1

General Science / Re: Skiving

« on: 29/05/2023 21:03:16 »

The proportion of the Tool was huge, in comparison to the job/product.

It had a yellowish oily fluid in place of a milky white cutting fluid.

Anyways, i think the Thickness of the plates being cut is not allowing it to Curl.
(guessing)

See here:


Skiving.png (8.13 kB . 1717x656 - viewed 134 times)

In order for the shaving to separate, it must bend at A in order to make room for the tool, but before A it had to bend at B, and before B, C, etc. Hence the shaving curls, because once it has bent at the tip, there's nothing applying a force to straighten it again.

If you look at the video however, you'll see that the finished fin is less that half the length of material shaved off, so it must be being compressed, and I think it might be the deformation beyond it's elastic limit as it's compressed that's straightening it, but I'm not conviced I can see where the force to do that would come from either. The shaving is sliding over a smooth lubricated surface, after all.

And if it that's it, why doesn't all swarf come off the tool straight?

ps - Why is it a $64,000 question?

It's just a turn of phrase. It derives from an old 1960s TV contest in the USA where people answered questions with a prize that doubled each time. The final question was the $64,000 question.

2

Question of the Week / Re: QotW - 23.05.05 - How fast does evolution happen?

« on: 06/05/2023 22:27:17 »

& the ones who followed Chastity or observed Abstinence.

Even Children & Adult asexuals.

(Vampires...no chance!)

They might survive as individuals, but if they're not reproducing they won't survive as a lineage.

3

Physiology & Medicine / Re: What's the Evolutionary Significance of Fashion?

« on: 05/05/2023 12:21:03 »

This is Prof Steven Pinker's analysis, you'll find it in The Blank Slate or How the Mind Works, I forget which.

Firstly, high status is an evolutionary advantage: high status individuals find it easier to get a mate because it's a marker for access to resources, so people will compete for it. There are many ways in which they do this, but one of them is what Pinker calls 'Conspicuous Outrage', in a nod to the term Conspicuous Consumption, which is another means of status competition.

If people want to be accepted in society they have to conform: to 'fit in', and those that don't or won't come in for all sorts of mistreatment. This offers a high status individual an opportunity: be overtly different to everyone else and get away with it without being abused because of your status in society: Conspicuous Outrage. This then sets in place a chain reaction.

People in the strata of society immediately below the non-conformer seek to obtain some of his status by copying his behaviour and wearing the same clothes or whatever, then the level below them copies, then the one below that etc. However as soon as the person at the top sees lower status people copying him, he loses status unless he changes his behaviour and does something different again, then again, and again.

So what you have is a series of novel behaviours continually originating at the top of social groups then rippling their way down to the bottom one after the other: "fashion". The 'top' may be a pop star or a page three model, or perhaps just the 'it' kid in your class at school, the point is they have some status to assert within the group they mix among.

The problem with fashion is that it's socially destructive. Not only is it exclusive, seeking to marginalise those who don't conform, but it's also criminally wasteful to throw away stuff just because it's unfashionable rather than unserviceable. Copying others and following like a sheep rather than having a mind of your own is also fatuous.

4

General Science / Re: Should countries phase out the making of glass and plastic to save our planet?

« on: 19/04/2023 23:18:01 »

It's about time the cost of waste disposal was put on the selling price of commodities instead of at the local dump, so that you disincentivise waste instead of incentivising fly tipping.

5

Technology / Re: Can you explain this demonstration of a capacitor?

« on: 22/03/2023 14:35:48 »

I don't know where the ammeter is connected.

Yes you do, follow the wiring:


MIT vid.png (13.57 kB . 1048x591 - viewed 2018 times)

So there is at least one path from plate to plate through the ammeter.

No there isn't, the power supply has been disconnected, so the only connnection to the live plate is the insulated support on the stand, and the electroscope.

Is there any discernible pattern or explanation for the deflections shown on the ammeter during this part of the demonstration?

Yes, as above, the knob is on the live side of the meter.

6

Chemistry / Re: Why adding a fizzy drink to ice does the temp drop below the temp of the ice?

« on: 26/02/2023 18:24:47 »

I heard that

Have you checked to see whether it does?

I can see why the evaporation of CO2 will reduce the temperature, with or without the ice.

7

General Science / Re: Why Does Making A Sandwich Enable Ewe To Cut Anything?

« on: 02/02/2023 12:19:55 »

If I have a stack of sandwiches to cut, I do them one at a time, cutting them all in one just squashes them. I cut by rolling the curvature of the blade, drawing the blade across them just tears.

8

Technology / Re: Electricity Generation via treadmill. Can one person generate enough?

« on: 20/01/2023 11:37:14 »

The issue isn't whether you can produce a useful amount of power (useful for doing what? cycle lights run off a dynamo), it's whether you can do it at a useful efficiency. The human body is about 20% efficient, far worse than a combined cycle power station (55-60%), and growing the food to power it accounts for a quarter of global CO2 emissions.

9

Chemistry / Re: Strange aroma off smokeless fuel or has covid ruined my snout?

« on: 05/01/2023 16:08:21 »

A small unrelated Query...

Is Covid never ever gonna go away?

Will WE have to keep dealing with it, live & die with it like ForEver?

This doesn't bode well:


Covid.jpg (115.87 kB . 900x648 - viewed 1138 times)

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General Science / Re: Advent calendar maths question!

« on: 15/12/2022 00:37:42 »

0,1,2,3,4,5

0,1,2,6/9,7,8

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Technology / Re: How to learn process control system in practice?

« on: 17/11/2022 17:33:53 »

bends in the road can take the car in front out of the beam for a few seconds. So it appears to "remember" the speed of the car in front for perhaps 5 seconds

But the car in front could do an emergency stop in the 5 seconds it's out of view, can the assisted braking respond in the time left after the car reappears?

The more complexity in the control system, the more responsibility on the driver to understand it in detail, and to understand (and take action) when it hits corner cases where it doesn't do what you intend.

The more complexity in the control system, the more opaque it generally gets.

if the car in front is slowing to turn a corner, and I can see that it will be safely out of the way before I get close; the radar system (configured for sensitive mode) sees the car in front slowing to a near stop in the line of sight, and rapidly slows down my car. Flicking off the speed control for a second resolves this problem.

The problem with automation is fighting it to stop it doing what you don't want can often make more work than doing the job yourself.

12

Technology / Re: Does wi-fi harm the environment?

« on: 08/11/2022 14:15:26 »

Radio engineers have been working with radio for a century, and so have groups of professional users, if it were harmful they would have showed some signs of increased morbidity & mortality by now, but I'm not aware of any evidence of that. Concerns about safety didn't start to gain any currency until mobile phones put radio into the hands of lay people.

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Cells, Microbes & Viruses / Re: Why are arm pit stains so difficult to remove?

« on: 25/10/2022 18:18:42 »

i suspect the deodorant to be the Cause

Me too.

I don't use deodorant, and my clothes don't stain.

14

Technology / Re: Can I get an electric gas boiler?

« on: 15/10/2022 13:24:22 »

Do you have any links ?

12 million of them in less than 10 seconds:
https://www.bing.com/search?q=domestic+chp&qs=n&form=QBRE&sp=-1&pq=domestic+chp&sc=10-12&sk=&cvid=8865F76F517743F9A56CF487A783354A&ghsh=0&ghacc=0&ghpl=

15

Physiology & Medicine / Re: Link between supercentenarians and smoking?

« on: 31/05/2022 10:51:24 »

"a good deal of" is not an objective way of measuring things. Relevant questions are how many smokers vs non-smokers reach the age of 100, and what proportion of centenarians are smokers compared with nonagenarians, octogenarians and septuagenarians.

16

Plant Sciences, Zoology & Evolution / Re: Have animal reactions to mirrors and windows been studied?

« on: 28/05/2022 00:50:28 »

https://twitter.com/buitengebieden/status/1523065975654195201
https://twitter.com/buitengebieden/status/1527524346872332289
https://twitter.com/philipnolan1/status/1515260865892732928
https://twitter.com/Yoda4ever/status/1519881660744962049

17

Marine Science / Re: Why is the ocean salty?

« on: 26/05/2022 14:10:16 »

There are salts in the soil which get flushed into the rivers and then the sea by rainfall. When the sun evaporates the water to form more clouds and rain the salt gets left behind in the sea, so if you repeat that cycle for billions of years the salt in the sea becomes more and more concentrated.

18

Physiology & Medicine / Re: is psychiatric labelling complete nonsense?

« on: 18/04/2022 17:15:20 »

This makes an interesting read. In essence, Smail argues that most mental health problems are a normal reaction to abnormal circumstances, and therapy fails because it seeks to gaslight the patients into believing that they having an abnormal reaction to normal circumstances. The only therapist I've met who could communicate rationally without being deliberately obtuse left the job saying "I'm fed up of the way the patients are patronised, and fed up of pretending we're helping when we know we aren't".

My advice to anyone contemplating getting themselves a mental health record would be think very carefully about whether you want your healthcare blighted by Diagnostic Overshadowing for the rest of your life.

Connections by Johan Hari is a thoughtful and intelligent look at how our modern way of life creates many of the health problems that are reaching epidemic levels.

19

Physics, Astronomy & Cosmology / Re: Which weighs more, a litre of ice or a litre of water?

« on: 15/04/2022 16:15:39 »

"Houston, we have a problem. We have a leak. Our oxygen is rapidly venting"

"Hello, this is NASA Houston here. We are currently experiencing unprecedented call volume, and all our operators are busy. Please be assured that your call is important to us. If you're calling to order a pizza, please press #, otherwise hold the line and your query will be dealt with as soon as possible. You are currently number 46 in the queue."

20

Physics, Astronomy & Cosmology / Re: How do you calaculate the capacitance of two unsually shaped plates?

« on: 21/03/2022 17:46:38 »

The quick way is to calculate the capacitance of the wide end, then either triple it if the spacing is 2mm as in the diagram, or quadruple it if the spacing is 3mm as in the text.