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排序方式: 共有1341条查询结果,搜索用时 15 毫秒
91.
Felipe de Lucia Lobo Evlyn Márcia Leão de Moraes Novo Claudio Clemente Faria Barbosa Lênio Soares Galvão 《International journal of remote sensing》2013,34(11):3422-3442
Reference spectra extracted from spectral libraries can distinguish different water types in images when associated with limnological information. In this study, we compiled available databases into a single spectral library, using field water reflectance spectra and limnological data collected by different researchers and campaigns in the Amazonian region. By using an iterative clustering procedure based on the combination of reflectance and optically active components (OACs), reference spectra representative of the major Amazonian water types were defined from this library. Differences between the resultant limnological classes were also evaluated by paired t-tests at significance level 0.05. Finally, reference spectra were tested for Spectral Angle Mapper (SAM) classification of waters in Hyperion/Earth Observing-One (EO-1) and Medium Resolution Imaging Spectrometer (MERIS)/Environment Satellite (Envisat) images acquired simultaneously as the field campaigns. Results showed highly variable concentrations of OACs due to the complexity of the Amazonian aquatic environments. Ten classes were defined to represent this complexity, broadly grouped into four limnological characteristics: clear waters with low concentrations of OACs (class 1); black waters rich in dissolved organic carbon (DOC) (class 2); waters with large concentrations of inorganic suspended solids (ISSs) (classes 3–7); and waters dominated by chlorophyll-a (chl-a) (classes 8–10). Using the ten reference spectra, SAM classification of the field water curves produced an overall accuracy of 86% with the highest values observed for classes 3, 4, 6 and 7 and the lowest accuracy for classes 1 and 2. The results of paired t-tests confirmed the class differences based on the concentrations of OACs. SAM classification of the Hyperion and MERIS images using ground truth information resulted in overall classification accuracies of 48% and 67%, respectively, with the highest errors associated with specific portions of the scenes that were not adequately represented in the spectral library. 相似文献
92.
Johanna Lieb Valeria Demontis Domenic Prete Daniele Ercolani Valentina Zannier Lucia Sorba Shimpei Ono Fabio Beltram Benjamin Sacp Francesco Rossella 《Advanced functional materials》2019,29(3)
Here, the operation of a field‐effect transistor based on a single InAs nanowire gated by an ionic liquid is reported. Liquid gating yields very efficient carrier modulation with a transconductance value 30 times larger than standard back gating with the SiO2/Si++ substrate. Thanks to this wide modulation, the controlled evolution from semiconductor to metallic‐like behavior in the nanowire is shown. This work provides the first systematic study of ionic‐liquid gating in electronic devices based on individual III–V semiconductor nanowires: this architecture opens the way to a wide range of fundamental and applied studies from the phase transitions to bioelectronics. 相似文献
93.
A number of energetic materials and explosives have been studied by laser-induced breakdown spectroscopy (LIBS). They include black powder, neat explosives such as TNT, PETN, HMX, and RDX (in various forms), propellants such as M43 and JA2, and military explosives such as C4 and LX-14. Each of these materials gives a unique spectrum, and generally the spectra are reproducible shot to shot. We observed that the laser-produced microplasma did not initiate any of the energetic materials studied. Extensive studies of black powder and its ingredients by use of a reference spectral library have demonstrated excellent accuracy for unknown identification. Finally, we observed that these nitrogen- and oxygen-rich materials yield LIBS spectra in air that have correspondingly different O:N peak ratios compared with air. This difference can help in the detection and identification of such energetic materials. 相似文献
94.
Maria Paola Bianchi Hans-Joachim Böckenhauer Juraj Hromkovič Lucia Keller 《Algorithmica》2014,70(1):92-111
In the online version of the well-known graph coloring problem, the vertices appear one after the other together with the edges to the already known vertices and have to be irrevocably colored immediately after their appearance. We consider this problem on bipartite, i.e., two-colorable graphs. We prove that at least ?1.13746?log2(n)?0.49887? colors are necessary for any deterministic online algorithm to be able to color any given bipartite graph on n vertices, thus improving on the previously known lower bound of ?log2 n?+1 for sufficiently large n. Recently, the advice complexity was introduced as a method for a fine-grained analysis of the hardness of online problems. We apply this method to the online coloring problem and prove (almost) tight linear upper and lower bounds on the advice complexity of coloring a bipartite graph online optimally or using 3 colors. Moreover, we prove that \(O(\sqrt{n})\) advice bits are sufficient for coloring any bipartite graph on n vertices with at most ?log2 n? colors. 相似文献
95.
Efficient Decomposition Techniques for Symbolic Analysis of Large-Scale Analog Circuits by State Variable Method 总被引:1,自引:0,他引:1
New tearing techniques for the systematic formulation of the state equations in symbolic normal-form for linear and nonlinear time-invariant large-scale analog circuits are developed. Some examples are given to illustrate the decomposition procedure and the assignment of the connection sources. The partial symbolic state equations of the opamp A 741 are obtained using the tearing approach, while these equations cannot be written working on the whole circuit. 相似文献
96.
Vincenzo De Leo Anna Maria Maurelli Chiara Ingrosso Fabio Lupone Lucia Catucci 《International journal of molecular sciences》2021,22(21)
Mussel-inspired chemistry was usefully exploited here with the aim of developing a high-efficiency, environmentally friendly material for water remediation. A micro-structured material based on polydopamine (PDA) was obtained by using liposomes as templating agents and was used for the first time as an adsorbent material for the removal of methylene blue (MB) dye from aqueous solutions. Phospholipid liposomes were made by extrusion and coated with PDA by self-polymerization of dopamine under simple and mild conditions. The obtained Liposome@PDA microspheres were characterized by DLS and Zeta potential analysis, TEM microscopy, and FTIR spectroscopy. The effects of pH, temperature, MB concentration, amount of Liposome@PDA, and contact time on the adsorption process were investigated. Results showed that the highest adsorption capacity was obtained in weakly alkaline conditions (pH = 8.0) and that it could reach up to 395.4 mg g−1 at 298 K. In addition, adsorption kinetics showed that the adsorption behavior fits a pseudo-second-order kinetic model well. The equilibrium adsorption data, instead, were well described by Langmuir isotherm. Thermodynamic analysis demonstrated that the adsorption process was endothermic and spontaneous (ΔG0 = −12.55 kJ mol−1, ΔH0 = 13.37 kJ mol−1) in the investigated experimental conditions. Finally, the applicability of Liposome@PDA microspheres to model wastewater and the excellent reusability after regeneration by removing MB were demonstrated. 相似文献
97.
Lucia?Bonoldi Anna?Calabrese Andrea?Pellegrino Nicola?Perin Riccardo?PoEmail author Silvia?Spera Alessandra?Tacca 《Journal of Materials Science》2011,46(11):3960-3968
A new family of 9,9-bisalkylfluorene (F)/thiophene (T)/benzothiadiazole (B) π-conjugated copolymers for organic solar cells
is reported. The structure of the reported copolymers is pseudorandom: in turn each F, T, B monomer unit is alternated to
the other randomly distributed two units. Voltammetric, UV–visible, and photoluminescence measurements have been carried out
to assess the optical and electronic properties of the synthesized materials. The occurring of photoinduced charge transfer
towards a fullerene electron acceptor was investigated by photoluminescence quenching and light-induced electron spin resonance
experiments. The copolymer having alternating thiophene monomer units and randomly distributed fluorene and benzothiadiazole
units exhibits the most promising characteristics; the photophysic study shows that such polymer/fullerene blend could represent
a novel and cheaper material to be used as convenient donor–acceptor system for polymer solar cells. 相似文献
98.
99.
Yasin Kanbur Mihai Irimia-Vladu Eric D. Głowacki Gundula Voss Melanie Baumgartner Günther Schwabegger Lucia Leonat Mujeeb Ullah Hizir Sarica Sule Erten-Ela Reinhard Schwödiauer Helmut Sitter Zuhal Küçükyavuz Siegfried Bauer Niyazi Serdar Sariciftci 《Organic Electronics》2012,13(5):919-924
We report on the fabrication and performance of vacuum-processed organic field effect transistors utilizing evaporated low-density polyethylene (LD-PE) as a dielectric layer. With C60 as the organic semiconductor, we demonstrate low operating voltage transistors with field effect mobilities in excess of 4 cm2/Vs. Devices with pentacene showed a mobility of 0.16 cm2/Vs. Devices using tyrian Purple as semiconductor show low-voltage ambipolar operation with equal electron and hole mobilities of ~0.3 cm2/Vs. These devices demonstrate low hysteresis and operational stability over at least several months. Grazing-angle infrared spectroscopy of evaporated thin films shows that the structure of the polyethylene is similar to solution-cast films. We report also on the morphological and dielectric properties of these films. Our experiments demonstrate that polyethylene is a stable dielectric supporting both hole and electron channels. 相似文献
100.
Daniel Dominguez Gouvêa Cyro de A. Assis D. Muniz Gilson A. Pinto Alberto Avritzer Rosa Maria Meri Leão Edmundo de Souza e Silva Morganna Carmem Diniz Vittorio Cortellessa Luca Berardinelli Julius C. B. Leite Daniel Mossé Yuanfang Cai Michael Dalton Lucia Happe Anne Koziolek 《Software and Systems Modeling》2013,12(4):765-787
In this paper, we report on our experience with the application of validated models to assess performance, reliability, and adaptability of a complex mission critical system that is being developed to dynamically monitor and control the position of an oil-drilling platform. We present real-time modeling results that show that all tasks are schedulable. We performed stochastic analysis of the distribution of task execution time as a function of the number of system interfaces. We report on the variability of task execution times for the expected system configurations. In addition, we have executed a system library for an important task inside the performance model simulator. We report on the measured algorithm convergence as a function of the number of vessel thrusters. We have also studied the system architecture adaptability by comparing the documented system architecture and the implemented source code. We report on the adaptability findings and the recommendations we were able to provide to the system’s architect. Finally, we have developed models of hardware and software reliability. We report on hardware and software reliability results based on the evaluation of the system architecture. 相似文献