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Fermat Conjecture Is Not Proved
xshi 2016-8-26 09:24
Yesterday, I read a blog about Fermat conjecture, reviewed its proof and find that this conjecture is not proved. Its proof did not prove anything at all. Analyses: Its proof idea is to try proving that X ^ n + Y ^ n = Z ^ n have at least one condition that satisfy this formula. The contradiction reached does not imply anything. It can only imply that the proof works so far are not correct. Following are the facts: 1. Elliptic curve is modular; actually there are infinitely many ways for its modularity calculations, so proofs of modularity is a trivial task that will not involve enormous works. 2. Modularity mapping may be divided into different categories, with each category’s works less a few days. 3. The Frey curve will not change its genus,that's determined by the nature of the curve structure. 4. By introducing Fermat Formula into Elliptic Curve, this make the difficult work even more difficult because you have the ambiguous modularity problem of the elliptic curves, and you add one more difficult problem of infinite polynomial equation to solve. 5. Its base conjecture, the epsilon conjecture, and or Ribet's theory have problems. Fermat Equation have infinitely many solutions that have nearly zero errors which should be all right for any mod calculation but the Frey curve do not have the ability to show these at all, and that 's the obvious problem. Readers can check out the theses for these to verify. The original proof not only contain many errors, but also logically disordered. Fermat Conjecture is not proved at all. A problem went so long to solve,something must go wrong just like religions. Now, let ’s see why it was not proved. Let a ^ n + b ^ n = c ^ (n + d) be always right, where a, b, c, n, are all positive integers and delta d is a real , and Y ^ 2 = X (X - a ^ n) (X + b ^ n) is elliptic curve, always modular, this is also a true Frey curve, always has genus of one, and this reasoning is always true because it is from identity equations. Because a, b, c, d can take any values, and delta can be zero or not, it just do not care, this proved that Fermat Conjecture has nothing to do with Frey curve. Some theses claimed that Frey curve will not be modular or level reduction will make genus to become zero.This is not true except that wrong mod operations are performed. So Frey curve and or Ribet's theory do not provide a way to Fermat Conjecture at all. If you cannot see this, let’s further assume that a ^ n + b ^ n = 0 This equation is always wrong, but no matter what values a, b, n are taken, following is always true. The Frey curve is still elliptic, modular, it only change its locations for different a, b, and n. It is very clear that Frey curve cannot tell right or wrong. Now,assume that a ^ n + b ^ n = c ^ n This is the Fermat Equation and the result is still the same. The Frey curve is still elliptic, modular, it only change possible locations for different a, b, c, and n values if the equation need to be matched. Acyually, this time, there is no condition to match and the only possible condition is: Ribet's Theory is wrong. The conclusion is that: Frey curve only act as it is told what should be done, it do not have the ability to judge right or wrong. Fermat Conjecture has nothing to do with Frey curve and it need to be proved separately/ Actually, modularity theory can be defined by many different ways. Proof: The complete proof will use number theory, the theories of rational, real, complex numbers, modularity theory, the theories of modular form and modular curve, group theory, the theory of topology, and graph theory, etc. of course this will include arithmetic. Because this will take some formal works and it is not necessary, I think knowing its analyses is enough. So with so many stories behind, it must be true that history is written to think, not to believe. The touching story is not so touching because almost everyone involved was wrong, and the story is actually very sad. Many life were lost, many families were broken, and many dreams that should continue were stopped. We need only ask the question: Do we have true experts? Let alone top experts. There are more errors in mathematical world and science and in every works of life. Expected to improve.
1792 次阅读|0 个评论
[转载][恐怖] [最后一日 Re-Kill (2015)][720p][美国][主演: 斯科特·阿
lcj2212916 2015-12-10 21:13
导演: 瓦列·米利夫 编剧: 迈克·赫斯特 主演: 斯科特·阿金斯 类型: 恐怖 制片国家/地区: 美国 语言: 英语 上映日期: 2015-10-16(美国) 又名: 杀杀 IMDb链接: tt1612319  Because this project is categorized as being in production, the data is subject to change; some data could be removed completely. 下载地址: http://page92.ctfile.com/file/137286961
3106 次阅读|0 个评论
you should be brave because of the support of me
cosismine 2013-8-3 15:54
finally I decided to support you with whatever I have in my life. ​I wish you can go ahead bravely under the stare of your mother......don't live up with your mother.....I wishes you all the best from the bottom of my heart.
2458 次阅读|0 个评论
[转载]交叉验证(Cross Validation)
热度 1 zt2730 2013-3-1 08:07
Breiman and Spector (1992) demonstrated that leave-one-out cross-validation has high variance if the prediction rule is unstable, because the leave-one-out training sets are too similar to the full data set. 5-fold or 10-fold cross-validation displayed lower variance. Efron and Tibershirani (1997) proposed a 0.632+ bootstrap method , which is a bootstrap smoothing version of cross validation and has less variation. LOOCV的误差比较大,而bootstrap的误差相对较小。 All of the data being used to select the genes and cross-validation used only for fitting the parameters of the model. 在高维情况下,容易错误的使用交叉验证/ In a pilot study, we generated 100 samples with 1000 features for each sample, all coming invariably from the Gaussian distribution N(0,1). We randomly assigned the samples into two classes ("fake-classes"). Since the data set is totally non-informative, the faithful CV error should be around 50% no matter what method is used. But by CV1 scheme we could achieve a CV error as low as 0.025 after recursive feature selection, which shows that the bias caused by the improper cross-validation scheme can be surprisingly large. A more proper approach is to include the feature selection procedure in the cross validation, i.e., to leave the test sample(s) out from the training set before undergoing any feature selection. In this way, not only the classification algorithm, but also the feature selection method is validated. We call this scheme CV2 and use it in all of our investigations throughout. For the above "fakeclass" data, the error rate evaluated by CV2 was always around 50% regardless of the specific method used for feature selection and classification. 以下简称交叉验证(Cross Validation)为CV.CV是用来验证分类器的性能一种统计分析方法,基本思想是把在某种意义下将原始数据(dataset)进行分组,一部分做为训练集(train set),另一部分做为验证集(validation set),首先用训练集对分类器进行训练,在利用验证集来测试训练得到的模型(model),以此来做为评价分类器的性能指标.常见CV的方法如下: 1).Hold-Out Method 将原始数据随机分为两组,一组做为训练集,一组做为验证集,利用训练集训练分类器,然后利用验证集验证模型,记录最后的分类准确率为此Hold-OutMethod下分类器的性能指标.此种方法的好处的处理简单,只需随机把原始数据分为两组即可,其实严格意义来说Hold-Out Method并不能算是CV,因为这种方法没有达到交叉的思想,由于是随机的将原始数据分组,所以最后验证集分类准确率的高低与原始数据的分组有很大的关系,所以这种方法得到的结果其实并不具有说服性. 2).K-fold Cross Validation(记为K-CV) 将原始数据分成K组(一般是均分),将每个子集数据分别做一次验证集,其余的K-1组子集数据作为训练集,这样会得到K个模型,用这K个模型最终的验证集的分类准确率的平均数作为此K-CV下分类器的性能指标.K一般大于等于2,实际操作时一般从3开始取,只有在原始数据集合数据量小的时候才会尝试取2.K-CV可以有效的避免过学习以及欠学习状态的发生,最后得到的结果也比较具有说服性. 3).Leave-One-Out Cross Validation(记为LOO-CV) 如果设原始数据有N个样本,那么LOO-CV就是N-CV,即每个样本单独作为验证集,其余的N-1个样本作为训练集,所以LOO-CV会得到N个模型,用这N个模型最终的验证集的分类准确率的平均数作为此下LOO-CV分类器的性能指标.相比于前面的K-CV,LOO-CV有两个明显的优点: ① 每一回合中几乎所有的样本皆用于训练模型,因此最接近原始样本的分布,这样评估所得的结果比较可靠。 ② 实验过程中没有随机因素会影响实验数据,确保实验过程是可以被复制的。 但LOO-CV的缺点则是计算成本高,因为需要建立的模型数量与原始数据样本数量相同,当原始数据样本数量相当多时,LOO-CV在实作上便有困难几乎就是不显示,除非每次训练分类器得到模型的速度很快,或是可以用并行化计算减少计算所需的时间. Test-set estimator of performance has high variance. CV涉及到模型评价与选择,获得最有的模型后,使用所有观测训练作为预测模型。whichever model gives the best CV score: train it with all data,and that's the predictive model you'll use. AIC(AKaike information criterion 赤池 信息标准) ,BIC( bayesion information criterion) how can we use cross-validation to find useful subset! intensive use of cross validation can overfit. hold out an additional testset before doing any model selection. 在pattern recognition与machine learning的相关研究中,经常会将dataset分为training跟test这两个subsets,前者用以建立model,后者则用来评估该model对未知样本进行预测时的精确度,正规的说法是generalization ability。在往下叙述之前,这边就必须点出一个极为重要的观念:只有training data才可以用在model的训练过程中,test data则必须在model完成之后才被用来评估model优劣的依据。 怎么将完整的dataset分为training set与test set也是学问,必须遵守两个要点: training set中样本数量必须够多,一般至少大于总样本数的50%。 两组子集必须从完整集合中均匀取样。 其中第2点特别重要,均匀取样的目的是希望减少training/test set与完整集合之间的偏差(bias),但却也不易做到。一般的作法是随机取样,当样本数量足够时,便可达到均匀取样的效果。然而随机也正是此作法的盲点,也是经常是可以在数据上做手脚的地方。举例来说,当辨识率不理想时,便重新取样一组training set与test set,直到test set的辨识率满意为止,但严格来说这样便算是作弊了。 Cross-validation正是为了有效的估测generalization error所设计的实验方法,可以细分为double cross-validation、k-fold cross-validation与leave-one-out cross-validation。Double cross-validation也称2-fold cross-validation(2-CV),作法是将dataset分成两个相等大小的subsets,进行两回合的分类器训练。在第一回合中,一个subset作为training set,另一个便作为test set;在第二回合中,则将training set与test set对换后,再次训练分类器,而其中我们比较关心的是两次test sets的辨识率。不过在实务上2-CV并不常用,主要原因是training set样本数太少,通常不足以代表母体样本的分布,导致test阶段辨识率容易出现明显落差。此外,2-CV中分subset的变异度大,往往无法达到「实验过程必须可以被复制」的要求。 K-fold cross-validation (k-CV)则是double cross-validation的延伸,作法是将dataset切成k个大小相等的subsets,每个subset皆分别作为一次test set,其余样本则作为training set,因此一次k-CV的实验共需要建立k个models,并计算k次test sets的平均辨识率。在实作上,k要够大才能使各回合中的training set样本数够多,一般而言k=10算是相当足够了。 最后是leave-one-out cross-validation (LOOCV),假设dataset中有n个样本,那LOOCV也就是n-CV,意思是每个样本单独作为一次test set,剩余n-1个样本则做为training set,故一次LOOCV共要建立n个models。相较于前面介绍的k-CV,LOOCV有两个明显的优点: 每一回合中几乎所有的样本皆用于训练model,因此最接近母体样本的分布,估测所得的generalization error比较可靠。 实验过程中没有随机因素会影响实验数据,确保实验过程是可以被复制的。 但LOOCV的缺点则是计算成本高,因为需要建立的models数量与总样本数量相同,当总样本数量相当多时,LOOCV在实作上便有困难,除非每次训练model的速度很快,或是可以用平行化计算减少计算所需的时间。 使用Cross-Validation时常犯的错误 由于实验室许多研究都有用到evolutionary algorithms(EA)与classifiers,所使用的fitness function中通常都有用到classifier的辨识率,然而把cross-validation用错的案例还不少。前面说过,只有training data才可以用于model的建构,所以只有training data的辨识率才可以用在fitness function中。而EA是训练过程用来调整model最佳参数的方法,所以只有在EA结束演化后,model参数已经固定了,这时候才可以使用test data。 那EA跟cross-validation要如何搭配呢?Cross-validation的本质是用来估测(estimate)某个classification method对一组dataset的generalization error,不是用来设计classifier的方法,所以cross-validation不能用在EA的fitness function中,因为与fitness function有关的样本都属于training set,那试问哪些样本才是test set呢?如果某个fitness function中用了cross-validation的training或test辨识率,那么这样的实验方法已经不能称为cross-validation了。 EA与k-CV正确的搭配方法,是将dataset分成k等份的subsets后,每次取1份subset作为test set,其余k-1份作为training set,并且将该组training set套用到EA的fitness function计算中(至于该training set如何进一步利用则没有限制)。因此,正确的k-CV 会进行共k次的EA演化,建立k个classifiers。而k-CV的test辨识率,则是k组test sets对应到EA训练所得的k个classifiers辨识率之平均值。
个人分类: 统计学|19959 次阅读|1 个评论
逗号、连字符和“which”
liwenbianji 2013-2-19 10:35
逗号、连字符和“which” 如 果以上述三种形式使用错误,将导致写作意思表达模糊,进而引起读者的误解。例如,“Because Aβ42 levels were elevated in 75% of AD patients in studies using our method , it is critical to obtain fresh samples”,如果把“method”后的逗号移到“patients”后面(或在这里再加入新的逗号)将完全改变句子的意思。同样,在短语 “calcium-induced calcium release”中,如果删除了连字符也将完全改变句子的意思。如果使用了连字符,“calcium-induced”是复合性形容词,修饰名词 “calcium release”;如果不使用连字符“induced”则是动词,描述“effect of calcium on calcium release”。因此,使用连字符构成的复合性形容词对于避免误解是非常重要的。然而,介词和形容词之间是不需要加连字符的,例如“highly intense staining”和“high-intensity staining”都是正确的,但是“highly-intense staining”的用法是错误的。 • “Glutamate receptors mediated synaptic plasticity…” (此句子告诉作者Glu受体参与突触可塑性生成) • “Glutamate receptor-mediated synaptic plasticity…” (与Glu受体相关的突触可塑性成了句子的主语;注意这里“receptor”由复数形式改为单数形式,但并不是指单一一种受体而是泛指受体) “which” 一字如果使用不当,也可引发诸多混淆。它常与“that”混用。“that”和“which”都引导用于修饰名词的从句,但“that”用于引导限定性从 句,而“which”用于引导非限定性从句。例如,“the sections that were positive for GFP were subjected to cell counting procedures”,在这个句子中,“that”引导的是限定性从句明确规定了是哪些切片用于细胞计数。相比之下,“the sections, which were positive for GFP, were subjected to cell counting procedures”,在这个句子中,对用于细胞计数的切片的规定相当宽松,可能指的是前一个句子或相临句子中提及的切片。提及GFP阳性的从句可以向 读者提供一些额外的信息,但对于理解该句子的意义来说并非必不可少;也就是说,它是可有可无的。考虑到“which”的这种角色,研究人员在撰写论文时应 明确“which”一词确切指代的东西 — 有时指代的是该词所紧跟的事物(这是最常见的),有时指代的则是该句子的主语。例如,“microglia migrated to the site of the lesion, which was associated with increased levels of ED-1”,这个句子就写得含混不清,因为我们很难确定“which”所指的到底是lesion,还是migration of microglia。如果读者可能会对此类句子产生疑惑,最好是推翻重写;例如,可以改为“migration of microglia to the site of the lesion was associated with increased levels of ED-1”,也可改为“microglia migrated to the site of the lesion, and immunohistochemical analysis revealed increased levels of ED-1 at this site”。两者均无歧义。 • “Data were normalised to the housekeeping gene actin, which was used as an internal reference…” (在这个句子中, “which”指代的是actin,因此actin也就是该从句的主语) • “Data were normalised to the internal reference housekeeping gene actin, revealing increases in the levels of…” (如果在后续从句中提及所分析的资料,使用“which”不仅没有必要,反而会引发歧义) Commas, hyphens and “which” Used incorrectly these three elements of writing can introduce ambiguities, and the potential for subsequent misunderstanding, into your writing. For example, in the sentence “Because Aβ42 levels were elevated in 75% of AD patients in studies using our method , it is critical to obtain fresh samples”, moving the comma after method to follow the word “patients” (or addition of a new comma there) would completely change the meaning. Similarly, in the phrase “calcium-induced calcium release”, omission of the hyphen completely changes the meaning of the sentence. When the hyphen is present “calcium-induced” is a compound adjective modifying the noun “calcium release”; when the hyphen is absent, “induced” is a verb describing the effect of calcium on calcium release. Thus, it is critically important to use hyphens with such compound adjectives to avoid misunderstandings. However, no hyphen is required to combine an adverb and an adjective; for example “highly intense staining” and “high-intensity staining” are both correct, but “highly-intense staining” is not. • “Glutamate receptors mediated synaptic plasticity…” (tells the reader that Glu receptors are involved in the development of synaptic plasticity). • “Glutamate receptor-mediated synaptic plasticity…” (identifies synaptic plasticity involving Glu receptors as the subject of the sentence; note the change from plural to singular because “receptor” is being used in a general sense and not to refer to a single receptor). The word “which”, when used incorrectly, can also induce considerable confusion. It is often used incorrectly instead of “that”. Both introduce clauses that modify nouns, but “that” should be used to introduce defining or restrictive clauses and “which” should be used to introduce non-defining or non-restrictive clauses. For example, in “the sections that were positive for GFP were subjected to cell counting procedures”, the “that” introduces a defining clause that defines exactly which sections were subjected to cell counting. By contrast, in “the sections, which were positive for GFP, were subjected to cell counting procedures”, the sections that were subjected to cell counting are rather loosely defined, possibly referring to sections that have been described in the previous or recent sentences. The clause about GFP positivity provides the reader with additional information, but is not essential to understand the meaning of the sentence; that is, it is disposable. Because “which” is used in this way, writers need to ensure that it is absolutely clear what the “which” is actually referring to, possibly whatever immediately precedes it (most commonly) or possibly the main subject of the sentence. For example, the sentence “microglia migrated to the site of the lesion, which was associated with increased levels of ED-1” is somewhat vague, because it is unclear if the “which” is referring to the lesion or to the migration of microglia. If there is ever any doubt about such a sentence, it is best to rephrase it completely; for example “migration of microglia to the site of the lesion was associated with increased levels of ED-1” or “microglia migrated to the site of the lesion, and immunohistochemical analysis revealed increased levels of ED-1 at this site”, both of which are unambiguous. • “Data were normalised to the housekeeping gene actin, which was used as an internal reference…” (here, the “which” refers to actin, which is therefore the subject of the following clause). • “Data were normalised to the internal reference housekeeping gene actin, revealing increases in the levels of…” (to refer to the analyzed data in a subsequent clause, “which” would be inappropriate and introduce an ambiguity). Dr Daniel McGowan 分子神经学博士 理文编辑学术总监
3402 次阅读|0 个评论
A Letter to Dr. Li! Richard of Harvard Medical School
热度 1 Richardbg 2013-2-4 05:04
Hi, Dear Dr. Li: It is nice to see you! As you knew you are the only one of my friend on the website. And Because I will leave the website, so it is my pleasure to send some info to you and thank you for whatever if you consider I am possibly your good friend. I leave the scincenet because I need finishing my discovery and let the world know it in the year or half of year. The website is really not good place for me to stay and leave some information here when I become the one of best scientists as same as Dr. Xueshen Qian. If you still have interests to talk three to six months later, I will try to talk with you again. By the way, I will hide all my blog papers except one that to remind everyone I have worked here and sending my letter to those presidents of top ten universities in China without any answer. If I am smartest one or stupidest one in the world, I just feel too cold when standing up an icy mountain of science. When I get the recognition, I would not like talking with any one, any scientists six months later. The Dr. Richard Qian Or Baogang Qian will be their name tag for worship, it is not mine. Best wish and Happy New Year! Richard Baogang Qian, MD
个人分类: 科学发现|3615 次阅读|1 个评论
I do it, just because I am good at it
热度 1 wuqingqing1 2012-12-19 00:14
一直都很忙很忙,没有时间也没有心思去想太多,似乎很多时候,也没有必要去想太多。 简单生活,是好事。 偶然间,还是会有一些人,一些事,一些时刻,会让自己瞬间感悟。像蜻蜓点水,迅速在水面激起涟漪,虽然涟漪渐渐消散,但心间毕竟是留下了一颗种,会在另外的某一天,某一时刻,跃出水面,翩翩飞舞。 今天很想说的是,选择,或者不选择,很多时候其实并没有那么多理由。 需要做的是,好好学着让自己喜欢上所从事的事情,爱上自己所选择的生活。 就像《战争之王》中的一句台词“I do it, just because I am good at it.” I hope that's theright reason for what we want.
3031 次阅读|1 个评论
[转载]贫困陷阱
zhao1198 2012-10-3 11:35
发展经济学中的贫困陷阱,就是指由于经济中存在恶性循环,而使发展中国家陷于贫困落后之中难以摆脱。贫困陷阱可分为两种:技术陷阱和人口陷阱. 所谓“贫困陷阱”,通常地讲是指这样一种情况,处于贫困状态的个人、家庭、群体、区域等主体或单元由于贫困而不断地再生产出贫困,长期处于贫困的恶性循环中而不能自拔。一旦掉进这种“贫困陷阱”,要想从里边跳出来就不是一件容易的事情了。 20世纪50年代有三位经济学家揭示了“贫困陷阱”的产生根源: (1)纳克斯(Nurkse)于1953年提出“贫困恶性循环”(vicious circle of poverty)理论; (2)纳尔逊(Nelson)于1956年提出“低水平均衡陷阱”(low-level equilibrium trap)理论; (3)缪尔达尔与1957年提出“循环积累因果关系”理论。 这些理论认为发展中国家总是陷入低收入和贫困的累积性恶性循环之中,用纳克斯的话说:“一国穷是因为它穷”(A country is poor because it is poor)。 “贫困陷阱”为什么能够相对地把人锁定在贫困中,其基本原理是这样的:因为你穷,你就享受不到良好的教育,引起人力资本的退化;因为你穷,你就缺少物质资本的投入,许多赚钱的机会因而与你无缘;因为你穷,就限制了你的活动范围和自由,因而使你游离于主流社会之外而日益边缘化;因为你穷,就可能影响你的情绪和精神状态,从而一蹶不振而荒度人生。 扩展阅读: 1 《贫穷的终结》,杰弗里·萨克斯,上海人民出版社 2 《发展经济学》,谭崇台等,上海人民出版社,1989年版
个人分类: 百科|2792 次阅读|0 个评论
[转载]Time
wanghairan123 2012-9-19 15:57
Time to get our hearts and minds right, and make today the best day ever, because it will never come again!
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[转载]转载 What makes a good PhD student
lijuan9610001 2012-7-5 13:05
What makes a good PhD student? --- Nature, Vol 441, May 11, 2006 —— 《自然》,第441期,2006年5月11日 Doing a PhD should be fun and rewarding, because you can spend all your working time discovering things and pursuing ideas -- and getting paid for it, without any administrative responsibilities. Those who stick with a career in science do so because, despite the relatively poor pay, long hours and lack of security, it is all we want to do. 做一名博士研究生充满了乐趣,也是非常值得的,因为你可以把所有的时间都用在探索事物、追求理念上——并且可以获得报酬,没有任何行政上的责任。那些有志于从事科学研究的人之所以能这样做,是因为这些都是他们真正想做的——虽然报酬相对较少,工作时间很长,也缺乏保障。 Unfortunately most new PhD students are ill-prepared, and as a consequence very few will fulfil their aspirations to be independent scientists. The main reasons for this are the 'grade creep' inherent at most universities, making it difficult to identify the really talented first-class graduates from the rest, and the pressure on universities to graduate as many PhD students as possible. The consequence is that we enrol far too many of them without telling them clearly what doing a doctorate should entail. We therefore set ourselves, and the students, on a path of frustration and disappointment. 不幸的是大多数博士新生并没有做好充分的准备,其结果就是几乎没有人能从事独立研究。造成这种现象的原因主要是多数大学评价学生的“等级差”太小,很难将真正优秀的研究生区别出来,同时各大学也面临着让尽可能多的博士生毕业的巨大压力。结果导致我们招了太多的博士生,但没有让他们明白博士因该具备哪些素质。这不但使我们自己,同时也使博士生们感到万分痛苦和失望。 So what should we be telling prospective PhD students? 那么,我们应该对未来的博士生们说些什么呢? (1) Choose a supervisor whose work you admire and who is well supported by grants and departmental infrastructure. 选择研究经费充足、设备齐全,同时其工作受到你认同的导师。 (2) Take responsibility for your project. 对你的研究项目负责。 (3) Work hard -- long days all week and part of most weekends. If research is your passion this should be easy, and if it isn't, you are probably in the wrong field. Note who goes home with a full briefcase to work on at the end of the day. This is a cause of success, not a consequence. 努力工作——所有工作日的大部分时间,以及部分周末。如果你所从事的研究是你感兴趣的,做到这点很容易,但如果不是,那你就要好好想想是不是进错研究领域了。有些人在每天回家时总会带上塞得慢慢的公文包,以便在家里继续工作——这是成功的一个重要因素,而非结果。 (4) Take some weekends off, and decent holidays, so you don't burn out. 周末、假期偶尔也出去放松放送,以免自己精疲力竭。 (5) Read the literature in your immediate area, both current and past, and around it. You can't possibly make an original contribution to the literature unless you know what is already there. 阅读与你的研究领域直接相关的 文献 ,当前的和过去的,同时也应阅读一些与研究领域相近的文献。除非你已了解文献的内容,否则不可能做出原创性的贡献。 (6) Plan your days and weeks carefully to dovetail experiments so that you have a minimum amount of downtime. 根据 实验 进度仔细地安排好每一天、每一周,这样能最大限度地减少时间的浪费。 (7) Keep a good lab book and write it up every day. 每天做好实验记录,并保存好。 (8) Be creative. Think about what you are doing and why, and look for better ways to go. Don't see your PhD as just a road map laid out by your supervisor. 创造性思考。思考正在做什么以及为什么这样做,寻找更好的实现方式。不要将博士生活看作是导师帮你画好的路线图。 (9) Develop good writing skills: they will make your scientific career immeasurably easier. 练就出色的写作技能:它能使你的科研道路平坦许多。 (10) To be successful you must be at least four of the following: smart, motivated, creative, hard-working, skilful and lucky. You can't depend on luck, so you had better focus on the others! 想要获得成功,你至少得具备以下要素中的四种:聪明,主动,有创造力,工作努力, 技术 熟练,以及运气好。运气太不可靠,所以你应当将精力放在其它几个要素上。
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[转载]国外某教授收集的名言-great!
热度 1 swjyeah 2012-6-12 19:46
To the world, you may be one person, but to one person you may be the world Oppenheimer: "When ordinary people give a talk it is to tell you how to do it. However, when Julian Schwinger gives a talk, it is to tell you that only he can do it" Bernard Shaw : "There are two types of people, those who adjust to the world and those who do not. It is the later type that change the world." Einstein:"I would have been sorry for the dear Lord, because "the theory is correct" ", was what Einstein replied when a student asked him what he would have done if his predictions were refuted in the experiment that confirmed defection of light by the sun. I wanted movement and not a calm course of existence. I wanted excitment and danger and the chance to sacrifice myself for my love. I felt in myself a superabundance of energy which found no outlet in our quite lefe, ... Leo Tolstoy "I hope it will not shock experimental physicists too much if I say that we do not accept their observation unless they are confirmed by theory"----Sir Arthur Eddinton, 11 September 1933 Dirac: "Principle of Mathematical Beauty" we do not really know what the basic equations of physics are, but they have to have a great mathematical beauty. We must insist on that. On QED: " I might have thought that new ideas were correct, if they had not been so ugly" Freeman Dyson: " My mother used to say that life begins at fourty. That was her age when she had her first baby. I say , that the life begins at fifty-five, the age at which I published my first book". Dyson: " At its worst, work is slavery. At its best, work is a sustained and lifelong conversation". Feynman: " When we do scientific research, when we publish our results", we should try to think of every possible way we could be wrong". Poet Stanley Kunitz: " A poet cannot concern himself with being fair to the reader. Time will tell. All poems contain a degree of mystry, as poetary is a discovery of one's hidden self. .... Poetary is not concerned with communication; it has roots in magic, incantation, and spell-casting" Our greatest glory is not in never falling, but in getting up every time we do. ... Confucius I worship individuals for their highest possibilities as individuals and I loathe humanity for its failure to live up to these possibilities.--- Ayn Rand "There are men who fight one day and are good. There are men who fight one year and are better. There are some who fight many years and they are better still. But there are some that fight their whole lives, these are the ones that are indispensable", ....Berthold Brecht The artist has to transcend a subject, or he loses the battle. The subject wins.--- Fritz Scholder The first step to getting the things you want out of life is this: Decide what you want. Ben Stein I live in that solitude which is painful in youth, but delicious in the years of maturity. Albert Einstein Logic will get you from A to B. Imagination will take you everywhere. Albert Einstein Most people say that is it is the intellect which makes a great scientist. They are wrong: it is character. Albert Einstein I consider myself a natural optimist. I like the dark side of things.--- Fritz Scholder " You need a village, if only for the pleasure of leaving it. A village means that you are not alone, knowing that in the people, the tree, the earth, there is something that belongs to you, waiting for you when you are not there", --- Cesare Pavese The important thing in science is not so much to obtain new facts as to discover new ways of thinking about them.' -- Sir William Bragg "There isn't a clear task," Ed Witten told CNN. "If you are a researcher you are trying to figure out what the question is as well as what the answer is. You want to find the question that is sufficiently easy that you might be able to answer it, and sufficiently hard that the answer is interesting. You spend a lot of time thinking and you spend a lot of time floundering around." -- 6/30/05 "All our knowledge has its origins in our perceptions."--Da Vinci "The great moments, when the world cheers are not the moments that count. The ones that count are when it is just you and the people have stopped believing in you. That are the moments that define you." To be an artist, you don't have to compose music or paint or write books. It is just a way of living. "Things that are countable do not count and things that are not countable are the ones that count" "The job of a theoretical physicist is to make mistakes as fast as possible". -- John A. Wheeler " The best way to predict the future is to invent it" Alan Kay " Life is like riding a bicycle. To keep your balance you must keep moving" Albert Einstein " You can only go halfway into the deepest forest.. then you are coming out on the other side. ( Chinese proverb) " We do not see things as they are, we see them as we are." Anais Nin " I know God will not give me anything I cannot handle. I just wish He did not trust me so much", Mother Teresa " If you are ready, you say you are going home. If you are not ready, you say you are going to the office", Art Buchwald Whatever can be said, can be said clearly; and whereof one cannot speak , thereof one should keep silent: L. Wittgenstein Time is at once the most valuable and the most perishable of all our possessions The Universe speaks its truth to us in the language of LOVE, and its laws in the language of MATHEMATICS (December 9, 2001) (Prince, to Cinderella): "You are not tempted by grandeur and riches?" (Cinderella): "My grandeur is virtue, my wealth is love" -From "La Cenerentola", Act II, Scene 2 You give me space to belong to myself yet without separating me from your own life. May it all turn out to your happiness. -- Goethe "Through many years At great expense Journeying through many countries I went to see high mountains I went to see oceans Only I had not seen At my very doorstep The dew drop glistering On the ear of the corn" ------ Tagore Death is not putting out the lights. It is extinguishing the lamps because the dawn has come. Tagore "Not all those who wander are lost"---J.R.R. Tolkien "Assumptions are termites of relationships"---- Ben Stein Teachers open the doors, but you must enter yourself You are what you make yourself. You are not free because you do not free yourself The work is not done for the sake of application. It is done for the excitement of what is found. Feynman The prize is the pleasure of finding the things out, the kick in the discovery, the observation that other people use it- those are the real things, the honors are unreal to me. --Feynman I am sorry, after many years of trying to teach and trying all different methods, I really do not know how to do it. Feynman When the kids learn from one another, the class is not teacherless, it is teacherful Doubt is clearly a value in science. It is important to doubt and that the doubt is not a fearful thing, but a thing of great value. R.Feynman Fearlessness is the king of virtues Death is not putting out the lights. It is extinguishing the lamps because the dawn has come. Tagore To every man is given the key to the gates of heaven; the same key opens the gates of hell. There is no greater loss to a man than the loss of his self-respect. "You have got to be original, because if you are like everyone else, what do they need you for?" ----Bernadette Peters" ` generally gave herself very good advice,(though she very seldom followed it)' -- Lewis Carroll, Alice in Wonderland I don't mind you thinking slowly. I mind you writing papers faster than you think -- W. Pauli Knowledge is free. But you have to bring your own tin cans. Be the change you wish to see in the world -- Mohandas K. Gandhi To err is human. To really screw things up takes a human and a computer. -- Murphy's Law of Computing Grant me the serenity to accept the things I cannot change, the courage to change the things I can, and the wisdom to know the difference. -- R. Niebuhr Believe those who are seeking the truth; doubt those who find it.' -- A.Gide The greatest good you can do for another is not just to share your riches, but to reveal to him his own.' -- Benjamin Disraeli The day is committed to error and floundering; success and achievement are matters of long range.-- Goethe. The irony of life is that it is lived forward but understood backward. -- Soren Kierkegaard 'Happiness isn't good enough for me. I demand euphoria!'-- Calvin (+Hobbes) Lying is an indispensable part of making life tolerable. -- Bergan Evans Be regular and orderly in your life so that you may be violent and original in your work. -- Gustave Flaubert The mind is the limit. As long as mind can envision something, you can do it. Arnold Schwarzenegger Happiness hides in life's small details. If you are not looking, it becomes invisible. Stress is an ignorant state. It believes that everything is an emergency The key is the acceptance- not to flight ones disability but to learn to work within it, not to transcend it but to understand what one is capable of achieving within it; not to pretend but to build systems that allow you to excel without it
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[转载]Ordinary percolation with discontinuous transitions
Fangjinqin 2012-4-19 08:01
Ordinary percolation with discontinuous transitions nature communications | 3:787 | DOI: 10.1038/ncomms1774 | www.nature.com/naturecommunications http://www.nature.com/ncomms/journal/v3/n4/full/ncomms1774.html 2012 Macmillan Publishers Limited. All rights reserved. Received 25 Jul 2011 | Accepted 5 Mar 2012 | Published 17 Apr 2012 DOI: 10.1038/ncomms1774 Percolation on a one-dimensional lattice and fractals, such as the Sierpinski gasket, is typically considered to be trivial, because they percolate only at full bond density. By dressing up such lattices with small-world bonds, a novel percolation transition with explosive cluster growth can emerge at a non-trivial critical point. There, the usual order parameter, describing the probability of any node to be part of the largest cluster, jumps instantly to a finite value. Here we provide a simple example in the form of a small-world network consisting of a one-dimensional lattice which, when combined with a hierarchy of long-range bonds, reveals many features of this transition in a mathematically rigorous manner. 002-ncomms1774 .pdf
个人分类: 学术文章|2441 次阅读|0 个评论
[转载]英语中的连词概述
syfox 2012-3-8 21:39
一、概说 连词是一种虚词,用于连接单词、短语、从句或句子,在句子中不单独用作句子成分。连词按其性质可分为并列连词和从属连词。并列连词用于连接并列的单词、短语、从句或句子,如and, but, or, for等;从属连词主要引出名词性从句(主语从句、宾语从句、表语从句等)和状语从句(时间状语从句、条件状语从句、目的状语从句等),引出名词性从句的连词如that, whether等,引出状语从句的连词如when, because, since, if 等。 二、并列连词的用法 1. 表示转折关系的并列连词。这类连词主要有 but, yet 等。 如: Someone borrowed my pen, but I don’t remember who. 有人借了我的钢笔,但我不记得是谁了。 He said he was our friend, yet he wouldn’t help us. 他说他是我们的朋友,但却不肯帮助我们。 2. 表示因果关系的并列连词。这类连词主要有 for, so 等。 如: The child had a bad cough, so his mother took him to the doctor. 这孩子咳得很利害,所以他妈妈带他去看医生。 You are supposed to get rid of carelessness, for it often leads to serious errors. 你们一定要克服粗枝大叶,因为粗枝大叶常常引起严重的错误。 注意:for表示结果通常不能放句首,也不能单独使用。 3. 表示并列关系的并列连词。这类连词主要有 and , or , either…or , neither…nor , not only…but (also) , both…and , as well as 等。 如: He didn’t go and she didn’t go either. 他没去,她也没去。 The weather is mild today; it is neither hot nor cold. 今天天气很温暖,不冷也不热。 Both New York and London have traffic problems. 纽约和伦敦都存在交通问题。 It is important for you as well as for me. 这对你和对我都很重要。 People who are either under age or over age may not join the army. 年龄不到或者超龄的人都不得参军。 三、从属连词的用法 1. 引导时间状语从句的从属连词 (1) 表示“当…时候”或“每当”的时间连词。主要的 when, while, as, whenever。 如: Don’t talk while you’re eating. 吃饭时不要说话。 Vegetables are best when they are fresh. 蔬菜新鲜时最好吃。 He came just as I was leaving. 我正要走时他来了。 (2) 表示“在…之前(或之后)”的时间连词。主要的有before, after。 如: Try to finish your work before you leave. 离开前设法把工作做完。 After we have finished tea, we will sit on the grass. 喝完茶之后我们将坐在草地上。 (3) 表示“自从”或“直到”的时间连词。主要的有since, until, till。如: She’s been playing tennis since she was eight. 她从八岁起就打网球了。 Hold on until I fetch help. 坚持一下,等我找人来帮忙。 Never trouble trouble till trouble troubles you. (谚)不要无事惹事。 (4) 表示“一…就”的时间连词。主要的有as soon as, the moment, the minute, the second, the instant, immediately, directly, instantly, once, no sooner…than, hardly…when等。如: I’ll let you know as soon as I hear from her. 我一接她的信就通知你。 The moment I have finished I’ll give you a call. 我一干完就给你打电话。 I came immediately I heard the news. 我一听到这个消息,马上就来了。 Once you begin you must continue. 你一旦开始, 便不可停下来。 (5) 表示“上次”、“下次”、“每次”等的时间连词。主要的有every time(每次),each time(每次),(the) next time(下次),any time(随时),(the) last time(上次),the first time(第一次)。如: I’ll tell him about it (the) next time I see him. 我下一次见到他时,我就把这个情况告诉他。 We lose a few skin cells every time we wash our hands. 每当我们洗手的时候,我们都要损失一些皮肤细胞。 You can call me any time you want to. 你随时都可以给我打电话。 注意:every time, each time, any time前不用冠词,(the) next time, (the) last time中的冠词可以省略,而the first time中的冠词通常不能省略。 Practice today: Choose the best answer for each of the following sentences 1. —Oh, I failed again —Don’t lose heart. One more effort, ________ you will succeed. A. so that B. therefore C. however D. and 2. ________ a difficult situation, so you should send him a message and give him some advice. A. As he is in B. He is in C. Being in D. He being in 3. She said she would work it out herself, ________ ask me for help. A. and not to B. but not C. and prefer not D. rather than 答案与解析: 1. D. 考查“祈使句/名词+and+陈述句”句型。句意为:“再努力点,你就会成功的” 2. B. so(因此)是并列连词,引出一个表示结果的分句,前面应是一个表示原因的分句,而无需再用连词,排除A;C和D又不是句子,也错了。 3. D. 因为rather than是对称连词,意为“而不” 三、从属连词的用法 2. 引导条件状语从句的从属连词。这类连词主要有if, unless, as long as, in case 等。 如: Do you mind if I open the window? 我开窗你不介意吧? Don’t come unless I telephone. 除非我打电话,否则你别来。 As long as you’re happy,it doesn’t matter what you do. 只要你高兴,你做什么都没关系。 In case it rains they will stay at home. 万一下雨,他们就呆在家里。 注意:在条件状语从句中,通常要用一般现在时表示将来意义,而不能直接使用将来时态。不过,有时表示条件的 if之后可能用 will,但那不是将来时态, 而是表示意愿或委婉的请求(will为情态动词)。 如: If you will sit down for a few moments, I’ll tell the manager you’re here. 请稍坐, 我这就通知经理说您来了。 3. 引导目的状语从句的从属连词。主要的有 in order that, so that, in case, for fear等。 如: He raised his voice so that everyone could hear. 他提高了嗓音,以便每个人都能听见。 Take your umbrella (just) in case it rains. 带上雨伞,以防下雨。 She repeated the instructions slowly in order that he should understand. 她把那些指示慢慢重复了一遍好让他听明白。 4. 引导结果状语从句的从属连词。主要的有so that, so…that, such…that等。 如: I went to the lecture early so that I got a good seat. 我去听演讲去得很早, 所以找个好座位。 I had so many falls that I was black and blue all over. 我摔了许多跤,以致于全身都是青一块紫一块的。 He shut the window with such force that the glass broke. 他关窗子用力很大, 结果玻璃震破了。 5. 引导原因状语从句的从属连词。主要的有because, as, since, seeing (that), now (that), considering (that) 等。 如: He distrusted me because I was new. 他不信任我,因为我是新来的。 As you are sorry,I’ll forgive you. 既然你悔悟了,我就原谅你。 Since we’ve no money, we can’t buy it. 由于我们没钱,我们无法购买它。 Seeing that he’s ill he’s unlikely to come. 因为他病了,他大概不会来了。 Now that she has apologized, I am content. 既然她已经道了歉, 我也就满意了。 6. 引导让步状语从句的从属连词。主要的有although, though, even though, even if, while, however, whatever, whoever, whenever, wherever等。 如: Although they are twins, they look entirely different. 他们虽是孪生, 但是相貌却完全不同。 I like her even though she can be annoying. 尽管她有时很恼人, 但我还是喜欢她。 You won’t move that stone, however strong you are. 不管你力气多大, 也休想搬动那块石头。 Whatever we have achieved, we owe to your support. 我们取得的一切成就都归功于你们的支持。 Whoever you are, you can’t pass this way. 不管你是谁,你都不能从这里通过。 Whenever I see him I speak to him. 每当我见到他,我都和他讲话。 7. 引导方式状语从句的从属连词。主要的有as, as if, as though, the way等。 如: Why didn’t you catch the last bus as I told you to? 你怎么不听我的话赶乘末班公共汽车呢? He bent the iron bar as if it had been made of rubber. 他将铁棍折弯,仿佛那是用橡皮做成的。 Nobody else loves you the way(=as) I do. 没有人像我这样爱你。 8. 引导地点状语从句的从属连词。主要的有where, wherever, everywhere, anywhere等。 如: The church was built where there had once been a Roman temple. 这座教堂盖在一座罗马寺庙的旧址。 I’ll take you anywhere you like. 你想到哪儿我就带你到哪儿。 Everywhere I go,I find the same thing. 不管我走到哪里,我都发现同样情况。 9. 引导比较状语从句的从属连词。主要的有than和as…as。 如: She was now happier than she had ever been. 现在她比过去任何时候都快活。 I glanced at my watch. It was earlier than I thought. 我看了看表,时间比我想像的早。 He doesn’t work as hard as she does. 他工作不像她那样努力。 10. 引起名词从句的从属连词。主要有that, whether, if 等,它们用于引导主语从句、表语从句、宾语从句和同位语从句。其中that 不仅没不充当句子成分,而且没有词义,在句子中只起连接作用;而 if, whether 虽不充当句子成分,但有词义,即表示“是否”。 如: He replied that he was going by train. 他回答说他将坐火车去。 I wonder if it’s large enough. 我不知道它是否够大。 I worry about whether I hurt her feelings. 我为是否伤了她的感情而担心。 Practice today: Choose the best answer for each of the following sentences 1. ________ enough time, but I couldn’t do it better. A. I was given B. Given C. To be given D. Though I was given 2. —How can I wake up so early? —Set the alarm at 5 o’clock, ________ you’ll make it. A. but B. or C. and D. so 3. For a person with reading habits, a printed page contains not only words ________ ideas, thoughts and feelings. A. yet B. and C. or D. but 答案与解析: 1. A. 因为but是并列连词,后面是个句子,前面也一定是个句子,而不是一个分词短语或不定式短语,更不能再用连词though,所以排除B、C和D。 2. C. 考查“祈使句+and+陈述句”句型,意为“如果…就…”。虽然or也可用于此句型,但or是“否则、要不然”之意,如:Work hard, or you’ll fail. (努力学习,否则就会不及格。) 3. D. 因为not only…but (also)…是固定搭配 本文来源于:http://www.tooben.com/grammar/200909/4317.html 写作考试常用词汇--连词篇 1)表层次: first,firstly, to begin with, further, in the first place second,secondly, to start with, still, furthermore third,thirdly, what is more, last, last but not least also, and then, next, besides and equally important too moreover besides in addtion finally 2)表转折; by contrast although though yet at the same time but despitethe fact that even so in contrast nevertheless even though for all that notwithstanding on the contarary however in spite of on the other hand otherwise instead still regardless 3)表因果; therfore consequently because of for the reason thus hence due to owing to so accordingly thanks to on this account since as on that account in this way for as a result as a consequence 4)表让步: still nevertheless concession granted naturally in spite of all the same of course despite even so after all 5)表递近: furthermore moreover likewise what is more besides also not only...but also... too in addtion 6)表举例: for example for instance for one thing that is to illustrate as an illustration a case in point 7)表解释: as a matter of fact frankly speaking in this case namely in other words 8)表总结: in summary in a word thus as has been said in brief in conclusion altogether in other words to conclude in fact finally in simpler terms indeed in short in particular that is in other words of course on the whole to put it differently namely in all therefore to summarize
个人分类: ENG|2537 次阅读|0 个评论
[转载]How Great Was 2012!
whyhoo 2012-1-1 11:14
Happy New Year! And I really mean it! Because 2012 is going to be the best year ever! Seriously! I know, because I’m a person from the future! And here in the future, guess what? It’s 2112 and we’re celebrating the centennial of 2012! That’s how amazing 2012 is going to be! You 2012ers are so lucky! Where to start? Politics? Your 2012 presidential election has gone down in history for all the right reasons! Our students still memorize Newt Gingrich’s famous “#EpicObamaFails” tweet, revered by all for its eloquence and erudition! Same thing with Mitt Romney’s South Carolina 20-Second Robocall Address! Because unlike most 21st-century elections, your 2012 campaign was fought on a battleground of principled insinuation, thoughtful pandering and only occasional pistol-whippings! Also, your 2012 candidates refused to make a criminal issue of one another’s religion! No aspirant to higher office was stoned, doused or burned at the stake! At least from a major party! But that’s not all! We in the future remember 2012 as the year the American economy finally got back on track! The same can-do spirit that built the transcontinental railroad and designed the computer chip managed to slap together a barter system that remains the envy of the organized world! Plus, whole new classes of jobs were created in 2012! Certified public organ donor! Accredited squatter! 7-Eleven clerk practitioner! The jobs that defined the 21st century! And who can forget the London Olympics? Truly, yours was an era when athletes still hewed to noble ideals of sportsmanship and human ideals of DNA! A full 57 percent of 2012’s medals were not voided by subsequent drug or chromosome testing — a record that has stood for 100 years and counting! You should be proud, 2012! Plus, you still had a London! The arts! Oh my gosh, the arts! How we in the 22nd century envy you the chance to see “The Real Housewives of Orange County,” Season 7, for the very first time! No spoilers here! But more to the point, how we envy you the chance to see it, period! Thank God for the oral tradition! And meanwhile, enjoy your electricity, 2012! And speaking of periods — and semicolons — 2012 was the year we finally got rid of them! Yay, 2012! Even the weather in 2012 was memorably awesome! Sweden enjoyed its last hurricane-free summer! They still talk about it in what’s left of Stockholm! There’s so much more I want to tell you! But I have to get back to the New York of 2112 so I can help the Lexington Avenue Tribe fend off the giant undead flesh-eating mayor-for-life Michael Bloomberg! What? I didn’t say anything about the giant undead flesh-eating mayor-for-life Bloomberg? He’s not so bad, once you get used to him! And his appetite! You’ll see! Soon! We just leave him offerings on his side of the Great Fifth Avenue Wall! That’s what we farm children for, when we have dry land! Anyway, I swear: you’ll love 2012! I mean, with a year like that — and I didn’t even mention how all the radiation from Korean War II was successfully limited to just the Northern and Eastern Hemispheres! — how could you not? 原文见 http://www.nytimes.com/2012/01/01/opinion/sunday/how-great-was-2012.html?_r=1
个人分类: 社会|1093 次阅读|0 个评论
为何度符合幂函数分布的网络被称为无标度网络
cosismine 2011-12-30 23:21
不好意思,还号称做过一点点网络研究的,结果到今天才知道原因: a normal distribution, which curves sharply on a log-log plot, such that the probability of a node having a degree greater than a certain “cutoff” value is effectively zero. A cutoff therefore implies a characteristic scale for the degree distribution of the network, and because a power law degree distribution lacks any such cutoff value, it is often called a scale-free distribution. A Study of NK Landscapes’ Basins and Local Optima Networks A second important aspect in the study of networks has been the realization that in many real-world networks, the distribution of the number of neighbours (the degree distribution) is typically right-skewed with a "heavy tail", meaning that most of the nodes have less-than-average degree whilst a small fractions of hubs have a large number of connections. These qualitative description can be described mathematically by a power-law , which has the asymptotic form p(k)  k− . This means that the probability of a randomly chosen point having a degree k decays like a power of k, where the exponent (typically in the range ) determines the rate of decay. A distinguishing feature of power-law distributions is that when plotted on a double logarithmic scale, a powerlaw appears as a straight line with negative slope . This behavior contrasts with a normal distribution which would curve sharply on a log-log plot, such that the probability of a node having a degree greater than a certain "cutoff" value is nearly zero. The mean would then trivially represent a characteristic scale for the network degree distribution. Since networks with power-low degree distribution lack any such cutoff value, at least in theory, they are often called scale-free networks . Examples of such scale-free networks are the world-wide-web, the internet, scientific collaboration and citation networks, and biochemical networks. 在网络研究第二个重要方面是在很多现实世界的网络结构中,节点邻居数量的分布通常是有着厚重尾巴的右倾斜分布,这意味着大多数节点的度少于平均数,而很少一部分的节点有很大的节点。这种数量描述可以用数学中的幂律来描述,这种幂律有着渐近线是。。。这意味着随机选择一个度为k的节点的概率随着幂k而减少,指数通常在2-3之间,指数大小决定着衰减的速度。幂律分布的典型特征是如果把这些点房子双Log坐标轴上的话,幂律分布就是一条斜率为负数的直线。这种性质和其整台分布相对。正态分布要是画在双LOG坐标轴上的话,会急剧弯曲。这种正态分布,选择一个比一个截止值更大的度的概率近乎为零。平均值就明显地代表着网络度分布的一个标度。而幂律分布的网络没有这样一个截止值,至少在理论上缺乏这么一个截止值。符合幂律分布的网络就要无标度网络。无标度网络有万维网,internet, 科学合作网和引文网,,生物化学网等。
3275 次阅读|0 个评论
[转载]less pesticide, more pest-eating spiders and less pest
weicunzheng 2011-10-22 12:09
Agricultural ecology Organic farms flourish in the rain Japan produce the highest quality organic food in the world,the use less pesticide and following more pest-eat to control pest. Scientist from university of Cambridge study their efforts on organic farms and across a large scale,and find where (climate areas) will benefit most from organic farms. we might spent some funds to see what happens when increasing more nematode pesticide used in china, such as Shouguang vegetation greenhouse. this is not a difficult work, but might have good results. Organic farming is touted as a way to conserve wildlife while still producing food, but some organic farms are more biodiverse than others. This may be because of regional climatic differences. Tatsuya Amano, now at the University of Cambridge, UK, and his colleagues examined the influence of topography and climate on the diversity of 230 rice fields in Japan with varying levels of pesticide use. The researchers measured the abundance of pest-eating Tetragnatha spiders as a proxy for biodiversity. They modelled the data and found that fields with reduced pesticide use had more spiders, with the greatest abundance in cold or wet areas. The authors also used their model to predict which regions of Japan might benefit most from organic farming through increasing Tetragnatha numbers. Ecol. Lett. 10.1111/j.1461-0248.2011.01699.x ( 2011 )
2068 次阅读|0 个评论
To mentor or not to mentor...That's the question
热度 2 zuojun 2011-10-18 10:50
Right now, I am a sandwich, because my parents still try to "mentor" me while I try to "mentor" my son. Even before my son turned 18, he told me not to "lecture" him about dating, since "it's all old school stuff." I couldn't agree more, but whenever I had a chance I would sneak in a sentence or two about "how to." More than a year ago, I asked a young woman whether or not I could mentor her. That turned out to be more than I asked for, because she and I are friends now. I help her sometimes, and she helps me sometimes. This week, I was asked by a Ph.D. candidate to have a chat. I gladly said "sure." We had a nice lunch today, and agreed to meet again. Because the conversation was about first years living in the US, it brought back a lot of memories of my own experience, which I almost forgot (or too busy to think about it anymore). Maybe it's time to go back, and re-exam what I did right and what I did wrong? I hope being a mentor does not mean I am “successful” enough to guide a young person. I clearly sense the generation gap. Even so, it might be fun to “talk stories” (a very local expression in Hawaii). I will only go as far as “this is what I did or didn’t do,” but I will never say “You should do this and that.” Mom, Dad, do you read my Blog?
2237 次阅读|4 个评论
[转载]Address at Stanford University (2005) Steve Jobs
pathologysmu 2011-10-7 16:06
Death is the destination we all share, no one has ever escaped it. And that is as it should be because death is very likely the single best invention of life. Your time is limited, so don't waste it living someone else's life. Don't be trapped by dogma — which is living with the results of other people's thinking. Don't let the noise of others' opinions drown out your own inner voice. And most important, have the courage to follow your heart and intuition. They somehow already know what you truly want to become. Everything else is secondary. Remembering that I'll be dead soon is the most important tool I've ever encountered to help me make the big choices in life. Because almost everything — all external expectations, all pride, all fear of embarrassment or failure — these things just fall away in the face of death, leaving only what is truly important. Remembering that you are going to die is the best way I know to avoid the trap of thinking you have something to lose. You are already naked. There is no reason not to follow your heart. No one wants to die. Even people who wanna go to heaven don't wanna die to get there.
0 个评论
linux下的软链接上带红圈斜杠,Qt version 4.6,GLIBCXX_3.4.9
piaoxue001 2011-9-4 11:16
在同一个文件夹下,不用写链接路径,竟然软链接上红圈斜杠消失了。真奇怪。 linux下无法读取软链接的文件的问题,这很可能是你所链接的文件,所以解决的办法可以是:对软链接所链接的原始文件使用:chmod 777 文件名 注:用chmod,用法为chmod 权限代码 文件名 权限代码主要为三位,每一位都遵循:r = 4 w = 2 x = 1 - = 0 其中r为读,w为写,x为执行,若有多个属性,则相加。如6表示有读写权限,7表示有读写执行权限。而三位的顺序是:所有者、组群、其他人 问题:Using bundled Qt version 4.6 because no system Qt version was found。 解决方法:系统没有安装Qt 4.6 以上版本,先安QT4 问题:/usr/lib/libstdc++.so.6: version `GLIBCXX_3.4.9' not found 解决方法: 终端输入: strings /usr/lib/libstdc++.so.6 | grep GLIBC 返回结果没有 `GLIBCXX_3.4.9', 接着输入: ls-l /usr/lib/libstdc++.so.6 lrwxrwxrwx 1 root root 28 05-03 13:15 /usr/lib/libstdc++.so.6 - /usr/lib/libstdc++.so.6.0.8 这里libstdc++.so.6是个软链接,它链接到libstdc++.so.6.0.8。而libstdc++.so.6.0.8没有 `GLIBCXX_3.4.9',这里需要 libstdc++.so.6.0.10。那么从网上下载libstdc++.so.6.0.10文件,放到/usr/lib64目录下。然后我们重新做libstdc++.so.6.软链接:1.删除libstdc++.so.6,终端输入:rm -rf /usr/lib/libstdc++.so.6,回车执行 2..重做libstdc++.so.6软链接,终端输入:ln -s /usr/lib64/libstdc++.so.6.0.10 /usr/lib64/libstdc++.so.6 或者ln -s libstdc++.so.6.0.10 libstdc++.so.6
个人分类: linux|4778 次阅读|0 个评论
[转载]toy"pig"
AlinaDong 2011-6-19 13:51
Mother gave me a toy"pig" on my tenth birthday. It was very lovely. The pig wears a blue dress.Her face is pink.Her eyes are round and black. Her mouth is small and red. Her two ears are very big. They seem like two fans. She looks very happy, because she always smiles. So I think she must be a happy "pig"
个人分类: English|1047 次阅读|0 个评论
Determination and Characterization of 20th Century Sea
ppthelion 2011-6-18 23:14
个人分类: Study_little_thing|0 个评论

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