Dynamics of a CW single-mode Nd:YAG laser with a Cs2 narrow-band saturable absorber

We present the results of experiments with a CW single-mode Nd:YAG laser, tunable in the vicinity of 1064 nm, with an intracavity narrow-band Cs ₂ vapor saturable absorber. It is shown that the laser dynamics is determined by both the pump level and detuning of the laser frequency from the absorption-line center.     

Silicon migration in N-(trimethylsilyl)-3,5-dimethylazoles

The ¹H and ¹³C NMR spectra of the following six compounds have been examined over a wide range of temperatures: four derivatives of 3,5-dimethylpyrazole substituted at the nitrogen atom by organometallic groups such as Si(CH₃)₃ (I), Si(C₂H₅)₃ (II), Si(OC₂H₅)₃ (III), Ge(CH₃)₃ (IV), 3,5-dimethyl-1-trimethylsilyl-1,2,4-triazole (V) and 1-trimethylsilylimidazole (VI). Activation energies of the metal migration have been found for the compounds (I–V) by the total NMR line-shape analysis. Proton and carbon spectra of the compound (VI) show equivalence of the positions 4 and 5 in the imidazole ring. No temperature-dependent changes in the spectra were observed at –80 to +80°. These facts may be interpreted by assuming that the organometallic group undergoes an intermolecular exchange.     

Actively compensated aerostatic thrust bearing: design,modelling and experimental validation

Active compensation is an effective method for increasing air bearing static and dynamic performance. This paper describes the design, modelling and experimental validation of an actively compensated externally pressurized gas bearing. The active compensation is obtained through the support compensation strategy. With this strategy, the system’s initial working position is restored by compensating for air gap variations through adjustments to the bearing vertical dimension. The described bearing consists in a conventional thrust bearing which is integrated with a multilayer piezoelectric actuator, a compliant mechanism and a digital controller. Nevertheless the non-linear nature of the air system, a simple linear model results to be an effective choice for neighbour of equilibrium conditions. Results demonstrate the good accuracy of the model and the system’s good capacity of rejecting external force disturbances.     

Identification of aerodynamic characteristics with discontinuities of the first kind from trajectory data for a free-flying object

A method is proposed for identifying the aerodynamic characteristics of a model the flow about which varies considerably in the course of motion. In this method, the trajectory of the model is split into sections with different types of the flow and then similar data from these sections are collected into groups and processed. The aerodynamic characteristics are identified by the method of successive approximation using a differential correction algorithm. The accuracy of the results is analyzed.     

Optical Properties of Films of Cu x Ag1−x InSe2 Solid Solutions Obtained by Laser Evaporation

The structure and optical properties of the films of ternary compounds AgInSe₂, CuInSe₂ and Cu _x Ag_1–x InSe₂ solid solutions obtained by pulsed laser evaporation are investigated. It has been established that the films like bulk crystals have the structure of chalcopyrite. By the transmission and reflection spectra near the edge of natural absorption the refractive index and coefficient of optical absorption are calculated and the energies of interband transitions and the crystalline and spinorbit splitting are determined.     

Locked localized states in a multimode semiconductor laser subject to optical injection

We study a multimode semiconductor laser subject to a multimode injection. Multimode output exhibits antiphase dynamics and coexisting attractors. When the output of the laser is only partially locked to the multimode optical injection, the multimode locking can be complete or localized.     

Hard magnetic materials based on iron nanoparticles

The processing of ferric oxide Fe₂O₃ in a high-energy planetary-type ball mill and its subsequent postannealing create properties characteristic of hard magnetic materials. The additional introduction of iron powder into the mixture increases magnetization, resulting in great coercive force. Computer simulations show that the highly coercive state of the material is due to its nanocrystalline iron particles. Press-compacting and thermomagnetic treatment enhance the magnetic texture in samples.     

Synthesis of nanosized titanium dioxide from tetrabutoxytitanium

Mesoporous TiO₂ has been obtained by template synthesis. The introduction of a surfactant in the hydrolysis of tetrabutoxytitanium in aqueous ethanol allows the structure of the resulting material to be controlled. The amorphous TiO₂ resulting from hydrolysis turns into anatase on being calcined at 300°C. As determined by X-ray diffraction, the anatase crystallite size is 70 nm in the presence of the highest surfactant concentration examined and 210 nm in the absence of a surfactant. Amorphous materials have been characterized by electron microscopy and differential thermal analysis. The ultimate benzene adsorption value has been determined for calcined mesoporous TiO₂.     

Approaches to mathematical design of ballistic experiment: Part I

Mathematical expedients used in designing ground tests of aerodynamic object models with the aim of finding experimental conditions optimal in terms of the body and accuracy of extracted information are described. In the first part of this paper, the method used in designing ballistic experiment is demonstrated with processing of single-experiment data. In the second part, the validity of the design approach is illustrated by simultaneously processing trajectory data obtained in several experiments.