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南通大学操作系统第2章作业参考答案 (1)

南通大学操作系统第2章作业参考答案 (1)

13简答题:简述处理机管理的主要功能。

进程控制和管理;⑵进程同步和互斥;⑶进程通信;⑷进程死锁;⑸线程控制和管理;⑹处理器调度。

(每条1分,总分4分)14简答题:简述中断和异常的区别中断是由与现行指令无关的中断信号触发的(异步的),且中断的发生与CPU处在用户模式或内核模式无关,在两条机器指令之间才可响应中断;异常是由处理器正在执行现行指令而引起的,一条指令执行期间允许响应异常。

(1分)⑵中断处理程序处理过程中是不能阻塞的,异常处理程序处理过程中是可以阻塞的。

(1分)⑶中断允许发生嵌套,但异常大多为一重。

(1分)异常处理过程中可能会产生中断,但中断处理过程中决不会被异常打断。

(1分)15简述进程的主要属性。

(1)动态性:有一定的生命周期⑵共享性:多个进程可执行同一程序,进程可以共享公共资源⑶独立性:是一个独立实体,有自己的虚存空间、程序计数器和内部状态,是资源分配、保护和调度的基本单位⑷制约性:存在制约关系(5)并发性:执行时间上会有所重叠16(每条1分,总分4分)16简答题:简述引起进程状态转换的具体原因。

(1)运行态→等待态:等待使用资源或某事件发生;(1分)⑵等待态→就绪态:资源得到满足或事件发生;(1分)⑶运行态→就绪态:运行时间片到;出现有更高优先权进程;(1分)⑷就绪态→运行态:CPU空闲时选择一个就绪进程。

(1分)17、简答题:进程的基本状态有哪些?请画出进程的状态转换图。

进程的基本状态包括:就绪态、运行态和等待态;(2分)⑵进程的状态转换图如下:(2分)18、简答题:简述进程映象的要素。

(1)进程控制块:标志信息、现场信息、控制信息;(1分)⑵进程核心栈:中断/异常现场、函数调用的参数和返回地址;(1分)⑶进程程序块:进程执行的程序;(1分)⑷进程数据块:私有地址空间,私有数据、用户栈。

(1分)19、简答题:简述引起进程调度的原因。

(1)进程终止⑵进程阻塞⑶进程时间片用完经,⑷进程创建⑸进程请求I/O操作完成⑹进程优先级改变⑺进程运行过程中发生中断或异常⑻进程执行系统调用(每条1分,总分4分)20、下列指令中,哪些是特权指令?⑴关中断;⑵访管指令;⑶设置系统时钟;⑷移位指令;⑸启动I/O;⑹读时钟日期;⑺控制中断屏蔽位(1)、⑶、⑸、⑺(每答对1个得1分,答错1个扣1分)。

厦门外国语学校2016届3.14生物作业

厦门外国语学校2016届3.14生物作业

3.14生物作业(2011海南高考生物)31.[生物——选修3:现代生物科技专题](15分)回答有关基因工程的问题:(1)构建基因工程表达载体时,用不同类型的限制酶切割DNA后,可能产生粘性末端,也可能产生_____末端。

若要在限制酶切割目的基因和质粒后使其直接进行连接,则应选择能使二者产生_____(相同,不同)粘性末端的限制酶。

(2)利用大肠杆菌生产人胰岛素时,构建的表达载体含有人胰岛素基因及其启动子等,其中启动子的作用是_____。

在用表达载体转化大肠杆菌时,常用_____处理大肠杆菌,以利于表达载体进入:为了检测胰岛素基因是否转录出了mRNA,可用标记的胰岛素基因片段作探针与mRNA杂交,该杂交技术称为______。

为了检测胰岛素基因转录的mRNA是否翻译成_____,常用抗原-抗体杂交技术。

(3)如果要将某目的基因通过农杆菌传话法导入植物细胞,先要将目的基因插入农杆菌Ti质粒的_____中,然后用该农杆菌感染植物细胞,通过DNA重组将目的基因插入植物细胞的______上。

【答案】(1)平相同(2)驱动基因转录产生mRNA CaCl2 分子杂交技术胰岛素(3)T-DNA DNA【命题立意】本题考查基因工程相关知识,主要考查学生识记、分析和应用能力。

【解析】限制酶切割DNA后,根据识别切点的不同,可产生粘性末端或平末端。

在构建重组质粒时,通常使用同一种限制酶切割目的基因和质粒,以获得相同的粘性末端。

启动子的作用是驱动基因转录产生mRNA。

用CaCl2处理大肠杆菌可增加细菌细胞壁的通过性,使重组质粒容易进入菌体内部。

可用标记的胰岛素基因片段作探针与mRNA杂交技术为分子杂交技术,胰岛素基因在受体细胞中表达的产物是胰岛素。

若通过农杆菌转化法将目的基因导入植物细胞,则需将目的基因插入农杆菌Ti质粒的T-DNA中,然后用该农杆菌感染植物细胞,通过DNA 重组将目的基因插入植物细胞的DNA上。

2012年海南高考生物31.【生物——选修3:现代生物科技专题】(15分)。

计算机网络(王小茹)计算机网络作业参考答案1-3章

计算机网络(王小茹)计算机网络作业参考答案1-3章

《计算机网络》1‐3章课后习题参考解答第一章 概述习题2. 有两个主要网络特性对客户-服务器系统的性能有很大影响:网络的带宽和时延。

举一个高带宽高时延的网络示例;再举一个低带宽和低时延的例子。

解题思路:本题考查对于重要的网络性能指标:带宽和时延的理解答:高带宽高时延的一个例子是横跨大陆的光纤连接,其带宽可达数千兆bps,但是因为传输距离要达数千公里,时延也高。

低带宽和低时延的一个例子是使用双绞线相连的LAN,带宽是10Mbps,时延却可以忽略不计。

习题3.除了带宽和时延,要描述下列业务网络的QoS还需要什么参数:(1)数字化语音业务(2)视频业务(3)金融事务业务?解题思路:本题考查对于除带宽和时延之外的其它网络性能指标的理解答:(1)数字化语音业务还需要时延抖动(jitter)(2)视频业务也需要时延抖动(3)对于金融事务业务,可靠性和安全性也非常重要。

习题4. 存储转发分组交换系统的时延中的一个因素是交换机存储和转发一个数据包所用的时间。

如果交换时间是10微秒,对于一个客户-服务器系统的响应时间是否可能是一个主要因素。

假定客户机在纽约,而服务器在加利福尼亚;假定铜缆和光纤的传播速度是真空中光速的2/3。

解题思路:本题考查对于组成时延的一个因素——节点交换时间的理解,并且比较交换时间和传播时延的大小。

答:传播速度v = c×(2/3) = 3×108×2/3 = 2×108 米/秒交换机存储转发的时延相当于传输距离:s= v×t = 2×108 ×10×10-6 = 2000米而纽约到加利福尼亚的距离超过2000公里,远大于2000米,因此交换机的处理时间对于响应时间影响不大,可以忽略。

习题5. 一个客户-服务器系统使用卫星网络,卫星在40000公里的高空。

从发出请求到收到响应至少需要多少时间?解题思路:本题考查对于传播时延概念的理解及计算。

大工22夏《神经网络》大作业

大工22夏《神经网络》大作业

大工22夏《神经网络》大作业
1. 项目介绍
本次《神经网络》大作业旨在让同学们深入理解神经网络的工作原理,并能够独立实现一个简单的神经网络模型。

通过完成本次作业,同学们将掌握神经网络的基本结构,训练过程以及参数优化方法。

2. 任务要求
1. 独立实现一个具有至少三层神经网络的结构,包括输入层、隐藏层和输出层。

2. 选择一个合适的激活函数,并实现其对应的激活和导数计算方法。

3. 实现神经网络的正向传播和反向传播过程,包括权重更新和偏置更新。

4. 在一个简单的数据集上进行训练,评估并优化所实现的神经网络模型。

3. 评分标准
1. 神经网络结构实现(30分)
2. 激活函数实现(20分)
3. 正向传播和反向传播实现(20分)
4. 模型训练与评估(20分)
5. 代码规范与文档说明(10分)
4. 提交要求
1. 提交代码文件,包括神经网络结构、激活函数、正向传播、反向传播以及训练与评估的实现。

2. 提交一份项目报告,包括项目简介、实现思路、实验结果及分析。

3. 请在提交前确保代码的可运行性,并在报告中附上运行结果截图。

5. 参考资料
1. Goodfellow, I. J., Bengio, Y., & Courville, A. C. (2016). Deep learning. MIT press.
2. Russell, S., & Norvig, P. (2016). Artificial intelligence: a modern approach. Pearson Education Limited.
祝大家作业顺利!。

重大信号与系统作业

重大信号与系统作业

Signals and SystemChap11.6 Determine whether or not each of the following signals is periodic: (a): (/4)1()2()j t x t e u t π+= (b): 2[][][]x n u n u n =+- (c): 3[]{[4][14]}k x n n k n k δδ∞=-∞=----∑1.9 Determine whether or not each of the following signals is periodic, If a signal is periodic , specify its fundamental period:(a): 101()j t x t je = (b): (1)2()j t x t e -+= (c):73[]j n x n e π=(d): 3(1/2)/54[]3j n x n e π+= (e): 3/5(1/2)5[]3j n x n e += 1.14 considera periodic signal 1,01()2,12t x t t ≤≤⎧=⎨-<<⎩with period T=2. Thederivative of this signal is related to the “impulse train”()(2)k g t t k δ∞=-∞=-∑,with period T=2. It can be shown that 1122()()()dx t A g t t A g t t dt=-+-. Determine the values of 1A , 1t , 2A , 2t .a system S with input x[n] and output y[n].This system is obtained through a series interconnection of a system S 1 followed by a system S 2. The input-output relationships for S 1 and S 2 are S 1: ],1[4][2][111-+=n x n x n y S 2: ]3[21]2[][222-+-=n x n x n yWhere ][1n x and ][2n x denote input signals.(a) Determine the input-output relationship for system S.(b)Does the input-output relationship of system S change if the order in which S 1 and S 2 are connected in series is reversed(i e ,if S 2 follows S 1)? a discrete-time system with input x[n] and output y[n].The input-output relationship for this system is]2[][][-=n x n x n y(a) Is the system memoryless?(b) Determine the output of the system when the input is ][n A δ, where A is any real or complex number. (c) Is the system invertible?a continuous-time system with input x(t) and output y(t) related by))(sin()(t x t y =(a) Is this system causal? (b) Is this system linear?1.21.A continous-time signal ()x t is shown in Figure P1.21. Sketch and label carefully each of the following signals:(a): (1)x t - (b): (2)x t - (c): (21)x t + (d): (4/2)x t - (e): [()()]()x t x t u t +- (f):()[(3/2)(3/2)]x t t t δδ+--1.22. A discrete-time signal ()x t is shown in Figure P1.22. Sketch and label carefully each of the following signals:(a): [4]x n - (b): [3]x n - (c): [3]x n (d): [31]x n + (e): [][3]x n u n - (f): [2][2]x n n δ-- (g):11[](1)[]22n x n x n +- (h): 2[(1)]x n - whether or not each of the following continuous-time signals is periodic. If the signal is periodic, determine its fundamental period.(a): ()3cos(4)3x t t π=+ (b): (1)()j t x t e π-= (c):2()[cos(2)]3x t t π=-(d): (){cos(4)()}x t t u t ενπ= (e): (){sin(4)()}x t t u t ενπ= (f): (2)()t n n x t e∞--=-∞=∑1.26. Determine whether or not each of the following discrete-time signals is periodic. If the signal is periodic, determine its fundamental period. (a):6[]sin(1)7x n n π=+ (b): []cos()8nx n π=- (c): 2[]cos()8x n n π= (d):[]cos()cos()24x n n n ππ=(e):[]2cos()sin()2cos()4826x n n n n ππππ=+-+Chap 22.1 Let]3[]1[2][][---+=n n n n x δδδ and ]1[2]1[2][-++=n n n h δδCompute and plot each of the following convolutions: (a)][*][][1n h n x n y = (b)][*]2[][2n h n x n y += (c)]2[*][][3+=n h n x n y2.3 Consider an input x[n] and a unit impulse response h[n] given by],2[)21(][2-=-n u n x n].2[][+=n u n hDetermine and plot the output ].[*][][n h n x n y = 2.7 A linear system S has the relationship[][][2]k y n x k g n k ∞=-∞=-∑Between its input x[n] and its output y[n], where g[n]=u[n]-u[n-4]. (a) Determine y[n] where ]1[][-=n n x δ (b) Determine y[n] where ]2[][-=n n x δ (c) Is S LTI?(d) Determine y[n] when x[n]=u[n] 2.10 Suppose that⎩⎨⎧≤≤=elsewhere t t x ,010,1)( And )/()(αt x t h =,where 10≤<α.(a) Determine and sketch )(*)()(t h t x t y =(b) If dt t dy /)( contains only three discontinuities, what is the value ofα?2.11 Let)5()3()(---=t u t u t x and )()(3t u e t h t -=(a) Compute )(*)()(t h t x t y =. (b) Compute )(*)/)(()(t h dt t dx t g =. (c) How is g(t) related to y(t)? 2.20 Evaluate the following integrals: (adt t t u )cos()(0⎰∞∞-(b)⎰+50)3()2sin(dt t t δπ (c)⎰--551)2cos()1(τπττd u2.27 We define the area under a continuous-time signal )(t v as⎰∞∞-=dt t v A v )(Show that if )(*)()(t h t x t y =, thenh x y A A A =2.40 (a) an LTI system with input and output related through the equationτττd x e t y tt )2()()(-=⎰∞---What is the impulse response h(t) for this system?(b) Determine the response of the system when the input x(t) is as shown in Figure P2.40.Chap 33.1 A continuous-time periodic signal x(t) is real value and has a fundamental period T=8. The nonzero Fourier series coefficients for x(t) arej a a a a 4,2*3311====--.Express x(t) in the form)cos()(0k k k k t A t x φω+=∑∞=3.2 A discrete-time periodic signal x[n] is real valued and has a fundamental period N=5.The nonzero Fourier series coefficients for x[n] are10=a ,4/2πj e a --=,4/2πj e a =,3/*442πj ea a ==- Express x[n] in the form)sin(][10k k k k n A A n x φω++=∑∞=3.3 For the continuous-time periodic signal)35sin(4)32cos(2)(t t t x ππ++= Determine the fundamental frequency 0ω and the Fourier series coefficients k a such thattjk k kea t x 0)(ω∑∞-∞==.3.5 Let 1()x t be a continuous-time periodic signal with fundamental frequency 1ω and Fourier coefficients k a . Given that211()(1)(1)x t x t x t =-+-How is the fundamental frequency 2ω of 2()x t related to ?Also, find a relationship between the Fourier series coefficients k b of 2()x t and the coefficients k a You may use the properties listed in Table 3.1. 3.8 Suppose we are given the following information about a signal x(t): 1. x(t) is real and odd.2. x(t) is periodic with period T=2 and has Fourier coefficients k a .3. 0=k a for 0||>k .4 1|)(|21202=⎰dt t x .Specify two different signals that satisfy these conditions.3.13 Consider a continuous-time LTI system whose frequency response is⎰∞∞--==ωωωω)4sin()()(dt e t h j H t jIf the input to this system is a periodic signal⎩⎨⎧<≤-<≤=84,140,1)(t t t x With period T=8,determine the corresponding system output y(t). 3.15 Consider a continuous-time ideal lowpass filter S whose frequency response is1, (100)()0, (100)H j ωωω⎧≤⎪=⎨>⎪⎩When the input to this filter is a signal x(t) with fundamental period6/π=T and Fourier series coefficients k a , it is found that)()()(t x t y t x S=→.For what values of k is it guaranteed that 0=k a ?a continuous-time LTI system S whose frequency response is 1,||250()0,H j otherwiseωω≥⎧=⎨⎩When the input to this system is a signal x(t) with fundamental period/7T π= and Fourier series coefficients k a ,it is found that the output y(t)is identical to x(t).For what values of k is it guaranteed that 0k a =?Chap 44.1 Use the Fourier transform analysis equation(4.9)to calculate the Fourier transforms of;(a))1()1(2---t u e t (b)|1|2--t eSketch and label the magnitude of each Fourier transform.4.2 Use the Fourier transform analysis equation(4.9) to calculate the Fourier transforms of: (a))1()1(-++t t δδ (b))}2()2({-+--t u t u dtdSketch and label the magnitude of each Fourier transform.4.5 Use the Fourier transform synthesis equation(4.8) to determine the inverse Fourier transform of ()()|()|jX j X j X j e ωωω=,where|()|2{(3)(3)}X j u u ωωω=+-- 3()2X j ωωπ=-+Use your answer to determine the values of t for which x(t)=0. 4.6 Given that x(t) has the Fourier transform ()X j ω, express the Fourier transforms of the signals listed below in the terms of ()X j ω.You may find useful the Fourier transform properties listed in Table4.1. (a))1()1()(1t x t x t x --+-= (b))63()(2-=t x t x(c) )1()(223-=t x dtd t x4.11 Given the relationships)()()(t h t x t y *=And)3()3()(t h t x t g *=And given that x(t) has Fourier transform )(ωj X and h(t) has Fouriertransform )(ωj H ,use Fourier transform properties to show that g(t) has the form)()(Bt Ay t g =Determine the values of A and B.4.13 Let x(t) be a signal whose Fourier transform is()()()(5)X j ωδωδωπδω=+-+-And let()()(2)h t u t u t =--(a) Is x(t) periodic? (b) Is ()*()x t h t periodic?(c) Can the convolution of two aperiodic signals be periodic?4.14 Consider a signal x(t) with Fourier transform )(ωj X .Suppose we are given the following facts: 1. x(t) is real and nonnegative.2. ),()}()1{21t u Ae j X j F t --=+ωωwhere A is independent of t.3.⎰∞∞-=πωω2|)(|d j X .Determine a closed-form expression for x(t).Chap 66.1 Consider a continuous-time LTI system with frequency response()()|()|H j H j H j e ωωω=and real impulse response h(t). Supposethat we apply an input 00()cos()x t t ωφ=+ to this system .Theresulting output can be shown to be of the form0()()y t Ax t t =-Where A is a nonnegative real number representing an amplitude-scaling factor and 0t is a time delay.(a)Express A in terms of |()|H j ω.(b)Express 0t in terms of 0()H j ω6.3 Consider the following frequency response for a causal and stable LTI system:1()1j H j j ωωω-=+ (a) Show that |()|H j A ω=,and determine the values of A.(b)Determine which of the following statements is true about ()τω,the group delay of the system.(Note ()(())/d H j d τωωω=-,where()H j ωisexpressed in a form that does not contain any discontinuities.)1.()0 0for τωω=>2.()0 0for τωω>>3 ()0 0for τωω<>6.5 Consider a continuous-time ideal bandpass filter whose frequency response is⎩⎨⎧≤≤=elsewherej H c c ,03||,1)(ωωωω (a) If h(t) is the impulse response of this filter, determine a function g(t)such that)(sin )(t g tt t h c πω= (b) As c ω is increased, dose the impulse response of the filter get moreconcentrated or less concentrated about the origin?Chap 77.1 A real-valued signal x(t) is know to be uniquely determined by its samples when the sampling frequency is 10,000s ωπ=.For what values of ω is ()X j ω guaranteed to be zero?7.2 A continuous-time signal x(t) is obtained at the output of an ideal lowpass filter with cutoff frequency 1,000c ωπ=.If impulse-train sampling is performed on x(t), which of the following sampling periods would guarantee that x(t) can be recovered from its sampled version using an appropriate lowpass filter?(a) 30.510T -=⨯(b) 3210T -=⨯(c) 410T -=7.3 The frequency which, under the sampling theorem, must be exceeded by the sampling frequency is called the Nyquist rate. Determine the Nyquist rate corresponding to each of the following signals:(a)()1cos(2,000)sin(4,000)x t t t ππ=++ (b)sin(4,000)()t x t tππ=(c) 2sin(4,000)()()t x t t ππ= 7.4 Let x(t) be a signal with Nyquist rate 0ω. Determine the Nyquist ratefor each of the following signals:(a)()(1)x t x t +- (b)()dx t dt(c)2()x t(d)0()cos x t t ω 7.9 Consider the signal2sin 50()()t x t tππ= Which we wish to sample with a sampling frequency of 150s ωπ= to obtain a signal g(t) with Fourier transform ()G j ω.Determine the maximum value of 0ω for which it is guaranteed that0()75() ||G j X j for ωωωω=≤Where ()X j ω is the Fourier transform of x(t).Chap 88.1 Let x(t) be a signal for which M ()0 when ||> X j ωωω=.Another signal y(t) is specified as having the Fourier transform ()2(())c Y j X j ωωω=-.Determine a signal m(t) such that8.3 Let x(t) be a real-valued signal for which()0 ||2,000X j when ωωπ=>.Amplitude modulation is performed toproduce the signal()()sin(2,000)g t x t t π=A proposed demodulation technique is illustrated in Figure P8.3 where g(t) is the input, y(t) is the output, and the ideal lowpass filter has cutoff frequency 2,000πand passband gain of 2. Determine y(t).FigureP8.38.22 In Figure P8.22(a), a system is shown with input signal x(t) and output signal y(t).The input signal has the Fourier transform ()X j ω shown in Figure P8.22(b). Determine and sketch ()Y j ω, the spectrum of y(t).8.28 In Section 8.4 we discussed the implementation of single-sideband modulation using 090 phase-shift networks, and in Figure8.21 and 8.22 we specifically illustrated the system and associated()()()x t y t m t =spectra required to retain the lower sidebands.Figure P8.28(a) shows the corresponding system required to retain the upper sidebands.(a) With the same ()X j ω illustrated in Figure8.22, sketch12(),()Y j Y j ωω,and ()Y j ω for the system in FigureP8.28(a), and demonstrate that only the upper sidebands are retained.(b) F or ()X j ω imaginary, as illustrated in FigureP8.28(b), sketch12(),()Y j Y j ωω and ()Y j ω for the system in FigureP8.28(a), and demonstrate that , for this case also, only the upper sidebands are retained.Chap 99.2 Consider the signal 5()(1)t x t e u t -=- and denote its Laplace transform by X(s).(a)Using eq.(9.3),evaluate X(s) and specify its region of convergence. (b)Determine the values of the finite numbers A and 0t such that theLaplace transform G(s) of 50()()t g t Ae u t t -=-- has the same algebraic form as X(s).what is the region of convergence corresponding to G(s)?9.5 For each of the following algebraic expressions for the Laplace transform of a signal, determine the number of zeros located in the finite s-plane and the number of zeros located at infinity: (a)1113s s +++ (b) 211s s +- (c) 3211s s s -++9.7 How many signals have a Laplace transform that may be expressed as2(1)(2)(3)(1)s s s s s -++++ in its region of convergence? Solution:There are 4 poles in the expression, but only 3 of them have different real part.∴ The s-plane will be divided into 4 strips which parallel to the jw-axis and have no cut-across.∴ There are 4 signals having the same Laplace transform expression.9.8 Let x(t) be a signal that has a rational Laplace transform with exactly two poles located at s=-1 and s=-3. If 2()() ()t g t e x t and G j ω=[ the Fourier transform of g(t)] converges, determine whether x(t) is left sided, right sided, or two sided. 9.9 Given that1(),{}Re{}sat e u t Re s a s a -↔>-+ Determine the inverse Laplace transform of22(2)(),Re{}3712s X s s s s +=>-++ 9.10 Using geometric evaluation of the magnitude of the Fourier transform from the corresponding pole-zero plot ,determine, for each of the following Laplace transforms, whether the magnitude of the corresponding Fourier transform is approximately lowpass, highpass, or bandpass. (a): 11(),{}1(2)(3)H s e s s s =ℜ>-++ (b): 221(),{}12s H s e s s s =ℜ>-++ (c): 232(),{}121s H s e s s s =ℜ>-++ 9.13 Let ()()()g t x t x t α=+- ,Where ()()t x t e u t β-=. And the Laplace transform of g(t) is 2(),1{}11s G s e s s =-<ℜ<-. Determine the values of the constants αand β.。

计算机网络作业题解答

计算机网络作业题解答

Computer NetworksSolution#6Problem1(P4of chapter4in[1])Consider the network below.(a)Suppose that this network is a datagram network.Show the forwarding table in router A,such that alltraffic destined to host H3is forwarded through interface3.(b)Suppose that this network is a datagram network.Can you write down a forwarding table in router A,such that all traffic from H1destined to host H3is forwarded through interface3,while all traffic from H2destined to host H3is forwarded through interface4?(Hint:this is a trick question.)(c)Now suppose that this network is a virtual circuit network and that there is one ongoing call betweenH1and H3,and another ongoing call between H2and H3.Write down a forwarding table in router A, such that all traffic from H1destined to host H3is forwarded through interface3,while all traffic from H2destined to host H3is forwarded through interface4.(d)Assuming the same scenario as(c),write down the forwarding tables in nodes B,C,and D.Solution:(a)Data destined to host H3is forwarded through interface3Destination Address Link InterfaceH33(b)No,because forwarding rule is only based on destination address.(c)One possible configuration is:Incoming interface Incoming VC#Outgoing Interface Outgoing VC#112322263418Note,that the twoflows could actually have the same VC numbers.d.One possible configuration is:Router BIncoming interface Incoming VC#Outgoing Interface Outgoing VC#1222241Router CIncoming interface Incoming VC#Outgoing Interface Outgoing VC#118250Router DIncoming interface Incoming VC#Outgoing Interface Outgoing VC#124370250376Problem2(P5of chapter4in[1])Consider a VC network with a2-bitfield for the VC number.Suppose that the network wants to set up a virtual circuit over four links:link A,link B,link C,and link D.Suppose that each of these links is currently carrying two other virtual circuits,and the VC numbers of these other VCs are as follows:Link A Link B Link C Link D0001101101101100In answering the following questions,keep in mind that each of the existing VCs may only be traversing one of the four links.a.If each VC is required to use the same VC number on all links along its path,what VC number couldbe assigned to the new VC?b.If each VC is permitted to have different VC numbers in the different links along its path(so thatforwarding tables must perform VC number translation),how many different combinations of four VC numbers(one for each of the four links)could be used?Solution:a.No VC number can be assigned to the new VC;thus the new VC cannot be established in the network.b.Each link has two available VC numbers.There are four links.So the number of combinations is24=16.One example combination is(10,00,00,10).Problem3(P11of chapter4in[1])Consider a datagram network using8-bit host addresses.Suppose a router uses longest prefix matching and has the following forwarding table:Prefix Match Link Interface00001010112102113For each of the four interfaces,give the associated range of destination host addresses and the number of addresses in the range.Solution:Destination Address Range Link Interface00000000through00111111001000000through01011111101100000through01111111210000000through10111111211000000through111111113The number of addresses for interface0=26=64.The number of addresses for interface1=25=32.The number of addresses for interface2=26+25=96.The number of addresses for interface3=26=64.References[1]James F.Kurose and Keith puter networking:a top-down approach.Addison-Wesley/Pear-son,6th edition,2012.。

2017软件学院物理作业题

2017软件学院物理作业题

作业1 姓名 学号班级 提交日期 成绩1.关于电场强度定义式0q FE=,下列说法中哪个是正确的?[ ]A.场强E的大小与试探电荷0q 的大小成反比;B.对场中某点,试探电荷受力F与0q 的比值不因0q 而变; C.试探电荷受力F 的方向就是场强E的方向;D.若场中某点不放试探电荷0q ,则0F = ,从而0E =。

2.一个质子,在电场力作用下从A 点经C 点运动到B 点,其运动轨迹如图所示,已知质子运动的速率是递增的,下面关于C点场强方向的四个图示哪个正确?[ ]1-2 题图简单说明理由:3.带电量均为q +的两个点电荷分别位于X 轴上的a +和a -位置,如图所示,则Y 轴上各点电场强度的表示式为E= ,场强最大值的位置在y = 。

1-3 题图4. 如图所示,在一无限长的均匀带电细棒A 旁垂直放置一均匀带电 的细棒B.且二棒共面,若两棒的电荷线密度均为λ,细棒B 长为l , 左端到A 棒距离也为l ,求:B 受到的电场力.5.以点电荷为中心,半径为R 的球面上,场强的大小一定处处相等吗?为什么?6. 用不导电的细塑料棒弯成半径为R 的圆弧,两端间空隙为l ()l R <<,若正电荷Q 均匀分布在棒上,求圆心处场强的大小和方向。

7.如图所示,将一绝缘细棒弯成半径为R 的半圆形,其上半段均匀带有电荷Q ,下半段均匀带有电量Q -,求半圆中心处的电场强度。

1-7 题图8. 线电荷密度为 的“无限长”均匀带电细线,弯成图示形状,若圆弧半径为R ,试求O 点的场强。

9.金属最容易带上正电荷的方式是什么?这样带了正电荷的金属质量有所增大?减小?不变?B图17-7 1-8题图作业2 姓名 学号班级 提交日期 成绩1.如图所示,把点电荷q +从高斯面外P 移到R 处()OP OR =,O 为S 上一点,则[ ]. A. 穿过S 的电通量e φ发生改变,O 处E变;B. e φ不变,E变; C. e φ变,E不变;D. e φ不变,E不变。

大连理工大学《操作系统》大作业离线作业答案

大连理工大学《操作系统》大作业离线作业答案

学习中心:专业:计算机科学与技术年级: 18年秋季学号:学生:题目:进程同步与互斥生产者与消费者问题1.谈谈你对本课程学习过程中的心得体会与建议:在学习操作系统之前,我只是很肤浅地认为操作系统只是单纯地讲一些关于计算机方面的操作应用,并不了解其中的具体操作过程和实用性。

通过这一学期的学习,我才知道操作系统(Operating System,简称OS)是管理计算机系统的全部硬件资源包括软件资源及数据资源;控制程序运行;改善人机界面;为其它应用软件提供支持等,使计算机系统所有资源最大限度地发挥作用,为用户提供方便的、有效的、友善的服务界面。

经过一个学期的学习,我也知道了计算机操作系统是铺设在计算机硬件上的多层系统软件,不仅增强了系统的功能,而且还隐藏了对硬件操作的细节,由它实现了对计算机硬件操作的多层次的抽象。

操作系统的一些原理在生活中也有所应用本次课程设计中,完成本题我觉得还可以用其他语言来做,也让我更加熟悉掌握学习过的编程语言。

为实现生产者和消费者问题,使用的是C++语言,自我感觉比较好的是运用到了线程,将缓冲区作为一个循环队列,简单模拟了生产者和消费者对于缓冲区的输入输出,结果是比较成功的。

2.《操作系统》课程设计,从以下5个题目中任选其一作答。

《操作系统》课程设计题目四:进程同步与互斥生产者与消费者问题要求:(1)撰写一份word文档,里面包括(设计思路、流程(原理)图、源代码)章节。

(2)设计思路:简单描述生产者与消费者问题。

可设计生产者进程主要计算进程,消费者进程输出打印进程,二者彼此独立,运行速度不确定,可能会产生还未生产就需要消费这种情况,此时引用一个或若干个缓冲区,存放生产者生产的信息,解决速度不确定带来的问题。

(3)流程(原理)图:绘制流程图或原理图。

(4)源代码:列出源代码,也可以仅列出伪代码。

1. 需求分析1.1问题描述:一组生产者向一组消费者提供消息,它们共享一个有界缓冲区n,生产者向其中投放消息,消费者从中取得消息。

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IAH 204: Asia and the WorldSpring 2015: Professor KeithPaper #2Due date: Thursday, 4/2, in class, in hard copy.Question:Imagine that How To Get Filthy Rich In Rising Asia is the only book you’ve ever read about the country where the novel takes place. The country is unnamed in the novel, so call it “Youland.” A friend is about to visit Youland, they know you’ve read this book, so they ask you to tell them about it. Write a 5-page introduction to Youland for your friend to read on the plane.Formal Guidelines:The paper should be 5 pages, double-spaced, 12-point font, 1-inch margins. No title, cover page, or bibliography are necessary, and please do not restate the question at the top of the paper.When citing from the book, which you should do, please do not use conventional footnotes. Instead, simply place the page number for the passage you are quoting in parentheses. The page number should come from the original pagination and not the page number in the course pack.Example: “Your city is not laid out as a single-celled organism, with a wealthy nucleus surrounded by an ooze of slums” (20).Please note that the parentheses come after the quotation, but before the punctuation mark ending the sentence or the phrase (comma, semicolon, colon, period, etc.).IMPORTANT NOTE: you’ll probably use the main character’s life and experiences as your main example s in the description of “Youland.” But because this novel is written in the second person, you might find it difficult to refer to the character in the third person. When describing the character, refer to him as “Mr. You.” This will avoid confusion, espe cially in constructions like the possessive (it’ll be “Mr. You’s life” instead of “your life.”)Jiabao WenA47013749IAH 204-008, Paper 2Dear friend,I have heard you are going to travel Youland. I would probably say this is going to be an exciting trip, since Youland is utterly different from United States in many aspects. Reading the book “how to get filthy rich in rising Asia” allows me experiencing the scenes of an Islamic country with its unique ethics. As more places you travel in Youland, you will not only see how people in different social groups live together, but also witness the characteristics of social stability in such a place filled with terrorism and lawlessness which you could not imagine in America. As many other developing countries, Youland does not seem to have a set of rules to regulate the operation of society. However, I think complex social network and Islamic ethic replace its governance to enable Youland continuously develop instead of sliding into chaos. In this letter, I would like to tell you Mr. You‟s experiences, to demonstrate the feature of this place.Through the reading, my first impression is that Youland has poor governance combined with other social unrest elements. Such phenomenon is derived from corruption, unfairness and violence. Initially, corruption is evident in the entire society, which is not limited in social groups. On the one hand, common citizens are busy with various kinds of corruption. For example, Mr. You‟s primary school teacher wishes to be better off through utilization of power as a meter reader. “and what is more important,have greater opportunity for corruption and are hence both better off and held in higher regard by society”(23). On the other hand, corruption is also popular among officials and businessmen, which leads to a situation of interdependence. “Entrepreneurship in the barbaric wastes furthest from state power is a fraught endeavor, a constant battle, a case of kill or be killed, with little guarantee of success”(140). More specifically, after Mr. You launches his bottled water business, Befriend a bureaucrat is going to be indispensible. When he intends to become a municipal vendor, official‟s approval authorizes his plan. Their conversation‟s explicitness indirectly exposes the popularity of corruption. “…All our quantifiable requirements. It is my duty to ensure our unquantifiable requirements are also met. Reputational requirements, for example.‟ …Our reputation is that we‟re friendly.‟ …Good.‟”(142). Throughout their conversation, we can easily notice the sense of corruption not only exist in people‟s life and work, but also fills in their hearts. Theoretically, poverty and injustice is the root of corruption. You are also going to see the inequality and unfairness of wealth distribution in Youland.Unfairness among people is initially demonstrated from the incredible gap between the rich and the poor. Unlike most developed nations, such inequality is magnified in an exaggerative way. Some officials in high positions are extremely powerful to some extent, seemingly no constraints in the law, whereas many common citizens with no education hardly maintain their safety and dignity. The key determinant of your fate is where you are born. Persons who are born in rural areas are keen on migration into urbanareas, even though many of them are incapable to overcome financial barrier. For instance, Mr. You‟s parents argue whether or not undertake the rural-urban migration. Mr. You‟s mother believes her husband earn a fair salary and get rid of poverty, while Mr. You‟s father claims his salary makes him a poor man in the city. “Moving to the city is the first step to getting filthy rich in rising Asia”(15), so many farmers move into metropolitans leading to cities‟expansions despite the economic burdens they bear. However, being an urban resident is obviously inadequate to have a high living standard in Youland, since Mr. You‟s family are always in lack of proteins in the dinner table. From this point onwards, obtaining education and rampant nepotism are also vitally important, as Mr. You‟s father realizes his employer, “who were the world a festival of unarmed banditry, he would have beaten, bound, and relieved of their possessions in a few quick minutes”(59), benefit from these two things he lacks. Therefore, the permission to enter into Youland‟s upper class also depends on your family background and the opportunity to get educated, whilst most citizens do not possess either of them.Unfairness of life in Youland, as a country with no certain regulation and legislation, leads to a series of violence as well. Similarly with corruption, violence is universal in Youland and not the privilege of those who are powerful. Mr. You‟s primary school teacher is openly abusive his pupils. “You, as one of the brightest students, have drawn some of the most severe punishment”(22). This teacher‟s torture is simply out of abnormal sense of satisfaction, while others applying violence are for certain purposes.Moreover, as Mr. You‟s business is gradually blooming, he is threatened and given an ultimatum. If he do not exit the bottled water business, he will be likely assassinated by the killer. “So you are frightened, but nor only frightened, you are also angry, seethingly furious”(124). The similar human right violation happened in Mr. You is uncommon in country with regular legal system.As far as I concerned, there are multiple social problems sticking to Youland. Thus, many citizens hardly retain their dignities, safeties and other basic personal rights. However, most people also form a social network in this culture to assist each other there. Mr. You and his family benefits from such network when he is young, and he and his wife also contribute to others after being rich. Based on my understanding, the Youland social network of assistance could be classified into different categories. Some kinds of assistances are because of unbreakable family bonds, while benevolences also arise from the rich to help someone unrelated them. When Mr. You are in the university, Mr. You‟s mother has a cancer, and his family cannot afford the surgical charge. Mr. You‟s father‟s matriarch agrees with Mr. You‟s father sponsoring his wife‟s surgery, which is a figure greater than his annual salary. Mr. You‟s father shows great appreciation towards his employer. “He bows at the neck to her, again and again, a gesture like a nervous tic. You have not seen him in the presence of one of his employers since you were a child”(65). Meanwhile, Mr. You‟s college organization senior grants Mr. You‟s mother a referral in the clinic for free. On the other hand, after Mr. You starts the bottle water business, he hasa better financial ability, and employs his clansmen to improve their living conditions. “The three of you eat together in fellowship, chatting among yourselves like siblings, which in a way you are, since these two are your clansmen, distant relatives bound by blood, and so yes, like siblings, except of course that when you tell these siblings to finish quickly, they must and do obey”(102). Because of the Islamic ethics, the awareness of benevolence influence Youland people. To some extent, this virtue might greatly alleviate social conflict and generate warmth in the society.Finally, I would elect my feelings toward Youland, and some suggestions in your journey. Because this country is filled with many social unrest elements, and no certain plan on its development and regulations, you would actually see something exciting and surprising. In comparison with other many western countries, its unique social network system and importance of family bonds are really going to give you an engraving impression. I hope you get involved in Youland group, and experience the wonderful culture and atmosphere.。

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