Why are these 32 symbols found in caves all over Europe | Genevieve von Petzinger | applicability คือ

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Why are these 32 symbols found in caves all over Europe | Genevieve von Petzinger

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นอกจากการดูบทความนี้แล้ว คุณยังสามารถดูข้อมูลที่เป็นประโยชน์อื่นๆ อีกมากมายที่เราให้ไว้ที่นี่: ดูความรู้เพิ่มเติมที่นี่

Written language, the hallmark of human civilization, didn’t just suddenly appear one day. Thousands of years before the first fully developed writing systems, our ancestors scrawled geometric signs across the walls of the caves they sheltered in. Paleoanthropologist and rock art researcher Genevieve von Petzinger has studied and codified these ancient markings in caves across Europe. The uniformity of her findings suggest that graphic communication, and the ability to preserve and transmit messages beyond a single moment in time, may be much older than we think.
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Small Scale Aluminium Anodising in the Home Workshop

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A short film sharing what I’ve learnt about low current density anodising of aluminium from my limited experience in the home workshop. This isn’t meant to be the right way, or even a good way, it’s just the way I do it.
The technique provides a measure of improved durability / corrosion resistance to parts, as well as changing the aesthetic.
I didn’t mention that the chemical baths can be reused over and over, so no need to remix for every job.

Useful links and further reading:
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Changes to the rules surrounding the supply and possession of sulphuric acid in the UK during 2018:
https://www.gov.uk/government/publications/licensingforhomeusersofexplosivesprecursors/licensingforhomeusersofpoisonsandexplosiveprecursors
and
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/694030/FAQs_general_public_v4__Mar_2018.pdf
For those speculating about the reason for the withdrawal of concentrated sulphuric acid products from general sale in the UK, this article might give food for thought:
https://www.bbc.co.uk/bbcthree/article/5d38c003c54a4513a369f9eae0d52f91
https://youtu.be/9pZIl2EwlvY
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The use of sodium bisulphate in place of sulphuric acid:
http://www.observationsblog.com/sciencetechnologyexperiments/anodizinganddyingaluminumwithoutbatteryacid
https://www.youtube.com/watch?v=7jFN3l_mrKk
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A 15% acid solution seems to be what many people aim for. There’s pros and cons to higher and lower concentrations but they’re beyond the scope of my little setup. finish.com has a wealth of information:
https://www.finishing.com/11/30.shtml
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Some 720 rule calculators.
The one featured is by by ‘kreutz’, mainly as I can use metric sizes with it. 1 mil is an optimistic coating thickness for sulphuric anodising thicker coatings require hard anodising which is beyond the scope of this film.
https://chemeon.com/p/calculator/
http://www.ndhsubmersiblescience.com/ano/720rule.html
https://www.hobbymachinist.com/threads/diyanodizingathome720rulecalculatorforlowcurrentanodizingmethod.6775/
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POST UPLOAD UPDATE:
Thanks for all the comments and feedback 🙂
I’ve read them all, but I’ve not the time to respond individually. There’s some interesting ideas I can play with next time I get the anodising stuff out.
Some (mainly US) viewers seem annoyed that the UK government would take steps to try to ensure the safety of their citizens by making it more difficult to obtain something that (a small minority of) the general public has demonstrated they’re too stupid to have free access to. It’s a minor inconvenience to me, and good reason to revisit bisulphate method. I dare say the persistent shopper will still be able to obtain it, but I wanted viewers to be aware of which side of the law both buyer and seller will be on if the relevant paperwork is not available. Perhaps there’s a market for selling prediluted 14.9% H2SO4 to the home anodiser?
As for the availability of lead, I should probably have said “small quantities of clean lead sheet are surprisingly hard to get hold of”. Larger fishing weights are still made from lead, as are old tyre weights (new ones are other metals) and these could be fashioned into sheets if I had the inclination. Lead flashing is available at every DIY store, but I can’t justify the cost of a 3 metre roll for the sake of a couple of small pieces. I’ve since obtained some from a friendly roofer 😉
I’m not a chemist, but I believe having too little acid to mix to the original calculation left me with a solution of around 14.5%. Given my uncalibrated scales and general ball park approach, I didn’t think it was worth the recalculation / reweighing / refilming for a couple of percent difference. With concentration, time, temperature, current density and material all playing a part (and being beyond the scope of my simple setup) I just wanted to get on with it. Note: You can’t just divide the weight of acid by the weight of water to get a percentage, it needs to be the weight of acid by the weight of solution (i.e. acid plus water).

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Shot: DMCTZ70 1280×720 50P AVCHD
Edit: FCP7 ProRes 422
Mic: C01U

BLD11 2Slab 3

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Building Design
Lecture 11 : Twoway Slab 3

ฟันธง หุ้นทำกำไรไตรมาส 4

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