Posts by IanRS 83 posts • joined 24 Sep 2013
I had a Gateway in the second half of the 90s. Various bits got swapped out occasionally until just the original case survived. Eventually the changing form factors of various components meant it too had to go, but it was still in perfect condition. Built like the proverbial outhouse.
I am sure mine must still be around somewhere, although it was a little smaller. An open case with a 25 way connector on each end and 25 pins sticking up. Jumper leads could be added as necessary. The last resort in my serial toolkit, which also included a long straight-through cable (1-1, 2-2, ... 25-25), short adapters for common requirements such as null-modem or 25-9 serial, gender-benders. If two boxes could talk via a common protocol through a 9 or 25 pin D socket, I could probably connect them.
False positive rates should be low. Really low if you are dealing with a potentially large pool of candidates. A rate of 1% would mean that 1 person in 100 would be falsely recognised as being somebody 'of interest', and in any kind of crowded event there will probably be thousands of facing passing in front of each camera, so 10s of false positives. A 98% rate means this facial recognition system is working at the level of 'yes, that is a face'. It probably even triggers on the police horses.
It might be that 98% of the flagged faces were false alarms which is still stupidly high, but that is not what is properly meant by false positive rate.
When I used to interview graduates for a coding position I liked this test (although back then it was in C rather than C++).
What is the output of the following code:
#include <iostream>
int main()
{
std::cout << 001;
std::cout << 010;
std::cout << 100;
return 0;
}
Most candidates realise the leading zeros will not be printed, and write down 1 10 100 on separate lines. They are wrong. Some candidates realise that the output has no \n and write 110100. They are still wrong.
Gran: up two generations (mother of mother, or mother of father)
Aunt: up another generation then across to a sister
Cousin: shared grandparents, so up two then down two along a different branch of the family tree.
Total: Up five, down two.
So a common ancestor exists five generations up from the starting point, two up from the end point.
Take the lowest number: two, which implies cousin (three would be 2nd cousin, 4 = 3rd cousin, etc)
Take the generation difference: three.
Final result: Cousin three times removed, aka Sherryl.
"Antimatter is just an atom, whose core contains the electrons while the orbits are filled with protons - in "normal" matter it is the other way around."
No it isn't. It really isn't. An anti-matter is made of of anti-protons and anti-neutrons, surrounded by anti-electrons (positrons). It is not just a normal atom flipped inside-out.
A few years ago I had a problem with the house main fuse tripping several times a day. After a couple of electricians failed to find any fault the local electric board sent one of their more competent ones. He asked whether I used surge protectors for any equipment. I did, and he said to remove them. They can cause problems with tripping and are of little practical use: A distant lightning strike will be handled by the mains grid and a too close strike will blow straight through them anyway. Once I removed them the trip faults stopped, and if there is a close storm I just unplug the computers.
As a teenager, so a long time ago, I had a Saturday job in a clothing chain warehouse. Four floors (with perforated metal grid flooring, allowing for good ventilation / fire spreading, and causing vertigo for those working on the upper floors) full of cardboard, plastic and fabric. The safety briefing for new starters stated that in the case of a fire, the fire crew would come in and try to rescue anybody known to be trapped inside, but otherwise would just keep their distance and let it burn.
Flying lego: https://www.popularmechanics.com/flight/a23667/lego-plane-that-can-fly/
Some of the cheap alternatives are so bad that you can put one piece on top of another, pick up the assembly by the top piece, and the bottom piece stays behind. The tolerances that Lego is made to really are very tight, but they have had a lot of practice at making blocks by now and I don't think the price premium is completely justified by that alone.
My son got the Saturn V set (target age 14+) for his 6th birthday recently, which I was banned from 'helping' with. It took him a while, but he was able to build it. He now refuses to consider any sets which are not intended for at least age 8. He has an enormous lego collection, plus occasional access to my old Lego Technic sets, but he still likes building things out of standard 2x4 blocks. The specialised pieces are too specialised these day and no good for anything beyond that one function. Ebay comes in very handy for 'vintage' lego.
Wrong. The escape velocity from a given body is sqrt(2GM/r), where M is the mass of the body you are trying to escape from, r is the distance from the centre of mass that you start at, and G is 6.67E-11. Density does not matter. Size does not matter other than letting you start from nearer the centre of gravity, but if you try and escape from two different size bodies with the same mass, starting at the same distance, then the escape velocity will be the same.
If you start at planetary orbit distances then the escape velocity required to get away from a black hole is the same as from a star of the same mass. It is only because the mass of a black hole is in such a small space that you can start closer which changes the escape velocity.
There is an important difference between public data and data about 'The Public'. A lot of the data which the NHS holds is medical data relating to individuals, and it is this data which presumably makes up the bulk of the 'valuable' information. However, without explicit authorisation from every single person they want to sell the data on, they simply do not have consent to use it this way, either under the old DPA or the new GDPR. It is clearly a change in the data usage stated at the time of collection.
I used to help run a semi-official (i.e. management approves of it, but will not dedicate any resources to running it) anti-virus service. A honey-pot system ran on a spare PC and whenever something tried to contact it we checked what was the cause. Normally a virus that had somehow found its way onto the internal network. We then tracked down the normal user of that PC and called them to tell them of the problem and that they should shut down their computer and ring the local helpdesk. After one contact proved particularly IT inept and could not be talked through the steps to shut her PC down cleanly we just told her to press the power button. She did so, and the ping to her PC we were running kept going. Presumably she had just turned the monitor off. We debated telling her to pull the network cable out, but decided she would probably electrocute herself with the power lead instead, so we called her helpdesk for her. It was only an major IT systems integration and out-sourcing company. No real reason to expect internal competence.
There are worse systems. Not many, but they do exist. Does anybody know of anything worse than the HMRC website? Last time I tried to get into that it would not accept my credentials and I had to go through their weird process of identity verification based on whatever various other government departments and outside agencies (such as credit assessment companies!) knew about you. e.g. Which mobile operator did you open an account with in 2001?
One of the nice things about GDPR (from the viewpoint of a person, not the data-holding corporation), is that data holding must not be opt-out, it must be opt-in. Shell..user had it correct: there must be permission explicitly given, and if it is not explicitly given then it is implicitly denied.
Even systems which already hold data do not seem to be exempt - the data controllers are meant to come back and ask for permission anew.
With 'ribboned' applications determined to rob you of as much vertical screen estate as possible, a low vertical resolution might be OK for gaming, but is very poor for productive work. I run a dual 20"/21" screen setup, with one in portrait mode at 1050x1680. (Hey, it's old - that was good when I got it.) It makes working on A4 documents so much easier. That could be tricky with this one.
A 'scalar' is a single number. Think of a single point in space.
A 'vector' is a column (or row, depending on your notation) of numbers. Stretch the dot out into a line, and the values of the numbers gives the direction of the line in however many dimensions you are using. e.g. A two number vector is like coordinates on graph paper, adding a third gives height as well, and so on into harder to visualise directions.
A 'matrix' is a grid of numbers, and can be thought of as a collection of stacked vectors wrapped up in an easy to process format. It can also represent a transformation - a way of converting one vector into another. The representation is the same, just the use has changed.
All of these are also tensors, of zero, one and two dimensionality. This can be extended, so a three dimensional tensor could be displayed as a 3D grid of numbers - a stack of matrices. Then stack those into 4D, etc, until your head turns inside-out.
However, the term 'dimension' starts to get confusing, as a vector with three numbers in it can be said to represent a vector in three dimensions, but it is also a one dimensional tensor.
Back in the mid 90s, I had a hard drive die on me, when because of departmental miserliness there was no backup facility other than floppy discs. HDDs in those days had a ribbon cable (copper tracks on a flexible plastic strip, not individual wires joined by the insulation) going through the join of the two halves of the case. The fault turned out to be that the plastic strip had cracked, and broken several of the copper tracks. I fixed the strip back together with sticky tape and then used conductive paint to repair the tracks, and it worked long enough to back up all the critical data onto floppies.
"You've fixed the disc. Why do you need a new one?" was then the question from the purse holders.
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