- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Dynamically Tunable Plasmon-Induced Transparency Based on Radiative–Radiative-Coupling in a Terahertz Metal–Graphene Metamaterial
摘要： The thin aluminum liners with an aspect ratio R/?r (cid:28) 1 have been imploded on the primary test stand (PTS) facility, where R is the outer radius of the liner and ?r is the thickness. The x-ray self-emission images present azimuthally correlated perturbations in the liner implosions. The experiments show that at ?10 ns before the stagnation, the wavelengths of perturbation are about 0.93 mm and 1.67 mm for the small-radius and large-radius liners, respectively. We have utilized the resistive magnetohydrodynamic code PLUTO to study the development of magneto-Rayleigh–Taylor (MRT) instabilities under experimental conditions. The calculated perturbation amplitudes are consistent with the experimental observations very well. We have found that both mode coupling and long implosion distance are responsible for the more developed instabilities in the large-radius liner implosions.
关键词： Z-pinches,thin liner implosion,primary test stand (PTS),magneto-Rayleigh–Taylor instability,magnetohydrodynamic (MHD)
更新于2025-09-11 14:15:04
-
Modulational instability and soliton trains in a model for two-mode fiber ring lasers
摘要： A model of orthogonally polarized two-field fiber ring laser with a linear gain is considered, with emphasis on the continuous-wave stability and the existence of soliton trains. The continuous-wave stability analysis is carried out within the framework of the modulational-instability approach, the variations of the gain spectrum with the modulation frequency and characteristic parameters of the model give rise to a rich variety of stability features including single-band and multiband stability regions. Seeking for pulse structures of the model, the two coupled cubic complex Ginzburg–Landau equations describing individual mode propagations are transformed into a set of coupled, first-order nonlinear ordinary-differential equations for the amplitudes and phases of the two modes. Numerical simulations of the last set of coupled equations indicate that in the anomalous dispersion regime, envelopes of the two fields are periodic trains of pulses the amplitudes of which are affected by the linear gain.
关键词： Pulse trains,Modulational instability,Orthogonally polarized two-mode fields,Fiber ring laser
更新于2025-09-11 14:15:04
-
Low temperature wet-O <sub/>2</sub> annealing process for enhancement of inversion channel mobility and suppression of <i>V</i> <sub/>fb</sub> instability on 4H-SiC (0001) Si-face
摘要： For improvement of 4H-SiC metal-oxide-semiconductor ?eld-effect-transistor performance, a post-oxidation annealing (POA) process in a wet environment after dry oxidation was systematically investigated. By tuning the wet-POA conditions, we clari?ed that wet-POA at low temperatures is more advantageous for both the enhancement of channel mobility and the suppression of ?atband voltage instability. One of the mechanisms of channel mobility enhancement is attributed to the decrease in the density of traps in oxide near the MOS interface, rather than conventional interface traps. The effects of the wet environment on interfacial properties were also discussed based on oxide growth kinetics on 4H-SiC.
关键词： channel mobility,Vfb instability,MOSFET,4H-SiC,wet-O2 annealing
更新于2025-09-10 09:29:36
-
[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Evaluation Standard Uncertainty Depends on Travelling Standard Instability During Key Comparison
摘要： This paper deals with some problems concerning the evaluation of standard uncertainty depends on travelling standard instability and its further influence on evaluation uncertainty of key comparison reference value during a key comparison of national standards. The authors have proposed an explicit practical approach for evaluating standard uncertainty depends on travelling standard instability when the radial scheme of comparisons is used. As an example, the approach is applied to key comparison COOMET.EM–K5.
关键词： key comparison,travelling standard,uncertainty,Electric power,instability
更新于2025-09-10 09:29:36
-
[Springer Tracts in Modern Physics] Parity-time Symmetry and Its Applications Volume 280 || Krein Signature in Hamiltonian and P T $$\mathbb {PT}$$ -Symmetric Systems
摘要： We explain the concept of Krein signature in Hamiltonian and PT -symmetric systems on the case study of the one-dimensional Gross–Pitaevskii equation with a real harmonic potential and an imaginary linear potential. These potentials correspond to the magnetic trap, and a linear gain/loss in the mean-?eld model of cigar-shaped Bose–Einstein condensates. For the linearized Gross–Pitaevskii equation, we introduce the real-valued Krein quantity, which is nonzero if the eigenvalue is neutrally stable and simple and zero if the eigenvalue is unstable. If the neutrally stable eigenvalue is simple, it persists with respect to perturbations. However, if it is multiple, it may split into unstable eigenvalues under perturbations. A necessary condition for the onset of instability past the bifurcation point requires existence of two simple neutrally stable eigenvalues of opposite Krein signatures before the bifurcation point. This property is useful in the parameter continuations of neutrally stable eigenvalues of the linearized Gross–Pitaevskii equation.
关键词： Hamiltonian systems,Instability bifurcations,PT -symmetry,Gross–Pitaevskii equation,Krein signature
更新于2025-09-10 09:29:36
-
[Springer Tracts in Modern Physics] Parity-time Symmetry and Its Applications Volume 280 || Constant-Intensity Waves in Non-Hermitian Media
摘要： When waves propagate through a non-uniform potential landscape their interference typically gives rise to a complex intensity pattern. In this chapter we review our work on how to entirely suppress these intensity variations by adding system-specific gain and loss components to the potential. The resulting constant-intensity (CI) waves are entirely free of interference fringes and get perfectly transmitted across any such non-Hermitian scattering landscape that is put in their way. We discuss how to generalize this concept to more than one dimension and to the non-linear regime where these special wave states open up the way to study the phenomenon of modulation instability in non-uniform potentials. Experimental implementations of these unique wave states are envisioned not just in optics, but also in other fields of wave physics such as in acoustics.
关键词： Acoustics,Modulation instability,Optics,Constant-intensity waves,Wave propagation,Non-Hermitian media
更新于2025-09-10 09:29:36
-
Multisoliton spectrum breaking due to small harmonic perturbations
摘要： We demonstrate analytically and numerically that velocities and amplitudes of the single-soliton components of a high-intensity light pulse with a linear frequency chirp and a parabolic pro?le are highly sensitive to small harmonic phase perturbations from certain frequency band. This exponential sensitivity with respect to the pulse amplitude and chirp rate product should be taken into account for the characterization and applications of such pulses.
关键词： Solitons,Zakharov–Shabat scattering problem,Instability
更新于2025-09-10 09:29:36
-
Comparison of plasma properties in normal and multiple holes hollow cathode RF PECVD and their utility in a-SiNx:H thin film deposition
摘要： Conventional and multiple-hole hollow cathode (MHHC) showerhead electrodes of an RF capacitively coupled plasma (CCP) source were experimentally studied to investigate their capability of plasma generation and suitability of plasma application like PECVD. The plasma characteristics of the CCPs were critically examined for the PECVD plasmas produced by various showerhead configurations. The optimum performance in terms of high-density plasma generation and high emission intensity of excited species was observed for the operation using MHHC discharge. The MHHC discharge is characterized by an anode glow and a strong low-frequency fluctuation in the range of ~ a few kHz that is measured by the Langmuir probe (LP). The LP measurements in a broad pressure range revealed the scenario of hollow cathode discharge characterized by the enhanced electron temperature and the highest plasma density around 120 mTorr. It is realized that the bulk plasma intrusion inside the hole of the electrodes of the showerhead and the enhanced ionization in the plasma sheath regions of each hole facilitated the generation of high-density plasmas when the hole diameter is slightly bigger than twice or thrice the sheath length. The effectiveness of MHHC PECVD for high rate and low-temperature deposition of a-SiNx:H thin films is realized.
关键词： Hollow cathode discharge,Plasma instability,Silicon nitride film,RF Plasma source
更新于2025-09-10 09:29:36
-
Machine learning analysis of extreme events in optical fibre modulation instability
摘要： A central research area in nonlinear science is the study of instabilities that drive extreme events. Unfortunately, techniques for measuring such phenomena often provide only partial characterisation. For example, real-time studies of instabilities in nonlinear optics frequently use only spectral data, limiting knowledge of associated temporal properties. Here, we show how machine learning can overcome this restriction to study time-domain properties of optical fibre modulation instability based only on spectral intensity measurements. Specifically, a supervised neural network is trained to correlate the spectral and temporal properties of modulation instability using simulations, and then applied to analyse high dynamic range experimental spectra to yield the probability distribution for the highest temporal peaks in the instability field. We also use unsupervised learning to classify noisy modulation instability spectra into subsets associated with distinct temporal dynamic structures. These results open novel perspectives in all systems exhibiting instability where direct time-domain observations are difficult.
关键词： machine learning,extreme events,optical fibre modulation instability,unsupervised learning,supervised neural network
更新于2025-09-10 09:29:36
-
Straight for the sun
摘要： Certain types of star evolve into supernovae (pictured), whose light we can observe with telescopes. Supernovae are classified according to the presence or absence of elements in their optical spectra. But the supernova SN 2017ens shows a spectrum in the ultraviolet and near-infrared range, which fits none of the known categories — so astrophysicists are curious to understand the formation and evolution of this particular supernova. Now, Ting-Wan Chen and colleagues have reported the observation of SN 2017ens over more than 260 days. The supernova was initially a hot blue object without features. Shortly after the spectral peak was observed, narrow emission lines started to appear in the spectrum, and over time, broader features developed. After 160 days, the spectrum evolved dramatically: although it remained within the blue, the spectrum was dominated by wide emission lines. Accompanying measurements show that SN 2017ens could have been a pulsational pair instability supernova, in which a fraction of the star’s mass is disrupted followed by a core collapse or hypernova.
关键词： supernovae,ultraviolet,SN 2017ens,near-infrared,pulsational pair instability supernova
更新于2025-09-10 09:29:36