tcpekin

Materials Science PhD student - electron microscopy

I've spent a lot of time in both Word and LaTeX writing papers and reports in grad school, and nowadays, strictly use LaTeX. I feel like the author missed some crucial elements as to why people use the latter. First, references, cross-references, and citations. These are all shockingly simple in LaTeX. \ref or \cite is all you have to think about to cite papers or reference figures, tables, etc. In Word, I have used Mendeley's citation system, and the built in cross reference system to the same task, but when it comes to the editing process between multiple people and having different files sent around, it invariably breaks, leading to hours of extra work either doing it manually (have fun updating figure numbers if you add another one, or citation superscript), or reinserting all the necessary cross references. With a LaTeX file, this is pretty hard to break.

Secondly, LaTeX handles figures 10000x better than Word, in that you just let it figure out placement inline. Captions are as simple as possible. Meanwhile, have you ever had that Word document with 10 figures in which you move one inline image, and every figure jumps to a different page, leading to spam clicking Ctrl+z? Or how about adding figure captions? Inline you have to use the caption tool, which isn't fantastic and often creates a text box that isn't strictly tied to the figure. The method I found best was just to have another document simply for figures and write the captions in regular text. This both looks bad, and during the editing process, requires you to switch between files to keep track of the figures that are being referenced in the text. Additionally, automatic figure numbering depends on where the figure anchor is, often leading to improper numbering. Again, referencing figures by number in Word is a nightmare that LaTeX handles amazingly.

Third, I agree, setting up LaTeX on a machine isn't fun, and I have always been bad at it. However, I don't do it anymore. ShareLaTeX has solved all of those problems for me. All packages are available, you don't have the funny "compile three times to get reference numbering correct", it's amazing at collaboration with both git-like diffs as well as Word-like track changes/commenting system, and has tons of templates so the pain of setting up your document's preamble is done for you.

One tip I have is if someone you work with doesn't know LaTeX and can't be convinced to learn it, still write in LaTeX, compile to pdf, and use Acrobat to convert to Word. That works surprisingly well. The Lyx version conversion does not work nearly as well. I can't say I've tried pandoc though, I would like to try that next.

Engine blocks will almost certainly remain as a cast part, simply due to the production capacity of casting is orders of magnitude higher than additive manufacturing, as well as being relatively cheap. Metal additive manufacturing is currently used in aerospace to reduce complex assemblies of parts into a single piece, or to make small complex shapes that can't be made by a traditional machining or casting process. Additive manufacturing, for the foreseeable future will not replace load bearing parts as well, mainly due to the different processing steps load bearing parts undergo. It will also most likely stay with aerospace for the time being, since the price per part is prohibitive for automotive use currently.

http://www.computerworld.com/article/3188899/3d-printing/boe...

http://www.additivemanufacturing.media/articles/the-aircraft...

Also quantum physics is about as gnarly as it gets. And not many people enter PhD's knowing all they need at the end. I'm doing a PhD at what I would consider a great school (Berkeley), and the quality still varies! People are smart yes, there is somewhat of a baseline to get in, but (most of) the smartest ones at the end have gotten there mostly through working hard, asking lots of questions, and being curious. I've seen this happen with my cohort over the past four years. Very few people came in where I thought they were geniuses, but they have all learned and grown so much in their specialty. Even if you're not the smartest one, a PhD can give you 4-7 (low) paid years of freedom to research whatever you're interested in (this depends on group), which is intellectually awesome. It's a process. You can always leave with a masters as well, but if you're interested in some sort of CS problem or engineering or science in general where CS is used for analysis (all of them), I'm sure there's a group that would be a great fit.

I use their cloud sync and love it. One of the few subscription services I pay for. I also use the browser extension, which others have pointed out might not be the best, but I think it's better than one to five universal easy to guess passwords I was using before. I have it on Windows, Mac and Android and it syncs seamlessly.

Yeah, I think you kind of hit the problem that people have with this paper, namely, how does Li exist un-ionized on both sides of the battery. They have a figure that shows that based on the amount of S they have in the battery, they can discharge like 9000x the amount of sulfur available to react, which is their basis for saying that it remains unreacted. There could be a multistep process, some sort of odd structure could be forming, but I don't think anyone knows yet, which is why it's both interesting and a little confusing.

Sure, all valid assumptions, but a lot of these are discussed in the paper. If you let me know your email, I can send you a copy. But in response to your points/anyone else who is interested,

1) It's a button or coin cell [1] (halfway down). So the conductor is the steel casing, the e- travel as you put a wire from either side wrapping around the cell. The copper current collector is only on one side. You're right in that they don't really fully describe the cathode in the methods portion. They simply state the cathode consists of a redox center (S or MnO2) embedded in electrolyte and carbon in contact with the copper, which is pressed against the glass electrolyte. It could be a slurry that they press, or something that has water, but that is never mentioned. I think the problem is that nobody really knows what the atoms at the cathode are doing. I would be hesitant to say anything is aqueous, but I guess there is the possibility.

2) Cathode is reported at 0.06 mm. They show SEM pictures of Li plated on the cathode, and directly call the cell a metal plating cell. From their conclusion, "With the Li-glass and Na-glass electrolytes, we have demonstrated in this paper one possible new strategy in which the cathode consists of plating the anode alkali-metal on a copper–carbon cathode current collector at a voltage V > 3.0 V." Additionally, from the results, they "examined the electrodes with the naked eye and with SEM EDS analysis, as shown in Fig. 2, which indeed shows lithium plated on the cathode current collector and no evidence of metallic lithium remaining on the stainless steel at the anode or the anode side of the electrolyte after full discharge of the lithium anode."

3) The e- are pulled off by the voltage applied during charging with any voltage higher than the work function of whatever state the plated Li is in (I think), causing a charge imbalance and Li ionization. This is balanced by the ionized Li moving back through the electrolyte to the anode side. The role of the sulfur is debated and I would say not understood, but they claim it's a redox center, where redox does not actually happen. Here is the key part:

We therefore conclude that the sulfur acts as a redox center determining the voltage of the cell at which electrons from the anode reduce the Li+ at the electrolyte/cathode interface to plate lithium rather than reducing the sulfur, so long as the voltage remains above 2.34 V; below 2.34 V, the S8 molecules are reduced to Li2Sx (1 r<= x <= 8) and the lithium on the anode becomes exhausted after 28 days in the cell of Fig. 1. The cell reaction was no longer reversible after this full discharge. At voltages V > 2.34 V, the cell is rechargeable and the sulfur is not reduced. The Fermi level of the lithium plated on the carbon–copper composite cathode current collector is determined by the Fermi level of the cathode current collector, whereas the Fermi level of the lithium anode remains that of metallic lithium, but the cell voltage is determined by the energy of the redox couple of the unreduced redox center

That is the part that I think is confusing a lot of people, myself included, on how that happens exactly. They have some evidence that supports their claim, but I'm sure that's the next paper, how this actually works.

4) With a cathode that is 60 microns thick that they dry from a slurry, there is no real basis for "apertures" through the thickness, especially in a disordered glassy structure. Instead, ion transport is through vacancy mediated diffusion. This does have a dependence on atomic radii, but from what I'm reading, is more dependent on the atom species being ionic as opposed to neutral. Again though, the important portion of the finding is that the electrolyte is solid, not liquid, and therefore during lithium deposition on either the cathode or anode, ions cannot easily preferentially grow dendritic structures as opposed to evenly plating the anode/cathode.

I would agree that more characterization needs to be done of the role o the components during all stages of charging and usage. Comparing a recharged and emptied batteries in a microscope would be helpful, as well as more careful chemical analysis as to what is actually going on.

[1] http://batteryuniversity.com/learn/article/types_of_battery_...

I think they start with Li on one side, and a Cu/C/S cathode on the other, and then plate the lithium on the anode. They measure a difference in chemical potentials between cathode and anode, so there is reason for the Li to move, and as the Li moves, I think I remember the V_cell decreasing.

From the paper:

> At the cathode, the build-up of plated metallic lithium changes the morphology of the cathode to increase C_C and create a very slow fade of V_cell with time of discharge

There are a couple things wrong with what you said, here's just a clarification after I've read the paper and some of the references a few times.

1) The cross section is given in an image in the original article, and explained in a Medium post [1]. It is Li-(fancy) glass-(Cu/C/S combination) encased in steel. I think for now, you can ignore the steel. Nothing is aqueous, as it's a solid state battery.

2) During discharge, e- leave the anode, travel through the wire and end up in the Cu/C/S cathode. This leaves a Li+ cation which then travels through the glass, (most likely) does not remain there, and deposits itself on the cathode. Hence, in the original paper [2], they see a build up of lithium on the cathode via SEM. From what I understand, the contentious part of the paper is that the researchers state that the S provides the driving force for the reaction, but then isn't reacted (the main point in [1]), hence the "perpetual motion" attack. The deposited lithium does have a sort of screening effect on the cell voltage, slowly decreasing it with discharge time. From my understanding, the battery capacity is limited by the amount of Li before it is all oxidized, and not dependent on the amount of reduction the cathode can handle, very interesting. This cross section at full discharge would be nothing-glass-Li-(Cu/C/S cathode), again encased in steel, but ignore that.

3) During recharge, the opposite happens, e- are forced back to the anode, and the preponderance of e- cause a driving force to remove the Li that has been deposited on the (Cu/C/S) and transfer it back to the metallic Li side. The key part is that the electrolyte shouldn't be holding onto any ions, if the paper description is to believed. The Medium article states that some sort of reaction may be occurring in the electrolyte, I can't really weigh on on that. Once all of the Li is back on its anode side, recharging is done.

4) It is important that the glass electrolyte is a solid, not that the cathodic atoms/ions cannot enter it. They most likely can, it would just take a recharging voltage much higher than the one they use to recharge the cell. The fact that it is a solid means that lithium dendrites (tree like growths) cannot grow during redeposition, as dendrites that span the distance between anode and cathode short circuit the battery.

Feel free to ask me any questions about it, I am not a battery person so there's a high chance I got something wrong, but I am a MSE grad student so I might be able to say something that sounds intelligent.

[1] https://medium.com/@steingart/a-potential-big-deal-in-batter...

[2] http://pubs.rsc.org/en/content/articlepdf/2017/ee/c6ee02888h

The atoms are manipulated by a scanning tunneling microscope [1], which allows you to both image and manipulate single atoms, as shown in the movie "A Boy and His Atom" [2], also made by IBM. You can make sure there's only one by just taking an image at a resolution high enough to see single atoms.

This is fundamentally a scanning technique. A very sharp tip, down to a few atoms at the point, sometimes capped with a single carbon nanotube, is scanned across the surface of whatever sample you have, which for a measurement like this, must be almost atomically flat. A bias is applied between the sample and the tip, and quantum tunnelling can allow for electrons to move between the sample and the tip. This current can then be measured, and correlated with sample height or electronic properties of the sample. If you scanning step size is less than that of the size of an atom, you can then image single atoms by detecting the change in current due to a different species of atom, or due to the change in height between your flat surface and tip when an atom is sticking out of the top of the surface.

To manipulate the atoms, the tip is moved close enough to an adatom that it begins to form a weak bond with the tip. The tip then can move and essentially drag the adatom with it to wherever the researchers want. [3]

[1] https://en.wikipedia.org/wiki/Scanning_tunneling_microscope

[2] https://en.wikipedia.org/wiki/A_Boy_and_His_Atom

[3] https://www.nist.gov/programs-projects/atom-manipulation-sca...

That is awesome, I would love to see that database!

Microsoft Word - after using LaTeX, especially ShareLaTeX, it's such a pain to write documents in Word that require multiple images, references, or even semi-unique formatting.

How did you get to 18000 references? What field are you in?

If you make that Porsche a 911 R, you can spend half a million dollars used, and it'll look less flashy than even a Turbo S.

I had the same issue with finding the tree log, it's under graphs and called network.

https://github.com/altmany/export_fig/network

Car and Driver just compared another 20 or so cars at their resident Lightning Lap track a few months ago, including a Tesla. The Tesla was not fast, approx. 30 sec slower on a track that fast cars were finishing in the 2:45 range.

http://www.caranddriver.com/features/tesla-model-s-p85d-at-l...

http://www.caranddriver.com/flipbook/lightning-lap-2016-ever...

Yeah, I'm pretty sure the rule of thumb is that standard towers can be quieter because unless the SFF computers are passively cooled, larger towers can have larger fans spinning at a slower RPM to move the same amount of air, as well as have larger radiators.

Massdrop usually has interesting mech kb's as well.

I would argue that cars are not extremely risky to modify mechanically - the parts are usually large, almost everything you'd want to do on your car has youtube videos and forum threads with people doing the exact same procedure, and you have pretty immediate feedback if you really messed anything up/the car is inoperable.

I don't think that is the same for self-driving software if you were allowed to hack it. It is easy to test if your brakes work, I think it may be harder to test modified software with the huge number of interactions it must deal with.

So you must use a Mac to comment on Tim Cook or Apple?

There's also the option that papers are written the way they are so that they still remain papers and not books. A five page paper on someone's findings is much easier to read than a 20-30 page paper where field specific knowledge is redefined and explained instead of referenced.

Did your father publish the research and try to keep the hardware test environment secret? If not, and the research was proprietary for companies, that is messed up. Otherwise, graduate students leaving and taking their work with them, as well as experiences and knowledge from the research they provided during their time as students is pretty par for the course. It's a two way street, your father provided funding, the student provided labor in return for education. After you're done, you don't just leave that research in your adviser's lab, you often build on it at either a postdoc or professorship, in return for citations and a working relationship.

That is exactly what the link/paper says, "By sending an email that repels all but the most gullible the scammer gets the most promising marks to self-select, and tilts the true to false positive ratio in his favor."

What kind of research are you doing? Sounds pretty cool!

Some journals require a lay-person abstract, which I think is very nice.

Are you on the extreme ends of mmr? I have a high rating and rarely get people that don't get along. On the other hand, with the introduction of international ranked, maybe they shelved this for a consolidated pool.

There is such a system in place actually [0]. It is believed that the playerbase is separated into pools [1] somewhat based of this number. How it is calculated is anyone's guess.

[0] https://www.reddit.com/r/DotA2/comments/46y4v8/dota_2_behavi...

[1] https://www.reddit.com/r/DotA2/comments/351mdk/discussion_do...

I don't really get the difference. I'm in academia i guess (grad school) and use MATLAB a bunch, as well as Python (not a CS major). I don't think it's that much work to switch between the two, and I don't understand why there's such a division. Why is this such a huge deal?

I'm a grad student as well, just finished my third year. Yeah it's super fun and I have a ton of freedom, but I make roughly 1/5 of what people I graduated with. I'm sure that holds a lot of people back. That being said, I really enjoy it, especially since you continually get to learn new things.

Carmakers continually buy all sorts of competitors' models for comparison testing and R&D purposes. From what I remember, the company I interned for (one of the big 3 in Detroit) bought Ferraris, Porsches, BMWs, etc to compare drive quality and for R&D. Additionally, sometimes they don't want a new car, they want one that is 10 years old and has real world wear and tear. They essentially have a broker who will find any car they ask for. I worked on the alloy design team, and one of the more unique stories I heard was about 10 years ago, they bought a 20 year old Mercedes to essentially cut into pieces. Why? The model they bought was one of the first cars with a unique alloy in the body IIRC, and they wanted to run mechanical as well as characterization tests on it to see how it aged.