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#measure

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Continued thread
C.

In case anyone's keeping score, the idea that JFETs have hugely variable properties and that this problem cannot be - or at least has not been - fixed with different design or manufacturing practices, this batch showed it pretty clearly to me.

20 J113s, minus 1 fake, equals 19 devices. I measured the Vgs / pinch-off voltage and the Id / drain current in my test rig. The result?

6 very distinct bins with between 2 and 6 devices in each. Vgs overall varied from (-) 1.30 V to 2.11 V (variance is 38% of the larger value, or 62% of the smaller...), and Id from 5.7 mA to 12.8 mA, a spread of 125% (!) of the smaller value.

No wonder so many JFET circuits just don't work if you don't hand-match the devices.

#variance#variability#characteristics
United States

Supreme Court joins Trump and GOP in targeting California’s emission standards

WASHINGTON — The Supreme Court on Friday joined President Trump and congressional Republicans in siding with the oil and gas…
#UnitedStates #US #USA #California #californiaregulation #cleanairact #climatechange #court #decision #DonaldTrump #electricvehicle #emissionstandard #fuelmaker #gasindustry #GOP #measure #state #SupremeCourt #trump
europesays.com/2180000/

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Bharath Krishnan

Motivation:

Let \(X\subseteq \mathbb{R}\) and \(Y\subseteq\mathbb{R}\) be arbitrary sets, where we define a function \(f:X\to Y\).

I want a measure of discontinuity which ranges from zero to positive infinity, where

• When the limit points of the graph of \(f\) is continuous almost everywhere, the measure is zero
• When the limit points of graph of \(f\) can be split into functions, where \(n\) of those functions are continuous almost everywhere, the measure is \(n-1\)
• When \(f\) is discrete, the measure is \(+\infty\)
• When \(f\) is "hyper-discontinuous" [1], the measure is \(+\infty\)
• When the graph of \(f\) is dense in the derived set of \(X\times Y\), the measure is \(+\infty\)
• When the measure of discontinuity is between zero and infinity, the more "disconnected" the graph of \(f\), the higher the measure of discontinuity.

Question 1: How do we fix the criteria in the motivation, so they are consistent with eachother?

Question 2: Is there a measure of discontinuity which gives what I want?

Attempt: I tried to answer [2] this using a previous question, but according to users it's needlessly complicated and likely is incorrect. I'm also struggling to explain why this answer [2] has potential.

[1]: math.stackexchange.com/questio

[2]: math.stackexchange.com/a/50252

Mathematics Stack ExchangeDo these "hyper-discontinuous" functions exist?Suppose $\ X\subset \mathbb{R}\ $ and $\ Y\subset \mathbb{R}.$ Definition: A function $\ f: X \to Y\ $ is hyper-discontinuous if for every $\ x\in X,\ \ \exists\ \delta>0,\ \varepsilon>0\ $ s...
#measure#continuity#discontinuity
Replied in thread
Mathzy

2024 Vinyl Purchase Revisit 11/12

#NowPlaying: 'Field Music (Measure)' by Field Music (2009 - 2019 yellow and red vinyl).

Another one by this band and - for me - their definitive album. Wondrous music across two records. These guys can do more in three minutes than some bands manage on one side of vinyl.

#Vinyl#NowSpinning#NowListening
C.

#AliExpress / cheap #Chinese goods / #questionable sellers, part 37:

1. Order #rechargeable 3-speed folding desk #fan.
2. Receive different version of same fan - no #electronics, no #battery, just a USB lead, it runs at one speed when plugged in, unplug it to turn off.
3. File "item not as described" ticket with photos clearly showing it's the wrong item.
4. AliExpress rejects ticket, the human who spent 0.3s reviewing it didn't read it and just clicked "#reject".
5. Edit #photos, adding big red "NO BATTERY HERE -->" and "NO ELECTRONICS HERE -->" etc and resubmit ticket.
6. AliExpress accepts claim this time. Get refund.
7. Place order for same rechargeable fan from different #seller.
8. Receive fan. #Charge. Give to partner.

"It turns off after a few seconds", she says.

Take it apart. Examine the circuit board, #probe it various ways, all looks good. #Measure #voltages. Manually #power the fan and see it draws half an #amp. See the suspiciously undersized lithium-ion #cell and think "they didn't just #cheap out so much that the thing doesn't work, did they?"...

Yup. The plastic casing has a slot & tabs arrangement inside sized for an 18650 cell, but they've got a much smaller cell in there with some padding to keep it in place. It's a 14500.

When the fan's on, the load is too much for the cell. The voltage drops enough that the little 3-speed management #chip thinks the cell is flat, and it turns off.

Put in a good 18650, runs like a charm.

Sheesh.

#LiIon
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Mx Verda

" "Today’s assessment from the World Meteorological Organization is clear:
Global heating is a cold, hard fact,"
United Nations Secretary-General António Guterres said in a statement.
"There's still time to avoid the worst of climate catastrophe. But leaders must act
– now."

The planet's average temperature in 2024 was 1.6 degrees Celsius higher than in the 1850-1900 pre-industrial period, C3S said.
The last 10 years have all been in the top 10 hottest years on record, according to the World Meteorological Organization. "

federated.press/@ClimateNewsNo

reuters.com/business/environme
(And previous toot in thread I fucked up lgbtqia.space/@MxVerda/1138058 )

MastodonClimate News Now (@ClimateNewsNow@federated.press)2024 was the hottest year on record, scientists say. The WMO said climate change was pushing the planet's temperature to levels never before experienced by modern humans. #ClimateChange https://www.reuters.com/business/environment/2024-was-first-year-above-15c-global-warming-scientists-say-2025-01-10/
#Climate#ClimateDiary#ClimateStrike
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