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Modal Analysis of 2-D Material-based Plasmonic Waveguides by Mixed Spectral Element Method with Equivalent Boundary Condition
摘要： For long-wavelength space-based radars, such as the P-band radar on the recently selected European Space Agency BIOMASS mission, system distortions (crosstalk and channel imbalance), Faraday rotation, and system noise all combine to degrade the measurements. A first-order analysis of these effects on the measurements of the polarimetric scattering matrix is used to derive differentiable expressions for the errors in the polarimetric backscattering coefficients in the presence of Faraday rotation. Both the amplitudes and phases of the distortion terms are shown to be important in determining the errors and their maximum values. Exact simulations confirm the accuracy and predictions of the first-order analysis. Under an assumed power-law relation between σhv and the biomass, the system distortions and noise are converted into biomass estimation errors, and it is shown that the magnitude of the deviation of the channel imbalance from unity must be 4–5 dB less than the crosstalk, or it will dominate the error in the biomass. For uncalibrated data and midrange values of biomass, the crosstalk must be less than ?24 dB if the maximum possible error in the biomass is to be within 20% of its true value. A less stringent condition applies if the amplitudes and phases of the distortion terms are considered random since errors near the maximum possible are very unlikely. For lower values of the biomass, the noise becomes increasingly important because the σhv signal-to-noise ratio is smaller.
关键词： Biomass,Faraday rotation,polarimetric measurements,system distortion,calibration,long-wavelength radar
更新于2025-09-23 15:19:57
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Ice Confinement-Induced Solubilization and Aggregation of Cyanonaphthol Revealed by Fluorescence Spectroscopy and Lifetime Measurements
摘要： When an aqueous salt solution freezes, a freeze concentrated solution (FCS) separates from ice. The properties of the FCS may differ from those of a supercooled bulk solution of the same ionic strength at the same temperature. The fluorescence and lifetime characteristics of 6-cyano-2-naphthol (6CN) were studied in frozen NaCl solutions to provide an insight into the solution properties of the FCS. While the photoacidity of 6CN in an FCS is similar to that in solution, several anomalous behaviors are observed. Fluorescence spectra indicate that the solubility of 6CN is significantly enhanced in the FCS (50 mM or higher) compared to that in bulk NaCl solution, where the solubility limit is 250 μM. The high solubility induces aggregation of 6CN in the FCS, which is not detected in bulk solutions. This trend becomes marked as the initial NaCl concentration decreases, that is, the FCS is confined in a small space. The fluorescence lifetimes of 6CN in the FCS support the spectroscopy results. In addition to the species identified by fluorescence spectroscopy, excimers are assigned from lifetime measurements in the FCS. The excimer formation is also a result of the enhanced solubility of 6CN in the FCS.
关键词： solubility enhancement,aggregation,lifetime measurements,excimer formation,6-cyano-2-naphthol,freeze concentrated solution,Fluorescence spectroscopy
更新于2025-09-23 15:19:57
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Kinetic and Mechanistic Investigation of the Photocatalyzed Surface Reduction of 4-Nitrothiophenol Observed on a Silver Plasmonic Film via Surface-Enhanced Raman Scattering
摘要： Hot electrons generated by photo-induced plasmon decay from plasmonic metal surface can reduce 4-nitrothiophenol (4-NTP) to 4-aminothiophenol (4-ATP). Comparing to the reduction with a reducing agent such as sodium borohydride, Surface-Enhanced Raman scattering (SERS) measurements were performed here to elucidate the complex molecular mechanism of the reduction in presence of halide ions and hydrogen ions. The SERS measurements were performed using a simply prepared silver plasmonic film (AgPF), which enables monitoring of the reaction in different conditions at a solid-liquid surface, and eliminates the need for use of a reducing agent. As the concentration of H+ and Cl- could controlled, the observation of the reaction under a systematic set of condition was possible. Based on the kinetic traces of the intermediates, a reaction mechanism for the 4-NTP to 4-ATP reduction is suggested. Rate constants for the individual reactions are presented that fit the measured kinetic traces, and the role of hydrogen in each reaction step is characterized. This work provides clarification on the molecular transformation directly using protons as hydrogen source and demonstrates an effective method of applying a simple and low-cost silver surface catalyst for SERS studies. Moreover, the monitoring of Cl--concentration-dependent spectra gained insight into the hot-electron conversion process during the photoreduction and strongly support the formation of AgCl for activation of H+.
关键词： in-situ SERS spectra,kinetic rate constants,reaction mechanism,time-resolved measurements,selective surface photocatalytic reaction
更新于2025-09-23 15:19:57
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Toward reliable high performing organic solar cells: Molecules, processing, and monitoring
摘要： A steady surge in device efficiencies of organic solar cells (OSCs) along with improvement in associated features, such as stability and facile processing methods, is expected to provide a realistic, feasible commercial option. The introduction of high performing donor and acceptor molecules along with tailored buffer layers has provided the impetus for the resurgence of this field. Further options of ternary and tandem architectures of these OSC systems should push this technology to competitive levels. A major hurdle, which is expected when these devices are evaluated for long-term performance in all weather conditions, is the level of degradation. We examine and address these stability-limiting factors in this perspective article. Modifications in microstructure/morphology and interfaces with time and energy levels defining the molecules form some of the critical intrinsic degradation pathways. Various strategies that have been used to limit the associated pathways of degradation of the active layer will be discussed. One such strategy is electric field-assisted thermal annealing treatment, which concomitantly also brings in a favorable vertical phase segregated active layer morphology. We also emphasize the utility of photocurrent noise measurements to monitor the level of degradation and possibly forecast the trajectory of long-term performance of OSCs.
关键词： processing methods,photocurrent noise measurements,electric field-assisted thermal annealing,device efficiencies,degradation,donor and acceptor molecules,organic solar cells,stability,ternary and tandem architectures
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE International Conference on Microwaves, Antennas, Communications and Electronic Systems (COMCAS) - Tel-Aviv, Israel (2019.11.4-2019.11.6)] 2019 IEEE International Conference on Microwaves, Antennas, Communications and Electronic Systems (COMCAS) - Results of the Radio Optical Modeling and Application of the New Radio Holography Method of the RATAN-600 Radio Telescope Surface Diagnosis
摘要： We describe a new radio holography method of the RATAN-600 radio telescope antenna diagnosis and adjustment, using the radial movement of the reference panel. We present the results of geometric optical ray tracing of the “South + Flat” antenna system in the autocollimation mode and radio optical modeling of the hologram recording and field reconstruction procedure, taking noise into account. Estimates for necessary isolation and acceptable spatial separation between transmitting and receiving feeds, geometrical tolerances, and requirements to the reference panel motion control are discussed. The experimental results of the method application to the diagnosis of radial errors in the positioning of panels of the RATAN-600 main mirror are reported.
关键词： radio astronomy,telescopes,Antenna measurements,holography,electromagnetic modeling
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting - Atlanta, GA, USA (2019.7.7-2019.7.12)] 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting - A Unit-Cell Discontinuous Galerkin Scheme for Analyzing Plasmonic Photomixers
摘要： Disordered ionic-bonded transition metal oxide thin-film transistors (TFTs) show promise for a variety of dc and RF switching applications, especially those that can leverage their low-temperature, substrate-agnostic process integration potential. In this paper, enhancement-mode zinc-oxide TFTs were fabricated and their switching performance evaluated. These TFTs exhibit the drain-current density of 0.6 A/mm and minimal frequency dispersion, as evidenced by dynamic current–voltage tests. A high-frequency power switch figure of merit RON QG of 359 mΩ · nC was experimentally determined for 0.75-μm long-channel devices, and through scaling 45.9 mΩ · nC is achievable for 11 V-rated devices (where RON is ON-state drain–source resistance, and QG is gate charge). An RF switch cutoff frequency fc of 25 GHz was measured for the same 0.75-μm TFT, whereas fc exceeding 500 GHz and power handling in the tens of watts are projected with optimization.
关键词： zinc oxide,dc switch,Cutoff frequency,pulse measurements,gate charge,monolithic ICs,RF switch,ionic semiconductors,thin-film transistors (TFTs)
更新于2025-09-23 15:19:57
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Extraction of uncertain parameters of single-diode model of a photovoltaic panel using simulated annealing optimization
摘要： In this article, our goal is to improve the estimation of the parameters of solar photovoltaic models, we propose a method based on Simulated Annealing (SA) Optimization, the proposed algorithm takes into account the uncertainties of measurements. This algorithm consists of three steps such as the extraction of the parameters in a conventional manner, then the determination of the uncertainties of each parameter, finally the determination of the instantaneous parameters taking into account the results of the first two steps. For the validation of the proposed theoretical developments, the algorithm is applied to four different PV parameter estimation problems. The results obtained are compared with well-established algorithms to confirm its effectiveness. These comparisons have shown that the proposed method exhibits largely effective performances than existing methods in the literature.
关键词： Uncertainties measurements,Photovoltaic model,Simulated annealing optimization,Parameter estimation
更新于2025-09-23 15:19:57
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Benefit of depolarization ratio at λ = 1064 nm for the retrieval of the aerosol microphysics from lidar measurements
摘要： A better quantification of aerosol properties is required for improving the modelling of aerosol effects on weather and climate. This task is methodologically demanding due to the diversity of the microphysical properties of aerosols and the complex relation between their microphysical and optical properties. Advanced lidar systems provide spatially and temporally resolved information on the aerosol optical properties that is sufficient for the retrieval of important aerosol microphysical properties. Recently, the mass concentration of transported volcanic ash, which is relevant for the flight safety of aeroplanes, was retrieved from measurements of such lidar systems in southern Germany. The relative uncertainty of the retrieved mass concentration was on the order of ±50 %. The present study investigates improvements of the retrieval accuracy when the capability of measuring the linear depolarization ratio at 1064 nm is added to the lidar setup. The lidar setups under investigation are based on those of MULIS and POLIS of the Ludwig-Maximilians-Universit?t in Munich (Germany) which measure the linear depolarization ratio at 355 and 532 nm with high accuracy. The improvements are determined by comparing uncertainties from retrievals applied to simulated measurements of this lidar setup with uncertainties obtained when the depolarization at 1064 nm is added to this setup. The simulated measurements are based on real lidar measurements of transported Eyjafjallaj?kull volcano ash. It is found that additional 1064 nm depolarization measurements significantly reduce the uncertainty of the retrieved mass concentration and effective particle size. This significant improvement in accuracy is the result of the increased sensitivity of the lidar setup to larger particles. The size dependence of the depolarization does not vary strongly with refractive index, thus we expect similar benefits for the retrieval in case of measurements of other volcanic ash compositions and also for transported desert dust. For the retrieval of the single scattering albedo, which is relevant to the radiative transfer in aerosol layers, no significant improvements were found.
关键词： depolarization ratio,volcanic ash,aerosol properties,microphysical retrieval,lidar measurements
更新于2025-09-23 15:19:57
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Quantum control with measurements and quantum Zeno dynamics
摘要： We introduce an efficient iterative method to prepare a target state in Hilbert spaces with high dimensionality using a combination of unitary evolution, measurements, and quantum Zeno dynamics. The latter confines the evolution within Zeno subspaces of decreasing size. This gives an exponential speedup relative to the case of states evolving in the full Hilbert space between projective measurements. We demonstrate our approach on the control problem of rapidly transferring a superfluid into the Mott insulator in the Bose-Hubbard model. We discuss the general applicability of the method by preparing arbitrary superpositions with random Hamiltonians.
关键词： quantum Zeno dynamics,quantum control,Mott insulator,Bose-Hubbard model,measurements
更新于2025-09-23 15:19:57
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Improving the Reliability of Interference Measurements by using Several Wavelengths
摘要： Methods are proposed to improve the reliability of interference measurements of surface nanotopography with sharp height gradients that lead to ambiguity in determining the phase of interference signals. The effect of the total measurement error on the range of multiwavelength measurements is considered. The results of field experiments demonstrating an increase in the range of measurements of nanotopography by the proposed methods in comparison with single-wavelength measurements are given.
关键词： multiwavelength measurements,surface topography,interference measurements,partially coherent interferometry
更新于2025-09-19 17:15:36