Numerical methods for the inverse dynamics simulation of underactuated mechanical systems

The present work deals with the inverse dynamics simulation of underactuated multibody systems. In particular, the study focuses on solving trajectory tracking control problems of differentially flat underactuated systems. The use of servo constraints provides an approach to formulate trajectory tracking control problems of underacutated systems, which are also called underactuated servo constraint problems

Etudes de la croissance anisotrope de ZnO synthétisés par une méthode organométallique et étude cinétique de la gélification concomitante

Aujourd'hui, les nanosciences sont définies comme l'étude des structures (moléculaires) et dispositifs dont au moins une des dimensions caractéristiques se situe 1 - 100 nm. Ces nanomatériaux agissant comme des ponts entre les matériaux massifs et les structures atomiques et démontrent de nombreuses modifications dans les propriétés physiques, chimiques ou biologiques en raison de la taille réduite. Les nanomatériaux composés d'oxydes métalliques sont un tel type de matériaux intéressants. Leurs caractéristiques sont très intéressantes pour le développement d'applications électroniques, optiques, de capteurs et autres. Pour certains des oxydes métalliques, un manque d'oxygène crée des vacances agissant comme donneur d'électrons et induisant des propriétés de semi-conducteurs de type n. ZnO est un exemple typique. Il est caractérisé par une large bande interdite d'environ 3.4 eV, une énergie grande exciton de 60 meV, une grande mobilité électronique et une luminescence dans le visible et le proche ultraviolet. Ces caractéristiques électroniques en font un bon candidat pour le développement de sources d'émission lumineuse et de détecteurs. Il a été ainsi montré que ZnO pouvait, selon les conditions de préparation, émettre dans l'ultraviolet, le violet, le vert, le jaune et même le rouge. Ces propriétés optiques de ZnO dépendent fortement de la morphologie des matériaux. Dans le travail précédent, une méthode mature de synthèse des nanomatériaux ZnO a été développée - la méthode organométallique. Les nano ZnO bien définis avec différentes tailles, formes et morphologies (isotrope, anisotrope) peuvent être obtenus en changeant différents paramètres (milieu de réaction, types de ligands ou de surfactants, température, temps d'incubation, etc.). Cependant, lorsque des amines primaires sont utilisées comme ligands, le mécanisme de la croissance anisotrope n'est toujours pas clair. Les influences des amines secondaires et tertiaires sur nano ZnO obtenus ne sont pas encore dévoilées. Ainsi, la thèse s'attache tout d'abord à étudier les deux points ci- dessus. Premièrement, nous utilisons la méthode d'analyse de tracé 2D et d'analyse statistique pour extraire les informations sur la taille des particules à partir des images TEM. Les données traitées suggèrent que le mécanisme de croissance anisotrope est le processus d'attachement orienté, et finalement entravé par un processus de gélification induit par l'interaction du Zn précurseur avec les aminés. Deuxièmement, nous adoptons une amine de même longueur de chaîne mais de structure différente comme tensioactif (amine primaire, secondaire et tertiaire) pour synthétiser les NCs de ZnO. Les analyses RMN et DFT ont démontré que la différence de morphologie entre les NCs de ZnO viens d'une forte différence dans leur dynamique à la surface des NCs en croissance. L'interaction des liaisons H multiples à la surface du ZnO pour les amines primaires, conduit à une mobilité réduite de ces amines par rapport aux amines secondaires, qui restent mobiles à la surface des NCs dans toutes les dimensions de l'espace. Cette thèse s'intèresse aussi à la gélification qui a été trouvée pendant la synthèse du ZnO. Il a été démontré qu'elle était associée à la formation d'oligomères. Cependant, pour comprendre sa force motrice et étudier la révolution des propriétés rhéologiques avec le temps, d'autres amines primaires avec une longueur de chaîne différente sont utilisées. Les résultats de RMN montrent que la force intermoléculaire (force de Van der Waals, réticulation) contribue à la vitesse de gélification et explique les différents temps de début de gélification. Plus la chaîne est longue, plus la gélification est rapide. La première est déterminée par la force de VdW, et la seconde est déterminée par la réticulation entre les oligomères formés. Les résultats de la mesure rhéologique ont montré que le gel était composé d'une phase organique tridimensionnelle.Nowadays, nanoscience is defined as the studies of structures (molecules) and devices, in which at least one characteristic size is between 1 nm and 100 nm. These nanomaterials act as a bridge between bulk materials and atomic structures, and show many changes in the properties of physical, chemical or biological properties due to the reduction of the size of these structures. Nano materials composed of metal oxides are such kind of interesting materials. Their characteristics are very interesting for the development of electronic, optical, sensor and other applications. For some metal oxides, oxygen deficit will produce vacancies, act as electron donors, and naturally induce the performance of n-type semiconductors. ZnO is a typical example. It has characters of wide band gap of about 3.4 ev, high electron hole interaction energy (60 meV), high electron mobility, visible and near ultraviolet luminescence. These electronic characteristics make it a good candidate for the development of light source and detector. Recent studies have shown ZnO can emit in ultraviolet, violet, green, yellow and even red according to the preparation conditions. These optical properties of ZnO are closely related to the morphology of the material. In the previous work, we first developed a mature synthesis method of ZnO nano materials with organometallic method. By changing different parameters (reaction medium, type of ligand or surfactant, temperature, incubation time, etc.), clear ZnO nano objects with different sizes, shapes and morphologies (isotropic and anisotropic) can be obtained. However, when primary amine is used as ligand, which is the factor controlling this anisotropic growth, the mechanism of anisotropic growth is not clear. The effects of secondary and tertiary amines on nano ZnO are not clear either. Therefore, this paper first studies the above two points. First, we use 2D-plot analysis and statistical analysis to extract particle size information from TEM images. The processed data showed the anisotropic growth mechanism is realized firstly through the orientated attachment process, then finally hindered by the gelation process induced by the interaction between Zn precursor and amino ligand. Second, ZnO NCs was synthesized by using amines with the same aliphatic chain length but different structures as surfactants (primary, secondary and tertiary amines). The interaction between these surfactants and ZnO NCs metal precursors in the whole synthesis process was revealed by the complementary analysis of NMR and DFT. The results show the morphology of ZnO NCs varies with the amine structure, which is due to the great difference of their kinetics on the surface of growing NCs. The interaction of multiple H bonds of primary amines on the surface of ZnO leads to the decrease of the mobility of these amines relative to secondary amines, and the secondary amines remain on the surface of NCs in all spatial dimensions. This thesis work also contains topic of gelation which is discovered during the synthesis of ZnO. It was found the gel formation was related to the formation of oligomers. However, in order to understand the driving force of gelation and study the evolution of gel rheological properties over time, we used primary amines with different fatty chain lengths to study their effects. The NMR results showed the intermolecular force (van der Waals force, crosslinking) had a certain effect on the gelation rate, and explained the different gel initiation time. The longer the chain, the faster the gelation. The results of the rheological measurement showed the gel was composed of three- dimensional organic phase

Numerical methods for the inverse dynamics simulation of underactuated mechanical systems

In der vorliegenden Dissertation wird die Simulation der inversen Dynamik unteraktuierter Mehrkörpersysteme behandelt. Insbesondere werden Steuerungsprobleme der Bahnverfolgung für differentiell flache unteraktuierte Systeme untersucht. Mit Hilfe von Servobindungen werden die Steuerungsprobleme der Bahnverfolgung für unteraktuierte Systeme formuliert. Die betrachteten Probleme werden unteraktuierte Servobindungsprobleme genannt. Minimalkoordinaten, abhängige oder redundante Koordinaten werden zur Formulierung unteraktuierter Servobindungsprobleme verwendet. Die Formulierung ergibt differential-algebraische Gleichungen mit hohem Index. Die diskrete Nullraum-Methode ermöglicht den Übergang von redundanten Koordinaten zu Minimalkoordinaten. Da die numerische Lösung der differential-algebraischen Gleichungen mit hohem Index anspruchsvoll ist und die flachheitsbasierte analytische Lösung für komplizierte unteraktuierte Systeme nicht praktikabel ist, werden Methoden zur Indexreduktion vor der direkten Zeitdiskretisierung eingesetzt. Eine spezielle Projektionsmethode wird angewendet, um den Index von fünf auf drei zu reduzieren. Die Methode erfordert die Berechnung von Projektionsmatrizen, die in der redundanten Koordinaten Formulierung konstant und in der Minimalkoordinaten Formulierung zeitabhängig sind. Eine neue Methode, Indexreduktion durch minimale Erweiterung genannt, wird in dieser Dissertation entwickelt und für Servobindungsprobleme unteraktuierter Systeme verwendet. Die beiden Methoden werden auf repräsentative numerische Beispiele angewandt. Insbesondere wird schon gezeigt, dass sich die neu entwickelte Indexreduktionsmethode zur Lösung involvierter Probleme eignet, die bislang mit der Projektionsmethode nicht gelöst werden konnten

Identification of novel maize miRNAs by measuring the precision of precursor processing

<p>Abstract</p> <p>Background</p> <p>miRNAs are known to play important regulatory roles throughout plant development. Until recently, nearly all the miRNAs in maize were identified by comparative analysis to miRNAs sequences of other plant species, such as rice and <it>Arabidopsis</it>.</p> <p>Results</p> <p>To find new miRNA in this important crop, small RNAs from mixed tissues were sequenced, resulting in over 15 million unique sequences. Our sequencing effort validated 23 of the 28 known maize miRNA families, including 49 unique miRNAs. Using a newly established criterion, based on the precision of miRNA processing from precursors, we identified 66 novel miRNAs in maize. These miRNAs can be grouped into 58 families, 54 of which have not been identified in any other species. Five new miRNAs were validated by northern blot. Moreover, we found targets for 23 of the 66 new miRNAs. The targets of two of these newly identified miRNAs were confirmed by 5'RACE.</p> <p>Conclusion</p> <p>We have implemented a novel method of identifying miRNA by measuring the precision of miRNA processing from precursors. Using this method, 66 novel miRNAs and 50 potential miRNAs have been identified in maize.</p

Mitigating Risk Propensity in Healthcare Service Supply Chain: A Theoretical Background

Comparatively both traditional manufacturing supply chain networks and service supply chain network faces multiple uncertainties that affects the growth, sustainability and performance of each particular network. Despite the significant hurdles that risk posses to business entities and its activities there have been relatively larger amount of studies considering this phenomenon in traditional manufacturing supply chain network as compared with service supply chain network. Due to this limitation or gap in the body of literature the study examines this phenomenon from a theoretical approach to outline relevant prepositions that can be tested empirical in further research. The theoretical preposition stated provides a clear direction to guide further research into risk management in healthcare service supply chain network. Keywords: risk propensity, risk mitigation, competitive advantage, collective risk managemen

Introduction and Suggestions on the Chinese Securities Credit Rating System from a Comparative Perspective

Credit rating is a burgeoning industry in China. However, ever since it was established by State Council in 1993, the development of the industry has faced various impediments. There are currently three major problems hindering its further development, as result of a lack of systematic statutory and judicial guidelines. These problems are: limited competition in the industry, rampant rating shopping and conflicts of interest, and limited remedy in a suit against false ratings. The rating industry in China has followed a different pattern. The statutory threshold requirement has proven too demanding for most rating agencies to comply with, barring many potential participants from the market. In addition, provisions prohibiting rating shopping and regulating conflicts of interest are narrowly drawn, targeting only direct conflicts of interest. While freedom of speech remains an invalid defense, judges\u27 reluctance to recognize substantial intangible harm combined with an insufficient judicial framework together make it hard for plaintiffs to prevail in lawsuits against false ratings

Served as Social Actors or Instrumental Role? Understanding the Usage of Smart Product from the Dual Processing Perspective

Based on the Dual processing theory, this study proposes that customers form their decision of smart products usage through two paths of: emotional and functional, at the same time. These paths are related to two types of behavior modes: affect-oriented which reflects the emotional or psychological demands we need, and the task-oriented which reflects essential needs for us to make use of these products. The behavior modes, represented by anthropomorphism cues and functional cues respectively, influence different kinds of trust, affect-based and cognition-based, and then determine the usage of smart products. The results will be examine through data collection in the near future. And we hope that the results could unravel several important findings and bring some managerial implications for manufacturers to improve their products

Global Reactions to COVID-19 on Twitter: A Labelled Dataset with Latent Topic, Sentiment and Emotion Attributes

This paper presents a large, labelled dataset on people's responses and expressions related to the COVID-19 pandemic over the Twitter platform. From 28 January 2020 to 1 Jan 2021, we retrieved over 132 million public Twitter posts (i.e., tweets) from more than 20 million unique users using four keywords: "corona", "wuhan", "nCov" and "covid". Leveraging natural language processing techniques and pre-trained machine learning-based emotion analytic algorithms, we labelled each tweet with seventeen latent semantic attributes, including a) ten binary attributes indicating the tweet's relevance or irrelevance to the top ten detected topics, b) five quantitative emotion intensity attributes indicating the degree of intensity of the valence or sentiment (from extremely negative to extremely positive), and the degree of intensity of fear, of anger, of sadness and of joy emotions (from barely noticeable to extremely high intensity), and c) two qualitative attributes indicating the sentiment category and the dominant emotion category the tweet is mainly expressing. We report the descriptive statistics around the topic, sentiment and emotion attributes, and their temporal distributions, and discuss the dataset's possible usage in communication, psychology, public health, economics, and epidemiology research.Comment: Updated with the complete 2020 data (28 Jan 2020-1 Jan 2021