Application of Capacitors in Low Frequency and Long Time Constant Circuits

1964 ◽  
Vol 11 (2) ◽  
pp. 216-219
Author(s):  
W. Elsen
Keyword(s):  
Time Constant ◽  
Low Frequency ◽  
Long Time

scholarly journals Activity-dependent increases in [Ca2+]i contribute to digital-analog plasticity at a molluscan synapse

2017 ◽  
Vol 117 (6) ◽  
pp. 2104-2112 ◽  
Author(s):  
Bjoern Ch. Ludwar ◽  
Colin G. Evans ◽  
Monica Cambi ◽  
Elizabeth C. Cropper
Keyword(s):  
Synaptic Transmission ◽  
Intracellular Calcium ◽  
Time Constant ◽  
Calcium Concentration ◽  
Low Frequency ◽  
Intracellular Calcium Concentration ◽  
Calcium Signal ◽  
Presynaptic Neuron ◽  
Calcium Dependent ◽  
Long Time

In a type of short-term plasticity that is observed in a number of systems, synaptic transmission is potentiated by depolarizing changes in the membrane potential of the presynaptic neuron before spike initiation. This digital-analog form of plasticity is graded. The more depolarized the neuron, the greater the increase in the efficacy of synaptic transmission. In a number of systems, including the system presently under investigation, this type of modulation is calcium dependent, and its graded nature is presumably a consequence of a direct relationship between the intracellular calcium concentration ([Ca2+]i) and the effect on synaptic transmission. It is therefore of interest to identify factors that determine the magnitude of this type of calcium signal. We studied a synapse in Aplysia and demonstrate that there can be a contribution from currents activated during spiking. When neurons spike, there are localized increases in [Ca2+]i that directly trigger neurotransmitter release. Additionally, spiking can lead to global increases in [Ca2+]i that are reminiscent of those induced by subthreshold depolarization. We demonstrate that these spike-induced increases in [Ca2+]i result from the activation of a current not activated by subthreshold depolarization. Importantly, they decay with a relatively slow time constant. Consequently, with repeated spiking, even at a low frequency, they readily summate to become larger than increases in [Ca2+]i induced by subthreshold depolarization alone. When this occurs, global increases in [Ca2+]i induced by spiking play the predominant role in determining the efficacy of synaptic transmission. NEW & NOTEWORTHY We demonstrate that spiking can induce global increases in the intracellular calcium concentration ([Ca2+]i) that decay with a relatively long time constant. Consequently, summation of the calcium signal occurs even at low firing frequencies. As a result there is significant, persistent potentiation of synaptic transmission.

Experience with the Relay Procedure for Tuning Controllers in Automatic Control of Chlorination

1993 ◽  
Vol 28 (11-12) ◽  
pp. 257-261
Author(s):  
M. Truett Garrett ◽  
Zaki Ahmad ◽  
Shelly Young
Keyword(s):  
Wastewater Treatment ◽  
Automatic Control ◽  
Time Constant ◽  
Wastewater Treatment Plants ◽  
Relay Feedback ◽  
Quality Of Control ◽  
Incomplete Mixing ◽  
Long Time ◽  
Chlorine Demand

The recent requirements by U.S.E.P.A. for dechlorination and biomonitoring have increased the importance of automatic control of effluent chlorination in wastewater treatment plants. Difficulties with the Ziegler-Nichols controller tuning procedure were reported at the Kyoto Workshop, 1990. Problems are caused by the noise of incomplete mixing, a long time constant, and the disturbances of changing flow and chlorine demand. The Astrom-Hagglund relay feedback procedure provides acceptable control while data is logged to determine the controller constants. Experiences in using the procedure in existing facilities (not redesigning the mixing point) and the quality of control are presented.

scholarly journals Electromagnetic power of lightning superbolts from Earth to space

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
J.-F. Ripoll ◽  
T. Farges ◽  
D. M. Malaspina ◽  
G. S. Cunningham ◽  
E. H. Lay ◽  
...  
Keyword(s):  
Low Frequency ◽  
Optical Emission ◽  
High Energy ◽  
Very Low Frequency ◽  
Electromagnetic Power ◽  
Power Spectral ◽  
High Energy Tail ◽  
Van Allen Probes ◽  
Long Time ◽  
Low Frequency Waves

AbstractLightning superbolts are the most powerful and rare lightning events with intense optical emission, first identified from space. Superbolt events occurred in 2010-2018 could be localized by extracting the high energy tail of the lightning stroke signals measured by the very low frequency ground stations of the World-Wide Lightning Location Network. Here, we report electromagnetic observations of superbolts from space using Van Allen Probes satellite measurements, and ground measurements, and with two events measured both from ground and space. From burst-triggered measurements, we compute electric and magnetic power spectral density for very low frequency waves driven by superbolts, both on Earth and transmitted into space, demonstrating that superbolts transmit 10-1000 times more powerful very low frequency waves into space than typical strokes and revealing that their extreme nature is observed in space. We find several properties of superbolts that notably differ from most lightning flashes; a more symmetric first ground-wave peak due to a longer rise time, larger peak current, weaker decay of electromagnetic power density in space with distance, and a power mostly confined in the very low frequency range. Their signal is absent in space during day times and is received with a long-time delay on the Van Allen Probes. These results have implications for our understanding of lightning and superbolts, for ionosphere-magnetosphere wave transmission, wave propagation in space, and remote sensing of extreme events.

Interaction of Point Defects in Ice

1978 ◽  
Vol 21 (85) ◽  
pp. 115-122
Author(s):  
J. H. Bilgram ◽  
H. Gränicher
Keyword(s):  
Experimental Data ◽  
Dielectric Properties ◽  
Temperature Dependence ◽  
Point Defects ◽  
Low Frequency ◽  
Defect Concentration ◽  
Dielectric Measurements ◽  
Long Time ◽  
Nmr Techniques ◽  
Bjerrum Defect

AbstractThe interaction of point detects in ice has been neglected for a long time. Experimental data obtained from dielectric measurements on HF-doped crystals stimulated a new evaluation of the possibility of an interaction between Bjerrum defects and ions. In a previous paper it has been shown that this leads us to assume the existence of aggregates of Bjerrum defects and ions. In this paper these aggregates and Bjerrum defects are used to explain the dielectric properties of ice, especially the temperature dependence of the product of the high and low frequency conductivity σ0σ∞.The interaction of Bjerrum defects and impurity molecules leads to a dependence of the concentration of frenkel pairs on Bjerrum-defect concentration. At HF concentrations above the native Bjerrum-defect concentration the formation of a Frenkel pair is enhanced. This leads to the fast out-diffusion which has been studied in highly doped crystals by means of NMR techniques.

Prognostic relevance of anamnestic and diagnostic parameters in low-frequency hearing impairment

2006 ◽  
Vol 120 (8) ◽  
pp. 613-618 ◽  
Author(s):  
W Maier ◽  
J Schipper
Keyword(s):  
Prognostic Factor ◽  
Hearing Impairment ◽  
Hearing Threshold ◽  
Low Frequency ◽  
Prognostic Indicators ◽  
Infusion Therapy ◽  
Prognostic Relevance ◽  
Long Time ◽  
Dehydration Therapy

Low-frequency hearing impairment (LFHI) is mainly attributed to endolymphatic hydrops and has a great variety of possible outcomes. At present, no conservative therapeutic regimen has proven to be ‘gold-standard’, and information about the prognostic indicators of LFHI is scarce.In a retrospective investigation, we evaluated the records of 90 patients who had been treated with infusions improving blood perfusion. In patients lacking complete remission, dehydration infusion therapy was added. We also undertook audiometric follow up. We calculated the outcomes after infusion therapy, dehydration therapy and after long-time hearing follow up, and we determined the prognostic relevance of several parameters of anamnesis and clinical examination to outcomes, for both therapeutic interventions and long-time hearing.The prognosis of LFHI was significantly correlated to certain anamnestic and clinical parameters; a short duration of the disease, lack of vertigo and female gender implied a better outcome. The pretherapeutic hearing threshold was an important prognostic factor; the outcome was significantly worse in patients with distinct hearing impairment in low or high frequencies, compared with that in patients with little hearing loss. Whereas vertigo was a negative prognostic factor, the results of quantitative vestibular testing were irrelevant to the outcome. The glycerol test failed to predict the effectiveness of dehydration therapy and lacked any value in predicting prognosis.These results allow the clinician to focus the anamnesis and diagnostic examination on prognostically relevant parameters, thus enabling a better estimation of the long-term disease course and improved counselling of patients. Furthermore, these results help to distinguish valuable from irrelevant diagnostic procedures.

scholarly journals A sensory integration account for time perception

2020 ◽  
Author(s):  
Alessandro Toso ◽  
Arash Fassihi ◽  
Luciano Paz ◽  
Francesca Pulecchi ◽  
Mathew E. Diamond
Keyword(s):  
Time Perception ◽  
Time Constant ◽  
Sensory Integration ◽  
Neuronal Firing ◽  
Elapsed Time ◽  
Leaky Integrator ◽  
Long Time ◽  
Integrator Model ◽  
Short Time ◽  
Sense Of Touch

ABSTRACTThe connection between stimulus perception and time perception remains unknown. The present study combines human and rat psychophysics with sensory cortical neuronal firing to construct a computational model for the percept of elapsed time embedded within sense of touch. When subjects judged the duration of a vibration applied to the fingertip (human) or whiskers (rat), increasing stimulus mean speed led to increasing perceived duration. Symmetrically, increasing vibration duration led to increasing perceived intensity. We modeled spike trains from vibrissal somatosensory cortex as input to dual leaky integrators – an intensity integrator with short time constant and a duration integrator with long time constant – generating neurometric functions that replicated the actual psychophysical functions of rats. Returning to human psychophysics, we then confirmed specific predictions of the dual leaky integrator model. This study offers a framework, based on sensory coding and subsequent accumulation of sensory drive, to account for how a feeling of the passage of time accompanies the tactile sensory experience.

scholarly journals Low-frequency unsteadiness in the wake of a normal flat plate

1998 ◽  
Vol 370 ◽  
pp. 101-147 ◽  
Author(s):  
F. M. NAJJAR ◽  
S. BALACHANDAR
Keyword(s):  
Shear Layer ◽  
Flat Plate ◽  
Free Stream ◽  
Low Frequency ◽  
Separated Flow ◽  
Phase Mismatch ◽  
Streamwise Vortices ◽  
Long Time ◽  
Drag And Lift ◽  
High Degree

The separated flow past a zero-thickness flat plate held normal to a free stream at Re=250 has been investigated through numerical experiments. The long-time signatures of the drag and lift coefficients clearly capture a low-frequency unsteadiness with a period of approximately 10 times the primary shedding period. The amplitude and frequency of drag and lift variations during the shedding process are strongly modulated by the low frequency. A physical interpretation of the low-frequency behaviour is that the flow gradually varies between two different regimes: a regime H of high mean drag and a regime L of low mean drag. It is observed that in regime H the shear layer rolls up closer to the plate to form coherent spanwise vortices, while in regime L the shear layer extends farther downstream and the rolled-up Kármán vortices are less coherent. In the high-drag regime three-dimensionality is characterized by coherent Kármán vortices and reasonably well-organized streamwise vortices connecting the Kármán vortices. With a non-dimensional spanwise wavelength of about 1.2, the three-dimensionality in this regime is reminiscent of mode-B three-dimensionality. It is observed that the high degree of spanwise coherence that exists in regime H breaks down in regime L. Based on detailed numerical flow visualization we conjecture that the formation of streamwise and spanwise vortices is not in perfect synchronization and that the low-frequency unsteadiness is the result of this imbalance (or phase mismatch).

scholarly journals Driving Waveform Design of Electrowetting Displays Based on an Exponential Function for a Stable Grayscale and a Short Driving Time

Micromachines ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 313 ◽  
Author(s):  
Zichuan Yi ◽  
Zhenyu Huang ◽  
Shufa Lai ◽  
Wenyao He ◽  
Li Wang ◽  
...  
Keyword(s):  
Time Constant ◽  
Exponential Function ◽  
Waveform Design ◽  
Hysteresis Curve ◽  
Optimal Time ◽  
Driving Voltage ◽  
Aperture Ratio ◽  
Driving Time ◽  
Long Time ◽  
Driving Waveform

The traditional driving waveform of the electrowetting display (EWD) has many disadvantages, such as the large oscillation of the target grayscale aperture ratio and a long time for achieving grayscale. Therefore, a driving waveform based on the exponential function was proposed in this study. First, the maximum driving voltage value of 30 V was obtained by testing the hysteresis curve of the EWD pixel unit. Secondly, the influence of the time constant on the driving waveform was analyzed, and the optimal time constant of the exponential function was designed by testing the performance of the aperture ratio. Lastly, an EWD panel was used to test the driving effect of the exponential-function-driving waveform. The experimental results showed that a stable grayscale and a short driving time could be realized when the appropriate time constant value was designed for driving EWDs. The aperture ratio oscillation range of the gray scale could be reduced within 0.95%, and the driving time of a stable grayscale was reduced by 30% compared with the traditional driving waveform.

Probabilistic Risk Analysis of Broken Rail-Caused Train Derailments

2020 ◽  
Author(s):  
Zhipeng Zhang ◽  
Kang Zhou ◽  
Xiang Liu
Keyword(s):  
Risk Model ◽  
Quantitative Estimation ◽  
Low Frequency ◽  
Machine Learning Techniques ◽  
Affecting Factors ◽  
Efficient Manner ◽  
Major Activity ◽  
Long Time ◽  
Cost Efficient ◽  
Railroad Company

Abstract Broken-rail prevention and risk management have been being a major activity for a long time for the railroad industry. The major objective of this research is to evaluate and analyze the broken rail-caused derailment risk using Artificial Intelligence (AI) approaches. The risk model is primarily built upon 1) broken rail probability; 2) probability of broken-rail derailment given a broken rail; and 3) derailment severity, measured by the number of cars derailed. The train derailment risk accounts for derailment probability and derailment consequences simultaneously. Due to the low frequency of broken-rail derailments, it is desirable to estimate the probability of broken rail-caused derailments through the broken rail occurrence. The estimation of the probability of broken rail-caused derailment includes the conditional probability of derailment given broken rail occurrence and the probability of broken rail occurrence. More specially, the probability of broken-rail derailment given a broken rail can be estimated by the statistical relationship between broken-rail derailment and broken rail, given specific variables (e.g., track curvature, signal condition, and annual traffic). The probability of broken rails can be estimated using machine learning techniques based on railroad big data, including maintenance, track layout, traffic and historical inspection records. In terms of derailment consequence, it is defined as the number of cars (both loaded and empty) derailed per derailment that would be estimated based on potentially affecting factors, such as train length, train speed, and train tonnage. The quantitative estimation and analysis of broken rail-caused derailments are based upon the historical records from one Class I railroad company from 2012 to 2016, covering over 20,000 track miles on mainlines. The developed integrated risk model is able to contribute to the prediction of location-centric broken rail-caused derailment risk. Ultimately, the identification of high-risk locations can ultimately aid the railroads to mitigate broken rail risk in a cost-efficient manner and improve railroad safety.

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