Numerical Study of the Working Space of the Furnace of a Methodical Pusher Furnace with a Production Furnace of 10 Tons/Hour

В статье представлены результаты теплового расчета распределения температур внутри рабочего пространства топки методической толкательной печи. Рассмотренные тезисы направленны на изучение методов проектирования теплотехнических установок при использовании компьютерных расчетов. CFD-моделирование задачи выполнено в программном продукте Ansys Fluent.The work analyzes the results of the thermal calculation of the distribution inside the working space of the furnace of the methodical pusher furnace. The considered theses are aimed at studying the methods of designing heat engineering installations using computer calculations. CFD modeling was carried out in the Ansys Fluent software product

Investigation of Combustion Fuel in a Ring Metallurgical Furnace Using CFD Modeling

В статье представлено исследование численного моделирования горения топлива в рабочей камере кольцевой методической печи. Определено распределение продуктов сгорания по рабочей камере. CFD-моделирование исследования горения выполнено в программном продукте Ansys Fluent.This paper presents a study of numerical simulation of fuel combustion in the working chamber of the ring methodical furnace. The distribution of combustion products in the working chamber is determined. CFD modeling of combustion research is performed in the Ansys Fluent software product

Tunneling current modulation in atomically precise graphene nanoribbon heterojunctions

Lateral heterojunctions of atomically precise graphene nanoribbons (GNRs) hold promise for applications in nanotechnology, yet their charge transport and most of the spectroscopic properties have not been investigated. Here, we synthesize a monolayer of multiple aligned heterojunctions consisting of quasi-metallic and wide-bandgap GNRs, and report characterization by scanning tunneling microscopy, angle-resolved photoemission, Raman spectroscopy, and charge transport. Comprehensive transport measurements as a function of bias and gate voltages, channel length, and temperature reveal that charge transport is dictated by tunneling through the potential barriers formed by wide-bandgap GNR segments. The current-voltage characteristics are in agreement with calculations of tunneling conductance through asymmetric barriers. We fabricate a GNR heterojunctions based sensor and demonstrate greatly improved sensitivity to adsorbates compared to graphene based sensors. This is achieved via modulation of the GNR heterojunction tunneling barriers by adsorbates

Hopping conduction in strong electric fields: Negative differential conductivity

Effects of strong electric fields on hopping conductivity are studied theoretically. Monte-Carlo computer simulations show that the analytical theory of Nguyen and Shklovskii [Solid State Commun. 38, 99 (1981)] provides an accurate description of hopping transport in the limit of very high electric fields and low concentrations of charge carriers as compared to the concentration of localization sites and also at the relative concentration of carriers equal to 0.5. At intermediate concentrations of carriers between 0.1 and 0.5 computer simulations evidence essential deviations from the results of the existing analytical theories. The theory of Nguyen and Shklovskii also predicts a negative differential hopping conductivity at high electric fields. Our numerical calculations confirm this prediction qualitatively. However the field dependence of the drift velocity of charge carriers obtained numerically differs essentially from the one predicted so far. Analytical theory is further developed so that its agreement with numerical results is essentially improved.Comment: 12 pages, 12 figures. References added, figures improve

The Role of Interdiffusion and Spatial Confinement in the Formation of Resonant Raman Spectra of Ge/Si(100) Heterostructures with Quantum-Dot Arrays

The phonon modes of self-assembled Ge/Si quantum dots grown by molecular-beam epitaxy in an apparatus integrated with a chamber of the scanning tunneling microscope into a single high-vacuum system are investigated using Raman spectroscopy. It is revealed that the Ge-Ge and Si-Ge vibrational modes are considerably enhanced upon excitation of excitons between the valence band $\Lambda_3$ and the conduction band $\Lambda_1$ (the E1 and E1 + $\Delta_1$ transitions). This makes it possible to observe the Raman spectrum of very small amounts of germanium, such as one layer of quantum dots with a germanium layer thickness of 10 \r{A}. The enhancement of these modes suggests a strong electron-phonon interaction of the vibrational modes with the E1 and E1 + $\Delta_1$ excitons in the quantum dot. It is demonstrated that the frequency of the Ge-Ge mode decreases by 10 cm^-1 with a decrease in the thickness of the Ge layer from 10 to 6 \r{A} due to the spatial-confinement effect. The optimum thickness of the Ge layer, for which the size dispersion of quantum dots is minimum, is determined.Comment: 14 pages, 9 figure

Spin Relaxation in Ge/Si Core-Shell Nanowire Qubits

Controlling decoherence is the most challenging task in realizing quantum information hardware. Single electron spins in gallium arsenide are a leading candidate among solid- state implementations, however strong coupling to nuclear spins in the substrate hinders this approach. To realize spin qubits in a nuclear-spin-free system, intensive studies based on group-IV semiconductor are being pursued. In this case, the challenge is primarily control of materials and interfaces, and device nanofabrication. We report important steps toward implementing spin qubits in a predominantly nuclear-spin-free system by demonstrating state preparation, pulsed gate control, and charge-sensing spin readout of confined hole spins in a one-dimensional Ge/Si nanowire. With fast gating, we measure T1 spin relaxation times in coupled quantum dots approaching 1 ms, increasing with lower magnetic field, consistent with a spin-orbit mechanism that is usually masked by hyperfine contributions

Modern journalism: a condition, tendencies, problems (analysis attempt)

Проаналізовано сучасний стан, тенденції розвитку і проблеми сучасної журналістики.The modern condition, tendencies of development and a problem of modern journalism is analysed.Проанализировано современное состояние, тенденции развития и проблемы современной журналистики