Inclusion of Geometrically Nonlinear Aeroelastic Effects into Gradient-Based Aircraft Optimization

While aircraft have largely featured flexible wings for decades, more recently, aircraft structures have rapidly become more flexible. The pursuit of longer ranges and higher efficiency through higher aspect ratio wings, as well as the introduction of modern, light-weight materials has yielded moderately and very flexible aircraft configurations. Past accidents, such as the loss of the Helios High Altitude Long Endurance (HALE) aircraft have highlighted the limitations of linear analysis methods and demonstrated the peril of neglecting nonlinear effects when designing such aircraft. In particular, accounting for geometrical nonlinearities in flutter analyses become necessary in aircraft optimization, including transport aircraft, or future aircraft may require costly modifications late in the design process to fulfill certification requirements. As a result, there is a need to account for geometrical nonlinearities earlier in the design process and integrate these analyses directly into the multi-disciplinary design optimization (MDO) problems. This thesis investigates geometrically nonlinear flutter problems and how these should be integrated into aircraft MDO problems. First, flutter problems with and without geometrical nonlinearities are discussed and a unifying interpretation is presented. Furthermore, methods for interpreting nonlinear flutter problems are proposed and differences between linear and nonlinear flutter problem interpretation are discussed. Next, a flutter constraint formulation which accounts for geometrically nonlinear effects using beam-based analyses is presented. The resulting constraint uses a Kreisselmeiser-Steinhauser aggregation function to yield a scalar constraint from flight envelope flutter damping values. While the constraint enforces feasibility over the entire flight envelope, how the flight envelope is sampled largely determines the flutter constraint’s accuracy. To this end, a constrained Maximin approach, which is applicable for non-hypercube spaces, is used to sample the flight envelope and obtain a low-discrepancy sample set. The flutter constraint is then implemented using a beam-based geometrically nonlinear aeroelastic simulation code, UM/NAST. As gradient-based optimization methods are used in MDO due to the large number of design variables in aircraft design problems, the flutter constraint requires the recovery of flutter damping sensitivities. These are obtained by applying algorithmic differentiation (AD) to the UM/NAST code base. This enables the recovery of gradients for any solution type (static, modal, dynamic, and flutter/stability) with respect to any local design variable available within UM/NAST. The performance of the gradient prediction is studied and a hybrid primal-AD scheme is developed to obtain the coupled nonlinear aeroelastic sensitivities. After verifying the accuracy and performance of the gradient evaluation, the flutter constraint was implemented in a sample optimization problem. Finally, a roadmap for including the beam-based flutter constraint within an aircraft design problem is presented using analyses of varying fidelity. To this end, analyses of appropriate fidelity are used depending on the output of interest. While a shell-based FEM model can recover stress distributions, and is therefore well-suited for strength constraints, they are ill-suited for geometrically nonlinear flutter constraints due to their computational cost. Analyses are presented for a high aspect ratio transport aircraft configuration to illustrate the proposed approach and highlight the necessity for the inclusion of a geometrically nonlinear flutter constraint.PHDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/163259/1/clupp_1.pd

Linkage of Arctic atmospheric circulation and Siberian shelf hydrography: a proxy validation using δ18O records of bivalve shells

High resolution oxygen isotope profiles of aragonitic bivalve shells (Astarte borealis) collected alive in different years are used to trace hydrographical changes on the Laptev Sea shelf, which are mainly forced by changes in riverine freshwater discharge and arctic atmospheric circulation patterns. By merging individual isotope profiles, a high resolution time series of relative changes in bivalve δ18O is obtained for the eastern Laptev Sea for the period 1969 to 1998. The resulting pattern in the δ18O time series reflects seasonal bottom-water salinity changes in the Laptev Sea, which is dominated by the peak input of freshwater discharged by the Lena River onto the Laptev Sea shelf during summer. The relative changes in summer bottom-water salinity, deduced from the δ18O values in the bivalves and the discharge anomaly of the Lena River, show a significant negative correlation. It is therefore suggested that the annual and subdecadal variations of the riverine freshwater and its influence on the shelf hydrography are imprinted in the bivalve shells. Moreover, we note that extreme summer precipitation anomalies in the Lena River catchment area affect the river discharge characteristics, events which are detectable in the δ18O time series. This all implies that δ18O records of bivalve shells have the potential to build long-term records of atmospheric-forced changes in arctic circulation

Mapping Data to Ontologies with Exceptions Using Answer Set Programming

In ontology-based data access (OBDA), databases are connected to an ontology via mappings from queries over the database to queries over the ontology. In this paper, we define an ASP-based semantics for mappings from relational databases to first-order ontologies, augmented with queries over the ontology in the mapping rule bodies. The resulting formalism can be described as ”ASP modulo theories”, and can be used to express constraints and exceptions in OBDA systems, as well as being a powerful mechanism for succinctly representing OBDA mappings. Furthermore, we show that brave reasoning in this setting has either the same data complexity as ASP, or is at least as hard as the complexity of checking entailment for the ontology queries. Moreover, despite the interaction of ASP rules and the ontology, most properties of ASP are preserved. Finally, we show that for ontologies with UCQ-rewritable queries there exists a natural reduction from our framework to ASP with existential variables

A Streamlined Synthesis of Androstadiene C-17 Ester Derivatives

The development of a fully telescoped synthesis of a derivative of androstadiene C-17 esters made from epoxyparamethasone was demonstrated. This streamlining allowed for the elimination of isolation and solvent change after each synthetic step. Thus it not only drastically reduced the solvent waste, but also minimized the potential exposure to highly active intermediates thereby increasing the overall yield. The intuitively obvious advantage inherent to lowering the number of solvents was illustrated by applying standard green metrics

The New Organic: It's Time for a National "Green" Certification Program

Article published in the Michigan State University School of Law Student Scholarship Collection

Der Mensch an der Leine

Die Gründe, warum Menschen die Hundeschule Blohm besuchen, lassen sich auf folgende zusammenfassen: Die Hundeführer wählen eine Hundeschule in erster Linie nach ihrem Standort und den Ausbildungsmethoden. Diejenigen, die nach der Grund-ausbildung dieser Schule erhalten bleiben, haben neben einem ausgeprägten Ehrgeiz und Sportssinn auch Freunde auf diesem Abrichteplatz gefunden. Zusammenhalt, Rücksichtnahme und gegenseitige Hilfestellungen sind stark verbreitete Verhaltensweisen in den fortgeschrittenen Kursen. Aber auch das Entgegenkommen des Hundeschulleiters, ab einer gewissen Prüfungsstufe den Unterricht kostenlos anzubieten, ist ein Grund mit dem Hund immer weiter zu trainieren und sich in seiner Freizeit auf dem Hundeplatz einzubringen. Der Hundeschulleiter nimmt eine besondere Stellung auf seinem Abrich-teplatz ein. Er ist zugleich oberster „Führer“, respektierter Hundeprofi, väter-licher Ansprechpartner und humorvoller Unterhalter. Er achtet in militärischer Art auf Disziplin und die Einhaltung gewisser Regeln. In diesem Zusammenhang entwickelten sich zahlreiche Rituale in der Hundeschule, die alle in erster Linie einem zugute kommen – dem Hund. Diese Bräuche werden an neue Hundeführer weitergegeben und deren Anpassung wird verlangt und kontrolliert. Weitere Regeln werden durch den Dachverband ÖKV aufgestellt, die sich hauptsächlich auf Prüfungsveranstaltungen beziehen. Da aber diese Ver-ordnungen genaue Angaben zum Vorzeigen der Leistungen enthalten, richten sich die Kursabläufe nach diesen Vorschriften. Unterschiedliche Hundeführer-Typen gibt es in den verschiedenen Kursstufen. Nur die ehrgeizigsten, diszipliniertesten und „härtesten“ schaffen es in den Fortgeschrittenenkurs, in dem die Teilnehmer zu einer Familie werden