Distribution Of Thermodynamic Variables Research Articles

Solving protoplanetary structure equations using Adomian decomposition method

In this paper, the distribution of thermodynamic variables in the protoplanets formed by gravitational instability in the mass range 0.3−10MJ (1MJ=1 Jupiter mass = 1.8986×1030 gm) is investigated in their initial state by solving the structure equations via the Adomian decomposition method. Concerning the heat transfer in the protoplanets, the mode of convection is taken into account. The outcomes indicate that there is a reasonably good agreement between the Adomian semi-analytical solution containing only first 8 terms and the numerical results.

Solidification prediction of laser cladding 316L by the finite element simulation

Laser cladding technology has been widely applied in industrial production because of its prominent advantage in surface modification. To achieve improved microstructure characteristics and performance, it is essential to investigate the solidification mechanism of the microstructures formed during laser cladding. In this study, the columnar-to-equiaxed transition for laser-clad 316L was predicted using a three-dimensional finite element model coupled with electron backscatter diffraction analysis. First, the distribution of thermodynamic variables at different laser powers was examined. Then, the fitting curve for predicting the columnar-to-equiaxed transition was established, and the results indicate that the solidification of laser-clad 316L can be accurately predicted. Moreover, the grain size distribution for different laser powers was counted, and the average grain size of the molten pool was shown to increase with increasing laser power. This work will serve as a guide for the crystal transition in the solidification process for laser cladding.

Modelo adiabático da atmosfera terrestre compatível com o aquecimento global e o efeito estufa

Apresentamos um modelo adiabático da atmosfera terrestre, que descreve o aquecimento global atribuído ao efeito estufa. O regime adiabático assume as distribuições médias das grandezas termodinâmicas, que são dependentes apenas da altitude. As contribuições térmicas não radiativas são introduzidas através do ajuste do coeficiente adiabático do gradiente térmico da troposfera nas regiões dos trópicos, igual a 6,5 K/km. O aquecimento global deriva-se com o balanço energético entre o sol e as radiações emitidas na superfície e troposfera terrestres. Assume-se como principal causa do aquecimento global, o aumento da concentração de CO2 na troposfera na era pós-industrial. Derivam-se as expressões de emissividade do CO2 em função de sua concentração na troposfera, a partir do o forçamento radiativo associado ao efeito estufa sobre a terra. Ademais, estabelece-se uma relação quantitativa simples para descrever o comportamento do gradiente térmico com o aumento da concentração de CO2 na troposfera. Por fim, destacamos algumas técnicas de medidas visando uma possível detecção do aquecimento global nos próximos decênios.