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101.
Giannantonio Sacchi 《Meccanica》1971,6(2):101-103
Summary By going back to a theorem[1] [2] which gives an upper bound of the average plastic collapse load of a structure whose elements have random resistance, a method is demonstrated for supplying a lower bound.It will then be shown how it is possible to find an upper and a lower bound of the variance of collapse load of all structures conceivable in terms of random resistance.As far as limit analysis is concerned only a deterministic calculation is requested by the above methods.
The results presented in this paper were obtained in the course of research sponsored by the C.N.R. 相似文献
Sommario Richiamato un teorema[1] [2] che fornisce un maggiorante della media dei moltiplicatori di collasso plastico di una struttura dotata di elementi a resistenza aleatoria, si dimostra come sia possibile fornirne un minorante. Si dimostra poi come sia possibile fornire un minorante ed un maggiorante della varianza dei moltiplicatori di collasso.I limiti indicati sono, benchè basati su quantità fornite dalla elaborazione di variabili aleatorie, calcolati con criteri deterministici dal punto di vista dell'analisi limite.
The results presented in this paper were obtained in the course of research sponsored by the C.N.R. 相似文献
102.
Summary Some failure conditions for heterogeneous layered media, formed by two alternating homogeneous materials, are presented. The failure criteria have been obtained by a homogenization procedure, on the basis of the criteria of the materials forming the layered medium. The paper deals with layers formed by Mohr-Coulomb's type materials (the cases of cohesionless materials or materials provided by the same friction angle are discussed), as well as with layers undergoing the maximum tensile stress criterion. Theoretical predictions are in good agreement with the experimental results obtained by other authors on layered sands and laminated rocks.
Sommario Vengono presentati alcuni criteri di rottura per materiali stratificati eterogenei, caratterizzati da regolare altenanza di due materiali omogenei. Tali criteri sono stati ottenuti mediante una procedura di omogeneizzazione, sulla base delle condizioni di rottura dei materiali che compongono il continuo stratiflcato. Sono stati considerati strati formati da materiali del tipo di Mohr-Coulomb (per i casi in cui i materiali sono o privi di coesione, oppure sono dotati dello stesso angolo d'attrito), o da materiali che obbediscono al criterio della massima trazione. Le pre-dizioni teoriche mostrano un buon accordo con i risultati di prove sperimentali eseguite da altri autori su sabbie e rocce stratificate.相似文献
103.
Eleonora Polo Simona Losio Maria Carmela Sacchi Maurizio Galimberti 《Journal of polymer science. Part A, Polymer chemistry》2013,51(6):1436-1447
New ω‐alkenyl‐substituted ansa‐bridged bisindenyl zirconium complexes are prepared and tested as self‐immobilized catalysts for ethene polymerization. But, even at very high concentration of the tethered complexes and low pressure of ethene, there is no evidence of their insertion into the polyethene chain. A “cross polymerization” test, performed by copolymerizing the tethered complexes with ethene using rac‐Me2Si(2‐MeBenzInd)2ZrCl2 ( MBI ), does not lead to their incorporation into the polyethene chain. However, the corresponding ligand proves to be a suitable comonomer for ethene, and, through copolymerization promoted by MBI, innovative poly(ethene‐co‐2,2′‐bis[(1H‐inden‐3′‐yl)‐hex‐5‐ene) copolymers are prepared and characterized by 13C NMR. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
104.
A. Demski L. Guitton A. Portevin I. G. Farbenindustrie A. G. H. Reichert W. R. G. Atkins P. Bastien V. P. Sacchi und A. V. Blom 《Fresenius' Journal of Analytical Chemistry》1940,119(1-2):64-67
Ohne Zusammenfassung 相似文献
105.
Incoronata Tritto Laura Boggioni Maria Carmela Sacchi Paolo Locatelli Dino R. Ferro Augusto Provasoli 《Macromolecular rapid communications》1999,20(5):279-283
A series of ethylene‐norbornene copolymers were synthesized in the presence of zirconocenes with different symmetries and ligand patterns and at different norbornene (N)/ethylene (E) mole ratios. Copolymers were characterized by 13C NMR spectroscopy; Inadequate NMR sequences were used also. The comparison of 13C NMR spectra of copolymers prepared with different norbornene content and the correlation between 13C NMR chemical shifts and conformational structures of the chain on the basis of molecular mechanics calculations were performed. Preliminary assignments were revised and new comonomer sequences such as ENNE which contain meso and racemo NN dyads were assigned. 相似文献
106.
R. Bonetti A. Guglielmetti G. Poli E. Sacchi D. Fink M.A.C. Hotchkis G.E. Jacobsen E.M. Lawson Q. Hua A.M. Smith C. Tuniz 《The European Physical Journal A - Hadrons and Nuclei》1999,5(2):235-238
Various uranium and thorium minerals have been analysed with accelerator mass spectrometry to determine their 14C content. It is found that, whenever the contribution from secondary reactions such as the 11B(α,p)14C is sufficiently low, the 14C concentration is consistent with that expected from 14C (spontaneous) cluster radioactivity from radium isotopes of the uranium and thorium natural series.
Received: 15 February 1999 相似文献
107.
Jan Vogel Maurizio Sacchi Ronald J. H. Kappert John C. Fuggle Jeroen B. Goedkoop Nicholas B. Brookes Gerrit van der Laan Ernesto E. Marinero 《Journal of magnetism and magnetic materials》1995,150(3):293-303
We have used linearly and circularly polarized X-rays to determine the magnetic properties of several TbxFe1−x amorphous films. Absorption measurements on the M4.5 edges of Tb and the L2.3 edges of Fe allowed us to obtain information about the size and direction of local magnetic moments. Our results confirm that linear dichorism in rare earth M4.5 edges can give useful information about both crystal field and magnetic effects. 相似文献
108.
109.
F. Aliotta M. E. Fontanella M. Sacchi C. Vasi G. La Manna V. Turco-Liveri 《Colloid and polymer science》1996,274(9):809-818
We report new results from small-angle neutron scattering ond
12-cyclohexane/lecithin/water micellar solutions performed as a function of the water content (w
0), temperature (T) and dispersed phase volume fraction (). The data from dilute samples are interpretable in terms of the existence of giant cylindrical reverse micelles and are well fit with a core-shell model (that provides the micelle structure and dimensions) with values of 28 and 45 Å for the inner core and the outer shell radii, almost independent on temperature and concentration. Such a result could appear consistent with the current idea that worm-like micelles are living polymers. On the contrary, the appearance of a sharp interference maximum at high concentrations (>0.15) suggests arguments against the current hypothesis of an entangled network of giant flexible cylinders. Further arguments against the current hypothesis are given by the close similarity between the above described results and those from free of water micelles (for sure not cylinders). All the data are well fitted in terms of a unique model taking into account the micellar form factor plus a hard sphere structure factor. The data analysis suggests a micellar size distribution determined by the competition between concentration and interaction effects on which temperature plays not a minor role. Following our results, the current hypothesis of a gel structure in terms of an entangled network can be assumed as wrong and some caution has to be taken in assuming wormlike micelles as living polymers. 相似文献
110.
G. Bottiroli G. Prenna A. Andreoni C. A. Sacchi O. Svelto 《Photochemistry and photobiology》1979,29(1):23-28
The fluorescence of several bacterial DNAs stained with quinacrine mustard have been investigated using a laser microfluorometer with a spatial resolution of - 0.3 μm and a temporal resolution of ?0.3 ns connected to a digital signal averager. Experiments performed on Micrococcus lysodeikticus samples show that both cytological preparations and the corresponding purified DNAs give coincident fluorescence curves, thus indicating that the fluorescence observed in the former case is to be attributed to the bacterial DNA only. Experiments thereafter performed on smears of several bacteria with known AT percentages show that each fluorescence decay curve, after a fast transient, can be fitted by an exponential decay law with a single time constant. This time constant has been found to depend linearly on the square of the AT percentage. We explain this result on the basis of an energy transfer mechanism between dye molecules intercalating AT:AT sequences (donors) and dye molecules bound to either GC:GC or GC:AT sequences (acceptors). The agreement with the experimental data requires that all the bacteria considered present a common value for both the number of base pairs contained in a Förster sphere and for the maximum saturation of the strong binding process. 相似文献