International Evidence on Monetary Neutrality Under Broken Trend Stationary Models

We analyze the issue of the impact of multiple breaks on monetary neutrality results, using annual data on real output and monetary aggregates for Argentina (1884-1996), Australia (1870-1997), Brazil (1912-1995), Canada (1870-2001), Italy (1870-1997), Mexico (1932-2000), Sweeden (1871-1988), and the UK (1871-2000). In particular, we empirically verify, whether neutrality propositions remain addressable (and if so, whether they hold or not), when unit root tests are carried out allowing for multiple structural breaks in the long-run trend function of the variables. It is found that conclusions on neutrality are sensitive to the number of breaks allowed. In order to interpret the evidence for structural breaks, we utilize a notion of deterministic monetary neutrality, which naturally arises in the absence of permanent stochastic shocks to the variables. We utilize a resampling procedure based on the fact that changes in the trend function bias unit root tests towards a non-rejection. In particular, using a dynamic programming algorithm to obtain global minimizers of the RSS for locating breaks, we simulate the distribution of the t-statistic for the null hypothesis of a unit root, under the hypotheses that the true models are both a Trend Stationary (TS) model with up to four structural breaks, and a Difference-Stationary (DS) model, both estimated from the data. We then compare the position where the sample estimate of the t-statistic for testing a unit root lies relative to the empirical densities of the t-statistic, under both the estimated TS and DS models. We present evidence in favour of models in which the cycle fluctuates in a stationary way around a broken trend. In other words, the (unit root) permanent stochastic changes vanish, giving rise to stationary behaviour affected by infrequent structural breaks. This leads to interesting questions about the testing for monetary neutrality, and allows us to introduce the concept of deterministic monetary neutrality.Neutrality and Superneutrality of Money, Stationarity, Structural Breaks, Resampling Methods

Simulation of fuel particles motion in a 2D fluidized bed using a hybrid-model considering wall friction

The mixing of fuel particles is a key issue on the performance of fluidized bed reactors. In this work, the motion of a non-reactive fuel particle in a 2D bubbling fluidized bed at ambient conditions is simulated employing a hybrid-model. The hybrid-model, implemented in the code MFIX, simulates the dense and gas phases using a Two-Fluid Model (TFM) while the fuel particles are modeled using a Discrete Element Method (DEM). The importance of the present hybrid-model is that the interaction of the continuum phases with the fuel particles behavior is fully coupled. In a previous study, Hernández-Jiménez et al. (1) compared the fuel particles motion obtained from the simulation with experimental results measured in a cold 2D fluidized bed by Soria-Verdugo et al. (2, 3). The simulation results related to the location of the fuel particle in the bed were similar to the experimental data (Figure-1). Nevertheless, some discrepancies were found in important parameters such as the circulation time of the fuel particles. These discrepancies were associated to the overprediction of the simulated solids velocity. In the present work, in order to improve the accuracy of the simulated fuel particle motion in a bubbling fluidized bed, a friction term accounting for the effect of the walls of the bed on the continuum solid phase is introduced in the hybrid-model, as proposed by Hernández-Jiménez et al. (4). According to the results, prediction of the fuel circulation time is clearly improved when the friction term is included in the simulation (Figure-2). REFERENCES Hernández-Jiménez F. , Garcia-Gutierrez L.M., Soria-Verdugo A., Acosta-Iborra A. 2015. Fully coupled TFM-DEM simulations to study the motion of fuel particles in a fluidized bed, Chem. Eng. Sci.,134, 29, 57-66. Soria-Verdugo, A., Garcia-Gutierrez, L.M., Sánchez-Delgado, S., Ruiz-Rivas,U., 2011a. Circulation of an object immersed in a bubbling fluidized bed. Chem. Eng. Sci. 66, 78–87. Soria-Verdugo, A., Garcia-Gutierrez, L.M., García-Hernando, N., Ruiz-Rivas, U., 2011b. Buoyancy effects on objects moving in a bubbling fluidized bed. Chem. Eng. Sci.66, 2833–2841. Hernández-Jiménez, F., Cano-Pleite, E., Sánchez-Prieto, J., Garcia-Gutierrez, L.M., Acosta-Iborra, A. Development of an empirical wall-friction model for 2D simulations of pseudo-2D fluidized beds. Submitted for publication. Please click Additional Files below to see the full abstract

Analysis of biomass and sewage sludge devolatilization using the distributed activation energy model

Procceedings of: 3th Conference on renewables for desert regions. Global Conference on Renewable energy and Energy Efficiency for Desert Regions 2011 "GCREEDER 2011". Tokk place 2011 April 26-28,in Aman (Jordanian). The Event Web site is http://www.solarthermalworld.org/content/gcreeder-2011-amanThe thermal decomposition of biomass (pine pellets) and sewage sludge was studied using thermogravimetric analysis under an inert atmosphere and the Distributed Activation Energy Model (DAEM) was employed. The activation energy and the frequency factor that characterize the kinetics were determined for both samples. A simplification of the process for prediction of devolatilization curves was proposed, evaluating its validity for both cases. The simplified method was found to combine both simplicity and low deviations with experimental data.This work has been partially supported by the National Energy Program of the Spanish Department of Science and Education (ENE2006-01401), the Spanish Government (DPI2009-10518 MICINN) and the Madrid Community (CCG07-uc3 m/amb-3412, CCG08-uc3 m/amb-4227 and P2009/ENE- 1660).Publicad

Buoyancy effects on objects moving in a bubbling fluidized bed

The effect of buoyant forces on the motion of a large object immersed in a bubbling fluidized bed (BFB) was experimentally studied using digital image analysis. The experiments were performed in a 2 D bubbling fluidized bed with glass spheres as bed material and cylindrical objects with different densities and sizes. The object motion was measured using non intrusive tracking techniques. The effect of gas velocity was also analyzed. The circulation of an object in a BFB is defined by several parameters. The object might be able to circulate homogeneously throughout the bed or stay in preferred regions, such as the splash zone or the bottom zone. While circulating, the object moves back and forth between the surface of the bed and the inner regions, performing a series of cycles. Each cycle is composed by sinking and rising paths, which can be one or several, depending on whether a passing bubble is able to lift the object to the surface or the object is detached from it or its drift at an intermediate depth. Therefore, the number of rising paths or number of jumps that the object undergo in a cycle, interleaved with sinking paths, and the maximum attained depth characterize each cycle, together with the mean sinking and rising velocities of the object. In this work, experimental measurements of the probability distributions of the number of jumps and the maximum attained depth, the axial homogeneity of object motion and rising and sinking object velocities are presented for objects with different sizes and densities. The results show a coherent behavior, independent of density and size, for the probability distributions of the number of jumps. This is also true for the maximum attained depth, but only when a proper circulation throughout the bed is ensured. Such a proper circulation and axial homogeneity is, on the other hand, much affected by object density, size and gas velocity. Rising and sinking velocities are highly dependent on gas velocity, as established in well known models of bubble and dense phase velocities. Nevertheless, rising velocities are practically unaffected by object density or size, while sinking velocities show a low dependence on density and a steeper one on size. These results suggest that buoyant forces are relevant during the sinking process, and almost neutral during the rising pathThis work has been partially supported by the National Energy Program of the Spanish Department of Science and Education (ENE2006-01401), the Spanish Government (DPI2009-10518 MICINN) and the Madrid Community (CCG07-uc3m/amb-3412 and CCG08-uc3m/amb-4227)Publicad

Circulation of an object immersed in a bubbling fluidized bed

The motion of a large object in a bubbling fluidized bed was experimentally studied using digital image analysis (DIA). The experiments were performed in a 2 D bubbling fluidized bed with glass spheres as bed material. The object motion was measured using non intrusive tracking techniques, while independent measurements of the dense phase velocity (using Particle Image Velocimetry (PIV)) and bubble velocity (using DIA) were carried out. The effect of the dimensionless gas velocity on the object motion was also analyzed. This work characterizes the circulation patterns of an object with a density similar to that of the bed, but much larger in size. Object size and density remained constant throughout the experiments. A comparison between the motion of sinking objects and the motion of the dense phase provided evidence of the feeble effect of buoyant forces on the motion of sinking objects. In contrast, the motion of rising objects is linked to the motion of bubbles. It was found that objects may be raised to the surface of the bed either by the action of a single bubble (one jump) or by several passing bubbles (multiple jumps). Based on these results, the circulation time of objects throughout the bed is a function of two parameters: the maximumdepth attained by an object and the number of jumps during its rising path. This relationship is presented along and the multiple jumps phenomenon is studied in detail. Finally, an estimate of the circulation time of an object based on semi empirical expressions is presented for different dimensionless gas velocities. The probability density function of the circulation time shows two different modes as the object was less prone to be raised atmoderate depths. The estimate of the circulation time was found to be in good agreement with our experimental dataThis work has been partially supported by the National Energy Program of the Spanish Department of Science and Education (ENE2006-01401) and the Madrid Community (CCG07-uc3m/amb-3412 andCCG08-uc3m/amb-4227)Publicad

Simulation of object motion in a bubbling fluidized bed using a Monte Carlo method

The motion of a large neutrally-buoyant object immersed in a 2D bubbling fluidized bed was simulated using a Monte Carlo method. The object vertical trajectory within the bed was simulated for a range of dimensionless gas velocities using a simple 1D model. The main characteristics of the object motion were obtained from the trajectory simulation and compared with experimental evidence giving good results. On a second step, the time scale of the motion is introduced in the simulated data by means of well-known 2D correlations for the bubble and dense phase velocity. The circulation time of an object (from the instant when it leaves the freeboard and sinks in the dense phase till the moment it reappears back in the surface) was then obtained and compared with experimental data, showing a general agreement. Finally, an extrapolation for a 3D fluidized bed was made following a similar procedure.This work has been partially supported by the National Energy Program of Spanish Government (DPI2009-10518 MICINN) and the Madrid Community (CARDENER-CM S2009ENE-1660).Publicad

Advertising Liking Recognition Technique Applied to Neuromarketing by Using Low-Cost EEG Headset

In this paper a new neuroscience technique is applied into Marketing, which is becoming commonly known as the field of Neuromarketing. The aim of this paper is to recognize how brain responds during the visualization of short advertising movies. Using low cost electroencephalography (EEG), brain regions used during the presentation have been studied. We may wonder about how useful it is to use neuroscience knowledge in marketing, what can neuroscience add to marketing, or why use this specific technique. By using discrete techniques over EEG frequency bands of a generated labeled dataset, C4.5 and ANN learning methods have been applied to obtain the score assigned to each ads by the user. This techniques allows to reach more than 82% of accuracy, which is an excellent result taking into account the kind of low-cost EEG sensors used.Ministerio de Economía y Competitividad TIN2013-46801- C4-1-rJunta de Andalucía TIC-805

Experimental study of solid mixing mechanism in a 2D fluidized bed

The main mechanism of solids mixing in bubbling fluidized beds is well understood. When a bubble rises through the bed, it carries a wake of particles to the bed surface. A downflow of solids exists in the region surrounding the rising bubbles, resulting on an overall convective circulation of particles in the axial direction (1). In this work, a new method to characterize solids mixing in a 2D fluidized bed is developed. This mixing index is able to macroscopically characterize the rate of mixing in a fluidized bed by means of DIA. The mixing index is analogous to the Lacey’s mixing index of particle mixing (2). The experiments are carried out in a pseudo-2D fluidized bed using glass beads as bed material. These glass beads have the same density and diameter but half of them are painted in black (Figure-1). At the beginning of each experiment, the particles are placed in a perfectly lateral segregated state and then the fluidizing air is suddenly injected while images are recorded. Two different regions are detected in the time evolution of the mixing index. The first one is a region with a fast convective mixing, where the initial boundary between the black and white particles is broken. The second one is a region where diffusive mixing is dominant and the particles clusters are mixed with the bulk following an exponential trend (Figure-1). These two mechanisms, as well as the overall mixing time are characterized for different superficial gas velocities and particle sizes. REFERENCES M.J. Rhodes, X.S. Wang, M. Nguyen, P. Stewart, K. Liffman. Study of mixing in gas-fluidized beds using DEM model. Chem. Eng. Sci., 56(8):2859-2866, 2001. P.M.C. Lacey. Developments in the theory of particle mixing. J. Appl. Chem., 4:257-268, 1954. Please click Additional Files below to see the full abstract

Bridging the gap between stellar-mass black holes and ultraluminous X-ray sources

The X-ray spectral and timing properties of ultraluminous X-ray sources (ULXs) have many similarities with the very high state of stellar-mass black holes (power-law dominated, at accretion rates greater than the Eddington rate). On the other hand, their cool disk components, large characteristic inner-disk radii and low characteristic timescales have been interpreted as evidence of black hole masses ~ 1000 Msun (intermediate-mass black holes). Here we re-examine the physical interpretation of the cool disk model, in the context of accretion states of stellar-mass black holes. In particular, XTE J1550-564 can be considered the missing link between ULXs and stellar-mass black holes, because it exhibits a high-accretion-rate, low-disk-temperature state (ultraluminous branch). On the ultraluminous branch, the accretion rate is positively correlated with the disk truncation radius and the bolometric disk luminosity, while it is anti-correlated with the peak temperature and the frequency of quasi-periodic-oscillations. Two prototypical ULXs (NGC1313 X-1 and X-2) also seem to move along that branch. We use a phenomenological model to show how the different range of spectral and timing parameters found in the two classes of accreting black holes depends on both their masses and accretion rates. We suggest that ULXs are consistent with black hole masses ~ 50-100 Msun, moderately inefficiently accreting at ~20 times Eddington.Comment: 11 pages, accepted for publication in Astrophysics and Space Science. Based on work presented at the Fifth Stromlo Symposium, Australian National University, Dec 200