I think the answer is no, but Marimuthu's example isn't right.
You can create a has-a relationship by using composition (which is the normal way to represent a has-a relationship in an object oriented program). But the member variable can be of an interface type; that way, the containing class isn't tightly coupled to the implementation of the contained class.
what Jesper said is correct. But i interpreted it in this way.
Has-a relationships can be implemented by using both Composition and Aggregation. Here the difference is that in Composition, the lifetime of the contained object is controlled by the class which contains it. That means in my example,
If i delete a car object, the engine object should also be deleted. (the engine alone cannot alone live without a car) (Another example, Human & heart). This is composition (Strong relationship).
But if i remove a department, employees can still live without that department. (Aggregation) (Another Example - Computer & Printer)
From Jesper's statements ("coupled to the implementation of the contained class"), I think aggregation and composition are not related to coupling.