Synchronization method for distributed systems with functional safety

[EN] Time synchronization is a key requirement in several application domains based on real-time distributed systems. Therefore, it is a research area of interest, especially in lines such as the transfer of time and frequency, the design of clocks and oscillators, and the use of synchronization in communication networks. This work focuses on the transfer of time between elements of a distributed system for the synchronization of their clocks and the software they execute. Currently, there are different protocols to synchronize autonomous nodes, but they have some drawbacks that make them unsuitable for certain types of distributed systems. This paper presents a method for synchronizing the execution of distributed software on a local area network. Additionally, the functional safety analysis of the method is developed and the measures it must implement to achieve a SIL2 are proposed. The method has been implemented and validated by executing it in a realistic physical distributed system, obtaining promising results.[ES] La sincronización temporal es un requisito clave en varios dominios de aplicación basados en sistemas de tiempo real distribuidos. Por ello es un campo de investigación que despierta interés, especialmente en líneas como la transferencia del tiempo y la frecuencia, el diseño de relojes y osciladores, y el uso de sincronización en redes de comunicación. El presente trabajo se centra en la transferencia del tiempo entre elementos de un sistema distribuido para la sincronización de sus relojes y el software que ejecutan. En la actualidad existen diferentes protocolos para sincronizar relojes distribuidos, pero tienen una serie de inconvenientes que los hace inadecuados para determinados tipos de sistemas. En este trabajo se presenta un método para sincronizar la ejecución de software distribuido en una red de área local. Adicionalmente, se desarrolla el análisis de seguridad funcional del método y se proponen las medidas que tiene que implementar para alcanzar un nivel SIL2. El método se ha implementado y se ha validado ejecutándolo en un sistema distribuido físico realista, obteniendo unos resultados prometedores.Azketa, E.; Mendialdua, X.; Ibarguren, I.; Solís, A. (2021). Método de sincronización para sistemas distribuidos con seguridad funcional. Revista Iberoamericana de Automática e Informática industrial. 18(2):113-118. https://doi.org/10.4995/riai.2020.14022OJS113118182Eidson, J. C., 2006. Measurement, Control, and Communication Using IEEE 1588 (Advances in Industrial Control). Springer.EN, 2011. EN 50159: Railway applications - Communication, signalling and processing systems - Safety-related communication in transmission systems.EN, 2012. EN 50128: Railway applications - Communication, signalling and processing systems - Software for railway control and protection systems.Hofmann-Wellenhof, B., Lichtenegger, H., Wasle, E., 2007. GNSS-global navigation satellite systems: GPS, GLONASS, Galileo, and more. Springer Science & Business Media.IEC, 2005. IEC 62061: Safety of machinery - Functional safety of safety-related electrical, electronic and programmable electronic control systems.IEC, 2010. IEC 61508: Functional safety of electrical/electronic/ programmable electronic safety-related systems.IEC, 2015. IEC 62304: Medical device software - Software life cycle processes.ISO, 2018. ISO 26262: Road vehicles - Functional safety.Lévesque, M., Tipper, D., 2016. A survey of clock synchronization over packet-switched networks. IEEE Communications Surveys & Tutorials 18.4, 2926-2947. https://doi.org/10.1109/COMST.2016.2590438Mills, D. L., 2010. Computer Network Time Synchronization: The Network Time Protocol on Earth and in Space, Second Edition. CRC Press.Green Hills Software. INTEGRITY Real-Time Operating System, https://www.ghs.com/products/rtos/integrity.html.Green Hills Software. MULTI Integrated Development Environment, https://www.ghs.com/products/MULTI_IDE.html.Weiss, M., Eidson, J., Barry, C., Broman, D., 2015. Time-aware applications, computers, and communication systems (TAACCS). NIS. https://doi.org/10.6028/NIST.TN.186

Optimization of a high work function solution processed vanadium oxide hole-extracting layer for small molecule and polymer organic photovoltaic cells

We report a method of fabricating a high work function, solution processable vanadium oxide (V2Ox(sol)) hole-extracting layer. The atmospheric processing conditions of film preparation have a critical influence on the electronic structure and stoichiometry of the V2Ox(sol), with a direct impact on organic photovoltaic (OPV) cell performance. Combined Kelvin probe (KP) and ultraviolet photoemission spectroscopy (UPS) measurements reveal a high work function, n-type character for the thin films, analogous to previously reported thermally evaporated transition metal oxides. Additional states within the band gap of V2Ox(sol) are observed in the UPS spectra and are demonstrated using X-ray photoelectron spectroscopy (XPS) to be due to the substoichiometric nature of V2Ox(sol). The optimized V2Ox(sol) layer performance is compared directly to bare indium–tin oxide (ITO), poly(ethyleneoxythiophene):poly(styrenesulfonate) (PEDOT:PSS), and thermally evaporated molybdenum oxide (MoOx) interfaces in both small molecule/fullerene and polymer/fullerene structures. OPV cells incorporating V2Ox(sol) are reported to achieve favorable initial cell performance and cell stability attributes

X Ray Photoelectron Spectroscopy studies of laterite standard reference material

X-ray photoelectron spectroscopy is used to characterize two natural samples of laterite standard reference materials (certified geologically), a mechanical mixture of Fe2O3, SiO2 and Al2O3 in a 4/2/1 proportion. Fe2O3, SiO2, and Al2O3 samples were analyzed for, comparison purposes. Special attention was paid to peak shape, FWHM, comparison of the same XPS peaks of different samples, and peak shifts. The XPS results reveal the presence of some kind of iron aluminate prevailing on the surface of the laterite standard reference materials. It is also observed that the mechanical mixture exhibits a differential charging effect. Our report provides important information for the researchers doing XPS on these materials when they are used in catalytic reactions

Caracterizacion por XPS de lateritas estandar

Photoelectron spectroscopy (XPS) is used to characterize mainly two standard laterite samples. Samples of Fe2O3, SiO2, and Al2O3 were also analysed for comparison purposes. A detailed study of the O1s band of oxygen present in these samples allowed us to obtain information which was used to distinguish clearly the samples