The phrase "are often very weak" is correct and usable in written English.
It can be used to describe something that frequently lacks strength or effectiveness.
Example: "The arguments presented in the debate are often very weak, failing to convince the audience."
Alternatives: "tend to be quite feeble" or "are frequently lacking in strength."
De-noising and extraction of the weak signature are crucial to fault prognostics in which case features are often very weak and masked by noise.
When you look at the PCR data on all the recent tests, they are often very weak signals.
Our measurement (detailed results in Section 3) demonstrates that, due to highrises along two sides of the roads, the GPS signals are often very weak and unstable, and in some complicated road segments (e.g., tunnels and underground), the GPS signals are totally blocked.
The use of tissue-specific promoters allows for neuron-restricted gene expression, even though gene expression driven by these promoters is often very weak.
Further complicating the situation, Orad explains, is "the fact that the cyber-attack's signal is often very weak and obstructed by a lot of organizational noise, i.e. there will only be a very slight change in patterns recognizable".
Further complicating the situation, Orad explains, is "the fact that the cyber-attack's signal is often very weak and obstructed by a lot of organizational noise, i.e. there will only be a very slight change in patterns recognizable". This is in turn means that using the wrong algorithms can easily create a lot of false positives, Orad warns.
That boundary is often very weak, and in some cases it is even marked by a black edge rather than a white one.
The gradualist view of evolution suggests that natural selection is often very weak, causing little change to accumulate over time, and that evolution ends up being uncoupled from ecology (for a recent review see Bell, 2013).
The A-scan optimization seeks black to white transition, given the fact that the choroid is usually darker than the post-choroidal region (though this boundary is often very weak or non-existent): G D W gives the average intensity of the choroidal region, CSI boundary minus 50 pixels, while G A W of the post choroidal region, CSI plus 50 pixels.
Women were often very physically weak, and felt bed or wheelchair-bound, when discharged.
Unfortunately, owing to the relatively small amount of emissive materials involved, light emission from the planar thin films is often very inefficient with weak intensity, and therefore, it may seriously hinder the possibility of any practical applications.
