Bubble

International Journal of Mineral Processing, 14 (1985) 195--215 195 Elsevier Science Publishers BV, Amsterdam --Printed in The Netherlands THE EFFECT OF BUBBLE SIZE ON THE RATE OF FLOTATION OF FINE PARTICLES N. AHMED* and GJ JAMESON Department of ...

One of the reasons for the emergency use of a hyperbaric chamber concerns a diving-related accident. Decompression sickness is potentially serious; it requires urgent treatment and hyperbaric recompression. It is caused by the formation of nitrogen bubbles in the organism which appear during the diver's ascent and throughout his or her decompression.

Models for the growth of bubbles are reviewed. A model of the growth of bubbles during proving of bread dough is then presented, based on diffusive mass transfer of carbon dioxide gas into a population of bubbles. The model incorporates the rate of gas production by yeast and the bubble size distribution, and is solved to simulate the dynamic growth of these bubbles. The effects of the number and size of bubbles and the proving temperature and yeast concentration on the growth of the dough piece are simulated. A greater number of bubbles in the dough, which would be achieved by mixing at higher pressures, results in an initially more rapid transfer of gas into the bubbles. Consequently there is a slower increase in carbon dioxide concentration in the liquid dough phase, such that later during proving the rate of bubble growth slows. Increasing yeast level increases the rate of gas production and hence the growth of the dough piece. Increasing temperature similarly increases the rate of growth of bubbles, partly due to the increased rate of gas production, but also as a result of the decreased gas solubility at higher temperatures.

This paper provides a comprehensive critical review of available studies on analytical and numerical modeling including computational fluid dynamics (CFD), as well as experimental approaches to determine the parti-cle–bubble interactions in flotation cells. The effects of some significant factors such as particle density, bubble size and velocity, and cell turbulence on the particle–bubble encounter are investigated in detail. This review indicates that interception collision models established based on stream functions are not applicable as they ignore the turbulence effect. The streamlines are not stationary in turbulent conditions and constantly change throughout time and space. Furthermore, the analytical models are restricted because of poor estimation of collision angle, Stokes numbers, effect of particle density and disregarding microhydrodynamic forces and turbulence effects. Unlike analytical modeling, numerical modeling is a very powerful technique for evaluating particle–bubble encounter interactions. The role of particle density and turbulence in particle–bubble encounter can be best identified by numerical methods. However, there is lack of experimental data to verify these models. Therefore, more specific and direct measurement techniques are required to develop accurate estimation of particle–bubble encounter probabilities. This review finally highlights the gaps in the evaluation of particle–-bubble encounter efficiency and recommends further works to investigate relationships between hydrodynamic properties, particle–bubble characterizations, flotation kinetic rates and particle–bubble encounter interactions.

Many industry experts believe that, although there is no basis to say that the market has a bubble in the next 1-2 years, the bubble may appear in the period after 2021. By 2018, demand for real estate. New equilibrium with bows. And now supply is still a little higher than demand. After 2018, demand will be greater than supply, and there will be a "bubble" in 2021-2023. When the financial market is unstable, the most stable shelter is real estate. 2.5-3 million people from rural to urban areas, creating a second wave of urbanization, thereby increasing the demand for real estate. After a year of high volatility, the real estate market has surpassed through the forecast of a real estate bubble burst scenario at the end of 2018. More optimistic when in the second half of 2018, a series of positive signals appeared with liquidity in some segments. vibrant, loans for real estate businesses become diverse.Finally a year full of haunting real estate bubble risk, many experts said that this year In 2019, the real estate market will record positive and optimistic signals.

A possibilidade de interação que a web passou a oferecer em seu processo de evolução alterou a condição do usuário, que se tornou um potencial produtor de conteúdo. A mudança desencadeou um aumento exponencial de dados no ciberespaço. A configuração vigente trouxe o desafio de fazer a curadoria das informações disponíveis. O conceito, oriundo do campo das artes e do direito, foi apropriado pela mídia para se referir ao trabalho desempenhado pelo jornalista e às soluções algorítmicas, que têm como finalidade filtrar e curar os conteúdos disponíveis na web. O presente trabalho acadêmico visa a refletir sobre o papel do jornalista em um cenário de abundância informativa e os meios para que ele se mantenha relevante em um ambiente permeado por algoritmos dotados de inteligência artificial.

Modelling of the expansion of 3-D single bubble using a multi-phase model has been developed for GIVE APPLICATION AREA with the potential of a meshless numerical simulation method, Smoothed Particle Hydrodynamics (SPH), and the consideration of the surface tension between phases and viscosity effect of the polymer melt surrounding the bubble. Mainly, bubble growth in the polymer material occurs because of the mass conversion (mass loss) from the polymer melt to gas due to heat such as fire. This mass conversion drives the expansion process of the gas bubble by increasing the pressure inside. To represent the mass transfer the from the polymer melt to the bubble, this paper proposes a novel algorithm to increase number of SPH gas particles inside the bubble during the simulation. The present paper aims to explain this new developed method including particle shifting scheme identifying the main challenges of dynamic and non-spherical bubble modelling which have a nonlinear multi-phase behaviour. In order to develop stable simulations for the multi-phase bubble growth in isothermal conditions in millimeter scale, surface tension effects have been scaled according to the Capillary number. The insertion of the new gas particles into the bubble centre has been performed at regular intervals to identify the influence of time period of particle insertion. The predicted results from the numerical study have been compared with the well-known analytical solution for single bubble growth for final bubble radius and bubble growth rate. Time step analysis has also been performed to show the numerical stability for this kind of bubble growth simulation. The importance of the particle shifting scheme has also been addressed for simulating bubble growth in this multi-phase problem.

A three dimensional transient model is developed to simulate the local hydrodynamics of a gas–liquid–solid three-phase fluidised bed reactor using the computational fluid dynamics (CFD) method. The CFD simulation predictions are compared with the experimental data of Kiared et al. [1999. Mean and turbulent particle velocity in the fully developed region of a three-phase fluidized bed. Chemical Engineering & Technology 22, 683–689] for solid phase hydrodynamics in terms of mean and turbulent velocities and with the results of Yu and Kim [1988. Bubble characteristics in the racial direction of three-phase fludised beds. A.I.Ch.E. Journal 34, 2069–2072; 2001. Bubble-wake model for radial velocity profiles of liquid and solid phases in three-phase fluidised beds. Industrial and Engineering Chemistry Research 40, 4463–4469] for the gas and liquid phase hydrodynamics in terms of phase velocities and holdup. The flow field predicted by CFD simulation shows a good agreement with the experimental data. From the validated CFD model, the computation of the solid mass balance and various energy flows in fluidised bed reactors are carried out. The influence of different interphase drag models for gas–liquid interaction on gas holdup are studied in this work.

There was a notable housing price inflation in aggregate/local levels in Turkey during the last few years. Although the country's economic fundamentals remain strong, the probability of a housing bubble is a heated debate among market participants. This timely investigation brings greater clarity to whether the Turkish housing market is in a bubble. The study uses a multi-strand approach to dissect the bubble over the period of Jan. 2010-Dec. 2014. First, monthly/annual price-to-income and monthly price-to-rent ratios are examined for the national Turkish as well as regional Istanbul, Izmir and Ankara housing markets. Second, an extended CASE and SHILLER (2003) model is applied assessing the interdependence between housing prices and a series of explanatory variables. Lastly, the Right Tail Augmented Dickey-Fuller (Rtadf) test is performed to support the overall analysis. This study finds that neither affordability ratios nor regression estimates support the existence of the bubble in Turkey.