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The Bianchi type-III cosmological model for a cloud string with bulk viscosity are studied. To obtain a determinate solution, it is assumed that the coefficient of bulk viscosity is a power function of the scalar of expansion ζ = kθm and the shear scalar is proportional to scalar of expansion σ∝θ, which leads to the relation between metric potentials B = Cn. The physical features of the model are also discussed. It is found that the power index m has significant influence on the string model. There is a ``big bang'' start in the model when m≤1 but there is no the big-bang start when m>1. In the special case m = 0, the model reduces to the string model of constant coefficient of bulk viscosity that was the result previously given in the literature.

The Bianchi type III cosmological model for a cloud string with bulk viscosity are presented. To obtain a determinate model, an equation of state and a relation between metric potentials are assumed. The physical and geometric aspects of the model are also discussed. The model describes a shearing non-rotating continuously expanding universe with a big-bang start, and the relation between the coefficient of bulk viscosity and the energy density is .

Some locally rotationally symmetric Bianchi type-I cosmological solutions for a cloud string with bulk viscosity are presented. In the first case, an equation of state ρ = kλ and the relation between metric potentials R = ASn are considered, and the solution represents shearing non-rotating model with the bulk viscosity ζ∝ρ1/2, where ρ is the rest energy density of the cloud of strings with particles attached to them, λ is the tension density of the cloud of strings, ζ is the coefficient of the bulk viscosity, R and S are only the functions of time t, while A and k are constant. In the second case, the constant coefficient of bulk viscosity is considered.

The Bianchi type-III cosmological model for a cloud string in the presence of bulk viscosity and magnetic field are presented. To obtain the determinate model it is assumed that there is an equation of state ρ = kλ and the scalar of expansion is proportional to the shear scalar θσ, which leads to a relation between metric potentials B = mCn. The physical and geometric aspects of the model are also discussed. The model describes a shearing non-rotating continuously expanding universe with a big-bang start. In the absence of magnetic field, it reduces to the string model with bulk viscosity that was previously given in the literature.

The locally rotationally symmetric Bianchi-type II string cosmological models with bulk viscosity are obtained, where an equation of state, , and a relation between metric potentials, , are adopted. The physical features of the models are also discussed. In special cases the model reduces to the string models without viscosity that was previously given in the literatures.

Some more general cosmological solutions of Bianchi types II, VIII, and IX for a cloud string are presented. The physical implications of the solutions are briefly discussed. Our solutions include some of the results previously given in the literature as special cases.

An exact solution of the field equations of general relativity is obtained for a static, spherically symmetric distribution of charge and mass. Their physical properties are studied in some detail. Our solution includes as special cases the results given previously by Cooperstock and De La Cruz, Mehra and Bohra, Santos, and Shi-Chang.