Geometry modeling in cellular network planning

To design a cellular radio network (GSM, UMTS, WiFi …) it is indispensable today to use a radio planning software. In current commercialized tools, radio network planning is based on a numerical evaluation of a set of radio metrics, directly linked to quality of service notion, such as interference, throughput, coverage, capacity … The network configurations produced by such tools are generally faced with the human expert judgment who attaches great importance to the organizational aspects such as cells size and the topology. In other words, all those concepts related to the visual cells shape and geometry. In this article we emphasize the simplicity and the strength by which the geometrical concepts helps to bring out good network properties which are not taken into account by conventional radio criteria. On one hand, well-formed cells lead to reduce the number of handover calls, and to form transition zones between cells allowing proper completion of the handover procedure. On the other hand, cell geometry optimization produce performing network schemes in which the frequencies reuse (frequencies planning in GSM, WiFi) is simplified. We describe in this paper an original and practical modeling of the cellular geometry criteria granting the integration of this concept into the automatic planning process of mobile radio networks. The relevance of this criterion is assessed on three different levels. On a local level, we first establish the correlation between the geometric criteria and the improvement of point-by-point radio quality indicators. We secondly show geometry impact on radio frequency planning and the improving of the handover zones. Finally we analyze the impact of geometric criterion on improving indoor positioning systems.     

A high-level application using belief functions for exchanging and managing uncertain events on the road in vehicular ad hoc networks

This article introduces a high-level system using belief functions for exchanging and managing imperfect information about events on the road in vehicular ad hoc networks. The main purpose of this application is to provide the most reliable information for the driver from multiple messages received informing the driver about events on the roads. This system and some variants are tested using a MATLAB? simulator. An implementation with Android smartphones using a Bluetooth technology to exchange the messages is also introduced.     

Uranium-bearing francolites present in organic-rich limestones of NW Greece: a preliminary study using synchrotron radiation and fission track techniques

Synchrotron radiation techniques (μ-XRF and μ-XANES) were applied to the study of organic-rich phosphatized limestones of NW Greece (Epirus). The results revealed uranium accumulation in areas of the material containing, among others, carbonate apatite (francolite) and organic matter. The UL ₃-edge of μ-XANES spectra showed that uranium was present in tetravalent form. U-bearing francolite crystals were separated from the rock and characterized by Raman spectroscopy and microprobe. The analysis of the crystals also indicated the presence of sodium and sulfur. The uranium presence in the crystals was also visualized, after neutron irradiation and etching, by the observation of the fission tracks.

     

Vertex partitions of (C3,C4,C6)-free planar graphs

A graph is $(k_1,k_2)$-colorable if it admits a vertex partition into a graph with maximum degree at most $k_1$ and a graph with maximum degree at most $k_2$. We show that every $(C_3,C_4,C_6)$-free planar graph is $(0,6)$-colorable. We also show that deciding whether a $(C_3,C_4,C_6)$-free planar graph is $(0,3)$-colorable is NP-complete.     

Equivalence of Ensembles,Condensation and Glassy Dynamics in the Bose–Hubbard Hamiltonian

Journal of Statistical Physics - We study mathematically the equilibrium properties of the Bose–Hubbard Hamiltonian in the limit of a vanishing hopping amplitude. This system conserves the...     

Travelling wave mathematical analysis and efficient numerical resolution for a one-dimensional model of solid propellant combustion

We investigate a model of solid propellant combustion involving surface pyrolysis coupled to finite activation energy gas-phase combustion. Existence and uniqueness of a travelling wave solution are established by extending dynamical system tools classically used for premixed flames, dealing with the additional difficulty arising from the surface regression and pyrolysis. An efficient shooting method allows to solve the problem in phase space without resorting to space discretisation nor fixed-point Newton iterations. The results are compared to solutions from a CFD code developed at ONERA, assessing the efficiency and potential of the method, and the impact of the modelling assumptions is evaluated through parametric studies.