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Thursday, December 2 2010

Random Resistance

The following is taken from Example 7.17, pg 259 of "Mathematical Statistics with Applications" by John E. Freund, 7th edition.

Suppose the resistance in a simple circuit varies randomly in response to environmental conditions. To determine the effect of this variation on the current flowing through the circuit an experiment was performed in which the resistance (R) was varied at random on the interval 0 < R <= A and the ensuing voltage (E) was measured. Find the distribution of the random variable I, the current flowing through the circuit.

All I can say, is that I hope never to run into such a circuit!

Saturday, August 28 2010

Open-Source Defined (by a sexagenarian)

From a brand-new textbook, I give you the paragraph on open-source software.

Open-source software is becoming extremely popular. An open-source software product is developed and maintained by a team of volunteers and may be downloaded free of charge and used by anyone. Widely used open source products include the Linux operating system, the Firefox Web browser, and the Apache Web server. The term open source refers to the availability of the source code to all, unlike most commercial products where only the executable version is sold. Because any user of an open-source product may scrutinize the source code and report faults to the developers, many open-source software products are of high quality. The expected consequence of the public nature of faults in open-source software was formalized by Raymond in The Cathedral and the Bazaar as Linus's Law, named after Linus Torvolds, the creator of Linux [Raymond, 2000]. Linus's Law states that "given enough eyeballs, all bugs are shallow." In other words, if enough individuals scrutinize the source code of an open-source software product, someone should be able to locate that fault and suggest how to fix it. A related principle is "Release early. Release often" [Raymond, 2000]. That is, open-source developers tend to spend less time on testing than closed-source developers, preferring to release a new version of a product virtually as soon as it is finished, leaving much of the responsibility of testing to users.

Whoa. Talk about a disjointed paragraph. I think he says that open-source projects are both unstable (because of fast release cycles and less testing) and of high quality (this is explicitly stated).

Excerpt from Schach, "Object Oriented and Classical Software Engineering", 8th edition, pp. 23-24. As this is a few words out of a 700-page book, I don't suppose I'll have any rights issues.

Tuesday, August 3 2010

Its Textbook Time (again)

Campus Bookstore: $449.50
Chegg.com (and Amazon): $254.59

A savings of:

43%

When you factor in the fact that the above is not apples-to-apples because Chegg does not stock two of the books I need, the savings is actually:

62.5%

One of the nice things about Chegg is how I know up-front what my net cost will be for books for the semester. It is the price I pay in August. If I deal with the campus bookstore, I learn nothing. I only know from previous experience that the best I can hope for is 40% of what I paid, and nothing if the publisher decided it was time for a new edition. Information makes markets work better.

Thursday, July 29 2010

Book Review: "The Entrepreneurial Engineer"

Almost universally, students hate textbooks. Well, I'm a student, and this is a textbook. (The price tag of $50 list proves it!) This book from David E. Goldberg serves as a good introduction to business for people who aren't inclined to The Wall Street Journal. Goldberg actually suggests reading the Journal, although I doubt more than 5% of his readers ever will.The Entrepreneurial Engineer

At 200 pages and in a breezy style, The Entrepreneurial Engineer can be easily read in a week (likely 2-3 days if you're dedicated). The book is based around Goldberg's Ten Competencies, each of which becomes a chapter of the book. A number of them are actually overlaps from Seven Habits of Highly Effective People, but this is far more focused on the specifics of business and less on general interpersonal relationships.

The thing that I love about this book is the fourth, fifth, and sixth competencies. Write well, speak well, and "Do Unto Others". There is no reason for anyone to not be able to do these three things. Aside from admonishing those who think they can get by without being able to write and give a product presentation, Goldberg actually offers tips and methods to improve skills.

Yes, giving your presentations to the bathroom mirror actually does work (that's mine, not Goldberg's).

There's also good opinion writing about where Goldberg things the future of business lies.

Due to the prohibitive price, I give this book four libraries out of five. Barnes & Noble link