This is the 5122nd most frequent Russian word.
накопленных
"Accumulated" or "gathered."
Here, 'накопленных' is used as an adjective describing the state of 'knowledge' (знаний) that has been gathered over time.
Объем накопленных знаний студентов впечатляет.
The amount of accumulated knowledge of the students is impressive.
In this context, 'накопленных' characterizes 'assets' (активов), indicating that these assets have been gathered or accumulated over a period.
Он вложил деньги в покупку накопленных активов.
He invested money in the purchase of accumulated assets.
Here, 'накопленных' describes 'data' (данных) to show that this data has been systematically collected over time.