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All Questions

103 views

Implementing a web app where the server cannot decrypt its own data?

I'm a cryptography novice, but I think that the world needs to move towards an "encrypt everything" mentality as much as possible. As a result, I've been thinking a lot about ways to build a web app ...
53 views

Output of a Feistel network with all “0” round function

What is the output of an r-round Feistel network when the input is $(L_0, R_0)$ and each round function outputs all 0s, regardless of the input?
35 views

How to encrypt letters less than block n using Hill Cipher

I am learning about Hill Cipher and know that it is a block cipher where each block of n letters (considered as an n-component vector) is multiplied by an invertible n × n matrix, again modulus 26. ...
42 views

Need help solving a shift cipher problem?

A three letter alphabet {a, b, c} has probabilities p(a) = .5 and p(b) = p(c) = .25. A shift cipher is applied to pairs of letters. More precisely: plaintexts consist of two-letter sequences of ...
58 views

Is it safe to derive a password from a signature provided by ssh-agent?

I'd like to use a password-based system on a remote host (accessed via SSH) without having to copy-and-paste the password and without storing it on disk. Using the system with some other form of ...
46 views

Create collision examples with MD5 hash with salt

I'm using the following lines to create a hashed string String source = String.format(%s %s %s", salt, firstPart, secondPart); byte[] bytes = md5(source); ...
48 views

Key management protocol for end-to-end security on Advanced Metering Infrastructure

I am currently working on a research on end-to-end security implementation for Advanced Metering Infrastructure (AMI). Pardon me if I a bit off topic or not asking the right question as I am ...
58 views

Can Diffie-Hellman be scaled up or force-multiplied?

I'm not too familiar with the math involved with the exchange of keys, I've read it over several times, but math isn't my strong point. My understanding is that smart people are hard at work to ...
46 views

How to calculate the entropy of passwords? [duplicate]

Here is a cartoon about password entropy. http://xkcd.com/936/ I dont quite understand how the entropy is calculated in the cartoon assuming they are calculate correctly. But in general, I dont have ...
44 views

Does NSS fully implement PKCS 11?

I am looking towards using NSS in a Linux application that makes use of a TPM (HSM). So, I am checking the support of PKCS 11 in NSS, at least for the management of Elliptic Curve keys, signature with ...
2k views

What is the recommended replacement for MD5?

Since MD5 is broken for purposes of security, what hash should I be using now for secure applications?
65 views

RSA-KEM construction

"Create a random key for CCPA2 scheme, encrypt m, send it along with a PK encryption of the symmetric key. " Say in the process, the KDF is HMAC, then: get a random key (128-bit) C1 = encrypt ...
44 views

How to use the key from a Diffie Hellman exchange? [closed]

I watched a YouTube video about Diffie-Hellman called "Diffie-Hellman Key Exchange", and it said after doing some modulo operations with the public modulus and generator and the random private ...
60 views

Is it possible to 'fake' time for TOTP? (Time-based One-time Password)

TOTP (Time-based One-Time Password) Algorithm is used in Two factor authentication. I understand the algorithm and that current time is used as a variable to generate a token. Wiki page for reference: ...
39 views

online Vickrey auction using remote coin flip

Is there any published work on implementing a online auction, which uses "remote coin flip" to prevent auctioneer cheating when choosing winner and bid value? Is there any possible way to use remote ...
43 views

Forward Secrecy with pseudorandom functions

Let $H_1$, $H_2$ be keyed hash functions (e.g. $H_i(x) = SHA_{256}(s_i||x)$ for pseudorandom $s_1$, $s_2$). Let $s_n = H_1^k(s_0)$, $k_n = H_2(s_n)$, where $s_0$ is a secret (pseudorandomly chosen ...
44 views

SpongeWrap without padding and frame bit

Assuming all inputs are same length as rate except last can be shorter. Is it necessary to pad every input (not just last) to sponge for authenticated encryption to be secure? Is this just, because ...
73 views

How do RSA and ElGamal key sizes compare?

I have a rather silly question regarding the comparison of RSA with ElGamal over integers. If you want to compare their performance in the same level of security, does the modulus of both of them need ...
2k views

How does order-preserving encryption work?

Order-preserving encryption (OPE) is, apparently, a method of encrypting data so that it's possible to make efficient inequality comparisons on the encrypted items without decrypting them. I've been ...
272 views

38 views

how does the order-preserving encryption scheme distribute the buckets?

Recently ,I want to know the order-preserving-encryption scheme(OPES in short).But ,I couldnt understand how the buckets are distributed,and if the values in my input database are in a small range, ...
279 views

What is the sign bit for in Feige-Fiat-Shamir?

The Feige-Fiat-Shamir identity scheme is based on a ZKP assuming that square roots are "hard" modulo an integer of unknown factorization. The "parallel version" of this protocol includes a "sign bit" ...
51 views

RFC3447 OBJECT IDENTIFIER semantic

http://tools.ietf.org/html/rfc3447#appendix-B.1 ...
61 views

Is .NET DESCryptoServiceProvider secure in this case?

I have the following piece of .NET code (see below). I know that DES is not quite secure, I saw that MSDN does not recommend using DES, only for compatibility with legacy programs. I also saw that ...


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[–] 85 points86 points ago

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Use LaTeX for Christ's sake. MS Word blows serious dongs for any technical write up

[–] 4 points5 points ago

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How does LaTex compare with MathType? I'm used to mathtype, but I keep hearing about LaTex and that I should familiarize myself with it.

[–] 15 points16 points ago

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LaTeX is completely different. You type out what is essentially code, and it will render what you type as excellently formatted and beautifully rendered text. If you've ever read a scientific journal for mathematics or any hard science, you've seen the product of LaTeX. It's very easy to begin and there's a huge amount of documentation out there. you can get it here.

For an introduction, look here. Hope I helped! LaTeX is great, and it makes your life 10x easier if you're involved in any field where you need to typeset mathematical functions.

[–] 14 points15 points ago

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It's very easy to begin

nope.avi

[–] 2 points3 points ago

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If you have a coding background and enough templates, it is easy enough. Took me two days to get proficient enough to work; took me twice that to unfuck a semi-complicated MS word workflow after they introduced the ribbon interface.

Once you go LaTeX, WYSIWYG feels too clumsy.

[–] 0 points1 point ago

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I think this is what I should have said. I agree with you completely.

[–] 4 points5 points ago

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I agree, LaTex is not easy to begin, and it takes a while to write a simple document, but once you get used to it (which actually doesn't take very long) and you learn the tricks, then you can write beautiful papers very very quickly.

[–]chemistry 2 points3 points ago

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I just it wish it actually wrote my papers.

[–] 1 point2 points ago

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I take notes in latex, so yea, you can write very very quickly

[–] -1 points0 points ago

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What? It's easy as hell to begin. Here's an equation:

E = mc^2

Wow, that was incredibly difficult. I can't believe how hard that was.

[–] 0 points1 point ago

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But that won't compile properly, you want either:

  $$E = mc^2$$

or

   $E=mc^2$

It isn't hard once you write a paper or two, but there is a learning curve that is enough to turn the average person off.

[–] 1 point2 points ago

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You type out what is essentially code

More like markup /pedantic

[–] 0 points1 point ago

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i was just assuming that the person I was replying to wasn't familiar with coding, but you're right, it is more like markup.

[–] 16 points17 points ago

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None of my fellow engineers have even heard of TeX! I don't understand how; it makes your reports sooooo beautiful. Until you have to add figures and want to pull your hair out.

[–] 9 points10 points ago

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Here's an example of the lovely typesetting it does, from my control systems notes: http://imgur.com/nwb65

There are workarounds for the figures, mainly the float package which allows you to place figures exactly where they appear in the source, amongst other things.

[–] 8 points9 points ago

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I came

[–] 1 point2 points ago

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Now draw the root locus diagram!

[–] 2 points3 points ago

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[–] 0 points1 point ago

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Damn, if only I read this 2 weeks ago before my final.

[–] 1 point2 points ago

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Want to teach me controls? Or rather do you have a good source for online learning?

[–] 0 points1 point ago

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Here is what I learned from: http://en.wikibooks.org/wiki/LaTeX

I recommend using installing the TeX distribution "texlive" if you don't already have one, and the editor "texworks" (which I believe is actually included in texlive now) and changing the default typesetting engine in texworks to pdflatex.

Here is the source of the picture I posted:

$T_p\omega_{\text{BW}} = \frac{\pi}{\sqrt{1-\zeta^2}}\sqrt{(1-2\zeta^2)+ \sqrt{4\zeta^4-4\zeta^2+2}}.$

The phase margin is the difference in phase from $$-180^{\circ}$$ at the gain crossover frequency $$\omega_{gc}$$.  That is for (open loop)
$G(s) = \frac{\omega^2_n}{s(s+2\zeta\omega_n)}$
we have
$|G(j\omega)| = \frac{\omega_n^2}{\sqrt{\omega^4 + (2\zeta\omega_n\omega)^2}} = 1$
which gives
$\omega_{\text{gc}} = \omega_n\sqrt{-2\zeta^2+\sqrt{1+4\zeta^4}}$
which gives
$\phi_M = \tan ^{-1} \left( \frac{2\zeta}{\sqrt{-2\zeta^2+\sqrt{1+4\zeta^4}}} \right)$

It's not that tidy, because I didn't intend to share it. Try pasting some of the things enclosed in $these brackets$ into this online latex equation editor: http://www.codecogs.com/latex/eqneditor.php

Feel free to message me with questions.

[–] 0 points1 point ago

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I can do that in Word no problem

[–] 0 points1 point ago*

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Yes, but when you start getting 100+ pages the automation of latex is a godsend. Automatic hyperlinked and cross referencing numbering on everything eg tables, figures, equations, sections. A fully automated bibliography which includes in text citations and the ability to change style at will.

It also has a much higher quality typography than word with things like ligatures, a higher quality linebreaking/justification algorithm, microtypography (optically straight margins and fine adjustment of spacing).

It also supports "packages" which are kind of like addons that extend the functionality. For instance, I used the "theorem" package for my maths notes to produce automatically styled, numbered and cross referenced theorems, lemmas, corollarys, examples and so on in my maths notes.

Once you get over its not so intuitive markup language, it really makes Word feel like a toy.

Edit: It's also far more cross-platform compatible than Word. It's handy because at home I run windows and ubuntu, and at uni they run various linux distros, windows and mac os. TeX source files are just text, so they are small and portable, and LaTeX has been largely unchanged since at least the 90s. The language of TeX itself has been frozen now such that a tex document written post 1989 will compile the same exactly the same now.

[–] 1 point2 points ago

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Ok yea that is nice. Though I would be annoyed at having to basically program to write a paper.

[–] 0 points1 point ago

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I won't try and sugar coat it; sometimes it's a huge pain when what you want it to do seems so simple and you need some ridiculously obscure/complex code to do it. But overall it's a good system I think.

[–] 0 points1 point ago

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Can you explain how latex can be used in a word document? I've only ever used latex on math forums; using it in word would be awesomely convenient.

[–] 0 points1 point ago

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I'm not sure if you can tbh. I remember reading somewhere about being able to use the maths syntax in the Word equation editor? It's not really designed with word in mind though. There is a program called LyX which is a WYSIWYG editor for LaTeX.

[–] 0 points1 point ago

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I think I was just too clueless about LaTeX to even know what to ask. I had no idea there were dedicated TeX editors out there but I always wondered how neatly formatted research papers were composed. I'm going to try learning the dedicated TeX editor instead of trying to incorporate it into word.

I'll check out LyX, thank you.

[–] 0 points1 point ago

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Although I pointed out LyX I would most highly recommend TeXworks. This is the resource I learned most of my LaTeX from: http://en.wikibooks.org/wiki/LaTeX

Good luck!

[–] 1 point2 points ago

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Figures are not that bad. It's a bit more boring than word (where you can just drag them), but it's still ok. Save them in a folder and type their filename.

[–] 3 points4 points ago

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Figures never stay in place for me. Sometimes they just decide they'd rather live 4 pages away for no reason.

[–] 11 points12 points ago

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Oh, that's a feature.

Jokes aside, there's normally a reason for that. You can influence it that way:

\begin{figure}[b] %at the bottom please
\begin{figure}[!b] %I said at the bottom!
\begin{figure}[bt] %at the bottom, but the top is ok too
\begin{figure}[H] %PUT IT HERE!

Generally I leave it alone, and when I finish the chapter (or the whole report) I go through it and check the position of the figures (and correct them). It takes me like 20 minutes for a 150-pages report.

Compared to the mess that is Word with that kind of document it's really great.

[–] 0 points1 point ago

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I agree it's much better than using word. Even using [H] I was fighting the editor when writing my thesis. I got it sorted eventually but it took some massaging.

[–] 0 points1 point ago

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A slight addition, you need the float package for the last one. It's very useful.

My only real problem with LaTeX is the way it handles floats by default. Especially when it can't place one of them and sends them all to the end.

[–] 1 point2 points ago

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It's really just the two column floats that make you go mad. For longer documents, its not a big problem, but damn trying to get everything to fit on a nice page limit, editing a couple lines and having it blow up on you. Still totally worth it though.

[–] 1 point2 points ago

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\begin{figure}[h!tbp]
\centering
\scalebox{.7}{\includegraphics{figures/figure.pdf}}
\caption{(a) TEXT TEXT TEXT \cite{Bibtexentry}      \label{fig:Figure}}
\end{figure}

This about does it for me

[–] 2 points3 points ago

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I came here just to make sure someone already said this.

Ph.D. student in Aerodynamics, here, and I went back to University after working in industry for a while - one of the reasons I enjoy being back is not having to produce report in MS Word!

PM me and I can send you an old report or something so you can get an idea of how to actually construct and format something.

[–] 1 point2 points ago

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It sucks if you have to keep selecting stuff from the ribbon. I normally just recycle old ones from previous reports or copy/paste similar equations and modify. A lot easier and doesn't take up much time at all.

[–] 1 point2 points ago

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Press Alt and you can access every button very fast. If you get used to it, you will love ribbon...

And of course you actually don't need ribbon for the equation editor, which understands very much latex..

[–] 1 point2 points ago

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MS Word blows serious dongs for any technical write up

By itself it does, not when you use it with Mathematica.

You can copy and paste into word from Mathematica, which formats things nicely. You can achieve the same level of formatting, plus its great if you have to solve for stuff on the fly. Along with some macros and templates, you can the same level of formatting as you see in LaTeX, with the added benefit that you work faster because you don't have to compile the document.

For stuff like lectures, official papers, formal reports, LaTeX is worth while to learn. However for small crap like lab reports, which take time to do and that time is often subtracted from our sleeping time, there is nothing wrong with using Word, because the TA's who grade them aren't even going to look at the equations, because the amount of time it takes to grade 15 lab reports if you actually read them and look for errors is insane.

[–] 0 points1 point ago

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I disagree - LaTeX proved excellent for various problem sets this year. I haven't quite mastered it for producing documents proper, but for anything dense in equations it's simply magical.

[–] 0 points1 point ago

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Right, just like lecture notes. LaTeX is good for when you have all the equations already in front of you.

However, when I was writing reports, a lot of the times I would stop and realize that the equation that I am about to put down is not clear. In that case, I go back to Mathematica, make it solve for an intermediate step, copy and paste, continue on. If I am doing this more then a couple of times, the LaTeX compiling can get annoying. Overall, its just a personal preference in terms of efficiency.

[–] 0 points1 point ago

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Now that i've learned most of the shortcut keys for MS Word I actually really don't mind it. But I think I will try out LaTex just to see.

[–] 0 points1 point ago

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I think the main reason for using MS word vs latex is that those of us writing these reports give 0 shits about them and word is slightly faster/easier

[–] 19 points20 points ago

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Non metric units?

[–] 21 points22 points ago

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Foot pounds per slug Rankin? Kill me now!

[–] 7 points8 points ago

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Welcome to the pain that is being an American engineering student.

[–] 5 points6 points ago

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US AeroE student in 1990s: I am thankful that only about 1/5th of my homework questions were in those silly units. It was their way of saying "goodness, use metric, but you should probably be comfortable with the dumb way, too."

[–] 7 points8 points ago

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I wonder if there are enough engineers that we could start a PAC whose sole purpose is the complete metrication of the US.

[–] 2 points3 points ago

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Or Canadian. We have to learn these stupid, useless units because you assholes won't conform wit the rest of the developed world.

Half of the problems we have to do are made arbitrarily more difficult by giving every bit of information in different units. So much fun...

[–] 0 points1 point ago

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Umm, what school did you go to that used english units?

[–] 0 points1 point ago

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Currently at RPI, have had to use: feet, inches, btu, lb (mass and force), Fahrenheit/Rankin, atm. Most schools in the US will require you to do some course work in both systems (depending on subject), and yes metric is always easier.

Where did you go (and major) that they didn't?

[–] 0 points1 point ago

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University of Arizona, Electrical Engr. I'm not saying we NEVER had a problem that dealt with english units. But it would have only been in the context of a specific problem. Never on a test, or required that we know anything specific about them, or anything like that.

[–] 0 points1 point ago

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Are there even non metric equivalents to most electrical units?

Professors give you all the conversion factors for the non metric, you just need to be able to not freak out when you see them.

[–] 16 points17 points ago

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I hate you aerospace engineering equation editor.

[–] 22 points23 points ago

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I hated it, until I learned that LaTeX syntax works within the editor.

For example, if I want to put in the symbol for freestream density, it goes in as \rho _\infty, generating a rho with a subscript infinity.

[–] 5 points6 points ago

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This is the best news. Glad learning LaTeX wasn't a total wash, though.

[–] 13 points14 points ago

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Careful with your notation here. Displacement thickness is usually represented by delta* and momentum thickness is usually represented by theta. You seem to be using delta for both.

And you also have a summation from n=0 to delta, but in the next line you show numbers just for the n=1 term inside that summation and you've dropped the others. But then you pick them back up for the last line, which looks correct. So I think the middle lines there are a bit sloppy.

Congrats on finishing that though. 72 pages is insane.

[–][deleted] ago

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[deleted]

[–] 26 points27 points ago

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That's cheating brah, sorry you can't get your degree now.

[–][deleted] ago

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[deleted]

[–] 36 points37 points ago

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TIL I am really bad at making jokes.

[–] 32 points33 points ago

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Your joke was fine, I guess someone who's just finished a 72 page lab report isn't the most receptive to it though!

[–] 12 points13 points ago

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next time, latex. texworks is the shit.

[–] 3 points4 points ago

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I thought LaTeX was good when I was using notepad. TeXworks blew my mind. Even more so when I discovered the shortcuts with the tab key.

[–] 6 points7 points ago

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holy shit! And I want to go into aerospace engineering.................... What am I thinking

[–] 22 points23 points ago

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As a mechanical engineer, don't let big equations scare you. Of course you don't understand them right away, that's why you take courses that last an entire semester. Big equations can always be parsed down into smaller chunks and understood. Learning is a process!

[–] 3 points4 points ago

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it's not big equations that scare me, it's 70 page lab reports on the (probably) weekly

[–] 0 points1 point ago

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School is about preparing for work. Work is about communicating. Communicating precisely is about reports. Get used to writing as soon as you can. Most of us didn't, and got hammered in our first engineering lab class.

[–]ME-Electrical Component Mfg. 9 points10 points ago

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Just fucking do it.

A lot of people are deterred from doing hard to do things simply because they aren't willing to take the first step.

I'm less than one week away from graduation and I basically was able to make it through by simply concentrating on the moment and not fixating on how far I have to go yet.

You'll drive yourself crazy if you think of it in terms of a countdown to a degree.

[–] 0 points1 point ago

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freshman in aerospace here. I feel like im on the brink of a world of pain

[–] 3 points4 points ago

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You build up to it, fret not.

[–] 5 points6 points ago

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Half of that is figures and another quarter is equations straight from the book, you big baby. :p

[–] 2 points3 points ago

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I had a class like that in Mechanical engineering. The lab reports were like 40 hours of work each each week. The lab itself was 4 hours.

[–][deleted] ago

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[deleted]

[–]ME-Electrical Component Mfg. 5 points6 points ago

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Pretty much the same scenario I was in with thermal fluids.

Its a two credit hour class and never spent more than 2 hours a week in the lecture or the lab, yet I easily wrote over 200 pages worth for that class.

71 pages for a single report is pretty ridiculous.

[–] 0 points1 point ago

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Most of my labs were like this - 2 credits for insane amounts of work. I think the idea was that if you didn't do too well it wouldn't hurt your GPA too badly.

[–] 0 points1 point ago

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When I was an engineering student I spent most of my time looking for a stapler that could accommodate my lab reports. Living next to kinko's helped.

[–] 2 points3 points ago

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Imperial? vomits

[–] 2 points3 points ago

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Even with LaTeX, it takes FOREVER to typeset any sort of mathematical formulae of any kind. Classes that require this sort of work should reflect that in the credits you get for them ಠ_ಠ

[–] 3 points4 points ago

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once you learn the syntax, you're good for doing this stuff super fast.

[–] 2 points3 points ago

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The appendix never counts. Most markers will just flick through the appendix and not bother. If that isn't the appendix, then 72 pages for one lab seems ridiculous no matter what it is.

[–] 2 points3 points ago

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LaTex + vim (or emacs ಠ_ಠ). Huge learning curve to both, but completely worth it.

[–] 2 points3 points ago

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"Momentum Thickness"? Now I know that you are just making stuff up.

[–] 1 point2 points ago

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[–] 2 points3 points ago

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Unrelated, but as an AeroE student are you guys expected to design airfoil profiles yourself? I was MechE and it bothered me that we never once were expected to test our own airfoil designs we were just tossed a book of NACA profiles and told to work from there.

Also who seriously uses slugs in calculations anymore, I have very rarely seen any engineer under the age of 60 use slugs instead of pound-mass? If you are doing it to make gravity calculations easier for when you fly to the moon then you should be using metric anyways.

[–] 2 points3 points ago

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There are very few people designing airfoil profiles any more. That's a pretty specialized field, and full of decent designs. Aerospace engineering is about harder stuff.

Second the slugs observation!

[–] 4 points5 points ago

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W-w-w-w-w-what!? I.... Um.... But..... OH GOD!!!

I'm already 3 years in! There's nothing I can do to stop this from happening to me!!

[–] 1 point2 points ago

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It doesn't seem to be that common, at most you might have to do this once or twice. Or at the worst for like one class. It won't be thrown at you though, you'll see it coming.

Plus there is a lot of white space on that page.

[–] 0 points1 point ago

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Yes, but the microsoft word equation writer is... just awful.

[–] 0 points1 point ago

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Make a better one.

Market

Profit

[–] 1 point2 points ago

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What course was this for? I thought my 20some page fluids I labs were bad :/ ...

[–] 1 point2 points ago

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ME here, just finished my midterm ME senior design report; 149 pages! Should be well over 200 when finalized for submission in April!

[–] 1 point2 points ago

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My final Computer Science course project this semester took up about 50 pages. Most of that was code. About 2 pages were discussion, 2 pages were screenshots.

[–] 1 point2 points ago

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I seriously pity the person who has to grade more than one of those...

[–][deleted] ago

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[deleted]

[–] 9 points10 points ago

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And you think we actually grade the whole thing? I'll flip through look for some equations and numbers and be done with it.

[–] 1 point2 points ago

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Aerospace eh... you're in for worse documents than 72 pagers pal. :-)

[–]Electrical Engineering 1 point2 points ago

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Ugh that sucks. Other posts were right though, wtf are you thinking not using LaTeX?

Also, you should post this in /r/engineeringStudents.

[–] 0 points1 point ago

sorry, this has been archived and can no longer be voted on

I had a class like this my junior year. On the first day our professor says "Welcome to mech/aero lab. This class is worth 4 credits. I think it should be worth 7". I had to do 5 of these that semester.

[–]Electrical - Power 0 points1 point ago

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The real world gets no easier. I have dozens upon dozens of multiple-hundred page reports under my belt.

[–] 0 points1 point ago

sorry, this has been archived and can no longer be voted on

[–] 0 points1 point ago

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As a third-year aerospace engineering student, can you (briefly) explain what your lab report was about?

[–] 0 points1 point ago

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Hahahaha, my first year of college was spent as an aerospace engineer. I very quickly realized it wasn't for me. Glad I got out of that shit.

[–] 0 points1 point ago

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What on earth could possibly fill 72 pages? I'm seriously flabbergasted by this. I can imagine, perhaps, a PHd thesis being this long, but just a lab report? Goddamn, what the hell was the lab? Building an airplane?

[–]Aerospace 0 points1 point ago

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Lots of figures. It's not as bad as it seems.

[–] 0 points1 point ago

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With all the LaTeX love in here, i'd like to show my support for MathCAD. I only use LaTeX for my thesis and a few manuscripts.

[–] 0 points1 point ago

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That's hot.

[–] 0 points1 point ago

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All the people freaking out about huge papers are making me giggle. I'm an ME, and while my lab reports aren't bad (average 15 pages, depends on appendices) my senior design report topped off at 100 pages. I always found it more irritating when there were page limits on my engineering papers. Virtual high five for finishing your beastly paper!

[–] 0 points1 point ago

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I'm an EE. My lab reports were circuit diagrams and a table of voltages/currents most of the time (unless it was for a programming class).

Senior design report was like 200 though, we designed a mid stream hydroelectric generator, so there were tests on everything from fluids flow, to power pulled from a fluid, to power amount and quality retrieved from our electrical design, to alternative but more expensive solutions. Granted, my engineering department was all about the multidisciplinary stuff, so we had MechE, CivE, and EE all working together.

[–] 0 points1 point ago

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You guys think those are big? I'm an ME at Texas A&M, and our senior design project was a spaceship. Our class of 80 people produced a 1000 page report. Not a typo. The presentation to NASA had 500 slides (mostly hidden equations) and took 4.5 hours. Now THAT'S a senior design project.

[–] 0 points1 point ago

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...you had 80 people working on it? That's ten pages per person (okay, 12.5, fine). I had 3 people on my team including myself and we designed and built a damn hydroelectric generator.

I mean, cool, a spaceship, but still, the hardest part of that project is coordinating the people, not writing the paper.

[–] 0 points1 point ago

sorry, this has been archived and can no longer be voted on

Ah, I didn't know you only had 3 people, and actually built the thing. That's awesome.

format: plain


text:
Allophonic Rule
Get Allophonic Rule essential facts below. View Videos or join the Allophonic Rule discussion. Add Allophonic Rule to your PopFlock.com topic list for future reference or share this resource on social media.
Allophonic Rule

A phonological rule is a formal way of expressing a systematic phonological or morphophonological process or diachronic sound change in language. Phonological rules are commonly used in generative phonology as a notation to capture sound-related operations and computations the human brain performs when producing or comprehending spoken language. They may use phonetic notation or distinctive features or both.

John Goldsmith (1995) defines phonological rules as mappings between two different levels of sounds representation[1]—in this case, the abstract or underlying level and the surface level—and Bruce Hayes (2009) describes them as "generalizations" about the different ways a sound can be pronounced in different environments.[2] That is to say, phonological rules describe how a speaker goes from the abstract representation stored in their brain, to the actual sound they articulate when they speak. In general, phonological rules start with the underlying representation of a sound (the phoneme that is stored in the speaker's mind) and yield the final surface form, or what the speaker actually pronounces.[3] When an underlying form has multiple surface forms, this is often referred to as allophony. For example, the English plural written -s may be pronounced as [s] (in "cats"), [z] (in "cabs", "peas"), or as [?z] (in "buses"); these forms are all theorized to be stored mentally as the same -s, but the surface pronunciations are derived through a series of phonological rules.[4]

## Example

In most dialects of American English, speakers have a process known as intervocalic alveolar flapping that changes the consonants /t/ and /d/ into a quick flap consonant ([?] in words such as "butter" (['b]) and "notable" (['nobl]).[note 1] The stop consonants /t/ and /d/ only become a flap in between two vowels, where the first vowel is stressed and the second is stressless. It is common to represent phonological rules using formal rewrite rules in the most general way possible. Thus, the intervocalic alveolar flapping described above can be formalized as

## Format and notation

The rule given above for intervocalic alveolar flapping describes what sound is changed, what the sound changes to, and where the change happens (in other words, what the environment is that triggers the change). The illustration below presents the same rule, with each of its parts labelled and described.

 Title of the rule The underlying sound that is changed. In this example, the brackets represent all the features the changed sounds have in common; /t/ and /d/ are both stop consonants and both articulated with the tongue touching the alveolar ridge. Therefore, this rule applies to all sounds that share those features (in English, only /t/ and /d/). Rules can be written with just the individual sound to be changed, but using square bracket notation allows the rule to apply to a class of related sounds.[5][note 2] Suggestions for refining the traditional notation to better reflect the set theoretic types of segments and natural classes are made in some recent work.[6] The arrow represents that the sound on the left changes to have the features on the right. The sound that /t/ and /d/ (in this example) change to, or the individual features that change. The slash is a shorthand notation for "in the environment where...".[5] It means that the notation to the right describes where the phonological rule is applied. The sound, or the features of the sound, that precedes the one to be changed. In this example, the /t/ or /d/ that becomes flapped must be preceded by a stressed vowel. The location of the sound that is going to be changed. In this example, the underline means that the /t/ or /d/ that becomes flapped must be in between two vowels (where the first is stressed and the second is not). The sound, or the features of the sound, that follows the one to be changed. In this example, the /t/ or /d/ that becomes flapped must be followed by an unstressed vowel. A prose description of the rule, specifying when it applies and what it changes.

Taken together and read from left to right, this notation of the rule for intervocalic alveolar flapping states that any alveolar stop consonant (/t/ or /d/) becomes a tap ([?]) in the environment where it is preceded by a stressed vowel and followed by an unstressed one.

Phonological rules are often written using distinctive features, which are (supposedly[note 3]) natural characteristics that describe the acoustic and articulatory makeup of a sound; by selecting a particular bundle, or "matrix," of features, it is possible to represent a group of sounds that form a natural class and pattern together in phonological rules.[8] For example, in the rule above, rather than writing /t/ and /d/ separately, phonologists may write the features that they have in common, thus capturing the whole set of sounds that are stop consonants and are pronounced by placing the tongue against the alveolar ridge. In the most commonly used feature system, the features to represent these sounds would be [+delayed release, +anterior, -distributed], which describe the manner of articulation and the position and shape of the tongue when pronouncing these two sounds.[9] But rules are not always written using features; in some cases, especially when the rule applies only to a single sound, rules are written using the symbols of the International Phonetic Alphabet.[10]

## Characteristics

Hayes (2009) lists the following characteristics that all phonological rules have in common:[11]

• Language specificity: A phonological rule that is present in one language may not be present in other languages, or even in all dialects of a given language.
• Productivity: Phonological rules apply even to new words. For example, if an English speaker is asked to pronounce the plural of the nonsense word "wug" (i.e. "wugs"), they pronounce the final s as [z], not [s], even though they have never used the word before. (This kind of test is called the wug test.)
• Untaught and unconscious: Speakers apply these rules without being aware of it, and they acquire the rules early in life without any explicit teaching.
• Intuitive: The rules give speakers intuitions about what words are "well-formed" or "acceptable"; if a speaker hears a word that does not conform to the language's phonological rules, the word will sound foreign or ill-formed.

## Types

Phonological rules can be roughly divided into four types:

• Assimilation: When a sound changes one of its features to be more similar to an adjacent sound. This is the kind of rule that occurs in the English plural rule described above—the -s becomes voiced or voiceless depending on whether or not the preceding consonant is voiced.
• Dissimilation: When a sound changes one of its features to become less similar to an adjacent sound, usually to make the two sounds more distinguishable. This type of rule is often seen among people speaking a language that is not their native language, where the sound contrasts may be difficult.[12]
• Insertion: When an extra sound is added between two others. This also occurs in the English plural rule: when the plural morpheme z is added to "bus," "bus-z" would be unpronounceable for most English speakers, so a short vowel (the schwa, [?]) is inserted between [s] and the [z].
• Deletion: When a sound, such as a stress-less syllable or a weak consonant, is not pronounced; for example, most American English speakers do not pronounce the [d] in "handbag".

## Rule Ordering

According to Jensen, when the application of one particular rule generates a phonological or morphological form that triggers an altogether different rule, resulting in an incorrect surface form, rule ordering is required.[13]

### Types of Rule Ordering

Given two rules, A and B, if we assume that both are equally valid rules, then their ordering will fall into one of the following categories:[14]

• Feeding: the application of A creates the opportunity for B to apply.
• Bleeding: the application of A prevents B from being able to apply.
• Counterfeeding: the application of B creates the opportunity for A
• Counterbleeding: the application of B prevents A from being able to apply.

### Derivations

When a distinct order between two rules is required, a derivation must be shown. The derivation must consist of a correct application of rule ordering that proves the phonetic representation to be possible as well as a counterexample that proves, given the opposite ordering, an incorrect phonetic representation will be generated.[15][13]

#### Example Derivation

Below is an example of a derivation of rule ordering in Russian as presented by Jensen:[13] Given the following rules with rule 1 applying before rule 2:

1. ${\displaystyle l\rightarrow \emptyset /C}$___# (l-Deletion)[13]
2. ${\displaystyle \left[-sonorant\right]\rightarrow \left[-voice\right]/}$___ # (Final Devoicing)[16]
##### Correct Derivation:[13]
1. /#greb+l#/ (Underlying Representation)
• greb (Application of l-Deletion)
• grep (Application of Final Devoicing)
2. [grep*=] (Correct Phonetic Representation)
##### Incorrect Derivation:[13]
1. /#greb+l#/ (Underlying Representation)
• ------ (Application of Final Devoicing)
• greb (Application of l-Deletion)
2. *[greb] (Incorrect Phonetic Representation)

## Expanded Notation

On their own, phonological rules are intended to be comprehensive statements about sound changes in a language. However, languages are rarely uniform in the way they change these sounds. For a formal analysis, it is often required to implement notation conventions in addition to those previously introduced to account for the variety of changes that occur as simply as possible.[17]

• Subscripts: Indicate the number of occurrences of a phoneme type.[17]
• ${\displaystyle C_{x}}$ indicates that or more consonants occur, where ${\displaystyle x\geq 0}$.
• ${\displaystyle V_{x}}$ indicates that or more vowels occur, where ${\displaystyle x\geq 0}$.
• Word Boundaries: indicate the left and right boundaries that, between them contain a complete string, represented with a hashtag symbol.[17] For example, the word "cat".
• #cat#, the beginning and end hashtags indicate the respective beginning and end of the word "cat".
• { } (Curly Braces): Indicate a logical-disjunction relationship of two expressions.[18] For example,
• The two expressions, ABD and AED and be written with curly braces as:
• ${\displaystyle A{\begin{Bmatrix}B\\E\end{Bmatrix}}D}$, A is followed by either B or E and then D.
• ( ) (Parenthesis): Indicate a logical-disjunction relationship of two expressions and an abbreviated version of the curly braces notation,[17] while maintaining the same disjunctive relationship function. For example,
• The two expressions, ABD and AD and be written with parentheses as:
• ${\displaystyle A(B)D}$, B is optionally permitted to come between A and D.
• < > (Angled Brackets): Indicate a conditional relationship within a set.[13][18] For example, vowel harmony in Turkish,
• ${\displaystyle {\begin{bmatrix}+syll\\\langle +high\rangle \end{bmatrix}}\rightarrow {\begin{bmatrix}\alpha back\\\langle \beta round\rangle \end{bmatrix}}/{\begin{bmatrix}+syll\\\alpha back\\\beta round\end{bmatrix}}C_{0}}$__ , All vowels will take on the [+/- back] value of the vowel that precedes it, regardless of the number of intervening consonants. If a vowel is [+ high], it will also take on the [+/- round] value of the preceding vowel, regardless of the number of intervening consonants.

## Notes

1. ^ See International Phonetic Alphabet for information about how to read these transcriptions.
2. ^ See Place of articulation and Manner of articulation for a description of these terms.
3. ^ Some phonologists have questioned the "naturalness" or "innateness" of distinctive features.[7]

## References

### Citations

1. ^ Goldsmith 1995:2.
2. ^ Hayes 2009:26.
3. ^ Idsardi, William James (2 September 2003). "LING 101: Phonology". University of Delaware. pp. A Rule of English. Archived from the original on March 5, 2009. Retrieved 2009.
4. ^ Idsardi, William James (2 September 2003). "LING 101: Phonology". University of Delaware. pp. The pronunciation of the English plural. Archived from the original on March 5, 2009. Retrieved 2009.
5. ^ a b Hayes 2009, p. 28.
6. ^
7. ^ Mielke, Jeff (2005). "Ambivalence and ambiguity in laterals and nasals". Phonology. 22 (2): 193. doi:10.1017/S0952675705000539.
8. ^ Hayes 2009:71.
9. ^ Hayes 2009, pp. 79, 84–85.
10. ^ Hayes 2009, p. 92.
11. ^ Hayes 2009, pp. 26–7.
12. ^ Schramm, Andreas (17 March 2001). "Lesson 9.2: Phonological Rules". Hamline University. Retrieved 2009.
13. Jensen, John T. (John Tillotson) (2004). Principles of Generative Phonology: An Introduction. Amsterdam: J. Benjamins. p. 156. ISBN 978-90-272-7517-2. OCLC 769188823.
14. ^ The Handbook of Phonological Theory. Goldsmith, John A., 1951-, Riggle, Jason., Yu, Alan C. L. (2nd ed.). Chichester, West Sussex, UK: Wiley-Blackwell. 2011. p. 41. ISBN 978-1-4443-4306-9. OCLC 758478759.CS1 maint: others (link)
15. ^ Chomsky, Noam. (1991). The Sound Pattern of English. Halle, Morris. (1st MIT Press pbk. ed.). Cambridge, Mass.: MIT Press. p. 60. ISBN 0-262-03179-5. OCLC 778785348.
16. ^ Jensen, John T. (John Tillotson) (2004). Principles of Generative Phonology: An Introduction. Amsterdam: J. Benjamins. p. 116. ISBN 978-90-272-7517-2. OCLC 769188823.
17. ^ a b c d Chomsky, Noam. (1991). The Sound Pattern of English. Halle, Morris. (1st MIT Press pbk. ed.). Cambridge, Mass.: MIT Press. pp. 61, 367. ISBN 0-262-03179-5. OCLC 778785348.
18. ^ a b Chomsky, Noam. (1991). The Sound Pattern of English. Halle, Morris. (1st MIT Press pbk. ed.). Cambridge, Mass.: MIT Press. p. 77. ISBN 0-262-03179-5. OCLC 778785348.

### Sources

Books cited
• Bale, Alan; Reiss, Charles (2018). Phonology: A formal introduction. MIT Press.
• Goldsmith, John A. (1995). "Phonological Theory". In John A. Goldsmith (ed.). The Handbook of Phonological Theory. Blackwell Handbooks in Linguistics. Blackwell Publishers.
• Hayes, Bruce (2009). Introductory Phonology. Blackwell Textbooks in Linguistics. Wiley-Blackwell. ISBN 978-1-4051-8411-3.


text:
# Tag Info

31

I was starting to get an exception as well: make: Interrupt/Exception caught (code = 0xc00000fd, addr = 0x4227d3) Might be a different reason, but this problem is apparently caused when the PATH variable contains parentheses (, ), as it does on Win Vista/7. Unfortunately, the available GNU for Windows is hopelessly outdated. My problem was fixed by ...

18

bash is probably getting started as a login shell, in which case it doesn't read .bashrc automatically. Instead, it reads .bash_profile. From the Bash manual: So, typically, your ~/.bash_profile' contains the line if [ -f ~/.bashrc ]; then . ~/.bashrc; fi' after (or before) any login-specific initializations. So in summary, create a ...

14

Rather than removing Windows' find.exe, I strongly recommend putting GNU in your path before Windows\System32. For example, with Cygwin, you can use something like: path c:\cygwin\bin;c:\windows\system32;c:\windows;c:\program files\foo;c:\program files\bar;c:\windows\system32\wbem

7

You can check out my releases of Vim for Windows to save yourself some time. It's built using MinGW-w64 toolchain (don't worry, you don't need its runtime libraries for my build to work). Have support for both x86 (32-bit) and x64 (64-bit) architectures, "huge" feature set, and scripting interfaces for most popular programming languages: Python; Ruby; Lua; ...

6

If I'm understanding you correctly, you're looking for a tabbed interface for multiple bash shells, right? If so, you could use Console2 to host your mingw windows. I use it for Cygwin and it works great! Just configure each tab in Console2 to start the MinGW bash shell.

5

$pwd -W C:/MinGW/msys/1.0/home/Steven 4 Aliases are available for the NT Command Prompt through the doskey command: doskey word="%ProgramFiles%\Windows NT\Accessories\wordpad.exe"$* You may now use the alias instead of the (full) name of the executable: word %SystemDrive%\boot.ini

4

mingw-get is available at sourceforge.net/projects/mingw/files/Installer/mingw-get After you have that installed run mingw-get install msys-coreutils

4

I found this one somewhere: rm -r */ Seems the easiest way to go. With your example, you would have to confirm each case, if you have 5 files it's OK, but with bigger file structures an interactive mode is't the way to go... Just as a suggestion, if it's important information, make a backup...

4

I had the same issue, linking an icon from a folder without whitespace in it did a trick (I had Git installed to C:\Program Files (x86) which has whitespace in it). Simply copy the icon somewhere else, e.g. C:\icons.

4

I have just found the solution to this problem on the NetBeans forums here: http://forums.netbeans.org/topic54884.html All you need to do is: Go to C:\MinGW\bin and make a copy of mingw32-make.exe. Then rename it to make.exe Now go to C:\MinGW\msys\1.0\bin and rename make.exe to makeOLD.exe (just in case) Then move your new make.exe into ...

3

I'm not sure what version of msysgit you are using, but for me calling msys.bat does not change the current directory. If you see the directory being changed, check the etc/profile file in the msysgit directory for cd commands. As this file gets executed when a login shell is started it might be the cause for you to always land in your home directory.

3

Some console replacements support changing the colors along with other features missing with the one that comes with Windows. One example Console2. Note that behind it is still the same cmd.exe as the normal console window or another command processor if desired. An example of the settings dialog where Yellow has been made to show as blue. To setup Git ...

3

You can "escape" specific metacharacters by prefixing with backslash. $touch 'aaa(bbb)ccc'$ rm *$$*$$* $ls$

3

cd to the parent directory, then: for f in */abcd*; do mv $f ./ done that will match mydir1/abcdfoo, mydir2/abcdbar etc. and move them to the pwd (which is the parent directory). If you only want to look in directories called mydir* you could specify for f in mydir*/abcd*; do mv$f ./ done You could also do find . -name "abcd*" -type f -exec mv {} ./ ...

3

No that would give you "missing operand" since you didn't specify anything. Putting a "*" would prompt also for files. I'd give a try to: find -mindepth 1 -maxdepth 1 -type d -exec rm -r {} \; The "mindepth 1" will exclude "." from the results, the "maxdepth 1" will exclude trying to do under the directories that will anyway get deleted (therefore ...

3

The problem is that gcc cross-compilers can be names differently. It depends on how it is built in the first place. The programs you are referring to (i686-pc-mingw32-g++ and i586-mingw32msvc-g++) are two of the many possibilities when naming the MinGW binaries. But they should behave more or less similarly. If the third-party Makefile uses this name ...

3

I've gone down basically the same path with the following exception: Checking for gnutls >= 2.5.0 : fail --- libeio --- Checking for library pthread : not found Checking for function pthread_create : not found error: the configuration failed (see 'd:\\Code\\Javascript\\node\\build\\config.log') config.log basically says it ...

3

Ok, the proper answer follows. To escape the arguments such that dos executables can be used, you double the slashes, such as: growlnotify //a:Application //t:Title "message here" The reason it would fail for me was because somehow I wasn't using the same application name as I had when I started the day before (and as a different application it was ...

3

To make your command work I don't think you can avoid sub-shelling, something like: find /cygdrive/c/MinGW/bin/ -name "*.exe" -print0 | xargs -0 -n1 bash -c 'ln -s {} $(basename {})' If all the files are in the same directory, you can also use cp -s: cp -s /cygdrive/c/MinGW/bin/* . 3 Since ln accepts directories as targets: ln -s /cygdrive/c/MinGW/bin/*.exe /path/to/otherdirectory/ 3 CtrlU will erase from the current cursor position back to the beginning of the line, so you can then type your correct password. 3 I managed to compile a 64-bit version of gVim.exe using the full version of Visual Studio 2010 and the commands from this superuser answer: nmake -f Make_mvc.mak GUI=yes CPU=AMD64 PYTHON=C:\Python27 DYNAMIC_PYTHON=yes PYTHON_VER=27 It's probably possible with the 64-bit mingw toolset linked by heavyd too, but I couldn't find anything that worked on ... 3 I am running Windows XP and had the same problem. I found HOWTO Create an MSYS Build Environment. This is the important line: To help identify the runtime build and the current working directory, the following can be added to the ~/.profile file. In MinGW shell, I created .profile: cd ~ touch .profile I used Notepad++ to edit it as a Unix format text ... 3 Futher to Norbet P.'s answer, I found that adding: PATH= to the top of my Makefile fixed this particular problem for me. 2 I used GnuWin until I realised last release was posted back in 26 Nov in 2006 . Thats a bit lame, and caused such problems as seen above. Setting SHELL=C:/Windows/System32/cmd.exe does solve some problems but running such old code on new operatingsystems feels unsafe MinGw is a safer bet. MinGw is acronym for "Minimalist GNU for Windows" and is up to date ... 2 I had that issue when I added Git's bin directory to the PATH environment variable. The reason seems to be that Git ships with a version of MSYS and that seems to conflict with MinGW (maybe it doesn't conflict when it's the right version of MSYS and/or MinGW but that's just guessing). So make sure that there is no (other) MSYS distribution in your PATH. 2 super-user (root) is the only account able to use rm -d flag From the rm man page -d, --directory unlink FILE, even if it is a non-empty directory (super-user only; this works only if your system supports ‘unlink’ for nonempty directories) I don't think mingw supports su root or anything like it so using rm -d is ... 2 Perhaps the first "g++" found in your PATH is a script that contains a "perl" command or which starts with a shebang line that specifies "perl" without giving a full and correct path to a perl executable. 2 for i in /source/directory/*.exe; do ln -s$i /destination/directory/basename \$i done

Only top voted, non community-wiki answers of a minimum length are eligible


text: dc.creator Lowe, R. S. en_US dc.date.accessioned 2006-06-15T14:33:04Z dc.date.available 2006-06-15T14:33:04Z dc.date.issued 1980 en_US dc.identifier 1980-RF-7 en_US dc.identifier.uri http://hdl.handle.net/1811/11301 dc.description $^{1}$ P. B. Davies, B.J. Hardy, E.K. Murray Lloyd and D.K. Russell, Mol. Phys. 36, 1005 (1978). en_US dc.description Author Institution: en_US dc.description.abstract Vibration-rotation transitions have been observed in the $^{2}\Pi_{3/2}$ component of the ground electronic state of SD. The radical was produced by passing D atoms over elemental S or from the reaction F$+ D_{2}S \to SD +$DF at a total pressure of 0.5 Torr. The Q(3/2) transition was detected at $1885.610 cm^{-1}$ using lines from the $^{13}C^{16}O$ and $^{13}C^{18}O$ isotopic lasers. A resonance observed with a $^{13}C^{16}O$ laser line at $1861.433 cm^{-1}$ has been identified as one component of the P(5/2) transition. This observation serves to confirm that the carrier is SD but provides no additional information on the excited state energy levels (the ground state rotational constant is already well $known^{1}$). Further transitions re being sought in the hopes of obtaining accurate values for the vibrational band origin and the B rotational constant in the v = 1 state. en_US dc.format.extent 112062 bytes dc.format.mimetype image/jpeg dc.language.iso English en_US dc.publisher Ohio State University en_US dc.title LASER MAGNETIC RESONANCE DETECTION OF THE SD RADICAL AT 5.3 $\mu$m en_US dc.type article en_US


text:
# Intrinsic processes drive variability in basal melting of the Totten Glacier Ice Shelf

## Abstract

Over the period 2003–2008, the Totten Ice Shelf (TIS) was shown to be rapidly thinning, likely due to basal melting. However, a recent study using a longer time series found high interannual variability present in TIS surface elevation without any apparent trend. Here we show that low-frequency intrinsic ocean variability potentially accounts for a large fraction of the variability in the basal melting of TIS. Specifically, numerical ocean model simulations show that up to 44% of the modelled variability in basal melting in the 1–5 year timescale (and up to 21% in the 5–10 year timescale) is intrinsic, with a similar response to the full climate forcing. We identify the important role of intrinsic ocean variability in setting the observed interannual variation in TIS surface thickness and velocity. Our results further demonstrate the need to account for intrinsic ocean processes in the detection and attribution of change.

## Introduction

Understanding the rate of change of ice shelf thinning and the processes governing change is critical for understanding mass balance and hence the Antarctic ice sheet contribution to sea level rise. Over the period 2003–2008 (~5 years), the Totten Glacier Ice Shelf (TIS) was observed1 to be lowering at ~0.41 m yr−1. However, extending the observational satellite record to encompass the period 1994–2012 (~18 years)2 showed that the thickness of the TIS was subject to large periodic 3–4 year fluctuations of approximately ±40 m with almost no net thickness change (within the error bars) over the 18 year period. Further, interannual variation has been detected in surface velocity3,4,5 and the grounding line location is showing change6. It is not clear how much of the observed temporal change in TIS is as a result of internal glacier-ice shelf dynamics or is in response to variability in ocean-driven basal melting. We have chosen to characterise the part of melt rate variability that arises in response to variability intrinsic to the ocean. This study serves as a necessary basis for understanding and quantifying what fraction of the observed variations in melt rate are independent of natural fluctuations in the climate modes and trends arising from anthropogenic forcing.

Basal melting thermodynamically couples the ocean to the ice shelf system. As a result, ice shelf thickness responds to variability in the nearby ocean system. This variability could be externally forced, for example, by climate change, interannual and multidecadal climate modes, the annual cycle, or tides. In addition, variability could also be generated by the non-linear intrinsic ocean response to forcing, as opposed to the deterministic response from interannual atmospheric forcing. Low-frequency intrinsic ocean variability results from non-linear interactions within the ocean and in response to stochastic-to-seasonal timescale changes in atmospheric forcing7,8,9,10,11,12,13,14,15, in line with the paradigm of Stochastic Climate Models16,17. As a result, the ice sheet will exhibit a combined response to both intrinsic and externally forced climate variability.

Observations of basal melting and ice shelf change generally consist of short records which limit the ability to distinguish intrinsic from forced variability. Advances have been made in identifying the ice shelf response to observed low-frequency internal variations in the Southern Hemisphere climate. For example, El Niño-Southern Oscillation (ENSO) has been suggested to drive stronger cross-shelf transport of oceanic heat leading to a lowering of Amundsen Sea ice shelves18. Conversely, atmospheric hindcast models for 1979–2015 have suggested that ENSO has a statistically non-significant impact on the westerly winds which drive stronger cross-shelf transport19. This highlights the complex impact that low-frequency climate variations have on ice shelf mass loss. It also emphasises the importance of ensuring that correlations and trends are statistically significant, particularly given the short satellite record relative to the timescale of climate variations like ENSO.

Ocean models can be used to simulate and quantify variability beneath ice shelves. Idealised coupled ice sheet-ocean models subject to periodic variability in oceanic heat content have indicated the ice sheet response is dependent on the forcing periodicity in relation to the ice shelf residence time20. However, the origin of this periodic forcing and the response of a realistic ice shelf is uncertain.

In this work, we present simulations of the response of basal melting beneath TIS to intrinsic ocean variability (model domain shown in Fig. 1a). We use lateral boundary conditions that contain only intrinsic ocean variability and repeated normal-year atmospheric forcing (Coordinated Ocean ice Reference Experiment version 1; COREv1)21 to quantify the interannual intrinsic variability that impacts basal melting. Non-linear ocean processes and the response to rapid wind changes produces a significant degree of intrinsic variability in water properties on the continental shelf and thus basal melting beneath TIS. Further simulations compare the basal melt response from only intrinsic variability to the full climate response from 1949 to 2007 (Coordinated Ocean ice Reference Experiment version 2; COREv2)22 and show that intrinsic ocean variability can produce a similar magnitude response to the interannual climate forcing. These results demonstrate the need to account for the contribution of intrinsic ocean processes in order to correctly detect and attribute ice shelf change.

## Results

### Melt rate interannual variability

As the COREv1 run is not forced with any interannual climate modes, any resulting low-frequency variability must be internally generated by the model or enters as intrinsic variability through the ocean boundaries. In contrast, the COREv2 run represents the response of the ice shelf to externally forced interannual variability. The COREv1 and COREv2 simulations produce a mean basal melting of 5.0 ± 0.5 m yr−1 (for years 30–150) and 5.2±0.5 m yr−1 (for years 1949–2007), respectively (Fig. 1b). This is half the glaciological inferred value23, however the mean spatial distributions (see Results section ‘Intrinsic variability in melt rate’) are similar to previous studies4,24,25. The mean lower melt rate results mainly from the cooler CORE ocean boundary conditions that introduce a constant cold bias as compared to previous modelling studies which utilised different forcing conditions (see Methods).

Both the intrinsic ocean variability model (COREv1 run) and the interannual variability model (COREv2 run) exhibit basal melting variability on a range of timescales. As the COREv1 run is forced with a repeated normal-year atmosphere and the intrinsically varying ocean resulting from the application of that atmosphere forcing, it represents the intrinsic melt rate response. In contrast, the COREv2 run contains the ice shelf response to the interannually varying ocean and atmosphere over the period 1949–2007. The ratio of COREv2 (with all natural, intrinsic, internal and anthropogenic forcings) to COREv1 (intrinsic-only) melt rate anomaly variances is 1.7. This is equivalent to a signal-to-noise ratio, where the ‘signal is the combined deterministic and intrinsic response from COREv2 and the ‘noise is the intrinsic response from COREv1 (see Methods). This highlights the potential for intrinsic processes to drive significant low-frequency variability in mean melt rates.

Quantifying changes in basal melting of TIS due to anthropogenic climate change and known climate modes (e.g. ENSO), requires a knowledge of the response due to intrinsic ocean dynamics. This study hereafter focusses on the low-frequency response of basal melting to intrinsic ocean variability. Here we are only concerned with this type of variability, noting that additional questions about the thermodynamic response of the ice shelf to the longer term climate (COREv2) are the subject of follow-up studies.

### Ocean drivers of TIS variability

Ocean conditions at the ice shelf cavity entrance drive melt rate changes (Fig. 2a, location A). Depth-time plots of the temperature (Fig. 2b) profile show winter water (WW), the product of the seasonal sea ice formation cycle, overlaying modified circumpolar deep water (MCDW). There is also occasional formation of Antarctic surface water (not shown). These water mass properties are very similar to previous observations in this region26,27,28,29. The thickness of the MCDW layer, here shown by fluctuations in the −1.5 °C contour (white line in Fig. 2b), displays low-frequency variability. The interannual variability in melt rate (Fig. 2c) correlates very well with MCDW thickness (r-value = 0.87, with lag = 0 months) and responds linearly. This MCDW thickness variability is an intrinsic ocean response to normal-year surface forcing (wind and fluxes) and directly drives interannual variability in melt rate. Near to the continental shelf break (Fig. 2a, location B), the flow characteristics show interannual variability. This location, chosen to coincide with high variability in bottom temperature anomaly from an Empirical Orthogonal Function analysis (see Results section ‘Bottom temperature interannual variability’), shows significant interannual variability in southward depth-integrated volume flux across the grid cell, with an approximately 5–7-year period. This shows the intrinsic ocean variability associated with exchange onto the continental shelf, but the low correlation with melt rate (r-value = 0.02) suggests that local processes have the biggest impact on melting.

### Intrinsic variability in melt rate

The area-averaged melt rate of the TIS (Fig. 3a) contains significant low-frequency variability, with a range of 4.5–6 m yr−1 (Fig. 3b) and power in the ~3–7 yr time band (Fig. 3c).

To identify and characterise modes of variation, we applied two different methodologies commonly used for analysing climate data (see Methods). Empirical orthogonal function (EOF) analysis identifies spatially invariant patterns in the data and accompanying time series that maximise variance. This was used to reduce the dimensionality and to decompose spatial and temporal variation into the EOF spatial modes, temporal principal components (PCs) and the variance explained by each mode. We restrict our analysis to modes explaining >5% of the variance (see Supplementary Fig. 1 for first 6 modes). The data has been linearly detrended and the climatological mean removed prior to analysis.

The EOF analysis of melt rate anomaly suggests that most variability (57% of variance) is explained by mode 1 (EOF1; Fig. 3d) which shows wide-scale coherent fluctuations in basal melting, similar to the time-mean spatial pattern in Fig. 3a. EOF mode 2 (EOF2; 8% of variance) captures enhanced shallow or deep melting, and results from water flowing either along the ice shelf front or below the ice shelf (Fig. 3g). Interannual fluctuations in average melt rate are represented strongly in the first PC of the EOF analysis (compare Fig. 3e to Fig. 3b), which contains ~3-, 5-, ~7-year and multidecadal modes (Fig. 3f). The second PC (Fig. 3h) contains mostly intra-annual variability (Fig. 3i).

While the EOF analysis captures spatial patterns of covariability it does not necessarily separate physical modes over different timescales. To achieve this, we apply singular spectrum analysis (SSA)12,30, which identifies spatially coherent regions of variance for a chosen time band, to analyse the leading PCs of melt rate and extract secular behaviour present at intra-annual (<1 year), interannual (1–5 and 5–10 years) and multidecadal (10–30 year) time bands (see Methods).

The in-band SSA variance shows the percentage of total variance at each location within defined time bands (Fig. 3j–m). Intra-annual modes explain ~40–50% of total variance, and closer to 90% of total variance near to the ice front (Fig. 3j). These intra-annual modes result from the seasonal cycle in sea ice production and winds. As this study focusses on interannual variability, these <1-year modes will not be further discussed. Modes with a period of 1–5 years explain on average ~23% (maximum of 44% in certain locations) of the total variance in basal melting (Fig. 3k), while ~7% (maximum of 21%) of the total variance is explained by modes that occur over 5–10 years (Fig. 3l). Multidecadal modes in basal melting are present but explain on average ~6% (maximum of 24%) of the total variance (Fig. 3m). Histograms of in-band SSA variance for the chosen time bands are shown in Supplementary Fig. 2.

### Bottom temperature interannual variability

Low-frequency variation in melt rate is being driven by intrinsic ocean variability. EOF analysis of bottom temperature anomaly shows that 32% of variability is explained in the shallower, coastal region (Fig. 4a, b), and has a multimodal spectrum with power in the interannual time band (Fig. 4c). Shelf break exchange (Fig. 4d, e) explains 15% of variability and temperature anomaly EOF1 has multimodal power in the interannual band (Fig. 4f). The intra-annual in-band variance in bottom temperature anomaly peaks along the ice front, explaining up to 71% of total variability (Fig. 4g), while 1–5 year modes (Fig. 4h) produce 40–60% of total variability over the continental shelf. The 5–10 year mode (Fig. 4i) explains 20–30% of total variability on the continental shelf, while the multidecadal mode (Fig. 4j) explains 20% of total variance deeper than ~500 m. Bottom temperature variability is generally aligned along bathymetric features, indicating that ocean–bathymetry interactions are a significant source of variability.

## Discussion

We show melting responds rapidly and linearly to the thickness of the relatively warm MCDW layer (Fig. 2b) present at the ice front. Cross-shelf exchange displays intrinsic variability but low correlation with melting, suggesting that intrinsic variability in melting results from local processes like wind-driven changes to the MCDW layer thermocline depth, rather than cross-shelf exchange. Comparison of the COREv1 (intrinsic ocean variability) run to a sensitivity study where the interannual intrinsic ocean variability is removed from the lateral boundary conditions, shows that indeed the variability that impacts the supply of ocean heat to the ice shelf cavity is generated within our model (see Supplementary Fig. 3). We can speculate that the non-linear ocean processes that generate such intrinsic ocean variability could include long-period baroclinic instabilities, which when subject to essentially stochastic winds, give rise to variability in ocean properties across a wide band of frequencies. This includes low-frequency modulation of the thickness of the MCDW layer on the continental shelf.

The chosen surface and lateral boundary conditions mean that any model variability with a period of greater than one year must be intrinsic ocean variability that is generated within the model, or imported through the Northern, Eastern and Western lateral boundaries (see Supplementary Figs. 46). Intrinsic variability in melting occurs underneath the entire ice shelf with a maximum range of ~1 m yr−1 (Fig. 3b). The period of variation is multimodal but has dominant periods of ~3 and ~7 years (Fig. 3f, i). The presence of intrinsic variability is weakest at the shallow ice front, which is most susceptible to seasonal sea ice and wind processes, and is stronger at depth (Fig. 3k–m). Up to 44% of 1–5 year variability and up to 21% of 5–10 year variability in melt rate results from intrinsic processes.

The in-phase response and high degree of variability that is explained by melt EOF1 suggests that cavity waters rapidly adjust to ocean heat entering this relatively small volume (Fig. 3d). Furthermore, the coherent response suggests that a reasonably representative assessment of basal melting can be obtained with few observations. The in-phase response also makes basal melting beneath TIS a good candidate for data assimilation and for parameterisation into an ice sheet model.

The high degree of variability in basal melting that results from intrinsic modes present in the 1–5 year time band (up to 44%) could contribute to the ~3–4 year period variations observed in TIS thickness2. Futhermore, the 5–10 year modes (explaining up to 21% of variation) likely contribute to the measured decadal period variations in flux3 and surface velocity4.

In general, we find that variability in bottom temperature occurs mainly on the shallower regions of the continental shelf (Fig. 4a), likely resulting from changes in thermocline depth in response to surface wind forcing with a peak 5–10 year periodicity (Fig. 4c). The second EOF (Fig. 4d) captures cross-shelf exchange and associated warm water pathways. Both MCDW layer thickness and cross-shelf exchange are shown to contain large low-frequency variations (Fig. 2b, c). The similar periodicity to EOF mode 1 results from a common mechanism as upwelling responds to wind forcing. The relationship between basal melting and wind stress is elsewhere demonstrated to be caused by Ekman pumping and upwelling of oceanic heat, which in turn correlates well with observed TIS surface velocity anomalies5. As melting underneath the Totten Ice Shelf has been identified to be driven by the relatively dense, warm and salty MCDW in models25 and observations28,29, it follows that intrinsic variability in ocean water properties near the seabed produces a response in basal melting.

Intrinsic variability has been previously identified in Antarctic sea ice patterns10,31,32, in the Southern Ocean9,10, as well as hypothesised in the ice sheet response to accumulation variability33 and in palaeoclimate dynamics34. Our results demonstrate that basal melting can vary on interannual timescales purely as a result of internally generated ocean variability, with broad implications for the identification of variability in an ice shelf/ocean system.

Interannual variability is present in ice shelf elevation change2, surface velocity3,4,5 and grounding line location6. However, it is difficult to extract the impact of intrinsic interannual variability in melt rate from these broad-scale products due to the disparate temporal and spatial scales, and relatively short observation periods. Nevertheless, the presence of interannual variability in multiple sources, with similar modes, suggests that some degree of the observed variability results from intrinsic processes.

This study has implications for observing and understanding ice shelf-ocean interaction. Basal melting can vary periodically with low-frequency variability, even in the absence of interannual atmospheric forcing. This implies that at least part of the variability associated with ice shelf thickness and consequently mass balance could arise purely through intrinsic ocean processes. This intrinsic variability is subsequently modified by external climate drivers to produce the observed record. However, to fully understand the temporal and spatial impact on ice shelf flow and thickness dynamics, a coupled ocean-ice sheet model is required.

We have highlighted the emergence of low-frequency intrinsic variability in cross-shelf flow and MCDW layer thickness, which arises through non-linear ocean processes and in response to daily-to-seasonal changes in wind stress. Basal melting beneath TIS responds linearly to MCDW thickness, but has a low correlation with cross-shelf flow, suggesting locally generated intrinsic variability influences the heat available to drive melting. This complex variability in basal melting limits the ability of short-term observational missions to draw conclusions about the long-term response to anthropogenic factors. In this sense, short oceanographic voyages and mooring deployments should be employed together with modelling studies to explore longer term trends. In regions which display significant interannual intrinsic ocean variability, long-term observational time series are critically important. Furthermore, many other ice shelves around Antarctica display some form of interannual variability (e.g. Filchner-Ronne, Amery, Shackleton and Ross2). The contribution of intrinsic ocean processes to the observed interannual variability ice shelves around Antarctica is yet unknown. Understanding and distinguishing this component of the signal through modelling studies is important for predicting and detecting climate change, planning observational missions that target regions of low intrinsic variability, and interpreting satellite and in situ observations.

## Methods

### Model details

To investigate the response of basal melting to intrinsic ocean variability, we ran numerical ocean model simulations of the TIS over a period of 150 years. The ocean model is based on the Regional Ocean Modelling System (ROMS)35 framework, with modifications to allow thermodynamic interaction between the ocean and a steady-state ice shelf36,37. The model domain extends 25.5° in longitude (104.5° E–130° E) and 8° in latitude (60° S–68° S), with a longitudinal resolution 1/15° and latitudinal resolution of 1/30° (Fig. 1a). Ice/ocean thermodynamics are parameterised using the three-equation formulation38. More details of the model setup are given in Gwyther et al.25 The model bathymetry is based on RTopo39, which provides the deep ocean and continental shelf bathymetry. RTopo does not included realistic bathymetry for TIS so we blended it with a TIS cavity bathymetry inverted from airborne gravity measurements that also includes a hypothesised trough connecting the continental shelf to an eastward extension of the TIS cavity40. This modelling study includes direct ocean access to the eastern extension of the TIS cavity, which satellite altimetry missions indicate hosts a surface lowering signal distinct from the deeper TIS grounding zone41. Ice draft was determined with airborne radar sounding measurements acquired by the ICECAP (International Collaborative Exploration of the Cryosphere through Aerogeophysical Profiling) consortium.

The first simulation has surface wind forcing from COREv1 which corresponds to repeating normal-year (1995) momentum fluxes21. Surface heat and salt fluxes are taken from the 1995 record of sea ice formation from Special Sensor Microwave Imager (SSM/I) satellite observations42. This year is chosen as it represents a normal climate year, and unlike CORE forcing, SSM/I observations better capture the timing, magnitude and spatial extent of sea ice and polynya formation42. Lateral forcing consisted of downscaled results from a general circulation model10, which itself was forced with repeated normal-year COREv121 forcing. The lateral boundary conditions are applied interannually, so as to capture intrinsic oceanic variability in Southern Ocean properties (Supplementary Figs. 4 and 5), in particular, the 20-year South Pacific Intrinsic Mode10, but no other modes of variability (e.g. coupled land–ice–ocean-atmosphere processes such as climate modes). If a repeated normal-year forcing were applied to the lateral boundary conditions, then slow oceanic modes would not be excited and in effect, the ocean variability spectrum would be truncated. Here we are concerned with variability in melt rate rather than the mean value, and so the choice of lateral boundary conditions is valid, despite the reduced mean melt rates. The mean value is low due to cooler conditions in the Southern Ocean, a common model bias in ocean GCMs forced with COREv1 conditions.

The second run (COREv2) of 120 years was forced with two periods of 1949–2007 interannual climate forcing. Surface wind forcing is from the COREv2 1949–2007 air–sea flux data set22, while surface heat and salt fluxes are composed of the climatology of surface heat and salt fluxes from SSM/I observations for 199542 but scaled by the E − P (evaporation minus precipitation) fields for 1949–2007 from COREv2. These data sets are combined in this way to provide long-term estimates of polynya activity and sea ice formation, which are not obtainable from a data set of comparable length. The lateral boundary forcing is analogous to that in the first simulation, but now the global ocean circulation model10 is itself forced with the COREv2 1949–2007 interannually varying air–sea fluxes22. As a result, the lateral boundary forcing is representative of the oceanic response to the large-scale atmospheric climate variability including the complete forcing spectrum with all natural, intrinsic, internal (e.g. climate modes) and anthropogenic forcing components. The first period of 60 years is considered spin-up.

A sensitivity study investigating whether intrinsic variability in melt rate originates locally or is imported through the boundary conditions was conducted (see Supplementary Fig. 3). In this run, we force with the same normal-year atmospheric conditions as previously. However, we have changed the lateral boundary conditions to remove the interannual intrinsic variability, replacing them with a repeated seasonal cycle calculated as the climatology of the previously-used interannual COREv1 intrinsic variability forcing10. These new boundary conditions, where we removed any interannual variability, enable an estimate of the variability intrinsic to the ROMS domain.

### Analysis techniques

For all analyses, the first 30 years of time series of melt and bottom temperature, which contain the model spin-up signal, are excluded. The resulting time series are detrended with a linear fit.

Signal-to-noise ratio is calculated as the ratio of variances σ2, calculated as

$${\mathrm{SNR}} = \frac{{\sigma _{{\mathrm{COREv}}2}^2}}{{\sigma _{{\mathrm{COREv}}1}^2}},$$
(1)

where $$\sigma _{{\mathrm{COREv}}2}^2$$ is the square of the standard deviation of the melt rate anomaly for the interannually varying run with COREv2 forcing, while $$\sigma _{{\mathrm{COREv}}1}^2$$ is the square of the standard deviation of the melt rate anomaly for the intrinsic variability-only run with COREv1 forcing.

Cross correlations of MCDW depth and volume flux with melt rate were calculated and a lag of 0 months is found to be optimal. As analysis is computed on monthly averages, a short lag or lead of less than 1 month is possible.

Empirical orthogonal function (EOF) analysis is used to decompose a time series into orthogonal spatial patterns (EOFs) along with the associated time series or principal components (PCs) and the variance explained by each mode43. While EOF analysis can provide useful decomposition of data, it has limitations such as domain dependence. While the leading mode(s) may often be physical, successively higher order modes, which explain less of the remaining variance, are unphysical as a consequence of the mode orthonormalisation.

Consequently, we employ singular spectral analysis (SSA) to express the original time series as a linear combination of components derived from singular value decomposition of the (time) lagged covariance matrix with maximum lag M. The resulting modes together sum to the original time series, while the slowest varying mode represents the non-linear trend with (time) variability of the order of the chosen embedding dimension M or longer. The decomposition is data driven (based on smaller, lagged portions of the original time series) and does not require projection on predefined basis functions, as required for example with Fourier transform methods. SSA readily provides non-linear smoothing of the original time series with the degree of smoothing controlled by M12,30. The SSA in-band variance shows the percentage of total variance present in the chosen time band bounded by predefined embedding dimension values, i.e. 0–1, 1–5, 5–10 and 10–30 years as in Figs. 3j–m and 4g–j.

Plots made with assistance from the Antarctic Mapping Tools for MATLAB toolbox44 and cmocean45 colourmaps.

### Data availability

Model output that supports the findings of this study are available from the corresponding author on request.

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## Acknowledgements

D.E.G. is grateful for the insightful input from K. Kelly, R. Gwyther, A. Fraser, F. McCormack, G. Williams, R. Hart, C. Greene and L. Padman. Research was supported by the Australian Research Council’s Special Research Initiative for Antarctic Gateway Partnership (Project ID SR140300001). This research was undertaken with the assistance of computing resource grants gh9 and nk1 from the National Computational Infrastructure (NCI), which is supported by the Australian Government. T.J.O’K. and D.P.M. were supported by the Australian Commonwealth Scientific and Industrial Research Organisation (CSIRO) Decadal Forecasting Project (https://research.csiro.au/dfp). J.S.G. was supported by NSF grants PLR-1543452 and PLR-1143843, as well as the G. Unger Vetlesen Foundation. This is University of Texas Institute for Geophysics contribution number #3276.

## Author information

Authors

### Contributions

D.E.G. ran simulations and performed analysis. D.E.G., T.J.O’K., D.P.M. and B.G-F. designed and guided the research. D.P.M. assisted with analysis. T.J.O’K. developed and provided the large-scale ocean forcing data. J.S.G. provided grids of ice draft and the TIS bathymetry. All authors contributed to the interpretation of results and manuscript preparation.

### Corresponding author

Correspondence to David E. Gwyther.

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### Competing interests

The authors declare no competing interests.

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Gwyther, D.E., O’Kane, T.J., Galton-Fenzi, B.K. et al. Intrinsic processes drive variability in basal melting of the Totten Glacier Ice Shelf. Nat Commun 9, 3141 (2018). https://doi.org/10.1038/s41467-018-05618-2

• Accepted:

• Published:

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