A kind of a pin used to hold your cloak together, called a fibula, unknown in the previous period.

一种别住披风的别针,称之为扣针,这在之前的时期从未出现过

耶鲁公开课 - 古希腊历史简介课程节选

That's how by either balancing the unknown force with a known force or by simply measuring the acceleration as I fall towards this podium and multiplying by mass, you can find the force that exerts on me.

我们既可以让未知力与已知力平衡,也可以只测量我冲向讲台时加速度的大小,再与我的质量相乘,都能求出作用在我身上的力的大小

耶鲁公开课 - 基础物理课程节选

Well let's talk about some mechanisms for using this and I'll start with a simple example of how one can detect a gene in a fluid, in a blood sample for example, where that gene is unknown.

我们来说说这项技术在实际应用中的机制,先从一个简单例子着手,如何在一个血样中,侦测是否存在某段基因序列,某段未知基因序列

耶鲁公开课 - 生物医学工程探索课程节选

You can use PCR for fingerprinting as well, for looking in some unknown fluid for example, is a gene that I'm interested in there?

也可以用PCR做生物指纹鉴定,比如在一个未知溶液样本中,里面是不是有我感兴趣的那段基因呢

耶鲁公开课 - 生物医学工程探索课程节选

There's only one unknown a.

所以只有一个未知量,a

耶鲁公开课 - 基础物理课程节选

So, what we have found out so far, I'm purposely going from x to y because I want you to know that the unknown variable can be called an x or can be called a y.

到目前为止,我们有这些结论,我特地把x换成y,因为我想让你们明白,未知变量既可以写成x,也可以写成y

耶鲁公开课 - 基础物理课程节选