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Vibration analysis of a Timoshenko beam carrying 3D tip mass by using differential transform method
Hilal Doğanay Katı,Hakan Gökdağ 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.4
Dynamic behaviour of beam carrying masses has attracted attention of many researchers and engineers. Many studies on the analytical solution of beam with concentric tip mass have been published. However, there are limited works on vibration analysis of beam with an eccentric three dimensional object. In this case, bending and torsional deformations of beam are coupled due to the boundary conditions. Analytical solution of equations of motion of the system is complicated and lengthy. Therefore, in this study, Differential Transform Method (DTM) is applied to solve the relevant equations. First, the Timoshenko beam with 3D tip attachment whose centre of gravity is not coincident with beam end point is considered. The beam is assumed to undergo bending in two orthogonal planes and torsional deformation about beam axis. Using Hamilton’s principle the equations of motion of the system along with the possible boundary conditions are derived. Later DTM is applied to obtain natural frequencies and mode shapes of the system. According to the relevant literature DTM has not been applied to such a system so far. Moreover, the problem is modelled by Ansys, the well-known finite element method, and impact test is applied to extract experimental modal data. Comparing DTM results with finite element and experimental results it is concluded that the proposed approach produces accurate results.
( Hilal Kaya Erdogan ),( Isil Bulur ),( Zeynep Nurhan Saracoglu ),( Muzaffer Bilgin ) 대한피부과학회 2018 Annals of Dermatology Vol.30 No.3
Background: Rosacea is a common dermatosis characterized by erythema, telangiectasia, papules and pustules. Objective: We aimed to evaluate contact sensitivity in the rosacea patients. Methods: We included 65 rosacea patients and 60 healthy volunteers in the study. The patient and control groups were patch tested with European baseline series and cosmetic series. Results: A positive reaction to at least 1 allergen in the European standard series was found in 32.3% of rosacea patients and 20.0% of subjects in the control group while the relevant numbers were 30.8% of rosacea patients and 10% of controls with the cosmetic series (p=0.08). In total, we found a positive reaction to at least 1 allergen in 38.5% of patients and 25.0% of controls (p=0.15). We did not find a statistically significant relationship between a positive reaction to 1 allergen in total and the gender, skin type, rosacea type, ocular involvement, age and disease duration. There were more symptoms in patients with a positive reaction to allergens (p<0.001). Conclusion: Contact sensitivity was detected more common in rosacea patients. Patch testing may be useful in the treatment and follow up of rosacea patients especially if symptoms such as itching, burning and stinging are present. (Ann Dermatol 30(3) 290∼295, 2018)