Viscoelastic properties of dispersed chitosan/xanthan hydrogels

Abstract

Online assessment and control of low-damping power system oscillations is a challenging problem. This paper discusses the use of subspace stochastic method to visualize and characterize the time evolution of power system electromechanical modes. Using normalized instantaneous amplitudes of modal components, two time-varying indexes to determine mode distribution maps are proposed and tested. The method is well suited to automation and can be incorporated to existing wide-area monitoring systems. Simulation studies on a 16-machine, 68-bus test system show the applicability of the proposed technique. " 2013 IEEE.",,,,,,"10.1109/NAPS.2013.6666931",,,"http://hdl.handle.net/20.500.12104/45697","http://www.scopus.com/inward/record.url?eid=2-s2.0-84893326434&partnerID=40&md5=2fad6b735b8f3ee7200f291c7f1420e9",,,,,,,,"45th North American Power Symposium, NAPS 2013",,,,,,"Scopus",,,,,,,,,,,,"Visualization of interarea oscillations using an extended subspace identification technique",,"Conference Paper" "47464","123456789/35008",,"Martínez-Ruvalcaba, A., Departamento de Ingeniería Química, Universidad de Guadalajara, Guadalajara, Jalisco 44430, Mexico; Chornet, E., Department of Chemical Engineering, University de Sherbrooke, Sherbrooke, Que. J1K 2R1, Canada; Rodrigue, D., Department of Chemical Engineering, University Laval, Québec, Que. G1K 7P4, Canada",,"Martinez-Ruvalcaba, A.

Chornet, E.

Rodrigue, D.",,"2007",,"In this work a gel was formed by complexation of two natural polyelectrolytes, chitosan and xanthan. Changes in the hydrogels rheological properties have been studied in terms of hydrogel concentration (7-10% w/w), chemical media used for the hydrogel dispersion, and 'test lag time'; i.e., the time between hydrogel dispersion in the chemical media and the start of the rheological test (up to 390 min). The viscoelastic properties of this polysaccharide system were characterized by oscillatory shear measurements under small-deformation conditions and the results show that chitosan/xanthan hydrogels behave like weak gels. The shear modulus increased almost linearly with frequency in the range studied (0.1-65 s-1). The effects of hydrogel concentration and dispersion medium have been related to electrostatic equilibrium and by the presence of counter-ions modifying the internal structure of the hydrogel. " 2006 Elsevier Ltd. All rights reserved.