The h Bar

Bernardo Meurer

12:28 AM

@JohnRennie I have to say, for all my dislike of Windows, it does handle hardware failures really well

Emilio Pisanty

12:47 AM

@0celo7 that's interesting

did they run out of old ships to shoot at?

Artificial reef

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►

this kinda thing

Bernardo Meurer

Pro tip fellas: never, never, NEVER unplug a drive or allow system failure during low-level operations.

It's harder to fix than I imagined

After two days I finally recovered this bricked drive

Emilio Pisanty

1:05 AM

@BernardoMeurer unlike you, we actually listen to the folks like you who tell us not to do stupid shit like that

¯\ _(ツ)_/¯

Bernardo Meurer

@EmilioPisanty I am the guy who tells you not to do it :P

Someone has to try it :P

Emilio Pisanty

@BernardoMeurer Like you didn't know it was a bad idea

Bernardo Meurer

In my defense it was half-needed

Emilio Pisanty

just sayin'

Bernardo Meurer

I was creating a ZFS pool on a drive and my girlfriend decided she had other plans than waiting

I ain't confronting her because I need to wait on ZFS ;P

Shit I broke it

again

AH

I'm throwing this drive away

it's dead

Emilio Pisanty

1:15 AM

@BernardoMeurer quitter

Bernardo Meurer

@EmilioPisanty I know how to fix it

Emilio Pisanty

You gonna give up that easily?

Bernardo Meurer

Boot into a vanilla kernel with the default scheduler, dd /dev/zero into the block device, and wait

problem is writing 500GB through a USB2 link takes like 16h

This drive costs like $10, my 16 hours is worth more than $10

The problem is that the bfq IO scheduler causes the -ck kernel to panic when a block-dev driver hangs; which this drive does because it has a corrupt superblock somewhere that I cannot get rid of

[ 1226.710194] INFO: task kworker/u16:3:28760 blocked for more than 120 seconds.
[ 1226.710200]       Tainted: P        W  O     4.15.18-1-ck-ivybridge #1
[ 1226.710201] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 1226.710203] kworker/u16:3   D    0 28760      2 0x80000000
[ 1226.710218] Workqueue: events_freezable_power_ disk_events_workfn
[ 1226.710221] Call Trace:
[ 1226.710236]  ? __schedule+0x7d3/0xe20
[ 1226.710243]  schedule+0x32/0xc0
[ 1226.710249]  io_schedule+0x12/0x40

See ^

Oh, I know what to do!

I have a NetBSD machine!

Bernardo Meurer

1:38 AM

Yeah, apparently my custom kernel was the issue

preliminary results

Yep, the problem is bfq :)

Pro-tip: If you have a drive with shitty sectors, don't use an asynchronous scheduler :)

Abhinav

2:01 AM

I have 18 reputation but I can still talk here

0celo7

@EmilioPisanty this reef is crazy

these people just dumped 2,000,000 tires in the ocean

complete madlads

and now when there's a big storm they get scattered everywhere and destroy all of the natural reefs

dmckee

2:14 AM

I'm temped to start collecting statistics about questions that involve the concept of centripetal force/acceleration. I conjecture that nine of of ten times they can be resolved by (getting the the OP to believe/understand that) "the system is not in equilibrium!"

rob

@Abhinav You also have reputation on Mathematics. That's the difference.

vzn

@0celo7 lol since when are you concerned about the environment? your chat record shows quite the opposite sentiments repeatedly :P

Bernardo Meurer

@EmilioPisanty There, now I have a raspberry pi wiping the drive for me

Abhinav

2:35 AM

@rob So it works like that.Thanks for telling me

Cows

I feel a warmth inside

I am going to be live studying category theory later

I feel like I will make a lot of progress tonight. Will begin in an hour

Ok let me grab a bottle and start. Will be making strides in the associated fora.

* a bottle of water that is * I don't drink alcohol (anymore hehe)

alright

Cows

3:02 AM

Actually, let me just read and scribble first

Sid

6:10 AM

@JohnRennie HELP required!!

John Rennie

@Sid whats up?

Sid

I hope you are okay with magnetic circuits..

John Rennie

Magnetic circuits. Hmm. Well, what's the question?

Sid

Suppose, we are given flux through the airgap and Area of Cross section of the air gap. Then, we can find flux density. And from a table given to us, the corresponding values of Magnetic field strength for different values of flux density are given

John Rennie

OK ...

Sid

6:17 AM

From this, we can find the permeability. However, the flux density that I get from calculation is, say 0.5. But, the value of H (Magnetic field strength) corresponding to 0.5 isn't given in the table. But that of 0.4 and 0.6 are given.

How do I calculate the value of H corresponding to 0.5?

John Rennie

Graph the figures you are given then estimate the value for 0.5 by interpolation?

Sid

Won't that be approximation?

John Rennie

I'd draw the graph and see what it looks like. It might be linear in which case you'd get a pretty accurate value.

Sid

No, it's not linear. If it had been, I wouldn't have been asking you..

I did draw the graph and approximated the value of H. My final answer of current came out to be about 2mA more than the answer given in the book

John Rennie

Unless you know some formula that relates H to the flux density I'm not sure what more you can do. Does the curve look like anything obvious? A parabola for example?

Sid

6:32 AM

Well, it's sort of straight line.

(How do you upload pictures in mobile version of chat?)

John Rennie

6:51 AM

@Sid Upload to imgur and post the link?

Or use the desktop version of the web site

Sid

7:07 AM

I will post once I am in the vicinity of a laptop

Slereah

Morning my dudes

Abhinav

How to write a good answer so to get votes....my answers are not good results

getting*

user228700

9:23 AM

@JohnR: Hi! :-) You around?

John Rennie

Morning :-)

user228700

How's it going?

John Rennie

Though i'm only around for a few minutes as I have deliver a laptop (one I've fixed)

@KaumudiH Mondays aren't my favourite day, but it's OK. The weather is nice :-)

user228700

@JohnRennie Ah, haha, yet another has fallen victim! :-)

user228700

@JohnRennie Cool :-)

John Rennie

9:25 AM

I do the washing on a Monday morning but it's mostly done so that's Ok too :-)

How is life in Kochi? I guess the exams are about to start - or shouldn't I mention that? :-)

user228700

Actually, in a stunning turn of events, I find myself in Chennai again!

John Rennie

Ah, do go on ...

user228700

(That's why my replies aren't coming in minutes later, haha.)

user228700

@JohnRennie Well, it turned out that I had a few days of study holidays left, so I came back home with my parents.

John Rennie

Presumably the theory is that you'll use the peace and quiet to get lots of work done? :-)

user228700

9:28 AM

I will be leaving on Wednesday, and they will follow either this Sunday, or the next Saturday.

user228700

@JohnRennie Sort of :-)

John Rennie

How are the plans for the move to Kochi going?

user228700

Great! We've found an excellent apartment, my Father's been looking into Packers & Movers options, and I'm vacating my room at the hostel this Friday, right after my exam, and taking my stuff to the new house!

user228700

I'll be staying there on my own until my parents move in with all the stuff, but I'll still have a few essentials from hostel to live on till then- a bed, a bucket, soap, etc.

John Rennie

@KaumudiH have they sorted out the Internet connection? You have to take care of the important things first!!!

user228700

9:32 AM

No, no, they have not :-) Not to worry, I'll be able to use my mobile as a hotspot till they do.

user228700

You're not adequately excited about "I'm vacating my room at the hostel this Friday..."

John Rennie

How far is it from MEC? What's the travel time like?

user228700

VACATING MY ROOM AT THAT WRETCHED HOSTEL, JOHN!

John Rennie

@KaumudiH Free! Free, at last!! :-)

user228700

:-D Yes!

user228700

9:33 AM

@JohnRennie Around 5 Kms, so roughly 20 minutes (on a scooter my parents are going to buy me soon!), give or take.

John Rennie

You'll be able to go out after 6 p.m. How will you cope with the freedom after your long incarceration? :-)

@KaumudiH Cycle distance?

user228700

@JohnRennie :-D Hahaha, yes!

user228700

The apartment's on the 17th floor, inside a gated community of four other buildings. So, they have a gym, a swimming pool, a shopping complex, a cafeteria, etc.

user228700

@JohnRennie True, but the roads are too hilly to cycle on.

John Rennie

@KaumudiH Wow, that's a step up from the hostel!

Do you have free use of the gym and swimming pool, or do you have to pay?

user228700

9:36 AM

@JohnRennie "Free". We'll be paying Rs. 3000 for maintenance every month, which includes all this stuff.

John Rennie

@KaumudiH ah, I just noticed you said in an earlier post that you were getting a scooter.

user228700

Second hand, but still!

John Rennie

@KaumudiH In the UK that would be really cheap - I don't know how it is in Kochi.

user228700

Eh, it's not too cheap by modern standards over here, but not too expensive, either. Affordable.

John Rennie

@KaumudiH I don't think I've ever owned a brand new motorcycle or car. I actually quite like driving a slightly battered car as I feel I don't have to be ultra careful with it.

user228700

9:39 AM

Oh, what, I thought your car was new when you bought it!

John Rennie

@KaumudiH No. I do so little driving these days that it wouldn't be worth spending lots of money on a new car. I tend to look for cars that are about ten years old but with a low mileage.

user228700

Ah, I see!

John Rennie

Those tend to be cheap, and as I said it allows me to be careless with them without feeling guilty.

With a brand new car I'd be terrified of scratching it.

Nehal Samee

Can anyone tell me how can I represent acceleration in respect to distance $x$ ...? Like , *x double dot *...

user228700

@JohnRennie Right, like that time it hit that tree in your driveway :-P

John Rennie

9:41 AM

@KaumudiH ah, erm .. yes :-)

And I managed to back into a wall so the corner of the rear bumper is bent now. Oh well :-)

But the car just passed its MOT with no repairs needed so it's good for another year.

user228700

@JohnRennie x'D When did this happen?

John Rennie

@KaumudiH A while back. I was at my Mum's and we were visiting a friend of hers who is in a care home. When I was backing out of the parking space there was a low wall - so low I couldn't see it through the rear window.

user228700

@NehalSamee x double dot is quite correct-acceleration is the double derivative of distance with respect to time.

user228700

@JohnRennie Oh, dang.

John Rennie

But it's OK - just a slightly bent bumper. Hardly noticable given all the other dents on the car :-)

user228700

9:44 AM

:-) Right...

John Rennie

That's the thing about an old car. You don't care if you add another dent or two.

user228700

I like your car. It's cute :-)

Nehal Samee

@KaumudiH Ah , sorry... I couldn't complete it ... Using Math jax ...

Of course ...

user228700

@NehalSamee Ah, you wanted the MathJax for it?

John Rennie

It is a nice car. I don't get attached to cars like some people do, but I will be sorry when it finally dies of old age.

user228700

9:45 AM

@JohnRennie :-) How old is it now?

Nehal Samee

@KaumudiH yeah ...

John Rennie

@NehalSamee $\ddot{x}$ or $\frac{d^2x}{dt^2}$

@KaumudiH 15 years!

Nehal Samee

@JohnRennie Thanks ...😄

user228700

@JohnRennie Wow! :-o That's not normal for a car, no?

John Rennie

Modern cars last ages. It's not uncommon to see 20 year old cars.

What tends to happen is they get gradually more expensive to keep running, then eventually something big and expensive goes wrong and it's cheaper to buy a new car than fix the old one.

user228700

9:47 AM

Wow, I see. My Dad's car is now...almost 10 years old, and works just fine! Guess we'll be seeing loads more of him (the car), thank God! It's such a good car.

user228700

@JohnRennie Ah, right, right.

John Rennie

Anyhow I need to go. My drier has just pinged to say it's finished, and I need to get the clothes out then dash off with the laptop.

user228700

How's the new cycle doing?

user228700

Ah, OK :-) Catch you later!

John Rennie

Bye :-)

Bernardo Meurer

10:38 AM

ZFS is kind of amazing

@0celo7 50% confirmed for Brazil

Just getting things set-up with Standard Cognition

Should be in Rio from August 2-25

Rumplestillskin

11:08 AM

Can anyone help me out with some index notation: I've got the following expression $$ -4/c^2 \mathbf{v} \times (\nabla \times \mathbf{w}).$$ So far I've re-written it as $$ \mathbf{v} times (\epsilon_{ijk} \partial_j w_k)$$ but I'm not really sure how to handle the rest any suggestions. I know I want to get it so that we can write it in terms on Kroneckers deltas but I currently having a brain fart. $$ \mathbf{v} $$ is used to denote a boldface vector and the $$-4/c^2$$ is just a constnat

Slereah

You can rewrite the levi-civita tensor as a sum of Kronecker symbols

Also I don't know what you want to prove so that doesn't help

Rumplestillskin

11:34 AM

Ah I got it! When you don't use something for a while the tricks fade away! Thanks @Slereah

0celo7

12:03 PM

@BernardoMeurer sick dude I’m going earlier than expected

We’re gonna have 4 days to ruin my life before the conference

@vzn that shows you just don’t know anything about me

@ACuriousMind unexpected porno imgur.com/a/uB4aPIW