Conditions for Instability of One Class of Nonlinear Nonautomomous Dynamic Systems

Consideration was given to the conditions for instability of the equilibrium states of a nonlinear nonautonomous dynamic systems obeying an ordinary vector differential equation of arbitrary order whose right-hand side satisfies the following conditions: (i) for any t 0, div 0$$ " align="middle" border="0"> almost everywhere on the set H that is a neighborhood of the equilibrium point of the system and (ii) at any point . The equilibrium states of such systems can be both stable and unstable. For one class of these systems, sufficient instability conditions were given, which enables one to carry out studies using only the information about the right-hand side of the system.     

Instability Conditions for Nonlinear Nonautonomous Dynamic Systems. II. Sufficient Conditions of Instability

In Part I, using a special class of scalar functions V(x, t, ) dependent on a parameter , we have derived new necessary and sufficient conditions for the instability (in some domain) of the equilibrium states of nonlinear nonautonomous dynamic systems of arbitrary order. In Part II, we derive new sufficient conditions for the instability of a class of unstable systems in terms of functions admitting a simple geometric interpretation.     

Preparation of High-Purity Arsenic via Hydrogen Reduction of Arsenic Trichloride

The chemical equilibria involved in the hydrogen reduction of arsenic trichloride under reaction conditions of practical interest are assessed by thermodynamic modeling. Experimental data for high-purity arsenic trichloride are used to optimize the reduction conditions. The optimal residence time of the gas mixture in the reaction zone is 30–50 s. The optimal reduction temperature is 1023 K. Condensation temperatures in the range 600–650 K make it possible to minimize the percentage of amorphous arsenic. The yield of elemental arsenic is 99.99%.     

Peat fires detected by the BIRD satellite

Tropical peat swamp forests store huge amounts of carbon, which is released to the atmosphere as carbon dioxide during fires. Recurrent peat swamp forest fires are local catastrophic events that can have a serious impact on the global carbon balance. Urgent tasks in this regard are the provision of information on the fire locations and magnitude of the carbon emissions. The experimental Bi-spectral InfraRed Detection (BIRD) satellite enables early detection of peat swamp forest fires and retrieval of their quantitative characteristics, such as the effective fire temperature, area and radiative energy release. The combination of ground truth measurements and data obtained by BIRD can improve the accuracy of estimates of carbon emissions into the atmosphere and related trace gas composition.     

A coordinate muon chamber based on thin-walled drift tubes

The design and manufacturing technology of a prototype coordinate detector module with dimensions of 2.0 × 0.5 m² on the basis of 2-m-long drift straw tubes are described. The selected design and technology allow large-area detectors to be constructed from these modules. Results of the module testing at gas pressures of 1–4 bar are described. The characteristic features of the module are a small radiation thickness, a high radiation hardness, a high detection efficiency for charged particles, as well as the feasibility of its high granularity (using small-diameter straw tubes and segmentation along the tube length). The possibility of optimizing the operating conditions of the module over a wide range of the working gas pressure is shown.     

Synchronous extraction of the microwave energy from two resonators through a waveguide bridge

Results of the experimental investigation of the resonant microwave pulse compression system operating in a 10-cm wavelength region are presented. The system contains two multimode resonators for storing high-frequency energy and a waveguide bridge for the fast and synchronous energy extraction. When powered from a magnetron generator having a radiation power of 5 MW and pulse duration of 4 μs, microwave pulses with an output power of ～0.8 GW, duration of ～5 ns, and pulse repetition rate up to 100 Hz were obtained in this compression system.     

A single-spatial-mode semiconductor laser based on InAs/InGaAs quantum dots with a diffraction filter of optical modes

The concept of a diffraction optical filter is used for prevention of high-order mode oscillation in a design of stripe laser diodes with an active region based on InAs/InGaAs quantum dots emitting in the 1.3-μm wavelength range grown on GaAs substrates. Incorporation of such a filter made it possible to increase the width of the stripe and obtain an output power as high as 700 mW with retention of a single-spatial-mode character of lasing.