The presented work illustrates the synthesis of a nonlinear model-based observer for the longitudinal dynamics estimation of a wheelset. This approach offers some significant improvements, such as an enhanced adherence to prescribed brake distances and an advanced usability of the condition-based maintenance of brake systems. The investigation of a single wheelset in a test rig environment enables, for example, the usage of an extended set of sensors to reliably validate the observers. The presented observer design process covers three main steps: identification of the characteristic system disturbances, implementation of the nonlinear observer dynamics, and parametrization of the observer via multicase optimization. With regard to the longitudinal dynamics, the variations of the friction conditions in the wheel–rail interface and in the interface between brake pads and brake disc have a crucial influence. Therefore, a parameter estimator and a disturbance observer are implemented, since these methods allow for a specific consideration of these disturbances. The obtained results prove that the observers accurately estimate the system behavior and provide reliable information on the longitudinal dynamics.

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A new approach to control a rubbing rotor by applying an active auxiliary bearing has been developed. The control force is applied indirectly using the auxiliary bearing, only in case of rotor rubbing. The auxiliary bearing is actuated using two unidirectional actuators. A three-phase control strategy has been developed which stabilizes the rotor system in case of an impact load and effectively avoids “backward whirling” which is very destructive. As soon as the load ceased the auxiliary bearing is separated from the rotor again and normal operation mode is continued. During the normal operation state, the feedback control does not interfere with the rotor system at all. A test rig has been developed to experimentally verify the control system. Various experiments show the success of the control strategy. In case of rubbing, the contact forces are reduced up to 95 percent. At the same time, the rotor deflection is decreased too. The activation and deactivation of the control system is operated fully automatically. A simulation framework for an elastic rotor including the non-smooth nonlinear dynamics of contacts is presented, which has been used to develop the feedback controller.

The nursing workforce does not mirror the demographics of the United States, contributing to health disparities related to race. The purpose of this study was to assess possible changes in racial bias among undergraduate nursing students. Students in their first (n = 58) or fifth (n = 50) semester completed the Color-Blind Racial Attitudes Scale via an online survey. Fifth-semester students reported significantly more racial bias than first-semester students. Further investigation revealed more influence of students' race: White students indicated greater color-blind attitudes than students of color. Recommendations for integrating multicultural curricula into nursing programs are included.