86 research outputs found
Forecasting the condition of petroleum impregnated load bearing concrete and reinforced concrete structures
Petroleum products (PP) used in industrial processes systematically fall on the load-bearing CRC structures and gradually impregnate therein. Currently, available guidelines for the assessment of technical condition and reliability of load-bearing CRC structures do not fully take into account the effect of viscosity of PP that impregnated therein. Our study was performed on the basis of analyzing, generalizing and evaluations of experimental data on the effect of PP of different viscosities on the physical and mechanical properties (PMP) of concrete using the methods of probability theory and mathematical statistics. The obtained results allow to constitute a scientifically substantiated forecast of changes in PMP of PP impregnated load-bearing CRC structures and to provide a quantitative characterization of their technical condition.Keywords: viscosity, strain, endurance, fatigue
Технология капитального ремонта инженерных силосных сооружений
Introducing results of research and improved technology of overhaul of reinforced concrete silos through the erection of reinforced concrete sleeve in the sliding form with concrete heated by infrared radiation.Представлены результаты исследования и совершенствования технологии капитального ремонта железобетонных силосов посредством возведения железобетонной гильзы в скользящей опалубке с обогревом бетона инфракрасным излучением
Zero-bias photodetection in 2d materials via geometric design of contacts
Structural or crystal asymmetry are necessary conditions for emergence of
zero-bias photocurrent in light detectors. Structural asymmetry has been
typically achieved via doping being a technologically complex process.
Here, we propose an alternative approach to achieve zero-bias photocurrent in
2d material flakes exploiting the geometrical non-equivalence of source and
drain contacts. As a prototypical example, we equip a square-shaped flake of
PdSe with mutually orthogonal metal leads. Upon uniform illumination with
linearly-polarized light, the device demonstrates non-zero photocurrent which
flips its sign upon 90 polarization rotation. The origin of zero-bias
photocurrent lies in polarization-dependent lightning-rod effect. It enhances
the electromagnetic field at one contact from the orthogonal pair, and
selectively activates the internal photoeffect at the respective metal-PdSe
Schottky junction. The proposed technology of contact engineering can be
extended to arbitrary 2d materials and detection of both polarized and natural
light
Cyclotron resonance overtones and near-field magnetoabsorption via terahertz Bernstein modes in graphene
Two-dimensional electron systems subjected to a perpendicular magnetic field
absorb electromagnetic radiation via the cyclotron resonance (CR). Here we
report a qualitative breach of this well-known behaviour in graphene. Our study
of the terahertz photoresponse reveals a resonant burst at the main overtone of
the CR, drastically exceeding the signal detected at the position of the
ordinary CR. In accordance with the developed theory, the photoresponse
dependencies on the magnetic field, doping level, and sample geometry suggest
that the origin of this anomaly lies in the near-field magnetoabsorption
facilitated by the Bernstein modes, ultra-slow magnetoplasmonic excitations
reshaped by nonlocal electron dynamics. Close to the CR harmonics, these modes
are characterized by a flat dispersion and a diverging plasmonic density of
states that strongly amplifies the radiation absorption. Besides fundamental
interest, our experimental results and developed theory show that the radiation
absorption via nonlocal collective modes can facilitate a strong photoresponse,
a behaviour potentially useful for infrared and terahertz technology.Comment: 27 pages, 22 figure
Resonant Terahertz Detection Using Graphene Plasmons
Plasmons, collective oscillations of electron systems, can efficiently couple
light and electric current, and thus can be used to create sub-wavelength
photodetectors, radiation mixers, and on-chip spectrometers. Despite
considerable effort, it has proven challenging to implement plasmonic devices
operating at terahertz frequencies. The material capable to meet this challenge
is graphene as it supports long-lived electrically-tunable plasmons. Here we
demonstrate plasmon-assisted resonant detection of terahertz radiation by
antenna-coupled graphene transistors that act as both plasmonic Fabry-Perot
cavities and rectifying elements. By varying the plasmon velocity using gate
voltage, we tune our detectors between multiple resonant modes and exploit this
functionality to measure plasmon wavelength and lifetime in bilayer graphene as
well as to probe collective modes in its moir\'e minibands. Our devices offer a
convenient tool for further plasmonic research that is often exceedingly
difficult under non-ambient conditions (e.g. cryogenic temperatures and strong
magnetic fields) and promise a viable route for various photonic applications.Comment: 19 pages, 12 figure
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