The phrase "accelerate markedly" is correct and usable in written English.
It can be used to describe a significant increase in speed or progress in a particular context, such as business, technology, or personal development.
Example: "The company's efforts to improve efficiency have allowed them to accelerate markedly in their production rates."
Alternatives: "speed up significantly" or "increase dramatically".
Investment accelerated markedly after a devastating earthquake on Taiwan in 1999.
The country's engagement with the developing world has accelerated markedly in the wake of the economic crisis.
Buoyed by a big pickup in public works spending and a Bank of Japan policy of flooding the economy with low-interest money, growth has accelerated markedly.
The pace of detentions and harassment accelerated markedly this spring after pro-democracy uprisings in the Middle East prompted an anonymous online campaign for a "jasmine revolution" in China.
Early gains accelerated markedly in midmorning after Alan Greenspan, the Federal Reserve chairman, strongly suggested that the central bank would cut short-term rates if the economy's deceleration, already pronounced, threatened to become too rapid.
The tensions accelerated markedly this month after Hezbollah fighters entered Syria in large numbers and helped the government of President Bashar al-Assad rout Sunni rebels from an important border city, Qusayr, which the insurgency had used for supplies and coordination.
For copper, imports had fallen before the onset of the global crisis in August 2008, but they started accelerating markedly from February 2009 onward, again as the official P.M.I. was bullish at a time when the HSBC flash reading was bearish.
As a result of these intermittent persecutions and the destruction of churches, it is believed that the rate of conversion to Islam accelerated markedly in the Mamlūk period and that Coptic virtually disappeared except as a liturgical language.
The farthest point south that was reached during Henry's lifetime was probably present-day Sierra Leone; after his death, the pace of progress in Portuguese exploration accelerated markedly, suggesting that the prince's reputation as a patron of explorers has been exaggerated.
It was shown that ceria accelerated markedly the decomposition of parathion methyl causing the cleavage of the P-O-aryl bond in the pesticide molecule.
