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Cake day: 2023年6月22日

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  • solrize@lemmy.mlOPtoflashlight@lemmy.worldCell welder advice?
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    2 天前

    Thanks! There is a Torque Test channel video where they tested Milwaukee and Ryobi jump starters and found they delivered around 4WH and 3WH of energy respectively. They use a tool battery to charge a capacitor, then use the capacitor to jump start the motor. I thought I had seen a teardown of the Ryobi once, that showed the capacitance, but I don’t seem to have saved a link. But let’s see, E= 4WH = 14.4kJ = 1/2CV^2 where let’s say V is initially 14.14 volts so 1/2 C V^2 = 1/2 C 200 = 100C = 14400J. So C = 144 farads, can that be right? They are supercapacitors after all, and the jump starter is a fairly large box of them.

    Here’s the jump starter test vid: https://www.youtube.com/watch?v=z4N5txe7oZA

    This claims to be a 100 farad 13.5V capacitor bank (5x 500 farad 2.7V in series): https://www.aliexpress.us/item/3256804444528644.html

    The jump starters are a fair amount bigger than that bank.


  • Hard to pierce pseudonymity doesn’t interest me that much, because it’s bad enough having all your posts connected together.

    I want something like 4chan (but heavily moderated), where all posts are just marked “Anonymous” and if you make 3 different comments, it’s not publicly shown that they came from the same person. It’s ok to retain the info privately for a short period, for moderation purposes. It could be ok to assign a persistent pseudonym for each thread, so if you comment 3 times in the same thread, those comments are connected to each other, but not to other comments in other threads.

    This is a good article about the attractions of completely anonymous posting, though it’s from the pre-supertoxic internet era: https://wakaba.c3.cx/shii/shiichan






  • In the US, the cover (as long as it doesn’t mess up the song too much) is automatically allowed, as long as you pay what is called a compulsory royalty (a certain amount per record sold, or per audience member in case of a live performance). ASCAP and/or the Harry Fox Agency (iirc) act among other things as clearinghouses for these payments. You have to notify them ahead of time of the cover you’re releasing, and maybe pay something up front.

    Normally if you seek permission from the publisher of the song you want to cover, it’s because you want to negotiate a lower royalty than the compulsory one. You can often do that if you can convince them that your record is going to sell a lot of copies. It’s just a discussion about money and business people are used to that.

    If your performance copies from the original but is not a straightforward cover, then you do need permission ahead of time as the compulsory license doesn’t apply, with some limited free-speech exceptions for parodies.

    IANAL bla bla bla.

    https://en.wikipedia.org/wiki/Compulsory_license#United_States





  • Wow I didn’t know about car audio capacitors. What capacitance did you use? What voltage, typically? They are on the expensive side, but impressive. I bet they could also jump start car engines. I’m not keen on using a lead-acid battery so capacitors seem like an ok alternative.








  • I think it’s hard, and even if there is something that works, its use can probably be detected somehow, and that could get your family in trouble.

    Tbh I’d probably use snail mail letters for anything private on the theory that the RU govt doesn’t have the resources to open all the envelopes, and you can use special phrases for particularly private meanings. All that stuff like media attachments is asking for trouble. You could also send microSD cards by snail mail though that might attract attention.

    Remember that Osama bin Laden’s compound in Pakistan had no internet connectivity at all. If he wanted to send an email, he’d write it to a USB drive and have a guy on a motorcycle take it to a café 70 km away or something like that. Replies would be brought to him the same way. They still managed to find him and kill him in his bedroom.

    Today with AI analysis of massive amounts of traffic logs, I’m sure signal ID is far easier than it was in 2011.



  • The 3 diseases:

    The woman had a rare, life-threatening blood disorder, autoimmune haemolytic anaemia (AIHA), whereby rogue immune defences destroy red blood cells. … In addition to AIHA, the woman had two other autoimmune diseases. One, immune thrombocytopenia (ITP), is driven by immune cells destroying platelets, which raises the risk of bleeding. The other, known as antiphospholipid syndrome (APS), has an opposing effect and raises the risk of harmful blood clots. All three diseases were due to wayward B-cells which make infection-fighting antibodies.