Reducing the variability in random-phase initialized Gerchberg-Saxton Algorithm

Gerchberg-Saxton Algorithm is a common tool for designing Computer Generated Holograms. There exist some standard functions for evaluating the quality of the final results. However, the use of randomized initial guess leads to different results, increasing the variability of the evaluation functions values. This fact is especially detrimental when the computing time is elevated. In this work, a new tool is presented, able to describe the fidelity of the results with a notably reduced variability after multiple attempts of the Gerchberg-Saxton Algorithm. This new tool results very helpful for topical fields such as 3D digital holography

A new manual wheelchair propulsion system with self-locking capability on ramps

A wheelchair user faces many difficulties in their everyday attempts to use ramps, especially those of some length. The present work describes the design and build of a propulsion system for manual wheelchairs for use in ascending or descending long ramps. The design is characterized by a self-locking mechanism that activates automatically to brake the chair when the user stops pushing. The system consists of a planetary transmission with a self-locking capacity coupled to a push rim with which the user moves the system. Different transmission ratios are proposed, adapted to the slope and to the user’s physical capacity (measured as the power the user can apply over ample time periods). The design is shown to be viable in terms of resistance, and approximate dimensions are established for the height and width of the propulsion system. Also, a prototype was built in order to test the self-locking system on ramps

Iluminación de vías públicas: mejora eficiencia energética del túnel de la Alcazaba (Málaga)

Ante la deficiente iluminación que actualmente está instalada en el túnel de la Alcazaba en Málaga,se realiza un estudio sobre cómo se podría mejorar este importante factor y a la vez reducir el consumo energético

Optimized square Fresnel zone plates for microoptics applications

Polygonal Fresnel zone plates with a low number of sides have deserved attention in micro and nanoptics, because they can be straightforwardly integrated in photonic devices, and, at the same time, they represent a balance between the high-focusing performance of a circular zone plate and the easiness of fabrication at micro and nano-scales of polygons. Among them, the most representative family are Square Fresnel Zone Plates (SFZP). In this work, we propose two different customized designs of SFZP for optical wavelengths. Both designs are based on the optimization of a SFZP to perform as close as possible as a usual Fresnel Zone Plate. In the first case, the criterion followed to compute it is the minimization of the difference between the area covered by the angular sector of the zone of the corresponding circular plate and the one covered by the polygon traced on the former. Such a requirement leads to a customized polygon-like Fresnel zone. The simplest one is a square zone with a pattern of phases repeating each five zones. On the other hand, an alternative SFZP can be designed guided by the same criterion but with a new restriction. In this case, the distance between the borders of different zones remains unaltered. A comparison between the two lenses is carried out. The irradiance at focus is computed for both and suitable merit figures are defined to account for the difference between them

Octave-spanning supercontinuum generation in highly nonlinear silica fibres based on cost-effective fibre amplifiers

We report a simple method for supercontinuum generation. The set-up consists of an Er-doped mode-locked fibre laser, used as seed, and a highly nonlinear fibre with zero dispersion at 1550¿nm. Thus, all the components are easily attainable. With this novel system the requirements in terms of control of dispersion are reduced. In addition, the spectral width is optimized using fibres with positive and negative dispersion. The supercontinuum emission is characterized by means of an optical spectrum analyser and a PbS photodetector, showing an octave-spanning spectral width, with a flat profile from 1100¿nm up to 2100¿nm. Compared to other supercontinuum sources, this new proposal results in a very competitive and attainable system, particularly in the 1500–2100 nm region

Adaptation and psychometric study of the scale for the measurement of fear and anxiety of COVID-19 disease in pregnant women (AMICO_Pregnant)

https://www.frontiersin.org/articles/10.3389/fpubh.2023.1225822/full#supplementary-materialObjective: The aim of this research was to adapt and explore the psychometric properties of a specific scale to assess the levels of fear and anxiety of COVID-19 disease in pregnant women. Methods: An adaptation phase, by a panel of experts, and a psychometric descriptive cross-sectional study were carried out on the final version of the 16- item, self-administered AMICO_Pregnant scale. Univariate and bivariate analyses were carried out, followed by exploratory factor analysis (EFA) and confirmatory factor analysis (CFA). The consistency of the scale was assessed using the Omega coefficient and Cronbach’s Alpha. Results: With a sample of 1,013 pregnant women living in Spain and over 18 years of age, the mean age was 33 years. The scale showed a bifactor structure (anxiety and fear) that was confirmed with good fit parameters. Reliability was assessed in terms of internal consistency by calculating Cronbach’s Alpha coefficient (0.95) and McDonald’s Omega coefficient (0.94) as indicators of robustness of the scale’s reliability. Conclusion: The AMICO_Pregnant scale of 16 items with scores ranging from 1 to 10 is a valid and reliable tool to assess levels of anxiety and fear of COVID_19 in Spanish pregnant women. Pregnant women have shown moderate levels of anxiety and fear regarding the COVID_19 disease in the final phase of the pandemic

ELEMENTOS MICRO-ÓPTICOS DE BAJO COSTE

Las técnicas actuales de impresión digital permiten generar elementos difractivos para el visible a muy bajo coste, por ello, con este trabajo, queremos comprobar si, con una impresora convencional, se pueden fabricar elementos difractivos que respondan con un buen comportamiento y cuyo coste sea mínimo. El objetivo fundamental de este trabajo es el estudio de técnicas difractivas en aproximación de Fresnel o campo cercano. Precisamente, en este trabajo se aprenderá a caracterizar estos elementos micro-ópticos, tanto redes de difracción como lentes zonales para su uso en aproximación de Fresnel. De esta manera damos un valor añadido al trabajo, puesto que existe poca literatura sobre la fabricación de elementos difractivos con una impresora para su uso en aproximación de campo cercano (Fresnel) en comparación a la de campo lejano. Se determinarán, además, las limitaciones en cuanto a la resolución de la impresora empleada para la caracterización de los elementos difractivos. Para ello se utilizarán elementos comunes en laboratorios de micro-óptica (lentes, polarizadores, fuentes láser, cámaras digitales). El objetivo resultante de todo ello es la adquisición de destreza experimental en el campo de óptica difractiva y la familiarización con el formalismo de Fresnel

Fear and Anxiety in Pregnant Women During the COVID-19 Pandemic: A Systematic Review

Objectives: The aim of this study was to explore the impact of the 2020–2022 pandemic on the levels of fear and anxiety in pregnant women and to identify risk and protective factors.Methods: A systematic review was conducted. Electronic databases were consulted for studies published between January 2020 and August 2022. The methodological quality was assessed using a critical appraisal tool for non-randomised studies.Results: Seventeen studies were included in the review. A high prevalence of levels of fear and anxiety were observed. Risk factors such as unplanned pregnancy, poor support from partners, or intolerance of uncertainty were identified for high levels of fear. Regarding anxiety, risk factors such as maternal age, social support, financial status, or concern about being able to maintain antenatal follow-ups were identified.Conclusion: The COVID-19 pandemic had a significant impact on the mental health of pregnant women through increased levels of fear and anxiety. It has not been possible to establish a relationship between significant factors such as gestational age or health emergency control measures with high levels of fear or anxiety