Bulgarian Academy of Sciences

About: Bulgarian Academy of Sciences is a government organization based out in Sofia, Bulgaria. It is known for research contribution in the topics: Coupling constant & Catalysis. The organization has 17989 authors who have published 36276 publications receiving 642820 citations. The organization is also known as: Bulgarian Academy of Sciences，簡稱：BAS & Balgarska Akademiya na Naukite.

Mobility Tracking in Cellular Networks Using Particle Filtering

Abstract: Mobility tracking based on data from wireless cellular networks is a key challenge that has been recently investigated both from a theoretical and practical point of view. This paper proposes Monte Carlo techniques for mobility tracking in wireless communication networks by means of received signal strength indications. These techniques allow for accurate estimation of mobile station's (MS) position and speed. The command process of the MS is represented by a first-order Markov model which can take values from a finite set of acceleration levels. The wide range of acceleration changes is covered by a set of preliminary determined acceleration values. A particle filter and a Rao-Blackwellised particle filter are proposed and their performance is evaluated both over synthetic and real data. A comparison with an extended Kalman filter (EKF) is performed with respect to accuracy and computational complexity. With a small number of particles the RBPF gives more accurate results than the PF and the EKF. A posterior Cramer Rao lower bound (PCRLB) is calculated and it is compared with the filters' root- mean-square error performance.

High-T c superconductivity: New applications of ferroelectrics at microwave frequencies

Abstract: The initial success in high-T c superconductivity applications at microwaves leads to the creation of new branch in microwave electronics operating at liquid nitrogen temperature. In this connection one should reconsider the behaviour of nonlinear dielectrics at microwaves. The characteristics of a capacitor in the form of trilayer structure YBa2Cu9O7−x/(BaxSr1−x)TiO9/YBa2Cu9O7−x are discussed. The crucial influence of oxygen stoichiometry on the structure properties is assumed. The layered structures including non-linear dielectrics could be used as a basis for devices with voltage control of the microwave circuit parameters.

Lithium−Cobalt Citrate Precursors in the Preparation of Intercalation Electrode Materials

Abstract: Noncrystalline solids with LiCoC6H5O7·5H2O and (NH4)3LiCo(C6H5O7)2 compositions were obtained by ethanol dehydration of concentrated lithium−cobalt citrate solutions. Electron spectroscopy of solut...

Polymer brushes under flow and in other out-of-equilibrium conditions

Abstract: Polymer brushes are formed from flexible linear macromolecules tethered at one chain end to a solid substrate, forming a dense polymeric layer of polymer chains which are more or less stretched in the direction perpendicular to the substrate surface. These systems find interest also due to numerous applications (colloid stabilization, improvement of lubrication properties when the surfaces are exposed to shear, protection of the surface against adsorption of nanoparticles or proteins, etc.), for which often the dynamic non-equilibrium response of these brushes to external perturbation is important. The present review summarizes recent computer simulation studies pertinent to these questions. Polymer brushes exposed to shear due to flow of the solvent or a polymer melt the brush interacts with are discussed, and the friction between two brushes is discussed. Another topic that is emphasized is the interaction of polymer brushes with “nanoinclusions” (i.e., small colloidal particles or linear macromolecules down to oligomers), discussing the absorption or expulsion of these objects, and again the response to shear. The simulations are interpreted in terms of scaling concepts and other phenomenological theories wherever possible, and an outlook to related experiments is given.