Radiative lifetimes of electrons and holes in a thin semiconductor layer

Radiative lifetimes of nondegenerate electrons and holes distributed uniformly in a semiconductor layer either deposited on a substrate or bounded by two dielectric media are calculated. The obtained expression takes into account the radiation reabsorbtion and interference effects and determines the dependences of the radiative lifetimes on the refractive indices of the external media and on the layer thickness.     

Is Deep-Learning and Natural Language Processing Transcending the Financial Forecasting? Investigation Through Lens of News Analytic Process

Computational Economics - This study tries to unravel the stock market prediction puzzle using the textual analytic with the help of natural language processing (NLP) techniques and Deep-learning...     

Development of an Autonomous Robot for Gas Storage Spheres Inspection

Inspection for corrosion of gas storage spheres at the welding seam lines must be done periodically. Until now this inspection is being done manually and has a high cost associated to it and a high risk of inspection personel injuries. The Brazilian Petroleum Company, Petrobras, is seeking cost reduction and personel safety by the use of autonomous robot technology. This paper presents the development of a robot capable of autonomously follow a welding line and transporting corrosion measurement sensors. The robot uses a pair of sensors each composed of a laser source and a video camera that allows the estimation of the center of the welding line. The mechanical robot uses four magnetic wheels to adhere to the sphere’s surface and was constructed in a way that always three wheels are in contact with the sphere’s metallic surface which guarantees enough magnetic atraction to hold the robot in the sphere’s surface all the time. Additionally, an independently actuated table for attaching the corrosion inspection sensors was included for small position corrections. Tests were conducted at the laboratory and in a real sphere showing the validity of the proposed approach and implementation.     

Experimental determination of dielectric barrier discharge capacitance

The determination of electrical parameters (such as instantaneous power, transferred charge, and gas gap voltage) in dielectric barrier discharge (DBD) reactors relies on estimates of key capacitance values. In the classic large-scale sinusoidal-voltage driven DBD, also known as silent or ozonizer discharge, capacitance values can be determined from charge-voltage (Q-V) plot, also called Lissajous figure. For miniature laboratory reactors driven by fast pulsed voltage waveforms with sub-microsecond rise time, the capacitance of the dielectric barriers cannot be evaluated from a single Q-V plot because of the limited applicability of the classical theory. Theoretical determination can be problematic due to electrode edge effects, especially in the case of asymmetrical electrodes. The lack of reliable capacitance estimates leads to a "capacitance bottleneck" that obstructs the determination of other DBD electrical parameters in fast-pulsed reactors. It is suggested to obtain capacitance of dielectric barriers from a plot of the maximal charge versus maximal voltage amplitude (Q(max) - V(max) plot) in a manner analogous to the classical approach. The method is examined using measurements of current and voltage waveforms of a coaxial DBD reactor in argon at 100 mbar driven by square voltage pulses with a rise time of 20 ns and with different voltage amplitudes up to 10 kV. Additionally, the applicability of the method has been shown for the data reported in literature measured at 1 bar of nitrogen-oxygen gas mixtures and xenon.     

Mapping of visual receptive fields by tomographic reconstruction

The moving bar experiment is a classic paradigm for characterizing the receptive field (RF) properties of neurons in primary visual cortex (V1). Current approaches for analyzing neural spiking activity recorded from these experiments do not take into account the point-process nature of these data and the circular geometry of the stimulus presentation. We present a novel analysis approach to mapping V1 receptive fields that combines point-process generalized linear models (PPGLM) with tomographic reconstruction computed by filtered-back projection. We use the method to map the RF sizes and orientations of 251 V1 neurons recorded from two macaque monkeys during a moving bar experiment. Our cross-validated goodness-of-fit analyses show that the PPGLM provides a more accurate characterization of spike train data than analyses based on rate functions computed by the methods of spike-triggered averages or first-order Wiener-Volterra kernel. Our analysis leads to a new definition of RF size as the spatial area over which the spiking activity is significantly greater than baseline activity. Our approach yields larger RF sizes and sharper orientation tuning estimates. The tomographic reconstruction paradigm further suggests an efficient approach to choosing the number of directions and the number of trials per direction in designing moving bar experiments. Our results demonstrate that standard tomographic principles for image reconstruction can be adapted to characterize V1 RFs and that two fundamental properties, size and orientation, may be substantially different from what is currently reported.     

Prevalence of several cardiovascular risk factors in a population in the municipality of Viseu

STUDY OBJECTIVE: To assess the prevalence of the main changeable cardiovascular risk factors (hypertension, hypercholesterolemia and smoking) in the population of the Viseu municipality. MATERIAL AND METHODS: The population was obtained through a publicity campaign in local radios and on lighted placards in the town of Viseu. We chose a set of volunteers above 20 years of age, who answered a questionnaire about smoking habits, academic qualifications, profession and residence. After the inquiry, the total cholesterol and blood pressure were determined. We considered hypertension (HBP) values > or = 140/90 mmHg and hypercholesterolemia > 200 mg/dl. RESULTS: 1852 persons were inquired (3.2% of the population of the Viseu municipality) 1173 of which were females. According to the age groups, we verified that the ages between 50 and 69 years represented 47.9% of the total amount of volunteers. In what concerns smoking habits, we found a prevalence of 9.1% (15.9% in males and 5.2% in females). In the study of the prevalence of HBP we found a value of 38.5%, higher in males (42.8%) than in females (35.9%). The prevalence of hypercholesterolemia found was 34.9% (no significant differences between the sexes). CONCLUSION: In comparison with other studies carried out in the Portuguese population, a low prevalence of smoking habits, high hypertension and similar hypercholesterolemia were found.     

Faraday-active Fabry-Perot resonator: transmission, reflection, and emissivity

The propagation of light within a semiconductor Faraday-active Fabry-Perot resonator is investigated theoretically and experimentally. It is shown that an external magnetic field radically changes the angular and spectral characteristics of transmission, reflection, and emissivity of the resonator not only for polarized, but also for unpolarized, light. Suppression of interference patterns and phase inversion of the interference extrema were observed in both monochromatic and polychromatic light. The investigations were carried out for the plane-parallel plates of n-InAs in the spectral range of free charge carrier absorption. The results can be used to create new controllable optical and spectroscopic devices for investigation of Faraday-active material properties and for control of parameters of plane-parallel layers and structures.