Light trapping properties of cylindrical well diffraction gratings in solar cells: Computational calculations

Light trapping using diffraction gratings is a promising approach to increasing absorption in solar cells. In this paper, the computationally calculated absorption enhancement expected from a diffraction grating consisting of a triangular array of cylindrical wells is presented. Angle-extended polychromatic illumination is considered, and special attention is paid to absorption of sub-bandgap photons in an intermediate band solar cell. Results are compared to the absorption enhancement expected from an ideal Lambertian (randomizing) scatterer, which is considered as a baseline. It is found that for cells which absorb very weakly, the diffraction grating provides absorption enhancement above that of the ideal Lambertian scatterer over a wide wavelength range. For cells which absorb more strongly, the grating underperforms the ideal Lambertian scatterer over almost all wavelengths. Finally, the grating period, well height and well radius are optimised. Keywords: Light Trapping, Diffraction Grating, Intermediate Band Solar Cel

3D Reconstruction with Uncalibrated Cameras Using the Six-Line Conic Variety

We present new algorithms for the recovery of the Euclidean structure from a projective calibration of a set of cameras with square pixels but otherwise arbitrarily varying intrinsic and extrinsic parameters. Our results, based on a novel geometric approach, include a closed-form solution for the case of three cameras and two known vanishing points and an efficient one-dimensional search algorithm for the case of four cameras and one known vanishing point. In addition, an algorithm for a reliable automatic detection of vanishing points on the images is presented. These techniques fit in a 3D reconstruction scheme oriented to urban scenes reconstruction. The satisfactory performance of the techniques is demonstrated with tests on synthetic and real data

Propuesta de un plan de mantenimiento preventivo para la caldera de diésel York Shipley instalada en Planta de sub-producto COESA, de Avícola La Estrella, S.A, en el periodo comprendido de agosto a noviembre, 2015

El presente trabajo se realizó en el área de calderas de la Planta de Sub-producto COESA de Avícola La Estrella, S.A., ubicada en el Km 29 ½ de la carretera norte. Esta pequeña planta comenzó operaciones a mediados del mes de mayo de presente año. En la planta se realiza el proceso de elaboración de harina de pollo de todas las aves que son desechadas en las galeras de la empresa. En el inicio del presente trabajo se plantearon los objetivos (general y específicos) cuyo propósito es la mayor optimización productiva del equipo, de la misma manera en el planteamiento del problema se expone que los paros repentinos de la máquina son el principal problema por la falta de un adecuado mantenimiento. En cuanto al marco referencial se establecieron las respectivas teorías, definiciones, las especificaciones de las leyes con las que regir el presente estudio, la localización de la empresa y la especificación temporal en la que se realizó. Este estudio tiene un enfoque de carácter mixto ya que se describen y analizan los datos que generan la información encontrada de la máquina. De la misma manera se estableció el universo, población y muestra que corresponde a la empresa, la planta de subproducto y la máquina evaluada respectivamente y luego las herramientas de investigación que se utilizaron como entrevista, observación y métodos como el árbol de problemas y de fallos y la metodología HAZOP. En el desarrollo se caracteriza el proceso de producción por medio del diagrama de flujo de la norma ISO, se analizan las fallas con el árbol de problemas y árbol de fallo, se implementa la metodología HAZOP en donde se encuentra la “presión” como el mayor factor de riesgo y finalmente la aplicación del correspondiente “Manual MPP” para la caldera con un breve análisis de los costos de mantenimiento, los resultados de la entrevista y la observación aplicada. Finalmente la conclusión basada en los objetivos que se establecieron y luego las respectivas recomendaciones de mejoras para la planta y la caldera en estudio

Novel educational assessment for building structures: Automatic evaluation of on-line graphics

This article presents a new automatic evaluation for on-line graphics, its application and the numerous advantages achieved applying this developed correcting method. The software application developed by the Innovation in Education Group “E4”, from the Technical University of Madrid, is oriented for the online self-assessment of the graphic drawings that students carry out as continuous training. The adaptation to the European Higher Educational Area is an important opportunity to research about the possibilities of on-line education assessment. In this way, a new software tool has been developed for continuous self-testing by undergraduates. Using this software it is possible to evaluate the graphical answer of the students. Thus, the drawings made on-line by students are automatically corrected according to the geometry (straight lines, sloping lines or second order curves) and by sizes (depending on the specific values which define the graphics)

Embedment of metal nanoparticles in GaAs and Si for plasmonic absorption enhancement in intermediate band solar cells

The high near-field enhancement occurring in the vicinity of metallic nanoparticles (MNPs) sustaining surface plasmons can only be fully exploited in photovoltaic devices if the MNPs are placed inside their semiconducting material, in the photoactive region. In this work an experimental procedure is studied to embed MNPs in gallium arsenide (GaAs) and silicon (Si), which can be applied to other semiconductor host materials. The approach consists in spin-coating colloidal MNPs dispersed in solution onto the substrate surface. Then a capping layer of the same material as the substrate is deposited on top to embed the MNPs in the semiconductor. The extinction spectra of silver (Ag) and gold (Au) MNPs embedded in GaAs and Si is modeled with Mie theory for comparison with optical measurements. This contribution constitutes the initial step towards the realization of quantum-dot intermediate band solar cells (QD-IBSC) with MN

Construction of an Instrument for the Evaluation of the Effects of Information and Communication Technologies among Young People

The aim of this paper is to investigate the issue of access to Information and Communication Technologies (ICT) at younger ages, which is leading to dependency on mobile phones, video games, and compulsive aimless internet surfing—an issue that schools have been increasingly seeking to tackle. With the appearance of emerging technologies, and not forgetting those already established, an instrument is required that will adapt to new casuistry and help to design intervention programmes in accordance with present and future patterns of use, abuse, and addiction. Studies such as the one proposed here will provide data about the profile of this population in order to improve programmes and influence the ICT policies rolled out by central and local governments. The chief aim of this paper is to construct and validate an instrument capable of evaluating problems experienced by young people in relation to technology use, abuse, and addiction within the programmes developed in Spain. The research design used in this study is mixed empirical, non-experimental, and sequential in nature in three stages: interviews conducted with 11 prevention professionals, group of 11 experts and pilot group of 30 participants in indicated prevention programmes. The findings of the study indicate that the instrument fulfills the parameters established to be considered a systematic empirically sustainable instrument, since the young population needs to identify these patterns in order to understand and prevent risk behaviours associated with their use.This research was funded by Fundación Bancaria “La Caixa” and Proyecto Hombre Association

Radiative thermal escape in intermediate band solar cells

To achieve high efficiency, the intermediate band (IB) solar cell must generate photocurrent from sub-bandgap photons at a voltage higher than that of a single contributing sub-bandgap photon. To achieve the latter, it is necessary that the IB levels be properly isolated from the valence and conduction bands. We prove that this is not the case for IB cells formed with the confined levels of InAs quantum dots (QDs) in GaAs grown so far due to the strong density of internal thermal photons at the transition energies involved. To counteract this, the QD must be smaller

Atazanavir-Based Therapy Is Associated with Higher Hepatitis C Viral Load in HIV Type 1-Infected Subjects with Untreated Hepatitis C

Comunicación cortaWe assessed the relationship between atazanavir (ATV)-based antiretroviral treatment (ART) and plasma hepatitis C virus (HCV) viral load in a population of HIV/HCV-coinfected patients. HIV/HCV-coinfected patients who received ART based on a protease inhibitor (PI) or nonnucleoside reverse transcriptase inhibitor (NNRTI) were included. Patients were stratified by ART drug [ATV/rtv, lopinavir (LPV/rtv), efavirenz (EFV), nevirapine (NVP), and other PIs], HCV genotype (1/4 and 2/3), and IL28B genotype (CC and non-CC). The Kruskal-Wallis test and chi-squared test were used to compare continuous and categorical variables, respectively. Multivariate analysis consisted of a stepwise linear regression analysis. Six hundred and forty-nine HIV/HCV-coinfected patients were included. HCV genotype 1/4 patients who received ATV had higher HCV RNA levels [6.57 (5.9-6.8) log IU/ml] than those who received LPV [6.1 (5.5-6.5) log IU/ml], EFV [6.1 (5.6-6.4) log IU/ml], NVP [5.8 (5.5-5.9) log IU/ml], or other PIs [6.1 (5.7-6.4) log IU/ml] (p=0.014). This association held for the IL28B genotype (CC versus non-CC). The association was not found in patients carrying HCV genotypes 2/3. The linear regression model identified the IL28B genotype and ATV use as independent factors associated with HCV RNA levels. ATV-based therapy may be associated with a higher HCV RNA viral load in HIV/HCV-coinfected patients

Light concentration in the near-field of dielectric spheroidal particles with mesoscopic sizes

This paper presents a numerical study of the light focusing properties of dielectric spheroids with sizes comparable to the illuminating wavelength. An analytical separation-of-variables method is used to determine the electric field distribution inside and in the near-field outside the particles. An optimization algorithm was implemented in the method to determine the particles’ physical parameters that maximize the forward scattered light in the near-field region. It is found that such scatterers can exhibit pronounced electric intensity enhancement (above 100 times the incident intensity) in their close vicinity, or along wide focal regions extending to 10 times the wavelength. The results reveal the potential of wavelength-sized spheroids to manipulate light beyond the limitations of macroscopic geometrical optics. This can be of interest for several applications, such as light management in photovoltaic

Generación de pulsos ópticos a 1,5 μm mediante computación de ganancia en láseres de cavidad vertical

Optical pulses with duration below 60 ps were generated by gain-switching a Vertical Cavity Surface Emitting Laser (VCSEL) at 1535 nm. We used a radio frequency (RF) sinusoidal signal to modulate the device near threshold. Relaxation oscillations or pulse train generation were observed depending on the gain switching conditions. Repetition rates between 100 MHz and 2 GHz were tested. The dependence of the pulse width and amplitude was investigated in relation with the bias current and excitation frequency and amplitude. The optimal configuration of the current bias and RF modulating signal provided the shortest pulse duration of 57 ps at repetition rate of 800 MH