- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Unlocking higher harmonics in atomic force microscopy with gentle interactions
摘要： In dynamic atomic force microscopy, nanoscale properties are encoded in the higher harmonics. Nevertheless, when gentle interactions and minimal invasiveness are required, these harmonics are typically undetectable. Here, we propose to externally drive an arbitrary number of exact higher harmonics above the noise level. In this way, multiple contrast channels that are sensitive to compositional variations are made accessible. Numerical integration of the equation of motion shows that the external introduction of exact harmonic frequencies does not compromise the fundamental frequency. Thermal fluctuations are also considered within the detection bandwidth of interest and discussed in terms of higher-harmonic phase contrast in the presence and absence of an external excitation of higher harmonics. Higher harmonic phase shifts further provide the means to directly decouple the true topography from that induced by compositional heterogeneity.
关键词： composition,phase,heterogeneity,chemistry,higher harmonics,atomic force microscopy
更新于2025-09-09 09:28:46
-
[IEEE 2017 51st Asilomar Conference on Signals, Systems, and Computers - Pacific Grove, CA, USA (2017.10.29-2017.11.1)] 2017 51st Asilomar Conference on Signals, Systems, and Computers - Frequency invariant beamforming for arbitrary planar arrays
摘要： In this paper, we present the adaptation to the least-square solution for frequency invariant beamforming to arbitrary planar arrays. This formulation is easily steerable thanks to the decoupling of spatial and spectral constraints. This is achieved with a basis of spherical harmonics polynomials, which parametrize the array response in a term dependent on frequency and a term dependent on the array geometry. Furthermore, the parametrization of the array response Bessel functions decouples the frequency term, which becomes independent of the geometry of the planar array, and allows steering in azimuth and elevation independently. The planar array response is approximated using virtual sensor modeling, which transform any two dimensional planar array in a virtual linear sensors, where azimuth and elevation are separable and can be steered independently.
关键词： frequency invariant beamforming,virtual sensor modeling,planar arrays,spherical harmonics
更新于2025-09-09 09:28:46
-
[IEEE 2018 XIV International Scientific-Technical Conference on Actual Problems of Electronics Instrument Engineering (APEIE) - Novosibirsk, Russia (2018.10.2-2018.10.6)] 2018 XIV International Scientific-Technical Conference on Actual Problems of Electronics Instrument Engineering (APEIE) - Virtual Instrument for Assessment of Simulated Signal Integrated Harmonics Factors
摘要： The block diagram of the LabVIEW virtual instrument for the assessment of simulated signal integrated harmonics factors is presented. This virtual device version is equipped with the input module for waveform data points import file. The examples of measurement and use of the integrated harmonics factors values of the investigated voltage for estimating the harmonic distortion of the load circuit current are shown.
关键词： method of the differential equations algebraization (ADE),Weighted THD,n-order integrated voltage (current) harmonics factor (IHF),LabVIEW virtual instrument,PSIM
更新于2025-09-04 15:30:14
-
[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Concept of an Asymmetric Metasurface Absorber
摘要： In this talk we show how to break the angular symmetry of electromagnetic response of thin absorbers. Based on our recent results on multichannel metasurfaces, we propose a new concept of asymmetric absorbers in which the absorption coefficient for waves impinging from a given oblique angle is extraordinarily different from that for waves incident from the oppositely tilted direction. The proposed asymmetric structure realizes controllable reflectance (from 0 to 0.99) for waves incident from one direction, exhibiting total absorption when the sign of the incidence angle is reversed. We provide a theoretical analysis for the asymmetric absorber as well as a numerical verification.
关键词： surface impedances,asymmetric,Floquet harmonics,absorbers,multichannel metasurfaces
更新于2025-09-04 15:30:14
-
[IEEE 2018 19th International Conference of Young Specialists on Micro/Nanotechnologies and Electron Devices (EDM) - Erlagol (Altai Republic), Russia (2018.6.29-2018.7.3)] 2018 19th International Conference of Young Specialists on Micro/Nanotechnologies and Electron Devices (EDM) - Examination of Physical Phenomena and Processes in the Magnetophotonic Composite Media. Magnetophotonics Material Medium
摘要： The development of radioelectronics and informative–and–communicative technologies of the XXI century is associated with the transmission of ever increasing volume of data and is oriented to use of subTHz and THz bands – SHF, EHF, and HHF (0.1 – 10 THz). Elements and devices of these bands can be conditionally divided into 2 levels: up to 1THz electronic equipments are effectively uses, over 1 THz –are photonic devices. The development of photonic technologies is of increasing importance both in the telecommunicative and in the space communication systems. In this report the physical phenomena and processes occurring in magnetooptical (magnetophotonic) composite material media capable of optimally ensuring their efficiency have been investigated to create new element baseline for domestic radioelectronics. The creation of new–generation functional devices capable of operating in subTHz and THz frequency bands will entail the rapid development of telecommunications.
关键词： Kerr effect,laser radiation,magnetophotonics,Maxwell's equations,self–focusing of light,nonlinear photonic media,Green's functions,Nanophotonics,current harmonics
更新于2025-09-04 15:30:14
-
Robust EnKF with Improved RCGA based Control for Solar Energy Conversion Systems
摘要： The robust ensemble Kalman filter (EnKF) based control is proposed for multifunctional three phase grid-connected solar energy conversion system with distribution static compensator (DSTATCOM) abilities. The robust EnKF based control facilitates the various functionalities of power quality (PQ) enhancement of the distribution grid such as grid currents balancing, harmonics current mitigation and unity power factor. The improved real coded genetic algorithm (RCGA) based metaheuristic approach is used to tune the proportional integral (PI) controller of the DC link voltage. Simulation results comparative dynamic performance, which demonstrates that the robust EnKF exhibits superior response as compared to state of the art techniques. The relative computational complexity of the proposed robust EnKF algorithm is analyzed with conventional stochastic filters such as Kalman filter (KF) and extended Kalman filter (EKF). To substantiate the proposed control, a prototype is realised in the laboratory and test results demonstrate satisfactory response of the grid-connected system subjected to various dynamic scenarios such as load currents imbalancing, harmonics compensation, imbalanced grid voltages, under voltage and over voltage. The response of grid currents are achieved within the IEEE-519, 1564 and 1159 standards.
关键词： DSTATCOM,MPPT,Power Quality,Harmonics,VSC,EnKF
更新于2025-09-04 15:30:14
-
[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Spherical Harmonic-Based Spectral Projection Model for Holographic SAR Imaging
摘要： A spectral projection model which is based on spherical harmonics is developed for three-dimensional holographic SAR imaging. The addition theorem for spherical harmonics is used for describing the SAR measurement process as a projection of a source spectral vector onto an observation spectral vector. The source vector for a particular scatterer is determined by the spherical coordinates of that scatterer. The dimension of the source vector is determined by the largest dimension of the SAR viewing area. The observation vectors are similarly defined in terms of the spherical coordinates of each measurement point along the SAR flight path. By separating the source and observation terms in the addition theorem, the contribution from each scatterer to each specific SAR measurement is described as the projection of the source spectral vector onto the observation spectral vector. Simulations are used to investigate the spectral properties of a variety of source distributions and SAR flight paths. Sample holographic images are simulated using this spectral projection model.
关键词： addition theorem,Holographic SAR,spectral projection model,spherical harmonics
更新于2025-09-04 15:30:14