scholarly journals The kinetic energy of electrons emitted from a hot tungsten filament

1923 ◽  
Vol 102 (719) ◽  
pp. 734-751 ◽  
Keyword(s):  
Kinetic Energy ◽  
Electric Fields ◽  
Average Energy ◽  
Current Method ◽  
Absolute Temperature ◽  
Electronic Charge ◽  
Normal Velocity ◽  
Electric And Magnetic Fields ◽  
The Individual ◽  
Good Agreement

The first measurements of the kinetic energy of the electrons emitted from hot bodies were made by Prof. Richardson and Dr. F. C. Brown in 1907-1909. These experiments showed that the velocity distribution among the emitted electrons was in close agreement with Maxwell’s law of distribution for a gas, of molecular weight equal to that of the electrons, in thermal equilibrium at the temperature of the source. In the simple unidimensional case where the cathode and anode form parallel planes of indefinite extent, the current which flows against a retarding potential, V, depends only on the normal velocity component and with Maxwell’s distribution is given by i = i 0 e -2 hℯ V , where h = 1/2 k T, k being Boltzmann’s constant, T the absolute temperature of the source, and e is the electronic charge. The mean kinetic energy of the electrons in the stream is given by the quantity 2 k T. These experiments showed that with platinum, which was the only metal tried, the exponential equation was very accurately obeyed, and the average of eight determinations of k agreed with the theoretical value to within a fraction of 1 per cent. although the individual determinations differed from the average by almost ±20 per cent. These experiments were,- however, subject to a number of defects, the most important of these being due to the presence of electric and magnetic fields caused by the electric currents used in heating the source. Schottky carried out some experiments in 1914, and he used the case of a filament surrounded by a concentric cylindrical anode. The effects of the magnetic and electric fields of the current used to heat the filament were avoided by an interrupted current method due to v. Baeyer. Schottky’s experiments were made with carbon and tungsten, and the data were in good agreement with the requirements of Maxwell’s law, except that the average energy of the emitted electrons was in every case in excess of the value calculated from the temperature of the source. This, however, was estimated from the value of the saturation current using the emission constants given by other authors. This makes his temperature determinations very uncertain, because of the known large effects on the emission of traces of certain contaminants.

scholarly journals Experiments on electron emission from hot bodies

1921 ◽  
Vol 98 (693) ◽  
pp. 374-394 ◽  
Keyword(s):  
Velocity Distribution ◽  
Plane Surface ◽  
Absolute Temperature ◽  
Electronic Charge ◽  
Normal Velocity ◽  
Hot Metal ◽  
Exponential Equation ◽  
Electric And Magnetic Fields ◽  
The Individual ◽  
Obvious Source

The first measurements of the kinetic energy of the electrons emitted from hot bodies were made by myself, partly in collaboration with Dr. F. C. Brown, in 1907-1909. The completed experiments were practically confined to platinum as a source of emission, largely on account of technical difficulties experienced with other materials. These experiments showed that the velocity distribution among the emitted electrons was in close agreement with Maxwell’s law of distribution for a gas, of molecular weight equal to that of the electrons, in thermal equilibrium at the temperature of the source. This applies both to the component of velocity normal to the emitting surface and to that in a perpendicular direction. In the simple unidimensional case, where the cathode and anode form parallel planes of indefinite extent, the current, i , which flows against a retarding potential, V, depends only on the normal velocity component, and with Maxwell’s distribution is given by i = i 0 exp. ( — α V), (1) where α = e / k T, e being the electronic charge, k the Boltzmann constant, T the absolute temperature, and i 0 the current when V = 0. The inverse of the factor α is in fact a measure of the energy with which the electrons are ejected from the surface. The experiments showed that, with platinum under a very considerable variety of conditions, the exponential equation was obeyed with considerable accuracy. The average of eight determinations of k / e by this method agreed with the theoretical value to within a fraction of 1 per cent., although the individual determinations differed from the average by almost 20 per cent.These variations were undoubtedly large, and in excess of expectation from any obvious source of experimental error. At the same time, these experi­ments were subject to a number of defects such as might arise from (1) inequalities in the temperature of the source, (2) unsatisfactory methods of determining these temperatures, (3) the difficulty of realising a truly plane surface of hot metal, and (4) the presence of the electric and magnetic fields caused by the electric currents used in heating the source. In view of these and other known sources of uncertainty, the foregoing experiments, as a whole, were taken to indicate that the electrons emitted from platinum under the conditions to which the tests were subjected, possessed a velocity distribution in accordance with Maxwell’s law.

A CALORIMETRIC DETERMINATION OF THE AVERAGE KINETIC ENERGY OF THE FRAGMENTS FROM U235 FISSION

1955 ◽  
Vol 33 (7) ◽  
pp. 357-363 ◽  
Author(s):  
R. B. Leachman ◽  
W. D. Schafer
Keyword(s):  
Kinetic Energy ◽  
Average Energy ◽  
Fission Products ◽  
Average Kinetic Energy ◽  
U235 Fission ◽  
Induced Fission ◽  
Differential Calorimeter ◽  
Calorimetric Determination ◽  
Good Agreement

The average heat of thermal-neutron induced fission of U235 has been measured by a differential calorimeter. The average energy per fission observed by the calorimeter was 170.1 ± 1.2 Mev. On the basis of the thicknesses of the calorimeter materials and the theoretical energy loss equation, the β energy per fission observed by the calorimeter is 3.0 ± 1 Mev. and, on the same basis, the γ and neutron energy observed is negligible. The resulting 167.1 ± 1.6 Mev. for the average kinetic energy of the fission products is shown to be in good agreement with less direct determinations of this quantity.

Elastic Constants of Nematic Liquid Crystals

1972 ◽  
Vol 27 (6) ◽  
pp. 966-976 ◽  
Author(s):  
Hans Gruler ◽  
Terry J. Scheffer ◽  
Gerhard Meier
Keyword(s):  
Magnetic Fields ◽  
Electric Fields ◽  
Detailed Comparison ◽  
Theoretical Treatment ◽  
Electrical Capacitance ◽  
Normal Deformation ◽  
Electric And Magnetic Fields ◽  
The Magnetic Field ◽  
Dynamic Phenomena ◽  
Good Agreement

Abstract We present a theoretical treatment and give experimental observations of the deformation that occurs in a nematic liquid crystal when electric or magnetic fields are applied. We consider only normal deformations in the nematic material where fluid flow and other dynamic phenomena play no role. Three important sample geometries are considered in the magnetic field, and the experimentally observed deformations are in good agreement with theory. The normal deformation induced by electric fields is of interest from a device standpoint, and we give a solution for the deformation that is valid even for large dielectric anisotropics. This solution has been experimentally verified. We give a detailed comparison of the distortions produced by electric and magnetic fields and show that the deformations are of a similar form even though the field is nonuniform in the electric case. The change in birefringence and electrical capacitance as a function of distortion is discussed as a means of observing the deformation.

Simulation-based assessment of coupled frequency response of magneto-electro-elastic auxetic multifunctional structures subjected to various electromagnetic circuits

2021 ◽  
pp. 146442072110219
Author(s):  
Vinyas Mahesh ◽  
Vishwas Mahesh ◽  
Dineshkumar Harursampath ◽  
Ahmed E Abouelregal
Keyword(s):  
Electric Fields ◽  
Solid Mechanics ◽  
Natural Frequencies ◽  
Comsol Multiphysics ◽  
Simulation Based ◽  
Electric And Magnetic Fields ◽  
Auxetic Structures ◽  
Triangular Elements ◽  
Benchmark Solutions ◽  
Free Vibration Response

This article deals with the modeling of magneto-electro-elastic auxetic structures and developing a methodology in COMSOL Multiphysics® to assess the free vibration response of such structures when subjected to various electromagnetic circuit conditions. The triple energy interaction between elastic, magnetic, and electric fields are established in the COMSOL Multiphysics® using structural mechanics and electromagnetic modules. The multiphase magneto-electro-elastic material with different percentages of piezoelectric and piezomagnetic phases are used as the material. In the solid mechanics module, the piezoelectric and piezomagnetic materials were created in stress-charge and stress-magnetization forms, respectively. The electric and magnetic fields are defined in COMSOL Multiphysics® through electromagnetic equations. Further, the customized controlled meshing constituted of free tetrahedral and triangular elements is adapted to trade-off between the accuracy and the computational expenses. The eigenvalue analysis is performed to obtain the natural frequencies of the MEE re-entrant auxetic structures. Also, the efficiency of smart auxetic structures over conventional honeycomb structures is presented throughout the manuscript. In addition, the discrepancy in the natural frequencies of the structures considering coupled and uncoupled state is also illustrated. It is believed that the modeling procedure and its outcomes serve as benchmark solutions for further design and analysis of smart auxetic magneto-electro-elastic structures.

Heat Transfer Committee and Turbomachinery Committee Best Paper of 1996 Award: The Path to Predicting Bypass Transition

1997 ◽  
Vol 119 (3) ◽  
pp. 405-411 ◽  
Author(s):  
R. E. Mayle ◽  
A. Schulz
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Energy Equation ◽  
Free Stream ◽  
Bypass Transition ◽  
Turbulence Level ◽  
Free Stream Turbulence ◽  
Energy Profiles ◽  
Computer Codes ◽  
Good Agreement

A theory is presented for calculating the fluctuations in a laminar boundary layer when the free stream is turbulent. The kinetic energy equation for these fluctuations is derived and a new mechanism is revealed for their production. A methodology is presented for solving the equation using standard boundary layer computer codes. Solutions of the equation show that the fluctuations grow at first almost linearly with distance and then more slowly as viscous dissipation becomes important. Comparisons of calculated growth rates and kinetic energy profiles with data show good agreement. In addition, a hypothesis is advanced for the effective forcing frequency and free-stream turbulence level that produce these fluctuations. Finally, a method to calculate the onset of transition is examined and the results compared to data.

scholarly journals The viscosity of strong electrolytes measured by a differential method

1934 ◽  
Vol 145 (855) ◽  
pp. 475-488 ◽  
Keyword(s):  
Dielectric Constant ◽  
Empirical Equation ◽  
Relative Viscosity ◽  
Absolute Temperature ◽  
Differential Method ◽  
Theoretical Equation ◽  
Electronic Charge ◽  
Accurate Data ◽  
Avogadro’S Number ◽  
Strong Electrolytes

Until quite recently no satisfactory equation had been obtained for the representation of the viscosity of dilute solutions of strong electrolytes. An empirical equation was recently proposed by Jones and Dole to fit the only accurate data then available. Their equation may be represented thus : η = 1 + A √ c + B c , η = relative viscosity of the solution c = concentration in moles per litre A and B are constants. Jones and Dole realized that the coefficient A is due to interionic forces and in a series of later publications Falkenhagen, Dole and Vernon have deduced a theoretical equation giving values of A in terms of well-known physical constants. Their complete equation may be written η = 1 + ε √N v 1 z 1 /30η 0 √1000D k T ( z 1 + z 2 ) 4 π × [¼ μ 1 z 2 + μ 2 z 1 / μ 1 μ 2 - z 1 z 2 (μ 1 - μ 2 ) 2 /μ 1 μ 2 (√μ 1 z 1 + μ 2 z 2 + √(μ 1 + μ 2 ) ( z 1 + z 2 ) ) 2 ]√ c , where N = Avogadro's number v 1 , v 2 = numbers of ions z 1 , z 2 = valencies of ions μ 1 , μ 2 = absolute mobilities of ions D = dielectric constant of solvent k = Boltzmann's constant ε = electronic charge η 0 = viscosity of solvent T = absolute temperature.

Expressions for the effective diffusivity in materials with interphase boundaries

2004 ◽  
Vol 819 ◽  
Author(s):  
Irina V. Belova ◽  
Graeme E. Murch
Keyword(s):  
Polycrystalline Material ◽  
Effective Diffusivity ◽  
Poor Agreement ◽  
Two Phase ◽  
Interphase Boundaries ◽  
Long Time ◽  
Simulation Results ◽  
The Individual ◽  
Individual Grains ◽  
Good Agreement

AbstractWe address the problem of calculating the long-time-limit effective diffusivity in stable two- phase polycrystalline material. A phenomenological model is used where the high diffusivity interphase boundaries are treated as connected “coatings” of the individual grains. Derivation of expressions for the effective diffusivity with segregation is made along Maxwell lines. Monte Carlo simulation using lattice-based random walks is used to test the validity of the expressions. It is shown that for the case analysed the derived expressions for the effective diffusivity are in very good agreement with simulation results. The equivalent of the Hart equation is also derived. It is shown to be in poor agreement with simulation results.

Rheological Properties of Tomato Concentrate

2008 ◽  
Vol 4 (7) ◽  
Author(s):  
Manish Dak ◽  
Radha Charan Verma ◽  
S N A Jaaffrey
Keyword(s):  
Rheological Properties ◽  
Absolute Temperature ◽  
Power Law Model ◽  
Arrhenius Model ◽  
Rotational Viscometer ◽  
Consistency Coefficient ◽  
Flow Behaviour Index ◽  
Different Temperatures ◽  
Wide Gap ◽  
Good Agreement

Rheological properties of tomato concentrate were evaluated using a wide-gap rotational viscometer (Brookfield Engineering Laboratories: Model LVDV-II) at different temperatures of 20, 30, 40, 50, and 60oC, at concentration of 18, 12.18 and 8.04 % total solids, and at appropriate shear rate(1-100 RPM). The power law model was fitted to the experimental results. The values of flow behaviour index (n) were found less than unity (0.23 to 0.82) at all the temperature and the concentration indicating shear-thinning (pseudoplasticity) behaviour of the concentrate. The correlation between the observed consistency coefficient ranging from 0.09 to 65.87 Pa.sn and the inverse absolute temperature has been exhibited by Arrhenius model. Consistency coefficient increased exponentially with increase in the concentration. Statistical model was used for prediction of the consistency coefficient as a function of temperature and concentration which showed a good agreement (r2=0.99) between experimental and theoretical values. The magnitude of activation energy were found to be in the range of 8.6 to 14.08 kJ/mol.K.

scholarly journals Accuracy of Wind Observations from Open-Ocean Buoys: Correction for Flow Distortion

2020 ◽  
Vol 37 (4) ◽  
pp. 687-703 ◽  
Author(s):  
Michael Schlundt ◽  
J. Thomas Farrar ◽  
Sebastien P. Bigorre ◽  
Albert J. Plueddemann ◽  
Robert A. Weller
Keyword(s):  
Flow Distortion ◽  
Error Sources ◽  
Neutral Winds ◽  
Flow Simulations ◽  
Temporal Sampling ◽  
Empirical Correction ◽  
The Individual ◽  
Wind Vane ◽  
Subsequent Comparison ◽  
Good Agreement

AbstractThe comparison of equivalent neutral winds obtained from (i) four WHOI buoys in the subtropics and (ii) scatterometer estimates at those locations reveals a root-mean-square (RMS) difference of 0.56–0.76 m s−1. To investigate this RMS difference, different buoy wind error sources were examined. These buoys are particularly well suited to examine two important sources of buoy wind errors because 1) redundant anemometers and a comparison with numerical flow simulations allow us to quantitatively assess flow distortion errors, and 2) 1-min sampling at the buoys allows us to examine the sensitivity of buoy temporal sampling/averaging in the buoy–scatterometer comparisons. The interanemometer difference varies as a function of wind direction relative to the buoy wind vane and is consistent with the effects of flow distortion expected based on numerical flow simulations. Comparison between the anemometers and scatterometer winds supports the interpretation that the interanemometer disagreement, which can be up to 5% of the wind speed, is due to flow distortion. These insights motivate an empirical correction to the individual anemometer records and subsequent comparison with scatterometer estimates show good agreement.

scholarly journals Development of multiplex real-time RT-PCR assay for the detection of SARS-CoV-2

PLoS ONE ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. e0250942
Author(s):  
Huseyin Tombuloglu ◽  
Hussein Sabit ◽  
Ebtesam Al-Suhaimi ◽  
Reem Al Jindan ◽  
Khaled R. Alkharsah
Keyword(s):  
Real Time ◽  
Single Gene ◽  
False Negative ◽  
Diagnostic System ◽  
Virus Detection ◽  
Current Method ◽  
Pcr Method ◽  
Polymerase Chain ◽  
Positive Results ◽  
Good Agreement

The outbreak of the new human coronavirus SARS-CoV-2 (also known as 2019-nCoV) continues to increase globally. The real-time reverse transcription polymerase chain reaction (rRT-PCR) is the most used technique in virus detection. However, possible false-negative and false-positive results produce misleading consequences, making it necessary to improve existing methods. Here, we developed a multiplex rRT-PCR diagnostic method, which targets two viral genes (RdRP and E) and one human gene (RP) simultaneously. The reaction was tested by using pseudoviral RNA and human target mRNA sequences as a template. Also, the protocol was validated by using 14 clinical SARS-CoV-2 positive samples. The results are in good agreement with the CDC authorized Cepheid`s Xpert® Xpress SARS-CoV-2 diagnostic system (100%). Unlike single gene targeting strategies, the current method provides the amplification of two viral regions in the same PCR reaction. Therefore, an accurate SARS-CoV-2 diagnostic assay was provided, which allows testing of 91 samples in 96-well plates in per run. Thanks to this strategy, fast, reliable, and easy-to-use rRT-PCR method is obtained to diagnose SARS-CoV-2.

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