Using PlanetLab for network research: Myths, realities, and best practices

PlanetLab is a research testbed that supports 428 experiments on 276 sites, with 583 nodes in 30 countries. It has lowered the barrier to distributed experimentation in network measurement, peer-to-peer networks, content distribution

Cusp Volumes of Alternating Knots on Surfaces

We study the geometry of hyperbolic knots that admit alternating projections on embedded surfaces in closed 3-manifolds. We show that, under mild hypothesis, their cusp area admits two sided bounds in terms of the twist number of the alternating projection and the genus of the projection surface. As a result, we derive diagrammatic estimates of slope lengths and give applications to Dehn surgery. These generalize results of Lackenby and Purcell about alternating knots in the 3-sphere. Using a result of Kalfagianni and Purcell, we point out that alternating knots on surfaces of higher genus, can have arbitrarily small cusp density, in contrast to alternating knots on spheres whose cusp densities are bounded away from zero due to Lackenby and Purcell.Comment: 48 pages, 16 figures; Typo of $\chi(F)<0$ fixed to $\chi(F)\le 0$ in main theore

SILICON ON INSULATOR BIPOLAR JUNCTION TRANSISTORS FOR FLEXIBLE MICROWAVE APPLICATIONS

Microwave frequency flexible electronic devices require a high quality semiconducting material and a set of fabrication techniques that are compatible with device integration onto flexible polymer substrates. Over the past ten years, monocrystalline silicon nanomembranes (SiNMs) have been studied as a flexible semiconducting material that is compatible with industrial Si processing. Fabricated from commercial silicon on insulator (SOI) wafers, SiNMs can be transferred to flexible substrates using a variety of techniques. Due to their high carrier mobilities, SiNMs are a promising candidate for flexible microwave frequency devices. This dissertation presents fabrication techniques for flexible SiNM devices in general, as well as the progress made towards the development of a microwave frequency SiNM bipolar junction transistor (BJT). In order to overcome previous limitations associated with adhesion, novel methods for transfer printing of metal films and SiNMs are presented. These techniques enable transfer printing of a range of metal films and improve the alignment of small transfer printed SiNM devices. Work towards the development of a microwave frequency BJT on SOI for SiNM devices is also described. Utilizing a self-aligned polysilicon sidewall spacer technique, a BJT with an ultra-narrow base region is fabricated and tested. Two regimes of operation are identified and characterized under DC conditions. At low base currents, devices exhibited forward current gain as high as &#946;F = 900. At higher base current values, a transconductance of 59 mS was observed. Microwave scattering parameters were obtained for the BJTs under both biasing conditions and compared to unbiased measurements. Microwave frequency gain was not observed. Instead, bias-dependent non-reciprocal behavior was observed and examined. Limitations associated with the microwave impedance-matched electrode configuration are presented. High current densities in the narrow electrodes cause localized heating, which leads to electrode material damage and ultimately dopant diffusion in the BJT. Finally, device design improvements are proposed to address the problem of localized heating and increase device lifetime under testing conditions. High values for DC current gain suggest that future modifications should improve microwave frequency performance and measurement reproducibility

Diagrammatic and Geometric Invariants of Hyperbolic Weakly Generalized Alternating Knots

We study the relationship between knot and link diagrams on surfaces and their invariants coming from hyperbolic geometry. A \indef{link diagram on a surface}, denoted $\pi(L)\subset F$, is a way of projecting a link $L$ in some manifold $M$ onto some surface $F\subset M$. This generalizes the notion of a link diagram, and has been studied with a variety of conditions. We will work with the weakly generalized alternating knots and links of Howie and Purcell, which gives certain criteria to ensure the diagram is interesting. A cusp of a hyperbolic knot $K$ is a neighborhood of $K$ in $M\setminus K$, and the cusp volume is the Euclidean volume of a maximal cusp. We show that the cusp volume of a weakly generalized alternating knot, with some additional conditions, is bounded both above and below based on the twist number of $\pi(K)$ and $\chi(F)$. This is done by constructing a new essential surface for $K$ that has nice properties, including having Euler characteristic based on the twist number as opposed to the crossing number. Our bound on cusp volume leads to interesting bounds on other geometric properties of $K$, including slope length and volumes of Dehn surgery. The volume}of a hyperbolic link $L$ in a manifold $M$ is the hyperbolic volume of the complement $M\setminus L$. We can show that volume is also bounded below by the twist number of $\pi(L)$ and $\chi(F)$. We do this by generalizing the Jones polynomial to weakly generalized alternating links, and showing that there is a relation between this polynomial and the twist number, and this polynomial and the volume. Through the course of proving this bound, we also get relations between the guts of the checkerboard surfaces of $L$ and this generalized Jones polynomial. In addition, if we are working inside a thickened surface, the twist number becomes an isotopy invariant of $L$.Thesis (Ph.D.)--Michigan State University. Mathematics - Doctor of Philosophy, 2021Includes bibliographical reference

As normas constitucionais fundamentais e suas aplicações à atividade tributária

O presente trabalho de conclusão de curso possui o objetivo de analisar as normas constitucionais basilares, quais sejam, as que estabelecem os princípios fundamentais, os direitos e garantias fundamentais, a organização do Estado e a organização dos Poderes, a fim de determinar quais possuem aplicação, ainda que indireta, na atividade tributária. Como metodologia foi adotada a revisão de literatura de obras jurídicas de Direito Constitucional majoritariamente. Ao término do presente texto, vislumbrou-se como resultado que existem inúmeras normas constitucionais não inseridas no capítulo do Sistema Tributário Nacional que possuem aplicação direta ou indireta à atividade tributária, por vezes atuando de maneira independente, ou em outras de maneira complementar ao contido no referido capítulo. Nesse sentido, conclui-se que o operador da legislação tributária deve, no âmbito de seu exercício profissional, se atentar à Constituição Federal de 1988 como um todo, aplicando os mais variados institutos e princípios à fim de auxiliar no desenvolvimento de um trabalho de excelência

Coaches’ thinking process: Analysis of decisions related to tactics during sports games

peer reviewedA three-step model of coaches’ tactical thinking process is proposed: pre-interactive, interactive and post-interactive decisions. This study focuses on the interactive decisions. Its first objective was to verify if a coach is able to report these decisions at the end of a game. The second objective was to analyse the goals and factors inducing the decisions. Data were collected during and after four games directed by two coaches, one in basketball, and the other in volleyball. Their teams participated in the second division of the Belgian national championship (1998-1999). The research method was similar to that developed by Gilbert, Trudel, and Haughian (1999). Coaches reported a limited number (1 to 9) of tactical decisions immediately after each game. Decisions reported by the coaches and additional decisions selected by researchers from videotapes of the games were used for stimulated recall interviews. A total of 82 decisions were analysed with the basketball coach and 88 with the volleyball coach. Data analysis was considered separately for each coach. Calling time out, player substitutions, and tactical cues were the most frequently analysed decisions. Adapting the team strategy and providing information or directives were the priority goals of the decisions. Most of the decisions were determined by subjective field information