Tsinghua Science and Technology

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Volume 15 No. 2
20 February 2010

Rendering Grass Blowing in the Wind with Global Illumination

2010, 15(2): 133-137. doi:10.1016/S1007-0214(10)70042-0

Abstract ( 180 ) ( 48 )

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We have simulated a time varying wind field using the lattice Boltzmann model, and its effect on blades of grass with a simple mass-spring model. We present a global illumination model for multiple scattering of incident sun and sky illumination within the field of grass. We model the grass as a continuous distribution of infinitesimal colored scattering flakes and solve a system of differential equations for the radiance transport. We repeat this for a collection of grass bending directions and...

On the Application of PCA Technique to Fault Diagnosis

2010, 15(2): 138-144. doi:10.1016/S1007-0214(10)70043-2

Abstract ( 230 ) ( 30 )

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In this paper, we briefly address the application of the standard principal component analysis (PCA) technique to fault detection and identification. Based on an analysis of the existing test statistic, we propose a new test statistic, which is similar to the Hawkin's

Microring-Assisted Coupling Between Dissimilar Waveguides

2010, 15(2): 145-150. doi:10.1016/S1007-0214(10)70044-4

Abstract ( 220 ) ( 38 )

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The use of microring resonators to assist in the evanescent field coupling between dissimilar waveguides is proposed and analyzed. Theoretical analysis based on the coupled mode theory and numerical example show that complete cross power transfers can be obtained near the microring resonances. Applications of the device include power dividers, low-power thermo-optic or electro-optic switches, and modulators.

Recent Advance in Non-Krylov Subspace Model Order Reduction of Interconnect Circuits

2010, 15(2): 151-168. doi:10.1016/S1007-0214(10)70045-6

Abstract ( 146 ) ( 41 )

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Model order reduction of interconnect circuits is an important technique to reduce the circuit complexity and improve the efficiency of post-layout verification process in the nanometer VLSI design. Existing works using the Krylov subspace method are very efficient, but the resulting models are less compact and lack global accuracy. Also, existing methods cannot handle interconnect circuits with large input and output ports. Recent advances in reduction techniques using non-Krylov subspace techn...

Range Extension and Channel Capacity Increase in Impulse-Radio Ultra-Wideband Communications

2010, 15(2): 169-173. doi:10.1016/S1007-0214(10)70046-8

Abstract ( 174 ) ( 51 )

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We theoretically analyze the channel capacity of a 5th-order Gaussian pulse-based ultra-wideband (UWB) system and experimentally demonstrate 2 Gbit/s UWB-over-fiber transmission systems incorporating wireless transmission. Both electrical and photonic UWB pulse generation methods are employed and its performance is compared. By utilizing optimum UWB pulse design and employing a digital signal processing (DSP) receiver, a bit-error-rate above the forward error correction (FEC) limit for 8 meters ...

Fault-Tolerant Control for a Class of Uncertain Systems with Actuator Faults

2010, 15(2): 174-183. doi:10.1016/S1007-0214(10)70047-X

Abstract ( 192 ) ( 52 )

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The problem of fault-tolerant controller design for a class of polytopic uncertain systems with actuator faults is studied in this paper. The actuator faults are presented as a more general and practical continuous fault model. Based on the affine quadratic stability (AQS), the stability of the polytopic uncertain system is replaced by the stability at all corners of the polytope. For a wide range of problems including

Deterministic Teleportation Channel Using Bell State Measurements Only

2010, 15(2): 184-189. doi:10.1016/S1007-0214(10)70048-1

Abstract ( 177 ) ( 68 )

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Teleportation schemes based on probabilistic channels usually rely heavily on the implementation of high-dimensional unitary operations. Since high-dimensional unitary operations are very difficult to directly implement in physics experiments, methods are used to avoid high-dimensional unitary operations during the teleportation process. This paper describes how to construct a deterministic teleportation channel and a control channel using Bell state measurements only instead of high-dimensional...

One-Class Support Vector Machine with Relative Comparisons

2010, 15(2): 190-197. doi:10.1016/S1007-0214(10)70049-3

Abstract ( 132 ) ( 35 )

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One-class support vector machines (one-class SVMs) are powerful tools that are widely used in many applications. This paper describes a semi-supervised one-class SVM that uses supervision in terms of relative comparisons. The analysis uses a hypersphere version of one-class SVMs with a penalty term appended to the objective function. The method simultaneously finds the minimum sphere in the feature space that encloses most of the target points and considers the relative comparisons. The result i...

Incident Light Influence on the Transmission of Coupled Ring Resonators

2010, 15(2): 198-201. doi:10.1016/S1007-0214(10)70050-X

Abstract ( 140 ) ( 34 )

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The transmission matrix method is used to analyze the influence of incident light on coupled resonators. Two different types of incident light on the same coupled resonator geometry are shown to lead to different system transmission features. The EIT-like phenomenon occurs in the type I case with the transmission being symmetric around the zero-single-pass-phase-shift frequency. In the type II case the resonant frequency has a blue shift corresponding to the increasing coupling strength between ...

Improved Adaptive Compression Arbitration System for Wireless Sensor Networks

2010, 15(2): 202-208. doi:10.1016/S1007-0214(10)70051-1

Abstract ( 146 ) ( 41 )

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Previous studies have indicated that data compression in wireless sensor networks is not always beneficial to energy conservation due to the additional computational energy costs. This work gives an energy-efficient arbitration mechanism that enhances the performance of compression algorithms by avoiding unnecessary energy losses. The adaptive compression arbitration system uses a new prediction modeling and adaptation. Tests show that the modeling method gives better predictions with the adapti...

Opportunistic Video Communication over Cooperative Decode-Forward Networks

2010, 15(2): 209-215. doi:10.1016/S1007-0214(10)70052-3

Abstract ( 166 ) ( 37 )

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An opportunistic automatic repeat request (ARQ) scheme was developed to support high-quality video transmission over cooperative decode-forward networks. The opportunistic ARQ is implemented in the form of distributed space-time block codes (STBCs) and the desired STBC for a certain channel state is determined by the diversity-multiplexing tradeoff principle. With good channel states, the source and relay may jointly retransmit the lost video packets using high-rate low-diversity codes while wit...

Improved Adaptive Interpolation Filter for H.264/AVC

2010, 15(2): 216-220. doi:10.1016/S1007-0214(10)70053-5

Abstract ( 162 ) ( 51 )

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Motion compensation with adaptive interpolation filters (AIF) was developed to compensate for temporary varieties in the aliasing of video signals and improve the coding efficiency. The AIF achieves better RD performance than common static interpolation filtering by exploiting the statistics in the reference frames' local auto-correlation and the local cross-correlation between the current encoding frame and the reference frames. This paper presents an interpolation filter buffering structure th...

Dual-Mode Low Power Pipelined ADC with Pre-charged Switched Operational Amplifier

2010, 15(2): 221-227. doi:10.1016/S1007-0214(10)70054-7

Abstract ( 151 ) ( 39 )

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This paper describes a 12-bit 40-MS/s and 8-bit 80-MS/s dual-mode low power pipelined analog-to-digital converter (ADC). An improved multiplying digital-to-analog converter is used to provide the dual-mode operation. A pre-charged fast power-on switched operational amplifier is used to reduce the power consumption of the pipelined ADC to 28.98 mW/32.74 mW at 40 MHz/80 MHz sampling rates. The ADC was designed in a 1.8-V 1P6M 0.18-μm CMOS process. Simulations indicate that the ADC exhibits a spuri...

Radar Sea Clutter Suppression and Target Indication with a Spatial Tracking Filter

2010, 15(2): 228-234. doi:10.1016/S1007-0214(10)70055-9

Abstract ( 152 ) ( 47 )

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It is an important issue to study sea clutter suppression because it could interfere with the detection of targets above the sea surface severely. Spatial spectrum analyses show that the majority of sea clutter has low-frequency characteristics, compared to the high-frequency characteristics of the targets. This paper proposes a frequency-based spatial tracking filter to suppress sea clutter to facilitate targets identification. Experimental results show that the signal-to-clutter ratio can incr...

Empirical Research on User Acceptance of Mobile Searches

2010, 15(2): 235-245. doi:10.1016/S1007-0214(10)70056-0

Abstract ( 152 ) ( 38 )

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The mobile search, a combination of a web search engine and a mobile communication system, is viewed as the most influential application in the 3G era. Therefore, mobile search service providers are eager to know which factors most influence user acceptance of mobile searches. Based on the characteristics of mobile searches and a review of previous information technology acceptance research, this study integrates the task technology fit model and the unified theory of acceptance and use of techn...

Optimal Scheduling Method in MIMO WLAN with Distributed Coordination Function

2010, 15(2): 246-250. doi:10.1016/S1007-0214(10)70057-2

Abstract ( 128 ) ( 62 )

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This paper addresses the optimal number of simultaneous data transmissions that maximize the system throughput in an MIMO WLAN. To facilitate simultaneous packet transmissions, both transceivers have to exchange preambles to calculate the channel state information. This exchange is combined with the RTS (request to send)/CTS (clear to send) handshake which is used to contend for the channel in WLANs. This study presents an expression for the optimal number of simultaneous data transmissions unde...