Dielectric dissipation relative

In the high-temperature part, opposite effects are observed in mechanics and dielectrics, except for MGIM76. Indeed, the decrease of mechanical dissipation (relatively to the MMA content response) increases with increasing temperature, but it is the opposite with dielectric dissipation. For MGIM76, in both experiments, the dissipation is larger than expected from the MMA content. 

IEC60247 Measurements of relative permittivity, dielectric dissipation. Eactor and DC... 

As indicated earlier, those properties that govern whether a material may be successfully heated by a dielectric or microwave field are the dielectric properties relative dielectric constant s, loss tangent or dissipation factor (tan 8), and the loss factor s". 

Thus far we have discussed the direct mechanism of dissipation, when the reaction coordinate is coupled directly to the continuous spectrum of the bath degrees of freedom. For chemical reactions this situation is rather rare, since low-frequency acoustic phonon modes have much larger wavelengths than the size of the reaction complex, and so they cannot cause a considerable relative displacement of the reactants. The direct mechanism may play an essential role in long-distance electron transfer in dielectric media, when the reorganization energy is created by displacement of equilibrium positions of low-frequency polarization phonons. Another cause of friction may be anharmonicity of solids which leads to multiphonon processes. In particular, the Raman processes may provide small energy losses. 

Relative to microelectronic applications, the out-of-plane dielectric constant for BPDA-PFMB films measmed after aging at 50% relative humidity for 48 h at 23°C was between 2.8 and 2.9 (0.1 kHz to 1 MHz) (ASTM D-150-81These values are considerably lower than that of commercial polyimides such as PMDA-ODA (pyromellitic dianhydride, PMDA) (s = 3.5 at 1 kHz and 3.3 at 10 MHz). The dielectric constant and tan 8 (dissipation factor) were temperature- and frequency-dependent. The dielectric constant, which was independent of temperature until near 210°C increased above this point until a frequency-dependent maximum was reached at about 290°C. The dissipation factor, which was also independent of temperatme below 200°C, underwent a rapid increase with no maximum between 200 and 400°C owing to ion conductivity. The temperatme at which this increase occurred increased as the frequency increased. The films also... 

ASTM D1531, 2001. Standard test methods for relative permittivity (dielectric constant) and dissipation factor by fluid displacement procedures. 

In general, fluoropolymers possess the unique combination of high thermal stability, chemical inertness, unusual surface properties, low dielectric constants and dissipation factors, low water absorptivities, excellent weatherability and low flammabilities. Therefore there appears to be an ever-increasing market for fluoropolymers in spite of their relatively high cost [211,212],... 

A disc capacitor of thickness 1 mm carries circular electrodes of diameter 1 cm. The real and imaginary parts of the relative permittivity of the dielectric are 3000 and 45 respectively. Calculate the capacitance and the power dissipated in the dielectric when a sinusoidal voltage of amplitude 50 V and frequency 1 MHz is applied to the capacitor. [Answer 245 mW]... 

A higher-permittivity dielectric based on CaTi03 is sometimes used. It has a relative permittivity of about 140 and a dissipation factor of 2 x 10 4. The TCC is about double that of rutile-based dielectrics. 

This equation gives the mean-square value of the voltage appearing across the terminals of a capadtor filled with a dielectric of zero-frequency relative permittivity, s in terms of Co, the capacitance without a dielectric, and the absolute temperature, T. This noise voltage is caused by the thermally induced dipole-moment fluctuations which are themselves inextricably bound up with the dissipative processes. That this is so is indicated by the fact that equation (42) applied to aJ,to) leads to the relation... 

The relative permittivity of a medium, K=Kr-iKi, is in general a complex quantity whose real part k, (also known as the dielectric constant) is associated with the increase in capacitance due to the introduction of a dielectric. The imaginary component tq is associated with mechanisms that contribute to the energy dissipation in the system, due to viscous damping of the rotational motion of the molecules in alternating fields this effect is frequency dependent. The experimental setup consisted of a parallel plate capacitor of... 

The relative contribution of these two heating mechanisms depends on the mobility and concentration of the sample ions and on the relaxation time of the sample. If the ion mobility and concentration of the sample ions are low, then sample heating will be entirely dominated by dipole rotation. On the other hand, as the mobility and concentration of the sample ions increase, microwave heating will be dominated by ionic conduction and the heating time will be independent of the relaxation time of the solution. As the ionic concentration increases, the dissipation factor will increase and the heating time decrease. The heating time depends not only on the dielectric absorptivity of the sample but also on the microwave system design and the sample size. 

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