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51.
Lucio Lazzarino 《Meccanica》1969,4(1):12-15
Summary The most important applications of Mechanics to flight and space problems are critically examined from the engineer's point of view. In particular the present status of knowledge of the determination of flight paths stability and control characteristics is analyzed on the basis of experimental methods applied to resolving engineering problems of Flight and Space Mechanics.
Inaugural Lecture of National Congress 1967 of A.I.D.A. (Associazione Italiana di Aerotecnica), Milano, October 5–8, 1967. 相似文献
Sommario Dopo aver brevemente esaminato le più importanti applicazioni della Meccanica ai problemi di Ingegneria del volo aereo e spaziale si analizza criticamente da un punto di vista sostanzialmente applicativo lo stato attuale delle conoscenze relativo allo studio del moto delle aerodine, ai problemi di stabilità e di pilotaggio ed allo sviluppo delle tecniche sperimentali più diffusamente impiegate per la risoluzione dei problemi di Meccanica del volo di maggiore interesse pratico.
Inaugural Lecture of National Congress 1967 of A.I.D.A. (Associazione Italiana di Aerotecnica), Milano, October 5–8, 1967. 相似文献
52.
Mariana R. Almeida Deleon N. Correa Jorge J. Zacca Lucio Paulo Lima Logrado Ronei J. Poppi 《Analytica chimica acta》2015
The aim of this study was to develop a methodology using Raman hyperspectral imaging and chemometric methods for identification of pre- and post-blast explosive residues on banknote surfaces. The explosives studied were of military, commercial and propellant uses. After the acquisition of the hyperspectral imaging, independent component analysis (ICA) was applied to extract the pure spectra and the distribution of the corresponding image constituents. The performance of the methodology was evaluated by the explained variance and the lack of fit of the models, by comparing the ICA recovered spectra with the reference spectra using correlation coefficients and by the presence of rotational ambiguity in the ICA solutions. The methodology was applied to forensic samples to solve an automated teller machine explosion case. Independent component analysis proved to be a suitable method of resolving curves, achieving equivalent performance with the multivariate curve resolution with alternating least squares (MCR-ALS) method. At low concentrations, MCR-ALS presents some limitations, as it did not provide the correct solution. The detection limit of the methodology presented in this study was 50 μg cm−2. 相似文献
53.
Although alkyl carbonic acids (ACAs) and their salts are referred to as instable species in aqueous medium, we demonstrate that a monoalkyl carbonate (MAC) can in fact be easily formed from bicarbonate and an alcohol even in the presence of a high amount of water. A CE system with two capacitively coupled contactless conductivity detectors (C?Ds) was used to obtain different parameters about these species and their reactions. Based on the mobilities obtained for a series of alcohols ranging from 1 to 5 carbons, the coefficients of diffusion and the hydrodynamic radii were calculated. When compared with the equivalent carboxylates, MACs have radii systematically smaller. Although the precise pK(a) values of the ACAs could not be obtained, because of the fast decomposition in acid medium, it was possible, for the first time, to show that they are below 4.0. This result suggests that the acidity of an ACA is quite similar to the first hydrogen of H?CO?. Using a new approach to indirectly calibrate the C?D, the kinetic constants and the equilibrium constants of formation were also obtained. The results suggest that the increase in the chain length makes the MACs less stable and more inert. 相似文献
54.
55.
Diels-Alder reactions of a range of 1-(alkoxy/alkyl-substituted phenyl)buta-1,3-dienes with methyl vinyl ketone and methyl acrylate carried out in ethanol as the reaction medium under 9 kbar pressure were investigated. The use of high pressure as the activating method of the Diels-Alder reactions allows the efficient and endodiastereoselective generation of a series of cis-cyclohexenyl-benzene cycloadducts, which are selectively converted into their trans-epimers. The cis-cyclohexenyl-benzenes and trans-cyclohexenyl-benzenes produced are useful precursors for accessing substituted privileged cis-6a,7,8,10a-tetrahydro-6H-benzo[c]chromene and trans-6a,7,8,10a-tetrahydro-6H-benzo[c]chromene skeletons. The total syntheses of Δ(9)-cis-tetrahydrocannabinol (THC) and Δ(9)-trans-THC, through the use of selected Diels-Alder adducts, are described. Finally, a route for obtaining Δ(9)-trans-THC in both enantiomeric pure forms based on the (S)-(-)-1-amino-2-(methoxymethyl)pyrrolidine (SAMP)-hydrazone method is also reported. 相似文献
56.
Pietro Caputo Fabio Martinelli François Simenhaus Fabio Lucio Toninelli 《纯数学与应用数学通讯》2011,64(6):778-831
We consider the Glauber dynamics for the Ising model with “+” boundary conditions, at zero temperature or at a temperature that goes to zero with the system size (hence the quotation marks in the title). In dimension d = 3 we prove that an initial domain of linear size L of “−” spins disappears within a time τ+, which is at most L2(log L)c and at least L2/(c log L) for some c > 0. The proof of the upper bound proceeds via comparison with an auxiliary dynamics which mimics the motion by mean curvature that is expected to describe, on large time scales, the evolution of the interface between “+” and “−” domains. The analysis of the auxiliary dynamics requires recent results on the fluctuations of the height function associated to dimmer coverings of the infinite honeycomb lattice. Our result, apart from the spurious logarithmic factors, is the first rigorous confirmation of the Lifshitz law τ+ ≃ const × L2, conjectured on heuristic grounds [8, 13]. In dimension d = 2, τ+ can be shown to be of order L2 without logarithmic corrections: the upper bound was proven in [6], and here we provide the lower bound. For d = 2, we also prove that the spectral gap of the generator behaves like for L large, as conjectured in [2]. © 2011 Wiley Periodicals, Inc. 相似文献
57.
We present a simple strategy in order to show the existence and uniqueness of the infinite volume limit of thermodynamic
quantities, for a large class of mean field disordered models, as for example the Sherrington-Kirkpatrick model, and the Derrida
p-spin model. The main argument is based on a smooth interpolation between a large system, made of N spin sites, and two similar but independent subsystems, made of N
1
and N
2
sites, respectively, with N
1
+N
2
=N. The quenched average of the free energy turns out to be subadditive with respect to the size of the system. This gives immediately
convergence of the free energy per site, in the infinite volume limit. Moreover, a simple argument, based on concentration
of measure, gives the almost sure convergence, with respect to the external noise. Similar results hold also for the ground
state energy per site.
Received: 19 April 2002 / Accepted: 22 April 2002 Published online: 6 August 2002 相似文献
58.
A theoretical model of disorder for the etched holes or pillars in a generic two-dimensional photonic crystal slab is presented. This model is employed to calculate the effects of size disorder on propagation losses in linear photonic crystal waveguides as well as on quality (Q)-factors in photonic crystal nano-cavities. The main results obtained by the present theory and shown in this work are: (a) large single-mode bandwidth and low-loss (<0.1 dB/mm) propagation of light is predicted for increased-width membrane-type photonic crystal waveguides, (b) pillar-based lattices show reduced sensitivity to size fluctuations than hole-based ones, (c) the effects of disorder on cavity Q-factors are quantitatively evaluated. An extension of the model is also introduced in order to take into account the side-wall micro-roughness of the perfectly vertical holes, and preliminary results of this more general approach are discussed. 相似文献
59.
Lucio Randaccio Silvano Geremia Jochen Wuerges 《Journal of organometallic chemistry》2007,692(6):1198-1215
This review deals with results from crystallographic studies on proteins that interact with the essential micronutrient cobalamin (vitamin B12). Both B12-dependent enzymes and B12-transport proteins are described with an emphasis on structural aspects of cobalamin and its protein environment. 相似文献