Show HN: React Timekeeper – Time picker based on the style of Google Keep - <AUTHOR> https://catc.github.io/react-timekeeper/ <comment><USER3> That's actually a default time picker on Android, used in all native apps; Keep is just one of them. [https://material.io/guidelines/components/pickers.html#picke...](https://material.io/guidelines/components/pickers.html#pickers- time-pickers)

<comment><USER4> What does it look like for 24 hour format?

<comment><USER5> You get two hours rings, outer is for 1-12, inner is for 13-00.

</comment></comment></comment><comment><USER6> This is a nice start but i was confused how i should change my hour selection once i had made it. I was looking for an "Undo" button. Once i selected a minute value the component hid entirely, forcing me to refresh just to figure it out.

Rule of thumb: when designing components it is a good practice to ask, on every user click/keypress, "what happens if they made a mistake here?"

<comment> X-Cubed Just like on Android, you can change the hours from the minute screen by clicking the hour number in the top bar.

You can also reopen the popup without refreshing the page by clicking the link that appears once the popup has closed, just under the selected time.

<comment><USER7> Not intuitive at all. Instead of the snazzy animation on the clock face after selecting hour, the animation should focus more on the hour vs. minute transition.

<comment><USER8> Yet it is the first thing I tried and it worked. The color feedback on the currently selected number is a good hint.

</comment></comment></comment></comment><comment><USER9> I'm having trouble using the demo on my phone. Is there a way to prevent the page from scrolling?

<comment><USER10> I think this should always be the first question: how does my code behave on mobile? Considering that most (or a huge percent of) people are accessing the web on mobile now and that thos is targeted towards them, this is a kind of a blocking issue that would prevent me for using it.

<comment><USER11> My first experience with mini laptops was similar... the vertical space was very limited, and can't say how many times I had to zoom out to dismiss the takover popups on some sites.

Phone tends to be even worse, especially when zooming is disabled by a site, I get why, still bugs me though.

</comment></comment></comment><comment><USER12> This isn't to take away from the awesome work of the OP, but Google has a library of React UI components based on material design, and a similar time picker is one of them - [http://www.material-ui.com/#/components/time- picker](http://www.material-ui.com/#/components/time-picker)

<comment><USER13> FYI. That is not a Google library. It's some company called Call-Em-All

<comment><USER12> Oh wow, I haven't noticed that. I somehow assumed that you wouldn't be putting Google in your tagline if you were not associated with the company. Shame on me.

</comment></comment></comment><comment><USER14> The thing I like about this the most is that is uses SVGs. This made me very happy! It's a very cool project otherwise too, and I can definitely see myself using it.

EDIT: Alternative would be to use HTML and CSS transforms or similar hacky techniques. So, I am glad to see SVGs gaining more popularity.

</comment><comment><USER15> When opening the minute selection dropdown and the selecting time with the dial the dropdown disappears on mouseup instead of mousedown. The same happens when using the hour drop down. I think it should disappear once you mousedown on the dial.

Using the dial, you can sometimes start selecting or even drag/dropping some parts of the page. Use the css property user-select to prevent users from selecting visual elements that should not be selected. No one is ever going to want to select the text on your AM / PM buttons, so don't make it selectable.

Do people really prefer this over two infinite spinning number selection dials (one for the minute, the other for the hour) like on iOS?

</comment><comment><USER16> I've designed and built a few of these. I've heard both sides of the argument (digital/analog). I find analog better in every way, but in my experience those who prefer digital time pickers are definitely vocal.

I've typically created a user config option in any app I've designed so the user can choose whether time pickers are digital or analog.

EDIT: I see that clicking on the numbers at the top pull up a dropdown, which I think is a nice touch. Designs in the past I've opted for a double-click or double-tap to activate the keyboard so user can type in the number if they wish.

</comment><comment><USER17> I actually like the design of this much more than the default time picker on Android!

The AM/PM selection in is selector very clear - this is something I choose incorrectly every time I set an alarm on Android. On Android, the AM/PM pickers are inline with the time preview at the top - and you have to guess which one - blue or white - is the currently selected one.

Sure, if you stop and think about it, you can figure it out. This separate picker method in catc's selector seems much clearer in every case - <USER2> when a user is in a rush or sleepy!

<comment><USER18> It actually used to be exactly like this in Android, but it got changed to have in-line AM/PM pickers like you said.

</comment></comment><comment><USER19> You need to e.preventDefault(). On mobile it scrolls the phone when I drag the handle around.

</comment><comment><USER20> Awful contrast.

#6c6c6c on #00000

You need to bold your text if you really want that. [https://www.w3.org/TR/WCAG/#visual-audio- contrast](https://www.w3.org/TR/WCAG/#visual-audio-contrast)

<comment><AUTHOR> Open an issue and I'll change it.

</comment></comment><comment><USER21> Why not just let me type it?

<comment><USER9> This is for a phone.

<comment><USER22> Personally I prefer a digit "touchpad" and 24h digital entry - just as for entering phone numbers. So "why not let me type it (on my smart phone)?" is a perfectly sensible question for me as well.

But see the comment above about pro-digital possibly being a vocal minority - we very well could be.

I suppose there's a big difference with never really growing up with analog clocks, and being used to relate to analog clocks for time keeping. All my watches were casio digital clocks, set for 24h display - similar with alarm clocks. I readily think in terms of 24h, not 2x12.

[ed: I'm also used to be able to tell the time by the sun for 24h two months in summer - 0100 being due north with dst (ironic, but true) - just as 1300 is south, 0700 is East, 1900 is West.]

</comment></comment></comment><comment><USER23> This is neat, it'd be cool if there were support for choosing a time range from the same clock. I have that use case right now and I'm using one of those two handled slider widgets.

</comment><comment><USER24> Why this instead of [https://github.com/ecmadao/react- times](https://github.com/ecmadao/react-times)?

</comment><comment><USER25> Great library, and great documentation! Thanks for sharing :)

</comment><comment><USER26> How would I go about using my own style?

<comment><USER12> Having read the docs I'd assume you need to pass your styles using a `config` prop.

<comment><AUTHOR> Yeah, for now. I'll eventually add some way to pass in custom classes or something.

<comment><USER12> I personally find a prop to be a perfectly acceptable solution - you can define styles in your JS and share between components if need be. But I reckon there are folks who'd prefer passing class names to define their styles in CSS.

</comment></comment></comment></comment><comment><USER27> Very cool.

Unfortunately I don't use React :(</comment>


Ask HN: What's the biggest challenge developing open source projects - <AUTHOR> <comment><USER2> The community, building and maintaining that is much harder than software</comment>


The musical side of my dad's dementia - <AUTHOR> http://www.bbc.com/future/story/20171213-the-musical-side-of-my-dads-dementia <comment><USER2> My grandfather started playing piano at the age of four. He taught music as an adult.

In the last years of his Alzheimer's, he didn't know who I was and could barely remember conversations we'd had 5 minutes prior.

But, if you put him in front of a piano, he could play songs for hours.

<comment><USER3> Amazing, and interesting.

</comment></comment><comment><USER4> I've heard before of how people with dementia will sing the songs of their youth. And I have wondered, when I'm old, if my mind goes, will I too start singing the sweet notes of Blood, Fire, Death; Equimanthorn; Zombie Ritual; Mutilation; Hammer Smashed Face; Skullfull of Maggots; and the like? Will I walk around the corridors of whatever care home I end up in, belting out Tom Araya's blood-curdling screams at the beginning of Angel of Death, like I loved to do as a teenager?

</comment><comment> wu-ikkyu Anyone interested in this should watch Alive Inside: A Story of Music and Memory.[1]

Here[2] is an astonishing excerpt from the film where an unresponsive old man is given a pair of earbuds playing music from his era. The effects are profound.

[1][http://www.aliveinside.us](http://www.aliveinside.us)

[2][https://youtu.be/NKDXuCE7LeQ](https://youtu.be/NKDXuCE7LeQ)

</comment><comment><USER5> This article is also reminiscent of the case of Clive Wearing [1], who lost his memory to disease. His short term memory was reduced to seconds, and yet he remembers music he once played and conducted.

[1] [https://www.youtube.com/watch?v=ymEn_YxZqZw&index=2&list=PLA...](https://www.youtube.com/watch?v=ymEn_YxZqZw&index=2&list=PLA84D07CA0BFC4356)

</comment><comment><USER6> This is really weird. My granny died several weeks ago from dementia and she somehow managed to memorize really old song from TV. Even just before death she tried to sing several notes... it was really amusing. Reading this article is exactly what was going on. So... weird timing for me I guess.</comment>


Postfix 2.11.0 stable release available - <AUTHOR> http://permalink.gmane.org/gmane.mail.postfix.announce/146

<comment><AUTHOR> Postfix now supports DANE [0] as an alternative to certificate authorities.

[0] - [https://en.wikipedia.org/wiki/DANE](https://en.wikipedia.org/wiki/DANE)</comment>


Silicon Valley Seasteaders Go Looking for Low-Tax Sites on Land - <AUTHOR> https://www.bloomberg.com/news/articles/2019-12-20/silicon-valley-seasteaders-go-looking-for-low-tax-sites-on-land <comment><USER2> So let's get this straight — rich, educated guys — all from countries where having a super developed functional government was key to their ability to have something to generate capital off of — want to take their riches (along with future capitals riches) and run for the hills... giving back... what? Nothing? And where to take to? Places that don't have a developed, functional government, with uneducated and impoverished populations. Places that don't have a labor force suited for sophisticated multi-nationals that want a tax haven despite promises that somehow the impoverished will he marginally better.

All this libertarian nonsense coming from the wealthy has gotten to the point where no longer do people understand the lives dedicated to making theirs possible has indeed been a key factor in their own personal success.

We need more civic-minded leadership across the population, not less. The greed is just excessive.

<comment><USER3> The riches already gave back, because they got rich making things people want.

>We need more civic-minded leadership across the population, not less. The greed is just excessive.

This is the wishful thinking that statists will always use. the state will be fine if only people would be better. Well people are not better and never will be, so we need a system whereby we do not grant people, who will never be better, power over their fellow men.

</comment></comment><comment><USER4> There is another thread on this:

[https://news.ycombinator.com/item?id=21866017](https://news.ycombinator.com/item?id=21866017)

</comment><comment><USER5> I feel like humans have been trying to achieve some variation of this "utopia" for so long. I like to think it could work (in theory). But seeing so much failure due to greed, hubris, naiveté, etc. Makes me doubt it can work

<comment><USER6> It can't work because all utopias assume the world is full of people exactly like the founder.

<comment><USER7> All naive utopias do.</comment></comment></comment>


A Brief History of CNNs in Image Segmentation: From R-CNN to Mask R-CNN - <AUTHOR> https://blog.athelas.com/a-brief-history-of-cnns-in-image-segmentation-from-r-cnn-to-mask-r-cnn-34ea83205de4 <comment><USER2> Very nice review article. Usually all the deep learning details are over my head, but I was able to follow this article in its entirety.

Now if only there were jupyter notebooks with implementations of the different approaches, folks at home would be able to follow along with code, which is always the best.

<comment><USER3> Thanks for the kind words! I feel as though research papers are not always the easiest way to communicate ideas with a non-research focused audience. I think there's room for more people (like distill.pub) to take the main ideas from the research papers are share the underlying intuition with a larger audience.

I'll try and add more notebooks next time - totally fair point and would make it more interactive.

Thanks for the feedback!

Dhruv

</comment></comment><comment><USER4> So is Athelas using CNNs to count white blood cells?

<comment><USER3> Hi!

We are indeed using CNNs in some parts of our pipeline. You can read more about the general idea of how we use them here: [https://blog.athelas.com/classifying-white-blood-cells- with-...](https://blog.athelas.com/classifying-white-blood-cells-with- convolutional-neural-networks-2ca6da239331)

<comment><USER4> This is pretty clever. That's a really nice write up too.</comment></comment></comment>


Creating your own language. For example, Toki Pona has just 120 words. - <AUTHOR> http://www.marginalrevolution.com/marginalrevolution/2007/09/the-origin-of-l.html <comment><USER2> Some people make do with eight:

<http://en.wikipedia.org/wiki/Brainfuck>

But it can't be too hard to create a second language that maps onto a more common language. What would be hard is to design a 120-word language that you could teach someone, such that they could learn English a few years later and still get a decent score on their SAT. But that would be cruel.</comment>


The Complete iPhone Development Toolbox - <AUTHOR> http://iphone.appstorm.net/roundups/developer/the-complete-iphone-development-toolbox/

<comment><USER2> No list of iPhone development resources is complete without the Three20 framework, which provides various UI (and other) components extracted from the Facebook app and used all over the place.

<http://github.com/facebook/three20>

</comment><comment><USER3> Typo in the first sentence:

"Nobody could argue that the iPhone has been a revolutionary product in the cell phone industry"

Surely there should be a "not" in there somewhere?

<comment><USER4> That usage is pretty standard. The "against" is sort of implied.

<comment><USER5> argue has two meanings, to disagree and to assert. –verb (used without object) 1\. to present reasons for or against a thing.

I agree that it's ambiguous.

<comment><USER6> To argue is to present an argument. If you argue about something then your stance is unclear. However, if you argue a stance then you are arguing for that stance.

Example:

Tom argued about the war (unclear stance).

Tom argued the war was a bad thing (clear stance, Tom disliked war).

However, there may be a regional usage of 'argue' as 'question' or 'dispute' ("nobody could question/dispute the iphone's success") that I am unaware of.

<comment><USER7> puffythefish was just arguing the arguer's argument was arguably arguable.

<comment><USER5> Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo

</comment></comment></comment></comment></comment></comment><comment><USER8> I can not recommend the Stanford class enough. It covers pretty much everything one would need to know to develop an app and put it on the App Store, including your first steps with Objective-C and XCode.

<comment><USER9> The class is great. I'm currently reading the lectures. One thing I wish could improve is the assignments. If you aren't in the class you get no guidance at all. If they include hints to complete the last assignment in the next one that would be perfect. Occassionally I've run into problems and since I don't have the free time to dedicate to completing the assignments I've skipped a few.

<comment><USER8> I see what you mean. There is a Google Groups about the class: <http://groups.google.com/group/iphone-appdev-auditors> You should be able to find or ask for hints or walkthrough.

</comment></comment></comment><comment><USER10> Very impressive list of info for iPhone developers. _Very_. Lots of good stuff there. I can't find a comparable OSX development list on their site, sadly.

<comment><USER11> There's an entire site dedicated to this sort of thing, thats slightly more organized than a big list: <http://www.cocoadev.com/>. Its Mac-centric, but it covers the Foundation framework, so its worth knowing about, even if you only do iPhone stuff.

</comment></comment><comment><USER12> I would love a similar guide for Android-based phones like the Nexus One. Anybody know of such a link?

<comment><USER13> Me too.. especially for a web developer (someone who's used to python, php, ruby, etc.. (scripted languages) moving to something like Java.

But.. ugh... XML is so gross. It would be nice to build something that abstracts a lot of the boilerplate crap you have to go through when doing Java.

<comment><USER14> The Android UI XML isn't actually that difficult. Designing layouts is more straightforward than CSS. Use Linear and Relative layouts with margin, padding, gravity, weight, and "dip" units. Throw in some transparent PNGs and things look half decent.

</comment></comment></comment><comment><USER15> cool, glad to see my getappsdone.com in the list :)

</comment><comment><USER16> Looks very interesting. Nice to see a compilation like this.</comment>


The Future of Mobile Payments - <AUTHOR> http://www.charlesvbonello.com/post/35057571693/the-future-of-mobile-payments

<comment><USER2> Having worked in several retail, wholesale, and restaurant positions with a variety of POS, I think this is a very interesting space ripe for disruption from multiple angles. Marketing seems to be the differentiating factor between the major players at this time, as the article states.

What I think the article misses to point out, is the great variations in actual usability of the systems. POS analytics and systems with robust central backups are not new. Having so many UX designers now able to participate, and being able to rapidly iterate versions with fixes users actually need, is very new. Without saying too much, I am very excited to be moving these technologies forward at this particular time.

<comment><AUTHOR> Thanks for the feedback. I tend to agree with you about the fact that the analytics and backups offered are not new, but the accessibility to designers is, and I'm glad that you pointed it out more explicitly than I have -- especially given your experience.

I also think that in some ways, the 'usability' of each technology is the big hurdle that must first be cleared before "marketing" becomes the key differentiator. I approached this with the thought that among the existing (or discussed) technologies, any improvement in the technology or functionality is, at best, incremental. That, along with some other factors, is why I suggested that marketing would represent the key differentiator. Glad to hear other thoughts on that, too.

<comment><USER2> Traditionally this has been the case, and largely because POS required such a large upfront investment that merchants needed to be sure (or be 'sure' thanks to a product already having been established in the market) of what the details of the implementation are. When changing POS is as easy as uninstalling one app and installing another... UI will be a much greater factor. I expect many players to attempt to tie-in users through one method or another as a crutch for lacking quality UX.</comment></comment></comment>


Things I Think I Think on Bitcoin - <AUTHOR> http://daslee.me/10-things-i-think-i-think-on-bitcoin

<comment><USER2> > 6\. I think that the FBI's recent takedown of Silk Road, a black market > whose primary currency was Bitcoin, was an inflection point. That the price > of Bitcoin bounced back so quickly means that it's being used for more than > just illicit activity.

That's one interpretation, but there are lots of other reasons that may have occurred. Speculators can do lots of curious things, as can those who might benefit from perpetuating the idea that Bitcoin is stable.

<comment><USER3> > Speculators can do lots of curious things, as can those who might benefit > from perpetuating the idea that Bitcoin is stable.

"Speculators" are the ones determining exchange rates. There is no other "true value of Bitcoin in USD" that "speculators" are trying to conceal.

<comment><USER4> Those buying bitcoins to exchange them for goods and services have some expectation about the amount of goods and services they will obtain, and the "true value of Bitcoin in USD" is the value that reflects this (aggregated) amount. Those buying bitcoin to hold in the hopes that it goes up eventually don't care what goods and services they can get for bitcoins today, just how the price will be moving tomorrow. The two types of behavior are not unrelated, but distinction is meaningful.

</comment></comment></comment><comment><USER5> > unclear business model or applications

Bitcoin is not a business. But no applications?! How could you think this? Fast and cheap money transfer without geographic restrictions? Immigrant workers repatriating earnings? Low-cost online payment processing? I use money every day and wish I had the same option online. Visa has ~$4B in earnings. Western Union, ~$1B. Micro payments? (See reddit tip bot).

edit: Fixed earnings numbers. Current numbers are Shares*EPS for V, WU according to Google Finance.

<comment><USER6> Your earnings numbers are way off. Visa does about $10 billion in revenues, Western Union does $5-6 billion.

<comment><USER5> You're right. Math error. Fixed. Using Shares*EPS from Google Finance, I get $4B and $1B, respectively.

</comment></comment></comment><comment><USER7> > 3\. I think if you study Bitcoin, you realize that the currency is an > application of the protocol. Bitcoin is actually a chain of digital > signatures. Each "bitcoin" is just a ledger of all transactions of that > "coin." In other words, applications that have nothing to do with currency > or payments (e.g., like Bitmessage) can exist.

I disagree.

Despite the name resemblance, Bitmessage is not really comparable with Bitcoin. I think about Bitmessage more like Freenet for messages. It's just a p2p temporary distributed datastore.

In fact BM has no blockchain and there's no concept of mining (which would not make economic sense since you wouldn't get rewarded for it). Relaying messages to get yours relayed is much cheaper, and messages get deleted after 2 days, so there's no huge blockchain to maintain.

The real Bitcoin breakthrough was the blockchain and POW as an agreement protocol, and I don't think that's applicable outside of currencies because mining is very costly and the entire security relies on it.

<comment><USER8> Actually there is a proof of work concept. You have to compute a partial hash collision that is proportional to the size of the message you want to send. The reason Bitcoin clients hold the full blockchain is to acheive distribution and so that wallet balances can be computed by walking over the entire chain and summing. Bitmessage only needs the distributed aspect so its partial streams are good enough and less expensive for a user to get started.

<comment><USER7> I'm aware of BM's POW but it's in no way related to Bitcoin's use of it.

Bitmessage's POW is not a way to reach consensus about a chain of events. POW as a means to limit email spam messages was already proposed with Hashcash in 1997. BM just added a P2P distributed message database to provide decentralization.

The POW was no breakthrough from Bitcoin either: IMO Bitcoin's core concept (and the real genius) is the distributed agreement protocol, which is nowhere found in Bitmessage.

That's what I meant with "POW as an agreement protocol", not just "POW", and why I think Bitmessage does not really benefit from Bitcoin's protocol.

</comment></comment></comment><comment><USER9> > I think if I were in my early 20's, looking for a startup idea and willing > to do what the other person isn't (e.g., move to a different part of the > world), I'd spend all my time trying to understand this topic.

I don't understand this final item. Is this because the author thinks the US is or will be hostile toward bitcoin, or because he thinks that it can thrive more quickly in other parts of the world (like M-Pesa)?

<comment><USER10> Can't speak for the author, but the US is hostile to all business.

<comment><USER11> It's very welcoming to the large ones that have lobbyists.

<comment><USER10> That is not business, it's pull.

The US is hostile to business as such.</comment></comment></comment></comment>


HN's most controversial topic - <AUTHOR> https://blog.alexrohde.com/archives/638 <comment><USER2> This is probably a prank, but if it isn't, I'd encourage the writer to tell us what "Damore" is, as the article discusses a pro-Damore stance, but assumes we are willing to look elsewhere for a definition.

<comment><USER3> Agreed, I read it and just got the feelig of some dude judging his friends.

<comment><USER4> You read the last line? :

> disclaimer: I lied, both Bill and sam are actually me. All right reserved.

<comment><USER5> In that case, what else is a lie?

FWIW, the article says things like "If you accept the issue as nuanced and that all parties are well-intentioned, then you're giving up the joy of being the Good Side crusading against the Bad Side".

That means the introduction, "trying to unprovactively discuss a topic", is also a lie. The word "crusade" is provocative, as we learned after G.W. Bush used it shortly after 9/11, and the structuring of "all parties are well- intentioned" vs. Good/Bad-Sideism, is also a lie, as those are not the only two ways to structure this argument.

For example, one could argue about what "hostile workplace" means in the context of civil rights law, what a company might need to do to defend itself against an EEOC claim, and a discussion of what a "quite severe" incident might be ("quite severe" comes from the EEOC guidelines).

Bringing up "political correctness" is also part of the provocative language choice, as it is only really used as an off-hand dismissal of any challenges to the existing status quo based on a history of white, male, rich power.

For example, if "political correct" had a broader meaning, then we should say that politicians who defend the Constitutionally protected right to bear arms far more than they defend the Constitutionally protected right to an abortion are also being politically correct.</comment></comment></comment></comment>


Windows 8 Pro on a phone - <AUTHOR> http://pocketnow.com/2013/02/27/windows-8-pro-phone

<comment><AUTHOR> This article is 18 months old, 4.7" doesn't seem that big now and CPU's are a bit further ahead. I wonder what happened to them? I want one.</comment>


How to Secure Your Web App with HTTP Headers - <AUTHOR> https://www.smashingmagazine.com/2017/04/secure-web-app-http-headers/ <comment><USER2> Good starting point, but these headers won't protect your site from data breaches (just a bit with not caching confidential information).

<comment><USER3> Read the piece - it's more than about caching. It's about framing, XSS, code injections, TLS enforcement and more.</comment></comment>


An Introduction to Mathematical Optimal Control Theory [pdf] - <AUTHOR> https://math.berkeley.edu/~evans/control.course.pdf <comment><USER3> A note about this: much of the optimal control theory work surrounding Pontrayagin's Principle are theoretical building blocks whose primary utility is for mathematical analysis.

In practice, they result in boundary-value problems that are impractical to solve for systems of non-trivial size, and are almost never implemented in practice. Occasionally they are used to construct parameterized solutions for extremum control (e.g. NCO tracking) for very small systems, but these tend to be rarer cases. One runs into dimensionality issues very quickly.

In industrial control systems, optimal control models are almost always discretized and the optimization is done on algebraic systems of equations. Linear algebra dominates there.

<comment><USER4> > ... are theoretical building blocks whose primary utility is for > mathematical analysis.

When you say 'mathematical analysis' here, is that just a broader category that encompasses e.g. real and complex analysis? Or something else?

<comment><USER3> Yes, that is what I meant [1]. For example, you can use ideas from differential equations/analysis to determine say, the existence and uniqueness of solutions for continuous ODEs. Pontryagin's Principle and the calculus of variations in general gives you theoretical machinery for working with models in analytic form. Some problems such as minimum time optimization are more tractable in continuous time form than in discrete time. You can also in some simple cases derive the set of closed-form optimal solution trajectories (unconstrained case) and analyze that directly.

Once the models are transformed into discrete form for numerical solution, the tools used lie more in the realm of linear algebra (positive definiteness of Hessians, etc.)

[1] [https://en.wikipedia.org/wiki/Mathematical_analysis](https://en.wikipedia.org/wiki/Mathematical_analysis)

</comment></comment></comment><comment><USER5> Craig Evans (the author) is the most selfless mathematician I've ever studied under—-hands down a life-changing teacher. These notes, as are all his teaching notes, are magnificent.

</comment><comment><USER6> >Those comments explain how to reformulate the Pontryagin Maximum Principle for abnormal problems.

Please tell? I have yet to see anyone give a satisfactory approach on how to deal with the abnormal case.

For context there are sometimes optimal solutions which are not given by Pontryagin's Maximum Principle (PMP). An analogous situation can occur with Lagrange multipliers. The necessary conditions given by the Lagrange multipliers are not related to the maximization of the object functional. I surely think the situation is worse with the PMP because you are now in a continuous setting. I think [0] offers some good discussion for the abnormal case in Lagrange multipliers.

I would be interested if anyone has made any recent progress in dealing with the abnormal case for the PMP.

[0] Optimality Conditions: Abnormal and Degenerate Problems By A.V. Arutyunov

</comment><comment><AUTHOR> Trying to dig into Optimal Control Theory a bit, after realizing that - <USER2> many ways - OCT and (certain aspects of) Machine Learning are just opposite sides of the same coin. Reinforcment Learning in particular shares a lot of concepts with OCT.

<comment><USER7> for more on that subject - check out this recent RL and OCT survey by Ben Recht, also from UC Berkeley: [https://arxiv.org/abs/1806.09460](https://arxiv.org/abs/1806.09460)

<comment><USER8> Ben Recht also has an excellent series of blog posts (very related to this survey on arXiv, but broader) on the intersection between reinforcement learning and optimal control. An index is available here: [http://www.argmin.net/2018/06/25/outsider- rl/](http://www.argmin.net/2018/06/25/outsider-rl/)

<comment><AUTHOR> I was just reading those last night. Definitely good stuff.

</comment></comment></comment></comment><comment><USER9> Is this a very crude summary of Pontryagin's principle? Basically, you use Lagrange multipliers to solve a constrained optimization.

In contrast, dynamic programming is based on stitching together optimal sub- solutions.</comment>


The best things and stuff of 2012 - <AUTHOR> http://blog.fogus.me/2012/12/26/the-best-things-and-stuff-of-2012/ <comment><USER2> Did you know about a "hidden" page: <http://news.ycombinator.com/best> Looks like an experimental feature to me but it will be nice to have something like this.

Waiting for: <http://news.ycombinator.com/best/2012>

<comment><USER3> thanks ... how did you find that?

<comment><USER4> go to the bottom of any hn page and you'll see a "lists" link

</comment></comment></comment><comment><USER5> I don't know if this is from 2012, but I just found out about this page -- it's the best papers from computer science from 1996 to 2012 <http://jeffhuang.com/best_paper_awards.html> (based on awards given by committees at the top conferences)

</comment><comment><USER6> Best thing I've done all year is learning how to code. I feel like I've broken the cycle of illiteracy.

</comment><comment><USER7> Apropos Engelbart's Violin, I'd be interested to try a Microwriter. I think I'd pick it up quite well as I played piano for years. Did they ever make it into widespread production? Though I suppose you could make one quite easily with an Arduino.

<comment><USER8> they certainly existed; i used to know someone who used one.

see also <http://www.cykey.co.uk/> (same people; available now)

<comment><USER7> Thanks! That's affordable enough to buy and find out.

</comment></comment></comment><comment><USER9> _Favorite musicians discovered: ... Klaus Nomi ..._

As a card-carrying member of the Klaus Nomi Fan Club (well, formerly – I lost the card), I heartily approve.

</comment><comment><USER10> I recently went through the HN posts I upvoted/saved this year and maybe someday will get around summarizing the ones that taught/inspired me the most...here are two technical ones that stuck out for me:

SiteChat: a postmortem. Or, the rise and fall of a society. [http://burakkanber.com/blog/sitechat-a-postmortem-or-the- ris...](http://burakkanber.com/blog/sitechat-a-postmortem-or-the-rise-and- fall-of-a-society/) This to me was the epitome of a great HN post: the author decides he wants to learn how to build Chrome extensions and implement WebSockets and builds a chat app from scratch. It becomes a runaway hit and he leaves it alone, only to rediscover later that it developed into its own online civilization of sorts.

How We Nearly Lost Discovery [http://waynehale.wordpress.com/2012/04/18/how- we-nearly-lost...](http://waynehale.wordpress.com/2012/04/18/how-we-nearly- lost-discovery/) A former NASA engineer describes how Discovery nearly ended up as tragedy, and "how I found out that we were never really as smart as we thought we were."</comment>


Why the Internet will fail from 1995 - <AUTHOR> http://threewordchant.com/2010/02/24/why-the-internet-will-fail-from-1995/

<comment><USER2> Interestingly enough, some parts are still relavent:

"Every voice can be heard cheaply and instantly. The result? Every voice is heard. The cacophany more closely resembles citizens band radio, complete with handles, harrasment, and anonymous threats. When most everyone shouts, few listen."

"Lacking editors, reviewers or critics, the Internet has become a wasteland of unfiltered data. You don't know what to ignore and what's worth reading."

I feel it's getting better though...</comment>


What Is a Slip Ring? - <AUTHOR> https://www.heason.com/article-detail.php?aid=327&did=What-is-a-Slip-Ring? <comment><USER2> I've used these to mount spinning LEDs and connect the LEDs to power/arduino that is not spinning. This blew my mind- when I was a kid I spend a lot of time wondering how lights on a car wheel wouldn't need a very long roll of wire.</comment>


Facial recognition now lets you find porn stars who look like people you know - <AUTHOR> http://www.thememo.com/2016/09/23/porn-cleebrity-porn-megacams-facial-recognition-porn/ <comment><USER2> The opposite would be required: find people on meetic who look like porn stars you know! :-}</comment>


Ask HN: What industries suffer from "it's how it's always been done" thinking? - <AUTHOR> <comment><AUTHOR> Goes without saying that this is very subjective, but I'd love to hear your opinions</comment>


Ask HN: I missed upgrading to Windows 10 from Windows 8.1 - <AUTHOR> Is there any way I can upgrade now for free?  I don't have that kinda dough to upgrade now.  The Bash in Windows 10 is irresistible to me.  I can then get rid of the dual boot Ubuntu on my machine.  Thanks. <comment><USER2> [https://www.microsoft.com/en- us/accessibility/windows10upgra...](https://www.microsoft.com/en- us/accessibility/windows10upgrade)

</comment><comment><USER3> A while back, the 8.1 activation key worked with 10... not sure if still the case...</comment>


Linus Tech Tips Launches Floatplane - <AUTHOR> https://youtu.be/oOOOfZWXPu4 <comment> coddle-hark I'm interested to see how this plays out. I subscribed to LTT on Floatplane a couple of weeks ago but the lack of iOS app combined with the kind of unfinished feel of the website made the experience not very pleasant.

I really like the idea of paying for content though.

</comment><comment><USER2> How will compare to Nebula?</comment>


The W3C's plan for DRM in HTML5 is a betrayal to all Web users - <AUTHOR> https://app.classeur.io/#!/files/EwZcHUKt79Zqc6RgVrNa <comment><USER2> does it even matter, browsers don't follow w3c anymore do they?

Didn't all major browsers follow the [https://whatwg.org/](https://whatwg.org/) spec instead?</comment>


Ask HN: What cost the most of your AWS usage? - <AUTHOR> bandwidth(including s3) or ec2? <comment><USER2> Raw cash, or Man-hours included? Assuming money alone.

EC2. Definitely not S3.

</comment><comment><USER3> ec2

</comment><comment><USER4> ec2, cloudfront, and data transfer</comment>


Confirmation that Windows Server Is Moving Away from GUI  - <AUTHOR> http://redmondmag.com/blogs/it-decision-maker/2012/01/the-gui-on-the-way-out.aspx

<comment><USER2> unfortunately almost all their system administration tools are GUI-based, so it will take awhile before they really make GUI optional.

besides, if you have a non-GUI server system, it's already from the Unix family anyway :)

<comment><USER3> But do those tools have to run on the server itself?

<comment><USER2> not during normal operation.

but if the network connection is broken or you need to do disaster recovery, there's no way around and you ought to have a console graphical screen.

what I love about old Sun servers, you can do all system administration via a serial RS-232 connection.</comment></comment></comment>


Touch Typing on a Gamepad - <AUTHOR> https://darkshadow.io/2020/07/07/touch-typing-on-a-gamepad.html <comment><USER2> A little over a decade ago now, back when the Sony PSP was current, there was a neat little homebrew IM client called AFKIM. It used bitlbee to connect to various IM services (AIM, GTalk, MSN, etc.) and worked pretty well for something running on a PSP.

The keyboard, though, was great:

[http://localhost.geek.nz/afkim/docs/usingafkim.html](http://localhost.geek.nz/afkim/docs/usingafkim.html)

It's a 3x3 matrix. You use the analog stick to pick a square, then hit one of the face buttons to enter a character. Left and right shoulder buttons shifted the keyboard to uppercase, numbers, specials, etc.

IIRC it was a Lua module that any PSP homebrewer could drop into their application for a pretty decent OSK.

<comment><USER3> That looks very similar to MessagEase keyboard available for Android and iOS. It is pretty cool, I was an avid user when I had an Android phone and I was barely making any typos. It's very customizable and I particularly enjoyed clipboard integration. On iPhone third party keyboards don't work as good so I had to stop using it.

</comment></comment><comment><USER4> Unfortunately I can't find a direct reference on any Valve official channels, but I'd say that typing on a Steam Controller is quite good; I'd even go so far to say that it's going to be hard to beat it for keyboard input on a controller.

Anecdotally, most people hated the Steam Controller's touchpads, and I'll admit I wasn't a fan at first either. But the ability to remap them to be: sticks, trackballs, d-pads, bring up (multi-level) radial menus, etc. is an absolutely killer feature.

I think one of the reasons they "failed" is because they absolutely were not plug-and-play, because to truly utilize their full capabilities, you had to configure them per game.

<comment><USER5> As someone who actually enjoys tinkering with these settings. I grew to love the controllers quite quickly. But it's exactly as you said.

Steam Controllers are not plug-and-play. They're really a niche thing.

I was able to set up a reasonable competetive setup for Metal Gear Online. I had the left pad for walking. Then set up the right one with extremely sensitive camera control, so I could turn around really quickly. But configured it in such a way that it slowed down a bit when I pressed down the aim button. After which I also enabled gyro controls for fine-aiming.

For Fallout 4 it was a more casual layout. But here I made the right trigger hipfire if you fully pressed it immediately. But a half-press would go into iron-sights first, while also enabling gyro aiming. This felt really intuitive for me.

<comment><USER6> >Steam Controllers are not plug-and-play

I gotta say, for old games I had already played it was a great experience since I knew what I wanted to configure and how. However, new games were a pain since I was still trying to figure everything out

</comment></comment></comment><comment><USER7> I think all the "optimization" was a mistake. Instead of optimizing for the most-used keys, I think it's better to optimize to make it easy to remember.

Phone typing was easy to learn because the letters were both predictable (alphabetical) and because you could look at the letters when you forgot, especially while learning.

Since looking at the keys isn't possible here, I think it's even more important that being able to predict the locations of letters is possible and easy.

<comment><USER8> T9 was amazing. Any upcoming human interface industrial engineer ought to study it. When driving or in class, I used to regularly send SMS messages without looking at my phone's screen. It was THE biggest thing I missed when I got my first iPhone 3G.

Only recently have Google's and Apple's TTS come close to matching it. Occasionally I still miss T9 like when in a movie theater where I can't speak to type and don't want to look at my screen.

<comment><USER9> I'm a bit of a keyboard maniac. I don't know why I am this way, but I am. On my computer I have a lovely split mechanical keyboard which I've remapped to Colemak, but I've always wished I could get a good typing experience on my phone.

I like being able to type while walking and without looking, and by far the best phone keyboard for that is 8pen [0]. A masterclass in innovative UX imo, and clearly a ton of work went into it. Unfortunately, they pulled it from the play store (and deleted all the tweets on their twitter) some years ago for reasons unknown to me.

Related is MessageEase [1], which is not as good but still passable. But it's incredibly ugly and takes up a ton of space on my screen, so I don't like to use it.

[0]: [http://www.8pen.com/](http://www.8pen.com/)

[1]: [https://www.exideas.com/ME/index.php](https://www.exideas.com/ME/index.php)

<comment><USER10> 8pen was definitely the most interesting/promising alternative input methods I've ever seen.

</comment></comment></comment></comment><comment><USER11> So basically, typing via Street Fighter moves.

Feh. Everybody knows Real Programmers type by manipulating the locations of specific koopa troopas so that when the glitch is triggered, exactly what they intended to type will be written into memory.

</comment><comment><USER12> As someone with RSI-strained fingers, there's no way I am concentrating all fingers' worth of input movement into just my two thumbs. Sounds like a recipe for carpal tunnel/tendinitis/miscellaneous other flavors of RSI.

<comment><AUTHOR> You do have to be careful and stop when symptoms occur especially in the beginning but I believe the issue can be avoided. The key is to stay relaxed and focus on minimizing mistakes rather than trying to type very fast from the get-go. Typing with this system is actually not that different from playing a console game.

<comment><USER13> So I guess the question is, do people who play LOTS of console games (e.g. professional streamers) get RSI?

<comment><AUTHOR> Some do but as with RSI from keyboard/mouse usage it affects everyone differently. One thing they usually have in common is excessive repetition for example by constantly using shortcuts with CTRL. While practicing typing (both keyboard and gamepad) I noticed that highly repetitive lessons with lots of text like "jf jf jf fj fj fj jfjfjfj" cause much more strain than lessons with more realistic text. In the end it all comes down to responsible usage, nothing is completely safe.

</comment></comment></comment></comment><comment><USER14> A chorded keyboard would also map well to gamepads

[https://en.wikipedia.org/wiki/Chorded_keyboard](https://en.wikipedia.org/wiki/Chorded_keyboard)

<comment><AUTHOR> Good idea, I will give it a try!

</comment></comment><comment><USER15> I was a bit disappointed at how limited the linked Gamasutra's article was. For example, it didn't even mention helical keyboards that arrange letters and numbers into a 3D helix that allows very fast character selection. For example, when you can immediately see that the character you need is one and a half loops away ending on the 3 o'clock position, twirling your analog stick to that position takes a fraction of a second.

<comment><USER16> You mean this type of keyboard? [https://www.youtube.com/watch?v=euquOpUmUyk](https://www.youtube.com/watch?v=euquOpUmUyk) I had so much fun playing beyond good and evil on the PS2!

It's not the best but it is both easy and fun to use so if you want to avoid frustrating your players it may be the safest choice.

</comment></comment><comment><USER17> I would be interested to see a video of the article author using this system. It's a bit difficult to understand how it works without visuals.

<comment><AUTHOR> Good point! I will add a video soon.

</comment></comment><comment><USER18> > _Whenever one of the sticks left the center by crosssing the threshold, an > input sequence was started. As soon as both sticks were back in the center > within the threshold, the sequence was considered completed and transformed > into a pair of tuples that described the movement of the sticks._

I wonder if it was easier in practice to move both sticks simultaneously, or one after the other and then release them simultaneously. Because the currently most commonly accepted psychological model two-handedness[0] would suggest the latter, and that you start with your off-hand and finish with your main hand.

[0] [http://cogprints.org/625/](http://cogprints.org/625/) _Asymmetric Division of Labor in Human Skilled Bimanual Action: The Kinematic Chain as a Model_

<comment><AUTHOR> Indeed, when entering combined inputs one by one starting with my off-hand my accuracy was higher and I found myself using that technique occasionally during practice, especially when I had made a mistake and needed to repeat an input. However, as my speed increased, eventually I tended to move the sticks simultaneously.

</comment></comment><comment><USER19> Cool idea, but wouldn't it make sense to remove the letter J from the most used letters?

If you don't use that letter for Vim it drops from the top 8 all the way to the bottom of the frequency chart (assuming you only type English). If you than map whatever J does in Vim to a more frequently used letter your typing speed should go up.

Alternatively since J seems to be used mostly for navigation (not sure, I don't use Vim) use the d-pad to do that instead.

\---

> After I upgraded my gamepad to the DualShock4, I realized I could make > diagonal inputs relatively accurately. Integrating diagonal inputs would > reduce the number of more complex inputs required thus increasing speed.

Any plans to do that?

<comment><AUTHOR> You're right of course about removing the letter j from the most used letters. My strategy is to continue logging the inputs made with this system and adjust the mapping as frequencies change. If I indeed use the d-pad more often than j when using this system, the letter j will eventually be flagged for remapping. By making only one adjustment at a time the relearning effort is manageable.

As for diagonal inputs, I've actually done it and I'm still experimenting with it. I can accurately target 8 sectors when there is no dialing involved but with dialing I would stick to 4. I think a hybrid system that allows for 8 sectors but switches to 4 when I start rotating the stick would be the best of both.

</comment></comment><comment><USER20> Single hand chording inputs are supposed to best touch typing, I'm surprised they can't do similar things with the gamepad and its shoulder buttons and other inputs.

<comment><USER21> Yeah, I was kind of really surprised to see this instead of a chording system.

</comment></comment><comment><USER22> Reminds me of the chorded keyset from Doug Engelbart (inventor of the mouse)[1]

The idea of simultaneously using a mouse with the right hand and keyboard with the left is intriguing.

[1]: [https://www.dougengelbart.org/content/view/273/309/](https://www.dougengelbart.org/content/view/273/309/)

</comment><comment><USER23> There is actually a gamepad-type keyboard as a real product. It doesn't work with gestures but with dedicated buttons. From the looks of it, you can type pretty fast on it, too.

It's called AlphaGrip [http://www.alphagrips.com/](http://www.alphagrips.com/)

Never used one, though.

</comment><comment><USER24> This reminds me of the orbitouch, which is a keyless keyboard for people with disabilities. It works by having one stick chose a subset of letters, and the other to letter within that subset. [https://orbitouch.com/](https://orbitouch.com/)

</comment><comment><USER25> Nice, but I still don't know why Dasher[0] didn't get more "mainstream"?

[0]: [https://en.wikipedia.org/wiki/Dasher_(software)](https://en.wikipedia.org/wiki/Dasher_\(software\))

</comment><comment><USER26> This seems like it could be really useful for text entry in VR! Using a keyboard is impractical in that scenario, but you typically are holding two controllers with joysticks. A system like this could make VR workspaces more practical.

</comment><comment><USER27> Reminds me of Hadouken and Shoryuken moves :)

[https://streetfighter.fandom.com/wiki/Hadoken](https://streetfighter.fandom.com/wiki/Hadoken)

</comment><comment><USER28> Selfless plug. Have been obsessing over this for a few years.

Do not hesitate to contact me via contact form if you share this passion and or wants to take it further.

tbf-rnd.life/

</comment><comment><USER29> Are there any usable 1 handed typing systems out there? I just want an media remote with a touchpad+trigger and T9 input.

<comment><USER30> For a traditional style remote, held in a pointing grasp with thumb on top, I have a hard time imagining something much better than a T9 layout.

Personally, I'm kind of enamored with the idea of a phone or tablet for media selection & control.

On touchscreen based devices, I'm a big fan of [https://en.wikipedia.org/wiki/MessagEase](https://en.wikipedia.org/wiki/MessagEase).

When I started looking into alternative text entry for a phone, the big thing I was looking for was the ability to completely disable predictive text entry. Messagease allows for that - I'm able to input text quickly, accurately, and without the use of predictive input.

I've used it while holding my phone in either hand and using the thumb of that same hand (though it works better in my dominant hand). I've also used while holding the phone in my non-dominant hand and using the index finger of my dominant hand.

I can _almost_ , but not quite, use it without looking.

So, if you're thinking of a custom remote project to scratch that itch, that layout may provide inspiration.

<comment><USER31> Looks like it's patented? That might inhibit use a lot.

</comment></comment></comment><comment><USER32> I did not get your idea! Explain me please

<comment><USER33> Which part of the article confused you?</comment></comment>


Don't Break the Chain made lifehacker. - <AUTHOR> http://lifehacker.com/software/goals/follow-seinfelds-advice-at-dont-break-the-chain-298908.php

<comment><AUTHOR> If anyone around here creates something based upon a lifehacker post and then subsequently would like them to feature what you've built I can now recommend from experience simply emailing them at firstname.lastname@example.com.

<comment><USER2> Congrats Brett!</comment></comment>


Ask HN: My App's Pricing plans.  - <AUTHOR>

Hey HN, I'm launching an SaaS app soon(description is below) and would like your opinion on the way we should go in terms of pricing.
Quick description of app: Questionify manages your site's FAQ page by letting your customers ask questions(no login required). Questions are placed into categories(which of course you can manage) and are displayed according to the view count. Customers can subscribe to questions(there's a "I had that question too!" button which encourages this).
Do you think we should do Freemium? How do you think pricing plans would be ok, based on number of users/questions?
Feedback would be greatly appreciated. <comment><USER2> In my completely unprofesional opinion, and with absolutly no experiance in this area, I would advise you to skip freemium. I am guessing that if you go with freemium you are going to get a bunch of people using it who are just adding an FAQ to their freepages 'website' and are unable to or never plan to upgrade to a paid version. The money will probably be in going after big buisnesses, colleges, NPOs, etc. who want to find out what their customer's questions really are. (Or possibly you could have a freemium version that had advertisements in it, and have the ads pay for everything.)

I also recall seeing several people complain about how it is often those who are not paying for the service that cause the most customer service difficulties.

<comment><AUTHOR> haha yeah, dealing with customer that aren't really paying can be a pain. In fact, I'm going after businesses, focusing on B2B, so I agree with skipping freemium.

<comment><USER3> My next SAAS app will be paid-only, at least at the beginning.

</comment></comment></comment><comment><USER3> On freemium: I'd really follow the advice of "It is a numbers game, so bust out your Excel spreadsheet" (from [http://gigaom.com/2010/03/26/case-studies- in-freemium-pandor...](http://gigaom.com/2010/03/26/case-studies-in-freemium- pandora-dropbox-evernote-automattic-and-mailchimp/)).

I would really try to understand how much a freemium user cost in your case, and how many (and which) premium users you would need to cover the free ones.

<comment><USER4> I would suggest not basing your pricing on costs. Instead, base it on the value your users will perceive from your service. On reason is that the per- user costs are likely to be too small for you to measure. (Pricing based on costs also auto-commoditizes your offering.)

<comment><USER3> I second that actually, totally :)

I would just ensure that the freemium costs remain under control (that was the meaning I wanted to convey, at least).

</comment></comment></comment><comment><USER5> The problem that I have with your question is that I'm having trouble what you mean when you suggest you base pricing on "number of users/questions". What does that mean? To me, as a webmaster, I start thinking, "Wait - do I have to know how many users are hitting my website or do they mean how many users can manage/edit the questions/answers?" It's a bit confusing.

I'm going to assume that you are thinking along the lines of "How many users the company appoints to edit/manage the entries." Okay - if that's the case then what happens if a big company (like MSFT) decides to try you out on 10 pages that have 1-2 editors? You might get tens of thousands of hits but still get the same revenue that a one-person site with 1k uniques a month gets you. Can you scale that?

I don't know - it's a tough slope but I think you have to put something in there to prevent DOS to other clients because you are fulfilling one big client's requests ten-fold over the others.

<comment><AUTHOR> Sorry, I didn't really define my question well. Basically by users I mean people that may edit the website. You have really good arguments. I don't really find this being fit for big companies, but I suppose one way of pricing would be by how much traffic your site gets which sort of directly imposes how much money your business is making. In my opinion this is by far the best way to go.

</comment></comment><comment><USER6> There was an interesting article on HN recently: [http://blog.boxedice.com/2010/03/07/choosing-a-price-for- you...](http://blog.boxedice.com/2010/03/07/choosing-a-price-for-your-webapp- or-startup-using-multivariate-testing/)

Might be of relevance to you.

<comment><AUTHOR> Wow this looks really good. Thanks for the link.

</comment></comment><comment><USER7> Freemium may work if the free package has your logo/name and and a link back to your site on the users FAQ page.

If you get any reasonable volume on your free product, this could work well for your SEO & brand.

</comment><comment><USER8> Do you have any high-end premium features? Or are users and questions the only knobs you have turn?

<comment><AUTHOR> Well, you can brand your page using logos, colors. Another feature is you can upload screenshots along with pasting a youtube video link and we convert it into a video object.

Besides that, I guess stuff like live search etc.</comment></comment>


Game release learnings: iOS sales, breaking even and impact of App Store feature - <AUTHOR> https://blog.sheepingaround.com/post/183090206855/one-month-of-sheeping-around-thoughts-and-numbers <comment><AUTHOR> This is a two-part post:

Part 1: 10 day retrospective [https://blog.sheepingaround.com/post/182394390565/sheeping-a...](https://blog.sheepingaround.com/post/182394390565/sheeping- around-retrospective-by-the-numbers)

Part 2 (currently the url): 1 month retrospective [https://blog.sheepingaround.com/post/183090206855/one- month-...](https://blog.sheepingaround.com/post/183090206855/one-month-of- sheeping-around-thoughts-and-numbers)</comment>


IE6 is not going away for a long time because of corporate nightmares like these - <AUTHOR> http://calink.sprint.com/phase1

<comment><USER2> Realism? On Hacker News? I thought we had all agreed to act as if IT consists entirely of web start-ups with no such thing as legacy, even though that's probably 99% of the pie.

</comment><comment><USER3> Why can't Microsoft simply take the IE6 codebase and refactor it into a static, standalone "Legacy Intranet Browser" that, similar to Mozilla Prism, will generate a locked-in "site launcher" for each site it must be used on?

<comment><USER4> Done (more or less). IE6 application compatibility virtual PC image: [http://www.microsoft.com/downloads/details.aspx?FamilyId=21E...](http://www.microsoft.com/downloads/details.aspx?FamilyId=21EABB90-958F-4B64-B5F1-73D0A413C8EF&displaylang=en)

I use it at work to test our sites against IE6. Boots in about 5 seconds and runs IE6 as well as can be expected.

<comment><USER5> Not gonna work if the whole reason for needing IE6 was some ActiveX control that interacts with your desktop.

<comment><USER6> That is why Windows 7 has a mostly-seemless Windows XP virtualization add-on.

</comment></comment></comment></comment><comment><USER7> There are unfortunately ALOT of corporate programs that will only run on IE6. At work, our main app is optimized for IE6 but we are trying to ween our customers off of it and onto IE7... but all IE7 bugs are P2s at worst because IE6 is what our customers are using.

<comment><USER8> At the day job, legacy installations mean IE6 compatibility is a requirement and all other compatibility is a luxury. I prioritize accordingly.

Its not like I can tell my customer "Look, I know telling you to upgrade your browser is going to break that 3 million dollar CRM system you've been using for the last 8 years... but you'll get transparent PNGs!"

<comment><USER9> Well eventually the argument will be "You'll be able to use the real internet!"

</comment></comment></comment><comment><USER10> This has nothing to do with IE6's rendering engine, and everything to do with ActiveX.

<comment><AUTHOR> Absolutely. Now if you're a small vendor, you have no choice but to downgrade all your computers to IE6 in order to enable your employees to access business critical information. Because of how complex the configuration is, running IE6 in parallel with IE7/8 with hacks will not work. And there is no other way to access this data. So now even though other browsers might be installed, most users will use IE6 for regular browsing. I want IE6 to die but I'm afraid it'll be a while.

<comment><USER11> I run IE6 (an a virtualbox VM with WinXP) alongside IE8 and FF, Saf, Op, Chrome, etc., for testing purposes. It even runs IE5, IE4 but I don't have to bother with them except when I want a laugh.

MultipleIE (from tredosoft.com), simples.

</comment></comment></comment><comment><USER12> So I guess I'm blessed that my workplace's intranet is coded to Firefox, and we dropped support for IE6 for our customer-facing sites a year ago?

<comment><USER11> If it's "coded to Firefox" then they're doing it wrong. If it's coded to web standards and only FF is supported, that's a different matter.

Suppose a patent problem came up (as with GIFs in the past) and FF couldn't be used legally any more. If you code to FF you'll probably find you're OK, but if you code to standards then any standards compliant browser should be a drop-in replacement.

<comment><USER12> It's coded so that we only have to check if it works in Firefox. It's not like we're explicitly trying to leverage Firefox-only markup or CSS. I believe the idea is to reduce waste of development time and effort. I think I'm going to call YAGNI at this point re: future patent problems. I don't see that happening soon, and I'd gladly take the time savings now, and cross that bridge when we get to it -- if it comes at all.

</comment></comment></comment><comment><USER13> Not surprisingly, above page created in MS Word. What one can expect further.

<meta name=Generator content="Microsoft Word 12"> <meta name=Originator content="Microsoft Word 12">

</comment><comment><USER14> Oh god that's depressing.

</comment><comment><USER15> I work for a major law firm (think top 6 worldwide) and we run a DM system that requires IE6 only (ie, doesn't work in IE7 even) so every office worldwide is tied into IE6.

Only recently have we started rewriting it to work in newer browsers ... and I don't expect a working prototype before middle of next year!

<comment><USER11> The docs and metadata are in a DB, just have a new frontend written to match the old UI but with knobs on. Should be done and ready to test by next weekend (inside joke ;0).

Or just get an OSS DM system and munge it together with the old DB. Perhaps knowledgetree would be a starting point for that.

</comment></comment><comment><USER16> What is special about IE6 that doesn't work on other versions?

<comment><USER7> A lot of things about IE6 are not standards compliant, so it's either programs for both or program for just IE6 and there is never enough time/resources to develop for both.

<comment><USER16> I thought the later IE's had special rendering compatibility modes that do the same as IE6.

<comment><USER17> The same as IE7.

</comment></comment></comment></comment><comment><USER18> I can't see a date anywhere. Does anyone know how old this is (please, _please_ don't say it's current)?

<comment><USER19> view source:

       <o:Created>2009-04-10T21:20:00Z</o:Created>
       <o:LastSaved>2009-04-10T21:56:00Z</o:LastSaved>

</comment></comment><comment><USER20> Insanity.

<comment><USER21> Maybe, but as numerous people have said before, there are likely thousands of businesses that have internal websites that only work with IE6.

<comment><USER20> Agreed, and quite expensive to rewrite.

</comment></comment></comment><comment><USER22> Why doesn't somebody just write a goddamn dedicated IE6 emulator and be done with it...

</comment><comment><USER23> what's the big deal? looks like a nice site.

</comment><comment><USER24> It's either us or them - personally, I choose the former.</comment>


A Surveillance Net Blankets China's Cities - <AUTHOR> https://www.nytimes.com/2019/12/17/technology/china-surveillance.html <comment><USER2> Crime in China used to be really bad, years ago. I recall one visit as a teen, some 15 years ago, where someone attempted to snatch my mother's purse as she was riding on a bike, in broad daylight in a major city. In the last five years, such incidents seem to be significantly rarer; while I don't have crime stats handy, I can definitely say that I haven't worried about crime.

The thing is, everyone already expects to be watched in public. The government in this sense is really just living up to the expectation.

To the average citizen, they can ascribe lower crime rates to the surveillance program, which makes them feel safer. Fitting with the cultural inclination towards societal stability and harmony, surveillance does not seem out of place or unusual in public for folks.

<comment><USER3> Is it a crime to protest in the streets? I wonder if the Hong Kong citizens would feel safer for a surveillance net across their city.

</comment></comment><comment><USER3> What is authoritarian for the goose is authoritarian for the gander. Makes me wonder where this kind of thing is at in the US now.

[https://arstechnica.com/tech-policy/2016/08/persistent- surve...](https://arstechnica.com/tech-policy/2016/08/persistent-surveillance- systems-has-been-watching-baltimore-for-months/)

<comment><USER4> It's not okay just because America does it to a limited extent in a miniature percentage of land. It's actually a false equivalence.

<comment><USER5> > It's not okay just because America does it to a limited extent in a > miniature percentage of land. It's actually a false equivalence.

America does not do it to a limited extent. America spies all the western world. Everything which goes on internet is watched by NSA and CIA.</comment></comment></comment>


First proof that infinitely many prime numbers come in pairs (2013) - <AUTHOR> http://www.nature.com/news/first-proof-that-infinitely-many-prime-numbers-come-in-pairs-1.12989

<comment><USER2> Oh, this is from 2013. I was getting excited to read about a new discovery.

<comment><USER3> If you didn't know about it, what's the difference to you? As long as it hasn't been disproven, and you'd have been interested hearing it then, what changes?

On a related topic, I sometimes wonder why people seek out new entertainment (movies, tv shows), when it's unlikely to be better than everything already made in the past. Why would you prefer watching a new movie over an old one? The obvious answers (better CGI, closer similarity to current culture, social reasons aka "what other people are watching") don't seem to fully explain it. There seems to be some "new thingy pull" that affects many people (even myself at times), yet I can't explain it.

<comment><USER2> Sorry, I meant that I have already read this article a long time ago, and the title of this post got me excited to read about some new developments.

As for your second point, I think you mentioned a lot of the main reasons. But I disagree that new media is unlikely to be better than everything made in the past. In fact, I would say that it's very likely that a new movie or TV show will be far better than something made in the past, simply because they have much bigger budgets now, better technology, and even a better understanding of filmmaking and storytelling. Especially with recent TV shows such as Breaking Bad, Game of Thrones, True Detective. The bar has been raised very high.

<comment><USER3> It's possible that a random new movie will be better than a random movie in the past, but you're not talking about random low-budget ones, you're talking about high-budget ones. It's not like they didn't have some big budget films in the past, and I doubt a "better understanding of filmmaking and storytelling" is responsible for more enjoyment of current things. Also, I'm more referring to even movies from 5-10 years ago, which don't suffer from lack of technology in general, or most of the other reasons, and yet there doesn't seem to be as much consumption of them than the "new thing". Personally, I'm fine with consuming old media, but the world doesn't seem to share that with me, and I don't fully get why.

There's also the availability of extensive ratings for past media, which means you can pick and choose the good ones, something harder to do when picking stuff still in theaters.

As a counterpoint, I do enjoy sequels of things I've previously enjoyed (and understand the sequel effect), but that doesn't seem big enough to account for the general phenomenon either.

</comment></comment></comment></comment><comment> daniel-levin No, this is absolutely _not_ the first (correct) proof that infinitely many prime numbers come in pairs! That is the twin prime conjecture, and at the time of writing this comment, steadily remains a conjecture. I wonder why _Nature_ , a publication held in high regard, would publish an article with such a title. This is not to say that the result is anything less than incredible.

Terence Tao delivered a very good lecture on this result here [0]

[0] [https://www.youtube.com/watch?v=pp06oGD4m00](https://www.youtube.com/watch?v=pp06oGD4m00)

<comment><AUTHOR> More precise quote from the Nature article: "... Yitang Zhang ... finds that there are infinitely many pairs of primes that are less than 70 million units apart without relying on unproven conjectures."

I agree that there is a difference between "twin primes" and "pairs of primes".

<comment><AUTHOR> Twin primes are pairs of primes which differ by two.

</comment></comment></comment><comment><USER4> Note: 2013.

<comment><AUTHOR> In 2014 they were able to further improve the results of Zhang. Polymath8 project "Bounded gaps between primes" [http://michaelnielsen.org/polymath1/index.php?title=Bounded_...](http://michaelnielsen.org/polymath1/index.php?title=Bounded_gaps_between_primes) .</comment></comment>


Show HN: SPACE 16.12 with redesigned UI – multi-tasking with your VR headset - <AUTHOR> https://getspace.io/?v=16.12 <comment><USER2> This looks exciting, and is a realization of my number-one favorite use-case for a VR headset.</comment>


Another 'Too Big to Fail' System in G.M.O.s - <AUTHOR> http://www.nytimes.com/2015/07/14/business/dealbook/another-too-big-to-fail-system-in-gmos.html?_r=0 <comment><AUTHOR> Last sentence of NY Times piece by Taleb and Spitznagel: "The G.M.O. experiment, carried out in real time and with our entire food and ecological system as its laboratory, is perhaps the greatest case of human hubris ever. It creates yet another systemic, "too big too fail" enterprise — but one for which no bailouts will be possible when it fails." If this is not scary enough for reading the article, I don't know what is.

</comment><comment><USER2> I was going through this point-by-point, but I don't really want to leave a huge wall of text. In short, many of the arguments they present are attacking strawmen, others are intellectually dishonest for other reasons, and they really don't offer any support for their opinions.

</comment><comment><USER3> And here I thought that the liberation of gigatons of carbon into the atmosphere was the greatest case of our hubris. I guess we just keep outdoing ourselves... Somehow it worries me a bit more that GM tomatoes...

</comment><comment><USER4> TL;DR; Anti-science article that knows it is, but preemptively calls that it will be called that. Scientists don't start out by saying I will be called anti-science. They prove points through facts.

Nothing they state in the 5 points has the facts to back it up.

> Ireland's population was decimated by the effect of monoculture during the > potato famine. Just consider that the same can happen at a planetary scale.

We have famine at a planetary scale, just the writers are not in that famine.

"Some 795 million people in the world do not have enough food to lead a healthy active life. " [https://www.wfp.org/hunger/stats](https://www.wfp.org/hunger/stats)

[edit] "The Black Swan" is just plan wrong, I really don't get why people buy into that book. It's a cute idea. But wrong.

</comment><comment><USER5> _sigh_ More anti-science, liberal, woo crap. (This coming from someone who identifies as liberal). These scare mongering tactics are turning people off to great advantages in the agricultural industry.

<comment><USER6> I think the biggest irony of your comment is calling the article "anti- science"; a criticism they address directly in the article not just once, but multiple times.

<comment><USER2> They acknowledge that anti-GMO people are often considered anti-science. They don't really address it in any meaningful way other than to make a few snide swipes about snake oil peddlers.</comment></comment></comment>


Japanese company develops a solar cell with record-breaking efficiency - <AUTHOR> https://arstechnica.co.uk/science/2017/03/japanese-company-develops-a-solar-cell-with-record-breaking-26-efficiency/ <comment><USER2> There seems to be a lot of confusion about efficiency. For a single junction solar cell (like the type of solar cell talked about in the article) the theoretical efficiency is 34% (under 1 sun illumination). The best a silicon device can do is ~29% because silicon has a slightly lower than ideal bandgap. Single junction solar cells made out of GaAs have gotten to ~31% efficiency because GaAs has an ideal bandgap. However, GaAs is super expensive. Achieving 26% efficiency when the theoretical efficiency for silicon is 29% is super impressive. Engineers have basically squeezed every ounce of potential real world performance out of single junction silicon solar cells.

</comment><comment><USER3> [https://news.ycombinator.com/item?id=13939040](https://news.ycombinator.com/item?id=13939040) ~34%

[https://news.ycombinator.com/item?id=13938690](https://news.ycombinator.com/item?id=13938690) ~40%

[https://news.ycombinator.com/item?id=13938953](https://news.ycombinator.com/item?id=13938953) 46%

[https://news.ycombinator.com/item?id=13939181](https://news.ycombinator.com/item?id=13939181) ~86.8%

[https://news.ycombinator.com/item?id=13939399](https://news.ycombinator.com/item?id=13939399) 95%

One... two... three... four... five theoretical maximums in comments.

Something tells me that there's a lot more research to be done (or knowledge to be learned, at the very least) available here than we realize.

<comment><USER4> Admittedly, there still a lot of room for solar panel research for the upcoming years which is pretty exciting!

The discrepancies is often due to fact we're defining "solar panels" quite different for each application and also the definition of input energy is different.

A great example is engines. The theoretical (Carnot) efficiency is limited by the heat difference between the source and the sink. You can burn fuel at a higher temperature and pressure which will give you great efficiency, but it's not realistically possibly due to physical constraints (usually the steel that houses the explosions). That's why steel engines are often said to have a maximum fuel efficiency of 37%.

This same idea applies to solar panel but it's even more convoluted. What is input energy? Is it all the energy from the sun or is it only the energy within the energy band that the panel can "see"? What is efficiency? The efficiency for different energy band is different for each solar panel as well. Worst of all, this efficiency changes for different temperature and is effected by hysteresis! By the time you store the energy, you also lose efficiency depending on the internal resistance of the energy storage (That's why MPPT exist and fun fact of the day, from what I know, there is still no reliable analytical method to account for this. Most MPPT trackers are done empirically).

Sorry for the long rant, but yeah, solar panels are confusing and there is a surprising about of research that still needs to be done!

<comment><USER5> I heard about carnot energy but didn't realize the calculation was this simple. Suppose we say we get a insulated material that is string enough to handle high temperatures. We can beat the 37% right?

<comment><USER4> It's a partial yes. You have to worry about pressure as well. You can burn fuel at a higher temperature by igniting the gas at a higher pressure. But there are certain constraints due to the fuel. If the pressure is too high, the fuel will spontaneous combust. That's why there are different octane rating of fuels and why higher octane fuel gives you better fuel efficiency (given your engine has some sort of valve timing like VTEC). This is also why Diesel engines tend to have better mileage than gasoline engines. Even though gasoline engines will perform better at the same pressure as Diesel, there just no way to bring the gasoline to the same pressure that the Diesel can handle.

When and how you combust the fuel can give you different fuel efficiencies as well. For instance, the Brayton cycle can achieve easily over 50% fuel efficiency. But in order to achieve this, you need a special housing (jet engines uses this cycle) to be able to compress the fuel to the specific pressure and also handle the pressure. Also, special fuel is required. These two things makes it not really practical for the standard consumer.

On a tangent, Internal combustion engines is probably one of the funnest and hardest class I took in graduate school...

</comment></comment></comment></comment><comment><USER6> This is what I understand about efficiency after working with photodetectors (not used as solar cells, but similar in principle).

1\. The sun emits a wide spectrum, with a long tail in the infrared.

2\. Materials are only photoelectric at certain wavelengths.

3\. The sensitivity to each wavelength depends upon design which is ultimately is related to the penetration depth of light in the material (longer wavelengths travel longer distances before reacting with the crystal structure).

4\. Silicon is the most common and cheapest material, but its sensitivity rolls off sharply towards UV and infrared. Other materials are orders of magnitude more expensive. Not just in manufacturing, but the materials themselves.

5\. To capture a wide range of spectrum you need a very long depletion region (kind of neutral area between p-n junctions). This has its own design tradeoffs.

So the end result is that the real world efficiency limit can have many reported figures, from theoretical energy physics to practical material, design, and manufacturing limits. The biggest contributor to loss is that silicon is simply not able to capture much more than the visible spectrum. Next is that even with silicon there is a sensitivity curve (efficiency of converting photons to current per wavelength), and then designing so that you can capture the current (or else it would just recombine in the crystal).

This is why gain in solar seems to be slow. There are tremendous limitations, and I have my doubts that there will be overcome any time soon.

But, there is plenty of sunlight, so I would say the real challenge is energy storage. If sunlight can be stored cheaply and efficiently, then what we have is good enough.

<comment><USER7> I often wonder how good/cost effective optics would be, given the price of glass is cheap and that could be used to focus a larger area upon a small, more costly and yet efficient material.

But as you highlight, cost and with that a balance of cost/return is a huge factor and whilst scale can help in many area's. It gets more detrimental with more expensive materials.

<comment><USER6> I don't know the exact answer, but one should be able to calculate how effective this method would be. You are knocking out electrons from a crystal. Those electrons have to be replaced, so you are limited by the rate of replacement. Also heat generation from the current.

My hand wavy gut feel is that optics wouldn't buy you that much. Silicon is orders of magnitude cheaper. To give you an idea, an infrared detector made of InGaAs about the size of a dime can already cost $5-10k. Solar cells of that size are priced in ... dollars?

On the other hand, optics have been used for energy/storage in the form of a heating crucible. I've heard that promoted by some experts.

</comment></comment></comment><comment><USER4> To put things in perspective, the current theoretical maximum efficiency for solar panels is about 34% [1]. There are a couple assumptions that are made to derive this number so there are ways to exceed this maximum efficiency. Though the assumptions made in the equations are fairly application to most solar panels product (not the ones made in labs).

[1] [https://en.wikipedia.org/wiki/Shockley%E2%80%93Queisser_limi...](https://en.wikipedia.org/wiki/Shockley%E2%80%93Queisser_limit)

<comment><USER8> There are already 46% efficient solar cells, the 33.7% limit is for a specific type of solar cell (single p-n junction) which are cheaper to manufacture.

The maximum theoretical limit is ~86.8% for solar panels.

<comment><USER9> Is the maximum theoretical efficiency I often see stated just for type of technology we use today (pn junctions)? Or is it a hard physical limit for any light -> electricity system? Would it be possible that some new technology for solar cells could be more efficient?

<comment><USER10> I think the highest physical limit would be Carnot efficiency for a heat engine driven by the temperature difference between the sun and the earth. (6000K - 300 K) / 6000 K = 95%. There could be a different lower limit we hit before that though.

<comment><USER9> That does make sense for an absolute upper limit, thanks.

</comment></comment></comment></comment></comment><comment><USER11> Around here it seems like solar installation companies are taking every decrease in material costs and increase in efficiencies and eating it up by increasing labour costs or profit margins.

It always works out to a bullshit calculation that "the system pays for itself in 10 years" [if you ignore inflation, opportunity cost, and accept their electricity rate projections and assume the gov't won't cut green electricity subsidies]. That number never seems to change, it's always 10 years.

I'd love to get panels put on my house and shop, I have a lot of square footage. But it seems like there's some very greedy middlemen between me and the panels and I lack the skill to install myself.

<comment><USER12> You're only considering grid tie when you say that a system won't really pay for itself in ten years. For off grid solar there are a number of places (example: very rural parts of ID and WA) where it might cost $40,000 to extend code compliant grid electricity from the nearest road to a new bare land property. And that is before you pay any monthly bills for ten years. Versus spending $35,000 one time on a big ground mounted solar system, charge controllers and a set of Tesla power wall 2 for battery storage.

Cost and efficiency also hugely impacts developing nation solar (most of rural Africa) where no grid whatsoever currently exists.

<comment><USER13> Interestingly, this applies on very small scales too. For certain street furniture like parking meters etc. it can be cheaper to install solar and a battery than to dig a cable.

<comment><USER12> In terms of city government unionized labor salaries and equipment cost, or hiring a contractor cost, it can be VERY expensive per meter to dig up an existing concrete sidewalk/curb and road to run code compliant AC electrical to a parking meter. Or something like a bus stop arrival time sign. Looking at $20,000 per unit in some cases, or more. And then there's the question of where do you get the AC power from in a built up downtown type area, you can't just tap into the nearest building, it usually involves dealing with the electrical grid for the streetlight system which was not designed to support thousands of small accessory loads hanging off it.

</comment></comment></comment></comment><comment><USER14> I'm not sure I like this. It seems that we're very clearly in the area of diminishing returns when it comes to solar panels.

[https://upload.wikimedia.org/wikipedia/commons/4/42/Efficien...](https://upload.wikimedia.org/wikipedia/commons/4/42/Efficiency_chart_rev_05-2012.png)

The conclusion of that chart seems to be : concentrated solar power (even on small scale) is unbeatable, and tops out (realistically) at ~40% efficiency.

So now we should probably work on very, very cheap lenses if we want to advance solar panels, and quick ways to make small, very cheap panels.

<comment><USER15> Why?

AFAICT, there are three ways to double the output of a solar cell: Double the area, double the efficiency, and move the cell to somewhere with twice as bright sunlight and install a cable. That one option presents intractable problems doesn't seem to matter very much when either of the two others are available.

<comment><USER16> Area isn't unlimited in the residential market, place is fixed and installation is expensive.

<comment><USER17> That's why you need to install the cable.

</comment></comment></comment></comment><comment><USER18> The highest efficiency for solar cells is at 46% already (multi-junction, concentrating). So this is not record breaking per se but record breaking for this particular set-up.

Also: The best way to look at solar panel breakthroughs is to look at what actually makes it to market. If I had a dollar for every solar cell breakthrough that eventually did not make it to market I'd be fairly wealthy.

<comment><USER19> I think your comment is the first use of "breakthrough," to be fair. The article title and body refer to it as "breaking" the record. You are correct about the (vastly more expensive) multi-junction concentrating cells having higher efficiency, of course.

You're also correct that not all improvements make it to market. Without research and continuing efforts to improve, nothing makes it to market. What's the point of your second paragraph? The article makes it _very_ clear that this is not in production, and speaks specifically to concerns about whether the process is suitable for industrialization.

<comment><USER18> The point is that you see announcements like these at a rate of 4 to 5 every year and hardly any of those ever make it to market. I've been active in the renewable energy-scene off-and-on for two decades and I really can't count how many times there have been announcements like the one here that did not go anywhere. It makes me quite skeptical of announcements like these, they do not really convey much in terms of information other than to create an optimism about solar panel efficiency gains that is usually met with disappointment when someone actually costs out a system and realizes that over approximately a decade we tend to see gains on the order of 1 to 2%.

Hype simply doesn't help, at best this is 10 years away, worst you'll never hear from it again.

<comment><USER20> This paper is closer to industrialization than most and I expect production on scale in less than 10 years. It uses process steps that are already operating on an industrial scale. It's achieved on an industrial area wafer (compare with many academic records where cells are _tiny_ , less than 10 cm^2). It's achieved on an industrial thickness wafer (some records use thinner wafers that are closer to the theoretical optimum, but those thinner wafers are too fragile to process industrially with current technology). It's just combining features of two cell concepts that are already manufactured on an industrial scale (interdigitated back contact cells and heterojunction cells). The core patents on heterojunction silicon cells expired just a few years ago so I expect more vanilla heterojunction and heterojunction-plus-other manufacturing going forward.

<comment><USER18> Well, I certainly hope you are right and I'm wrong. Still, the devil will be in the details and even with expired patents multi-junction cells are simply more expensive to produce. Keep in mind they only have to be ~24% more expensive to make to wipe out any efficiency gains and that's not a whole lot of margin. If this succeeds you might see a fraction of that passed on to the consumer and the cost of the bare panels long ago ceased to be the dominant factor in a regular (domestic) installation.

For large areas it might work out to be beneficiary earlier.

<comment><USER20> Heterojunction cells are an approach to reducing recombination losses near contacts in single junction silicon cells. Sanyo (now Panasonic) developed them in the 1990s and has shipped gigawatts of them. It's the same Panasonic cell technology that SolarCity (now Tesla) is expected to use in their New York factory. The vanilla heterojunction cell design is actually one of the simplest high-efficiency cells in terms of process flow. The main drawbacks are patents (until recently) and the limited heat tolerance of a-Si layers; standard screen printed silver metallization, fired at high temperatures, does not work for these cells.

[https://www.researchgate.net/profile/Stefaan_De_Wolf/publica...](https://www.researchgate.net/profile/Stefaan_De_Wolf/publication/239735318_High- efficiency_Silicon_Heterojunction_Solar_Cells_A_Review/links/0deec51c2bde240fb8000000.pdf)

<comment><USER18> I spent some time reading that, thank you very much for the pointers. Looks like you are right and this is in fact something that might just happen. Here's to hoping that it does.

</comment></comment></comment></comment></comment></comment></comment><comment><USER21> What does this mean? Of the energy that all photons hitting the solar panel represent, 26.3% of it is converted into electricity?

<comment><USER22> For reference, in [https://en.wikipedia.org/wiki/Photosynthetic_efficiency](https://en.wikipedia.org/wiki/Photosynthetic_efficiency) there is mention that photosynthesis has a nominal efficiency of about 30%, but in practice the absorbed energy stays in the 3-6% range, with sugar cane being exceptionally efficient at 8%.

<comment><USER23> That 3-6% range is stored energy after the plant consumed some of the produced glucose to maintain itself and grow.

Photovoltaics don't do that on their own, so you can't compare that to a solar cell's nameplate efficiency.

Either you have to compare PV efficiency with gross glucose production or you need to compare the full PV lifecycle (production, installation, maintenance and recycling) with the harvestable sugar content.

</comment></comment></comment><comment><USER24> Rectennas are another interesting possibility. The theoretical conversion efficiency is 44% according to this:

[http://ecee.colorado.edu/~moddel/QEL/Papers/Joshi13a.pdf](http://ecee.colorado.edu/~moddel/QEL/Papers/Joshi13a.pdf)

</comment><comment><USER25> Zooming out a little, is it not true to say that minor efficiency gains in collection are still dwarfed in comparison to storage and current conversion losses?

<comment><USER26> No - because 2.7% (or 0.7 efficiency difference) increase is not insignificant when you scale up. As an analogy, think of what 0.7% tax saving would mean to you annually.

In reality solar-cells and batteries are not at all cheap to install and maintain. We can scale up the solar cells and collect more energy. However, that needs more surface area to be covered with these panels. We still need better ways to store the energy efficiently.

<comment><USER27> Storing huge amounts of energy is easy: use pumps to add potential energy to water.

This isn't ultra efficient, but it's cheap and probably good enough. We have lots of experience with hydroelectric power.

</comment></comment></comment><comment><USER28> Will be interesting to see manufacturing yields but also efficiency losses over time, compared to cells made currently.

</comment><comment><USER29> [https://en.wikipedia.org/wiki/Quantum_dot_solar_cell](https://en.wikipedia.org/wiki/Quantum_dot_solar_cell)

Could you tune/adjoin these to span a very wide band of wavelengths?

</comment><comment><USER30> Media is a few days lag behind academic publication on this one [http://www.nature.com/articles/nenergy201732](http://www.nature.com/articles/nenergy201732)

</comment><comment><USER31> Ah, that's interesting. I didn't know there were a theoretical limit of 29%

</comment><comment><USER32> Isn't that a duplicate of [https://news.ycombinator.com/item?id=13936480](https://news.ycombinator.com/item?id=13936480) ?

<comment><USER33> Yes. However:

> If a story has had significant attention in the last year or so, we kill > reposts as duplicates. If not, a small number of reposts is ok.

This submission got traction, the other one was posted 12hrs ago and didn't really get anywhere.

<comment><USER32> I didn't know that. Ok.</comment></comment></comment>


Ask HN: How would you use your knowledge in a pre-modern society? - <AUTHOR> As modern humans we have a whole ton of knowledge that our ancestors didn't, but making use of it seems largely to require the infrastructure of modern life as well. If, via time travel or an apocalyptic scenario, you found yourself in a pre-modern society with no technology but your knowledge intact, how would you put it to use? Of what practical value would common scientific or technological knowledge be?  Your goals may be to accelerate human development, make yourself dictator, impress people or anything else. <comment><USER2> I feel like this has been a common question on other fora like Reddit, Stack Exchange, and Quora.

You can probably find a few of them with

[https://www.google.com/search?q=if+you+were+transported+back...](https://www.google.com/search?q=if+you+were+transported+back+in+time)

although I'm sure there are more out there!

<comment><AUTHOR> Yeah, most of the answers are either related to the butterfly effect or are just silly like "sliced bread" or "the printing press." I was hoping for more serious/well-thought-out responses.

<comment><USER2> I've seen a couple of more substantive ones although unfortunately I didn't save links to them.

I remember a couple of cautionary themes were that (1) you might easily offend or alienate people, or make them suspicious of you, (2) you might find it hard to persuade people that things you knew about had much merit or utility, (3) you might not be able to take much advantage of your modern technical knowledge without infrastructure and supply chains, and (4) you might not be able to support yourself easily in an unfamiliar economy while attempting to teach others or manufacture things with your modern knowledge. Although you might feel that there are lots of cool scientific principles that you could demonstrate to convince people that your knowledge was important, it's also likely that you wouldn't know all the necessary details or have easy access to the necessary apparatus or raw materials.

Anyway, those were someone else's ideas from one of those threads—and they were expressed better there and with more specifics.</comment></comment></comment>