Numerical modelling of a high temperature silicification process in the carbon-carbon porous medium

A mathematical model has been developed to describe the process of a high-temperature silicification process in a carbon-carbon porous material. The statement of the problem is based on general equations describing the clogging of tubules in a porous medium with various kinds of impurities. In the problem under consideration, the cause of blockage is the condensation of gaseous silicon on the inner walls of the pores. Temperature dependences for the coefficients of condensation and evaporation are proposed, which characterize the intensity of this process. It is assumed that the diffusion of gas is the main mechanism of initial filling pores of the material. Numerical modeling was carried out by the finite difference method using an explicit scheme in the case of a constant value of the mobile concentration at the input and for imposed linear temperature distribution on the vertical boundaries of the sample. Such temperature distribution made it possible to describe a partially silicified region and to delimit from it the sample part that remains “dry” during this process. The dynamics of the main physical characteristics, i.e. porosity of the composite material and concentration of the immobile component in the volume, is analyzed. The external factors influencing the intensity of the condensation process are considered quantitatively, namely, the concentration of the mobile component in the volume is calculated as a function of time. For the characteristic time interval, the maximum change in the porosity of the medium is calculated, on the basis of which the time of complete saturation of the material is estimated, which, as it turned out, is equal about 2 hours. The results of numerical simulation for silicification time and weight gain of the product are in qualitative and quantitative agreement with the known experimental data.

On Application of Hyperfree Energy for the Description of Thermodynamics of Mobile Components in Nonstoichiometric Partially Open Ceramic Systems

Nonstoichiometric oxides form a new chapter in tailored materials. Founding and construction of thermodynamic functions related to solid (geologic, metallurgic) materials is traced showing interactions between Czech Professor F. Wald and Russians R.S. Kurnakov and D.S. Korzhinskiĭ and further developed by Czech P. Holba in the initial phase definition and related characterization of partially open systems. A gradual increase in thermodynamic concepts related to solid-state description is investigated in more detail. For the associated thermodynamic definition of the mobile component, the previously formulated hyperfree energy function, which was recently applied to several systems, was used. As a measure of the material disposition for the absorption of the free component, an innovative term of plutability is proposed, which allows the introduction of various forecaster variables such as temperature, pressure, and activity. Examples of practical application are examples of high-temperature superconducting materials, where the Czech school of thermodynamics is emphasized.

A Citizen-Centric Approach for the Improvement of Territorial Services Management

In the last decade, there has been a growing awareness that the involvement of citizens in decision making can produce an immediate and positive impact on actions to be taken, as they are the real owners of knowledge about the place where they live. By collecting and geolocating data through smartphones and the Internet, citizens in fact can help decision makers both create sharable spatio-temporal information about objects and phenomena and interpret territorial dynamics. However, although such a role has been definitely recognized, the lack of a homogeneous paradigm for structuring the sensing process, managing the geo big data produced and handling services makes it difficult to exploit such a potentiality. In this paper, we describe a citizen-centric approach conceived to build territorial knowledge useful to provide decision makers with a timely and reliable picture of the status of a given territory. In particular, a visual representation of geospatial knowledge is described, which summaries context-sensitive information about a territory and its citizens, thus improving the land monitoring tasks. An information system, SAFE, is finally presented, which consists of a Web and a mobile component to manage citizen supplied data to be integrated for building reliable dynamic scenarios.

Monte Carlo Simulation of Correlation Effects in a Random SC Alloy via Interstitialcy Mechanisms

In this paper some recent progress in the area of Monte Carlo simulation of diffusion via the interstitialcy mechanism in a randomly ordered binary alloy is reviewed. Topics discussed include the calculation of tracer correlation factorsfA and fBas a function of composition and jump frequency ratiowA/wBand interstitialcy correlation factors fI; which play a crucial role in the interpretation of ion-conductivity data. The percolation behavior of fI when wA ≪ wB is analysed in detail and limits of the tracer diffusivity ratios bD A/bD B for alloy compositions below thepercolation threshold are presented. Allowance for non-collinear jumps (partly) replacing concurrent collinear site exchanges leads to a reduction of diffusion correlation effects.This goes along with a shift of the diffusion percolation threshold to lower concentrations of the (more) mobile component B. Even stronger changes of mass and charge transport compared to an exclusively collinear interstitialcy scheme are observed for additional contributions of direct interstitial jumps. It is remarkable that for both extensions of interstitialcy-mediated diffusion the Haven ratio appears to be greater than unity in certain compositionranges poor in B.

A Context-Aware Museum-Guide System Based on Cloud Computing

This paper proposes a context-aware museum-guide system, which is able to present information on exhibits in accordance with visitor needs. Other features of the system include planning and directing a visit as well as providing locations, facilities and additional services. The architecture is designed based on the attribute-driven design method. It consists of two components including mobile and server components. The server component is located in the cloud and is regarded as the backup for the mobile component. The software architecture analysis method is employed to evaluate the proposed architecture. To this end, some scenarios have been codified for system functionalities by consulting museum experts. The proposed architecture satisfies the scenarios by resolving the issues arisen in each one. The CIF-based questionnaire method indicates a high usability score for the proposed system. Finally, comparison of the capabilities of the proposed system with related research reveals that it benefits from a comprehensive design.

Beyond Mapping: Seizing Affective Geographies in Toronto

In this article, I use a recent research creation project and its mobile component (the TiP lab) to emphasize the importance of regarding the city as an entanglement of sometimes evident, sometimes hidden naturecultural geographies and more-than-human encounters. While official narratives are not interested in narrating such vibrant multidimensionality, traditional cartographic practices do not seem to be able to seize them. In exploring ways to illuminate such complexity, I interrogate the ability of contemporary mapping devices to capture, and valorize, the vectors through which the human and the nonhuman, people and infrastructures shape the urban landscapes in which they live and through which they pass.

Extensive horizontal exchange of transposable elements in the Drosophila pseudoobscura group

While the horizontal transfer of a parasitic element can be a potentially catastrophic, it is increasingly recognized as a common occurrence. The horizontal exchange, or lack of exchange, of TE content between species results in different levels of divergence among a species group in the mobile component of their genomes. Here, we examine differences in the TE content of the Drosophila pseudoobscura species group. We identify several putative horizontal transfer events, and examine the role that horizontal transfer plays in the spread of TE families to new species and the homogenization of TE content in these species. Despite rampant exchange of TE families between species, we find that both TE content differs hugely across the group, likely due to differing activity of each TE family and differing suppression of TEs due to divergence in Y chromosome size, and its resulting effects of TE regulation. Overall, we show that TE content is highly dynamic in this species group, and that it plays a large role in shaping the differences seen between species.Data availabilityAll data used in this study (summarized in table S1) is freely available online through the NCBI short read archive (NCBI SRA: ERR127385, SRR330416, SRR330418, SRR1925723, SRR330426, SRR330420, SRR330423, SRR617430-74). All genomes used are either available through flybase.org or popoolation.at.