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Tsinghua Science and Technology

Issue 5 • Date Oct. 2009

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Displaying Results 1 - 20 of 20
  • [Front cover]

    Page(s): c1
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    Freely Available from IEEE
  • Contents

    Page(s): 1
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    Freely Available from IEEE
  • A fast leak locating method based on wavelet transform

    Page(s): 551 - 555
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    The problem of leak location is actually a time delay estimation (TOE) problem. Since most existing TDE methods may encounter the problem of high computational complexity when used for online leak location. This paper presents a fast leak locating method based on wavelet transform (WT). The method first gets a rough estimate of the time delay from the WT coefficients of the pressure signals at the largest scale, then keeps refining the estimate using WT coefficients on smaller and smaller scales. Quantitative analyses and test results based on real data show that the method reduces the computational complexity while maintaining the time delay estimation accuracy. View full abstract»

    Open Access
  • Multistep linear programming approaches for decoding low-density parity-check codes

    Page(s): 556 - 560
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    The problem of improving the performance of linear programming (LP) decoding of low-density parity-check (LDPC) codes is considered in this paper. A multistep linear programming (MLP) algorithm was developed for decoding LDPC codes that includes a slight increase in computational complexity. The MLP decoder adaptively adds new constraints which are compatible with a selected check node to refine the results when an error is reported by the original LP decoder. The MLP decoder result is shown to have the maximum-likelihood (ML) certificate property. Simulations with moderate block length LOpe codes suggest that the M LP decoder gives better performance than both the original LP decoder and the conventional sum-product (SP) decoder. View full abstract»

    Open Access
  • Architecture design of a variable length instruction set VLIW DSP

    Page(s): 561 - 569
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1095 KB)  

    The cost of the central register file and the size of the program code limit the scalability of very long instruction word (VLIW) processors with increasing numbers of functional units. This paper presents the architectural design of a six-way VLIW digital signal processor (DSP) with clustered register files. The architecture uses a variable length instruction set and supports dynamic instruction dispatching. The one-level memory system architecture of the processor includes 16-KB instruction and data caches and 16-KB instruction and data on-chip RAM. A compiler based on the Open 64 was developed for the system. Evaluations show that the processor is suitable for high performance applications with a high code density and small program code size. View full abstract»

    Open Access
  • Bit-depth scalable coding using a perfect picture and adaptive neighboring filter

    Page(s): 570 - 574
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (437 KB)  

    Bit-depth scalability is a new research field in the on-going scalable extension of the H.264/AVC (SVC) video coding standard. The key point is to accurately predict the enhancement layer, whose bit depth is 10 or more, from the 8 bit base layer. An improved inter-layer prediction scheme for bit-depth scalability was developed that ensures compatibility with the standard and improves the encoding efficiency. The scheme uses a “perfect” 8 bit picture with an adaptive neighbor filter whose coefficients are optimized by minimizing the block distortion between the 8 bit reconstructed picture and the “perfect” picture to achieve a more precise 10 bit prediction based on the filtered picture. Double arithmetic precision is used to further improve the encoding efficiency. Experimental results show that the scheme outperforms the recent joint video team (JVT) proposal in the joint scalable video model (JSVM). View full abstract»

    Open Access
  • Efficiency of cache mechanism for network processors

    Page(s): 575 - 585
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (684 KB)  

    With the explosion of network bandwidth and the ever-changing requirements for diverse network-based applications, the traditional processing architectures, i.e., general purpose processor (GPP) and application specific integrated circuits (ASIC) cannot provide sufficient flexibility and high performance at the same time. Thus, the network processor (NP) has emerged as an alternative to meet these dual demands for today's network processing. The NP combines embedded multi-threaded cores with a rich memory hierarchy that can adapt to different networking circumstances when customized by the application developers. In today's NP architectures, multithreading prevails over cache mechanism, which has achieved great success in GPP to hide memory access latencies. This paper focuses on the efficiency of the cache mechanism in an NP. Theoretical timing models of packet processing are established for evaluating cache efficiency and experiments are performed based on real-life network backbone traces. Testing results show that an improvement of nearly 70% can be gained in throughput with assistance from the cache mechanism. Accordingly, the cache mechanism is still efficient and irreplaceable in network processing, despite the existing of multithreading. View full abstract»

    Open Access
  • Smart image sensor with integrated low complexity image processing for wireless endoscope capsules

    Page(s): 586 - 592
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1274 KB)  

    A smart image sensor was developed which integrates a digital pixel image sensor array with an image processor, designed for wireless endoscope capsules. The camera-on-a-chip architecture and its on-chip functionality facilitate the design of the packaging and power consumption of the integrated capsule. The power reduction techniques were carried out at both the architectural and circuit level. Gray coding and power gating in the sensor array to eliminate almost 500/0 of the switch activity on the data bus and more than 99% of the power dissipation in each pixel at a transmitting rate of 2 frames per second. Filtering and compression in the processor reduces the data transmission by more than 2/3. A parallel fully pipelined architecture with a dedicated clock management scheme was implemented in the JPEG-LS engine to reduce the power consumption by 15.7%. The smart sensor has been implemented in 0.18 urn CMOS technology. View full abstract»

    Open Access
  • Reliable remote-monitoring electrochemical potentiostat for glucose measurements

    Page(s): 593 - 600
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (567 KB)  

    Electrochemical methods have been widely used in the chemical and pharmaceutical industries, which require accurate concentration measurements, chemical reaction detections and analyses. The electrochemical potentiostat, the core element in electrochemical instruments, have been discussed as a hot topic addressing the difficulty of applying high-precision constant voltage and picoampere current measurements. Meanwhile, reliable potentiostats are in demand for complicated industrial environments with noises as well as requirements of remotemonitors. This paper describes a potentiostat for industrial glucose measurement that is not only accurate but also fault tolerant to guarantee high reliability in industrial environments. The instrument uses standard industrial communication protocols, profibus, and a 4–20 mA current loop, for remote control and monitoring. Experimental results show that this design has 0.01 % accuracy with 1 mV resolution for voltage applications and 0.01 % accuracy with 1 pA resolution for current measurements. The design is also shown to be highly reliable in noisy environments. View full abstract»

    Open Access
  • Digital 1 V 82 μW pseudo-two-stage Class-AB OTA

    Page(s): 601 - 605
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    A low power digital operational transconductance amplifier (OTA) was developed for low voltage switched capacitor applications. The OTA has a high slew rate (SR) and a large open loop gain with a differential pseudo-two-stage Class-AB structure. A fully compensated depletion mode capacitor is used in the switched capacitor common mode feedback block instead of a metal-insulator-metal (MIM) capacitor to reduce the fabrication cost. Simulations show that with a 1.0-V supply voltage and a 34-pF load at each output terminal, this digital differential pseudo-two-stage Class-AB OTA realized in O.13-μm technology achieves a 63.5-dB DC gain and a O.83-V output swing. The slew rate is ±16.29 V/μs and the total power dissipation is only 82 μW. View full abstract»

    Open Access
  • Improved grapheme-to-phoneme conversion for mandarin TTS

    Page(s): 606 - 611
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (303 KB)  

    Several methods were developed to improve grapheme-to-phoneme (G2P) conversion models for Chinese text-to-speech (TTS) systems. The critical problem of data sparsity was handled by combining approaches. First, a text-selection method was designed to cover as many G2P text corpus contexts as possible. Then, various data-driven modeling methods were used with comparisons to select the best method for each polyphonic word. Finally, independent models were used for some neutral tone words in addition to the normal G2P models to achieve more compact and flexible G2P models. Tests show that these methods reduce the relative errors by 50% for both normal polyphonic words and Chinese neutral tones. View full abstract»

    Open Access
  • Dynamic simulations of nonlinear multi-domain systems based on genetic programming and bond graphs

    Page(s): 612 - 616
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (298 KB)  

    A dynamic simulation method for non-linear systems based on genetic programming (GP) and bond graphs (8G) was developed to improve the design of nonlinear multi-domain energy conversion systems. The genetic operators enable the embryo bond graph to evolve towards the target graph according to the fitness function. Better simulation requires analysis of the optimization of the eigenvalue and the filter circuit evolution. The open topological design and space search ability of this method not only gives a more optimized convergence for the operation, but also reduces the generation time for the new circuit graph for the design of nonlinear multi-domain systems. View full abstract»

    Open Access
  • Feedforward control of a 3-D physiological articulatory model for vowel production

    Page(s): 617 - 622
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (837 KB)  

    A three-dimensional (3-D) physiological articulatory model was developed to account for the biomechanical properties of the speech organs in speech production. Control of the model to investigate the mechanism of speech production requires an efficient control module to estimate muscle activation patterns, which is used to manipulate the 3-D physiological articulatory model, according to the desired articulatory posture. For this purpose, a feedforward control strategy was developed by mapping the articulatory target to the corresponding muscle activation pattern via the intrinsic representation of vowel articulation. In this process, the articulatory postures are first mapped to the corresponding intrinsic representations; then, the articulatory postures are clustered in the intrinsic representations space and a nonlinear function is approximated for each cluster to map the intrinsic representation of vowel articulation to the muscle activation pattern by using general regression neural networks (GRNN). The results show that the feedforward control module is able to manipulate the 3-D physiological articulatory model for vowel production with high accuracy both acoustically and articulatorily. View full abstract»

    Open Access
  • A unified framework for multilingual text-to-speech synthesis with SSML specification as interface

    Page(s): 623 - 630
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (557 KB)  

    This paper describes the design of a unified framework for a multilingual text-to-speech (TTS) synthesis engine — Crystal. The unified framework defines the common TTS modules for different languages and/or dialects. The interfaces between consecutive modules conform to the speech synthesis markup language (SSML) specification for standardization, interoperability, multilinguality, and extensibility. Detailed module divisions and implementation technologies for the unified framework are introduced, together with possible extensions for the algorithm research and evaluation of the TTS synthesis. Implementation of a mixed-language TTS system for Chinese Putonghua, Chinese Cantonese, and English demonstrates the feasibility of the proposed unified framework. View full abstract»

    Open Access
  • Friction effects in pedestrian headform impacts with engine hoods

    Page(s): 631 - 638
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (12922 KB)  

    In the pedestrian headform impact test mandated by the European pedestrian safety requirements, the contact friction between the headform and the engine hood affects the headform kinematics and head injury criterion (HIC) to some extent. This study shows that the friction effect is more significant with child headform impact than with adult headform impact and the relative angle between the headform impact direction and the hood surface greatly affects the headform impact sensitivity to the friction coefficient. The sensitivity of the headform kinematics to the friction coefficient is also analyzed. The results show that accurate friction coefficients are needed to improve predictions of pedestrian headform impacts with hoods. View full abstract»

    Open Access
  • Modeling and experimental study of PEM fuel cell transient response for automotive applications

    Page(s): 639 - 645
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3692 KB)  

    This paper presents an analysis of the dynamic response of a low pressure proton exchange membrane (PEM) fuel cell stack to step changes in load, which are characteristic of automotive fuel cell system applications. The goal is a better understanding of the electrical and electrochemical processes when accounting for the characteristic cell voltage response during transients. The analysis and experiment are based on a low pressure 5 kW proton exchange membrane fuel cell (PEMFC) stack, which is similar to those used in several of Tsinghua's fuel cell buses. The experimental results provide an effective improvement reference for the power train control scheme of the fuel cell buses in Olympic demonstration in Beijing 2008. View full abstract»

    Open Access
  • Invariants for parallel mapping

    Page(s): 646 - 654
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (591 KB)  

    This paper analyzes the geometric quantities that remain unchanged during parallel mapping (i.e., mapping from a reference curved surface to a parallel surface with identical normal direction). The second gradient operator, the second class of integral theorems, the Gauss-curvature-based integral theorems, and the core property of parallel mapping are used to derive a series of parallel mapping invariants or geometrically conserved quantities. These include not only local mapping invariants but also global mapping invariants found to exist both in a curved surface and along curves on the curved surface. The parallel mapping invariants are used to identify important transformations between the reference surface and parallel surfaces. These mapping invariants and transformations have potential applications in geometry, physics, biomechanics, and mechanics in which various dynamic processes occur along or between parallel surfaces. View full abstract»

    Open Access
  • A method for reducing disorientation in hypermedia educational systems

    Page(s): 655 - 662
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (270 KB)  

    Learners in hypermedia educational systems (HES) often become disorientated and experience cognitive overhead. This study presents a method for reducing disorientation in HES. The study uses two usability methods, retrospective thinking aloud (RTA) and performance measure (PM), to find usability problems in HES that impact participant disorientation. The participants had field independent (FI) and field dependent (FD) cognitive styles. The results indicate that the participants' disorientation degree using the RTA method is significantly less than those using the PM method. For the effect of cognitive styles, only the average search steps index showed that FI learners are significantly less disorientated than FD learners. The results can help designers of hypermedia systems design tools to reduce user disorientation. View full abstract»

    Open Access
  • Optimum kinematic design of the 4R 2-DOF parallel mechanism

    Page(s): 663 - 668
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (11977 KB)  

    This paper analyzes the kinematic optimization design of the 4R 2-DOF parallel mechanism taking into account the force transmissibility. Three indices are introduced to reflect the force transmissibility. Based on these indices and their performance charts, the optimization design process with respect to the workspace is presented in detail. The results show that the designed mechanism is not only far from every singularity but also has good force transmissibility in its workspace. These kinematic optimization indices can be extended to other parallel mechanisms. View full abstract»

    Open Access
  • Infection functions for virus propagation in computer networks: An empirical study

    Page(s): 669 - 676
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (822 KB)  

    There has been an increasing amount of interest in modeling virus propagation in recent years. However, the group-based infection mechanism of computer viruses is not well understood and the selection of infection function in virus propagation modeling has not been well studied. This paper describes a point-to-group (P2G) infection mode to describe virus propagation in networks with information sharing groups. Simulations compare the constant infection and I-type infection functions with the new E-type infection function in the small-world-network environment. The simulation results show that the E-type infection function shows superior performances to that of the traditional I-type infection function in modeling the P2G virus infection mechanism and the I-type infection function shows better performance in modeling the random infection mechanism. View full abstract»

    Open Access

Aims & Scope

Tsinghua Science and Technology (Tsinghua Sci Technol) aims to highlight scientific achievements in computer science, electronic engineering, and other IT fields. Contributions all over the world are welcome.

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