Laser emitters (λ = 808 nm) based on AlGaAs/GaAs heterostructures

AlGaAs/GaAs laser heterostructures with various active-region geometries, namely, with broadened asymmetric and narrow symmetric waveguides, and with various depths of quantum wells, are obtained by MOC hydride epitaxy. Single laser elements, bars, and arrays of laser diodes are fabricated from these samples, and their output characteristics are investigated. It is shown that the geometry of the narrow-waveguide structure is more preferable for laser-diode bars (λ = 808 nm). Increasing the charge-carrier barrier also favorably affects the output parameters of the bars in the case of heterostructures with a narrow symmetric waveguide, and the slope of the power-current (P-I) characteristics for these structures increases from 0.9 W/A to 1.05 W/A. The laser diode array of 5 × 5 mm, which is assembled based on the best heterostructure, shows an output power above 1500 W in the quasi-continuous mode at a pump current of 150 A.     

High-power pulse-emitting lasers in the 1.5–1.6 μm spectral region

The metalorganic chemical vapor deposition (MOCVD) method is used for growing heterostructures in the system of AlGaInAs/InP materials with different versions of the configuration of the active region. Laser diodes are fabricated from the grown heterostructures; with the purpose of increasing the output optical power, the laser diodes are integrated into bars and arrays. Single laser diodes exhibit a high output power of ～6 W in the pulse mode. The laser bars exhibit an output power of 20 W in the pulse mode. The highest achieved pulse output optical power for an array of 30 elements amounts to ～110 W.     

Demonstration of a scaled-down autothermal membrane methane reformer for hydrogen generation

A novel concept for hydrogen generation by methane steam reforming in a thermally coupled catalytic fixed bed membrane reformer is experimentally demonstrated. The reactor, built from three concentric compartments, indirectly couples the endothermic methane steam reforming with the exothermic methane oxidation, while hydrogen is separated by a permselective Pd membrane. The study focuses on the determination of the key operation parameters and understanding their influence on the reactor performance. It has been shown that the reactor performance is mainly defined by the dimensionless ratio of the methane steam reforming feed flow rate to the hydrogen maximal membrane flow rate and by the ratio of the oxidation and steam reforming methane feed flow rates.     

Effect of plasma surface treatment on the structure and hardness of spherulitic iron

The microstructure of surface layers of roll-foundry iron of grade SShKhNF after plasma treatment performed with end-to-end overlapping or crossing of plasma flow tracks is studied. Dependences of the thickness and microhardness of the surface layers on the process parameters are determined. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 6, pp. 34–37, June, 2006.     

Algorithmic method of correcting the temperature error of extensometric force and pressure transducers

Results are presented from experimental studies of functional relations for semiconducting force and pressure transducers. The study results are used to develop an algorithm to correct temperature errors in the microprocessor.Translated from Izmeritel'naya Tekhnika, No. 3, pp. 43–44, March, 1995.     

Microprocess measurement channel under group switching of resistive sensors

A method and a version of designing multichannel measurement converter of a microprocessor system designated for carrying out measurements utilizing resistive sensors are described. To simplify the circuitry implementation of the hardware it is suggested to combine algorithmic methods of providing accuracy with the measuring procedures. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 9–11, May, 1995     

Method of temperature error compensation in strain transducers

A method of compensation for the temperature error of semiconductor bridge strain transducers is described. It is based on the use of a strain gage bridge as the temperature-sensitive element and controllable source of current for supply to the bridge. The supply current is regulated to compensate for variation in temperature sensitivity in relation to bridge resistance by means of positive feedback while a correcting voltage proportional to the temperature is formed for correcting zero drift. The method facilitates the temperature error of strain transducers to be reduced up to 0.5% at 70–80°C.Translated from Izmeritel'naya Tekhnika, No. 7, pp. 39–40, July, 1993.     

Phase transitions in shock-loaded titanium at pressures up to 150 GPa

Phase transformations in VT1-0 titanium were studied. Shock profiles in the pressure range of 10–26 GPa were recorded by polyvinylidene fluoride sensors. Sound velocities in shock-compressed titanium samples were measured by two methods. At a pressure less than 30 GPa, the speed of sound in titanium was determined by the counter unloading method using Manganin gauges, and at a pressure of 30–150 GPa, it was determined by the overtaking unloading method using indicator liquids. At a pressure of 20–40 and 60–90 GPa, the pressure dependences of the speed of sound have breaks, the first of which is apparently associated with the α → ω conversion, and the second with melting. X-ray analysis revealed the presence of the ω phase in the samples in steel capsules recovered after loading at a pressure of 9–23 GPa. The dependence of the yield of the ω phase on the loading pressure has the form of a curve with a maximum at p ≈ 15 GPa.