In this paper, a high-frequency isolated dual-bridge LLC -type resonant converter is proposed. The steady-state analysis of the proposed converter is performed using a modified fundamental harmonics ...approximation approach, by which the component stress can be obtained quickly without complicated calculation. Necessary and sufficient conditions for zero-voltage switching of all switches are derived too. To illustrate the usefulness of the FHA analysis for a fast design, a design example of a 100 kHz, 200 V input, 40-48 V output 300 W converter is given. Computer simulation and experiment results are included for the purpose of validation. It is shown that this converter is able to maintain zero-voltage switching operation for a wide load range while keeping high efficiency.
This review provides an up‐to‐date review about the small molecule interlayers (SMIs) in organic solar cells (OSCs). Compared to polymer interlayers, SMIs exhibit intrinsic advantages such as easy ...synthesis and purification, monodispersity, well‐defined chemical structure, and high batch‐to‐batch reproducibility. Recently, various SMIs have been reported with landmark efficiencies of over 10% in both conventional and inverted OSCs, exhibiting promising potential in commercial application. In this review, the authors summarize the progress of SMIs from a device fabrication point of view, paying particular attention to the material categories, molecular design, preparation process, and applicable device structure. In addition, the working mechanisms of different SMIs are also discussed, including the structure–property relationships and the corresponding impact on device performance. Finally, a brief outlook is provided that includes opportunities and challenges in this emerging area.
Small molecule interlayers (SMIs) have attracted considerable attention in organic solar cells due to their simple syntheses, well‐defined structures, and high batch‐to‐batch reproducibility. This article provides an overview of SMIs from a device fabrication point of view, focusing on the material categories, preparation methods, film properties, and applicable device configurations. The structure–property relationships and their impact on device performance are also discussed.
Snow cover is an informative indicator of climate change because it can affect local and regional surface energy and water balance, hydrological processes and climate, and ecosystem function. Passive ...microwave (PM) remote sensing data have long been used to retrieve snow depth and snow water equivalent with large uncertainties. The objective of this study is to develop snow-depth retrieval algorithm based on support vector regression (SVR) technique using PM remote sensing data and other auxiliary data. Ground-based daily snow depth data from 1223 stations across Eurasian continent were used to construct and validate the snow-depth retrieval algorithm. This SVR snow-depth retrieval algorithm partitioned three snow cover stages, and four land cover types then generated twelve snow-depth models for each phases. A non-linear regression method based on support vector regression (SVR) was used to retrieve snow depth with PM brightness temperatures, location (latitude and longitude), and terrain parameters (elevation) as input data and land cover as auxiliary data. In addition, we compared the performance of the SVR snow-depth retrieval algorithm with four alternative algorithms: the Chang algorithm, the Spectral Polarization Difference (SPD) algorithm, the Artificial/Neural Networks (ANN) and, an algorithm based on linear regression. Comparing results obtained from these five snow-depth retrieval algorithms against the ground-based daily snow depth data, the SVR snow-depth retrieval algorithm performs much superior with reduced uncertainties. We report the results aimed at evaluating the impact of the variation of snow cover stages and land cover types. The preliminary results suggest that the SVR snow-depth algorithm could detect deep snow with high accuracy and decrease the impact of saturation effects. These results suggest that the SVR snow-depth retrieval algorithm integrating PM remote sensing data and other auxiliary data (land cover types, location, terrain, snow cover stage with indirectly considering grain size variation) can be a more efficient and effective algorithm for retrieving snow depth and snow water equivalent over various scales.
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•A snow-depth retrieval algorithm were developed based support vector regression.•The algorithm outperformed other snow-depth retrieval algorithms.•The impact of saturation effect could be decreased by this retrieval algorithm.•Two formulas were proposed to describe snow retrieval and forward processes.
Doping with pyridinic nitrogen atoms is known as an effective strategy to improve the activity of carbon-based catalysts for the oxygen reduction reaction. However, pyridinic nitrogen atoms prefer to ...occupy at the edge or defect sites of carbon materials. Here, a carbon framework named as hydrogen-substituted graphdiyne provides a suitable carbon matrix for pyridinic nitrogen doping. In hydrogen-substituted graphdiyne, three of the carbon atoms in a benzene ring are bonded to hydrogen and serve as active sites, like the edge or defect positions of conventional carbon materials, on which pyridinic nitrogen can be selectively doped. The as-synthesized pyridinic nitrogen-doped hydrogen-substituted graphdiyne shows much better electrocatalytic performance for the oxygen reduction reaction than that of the commercial platinum-based catalyst in alkaline media and comparable activity in acidic media. Density functional theory calculations demonstrate that the pyridinic nitrogen-doped hydrogen-substituted graphdiyne is more effective than pyridinic nitrogen-doped graphene for oxygen reduction.
Long-term operational stability is the foremost issue delaying the commercialization of perovskite solar cells (PSCs). Here we demonstrate an in-situ cross-linking strategy for operationally stable ...inverted MAPbI
PSCs through the incorporation of a cross-linkable organic small molecule additive trimethylolpropane triacrylate (TMTA) into perovskite films. TMTA can chemically anchor to grain boundaries and then in-situ cross-link to a robust continuous network polymer after thermal treatment, thus enhancing the thermal, water-resisting and light-resisting properties of organic/perovskite films. As a result, the cross-linked PSCs exhibit 590-fold improvement in operational stability, retaining nearly 80% of their initial efficiency after continuous power output for 400 h at maximum power point under full-sun AM 1.5 G illumination of Xenon lamp without any UV-filter. In addition, under moisture or thermal (85 °C) conditions, cross-linked TMTA-based PSCs also show excellent stability with over 90% of their initial or post burn-in efficiency after aging for over 1000 h.
The circadian clock regulates daily changes in behavioral, endocrine, and metabolic activities in mammals. Circadian rhythms in cellular physiology are significantly affected by aging. In particular, ...we previously found that aging has a profound impact on daily rhythms in mitochondrial functions in mouse liver, leading to increased oxidative stress. This is not due to molecular clock malfunctions in peripheral tissues in old mice, however, as robust clock oscillations are observed therein. Nonetheless, aging induces changes in gene expression levels and rhythms in peripheral and probably central tissues. In this article, we review recent findings on the roles of the circadian clock and the aging process in regulating mitochondrial rhythms and redox homeostasis. Chronic sterile inflammation is implicated in mitochondrial dysfunction and increased oxidative stress during aging. In particular, upregulation of the NADase CD38 by inflammation during aging contributes to mitochondrial dysregulation.
Solar CO2 reduction efficiency is largely limited by poor photoabsorption, sluggish electron–hole separation, and a high CO2 activation barrier. Defect engineering was employed to optimize these ...crucial processes. As a prototype, BiOBr atomic layers were fabricated and abundant oxygen vacancies were deliberately created on their surfaces. X‐ray absorption near‐edge structure and electron paramagnetic resonance spectra confirm the formation of oxygen vacancies. Theoretical calculations reveal the creation of new defect levels resulting from the oxygen vacancies, which extends the photoresponse into the visible‐light region. The charge delocalization around the oxygen vacancies contributes to CO2 conversion into COOH* intermediate, which was confirmed by in situ Fourier‐transform infrared spectroscopy. Surface photovoltage spectra and time‐resolved fluorescence emission decay spectra indicate that the introduced oxygen vacancies promote the separation of carriers. As a result, the oxygen‐deficient BiOBr atomic layers achieve visible‐light‐driven CO2 reduction with a CO formation rate of 87.4 μmol g−1 h−1, which was not only 20 and 24 times higher than that of BiOBr atomic layers and bulk BiOBr, respectively, but also outperformed most previously reported single photocatalysts under comparable conditions.
BiOBr atomic layers with abundant oxygen vacancies were synthesized. The photoresponse of BiOBr extends into the visible range, while charge delocalization around the vacancies contributes to CO2 conversion into COOH*. The material catalyzes visible‐light‐driven CO2 reduction with a CO formation rate of 87.4 μmol g−1 h−1, which is 20 and 24 times greater than that of BiOBr atomic layers and bulk BiOBr, respectively.
•Novel feature selection approaches based on Binary Dragonfly Algorithm (BDA) are proposed.•Eight time varying S-shaped and V-shaped transfer functions are proposed.•The leverage of using ...time-varying transfer functions on exploration and exploitation behaviors is investigated.•Extensive tests are made to assess the proposed algorithms on the datasets to prove their merits.
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The Dragonfly Algorithm (DA) is a recently proposed heuristic search algorithm that was shown to have excellent performance for numerous optimization problems. In this paper, a wrapper-feature selection algorithm is proposed based on the Binary Dragonfly Algorithm (BDA). The key component of the BDA is the transfer function that maps a continuous search space to a discrete search space. In this study, eight transfer functions, categorized into two families (S-shaped and V-shaped functions) are integrated into the BDA and evaluated using eighteen benchmark datasets obtained from the UCI data repository. The main contribution of this paper is the proposal of time-varying S-shaped and V-shaped transfer functions to leverage the impact of the step vector on balancing exploration and exploitation. During the early stages of the optimization process, the probability of changing the position of an element is high, which facilitates the exploration of new solutions starting from the initial population. On the other hand, the probability of changing the position of an element becomes lower towards the end of the optimization process. This behavior is obtained by considering the current iteration number as a parameter of transfer functions. The performance of the proposed approaches is compared with that of other state-of-art approaches including the DA, binary grey wolf optimizer (bGWO), binary gravitational search algorithm (BGSA), binary bat algorithm (BBA), particle swarm optimization (PSO), and genetic algorithm in terms of classification accuracy, sensitivity, specificity, area under the curve, and number of selected attributes. Results show that the time-varying S-shaped BDA approach outperforms compared approaches.
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