Analysis of the interference immunity during reception of ultrawideband chaotic signals in an indoor multipath propagation environment

The models of indoor multipath propagation of wideband and ultrawideband (UWB) signals are considered. Application of these models is recommended by an IEEE working group. In the framework of one of the models corresponding to the line-of-sight conditions, the algorithms for reception of UWB chaotic signals in the presence of reflection from multiple surfaces (echo signals) are proposed and analyzed. The efficiency of reception techniques is estimated from the viewpoint of the error probabilities. Limitations caused by the specific properties of echo signals are revealed, and the methods for improvement of reception quality are discussed.     

A technique for measuring charges of relativistic nuclei in a nuclear emulsion on the PAVICOM automated facility

A technique for measuring the charges of relativistic nuclei in thick emulsion layers irradiated in a longitudinal direction is described. This technique has been implemented on the PAVICOM completely automated facility at the Lebedev Physical Institute. The calibration curves for relativistic nuclei with Z > 3 are presented. The advantages of this technique are demonstrated using charge measurements of ²⁸Si nuclear fragments as an example.     

Nanopores in Macroporous Silicon

Macroporous silicon is studied by IR absorption spectroscopy, x-ray diffraction, and the electron–positron annihilation method in comparison with single-crystal Si (substrate), polycrystalline Si (powder), anda-SiO₂ (silica glass). According to IR absorption data, as-prepared macroporous silicon contains a significant amount of oxidized material. Annihilation spectra of macroporous silicon attest to the presence of a system of nanopores, in which positronium atoms are likely to localize. Diffraction patterns reveal considerable amounts of silicon particles oriented at random. Both the polycrystalline phase and nanopores reside on the surface of macropores.     

Materials-technology investigations of fuel elements, irradiated in a reactor at the obninsk nuclear power plant, after standing for 38 years in a depository

The results of materials-technology investigations of a spent fuel assembly from a reactor at the Obninsk nuclear power plant, the first nuclear power plant in the world, before the rated burnup and after prolonged dry storage (for about 40 years) were presented. It was established that the fuel elements from the fuel assembly studied are in satisfactory condition. No appreciable damage due to the prolonged storage was found: the outer diameter remains within the technological tolerance limits and the strength and the plasticity of the jackets are high. Only surface corrosion damage to 10 μm depth was found on the fuel-element jackets. The fuel composition remained whole. 6 figures, 1 table, 3 references. State Science Center of the Russian Federation—A. I. Leipunskii Physics and Power-Engineering Institute. Translated from Atomnaya énergiya, Vol. 88, No. 3, pp. 183–188, March, 2000.     

Method for Studying Internal-Conversion Electrons on the Fully Automated PAVIKOM Microscope-Based Complex

The results of test measurements of a photoemulsion plate on the PAVIKOM-1 measurement complex are presented. The plate was exposed in a -ray spectrograph at the Laboratory of Nuclear Problems of the JINR. The plate was irradiated with internal-conversion electrons resulting from the decay of erbium isotopes. A precision television data-readout system with a CCD array containing 1360 × 1024 photodetecting elements ensured an accuracy of 0.5 m along all coordinates.     

Surface-layer properties of turbine-blade tailpiece in deep grinding by highly porous wheels

The development of the surface-layer properties of high-temperature nickel-alloy turbine-blade tailpieces is investigated in complex deep grinding by highly porous wheels.     

Carbon nanofibers in a gradient-porous silicon structure

Silicon membranes with through pores have been manufactured based on silicon plates with a gradient-porous structure, in which the pore cross section and structure varies with depth. In order to increase the specific surface of membranes, a layer of carbon nanofibers and nanotubes has been formed on the surface of macropores in silicon. The obtained structure can serve as a basis for the development of electrodes for solid polymer fuel cells with a specific area of conducting surface (with respect to carbon) of no less than 100 m²/g.     

Fuchsian groups from the dynamical viewpoint

Here we survey the results on the structure of Fuchsian groups due to Hopf, Hedlund, Sullivan, Nicholls, Pommerenke, and others from the viewpoint of the dynamics of the geodesic and horocycle flows on the corresponding surfaces. Special attention is given to the structure of horocycle orbits; in particular, we construct Fuchsian groups with new types of horocycle orbits which are neither closed nor dense in the nonwandering set. We give a unique classification of Fuchsian groups from the dynamical viewpoint and indicate some open problems.     

Determining the heat-transfer constants of an orthotropic layer

We propose a method for the calculation of the principal coefficients of the heat-conduction sensor of aflat orthotropic layer, based on results from a nonsteady experiment.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 60, No. 3, pp. 474–477, March, 1991.