Phase space dependence of the multiplicity distribution in π+ andpp collisions at 250 GeV/c

The charged particle multiplicity distribution has been studied for non-single-diffractive π⁺ p andpp collisions at \(\sqrt s = 22\) GeV, for full phase space as well as for intervals in rapidity, azimuthal angle and transverse momentum. In general, the multiplicity distribution is well described by a negative binomial. From comparison of the distribution for negative or positive particles to that of all charged particles, cascading is favoured as an interpretation over stimulated emission. Interesting consequences follow from a comparison of our results to those at collider energies and toe ⁺ e ^? data at comparable energy. Furthermore, evidence is given that the multiplicity distribution is not exactly of negative binomial type in every (connected or disconnected) phase space region.     

Forward-backward multiplicity correlations in σ+ p,K + p andpp collisions at 250 GeV/c

Forward-backward multiplicity correlations in σ⁺,K ⁺ p andpp collisions at 250 GeV/c ( \(\sqrt s \) =22 GeV) are given for all charges and for the different charge combinations. The correlations are found to be caused predominantly by centrally produced particles. It is demonstrated that this result is an agreement with observations at the ISR and the CERNp \(\bar p\) -Collider. The results are compared to expectations from LUND, DPM and FRITIOF Monte Carlo models and a geometrical picture relating correlations in hadron-hadron collisions toe ⁺ e ^? data in terms of impact parameters is tested.     

聚醚醚酮酮和含联苯聚醚醚酮酮共聚物的熔融热

根据Ｆｌｏｒｙ热力学统计理论和比容－熔融热作国法，由ＤＳＣ结果得到了不同联苯含量的聚醚醚酮酮－含联苯聚醚醚酮酮（ＰＥＥＫＫ－ＰＥＢＥＫＫ）共聚物的熔融热，两种方法获得的结果吻合。在此基础上给出了ＰＥＥＫＫ－ＰＥＢＥＫＫ共聚物不同联苯含量的熔点计算表达式。结果还表明，随着联苯含量ｎＢ，的变化，明显改变；当ｎＢ＝０．３５时，ＰＥＥＫＫＰＥＢＥＫＫ共聚物的值最小。     

蒙药材肋柱花中盐酸小檗碱的反相高效液相色谱法分析

用高效液相色谱法测定蒙药材肋柱花中小檗碱的含量.色谱流动相为乙腈:水(V:V=30:70,每1000mL水中加入KH2PO43.4g),流速为0.8mL/min,紫外检测波长为345nm.结果表明,盐酸小檗碱在6.25-50μg/mL范围内具有良好的线性关系,相关系数为0.9992,实验测得平均回收率为97.7%,RSD=0.94%(n=6).方法操作简便,灵敏度高,结果准确可靠.     

强脉冲电磁场对金属凝固组织影响的研究

提出了用强脉冲磁场和电流细化金属凝固组织的新工艺.与未经磁场或电流处理的凝固样品相比,强脉冲电磁场能够显著地改善LY12铝合金的凝固组织,使晶粒明显细化、球化;电磁场的强度愈强,这种改善效果愈明显.对该新工艺的细化机理进行了理论分析,同时,指出了实验中的新现象和新问题. 关键词：     

Strain localization under dynamic loading

A spallation model of strain localization is suggested according to which localization bands under pulsed loading result from unloading wave interference such that negative stresses in the extension zone are lower than the ultimate strength of the material. The temperature in the localization band is estimated to be close to the environmental temperature.     

气相色谱法测定海洋沉积物中十氯酮残留

研究了提取溶剂效率、毛细管柱极性、净化条件及共溶出干扰物等因素对十氯酮测定的影响;对比了加速溶剂提取及超声波提取方式,考察了DB-17、DB-1701与DB-5毛细管柱分离度,及不同比例甲醇/正己烷混合溶液作为定容溶液的分析结果。建立了加速溶剂萃取,H2SO4净化分离,DB-5毛细管柱电子捕获检测器(ECD)-气相色谱法(GC)测定海洋沉积物介质中有机氯农药类持久性有机污染物十氯酮残留分析方法。将5 g沉积物干样与3 g活化铜粉及3 g无水Na2SO4混匀后,采用二氯甲烷-丙酮(1∶1,V/V)进行加速溶剂萃取;萃取液浓缩后,用H2SO4净化,以1%甲醇-正己烷混合溶液定容后,采用DB-5非极性毛细管柱,及配备电子捕获检测器气相色谱测定十氯酮含量。本方法采用外标法进行定量分析,在0.005～0.1 mg/L浓度范围内,线性相关系数为0.9989;加标回收率为75%～98%;相对标准偏差为3.7%～9.6%(n=6);检出限为0.12 ng/g。     

物理化学混合式教学设计与实践——以“单组分系统相变热力学”为例*

以“单组分系统相变热力学”为例介绍了物理化学混合式教学设计与教学实践。围绕课程教学目标,在课前、课中、课后的每一个教学环节中践行课程教学理念,通过“问题+案例”方式突出物理化学基本方法的应用性、普适性与前沿性,让学生在教学过程中获取原理、体验探究、发展思维、生成智慧。教学评价结果显示,绝大部分学生对混合式教学模式给予了积极的评价。     

Finely striped structure at the edges of localized deformation bands

Under conditions of high-rate loading, plastic strain localization is a result of tension in the zone of interference of unloading waves rather than of thermal softening. At stresses close to the dynamic strength of the material, the microstructure of localized strain bands consists of strongly deformed material, with a large number of incipient microdiscontinuities. At stresses below the Hugoniot elastic limit, the microstructure looks as a set of barely visible stripes. The finely striped structure at the edges of the bands of a spall damage arises as a result of the stretching of initially rounded damage centers attached to the matrix material during dynamic deformation.