Browsing by Author "Mendoza, Hector"
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- An Architecture of Light: A Catholic Church for Blacksburg, VirginiaMendoza, Hector (Virginia Tech, 2008-01-31)This thesis is an investigation on how in architecture structure and material modulate the perception of light. This idea was implemented in the design of a catholic church for the parish of Blacksburg,Virginia. The vision of the church as a community in constant interaction resulted in the design of a complex, in which the chapel is accompanied by a pre-school and a third building containing facilities for the administration of the parish and the residence for the priest. The plaza on which all the buildings have been arranged allows the opportunity for outdoor activities, as well as the contemplation of the beautiful ever-changing views of the mountains that surround the church. The difference in the nature of the activities that take place in each one of the buildings has been expressed through the way structure and materials interact with the natural light producing a distinctive interior quality.
- Evaluation of the Effectiveness of an Active Magnetic Damper (AMD) in Damping Subsynchronous Vibrations in a Flexible RotorMendoza, Hector (Virginia Tech, 2000-06-22)Subsynchronous vibrations such as those caused by rotor instability represent one of the most harrowing scenarios of rotor vibration. They are related to a great diversity of destabilizing forces and some of them are not well understood yet. Therefore, special attention must be paid to this type of vibration. Active Magnetic Bearings (AMBs) monitor the position of the shaft and change the dynamics of the system accordingly to keep the rotor in a desired position, offering the possibility of being used as dampers for vibration control. In the present work, a single-disk and a three-disk rotor were built to evaluate the effectiveness of an Active Magnetic Damper (AMD) in damping subsynchronous vibrations. An AMD was used to inject a signal simulating a subsynchronous vibration in the rotor, as another AMD was used to perform active control. Two locations of the AMD were considered for each rotor. For the single-disk rotor, experimental data was taken with the AMD located at three-quarters of the rotor-span and with the AMD located at midspan. For the three-disk rotor, experimental data was taken with the AMD located at a quarter-span and with the AMD at two-thirds of the rotor span. An undamped critical speed and a forced response analysis were performed on the rotors in order to predict the dynamic characteristics of the rotors with and without the AMD. It was demonstrated that an AMD is effective in damping subsynchronous vibrations. The addition of an AMD introduces damping and stiffness to the rotor-bearing system resulting in a change in the synchronous response and a consequent increase of the amplitude of vibrations at synchronous frequencies. This effect must be carefully considered when designing a system with an AMD.