Development of processes for C<Subscript>4</Subscript> hydrocarbons separation and 1,3-butadiene purification

Physicochemical substantiation and improved more effective technologies for C₄-hydrocarbons separation and 1,3-butadiene purification with the help of polar extragents are given, such as compressorless extractive rectification with the use of an intermediate desorbent, extractive rectification of the butane-n-butene fraction with preliminary isomerization of 1-butene into 2-butenes, the combined removal of -acetylenes C₄ and methylallene by rectification with a small introduction of the extragent, and the hydration of butenyne in the C₄ fraction and distillation of propyne from it.     

Validated methods of parts machining for nonleaking hydraulic cylinders in drilling installations

The article reports the studies aimed at ensuring stable quality surface treatment of inner grooves of hydraulic cylinder bushes without redesigning.     

Intraband Radiation Absorption by Holes in InAsSb/AlSb and InGaAsP/InP Quantum Wells

Microscopic analysis of intraband radiation absorption by holes with their transition to the spin-split band for InAsSb/AlSb and InGaAsP/InP semiconductor quantum wells is performed in the context of the four-band Kane model. The calculation is performed for two incident-radiation polarizations: along the crystal-growth axis and in the quantum-well plane. It is demonstrated that absorption with transition to the discrete spectrum of spin-split holes has a higher intensity than absorption with transitions to the continuous spectrum. The dependences of the intraband absorption coefficient on temperature, hole density, and quantum- well width are thoroughly analyzed. It is shown that intraband radiation absorption can be the main mechanism of internal radiation losses in lasers based on quantum wells.     

Intraband Radiation Absorption by Free Holes in GaAs/InGaAs Quantum Wells with Allowance for Nonsphericity of the kP Hamiltonian

Technical Physics Letters - A system of Kane’s equations has been derived and solved with allowance for elastic stresses and nonsphericity of the kP Hamiltonian. On this basis, analytic...     

The thermal stability of nonalloyed ohmic contacts to AlGaN/GaN heterostructures

Degradation of nonalloyed ohmic contacts with heavily doped GaN epitaxially grown to the heterostructures with two-dimensional electron gas has been investigated. The change in the relative contact resistivity at temperatures of up to 600°C for the Ti/Pd/Au, Cr/Au, and Cr/Pd/Au metallization compositions has been studied. It is demonstrated that the Cr/Pd/Au metallization composition, the resistivity of which decreases at working temperatures of 400°C, is the most resistant to the effect of temperature. It is shown for the first time that the largest contribution to the increase in the contact resistivity to two-dimensional electron gas upon heating above 400°C is made by the resistivity of the Cr/Pd/Au–n⁺-GaN metal–dielectric structure, while, at temperatures of 400°C and higher, the resistance between heavily doped GaN and two-dimensional electron gas decreases.

     

Theoretical and Experimental Study of Non-Steady-State Pipe Reduction Process Using a Tesa 20-102 Mill

Metallurgist - We describe the results of an experimental study of longitudinal and transverse variations in wall thickness at the ends of pipes after rolling in a stretch-reducing mill (SRM). We...