泵浦光波形和脉宽对飞秒激光对比度的影响

 采用宽带数值模型，应用四阶龙格-库塔数值算法对三波耦合方程进行数值分析，研究了泵浦光的波形和脉宽在提高光参量啁啾脉冲放大系统输出飞秒激光对比度的作用。结果表明：在泵浦光脉宽较小的条件下，采用平滑的泵浦光波形更有利于提高飞秒激光对比度；在泵浦光脉宽较宽时，飞秒激光对比度得到很好地提高，而对泵浦光波形不敏感；但继续提高泵浦光脉宽并不能进一步改善飞秒激光对比度，而系统的转换效率却显著降低。     

用节点变分的代数方法研究双原子体系的完全振动能谱和离解能

对于使用实验数据作为原数据进行的数值计算, 由于实验误差的普遍存在, 在数值计算过程中可能存在对实验误差的放大效应, 使得微小的实验误差对数值计算的结果产生明显影响. 因此本文通过在AM (algebraic method) 方法中加入用以抵消实验误差的微小变分项δE, 从而将AM改进为节点变分的代数方法VAM (variational algebraic method). 该方法具有更广泛的适用范围, 尤其对处理那些实验数据较少、 误差较大、 已知的实验振动能级远离体系离解能的双原子体系效果明显. 本文利用VAM方法研究了AM方法难以处理的5¹Π_u⁷Li₂, (6d)¹Δ_g Na₂, (7d)¹Δ_gNa₂ 和5¹∑⁺ NaK 等不同碱金属双原子分子的完全振动能谱与离解能, 不但得到了与实验数据精确相符的理论结果, 还正确地预言了许多由于实验条件与技术原因而未能测得的物理数据. 充分表明了VAM 方法的可行性与正确性. 此处对数值误差的分析和物理思考对其他精确的数值计算 或数值模拟研究也有积极的参考意义.     

Control of oxygen contamination during the growth of optical calcium fluoride and calcium strontium fluoride crystals

The progress, current state, and prognosis for CaF₂ as an optical material with wide applicability are reviewed by outlining the basic issues: technology, demand, supply, and metrology. To achieve perfect quality for all application grades of CaF₂ grown using a natural fluorite, investigations of the effect of PbF₂ and ZnF₂ scavengers for removal of oxygen contaminants from the starting material, representing chemically purified fluorspar, either granular or as dense precursors is reported. The chemical and crystal-chemical reactions occurring during the crystallization due to the presence of oxygen contaminants, scavengers, and rare-earth impurities are discussed based on data for the composition of the residual atmosphere in the reactor chamber. The water vapors have been shown to have a major impact in deteriorating the optical properties of the grown crystals. The use of precursors, together with 0.1n% ZnF₂ additive, is shown to be highly recommendable for the production of ultraviolet and vacuum ultraviolet grades of CaF₂ and Ca_1−xSr_xF₂ crystals. For visible and infrared grades PbF₂ appears to be a better additive than ZnF₂. The technique for growth of Ca_1−xSr_xF₂ in an argon flow with a 5 nines inlet purity has proved to be suitable for producing high-quality crystals, whose optical properties satisfy the demands of micro-photolithography provided that precise control over the total pressure inside the crucible is implemented.     

Quantum-Mechanical Study of Small Au2Pdn (n = 1～4) Clusters

Gold-doped palladium clusters, Au2Pdn (n = 1～4), are investigated using the density functional method B3LYP with relativistic effective core potentials (RECP) and LANL2DZ basis set. The possible geometrical configurations with their electronic states are determined, and the stability trend is investigated. Several low-lying isomers are determined, and many of them are in electronic configurations with a high-spin multiplicity. Our results indicate that the palladium-gold interaction is strong enough to modify the known pattern of bare palladium clusters, and the lower stability as the structures grow in size. The present calculations are useful to understanding the enhanced catalytic activity and selectivity gained by using gold-doped palladium catalyst.     

销售商出售看跌期权的供应链优化研究

在由一个供应商和一个销售商组成的单期两级供应链中,处于主导地位的销售商以其卖场所具有的销售能力参与供应链合作,并从销售的每一个产品中获取既定收益。同时,销售商还向供应商出售建立在产品销售量保障基础上的看跌期权,以激励供应商参与供应链合作。论文对上述情形的销售商出售看跌期权的供应链合作问题进行了研究,通过建模与优化分析,证明了在销售商提供看跌期权的供应链合作中,供应商存在唯一的最优生产批量和看跌期权采购量,以及销售商存在最优的从每一单位产品销售中获取的既定收益。论文还揭示了销售商提供看跌期权,虽然无法实现供应链协调,但可以实现供应链参与企业所获得的收益与其所承担的风险相匹配。最后,论文论证了在销售商出售看跌期权机制下,供应链存在收益损失较小的理想合作区域。     

Pressure effect on the structural and elastic property of Hf2InC

Using plane-wave pseudopotential (PW-PP) method based on the density functional theory (DFT) within the Local Density Approximation (LDA), we have performed a study of the structural and elastic properties of selected Hf₂InC compound belonging to the so-called MAX phases. The calculated equilibrium lattice parameters are in accordance with the experimental results. The result of high pressures on the lattice parameter shows that the contractions along the c-axis were more than along the a-axis. In order to gain further information on the mechanical properties, we have also calculated the anisotropy factor, Poison's ratio, Young's modulus, sound velocities and Debye temperature for Hf₂InC.     

Identification of the alkalide,Na−, in Na/NH3 matrices using MCD

Codeposition of Na and NH₃ at ≈ 35 K gives rise to an absorption band at ≈ 16950 cm⁻¹ with a positive MCD å term. This band is assigned to the ¹S → ¹P transition of Na⁻ marking the first direct evidence for the existence of an alkalide in NH₃. The absorption and MCD of the solvated electron band are also observed in the near infrared at ≈ 8000 cm⁻¹.     

A conductivity probe for measuring local concentrations in slurry systems

A simple, economical and accurate technique has been developed to measure local in situ solids concentration in slurry systems. The instrument relies on measuring slurry resistivity, as it changes with the solids concentration, for a small region in space. The device was tested in comparison with isokinetic sampling and γ-ray absorption for a variety of slurry pipeline flows. The effects of fluid properties, temperature, velocity, particle size and pipe wall material were examined experimentally. In contrast with previous techniques the effect of fluid velocity upon the measurements was eliminated by a dual electrode-pair system.     

Ethylen(hydrido)-metallkomplexe aus M(CH2)CH3-vorstufen: modellreaktionen für einen elementarschritt der fischer-tropsch-synthese

The compounds C₆Me₆Ru(Ch₃)₂, C₆H₆Os(CH₃)₂PMe₃ and C₅H₅Ir(CH₃)₂-Pprⁱ₃ react with [CPh₃]PF₆ in Ch₂Cl₂ to give the ethylene(hydrido)metal complexes [C₆Me₆RuH(C₂H₄)PR₃]PF₆, [C₆H₆OsH(C₂H₄)PMe₃]PF₆ and [C₅H₅IrH(C₂H₄)PPrⁱ₃]PF₆, respectively. Treatment of C₆Me₆RuCH₃(C1)PMe₃ with [CPh₃]PF₆ leads to cleavage of the RuCH₆ bond instead of hydride elimination; in the presence of PMe₂Ph the compound [C₆Me₆RuCl(PMe₂Ph)PMe₃]PF₆ is obtained. The reaction of C₅H₅RhCH₂OMe(PMe₃)CH₃ with HBF₄ gives [C₅H₅RhH(C₂H₄)PMe₃]BF₄ and methanol. It is assumed that the formation of the ethylene(hydrido)metal complexes always occur via a M(CH₂)CH₃ intermediate, radical intermediates not being observed. The crystal structure of [C₆Me₆RuH(C₂H₄)PPh₃]PF₆ has been determined. The cation of 1.50 Å. The CC distance in the ethylene ligand is 1.41(1) Å and thus is significantly longer than in the free olefin.     

线性啁啾脉冲高斯光束载波相位漂移的近似解

利用复q参数法,研究了几周期线性啁啾脉冲高斯光束在自由空间中的传播,在振幅零阶和相位一阶近似的条件下,得到其载波相位的解析公式,该公式的显著特点是载波相位与线性啁啾系数无关。研究了载波相位在传播方向的分布,并与数值计算方法比较,结果表明,啁啾系数在－1～1的范围内,在光轴附近,其载波相位解析公式结果与数值结果符合很好。