A 33–year-old woman was visited at the dermatological clinic of Loghman-e-Hakim Hospital with multiple hypopigmented patches on her right arm, buttocks and flanks. Her lesions developed over the past year with no regression. Lesions were resistant to multiple antifungal therapies. Clinical examination revealed multiple circular or oval patches on the right arm, flank and sacral area. There was ...

In the present study, some perturbation methods are applied to Duffing equations having a displacement time-delayed variable to study the stability of such systems. Two approaches are considered to analyze Duffing oscillator having a strong delayed variable. The homotopy perturbation method is applied through the frequency analysis and nonlinear frequency is formulated as a function of all the ...