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# Code snippets are not runnable on the Stack Overflow mobile website

Code snippets are shown as "code blocks", but without the Run button on mobile devices. (e.g. on Chrome / Android phone).

It would sometimes be very useful to be able to run code snippets on mobile.

Examples:

• I don't see why running this code snippet from this answer should be possible only on desktop browsers, and not on mobile browsers. Running such a code snippet on both could be equally useful.

• It would be particularly interesting to be able to run code snippets from questions with responsive-design tag

Could we enable code snippets Run button on the mobile version of SO?

• I really don't see why is it relevant how well received the answer that contains the code snippet is. If you are requesting a feature, you should request all code snippets to be runnable, so I really don't see why you should mention any specific answers containing a code snippet. – Dávid Pásztor Feb 21 '18 at 1:31
• Your question is inaccurate. I just ran the snippet in the answer you linked on my Android phone using Google Chrome. So, if someone wants to run it they certainly can. All they have to do is click to load the desktop version of the site, which is an option both as part of the menu system for Google Chrome & Firefox, and is also a link at the bottom of each SO "mobile" page. The text of your question implies that this is impossible, when the reality is that it is just not available in the simplified display which is "mobile", but is possible, if you want it. – Makyen Feb 21 '18 at 5:38
• @DávidPásztor It was just an example. You're totally right: the request is about all code snippets, I agree with you. – Basj Feb 21 '18 at 7:50
• @Makyen if it's possible with a complex UX/UI (Is "Reload the desktop version" available on all mobile browsers?), there's room for improvement. Also, one important thing: with the current mobile display, you don't know in advance that there is a code snippet. On mobile there's no notice "There is a code snippet but you can't run it": there is just a normal code block with no evidence of a code snippet. So what you are saying involves always browsing SO pages on mobile with "Desktop view" enabled (not very handy), or missing code snippets because you don't know that there's one. – Basj Feb 21 '18 at 8:04
• @Basj I haven't checked browsers beyond Chrome and Firefox wrt. a browser-native option to load the desktop version of any page. However, the in-page link should always be available. At a minimum, indicating that there's a snippet available would be a good idea. OTOH, on most complex webpages (or applications) the mobile version drops information, as part of fitting into the mobile format, which is the nature of fitting into a small number of pixels. It usually results in a dumbed-down UI, which is one of the things I significantly dislike about sites/apps using a mobile-only design. – Makyen Feb 21 '18 at 15:26

I agree that this distinction should be removed.
Nowadays, mobile devices that can run JS are perfectly capable of running it properly.

The only issue SO would have with implementing this, would be the layout on smaller screens, but I'm sure they can figure that one out.

I agree it's 2018 and would be useful to allow snippets on mobile. I'd suggest the option to open them, at least the running version, if not also the editing version, in their own tab.

As an example right now I want to ask a question about disabling scrolling on iOS Safari 11.3.1 (which seems to be broken as no previous answers work). I'd like to post working snippets. I can't because it's impossible to run them in a mobile context so I have to setup a github repo and use github pages or set them up somewhere else. Even codepen, jsbin, jsfiddle, can't do this currently which makes it hard to ask questions about mobile html topics on SO. Well, not hard to ask but hard for people to help out since they too end up having to setup some other environment with which to test. This happens often where you want to post an MCVE except the only way to run the MCVE is for the user to setup their own server with your snippet.

It seems ideally you could click "run snippet in new tab" which would run the snippet not in an iframe but as the top frame. You should also be able to set the meta tags since there are meta tags that change mobile browser behavior (probably the html part already covers that) but I can't check since I can't run snippets outside a frame. Settings like scrolling=no and user-scalable=no etc...

Note that pages can send messages across tabs if on the same domain (not sure that works everywhere).

That means for example even if a snippet editor opened in a new tab it can send it's snippet content back to the main tab directly.

Pages can also open tabs using blobs meaning no round trip to the server is needed when pressing run (though async sending the current snippet to the server might be good for recovering snippet state after a crash).

Example of both. Would have used a snippet but snippets disable popups. That restriction also seems like it should be lifted since it's yet another feature people want to be able to discuss and debug using snippets.

I don't think it is worth implementing this.

You can still run snippets in the Desktop edition of Stack Overflow, even from a Mobile.

A full site pseudo-link is available at the bottom of any SE page.

And to add a bit more argumentation:

As a fervent user of StackSnippets, I prepare mine for the reduced view that you get from the page, and sometimes for the full page view.
Both views can be tested when writing the post, but if such a feature were to be implemented, it would have to have different proportions than in the desktop edition, and I wouldn't be able to test this set of proportions while writing my posts.

• Mobile web browsing will always be sub-optimal. We shouldn't block a feature this practical, just because it might not look good on some cases. – Cerbrus Feb 21 '18 at 7:59

If all you're looking to do is test the mobile responsiveness of your functionality...then there are two things which don't directly involve Stack Overflow that can be done.

• Run the code locally using your browser's responsive toolkit
• Run the code as a snippet in full screen using your browser's responsive toolkit

Allowing mobile devices to run what is essentially arbitrary JavaScript sounds like a nightmare for device longevity and safety. Worse, you have to contend with slightly different Webkits running or the quirks of the mobile browser and its JavaScript engine. This creates unnecessary support work for little gain.

• There might be a misunderstanding, but I'm not speaking about how to test the mobile responsiveness of my functionality (for my own testing I don't use SO of course, I use local tools). I'm not sure to understand your answer, but I don't see any valid argument why running this code snippet from a 3900+ upvoted answer should be possible only on desktop browsers, and not on mobile browsers. – Basj Feb 20 '18 at 19:47
• @Basj: You now introduce a whole host of new browsers for Stack Overflow to support for very little gain. Most of the flagships use some variant of Chrome or Firefox for the truly adventurous, but there are some users out there with older or outdated or horrendously patched versions of Webkit, none the wiser. It makes for more work for again, little gain. The mobile responsiveness piece I feel I made my concise point on; if you want to thoroughly test that, then you're going to want to not do it on a third-party site. – Makoto Feb 20 '18 at 19:59
• I respectfully disagree @Makoto, "People have outdated mobile browsers or horrendously patched versions" is not a valid agument for preventing all people to run a code snippet on mobile. – Basj Feb 20 '18 at 20:03
• Example of use case: 1) I read a good answer on SO (on desktop browser), I run the snippet, it works. 2) After some further research (checking documentation, etc.), I implement it on my website. 3) I visit my website on mobile, it doesn't work... ouch.... This could have been avoided by adding 1bis) I read the same answer on my mobile, run the snippet, it doesn't work => now I know that this solution is a desktop-only solution. – Basj Feb 20 '18 at 20:05
• @Basj: At one point in my career I worked for a company that required that we support IE5, up until it finally became enough of a security concern (in terms of SSL and SSL alone) that we had to abandon it. Our development efforts to support and retrofit any work we had with that older browser (and other older browsers like it) cost the company on the order of hundreds of thousands of dollars. If you can choose the browsers you want to support, choose them! – Makoto Feb 20 '18 at 20:06
• @Basj: Additionally your use case is a typical yet unfortunate side-effect of using Stack Overflow; copying this code in to see if it works for all of your use cases without actually taking the time to see what all of your use cases are. I confess to being guilty to it too from time to time. Don't put the onus of mobile validation on Stack Overflow. – Makoto Feb 20 '18 at 20:07
• Once again, with all my respect @Makoto, I don't see why a reader of SO on a phone shouldn't be allowed to run this code snippet. (By reading it on phone, he doesn't even know there is a code snippet, strangely). – Basj Feb 20 '18 at 20:09
• @Basj: So you don't see a problem with including more browsers for support? You don't see any issues with making Stack Overflow's snippet project ultimately responsible for any quirks between mobile and desktop snippet execution? Well, alright then. I suppose I can't convince you. But I will state I remain unconvinced that this is worth the risk and development effort as opposed to fixing a few other things around here that need fixing. – Makoto Feb 20 '18 at 20:12
• "Allowing mobile devices to run what is essentially arbitrary JavaScript sounds like a nightmare for device longevity and safety." So, are you saying all browsers on all mobile devices should just block JavaScript? Imo, this falls under the category Irrational paranoia. Were this answer posted 5 years ago, I'd have agreed, but nowadays, the vast majority of mobile devices are perfectly capable of properly running JS. – Cerbrus Feb 21 '18 at 7:53
• @Cerbrus: I recognize that all sites utilize JavaScript, but the "arbitrary" factor comes in from others writing code that runs on Stack Overflow (in some capacity) that doesn't really impact how you interact with Stack Overflow, which is...unsettling. That code could be dangerous; it could overflow your phone's tiny memory capacity at whim. Again, I recognize that there are other sites that are perfectly capable of doing this too, but I remain unconvinced that making this easier to execute would be a wise decision. – Makoto Feb 21 '18 at 21:05
• @Makoto Why should I be unable to run a snippet that executes JavaScript on my phone? The JavaScript will only run when I click/tap Run snippet.The issues you are talking about exist for any website you might visit. And a very large portion of the JavaScript running on those websites (e.g. frameworks, libraries, etc.) is not written by the owners/webmasters/admins. And most websites run some form of JavaScript for analytics (e.g. Google Analytics). Most browsers in existence support disabling JavaScript if you don't want to run any other code. Do that if you don't care about functionality. – Toothbrush Feb 21 '18 at 22:25
• @Makoto But then why do you trust the browser itself? Browsers and the libraries they depend on are regularly patched to fix security issues. – Toothbrush Feb 21 '18 at 22:31
• @Makoto: Why the distinction between mobile and desktop? You're not implying mobile browsers are less capable of handling malicious JS, are you? All significant browsers have methods of dealing with such scripts. Besides, this is SO. Any code on here that's actually malicious, will be curated. – Cerbrus Feb 22 '18 at 7:57


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# Interpreting R coxph() cox.zph()

The results of my coxph() are significant, yet the cox.zph() test is significant too.

From my understanding of it, the significance of cox.zph() means that the Cox model is not fit to model the relationship between my covariates and the dependent variable. The reason being that this relationship is not linear, while the Cox model only accounts for linear relationships.

I want to know whether there is a relationship between my covariates and survival. Do the results of the cox.zph() test invalidate the results of the coxph()?

• Not specifying the correct linear relationship between a covariate and the log-hazard can lead to a violation of the proportional hazards (PH) assumption. See this page. In that case fixing the model specification might also fix the PH problem, although time-dependendent coefficients can be needed. One could also consider parametric survival models that don't depend on (or even allow for) PH, like log-normal models or other accelerated failure time models outside the Weibull family. – EdM Jul 25 at 15:21

zph() checks for proportionality assumption, by using the Schoenfeld residuals against the transformed time. Having very small p values indicates that there are time dependent coefficients which you need to take care of. That is to say, the proportionality assumption does not check linearity - the Cox PH model is semi parametric and thus makes no assumption as to the form of the hazard. The proportionality assumption is that the hazard rate of an individual is relatively constant in time, and this is what cox.zph() tests.

If a covariate breaks the assumption, it might need fixing as there are time dependent coefficients. To solve this you can either interact the coefficient with explicit time, or use strata based on the plotted residuals. For a detailed guide on doing this, see my answer here: Extended Cox model and cox.zph

Without doing something about it, it might invalidate the results, in a similar manner to how breaking linear regression assumptions might.

Edit:

the effect of holding a diploma on the length of job search vs no diploma. Same scenario : coxph() and zph() significant. Can I say that holding a diploma has an effect on the length of job search?

In all likelihood yes, you could say that. However, given the failed proportionality assumption test, you cannot trust the coefficient of having a diploma (lets call this $diploma$). The Cox model assumes that the effect $diploma$ has on the time to find a job (lets call this $t_{job}$) is constant in time. That means that If $diploma$ increases the % of finding a job by 35%, this increase is irregardless of time.

In the case that $diploma$ failed the proportionality assumption, as when the cox.zph() test for it is significant, adjustments need to be had. If $diploma$'s coefficient changes linearly with time (i.e., the more time it takes to find a job, the relative benefit of having a diploma linearly declines), than you need to add an interaction: $diploma \times t_{job}$. In this case, the value of $diploma$ will be the initial (at $t_0$ difference between having a diploma and not having a diploma), and the interaction would mean the decrease/increase in that initial value with every passing unit of time (hours/days etc.. however you count time). Do this and check cox.zph() again. If it it non-significant, you can probably leave it at that. It makes more theoretical sense that having the coefficient change at specific time points.

• Thanks for this detailed answer ! I'm not sure I follow completely the last part though so I'll use an example. Say I'm working on the effect of holding a diploma on the length of job search vs no diploma. Same scenario : coxph() and zph() significant. Can I say that holding a diploma has an effect on the length of job search ? – Negarev Dec 13 '17 at 0:21
• answered in the text – Yuval Spiegler Dec 13 '17 at 9:17
• Defining a time-dependent coefficient as an interaction of a covariate with time, proposed above and illustrated in the answer linked from this answer, is incorrect. This is a common error; see the vignette on time-dependency in Cox models. There is a tt() function to allow correct specification of time-dependent covariates, but the result cannot currently be checked by cox.zph(). See this answer for details. – EdM Jul 25 at 14:38
• @EdM - absolutely true. Will edit this and other answer shortly. Sorry for causing some confusion. – Yuval Spiegler Jul 26 at 15:37
• No apology needed. Most of your points in both answers were spot-on, except for this one common misunderstanding. Some of my best final answers here came from responding to others' comments about issues they found in my first attempts. That helpful and generally respectful give-and-take is one of the things I like most about this site. – EdM Jul 26 at 16:02

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# Splitting off finite groupoids

Yesterday, David Rydh in this comment found a wonderful approach to proving Lemma Tag 03FM. In fact I had already more or less given up hope that the lemma could be fixed! I am so exited about David’s idea that I am going to try to explain it in this post. Of course any mistakes are mine.

First we are going to discuss a completely general construction. Namely, suppose that f : X —> Y is a morphism of schemes which is separated and locally of finite type. On the small etale site Y_{etale} of Y consider the following presheaf

(*) V/Y |—> {Z \subset X_V open, Z —> V is finite}

Note that as we assumed X —> Y is separated such a Z is also closed in X_V. Also note that the empty set is closed and finite over any scheme. Finite morphisms satisfies descent for the etale topology. This implies that the presheaf above is a sheaf on Y_{etale}. Now, it is a general fact that any sheaf on Y_{etale} is representable by an algebraic space etale over Y. Hence we obtain an algebraic space, which I am going to denote f_!X which comes equipped with an etale morphism f_!X —> Y and we get a universal open and closed subspace Z_{univ} \subset f_!X \times_Y X which is finite over f_!X.

Before we say more about this construction let us point out that f_!X is really an algebraic space and not a scheme. For example suppose that X = Spec(C) and Y = Spec(R[t]) and the morphism f : X —> Y maps the unique point of X to (t = 0) inside Y. In that case f_!X is a copy of Y with {0} replaced by {0_1, 0_2} with residue fields R, respectively C (but of course f_!X is still etale over Y). The complement of {0_1} in f_!X is an open subspace which is a copy of Example Tag 03FN. And this is the simplest example of an algebraic space etale over a scheme which is not a scheme.

Now a very important property of the construction above is that it commutes with arbitrary base change. This is the analogue of the fact that cohomology with proper supports commutes with any base change. Namely, suppose that Y’ —> Y is any morphism of schemes, and denote f’ : X’ —> Y’ the base change of f. By universality of f’_!X’ we obtain a morphism f_!X \times_Y Y’ —> f’_!X’ over Y’. To prove this map is an isomorphism it suffices to show that the stalks of the sheaf (*) can be computed from the geometric fibres of the morphism X —> Y. And this is almost exactly the content of Lemma Tag 02LN.

As in Keel-Mori we are going to use a slight modification of f_! in the case that the morphism f : X —> Y comes equipped with a section e : Y —> X. Namely, in that case we consider the sub presheaf of (*) consisting of those Z \subset X_V with e(V) contained in Z. In the same manner as above you show that this is representable by an algebraic space fe_!X etale over Y whose formation commutes with base change.

OK, so how do we apply this construction to a groupoid scheme (U, R, s, t, c, e, i) with s, t separated and locally of finite type? Well, consider U’ = se_!R and the universal closed sub space Z \subset R \times_{U, s} U’. The inverse map of the groupoid scheme shows that U’ is canonically isomorphic to te_!R which gives that i(Z) \subset U’ \times_{U, t} R is universal. Compatibility with base change and the fact that R \times_{s, U, t} R is isomorphic to R \times_{s, U, s} R over (the second) R shows that there is a canonical isomorphism U’ \times_{U, t} R = R \times_{s, U} U’ over R. Then you check by chasing some diagrams that this isomorphism maps the universal closed subscheme Z into i(Z). Hence if

R’ = U’ \times_{U, t} R \times_{s, U} U’

is the restriction of R to U’, then we conclude that Z is an open sub space of R’ which is finite under both s’ : R’ \to U’ and t’ : R’ \to U’. (Here we use that U’  \times_{U, t} R = R \times_{s, U} U’ can be identified with an open in R’ as these spaces are etale over R.) Because we have e’ inside of Z by construction some more diagram chasing shows that Z is a sub groupoid space! Awesome.

Of course it is possible that U’ is empty. But, as in the statement of Lemma Tag 03FM if we have a point u of U where the set of points {r_1, …, r_n} of R mapping to u under both s and t is finite, and if s, t are quasi-finite at each of those points, then we get a canonical point u’ of U’ whose residue field is the same as the residue field of u, and which corresponds to an open and closed sub scheme of the fibre of R —> U whose points are exactly the set {r_1, …, r_n}.

OK, so this utterly general construction allows us to find an open subgroupoid which is a finite groupoid, at the cost of replacing U by an algebraic space etale over U. And, as pointed out by David Rydh in his further comments we can then use further properties of the original groupoid (U, R, s, t, c, e, i) to prove that U’ has additional properties. For example, in case the morphisms s, t are also of finite presentation and flat, then (I think) U’ agrees with an open of the Hilbert scheme used by Keel and Mori and it is a quasi-projective scheme over U. Wonderful.

## 4 thoughts on “Splitting off finite groupoids”

1. I am curious why you insist on defining f_! as open closed subschemes with FINITE support and not PROPER support (so that f_!X = f_! (Z/2Z)_X is the usual zeroth part of cohomology with proper support). Of course, it doesn’t matter when f is quasi-finite which is the only really interesting case for this construction anyway.

Another curious fact (unless I am mistaken): If f:X->Y is flat (and perhaps we need quasi-finite), then f_! Z_X (a non-constructible etale sheaf) is the coarse moduli space of the Hilbert stack H of proper flat families mapping etale to X. Note that H->Y is etale so that the coarse moduli space of H is simply the sheafification of \pi_0 H. Also, f_! Z_X (resp. H) is an abelian group (resp. abelian group stack) and this structure is preserved. This also works if f is non-separated and gives a construction of f_!Z in this case.

• I really intended to use finite support instead of proper support in the post, because it gives me exactly what I want without changing the hypotheses of Lemma Tag 03FM. However, I should have used another symbol (not f_!X) to denote the algebraic space representing the sheaf (*). Sorry for the confusion.

2. Pingback: Dimension « Stacks Project Blog


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# Clarifying Planck's law

I've edited this. The 2 answers i've received so far were confused as to my meaning.

I'm in an endless argument with a guy who insists that Planck's law predicts that a black body where $$T>0$$ radiates at all wavelengths.

I insist that a black body can only radiate the wavelengths that it receives from it's surroundings because it's in thermal equilibrium.

So who's right?

Edit:

I think that you guys are trying to answer this question without knowing the definition of a black body. A black body is called "black" because it's indistinguishable from it's surroundings. It's in thermal equilibrium with it's surrounding environment. I don't see how any of you guys can say that real-world objects behave like black bodies since A) black bodies are an idealized state, and B) black bodies can not exist in nature.

Given a black body where T=300K (15C). The other guy claims that the BB will radiate at all wavelengths, while I say that radiation will peak at ~10um. He says that any BB, regardless of temperature will radiate the full spectrum including visible light and x-rays. That is simply ludicrous. What he's saying is that we can get more out of a system than we put into it.

Given all that, if you have the interest to answer then would you please stick to the question and not bring real world objects like the Earth and Sun into it. Neither are black bodies. Please stick to black bodies.

• If blackbodies radiate at all wavelengths, then, since most things are approximate blackbodies, the "surroundings" contain radiation of all wavelengths! It's not clear to me why you think the condition of thermal equilibrium would restrict the possible wavelengths. – ACuriousMind Nov 10 at 14:48
• The definition of a black body is that it is thermal equilibrium with its surroundings. That's why it's called "black" because it's indistinguishable from it's surroundings. – Oortcloud Nov 11 at 11:52
• The short answer: The other guy is right and you are wrong. Black body radiation is a continuous spectra (probability distribution, if you like) from $\lambda = 0$ to $\lambda= +\infty$. – J. Manuel Nov 11 at 14:47
• I don't know much as I haven't been started thermodynamics but once while reading about black bodies and their continuous spectrum I found an analogy from University Physics which states:... – The Last Airbender Nov 11 at 16:18
• ...A tuning fork emits sound waves of a single definite frequency (a pure tone) when struck. But if you tightly pack a suitcase full of tuning forks and then shake the suitcase, the proximity of the tuning forks to each other affects the sound that they produce. What you hear is mostly noise, which is sound with a continuous distribution of all frequencies. In the same manner. isolated atoms in a gas emit light of certain distinct Frequencies when excited, but if the same atoms are crowded togethe or liquid they produce a continuous spectrum of light. – The Last Airbender Nov 11 at 16:20

A blackbody will radiate at all wavelengths. The radiation is determined by the body's temperature, and is not related to incoming radiation.

For example, the Sun radiates a blackbody spectrum with a peak around the wavelengths of visible light. But it hardly absorbs any radiation at all (probably mostly from the CMB, which has a peak in the microwave region).

Another example: The Earth absorbs sunlight, but since it is colder than the Sun, it radiates a blackbody spectrum with a peak in the infrared. The difference in outgoing and incoming radiation is exactly what makes the greenhouse effect work.

Edit: Since you edited your question, I will explain more. The Earth and the Sun are in fact blackbodies, to a good approximation; see here. The essential feature of blackbody radiation is that some physical system (the blackbody) is in equilibrium with a photon gas. It is assumed that the small amount of radiation that escapes into the surroundings does not significantly affect the thermal equilibrium. By the Planck law, this photon gas will indeed contain some photons of all wavelengths, including visible light, x-rays and even gamma rays.

However, you are also right that the spectrum has a peak at a temperature-dependent wavelength ($$\lambda_\max = \frac{2.9\, \mathrm{mK\,m}}{T}$$). There will be comparatively few photons with wavelengths far away from this peak.

A blackbody does not need to be "indistinguishable from its surroundings". It is called "black" because it absorbs all light that hits it; it does not reflect anything. So in a very narrow way you are right that it "can only radiate the wavelengths that it receives from its surroundings": In thermal equilibrium, all wavelengths are present, and the blackbody also absorbs and emits all wavelengths; therefore it only emits those wavelengths it absorbs.

• Thanks, but that's not quite what I was asking. Please see my edit. – Oortcloud Nov 11 at 12:18
• @Oortcloud I have added some more discussion in response to your edits. – Elias Riedel Gårding Nov 11 at 15:50

A blackbody will radiate at any wavelength, as you can infer from the Planck's law $$B_\lambda(\lambda, T) =\frac{2hc^2}{\lambda^5}\frac{1}{ e^{\frac{hc}{\lambda k_\mathrm B T}} - 1}$$ which is different from zero for any $$\lambda$$.

• Thanks, but that's not quite what I was asking. Please see my edit. – Oortcloud Nov 11 at 12:18
• Thanks for the comment. What do you think is the problem with this answer? Do you agree that this formula gives the spectrum of the radiation emitted by a blackbody, or not? Because if you do, then this gives a clear answer to your question I think.. – pp.ch.te Nov 12 at 17:51


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# Trance (Final Fantasy IX)

15,992 pages on
this wiki
Trance is induced by a surge of emotion.
—Steiner in battle

Trance (トランス, Toransu?) is the Limit Break system in Final Fantasy IX that temporarily transforms a character into a more powerful form, increasing all physical damage by a factor of 1.5x (except for Steiner, who becomes even more powerful). While in Trance party members have their innate unique skills enhanced in some fashion.

## Entering TranceEdit

Trance is induced by a surge of powerful emotions. Thus, in three battles during which time they are particularly emotional, Zidane, Vivi and Steiner automatically enter Trance at the beginning of the battle.

During a time she is going through emotional turmoil, Dagger's Trance bar will not fill and is not even displayed. The temporary player charactersMarcus, Blank, Cinna, and Beatrix — have no Trance gauges. Besides these exceptions, the plot events do not affect characters' Trance.

Trance is accumulated as the character is attacked by enemies, filling the gauge underneath their ATB bar. If a character is afflicted with Zombie, the Trance bar is reduced to zero. Once the Trance bar is filled, the character immediately enters Trance, changing their appearance and giving the character a mysterious glow. All attacks are equal in filling the Trance bar, and thus even attacks that do no damage count towards it. As the character enters Trance as soon as the filling blow has been dealt, it is possible for an enemy's final attack to trigger it, giving a character a Trance at what is the end of the battle, effectively wasting it. Thus, using Trance strategically can be tough as one cannot easily control who enemies attack and how often.

Being in Trance raises the character's attributes, and they are healed of all status ailments (but do not become immune to them). In Trance special abilities become available, depending on the character who has entered Trance. The Trance bar decreases with every action taken and Trance is reverted when the bar is depleted, when the battle ends, or the character becomes afflicted with the Zombie status. If the battle ends while the Trance bar is still partially full while in Trance, the bar is emptied after the battle.

The amount that the Trance gauge fills up is equal to a random MOD Spirit. If the support ability High Tide is equipped, the gauge fills up equal to the character's Spirit stat instead.

The amount that the Trance gauge decreases while in Trance is as follows:

$Deduction Rate = ([(300 - Level) / Spirit] * 10) MOD 256$

Certain types of actions unique to a character empty out the Trance gauge less than other actions. For instance, when Vivi uses Black Magic in Trance, the action expends less of the Trance bar, than it would have if Vivi used an item.

## StoryEdit

Spoiler warning: Plot and/or ending details follow. (Skip section)

Trance is a surge of powerful emotions that momentarily enhances one's inner capabilities, and thus the effects are unique to each individual. As explained in Final Fantasy IX Ultimania, Kuja lacks the ability to express complex emotions due to having been denied a childhood, and thus is unable to naturally enter Trance. Garland saw the flaws in his design, and created Zidane to one day replace Kuja, but created Zidane as a child, allowing him to grow and thus develop a full range of emotions, granting him the ability of Trance and thus making him ultimately superior to Kuja. Kuja, jealous Garland had created another Genome, kidnapped Zidane and abandoned him on Gaia, where Zidane was raised by Baku and his Tantalus Theater Troupe.

Zidane grows up on Gaia never learning of his Terran origins, and by the age of 16 is a full-fledged member of the troupe and able to enter Trance. After Tantalus kidnaps Princess Garnet and crashes in Evil Forest, Zidane enters Trance when trying to save her from the forest's monsters. Even the young members of the party like Eiko and Vivi, and despite the latter being an artificially produced black mage, have the emotional capacity for Trance, Vivi spontaneously Trancing when his brethren are attacked by a Black Waltz on the cargo ship.

Eiko's pet moogle, Mog, enters Trance as a result of her strong desire to protect Eiko, revealing her true form as the eidolon Madeen. Kuja witnesses the feat and realizes the true power of Trance, and abandons his quest for powerful eidolons, beginning to seek the power of Trance instead. Although Kuja is unable to enter Trance naturally, being a Genome, he can absorb dormant souls into his being, and thus absorbs the souls from within the Invincible and, using the soul of Queen Brahne as a catalyst, has the souls all enter Trance simultaneously, giving him an incredibly powerful Trance that he is able to sustain for an extended period of time.

Reveling in his new-found powers, Kuja kills Garland but is driven to madness upon learning of his impending death, and destroys Terra before setting out to destroy the crystal, source of all life. Zidane and his friends follow Kuja to the Crystal World and defeat him, and as Kuja returns to the Iifa Tree, his Trance is gone.

## List of TrancesEdit

### ZidaneEdit

Trance Command. Use special powers.
—Description
Main article: Dyne (Command)

Zidane's Skill command changes into Dyne while in Trance. It grants special attacks that cost MP. The more Skills Zidane learns, the more powerful Dyne abilities become available. In Trance, Zidane's hair turns pink and becomes longer, and his clothes are replaced with pink fur, as an allusion to Terra Branford's Trance from Final Fantasy VI.

### DaggerEdit

Trance Command. Summon eidolons.
—Description

Dagger's Summon command changes to Eidolon, increasing the chance of a summon having a stronger attack (full animation) and the summoned eidolon has a chance of reappearing during the rest of the battle as long as Dagger stays in Trance, continuing to reappear at random intervals. If Dagger summons multiple eidolons, the last eidolon she summons will be the one to reappear. The random summons do not use MP or expend the Trance gauge, but are weaker than regular summonings, always using the short animation. As the random summons don't deplete the Trance gauge, one can let Dagger idle. When Garnet enters Trance, her hair turns blonde, her skin turns pink with white glyphs along her legs, and her outfit transforms into a white leotard with a low neckline and light green sleeves and boots.

### ViviEdit

Trance Command. Use black magic twice.
—Description

Vivi's Blk Mag command changes to Dbl Blk, allowing Vivi to cast two consecutive Black Magic spells per turn, providing he has MP for both. The spells count as two actions, and deplete the Trance gauge individually. In Trance, Vivi's clothes are replaced by a full-length white robe, gloves, and a hat that stands at a point, as opposed to his usually steeped hat. The straps crossing over his chest are replaced by a stylized design down the middle of his robe, including a wing-like design on his chest. The black shadow under his hat gives off a dark bluish hue while his eyes become stark white instead of yellow.

### SteinerEdit

Steiner does not have any unique Trance skills, but his physical attack power triples. If attacking with the Blood Sword, Steiner will only get the normal 50% increase bonus instead. When in Trance, Steiner's armor is replaced by paladin armor complete with a faceplate with runes on the torso and gold highlights on his gauntlets, chestplate, and the spiky decorative metal jutting out of the front at his ankles. His lower mail is replaced by black pants and silver shin armor. The feather in his hat turns black and becomes jagged.

### FreyaEdit

Trance Command. Aerial attack.
—Description

Freya's Jump ability gets powered up, but doesn't receive a name change. Freya stays in the air instead of landing after a Jump and while airborne, rains spears on all enemies whenever it is her turn. When her Trance gauge expires, or the battle ends, she performs a final attack and lands. Her trance can be exploited when all party members except Freya are KO as while she stays in the air most enemies will do nothing except supportive moves since they can't target Freya, or even attack themselves with their own attacks when it is their turn, and Freya will deal damage to them until the Trance expires. During Trance, Freya's clothing is replaced with full platemail armor, complete with a pair of gauntlets and greaves that cover her hands and legs, and her hat is replaced with a knight's helmet that covers all but the back of her head.

### QuinaEdit

Trance Command. Learn enemy skill.
—Description

Quina's Eat command changes to Cook. This means Quina can attempt to eat the enemy when it has 50% or fewer HP instead of the usual requirement of having lost 75% of their total HP. In Trance, Quina's face disappears into a void with only bright white eyes showing. His/her clothes are replaced by an obese armor set, his/her chef's hat turning into a helmet.

### EikoEdit

Trance Command. Use white magic twice.
—Description

Eiko's Wht Mag changes to Dbl Wht, allowing Eiko to cast two consecutive White Magic spells in one turn, providing she has MP for both. The spells count as separate actions and will deplete the Trance gauge individually. In Trance, Eiko's horn lengthens and turns sky-blue and her ornamental wings grow bigger. Her hair and sleeves turn light green; her bow, chest plate, pants, and boots become white; and her turtleneck and bodysuit change to purple.

### AmarantEdit

Trance Command. Use monk techniques.
—Description
Main article: Flair (Final Fantasy IX)

Amarant's Flair changes to Elan, making all of Amarant's Flairs apply to multiple targets. While in Trance, Amarant's clothes disappear and his skin turns dark with purple highlights, and his facial hair and dreadlocks turn black.

## Other AppearancesEdit

### Dissidia Final FantasyEdit

Time to get serious!
—Zidane enters Trance
—Kuja enters Trance

Zidane and Kuja enter their Trance forms during their EX Modes, but the nature of these abilities is different from their Trance abilities in Final Fantasy IX. Zidane gains the abilities Aerial Jump, which allows him to jump ten times in a row, and Dodge Jump, which makes him invincible to some attacks while jumping.

Kuja gains the abilities Hyper Glide and Auto Magic. Hyper Glide lets him maintain altitude longer while Gliding, and Auto Magic leaves Flare and Holy orbs as Kuja moves through the air to damage opponents. Both execute their EX Bursts while in their Trance forms.

#### Dissidia 012 Final FantasyEdit

Zidane and Kuja retain Trance as their EX Mode, though their abilities are modified. Zidane's Trance has a new effect that resets his jump count when he dodges, letting him jump again, while Kuja's Auto Magic has lower damage priority. Dodging to reset jumps was available to all characters in the first Dissidia Final Fantasy, but was removed in Dissidia 012 for all but Zidane's Trance mode.

### Final Fantasy Trading Card GameEdit

One of Eiko's cards has W-White [Holy] as its ability. W-White [Holy] requires the discard of an Eiko card, Dulling Eiko, and paying two Earth CP, and allows the player to select up to two Forwards and deal them 8000 damage, if the player has taken at least 5 damage.

Quina's card has Eat, requiring the discard of a Quina card and two Water CP. Eat allows the player to select an opponent's Forward that has taken damage the turn Eat is used, and if it has a Special Ability or Action Ability, the player can Break it.


text:
By Topic

# IEEE Transactions on Pattern Analysis and Machine Intelligence

## Filter Results

Displaying Results 1 - 19 of 19
• ### [Front cover]

Publication Year: 1980, Page(s): c1
| PDF (719 KB)
• ### List of Contributors

Publication Year: 1980, Page(s): nil1
| PDF (252 KB)
• ### [Breaker page]

Publication Year: 1980, Page(s): nil1
| PDF (252 KB)
• ### The Relationship of the Bayes Risk to Certain Separability Measures in Normal Classification

Publication Year: 1980, Page(s):97 - 100
Cited by:  Papers (3)
| | PDF (1467 KB)

For the problem of classifying an element (e.g., an unknown pattern) into one of two given categories where the associated observables are distributed according to one of two known multivariate normal populations having a common covariance matrix, it is shown that the minimum Bayes risk is a strict monotonic function of certain separability or statistical distance measures regardless of the a prio... View full abstract»

• ### Locally Trained Piecewise Linear Classifiers

Publication Year: 1980, Page(s):101 - 111
Cited by:  Papers (54)  |  Patents (1)
| | PDF (3046 KB)

We describe a versatile technique for designing computer algorithms for separating multiple-dimensional data (feature vectors) into two classes. We refer to these algorithms as classifiers. Our classifiers achieve nearly Bayes-minimum error rates while requiring relatively small amounts of memory. Our design procedure finds a set of close-opposed pairs of clusters of data. From these pairs the pro... View full abstract»

• ### A Structural Model of Shape

Publication Year: 1980, Page(s):111 - 126
Cited by:  Papers (68)
| | PDF (3724 KB)

Shape description and recognition is an important and interesting problem in scene analysis. Our approach to shape description is a formal model of a shape consisting of a set of primitives, their properties, and their interrelationships. The primitives are the simple parts and intrusions of the shape which can be derived through the graph-theoretic clustering procedure described in [31]. The inte... View full abstract»

• ### Three-Dimensional Moment Invariants

Publication Year: 1980, Page(s):127 - 136
Cited by:  Papers (177)  |  Patents (4)
| | PDF (1860 KB)

Recognition of three-dimensional objects independent of size, position, and orientation is an important and difficult problem of scene analysis. The use of three-dimensional moment invariants is proposed as a solution. The generalization of the results of two-dimensional moment invariants which had linked two-dimensional moments to binary quantics is done by linking three-dimensional moments to te... View full abstract»

• ### Use of Fuzzy Algorithms for Phonetic and Phonemic Labeling of Continuous Speech

Publication Year: 1980, Page(s):136 - 148
Cited by:  Papers (28)  |  Patents (7)
| | PDF (3828 KB)

A model for assigning phonetic and phonemic labels to speech segments is presented. The system executes fuzzy algorithms that assign degrees of worthiness to structured interpretations of syllabic segments extracted from the signal of a spoken sentence. The knowledge source is a series of syntactic rules whose syntactic categories are phonetic and phonemic features detected by a precategorical and... View full abstract»

• ### Pattern-Based Interactive Diagnosis of Multiple Disorders: The MEDAS System

Publication Year: 1980, Page(s):148 - 160
Cited by:  Papers (51)  |  Patents (1)
| | PDF (4833 KB)

A knowledge-based interactive sequential diagnostic system is introduced which provides for diagnosis of multiple disorders in several body systems. The knowledge base consists of disorder patterns in a hierarchical structure that constitute the background medical information required for diagnosis in the domain under consideration (emergency and critical care medicine, in our case). Utilizing thi... View full abstract»

• ### Pattern Recognition as Conceptual Morphogenesis

Publication Year: 1980, Page(s):161 - 165
Cited by:  Papers (6)
| | PDF (1139 KB)

Pattern recognition is our mental activity in which we formulate, select, modify, and adjust our concepts or our frames of reference so that we can see a form'' in objects. We can tentatively formulate this viewpoint as the principle of minimum entropy (or entropy-like function). Different algorithms in clustering and pattern recognition are given new interpretations in the light of this unifyin... View full abstract»

• ### Digital Image Enhancement and Noise Filtering by Use of Local Statistics

Publication Year: 1980, Page(s):165 - 168
Cited by:  Papers (1019)  |  Patents (38)
| | PDF (3148 KB)

Computational techniques involving contrast enhancement and noise filtering on two-dimensional image arrays are developed based on their local mean and variance. These algorithms are nonrecursive and do not require the use of any kind of transform. They share the same characteristics in that each pixel is processed independently. Consequently, this approach has an obvious advantage when used in re... View full abstract»

• ### Model-Based Texture Measures

Publication Year: 1980, Page(s):169 - 171
Cited by:  Papers (4)
| | PDF (1937 KB)

Many measures have been developed to quantify the structural properties of image texture. This correspondence explores their applicability to textures generated by several standard models. View full abstract»

• ### On the Problems of Constructing Minimal Realizations for Two-Dimensional Filters

Publication Year: 1980, Page(s):172 - 176
Cited by:  Papers (11)
| | PDF (972 KB)

The input-output behavior of a two-dimensional linear filter is defined by a formal power series in two variables. If the power series is rational the dynamics of the filter is described by updating equations on finite dimensional local state spaces. The class of realizations considered in this paper is constituted by doubly indexed dynamical systems of reduced structure. The construction of the c... View full abstract»

• ### The Approximation of Image Blur Restoration Filters by Finite Impulse Responses

Publication Year: 1980, Page(s):176 - 180
Cited by:  Papers (5)
| | PDF (1556 KB)

Image blur can often be modeled by a linear spatially invariant, symmetric point spread function. For this class of functions, several restoration filters are known in the literature. The approximation of their frequency transfer functions (ftf's) by the ftf's of small finite impulse response (FIR) filters has been studied. Accurate approximations will be possible by 9 Ã 9 FIR's with 8-bit elemen... View full abstract»

• ### The Sensitivity of the Modified Viterbi Algorithm to the Source Statistics

Publication Year: 1980, Page(s):181 - 185
Cited by:  Papers (9)
| | PDF (986 KB)

The modified Viterbi algorithm is a powerful, and increasingly used, tool for using contextual information in text recognition in its various forms. As yet, no known studies have been published concerning its robustness with respect to source statistics. This paper describes experiments performed to determine the sensitivity of the algorithm to variations in source statistics. The results of the e... View full abstract»

• ### Image Segmentation with Directed Trees

Publication Year: 1980, Page(s):185 - 191
Cited by:  Papers (29)
| | PDF (5387 KB)

This correspondence presents a simple algorithm to detect and label homogeneous areas in an image, using directed trees for region labeling. The scheme constructs directed trees with the image points as nodes, guided by an edge value computed at every point. These directed trees segment the image into disjoint regions. Because of a valley seeldng property of the tree construction procedure, the bo... View full abstract»

Publication Year: 1980, Page(s): 192
| PDF (1958 KB)
• ### List of Contributors

Publication Year: 1980, Page(s): nil2
| PDF (158 KB)
• ### [Front cover]

Publication Year: 1980, Page(s): c2
| PDF (379 KB)

## Aims & Scope

The IEEE Transactions on Pattern Analysis and Machine Intelligence (TPAMI) is published monthly. Its editorial board strives to present most important research results in areas within TPAMI's scope.

Full Aims & Scope

## Meet Our Editors

Editor-in-Chief
Sven Dickinson
University of Toronto
e-mail: sven@cs.toronto.edu


text:
The stress-life $S-N$ method along with the Palmgren-Miner cumulative damage theory is the simplest and the most commonly used fatigue life prediction technique. Its main advantage is that the material properties needed are easy to collect and life calculation is simple. However under many variable amplitude loading conditions, life predictions have been found to be unreliable. Various modifications have been proposed to the Palmgren-Miner theory, but they have not lead to more reliable life predictions. In this paper, a two-stage cumulative damage model will be developed and validated. This model divides fatigue life into two phases—a crack initiation phase and a crack propagation phase. It will be shown that the proposed method results in greatly improved life prediction capabilities. Also, the proposed method retains the simplicity of the S-N based approach in that the material data is still relatively simple to generate and the calculations are straightforward.

1.
Corten, H. T., and Dolan, T. J., 1956, “Cumulative Fatigue Damage,” Proc. of the International Conference on Fatigue of Metals, Institute of Mechanical Engineers, London, pp. 235–245.
2.
Haibach, E., “Modifizierte lineare Schadenakkumulationshypothese zur Berucksichtigung des Dauerfestigkeitsabfalls mit fortschreitender Schadigung,” Technische Mitteilungen No. 50/70 der Lab. Fur Betriebsfestigkeit, Darmstadt, Germany.
3.
Grover, H. J., 1960, “An Observation Concerning the Cycle Ratio in Cumulative Damage,” Fatigue in Aircraft Structures, STP-274, American Society for Testing and Materials, Philadelphia, pp. 120–124.
4.
Manson
,
S. S.
,
1966
, “
Interfaces between Fatigue, Creep, and Fracture
,”
Int. J. Fract. Mech.
,
2
, pp.
327
363
.
5.
Manson, S. S., Frecke, J. C., and Ensign, C. R., 1967, “Applications of a Double Linear Damage Rule to Cumulative Fatigue,” Fatigue Crack Propagation, STP-415, American Society for Testing and Materials, Philadelphia, p. 384.
6.
Singh
,
A.
,
2001
, “
An Experimental Investigation of Bending Fatigue Initiation and Propagation Lives
,”
ASME J. Mech. Des.
,
123
, pp.
431
435
.
7.
Singh
,
A.
,
2002
, “
The Nature of Initiation and Propagation S-N Curves at and Below the Fatigue Limit
,”
Fatigue Fract. Eng. Mater. Struct.
,
25
, pp.
79
89
.


text:
2014
03-16

# Seashells

Bob lived on an island which has many kinds of beautiful seashells. We can regard this island as a rectangular grid that is n rows by m columns. Assume that the coordinates of the j-th column of the i-th row is (i, j). The coordinates of Bob’s house is (x, y). There is at most one kind of seashells in each cell. Bob likes collecting seashells very much. However, he can only go the place of coordinates (x0, y0) with |x0-x|+|y0-y|<=A and max(|x0-x|, |y0-y|) <= B. How many kinds of seashells can Bob get at most?

The first line contains the number T of test cases (T<=5). The first line of each test cases contains four integer numbers n, m, x and y (1<=x<=n<=1000, 1<=y<=m<=1000). The following n lines each containing m integers indicating the type of the seashells. The seashells are different if and only if the corresponding integers are different. The next line contains a single integer q (q <= 105) indicating the number of queries. Each of the following q lines contains two integers A and B(0<=A,B<1000).

The first line contains the number T of test cases (T<=5). The first line of each test cases contains four integer numbers n, m, x and y (1<=x<=n<=1000, 1<=y<=m<=1000). The following n lines each containing m integers indicating the type of the seashells. The seashells are different if and only if the corresponding integers are different. The next line contains a single integer q (q <= 105) indicating the number of queries. Each of the following q lines contains two integers A and B(0<=A,B<1000).

1
4 4 1 2
1 2 3 4
3 2 1 4
5 3 2 654321
2 3 4 6
4
2 1
1 0
3 2
999 999

3
1
5
7

1. 第2题，TCP不支持多播，多播和广播仅应用于UDP。所以B选项是不对的。第2题，TCP不支持多播，多播和广播仅应用于UDP。所以B选项是不对的。


text:
## Sergey vs Teachassist

View as PDF

Points: 7 (partial)
Time limit: 1.5s
Memory limit: 64M

Author:
Problem type

When he isn't asserting his dominance with chess skills, Serog1sPerog1s can be found staring at his computer while frantically reloading TeachAssist. Because of this, he never has time to do his chemistry homework and now his mark has plummeted.

Fortunately his teacher Mr. Bemistry has given him an opportunity to save his mark and his sanity. He offered to let him substitute some of his test marks for his corresponding project mark from the same unit. However, he must make sure that he subs in no more than 2 projects from consecutive units. Mr. B also reminds him that each unit has a unique weighting in the course and that his marks are extremely accurate, down to 5 decimal places.

With his busy schedule of chess and reloading, Serog1sPerog1s is in panic has no time to figure out what to do. With a face as red as sriracha and tears flowing down like the Niagara, he begs you to tell him the fate of his precious mark.

#### Input Specification

The first line of the input will contain an integer , representing the number of units in the course.

The second line will contain floating point numbers denoting the weighting of each unit .

The third line will contain floating point numbers denoting the test percentage for each unit .

The fourth line will contain floating point numbers denoting the project percentage for each unit .

All decimal input can have up to 5 decimal places. The sum of will always be 100.

#### Output Specification

The maximum mark he can get, rounded down to the nearest integer.

#### Sample Input

4
30.00000 20.00000 10.00000 40.00000
90.00000 91.00000 92.00000 93.00000
94.00000 95.00000 96.00000 97.00000

#### Sample Output

95

#### Explanation

Serog1sPerog1s can switch to his first, second, and fourth project marks to get a mark of , or .


text:
# Track Changes in LaTeX with trackchanges

Author
writeLaTeX
View Count
36843
AbstractNote: TrackChanges is not part of TeX Live, and hasn't been updated in a while. Instead, changes.sty, a package for the same purpose, is available in TeX Live and more recent. You can find the example template here. TrackChanges is a package for collaboratively editing LaTeX documents which allows multiple editors to make changes & add annotations to a document. Here we present a short example of it's use, which you can use as a template to get started.


text:
I have been quiet about this year’s election, but not for lack of caring.  The last few months have been extremely busy for me; to my shame, my busy schedule has meant that I have been silent about what is likely the most important presidential election in more than 30 years, not to mention extremely important battles for control of Congress, many governorships, and thousands of other state and local elections.

The first and most important thing that I want to say is this: go vote.  Voting for our executive, legislative, and — at the local level, anyway — many judicial and administrative offices is a huge part of what makes this country special.  It made America unique at the time of her founding, and it still makes us unique today for the orderly, peaceful, and overwhelmingly honest and fair way in which we manage transitions of power.  So, vote.  Please.  If you don’t, you can’t complain when whomever we elect does things you don’t like.  Yes, you may still have the constitutional right to complain about it, but the choice not to vote is a choice to waive any moral right to whine about the outcome.  At the very least, it waives any chance of the rest of us taking you seriously.  If you care about how this country — or your state, or your city — is run, go vote.

As for my take on the election, well, I don’t expect to persuade anyone here and now, but I have to share my thoughts anyway, just in case.

I am a conservative first and foremost, in the tradition of Edmund Burke.  My heroes are people like Ronald Reagan and Russell Kirk.  In this post, if I can accomplish nothing else (beyond reminding you again to go vote), I hope to outline briefly why conservatism is the only safe choice for this election.  I am not going to delve into social issues such as abortion, not because they are not important, but because, realistically, how we vote in this election has little to no impact on these issues.

Our nation is at great risk, due to years of inattention to the federal budget, a military with aging equipment and little new materiel coming online, and a foreign policy that is naive at best and timid, even spineless, at worst.  Government increasingly intrudes upon the lives of average citizens, making it harder and harder to afford a good education; harder for our teachers, schools, and universities to pursue knowledge and learning rather than focusing first and foremost on the bottom line; harder to get and keep a good job; harder to start and run a business; and harder even to exercise everyday rights such as freedom of speech, freedom of religion, and freedom of conscience.  Every new statute, rule, regulation, executive order, permit requirement, or other government action serves only to make government’s powers larger at the expense of the rights of the people.  More startling still, those powers are increasingly concentrated in a national — not federal — government, of which, as Reagan warned, the states are becoming mere administrative districts.  Our democratic federalism is dying, and it is being replaced by a monolithic, paternalistic government of bureaus, administrations, agencies, and czars.

The result is this: our official national debt is 16 trillion dollars — that’s $16,000,000,000,000 — and counting, or more than$51,000 per citizen.  But the real story is far, far worse.  By the standards that public companies must use (known as GAAP), the government has unfunded liabilities in excess of $120 trillion, or more than$1,058,000 per taxpayer.  And it only gets worse; every time the government passes a “stimulus” package which fails to stimulate, engages in quantitative easing, or even repairs a pothole, that number — and your share of it — gets bigger.  This is scary enough when we are only talking about legitimate functions of government, such as defense and administration of a justice system.  But that’s not all we’re talking about; we are also buying countless handouts to private parties, pork-barrel projects, and a reality in which more people than ever are on food stamps, even as it gets harder for employers to offer good jobs due to the crushing regulatory and tax burdens they face.

To fund all of this, we are borrowing trillions of dollars from China, Japan, Brazil, Russia, Taiwan, Switzerland, and so on.  Even worse: the single biggest creditor of the United States government is our own Social Security system, which, when combined with other federal pension systems, holds 5 trillion dollars in federal debt.  Who will be left holding the bag for that?  Our children and even my own generation, because the debt train will run out of track long before we reach retirement.  We need to spend less.  We need fiscal responsibility, but our elected officials don’t seem to have any.

Meanwhile, our military is weak.  Our navy and coast guard have aging ships, and fewer of them than anytime in the last decades.  The air force is flying old and increasingly obsolete planes, leaving us entirely dependent on drones to project air power; it’s not the same, and it’s not enough.  The army drives vehicles that are ill-equipped for a world of IEDs and fighting wars in which the enemy does not always do us the courtesy of wearing uniforms.  Our ever-faithful marines are underfunded, with all of the problems of the other forces.  Our elected officials seem to think the military is an obsolete relic of a dangerous world that no longer exists, which we can always “turn on” again if the world becomes dangerous.  Yet that same military is engaged in multiple undeclared wars and countless “peacekeeping” missions, even as our nation’s diplomatic representatives come under attack and die due to a lack of security.  We need to maintain a strong defense, but we are at risk of losing it.

We need a foreign policy that other nations respect, even if they do not find it pleasant.  There is a reason that President Obama has been endorsed for reelection by the likes of Putin, Chavez, and Castro, and it is not that they think he is strong.  We need a president who recalls that he is President of the United States of America, not of the world, and who bows to no one.

Our country was founded on a simple idea: the people, not their rulers, are supreme.  They have endowed the government with certain powers; the government has not bestowed upon the People the rights that they received from their Creator.  The Founding Fathers gave us an intricate system, balancing the need for unity with the demands of individualism, local needs with national interests, and the need for a strong government with the even more important need that it never be too powerful.  It’s time to reclaim their great idea, and restore a government of the people, by the people, and for the people, not of technocrats and career politicians, by the same, for the same.

It’s time for some real hope and change — hope for a stronger future, in which America is prosperous, strong, and free, and in which Americans do not fear their own government’s excesses.  It’s time for a real conservative.  Not a neoconservative who runs up our debt and needlessly engages in protracted wars, not a statist who sees government as the solution, but a Reaganite conservative who sees government for what it is: the problem, not the solution.

As in 2008, I am again endorsing Mitt Romney and other Republican candidates for office.  Governor Romney is a proven leader and strong conservative, as is his running mate, Paul Ryan.  They are merely men, with no pretensions to be more than men, but they are good men and proven leaders.  I honestly believe that this presidential ticket is the most genuinely conservative ticket this country has seen since Reagan proclaimed that “it’s morning in America.”  They are the right choice for America in this election cycle.  When you vote, please vote for these proven leaders and all of the others who want to get this country back on track by restoring the proper balance between the People and their government.

If you are so inclined, please consider donating to help Governor Romney and Representative Ryan bring real hope back to America.

Hard Times

You know times are bad when large corporations start accepting advertising money to do product placement in their web chat tech support sessions. For example: “Thank you, I’ve found your account information.Â  While I’m looking up your account info, be sure to check out _____, where you can meet friends, play games, etc.” That just happened.Â  And yes, I really was told that my account info had been located, then pitched some nonsense third-party garbage while the tech support person “looked up” my account.

Oh, and said company did not resolve my issue. This, despite the fact that this was my second contact with tech support stemming from the complete failure of their website to display the option I need to access, except in how-to diagrams.

Truly impressive.

A number of people have asked me lately what I’m reading on economics and the financial markets right now.Â  Truth is, I’m always reading such things, and no short list can even come close to covering the variety of material I try to read, from the scholarly and serious (e.g., Posner, Becker, Mankiw, etc.) to the popular and light.Â  That said, I thought my other readers might appreciate a list of some of what I’ve been looking at on the internet in the last few weeks, at least.Â  Without commentary, opinion, analysis, or even a particular ordering (in fact, the first list was intentionally randomized), here it is.Â  I express no public opinion on the accuracy, validity, merit, or usefulness of anything below; these are just links I have found interesting – in some cases because I think the contents to which I’m linking are totally wrong or even bordering on insane… but I think I’ll decline to say which ones.Â  Read the material for yourself, if you’re interested – it’s more likely to be useful, that way, anyway.

Sites or people with lots of information in general, some good, some bad, some possibly crazy:

Slope of Hope – We’re on it

My favorite new (but not new favorite) blog is Evil Speculator (tagline, “bent on market domination, one nefarious trade at a time”). It posted a fantastic and disturbing chart from Gold-Eagle. The chart is one of the best demonstrations I’ve seen of a concept called the “slope of hope.” The idea is that (in significant declines) markets go down slopes of hope – long, bumpy slides in which optimism repeatedly kicks in early and causes dramatic, but short-lived and futile, rallies. In contrast, bull markets start by climbing a “wall of worry” – pessimism is so extreme near bottoms that most investors are late in realizing the worst is over.

$8,500,000,000,000 For reference: this is only 8 days after the$7.4 trillion estimate and only 14 days after the $4.284 trillion estimate. That’s$4,216,000,000,000 in two weeks.

If you really want a fright, keep reading. If we were to keep spending at this rate through the first 100 days of the Obama presidency (149 days from now), the tab for the crisis would hit a whopping $53,370,285,714,285. That’s about 4 times GDP, 4 times the national debt prior to the crisis, and 21 times what the federal government receives in taxes each year. That would only be, oh, about$177,901 for every man, woman, and child in the country. Chump change.

$4,284,500,000,000 That’s what the so-called “financial crisis” of 2008 has cost the federal government directly… so far.* Wonder how that stacks up to other crises? CNBC has a slideshow showing the costs (inflation-adjusted) of some of the biggest government projects ever. There are many events not listed in that slide show, of course. Two of the most notable: the Civil War ($60.4 billion in 2008 dollars, for both sides) and World War I ($253 billion in 2008 dollars). For comparison,$4.28 trillion is approximately 31% of 2007 US GDP. It’s also 167% of 2007 federal tax revenues. How’s that for deficit spending?

You may bring your eyebrows back to earth now.

* Some of this money is in the form of loans. Many of these loans are to companies hemorrhaging cash faster than they can borrow it and are explicitly designed as relief against bad assets, however, and the crisis is hardly over. So, counting this money as lost is only wise.


text:
How to release $Mathematica$ from the $Pre HoldAllComplete lock Not sure if posted before, but I'm asking this question from a Mathematica fellow user who tried to load expressions, whose problem soon turned into a prison break game featuring the following code. SetAttributes[hold, HoldAllComplete]; GetOut /: hold[GetOut] := Unset[$Pre];

$Pre = hold;  After executing this code, all subsequent evaluations are hold, including the GetOut "key" and the reset expression. GetOut$Pre = .

Are there any ways to unhold subsequent evaluations, in addition to rebooting Mathematica?

-
Are you looking for a good solution, or the user's physical integrity should be preserved? –  belisarius Oct 26 '13 at 2:36
@belisarius Definitely both, if possible. I don't feel like hurting executed evaluations preceeding the lock. –  FrenzY DT. Oct 26 '13 at 2:39
Good question. I've always just restarted my kernel when I bungle up $Pre or $PreRead, since I didn't think there was any other way around. Would be interesting if there was... –  rm -rf Oct 26 '13 at 2:46
@rm-rf It's interesting that once we change HoldAllComplete to Hold, both the original attempts work. –  FrenzY DT. Oct 26 '13 at 2:49
Ooh... I have a way out. Writing an answer. –  rm -rf Oct 26 '13 at 2:52

There's nothing that can break out of a HoldAllComplete as long as it has to pass through the kernel. But what if we had a way to bypass the kernel? Hmmm... buttons!

I suggest using the following button as an escape mechanism instead of your GetOut:

Button["Clear $Pre", Unset[$Pre]]

With this, you can clear $Pre by simply clicking it — even with the HoldAllComplete. It works because the evaluation is done via the Front End and not the kernel, thus bypassing $Pre.

-
How does the Button function get evaluated? Is it through the Front End? –  FrenzY DT. Oct 26 '13 at 4:34
@FrenzYDT. Read the last paragraph? –  Sjoerd C. de Vries Oct 26 '13 at 6:45


text:
# zbMATH — the first resource for mathematics

Weakly Whyburn spaces of continuous functions on ordinals. (English) Zbl 1121.54011
Summary: We characterize those ordinals $$\xi$$ for which $$C_p(\xi)$$ is a weakly Whyburn space. As a byproduct we obtain the coincidence of the Fréchet property and the Whyburn one on $$C_p(\xi)$$.

##### MSC:
 54A25 Cardinality properties (cardinal functions and inequalities, discrete subsets) 54C35 Function spaces in general topology 54B99 Basic constructions in general topology 46E10 Topological linear spaces of continuous, differentiable or analytic functions
Full Text:
##### References:
 [1] Arhangel’skiı̆, A.V., Topological function spaces, Math. appl., 78, (1992), Kluwer Academic Dordrecht [2] Bella, A.; Yaschenko, I.V., On AP and WAP spaces, Comm. mat. univ. carolin., 40, 531-536, (1999) · Zbl 1010.54040 [3] Gerlits, J.; Nagy, Z.; Szenntmiklossy, Z., Some convergence properties in function spaces, (), 211-222 [4] K. Kunen, Set Theory, An Introduction to Independence Results, North-Holland, Amsterdam · Zbl 0443.03021 [5] F. Obersnel, Some notes on weakly Whyburn spaces, Topology Appl. (2000), in press
This reference list is based on information provided by the publisher or from digital mathematics libraries. Its items are heuristically matched to zbMATH identifiers and may contain data conversion errors. It attempts to reflect the references listed in the original paper as accurately as possible without claiming the completeness or perfect precision of the matching.


text:
# How do you divide (3x^2+7x-20) / (x+4)?

Jul 30, 2015

$3 x - 5$

#### Explanation:

Hint: If you see the question carefully, you might notice that the question was intended so that you may have to factor the numerator in such a way that $x + 4$ is a factor, and gets cancelled with the denominator. Let's try doing that.

Let $N = 3 {x}^{2} + 7 x - 20$.
Note that $3 x \left(x + 4\right) = 3 {x}^{2} + 12 x$

Thus, we write:
$N = 3 {x}^{2} + 12 x - 5 x - 20 = 3 x \left(x + 4\right) - 5 \left(x + 4\right) = \left(3 x - 5\right) \left(x + 4\right)$

Now we come to the question itself
$\frac{3 {x}^{2} + 7 x - 20}{x + 4} = \frac{\left(3 x - 5\right) \cancel{\left(x + 4\right)}}{\cancel{\left(x + 4\right)}} = 3 x - 5$


text:
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text:
### Conflict measures bases on correlations

#### Description

The first approach to mathematically derive a conflict measure based on grid data was presented by (1979). They based their operationalization on an approach by Lauterbach (1975) who applied Heider’s (1946) balance theory for a quantitative assessment of psychological conflict. The measure uses inter-construct correlation as a basis. It assess via the sign of the correlations of a triad of constructs if the constructs triad is balanced or imbalanced. A triad is imbalanced if one or three of the correlations are negative, i. e. when they leading to contrary implications (Slade & Sheehan, 1979). The function indexConflict1 in OpenRepGrid calculates the proportion of conflictive triads in the grid as devised by Slade and Sheehan.

Slade and Sheehan’s approach has several drawbacks, as it does not take into account the magnitude of the inter-construct correlations. As a consequence significant and insignificant correlations are not differentiated. Also, correlations of small magnitude, i.e. near zero, which may have a positive or negative signe due to chance alone distort the measure (Bassler, Krauthauser, & Hoffmann, 1992; Winter, 1982). An improved version of the index that overcomes these shortcomings was proposed by (1992) and incorporated into the program CT (correlation test). The index enhances the identification of imbalanced triads by using a criterion that incorporates the magnitudes of correlations. From a psychological viewpoint, it remains unclear though what is measured. Connections to the concept of cognitive differentiation have been presumed (Krauthauser, Bassler, & Potratz, 1994). The function indexConflict2 in OpenRepGrid calculates the proportion of conflictive triads in the grid as devised by (1992).

#### Calculation

##### Slade & Sheehan (1979) approach

Multiply all correlations from a triad (formed by the constructs A, B and C) $$r_{AB} r_{AC} r_{BC}$$. If the sign of the result is negative, the triad is imbalanced.

The table below shows when a triad made up of the constructs A, B, and C is balanced and imbalanced.

$$r_{AB}$$ $$r_{AC}$$ $$r_{BC}$$ Triad characteristic
+ + + balanced
+ + - imbalanced
+ - + imbalanced
+ - - balanced
- + + imbalanced
- + - balanced
- - + balanced
- - - imbalanced
##### Bassler et al. (1992) approach

Order correlations of the triad by absolute magnitude, so that $$r_{max} > r_{mdn} > r_{min}$$.

Apply Fisher’s Z-transformation and devision by 3 to yield values between 1 and -1 Check whether the triad is balanced by assessing if the following relation holds:

• If $$Z_{max} Z_{mdn} > 0$$, the triad is balanced if $$Z_{max} Z_{mdn} - Z_{min} <= crit$$
• If $$Z_{max} Z_{mdn} < 0$$, the triad is balanced if $$Z_{min} - Z_{max} Z_{mdn} <= crit$$

#### R-Code

To use the Slade and Sheehan approach use

indexConflict1(boeker)

################################
Conflicts based on correlations
################################

As devised by Slade & Sheehan (1979)

Proportion of balanced triads: 70.9 %
Proportion of imbalanced triads: 29.1 %

For the Bassler et al. approach use

indexConflict2(boeker)

###############################
Conflicts based on correlations
###############################

As devised by Bassler et al. (1992)

Proportion of balanced triads: 34.1 %
Proportion of imbalanced triads: 65.9 %
indexConflict2(boeker, crit =.05)   # change critical value

###############################
Conflicts based on correlations
###############################

As devised by Bassler et al. (1992)

Proportion of balanced triads: 39.8 %
Proportion of imbalanced triads: 60.2 %

### Conflict measures based on distances

#### Description

Measure of conflict or inconsistency as proposed by Bell (2004). The identification of conflict is based on distances rather than correlations as in other measures of conflict indexConflict1 and indexConflict2. It assesses if the distances between all components of a triad, made up of one element and two constructs, satisfies the “triangle inequality” (cf. Bell, 2004). If not, a triad is regarded as conflictive. An advantage of the measure is that it can be interpreted not only as a global measure for a grid but also on an element, construct, and element by construct level making it valuable for detailed feedback. Also, differences in conflict can be submitted to statistical testing procedures.

#### R-Code

indexConflict3(leach2001a)

##########################################################
CONFLICT OR INCONSISTENCIES BASED ON TRIANGLE INEQUALITIES
##########################################################

Potential conflicts in grid:  819
Actual conflicts in grid:  340
Overall percentage of conflict in grid:  41.51 %

ELEMENTS
########

Percent of conflict attributable to element:

percentage
1 Child self             1088.24
2 Self now                794.12
3 Women in general        176.47
4 Men in general          823.53
5 Father                 1647.06
6 Partner                1029.41
7 Ideal self             1470.59
8 Mother                 1058.82
9 Abuser in childhood    1911.76

Chi-square test of equal count of conflicts for elements.

Chi-squared test for given probabilities

data:  x$e.count X-squared = 65, df = 8, p-value = 4.826e-11 CONSTRUCTS ########## Percent of conflict attributable to construct: percentage 1 assertive - not assert 8.09 2 confident - unconfiden 7.65 3 does not f - feels guil 9.12 4 abusive - not abusiv 7.35 5 frightenin - not fright 6.47 6 untrustwor - trustworth 6.76 7 powerful - powerless 6.18 8 big headed - not big he 6.18 9 independen - dependent 6.03 10 confusing - not confus 6.91 11 guilty - not guilty 6.18 12 cold - shows feel 6.03 13 masculine - feminine 7.50 14 interested - not intere 9.56 Chi-square test of equal count of conflicts for constructs. Chi-squared test for given probabilities data: x$c.count
X-squared = 16.171, df = 13, p-value = 0.24

### Literature

Bassler, M., Krauthauser, H., & Hoffmann, S. O. (1992). A new approach to the identification of cognitive conflicts in the repertory grid: An illustrative case study. Journal of Constructivist Psychology, 5(1), 95–111.

Bell, R. C. (2004). A new approach to measuring inconsistency or conflict in grids. Personal Construct Theory & Practice, 1, 53–59.

Heider, F. (1946). Attitudes and cognitive organization. Journal of Psychology, 21, 107–112.

Krauthauser, H., Bassler, M., & Potratz, B. (1994). A new approach to the identification of cognitive conflicts in the repertory grid: A nomothetic study. Journal of Constructivist Psychology, 7(4), 283–299.

Lauterbach, W. (1975). Assessing psychological conflict. The British Journal of Social and Clinical Psychology, 14(1), 43–47. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/1091319

Slade, P. D., & Sheehan, M. J. (1979). The measurement of “conflict” in repertory grids. British Journal of Psychology, 70(4), 519–524.

Winter, D. A. (1982). Construct relationships, psychological disorder and therapeutic change. The British Journal of Medical Psychology, 55 (Pt 3), 257–269. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/7126491


text:
# Is a differentiable (but not $C^1$) function $f: \mathbb{R}^n \rightarrow \mathbb{R}^n$ with invertible derivative everywhere an open map?

Is a differentiable (but not $$C^1$$) function $$f: \mathbb{R}^n \rightarrow \mathbb{R}^n$$ with invertible derivative everywhere an open map? I know that if we assume the function is $$C^1$$, then this is a consequence of the inverse function theorem (or a step on the way to proving the inverse function theorem). I've convinced myself no counter-example exists if $$n = 1$$, but I haven't been able to prove it or come up with a counter-example in the case $$n = 2$$. I've spent more time trying to come up with a counter-example, mostly trying variants involving $$x^2 \sin(1/x)$$.

The result holds in every dimension.

For the sake of simplicity, we assume that $$f(0)=0$$ and $$f’(0)=Id$$.

There is a continuous function (with vector values) $$\epsilon$$ such that for each $$x$$, $$f(x)=x+|x|\epsilon(x)$$.

Let $$R >0$$ be such that if $$|x| \leq R$$, $$|\epsilon(x)| \leq 0.5$$.

Let $$0, let $$z$$ be such that $$|z| < r/4$$.

It is easy to prove that for any $$x$$ with $$|x|=r$$, $$|f(x)-z| > |f(0)-z|$$.

So consider $$g(x)=f(x)-z$$ and $$h(x)=|g(x)|$$ for $$|x| \leq r$$.

Assume that $$g$$ does not vanish, then $$h$$ is differentiable, without critical points, and does not reach its minimum on the border of the disc, which is impossible.

So $$g$$ does vanish, ie, for all $$z$$ with $$|z|$$ small enough, there is some $$y$$ with $$|y| \leq 5|z|$$ sich that $$f(y)=z$$.

In other words: if $$V$$ is a neighborhood of $$0$$, so is $$f(V)$$, which ends the proof.

• Thank you very much for the answer. Unfortunately I only had time to skim what you wrote now. May I ask, how do you know that h has no critical points? But I might be able to figure this out for myself in a few hours when I come back to the computer. Thanks again. – CJD May 8 at 19:47
• Since $|\cdot|$ is a submersion from $\mathbb{R}^n\backslash \{0\}$ to $\mathbb{R}^{+*}$, if $\nabla h(x)=0$, then $g’(x)=0$, ie $f’(x)=0$, a contradiction. – Mindlack May 8 at 19:53
• Perhaps it's easier to understand the argument if expressed this way: consider $h(x) = |g(x)|^2$. It reaches its minimum somewhere on the disk $B(0, r)$. It can't be at the boundary, so its gradient must vanish at some point. Computing the gradient, this shows that either $g$ has a zero at that point, or that the differential of $g$ is singular. The latter does not happen by assumption. – punctured dusk May 8 at 20:07
• I do like your formulation better, it is much nicer. Do you mind if I edit it in (and credit you :) )? – Mindlack May 8 at 20:14
• Thank you again! As far as I can tell, this is very similar to part of the proof of the inverse function theorem in Munkres's "Analysis on Manifolds". I was suspicious at first because that proof requires $C^1$, but as far as I can tell, your use of the function $\varepsilon(x)$ replaces the part of Munkres's proof where $C^1$ is used. – CJD May 8 at 22:34


text:
CMStatistics 2020: Start Registration
View Submission - CMStatistics
B0619
Title: Corrected information criterion for coefficient selection and estimation in structured sparse linear regression Authors:  Bastien Marquis - Université libre de Bruxelles (Belgium) [presenting]
Maarten Jansen - ULB Brussels (Belgium)
Abstract: In high-dimensional linear regression, when the vector of coefficients is sparse, regularisation is widely used to obtain an estimate. In particular, $\ell_1$-regularisation has many attractive qualities as it allows a selection of nonzero coefficients, in addition, to be computationally efficient; however, its solutions are shrunk versions of the ordinary least squares estimator. This can lead to a bias amongst the large coefficients but also results in an overestimation of the model size from the optimisation of an information criterion. To prevent these effects, we propose to use $\ell_1$-regularisation as a method to select nonzero coefficients while using a least-squares projection for the estimation of the selection, avoiding the shrinkage this way. Then the optimal balance between the sum of residual squares and the regularisation should shift towards smaller models. This requires a correction of the expression of the information criterion. Looking into the difference between the Prediction Error and the expected Mallows's Cp, a corrected Mallows's Cp is developed for multiple linear regression. The correction is further analysed in structured models; in particular, group selection is considered.


text:
# Thread to share Good Questions from Calculus which requires deep thinking

#473

3 Likes
#474

@Azimuddin_Sheikh @Hari_Shankar @Viraj @Viraam_Rao @Amay_2018 help

#475

I am getting answer as \frac {sqrt(\pi)}{2}

2 Likes
#476

@Azimuddin_Sheikh

Bro, what was your method? Only thing I could think of trying was reduction formula but it isnt leading me to any answer.

2 Likes
#477

Did you use differentiating under integral?

2 Likes
#478

I tried to bound the integrand with the Gaussian function

1 Like
#479

How bro ? Pls show

1 Like
#480

@pratyaksh_tyagi

Is this from any Allen test?

If it is, then there should be some solution with techniques within JEE syllabus right.
Gaussian function JEE syllabus mein Hain @Azimuddin_Sheikh ?

2 Likes
#481

Kvpy 2019 as I rmmbr

3 Likes
#482

A friend sent me this.
No gaussian function and integral out of syllabus. Maybe there is some other method

2 Likes
#483

I remember this problem was in kvpy and they ask some problems of the level of isi , so we can expect to use some out of syllabus theorems for this problem

1 Like
#484

One thing we can also notice is that : Using binomial approximation, we have (for n>1),
(1+x^2)^n > 1+nx^2
Hence,
I_n=\int_0^1 \frac{dx}{(1+x^2)^n} < \int_0^1 \frac{dx}{1+nx^2} = \frac{1}{\sqrt{n}} \int_0^1 \frac{dp}{1+p^2}=\frac{\pi }{4\sqrt{n}} where p=\sqrt{n} x

Hence, \sqrt{n} I_n < \frac{\pi }{4} < 2 Hence, L<2

10 Likes
Doubt from Limits
#485

Nice.
Thanks bro

3 Likes
#486

Bro you didn't change the limits?
But the conclusion will be same nevertheless

2 Likes
#488
3 Likes
#489

2 Likes
#490
4 Likes
#491

Thanks sir

#492

Nice problem

1 Like
#493

2 Likes


text:
# Hydrogen gas bombarded by electrons

## Homework Statement

What wavelengths will be emitted if you bombard hydrogen gas (in its ground state) with 13 eV electrons.

## The Attempt at a Solution

I talked to my professor about this one and he mumbled something about the ratio of the energies. I know the ground state energy is -13.6 eV and it's getting hit with 13 eV electrons. The ratio is 13/-13.6 = -.956

Or, I was reading that I should add the energies and then find the wavelength. Either way, the wavelength is pretty tiny.....

Can I get a hint at what to do?

Last edited:

Related Introductory Physics Homework Help News on Phys.org
ehild
Homework Helper
The -13.6 eV means the energy with respect to the ionized state, when the electron is not bound to the atom. But hydrogen has many excited levels. You certainly know the formula about the energy of the n-th level.

ehild

Last edited:
I got tiny wavelengths because I didn't convert to joules. lol

Now, you say that -13.6 is the energy in an unbound electron. The formula I have is E = (-13.6 eV)/n^2. If n = 1, E = -13.6 eV. If it's unbound, n = infinity and E = 0. That's the way I understood it, anyways...

vela
Staff Emeritus
Homework Helper
You two are saying essentially the same thing. Ehild just meant the energy of the ground state is 13.6 eV lower than the energy of the unbound or ionized state of the atom, so if you take the zero of energy as that of the unbound state, then the energy of the ground state is -13.6 eV.

You two are saying essentially the same thing. Ehild just meant the energy of the ground state is 13.6 eV lower than the energy of the unbound or ionized state of the atom, so if you take the zero of energy as that of the unbound state, then the energy of the ground state is -13.6 eV.
I see what you're saying. I don't think I was reading the post right. It's 5 a.m., lol. I'm still not sure how to figure out what happens with the gas. My gut says to add 13 and -13.6 because there will be energy left over and figure out a wavelength from that.... If that makes any sense. I really don't understand this stuff...

ehild
Homework Helper
What is the energy of the electron on the second , third, fourth level (n= 2, 3, 4 ? Is the 13.6 eV enough to excite an electron from the ground level onto the second, third, fourth one?

The electron can jump onto a lower level from an excited one, emitting a photon which energy is equal to the energy difference between the initial and final levels.

ehild

What is the energy of the electron on the second , third, fourth level (n= 2, 3, 4 ? Is the 13.6 eV enough to excite an electron from the ground level onto the second, third, fourth one?

The electron can jump onto a lower level from an excited one, emitting a photon which energy is equal to the energy difference between the initial and final levels.

ehild
+13.6 would free the electron. +13 comes close so, um, what happens then? :*)

ehild
Homework Helper
Remember the Bohr model of the hydrogen atom. You have written in a previous post : "The formula I have is E = (-13.6 eV)/n^2". These are the possible energy values of an electron in a hydrogen atom. The electron can jump to a higher energy level if it gets enough energy from somewhere. A high-energy electron can kick up an electron to a higher energy level. What is the energy difference between the second level and the first level? The third and the first ones? The fourth and the first ones? Is that 13 eV enough to rise the electron to a higher level?

ehild

Remember the Bohr model of the hydrogen atom. You have written in a previous post : "The formula I have is E = (-13.6 eV)/n^2". These are the possible energy values of an electron in a hydrogen atom. The electron can jump to a higher energy level if it gets enough energy from somewhere. A high-energy electron can kick up an electron to a higher energy level. What is the energy difference between the second level and the first level? The third and the first ones? The fourth and the first ones? Is that 13 eV enough to rise the electron to a higher level?

ehild
I believe you're telling me to find what energy level 13 eV will bump the hydrogen electrons up to.

$$\Delta E = -13.6(\frac{1}{n^{2}_{f}} - \frac{1}{n^{2}_{i}})$$
$$\Delta E = 13 = -13.6(\frac{1}{n^{2}_{f}} - 1)$$
This give me a value of 4.761 for n but, since n is quantized, I have to round down to 4. With n = 4, I have Ef = 12.75 eV, so what happens to the other .25 eV?

Am I getting there?

ehild
Homework Helper
I believe you're telling me to find what energy level 13 eV will bump the hydrogen electrons up to.

$$\Delta E = -13.6(\frac{1}{n^{2}_{f}} - \frac{1}{n^{2}_{i}})$$
$$\Delta E = 13 = -13.6(\frac{1}{n^{2}_{f}} - 1)$$
This give me a value of 4.761 for n but, since n is quantized, I have to round down to 4. With n = 4, I have Ef = 12.75 eV, so what happens to the other .25 eV?

Am I getting there?
It is much better... Never mind that 0.25 eV. The incoming electron can keep it or it goes to the nucleus. Now, you have the electron on the fourth level. It will not stay there, but jumps down, emitting a photon. It can go to the 3rd or to 2nd or to the first level, then can be transitions from n=3 to n= 2 or n=1. From n=2 to n=1. What are the photon energies?

ehild

So, I would use the Rydberg formula to figure out the wavelength emitted by each transition down?

Related question, I did the same problem but instead of the gas being in the ground state, it's in the n=5 state. I get an imaginary number for n. How do I resolve this?

ehild
Homework Helper
Yes, use the Rydberg formula. It is quite an ugly job to calculate so many wavelengths, I admit.

As for the other problem, was the gas bombarded by electrons of the same energy? If so, this energy is plenty enough to ionize the atom. The Rydberg formula is no more valid when the electron gets free. It can have any (non-negative) kinetic energy.

ehild


text:
# How do you find the asymptotes for f(x)= x/(x(x-2))?

Mar 28, 2016

Vertical asymptotes, horizontal asymptotes and "holes" can be found in this function.

#### Explanation:

First, cancel the factor of x from both the numerator and denominator of the expression:
$f \left(x\right) = \frac{1}{x - 2}$

That factor being removed, causes a "hole" in the graph. This is sometimes called a removable discontinuity. So, at $x \ne 0$, there is a "hole".

To find a vertical asymptote, set the denominator equal to 0 and solve:
$x - 2 = 0$ so x = 2 is the vertical asymptote.

To find a horizontal asymptote, notice that the degree of x in the denominator is higher than the degree of x in the numerator. That is, ${x}^{0}$ in the numerator and ${x}^{1}$ in the denominator. Therefore, large positive or negative values of x will cause the expression to approach 0. That means that a horizontal asymptote will be y = 0.

Still not sure about this? Substitute in large positive and negative values for x like 1000000 or -1000000...Your output values will be very, very small!


text:
# aliquote

## < a quantity that can be divided into another a whole number of time />

TIL about dumb-jump (via Irreal), an Emacs “jump to definition” package for 40+ languages. I became quite used to LSP jump-to- definitions and references, until I realized today that dumb-jump is included in Doom Emacs toolbet! #emacs