基于Dual-Mode MMA+MDD双模式T/2分数间隔盲均衡算法的研究

均衡技术是用来解决通信系统中码间干扰的常用方法.针对传统恒模算法的收敛速度和稳态剩余码间干扰大的缺点,将双模式多模算法和改进型判决引导算法结合起来,并且应用于分数间隔盲均衡器中.该算法初期用双模式算法收敛均衡器,然后切换到改进型判决引导算法中进一步收敛,由于分数间隔均衡器解决了波特间隔均衡器因抽样率不高带来的频谱混叠问...     

DAC加载下材料高压声速的激光超声测量技术

 设计并建立了可测量金刚石压砧（DAC）加载下材料高压声速的激光超声系统。该系统采用脉宽为6.3 ns的调Q激光器作为超声波激发光源,使用光纤位移干涉仪和速度干涉仪混合系统进行超声位移探测,不需要借助其它任何参数即可直接测量样品的高压声速和原位厚度。利用该系统,测量了2.6 GPa压力下铜样品的高压纵波声速和原位厚度,并给出了测量结果。     

Ruby fluorescence pressure scale： Revisited

Effect of non-hydrostatic stress on X-ray diffraction in a diamond anvil cell (DAC) is studied. The pressure gradient in the sample chamber leads to the broadening of the diffraction peaks, which increase with the hkl index of the crystal. It is found that the difference between the determined d-spacing compressive ratio d/d0 and the real d-spacing compressive ratio dr/d0 is determined by the yield stress of the pressure transmitting media (if used) and the shear modulus of the sample. On the basis of the corrected experiment data of Mao et al. (MXB86), which was used to calibrate the most widely used ruby fluorescence scale, a new relationship of ruby fluorescence pressure scale is corrected, i.e., P = (1904/9.827)[(1+λ/λ0)9.827-1].     

蒲葵籽活性单体的分离及其抗癌活性研究

通过乙醇浸提、乙酸乙酯萃取、减压蒸馏得到蒲葵籽乙酸乙酯相,经过硅胶色谱柱及TLC分离、结晶及重结晶等方法,获得7种主要的单体化合物,质谱表征结果显示分别为豆甾醇、薯蓣皂苷元、棕榈酸乙酯、小麦黄素、芹菜素、β-胡萝卜苷和正十六酸,其中薯蓣皂苷元首次从蒲葵籽乙酸乙酯相中获得。对分离出的单体化合物进行MTT法抗肿瘤实验,结果表明:薯蓣皂苷元及β-胡萝卜苷对肝癌细胞株Bel-7402、宫颈癌细胞株Hela及胃癌细胞株SGC7901的生长具有明显的抑制作用,是蒲葵籽抑制癌细胞功能的主要有效成分。     

Evidence of polymorphic transformations of Sn under high pressure

The high-pressure polymorphs and structural transformation of Sn were experimentally investigated using angledispersive synchrotron x-ray diffraction up to 108.9 GPa. The results show that at least at 12.8 GPa β-Sn→bct structure transformation was completed and no two-phase coexistence was found. By using a long-wavelength x-ray, we resolved the diffraction peaks splitting and discovered the formation of a new distorted orthorhombic structure bco from the bct structure at 31.8 GPa. The variation of the lattice parameters and their ratios with pressure further validate the observation of the bco polymorph. The bcc structure appears at 40.9 GPa and coexists with the bco phase throughout a wide pressure range of40.9 GPa–73.1 GPa. Above 73.1 GPa, only the bcc polymorph is observed. The systematically experimental investigation confirms the phase transition sequence of Sn as β-Sn→bct→bco→ bco + bcc→bcc upon compression to 108.9 GPa at room temperature.     

Equation of State of Tantalum up to 133GPa

The static equation of state （EOS） of tantalum （Ta） is determined by in situ energy-dispersive synchrotron powder x-ray diffraction in a diamond anvil cell （DAC） up to 133GPa. The body-centered-cubic （bcc） phase of Ta is found to be stable over the entire pressure range investigated. The bulk moduli and its first pressure derivative of Ta are constrained by fitting the determined pressure-volume data to Vinet form EOS： B0 =192.65±（3.08）GPa and B＇0 =3.58±（0.11）. For the sake of avoiding the affect of non-hydrostatic stress, argon is used as a pressure media. A careful checking of the stress state of the sample is presented simultaneously.     

基于Dual-Mode MMA+MDD 双模式T/2分数间隔盲均衡算法的研究

均衡技术是用来解决通信系统中码间干扰的常用方法.针对传统恒模算法的收敛速度和稳态剩余码间干扰大的缺点,将双模式多模算法和改进型判决引导算法结合起来,并且应用于分数间隔盲均衡器中.该算法初期用双模式算法收敛均衡器,然后切换到改进型判决引导算法中进一步收敛,由于分数间隔均衡器解决了波特间隔均衡器因抽样率不高带来的频谱混叠问题,从而进一步地提高了均衡效果.蒙特卡罗仿真表明,该算法不仅收敛速度快,而且得到较低的剩余码间干扰.     

NiO的高压结构和等温状态方程研究

 运用金刚石对顶砧（Diamond Anvil Cell,DAC）技术,以液氩作为传压介质,在最高压力为67 GPa的压力范围内对NiO进行了原位的同步辐射X射线衍射研究。在整个实验过程中,并未发现第一类结构相变,也没有发现T.Sasaki等预测的在60 GPa左右轴比c/a随压力的变化率而突然增大的现象,且此压力范围内NiO的结构畸变程度随压力的变化趋势相比以前的研究结果要平缓一些。用三阶的Brich-Murnaghan方程对实验数据进行拟合,得到的体弹模量及其对压力的一阶导数分别为B₀=195(4) GPa和B₀′=5.3(2)。     

极端条件下液体结构和物性的实验研究进展北大核心CSCD

极端条件下液体(熔体)的结构和物性是凝聚态物理、材料科学和地球科学关注的重要问题之一。由于长程周期性的缺失,液体在极端条件下的结构和物性的实验和理论研究都面临着巨大的挑战。与晶体相比,人们对极端条件下液体的结构和物性的演化规律所知甚少。本文系统介绍了近年来高温高压条件下液体的结构、密度和黏度测量的研究进展,以及取得的重要科学认识,以期对今后极端条件下液体的结构和物性研究起到一定的参考作用。     

γ-Ce中的高压纵波声子模软化和状态方程描述

利用同步辐射角散X射线衍射技术测量了室温条件下0---0.74 GPa 压力范围内Ce的等温压缩线.发现γ-Ce的室温等温压缩线呈外凸形, 这是由其纵波声子模软化所致.利用超声测量得到的体弹性模量随压力变化的规律, 对实验所得到的压力与体积数据, 用二阶和三阶Murnaghan 方程、 二阶和三阶Birch 方程、 三阶Xu方程以及二阶Vinet方程进行比较, 并且对这些状态方程得到的体弹性模量随压力的变化规律与超声实验的结果相对比, 发现三阶Murnaghan 方程和三阶Xu方程对γ-Ce最适用.