Doppler effect joke

December 4, 2009

This is the first doppler effect joke iv’e ever seen 😀

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periodic table

November 17, 2009


Transmissivity

November 17, 2009

A little story bit about heat and light.

 

Transmittance is defined as the fraction of incident light that passes through a sample. The fraction that is absorbed is as mentioned earlier, the absoptance. By this deffenition we realize that trancmittance is dependant on the sample geometry, material and surface finish. We also must realize that transmittance is specific to specific wavelength.

Outline of the experiment

Meassuring transmissivity of an object is relatively straight forward. Our meassuring device will be this thermal imaging camera that senses infra red light. The setup is shown here:

 

  • Since we want to find the reduction in radiation that reaches the measuring device, we first use a reference measurement. ( It is important to note here, that we adjust the emmisivity of our reference object to 1, and note the temperature )
  • Then the samples of interest are placed in-between the reference and the measuring device. This will affect the amount of radiation reaching the device.
  • We manually adjust the input emissivity on the device’ computer terminal, until we arrive at our known reference temperature. The value of emissivity is noted. The difference between the new value and the reference is value is the transmissibility of our sample.

Data

The computed data are listed in the table. It is observed that the dark plastic material has a higher transmissibility than the clear. Initially this seems counter intuitive, as we with our eyes can see through the clear bag, but not the dark. But when we consider that visible light and infra red are merely traveling at different wavelengths, we can conclude that the two materials impede radiation at different bandwidths. The camera used, detects only certain a band of electromagnetic waves traveling at higher frequencies, in the infra red spectrum. Our eyes, detects waves moving in a lower band of frequencies, and the result is clear, as the plastic bag turns opaque in the cameras view.

Transmissivity measurements and values

Experimental-grade PE plastic garbage bag. Placed in the cameras FOV during one of the measurements.

 

The image below is from a different experiment, where we investigated the cameras capability with rounded surfaces. We are looking at a round aluminium block, standing upm It is clear that depending on the angle between the camera and the surface, the meaaurements will vary. The object seems to be warmer near the top and bottom, and also in the middle. The top and bottom are because here we have a larger density of molecules pr. viewed surface area. ( A bit like the reverse of the sun shining on earth, giving rise to temperature differences. )

 

The part in the middle that seems warmer is a reflection from the camera, and corrosponds to the camera being heated to 35 degrees. The very bright parts below are reflections.

Here we have a picture of the “cavity effect”. The cavity effect describes the circumstances at wich the radiation enters a caity and is reflected, multiple times. This results in multiples of radiation summing together, and exiting together. This will make the cavity appear warmer. Shown in the picture below, is a horisontal row of 4 holes woth the only varing parametre being the depth. From left to right: D: 5, 10, 15, 20 mm

Cavity effect

So now you know, a little bit about non-contact heat meassurement 🙂 And i didnt even tell you about emmissivity and reflectance 😛


Wave Mechanics – Human Behaviour?

October 21, 2009

After comming home from my days lecture on “Mechanical vibrations”, i stumbled uppon the concept of, switching your signal input in some experimental analasys, from some frequensy response, with that of a data values of some measurand of behaviour. And here i mean any kind of behaviour, in a living organism. Animal or plant for that matter. Or maybe even crystal growth or, what ever you can consider behaviour.

If it is possible to reduce the noise on your data, and produce some relatively coherent results that shows, that behaviour folows patterns simmilar to that of physical systems, what implications does this have? Can we then use this to alter, or even predict behaviour?

Would this be a way to tie together pschology and physics? Psychology being the empirical data set, to support the theory? Just some quick thoughts here, hehe…

I find this very interesting, and am pondering how to make some simple experiment that will definately debunk this hypothesis, so that i can stop wondering about it. Please, do join in 🙂


Homemade: Blackberry icecream

August 18, 2009

This one is a little bit more tricky, but equally delicius 🙂 Its my recipy for Italian style blackberry icecream. Its not that fatty, and you can vary the amount of sugar to some extent. And its CHEAP TO MAKE!

Here is the almost finished product: 1.2L of OM NOM NOM NOM!

Ok what you need: for 1 Liter+ icecream:

5 Egg yolks

180 – 190 grams of sugar

1 Liter of milk, i used 3%, you can use any substitute or combination, but 3% is definately fine

1 Large bowl of berries, or as many as you like.

Vanilla. Preferably fresh – 1 stick.

And time to spare. This will take a bit…

Start  by heating up the milk, and add the vanialla. Dont boil it, heat it up just barely to the boiling point. It will start frothing a bit, around the edges of the pot.

Take your yolks, and whisk them in a pot with the sugar. This being a seperate pot, from the milk one. Whisk till they are white and foamy.

Now comes the bit tricky part. You are going to put the yolk mixture on a relatively low heat, and then graduately add the warm milk mixture to it,  whil stirring and whisking it. DONT let it boil. If it gets to hot, the yolks wil start to curdle, and you will have failed… It should look something like this when youre done. very light and frothing:

While this was going on, you were using your 3rd arm for mushing the berries through a strainer, to get rid of the skin, centerpieces and whatnot parts. Leave a cople of handfulls of berries, to add to the icecream later on.

Add the juicy goodness to the milk-yolk mixture. Let it cool.

I pored my mix in a plastic container like this. This is after some freezing:

Unless you have acces to a proper icecream machine, its a realy realy realy good idea to take out the icecream, as its solidifying, and whisk it through, and break down the crystal that are forming. This wil give it a much more plesant consistence. And at the point where the mixture has gotten to a low enough viscousity, add the remaining berries! This will make you icecream even better 🙂

A tip: Remember, that water freezing  expands about 10% in volume. I accounted for that in this container, but forgot to account for the addition of berries! So i had to pour some of this into a smaller plastic box, to avoid a bit of spillage in the freezer 😛 Another thing: If you are concerned with salmonella, scold the eggs before you them, with boiling water, or buy pastourized yolks. There is no gurantee that you reach sufficeint temperature during heating, unless you use a thermometre, and you might risk ruining the icecream.

I hope you enjoy this easy to make, cheap and not too unhealthy, organic and lovely icecream recipy.


Homemade: Blackberry rum

August 18, 2009

The schrubs of our garden are at places dominated by this lovely plant, the blackberry (Danish;brombær). As they suddently all started ripening, i went out and quickly filled up a bowl.

After some delicious consumption…

I decided to try and improve on a rather cheap and foul tasting rum that i had bought, with some of the berries. And since the were in such an abundance, and we are having summer, i wanted to try and make some italien style icecream, wich is actually based on milk, not cream.

Recipy for my Blackberry infused rum:

1 Large jar, that can be sealed airtight

1 Bottle, or as much as you have left, of rum

As many berries as you bother to pick.

0 – a few cups of Sugar

Process: Since the alcohol will sterilize the berries, you dont neccicarily have to clean them all that well. Some recipies actualy say you should avoid washing them, if possible. But i had so many, that i decides to swirl and rinse them in water 3 times or more, a small batch at the time. Then I simply filled up my jar with berries, then i poured half a cup of white sugar, and some nice honey over them. Not that much though. Then I poured over my rum, sealed it up and left it to infuse, in a dark cool place:

Then shake it once in a while, and let it sit for anywhere between a couple of weeks to a couple of months. This stuff will stay good for a long time. It will only get “better”. You can use any type of berries, and alcohol. I dont know if its important, but i made sure that there was enough alcohol to cover the berries, but its probably not important.

When you want to drink it, do a rough filtration, maybe “smush” the berries into a pulp, and do a clean filtration through a cloth or a paper coffee filter. The leftover berries, can be served with icecream, or made into a nice marmelade! But dont waste them!


Homemade: Corner mount for speaker

August 17, 2009

This how my smasung speakers are mounted. The can even be pointed 45 degrees to either side, from the middle position. Very flexible. Made the mounts from screap pieces of wood, and a large screw.