1,720,997 research outputs found
Technical approach for the measurement of surface runoff
No full textIn this paper we describe practical application, design and installation of an in-field runoff collector exploitable for monitoring nutrients, pesticides and sediments loadings in runoff, improved with a home made level reading system able to measure with high temporal resolution, the runoff rate variation.
This configuration simplifies and lower the cost of conventional instruments used for measuring runoff. A multislot divisor was used to reduce the volume of runoff and plastic tank were use to collect it. An electro-mechanic type, floating level transducer was proposed. The homemade level reading system is composed of three parts: floating level transducer, signal conditioning system and data storage. The total cost for entire system is approximately € 642
AMMONIA EMISSIONS FROM ARABLE LANDS IN PO VALLEY: METHODOLOGIES, DYNAMICS AND QUANTIFICATION.
Full text linkAlthough the Po Valley (north Italy) is considered one of the most important ammonia (NH3) emitting regions in Europe, few data are available for an evaluation of the ammonia budget at field level in arable lands. Here the NH3 losses were quantify, considering different measurement and estimation approach, fertilisers and agronomic managements. The outputs of two concentration based-inverse dispersion models, together a mechanistic model were assessed with the direct measurements of ammonia fluxes by the micrometeorological technique eddy covariance, at hourly, daily and seasonal scales. A discussion on advantages, disadvantages and performances of each model is given in order to determine the most suitable method able to evaluate the ammonia emission in Po Valley at field scale. The selected inverse dispersion models were assessed in their uncertainty to quantify ammonia emissions rates, and their significance with regards to the Italian context. Moreover emissions from cattle slurry and urea application were performed in seven field trials in three different locations of Po Valley, in order to evaluate the best practices in reducing NH3 loss from arable land. The emission factors relative to different agronomical practices (slurry injection, slurry surface spreading with and without incorporation, urea surface spreading) are given, taking into account the main factors affecting the NH3 volatilization phenomenon and describing its dynamics
Tecnica di misura dei fenomeni di ruscellamento superficiale
Full text linkIl suolo è una risorsa non rinnovabile capace di assicurare funzioni essenziali non solo a livello ambientale ma anche sociale ed economico, assumendo quindi un ruolo centrale nel contesto di sostenibilità dell’agricoltura. Tuttavia il suolo è soggetto ad un continuo degrado dovuto in particolare al fenomeno dell’erosione che non solo ne influenza negativamente le proprietà nutritive ma diventa una potenziale fonte di inquinamento per le acque superficiali. I fenomeni erosivi sono influenzati da notevoli fattori che il più delle volte vengono meglio descritti se studiati a scala di campo, piuttosto che a piccola scala. Inoltre gli alti costi degli strumenti e la quantità enorme di ruscellato limitano il più delle volte il numero di siti che possono essere studiati. Sono stati quindi sperimentati strumenti, per parcelle di più ampia superficie, che permettono di ripartire l’acqua ed il ruscellato e di ridurre in questo modo il campione raccolto mantenendolo rappresentativo. In questo lavoro viene presentata l’applicazione pratica di uno di questi strumenti di misura opportunamente adattato che permette con ampia soluzione temporale di monitorare i fenomeni di ruscellamento superficiale a scala di campo
Evaluation of mitigation strategies to reduce ammonia losses from slurry fertilisation on arable lands
No full textTo evaluate the best practices in reducing ammonia (NH3) losses from fertilised arable lands, six field trials were carried out in three different locations in northern Italy. NH3 emissions from cattle slurry were estimated considering the spreading techniques and the field incorporation procedures. The measurements were performed using long term exposure samplers associated to the determination of the atmospheric turbulence and the use of the backward Lagrangian stochastic (bLS) model WindTrax. The results obtained indicate that the NH3 emission process was exhausted in the first 24-48h after slurry spreading. The slurry incorporation technique was able to reduce the NH3 losses with respect to the surface spreading, where a contextual incorporation led to reductions up to 87%. However, the best abatement strategy for NH3 losses from slurry applications has proved to be the direct injection into the soil, with a reduction of about 95% with respect to the surface spreading. The results obtained highlight the strong dependence of the volatilisation phenomenon by soil and weather conditions
Analisi del contenuto idrico del suolo per due differenti sistemi di irrigazione
Full text linkL’esigenza di attuare interventi mirati alla razionalizzazione della risorsa idrica è avvertita in modo specifico nel comparto agricolo, in considerazione dei notevolissimi volumi di acqua richiesti per il compimento del ciclo produttivo delle coltivazioni. La scelta del sistema di irrigazione risulta determinante per il contenimento delle perdite e il miglioramento dell’efficienza d’irrigazione. A tal proposito è stata condotta una sperimentazione in Pianura Padana su due appezzamenti per confrontare due differenti sistemi irrigui: per gravità tramite scorrimento superficiale, e per aspersione con pivot ad ala imperniata. Il monitoraggio dei contenuti idrici è stato eseguito a diverse profondità, sia con un metodo diretto e discontinuo (metodo gravimetrico), sia con metodo indiretto e continuo, che accoppia la misura tensiometrica in campo, allo studio della curva di ritenzione idrica in laboratorio. La prova di campo ha dimostrato una maggiore perdita per percolazione nel sistema a scorrimento, confermando la bassa efficienza del metodo stesso e la necessità di apportare maggiori volumi complessivi
Stima delle emissioni di NH3 con l'uso di modelli a dispersione
Full text linkIl problema ambientale e gestionale della volatilizzazione di ammoniaca (NH3) ricopre un ruolo sostanziale a causa dell'effetto negativo di tale gas su suolo, acque e stato nutrizionale delle colture. La misura dei flussi di NH3 a scala di campo è resa difficoltosa dalla rapidità di reazione in atmosfera della molecola. In questo lavoro viene presentata una metodologia per quantificare i rilasci di NH3 a scala di campo basata sull’impego di modelli a dispersione. Questi modelli sono in grado di caratterizzare il trasporto degli inquinanti in atmosfera sulla base della misura della turbolenza atmosferica ad alta frequenza e sulla misura delle concentrazioni del gas in analisi con campionatori a diffusione passiva a lunga esposizione. La durata dell’esposizione dei campionatori ed il suo effetto sulla stima del flusso è stata discussa attraverso una prova di campo con spandimento superficiale di liquame bovino
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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