Information content of a random variable Random variable x Outcome of a random experiment Discrete R V takes on values from a finite set of possible outcomes PMF: P(X=y)=Py) How much information is contained in the event X=y? Will the sun rise today Revealing the outcome of this experiment provides no information Will the Celtics win the NBa championship? Since this is unlikely, revealing yes provides more information than revealing Events that are less likely contain more information than likely events

Sampling Sampling provides a discrete-time representation of a continuous waveform Sample points are real-valued numbers In order to transmit over a digital system we must first convert into discrete valued numbers

The signal suffers an attenuation loss l Received power PR= PT/L Received snr=E,/No, Eb=Pr/Rb Antennas are used to compensate for attenuation loss Capture as much of the signal as possible

Noise is additional\unwanted \signal that interferes with the transmitted signal Generated by electronic devices The noise is a random process Each\sample \ of n(tis a random variable Typically, the noise process is modeled as\Additive White Gaussian noise”(AWGN) White: Flat frequency spectrur Gaussian noise distribution

Cyclic Codes a cyclic code is a linear block code where if c is a codeword, so are all cyclic shifts of c E.g., 1000, 110, 101,011 is a cyclic code Cyclic codes can be dealt with in the very same way as all other lbc s Generator and parity check matrix can be found a cyclic code can be completely described by a generator string G All codewords are multiples of the generator string In practice, cyclic codes are often used for error detection(CRc) Used for packet networks When an error is detected by the received, it requests retransmission

四爪陆龟 别名草原陆龟,属于陆龟科,学名为 Testudo horsfieldi 爪陆龟是生活在内陆草原地区的龟类。背甲长12~16厘米,宽10~14厘米。头部与四肢均 具黄色;头小,顶部有对称的大鳞;喙缘锯齿状。盾片中央棕黑色,边缘黄色,并有同心 环纹。四肢均有四爪,指、趾间无蹼。前臂与胫部有坚硬大鳞,股后有一丛锥形大鳞。 生活在海拔700~1000米的黄土丘陵地,常在蒿草丰富、土质湿润、螺壳较多的阴坡凹地 栖息。阴天或夜晚躲藏在洞穴中。喜食植物的花果及肉质叶片,好饮水。4~5月份交配, 产卵2~4枚,卵白色椭圆形,孵化期60天左右。幼龟出壳后仍在土里,翌年春季才爬出来 活动。7月下旬入洞穴夏眠,休眠洞较深,常在阳坡栖居

短尾猴 别名红面猴,属于猴科(Macaca arctoides)。 体型比猕猴大,体长50-56厘米。成体 颜面鲜红色,老年紫红色,幼体肉红 色。耳较小,尾短 光秃无毛。体背毛色棕褐,披毛较长 ,腹面略浅;头顶毛较长,由中央向 两侧披开。 短尾猴栖息于亚热带常绿阔叶林中, 生活在树上,也常集群在地面活动。 食性较杂,既取食野果、树叶、竹笋 ,也捕食蟹、蛙等小动物。短尾猴的 数量稀少。目前人工饲养比较困难。 产于西南及广东、广西。 属于国家二级保护动物

第二讲动物学的基本知识 一、动物学的含义和研究历史 动物学是研究动物生命活动的科学,它是以辨证唯物主 义的观点和方法,系统地研究动物的种类组成、形态结 构、生活习性、繁殖与选种、分布规律、历史发展、生 命活动等的特征和规律的学问

目录: 制冷、制热问题 漏水及相关问题 不能启动、启动跳停、频繁启动等 噪声问题 风速、导风问题

例题11994年,人们曾经为106号元素的命名发生过激烈 争论。美国科学家建议把该元素命名为 seaborgium,用 来纪念诺贝尔奖获得者 Glenn Seaborg.请写出该元素的 核外电子排布,用[Rn]来表示内层的86个电子