Current Issue : January-March Volume : 2024 Issue Number : 1 Articles : 5 Articles
The laser interference patterning of a silicon surface via UV femtosecond pulse irradiation, resulting in 350 nm periodic structures, is demonstrated. The structuring process was performed using a laser with a 450 fs pulse duration at a wavelength of 248 nm in combination with a mask projection setup. Depending on the laser fluence, single-pulse irradiation leads to amorphization, structure formation via lateral melt flow or the formation of voids via peculiar melt coalescence. Through multipulse irradiation, combined patterns of interference structures and laser-induced periodic surface structures (LIPSS) are observed....
The unprecedented sensitivity provided by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) could shed light on studies of the magnetic field and plasma properties of brown dwarfs by catching polarized radio flares. With the FAST L-band 19-beam receiver, we observe a nearby dwarf stellar system 2MASSW J0746425 + 200032 which has been reported to show 4.86 GHz and 8.46 GHz radio flare emission. The L-band radio signals from the target are searched in both total intensity and circular polarization during the entire 147 min tracking observation. No radio flare down to a sensitivity of ∼13 mJy and ∼2 mJy (5σ) in Stokes I and V can be identified. The non-detection may lie in the intrinsic physical condition of the stellar system, e.g., the magnetic field strength and the electron density distribution and/or the sampling rate, which should be higher to reveal the sub-second structures but are smeared out with a lower rate in our observations....
We measured spectra of low energy electrons emitted in the interaction of singly charged Ne+ ions with the Mg surface at incident ion energies ranging from 50 eV to 4 keV. The study examines issues related to the excitation of both the surface and the bulk plasmons of the target. We will also focus on the dynamics of the production of the singlet Ne2p4(1D)3s2 and triplet Ne2p4(3P)3s2 autoionizing states of projectiles scattered in a vacuum. The threshold behavior of the autoionization lines show that double excitation occurs simultaneously in a single scattering. The predominant excitation of the triplet state indicates the importance of charge rearrangement and the electron correlation effects during the collisional excitation....
Science is losing some fixed references shifting from universality to relativity: time and space become space time, the meter is related to the velocity of light and the second is fixed by the ticketing of a Cesium atom. In the case of Gravity, Nature was so friendly to Newton to allow him the writing of the Universal Gravitational Law, that changed the view of the Universe for the last three centuries. However, the way matter generates Gravity was unknown to Newton and the problem is still nowadays ignored by most scientists and remains the ultimate question mark of physics. We paid attention to the ticketing of all existing nuclides and found that the parameters of the neutronproton transformations are so precise, in describing these reactions, that can be considered universal constants. Instead, the emitted neutrino flux Fo is almost constant with a mean value of 6.668E20 neutrino per gram and second over the wide range of all nuclides with some deviation for lighter nuclei. This is the reason why Newton was able to find his Universal Gravitational Law and allows us today to state a relation of this flux with the Gauss constant G on the basis of nuclear properties. Moreover, it explains the mechanism that bodies use for their mutual attraction with a simplification of the three-body problem in celestial bodies computation. We have to remember that Newton model, with a fixed gravitational Gauss constant G, or the equivalent with a fixed neutrino flux Fo , have been used for the determination of the mass of the celestial bodies in motion with the implicit assumption that the gravitational and inertial mass are the same. In this paper we recognize the big difference in composition of the Sun and the gaseous planets compared to the terrestrial ones and show how the relatively small difference of the neutrino flux can change our vision of the Universe....
Wind turbines (WT) are a popular method used in energy production, but blade failure and maintenance costs pose significant challenges for the industry. Early detection of blade defects is vital to prevent collapse. This paper examines the modulation of blade vibrations via low-frequency blade rotation, mirroring the vibro-acoustic modulation (VAM) method. Specifically, we study the modulation of blade vibrations, which are generated via blade interactions with air turbulence and have a wide frequency range. These vibrations are modulated by the alternating bending stress experienced during blade rotation. For the simulation of VAM, we employ a simple breathing crack model, which considers a mechanical oscillator with parameters that are periodically changed in response to low-frequency blade rotation. The modulation of the wideband signal by blade rotation can be extracted using the detection of envelope modulation on noise (DEMON) algorithm. This model was applied for the estimation of the modulation of a large (52-m-long) WT blade. Steel specimens have been used in laboratory experiments to demonstrate the feasibility of VAM using a probe broadband noise signal. This paper presents the first work to experimentally and theoretically apply wideband signals in VAM. It further explores the analysis of the use of natural vibrations within VAM for the SHM of WT blades....
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