Screening of magnetic fields by superconducting and hybrid shields with circular cross-section

The use of superconducting (SC) materials is crucial for shielding quasi-static magnetic fields. However, the frequent requisite of space-saving solutions with high shielding performance requires the development of a 3D modelling procedure capable of predicting the screening properties for different orientations of the applied field. In this paper, we exploited a 3D numerical model based on a vector potential formulation to investigate the shielding ability of SC screens with cylindrical symmetry and a height/diameter aspect ratio close to unity, without and with the superimposition of a ferromagnetic (FM) circular shell. The chosen materials were MgB2 and soft iron. First, the calculation outcomes were compared with the experimental data obtained on different shielding arrangements, achieving a notable agreement in both axial-field (AF) and transverse-field (TF) orientations. Then, we used the thus validated modelling approach to investigate how the magnetic mitigation properties of a cup-shaped SC bulk can be improved by the superimposition of a coaxial FM cup. Calculations highlighted that the FM addition is very efficient in enhancing the shielding factors (SFs) in the TF orientation. Assuming a working temperature of 30 K and using a layout with the FM cup protruding over the SC one, shielding factors up to 8 times greater than those of the single SC cup were attained at low applied fields, reaching values equal or higher than 102 in the inner half of the shield. In the AF orientation, the same FM cup addition costs a modest worsening at low fields, but at the same time, it widens the applied field range, where SF ≥ 104 occurs near the close extremity of the shield, up over 1 T.

Medical rehabilitation and infectious diseases in children

Today, medical rehabilitation is undergoing significant transformation. The new system built around the biopsychosocial model includes assessment of physical constraints and rehabilitation diagnosis, determination of rehabilitation potential, formulation of goals and objectives of individual interventions, development of rehabilitation plans, and progress evaluation. All of these rehabilitation components can be implemented using a personalized, problem-oriented, multidisciplinary approach, which is now being actively introduced into clinical practice. The current pandemic of the novel coronavirus infection has demonstrated that medical rehabilitation is crucial for convalescents. However, its principles and techniques have not been fully elaborated yet. This review describes the current state of medical rehabilitation of children with or after infectious diseases and identifies its avenues and prospects.

Magnetic field simulations using explicit time integration with higher order schemes

Purpose A transient magneto-quasistatic vector potential formulation involving nonlinear material is spatially discretized using the finite element method of first and second polynomial order. By applying a generalized Schur complement the resulting system of differential algebraic equations is reformulated into a system of ordinary differential equations (ODE). The ODE system is integrated in time by using explicit time integration schemes. The purpose of this paper is to investigate explicit time integration for eddy current problems with respect to the performance of the first-order explicit Euler scheme and the Runge-Kutta-Chebyshev (RKC) method of higher order. Design/methodology/approach The ODE system is integrated in time using the explicit Euler scheme, which is conditionally stable by a maximum time step size. To overcome this limit, an explicit multistage RKC time integration method of higher order is used to enlarge the maximum stable time step size. Both time integration methods are compared regarding the overall computational effort. Findings The numerical simulations show that a finer spatial discretization forces smaller time step sizes. In comparison to the explicit Euler time integration scheme, the multistage RKC method provides larger stable time step sizes to diminish the overall computation time. Originality/value The explicit time integration of the Schur complement vector potential formulation of eddy current problems is accelerated by a multistage RKC method.

CONDENSED TANNINS OF THE SPECIES PINUS TAEDA: EXTRACTION, CHARACTERIZATION AND POTENTIAL FORMULATION OF WOOD BIOADHESIVE

The species Pinus taeda was evaluated as a source of condensed tannins for the potential formulation of phenolic adhesives from the extraction of the wood cortex. Extraction yield, percentage of tannins and non-tannins, and reactivity to the formaldehyde by the Stiasny number were analyzed in the responses of the extraction processes with extractive agents sodium sulfite (Na2SO3), sodium hydroxide (NaOH), and urea [(NH2)2CO] in the percentages of 2, 4, 6, 8, and 10 in relation to the weight of the bark of this species. The extracts were analyzed using the techniques of IR - Infrared Spectroscopy, SEM - Scanning Electron Microscopy, DRX- X-ray Diffractometry, and EDS - Energy-Dispersive X-ray Spectrometry. In another step, the formation time of the commercial tannin gel and of the P. taeda were compared in relation to formaldehyde. The results show that the specie have condensed tannins, and sustain that they are catechins. These catechins form polymers identified by SEM in less time in relation to the formaldehyde in the formation of the gel, suggesting that the tannins can be extracted from the species as a potentially new commercial source that lumber companies can use to manufacture phenolic resins.

Weak entropy solutions to a model in induction hardening, existence and weak-strong uniqueness

In this paper, we investigate a model describing induction hardening of steel. The related system consists of an energy balance, an ordinary differential equation (ODE) for the different phases of steel, and Maxwell’s equations in a potential formulation. The existence of weak entropy solutions is shown by a suitable regularization and discretization technique. Moreover, we prove the weak-strong uniqueness of these solutions, i.e. that a weak entropy solutions coincides with a classical solution emanating form the same initial data as long as the classical one exists. The weak entropy solution concept has advantages in comparison to the previously introduced weak solutions, e.g. it allows to include free energy functions with low regularity properties corresponding to phase transitions.