如果桁架上弦杆最大受力节间的轴向力及局部弯矩设计值分别为N=1150kN,Mx=165kN.m。上弦杆选用轧制H型钢HM482×300×11×15,截面特性Wx=2520×103mm3,A=146.4×102mm2。考虑露天的腐蚀性环境影响,杆截面抵抗矩及截面积的净截面折减系数取0.9。试问,对上弦杆作强度验算时,其截面上最大拉应力设计值(N/mm2)应与下列何项数值最为接近?
A. 126.2
B. 140.9
C. 156.6
D. 185.0
The sum of the lengths of two sides of isosceles triangle K is 7. K has a side of length 4.
Column A Column B
The perimeter of K 11
A. if the quantity in Column A is greater
B. if the quantity in Column B is greater
C. if the two quantity are equal
D. if the relationship cannot be determined from the information given
Task 2
Directions: This task is the same as Task 1. The 5 questions or unfinished statements are numbered 41 through 45.
In China phone talk is expensive. If you want to make it cheaper, make phone calls using the Internet, which can cost as little as 30% or even 5% of a traditional call.
But changing your DDD (domestic direct dial) and your IDD (international direct dial) calls for the net version, called voice over the internet protocol (互联网协议) or VoIP, requires you to choose between different types of technology, with different advantages.
If a telephone connection was a road, a regular phone call allows you and the person you are calling to share the road without anyone else. On this empty road, the connection is fast, efficient, and uninterrupted. But with VoIP technology, your voice is broken into millions of separated packets of information that share the road with all the billions of other bits of information on the Internet. When the packets reach the person you are calling, they are gathered to resemble your voice. Depending on which type of VoIP you are using, the speed of the Internet connection, Internet traffic, and the service provider, the resulting voice quality can vary -- from quite good to quite awful.
The three main ways of using the internet to make calls are PC-to-PC (家用电脑) calls, PC-to-Phone calls and China's popular IP phone card.
VoIP calls are cheapest when they are made between two computers or between a PC and a telephone. For both, make sure you have a computer, an internet connection, a sound card, and most importantly, a headset (套头耳机) with a microphone.
People prefer IP phone calls to ordinary ones because the former is ______.
A. much more convenient
B. much cheaper
C. more dependable
D. more efficient