Evidence of the Zn vacancy acting as the dominant acceptor in n-type ZnO

We have used positron annihilation spectroscopy to determine the nature and the concentrations of the open volume defects in as-grown and electron irradiated (E(el)=2 MeV, fluence 6 x 10(17) cm(-2)) ZnO samples. The Zn vacancies are identified at concentrations of [V(Zn)] approximately 2 x 10(15) cm(-3) in the as-grown material and [V(Zn)] approximately 2 x 10(16) cm(-3) in the irradiated ZnO. These concentrations are in very good agreement with the total acceptor density determined by temperature dependent Hall experiments. Thus, the Zn vacancies are dominant acceptors in both as-grown and irradiated ZnO.     

11B and constraints on neutrino oscillations and spectra from neutrino nucleosynthesis

We study the sensitivity to variations in the triple-alpha and 12C(α,γ)16O reaction rates, of the yield of the neutrino-process isotopes 7Li, 11B, 19F, 138La, and 180Ta in core-collapse supernovae. Compared to solar abundances, less than 15% of 7Li, about 25%-80% of 19F, and about half of 138La is produced in these stars. Over a range of ±2σ for each helium-burning rate, 11B is overproduced and the yield varies by an amount larger than the variation caused by the effects of neutrino oscillations. The total 11B yield, however, may eventually provide constraints on supernova neutrino spectra.     

An Approach for Microprobe Measurement and Modeling for Millimeter-Wave Application

This paper describes a simple method to check the performance of microprobe. The two-port S-parameters of the microprobe are determined by one-port S-parameters measurement using HP 8510XF Network Analyzer. Based on the measurement, an equivalent circuit model for the microprobe is presented and good agreement between the measurement results and modeling results is obtained.     

Electron and hole conductivity in CuInS2

Single crystals of CuInS₂ have been grown from the melt and annealed in In or S to produce good n- or p-type conductivity, respectively. Two donor levels, one shallow and one deep (0.35 eV), and one acceptor level at 0.15 eV are identified. The hole-mobility data are best fitted with an effective mass $\text{m}{}_{\mathrm{<mtext>p</mtext>}}\text{1?1.3m}{}_{\mathrm{e}}$, which can be explained by simple, two band $\text{k}$. $\text{p}$ theory if the valence band has appreciable d character. Above 300°K, the hole mobility falls rapidly, evidently due to multiband conduction and/or interband scattering between the nondegenerate and degenerate valence bands. The conduction band mobility appears to be dominated, in many samples, by large concentrations ( >10¹⁸cm^?3) of native donors and acceptors, which are closely compensated.     

Fitness Landscape Analysis and Metaheuristics Efficiency

Landscape analysis has been identified as a promising way to develop efficient optimization methods. Nevertheless, the links between properties of the landscape and efficiency of methods is not easy to understand. In this article, we propose to give a contribution in this field using a vehicle routing problem as an illustration. Metaheuristics use a neighborhood operator that connects solutions of the search space. Thus, this operator acts on the dynamics of the search and impacts metaheuristics efficiency. Therefore, we characterize two landscapes differenciated by their neighborhood function and then, we analyze the performance of classical metaheuristics using one or the other neighborhood operator. Finally, a discussion provides insights on the relations between results of the landscape analysis and results of methods performance.     

On the structure of multiobjective combinatorial search space: MNK-landscapes with correlated objectives

The structure of the search space explains the behavior of multiobjective search algorithms, and helps to design well-performing approaches. In this work, we analyze the properties of multiobjective combinatorial search spaces, and we pay a particular attention to the correlation between the objective functions. To do so, we extend the multiobjective NK-landscapes in order to take the objective correlation into account. We study the co-influence of the problem dimension, the degree of non-linearity, the number of objectives, and the objective correlation on the structure of the Pareto optimal set, in terms of cardinality and number of supported solutions, as well as on the number of Pareto local optima. This work concludes with guidelines for the design of multiobjective local search algorithms, based on the main fitness landscape features.     

Connecting free volume with shape memory properties in noncytotoxic gamma‐irradiated polycyclooctene

The free volume holes of a shape memory polymer have been analyzed considering that the empty space between molecules is necessary for the molecular motion, and the shape memory response is based on polymer segments acting as molecular switches through variable flexibility with temperature or other stimuli. Therefore, thermomechanical analysis (TMA) and positron annihilation lifetime spectroscopy (PALS) have been applied to analyze shape recovery and free volume hole sizes in gamma‐irradiated polycyclooctene (PCO) samples, as a noncytotoxic alternative to more conventional PCO crosslinked via peroxide for future applications in medicine. Thus, a first approach relating structure, free volume holes and shape memory properties in gamma‐irradiated PCO is presented. The results suggest that free volume holes caused by gamma irradiation in PCO samples facilitate the recovery process by improving movement of polymer chains and open possibilities for the design and control of the macroscopic response. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1080–1088