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In this work, coatings of composite carbide materials applied via electrospark deposition (ESD) with a low pulse energy on the most widely used titanium alloy Ti6Al4V and on a commercially pure titanium Ti-GR2 were obtained and studied. Dense coatings with sparse micropores and roughness Ra 2–5 μm, thickness 10–25 μm, and microhardness up to 3–4 times higher than those of the substrate were obtained. The influence of the electrode materials and the energy parameters of the ESD process on the roughness, thickness, microhardness, composition, and structure of the coatings and on their wear resistance were studied. A comparative analysis of the qualitative characteristics, composition, structure, and properties of the obtained coatings was made. The results of comparative studies at dry friction show that coatings from the TiCN-based composite electrodes, of the multicomponent ones based on WC, TiB2, and B4C, and from the electrodes based on TiB2 with nanostructured additives can achieve up to a threefold increase in the wear resistance of layered surfaces. Based on the results obtained, suitable materials for electrodes and parameters of the modes for their deposition were indicated. [ABSTRACT FROM AUTHOR]

This paper discusses the essence and technological characteristics of the process of electrospark deposition (ESD), its advantages and disadvantages with a view to its application for improving the tribological properties of titanium and its alloys. A summary of the available data and results in the literature devoted on the ESD of titanium and its alloys has been made. Based on the published data, a comparative analysis of the technical parameters and technological capabilities of the most common equipment, including contactless ESD, is presented. The geometrical and physico-mechanical characteristics of the coatings obtained with different equipment and the nature of their change depending on the technological parameters of the ESD mode and the type of the anode and cathode materials are shown. A summary of the data on the wear resistance of the coatings obtained with different electrode materials and modes are given. It has been demonstrated that ESD can be successfully applied to improve the wear resistance of titanium surfaces. Suitable electrode materials and process parameters for ESD on titanium alloys are indicated. [ABSTRACT FROM AUTHOR]

The advanced research version of the weather research and forecasting model was employed to simulate Intense Operational Periods of the field campaigns of the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program with a 0.5 km horizontal resolution. The focus was on synoptically dominated stably stratified periods, with the mean flow approaching a strongly non-symmetrical rugged topography—the Granite Mountain of the US Army Dugway Proving Ground, Utah. The model was validated against a comprehensive set of MATERHORN data. The special in-house developed software enabled calculations of energetics and pressure anomalies along individual streamlines and tracing of spatial trajectories of streamlines. Owing to complexities of natural flows, for example, the directional shear (skewed vertical velocity profiles) and irregular topographic shape, the flow patterns depend on multiple parameters, although in idealized cases the flow is described by a single parameter (Froude number or a variant). Streamlines at different altitudes of a given location diverged rapidly, making it difficult to study the dividing streamline concept. The new software allowed identification of the dividing streamline passing over the highest crest (summit) of the mountains and its trajectory. The upstream height of the dividing streamline did not follow the well-known Sheppard's formula. Three cases of flow patterns are presented, identified based on the presence of lee waves, flow separation, horizontal vortex shedding and hydraulics jumps. [ABSTRACT FROM AUTHOR]

Micrometeorological conditions in the vicinity of urban buildings strongly influence the requirements that are imposed on building heating and cooling. The goal of the present study, carried out within the Advance Tools for Rational Energy Use towards Sustainability (ATREUS) European research network, is the evaluation of the wind field around buildings with walls heated by solar radiation. Two computational fluid dynamics (CFD) codes were validated against extensive wind-tunnel observations to assess the influence of thermal effects on model performance. The code selected from this validation was used to simulate the wind and temperature fields for a summer day in a specific region of the city of Lisbon. For this study, the meteorological data produced by a non-hydrostatic mesoscale atmospheric model (MM5) were used as boundary conditions for a CFD code, which was further applied to analyze the effects of local roughness elements and thermodynamic conditions on the air flow around buildings. The CFD modelling can also provide the inflow parameters for a Heating, Ventilation and Air Conditioning (HVAC) system, used to evaluate the building energy budgets and to predict performance of the air-conditioning system. The main finding of the present three-dimensional analyses is that thermal forcing associated with the heating of buildings can significantly modify local properties of the air flow. [ABSTRACT FROM AUTHOR]

The chemical properties of beta zeolite are interconnected with its structure in a complicated way. In general terms, the strength of the acid sites in the beta phase depends strongly on its structure, topology and composition. The quantum chemical calculations of the beta zeolite cluster model have been carried out in order to predict how the cluster's local structure influences the geometric parameters and thus affects the chemical functionality of the beta zeolite. Computer simulations of a beta zeolite model with one lattice aluminium, or boron, or titanium or vanadium ions and of its acidic centres have been carried out. The acidity of the framework oxygen atoms in the vicinity of the lattice atom centre has been calculated and compared. The reactivity of catalytic species comprisingthe lattice ion and a hydroperoxo ligand has been studied as an oxidising site. [ABSTRACT FROM AUTHOR]

Different methods and vanadium compounds have been used to carry out proton exchange of zeolite HZSM-5 by vanadium cations. The catalysts are characterized by specific surface area, XRD, IR spectroscopy and TPD of ammonia. The catalysts' activity in the oxidation of 1,3-pentadiene and the selectivity to carbonyl compounds are compared. [ABSTRACT FROM AUTHOR]

Three types of aluminum alloys such as AlSi7Mg, AlSi12Cu2MgNi and AlZn4 are refined by introducing nanoparticles of high melting temperature compounds-nitrides and carbides as well as diamonds in the melt. Their influence on microstructure, mechanical and some electrochemical properties of castings of these alloys is investigated. It is established that the microstructure is refined, the porosity is decreased, and some mechanical and electrochemical properties such as protection potential in drinking water are increased. The mechanism of grain refinement and silicon modification is discussed. [ABSTRACT FROM AUTHOR]