A novel adaptive digital image watermark algorithm is proposed. Fuzzy c-means clustering （FCM） is used to classify the original image blocks into two classes based on several characteristic parameters of human visua...A novel adaptive digital image watermark algorithm is proposed. Fuzzy c-means clustering （FCM） is used to classify the original image blocks into two classes based on several characteristic parameters of human visual system （HVS）. One is suited for embedding a digital watermark, the other is not. So the appropriate blocks in an image are selected to embed the watermark. The wetermark is embedded in the middle-frequency part of the host image in conjunction with HVS and discrete cosine transform （DCT）. The maximal watermark strength is fixed according to the frequency masking. In the same time, for the good performance, the watermark is modulated into a fractal modulation array. The simulation results show that we can remarkably extract the hiding watermark and the algorithm can achieve good robustness with common signal distortion or geometric distortion and the quality of the watermarked image is guaranteed.展开更多
The high peak-to-average (PAPR) is one of the serious problems in the application of OFDM technology. The com-panding transform approach is a very attractive technique to reduce PAPR, but large PAPR reduction leads to...The high peak-to-average (PAPR) is one of the serious problems in the application of OFDM technology. The com-panding transform approach is a very attractive technique to reduce PAPR, but large PAPR reduction leads to a high bit error rate (BER) by the available companding transform techniques. In this paper, a joint reduction in PAPR of the OFDM signals based on combining the discrete cosine transform (DCT) with companding is proposed. In the first step of the proposed scheme, the data are transformed by a DCT into new modified data. In the second step, the proposed scheme utilizes the companding technique to further reduce the PAPR of the OFDM signal. The performance of the PAPR is evaluated using a computer simulation. The simulation results indicate that the proposed scheme may obtain about 1 dB PAPR reduction compared with the conventional companding algorithm.展开更多
The principle of digital watermark is the method of adding digital watermark in the frequency domain. The digital watermark hides the watermark in digital media, such as image, voice, video, etc., so as to realize the...The principle of digital watermark is the method of adding digital watermark in the frequency domain. The digital watermark hides the watermark in digital media, such as image, voice, video, etc., so as to realize the functions of copyright protection, and identity recognition. DCT for Discrete Cosine Transform is used to transform the image pixel value and the frequency domain coefficient matrix to realize the embedding and extracting of the blind watermark in the paper. After success, the image is attacked by white noise and Gaussian low-pass filtering. The result shows that the watermark signal embedded based on the DCT algorithm is relatively robust, and can effectively resist some attack methods that use signal distortion to destroy the watermark, and has good robustness and imperceptibility.展开更多
Based on the QuikSCAT data, the features of surface wind distribution of the typhoon Vongfong landfall process are analyzed. We have also studied the variance spectral configuration of the surface wind field using DCT...Based on the QuikSCAT data, the features of surface wind distribution of the typhoon Vongfong landfall process are analyzed. We have also studied the variance spectral configuration of the surface wind field using DCT (Discrete Cosine Transform). The conclusions are as follows: The near-surface wind field is highly asymmetric; the variance components of asymmetric surface wind field depend mainly on the airflow direction of wavenumber 1 and 2. When the typhoon moves west, there are two wave spectral centers lining up in the zonal direction, mainly the airflow from zonal wavenumber 2 and meridional wavenumber 2; when it moves north, there are two wave spectral centers in a meridional array, mainly the airflow from zonal wavenumber 1 and meridional wavenumber 2. The airflow for wavenumber 1 mainly contributes to the variance of the tangential wind while that for wavenumber 2 to the variance of the radial wind. The asymmetrical distribution changes with the large-scale environment and self-rotating circulation around the typhoon. When it approached land, the associated gale appears in front portion in the advancing direction of the storm. It is in effect similar to the model of Chen Lian-shou for typhoon-related gales NNW on the left front portion and SE on the right front portion.展开更多
The present study is a comparison study of research instrument in the field of interlanguage pragmatics. Sixty-two Chinese EFL university students participated in the study. Written DCT and oral role-plays were design...The present study is a comparison study of research instrument in the field of interlanguage pragmatics. Sixty-two Chinese EFL university students participated in the study. Written DCT and oral role-plays were designed in four stimulus types of refusal strategies--refusals to invitations, suggestions, offers and requests. Chi-square test and frequency were used for quantitative data and transcription of the tests was used for the qualitative data. The results show that there is no significant difference between the two tests in terms of strategies choices, but written DCT can produce a longer sentence while oral role-plays can yield a more natural expression.展开更多
Discrete Cosine Transform(DCT)is the most widely used technique in image and video compression.In this paper,the structure of DCT and Inverse DCT(IDCT)algorithm is split in the form of COordinate Rotation DIgital Comp...Discrete Cosine Transform(DCT)is the most widely used technique in image and video compression.In this paper,the structure of DCT and Inverse DCT(IDCT)algorithm is split in the form of COordinate Rotation DIgital Computer(CORDIC)rotation matrix.The two-dimensional(2-D)8×8 DCT/IDCT units based on the improved rotation CORDIC algorithm is proposed.The shift and addition operations of the CORDIC algorithm are used to replace the cosine multiplication operations in the algorithm.The design does not contain any multiplier unit,which reduces the complexity of the hardware unit.The row-column transform unit composed of register arrays connects two 1-D 8-point DCT units to complete the calculation of 2-D 8×8 DCT.The pipeline latency of proposed architecture is 28 clock cycles.The proposed efficient two-dimensional DCT architecture has been synthesized on the Xilinx’s Kintex-7 FPGA.The resource utilization is 17.36%for Slice LUTs,3.49%for Slice Registers,and the maximum operating frequency is 172 MHz.It takes only 0.161μs to complete a process of block of 8×8 samples.A frame of image is processed by the designed DCT unit and then reconstructed by the IDCT unit to verify the function.The Peak Signal to Noise Ratio(PSNR)can reach 51.99 dB.展开更多
基金Supported by the National Natural Science Foundation ofChina (10571127) the Doctoral Foundation of the Ministry of Educationof China (20040610004)
文摘A novel adaptive digital image watermark algorithm is proposed. Fuzzy c-means clustering （FCM） is used to classify the original image blocks into two classes based on several characteristic parameters of human visual system （HVS）. One is suited for embedding a digital watermark, the other is not. So the appropriate blocks in an image are selected to embed the watermark. The wetermark is embedded in the middle-frequency part of the host image in conjunction with HVS and discrete cosine transform （DCT）. The maximal watermark strength is fixed according to the frequency masking. In the same time, for the good performance, the watermark is modulated into a fractal modulation array. The simulation results show that we can remarkably extract the hiding watermark and the algorithm can achieve good robustness with common signal distortion or geometric distortion and the quality of the watermarked image is guaranteed.
文摘The high peak-to-average (PAPR) is one of the serious problems in the application of OFDM technology. The com-panding transform approach is a very attractive technique to reduce PAPR, but large PAPR reduction leads to a high bit error rate (BER) by the available companding transform techniques. In this paper, a joint reduction in PAPR of the OFDM signals based on combining the discrete cosine transform (DCT) with companding is proposed. In the first step of the proposed scheme, the data are transformed by a DCT into new modified data. In the second step, the proposed scheme utilizes the companding technique to further reduce the PAPR of the OFDM signal. The performance of the PAPR is evaluated using a computer simulation. The simulation results indicate that the proposed scheme may obtain about 1 dB PAPR reduction compared with the conventional companding algorithm.
文摘The principle of digital watermark is the method of adding digital watermark in the frequency domain. The digital watermark hides the watermark in digital media, such as image, voice, video, etc., so as to realize the functions of copyright protection, and identity recognition. DCT for Discrete Cosine Transform is used to transform the image pixel value and the frequency domain coefficient matrix to realize the embedding and extracting of the blind watermark in the paper. After success, the image is attacked by white noise and Gaussian low-pass filtering. The result shows that the watermark signal embedded based on the DCT algorithm is relatively robust, and can effectively resist some attack methods that use signal distortion to destroy the watermark, and has good robustness and imperceptibility.
基金Special Fund Project for Social Benefit Research Study on the Monitoring and Predicting Techniques of Desasters by landding typhoons in China (2002DCA20026-01) Knowledge Innovation Project of The Chinese Academy of Sciences (ZKCXZ-SW-210)
文摘Based on the QuikSCAT data, the features of surface wind distribution of the typhoon Vongfong landfall process are analyzed. We have also studied the variance spectral configuration of the surface wind field using DCT (Discrete Cosine Transform). The conclusions are as follows: The near-surface wind field is highly asymmetric; the variance components of asymmetric surface wind field depend mainly on the airflow direction of wavenumber 1 and 2. When the typhoon moves west, there are two wave spectral centers lining up in the zonal direction, mainly the airflow from zonal wavenumber 2 and meridional wavenumber 2; when it moves north, there are two wave spectral centers in a meridional array, mainly the airflow from zonal wavenumber 1 and meridional wavenumber 2. The airflow for wavenumber 1 mainly contributes to the variance of the tangential wind while that for wavenumber 2 to the variance of the radial wind. The asymmetrical distribution changes with the large-scale environment and self-rotating circulation around the typhoon. When it approached land, the associated gale appears in front portion in the advancing direction of the storm. It is in effect similar to the model of Chen Lian-shou for typhoon-related gales NNW on the left front portion and SE on the right front portion.
文摘The present study is a comparison study of research instrument in the field of interlanguage pragmatics. Sixty-two Chinese EFL university students participated in the study. Written DCT and oral role-plays were designed in four stimulus types of refusal strategies--refusals to invitations, suggestions, offers and requests. Chi-square test and frequency were used for quantitative data and transcription of the tests was used for the qualitative data. The results show that there is no significant difference between the two tests in terms of strategies choices, but written DCT can produce a longer sentence while oral role-plays can yield a more natural expression.
文摘Discrete Cosine Transform(DCT)is the most widely used technique in image and video compression.In this paper,the structure of DCT and Inverse DCT(IDCT)algorithm is split in the form of COordinate Rotation DIgital Computer(CORDIC)rotation matrix.The two-dimensional(2-D)8×8 DCT/IDCT units based on the improved rotation CORDIC algorithm is proposed.The shift and addition operations of the CORDIC algorithm are used to replace the cosine multiplication operations in the algorithm.The design does not contain any multiplier unit,which reduces the complexity of the hardware unit.The row-column transform unit composed of register arrays connects two 1-D 8-point DCT units to complete the calculation of 2-D 8×8 DCT.The pipeline latency of proposed architecture is 28 clock cycles.The proposed efficient two-dimensional DCT architecture has been synthesized on the Xilinx’s Kintex-7 FPGA.The resource utilization is 17.36%for Slice LUTs,3.49%for Slice Registers,and the maximum operating frequency is 172 MHz.It takes only 0.161μs to complete a process of block of 8×8 samples.A frame of image is processed by the designed DCT unit and then reconstructed by the IDCT unit to verify the function.The Peak Signal to Noise Ratio(PSNR)can reach 51.99 dB.
