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排序方式: 共有860条查询结果,搜索用时 248 毫秒
851.
Markus Wirsing Armin Dammann Ronald Raulefs 《International Journal of Satellite Communications and Networking》2023,41(2):158-177
Global Navigation Satellite Systems (GNSS) have become an essential part of maritime navigation, in particular to improve situational awareness and vessel traffic management. The dependence on GNSS creates vulnerability for maritime shipping. Driven by this vulnerability, the desire for a backup system for maritime navigation has been emerging. The VHF Data Exchange System (VDES) standard provides communication capabilities for maritime applications. VDES is currently being revised. As part of this revision, VDES will be extended by ranging and navigation functionalities, called R-Mode, as an alternative for maritime navigation. In this paper, we address system design aspects and evaluate the positioning performance of VDES R-Mode. We derive estimation theory bounds on the accuracy of VDES R-Mode distance and velocity. In a case study, we discuss and evaluate the benefit of satellite links to complement VDES R-Mode positioning. Furthermore, we introduce a Kalman filter for position and velocity tracking, which we apply to experimental data. We describe an experiment we conducted at Lake Ammer, southwest of Munich, and evaluate the VDES R-Mode positioning performance for this setup. Our experimental results show that VDES R-Mode is capable of achieving a 95th-percentile horizontal position error of 22 m. Thus, VDES R-Mode is a promising approach for a maritime backup system that can meet the IALA accuracy requirements. 相似文献
852.
Armin G. Aberle Burkhard Kuhlmann Rüdiger Meyer Andreas Hübner Carsten Hampe Rudolf Hezel 《Progress in Photovoltaics: Research and Applications》1996,4(3):193-204
Inversion-layer solar cells can be fabricated on crystalline silicon in a time- and energy-efficient way. In this article we experimentally investigate inversion layer cells of the type developed in the 1980s at the University of Erlangen. The best cell has an independently confirmed one-sun efficiency of 15.7%, the highest reported to date for this simple cell technology. In order to gain insight into the performance-limiting mechanisms, these cells are compared to p-n junction cells fabricated on identical substrates. Subsequently, the impact of the most important emitter parameters on the performance of both cell types is determined by means of two-dimensional numerical modelling. These simulations reveal that inversion-layer cells can principally produce the same efficiencies (> 23%) as p-n junction cells, provided the emitter parameters are properly adjusted and the front contact is of a sufficiently high quality. Therefore, a research project is presently under way at ISFH aiming at an improvement of inversion-layer cell efficiency above 18%. The basis for these new cells is the fact that silicon nitride films deposited at higher temperatures (∼400°C) demonstrate strongly improved passivation properties compared to the present 250° C silicon nitride films. 相似文献
853.
Shubham Duttagupta Fen Lin Marshall Wilson Matthew B. Boreland Bram Hoex Armin G. Aberle 《Progress in Photovoltaics: Research and Applications》2014,22(6):641-647
Extremely low upper‐limit effective surface recombination velocities (Seff.max) of 5.6 and 7.4 cm/s, respectively, are obtained on ~1.5 Ω cm n‐type and p‐type silicon wafers, using silicon nitride (SiNx) films dynamically deposited in an industrial inline plasma‐enhanced chemical vapour deposition (PECVD) reactor. SiNx films with optimised antireflective properties in air provide an excellent Seff.max of 9.5 cm/s after high‐temperature (>800 °C) industrial firing. Such low Seff.max values were previously only attainable for SiNx films deposited statically in laboratory reactors or after optimised annealing; however, in our case, the SiNx films were dynamically deposited onto large‐area c‐Si wafers using a fully industrial reactor and provide excellent surface passivation results both in the as‐deposited condition and after industrial‐firing, which is a widely used process in the photovoltaic industry. Contactless corona‐voltage measurements reveal that these SiNx films contain a relatively high positive charge of (4–8) × 1012 cm−2 combined with a relatively low interface defect density of ~5 × 1011 eV−1 cm−2. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
854.
Katharina Kruppa Itzhak I. Maor Frank Steinbach Vadim Beilin Meirav Mann-Lahav Mario Wolf Gideon S. Grader Armin Feldhoff 《Journal of the American Ceramic Society》2023,106(2):1170-1181
Oxide-based ceramics offer promising thermoelectric (TE) materials for recycling high-temperature waste heat, generated extensively from industrial sources. To further improve the functional performance of TE materials, their power factor should be increased. This can be achieved by nanostructuring and texturing the oxide-based ceramics creating multiple interphases and nanopores, which simultaneously increase the electrical conductivity and the Seebeck coefficient. The aim of this work is to achieve this goal by compacting electrospun nanofibers of calcium cobaltite Ca3Co4−xO9+δ, known to be a promising p-type TE material with good functional properties and thermal stability up to 1200 K in air. For this purpose, polycrystalline Ca3Co4−xO9+δ nanofibers and nanoribbons were fabricated by sol–gel electrospinning and calcination at intermediate temperatures to obtain small primary particle sizes. Bulk ceramics were formed by sintering pressed compacts of calcined nanofibers during TE measurements. The bulk nanofiber sample pre-calcined at 973 K exhibited an improved Seebeck coefficient of 176.5 S cm−1 and a power factor of 2.47 μW cm−1 K−2 similar to an electrospun nanofiber-derived ceramic compacted by spark plasma sintering. 相似文献
855.
Gregory Burwell Klaudia Rejnhard Jon Evans Jacob Mitchell Michael T. Grimes Matt Elwin Ardalan Armin Paul Meredith 《Advanced Engineering Materials》2023,25(12):2201901
High-quality, alumina thin films are extensively used as dielectrics, passivation layers, and barrier layers in electronics and many other applications. However, to achieve optimum stoichiometry and thus performance, the layers are often grown at elevated temperatures (>200 °C) using techniques such as atomic layer deposition (ALD). This is problematic for substrates or structures with low thermal budgets. Herein, alumina thin films are grown on 200 mm silicon substrates employing a versatile deposition method known as MVD at low deposition temperatures (35–150 °C). The chemical composition of the resulting films is investigated postdeposition using X-ray photoelectron spectroscopy (XPS) and variable angle spectroscopic ellipsometry, with fully stoichiometric Al2O3 achieved at deposition temperatures as low as 100 °C. Dielectric measurements confirm outstanding dielectric properties compared to typical thermal ALD layers deposited at much higher temperatures. This low-temperature deposition performance by considering the MVD reactor design and the “pump-type” regime of precursor delivery versus the “flow-type” regime of ALD is rationalized and understood. The results clearly demonstrate that alumina thin films grown with MVD are highly versatile for electronic applications and are of particular relevance and interest for the high-volume processing of dielectric, passivation, and barrier layers at low temperatures. 相似文献
856.
Prof. Dr. Armin Bunde 《化学,工程师,技术》2023,95(11):1758-1767
Random (noisy) processes can be characterized by the way consecutive data are correlated. The data can be uncorrelated (white noise), short-range correlated (often called red noise), or long-range correlated (sometimes called pink noise). Here we describe the properties and applications of these different kinds of noise. We discuss, how they influence (i) the diffusion process, (ii) the occurrence of rare extreme events and (iii) the detection of an external trend that is superimposed on the noise; (ii) and (iii) are particularly relevant in the context of detecting anthropogenic global warming by data analysis. 相似文献
857.
Christin Kirst Fabian Knechtel Manuel Gensler David Fischermeier Jens Petersen Nader A. Danaf Jonathan Tietze Armin Wedel Don C. Lamb Roland Mitrić Konstantin Karaghiosoff 《Advanced functional materials》2023,33(13):2212436
Easily accessible blue-emitting materials are in the focus of ongoing research, as they still lack the efficiency and lifetime of their red and green counterparts. The new multidentate phosphine oxide ligands and two respective ZnCl2 complexes presented here combine a straightforward synthesis with high yields and show interesting luminescent properties. The free ligand exhibits blue luminescence in the crystalline state, but not in amorphous films or diluted solution. In contrast, the Zn(II) complexes shows intense blue luminescence in the crystalline state as well as in amorphous thin films and in solution. Fluorescence lifetime imaging microscopy measurements show luminescence lifetimes of 3–6 ns indicative of fluorescence. By combining the experimental data with quantum chemical calculations, we propose a model where the conformation of the molecule is restricted, either via the crystal environment, aggregation, or the steric fixation by the coordinating central atom, blocking the nonradiative relaxation from the excited into the ground electronic state. However, this nonradiative relaxation is still possible in the gas phase via elongation of a P C bond. These results may provide a general mechanism to explain the luminescence properties in a whole class of organic phosphine oxides. 相似文献
858.
859.
Gholinataj-Jelodar Ehsan Aghanejad Ahmadchally Alireza Gooran-Shoorakchaly Armin Gholipour Morteza 《Journal of Computational Electronics》2022,21(5):1108-1115
Journal of Computational Electronics - An analytical I–V model for a double-gate ballistic monolayer molybdenum disulfide (MoS2) field-effect transistor (FET) with 5 nm channel... 相似文献
860.
Armin G. Aberle Stephen J. Robinson Aihua Wang Jianhua Zhao Stuart R. Wenham Martin A. Green 《Progress in Photovoltaics: Research and Applications》1993,1(2):133-143
Despite exceptionally high open-circuit voltages, record high-efficiency PERL (passivated emitter, rear locally diffused) silicon solar cells recently developed at the University of New South Wales demonstrate relatively low fill factors. This behaviour is shown to result from a surface recombination velocity at the rear Si-SiO2 interface that increases with reducing voltage across the cell, leading to non-ideal I-V curves with high ideality factors (>1.3) near the maximum power point. When corrected for series resistance losses, the Air Mass 1.5 (AM1.5) fill factor of actual PERL cells is found to be limited to values below 82.9%, as opposed to the ideal theoretical limit of 85-86% for silicon cells operating in low injection conditions. Relatively large series resistance losses (Rs > 0.35 ω cm2) further reduce this value to the experimentally observed fill factors below 81.4%. Analysis of measured illuminated and dark I-V characteristics of PERL cells reveals that the AM1.5 efficiency is mainly limited by recombination losses at the rear oxidized surface. Optimum PERL cell resistivity is about 2 ω cm. Owing to increased rear surface recombination velocity, lower resistivity material shows no advantage in open-circuit voltage and suffers from short-circuit current losses, while a strong reduction in the surface recombination velocity above the maximum power point results in smaller fill factors. High-resistivity cells do show an improved short-cuircuit current but suffer from voltage and fill factor losses. 相似文献