Optimizing tuning masses for helicopter rotor blade vibration reduction including computed airloads and comparison with test data

The development and validation of an optimization procedure to systematically place tuning masses along a rotor blade span to minimize vibratory loads are described. The masses and their corresponding locations are the design variables that are manipulated to reduce the harmonics of hub shear for a four-bladed rotor system without adding a large mass penalty. The procedure incorporates a comprehensive helicopter analysis to calculate the airloads. Predicting changes in airloads due to changes in design variables is an important feature of this research. The procedure was applied to a one-sixth, Mach-scaled rotor blade model to place three masses and then again to place six masses. In both cases the added mass was able to achieve significant reductions in the hub shear. In addition, the procedure was applied to place a single mass of fixed value on a blade model to reduce the hub shear for three flight conditions. The analytical results were compared to experimental data from a wind tunnel test performed in the Langley Transonic Dynamics Tunnel. The correlation of the mass location was good and the trend of the mass location with respect to flight speed was predicted fairly well. However, it was noted that the analysis was not entirely successful at predicting the absolute magnitudes of the fixed system loads

Greenhouse Gas Emissions and Climate Change Policies around the World

Country briefings provided by: Master Course GE_4_300 “Climate Change and Climate Policy”. Preparatory material for the climate change negotiation game "World Climate"This briefing provides an overview on major countries sumrnarizing their greenhouse gas emission profiles, economic and political situation, major societal challenges and national policies relevant to tackle global climate change. The countries are marked green in above map. In alphabetical order these are: Australia, Brazil, Canada, Indonesia, Japan, Mexico, New Zealand, Nigeria, Norway, Russia, Saudi Arabia , South Africa, and Turkey . We developed a common template to structure country briefings bringing together many different national but also international sources, such as assessments by Climate Action Tracker (CAT). For providing a comprehensive picture, briefings for China, the European Union, India, and USA are additionally included .These briefings are taken from 'Ciimate lnteractive', a not-for-profil organization based in Washington DC (see the countries & regions marked in blue in above figure). All material is designed as preparatory material for the climate change negotiation game (https://www .climateinteractive.org/).The new material compiled by HVL students of the master course "Climate Change and Climate Policy" enables to play the IS-region version of the game

Miss Lindquist : un système fondé sur le dialogue pour apprendre à exprimer algébriquement des énoncés en langage naturel

Symbolization is the ability to translate a real world situation into [NTH1J the language of algebra. We believe that symbolization is the single most important skill students learn in high school algebra. We present research on what makes this skill difficult and report the discovery of a “ hidden ” skill in symbolization. Contrary to past research that has emphasized that symbolization is difficult due to both comprehension difficulties and the abstract nature of variables , we found that symbolization is difficult because it is the articulation in the “foreign” language of “algebra”. We also present Mrs Lindquist, an Intelligent Tutoring System (ITS) designed to carry on a tutorial dialog about symbolization. Mrs Lindquist has a separate tutorial model encoding pedagogical content knowledge in the form of different tutorial strategies, which were partially developed by observing an experienced human tutor. We discuss aspects of this human tutor’s method that can be modeled well by Mrs Lindquist. Finally, we present an early formative showing that students can leam from the dialogs Mrs Lindquist is able to engage student in. Mrs Lindquist has tutored over one thousand of students at wwwAlgebraTutor.org.La symbolisation est la compétence permettant de traduire en langage algébrique une situation du monde réel. A notre sens, c’est la compétence principale à acquérir par les élèves pour l’apprentissage de l’algèbre au niveau de l’enseignement secondaire. Nous présentons une recherche portant sur les problèmes posés par l’acquisition de cette compétence, étude qui a mis en évidence une «compétence cachée » à l’intérieur de la symbolisation. Contrairement à des recherches antérieures qui ont analysé cette acquisition en termes de difficultés de compréhension des textes des énoncés et de compréhension du rôle abstrait des variables, nous pensons que l’algèbre est une langue étrangère pour les élèves et que c’est la difficulté pour eux à s’exprimer dans cette langue étrangère qui pose problème pour l’acquisition de la symbolisation. Nous présentons également Mrs Lindquist, un tuteur intelligent (TI) conçu pour mener un dialogue pédagogique sur des exercices de symbolisation. Mrs Lindquist possède un modèle pédagogique spécifique pour représenter la connaissance pédagogique sous forme de différentes stratégies mises au point en observant un enseignant (humain) expérimenté. Nous discutons certains des aspects de la méthode mise en œuvre par le tuteur humain que nous avons modélisés dans Mrs Lindquist. Enfin, nous présentons une première évaluation formative de notre système qui montre que les élèves peuvent apprendre à partir des dialogues où ils peuvent s’engager grâce à Mrs Lindquist. Mrs Lindquist a ainsi formé plus de mille élèves sur le site www.AlgebraTutor.org.Heffeman Neil T., Koedinger Kenneth R. Miss Lindquist : un système fondé sur le dialogue pour apprendre à exprimer algébriquement des énoncés en langage naturel. In: Sciences et techniques éducatives, volume 9 n°1-2, 2002. Logiciels pour l'apprentissage de l'algèbre (dir. Jean-François Nicaud, Elisabeth Delozanne, Brigitte Grugeon) pp. 11-35

Cooperatives in a Changing Global Food System

This study examines how U.S. agricultural cooperatives are responding to current trends toward the globalization of the agricultural and food sector. Information from three case studies illustrates the extent to which cooperatives’ organizational structure may limit or enhance their ability to compete with investor-owned firms (IOFs) on a global scale. Concentration levels in key agricultural production, processing, and distribution markets are reviewed. Next, the report examines new global strategies being employed by IOFs and their impact on farmer-owned cooperatives. The international activities of three regional cooperatives are examined in detail and data are used to highlight advantages and disadvantages that cooperatives may experience in global competition with IOFs. Factors limiting international involvement by cooperatives include the diverse interests of their members, ties to domestic resource bases and social groups, the high risk levels and long-term nature of international investment, and symbolic barriers, including language barriers and the different connotations of the term “cooperative” in other nations. Potential advantages for cooperatives include their reputation as reliable, high-quality suppliers and ethical business partners and their ability to meet specialty, niche demand created within a global food system. Cooperatives must seek opportunities in the new global system that their organizational structure makes them uniquely qualified to fill. They must also seek member response to questions of international involvement and encourage a spirit of “permanent innovation” among cooperative members and staff. Finally, cooperatives must enhance the potential social, cultural and economic benefits from international cooperation for their membership

Cooperatives in a Changing Global Food System

This study examines how U.S. agricultural cooperatives are responding to current trends toward the globalization of the agricultural and food sector. Information from three case studies illustrates the extent to which cooperatives’ organizational structure may limit or enhance their ability to compete with investor-owned firms (IOFs) on a global scale. Concentration levels in key agricultural production, processing, and distribution markets are reviewed. Next, the report examines new global strategies being employed by IOFs and their impact on farmer-owned cooperatives. The international activities of three regional cooperatives are examined in detail and data are used to highlight advantages and disadvantages that cooperatives may experience in global competition with IOFs. Factors limiting international involvement by cooperatives include the diverse interests of their members, ties to domestic resource bases and social groups, the high risk levels and long-term nature of international investment, and symbolic barriers, including language barriers and the different connotations of the term “cooperative” in other nations. Potential advantages for cooperatives include their reputation as reliable, high-quality suppliers and ethical business partners and their ability to meet specialty, niche demand created within a global food system. Cooperatives must seek opportunities in the new global system that their organizational structure makes them uniquely qualified to fill. They must also seek member response to questions of international involvement and encourage a spirit of “permanent innovation” among cooperative members and staff. Finally, cooperatives must enhance the potential social, cultural and economic benefits from international cooperation for their membership