Jul 13

    Proofs from THE BOOK的第六章相当精彩,这一章循序渐进地介绍了多个无理性证明。先证明e是无理数,证明方法和高数课本上的基本相同;试图用类似的办法证明e^2也是无理数时,这一章的内容开始牛B了起来,一些巧妙的变换就让原来的办法继续适用于e^2的证明;加上一些更有趣的技巧,我们还能继续证明e^4也是无理数;当证明对除0外的所有有理数r,e^r都是无理数时,全章达到了高潮。
    这一章还提到了pi^2是无理数的证明方法。这个证明建立在Ivan Niven于1947年提出的“pi是无理数”的经典证明的基础上:仅仅是在原证明过程中加了一些微妙的变化就得到了pi^2也是无理数的结论。注意到,“pi^2是无理数”是一个比“pi是无理数”更强的结论。由于有理数的平方还是有理数,因此证到了pi^2是无理数也就说明了pi必然是无理数;但反过来却不行,因为无理数的平方不一定也是无理数,比如根号2的平方就不是无理数。

    证明过程用到了一个函数,其中n是一个任取的大于等于1的常数。可以想像,这个函数的分子部分展开后是一个关于x的整系数多项式,最低次数为n,最高次数为2n。我们将用到这个函数的两个性质:首先,当0<x<1时,显然有0 < f(x) < 1/n!;其次,函数f及其任意阶导数在x=0和x=1处都是整数。为了证明后一个结论,首先注意到当x=0时,不管是多少阶的导数,除了常数项以外其余项都是0;常数项只可能在n<=k<=2n时出现(k表示k阶导数),但此时它等于一个整系数乘以k!/n!,显然也是个整数。另外,由于f(x)=f(1-x),根据复合函数的微分法我们立即得到对任意x都成立,当然也就有

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Jun 21

  

    哈哈,我考完啦~~~非常happy地上来更新~~
    上图是在Wiltshire的Wroughton附近出现的麦田圈,被称为是目前“最复杂的”麦田圈图形。天体物理学家Mike Reed最近发现,这个麦田圈的图案是一个十进制圆周率的图形编码。这对于麦田圈之谜的研究是一个重大的突破。

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Mar 14

    

正好今天是星期五……大家有没有想过出去喝一杯,庆祝一下属于我们自己的节日呢?

Jan 28

点击这里下载
推荐大家都下载来听听,非常强大,不强我不发
我暂时先不说音频的内容,你一定要亲自听一听,这个“剧透”了就没意思了
另外,我用的是自己的空间,麻烦大家转载时不要盗链

Dec 27

    警告,千万不要去计算pi的二进制表达。数学家们猜想pi是一个正规数(normal number),也就是说它包含了任意一个有限长的01串,所有n位长的01串都以相等的概率出现在pi的二进制中。

    如果你偏要去计算它,你会:

  • 侵犯版权(包括所有书籍、小说、报纸、杂志、网站、音乐、电影、软件,甚至是Windows源码);
  • 侵犯商标权;
  • 拥有大量非法的激情无码大片;
  • 拥有大量国家最高机密;
  • 制造出非法的DVD破解软件;
  • 制造对小胡同志的恐吓信;
  • 拥有所有人的身份证号、信用卡号、电话号码和各种密码;
  • 亵渎伊斯兰教(理论上并不是非法的,但你下半辈子得和Salman Rushdie躲在一起);
  • 亵渎科学论派(非法!问问Keith Henson就知道)。


    同时,你的电脑里会包含有目前所有已知的最邪恶的电脑病毒──事实上还包括有所有未知的最邪恶的病毒。
    我的电脑上有很多极度私密的文件,我不希望你把它们浏览个遍。
    你或许想,我只计算几位就行了;但何必去冒这个险呢?谁也说不准,算到哪一位时你会找到关于Kennedy刺杀案的秘密文件,或者你邻居的六岁小女孩和家里的狗狗XX的恶心照片,或者还未发行的最新一部Star Wars的完整拷贝。反正,千万别去算它。
    同样的警告还适用于e、根号2、Euler常数、phi、除0以外的代数数的余弦值和其它各种各样的实数。
    这也是为什么这些数总是被表示成十进制数的原因。

来源:http://everything2.net/index.pl?node_id=1302963

Dec 2
真实与理性
icon1 Matrix67 |icon2 Brain Storm | icon4 2007-12-02 11:47 | icon32 Comments »

    

Nov 7

    这个可能比较火星,很多人可能已经知道了这个彩蛋;但如果你事先不知道这个彩蛋而碰巧遇上了,你能找出触发这个彩蛋的条件吗?刚才打开iGoogle,发现一件神奇的事件:我的iGoogle主题的顶部图片上居然出现了一个圆周率π──天上的星星排列出来的形状。我立即想到这是iGoogle的一个彩蛋,但我却不知道是什么东西触发了这个彩蛋。仔细想了一下后,突然恍然大悟,这个触发条件确实符合Google的Geek精神。把当时的截屏放出来给大家看一看,如果你还不曾听说过这个彩蛋,你完全可以通过这个截屏找出这个彩蛋的触发条件。继续看下去前不妨先来找找看~~


































    图上显示截屏的时间是11点15分。中国是东八区,比标准时间早8小时,因此国际标准时间是3点15分。考虑到本机时间准确性、截屏时间稍晚等原因,很容易想到iGoogle页面的实际生成时间是3点14分。也就是说,当国际标准时间恰为3:14时,iGoogle将会出现彩蛋。

图片地址:http://www.google.com/ig/images/skins/sweetdreams/3.14am/header_bg.jpg
了解更多:http://www.gseeker.com/50226711/googleaeaeeceee_66197.php

Aug 15

Ambigram
    Ambigram是指把一个单词或短语写成对称的样子,这样从两个不同的角度看这个图形都能读出这个单词或短语。例如,下面一个图形就是单词Ambigram的Ambigram:
      

    ambigram.com的首页有个这样的图片:
      

    Wikipedia上有这样一个Ambigram:
      

    最后来看一个左右轴对称的Ambigram(献丑了):
      

    Erich Friedman教授为他的朋友创作了很多Ambigram。你可以在他的个人主页上看到。

Alphametic
    Alphametic是指,把一句话写成加法算式,每一个字母表示一个数字,那么这个“虫食算”有唯一解。最常见的Alphametic可能是这个:
    SEND + MORE = MONEY
    它的唯一解是9567 + 1085 = 10652

    另一些Alphametic如下:
    FIFTY + STATES = AMERICA
    TERRIBLE + NUMBER = THIRTEEN
    EARTH + AIR + FIRE + WATER = NATURE
    SATURN + URANUS + NEPTUNE + PLUTO = PLANETS

    1969年,有人发现了这样一个有趣的Alphametic:
    THREE + THREE + TWO + TWO + ONE = ELEVEN

    这样的Alphametic叫做Doubly-True Alphametic。可以证明上面这个Doubly-True Alphametic是合法的Alphametic中“最小的”一个。另外两个稍微大一点的Doubly-True Alphametic为:
    SEVEN + SEVEN + SIX = TWENTY
    EIGHT + EIGHT + TWO + ONE + ONE = TWENTY

Mnemonic
    Mnemonic本意是可以帮助记忆的句子。例如,我原来记together这个单词就记作We want to get her。再比如,arithmetic可以记作A Rat In Tom's House Might Eat Tom's Ice Cream(每个单词的首字母)。当然,也有一些专门搞笑的Mnemonic,比如Microsoft = Most Intelligent Customers Realize Our Software Only Fools Them,而Macintosh = Most Applications Crash. If Not, The Operating System Hangs。
    数学家George Pólya(就是Pólya置换定理的那个Pólya)曾说过一句经典的话:How I need a drink, alcoholic of course, after the heavy chapters involving quantum mechanics! 依次数出每个单词的字母个数,你会惊讶的发现它正好是圆周率的前15位。后来又有人在后面加上一句All of thy geometry, Herr Planck, is fairly hard,让圆周率长度增加到24位。另一些圆周率的Mnemonic如下:
    Can I have a large container of orange juice?
    May I have a white telephone, or pastel color?
    How I wish I could calculate pi faster.
    For a girl I loved contrived; by nature tough, her heart survived.

    下面这首诗给出了圆周率的前740位。其中10个字母的单词表示一个数字0,字母数大于10的单词则表示两位数。

Poe, E.
      Near a Raven

Midnights so dreary, tired and weary.
    Silently pondering volumes extolling all by-now obsolete lore.
During my rather long nap - the weirdest tap!
    An ominous vibrating sound disturbing my chamber's antedoor.
        "This", I whispered quietly, "I ignore".

Perfectly, the intellect remembers: the ghostly fires, a glittering ember.
    Inflamed by lightning's outbursts, windows cast penumbras upon this floor.
Sorrowful, as one mistreated, unhappy thoughts I heeded:
    That inimitable lesson in elegance - Lenore -
        Is delighting, exciting...nevermore.

Ominously, curtains parted (my serenity outsmarted),
    And fear overcame my being - the fear of "forevermore".
Fearful foreboding abided, selfish sentiment confided,
    As I said, "Methinks mysterious traveler knocks afore.
        A man is visiting, of age threescore."

Taking little time, briskly addressing something: "Sir," (robustly)
    "Tell what source originates clamorous noise afore?
Disturbing sleep unkindly, is it you a-tapping, so slyly?
    Why, devil incarnate!--" Here completely unveiled I my antedoor--
        Just darkness, I ascertained - nothing more.

While surrounded by darkness then, I persevered to clearly comprehend.
    I perceived the weirdest dream...of everlasting "nevermores".
Quite, quite, quick nocturnal doubts fled - such relief! - as my intellect said,
    (Desiring, imagining still) that perchance the apparition was uttering a whispered "Lenore".
        This only, as evermore.

Silently, I reinforced, remaining anxious, quite scared, afraid,
    While intrusive tap did then come thrice - O, so stronger than sounded afore.
"Surely" (said silently) "it was the banging, clanging window lattice."
    Glancing out, I quaked, upset by horrors hereinbefore,
        Perceiving: a "nevermore".

Completely disturbed, I said, "Utter, please, what prevails ahead.
    Repose, relief, cessation, or but more dreary 'nevermores'?"
The bird intruded thence - O, irritation ever since! -
    Then sat on Pallas' pallid bust, watching me (I sat not, therefore),
        And stated "nevermores".

Bemused by raven's dissonance, my soul exclaimed, "I seek intelligence;
    Explain thy purpose, or soon cease intoning forlorn 'nevermores'!"
"Nevermores", winged corvus proclaimed - thusly was a raven named?
    Actually maintain a surname, upon Pluvious seashore?
        I heard an oppressive "nevermore".

My sentiments extremely pained, to perceive an utterance so plain,
    Most interested, mystified, a meaning I hoped for.
"Surely," said the raven's watcher, "separate discourse is wiser.
    Therefore, liberation I'll obtain, retreating heretofore -
        Eliminating all the 'nevermores' ".

Still, the detestable raven just remained, unmoving, on sculptured bust.
    Always saying "never" (by a red chamber's door).
A poor, tender heartache maven - a sorrowful bird - a raven!
    O, I wished thoroughly, forthwith, that he'd fly heretofore.
        Still sitting, he recited "nevermores".

The raven's dirge induced alarm - "nevermore" quite wearisome.
    I meditated: "Might its utterances summarize of a calamity before?"
O, a sadness was manifest - a sorrowful cry of unrest;
    "O," I thought sincerely, "it's a melancholy great - furthermore,
        Removing doubt, this explains 'nevermores' ".

Seizing just that moment to sit - closely, carefully, advancing beside it,
    Sinking down, intrigued, where velvet cushion lay afore.
A creature, midnight-black, watched there - it studied my soul, unawares.
    Wherefore, explanations my insight entreated for.
        Silently, I pondered the "nevermores".

"Disentangle, nefarious bird! Disengage - I am disturbed!"
    Intently its eye burned, raising the cry within my core.
"That delectable Lenore - whose velvet pillow this was, heretofore,
    Departed thence, unsettling my consciousness therefore.
        She's returning - that maiden - aye, nevermore."

Since, to me, that thought was madness, I renounced continuing sadness.
    Continuing on, I soundly, adamantly forswore:
"Wretch," (addressing blackbird only) "fly swiftly - emancipate me!"
    "Respite, respite, detestable raven - and discharge me, I implore!"
        A ghostly answer of: "nevermore".

" 'Tis a prophet? Wraith? Strange devil? or the ultimate evil?"
    "Answer, tempter-sent creature!", I inquired, like before.
"Forlorn, though firmly undaunted, with 'nevermores' quite indoctrinated,
    Is everything depressing, generating great sorrow evermore?
        I am subdued!", I then swore.

In answer, the raven turned - relentless distress it spurned.
    "Comfort, surcease, quiet, silence!" - pleaded I for.
"Will my (abusive raven!) sorrows persist unabated?
    Nevermore Lenore respondeth?", adamantly I encored.
        The appeal was ignored.

"O, satanic inferno's denizen -- go!", I said boldly, standing then.
    "Take henceforth loathsome "nevermores" - O, to an ugly Plutonian shore!
Let nary one expression, O bird, remain still here, replacing mirth.
    Promptly leave and retreat!", I resolutely swore.
        Blackbird's riposte: "nevermore".

So he sitteth, observing always, perching ominously on these doorways.
    Squatting on the stony bust so untroubled, O therefore.
Suffering stark raven's conversings, so I am condemned, subserving,
    To a nightmare cursed, containing miseries galore.
        Thus henceforth, I'll rise (from a darkness, a grave) -- nevermore!

                        -- original: E. Poe
                        -- Redone by measuring circles.



Lipogram
    看看下面这句话有什么问题?

This is an unusual paragraph. I'm curious how quickly you can find out what is so unusual about it. It looks so plain you would think nothing was wrong with it! In fact, nothing is wrong with it! It is unusual though. Study it, and think about it, but you still may not find anything odd. But if you work at it a bit, you might find out! Try to do so without any coaching!



    答案:这段话里竟然没有一个字母e !
    Lipogram就是指的这样一个段落(甚至文章),里面缺少某个常用的字母。在所有的Lipogram中,写一个没有字母e的文章是最难的,因为字母e出现的频率最高。
    看一个比较长的Lipogram。下面这篇文章里硬是没有一个字母e!


Looking at this paragraph with confusion? I'll aid you slightly. Is any odd gap, lacuna or omission obvious to you? Got it now? No?

That's right - this is a lipogram - a book, paragraph or similar thing in writing that lacks a symbol, particularly (but not always) that symbol fifth in rank out of our 26 script-signs (found amidst 'd' and 'f'), which stands for a sound such as that in 'kiwi'. I won't bring it up right now, to avoid spoiling it. I could play with lipograms morning, noon and night. So it is with joy that I submit to you this location – truly, a loquacious location – for lipogram fanatics to join as a unit to glorify this form of wordplay.

As far as I know, this location has a distinct honour: it contains such an abundant quantity of words without using this taboo glyph that no WWW location can outmatch it. As of right now, it contains 1500 words without any hint of that symbol. Naturally, many long lipograms abound in print, including books, rhyming stanzas, and similar works of fiction. Most notably, La Disparition (A Void) by a famous author of a writing group known as Oulipo, stands out as a paragon of lipogrammaticity. I cannot aim to surpass it, but as a fan, I can look upon it with admiration.

Writing lipograms is, as you might think, a difficult task. In my lingo, 2/3 of all words contain that symbol which I am now avoiding, including many common pronouns and similar words commonly found in writing. Without using abbrvs., slang and odd jargon, which most purists scorn as cop-outs, it's darn tough to impart information in a stylistically satisfying way. Stripping paragraphs of particular symbols has a way of making looking at lipograms jarring. No doubt about it, a lipogram is a particularly arduous form of wordplay.

Having said this, acquiring a knack for lipogram composition isn't that hard, and may assist you in your non-lipogrammatic writing. Not to say that I'm without aid in this activity; my dictionary is always handy, as is a book with synonyms for words. And, notwithstanding any drawbacks flowing from passing many an hour looking for unusual ways to say ordinary things, it might aid your socialization skills. Chicks truly dig lipogrammatists, or so my old lady says.

Sadly, a handful of critics find lipograms ridiculous, ugly or without worth (as fiction or as wordplay). To such sorry saps, I say only that in constraining your thoughts and writing in a particular way aids in promoting branching paths of thought, thus amplifying vocabulary and instilling adroit linguistic skills among both young and old. By putting into praxis ways of thinking that wouldn't occur normally, lipograms call for authors to look at writing as an activity in ways that, frankly, wouldn't occur to such niggling adjudicators of linguistic conduct.

Withholding a symbol found in so many words has drastic symptoms that disallow many topics of discussion. (From this point on, I'll stick to talking about that sign I'm skipping right now). Using math is almost an impossibility; you can only maintain 15 of all non-digital words for cardinal quantity up to 100, and hardly any at all past that point, though using digits is a good way out. You can go north or south, but talking about circumnavigating our world latitudinally is an impossibility. How can I possibly talk about various kinds of malt liquor, or parts of my body, without it? To top it all off, as an Anglo, strict prohibitions apply to naming of my own form of linguistic communication. I ought to thank my lucky stars that I'm not writing in lipogrammatic français, though, which holds on to only an octal portion of its original vocabulary.

But all is not lost. Surprisingly, profanity is mostly intact. As a practicing lipogrammatist, you'll find you want many such words, for it is a task so awkward as to call for cussing and cursing on a normal basis. A world map is truly a blissful oasis; my country (Canada) is totally satisfactory, as with most toponyms for nations (111 out of 186, by my count); with a bit of work, USA, UK, and so on, can still show up, and with twin island nations Trinidad and Tobago and Antigua and Barbuda (both with 17 glyphs) topping my list for prolongation. Musicians (particularly classical artists), astonishingly, hold firm as topics of discussion, with Bach, Bartok, Brahms, Chopin, Dvorak, Haydn, Holst, Liszt, Mozart, orff, Puccini, Rachmaninov, Rossini, Scarlatti, Schumann, Strauss, Stravinsky, Tchaikovsky and Vivaldi void of my lost non-consonant.

An additional branch of family Lipogrammatica consists of univocalics. This form of wordplay is akin to a lipogram, but contains a solitary sign that's not a consonant. To wit, a univocalic might omit 'a', 'i', 'o', and 'u' (but what about 'y'?). A univocalic has a sonorant quality that a lipogram lacks, so you must look at a lipogram, but contrarily, a univocalic is both auditory and visual, and has a strong sound if said aloud. Univocalic writing is hard to pull off, but if it's good, its payoff is gigantic.




另外推荐本Blog里的两个相关内容:
http://www.matrix67.com/blog/article.asp?id=104
http://www.matrix67.com/blog/article.asp?id=173

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