THE RESONANCE METHOD OF MEASURING THE RATIO OF THE SPECIFIC HEATS OF A GAS, Cp/Cv: PART V: SECTION A: AN IMPROVED APPARATUS FOR MEASURING THE RATIO OF THE SPECIFIC HEATS OF A GAS: SECTION B: THE USE OF ELECTRONIC COUNTER CIRCUITS TO MEASURE LOW FREQUENCIES AND A VARIABLE LOW FREQUENCY OSCILLATOR

1949 ◽  
Vol 27a (3) ◽  
pp. 27-38 ◽  
Author(s):  
L. Katz ◽  
S. B. Woods ◽  
W. F. Leverton
Keyword(s):  
Specific Heat ◽  
Low Frequency ◽  
Resonance Method ◽  
Time Interval ◽  
Low Frequencies ◽  
Specific Heats ◽  
Wide Range ◽  
New Apparatus ◽  
The Stability ◽  
Number Of Cycles

This paper describes an improved apparatus for the determination of γ = Cp/Cv, the ratio of the specific heat at constant pressure to the specific heat at constant volume for a gas. With this apparatus, γ is determined by the resonance method of Clark and Katz. The new apparatus is constructed of stainless steel and is designed to withstand pressures up to 100 atm. This new apparatus is more compact and can be used with corrosive gases. Provision is made for the control and accurate measurement of the temperature of the enclosed gas over a wide range of temperatures. An electronic counter which will measure time intervals, in units of 10 μsec., from 100 μsec. to several seconds in length is described in Section B. An unknown frequency may be determined by measuring the time interval in which a preselected number of cycles occurs. The accuracy is such that frequencies may be measured to within approximately 1 part in 105. The circuit for a variable frequency transitron oscillator with an output of 30 w. in a range of 15 to 250 c.p.s. is shown. The stability of the oscillator is such that the frequency may easily be maintained within 1 part in 10,000 for long periods, and with care in temperature control and choice of electrode voltages much greater stabilities may be obtained.

scholarly journals A flow method for comparing the specific heats of gases part I.―The experimental method

1930 ◽  
Vol 126 (801) ◽  
pp. 319-332 ◽  
Keyword(s):  
Specific Heat ◽  
Measured Temperature ◽  
Constant Flow ◽  
Technical Problems ◽  
Specific Heats ◽  
Resistance Thermometers ◽  
Wide Range ◽  
Exact Temperature ◽  
Careful Design ◽  
Theoretical Developments

Recent theoretical developments of kinetic theory, especially in the theory of pseudo-unimolecular reactions, have led to the demand for further measurements of the specific heats of vapours and gases, especially at high temperatures. Again many technical problems are demanding a better knowledge of the specific heats of gases over a wide range of conditions. The method to be described enables the ratio of the specific heats of two gases to be measured accurately. Since the monatomic gases are available as reliable standards, the fact that the method gives relative values only is of little account. There appear to be possibilities of wide application for the method on account both of its simplicity and its adaptability to a wide range of temperature and pressure. The method consists essentially in passing a slow stream of gas through a narrow tube, along which a temperature gradient has been established. The change of the temperature distribution along the tube depends on the properties of the gas and the rate of flow. It is found possible to choose the arrangement so that the measured temperature difference between two parts of the tube is a direct measure of the specific heat of the gas flowing in the tube. It will be seen that, though the method belongs to the "constant flow" class, it differs considerably in principle from that originally devised by Callendar and used for liquids by Callendar and Barnes, and Lang; and for gases by Swann, Nernst, and Scheel and Heuse. In the first place, all these experimenters measured the rate of supply of heat electrically, whilst the heat lost by conduction and radiation appeared as an experimentally determined correction; in the method to be described, the heat losses, though playing an essential part in the theory of the apparatus, do not enter at all into the measurement of the specific heat. Secondly, in previous constant flow methods the temperature of the gas itself has been measured by resistance thermometers, a proceeding which involves very careful design of the thermometer, the thorough mixing of the gas, and which has constituted the essential difficulty of specific heat measurements. In the present method the difficulty is avoided by never requiring to measure the exact temperature of the gas. Instead the temperature of the tube containing the gas is measured without in any way disturbing the flow.

PIV Analysis of Dynamic Velocity Profiles in Non-Newtonian Drilling Fluids Exposed to Oscillatory Motion

2018 ◽  
Author(s):  
Maduranga Amaratunga ◽  
Roar Nybø ◽  
Rune W. Time
Keyword(s):  
Low Frequency ◽  
Velocity Profiles ◽  
Liquid Column ◽  
Oscillatory Motion ◽  
Velocity Shear ◽  
Drilling Fluids ◽  
Cross Sectional ◽  
Low Frequencies ◽  
Wide Range ◽  
Dynamic Velocity

Drilling fluids experience a wide range of shear rates and oscillatory motion while circulating through the well and also during the operations for solids control. Therefore, it is important to investigate the influence of oscillatory fields on the velocity profiles, shear rate and resulting rheological condition of non-Newtonian polymers, which are additives in drilling fluids. In this paper, we present the dynamic velocity profiles within both Newtonian (deionized water) and non-Newtonian liquids (Polyanionic Cellulose – PAC) exposed to oscillatory motion. A 15 cm × 15 cm square cross-sectional liquid column was oscillated horizontally with very low frequencies (0.75–1.75 Hz) using a laboratory made oscillating table. The dynamic velocity profiles at the bulk of the oscillating liquid column were visualized by the Particle Image Velocimetry (PIV) method, where the motion of fluid is optically visualized using light scattering “seeding” particles. Increased frequency of oscillations lead to different dynamic patterns and ranges of velocity-shear magnitudes. The experiments are part of a comprehensive study aimed at investigating the influence of low frequency oscillations on particle settling in non-Newtonian drilling fluids. It is discussed, how such motion imposed on polymeric liquids influences both flow dynamics as well as local settling velocities of cuttings particles.

scholarly journals Assessment of the Effects of Superior Canal Dehiscence Location and Size on Intracochlear Sound Pressures

2014 ◽  
Vol 20 (1) ◽  
pp. 62-71 ◽  
Author(s):  
Marlien E.F. Niesten ◽  
Christof Stieger ◽  
Daniel J. Lee ◽  
Julie P. Merchant ◽  
Wilko Grolman ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Temporal Bone ◽  
Semicircular Canal ◽  
Low Frequency ◽  
Low Frequencies ◽  
Superior Canal Dehiscence ◽  
Superior Semicircular Canal ◽  
Wide Range ◽  
Before And After ◽  
Canal Dehiscence

Superior canal dehiscence (SCD) is a defect in the bony covering of the superior semicircular canal. Patients with SCD present with a wide range of symptoms, including hearing loss, yet it is unknown whether hearing is affected by parameters such as the location of the SCD. Our previous human cadaveric temporal bone study, utilizing intracochlear pressure measurements, generally showed that an increase in dehiscence size caused a low-frequency monotonic decrease in the cochlear drive across the partition, consistent with increased hearing loss. This previous study was limited to SCD sizes including and smaller than 2 mm long and 0.7 mm wide. However, the effects of larger SCDs (>2 mm long) were not studied, although larger SCDs are seen in many patients. Therefore, to answer the effect of parameters that have not been studied, this present study assessed the effect of SCD location and the effect of large-sized SCDs (>2 mm long) on intracochlear pressures. We used simultaneous measurements of sound pressures in the scala vestibuli and scala tympani at the base of the cochlea to determine the sound pressure difference across the cochlear partition - a measure of the cochlear drive in a temporal bone preparation - allowing for assessment of hearing loss. We measured the cochlear drive before and after SCDs were made at different locations (e.g. closer to the ampulla of the superior semicircular canal or closer to the common crus) and for different dehiscence sizes (including larger than 2 mm long and 0.7 mm wide). Our measurements suggest the following: (1) different SCD locations result in similar cochlear drive and (2) larger SCDs produce larger decreases in cochlear drive at low frequencies. However, the effect of SCD size seems to saturate as the size increases above 2-3 mm long and 0.7 mm wide. Although the monotonic effect was generally consistent across ears, the quantitative amount of change in cochlear drive due to dehiscence size varied across ears. Additionally, the size of the dehiscence above which the effect on hearing saturated varied across ears. These findings show that the location of the SCD does not generally influence the amount of hearing loss and that SCD size can help explain some of the variability of hearing loss in patients. i 2014 S. Karger AG, Basel

scholarly journals Millisecond pulsars at low frequencies

2017 ◽  
Vol 13 (S337) ◽  
pp. 311-312
Author(s):  
N. D. Ramesh Bhat ◽  
Steven E. Tremblay ◽  
Franz Kirsten
Keyword(s):  
South African ◽  
Southern Hemisphere ◽  
Low Frequency ◽  
Pulsar Emission ◽  
Millisecond Pulsars ◽  
Low Frequencies ◽  
Pulsar Timing ◽  
Wide Range ◽  
Propagation Effects ◽  
Murchison Widefield Array

AbstractLow-frequency pulsar observations are well suited for studying propagation effects caused by the interstellar medium (ISM). This is particularly important for millisecond pulsars (MSPs) that are part of high-precision timing applications such as pulsar timing arrays (PTA), which aim to detect nanoHertz gravitational waves. MSPs in the southern hemisphere will also be the prime targets for PTAs with the South African MeerKAT, and eventually with the SKA. The development of the Murchison Widefield Array (MWA) and the Engineering Development Array (EDA) brings excellent opportunities for low-frequency studies of MSPs in the southern hemisphere. They enable observations at frequencies from 50 MHz to 300 MHz, and can be exploited for a wide range of studies relating to pulsar emission physics and probing the ISM.

Threshold Firing Frequency–Current Relationships of Neurons in Rat Somatosensory Cortex: Type 1 and Type 2 Dynamics

2004 ◽  
Vol 92 (4) ◽  
pp. 2283-2294 ◽  
Author(s):  
T. Tateno ◽  
A. Harsch ◽  
H. P. C. Robinson
Keyword(s):  
Somatosensory Cortex ◽  
Low Frequency ◽  
Firing Frequency ◽  
Spike Generation ◽  
Low Frequencies ◽  
Subthreshold Oscillations ◽  
Wide Range ◽  
Rat Somatosensory Cortex

Neurons and dynamical models of spike generation display two different types of threshold behavior, with steady current stimulation: type 1 [the firing frequency vs. current ( f– I) relationship is continuous at threshold) and type 2 (discontinuous f– I)]. The dynamics at threshold can have profound effects on the encoding of input as spikes, the sensitivity of spike generation to input noise, and the coherence of population firing. We have examined the f– I and frequency–conductance ( f– g) relationships of cells in layer 2/3 of slices of young (15–21 DIV) rat somatosensory cortex, focusing in detail on the nature of the threshold. Using white-noise stimulation, we also measured firing frequency and interspike interval variability as a function of noise amplitude. Regular-spiking (RS) pyramidal neurons show a type 1 threshold, consistent with their well-known ability to fire regularly at very low frequencies. In fast-spiking (FS) inhibitory interneurons, although regular firing is supported over a wide range of frequencies, there is a clear discontinuity in their f– I relationship at threshold (type 2), which has not previously been highlighted. FS neurons are unable to support maintained periodic firing below a critical frequency fc, in the range of 10 to 30 Hz. Very close to threshold, FS cells switch irregularly between bursts of periodic firing and subthreshold oscillations. These characteristics mean that the dynamics of RS neurons are well suited to encoding inputs into low-frequency firing rates, whereas the dynamics of FS neurons are suited to maintaining and quickly synchronizing to gamma and higher-frequency input.

scholarly journals Time-Delay Vibration Reduction Control of 3-DOF Vehicle Model with Vehicle Seat

2021 ◽  
Vol 11 (20) ◽  
pp. 9426
Author(s):  
Kaiwei Wu ◽  
Chuanbo Ren ◽  
Yuanchang Chen
Keyword(s):  
Time Delay ◽  
Performance Optimization ◽  
Low Frequency ◽  
Active Suspension ◽  
Random Excitation ◽  
Feedback Gain ◽  
Time Interval ◽  
On The Road ◽  
The Stability ◽  
Vehicle Seat

Vehicles driving on the road continuously suffer low-frequency and high-intensity road excitation, which can cause the occupant feelings of tension and dizziness. To solve this problem, a three-degree-of-freedom vehicle suspension system model including vehicle seat is established and a linear function equivalent excitation method is proposed. The optimization of the random excitation is transformed into the optimization of constant force in a discrete time interval, which introduces the adaptive weighted particle swarm optimization algorithm to optimize the delay and feedback gain parameters in the feedback control of time delay. In this paper, the stability switching theory is used for the first time to analyze the stability interval of 3-DOF time-delay controlled active suspension, which ensures the stability of the control system. The numerical simulation results show that the algorithm can reduce vertical passenger acceleration and vehicle acceleration, respectively, by 13.63% and 28.38% on average, and 29.99% and 47.23% on random excitation, compared with active suspension and passive suspension based on inverse control. The effectiveness of the method to suppress road random interference is verified, which provides a theoretical reference for further study of suspension performance optimization with time-delay control.

scholarly journals Providing Invariance to Disturbing Effects in Rail Lines

2019 ◽  
pp. 152-168 ◽  
Author(s):  
Evgeniy M. Tarasov ◽  
Dmitry V. Zheleznov ◽  
Nicolay N. Vasin ◽  
Anna E. Tarasova
Keyword(s):  
Dynamic Range ◽  
Input Resistance ◽  
Indirect Measurement ◽  
Open Circuit ◽  
Time Interval ◽  
Informative Signal ◽  
Wide Range ◽  
Rail Line ◽  
The Stability

Introduction. The time interval systems for controlling train movement operated under the influence of significant industrial disturbances, interference from the electric current of traction rolling stocks, and significant climate changes that result in fluctuations of parameters of circuit elements. These factors lead to the appearance of internal disturbances. The fluctuations in a wide range of the conductivity of rail lines insulation are the main external disturbances leading to considerable changes of the informative parameter, the voltage at the output end of the rail line. At present, there are many methods for suppressing disturbances, which allow correcting fluctuations in the informative signal without deteriorating the quality of classification. The article deals with the problem of providing insensitivity of the output informative signal to the influence of disturbance by principles of coordinate compensation with a correcting link. Materials and Methods. To solve the problem, various methodologies of compensation for disturbances are considered in the paper; the method of coordinate compensation for disturbances at the input of a quadripole of rail lines is adopted as the main one. The equation of the transfer function of the correcting link is determined, assuming an indirect measurement of the input resistance of the rail line, which is a function of the conductivity of the insulation. Results. The article presents the results of the research of the invariant capabilities of the disturbance compensation principle. It is shown that disturbances compensation with a corrective link included at the input of a quadripole allows one to significantly reduce the dynamic range of the output informative signal change in each of the classes, i.e. classes have become more compact, and the quality of classification has become 5 times higher than in the absence of compensation of disturbances. Discussion and Conclusion. The results confirm the effectiveness of the proposed method for the coordinate compensation of disturbances in rail lines with an open circuit in the absence of the possibility for organizing feedback, a variable circuit in each of the classes of states, and the impossibility of creating a physical additional channel for the transmission of the disturbance. Using the proposed method in the construction of modern classifiers will significantly improve the stability of the functioning of train control systems; eliminate errors of the first kind, leading to unproductive idle train, and errors of the second kind, leading to accidents and crashes.

scholarly journals Polyaniline/Polystyrene Blends: In-Depth Analysis of the Effect of Sulfonic Acid Dopant Concentration on AC Conductivity Using Broadband Dielectric Spectroscopy

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Noora Al-Thani ◽  
Mohammad K. Hassan ◽  
Jolly Bhadra
Keyword(s):  
Dielectric Spectroscopy ◽  
Ac Conductivity ◽  
Sulfonic Acid ◽  
Low Frequency ◽  
Lone Pair ◽  
Interfacial Polarization ◽  
Low Frequencies ◽  
Broadband Dielectric Spectroscopy ◽  
Wide Range ◽  
Depth Analysis

This work presents an in-depth analysis of the alternating current (AC) conductivity of polyaniline-polystyrene (PANI-PS) blends doped with camphor sulfonic acid (CSA) and prepared using an in situ dispersion polymerization technique. We prepared the blends using fixed ratios of PS to PANI while varying the concentration of the CSA dopant. The AC conductivity of the blends was investigated using broadband dielectric spectroscopy. Increasing CSA resulted in a decrease in the AC conductivity of the blends. This behaviour was explained in terms of the availability of a lone pair of electrons of the NH groups in the polyaniline, which are typically attacked by the electron-withdrawing sulfonic acid groups of CSA. The conductivity is discussed in terms of changes in the dielectric permittivity storage (ε′), loss (ε′′), and modulus (M′′) of the blends over a wide range of temperatures. This is linked to the glass transition temperature of the PANI. Dielectric spectra at low frequencies indicated the presence of pronounced Maxwell-Wagner-Sillars (MWS) interfacial polarization, especially in samples with a low concentration of CSA. Electrical conduction activation energies for the blends were also calculated using the temperature dependence of the direct current (DC) conductivity at a low frequency (σdc), which exhibit an Arrhenius behaviour with respect to temperature. Scanning electron microscopy revealed a fibrous morphology for the pure PANI, while the blends showed agglomeration with increasing CSA concentrations.

scholarly journals Numerical validation of an analytical seal flutter model

2021 ◽  
Vol 5 ◽  
pp. 191-201
Author(s):  
Michele Greco ◽  
Roque Corral
Keyword(s):  
Analytical Model ◽  
Fluid Dynamic ◽  
Stability Limit ◽  
Labyrinth Seal ◽  
Analytical Models ◽  
Mode Shapes ◽  
Labyrinth Seals ◽  
Low Frequencies ◽  
Wide Range ◽  
The Stability

An analytical model to describe the flutter onset of straight-through labyrinth seals has been numerically validated using a frequency domain linearized Navier-Stokes solver. A comprehensive set of simulations has been conducted to assess the stability criterion of the analytical model originally derived by Corral and Vega (2018), “Conceptual Flutter Analysis of Labyrinth Seals Using Analytical Models - Part I: Theoretical Support,” ASME J. Turbomach., 140 (12), pp. 121006. The accuracy of the model has been assessed by using a simplified geometry consisting of a two-fin straight-through labyrinth seal with identical gaps. The effective gaps and the kinetic energy carried over are retained and their effects on stability are evaluated. It turns out that is important to inform the model with the correct values of both parameters to allow a proper comparison with the numerical simulations. Moreover, the non-isentropic perturbations included in the formulations are observed in the simulations at relatively low frequencies whose characteristic time is of the same order as the discharge time of the seal. This effect is responsible for the bending of the stability limit in the <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mn>0</mml:mn><mml:mi>t</mml:mi><mml:mi>h</mml:mi></mml:math></inline-formula> ND stability map obtained both in the model and the simulations. It turns out that the analytical model can predict accurately the stability of the seal in a wide range of pressure ratios, vibration mode-shapes, and frequencies provided that this is informed with the fluid dynamic gaps and the energy carried over to the downstream fin from a steady RANS simulation. The numerical calculations show for the first time that the model can be used to predict accurately not only the trends of the work-per-cycle of the seal but also quantitative results.

Coupling of sympathetic nerve traffic and BP at very low frequencies is mediated by large-amplitude events

2003 ◽  
Vol 284 (3) ◽  
pp. R802-R810 ◽  
Author(s):  
Don E. Burgess ◽  
David C. Randall ◽  
Richard O. Speakman ◽  
David R. Brown
Keyword(s):  
Sympathetic Nerve ◽  
Wavelet Transforms ◽  
Large Amplitude ◽  
Low Frequency ◽  
Functional Connection ◽  
Low Frequencies ◽  
Very Low Frequency ◽  
Arterial Blood ◽  
Wide Range ◽  
Transient Events

This study explores the functional association between renal sympathetic nerve traffic (NT) and arterial blood pressure (BP) in the very-low-frequency range (i.e., <0.1 Hz). NT and BP ( n = 6) or BP alone ( n = 17) was recorded in unanesthetized rats ( n = 6). Data were collected for 2–5 h, and wavelet transforms were calculated from data epochs of up to 1 h. From these transforms, we obtained probability distributions for fluctuation amplitudes over a range of time scales. We also computed the cross-wavelet power spectrum between NT and BP to detect the occurrence in time of large-amplitude transient events that may be important in the autonomic regulation of BP. Finally, we computed a time sequence of cross correlations between NT and BP to follow the relationship between NT and BP in time. We found that NT and BP follow comparable self-similar scaling relationships (i.e., NT and BP fluctuations exhibit a certain type of power law behavior). Scaling of this nature 1) points to underlying dynamics over a wide range of scales and 2) is related to large-amplitude events that contribute to the very-low-frequency variability of NT and BP. There is a strong correlation between NT and BP during many of these transient events. These strong correlations and the uniformity in scaling imply a functional connection between these two signals at frequencies where we previously found no connection using spectral coherence.

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