Note on dust trapping in inviscid vortex pairs with unequal strengths

We investigate theoretically the motion of tiny heavy passive particles transported in a plane inviscid flow consisting of two point vortices, in order to understand particle dispersion and trapping during vortex interaction. In spite of their large density, particles are not necessarily centrifugated away from vortices. It is observed that they can have various equilibrium positions in the reference frame rotating with the vortices, provided the particle response time and the vortex strength ratio lie in appropriate ranges. A stability analysis reveals that some of these points can be asymptotically stable, and can therefore trap particles released in their basin of attraction. A complete trapping diagram is derived, showing that any vortex pair can potentially become a dust trap, provided the vortex strength ratio is different from 0 (single vortex) and -1 (translating symmetrical vortices). Trapping exists for both co-rotating or contra-rotating vortex pairs. In the latter case, particle trapping on a limit cycle is also observed, and confirmed by using Sapsis and Haller's method [Chaos, 20, 017515, 2010] generalized to non-inertial reference frames

Schreier graphs of the Basilica group

With any self-similar action of a finitely generated group $G$ of automorphisms of a regular rooted tree $T$ can be naturally associated an infinite sequence of finite graphs $\{\Gamma_n\}_{n\geq 1}$, where $\Gamma_n$ is the Schreier graph of the action of $G$ on the $n$-th level of $T$. Moreover, the action of $G$ on $\partial T$ gives rise to orbital Schreier graphs $\Gamma_{\xi}$, $\xi\in \partial T$. Denoting by $\xi_n$ the prefix of length $n$ of the infinite ray $\xi$, the rooted graph $(\Gamma_{\xi},\xi)$ is then the limit of the sequence of finite rooted graphs $\{(\Gamma_n,\xi_n)\}_{n\geq 1}$ in the sense of pointed Gromov-Hausdorff convergence. In this paper, we give a complete classification (up to isomorphism) of the limit graphs $(\Gamma_{\xi},\xi)$ associated with the Basilica group acting on the binary tree, in terms of the infinite binary sequence $\xi$.Comment: 32 page

On the characterization of flowering curves using Gaussian mixture models

In this paper, we develop a statistical methodology applied to the characterization of flowering curves using Gaussian mixture models. Our study relies on a set of rosebushes flowering data, and Gaussian mixture models are mainly used to quantify the reblooming properties of each one. In this regard, we also suggest our own selection criterion to take into account the lack of symmetry of most of the flowering curves. Three classes are created on the basis of a principal component analysis conducted on a set of reblooming indicators, and a subclassification is made using a longitudinal $k$--means algorithm which also highlights the role played by the precocity of the flowering. In this way, we obtain an overview of the correlations between the features we decided to retain on each curve. In particular, results suggest the lack of correlation between reblooming and flowering precocity. The pertinent indicators obtained in this study will be a first step towards the comprehension of the environmental and genetic control of these biological processes.Comment: 28 pages, 27 figure

Rheological properties of molten flax- and Tencel®-polypropylene composites: Influence of fiber morphology and concentration

International audienceThe rheological properties of short fiber reinforced polypropylene were investigated. Flax and Tencel® are two cellulose based fibers used in this study. Flax fibers are extracted from the bast of plants. They are composed of thin elementary fibers and rigid thick bundles made of elementary fibers “glued” together. Tencel® is a man-made cellulosic fiber spun from cellulose solution, with a uniform diameter, thin, and flexible. First, fiber dimensions before and after compounding were analyzed. Both types of fibers were broken during compounding. Flax shows larger length and diameter than Tencel®, but aspect ratio of flax is smaller. The reason is that after compounding flax remained in bundles. Dynamic viscosity, elastic and viscousmoduli were studied as a function of fiber type, concentration (from 0 to 30 wt. %), and composite temperature (from 180 to 200 °C). All Tencel®-based composites showed higher apparent yield stress,viscosity, and moduli compared to flax-based composites at the same fiber concentrations. The results are analyzed in terms of the influence of fiber type, aspect ratio, and flexibility. The importance of considering fiber morphology is demonstrated as far as it controls fiber flexibility and fiber-fiber interactions

Model synchronization: a formal framework for the management of heterogeneous models

International audienceIn this article, we present the conceptual foundations and implementation principles of model synchronization, a formal framework for the management of heterogeneous models. The proposed approach relies on S2ML (System Structure Modeling Language) as a pivot language. We show, by means of a case study, that model synchronization can be used to ensure the consistency between system architecture models designed with Capella and safety models written in AltaRica 3.0

Selection of sensors by a new methodology coupling a classification technique and entropy criteria

Complex industrial processes invest a lot of money in sensors and automation devices to monitor and supervise the process in order to guarantee the production quality and the plant and operators safety. Fault detection is one of the multiple tasks of process monitoring and it critically depends on the sensors that measure the significant process variables. Nevertheless, most of the works on fault detection and diagnosis found in literature emphasis more on developing procedures to perform diagnosis given a set of sensors, and less on determining the actual location of sensors for efficient identification of faults. A methodology based on learning and classification techniques and on the information quantity measured by the Entropy concept, is proposed in order to address the problem of sensor location for fault identification. The proposed methodology has been applied to a continuous intensified reactor, the "Open Plate Reactor (OPR)", developed by Alfa Laval and studied at the Laboratory of Chemical Engineering of Toulouse. The different steps of the methodology are explained through its application to the carrying out of an exothermic reaction

Taxing Profits from International Maritime Shipping in Africa: Past, Present and Future of UN Model Article 8 (Alternative B)

International maritime shipping is an essential part of global business. Since the establishment of the current international tax regime in the 1920s, there has been a consensus that profits generated by this business are taxable only in the residence state –the state where the shipowners are located. Source states – the port states where business physically takes place – are generally expected to exempt income from international shipping. This standard is currently reflected in Article 8 of the OECD Model and Article 8 (Alternative A) of the UN Model, and is incorporated in the vast majority of bilateral tax treaties currently in force. Exclusive residence state taxation of shipping profits is problematic when the size of mercantile fleets and shipping flows between two states are of unequal size. This is often the case in relations between a developed and developing country. The latter often lack a substantial domestic mercantile fleet, but serve as an important revenue-generating port state for the fleet of the developed country. To come to a more balanced allocation of taxing rights in such a case, a source taxation alternative has been inserted in UN Model Article 8 (Alternative B). From its inception, Article 8B has been labelled impractical due to the lack of guidance on core issues, like sourcing rules and profit allocation. This gap is said to explain the low adoption rate of Article 8B in global tax treaty practice. In reality, tax treaty practice regarding Article 8B is heavily concentrated and flourishing in a handful of countries in South/South-East Asia – Bangladesh, India, Indonesia, Myanmar, Pakistan, the Philippines, Sri Lanka and Thailand. All these countries subject non-resident shipping income to tax in their domestic income tax laws. Except for India, all countries are able to exercise these domestic tax law rules in relation to shipping enterprises located in the biggest shipowner states, either because they have a treaty in place that provides for source taxation or because there is no treaty at all and thus no restriction of domestic law. None of the relevant tax treaties contain a provision that incorporates the exact wording of Article 8B of the UN Model. If other countries, like coastal countries in sub-Saharan Africa, are looking to implement source taxation of maritime shipping income in the future, they are advised to draw on the South/South-East Asian experience. Best practice can be distilled regarding sourcing rule, source tax limitation, profit attribution and method of taxation (on gross or net basis). In addition to technical guidance on tax, the South/South-East Asian experience also provides important general policy considerations countries should take into account when determining whether source taxation of maritime shipping profits is an appropriate target for their future tax treaty negotiations

Taxing Profits From International Transport In Africa: Past, Present and Future of Article 8 (Alternative B) of the UN Model

International maritime shipping is an essential part of global business. Since the establishment of the current international tax regime in the 1920s, there has been a consensus that profits generated by this business are taxable only in the residence state –the state where the shipowners are located. Source states – the port states where business physically takes place – are generally expected to exempt income from international shipping. This standard is currently reflected in Article 8 of the OECD Model and Article 8 (Alternative A) of the UN Model, and is incorporated in the vast majority of bilateral tax treaties currently in force. Exclusive residence state taxation of shipping profits is problematic when the size of mercantile fleets and shipping flows between two states are of unequal size. This is often the case in relations between a developed and developing country. The latter often lack a substantial domestic mercantile fleet, but serve as an important revenue-generating port state for the fleet of the developed country. To come to a more balanced allocation of taxing rights in such a case, a source taxation alternative has been inserted in UN Model Article 8 (Alternative B). From its inception, Article 8B has been labelled impractical due to the lack of guidance on core issues, like sourcing rules and profit allocation. This gap is said to explain the low adoption rate of Article 8B in global tax treaty practice. In reality, tax treaty practice regarding Article 8B is heavily concentrated and flourishing in a handful of countries in South/South-East Asia – Bangladesh, India, Indonesia, Myanmar, Pakistan, the Philippines, Sri Lanka and Thailand. All these countries subject non-resident shipping income to tax in their domestic income tax laws. Except for India, all countries are able to exercise these domestic tax law rules in relation to shipping enterprises located in the biggest shipowner states, either because they have a treaty in place that provides for source taxation or because there is no treaty at all and thus no restriction of domestic law. None of the relevant tax treaties contain a provision that incorporates the exact wording of Article 8B of the UN Model. If other countries, like coastal countries in sub-Saharan Africa, are looking to implement source taxation of maritime shipping income in the future, they are advised to draw on the South/South-East Asian experience. Best practice can be distilled regarding sourcing rule, source tax limitation, profit attribution and method of taxation (on gross or net basis). In addition to technical guidance on tax, the South/South-East Asian experience also provides important general policy considerations countries should take into account when determining whether source taxation of maritime shipping profits is an appropriate target for their future tax treaty negotiations. Summary of Working Paper 133 by Tatiana Falcão and Bob Michel