7.1数据库安全 计算机系统的三类安全问题:技术安全管理安全,政策法律 1985 DOD Trusted Computer System Evaluation Criteria)) TCSEC将系统分为四组七个等级:D,(c,c2)(b1,b2,b3)a

1留数的图解确定法(复共轭极点)(vdv1.8,1.9) (a)在这里应用对于实数极点的图解确定法(第7讲),但是留数 是共轭复数对

1、相对稳定性:在穿越点或穿越点附近斜率为-20 db/ dec(仅当 没有右半平面的零点)。 2、稳态精度:低频段渐近线 3、工作区间内的精度:在适当的频段需要至少20dB 穿越频率:是带宽和响应速度的度量。a

1.1试举几个开环控制系统与闭环控制系统的例子,画出它们的框图,并说明它们的工作原理。 1.2根据图题1.2所示的电动机速度控制系统工作原理图 (1)将a,b与c,d用线连接成负反馈系统; (2)画出系统方框图

分离气体混合物吸收;分离液体混合物-蒸馏与萃取 一、取适用范围 相对挥发度a=1的液体混合物(或两相沸点接近)另外还适用于蒸馏的热稳定性很差的物 质、分解或聚合、用萃取分离。如:从发酵液中提取青酶素、咖啡因。 如组分浓度很稀,且沸点较高,用液液萃取较为合适。 如从醋酸水溶液中分离醋酸;从稀醋酸水溶液制备无水醋酸。(因为醋酸浓度很低,用水蒸气 蒸馏、需能量很高,经济上不合理,用萃取合适。如:多种金属物质的分离、钴一镍分离等

3-11某APD管用于波长1.55μm,其平均雪崩增益为20,响应度为0.6A/W,当每秒钟有 1000个光子入射时,计算其量子效率和输出光电流

1、计算结构位移主要目的Ja)验算结构的刚度; b)为超静定结构的内力分析打基础。 a)荷载作用 2、产生位移的原因主要有三种b)温度改变和材料胀缩 c)支座沉降和制造误差

一、试验目的及任务 l、掌握传热膜系数α及传热系数K的测定方法。 2、通过实验掌握确定传热膜系数准数关联式中的系数A和指数m、n的方法。 3、掌握测温热电偶的使用方法

The regulations relating to food production are continually being tightened with the aim of improving the safety of food products and the safety of people working in food factories If you work in a food factory you must be acquainted with the potential dangers and constantly endeavour to prevent the food becoming contaminated with noxious substances. You must also

All the ingredients included here are derived from milk or eggs. In their principal value is there are also tenderising properties associated with the fats and emulsifying compounds which they contain. Milk, butter, cheese and eggs have been traditional ingredients for baking due to their exceptional nutritional values as well as their flavour. The techmology of milk production has now developed to such an extent that there are a large