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介绍了湖北卫视《穿越长江——神奇魔幻之夜》直播晚会节目中,如何依托参考声系统解决远程多地实况电视直播中的信号传输延时、声画不同步问题。 相似文献
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First-principles study of the elastic and thermodynamic properties of thorium hydrides at high pressure
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The high pressure behaviors of Th_4H_(15) and ThH_2 are investigated by using the first-principles calculations based on the density functional theory(DFT). From the energy–volume relations, the bct phase of ThH_2 is more stable than the fcc phase at ambient conditions. At high pressure, the bct ThH_2 and bcc Th_4H(15) phases are more brittle than they are at ambient pressure from the calculated elastic constants and the Poisson ratio. The thermodynamic stability of the bct phase ThH_2 is determined from the calculated phonon dispersion. In the pressure domain of interest, the phonon dispersions of bcc Th_4H(15) and bct ThH_2 are positive, indicating the dynamical stability of these two phases, while the fcc ThH_2 is unstable. The thermodynamic properties including the lattice vibration energy, entropy, and specific heat are predicted for these stable phases. The vibrational free energy decreases with the increase of the temperature, and the entropy and the heat capacity are proportional to the temperature and inversely proportional to the pressure. As the pressure increases, the resistance to the external pressure is strengthened for Th_4H_(15) and ThH_2. 相似文献
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对甘肃定西地区成熟期的5种中草药药用部分的Cr元素含量及这5种中草药根系部分土壤中Cr元素的含量用火焰原子吸收光谱进行了分析,比较了微波消解和高温灰化两种样品预处理方法,选定了微波消解法.实验结果发现,除了黄芪外,中草药中的铬含量明显高于土壤中铬的含量,表明5种中草药对土壤中Cr元素都有生物迁移作用,其迁移作用由强到弱依次是柴胡、甘草、当归、板蓝根和黄芪.原子吸收光谱对这5种中草药及其土壤中的铬的检测结果的相对平均标准偏差分别是0.06%、0.50%,对所有样品的回收率都在94%-105%之间. 相似文献
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四态极化捷变宽带微带天线线阵由八个单元组成.单元采用双馈点口径耦合微带贴片.这种辐射单元具有宽频带以及两馈点之间高隔离度的特性.通过改变连接合成通道的移相器的相位,可以实现水平线极化,垂直线极化、左旋圆极化和右旋圆极化四种极化态.实测的数据表明,在四种极化状态下阵列在8~10.95 GHz的频率范围内都满足VSWR<1.5,在8.85~10.95 GHz的频率范围内阵列的圆极化轴比优于6dB,线极化的交叉极化优于-10 dB,按10 GHz的中心频率计算,带宽均为19%.该线阵也可用于柱抛物面天线的初级馈源,或通过适当的馈电网络组成二维阵. 相似文献