We have studied the energy spectrum of a system formed by two concentric, coupled, semiconductor quantum rings. We have investigated the effect of a uniform magnetic field applied along the rings axis, on the energy spectrum of the system. We found that the spectrum of the coupled rings with similar confinement length corresponds roughly to the superposition of the spectra of two separate rings, although modified by the anticrossings produced among different states of the individual rings with same angular momentum. The Aharonov-Bohm oscillations do not have a definite period.

An IEEE 802.11 analytical perfonnance evaluation model for ad-hoc WLAN's comprising tenninals with different traffk source characteristics is presen ted. Although some publications address this issue, most of them propose to modify the original standard by some means that will affect the probability of transmission of a device when the network reaches congestion. The approach of this publication is to be able to establish a set of equations such that an intelligent choice of configuration parameters of standard horne devices may improve the perfonnance of the wireless network. Actually, two models are presented and compared, a simple one based on stationary behavior ofthe network assuming collisions have a negligible effect on network perfonnance, and a second model based on a stationary stochastic model of a network, where devices have a packet ready for transmission at all times.

For functions f whose Taylor coefficients at the origin form a Hausdorff moment sequence we study the behaviour of w(y) := |f(γ + iy)| for y > 0 (γ ≤ 1 fixed)

The nth cyclic function is defined by jn (z)=C . n=0 znn (nn)! (z ¥ C, 2 [ n ¥ N). We prove that if k is an integer with 1 [ k [ n−1, then R (n − k)! j(k) n (x) xn−k S a < jn (x) < R (n − k)! j(k) n (x) xn−k S b holds for all positive real numbers x with the best possible constants a=1 and b=R2n − k n S .

The field of astronomical data analysis has experienced an important paradigm shift in the recent years. The automation of certain analysis procedures is no longer a desirable feature for reducing the human effort, but a must have asset for coping with the extremely large datasets that new instrumentation technologies are producing. In particular, the detection of transit planets --- bodies that move across the face of another body --- is an ideal setup for intelligent automation. Knowing if the variation within a light curve is evidence of a planet, requires applying advanced pattern recognition methods to a very large number of candidate stars. Here we present a supervised learning approach to refine the results produced by a case-by-case analysis of light-curves, harnessing the generalization power of machine learning techniques to predict the currently unclassified light-curves. The method uses feature engineering to find a suitable representation for classification, and different performance criteria to evaluate them and decide. Our results show that this automatic technique can help to speed up the very time-consuming manual process that is currently done by expert scientists.

This article describes the impact of restricting the air intake in industrial 250 m3 WEMCO flotation cells at Los Pelambres concentrator. The influence of air restriction on the hydrodynamic and metallurgical performance of this type of machine was evaluated. The experiments were conducted in single flotation cells and entire rougher banks. In all cases, the gas holdup was measured to estimate the effectiveness of the obstruction system to decrease the air concentration. In single cells, axial profiles for solid percentage and particle size were evaluated. In addition, mass balances were conducted to assess the copper recoveries and concentrate features. In individual cells, air restriction led to a decrease in the gas holdup. However, this slight change was enough to obtain a more stable froth zone and a better solid suspension. The latter was observed as: (i) a higher P80 below the pulp–froth interface, (ii) a less diluted pulp at this level, (iii) a slightly higher Cu recovery, and (iv) a coarser concentrate product. A mineralogical analysis of the concentrate sample also showed the presence of coarser liberated Cu-sulfide particles. The results in single cells suggested an improvement in the recovery of coarse particles via more intense solid suspension. The air intake was also restricted in three rougher banks to assess the impact of air obstruction on the overall performance of the respective circuit. Eleven out of fourteen cells were operated with air restriction, which led to a significant improvement in recovery of 0.9%–1.6% (absolute), at a 95% confidence level. Size-by-size mass balances were also conducted for the rougher circuits, which proved that the recovery improvements were justified by the simultaneous increase in the recovery of coarse and fine particles. Thus, a restriction in the air intake showed that a decrease in the gas holdup (and in the bubble surface area flux) was compensated by better solid suspension and a higher collision efficiency in the draft tube. The former promoted the recovery of coarse particles in the quiescent zone, whereas the latter improved the interaction between bubbles and fine particles. Further developments are being made to implement a regulatory control strategy for the air intake in self-aspirated flotation cells and to use this approach for optimizing industrial flotation banks.

Miniature high-bandwidth accelerometers on the anterior neck surface are used in laboratory and ambulatory settings to obtain vocal function measures. This study compared the widely applied L1–L2 measure (historically, H1–H2)—the difference between the log-magnitude of the first and second harmonics—computed from the glottal airflow waveform with L1–L2 derived from the raw neck-surface acceleration signal in 79 vocally healthy female speakers. Results showed a significant correlation (r = 0.72) between L1–L2 values estimated from both airflow and accelerometer signals, suggesting that raw accelerometer-based estimates of L1–L2 may be interpreted as reflecting glottal physiological parameters and voice quality attributes during phonation.

In this work, we report the magnetocaloric effect (MCE) for an electron interacting with an antidot, under the effect of an Aharonov-Bohm flux (AB-flux) subjected to a parabolic confinement potential. We use the Bogachek and Landman model, which additionally allows the study of quantum dots with Fock-Darwin energy levels for vanishing antidot radius and AB-flux. We find that AB-flux strongly controls the oscillatory behaviour of the MCE, thus acting as a control parameter for the cooling or heating of the magnetocaloric effect. We propose a way to detect AB-flux by measuring temperature differences.