插入式铜条转子并头套电阻硬钎焊工艺

为提高电动机中插入式铜条转子并头套的焊接质量，采用了电阻硬钎焊工,这样在改善劳动环境、降低劳动强度的同时提高了生产效率。     

Influence of withdrawal rate on the microstructure of Ni-base single-crystal superalloys containing Re and Ru

The influence of elevated withdrawal rate on the microstructure and segregation behavior of Ni-base single-crystal superalloys containing Re and Ru is investigated. The experimental superalloys are processed under a high thermal gradient of approximately 250 K/cm and withdrawal rates between 10 and 500 μm/s. With increasing withdrawal rate, the dendritic structures and γ′ precipitates in as-cast microstructures are apparently refined. Electron-probe microanalyzer (EPMA) results indicate that the degree of segregation for the constituent elements (e.g. Al, Ta, W, Re etc.) increases initially and then decreases with increasing withdrawal rate. In addition, the Re and Ru additions obviously increase the amounts of γ-γ′ eutectic and the tendency of segregation for Al and Ta.     

Spectroscopic,stability and radical-scavenging properties of a novel pigment from gardenia

A novel pigment, named gardecin, has been isolated from gardenia fruits, together with another five known crocins. The pigment, which possessed a structure which is unique among crocins, was characterised using spectrometric techniques, particularly 1D and 2D NMR. The NMR assignments were based on data from ¹H NMR, ¹³C NMR, DEPT, ¹H–¹H COSY, NOESY, HMQC and HMBC measurements. The five known crocins were identified on the basis of MS, UV/visible and 1D NMR data. Chemical stability and antioxidant ability of gardecin in comparison with the other five crocins were studied. The stronger DPPH free radical-scavenging ability of gardecin compared, with the other crocins, was observed. Kinetic studies have shown that all crocins were unstable under various conditions, but surprisingly gardecin was fairly stable.     

茄子皮中黄酮的提取工艺研究

本试验采用乙醇热浸提法对茄子皮中总黄酮提取工艺条件进行优化,并对其抗氧化活性进行研究。通过单因素试验和正交试验研究茄子皮中黄酮提取的最佳条件:提取溶剂为乙醇、乙醇浓度75%、料液比1∶30、提取时间2.5h和提取温度73℃,其影响的主次顺序依次为提取温度提取时间乙醇浓度液料比。     

Optical properties of water-soluble Co:ZnS semiconductor nanocrystals synthesized by a hydrothermal process

Water-soluble ZnS:Co²⁺ nanocrystals (NCs) were synthesized by a low temperature hydrothermal process using 3-mercaptopropionic acid (MPA) as capping agent and the influence of doping on the optical properties of ZnS:Co²⁺ NCs was investigated. It was found that the ZnS:Co²⁺ NCs are highly crystalline and show zinc blende structure with an average particle size of about 7 nm. The lattice constant of the ZnS:Co²⁺ NCs decreases slightly by the introduction of Co²⁺. The Co dopants were well doped into the ZnS:Co²⁺ NCs, as confirmed by X-ray photoelectron spectroscopy(XPS) and the ⁴A₂(F) → ⁴T₁(P) transition of Co²⁺ was detected from the UV-vis absorption spectra. The absorption edge of the ZnS:Co²⁺ NCs is blue-shifted as compared with that of bulk ZnS, indicating the quantum confinement effect. The PL intensity of the NCs shows the maximum value when the Fe-doping concentration is 0.5 at.%.     

Antioxidant potential of crocins and ethanol extracts of Gardenia jasminoides ELLIS and Crocus sativus L.: A relationship investigation between antioxidant activity and crocin contents

Crocins are water-soluble carotenoids responsible for the colour of saffron and gardenia. In this study, we isolated and identified three major crocins from gardenia, and then evaluated their antioxidant potential using four in vitro antioxidant tests in comparison with saffron ethanol extract (SE), gardenia ethanol extract (GE) and gardenia resin fraction (GRF). The relationship between total crocin contents and antioxidant activity of ethanol extracts of two herbs was investigated and the antioxidant potentials of three different polar crocins were compared. The crocins appeared to possess antioxidant activity when tested by four in vitro antioxidant models. However, in anti-hemolysis, DPPH radical-scavenging and lipid peroxidation assays, GRF exhibited significantly stronger antioxidant activity than crocins and no correlation between total crocin contents and antioxidative function was revealed, which implied that ingredients other than crocins in gardenia gave markedly strong antioxidant activity. In the phosphomolybdenum assay, antioxidant capacities of fractions and extracts correlated with total crocin contents (R = 0.93). Moreover, comparison of results indicated that sugars attached to the crocetin moiety seemed to be beneficial for the antioxidant activity of these water-soluble pigments.     

Computer modeling of isothermal crystallization in short fiber reinforced composites

Computer modeling and simulation for the isothermal crystallization of short fiber reinforced composites with athermal nucleation is presented. The “pixel coloring” technique which is capable of capturing the morphology evolution and calculating the crystallization kinetics is implemented. A parametric study is used to explore the influences of fibers on the crystallization in the reinforced system. The results indicate that the fibers depress the crystallization rate when compared to that of neat polymers or accelerate the crystallization rate by providing nucleation sites. The constraining effect is mainly dependent on fiber content while the enhancing effect is mainly determined by fiber surface and fiber nucleation density. Fiber orientation has almost no effect on the crystallization kinetics but changes the ultimate morphology. Fiber length and fiber diameter have different influences on crystallization kinetics and mean size of spherulites. Results show that fiber diameter affects the crystallization much more than that of fiber length.     

Synthesis and solid-state studies of self-assembled C60 microtubes

C₆₀ microtubes were fabricated by a modified solution evaporation method, evaporating a solution of C₆₀ in toluene in an atmosphere of m-xylene at room temperature. The C₆₀ microtubes have outer diameters ranging from 2 to 8 μm. IR spectra, TG analysis and X-ray diffraction showed a solvated structure for the as-grown C₆₀ microtubes. Through a gentle heat-treatment in vacuum, pure C₆₀ microtubes with single crystalline fcc structure were obtained after the elimination of solvents. It is suggested that the C₆₀ microtubes form through self-assembly from several individual C₆₀ nanorods.     

Characterization of hot-dip galvanized coating on dual phase steels

This work explored the microstructure of continuous hot-dip galvanized zinc coating on two dual phase steels, focusing on the sample preparation methods for cross-sectional microstructure and Fe-Al intermetallic compound observation. Based on the microstructure revealed by proper method, we established a relationship between the annealing atmosphere and coating microstructure. The experimental results showed that the coating thickness and Fe-Al intermetallic compound's size are relevant to the annealing atmosphere. And the coexistence of Fe-Al intermetallic compound and Fe-Zn phase has proved indirectly that the aluminothermic reduction is working during hot-dip galvanizing.