The phrase "a major challenge when" is correct and usable in written English.
It can be used to introduce a situation or context where a significant difficulty arises.
Example: "A major challenge when implementing new technology is ensuring that all employees are adequately trained."
Alternatives: "a significant obstacle when" or "a key difficulty when".
However, computing time remains a major challenge when a large model is calibrated using optimization techniques.
A major challenge when designing such restricted languages is habitability how easily, naturally and effectively users can use the language to express themselves within the constraints imposed by the system.
The heterogeneity of the deposits can be a major challenge when designing a monitoring program: Do the deposits consist of innumerable small, completely different micro-environments, or are there some general trends that allow us to look at larger units?
Moreover, determining the direction of causality is a major challenge when examining the relationship between turnover and training.
The need for side information (SI) estimation poses a major challenge when selected mapping (SLM) is implemented to reduce peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems.
Data security is a common concern for any technology, but it becomes a major challenge when SaaS users have to rely on their providers for proper security [12, 21, 36].
Indeed, a survey of the literature reveals that this composite null hypothesis is the major challenge when a traditional hypothesis testing approach is taken.
Willis stated that the major challenge when creating the brand identity for Beckham was: "How do you convey through a brand mark the sheer diversity of the David Beckham world?".
Finding the right balance and timing will be the major challenge when developing therapies to target the Ang/Tie system.
A major challenge to "when it's wanted" consumption is that in complex, multifirm provision streams, the interests of the customer, the retailer, the producer, and the suppliers must be aligned.
Therefore, quantifying cumulative exposure over a long period of time is a major challenge, especially when variable and multiple sources of exposure must be considered.
