434 research outputs found
Architettura, storia, infrastrutture urbane
No full textIl settore dei collegamenti urbani è un elemento fondamentale della più ampia sfera dei servizi pubblici dello città, che costituiscono, nello loro architettura, occasione attraverso cui delineare possibili scenari di qualità del vivere nello città contemporanea, a cui pervenire attraverso l'interpretazione progettuale degli spazi collettivi e pubblici.
Questo concezione ancor più risulta ricca di possibili operatività se riferita ad aggregati urbani o parti di essi di piccola e media ampiezza, dove la misura delle relazioni tra i vuoti e i pieni e tra i tessuti residenziali e i servizi risulta meglio controllabile in quanto affidato a quantità non esasperate ed è anche verificabile un rapporto più profondo e diretto tra i cittadini e i propri spazi di vita.
Nelle città di piccola e media dimensione, infatti, diversamente che nelle grandi conurbazioni, è successo in parecchi cosi che i fenomeni di modificazione dello seconda metà del secolo scorso hanno soltanto in parte compromesso le compagini edilizie e gli assetti urbanistici esistenti
A Novel Micromechanical - Analogical Model for Low Temperature Creep Properties of Asphalt Binder and Mixture
No full textThe ENTPE transformation is commonly used to predict the low temperature properties of asphalt binders from the corresponding mixtures experimental data and vice-versa. Nevertheless, the transformation parameter, α, associated to the ENTPE equation, cannot be directly obtained without relying on both binder and mixture testing. This paper presents a comprehensive investigation to link the ENTPE transformation to the mixture microstructure. This is accomplished by three-point bending tests on asphalt binders and mixtures, digital image processing and statistical evaluation of mixture microstructure, together with a newly proposed micromechanical-analogical model, called MCF (Moon-Cannone Falchetto), used for deriving an explicit expression of α. The values of α obtained from asphalt binder and mixture laboratory measurement are compared to the values predicted by the new formulation. The results indicate that reasonable predictions of low temperature creep stiffness of asphalt binder can be obtained when the new expression of α is used in the ENTPE transformation.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
Climate Warming Persistence Triggered Tree Ingression After Shrub Encroachment in a High Alpine Tundra
No full textClimate warming can induce the encroachment of shrubs and may trigger treeline dynamics. However, the responses of shrubs and trees to climate change may be modulated by other environmental drivers such as land-use change and biological interactions. The European Alps are one of the three areas experiencing the most intense warming globally in the twentieth century. We analyse, through a multidisciplinary approach, the shrub and tree encroachment at the Stelvio Pass (Italian Alps) focusing on three target species (Rhododendron ferrugineum, Larix decidua, Pinus mugo) to reconstruct their dynamics and assess which drivers (climate change, land-use change, biological interactions provided by shrub facilitation) promoted their ingression. Shrub colonization started in 1867, in coincidence with the end of the Little Ice Age. Tree recruitment started since 1960 for P. mugo and 1972 for L. decidua and correlated strongly with air warming and shortening of the snow cover duration. Climate (air temperature, snow cover) exhibited the highest correlation with shrub and tree dynamics both during the period of recruitment and in the following and preceding 5-year period. Air warming appeared to be crucial for tree ingression and persistence. Land-use change was not related to shrub encroachment, and only weakly to tree recruitment. Both the correlation analysis as well as the patterns of recruitment highlighted that shrubs were characterized by different ecological requirements from trees. There was not a “nurse effect” of shrubs on trees, and this biotic interaction changed with the developmental stage of the involved species, being lowest for seedlings and highest for adults, requiring further investigations. Future scenarios of climate change indicate a further and intense warming, and our data show that it is likely that shrub and tree encroachment will proceed, with relevant consequences on the extremely vulnerable high-elevation alpine ecosystems
Climate change triggered synchronous woody plants recruitment in the last two centuries in the treeline ecotone of the Northern Hemisphere
No full textClimate change triggers several ecosystem responses, including woody plant encroachment. We analyse woody plant recruitment across the treeline ecotone (the forest -tundra ecotone) of the Northern Hemisphere (NH) over an extended period (1801-2010) and its relation with atmospheric CO2 and air temperature. We detected a synchronous trend of woody plant recruitment across the NH, indicating a major climatic and environmental change, triggered by a combination of CO2 fertilization and air temperature changes. The drivers of woody plant recruitment changed with time: CO2 fertilization was the main driver in the period 1801-1950, while air temperature was the main driver after 1950, despite the drastic acceleration of CO2 increase in the last decades. These data support the hypothesis that we are shifting from a fertilization -dominated to a warming -dominated period. The temporal patterns of woody plant recruitment are consistent with the occurrence of the 1980 regime shift, a major change occurred in the Earth's biophysical systems. Indeed, the recruitment drop promoted by the 1960s-1980s air cooling, was followed by an intensive recruitment increase triggered by the restart of air warming in the last decades. The largest sensitivity and fastest resilience of evergreen and Pinaceae to the restart of air warming allows to hypothesize that, among the woody plant functional and taxonomic groups, they could perform the largest expansion also in future decades
Multi-Band VCO Based On Distributed VCO And Switched-Capacitors Banks
No full textThe paper introduces a new approach for the design of multi-band distributed VCOs for mobile TLC applications. The techniques exploits the potentialities of a switched-capacitor approach, joint to, the versatility of a distribute VCO. The design procedure is discussed. The measured characteristics of a hybrid prototype are reported, validating the potentialities of the approach
Monitoring long-term vegetation changes (1953-2018) in an alpine tundra ecosystem of the Italian Central Alps
No full textAlpine grassland and snowbed species after five years of manipulation experiments: phenology and growth
No full textPhytosociology of the vegetation communities of the Stelvio Pass area
No full textHigh elevation areas are sensitive and vulnerable to climate change and exhibited relatively rapid changes in response to warming involving changes of floristic composition, species upward migration, shrub and tree encroachment and surface area changes. For this reason, it is important to provide quantitative studies as tools allowing a long-term monitoring of vegetation in response to climate change. The Stelvio Pass area is a high elevation site located in the European Alps, and a unique case study on the alpine range providing historical detailed information on vegetation with the availability of phytosociological maps of vegetation elaborated in 1953 and 2003. Here we show and describe an updated and detailed phytosociological vegetation mapping which will constitute a robust base for the monitoring and quantitative assessment of any impacts of future climate and/or environmental change as well as a tool to plan suitable vegetation and biodiversity conservation actions in the alpine environment
A 12-bit track and hold amplifier for giga-sample applications
No full textThe paper presents a track-and-hold amplifier (THA), based on the switched emitter follower topology, suitable for emerging receivers architectures and data acquisition systems. The THA exploits four concurrent techniques, all described in the paper, which allow to reduce the hold-mode feedthrough; to attenuate the differential droop rate; to improve the linearity of the input buffer; and to optimize the third order harmonic distortion for RF sampling operation. The effectiveness of this novel approach is demonstrated using a low cost 0.35 μm SiGe technology. The THA core draws about 145 mA from 3.5 V supply. The THA provides a spurious-free dynamic range (SFDR) better than 72 dB when it is used for sampling an incoming signal of 0.9 Vpp centered around 925 MHz at a sampling rate of 0.5 GS/s. The THA allows a max sampling frequency equal to 6 GS/s and a max input frequency equal to 2.5 GHz and provides a SFDR better than 50 dB in all the available working conditions
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