196,327 research outputs found
La gestione del patrimonio culturale, intervista a Mariella Zoppi Assessore alla Cultura della regione Toscana
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Effects of perfluorination on the electronic, optical, and transport properties of polyaromatic hydrocarbons: pentaceneand pyrene in the molecular and solid phase
No full textWe report a comparative study on pentacene and pyrene polyaromatic
hydrocarbons (PAHs) and their perfluorinated counterparts. The study
has been performed for both the isolated molecule and their molecular
solid phases. The former are investigated, performing all-electron
calculations, using Density Functional Theory (DFT) and Time Dependent
DFT with localized gaussian basis set and hybrid B3LYP exchange
correlation functional, in order to quantify the effects of morphology
and chemical modifications on their electronic, optical, and
transport properties: in particular electron affinity, ionization energy,
fundamental gap, optical absorption, exciton binding energy, and reorganization
energies for holes and electrons. The molecular solids using
DFT-LDA with plane-waves basis set and ionic pseudopotentials in
order to determine and compare ground state properties. In contrast,
different exchange-correlation functionals (LDA, PBE0) are considered
A High-Efficiency Heat Exchanger for Closed Cycle and Heat Recovery Gas Turbines
No full textDesigning and manufacturing high-efficiency heat exchangers is usually considered a limiting factor in the development of both heat recovery Joule-Brayton cycles and closed-cycle (external combustion) gas turbine plants. In this work, an innovative heat exchanger is proposed, modeled and partially tested to validate the developed numerical model employed for its design. The heat exchanger is based on an intermediate medium (aluminum oxide Al2O3) flowing in counter-current through an hot stream of gas. In this process, heat can be absorbed from the hot gas, temporarily stored and then similarly released in a second pipe, where a cold stream is warmed up. A flow of alumina particles with very small diameter (of the order of hundreds of micron) can be employed to enhance the heat transfer. Experimental tests demonstrate that simple one-dimensional steady equations, also neglecting conduction in the particles, can be effectively employed to simulate the flow in the vertical part of the pipe, namely to compute the pipe length required to achieve a prescribed heat exchange. On the other side, full three-dimensional Computational Fluid Dynamics (CFD) simulations have been performed to demonstrate that a more thorough gas flow and particle displacement analysis is needed to avoid some geometrical details that may cause a bad distribution of alumina particles, and thus to achieve high thermal efficiency.</jats:p
An Immersed Particle Heat Exchanger for Externally Fired and Heat Recovery Gas Turbines
No full textDesigning and manufacturing high-efficiency heat exchangers is usually considered a limiting factor in the development of gas turbines employing either heat recovery Joule–Brayton cycles or external combustion. In this work, an innovative heat exchanger is proposed, modeled, and partially tested to validate the developed numerical model employed for its design. The heat exchanger is based on an intermediate medium (aluminum oxide Al2O3) flowing in countercurrent through an hot stream of gas. In this process, heat can be absorbed from the hot gas, temporarily stored, and then similarly released in a second pipe, where a cold stream is warmed up. A flow of alumina particles with very small diameter (of the order of hundreds of microns) can be employed to enhance the heat transfer. Experimental tests demonstrate that simple one-dimensional steady equations, also neglecting conduction in the particles, can be effectively employed to simulate the flow in the vertical part of the pipe, namely, to compute the pipe length required to achieve a prescribed heat exchange. On the other side, full three-dimensional computational fluid dynamics simulations have been performed to demonstrate that a more thorough gas flow and particle displacement analysis is needed to avoid a bad distribution of alumina particles and, thus, to achieve high thermal efficiency.</jats:p
Small historical towns between conservation and revitalization
No full textIn the architectural context, there is an increasing need to deve- lop project strategies to protect and revitalize the villages that characterize the Italian territory, now at risk of survival, preserving their material and immaterial values.
Locorotondo, one of the most important settlements in the Valle d’Itria in Puglia, represents a particularly signi cant case study, since it is unique, and yet with general problems. It is an urban or- ganism with a strong identity, expressed in the close relationship between rural landscape, orography, urban morphology, types of buildings and construction techniques. This raises delicate problems of protection, recovery and reuse compatible with its characters. The paper illustrates an experience conducted in a Master Degree Workshop at the Politecnico di Bari.
Guidelines have been formulated for a recovery plan at the va- rious scales, for the purposes of conservation and enhancement of the old core, based on a careful reading of the context and the existing building heritage.
Then, on the basis of the guidelines, a pilot project was deve- loped for the recovery of an area located on the edge of the original urban settlement, framing it in a system of overall en- hancement of public spaces and of the itineraries for the fruition of the old town center. Finally, the focus was on the problems of some marginal areas, with the aim of recovering the relationship between the historical center, the residential expansions and the diffuse built heritage
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
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