Multiple-unit computer systems which are to be tolerant of intermittently faulty units or transiently upset units are considered in this paper. Designs for such systems, which exploit a new so-called greedy diagnosis ...
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Multiple-unit computer systems which are to be tolerant of intermittently faulty units or transiently upset units are considered in this paper. Designs for such systems, which exploit a new so-called greedy diagnosis theory, are developed. Using greedy diagnosis, assessments on the condition of a unit (intermittent-fault case) or the integrity of data (transient-upset case) can be made on the basis of syndromes formed from comparisons of the results of jobs performed by pairs of units. Greedy diagnosis avoids the requirement that for such syndromes to be useful, they must be interpretable from a permanent-fault/continuous-upset perspective.
We describe how two-wave mixing of light scattered at the entrance face of a photorefractive crystal can be used to measure the frequency difference between two independent lasers. This method can be used to accomplis...
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We describe how two-wave mixing of light scattered at the entrance face of a photorefractive crystal can be used to measure the frequency difference between two independent lasers. This method can be used to accomplish initial frequency acquisition in coherent optical homodyne receivers.
The performanceof two concatenated coding systems usinga K = 3, r = 1/2 convolutional inner code and a Reed-Solomon (15,9)or (15, 7) outer code was measured over a 5.76 km long atmosphericdirect detection optical comm...
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The performanceof two concatenated coding systems using
a K = 3, r = 1/2 convolutional inner code and a Reed-Solomon (15,9)
or (15, 7) outer code was measured over a 5.76 km long atmospheric
direct detection optical communicationchannel. Inner code interleaving
of 100 ps combined with outer code interleaving of 240 bits (60RS
symbols)was found to be sufficientto obtain a decodedBER of less than
under conditions of moderate channel turbulence(U; = 0.6) and
~
an average of 6-10 detected photons per channel bit.
We propose to use initially neutral Li and He gases to observe x-ray stimulating Raman scattering. We solve the Maxwell-Bloch equations for the Raman scattering in the presence of a strong photoionization atomic deple...
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We propose to use initially neutral Li and He gases to observe x-ray stimulating Raman scattering. We solve the Maxwell-Bloch equations for the Raman scattering in the presence of a strong photoionization atomic depletion and show that very high conversion efficiencies can be obtained, although the required intensities are significantly high to cause very fast photoionization.
Perturbative analysis is used to solve the material equations in InP:Fe (including both temperature and electron-hole effects under an applied dc field) for the second spatial harmonic of the electric space charge fie...
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Perturbative analysis is used to solve the material equations in InP:Fe (including both temperature and electron-hole effects under an applied dc field) for the second spatial harmonic of the electric space charge field and the correction term to the fundamental component.
A new technique capable of enhancing optical nonlinearity is proposed. In the suggested scheme, weak optical fields create a three-dimensional real-time hologram written as a carrier distribution, and then an applied ...
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A new technique capable of enhancing optical nonlinearity is proposed. In the suggested scheme, weak optical fields create a three-dimensional real-time hologram written as a carrier distribution, and then an applied microwave field develops the hologram by heating the carriers and increasing the nonlinear refractive index locally. As an example, we have calculated the diffraction efficiency for the case of four-wave mixing. A value as high as 1% can be achieved in a 5-mm sample of CdS microcrystallites in glass.
A linearized, input-output model-matching problem for single-input, multioutput nonlinear systems is formulated in the frequency domain, and solved using dynamic output feedback. The objective is to obtain a desired t...
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A linearized, input-output model-matching problem for single-input, multioutput nonlinear systems is formulated in the frequency domain, and solved using dynamic output feedback. The objective is to obtain a desired transfer function for the family of closed-loop linearized systems. A disadvantage of this approach is that extension to the multi-input case is difficult.< >
This paper presents a new approach to modeling file systems using queueing networks. The delays due to locking the files are modeled using service centers whose service times and probabilities of access are estimated ...
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This paper presents a new approach to modeling file systems using queueing networks. The delays due to locking the files are modeled using service centers whose service times and probabilities of access are estimated from the values of measurable quantities. The model of a lock is based on the analysis of execution of transactions in the system. The lock for every file is modeled as a sequence of service centers. The decomposition method can be used to solve the model, which allows multiple classes of transactions and shared files to be represented. An example involving measurement data collected in a small business installation is given to compare performance measures provided by the simulation and analytic models.
We show that the autocorrelation function of mode-locked laser pulses can be measured by interfering a pulse with its time-delayed replica in a conventional photoconductor to generate a pulsating grating that can be r...
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We show that the autocorrelation function of mode-locked laser pulses can be measured by interfering a pulse with its time-delayed replica in a conventional photoconductor to generate a pulsating grating that can be represented as a superposition of moving gratings. The resonance current peak resulting from matching the carrier drift velocity to the velocity of one of the grating components is proportional to the autocorrelation function. Unlike conventional autocorrelators, the proposed method uses no nonlinear effects and thus can be utilized for measuring weak pulses. (C) 1997 American Institute of Physics.
Communication over a waveform channel corrupted by additive white Gaussian noise, and by an unknown and arbitrary interfering signal of bounded power is considered. For this channel, we derive an upper bound to the wo...
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Communication over a waveform channel corrupted by additive white Gaussian noise, and by an unknown and arbitrary interfering signal of bounded power is considered. For this channel, we derive an upper bound to the worst case error probability of direct-sequence with a correlation receiver, and also a lower bound applicable to any binary signaling technique and any receiver. By comparing these two bounds, we show that, if a small error probability is required, then no other binary signaling scheme or receiver can substantially improve upon the performance of direct-sequence with a correlation receiver for the same power and bandwidth.
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