1,720,963 research outputs found
Influence of new factors on global energy prospects in the medium term: comparison among the 2010, 2011 and 2012 editions of the IEA’s World Energy Outlook reports”
No full textSeveral economic, geopolitical, demographic and environmental factors drive world’s energy scenario; among them, the reduction of greenhouse gases emissions and the consequent development of renewable energy sources, the global financial crisis, the increase in global population and urbanization, the increase of fossil fuels prices have had a particularly strong impact in recent years. Furthermore, exceptional events, such as the accident at the Fukushima nuclear power plant in Japan, may occur to complicate World energy scenarios.
The most recent reports on world energy markets, especially the WEO - World Energy Outlook, are characterized by the introduction of new prospects and scenarios, as a result of unpredictable events such as Fukushima accident or of emerging factors, such as the increasing share of unconventional resources in the future energy mix (shale gas and shale oil) and the importance of energy efficiency, proposing an “Efficient World Scenario”. Disappointing signals about the development of renewables are also recorded.
The paper focuses on the comparison among the major reports and statistical energy data, especially the 2010, 2011 and 2012 editions of the World Energy Outlook issued by IEA. Mid-term energy scenarios are presented and discussed, with particular emphasis on the increasing importance of energy efficiency, on the new prospects concerning nuclear power and on the role of unconventional fossil fuels
Albedo and surface temperature relation in urban areas: Analysis with different sensors
No full textUrban areas exhibit a variable land surface temperature (LST) pattern that can be linked to albedo variations. In this work, different spaceborne and airborne sensors have been considered to infer the albedo-LST relation in two urban areas (the cities of Perugia and Aprilia, in Central Italy), in July. Also, an in situ campaign for the measurement of albedo and LST values was carried out in Perugia. The study reveals the expected “inverse” relation albedo-LST (growing LST with decreasing albedo), with surfaces having albedo around 0.10 that can produce an average surface heating greater than 60 °C in July. The observations provide an indication of the global variability of these parameters and their relation in space and time. Furthermore, an analysis at different times can point out an average albedo variation for the same built-up area that could be ascribed to the materials used for new settlements and for existing construction refurbishmen
Energy Performance Database of Building Heritage in the Region of Umbria, Central Italy
No full textHousehold energy consumption has been increasing in the last decades; the residential sector is responsible for about 40% of the total final energy use in Europe. Energy efficiency measures can both reduce energy needs of buildings and energy-related CO2 emissions. For this reason, in recent years, the European Union has been making efforts to enhance energy saving in buildings by introducing various policies and strategies; in this context, a common methodology was developed to assess and to certify energy performance of buildings. The positive effects obtained by energy efficiency measures need to be verified, but measuring and monitoring building energy performance is time consuming and financially demanding. Alternatively, energy efficiency can also be evaluated by specific indicators based on energy consumption. In this work, a methodology to investigate the level of energy efficiency reached in the Umbria Region (Central Italy) is described, based on data collected by energy certificates. In fact, energy certificates, which are the outcomes of simulation models, represent a useful and available tool to collect data related to the energy use of dwellings. A database of building energy performance was developed, in which about 6500 energy certificates of residential buildings supplied by Umbria region were inserted. On the basis of this data collection, average energy and CO2 indicators related to the building heritage in Umbria were estimated and compared to national and international indicators derived from official sources. Results showed that the adopted methodology in this work can be an alternative method for the evaluation of energy indicators; in fact, the ones calculated considering simulation data were similar to the ones reported in national and international sources. This allowed to validate the adopted methodology and the efficiency of European policies
Straw bale constructions: Laboratory, in field and numerical assessment of energy and environmental performance
No full textThe use of straw in buildings has been common since ancient times, but only at the beginning of the twentieth century house made of straw bales were built in Nebraska. After a period of abandon, due mainly to the spread of Portland concrete, this building technique has gained a new attention in the last decades, at least in a niche sector of self-builders. Indeed, the main issue that an engineer or an architect must face when he/she decides to build a straw bale house is the absence of certain data about technical performance. The aim of the present paper is to investigate a straw bale wall, both in laboratory and in situ, and to perform a Life Cycle Assessment to identify strong and weak points of this building technique. After a section reporting the state of the art of the main features of straw bale constructions, including the most important physical parameters that affect durability and indoor comfort conditions, the paper reports the results of laboratory measurements aimed at assessing the sound absorption coefficient with an impedance tube and thermal conductivity with a guarded hot plate apparatus. Then, results of in-situ measurements of thermal and sound insulation are reported. Data show that in winter (steady-state) conditions the investigated wall offers adequate thermal insulation, but the lightness of the structure can be detrimental for the summer (unsteady-state) season, leading to possible overheating in warm climates. Furthermore, the sound insulation is limited by the lightness of the structure. Finally, the Life Cycle Assessment demonstrates that the use of straw bales in walls is capable of reducing the energy and carbon embodied in the building
Experimental and environmental analysis of new sound-absorbing and insulating elements in recycled cardboard
No full textPaper andcardboard,madewithrecovered fibers obtainedbyrecycling,areanattractive,sustainable
material. Recoveredpaperandcardboardaremainlyusedforpackagingpurposes,evenif,inrecentyears,
variousresearchesfocusedonthepossibilitytodevelopnewproductsandproposedalternativeappli-
cations.
This paperpresentsnewdesignsofacousticabsorbersmadeofpartiallyrecycledcardboard,inorder
to reducetheenvironmentalimpactofthematerialsusuallyusedfortheacousticcorrectiononindoor
environments.Someofthesenewdesignedabsorbersareporousandmakeuseofthevisco-thermal
absorption effectsintheporespace.OtherabsorbersarebasedontheHelmholtzresonatorprinciple.
Computer modelingsoftwarewasusedtopredicttheperformanceoftheabsorbers;inparticular,
different optionsofcardboard-basedpanelsandpaperboardtubeswereinvestigatedtoidentifythe
solutions withthebestacousticperformance.Areal-sizeprototypeofasandwichpanelwasthenex-
perimentally characterizedinlaboratory.Theabsorptioncoefficient spectrumoftheprototypewas
measured accordingtotheprocedureindicatedintheISO354standard.Theresultsshowthatthe
measured acousticabsorptioncoefficient ofthematerialmadeusingcardboardwashigherthantheone
of traditionalgypsumabsorbers,givinginparticularanincreaseoftheacousticabsorptionatmidand
high frequenciesintheorderof40%.
A LifeCycleAssessmentanalysiswasalsoperformedtoevaluatetheenvironmentaladvantagesof
these materials.Theenvironmentalimpactsoftheproductionofthecardboard-basedpanelwere
compared withtheimpactsofconventionalacousticmaterials.Theanalysishighlightedapotentialre-
duction ofbothenergydemandandgreenhousegasemissionsduringtheproductionprocessofthe
cardboard-basedacousticmaterials.
The estimatedCEDandGWPvaluesresult10%and34%respectivelylowerthantheimpactsofa
conventionalgypsumboard
Misure sperimentali per la caratterizzazione termica dinamica dei materiali
No full textLa tutela ambientale si occupa da tempo della riduzione del fabbisogno energetico degli edifici, da qui nasce la necessità dello studio di tecniche per il raggiungimento di tale obiettivo. Uno degli aspetti di cui si deve tener conto è sicuramente l’involucro dell’edificio e pertanto dei materiali con i quali esso viene realizzato. L’isolamento che l’involucro offre all’ambiente interno deve da un lato soddisfare i requisiti delle condizioni invernali, ma sono di notevole interesse anche le prestazioni dell’edificio in condizioni estive. L’andamento della temperatura dell’aria esterna viene assimilato ad una funzione sinusoidale, si assiste dunque ad un’oscillazione attorno ad un valor medio, tra un massimo ed un minimo. Oltre che di tale variabilità, occorre tener conto del fatto che la radiazione solare viene assorbita dalle strutture che accumulano il calore e poi lo restituiscono all’ambiente in tempi successivi, in funzione dell’inerzia termica delle strutture stesse. Il presente lavoro si occupa dei parametri termici dinamici dei materiali e in particolare dello studio di un metodo che possa consentire la valutazione del calore specifico attraverso la piastra calda con anello di guardia, strumento usato tipicamente per valutazioni in regime stazionario. La norma UNI EN ISO 13786 definisce i metodi per il calcolo del comportamento termico in regime variabile, partendo dalle caratteristiche dei materiali di cui è composta la parete. Dalle basi teoriche della norma si sono create le condizioni per poter valutare sperimentalmente, con l’uso della piastra calda, le principali grandezze che descrivono il comportamento dinamico dei materiali validando i risultati con una seconda metodologia: la tecnica Hot Disc. I test preliminari presentati sono stati condotti su marmo artificiale, ottenendo ampie oscillazioni di temperatura e di flusso termico sulle superfici estreme del campione per definire in maniera ottimale i parametri di ampiezza e sfasamento delle sinusoidi e calcolare le caratteristiche termofisiche del materiale
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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