The positioning accuracy of spacecraft in orbit is easily affected by low-frequency micro-vibrations of the environment and internal disturbances caused by the payload. Inspired by the neck structure of birds, this study devised a piezo-driven active vibration isolation unit with high stiffness. First, a dynamic model and two-sensor feedback control method for the isolation unit were developed, and the isolation mechanism and anti-disturbance characteristics were analyzed. Further, the stability of the closed-loop was verified. Simulation models of serial and parallel systems based on the proposed vibration isolation unit were implemented to demonstrate its feasibility. The results indicate that the proposed isolation units can provide excellent low-frequency vibration isolation performance and inertial stability and that they can effectively resist the internal disturbance of the payload. Moreover, its performance can be further improved via serial or parallel reconfiguration that facilitates its adaptation to the varied isolation requirements of spacecraft.
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http://dx.doi.org/10.3390/biomimetics9010029 | DOI Listing |
PLoS One
January 2025
Department of Electrical and Electronic Engineering, Pabna University of Science and Technology, Pabna, Bangladesh.
Waterborne bacteria pose a serious hazard to human health, hence a precise detection method is required to identify them. A photonic crystal fiber sensor that takes into account the dangers of aquatic bacteria has been suggested, and its optical characteristics in the THz range have been quantitatively assessed. The PCF sensor was designed and examined as computed in Comsol Multiphysics, a program in which uses the method of "Finite Element Method" (FEM).
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January 2025
Southern Methodist University, Chemistry, 3251 Daniel Ave, 75275, Dallas, UNITED STATES.
We analyzed the intrinsic strength of distal and proximal FeN bonds and the stiffness of the axial NFeN bond angle in a series of cytochrome b5 proteins isolated from various species, including bacteria, animals, and humans. Ferric and ferrous oxidation states were considered. As assess- ment tool, we employed local vibrational stretching force constants ka(FeN) and bending force constants ka(NFeN) derived from our local mode theory.
View Article and Find Full Text PDFPolymers (Basel)
January 2025
Department of Mechanical Engineering, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia.
Metamaterials are pushing the limits of traditional materials and are fascinating frontiers in scientific innovation. Mechanical metamaterials (MMs) are a category of metamaterials that display properties and performances that cannot be realized in conventional materials. Exploring the mechanical properties and various aspects of vibration and damping control is becoming a crucial research area.
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January 2025
Institute of Environmental Sciences, Hungarian University of Agriculture and Life Sciences, Páter Károly u. 1, H-2100 Gödöllő, Hungary.
This study attempted to isolate and identify pedospheric microbes originating in dumpsites and utilized them for the degradation of selected synthetic polymers for the first time in a cost-effective, ecologically favorable and sustainable manner. Specifically, low-density polyethylene (LDPE) and polyurethane (PUR) were converted by the isolated fungi, i.e.
View Article and Find Full Text PDFMolecules
January 2025
Instituto Andaluz de Ciencias de la Tierra (IACT-CSIC), Consejo Superior de Investigaciones Científicas, Av. de las Palmeras 4, 18100 Armilla, Granada, Spain.
Many properties of 2,4-dichlorophenoxyacetic acid (2,4-D) depend on its molecular environment, such as whether it is an isolated molecule, a dimer, or in a crystalline state. The molecular geometry, conformational analysis, and vibrational spectrum of 2,4-D were theoretically calculated using Density Functional Theory (DFT) methods. A new slightly more stable conformer was found, which is different to those previously reported.
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