Chemical composition, structural characterization and source identification of DOM in urban stormwater runoff collected from three typical regions in Beijing were investigated.

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A new type of conserved quantity which is directly induced by Mei symmetry of Hamilton system is studied. Firstly, the definition and criterion of Mei symmetry for Hamilton system are given. Secondly, a coordination function is introduced; the conditions from which the new type of conserved quantity can be induced by Mei symmetry and the form of the new type of conserved quantity are obtained. Lastly, an illustration example is given. The result indicates that the coordination function should be selected properly according to the demand of the gauge function, thereby the gauge function can be find out more easily. Furthermore, since the choice of the coordination function is not unique more conserved quantities of Mei symmetry for Hamilton system can be obtained.

By Kirchhoff dynamic analogy, the thin elastic rod static equals to rotation of rigid body dynamic. The analytical mechanics methods reflect their advantages in the study of the modeling and equilibrium and stability of elastic rod static, especially for the constrained problems. The Lagrangian structure of the equation of motion for elastic rod is deduced from the integral variational principle. The definition of conformal invariance of Mei symmetry of elastic rod in Lagrangian form is given. The determining equation of conformal invariance of Mei symmetry is obtained based on the Lie point transformation group. The relation between conformal invariance of Mei symmetry and Mei symmetry is discussed. The structure equation and conserved quantity by using the Lagrangian structure along arc coordinate deduced from conformal invariance of Mei symmetry of elastic rod are constructed. Take rod with circular cross section as example to illustrate the application of the results get in this paper. These conserved quantities will be helpful in the study of exact solutions and stability, as well as the numerical simulation of the thin elastic rod nonlinear mechanics.