1,722,637 research outputs found
Wet Gas Flow Metering Technique Using a Venturi With Conductance Sensors
No full textWet gas metering is becoming an increasingly important problem to the oil and gas industry. Much research has been done to measure the water and gas flow rates of two-phase flows using a Venturi meter. The Venturi meter is a favoured device for metering of unprocessed wet natural gas production flows. In this thesis, various combinations of techniques have been employed in annular gas-liquid two phase flows to measure the flow parameters (e.g. liquid film thickness, gas volume fraction and gas and water flow rates). One of the most useful techniques which was used and which has proven attractive for many previous multiphase flow applications is the electrical conductance technique used in conjunction with the Venturi.
In this thesis, research has been done on designing a novel wet gas flow metering technique, which combines a Venturi with conductance sensors at the inlet and throat to measure the gas and the water flow rates and gas mass flow rate in vertical annular (wet gas) flows. Two ring conductance sensors at the inlet of the Venturi were used to measure the film velocity by cross correlation, one of the inlet ring conductance sensors was used to measure the film thickness and the inlet gas volume fraction. A ring conductance sensor at the throat was used to measure the gas volume fraction at the Venturi throat. A digital level sensor was also used to measure the film thickness (and the gas volume fraction) at the inlet of the Venturi. The reason for measuring the film thickness, the film velocity, the gas volume fraction at the inlet and the throat of the Venturi was to determine the gas and water flow rate and the gas mass flow rate in annular wet gas two phase flow using a variety of mathematical models of Venturis.
This work included both static ‘bench’ and flow loop experiments. In the flow loop experiments, which were limited to air-water two-phase flow, the test section included a Venturi meter with a 50mm inlet diameter with conductance sensors at inlet and the throat. Reference measurements of the water and air were made with a turbine flow meter and a variable area flow meter respectively. A Honeywell DP cell sensor was used to measure the differential pressure between the inlet and the throat of the Venturi.
A NI USB 6009 data acquisition device was used to integrate the system measurements and to control the operation of the overall Venturi system. A program was created using Labview software to read the input signals from the throat conductance ring sensor; the inlet conductance ring sensors; the digital level sensor; the DP cell sensor; the variable area flow meter and the turbine meter. From these measurements the gas volume fraction at the Venturi inlet and the throat, the differential pressure between the inlet and the throat of the Venturi, the film thickness and the film velocity at the Venturi inlet were calculated and were used with appropriate mathematical models to calculate the gas volumetric rate; gas mass flow rate; and the water mass and volumetric flow rates. Reference values of the gas a water flow rates were also calculated from the turbine meter and variable area flow meter outputs
La riorganizzazione dei servizi al lavoro in prospettiva comparata : prime considerazioni
Full text linkL'articolo approfondisce la disciplina del diritto al lavoro nella dimensione della creazione di servizi volti a favorire la sua realizzazione, prendendo spunto anche sul piano comparato al panorama europeo ed internazionale
Method for artificially reproducing an output signal of a nonlinear time-invariant system
No full textThe invention relates to a method for reproducing an output
signal of a non-linear time invariant system, in particular
a method used for example for artificially reproducing a
particular acoustic effect going close to the real one. Such
acoustic effect can be, for example, the sound that can
produce a sound chest of a particular musical instrument
when it is played or a sound amplified by a non-linear
amplifier such as a tube amplifier.
Each of the aforesaid systems, namely a sound chest of a
musical instrument or a tube amplifier, or the sound
produced by combinations of the aforesaid systems, is a nonlinear
system. As a result, each of the aforesaid systems
modifies the input signals sent, so the corresponding output
signals are distorted with respect the respective input
signals. This means that the output signal has different
frequency components compared to the input signal. In
particular, the output signal may have a plurality of
harmonics at frequencies that are different the one from
each other and different from the frequency/frequencies of
the input signal, even if the input signal has only one
component at fundamental frequency.
The harmonic distortions introduced by each system
characterize the sound generated by each system, making the
sound unique and recognizable among others. This means that
each sound generated by a system differs from the sound
generated by another system because of its harmonic content.
It follows that a system is distinguished from another one
because of the harmonic distortions it introduces in the
sound produced by the system
Investimenti e strumenti di investimento pubblici per la smart city
No full textDopo aver indicato che si sono affermati due diversi modi di concepire il ruolo dei pubblici poteri in relazione alla smart city o per meglio dire due modelli (i.e. quello statunitense e quello europeo) si è evidenziato come nell’ordinamento italiano l’approccio seguito finora sia stato soprattutto di tipo top-down, come si evince, per un verso, dall’istituzione dell’Agenzia per l’Italia digitale, dal ruolo assegnato al Comitato tecnico delle comunità intelligenti, per l’altro, dall’obbligo di inserire nella programmazione la realizzazione delle opere pubbliche e degli interventi infrastrutturali, nonché, più in generale, dalle funzioni attribuite ai competenti enti territoriali in tema di governo del territorio e di tutela dell’ambiente. E' stato poi evidenziato come il tema degli investimenti pubblici evochi soprattutto l’impegno economico-finanziario che enti pubblici, organismi di diritto pubblico, imprese pubbliche possono mettere in campo, per la realizzazione e la gestione di nuove infrastrutture o nuovi servizi per i cittadini, infrastrutture che debbono essere preventivamente programmate e finanziate. Si è altresì osservato come Il tema del finanziamento appaia centrale, non soltanto perché la realizzazione di infrastrutture ha sempre comportato l’impiego di rilevanti risorse pubbliche, ma anche in ragione del particolare favor riservato dal diritto europeo agli investimenti (rilevanti appaiono soprattutto quelli destinati alle infrastrutture), quand’anche siano finanziati in disavanzo. Inoltre, si è sottolineato, per un verso, come una particolare attenzione debba essere rivolta, con riferimento alla smart city/community, alla nuova definizione di infrastruttura di cui all’art. 2, comma 2, decreto del MEF 26 novembre 2010, che unifica i concetti di opera pubblica e di servizio pubblico, per l'altro, che se le smart city debbono coniugare in “un unico modello urbano tutela dell’ambiente, efficienza energetica e sostenibilità economica, con l’obiettivo di migliorare la qualità della vita delle persone che vi abitano e creare nuovi servizi per i cittadini e per le Pubbliche Amministrazioni” , attraverso l’utilizzo delle tecnologie, appare inevitabile che si proceda ad un complessivo ripensamento di quali e quante infrastrutture debbano essere realizzate al fine di soddisfare i nuovi bisogni individuali e collettivi dei cittadini
Study of the properties of turbulent flow through a venturi using LDA techniques
No full textVenturi flow meters are originall)' applied in single phase flows. Currently, Shell investigates their application in so-called 'wet gas' production mea,surement. Wet gas consists of a mixture of gas, condensate (light oil) and water. The liquids have been condensed from the gas, due to the pressure and temperature drop while producing. The flow rate of such a three phase mixture is not easy to measure, though necessary for e.g. allocation of the fuel and reservoir management. The determination of the gas and liquid flow rates requires understanding of the multi phase flow in a venturi, including the phenomena downstream of the throat of a venturi in order to apply such a device in wet gas metering. The project is a continuation of the worlc of Nievaart [Nievaart, 2000], who has been investigating the applied measurement technique, Laser Doppler Anemometry (LDA). This research is focussed on the effects of a venturi in turbulent flow. Therefore, measurements have been performed at eight locations, distributed upstream, in and downstream of a venturi in a single phase flow, in order to obtain more information about the velocity and turbulence intensity profiles, as well as the production and dissipation of turbulent kinetic energy. Performing LDA measurements is not that easy. First, all parameters of the LDA set-up have to be adjust carefully and the laser beams liave to be aligned very accurate, as the measuring volume has to be positioned very precisely. In order to reduce the effects of the wall, these have been replaced by thin foils in the throat and diffuser of the venturi. This has led to several adjustments to the set-up. Al the other nuiasuring locations, glass 'screws' have been applied. Furthermore, the LDA data had to be corrected for velocity bias. The time between data correction method proved to be the best out of five different methods for the performed measurements. All data sets have been tested using diagnostic techniques in order to verify their validity. The sudden contraction of the venturi influences all flow properties in and downstream of this device. It creates a 'plug'flow in the throat with a flat axial velocity profile and a turbulence intensity of almost zero, except very close to the wall. In the throat, the flow is no longer in equilibrium according to the local power spectra. Here, dissipation dominates the flow. This 'plug' flow manifests itself as a jet-like flow in the divergent section of the venturi, leading to a strong increase in the production of turbulent kinetic energy near the wall. The significant change in turbulent flow properties is persistent, as 5 diameters downstream of the venturi the turbulence intensity is three times the value of that in turbulent pipe flow. Only, production has shifted towards the centerline and the flow is in equilibrium all along the traverse. Dissipation occurs mainly close to the wall. This downstream behavior is in contrast with turbulent pipe flow, where dissipation occurs in the core region, the only region where the flow is in equilibrium.Kramers Laboratorium voor Fysische TechnologieApplied Science
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
Una concezione capitalistica della modernità: Ivan Kondrat'evič Babst sullo sviluppo della Russia (1852 - 1861)
No full textVariations 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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