Reactive SPS of Al2O3–RE:YAG (RE = Ce; Ce+Gd) composite ceramic phosphors

Ultrafine-grained Al2O3–rare earth:yttrium aluminium garnet (Al2O3–RE:YAG) (RE = Ce; Ce+Gd) composite ceramics were obtained for the first time by reactive spark plasma sintering (SPS) using commercially available initial oxide powders. The effect of key sintering parameters (temperature, dwell time, and external pressure (Pload)) on densification peculiarities, structural-phase states, and luminescent properties of composites was studied comprehensively. Differences in phase formation and densification between Ce-doped and Ce,Gd-codoped systems were shown. Parameters of reactive SPS, at which there is partial melting with the formation of near-eutectic zones of the Al2O3–YAG system/coexistence of several variations of the YAG-type phase, were established. Pure corundum–garnet biphasic ceramics with an optimal balance between microstructural and luminescence performance were synthesized at 1425 ℃/30 min/30–60 MPa. The external quantum efficiency (EQE) of the phosphor converters reached 80.7% and 72% with close lifetime of ~63.8 ns, similar to those of commercial Ce:YAG materials, which is promising for further applications in the field of high-power white light-emitting diodes (WLEDs) and laser diodes (LDs)

Mathematical Modeling of Production Processes of Discrete Machine-Building Enterprises Based on the Interaction of Simulation Systems and Operational Planning Systems

Analysis of production systems (PS) of discrete multi-nomenclature machine-building enterprises is a complex task, its solution is necessary to support decision-making during technical re-equipment, modernization or technological preparation of production. The paper shows a concept of joint use of operational scheduling systems and simulation modeling systems to improve the efficiency and adequacy of PS analysis. The problem of determining the deviation of the planned state of the PS from the simulated state and evaluating the level of stability and stability of the PS behaviour on its basis is considered. It is revealed that the proposed approach allows us to more adequately determine the timing of the production program, assess the stability of the PS behaviour when using various planning logics and algorithms, and choose the best one for subsequent use in a real PS

Mathematical Modeling of Production Processes of Discrete Machine-Building Enterprises Based on the Interaction of Simulation Systems and Operational Planning Systems

Analysis of production systems (PS) of discrete multi-nomenclature machine-building enterprises is a complex task, its solution is necessary to support decision-making during technical re-equipment, modernization or technological preparation of production. The paper shows a concept of joint use of operational scheduling systems and simulation modeling systems to improve the efficiency and adequacy of PS analysis. The problem of determining the deviation of the planned state of the PS from the simulated state and evaluating the level of stability and stability of the PS behaviour on its basis is considered. It is revealed that the proposed approach allows us to more adequately determine the timing of the production program, assess the stability of the PS behaviour when using various planning logics and algorithms, and choose the best one for subsequent use in a real PS

Influence of natural production conditions on efficient operation of wheel tractors

For the zones of “risky farming” characteristic of the Far East of the Russian Federation, the natural production conditions of the region are an important problem in preparing the soil for further basic agricultural work. So, when carrying out early spring agricultural work, due to presence of a solid underlying layer in the form of permafrost, they shall be completed in operational terms no more than 10 days, until the permafrost base thaws and the soil has not lost its bearing capacity. In addition, due to the peculiarities of the relief, the soil does not thaw equally in depth everywhere, which reduces the quality of field work and harrowing, as the most common operation, namely. This article provides theoretical and experimental studies on the adaptation of a wheeled tractor as part of a machine-tractor unit (MTU) used in harrowing to natural production conditions by installing a device that automatically regulates the load on the working body of the disc harrow or on the propellers of the energy device, depending on the conditions of use or the state of the motion surface

Band Structure and Intersubband Transitions of Three-Layer Semiconductor Nanoplatelets

This paper presents the first general theory of electronic band structure and intersubband transitions in three-layer semiconductor nanoplatelets. We find a dispersion relation and wave functions of the confined electrons and use them to analyze the band structure of core/shell nanoplatelets with equal thicknesses of the shell layers. It is shown that the energies of electrons localized inside the shell layers can be degenerate for certain electron wave vectors and certain core and shell thicknesses. We also show that the energies of intersubband transitions can be nonmonotonic functions of the core and shell thicknesses, exhibiting pronounced local minima and maxima which can be observed in the infrared absorption spectra. Our results will prove useful for the design of photonic devices based on multilayered semiconductor nanoplatelets operating at infrared frequencies