Hybrid SGP4 orbit propagator

Two-Line Elements (TLEs) continue to be the sole public source of orbiter observations. The accuracy of TLE propagations through the Simplified General Perturbations-4 (SGP4) software decreases dramatically as the propagation horizon increases, and thus the period of validity of TLEs is very limited. As a result, TLEs are gradually becoming insufficient for the growing demands of Space Situational Awareness (SSA). We propose a technique, based on the hybrid propagation methodology, aimed at extending TLE validity with minimal changes to the current TLE-SGP4 system in a non-intrusive way. It requires that the institution in possession of the osculating elements distributes hybrid TLEs, HTLEs, which encapsulate the standard TLE and the model of its propagation error. The validity extension can be accomplished when the end user processes HTLEs through the hybrid SGP4 propagator, HSGP4, which comprises the standard SGP4 and an error corrector.Comment: 18 pages, 4 figure

High-Fidelity Semianalytical Theory for a Low Lunar Orbit

We have developed a semi-analytical theory for low-altitude lunar orbits with the aim of verifying what the minimum order of the gravitational model to be considered should be in order to produce realistic results that can be applied to the analysis and design of real missions. With that purpose, we have considered a perturbation model that comprises a 50x50 gravitational field and the third-body attraction from the Earth. Initially, the process of developing the theory is briefly described. Then, the discussion is focused on the search for frozen orbits, for which the effect of each harmonic term of the gravitational model is analyzed separately. As higher-order zonal harmonics are included, new families of frozen orbits can appear. In addition, the eccentricity and inclination values for which frozen orbits can exist change. This effect is very important and needs to be taken into consideration, because ignoring high-order harmonics can lead to predict the existence of frozen orbits at certain inclinations at which the frozen-orbit eccentricity actually falls beyond the impact limit. Consequently, it has been verified that, in agreement with other authors, a 50x50 gravitational model should be the minimum to be considered for real applications.Comment: 8 pages, 5 figure

Evolution of covalent organic frameworks: from design to real-world applications

Covalent Organic Frameworks are highly versatile porous materials that have attracted much attention over the last few years. This review summarizes the timeline of its development, highlighting the shifts in the targets deemed necessary to use them in real-world applications. We have collected aspects concerning COF formation and the strategies developed to gain chemical stability by using different linkages between the initial building blocks and modulating the structural characteristics of COFs. Importantly, we have also included elements concerning material processability that has been incorporated in the research field of COFs but are essential to solving many different applications of COFs. Finally, we included a summary section providing headlines of this research field to get closer to real applicationsThis work has been supported by the Spanish MICINN (PID2019- 106268GB-C32, and TED2021-129886B-C42) and through the “María de Maeztu” Programme for Units of Excellence in R&D (CEX2018- 000805-M). We also thank financial support to the Comunidad de Madrid (MAD2D-CM) and MICINN (Planes complementarios, Materiales Avanzados

Análisis de la calidad de vida de la familia antes y después de la apertura de un servicio de vivienda por parte de Gautena

Este estudio tiene como objeto evaluar la eficacia de un programa de viviendas para adultos con discapacidad intelectual severa, a la vez que pretende informar del cambio en la calidad de vida familiar y personal de las familias con algún miembro con discapacidad intelectual severa. Se ha llevado a cabo mediante contacto directo con todas las familias que se han incorporado en el programa de viviendas para adultos con discapacidad intelectual severa. Los resultados muestran una mejoría tanto en la calidad de vida familiar como en la personal. Dicha mejoría se aprecia en el adulto con discapacidad intelectual severa y también en sus familiares. La evolución se ha medido mediante un diseño pre-post. Los datos se han obtenido, por una parte, mediante entrevistas semiestructuradas y, por otra, mediante un cuestionario. Ambos instrumentos se han desarrollado con base en el modelo de calidad de vida de Schalock y Verdugo (2003)

Study of the distribution of temperatures in the windings of a transformer after suffering a short-circuit

Power transformers are electrical machines that allow us to transport electric energy, with reduced losses, from generation stations to consumption points. This definition gives us an idea of the number of machines of this type that are used in power distribution systems worldwide. The lifespan of this equipment often exceeds 30 years of operation. Therefore, they can be described as very robust equipment. The main problem that may affect power transformers is the operation at high temperature. This paper summarizes the results of a post mortem study carried out on an 800 kVA distribution transformer. The methodology that is considered for estimating the temperature distribution in the windings of the machine is based on the calculation of the degree of polymerization of the dielectric paper. This parameter is associated with the state of the paper insulation that protects the conductors of the windings. By knowing the value of this magnitude for a new and for an aged paper, and the period of operation of a transformer, the temperature distribution along the height of the windings can be estimated. With these results and the loading regime that a transformer has endured throughout his life, one can draw conclusions for future designs or for similar transformers still in operation

Synergistic enhancement of electrochemiluminescence through hybridization of α-Ge nanolayers and gold nanoparticles for highly sensitive detection of tyramine

This work presents a novel approach for detecting biogenic amine tyramine using a sensitive and disposable electrochemiluminescent sensor. The sensor is fabricated by modifying a screen-printed carbon electrode surface with two nanomaterials, α-Ge nanolayers and AuNP, which synergistically enhance the electrochemiluminescence response. The sensor was characterized using various techniques such as SEM-EDX, EIS, Raman, and AFM. The principle of the biosensor relays on the fact that tyramine molecule acts as an analyte and co-reactant, which interacts with the luminophore [Ru(bpy)3] 2+ on the sensor surface. The proposed sensor shows a linear response to tyramine concentration, with a detection limit of 2.28 µM. The sensor successfully detected tyramine in avocado samples, demonstrating its potential for practical applicationsThis work has been supported the Comunidad Autonoma ´ de Madrid (2021-5A/BIO-20943 Talent Attraction Project, SI3/PJI/2021-00341 and S2018/NMT-4349 TRANSNANOAVANSENS-CM Program) and by the Spanish Ministerio de Ciencia e Innovacion ´ (PID2020-116728RBI00, PDC2021-120782-C21, PID2019-106268GB-C32 and TED2021- 129738B-I00). This work has also been supported by the Spanish MINECO (PID2019-106268GB-C32, CEX2018-000805-M and PDC2021- 120782-C21). We acknowledge the support from the “(MAD2D-CM)- UAM” project funded by Comunidad de Madrid, by the Recovery, Transformation and Resilience Plan, and by NextGenerationEU from the European Unio

Study of the current performance of the European power transformer fleet

In many countries, diverse legislations are today asking for more rational use of energy. For this reason, several initiatives are nowadays promoting a reduction of the overall energy consumption. The European Union has published a Directive 2009/125/EC which fix eco-design requirements to energy-related products. One of these products is power transformers which are a basic piece of generation, transmission, distribution and consumption of electrical energy. The operation of these machines implies the transformation of energy, a part of this energy is dissipated in electrical and magnetic circuits. The amount of losses produce by transformers is defined during the design of these machines. So, they must comply with the above EU Directive. In fact, the Official Journal of the European Union has set a list of energy efficiency limits to be fulfilled by new machines sold in Europe (Commission Regulation 548/2014). This article presents three parts. The calculation of the maximum performance is presented in the first part. This is independent of the load percentage, the impedance and the voltage level. A description of the European fleet of power transformer, up to 100MVA is presented on the second section. In the last part of this work, the efficiency of the fleet is analysed using the maximum performance concept and considering the EU Regulation