An Active Damping at Blade Resonances Using Piezoelectric Transducers

The NASA Glenn Research Center (GRC) is developing an active damping at blade resonances using piezoelectric structure to reduce excessive vibratory stresses that lead to high cycle fatigue (HCF) failures in aircraft engine turbomachinery. Conventional passive damping work was shown first on a nonrotating beam made by Ti-6A1-4V with a pair of identical piezoelectric patches, and then active feedback control law was derived in terms of inductor, resister, and capacitor to control resonant frequency only. Passive electronic circuit components and adaptive feature could be easily programmable into control algorithm. Experimental active damping was demonstrated on two test specimens achieving significant damping on tip displacement and patch location. Also a multimode control technique was shown to control several modes

Source Characteristics, Chemical Weathering, and Lithification of the Stimson Sandstone and Lessons for the Martian Sedimentary Record

The Stimson formation is a basaltic eolian sandstone perched unconformably above the Mount Sharp group rocks in Gale crater, and it is exposed in a number of plateaus observed by the Mars Science Laboratory Curiosity rover. Despite being one of the least geochemically and mineralogically diverse units observed by the Curiosity rover, the Stimson formation is uniquely positioned to offer significant information about sand weathering and lithification processes on Mars because of two factors: (1) the Stimson formation is the only lithologic formation on Mars for which we have a modern analog, the basaltic eolian Bagnold dunes, and (2) Curiosity obtained 33 chemistry analyses of 18 unique targets with the Alpha-Particle X-ray Spectrometer and 2 mineralogical samples of unaltered Stimson sandstone (discounting samples of Stimson altered by late-stage fluid events). Comparison between the Stimson sandstone and the Bagnold sands yields clues to source rock and lithification processes on Mars, and differences between different Stimson samples reveal weathering trends affecting the ancient dune field

Active Vibration Reduction of Titanium Alloy Fan Blades (FAN1) Using Piezoelectric Materials

The NASA Glenn Research Center is developing smart adaptive structures to improve fan blade damping at resonances using piezoelectric (PE) transducers. In this paper, a digital resonant control technique emulating passive shunt circuits is used to demonstrate vibration reduction of FAN1 Ti real fan blade at the several target modes. Single-mode control and multi-mode control using one piezoelectric material are demonstrated. Also a conceptual study of how to implement this digital control system into the rotating fan blade is discussed

On the Hardness of Computing Endomorphism Rings of Supersingular Elliptic Curves

Cryptosystems based on supersingular isogenies have been proposed recently for use in post-quantum cryptography. Three problems have emerged related to their hardness: computing an isogeny between two curves, computing the endomorphism ring of a curve, and computing a maximal order associated to it. While some of these problems are believed to be polynomial-time equivalent based on heuristics, their relationship is still unknown. We give the first reduction between these problems, with the aid of one more problem which we call Action-on-$\ell$-Torsion. We show that computing $\ell$-power isogenies reduces to computing maximal orders and Action-on-$\ell$-Torsion. We also define the notion of a compact representation of an endomorphism, and use this to show that endomorphism rings always have polynomial representation size. We then reduce the endomorphism ring problem to computing maximal orders and Action-on-$\ell$-Torsion, thus laying the foundation for analysis of the hardness of endomorphism ring computation. This identifies these last two problems as one possible way to attack some systems, such as hash functions based on the $\ell$-isogeny graph of supersingular elliptic curves. This gives the potential to use algebraic tools in quaternion algebras to solve the problems. We also discuss how these reductions apply to attacks on a hash function of Charles, Goren, and Lauter

Discipline in Context: Suspension, Climate, and PBIS in the School District of Philadelphia

The report details a two-year exploratory, mixed-methods research study on the disciplinary practices and climate of schools serving K–8 students in the School District of Philadelphia (SDP). Findings reveal that SDP schools are making efforts to reduce suspensions and improve climate, but critical barriers to these efforts include resource limitations and philosophical misalignments between teachers and school leaders. The study identified three profiles among SDP schools serving K–8 students based on information about disciplinary practices and climate, and found that these profiles are predictive of suspension and academic outcomes. Students attending schools with collaborative climates and less punitive approaches to discipline have lower risk of being suspended and better academic outcomes. The report offers a series of recommendations for strengthening the implementation of climate initiatives, including Positive Behavioral Interventions and Supports (PBIS), in challenging urban settings

Discipline in Context: Suspension, Climate, and PBIS in the School District of Philadelphia

The report details a two-year exploratory, mixed-methods research study on the disciplinary practices and climate of schools serving K–8 students in the School District of Philadelphia (SDP). Findings reveal that SDP schools are making efforts to reduce suspensions and improve climate, but critical barriers to these efforts include resource limitations and philosophical misalignments between teachers and school leaders. The study identified three profiles among SDP schools serving K–8 students based on information about disciplinary practices and climate, and found that these profiles are predictive of suspension and academic outcomes. Students attending schools with collaborative climates and less punitive approaches to discipline have lower risk of being suspended and better academic outcomes. The report offers a series of recommendations for strengthening the implementation of climate initiatives, including Positive Behavioral Interventions and Supports (PBIS), in challenging urban settings

Moving for Employment Reasons

While most models of population migration assume that members of the labour force migrate to enhance returns to their labour, major surveys in the USA (PSID and CPS), in the UK (BHPS) and Australia (HILDA) all show that only around 10 percent of all individuals who change residence are motivated primarily by employment reasons. Of those moving between local labour markets only about 30 percent say they are motivated by employment reasons. We explore this apparent paradox by drawing on evidence from the Dynamics of Motivation and Migration Survey (DMM), which recorded the reasons people of working age, changed their permanent residence in New Zealand over the two-year period 2005 and 2006. The need to solve the employment problem before moving means that reasons offered retrospectively for moving usually reflect a wish to adjust consumption even in the case of those moving between local labour markets. For most people of working age employment remains a necessary condition rather than sufficient reason for moving and this is why the pattern of net flows among local markets appear to support theories of migration change even though few people say they move for employment reasons