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A (new) study, conducted|completed{conducted | completed | held} by our university in 2016, {shows | has shown} that ....

The present perfect asserts a relevance to the present, and so has shown is fine. You wouldn't want to use the present perfect in the clause that states when the study was conducted ("...in 2016") because that is indeed confined to the past; there, you'd use the simple past.

A (new) study, conducted|completed by our university in 2016, has shown that ....

A (new) study, {conducted | completed | held} by our university in 2016, {shows | has shown} that ....

The present perfect asserts a relevance to the present, and so has shown is fine. You wouldn't want to use the present perfect in the clause that states when the study was conducted ("...in 2016") because that is indeed confined to the past; there, you'd use the simple past.

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A (new) study, conducted|completed by our university in 2016, has shown that ....

The -ing form, showing, is used in the example you cited from the BBC site because the sentence says "every couple of years". The continuous can be used with recurrent actions.

A (new) study, conducted|completed by our university in 2016, has shown that ....

The -ing form, showing, is used in the example you cited from the BBC site because the sentence says "every couple of years". The continuous can be used with recurrent actions.

A (new) study, conducted|completed by our university in 2016, has shown that ....

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A (new) study, conducted|completed by our university in 2016, has shown that ....

The -ing form, showing, is used in the example you cited from the BBC site because the sentence says "every couple of years". The continuous can be used with recurrent actions.