Addressing real-time constraints in the design of autonomous agents

The Phoenix project is an experiment in the design of autonomous agents for a complex environment. The project consists of a simulator of the environment, a basic agent architecture, and specific implementation of agents based on real-time techniques; the first two parts have been constructed, the third is on-going. The facets of Phoenix that facilitate real-time research are: a simulator parameterized for varying environmental conditions and instrumented to record behaviors, an agent architecture designed to support adaptable planning and scheduling, and methods for reasoning about real-time constraints.This research has been supported by DARPA, # F30602-85-C-0014; the Office of Naval Research, under a University Research Initiative grant, N00014-86-K-0764; the Office of Naval Research, # N00014-88-K0009, and a grant from the Digital Equipment Corporation. We wish to thank Mike Greenberg for his keen understanding of design issues and mastery of programming that made Phoenix what it is today. We also wish to thank Paul Silvey and David Westbrook for their help.     

Determination of the length of polymethylene chains in salts of saturated and unsaturated fatty acids by infrared spectroscopy

The length of polymethylene chains is determined by counting the number of, or measuring the position of, methylene vibration peaks in the 1070–710 cm⁻¹ and/or the 1380–1170cm⁻¹ regions of the IR spectrum of salts of fatty acids. Plotting this peak position against the phase relationship of the vibration in adjacent methylenes gives a curve which is independent of the chain length. (Thephase relationship, Φ/π=k/(m+1); where φ is the phase difference in radians between adjacent methylenes in a chain;m is the number of methylenes in the chain;k=1,2,3,…m, withk=1 generally assigned to the in-phase vibration.) Separate curves are obtained for methylene wagging and for two arrays of coupled twisting-rocking vibrations. Coupled twisting-rocking vibrations give as many as one peak per methylene group in the 1070–710 cm⁻¹ region with silver, sodium, potassium and barium salts of saturated acids. Lead salt peaks split. These peaks show the total length of salts of both saturated andtrans-unsaturated acids, but only the length of the carboxylate segment in salts ofcis-unsaturated acids. (The carboxylate segment comprises the carbons from the carboxylate carbon to the first unsaturated carbon, inclusive.) Wagging vibrations in the 1380–1170 cm⁻¹ region show the total chain length of saturated salts and the length of the carboxylate segment in unsaturated salts, bothcis andtrans. This region also has peaks for twisting-rocking vibrations, and they are most conspicuous in the spectra of silver and barium salts. Presented in part at the AOCS meeting in Toronto, Canada, 1962.     

Scheduling Space–Ground Communications for the Air Force Satellite Control Network

We present the first coupled formal and empirical analysis of the Satellite Range Scheduling application. We structure our study as a progression; we start by studying a simplified version of the problem in which only one resource is present. We show that the simplified version of the problem is equivalent to a well-known machine scheduling problem and use this result to prove that Satellite Range Scheduling is NP-complete. We also show that for the one-resource version of the problem, algorithms from the machine scheduling domain outperform a genetic algorithm previously identified as one of the best algorithms for Satellite Range Scheduling. Next, we investigate if these performance results generalize for the problem with multiple resources. We exploit two sources of data: actual request data from the U.S. Air Force Satellite Control Network (AFSCN) circa 1992 and data created by our problem generator, which is designed to produce problems similar to the ones currently solved by AFSCN. Three main results emerge from our empirical study of algorithm performance for multiple-resource problems. First, the performance results obtained for the single-resource version of the problem do not generalize: the algorithms from the machine scheduling domain perform poorly for the multiple-resource problems. Second, a simple heuristic is shown to perform well on the old problems from 1992; however it fails to scale to larger, more complex generated problems. Finally, a genetic algorithm is found to yield the best overall performance on the larger, more difficult problems produced by our generator.     

A reuse business model

This paper summarizes the decision framework for forming reuse business models and offers the Expert Services Model as a preferred first application of that framework. The Expert Services Model is only one possible approach, but one that we found is a good starting point. The framework for setting up a reuse plan consists of four major steps: define reuse, populate a library of reusable assets, share reusable assets, and maintain reusable assets.     

LOX-induced lipid peroxidation mechanism responsible for the detrimental effect of marine diatoms on zooplankton grazers

Some marine diatoms negatively affect the reproduction of dominant zooplankton grazers such as copepods, thus compromising the transfer of energy through the marine food chains. In this paper, the metabolic mechanism that leads to diatom-induced toxicity is investigated in three bloom-forming microalgae. We show that copepod dysfunctions can be induced by highly reactive oxygen species (hROS) and a blended mixture of diatom products, including fatty acid hydroperoxides (FAHs); these compounds display teratogenic and proapoptotic properties. The process is triggered by the early onset of lipoxygenase activities that elicit the synthesis of species-specific products, the basic structures of which were established (1-20); these compounds boost oxidative stress by massive lipid peroxidation. Our study might explain past laboratory and field results showing how diatoms damage zooplankton grazers even in the absence of polyunsaturated aldehydes, a class of molecules that has been formerly implicated in mediating the toxic activity of diatoms on copepods.     

Towards a heat- and mass-balanced kinetic model of TATB decomposition

TATB (1,3,5-triamino-2,4,6-trinitrobenzene) was thermally degraded by two small-scale analytical methods – simultaneous differential scanning calorimetry and thermogravimetric analysis (SDT) and a hot-stage microscope with Fourier Transform Infrared (FTIR) analysis capabilities. SDT used ramped heating, isothermal soaking, and thermal pretreatment at various conditions. The heat flow and mass loss were monitored during various treatment conditions to derive chemical decomposition kinetics and Arrhenius parameters. FTIR experiments used isothermal heating, and changes were monitored spectroscopically. Solid samples generated at specific conditions were collected from both methods and were analyzed by DMSO extraction followed by chemical speciation by optical and mass spectrometric methods. Characterization provided the following reaction insights: 1. TATB decreases in a sigmoidal pattern in isothermally heated samples. Other soluble products gradually increase in concentration and then abruptly decline in concentration during the second exotherm, such as diamino-dinitro-benzofurazan and amino-nitro-benzodifurazan. 2. FTIR showed gradual changes in the amino and nitro functionality, shifting positions and decreasing intensity for the first 40 min. Then the solid gradually appeared more like an amorphous C with N incorporated, similar to previous studies on thermally degraded TATB-type materials. 3. Extracted residues (DMSO-soluble components removed) examined by FTIR showed an abrupt change in chemical composition between 40- and 45-min isothermal treatment, indicating early forming solids are different than later forming residues. 4. A reliable mass- and energy-balanced global reaction network must include at least two autocatalytic reactions, either in parallel or series, and at least one must have an explicit initiation reaction having a low activation energy.     

Depolymerization of chromophoric natural organic matter

Although the importance of natural organic matter (NOM) in the environment and in drinking water treatment is well-known, its structure is still ill-defined. The fragmentation patterns of NOM treated by irradiation (various wavelengths--185-400 nm), hydroxyl radicals, chlorine, ozone, and breakdown by a white rot fungus were studied to investigate the structure of chromophoric NOM molecules. Size exclusion chromatography was used to monitor the size distributions of NOM in two natural water waters and two NOM isolates. Three distinct fragmentation patterns were observed: ozone attack appeared to be nonsize specific, UV (> or = 254 nm) irradiation preferentially removed higher molecular weight chromophores, while processes involving hydroxyl radical showed intermediate size specificity. For the samples studied, the UV (> or = 254 nm) irradiation-induced fragmentation of NOM followed the patterns suggested by a simple trimer depolymerization model, supporting the viewpoint that NOM has repeating structural units joined by photolabile chemical bonds. The largest molecules reacted most rapidly, progressively fragmenting into slower reacting smaller molecules, which initially accumulated before breaking down to become nonchromophoric. This dependency of rate on molecular size appears to follow from the law of photochemistry which states the rate of reaction is proportional to the rate of light absorption: larger chromophores had higher molar absorptivities, absorbed more photons, and hence reacted faster than smaller chromophores.