the issue of scale plays a prominent role in several of the best-known theories of edge detection.marr and hildreth [8] employed a laplacian of gaussian operator to construct zero-crossing segments at a number of scales and proposed that the presence of a physical edge be asserted if a segment exists at a particular position and orientation over a contiguous range of scale.두번째 문단의 문장구조를 잘 모르겠습니다.be asserted 이부분이 동사 같은데 be가 좀 걸리네요.논문읽다가 문장구조가 잘 안들어와서 이렇게 질문 올려 봅니다.