Growth curve in Santa Ines sheep

The objective of this research was to use non-linear models to describe the growth pattern in Santa Ines sheep and to study the influence of environmental effects on curve parameters with the best-fit model. The models included the Brody, Richards, Von Bertalanffy, Gompertz, and Logistic models. We used 773 field reports on 162 animals ranging in age from 120 to 774 days, including 46 males and 116 females. The statistics used to evaluate the quality of fit included RMS (residual mean square), C% (percentage of convergence), R-2 (adjusted determination coefficient) and MAD (mean absolute deviation). Of the fixed effects studied, the only significant relationship was the effect of sex on parameter A. The Richards model was problematic during the process of convergence. Considering all studied criteria, the Logistic model presented the best fit in describing the growth pattern in Santa Ines sheep. (C) 2011 Elsevier B.V. All rights reserved.

Fracture and resistance-curve behavior in hybrid natural fiber and polypropylene fiber reinforced composites

This article presents the results of a combined experimental and theoretical study of fracture and resistance-curve behavior of hybrid natural fiber- and synthetic polymer fiber-reinforced composites that are being developed for potential applications in affordable housing. Fracture and resistance-curve behavior are studied using single-edge notched bend specimens. The sisal fibers used were examined using atomic force microscopy for fiber bundle structures. The underlying crack/microstructure interactions and fracture mechanisms are elucidated via in situ optical microscopy and ex-situ environmental scanning microscopy techniques. The observed crack bridging mechanisms are modeled using small and large scale bridging concepts. The implications of the results are then discussed for the design of eco-friendly building materials that are reinforced with natural and polypropylene fibers.

Generalized Metropolis dynamics with a generalized master equation: An approach for time-independent and time-dependent Monte Carlo simulations of generalized spin systems

The extension of Boltzmann-Gibbs thermostatistics, proposed by Tsallis, introduces an additional parameter q to the inverse temperature beta. Here, we show that a previously introduced generalized Metropolis dynamics to evolve spin models is not local and does not obey the detailed energy balance. In this dynamics, locality is only retrieved for q = 1, which corresponds to the standard Metropolis algorithm. Nonlocality implies very time-consuming computer calculations, since the energy of the whole system must be reevaluated when a single spin is flipped. To circumvent this costly calculation, we propose a generalized master equation, which gives rise to a local generalized Metropolis dynamics that obeys the detailed energy balance. To compare the different critical values obtained with other generalized dynamics, we perform Monte Carlo simulations in equilibrium for the Ising model. By using short-time nonequilibrium numerical simulations, we also calculate for this model the critical temperature and the static and dynamical critical exponents as functions of q. Even for q not equal 1, we show that suitable time-evolving power laws can be found for each initial condition. Our numerical experiments corroborate the literature results when we use nonlocal dynamics, showing that short-time parameter determination works also in this case. However, the dynamics governed by the new master equation leads to different results for critical temperatures and also the critical exponents affecting universality classes. We further propose a simple algorithm to optimize modeling the time evolution with a power law, considering in a log-log plot two successive refinements.

ABSENCE OF STABILIZATION POINT OF THE SPECIES ACCUMULATION CURVE IN TROPICAL FORESTS

The definition of the sample size is a major problem in studies of phytosociology. The species accumulation curve is used to define the sampling sufficiency, but this method presents some limitations such as the absence of a stabilization point that can be objectively determined and the arbitrariness of the order of sampling units in the curve. A solution to this problem is the use of randomization procedures, e. g. permutation, for obtaining a mean species accumulation curve and empiric confidence intervals. However, the randomization process emphasizes the asymptotical character of the curve. Moreover, the inexistence of an inflection point in the curve makes it impossible to define objectively the point of optimum sample size.

Fatigue Reliability of 3 Single-Unit Implant-Abutment Designs

Objectives: Because the mechanical behavior of the implant-abutment system is critical for the longevity of implant-supported reconstructions, this study evaluated the fatigue reliability of different implant-abutment systems used as single-unit crowns and their failure modes. Methods and Materials: Sixty-three Ti-6Al-4V implants were divided in 3 groups: Replace Select (RS); IC-IMP Osseotite; and Unitite were restored with their respective abutments. Anatomically correct central incisor metal crowns were cemented and subjected to separate single load to failure tests and step-stress accelerated life testing (n = 18). A master Weibull curve and reliability for a mission of 50,000 cycles at 200 N were calculated. Polarized-light and scanning electron microscopes were used for failure analyses. Results: The load at failure mean values during step-stress accelerated life testing were 348.14 N for RS, 324.07 N for Osseotite, and 321.29 N for the Unitite systems. No differences in reliability levels were detected between systems, and only the RS system mechanical failures were shown to be accelerated by damage accumulation. Failure modes differed between systems. Conclusions: The 3 evaluated systems did not present significantly different reliability; however, failure modes were different. (Implant Dent 2012;21:67-71)

Probabilistic Envelope Curves for Extreme Rainfall Events - Curve Inviluppo Probabilistiche per Precipitazioni Estreme

A regional envelope curve (REC) of flood flows summarises the current bound on our experience of extreme floods in a region. RECs are available for most regions of the world. Recent scientific papers introduced a probabilistic interpretation of these curves and formulated an empirical estimator of the recurrence interval T associated with a REC, which, in principle, enables us to use RECs for design purposes in ungauged basins. The main aim of this work is twofold. First, it extends the REC concept to extreme rainstorm events by introducing the Depth-Duration Envelope Curves (DDEC), which are defined as the regional upper bound on all the record rainfall depths at present for various rainfall duration. Second, it adapts the probabilistic interpretation proposed for RECs to DDECs and it assesses the suitability of these curves for estimating the T-year rainfall event associated with a given duration and large T values. Probabilistic DDECs are complementary to regional frequency analysis of rainstorms and their utilization in combination with a suitable rainfall-runoff model can provide useful indications on the magnitude of extreme floods for gauged and ungauged basins. The study focuses on two different national datasets, the peak over threshold (POT) series of rainfall depths with duration 30 min., 1, 3, 9 and 24 hrs. obtained for 700 Austrian raingauges and the Annual Maximum Series (AMS) of rainfall depths with duration spanning from 5 min. to 24 hrs. collected at 220 raingauges located in northern-central Italy. The estimation of the recurrence interval of DDEC requires the quantification of the equivalent number of independent data which, in turn, is a function of the cross-correlation among sequences. While the quantification and modelling of intersite dependence is a straightforward task for AMS series, it may be cumbersome for POT series. This paper proposes a possible approach to address this problem.

La sensitività delle curve a fatica oligociclica rispetto alle colate di derivazione per i provini: applicazione alla caratterizzazione di un materiale per cappe di turboalternatore

In questo studio vengono riportati i risultati di prove di fatica oligociclica eseguiti su provini dello stesso materiale ottenuti con uguali processi tecnologici ma provenienti da differenti colate di metallo. Il materiale in questione è un acciaio di elevata qualità frequentemente utilizzato per la realizzazione di cappe per turboalternatori. Obiettivo dello studio è stato ricavare i coefficienti necessari per tracciare le curve di fatica del materiale, non ancora presenti in letteratura, ed infine indagare la bontà del risultato ottenuto con un’analisi statistica delle curve e dei risultati ottenuti. Nella prima parte è descritto l’attuale stato dell’arte e la situazione in cui si colloca il presente studio. Nella seconda parte viene fornita una descrizione dettagliata del materiale studiato, delle condizioni nelle quali sono state eseguite le prove e delle attrezzature utilizzate a tale scopo. Si conclude esponendo i risultati ottenuti, comprensivi dei confronti e delle considerazioni derivate dalle analisi statistiche eseguite.

Il gruppo dei punti razionali sulle curve ellittiche

Il primo capitolo espone nozioni generali sulle varietà e sulle curve algebriche, sulle mappe fra di esse e su alcune proprietà geometriche importanti per caratterizzare le curve ellittiche. Il secondo capitolo propone un'introduzione allo studio geometrico e algebrico di tali curve. Il terzo e il quarto capitolo affrontano lo studio dei punti a coordinate razionali, per curve definite prima su campi locali e poi su campi globali: l'insieme di tali punti è un gruppo. Il risultato fondamentale, contenuto nel teorema di Mordell-Weil, è che tale gruppo è finitamente generato. Tutto il quarto capitolo propone i risultati necessari per la dimostrazione di tale affermazione.