He has concluded his research. 他已完成了他的研究工作。
conclude的名词形式是：conclusion；过去式concluded 过去分词concluded 现在分词concluding。
1. concluded表示“结束”意思时，可用作及物或不及物动词，表示以某种方式结束通常用介词 with, by 等。如： He has concluded his research. 他已完成了他的研究工作。
He concluded his talk with a funny story. 他以一个有趣的故事结束讲话。
He concluded by giving us some advice. 他结束时给我们提了些建议。
2. concluded表示“断定”或“推出”意思时，是及物动词，但通常只接 that 从句或不定式的复合结构（且不定式只能是 to be型）作宾语，通常不接简单宾语，也不用于进行时态。如：
正：We concluded that he was wrong.
正：We concluded him to be wrong.
正：I concluded that he must have met with an accident.
误：I concluded him to have met with an accident.
3. concluded表示“决定”意思时，其后通常接不定式或 that 从句。如：
We concluded to wait for fair weather. /We concluded that
We would wait for fair weather. 我们决定等待好天气。
4. 期刊杂志等在连载文章时，表示“待续”用 to be continued, 表示“下期续完”用 to be concluded, 表示“全部载完”则通常用 concluded。