Current Issue : April - June Volume : 2012 Issue Number : 2 Articles : 5 Articles
The adaptive stabilization scheme based on tuning function for stochastic nonlinear systems with\r\nstochastic integral input-to-state stability SiISS inverse dynamics is investigated. By combining\r\nthe stochastic LaSalle theorem and small-gain type conditions on SiISS, an adaptive output feedback\r\ncontroller is constructively designed. It is shown that all the closed-loop signals are bounded\r\nalmost surely and the stochastic closed-loop system is globally stable in probability....
The characteristics of the patch antenna based on photonic band-gap PBG substrate with\r\nheterostructures were studied numerically by using the method of finite difference time domain\r\nFDTD. The results indicate that, comparing to the conventional patch antennas, the expansion of\r\nworking frequency band of the new patch antenna can be realized and its radiation efficiency also\r\ncan be improved notably with the influence of PBG. In addition, for this new kind of patch antenna,\r\nits return loss is much less and there are two minimum values for return loss corresponding to\r\nthe resonant frequency of the two different photonic crystals made of the substrate. Its physical\r\nmechanism lies on the PBG which suppresses the surface waves propagating along the surface\r\nof the substrate and reflects most of electromagnetic wave energy radiated to the substrate\r\nsignificantly....
The Magnetohydrodynamic stability of a streaming cylindrical model penetrated by varying\ntransverse magnetic field has been discussed. The problem is formulated, the basic equations are\nsolved, upon appropriate boundary conditions the eigenvalue relation is derived and discussed\nanalytically, and the results are verified numerically. The capillary force is destabilizing in a small\naxisymmetric domain 0 < x < 1 and stabilizing otherwise. The streaming has a strong destabilizing\neffect in all kinds of perturbation. The toroidal varying magnetic field interior the fluid has no\ndirect effect at all on the stability of the fluid column. The axial exterior field has strong stabilizing\neffect on the model. The effect of all acting forces altogether could be identified via the numerical\nanalysis of the stability theory of the present model....
Security-constrained unit commitment SCUC is an important tool for independent system\r\noperators in the day-ahead electric power market. A serious issue arises that the energy\r\nrealizability of the staircase generation schedules obtained in traditional SCUC cannot be\r\nguaranteed. This paper focuses on addressing this issue, and the basic idea is to formulate the\r\npower output of thermal units as piecewise-linear function. All individual unit constraints and\r\nsystemwide constraints are then reformulated. The new SCUC formulation is solved within the\r\nLagrangian relaxation LR framework, in which a double dynamic programming method is\r\ndeveloped to solve individual unit subproblems. Numerical testing is performed for a 6-bus\r\nsystem and an IEEE 118-bus system on Microsoft Visual C# .NET platform. It is shown that the\r\nenergy realizability of generation schedules obtained from the new formulation is guaranteed.\r\nComparative case study is conducted between LR and mixed integer linear programming MILP\r\nin solving the new formulation. Numerical results show that the near-optimal solution can be\r\nobtained efficiently by the proposed LR-based method....
The design of slender beams, that is, beams with large laterally unsupported lengths, is commonly\r\ncontrolled by stability limit states. Beam buckling, also called ââ?¬Å?lateral torsional buckling,ââ?¬Â is\r\ndifferent from column buckling in that a beam not only displaces laterally but also twists about its\r\naxis during buckling. The coupling between twist and lateral displacement makes stability analysis\r\nof beams more complex than that of columns. For this reason, most of the analytical studies in the\r\nliterature on beam stability are concentrated on simple cases: uniform beams with ideal boundary\r\nconditions and simple loadings. This paper shows that complex beam stability problems, such as\r\nlateral torsional buckling of rectangular beams with variable cross-sections, can successfully be\r\nsolved using homotopy perturbation method HPM....
Loading....