2,527 research outputs found
Unidirectional Amplification and Shaping of Optical Pulses by Three-Wave Mixing with Negative Phonons
A possibility to greatly enhance frequency-conversion efficiency of
stimulated Raman scattering is shown by making use of extraordinary properties
of three-wave mixing of ordinary and backward waves. Such processes are
commonly attributed to negative-index plasmonic metamaterials. This work
demonstrates the possibility to replace such metamaterials that are very
challenging to engineer by readily available crystals which support elastic
waves with contra-directed phase and group velocities. The main goal of this
work is to investigate specific properties of indicated nonlinear optical
process in short pulse regime and to show that it enables elimination of
fundamental detrimental effect of fast damping of optical phonons on the
process concerned. Among the applications is the possibility of creation of a
family of unique photonic devices such as unidirectional Raman amplifiers and
femtosecond pulse shapers with greatly improved operational properties.Comment: 6 pages, 4 figures. arXiv admin note: text overlap with
arXiv:1304.681
Individual addressing of ion qubits with counter-propagating optical frequency combs
We propose a new method of individual single-qubit addressing of linear
trapped-ion chains utilizing two ultrastable femtosecond frequency combs. For
that, we suggest implementing the single-qubit gates with two
counter-propagating frequency combs overlapping on the target ion and causing
the AC Stark shift between the qubit levels. With analytical calculations and
numerical modeling, we show that the arbitrary single-qubit rotations can be
indeed realized using only laser fields propagating along the ion chain. We
analyze the error sources for the proposed addressing method and prove that it
allows implementing the single-qubit gates with high fidelity
Structure, Properties, and Phase Transformations of Water Nanoconfined between Brucite-like Layers: The Role of Wall Surface Polarity
The interaction of water with confining surfaces is primarily governed by the wetting properties of the wall materialβin particular, whether it is hydrophobic or hydrophilic. The hydrophobicity or hydrophilicity itself is determined primarily by the atomic structure and polarity of the surface groups. In the present work, we used molecular dynamics to study the structure and properties of nanoscale water layers confined between layered metal hydroxide surfaces with a brucite-like structure. The influence of the surface polarity of the confining material on the properties of nanoconfined water was studied in the pressure range of 0.1β10 GPa. This pressure range is relevant for many geodynamic phenomena, hydrocarbon recovery, contact spots of tribological systems, and heterogeneous materials under extreme mechanical loading. Two phase transitions were identified in water confined within 2 nm wide slit-shaped nanopores: (1) at p1 = 3.3β3.4 GPa, the liquid transforms to a solid phase with a hexagonal close-packed (HCP) crystal structure, and (2) at p2 = 6.7β7.1 GPa, a further transformation to face-centered cubic (FCC) crystals occurs. It was found that the behavior of the confined water radically changes when the partial charges (and, therefore, the surface polarity) are reduced. In this case, water transforms directly from the liquid phase to an FCC-like phase at 3.2β3.3 GPa. Numerical simulations enabled determination of the amount of hydrogen bonding and diffusivity of nanoconfined water, as well as the relationship between pressure and volumetric strain
New data on the granite pedestal of the monument to Peter the Great βThe Bronze Horsemanβ in Saint Petersburg
In order to expand and popularize knowledge about the stone decoration of Saint Petersburg, we present new data on the mineralogy and petrography of the famous Thunder-Stone, the parts of which were the basis for the monument to Peter the Great β the legendary βBronze Horsemanβ. In the course of studying geological documentation of the monument's granite base, we examined the mineral composition and internal structure of granite, as well as the fragments of a pegmatite vein and veinlets found in it. 25 single-mineral samples were collected from the available micro-scaled shear fractures within the pedestal surface and studied by electron microscopy, electron probe and X-ray phase analysis. It was established that K-Na feldspar in the granite composition was represented by microcline, whereas micas were represented by annite-siderophyllite and muscovite.Β Accessory minerals included monazite, xenotime, thorite, zircon, rutile, apatite, fluorite, Ti-, Nb-, Ta-bearing minerals, uranium phosphates. The presence of topaz is characteristic of pegmatites. The revealed structural and textural features of four granite boulders in the monument pedestal, as well as mineralogical and chemical composition of their rock-forming and accessory minerals, showed the similarity of this rock to Precambrian biotite-muscovite granites and topaz-containing pegmatites (stockscheiders) of the late formation phase of the Vyborg rapakivi granite massif. The research results are considered as the basis for further geological and mineralogical study of the Thunder-Stone origin and determining the place of its separation from the primary source
Coupled Pendulums System Under Control by Vertical Oscillations
Π ΡΡΠ°ΡΡΠ΅ ΡΠ°ΡΡΠΌΠ°ΡΡΠΈΠ²Π°Π΅ΡΡΡ ΠΌΠ°ΡΠ΅ΠΌΠ°ΡΠΈΡΠ΅ΡΠΊΠ°Ρ ΠΌΠΎΠ΄Π΅Π»Ρ ΡΠΈΡΡΠ΅ΠΌΡ, ΡΠΎΡΡΠΎΡΡΠ΅ΠΉ ΠΈΠ· Π΄Π²ΡΡ
ΠΎΠ±ΡΠ°ΡΠ½ΡΡ
ΠΌΠ°ΡΡΠ½ΠΈΠΊΠΎΠ² Ρ ΡΠΏΡΡΠ³ΠΎΠΉ ΡΠ²ΡΠ·ΡΡ (ΠΏΡΡΠΆΠΈΠ½ΠΎΠΉ). Π‘ΠΈΡΡΠ΅ΠΌΠ° ΡΠΏΡΠ°Π²Π»ΡΠ΅ΡΡΡ ΠΏΡΠΎΠ³ΡΠ°ΠΌΠΌΠ½ΠΎ, ΠΏΠΎΡΡΠ΅Π΄ΡΡΠ²ΠΎΠΌ
Π²Π΅ΡΡΠΈΠΊΠ°Π»ΡΠ½ΡΡ
ΠΎΡΡΠΈΠ»Π»ΡΡΠΈΠΉ ΡΠΎΡΠΊΠΈ ΠΊΡΠ΅ΠΏΠ»Π΅Π½ΠΈΡ ΠΎΠ΄Π½ΠΎΠ³ΠΎ ΠΈΠ· ΠΌΠ°ΡΡΠ½ΠΈΠΊΠΎΠ². ΠΡΠΎΠ²Π΅Π΄Π΅Π½ΠΎ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠ΅
Π΄ΠΈΠ½Π°ΠΌΠΈΠΊΠΈ ΡΠΊΠ°Π·Π°Π½Π½ΠΎΠΉ ΠΌΠ΅Ρ
Π°Π½ΠΈΡΠ΅ΡΠΊΠΎΠΉ ΡΠΈΡΡΠ΅ΠΌΡ, ΡΡΠΎΡΠΌΡΠ»ΠΈΡΠΎΠ²Π°Π½Ρ ΡΡΠ»ΠΎΠ²ΠΈΡ, ΠΎΠ±Π΅ΡΠΏΠ΅ΡΠΈΠ²Π°ΡΡΠΈΠ΅
Π΅Π΅ ΡΡΠ°Π±ΠΈΠ»ΠΈΠ·Π°ΡΠΈΡ. ΠΠΎΡΡΡΠΎΠ΅Π½Ρ Π·ΠΎΠ½Ρ ΡΡΡΠΎΠΉΡΠΈΠ²ΠΎΡΡΠΈ Π² ΠΏΡΠΎΡΡΡΠ°Π½ΡΡΠ²Π΅ ΠΈΡΡ
ΠΎΠ΄Π½ΡΡ
ΠΏΠ°ΡΠ°ΠΌΠ΅ΡΡΠΎΠ².
ΠΡΠ΅Π΄ΡΡΠ°Π²Π»Π΅Π½Π° ΡΠ²ΠΎΠ»ΡΡΠΈΡ Π·ΠΎΠ½ ΡΡΡΠΎΠΉΡΠΈΠ²ΠΎΡΡΠΈ Π² Π·Π°Π²ΠΈΡΠΈΠΌΠΎΡΡΠΈ ΠΎΡ Π·Π½Π°ΡΠ΅Π½ΠΈΠΉ ΠΆΠ΅ΡΡΠΊΠΎΡΡΠΈ ΠΏΡΡΠΆΠΈΠ½Ρ. Π
ΡΠ°Π±ΠΎΡΠ΅ ΡΠ°ΠΊΠΆΠ΅ ΠΏΡΠΈΠ²Π΅Π΄Π΅Π½Ρ ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΡ ΡΠΈΡΠ»Π΅Π½Π½ΡΡ
ΡΠΊΡΠΏΠ΅ΡΠΈΠΌΠ΅Π½ΡΠΎΠ², ΠΈΠ»Π»ΡΡΡΡΠΈΡΡΡΡΠΈΡ
Π΄ΠΈΠ½Π°ΠΌΠΈΠΊΡ
ΡΠΈΡΡΠ΅ΠΌΡIn this paper we propose a mathematical model consisting of two inverse pendulums with an elastic
coupling (by spring). We propose a dynamic programmed control of the model motion, implemented
through vertical oscillations of the common pendulums pivot point. We investigate dynamics of this
mechanical system, and formulated a condition for identifying stability of the system. We constructed
stability zones in the spaces of the original and dimensionless parameters. Also, we obtain evolution of
stability zones depending on spring stiffness values. In conclusion, we presented results of numerical
software experiments for various system configuration
Electron Beam-Assisted Synthesis of YAG:Ce Ceramics
The work was carried out within the framework of the grant AP14870696 of the Ministry of Education and Science of the Republic of Kazakhstan. This research was funded by the Russian Science Foundation of the Russian Federation. (Grant No. 23-73-00108). A.I.P is also thankful for financial support from Latvian Project LZP-2018/1-0214. In addition, A.I.P. is thanking the Institute of Solid State Physics, University of Latvia (ISSP UL). ISSP UL as the Centre of Excellence has received funding from the European Unionβs Horizon 2020 Framework Programme H2020-WIDESPREAD01-2016-2017-Teaming Phase2 under grant agreement No. 739508, project CAMART2.In this work, we present the results of the structure and luminescence properties of YAG:Ce (Y3Al5O12 doped with Ce3+ ions) ceramic samples. Their synthesis was carried out by sintering samples from the initial oxide powders under the powerful action of a high-energy electron beam with an energy of 1.4 MeV and a power density of 22β25 kW/cm2. The measured diffraction patterns of the synthesized ceramics are in good agreement with the standard for YAG. Luminescence characteristics at stationary/time-resolved regimes were studied. It is shown that under the influence of a high-power electron beam on a mixture of powders, it is possible to synthesize YAG:Ce luminescent ceramics with characteristics close to the well-known YAG:Ce phosphor ceramics obtained by traditional methods of solid-state synthesis. Thus, it has been demonstrated that the technology of radiation synthesis of luminescent ceramics is very promising. Β© 2023 by the authors. --//-- Karipbayev Z.T., Lisitsyn V.M., Golkovski M.G., Zhilgildinov Z.S., Popov A.I., Zhunusbekov A.M., Polisadova E., Tulegenova A., Mussakhanov D.A., Alpyssova G., Piskunov S.; Electron Beam-Assisted Synthesis of YAG:Ce Ceramics; (2023) Materials, 16 (11), art. no. 4102; DOI: 10.3390/ma16114102; https://www.scopus.com/inward/record.uri?eid=2-s2.0-85161490971&doi=10.3390%2fma16114102&partnerID=40&md5=e33da4c2d44c563881bdeffe410d734b published under the CC BY 4.0 licence.Grant AP14870696 of the Ministry of Education and Science of the Republic of Kazakhstan; Russian Science Foundation of the Russian Federation Grant No. 23-73-00108; the Latvian Council of Science LZP-2018/1-0214; ISSP UL as the Centre of Excellence has received funding from the European Unionβs Horizon 2020 Framework Programme H2020-WIDESPREAD01-2016-2017-Teaming Phase2 under grant agreement No. 739508, project CAMART2
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