Extracting fixed base modal models from vibration tests on flexible tables.
a acceleration dof degree of freedom H Frequency response function f Applied force FE Finite Element FRF Frequency Response Function Φc The mode shape matrix of the bare table at dof to be constrained Subscripts c degree of freedom at locations to be constrained f dof at free locations t dof at tip of the slip table s dof at the classic shaker input location on the slip table i any other dof not including t or s
Quantifying the Effect of Dynamic Boundary Condition Differences Between the Vibration Laboratory and the Field Operating Environment
Vibration qualification testing of components or subassemblies is performed on shaker tables. The uncertainty associated with the boundary condition difference between the field and the shaker table is usually ignored. It will be shown with analytical and hardware demonstrations that component response can be significantly different even if controlled at one accelerometer. The quantification of this uncertainty would be useful for characterizing margin associated with the laboratory boundary condition. Assuming that a rigid body representation of the field base input is known, a method is proposed that uses a modified version of structural modification, to attempt to correct for the difference using a modal characterization of the shaker table. Disappointing results are shown for a first time implementation with actual hardware. However, the experience provides important insights to guide future efforts for the quantification of the response uncertainty due to the boundary condition difference between the field and laboratory.
Design and Development of an In Vitro Tear Replenishment System
Understanding the cellular and molecular mechanisms of the corneal tissue and translating them into effective therapies requires organotypic culture systems that can better model the physiological conditions of the front of the eye. Human corneal in vitro models currently exist, however, the lack of tear replenishment limits corneal in vitro models’ ability to accurately simulate the physiological environment of the human cornea. The tear replenishment system (TRS), a micro-fluidic device, was developed to mimic the in vivo tear replenishment in the human eye in an in vitro corneal model. The TRS is capable of generating adjustable intermittent flow from 0.1 µL in every cycle. The TRS is a sterilizable device that is designed to fit standard 6-well cell culture plates. Experiments with the corneal models demonstrated that exposure to the TRS did not damage the integrity of the stratified cell culture. Contact lenses “worn” by the in vitro corneal model also remained moist at all times and the cytotoxicity of BAK could also be verified using this model. These in vitro results confirmed that the TRS presents novel avenues to assess lens-solution biocompatibility and drug delivery systems in a physiologically relevant milieu.