Dongdong Zhang - Academia.edu (original) (raw)
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Humanitas University ; Humanitas Clinical and Research Center
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Papers by Dongdong Zhang
Journal of Manufacturing Science and Engineering-transactions of The Asme, 2009
This paper presents an approach for generating curvature-adaptive finishing tool paths with bound... more This paper presents an approach for generating curvature-adaptive finishing tool paths with bounded error directly from massive point data in three-axis computer numerical control (CNC) milling. This approach uses the moving least-squares (MLS) surface as the underlying surface representation. A closed-form formula for normal curvature computation is derived from the implicit form of MLS surfaces. It enables the generation of curvature-adaptive tool paths from massive point data that is critical for balancing the trade-off between machining accuracy and speed. To ensure the path accuracy and robustness for arbitrary surfaces where there might be an abrupt curvature change, a novel guidance field algorithm is introduced. It overcomes potential excessive locality of curvature-adaptive paths by examining the neighboring points' curvature within a selfupdating search bound. Our results affirm that the combination of curvature-adaptive path generation and the guidance field algorithm produces high-quality numerical control (NC) paths from a variety of point cloud data with bounded error.
Signal Processing-image Communication, 2009
IEEE Transactions on Consumer Electronics, 2008
Quality consistency has been an important issue in video applications. However, the quality fluct... more Quality consistency has been an important issue in video applications. However, the quality fluctuation cannot be avoided in single pass video coding due to the variation of the video content, flexible coding structure, different frame types, etc. In this paper, we propose an efficient method to reduce the quality fluctuation for H.264/AVC high definition (HD) video coding. We aim to reduce the distortion variation among frames at different types. A single-pass distributed control algorithm is introduced which provides different control mechanism for different frame type. For P frame, the quantization parameter is decided by the relationship between the quantization step and the given target bit rate and the buffer status to satisfy the bit rate constraints. For B frame, the quantization parameter is determined by the relationship between the quantization step and the given target distortion to reduce the quality fluctuation between P and B frames. Extensive simulation results are provided to demonstrate the efficiency of the proposed method. When compared to the traditional method used in current H.264/AVC video coding, the quality fluctuations are significantly reduced. Moreover, the bit rate constraints of the high definition video coding are satisfied 1 .
Catalysis Communications, 2007
Preparation methods and photocatalytic activity of the photocatalyst nanometer TiO 2 /poly-(fluor... more Preparation methods and photocatalytic activity of the photocatalyst nanometer TiO 2 /poly-(fluorene-co-thiophene) (PFT) were studied under GaI 3 lamp irradiation in the present research. The degradation rate of phenol using the target photocatalyst was much higher than it was using TiO 2 /rhodamine B. Diffuse reflectance spectra showed that the absorbance range of TiO 2 /PFT was expanded from 387 nm (TiO 2 ) to about 500 nm, and fluorescent emission spectra showed that the spectral shape of TiO 2 /PFT was identical with that of pure PFT. The fluorescent quantum efficiency of TiO 2 /PFT was estimated at 3.8% while that of PFT film was about 14.7%, which indicated that electrons transferred from the PFT into the conduction band of TiO 2 .
Journal of Manufacturing Science and Engineering-transactions of The Asme, 2009
This paper presents an approach for generating curvature-adaptive finishing tool paths with bound... more This paper presents an approach for generating curvature-adaptive finishing tool paths with bounded error directly from massive point data in three-axis computer numerical control (CNC) milling. This approach uses the moving least-squares (MLS) surface as the underlying surface representation. A closed-form formula for normal curvature computation is derived from the implicit form of MLS surfaces. It enables the generation of curvature-adaptive tool paths from massive point data that is critical for balancing the trade-off between machining accuracy and speed. To ensure the path accuracy and robustness for arbitrary surfaces where there might be an abrupt curvature change, a novel guidance field algorithm is introduced. It overcomes potential excessive locality of curvature-adaptive paths by examining the neighboring points' curvature within a selfupdating search bound. Our results affirm that the combination of curvature-adaptive path generation and the guidance field algorithm produces high-quality numerical control (NC) paths from a variety of point cloud data with bounded error.
Signal Processing-image Communication, 2009
IEEE Transactions on Consumer Electronics, 2008
Quality consistency has been an important issue in video applications. However, the quality fluct... more Quality consistency has been an important issue in video applications. However, the quality fluctuation cannot be avoided in single pass video coding due to the variation of the video content, flexible coding structure, different frame types, etc. In this paper, we propose an efficient method to reduce the quality fluctuation for H.264/AVC high definition (HD) video coding. We aim to reduce the distortion variation among frames at different types. A single-pass distributed control algorithm is introduced which provides different control mechanism for different frame type. For P frame, the quantization parameter is decided by the relationship between the quantization step and the given target bit rate and the buffer status to satisfy the bit rate constraints. For B frame, the quantization parameter is determined by the relationship between the quantization step and the given target distortion to reduce the quality fluctuation between P and B frames. Extensive simulation results are provided to demonstrate the efficiency of the proposed method. When compared to the traditional method used in current H.264/AVC video coding, the quality fluctuations are significantly reduced. Moreover, the bit rate constraints of the high definition video coding are satisfied 1 .
Catalysis Communications, 2007
Preparation methods and photocatalytic activity of the photocatalyst nanometer TiO 2 /poly-(fluor... more Preparation methods and photocatalytic activity of the photocatalyst nanometer TiO 2 /poly-(fluorene-co-thiophene) (PFT) were studied under GaI 3 lamp irradiation in the present research. The degradation rate of phenol using the target photocatalyst was much higher than it was using TiO 2 /rhodamine B. Diffuse reflectance spectra showed that the absorbance range of TiO 2 /PFT was expanded from 387 nm (TiO 2 ) to about 500 nm, and fluorescent emission spectra showed that the spectral shape of TiO 2 /PFT was identical with that of pure PFT. The fluorescent quantum efficiency of TiO 2 /PFT was estimated at 3.8% while that of PFT film was about 14.7%, which indicated that electrons transferred from the PFT into the conduction band of TiO 2 .