scholarly journals The fluctuation-dissipation theorem and the autocorrelation function of thermal radiation

2021 ◽  
pp. 7-18
Author(s):  
Evgeniy Krasnopevtsev ◽  
Keyword(s):  
Transfer Function ◽  
Field Strength ◽  
Electric Field ◽  
Thermal Radiation ◽  
Electric Field Strength ◽  
Thermal Motion ◽  
Spectral Densities ◽  
Fluctuation Dissipation ◽  
Fluctuation Dissipation Theorem ◽  
Generalized Coordinate

A new relatively simple derivation of the fluctuation-dissipation theorem (FDT) is presented. The generalized coordinate of the system is changed by an external force and is expressed by means of causal susceptibility, its Fourier transform – the transfer function, generalized impedance and active resistance. These characteristics describe heat dissipation on the resistor and the result is generalized to the dissipative system which is under the action of macroscopic force. The fluctuation voltage on the resistor is obtained by decomposing the thermal chaotic motion of free charges along the conductor into a Fourier series. The number of standing waves and the average energy of the quantum oscillation state at a fixed temperature give the thermal power of charge transfer. By comparing with the Joule-Lenz law and by generalizing the result to an arbitrary isothermal system, the mean square of the fluctuating force and dispersion of the generalized coordinate caused by the thermal motion are obtained. The autocorrelation functions of the generalized coordinate and the random force, and their spectral densities are expressed through the considered characteristics. The content of FDT is that the power of heat release, the spectral densities of the fluctuating force and the autocorrelation are proportional to the imaginary part of the transfer function of the system. The result is used for thermal radiation in a cavity the walls of which contain electric dipoles excited by thermal motion. The transfer function, the fluctuating force acting on the charge, the dispersion of the electric field strength, time autocorrelation of the electric field strength and its spectral density are obtained. Real and imaginary components, the modulus and phase are found for complex relative autocorrelation of the electric field strength and the coherence time is determined.

Optical Measurement of the Electric Field Strength in a Gel Insulator

2016 ◽  
Vol 136 (10) ◽  
pp. 1420-1421
Author(s):  
Yusuke Tanaka ◽  
Yuji Nagaoka ◽  
Hyeon-Gu Jeon ◽  
Masaharu Fujii ◽  
Haruo Ihori
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Optical Measurement

Effect of external magnetic field on lane formation in driven pair-ion plasmas

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Swati Baruah ◽  
U. Sarma ◽  
R. Ganesh
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Coupling Parameter ◽  
Critical Parameters ◽  
Coulomb Coupling ◽  
Lane Formation ◽  
Parameter Values

Lane formation dynamics in externally driven pair-ion plasma (PIP) particles is studied in the presence of external magnetic field using Langevin dynamics (LD) simulation. The phase diagram obtained distinguishing the no-lane and lane states is systematically determined from a study of various Coulomb coupling parameter values. A peculiar lane formation-disintegration parameter space is identified; lane formation area extended to a wide range of Coulomb coupling parameter values is observed before disappearing to a mixed phase. The different phases are identified by calculating the order parameter. This and the critical parameters are calculated directly from LD simulation. The critical electric field strength value above which the lanes are formed distinctly is obtained, and it is observed that in the presence of the external magnetic field, the PIP system requires a higher value of the electric field strength to enter into the lane formation state than that in the absence of the magnetic field. We further find out the critical value of electric field frequency beyond which the system exhibits a transition back to the disordered state and this critical frequency is found as an increasing function of the electric field strength in the presence of an external magnetic field. The movement of the lanes is also observed in a direction perpendicular to that of the applied electric and magnetic field directions, which reveals the existence of the electric field drift in the system under study. We also use an oblique force field as the external driving force, both in the presence and absence of the external magnetic field. The application of this oblique force changes the orientation of the lane structures for different applied oblique angle values.

scholarly journals Investigating the feasibility of cerebellar transcranial direct current stimulation to facilitate post-stroke overground gait performance in chronic stroke: a partial least-squares regression approach

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Dhaval Solanki ◽  
Zeynab Rezaee ◽  
Anirban Dutta ◽  
Uttama Lahiri
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Chronic Stroke ◽  
Least Squares Regression ◽  
Significance Level ◽  
Gait Performance ◽  
Wilcoxon Rank Sum Test ◽  
Gait Parameters ◽  
The Mean

Abstract Background Investigation of lobule-specific electric field effects of cerebellar transcranial direct current stimulation (ctDCS) on overground gait performance has not been performed, so this study aimed to investigate the feasibility of two lobule-specific bilateral ctDCS montages to facilitate overground walking in chronic stroke. Methods Ten chronic post-stroke male subjects participated in this repeated-measure single-blind crossover study, where we evaluated the single-session effects of two bilateral ctDCS montages that applied 2 mA via 3.14 cm2 disc electrodes for 15 min targeting (a) dentate nuclei (also, anterior and posterior lobes), and (b) lower-limb representations (lobules VIIb-IX). A two-sided Wilcoxon rank-sum test was performed at a 5% significance level on the percent normalized change measures in the overground gait performance. Partial least squares regression (PLSR) analysis was performed on the quantitative gait parameters as response variables to the mean lobular electric field strength as the predictors. Clinical assessments were performed with the Ten-Meter walk test (TMWT), Timed Up & Go (TUG), and the Berg Balance Scale based on minimal clinically important differences (MCID). Results The ctDCS montage specific effect was found significant using a two-sided Wilcoxon rank-sum test at a 5% significance level for 'Step Time Affected Leg' (p = 0.0257) and '%Stance Time Unaffected Leg' (p = 0.0376). The changes in the quantitative gait parameters were found to be correlated to the mean electric field strength in the lobules based on PLSR analysis (R2 statistic = 0.6574). Here, the mean electric field strength at the cerebellar lobules, Vermis VIIIb, Ipsi-lesional IX, Vermis IX, Ipsi-lesional X, had the most loading and were positively related to the 'Step Time Affected Leg' and '%Stance Time Unaffected Leg,' and negatively related to the '%Swing Time Unaffected Leg,' '%Single Support Time Affected Leg.' Clinical assessments found similar improvement in the TMWT (MCID: 0.10 m/s), TUG (MCID: 8 s), and BBS score (MCID: 12.5 points) for both the ctDCS montages. Conclusion Our feasibility study found an association between the lobular mean electric field strength and the changes in the quantitative gait parameters following a single ctDCS session in chronic stroke. Both the ctDCS montages improved the clinical outcome measures that should be investigated with a larger sample size for clinical validation. Trial registration: Being retrospectively registered.

scholarly journals Optical properties of c-Plane InGaN/GaN single quantum wells as a function of total electric field strength

2019 ◽  
Vol 58 (SC) ◽  
pp. SCCB09 ◽  
Author(s):  
George M. Christian ◽  
Stefan Schulz ◽  
Simon Hammersley ◽  
Menno J. Kappers ◽  
Martin Frentrup ◽  
...  
Keyword(s):  
Optical Properties ◽  
Field Strength ◽  
Electric Field ◽  
Quantum Wells ◽  
Electric Field Strength ◽  
Single Quantum ◽  
Total Electric Field

scholarly journals International Intercomparison of Electric-Field Strength at 100 MHz

1983 ◽  
Vol 32 (1) ◽  
pp. 235-237 ◽  
Author(s):  
Carl F. Stubenrauch ◽  
Pier Giorgio Galliano ◽  
Tadeusz M. Babij
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
International Intercomparison
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