67 research outputs found

    Modelling of electromagnetic breaking and electromagnetic stirring in the process of continuous casting of steel

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    More than 95 % of crude steel is nowadays processed by Continuous Casting (CC) [1]. To further advance the quality of the products and efficiency of the process, electromagnetic (EM) field, which affects the fluid flow as well as the temperature and segregation is added to the CC process. In general, there are two types of electromagnetic devices applicable to the CC process; the electromagnetic breakers (EMBR) which employ the direct current, and the electromagnetic stirrers (EMS), which employ the alternating current. Which of the devices is employed depends on what are the desired effects. Both of the processes are modelled by implementing the Lorentz force into the momentum equation, and if necessary, the Joule heating term into the energy equation. However, the way how these two terms are modelled, depends on the type of the implemented device. In case of EMBRs, the assumption of low magnetic Reynolds number Rem is made, and consequently, the current density is calculated by solving the Poisson’s equation for the electric potential. The EMSs on the other hand, require a low-frequency approximation and the solution of induction equation. The complete set of governing equations for CC process [2] under the influence of magnetic field includes mass, momentum, energy, and species transfer equations, and Maxwell’s equations together with Ohm’s law and charge conservation equation. Additionally, the turbulent kinetic energy and dissipation rate equations together with Abe-Kondoh-Nagano closures are used to account for the turbulence, the lever rule model is used to model the microsegregation, the mixture continuum model is used to model the macrosegregation, fractional step method is used to model pressure-velocity coupling and the enthalpy-temperature relation is used to calculate the temperature from the enthalpy. The solution is sought for on a five-nodded local subdomains by constructing an approximation with multiquadric radial basis functions as a basis and collocation to find the expansion coefficients [3,4]. Present paper presents the discretization of governing equations, together with boundary conditions for both EMBR and EMS devices with meshless Local Radial Basis Function Collocation Method (LRBFCM) [5]

    Meshless modelling of microstructure evolution in the continuous casting of steel

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    A two-dimensional two-scale slice model has been developed to predict the microstructure evolution in the solidifying strand with an arbitrary cross section geometry during continuous casting of steel. The enthalpy equation is solved at the macro level by using meshless local radial basis function collocation method (LRBFCM) based on multiquadrics for spatial discretization and explicit Euler scheme for temporal discretization. The temperature and the solid fraction in computational nodes are calculated by using a continuum model formulation while the lever rule is used as the supplementary microsegregation relation. The temperature field is interpolated to the micro level by using LRBFCM. At the micro level, the normal distribution and Kurz-Giovanola-Trivedi model are proposed to determine temperature dependent nucleation rate and grain growth velocity, respectively. Meshless point-automata algorithm is applied to implement nucleation and grain growth equations. Several examples of computations of the strand with different cross-sections are shown

    Simulation of multiscale industrial solidification problem under influence of electromagnetic field by meshless method

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    Simulation and control of macrosegregation, deformation and grain size under  electromagnetic (EM) processing conditions is important in industrial solidification systems,  since it influences the quality of the casts and consequently the whole downstream processing  path. Respectively, a multiphysics and multiscale model is developed for solution of Lorentz  force, temperature, velocity, concentration, deformation and grain structure of the casts. The  mixture equations with lever rule, linearized phase diagram, and stationary thermoelastic solid  phase are assumed, together with EM induction equation for the field imposed by the low  frequency EM field or Ohm’s law and charge conservation equation for stationary EM field.  Turbulent effects are incorporated through the solution of a low-Re turbulence model. The  solidification system is treated by the mixture-continuum model, where the mushy zone is  modeled as a Darcy porous media with Kozeny-Karman permeability relation and columnar  solid phase moving with the system velocity. Explicit diffuse approximate meshless solution  procedure [1] is used for solving the EM field, and the explicit local radial basis function  collocation  method  [2]  is  used  for  solving  the  coupled  transport  phenomena  and  thermomechanics  fields.  Pressure-velocity  coupling  is  performed  by  the  fractional  step  method [3]. The point automata method with modified KGT model is used to estimate the  grain structure [4] in a post-processing mode. Thermal, mechanical, EM and grain structure  outcomes of the model are demonstrated for low frequency EM casting of round aluminium  billets. A systematic study of the complicated influences of the process parameters on the  microstructure can be investigated by the model, including intensity and frequency of the  electromagnetic field

    Medidor de inalámbrico de temperatura y humedad para silos-bolsa

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    La medición de temperatura y humedad en silos-bolsa resulta de vital importancia para monitorear el estado de los granos almacenados. Una elevada temperatura y humedad dentro del silo-bolsa indica la actividad de bacterias, que provocan un deterioro del grano. El presente trabajo describe el desarrollo de un sistema completo para la medición de estos parámetros en campos con gran cantidad de silos. El sistema está constituido por los sensores y transmisores ubicados en cada uno de los silos-bolsa, y por un receptor de mano que permite observar en un display las mediciones realizadas. Se utilizaron sensores de temperatura y humedad integrados con salida digital. Para la transmisión de los datos, el protocolo Zigbee, con los módulos X-bee que poseen un bajo consumo de energía y alto alcance de transmisión. Los resultados obtenidos permiten afirmar que este sistema representa una mejora respecto de los existentes en la actualidad, aumentado la frecuencia con las que se obtienen las mediciones y simplificando de forma notable la metodología para obtenerlas.The measurement of temperature and moisture in silos-bag has vital importance to monitor the status of stored Grains A high temperature and humidity environment inside the silo-bag indicates the activity of bacteria, which causes a deterioration of the grain. This paper describes the development of a comprehensive system for measuring these parameters in areas with lots of silos. The system is composed of sensors and transmitters located in each bag silos, and a handheld receiver that has a display where we can see the measurements taken. We use temperature and humidity sensors integrated with digital output for measurement. For the transmission of data, the Zigbee protocol with X-bee modules that have low power consumption and high transmission range. The results confirms that this system represents an improvement over the ones currently available, increasing the frequency used to obtain the measurements and dramatically simplifying the methodology to acquired them.Sociedad Argentina de Informática e Investigación Operativ

    A generalised finite difference scheme based on compact integrated radial basis function for flow in heterogeneous soils

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    In the present paper, we develop a generalised finite difference approach based on compact integrated radial basis function (CIRBF) stencils for solving highly nonlinear Richards equation governing fluid movement in heterogeneous soils. The proposed CIRBF scheme enjoys a high level of accuracy and a fast convergence rate with grid refinement owing to the combination of the integrated RBF approximation and compact approximation where the spatial derivatives are discretised in terms of the information of neighbouring nodes in a stencil. The CIRBF method is first verified through the solution of ordinary differential equations, 2-D Poisson equations and a Taylor-Green vortex. Numerical comparisons show that the CIRBF method outperforms some other methods in the literature. The CIRBF method in conjunction with a rational function transformation method and an adaptive time-stepping scheme is then applied to simulate 1-D and 2-D soil infiltrations effectively. The proposed solutions are more accurate and converge faster than those of the finite different method employed with a second-order central difference scheme. Additionally, the present scheme also takes less time to achieve target accuracy in comparison with the 1D-IRBF and HOC schemes

    THE IMPORTANCE OF SPORT ACTIVITIES FOR THE MOTOR DEVELOPMENT OF THE CHILD

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    V diplomskem delu z naslovom Pomen športnih dejavnosti za gibalni razvoj otroka smo ugotavljali gibalno aktivnost predšolskih otrok, koliko so starši gibalno aktivni z otroki in kakšno je zavedanje staršev o pomenu športne dejavnosti za gibalni razvoj otroka. V teoretičnem delu smo predstavili šport, gibalno-športno dejavnost, gibalni razvoj otroka ter vlogo gibalne dejavnosti pri gibalnem razvoju. V empiričnem delu naloge smo uporabili kavzalno-neeksperimentalno metodo. S pomočjo anketnega vprašalnika na neslučajnostnem vzorcu 100 naključno izbranih staršev predšolskih otrok smo želeli ugotoviti dnevno telesno dejavnost njihovih otrok, športne aktivnosti, ki jih starši izvajajo skupaj s svojim otrokom in njihovo pogostost izvajanja, vključitev otroka v katero od oblik organizirane športne vadbe in razlog za vključitev ter zavedanje staršev o pomenu športnih dejavnosti za gibalni razvoj otrok. Za pridobivanje podatkov smo uporabili kvantitativno tehniko. Na podlagi dobljenih rezultatov kvantitativne obdelave podatkov smo ugotovili, da je večina otrok gibalno aktivnih več kot eno uro na danda so starši, katerih otroci ne obiskujejo organizirano vadbo, pogosteje športno aktivni skupaj s svojimi otroki kot starši, katerih otroci so vključeni v organizirano vadboda se starši zavedajo pomena športnih dejavnosti za gibalni razvoj otroka.The diploma thesis The importance of sport activities for the motor development of the child consists of theoretical and empirical part. Its objective is to establish the physical activity of pre-schoolers, parents’ participation in it and their awareness about the significance of sports activities for child’s motor development. The theoretical part presents sport, physical-sports activities, child’s motor development and the role of physical activity in child’s motor development. In the empirical part the causal non-experimental method was used. A questionnaire was administered to nonprobability sample of 100 random chosen pre-schoolers’ parents. The aim was to establish: the amount of children’s daily physical activity, parents’ participation in child’s sports activities and the frequency of those activities, involvement of children in organized forms of sports activities and reasons for it, parents’ awareness about the importance of sports activities for child’s motor development. To obtain data, the quantitative method was used. Based on the acquired results, it was established that most of the children are physically active more than an hour per day. Parents, whose children do not participate in organized forms of activities, are more involved in sports activities of their children than the parents whose children attend organized forms. It was also established that the parents are aware of the significance of sports activities for child’s motor development

    The interconnectedness between physical symptoms, anger and gratitude

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    Ugotovili smo, da obstaja povezanost med prisotnostjo fizičnih simptomov in posameznimi dimenzijami jeze in hvaležnosti (ruminacije, neposredno izražanje jeze navzven, preusmerjanje pozornosti, asertivnost in odsotnost občutka prikrajšanosti) in hkrati nepovezanost (izogibanje, iskanje socialne podpore, hvaležnost za majhne stvari in hvaležnost drugim ljudem). Ugotovili smo tudi, da je med ženskami in moškimi statistično pomembna razlika v prisotnosti fizičnih simptomov, ruminacij in iskanju socialne podpore. Te razlike nismo odkrili pri vseh ostalih dimenzijah jeze in pri vseh dimenzijah hvaležnosti. Potrdili smo tudi, da posamezniki, ki imajo več somatskih simptomov pri svojem soočanju z jezo, pogosteje uporabljajo neposredno izražanje jeze, ruminacije in preusmerjanje pozornosti, ter posamezniki, ki imajo najmanj somatskih simptomov, pogosteje uporabljajo asertivni pristop. Po drugi strani pa smo ugotovili, da med posamezniki, ki imajo najmanj in največ somatskih simptomov, ni razlik v doživljanju in izražanju hvaležnosti.We have determined that there is a correlation between the presence of physical symptoms and certain dimensions of anger and gratitude (rumination, direct anger-out, diffusion, assertion and lack of sense of deprivation), but found no correlation with other dimensions (avoidance, social support-seeking, simple appreciation, appreciation for others). We have also determined that there is a statistically important distinction between men and women with regards to the presence of physical symptoms, rumination and social support-seeking. Such distinction was not observed with other dimensions of anger nor with any of the dimensions of gratitude. We have also confirmed that individuals with the most pronounced somatic symptoms are more likely to use direct anger-out, rumination and diffusion when dealing with anger, while individuals with the fewest somatic symptoms use assertion more frequently. On the other hand, we have established that there is no difference in experiencing and expressing gratitude between individuals with the most and the least pronounced somatic symptoms
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