An Analysis of Principal Attrition in a Large Urban School District

Principal attrition is a national problem particularly in large urban school districts. Research confirms that schools that serve high proportions of children living in poverty have the most difficulty attracting and retaining competent school leaders. Principals who are at the helm of high poverty schools have a higher turnover rate than the national average of three to four years and higher rates of teacher attrition. This leadership turnover has a fiscal impact on districts and negatively affects student achievement. Research identifies a myriad of reasons why administrators leave the role of principal: some leave the position for retirement; some exit based on difficulty of the role and lack of support; and some simply leave for other opportunities within and outside of the profession altogether. As expectations for both teacher and learner performance drive the national education agenda, understanding how to keep effective principals in their jobs is critical. This study examined the factors that principals in a large urban district identified as potentially affecting their decisions to stay in the position. The study utilized a multi-dimensional, web-based questionnaire to examine principals’ perceptions regarding contributing factors that impact tenure. Results indicated that: • having a quality teaching staff and establishing a positive work-life balance were important stay factors for principals; • having an effective supervisor and collegial support from other principals, were helpful supports; and • having adequate resources, time for long-term planning, and teacher support and resources were critical working conditions. Taken together, these indicators were the most frequently cited factors that would keep principals in their positions. The results were used to create a framework that may serve as a potential guide for addressing principal retention.

Analysis of ocean power extraction capabilites of a rotary wave energy conversion system

Gemstone Team WAVES (Water and Versatile Energy Systems)

An Acoustic Analysis of Valveless Pulsejet Engines

Valveless pulsejets are extremely simple aircraft engines; essentially cleverly designed tubes with no moving parts. These engines utilize pressure waves, instead of machinery, for thrust generation, and have demonstrated thrust-to-weight ratios over 8 and thrust specific fuel consumption levels below 1 lbm/lbf-hr – performance levels that can rival many gas turbines. Despite their simplicity and competitive performance, they have not seen widespread application due to extremely high noise and vibration levels, which have persisted as an unresolved challenge primarily due to a lack of fundamental insight into the operation of these engines. This thesis develops two theories for pulsejet operation (both based on electro-acoustic analogies) that predict measurements better than any previous theory reported in the literature, and then uses them to devise and experimentally validate effective noise reduction strategies. The first theory analyzes valveless pulsejets as acoustic ducts with axially varying area and temperature. An electro-acoustic analogy is used to calculate longitudinal mode frequencies and shapes for prescribed area and temperature distributions inside an engine. Predicted operating frequencies match experimental values to within 6% with the use of appropriate end corrections. Mode shapes are predicted and used to develop strategies for suppressing higher modes that are responsible for much of the perceived noise. These strategies are verified experimentally and via comparison to existing models/data for valveless pulsejets in the literature. The second theory analyzes valveless pulsejets as acoustic systems/circuits in which each engine component is represented by an acoustic impedance. These are assembled to form an equivalent circuit for the engine that is solved to find the frequency response. The theory is used to predict the behavior of two interacting pulsejet engines. It is validated via comparison to experiment and data in the literature. The technique is then used to develop and experimentally verify a method for operating two engines in anti-phase without interfering with thrust production. Finally, Helmholtz resonators are used to suppress higher order modes that inhibit noise suppression via anti-phasing. Experiments show that the acoustic output of two resonator-equipped pulsejets operating in anti-phase is 9 dBA less than the acoustic output of a single pulsejet.