Path-dependent Vortex Switching in Ferroelectric Nanoplate Junctions Toward a Memory Device Concept

Ferroelectric vortex has attracted much attention as a promising candidate for memories with high density and high stability. It is a crucial problem to precisely manipulate the vortex chirality in order to utilize it to store information. Nevertheless, so far, a practical and direct strategy for vortex switching is still lacking. Moreover, the strong coupling of chirality between neighboring vortices in continuous systems like superlattices limits the application of ferroelectric-vortex-based memories. Here, we design a ferroelectric nanoplate junction to break the strong coupling between neighboring vortices. Phase-field simulation results demonstrate that the vortex chirality of the nanoplates could be efficiently tuned by sweeping local electric and thermal fields in the nanoplate junction. More importantly, the weak coupling between two neighboring nanoplates through the intermediate junction brings a deterministic vortex switching behavior. Based on this, we propose a concept of vortex memory devices. Our study provides an effective way to control the vortex chirality and suggests an opportunity for designing new memory devices based on ferroelectric vortex.

Variations in intensity and structure of a westward-propagating monsoon depression

The study deals with a monsoon depression which developed over the Bay of Bengal, moved westward across central India and turned into a mid-tropospheric disturbance (MTD) over the northeastern : corner of the Arabian Sea. Its interactions with the thermal fields associated with the basic monsoon, subtropical westerly troughs and a new depression over the Bay of Bengal are examined. Evidence suggests the involvement of all the three factors in causing the observed variations in its intensity and structure. The low pressure system turned into a mid-tropospheric disturbance when it re-entered the warm sector of the basic monsoon field and received increased warm advection from the north to the west of its centre and cold advection from the south to the east in mid-troposphere. The importance of thermal advection is confirmed by computation of a heat budget. The role of condensation heating is also briefly discussed.

THE DISTRIBUTION OF MAGNETIC AND THERMAL FIELDS, POWER LOSSES IN ELECTROMAGNETIC SHIELD OF UNDERGROUND TWO-CIRCUIT CABLE LINE

In the article, the magnetic and thermal field distributions generated by underground two-circuit extra-high voltage power cable line in the environment, particularly near the cables and flat aluminum shield, which is located at a different distance from the cables and has different thicknesses, are analyzed. The unique features of the magnetic field and temperature distributions inside the shield are computed and studied. For the cases under consideration, the Joule losses in the external shield do not exceed 3% of the losses in the cables. The primary electromagnetic characteristics are compared for the aluminum shield (shielding efficiency is 1,94) and the shield with lower conductivity (shielding efficiency is equal to 1,2). As shown, the thicker shield helps to increase the ampacity of the cable line owing to lower heating. The actual operating current of the cable line under consideration depends on the distance of the shield from the cables owing to the relation between their maximum temperature and this distance. Ref. 15, fig. 7, table.

Investigation of effect of electrode polarity on electrochemistry and magnetohydrodynamics using tertiary current distribution in electroslag remelting process

Transport phenomena including the electromagnetic, concentration of ions, flow, and thermal fields in the electroslag remelting (ESR) process made of slag, electrode, air, mold, and melt pool are computed considering tertiary current distribution. Nernst–Planck equations are solved in the bulk of slag, and faradaic reactions are regarded at the metal–slag interface. Aiming at exploring electrochemical effects on the behavior of the ESR process, the calculated field structures are compared with those obtained using the classical ohmic approach, namely, primary current distribution whereby variations in concentrations of ions and faradaic reactions are ignored. Also, the influence of the earth magnetic field on magnetohydrodynamics in the melt pool and slag is considered. The impact of the polarity of electrode, whether positive, also known as direct current reverse polarity (DCRP), or negative, as known as direct current straight polarity (DCSP), on the transport of oxygen to the ingot of ESR is investigated. The obtained modeling results enabled us to explain the experimental observation of higher oxygen content in DCSP than that of DCRP operated ESR process.

Thawing of Permafrost During the Operation of Wells of North-Mukerkamyl Oil and Gas Field

Thawing of ice-saturated rocks due to climate change or various technological impacts will be accompanied by subsidence of the earth’s surface and development of dangerous permafrost geological processes called thermokarst, leading to accidents, which may destruct the wells. Currently, the investment programs of the development of new northern oil and gas fields are restricted. In this regard, reducing the cost of developing the oil and gas fields is an urgent problem. For example, diminishing the area of well pads and maintaining efficiency in the northern oil and gas fields can significantly reduce the costs, in particular, during the design stage. A model of unsteady thermal fields propagation in frozen soil from new well construction for the North Mukerkamyl oil and gas field is developed, taking into account the construction features, the annulus, and the complex lithology of the soil surrounding the well. It is planned to take into account climatic and technological factors, in particular, an annual rest period of well operation, which held from several hours to two weeks. The paper discusses the computational features of the thermal fields calculating in frozen ground from wells and explores the influence of various parameters, which in the computations may lead to a significant increasing of thawing area in the well pads

Wear resistance discrete management of formative tool

The article is devoted to the organization of management of the application of wear-resistant materials on the formative tool at set intervals by the method of electro-acoustic spraying. A complex highly concentrated effect of the ultrasonic method in a permanent process, based on the pulse energy, which leads to an increase in the plasticity of the material and is not associated with its heating. The law of electro-plastic deformation for a conducting material, taking into account the high density of the acting amperage in the process of active deformation at a constant rate, considered in this article, establishes a clear dependence of the strengthening of the substrate material. The process of concentration of electromagnetic and thermal fields in a conductive material with defects such as a crack makes it possible to use this technology to slow down the propagation of cracks while reducing the concentration of mechanical stresses.

Numerical Simulation of Coal Microwave Heating and Evaluation of The Reliability of The Results By Changing The Parameters Affecting It

In most mines, methane gas is accumulated in pores inside coal, the highest amount of which is found in coal mines, and methane is the most important polluting gas in underground coal mines. In coal mining operations, coalbed methane is one of the potential hazards that must be extracted to prevent an explosion of the accumulated gas and environmental pollution. One of the mechanisms is using microwave irradiation so that the thermal stress caused by microwave heating generates fractures. In this research, we investigated the most important parameters affecting the electric and thermal fields’ distribution in coal in order to identify the effective parameters that achieve the highest temperature increase rate and to reach the highest impact and efficiency of the system with the least amount of consumed energy. The results of this study show that the most effective parameter on the electric and thermal fields’ distribution within coal is the size of the resonance chamber.

On the circulation of hydrogen in the atmosphere and the Earth’s crust

A review of data on sources and sinks of hydrogen of various origins in the atmosphere and in the near-surface part of the Earth’s crust is given (only some cases we are talking about the crust as a whole). Based on the results of the consideration of this information, it was concluded that the influence of underground non-biogenic («geological») hydrogen on the content and balance of gas in the atmosphere, up to the stratosphere, is insignificant. The complexity of the experimental determination of the flow of geological hydrogen, free of biogenic and anthropogenic interference, the influence of the testable excavation, etc. is obvious. Probable sources of deep hydrogen are considered: the remains of magmatic gases (outside the areas of volcanism), metamorphic reactions, and radiolysis of water. The potential for significant H2 flow is only apparent in areas of currently activated faults. The data on the most powerful suppliers of geological hydrogen — modern active volcanoes and thermal fields are given. The gas circulation scheme of the Avachinsky volcano is built, based on the thermal model. The latter is controlled by data from geothermometers, the results of direct temperature measurements in deep wells, and a velocity model. The possibility of fumaroles carrying unchanged hydrogen from the magma chamber has been shown. The prospects for the formation of hydrogen deposits are estimated as uncertain. Magmatic and metamorphogenic gas in some areas is formed enough to accumulate a significant deposit over several tens of thousands of years. But the possibility of its preservation during this period or longer raises doubts. Hydrocarbon deposits without material input from great depths can lose reserves in much less time. Higher rocks permeability to hydrogen contributes to much greater gas leakage.

Heat Transfer Enhancement of Water Based Al2O3- Cu Hybrid Nanofluid Trough Square Cavity

The present numerical work, based on the finite volume method, deals with the characterization of natural convective flow and thermal fields inside differentially vertical heated square cavities filled with a nanofluid as well as the quantification of the convective exchanges. The investigation is devoted to study the influence of the hybrid nanofluid (Al2O3-Cu / water) on the flow’s general structure with a particular attention to the Nusselt number. An exhaustive parametric study is conducted considering different combinations of Al2O3 and Cu nanoparticles (NPs) dispersed in water for a range of Rayleigh numbers (Ra) and total volume fractions An appropriate agreement with experimental data was observed for the estimation of the hybrid nanofluid thermal conductivity. From the results, it is observed that the heat transfer intensifies by increasing the Ra number and the nanoparticles volume fraction. The hybrid nanofluid seems to be the most efficient nanofluid in comparison with a base fluid and a single nanofluid. This heat transfer enhancement becomes more convincing with the increase of the Cu NPs content (% in volume).

Modelling turbulent heat transfer in rough channels using phenomenological theory

Rough walls are often encountered in industrial heat transfer equipment. Even though it is well known that a rough wall affects velocity fields and thermal fields differently (and therefore also skin friction factors and Stanton or Nusselt numbers), predicting the effect of rough walls on turbulent heat transfer remains difficult. A relation between the scalar spectrum and the Stanton number is derived for channels with both smooth and rough walls. It is shown that the new relation agrees reasonably well with recent DNS experiments for wall roughness sizes of k + < 150 and when Pr = 0.7 − 1.0. Under these conditions, a thermal analogue of Moody’s diagram can be created using the newly developed relation.