Multiplication Factor for Subcritical Multiplying System and the Efficiency of Source Neutrons

Physics of Atomic Nuclei - In this paper, the analysis of the relation between the multiplication factor of neutrons of the multiplying system measured in critical experiments and the system...     

Effective Information for Offline Stochastic Feedback and Optimal Control of Dynamic Systems

The impact of uncertain future events on decision making in a stochastic environment is modeled in this paper. Such modeling is presented for both feedback and optimal control problems. This research overcomes the difficulties of forecasting that arise when considering future information. In this paper, we seek to find the minimum amount of information (effective information) necessary to evaluating system performance offline or to optimally control a system. The existence of effective information is proved and a methodology for determining it is developed. It is also shown that ignoring information beyond the planning horizon leads to significant performance loss and may even lead to violating the constraints of a control problem.     

Coherent Excitation of Gigahertz Range Vibrations in Single Crystal Diamond with a Built-In Graphitized Layer

The paper presents the results of experimental observations of stimulated low-frequency Raman scattering (SLFRS) on acoustic eigenvibration of graphitized layers of different thicknesses in single-crystal diamond volume excited by a nanosecond laser pulse.     

Transformation of diamond to graphite under heat treatment at low pressure

Diamond is a very persistent metastable form of carbon. At low pressure, graphitization of the diamond surface is observed at temperatures lower than 1700 °C. The basic cause of this is known to be interaction with oxygen. In the present paper, the microphysics of the phenomenon of diamond surface graphitization was studied. It has been shown that surface graphitization proceeds in several stages. First, a thin surface layer of graphite is developed due to interaction with oxygen (and probably other substances). As temperature is increased, nuclei of 5–10 nm in size are formed within it. The graphite nuclei are capable of migrating along the surface of diamond. They form ‘nests,’ where they are coalesced into aggregates 10–100 nm in size. These ‘nests’ give rise to diamond surface layer graphitization, which proceeds along diamond {211} crystallographic planes and forms graphitization figures. At this stage, the factor that determines the transformation is the pressure exerted on graphitizing material by the surrounding diamond.     

Suppression of localization effects by the high frequency field and the nyquist noise

It is shown that strong inelastic processes are not necessary for suppression of localization effects in disordered conductors. The influence of an external high frequency electric field on quantum corrections to conductivity is considered. Relatively weak fields are found to suppress localization. Thermal electromagnetic fluctuations act in the same way. These fluctuations lead to new dependences of localization effects in films and wires on temperature, impurity concentration and transversal size of the sample.