Articoli di riviste: "Gas-particles"

1

Dac Dien, Nguyen, Luong Huu Phuoc, Do Duc Tho, Nguyen Anh Phuc Duc, Nguyen Duc Chien e Dang Duc Vuong. "HYDROTHERMAL SYNTHESIS AND NH3 GAS SENSING PROPERTY OFWO3 NANO PARTICLES". Journal of Science, Natural Science 60, n. 7 (2015): 68–74. http://dx.doi.org/10.18173/2354-1059.2015-0034.

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KASHU, SEIICHIRO. "Gas deposition of ultrafine particles." SHINKU 35, n. 7 (1992): 649–53. http://dx.doi.org/10.3131/jvsj.35.649.

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3

Sychevskii, V. A. "Gas-detonation processing of particles". High Temperature 46, n. 5 (23 settembre 2008): 686–94. http://dx.doi.org/10.1134/s0018151x08050143.

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Burde, Jan-Philipp, Thomas Wilhelm, Jochen Kuhn e Stephan Lück. "“Particles” simuliert ein ideales Gas". Physik in unserer Zeit 45, n. 1 (gennaio 2014): 46–47. http://dx.doi.org/10.1002/piuz.201490007.

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5

x, Shubham. "CFD DEM Study of Gas Solid Fluidized Bed for Non Spherical Particles". International Journal of Science and Research (IJSR) 12, n. 7 (5 luglio 2023): 447–51. http://dx.doi.org/10.21275/sr23701235635.

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GILBERTSON, M. A., e I. EAMES. "Segregation patterns in gas-fluidized systems". Journal of Fluid Mechanics 433 (25 aprile 2001): 347–56. http://dx.doi.org/10.1017/s0022112001003950.

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The formation of segregation patterns in initially homogeneous, fluidized, binary mixtures of particles has been studied. The adjustment of the bed depends on the proportions of fine and coarse particles in the mixture and the gas flow rate relative to the minimum fluidization velocities of the two components. The particles are immobile until the gas flow rate is sufficiently large to fluidize the mixture of particles. When the gas flow rate exceeds this critical value, alternating vertical bands of coarse and fine particles form. At a second critical gas velocity this pattern breaks down and the more familiar pattern of a mixed horizontal band on top of a layer of coarse particles forms. A phase diagram, constructed from experimental observations, shows the conditions for which each of these regimes exists. Its structure is explained in terms of the fluidization and consequent mobility of the mixture components. When horizontal bands are present, the thickness of the lower layer of coarse particles decreases with increasing gas flow rate depending on the proportion of fine particles in the bed. This, and its development, can be understood by analogy with the sedimentation of particles through a turbulent fluid. The experiments imply that the efficiency of mixing by the bubbles in the fluidized bed is very much less than that expected from gas bubbles in a liquid.

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Wooldridge, Margaret S. "Gas-phase combustion synthesis of particles". Progress in Energy and Combustion Science 24, n. 1 (gennaio 1998): 63–87. http://dx.doi.org/10.1016/s0360-1285(97)00024-5.

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Bischof, Oliver F., e Henna Tuomenoja. "Measurement of blow-by gas particles". MTZ worldwide 64, n. 7-8 (luglio 2003): 18–21. http://dx.doi.org/10.1007/bf03227601.

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9

Epstein, Norman, e Pratap P. Chandnani. "Gas spouting characteristics of fine particles". Chemical Engineering Science 42, n. 12 (1987): 2977–81. http://dx.doi.org/10.1016/0009-2509(87)87069-0.

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10

Wang, Shining, Jian Xu, Weisheng Wei, Gang Shi, Xiaojun Bao, H. T. Bi e C. Jim Lim. "Gas spouting hydrodynamics of fine particles". Canadian Journal of Chemical Engineering 78, n. 1 (febbraio 2000): 156–60. http://dx.doi.org/10.1002/cjce.5450780120.

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Zhumaev, M. R. "INVARIANT RELATIVISTIC THEORY OF IDEAL GAS". Eurasian Physical Technical Journal 18, n. 4 (38) (21 dicembre 2021): 88–101. http://dx.doi.org/10.31489/2021no4/88-101.

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The purpose of this study is to develop an original theory of a relativistic ideal gas and to prove the validity of the postulate of the special theory of relativity for the characteristic (i.e., arithmetic mean, root-mean-square) velocities of particles of a relativistic ideal gas even in the massless limit. In this work, the following original methods are used for the first time in the theory of a relativistic ideal gas: the method of nonlinear transformation to prove of the distribution function to find the distribution function of the velocities of particles of a relativistic ideal gas; the equation of state of a relativistic ideal gas was first obtained by averaging the relativistic - invariant components of the energy - momentum tensor of a system of noninteracting particles, i.e. ideal gas by the distribution function of the velocities of their particles. The uniqueness and definiteness of the distribution function of the velocities of the particles of a relativistic ideal gas are proved on the basis of the well-known relativistic invariance of the distribution function. For the first time, expressions were obtained for the arithmetic mean and mean square velocities of particles of a relativistic ideal gas. For the first time, a fundamental conclusion is made about the validity of the postulates of the special theory of relativity for the characteristic velocities of particles of a relativistic ideal gas. An equation of state for a relativistic ideal gas is obtained, which relates its pressure, average energy density and temperature.

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Lv, Hua, Zhongqi Wang, Yunming Zhang e Jianping Li. "Initial Moving Mechanism of Densely-Packed Particles Driven by a Planar Shock Wave". Shock and Vibration 2021 (17 aprile 2021): 1–12. http://dx.doi.org/10.1155/2021/8867615.

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The initial moving mechanism of densely packed particles driven by shock waves is unclear but vital for the next accurate calculation of the problem. Here, the initial motion details are investigated experimentally and numerically. We found that before particles show notable motion, shock waves complete reflection and transmission, and stress waves propagate downstream on particle skeleton. Due to the particle stress wave, particles successively accelerate and obtain an axial velocity of 6–8 m/s. Then, the blocked gas pushes the upstream particles integrally to move downstream, while the gas flow in the pores drags the downstream particles to separate dramatically and accelerate to the velocity of 60–70 m/s. This gas push-drag dual mechanism transforms densely packed particles into a dense gas-particle cloud, which behaves as the expansion phenomena of the dense particles.

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Tomanovic, Ivan, Srdjan Belosevic, Aleksandar Milicevic, Nenad Crnomarkovic e Dragan Tucakovic. "Numerical tracking of sorbent particles and distribution during gas desulfurization in pulverized coal-fired furnace". Thermal Science 21, suppl. 3 (2017): 759–69. http://dx.doi.org/10.2298/tsci160212196t.

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Furnace sorbent injection for sulfur removal from flue gas presents a challenge, as the proper process optimization is of crucial importance in order to obtain both high sulfur removal rates and good sorbent utilization. In the simulations a two-phase gas-particle flow is considered. Pulverized coal and calcium-based sorbent particles motion is simulated inside of the boiler furnace. It is important to determine trajectories of particles in the furnace, in order to monitor the particles heat and concentration history. A two-way coupling of the phases is considered ? influence of the gas phase on the particles, and vice versa. Particle-to-particle collisions are neglected. Mutual influence of gas and dispersed phase is modeled by corresponding terms in the transport equations for gas phase and the equations describing the particles turbulent dispersion. Gas phase is modeled in Eulerian field, while the particles are tracked in Lagrangian field. Turbulence is modeled by the standard k-? model, with additional terms for turbulence modulation. Distribution, dispersion and residence time of sorbent particles in the furnace have a considerable influence on the desulfurization process. It was shown that, by proper organization of process, significant improvement considering emission reduction can be achieved.

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Nguyen, Q. P. P., Peter K. Currie e P. S. R. S. R. Bouzanga. "The Effect of Gas on the Injectivity of Particles in Sandstone". SPE Journal 16, n. 01 (11 novembre 2010): 95–103. http://dx.doi.org/10.2118/121637-pa.

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Summary Many operations involve the injection of fluids into the formation around a well. In many cases, the fluids contain colloidal particles, either initially present or introduced during the operation through dirt or naturally occurring particles. Therefore, all injection schemes potentially suffer from injectivity decline. This injectivity decline is caused by clogging of the formation by particles, forming an external filter cake on the surface of the formation and blocking the pores inside the formation. This paper reports on the effects of gas on the injectivity of particles in sandstone. Experiments were performed in which water containing micron-sized particles (hematite) was injected into sandstone cores with or without small gas bubbles (nitrogen) present in the water. The position and amount of particle deposition could be determined both visually and by chemical analysis. It was found that the presence of gas reduces the external filter cake formed on the inlet surface of the core. Also, with gas, the particles penetrate deeper inside the core and more particles pass through the core and are detected in the effluent stream. The same effects are enhanced when the mixture of gas bubbles and water is replaced by foam. This suggests that the presence of gas/water interfaces has a major influence on the retention of particles in the sandstone. Possible mechanisms are discussed. The pressure drop across the core when gas or foam is present is initially higher than in an identical test without gas because of relative permeability effects or foam-flow resistance. However, because fewer particles are retained, ultimately the pressure drop is significantly less when gas is present. This effect may be significant in injection operations involving foam and offers ways to mitigate injectivity loss.

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Xu, Zhongyi, Shaohua Gu, Daqian Zeng, Bing Sun e Liang Xue. "Numerical Simulation of Sulfur Deposit with Particle Release". Energies 13, n. 6 (23 marzo 2020): 1522. http://dx.doi.org/10.3390/en13061522.

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Sulfur deposition commonly occurs during the development of a high-sulfur gas reservoirs. Due to the high gas flow velocity near the wellbore, some of the deposited sulfur particles re-enter the pores and continue to migrate driven by the high-speed gas flow. The current mathematical model for sulfur deposition ignores the viscosity between particles, rising flow caused by turbulence, and the corresponding research on the release ratio of particles. In order to solve the above problems, firstly, the viscous force and rising force caused by turbulence disturbance are introduced, and the critical release velocity of sulfur particles is derived. Then, a release model of sulfur particles that consider the critical release velocity and release ratio is proposed by combining the probability theory with the hydrodynamics theory. Notably, based on the experimental data, the deposition ratio of sulfur particles and the damage coefficient in the sulfur damage model are determined. Finally, a comprehensive particle migration model considering the deposition and release of sulfur particles is established. The model is then applied to the actual gas wells with visible sulfur deposition that target the Da-wan gas reservoir, and the results show that the model correctly reflects flow transport during the process of sulfur deposition in porous media. In addition, through the numerical simulation experiments, it was found that considering the release of sulfur particles reduces the saturation of sulfur particles within a specific range around the well and improve the reservoir permeability in this range. From the perspective of gas production rate, the release of sulfur particles has a limited effect on the gas production rate, which is mainly due to the sulfur particle release being limited, having only a 5 m range near the wellbore area, and thus the amount of gas flow from the unaffected area is basically unchanged.

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Alquaity, Awad B. S., e Bekir S. Yilbas. "Investigation of Spatter Trajectories in an SLM Build Chamber under Argon Gas Flow". Metals 12, n. 2 (16 febbraio 2022): 343. http://dx.doi.org/10.3390/met12020343.

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Spatter particles ejected from the melt pool during selective laser melting processes can get redeposited on the build plate region and impact final part quality. Although an inert gas flow is used to purge the spattered particles away from the build plate region, some of the spatter particles get redeposited on the plate region leading to increased porosity and surface roughness. In this regard, the current study focuses on the numerical modeling of the interactions between the inert gas flow and spatter particles by using the discrete phase model. A Renishaw AM250 build chamber is used as the base geometry and the flow field within the build chamber is evaluated for various inert gas flow rates and nozzle diameters of 6 mm and 12 mm. For the first time, spatter trajectories are tracked at specific spatter diameters and ejection angles to pinpoint the influence of drag and gravitational forces on the evolution of spatter trajectories. The findings reveal that the spatter particles between 120 and 180 μm diameter travel beyond the build plate only at specific gas ejection angles and gas flow rates (≥750 L/min). Reducing the nozzle diameter to 6 mm increases the inert gas flow velocity in the build region and enhances the range of spatter particles. New correlations are proposed to relate the range of particles and inert gas flow rates, which can be used to identify the spatter diameters, ejection angles, and inert gas flow rates required to transport the particles beyond the sensitive build plate region.

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17

Medvedev, Yu D. "On gas productivity of elongated cometary nucleus in rotation". International Astronomical Union Colloquium 173 (1999): 211–16. http://dx.doi.org/10.1017/s0252921100031432.

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AbstractDynamics and distribution of dust and ice particles in the cometary head is investigated for the elongated nucleus in rotation. Three kinds of particles are considered: the dust particles, the ones with volatile fraction and the ice ones. The particles with volatile fraction and sublimated from larger particles are in the cometary head for rather a long time and some abundance of particles and gas can be observed in the region of the head facing the Sun.To estimate the influence of dust density on the gas productivity a numerical simulation was done. The results show that the presence of grains in the coma causes the effects of damping and time delay for gas productivity of an elongated nucleus.

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Yokoyama, Seiji, e Katsuyoshi Saito. "Synthesis of Ultrafine Particles of Iron and Iron Nitride by Evaporation of Iron in Gas Mixtures of Argon and Ammonia or Argon and Nitrogen". Materials Science Forum 561-565 (ottobre 2007): 1047–50. http://dx.doi.org/10.4028/www.scientific.net/msf.561-565.1047.

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As a series of fundamental study on the gas evaporation method, a levitation-melted iron was evaporated in the gas mixtures of argon + ammonia, argon + nitrogen to synthesize ultrafine particles of iron nitride that got attention as one of the magnetic materials. The particles that were obtained in the gas mixture of argon and nitrogen were α-Fe. But nitrogen was chemisorbed on the surface of the particle, because nitrogen content in the particles was larger than the solubility of nitrogen in iron. The particles that formed in the mixed gas of argon and ammonia were Fe4N. The mean size of the particles of iron nitride was approximately 60 nm. The formation ratio of iron nitride was about 86 %.

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Wang, K. Y., e W. W. Yuen. "Rapid Heating of Gas/Small Particle Mixture". Journal of Solar Energy Engineering 109, n. 2 (1 maggio 1987): 143–49. http://dx.doi.org/10.1115/1.3268191.

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The concept of using a mixture of particles and air as a medium to absorb radiative energy has been proposed for various applications. In this paper, carbon particles mixed with gas form a medium that absorbs radiation from sources such as concentrated solar energy. A single-particle, two-temperature model is used to study the transient temperature of the particle/gas mixture as it undergoes a constant pressure expansion process. The results indicate that for particles smaller than 1 μm in diameter, the surrounding air can be heated as quickly as the particles, while for particles larger than 1 mm in diameter, the air temperature stays relatively unchanged and the particles are heated to a very high temperature. The scattering albedos from the particles are also calculated, revealing that their contribution from scattering to the heating process is insignificant for particles with diameter less than 1 μm.

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Dr. W.S. Abdul Wahab. "Coating Technology By Two – Phase (Cold gas – Solid particles) Flow". journal of the college of basic education 21, n. 87 (26 dicembre 2022): 157–69. http://dx.doi.org/10.35950/cbej.v21i87.8862.

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The surface coating process which is known as a cold spray (CS) of solid particles is performed by acceleration the solid particles for a certain metal to supersonic speeds through nozzle gas flow , are subsequently deposited by impact onto surface . Also this paper presents an analytical model for (CS) process , by assuming one dimensional isentropic flow , to demonstrate the dynamics of dilute two – phase (powder particles plus carrier gas) flow . Furthermore the equations for particle model are introduced , when heat transfers between the solid particles and assumed gas. The velocity of the solid particles must be achieved to a critical value for carrying out an optimal deposition efficiency and a high coating quality , also several parameters , including gas condition such as stagnation pressure and temperature , the density of gas , in addition the particle characteristics and nozzle geometry affect on particle velocity then on the quality of coating .

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21

Shorinov, О., e S. Polyvianyi. "DETERMINATION OF ENERGY PARAMETERS OF Ni+Al2O3 POWDER PARTICLES IN A SUPERSONIC NOZZLE DURING COLD GAS-DYNAMIC SPRAYING USING THE ANALYTICAL METHOD". Innovative Materials and Technologies in Metallurgy and Mechanical Engineering, n. 2 (9 gennaio 2023): 64–70. http://dx.doi.org/10.15588/1607-6885-2022-2-11.

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Purpose. To calculate the temperature and velocity of nickel and aluminum oxide particles in the supersonic flow in the low-pressure cold gas-dynamic spraying nozzle. To investigate the effect of gas parameters at the nozzle inlet, in particular temperature and pressure, on the velocity and temperature of particles at the nozzle outlet. Research methods. The calculation of the temperature-velocity characteristics of the powder particles is performed after determining the parameters of the gas flow in the supersonic nozzle channel using well known gas-dynamic dependencies. The initial data for the calculation are the following: the geometry of the nozzle, the temperature and pressure of the gas (air) at the nozzle inlet. The density of the material from which particles are obtained, as well as their diameter, were taken into account in the calculation of the energy parameters. Nickel particles with a diameter of 25 µm and aluminum oxide particles with a diameter of 22 µm were used. Results. Based on the calculations results, graphs of changes in the velocities and temperatures of the particles of the investigated powders, as well as working gas, in the channel of the low-pressure cold gas-dynamic spraying supersonic nozzle were developed. The dependences of the temperature-velocity parameters of the particles at the nozzle exit in the range of initial values of temperature at the nozzle inlet from 300 to 600 C° and pressure from 0.6 to 1.0 MPa were also developed. Scientific novelty. The influence of the initial parameters of the gas at the nozzle inlet in a wide range of values on the temperature and velocity of nickel and aluminum oxide particles during the low-pressure cold gas-dynamic spraying is shown. Practical value. The obtained results can be used to determine rational spraying parameters in the development of technological processes of deposition of protective and restorative coatings from Ni+Al2O3 powder mixture.

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Nath, G. "A self-similar solution for shock waves in conducting rotating non-ideal dusty gas medium with monochromatic radiation and magnetic field". Zeitschrift für Naturforschung A 77, n. 4 (17 febbraio 2022): 379–401. http://dx.doi.org/10.1515/zna-2021-0292.

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Abstract In this paper, the cylindrical shock wave propagation in a perfectly conducting rotating mixture of micro size dust particles and van der Waal gas with magnetic field either axial or azimuthal and monochromatic radiation is investigated. The effect of thermal radiation is included in the energy equation of the governing system. In our study, it is assumed that the flux of radiation moves in the mixture of particles and real gas with invariable intensity and the shock wave is moving appositive to the direction of radiation heat flux and the energy is engrossed behind the cylindrical shock only. In the present model, dusty gas is assumed to be a mixture of micro size dust particles and van der Waal gas in which solid particles are continuously distributed and the equilibrium flow conditions are assumed to hold in the entire flow-field region. The effects of the particles’ density to the initial gas density ratio, the real gas effect, rotational parameter, the concentration of mass of the micro size dust particles in the conducting mixture, Alfven-Mach number and the adiabatic exponent on shock and on the physical variables such as velocity, density etc. are discussed. It is found that due to the rotating medium consideration or by an increase in small particles density to the initial gas density ratio, the shock wave strength increases. Also, it is significant to memorize that the strength of the shock wave decreases by an increase in the strength of initial magnetic field or gas non-ideal parameter or the adiabatic index.

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Isayeva, S. A. "The effect of gas velocity on the specification of inner diameter of production tubing". Azerbaijan Oil Industry, n. 11 (15 novembre 2021): 30–33. http://dx.doi.org/10.37474/0365-8554/2021-11-30-33.

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Based on the gas dynamics laws, the method of gas well calculation considering the solid particles in the flow is offered. The equation for the motion of gas with solid particles in various operation regimes of gas well is suggested. Obtained equations allow to specify the velocity of upwardly moving gas stream considering the rate of solid particles, to define the most optimum conditions for the extraction of particles in the borehole of gas well. The impact of the main parameters of gas well in the extraction process of solid phase has been considered. It should be noted that the improvement of gas motion process in lifting tubes is seen, however, in this respect, it is necessary to consider all technological parameters of well operation. In such cases, the regulation process considering wellhead pressure is essential. While changing the gas motion velocity, the extraction from the well borehole with definite flow rate is seen. The velocity increase may create significant additional pressure in the reservoir, which can break down the bottomhole zone.

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HOGENDOORN, J. A., W. P. M. VAN SWAAIJ e G. F. VERSTEEG. "CONTINUOUS GAS SEPARATION WITH LIQUID IMPREGNATED PARTICLES IN GAS-SOLID REACTORS". Chemical Engineering Communications 144, n. 1 (febbraio 1996): 19–50. http://dx.doi.org/10.1080/00986449608936443.

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Oman, Janez, e Peter Novak. "Volumetric absorption in gas—properties of particles and particle-gas suspensions". Solar Energy 56, n. 6 (giugno 1996): 597–606. http://dx.doi.org/10.1016/0038-092x(96)00009-6.

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Pongó, Tivadar, Dmitry Puzyrev, Kirsten Harth, Ralf Stannarius e Raúl Cruz Hidalgo. "Continuously heated granular gas of elongated particles". EPJ Web of Conferences 249 (2021): 04003. http://dx.doi.org/10.1051/epjconf/202124904003.

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Some years ago, Harth et al. experimentally explored the steady state dynamics of a heated granular gas of rod-like particles in microgravity [K. Harth et al. Phys. Rev. Lett. 110, 144102 (2013)]. Here, we report numerical results that quantitatively reproduce their experimental findings and provide additional insight into the process. A system of sphero-cylinders is heated by the vibration of three flat side walls, resulting in one symmetrically heated direction, one non-symmetrically heated direction, and one non-heated direction. In the non-heated direction, the speed distribution follows a stretched exponential distribution $$p(\upsilon )\, \propto \,{\rm{exp}}\left( { - {{\left( {{{\left| \upsilon \right|} \mathord{\left/ {\vphantom {{\left| \upsilon \right|} C}} \right. \kern-\nulldelimiterspace} C}} \right)}^{1.5}}} \right)$$. In the symmetrically heated direction, the velocity statistics at low speeds is similar but it develops pronounced exponential tails at high speeds. In the non-symmetrically heated direction (not accessed experimentally), the distribution also follows $$p(\upsilon )\, \propto \,{\rm{exp}}\left( { - {{\left( {{{\left| \upsilon \right|} \mathord{\left/ {\vphantom {{\left| \upsilon \right|} C}} \right. \kern-\nulldelimiterspace} C}} \right)}^{1.5}}} \right)$$ , but the velocity statistics of rods moving toward the vibrating wall resembles the indirectly excited direction, whereas the velocity statistics of those moving away from the wall resembles the direct excited direction.

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YAMAZOE, Noboru, Norio MIURA e Jun TAMAKI. "Ultrafine particles as semiconductor gas sensor materials." RESOURCES PROCESSING 37, n. 2 (1990): 75–81. http://dx.doi.org/10.4144/rpsj1986.37.75.

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Hakonen, Aron, Anders Karlsson, Lena Lindman, Oliver Büker e Karine Arrhenius. "Particles in fuel-grade Liquefied Natural Gas". Journal of Natural Gas Science and Engineering 55 (luglio 2018): 350–53. http://dx.doi.org/10.1016/j.jngse.2018.05.005.

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Sethi, S. A. "Generation of small particles by gas fluidization". Journal of Aerosol Science 28 (settembre 1997): S539—S540. http://dx.doi.org/10.1016/s0021-8502(97)85269-x.

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Zolotko, A. N., N. I. Poletaev e Ya I. Vovchuk. "Gas-disperse synthesis of metal oxide particles". Combustion, Explosion, and Shock Waves 51, n. 2 (marzo 2015): 252–68. http://dx.doi.org/10.1134/s0010508215020094.

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Tian, Lei, Debraj Ghosh, Wei Chen, Sulolit Pradhan, Xijun Chang e Shaowei Chen. "Nanosized Carbon Particles From Natural Gas Soot". Chemistry of Materials 21, n. 13 (14 luglio 2009): 2803–9. http://dx.doi.org/10.1021/cm900709w.

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Hayashi, S., e M. Samejima. "SERS activity of gas-evaporated silver particles". Solid State Communications 55, n. 12 (settembre 1985): 1085–88. http://dx.doi.org/10.1016/0038-1098(85)90138-3.

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Burtscher, H., e A. Schmidt-Ott. "Experiments on small particles in gas suspension". Surface Science Letters 156 (giugno 1985): A333. http://dx.doi.org/10.1016/0167-2584(85)90461-x.

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Burtscher, H., e A. Schmidt-Ott. "Experiments on small particles in gas suspension". Surface Science 156 (giugno 1985): 735–40. http://dx.doi.org/10.1016/0039-6028(85)90243-2.

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BENTZON, M. D., A. KARLEN e A. R. THÖLÉN. "GRAIN BOUNDARIES BETWEEN SMALL GAS EVAPORATED PARTICLES". Le Journal de Physique Colloques 51, n. C1 (gennaio 1990): C1–89—C1–94. http://dx.doi.org/10.1051/jphyscol:1990111.

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Levdanskii, V. V., J. Smolik, V. Zdimal e P. Moravec. "Incorporation of gas molecules into nanosized particles". Journal of Engineering Physics and Thermophysics 86, n. 3 (maggio 2013): 547–50. http://dx.doi.org/10.1007/s10891-013-0867-2.

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Oda, M., E. Fuchita, M. Tsuneizumi, S. Kashu e C. Hayashi. "Gas deposition films of ultra fine particles". Nanostructured Materials 1, n. 3 (maggio 1992): 203–6. http://dx.doi.org/10.1016/0965-9773(92)90095-f.

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Fidaleo, Francesco. "Gas of Particles Obeying the Monotone Statistics". Entropy 25, n. 7 (21 luglio 2023): 1095. http://dx.doi.org/10.3390/e25071095.

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Abstract (sommario):

The present note is devoted to the detailed investigation of a concrete model satisfying the block-monotone statistics introduced in a previous paper (joint, with collaborators) of the author. The model under consideration indeed describes the free gas of massless particles in a one-dimensional environment. This investigation can have consequences in two fundamental respects. The first one concerns the applicability of the (block-)monotone statistics to concrete physical models, yet completely unknown. Since the formula for the degeneracy of the energy-levels of the one-particle Hamiltonian of a free particle is very involved, the second aspect might be related to the, highly nontrivial, investigation of the expected thermodynamics of the free gas of particles obeying the block-monotone statistics in arbitrary spatial dimensions. A final section contains a comparison between the various (block, strict, and weak) monotone schemes with the Boltzmann statistics, which describes the gas of classical particles. It is seen that the block-monotone statistics, which takes into account the degeneracy of the energy-levels, seems the unique one having realistic physical applications.

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39

Jiang, Zhaohua, Takuya Tsuji, Jun Oshitani, Kimiaki Washino e Toshitsugu Tanaka. "Reverse to forward density segregation depending on gas inflow velocity in vibrated fluidized beds". Physics of Fluids 35, n. 3 (marzo 2023): 033313. http://dx.doi.org/10.1063/5.0138556.

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Particle density segregations in vibrated fluidized beds depending on gas inflow velocity under the same vertical vibration condition are studied. Coarse-graining discrete element method and computational fluid dynamics numerical simulations are employed to capture the behaviors of reverse segregation in which heavy particles are located above light particles at zero gas inflow velocity or at velocities considerably lower than the minimum fluidization velocity of light particles. Furthermore, upon increasing the gas inflow velocity slightly, the forward segregation occurs, such that heavy particles are located below light particles. The mechanisms are also elucidated using the simulation results. Because of the relative motions between the particles and bed caused by vertical vibration, negative gauge pressure is observed to be dependent on the vibration phase. In the reverse segregation case, the accumulative effect of the downward gas pressure gradient force induced by vibration overcomes the upward force of the forced air flow. The wall friction transports both the heavy and light particles in the vicinity of the sidewall to the bed bottom, where the local void fraction is comparatively high and reverse segregation mainly occurs. Reverse segregation results from the combined effects of the downward gas pressure gradient force, particle transport, and local formation of the high void region. The increase in gas inflow velocity enhances the upward pressure gradient force, resulting in forward segregation.

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40

Gomes, J. F., R. M. Miranda, P. A. Carvalho e M. L. Quintino. "The effect of metal transfer modes and shielding gas composition on the emission of ultrafine particles in MAG steel welding". Soldagem & Inspeção 19, n. 2 (giugno 2014): 168–76. http://dx.doi.org/10.1590/0104-9224/si1902.09.

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The present study aims to characterize ultrafine particles emitted during gas metal arc welding of mild steel and stainless steel, using different shielding gas mixtures, and to evaluate the effect of metal transfer modes, controlled by both processing parameters and shielding gas composition, on the quantity and morphology of the ultrafine particles. It was found that the amount of emitted ultrafine particles (measured by particle number and alveolar deposited surface area) are clearly dependent from the main welding parameters, namely the current intensity and the heat input of the welding process. The emission of airborne ultrafine particles increases with the current intensity as fume formation rate does. When comparing the shielding gas mixtures, higher emissions were observed for more oxidizing mixtures, that is, with higher CO2content, which means that these mixtures originate higher concentrations of ultrafine particles (as measured by number of particles by cubic centimeter of air) and higher values of alveolar deposited surface area of particles, thus resulting in a more hazardous condition regarding welders exposure.

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41

Bikkulov, Rustem Ya, Andrey V. Dmitriev, Vadim E. Zinurov e Guzel R. Badretdinova. "Separation of Fine Particles from Gas in Paint-Spraying Booths". MATEC Web of Conferences 346 (2021): 03070. http://dx.doi.org/10.1051/matecconf/202134603070.

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Nowadays, at production facilities with paint-spraying booths that use paint and varnish materials to cover the surfaces of product, the problem of gas flow contamination with finely dispersed solid particles of dust and rubbish, which negatively affect the quality of products, is increasingly being raised. In order to minimize the content of solid particles in the gas flow, coarse and fine filters are installed in the paint-spraying booths, which prevent dust particles from entering the surface of products. However, the existing purification devices have a number of disadvantages that affect the efficiency of collecting finely dispersed particles from the gas flow with a size of 0.5-5 microns. The authors of article developed a square separator to increase the efficiency of collecting finely dispersed particles from gas flows in the paint-spraying booths. The installation of proposed separation device in the paint-spraying booths affects not only the quality of collecting solid particles, but also increases the service life of fine and coarse filters In the course of numerical studies, the results of impact of structural and technological parameters, namely, the impact of inlet rate and scale of separation device on the efficiency of collecting solid particles from the gas flow, were obtained.

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42

He, Jie, Xiang Huang e Pei Cao. "Fine Particle Migration in a Gas Hydrate Sand: Single- and Two-Phase Fluid Using a Device for Observation at the Pore Scale". Journal of Marine Science and Engineering 12, n. 1 (6 gennaio 2024): 109. http://dx.doi.org/10.3390/jmse12010109.

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The production of natural gas hydrates will change the cementation strength, porosity, and effective stress in the stratum, which may lead to engineering and geological disasters. Sand production is a phenomenon where sand particles are carried out of the reservoir along with fluids during gas extraction, posing challenges to safe and sustainable production. This study explored the mechanism of fine particle migration in multiphase flow by a microscopic visualization test device. The device can inject a gas–liquid–solid phase at the same time and allow real-time observation. Experimental tests on fine particle migration of single- and two-phase fluid flow were carried out considering different conditions, i.e., fine particle concentration, fine particle size, fluid flow rate, and gas–liquid ratio. The results show that in single-phase fluid flow, the original gas will gradually dissolve in the liquid phase, and finally stay in the test device as bubbles, which can change the pore structures, resulting in the accumulation of fine particles at the gas–liquid interface. In two-phase fluid flow with mixed gas–water fluids, there are two flow modes of gas–liquid flow: mixed flow and separated flow. The interfacial tension at the gas–liquid interface can effectively migrate fine particles when the gas–liquid flows alternately and the sand production rate further increases as the gas–liquid ratio increases. In addition, changes in the concentration of fine particles, particle size, fluid flow rate, and the gas–liquid ratio will affect the migration of fine particles, leading to differences in the final sand production.

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43

Li, Wen-Jun, Er-Wei Shi, Ming-Yuan Tian, Wei-Zhuo Zhong e Zhi-Wen Yin. "The Synthesis of ZnO Acicular Particles by the Hydrothermal Discharging-gas Method". Journal of Materials Research 14, n. 4 (aprile 1999): 1532–37. http://dx.doi.org/10.1557/jmr.1999.0205.

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In this paper, a new hydrothermal method—discharging-gas method—is introduced. ZnO acicular particles with the ratio of length and diameter 16: 1 are synthesized by the hydrothermal discharging-gas method using a mixed solution of Zn(CH3COO)2 with NaNO2 as precursor at 190 °C for 1 h. The effects of reaction temperature and precursor concentration on formation of acicular particles are investigated. The results show that the main factor for formation of acicular particles prepared by the hydrothermal discharging-gas method is the extent of crystallinity of ZnO powders before releasing gas.

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Orlovska, S. G. "Study of the influence of external heat and mass exchange on the features of combustion and extinction of gas suspensions of carbon particles". Physics of Aerodisperse Systems, n. 61 (9 dicembre 2023): 124–30. http://dx.doi.org/10.18524/0367-1631.2023.61.292232.

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In the work, the regularities of the influence of heat and mass exchange of gas suspensions of carbon particles with the external gas environment on the processes of ignition, burning and quenching at different mass concentrations of carbon fuel are studied. A monodisperse gas suspension of carbon particles located in a gas heated to a high temperature, which contains an oxidant, is considered. As a result of the conducted physical and mathematical modeling, the following characteristics of high-temperature processes were determined: induction period, burning time and time of complete transformation of particles, critical parameters of ignition and extinction of particles. The influence on these characteristics of the initial particle diameter, mass concentration and temperature of the surrounding gas was analyzed. It was found that the external heat and mass exchange has a slight effect on the induction period and critical parameters of the ignition of gas suspensions, but it has a sufficiently strong effect on the characteristics of the combustion and extinguishing processes. The existence of an upper limit for fuel concentrations and particle diameters at which complete combustion of gas suspensions is not observed in the absence of external mass transfer is proved. Ranges of mass concentrations were found for which complete conversion of carbon fuel burning in the form of gas suspensions is carried out. It is shown that for open gas suspensions, the range of mass concentrations, where complete transformation of particles is observed, expands to the side of large values. The diameters of the particles characterizing the quenching of gas suspensions, taking into account the external mass transfer, are smaller, as a result of a greater supply of oxygen to the volume of the gas suspension.

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45

GANGWAR, P. K., Y. SINGH e D. KUMAR. "Analytical Study of Cylindrical Imploding Strong Shock in a Uniform Real Dusty Gas". Journal of Ultra Scientist of Physical Sciences Section B 34, n. 6 (16 agosto 2022): 46–64. http://dx.doi.org/10.22147/jusps-b/340601.

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In the present study, we have investigated the motion of cylindrical imploding shock in a real dusty gas having uniform initial density distribution by using (CCW) Chester2 -Chisnell3 -Whitham (1958) method. It is considered that the real dusty gas is the mixture of real gas and a large number of small spherical solid particles of uniform size. Initial volume fraction of the solid particles is also assumed constant in this particular study. The particles do not interact with each other therefore their thermal motion is negligible. Initial density of the medium is taken to be constant and medium ahead of the shock front is at rest with small counter pressure. Here the particles behave like a pseudo-fluid. Maintaining the equilibrium flow condition in the flow field, the analytical expressions for the shock velocity, shock strength, pressure, and flow velocity have been derived. The variation of flow variables with propagation distance (r), mass concentration of solid particles in the mixture (kp) and the ratio of the density of solid particles to the initial density of gas (G) are obtained and discussed through figures. The results accomplished are compared with those for dusty ideal gas Yadavet, al. 28

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46

Thomasson, Magnus. "Simulations of Gas Clouds in Interacting Galaxies". International Astronomical Union Colloquium 124 (1990): 749–53. http://dx.doi.org/10.1017/s0252921100005923.

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A companion can induce a varitey of morphological changes in a galaxy. I use N-body simulations to study the effects of different kinds of perturbations on the dynamics of a disk galaxy. The model is two-dimensional, with a disk consisting of about 60,000 particles. Most of the particles (80 %) represent the old stellar population with a high velocity dispersion, while the rest (20 %) represent gas clouds with a low velocity dispersion. Initially, the velocity dispersion corresponds to Q = 1 for the “star” particles, and Q = 0 for the “gas” particles, where Q is Toomre’s (1964) stability parameter. The gas clouds can collide inelastically. The disk is stabilized by a rigid halo potential, and by the random motions of the old “star” particles. To simulate the effect of an encounter on the disk, a companion galaxy, modelled as a point mass, can move in a co-planar orbit around the disk. A complete description of the N-body code is found in Thomasson (1989).

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47

Pervan Mursalov, Yusif Alakbarov, Pervan Mursalov, Yusif Alakbarov. "CLEANING OF NATURAL GASES FROM MECHANICAL MIXTURES". PAHTEI-Procedings of Azerbaijan High Technical Educational Institutions 26, n. 03 (14 marzo 2023): 98–103. http://dx.doi.org/10.36962/pahtei26032023-98.

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Mechanical impurities in natural gas are understood as rock particles removed from the well by the gas flow, construction slurries remaining after the completion of the construction of mining gas collection networks and main pipelines, corrosion and erosion products of the internal surfaces of pipelines, as well as water and condensate particles. In this article, existing apparatus and devices for cleaning gases from mechanical mixtures will be reviewed according to the working principle and innovations related to this issue will be discussed. Cleaning of natural gas from mechanical particles is carried out in several stages on the way from the field to the gas demander. As a rule, a special filter is placed at the bottom of the well in order to limit the movement of rock particles entering from the deposits. Keywords: mechanical mixing, gravity devices.

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48

Cadiou, Corentin, Yohan Dubois e Christophe Pichon. "Accurate tracer particles of baryon dynamics in the adaptive mesh refinement code Ramses". Astronomy & Astrophysics 621 (gennaio 2019): A96. http://dx.doi.org/10.1051/0004-6361/201834496.

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We present a new implementation of the tracer particles algorithm based on a Monte Carlo approach for the Eulerian adaptive mesh refinement code RAMSES. The purpose of tracer particles is to keep track of where fluid elements originate in Eulerian mesh codes, so as to follow their Lagrangian trajectories and re-processing history. We provide a comparison to the more commonly used velocity-based tracer particles, and show that the Monte Carlo approach reproduces the gas distribution much more accurately. We present a detailed statistical analysis of the properties of the distribution of tracer particles in the gas and report that it follows a Poisson law. We extend these Monte Carlo gas tracer particles to tracer particles for the stars and black holes, so that they can exchange mass back and forth between themselves. With such a scheme, we can follow the full cycle of baryons, that is, from gas-forming stars to the release of mass back to the surrounding gas multiple times, or accretion of gas onto black holes. The overall impact on computation time is ∼3% per tracer per initial cell. As a proof of concept, we study an astrophysical science case – the dual accretion modes of galaxies at high redshifts –, which highlights how the scheme yields information hitherto unavailable. These tracer particles will allow us to study complex astrophysical systems where both efficiency of shock-capturing Godunov schemes and a Lagrangian follow-up of the fluid are required simultaneously.

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Li, Liangchao, e Bin Xu. "CFD simulation of gas-liquid floating particles mixing in an agitated vessel". Chemical Industry and Chemical Engineering Quarterly 23, n. 3 (2017): 377–89. http://dx.doi.org/10.2298/ciceq160129052l.

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Gas dispersion and floating particles suspension in an agitated vessel were studied numerically by using computational fluid dynamics (CFD). The Eulerian multi-fluid model along with standard k-? turbulence model was used in the simulation. A multiple reference frame (MRF) approach was used to solve the impeller rotation. The velocity field, gas and floating particles holdup distributions in the vessel were first obtained, and then, the effects of operating conditions on gas dispersion and solid suspension were investigated. The simulation results show that velocity field of solid phase and gas phase are quite different in the agitated vessel. Floating particles are easy to accumulate in the center of the surface region and the increasing of superficial gas velocity is in favor of floating particles off-surface suspension. With increasing solids loading, the gas dispersion becomes worse, while relative solid holdup distribution changes little. The limitations of the present modeling are discussed and further research in the future is proposed.

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van Ommen, J. "(Invited) Gas Phase Coating of Particles for Energy Applications". ECS Meeting Abstracts MA2022-02, n. 31 (9 ottobre 2022): 1114. http://dx.doi.org/10.1149/ma2022-02311114mtgabs.

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Advanced materials, often relying on nanostructured particles as building blocks, are crucial in meeting grand challenges in energy: battery materials, electrocatalysts, phase change materials, etc. etc. Gas phase deposition techniques, such as chemical vapour deposition (CVD), atomic layer deposition (ALD), and molecular layer deposition (MLD) are excellent methods to make such nanostructured particles: particles of which the surface is either covered by an ultrathin film or by nanoclusters. When combined with proper particle handling, these coating methods are also very well suitable for scaling up. This requires adequate reactor technology to optimize the contacting of particles and gaseous reactants. Gas phase coating such as CVD and ALD is already widely applied in the semiconductor industry. Although the underlying mechanisms are similar, there are quite some differences between gas phase deposition on wafers and coating particles. This tutorial will discuss recent developments and insights in the field of applying gas phase deposition to particles, with an emphasis on reactor technology, precursor utilization, operating conditions, and scaling up. I will show that we can produce nanostructured particles with very high precision in a scalable way. I will focus on energy applications, and will discuss how this approach can also be of value in light of the increasing demand for critical raw materials.

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