Monotone Mappings and Flows of Viscous Media

We establish solvability of the boundary-value problems describing stationary and periodic flows of viscoplastic media. In the case of stationary flows we study the question of convergence of the Galerkin method. For the problem of periodic flows we prove a version of the second Bogolyubov theorem.     

Galactic Metrics

The paths of stars in galaxies have circular velocity independent of their distance from the centre of the galaxy. Newtonian mechanics with a logarithmic potential has such paths. In relativity these paths can be taken to be geodesics and this requirement places a restricting equation on the spacetime metric. This equation has a non-unique spherically symmetric solution that in the Newtonian limit has a logarithmic potential. It also can be solved in terms of a conformal factor. In particular it has solutions which are conformal to the vacuum-Einstein solutions and such spacetimes are solutions to the vacuum-Bach equations. Therefore it is suggested that the Bach equations describe dynamics on galactic length scales.     

Anomalies of attenuation and phase velocity of surface acoustic waves in YBa2Cu3O7‒δ thin films in the vicinity of Tc

We present measurements of the attenuation and phase velocity of surface acoustic waves in thin YBa₂Cu₃O films as a function of temperature, in magnetic fields up to 3.6 T applied parallel to the c-axis of the films. We have observed anomalies in both, the attenuation and the phase velocity in the vicinity of the superconducting critical temperature which do not depend on the magnetic field. Possible origins of these anomalies, observed, to our knowledge, for the first time in YBa₂Cu₃O thin films, are discussed and compared to bulk acoustic wave experiments. We present a kind of feedback technique for surface acoustic waves which improves the sensitivity of this type of measurement. The actual sensitivity limits are mentioned. Received: 7 August 1997 / Revised: 7 November 1997 / Accepted: 17 November 1997     

垂直低温两相流管底液氮汽泡上升速度的实验研究

本文对垂直低温两相流管底部液氮汽泡的上升速度运用高速摄像机进行了可视化实验研究,对所采集的实时图像进行处理.在Cole和Mendelson汽泡上升速度经验公式的基础上,通过对液氮汽泡的上升速度的分析,提出了圆管管路底部液氮汽泡的上升速度的拟合公式,分析研究其变化规律,为进一步探求圆管内液氮弹状汽泡的生成机理提供依据.     

钛合金（TC-6）二阶和三阶弹性常数

 用脉冲回波重叠法测量了钛合金（TC-6）的二阶、三阶弹性常数。实验中发现dμ/dp<0（p<0.17 GPa）,dμ/dp>0（p>0.17 GPa）。     

超声波辐射下的固—液相转移催化法合成苯乙酰基芳基硫脲化合物

合成酸基硫减类化合物常用的方法是固一液相转移催化法“‘．因超声波辐射可以加快有机合成反应，提高产率，本文采用了超声波辐射与相转移催化相结合的方法，以聚乙二醇一400（PEG－400）为催化剂，二氯甲烷为溶剂，在常温下合成了10种N一苯乙酸基一N‘一芳基硫腺新化合物，产率大部分比相应的相转移催化法合成高．本法条件温和、操作简便、产率较高．仪器为CQ－250型超声波清洗器，频率33土2kHZ；PE1730FT－IR红外光谱仪，溪化钾压片；BRUKERAC七0核磁共振仪，CDCI。为溶剂，TMS为内标；PE－2400CHN元素分析仪．化合物（皿…     

Comparison of the Dynamics of Water Molecules in Crystals of Proton-Ordered Ice IX and Its Proton-Disordered Analog III

A computer simulation of proton-ordered ice IX and its proton-disordered analog III (768 molecules, 90 K) was carried out by the molecular dynamics method using Poltev–Malenkov's potential. For ice IX, the differences in the dynamic characteristics of molecules with O(1) and O(2) are much wider than those in the case of ice III. The libration spectrum of ice IX has a number of distinct acute peaks, and the spectrum of ice III is strongly smoothed. These peculiarities are explained by the proton ordering of ice IX and disordering of ice III. The latter is responsible for the great differences in the short- and especially long-range environment of water molecules in ice crystals and hence for the presence of many molecules with different dynamic characteristics. Thus averaging over a large number of different vibrational spectra of molecules leads to a smoothed total spectrum in the case of the proton-disordered crystal modification of ice.     

超声提取-超高效液相串联质谱分析沉积物中15种抗生素

在现有方法基础上对沉积物中磺胺类、喹诺酮类、大环内脂类和四环素类抗生素的提取、富集、净化以及仪器分析方法进行了优化。以EDTA-Mcllvaine缓冲溶液与乙腈(V:V,1:1)混合液作为提取液,利用超声波细胞破碎仪进行超声提取,串联强阴离子交换柱(SAX)和HLB固相萃取柱进行固相萃取(SPE),通过超高效液相/串联质谱(UPLC-MS/MS)测定沉积物中抗生素的含量。抗生素基质加标回收率在56.4%~110%,相对标准偏差为1.1%~24.3%,方法检出限0.0055~0.716 ng/g。本方法有效地提高了沉积物中抗生素的提取效率,并应用于实际样品的测定中。     

Optimum gas chromatographic conditions in wall-coated capillary columns. Extended and simplified forms of the Golay-equation

Band broadening in capillary columns is satisfactorily described by the Golay-equation extended to situations of appreciable pressure drop by Giddings. In practice, however, several simplifications are often made. The effect of these simplifications on the calculated values of the minimum plate height and optimum carrier gas velocity are treated systematically.     

毛细管电色谱中双电层叠加的研究

通过流动相中电解质浓度对毛细管电色谱柱效能的流动相平均线速度的影响，研究了ＣＥＣ中双电层叠加现象。提出选择合适电解质组成的浓度及在制备色谱柱过程中避免细小和破碎的固定相颗粒进入柱中，以有效地减小双电层叠加作用。