Friday, December 23, 2011

Follow the pack

The Broadcom STA driver in the package bcmwl-kernel-source is pure evil, and almost everyone knows it. So don't waste any more time. Remove it and install firmware-b43-installer now.
The Broadcom driver was installed by default on my laptop with bcm4311 wifi card during a clean install of Ubuntu (11.10) Oneiric Ocelot, but I couldn't get it to work. Under the wifi icon enable wifi was greyed out, even though bcmwl was activated in additional drivers. Some posts on Ubuntu forums and ask Ubuntu said that the driver had a bug in 11.10. Searching the internet, it gradually became apparent that b43 firmware from Linux wireless is preferred to bcmwl. I removed it from the software center, and it also removed a package called dkms. Then I installed b43 from the software center (but I have used apt-get on my other box to install b43legacy) and rebooted. Viola, wifi.
See (current) & (slightly outdated) for more info.

Thursday, December 15, 2011

Sharing files

Sharing files should be a piece of cake?  Right click, select sharing, enable, done.

Well almost. First off, samba is not installed by default with my distro (Ubuntu 11.10), but Ubuntu kindly offers to install samba the first time you click file sharing. And if you are the only user on the box, then that's it. Piece of cake.Hooray!

However, if you have another user, then you enter into the murky CLI territory for which Linux is so famous. But in this case the command is easy. All you have to do is add the user to the sambashare group using the usermod command. As always read the man pages completely before trying any hack (man usermodman sudo), then hit ctrl-alt-T and presto, a terminal window will appear. Then enter the following command, if you dare.

$ sudo usermod -a -G sambashare

I've used the sudo command many times blindly following the directions posted online, without really appreciating how powerful this command is. Even more power is the su command (man su) which can seriously mess up your system if you're like me and don't know what you're doing. In this case sudo just says run the following commands as root, and prompts you for your password before running the command. Therefore you must be logged in as an administrator for this to work. Then the usermod command modifies the user. In this case I used the -a option with the -G option to append the user to a supplementary group. I don't wan't the user to be removed from it's current groups so that's why I have to use the -a option. If I only used the -G option, the user would be removed from any group it was currently a member of that was not listed following the -G option. I know, tricky, right?

When I first tried to share the public folder in the other users home I get a warning message, that I do not own the file and so I can't share it. But if I wanted I could edit the global smb.conf file to force sharing even if I don't own it. Really, that's way too much work. Logging in as the other user, who is not an administrator, gave me another clue about what to do. It says can't enable file sharing because the user was not a member of the sambashare group. Ubuntu actually said to ask the administrator to add me to the group. Then of course, as you are doing now, I went to the internet, and tried to find out how to do this. But first I managed to totally mess up my system by running su without the -c option for commands. How I have managed to not totally brick my Android is beyond me. Luckily there is a file system checker that fixed my errors. Again friendly Ubuntu tells you what to do, but I'll save that for another post.

Not quite like snowboarding

Linux seems like something you know, kind like Unix, kind of like windows or mac, but no it's new territory, with a very steep and treacherous learning curve; I've already broken my 1st box 3 times
But it's addictive, although not as outdoorsy as snowboarding, I'm really hoping I'll catch on fast. This series will be dedicated to my blunders, because how else do you learn.

Monday, October 24, 2011

Sunday, August 21, 2011

Staggered mesh

Someone out there has encountered the zigzag garbage a numerical solution spits out when there is pressure-velocity decoupling. You can try to refine the mesh, smooth forcing functions or adjust the Peclet number, but in the end you are undone by a fundamental flaw in the advection terms and the central difference approximation of a first derivative. The problem is advection requires a first derivative, and the central difference may be very weakly coupled to its own node. The result is essentially two solutions, one for the odd nodes, and one for the even. This is why it is often called odd-even decoupling. But why not turn this apparent weakness into an advantage? Cut your degrees of freedom in half, and just use a staggered mesh. Solve for enthalpy (energy) at the odd  nodes, solve for momentum (pressure) at the even nodes, and solve both in the half nodes at the inlet and exit, where forward or backward difference approximations are used. Use linear averages everywhere else. This has worked very well for me. I also solve for all of the mass flow everywhere at once since it is explicit on boundary conditions and the time rate of change of mass in the system (i.e. continuity or mass balance). Given the enthalpy and pressure at every node, I can explicitly calculate the density using the IAPWS-IF97 steam tables, and given the mass flux from continuity, I can now calculate the velocity. No more zig-zags, I've reduced my degrees of freedom nearly in half, and I didn't have to add artificial diffusion or any other fudge factors. Yay!

Apple drama

I can't wait for Google to start making their own hardware. Or for Android machines to start taking over a larger market share. I get Android. I don't get Apple. For all the hype, so far not a single thing has worked hitch free. Ah, but the gadgets are sexy. The macbookpro is so sleek and cool, the iPad so convenient.

Sunday, August 14, 2011


I must be fun-challenged, because while everyone else is lapping up carny food and gawking over watercolored bears and jewelry made from scrap flatware, I'm completely miserable. I'm irritated that I've spent gobs of money on crap. To me the whole thing is a sham. The idea of carny food always sounds delicious, but the reality is usually grossly-overpriced over-glorified gut-busting greasy garbage. The bands are fine, I love music, so the free fairs have at least got that, but I haven't been wowed enough by carny music to justify paying. And pay dear. Movies at the Parkway (RIP) were cheaper! I guess the only thing I like is the people watching. And as a kid I remember liking the rides. Maybe I've got to just suck it up and pretend to have fun for the kids. But honestly I'd rather be outside, walking, not choking my arteries, relaxing, enjoying nature for free. Ah, that sounds nice.

Friday, August 12, 2011

new os

I'm sure linux or android already do this, but I'm tired of folders and directories. Isn't that idea a bit antiquated? I was thinking that in this day of objects and tags, can't files just have a tag attribute that can be set so that you can sort and cross reference your files anyway you want? to this user this could be transparent, so that it looks just like folders except it's so much better. Then you wouldn't have all of there ridiculous pathnames, everything would be in root/files.

corporate batman belt

I was thinking with 3G (and 4G lite) access, it wouldn't be too hard to develop a device, actually a system, that would be a corporate office away from the office. This device let's you receive and make calls of course, but also lets you access your laptop if you leave it in the office, even control the desktop, access the network. But most importantly, allows complete customization, for example, would allow an app to be installed that automatically detect when it was going into roaming and shut down all data transfer, and switch to something like Skype for calls.

Saturday, July 30, 2011

Second law of infodynamics

Entropy of information always decreases in a closed system unless work is done on the system to increase it. I know it's hard to believe, but if you think about it you'll realize it to be true. In the long run, information always becomes more organized. Just like the 2nd law of thermodynamics, this law has no proof, but an observation of history demonstrates that the 2nd law of infodynamics is true. An obvious counter example might be the dark ages. In the most general sense, it is evident that energy was spent (i.e. work was done) on that society, either through acts of man (i.e. warfare, politics) or nature (i.e. natural disasters, weather), causing it to become disorganized.
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