assitant professor 和associate professor有什么区别

我在网上看到一个加州大学的华裔教授,新闻里写他是副教授,如果翻译过来就是associate professor 啊,但是上网查他名字却发现他叫做assistant professor,两者可以肯定是不一样的~
下面做一个比较：
英制 —— 美制
Senior Lecturer 高级讲师-----Associate Professor 副教授
Lecturer 讲师 ---------------Assistant Professor 助理教授
可以知道级别高于讲师而低于副教授,
Assistant professor:Once a senior teaching assistant obtains a doctorate,s/he is hired as an assistant professor,and receives tenureship.Assistant professors duties include delivering lectures,supervising graduation projects,master theses,and doctorate dissertations.
Associate professor:After at least five years,an assistant professor can apply for a promotion to the rank of associate professor.The decision is based on the scholarly contributions of the applicant,in terms of publications and theses and dissertations supervised.
值得一提的是助理教授,
例如有的学校长期雇佣未拿到PHD的ABD（ All But Dissertation）.在他们正式毕业前以Lecturer/Instructor称之,答辩后改称Assistant Professor.一般工作合同每年三四月敲定,答辩则在五至八月,难保绝对通过,有学校合同上就写Assistant Professor.assistant professor只是一个校内职务,和他的招生资格没有直接联系.所以,如果他在校内是硕导的话,就可以带研究生.Associate professor可以带硕士和博士的.