The magnetic interactions in spin-glasslike Ge/1-x-y/Sn/x/Mn/y/Te diluted magnetic semiconductor

We investigated the nature of the magnetic phase transition in the Ge/1-x-y/Sn/x/Mn/y/Te mixed crystals with chemical composition changing in the range of 0.083 < x < 0.142 and 0.012 < y < 0.119. The DC magnetization measurements performed in the magnetic field up to 90 kOe and temperature range 2-200 K showed that the magnetic ordering at temperatures below T = 50 K exhibits features characteristic for both spin-glass and ferromagnetic phases. The modified Sherrington - Southern model was applied to explain the observed transition temperatures. The calculations showed that the spin-glass state is preferred in the range of the experimental carrier concentrations and Mn content. The value of the Mn hole exchange integral was estimated to be J/pd/ = 0.45+/-0.05 eV. The experimental magnetization vs temperature curves were reproduced satisfactory using the non-interacting spin-wave theory with the exchange constant J/pd/ values consistent with those calculated using modified Sherrington - Southern model. The magnetization vs magnetic field curves showed nonsaturating behavior at magnetic fields B < 90 kOe indicating the presence of strong magnetic frustration in the system. The experimental results were reproduced theoretically with good accuracy using the molecular field approximation-based model of a disordered ferromagnet with long-range RKKY interaction.Comment: 9 pages, 6 figure

Innovative Technologies for District Heating and Cooling: InDeal Project

The paper discusses the outcomes of the conference organized by the InDeal project. The conference took place on 12 December 2018 in Montpellier as part of the EnerGaia energy forum 2018. A holistic interdisciplinary approach for district heating and cooling (DHC) networks is presented that integrates heterogeneous innovative technologies from various scientific sectors. The solution is based on a multi-layer control and modelling framework that has been designed to minimize the total plant production costs and optimize heating/cooling distribution. Artificial intelligence tools are employed to model uncertainties associated with weather and energy demand forecasts, as well as quantify the energy storage capacity. Smart metering devices are utilized to collect information about all the crucial heat substations’ parameters, whereas a web-based platform offers a unique user environment for network operators. Three new technologies have been further developed to improve the efficiency of pipe design of DHC systems: (i) A new sustainable insulation material for reducing heat losses, (ii) a new quick-fit joint for an easy installation, and (iii) a new coating for reducing pressure head losses. The results of a study on the development and optimization of two energy harvesting systems are also provided. The assessment of the environmental, economic and social impact of the proposed holistic approach is performed through a life cycle analysis. The validation methodology of the integrated solution is also described, whereas conclusions and future work are finally given

Barbarie. La nostra civilt\ue0 \ue8 al tramonto?

Raccolta di saggi e traduzioni da testi antichi sul tema del rapporto tra barbarie e civilt\ue0