Various algorithms for optimization and learning in adaptive systems

This thesis discusses various methods for learning and optimization in adaptive systems. Overall, it emphasizes the relationship between optimization, learning, and adaptive systems; and it illustrates the influence of underlying hardware upon the construction of efficient algorithms for learning and optimization. Chapter 1 provides a summary and an overview.

Chapter 2 discusses a method for using feed-forward neural networks to filter the noise out of noise-corrupted signals. The networks use back-propagation learning, but they use it in a way that qualifies as unsupervised learning. The networks adapt based only on the raw input data-there are no external teachers providing information on correct operation during training. The chapter contains an analysis of the learning and develops a simple expression that, based only on the geometry of the network, predicts performance.

Chapter 3 explains a simple model of the piriform cortex, an area in the brain involved in the processing of olfactory information. The model was used to explore the possible effect of acetylcholine on learning and on odor classification. According to the model, the piriform cortex can classify odors better when acetylcholine is present during learning but not present during recall. This is interesting since it suggests that learning and recall might be separate neurochemical modes (corresponding to whether or not acetylcholine is present). When acetylcholine is turned off at all times, even during learning, the model exhibits behavior somewhat similar to Alzheimer's disease, a disease associated with the degeneration of cells that distribute acetylcholine.

Chapters 4, 5, and 6 discuss algorithms appropriate for adaptive systems implemented entirely in analog hardware. The algorithms inject noise into the systems and correlate the noise with the outputs of the systems. This allows them to estimate gradients and to implement noisy versions of gradient descent, without having to calculate gradients explicitly. The methods require only noise generators, adders, multipliers, integrators, and differentiators; and the number of devices needed scales linearly with the number of adjustable parameters in the adaptive systems. With the exception of one global signal, the algorithms require only local information exchange.

Modeling ocean primary production: sensitivity to spectral resolution of attenuation and absorption of light

Modeling the vertical penetration of photosynthetically active radiation (PAR) through the ocean, and its utilization by phytoplankton, is fundamental to simulating marine primary production. The variation of attenuation and absorption of light with wavelength suggests that photosynthesis should be modeled at high spectral resolution, but this is computationally expensive. To model primary production in global 3d models, a balance between computer time and accuracy is necessary. We investigate the effects of varying the spectral resolution of the underwater light field and the photosynthetic efficiency of phytoplankton (α∗), on primary production using a 1d coupled ecosystem ocean turbulence model. The model is applied at three sites in the Atlantic Ocean (CIS (∼60°N), PAP (∼50°N) and ESTOC (∼30°N)) to include the effect of different meteorological forcing and parameter sets. We also investigate three different methods for modeling α∗ – as a fixed constant, varying with both wavelength and chlorophyll concentration [Bricaud, A., Morel, A., Babin, M., Allali, K., Claustre, H., 1998. Variations of light absorption by suspended particles with chlorophyll a concentration in oceanic (case 1) waters. Analysis and implications for bio-optical models. J. Geophys. Res. 103, 31033–31044], and using a non-spectral parameterization [Anderson, T.R., 1993. A spectrally averaged model of light penetration and photosynthesis. Limnol. Oceanogr. 38, 1403–1419]. After selecting the appropriate ecosystem parameters for each of the three sites we vary the spectral resolution of light and α∗ from 1 to 61 wavebands and study the results in conjunction with the three different α∗ estimation methods. The results show modeled estimates of ocean primary productivity are highly sensitive to the degree of spectral resolution and α∗. For accurate simulations of primary production and chlorophyll distribution we recommend a spectral resolution of at least six wavebands if α∗ is a function of wavelength and chlorophyll, and three wavebands if α∗ is a fixed value.

The New American cyclopaedia : a popular dictionary of general knowledge /

Later editions have title: The American cyclopædia.

The American cyclopaedia: a popular dictionary of general knowledge.

Mode of access: Internet.

The life of Ulysses S. Grant, general of the armies of the United States.

"Dana wrote three chapters--The thirty-sixth, thirty-eighth, and thirty-ninth--he read, approved, and passed all the rest, rarely ever changing the text in the slightest degree."--James Harrison Wilson, The life of Charles A. Dana ... 1907, p. 385.

The household book of poetry.

Mode of access: Internet.

Counterpoint: Kenneth Burke and Aristotle's theories of rhetoric.

Mode of access: Internet.

Fifty perfect poems.

Mode of access: Internet.

The auto-biography of Goethe. Truth and poetry: from my life.

Preface by the editor contains this statement: "Several years since there was what purported to be a translation published in London; but this was a disgraceful imposture. Mrs. Austin speaks of it as the most flagrant piece of literary dishonesty on record, not without justice; and Mr. Carlyle refers to it much in the same spirit. It was a poor copy of a wretched French version, in which frequently twenty pages of the original are omitted at a time, and hardly a sentence is rendered with fidelity." This refers to an anonymous translation published in 2 vols., London, 1824, and reprinted in 1 vol., New York, 1824 and 1844. cf. Characteristics of Goethe. From the German of Falk, von Müller, etc., with notes ... by S. Austin, vol. II (1833) p. 129, and Carlyle's Crit. and miscell. essays, New York, 1872, vol. I, p. 178.

The household book of poetry.

Mode of access: Internet.