9 research outputs found
Optimization of laser stabilization via self-injection locking to a whispering-gallery-mode microresonator: experimental study
Self-injection locking of a diode laser to a high-quality-factor
microresonator is widely used for frequency stabilization and linewidth
narrowing. We constructed several microresonator-based laser sources with
measured instantaneous linewidths of 1 Hz and used them for investigation and
implementation of the self-injection locking effect. We studied analytically
and experimentally the dependence of the stabilization coefficient on tunable
parameters such as locking phase and coupling rate. It was shown that precise
control of the locking phase allows fine tuning of the generated frequency from
the stabilized laser diode. We also showed that it is possible for such laser
sources to realize fast continuous and linear frequency modulation by injection
current tuning inside the self-injection locking regime. We conceptually
demonstrate coherent frequency-modulated continuous wave LIDAR over a distance
of 10 km using such a microresonator-stabilized laser diode in the
frequency-chirping regime and measure velocities as low as sub-micrometer per
second in the unmodulated case. These results could be of interest for
cutting-edge technology applications such as space debris monitoring and
long-range object classification, high resolution spectroscopy and others
Nonlinear Aeroelastic vibrations and galloping of iced conductor lines under wind.
peer reviewedgalloping model for one span single conductor dead ended
FIRE RESISTANCE OF REINFORCED CONCRETE AND STEEL STRUCTURES
The scientific bases of ensuring fire resistance of reinforced concrete and steel building structures in the conditions of modern extreme influences are laid.
The current state of fire safety of buildings and structures, as well as approaches, methods and tools for its assessment are analyzed. Analysis of emergencies and fires in the world has shown that the vast majority of them occur in buildings and structures. It is shown that the cause of catastrophic consequences and destruction is the non-compliance of the actual limit of fire resistance of building structures with regulatory requirements. This is due to the imperfection of methods and means of assessing the fire resistance of building structures, including fire-retardant.
To overcome the shortcomings identified during the analysis, the paper develops physical and mathematical models of thermal processes occurring in the fire-retardant reinforced concrete structure. Based on the proposed models, a computational-experimental method for estimating the fire resistance of such structures has been developed. The efficiency of the proposed method was tested by identifying the relationship between the parameters of the fire-retardant plaster coating “Neospray” and the fire resistance of fire-retardant multi-hollow reinforced concrete floor.
The study of fire resistance of steel structures is proposed to be carried out using reduced samples in the form of steel plates with dimensions of 500×500×5 mm. Based on the proposed models, a calculation and experimental method for estimating the fire resistance of steel structures, as well as an algorithm and procedures for its implementation have been developed. The verification of the efficiency of the proposed method was carried out in the ANSYS software package using the aged coating “Phoenix STS” and the coating “Amotherm Steel Wb” under heating conditions at the temperature of the hydrocarbon fire.
The reliability of the developed models and methods is checked. It is established that random errors in temperature measurement significantly affect the accuracy of determining the thermophysical characteristics and limits of fire resistance. In general, the efficiency of the proposed calculation and experimental methods with sufficient accuracy for engineering calculations is confirmed