However, congestion pricing (charging more) does not work, if you are not setup to charge anything at all!  So a different mechanism is used at times – the one to only allow some vehicles on the roads.  This is typically known as road space rationing.  For example, you could choose to allow only blue cars on the road at one day, and the red cars on the road another day.  Oh wait, you can’t actually do that as that appears to be politically motivated.  So, let us try again.  You can try to allow the cars that have the last digit of the license plate numbers odd on the road on one day, and the cars for which the last digit is even on another day.  Then, you can turn those digits and days around as you wish to make sure that the system is fair and not gameable (and you may need to have some provision for vanity plates).

The best example of this that I have come up is in Bogota, where the system is called pico y placa, which combines the peak traffic hour (pico) also with the license plata (placa), although the peak hours have since 2009 been extended to almost the entire day (6 am to 8 pm).  Knowing Bogota’s traffic, I think that is a fair characterization of the peak hour.  The way the system works is that cars with number plates ending in 5, 6, 7 or 8 cannot driving between 6 AM and 8 PM on Mondays.  Last digits for other days are:

• 9012: Tuesday
• 3456: Wednesday
• 7890: Thursday
• 1234: Friday

There are no restrictions on the weekends.

So, firstly we observe that if you have two cars, one ending in 5 and the other ending in 0, then you have at least one good car every day.  So, the people with means try to have two cars with different number plates.  For that reason, the Bogota pico y placa changes the digits every year.  So, it is theoretically possible that your good combination may not be that good next year.  However, based on my understanding of Bogotá pico y placa, the digits are always in contiguous blocks of 4, so if your two license plates end in 0 and 5, then you are perpetually safe.  If my understanding is correct, then that is a limitation of the system, and the numbers should be mixed up more thoroughly.  To put in perspective though, that limitation is small as only a limited number of people buy two cars to circumvent the system.

Could pico y placa work in DC?

Granted, we would have to call it peak and plate here, but could the concept work?  For about 8 months of 2011 I participated in ride share program wherein me and my ride share partner would drive during alternate weeks, to take advantage of the HOV restriction on I-66.  The ride share program works as is, and there is even a full slugging system in DC, but if there were more people participating in ride share programs, that would perhaps be easier to find people leaving from and going to same places, and the ride share could really work even better.  Participation would of course be almost mandated by peak and plate in DC.

Although WMATA stopped trying to be price-competitive a very long time ago, it is even possible that due to increased ridership, even the metro fares may come down a little. (For a visual on how high metro fares suppresses ridership which raises fares, consider this.)

After a lengthy preamble, here is a question for you:

Buy chuck e cheese tokens to play their games. Win the tickets from the games and buy soft toys using the tickets. Sell soft toys to retailers. Pocket the difference as your profit.

Is that simple enough for you?

Topics

Scripting and Shell, Access Control, Process management, File system, User management, Software management, Setting up Cron, Backup – Dump and Restore, Drivers, Devices and Kernel, Networking, Routing and DNS, Web Applications, Performance Monitoring

Broad Questions

There is really only one basic question that I want to ask at the end of my class, and that question is the same, at the end of every class, and the end of every semester (or a weekend, if I happen to be teaching a weekend seminar class). That question is: How has this class changed your outlook on the subject matter covered, and what are some of the things that you may do differently now, with the benefit of this class.

Since that question has the abstractness of Eliot’s poetry in it, sometimes I use other questions in it’s stead. These are some examples of questions that are intentionally vague. Focus is on checking how broad you think. Real life problems are usually this vague. In each of these, the setting is that you are the system administrator for the IT system (the set of servers, etc,) for that organization.

1. A user complains that another user has been able to read his private files. What measures would you take to prevent this from happening again.
2. Your applications team wants to build and deploy a web application that will allow the employees to see how much vacation time they have left. What are some of the security considerations you will check/ensure/discuss with them.
3. Some of the servers seem to slow down suddenly at different times. What debugging would you perform to check the server performance, see who & what is causing the slowness, and then to possibly improve it?
4. You have many users who are business analysts, and they have secretly confided in you that their definition of computer usage involves Facebook more than it involves UNIX/Linux. When they log into a UNIX server that you manage, they go through a list of items: set system color settings so they can read the system outputs, connect to an Oracle database, run some reports, download those reports, etc. They would like to not have to do all these repetitive work. The reports that they run can change from day to day, but the rest of it is pretty much the same. How can you help them get through the repetitive work?
5. Your users occasionally delete some files and ask you to “restore” them. How can you create a scheme or a framework for preparing for these kinds of requests? You may not be able to prevent data loss completely, but your goal is to create a framework for “reasonable” backups. For example, if the total size for files for all users is 20 TB, approximately how much space are you allocating for backups?
6. Your users would like to share some files. What options will you consider?
7. Your application team is using a database which has many reads and writes. They have heard that RAIDing is a “good idea”. What are some of the RAID choices that you may consider, and what are their advantages and disadvantages?
8. When might you need to write a device driver?

Scripting Questions (1 Example)

Write a script that counts all unique words that appear in any of *.txt files that exist anywhere inside the folder /home/courses/cs4418. For example, suppose these are the two files:
/home/courses/cs4418/a/b/c/d/e/f/abc.txt: {Justin Bieber is a great singer.}
/home/courses/cs4418/de/f/xyz.txt: {Lady Gaga is a superb singer.}
Then, your script should print the answer that there are a total of 9 unique words in 2 files.

Objective Questions

Objective questions for this question typically test the student’s knowledge of specific commands, and specific concepts. For example:

• How many times would a given cron job run between two given dates.
• ______ command does x.
• Command y does ____.
• What is kernel space?
• What are two broad kernel architectures?

Domingo Chinea (Port of Buenaventura, Colombia), Rafael Plaza Perdomo (Port of Esmeraldas, Ecuador) and Valentin Moran (Port of Bahia Blanca, Argentina) present their views on the how the ports can lower their logistics costs and become more competitive. A common thread between their presentations is the cost of the movement of the goods from the port to the hinterland.

From my work in the various Latin American ports, the land transportation costs are still relatively higher compared to the cost of goods. There are a lot of opportunities for improving the IT infrastructure and processes for trucks to load and unload the goods at the ports. Many times there is not enough visibility of the trucking operations to allow the terminals to plan ahead for their arrival, and that leads to unnecessary congestion inside and around the terminals. Sometimes the trucks simply queue up outside, and sometimes the trucks simply linger outside after doing a drop off, hoping to pick up another load. One KPI that is sometimes used is the “turn time”, which tries to measure the total time that a truck spends inside the port (or the terminal) in order to do an operation. Of course, the turn time depends on the port and also on the operation, but the trend on that KPI value with time can at least provide us with if the efficiency with respect to trucking operations is improving or not.

Franc Pigna (AEGIR) focused significantly on the implications of the Panama canal expansion, and with the knowledge that only one port on the US East Coast that is currently ready for very large vessels (and that port is Norfolk, as you all know), the question becomes if the situation will change for a lot of non US Atlantic ports, such as Cartagena, Kingston, etc.

Kenneth O’Hollaren focused his presentation on opportunities of bulk exports from Latin America to North America. There are significant bulk supply chains currently between these two regions, and some of my past work has focused on that.

So the question then is – how come something that is good for the mobile platforms (apps) is considered bad for desktop? How is it possible that while most of the desktop world has moved into web applications, the mobile world is getting more and more entrenched into apps (and then apps that manage those apps)?

Well, there are at least two factors that we should look at closely:

• The immaturity of the universal turing machine (aka the browser) on the mobile: there is as yet no dominant browser configuration in the mobile world. So, if you designed a web application, there is a possibility you cannot easily test how that would really work on a browser on that specific cellphone model with that specific configuration (JavaScript off, say?).
• The form factor of cell phones: How long and how wide can the pages be?

Are there other factors that we should look at closely?

Anyhoo, if you do use toners, then one of the best brand names for toners is of course the Brother toner.  [Brother brand, or Buraza Kogyo Kabushiki-gaisha, incidentally dates back to 1908 and made a name for itself using its multi-function printers!]

Rather than being penny wise and pound foolish, I find it much better to stick to high quality cartridges. For example, if you are using other HP products, you might as well bite the bullet and get original HP ink cartridges from some supplier of genuine HP products like the hp 564xl wherein you can buy black, cyan, magenta and yellow cartridges.

And yes, while there is no guarantee that the blue color that you see is the same as the blue color that I see but if you buy good printer and good cartridges, at least the blue color that you see today will likely look similar to you next time you order the same cartridge. And while I don’t have answer to the perrenial question of theory of colors, at least I can point out that cyan, yellow and magenta are used as 3 primary colors in printing instead of red, green and blue based on subtractive coloring instead of additive coloring. In simple terms, cyan, yellow and magenta dyes and inks absorb some wavelengths allowing others to be reflected and giving the object the “subtracted” color starting from white light. If all three dyes – cyan, magenta and yellow are mixed, then all wavelengths get absorbed, leading to black color, which stands for K in the CMYK color system.

View the entire Rum Raisin Toon book.