1,284 research outputs found
A Political History of the Valorisation of Cultural Heritage in Italy: Conflicts in a Controversial Social Process
Valorisation is one of the two functions used by institutions in the transmission of cultural heritage in Italy. While valorisation is a polysemic concept with an uncertain use and wide-ranging implications, the relationships that have been forged between protection, management, realisation, and valorisation are the subject of a controversy that is in conflict with both scholars and the two different aims of social life: social and cultural progress and economic growth. Through a critical approach and from a sociological perspective, this article shows how these two dimensions are in a conflict that touches both the social purposes attributed to cultural heritage and the cultural process through which heritage is produced
Sinusoidal nanotextures for light management in silicon thin film solar cells
Recent progresses in liquid phase crystallization enabled the fabrication of thin wafer quality crystalline silicon layers on low cost glass substrates enabling conversion efficiencies up to 12.1 . Because of its indirect band gap, a thin silicon absorber layer demands for efficient measures for light management. However, the combination of high quality crystalline silicon and light trapping structures is still a critical issue. Here, we implement hexagonal 750 nm pitched sinusoidal and pillar shaped nanostructures at the sun facing glass silicon interface into 10 m thin liquid phase crystallized silicon thin film solar cell devices on glass. Both structures are experimentally studied regarding their optical and optoelectronic properties. Reflection losses are reduced over the entire wavelength range outperforming state of the art anti reflective planar layer systems. In case of the smooth sinusoidal nanostructures these optical achievements are accompanied by an excellent electronic material quality of the silicon absorber layer enabling open circuit voltages above 600 mV and solar cell device performances comparable to the planar reference device. For wavelengths smaller than 400 nm and higher than 700 nm optical achievements are translated into an enhanced quantum efficiency of the solar cell devices. Therefore, sinusoidal nanotextures are a well balanced compromise of optical enhancement and maintained high electronic silicon material quality which opens a promising route for future optimizations in solar cell designs for silicon thin film solar cells on glas
Sum Rules and Ward Identities in the Kondo Lattice
We derive a generalized Luttinger-Ward expression for the Free energy of a
many body system involving a constrained Hilbert space. In the large limit,
we are able to explicity write the entropy as a functional of the Green's
functions. Using this method we obtain a Luttinger sum rule for the Kondo
lattice. One of the fascinating aspects of the sum rule, is that it contains
two components, one describing the heavy electron Fermi surface, the other, a
sea of oppositely charged, spinless fermions. In the heavy electron state, this
sea of spinless fermions is completely filled and the electron Fermi surface
expands by one electron per unit cell to compensate the positively charged
background, forming a ``large'' Fermi surface. Arbitrarily weak magnetism
causes the spinless Fermi sea to annihilate with part of the Fermi sea of the
conduction electrons, leading to a small Fermi surface. Our results thus enable
us to show that the Fermi surface volume contracts from a large, to a small
volume at a quantum critical point. However, the sum rules also permit the
possible formation of a new phase, sandwiched between the antiferromagnet and
the heavy electron phase, where the charged spinless fermions develop a true
Fermi surface.Comment: 24 pages, 4 figures. Version two contains a proof of the "Entropy
formula" which connects the entropy directly to the Green's functions.
Version three contains corrections to typos and a more extensive discussion
of the physics at finite
Schwinger Boson approach to the fully screened Kondo model
We apply the Schwinger boson scheme to the fully screened Kondo model and
generalize the method to include antiferromagnetic interactions between ions.
Our approach captures the Kondo crossover from local moment behavior to a Fermi
liquid with a non-trivial Wilson ratio. When applied to the two impurity model,
the mean-field theory describes the "Varma Jones" quantum phase transition
between a valence bond state and a heavy Fermi liquid.Comment: 4 pages, 4 figures. Changes to references and text in v
Improved Light Management in Crystalline Silicon Thin Film Solar Cells by Advanced Nano Texture Fabrication
We present a texturing method for liquid phase crystallized silicon thin film solar cells enabling a maximum achievable short circuit current density of 36.5mA cm 2 due to optimized light management compared to current textured device
Tailoring nano textures for optimized light in coupling in liquid phase crystallized silicon thin film solar cells
Thin film solar cells based on liquid phase crystallized silicon LPC Si with 8 20 m thick absorber layers demand for advanced light management to achieve high photocurrent densities. Open circuit voltages Voc gt;600 mV underline the high silicon material quality of LPC silicon thin films on nano textured glass superstrates. We present a 500 nm pitched sinusoidal nano texture which outperforms larger pitched gratings with respect to light in coupling at the buried glass silicon interface. In the wavelength range of interest reflection of incident light is minimized to values close to 4 , which is the reflection at the sun facing air glass interface. Further, the electronic material quality of sinusoidally textured devices is analyzed on basis of a comparison of maximum achieved open circuit voltages on different texture types. The Voc on sinusoidally textured glass superstrates could be raised to 630 mV by changing the interlayer deposition method from a PVD to a PECVD process. Thus, we are able to unify high optical and electronic properties of silicon absorber layers on sinusoidal textured glass substrates. These results constitute a crucial step towards fully exploiting the optical potential of LPC silicon thin film solar cell
Imprinted Nanostructures for Light Management in Crystalline Silicon Thin Film Solar Cells on Glass
We present various imprinted nanostructures for light management in liquid phase crystallized silicon thin film solar cells enabling both, increased jsc by enhanced absorption and excellent electronic material quality with Voc values above 640 m
High-efficiency transformation by biolistics of soybean, common bean and cotton transgenic plants.
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Previous issue date: 2009-01-1
Territori resilienti e paesaggi digitali: il turismo culturale nelle Langhe, Roero e Monferrato
Il progetto SPOT, finanziato dalla Commissione Europea nell’ambito di Horizon 2020, è iniziato in contemporanea alla pandemia da COVID-19. Gli obiettivi di proporre e sviluppare un nuovo approccio al turismo culturale di 15 casi studio, dove alcune aree erano caratterizzate da overtourism e altre da undertourism, si è scontrato con una situazione del tutto inedita: assenza di turismo e impossibilità di praticarlo. Il caso studio italiano è l’area di Langhe, Monferrato e Roero dove il turismo è motivato dall’enogastronomia, ma presenta notevoli potenzialità culturali sia sotto il profilo del patrimonio materiale che di quello immateriale. Questo articolo illustra sinteticamente parte dei risultati della prima survey svoltasi nell’autunno del 2020, discutendo delle rappresentazioni del turismo culturale quale vettore di resilienza per il territorio e di impegno nella promozione e valorizzazione, a partire dalla reputazione digitale
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