下列几个方程，表示质点振动为“拍”现象的是：（）
A:
B:
C:
D:
A:
B:
C:
D:
举一反三
- 时序逻辑电路如下图所示，其状态方程组是。（）<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202003/75fb6bc0f79d4332b5bdc69605562aba.png" > A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202003/5f963aec69ea48089a47d3cea9ec8f96.png" > B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202003/4a0262f12d584d86a85b3d0917a539aa.png" > C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202003/0733702e95cb4432b6847bfa287c88cc.png" > D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202003/b4619d1e5055487c984ea3b0b338ee02.png" >
- 用三线-八线译码器74LS138和辅助门电路实现逻辑函数<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202003/c871492b27384497a59d367211b93efb.png" >，应：（） A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202003/37b75181b0ad4fba92ee10f87ffa0bbb.png" > B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202003/453b2c724d1d4d41898e10c9ba036a39.png" > C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202003/2c10ee737f77406fa0457e0f02318515.png" > D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202003/9cbe3266526b4e8eab204cf96440be55.png" >
- 钢号Q345A中的345表示钢材的（）。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202003/af6807e52a454663a6eaf1728a03a050.png" >值 B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202003/3cf447dcca4b4032bf4df7ef7b7a8f7f.png" >值 C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202003/390a6cad6f4746668ba550f409ead899.png" >值 D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202003/f0782fccfc8047bb9aea1b0934a4dfed.png" >值
- 下列方程为伯努利方程的是（ ）。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/0622f56257874ab19e680d587fd8a4fc.png"> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/5ce3fc785b724e3da7d07b8d6a0ecaf3.png"> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/ab3de1c35e9e419fa301a33bddd5ee0c.png">+<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/2c226f2daecf40448b08c3b26a4db60e.png"> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/88be95dd74814341a1894f32f073b9ec.png"><img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/00fbcbc7c3574f94934fa3adc8843ccf.png">
- 图示结构，忽略各杆件的轴向变形。已知各杆件的长度均为l，刚度均为EI，受均布荷载作用，用位移法计算时的基本体系如图所示，求出位移法方程中的系数和自由项为（）<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202003/d7f9da9f3d7d4a1ca3aacc9d78b287bc.png" /> A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202003/4e6dd0d1ad09433f951a2ff19b298211.png"/>； B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202003/3b01d536637e445e841b61e5a9fa3506.png"/>。 C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202003/0969ea96f00849a09cccad36566fbf50.png"/>； D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202003/f03eca36624f4c51aff26a8015294edc.png"/>；