Structureborne noise control in advanced turboprop aircraft

Structureborne noise is discussed as a contributor to propeller aircraft interior noise levels that are nonresponsive to the application of a generous amount of cabin sidewall acoustic treatment. High structureborne noise levels may jeopardize passenger acceptance of the fuel-efficient high-speed propeller transport aircraft designed for cruise at Mach 0.65 to 0.85. These single-rotation tractor and counter-rotation tractor and pusher propulsion systems will consume 15 to 30 percent less fuel than advanced turbofan systems. Structureborne noise detection methodologies and the importance of development of a structureborne noise sensor are discussed. A structureborne noise generation mechanism is described in which the periodic components or propeller swirl produce periodic torques and forces on downstream wings and airfoils that are propagated to the cabin interior as noise. Three concepts for controlling structureborne noise are presented: (1) a stator row swirl remover, (2) selection of a proper combination of blade numbers in the rotor/stator system of a single-rotation propeller, and the rotor/rotor system of a counter-rotation propeller, and (3) a tuned mechanical absorber

In-flight near- and far-field acoustic data measured on the Propfan Test Assessment (PTA) testbed and with an adjacent aircraft

Flight tests to define the far-field tone source at cruise conditions were completed on the full-scale SR-7L advanced turboprop that was installed on the left wing of a Gulfstream 2 aircraft. This program, designated Propfan Test Assessment (PTA), involved aeroacoustic testing of the propeller over a range of test conditions. These measurements defined source levels for input into long-distance propagation models to predict en route noise. In-flight data were taken for seven test cases. Near-field acoustic data were taken on the Gulfstream fuselage and on a microphone boom that was mounted on the Gulfstream wing outboard of the propeller. Far-field acoustic data were taken by an acoustically instrumented Learjet that flew in formation with the Gulfstream. These flight tests were flown from El Paso, Texas, and from the NASA Lewis Research Center. A comprehensive listing of the aeroacoustic results from these flight tests which may be used for future analysis are presented

Inflight source noise of an advanced full-scale single-rotation propeller

Flight tests to define the far field tone source at cruise conditions were completed on the full scale SR-7L advanced turboprop which was installed on the left wing of a Gulfstream II aircraft. This program, designated Propfan Test Assessment (PTA), involved aeroacoustic testing of the propeller over a range of test conditions. These measurements defined source levels for input into long distance propagation models to predict en route noise. Inflight data were taken for 7 test cases. The sideline directivities measured by the Learjet showed expected maximum levels near 105 degrees from the propeller upstream axis. However, azimuthal directivities based on the maximum observed sideline tone levels showed highest levels below the aircraft. An investigation of the effect of propeller tip speed showed that the tone level of reduction associated with reductions in propeller tip speed is more significant in the horizontal plane than below the aircraft

What I believe about leadership and education : a reflective essay

The key topics of education will be revealed throughout the entirety of this essay. The purpose of education and why leaders are important to school success will be the first topic. The section describes how leaders mold the school and work with teachers to find best practice is key to school-wide success. The next area the essay dissects is how the principal leads learning for students and teachers. School leaders have to bring teachers up to the maximum potential through staff development. The third section will explain the importance of leadership during the change process. The fourth portion addresses how to make improvements in the school as an administrator. The final segment the essay confronts the servant leader. To be successful every school leader must put the needs of the children and staff before their own

Learner-centered social support: enhancing online distance education for underserved rural high school students in the United States

Over the past decade, federal programs in the United States have largely addressed the well-documented problem of differences in basic access to technology between rural schools and their suburban and urban counterparts. Consequently, rural schools are better able to prepare their students for post-secondary education and the workplace where digital literacy is essential. As technology access improves, online distance education (ODE) is seen as a solution to significant challenges faced by rural schools, including a lack of highly-qualified teachers and declining population. However, ODE has high attrition rates, partly because participants’ social needs are often neglected. Additionally, students' success depends on their abilities to engage in self-regulated learning, effective time management and self-reflection, skills that many high school students are still developing. This paper describes an experimental research study funded by the U.S. Department of Education, currently underway in rural high schools across the U.S. The research adds to a growing body of work that attempts to expand understanding of the digital divide. Increasingly, schools realise that this is no longer an issue of mere access to equipment; education technology projects should incorporate strategies that ensure the success of previously marginalised communities. Our intervention, based on the APA’s Learner- Centered Principles, involves training on-site facilitators to provide social support for students involved in ODE. Preliminary findings indicate that the intervention group has a significantly lower dropout rate

Crossing the race divide : interracial sex in antebellum Savannah

This article explores the social significance of inter-racial sexual contact in an antebellum Southern city. How did inter-racial sex challenge the established social hierarchy in Savannah? Was it a controversial issue, viewed as a threat to the social order, or was it accepted as an inevitable evil resulting from a mixed population residing in close proximity

Optimal Control Strategies for Constrained Relative Orbits

The US Air Force\u27s ability to protect space assets is enhanced by a proficiency in satellite proximity operations and Space Situational Awareness (SSA). In pursuit of that proficiency, this research develops a key capability of interest to mission planners; the ability of a deputy satellite to hover within a defined volume fixed in the vicinity of a chief satellite for an extended period of time. This research finds optimal trajectories, produced with discrete-thrusts, that minimize fuel spent per unit time and stay within the user-defined volume, thus providing a practical hover capability in the vicinity of the chief. The work assumes the Clohessy-Wiltshire closeness assumption between the deputy and chief is valid, however, elliptical chief orbits are allowed. Using the new methodology developed in this work, feasible closed and non-closed relative orbits are found and evaluated based on a fuel criterion and compared to an easily calculated continuous-thrust baseline. It is shown that in certain scenarios the discrete-thrust solution provides the lowest overall fuel cost. These scenarios are generally constrained to a smaller total time-of-flight. A simple check is proposed that enables the mission planner to make the correct strategy choice

The effect of the essential oil of rosemary and lemon on memory ability in eighth graders

The significance of the effect of the aromatic fragrances of rosemary and lemon on memory was investigated. One hundred and four eighth grade students participated in the study. Students were randomly assigned to encoding groups of 30-35 for exposure to an aromatic fragrance condition. A 30-item word list was visually presented during exposure to the aromatic fragrance from water or the essential oil of rosemary or lemon. After a 1-½ hour delay, students were reassigned groups and asked to recall, directly and indirectly, the previously presented words while exposed to one of the three conditions. A test of direct recall asked the student to write as many previously presented words as possible. The indirect recall test consisted of 20 word fragments of words from the previous list and 20 additional filler words. Test order was randomly alternated. A 3 x 3 factorial analysis of variance was run to determine any level of significance. Findings indicated an interaction by order of test taken for direct recall. Students who took the direct recall test prior to the word fragment test did significantly better than those who took the word fragment test first. Also, those students exposed to lemon at encoding showed a higher average number of correct responses on the direct recall test. These findings suggest a positive link for children\u27s memory ability to the aromatic fragrance of lemon. It may be plausible for lemon to facilitate young students in the learning and recall of information