Presented herein is an efficient simulation technique enabling systematic investigation of the soft programming over-erased flash EEPROM cells. The simulation provides a method by which to find the optimal soft progra...
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The effect of roundoff noise in a digital controller is analysed for a digital feedback control system. An analytical expression for the roundoff noise gain, defined as the ratio between the variances of the output er...
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The effect of roundoff noise in a digital controller is analysed for a digital feedback control system. An analytical expression for the roundoff noise gain, defined as the ratio between the variances of the output error and the rounding error, is obtained. The problem of identifying the minimum roundoff noise realisations can be solved using an existing procedure. Noting that the optimal realisations are fully parametrised, based on a polynomial operator approach a new sparse controller realisation is derived. This realisation is a generalisation of the direct forms in the classical shift operator and the prevailing delta-operator. It provides more degrees of freedom with which to reduce the roundoff noise. The problem of finding optimal polynomial operators can be solved by an exhaustive search, and a design example is given. It is shown that with the proposed sparse realisation the optimal polynomial operators can outperform the shift- and delta-operators.
In this paper, a volume management scheme that supports multi-host environments is designed and implemented. The proposed scheme provides various features for enterprise internet services such as online resizing, onli...
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The SCSI or the fibre channel (FC) disk drive, called SCSI-FC disk drive has its own internal queue and internal scheduler which maximize its own throughput. The request service order scheduled by the block device dri...
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The internet SCSI(iSCSI)[6] disk has been studied as a storage system which can be directly connected to TCP/IP network. We designed and implemented a shared disk following the iSCSI protocol and providing cache consi...
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We propose a novel model-based HMM distance computation framework to estimate run-time recognition errors and adapt recognition parameters without the need of using any testing or adaptation data. The key idea is to u...
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We propose a novel model-based HMM distance computation framework to estimate run-time recognition errors and adapt recognition parameters without the need of using any testing or adaptation data. The key idea is to use HMM distances between competing models to measure the confusability between phones in speech recognition. Starting with a set of simulated models in a given noise condition, the corresponding error rate could be estimated with a smooth approximation of the error count computed form the set of phone distances without using any testing data. By minimizing the estimated error between the desired and simulated models, the target model parameters could also be adjusted without using any adaptation data. Experimental results show that the word errors, estimated with the proposed framework, closely resemble the errors obtained by running actual recognition experiments on a large testing set in a number of adverse conditions. The adapted models also gave better recognition performances than those obtained with environment-matched models, especially in low signal-to-noise conditions.
Single-phase induction motors suffer from low torque average and high torque pulsations. These problems can be overcome by a switching capacitor in series with the stator auxiliary winding. However, the switching of t...
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Single-phase induction motors suffer from low torque average and high torque pulsations. These problems can be overcome by a switching capacitor in series with the stator auxiliary winding. However, the switching of the capacitor requires the motor speed signal over the entire speed range to provide performance optimization in terms of high torque average and low torque pulsations. In this paper a simple speed estimation method for single-phase induction motors is proposed in the stationary reference frame to overcome the problems associated with the use of speed sensors. Based on this method, a sensorless torque optimization system is suggested. The system is then validated by extensive simulation results. The speed estimation method was used in the sensorless control of the motors.
Broken rotor bars in an induction motor create asymmetries and result in abnormal amplitude of the sidebands around the fundamental supply frequency and its harmonics. Applying a spectrum analysis technique on motor c...
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Broken rotor bars in an induction motor create asymmetries and result in abnormal amplitude of the sidebands around the fundamental supply frequency and its harmonics. Applying a spectrum analysis technique on motor current and inspecting the spectrum amplitudes at the broken rotor bar specific frequencies for abnormality is a well-known procedure for broken rotor bar fault detection and diagnosis. Among the spectrum analysis techniques for broken rotor bar fault detection, the fast Fourier transform (FFT) is the most widely used technique. There are other spectrum techniques, which are based on the power spectral density estimates. In this paper we compare the three well-known spectrum analysis methods: FFT, periodogram and Welch's periodogram methods according to their performance on the broken rotor bar fault detection problem. The results indicate that Welch's periodogram method has better fault discrimination capability and is more robust compared to the other two methods. A statistical hypothesis test applied to the results of the three methods depicts the comparison results quantitatively.
The authors present a study of the finite word length (FWL) implementation for digital controller structures with sparseness consideration. A closed-loop stability related measure is derived, taking into account the n...
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The authors present a study of the finite word length (FWL) implementation for digital controller structures with sparseness consideration. A closed-loop stability related measure is derived, taking into account the number of trivial elements in a controller realisation. A practical design procedure is presented, which first obtains a controller realisation that maximises a lower bound of the proposed measure, and then uses a stepwise algorithm to make the realisation sparse. Simulation results show that the proposed design procedure yields computationally efficient controller realisations with an enhanced FWL closed-loop stability performance.
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