Projection method for flows with large local density gradients: Application to dendritic solidification

2008 ◽  
Vol 57 (9) ◽  
pp. 1211-1226 ◽  
Author(s):  
J. C. Heinrich ◽  
U. K. Sajja ◽  
S. D. Felicelli ◽  
D. G. Westra
Keyword(s):  
Projection Method ◽  
Local Density ◽  
Density Gradients ◽  
Dendritic Solidification

scholarly journals The attraction of urban cores: Densification in Dutch city centres

Urban Studies ◽  
2019 ◽  
Vol 57 (9) ◽  
pp. 1920-1939 ◽  
Author(s):  
Dani Broitman ◽  
Eric Koomen
Keyword(s):  
Local Density ◽  
Basic Feature ◽  
Density Gradients ◽  
Transport Costs ◽  
Urban Density ◽  
Urban Economic ◽  
Empirically Supported ◽  
Spatio Temporal ◽  
The Impact ◽  
Dutch Cities

Urban growth is typically considered a process of expansion. As population grows and transport costs decrease urban density gradients are expected to gradually flatten. This is a basic feature of cities, explained by urban economic models and empirically supported by a plethora of studies about urban density development from all over the world. However, additional forces, such as changes in demographic composition and locational preferences of the urban population acting at local levels, may counteract the flattening tendency of urban gradients. In this paper, we suggest a methodology to test the impact of local density changes on urban gradients, looking at spatio-temporal developments in terms of housing and population. Using highly detailed data on individual housing units and inhabitants in major Dutch cities, we first assess and compare urban density gradients during the period 2000–2017. In all the analysed Dutch cities, both dwelling and population density gradients are becoming steeper over time, contradicting standard predictions from urban economic literature and empirical reports worldwide. The observed trend of steepening urban gradients is partly explained by the presence of historical monuments and urban amenities.

Ab initio band theory approach to electron energy loss near edge structures

1988 ◽  
Vol 46 ◽  
pp. 506-507
Author(s):  
Xudong Weng ◽  
O.F. Sankey ◽  
Peter Rez
Keyword(s):  
Ab Initio ◽  
Local Density ◽  
Interpolation Method ◽  
Atomic Orbital ◽  
Plane Waves ◽  
Large Set ◽  
Theory Approach ◽  
Band Theory ◽  
Atomic Orbitals ◽  
Pseudopotential Calculations

Single electron band structure techniques have been applied successfully to the interpretation of the near edge structures of metals and other materials. Among various band theories, the linear combination of atomic orbital (LCAO) method is especially simple and interpretable. The commonly used empirical LCAO method is mainly an interpolation method, where the energies and wave functions of atomic orbitals are adjusted in order to fit experimental or more accurately determined electron states. To achieve better accuracy, the size of calculation has to be expanded, for example, to include excited states and more-distant-neighboring atoms. This tends to sacrifice the simplicity and interpretability of the method.In this paper. we adopt an ab initio scheme which incorporates the conceptual advantage of the LCAO method with the accuracy of ab initio pseudopotential calculations. The so called pscudo-atomic-orbitals (PAO's), computed from a free atom within the local-density approximation and the pseudopotential approximation, are used as the basis of expansion, replacing the usually very large set of plane waves in the conventional pseudopotential method. These PAO's however, do not consist of a rigorously complete set of orthonormal states.

Flux-pinning-related defect structures in melt-processed YBa2Cu3O7-x

1993 ◽  
Vol 51 ◽  
pp. 936-937
Author(s):  
Z. L. Wang ◽  
R. Kontra ◽  
A. Goyal ◽  
D. M. Kroeger ◽  
L.F. Allard
Keyword(s):  
Volume Fraction ◽  
Local Density ◽  
Stacking Faults ◽  
Image Resolution ◽  
Defect Structures ◽  
Atomic Structures ◽  
Transmission Electron ◽  
Point Image ◽  
Related Defect ◽  
Point To Point

Previous studies of Y2BaCuO5/YBa2Cu3O7-δ(Y211/Y123) interfaces in melt-processed and quench-melt-growth processed YBa2Cu3O7-δ using high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS) have revealed a high local density of stacking faults in Y123, near the Y211/Y123 interfaces. Calculations made using simple energy considerations suggested that these stacking faults may act as effective flux-pinners and may explain the observations of increased Jc with increasing volume fraction of Y211. The present paper is intended to determine the atomic structures of the observed defects. HRTEM imaging was performed using a Philips CM30 (300 kV) TEM with a point-to-point image resolution of 2.3 Å. Nano-probe EDS analysis was performed using a Philips EM400 TEM/STEM (100 kV) equipped with a field emission gun (FEG), which generated an electron probe of less than 20 Å in diameter.Stacking faults produced by excess single Cu-O layers: Figure 1 shows a HRTEM image of a Y123 film viewed along [100] (or [010]).

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