Parallel hydraulic pressure assist/work circuit hybrids for automated side loader refuse vehicles

2012 Summer.Includes bibliographical references.Hydraulic hybrids have been a subject of study for some time now and the application of these hybrids to refuse vehicles has been thoroughly explored. There is a lesser known subset of these which are known as pressure assist or work circuit hybrids that have unique potential to the field. Work circuit hybrids operate similar to a parallel hydraulic hybrid in that energy is captured and stored during regenerative braking. These hybrids differ in that the energy is then used to operate the hydraulic cylinders that handle and compact the refuse rather than reaccelerating the vehicle. Work circuit hybrids can be applied to many types of vehicles but the refuse vehicle application is the focus of this study. It was known prior to this study that work circuit hybrids are a potential solution to improve the fuel economy of refuse vehicles. However, prior to this study, the design of a work circuit hybrid had not been outlined in the literature. It was the goal of this thesis to answer the following questions. What are the fuel economy and cost characteristics of an optimized work circuit hybrid, and can an advanced hydraulic work circuit design justify further development towards productization? To answer these questions the study began by exploring, at a high level, the feasibility of work circuit hybrids on refuse vehicles. Then, two automated side loader, 28 cubic yard (21.4 m3), McNeilus Street Force MA refuse vehicles that operate on residential routes throughout Denver's surrounding areas were instrumented to produce drive cycle and hydraulic duty cycle data. This data was used to understand vehicle operation and to validate a reverse facing dynamic model of the stock refuse vehicle. A hybrid model was then produces and used in conjunction with a non-linear optimization algorithm to determine the potential benefit of this technology. This study concluded that a work circuit hybrid providing energy to the arm of a side loader refuse vehicle could achieve a 2.3% reduction in fuel consumption with a 4 year payback period using optimally sized hybrid components. The fuel usage reduction for these hybrids is limited to how well the available energy from regenerative braking is matched with the energy required by the work circuit. For this study, only 16% of the braking energy was utilized due to the selection of vehicle and hydraulic circuit. Work circuit hybrids also enable the use of an idle stop control logic, creating a unique opportunity to combine these two technologies yielding a fuel savings of 21.6% for the same vehicle. There are still some challenges to overcome before this technology can be truly understood. One such challenge is the fact that these hybrids require control of the torque converter lock up clutch and the transmission shifting strategy to make an engine driven configuration feasible. Implementing idle stop may also have hidden challenges including energy losses and emissions issues. However, it is the conclusion of this study that work circuit hybrids do offer a unique set of desired characteristics that warrant further development for future use in the field

Some Aspects of Medieval Historic Town Management Tradition in the Book of Aksum

Short Communication: Some Aspects of Medieval Historic Town Management Tradition in the Book of Aksu

“Undoing” Gender: how the School of Science, Engineering and Information Technology (SEIT) Women’s Group works across university and community lines to promote inclusive STEMM.

Research on gender and education in industrialised and developing countries suggests that schools and universities are sites of ‘doing’ rather than ‘undoing’ gender. Deutsch (2007) contends that ‘doing gender’ refers to social interactions that reproduce conventional and limiting notions of gender construction and that ‘undoing gender’ refers to social interactions that reduce gender difference and open up other possibilities. In this paper we consider how educational institutions can be strategic sites of influence in undoing gender and we investigate some ways that gender is ‘undone’ through the example of the work of the Science, Engineering and Information Technology Women’s Group (SEITWG) located in the Faculty of Science and Technology at Federation University Australia. For this purpose, a self-study methodology understood as a professional reflection was used. The paper explores how the informal coalition of SEITWG works as ‘wilful subjects’, on the one hand, coming up against some of the ‘brick walls’ of dominant discourse that attempt to limit women’s participation in STEMM (science, technology, engineering, mathematics, and medicine). On the other hand, SEITWG attempts to move beyond the restrictions of conventional gender narratives to encourage more women to participate in STEMM by foregrounding the presence of women already active in the area; mentoring women students and staff; supporting a range of their colleagues’ endeavours to research and teach for inclusion; embedding gender analysis into the curriculum; and promoting workplace cultural change

Isogeometric analysis: an overview and computer implementation aspects

Isogeometric analysis (IGA) represents a recently developed technology in computational mechanics that offers the possibility of integrating methods for analysis and Computer Aided Design (CAD) into a single, unified process. The implications to practical engineering design scenarios are profound, since the time taken from design to analysis is greatly reduced, leading to dramatic gains in efficiency. The tight coupling of CAD and analysis within IGA requires knowledge from both fields and it is one of the goals of the present paper to outline much of the commonly used notation. In this manuscript, through a clear and simple Matlab implementation, we present an introduction to IGA applied to the Finite Element (FE) method and related computer implementation aspects. Furthermore, implemen- tation of the extended IGA which incorporates enrichment functions through the partition of unity method (PUM) is also presented, where several examples for both two-dimensional and three-dimensional fracture are illustrated. The open source Matlab code which accompanies the present paper can be applied to one, two and three-dimensional problems for linear elasticity, linear elastic fracture mechanics, structural mechanics (beams/plates/shells including large displacements and rotations) and Poisson problems with or without enrichment. The Bezier extraction concept that allows FE analysis to be performed efficiently on T-spline geometries is also incorporated. The article includes a summary of recent trends and developments within the field of IGA

Isogeometrische Analyse von Schalen

This work is concerned with the isogeometric analysis of shells. A new hierarchic family of NURBS-based shell finite elements is developed. Besides a shear-rigid 3-parameter shell element formulation with Kirchhoff-Love kinematics, both a shear flexible 5-parameter Reissner-Mindlin-type and a 7-parameter 3D shell element which accounts for thickness change are derived. Compared to existing isogeometric shell elements the hierarchy showing up in the shell mechanics is transferred to the parameterization of the kinematic shell equations by gradually enhancing the minimalistic 3-parameter shell model with additional degrees of freedom in order to systematically increase the approximation quality of the shell formulation. This represents the key innovation of this thesis with significant benefits both with regard to finite element technology and model adaptivity. The continuity requirements on the displacement functions for the proposed hierarchic shell models are C1, which can be naturally satisfied with the applied higher-continuity NURBS discretizations. All shell models of the hierarchy utilize a pure displacement ansatz. Due to the concept of a hierarchic parameterization both transverse shear locking and curvature thickness locking are avoided by default for the Reissner-Mindlin-type and the 3D shell formulations. In order to remove membrane locking two new strategies for higher-order and higher-continuity discretizations – a NURBS-based Discrete Strain Gap method and a mixed displacement-stress formulation – are developed and applied to the in-plane part of the isogeometric shell finite elements, which ultimately lead to isogeometric shell element formulations that are completely free from geometric locking.Die vorliegende Arbeit befasst sich mit der Entwicklung einer hierarchischen Familie von Schalenmodellen und deren Diskretisierung basierend auf NURBS (Non-Uniform Rational B-Splines) Funktionen für die numerische Analyse von Schalenstrukturen. Als mechanisches Basismodell wird eine mittelflächenparametrisierte 3-Parameter-Formulierung mit Kirchhoff-Lovescher Schalenkinematik verwendet. Für das in dieser Arbeit entwickelte Schalenmodell mit Reissner-Mindlin-Kinematik, werden die Annahmen der Kirchhoff-Loveschen Schalenkinematik durch Einführen zusätzlicher, von den Verschiebungsableitungen unabhängigen Parametern erweitert. Für die Berücksichtigung der Dickenänderung der Schale wird in dieser Arbeit zudem ein 7-Parameter-Schalenmodell entwickelt, welches einer Erweiterung des Reissner-Mindlin-Modells mit fünf Parametern entspricht. Die wesentliche Neuerung und Innovation in dieser Arbeit ist die hierarchische Parametrisierung der Familie von 3-, 5- und 7-Parameter-Schalenmodellen, welche signifikante Vorteile im Hinblick auf Modelladaptivität und Elementtechnologie mit sich bringt. Mit Blick auf das diskretisierte Modell führt die hierarchische Parametrisierung dazu, dass Reissner-Mindlin-Schalenelemente bereits bei einer reinen Verschiebungsformulierung durch die Entkopplung von Biege- und Schubdeformationen kein Querschublocking aufweisen. Die hierarchische 7-Parameter-Formulierung stellt eine Erweiterung der hierarchischen 5-Parameter-Variante dar, bei der bei einer reinen Verschiebungsformulierung neben Querschublocking auch Krümmungs-Dicken-Locking automatisch vermieden wird. Alle hierarchischen Varianten müssen die Anforderungen der schubstarren Kirchhoff-Love-Schale erfüllen, welches das Basismodell der hierarchischen Formulierungen ist. Ansatzfunktionen mit C1-Kontinuität lassen sich mit den in dieser Arbeit verwendeten höher-kontinuierlichen NURBS Funktionen definieren. Zur Vermeidung von Membranlocking werden zudem zwei neue Methoden - eine NURBS basierte Discrete-Strain-Gap Methode und ein gemischte Spannungs-Verschiebungs Formulierung entwickelt- welche zu isogeometrischen Finite-Elemente Formulierungen führen, die komplett frei von geometrischen Lockingeffekten sind