Three days of mathematical modeling competition, will happen to flush out two big thing classes. 数学建模大赛的三天,正好会冲掉两节大物课。 Although is receives orders to ask for leave, but considering that the first class asks for leave is not quite good, Lu Zhou decides to send to the leave application personally, did not trouble the class leader to do for somebody. 虽然是奉旨请假,但考虑到第一堂课就请假不太好,陆舟决定还是亲自把假条送去,就不麻烦班长代劳了。 Looked the class schedule information that the school administration office gives, the big thing teacher name was Li Rongen, was the qualifications very high senior professor. Asked the telephone number after school group, Lu Zhou first telephones, confirmed that the teacher in the office, then on takes the leave application in the past. 看教务处给出的课表信息,大物老师名字叫李荣恩,是个资历挺高的老教授。在学校群里问到电话号码之后,陆舟先打了个电话过去,确认老师在办公室,然后才上拿着假条过去。 After knocking on a door, Lu Zhou walks, placed on the leave application the desk, explained own purpose in coming. 敲了门后,陆舟走进去,将假条放在了办公桌上,说明了自己的来意。 „Asks for leave?” Read a leave application, Professor Li took off the presbyopic glasses, raised the head to smile, „was your name, Lu Zhou?” “请假？”看了眼假条,李教授摘下老花镜,抬起头笑了笑,“你的名字,是陆舟吧？” „Yes.” Lu Zhou nods. “是的。”陆舟点头。 Professor Li smiles, said: „That line, I test your two problems, if you solve together, I approve your leave application.” 李教授笑了笑,说:“那行,我考你两道题,如果你解出来一道,我就批你的假条。” This operation?! 还有这种操作？！ Lu Zhou was scared. 陆舟傻眼了。 „What's wrong? Feared?” Li Rongen asked with a smile. “怎么？怕了？”李荣恩笑着问道。 „No,” Lu Zhou calms down, shakes the head saying that „teacher you sets the topic.” “没有,”陆舟定了定神,摇头道,“老师您出题吧。” „The first problem, takes away,” flings on a A4 paper Lu Zhou, Li Rongen smilingly looks at Lu Zhou, the old god was saying in the place, „can write many to write many, I must look at the process.” “第一道题,拿去吧,”将一张A4纸甩到陆舟手上,李荣恩笑眯眯地看着陆舟,老神在在地说道,“能写多少写多少,我要看过程。” Even did the topic prepare?! 连题目都准备好了？！ Lu Zhou always felt that this fellow is deliberate, how otherwise should explain why this problem has printed on the A4 paper? 陆舟总感觉这家伙是有预谋的,否则该怎么解释,为什么这道题都已经打印在了A4纸上？ Even if guessed correctly a point, Lu Zhou has not said anything, takes up the A4 paper to start to read the topic. 然而即便猜到了一点,陆舟也没说什么,拿起A4纸开始读题。 【 In the nuclear-powered submarine the half-life of U238 nuclear is the 4.5 × 10 ^ 9 year, in the decay has 0.7% probability to become the U234 nuclear, simultaneously emits an energetic photon, in these photons 93% by submarine steel plate absorption. In 1981, the former Soviet Union serial number U137 nuclear-powered submarine shone through outside the energetic photon to ship( processing away the nuclear source for punctual) the detection device of 1.5 m place to be obtained. The instrument normal incidence area is 22 cm ^ 2, the efficiency is 0.25%( every 400 incident photons may have a pulse signal), obtains 125 signals each hour. 【核潜艇中U238核的半衰期为4.5×10^9年,衰变中有0.7%的概率成为U234核,同时放出一个高能光子,这些光子中的93%被潜艇钢板吸收。1981年,前苏联编号U137的核潜艇透射到艇外的高能光子被距核源(处理为点状)1.5m处的探测仪测得。仪器正入射面积为22cm^2,效率为0.25%(每400个入射光子可产生一个脉冲讯号),每小时测得125个讯号。 ① sought the mean lifetimes of U238 nuclear ( ln2 = 0.693 ). ①求U238核的平均寿命(ln2=0.693)。 ② asked in this/should nuclear-powered submarine the U238 quality( unit kg, took 2 figures) ②求该核潜艇中U238的质量(单位kg,取二位数) 】 】 Reads off the topic, in the Lu Zhou heart sighs in a soft voice. 读完题目,陆舟心中轻声一叹。 Worthily by the former years seniors seal as „thing institute four devils” Professor Li, acts is this topic? 不愧是被往届前辈们封为“物院四恶魔”的李教授,一出手就是这种题目吗？ The words saying, next has the largest thing class on Monday, tests itself with the nuclear physics knowledge of this hitting ultra outline edge ball directly, really doesn't have the issue? 话说,下个周一才开第一堂大物课,直接拿这种打超纲擦边球的核物理知识考自己,真的没问题？ „Or finds a place to sit calculates?” “要不找个地方坐着算？” „Does not use, in this.” “不用了,就在这吧。” Received Professor Li along with handing over the pen and scratch paper, Lu Zhou stood by the desk, wrinkled the brow, thought deeply about the moment. 接过了李教授随手递来的笔和草稿纸,陆舟站在办公桌旁边,皱紧眉头,思索了片刻。 The physics truly is not the domain that he excels. 物理确实不是他擅长的领域。 However, after a summer vacation exploding liver learn/study, stood he here to be impregnable! 不过,经过了一个暑假的爆肝式学习,站在这里的他无懈可击！ Probably five minutes pass by, a Lu Zhou brow loosen, pen tip earth movement. 大概五分钟过去,陆舟眉头一松,笔尖唰唰唰地动了。 【 The decay rule of radionuclide: N = N 0 e ^(- λt) 【放射性核素的衰变规律:N=N0e^(-λt) The relations of the decay constant and half-life are: N0 / 2 = N 0 e ^(- λT1 / 2), may result in T1 / 2 = ln 2 / λ from this 衰变常数与半衰期的关系为:N0/2=N0e^(-λT1/2),由此可得T1/2=ln2/λ 】 】 Writes down these two lines of mathematical formulas, the Lu Zhou vision glitters slightly. 写下这两行算式,陆舟目光微微闪烁。 He had successfully become the high number issue the physical problem. 他已经成功将物理问题变成了高数问题。 Then, defeats one by one! 接下来,就是逐个击破！ First first asked! 首先第一问！ The pen tip walks randomly on the A4 paper fast. 笔尖在A4纸上飞快游走。 【 ( 1 ) radionuclide mean lifetime t = ∫ λ Ntdt / N 0 =...... = 1.1443 T 1 / 2 【放射性核素的平均寿命t=∫λNtdt/N0=……=1.1443T1/2 The substitution data may result, t = 6.49 * 10 ^ 9 year. 代入数据可得,t=6.49*10^9年。 】 】 Swept eye that A4 paper, the Professor Li Rongen eyebrow selected, in the eye appeared wipes the interesting look. 扫了眼那张A4纸,李荣恩教授眉毛挑了下,眼中浮现一抹有趣的神色。 Has not noticed the change of Professor Li expression, Lu Zhou of the attention high degree of concentration on paper, starts to continue under the explanation to ask. 并没有注意到李教授表情的变化,注意力高度集中在纸上的陆舟,开始继续解答下一问。 【 Is done the information to be solvable by the topic, fades to turn into the energetic photon quantity that U234 has in the dt time is n0 = n 0 λ Ndt 【由题干信息可解得,在dt时间衰变成U234所产生的高能光子数量为-dN・n0=n0λNdt Supposes the photon again across the efficiency of steel plate is n1, figures out the dt time internal breaks to cross the photon number of steel plate is dN1 = n 0 λ Ndt n1 再设光子穿过钢板的效率为n1,算出dt时间内穿过钢板的光子数为dN1=n0λNdt・n1 Enters the photon number of detector...... 进入探测器的光子数…… Signal number that in the detector has...... 探测器中产生的信号数…… Is considered as the U238 number in submarine, and from this calculates the quantity of U238 nuclear. 算得潜艇中的U238数量,并且由此计算U238核的数量。 】 】 Lu Zhou substitutes all data, figures out in the submarine U238 nuclear quantity N = 7.456 * 10 ^ 25. 陆舟代入所有数据,算出潜艇中U238核的数量N=7.456*10^25。 However in he is preparing to lead into M = N * 238 u N, finally completes to the spring water of enemy side strikes, Professor Li Rongen suddenly opens the mouth. 然而就在他正准备将N带入M=N*238u中,对敌方的泉水完成最后一击的时候,李荣恩教授忽然开口了。 „Ok, calculates that you crossed.” “好了,算你过了。” Lu Zhou:??? 陆舟:？？？ He is not glad immediately. 他顿时就不乐意了。 What is calculates that I did cross? 什么叫算我过了？ I calculate that here, you cannot wait for me to calculate is speaking! 我都算到这里了,你就不能等我算完在说话吗！ „Professor, I have not calculated......” “教授,我还没算完……” „Is calculated by you this step, looked for Junior High School to calculate since birth,” Li Rongen said with a smile, „you want to calculate even ends, as you like then.” “都被你算到了这一步,找个初中生来都能算出来,”李荣恩笑着说道,“你想算就算完吧,随你便。” Presented the topic the atmosphere to destroy up, Lu Zhou speechless. 做题的气氛都破坏光了,陆舟一阵无语。 Cannot support the entanglement of obsession, he wrote down the result in the rear. 架不住强迫症的纠缠,他还是在最后面写下了结果。 Answer M = 29.634 kg, taking two is about 30 kg 答案M=29.634kg,取两位约为30kg Step right, the correctness of result no suspense. 步骤没错,结果毫无悬念的正确。 Lu Zhou marked the successful conclusion to this problem. 陆舟给这道题画上了圆满的句号。 „To listen to the second problem?” Li Rongen said with a smile. “想不想听下第二道题？”李荣恩笑着说道。 Although Lu Zhou wants saying that „does not think”, but thinks that the professor has not approved own leave application, helpless said: „You said.” 虽然陆舟想说“不想”,但想到教授还没批自己的假条,不由无奈道:“您说吧。” Li Rongen smiles , to continue: „Do not be anxious, the second problem is very simple, you said with me, agrees of this second law of thermodynamics indicates.” 李荣恩笑了笑,继续说:“别紧张,第二道题很简单,你就和我说说,这热力学第二定律的肯南表述吧。” Hears this issue, Lu Zhou relaxes. 听到这问题,陆舟松了口气。 Originally he also thinks that this professor's second topic, will make a debut the difficult problem that he cannot write to strike him, warned that he should not be arrogant and complacent anything, the result has not thought that this Professor Li simply has not played a card according to the repertoire, let off him simply. 本来他还以为这教授第二题,会出道他根本写不出来的难题敲打敲打他,告诫他不要骄傲自满什么的,结果没想到这李教授根本没按套路出牌,就这么简单的放过他了。 Generally speaking, the second law of thermodynamics mainly has two indications, one type is the famous kelvin expression, another type is Clausius in the indication that 1850 in the paper mentioned. 一般来说,热力学第二定律主要存在两种表述,一种是著名的开尔文表述,另一种则是克劳修斯在1850年论文中提到的表述。 Indicates as for agrees, is the one novel indication law of the near future having. 至于肯南表述,是近期产生的一种较新颖的表述法。 Looks at the teaching material time earnest, will not leave out. 看教材的时候认真点,就不会漏掉。 Namely- 即- „Has to assign the energy regarding one, the material composition, the system of parameter, has such a stable equilibrium state: Other conditions can always achieve it through the reversible process.” Probably the back text is the same, Lu Zhou repeated this indication. “对于一个有给定能量,物质组成,参数的系统,存在这样一个稳定的平衡态:其他状态总可以通过可逆过程达到之。”像是背课文一样,陆舟复述了这段表述。 „Good.” The Li Rongen applause nods. “不错。”李荣恩赞许地点了点头。 On the teaching material of non- physical speciality use, will not mention the indication of this quite front in the main text, but will put on such a in the appendix. Generally does not have the interest student to Physics, will graduate not to turn there. 非物理专业使用的教材上,并不会在正文中提到这种较为前沿的表述,不过还是会在附录中提上那么一句。一般对物理学没有兴趣的学生,毕业了都不会翻到那里。 If Lu Zhou grasps this deserted knowledge node so clear, showed sufficiently he has had a thorough understanding has put in order this «University Physics» teaching material. 如果陆舟连这个冷僻的知识点都掌握的如此清楚,足以证明他已经吃透了整本《大学物理》教材了。 After this shallow deep inspection, Li Rongen can confirm now, oneself this faces the curriculum of undergraduate non- physics student, truly there is no thing to teach him. 经过这一浅一深的考察,李荣恩现在可以确认,自己这面向本科非物理专业学生的课程,确实没什么东西可教他的了。 It seems like old Tang has not truly boasted, this boy is a talent! 看来老唐确实没吹牛,这小子是个人才啊！ Actually said that anything answered to respond approved the false, that was the joke that and young people played. 其实说什么答题答对了才批假,那都是和年轻人开的玩笑。 Starting from yesterday, the leave application of mathematics modeling contest he approved dozens to open, can miss such a leave application? 从昨天开始,数学建模竞赛的假条他都批了几十张了,会差这么一张假条？ Even if Lu Zhou cannot answer, he most still teased two, finally can approve. 就算陆舟答不出来,他最多也就调侃两句,最后还是会批的。 Signs in the leave application, Li Rongen turns out the roll-call itself/Ben in drawer, drew two checks above, while said with the tone of elder. 在假条上签了字,李荣恩翻出抽屉里的点名本,一边在上面画了两个勾,一边用长者的口吻说道。 „Lu Zhou.” “陆舟啊。” „What's wrong?” “怎么了？” „Plans to read the research?” “有没有计划读研？” Lu Zhou thinks, said with the tone indefinitely: „Has.” 陆舟想了想,用不确定地口吻说:“有吧。” The future matter who says good? 未来的事谁说的好呢？ However the Professor Li intuition, apparently does not have old Tang is so keen, simply has not listened to the uncertainty in Lu Zhou tone, is the applause nods on the contrary, then continues to say. 不过李教授的直觉,显然没有老唐那么敏锐,根本没有听出来陆舟语气中的不确定,反倒是赞许地点了点头,然后继续说道。 „The physics department of our Nanjing University, in the national university is also the top level, the modest point, even Peking University and we post for first. However if makes concrete to the research direction, superconductivity Physics and strongly correlated electron system, and coherence physics and design of material these domains, they are inferior to us. If you are interested in the physics, exams for postgraduate schools time can look for me, our carbon nanotube laboratory, needed is the world of mathematics notch talent.” “咱们南大的物理系,在全国高校中也算是顶尖的水准,谦虚点来讲,就算北大和咱并列第一吧。不过若是具体到研究方向,超导物理学和强关联电子系统、以及凝聚态物理和材料设计这些领域,他们都不如我们。如果你对物理感兴趣,考研的时候可以来找我,我们碳纳米管实验室,需要的就是数学领域的顶尖人才。” This is...... 这是…… Is suggesting me, later reported his graduate student? 在暗示我,以后报他的研究生吗？ Lu Zhou does not know whether to laugh or cry at heart, he now just big two, to exams for postgraduate schools. 陆舟心里哭笑不得,他现在才刚刚大二,离考研还远着呢。 But how regardless to say, this is the good intention of teacher. 但无论怎么说,这都是老师的好意。 Lu Zhou sincere saying: „Thanks the teacher.” 陆舟诚恳的说道:“谢谢老师。” Li Rongen nods with a smile: „Ok, takes the leave application. This competition has the opportunity to participate much, if you politics. Does not govern good, under can pay attention guarantees the research the opportunity. You will arrive next year in a big way three, asks me, asked your Teacher Tang, Ok.” 李荣恩笑着点了点头:“行了,拿着假条去吧。这种比赛有机会多参加参加,你要是政.治不行,可以留意下保研的机会。或者等明年你到了大三,来问我,问你唐老师,都可以。” Lu Zhou expressed gratitude with a smile, has not spoken again, takes this hard-won leave application to say goodbye rapidly. 陆舟笑着表示了感谢,没再多说话,拿着这份来之不易的假条迅速告辞。