Development and Evaluation of Modeling Approaches for Extrusion-based Additive Manufacturing of Thermoplastics

This work focuses on evaluating different modeling approaches and model parameters for thermoplastic AM, with the goal of informing more efficient and effective modeling approaches. First, different modeling approaches were tested and compared to experiments. From this it was found that all three of the modeling approaches provide comparable results and provide similar results to experiments. Then one of the modeling approaches was tested on large scale geometries, and it was found that the model results matched experiments closely. Then the effect of different material properties was evaluated, this was done by performing a fractional factorial design of experiments where the factors were ±15% of the baseline material properties. From this it was found that coefficient of thermal expansion (CTE) is by far the most important material property for the simulated warpage. This test was repeated with a simulated desktop printer, simulated commercial printer and a simulated room scaled printer to evaluate if the relevant material properties change as a function of length scale; it was found that as length scale increases, conduction becomes increasingly important, but this effect was still small compared to that of CTE. Finally, the effect of the environment was evaluated by running a Latin hypercube Design of Experiments (DOE) over environmental factors; it was found that the most important effects are the bed and enclosure temperatures. It also pointed to the feasibility of using radiative heating to mitigate warpage, because as length scale increases natural convection becomes less important. This work is significant because it leverages modeling and simulation to evaluate the effects of the different phenomena in 3D printing and points out some of the gaps in the current state of the art that are not evident from performing simple experiments or simple simulations, namely implementing a model for build plate adhesion

Particle Separation Through Taylor-couette Flow And Dielectrophoretic Trapping

As the world population approaches seven billion, a greater strain is put on the resources necessary to sustain life. One of the most basic and essential resources is water and while two thirds of the earth is covered by water, the majority is either salt water (oceans and seas) or it is too contaminated to drink. The purpose of this project is to develop a portable device capable of testing whether a specific source of water (i.e. lake, river, well…) is potable. There are numerous filtration techniques that can remove contaminants and make even the dirtiest water clean enough for consumption but they are for the most part, very time consuming and immobile processes. The device is not a means of water purification but rather focuses on determining the content of the water and whether it is safe. Particles within the water are separated and trapped using a combination of a Taylor Couette fluid flow system and Dielectrophoretic electrodes. This paper explores Taylor Couette flow in a large gap and low aspect ratio system through theory and experimentation with early stage prototypes. Different inner cylinder radii, 2.12cm, 1.665cm and 1.075cm, were tested at different speeds approaching, at and passing the critical Taylor number, 3825, 4713 and 6923 respectively for each cylinder. Dielectrophoretic (DEP) electrodes were designed, fabricated, coated and tested using latex beads to determine the method of integrating them within the fluid flow system. Taylor Couette theory, in terms of the formation of vortices within the large gap, small aspect ratio system, was not validated during testing. The flow pattern generated was more akin to a chaotic circular Couette flow but still served to move the particles toward the outer wall. Fully integrated tests were run with limited success. Recommendations were made to pursue both circular Couette flow as the basis for iv particle separation and dimensional changes in the setup to allow for the formation of Taylor vortices by increasing the radius ratio but still allowing for a larger volume of fluid

Search for supersymmetry in final states containing two hadronically decaying taus with the ATLAS detector at √(s) = 8 and 13 TeV

In dieser Arbeit werden zwei Analysen vorgestellt die sich mit der Suche nach supersymmetrischen Teilchen in Proton-Proton Kollisionen auseinander setzen. Im Endzustand werden in beiden Analysen mindestens zwei hadronisch zerfallende Taus, sowie fehlende transversale Energie erwartet. Die genutzten Daten wurden mit dem ATLAS Detektor am LHC aufgenommen. Zwei Datensätze werden analysiert, der eine wurde bei einer Schwerpunktsenergie von 8 TeV im Jahr 2012 aufgezeichnet, der andere bei einer Schwerpunktsenergie von 13 TeV im Jahr 2015. Die erste Analyse nutzt den bei einer Schwerpunktsenergie von 8 TeV aufgezeichneten Datensatz. Er umfasst Daten entsprechend einer integrierten Luminosität von 20.3 fb−1. Gesucht wird nach supersymmetrischen Teilchen die über die elektroschwache Wechselwirkung produziert werden und anschließend in Endzustände mit mindestens zwei hadronisch zerfallenden Taus, fehlender transversaler Energie und wenig bis garkeine Jets zerfallen. Spezielles Augenmerk wird auf die Validierung des Di-Boson Untergrunds, die Kombination des Kanals in dem beide Taus hadronisch zerfallen mit dem in dem eines leptonisch zerfällt, sowie auf eine Abschätzung der Sensitivität der Analyse bei einer Schwerpunktsenergie von 13 TeV gelegt. Da, verglichen mit der Erwartung aus Abschätzungen aus dem Standard Modell, kein Überschuss an Ereignissen gefunden wurde, werden mithilfe der CLs-Methode neue Grenzen auf den untersuchten Prozess gesetzt. Modellunabhängig kann ein sichtbarer Wirkungsquerschnitt größer als 0.37 fb ausgeschlossen werden. Modellabhängige Ausschlussgrenzen werden für drei Szenarien des phänomenologisch motivierten minimalen supersymmetrischen Standardmodells (pMSSM), sowie zwei vereinfachte Modelle berechnet. In einem der vereinfachten Modelle werden Charginos in Paaren produziert und zerfallen über Staus oder Tau-Sneutrinos in Neutrinos, Taus und das leichteste Neutralino. Im anderen vereinfachten Modell wird ein Chargino zusammen mit dem nächstleichtesten Neutralino produziert und zerfällt, genau wie im anderen vereinfachten Modell, über Staus oder Tau-Sneutrinos in Neutrinos, Taus und das leichteste Neutralino. Eines der untersuchten pMSSM Szenarien ist so gewählt, dass vorwiegend Paare von Staus produziert werden die wiederum in Taus zerfallen. Die anderen beiden pMSSM Szenarien sind so ausgewählt, dass vorwiegend die drei zuvor genannten Prozesse miteinander konkurrieren, die Paarproduktion von Charginos, die assoziierte Produktion eines Charginos mit einem nächstleichtesten Neutralino, sowie die Paarproduktion von Staus. In einem der Modelle ist die Masse des Staus fix, im anderen wird sie auf die Hälfte der Summe der Massen des leichtesten Neutralinos und des leichtesten Charginos gesetzt. Betrachtet man die beiden Produktionskanäle der vereinfachten Modelle gemeinsam, so kann man chi_1^± / chi_1^0 Massen bis zu 410/140 GeV ausschliessen. Betrachtet man nur die Paarproduktion von Charginos, so kann man chi_1^± / chi_1^0 Massen bis zu 345/90 GeV ausschliessen. Im Fall des pMSSM Modells in dem vorwiegend Paare von Staus produziert werden ist die vorgestellte Analyse auf große Teile des Phasenraumes noch nicht sensitiv, da der Wirkungsquerschnitt fü r die Paarproduktion von Staus zu klein ist. In den verbleibenden beiden pMSSM Modellen können vergleichbare Ausschlussgrenzen auf die Masse des leichtesten Charginos gesetzt werden: ein Bereich von 100 GeV bis 350 GeV kann ausgeschlossen werden. Die zweite Analyse verwendet den bei einer Schwerpunktsenergie von 13 TeV im Jahr 2015 aufgezeichneten Datensatz. Er umfasst Daten entsprechend einer integrierten Luminosität von 3.2 fb−1. Es wird nach supersymmetrischen Teilchen gesucht, die über die starke Wechselwirkung produziert werden und in Endzustände zerfallen die sich durch mindestens zwei hadronisch zerfallende Taus, fehlende transversale Energie und, im Gegensatz zur ersten Analyse, Jets auszeichnen. Der Schwerpunkt der Analyse liegt dabei auf der Entwicklung einer Signalregion die speziell auf komprimierte Massenspektren sensitiv ist, sowie der Abschätzung des Untergrunds aus Multi-Jet Ereignissen. Verglichen mit einer Abschätzung aus dem Standard Modell konnte kein Überschuss an Ereignissen festgestellt werden. Deswegen werden Ausschlussgrenzen auf den untersuchten Prozess mithilfe der CLs-Methode berechnet. Modellunabhängig kann ein Wirkungsquerschnitt von 1.07 fb ausgeschlossen werden. Modellabhängige Ausschlussgrenzen werden für ein vereinfachtes Modell, sowie ein gauge-mediated-symmetrybreaking, GMSB, Modell berechnet. Im vereinfachten Modell werden Gluinos in Paaren produziert und zerfallen danach asymmetrisch über ein leichtestes Chargino und ein nächstleichtestes Neutralino. Diese zerfallen wiederum über Staus und ihre Sneutrinos in Endzustände die Neutralinos, Jets, Taus und Netrinos enthalten. Im GMSB Modell werden außerdem Squarks in Paaren produziert und zerfallen via Neutralinos und Staus oder Sleptonen in Endzustände die sich durch Quarks und bis zu vier Taus auszeichnen. Weitere Prozesse sind im GMSB Modell möglich, aber der Wirkungsquerschnitt ist für diese vernachlässigbar. Gluino Massen bis zu 1550 GeV können im vereinfachten Modell ausgeschlossen werden, während Massen des leichtesten Neutralinos bis zu 750 GeV ausgeschlossen werden können. Für das GMSB Modell können sogar Gluino Massen bis 2.2 TeV ausgeschlossen werden für große Werte von tan beta, während für kleinere Werte immerhin noch Gluino Massen bis 2.0 TeV ausgeschlossen werden können.Two analyses will be presented searching for the production of supersymmetric particles decaying into final states containing at least two hadronically decaying taus and missing transverse energy in proton-proton collisions. The collisions were recorded by the ATLAS experiment at the LHC. Two different datasets are analyzed, one recorded at a center-of-mass energy of 8 TeV in 2012 and one recorded at a center-of-mass energy of 13 TeV in 2015. The first analysis is performed using data collected at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 20.3 fb−1. The electroweak production of supersymmetric particles which decay into final states containing at least two hadronically decaying taus, missing transverse energy, as well as few to no jets, is studied. Particular attention is paid to the validation of the diboson background, the combination with the channel where one of the two taus decays hadronically and the other one leptonically, as well as the estimate of the sensitivity of the analysis at sqrt(s) = 13 TeV. No excess over the Standard Model expectation is found, thus limits are set using the CLs method. Model independent limits on the cross section are computed, the observed upper limit on the visible cross section is 0.37 fb. Model dependent limits are computed for three different pMSSM scenarios as well as two simplified models. One of the simplified models is characterized by chargino pair production, decaying via intermediate staus or tau sneutrinos into neutrinos, taus and the lightest neutralino. The other simplified model is characterized by the associated production of a lightest chargino and a next-to-lightest neutralino, also decaying via intermediate staus into taus, neutrinos and the lightest neutralino. The parameters of one of the pMSSM models are chosen such that the dominant process is the direct pair production of staus decaying into taus. The parameters of the other two pMSSM models are chosen such that the three processes compete. For one of the pMSSM models the stau mass is chosen to be fixed, while for the other it is chosen to be halfway between the chi_1^± and chi_1^0 mass. In the case of simultaneous chi_1^±chi_1^± and chi_1^±chi_1^0 production, chi_1^± / chi_1^0 masses of up to 410/140 GeV and in the case of chi_1^± pair production alone, chi_1^± / chi_1^0 masses of up to 345/90 GeV can be excluded. The presented analysis is not yet sensitive to large parts of the phase-space of the pMSSM model targeting direct-stau pair production, because the cross section is too small. In the other two pMSSM parameter planes, similar lightest chargino mass ranges can be excluded, namely approximately 100 GeV − 350 GeV. The second analysis makes uses of data collected throughout 2015 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 3.2 fb−1. The strong production of supersymmetric particles is studied which decay into final states containing at least two hadronically decaying taus, missing transverse energy, as well as jets. The focus of the analysis is on the development of the signal region targeting low mass-splittings and the estimate of the multi-jet contribution to the signal, as well as control regions. Again, no excess over the Standard Model expectation is found and thus limits are set using the CLs method. The obtained model independent observed upper limit on the visible cross section is 1.07 fb. Model dependent limits are interpreted in two models: a simplified model of gluino pair production, subsequently decaying asymmetrically via a lightest chargino and a next-to-lightest neutralino which decay via staus or tau sneutrinos into final states containing lightest neutralinos, jets, taus as well as tau neutrinos; and a gauge-mediated-symmetry-breaking, GMSB, model where, in addition to the previous process, squarks are produced in pairs and decay via intermediate neutralinos and staus/sleptons into a pair of quarks and up to four taus. Other processes are possible as well in the GMSB modell, but they are sub-dominant for most of the studied phase-space. In the first model gluino masses up to 1550 GeV can be excluded while masses of the lightest neutralino up to 750 GeV can be excluded. In case of the GMSB model gluino masses up to 2.2 TeV can be excluded for large values of tan beta, while for lower values only gluino masses up to 2.0 TeV can be excluded

Initial test results on bolometers for the Planck high frequency instrument

We summarize the fabrication, flight qualification, and dark performance of bolometers completed at the Jet Propulsion Laboratory for the High Frequency Instrument (HFI) of the joint ESA/NASA Herschel/Planck mission to be launched in 2009. The HFI is a multicolor focal plane which consists of 52 bolometers operated at 100 mK. Each bolometer is mounted to a feedhorn-filter assembly which defines one of six frequency bands centered between 100-857 GHz. Four detectors in each of five bands from 143-857 GHz are coupled to both linear polarizations and thus measure the total intensity. In addition, eight detectors in each of four bands (100, 143, 217, and 353 GHz) couple only to a single linear polarization and thus provide measurements of the Stokes parameters, Q and U, as well as the total intensity. The measured noise equivalent power (NEP) of all detectors is at or below the background limit for the telescope and time constants are a few ms, short enough to resolve point sources as the 5 to 9 arc min beams move across the sky at 1 rpm

Shapeshifters and shamans: Topologies of multilingualism

This paper is a radical break with a view of multilingualism as an arrangement or hierarchy of different languages which produces more or less visibility for these named varieties. Rather, it takes as its starting point a view of multilingualism as situated within a matrix of social relations, constituted in different times and spaces, between people carrying different histories, attitudes, and feelings. In an attempt to find new ways of representing these social rationalities, we argue for a topological view of multilingualism. This perspective draws attention to the ways in which the diverse facets of multilingualism interconnect and relate in different time-spaces. Our data draw on four artistic visualisations of multilingualism produced by students on a course which sought to explore new ways of re-imagining multilingualism. The posters and artefacts produced on this course stimulated our view of multilingualism as a networked, fluid and mobile typology, or as an n-dimensional form which shifts and changes as it rotates through time and space. We then link this conception to our discussion of Linguistic Citizenship as an n-dimensional topological phenomenon

Project proposal for Mellon Supra-Institutional project on the decolonial turn (unsettling paradigms) – 2018.

This is a proposal text submitted to the Mellon Foundation entitled "Languages and Literacies in Higher Education: Reclaiming voices from the south", to secure funding for the module

From aptamer-based biomarker discovery to diagnostic and clinical applications: an aptamer-based, streamlined multiplex proteomic assay

Recently, we reported an aptamer-based, highly multiplexed assay for the purpose of biomarker identification. To enable seamless transition from highly multiplexed biomarker discovery assays to a format suitable and convenient for diagnostic and life-science applications, we developed a streamlined, plate-based version of the assay. The plate-based version of the assay is robust, sensitive (sub-picomolar), rapid, can be highly multiplexed (upwards of 60 analytes), and fully automated. We demonstrate that quantification by microarray-based hybridization, Luminex bead-based methods, and qPCR are each compatible with our platform, further expanding the breadth of proteomic applications for a wide user community

Lattice Gauge Fixing and the Violation of Spectral Positivity

Spectral positivity is known to be violated by some forms of lattice gauge fixing. The most notable example is lattice Landau gauge, where the effective gluon mass is observed to rise rather than fall with increasing distance. We trace this violation to the use of quenched auxiliary fields in the lattice gauge fixing process, and show that violation of spectral positivity is a general feature of quenching. We illustrate this with a simple quenched mass-mixing model in continuum field theory, and with a quenched form of the Ising model. For lattice gauge fixing associated with Abelian projection and lattice Landau gauge, we show that spectral positivity is violated by processes similar to those found in quenched QCD. For covariant gauges parametrized by a gauge-fixing parameter $\alpha$, the SU(2) gluon propagator is well described by a simple quenched mass-mixing formula. The gluon mass parameter appears to be independent of $\alpha$ for sufficiently large $\alpha$.Comment: 8 pages, 6 eps figures, RevTeX4; shortene