Calcul et mesure des forces et couples appliqués à un cristal uniaxe traversé par l'onde extraordinaire

1974 ◽  
Vol 52 (19) ◽  
pp. 1903-1913 ◽  
Author(s):  
Gérald Roosen ◽  
Christian Imbert
Keyword(s):  
Poynting Vector ◽  
Extraordinary Wave ◽  
Momentum Density ◽  
Experimental Results ◽  
Variable Pressure ◽  
Anisotropic Crystal ◽  
Torque Measurements ◽  
Maxwell Tensor

We derive from the Maxwell tensor the forces and torques applied to a uniaxial anisotropic crystal when an extraordinary wave passes through it, and we show that the momentum to be associated with the wave in the crystal is collinear with the Poynting vector. Next, we present experimental results of torque measurements using, successively, two uniaxial anisotropic crystals placed inside a variable pressure container. We finally compare our results with those obtained by other authors and show that, according to the types of experiments, either Abraham's or Minkowski's momentum density will appear. [Translated by the journal]

Experimental Study of a Variable Pressure Damper on Automotive Valve Motion

1996 ◽  
Author(s):  
Jin-Jang Liou ◽  
Grodrue Huang ◽  
Wensyang Hsu
Keyword(s):  
Experimental Study ◽  
Friction Coefficient ◽  
Friction Force ◽  
High Speed ◽  
Experimental Results ◽  
Variable Pressure ◽  
Friction Forces ◽  
Valve Spring ◽  
Valve Motion

Abstract A variable pressure damper (VPD) is used here to adjusted the friction force on the valve spring to investigate the relation between the friction force and the valve bouncing phenomenon. The friction force on the valve spring is found experimentally, and the corresponding friction coefficient is also determined. Dynamic valve displacements at different speeds with different friction forces are calibrated. Bouncing and floating of the valve are observed when the camshaft reaches high speed. From the measured valve displacement, the VPD is shown to have significant improvement in reducing valve bouncing distance and eliminating floating. However, experimental results indicate that the valve bouncing can not be eliminated completely when the camshaft speed is at 2985 rpm.

scholarly journals Polyhydroxybutyrate Production from Natural Gas in A Bubble Column Bioreactor: Simulation Using COMSOL

2019 ◽  
Vol 6 (3) ◽  
pp. 84 ◽  
Author(s):  
Moradi ◽  
Rashedi ◽  
Mofradnia ◽  
Khosravi-Darani ◽  
Ashouri ◽  
...  
Keyword(s):  
Natural Gas ◽  
Bubble Column ◽  
Biomass Concentration ◽  
Volume Ratio ◽  
Momentum Density ◽  
Experimental Results ◽  
Bubble Column Bioreactor ◽  
Phb Production ◽  
Column Bioreactor ◽  
Transfer Momentum

In this study, the simulation of microorganism ability for the production of poly-β-hydroxybutyrate (PHB) from natural gas (as a carbon source) was carried out. Based on the Taguchi algorithm, the optimum situations for PHB production from natural gas in the columnar bubble reactor with 30 cm length and 1.5 cm diameter at a temperature of 32 °C was evaluated. So, the volume ratio of air to methane of 50:50 was calculated. The simulation was carried out by COMSOL software with two-dimensional symmetric mode. Mass transfer, momentum, density-time, and density-place were investigated. The maximum production of biomass concentration reached was 1.63 g/L, which shows a 10% difference in contrast to the number of experimental results. Furthermore, the consequence of inlet gas rate on concentration and gas hold up was investigated Andres the simulation results were confirmed to experimental results with less than 20% error.

scholarly journals Relativistic Rotating Electromagnetic Fields

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
H. Vargas-Rodríguez ◽  
A. Gallegos ◽  
M. A. Muñiz-Torres ◽  
H. C. Rosu ◽  
P. J. Domínguez
Keyword(s):  
Electromagnetic Field ◽  
Electromagnetic Fields ◽  
Symmetry Axis ◽  
Poynting Vector ◽  
Momentum Density ◽  
Axially Symmetric ◽  
Speed Of Light ◽  
Vector Form ◽  
Magnetic Dipoles ◽  
Axis Of Symmetry

In this work, we consider axially symmetric stationary electromagnetic fields in the framework of special relativity. These fields have an angular momentum density in the reference frame at rest with respect to the axis of symmetry; their Poynting vector form closed integral lines around the symmetry axis. In order to describe the state of motion of the electromagnetic field, two sets of observers are introduced: the inertial set, whose members are at rest with the symmetry axis; and the noninertial set, whose members are rotating around the symmetry axis. The rotating observers measure no Poynting vector, and they are considered as comoving with the electromagnetic field. Using explicit calculations in the covariant 3 + 1 splitting formalism, the velocity field of the rotating observers is determined and interpreted as that of the electromagnetic field. The considerations of the rotating observers split in two cases, for pure fields and impure fields, respectively. Moreover, in each case, each family of rotating observers splits in two subcases, due to regions where the electromagnetic field rotates with the speed of light. These regions are generalizations of the light cylinders found around magnetized neutron stars. In both cases, we give the explicit expressions for the corresponding velocity fields. Several examples of relevance in astrophysics and cosmology are presented, such as the rotating point magnetic dipoles and a superposition of a Coulomb electric field with the field of a point magnetic dipole.

Experimental Study of a Variable Pressure Damper on an Automotive Valve Train

1998 ◽  
Vol 120 (2) ◽  
pp. 279-281 ◽  
Author(s):  
Jin Jang Liou ◽  
Grodrue Huang ◽  
Wensyang Hsu
Keyword(s):  
Experimental Study ◽  
Friction Force ◽  
Frictional Force ◽  
Component Separation ◽  
Experimental Results ◽  
Valve Train ◽  
Variable Pressure ◽  
Valve Spring ◽  
High Speeds ◽  
Speed Range

A variable pressure damper (VPD) is proposed here to adjusted the friction force on the valve spring to investigate the relation between the friction force and the valve train. Valve bounce, component separation, spring vibration are observed in the testing. The VPD is shown to have significant improvement in reducing valve bouncing distance and surge vibration under 2985 rpm. Also, experimental results indicate that the component separation becomes more imminent at high speeds with larger damping forces. Here, in certain speed range, a proper frictional force provided by VPD is shown to be able to eliminate bouncing completely without causing component separation.

Contact Force Measurements Under a Brush Seal

1995 ◽  
Author(s):  
Christopher A. Long ◽  
Yannis Marras
Keyword(s):  
Theoretical Model ◽  
Contact Force ◽  
Experimental Results ◽  
Experimental Techniques ◽  
Force Measurements ◽  
Rotating Shaft ◽  
Simple Theoretical Model ◽  
Brush Seal ◽  
Torque Measurements ◽  
Theoretical Predictions

This paper discusses results of experiments carried out to measure the bristle contact force of a brush seal on a shaft. Two separate experimental techniques were used: i) indirectly through torque measurements and ii) directly using a force blade located under the bristle tips. The tests were conducted on a non-rotating shaft having a nominal diameter of 122 mm, with static radial interferences of 0.4, 0.2, 0.1 and 0.05 mm; and for the range of pressure ratios 1 to 4.5. The experimental results obtained from these measurements are compared with predictions from a simple theoretical model. Although there are some large differences, the experimental results do show some agreement with the theoretical predictions. However, both this current simple theoretical model and the experiments have their limitations. Despite these shortcomings, the experimental results are considered to support the qualitative value of the current theoretical model.

Electromagnetic momentum density and the Poynting vector in static fields

1994 ◽  
Vol 62 (1) ◽  
pp. 33-41 ◽  
Author(s):  
Francis S. Johnson ◽  
Bruce L. Cragin ◽  
R. Richard Hodges
Keyword(s):  
Poynting Vector ◽  
Momentum Density ◽  
Electromagnetic Momentum
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