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。     

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：     

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。     

中学化学教学中的科学思维与逻辑辨析

化学是一门具有创造性的基础科学,是环境、生命、医药、材料等科学的基础,在思维逻辑上彰显和蕴含了丰富的科学思维方法。系统总结化学科学思维方法,可以有效破解中学化学学习中的“繁,难,乱”。在多年的教学实践中,提出了化学科学多向思维方法体系,强调多层次思维过程中对多因素的立体逻辑思维辨析。重点介绍了与中学化学教学相关的零阶、初阶、中阶和高阶逻辑思维辨析的内涵,期望化学教学中重视化学思维逻辑过程,实现化学教与学在思维模式上的深层次发展与提升。     

Hybrid improper ferroelectricity: a mechanism for controllable polarization-magnetization coupling

First-principles calculations are presented for the layered perovskite Ca3Mn2O7. The results reveal a rich set of coupled structural, magnetic, and polar domains in which oxygen octahedron rotations induce ferroelectricity, magnetoelectricity, and weak ferromagnetism. The key point is that the rotation distortion is a combination of two nonpolar modes with different symmetries. We use the term "hybrid" improper ferroelectricity to describe this phenomenon and discuss how control over magnetism is achieved through these functional antiferrodistortive octahedron rotations.     

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.