Bridge Method for Studying the Spectra of Current Fluctuations in Tungsten Filaments in the Frequency Range 1.5·10–5–5·10–1 Hz

2021 ◽  
Author(s):  
Yu. A. Zakharov ◽  
S. S. Gots ◽  
R. Z. Bakhtizin
Keyword(s):  
Current Fluctuations ◽  
Frequency Range ◽  
Bridge Method ◽  
Tungsten Filaments

Bridge method for studying the spectra of current fluctuations in tungsten filaments at the frequency range 1.5∙10–5–5∙10–1 Hz

2021 ◽  
pp. 18-25
Author(s):  
Yuriy A. Zakharov ◽  
Sergey S. Gots ◽  
Rauf Z. Bakhtizin
Keyword(s):  
Spectral Analysis ◽  
High Temperatures ◽  
Personal Computer ◽  
Low Frequency ◽  
Current Fluctuations ◽  
Frequency Range ◽  
Bridge Method ◽  
Measurement Results ◽  
Tungsten Filaments ◽  
Frequency Current

The problem of the absence of methods for measuring low-frequency fluctuation processes at high temperatures is considered. An original bridge method is proposed for measuring the spectra of low-frequency current fluctuations in tungsten filaments of electric lamps in a controlled temperature range of 300–2700 K. Application of the bridge measurement scheme allows us to reduce the influence of degradation processes in the filament and the power source's own noise on the measurement results by several orders of magnitude. Spectral analysis of low frequency current fluctuations is performed at the frequency range 1.5∙10–5–5∙10–1 Hz using an automated setup based on a personal computer under the control of specially developed software.

1 / f Noise in Hydrogenated Amorphous Silicon

1991 ◽  
Vol 219 ◽  
Author(s):  
C. Parman ◽  
J. Kakalios
Keyword(s):  
Amorphous Silicon ◽  
Power Law ◽  
Room Temperature ◽  
Hydrogenated Amorphous Silicon ◽  
Current Fluctuations ◽  
Surprising Result ◽  
Frequency Range ◽  
Temperature Dependent ◽  
Power Law Exponent ◽  
Hydrogenated Amorphous

ABSTRACTMeasurements of co-planar current fluctuations in n-type doped hydrogenated amorphous silicon (a-Si:H) find that the spectral density of the noise accurately obeys a 1/f frequency dependence over the frequency range of 1 Hz to 1 kHz for temperatures ranging from room temperature to 450K. The noise displays a power law dependence on the d.c. curent passing through the sample, with a temperature dependent power law exponent. In addition, the resistance of the a-Si:H as a function of time displays switching phenomena; a surprising result given the effective volume ( ∼10-6 cm3) of the sample.

A controller for safe, convenient operation of LaB6 emitters on electron-beam instruments

1983 ◽  
Vol 41 ◽  
pp. 408-409
Author(s):  
W. J. Abramson ◽  
H. W. Estry ◽  
L. F. Allard
Keyword(s):  
Electron Beam ◽  
Control System ◽  
Thermal Shock ◽  
Appropriate Care ◽  
Electron Guns ◽  
Tungsten Filaments ◽  
Order Of Magnitude ◽  
Main Components

LaB6 emitters are becoming increasingly popular as direct replacements for tungsten filaments in the electron guns of modern electron-beam instruments. These emitters offer order of magnitude increases in beam brightness, and, with appropriate care in operation, a corresponding increase in source lifetime. They are, however, an order of magnitude more expensive, and may be easily damaged (by improper vacuum conditions and thermal shock) during saturation/desaturation operations. These operations typically require several minutes of an operator's attention, which becomes tedious and subject to error, particularly since the emitter must be cooled during sample exchanges to minimize damage from random vacuum excursions. We have designed a control system for LaBg emitters which relieves the operator of the necessity for manually controlling the emitter power, minimizes the danger of accidental improper operation, and makes the use of these emitters routine on multi-user instruments.Figure 1 is a block schematic of the main components of the control system, and Figure 2 shows the control box.

Density-based discrimination of protein and RNA in the ribosome

1992 ◽  
Vol 50 (1) ◽  
pp. 464-465
Author(s):  
Joachim Frank
Keyword(s):  
Transfer Function ◽  
Spatial Frequency ◽  
Three Dimensional ◽  
Wiener Filter ◽  
Dark Field Image ◽  
Dark Field ◽  
Frequency Range ◽  
Bright Field ◽  
Contrast Transfer Function ◽  
Pass Filter

Cryo-electron microscopy combined with single-particle reconstruction techniques has allowed us to form a three-dimensional image of the Escherichia coli ribosome.In the interior, we observe strong density variations which may be attributed to the difference in scattering density between ribosomal RNA (rRNA) and protein. This identification can only be tentative, and lacks quantitation at this stage, because of the nature of image formation by bright field phase contrast. Apart from limiting the resolution, the contrast transfer function acts as a high-pass filter which produces edge enhancement effects that can explain at least part of the observed variations. As a step toward a more quantitative analysis, it is necessary to correct the transfer function in the low-spatial-frequency range. Unfortunately, it is in that range where Fourier components unrelated to elastic bright-field imaging are found, and a Wiener-filter type restoration would lead to incorrect results. Depending upon the thickness of the ice layer, a varying contribution to the Fourier components in the low-spatial-frequency range originates from an “inelastic dark field” image. The only prospect to obtain quantitatively interpretable images (i.e., which would allow discrimination between rRNA and protein by application of a density threshold set to the average RNA scattering density may therefore lie in the use of energy-filtering microscopes.

Evaluation of Special Hearing Aids for Deaf Children

1971 ◽  
Vol 36 (4) ◽  
pp. 527-537 ◽  
Author(s):  
Norman P. Erber
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Hearing Aid ◽  
Low Frequency ◽  
Acoustic Stimulation ◽  
Deaf Children ◽  
Frequency Range ◽  
Frequency Limit ◽  
Unpublished Studies ◽  
Published Research

Two types of special hearing aid have been developed recently to improve the reception of speech by profoundly deaf children. In a different way, each special system provides greater low-frequency acoustic stimulation to deaf ears than does a conventional hearing aid. One of the devices extends the low-frequency limit of amplification; the other shifts high-frequency energy to a lower frequency range. In general, previous evaluations of these special hearing aids have obtained inconsistent or inconclusive results. This paper reviews most of the published research on the use of special hearing aids by deaf children, summarizes several unpublished studies, and suggests a set of guidelines for future evaluations of special and conventional amplification systems.

The influence of external conditions on sound pressure in the pistonphone at the infrasound frequency range

2020 ◽  
pp. 67-72
Author(s):  
A. V. Konkov ◽  
D. V. Golovin
Keyword(s):  
Environmental Conditions ◽  
Sound Pressure ◽  
Primary Method ◽  
Frequency Range ◽  
External Conditions ◽  
Numerical Estimations

The influence of environmental conditions on a sound pressure reproduced by the primary method in the measuring chambers of the Pistonphone in the frequency range from 1 mHz to 250 Hz is estimated. Numerical estimations of influence of environmental conditions on sound pressure in pistonphone measuring chambers are given and special requirements to system of maintenance of required external conditions are specified.

The working standard of the unit of power of electromagnetic waves in the frequency range from 37,5 to 220 GHz

2020 ◽  
pp. 53-58
Author(s):  
A. V. Koudelny ◽  
I. M. Malay ◽  
V. A. Perepelkin ◽  
I. P. Chirkov
Keyword(s):  
Microwave Power ◽  
Electromagnetic Waves ◽  
Primary Standard ◽  
The State ◽  
Frequency Range ◽  
Working Standard ◽  
Extended Frequency Range ◽  
Effective Efficiency ◽  
Extended Frequency ◽  
Good Agreement

The possibility of using bolometric converters of microwave power from the State primary standard of the unit of power of electromagnetic waves in waveguide and coaxial paths GET 167-2017, which has a frequency range from 37,5 to 78,33 GHz, in an extended frequency range up to 220 GHz, is shown. Studies of semiconductor bolometric converters of microwave power in an extended frequency range have confirmed good agreement and smooth frequency characteristics of the effective efficiency factor of the converters. Based on the research results, the State working standard of the unit of power of electromagnetic waves of 0,1–10 mW in the frequency range from 37,5 to 220 GHz 3.1.ZZT.0288.2018 was approved. The technical characteristics of the working standard of the unit of power of electromagnetic oscillations in an extended frequency range from 37,5 to 220 GHz are given.

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