A comparison of two microplane constitutive models for quasi-brittle materials

This article presents a comparison of two microplane constitutive models. The basis of the microplane constitutive models are described and the adopted assumptions for the conception of these models are discussed, with regard to: decomposition of the macroscopic strains into the microplanes, definition of the microplane material laws, including the choice of variables that control the material degradation, and homogenization process to obtain the macroscopic quantities. The differences between the two models, with respect to the employed assumptions, are emphasized and expressions to calculate the macroscopic stresses are presented. The models are then used to describe the behavior of quasi-brittle materials by finite element simulations of uniaxial tension and compression and pure share stress tests. The results of the simulations permit to compare the capability of the models in describing the post critical strain-softening behavior, without numerically induced strain localization.     

Spatial variation of bandgap energy in In0.53Ga0.47As

We report the observation of spatial variation of the bandgap energy of In_0.53Ga_0.47As in high quality epitaxial samples grown lattice matched to InP. Nine samples grown by three different techniques (LPE, VPE and MBE) were investigated and they all showed this apparently random spatial variation. A bandgap variation as large as 15 meV was observed over distances of the order of 1 mm, an effect corresponding to two percent of bandgap energy.     

Amplification and spectral shifts of vocalizations inside burrows of the frog Eupsophus calcaratus (Leptodactylidae)

A variety of animals that communicate by sound emit signals from sites favoring their propagation, thereby increasing the range over which these sounds convey information. A different significance of calling sites has been reported for burrowing frogs Eupsophus emiliopugini from southern Chile: the cavities from which these frogs vocalize amplify conspecific vocalizations generated externally, thus providing a means to enhance the reception of neighbor's vocalizations in chorusing aggregations. In the current study the amplification of vocalizations of a related species, E. calcaratus, is investigated, to explore the extent of sound enhancement reported previously. Advertisement calls broadcast through a loudspeaker placed in the vicinity of a burrow, monitored with small microphones, are amplified by up to 18 dB inside cavities relative to outside. The fundamental resonant frequency of burrows, measured with broadcast noise and pure tones, ranges from 842 to 1836 Hz and is significantly correlated with the burrow's length. Burrows change the spectral envelope of incoming calls by increasing the amplitude of lower relative to higher harmonics. The call amplification effect inside burrows of E. calcaratus parallels the effect reported previously for E. emiliopugini, and indicates that the acoustic properties of calling sites may affect signal reception by burrowing animals.     

Luminescence in high purity In0.53Ga0.47As

We have investigated luminescence processes in high purity In_0.53Ga_0.47As grown by liquid phase epitaxy on InP substrate. The origins of luminescence processes have been determined by studying the dependence of emission intensity and spectrum on temperature. We show that exciton-ionized donor complex dominates the luminescence at 2K. With increasing temperature, the luminescence spectrum is dominated by donor-valence band and free electron-free hole recombination. Spectrum and bandgap energy are found to be dependent on the excitation position.     

Sudden onset of log-periodicity and superdiffusion in non-Markovian random walks with amnestically induced persistence: exact results

We consider strongly interacting boson-boson mixtures on one-dimensional lattices and, by adopting a qualitative mean-field approach, investigate their quantum phases as the interspecies repulsion is increased. In particular, we analyze the low-energy quantum emulsion metastable states occurring at large values of the interspecies interaction, which are expected to prevent the system from reaching its true ground state. We argue a significant decrease in the visibility of the time-of-flight images in the case of these spontaneously disordered states.     

The price of anarchy and stability in general noisy best-response dynamics

Logit-response dynamics (Alós-Ferrer and Netzer in Games Econ Behav 68(2):413–427, 2010) are a rich and natural class of noisy best-response dynamics. In this work we revise the price of anarchy and the price of stability by considering the quality of long-run equilibria in these dynamics. Our results show that prior studies on simpler dynamics of this type can strongly depend on a sequential schedule of the players’ moves. In particular, a small noise by itself is not enough to improve the quality of equilibria as soon as other very natural schedules are used.     

A hybrid algorithm for the Heterogeneous Fleet Vehicle Routing Problem

This paper deals with the Heterogeneous Fleet Vehicle Routing Problem (HFVRP). The HFVRP generalizes the classical Capacitated Vehicle Routing Problem by considering the existence of different vehicle types, with distinct capacities and costs. The objective is to determine the best fleet composition as well as the set of routes that minimize the total costs. The proposed hybrid algorithm is composed by an Iterated Local Search (ILS) based heuristic and a Set Partitioning (SP) formulation. The SP model is solved by means of a Mixed Integer Programming solver that interactively calls the ILS heuristic during its execution. The developed algorithm was tested in benchmark instances with up to 360 customers. The results obtained are quite competitive with those found in the literature and new improved solutions are reported.