scholarly journals Химический сдвиг и энергия обменного взаимодействия 1s состояний доноров магния в кремнии. Возможность стимулированного излучения

2019 ◽  
Vol 53 (9) ◽  
pp. 1263
Author(s):  
В.Н. Шастин ◽  
Р.Х. Жукавин ◽  
К.А. Ковалевский ◽  
В.В. Цыпленков ◽  
В.В. Румянцев ◽  
...  
Keyword(s):  
Experimental Data ◽  
Population Inversion ◽  
Elevated Temperatures ◽  
Stimulated Raman Scattering ◽  
Stimulated Emission ◽  
Fano Resonances ◽  
Relaxation Rates ◽  
Specific Mechanism ◽  
S States ◽  
Mg Doped

AbstractThe results of experiments aimed at the observation of split 1 s states in Mg-doped Si are reported. From the results, it is possible to determine the chemical shift and exchange interaction energy of a neutral Mg donor in Si. The position of the 1 s ( E ), 1 s ( T _2), and 2 s ( A _1) parastates determines the possibility for attaining population inversion and the specific mechanism of stimulated Raman scattering. The energy of the 1 s ( T _2) parastate is determined from the position of the Fano resonances in the photoconductivity spectrum of Si:Mg at T = 4 K, and the energies of the 1 s ( T _2) and 1 s ( E ) orthostates from the transmittance spectra at elevated temperatures. On the basis of the experimental data, the relaxation rates are estimated, and the possible mechanisms of stimulated emission are analyzed.

Numerical analysis of short laser pulse superposition in a fluorescent dye medium

1979 ◽  
Vol 57 (2) ◽  
pp. 160-167 ◽  
Author(s):  
D. Faubert ◽  
S. L. Chin ◽  
M. Cormier ◽  
M. Boloten
Keyword(s):  
Experimental Data ◽  
Numerical Analysis ◽  
Laser Pulse ◽  
Rate Equation ◽  
Population Inversion ◽  
Fluorescent Dye ◽  
Numerical Results ◽  
Stimulated Emission ◽  
Short Laser Pulse ◽  
Equation Analysis

We present a rate equation analysis of passive short laser pulse superposition in a fluorescent dye medium, where it is seen that a single dye solution may act as both an absorber and an amplifier. Amplification proceeds via stimulated emission following a population inversion created with the energy the dye gained through absorption. Numerical results are compared with published experimental data. The agreement between the two is qualitative.

Stimulated Emission in the Hydrogen Maser and the H Spin-Exchange Cross Section

1973 ◽  
Vol 51 (18) ◽  
pp. 1901-1909 ◽  
Author(s):  
J. Vanier ◽  
R. Brousseau ◽  
R. Larouche
Keyword(s):  
Experimental Data ◽  
Cross Section ◽  
Spin Exchange ◽  
Analog Computer ◽  
Stimulated Emission ◽  
Rate Equations ◽  
Relaxation Rates ◽  
Hydrogen Maser ◽  
Pulse Technique ◽  
Exchange Cross Section

Experiments are described in which the phenomenon of stimulated emission with a delayed maximum of power is observed in a hydrogen maser and is studied in some detail. The results are coupled to measurements of relaxation rates made through a pulse technique in which the hydrogen beam is modulated. A solution of the rate equations describing the phenomenon for a two-level model is obtained on an analog computer and is compared with the experimental data. From the comparison, we conclude that the phenomenon is explained by the assumed theoretical model. It is found also that the published values of the spin-exchange cross section of hydrogen are consistent with our experimental data.

Effect Of Elevated Temperatures On Complete Concrete Deformation Diagrams

2019 ◽  
pp. 9-14
Keyword(s):  
Experimental Data ◽  
Elastic Modulus ◽  
Elevated Temperatures ◽  
Peak Load ◽  
Relative Deformation ◽  
Deformation Characteristics ◽  
Compression Tests ◽  
Strain Behavior ◽  
Different Temperatures ◽  
Deformation Diagrams

The analysis of the previous results of the study on concrete stress-strain behavior at elevated temperatures has been carried out. Based on the analysis, the main reasons for strength retrogression and elastic modulus reduction of concrete have been identified. Despite a significant amount of research in this area, there is a large spread in experimental data received, both as a result of compression and tension. In addition, the deformation characteristics of concrete are insufficiently studied: the coefficient of transverse deformation, the limiting relative compression deformation corresponding to the peak load and the almost complete absence of studies of complete deformation diagrams at elevated temperatures. The two testing chambers provided creating the necessary temperature conditions for conducting studies under bending compression and tension have been developed. On the basis of the obtained experimental data of physical and mechanical characteristics of concrete at different temperatures under conditions of axial compression and tensile bending, conclusions about the nature of changes in strength and deformation characteristics have been drawn. Compression tests conducted following the method of concrete deformation complete curves provided obtaining diagrams not only at normal temperature, but also at elevated temperature. Based on the experimental results, dependences of changes in prism strength and elastic modulus as well as an equation for determining the relative deformation and stresses at elevated temperatures at all stages of concrete deterioration have been suggested.

Dielectric Breakdown in Printed Circuit Boards at Elevated Temperatures

1996 ◽  
Author(s):  
P. Singh ◽  
G.T. Galyon ◽  
J. Obrzut ◽  
W.A. Alpaugh
Keyword(s):  
Experimental Data ◽  
Thermal Degradation ◽  
Printed Circuit Boards ◽  
Printed Circuit Board ◽  
Elevated Temperatures ◽  
Dielectric Breakdown ◽  
Circuit Board ◽  
Circuit Boards ◽  
Printed Circuit ◽  
Data Matching

Abstract A time delayed dielectric breakdown in printed circuit boards, operating at temperatures below the epoxy resin insulation thermo-electrical limits, is reported. The safe temperature-voltage operating regime was estimated and related to the glass-rubber transition (To) of printed circuit board dielectric. The TG was measured using DSC and compared with that determined from electrical conductivity of the laminate in the glassy and rubbery state. A failure model was developed and fitted to the experimental data matching a localized thermal degradation of the dielectric and time dependency. The model is based on localized heating of an insulation resistance defect that under certain voltage bias can exceed the TG, thus, initiating thermal degradation of the resin. The model agrees well with the experimental data and indicates that the failure rate and truncation time beyond which the probability of failure becomes insignificant, decreases with increasing glass-rubber transition temperature.

scholarly journals Cross-Linker Control of Vitrimer Flow

2020 ◽  
Author(s):  
Bassil El-Zaatari ◽  
Jacob Ishibashi ◽  
Julia Kalow
Keyword(s):  
Stress Relaxation ◽  
Elevated Temperatures ◽  
Bulk Material ◽  
Relaxation Rates ◽  
Exchange Reactions ◽  
Activation Barriers ◽  
Flow Activation Energy ◽  
Wide Range ◽  
Cross Linker ◽  
Frequency Sweeps

<div><p>Vitrimers are a class of covalent adaptable networks (CANs) that undergo topology reconfiguration via associative exchange reactions, enabling reprocessing at elevated temperatures. Here, we show that cross-linker reactivity represents an additional design parameter to tune stress relaxation rates in vitrimers. Guided by calculated activation barriers, we prepared a series of cross-linkers with varying reactivity for the conjugate addition—elimination of thiols in a PDMS vitrimer. Surprisingly, despite a wide range of stress relaxation rates, we observe that the flow activation energy of the bulk material is independent of the cross-linker structure. Superposition of storage and loss moduli from frequency sweeps can be performed for different cross-linkers, indicating the same exchange mechanism. We show that we can mix different cross-linkers in a single material in order to further modulate the stress relaxation behavior.</p></div>

scholarly journals Влияние одноосной деформации в направлении [110] на релаксацию состояний мелких доноров мышьяка в германии

2020 ◽  
Vol 54 (9) ◽  
pp. 918
Author(s):  
В.В. Цыпленков ◽  
В.Н. Шастин
Keyword(s):  
Energy Levels ◽  
Optical Excitation ◽  
Uniaxial Stress ◽  
Shallow Donor ◽  
Stimulated Emission ◽  
Relaxation Rates ◽  
Emission Frequency ◽  
Donor States ◽  
Uniaxial Compressive Stress ◽  
Intracenter Transitions

Analysis of acoustical phonon assisted relaxation rates of arsenic donor states has been carried out in depends on uniaxial compressive stress of crystal along [110] direction under low temperature (< 10 K). As shown, under optical excitation the inversion population of donor energy levels is formed that depends on deformation of crystal. This give grounds to suppose that stimulated emission on arsenic shallow donor intracenter transitions in THz range is possible under optical excitation. As shown, uniaxial stress along [110] direction can result to switch laser transition and stimulated emission frequency

Kinetic equations of creep and damage for description of materials with non-monotonic dependence of fracture strain on stress

2021 ◽  
Vol 23 (3) ◽  
pp. 139-154
Author(s):  
Inna Banshchikova ◽  
Keyword(s):  
Experimental Data ◽  
Comparative Analysis ◽  
Damage Accumulation ◽  
Elevated Temperatures ◽  
Fracture Strain ◽  
Least Squares Method ◽  
Kinetic Equations ◽  
Steel 12Kh18n10t ◽  
Static Mode ◽  
Creep Curves

Introduction. Reducing the level of damage accumulation during pressure treatment of materials at elevated temperatures in creep and close to superplasticity modes in the manufacture of parts can significantly increase its service life in the cold state. Finding temperature and power conditions leading to a reduction in damage of material during the production process and operation is an important task. The purposes of the work: 1) to show the possibility of using the Sosnin-Gorev creep and damage model for alloys with a non-monotonic dependence of strain at fracture on diagrams with creep curves; 2) to carry out comparative analysis of damage accumulation under conditions of uniaxial tension at constant stress and at constant strain rates for alloy with such a dependence. Research methods. Used scalar damage parameter is equated to the normalized deformation, i.e. to the ratio of the current strain to the fracture strain. To find the coefficients of relations creep and damage, the similarity of the creep curves in the normalized values “normalized strain – normalized time”, i.e. the presence of single normalized curve of damage accumulation is checked. The least squares method is used to approximate the experimental data. Numerical integration methods are used for comparative analysis of deformation modes. Results and discussion. Determination of the parameters of the creep and damage equations by the method of a single normalized curve is carried out on the example of experimental data for steel 12Kh18N10T (12Cr18Ni10Ti) at 850 °C, which has a minimum of fracture strain in diagrams with creep curves. Analysis of the static and kinematic modes of deformation for studied material showed that damage accumulation in both cases is practically the same for stresses close to the stress at which this minimum is reached. If the stresses are lower, then the lower level of damage accumulation will be in the kinematic mode; if the stresses above the minimum value, then the static mode will lead to a lower level of damage accumulation. Application. The obtained results can be useful when choosing rational modes of forming structural elements from alloys with a non-monotonic dependence of the fracture strain on stress, as well as in evaluating it for long-term strength during operation.

scholarly journals Applying the dimensional method for valuation of the strength loss of cement compositions exposed to elevated temperatures

2018 ◽  
Vol 251 ◽  
pp. 02005
Author(s):  
Nikita Levashov ◽  
Marina Akulova ◽  
Olga Potemkina ◽  
Alla Sokolova ◽  
Yulia Sokolova
Keyword(s):  
Experimental Data ◽  
Bearing Capacity ◽  
Fire Resistance ◽  
Elevated Temperatures ◽  
Classical Method ◽  
Strength Loss ◽  
Ultimate State ◽  
Load Bearing Capacity ◽  
Full Scale Tests ◽  
Loss Of Strength

The paper presents the basis of the analytical model for calcu-lating the loss of strength in ce-ment compositions exposed to elevated temperatures. This model is to replace the classical method of calculating the fire resistance of the loss of load-bearing capacity. The experimental data were taken as initial indicators. Based on the implemented calculations it would become possible to predict the occurrence of ultimate state by loss strength and the reliability of practical indicators obtained by means of full-scale tests

scholarly journals Energy spectra of muonic atoms in quantum electrodynamics

2019 ◽  
Vol 204 ◽  
pp. 05007 ◽  
Author(s):  
A. E. Dorokhov ◽  
A. A. Krutov ◽  
A. P. Martynenko ◽  
F. A. Martynenko ◽  
O. S. Sukhorukova
Keyword(s):  
Experimental Data ◽  
Perturbation Theory ◽  
Energy Spectrum ◽  
Hyperfine Structure ◽  
Nuclear Structure ◽  
Quantum Electrodynamics ◽  
Vacuum Polarization ◽  
Energy Spectra ◽  
Hyperfine Splittings ◽  
S States

Vacuum polarization, nuclear structure and recoil, radiative corrections to the hyperfine structure of S-states in muonic ions of lithium, beryllium and boron are calculated on the basis of quasipotential method in quantum electrodynamics. We consider contributions in first and second orders of perturbation theory which have the order α5 and α6 in the energy spectrum. Total values of hyperfine splittings are obtained which can be used for a comparison with future experimental data.

Study of the Effects of High Temperatures on the Engineering Properties of Steel 42CrMo4

2015 ◽  
Vol 34 (1) ◽  
Author(s):  
Josip Brnic ◽  
Goran Turkalj ◽  
Marko Canadija ◽  
Domagoj Lanc ◽  
Marino Brcic
Keyword(s):  
Experimental Data ◽  
Impact Energy ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Charpy Impact ◽  
Engineering Properties ◽  
Charpy Impact Energy ◽  
Rheological Models ◽  
Creep Curves ◽  
Low Levels

AbstractThe paper presents and analyzes the experimental results of the effect of elevated temperatures on the engineering properties of steel 42CrMo4. Experimental data relating to the mechanical properties of the material, the creep resistance as well as Charpy impact energy. Temperature dependence of the mentioned properties is also shown. Some of creep curves were simulated using rheological models and an analytical equation. Finally, an assessment of fracture toughness was made that was based on experimentally determined Charpy impact energy. Based on the obtained results it is visible that the tensile strength (617 MPa) and yield strength (415 MPa) have the highest value at the room temperature while at the temperature of 700 °C (973 K) these values significantly decrease. This steel can be considered resistant to creep at 400 °C (673 K), but at higher temperatures this steel can be subjected to low levels of stress in a shorter time.

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