81,809 research outputs found
Research on new techniques for the analysis of manual control systems Progress report, 15 Jun. 1969 - 15 Jun. 1970
Applying statistical decision theory to manual adaptive control system
PPM demodulation: On approaching fundamental limits of optical communications
We consider the problem of demodulating M-ary optical PPM (pulse-position
modulation) waveforms, and propose a structured receiver whose mean probability
of symbol error is smaller than all known receivers, and approaches the quantum
limit. The receiver uses photodetection coupled with optimized phase-coherent
optical feedback control and a phase-sensitive parametric amplifier. We present
a general framework of optical receivers known as the conditional pulse nulling
receiver, and present new results on ultimate limits and achievable regions of
spectral versus photon efficiency tradeoffs for the single-spatial-mode
pure-loss optical communication channel.Comment: 5 pages, 6 figures, IEEE ISIT, Austin, TX (2010
Utilizing Microcavities to Suppress Third-order Cascades in Fifth-order Raman Spectra
Nonlinear optical signals in the condensed phase are often accompanied by
sequences of lower-order processes, known as cascades, which share the same
phase matching and power dependence on the incoming fields and are thus hard to
distinguish. The suppression of cascading in order to reveal the desired
nonlinear signal has been a major challenge in multidimensional Raman
spectroscopy, i.e., the signal being masked by cascading signals
given by a product of two processes. Since cascading originates
from the exchange of a virtual photon between molecules, it can be manipulated
by performing the experiment in an optical microcavity. Using a quantum
electrodynamical (QED) treatment we demonstrate that the cascading
contributions can be greatly suppressed. By optimizing the cavity size and the
incoming pulse directions, we show that up to 99.5\% suppression of the
cascading signal is possible.Comment: 15 pages, 2 figures; Accepted by J. Phys. Chem. Let
Data-based fault detection in chemical processes: Managing records with operator intervention and uncertain labels
Developing data-driven fault detection systems for chemical plants requires managing uncertain data labels and dynamic attributes due to operator-process interactions. Mislabeled data is a known problem in computer science that has received scarce attention from the process systems community. This work introduces and examines the effects of operator actions in records and labels, and the consequences in the development of detection models. Using a state space model, this work proposes an iterative relabeling scheme for retraining classifiers that continuously refines dynamic attributes and labels. Three case studies are presented: a reactor as a motivating example, flooding in a simulated de-Butanizer column, as a complex case, and foaming in an absorber as an industrial challenge. For the first case, detection accuracy is shown to increase by 14% while operating costs are reduced by 20%. Moreover, regarding the de-Butanizer column, the performance of the proposed strategy is shown to be 10% higher than the filtering strategy. Promising results are finally reported in regard of efficient strategies to deal with the presented problemPeer ReviewedPostprint (author's final draft
A functional description of the advanced receiver
The breadboard Advanced Receiver 2 (ARX 2) that is currently being built for future use in NASA's Deep Space Network (DSN) is described. The hybrid analog/digital receiver performs multiple functions including carrier, subcarrier, and symbol synchronization. Tracking can be achieved for residual, suppressed, or hybrid carriers and for both sinusoidal and square-wave subcarriers. Other functions such as time-tagged Doppler extraction and monitor/control are also discussed, including acquisition algorithms and lock-detection schemes. System requirements are specified and a functional description of the ARX 2 is presented. The various digital signal-processing algorithms used are also discussed and illustrated with block diagrams
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