Comparison of 802.11ah,BLE and 802.15.4 for a Home Automation Use Case

Understanding the main short-range wireless technologies operating in unlicensed bands is an important step before deploying Internet of Things (IoT) applications. In this study, we have selected IEEE 802.11ah, Bluetooth Low Energy and IEEE 802.15.4 for performance comparison in terms of delay, service ratio, traffic loss, activity factor and battery lifetime in a home automation scenario. Also, a low overhead protocol stack suitable for IoT applications is considered. The analysis takes into account heterogeneous devices and different traffic loads. The results show advantages and disadvantages with respect to the different performance indicators with generally satisfactory behavior for the three technologies. Among them, BLE is recognized as the most suitable candidate technology for the home automation domain.     

Stability of a partially compensated electron beam

The author discusses the conditions for stability of a partially compensated electron beam in relation to deflection (snaking). It is shown that, with a continuous spectrum of perturbation wave vectors, there is always a region of strong instability (with relatively large increments). With a discrete spectrum (e.g., with a beam of finite length in an accelerator), instability occurs only at beam currents greater than a certain critical value. Landau damping and radiation friction do not eliminate the instability. A weak dissipative instability is discovered, caused by radiation friction. In some cases Landau damping stabilizes this instability, but can also increase it.The investigation is based on a model beam in the form of two pinches, electron and ion, with constant dimensions and uniform densities.Translated from Atomnaya Énergiya, Vol. 19, No. 3, pp. 239–244, September, 1965     

The thermal conductivity of electrical-insulating materials and insulation systems

The thermal conductivity of several electrical-insulating materials used in the insulation systems for windings in turbogenerators and hydroelectric generators, as well as of the Monolith-2 insulation system, was studied using the DTC-300 setup. A collector micaceous stratum (KIFE-A), carbon fiber, glass-fiber laminate with a semiconductor filler (STEF-P), epoxy (DER-438), PK-11 compound in a mixture with ED- 20 resin, and prepreg materials, which are also used for fastening windings when laying them down in a groove, have been studied. The temperature dependences of the thermal conductivity of the studied materials show a linear behavior in the relatively low range from room temperature to +150°C. The temperature distribution over the thickness of the plate that imitates insulation in a groove of an electric machine has been determined. It has been shown that a drop in the temperature between the heat source and the outer surface is a tenth of a degree. The temperature distribution in the groove with a length of 1.5 m and venting channels placed every 50 mm with two insulating rods with different means of fastening rods and insulation thicknesses has been studied using a model of a hydroelectric generator stator (U_w = 13.8 kV, power of 70 MW, Monolith-2 insulation).     

Numerical experiments on the statistical behaviour of dynamical systems with a few degrees of freedom

Numerical experiments concerning the arising statistical laws in a system of nonlinear interacting waves are described. A chain of particles coupled by nonlinear springs has been used as a model. Various statistical properties of the chain have been investigated numerically. A comparison with the theory of the Korteweg-de Vries equation is given.     

Resonance processes in magnetic traps

An analysis is made of resonances between the Larmor rotation of charged particles in a magnetic field and the slow oscillations along the field lines. It is shown that under certain conditions these resonances can lead to the complete exchange of energy between the degrees of freedom of a particle and can cause its escape from the trap. Consideration is also given to the effect of resonances on adiabatic processes associated with a variation of the magnetic field as a function of time.We wish to take this opportunity to thank G. I. Budker for valuable discussions.     

Controlling the Position of a Magnetic Vortex on a Nanostructured Surface in Magnetic Memory Elements

Russian Microelectronics - The experimental, technological, and theoretical regularities of the formation and change in the position of magnetic vortex structures depending on the external applied...     

Linear and Nonlinear Dynamical Chaos

Interrelations between dynamical and statistical laws in physics on the one hand, and between the classical and quantum mechanics on the other hand, are discussed with the emphasis on the new phenomenon of dynamical chaos.The principal results of the studies into chaos in classical mechanics are presented in some detail within the general picture of chaos as a specific case of dynamical behavior. These results include the strong local instability and robustness of motion, continuity of both the phase space as well as the motion spectrum, and time reversibility but nonrecurrency of statistical evolution.The analysis of apparently very deep and challenging contradictions of this picture with the quantum principles is given. The quantum view of dynamical chaos, as an attempt to resolve these contradictions guided by the correspondence principle and based upon the characteristic time scales of quantum evolution, is explained. The picture of the quantum chaos as a new generic dynamical phenomenon is outlined together with a few other examples of such a chaos, including linear (classical) waves and a digital computer.I conclude with the discussion of two fundamental physical problems: the quantum measurement (-collapse) and the causality principle, which both appear to be related to the phenomenon of dynamical chaos.