Open course ware

[Music] okay so lesson number one PA try to repeat with me and then you say your name instead of my name actually you canot say PA as you see literally it means hello I call myself paa my name is or I'm called something like this and typically we do not put the subject yeah yeah you can say but typically you don't want to do it unless you want to emphasize who you are okay now let's do this I say m PA and then I ask you you stand up you say then you ask somebody else okay wa a second I know many of you speak Spanish so you tend to say yeah let's try all together yes good that literally means pleasure nice to meet you so let's repeat okay good perfect so as you might have noticed we pronounce letters differently from English let's start first of all to see how we pronounce the vowels so we have a open your mouth as much as you can [Music] e e e or and O so forget saying U no o a a a e o o yes excellent Bim now this seems simple it's a little bit...

[Music] [Music] call chromatography the purification of chemicals is one of the most important jobs of a research chemist perhaps the most common purification technique in an organic laboratory is colum chromatography this technique takes advantage of the different polarities of different compounds to separate mixtures frequently on the gram scale technically column chromatography can be challenging but with a little practice you will be able to separate mixtures of compounds consistently and successfully as the name suggests a column of absorbent either silica or alumina is packed into a glass tube with a stopcock at the bottom the sample is applied to the top of the absorbent and solvent is run through the column until the compound is flushed out of the bottom in most cases flash column chromatography is used meaning that pressure is applied to the top of the column resulting in faster running times and better separation before you can run a column you need to decide on...

[Music] oh [Applause] [Music] [Applause] [Music] hi last time we had looked at an introduction to compensation of feedback systems in other words how do we modify Loop transmission of a feedback system in order to improve its performance possibly increase its speed of response or increase sensitivity improve the stability of the system those sorts of modifications that we very frequently want to make to to feedback systems the simplest kind of modification we can make is to change the low frequency magnitude of the loop Transmission in the notation we've been using the a fnot product and we've looked at how that influences the root Locust diagram for example and and last time looked at how that might improve the stability of the system today I'd like to look at somewhat more complicated modifications of the loop Transmission in particular ones that change the Dynamics associated with the loop transmission the simplest thing that we can do is to add a dominant ...

[Music] oh [Applause] [Music] [Applause] [Music] hi today I'd like to look at the stability problem in a somewhat different way we've found to this point that we have two methods for evaluating the stability of a feedback system one of them we looked at very briefly or principally via homework problems in particular the rowth test and what the Ralph test does is simply give us a a straightforward numerical way of determining the number of poles of a closed loop transfer function that lie on the right half of the S plane hi today I'd like to look at the stability problem in a somewhat different way we've found to this point that we have two methods for evaluating the stability of a feedback system one of them we looked at very briefly or principally via homework problems in particular the rowth test and what the rowth test does is simply give us a a straightforward numerical way of determining the number of poles of a closed loop transfer function that lie ...

[Music] oh [Applause] [Music] [Applause] [Music] hi today I'd like to continue our discussion of root Locust techniques and in particular I'd like to start by applying it to the stability analysis of several commonly occurring Loop transmission Loop Transmissions one of the things that always improves the stability of a system or generally improves the stability of a feedback system is to add a zero to the loop transmission and we'll see a number of different ways of of looking at at the reason for this as we go through the course but a good general rule is if there is a way to add a zero to the loop transmission that generally improves the stability of the resultant feedback system there may be very real practical limitations to our ability to do this and again we'll have more to say about that later on during the course let's start by looking at a second order system in other words assume that we have a loop transmission that has two poles associated...