PDMS表面织构润滑特性的研究

利用光刻-复模技术在PDMS表面制作凹坑阵列型表面织构,并采用球-盘式摩擦试验机对具有不同尺寸凹坑阵列的试样进行摩擦试验,研究了软质材料表面织构在混合至流体动压润滑区域的润滑特性.结果表明:对于PDMS材料,凹坑直径是影响摩擦特性的主要因素之一.与无织构试样相比,在低速条件下(0.005m/s)的混合润滑区域较小直径(d=50μm)的织构能够减小摩擦,而较大直径(d=200μm)的织构表现出增大摩擦的效果.在试验范围内凹坑的面积率越大,表面织构的作用越显著.     

Strangeness by Thermal Model Simulation at RHIC

The local temperature effect on strangeness enhancement in relativistic heavy ion collisions is discussed in the framework of the thermal model in which the K^＋ /h^＋ ratio becomes smaller with increasing freeze-out temperature. Considering that most strangeness particles of final-state particles are from the kaon meson, the temperature effect may play a role in strangeness production in hot dense matter where a slightly different temperature distribution in different areas could be produced by jet energy loss. This phenomenon is predicted by thermal model calculation at RHIC energy. The /Ф ratio in central Au＋Au collisions at 200GeV from the thermal model depends on the freeze-out temperature obviously when γs is different. It should be one of the reasons why strangeness enhancements of and Ф are different though they include two strange quarks. These results indicate that thermodynamics is an important factor for strangeness production and the strangeness enhancement phenomenon.     

相对论重离子碰撞的输运模型研究

美国的布鲁克海文国家实验室相对论重离子对撞机（RHIC）和欧洲核子中心的大型强子对撞机（LHC）的大量实验结果表明,在相对论重离子碰撞中已经产生了一种近似完美流体的强耦合部分子物质。基于一个多相粒子输运模型（AMPT）理论工具,对RHIC和LHC实验上的一些重要结果的开展了三个方面的理论研究工作（集体流、喷注淬火、手征磁效应）,研究结果揭示了初始的夸克胶子等离子体（QGP）能量密度涨落经过部分子输运演化产生末态粒子的各阶次的集体流、喷注和部分子物质的相互作用导致喷注的能量损失、末态相互作用严重影响手征磁效应的大小等物理过程作用机制。The experimental results from the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC) show that a nearly perfect fluid (i.e. strong-coupling Quark Gluon Plasma) has been created in relativistic heavy-ion collisions. I introduce our theoretical results based on a multi-phase transport (AMPT) model. Several important topics such as collective flow, jet quenching, chiral magnetic effect, are addressed. The simulation results indicate that the initial fluctuations of energy density of the QGP lead to all orders of harmonic flows of final particles via parton cascade, the strong interactions between jet and the QGP make jet lose much energy, and the final state interactions play an important role to affect the initial chiral magnetic effect in relativistic heavy-ion collisions.     

Search for the origin of double-peak structure at RHIC by AMPT model with triggered di-jet

With a multi-phase transport （AMPT） model,a γ-jet with known production point and momentum is triggered to search for the origin of double-peak structure in di-hadron azimuthal correlation in central Au＋Au collisions at RHIC energy.The different configurations of triggered γ-jet produce different shapes of medium responses.The key of the double-peak structure is found to be a strong shadowing effect of dense core,which is related to transverse expansion and radial flow of partonic matter.     

Investigation on the deformation of Ne and Mg isotope chains within relativistic mean-field model

Ne and Mg isotope chains are investigated based on constrained calculations in the framework of a deformed relativistic mean-field （RMF） model with the NL075 parameter set. The calculated quadrupole deformation and binding energy are compared with other theoretical results as well as the available experimental data. It shows that the calculated deformations of Ne and Mg with the NL075 are more accurate than those obtained with the NL-SH. It is predicted that ^19,29,32Ne and ^20,31Mg maybe have a triaxial deformation and ^25-28Ne and ^27-30Mg exhibit a shape coexistence probably. The closure effect of neutron number N=8 for ^20Mg is predicted to be very weak.     

相对论重离子碰撞的温度涨落与热容

使用LUCIAE3.0模型模拟了SPS能区Pb+Pb和C+C在不同能量(E_lab=20—200A GeV)和不同中心度下的重离子碰撞.并通过逐个事件的粒子温度涨落提取出了相应粒子的热容,发现对于同一碰撞系统,单位发射粒子的热容随碰撞能量的升高而下降直至饱和,随着碰撞参数b的增大而减小,而且发现单位发射粒子的热容具有随粒子质量的变大而变大的关系.同时还发现不同碰撞系统中同一种粒子具有相同的单位发射粒子热容,并给出了相应的解释.     

158A GeV的相对论重离子碰撞的强子快度分布及温度拟合

针对最近NA49在158A GeV的实验(C+C,Si+Si,Pb+Pb)数据,应用LUCIAE3.0模型进行模拟,得到了强子的快度分布和横向动量分布,并与实验数据进行比较,发现基本与实验数据相吻合。并对横向动量分布进行温度拟合,给出了和实验数据吻合很好的结果,但是对于重系统或重强子LUCIAE3.0给出的结果与实验符合相对较差.     

利用BUU模型研究11Li的核反应总截面和双中子剥去截面

发展了BUU模型,能够同时研究双中子晕结构核¹¹Li引起反应的核反应总截面和双中子剥去截面,计算中使用软的核物质状态方程和0.8倍的核子–核子碰撞截面,同时还用相对论平均场模型计算的中子和质子密度代替通常使用的方密度分布,计算结果可以很好地拟合不同反应系统的实验数据,假定对于晕核及其核芯核,彼此的核反应总截面与相互作用截面之间的差别相同,那么¹¹Li的双中子剥去截面可以表示成”Li及其核芯核⁹Li引起反应的核反应总截面之差,研究结果表明这一假定可以适用于高能,对于中能核反应需要更多的实验数据来检验.     

Hypertriton and light nuclei production at Λ-production subthreshold energy in heavy-ion collisions

High-energy heavy-ion collisions produce abundant hyperons and nucleons. A dynamical coalescence model coupled with the ART model is employed to study the production probabilities of light clusters, deuteron (d), triton (t), helion (³He), and hypertriton (_Λ³H) at subthreshold energy of Λ production (≈ 1 GeV per nucleon). We study the dependence on the reaction system size of the coalescence penalty factor per additional nucleon and entropy per nucleon. The Strangeness Population Factor (S₃ / (³He × (Λ/p))) shows an extra suppression of hypertriton comparing to light clusters of the same mass number. This model predicts a hypertriton production cross-section of a few μb in ³⁶Ar+³⁶Ar, ⁴⁰Ca+⁴⁰Ca and ⁵⁶Ni+⁵⁶Ni in 1 A GeV reactions. The production rate is as high as a few hypertritons per million collisions, which shows that the fixed-target heavy-ion collisions at CSR (Lanzhou/China) at Λ subthreshold energy are suitable for breaking new ground in hypernuclear physics.     

晶粒尺寸对1 MeV电子在金属Ni中能量沉积的影响

采用脉冲电沉积方法制备出高致密、高质量的纳米晶Ni, 并对其密度、组织成分和微观结构进行了表征. 利用高能粒子加速器产生的1 MeV高能电子为辐照源, 研究高能电子在纳米晶Ni和常规粗晶Ni中的能量损失. 通过辐照过程中放置的吸收剂量片来准确表征其电子的能量沉积. 结果表明, 晶粒尺寸对高能电子在材料中的能量沉积有明显的影响, 1 MeV电子在穿过一定厚度的金属Ni后, 在晶粒尺寸细小的纳米晶Ni中测得总的吸收剂量较大, 证明了高能电子在纳米材料中的总能量沉积较小, 从而表现出纳米材料抗辐照的优异性能. 关键词： 高能电子 纳米金属 辐射损伤