Sentence examples for are often not valid from inspiring English sources

Standard methods for generating randomness rely on assumptions about the devices that are often not valid in practice.

These assumptions are often not valid in case of NORM (Naturally Occurring Radioactive Materials) where long term lack of secular equilibrium in the uranium and/or thorium decay series is often observed.

For short fibre polymer composites such as chopped strand mat laminates (CSM), glass mat thermoplastics (GMT) and sheet moulding compounds (SMC), conventional methods to measure fracture energy are often not valid since linear elastic fracture mechanics (LEFM) criteria are not fulfilled.

This hypothesis is often not valid: AC losses induce temperature increases.

In this work, theoretical and experimental evidence is presented to show that a Bruggeman exponent of 1.5 is often not valid for real electrodes or separator materials.

If migrants fall seriously ill, they have little choice but to go back to their villages; their government-subsidised rural medical insurance is often not valid in a different province (or even, until last year, in a different part of Henan).

For conventional well testing which is carried out over several days or several weeks, reservoir properties are usually assumed to be constant, but this assumption is often not valid for analyzing long-term transient pressure data acquired from a permanent down-hole gauge, which can record down-hole transient pressure data for several years.

This assumption is often not valid due to channel estimation errors and/or feedback delays.

Hence the common perception (based upon all our experience in conventional enzymology) that enzymes are more efficient catalysts than chemical catalysts is often not valid in non-aqueous enzymology.

However, registration of smoking is often not valid or even omitted.

For higher frequencies or larger sample sizes, and equivalently for targets with high contrast relative to their background, the solution m = 0 is often not valid and a proper image can only be obtained if the phase of the signals at each receiver is unwrapped.