Verification of the proteus two-dimensional Navier-Stokes code for flat plate and pipe flows

The Proteus Navier-Stokes Code is evaluated for 2-D/axisymmetric, viscous, incompressible, internal, and external flows. The particular cases to be discussed are laminar and turbulent flows over a flat plate, laminar and turbulent developing pipe flows, and turbulent pipe flow with swirl. Results are compared with exact solutions, empirical correlations, and experimental data. A detailed description of the code set-up, including boundary conditions, initial conditions, grid size, and grid packing is given for each case

Analysis of cutting parameters in point machining of parts with complex shape

This paper presents developed SW module in the postprocessor, which is designed to backward analysis of CAM milling toolpath. The module is designed to analyze multi-axis finishing machining of complex shape parts with milling cutters with a circular cutting edge. In CAM, the milling cutter diameter is entered by a constant value of the maximum cutting diameter, but moving of the contact point between the milling cutter and the work piece, the actual cutting diameter changes over the machining cycle. By conventionally entering of the constant diameter into CAM, required technological cutting parameters are not adhered in some cases, and thus the resulting quality and productivity are not achieved. This developed SW tool is implemented directly into the postprocessor for generating NC programs. This Analysis Module designed as a tool for technologists and for CNC programators to visualize and to optimize the machining process with respect to adhere cutting parameters

Atomistic models of hydrogenated amorphous silicon nitride from first principles

We present a theoretical study of hydrogenated amorphous silicon nitride (a-SiNx:H), with equal concentrations of Si and N atoms (x=1), for two considerably different densities (2.0 and 3.0 g/cm3). Densities and hydrogen concentration were chosen according to experimental data. Using first-principles molecular-dynamics within density-functional theory the models were generated by cooling from the liquid. Where both models have a short-range order resembling that of crystalline Si3N4 because of their different densities and hydrogen concentrations they show marked differences at longer length scales. The low-density nitride forms a percolating network of voids with the internal surfaces passivated by hydrogen. Although some voids are still present for the high-density nitride, this material has a much denser and uniform space filling. The structure factors reveal some tendency for the nonstoichiometric high-density nitride to phase separate into nitrogen rich and poor areas. For our slowest cooling rate (0.023 K/fs) we obtain models with a modest number of defect states, where the low (high) density nitride favors undercoordinated (overcoordinated) defects. Analysis of the structural defects and electronic density of states shows that there is no direct one-to-one correspondence between the structural defects and states in the gap. There are several structural defects that do not contribute to in-gap states and there are in-gap states that do only have little to no contributions from (atoms in) structural defects. Finally an estimation of the size and cooling rate effects on the amorphous network is reported.

Mesoscopic study on historic masonry

This paper presents a comprehensive approach to the evaluation of macroscopic material parameters for natural stone and quarry masonry. To that end, a reliable non-linear material model on a meso-scale is developed to cover the random arrangement of stone blocks and quasi-brittle behaviour of both basic components, as well as the impaired cohesion and tensile strength on the interface between the blocks and mortar joints. The paper thus interrelates the following three problems: (i) definition of a suitable periodic unit cell (PUC) representing a particular masonry structure; (ii) derivation of material parameters of individual constituents either experimentally or running a mixed numerical-experimental problem; (iii) assessment of the macroscopic material parameters including the tensile and compressive strengths and fracture energy.Comment: 38 pages, 15 figure

European Demographic Datasheet 2016

The European Demographic Datasheet 2016 shows key demographic data, population trends and projections until 2050. It covers fertility, mortality, migration and population structure, including population ageing, and their changes. The datasheet combines data for all countries of Europe and for broader European regions, as well as maps, population pyramids, tables, graphs and featured thematic boxes. It pays special attention to the importance of migration for the current and future population changes across the continent and to the alternative indicators of population ageing. In comparison to the Data Sheet Poster, the online version provides expanded data coverage, additional maps and population pyramids, ranking charts and details about data sources and definitions. It also allows users to download all data and images

A jigsaw puzzle metamaterial concept

A concept of a planar modular mechanical metamaterial inspired by the nature's principle of local adaptivity is proposed. The metamaterial consists of identical pieces similar to jigsaw puzzle tiles. Their rotation within assembly provides a substantial flexibility in terms of structural behavior and mechanical interlocks enable reassembly. The tile design with a diagonal elliptical opening allows us to vary elastic properties--from stiff to compliant, with positive, zero, or negative Poisson's ratio. The outcomes of experimental testing on additively manufactured specimens confirm that the assembly properties can be accurately designed using optimization approaches with finite element analysis at heart.Comment: 9 pages, 8 figure