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Fully Coupled Model for Frequency Response Simulation of Miniaturized Cantilever-Based Photoacoustic Gas Sensors
摘要： To support the development of miniaturized photoacoustic gas sensors, a fully coupled ?nite element model for a frequency response simulation of cantilever-based photoacoustic gas sensors is introduced in this paper. The model covers the whole photoacoustic process from radiation absorption to pressure transducer vibration, and considers viscous damping loss. After validation with experimental data, the model was further applied to evaluate the possibility of further optimization and miniaturization of a previously reported sensor design.
关键词： photoacoustic spectroscopy,sensor miniaturization,viscous damping,COMSOL
更新于2025-09-12 10:27:22
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Precession damping in [Co <sub/>60</sub> Fe <sub/>40</sub> /Pt] <sub/>5</sub> multilayers with varying magnetic homogeneity investigated with femtosecond laser pulses
摘要： We report on the ultrafast magnetization dynamics of [Co60Fe40/Pt]5 multilayers studied with femtosecond laser pulses. The samples were grown at room temperature by DC magnetron sputtering with Ta capping and Pt buffer layers and present the same thickness and perpendicular magnetic anisotropy as determined by vibrating sample magnetometry. Controlled growth rate of the Pt buffer layer modified the anisotropy fields and magnetic domain sizes as measured by magnetic force microscopy (MFM). An estimation of the average magnetic domain sizes was obtained from the profile of the self-correlation transform of the MFM images. For multilayers having an average magnetic domain size of 490 nm, we report a damped precession of the magnetization which decays with a time constant of ～100 ps and which has a frequency which varies from 8.4 GHz to 17.0 GHz as the external field increases from 192 mT to 398 mT. Fitting the precession dynamics with the Landau-Lifshitz-Gilbert equation we evaluated the damping α, which decreases from 0.18 to 0.05 with increasing magnetic domain sizes (127 nm to 490 nm). These α values are higher than for single layers suggesting an enhanced scattering and spin pumping effects from the Pt adjacent layers. In addition, the precession frequency increases from 2.04 GHz to 11.50 GHz as the anisotropy field of the multilayers increases from 6.5 kOe to 13.0 kOe. Finally, a comparative analysis between micromagnetic simulations and MFM images allowed us to determine the exchange stiffness (Aex) in the [Co60Fe40/Pt]5 multilayers.
关键词： exchange stiffness,femtosecond laser pulses,Landau-Lifshitz-Gilbert equation,[Co60Fe40/Pt]5 multilayers,damping,magnetic force microscopy,ultrafast magnetization dynamics,perpendicular magnetic anisotropy
更新于2025-09-12 10:27:22
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A photocounting distribution formula for a laser channel
摘要： For a laser channel governed by the master equation of the density operator which involves both photon gain and loss parameters, g and κ, we derive a new formula for the photocount distribution at time t for an initial density operator ρ0. The formula brings convenience, since we need not derive the density operator ρt at time t. Moreover, this formula is applied to the case of a damping channel and a di?usion channel, respectively.
关键词： Photocount distribution,Damping channel,Evolution law,Di?usion channel,Laser channel
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE 10th International Symposium on Power Electronics for Distributed Generation Systems (PEDG) - Xi'an, China (2019.6.3-2019.6.6)] 2019 IEEE 10th International Symposium on Power Electronics for Distributed Generation Systems (PEDG) - Analysis of Inertia and Damping Characteristics of Grid-connected Photovoltaic Power Generation System Based on Droop Control
摘要： The grid-connected photovoltaic power generation system (GPPGS) with high proportion of renewable energy has the ability to load balance. A strategy is proposed for GPPGS based on droop control. The electric torque analysis method (ETAM) is used to establish mathematical model of the system with DC voltage timescale (DVT) and analyze the influence law of inertia, damping and synchronization characteristics from the physical mechanism perspective. The research finds that the equivalent inertia, damping and synchronization parameters of the system are determined by the control parameters, structural parameters and steady-state operating point parameters. Changing the control parameters is the simplest and most flexible way to influence the inertia damping and synchronization ability of the system. The inertia characteristics of the system are greatly influenced by the control parameter Kp and enhanced with the increase of Kp. The damping characteristics of the system are obviously affected by the control parameter Dp and weakened with the increase of Dp. The synchronization effect of the system is only controlled by the parameter Ki and enhanced with the increase of Ki. The effectiveness and correctness of the analysis conclusion are verified by simulation.
关键词： droop control,inertia and damping characteristics,DVT,ETAM,GPPGS
更新于2025-09-11 14:15:04
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Thin Films with Checkerboard-Ordered Oxygen Vacancies and Low Magnetic Damping
摘要： The possibility of affecting the magnetic properties of a material by dielectric means, and vice versa, remains an attractive perspective for modern electronics and spintronics. Here, we report on epitaxial Bi(Fe0.5Mn0.5)O3 thin films with exceptionally low Gilbert damping and magnetoelectric coupling above room temperature (< 400 K). The ferromagnetic order, not observed in bulk, has been detected with a total magnetization of 0.44 μB/formula units with low Gilbert damping parameter (0.0034), both at room temperature. Additionally, a previously overlooked check-board ordering of oxygen vacancies is observed, providing insights on the magnetic and dielectric origin of the multifunctional properties of the films. Finally, intrinsic magnetodielectric behavior is observed as revealed by the variation of dielectric permittivity well above room temperature. These findings show the possibility of electric-field-controlled magnetic properties, in low Gilbert-damping-based spintronic devices, using single-phase multiferroic materials.
关键词： magnetodielectric,Gilbert damping,thin films,Bi(Fe0.5Mn0.5)O3,magnetoelectric coupling
更新于2025-09-11 14:15:04
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Influences of relative humidity on the quality factors of MEMS cantilever resonators in gas rarefaction
摘要： In this paper, the effect of relative humidity of moist air is discussed on the quality factor (Q factor) of micro-electro-mechanical systems (MEMS) cantilever resonators in wide range of gas rarefaction (ambient pressure and accommodation coefficients, ACs). The modified molecular gas lubrication (MMGL) equation is used to model the squeeze film damping problem of MEMS cantilever resonators. Dynamic viscosity and Poiseuille flow rate are used to modify the MMGL equation to consider the coupled effects of relative humidity and gas rarefaction. Thermoelastic damping and anchor loss, which are dominant damping mechanisms of MEMS cantilever resonators, are also included to calculate total Q factor. Thus, the influences of relative humidity are discussed on the Q factors of MEMS cantilever resonators in wide range of gas rarefaction and dimension of cantilever. The results showed that the Q factor decreases as relative humidity increases in wide range of gas rarefaction (pressure, and ACs) and dimension of cantilever (length, width, and thickness). The influences of relative humidity on the Q factor become more significantly in larger length, larger width, smaller thickness of cantilever, and higher gas rarefaction (lower pressure and ACs). Whereas, the influences of relative humidity on the Q factor reduce or are neglected in smaller length, larger thickness of cantilever and lower gas rarefaction (higher pressure and ACs).
关键词： Anchor loss,Relative humidity,Quality factor,Gas rarefaction,Squeeze film damping,Thermoelastic damping,MEMS cantilever resonators
更新于2025-09-10 09:29:36
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[IEEE 2018 International Conference on Information , Communication, Engineering and Technology (ICICET) - Pune, India (2018.8.29-2018.8.31)] 2018 International Conference on Information , Communication, Engineering and Technology (ICICET) - New Control Technique to Improve the Grid Power by Using PV-STATCOM
摘要： This paper introduces novel control method to utilize the solar plant inverter as static synchronous compensator (STATCOM) which is also called as PV-STATCOM to improve the power transmission capacity of the grid. The solar farm is ideal for the nighttime and it produces less power in morning period and late afternoon period. Therefore these are the expensive assets which are remaining unutilized during this period of 24hrs. To overcome these problems solar plant along with maximum power point tracking [MPPT] produces active power during daytime and full capacity of solar plant inverter which is not used in night period is used with help of point of common coupling [PCC] voltage controller and damping controller to improve the power transmission capacity of line and also power factor of the grid line. The inverter capacity which is left after the real power generation is used to perform the given objective. This new control technique is used to increase the grid transfer capacity for which other alternatives are used like FACT devices.
关键词： flexible alternating current transmission system,inverter,solar system,damping controller,MPPT,STATCOM,dc voltage regulator,voltage controller
更新于2025-09-10 09:29:36
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The Noise Level of Total Scattering Cross Section Measurement in a Reverberation Chamber
摘要： A chamber can be used to measure the total scattering cross section (TSCS) of an object, in which the time-domain response needs to be analyzed to extract the scattering damping time. It has been observed in measurements that the noise level in extracting the scattering damping time is much higher than that in extracting the chamber decay time. The reasons behind this phenomenon are explored in this letter. Analytical distributions of the noise in TSCS measurements are derived and validated by measurements. Good agreements between analytical results and measurement results have been obtained, which gives guidelines on the prediction of noise level and the required independent sample number in the total scattering cross section measurement.
关键词： scattering damping time,total scattering cross section measurement,Reverberation chamber (RC)
更新于2025-09-10 09:29:36
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Enhance quantum teleportation under correlated amplitude damping decoherence by weak measurement and quantum measurement reversal
摘要： A scheme which aims to protect the quantum teleportation from correlated amplitude damping decoherence is proposed. Comparing with the results of uncorrelated amplitude damping noise, we ?nd that the correlated effects enable to improve the ?delity with the given decoherence parameter. Moreover, we show that the combination of weak measurement and quantum measurement reversal could drastically enhance the ?delity in both uncorrelated and correlated amplitude damping noise. Our results extend the ability of weak measurement as a technique in various quantum information processes which are affected by correlated noise.
关键词： Weak measurement,Correlated amplitude damping channel,Quantum teleportation
更新于2025-09-10 09:29:36
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Investigation and damping of low frequency oscillations of stochastic solar penetrated power system by optimal dual UPFC controller
摘要： Solar power being stochastic and asynchronous in nature, its integration with conventional power generation put so many challenges in damping of low frequency oscillations. This paper presents an investigation of low frequency oscillation and damping of stochastic solar power integrated power system by UPFC dual optimal controller, whose gains are optimized by a novel hybrid particle swarm optimization and improved grey wolf optimizer (PSO-IGWO). The dual controller simultaneously controls modulation index of series and phase angle of shunt converters of UPFC, who co-operate each other, optimizing its efficacy and thereby implementing the advantages of both SSSC and STATCOM. Detail eigen value analysis has been performed with time domain simulations to study the damped oscillatory response of variable and random solar penetration with power system along with interaction of solar power with variable synchronous power generations. For multi machine system multi input single output dual controller is proposed. Maximum sensor and time delay has been considered to design the controller providing a realistic approach. It is observed that random and heavy solar penetration has more detrimental effect on system oscillations and which can be damped heavily with proposed controller, in contrast to PSO, DE, GWO, DEPSO optimized lead-lag and dual controllers.
关键词： low frequency oscillations,damping controller,Solar power,PSO-IGWO,UPFC
更新于2025-09-10 09:29:36