1,720,986 research outputs found
Sviluppo di sistemi sensoriali per il monitoraggio della qualità dell'aria e per la sicurezza in ambienti esterni e confinati: i casi del CH4, CO2, CO
No full textQuesto lavoro di ricerca è mirato allo sviluppo di sistemi sensoriali per il monitoraggio della qualità dell'aria. Infatti quando si considera che il rischio di inquinamento può causare grossi problemi di salute anche in un breve periodo di tempo, si evince che il monitoraggio preciso di emissioni inquinanti risulta di fondamentale importanza per la sicurezza e la salute dell'uomo. Gli strumenti convenzionali di monitoraggio della qualità dell'aria non sono molto popolari a causa del fatto che essi risultano essere ingombranti e soprattutto molto costosi. Da qui la necessità di sviluppare un sistema sensoriale economico, compatto, affidabile e soprattutto accurato in grado di poter essere installato in qualunque abitazione ed in qualunque altro luogo ove ci sia bisogno di monitorare una determinata specie gassosa. Inoltre il crescente desiderio di vivere in un ambiente sicuro e confortevole spinge la ricerca verso lo sviluppo di sistemi sensoriali per il monitoraggio di gas tossici, esplosivi ed inquinanti sempre più performanti. In questo contesto vengono presentati due sistemi sensoriali per la rilevazione di gas: un sensore elettro-ottico ed un array capacitivo. Il principio di funzionamento del sensore elettro-ottico si basa sulla legge di Lambert Beer. Il sistema è costituito da un microriscaldatore su membrana (utilizzato come sorgente di radiazione infrarossa), da una cella multipasso (necessaria per aumentare il cammino ottico tra sorgente e rivelatore) e da un array di termopile con filtri ottici centrati nella regione di massimo assorbimento dei gas. Inoltre è stata sviluppata un’elettronica di condizionamento al fine di pilotare in regime sinusoidale il corpo nero ed un’elettronica di rivelazione per acquisire, amplificare, filtrare e visualizzare su un display grafico i segnali in uscita. I risultati sperimentali mostrano un limite di rivelazione di 100 ppm per il CH4, di 20 ppm per il CO ed inferiore a 50 ppm per la CO2.
Il sensore chimico basato su un array di 300x256 micro-capacità è stato realizzato utilizzando un fingerprint sensor commerciale. Sulla superficie del sensore sono state depositate differenti metallo-porfirine; in questo modo i composti volatili presenti nell’ambiente circostante che interagiscono con il materiale sensibile possono essere rivelati dal dispositivo attraverso la misura della variazione della costante dielettrica delle celle che compongono l’array. La variazione della costante dielettrica relativa provoca una variazione della capacità di ogni elemento dell’array. Le misure preliminari hanno evidenziato un limite di rivelazione di 30 ppm per il CO.
In questa tesi verranno descritte e commentate in dettaglio le caratteristiche di entrambi i sistemi, i risultati sperimentali ed i possibili sviluppi futuri.Due to the dramatic growth in industrial development and population, the natural atmospheric environment has become polluted. In fact, when the hazards of environmental pollution that can cause severe injury within a short time period is considered, the precise monitoring of pollutant emissions becomes rather important. Conventional instruments for monitoring the environment are not so popular because they are bulky, time consuming, and expensive. As a consequence, compact, robust, and inexpensive solid-state gas sensors are required as an effective alternative for environmental monitoring.
In this work we present two systems suitable for the detection of volatile compounds: an electro-optical infrared sensor and a capacitive chemical sensor array. The working principle of the electro-optical system is based on the absorption of infrared energy by gas molecules at their characteristic absorption bands; the absorbance is proportional to the concentration according to Lambert-Beer law. The system comprises a micro-heater (used as an infrared source), a multipass cell (required to direct the radiation toward the detector), a thermopile array (detector) with three different filters centered on the absorption peaks of CH4, CO2, CO, and a reference filter. Furthermore, an electronic system has been developed to drive the micro-heater with a sine modulation and to acquire, amplify, filter, and show on a graphic display the output signal.
The results show a limit of detection of 100 ppm for methane, 20 ppm for carbon monoxide and <50 ppm for carbon dioxide.
The capacitive chemical sensor array is based on a commercial fingerprint detector. The device is an array of 300x256 micro-capacitors. Chemical sensors were made by deposition of different metallo-porphryins on the device surface. The volatile compounds present in the close environment and interacting with the sensing materials are detected through the measure of the dielectric constant variation of the cells composing the array. The variation of the relative dielectric constant causes the variation of the capacitance of each element. Tests were performed exposing the sensor to CO with a limit of detection of 30 ppm.
In this thesis are described and commented with details the characteristics of both systems, the experimental results and the future developments
Monocarboxy Tetraphenylporphyrin functionalized ZnO nanorods photoactivated gas sensor
No full textAbstractIn this work, gas sensing properties of monocarboxy tetraphenylporphyrin functionalized ZnO nanorods under different light illumination, were investigated. These studies showed that the sensitivity to triethylamine of porphyrin functionalized ZnO nanorod device are greatly enhanced under illumination with visible light. This photoactivated nanostructure composition has the potential for gas sensor device applications
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Development of an UHF RFID chemical sensor array for battery-less ambient sensing
No full textBattery-less ultrahigh frequency (UHF) radio frequency identification (RFID) tags coated by proper sensitive layers have been recently demonstrated capable to play as low-cost sensors of some volatile compounds. The issue of cross-sensitivity and the possibility to develop an array of differently coated sensors are, however, still completely open. This paper investigates, through an experimental campaign involving a general-purpose sensor-antenna transducer, the potentiality of functionalized tags in the UHF RFID band to sense a multiplicity of volatile compounds, as well as the cross-sensitivity effects of different coatings in array configuration. Four effective materials, such as Pedot:PSS, doped PSS, SWCNT, and PDAC, revealed a remarkable sensitivity to ammonia, ethanol, octane, and water. Wireless sensing may be hence performed by narrowband processing of the power response of the RFID tags as well as by the broadband extraction of features related to the resonance shift. It was finally observed how the inter-antenna coupling may affect the sensor capability of an array of UHF tags in term of increased cross-sensitivity. © 2012 IEEE
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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