1,720,975 research outputs found
Analysis of peroxides decomposition by screening calorimetry
No full textIn this study the analysis of different kind of organic peroxides decomposition by screening calorimetry is proposed. Organic peroxides are liable to decompose exothermically at normal or high temperatures [1,2].
Screening calorimetry data allow us to define conditions and ranges of temperature and pressure evolved; useful results (such as onset temperature, time to maximum rate, maximum pressure, ...) are obtained. The experiments are carried out in safely even when there is rapid and large increases in temperature and pressure.
An Early Warning Detection System (EWDS) based on divergence criterion is also applied to experimental dat
Screening Analysis for Hazard Assessment of Peroxides Decomposition
No full textIn this study the analysis of different kind of organic peroxides decomposition by screening calorimetry
is proposed. The aim is to analyze the kinetic and thermodynamic of the decomposition reactions and to
evaluate the consequences in particular when the process undergoes to thermal explosion and may be
the cause of incidents. Screening calorimetry data allow us to define the conditions and ranges of
temperature and pressure evolved during the reaction. In the experimental apparatus used (a screening
calorimeter), the experiments have been carried out safely even when there is a rapid and large increase
in temperature and pressure. Scanning and isothermal conditions has been investigated. An Early
Warning Detection System (EWDS) for thermal runaway based on the divergence criterion has also
been applied off-line to the experimental isothermal data, in order to evaluate the sensitivity of the
method applied to both temperature and pressure profiles. The results of the application of the EWDS
have been compared to the ones obtained by Hub and Jones criterion
Learnig from accidents : Investigation and risk analysis on an incident in the transport and storage of Monomers
No full textIn this work the analysis of an accident in transport of dangerous goods is proposed.
The objective of this study is to contribute to the determination of the causes that brought about the self-polymerization of commercial divinylbenzene (DVB 63%) contained in an iso-container, in order to prevent this accident to happen in the future.
Time and conditions during transport and storage of monomers (in particular the storage temperature) are very important factors, that affect their self-polymerization aptitude.
In particular one hypothesis has been investigated: probably the quantity of oxygen in the tanker was insufficient to activate properly the inhibition mechanism. From this consideration the self-polymerization of DVB and the inhibition mechanism of 4-tert-Butylcatechol (TBC) have been studied as a function of temperature and monomer exposure to air with Differential Scanning Calorimetry and Adiabatic Calorimetry
La CO2 negli impianti frigoriferi commerciali: valutazione energetica di diverse soluzioni impiantistiche per la reiezione del calore
No full text
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
Reaction Calorimetry and UV-Vis Spectrophotometry Integration aimed at Runaway Reaction Early Detection
No full textThe use of different calorimetric techniques for process design and scale up is well consolidated, allowing
the definition of the kinetic and thermodynamic of the process and the evaluation of several parameters
useful to optimization and process safety. During a calorimetric analysis temperature (or a temperature
difference) is measured; from experimental data it is for example possible to calculate the heat flow and
the heat evolved by the reaction and consequently the conversion and the reaction rate constant just if
kinetics of the reaction is known. To overcome these limitations and to obtain additional information about
the reaction, it is possible to couple to a calorimeter different type of sensors such as densitometers,
refractometers, electrochemical, chromatographic and spectrophotometric probes (Schwedt, 1997). Some
of these sensors are able to log data on line during the process and so to monitor the reaction at the same
time of the calorimetric analysis. For safety aims, it is important to choose a sensor whose time for the
analysis is comparable to the reaction time in order to have an accurate profile of the monitored parameter
during the reaction (Moritz, 1989).
In a previous study (Parisi, 2002; Ampelli et al. 2003) an Ultra Violet - Visible spectrophotometer was
integrated to a reaction calorimeter to analyse the kinetic of a specific reaction. In this work a similar UV -
Vis probe has been coupled to an isoperibolic reaction calorimeter in order to study the feasibility of the
application of an Early Warning Detection System (EDWS) to a spectrophotometric signal. The innovation
of this integration of techniques is the analysis of the spectrophotometric signals with a reactor stability
criterion based on divergence theory in order to check if this method of monitoring allows detecting
runaway reactions at an early stage of the process, when it is still possible to take protective measures.
The innovation of the integration between the calorimetric and the spectrophotometric techniques is the
application of an Early Warning Detection System based on divergence criterion to spectrophotometric
signals in order to check if this method of monitoring high reactive processes could lead to a greater
advance in the detection of the thermal explosion with respect to temperature monitoring.
The results are that EWDS does not give a good result in the detection of the onset when applied to
Absorbance signal: it is not possible to define a ΔVLIM, and the profile of ΔV does not show a peak when
adding catalyst. This makes the analysis not reliable and subject to false alarm. This monitoring cannot be
used for process safety purpose.
The application of the method to the Intensity signal gives different results. There is the detection of the
onset 1 second before the profile of Intensity starts to decrease and the noise is more smoothed than in
the previous case. The algorithm is able to detect the runaway start 59 seconds before the maximum of
temperature is developed (6 seconds before the application to temperature signal). This monitoring could
be used at the same time than temperature monitoring, in order to improve the efficiency of the system in
detecting runaway reaction decreasing the possibilities of false alarms. The method could be very useful if
applied to those processes in which the accumulation of a reaction intermediate, that develops no
temperature increase in the system, could lead to thermal explosion by starting a secondary reaction: in
this case the EWDS working on Intensity signal (that can be monitored on line, during the process) could
detect the runaway at a very early stage, when the temperature in the system could still be kept under
control by some protective measure activated after the alarm.
The integration of calorimetry and spectrophotometry gave good results: spectrophotometry is able to
supply useful data for process modelling and also for safety purpose. This methodology could be easily
implemented in a plant-scale reactor providing a valid process safety monitoring against runaway
reactions.
The divergence criterion account reasonably well for the thermal runaway in the considered reaction. An
advantage of the Strozzi and Zaldívar criterion over existing criteria is that it is possible to reconstruct,
using non-linear time series analysis techniques, the divergence of the system from a monitored signal
without the necessity to have a model for the process. Hence, all the results and conclusions obtained
from an off-line analysis may be extended and applied on-line to develop a general early warning detection
device, based on a robust criterion
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