Efficient band monitoring with sensors outer positioning

The article considers models for monitoring a band with a preset width using sensor networks shaped as disc covers. Every cover disc is a centred sensor operation area. The researchers determine a min-density band cover with the discs of one, two and three radii. The specific requirement for the cover is that the disc centres shall not be inside the band (external monitoring). Various efficient cover models are proposed and their characteristics are determined.     

Synthesis and Photophysical Properties of a Series of Biscyclometalated Platinum(II) Complexes on the Basis of a Tridentate 2,6-Diphenylpyridine

The complexes C,C-trans-[Pt(C^N^C)L] ^z [C^N^C is bisdeprotonated 2,6-diphenylpyridinate (dppy^2-); L = CO, Me2SO (dmso), ethylenediamine (en), CN^-, pyrazine (pz), P(C₆F₅)₃, 4,4'-bipyridine (4,4'-bpy)] were synthesized and characterized by ¹H NMR, electronic, and emission spectroscopy. Spectralluminescence properties of the chromophoric group (platinum-cyclometalating ligand) in the C,C-trans-bis-cyclometalated complexes depend on the nature of the noncyclometalating ligand L, which is explained by its donor-acceptor effects on the form of existence of the complex in solution.     

On some polynomially solvable cases and approximate algorithms in the optimal communication tree construction problem

Considering an arbitrary undirected n-vertex graph with nonnegative edge weights, we seek to construct a spanning tree minimizing the sum over all vertices of the maximal weights of the incident edges. We find some particular cases of polynomial solvability and show that the minimal span whose edge weights lie in the closed interval [a, b] is a $\left( {2 - \frac{{2a}} {{a + b + 2b/(n - 2)}}} \right) $ -approximate solution, and the problem of constructing a 1.00048-approximate solution is NP-hard. We propose a heuristic polynomial algorithm and perform its a posteriori analysis.     

Prediction of the activity concentrations of 232Th, 238U and 40K in geological materials using radial basis function neural network

In this paper, three individual models and one generalized radial basis function neural network (RBFNN) model were developed for the prediction of the activity concentrations of primordial radionuclides, namely, ²³²Th, ²³⁸U and ⁴⁰K. To achieve this, gamma spectrometry measurements of 126 different geological materials were used in the development of the RBFNN models. The results indicated that individual and generalized RBFNN models are quite efficient in predicting the activity concentrations of ²³²Th, ²³⁸U and ⁴⁰K of geological materials.

     

Luminescence of defect centers in yttrium–aluminum garnet crystals

Spectral–kinetic properties of the 2.38 eV emission in neutron-irradiated and as-received yttrium aluminum garnet (Y₃Al₅O₁₂) crystals are investigated. This luminescence band as well as its lifetime and the temperature dependence are analyzed. It is suggested that the 2.38 eV luminescence band is due to the strongly allowed transition of the F⁺-center in garnet crystals. Possible reasons that may explain the observed temperature dependence of this emission intensity are discussed.     

Covering a plane with ellipses

Abstract

This paper is devoted to the construction of regular min-density plane coverings with ellipses of one, two and three types. This problem is relevant, for example, to power-efficient surface sensing by autonomous above-grade sensors. A similar problem, for which discs are used to cover a planar region, has been well studied. On the one hand, the use of ellipses generalizes a mathematical problem; on the other hand, it is necessary to solve these types of problems in real applications of wireless sensor networks. This paper both extends some previous results and offers new regular covers that use a small number of ellipses to cover each regular polygon; these covers are characterized by having minimal known density in their classes and give the new upper bounds for densities in these classes as well.     

Equilibrium resource distribution in a network model

A network is modeled by a weighted undirected graph G. Some certain time invariable resource is assigned to each node and is distributed among the incident edges at each time (time is assumed to be discrete). A state of the network corresponds to a distribution of resources of all nodes among the edges of G. At each time a vertex i evaluates its relationship with an adjacent vertex j according to a given function c _ij (x _ij , x _ji ) of the resources x _ij and x _ji provided by the nodes i and j to the edge (i, j). Since resources of the nodes are redistributed at every time, the state of the system varies in time. Some sufficient conditions are found for the existence of the limit and equilibrium states of the model; and precise formulas are given to compute these states in the case of a special function c _ij for an arbitrary graph G.