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A Sad Day, at an Uneasy Time, as US Marks 9-11 Attacks

美国纪念9.11恐怖袭击

These days, Americans worry most about an economic recovery that President Obama calls "painfully slow痛苦而缓慢." But on Saturday millions will remember the day

al-Qaida terrorists flew airplanes into the World Trade Center in New York and the Pentagon五角大楼in Washington.

Another hijacked plane crashed in a field in Pennsylvania宾夕法尼亚州when passengers rebelled反抗. Close to three thousand people died that day.

Next year will be a big anniversary周年纪念日, ten years since the day Americans call 9-11.

But this September eleventh comes at an uneasy time. A large number of Americans say they oppose plans to build an Islamic center near the World Trade Center site in New York.

This week attention centered on a Christian基督教的minister牧师with a small following in the state of Florida.

Reverend牧师Terry Jones said he would mark the 9-11 anniversary周年纪念日by burning copies of the Quran古兰经. He said he wanted to send a message to Islamic extremists极端分子.

TERRY JONES: "We are not hateful toward Muslims. We are not aiming this at Muslims, we are aiming this at Sharia law伊斯兰教义."

His church in Gainesville has maybe fifty members. On Thursday, Mr. Jones met with a local Islamic leader in Florida and agreed to cancel the burning. He said the decision was part of an agreement to move the proposed mosque in New York.

But the imam leading that project denied否认any such agreement. In reaction, Mr. Jones said he was not canceling the burning, but was suspending it.

Political and religious leaders around the world had condemned谴责him. The plan even led the State Department美国国务院to warn American travelers to avoid places where protests might take place.

President Obama said burning Qurans could endanger American troops and invite more extremism极端主义活动. Defense Secretary Robert Gates called Mr. Jones on Thursday to urge him to reconsider.

Administration officials called the idea of burning Qurans "un-American.不是美国人的做派" But they also agreed that it would be within constitutional rights, like protesters who burn American flags. The Constitution guarantees保证free speech and bars禁止the government from restricting限制the practice of religion.

President Obama has worked to improve改善relations with the Islamic world. On Thursday he extended greetings to the world's Muslims for Eid al-Fitr斋月, the end of the holy month of Ramadan.斋月

But many Muslim groups in the United States are limiting celebrations on Saturday because of the timing of Eid and 9-11 this year. A Muslim student leader at George Washington University, for example, called on Muslim students to take part in a day of community service.社区服务

On Friday, a new study said national security agencies美国国家安全机构have not changed enough to deal with new terrorist threats against the United States.

Experts warned of a growing threat from Americans going to other countries to train and work with terrorists. At least forty-three American citizens or residents居民linked to militant好战的groups were charged with or convicted明…有罪of terrorism crimes last year. These cases were in the United States and other countries, and were the most since 9-11.

The two former chairmen of the 9-11 Commission委员会that investigated the attacks led the study.

And that's IN THE NEWS in VOA Special English. I'm Steve Ember.

Includes reporting by Nico Colombant, Kent Klein, Elizabeth Lee and Brian Wagner

结构力学中必须掌握的弯矩图

各种结构弯矩图的绘制及图例：一、方法步骤 1、确定支反力的大小和方向（一般情况心算即可计算出支反力） ●悬臂式刚架不必先求支反力； ●简支式刚架取整体为分离体求反力； ●求三铰式刚架的水平反力以中间铰C的某一边为分离体； ●对于主从结构的复杂式刚架，注意“先从后主”的计算顺序； ●对于复杂的组合结构，注意寻找求出支反力的突破口。 2、对于悬臂式刚架，从自由端开始，按照分段叠加法，逐段求作M图（M图画在受拉一侧）；对于其它形式的刚架，从支座端开始，按照分段叠加法，逐段求作M图（M图画在受拉一侧）。二、观察检验M图的正确性 1、观察各个关键点和梁段的M图特点是否相符 ●铰心的弯矩一定为零； ●集中力偶作用点的弯矩有突变，突变值与集中力偶相等；

●集中力作用点的弯矩有折角； ●均布荷载作用段的M 图是抛物线，其凹凸方向与荷载方向要符合“弓箭法则”； 2、结构中的链杆（二力杆）没有弯矩； 3、结构中所有结点的杆端弯矩必须符合平衡特点。表1 简单载荷下基本梁的剪力图与弯矩图梁的简图剪力Fs 图弯矩M 图 1 l a F s F F l a F l a l -+ - F l a l a ) (-+ M 2 l e M s F l M e + M e M + 3 l a e M s F l M e + M e M l a l -e M l a + -

4 l q s F + -2 ql 2 ql M 8 2ql + 2 l 5 l q a s F + -l a l qa 2) 2(-l qa 22 M 2 228)2(l a l qa -+ l a l qa 2) (2 -l a l a 2)2(- 6 l q s F + -3 0l q 6 0l q M 3 92 0l q + 3 )33(l - 7 a F l s F F + Fa -M 8 a l e M s F + e M M

结构力学中必须掌握的弯矩图

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3 二、观察检验M 图的正确性 1、观察各个关键点和梁段的M 图特点是否相符 ●铰心的弯矩一定为零； ●集中力偶作用点的弯矩有突变，突变值与集中力偶相等； ●集中力作用点的弯矩有折角； ●均布荷载作用段的M 图是抛物线，其凹凸方向与荷载方向要符合“弓箭法则”； 2、结构中的链杆（二力杆）没有弯矩； 3、结构中所有结点的杆端弯矩必须符合平衡特点。表1 简单载荷下基本梁的剪力图与弯矩图梁的简图剪力Fs 图弯矩M 图 1 l a F s F F l a F l a l -+ - F l a l a ) (-+ M

4 2 l e M s F l M e + M e M + 3 l a e M s F l M e + M e M l a l -e M l a + - 4 l q s F + -2 ql 2 ql M 8 2ql + 2 l 5 l q a s F + -l a l qa 2) 2(-l qa 22 M 2 228)2(l a l qa -+ l a l qa 2) (2 -l a l a 2)2(- 6 l q s F + -3 0l q 6 0l q M 3 920l q + 3 )33(l -

结构力学弯矩图经典100题

静定结构弯矩图百绘制基本功强化训练 1 2 3 4 5 6 7 8 (8)(7) (5)(4) 一、梁 q M=PL 2P M L q L P PL 2PL P L/22M=qL q (9 (7) (6 (5) (4)(3 一、梁 M= q M=PL 2P M q L P L q L 2PL P L 2M=qL q (9)(8)(7) (6) (5) (4) (1) 、梁 2M=qL P=qL q q M=PL 2P q P=qL L q L L L L q P L L q PL 2PL P L L/2 2M=qL q L 7)(5)4)(3)(2)2 M=qL P=qL q q P=qL M=PL 2P q P=qL M L L 2P P L q P L P q L P L/22 M=qL (10)(4) 一、梁 q 2PL 2M=qL q ) (6) ) (3)2M=qL P=qL q P=qL q P=qL L L q q PL L (5)(4)(2) (1) 一、梁 q q q M=PL 2P L M q L L P L P L/2 2 M=qL q (1 (11) (10) (9)(8)(7)(6) (5) (4) (3) (2) (1) 一、梁 q q q M=q L q L L P L L P q L 2PL P L 2q

9 10 11 12 13 14 15 16 (20) (19) 二、悬臂式刚架 (18) P L /2 L/2 L/2L /2 30P L L M=2qa q 15 M=PL 二、悬臂式刚架 (18) (16) P L /2 L /2 30P L 4a 2a a a 2a 2a a 3a M=2qa q 15 M=PL (20) (19) 二、悬臂式刚架 P L /2 L/2 L/2L /2 30P L L M=2qa q a M=PL (15) (14) (13) (12) (11)(10) (9) (8) L/4 L/4q L L L q L P=qL L M L L L L L (14) (13) (12)(11) (10)(9) (7) L/4 L/4 q L L q L 2 M=qL L q L q M=PL 2P L L q L q L L (14 (13) (10) q L L (12) 11)(9) 8) L /2 L/4 P=qL L L q L P=qL M L

结构力学中必须掌握的弯矩图

4 4 l q s F + - 2 ql 2 ql M 8 2ql + 2 l 5 l q a s F + - l a l qa 2) 2(-l qa 22 M 2 228)2(l a l qa -+ l a l qa 2) (2 -l a l a 2)2(- 6 l q s F + - 3 0l q 6 0l q M 3 92 0l q + 3 )33(l - 7 a F l s F F + Fa - M 8 a l e M s F + e M M

5 9 l q s F ql + M 2 2ql - 10 l q s F 2 l q + M 6 20l q - 注：外伸梁 = 悬臂梁 + 端部作用集中力偶的简支梁

2．单跨梁的内力及变形表（表2-6~表2-10）（1）简支梁的反力、剪力、弯矩、挠度表2-6