Global Dynamics in the Singular Logarithmic Potential

We present an analytical description of the motion in the singular logarithmic potential. This potential plays an important role in the modeling of triaxial systems (like elliptical galaxies) or bars in the centers of galaxy disks. In order to obtain information about the motion near the singularity, we resort to McGehee -type transformations and regularize the vector field. In the axis-symmetric case (b=1), we offer a complete description of the global dynamics. In the non axis-symmetric case (b<1), we prove that all orbits, with the exception of a negligible set, are centrophobic and retrieve numerically partial aspects of the orbital structure.Comment: Journal of Physics, A; High res images available at: http://stacks.iop.org/0305-4470/36/i=28/a=30

Measuring Receptivity to Eurosceptic Media Discourses in the Vicinity of War: Evidence from Romania

Ever since its accession to the EU, Romania was considered an exceptional case among member states, given the unwavering high levels of popular support for the EU. However, the most recent elections held in Romania brought about the unexpected emergence of the Alliance for the Union of Romanians (AUR), a far-right populist party that strongly opposes the European project, which it accuses of resembling "a harmful hegemony." The war in Ukraine represented another chance for AUR to bash the EU for its reaction in supporting Ukraine. The current article examines the degree to which anti-EU appeals of AUR influence Eurosceptic attitudes in Romania. In doing so, the present research pursues two distinct, but complementary goals. The first is to perform a content analysis of Eurosceptic narratives disseminated by AUR through its main social media channels since the start of the war. The second goal is then, employing four logistic regression models and using unique data collected through an online interactive survey, to test which of these narratives matter the most in shaping Eurosceptic attitudes. The article allows us to develop a nuanced understanding of what triggered a change of heart in a significant part of the Romanian electorate vis-à-vis the EU and the influence of Eurosceptic media discourse in this sense

Reframing Leadership: Jacinda Ardern's Response to the Covid-19 Pandemic

Women's underrepresentation in political leadership has been a constant global challenge during recent decades. Although women’s leadership and its impact on organizational and country performance have been systematically explored, new research avenues are opened through the emergence of various crises. Crises constitute instances in which the intersection of leadership and communication is shaped and enforced, and how female leaders tackled and managed crises has been found to be different from that of their male counterparts in various instances. This study aims to examine the crisis communication approach taken by Jacinda Ardern during the 2020 global public health crisis generated by the Covid-19 pandemic. Female leaders were found to enforce a more effective and persuasive communication approach during the crisis, but Jacinda Ardern’s crisis management approach has been grounded in a feminist ethics of care since her response to the Christchurch mosque shootings in 2019. This article aims to emphasize the importance of communication in reframing leadership, by analyzing Jacinda Ardern’s Facebook communication from the beginning of the Covid-19 crisis. By examining how her messaging is embedded in values and attitudes specific to the ethics of care, we contribute to theorizing ways in which crisis communication is grounded in feminist ethics

Public Debt Expectations: The More You Know about Public Debt, the Less Optimistic You Are

Macroeconomic expectations influence long-term output, investment, and employment through households’ behavior. Policymakers and politicians attempt to predict the behavior of citizens and voters. How individuals form expectations and perceive sovereign indebtedness brings into question public finance sustainability and incumbents’ credibility. Based on a cross-country survey in Central and Eastern European countries, we estimate several probit regressions to uncover the effects of economic knowledge on sovereign debt expectations. Robustness tests and additional control confirm the initial results.  We find that knowledge about public debt increases the chances of forming negative expectations, while higher financial literacy tends to have the opposite effect. More specifically, individuals with higher public debt knowledge are 5.4 percentage points less likely to show positive expectations, while individuals with higher levels of financial literacy (interest rate and inflation knowledge) are approximately 3.5 percentage points more likely to form positive expectations. The results indicate that public debt expectations are driven by negative biases resulting from the lack of economic knowledge together with insufficiency in understanding economic causal mechanisms. Financial literacy programs could benefit from including information about macroeconomics in curricula. Improving individual abilities to understand macroeconomic mechanisms, including public debt, has the potential to influence expectations and shift behaviors towards desired policy outcomes

Relaxor-PbTiO3 single crystals and polycrystals: processing, growth and characterisation

Acoustic transducers operate using polycrystalline lead zirconate titanate (PZT) since the 1950s’. Recently, relaxor-lead titanate (relaxor-PT) single crystals have been developed and exhibit up to 650% higher piezoelectric charge coefficient and up to 50% higher electromechanical coupling factor, compared with PZT. Transducers built with relaxor-PT crystals show increased bandwidth, lower power consumption and increased sensitivity. Despite the significant advantages over PZT, a growth method for relaxor-PT single crystals that is both economical and able to produce homogeneous, highly dense crystals is yet to be found. Furthermore, one of the most important relaxor-PT solid solution is Mn modified Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3- PbTiO3 due to its thermal stability and low electrical and mechanical losses compared with other relaxor-PT solid solutions. However, the behaviour of Mn in this compound is not fully understood and control of properties, such as the mechanical quality factor, is difficult. The aim of this study was to compare Bridgman and Solid State techniques for growth of single crystalline Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3. Subsequent to this, several Mn modified compositions were designed and investigated to determine the mechanisms by which mechanical and electrical losses are lowered upon Mn incorporation. Bridgman experiments have shown that a 20 mm ø x 60 mm length and highly dense single crystal can be obtained, with (011) the natural growth direction. Seeded Bridgman was also investigated as a method of controlling the orientation of the grown crystal, but was proven challenging due to nucleation of several crystallites. Solid State experiments, which involve attaching a single crystal seed to a polycrystalline matrix and promoting boundary migration of the seed into the matrix, showed that crystal growth is encouraged when a Pb-based interlayer exists in between the seed and matrix. An epitaxially deposited, uniform thin film as interlayer was found particularly beneficial. More research is needed to determine conditions for growth of a single crystal of useful size by Solid State. Analysis of several relaxorPT compositions modified with the same amount of Mn revealed that alterations of the relaxor-PT formulation affects behaviour of the multi-valent Mn which in turn in- fluences electromechanical properties. These findings are of use to the industrial and scientific communities. Crystal growth results indicate Bridgman as suitable method if growth of crystals is desired in a short time frame, whilst Solid State results provide the basis of a new approach for growing relaxor-PT crystals. The study of Mn modified compositions provides new insights into the role of Mn substitution for manipulating the electrical and mechanical properties of complex, relaxor-PT solid solutions

Joshua Miller MEMS Independent Study Report – Fall 2019

µ-BEC: The stud µ-BEC: The study of microbes performing extracellular electron uptake (EEU) has multiple uses for biotechnological applications. To that end, a high-throughput platform comprising an array of bioelectrochemical cells (essentially small chambers for electrochemical analysis of biological cells) is necessary to provide the opportunity for proper study of microbes performing EEU. Utilizing traditional cleanroom microfabrication techniques (photolithography, metallization, and lift-off), a 16-chamber micro bio-electrochemical cell (µ-BEC) array was fabricated. Each cell utilized a 3-electrode system, achieving successful electrochemical measurements for 8 of 16 chambers. The 8 chambers that failed exhibited peeling of electrodes due to processing errors. More robust fabrication processes are being explored to improve yield. IDTs: µ-BEC: The study of microbes performing extracellular electron uptake (EEU) has multiple uses for biotechnological applications. To that end, a high-throughput platform comprising an array of bioelectrochemical cells (essentially small chambers for electrochemical analysis of biological cells) is necessary to provide the opportunity for proper study of microbes performing EEU. Utilizing traditional cleanroom microfabrication techniques (photolithography, metallization, and lift-off), a 16-chamber micro bio-electrochemical cell (µ-BEC) array was fabricated. Each cell utilized a 3-electrode system, achieving successful electrochemical measurements for 8 of 16 chambers. The 8 chambers that failed exhibited peeling of electrodes due to processing errors. More robust fabrication processes are being explored to improve yield. IDTs: The field of microscale acoustofluidics is extremely useful for numerous bioanalytical applications involved with studying swimming cells including bacteria. To that end, an experiment was performed using acoustic focusing devices that produce standing surface acoustic waves (SSAWs) excited in a piezoelectric substrate by micropatterned interdigital transducers (IDTs). These waves were used to trap bacterial cells at nodes and antinodes of the SSAWs, creating visible patterns. Experiments proved that 2 µm average diameter swimming cells can be successfully patterned with a 24.1-MHz actuation frequency. y of microbes performing extracellular electron uptake (EEU) has multiple uses for biotechnological applications. To that end, a high-throughput platform comprising an array of bioelectrochemical cells (essentially small chambers for electrochemical analysis of biological cells) is necessary to provide the opportunity for proper study of microbes performing EEU. Utilizing traditional cleanroom microfabrication techniques (photolithography, metallization, and lift-off), a 16-chamber micro bio-electrochemical cell (µ-BEC) array was fabricated. Each cell utilized a 3-electrode system, achieving successful electrochemical measurements for 8 of 16 chambers. The 8 chambers that failed exhibited peeling of electrodes due to processing errors. More robust fabrication processes are being explored to improve yield. IDTs: The field of microscale acoustofluidics is extremely useful for numerous bioanalytical applications involved with studying swimming cells including bacteria. To that end, an experiment was performed using acoustic focusing devices that produce standing surface acoustic waves (SSAWs) excited in a piezoelectric substrate by micropatterned interdigital transducers (IDTs). These waves were used to trap bacterial cells at nodes and antinodes of the SSAWs, creating visible patterns. Experiments proved that 2 µm average diameter swimming cells can be successfully patterned with a 24.1-MHz actuation frequency

MEMS 411 - Self-Leveling Drone

1.1 The objective of this senior design project was to design and build an aerial drone with a landing gear system that would allow leveling and take off from a sloped terrain. The drone should be able to level on a slope with a maximum incline of 20 degrees and the leveling process should not exceed 30 seconds. In addition, the leveling system must be automatic and deployed using the flight controller