Backstepping control law application to path tracking with an indoor quadrotor

This paper presents an application of the backstepping control to a path tracking mission using an indoor quadrotor. This study case starts on modeling the quadrotor dynamics in order to design a backstepping control which we applied directly to the Lagrangian dynamic equations. The backstepping control is chosen due to its applicability to this class of nonlinear and under-actuate system. To test the designed control law, a complete quadrotor model identification was performed, using a motion capture system. The procedure used to obtain a good model approximation is presented. Experimental results illustrate the validity of the designed control law, including rich simulations and real indoor flight tests

Equivalent Permeability of Step-Lap Joints of Transformer Cores: Computational and Experimental Considerations

The paper develops an efficient computational method for establishing equivalent characteristics of magnetic joints of transformer cores, with special emphasis on step-lap design. By introducing an equivalent material, the method allows the real three-dimensional structure of the laminated thin sheets to be treated computationally as a two-dimensional problem and enables comparative analysis of designs. The characteristics of the equivalent material are established by minimizing the magnetic energy of the system. To verify the proposed approach, a series of experiments have been conducted. First, the anisotropic characteristics of the step-lap were established, and then space components of the flux density at specified positions measured. This enabled detailed analysis of the flux distribution in the step-lap region, in particular the way in which the flux travels between the laminations close to the air-gap steps. Encouraging correlation between the homogenized 2-D model and experiment has been observed

Formulations mathématiques et résolution numérique en mécanique

INTRODUCTION GÉNÉRALEI - APPROXIMATION PAR RÉSIDUS PONDÉRÉS ET ÉLÉMENTS FINIS1 Théorie algébrique des milieux continus2 Méthode des résidus pondérés3 Méthode des éléments finis de type déplacementsII - ÉQUATIONS INTÉGRALES4 Principe et champs d'application5 Équation de poisson6 Problèmes d'élastostatiqueIII - DIFFÉRENCES FINIES7 Principes généraux8 Méthodes mehrstellen9 Méthodes hermitiennes10 Résolution de systèmes tridiagonal ou pentadiagonal11 Équations aux dérivées partielles paraboliquesRÉFÉRENCESDEALa modélisation d'un grand nombre de situations d'intérêt pratique pour l'ingénieur ou chercheur, conduit à la recherche de solutions d'équations aux dérivées partielles, assorties de conditions aux limites et de conditions initiales, notamment en mécanique du solide, en mécanique des fluides, en acoustique, en thermique ou en électromagnétisme.Ces équations sont posées en général sur des domaines géométriques qui ne permettent pas l'emploi des techniques classiques de recherche de solutions exactes. Elles doivent être alors résolues par des méthodes numériques et en particulier par la méthode des éléments finis, des équations intégrales (éléments de frontière, méthode des singularités) ou des différences finies.L'étude des équations intégrales a commencé il y a plus d'un siècle sous la forme de la théorie du potentiel ou de l'identité de Somigliana par exemple, mais les développements concernant la résolution numérique ne datent que des années 1960

Effet de l'angle de charge sur les harmoniques d'efforts magnétiques dans les machines synchrones à aimants permanents surfaciques

International audienceCet article étudie l'effet de l'angle de charge sur les efforts harmoniques de Maxwell (tangentiels et radiaux) et les bruits et vibrations d'origine magnétique dans deux machines synchrones à aimants permanents (MSAP) surfaciques d'architectures très différentes : une machine à 6 dents et 2 paires de pôles, à faible couple et très haute vitesse, et une autre à 120 dents et 58 paires de pôles, à fort couple et faible vitesse. Les efforts magnétiques en présence sont d'abord analysés de manière théorique. Des simulations numériques électromagnétiques et vibro-acoustiques sont ensuite réalisées à l'aide du logiciel MANATEE. Il est montré que l'angle du courant optimal permettant de minimiser les efforts et le bruit de « denture » liés à l'interaction entre pôles et encoches n'est pas identique à celui minimisant les couples pulsatoires ; de même l'angle du courant minimisant les efforts harmoniques radiaux n'est pas nécessairement celui minimisant les efforts harmoniques tangentiels. L'angle de courant minimisant le courant consommé (MTPA) n'est pas celui minimisant les vibrations d'origine magnétique : un compromis doit donc être effectué entre performances électromagnétiques et vibro-acoustiques.</div

Le 'modèle' allemand

L'économie allemande semble à nouveau évoluer en un cercle vertueux - croissance amorcée par les exportations, appréciation du mark, désinflation - qui en fait un modèle exemplaire pour l'Europe (...)

Estimation non invasive du couple électromagnétique des machines AC

International audienceLe papier présente deux méthodes non intrusives de détermination du couple électromagnétique des machines AC directement connectées au réseau. Les grandeurs exploitées sont le courant absorbé ainsi que le champ magnétique rayonné par la machine qui, lorsqu'il est mesuré avec des capteurs placés et orientés à des endroits spécifiques autour de la carcasse, permet d'extraire des informations sur l'état de charge de la machine. Des résultats expérimentaux portent sur une machine asynchrone pour laquelle il est montré qu'une image fine de l'évolution du couple électromagnétique peut être extraite avec les méthodes proposées. L'originalité porte également sur la technique de calibration de la seconde méthode qui donne une estimation plus précise du couple électromagnétique

Multiple and Variable NHEJ-Like Genes Are Involved in Resistance to DNA Damage in Streptomyces ambofaciens

International audienceNon-homologous end-joining (NHEJ) is a double strand break (DSB) repair pathway which does not require any homologous template and can ligate two DNA ends together. The basic bacterial NHEJ machinery involves two partners: the Ku protein, a DNA end binding protein for DSB recognition and the multifunctional LigD protein composed a ligase, a nuclease and a polymerase domain, for end processing and ligation of the broken ends. In silico analyses performed in the 38 sequenced genomes of Streptomyces species revealed the existence of a large panel of NHEJ-like genes. Indeed, ku genes or ligD domain homologues are scattered throughout the genome in multiple copies and can be distinguished in two categories: the " core " NHEJ gene set constituted of conserved loci and the " variable " NHEJ gene set constituted of NHEJ-like genes present in only a part of the species. In Streptomyces ambofaciens ATCC23877, not only the deletion of " core " genes but also that of " variable " genes led to an increased sensitivity to DNA damage induced by electron beam irradiation. Multiple mutants of ku, ligase or polymerase encoding genes showed an aggravated phenotype compared to single mutants. Biochemical assays revealed the ability of Ku-like proteins to protect and to stimulate ligation of DNA ends. RT-qPCR and GFP fusion experiments suggested that ku-like genes show a growth phase dependent expression profile consistent with their involvement in DNA repair during spores formation and/or germination

Molecular basis for intestinal mucin recognition by galectin-3 and C-type lectins

Intestinal mucins trigger immune responses upon recognition by dendritic cells via protein–carbohydrate interactions. We used a combination of structural, biochemical, biophysical, and cell-based approaches to decipher the specificity of the interaction between mucin glycans and mammalian lectins expressed in the gut, including galectin (Gal)-3 and C-type lectin receptors. Gal-3 differentially recognized intestinal mucins with different O-glycosylation profiles, as determined by mass spectrometry (MS). Modification of mucin glycosylation, via chemical treatment leading to a loss of terminal glycans, promoted the interaction of Gal-3 to poly-N-acetyllactosamine. Specific interactions were observed between mucins and mouse dendritic cell-associated lectin (mDectin)-2 or specific intercellular adhesion molecule–grabbing nonintegrin-related-1 (SIGN-R1), but not mDectin-1, using a cell-reporter assay, as also confirmed by atomic force spectroscopy. We characterized the N-glycosylation profile of mouse colonic mucin (Muc)-2 by MS and showed that the interaction with mDectin-2 was mediated by high-mannose N-glycans. Furthermore, we observed Gal-3 binding to the 3 C-type lectins by force spectroscopy. We showed that mDectin-1, mDectin-2, and SIGN-R1 are decorated by N-glycan structures that can be recognized by the carbohydrate recognition domain of Gal-3. These findings provide a structural basis for the role of mucins in mediating immune responses and new insights into the structure and function of major mammalian lectins.—Leclaire, C., Lecointe, K., Gunning, P. A., Tribolo, S., Kavanaugh, D. W., Wittmann, A., Latousakis, D., MacKenzie, D. A., Kawasaki, N., Juge, N. Molecular basis for intestinal mucin recognition by galectin-3 and C-type lectins

Identifying the Relationship Between Supplementary Educational Tools and Black Undergraduate Academic Performance

What is the relationship between supplementary educational tools and the success of undergraduate minority students of Black descent at Andrews University? About a third of all students who attend a private, non-profit, four-year college or university do not complete a degree in six years (Digest of Education Statistics, 2017). Andrews University is a Seventh-Day Adventist, private university, and thus is able to provide a greater quality of education as compared to public colleges and universities (Scholarships.com, 2020). This is reflected in higher six-year graduation rates of private universities, as well as higher grade point averages. Unfortunately, minorities, and specifically Black students, yield lower graduation rates and GPAs as compared to their Caucasian counterparts. Black students at Andrews University perform better than the national data, but they still follow this trend (The Chronicle of Higher Education, 2013). The participant pool was Black undergraduate students from various departments and disciplines at Andrews University. Participants completed a survey in which they indicated the degree to which they participate in academic performance-improving actions we called supplementary educational tools. Participants reported that supplementary educational tools, specifically study groups and tutoring, improved academic performance. All supplementary educational tools were helpful in reducing students’ anxiety and improving their understanding. We could not determine if duration and frequency of use were factors in this. Still, these tools were reported as being helpful in improving students’ academic performance, and we should make an effort to implement them systematically across the campus to improve the academic and professional success of Black students

Working to improve the management of sarcoma patients across Europe: a policy checklist

Background: The Sarcoma Policy Checklist was created by a multidisciplinary expert group to provide policymakers with priority areas to improve care for sarcoma patients. Main body: This paper draws on this research, by looking more closely at how France, Germany, Italy, Spain, Sweden and the United Kingdom are addressing each of these priority areas. It aims to highlight key gaps in research, policy and practice, as well as ongoing initiatives that may impact the future care of sarcoma patients in different European countries. A pragmatic review of the published and web-based literature was undertaken. Telephone interviews were conducted in each country with clinical and patient experts to substantiate findings. Research findings were discussed within the expert group and developed into five core policy recommendations. The five identified priority areas were: the development of designated and accredited centres of reference; more professional training; multidisciplinary care; greater incentives for research and innovation; and more rapid access to effective treatments. Most of the countries studied have ongoing initiatives addressing many of these priorities; however, many are in early stages of development, or require additional funding and resources. Conclusion: Gaps in access to quality care are particularly concerning in many of Europe’s lower-resourced countries. Equitable access to information, clinical trials, innovative treatments and quality specialist care should be available to all sarcoma patients. Achieving this across Europe will require close collaboration between all stakeholders at both the national and European level