The Motion of the Spherical Pendulum Subjected to a D_n Symmetric Perturbation

The motion of a spherical pendulum is characterized by the fact that all trajectories are relative periodic orbits with respect to its circle group of symmetry (invariance by rotations around the vertical axis). When the rotational symmetry is broken by some mechanical effect, more complicated, possibly chaotic behavior is expected. When, in particular, the symmetry reduces to the dihedral group D_n of symmetries of a regular n-gon, n > 2, the motion itself undergoes dramatic changes even when the amplitude of oscillations is small, which we intend to explain in this paper. Numerical simulations confirm the validity of the theory and show evidence of new interesting effects when the amplitude of the oscillations is larger (symmetric chaos)

Cooperative performance measurement proposal (a test with the cooperfic© tool for wine cooperatives in Languedoc-Roussillon)

Purpose: French wine cooperatives show differences of corporate objectives, but also common ones with private wine merchants, as they face a common economic environment. The traditional controlling and financial models do not seem adequate to measure ‘sustainable social economy’ performances advocated by the cooperatives’ philosophy. The main difficulty is that their specific corporate governance introduces competition between short term maximum payments to their grape suppliers-patrons and long term investment potentials. How, therefore, facing this “cooperative dilemma”, should they balance these conflicting objectives, and which performance measurement specificities should wine cooperatives adopt? Design/methodology: In order to try and answer this question, the design of an adapted data base appears to be necessary. It should take into account the apparent antinomy of the cooperatives’ short term and long term objectives, in the context of an economically sustainable development. An original economic and financial measurement model is proposed, and we test it with COOPERFIC?, a decision-aid tool for wine cooperatives, based upon a specially constructed data base in Languedoc-Roussillon. Findings: The exploratory results obtained from the test of an original performance measurement model on an ad hoc sample of wine cooperatives lead to new insights into cooperative performance and to some useful guidelines in terms of cooperative governance. Results show how the conflict between their short term and long term performances could be balanced, in order for this specific type of firm to reach its economic and social objectives Practical implications: A conjoint short and long term economic indicators approach illustrates the necessary balance in the cooperative governance, and constitutes a performance measurement model answering some of these wine cooperatives’ Board and management questions ...French Abstract : Propos: Les caves coopératives françaises font apparaître des points de divergence, mais aussi de convergence avec les négociants en vin, en matière d’objectifs d’entreprise, dans la mesure où elles font face au même environnement économique. Toutefois, les modèles traditionnels financiers et de contrôle de gestion ne semblent pas adaptés à la mesure des performances d’une économie sociale durable, dont les valeurs sont portées par la philosophie coopérative. La principale difficulté réside dans le fait que leur mode de gouvernance spécifique entraîne un conflit permanent entre la rémunération maximale à court terme des vignerons coopérateurs et les capacités d’investissement à long terme. Aussi, face à ce « dilemme coopératif », comment les entreprises coopératives viticoles doivent-elles concilier ces objectifs conflictuels et quels types de mesures de performance spécifiques devraient-elles adopter ? Design/méthodologie: Afin d’arriver à répondre à cette double question, la conception d’une base de données spécifique apparaît nécessaire. Elle se doit de prendre en compte l’apparente antinomie des objectifs à court terme et à long terme des coopératives, dans le cadre d’un développement économique durable. Un modèle de mesure de performance économique et financière est ici proposé et testé à l’aide de l’outil d’aide à la décision COOPERFIC?, spécifique aux caves coopératives du Languedoc-Roussillon. Résultats: Les résultats exploratoires provenant du test d’un modèle original de mesure de la performance sur un échantillon ad hoc de caves coopératives conduit à de nouvelles perspectives en matière de performance coopérative, ainsi qu’à des conseils utiles ayant trait à la gouvernance. Ces résultats montrent la façon dont le conflit entre performances à court terme et à long terme pourrait être maîtrisé en vue d’atteindre les objectifs économiques et sociaux de ce type particulier d’entreprise. Implications managériales: Une approche conjointe des indicateurs économiques à court et long terme illustre le nécessaire équilibre à trouver en matière de gouvernance coopérative et constitue un modèle de mesure de la performance répondant à un certain nombre de questions relatives au conseil d’administration et au management général des coopératives.WINE COOPERATIVES; GOVERNANCE; PERFORMANCE MEASUREMENT; INDICATORS; LANGUEDOC ROUSSILLON; FRANCE

Droplets displacement and oscillations induced by ultrasonic surface acoustic waves: a quantitative study

We present an experimental study of a droplet interacting with an ultrasonic surface acoustic wave (SAW). Depending on the amplitude of the wave, the drop can either experience an internal flow with its contact-line pinned, or (at higher amplitude) move along the direction of the wave also with internal flow. Both situations appear together with oscillations of the drop free-surface. The physical origins of the internal mixing flow as well as the drop displacement and surface waves are still not well understood. In order to give insights of the underlying physics involved in these phenomena, we carried out an experimental and numerical study. The results suggest that the surface deformation of the drop can be related as a combination between acoustic streaming effect and radiation pressure inside the drop.Comment: 9 pages, 14 figures. To appear in Physical Review

A Multiparameter, Numerical Stability Analysis of a Standing Cantilever Conveying Fluid

In this paper, we numerically examine the stability of a standing cantilever conveying fluid in a multiparameter space. Based on nonlinear beam theory, our mathematical model turns out to be replete with exciting behavior, some of which was totally unexpected and novel, and some of which confirm our intuition as well as the work of others. The numerical bifurcation results obtained from applying the Library of Continuation Algorithms (LOCA) reveal a plethora of one, two, and higher codimension bifurcations. For a vertical or standing cantilever beam, bifurcations to buckled solutions (via symmetry breaking) and oscillating solutions are detected as a function of gravity and the fluid-structure interaction. The unfolding of these results as a function of the orientation of the beam compared to gravity is also revealed

Dissipation-Induced Heteroclinic Orbits in Tippe Tops

This paper demonstrates that the conditions for the existence of a dissipation-induced heteroclinic orbit between the inverted and noninverted states of a tippe top are determined by a complex version of the equations for a simple harmonic oscillator: the modified Maxwell–Bloch equations. A standard linear analysis reveals that the modified Maxwell–Bloch equations describe the spectral instability of the noninverted state and Lyapunov stability of the inverted state. Standard nonlinear analysis based on the energy momentum method gives necessary and sufficient conditions for the existence of a dissipation-induced connecting orbit between these relative equilibria

Tippe Top Inversion as a Dissipation-Induced Instability

By treating tippe top inversion as a dissipation-induced instability, we explain tippe top inversion through a system we call the modified Maxwell--Bloch equations. We revisit previous work done on this problem and follow Or's mathematical model [SIAM J. Appl. Math., 54 (1994), pp. 597--609]. A linear analysis of the equations of motion reveals that the only equilibrium points correspond to the inverted and noninverted states of the tippe top and that the modified Maxwell--Bloch equations describe the linear/spectral stability of these equilibria. We supply explicit criteria for the spectral stability of these states. A nonlinear global analysis based on energetics yields explicit criteria for the existence of a heteroclinic connection between the noninverted and inverted states of the tippe top. This criteria for the existence of a heteroclinic connection turns out to agree with the criteria for spectral stability of the inverted and noninverted states. Throughout the work we support the analysis with numerical evidence and include simulations to illustrate the nonlinear dynamics of the tippe top

Reduction of the formaldehyde content in leathers treated with formaldehyde resins by means of plant polyphenols

Formaldehyde has applications in many industrial processes, including synthesis of resins and syntans to be used in the retanning process of leather. When resins are employed, they can hydrolyse, releasing formaldehyde. Due to the carcinogenicity of formaldehyde, its presence in leather should be avoided or kept below allowable limits. The aim of this study is to determine the effect of polyphenols contained in vegetable compounds (mimosa, quebracho and tara) in the reduction of the formaldehyde content in leathers treated with resins synthesized with formaldehyde (melamine-formaldehyde and dicyandiamide-formaldehyde). The formaldehyde content in leathers treated only with resin increases with time while the formaldehyde content in leathers treated additionally with vegetable compounds is reduced. The lower the formaldehyde content in the leather, the higher the ability of vegetable compounds to reduce such content. Mimosa shows the strongest ability to reduce the formaldehyde content, and this capacity increases with ageing. The addition of 4% (on shaved wet-blue weight) of mimosa gives rise to an 85% reduction in the formaldehyde content 140 days after leather processing of split hides treated with a formaldehyde resin of low formaldehyde content. However, this reduction is 68% in splits hides treated with a resin of high formaldehyde content. This is of great importance in baby’s leather articles, in which the formaldehyde content is low; therefore, the addition of a small amount (3%) of vegetable compounds (especially mimosa) guarantees that the formaldehyde content is below the allowed limits (16 mg/kg in the most restrictive regulation). Reducing the formaldehyde content using the polyphenols contained in vegetable compounds constitutes a good alternative not only in the leather sector but also in other industrial sectors (wood, textile, etc.) that use formaldehyde resins.Peer ReviewedPostprint (published version

Design and 3D printing of an electrochemical sensor for Listeria monocytogenes detection based on loop mediated isothermal amplification

The aim of this work is the design and 3D printing of a new electrochemical sensor for the detection of Listeria monocytogenes based on loop mediated isothermal amplification (LAMP). The food related diseases involve a serious health issue all over the world. Listeria monocytogenes is one of the major problems of contaminated food, this pathogen causes a disease called listeriosis with a high rate of hospitalization and mortality. Having a fast, sensitive and specific detection method for food quality control is a must in the food industry to avoid the presence of this pathogen in the food chain (raw materials, facilities and products). A point-of-care biosensor based in LAMP and electrochemical detection is one of the best options to detect the bacteria on site and in a very short period of time. With the numerical analysis of different geometries and flow rates during sample injection in order to avoid bubbles, an optimized design of the microfluidic biosensor chamber was selected for 3D-printing and experimental analysis. For the electrochemical detection, a novel custom gold concentric-3-electrode consisting in a working electrode, reference electrode and a counter electrode was designed and placed in the bottom of the chamber. The LAMP reaction was optimized specifically for a primers set with a limit of detection of 1.25 pg of genomic DNA per reaction and 100% specific for detecting all 12 Listeria monocytogenes serotypes and no other Listeria species or food-related bacteria. The methylene blue redox-active molecule was tested as the electrochemical transducer and shown to be compatible with the LAMP reaction and very clearly distinguished negative from positive food samples when the reaction is measured at the end-point inside the biosensor

Transport properties of the binary mixtures of the three organic liquids toluene, methanol, and cyclohexane

We report on the measurements of diffusion (D), thermodiffusion (DT), and Soret (ST) coefficients in binary pairs of the ternary system toluene-methanol-cyclohexane using different instrumental techniques: microgravity measurements (SODI/DCMIX2) on the International Space Station, thermogravitational column in combination with sliding symmetric tubes, optical beam deflection, optical digital interferometry, and counter flow cell. The binary systems have large regions where the mixtures are either not miscible or the Soret coefficient is negative. All the coefficients have been measured over a wide composition range with the exception of a miscibility gap. Results from different instruments and literature data are in favorable agreement over a broad composition range. Additionally, we have carefully measured the physical properties and the optical contrast factors (dn/dc) p, T and (dn/dT)p,c. The latter ones were also calculated using the Looyenga equation. The measurements in methanol-cyclohexane mixture revealed a decay of the diffusion coefficient when approaching the miscibility gap. We have interpreted this in the spirit of the pseudospinodal concept