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Video adaptation is a promising technique to bridge the gap between network status,device capabilities,and user preferences in pervasive media applications.However,conventional adaptation frameworks based on either transcoding or multiple pre-transcoding are not able to accommodate large numbers of users with diversified applications.This paper introduces an intermediate video description called "Intermedia",which consists of multiple level video signal components,such as texture,motion,and rate control information,as well as some semantic features,such as structural characteristics and Region Of Interest (ROI) information.It is generated off-line and stored in the video server or media gateway.Intermedia is then used to design a novel video adaptation system.The proposed adaptation system quickly and easily generates the required bit stream from Intermedia with very low complexity to fulfill a series of specific adaptation requirements,e.g.,bitrate conversion,temporal/spatial resolution reduction,video summarization,ROI browsing,and some multi-level adaptations involving both signal level and semantic level adaptation.The satisfactory performance of such a system demonstrates the effectiveness and efficiency of the proposed video adaptation framework.
2012年02期 v.17 113-127页 [查看摘要][在线阅读][下载 1139K] [下载次数：57 ] |[网刊下载次数：0 ] |[引用频次：3 ] |[阅读次数：0 ] Three-dimensional (3-D) video applications,such as 3-D cinema,3DTV,and Free Viewpoint Video (FVV) are attracting more attention both from the industry and in the literature.High accuracy of depth video is a fundamental prerequisite for most 3-D applications.However,accurate depth requires computationally intensive global optimization.This high computational complexity is one of the bottlenecks to applying depth generation to 3-D applications,especially for mobile networks since mobile terminals usually have limited computing ability.This paper presents a semi-global depth estimation algorithm based on temporal consistency,where the depth propagation is used to generate initial depth values for the computationally intensive global optimization.The accuracy of initial depth is improved by detecting and eliminating the depth propagation outliers before the global optimization.Integrating the initial values without outliers into the global optimization reduces the computational complexity while maintaining the depth accuracy.Tests demonstrate that the algorithm reduces the total computational time by 54%-65% while the quality of the virtual views is essentially equivalent to the benchmark.
2012年02期 v.17 128-135页 [查看摘要][在线阅读][下载 510K] [下载次数：48 ] |[网刊下载次数：0 ] |[引用频次：0 ] |[阅读次数：0 ] - Bruno Lepri;Sandy Pentland;
The co-evolution of social relationships and individual behavior in time and space has important implications,but is poorly understood because of the difficulty of closely tracking the everyday life of a complete community.We offer evidence that relationships and behavior co-evolve in a student dormitory,based on monthly surveys and location tracking through resident cellular phones over a period of nine months.We demonstrate that a Markov jump process could capture the co-evolution in terms of the rates at which residents visit places and friends.Our co-evolution model will be useful in bridging sensor networks data and organizational dynamics theories,simulating different ways to shape behavior and relationships,and turning mobile phone data into data products.
2012年02期 v.17 136-151页 [查看摘要][在线阅读][下载 1726K] [下载次数：66 ] |[网刊下载次数：0 ] |[引用频次：3 ] |[阅读次数：0 ] Extensive research in recent years has shown that dynamic spectrum sharing is a promising approach to address the artificial spectrum scarcity problem by improving spectrum utilization.This new communication paradigm,however,requires a well-designed spectrum allocation mechanism.This paper designs a double spectrum auction framework that allows unlicensed secondary users to obtain selected idle spectra assigned to licensed primary users.This is a win-win game because primary users can earn extra revenue and secondary users can obtain spectra they desperately need.The competition among primary users in the auction framework is studied combining game theory with a double spectrum auction in a non-cooperative game with the Nash Equilibrium (NE) as the best solution.Primary users use the prices obtained from the NE as their bid strategies to participate in the auction.In this auction sellers and buyers bid privately and confidentially,which means that the secondary users do not actually know the price and the spectrum size offered by the primary users,then a new net utility function was developed for the primary users with an iterative algorithm to find the Nash equilibrium point.Simulations demonstrate that this design effectively improves spectrum utilization.
2012年02期 v.17 152-160页 [查看摘要][在线阅读][下载 325K] [下载次数：49 ] |[网刊下载次数：0 ] |[引用频次：2 ] |[阅读次数：0 ] -
This study analyzes the impact of Physical-layer Network Coding (PNC) on the throughput of a large random wireless network,including one-dimensional and two-dimensional networks.Three different transmission schemes,(1) a traditional flow-based scheme,(2) a network coding scheme,and (3) the PNC scheme are compared to show that the PNC scheme improves wireless network throughput by a constant factor without changing the scaling law compared to the traditional flow-based and network coding schemes.Furthermore,PNC can reduce the effect of interference for the one-dimensional networks,and has a tighter throughput bound for the two-dimensional network.
2012年02期 v.17 161-171页 [查看摘要][在线阅读][下载 499K] [下载次数：47 ] |[网刊下载次数：0 ] |[引用频次：4 ] |[阅读次数：0 ] This paper describes a seamless three-dimensional (3-D) localization and navigation system for smartphones.The smartphone includes an atmospheric pressure sensor to measure the user's altitude that is combined with the outdoor Global Positioning System (GPS) and indoor WiFi-APs localization systems in a seamless 3-D localization system.The smartphone software also provides seamless navigation services by updating map information for both indoor and outdoor locations through the mobile Internet.The indoor floor information calculated from the altitude information is used to project localization anchor nodes,e.g.,WiFi-AP,on different floors onto the user's floor with an indoor 3-D localization algorithm using projection distances based on a Received Signal Strength (RSS) algorithm.Tests show that the 3-D method reduces systematic errors and achieves much higher accuracy than the traditional two-dimensional localization method.
2012年02期 v.17 172-178页 [查看摘要][在线阅读][下载 647K] [下载次数：61 ] |[网刊下载次数：0 ] |[引用频次：5 ] |[阅读次数：0 ] - Dudu Samba;
Trust management frameworks are used to evaluate and manage trust relationships between network nodes and enhance network security.However,trust management frameworks themselves are vulnerable to attacks.Attacks against trust management frameworks are described in this paper with a trust management framework to resist them.The trustworthiness between nodes is evaluated to classify node behavior using a three-dimensional classifier based on a fuzzy integral.Different behaviors are mapped to different behavioral spaces to detect malicious nodes and identify their behavior types.The security of ad hoc networks is then improved by various measures to handle different types of malicious behavior.Simulations of the model on the System In The Loop (SITL) platform show that this trust management framework can separate normal nodes and malicious nodes and can distinguish different types of malicious nodes.
2012年02期 v.17 179-185页 [查看摘要][在线阅读][下载 370K] [下载次数：49 ] |[网刊下载次数：0 ] |[引用频次：6 ] |[阅读次数：0 ] A fault-tolerant 1-spanner is used to preserve all the minimum energy paths after node failures to cope with fault-tolerant topology control problems in wireless ad hoc networks.A fault-tolerant 1-spanner is a graph such that the remaining graph after node failures will not only remain connected,but also have a stretch factor of one.The fault-tolerant 1-spanner is used in a localized and distributed topology control algorithm,named the k-Fault-Tolerant 1-Spanner (k-FT1S),where each node constructs a minimum energy path tree for every local failed node set.This paper proves that the topology constructed by k-FT1S is a k-fault-tolerant 1-spanner that can tolerate up to k node failures,such that the remaining network after node failures preserves all the minimum energy paths of the remaining network gained from the initial network by removing the same failed nodes.Simulations show that the remaining network after removal of any k nodes still has the optimal energy efficiency and is competitive in terms of average logical degree,average physical degree,and average transmission radius.
2012年02期 v.17 186-193页 [查看摘要][在线阅读][下载 304K] [下载次数：51 ] |[网刊下载次数：0 ] |[引用频次：6 ] |[阅读次数：0 ] -
A method was developed to detect generic objects using a single query image.The query image could be a typical real image,a virtual image,or even a hand-drawn sketch of the object.Without a training process,the key problem is how to describe the object class from only one query image with no pre-segmentation or other pre-processing procedures.The method introduces densely computed Scale-Invariant Feature Transform (SIFT) as the descriptor to extract "gradient distribution" features of the image.The descriptor emphasizes the edge parts and their distribution structures,which are very representative of the object class,so it is very robust and can deal with virtual images or hand-drawn sketches.Tests on car detection,face detection,and generic object detection demonstrate that the method is effective,robust,and widely applicable.The results using queries of real images compare well with other training-free methods and state-of-the-art training-based methods.
2012年02期 v.17 194-201页 [查看摘要][在线阅读][下载 1302K] [下载次数：45 ] |[网刊下载次数：0 ] |[引用频次：2 ] |[阅读次数：0 ] This paper presents a decision directed frequency tracking scheme to improve the spectrum efficiency of Orthogonal Frequency Division Modulation (OFDM) transmission for frequency selective channels.OFDM divides a broadband channel into parallel narrowband subchannels with different channel characteristics.The subcarriers with lower attenuation are selected to do the decision directed based frequency tracking.A phase error detection method is needed to keep the hard decision working stable during tracking.The algorithm ensures that the carrier frequency offset could be solved from the detected phase error.The Mean Square Error (MSE) estimate and the loop bandwidth are also presented.Simulations illustrate that this scheme has better MSE and bit error rate performance than the traditional scheme.Furthermore,the pilots are saved in this scheme,which lead to improved spectrum efficiency.
2012年02期 v.17 202-208页 [查看摘要][在线阅读][下载 390K] [下载次数：26 ] |[网刊下载次数：0 ] |[引用频次：1 ] |[阅读次数：0 ] -
This paper describes an identification system for Chinese Materia Medicas (CMMs) in microscopic powder images.The imaging processing of the microscopic powder image is very complex because of the low contrast,blurry boundaries,overlapping objects,and messy background.Therefore,the object detection must segment the significant microscopic structures from the complex image.The objects are detected in these images using an adaptable interactive method.After identifying the significant microscopic structures,the system identifies 14 features belonging to three main characteristics.These features form a 14-dimensional vector that represents the microscopic structures.The multi-dimensional vector is then analyzed using a feature assignment algorithm that picks the most notable features to construct a decision tree with thresholds.The identification system consists of a coarse classifier based on the decision tree and a fine classifier using similarity measurements to rank the possible results.Tests on 528 images from 24 different kinds of microscopic structures show the system effectiveness and applicability.
2012年02期 v.17 209-217页 [查看摘要][在线阅读][下载 1358K] [下载次数：54 ] |[网刊下载次数：0 ] |[引用频次：5 ] |[阅读次数：0 ] In continuous speech,the pitch contour of the same syllable may vary much due to its contextual information.The Parallel Encoding and Target Approximation (PENTA) model is applied here to Mandarin speech synthesis with a method to predict pitch contours for Chinese syllables with different contexts by combining the Classification And Regression Tree (CART) with the PENTA model to improve its prediction accuracy.CART was first used to cluster the syllables' normalized pitch contours according to the syllables contextual information and the distances between pitch contours.The average pitch contour was used to train the PENTA model with the average contour for each cluster.The initial pitch is required with the PENTA model to predict a continuous pitch contour.A Pitch Discontinuity Model (PDM) was used to predict the initial pitches at positions with voiceless consonants and prosodic boundaries.Initial tests on a Chinese four-syllable word corpus containing 2048 words were extended to tests with a continuous speech corpus containing 5445 sentences.The results are satisfactory in terms of the Root Mean Square Error (RMSE) comparing the predicted pitch contour with the original contour.This method can model pitch contours for Mandarin sentences with any text for speech synthesis.
2012年02期 v.17 218-224页 [查看摘要][在线阅读][下载 395K] [下载次数：56 ] |[网刊下载次数：0 ] |[引用频次：2 ] |[阅读次数：0 ] -
<正>Tsinghua Science and Technology (Tsinghua Sci Technol),an academic journal sponsored by Tsinghua University,is published bimonthly.This journal aims at presenting the up-to-date scientific achievements with high creativity and great significance in computer and electronic engineering.Contributions all over the world are welcome.
2012年02期 v.17 225页 [查看摘要][在线阅读][下载 820K] [下载次数：13 ] |[网刊下载次数：0 ] |[引用频次：0 ] |[阅读次数：0 ] 下载本期数据