Most Cited
2023, 72 (22): 224206.
doi: 10.7498/aps.72.20230579
Abstract +
The lock-in amplifier can perform high-precision measurement in both time and amplitude dimensions, so that it becomes a key component of instrumental system for precision measurement and control. This article overviews the concept, technology, and application of phase-locked amplifiers as a guide. It first explains the development and evolution of phase-locked amplifiers of analog, digital, and virtual phase-locked amplifiers, demonstrating their relationship and differences. Then, it classifies phase-locked amplifiers from a mathematical perspective based on the order and type of phase-locked loops. Subsequently, the testing process and metrological calibration progress of the main performance of phase-locked amplifiers, such as amplitude, frequency, and phase noise, are introduced. The conversion relationship between key indicators such as phase noise, time-domain jitter, Allan variance, and the coupling relationship with amplitude noise are discussed. Finally, the application forms and effects of phase-locked amplifiers in the fields of spectral enhancement, impedance analysis, magnetic measurement, microscopic imaging, and space exploration are listed. Through some new applications, the prospects of their transition from scientific instruments to industrial and even civilian products through intelligent computing, precise IoT, and other means are briefly given.
2023, 72 (22): 224203.
doi: 10.7498/aps.72.20231035
Abstract +
2023, 72 (1): 018401.
doi: 10.7498/aps.72.20222012
Abstract +
Dielectric capacitors have been widely used in crucial energy storage systems of electronic power systems because of their advantages such as fast charge discharge rates, long cycle lifetimes, low losses, and flexible and convenient processingc. However, the dielectric capacitors have lower energy storage densities than electrochemical energy storage devices, which makes them difficult to meet higher application requirements for electrical engineering at the present stage. Polyvinylidene fluoride (PVDF) based polymers show great potential in achieving improved energy storage properties, which is attributed to their high dielectric constants and high breakdown strengths. This work systematically reviews PVDF-based nanocomposites for energy storage applications. Dielectric constant, breakdown strength and charge discharge efficiency are three main parameters related to energy storage properties, which are proposed to discuss their mechanisms of action and optimization strategies. Finally, the key scientific problems of PVDF-based high energy storage composites are summarized and considered, and the future development trend of dielectric capacitors is also prospected.
2023, 72 (23): 234401.
doi: 10.7498/aps.72.20231546
Abstract +
“Heat death”, namely, overheating, which will deteriorate the function of chips and eventually burn the device and has become an obstacle in the roadmap of the semiconductor industry. Therefore, heat dissipation becomes a key issue in further developing semiconductor. Heat conduction in chips encompasses the intricate dynamics of phonon conduction within one-dimensional, two-dimensional materials, as well as the intricate phonon transport through interfaces. In this paper, the research progress of the complexities of phonon transport on a nano and nanoscale in recent three years, especially the size dependent phonon thermal transport and the relationship between anomalous heat conduction and anomalous diffusion are summarized. Further discussed in this paper is the fundamental question within non-equilibrium statistical physics, particularly the necessary and sufficient condition for a given Hamiltonian whose macroscopic transport behavior obeys Fourier’s law. On the other hand, the methods of engineering the thermal conduction, encompassing nanophononic crystals, nanometamaterials, interfacial phenomena, and phonon condensation are also introduced. In order to comprehensively understand the phononic thermal conduction, a succinct overview of phonon heat transport phenomena, spanning from thermal quantization and the phonon Hall effect to the chiral phonons and their intricate interactions with other carriers is presented. Finally, the challenges and opportunities, and the potential application of phonons in quantum information are also discussed.
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