37 research outputs found

    Automatizing Software Cognitive Complexity Reduction

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    We model the cognitive complexity reduction of a method as an optimization problem where the search space contains all sequences of Extract Method refactoring opportunities. We then propose a novel approach that searches for feasible code extractions allowing developers to apply them, all in an automated way. This will allow software developers to make informed decisions while reducing the complexity of their code. We evaluated our approach over 10 open-source software projects and was able to fix 78% of the 1,050 existing cognitive complexity issues reported by SonarQube. We finally discuss the limitations of the proposed approach and provide interesting findings and guidelines for developers.Universidad de Málaga (grants B1-2020_01 and B4-2019-05) Project PID2020-116727RB-I00 funded by MCIN/AEI /10.13039/501100011033 Rubén Saborido was recipient of a Juan de la Cierva grant FJC2018-038537-I funded by MCIN/AEI /10.13039/501100011033. Javier Ferrer was supported by a postdoc grant (DOC/00488) funded by the Andalusian Ministry of Economic Transformation, Industry, Knowledge and Universities

    Parallel and Distributed Computing

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    The 14 chapters presented in this book cover a wide variety of representative works ranging from hardware design to application development. Particularly, the topics that are addressed are programmable and reconfigurable devices and systems, dependability of GPUs (General Purpose Units), network topologies, cache coherence protocols, resource allocation, scheduling algorithms, peertopeer networks, largescale network simulation, and parallel routines and algorithms. In this way, the articles included in this book constitute an excellent reference for engineers and researchers who have particular interests in each of these topics in parallel and distributed computing

    An App Performance Optimization Advisor for Mobile Device App Marketplaces

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    On mobile phones, users and developers use apps official marketplaces serving as repositories of apps. The Google Play Store and Apple Store are the official marketplaces of Android and Apple products which offer more than a million apps. Although both repositories offer description of apps, information concerning performance is not available. Due to the constrained hardware of mobile devices, users and developers have to meticulously manage the resources available and they should be given access to performance information about apps. Even if this information was available, the selection of apps would still depend on user preferences and it would require a huge cognitive effort to make optimal decisions. Considering this fact we propose APOA, a recommendation system which can be implemented in any marketplace for helping users and developers to compare apps in terms of performance. APOA uses as input metric values of apps and a set of metrics to optimize. It solves an optimization problem and it generates optimal sets of apps for different user's context. We show how APOA works over an Android case study. Out of 140 apps, we define typical usage scenarios and we collect measurements of power, CPU, memory, and network usages to demonstrate the benefit of using APOA.Comment: 18 pages, 8 figure

    Embeddings Of Maximal Tori In Orthogonal Groups

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    We give necessary and sufficient conditions for an orthogonal group defined over a global field of characteristic not equal 2 to contain a maximal torus of a given type

    Utilizing Divisible Load Scheduling Theorem in Round Robin Algorithm for Load Balancing In Cloud Environment

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    Cloud Computing is a newly paradigm in computing that promises a shift from an organization required to invest heavily for limited IT resources that are internally managed, to a model where the organization can buy or rent resources that are managed by a cloud provider, and pay peruse. With the fast growing of cloud computing one of the areas that is paramount to cloud computing service providers is the establishment of an effective load balancing algorithm that assigns tasks to best Virtual Machines(VM) in such a way that it provides satisfactory performance to both, cloud users and providers. Among these load balancing algorithms in cloud environment Round Robin (RR) algorithm is one of them. In this paper firstly analysis of various Round Robin load balancing algorithms is done. Secondly, anew Virtual Machines (VM) load balancing algorithm has been proposed and implemented; i.e. ‘Divisible Weighted Round Robin(DWRR) Load Balancing Algorithm’. This proposed load balancing algorithm utilizes the Divisible Load Scheduling Theorem in the Round Robin load balancing algorithm. In order to evaluate the performance of this proposed algorithm (DWRR) the researcher used a simulator called CloudSim tool to conduct a test on the performances between the proposed algorithm (DWRR) and the types of Round Robin algorithms. After a thoroughly comparison between these algorithms, the results showed that DWRR outperforms the various types of Round Robin(Weighted Round Robin and Round Robin with server affinity )algorithms in terms of execution time (makespan) with the least complexity. Keywords: Scheduling Algorithm, performance, cloud computing, load balancing algorithm, Divisible Load scheduling Theory

    Advanced Reaction Systems for Hydrogen Production

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    [EN] This PhD work started in March 2010 with the support of the University of the Basque Country (UPV/EHU) under the program named “Formación de Personal Investigador” at the Chemical and Environmental Engineering Department in the Faculty of Engineering of Bilbao. The major part of the Thesis work was carried out in the mentioned department, as a member of the Sustainable Process Engineering (SuPrEn) research group. In addition, this PhD Thesis includes the research work developed during a period of 6 months at the Institut für Mikrotechnik Mainz GmbH, IMM, in Germany. During the four years of the Thesis, conventional and microreactor systems were tested for several feedstocks renewable and non-renewable, gases and liquids through several reforming processes in order to produce hydrogen. For this purpose, new catalytic formulations which showed high activity, selectivity and stability were design. As a consequence, the PhD work performed allowed the publication of seven scientific articles in peer-reviewed journals. This PhD Thesis is divided into the following six chapters described below. The opportunity of this work is established on the basis of the transition period needed for moving from a petroleum based energy system to a renewable based new one. Consequently, the present global energy scenario was detailed in Chapter 1, and the role of hydrogen as a real alternative in the future energy system was justified based on several outlooks. Therefore, renewable and non-renewable hydrogen production routes were presented, explaining the corresponding benefits and drawbacks. Then, the raw materials used in this Thesis work were described and the most important issues regarding the processes and the characteristics of the catalytic formulations were explained. The introduction chapter finishes by introducing the concepts of decentralized production and process intensification with the use of microreactors. In addition, a small description of these innovative reaction systems and the benefits that entailed their use were also mentioned. In Chapter 2 the main objectives of this Thesis work are summarized. The development of advanced reaction systems for hydrogen rich mixtures production is the main objective. In addition, the use and comparison between two different reaction systems, (fixed bed reactor (FBR) and microreactor), the processing of renewable raw materials, the development of new, active, selective and stable catalytic formulations, and the optimization of the operating conditions were also established as additional partial objectives. Methane and natural gas (NG) steam reforming experimental results obtained when operated with microreactor and FBR systems are presented in Chapter 3. For these experiments nickel-based (Ni/Al2O3 and Ni/MgO) and noble metal-based (Pd/Al2O3 and Pt/Al2O3) catalysts were prepared by wet impregnation and their catalytic activity was measured at several temperatures, from 973 to 1073 K, different S/C ratios, from 1.0 to 2.0, and atmospheric pressure. The Weight Hourly Space Velocity (WHSV) was maintained constant in order to compare the catalytic activity in both reaction systems. The results obtained showed a better performance of the catalysts operating in microreactors. The Ni/MgO catalyst reached the highest hydrogen production yield at 1073 K and steam-to-carbon ratio (S/C) of 1.5 under Steam methane Reforming (SMR) conditions. In addition, this catalyst also showed good activity and stability under NG reforming at S/C=1.0 and 2.0. The Ni/Al2O3 catalyst also showed high activity and good stability and it was the catalyst reaching the highest methane conversion (72.9 %) and H2out/CH4in ratio (2.4) under SMR conditions at 1073 K and S/C=1.0. However, this catalyst suffered from deactivation when it was tested under NG reforming conditions. Regarding the activity measurements carried out with the noble metal-based catalysts in the microreactor systems, they suffered a very quick deactivation, probably because of the effects attributed to carbon deposition, which was detected by Scanning Electron Microscope (SEM). When the FBR was used no catalytic activity was measured with the catalysts under investigation, probably because they were operated at the same WHSV than the microreactors and these WHSVs were too high for FBR system. In Chapter 4 biogas reforming processes were studied. This chapter starts with an introduction explaining the properties of the biogas and the main production routes. Then, the experimental procedure carried out is detailed giving concrete information about the experimental set-up, defining the parameters measured, specifying the characteristics of the reactors used and describing the characterization techniques utilized. Each following section describes the results obtained from activity testing with the different catalysts prepared, which is subsequently summarized: Section 4.3: Biogas reforming processes using γ-Al2O3 based catalysts The activity results obtained by several Ni-based catalysts and a bimetallic Rh-Ni catalyst supported on magnesia or alumina modified with oxides like CeO2 and ZrO2 are presented in this section. In addition, an alumina-based commercial catalyst was tested in order to compare the activity results measured. Four different biogas reforming processes were studied using a FBR: dry reforming (DR), biogas steam reforming (BSR), biogas oxidative reforming (BOR) and tri-reforming (TR). For the BSR process different steam to carbon ratios (S/C) from 1.0 to 3.0, were tested. In the case of BOR process the oxygen-to-methane (O2/CH4) ratio was varied from 0.125 to 0.50. Finally, for TR processes different S/C ratios from 1.0 to 3.0, and O2/CH4 ratios of 0.25 and 0.50 were studied. Then, the catalysts which achieved high activity and stability were impregnated in a microreactor to explore the viability of process intensification. The operation with microreactors was carried out under the best experimental conditions measured in the FBR. In addition, the physicochemical characterization of the fresh and spent catalysts was carried out by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), N2 physisorption, H2 chemisorption, Temperature Programmed Reduction (TPR), SEM, X-ray Photoelectron Spectroscopy (XPS) and X-ray powder Diffraction (XRD). Operating with the FBR, conversions close to the ones predicted by thermodynamic calculations were obtained by most of the catalysts tested. The Rh-Ni/Ce-Al2O3 catalyst obtained the highest hydrogen production yield in DR. In BSR process, the Ni/Ce-Al2O3 catalyst achieved the best activity results operating at S/C=1.0. In the case of BOR process, the Ni/Ce-Zr-Al2O3 catalyst showed the highest reactants conversion values operating at O2/CH4=0.25. Finally, in the TR process the Rh-Ni/Ce-Al2O3 catalyst obtained the best results operating at S/C=1.0 and O2/CH4=0.25. Therefore, these three catalysts were selected to be coated onto microchannels in order to test its performance under BOR and TR processes conditions. Although the operation using microreactors was carried out under considerably higher WHSV, similar conversions and yields as the ones measured in FBR were measured. Furthermore, attending to other measurements like Turnover Frequency (TOF) and Hydrogen Productivity (PROD), the values calculated for the catalysts tested in microreactors were one order of magnitude higher. Thus, due to the low dispersion degree measured by H2-chemisorption, the Ni/Ce-Al2O3 catalyst reached the highest TOF and PROD values. Section 4.4: Biogas reforming processes using Zeolites L based catalysts In this section three type of L zeolites, with different morphology and size, were synthesized and used as catalyst support. Then, for each type of L zeolite three nickel monometallic and their homologous Rh-Ni bimetallic catalysts were prepared by the wetness impregnation method. These catalysts were tested using the FBR under DR process and different conditions of BSR (S/C ratio of 1.0 and 2.0), BOR (O2/CH4 ratio of 0.25 and 0.50) and TR processes (at S/C=1.0 and O2/CH4=0.25). The characterization of these catalysts was also carried out by using the same techniques mentioned in the previous section. Very high methane and carbon dioxide conversion values were measured for almost all the catalysts under investigation. The experimental results evidenced the better catalytic behavior of the bimetallic catalysts as compared to the monometallic ones. Comparing the catalysts behavior with regards to their morphology, for the BSR process the Disc catalysts were the most active ones at the lowest S/C ratio tested. On the contrary, the Cylindrical (30–60 nm) catalysts were more active under BOR conditions at O2/CH4=0.25 and TR processes. By the contrary, the Cylindrical (1–3 µm) catalysts showed the worst activity results for both processes. Section 4.5: Biogas reforming processes using Na+ and Cs+ doped Zeolites LTL based catalysts A method for the synthesis of Linde Type L (LTL) zeolite under microwave-assisted hydrothermal conditions and its behavior as a support for heterogeneously catalyzed hydrogen production is described in this section. Then, rhodium and nickel-based bimetallic catalysts were prepared in order to be tested by DR process and BOR process at O2/CH4=0.25. Moreover, the characterization of the catalysts under investigation was also carried out. Higher activities were achieved by the catalysts prepared from the non-doped zeolites, Rh-Ni/D and Rh-Ni/N, as compared to the ones supported on Na+ and Cs+ exchanged supports. However, the differences between them were not very significant. In addition, the Na+ and Cs+ incorporation affected mainly to the Disc catalysts. Comparing the results obtained by these catalysts with the ones studied in the section 4.4, in general worst results were achieved under DR conditions and almost the same results when operated under BOR conditions. In Chapter 5 the ethylene glycol (EG) as feed for syngas production by steam reforming (SR) and oxidative steam reforming (OSR) was studied by using microchannel reactors. The product composition was determined at a S/C of 4.0, reaction temperatures between 625°C and 725°C, atmospheric pressure and Volume Hourly Space Velocities (VHSV) between 100 and 300 NL/(gcath). This work was divided in two sections. The first one corresponds to the introduction of the main and most promising EG production routes. Then, the new experimental procedure is detailed and the information about the experimental set-up and the measured parameters is described. The characterization was carried out using the same techniques as for the previous chapter. Then, the next sections correspond to the catalytic activity and catalysts characterization results. Section 5.3: xRh-cm and xRh-np catalysts for ethylene glycol reforming Initially, catalysts with different rhodium loading, from 1.0 to 5.0 wt. %, and supported on α-Al2O3 were prepared by two different preparation methods (conventional impregnation and separate nanoparticle synthesis). Then, the catalysts were compared regarding their measured activity and selectivity, as well as the characterization results obtained before and after the activity tests carried out. The samples prepared by a conventional impregnation method showed generally higher activity compared to catalysts prepared from Rh nanoparticles. By-product formation of species such as acetaldehyde, ethane and ethylene was detected, regardless if oxygen was added to the feed or not. Among the catalysts tested, the 2.5Rh-cm catalyst was considered the best one. Section 5.4: 2.5Rh-cm catalyst support modification with CeO2 and La2O3 In this part of the Chapter 5, the catalyst showing the best performance in the previous section, the 2.5Rh-Al2O3 catalyst, was selected in order to be improved. Therefore, new Rh based catalysts were designed using α-Al2O3 and being modified this support with different contents of CeO2 or La2O3 oxides. All the catalysts containing additives showed complete conversion and selectivities close to the equilibrium in both SR and OSR processes. In addition, for these catalysts the concentrations measured for the C2H4, CH4, CH3CHO and C2H6 by-products were very low. Finally, the 2.5Rh-20Ce catalyst was selected according to its catalytic activity and characterization results in order to run a stability test, which lasted more than 115 hours under stable operation. The last chapter, Chapter 6, summarizes the main conclusions achieved throughout this Thesis work. Although very high reactant conversions and rich hydrogen mixtures were obtained using a fixed bed reaction system, the use of microreactors improves the key issues, heat and mass transfer limitations, through which the reforming reactions are intensified. Therefore, they seem to be a very interesting and promising alternative for process intensification and decentralized production for remote application.[ES] La presente Tesis Doctoral tuvo su inicio en Marzo de 2010 gracias a la obtención de la beca perteneciente al programa de “Formación de Personal de investigación” impulsado por la Universidad del País Vasco / Euskal Herriko Unibertsitatea (UPV/EHU). Esta Tesis ha sido desarrollada prácticamente en su totalidad en el Departamento de Ingeniería Química y del Medio Ambiente de la Escuela Técnica Superior de Ingeniería de Bilbao, como miembro del grupo de investigación Sustainable Process Engineering (SuPrEn). Además, esta Tesis incluye el trabajo realizado durante el periodo de seis meses de estancia pre-doctoral en el centro Institut für Mikrotechnik Mainz GmbH, IMM, de Alemania. El trabajo llevado a cabo durante los cuatro años se centra en la obtención de hidrógeno, vector energético limpio y combustible del futuro, a partir de diversas materias primas. Sin embargo, el mayor aporte de esta Tesis a la comunidad científica viene dado por la utilización de los sistemas de reacción denominados microrreactores para la producción de hidrógeno. Este tipo de sistemas están siendo hoy en día objeto de estudio ya que son una solución viable a la producción de hidrógeno de manera descentralizada y porque además, presentan varias ventajas en comparación con los métodos actuales de producción de hidrógeno. Asimismo, la comparación entre sistemas de reacción convencionales y los microrreactores, también ha sido objeto de estudio en la presente Tesis. De igual modo, para los procesos de reformado estudiados, se han desarrollado varios sistemas catalíticos que han mostrado altas actividades en cuanto a conversión de reactivos se refiere, gran selectividad a hidrógeno y muy buena estabilidad en cuanto a operación y durabilidad se refiere. Inicialmente, se empleó metano y gas natural como fuentes de alimentación no renovables, llevando a cabo una comparativa de los dos sistemas de reacción previamente mencionados. Sin embargo, otro de los objetivos de la presente Tesis ha sido el uso de fuentes de alimentación renovables, ya que uno de los grandes retos de la comunidad científica recae en la obtención de un producto limpio, el hidrógeno, a partir de recursos renovables. De este modo, la mayor parte del trabajo se basa en el estudio de la producción de hidrógeno a partir de biogás. Este gas, procedente de la descomposición anaerobia de la materia orgánica, como puede ser la biomasa, se compone prácticamente de metano y dióxido de carbono. De esta forma, convirtiendo estos dos gases a hidrógeno, los beneficios económicos, ambientales y sociales alcanzables serían de gran relevancia dado que los dos contribuyen en gran medida al denominado efecto invernadero. Además de con biogás, también se han llevado a cabo ensayos de actividad catalítica con etilenglicol, recurso renovable mayoritario procedente de la conversión catalítica de la celulosa. Acorde a cada una de las materias primas a tratar se prepararon diferentes formulaciones catalíticas, con el objetivo de conocer el efecto de los diferentes soportes a utilizar, de sus modificaciones, de las cargas metálicas y cómo no, de las concentraciones de las propias especies metálicas presentes en los catalizadores. Con el objeto de poder interpretar los resultados obtenidos con los catalizadores utilizados en cada apartado, se llevó a cabo una exhaustiva caracterización de los mismos antes y después de haber sido probados en los ensayos de actividad catalítica, así como un estudio de la correlación entre las propiedades superficiales medidas mediante caracterización y los resultados de actividad catalítica. Para poder detallar de manera satisfactoria toda la información recabada a lo largo de los cuatro años de investigación, esta Tesis ha sido dividida en 6 capítulos independientes, los cuales se resumen a continuación: En el Capítulo 1, se justifica la necesidad de llevar a cabo este trabajo de investigación, mediante el cual se busca un cambio en el sistema energético actual basado en el petróleo. Sin duda, la creciente demanda energética existente y el agotamiento de los recursos fósiles hacen necesario la búsqueda de alternativas para poder mantener la calidad de vida actual. Además, en este apartado introductorio también se detalla el estado del arte en cuanto a los métodos de producción de hidrógeno se refiere, los reactores existentes y los catalizadores más comúnmente empleados. En el apartado siguiente, el Capítulo 2, se detalla el propósito establecido para el desarrollo de esta Tesis. Además de la producción de hidrógeno mediante sistemas de reacción convencionales y su comparación con los sistemas de reacción avanzados denominados microrreactores, el uso de diferentes fuentes de alimentación y tipos de catalizadores, también han sido metas a alcanzar en esta Tesis. Por otra parte no hay que olvidar que el propósito impulsado por la Universidad de País Vasco / Euskal Herriko Unibertsitatea, es el de formar a personas como futuros investigadores, siendo éste un objetivo alcanzado a medida que se ha desarrollado la Tesis Doctoral. El Capítulo 3, es el primero de los apartados correspondientes a la actividad experimental llevada a cabo. En él se detallan los ensayos realizados con metano y gas natural como reactivos para la obtención de hidrógeno. Además, en esta sección se hace una comparación de los dos sistemas de reacción empleados habiendo sido llevados a cabo los ensayos a iguales velocidades espaciales. Para el desarrollo de los correspondientes ensayos de actividad catalítica se prepararon cuatro catalizadores diferentes, basados en alúmina y magnesia con especies metálicas nobles (Pt y Pd) y no nobles (Ni). A lo largo de este capítulo se detalla la metodología empleada a la hora de preparar, impregnar y acondicionar los microrreactores, así como la llevada a cabo para preparar los reactores de lecho fijo empleados. También se describe el equipamiento utilizado para realizar los ensayos de reacción, así como para la identificación y cuantificación de los productos obtenidos en reacción. Entre los resultados obtenidos cabe destacar la gran estabilidad mostrada por los microrreactores y la alta actividad medida en operación para el catalizador de Ni/MgO tanto en el reformado de metano como en el de gas natural. En cuanto al catalizador de Ni/Al2O3, también se midieron altas conversiones de metano; sin embargo, sufrió una desactivación severa cuando fue utilizado para la producción de hidrógeno a partir de gas natural. En cuanto a los catalizadores basados en metales nobles y soportados sobre alúmina, éstos no mostraron actividad alguna posiblemente debido a la deposición de coque, que fue detectado por SEM. El Capítulo 4, se compone de tres secciones en función de los catalizadores empleados para el reformado de biogás, que se detallan a continuación: Sección 4.3: Estudio de los diferentes tipos de reformado de biogás con catalizadores basados en γ-Al2O3 En este apartado se prepararon 4 catalizadores basados en alúmina cuyos soportes fueron modificados con CeO2, ZrO2 o una mezcla de ambos. A uno de los catalizadores se le añadió una pequeña cantidad de Rh con el objetivo de estudiar su influencia. Además, se utilizó también un catalizador basado en MgO y otro comercial basado en alúmina con el propósito de poder comparar los resultados obtenidos. En cuanto a los procesos, cuatro fueron objeto de estudio utilizando el reactor de lecho fijo: reformado seco (dry reforming, DR), reformado de biogás con vapor de agua (biogas steam reforming, BSR), reformado oxidativo de biogás (biogas oxidative reforming, BOR) y tri-reformado (tri-reforming, TR). En ellos se probaron los catalizadores anteriormente mencionados para ratios crecientes de vapor de agua/carbono (S/C), O2/CH4 o ambos conjuntamente en el caso del proceso de tri-reformado. Una vez establecidos los parámetros de operación óptimos mediante el reactor de lecho fijo, los tres sistemas catalíticos que obtuvieron los mejores resultados se impregnaron y ensayaron en los microrreactores. De este modo, se pudo llevar a cabo una interesante comparación entre ambos sistemas de reacción. Asimismo, los sistemas catalíticos se caracterizaron antes y después de los ensayos realizados. Entre los resultados obtenidos, cabe destacar las altas conversiones alcanzadas por todos los catalizadores, cercanas a las calculadas por el equilibrio termodinámico. En el proceso de DR, el catalizador Rh-Ni/Ce-Al2O3 fue el que alcanzó el mayor rendimiento a hidrógeno. En cuanto al proceso de BSR, las mejores condiciones de operación fueron medidas para el ratio S/C=1.0 y para el catalizador Ni/Ce-Al2O3. El ratio óptimo de O2/CH4 para lograr una mayor conversión de reactivos fue de 0.

    Molecular Antennas and Photoactive Nanomaterials based on Energy Transfer Processes

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    110 p.The scope of this thesis deals is the development and description of photoactive nanomaterials and novel multichromophoric systems as artificial antenna systems. To this aim, the photophysical signatures of luminescent fluorophores (with absorption and emission at different regions of the visible electromagnetic spectrum) encapsulated into inorganic and organic hosts, or assembled in supramolecular structures have been exhaustively characterized. These systems are able to harvest the light over a broad spectral region (ultraviolet-visible) and transfer it to the target place and with a specific energy via successive energy transfer hops. As consequence the excitation can be performed far away from the emission region, improving the photostability of the acceptor emitting dye and a lowering the background interferences. In pursuit of such antennas, different alternatives have been considered, (i) Hybrid materials based on LTL zeolites doped with laser dyes working in the blue, green or red parts of the visible. (ii) Latex nanoparticles doped simultaneously with luminescent fluorophores, leading to stable aqueous colloids. (iii) Molecular cassettes based on energy donor and acceptor dyes covalently linked. All of them undergoing efficient and tunable energy transfer processes, the key factor for a successful development of luminescent antennas. In conclusion, the herein reported approaches (photoactive materials and novel dyes) towards the development of luminescent antennas are shown to be properly applied in photonic fields such as tunable dye lasers, light modulators or polarity probe
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