Articles de revues : « Suspensions de Poisson »

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PARREAU, FRANÇOIS, et EMMANUEL ROY. « Prime Poisson suspensions ». Ergodic Theory and Dynamical Systems 35, n^o 7 (4 août 2014) : 2216–30. http://dx.doi.org/10.1017/etds.2014.32.

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We establish a necessary and sufficient condition for a Poisson suspension to be prime. The proof is based on the Fock space structure of the $L^{2}$-space of the Poisson suspension. We give examples of explicit infinite measure-preserving systems, in particular of non-singular compact group rotations that give rise to prime Poisson suspensions. We also compare some properties of so far known prime transformations with those of our examples, showing that these examples are new.

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Élise Janvresse, Emmanuel Roy et Thierry de la Rue. « Poisson suspensions and SuShis ». Annales scientifiques de l'École normale supérieure 50, n^o 6 (2017) : 1301–34. http://dx.doi.org/10.24033/asens.2346.

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Élise Janvresse, Emmanuel Roy et Thierry de la Rue. « Poisson suspensions and SuShis ». Annales scientifiques de l'École normale supérieure 50, n^o 6 (2017) : 1301–34. http://dx.doi.org/10.24033/asens.2646.

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Ackerson, B. J., X. L. Lei et P. Tong. « Subtle order in settling suspensions ». Pure and Applied Chemistry 73, n^o 11 (1 janvier 2001) : 1679–88. http://dx.doi.org/10.1351/pac200173111679.

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A dilute suspension of uniform, non-Brownian spheres settles slowly in a viscous solvent. The initially well-mixed system showing Poisson or random occupancy statistics evolves to a system having reduced number fluctuations, but otherwise appearing random. The reduced number fluctuations are consistent with recent measurements of velocity fluctuations in settling suspensions. These experimental results test the assumptions leading to the theoretical predictions by Calflisch and Luke that the velocity fluctuations increase without limit with increasing sample dimension. The theoretical prediction assumes Poisson occupation statistics contrary to our observations.

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ROY, EMMANUEL. « Poisson suspensions and infinite ergodic theory ». Ergodic Theory and Dynamical Systems 29, n^o 2 (avril 2009) : 667–83. http://dx.doi.org/10.1017/s0143385708080279.

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AbstractWe investigate the ergodic theory of Poisson suspensions. In the process, we establish close connections between finite and infinite measure-preserving ergodic theory. Poisson suspensions thus provide a new approach to infinite-measure ergodic theory. Fields investigated here are mixing properties, spectral theory, joinings. We also compare Poisson suspensions to the apparently similar looking Gaussian dynamical systems.

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Zweimüller, Roland. « Poisson suspensions of compactly regenerative transformations ». Colloquium Mathematicum 110, n^o 1 (2008) : 211–25. http://dx.doi.org/10.4064/cm110-1-10.

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Janvresse, Élise, Tom Meyerovitch, Emmanuel Roy et Thierry de la Rue. « Poisson suspensions and entropy for infinite transformations ». Transactions of the American Mathematical Society 362, n^o 06 (17 décembre 2009) : 3069–94. http://dx.doi.org/10.1090/s0002-9947-09-04968-x.

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Ryzhikov, V. V. « Ergodic homoclinic groups, Sidon constructions and Poisson suspensions ». Transactions of the Moscow Mathematical Society 75 (5 novembre 2014) : 77–85. http://dx.doi.org/10.1090/s0077-1554-2014-00227-2.

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Tukmakov, D. A. « Comparison of Numerical Models of the Dynamics of Electrically Charged Gas Suspensions with Mass and Surface Charge Densities for Different Particles Dispersities ». Herald of the Bauman Moscow State Technical University. Series Natural Sciences, n^o 3 (102) (juin 2022) : 43–56. http://dx.doi.org/10.18698/1812-3368-2022-3-43-56.

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The purpose of the study was to mathematically model the dynamics of inhomogeneous electrically charged media, such as that of gas suspensions, i.e., solid particles suspended in a gas. The mathematical model implemented a continuum approach to modeling the dynamics of inhomogeneous media, which implies taking into account intercomponent heat transfer and momentum exchange. The carrier medium was described as a viscous, compressible, heat-conducting gas, the equations of the model were supplemented with initial and boundary conditions, and the system of the equations was integrated by an explicit finite-difference method. To obtain a monotonic grid function, a nonlinear scheme for correcting the numerical solution was used. The mathematical model was supplemented with the Poisson equation describing the electric field, which is formed by electrically charged disperse inclusions. The Poisson equation was integrated by finite-difference methods on a gas-dynamic grid. The flow of a gas suspension caused by the motion of dispersed particles under the action of the Coulomb force was studied numerically. Flows of gas suspensions with surface and mass densities of electric charge were modeled. For the surface charge density model, the Coulomb force acting on the unit mass of the gas suspension increases with a decrease in the dispersion of particles. For the mass charge density, the dispersion of particles does not affect the specific Coulomb force acting on the particles. The intensity of the gas suspension flow increases with decreasing particle size, both for the mass and surface models of charge density. For the surface charge density model, as the particle size decreases, the intensity of the gas pressure drop in the emerging gas suspension flow increases more than when modeling the gas suspension dynamics with a mass distribution of the electric charge density

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Ryzhikov, Valerii Valentinovich. « Polynomial rigidity and the spectra of Sidon automorphisms ». Sbornik : Mathematics 215, n^o 7 (2024) : 993–1006. http://dx.doi.org/10.4213/sm10023e.

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Continuum many spectrally disjoint Sidon automorphisms with tensor square isomorphic to a planar translation are produced. Their spectra do not have the group property. To show that their spectra are singular the polynomial rigidity of operators is used, which is related to the concept of linear determinism in the sense of Kolmogorov. In the class of mixing Gaussian and Poisson suspensions over Sidon automorphisms new sets of spectral multiplicities are realized. Bibliography: 12 titles.

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Denton, A. R. « Poisson–Boltzmann theory of charged colloids : limits of the cell model for salty suspensions ». Journal of Physics : Condensed Matter 22, n^o 36 (20 août 2010) : 364108. http://dx.doi.org/10.1088/0953-8984/22/36/364108.

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Hallez, Yannick, Joseph Diatta et Martine Meireles. « Quantitative Assessment of the Accuracy of the Poisson–Boltzmann Cell Model for Salty Suspensions ». Langmuir 30, n^o 23 (30 mai 2014) : 6721–29. http://dx.doi.org/10.1021/la501265k.

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Tamashiro, M. N., et H. Schiessel. « Where the linearized Poisson–Boltzmann cell model fails : Spurious phase separation in charged colloidal suspensions ». Journal of Chemical Physics 119, n^o 3 (15 juillet 2003) : 1855–65. http://dx.doi.org/10.1063/1.1579676.

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dos Santos, Alexandre P., Alexandre Diehl et Yan Levin. « Electrostatic correlations in colloidal suspensions : Density profiles and effective charges beyond the Poisson–Boltzmann theory ». Journal of Chemical Physics 130, n^o 12 (28 mars 2009) : 124110. http://dx.doi.org/10.1063/1.3098556.

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Michot, L. J., E. Paineau, I. Bihannic, S. Maddi, J. F. L. Duval, C. Baravian, P. Davidson et P. Levitz. « Isotropic/nematic and sol/gel transitions in aqueous suspensions of size selected nontronite NAu1 ». Clay Minerals 48, n^o 5 (décembre 2013) : 663–85. http://dx.doi.org/10.1180/claymin.2013.048.5.01.

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AbstractThe phase behaviour of aqueous suspensions of NAu1 nontronite was studied on size-selected particles by combining osmotic pressure measurements, visual observations under polarized light, rheological experiments and Small Angle X-ray Scattering (SAXS). NAu1 suspensions display a liquid crystalline behaviour as they exhibit a Isotropic/Nematic (I/N) transition that occurs before the sol/gel transition for ionic strengths below 10–3M/L. This I/N transition shifts towards lower volume fractions for increasing particle anisotropy and its position in the phase diagram agrees well with the theoretical predictions for platelets. SAXS measurements reveal the presence of characteristic interparticular distances in the isotropic, nematic and gel phases. In the gel phase a local lamellar order is observed which shows that the “house of cards” model is not appropriate for describing the gel structure in swelling clay materials at low ionic strength. Furthermore, by combining results from osmotic pressure measurements and X-ray scattering, it appears that the pressure of the system can be well described using a simple Poisson-Boltzmann treatment based on the repulsion between charged infinite parallel planes. In terms of rheological properties, even if the thermodynamical status of the sol/gel transition remains partially unclear, the yield stress and elasticity of the gels can be easily renormalized for all particle sizes on the basis of the volume of the particles. Furthermore, rheological modelling of the flow curves shows that for all the particles an approach based on excluded volume effects captures most features of nontronite suspensions.

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Lin, Wei C., et Huan J. Keh. « Electrophoretic Mobility and Electric Conductivity of Salt-Free Suspensions of Charged Soft Particles ». Colloids and Interfaces 5, n^o 4 (17 octobre 2021) : 45. http://dx.doi.org/10.3390/colloids5040045.

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A unit cell model is employed to analyze the electrophoresis and electric conduction in a concentrated suspension of spherical charged soft particles (each is a hard core coated with a porous polyelectrolyte layer) in a salt-free medium. The linearized Poisson–Boltzmann equation applicable to a unit cell is solved for the equilibrium electrostatic potential distribution in the liquid solution containing the counterions only surrounding a soft particle. The counterionic continuity equation and modified Stokes/Brinkman equations are solved for the ionic electrochemical potential energy and fluid velocity distributions, respectively. Closed-form formulas for the electrophoretic mobility of the soft particles and effective electric conductivity of the suspension are derived, and the effect of particle interactions on these transport characteristics is interesting and significant. Same as the case in a suspension containing added electrolytes under the Debye–Hückel approximation, the scaled electrophoretic mobility in a salt-free suspension is an increasing function of the fixed charge density of the soft particles and decreases with increases in the core-to-particle radius ratio, ratio of the particle radius to the permeation length in the porous layer, and particle volume fraction, keeping the other parameters unchanged. The normalized effective electric conductivity of the salt-free suspension also increases with an increase in the fixed charge density and with a decrease in the core-to-particle radius ratio, but is not a monotonic function of the particle volume fraction.

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Flatt, Robert J., et Paul Bowen. « Electrostatic repulsion between particles in cement suspensions : Domain of validity of linearized Poisson–Boltzmann equation for nonideal electrolytes ». Cement and Concrete Research 33, n^o 6 (juin 2003) : 781–91. http://dx.doi.org/10.1016/s0008-8846(02)01059-1.

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Lou, James, Chun-Yu Shih et Eric Lee. « Diffusiophoresis of Concentrated Suspensions of Spherical Particles with Charge-regulated Surface : Polarization Effect with Nonlinear Poisson−Boltzmann Equation ». Langmuir 26, n^o 1 (5 janvier 2010) : 47–55. http://dx.doi.org/10.1021/la902113s.

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Ploemacher, RE, JP van der Sluijs, JS Voerman et NH Brons. « An in vitro limiting-dilution assay of long-term repopulating hematopoietic stem cells in the mouse ». Blood 74, n^o 8 (1 décembre 1989) : 2755–63. http://dx.doi.org/10.1182/blood.v74.8.2755.2755.

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Abstract We have developed a limiting-dilution assay of long-term repopulating hematopoietic stem cells in the mouse using a miniturized stroma- dependent bone marrow culture assay in vitro. The cells were overlaid on irradiated stromal layers in microtiter wells in a range of concentrations, and frequencies of cobblestone area-forming cells (CAFC) were calculated by employing Poisson statistics. The production of secondary granulocyte/macrophage colony-forming units (CFU-G/M) in the adherent layer of individual wells was correlated with the presence of such cobblestone areas. CAFC frequencies were determined in bone marrow cell suspensions that were either enriched for marrow repopulating ability (MRA) in vivo, while depleted for spleen colony- forming units (CFU-S), or vice versa. The separation of bone marrow cells (BMC) was either based on centrifugal elutriation, or monoclonal antibody-mediated magnetic depletion of cells carrying cell surface differentiation antigens, and subsequent sorting on the basis of light scatter and rhodamine-123 retention as a measure of mitochondrial activity. In addition, 5-fluorouracil-resistant BMC were studied. Our investigations show that a time-dependent cobblestone area formation exists that reflects the turnover time and primitiveness of CAFC. The frequency of precursors forming cobblestone areas on day 28 after overlay is proposed to be a measure for MRA, whereas the day-7 CAFC frequency closely corresponds with day-12 CFU-S numbers in the suspensions tested.

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Ploemacher, RE, JP van der Sluijs, JS Voerman et NH Brons. « An in vitro limiting-dilution assay of long-term repopulating hematopoietic stem cells in the mouse ». Blood 74, n^o 8 (1 décembre 1989) : 2755–63. http://dx.doi.org/10.1182/blood.v74.8.2755.bloodjournal7482755.

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We have developed a limiting-dilution assay of long-term repopulating hematopoietic stem cells in the mouse using a miniturized stroma- dependent bone marrow culture assay in vitro. The cells were overlaid on irradiated stromal layers in microtiter wells in a range of concentrations, and frequencies of cobblestone area-forming cells (CAFC) were calculated by employing Poisson statistics. The production of secondary granulocyte/macrophage colony-forming units (CFU-G/M) in the adherent layer of individual wells was correlated with the presence of such cobblestone areas. CAFC frequencies were determined in bone marrow cell suspensions that were either enriched for marrow repopulating ability (MRA) in vivo, while depleted for spleen colony- forming units (CFU-S), or vice versa. The separation of bone marrow cells (BMC) was either based on centrifugal elutriation, or monoclonal antibody-mediated magnetic depletion of cells carrying cell surface differentiation antigens, and subsequent sorting on the basis of light scatter and rhodamine-123 retention as a measure of mitochondrial activity. In addition, 5-fluorouracil-resistant BMC were studied. Our investigations show that a time-dependent cobblestone area formation exists that reflects the turnover time and primitiveness of CAFC. The frequency of precursors forming cobblestone areas on day 28 after overlay is proposed to be a measure for MRA, whereas the day-7 CAFC frequency closely corresponds with day-12 CFU-S numbers in the suspensions tested.

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Bondarev, V. N., et G. S. Dragan. « Screening effects in dense Coulomb media : Beyond the Poisson–Boltzmann and Kirkwood approximations ». Physics of Plasmas 29, n^o 6 (juin 2022) : 063701. http://dx.doi.org/10.1063/5.0089918.

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A theoretical approach is proposed that allows giving a suitable description of the equilibrium characteristics of dense heterogeneous Coulomb media, for example, dusty plasma (DP) and ionic colloidal suspensions containing charged particles (grains) of finite size. It is shown that taking into account the Carnahan–Starling closed formula for the contribution of hard spheres of diameter d and number density n into the free energy of DP essentially improves the approximations by Poisson–Boltzmann (ideal gas of point ions) and Kirkwood (ideal gas of finite-sized ions). Thus, in systems like DP, along with the Kirkwood parameter (the ratio of d to the Debye–Hückel screening length), a second independent dimensionless parameter nd3 appears. As a result, for the first time, an opportunity opens up to give a natural explanation of the experimental fact, according to which the screening length in a concentrated electrolyte may turn out to be an increasing function of nd3. Useful evidence of the internal consistency of the theory is that it allows one to give a satisfactory numerical estimate of the dimensionless temperature of DP triple point (vapor–liquid–solid), in agreement with Monte Carlo simulations for concentrated electrolytes like CsCl. Furthermore, the results obtained are in quantitative agreement with a fairly wide set of experimental data on the melting of real ionic crystals (from LiF to CsI and from MgO to BaO) and, thus, provide a theoretical basis for the long-established empirical “similarity rule” that relates melting temperatures to effective ion sizes.

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Negrila, Catalin, Mihai Predoi, Simona Iconaru et Daniela Predoi. « Development of Zinc-Doped Hydroxyapatite by Sol-Gel Method for Medical Applications ». Molecules 23, n^o 11 (15 novembre 2018) : 2986. http://dx.doi.org/10.3390/molecules23112986.

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Zinc- (Zn) doped hydroxyapatite (HAp) were prepared by sol-gel method. Zinc-doped hydroxyapatite (ZnHAp) and HAp were analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The Rietveld analysis revealed that the HAp and 7ZnHAp powders obtained by sol-gel method have a monophasic hydroxyapatite structure belonging to the P63/m spatial group. The results obtained from the ultrasound characterization of HAp and ZnHAp are also presented in this study. The effect of zinc concentration on properties that were deduced from ultrasonic measurements are studied in the case of a significant zinc concentration (xZn = 0.07). From the values of the ultrasonic waves velocities were determined by the pairs of elastic coefficients of the suspensions (Young modulus E, Poisson coefficient ν), which have proven to be similar to those determined by other authors.

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Tukmakovkov, Dmetry A. « Comparison of mathematical models of the dynamics of electrically charged gas suspensions for various concentrations of the dispersed component ». Journal Of Applied Informatics 17, n^o 1 (97) (31 janvier 2022) : 39–54. http://dx.doi.org/10.37791/2687-0649-2022-17-1-39-54.

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This work is devoted to mathematical modeling of the dynamics of inhomogeneous electrically charged media. A dusty environment - solid particles suspended in a gas – was considered as an inhomogeneous medium. The mathematical model implemented a continuous approach to modeling the dynamics of inhomogeneous media. The complete hydrodynamic system of equations was solved for each component. The system of equations for the dynamics of each component included the equations of mass continuity, momentum components, and the energy conservation equation for the mixture component. Intercomponent interaction took into account momentum exchange and intercomponent heat transfer. The carrier medium was described as a viscous compressible heat-conducting gas. The flow was described as a flow with a two- dimensional geometry. The equations of the mathematical model were supplemented with initial and boundary conditions. The mathematical model took into account the wall viscosity in the channel. The system of equations of the mathematical model was integrated by McCormack's explicit finite-difference method. To obtain a monotonic grid function, a nonlinear scheme for correcting the numerical solution was used. The mathematical model was supplemented by the Poisson equation describing the electric field formed by charged dispersed particles. Poisson's equation was integrated by finite-difference methods on a gas-dynamic grid. Such a choice of the computational grid was necessary to calculate the concentration of particles required both for solving the electric field equation and for calculating the physical fields of the dynamics of inhomogeneous media. The reciprocal motion of a gas suspension caused by the movement of dispersed particles under the action of the Coulomb force was numerically investigated. The values of the surface and mass densities are determined, at which the models of the surface and mass densities of charges in the simulation of such a process are the same. It is revealed that the surface and mass models of charges are identical with respect to the volumetric content.

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Baranov, Pavel, Tamara Nesterenko, Evgenii Barbin et Aleksei Koleda. « Constructive approach to reduce the influence of temperature on spring suspension eigenfrequencies ». Sensor Review 40, n^o 3 (8 juillet 2020) : 297–309. http://dx.doi.org/10.1108/sr-11-2019-0290.

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Purpose One of the problems encountered by developers of inertial systems, such as gyroscopes and accelerometers, is the critical dependence of the eigenfrequencies of elastic suspensions (ES) on temperature when using substrates for sensors made of dielectric materials, such as borosilicate glass. The internal stresses arising in the ES caused by the difference in the temperature coefficients of linear expansion (TCLE) lead to deformation of the sensor and complication of the electronic part of the sensor. The purpose of this paper is to approach for in-plane and out-of-plane ES are considered that allow for minimization of the influence of internal stresses on eigenfrequencies. Design/methodology/approach Analytical, finite element and experimental results are considered. The temperature coefficient of thermal expansion, the Young’s modulus and the Poisson ratio are given as a function of temperature. The shape of the spring elements (SEs) and the construction of the elastic suspension are the main topics of focus in this study. The authors’ out-of-plane ES based on a meander-like spring element implemented via finite element modeling show good agreement with the experimental results. Findings Meander-like SEs have been developed that have lower temperature errors in comparison with traditional types of SEs. The main contribution to the change in the eigenfrequency from temperature is made by internal stresses that arose from the deformation of the bonded materials with different TCLE. The change of eigenfrequency from the temperatures that were calculated by finite element method did not exceed 0.15%, however, in practice, the scatter of the obtained characteristics for different samples showed a change of up to 0.3%. Originality/value This study shows a way to design and optimize the structure and theoretical background for the development of the microelectromechanical systems (MEMS) inertial module combining the functions of gyroscope and accelerometer. The obtained results will improve and expand the manufacturing technology of MEMS gyroscopes and accelerometers.

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Flatt, R. J., et P. Bowen. « Reply to the discussion by S. Chatterji of the paper “Electrostatic repulsion between particles in cement suspensions : domain of validity of linearized Poisson–Boltzmann equation for nonideal electrolytes” ». Cement and Concrete Research 34, n^o 10 (octobre 2004) : 1955–57. http://dx.doi.org/10.1016/j.cemconres.2004.03.004.

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Chatterji, S. « A discussion of the paper “Electrostatic repulsion between particles in cement suspensions : domain of validity of linearized Poisson–Boltzmann equation for nonideal electrolytes” by R.J. Flatt and P. Bowen ». Cement and Concrete Research 34, n^o 10 (octobre 2004) : 1953–54. http://dx.doi.org/10.1016/j.cemconres.2004.03.003.

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Seo, Eun-Young, Tae-Seok Ahn et Young-Gun Zo. « Agreement, Precision, and Accuracy of Epifluorescence Microscopy Methods for Enumeration of Total Bacterial Numbers ». Applied and Environmental Microbiology 76, n^o 6 (22 janvier 2010) : 1981–91. http://dx.doi.org/10.1128/aem.01724-09.

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ABSTRACT To assess interchangeability of estimates of bacterial abundance by different epifluorescence microscopy methods, total bacterial numbers (TBNs) determined by most widely accepted protocols were statistically compared. Bacteria in a set of distinctive samples were stained with acridine orange (AO), 4′-6-diamidino-2-phenylindole (DAPI), and BacLight and enumerated by visual counting (VC) and supervised image analysis (IA). Model II regression and Bland-Altman analysis proved general agreements between IA and VC methods, although IA counts tended to be lower than VC counts by 7% on a logarithmic scale. Distributions of cells and latex beads on polycarbonate filters were best fitted to negative binomial models rather than to Poisson or log-normal models. The fitted models revealed higher precisions of TBNs by the IA method than those by the VC method. In pairwise comparisons of the staining methods, TBNs by AO and BacLight staining showed good agreement with each other, but DAPI staining had tendencies of underestimation. Although precisions of the three staining methods were comparable to one another (intraclass correlation coefficients, 0.97 to 0.98), accuracy of the DAPI staining method was rebutted by disproportionateness of TBNs between pairs of samples that carried 2-fold different volumes of identical cell suspensions. It was concluded that the TBN values estimated by AO and BacLight staining are relatively accurate and interchangeable for quantitative interpretation and that IA provides better precision than does VC. As a prudent measure, it is suggested to avoid use of DAPI staining for comparative studies investigating accuracy of novel cell-counting methods.

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Dobnikar, J., D. Haložan, M. Brumen, H. H. von Grünberg et R. Rzehak. « Poisson–Boltzmann Brownian dynamics of charged colloids in suspension ». Computer Physics Communications 159, n^o 2 (mai 2004) : 73–92. http://dx.doi.org/10.1016/j.cpc.2003.10.001.

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Bonechi, F., N. Ciccoli et M. Tarlini. « Quantum Even Spheres S 2n q from Poisson Double Suspension ». Communications in Mathematical Physics 243, n^o 3 (1 décembre 2003) : 449–59. http://dx.doi.org/10.1007/s00220-003-0971-9.

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Charnyi, D. V., et Yu A. Onanko. « ANALYSIS OF ELECTROSTATIC PROPERTIES OF POLYSTYRENE FOAM FILTRATION MEDIA ». Міжвідомчий тематичний науковий збірник "Меліорація і водне господарство", n^o 2 (12 décembre 2019) : 167–74. http://dx.doi.org/10.31073/mivg201902-183.

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The relevance of research. The analysis of the aqueous suspension filtration initial stage through clean polystyrene foam filtration media carried out. Such feature of its work as hydro-sorting is considered. The degree of imbalance and interaction with other electrostatic systems in aqueous suspension determines the layer of potential-forming ions, which is formed around the core of the system. It determines system’s sign and most of the electrical double layer charge. It is usually determined using a physical quantity such as electrostatic or ζ-potential. The aim of this work is to determine the electrostatic properties of polystyrene foam granules and the degree of influence on the process of retaining various nature colloidal particles on their surface when filtering an aqueous suspension through them. Research results. The relationship between the sizes of polystyrene foam granules and the concentrations of electrostatic charge on their surface analyzed. Using the Poison-Boltzmann theory, a relationship between an electrostatic charge and an electric double layer of polystyrene foam granules in aqueous suspension showed. The importance of the ζ-potential researching for controlling of colloidal suspensions filtering process substantiated. The electrostatic properties of different morphology colloids studied. Analysis of research data confirms the hypothesis of a very close connection between the various morphologies colloids ζ-potential magnitude and their electric double layer interaction force with electric double layer of polystyrene foam granules in an aqueous suspension. This means that the polystyrene foam filter “charging” time is closely connected to the values of colloids ζ-potential in the filtered aqueous suspension. Conclusions. The initial filtration stage through clean polystyrene foam media is significantly different from the main stage of filtration due to the electrostatic interaction forces predominance. The time difference of the colloidal crusts complete formation completion on polystyrene foam granules of different diameters is so insignificant that it can be neglected and this time is considered the same for polystyrene foam granules of different diameters. Regardless of the origin nature, the retention intensity of the colloids by polystyrene foam filtration media granules and, consequently, the polystyrene filter “charging” time is directly depends on their z-potential value.

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Wang, Yuanlong, Liangmo Wang, Zheng-dong Ma et Tao Wang. « A negative Poisson's ratio suspension jounce bumper ». Materials & ; Design 103 (août 2016) : 90–99. http://dx.doi.org/10.1016/j.matdes.2016.04.041.

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Irungu, Beatrice Njeri, Lilian C. Koech, Joyce M. Ondicho et Lucia K. Keter. « Quality assessment of selected co-trimoxazole suspension brands marketed in Nairobi County, Kenya ». PLOS ONE 16, n^o 9 (22 septembre 2021) : e0257625. http://dx.doi.org/10.1371/journal.pone.0257625.

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Introduction Quality of medicines in both developed and developing countries is sometimes compromised due to infiltration of counterfeit, substandard or degraded medicines into the markets. It is a public health concern as poor quality medicines endanger public health where patients are exposed to chemical toxins and/or sub-therapeutic doses. This could lead to reduced treatment efficacy and promote development of drug resistance. Co-trimoxazole, a fixed dose combination of sulfamethoxazole and trimethoprim, is a broad spectrum for bacterial diseases and is also used as a prophylaxis for opportunistic infections in HIV infected individuals. This study evaluated quality of selected co-trimoxazole suspension brands marketed in Nairobi County, Kenya. Methods A total of 106 samples were collected, categorized into 15 brands and evaluated for active pharmaceutical ingredient content (API) and pH following United States Pharmacopeia. Assay for API was conducted using High Performance Liquid Chromatography. Results were compared with pharmacopeia references. Visual examination of labels and confirmation of retention status of the brands with Pharmacy and Poisons Board retention register was carried out. Results The samples were primarily of local origin (86.7%). On October 23, 2019, retention status of six of the fifteen brands documented were no longer listed in the Pharmacy and Poisons Board retention register. Of the 106 samples tested 70.6% and 86.8% were compliant with United States Pharmacopeia (USP) specifications for pH and API respectively while 84.0% adhered to packaging and labelling requirements. Conclusion This study has demonstrated that majority of co-trimoxazole suspensions tested were compliant with USP requirements. Additionally, it has provided evidence of poor quality co-trimoxazole medicines that could compromise treatment of infectious diseases in children. This emphasizes the need for regular quality assurance tests to ensure only quality medicines are in the market.

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TEE, SHANG-YOU, P. J. MUCHA, M. P. BRENNER et D. A. WEITZ. « Velocity fluctuations in a low-Reynolds-number fluidized bed ». Journal of Fluid Mechanics 596 (17 janvier 2008) : 467–75. http://dx.doi.org/10.1017/s0022112007009652.

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The velocity fluctuations of particles in a low-Reynolds-number fluidized bed have important similarities and differences with the velocity fluctuations in a low-Reynolds-number sedimenting suspension. We show that, like sedimentation, the velocity fluctuations in a fluidized bed are described well by the balance between density fluctuations due to Poisson statistics and Stokes drag. However, unlike sedimentation, the correlation length of the fluctuations in a fluidized bed increases with volume fraction. We argue that this difference arises because the relaxation time of density fluctuations is completely different in the two systems.

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Bhuiyan, L. B., et C. W. Outhwaite. « Symmetric Poisson–Boltzmann structural properties near the gas–liquid point of a de-ionized colloidal suspension ». Physica A : Statistical Mechanics and its Applications 339, n^o 3-4 (août 2004) : 199–206. http://dx.doi.org/10.1016/j.physa.2004.03.031.

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Gommes, Cedric J., Yang Jiao, Anthony P. Roberts et Dominique Jeulin. « Chord-length distributions cannot generally be obtained from small-angle scattering ». Journal of Applied Crystallography 53, n^o 1 (1 février 2020) : 127–32. http://dx.doi.org/10.1107/s1600576719016133.

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The methods used to extract chord-length distributions from small-angle scattering data assume a structure consisting of spatially uncorrelated and disconnected convex regions. These restrictive conditions are seldom met for a wide variety of materials such as porous materials and semicrystalline or phase-separated copolymers, the structures of which consist of co-continuous phases that interpenetrate each other in a geometrically complex way. The significant errors that would result from applying existing methods to such systems are discussed using three distinct models for which the chord-length distributions are known analytically. The models are a dilute suspension of hollow spheres, the Poisson mosaic and the Boolean model of spheres.

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Chovnyuk, Y., A. Priymachenko, P. Cherednichenko et N. Shudra. « MODELING AND OPTIMIZATION OF THE PROCESSES OF MOVEMENT AND ACCELERATION OF THE OVERHEAD CRANE TROLLEY IN THE MODE OF DAMPING UNCONTROLLED LOAD OSCILLATIONS ». Modern construction and architecture, n^o 4 (28 juin 2023) : 33–40. http://dx.doi.org/10.31650/2786-6696-2023-4-33-40.

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The paper deals with the modeling and optimization of the processes of movement and acceleration of a bridge crane trolley in the mode of damping uncontrolled oscillations of the load. For the dynamic system of a flat pendulum with vibration damping, which describes the oscillations of a bridge crane load on a flexible rope suspension in a separate vertical plane, it is proposed to use third-order time splines that model the motion and acceleration of the load suspension point in the horizontal direction of the trolley's movement. To determine the time dependence of the angle of deviation of the crane from the gravitational vertical, it is proposed to use the methods of classical calculus of variations (Euler-Poisson equation), which allow optimizing (minimizing) the value of this angle in the process of accelerating a trolley with a load suspended from the ropes of an overhead crane. An analytical solution to the problem of damping residual uncontrollable oscillations of the overhead crane load, which usually occur after full acceleration or braking of the load suspension point on the trolley, is obtained. To derive the dependencies, an analytical approach was used to calculate the value of the angle of deviation of the overhead crane's cargo rope from the gravitational vertical, depending on the acceleration and displacement of the load suspension point. The problem of loosening of a load moved by an overhead crane is considered and solved in a new way that allows to completely avoiding pendulum spatial oscillations of the load on a rope suspension. The mathematical apparatus of linear algebra (Kramer's rule, in particular) is used, which allows us to establish analytically the law of time motion of a rope with a load, the angle of deviation of which from the vertical takes minimum values in the process of acceleration of the cargo trolley.

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Tukmakov, D. A. « One-dimensional continuum finite-difference model of the dynamics of a dusty medium in aerodynamic, electric and gravitational fields ». Journal of Physics : Conference Series 2270, n^o 1 (1 mai 2022) : 012016. http://dx.doi.org/10.1088/1742-6596/2270/1/012016.

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Abstract This paper presents a mathematical model of the dynamics of a gas suspension under the action of an aerodynamic field, an electric field, and a gravitational field. The continuum model is used to describe the dynamics of the disperse component. The intercomponent momentum exchange included the aerodynamic drag force, the dynamic Archimedes force, and the added mass force. The Coulomb force acting on dispersed particles was taken into account. The model assumes the solution of the equations of conservation of “average density”, momentum and energy for the dispersed phase. The electric field was described by the Poisson equation. The equations of the mathematical model were supplemented with boundary conditions. The equations of mechanics were integrated by explicit finite-difference method of McCormack.

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Algar, D., et R. I. Brazell. « A bait-suspension device for the control of feral cats ». Wildlife Research 35, n^o 5 (2008) : 471. http://dx.doi.org/10.1071/wr07167.

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The use of poison baits is an effective method for controlling feral cats. However, take of baits by non-target animals may place those animals at risk of poisoning and also reduces the availability of baits to the target animal, feral cats. Therefore, techniques that reduce non-target take of baits are desirable. Earlier trials have suggested that suspending baits might prevent most non-target animals from removing the baits while maintaining their attractiveness and availability to feral cats. This paper assesses the efficacy of a bait-suspension device to provide a relatively simple means of controlling feral cats (across age and sex classes). In addition, it confirms the high target specificity of the bait-delivery mechanism on Australia’s Christmas Island, where non-target species would have posed a problem with baits laid on the ground. The technique may have potential application on other islands where similar non-target species are threatened by baiting programs or at specific sites on the mainland where aerial or on-track deployment of feral cat baits may pose an unacceptable risk to non-target species.

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Langlois, C., et H. Sloterdijk. « Contamination du lac Saint-Pierre (fleuve Saint-Laurent) par certains polluants organiques et inorganiques ». Revue des sciences de l'eau 2, n^o 4 (12 avril 2005) : 659–79. http://dx.doi.org/10.7202/705048ar.

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L'étude s'inscrit dans le cadre d'un programme de surveillance de la dispersion des substances toxiques dans le fleuve Saint-Laurent. Elle vise à identifier la nature et le cheminement des substances toxiques dans différents compartiments du lac Saint-Pierre. D'une superficie totale de plus de 400 km2, ce lac est un élargissement du fleuve et son bassin de drainage inclut la région métropolitaine de Montréal et la région inter-nationale des Grands lacs. L'échantillonnage a porté sur l'eau, les matières en suspension, les sédiments de fond, les poissons adultes (entiers, chairs, foie, oeufs et gonades) et les poissons juvéniles (âge 0+). Des analyses chimiques ont été effectuées pour les métaux, les pesticides organochlorés, les biphényles polychlorés (PCB), les hydrocarbures aromatiques polycycliques (PAH) et les chlorobenzènes. Les résultats indiquent que la contamination du milieu aquatique par les substances toxiques est très significative. Les contaminants majeurs retrouvés dans les divers compartiments sont l'arsenic, le mercure, le plomb, les biphényles polychlorés (PCB) et les différentes formes de DDT. Les concentrations excèdent fréquemment les critères de qualité pour le mercure dans les chairs de poissons, le plomb dans l'eau et les sédiments et les PCB dans plusieurs compartiments analysés. Plusieurs pesticides organochlorés ont été détectés dans l'eau, grâce à la technique d'échantillonnage à grand volume. Cette technique permet d'estimer 1a concentration de fond et le bilan massique annuel d'un polluant. Les poissons entiers et le foie de lottes constituent par ailleurs des indicateurs de choix de la présence et de l'étendue de la contamination par les substances toxiques bioaccumulables, alors que les sédiments de fond et les poissons juvéniles permettent d'étudier leur répartition spatiale. Sauf pour le mercure, les concentrations dans les chairs sont un mauvais indicateur de la contamination du milieu; la moyenne et la variabilité des teneurs en PCB et pesticides organochlorés y sont très faibles.

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Wang, Yuanlong, Liangmo Wang, Zheng-dong Ma et Tao Wang. « Finite element analysis of a jounce bumper with negative Poisson’s ratio structure ». Proceedings of the Institution of Mechanical Engineers, Part C : Journal of Mechanical Engineering Science 231, n^o 23 (6 janvier 2017) : 4374–87. http://dx.doi.org/10.1177/0954406216665415.

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Jounce bumpers in automotive suspension are key components that can improve the noise, vibration, and harshness performance of entire vehicle. Traditional jounce bumper made of polyurethane usually cannot satisfy the mechanical performances required by noise, vibration, and harshness optimization. In addition, the application of hyperelastic material influenced the efficiency and reliability of numerical calculations of polyurethane jounce bumper. In this paper, an engineering negative Poisson’s ratio structure was introduced and applied on the jounce bumper. The negative Poisson’s ratio jounce bumper can be mainly defined by few structure parameters. The finite element analysis of the negative Poisson’s ratio jounce bumper was conducted applied explicit method. The influences of loading velocity and material densities on computational time and numerical results were researched. The results indicated that enlargements of material densities and loading velocity can improve the computational efficiency and have limited influence on reliability. Furthermore, a negative Poisson’s ratio jounce bumper prototype was manufactured and tested to verify the numerical results. It was proved that the finite element analysis of the negative Poisson’s ratio jounce bumper was reliable both in load–displacement curve and deformation shapes. Compared to the traditional jounce bumper, the negative Poisson’s ratio jounce bumper can achieve similar mechanical behavior but with a smoother load–displacement curve, which is beneficial to the vehicle’s noise, vibration, and harshness performance.

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Dailloux, M., C. Henry et D. Terver. « Observation et étude expérimentale de mycobactéries atypiques en aquariums d'eau douce et d'eau de mer ». Revue des sciences de l'eau 5, n^o 1 (12 avril 2005) : 69–82. http://dx.doi.org/10.7202/705121ar.

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L'eau des aquariums est source de Mycobactéries atypiques qui peuvent être pathogènes pour l'homme et les poissons. Une étude a été réalisée à l'aquarium du Musée de Zoologie de Nancy. La recherche de Mycobactéries a été effectuée dans 40 aquariums équipés de lampes germicides à UV : 11 bassins étaient alimentés en eau douce et 29 en eau de mer. Deux aquariums non équipés de système de désinfection ont également été analysés, les propriétaires de ces derniers ayant présenté un granulome cutané à M. marinum. L'action des UV sur M. marinum en suspension dans l'eau a été testée expérimentalement dans des bassins d'eau douce peuplés de Cichlidés. Pour chaque aquarium, un échantillon de 250 ml a été prélevé. Les cultures après décontamination au lauryl sulfate de soude ont été réalisées sur milieu de Loewenstein. Les résultats indiquent que, quel que soit l'aquarium, la présence de mycobactéries est constante. L'isolement des mycobactéries peut être gêné par la présence d'une flore bactérienne ou fongique importante (≥ 103 U.F.C./ml). Les espèces les plus fréquemment isolées sont M. gordonae et M. fortuitum ; M. kansasii et M. marinum ont rarement été isolées (6140 aquariums). Différents facteurs peuvent intervenir sur la sélection des espèces. La salinité de l'eau limite le développement de certaines espèces, alors qu'elle permet la croissance de M. fortuitum. Dans notre étude, la température de l'eau n'a pas été un facteur sélectif. L'utilisation de lampes UV limite le nombre de Mycobactéries. Dans les bassins expérimentaux, les radiations UV se sont révélées très actives sur M. marinum en présence ou en l'absence de poissons. A l'inverse de M. gordonae, M. fortuitum est rarement isolée en présence d'UV. Un nombre important de poissons par aquarium augmente la flore bactérienne et mycobactérienne. La prévention des infections à Mycobactéries atypiques chez l'homme comme chez les poissons devrait pouvoir être assurée par des mesures d'hygiène élémentaire.

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Li, Zhiqi, Duowen Chen, Candong Lin, Jinyuan Liu et Bo Zhu. « Particle-Laden Fluid on Flow Maps ». ACM Transactions on Graphics 43, n^o 6 (19 novembre 2024) : 1–12. http://dx.doi.org/10.1145/3687916.

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We propose a novel framework for simulating ink as a particle-laden flow using particle flow maps. Our method addresses the limitations of existing flow-map techniques, which struggle with dissipative forces like viscosity and drag, thereby extending the application scope from solving the Euler equations to solving the Navier-Stokes equations with accurate viscosity and laden-particle treatment. Our key contribution lies in a coupling mechanism for two particle systems, coupling physical sediment particles and virtual flow-map particles on a background grid by solving a Poisson system. We implemented a novel path integral formula to incorporate viscosity and drag forces into the particle flow map process. Our approach enables state-of-the-art simulation of various particle-laden flow phenomena, exemplified by the bulging and breakup of suspension drop tails, torus formation, torus disintegration, and the coalescence of sedimenting drops. In particular, our method delivered high-fidelity ink diffusion simulations by accurately capturing vortex bulbs, viscous tails, fractal branching, and hierarchical structures.

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FRAT, L., S. GUERIN RECHDAOUI, R. RICHOUX, E. GARCIA-GONZALEZ, R. KRIMOU, I. QUINIO, C. FISSON et al. « Adaptation du fonctionnement de la station d’épuration Seine Aval (Yvelines) à la suite de l’incendie de l’unité de clarifloculation en 2019 et conséquences sur la Seine ». Techniques Sciences Méthodes 5 (22 mai 2023) : 103–18. http://dx.doi.org/10.36904/tsm/202305103.

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Seine Aval (SAV) est la plus grande usine de traitement des eaux usées (STEU) européenne. Le 3 juillet 2019, un incendie s’est déclaré au niveau de l’unité de clarifloculation dédiée à l’élimination du phosphore et d’une partie des matières en suspension (MES). En conséquence, la capacité hydraulique de traitement de l’usine a été diminuée et le phosphore ne dispose plus d’un traitement dédié. Face à cette situation, des solutions techniques ont été mises en œuvre sur l’usine pour retrouver des performances de traitement compatibles avec la préservation du milieu naturel. Afin d’apprécier les bénéfices de ces solutions techniques, trois périodes de fonctionnement ont été identifiées correspondant à (1) la période post-incident et avant le déploiement des solutions techniques, (2) la mise en place de la première solution technique (injection du chlorure ferrique FeCl3 en décantation primaire) et (3) la mise en place de la seconde solution technique (remise en route des bassins à boues activées). Les résultats montrent que l’impact du changement de fonctionnement de SAV est limité hors phosphore. En comparaison à la période antérieure à l’incendie, les performances de traitement restent globalement équivalentes par temps sec et logiquement plus faibles par temps de pluie au regard de la réduction de la capacité de traitement. Le suivi de la qualité physico-chimique et biologique de la Seine à l’aval proche (Poissy) et éloigné (Poses) de l’usine a démontré la résilience de la Seine face à ces apports additionnels. Aucune efflorescence algale associée à une désoxygénation n’a été observée sur la période étudiée en Seine. De plus, la qualité bactériologique de la Seine (E. coli et entérocoques intestinaux) est restée équivalente à celle des années précédentes. Enfin, il n’a pas été observé d’impact durable sur les populations piscicoles avec une diversité de poissons retrouvée dès deux semaines après l’incendie.

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Lankarani, Hamid M. « A Poisson-Based Formulation for Frictional Impact Analysis of Multibody Mechanical Systems With Open or Closed Kinematic Chains ». Journal of Mechanical Design 122, n^o 4 (1 octobre 1999) : 489–97. http://dx.doi.org/10.1115/1.1319160.

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Analysis of frictional impact in a multibody mechanical system requires a friction model capable of correct detection of all possible impact modes such as sliding, sticking, and reverse sliding. Conventional methods for frictional impact analysis have either shown energy gain or not developed for jointed mechanical system, and especially not for closed-chain multibody systems. This paper presents a general formulation for the analysis of impact problems with friction in both open- and closed-loop multibody mechanical systems. Poisson’s hypothesis is used for the definition of the coefficient of restitution, and thus the energy gains inherent with the use of Newton’s hypothesis are avoided. A canonical form of the system equations of motion using Cartesian coordinates and Cartesian momenta is utilized. The canonical momentum-balance equations are formulated and solved for the change in the system Cartesian momenta using an extension of Routh’s graphical method for the normal and tangential impulses. The velocity jumps are calculated by balancing the accumulated system momenta during the contact period. The formulation is shown to recognize all modes of impact; i.e., sliding, sticking, and reverse sliding. The impact problems are classified into seven types, and based on the pre-impact system configuration and velocities, expressions for the normal and tangential impulses are derived for each impact type. Examples including the tip of a double pendulum impacting the ground with some experimental verification, and the impact of the rear wheel and suspension system of an automobile executing a very stiff bump are analyzed with the developed formulation. [S1050-0472(00)02304-7]

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Tukmakov, D. A. « Numerical study of the velocity distribution of the disperse component in the generation of a gas suspension flow by an electric field ». Journal of Physics : Conference Series 2379, n^o 1 (1 décembre 2022) : 012022. http://dx.doi.org/10.1088/1742-6596/2379/1/012022.

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Abstract This paper presents a self-consistent mathematical model of the dynamics of an electrically charged dusty medium. The carrier medium was described as a viscous, compressible and heat-conducting gas. The simulated flow is self-consistent, the parameters of each of the mixture components are determined by changing the parameters of other components. The mathematical model took into account intercomponent momentum exchange and heat transfer between the dispersed component of the mixture and the gas. The equations of the mathematical model are supplemented with boundary conditions. The mixture dynamics equations and the Poisson equation describing the electric field were solved by a numerical finite-difference method. The channel is divided into two parts, in one part of the channel there is a homogeneous gas, in the other part of the channel there is a gas containing electrically charged particles. Under the action of an electric field, the particles of the disperse component begin to move, and a gas flow is formed. This paper presents the results of calculations of the physical fields of an electrically charged dispersed suspension.

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Le Louarn, H., et G. Bertru. « Influence des élevages extensifs en étang sur les rivièrese ». Revue des sciences de l'eau 4, n^o 3 (12 avril 2005) : 315–27. http://dx.doi.org/10.7202/705102ar.

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Si de nombreux travaux ont porté sur l'influence des piscicultures intensives sur les rivières, on s'est peu intéressé aux conséquences des nombreuses créations de plan d'eau sur le milieu. Le but de cet article est de présenter en s'appuyant sur des exemples précis les différentes modifications apportées sur le milieu par une surface en eau d'élevage extensif. Les aspects hydrologiques sont peu importants. Les changements physico-chimiques ont par contre de nombreuses conséquences, directes et indirectes : - la température : le réchauffement estival agit sur les réactions chimiques, l'équilibre des biocénoses, la pathologie des poissons, - le potentiel hydrogène, très variable en cas de faible dureté, - l'oxygénation, liée à la température dont le déficit agit directement sur la faune pisciaire, - la fertilisation par l'azote et les phosphates, - les matières en suspension : action surtout manifeste lors des vidanges, directe sur le colmatage des frayères, indirecte sur la structure des communautés floristique et faunistique. Le repeuplement des rivières par les poissons d'étang est fréquent. Les conséquences vont du déséquilibre faunistique à l'introduction d'espèces indésirables ou nuisibles. Dans l'ensemble, on note un impact négatif sur les eaux courantes, particulièrement sur les rivières à salmonidés (1ère catégorie). Sur les cours d'eau de 2e catégorie, l'impact est toujours plus faible et on peut noter une action bénéfique due au lagunage.Une hiérarchisation des influences est donnée en tenant compte du type de plan d'eau et de son mode de gestion.

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Quemeneur, F., P. Jaouen, J. P. Maleriat, J. P. Schlumpf, L. Bon et E. Lebegue. « Techniques à membranes appliquées à l'élimination des matières en suspension dans un circuit semi-fermé d'aquaculture ». Revue des sciences de l'eau 14, n^o 1 (12 avril 2005) : 21–34. http://dx.doi.org/10.7202/705406ar.

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Les piscicultures en circuits semi-fermés sont confrontées au problème de l'élimination permanente des matières en suspension (M.E.S.) et des substances azotées. Les procédés conventionnels utilisés pour retenir les M.E.S. (décantation, hydrocyclones, filtres mécaniques à tambour rotatif, filtration gravitaire) ne donnent par entière satisfaction. Par contre, la filtration sur membranes permet d'arrêter en totalité les particules en suspension et les bactéries. On montre d'abord que les teneurs en M.E.S. et leurs répartitions granulométriques mesurées sur des échantillons prélevés en bassins d'aquaculture varient avec la taille des poissons et l'heure du prélèvement et on met en évidence la présence en nombre important de particules submicroniques. Différents essais de filtration sur membranes sont ensuite présentés : - d'une part, avec des membranes d'ultrafiltration capillaires à peau interne utilisées en potabilisation des eaux : on examine l'influence des paramètres hydrodynamiques (pression transmembranaire, vitesse de recirculation) afin de rechercher les conditions optimales de fonctionnement. Le flux de perméat ne dépasse pas dans le meilleur des cas 100 l.h-1.m-2. - d'autre part, avec des membranes de microfiltration organiques planes en fluorure de polyvinylidène (PVDF) et tubulaires en céramique. Les flux obtenus avec les membranes organiques sont de l'ordre de 250 l.h-1.m-2 Dans tous les cas, la rétention des M.E.S. est totale. Cependant l'estimation de l'investissement et des coûts de fonctionnement pour une pisciculture en circuit fermé de taille industrielle conduit à des prix trop élevés pour que l'utilisation des membranes dans ce domaine soit à ce jour économiquement envisageable.

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Wang, Yuanlong, Wanzhong Zhao, Guan Zhou, Qiang Gao et Chunyan Wang. « Suspension mechanical performance and vehicle ride comfort applying a novel jounce bumper based on negative Poisson's ratio structure ». Advances in Engineering Software 122 (août 2018) : 1–12. http://dx.doi.org/10.1016/j.advengsoft.2018.04.001.

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Prokes, Bela. « Some laboratory blood indicators in tractor drivers exposed to pesticides ». Zbornik Matice srpske za prirodne nauke, n^o 119 (2010) : 97–104. http://dx.doi.org/10.2298/zmspn1019097p.

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Pesticides represent group of extremely different compounds or mixed compounds. They are produced in the form of powder for direct application, powder for suspension, concentrated suspension, concentration of emulsion, and in other forms as well. Influence of pesticides to exposed workers mainly depends on technology of pesticide application use. All poisons, just like pesticides that come in organism in some way and reach the location of their metabolism, accumulation in the body or extraction must get there through blood. Pesticides influence stem cells in bone marrow, then maturation process of blood elements and can damage mature blood cells in blood circulation. The sample encompassed 142 tractor drivers employed in state agricultural unions who were exposed to pesticides during their work. Concerning annual and daily exposure to pesticides in examined persons is determined that daily extent ranged from 3 to 12 hours and annual from 5 to 125 days, 60.93 in average. In the paper are analyzed following blood count parameters: erythrocytes, hemoglobin, leucocytes and thrombocytes The aim of the paper is to investigate whether pesticides influence changed blood count of tractor drivers exposed to pesticides during their work. Analysis of obtained results indicates that exposure to pesticides, like in examined group of workers, has not influenced damage in any of investigated blood count parameter.

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Hartmann, S., S. Augustin, T. Clauss, J. Voigtländer, D. Niedermeier, H. Wex et F. Stratmann. « Immersion freezing of ice nucleating active protein complexes ». Atmospheric Chemistry and Physics Discussions 12, n^o 8 (21 août 2012) : 21321–53. http://dx.doi.org/10.5194/acpd-12-21321-2012.

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Abstract. Biological particles, e.g. bacteria and their Ice Nucleating Active (INA) protein complexes, might play an important role for the ice formation in atmospheric mixed-phase clouds. Therefore, the immersion freezing behavior of INA protein complexes generated from a SnomaxTM solution/suspension was investigated as function of temperature in a range of −5 °C to −38 °C at the Leipzig Aerosol Cloud Interaction Simulator (LACIS). The immersion freezing of droplets containing small numbers of INA protein complexes occurs in a temperature range of −7 °C and −10 °C. The experiments performed in the lower temperature range, where all droplets freeze which contain at least one INA protein complex, are used to determine the average number of INA protein complexes present, assuming that the INA protein complexes are Poisson distributed over the droplet ensemble. Knowing the average number of INA protein complexes, the heterogeneous ice nucleation rate and rate coefficient of a single INA protein complex is determined by using the newly-developed CHESS model (stoCHastic model of idEntical poiSSon distributed ice nuclei). Therefore, we assume the ice nucleation process to be of stochastic nature, and a parameterization of the INA protein complex's nucleation rate. Analyzing the results of immersion freezing experiments from literature (SnomaxTM and Pseudomonas syringae bacteria), to results gained in this study, demonstrates that first, a similar temperature dependence of the heterogeneous ice nucleation rate for a single INA protein complex was found in all experiments, second, the shift of the ice fraction curves to higher temperatures can be explained consistently by a higher average number of INA protein complexes being present in the droplet ensemble, and finally the heterogeneous ice nucleation rate of one single INA protein complex might be also applicable for intact Pseudomonas syringae bacteria cells. The results obtained in this study allow a new perspective on the interpretation of immersion freezing experiments considering INA protein complexes and the derived simple parameterization of the heterogeneous ice nucleation rate can be used in cloud resolving models for studying the effect of bacteria induced ice nucleation.

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