Archive for October, 2009

zsync for karmic

Thursday, October 29th, 2009

Today is release day for Karmic Koala. That usually means that there is a lot of I’net traffic. Ubuntu tutorials has a description about how you can use zsync to update CD image files.

The download mirrors for this release have started to include .zsync files. zsync is similar to rsync, but it puts the load on the client vs the server, and it allows you to update your existing images in a fraction of the time it would take to re-download the full image.

The tutorial appears to be missing the zsync command on the first line of its examples. The process is first to install zsync and make sure your pre-release iso files have the release name. Then you run zsync against the proper server iso.zsync file to update the iso to the latest version

Medibuntu for karmic

Monday, October 26th, 2009

See Enchance Ubuntu 9.10 karmic koala repositories with Medibuntu for adding this repository of stuff that isn’t in the default Ubuntu repositories due to intellectual property or other legal issues. There are two things to do. One is to add the repository to the list searched by apt-get and the other is to install its security credentials.

echo deb http://packages.medibuntu.org/ karmic free non-free | sudo tee -a /etc/apt/sources.list

wget -q http://packages.medibuntu.org/medibuntu-key.gpg -O- | sudo apt-key add – && sudo apt-get update

See the Ubuntu Community Page for Medibuntu (Multimedia, Entertainment & Distractions In Ubuntu). You can find instructions for playing encrypted DVD’s here as well as installation customization notes and other good information.

lead acid batteries

Sunday, October 18th, 2009

Lead acid storage batteries are a heat generating topic on many renewable energy (RE) and recreational vehicle (RV) forums. People are passionate about their misbeliefs. Mike, at the Solar Electric Power Discussion thread on Sam’s Club batteries referenced the DECA service manual for the D series batteries. That one’s a keeper! The manual is about industrial batteries but the description of battery construction and operation applies to all lead acid batteries.

The cutaway illustration (Fig. A-1) shows the construction of an East Penn battery cell. Each positive plate consists of a lead-alloy grid structure which is filled with a paste of active material, made from lead oxide. The active material is forced into the positive grid structure during manufacturing and is held firmly to the grid by a system of vertical and horizontal glass fiber mats, which reinforce and insulate the positive plate. A retainer and bottom shield encase each positive plate and mat assembly to help prevent short circuits.

The negative plate also consists of a lead alloy grid structure that is filled with active material. But because negative plates undergo much less active material shedding, no reinforcing glass fiber mats are needed. Separators provide insulation between the positive and negative plates. The positive and negative plates are connected to their respective posts by positive and negative straps.

There’s also good stuff about battery safety, operations, and maintenance that apply even to small RV and RE applications.

When you run across someone promulgating the ‘true deep cycle 6v golf cart battery’ as the penultimate solution or carrying on about the ‘deep cycle and thick plates’ baloney, get back to a manual like this to find reality.

Copernicus, Waldseemüller, and concentric spheres

Saturday, October 17th, 2009

The Boston Globe has an enlightening column about A world redrawn. The proposition by Copernicus that moved the frame of reference from earth to sun is well known. The article describes two other aspects of this that are not so well known. One is the impact of a changing view of the world and the other is how that model included efforts to place ocean and land within the concentric spheres model of the universe.

Known today as the Waldseemüller map of 1507, it was the first to depict the lands discovered by Columbus and other early explorers as part of a vast and previously unknown continent. Earlier maps had shown the new discoveries only vaguely, as a still-to-be-determined part of Asia, but this new map boldly located them far out in the western ocean, on the other side of the globe from the known world, extending deep into the southern hemisphere. And it gave this place a memorable new name: America.

The concentric spheres model with the earth at the center of the universe and everything we see up as being a part of perfect spheres above it also implied that everything we see below had to be of similar structure to keep the model consistent. This meant that there was a sphere of water and another of land. That caused problems in that, since one was inside the other, you couldn’t have both at the same level. A solution for this was similar to the solution for planetary eccentricities. The sphere of water and that of land were offset just a bit so one showed up on one side of the earth and the other showed up on the other side of the earth.

The point made is that when Copernicus saw America on the Waldseemüller map he realized that land was visible on both sides of the earth so the concentric sphere idea didn’t work. Once that dissonance was settled, the Copernican view of the universe became thinkable.

This article by Toby Lester provides many ideas that are unfamiliar (to me, at least) and that means opportunity for looking for more about them. His book on the Fourth Part of the World might be a target for initial investigation.