数字通信系统具有许多优点。然而许多信源输出都是模拟信号。 若要利用数字通信系统传输模拟信号,一般需三个步骤: (1)把模拟信号数字化,即模数转换(A/D); (2)进行数字方式传输; (3)把数字信号还原为模拟信号,即数模转换(D/A) 由于A/D或D/A变换的过程通常由信源编(译)码器实现,所以我们把发端 的A/D变换称为信源编码,而收端的D/A变换称为信源译码,如语音信号的数字 化叫做语音编码

1.1用真值表证明下列恒等式 (1)⊕B=A⊙B=AB1 (2)A(B⊕C)=AB⊕AC (3)(A+B)(A+C)(B+C)=(a+B)(a+C)

System Concept Need (technology Pull Technologies can fulfill need or requirement a Technologies can overcome barriers(imitations, constraints, etc. Opportunity(Technology Push) a Technologies can Create Opportunities

• Application: Zone melting Morphology Instability of a S/L interface • Constitutional undercooling • Morphological instability of a S/L interface

Liabilities Definition Macintosh PICT image format is not supported A liability is probable future payment of assets or services that company is presently obligated to make as a result of past transactions or events

外研版（三起）（2012）小学英语五年级下册Module 1 Unit 2 She didn't have a television.Module 1 Unit 2 She didn't have a television.课件(3)

Compounding is a process of word formation by which two independent words are put together to make one word. The word formed in this way is c a lled co mpo und

Recall the definition of stress: o stress =\intensity of internal force at a point\ Figure 3.1 Representation of cross-section of a general body

Outline 11.1 Nitrogenous Bases 11. The pentoses of nucleotides and na 11.3 Nucleosides are Formed by joining a Nitrogenous Base to a Sugar 11.4 Nucleotides -Nucleoside Phosphates 11.5 Nucleic Acids are Polynucleotides 11.6 Classes of nucleic acids 11.7 Hydrolysis of Nucleic acids

高等数学第七章及上册综合题 一选择填空 1已知lim-ax-b=0,则( ) x→x+1 (A)a=1,b=1(B)a=1,b=-1(C)a=-1,b=1(d)a=-1,b=-1 2如果f(x)g(x)都在x点处间断,那么() (A)f(x)+g(x)都在x点处间断(B)f(x)-g(x)都在x点处间断 ()f(x)+g(x)都在x点处连续(D)fx)+g(x)都在x点处可能连续 3函数f(x)=xx(x2-3x+2)(x+2)有()个不可导点