32 research outputs found
Multiferroic (Nd,Fe)-doped PbTiO3 ceramics with coexistent ferroelectricity and magnetism at room temperature
We report the structural, dielectric, elastic, ferroelectric and ferromagnetic properties of multiferroic (Nd, Fe)-doped PbTiO3 perovskite ceramics with composition (Pb 0.88 Nd 0.08 )(Ti 0.94 Fe 0.04 Mn 0.02 )O 3 , prepared by different solid state reaction methods: the first one based on a single-stage calcination (Method I) and the second based on a double-stage calcination (Method II). Structural, dielectric and anelastic measurements evidenced a double phase transition for samples prepared by Method I, which has been attributed to phase separation. This phase separation has been confirmed also by TEM and HRTEM investigations. Samples prepared by Method II showed a single phase transition from paraelectric to ferroelectric phase. We found coexistent ferroelectric and ferromagnetic properties, also at room-temperature, but only for ceramics prepared by Method II. The crucial role of calcination process for avoiding phase separation and obtaining homogeneous structures with ferroelectric and ferromagnetic order is underlined
A century of human interventions on sediment flux variations in the Danube-Black Sea transition zone
Many deltas around the world have recorded a decreasing sediment input, mostly due to retention in dams constructed on the river or in the river basin. The Danube River has recorded a significant decrease of its sediment supply to the Danube Delta and the NW Black Sea. This study uses 210Pb and 137Cs dating, to investigate the effects of the decreasing sediment flux in lakes, lagoons, delta front and prodelta area. Both the effects of the Iron Gate I and II dams and other local factors are discussed. These results define the period of 1960-1990 as the ‘major anthropic interventions period’ in the Danube Delta. Results show a decrease in siliciclastic flux, especially in lakes, the Sahalin lagoon and the prodelta area and a general increase in the Musura lagoon and the delta front area. Sand content is also shown to decrease in most areas and is replaced by silt. The changes in sediment accumulation rates depend mostly on the hydrological connectivity of the area and the local hydrotechnical works. Overall, the local anthropic interventions in the delta affect sediment flux in the subaerial delta and the delta front, while the prodelta is affected by the overall decrease caused by interventions in the river basin. This study can contribute to improving management strategies in the area and to a better understanding of future research needs in the Danube Delta-Black Sea system
Advancing integrated research on European river–sea systems: the DANUBIUS-RI project
Research at the interface between terrestrial, riverine, estuarine and marine environments is frequently constrained by significant disciplinary and geographical boundaries. This article outlines an international initiative, DANUBIUS-RI, which aims to address these problems by facilitating biogeochemical monitoring and interdisciplinary research on river–sea systems. The scope of the project spans the environmental, social and economic sciences and was accepted into the European Strategy Forum on Research Infrastructures roadmap in 2016. When operational, DANUBIUS-RI will offer researchers access to interdisciplinary expertise, facilities and European river–sea systems, providing a comprehensive platform for multidisciplinary research and training
Advances in Vehicular Ad-hoc Networks (VANETs): challenges and road-map for future development
Recent advances in wireless communication technologies and auto-mobile industry have triggered a significant research interest in the field of vehicular ad-hoc networks (VANETs) over the past few years. A vehicular network consists of vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications supported by wireless access technologies such as IEEE 802.11p. This innovation in wireless communication has been envisaged to improve road safety and motor traffic efficiency in near future through the development of intelligent transportation system (ITS). Hence, governments, auto-mobile industries and academia are heavily partnering through several ongoing research projects to establish standards for VANETs. The typical set of VANET application areas, such as vehicle collision warning and traffic information dissemination have made VANET an interesting field of mobile wireless communication. This paper provides an overview on current research state, challenges, potentials of VANETs as well as the ways forward to achieving the long awaited ITS
Transition metal M(II) complexes with isonicotinoylhydrazone-9-anthraldehyde
New complexes of isonicotinoylhydrazone-9-anthraldehyde with Cu(II), Co(II) and Ni(II) have been prepared and characterized by analytical and physico-chemical techniques, such as elemental and thermal analyses, magnetic susceptibility and conductivity measurements, and electronic, EPR and IR spectral studies. The infrared spectral studies revealed the bidentate or monodentate nature of the Schiff base in the complexes; the pyridine nitrogen does not participate in the coordination. A tetrahedral geometry is suggested for the nitrate-complexes and an octahedral geometry for the others. Thermal studies support the chemical formulation of these complexes
Synthesis, characterisation and thermal behaviour of some complexes with ligands having 1,3,4-thiadiazole moieties
Generalized bent functions - sufficient conditions and related constructions
The necessary and sufficient conditions for a class of functions
, where is an even
positive integer, have been recently identified for and . In this
article we give an alternative characterization of the generalized
Walsh-Hadamard transform in terms of the Walsh spectra of the component Boolean
functions of , which then allows us to derive sufficient conditions that
is generalized bent for any even . The case when is not a power of two,
which has not been addressed previously, is treated separately and a suitable
representation in terms of the component functions is employed. Consequently,
the derived results lead to generic construction methods of this class of
functions. The main remaining task, which is not answered in this article, is
whether the sufficient conditions are also necessary. There are some
indications that this might be true which is also formally confirmed for
generalized bent functions that belong to the class of generalized
Maiorana-McFarland functions (GMMF), but still we were unable to completely
specify (in terms of necessity) gbent conditions.Comment: 20 page