装载机液压系统工作压力不足的原因可能是什么?
参考答案:
安全阀调压偏低;安全阀故障(滑阀卡死);压力弹簧损坏;泵失效;系统管路压力损失过大。
诊断骨折的主要依据是
A.病史和体征
B.X线检查结果
C.肢体较大的血肿
D.肢体功能障碍
E.全身性表现
Beijing: The United States and North Korea had their first ________in four months here this afternoon as part of the ________negotiations on how to end North Korea’’s nuclear program, but diplomats played down prospects for________.James A. Kelly, assistant________, and Kim Yong II, North Korea’’s deputy foreign minister, met ________of formal discussions, ________on direct dialogue that began after a stormy meeting ________in which North Korea warned that it was moving quickly to ________nuclear arms.The Bush administration had insisted ________that it would only hold talks with North Korea ________because, it argued, only ________pressure would persuade North Korea to________. It got its way when North Korea dropped its insistence on ________and agreed, after extensive efforts by China, to hold unusual simultaneous negotiations with ________,________,________and ________as well as the United States.Though Bush administration officials had not ________talking privately with the North Koreans during________, the fact that Mr. Kelly and Mr. Kim met on the first day was seen as a sign of ________by the American side.