641 research outputs found
New Clonopsis stick insects from Morocco: the amphigonic C. felicitatis sp.n., the parthenogenetic C. soumiae sp.n., and two androgenetic taxa.
No full textNew collections of Moroccan samples of the stick insect Clonopsis allowed the discovery of two new species (the bisexual C. felicitatis sp.n., the all-female parthenogenetic C. soumiae sp.n.), and two all-male clonal androgenetic strains (C. androgenes- 35 and C. androgenes-53). Together with the already known parthenogenetic C. gallica and the new all-female C. soumiae, C. felicitatis forms a numerically polyploid series with 2n535/36, 3n554 and 4n572; all karyotypes are structurally diploid, however, so that it has been suggested that most likely they became re-diploidized in the triploid and tetraploid parthenogens, as apparently happened in other stick insects. Also in the two androgens the karyotype is structurally diploid: therefore C. androgenes-53 should have originated as a re-diploidized triploid. Aside from their karyotype, the males of C. felicitatis are identified by colour stripes, whereas for the androgens and the females of the three Clonopsis taxa, only the chromosome numbers are diagnostic, since body and egg traits, also analysed at SEM level, did not reveal sound differentiating characters, suggesting a close relationship. In line with karyological and SEM observations, preliminary mitochondrial analyses support that C. felicitatis is the mother ancestor of ‘‘polyploid’’ C. gallica, C. soumiae and of both androgens. Together with C. gallica, these new taxa form a cohesive species-complex, well differentiated from the two already known bisexuals C. maroccana and C. algerica. Actually these species do not show directly comparable karyotypes, and their males can also be specifically recognized by their terminalia. These findings throw a significant new light on the hitherto obscure relationships of taxa within the genus. The overall reproductive and chromosomal diversification of North African Clonopsis suggests that the Rif region could well be the radiation centre of the genus, although the ‘‘triploid’’ C. gallica has been able to gain some pre-desert zones towards the South and to widely spread into Europe
Sequential Identification and Autotuning by Relay Techniques of Decentralised Controllers for Multivariable Chemical Processes
No full textImproved Qualitative Shape Analysis Technique for Automatic Detection of Valve Stiction in Flow Control loops
No full textValve stiction is a frequent cause of loop performance deterioration and in recent literature many techniques have been proposed for its automatic detection, [Yamashita (2006). An automatic method for detection of valve stiction in process control loops. Control Engineering Practice, 14, 503–510] proposes a method based on qualitative shape analysis, which is very effective for flow control loops where the valve position (or the proportional flow rate) is available as measurement.
However, additional stiction patterns observed in industrial data are not included in the original
algorithm. This paper provides an analysis and explanation of these patterns on the basis of valve type,
loop dynamics and control system setup, by means of simulation and comparison with industrial data.
The technique is then extended and applied to a plant data set in order to show the improved efficiency
in detecting stiction
Analysis of the molecular weight distribution in free radical polymerization: Modelling of the MWD from the analysis of experimental GPC curves
No full textIn this paper different techniques for the deconvolution of experimental gel permeation chromatography (GPC) curves of polymers obtained from batch reactors are examined with the aim of improving the modelling of the polymerization process. The deconvoution of the GPC curves gives insight into the effects of diffusive phenomena on the values of the average molecular weights (Mn and Mw) and the molecular weight distribution (MWD) of the polymer. Two methods, one based on a two-peak deconvolution and the other one based on a multi-peak deconvolution, are compared. The different characteristics and relative merits of the two methods are illustrated using several sets of experimental data. In conclusion, the first method is less accurate but allows a separation of the two contributions given by the chemical and diffusive control of the MWD; the second method has a sound theoretical background (confirms the prediction of the free volume theory) and is potentially much superior but the results prove to be more sensitive to the quality of the experimental part
Optimal operating conditions of batch reactors for the polymerization of Methylmethacrylate.
No full textA model for the simulation of suspension polymerization of MMA has been developed, which allows to accounts for the effect of diffusive phenomena on reaction rate and to evaluate molecular weight distribution under different operation conditions. The model has been validated by experimental runs carried out in a laboratory reactor. Obtained results show that an increase of the reaction temperature during the gel effect time can have a favourable influence on the polymer quality. The control of temperature profiles in the reactor is indicated as an interesting operating strategy to be adopted in industrial unit
A Systematic Comparison of Identification Techniques Used in Industrial Systems of Autotuning
No full textUn disegno per Isola delle Femmine. Indagini digitali su Gianni Pirrone
No full textPer tentare un primo approccio alla lettura del pensiero architettonico del periodo è sembrato utile prendere spunto proprio dal primo ‘lavoro’ di Gianni Pirrone, la sua tesi di laurea del 1950 di cui sono stati relatori Edoardo Caracciolo e Luigi Epifanio. Il ridisegno critico non solo fa prendere corpo al pensiero del giovane Pirrone ma evidenzia, attraverso la schedatura dei disegni, l’approccio, a quel tempo, della Scuola di Architettura di Palermo ai temi della progettazione architettonica e urbana
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