Semiotic Exograms: Extending the Mind Fully

This essay is an analysis and expanded defense of John Sutton’s essay “Exograms and Interdisciplinarity: History, the Extended Mind, and the Civilizing Process.” The first section of the essay surveys the extended mind literature, following the first and second waves of the Extended Mind theory. The second section explains Sutton’s exograms as external representations of internal thought. This section also details his argument that exograms extend the mind because, historically, exograms play a role in the internal functioning of a mind. The third section defends Sutton’s argument from objections against their place in mental processes, namely memory. The fourth section argues against the objection that the mind cannot be extended beyond the brain, by appealing to a computational view of functionalism. The conclusions drawn from the third and fourth sections are that the mind, through language, extends with culture and that, even in cognitive science, it is fruitful to study the mind extended as such

Semiotic Exograms: Extending the Mind Fully

This essay is an analysis and expanded defense of John Sutton’s essay “Exograms and Interdisciplinarity: History, the Extended Mind, and the Civilizing Process.” The first section of the essay surveys the extended mind literature, following the first and second waves of the Extended Mind theory. The second section explains Sutton’s exograms as external representations of internal thought. This section also details his argument that exograms extend the mind because, historically, exograms play a role in the internal functioning of a mind. The third section defends Sutton’s argument from objections against their place in mental processes, namely memory. The fourth section argues against the objection that the mind cannot be extended beyond the brain, by appealing to a computational view of functionalism. The conclusions drawn from the third and fourth sections are that the mind, through language, extends with culture and that, even in cognitive science, it is fruitful to study the mind extended as such

The Compelling Case for Indentation as a Functional Exploratory and Characterization Tool

The utility of indentation testing for characterizing a wide range of mechanical properties of brittle materials is highlighted in light of recent articles questioning its validity, specifically in relation to the measurement of toughness. Contrary to assertion by some critics, indentation fracture theory is fundamentally founded in Griffith–Irwin fracture mechanics, based on model crack systems evolving within inhomogeneous but well-documented elastic and elastic–plastic contact stress fields. Notwithstanding some numerical uncertainty in associated stress intensity factor relations, the technique remains an unrivalled quick, convenient and economical means for comparative, site-specific toughness evaluation. Most importantly, indentation patterns are unique fingerprints of mechanical behavior and thereby afford a powerful functional tool for exploring the richness of material diversity. At the same time, it is cautioned that unconditional usage without due attention to the conformation of the indentation patterns can lead to overstated toughness values. Limitations of an alternative, more engineering approach to fracture evaluation, that of propagating a pre-crack through a 'standard' machined specimen, are also outlined. Misconceptions in the critical literature concerning the fundamental nature of crack equilibrium and stability within contact and other inhomogeneous stress fields are discussed.This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1111/jace.1372

Metal-Ceramic Interfaces in Laser Coated Aluminium Alloys

A novel process was developed to firmly coat an aluminium alloy, Al6061, with α-Al2O3 by means of laser processing. In this approach a mixture of SiO2 and Al powder was used to inject in the laser melted surface of aluminium. A reaction product α-Al2O3 layer of a thickness of 100 µm was created which was well bonded to the aluminium surface. Various interfaces, Al/α-Al2O3, Al/mullite and α-Al2O3/mullite, were studied by conventional transmission electron microscopy (CTEM) and high resolution electron microscope (HREM). It turns out that the presence of the Al/mullite interface may be essential to form a well bonded oxide layer and the high Si-content α-Al2O3 intermediate layer may be wetted better by liquid Al. Investigations of the interface structures and wetting phenomena during laser processing are presented and a simple correlation between wetting phenomena and interface strength is derived.

Strategies to strengthen ceramics for windows and domes

Strengthening of transparent ceramics is highly constrained by the fact that the classic methods to toughen ceramics, via microstructure modification, increase light scattering. Nonetheless, improvements are possible when a composite approach is applied at the nanoscale. For example, attempts to toughen spinel by reinforcing with alumina show modest gains. This paper discusses those efforts and examines the possibility of applying the concept to other ceramics. Strategies and limitations for windows and domes, for which the transparency requirements are not as stringent as for some other optical applications, are discussed. Please click Additional Files below to see the full abstract

Elastic constants of beta-eucryptite: A density functional theory study

The five independent elastic constants of hexagonal $\beta$-eucryptite have been determined using density functional theory (DFT) total energy calculations. The calculated values agree well, to within 15%, with the experimental data. Using the calculated elastic constants, the linear compressibility of $\beta$-eucryptite parallel to the c-axis, $\chi_c$, and perpendicular to it, $\chi_a$, have been evaluated. These values are in close agreement to those obtained from experimentally known elastic constants, but are in contradiction to the direct measurements based on a three-terminal technique. The calculated compressibility parallel to the c-axis was found to positive as opposed to the negative value obtained by direct measurements. We have demonstrated that $\chi_c$ must be positive and discussed the implications of a positive $\chi_c$ in the context of explaining the negative bulk thermal expansion of $\beta$-eucryptite.Comment: 3 eps figures, submitted for publicatio

Variable fresh snow albedo: how snowpack and sub-nivean properties influence fresh snow reflectance

2021 Fall.Includes bibliographical references.The understanding of albedo, or ratio of outgoing to incoming shortwave radiation, is necessary for modeling the melt characteristics of a snowpack in snow-dominated areas. The timing and supply of meltwater downstream is influenced by the energy balance, and albedo is used in those calculations. Current snow albedo models range from simple models that only reset albedo with new snowfall to complex models that are not feasible for most applications. We present a variable fresh snow model that enhances a simple albedo model, initially created by the U.S. Army Corps of Engineers, and used extensively in the Canadian LAnd Surface Scheme (CLASS). The new approach considers conditions prior to and during a snowfall event to improve fresh snow albedo estimates, instead of resetting to a static value; it also considers differences in the albedo decay rate.Hourly shortwave radiation (incoming and outgoing), snow depth, temperature, and other meteorological data from two stations at the Senator Beck Basin in the San Juan Mountains of Southwest, Colorado were used for the period from 2005 to 2014. We evaluated changes in albedo of a high-elevation seasonal snowpack during fresh snow events and apply a set of multivariate regressions to recreate values of broadband albedo. The variable fresh snow albedo model approaches the Visible and Near-Shortwave Infrared portion of the electromagnetic spectrum differently and groups values by temperature. The model needs few inputs, specifically measurements of depth and temperature, an estimation of ground albedo, and for increased accuracy, a quantification of the number of aeolian dust deposition events on the snowpack every year. This variable fresh snow model showed higher accuracy in albedo values, both of fresh and decayed snow (R2 of 0.77 and Nash Sutcliffe Efficiency, NSE of 0.75) than of CLASS (R2 of 0.67 and NSE of 0.62). When isolating fresh snow events, the variable fresh snow albedo model was much more accurate than the single-reset albedo provided by CLASS but still had a weak correlation to measured values (R2 of 0.38). The variable fresh snow albedo model especially outperformed CLASS during the melt period, with ~24% more accurate absorption values to measured values than CLASS. Since fresh snow albedo is primarily weighted by albedo from the timestep before, we suggest this model also be used to correct erroneous values of albedo given incorrect sensor measurements, such as due to snow accumulation on the upward looking shortwave radiation sensor (pyranometer)

Nanostructured metal-ceramic composites by internal reduction

The nucleation and growth of metallic particles within metal-doped oxides exposed to reducing conditions is relevant to the processing of materials for catalysts, fuel cells, and structural applications. Here, the precipitation of metallic nickel during the internal reduction of nickel-doped yttria stabilized zirconia (YSZ) is studied with electron microscopy and SQUID magnetometry. It is shown that the microstructure evolution proceeds in three distinct stages, each with its own kinetics description, dependent on the porosity and grain size. The transitions between stages depend on concentration gradients and electrostatic potentials that act upon the relevant transporting species, namely oxygen vacancies, electrons, nickel ions and zirconium vacancies. An understanding of these mechanisms enables the design of specific nanostructure

Niobium Oxide-Metal Based Seals for High Temperature Applications

The present final report describes technical progress made in regards to evaluating niobium oxide/alumina as a high temperature seal material. Fabrication and characterization of specimens comprising niobium oxide and alumina composites of various compositions was performed. The goal was to identify regions where a glass formed. There were no experimental conditions where a glassy phase was unequivocally identified. However, the results led to the formation of an interesting class of fibrous composites which may have applications where high compliance and high toughness are needed. It is clear that vapor phase sintering is an active mass transport mechanism in Nb{sub 2}O{sub 5}-Al{sub 2}O{sub 3} composites (Figure 1), and it may be possible to design porous materials by utilizing vapor phase sintering. The compositions evaluated in the present work are 52, 60, 73, 82 and 95 mol. % Nb{sub 2}O{sub 5} with the remainder Al{sub 2}O{sub 3}. These were chosen so that some eutectic composition was present during cooling, in an attempt to encourage glass formation. However, the presence of large, elongated crystals, both in the slow cool and the quench experiments indicates that the driving force for crystallization is very high. Several joints were formed between high purity alumina with two compositions (60 and 82 mol. %) forming the joint. These were created by grinding and polishing alumina surfaces and stacking them end-to-end with the powdered Nb{sub 2}O{sub 5}-Al{sub 2}O{sub 3} material in between. Joining was accomplished in air at temperatures between 1400 C and 1450 C. The joints failed during subsequent machining for strength bars, indicating low strength. It may be possible to use the compositions evaluated here as a joint material, but it seems unlikely that a glassy phase could be produced while joining