Search results for "BUBBLE"

The rheology of three-phase suspensions at low bubble capillary number

2015

We develop a model for the rheology of a three-phase suspension of bubbles and particles in a Newtonian liquid undergoing steady flow. We adopt an 'effective-medium' approach in which the bubbly liquid is treated as a continuous medium which suspends the particles. The resulting three-phase model combines separate two-phase models for bubble suspension rheology and particle suspension rheology, which are taken from the literature. The model is validated against new experimental data for three-phase suspensions of bubbles and spherical particles, collected in the low bubble capillary number regime. Good agreement is found across the experimental range of particle volume fraction ([Formula: s…

Eulerian two-fluid model of alkaline water electrolysis for hydrogen production

2020

Hydrogen storage is a promising technology for storage of renewable energy resources. Despite its high energy density potential, the development of hydrogen storage has been impeded, mainly due to its significant cost. Although its cost is governed mainly by electrical energy expense, especially for hydrogen produced with alkaline water electrolysis, it is also driven by the value of the cell tension. The most common means of electrolyzer improvement is the use of an electrocatalyst, which reduces the energy required for electrochemical reaction to take place. Another efficient means of electrolyzer improvement is to use the Computational Fluid Dynamics (CFD)-assisted design that allows the…

A quantitative assessment of the effect of distributor type on particle circulation

1997

Abstract Garncarek's quantitative index of inhomogeneity has been used to compare the effect of distributor type on the degree of uniformity of solids mixing in a gas-fluidized bed assessed by following a tracer particle using the technique of Positron Emission Particle Tracking. The bed was a sand of 475 μm diameter fluidized at 2 U mf and contained within a column of 150 mm diameter. A porous and perforated plate distributor are compared. The index shows that tracer locations are generally more homogeneously distributed throughout the vertical section of the bed with the porous plate distributor. Behaviour varies with height and horizontal sections of the bed show that there is little dif…

A behavioural finance explanation of speculative bubbles: evidence from the bitcoin price development

2019

In 2008 a group of programmers, alias Satoshi Nakamoto, introduced bitcoin. Bitcoin is a cryptocurrency or virtual money derived from mathematical cryptography and is conceived as an alternative to government authorised currency. The founder anticipated, through bitcoin’s construction and his digital mining processes, that bitcoin prices would be relatively stable. However, the recent bitcoin price decline proves that bitcoin is extraordinarily volatile and is not that stable as hoped. Although some scientists have already shown that the fundamental value of bitcoin is zero, the price of bitcoin has reached over 19.000$ in December 2018. Since then, bitcoin prices dropped nearly 70% from th…

The chemistry of acetone at extreme conditions by density functional molecular dynamics simulations

2011

Density functional molecular dynamics simulations have been performed in the NVT ensemble (moles (N), volume (V) and temperature (T)) on a system formed by ten acetone molecules at a temperature of 2000 K and density ρ = 1.322 g cm(-3). These conditions resemble closely those realized at the interface of an acetone vapor bubble in the early stages of supercompression experiments and result in an average pressure of 5 GPa. Two relevant reactive events occur during the simulation: the condensation of two acetone molecules to give hexane-2,5-dione and dihydrogen and the isomerization to the enolic propen-2-ol form. The mechanisms of these events are discussed in detail.

Characterization of focal liver lesions

2005

Risk transmission between Islamic and conventional stock markets: A return and volatility spillover analysis

2017

Abstract This paper contributes to the current debate on the empirical validity of the decoupling hypothesis of the Islamic stock market from its mainstream counterparts by examining return and volatility spillovers across the global Islamic stock market, three main conventional national stock markets (the US, the UK and Japan) and a number of influential macroeconomic and financial variables over the period from July 1996 to June 2016. To that end, the VAR-based spillover index approach based on the generalized VAR framework developed by Diebold and Yilmaz (2012) is applied. The empirical analysis shows strong interactions in return and volatility among the global Islamic stock market, the…

The distribution of stock returns: international evidence

1994

Although financial theory rests heavily on the normality assumption, daily stock returns display significant departures from normality. Different researchers have proposed alternative distributions. In this paper, the distribution of stock returns is examined in six stock markets. The empirical distributions present common features and are best represented by Student's t-distribution, while several alternative distributions are rejected.

Bubbles and Crowding-in of Capital via a Savings Glut

2017

This paper uncovers a mechanism by which bubbles crowd in capital investment. If capital formation is initially depressed by a binding credit constraint, a bubble triggers a savings glut. Higher returns in a new bubbly equilibrium attract additional savings, which are channeled to expand investment at the extensive margin, leading to permanently higher capital, output, and wages. We demonstrate that crowding-in through this channel is a robust phenomenon that occurs along the entire time path.

The role of stock markets vs. the term spread in forecasting macrovariables in Finland

2011

Abstract A substantial body of stylized facts and empirical evidence exists regarding the relationships between financial variables and the macroeconomy in the United States. However, the question of whether this evidence is consistent with the cases of small open economies is less known. This paper focuses on the forecasting content of stock returns and volatility vs. the term spread for GDP, private consumption, industrial production and the inflation rate in Finland. Our results suggest that during normal times, the term spread is a much better tool than stock market variables for predicting real activity. However, during exceptional times, such as the recent financial crisis, the foreca…