Result of search for low velocity exotic particles

The L3＋C experiment, taking advantage of the L3 muon magnetic spectrometer, measured the spatial tracks of charged cosmic ray particles to obtain rigidity as well as velocity. One possible low velocity exotic particle is observed. The existing uncertainties are discussed, and the flux upper limit of the low velocity exotic particles from this observation is deduced based on the assumption of a null observation. The result is 6.2×10^-10 cm^-2·s^-1·sr^-1 at 90% confidence level in the velocity range from 0.04c to 0.5c.     

107号超重元素的测定

 一个放射化学合作组利用瑞士保罗谢勒研究所（ＰＳＩ）的菲利普回旋加速器测定了１０７号超重元素（Ｂｏｈｒｉｕｍ）的挥发性．该项研究的关键问题是要使用较长寿命（约１５秒）的同位素,这是１９９９年年初在美国伯克利实验室中探测到的．虽然科学家们已经鉴别出几个比还重的元素,包括去年在伯克利８８英寸回旋加速器上发现的１１６号和１１８号元素,还有在杜布纳所发现的１１４号元素,但最重的这些元素在周期表里的正确位置仍在研究中．一在发现新元素的实验中,只展示了有很重的新原子核的存在,但没有得到有关它们的化学性质的信息．目前,１０６元素（ｓｅａｂｏｒｔｇｉｕｍ）的化学性质已得到广泛研究．     

石墨型高能两电极气体开关

 为大型激光装置能源模块研制了一种采用石墨电极的两电极气体开关,阐述了石墨应用于高能两电极气体开关的技术关键,对气体开关中气体间隙的最优结构进行了电场强度分析。参考美国国家点火装置(NIF)能源模块中ST-300气体开关的已知参数,对研制成功的石墨型两电极开关进行了电气特性试验,证明了石墨型气体开关能够实现峰值电流达300 kA以上,单次转移电荷量100 C以上,寿命超过1 000次,满足1.2 MJ大型激光装置能源模块的工程技术要求。     

弱相互作用费米气体的热力学性质

根据赝势法导出无外势时弱相互作用费米气体的化学势、内能和定容热容的解析表达式.在此基础上，采用局域密度近似研究谐振势中弱相互作用费米气体的热力学性质，探讨粒子间相互作用对系统性质的影响. 关键词： 费米气体 相互作用 赝势法 局域密度近似 热力学性质     

Optimization of Single or Range of Harmonics by Using Two Gas Jets

The interference of high-order harmonics generated by two successive gas jets within a single laser pulse is discussed by a modeling with the inclusion of macroscopic propagation of the fundamental and harmonic fields in an ionizing medium. Based on the interference, we show that one can extract the laser Rayleigh range from the interference of harmonics and the accuracy of retrieve is independent of carrier-envelope phase while dependent on the pulse duration. Moreover~ we demonstrate that it is possible to optimize the single or range of harmonics with a high ratio relative to the adjacent orders by changing the separation of two gas jets, which is unavailable by using a single gas jet and linear polarized laser pulse.     

广义热波长:定义、意义和应用

光子气体和低温下强简量子气体都不是经典理想气体,通常的热波长没有意义.但是,它们存在每个粒子的平均动量,因此可以定义广义热波长.这个热波长是系统量子相干性的一个量度,在非简并条件下,实物粒子系统广义热波长回到通常的热波长.简并条件下,热力学系统的线度必须大于广义热波长,因此导致了对热力学系统出现相关现象的最小线度,即最...     

用电子管做等离子体诊断实验

用电子管代替气体放电管做等离子体诊断实验,分别使用X-Y自动记录仪和万用表进行测量,计算得出等离子体参量,并与使用放电管得出的等离子参量做比较,证明了用电子管代替气体放电管的可行性.     

测定不同形状物体空气阻力系数的实验

设计空气流速连续可调的小型风洞,对圆形平板、圆柱体、流线体的空气阻力系数进行测量.利用U型管中水柱的高度差表达孔板法中空气的流速,通过悬臂梁力传感器测量测试物受到的空气阻力,根据空气阻力和U型管中水柱的高度差的关系测定空气阻力系数.     

Steady state speed distribution analysis for a combined cellular automaton traffic model

Cellular Automaton （CA） based traffic flow models have been extensively studied due to their effectiveness and simplicity in recent years. This paper develops a discrete time Markov chain （DTMC） analytical framework for a Nagel-Schreckenberg and Fukui Ishibashi combined CA model （W^2H traffic flow model） from microscopic point of view to capture the macroscopic steady state speed distributions. The inter-vehicle spacing Maxkov chain and the steady state speed Markov chain are proved to be irreducible and ergodic. The theoretical speed probability distributions depending on the traffic density and stochastic delay probability are in good accordance with numerical simulations. The derived fundamental diagram of the average speed from theoretical speed distributions is equivalent to the results in the previous work.