高能重离子碰撞中正负荷电粒子比单事例起伏研究

用强子和弦级联模型,JPCIAE及相应的Monte Carlo事例产生器,研究相对论性核–核碰撞中有限快度区间内正负荷电粒子比单事例起伏与能量、中心度、共振态衰变及快度间隔的关系.JPCIAE模型能够较好地符合CERN/SPS能区Pb+Pb碰撞的实验结果.本文还用此模型预言了RHIC能区Au+Au碰撞和ALICE能区Pb+Pb碰撞中的正负荷电粒子比单事例起伏.可以看出碰撞能量、中心度、共振态衰变及快度间隔对正负荷电粒子比单事例起伏的影响都不大.     

Preparation and Storage of Silver Nanoparticles in Aqueons Polymers

以水溶性聚合物为保护剂,采用化学还原法制备了银纳米粒子,分别利用透射电子显微镜、紫外可见光谱、同步光散射光谱等手段对其进行了表征,并探索了制备银纳米粒子的最佳实验条件。通过将银纳米粒子-聚合物溶液进行脱水,得到含有银纳米粒子的固态聚合物膜。将固态聚合物膜重新溶解于水,其水溶液的紫外可见光谱与脱水前的溶液进行了比较,发现两者性质并无明显差异。因此,将银纳米粒子分散固定在聚合物膜中是一种崭新而有效的银纳米粒子制备和存储方法。     

Field-dependent electrode-chemisorbate bonding: sensitivity of vibrational stark effect and binding energetics to nature of surface coordination

Illustrative quantum-chemical calculations for selected atomic and molecular chemisorbates on Pt(111) (modeled as a finite cluster) are undertaken as a function of external field, F, by using Density Functional Theory (DFT) with the aim of ascertaining the sensitivity of the field-dependent metal-adsorbate binding energetics and vibrational frequencies (i.e., the vibrational Stark effect) to the nature of the surface coordination in electrochemical systems. The adsorbates selected--Cl, I, O, N, Na, NH(3), and CO--include chemically important examples featuring both electron-withdrawing and -donating characteristics. The direction of metal-adsorbate charge polarization, characterized by the static dipole moment, mu(S), determines the binding energy-field (E(b-F) slopes, while the corresponding Stark-tuning behavior is controlled primarily by the dynamic dipole moment, mu(D). Significantly, analysis of the F-dependent sensitivity of mu(S) and mu(D) leads to a general adsorbate classification. For electronegative adsorbates, such as O and Cl, both mu(S) and mu(D) are negative, the opposite being the case for electropositive adsorbates. However, for systems forming dative-covalent rather than ionic bonds, as exemplified here by NH(3) and CO, mu(S) and mu(D) have opposite signs. The latter behavior, including electron-donating and -withdrawing categories, arises from diminishing metal-chemisorbate orbital overlap, and hence the extent of charge polarization, as the bond is stretched. A clear-cut distinction between these different types of surface bonding is therefore obtainable by combining vibrational Stark-tuning and E(b)-F slopes, as extracted from experimental data and/or DFT calculations. The former behavior is illustrated by means of potential-dependent Raman spectral data obtained in our laboratory.     

Nuclear Liquid-Gas Phase Transition Shown in Multifragment ation

The Incomplete-Fusion-nagmentation Model has been used to reproduce nicely the experimental evidence of liquid-gas phase transition probed in the reaction of Au + Au at 600A MeV. The analysis of the relative yields of decay modes for the projectile remnant as a function of bound> shows clearly the competition and transformation processes of various decay modes of projectile remnant with decreasing of bound>. The agreement between theoretical and experimental results for the anaJysis of relative yield of decay modes indicates that the experimental evidence of liquid-gas phase transition is composed of the decay mode transformations.     

STUDY ON TARGET RESIDUES FROM THE INTERACTION OF COPPER WITH 44MeV/A12C IONS

Cross sections and average forward ranges were determined for 35 target residues from the interaction of copper with 44MeV/A¹²C ions with nuclear chemistry techniques.From these data the isobaric yield distribution,the mass yield distribution and the longitudinal momentum transfer were obtained.The mass yield distribution and the isobaric yield distribution are in good agreement with those calculated from a modified statistical model and corresponding Monte Carlo technique.     

STUDY OF πNN VERTEX FROM HADRON AND QUARK POINT OF VIEW

we have identified the first-order mixing amplitude of πNN process described by the hadron model with the second-order mixing amplitude of the same process described by the quark model.Then the expression for the coupling constant f_π of the πNN vertex with different quark wave functions and gluon propagators in different approximations has been derived. The calculation results of f_π have been compared with experimental data.     

Strangeness production in pA and AA collisions at 158 A GeV

LUCIAE, a hadronic and string cascade model and its corresponding event generator are used to analyse strangeness production singly and multiply in p-Pb and Pb-Pb collisions at 158 A GeV. Spectra of multiplicity and transverse mass for single (Λ, Λ) and multiple (Ξ-, Ξ-, Ω-, Ω-) strangeness are given. In LUCIAE model it suggests a physical mechanism, i.e. the dependence of the strange quark suppression factor on incident energy, projectile mass and centrality of colliding system might result in increase of yield of strange particles with increasing the above three parameters. Calculations from the model reconstruct well the WA97 experimental data: increase of yield of strange particles with increasing centrality and increase of strangeness enhancement with increasing number of strange quarks, in relativistic nucleus-nucleus collisions.     

Justification of the Kirchhoff hypotheses and error estimation for two-dimensional models of anisotropic and inhomogeneous plates, including laminated plates

Asymptotic analysis of the problem describing deformation ofa thin cylindrical plate with clamped lateral side is performed.The problem is considered under the most general statement withthe plate being laminated and consisting of an arbitrary numberof nonhomogeneous and anisotropic (21 elastic moduli) layers.Explicit integral representations of the differential operatorswhich form the two-dimensional model of the plate are derived.In the case when the elastic moduli of each of the layers areconstant, these integral representations turn into algebraicones. The asymptotic procedure is justified with the help ofa weighted inequality of Korn's type. The error estimates obtainedgive a rigorous mathematical proof of both of Kirchhoff's hypotheses(kinematic and static) and shed light on the well-known intrinsicinconsistency of two of the hypotheses.     

Theoretical Study of Hydrated Cd~（2＋） Interactions with Guanine

Theoretical study was performed to investigate how the hydration of cadmium ca-tion influences the structure and properties of guanine.The aqueous environment was simulated by both explicit solvent(1-5 water molecules) model and implicit solvent model.For complexes in which Cd2+ attached to the N(7) and O(6) sites of guanine,energy analysis together with the Natural Bonding Orbital(NBO) analysis were performed to elucidate the bonding characteristics in detail.The most stable structures are penta-coordinate complexes without aqua ligand located at the guanine site.Higher number of water ligands corresponds to higher stabilization energies.Average bonding energies of G-Cd increase with the number of water molecules.Bonding energies of water ligands depend on its position in the complexes.The charge distribution of guanine changed with increasing the number of water ligands,which may also influence the base-pairing pattern of guanine.There is positive charge transfer from guanine to aqua ligand as the number of the hydration waters increases.IEFPCM optimization has results comparable to the [CdG(H2O)5]2+ structure 5a.     

氧化钙和氯氧化钇为助烧剂对碳化硅陶瓷性能的影响

采用YOCl/CaO为助烧剂常压烧结制备SiC陶瓷,研究助烧剂的配比及烧结温度对陶瓷的显微结构、热学性能及介电性能的影响.结果表明:在高温烧结过程中YOCl及CaO会与SiC发生置换还原反应,生成部分含钇化合物,对比各样品的热膨胀系数发现,在1800 ℃下烧结的YOCl/CaO=4:5的样品与常压烧结制备的纯SiC热膨胀系数α=4.0×10 -6相接近,而其它样品热膨胀系数与单晶硅的热膨胀系数α=2.62×10 -6较为接近,有望成为较好的封装材料.