Performance of a Nozzle to Control Bath Level Oscillations and Turbulence of the Metal-Flux Interface in Slab Molds

The characterization of the turbulent flow of liquid steel in a slab mold using a commercial nozzle was carried out through physical experiments and mathematical models. Six ultrasonic sensors were located at each side of the nozzle to obtain real-time plotting of the bath levels during the experimental time. An ultrasonic transducer located in the mold, 20 mm below the meniscus, determines the velocities and the turbulent variables along with the distance from the narrow face to the position of the nozzle’s outer wall. These data, together with the mathematical simulations, demonstrated a high correlation of bath level oscillations and the time-dependent behavior of the discharging jets. The flow inside the mold shows low-frequency non-symmetric patterns without a severe turbulent in the meniscus. The source of this instability is the partial opening of the slide valve gate used to control the mass flow of liquid.

Current Harmonic Aggregation Cases for Contemporary Loads

Power electronic circuits in modern power supplies have improved the conversion efficiency on the one hand but have also increased harmonic emissions. Harmonic currents from the operation of these units affect the voltage waveforms of the network and could compromise the reliability of the network. Load and source non-linearity can, therefore, limit the renewable source’s hosting capacity in the grid, as a large number of inverter units may increase the harmonic distortions. As a result, voltage and current distortions could reach unbearable levels in devices connected to the network. Harmonic estimation modelling often relies on measurement data, and differences may appear in mathematical simulations as the harmonic aggregation or cancellation may generate different results due to the inaccuracies and limitations of the measurement device. In this paper, the effect of harmonic currents cancellation on the aggregation of different load currents is evaluated to show its impact in the network by presenting a comparison between the measurement and mathematical aggregation of harmonics. Furthermore, the harmonic cancellation phenomenon is also qualified for multiple loads connected to the power supply.

Vaccination Strategy for the COVID-19 Pandemic in Early 2021 Based on Differences in People's Behavior Between Tokyo and Osaka, Japan

Background: During the fourth COVID-19 wave in Japan, a marked difference was apparent in the scale of the epidemic between Metropolitan Tokyo in eastern Japan and Osaka prefecture in western Japan.Methods: Public epidemic data were analyzed, with performance of mathematical simulations using simplified SEIR models.Results: The increase in the number of infected persons per 100,000 population during the fourth wave of expansion was greater in Osaka than in Tokyo. The basic reproduction number in Osaka was greater than in Tokyo. Particularly, the number of infected people in their 20s increased during the fourth wave: the generation-specific reproduction number of people in their 20s was higher than people of other generations. Both Tokyo and Osaka had strong correlation between the increase in the number of infected people and the average number of people using the main downtown stations at night. Simulations showed vaccination of people in their 60s and older reduced the number of infected people among the high-risk elderly population in the fourth wave. However, age-specific vaccination of people in their 20s reduced the number of infected people more than vaccination of people in their 60s and older.Conclusions: Differences in the epidemic between Tokyo and Osaka are explainable by different behaviors of the most socially active generation. When vaccine supplies are adequate, priority should be assigned to high-risk older adults, but if vaccine supplies are scarce, simulation results suggest consideration of vaccinating specific groups among whom the epidemic is spreading rapidly.

Modeling of the dynamics of tornado structures in a pipe with turbulators of square, semicircular and triangular profiles

Objectives. To carry out mathematical simulations of changes in time of tornado compositions in channels with projections of semicircular, triangular, square profiles for average Reynolds criteria based on multiblock computing technology with the solution of finite- volume factorized methods of the Reynolds equation and energy equations.Method. The calculations were carried out on the basis of theoretical approaches based on the solution of Reynolds equations by finite-volume factorized methods, which were closed using the simulation of Menter stresses, and the energy of a structured grid.Result. The calculations of time-dependent flow and heat transfer parameters carried out in the article showed that the excess dissipation of turbulence generation for projections of sharp profiles - square profile, triangular profile - and rounded profiles - semicircular profile, segment profile - is provided with radically different hydraulic losses: channels with protrusions of rounded profiles, for example, semicircular, have much lower hydraulic resistance coefficients than channels with protrusions with sharp profiles, for example, triangular or square, rectangular.Conclusion. In the article, mathematical simulations of time-dependent tornado compositions were performed in channels with transversal profiles in the form of a square, triangle and semicircle, which is as informative as possible in terms of studying turbulent flows and heat transfer arising under average Reynolds criteria based on computer multiblock technology when using solutions of finite-volume factorized methods (FCOM-am) Reynolds equations and energy equations. The following protrusions were considered in the article: square transversal profiles, in which tornadoes are most pronounced, and side tornadoes affect the flow in the maximum way; triangular transversal profiles, where tornadoes are not so strong, and side tornadoes affect the main flow weaker than with square protrusions; semicircular transversal profiles, in which the incoming main tornado moves along the stream with the generation of limited side tornadoes. The calculated information obtained in the article correlates to a high degree with the available experimental data, which indicates the verification of the mathematical modeling involved in the article.

A retrograde mechanism coordinates memory allocation across brain regions

Memories engage ensembles of neurons across different brain regions within a memory system. However, it is unclear whether the allocation of a memory to these ensembles is coordinated across brain regions. To address this question, we used CREB expression to bias memory allocation in one brain region, and rabies retrograde tracing to test memory allocation in connected presynaptic neurons in the other brain regions. We find that biasing allocation of CTA memory in the basolateral amygdala (BLA) also biases memory allocation in presynaptic neurons of the insular cortex (IC). By manipulating the allocation of CTA memory to specific neurons in both BLA and IC, we found that we increased their connectivity and enhanced CTA memory performance. These results, which are corroborated by mathematical simulations and by studies with auditory fear conditioning, demonstrate that a retrograde mechanism coordinates the allocation of memories across different brain regions.

A Mathematical Model for Dehydration by Successive Pressure Drops: Simulation of Discarded Potatoes Dehydration

Dehydration by Successive Pressure Drops (SPD) is a process with high potential for treating heat-sensitive materials; this includes agro-industry by-products. However, the response of drying kinetics to operating conditions of SPD is not fully understood. The present manuscript refers to mathematical simulations to describe drying kinetics of discarded potatoes using SPD. While there are numerous theoretical, semi-theorical and empirical mathematical models, the selection of the appropriate model is a rigorous process. In this paper, the Thompson thin-layer semi-theoretical model was chosen since the assumptions for this model (e.g., product is arranged in thin layers) are fulfilled for the SPD. As a result of mathematical simulation, it was possible to describe the drying kinetics in terms of the major parameters of SPD namely pressurizing level (Pa) and the Frequency of Pressure Drop (FPD). The dehydration by SPD allows the removal of water from the material, mainly at the pressure drop. If this stage occurs more frequently, the drying rate increases. The model developed describes at less 91% of the variability of the experimental data. It is recommended to use high FPD and Pa equals to 0.50 MPa.

Modelling of a Permanent Magnet Synchronous Motor and its Control Circuit in Simulink Environment

The most commonly used electric motor in electric vehicles is the permanent magnet synchronous motor. The primary production and refinement of rare earth materials used in these motors are immensely damaging to the environment. A new wave of technology in the aspect of electric motors is emerging and that is the non-rare earth element magnet assisted synchronous reluctance motor. During the development process it is beneficial to keep the expenditures at the minimum. To reach that goal a comprehensive simulation of the designed motor and its control circuit could be the answer. It is reasonable to use software based on finite element calculations such as FEMM and mathematical simulations as Matlab Simulink. By implementing the equations and methods described in this paper the electric powertrain can be created generally. The specification is highly dependent on the input parameters that are extracted from finite element 2D calculations. In this case, the model approximates the expected behaviour of the investigated construction. A complete driving cycle can be examined, operating points can be determined, and the efficiency map can be created to help the research.

Gating of Ion Channels

Excitable cells, such as neurons and muscles, use ion channels to generate electrical and chemical signals that underlie their functions. Examples include the electrical signals underlying the complex neuronal circuitry in the brain, the secretion of hormones and neurotransmitters, skeletal and cardiac muscle contraction, and the signaling events that lead to fertility. Because of their pivotal role in cellular signaling and electrical excitability, a major goal in modern biology has been to determine the physical properties that control and modulate ion channel function. This chapter briefly reviews classical works about the gating of ion channels. Furthermore, it discusses some innovative approaches that when combined with biophysical and mathematical simulations have contributed to the current understanding of channel gating.