An optimization method for nacelle design

A multi-objective optimiZation method is demonstrated using an evolutionary genetic algorithm. The applicability of this method to preliminary nacelle design is demonstrated by coupling it with a response surface model of a wide range of nacelle designs. These designs were modelled using computational fluid dynamics and a Kriging interpolation was carried out on the results. The NSGA-II algorithm was tested and verified on established multi-dimensional problems. Optimisation on the nacelle model provided 3-dimensional Pareto surfaces of optimal designs at both cruise and off-design conditions. In setting up this methodology several adaptations to the basic NSGA-II algorithm were tested including constraint handling, weighted objective functions and initial sample size. The influence of these operators is demonstrated in terms of the hyper volume of the determined Pareto set

Lead and Zinc: The Gold of World War II and Picher, Oklahoma May 1st, 1942 to June 30th, 1947

Yesterday, Dec. 7, 1941 - a date which will live in infamy - the United States of America was suddenly and deliberately attacked by naval and air forces of the Empire of Japan. This was a quote from Franklin Roosevelt, one of the most recognized presidents of the United States, and it was the starting point of the events which would proceed after this day. Because of this event, the U.S. found the need to get involved in the midst of one of the bloodiest conflicts in modern day history. America and the world were brought together in the common cause of stopping Japan and Germany from all out domination of the world. But looking much deeper, the situation that the U.S. itself in was about so much more than the war; the war was one of the reasons that the American economy came from the depths of the Great Depression that dominated the 1930s. From the war, there was a rise in the economy as a total ware mobilization

Unsettling Colonial Relations in Experiential Education: Maya Ixil Perspectives on Decolonizing International Service Learning

International Service Learning (ISL) is a relatively young field of education research. Designed to be short-term experiential education programs, the traditional ISL curriculum harnesses direct interaction and cross- or inter-cultural exchanges between the Global North and Global South to provide opportunities for reflection and learning to occur. The field has focused on the impact of such programs for the Global North participants, primarily students, who participate. The existing literature highlights the benefits of this engaged form of learning citing academic, political, and moral growth. There are few studies that are critical of this approach to experiential education and fewer still that examine the impact of ISL on Global South host communities that receive these visitors. It is also the case that in the last decades the growth of ethical tourism has impacted educational programs such as ISL and, for host communities, the perceivable differences and impact are negligible. This study focuses on the community experience of ISL, narrowing the focus of the inquiry on one community in Guatemala that is home of the Maya Ixil people. The research design incorporates a theoretical framework that seeks to confront the colonial history that is deeply embedded in the practice of ISL and provide a lens through which to examine the transnational encounters that take place between people as Global North participants cross borders and bring with them historical and political identities in their visiting of Indigenous communities. For this reason this study also incorporates values and ideas from an Indigenous approach to research that emerged as the research team built relationships with the Ixil community. Over the course of four years several data gathering trips were made to the city of Nebaj, Guatemala where interviews and focus groups informed the bulk of the data. An important validation and feedback event that was called the Encuentro (gathering), took place in August 2017 and is a centerpiece of the research design and of this study. Recommendations were formed during this event, meant to be shared with host communities across Guatemala and Central America. The purpose of this study is to examine the impact of ISL on the Maya Ixil and tell the story of research that revealed the importance of identifying the colonial relations that have upheld both research practices in the Global South as well as the practice of ISL. The findings reveal that the impact of ISL on the Ixil community is misunderstood by Global North advocates and stakeholders. The necessity of unsettling colonial relations is recommended as an important step forward for the practice of ISL that seeks to facilitate experiential education in a good way

Surrogate model of complex non-linear data for preliminary nacelle design

Most response surface methods typically work on isotropically sampled data to predict a single variable and fitted with the aim of minimizing overall error. This study develops a metamodel for application in preliminary design of aircraft engine nacelles which is fitted to full-factorial data on two of the eight independent variables, and a Latin hypercube sampling on the other six. The specific set of accuracy requirements for the key nacelle aerodynamic performance metrics demand faithful reproduction of parts of the data to allow accurate prediction of gradients of the dependent variable, but permit less accuracy on other parts. The model is used to predict not just the independent variable but also its derivatives, and the Mach number, an independent variable, at which a certain condition is met. A simple Gaussian process model is shown to be unsuitable for this task. The new response surface method meets the requirements by normalizing the input data to exploit self-similarities in the data. It then decomposes the input data to interpolate orthogonal aerodynamic properties of nacelles independently of each other, and uses a set of filters and transformations to focus accuracy on predictions at relevant operating conditions. The new method meets all the requirements and presents a marked improvement over published preliminary nacelle design methods

An automated approach to nacelle parameterization using intuitive class shape transformation curves

A tool to create parametric aerodynamic shapes using intuitive design variables based on class shape transformation (CST) curves is presented. To enable this, a system has been developed which accepts arbitrary constraints and automatically derives the analytical expressions which describe the corresponding class shape transformation curves. Parametric geometry definitions for fan cowl and intake aero-lines were developed using the generalized method. Computational fluid dynamics (CFD) analysis of the fan cowl shows that despite the simple geometry definition, its performance characteristics are close to what would be expected of a finished design. The intake geometry was generated in a similar way and met the typical performance metrics for conventional intakes. This demonstrates the usefulness of the tool to quickly and robustly produce parametric aero-lines with good aerodynamic properties, using relatively simple intuitive design variables

A Nicaraguan/Guatemalan Encuentro: Villagers Hosting International Service Learning Groups Reflect on Their Experiences

In August 2017, 27 residents from four Nicaraguan and four Guatemalan communities met in Managua, Nicaragua, to discuss their experiences hosting International Service Learning (ISL) groups from the Global North. Despite having many positive recollections, these host community representatives identified a number of issues of concern. This article describes the background to this encuentro (gathering), the issues raised, and the solutions identified in order to encourage Global South host organizations to become better able to articulate their expectations of their Northern visitors and to insist that Northern-sending agencies become more responsive to the expectations of their Southern hosts.    Keywords: North–South partnerships, Southern epistemologies, international service learning, short-term study abroad, experiential educationEn août 2017, 27 résidents de quatre communautés nicaraguayennes et quatre communautés guatémaltèques se sont réunis à Managua, au Nicaragua, pour discuter de leurs expériences en tant qu’organisateurs de groupes d’apprentissage par le service international (International Service Learning, ISL) du nord global. En dépit de nombreux souvenirs positifs, ces représentants de la communauté d’accueil ont identifié un certain nombre de problèmes. Ce document décrit le contexte de cet encuentro (rassemblement), les problèmes soulevés et les solutions identifiées afin d’encourager les organisations hôtes du Global South à mieux exprimer leurs attentes vis-à-vis de leurs visiteurs du nord et à insister pour que les agences d’envoi du nord deviennent plus réactives aux attentes de leurs hôtes du sud.   Mots-clés : partenariat Nord–Sud, épistémologies du Sud, apprentissage par le serviceinternational, études à l’étranger à court durée, éducation expérientiell