This paper presents a method to detect the quantization index modulation(QIM) steganography in G.723.1 bit stream.We show that the distribution of each quantization index(codeword) in the quantization index sequence h...This paper presents a method to detect the quantization index modulation(QIM) steganography in G.723.1 bit stream.We show that the distribution of each quantization index(codeword) in the quantization index sequence has unbalanced and correlated characteristics.We present the designs of statistical models to extract the quantitative feature vectors of these characteristics.Combining the extracted vectors with the support vector machine,we build the classifier for detecting the QIM steganography in G.723.1 bit stream.The experiment shows that the method has far better performance than the existing blind detection method which extracts the feature vector in an uncompressed domain.The recall and precision of our method are all more than 90% even for a compressed bit stream duration as low as 3.6 s.展开更多
Refi ll friction stir spot welding,also known as friction spot welding(FSpW),is a solid-state welding process suitable for spot joining of lightweight materials.Through the eff orts of improving joint quality for simi...Refi ll friction stir spot welding,also known as friction spot welding(FSpW),is a solid-state welding process suitable for spot joining of lightweight materials.Through the eff orts of improving joint quality for similar and dissimilar materials,for example,aluminum and magnesium,this joining technology is well developed.The joining mechanism and process characteristics of FSpW have been widely studied.However,the application of FSpW in industry has not been entirely successful.In this review article,the research of similar and dissimilar material joints,such as,Al/Cu,Al/Ti,Al/Mg and Al/Steel,is summarized.The microstructural features and mechanical properties of the joints,welding tool and the application development are discussed in detail.展开更多
基金Project supported by the National Natural Science Foundation of China (No. 60970148)the National High-Tech R&D (863)Program of China (No. 2011AA010704)
文摘This paper presents a method to detect the quantization index modulation(QIM) steganography in G.723.1 bit stream.We show that the distribution of each quantization index(codeword) in the quantization index sequence has unbalanced and correlated characteristics.We present the designs of statistical models to extract the quantitative feature vectors of these characteristics.Combining the extracted vectors with the support vector machine,we build the classifier for detecting the QIM steganography in G.723.1 bit stream.The experiment shows that the method has far better performance than the existing blind detection method which extracts the feature vector in an uncompressed domain.The recall and precision of our method are all more than 90% even for a compressed bit stream duration as low as 3.6 s.
基金financially supported by the National Natural Science Foundation of China(No.51601117).
文摘Refi ll friction stir spot welding,also known as friction spot welding(FSpW),is a solid-state welding process suitable for spot joining of lightweight materials.Through the eff orts of improving joint quality for similar and dissimilar materials,for example,aluminum and magnesium,this joining technology is well developed.The joining mechanism and process characteristics of FSpW have been widely studied.However,the application of FSpW in industry has not been entirely successful.In this review article,the research of similar and dissimilar material joints,such as,Al/Cu,Al/Ti,Al/Mg and Al/Steel,is summarized.The microstructural features and mechanical properties of the joints,welding tool and the application development are discussed in detail.
