Optical conductivity of metal nanofilms and nanowires: The rectangular-box model

The conductivity tensor is introduced for the low-dimensional electron systems. Within the particle-in-a-box model and the diagonal response approximation, components of the conductivity tensor for a quasi-homogeneous ultrathin metal film and wire are calculated under the assumption $d\cong \lambda_{\rm F}$ (where $d$ is the characteristic small dimension of the system, $\lambda_{\rm F}$ is the Fermi wavelength for bulk metal). We find the transmittance of ultrathin films and compare these results with available experimental data. The analytical estimations for the size dependence of the Fermi level are presented, and the oscillations of the Fermi energy in ultrathin films and wires are computed. Our results demonstrate the strong size and frequency dependences of the real and imaginary parts of the conductivity components in the infrared range. A sharp distinction of the results for Au and Pb is observed and explained by the difference in the relaxation time of these metals.Comment: 13 pages, 8 figure

Development of automatic intelligent system for on-line voltage security control of power systems

The majority of recent large-scale blackouts have been caused by voltage instability. A prompt on-line assessment of voltage stability for preventive corrective control of electric power systems is one of the key objectives for Control centers. The use of classical approximation methods alone is complicated. Therefore, several modified methods combined with machine learning algorithms enabling security assessment in real time have been proposed over the last years. The paper presents an automatic intelligent system for on-line voltage security control, which is based on the model of decision trees Proximity Driven Streaming Random Forest (PDSRF). In this case, the combination of original properties of PDSRF and capabilities of L-index as a target vector makes it possible to provide the functions of dispatcher warning, localization of critical nodes, and ensure direct interaction with the security automation systems. The efficiency of the proposed system was demonstrated using various test schemes of IEEE

Density-functional theory of elastically deformed finite metallic system: work function and surface stress

The effect of external strain on surface properties of simple metals is considered within the modified stabilized jellium model. The equations for the stabilization energy of the deformed Wigner-Seitz cells are derived as a function of the bulk electron density and the given deformation. The results for surface stress and work function of aluminium calculated within the self-consistent Kohn-Sham method are also given. The problem of anisotropy of the work function of finite system is discussed. A clear explanation of independent experiments on stress-induced contact potential difference at metal surfaces is presented.Comment: 15 pages, 1 figur

Ensemble methods of classification for power systems security assessment

One of the most promising approaches for complex technical systems analysis employs ensemble methods of classification. Ensemble methods enable a reliable decision rules construction for feature space classification in the presence of many possible states of the system. In this paper the novel techniques based on decision trees are used to evaluate power system reliability. In this work a hybrid approach based on random forests models and boosting model is proposed. Such techniques can be applied to predict the interaction of increasing renewable power, storage devices and intelligent switching of smart loads from intelligent domestic appliances, storage heaters and air-conditioning units and electric vehicles with grid to enhance decision making. This ensemble classification method was tested on the modified 118-bus IEEE power system to examine whether the power system is secured under steady-state operating conditions. Keywords: Power system, Ensemble methods, Boosting, Classification, Heuristics, Random forests, Security assessment, 2010 MSC: 90C59, 68T0

The history and modern condition of the brown bear (Ursus arctos L., 1758) of the West Siberian plain

Ursus arctos is a large carnivore and a common species for Western Siberia. The earliest traces of it date back to the Middle Pleistocene. During the Holocene, its population grew and its range significantly extended northwards. The modern West Siberian habitat lies between 55° and 67°N, and its dynamics are being affected by human activity and climate change. The beginning of the twenty-first century has been marked by the growth of the population of the brown bear and its occurrence in unusual habitats. Earlier studies of the population genetic structure prove the existence of a Pleistocene refugium on this territory. The body size of the West Siberian brown bear is the largest for U. arctos subscpecies within its range

The history and modern condition of the brown bear (Ursus arctos L., 1758) of the West Siberian plain

Ursus arctos is a large carnivore and a common species for Western Siberia. The earliest traces of it date back to the Middle Pleistocene. During the Holocene, its population grew and its range significantly extended northwards. The modern West Siberian habitat lies between 55° and 67°N, and its dynamics are being affected by human activity and climate change. The beginning of the twenty-first century has been marked by the growth of the population of the brown bear and its occurrence in unusual habitats. Earlier studies of the population genetic structure prove the existence of a Pleistocene refugium on this territory. The body size of the West Siberian brown bear is the largest for U. arctos subscpecies within its range