Article
Construction & Building Technology
Ning Xu, Ming Li, Saiyin Fang, Changlin Huang, Chumin Chen, Yue Zhao, Feilong Mao, Tingting Deng, Yuan Wang
Summary: The intrinsic frequency of wood is investigated using frequency sweeping and pencil-lead break (PLB) tests to detect hole defects. The study examines the influence of hole diameter and number on the natural frequency of wood, and proposes effective measures for non-destructive detection of holes. The results show that holes affect the propagation of AE signals and the energy decay rate increases with larger hole diameters and numbers.
CONSTRUCTION AND BUILDING MATERIALS
(2023)
Article
Acoustics
Noura Sleiman, Loic Hallez, Rachel Pflieger, Sergey Nikitenko, Jean-Yves Hihn
Summary: The use of sweeping mode with a 3.6 MHz High Intensity Focused Ultrasound (HIFU) enables control of cavitation activity. This study reports the enhancement of cavitation activity under negative sweep and the detection of molecular emissions at high frequency for the first time. The intensity of cavitation noise spectra follows the behavior of acoustic broadband noise, indicating the same attenuation or intensification of cavitational activity under positive or negative scan. The intensification of SL and SCL was found to be related to the number of cavitation bubbles rather than a change in plasma nature inside the bubbles.
ULTRASONICS SONOCHEMISTRY
(2022)
Article
Astronomy & Astrophysics
Moritz Huebner, Daniela Huppenkothen, Paul D. Lasky, Andrew R. Inglis, Christopher Ick, David W. Hogg
Summary: Analyses of quasi-periodic oscillations (QPOs), including both frequency-domain and time-domain methods, are important for understanding the dynamic behavior of astrophysical objects during transient events. Gaussian process (GP) regression in the time domain is demonstrated as an effective alternative method to analyze QPOs, considering the heteroscedasticity and nonstationarity in data. By modeling QPOs as a stochastic process using GP and performing Bayesian inference, we can infer the hyperparameters of GP and give them physical meanings such as the QPO frequency. Furthermore, model selection can reliably identify QPOs among alternative models such as red noise. This method shows its applicability to various astrophysical data sets including gamma-ray bursts, magnetar flares, magnetar giant flares, and simulated solar flare data.
ASTROPHYSICAL JOURNAL
(2022)
Article
Chemistry, Multidisciplinary
Kyohei Yamagata, Matsuhiro Maeda, Zeno Tessari, Kunal S. Mali, Yoshito Tobe, Steven De Feyter, Kazukuni Tahara
Summary: Grain boundaries in polycrystals significantly affect material properties, leading to research on grain boundary engineering. Using scanning tunneling microscopy, the authors observed quasi-periodic nanoscale chirality switching and twinning in self-assembled molecular networks at the liquid/solid interface. The width of the chiral domain structure peaked at 12-19 nm, and adjacent domains were connected through interdigitated alkoxy chains, forming a defect-free domain border.
Article
Multidisciplinary Sciences
Yuankun Kou, Xin Cheng, Yulei Wang, Sijie Yu, Bin Chen, Eduard P. Kontar, Mingde Ding
Summary: Microwave quasi-periodic pulsations (QPPs) have been detected during solar flares, and they may be related to quasi-periodic magnetic reconnection and modulation of magnetic islands.
NATURE COMMUNICATIONS
(2022)
Article
Materials Science, Multidisciplinary
P. Karataev, G. Naumenko, A. Potylitsyn, M. Shevelev, K. Artyomov
Summary: The resonance Cherenkov diffraction radiation mechanism observed in this study is a promising technique for generating and monochromatizing THz and sub-THz radiation beams, with potential integration into short bunch linear accelerator facilities, offering new opportunities for user communities.
RESULTS IN PHYSICS
(2022)
Article
Engineering, Electrical & Electronic
Kaile Wang, Zengrun Wen, Ping Wang
Summary: A single-frequency self-sweeping fiber laser capable of both reverse and normal sweeping was constructed and realized in this study. Sweeping direction can be converted by using different lengths of fiber saturable absorber (FSA). The maximum sweeping ranges for normal and reverse sweeping are 5.072 and 3.457 nm, respectively, based on a unidirectional ring cavity. The study also analyzed the optical spectra, pulse dynamics, and longitudinal-mode feature of the fiber laser, revealing a phenomenon in which the frequency change interval is twice the spacing of the longitudinal-mode. Furthermore, the reflected spectra of FSA at different lengths and wavelengths were calculated to explain the sweeping direction and longitudinal-mode features.
JOURNAL OF LIGHTWAVE TECHNOLOGY
(2023)
Article
Engineering, Electrical & Electronic
Diego Luis Gonzalez, Lorenzo Grassi, Alberto U. G. Maurizi
Summary: This article presents a new nonlinear circuit called Quasi-Periodic Locked Loop (Q-PLL) which has the capability to lock onto a specific frequency even with different types of perturbations. The circuit is inspired by the pitch perception of complex sound in humans and has potential applications in medicine, robotics, and industrial and consumer electronics.
IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS I-REGULAR PAPERS
(2022)
Article
Astronomy & Astrophysics
Dmitrii Y. Kolotkov, Valery M. Nakariakov, Robin Holt, Alexey A. Kuznetsov
Summary: This study presents the first simultaneous detection of quasi-periodic pulsations in a superflare on a cool star, using soft X-rays and white light. The observed QPPs have periods that correlate well between the two wavelengths, indicating a unique relationship and providing insights into the dynamics of nonthermal electrons and thermal plasma in the flare loop.
ASTROPHYSICAL JOURNAL LETTERS
(2021)
Article
Nanoscience & Nanotechnology
B. S. Bhaskar, H. Koivisto, O. Tarvainen, T. Thuillier, V. Toivanen
Summary: This study presents the experimental investigation of quasi-periodical kinetic instabilities in magnetically confined electron cyclotron resonance heated plasmas. The instabilities are characterized by fast sequences of periodic plasma losses with approximately 100 μs intervals between bursts, followed by quiescent periods of 1-10 ms before the next event. Increasing the plasma energy content, particularly the magnetic field strength, enhances the chaos of the instabilities in the time domain. Statistical analysis shows that the energy released in an instability event is dependent on the magnetic field strength and microwave power, but not on the neutral gas pressure. The correlation between the energy dissipated in an instability event and the recovery time of the periodic bursts is also observed.
Article
Astronomy & Astrophysics
Brendan P. Clarke, Laura A. Hayes, Peter T. Gallagher, Shane A. Maloney, Eoin P. Carley
Summary: A common feature of solar flares is the presence of intensity pulsations known as quasi-periodic pulsations (QPPs), which exhibit periodic components and characteristic timescales. Through wavelet analysis, QPPs have been identified in X-ray, low-frequency radio, and extreme ultraviolet (EUV) wavelengths, suggesting a common progenitor for these fluctuations. Imaging analysis indicates that the pulsations originate from a hard X-ray footpoint linked to nearby open magnetic field lines, likely due to intermittent particle acceleration from bursty magnetic reconnection.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Zhenyan Fei, Ming Lyu, Mariano Mendez, D. Altamirano, Guobao Zhang, G. C. Mancuso, Fu-Yuan Xiang, X. J. Yang
Summary: The study on the harmonics of the millihertz quasi-periodic oscillations (mHz QPOs) in the neutron star low-mass X-ray binary 4U 1636-53 found that the ratio between the rms amplitude of the harmonic and that of the fundamental remains constant in a wide range of the fundamental frequency. Additionally, it was observed that the rms amplitude of both the harmonic and the fundamental decreases as the energy increases in the 2-5 keV range. Moreover, not all observations with mHz QPOs exhibit the harmonic component, although the reason for this remains unclear.
ASTROPHYSICAL JOURNAL
(2021)
Article
Multidisciplinary Sciences
Pengfu Tian, Ping Zhang, Wei Wang, Pei Wang, Xiaohui Sun, Jifeng Liu, Bing Zhang, Zigao Dai, Feng Yuan, Shuangnan Zhang, Qingzhong Liu, Peng Jiang, Xuefeng Wu, Zheng Zheng, Jiashi Chen, Di Li, Zonghong Zhu, Zhichen Pan, Hengqian Gan, Xiao Chen, Na Sai
Summary: GRS 1915 + 105 is a fast-spinning black-hole X-ray binary with a relativistic jet. It has shown persistent activity and periodic oscillations in the radio and X-ray bands, including transient periodic oscillation features with a frequency of approximately 5 Hz.
Article
Optics
Weizhao Cheng, Weijie Liu, Quancheng Liu, Feng Chen
Summary: In this study, the experimental observation of the topological Anderson phase in one-dimensional quasi-periodical waveguide arrays produced by femtosecond laser writing is reported. The researchers dynamically tuned the interdimer hopping amplitudes of the waveguide array to generate the quasi-periodic disorder of the coupling constants for the model. The experimental results are consistent with theoretical simulations, confirming the existence of the disorder-driven topological phase in the photonic lattice.
Article
Multidisciplinary Sciences
Teng Xiao, Dizhou Xie, Zhaoli Dong, Tao Chen, Wei Yi, Bo Yan
Summary: Experimental investigation reveals that in a critically localized regime, the topological properties of a quantum system are identified, with eigenstates that are neither fully extended nor completely localized.
Article
Physics, Fluids & Plasmas
I. Izotov, A. G. Shalashov, V. A. Skalyga, E. D. Gospodchikov, O. Tarvainen, V. E. Mironov, H. Koivisto, R. Kronholm, V Toivanen, B. Bhaskar
Summary: Experiments on a minimum-B electron cyclotron resonance ion source revealed the presence of a hump in the energy distribution of escaped electrons at 150-300 keV, which is independent of microwave power but increases with magnetic field strength. The hump formation is likely related to radio-frequency-induced momentum space diffusion, confirmed when microwave power is applied.
PLASMA PHYSICS AND CONTROLLED FUSION
(2021)
Article
Physics, Applied
V. Yu Goryainov, M. E. Viktorov, A. V. Vodop'yanov, A. V. Voronin
Summary: The investigation analyzed the structure of a plasma jet generated by a coaxial plasma accelerator, showing that the radiation intensity oscillates with characteristic frequencies for argon and deuterium. The behavior of the discharge in the accelerator revealed the initiation of a diffuse discharge at the base of the conical insert, eventually contracting and occurring between central and external electrodes. The results can be applied to gas ionization, material irradiation, and simulation of plasma flows interacting with magnetic fields in outer space.
Article
Physics, Fluids & Plasmas
Mikhail Viktorov, Alexander Chernyshov, Dmitry Chugunin, Mikhail Mogilevsky
Summary: Electromagnetic emissions above the electron gyrofrequency in mirror-confined electron cyclotron resonance plasma are reported and interpreted as the excitation of the fast extraordinary wave at the fundamental harmonic of the electron gyrofrequency, similar to Earth's auroral kilometric radiation. A method for studying the temporal characteristics of physical processes in the auroral electron acceleration region is proposed and applied to both satellite measurements and laboratory plasma emissions, revealing similarities in cyclotron instability development.
PLASMA PHYSICS AND CONTROLLED FUSION
(2021)
Article
Instruments & Instrumentation
A. G. Shalashov, E. D. Gospodchikov, T. A. Khusainov, L. V. Lubyako, A. L. Solomakhin, M. E. Viktorov
Summary: This paper describes the hardware developed for the CTS diagnostic for the GDT magnetic trap, which is used in fusion research and reconstructs fast ion distributions driven by high-power neutral beam injection. The diagnostic uses a 400 kW/54.5 GHz gyrotron as a source of probe radiation and employs large-aperture quasi-optical mirror systems for beam formation and scattered microwave radiation collection.
JOURNAL OF INSTRUMENTATION
(2021)
Article
Physics, Fluids & Plasmas
A. G. Shalashov, E. D. Gospodchikov
Summary: The study investigates how ECR plasma heating at a frequency exceeding the minimum electron cyclotron frequency affects the heating effect. It is found that under certain conditions, it may result in the formation of 'butterfly-like' distribution functions of fast electrons.
PLASMA PHYSICS AND CONTROLLED FUSION
(2021)
Article
Physics, Fluids & Plasmas
E. D. Gospodchikov, T. A. Khusainov, A. G. Shalashov
Summary: A method is proposed for tomography of the distribution function of energetic ions using collective Thomson scattering diagnostic data. Measurements of scattering spectra from successive plasma cross sections corresponding to different magnetic-field strengths allow for the restoration of the ion distribution function in velocity space. The problem is reduced to an integral equation of the first kind, which can be solved analytically through various exact and approximate methods.
PLASMA PHYSICS REPORTS
(2021)
Article
Engineering, Electrical & Electronic
Vladimir V. Parshin, Evgeny A. Serov, Alexander V. Vodopyanov, Dmitry A. Mansfeld
Summary: A method for measuring dielectric parameters of powder materials, specifically the refractive index and tan delta values, has been developed based on a high quality Fabry-Perot resonator. Results of measuring metal oxide powders in a specific frequency and temperature range are presented, with the method aimed at understanding powder processes under radiation influence.
IEEE TRANSACTIONS ON TERAHERTZ SCIENCE AND TECHNOLOGY
(2021)
Article
Engineering, Electrical & Electronic
L. Lubyako, A. G. Shalashov, A. F. Andriyanov, V. G. Bozhkov, E. D. Gospodchikov, D. S. Dorozhkina
Summary: The set of receiving equipment designed for experiments on the detection of Thomson collective scattering spectra of high-power millimeter-wave radiation in a large-scale open magnetic trap consists of two identical radiometers/spectrum analyzers. Each analyzer has an analysis band of 54.47 +/- 0.55 GHz and a sensitivity of no less than 0.080-0.025 eV, allowing for simultaneous measurements in two independent channels corresponding to different reception angles of the scattered radiation.
RADIOPHYSICS AND QUANTUM ELECTRONICS
(2021)
Article
Physics, Fluids & Plasmas
E. D. Gospodchikov, T. A. Khusainov, A. G. Shalashov
Summary: The electrodynamic reciprocity theorem is employed to study the scattering of finite-aperture microwave beams on density fluctuations in inhomogeneous magnetized plasma. The main result of this study is the representation of the spectral power density of scattered radiation detected by an antenna as a convolution of Wigner functions characterizing arbitrary spatially inhomogeneous distributions of the probe field and the field of the receiving antenna with the spectrum of the autocorrelation function of fluctuations of plasma density. The effects of wave field and medium inhomogeneity are analyzed in different limiting cases. The effective broadening of the scattering spectrum due to inhomogeneity in the planned experiment on collective scattering in the GDT setup is calculated as an example.
PLASMA PHYSICS REPORTS
(2022)
Article
Instruments & Instrumentation
V. A. Skalyga, I. V. Izotov, S. V. Golubev, S. V. Razin, A. V. Sidorov, M. E. Viktorov
Summary: The gasdynamic electron cyclotron resonance (ECR) ion source is a device that achieves ionization efficiency through high plasma density. It provides high-current and high-quality ion beams, making it suitable for applications such as high-current proton injectors. This paper discusses the physical aspects, diagnostic techniques, and future prospects of the gasdynamic ECR plasma.
REVIEW OF SCIENTIFIC INSTRUMENTS
(2022)
Article
Physics, Fluids & Plasmas
A. G. Shalashov, E. D. Gospodchikov, T. A. Khusainov, L. V. Lubyako, A. L. Solomakhin, D. V. Yakovlev
Summary: A fast-ion diagnostic method based on collective Thomson scattering of high-power gyrotron radiation has been developed at the gasdynamic trap facility in Budker Institute. This diagnostic aims to reconstruct the ion distributions over transverse and longitudinal velocities driven by strong neutral beam injection in the plasma core. The first experimental results show that the detected spectra, with an effective noise temperature of about 100 eV, are compatible with early theoretical predictions and can be interpreted as the expected scattering signal from fast ions.
PHYSICS OF PLASMAS
(2022)
Article
Physics, Fluids & Plasmas
A. G. Shalashov, E. D. Gospodchikov, T. A. Khusainov, A. L. Solomakhin, D. Yakovlev, P. A. Bagryansky
Summary: In the experiments conducted at the GDT facility, two different scenarios of plasma discharges were realized by combining ECRH and NBI plasma heating. The first scenario showed a broad distribution of absorbed ECRH power and a stable plasma with improved energy confinement, while the second scenario exhibited a highly peaked electron temperature profile but was susceptible to low-frequency instabilities.
Article
Physics, Fluids & Plasmas
A. G. Shalashov, E. D. Gospodchikov
Summary: In this paper, the structure of radiation from the evanescent layer in inhomogeneous gyrotropic plasma is analyzed for an incident beam with a finite aperture. It is found that the reflected beam has wave distributions with a non-zero angular momentum due to reflection. The helicity of the reflected beam leads to unusual effects in the plasma electrodynamics.
PHYSICS OF PLASMAS
(2023)
Article
Physics, Fluids & Plasmas
A. G. Shalashov, E. D. Gospodchikov, T. A. Khusainov
Summary: In this study, a quasi-optical wave code was combined with a simplified transport model to simulate the time evolution of electron temperature profile during ECR heating. By applying this hybrid code, the bifurcation of narrow and broad microwave heating regimes was successfully simulated and verified in experiments.
PLASMA PHYSICS REPORTS
(2022)
Article
Physics, Multidisciplinary
I. S. Abramov, E. D. Gospodchikov, A. G. Shalashov
Summary: The study demonstrates the possibility of efficiently emitting light in a wavelength range of 11.2 nm +/- 1% by sustaining a discharge in xenon using a subnanosecond terahertz radiation pulse from a modern free-electron laser. This method can achieve a high-intensity extreme ultraviolet radiation with an average power of 35 W, showing potential for applications in experiments using modern free-electron lasers.
JOURNAL OF EXPERIMENTAL AND THEORETICAL PHYSICS
(2021)