Addendum to "Nonlinear quantum evolution with maximal entropy production"

The author calls attention to previous work with related results, which has escaped scrutiny before the publication of the article "Nonlinear quantum evolution with maximal entropy production", Phys.Rev.A63, 022105 (2001).Comment: RevTex-latex2e, 2pgs., no figs.; brief report to appear in the May 2001 issue of Phys.Rev.

Cables and fire hazards

Besides describing the experiments conducted to develop a nonflammable cable, this article discusses several considerations regarding other hazards which might result from cable fires, particularly the toxicity and opacity of the fumes emitted by the burning cable. In addition, this article examines the effects of using the Oxygen Index as a gauge of quality control during manufacture

A nonlinear model dynamics for closed-system, constrained, maximal-entropy-generation relaxation by energy redistribution

We discuss a nonlinear model for the relaxation by energy redistribution within an isolated, closed system composed of non-interacting identical particles with energy levels e_i with i=1,2,...,N. The time-dependent occupation probabilities p_i(t) are assumed to obey the nonlinear rate equations tau dp_i/dt=-p_i ln p_i+ alpha(t)p_i-beta(t)e_ip_i where alpha(t) and beta(t) are functionals of the p_i(t)'s that maintain invariant the mean energy E=sum_i e_ip_i(t) and the normalization condition 1=sum_i p_i(t). The entropy S(t)=-k sum_i p_i(t) ln p_i(t) is a non-decreasing function of time until the initially nonzero occupation probabilities reach a Boltzmann-like canonical distribution over the occupied energy eigenstates. Initially zero occupation probabilities, instead, remain zero at all times. The solutions p_i(t) of the rate equations are unique and well-defined for arbitrary initial conditions p_i(0) and for all times. Existence and uniqueness both forward and backward in time allows the reconstruction of the primordial lowest entropy state. The time evolution is at all times along the local direction of steepest entropy ascent or, equivalently, of maximal entropy generation. These rate equations have the same mathematical structure and basic features of the nonlinear dynamical equation proposed in a series of papers ended with G.P.Beretta, Found.Phys., 17, 365 (1987) and recently rediscovered in S. Gheorghiu-Svirschevski, Phys.Rev.A, 63, 022105 and 054102 (2001). Numerical results illustrate the features of the dynamics and the differences with the rate equations recently considered for the same problem in M.Lemanska and Z.Jaeger, Physica D, 170, 72 (2002).Comment: 11 pages, 7 eps figures (psfrag use removed), uses subeqn, minor revisions, accepted for Physical Review

Probabilistic framework for multiaxial LCF assessment under material variability

The influence of material variability upon the multiaxial LCF assessment of engineering components is missing for a comprehensive description. In this paper, a probabilistic framework is established for multiaxial LCF assessment of notched components by using the Chaboche plasticity model and Fatemi-Socie criterion. Simulations from experimental results of two steels reveal that the scatter in fatigue lives can be well described by quantifying the variability of four material parameters Ï\u83fâ\u80²,εfâ\u80²,b,c. A procedure for choosing the safety factor for fatigue design has been derived by using first order approximation

Discussion of models for LCF small crack growth

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Analysis of Fatigue Strength of L-PBF AlSi10Mg with Different Surface Post-Processes: Effect of Residual Stresses

Space and aerospace industries has been starting in the recent years the replacement process of parts and components obtained by traditional manufacturing processes with those produced by Additive Manufacturing (AM). The complexity of the obtainable parts makes, in general, challenging the superficial post processing of some zones, making a stringent requirement the investigation of the fatigue performances of components with rough superficial state or machined. The aim of this work is then to analyse and compare the fatigue performances of an additively manufactured (AMed) AlSi10Mg material considering both the effects of the manufacturing defects and residual stresses related to three different superficial states, namely machined, net-shape and sandblasted. The residual stress profiles of the three superficial states were found to play a key role in determining the fatigue properties of the analysed material, while the manufacturing defects at the failure origin were found to be comparable among the three series. To take into account the combined effect of residual stresses and manufacturing defects a fracture mechanics approach was considered for the estimation of the fatigue performances in both infinite and finite life regimes. It was found that by considering the nominal measured residual stress profiles in the fracture mechanics model the estimations were satisfactory compared to the experimental data-point. To increase the accuracy of the fatigue life estimations a series of numerical analyses were performed aimed to investigate the residual stresses relaxation during the cyclic loading. The adoption of the relaxed residual stress profiles in the fracture mechanics model resulted in good estimations respect to the experimental data-points, highlighting the necessity in adopting such developed approaches during the design phase of AM parts and components

Total synthesis of tetracyclic kynurenic acid analogues isolated from chestnut honey

A short and efficient synthesis of novel tetracyclic Kynurenic acid analogues, isolated from chestnut honey, is described. The crucial step of the strategy was a MW-assisted cyclization of enamines of ethyl dioxohexahydropyrrolizine and 2,3-dioxooctahydroindolizine carboxylates to obtain 2,3,6,11b-tetrahydro-1H-pyrrolizino[2,1-b]quinoline-5,11-dione and 5,8,91,011,11a-hexahydroindolizino[2,1-b]quinoline-6,12-dione, respectively. Because of its modular nature, the synthetic strategy can have value as a general method for the preparation of compounds containing these new heterocyclic scaffolds

Editorial

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