bodmas blog

echo 30 > /proc/acpi/thermal_zone/THRM/polling_frequency
exit

Entering the code above in a terminal window under root sorted the fan problem on my little L400.

Previously, the kernel was not reading the temperature at regular intervals and so simply stuck to the fan state that applied when I booted into Ubuntu. Boot from cold, the fans were off and stayed off – very hot laptop after an hour or so. Boot from warm (re-boot from Ubuntu or Windows) the fans went on but stayed on.

I posted a question under Hoary Laptop Support on the Ubuntu forum and pestilence4hr posted back with his/her experience with a Gateway laptop. I think I posted enough information so that people could recognise the problem – vague posts don’t always get answers.

Support forums and OpenSource go together, no ‘smooth’ interfaces where the fans ‘just come on’ but someone somewhere may have seen the same problem and solved it. You save your disposable income and take your chances I suppose – I now have a secure virus free operating system that I can surf the Web with on this old laptop. For hacking out handouts Windows ME and Office ‘97 work fine and fast – I’m just not putting them near the Internet.

Suppose the game consists of tossing a coin and rolling a dice. You win by getting a 6 and a tail. These two events are independent – the dice cannot influence the fall of the coin – so you can combine the probabilities by multiplying. If the coin and the dice are fair, the chance of winning is one sixth × one half = one twelfth.

This simple rule cannot be applied if the events are not independent. That stark fact is being hammered home in the case of Professor Sir Roy Meadow currently under investigation by the BMC for gross professional misconduct.

According to the BBC article on the early stages of the hearing , the following logic was presented by Sir Roy as an expert witness in a murder trial

• “He said the odds of a single cot death in a non-smoking household where the mother was aged over 26 and there was at least one wage-earner were one in 8,543
• This meant the odds of both Clark boys dying of natural causes were the square of this figure – 73 million to one”

I have no idea how to evaluate the suspiciously accurate looking figure for the probability of a single child dying in such a household, but I do suggest that squaring this figure makes a very strong assumption about the biology of the situation. I’ll need to tread carefully using this context as an example in GCSE maths level classes, but it certainly shows how maths can be important.

Added July 15th: “The panel had earlier decided Sir Roy had not meant to mislead the Clark trial, but said his evidence had done so because it “erroneously implied” two natural deaths in a family would have to be independent of one another.” – GMC Panel statement after striking Sir Roy Meadow off the register.

• LaTiS Centre Image Archive from Essex University

Thanks for this resource – about 400 free pictures. Mostly .jpegs and around 400 to 600 pixels wide with white backgrounds.

• Neal Stephenson’s essay: In the Beginning was the Command Line
• Eric Raymond’s essay: The Cathedral and the Bazaar

Did either of these geezers need to cope with fan control in Linux on a 3 year old laptop and a wobbly combo drive on a brand new iBook?

Why can’t computers be like toasters – sealed units that just work™ until you need a new one (about every 10 years)?

Ubuntu runs really well on the Dell L400 but I can’t get the fans to switch on when the laptop begins to heat up. After about 90 minutes, the trip closes the computer down. With a default Ubuntu install, if I reboot while the computer is hot, the fans do switch on. It looks as if the temperature is being monitored only at boot time. I am now puggling deep into the relative merits of apm and acpi. Stephenson’s vision of taking control of the hardware becomes a reality big time.

The iBook combo drive has already been replaced once and the new one is playing up so paying serious money for a new computer does not guarantee performance either.

Computers really should be like toasters and televisions.

Kodak chromagenic black and white film… has a cyan mask on the negatives so the photolab prints come out close to greyscale with a nice duotone look.

Wall on outhouse in a yard in Wallasey.

The Isaac Newton Institute for Mathematical Sciences published a series of 12 monthly posters on tube trains in London during the year 2000. The posters are available at moderate resolution on the Web and can still be purchased as a set from The Mathematical Association’s online shop – a nice tie in.

The posters were designed by Dr. A. D. Burbanks and show mainly applications of mathematics in the simulation and modelling of complex and chaotic systems.

By popular request… Remember that a multiplying mixed signs gives a negative answer and multiplying same signs gives a positive answer!

Multiply out the following

1. 2(3x – 2) – 4(2x – 1)
2. 2xy(x + y)
3. 2(4x + 3) + 3(2x – 9)
4. 4(x + y) – 2(x + 2y)
5. 2x(x² – y³)
6. 2(5x – 4) – 3(2x + 7)
7. 4(10x + 3y) – 7(x + y)
8. 3x²(4x + 2y) – 4y(2x² – 3y)
9. 2(x – y) – (4x + 3y)
10. 14(2x – y) – 5(3x – 2y) + 4(4y – 2x)

Factorise the following expressions

• remember to find the largest common denominator and to divide through by the common denominator to find what goes inside the bracket
• remember that xy² means ‘x multiplied by y squared’ and is different to x²y

1. 6x²y – 9xy²
2. 12xy – 15x²y²
3. 18x² – 6x
4. 21p² + 28p
5. 24q² – 18q
6. 15r²s – 10rs²
7. 18xy – 27xy²
8. 15x²y³ – 20x³y⁴
9. 12py² – 9p²y
10. 144x⁴y⁸z³ – 84xy²z