text:
together guidelines organisation: question and improvement suggestions

This post is a wiki. Anyone with karma >75 is welcome to improve it.

First of all I want to tell that i am really new in sailor world. It make fast one month that i get my phone, and near of two week that i surf in together website. Like somebody could say, shortly described, i am a newbie (great). The first that i see of this new world (like a lots of people), new kind of thinking, new kind of acting. We are different, we are together. Other os, other design, other gesture, light.

It seems to be for me all easy, and quite here in together too. We can put a question, as improvement suggestion, as survey, as bug declaration, as protest... I could answer, make some suggestion, vote + for good idea, vote - for it won't bring something good for us. You get points and see you participate for a community project (more or less). It's easy, seems to work like every forum, just be sociable, and bring some experience, and ideas, help people to think clear (hmm that wil be now complicated).

So shortly I want to participate on a survey with good ideas. Made some suggestions. And then, bing! 200 points less. I don't care on the points really for the points, but as indicator of sociability and participation. What's happened when i think that i've productively and well, it's seems that the contrary?

Then came a lots of questions, and it goes complicated. I do now ask all those question. they may be easy, but it goes deeper on sense. The way i want to go is for everyone, that means it should be so easy as possible, that a child could understand. Question for child and fool avoiding misunderstanding:

First, The poll or survey, it seems to be an high need to have the answer as wiki. If you don't do that, then your bad. Maybe accepted as newbie, i don't know. Until now i thought i knew what is a wiki. But bound to the together use, i don't know. it's different.
1) why do we need to answer as wiki community? what is hidden behind it?
2) Please show me the wiki utility.
3) Is it possible to make it automatically when the thread creator informs that is a poll?

So i got my points less. was a bad feeling, i do something good, and i'm seen as bad. Aouch!
4) If there is something why not ask for if it serious or not? suggest to change it and give a little bit time for it.
5) I know, every people have a lots of things to do. but let's time for the people to discover the site. All the informations to know how all work, is disperse everywhere. Need time to gather all.

The problem was, that was obvious (not for me), that what i've was not fair form guidelines. The first that i read was the faq and the help, and some guidelines. And don't understand some things like, what is a poll, the wiki-community.
6) why should some people give minus point if people want participate? participate is always positive, even if it's duplicate or in wrong form. The understanding of them is a little bit different. Minus points should just for contra-productive reaction ONLY. Minus points means unsociable, unfriendly.
7) Give minus point to people who participate, but made wrong, is for me a form of laziness. Why people don't ask themself "what's wrong in the system that bring the people do wrong?" first, and ask then this one why?

8) guidelines are just to be found in this little link in features tag? why are they not in faq or help?
9) guidelines link is not red and flashy in bold ?
10) For those who create a guideline, it is always good if there is an explanation why it is needed. All the people are not skilled on this kind website usability. that not obvious for everyone.

There is no doubt, the people are here really nice with a lots of understanding, if we explain the fact. That really great, but something are little bit confused, maybe messy. Situation is fixed by me, but i ask me what did happened to someone if he has't the "loudmouth"? The community could loose him, and at last a lots of other one.

(end of first part. i'll think for more reaction or ideas of improvement, and make then an update).

11) 2 counters for upvote and downvote (new point added 22.01.2015):
I don't know if askbot could support it. But i think for a better overview, it will be find to separate the counter from upvote with downvote. Display 2 counters for each one. Voting is a kind of expression. should note attribute point especially negative one. downvote should not influence the counter of upvote, both are separate for better comparison.

have a nice sail

edit retag close delete

The day has been long.

My thoughts keep orbiting a few strange ideas. The smaller phone. The jollaDesk. Medical OtherHalves...

Not used to being asked... Especially about how to herd cats. But I will try to give some sort of answer tomorrow.

Now the hours of this day have all slipped by. New chores tomorrow.

( 2014-12-10 01:03:33 +0300 )edit

@vattuvarg: you're welcome. take your time. i couldn't react so fast since the last discussion. needed to make some order in personal life (is 1st prio ;-) )

( 2014-12-10 01:13:35 +0300 )edit

Sort by » oldest newest most voted

On guidelines and habits

This is the couch frontier. This is the wild-ish west. This is a blank page with some doodles, aye.

Things will get easier over time, but right now Jolla is a young company and we're the eager sidekicks that wish we had at least a clue to what's going on in this action drama. Innovation happens close to chaos and there's a lingering feel of disorder hanging around. That feeling comes from not knowing. Frustrating? Of course, but there has to be secrets. The mobile industry is fiercely competitive so to succeed some things have to remain hidden. Nagging for more info is just a waste of time. The Jolla doesn't leak...

So we create the missing parts in our heads. I've done so myself with the J3. We suggest some of those ideas to the forum. And then we get surprised by the response.

An added difficulty comes with the karma system. I've seen a few fora in my years on the net, but this is the first with that feature.

Unwritten social rules play out on the forum. Things we like get the thumbs up treatment and a few other posts fuel our anger instead. ...and it all depends on old habits.

We want new and fresh stuff and yet we want things to remain as they are.

...especially those unwritten rules. The reality is tough here for newcomers, sadly enough. The creative process is so close that the nearby chaos makes everything glow in the dark. It's an electronic aurora borealis. Wild, free and slightly unbelievable. It's the territory of the quick draw and even quicker mind. ...and the tension that fills the air makes people jumpy. Trigger happy.

Rules will of course help a bit, but too many (or too rigid) rules will take away too much of the creative spark that is needed to feed the innovation.

So the main tool has to be attitude.

Anyone on any of the ships in this armada sails together. Whether a golden tongue or a foul mouth we all get our say. Point your thumb down if you wish but do so with an argument.

We can find use for all hands here. Teach the new ones without weapons or fists. We are all still pirates looking for freedom.

Together.

I couldn't think of anything better to say. Sorry.

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Hi! Good questions, hope I can solve these being here for a while longer:

1) why do we need to answer as wiki community? what is hidden behind it?

• Wiki's are used in polls, as they gather so much answers and votes. This is only to remove karma hunting
• Wiki's are used in posts which are ment for everybody to edit, to make them better (for example the guidelines you mentioned)

2) Please show me the wiki utility.

• No separate utility. Just a checkbox under the question edit - In all other ways, the editing works just like in any questions / answers

3) Is it possible to make it automatically when the thread creator informs that is a poll?

• Currently no

4) If there is something why not ask for if it serious or not? suggest to change it and give a little bit time for it.

• agreed

5) I know, every people have a lots of things to do. but let's time for the people to discover the site. All the informations to know how all work, is disperse everywhere. Need time to gather all. The problem was, that was obvious (not for me), that what i've was not fair form guidelines. The first that i read was the faq and the help, and some guidelines. And don't understand some things like, what is a poll, the wiki-community.

• Let's improve the guidelines together, and if needed, make suggestions for a better help and wiki. They are all done together

6) why should some people give minus point if people want participate? participate is always positive, even if it's duplicate or in wrong form. The understanding of them is a little bit different. Minus points should just for contra-productive reaction ONLY. Minus points means unsociable, unfriendly.

• I didn't even know about a karma penalty even after being here for a year - Is that info shared in the poll guidelines? In my opinion, if this kind of penalty is in use, it should be limited to 10% to not punish new members. And in overall, a guidance is alweays better than a punishment.

7) Give minus point to people who participate, but made wrong, is for me a form of laziness. Why people don't ask themself "what's wrong in the system that bring the people do wrong?" first, and ask then this one why?

• agreed

8) guidelines are just to be found in this little link in features tag? why are they not in faq or help?

• There could be a link to all guidelines in both FAQ and HELP. Possible @Eric?

9) guidelines link is not red and flashy in bold ?

• Not possible in askbot, but hopefully a better linking makes them visible enough

10) For those who create a guideline, it is always good if there is an explanation why it is needed. All the people are not skilled on this kind website usability. that not obvious

• TODO: Let's improve them together - feel free to edit
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@simo@eric: we have a problem with eric. i know now why eric don't react on our request. it seems to have a problem with the askbot machine, it seems to make a link to an other person. Eric didn't get our request. he is normally as user 2, and askbot make an other one with @xxx, because is near the same tjc nickname. do you see this link above to eric ? and a lots of other goes to the 4986. In Principe the tjc system should not accept the same nickname, even if letter case (lower or upper ) are different. now we have maybe some user confusion. maybe first you and eric should speak with the other one to give him the situation

( 2014-12-15 11:20:33 +0300 )edit

@reviewjolla i take a little bit time to reread the thread here , and read other guidelines.
And i remarked that i didn't thank you for having reading my long thread and answering on it at every points. sorry....
But as a lot people tell, that's never too late for making good things. then, thank you for having take time to answer on it. :-)

( 2016-04-10 23:25:09 +0300 )edit

oh god i did it indeed. i saw it in an other answer below, what an ape could i do.... i see now that i use tjc in an other art than for 1 year. funny.

( 2016-04-10 23:29:30 +0300 )edit

I see the point to regulate TJC and improve the quality. I also like that you step forward and suggest doing something. However (sorry to say):

• I'm just too lazy to read and follow long complicated guidelines (but I try to stay reasonable and e.g. search before posting)
• TJC is a 'jack of all trades' between help, knowhow, feature requests, bug'tracker', rant, announcements, etc. I don't think one could deeply 'attack' these different aspects with 'sharp' guidelines
• karma hunting is a non problem. What should one do with such karma anyway? If a person 'disbehaves' he/she can be removed. But almost all people are very friendly here
• TJC should stay fun. Nothing against guidelines, but they need to be relaxed suggestions imho

Sometimes I was thinking, if it wouldn't be better to divide the aspects, e.g.

• bug-hunting --> github projects with issues
• knowhow --> wiki or a stackoverflow like site or a documentation project
• discussion, rant, announcements, etc --> discourse
• feature requests --> uservoice

But I'm not sure if this would be better, for me TJC seems quite nice. (Except that there is no good modern bug tracker like github/gitlab - TJC bug posts most likely perish within the huge 'post volume')

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I agree with you fully, on each point, and thanks for each too. Grapping to one: "Fun", which is actually one of the most important reasons why the guidelineing needs some attention. The current set of guidelines is all but fun, a mixed list nobody is interested to visit - And as such, not helping the development of the portal, not helping on having great posts here. Let's work towards somewhat attractive guideline, which might be also fun enough for people to link it some more, whenever useful. Just maybe, we can turn even you to visit it (I'm personally lazy on visiting guides as well, love to learn things the hard way)

On dividing, it seems Jolla also wants to keep us here with everything. For example a decent bugtracker has been requested for long, and they've been silent on that for long :) This is actually the first attempt to write a guideline including bug reporting, not sure how that goes here, let's see. Maybe focus on the "fun" on that too :D

( 2015-09-13 23:18:49 +0300 )edit

This post is a wiki. Anyone with karma >75 is welcome to improve it.

Hello Simo, thank you very much for your answer and that you take it really serious. so

1) why do we need to answer as wiki community? what is hidden behind it?

Wiki's are used in polls, as they gather so much answers and votes. This is only to remove karma hunting
Wiki's are used in posts which are ment for everybody to edit, to make them better (for example the guidelines you mentioned)

Wiki in reality are thus not a specific thread as knowhow, but more than fast one which become a lots of reaction, as answer, vote, suggestions right?

5) I know, every people have a lots of things to do. but let's time for the people to discover the site. All the informations to know how all work, is disperse everywhere. Need time to gather all. The problem was, that was obvious (not for me), that what i've was not fair form guidelines. The first that i read was the faq and the help, and some guidelines. And don't understand some things like, what is a poll, the wiki-community.

Let's improve the guidelines together, and if needed, make suggestions for a better help and wiki. They are all done together

Why not, but i need some time to read the points again. Then i suggest when the time comes, we work point to point here on (by this current thread). Or should we do it apart (per mail for example)?

6) why should some people give minus point if people want participate? participate is always positive, even if it's duplicate or in wrong form. The understanding of them is a little bit different. Minus points should just for contra-productive reaction ONLY. Minus points means unsociable, unfriendly.

I didn't even know about a karma penalty even after being here for a year - Is that info shared in the poll guidelines? In my opinion, if this kind of penalty is in use, it should be limited to 10% to not punish new members. And in overall, a guidance is always better than a punishment.

I didn't see it in guidlines, just + points attributions in faq. But I'm not really agree with you. This kind of attribution should not be done, if the person want to participate constructively in the thread. Maybe in case that someone else tells him to change the things he did because it is not guidlines friendly, and stay in his position, we could reconsider that...

9) guidelines link is not red and flashy in bold ?

Not possible in askbot, but hopefully a better linking makes them visible enough

asknots seems to be a mix between html and python. Maybe it is possible to reformat the fonts of featured tags. And the background too.

10) For those who create a guideline, it is always good if there is an explanation why it is needed. All the people are not skilled on this kind website usability. that not obvious

TODO: Let's improve them together - feel free to edit

That will be not so easy, put my changes or my remarks directly in the guideline thread, may destruct its integrity as rule. Needs a good organisation to. Where and how could we discuss about each of it. And the best is that we can ask for details to guidelines creators, and are agrees to make some changes it it's needed to. In short way explained, i have no problem to edit, if i present my changes and the peoples are agreed (i means guidelines creators an some moderators).

ps: i miss tags knowhow, how we could change the format of the text by answer or thread input. Some html tags, and wiki-like tags seem to work with askbots. Will not bad to have a small list of it in help section.

Have a nice weekend

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Would it be ok to add any further answers to your new questions editing them directly above, turning this into a "discussion pad" for a while? If so, please edit this to wiki, enabling everybody to add.

(Normally any further discussions takes place in the comments thread, but I guess that either way is good in this type of collective question)

( 2014-12-07 22:40:51 +0300 )edit

hello simo, yes naturally should be as wiki, sorry. now it is converted into this. hmm i'm sorry for what you means with "discussion pads" for a while, didn't understand what you mean. Do you thinks it is better to make an answer for each points of the handled questions?

( 2014-12-08 10:39:05 +0300 )edit

Good morning! I just ment that your answer could be used as a platform for discussion - so no need for separate answers. Now that it's a wiki, I hope others edit in their opinions as well.

( 2014-12-08 10:53:21 +0300 )edit

This post is a wiki. Anyone with karma >75 is welcome to improve it.

So for my part i want to react for the point 6). I have already read about some guideline Point. First, this one Deselecting answers revised from @pulsar. Id didn't understand why is it a guideline point. That is in mater of fact a problem., a big one which join my point of you, about point action which could be negative to a person even if he act for a good reason. I understand his incomprehension.

If pulsar is agree too, This point will be better for me to be rewritten in form that it touch all the point attribution concept. As i already said, pint are just a quantification to give a feeling how act a person. If it contribute for community. or if he is contra-productive. It should not be easy to give point less. Asking first if the person think seriously is more friendly. Maybe he could ask for help to do in right way. I can't understand, that point going left even if the person contribute positive. For example, a negative vote of a non-constructive question (i have already seen one but i don't find it anymore), is then good for community. the action should not be point with negative.

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This post is a wiki. Anyone with karma >75 is welcome to improve it.

@simo @eric: I found a new problem on the organisation on together website, and i ask my why no one has already seen it, or i didn't find a thread upon it. In reality after some thinking, it seems NOT to be a bug or concept-failure of askbot. So now to the fact. I observed that for some typical threads (the problem especially for polls i think), inside the threads there are vote counter for each answers. But it does not reflect the counter of the thread itself. Inside a thread could be more vote as the one of the thread itself. It reflect not truly the thread as it should do.

The example that i can give you is this one [Poll] Jolla 2 OtherHalf colours? As you can see the thread has 12 votes, but inside alone the cobalt answer as currently 17 votes!!! You can't tell me that is normal, that the thread has less votes that an answer which is inside!!! is really stupid i think. It is not a wonder if vattuvarg disappointed about the non success of his poll. The votes are less as it should do, and people don't react because of less changing in its votes...

One solution, would be for me that, a kind of guideline based on attitude for each one who vote inside a thread,give then a vote to the thread in accordance of his positiv or negative if he is against the thread or not.

I try to make a proposal for the guideline.-..

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The thread counter is for triage, more or less. It's a way for people to tell others that *I want an answer to this too". The most voted questions get extra attention and a higher priority from Jolla. ...or experts among us.

Within each thread there are answers. Good answers get votes and is a simple form of quality control. Even if the question might be completely obvious a good answer can still be worth more byte by byte than a pile of bitcoins. Difficult questions might need more than one good answer and the votes might be the only way of knowing the quality of each answer.

So voting for both question and answer(s) makes sense. Adding them up would mix all signals and make all numbers meaningless. Triage by the administrators would be impossible and finding the right answer would be equally difficult for the users of the forum.

The karma system still baffles me at times but it seems to work.

( 2014-12-11 23:41:08 +0300 )edit

that's right, but the counter between the answers and the thread should be consistent. if ind not normal that an answer of a thread get 18 votes (18 people like it) and the thread itself just 12 (12 like it), that make no sense, et make statistic wrong.

( 2014-12-12 00:12:03 +0300 )edit
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@cemoi71 Just as you mentioned me on the answer: I'm ok with the current calcs. IMO, vote for Q = vote for the importance of the matter, vote for A = supporting the idea/solution/suggestion presented

( 2014-12-12 06:38:05 +0300 )edit

I found threads with bad question and good answers. Or there is a good comment (e.g. above). When I voting the good posts I will not honored bad posts.

( 2014-12-12 19:02:46 +0300 )edit

@utkiek: ok you take care that you handle the answer and the thread. I think it is good if we could vote negative without bumping kharma points down, if the stuff try to be constructive. it should just inform if it is good or not. kharma point are for me an information how well has the person according to the community. inform if she constructive or not. (and we comes again to the issue of kharma point...)

( 2014-12-12 19:23:03 +0300 )edit

This post is a wiki. Anyone with karma >75 is welcome to improve it.

I've started a project on the guidelines, let's discuss that here (to keep the new guide clean of any comments) First, I'd like to share some motives why I started this project, and why I started it right now:

• TJC is getting a big group of new, unfamiliar users soon, including many countries where Jolla hasn't been available earlier
• Current guideline list is a non-attractive mess of posts with different layouts and outdated data. We could edit those, but after browsing through each, poersoinally I found it simply easier to start a new project
• Better guideline, attractive enough, up to date, might be useful to link to when the new questions by new users starts to roll in
• End result is not supposed to change how TJC works or restrict user freedom. Guides are supposed to be guides, not rules like few of them currently are.

Please join if you find it worth it :)

EDIT: Each older guideline now has a dedicated answer to handle the progress there.

EDIT2: There's been so few comments on this project that I feel it's not worth it to continue. It's not something I don't want to do just by myself, as without others it misses a common goal & DIT spirit. So, leaving the process for now. Updating the schedule, leaving stage 1 open in case if someone at some point finds there's something to do.

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@simo@reviewjolla may i ask the stupid question? are you simo behind the two tjc-account here?
Is just to verify an obvious observation...
And i would like to discuss with you about some points (and one particularly). if you want....

( 2016-04-07 16:21:53 +0300 )edit

You may, and yes those are mine. For personal chat I can send you my xmpp via email to my blog address or via DM on Twitter. But if your topic fits as a public discussion here, that would be great by me as well.

( 2016-04-07 16:50:33 +0300 )edit

hmmm for public discussions by you, means reviewjolla or simo tjc account? or never-mind which one...

( 2016-04-07 17:57:24 +0300 )edit

do mind: My old account started to gather so much notifications (=having red mail envelope on top all the time) that I'm currently better reached using this @reviewjolla mention. So, what's this about?

( 2016-04-07 18:23:24 +0300 )edit

ok.. first, thank very much for the answer.
concerning guidelines for answer to a question here I would suggest that an answer should handle on the subject given on the main thread question....
Sometimes i see that people answer nearby of the main question, for suggesting a workaround of it, without to handle directly or trying to solve it. According to the person, not mentioning it would be a problem... That's right but for this it is possible to comment.

Here i have a concrete example that right happened today on this thread.
One proposed as answer to opt-out to the early access program so that after this, the user will be proposed to downgrade sfos to the last release and the bug won't be appears.
That's right, that is an important info that for those who want to step out of the early access program it is possible to get the last release of the system. But it doesn't handle the main problem that a bug appears and should be observe on a futur release software. That as for me just an effect to pollute the main thread, and not give a real fix. However the info is important.

Then i want first to discuss about the point "answer to a question" and in which form... words are missing about it to me.
Do you see what i mean?

( 2016-04-07 19:24:07 +0300 )edit


text:
Why is inductive kickback not V=IR?

I'll preface by saying I'm aware of questions like these 1, 2, and 3, but none of them answer my specific question.

All of these questions say that the kickback from an inductor can be given by:

$$\V=L\frac{dI}{dt}\$$

However, I've seen other sources say things along the lines of "the inductor tries to keep the current flowing through it the same as it was before switching". The exact quote from the above source is:

this component now leaps into action and does everything in its power to maintain the status quo (keep the current flow going just as it was).

To me, keeping the current flowing exactly as it was means the current is the same. As in, if the steady state (i.e. after several time constants) current through the inductor was 1 A, then the inductor would try its hardest to keep the current at 1 A (at least at the instant after the switch switches). The inductor therefore acts as an instantaneous current source. If you had a resistive load connected in parallel with the inductor, the voltage over it would be $$\V=IR\$$ where $$\I=1\text{ A}\$$. This voltage will begin to drop though as the current is only 1 A for an instant.

To aid in understanding, I've drawn a circuit below. In this case, I would expect the voltage over the inductor/resistor after switching the current source off to be $$\V = IR = 100 \text{ V}\$$.

simulate this circuit – Schematic created using CircuitLab

But, as far as I'm aware, $$\L\frac{dI}{dt} \neq IR\$$. Since everyone says that $$\V=L\frac{dI}{dt}\$$, I'm inclined to think that it is correct, but I'm struggling to understand why $$\V=IR\$$ is wrong on this occasion. Surely the parallel resistance must come into play, otherwise flyback diodes would do nothing (as they would count as low resistance, therefore low kickback).

• "..if the steady state ... current through the inductor was 5 mA, then the inductor would try its hardest to keep the current at 1 A". How did you jump from 5 mA to 1 A? Nov 18, 2020 at 5:40
• @Transistor my bad. I changed the numbers but I guess I missed that one Nov 18, 2020 at 7:46
• Mistake 1. LdIdt≠IR is wrong equation because you used I on both sides instead left side (in equation ) it should be current (function) through inductor and in right side it should be current (function) through resistor Nov 18, 2020 at 10:56
• There will be always be some voltage and some di/dt for which Ldi/dt = IR. Nov 18, 2020 at 14:32
• Do you have Flash player? If so, visit this page and play with the Flash movie at the bottom; it is about the inductor property discussed here. Nov 22, 2020 at 21:57

To me, keeping the current flowing exactly as it was means the current is the same.

The inductor "tries" to keep the current constant, or "does everything in its power" to keep the current constant. That doesn't mean that it actually keeps the current constant.

Similarly, a resistor "resists" the flow of current. That doesn't mean the current through a resistor is always 0.

The inductor therefore acts as an instantaneous current source.

Correct. If you implement what SPICE calls a transient analysis, you will find that at each time step, the inductor is treated as a current source (representing this tendency to keep the current constant) in parallel with a resistor (representing the possibility, if the inductor is not shorted, of the current changing infinitesimally before the next time step).

Since everyone says that $$\V=L\frac{dI}{dt}\$$, I'm inclined to think that it is correct, but I'm struggling to understand why $$\V=IR\$$ is wrong on this occasion.

An ideal inductor doesn't have any parameter "$$\R\$$", so there's no way you could write the equation $$\V=IR\$$ to describe the ideal inductor.

$$\V=IR\$$ is an equation that describes the behavior of an ideal resistor.

$$\V=L\frac{dI}{dt}\$$ is an equation that describes the behavior of an ideal inductor.

In some particular circuit, $$\V=IR\$$ might well describe what is happening to a resistor that is connected in parallel with an inductor. But it can't describe what's happening to the inductor itself, because an inductor is not a resistor, and doesn't even have a parameter $$\R\$$ to determine its voltage or current.

I've drawn a circuit below. In this case, I would expect the voltage over the inductor/resistor after switching the current source off to be V=IR=100 V.

This is not correct. If $$\V\$$ is the voltage at the terminal where the resistor and inductor are connected, but not the one that is designated as ground, then for current to continue flowing top-to-bottom through the inductor, the resistor current must be flowing bottom to top. And thus the voltage must be -100 V, not +100 V.

Which is a good thing, because if it were +100 V, then the inductor current would be increasing rather than decreasing, and the whole circuit would be violating conservation of energy (since the resistor and inductor would both be absorbing power but nothing would be providing power).

• @JolonB, since the inductor and resistor are in parallel (after the source is turned off), the voltage across them is the same. So if you wrote a mesh equation for the loop they form, you'd find that $IR=L\frac{dI}{dt}$. But this is because of the way you connected the inductor and resistor to each other, not an inherent behavior of either component on its own. Nov 18, 2020 at 2:46
• Note that $V$ will actually be negative, and current will be flowing though the resistor from bottom to top. Nov 18, 2020 at 2:47
• @JolonB, by choosing a different resistor. Nov 18, 2020 at 3:41
• @JolonB, In the instant after the current source shuts off, the inductor current doesn't change. This means that current begins circulating in the inductor-resistor loop. And the voltage across the inductor is equal to the voltage across the resistor (nothing stops the voltage changing instantaneously). Then the current will drop with time constant L/R. If the supply shuts off quickly enough, the decay of the current will depend only on the inductor and resistor values, not on how quickly the supply changes from the intitial value to zero. Nov 18, 2020 at 19:59
• @ThePhoton The cleared up a lot for me, but that last sentence confused me a bit. When I switch it off quickly, all the current flows through the resistor the instant after switching. If I switched it off slowly, how could I find the voltage over the resistor/inductor? I'm assuming it'll still be $V=IR$, but would $I$ be smaller in this case? Nov 18, 2020 at 20:20

Without a component across the inductor, at transistor switch off, the voltage across the inductor will rise to be V = Ldi/dt.

With a resistor in place across the inductor, at transistor switch off, the voltage across the inductor (and resistor) will rise to be V = iR.

The resistor would usually be sized to make iR less than Ldi/dt without the resistor. That is to say a resistor would be put in place to limit the back EMF voltage. So typically iR is not equal to what Ldi/dt would be if there was no parallel resistor.

The resistor is being used to limit the back EMF so that it is below the VCE(max) of the driving transistor.

A resistor is used rather than the more usual parallel diode approach because the resistor technique speeds the decay of the inductor current.

di/dt = V/L and so rate of change of current, di/dt is proportional to the voltage across the inductor.

• The inductor always enforces the rule that V = Ldi/dt. It doesn't decide that sometimes it will ignore the rule. It ALWAYS enforces that rule. Whenever two components are in parallel (meaning they have the same voltage) the voltage will have to satisfy both of them. So V=IR AND V = Ldi/dt. Nov 18, 2020 at 16:47
• @mkeith I totally agree, I've edited to clarify. Nov 18, 2020 at 17:36

You are right about everything as far as I can see. If you have 100 Ohms in parallel with an inductor, and there is 1A flowing through the inductor, then you open the switch that was supplying the current, then you will have 100V across the resistor and inductor (briefly) because the only path available to the inductor current is to loop through the resistor and inductor. The current circulating in this loop will then decay exponentially with a time constant of R/L. As the current decays, the voltage will also decay.

If there is nothing in parallel with the inductor, then you may end up with very high voltage when you open the switch. An arc may even form on the switch.

Whenever you switch something inductive, you want to provide some place for the current to go. Often a freewheel diode will be used for this (you can search for that).

Consider the mechanical analog of flowing water. If you have a large mass of water, equivalent to a large current, but at a low speed, and you put an obstacle in it's way (e.g., a steep gradient or open switch), the water will rise to a much higher level, equivalent to an increase in voltage.

This abrupt change with time is $$\V=L\frac{dI}{dt}\$$, where dI is the change in current in "interval" dT. Of course, the time subdivision is infinitesimal in calculus, which is required to better understand this phenomena.

Abrupt shelving can cause a tsunami barely above sea-level to reach 500 meters, and the inductive "kick" of a doorbell running from 6 VDC can produce surge voltage of hundreds of volts. Put a neon lamp, e.g. NE-2, which requires ~70 V to light, across the contacts of a doorbell or buzzer, and it can light with input of just a few volts DC.

To further investigate how inductors work, and the use of a commutating diode, see Lekule Blog for a nice lab exercise!

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# Homework Help: Roller coaster change in acceleration?

1. Oct 28, 2012

### Arkane1337

1. The problem statement, all variables and given/known data

You have taken a job as senior
hench-person with Dr. Caasi Notwen, arch-nemesis of
James Bond. As with all of Bond’s enemies, Dr. Notwen
would like to develop an overly complicated method of
dispatching the British super-spy, so he has tasked you
with designing a “roller coaster of death.” This
frictionless roller coaster is to be designed such that
when the rider (James Bond) reaches the nadir (point B)
on the track, the acceleration he experiences will exceed
the limit of human survival (10 g’s where g = 9.8 m/s2).
At point B the track has a radius of curvature of 25.0 m..

(a) From what height h (Point A) must the cart start (from rest) to ensure Bond’s demise?

2. Relevant equations
ac=v2/R
PE=mgh
KE=(1/2)mv2

3. The attempt at a solution
10g's = 98.0 m/s2 ≥ ac = v2/R

v = sqrt{acR} = $\sqrt{98*25}$ = 49.5 m/s

PE = KE
mgh = (1/2)mv2
h = v2/2g = 49.52/(2*9.8) = 125.0m

*** I'm rather rusty on my centripetal concepts and am wary of my answer; does it look correct to all of you? ***

2. Oct 28, 2012

### TSny

There could be some ambiguity in the wording of the question. Your answer is correct if you want the actual acceleration of Bond to be 10 times g.

However, to "experience 10 g's" could be interpreted as experiencing an apparent weight of 10 times your normal weight. That would mean that you would want the normal force acting on Bond to be 10 times his weight. Or, to put it another way, even if bond just sat at rest at point B he would be experiencing 1 g. So, the effect of the motion should be to add another 9 g's if you wanted Bond to experience a normal force of 10 times his weight.

Not sure of the intended interpretation.

3. Oct 28, 2012

### Arkane1337

There seems to be a second part to the problem, which I'm rather confused on as well; could someone provide any hints?

(b) What force will Bond feel (presuming he survives past Point B) at Point C where the radius of
curvature has been reduced to 15.0 m and is 30 m above point B (i.e., what is the normal force at C)?

4. Oct 28, 2012

Anyone?


text:
# Importing Data Files into R

Preparing and managing data is one of the most time-consuming task for data scientists. Importing data into a data science software is the first step for the downstream analysis, which seems trivial but at times frustrating and time consuming to figure out the right way. Data can be directly entered into a system (often feasible only for small data), or imported into analytical and visualization software from different data file formats. In this post, I put together a list of R packages/functions (see Table below) with illustrations that, I hope, will ease the burden of locating the right package/function. Note that the table neither list all data file formats nor all available packages. For a comprehensive R import/export discussion you can read R Import/Export documentation.

R packages / functions to read/import data files

Before running the data import function, make sure that the required packages are installed. If the package is not base package or not installed previously, the first task is installing and loading the package. I wrote the following R function to install R packages along with any package that the given package depends on.

### Install R package¶

In [ ]:
#  R function (r.pkg.install) to install multiple packages at once.

r_pkg_install <- function(r_pkgs)
for (i in 1:length(r_pkgs)){
# "dependencies" option is TRUE to install all packages that a given package depends on.
install.packages(paste(r_pkgs[i]), lib="directory you want to install package",
repos = "https://cran.cnr.berkeley.edu/", dependencies = TRUE)
}

# List all R packages you need to install into your computer ;

r_pkg_install(r_pkgs=c("xlsx", "XML", "sas7bdat", "foreign", "R.matlab"))

In [4]:
# Locating the data file directory.
# You can specify the full directory in the R function or, or change the working directory so that you don't need to specify every time you run your R function.

setwd("C:/Users/TM/MWWW/dataset1/") # Replace by your working directory

# Check working directory
getwd()

"C:/Users/TM/MWWW/dataset1"
In [ ]:
# Note that each function has several arguments and can be checked using help() or ?. For example,

### Import tab delimeted text file¶

In [5]:
# using read.table ;

Sepal_LSepal_WPetal_LPetal_WSpecies
15.1 3.5 1.4 0.2 setosa
24.9 3 1.4 0.2 setosa
34.7 3.2 1.3 0.2 setosa
44.6 3.1 1.5 0.2 setosa
55 3.6 1.4 0.2 setosa
65.4 3.9 1.7 0.4 setosa

Caution should be taken in reading text files with an empty (" ") missing data value. For example, for missing data values within a tab delimited text file, you can specify sep="\t" option to read in the data properly.

In [ ]:
tab_data <- read.table("iris.txt", sep="\t", header = TRUE)

Some data files coded missing values differently, for example "?". We can read such data using the na.string option. This will automatically replace the special missing values by NA. For example, if you are reading a data with missing value recorded as "?", then use the following code

In [ ]:
tab_data_missing <- read.table("iris_missing.txt", na.strings=c("?"), header = TRUE)

On the other hand, if you want to replace NA by a different value, for example, replacing all NA by 0, you can use the following code

In [ ]:
tab_data[is.na(tab_data)] <- 0

### Import comma separated value (CSV) file¶

In [ ]:
csv_data <- read.csv("iris.csv" )

### Import excel file¶

In [ ]:
library(rJava)
library(xlsxjars)
library(xlsx)

xlsx_data <- read.xlsx("iris.xlsx", sheetName = "iris" )

### Import SPSS file¶

In [ ]:
library(foreign)

spss_data <- read.spss("iris.sav", to.data.frame = TRUE )

### Import STATA file¶

In [ ]:
library(sas7bdat)

### Import SAS file¶

In [ ]:
library(sas7bdat)

### Import SAS export file¶

In [ ]:
library(foreign)


text:
# Supercyclidic Nets

Alexander I. Bobenko, Emanuel Huhnen-Venedey, Thilo Rörig

### Description

Supercyclides are surfaces with a characteristic conjugate parametrization consisting of two families of conics. Patches of supercyclides can be adapted to a Q-net (a discrete quadrilateral net with planar faces) such that neighboring surface patches share tangent planes along common boundary curves. The resulting patchworks are called "supercyclidic nets", and every Q-net in $\mathbb{R}P^3$ can be extended to a supercyclidic net. The construction is governed by a multidimensionally consistent 3D system. One essential aspect of the theory is the extension of a given Q-net in $\mathbb{R}P^N$ to a system of circumscribed discrete torsal line systems. The latter can be described in terms of projective reflections generalizing the systems of orthogonal reflections which govern the extension of circular nets to cyclidic nets by means of Dupin cyclide patches.

### References

• Alexander I Bobenko, Emanuel Huhnen-Venedey, and Thilo Rörig.
Supercyclidic nets.
International Mathematics Research Notices, 2017(2):323–371, February 2017.
arXiv:1412.7422, doi:10.1093/imrn/rnv328.

#### Prof. Dr. Alexander I. Bobenko   +

Projects: A01, A02, C01, B02, Z, CaP, II
University: TU Berlin, Institut für Mathematik, MA 881


text:
# [tmql-wg] TMQL companion document

Robert Barta rho at bigpond.net.au
Sun Feb 4 04:26:41 EST 2007

Hi all,

I have updated/extended the companion document for TMQL

http://topicmaps.it.bond.edu.au/new/tmql/tmql-user.dbk

It contains an ultra-short Quick Tour, but also a more elaborate
discussion of language features which does not belong into the
standard. Specifically interesting, but very alpha is how TMQL deals
with prefixes.

I'll try to keep it in sync with the current editor's copy at

http://topicmaps.it.bond.edu.au/junk/tmql.html

which will hopefully evolve into the working document for the next
meeting in Oslo. We are currently reviewing it.

\rho

PS: As usual I have hidden a massive error in there to see whether
someone actually has really read it. Clever, ha? ;-)


text:
1. Math
2. Statistics And Probability
3. by definition a symmetric matrix with nonnegative eigenvalues is psd...


text:
#### Omnidirectional CNN for Visual Place Recognition and Navigation

##### Tsun-Hsuan Wang, Hung-Jui Huang, Juan-Ting Lin, Chan-Wei Hu, Kuo-Hao Zeng, Min Sun

Visual place recognition is challenging, especially when only a few place exemplars are given. To mitigate the challenge, we consider place recognition method using omnidirectional cameras and propose a novel Omnidirectional Convolutional Neural Network (O-CNN) to handle severe camera pose variation. Given a visual input, the task of the O-CNN is not to retrieve the matched place exemplar, but to retrieve the closest place exemplar and estimate the relative distance between the input and the closest place. With the ability to estimate relative distance, a heuristic policy is proposed to navigate a robot to the retrieved closest place. Note that the network is designed to take advantage of the omnidirectional view by incorporating circular padding and rotation invariance. To train a powerful O-CNN, we build a virtual world for training on a large scale. We also propose a continuous lifted structured feature embedding loss to learn the concept of distance efficiently. Finally, our experimental results confirm that our method achieves state-of-the-art accuracy and speed with both the virtual world and real-world datasets.

arrow_drop_up


text:
# American Institute of Mathematical Sciences

January  2017, 16(1): 25-68. doi: 10.3934/cpaa.2017002

## Invariant tori of a nonlinear Schrödinger equation with quasi-periodically unbounded perturbations

 1 School of Mathematics and Information Science, Henan Polytechnic University, Jiaozuo 454000, P. R. China 2 School of Mathematics, Shandong University, Jinan 250100, P. R. China

Received  June 2015 Revised  August 2016 Published  November 2016

Fund Project: The first author is supported by the National Natural Science Foundation of China (Grant 11171185, 11571201) and the Research Foundation for Doctor Programme of Henan Polytechnic University (Grant B2016-58). the second author is supported by the National Natural Science Foundation of China (Grant 11171185, 11571201).

This paper is concerned with the derivative nonlinear Schrödinger equation with quasi-periodic forcing under periodic boundary conditions
 ${\rm{i}} u_t+u_{xx}+{\rm{i}} (B+\epsilon g(\beta t))(f(|u|^2)u)_x=0, \ \ x\in \mathbb{T}:=\mathbb{R}/2\pi\mathbb{Z}.$
Assume that the frequency vector $\beta$ is co-linear with a fixed Diophantine vector $\bar{\beta}\in \mathbb{R}.{m}$, that is, $\beta=\lambda \bar{\beta}$, $\lambda \in [1/2, 3/2]$. We show that above equation possesses a Cantorian branch of invariant $n$--tori and exists many smooth quasi-periodic solutions with $(m+n)$ non-resonance frequencies $(\lambda\bar{\beta}, \omega_{\ast})$. The proof is based on a Kolmogorov--Arnold--Moser (KAM) iterative procedure for quasi-periodically unbounded vector fields and partial Birkhoff normal form.
Citation: Jie Liu, Jianguo Si. Invariant tori of a nonlinear Schrödinger equation with quasi-periodically unbounded perturbations. Communications on Pure and Applied Analysis, 2017, 16 (1) : 25-68. doi: 10.3934/cpaa.2017002
##### References:
 [1] P. Baldi, M. Berti and R. Montalto, KAM for quasi-linear and fully nonlinear forced perturbation of Airy equation, Math. Ann., 359 (2014), 471-536. doi: 10.1007/s00208-013-1001-7. [2] M. Berti and L. Biasco, Branching of Cantor manifolds of elliptic tori and applications to PDEs, Comm. Math. Phys., 305 (2011), 741-796. doi: 10.1007/s00220-011-1264-3. [3] M. Berti and M. Procesi, Quasi-periodic solutions of completely resonant forced wave equations, Comm. Partial Differential Eqautions, 31 (2006), 959-985. doi: 10.1080/03605300500358129. [4] J. Bourgain, Quasi-periodic solutions of Hamiltonian perturbations of 2D linear Schrödinger equations, Ann. of Math., 148 (1998), 363-439. doi: 10.2307/121001. [5] J. Bourgain, Green's Function Estimates for Lattice Schrödinger Operators and Applications, Annals of Mathematics Studies, 158, Princeton University Press, Princeton, 2005. doi: 10.1515/9781400837144. [6] L. Chierchia and J. You, KAM tori for 1D nonlinear wave equations with periodic boundary conditions, Comm. Math. Phys., 211 (2000), 497-525. doi: 10.1007/s002200050824. [7] W. Craig and C. Wayne, Newton's method and periodic solutions of nonlinear wave equations, Comm. Pure Appl. Math., 46 (1993), 1409-1498. doi: 10.1002/cpa.3160461102. [8] H. L. Eliasson and S. B. Kuksin, KAM for the non-linear Schrödinger equation, Ann. of Math., 172 (2010), 371-435. doi: 10.4007/annals.2010.172.371. [9] R. Feola and M. Procesi, Quasi-periodic solutions for fully nonlinear forced reversible Schrödinger equations, J. Differential Equations, 259 (2015), 3389-3447. doi: 10.1016/j.jde.2015.04.025. [10] R. Feola, KAM for quasi-linear forced Hamiltonian NLS, preprint, arXiv: 1602.01341. [11] J. Geng and J. You, A KAM theorem for Hamiltonian partial differential equations in higher dimensional spaces, Comm. Math. Phys., 262 (2006), 343-372. doi: 10.1007/s00220-005-1497-0. [12] J. Geng and Y. Yi, Quasi-periodic solutions in a nonlinear Schrödinger equation, J. Differential Equations, 233 (2007), 512-542. doi: 10.1016/j.jde.2006.07.027. [13] J. Geng, Invariant tori of full dimension for a nonlinear Schrödinger equation, J. Differential Equations, 252 (2012), 1-34. doi: 10.1016/j.jde.2011.09.006. [14] J. Geng and J. Wu, Real analytic quasi-periodic solutions for the derivative nonlinear Schrödinger equations, J. Math. Phys., 53 (2012), 102702. doi: 10.1063/1.4754822. [15] B. Grébert and L. Thomann, KAM for the quantum harmonic oscillator, Comm. Math. Phys., 307 (2011), 383-427. doi: 10.1007/s00220-011-1327-5. [16] S. B. Kuksin, Hamiltonian perturbations of infinite-dimensional linear systems with imaginary spectrum, (Russian) Funktsional. Anal. iPrilozhen., 21 (1987), 22-37; English translation in: Funct. Anal. Appl., 21 (1987), 192-205. [17] S. B. Kuksin, Perturbations of conditionally periodic solutions of infinite-dimensional Hamiltonian systems, (Russian) Izv. Akad. Nauk SSSR Ser. Mat., 52 (1988), 41-63; English translation in: Math. USSR-Izv., 32 (1989), 39-62. [18] S. B. Kuksin, Nearly Integrable Infinite-Dimensional Hamiltonian Systems, Lecture Notes in Mathematics, 1556, Springer-Verlag, Berlin, 1993. doi: 10.1007/BFb0092243. [19] S. B. Kuksin and J. Pöschel, Invariant Cantor manifolds of quasi-periodic oscillations for a nonlinear Schrödinger equation, Ann. of Math., 143 (1996), 147-179. [20] S. B. Kuksin, On small-denominators equations with large variable coefficients, Z. Angew. Math. Phys., 48 (1997), 262-271. doi: 10.1007/PL00001476. [21] S. B. Kuksin, Analysis of Hamiltonian PDEs, Oxford Lecture Series in Mathematics and its Applications, 19, Oxford University Press, Oxford, 2000. [22] T. Kappeler and J. Pöschel, KdV and KAM, Springer-Verlag, Berlin, 2003. doi: 10.1007/978-3-662-08054-2. [23] L. Jiao and Y. Wang, The construction of quasi-periodic solutions of quasi-periodic forced Schrödinger equation, Commun. Pure Appl. Anal., 8 (2009), 1585-1606. doi: 10.3934/cpaa.2009.8.1585. [24] J. Liu and J. Si, Invariant tori for a derivative nonlinear Schrödinger equation with quasiperiodic forcing, J Math. Phys. , 56 (2015), 032702. doi: 10.1063/1.4916287. [25] J. Liu, Periodic and quasi-periodic solutions of a derivative nonlinear Schrödinger equation, Appl. Anal., 95 (2016), 801-825. doi: 10.1080/00036811.2015.1032942. [26] J. Liu and X. Yuan, Spectrum for quantum Duffing oscillator and small-divisor equation with large variable coefficient, Comm. Pure. Appl. Math., 63 (2010), 1145-1172. doi: 10.1002/cpa.20314. [27] J. Liu and X. Yuan, A KAM theorem for Hamiltonian partial differential equations with unbounded perturbations, Comm. Math. Phys., 307 (2011), 629-673. doi: 10.1007/s00220-011-1353-3. [28] J. Liu and X. Yuan, KAM for the derivative nonlinear Schrödinger equation with periodic boundary conditions, J. Differential Equations, 256 (2014), 1627-1652. doi: 10.1016/j.jde.2013.11.007. [29] L. Mi and K. Zhang, Invariant tori for Benjamin-Ono equation with unbounded quasiperiodically forced perturbation, Discrete Contin. Dyn. Syst., 34 (2014), 689-707. doi: 10.3934/dcds.2014.34.689. [30] J. Pöschel, A KAM theorem for some nonlinear partial differential equations, Ann. Scuola Norm. Sup. Pisa. Cl. Sci., 23 (1996), 119-148. [31] J. Pöschel, Quasi-periodic solutions for a nonlinear wave equation, Comment. Math. Helv., 71 (1996), 269-296. doi: 10.1007/BF02566420. [32] J. Rui and J. Si, Quasi-periodic solutions for quasi-periodically forced nonlinear Schrödinger equations with quasi-periodic inhomogeneous terms, Phys. D, 286/287 (2014), 1-31. doi: 10.1016/j.physd.2014.07.005. [33] M. B. Sevryuk, The reversible context 2 in KAM theory: the first steps, Regul. Chaotic Dyn., 16 (2011), 24-38. doi: 10.1134/S1560354710520035. [34] J. Si, Quasi-periodic solutions of a non-autonomous wave equations with quasi-periodic forcing, J. Differential Equations, 252 (2012), 5274-5360. doi: 10.1016/j.jde.2012.01.034. [35] Y. Wang and J. Si, A result on quasi-periodic solutions of a nonlinear beam equation with a quasi-periodic forcing term, Z. Angew. Math. Phys., 63 (2012), 189-190. doi: 10.1007/s00033-011-0172-x. [36] C. E. Wayne, Periodic and quasi-periodic solutions of nonlinear wave equations via KAM theory, Comm. Math. Phys., 127 (1990), 479-528. [37] X. Yuan, Quasi-periodic solutions of nonlinear Schrödinger equations of higher dimension, J. Differential Equations, 195 (2003), 230-242. doi: 10.1016/S0022-0396(03)00095-0. [38] X. Yuan, Quasi-periodic solutions of completely resonant nonlinear wave equations, J. Differential Equations, 230 (2006), 213-274. doi: 10.1016/j.jde.2005.12.012. [39] M. Zhang and J. Si, Quasi-periodic solutions of nonlinear wave equations with quasi-periodic forcing, Phys. D, 238 (2009), 2185-2215. doi: 10.1016/j.physd.2009.09.003.

show all references

##### References:
 [1] P. Baldi, M. Berti and R. Montalto, KAM for quasi-linear and fully nonlinear forced perturbation of Airy equation, Math. Ann., 359 (2014), 471-536. doi: 10.1007/s00208-013-1001-7. [2] M. Berti and L. Biasco, Branching of Cantor manifolds of elliptic tori and applications to PDEs, Comm. Math. Phys., 305 (2011), 741-796. doi: 10.1007/s00220-011-1264-3. [3] M. Berti and M. Procesi, Quasi-periodic solutions of completely resonant forced wave equations, Comm. Partial Differential Eqautions, 31 (2006), 959-985. doi: 10.1080/03605300500358129. [4] J. Bourgain, Quasi-periodic solutions of Hamiltonian perturbations of 2D linear Schrödinger equations, Ann. of Math., 148 (1998), 363-439. doi: 10.2307/121001. [5] J. Bourgain, Green's Function Estimates for Lattice Schrödinger Operators and Applications, Annals of Mathematics Studies, 158, Princeton University Press, Princeton, 2005. doi: 10.1515/9781400837144. [6] L. Chierchia and J. You, KAM tori for 1D nonlinear wave equations with periodic boundary conditions, Comm. Math. Phys., 211 (2000), 497-525. doi: 10.1007/s002200050824. [7] W. Craig and C. Wayne, Newton's method and periodic solutions of nonlinear wave equations, Comm. Pure Appl. Math., 46 (1993), 1409-1498. doi: 10.1002/cpa.3160461102. [8] H. L. Eliasson and S. B. Kuksin, KAM for the non-linear Schrödinger equation, Ann. of Math., 172 (2010), 371-435. doi: 10.4007/annals.2010.172.371. [9] R. Feola and M. Procesi, Quasi-periodic solutions for fully nonlinear forced reversible Schrödinger equations, J. Differential Equations, 259 (2015), 3389-3447. doi: 10.1016/j.jde.2015.04.025. [10] R. Feola, KAM for quasi-linear forced Hamiltonian NLS, preprint, arXiv: 1602.01341. [11] J. Geng and J. You, A KAM theorem for Hamiltonian partial differential equations in higher dimensional spaces, Comm. Math. Phys., 262 (2006), 343-372. doi: 10.1007/s00220-005-1497-0. [12] J. Geng and Y. Yi, Quasi-periodic solutions in a nonlinear Schrödinger equation, J. Differential Equations, 233 (2007), 512-542. doi: 10.1016/j.jde.2006.07.027. [13] J. Geng, Invariant tori of full dimension for a nonlinear Schrödinger equation, J. Differential Equations, 252 (2012), 1-34. doi: 10.1016/j.jde.2011.09.006. [14] J. Geng and J. Wu, Real analytic quasi-periodic solutions for the derivative nonlinear Schrödinger equations, J. Math. Phys., 53 (2012), 102702. doi: 10.1063/1.4754822. [15] B. Grébert and L. Thomann, KAM for the quantum harmonic oscillator, Comm. Math. Phys., 307 (2011), 383-427. doi: 10.1007/s00220-011-1327-5. [16] S. B. Kuksin, Hamiltonian perturbations of infinite-dimensional linear systems with imaginary spectrum, (Russian) Funktsional. Anal. iPrilozhen., 21 (1987), 22-37; English translation in: Funct. Anal. Appl., 21 (1987), 192-205. [17] S. B. Kuksin, Perturbations of conditionally periodic solutions of infinite-dimensional Hamiltonian systems, (Russian) Izv. Akad. Nauk SSSR Ser. Mat., 52 (1988), 41-63; English translation in: Math. USSR-Izv., 32 (1989), 39-62. [18] S. B. Kuksin, Nearly Integrable Infinite-Dimensional Hamiltonian Systems, Lecture Notes in Mathematics, 1556, Springer-Verlag, Berlin, 1993. doi: 10.1007/BFb0092243. [19] S. B. Kuksin and J. Pöschel, Invariant Cantor manifolds of quasi-periodic oscillations for a nonlinear Schrödinger equation, Ann. of Math., 143 (1996), 147-179. [20] S. B. Kuksin, On small-denominators equations with large variable coefficients, Z. Angew. Math. Phys., 48 (1997), 262-271. doi: 10.1007/PL00001476. [21] S. B. Kuksin, Analysis of Hamiltonian PDEs, Oxford Lecture Series in Mathematics and its Applications, 19, Oxford University Press, Oxford, 2000. [22] T. Kappeler and J. Pöschel, KdV and KAM, Springer-Verlag, Berlin, 2003. doi: 10.1007/978-3-662-08054-2. [23] L. Jiao and Y. Wang, The construction of quasi-periodic solutions of quasi-periodic forced Schrödinger equation, Commun. Pure Appl. Anal., 8 (2009), 1585-1606. doi: 10.3934/cpaa.2009.8.1585. [24] J. Liu and J. Si, Invariant tori for a derivative nonlinear Schrödinger equation with quasiperiodic forcing, J Math. Phys. , 56 (2015), 032702. doi: 10.1063/1.4916287. [25] J. Liu, Periodic and quasi-periodic solutions of a derivative nonlinear Schrödinger equation, Appl. Anal., 95 (2016), 801-825. doi: 10.1080/00036811.2015.1032942. [26] J. Liu and X. Yuan, Spectrum for quantum Duffing oscillator and small-divisor equation with large variable coefficient, Comm. Pure. Appl. Math., 63 (2010), 1145-1172. doi: 10.1002/cpa.20314. [27] J. Liu and X. Yuan, A KAM theorem for Hamiltonian partial differential equations with unbounded perturbations, Comm. Math. Phys., 307 (2011), 629-673. doi: 10.1007/s00220-011-1353-3. [28] J. Liu and X. Yuan, KAM for the derivative nonlinear Schrödinger equation with periodic boundary conditions, J. Differential Equations, 256 (2014), 1627-1652. doi: 10.1016/j.jde.2013.11.007. [29] L. Mi and K. Zhang, Invariant tori for Benjamin-Ono equation with unbounded quasiperiodically forced perturbation, Discrete Contin. Dyn. Syst., 34 (2014), 689-707. doi: 10.3934/dcds.2014.34.689. [30] J. Pöschel, A KAM theorem for some nonlinear partial differential equations, Ann. Scuola Norm. Sup. Pisa. Cl. Sci., 23 (1996), 119-148. [31] J. Pöschel, Quasi-periodic solutions for a nonlinear wave equation, Comment. Math. Helv., 71 (1996), 269-296. doi: 10.1007/BF02566420. [32] J. Rui and J. Si, Quasi-periodic solutions for quasi-periodically forced nonlinear Schrödinger equations with quasi-periodic inhomogeneous terms, Phys. D, 286/287 (2014), 1-31. doi: 10.1016/j.physd.2014.07.005. [33] M. B. Sevryuk, The reversible context 2 in KAM theory: the first steps, Regul. Chaotic Dyn., 16 (2011), 24-38. doi: 10.1134/S1560354710520035. [34] J. Si, Quasi-periodic solutions of a non-autonomous wave equations with quasi-periodic forcing, J. Differential Equations, 252 (2012), 5274-5360. doi: 10.1016/j.jde.2012.01.034. [35] Y. Wang and J. Si, A result on quasi-periodic solutions of a nonlinear beam equation with a quasi-periodic forcing term, Z. Angew. Math. Phys., 63 (2012), 189-190. doi: 10.1007/s00033-011-0172-x. [36] C. E. Wayne, Periodic and quasi-periodic solutions of nonlinear wave equations via KAM theory, Comm. Math. Phys., 127 (1990), 479-528. [37] X. Yuan, Quasi-periodic solutions of nonlinear Schrödinger equations of higher dimension, J. Differential Equations, 195 (2003), 230-242. doi: 10.1016/S0022-0396(03)00095-0. [38] X. Yuan, Quasi-periodic solutions of completely resonant nonlinear wave equations, J. Differential Equations, 230 (2006), 213-274. doi: 10.1016/j.jde.2005.12.012. [39] M. Zhang and J. Si, Quasi-periodic solutions of nonlinear wave equations with quasi-periodic forcing, Phys. D, 238 (2009), 2185-2215. doi: 10.1016/j.physd.2009.09.003.
 [1] Meina Gao, Jianjun Liu. Quasi-periodic solutions for derivative nonlinear Schrödinger equation. Discrete and Continuous Dynamical Systems, 2012, 32 (6) : 2101-2123. doi: 10.3934/dcds.2012.32.2101 [2] Jean Bourgain. On quasi-periodic lattice Schrödinger operators. Discrete and Continuous Dynamical Systems, 2004, 10 (1&2) : 75-88. doi: 10.3934/dcds.2004.10.75 [3] Wenmeng Geng, Kai Tao. Lyapunov exponents of discrete quasi-periodic gevrey Schrödinger equations. Discrete and Continuous Dynamical Systems - B, 2021, 26 (6) : 2977-2996. doi: 10.3934/dcdsb.2020216 [4] Lei Jiao, Yiqian Wang. The construction of quasi-periodic solutions of quasi-periodic forced Schrödinger equation. Communications on Pure and Applied Analysis, 2009, 8 (5) : 1585-1606. doi: 10.3934/cpaa.2009.8.1585 [5] Peng Huang, Xiong Li, Bin Liu. Invariant curves of smooth quasi-periodic mappings. Discrete and Continuous Dynamical Systems, 2018, 38 (1) : 131-154. doi: 10.3934/dcds.2018006 [6] Yanling Shi, Junxiang Xu, Xindong Xu. Quasi-periodic solutions of generalized Boussinesq equation with quasi-periodic forcing. Discrete and Continuous Dynamical Systems - B, 2017, 22 (6) : 2501-2519. doi: 10.3934/dcdsb.2017104 [7] Xiaoping Yuan. Quasi-periodic solutions of nonlinear wave equations with a prescribed potential. Discrete and Continuous Dynamical Systems, 2006, 16 (3) : 615-634. doi: 10.3934/dcds.2006.16.615 [8] Mikhail B. Sevryuk. Invariant tori in quasi-periodic non-autonomous dynamical systems via Herman's method. Discrete and Continuous Dynamical Systems, 2007, 18 (2&3) : 569-595. doi: 10.3934/dcds.2007.18.569 [9] Àlex Haro, Rafael de la Llave. A parameterization method for the computation of invariant tori and their whiskers in quasi-periodic maps: Numerical algorithms. Discrete and Continuous Dynamical Systems - B, 2006, 6 (6) : 1261-1300. doi: 10.3934/dcdsb.2006.6.1261 [10] Bochao Chen, Yixian Gao. Quasi-periodic travelling waves for beam equations with damping on 3-dimensional rectangular tori. Discrete and Continuous Dynamical Systems - B, 2022, 27 (2) : 921-944. doi: 10.3934/dcdsb.2021075 [11] Yingte Sun. Floquet solutions for the Schrödinger equation with fast-oscillating quasi-periodic potentials. Discrete and Continuous Dynamical Systems, 2021, 41 (10) : 4531-4543. doi: 10.3934/dcds.2021047 [12] Sijia Zhang, Shengfan Zhou. Random uniform exponential attractors for Schrödinger lattice systems with quasi-periodic forces and multiplicative white noise. Discrete and Continuous Dynamical Systems - S, 2022  doi: 10.3934/dcdss.2022056 [13] Àngel Jorba, Pau Rabassa, Joan Carles Tatjer. Superstable periodic orbits of 1d maps under quasi-periodic forcing and reducibility loss. Discrete and Continuous Dynamical Systems, 2014, 34 (2) : 589-597. doi: 10.3934/dcds.2014.34.589 [14] Yanling Shi, Junxiang Xu. Quasi-periodic solutions for nonlinear wave equation with Liouvillean frequency. Discrete and Continuous Dynamical Systems - B, 2021, 26 (7) : 3479-3490. doi: 10.3934/dcdsb.2020241 [15] Zhichao Ma, Junxiang Xu. A KAM theorem for quasi-periodic non-twist mappings and its application. Discrete and Continuous Dynamical Systems, 2022, 42 (7) : 3169-3185. doi: 10.3934/dcds.2022013 [16] Claudia Valls. On the quasi-periodic solutions of generalized Kaup systems. Discrete and Continuous Dynamical Systems, 2015, 35 (1) : 467-482. doi: 10.3934/dcds.2015.35.467 [17] Jibin Li, Yi Zhang. Exact solitary wave and quasi-periodic wave solutions for four fifth-order nonlinear wave equations. Discrete and Continuous Dynamical Systems - B, 2010, 13 (3) : 623-631. doi: 10.3934/dcdsb.2010.13.623 [18] Xiaoming Wang. Quasi-periodic solutions for a class of second order differential equations with a nonlinear damping term. Discrete and Continuous Dynamical Systems - S, 2017, 10 (3) : 543-556. doi: 10.3934/dcdss.2017027 [19] Koichiro Naito. Recurrent dimensions of quasi-periodic solutions for nonlinear evolution equations II: Gaps of dimensions and Diophantine conditions. Discrete and Continuous Dynamical Systems, 2004, 11 (2&3) : 449-488. doi: 10.3934/dcds.2004.11.449 [20] Yingte Sun, Xiaoping Yuan. Quasi-periodic solution of quasi-linear fifth-order KdV equation. Discrete and Continuous Dynamical Systems, 2018, 38 (12) : 6241-6285. doi: 10.3934/dcds.2018268

2021 Impact Factor: 1.273


text:
# How could a fast powerful rover on Mars be powered electrically?

## Background

The rovers on Mars are slow and weak. If I am to believe what I read, MSL Curiosity only produces 1/6th of a horsepower electric effect, 125 watt. In order to perform tasks like deep drilling, excavation or fast roving, three orders of magnitude more power would be nice. It has been proposed to have astronauts orbit Mars and teleoperate a rover in real time, but that is hardly useful with a sleepwalker like MSL with a top speed of 1½ meter per minute and a 2 inch drill.

## Questions

What power sources will future capable rovers and construction equipment on Mars have?

The RTG's seem prohibitively expensive to scale up or multiply. Is other nuclear power feasible for caterpillar sized equipment on Mars, as such used for submarines and icebreakers? Could a rover have a tall mast with huge solar panels in the low gravity and weak winds of Mars? Or could chemical fuel, like methane and oxygen from the atmosphere, produced with solar power in advance and stored on Mars be a solution? Or huge stationary solar panels with cables or microwave beams to supply mobile equipment?

• What's your hurry? Oct 4, 2015 at 16:16
• Weather on Mars is still as crazy as Earths: space.com/4050-wild-weather-earth-mars.html Oct 4, 2015 at 23:47
• Though not as strong Oct 5, 2015 at 0:00
• The fast rover will bring medical help after I fall of my two-wheeled bicycle because I did not follow this advice.
– uhoh
Oct 26, 2016 at 3:23

An option not mentioned so far are solar power satellites. A large antenna in orbit could focus a tight, high-power microwave beam on the rover. From a low Mars orbit (300 km), a 1 km antenna could focus 1 cm wavelength microwaves on a 3 m target. They should be electronically steered to allow fast and accurate slewing. You would like to have several of these orbiters, with about 20 to 30 minutes of coverage from each orbiter per day. You could trade higher orbits with more coverage for longer time per orbit. However the antenna size gets ridiculous (or the wasted power becomes excessive) at areosynchronous orbits.

Make sure that the wire mesh antenna covers the entirety of the rover, so that the beam doesn't cook the rover or its occupants. And make sure that the beam isn't pointed at you when you're walking around outside the rover.

• This is a solution that NASA has been investigating for decades. Anyone interested can find the Armstrong Fact Sheet here [link] (nasa.gov/centers/armstrong/news/FactSheets/FS-087-DFRC.html). I think this is probably one of the better answers without trying to rely on exotic power supplies. Oct 4, 2015 at 23:49
• Just increase the size of the receiver and lower the power and you won't have to worry about anything getting "cooked" Oct 25, 2016 at 16:03
• Isn't laser beaming also possible with Martian atmosphere ? Certainly should be on the Moon
– kert
Oct 26, 2016 at 1:06
• You'd lose a lot of energy to scattering by dust in the atmosphere, and some days it will all be scattered with nothing getting to the rover. Microwaves cut right through all that. Oct 26, 2016 at 1:52
• @kert Electrical steering of an antenna array is a lot easier, faster, and no moving parts.
– uhoh
Oct 26, 2016 at 3:28

The limiting factor on rovers now is the power generation while moving. Incidentally, this same problem exists in Kerbal Space Program, and was covered by Andy Weir in "The Martian". The problem is, you can either generate power, or move, but it's difficult to do both at the same time. There are a few ways of overcoming this problem.

The best way is to have large amounts of power available while resting (Deploy solar panels, for instance), and take periodic breaks. This is unfeasible for current Mars rovers, because the deploying/ retracting of solar panels over time would prove to be difficult.

A second way is to contain the power generation to the vehicle while moving. There are 3 ways of doing this, namely fixed panel solar arrays, like Opportunity, which produce little power, but doesn't involve deploying anything. Secondly, you can have an RTG system (Based off of Radioactive Decay), like Curiosity. They aren't very popular to launch (As it contains radioactive material), have difficult fuel to produce, and produce a fixed amount of power with time (Somewhat fluctuating based on the background temperature). You can never get high power with one of these without high weight. Next you could have a nuclear power plant. These are very fickle, I can't imagine operating one remotely, and they are quite large. This might work for a very large rover (Think the size of, say, the Crawler), but is unfeasible for short term. Also, this would probably work better with some form of deployment, to reduce the heat. Lastly, one could do a fuel based system, capturing the exhaust. Unless you can bring enough fuel to be useful, this is a difficult process. Essentially this will work like an efficient battery. Note the exhaust could be captured to re-form fuel. Robert Zubrin in The Case for Mars proposes using Methane/ Oxygen, and capturing the exhaust water for future re-processing.

Bottom line is, without more power, you can't move very fast. And power is a difficult thing to do, especially with unmanned vehicles. I believe a manned vehicle, with a deployable solar cell system (As used in The Martian, for instance), would be the best way to drive fast. I believe Robert Zubrin's methane powered combustion engine would be the most effective way to store the power from the solar cells. With that kind of a system, you could drive at a reasonable speed, say 5-10 miles per hour, which is probably best for such an uncharted location. I imagine one could go faster too, if one wanted, it's all in trading off safety and efficiency for speed.

• You could instead make carbon monoxide and oxygen from the atmospheric CO2, which would avoid the need to use and recover hydrogen. (Eventually your hydrogen would escape, requiring that you find a source of water.) CO/O2 is a lousy rocket fuel, but would be perfectly fine for an internal combustion engine. Oct 4, 2015 at 18:55

Nuclear power is not feasible for vehicles. There have been some efforts in the past, but nothing remotely usable.
The smallest nuclear reactor I'm aware of is the ELENA design (still a concept), which produces 100 kWe and weighs 235 tons. A submarine power plant weighs in the region of 1000 tons and produces in the region of 50 MWe.

But I don't think power is the main obstacle in increasing a rover's top speed. Autonomous navigation is a difficult problem, and driving at a low speed reduces the risk of a crash.

• An experimental 1MW reactor massing 16 tons was flown aboard a bomber in the 1950s, and I imagine we could get smaller if we wanted to -- that doesn't change your conclusion; it would still make for a pretty hefty rover. en.wikipedia.org/wiki/Convair_B-36_Peacemaker#Experiments Oct 4, 2015 at 16:22
• The problem with that was it only had shielding in the direction of the cockpit, so they had to build special facilities for servicing the thing. It could work for vehicles that stay away from inhabited areas. Oct 4, 2015 at 17:00
• Well, it will be a while before avoiding inhabited areas is a big constraint on Mars rovers. ;) Oct 4, 2015 at 17:50
• There are smaller reactors, which have been used in space. Like the USA's SNAP and Russia's BES-5 and TOPAZ. Oct 4, 2015 at 21:12
• Space nuclear reactors are potentially much smaller. A 10kw kilopower is under 2 tons. May 28, 2020 at 11:05

How could we increase the efficiency of vehicle-sized solar cells? One approach might be an orbital concentrating mirror. These have occasionally been proposed on earth, but on earth it's much cheaper just to build a large solar farm. For a Mars mission, it's actually easier to put things in orbit than it is to put them on the ground. Pointing it at a moving vehicle is difficult but not impossible if you're moving smoothly in a straight line. It would certainly be useful for stationary drilling operations.

Various organisations keep promising compact Thorium reactors, and Lockheed Martin even claim to be working on fusion. If any of these make it into commercial production, they might be good options.

But it's worth considering how much speed is safe. Curiosity has been gradually accumulating wheel damage. The rocks are sharp as there is no real weather to smooth them. The faster you go, the greater the chances of a crippling accident.

• An orbiting reflector to enhance the yield of solar panels, that's maybe a really good idea. Providing strong light day and night from areostationary orbit, for both power and lighting for night operations. Unfolding a large reflector in orbit and pointing it to a radio beaming rover or station might be easier than landing a power plant. Receiving solar panels would not have to track the Sun. There was the Russian Znamya demo in 1992. Or an orbiting solar power plant that beams down microwaves, whatever is most advantageous. Oct 4, 2015 at 18:32

The following is sourced from Wikipedia's Kilopower:.

An actual 1-10 kW, small, self-contained nuclear reactor, with built-in Stirling power converters to output electrical energy.

They are very compact (even with allowance for the radiative cooling vanes, cheap, and reliable.

OK, I am lying about that second attribute. As with anything nuclear, cheap does not come anywhere near the device. I think cheap has a restraining order to stay 1 mile away at all times.

But they do seem to provide a means for providing very dependable, around-the-clock, good for about 10-15 year, continuous power.

The 10Kw unit masses about 1500 kg, which includes the reactor, power converter, cooling system, et al. It is in a package with a footprint of about 4 m2, 80% of which is just the radiative cooling "umbrella".

The 10 kW unit emits some 40 kW of thermal heat, which could be very handy indeed on a cold place like Mars, but will still be too much and need to be actively cooled.

Yes, 1500 kg for just the power source is not so great. But with 10 kW of electric and 40 kW of thermal, it will allow a somewhat larger rover to perform much higher energy tasks, such as actual drilling, high power experiment packages, etc.

The 110 w -- that the Perseverance rover needs to battle with is very feeble, just barely adequate to its miserly energy needs. And actually, inadequate to the rover's needs, as it needs to ration power between systems all the time, and simply cannot maintain a decent temperature except for the most essential of systems.

• +1 fyi I've just asked How cold do Curiosity's & Perseverance's appendages get at night with all those sensitive cameras and lasers?
– uhoh
Mar 31, 2021 at 0:05
• @uhoh full detail going to that question. quick answer: the cameras have survival heaters, keeping to a slightly more acceptable -85C for some, -40 for others. Unregulated structures might hit -128C Mar 31, 2021 at 9:20
• I've modified this question so as not to refer to anything in particular and updated this answer. I think your answer was fine and it was highly upvoted meaning others saw value in it as well. Can you consider un-deleting it?
– uhoh
Apr 19, 2021 at 0:58

You have to also differentiate between peak and average power. Just giving your mobile unit large enough batteries will give it substantial peak power capacity to move fast or do any other power hungry thing.

Curiosity has to drag it's radioisotope power source along with its batteries due to its mission, but for many of the things you mention, this will not be required. It will be entirely feasible to have a large stationary power source ( either solar or nuclear, there really aren't any other near term options ) charging multiple mobility platforms.

Batteries, and also regenerative fuel cells work just fine for decoupling the power source from the usage site.

Mars Direct, by the Mars Society/Robert Zubrin have proposed using ISRU (In Situ Resource Utilization) to produce methane and oxygen to power a large faster internal combustion manned rover. They also proposed landing modules within the powered distance of the rover, to allow backup possibilities. I.e. If there is a second earth return vehicle for the next mission, within the range of the rover away, there is a backup return vehicle for the current crew.

A base station with solar power to run the methane/oxygen generation process, acting as a gas station, could be one way to get to higher power rovers on Mars. Eventually scaling issues would come into play as the rover would be limited to a radius that is half the range of the rover.

• Methane and oxygen. The methane by itself is useless. Oct 4, 2015 at 16:34
• @MarkAdler We take our atmosphere for granted. Oct 25, 2016 at 16:25

A nuclear reactor could be located near the base; buried, as in Kim Stanley Robinson's "Red Mars". Then, a route could be selected that passed close to or right by selected investigatory sites. A means could be selected to pass current from the reactor to the vehicle as it went along the main route, providing electricity for quite rapid, but safe propulsion, while at the same time giving the rover's batteries a full charge.

When the rover reached an exit point along the main route, the crew would simply go on internal power and complete their mission, returning to the main route to return to base.

It seems to me the size and/or number of batteries would be much less a limiting factor than relying on solar power. A vehicle could be created that would easily transport a crew of 3 or 4 plus a generous equipment and supply list for extended missions, and do it at a fairly high speed, at least on the portion travelled on the main prepared, electrified road. A series of these electrified roads could be created to satisfy any mission requirement. A series of auxiliary nuclear power plants could also be placed along these roads to insure safety through redundancy, and also to power outposts.

The selection of buried nuclear power plants is a natural. With millions of watts available and reliable, everything becomes much easier.

As an aside, wouldn't it be a great idea to turn Kim Stanley Robinson's trilogy into 3 major motion pictures at the time we are getting ready to really launch into the program. KSR would love the idea, I think, and the pictures would help drum up worldwide support for and interest in the program.

In closing, while I loved "The Martian" and other films about going to Mars, they all involve a catastrophe of sorts and the struggle to repair the damage and get back to earth. The actual program would likely involve landing several payloads ahead of humans and extensive use of robotics before our arrival to do site prep, drilling for water, excavation and tunneling and some construction. The actual arrival on Mars would be almost routine were it not for the extraordinary hopes and emotions tied to the event.

Of course, probably there will be one, maybe two, "single event" landings, successful or not, preceding the above event, but the slow, complete approach is the best, I think.

A "Fast" Mars rover, by which I believe you mean automotive speeds? There's three potential power supplies - Solar charged with high capacity battery - Nuclear electric propulsion, either RTG charging a battery or reactor powering a generator. - Air independent oxygen carrying propulsion (AIP) look at submarines that use fuel cells or an engine with an onboard oxidant.

• Re-read the question which has already ruled out RTGs, AIP/fuel cell has a potential answer in it but as written says nothing that Geoffc does not. May 28, 2020 at 8:23


text:
org.apache.commons.math3.geometry.partitioning

## Interface Hyperplane<S extends Space>

• Type Parameters:
S - Type of the space.
All Known Implementing Classes:
Line, OrientedPoint, Plane

public interface Hyperplane<S extends Space>
This interface represents an hyperplane of a space.

The most prominent place where hyperplane appears in space partitioning is as cutters. Each partitioning node in a BSP tree has a cut sub-hyperplane which is either an hyperplane or a part of an hyperplane. In an n-dimensions euclidean space, an hyperplane is an (n-1)-dimensions hyperplane (for example a traditional plane in the 3D euclidean space). They can be more exotic objects in specific fields, for example a circle on the surface of the unit sphere.

Since:
3.0
Version:
$Id: Hyperplane.java 1416643 2012-12-03 19:37:14Z tn$
• ### Method Summary

Methods
Modifier and Type Method and Description
Hyperplane<S> copySelf()
Copy the instance.
double getOffset(Vector<S> point)
Get the offset (oriented distance) of a point.
boolean sameOrientationAs(Hyperplane<S> other)
Check if the instance has the same orientation as another hyperplane.
SubHyperplane<S> wholeHyperplane()
Build a sub-hyperplane covering the whole hyperplane.
Region<S> wholeSpace()
Build a region covering the whole space.
• ### Method Detail

• #### copySelf

Hyperplane<S> copySelf()
Copy the instance.

The instance created is completely independant of the original one. A deep copy is used, none of the underlying objects are shared (except for immutable objects).

Returns:
a new hyperplane, copy of the instance
• #### getOffset

double getOffset(Vector<S> point)
Get the offset (oriented distance) of a point.

The offset is 0 if the point is on the underlying hyperplane, it is positive if the point is on one particular side of the hyperplane, and it is negative if the point is on the other side, according to the hyperplane natural orientation.

Parameters:
point - point to check
Returns:
offset of the point
• #### sameOrientationAs

boolean sameOrientationAs(Hyperplane<S> other)
Check if the instance has the same orientation as another hyperplane.

This method is expected to be called on parallel hyperplanes. The method should not re-check for parallelism, only for orientation, typically by testing something like the sign of the dot-products of normals.

Parameters:
other - other hyperplane to check against the instance
Returns:
true if the instance and the other hyperplane have the same orientation
• #### wholeHyperplane

SubHyperplane<S> wholeHyperplane()
Build a sub-hyperplane covering the whole hyperplane.
Returns:
a sub-hyperplane covering the whole hyperplane
• #### wholeSpace

Region<S> wholeSpace()
Build a region covering the whole space.
Returns:
a region containing the instance


text:
# 20131003 (Thursday, 03 October 2013)¶

## Groupware and Calendar servers¶

I wanted to note a choir rehearsal into my calendar:

1. veebruar 2014      Segakooride  proov  15.00-19.00, Raplas

and observed that the Lightning calendar in in Thunderbird no longer collaborates with my Google calendar…

Since we’ll need some groupware system, and we need to make some decisions some day, so I surfed around and found an article The Five Best Open Source Calendar Servers for Linux which enumerates:

It also enumerates more general “groupware systems” which -among others- also include a calendar server:

## Payment orders and debit/credit¶

Uff! One might be tempted to believe that the direction of a finanical movement is easy: either Debit or Credit. But it’s not easy to decide where to change it and where not. The dc field of a lino.modlib.ledger.models.DueMovement (the volatile object used to express a “debt” by virtual tables like ExpectedMovements, SuggestionsByJournalEntry or SuggestionsByPaymentOrder in any case is very subtle. Here be dragons. I have 20 years of experience with TIM but still am sometimes struggling…

finan.FillToVoucher needed something which also lino_welfare.modlib.pcsw.models.ClientsTest had been waiting for:

One detail is missing: We should change the API to include ar. But that’s not so easy because we have for example lino.ui.extjs3.views.Templates.get

Concretely lino.core.actors.Actor.get_row_by_pk() now has signature (self,ar,pk) instead of (self,pk).

This again required some internal API changes: Request.setup() now takes the pks and converts them herself to instances…


text:
## Taiwanese Journal of Mathematics

### HOMOCLINIC SOLUTIONS FOR A CLASS OF NONLINEAR SECOND-ORDER DIFFERENTIAL EQUATIONS WITH TIME-VARYING DELAYS

#### Abstract

In this paper, by using Mawhin's continuation theorem of coincidence degree theory, we obtain some sufficient conditions for the existence of homoclinic solutions for a class of nonlinear second-order differential equations with time-varying delays. Moreover, we give an example to illustrate the feasibility of obtained results. Our results are completely new.

#### Article information

Source
Taiwanese J. Math., Volume 17, Number 6 (2013), 2149-2161.

Dates
First available in Project Euclid: 10 July 2017

https://projecteuclid.org/euclid.twjm/1499706290

Digital Object Identifier
doi:10.11650/tjm.17.2013.3198

Mathematical Reviews number (MathSciNet)
MR3141879

Zentralblatt MATH identifier
1288.34058

#### Citation

Li, Yongkun; Yang, Li. HOMOCLINIC SOLUTIONS FOR A CLASS OF NONLINEAR SECOND-ORDER DIFFERENTIAL EQUATIONS WITH TIME-VARYING DELAYS. Taiwanese J. Math. 17 (2013), no. 6, 2149--2161. doi:10.11650/tjm.17.2013.3198. https://projecteuclid.org/euclid.twjm/1499706290

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• C. J. Guo, D. O'Regan, Y. T. Xu and R. P. Agarwal, Homoclinic orbits for a singular second-order neutral differential equation, J. Math. Anal. Appl., 366 (2010), 550-560.
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• L. J. Chen and S. P. Lu, Existence and uniqueness of homoclinic solution for a class of nonlinear second-order differential equations, J. Appl. Math., 2012 (2012), Article ID 615303, 13 pages doi:10.1155/2012/615303.
• E. N. Dancer, On the ranges of certain damped nonlinear differential equations, Annali di Matematica Pura ed Applicata, 119 (1979), 281-295.
• P. Girg and F. Roca, On the range of certain pendulum-type equations, J. Math. Anal. Appl., 249 (2000), 445-462.
• P. Amster and M. C. Mariani, Some results on the forced pendulum equation, Nonlinear Anal., 68 (2008), 1874-1880.
• R. E. Gaines and J. L. Mawhin, Coincidence Degree and Nonlinear Differential Equations, Springer-Verlag, Berlin, 1977.
• X. H. Tang and L. Xiao, Homoclinic solutions for ordinary p-Laplacian systems with a coercive potential, Nonlinear Anal., 71 (2009), 1124-1132.
• S. P. Lu and W. G. Ge, Periodic solutions for a kind of Li$\acute{e}$nard equation with a deviating argument, J. Math. Anal. Appl., 289 (2004), 231-243.


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# Question #6649f

Mar 29, 2015

Oh yes, the good old rocket candy reaction.

The basic idea behind mixing sucrose, or ${C}_{12} {H}_{22} {O}_{11}$, and potassium nitrate, or $K N {O}_{3}$, is that the sucrose will be oxidized by the potassium nitrate.

In other words, sucrose will be the fuel, and potassium nitrate will provide the oxygen needed for the combustion reaction that takes place.

The balanced chemical equation for this reaction is

$5 {C}_{12} {H}_{22} {O}_{11} + 48 K N {O}_{3} \to 24 {K}_{2} C {O}_{3} + 36 C {O}_{2} + 55 {H}_{2} O + 24 {N}_{2}$

The products will be potassium carbonate, carbon dioxide, water, and nitrogen gas.

Here's a video that shows a rocket candy experiment


text:
NEET Chemistry Hydrogen Questions Solved

The oxide that gives hydrogen peroxide $\left({\mathrm{H}}_{2}{\mathrm{O}}_{2}\right)$ on the treatment with a dilute acid $\left({\mathrm{H}}_{2}{\mathrm{SO}}_{4}\right)$ is –

(A) ${\mathrm{MnO}}_{2}$

(B) ${\mathrm{PbO}}_{2}$

(C) ${\mathrm{Na}}_{2}{\mathrm{O}}_{2}$

(D) ${\mathrm{TiO}}_{2}$

Difficulty Level:

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text:
# Understanding a PWM signal on an oscilloscope

#### ericgibbs

Joined Jan 29, 2010
8,887
hi s200,
If there are only two codes to create, ie: On and Off.
It should be a fairly easy task to recreate the waveforms shown in your post #1.
As I suggested earlier, use a Arduino and a scope to generate those two Bit patterns.
E

#### s200bym

Joined Aug 9, 2017
75
I don't know if this makes any sense to you guys but this is the excel file taken from the scope with the ON signal.

#### Attachments

• 188.4 KB Views: 12

#### spinnaker

Joined Oct 29, 2009
7,837
I wish I had finished my CSV protocol analyzer.

Again. if that is synchronous then you are going to need both clock and data pulse to make any sense of the data.

#### ericgibbs

Joined Jan 29, 2010
8,887
hi,
Plotting your csv file in Lotus, produces a copy of the ON code image that you posted earlier.
E

#### AlbertHall

Joined Jun 4, 2014
8,552
I don't know if this makes any sense to you guys but this is the excel file taken from the scope with the ON signal.
It should be possible, yes. It looks like a list of the voltage at the sampling points. The first value looks like the sampling frequency in kHz, so 2000 means 2MHz, or one sample every 0.5uS.
The voltages are near zero or near 2V. The first 2V section lasts 413 samples - 413 * 0.5us = 207us. From the 'scope picture that first pulse is likely two bit times wide which makes the bit time 207us / 2 =103us which makes about 9700Hz which is a sensible approximation to the standard 9600 baud.
Anybody care to work through the rest of the file?

#### AlbertHall

Joined Jun 4, 2014
8,552
Again. if that is synchronous then you are going to need both clock and data pulse to make any sense of the data.
Already established - there is just one data line so it can't be synchronous or SPI.

#### KeepItSimpleStupid

Joined Mar 4, 2014
3,647
The standard serial protocol has a start bit 8 bits and 1 or 2 stop bits (1.5 stop bits is possible)
The 8 bits can be 7 real data followed by with one bit of even, odd or no parity.
No parity means 8 data bits.

Way back when, the character STX (start of Text) and EOT (End of Text) were used to define "messages".

See: https://en.wikipedia.org/wiki/ASCII

From:
Standard baud rates include 110, 300, 600, 1200, 2400, 4800, 9600, 14400, 19200, 38400, 57600, 115200, 128000 and 256000 bits per second

End quote.
There is an odd baud rate of 134.5 which was for the IBM Selectric terminals.

#### s200bym

Joined Aug 9, 2017
75
Could it be the 1 wire protocol?

It should be a fairly easy task to recreate the waveforms shown in your post #1.
Not for me

Sorry for my ignorance, I am learning as I go with this.

Mike.

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#### MrChips

Joined Oct 2, 2009
19,428
CAN use a specific message frame format for receiving and transmitting the data. The two types of frame format available are:

a) Standard CAN protocol or Base frame format
b) Extended Can or Extended frame format

The following figure (Fig 2) illustrates the standard CAN frame format, which consists of seven different bit-fields.

a) A Start of Frame (SOF) field - indicates the beginning of a message frame.
b) An Arbitration field, containing a message identifier and the Remote Transmission Request (RTR) bit. The RTR bit is used to discriminate between a transmitted Data Frame and a request for data from a remote node.
c) A Control Field containing six bits in which two reserved bits (r0 and r1) and a four bit Data Length Code (DLC). The DLC indicates the number of bytes in the Data Field that follows.
d) A Data Field, containing from zero to eight bytes.
e) The CRC field, containing a fifteen-bit cyclic redundancy check-code and a recessive delimiter bit.
f) The Acknowledge field, consisting of two bits. The first one is a Slot bit which is transmitted as recessive, but is subsequently over written by dominant bits transmitted from any node that successfully receives the transmitted message. The second bit is a recessive delimiter bit.
g) The End of Frame field, consisting of seven recessive bits.

An Intermission field consisting of three recessive bits is then added after the EOF field. Then the bus is recognized to be free.

(Fig 2)

Reference:
http://www.eeherald.com/section/design-guide/esmod9.html

#### ebp

Joined Feb 8, 2018
2,332
While CAN is common in automotive applications, there is nothing at all about that signal that suggests CAN to me. CAN uses differential transmission and unless the bit pattern happened to work out "just so" so that a much larger number of bits look like 29 (plus, as I contend, a 30 that merges into the idle state), there are far too few bits at a rate far to low to be CAN.

The only thing that prevents me from being totally convinced it is just weird upside-down conventional async serial is my uncertainty that there is a STOP bit at the end of what would be the second character (20th bit from the left, counting from 1).

The apparent bit rate is inconsistent with 1-wire.

[EDIT] - Ignore following; confirmed with CVS file
It would be helpful to me to see the waveforms expanded. Set the scope to trigger on the leading edge and put the trigger on the left-most graticule position. Set the horizontal scale to 250 µs per division if possible or 200 (more likely - most scopes use 1-2-5 sequence). The latter will overflow the screen a little, but that's OK. The think I would like to see is the 20th bit, as mentioned above.

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#### s200bym

Joined Aug 9, 2017
75
Hopefully, this helps. The only setting for the trigger are slope and falling. I have plotted the graph in excel if that helps.

I took the images from the leftmost and the rightmost.

#### Attachments

• 357.9 KB Views: 1

#### ericgibbs

Joined Jan 29, 2010
8,887
hi s200,
Look thru this list from your first csv file.
E
.... uSec hi/lo
1 207 1
2 209 0
3 103 1
4 105 0
5 103 1
6 105 0
7 103.5 1
8 104.5 0
9 103.5 1
10 104.5 0
11 311.5 1
12 208.5 0
13 207.5 1
14 105 0
15 207 1

#### ebp

Joined Feb 8, 2018
2,332
I looked at the CVS file.
- the rate about 9615 bits per second - well within acceptable tolerance for 9600 baud
- taken as 8 data bits, the stop bits are all in the correct position

#### MrChips

Joined Oct 2, 2009
19,428
I agree with @ebp.

The data is 9600 baud, 8N1.
OFF signal is $56$30 $0A. ON signal is$56 $31$0A.

#### AlbertHall

Joined Jun 4, 2014
8,552
I agree with @ebp.

The data is 9600 baud, 8N1.
OFF signal is $56$30 $0A. ON signal is$56 $31$0A.
That makes it easy to reproduce with any microcontroller such as the Arduino.

#### s200bym

Joined Aug 9, 2017
75
The data is 9600 baud, 8N1.
OFF signal is $56$30 $0A. ON signal is$56 $31$0A.
What format is that so I can try and work out how to put it into code.

Mike.

#### MrChips

Joined Oct 2, 2009
19,428
Set the UART to 9600, 8N1.
Send three bytes in succession, e.g. 0x56, 0x30, 0x0A.

Note that this is straight text, "V0" and "V1" followed by LF.
It does make sense but not very good for reliability as there is no error checking involved.

#### s200bym

Joined Aug 9, 2017
75
WOW! Thanks guys.

This is the OFF signal I am getting now with @MrChips data. Although it's inverted that can be changed. Looks pretty good to me.

Although the ON signal looks the same as the OFF

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