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From empirical engineering to science-based engineering: the assessment by three mathematicians of the “San Pietro” dome (1742)
Get PDFThe studies on the mechanic behaviour of domes, based on the static analysis of arches and vaults, started in the first half of the XVII century. At the end of 1741, when the Pope Benedetto XIV commissioned an assessment to three mathematicians Roger Joseph Boscovich, François Jacquier e Thomas Le Seur, belonging to the Repubblica Romana dei dotti. There where serious worries on the static conditions of the San Pietro vault where important cracks could be appreciated. Some interesting studies were developed on this problem, even followed by learned and heated arguments, that lead to compile treatises that systemized the knowledge on this argument. The historical documents even report the opinion of other experts, for example that one of the mathematician Giovanni Poleni from Padua. On spite of that, the study of the three previous mathematicians was different from the others carried out before because it had an important innovation: the assessment was accomplished, perhaps for the first time, using a scientific criterion in order to interpret the mechanic behaviour of an architectural structure. Its historical importance resides on the scientific theoretical conceptions used to analyze a structural problem that were completely different from the empirical rules, at most of geometric nature, used before. The principle of virtual works was further applied in the assessment. It was used to define the size of the metal rings for the drum of the vault. Some researchers intend this assessment as the moment when the change from the engineering based on artisan traditions to the engineering based on the application of new scientific theories has been accomplished
Ottimizzazione dei tempi di set-up nelle lavorazioni per asportazione di truciolo
No full textRIASSUNTO: Questo articolo, attraverso l'aiuto di un caso applicativo alla Piaggio, descrive un metodo per l'ottimizzazione del processo di lavorazione per asportazione di truciolo di un lotto di pezzi, mettendo in evidenza l'andamento dei costi in funzione del numero di sostituzioni degli utensili. SUMMARY This article, based on a case study about Piaggio, describes an optimization method for machining a batch of parts, focusing on costs as a function of tools chang
Omologazione di dispositivi di antipattinaggio per rotabili ferroviari. Prove su carrozza isolata
No full textRIASSUNTO: Descrizione di un piano di progetto per realizzare una procedura per testare le capacità di intervento di dispositivi di antipattinaggio montati su veicoli ferroviari sulla base dei requisiti dichiarati dal costruttore e nel rispetto di prescrizioni finalizzate all’accreditamento del Laboratorio da parte del SINAL. SUMMARY Description of a practical plan to design and implement a procedure to test the Anti-slip/slide devices assembled on Rail Vehicles
Pharmacokinetic differences of tramadol in several animal species and human beings
No full textSUMMARY: Tramadol is an opioid centrally acting analgesic used in the two last decades to trait pain in humans. This review takes into account the PK/PD data in different tramadol formulations administered to humans. Since T has been recently suggest as potential molecule for long term therapy in chronic pain in animals, an evaluation of its PK/PD data in several animal species is also reported
The critical behavior of 3D Ising glass models: universality and scaling corrections
No full textWe perform high-statistics Monte Carlo simulations of three three-dimensional
Ising spin-glass models: the +-J Ising model for two values of the disorder
parameter p, p=1/2 and p=0.7, and the bond-diluted +-J model for
bond-occupation probability p_b = 0.45. A finite-size scaling analysis of the
quartic cumulants at the critical point shows conclusively that these models
belong to the same universality class and allows us to estimate the
scaling-correction exponent omega related to the leading irrelevant operator,
omega=1.0(1). We also determine the critical exponents nu and eta. Taking into
account the scaling corrections, we obtain nu=2.53(8) and eta=-0.384(9)
Models of interaction
No full textThe present Technical Report contains two papers that have been accepted at the S.I.N.G. 4 Conference, Wroklav, Poland, 26-28 June 2008. Both papers have been also presented in seminars at the Computer Science Department, the former on June 3 2008 and the latter on January 23 2008. The first paper presents the use of auction mechanisms for the allocation of chores instead of goods. The latter paper presents and analyzes a small set of models that can be used by two players for the barter of goods without the intervention of any numerary good
BpMatch: an efficient algorithm for segmenting sequences, calculating genomic distance and counting repeats.
No full textThere are several important reasons (biological, evolutionary, clinical, etc.) to give a segment-based description of genomic sequences, and, in particular, to detect repeated segments, written both direct and complemented inverted. In some applications, in particular in medical genomics, it is also necessary to count the number of occurrences of a segment. Moreover, by detecting common segments shared by two different sequences it is possible to define a sort of genomic distance between them. Here we propose BpMatch: an algorithm that, working on a suitably modified suffix-tree data structure, allows us to achieve all these three goals (identify repeated segments, including the complemented inverted copies of them, count repeats number and calculate genomic distance) in a fast and efficient way.BpMatch is able to identify exact copies (and complemented inverted copies) of a segment. The operator should define a priori the minimum length of a string, in order to be considered a segment, and the minimum number of occurrences, so that only segments having a number of occurrences greater than are considered to be significant. BpMatch is very efficient; we determined the complexity in time to calculate the self-covering of a string, the alphabet dimension. On the worst case, assuming the alphabet dimension is a constant, the time required to calculate the coverage is O. On the average, using the time required to calculate the coverage is only O. It is important to note that this estimation includes the time required to complete all of the three different tasks: to identify copied segments, to localize them, to count the number of occurrences and to evaluate the sequence coverage
A Computational Comparison of Reformulations of the Perspective Relaxation: SOCP vs. Cutting Planes
No full textThe Perspective Relaxation is a general approach for constructing tight approximations to MINLP problems with semicontinuous variables. Two different reformulations have been proposed for solving it, one resulting in a Second-Order Cone Program, the other based on representing the perspective function by (an infinite number of) cutting planes. We compare the two reformulations on two sets of test problems to determine which one is most effective in the context of exact or approximate Branch-and-Cut algorithms
Static and dynamic structure factors in three-dimensional randomly diluted Ising models
No full textWe consider the three-dimensional randomly diluted Ising model and study the
critical behavior of the static and dynamic spin-spin correlation functions
(static and dynamic structure factors) at the paramagnetic-ferromagnetic
transition in the high-temperature phase. We consider a purely relaxational
dynamics without conservation laws, the so-called model A. We present Monte
Carlo simulations and perturbative field-theoretical calculations. While the
critical behavior of the static structure factor is quite similar to that
occurring in pure Ising systems, the dynamic structure factor shows a
substantially different critical behavior. In particular, the dynamic
correlation function shows a large-time decay rate which is momentum
independent. This effect is not related to the presence of the Griffiths tail,
which is expected to be irrelevant in the critical limit, but rather to the
breaking of translational invariance, which occurs for any sample and which, at
the critical point, is not recovered even after the disorder average
The uniformly frustrated two-dimensional XY model in the limit of weak frustration
No full textWe consider the two-dimensional uniformly frustrated XY model in the limit of
small frustration, which is equivalent to an XY system, for instance a
Josephson junction array, in a weak uniform magnetic field applied along a
direction orthogonal to the lattice. We show that the uniform frustration
(equivalently, the magnetic field) destabilizes the line of fixed points which
characterize the critical behaviour of the XY model for T <= T_{KT}, where
T_{KT} is the Kosterlitz-Thouless transition temperature: the system is
paramagnetic at any temperature for sufficiently small frustration. We predict
the critical behaviour of the correlation length and of gauge-invariant
magnetic susceptibilities as the frustration goes to zero. These predictions
are fully confirmed by the numerical simulations