怀柔EAS阵列对初级宇宙线“膝”区能谱的测定

仔细分析了近年来怀柔广延大气簇射阵列记录的65万个大气簇射事例,得到了簇射Size(即荷电总粒子数)谱和10¹⁵—5×10¹⁶eV能段的初级宇宙线微分能谱.此谱呈明显的、平滑过渡的“膝”样结构,拐点在3×10¹⁵eV附近.除了“膝”较平滑不象明野谱那样尖锐拐折而外,怀柔谱在绝对流强和“膝”的位置上都与日本明野组吻合得很好.在银河磁场刚度截止模型框架下,怀柔实验Size谱界定的宇宙线质子谱拐折能量Ec的取值范围在160到240TeV之间.     

利用宇宙线直接测量结果对初级宇宙线能谱参数的调整

由JACEE?,RUNJOB和SOKOL等宇宙线直接测量结果和刚度截断模型,对于10¹⁴—10¹⁶eV能区的初级宇宙线微分能谱参数进行调整.利用调整后的能谱与选取QGSJET模型的CORSIKA程序进行EAS模拟,同HD,PD谱进行对比研究.采用相同的标准对模拟数据与实验数据进行分析.结果表明,调整后的谱和HD谱的模拟结果与甘巴拉山乳胶室实验结果符合较好,而PD谱的模拟结果与实验结果偏离较大.     

一个和X级太阳耀斑相关的甚高能GLE事件

分析怀柔宇宙线EAS阵列在1991年6月份的计数率,数据表明在6月15日的太阳X12/3B级大耀斑后的GLE事件持续期间,TeV能区的宇宙线强度在25min内比通常有将近4a的超出,增强过程持续约25min.     

怀柔EAS阵列的Monte Carlo研究

用GENAS程序包为怀柔阵列产生了36万Monte Carlo模拟EAS事例,用它们研究了怀柔阵列的性能,确定了最佳的事例判造条件,对实验数据进行了正确性检验,得到了怀柔EAS Size(即簇射在观测面的总荷电粒子数)与初级宇宙线能量之间的转换关系.这项研究表明,怀柔阵列的EAS心位和方向测定精度分别好于3m和2.5°;EASSize测定误差典型值约8%;近垂直簇射的Size(N)与初能(E)的关系为E≈10^10.64N^0.84.     

Measurement of and the dipion contribution to the muon anomaly with the KLOE detector

We have measured the cross section σ(e⁺e⁻→π⁺π⁻γ(γ)) at DAΦNE, the Frascati -factory, using events with initial state radiation photons emitted at small angle and inclusive of final state radiation. We present the analysis of a new data set corresponding to an integrated luminosity of 240 pb⁻¹. We have achieved a reduced systematic uncertainty with respect to previously published KLOE results. From the cross section we obtain the pion form factor and the contribution to the muon magnetic anomaly from two-pion states in the mass range 0.592<M_ππ<0.975 GeV. For the latter we find Δ^ππa_μ=(387.2±0.5_stat±2.4_exp±2.3_th)×10⁻¹⁰.     

Non-Violation of Energy Conditions in the Future Accelerated Universe Due to Quantum Effects

Here, an accelerated phantom model for the late universe is explored, which is free from future singularity. It is interesting to see that this model exhibits strong curvature for all time in future, unlike models with ‘big-rip singularity’ showing high curvature near singularity time only. So, quantum gravity effects grow dominant as time increases in late universe too. More importantly, it is demonstrated that quantum corrections to FRW equations lead to non-violation of ‘cosmic energy conditions’ of general relativity, which are violated for accelerating universe without these corrections.     

On the response of LR-115 plastic track detector to 10 20 Ne-ion

The track etch rates of ₁₀ ²⁰ Ne-ion in cellulose nitrate (LR-115) have been measured for different temperatures and the activation energy is determined. The experimental results show that both the track etch rate and the normalized track etch rate depend on the energy loss as well as on etching temperature. The maximum etched track length of ₁₀ ²⁰ Ne-ion agrees with the theoretically computed range. The experimental results show that there is no sharp threshold, at least in CN(LR-115).     

Modeling the effects of cohesive energy for single particle on the material removal in chemical mechanical polishing at atomic scale

This paper proposes a novel mathematical model for chemical mechanical polishing (CMP) based on interface solid physical and chemical theory in addition to energy equilibrium knowledge. And the effects of oxidation concentration and particle size on the material removal in CMP are investigated. It is shown that the mechanical energy and removal cohesive energy couple with the particle size, and being a cause of the non-linear size-removal rate relation. Furthermore, it also shows a nonlinear dependence of removal rate on removal cohesive energy. The model predictions are in good qualitative agreement with the published experimental data. The current study provides an important starting point for delineating the micro-removal mechanism in the CMP process at atomic scale.     

Ni2分子结构和分子轨道密度(DMO)的成键贡献

用密度泛函(B3P86/6-311g*)方法研究了Ni2分子结构和势能函数.结果表明基态Ni2为5Πg,平衡间距为Re=0.223 196 nm,离解能为1.851 16 eV.定义了分子轨道密度(DMO, density of molecular orbital)并研究了镍双原子分子的s, p, d, f的DMO对成键的贡献,为进一步研究金属的态密度提供了有益的参考价值.     

On the perfection of cleavage planes of potassium bichromate single crystals

The relative perfection of the 001, 100 and 100 cleavage planes of potassium bichromate single crystals is analysed by calculations of the surface energy of main crystallographic planes. The surface energy was determined for the three cleavage planes as well as for planes corresponding to other theoretically possible orientations. It was found that: (1) among different planes the calculated values of the surface energy of the 001, 100 and 010 cleavage planes of potassium bichromate are the lowest, (2) among the three cleavage planes the 001 perfect cleavage plane has the lowest surface energy, (3) the relative perfection of different cleavage planes can be explained by using the coefficient δ proportional to the ratio of the surface energy of the hkl cleavage plane to the energy of dislocations emerging on the plane, and (4) the lower the values of the coefficient δ for a cleavage plane, the better is the cleavage perfection.     

A revised treatment of the non-electrostatic contribution to the solvation free energy of DNA-binding ligands

A revised magnitude of the microscopic surface tension coefficient, γ_vdW, is suggested to account for the van der Waals solvation energy, ΔG_vdW^solv, in the standard expression ΔG_vdW^solv = γ_vdW ⋅ ΔA, where ?A is the change in solvent accessible surface area on complexation. The revised value of γ_vdW = − 0.063(± 0.008) kcal/mol/Ų is based on the decomposition of the Gibbs free energy for 49 reactions of non-covalent bimolecular ligand-DNA and ligand-ligand complexation, involving 20 DNA-binding molecules that differ in structure and charge state. The total non-electrostatic contribution to the solvation free energy can also be calculated from the standard equation ΔG_nel^solv = γ_nel ⋅ ΔA with the revised coefficient γ_nel = − 0.013(± 0.008) kcal/mol/Ų. It is proposed that these results may be utilized for analysis of any ligand-DNA or ligand-ligand interaction, if the structure and other physical properties of the interacting molecules do not change on complexation.     

利用天然气管网压力能的小型液化流程设计

针对城市天然气高中压管网调压站的压力能回收利用,综合考虑LNG储运过程中广泛面临的BOG(Boiloff gas)问题,提出了一种结合混合工质循环、利用天然气压力能生产高品质LNG的小型液化流程。研究分析了预冷温度、动部件效率、低温换热器性能及液化天然气温度对流程天然气液化比的影响,优化的流程结果参数表明,当所得液化天然气储存在4bar,-160℃时,流入系统18.26%的天然气可被液化,其余部分外输中压管网;提出了在LNG买卖市场中根据LNG品质议价的建议,以从根本上减少LNG储运、装卸及使用过程的BOG排放量,进而减少经济损失与能源浪费。该流程可应用于城市燃气调峰,也可进行二次销售,具有较好实用性和经济性。     

The structure of the surface compound CrN formed by cosegregation on a Fe–15%Cr–N(100) single crystal surface

Cosegregation is known to cause the formation of two-dimensional chemical compounds (surface compounds) which can be epitaxed to substrate surfaces of a suitable structure. In the present work the cosegregation-induced formation of the CrN surface compound on nitrided Fe–15%Cr–N(100) single crystal surfaces was studied by means of Auger electron spectroscopy and low-energy electron diffraction. Intensity versus energy spectra (I(E)) were measured and analysed fully dynamically to investigate the structural details of the CrN surface compound. It is found that nitrogen is segregated to the surface forming the sample's top layer and substantial amounts of chromium are cosegregated with nitrogen. Nitrogen atoms reside in four-fold symmetric hollow sites about 0.1 Å above the metallic substrate. There is a huge relative expansion of the distance between the first and second metal atom layers (Δd₁₂/d₀≈26%), while the distances between deeper layers are almost bulk-like. The small distance between the nitrogen and the top metal layer as well as the huge layer expansion Δd₁₂/d₀ are in agreement with results found for N/Cr(100).     

On the spectroscopy of atomic electrons (positrons)in the energy range of 10 to 50 MeV from heavy-ion collisions at intermediate energies

The feasibility of the spectroscopy of dynamically ionized electrons (positrons) from heavy-ion collisions at intermediate energies, e.g. Pb+Pb at 60 AMeV has been studied. We propose a magnetic toroid spectrometer for lepton spectroscopy in an energy range between 5 and 50 MeV. Special emphasis was laid on large solid angles, on broad-band characteristics and on a good suppression of secondary events. The device is a versatile compact-size instrument for lepton detection in in-beam experiments at a moderate energy resolution of %. Received: 28 December 1999 / Accepted: 29 March 2000