Dynamic stability of multi-span frames subjected to periodic loading

In this study, in-plane dynamic stability analysis of multi-span frames, which are composed of columns and beams and subjected to periodic loading, is investigated by using the Finite Element Method. Periodic loading is considered to be applied to each column member as an axial load and no loading is applied on the beams. The effects of beam to column length ratio, beam to column cross-section ratio and beam to column moment of area ratio are investigated for in-plane frames. In addition, the effect of the number of span and static and dynamic load parameters on the free vibration, buckling and dynamic stability analysis is also investigated. The results are compared with the recent literature in terms of the fundamental natural frequency and critical buckling load. (C) 2011 Elsevier Ltd. All rights reserved

A Multicriteria Method to Form Optional Preventive Maintenance Plans: A Case Study of a Large Fleet of Vehicles

IEEEMotor vehicles are composed of a large number of parts, and planning the maintenance activities of different parts is a crucial decision that affects system reliability, operation costs, and capacity requirements of service providers. We propose a systematic method to determine the critical parts that should be handled with extra preventive maintenance (PM) and prepare alternative PM plans with different levels of cost and capacity usage. Our method uses a multicriteria decision-making approach to determine the critical parts and conducts statistical reliability analysis with failure data and expert knowledge to create the maintenance plans. We use the proposed method in a case study to determine optional PM packages that would support regular PM practices in the after-sales service of a large motor vehicle manufacturer. The main aim of the case study is to increase the satisfaction of customers who are more sensitive to failures, such as carriers of food and medical supplies. The results show that the optional PM packages can decrease the cost of failures while obeying the capacity limitation of the company

Electrical, optical and theoretical characterization of doped and undoped calamitic liquid crystal: (s)-5-octyloxy-2-[[[4-(2-methyl butoxy) phenyl] imino] methyl] phenol

The electrical conductivities of undoped and doped calamitic liquid crystalline compound, (S)-5-octyloxy-2-[[[4-(2-methylbutoxy) phenyl] imino] methyl] phenol (OMPIMP) with tetrabutylammonium tetrafluoroborate as dopant were determined as a function of temperature. Optical studies of undoped and doped OMPIMP thin films were also carried out using spectrophotometer. Optical band gaps of doped and undoped OMPIMP thin films were determined through absorption spectra using Tauc plot. The frontier orbital energies; E-HOMO, E-LUMO and the band gap energies were calculated from the DFT calculations which were carried out by the hybrid B3LYP functional