There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Wireless Communications

Herein we obtained a chemically bonded TiO2 (P25)-graphene nanocomposite photocatalyst with graphene oxide and P25, using a facile one-step hydrothermal method. During the hydrothermal reaction, both of the reduction of graphene oxide and loading of P25 were achieved. The as-prepared P25-graphene photocatalyst possessed great adsorptivity of dyes, extended light absorption range, and efficient charge separation properties simultaneously, which was rarely reported in other TiO2−carbon photocatalysts. Hence, in the photodegradation of methylene blue, a significant enhancement in the reaction rate was observed with P25-graphene, compared to the bare P25 and P25-CNTs with the same carbon content. Overall, this work could provide new insights into the fabrication of a TiO2−carbon composite as high performance photocatalysts and facilitate their application in the environmental protection issues.

P25-Graphene Composite as a High Performance Photocatalyst

Carbon nanotubes (CNTs) hold the promise of delivering exceptional mechanical properties and multi-functional characteristics. Ever-increasing interest in applying CNTs in many different fields has led to continued efforts to develop dispersion and functionalization techniques. To employ CNTs as effective reinforcement in polymer nanocomposites, proper dispersion and appropriate interfacial adhesion between the CNTs and polymer matrix have to be guaranteed. This paper reviews the current understanding of CNTs and CNT/polymer nanocomposites with two particular topics: (i) the principles and techniques for CNT dispersion and functionalization and (ii) the effects of CNT dispersion and functionalization on the properties of CNT/polymer nanocomposites. The fabrication techniques and potential applications of CNT/polymer nanocomposites are also highlighted.

Dispersion and functionalization of carbon nanotubes for polymer-based nanocomposites: a review

This article is essentially tutorial in nature. We show how any discrete wavelet transform or two band subband filtering with finite filters can be decomposed into a finite sequence of simple filtering steps, which we call lifting steps but that are also known as ladder structures. This decomposition corresponds to a factorization of the polyphase matrix of the wavelet or subband filters into elementary matrices. That such a factorization is possible is well-known to algebraists (and expressed by the formulaSL(n;R[z, z−1])=E(n;R[z, z−1])); it is also used in linear systems theory in the electrical engineering community. We present here a self-contained derivation, building the decomposition from basic principles such as the Euclidean algorithm, with a focus on applying it to wavelet filtering. This factorization provides an alternative for the lattice factorization, with the advantage that it can also be used in the biorthogonal, i.e., non-unitary case. Like the lattice factorization, the decomposition presented here asymptotically reduces the computational complexity of the transform by a factor two. It has other applications, such as the possibility of defining a wavelet-like transform that maps integers to integers.

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Factoring wavelet transforms into lifting steps

The problem of error control and concealment in video communication is becoming increasingly important because of the growing interest in video delivery over unreliable channels such as wireless networks and the Internet. This paper reviews the techniques that have been developed for error control and concealment. These techniques are described in three categories according to the roles that the encoder and decoder play in the underlying approaches. Forward error concealment includes methods that add redundancy at the source end to enhance error resilience of the coded bit streams. Error concealment by postprocessing refers to operations at the decoder to recover the damaged areas based on characteristics of image and video signals. Last, interactive error concealment covers techniques that are dependent on a dialogue between the source and destination. Both current research activities and practice in international standards are covered.

/pdf/error-control-and-concealment-for-video-communication-a-3tm7c48xjc.pdf

Error control and concealment for video communication: a review

From the Publisher:
Yao Wang received the B.S. and M.S. degrees in electrical engineering from Tsinghua University, Beijing, China, in 1983 and 1985, respectively, and the Ph.D. degree in electrical and computer engineering from the University of California at Santa Barbara in 1990. Since 1990, she has been with the Faculty of Electrical Engineering, Polytechnic University, Brooklyn, NY. Her research areas include video communications, multimedia signal processing, and medical imaging. She has authored and co-authored over 100 papers in journals and conference proceedings. She is a senior member of IEEE and has served as an Associate Editor for the IEEE Transactions on Circuits and Systems for Video Technology and the IEEE Transactions on Multimedia. She won the Mayor's Award of the City of New York for Excellence in Science and Technology in the Young Investigator category in 2000. 

Jvrn Ostermann studied electrical engineering and communications engineering at the University of Hannover and Imperial College London, respectively. He received Dipl.-Ing. and Dr.-Ing. from the University of Hannover in 1988 and 1994, respectively. He has been a staff member with Image Processing and Technology Research, AT&T Labs>Research since 1996, where he is engaged in research on video coding, shape coding, multi-modal human-computer interfaces with talking avatars, standardization, and image analysis. He is a German National Foundation scholar. In 1998, he received the AT&T Standards Recognition Award and the ISO award. He is a member of the IEEE, the IEEE Technical Committee on Multimedia Signal Processing, and chair of the IEEE CAS Visual Signal Processing and Communications (VSPC) TechnicalCommittee.

Ya-Qin Zhang received the B.S. and M.S. degrees in electrical engineering from the University of Science and Technology of China (USTC) in 1983 and 1985, respectively, and the Ph.D. degree from George Washington University in 1989. He is currently the Managing Director of Microsoft Research in Beijing, after leaving his post as the Director of Multimedia Technology Laboratory at the Sarnoff Corporation in Princeton, NJ (formerly the David Sarnoff Research Center, and RCA Laboratories). He has been engaged in research and commercialization of MPEG2/DTV, MPEG4/VLBR, and multimedia information technologies. He has authored and co-authored over 200-refereed papers in leading international conference proceedings and journals. He has been granted over 40 U.S. patents in digital video, Internet, multimedia, wireless and satellite communications. He was the Editor-in-Chief of the IEEE Transactions on Circuits and Systems for Video Technology from 1997 to 1999. He is a Fellow of the IEEE.

Video Processing and Communications

We review error resilience techniques for real-time video transport over unreliable networks. Topics covered include an introduction to today's protocol and network environments and their characteristics, encoder error resilience tools, decoder error concealment techniques, as well as techniques that require cooperation between encoder, decoder, and the network. We provide a review of general principles of these techniques as well as specific implementations adopted by the H.263 and MPEG-4 video coding standards. The majority of the article is devoted to the techniques developed for block-based hybrid coders using motion-compensated prediction and transform coding. A separate section covers error resilience techniques for shape coding in MPEG-4.

Error resilient video coding techniques

Multimedia content analysis refers to the computerized understanding of the semantic meanings of a multimedia document, such as a video sequence with an accompanying audio track. With a multimedia document, its semantics are embedded in multiple forms that are usually complimentary of each other, Therefore, it is necessary to analyze all types of data: image frames, sound tracks, texts that can be extracted from image frames, and spoken words that can be deciphered from the audio track. This usually involves segmenting the document into semantically meaningful units, classifying each unit into a predefined scene type, and indexing and summarizing the document for efficient retrieval and browsing. We review advances in using audio and visual information jointly for accomplishing the above tasks. We describe audio and visual features that can effectively characterize scene content, present selected algorithms for segmentation and classification, and review some testbed systems for video archiving and retrieval. We also describe audio and visual descriptors and description schemes that are being considered by the MPEG-7 standard for multimedia content description.

Multimedia content analysis-using both audio and visual clues

Multiple description coding (MDC) is an effective means to combat bursty packet losses in the Internet and wireless networks. MDC is especially promising for video applications where retransmission is unacceptable or infeasible. When combined with multiple path transport (MPT), MDC enables traffic dispersion and hence reduces network congestion. This work describes principles in designing MD video coders employing temporal prediction and presents several predictor structures that differ in their tradeoffs between mismatch-induced distortion and coding efficiency. The paper also discusses example video communication systems integrating MDC and MPT.

Yao Wang

Papers

Error control and concealment for video communication: a review

Video Processing and Communications

Error resilient video coding techniques

Multimedia content analysis-using both audio and visual clues

Multiple Description Coding for Video Delivery