.1631/jzus.A0820502
In H.264, computational complexity and memory access of deblocking filters are variable, dependent on video contents. This paper proposes a VLSI architecture of deblocking filters with adaptive dynamic power, which avoids redundant computations and memory accesses by precluding the blocks that can be skipped. The vertical and horizontal edges are simultaneously processed in an advanced scan order to speed up the decoder. As a result, dynamic power of the proposed architecture can be reduced adaptively (up to about 89%) for different videos, and the off-chip memory access is improved when compared to previous designs. Moreover, the processing capability of the proposed architecture is in particular appropriate for real-time deblocking of high-definition television (HDTV, 1920×1080 pixels/frame, 60 frames/s video signals) video operation at 62 MHz. Using the proposed architecture, power can be reduced by up to about 89% and processing time by from 25% to 81% compared with previous designs.
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A network-aware error-resilient method using prioritized intra refresh for wireless video communications
Han-jie MA, Fan ZHOU, Rong-xin JIANG, Yao-wu CHEN
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(8): 1169-1176.
https://doi.org/10.1631/jzus.A0820660
We propose a novel prioritized intra refresh method for the wireless video communication. The proposed method considers the characteristics of the human visual system, the error-sensitivity of the bitstream, and the state of the time-varying wireless channel jointly. An expected perceptual distortion model was used to adjust the intra refresh rate adaptively. This model consists of the perceptual weight map based on an attention model, the bit error probability map based on bitstream size, and the dynamic channel state information (CSI). Experimental results indicate that, compared with other intra refresh methods that consider only the content of the video or the CSI, the proposed method improves the average peak signal-to-noise ratio (PSNR) of the whole frame by about 0.5 dB, and improves the average PSNR of the attention-area by about 0.8 dB.
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A new coding scheme in coded ultrasound using staggering repetition interval
Cheng JIN, Si-ping CHEN, Zheng-di QIN
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(8): 1213-1216.
https://doi.org/10.1631/jzus.A0820762
The increase of frame rate, though with the potential in a coded ultrasound system, is generally concomitant with the simultaneous transmission of a number of apertures, and in consequence leads to increased cross-talks between different apertures. In view of this, a new coding scheme using staggering repetition interval was proposed. The transmitting signals were constructed by repeating the two (or more) modulated codes using staggering repetition interval, and then allocated to and transmitted simultaneously among different apertures. The decoding process was based on the subsection-matched filter under the assistance of different matched filters for different apertures. At last the outputs of subsection-matched filtering were added together. Staggering changed the positions of cross-correlation (CC) peaks from coinciding, which resulted in an effective reduction of CC. Our theoretical analysis and simulations showed that, the coding scheme can be used to reduce cross-talk, and a good cross-talk reduction will be achieved if the staggering delay is kept in an appropriate range.
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Analysis of dipole-like ultra high frequency RFID tags close to metallic surfaces
Ling-fei MO, Hong-jian ZHANG, Hong-liang ZHOU
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(8): 1217-1222.
https://doi.org/10.1631/jzus.A0820495
It is a challenge for passive RFID tags to be mounted on the surface of metal because the parameters of tag antennas, such as the impedance matching, the radiation efficiency and the radiation pattern, are seriously affected by the metallic surface. This paper presents the characteristics of the dipole-like antennas of ultra high frequency (UHF) radio frequency identification (RFID) tags that are placed close to metallic surfaces. The finite element method (FEM) and method of moment (MoM) were used to simulate the changes of the antenna parameters near the metallic surface. Two typical dipole-like antennas close to the metallic surface, a closed loop antenna and a loaded meander antenna, were modeled, and the performance was evaluated. Experiment was carried out and the results were in good agreement with the simulation, showing that a distance of 0.05λ~0.1λ (λ is the free space wavelength) from the metallic surface could make the dipole-like UHF RFID tag performance be acceptable.
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On-chip boost regulator with projected off- and on-time control
Xiao-ru XU, Meng-lian ZHAO, Xiao-bo WU
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(8): 1223-1230.
https://doi.org/10.1631/jzus.A0920160
The boost type power supplies are widely used in portable consumer electronics to step up the input voltage to adapt for the high voltage applications like light-emitting diode (LED) driving and liquid crystal display (LCD) biasing. In these applications, a regulator with small volume, fewer external components and high efficiency is highly desired. This paper proposes a projected off- and on-time boost control scheme, based on which a monolithic IC with an on-chip VDMOS with 0.2 Ω on-state resistance RDS-ON was implemented in 1.5 μm bipolar-CMOS-DMOS (BCD) process. A 12 V, 0.3 A boost regulator prototype is presented as well. With projected off-time and modulated on-time in continuous conduction mode (CCM), a quasi fixed frequency, which is preferred for ripple control, is realized. With projected on-time and modulated off-time in discontinuous conduction mode (DCM), pulse frequency modulation (PFM) operation, which is beneficial to light load efficiency improvement, is achieved without extra control circuitry. Measurement results show that an efficiency of 3% higher than that of a conventional method under 0.5 W output is achieved while a step load transient response comparable to that of current mode control is maintained as well.
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18 articles
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