风险规避供应商参与下基于实物期权的供应链协调

研究不确定性需求下,由风险规避的供应商和占主导地位的零售商组成的二级供应链的协调问题。构建了基于实物期权的协调机制,给出了实现协调的最优期权价格和期权执行价格的求解算法,分析了供应商风险规避特性对各方订货量和利润的影响。结果表明,在供应商风险规避条件下,基于实物期权的契约可以实现不确定需求下的供应链协调。     

Existence of solutions for fractional differential equations with multi-point boundary conditions

We discuss the existence of solutions for a nonlinear multi-point boundary value problem of integro-differential equations of fractional order q ∈ (1, 2]. Our analysis relies on the contraction mapping principle and the Krasnoselskii’s fixed point theorem. Example is provided to illustrate the theory.     

一种新型芒柄花素衍生物4′-甲氧基-7-乙氧基异黄酮的合成、晶体结构及量子化学研究

以芒柄花素为先导化合物,合成了一种新型的衍生物4′-甲氧基-7-乙氧基异黄酮,通过X射线单晶衍射法对它的结构进行了表征.为了研究化合物的电子结构,在其晶体结构基础上进行了量子化学计算.采用密度泛函理论(DFT),B3LYP方法,对其进行优化,优化结果与实验吻合良好并且被用于后面前线分子轨道及自然电荷布居分析的计算.     

Pt-Ni/γ-Al2O3 双金属催化剂上1,3-环己二烯的低温加氢和脱氢反应

 采用等体积浸渍法制备了 γ-Al2O3 负载的 Pt 和/或 Ni 双金属催化剂或单金属催化剂, 测定了它们的 CO 化学吸附量, 并在原位红外间歇反应装置上评价了其催化 1,3-环己二烯 (1,3-CHD) 的低温 (308 K) 加氢和脱氢性能. 结果表明, Pt-Ni/γ-Al2O3 催化剂性能优于 Pt/γ-Al2O3 或 Ni/γ-Al2O3. 结合密度泛函理论计算的不同催化剂上 1,3-CHD 的表面吸附能, 验证了具有较弱环烯烃吸附能的双金属催化剂加氢活性较高.     

PP films grafted with N-isopropylacrylamide and N-(3-aminopropyl) methacrylamide by γ radiation: synthesis and characterization

Simultaneous grafting of N-isopropylacrylamide (NIPAAm) and N-(3-aminopropyl) methacrylamide hydrochloride (APMA) on polypropylene (PP) was investigated for obtaining interfaces that are stimuli-responsive under physiological conditions. A pre-irradiation method was optimized tuning the γ-irradiation dose, reaction time, temperature, and monomers concentrations. FT-IR ATR and XPS analysis of the grafted copolymers evidenced a greater content in NIPAAm than in APMA; the APMA/NIPAAm ratio increasing with the concentration of APMA in the reaction medium and when the grafting was carried out in 1 M NaNO₃. The grafted films were characterized regarding their thermal properties (DSC and TGA) swelling behavior and contact angle. Immersion of the pre-irradiated films in 1 M NIPAAm/0.5 M APMA aqueous solution rendered PP-g-(1NIPAAm-r-0.5APMA) which exhibited rapid and reversible transitions showing a LCST around the physiological temperature. By contrast, a greater content in APMA enhanced the hydrophilicity and prevented the shrinking of PP-g-(1NIPAAm-r-1APMA).     

Dispersion in retentive pillar array columns

The method of volume averaging is applied to estimate the Taylor–Aris dispersion tensor of solute advected in columns consisting of ordered pillar arrays with wall retention of the type used in chromatographic separation. The appropriate closure equations are derived and solved in a unit cell with periodic boundary conditions to obtain the dispersion tensor (or the reduced plate height) as a function of the Peclet number (reduced velocity); pillar pattern, shape and size; partition coefficient; and resistance to mass transfer. The contributions of the velocity profile, the wall adsorption, and the mass transfer resistance to the dispersion tensor are identified and delineated. The model is verified by comparing its predictions and obtaining favorable agreement with results of direct numerical simulations and with experimental data for columns containing ordered pillars. The model is then used to study the effect of pillars’ shape and pattern on the longitudinal dispersion coefficient (plate height).     

DFT and TD-DFT studies on symmetrical squaraine dyes for nanocrystalline solar cells

Abstract  

The ground-state geometries, electronic structures, and electronic absorption spectra of symmetrical squaraine dyes SQ1–SQ4 were investigated using density functional theory and time-dependent DFT at the B3LYP level. The calculated geometries indicate that strong conjugation effects occur in the dyes. The highest occupied molecular orbital energy levels were calculated to be −4.95, −5.22, −5.09, and −5.06 eV, and the lowest unoccupied molecular orbital energies were −2.72, −3.05, −2.80, and −2.80 eV for SQ1–SQ4, respectively. Taking the conduction band energy of TiO₂ into account, these data reveal the sensitized mechanism: the interfacial electron transfer between the semiconductor TiO₂ electrode and the dye sensitizers SQ1–SQ4 are electron-injection processes from excited dyes to the semiconductor conduction band. The intense calculated absorption bands are assigned to π → π* transitions, which exhibit appreciable blue-shift compared with the experimental absorption maxima due to the inherent approximations in the TD-DFT.     

Luminescence enhancement of Eu, Ce co-doped Ba3Si5O13−δNδ phosphors

Host lattice Ba₃Si₅O_13−δN_δ oxonitridosilicates have been synthesized by the traditional solid state reaction method. The lattice structure is based on layers of vertex-linked SiO₄ tetrahedrons and Ba²⁺ ions, where each Ba²⁺ ion is coordinated by eight oxygen atoms forming distorted square antiprisms. Under an excitation wavelength of 365 nm, Ba₃Si₅O_13−δN_δ:Eu²⁺ and Ba₃Si₅O_13−δN_δ:Eu²⁺,Ce³⁺ show broad emission bands from about 400-620 nm, with maxima at about 480 nm and half-peak width of around 130 nm. The emission intensity is strongly enhanced by co-doping Ce³⁺ ions into the Ba₃Si₅O_13−δN_δ:Eu²⁺ phosphor, which could be explained by energy transfer. The excitation band from the near UV to the blue light region confirms the possibility that Ba₃Si₅O_13−δN_δ:Eu²⁺, Ce³⁺ could be used as a phosphor for white LEDs.     

Three-dimensional global analysis of thermal stress and dislocations in a silicon ingot during a unidirectional solidification process with a square crucible

A three-dimensional global model was used to obtain the solution of a thermal field within the entire furnace during a unidirectional solidification process of multicrystalline silicon with a square crucible. Then the thermal stress distribution in the silicon ingot was solved. Based on the solution of thermal stress, relaxation of stress and multiplication of dislocations were performed by using the Haasen–Alexander–Sumino model (HAS model). The influence of crucible constraint on stress levels and dislocations was investigated. It was found that the crucible constraint had significant influence on the thermal stresses and dislocations in the ingot. The results indicated that it is important to reduce the crucible constraint in order to relax thermal stresses and reduce dislocations in a silicon ingot during the solidification process.     

各向同性材料中微裂纹的最大屏蔽效应

通过对微裂纹屏蔽不同来源的分析及计算,发现在各向同性脆性材料中,残余应力释放引起的微裂纹对主裂尖产生最大屏蔽效应时该微裂纹的倾角与最大张应力的方向没有明显的对应关系．在Hutchinson[1]所指出的屏蔽效应的第二个来源中,还应计及微裂纹形成引起的远场应力在微裂纹处产生的应力场的释放从而导致应力场的再分布．