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This work investigates the thermal stability of point defects in high-purity SiC. Electron paramagnetic resonance measurements made after Ar annealing between 600°C and 1700°C reveal changes in at least two defects, a carbon vacancy related center (VC) and the shallow boron acceptor. Between 1000°C and 1400°C, the number of carbon vacancies decreased and the number of boron acceptors increased in about the same proportion. Above 1400°C, the concentration of B continued to grow, while the number of carbon vacancies fell below the detection limit. After the highest temperature anneal, the initial preannealed concentration of VC was restored by illumination with sub-bandgap 578-nm light. The effects of heat treatment between 1000°C and 1400°C are interpreted in terms of the charge exchange between a compensated B acceptor and VC. The observation of optically induced carbon vacancies after the final anneal suggests that they are thermally stable in these samples up to 1700°C.

Electron paramagnetic resonance (EPR) has been employed to examine thermo- and photo-activated interactions between as-grown intrinsic defects and nitrogen/boron impurities in nominally high-resistivity 4H SiC produced without intentional vanadium doping. The EPR spectra, recorded in the dark at 4 K, revealed either a low concentration of paramagnetic boron, nitrogen, or a carbon-vacancy-related defect (ID-1). The photo-induced charge transfer between ID-1 and both boron and nitrogen has been detected. In some samples, illumination with 0.9-1.6-eV light at 4.2 K quenched the ID-1 signal and produced an approximately equal amount of shallow paramagnetic boron. Exposure to 1.9-2.7-eV light restored the ID-1 center and produced shallow paramagnetic nitrogen. A model based on excitation from the band edges and the threshold energies obtained from the photo-EPR data placed the ID-1 level 0.9 ± 0.1 eV above the valence-band edge. Comparison of these data with that obtained from other samples that exhibited excess boron or nitrogen impurities suggested the presence of an additional defect no more than 0.9 eV below the conduction-band edge. This defect can exchange charge with the nitrogen donor.

An experiment aimed at testing the equivalence of the inertial and the gravitational mass is considered in which use is made of a facility including a vacuum chamber with two coupled oscillators (a pendulum and dynamical damper that form a vibrational system featuring two degrees of freedom) and falling onto the Sun. The layout of the facility and its basic parameters are presented. The pendulum and the dynamical damper have the same natural frequency, which is equal to the frequency of their rotation about the Sun. This frequency is dependent on the date of the experiment and can be calculated on the basis of the time equation. In the proposed facility, the amplitude of oscillations of the damper is 1.2×10−5 rad, which is much greater than the value of 10−7 rad previously achieved in the experiment that tested the equivalence principle to the highest precision of about 10−12. This precision can be considerably improved. The result is presented that was obtained from a measurement during the solar eclipse in Moscow on August 11, 1999.

The procedure is proposed for calculating the characteristics of flow and heat exchange of coal-water fuels as applied to the pipeline hydraulic transport and heat-mass exchange in the apparatus of ecologically clean combustion in the objects of power engineering.

An intrinsic defect (ID) has been identified in as-grown 4H–SiC by electron paramagnetic resonance (EPR). The EPR parameters of an ID measured in our nominally semi-insulating material are similar to the literature data of the EI5 defect produced in p-type 4H and 6H–SiC by 2.5 MeV electrons and assigned to the carbon vacancy (N.T. Son, P.N. Hai, E. Jansen, Phys. Rev. B 63 (2000) 201201). However, comparison of the ID and EI5 centers reveals that the as-grown and radiation-induced centers exhibit different annealing behavior. Photo-induced EPR locates the ID level 0.9 eV above the valence band edge.

The influence of the structure of phenol derivatives with hydrophobic orthosubstituents on their retention in microcolumn normal-phase high-performance liquid chromatography was considered. The dependence of the retention parameters of ortho-substituted phenols on the total polarity of the mobile phase was analyzed. The revealed trends were taken into account in the optimization of the chromatographic separation of the above compounds.

Acid-anodized aluminum forms amorphous alumina with long and columnar nanopores with approximately hexagonal ordering ("alumite"). Excellent hexagonal ordering of these nanopores has been achieved by 24 hours of anodization, but with restricted domain size (2-4 /spl mu/m/sup 2/), which can be increased to 100 /spl mu/m/sup 2/ with longer anodization. We have deposited Fe in disordered pores and Co in ordered pores; we can control the average length and diameter of these nanowires, but there is still a distribution of nanowire lengths. Previously, we described Fe nanowires with diameters down to 11 nm in disordered pores. Here we focus on longer (770 nm) and shorter (64 nm) Co nanowires with diameters of 25 nm in ordered pores with 100 nm pore-to-pore separation. The longer wires have an easy axis out-of-plane, with squareness >0.9, coercivity=1900 Oe, and a fluctuation field of 5.3 Oe. The shorter wires are more isotropic, with lower coercivities (/spl ap/1300 Oe) and larger fluctuation fields /spl ap/8.4 Oe.

The linear instability of a vapor film formed at the surface of a flat horizontal heater surrounded by an externally cooled liquid is investigated in the presence of a gravitational field. Consideration is given to the case when the stationary base state is characterized by the heat fluxes balanced at the interface between the two media. The critical value of the heat flux required for the complete suppression of the Rayleigh–Taylor instability by the phase transition has been evaluated mainly in the absence of the natural convection in the liquid layer and is found to be different from the known data obtained by approximate approaches. The case of the instability suppression in the system when long-wave disturbances have the longest lifetime is described. It has been shown that the media pressure influence on the phase transition, revealed in thin vapor films, can markedly increase the growth rate of long-wave disturbances and prevent their suppression.

The purpose of research is theoretical basis and an example of computer modeling load parameters for identifying hazardous sections in the design of the supporting levers. When designing new machines or upgrading their suspension, and also in the event of breakage of the chassis components have any questions related to designing services and strength calculations of elements of the chassis. A particular difficulty is the identification of the causes of failures of structural elements in the presence of the device lifting frame body (hopper) due to the rotation of the support levers move the wheels relative to the frame of the tank (body). The article is built the design scheme of static loading of the supports of the wheel mobile unit with adjustable height (hopper) and define expressions to determine the reaction of experiencing a fulcrum lever with different geometrical parameters with the angle of its location. Carried out theoretical researches have allowed to draw up the scheme of loading, to establish the analytical dependence of the internal forces and reactions of supports, which may of numerical modeling to optimize the design of the lever supports for the concrete governmental dimensions of their elements and profile rolled arm wheel support. The analysis of internal power factors shows that the most dangerous section in bending is the section in the vicinity of the cylinder mounts to the lever. In view of the availability of torque and its significant quantity threat the second section of the lever is the connection to the axle mount on the frame

Neurons of cranial cervical, stellate and celiac sympathetic ganglia containing calbindin (CALB) were studied in rats (n = 60) aged 3-90 days using immunohistochemical method. The results obtained indicate that the largest population of CALB-immunopositive neurons was located in the stellate ganglion. The proportion of CALB-containing neurons in sympathetic para- and prevertebral ganglia decreased during the development. Final formation of CALB-immunopositive group of neurons was observed by the end of the first month of life.

Photoinduced electron paramagnetic resonance studies performed on nominally semi-insulating, high purity 4H-SiC have revealed charge transfer from an intrinsic defect (ID) to both the shallow boron acceptor and nitrogen donor. At 4 K, incident photon energy between 1.0 and 1.7 eV produces an increase in paramagnetic boron of approximately the same magnitude as the decrease in the paramagnetic defect concentration. For T

The analysis of surface oscillations of liquid drops allows measurements of the surface tension and viscosity of the liquid. For small oscillations of spherical drops with a free surface, classical formulae by Rayleigh and Lamb relate these quantities to the frequency and damping of the oscillations. In many cases, however, the drop's surface is covered by a surface film, typically an oxide layer or a surfactant, exhibiting a rheological behaviour different from the bulk fluid. It is the purpose of this paper to investigate how such surface properties influence the oscillation spectrum of a spherical drop. For small bulk shear viscosity, the cases of small, finite and large surface viscosities are discussed, and the onset of aperiodic motion as a function of the surface parameters is also derived.

To check whether it is possible to make the construction of an oxygen-iodine laser less complicated and to give up in the future a cold water trap, we investigated the possibility for COIL operation at a high content of the water vapor in the active medium. With the oxygen pressure increase between 0.5 ... 2.5 Torr and the water vapor content between 0.3 ... 1.0 Torr at the constant iodine concentration [MATH] 10 mTorr, the generation power increased from 1.0 to 4.5 kW, saturation of the radiation power dependence on the oxygen pressure was not observed. The output power as a function of water vapor pressure remained nearly constant till [MATH] Torr and then rapidly decreased. The lasing region was 0.5 ... 3.5 cm downstream of the iodine injector. We observed molecular iodine to dissociate almost immediately ([MATH]) after injection into singlet oxygen flow in contradiction with kinetic model. The active medium gain varied with time non-monotonically in the experiment where the injected molecular iodine concentration monotonically decreased.

Electropolishing of single-crystal aluminum faces yield different patterns from (111), (110), and (100) faces at different potentials. The stripes that dominate the (110) face extend throughout a 1 cm2 sample in the same direction.

The paper reports on a study of oxygen-iodine laser operating on active mixture formed by electric discharge in pulseperiodic mode. Experiments were performed with a laser cavity 5 m long. Laser pulses obtained for three various chlorine flow rates ((62 ± 2) mmol/s, (92 ± 2) mmol/s, (105 ± 2) mmol/s) have been manipulated by the statistic rules. The repetition rate of pulses was 12.5 Hz. The chlorine concentration in the laser cavity was varied in the experiments from 1.0·10 15 to 1.0·1016 cm -3 .

The paper describes a study of pulse-periodic operation of a chemical oxygen-iodine laser. The generator in use was of the jet type with high chlorine utilization degree (• 97%). Atomic iodine was released by dissociating methyl-iodide ( KG 3 I) in volumetric electric discharge. Steady lasing was achieved at a repetition rate up to 30 Hz. The emission energy attained per individual pulse in a train was 1.1 J at a pulse energy repeatability of (3÷ 5) % and a specific energy extraction from the active medium of 1.7 J/L. The lasing pulse duration depended on the concentra-tion of methyl-iodide and the energy deposited into discharge. The minimal half-height duration of pulses was achieved as 10 µ m at a concentration of atomic iodine in the laser cavity ~1*10 15 cm -3 . Key words: chemical oxygen-iodine laser, pulse-periodic, methyl-iodide, volumetric electric discharge The pulse-periodic chemical oxygen-iodine laser (COIL) is considered by us as a likely applicant to technologies requiring the conditions that are unattainable so far with the aid of solid-state pulse-periodic lasers. It means the range of average lasing power from 1 to 10 kW at a per-pulse lasing energy up to 10 J. There are at least two approaches possible to get COIL in pulse-periodic mode of operation. The first consists of Q-switching in the laser cavity or gain modulation in the active medium. Along with this, the active medium is produced by mixing singlet oxygen with molecular iodine just as it takes place in cw lasing case. Application of this method to formation of large-volume active media has well-known restrictions applied to relaxation processes occurred during the interaction between singlet oxygen and iodine and we’d not describe it here. Another method proposed by scientists of the Lebedev Institution and confirmed by specialists in China assumes using an initially stable mix of singlet oxygen and iodine dissociating by one or another method upon filling the laser cavity by appropriate gases [1, 2, 3].

The paper reports on the experimental investigations into supersonic oxygen-iodine laser (COIL). Study efficiency results of the COIL unit driven by the singlet oxygen generator (SOG) with twisted gas flow (TA-SOG) are given for supersonic iodine- oxygen mixing at a broadly ranged singlet oxygen pressure and buffer gas flowrate. The measurements were performed for variations of the throat sizes and the positions of the iodine injection plane in supersonic nozzle part. The gas pressure at the input of the nozzle unit was varied from 50 to 150 Torr. The chemical efficiency achieved under optimal operational COIL conditions was 33%.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

First results of experimental and theoretical investigations concerning an industrial application of oxygen-iodine laser (COIL) are reported. The dependencies of the largest cut depth on the laser emission power, cut width and rate, and kind of processing gas (oxygen or nitrogen) were determined for carbon and stainless steels, and aluminium alloys. A developed simple engineering model determines parameters of separating gas-laser cutting of metals allowing for principal channels of heat loss: warming, melting, material evaporation and heat conductivity, convection and radiant heat exchange. It was shown that when oxygen is applied as a processing gas it is necessary to take into account the additional heat emanation that is usually about 10% of the material oxidation energy. A good agreement between calculative and experimental data was obtained.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The paper presents data from experimental study and optimization of the iodine gas and singlet oxygen mixing process in a supersonic chemical oxygen- iodine laser (COIL) with a two- dimensional or honeycomb nozzle unit. The iodine concentration and the lasant gain fields inside supersonic flow have been found for a wide range of key parameters.

The natural precessional response of the magnetization to an applied field has always complicated the high frequency switching process in magnetic devices. Until recently, magnetic recording, which has dominated on-line and archival storage, could be treated quasi-statically. However, as linear densities approach 500 Kbits/in at disk rotation speeds exceeding 10,000 RPM, recording must occur in ∼10-9s, the regime where precessional effects become important. At the same time, to achieve these extraordinary linear densities, grain size in media has been reduced to 18 orders of magnitude! Here, the experimental data on the time-dependent remanent coercivity H CR (υ)} in state-of-the-art media is presented and related to their basic properties. In all cases, H CR (υ)} is well described by a generic form of Sharrock’s Law, at least down to 10-9s. Below 10-9s, precessional effects increase H CR (υ)} more rapidly but the product of the field increment relative to H CR (υ)} at 10-9s and the field pulse width is only ∼ 100–400 Oe-ns. Therefore, existing high moment record head and media materials should be adequate up to several GHz.

The paper presents the most important efforts in the Chemical Oxygen-Iodine Laser (COIL) research carried on at Russian Federal Nuclear Center VNIIEF and some of their results. In particular, they include experimental data on the laser generation output of subsonic COIL on the water vapor concentration in singlet oxygen, calculated generation values of a supersonic COIL having high singlet oxygen pressure at the nozzle inlet, and experiments with the twisted-aerosol- flow singlet oxygen generator (TASOG) for up to 100 Torr pressures. Requirements are discussed for the supersonic high- pressure COIL components, such as singlet oxygen generator and the system for singlet oxygen mixing with iodine.

The physical properties of basic hydrogen peroxide solutions (BHP) such as viscosity, density, and freezing temperature as well as their variation during laser operation have been experimentally investigated. In these experiments (30 - 50%) commercial hydrogen peroxides have been used, containing stabilizers and an alkali of the following composition: 81.5% KOH and 5.5% K 2 CO 3 . The use of these substances for generation of singlet oxygen in the COIL has shown their good ability to operate. Consideration has been given to the possibilities of the basic hydrogen peroxide solutions recovery during the industrial COIL operation.

VNIIEF have been conducting chemical oxygen-iodine laser (COIL) research since 1982. With successive set-up optimizations, this laser had its power increased by 1986 from 10 mW to lkW and was used as a basis to design a new research set-up of about 4 kW power and about I min continuous operation [2]. COIL is traditionally designed to incoiporate a singlet oxygen generator (SOG), a heat exchanger, a laser volume and a pump out system. The schematic diagram of this laser is shown in fig. I. One of the most important parameters of COIL active medium is its temperature. One may use temperature measurements at various gas flow sections as indications of the gas flow and gas mixing homogeneity, processes kinetics, etc. During operation, alkali-solved hydrogen peroxide cooled down to T=255 is put into SOG. As chlorine gas is bubbled therethrough, singlet oxygen is generated. The oxygen together with water vapor enters the heat exchanger having temperature T= 193 K. While passing through the heat exchanger, the oxygen cools and becomes free of water vapor. The laser volume will have iodine - argon or iodine -nitrogen gas mixtme at T=393 K injected to the singlet oxygen flow. To protect the resonator mirrors, there will be also argon or nitrogen screen made in the laser volume, this being at room temperature. The gas flow has velocity up to I 00 mis in laser volume.

At VNIIEF work on chemical oxygen-iodine laser (COIL) was begun in 1982 at the Laboratory of Gas-Flow Chemical Lasers. The present report is a review of work performed at this laboratory, the same year generation at the 10 mW level was obtained. A year later the output power was increased up to 180 W. In 1986 optimization of the set-up operation allowed us to increase the laser power up to 900 W. Later a new research set-up was created. In 1990 it produced the output power of approximately 4 kW in 20 seconds.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Electron paramagnetic resonance measurements of high-purity semi-insulating 4H SiC reveals a spectrum characteristic of an S=1 defect, which appears only after exposure to light with a wavelength less than 690 nm. Analysis of the hyperfine structure of the spectrum suggests that the defect is an intrinsic pair or defect∕impurity complex. The center is stable in an inert ambient up to temperatures of 1200 °C, but a 1-h, 1600 °C anneal reduces the concentration by at least an order of magnitude. Because the spectrum is not affected by removal of the excitation light, it is concluded that the center is the ground state of an S=1 defect. A study of the angular dependence of the spectrum shows that g=2.0052, ∣D∣=(329±14)×10−4cm−1, and ∣E∣