Archive for November, 2012|Monthly archive page

The Internet of Things

In Embedded Systems, Engineering Principles, Interdisciplinary Science on November 29, 2012 at 2:43 PM

When I first attended a presentation on “The Internet of Things”, I was not very excited. It turned out to be nothing more than a glorified description of sensor networks. Though this phrase was first used in 1999 as reported in an article in RFID journal, it has been interpreted in many different ways by different people. Trying to find a way through that maze of descriptions is really difficult. However, after reading a lot about it and based on my own understanding of embedded systems, sensor networks and systems engineering, I would like to share what it means for a non-technical audience. I find it best to explain through examples. Take the case of a smart home. You can control the appliances in your home while driving your car as there is a communication network that links you up with them while you are driving. Your smartphone connects you to the internet where you can shop, play games together with your friends and download apps that make your phone more versatile. It syncs with your email accounts and any sync enabled application, helps you make payments on the go (mobile banking), provide access to your data anywhere through cloud based tools like dropbox etc.. The GPS on your phone helps you find your way in a city by showing you on a city map that has been downloaded on to your phone using a wi-fi or similar data connection. You can drive almost safely even in a city new for you! These examples demonstrate an interaction between humans, electronic devices which may have sensors, mechanical devices and the traditional internet. By traditional internet I mean the internet which was seen initially  as just a repository of information and which has now grown to include processing engines like  those which facilitate “voice enabled search and SMS” on your smartphones, storage and compute space for cloud applications (like Amazon’s EC service) etc. Thus the “Internet of Things” is nothing but a network where human actions, electrical and mechanical devices and the internet come together to interact in a meaningful way. The scope of this interaction can be as varied and wide as possible depending on the intended result.

A Case of Two Means:Geometric & Arithmetic

In Engineering Principles, Mathematics on November 7, 2012 at 11:55 PM

Why is this post there? I have come across several examples of quoting results (numbers) in papers, reports etc. where the authors have used arithmetic mean. For instance, people would run an application on different computing platforms and then calculate the time taken on each platform. They would present their results in a table and the last column would have an entry titled “mean”. Often, it is the arithmetic mean (AM) that is quoted. How many times have you seen the geometric mean (GM) being quoted? Not many. The primary reason being that we are too comfortable with the arithmetic mean. This is what pops up in our heads generally when we think of a mean. But we forget in the process if AM is the right choice. It is important to understand when to use AM and GM . AM is biased towards large data points in a data set while that is not the case with GM. GM is generally used when several quantities multiply together to produce a result while AM is generally used when they add up to produce a result. Sometimes it is obvious when they add up and when they multiply. Sometimes,it is not so obvious. So you have to put extra effort in finding out which mean to use  and what message you are trying to drive home through that mean value. In the example cited in the beginning, GM should be used. Some nice references to read are : ref1, ref2, ref3, ref4. Similary, understanding when to use Harmonic Mean (HM) is also important. Whichever mean you choose,you have to understand your data points as well as be clear about the message you are trying to convey. Means and averages are very important in economics, mathematical finance etc.