Low impact velocity wastage in FBCs : experimental results and comparison between abrasion and erosion theories

The use of technologies related to combustion of coal in fluidized bed combustors (FBCs) present attractive advantages over conventional pulverized coal units. Some of the outstanding characteristics are: excellent heat transfer, low emission of contaminants, good combustion efficiencies and good fuel flexibility. However, FBC units can suffer materials deterioration due to particle interaction of solid particles with the heat transfer tubes immersed on the bed (Hou, 2004, Oka, 2004, Rademarkers et al., 1990). Among other issues, some of the most important factors believed to cause wear problems are: the motion of slowly but relatively coarse particles, particles loaded onto the surface by other particles, erosion by relatively fast-moving particles associated with bubbles, and abrasion by blocks of particles thrown into the surface by bubble collapse. Thus, erosion or abrasion processes can occur by a variety of causes. For the case of particle movement against in-bed surfaces, it has been suggested that there is no difference in the ability to cause degradation between solid particle erosion and low stress three body abrasion, and distinctions between the two forms of wear should not to be made (Levy, 1987)

Free initial wave packets and the long-time behavior of the survival and nonescape probabilities

The behavior of both the survival S(t) and nonescape P(t) probabilities at long times for the one-dimensional free particle system is shown to be closely connected to that of the initial wave packet at small momentum. We prove that both S(t) and P(t) asymptotically exhibit the same power-law decrease at long times, when the initial wave packet in momentum representation behaves as O(1) or O(k) at small momentum. On the other hand, if the integer m becomes greater than 1, S(t) and P(t) decrease in different power-laws at long times.Comment: 4 pages, 3 figures, Title and organization changed, however the results not changed, To appear in Phys. Rev.

Examining the structure of ideas of reference in clinical and community samples

Aims: This study addresses the psychometric properties of a Spanish validation of the REF scale of ideas of reference (IRs) in detecting and following at-risk mental states and psychosis. Methods: A total of 9447 participants were distributed in three groups: 676 patients with various diagnoses-154 with psychotic disorders, 6291 youths aged 11 to 20, and 2480 adult participants aged 21 to 84. Results: Youths had higher scores than adults on IRs, observing a progressive decrease and stabilization in the twenties. Exploratory factor analysis provided a structure for the overall IRs score, with five first-order dimensions and one second-order dimension. Confirmatory factor analysis supported the structure with excellent fit. The REF scale was invariant across sex and samples. The internal consistency of the complete scale was excellent and acceptable across the five first-order factors. Strong relationships were found with the positive dimension of the community assessment of psychic experience-42, as well as with aberrant salience. Low and moderate relationships were found with public self-consciousness, anxiety, and depression. Youths and patients diagnosed with schizophrenia and other psychotic disorders had a high mean IRs frequency. Male sex, greater age (among the adults), and the "causal explanations", "Songs, newspapers, books" and laughing and commenting" REF subscales showed predictive power in the diagnostic categories of schizophrenia and other psychotic disorders

Dynamical description of the buildup process in resonant tunneling: Evidence of exponential and non-exponential contributions

The buildup process of the probability density inside the quantum well of a double-barrier resonant structure is studied by considering the analytic solution of the time dependent Schr\"{o}dinger equation with the initial condition of a cutoff plane wave. For one level systems at resonance condition we show that the buildup of the probability density obeys a simple charging up law, $| \Psi (\tau) / \phi | =1-e^{-\tau /\tau_0},$ where $\phi$ is the stationary wave function and the transient time constant $\tau_0$ is exactly two lifetimes. We illustrate that the above formula holds both for symmetrical and asymmetrical potential profiles with typical parameters, and even for incidence at different resonance energies. Theoretical evidence of a crossover to non-exponential buildup is also discussed.Comment: 4 pages, 2 figure