55 research outputs found
Una Finestra su: Tirana
L'Albania è nel mezzo di una profonda crisi identitaria. La tesi viene esposta attraverso una lettura dellâambiente costruito in una particolare area tra Tirana e Durazzo, caratterizzata da una mistura di stili arhitettonici, presi in prestito da luoghi e tempi diversi.
Le immagini che accompagnano questo articolo forniscono testimonianza visiva di questo cammino identitario del popolo albanese
The Small Unit Cell Reconstructions of SrTiO3 (111)
We analyze the basic structural units of simple reconstructions of the (111)
surface of SrTiO3 using density functional calculations. The prime focus is to
answer three questions: what is the most appropriate functional to use; how
accurate are the energies; what are the dominant low-energy structures and
where do they lie on the surface phase diagram. Using test calculations of
representative small molecules we compare conventional GGA with higher-order
methods such as the TPSS meta-GGA and on-site hybrid methods PBE0 and TPSSh,
the later being the most accurate. There are large effects due to reduction of
the metal d oxygen sp hybridization when using the hybrid methods which are
equivalent to a dynamical GGA+U, which leads to rather substantial improvements
in the atomization energies of simple calibration molecules, even though the
d-electron density for titanium compounds is rather small. By comparing the
errors of the different methods we are able to generate an estimate of the
theoretical error, which is about 0.25eV per 1x1 unit cell, with changes of
0.5-1.0 eV per 1x1 cell with the more accurate method relative to conventional
GGA. An analysis of the plausible structures reveals an unusual low-energy
TiO2-rich configuration with an unexpected distorted trigonal biprismatic
structure. This structure can act as a template for layers of either TiO or
Ti2O3, consistent with experimental results as well as, in principle, Magnelli
phases. The results also suggest that both the fracture surface and the
stoichiometric SrTiO3 (111) surface should spontaneously disproportionate into
SrO and TiO2 rich domains, and show that there are still surprises to be found
for polar oxide surfaces.Comment: 14 pages, 4 Figure
Building future societies? A brief analysis of Bragaâs school bus project
This paper seeks to demonstrate the importance of implementing trans-
port policies that meet home to school (and vice versa) mobility needs of children
and young people. Over the last few years familiesâ mobility has been given
increasing attention. One of the most investigated aspects is home to work mobil-
ity. Nowadays there is an urgent need to study and propose intervention measures
regarding childrenâs mobility to school. In fact, studies show that the car is the
preferred mode of transportation in Portugal. This trend has undoubtedly negative
social, environmental and health consequences. Based on an evaluation study on
the School Bus project in Braga (a research- intervention activity of BUILD-Braga
Urban Innovation Laboratory Demonstrator), this paper discusses the difficulties
in implementing sustainable mobility initiatives, pointing out anticipatory mea-
sures that can be taken in medium-sized cities in order to stop the expansion of
childrenâs transportation by car, and give them back spaces in the cities.UIDB/00736/202
First-principles study of the polar O-terminated ZnO surface in thermodynamic equilibrium with oxygen and hydrogen
Using density-functional theory in combination with a thermodynamic formalism
we calculate the relative stability of various structural models of the polar
O-terminated (000-1)-O surface of ZnO. Model surfaces with different
concentrations of oxygen vacancies and hydrogen adatoms are considered.
Assuming that the surfaces are in thermodynamic equilibrium with an O2 and H2
gas phase we determine a phase diagram of the lowest-energy surface structures.
For a wide range of temperatures and pressures we find that hydrogen will be
adsorbed at the surface, preferentially with a coverage of 1/2 monolayer. At
high temperatures and low pressures the hydrogen can be removed and a structure
with 1/4 of the surface oxygen atoms missing becomes the most stable one. The
clean, defect-free surface can only exist in an oxygen-rich environment with a
very low hydrogen partial pressure. However, since we find that the
dissociative adsorption of molecular hydrogen and water (if also the
Zn-terminated surface is present) is energetically very preferable, it is very
unlikely that a clean, defect-free (000-1)-O surface can be observed in
experiment.Comment: 10 pages, 4 postscript figures. Uses REVTEX and epsf macro
Sustainable Urban Transport in the Developing World: Beyond Megacities
Megacities have frequently received a disproportionate amount of attention over other sizes of cities in recent discourse on urban sustainability. In this article, the authors argue that a focus on smaller and medium-sized cities is crucial to achieving substantial progress towards more sustainable urban development, not only because they are home to at least a quarter of the worldâs population but because they also offer great potential for sustainable transformations. In principle, their size allows for flexibility in terms of urban expansion, adoption of âgreenâ travel modes, and environmental protection. At the same time, smaller and medium-sized cities often have fewer resources to implement new transport measures and can be more vulnerable to fluctuations in the world economy. This article critically reviews the potential role and impact of nine commonly considered options for sustainable urban transport in cities in developing countries: (1) road infrastructure; (2) rail-based public transport; (3) road-based public transport; (4) support for non-motorized travel modes; (5) technological solutions; (6) awareness-raising campaigns; (7) pricing mechanisms; (8) vehicle access restrictions; and (9) control of land-uses. Drawing on international research and examples of policies to reduce the environmental impacts of transport in urban areas, this article identifies some key lessons for sustainable urban transport in smaller and medium-sized cities in developing countries. These lessons are certainly not always identical to those for megacities in the global south.OTBArchitecture and The Built Environmen
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