Pathogenesis of SARS coronavirus infection using human lung epithelial cells: an in vitro model.

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A strategic study of establishing the industrial needs in pattern design and technology in Mainland China

2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

A distributed bandwidth reservation algorithm for QoS routing in TDMA-based mobile ad hoc networks

In this paper, we propose a distributed bandwidth reservation algorithm for QoS routing in mobile ad hoc networks (MANET). The bandwidth resource is organized into TDMA time slots. Previous methods either rely on global information for time slot reservation, which is impractical, or suffer from the shortcut collision problem. In our method, both the hidden terminal problem and the shortcut collision problem are eliminated. Furthermore, our method is performed in a distributed manner, thus has a low computational complexity. Simulation results show that the reserved bandwidth of our algorithm is close to the upper bound. ©2005 IEEE.published_or_final_versio

New method for designing two-channel causal stable IIR perfect reconstruction filter banks and wavelet bases

A new method for designing two-channel causal stable IIR PR filter banks and wavelet bases is proposed. It is based on the structure previously proposed by Phoong et al. (1995). Such a filter bank is parameterized by two functions α(z) and β(z), which can be chosen as an all-pass function to obtain IIR filterbanks with very high stopband attenuation. One of the problems with this choice is that a bump of about 4 dB always exists near the transition band of the analysis and synthesis filters. The stopband attenuation of the high-pass analysis filter is also 10 dB lower than that of the low-pass filter. By choosing β(z) and α(z) as an all-pass function and a type-II linear-phase finite impulse response (FIR) function, respectively, the bumping can be significantly suppressed. In addition, the stopband attenuation of the high-pass filter can be controlled easily. The design problem is formulated as a polynomial approximation problem and is solved efficiently by the Remez exchange algorithm. The extension of this method to the design of a class of IIR wavelet bases is also considered.published_or_final_versio

Theory and design of a class of M-channel IIR cosine-modulated filter banks

This letter proposes a method for designing a class of M-channel, causal, stable, perfect reconstruction (PR) IIR cosine-modulated filter banks (CMFB). The proposed CMFB has the same denominator for all its polyphase components in the prototype filter. Therefore, the PR condition is considerably simplified, and it is relatively simple to satisfy the PR and the casual-stable requirements of the IIR CMFB. Design examples show that the proposed IIR CMFB has sharper cutoff, higher stopband attenuation, and passband flatness than its FIR counterparts, especially when the system delay is small.published_or_final_versio

Designing two-channel causal stable IIR PR filter banks and wavelet bases by model order reduction and constrained optimization

In this paper, two methods for designing two-channel causal stable IIR PR filter banks are introduced. The first method makes use of model reduction and constrained optimization to obtain a causal stable IIR filter bank from the structural PR FIR filter bank proposed in [2]. It yields better frequency characteristics than the original FIR filter bank and avoids the dump at π/2 when allpass filters are used. Using the 1-D to 2-D transformation proposed in [2], two dimensional PR IIR filter bank can readily be obtained from these prototypes. The second method is based on constrained optimization technique using the general PR condition. Using this technique, filter banks with low system delay and flexible frequency characteristics can be designed. The technique can also be modified to design causal stable IIR dyadic wavelet bases with added regularity conditions. A number of design examples are used to demonstrate the usefulness of the proposed design methods.published_or_final_versio

Theory and design of causal stable IIR PR cosine-modulated filter banks

This paper proposes a novel method for designing two-channel and M-channel causal stable IIR PR filter banks using cosine modulation. In particular, we show that the PR condition of the two-channel IIR filter banks is very similar to the two-channel FIR case. Using this formulation, it is relatively simple to satisfy the PR condition and to ensure that the filters are causal stable. Using a similar approach, we propose a new class of M-channel causal stable IIR cosine modulated filter banks. Design examples are given to demonstrate the usefulness of proposed approach.published_or_final_versio

New design method for two-channel perfect reconstruction IIR filter banks

In this paper, a new method for designing perfect reconstruction (PR) two-channel causal stable IIR filter banks is introduced. It is based on a structure previously proposed by Phoong et al. [2]. By using a combination of allpass and linear-phase FIR functions, the bumping problem found in the conventional structural PR filter bank is significantly suppressed. The design problem is formulated as a polynomial approximation problem and is solved effectively using the Remez exchange algorithm. Filter banks with flexible stopband attenuation and system delay can readily be obtained using the proposed algorithm.published_or_final_versio

Switching characteristics and efficiency improvement with auxiliaryresonant snubber based soft-switching inverters

The auxiliary resonant snubber inverter (RSI) has demonstrated superiority in reduction of switching losses and dv/dt. It was found that the overall inverter system efficiency might not be improved if the resonant current was not controlled in accordance with the load current. This paper proposes an improved control scheme to minimize the operation of auxiliary circuit for efficiency improvement. The principle of this control scheme is to vary the resonant current with variable timing control based on the load current magnitude and to disable the auxiliary circuit operation when diode freewheeling occurs after switching. To illustrate the operation of this control scheme, this paper compares the switching characteristics and inverter power loss of hard-switching inverter, RSI with fixed-timing and variable-timing control and RSI with the proposed control scheme. Experimental results fully agree with the analyses and prove that the proposed control scheme is suitable for RSI to achieve better operating conditions.published_or_final_versio