Four new manganese germanates and silicates, AMnGeO (A = Li, Na) and AMnSiO (A = Na, Ag), were prepared, and their crystal structures were determined using the X-ray Rietveld method. All of them contain all components in tetrahedral coordination. LiMnGeO is orthorhombic (Pmn2) layered, isostructural with LiCdGeO, and the three other compounds are monoclinic (Pn) cristobalite-related frameworks. As in other stuffed cristobalites of various symmetry (Pn AMXO, Pna2 and Pbca AMO), average bond angles on bridging oxygens (here, Mn-O-X) increase with increasing A/X and/or A/M radius ratios, indicating the trend to the ideal cubic (Fd3̅m) structure typified by CsAlO. The sublattices of the magnetic Mn ions in both structure types under study (Pmn2 and Pn) are essentially the same; namely, they are pseudocubic eutaxy with 12 nearest neighbors. The magnetic properties of the four new phases plus LiMnSiO were characterized by carrying out magnetic susceptibility, specific heat, magnetization, and electron spin resonance measurements and also by performing energy-mapping analysis to evaluate their spin exchange constants. AgMnSiO remains paramagnetic down to 2 K, but AMnXO (A = Li, Na; X = Si, Ge) undergo a three-dimensional antiferromagnetic ordering. All five phases exhibit short-range AFM ordering correlations, hence showing them to be low-dimensional magnets and a magnetic field induced spin-reorientation transition at T < T for all AFM phases. We constructed the magnetic phase diagrams for AMnXO (A = Li, Na; X = Si, Ge) on the basis of the thermodynamic data in magnetic fields up to 9 T. The magnetic properties of all five phases experimentally determined are well explained by their spin exchange constants evaluated by performing energy-mapping analysis.

No abstract

For energy supply in the Arctic regions, hybrid systems should be designed and equipped to ensure a high level of renewable energy penetration. Energy systems located in remote Arctic areas may experience many peculiar challenges, for example, due to the limited transport options throughout the year and the lack of qualified on-site maintenance specialists. Reliable operation of such systems in harsh climatic conditions requires not only a standard control system but also an advanced system based on predictions concerning weather, wind, and ice accretion on the blades. To satisfy these requirements, the current work presents an advanced intelligent automatic control system. In the developed control system, the transformation, control, and distribution of energy are based on dynamic power redistribution, dynamic control of dump loads, and a bi-directional current transducer. The article shows the architecture of the advanced control system, presents the results of field studies under the standard control approach, and models the performance of the system under different operating modes. Additionally, the effect of using turbine control to reduce the effects of icing is examined. It is shown that the advanced control approach can reduce fuel consumption in field tests by 22%. Moreover, the proposed turbine control scheme has the potential to reduce icing effects by 2% to 5%.

No abstract

About two-thirds of the territory of Russia, which covers 11 million km2, lies in a region with severe climatic conditions. These northern ecosystems have a unique climate and are supplied with supplies by outdated diesel generation. Therefore, an urgent need has arisen to modernize the power supply systems in question using modern energy-efficient technologies, including power plants based on Arctic renewable energy sources that convert the high natural potential of renewable energy on these territories. For example, the coastal territories of the Russian North are situated in the zone of high wind power potential. In the article a method of modernization through the use of modular hybrid energy complexes are proposed. In total, about 4,700 such stations can be installed in Russia, and the total environmental effect from them will be about $1 million. Moreover, these power plants have a high science intensity. The problem of correct optimization of the parameters and architecture of wind-diesel power plants is also investigated in the article.