Showing papers in "CTIT technical reports series in 1993"

Food of salmonine predators in Lake Superior, 1981-87

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Transformational derivation of (parallel) programs using skeletons

Abstract: We describe a framework for the derivation of programs for arbitrary (in particular, parallel) architectures, motivated by a generalization of the derivation process for sequential algorithms. The central concept in this approach is that of a skeleton: on the one hand, a higher-order function for targeting transformational derivations at, on the other hand representing an elementary computation on the architecture aimed at. Skeletons thus form a basis for intermediate languages, that can be implemented once and for all, as a process separate from individual program developments. The available knowledge on the derivation of (higher-order) functional programs can be used for deriving parallel ones. In: H. Wijshoff, ed.: Computing Science in the Netherlands 1993, pp. 97-108. Copies on email request or (probably easiest) by clicking ftp://ftp.win.tue.nl/pub/math.prog.construction/skel.ps.Z.

On market dependencies of agents' learning for a hyperinflation model

Abstract: This paper discusses an economic model for hyperinflation considered by Marcet and Sargent The model describes the relation between the current price level, the money supply, and the agents' forecasting of the future price The agents' learning is described by an ARMA-model which is fitted to the available series of old prices It is shown that the agents' learning rate depends upon the inertia of the market, and an implicit formula is given for this dependence A generalization of the hyperinflation model is also discussed

Two-Parameter Crack Tip Field Associated With Stable Crack Growth in a Thin Plate-A Hybrid Analysis

Abstract: : Moire interferometry was used to determine the two orthogonal displacement fields surrounding a stably growing crack in a thin 2024-T3 aluminum alloy, single-edge notched (SEN) specimen. The measured displacements were used to compute the J-integral and the associated HRR and the second order Q displacement fields. Also a 2-D elastic-plastic finite element model of the fracturing specimen was executed in its generation mode to compute the crack tip displacement field and the J-integral for small crack extension. The numerically computed and experimentally derived J-values agreed prior to crack extension but differed increasingly with stable crack growth. The HRR and measured v- displacements agreed well but significant difference between the HRR and measured u displacements was noted. Thus the Q component of the v-displacement was negligible but the corresponding u-component varied nonlinearly with radial distance from the crack tip. Ductile fracture, Moire interferometry, Stable crack growth, J-integral, HRR Field.

Desert bighorn movements and habitat use in relation to the proposed Black Canyon Bridge Project: Nevada

Abstract: In this study, I used information on topography and the distribution of resources in the Eldorado Mountains, Nevada, to characterize bighorn sheep fOvis canadensis) habitat quality, and information on movements of radio-collared bighorn to estimate home range size and patterns of movement. Study results were used to evaluate potential impacts of three proposed highway alignments (Gold Strike Canyon, GSA; Sugarloaf Mountain, SLA; and Promontory Point, PPA) on bighorn sheep. Seasonal preferences for aspect, slope, elevation, distance to water, distance to escape terrain, and land surface ruggedness (LSR) were studied for male and female bighorn sheep. Distinct differences in habitat selection existed between the sexes throughout most of the year. Only during the breeding season did ram preferences approach those of female bighorn sheep. While habitat selection varied between seasons and within seasons between years, general patterns were evident and could be used for distinguishing quality habitat, in general, ewes selected northern and eastern aspects, slopes over 40%, 400-600 m elevations, a reas within 300 m of escape terrain, and areas with LSR index values between 300-750. Ewes averaged 1.1 km from water in summer with 90% of observations within 2.3 km. Rams preferred northern aspects, 20-40% slopes, elevations above 600 m, areas between 200-700 m of escape terrain, and areas with LSR index values between 150-450. Rams averaged 1.7 km from water in summer with 90% of observations within 2.9 km. Total home range size for ewes and rams averaged 19.0 and 49.7 km2, respectively. Mean seasonal home range size for ew es varied little between seasons (range 4.2 to 11.0 km2) with significant range overlap between seasons. No distinct seasonal movement patterns were evident. Mean seasonal home range size for rams varied from 6.7 to 19.6 km2. Larger home range sizes were associated with the breeding season as rams left their bachelor pastures in search of estrous females.

Simulated annealing: comparison of vector and parallel implementations

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Porous Silicon for Pumping Solid-State Lasers

Abstract: : Preliminary experiments were performed to investigate the feasibility of using silicon-based sources to pump solid-state lasers. Photoluminescent porous silicon and porous silicon-on-sapphire (SOS) have been fabricated using chemical, electrochemical, and photochemical techniques. An electrochemically fabricated porous silicon sample exhibited 5% quantum efficiency when pumped with 5 mW of 457.9 nm argon ion laser light with a peak emission wavelength of 720 nm. This is consistent with other reports that efficiencies between 1 and 10% have been observed. This room temperature performance exceeds the early development of light emission from III-V semiconductors and suggests that continued research and development of the emission mechanism and optimization of the fabrication process can produce, at the very least, functionally equivalent results in a less expensive material which is amenable to large-scale integration.

Be3(AsO4)2 2H2O: A new berylloarsenate phase containing bridged tetrahedral 3-rings

Abstract: The high-temperature/high-pressure hydrothermal synthesis and X-ray single crystal structure of Be3(AsO4)2 · 2H2O are described. The title compound contains a three-dimensional network of BeO4 and AsO4 tetrahedra, whose structural motif includes infinite layers of "bridged" tetrahedral 3- and 4-rings. 9Be MAS NMR data are consistent with the Be-atom environments in the crystal structure. Crystal data for Be3(AsO4)2 · 2H2O: Mr = 340.91, monoclinic, space group C2/c (No. 15), a = 16.318(2) A, b = 4.6664(3) A, c = 9.8755(7) A, β = 93.777(3)°, V = 750.37 A3, Z = 4. Final disagreement values of R = 3.59% and Rw = 3.79% were obtained for 1289 observed reflections with I > 3σ(I).

Acoustic-gravity waves from low-altitude localized disturbances

Abstract: : A physics-based analytic model of the ionospheric effects of low- altitude nuclear explosions due to acoustic-gravity waves (AGW) is produced. The model contains the essence of AGW theory predictions while including basic atmospheric chemistry effects to allow descriptions of AGW induced changes for both nighttime and daytime ionospheres. The model allows multiple explosions at arbitrary times and locations although its experimental basis is, of course, from single explosion data.

Chemical and biotic characteristics of two low-alkalinity lakes in northern Wisconsin: relation to atmospheric deposition

Abstract: Synoptic surveys of water chemistry in north-central Wisconsin documented the presence of many low alkalinity lakes potentially sensitive to acid deposition. Furthermore, lake hydrologic type proved to be a key factor in determining lake sensitivity: the low alkalinity systems were predominately seepage lakes. To test this hypothesis and identify the controls on the chemistry of these low alkalinity systems, the authors initiated hydrologic, chemical, biological and limnological studies at Lakes Clara and Vandercook in 1980. The report summarizes the results of those studies (including previously published hydrologic results) conducted between 1981 and 1983. The major goals are to assess the sensitivity of the study lakes to acid deposition and to identify key processes controlling the acid-base chemistry of these software seepage lakes.

Nonlinear Mode Coupling in Free Electron Lasers

Abstract: : The optical field in free electron lasers can sometimes develop sidebands and exhibit very complex behavior. The purpose of this report is to develop a two mode model of the optical field in a free electron laser in which the optical modes are coupled by the free electrons in the laser. This model may be used to study the long term stability of the optical wave and the development of sidebands in the optical field. In this report the equations of motion governing the interaction of an electron with the optical modes will be derived. Free electron lasers, Optical wave.

Statistics of Mass Production

Abstract: : This paper summarizes the statistical quality control methods and procedures that can be employed in mass producing electronic parts (integrated circuits, buffers, capacitors, connectors) to reduce variability and ensure performance to specified radiation, current, voltage, temperature, shock, and vibration levels. Producing such quality parts reduces uncertainties in performance and will aid materially in validating the survivability of components, subsystems, and systems to specified threats.... Survivability, Mass production, Quality control, Process control.

Structural characterization of nylon 7 by solid-state NMR, DSC, and ATR-FTIR

Abstract: : Samples of commercial nylon 7 were given different thermal or precipitation histories. Structure and crystallinity were followed by DSC, solid-state NMR, and attenuated total reflectance FTIR (ATR-FTIR). Delta H and T(sub m) values ranged from 52 to 93 J/g and 228 to 242 deg C, respectively. Surprisingly, annealing did not give material with the greatest delta H although it possessed the highest melting point. Solid-state 13C and 15N NMR methods were used to observe the amorphous and crystalline fractions. For example, the amide nitrogens show resonances near 86.5 ppm in amorphous domains, near 84 ppm in alpha-crystals, and near 89 ppm in gamma-crystals. 15N CP/MAS spectra of solution cast samples contained peaks consistent with all three domains in various intensity ratios but with the gamma-peak being the most intense for most samples. Solid-state 13C spectra contained peaks which supported the presence of these phases but with the alpha-phase peaks predominating.

Subset selection with a generalized selection goal based on a loss function

Abstract: Assume k (integer k = 2) populations are given. The associated independent random variables have continuous distribution functions with an unknown location parameter. The selection goal is to select a non-empty subset which contains the best, in the sense of largest location parameter, population with confidence level P* (k^{-1}

Evolving Information Systems : Meeting the everchanging environment

Abstract: Abstract. To meet the demands of organizations and their ever‐changing environment, information systems are required which are able to evolve to the same extent as organizations do. Such a system has to support changes in all time‐and application‐dependent aspects. In this paper, requirements and a conceptual framework for evolving information systems are presented. This framework includes an architecture for such systems and a revision of the traditional notion of update. Based on this evolutionary notion of update (recording, correction and forgetting) a state transition‐oriented model on three levels of abstraction (event level, recording level, correction level) is introduced. Examples are provided to illustrate the conceptual framework for evolving information systems.

Electric Field Induced Phenomena in STM: Tip Deformation and Au(111)- Surface Phase Transitions during Tunneling Spectroscopy Experiments

Abstract: : We report electric field induced phase transitions of Au(111) surfaces and electric field stress induced elongations of Pt-Ir and Au tips during current voltage measurements with an STM in air. Transitions between the reconstructed square root of 3 x 22 and the unreconstructed 1x1 phase of the Au(111) surface are attributed to changes in the electronic surface excess charge density induced by the electric field between tip and sample. Elongations of STM tips during tunneling spectroscopy give rise to a distinct non-linear current-voltage response at tip-to-sample biases greater than approx. absolute value of 0.5Vl. Similar behaviour is observed during tunneling measurements on pyrolytic graphite and oxidized Ag surfaces. Extensive elongations can result in tip-sample point-contact and tip-fracture. Artificially low values of the apparent barrier height are shown to result from tip elongation.

A current evaluation of the digital beamforming testbed at Rome Laboratory

Abstract: : The purpose of this report is to provide a recent evaluation of the digital beamforming (DBF) testbed at Rome Laboratory, Hanscom AFB, MA. Section 1 of the report provides a brief introduction to digital beamforming and some of the associated concepts. Section 2 briefly discusses each component of the digital beamforming system (form and function) in a top-down fashion. Section 3 discusses some system limitations associated with the receiver architecture and outlines the techniques used to investigate these limitations. Section 4 contains the measurement results, which show in-phase and quadrature errors approximately 27 dB below the signal, and dc offsets approximately 37 dB below the signal. Third order harmonics are also approximately equal 37 dB below the signal. Amplitude variation among the channels is + or -2dB. Removal of the dc offset error had little effect on a 40 dB Taylor pattern. However, removal of the in-phase and quadrature errors (the dominant errors) greatly improved the pattern. Also included are simple examples of super-resolution of two sources spaced about 1/2 beamwidth apart, and of open-loop adaptive nulling for a 20 dB Taylor pattern. Digital beamforming, Adaptive array, Error effects, Error corrections.

Monaural and binaural processing of complex waveforms

Abstract: : During the past year of the granting period, we have continued to make substantial progress consistent with the objectives outlined in our latest proposal. (1) We have completed an extensive analysis of and succeeded in publishing a very comprehensive set of data concerning the amount of 'comodulation masking release' (CMR) that can be obtained when the coherent envelope information is presented successively rather than simultaneously. It was determined that 'off-frequency' information, such as that which usually produces a CMR, can provide only a very small release from masking when it is presented prior and subsequent to the temporal interval containing the signal. The most striking finding was that the threshold for detecting a 1-kHz tone masked by an 50-Hz-wide band of noise centered on 1 kHz, was reduced by 7 dB when an identical, 'on frequency', masking noise was presented in all four intervals of our two-cue, two-interval, forced-choice procedure. (2) We finished three other papers, one of which was published and two of which have been revised and resubmitted. (3) We are currently collecting data concerning how varying the forward fringe of a masker affects the magnitude of the binaural masking-level difference. The experiments are being conducted with low-frequency signals where the interaural cues are conveyed by the fine-structure of the waveform and with high-frequency signals where the interaural cues are conveyed via the envelope of the waveform.

Defect Initiation/Growth and Energy Dissipation Induced by Deformation and Fracture

Abstract: : Based on our capabilities to (a) detect and characterize particle release from surfaces on fast time scales, (b) to measure rapid electrical transients, and (c) to obtain high resolution topographical information utilizing scanning tunneling and atomic force microscopy, we have investigated a number of defect initiation and growth processes which ultimately leads to fracture and energy dissipation. We employ dynamic methods as well as post- fracture examination in polymers, ceramics, metals, and interfaces. We have examined mechanisms, with interpretation and connections between these results and the creation and evolution of defects in materials under mechanical stress. The information we, are acquire with our techniques has important implications concerning dissipation of energy (e.g., plastic deformation, microcracking, crack branching, and crack deflection) which play critical roles in controlling the strength and toughness of materials. Deformation, Crack propagation, Fracture, Particle emission, Fractro-emission, Interfacial failure, Crazing, Electrical transients, Micro-Cracking, Contact charging, Fractography, Scanning tunneling, Microscopy, Atomic force microscopy, Photoluminescence, Chemisorptive electron emission.