12 习题答案

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大学物理第12章习题解答

第十二章习题答案12.1 选择题(1) 对位移电流,下述四种说法哪个正确( )A. 位移电流是由线性变化磁场产生的.B. 位移电流是指变化的电场.C. 位移电流的热效应服从焦耳-楞次定律.D. 位移电流的磁效应不服从安培环路定理.(2) 空气中有一无限长金属薄壁圆筒,在表面上沿圆周方向均匀地流着一层随时间变化的面电流i (t),则( )A. 圆筒内均匀地分布着变化磁场和变化电场.B. 任意时刻通过圆筒内假象的任一球面的磁通量和电通量均为零.C. 沿圆筒内任意闭合环路上电场强度的环流为零.D. 沿圆筒外任意闭合环路上磁感应强度的环流不为零.(3) 如图12.1(3)所示为一充电后的平行板电容器,A 板带正电,B 板带负电,开关K 合上时,A ､B 板间位移电流的方向为(按图上所标x 轴正方向回答)A ．x 轴正向B ．x 轴负向C ．x 轴正向或负向D ．不确定题12.1(3)图答案：(1) B, (2)B, (3)B.12.2 填空题1． S t B l E L S d d ⋅⋅⎰⎰∂∂-= ① 0d =⎰⋅S B S ②S t D I l H S L i d d ⋅⋅⎰⎰∑∂∂+= ③试判断下列结论是否包含于或等效于哪一个麦克斯韦方程式的.将确定的方程式用代号填在相应结论的空白处.(1) 变化的电场一定伴随有磁场__________________．(2) 变化的磁场一定伴随有电场__________________．(3) 磁感线是无头无尾的闭合曲线________________．2．平行板电容器的电容C 为20 μF ,两板上的电压变化率V/s 105.1d d 5⨯=tU ,则该平行板电容器中的位移电流为____________．3．一空气平行板电容器的两极板是半径为R 的圆形导体片,在充电时,板间电场强度的变化率为tE d d .若略去边缘效应,则两板间的位移电流为______________．答案: (1)③①②, (2)3 A, (3)20R dt dE πε12.3 圆柱形电容器内､外导体截面半径分别为R 1和R 2(R 1 <R 2) ,中间充满介电常数为ε的电介质.当两极板间的电压变化率为k tU =d d 时(k 为常数),求介质内距圆柱轴线为r 处的位移电流密度.解：设圆柱形电容器内、外导体单位长度分别带有±λ的电量，由高斯定理⎰==⋅l rl D S d D λπ2 内、外导体间的电位移矢量r D πλ2=；电场强度rD E πελε2== 内、外导体间的电势差：12ln 2221R R dr r l d E U R R πελπελ==⋅=⎰⎰ ∴ 12ln 2R R U πελ= 电位移矢量：R R e R R r U e r D 12ln 2επλ== ∴ 介质内距离圆柱轴线为r 处的位移电流密度R R d e R R r k e dt dU R R r t D j 1212ln ln εε==∂∂= 12.4 (1)试证明平行板电容器两极板之间的位移电流可写为tU C I d d d =,其中C 是电容器的电容,U 是两极板间的电势差.(2)要在1.0 μF 的电容器内产生1.0 A 的位移电流,加在电容器上的电压变化率应是多大?解：(1) 平行板电容器：d U E D εε== 电容：d SC ε= 由位移电流定义：()dt dU C CU dt d d U S dt d dt dD SS j I d d ==⎪⎭⎫ ⎝⎛===ε 得证。

工程经济学课后习题答案第二版答案

35.229.4
NP(BV )36 5102(0P/0A,IRB,R 5)0 (P/A,IRB,R 5)3.0417 i11% 5 ,NP1V36 5102 030 .352 327.624 i22% 0 ,NP2V36 5102 020 .990 66.128 IRR1% 5 37.624 (2% 01% 5 )1.92% 91% 5
第四章习题
4.某方案的现金流量如习题表4－1所示，基准收益率为15％，试计算(1)投资回收期（静态Pt和动态Pt′），(2)净现值NPV，(3)内部收益率IRR。
450 550 650 700
800
01
2
3
4
5
-2000
（3）内部收益率 N P 2V 0 4( 0 P 5 /F ,0 I 0 R ,1 ) 5 R ( P 5 /F ,I 0 R ,2 ) 6 R ( P 5 /F ,I 0 R ,3 ) R 7( P 0 /F ,I 0 R ,4 ) 8 R ( P 0 /F ,I 0 R ,5 ) 0 R
10
01
234
56
120
解: NPV 125 0(0 P/A,IR,6)R1(0 P/F,IR,6)R0 i13% 0 ,NP 1V 125 0 02.641 3 00.20 712.4 22 i24% 0 ,NP 2V 125 0 02.161 8 00.13 21 8.0 27 IRR i1NP N 1V N P 1 V P 2(iV 2i1)3% 01.4 21 2 .4 212 .0 2 7(4% 03% 0)3.5 8% 1
i
1.5 (F / A,10%1, 0) 15.9374 当i2 12%, (F / A,12%1, 0) 17.5487

直流稳压电源的习题答案

第12章直流稳压电源的习题答案判断下列说法是否正确，用“√”或者“×”表示判断结果并填入空内。

（1）直流电源是一种将正弦信号转换为直流信号的波形变换电路。

（）（2）直流电源是一种能量转换电路，它将交流能量转换为直流能量。

（）（3）在变压器副边电压和负载电阻相同的情况下，桥式整流电路的输出电流是半波整流电路输出电流的2倍。

（）因此，它们的整流管的平均电流比值为2:1。

（）（4）若V 2为电源变压器副边电压的有效值，则半波整流电容滤波电路和全波整流电容滤波电路在空载时的输出电压均为22V 。

（）（5）当输入电压V I 和负载电流I L 变化时，稳压电路的输出电压是绝对不变的。

（）（6）一般情况下，开关型稳压电路比线性稳压电路效率高。

（）（7）整流电路可将正弦电压变为脉动的直流电压。

（）（8）电容滤波电路适用于小负载电流，而电感滤波电路适用于大负载电流。

（）（9）在单相桥式整流电容滤波电路中，若有一只整流管断开，输出电压平均值变为原来的一半。

（）（10）对于理想的稳压电路，△V O /△V I ＝0，R o ＝0。

（）（11）线性直流电源中的调整管工作在放大状态，开关型直流电源中的调整管工作在开关状态。

（）（12）因为串联型稳压电路中引入了深度负反馈，因此也可能产生自激振荡。

（）（13）在稳压管稳压电路中，稳压管的最大稳定电流必须大于最大负载电流；（）而且，其最大稳定电流与最小稳定电流之差应大于负载电流的变化范围。

（）解：（1） × （2）√ （3）√；× （4）√ （5）× （6）√ （7）√ （8）√ （9） × （10）√ （11）√ （12） √（13）×；√ 选择填空题1.在题12.2.1图所示的桥式整流电容滤波电路中，已知变压器副边电压有效值V 2为10V ，2/3T RC （T 为电网电压的周期）。

机械设计基础课后习题答案第三版高等教育出版社课后答案(1-18章全)

机械设计基础课后习题答案第三版高等教育出版社课后答案(1-18章全)机械设计基础课后习题答案第三版高等教育出版社目录第 1 章机械设计概述??????????????????????????????????????????????????????????????????? ????????????????????????????????? 1第 2 章摩擦、磨损及润滑概述??????????????????????????????????????????????????????????????????? ????????????????? 3第 3 章平面机构的结构分析??????????????????????????????????????????????????????????????????? ????????????????????? 12第 4 章平面连杆机构??????????????????????????????????????????????????????????????????? ????????????????????????????????? 16第 5 章凸轮机构??????????????????????????????????????????????????????????????????? ??????????????????????????????????????????36第 6 章间歇运动机构??????????????????????????????????????????????????????????????????? ????????????????????????????????? 46第7 章螺纹连接与螺旋传动??????????????????????????????????????????????????????????????????? ????????????????????? 48第8 章带传动??????????????????????????????????????????????????????????????????? ??????????????????????????????????????????????60第9 章链传动??????????????????????????????????????????????????????????????????? ??????????????????????????????????????????????73第10 章齿轮传动??????????????????????????????????????????????????????????????????? ??????????????????????????????????????????80第11章蜗杆传动??????????????????????????????????????????????????????????????????? ??????????????????????????????????????????112第12 章齿轮系??????????????????????????????????????????????????????????????????? ??????????????????????????????????????????????124第13 章机械传动设计???????????????????????????????????????????????????????????????????????????????????????????????????? 131第14 章轴和轴毂连接??????????????????????????????????????????????????????????????????? ????????????????????????????????? 133第15 章轴承??????????????????????????????????????????????????????????????????? ??????????????????????????????????????????????????138第16 章其他常用零、部件??????????????????????????????????????????????????????????????????? ????????????????????????? 152第17 章机械的平衡与调速??????????????????????????????????????????????????????????????????? ????????????????????????? 156第18 章机械设计CAD 简介??????????????????????????????????????????????????????????????????? ???????????????????????163第1章机械设计概述1.1 机械设计过程通常分为哪几个阶段?各阶段的主要内容是什么?答:机械设计过程通常可分为以下几个阶段:1.产品规划主要工作是提出设计任务和明确设计要求。

2012版金融计量学课后习题答案

（2）证明：
若yt ~ I (1)，说明yt 存在一个单位根，一阶差分平稳，所以 Δyt = c + (α1 + α 2 −1) yt−1 − α 2Δyt−1 + ε t 是一个平稳过程，那么α1 + α 2 −1 = 0才能满足条件，所以α1 + α 2 = 1
2、
对于高于二阶的情况，需要从倒数第一项α p 开始往前推导，
《金融计量学-时间序列分析视角》
中国人民大学出版社 2012 年出版
课后习题答案
张成思 zhangcs@
第 1 章（略）
第2章
1、解：
（1）
yt = c0 + αyt−1； yt−1 = c0 + αyt−2； yt−2 = c0 + αyt−3； … y1 = c0 + αy0；由此，
= (1− α1 − α 2 )−1c
（3）证明：
将c = (1− α1 − α2 )μ代入原方程，得到
yt − μ = α（1 yt − μ）+ α（2 yt − μ）令yˆt = yt − μ,则 yˆt = α1 yˆt−1 + α 2 yˆt−2
( ) ( ) 那么，γ j = E yˆt yˆt− j = E α1 yˆt−1 + α 2 yˆt−2 yˆt− j ( ) ( ) = α1E yˆt−1 yˆt− j + α 2 E yˆt−2 yˆt− j
∂yt+ j ∂ε t
= α (j−1 αb1 + b2 )
（3）
∂yt+ j + ∂yt+ j + ∂yt+ j + … + ∂yt+ j

人教版数学八年级上册课后习题参考答案

人教版数学八年级上册课后习题参考答案(总41页)-CAL-FENGHAI.-(YICAI)-Company One1-CAL-本页仅作为文档封面，使用请直接删除第3页习题答案1. 2010年为+108.7mm; 2009年为-81.5 mm; 2008年为+53.5 mm.2．这个物体又移动了-1 m表示物体向左移动了1m这时物体又回到了原来的位置第4页习题答案1．解：有5个三角形，分别是△ABE，△ABC，△BEC，△BDC,△EDC.2．解：(1)不能；(2)不能；(3)能．理由略第5页习题答案：1.解：图(1)中∠B为锐角，图(2)中∠B为直角，图(3)中∠B为钝角，图(1)中AD在三角形内部，图(2)中AD 为三角形的一条直角边，图(3)中AD在三角形的外部．锐角三角形的高在三角形内部，直角三角形的直角边上的高与另一条直角边重合，钝角三角形有两条高在三角形外部．2.(1)AF(或BF) CD AC (2)∠2 ∠ABC ∠4或∠ACF第7页习题答案：解：(1)(4)(6)具有稳定性第8页习题11.1答案1．解：图中共6个三角形，分别是△ABD，△ADE,△AEC,△ABE,AADC,△ABC.2．解：2种.四根木条每三条组成一组可组成四组，分别为10，7，5；10，7，3；10，5，3；7，5，3．其中7+5>10，7+3=10,5+3<10，5+3>7，所以第二组、第三组不能构成三角形，只有第一组、第四组能构成三角形，3．解：如图11-1-27所示，中线AD、高AE、角平分线AF.4.(1) EC BC (2) ∠DAC ∠BAC (3)∠AFC (4)1/2BC．AF5．C6．解：(1)当长为6 cm的边为腰时，则另一腰长为6 cm，底边长为20-12=8(cm)，因为6+6>8，所以此时另两边的长为6 cm，8 cm.(2)当长为6 cm的边为底边时，等腰三角形的腰长为(20-6)/2=7(cm)，因为6+7>7，所以北时另两边的长分别为7 cm，7cm.7．(1) 解：当等腰三角形的腰长为5时，三角形的三边为5，5，6，因为5+5>6，所以三角形周长为5+5+6=16：当等腰三角形的腰长为6时，三角形的三边为6，6，5，因为6+5>6，所以三角形周长为6+6+5=17.所以这个等腰三角形的周长为16或17；(2)22．8.1：2 提示：用41/2BC．AD—丢AB．CE可得．9．解：∠1=∠2．理由如下：因为AD平分∠BAC，所以∠BAD=∠DAC.又DE//AC，所以∠DAC=∠1. 又DF//AB，所以∠DAB=∠2. 所以∠1=∠2.10.解：四边形木架钉1根木条；五边形木架钉2根木条；六边形木架钉3根木条人教版八年级上册数学第13页练习答案1．解：因为∠CBD=∠CAD+∠ACB，所以∠ACB=∠CBD-∠CAD=45°-30°=15°.2．解：在△ACD中，∠D+∠DAC+∠DCA=180°，在△ABC中，∠B+∠BAC+∠BCA=180°，所以∠D+∠DAC+∠DCA+∠B+∠BAC+∠BCA=∠D+∠B+ ∠BAD+∠BCD=180°+180°=360°.所以40°+40°+150°+∠BCD= 360°. 所以∠BCD=130°人教版八年级上册数学第14页练习答案1.解：∠ACD=∠B．理由：因为CD⊥AB，所以△BCD是直角三角形，∠BDC=90°，所以∠B+∠BCD=90°，又因为∠ACB= 90°，所以∠ACD+∠BCD=∠ACB=90°，所以∠ACD=∠B(同角的余角相等)．2．解：△ADE是直角三角形，理由：因为∠C=90。

（完整版）随机过程习题答案

（完整版）随机过程习题答案随机过程部分习题答案习题22.1 设随机过程b t b Vt t X ),,0(,)(+∞∈+=为常数，)1,0(~N V ，求)(t X 的⼀维概率密度、均值和相关函数。

解因)1,0(~N V，所以1,0==DV EV ，b Vt t X +=)(也服从正态分布，b b tEV b Vt E t X E =+=+=][)]([ 22][)]([t DV t b Vt D t X D ==+=所以),(~)(2t b N t X ，)(t X 的⼀维概率密度为),(,21);(222)(+∞-∞∈=--x ett x f t b x π，),0(+∞∈t均值函数 b t X E t m X ==)]([)(相关函数)])([()]()([),(b Vt b Vs E t X s X E t s R X ++==][22b btV bsV stV E +++=2b st +=2.2 设随机变量Y 具有概率密度)(y f ，令Yt e t X -=)(，0,0>>Y t ，求随机过程)(t X 的⼀维概率密度及),(),(21t t R t EX X 。

解对于任意0>t，Yt e t X -=)(是随机变量Y 的函数是随机变量，根据随机变量函数的分布的求法，}ln {}{})({);(x Yt P x e P x t X P t x F t Y ≤-=≤=≤=-)ln (1}ln {1}ln {tx F t x Y P t x Y P Y --=-≤-=-≥= 对x 求导得)(t X 的⼀维概率密度xtt x f t x f Y 1)ln ();(-=，0>t)(][)]([)(dy y f e eE t X E t m yt tY X相关函数+∞+-+---====0)()(2121)(][][)]()([),(212121dy y f e e E e e E t X t X E t t R t t y t t Y t Y t Y X 2.3 若从0=t 开始每隔21秒抛掷⼀枚均匀的硬币做实验，定义随机过程=时刻抛得反⾯时刻抛得正⾯t t t t t X ,2),cos()(π试求：（1）)(t X 的⼀维分布函数),1(),21(x F x F 和；（2）)(t X 的⼆维分布函数),;1,21(21x x F ；（3）)(t X 的均值)1(),(X X m t m ，⽅差 )1(),(22X Xt σσ。

北京工业大学通信电路原理第1-12章习题答案

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1 4 2 （465 103）2 202.6 1012
不对，没有考虑 3 个单元电路各自产生的噪声 Pnn1、Pnn2、Pnn3 正确：Pno= PniAPA1APA2APA3+ Pnn1 APA2APA3+ Pnn2 APA3+ Pnn3
（2）两个系统各自的噪声系数？系统 1：Nf = Nf1+ (Nf2-1)/APA1+ (Nf3-1)/(APA1APA2) = 1.5+(3-1)/20+(4-1)/(20×15) =1.5+2/20+3/300 = 1.61 系统 2：Nf = Nf1+ (Nf2-1)/APA1+ (Nf3-1)/(APA1APA2) = 3+(4-1)/15+(1.5-1)/(15×10) =3 +3/15+0.5/150 = 3.2003
465 103 19.4 kHz 24
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（4）中和电容 CN 的位置如图中所示，CN 的大致值为 0.5~5 pf
（5）放大器谐振时的电压增益
AV

数值计算方法课后习题答案(李庆扬等)

数值计算方法课后习题答案(李庆扬等)绪论（12）1、设x 0，x的相对误差为，求lnx的误差。

[解]设x* 0为x的近似值，则有相对误差为r*(x) ，绝对误差为*(x) x*，从而lnx的误差为*(lnx) (lnx*) (x*) 相对误差为(lnx)*r1*x ，x**(lnx)lnx*lnx*。

2、设x的相对误差为2%，求xn的相对误差。

[解]设x*为x的近似值，则有相对误差为r*(x) 2%，绝对误差为*(x) 2%x*，从而x的误差为(lnx) (x) 相对误差为(lnx)*rn*nx x*(x) n(x)**n 12%x 2n% x**n，*(lnx)(x)*n2n%。

3、下列各数都是经过四舍五入得到的近似数，即误差不超过最后一位的半个单位，试指出它们是几位有效数字：*****x1 1.1021，x2 0.031，x3 56.430，x5 385.6，x4 7 1.0。

***[解]x1 1.1021有5位有效数字；x2 0.0031有2位有效数字；x3 385.6有4**位有效数字；x4 56.430有5位有效数字；x5 7 1.0有2位有效数字。

****4、利用公式（3.3）求下列各近似值的误差限，其中x1均为第3题所给,x2,x3,x4的数。

***（1）x1；x2 x4f *******e*(x1 x2 x4) (x) (x) (x) (xk124) xk 1 k [解]；11110 4 10 3 10 3 1.05 10 3222n****（2）x1x2x3；f***e*(x1x2x3)k 1 xkn ********** (x) (xx) (x) (xx) (x) (xx) (x)k***-*****3*1[解] (0.031 385.6)1 10 4 (1.1021 385.6)1 10 3 (1.1021 0.031) 10 3；2220.***** 10 3 212.***** 10 3 0.***-***** 10 3213.***-***** 10 3 0.***-*****255**（3）x2。

大学物理习题答案

Pd LθxydE d θ习题1212-3．如习题12-3图所示，真空中一长为L 的均匀带电细直杆，总电量为q ，试求在直杆延长线上到杆的一端距离为d 的点P 的电场强度。

[解] 建立如图所示坐标系ox ，在带电直导线上距O 点为x 处取电荷元x Lqq d d =，它在P 点产生的电电场强度度为()()x x d L Lq x d L qE d 41d 41d 2020-+=-+=πεπε则整个带电直导线在P 点产生的电电场强度度为()()d L d qx x d L Lq E L+=-+=⎰002041d 41πεπε故()i E d L d q+=04πε12-4．用绝缘细线弯成的半圆环，半径为R ，其上均匀地带有正电荷Q ，试求圆心处点O 的场强。

[解] 将半圆环分成无穷多小段，取一小段dl ，带电量l Rq d d π=dq 在O 点的电场强度20204d 4d d R lR Q R q E πεππε== 从对称性分析，y 方向的电场强度相互抵消，只存在x 方向的电场强度l R Q E E d sin 4sin d d 302x ⋅=⋅=θεπθ θd d R l =θεπθd 4sin d 202x RQ E =2020202x x 2d 4sin d R QR Q E E E επθεπθπ====⎰⎰ 方向沿x 轴正方向 12-5. 如习题12-5图所示，一半径为R 的无限长半圆柱面形薄筒，均匀带电，沿轴向单位长度上的带电量为λ，试求圆柱面轴线上一点的电场强度E 。

[解] θd 对应的无限长直线单位长带的电量为θπλd d =q 它在轴线O 产生的电场强度的大小为d θRRq E 0202d 2d d επθλπε==因对称性y d E 成对抵消RE E 02x 2d cos cos d d επθθλθ=⋅= RR E E 02202x 2d cos 2d επλεπθθλπ===⎰⎰ 12-6．一半径为R 的半球面，均匀地带有电荷，电荷面密度为σ，求球心点O 处的场强。

Unit 12 A Case of “Severe Bias”习题答案综合教程四

Unit 12 A Case of "Severe Bias"Key to the ExercisesText comprehensionI. Decide which of the following best states the author's purpose of writing.AII. Judge, according to the text, whether the following statements are true or false.1. T (Refer to Paragraph 3. In American news media, black America is poor, criminal, addicted and dysfunctional. Indeed, the media have covered only a small segment of the black community and presented it as the norm.)2. T (Refer to Paragraph 3, where it is said that "it is an insidious practice, all the uglier for its blatancy," meaning that the media's practice of misrepresenting black America is obtrusive and offensive.)3. F (Refer to Paragraph 4, where it is indicated that media reports on crack babies, gang warfare, violent youth, poverty and homelessness are all featured as black, while rarely is there any article about blacks playing a positive role, or any role at all.)4. F (Refer to Paragraphs 6?, where it is shown that in numbers there are more white Americans on welfare, but among the urban underclass there is a larger proportion of blacks.)5. F (Refer to Paragraph 12, in which the author tells us that she has not seen a recognizable "gang" member or any "gang" activity, nor has she been the victim of "gang violence.")6. F (Refer to Paragraphs 14?6, which show that blacks' true characteristics and contributions are the biggest secret in America. Every black, even those with the strongest minds, craves affirmation of their contributions to American society.)III. Answer the following questions.1. Refer to Paragraph 3. It refers to the small group of blacks who are poor, criminal, addicted and dysfunctional.2. Refer to Paragraphs 3?, and 11. The author especially focuses on the news media, and she also touches upon the film industry.3. Refer to Paragraph 7. As presented in the media, white America is always whole and lovely and healthy, while black America is usually sick and pathetic and deficient.4. Refer to Paragraph 9. By "twilight zone," the author means that the image of black America is very confusing because of the discrepancy between its image in the media and its real character.5. Refer to Paragraph 12. According to the author, she has never experienced any"gang" activity in Denver, nor has she been the victim of "gang violence."6. Refer to Paragraphs 5?, and 13. Yes, news reports and journalism are always supposed to be the mirror on American reality.IV. Explain in your own words the following sentences.1. The media's malicious use of a small segment to represent all black America is shameless and offensive.2. The media are supposed to present American culture and American experience truthfully by reflecting American reality, and people usually accept news reports as truth without any doubt. Unfortunately, in many cases what they present is anything but the truth.3. The distorted, inaccurate news coverage is worse than covering nothing at all about blacks.4. I am not suggesting we close our eyes to the very real problems associated with the lower class in cities, nor denying that blacks are overrepresented in this class.5. Most black people work hard, obey the law and pay their taxes. We have made our contributions to American society, but the media never notice and cover it. That makes blacks resentful.Structural analysis of the textWith a series of sentences beginning with "I am not," the author shows how different the image of blacks established by the media is from reality. And using again the same sentence structure in Paragraph 6, the author emphasizes that she is not an exception but one of the majority of blacks. With this structural repetition, the author is comparing herself with the majority of blacks and contrasting the image of blacks in the media with that in real life.Rhetorical features of the textNor is it a matter of closing one's eyes to the very real problems of the urban underclass -- which undeniably is disproportionately black. (Interrupting a sentence)And as self-reliant as most black Americans are -- because we've had to be self-reliant -- even the strongest among us still crave affirmation. (Interrupting a sentence)I want America to know us -- all of us -- for who we really are. (Putting special emphasis) That is the real portrait of black America -- that we're strong people, surviving people, capable people. (Introducing an explanation)Vocabulary exercisesI. Explain the underlined part in each sentence in your own words.1. that's it2. supply3. people in the lowest social position4. hazy area; marginalized area5. independent; self-dependentII. Fill in the blank in each sentence with a word or phrase from the box in its appropriate form.1. are guilty of2. have been screaming out3. contribution4. was featured5. being reminded of6. in the light of7. in the eyes of8. deserving the attention ofIII. Fill in the blanks with the appropriate forms of the given words.1. victim2. blatant3. nutritional4. Vibrations5. denial6. relegation7. aberration 8. addictiveIV. Choose the word or phrase that can replace the underlined part in each sentence without changing its original meaning.1. C2. D3. D4. A5. B6. A7. C8. BV. Give a synonym or an antonym of the word underlined in each sentence in the sense it is used.1. Synonym: favour (support)2. Antonym: balanced (fair, objective)3. Antonym: honest (straightforward, sincere)4. Synonym: impaired (harmed, incomplete)5. Synonym: serious6. Synonym: infer (derive, conclude, reason)7. Synonym: inexact (faulty, mistaken, erroneous)8. Antonym: elite (gentry)VI. Explain the meaning of the underlined part in each sentence.1. provides space for2. because of3. makes interesting4. protect5. competitive6. carefulGrammar exercisesI. Rewrite the following sentences, omitting if.1. Had it not been for our adopted son, we would not now be surrounded by caring strangers.2. Had I known that, I wouldn't have said anything.3. Should the guests arrive early, no one will be here to greet them.4. Were I the President, I would make some changes.5. Had Susan not been so lazy, she could have passed her history final.6. Had Harry locked his door properly, the burglar would not have entered his apartment.7. Had I not seen it with my own eyes, I would not have believed it.8. Should there be a global nuclear war, some scientists predict that life on earth as we know it would end forever.II. Complete the following sentences with the proper forms of the verbs in brackets.1. would not be waiting2. would not be able to go3. had read4. had given5. would love6. had finished7. listened8. would have fallen9. had been10. will not dry outIII. Fill in the blanks with the words and phrases given.1. Given2. unless3. In the event of4. but for5. Supposing6. in case7. on condition that8. so long asIV. Explain the following sentences.1. If he laughs last, he laughs best.2. If you try to grasp everything, you will get nothing.3. If you give him an inch, he will take a mile.4. If he had been born in better times, he would have done credit to the profession of letters.5. If the same thing should happen in wartime, it would amount to disaster.6. If you should hear him talk, you'd think he had passed half his life in Australia.7. If you don't follow your doctor's advice, your cough will get worse.8. If you lose one hour in the morning, you will be looking for it the rest of the day.V. Improve the following sentences.1. The sheriff was looking for a middle-aged woman driving a dark green Buick sedan with a little Scotch terrier beside her.2. To start a conversation, I asked her for a light while waiting for the train.3. Seymour lay in a hammock and watched the vultures circling steadily overhead.4. Filled with eagerness, curiosity, and excitement, Nancy carefully unwrapped the small package.5. We watched with the aid of powerful binoculars the gulls flying over the windswept waves and barren rocks.6. The pair of antique candlesticks shining brightly on the table attracted the admiring glances of many visitors.7. With a smile the doctor said that there was nothing seriously wrong. / The doctor said with a smile that there was nothing seriously wrong.8. When discussing creativity, John E. Gibson stresses a person's ability to finish a pun.VI. Make sentences of your own after the sentences given below, keeping the underlined structures in your sentences.(Reference version)1. As sick as he was, he came to work.2. Visitors and the media teams all gathered to commemorate this breath-taking, record-breaking, epoch-making event.Translation exercisesI. Translate the following sentences into Chinese.1. 这些都不能用来界定我，也不能描述我40年生命中认识、共事、热爱、交往的任何其他黑人。

《金融学（第二版）》讲义大纲及课后习题答案详解十二章

《⾦融学（第⼆版）》讲义⼤纲及课后习题答案详解⼗⼆章CHAPTER 12CHOOSING AN INVESTMENT PORTFOLIOObjectivesTo understand the process of personal investing in theory and in practice.To build a quantitative model of the tradeoff between risk and reward.Outline12.1 The Process of Personal Portfolio Selection12.2 The Trade-off between Expected Return and Risk12.3 Efficient Diversification with Many Risky AssetsSummaryThere is no single portfolio selection strategy that is best for all people.Stage in the life cycle is an imp ortant determinant of the optimal composition of a person’s optimal portfolio of assets and liabilities.Time horizons are important in portfolio selection. We distinguish among three time horizons: the planning horizon, the decision horizon, and the trading horizon.In making portfolio selection decisions, people can in general achieve a higher expected rate of return only by exposing themselves to greater risk.One can sometimes reduce risk without lowering expected return by diversifying more completely either withina given asset class or across asset classes.The power of diversification to reduce the riskiness of an investor’s portfolio depends on the correlations among the assets that make up the portfolio. In practice, the vast majority of assets are positively correlated with each other because they are all affected by common economic factors. Consequently, one’s ability to reduce risk through diversification among risky assets without lowering expected return is limited.Although in principle people have thousands of assets to choose from, in practice they make their choices from a menu of a few final products offered by financial intermediaries such as bank accounts, stock and bond mutual funds, and real estate. In designing and producing the menu of assets to offer to their customers theseintermediaries make use of the latest advances in financial technology.Solutions to Problems at End of Chapter1. Suppose that your 58-year-old father works for the Ruffy Stuffed Toy Company and has contributed regularly to his company-matched savings plan for the past 15 years. Ruffy contributes $0.50 for every $1.00 your father puts into the savings plan, up to the first 6% of his salary. Participants in the savings plan can allocate their contributions among four different investment choices: a fixed-income bond fund, a “blend” option that invests in large companies, small companies, and the fixed-income bond fund, a growth-income mutual fund whose investments do not include other toy companies, and a fund whose sole investment is stock in the Ruffy Stuffed Toy Company. Over Thanksgiving vacation, Dad realizes that you have been majoring in finance and decides to reap some early returns on that tuition money he’s been investing in your education. He shows you the most recent quarterly statement for his savings plan, and you see that 98% of its current value is in the fourth investment option, that of the Ruffy Company stock..a.Assume that your Dad is a typical risk-averse person who is considering retirement in five years. Whenyou ask him why he has made the allocation in this way, he responds that the company stock has continually performed quite well, except for a few declines that were caused by problems in a division that the company has long since sold off. Inaddition, he says, many of his friends at work have done the same. What advice would you give your dad about adjustments to his plan allocations? Why?b.If you consider the fact that your dad works for Ruffy in addition to his 98% allocation to the Ruffy stockfund, does this make his situation more risky, less risky, or does it make no difference? Why? SOLUTION:a.Dad has exposed himself to risk by concentrating almost all of his plan money in the Ruffy Stock fund. This is analogous to taking 100% of the money a family has put aside for investment and investing it in a single stock.First, Dad needs to be shown that just because the company stock has continually performed quite well is no guarantee that it will do so indefinitely. The company may have sold off the divisions which produced price declines in the past, but future problems are unpredictable, and so is the movement of the stock price. “Past performance is no guarantee of future results” is the lesson.Second, Dad needs to hear about diversification. He needs to be counseled that he can reduce his risk by allocating his money among several of the options available to him. Indeed, he can reduce his risk considerably merely by moving all of his money into the “blend” fund because it is diversifi ed by design: it has a fixed-income component, a large companies component, and a small companies component. Diversification isachieved not only via the three differing objectives of these components, but also via the numerous stocks that comprise each of the three components.Finally, Dad’s age and his retirement plans need to be considered. People nearing retirement age typically begin to shift the value of their portfolios into safer investments. “Safer” normally connotes less variability, so that the risk of a large decline in the value of a portfolio is reduced. This decline could come at any time, and it would be very unfortunate if it were to happen the day before Dad retires. In this example, the safest option would be the fixed-income bond fund because of its diversified composition and interest-bearing design, but there is still risk exposure to inflation and the level of interest rates. Note that the tax-deferred nature of the savings plan encourages allocation to something that produces interest or dividends. As it stands now, Dad is very exposed to a large decline in the value of his savings plan because it is dependent on the value of one stock.Individual equities over time have proven to produce the most variable of returns, so Dad should definitely move some, probably at least half, of his money out of the Ruffy stock fund. In fact, a good recommendation given his retirement horizon of five years would be to re-align the portfolio so that it has 50% in the fixed- income fund and the remaining 50% split between the Ruffy stock fund (since Dad insists) and the “blend” fund.Or, maybe 40% fixed-income, 25% Ruffy, 15% growth-income fund, and 20% “blend” fund. This latterallocation has the advantage of introducing another income-producing component that can be shielded by the tax-deferred status of the plan.b.The fact that Dad is employed by the Ruffy Company makes his situation more risky. Let’s say that the companyhits a period of slowed business activities. If the stock price declines, so will th e value of Dad’s savings plan. If the company encounters enough trouble, it may consider layoffs. Dad’s job may be in jeopardy. At the same time that his savings plan may be declining in value, Dad may also need to look for a job or go onunemployment. Thus, Dad is exposed on two fronts to the same risk. He has invested both his human capital and his wealth almost exclusively in one company.2. Refer to Table 12.1.a.Perform the calculations to verify that the expected returns of each of the portfolios (F, G, H, J, S) in thetable (column 4) are correct.b.Do the same for the standard deviations in column 5 of the table.c.Assume that you have $1million to invest. Allocate the money as indicated in the table for each of the fiveportfolios and calculate the expected dollar return of each of the portfolios.d.Which of the portfolios would someone who is extremely risk tolerant be most likely to select? SOLUTION:d.An extremely risk tolerant person would select portfolio S, which has the largest standard deviation but also thelargest expected return.3. A mutual fund company offers a safe money market fund whose current rate is4.50% (.045). The same company also offers an equity fund with an aggressive growth objective which historically has exhibited an expected return of 20% (.20) and a standard deviation of .25.a.Derive the equation for the risk-reward trade-off line.b.How much extra expected return would be available to an investor for each unit of extra risk that shebears?c.What allocation should be placed in the money market fund if an investor desires an expected return of15% (.15)?SOLUTION:a.E[r] = .045 + .62b.0.62c.32.3% [.15 = w*(.045) + (1-w)*(.020) ]4. If the risk-reward trade-off line for a riskless asset and a risky asset results in a negative slope, what does that imply about the risky asset vis-a-vis the riskless asset?SOLUTION:A trade-off line wit h a negative slope indicates that the investor is “rewarded” with less expected return for taking on additional risk via allocation to the risky asset.5. Suppose that you have the opportunity to buy stock in AT&T and Microsoft.a.stocks is 0? .5? 1? -1? What do you notice about the change in the allocations between AT&T andMicrosoft as their correlation moves from -1 to 0? to .5? to +1? Why might this be?b.What is the variance of each of the minimum-variance portfolios in part a?c.What is the optimal combination of these two securities in a portfolio for each value of the correlation,assuming the existence of a money market fund that currently pays 4.5% (.045)? Do you notice any relation between these weights and the weights for the minimum variance portfolios?d.What is the variance of each of the optimal portfolios?e.What is the expected return of each of the optimal portfolios?f.Derive the risk-reward trade-off line for the optimal portfolio when the correlation is .5. How much extraexpected return can you anticipate if you take on an extra unit of risk?SOLUTION:a.Minimum risk portfolios if correlation is:-1: 62.5% AT&T, 37.5% Microsoft0: 73.5% AT&T, 26.5% Microsoft.5: 92.1% AT&T, 7.9% Microsoft1: 250% AT&T, short sell 150% MicrosoftAs the correlation moves from -1 to +1, the allocation to AT&T increases. When two stocks have negativec orrelation, standard deviation can be reduced dramatically by mixing them in a portfolio. It is to the investors’benefit to weight more heavily the stock with the higher expected return since this will produce a high portfolio expected return while the standard deviation of the portfolio is decreased. This is why the highest allocation to Microsoft is observed for a correlation of -1, and the allocation to Microsoft decreases as the correlationbecomes positive and moves to +1. With correlation of +1, the returns of the two stocks will move closely together, so you want to weight most heavily the stock with the lower individual standard deviation.b. Variances of each of the minimum variance portfolios:62.5% AT&T, 37.5% Microsoft Var = 073.5% AT&T, 26.5% Microsoft Var = .016592.1% AT&T, 7.9% Microsoft Var = .0222250% AT&T, short 150% Microsoft Var = 0c. Optimal portfolios if correlation is:-1: 62.5% AT&T, 37.5% Microsoft0: 48.1% AT&T, 51.9% Microsoft.5: 11.4% AT&T, 88.6% Microsoft1: 250% AT&T, short 150% Microsoftd. Variances of the optimal portfolios:62.5% AT&T, 37.5% Microsoft Var = 048.1% AT&T, 51.9% Microsoft Var = .022011.4% AT&T, 88.6% Microsoft Var = .0531250% AT&T, short 150% Microsoft Var = 0e. Expected returns of the optimal portfolios:62.5% AT&T, 37.5% Microsoft E[r] = 14.13%48.1% AT&T, 51.9% Microsoft E[r] = 15.71%11.4% AT&T, 88.6% Microsoft E[r] = 19.75%250% AT&T, short 150% Microsoft E[r] = -6.5%f.Risk-reward trade-off line for optimal portfolio with correlation = .5:E[r] = .045 + .66/doc/31dbf23b580216fc700afd59.html ing the optimal portfolio of AT&T and Microsoft stock when the correlation of their price movements is 0.5, along with the results in part f of question 12-5, determine:a.the expected return and standard deviation of a portfolio which invests 100% in a money market fundreturning a current rate of 4.5%. Where is this point on the risk-reward trade-off line?b.the expected return and standard deviation of a portfolio which invests 90% in the money market fundand 10% in the portfolio of AT&T and Microsoft stock.c.the expected return and standard deviation of a portfolio which invests 25% in the money market fundand 75% in the portfolio of AT&T and Microsoft stock.d.the expected return and standard deviation of a portfolio which invests 0% in the money market fundand 100% in the portfolio of AT&T and Microsoft stock. What point is this?SOLUTION:a.E[r] = 4.5%, standard deviation = 0. This point is the intercept of the y (expected return) axis by the risk-rewardtrade-off line.b.E[r] = 6.03%, standard deviation = .0231c.E[r] = 15.9%, standard deviation = .173d.E[r] = 19.75%, standard deviation = .2306. This point is the tangency between the risk-reward line from 12-5part f and the risky asset risk-reward curve (frontier) for AT&T and Microsoft.7. Again using the optimal portfolio of AT&T and Microsoft stock when the correlation of their price movements is 0.5, take $ 10,000 and determine the allocations among the riskless asset, AT&T stock, and Microsoft stock for:a. a portfolio which invests 75% in a money market fund and 25% in the portfolio of AT&T and Microsoftstock. What is this portfolio’s expected return?b. a portfolio which invests 25% in a money market fund and 75% in the portfolio of AT&T and Microsoftstock. What is this portfolio’s expect ed return?c. a portfolio which invests nothing in a money market fund and 100% in the portfolio of AT&T andMicrosoft stock. What is this portfolio’s expected return?SOLUTION:a.$7,500 in the money-market fund, $285 in AT&T (11.4% of $2500), $2215 in Microsoft. E[r] = 8.31%, $831.b.$2,500 in the money-market fund, $855 in AT&T (11.4% of $7500), $6645 in Microsoft. E[r] = 15.94%, $1,594.c.$1140 in AT&T, $8860 in Microsoft. E[r] = 19.75%, $1,975.8. What strategy is implied by moving further out to the right on a risk-reward trade-off line beyond the tangency point between the line and the risky asset risk-reward curve? What type of an investor would be most likely to embark on this strategy? Why?SOLUTION:This strategy calls for borrowing additional funds and investing them in the optimal portfolio of AT&T and Microsoft stock. A risk-tolerant, aggressive investor would embark on this strategy. This person would be assuming the risk of the stock portfolio with no risk-free component; the money at risk is not onl y from this person’s own wealth but also represents a sum that isowed to some creditor (such as a margin account extended by the investor’s broker).9. Determine the correlation between price movements of stock A and B using the forecasts of their rate of return and the assessments of the possible states of the world in the following table. The standard deviations for stock A and stock B are0.065 and 0.1392, respectively. Before doing the calculation, form an expectation of whether that correlation will be closer to1 or -1 by merely inspecting the numbers.SOLUTION:Expectation: correlation will be closer to +1.E[r A] = .05*(-.02) + .15*(-.01) + .60*(.15) + .20*(.15) = .1175, or, 11.75%E[r B] = .05*(-.20) + .15*(-.10) + .60*(.15) + .20*(.30) = .1250, or, 12.50%Covariance = .05*(-.02-.1175)*(-.20-.125) + .15*(-.01-.1175)*(-.10-.125) +.60*(.15-.1175)*(.15-.125) + .20*(.15-.1175)*(.30-.125) =.008163Correlation = .008163/(.065)*(.1392) = .90210.Analyze the “expert’s” answers to the following questions:a.Question:I have approx. 1/3 of my investments in stocks, and the rest in a money market. What do you suggestas a somewhat “safer” place to invest another 1/3? I like to keep 1/3 accessible for emergencies.Expert’s answer:Well, you could try 1 or 2 year Treasury bonds. You’d get a little bit more yie ld with no risk.b.Question:Where would you invest if you were to start today?Expert’s answer:That depends on your age and short-term goals. If you are very young – say under 40 –and don’tneed the money you’re investing for a home or college tuition or such, you would put it in a stockfund. Even if the market tanks, you have time to recoup. And, so far, nothing has beaten stocks overa period of 10 years or more. But if you are going to need money fairly soon, for a home or for yourretirement, you need to play it safer.SOLUTION:a.You are not getting a little bit more yield with no risk. The real value of the bond payoff is subject to inflationrisk. In addition, if you ever need to sell the Treasury bonds before expiration, you are subject to the fluctuation of selling price caused by interest risk.b.The expert is right in pointing out that your investment decision depends on your age and short-term goals. In addition, the investment decision also depends on other characteristics of the investor, such as the special character of the labor income (whether it is highly correlated with the stock market or not), and risk tolerance.Also, the fact that over any period of 10 years or more the stock beats everything else cannot be used to predict the future.。

物理性污染控制各章节习题答案(全)

物理性污染控制习题答案第一章略第二章噪声污染及其控制1. 什么是噪声？噪声对人的健康有什么危害？答：从心理学出发，凡是人们不需要的声音，称为噪声。

噪声是声的一种；具有声波的一切特性；主要来源于固体、液体、气体的振动；产生噪声的物体或机械设备称为噪声源。

噪声的特点：局部性污染，不会造成区域或全球污染；噪声污染无残余污染物，不会积累。

噪声源停止运行后，污染即消失。

声能再利用价值不大，回收尚未被重视噪声对人的健康危害有：引起耳聋、诱发疾病、影响生活、影响工作。

2. 真空中能否传播声波？为什么？答：声音不能在真空中传播，因为真空中不存在能够产生振动的弹性介质。

3.可听声的频率范围为20～20000Hz ,试求出500 Hz 、5000 Hz 、10000 Hz 的声波波长。

解：, c=340m/s,3400.6815003400.068250003400.0034310000c fm m m λλλλ======= 4. 声压增大为原来的两倍时，声压级提高多少分贝？解：2'20lg , 20lg 20lg20lg 2000'20lg 26()p ppe e e L L p p p pp L L L dB p p p===+∆=-==5.一声源放在刚性面上，若该声源向空间均匀辐射半球面波，计算该声源的指向性指数和指向性因数。

解：22S 4==2 DI=10lg 10lg 2 3.01W S 2S WS Ir Q Q I r θππ=====半全，半全6.在一台机器半球辐射面上的5个测点，测得声压级如下表所示。

计算第5测点的指向性指数和指向性因数。

0.18.58.78.68.48.91110lg(10)10lg (1010101010)86.6()510.110220.10.10.1(8986.6)01010 1.7420.1102010lg 10lg1.74 2.4L n piL dB p ni Lp L L I p p p p I L p pp DI Q θθθ==++++=∑=--=========.7.已知某声源均匀辐射球面波，在距声源4m 处测得有效声压为2Pa ，空气密度1.23/kg m 。

结构力学课后习题答案

结构力学课后习题答案(总23页)--本页仅作为文档封面，使用时请直接删除即可----内页可以根据需求调整合适字体及大小--习题及参考答案【习题2】【习题3】【习题4】【习题5】【习题6】【习题8】【习题9】【习题10】【习题11】【习题12】【习题13】【习题14】【参考答案】习题22-1～2-14试对图示体系进行几何组成分析，如果是具有多余联系的几何不变体系，则应指出多余联系的数目。

题2-1图题2-2图题2-3图题2-4图题2-5图题2-6图题2-7图题2-8图题2-9图题2-10图题2-11图题2-12图题2-13图题2-14图习题33-1 试作图示多跨静定梁的M 及Q 图。

(b)(a)20kN10kN40kN20kN/m40kN题3-1图3-2 试不计算反力而绘出梁的M 图。

(b)5kN/m40kN(a)题3-2图习题44-1 作图示刚架的M 、Q 、N 图。

(c)(b)(a)/20kN /m2kN /m题4-1图4-2 作图示刚架的M 图。

P(e)(d)(a)(b)(c)20k N /m4kN题4-2图4-3 作图示三铰刚架的M 图。

(b)(a)题4-3图4-4 作图示刚架的M 图。

(a)题4-4图4-5 已知结构的M 图，试绘出荷载。

(b)(a)题4-5图4-6 检查下列刚架的M 图，并予以改正。

(e)(g)(h)P(d)(c)(a)(b)(f)题4-6图习题55-1 图示抛物线三铰拱轴线方程x x l lfy )(42-=，试求D 截面的内力。

题5-1图5-2 带拉杆拱，拱轴线方程x x l lf y )(42-=，求截面K 的弯矩。

C题5-2图题5-3图5-3 试求图示带拉杆的半圆三铰拱截面K 的内力。

习题66-1 判定图示桁架中的零杆。

(c)(b)题6-1图6-2 用结点法计算图示桁架中各杆内力。

(b)题6-2 图6-3 用截面法计算图示桁架中指定各杆的内力。

(b)题6-3图6-4 试求图示组合结构中各链杆的轴力并作受弯杆件的M 、Q 图。

苏教版12册语文《补充习题》答案

长江之歌三、你是指长江，把你比作母亲，表达作者对长江的热爱、赞美。

四、星垂平野阔月涌大江流无边落木萧萧下不尽长江滚滚来孤帆远影碧空尽惟见长江天际流天门中断楚江开碧水东流至此回山随平野尽江入大荒流万里长江横渡极目楚天舒五、因为长江各种资源十分丰富，所以说它是“无穷的源泉”2、三亚落日三、1、“担心”一词体会到：三亚海水之蓝，海鸥十分的白。

2、“感染”一次体会到：在夕阳余晖的映照下，海天变成一片金红，突出了夕阳的光艳。

3、体会到：作者对三亚落日的留恋和惊叹。

四、3、这是伟大的奇观好处：加强语气3、烟台的海三、1、涌浪比做小山形象的写出了巨浪拍打堤岸的壮观景象。

因为冬天的还做有气势。

2、扑字写出了春天海浪的柔和，让人感觉到海浪如顽皮的小孩子。

3、总分总冬天凝重春天轻盈夏天浪漫秋天高远。

使他们有丰富多彩的物质文化生活。

短文《海》答案1、我的梦是指在培育人才．蓝色的希冀是指学生们拥有知识后成为建设祖国的栋梁之材，成为祖国明天的希望播种的含义是培养教育．2、聚涓滴，纳百川，不断地充实自己，永不满足，永不停息！3、文中写了两种海，一种是真实的大海，另一种指知识的海，它们共同的特点就是1、广博、无边无际、雄浑、大气、活力。

2、它们的存在都需要永不停息地充实、汇集。

4、《记金华的双龙洞》一、罗甸杜鹃油桐漆黑石笋臀部二、1．③⑤⑥2．①④③三、1．叶圣陶洞口外洞孔隙内洞2．窄小（1）两个人并排仰卧，……是这样小的小船。

（2）进船方式：船两头都系着绳子……船就出来。

（3）乘船必须仰卧在小船里，从后脑勺到肩背，到臀部，到脚跟，每一处都贴着船底。

（4）感受：眼前昏暗了可是还能感觉左右和上方的山石都在朝我挤压过来。

我又感觉要是把头稍微抬起一点儿，准会撞破额角，擦伤鼻子。

3．黑奇大，奇4．作者的整个游程处处不离泉水，和作者游览的顺序这条线索有机结合，使文章井然有序，条理清晰，读者一目了然。

四、1．桂林（秀）庐山（俊）泰山（尊）黄山（贵）2．山野水野人野3．这两段都用了总分的写法。

生物统计学(第3版)杜荣骞课后习题答案第十二章实验设计

第十二章实验设计12.1一项关于在干旱地区生长的一种杨树（Populus euphratica），在土壤中的水分逐渐丧失后，其基因表达、蛋白谱、生态生理学及生长性能等方面产生可逆性改变的研究。

作者在本实验的5个时间点上（H5为对照），用qPCR方法度量了该杨树叶子中的三个基因的转录丰度比[83]，表中给出的为阵列数据：GenBank ID 基因H1H2H3H4H5AJ 780 423 半胱氨酸蛋白酶0.7 1.0 2.3 13.1 1.9AJ 780 698 环核苷酸和钙调节的离子通道 1.5 1.2 3.0 4.3 1.5AJ 777 362 核糖体蛋白 1.1 1.1 1.0 0.9 1.2借用上述数据，以三个基因作为三个区组，计算在5个时间点上转录丰度比差异是否显著？答：随机化完全区组实验设计方差分析的程序，类似于两因素交叉分组实验设计。

以下是本题的程序和结果：options linesize=76 nodate;data poplar;do block=1 to 3;do time=1 to 5;input trans @@;output;end;end;cards;0.7 1.0 2.3 13.1 1.91.5 1.2 3.0 4.3 1.51.1 1.1 1.0 0.9 1.2;proc anova;class block time;model trans=block time;run;The SAS SystemThe ANOVA ProcedureClass Level InformationClass Levels Valuesblock 3 1 2 3time 5 1 2 3 4 5Number of observations 15The SAS SystemThe ANOVA ProcedureDependent Variable: transSum ofSource DF Squares Mean Square F Value Pr > F Model 6 72.5560000 12.0926667 1.53 0.2809Error 8 63.1013333 7.8876667Corrected Total 14 135.6573333R-Square Coeff Var Root MSE trans Mean0.534848 117.6745 2.808499 2.386667Source DF Anova SS Mean Square F Value Pr > F block 2 18.82533333 9.41266667 1.19 0.3519 time 4 53.73066667 13.43266667 1.70 0.2416从上表中的结果可以看出，如果按随机化完全区组设计进行分析，不同时间点之间的差异不显著。

42工程制图6版答案-第12章化工工艺图3

第十二章化工工艺图12-1 复习管道及仪表流程图内容，回答下列问题《习题答案》第十二章（化工高职）工程制图（第6版）习题集12-1-1 复习管道及仪表流程图内容，回答下列问题。

（1）工艺方案流程图亦称原理流程图或物料流程图。

（2）工艺管道及仪表流程图亦称 PID 、或施工流程图、或生产控制流程图。

（3）机械制图的图线宽度分为 2 种，化工工艺图的图线宽度分为 3 种。

（4）化工工艺图的图线宽度分为：粗线宽 0.9～1.2 mm 、中粗线宽 0.5～0.7 mm 、细线宽 0.15～0.3 mm 。

（5）在工艺管道及仪表流程图中，主物料管道用粗线绘制，其他物料管道用中粗线绘制。

（6）在设备布置图中，“设备轮廓”用粗实线绘制，“设备支架和设备基础”用中粗实线绘制。

（7）用单线绘制的管道布置图中，“管道”用粗实线绘制，“法兰及阀门”用细实线绘制。

（8）在工艺管道及仪表流程图中，仪表位号中的字母代号填写在圆圈的上半圆中，数字编号填写在圆圈的下半圆中。

（9）在工艺管道及仪表流程图中，气液两相流工艺物料用 PGL 表示；仪表用空气用 IA 表示；润滑油用 LQ 表示；冷冻盐水回水用 RWR 表示；工艺液体用 PL 表示。

（10）管道号由三个单元组成，即物料代号、工段号、管道顺序号。

（11）管道应标注四部分内容，即管道号、管道公称直径、管道压力等级代号、隔热（或隔声）代号，总称为管道组合号。

（12）仪表图形符号是一个直径为 10 mm 的细实线圆圈。

（13）在工艺方案流程图中，用粗实线画出各设备之间的主要物料流程；用中粗实线画出其他辅助物料的流程线。

流程线一般画成水平线和垂直线，转弯画成直角。

（14）当同一物料线交错时，按流程顺序先不断、后断；不同物料线交错时，主物料线不断，辅助物料线断。

离散12习题

离散12习题(总22页)--本页仅作为文档封面，使用时请直接删除即可----内页可以根据需求调整合适字体及大小--第1章习题答案1. 说明下列语句哪些是命题及命题的真值（1）(2)(5)(7)(8)(9)(10)(11)是命题，其中（1）（5）（8）（10）是真命题，（9）的真值现在不知道。

2. 将下列命题符号化。

（1） ,p q ∧其中:p 小王聪明，:q 小王用功。

（2） ,p q ∧⌝其中:p 天气很冷，:q 下雪。

（3） ,p q ∨其中:p 晚上有英语课，:q 晚上有数学课。

（4）(),r p q →∨其中:p 你年满14岁，:q 你身高超过米，:r 你坐过山车。

（5） p q →，其中 :p 产量上升，:q 工资提高。

（6） ()p q ⌝∧，其中:p 销量下降，:q 价格上涨。

（7） p q →，其中:p 你给我发个电子邮件，:q 我有你的邮件地址。

（8） p q ↔，其中 :p 两个三角形全等，:q 它们的三条对应边相等。

（9）(),r p q s →∧∧⌝其中:p 阳光充足，:q 在夏天，:s 下雨，:r 我去游泳。

（10）p q ↔，其中:p 热带风暴来临，:q 下大雨。

3.（1）小王至少会讲汉语或英语的一种。

（2）小王会讲汉语和英语 (3) 小王会讲汉语但不会英语1（4）小王不会讲汉语或不会讲英语。

（5）小王会讲汉语。

（6）小王既不会讲汉语也不会讲英语是不可能的。

4. 设命题p :天下雨，q ：我去打球，r :我有空。

用自然语言写出下列命题。

（1）如果我去打球，那么一定是我有空且天没下雨；我有空且天没下雨我就一定去打球。

(2) 若天下雨或我有空我就去打球。

(3) (qr )˄(rq )(4) 天下雨或我有空那是不可能的。

5. 设命题p :这个材料很有趣；q :这些习题很难；r :学生喜欢这门课。

（1）p q ∧ （2）()p q r ∧⌝→ （3）p r ↔ （4）p q r ⌝∧⌝∧⌝ （5）p q ∀6. 构造下列各题的真值表，写出成真赋值和成假赋值。

90年老版初中数学人教版课后习题答案

90年老版初中数学人教版课后习题答案1、二次函数y=3x2-4x+5的常数项是（）。

[单选题] *345(正确答案)12、12．下列说法正确的是（）[单选题] *A．一个数前面加上“–”号这个数就是负数B．非负数就是正数C．0既不是正数，也不是负数(正确答案)D．正数和负数统称为有理数3、下列说法正确的是[单选题] *A.绝对值最小的数是0(正确答案)B.绝对值相等的两个数相等C.-a一定是负数D.有理数的绝对值一定是正数4、23.将x-y-6=0改写成用含x的式子表示y的形式为（）[单选题] *A. x=y+6B. y=x-6(正确答案)C. x=6-yD. y=6=x5、1、如果P（ab，a+b）在第四象限，那么Q（a，﹣b）在（）[单选题] * A．第一象限B．第二象限(正确答案)C．第三象限D．第四象限6、14．数﹣在数轴上的位置可以是（）[单选题] *A．点A与点B之间(正确答案)B．点B与点O之间C．点O与点D之间D．点D与点E之间7、已知sina<0且cota＞0，则是（）[单选题] *、第一象限角B、第一象限角C、第三象限角(正确答案)D、第四象限角8、14．命题“?x∈R，?n∈N*，使得n≥x2（x平方）”的否定形式是（）[单选题] * A．?x∈R，?n∈N*，使得n<x2B．?x∈R，?x∈N*，使得n<x2C．?x∈R，?n∈N*，使得n<x2D．?x∈R，?n∈N*，使得n<x2(正确答案)9、已知直线l的方程为2x-y+7=0，（）是直线l上的点[单选题] *A、（2，3）B、（2，4）(正确答案)C、（2，-3）D、（-2，-3）10、如果平面a和平面β有公共点A，则这两个平面就相交（）[单选题] *A、经过点A的一个平面B、经过点A的一个平面(正确答案)C、点AD、无法确定11、9．已知关于x，y的二元一次方程组的解满足x＋y＝8，则k的值为( ) [单选题] * A．4B．5C．－6D．－8(正确答案)12、下列运算正确的是（）[单选题] *A. a2?a3=a?B. （﹣a3）2=﹣a?C. （ab）2=ab2D. 2a3÷a=2a2(正确答案)13、两数之和为负数，则这两个数可能是? [单选题] *A.都是负数B.0和负数(正确答案)C.一个正数与一个负数D.一正一负或同为负数或0和负数14、31、点A(-2,-3)关于y轴对称的点的坐标是（）[单选题] *(2,3)(-2,-3)(3,-2)(2,-3) (正确答案)15、4、已知直角三角形的直角边边长分别是方程x2-14x+48=0的两个根，则此三角形的第三边是（）[单选题] *A、6B、10(正确答案)C、8D、216、5．在下列四点中，与点所连的直线不与y轴相交的是（）．[单选题] * A．（-2，3）B．（2，-3）C（3，2）D（-3，2）(正确答案)17、为筹备班级联欢会，班长对全班同学爱吃哪几种水果做了民意调查，然后决定买什么水果，最值得关注的应该是统计调查数据的( ) [单选题] *A．中位数B．平均数C．众数(正确答案)D．方差18、9、横坐标为3的点一定在（）[单选题] *A.与x轴平行，且与x轴的距离为3的直线上B.与y轴平行，且与y轴的距离为3的直线上C.与x轴正半轴相交，与y轴平行，且与y轴的距离为3的直线上(正确答案)D.与y轴正半轴相交，与x轴平行，且与x轴的距离为3的直线上19、-120°是第（）象限角？[单选题] *第一象限第二象限第三象限(正确答案)第四象限20、29.若（2，a）和（3，b）是直线y=x+k上的两点，那么这两点间的距离为（）[单选题] *A.8B.10C.√2(正确答案)D.221、y=k/x（k是不为0的常数）是（）。