Waveguide detachable joints

Conclusions The theoretical formulas (1)-(4) represent correctly the effect of small gaps in waveguides. In the case of longitudinal sections (Fig. 1) with a gap amounting to 0.01 of a waveguide height, the measured attenuation amounts to 0.8 of the computed one. In the case of a transverse section with a gap between flanges of 0.1 of a rectangular-waveguide height or a circular-waveguide radius the attenuation value amounts to 0.8–0.9 of the computed one (rectangular waveguide) and to 1–1.2 of the computed one (circular waveguide).Justification for idealizing the contact connections due to adopting the concept of an effective gap consists of good agreement among gap values obtained in measuring at various frequencies the attenuation of different contact couplers whose contacting surfaces were subjected to the same production technology. The effective gap values were in good agreement with the directly measured deviations from flatness.Translated from Izmeritel'naya Tekhnika, No. 10, pp. 57–59, October, 1978.     

Innovative designs of steel-casting systems developed by the NPP “Vulkan-TM” for metallurgical plants and foundries

This article examines the latest innovations from the NPP “Vulkan-TM” for stopper-less casting and the treatment of steel outside the furnace. It presents the main characteristics and design features of slide gates, equipment for the bottom-blowing of steel with argon, and equipment for making vibroformed refractory products.     

Rotor synchronization of two motors on an elastic base

Hydraulic bearings may be used to reduce the vibration and noise levels of induction motors, as well as their energy consumption.     

Long-term sealing loss of hydraulic bearings

The factors responsible for the loss of sealing of hydraulic bearings in long-term operation are considered. The appearance of cavitation zones in the working fluid of hydraulic bearings and microscopic hydraulic bearings is explained.     

VCSELs based on arrays of sub-monolayer InGaAs quantum dots

Vertical-cavity surface-emitting lasers (VCSELs) with an active region based on sub-monolayer InGaAs quantum dots and doped AlGaAs/GaAs distributed Bragg reflectors were grown by MBE. VCSELs with current aperture of 3 μm in diameter demonstrate single-mode lasing in 980-nm range with the threshold current of 0.6 mA, maximum output power up to 4 mW, and external differential efficiency of 68%. Multimode VCSELs with a (10–12)-μm aperture demonstrate ultralow internal optical loss of 0.09% per pass, which compares favorably with the best results obtained in similar lasers with undoped distributed Bragg reflectors. Original Russian Text ? S.A. Blokhin, N.A. Maleev, A.G. Kuz’menkov, Yu. M. Shernyakov, I.I. Novikov, N.Yu. Gordeev, V.V. Dyudelev, G.S. Sokolovskiĭ, V.I. Kuchinskiĭi, M.M. Kulagina, M.V. Maximov, V.M. Ustinov, A.R. Kovsh, S.S. Mikhrin, N.N. Ledentsov, 2006, published in Fizika i Tekhnika Poluprovodnikov, 2006, Vol. 40, No. 5, pp. 633–638.     

Effect of <Emphasis Type="Italic">p</Emphasis>-doping of the active region on the temperature stability of InAs/GaAs QD lasers

A detailed study of the effect of p-doping of the active region on characteristics of long-wavelength InAs/GaAs QD lasers is performed. As the doping level increases, the characteristic temperature rises and the range of temperature stability for the threshold current density is broadened. In a laser doped with 2 × 10¹² cm^?2 acceptors per QD sheet, the characteristic temperature of 1200 K is obtained in the temperature range 15–75°C and the differential quantum efficiency is stable in the range 15–65°C. A maximum CW output power of 4.4 W is reached in an optimized structure.     

Effect of the Active Region and Waveguide Design on the Performance of Edge-Emitting Lasers Based on InGaAs/GaAs Quantum Well-Dots

Semiconductors - Edge-emitting lasers with active regions based on novel InGaAs/GaAs quantum heterostructures of transitional dimensionality, i.e., quantum well-dots, which are intermediate in...     

Gas evolution in acetate-nitrate aqueous solutions in a wide pH range under the action of ionizing radiation

The influence of the initial pH value on the gas evolution from aqueous acetate-nitrate solutions under the action of ionizing γ-radiation was studied. With an increase in pH from 0.5 to 11.0, the total pressure of gases over the solution decreases by a factor of 4–5. The most noticeable decrease in the pressure is observed in the pH range 3–7. The major gaseous radiolysis products are CO₂ and N₂O, with H₂ and CH₄ formed to a considerably lesser extent (by a factor of 10). Other gases such as N₂, O₂, NO, CO at an absorbed dose of 0.2 MGy either were formed in extremely small amounts or were not detected at all. On the basis of the dependences of the CO₂ solubility on temperature, pressure, ionic strength, and pH, an estimate was obtained for its total content in the system throughout the examined pH range.     

Fabrication and buckling dynamics of nanoneedle AFM probes

A new method for the fabrication of high-aspect-ratio probes by electron beam induced deposition is described. This technique allows the fabrication of cylindrical 'nanoneedle' structures on the atomic force microscope (AFM) probe tip which can be used for accurate imaging of surfaces with high steep features. Scanning electron microscope (SEM) imaging showed that needles with diameters in the range of 18-100?nm could be obtained by this technique. The needles were shown to undergo buckling deformation under large tip-sample forces. The deformation was observed to recover elastically under vertical deformations of up to ～ 60% of the needle length, preventing damage to the needle. A technique of stabilizing the needle against buckling by coating it with additional electron beam deposited carbon was also investigated; it was shown that coated needles of 75?nm or greater total diameter did not buckle even under tip-sample forces of ～ 1.5?μN.