Generation of bivariate Nakagami-m fading envelopes with arbitrary not necessary identical fading parameters

[EN] In this paper, a generation procedure of two correlated Nakagami-m random variables for arbitrary fading parameters values (not necessary identical) is described. For the generation of two correlated Nakagami-m samples, the proposed method uses the generalized Rice distribution, which appears in the conditional distribution of two correlated Nakagami-m variables. This procedure can be applied to simulate diversity systems such as selection combiners, equal-gain combiners, and maximal-ratio combiners as well as multiple-input multipleoutput (MIMO) receiver systems, in Nakagami-m channels.Contract/grant sponsor: Generalitat Valenciana; contract/grant number: GV04B/357.Reig, J.; Martínez Amoraga, MÁ.; Rubio Arjona, L. (2007). Generation of bivariate Nakagami-m fading envelopes with arbitrary not necessary identical fading parameters. Wireless Communications and Mobile Computing. 7(4):531-537. https://doi.org/10.1002/wcm.386S5315377

Highly mobile hot holes in Cs₂AgBiBr₆ double perovskite

Highly mobile hot charge carriers are a prerequisite for efficient hot carrier optoelectronics requiring long-range hot carrier transport. However, hot carriers are typically much less mobile than cold ones because of carrier-phonon scattering. Here, we report enhanced hot carrier mobility in Cs(2)AgBiBr(6) double perovskite. Following photoexcitation, hot carriers generated with excess energy exhibit boosted mobility, reaching an up to fourfold enhancement compared to cold carriers and a long-range hot carrier transport length beyond 200 nm. By optical pump–infrared push-terahertz probe spectroscopy and frequency-resolved photoconductivity measurements, we provide evidence that the conductivity enhancement originates primarily from hot holes with reduced momentum scattering. We rationalize our observation by considering (quasi-)ballistic transport of thermalized hot holes with energies above an energetic threshold in Cs(2)AgBiBr(6). Our findings render Cs(2)AgBiBr(6) as a fascinating platform for studying the fundamentals of hot carrier transport and its exploitation toward hot carrier–based optoelectronic devices

Degradation of methylammonium lead iodide perovskite structures through light and electron beam driven ion migration

[Image: see text] Organometal halide perovskites show promising features for cost-effective application in photovoltaics. The material instability remains a major obstacle to broad application because of the poorly understood degradation pathways. Here, we apply simultaneous luminescence and electron microscopy on perovskites for the first time, allowing us to monitor in situ morphology evolution and optical properties upon perovskite degradation. Interestingly, morphology, photoluminescence (PL), and cathodoluminescence of perovskite samples evolve differently upon degradation driven by electron beam (e-beam) or by light. A transversal electric current generated by a scanning electron beam leads to dramatic changes in PL and tunes the energy band gaps continuously alongside film thinning. In contrast, light-induced degradation results in material decomposition to scattered particles and shows little PL spectral shifts. The differences in degradation can be ascribed to different electric currents that drive ion migration. Moreover, solution-processed perovskite cuboids show heterogeneity in stability which is likely related to crystallinity and morphology. Our results reveal the essential role of ion migration in perovskite degradation and provide potential avenues to rationally enhance the stability of perovskite materials by reducing ion migration while improving morphology and crystallinity. It is worth noting that even moderate e-beam currents (86 pA) and acceleration voltages (10 kV) readily induce significant perovskite degradation and alter their optical properties. Therefore, attention has to be paid while characterizing such materials using scanning electron microscopy or transmission electron microscopy techniques

Разработка системы измерения производительности реализаций blockchain

Долголев Филипп Петрович Разработка системы измерения производительности реализаций blockchain Старший преподаватель кафедры системного программирования Кириленко Яков Александрович При разработке приложений на основе технологии blockchain, из-за наличия множества различных реализаций, разработчики сталкиваются с проблемой выбора. Один из важных критериев при выборе - производительность. В процессе поиска системы, позволяющей измерить производительность различных реализаций blockchain, не обнаружены ни проприетарные системы, ни с открытым исходным кодом. В рамках этой работы рассматривается разработка модульной системы, решающей эту проблему. Использованных источников: 18 Долголев, Ф. П. Разработка системы измерения производительности реализаций blockchain: выпускная квалификационная работа: защищена 01.06.2017 / Долголев Филипп Петрович. – СПб., 2017. – 21 с. – Библиография: с. 20–21.Filipp Dolgolev Blockchain Implementations Benchmarking Tool senior lecturer, dept. of software engineering Iakov Kirilenko Mathematics & mechanics, software engineering department Since there are many different types of blockchain technologies, developers are faced with a dilemma of which technology to choose when developing applications for a particular use case. One of the most important criteria effecting the selection is performance. During our research, we were unable to source either proprietary, or open source solutions allowing to benchmark various blockchain technologies performances. In this context, we are considering the development of such a solution. Sources cited: 18 Dolgolev, F. Blockchain Implementations Benchmarking Tool: Graduation thesis: Defended 01.06.2017 / Filipp Dolgolev. – St. Petersburg., 2017. – 21 pp. – Bibliography: pp. 20–21

An embedded interfacial network stabilizes inorganic CsPbI₃ perovskite thin films

The black perovskite phase of CsPbI(3) is promising for optoelectronic applications; however, it is unstable under ambient conditions, transforming within minutes into an optically inactive yellow phase, a fact that has so far prevented its widespread adoption. Here we use coarse photolithography to embed a PbI(2)-based interfacial microstructure into otherwise-unstable CsPbI(3) perovskite thin films and devices. Films fitted with a tessellating microgrid are rendered resistant to moisture-triggered decay and exhibit enhanced long-term stability of the black phase (beyond 2.5 years in a dry environment), due to increasing the phase transition energy barrier and limiting the spread of potential yellow phase formation to structurally isolated domains of the grid. This stabilizing effect is readily achieved at the device level, where unencapsulated CsPbI(3) perovskite photodetectors display ambient-stable operation. These findings provide insights into the nature of phase destabilization in emerging CsPbI(3) perovskite devices and demonstrate an effective stabilization procedure which is entirely orthogonal to existing approaches

Lead-Free Halide Perovskite Materials and Optoelectronic Devices: Progress and Prospective

Halide perovskites, in the form of thin films and colloidal nanocrystals, have recently taken semiconductor optoelectronics research by storm, and have emerged as promising candidates for high-performance solar cells, light-emitting diodes (LEDs), lasers, photodetectors, and radiation detectors. The impressive optical and optoelectronic properties, along with the rapid increase in efficiencies of solar cells and LEDs, have greatly attracted researchers across many disciplines. However, most advances made so far in terms of preparation (colloidal nanocrystals and thin films), and the devices with highest efficiencies are based on Pb-based halide perovskites, which have raised concerns over their commercialization due to the toxicity of Pb. This has triggered the search for lower-toxicity Pb-free halide perovskites and has led to significant progress in the last few years. In this roadmap review, researchers of different expertise have joined together to summarize the latest progress, outstanding challenges, and future directions of Pb-free halide perovskite thin films and nanocrystals, regarding their synthesis, optical spectroscopy, and optoelectronic devices, to guide the researchers currently working in this area as well as those that will join the field in the future.I.L.-F., D.V., C.-Y.W., S.S., T.O., Y.-T.H., K.S., Y.L., V.S.C., J.Z., L.D.T., and D.G. contributed equally to this work. L.P. acknowledges the support from the Spanish Ministerio de Ciencia e Innovación through the Ramón y Cajal grant (RYC2018-026103-I) and the Spanish State Research Agency (Grant No. PID2020-117371RA-I00; TED2021-131628A-100), as well as the grant from the Xunta de Galicia (ED431F2021/05). C.-Y.W. acknowledges the financial support from Alexander von Humboldt Foundation. K.S. acknowledges the financial support from China Scholarship Council (CSC), and P.M.-B. acknowledges support from Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy – EXC 2089/1–390776260 (e-conversion). V.B. and T.O. acknowledge the MEXT JSPS Grants 20J00974, 21K14580, and 23H01781. H.Z acknowledges the financial supported by NSFC (62222405, 52131304), the Natural Science Foundation of Jiangsu Province (BK20220142), the Fundamental Research Funds for the Central Universities (30922010713), and NSFC-RGC (62261160392). H.-T.S. acknowledges the financial support from JSPS KAKENHI (21H01743). Y.-T.H and R.L.Z.H. would like to thank the Engineering and Physical Sciences Research Council (EPSRC) for funding (no. EP/V014498/2). R.L.Z.H. also thanks the Royal Academy of Engineering through the Research Fellowships scheme (no. RF∖201718∖17101). D.V. and E.D. acknowledge financial support from the Research Foundation – Flanders through an FWO doctoral fellowship to D.V. (FWO Grant Number 1S45223N) and the KU Leuven Internal Funds (Grant Numbers STG/21/010, C14/23/090, and CELSA/23/018). T.D. acknowledges the Department of Science and Technology (DST) and the Science and Engineering Research Board (SERB) for the Ramanujan Fellowship Award (RJF/2021/000125). I.M.-S. acknowledges Ministry of Science and Innovation of Spain under Step-Up (TED2021-131600B-C31) project and by Generalitat Valenciana under Print-P (MFA/2022/020) project. V.S.C., I.M.-S. and J.P.M.-P acknowledges the support of the Horizon 2020 research and innovation program through the DROP-IT project (grant agreement no. 862656)

Synthesis and photophysical properties of iron-carbonyl complex-coumarin conjugates as potential bimodal IR-fluorescent probes

An expedient synthesis of the first examples of iron-carbonyl complex-coumarin conjugates is reported. 7-Amino/7-hydroxycoumarin derivatives have been readily derivatized through an easily implemented single-step reaction involving the tricarbonyl(η5-cyclohexadienyl)iron(1+) cation [(C6H7)Fe(CO)3]+. The scope and limitations of this N-/O-alkylation reaction were also investigated. The fluorescence properties of these novel metal-carbonyl complexes have been studied and support their further use as valuable building blocks in the design of bimodal contrast agents for combined vibrational and fluorescence imaging