纳米铜银核壳焊膏脉冲电流快速烧结连接铜基板研究

一种温和的两步液相法制备的纳米铜银核壳颗粒,实现了均径为6.9 nm的小尺寸纳米银颗粒包覆在均径为57.5 nm的纳米铜颗粒的表面,采用扫描电子显微镜、透射电子显微镜和高分辨率射像对其结构进行了表征。采用模板印刷法制备铜基板/纳米铜银核壳焊膏/铜基板三明治结构,研究了脉冲电流对三明治结构的剪切强度大小和微结构特征的影响。试验结果表明脉冲电流烧结纳米铜银核壳焊膏连接Cu-Cu基板可在短时间（小于200 ms）内快速获得高致密度且实现冶金连接的高强度焊点结构。三明治结构的剪切强度随脉冲电流的增加而增大,在1.0 kA的脉冲电流下,可获得高达80 MPa的剪切强度。经研究脉冲电流烧结后的纳米铜银核壳焊膏内部显微组织结构,提出双脉冲电流下纳米铜银核壳焊膏烧结连接的机理。     

白酒大曲风味物质研究进展

白酒大曲是以小麦、大麦和（或）豌豆为主要原料、经人工制曲而成,是白酒酿造所需的糖化发酵剂和生香剂。 其原料的分解 产物和微生物的代谢产物,直接或间接构成了白酒的风味物质。研究大曲风味物质对研究酒香、改善基酒质量有重要意义。该文简要 介绍了大曲的制作工艺及分类,总结了大曲风味物质研究现状,包括前处理方法、定性定量方法和已检测的风味物质,以期为今后研 究大曲风味物质提供参考。     

黑线鳕鱼皮胶原蛋白胰蛋白酶酶解多肽对UVB诱导HaCaT光损伤的抑制作用

目的：研究黑线鳕鱼（Melanogrammus aeglefinus）皮胶原蛋白胰蛋白酶酶解多肽的抗氧化、抑制光损伤作用,提高鱼皮的再利用价值。方法：利用单因素试验和响应面试验设计,探讨黑线鳕鱼皮胶原蛋白的最佳酶解工艺。将制得的酶解多肽通过基质辅助激光解离飞行时间串联质谱仪（matrix-assisted laser desorption/ionization time of flight tandem mass spectrometry,MALDI-TOF MS/MS）测定多肽序列。利用Discovery Studio中CDOCKER模块将所得的优势肽与抗氧化相关的Kelch样环氧氯丙烷相关蛋白-1（Keap1）进行分子对接。用不同质量浓度的多肽预处理人表皮角质形成细胞（HaCaT）后,使用中波紫外线诱导HaCaT细胞构建光损伤模型,通过超氧化歧化酶（superoxide dismutase,SOD）、谷胱甘肽过氧化物酶（glutathione peroxidase,GSH-Px）活性、丙二醛（malondialdehyde,MDA）含量及细胞凋亡与周期来研究酶解多肽抑制光损伤的能力。结果：黑线鳕鱼皮胶原蛋白在胰蛋白酶质量分数1.23%、酶解温度52.95?℃、酶解时间1.75?h条件下,水解度为78.33%。MALDI-TOF MS/MS测定出酶解液中的优势肽序列为V-IFFVTMGTP-R、L-SIVPV-R和L-MHT-T。通过分子对接发现V-IFFVTMGTP-R与Keap1结合最稳定,从而预测其具有抗氧化的作用。用250?mg/mL酶解液处理光损伤的HaCaT细胞,其SOD、GSH-Px活性较模型组极显著提高（P＜0.01）,MDA含量极显著降低（P＜0.01）。结论：黑线鳕鱼皮胶原蛋白胰蛋白酶酶解多肽具有抗氧化活性,对光损伤具有一定的抑制作用。     

Effect of Al Film on the Electromagnetic Properties of Glass Fiber Reinforced Resin Matrix CompositeEI北大核心CSCD

Metallic thin films have many properties that bulk metals do not possess, such as high impedance. Recently, increasing attention has been paid to high impedance surface in the design of antennas and absorbers. Metallic thin films used in composite materials can realize the perfect matching of electromagnetic wave in different materials. The use of metallic thin films in electromagnetic functional materials results in significant increase of the absorbing intensity and operating bandwidth. But it usually needs to pay a huge amount of manpower, material resources and a longer period of time to design excellent electromagnetic functional materials with metallic films. So it is greatly significant to understand clearly the electromagnetic influence of metallic film for designing excellent performance materials and saving costs by simulation software. Al film is a typical non-magnetic metal film. In this work, the electromagnetic reflectivity of Al films and glass fiber reinforced resin matrix composite had been studied. High frequency electromagnetic field calculation software FEKO was employed to calculate the reflection coefficient of the composites. The effect of composites' real part of permittivity epsilon(r), dielectric loss tangent tan delta(epsilon), permeability mu(r) and magnetic loss tangent tan delta(mu) on microwave reflectivity had been discussed. The equivalent electromagnetic parameters of glass fiber reinforced resin matrix composite had been obtained through a comparison between simulation and experimental results. Due to resonance phenomena of the embedded Al film in the glass fiber reinforced resin matrix composite with certain thickness, there is an optimum resistance value of Al film that makes the composite structure have minimum reflection. Through the calculation of Al film and glass fiber reinforced resin matrix composite with different structure, the thickness relationship between Al films in calculation and Al films prepared by magnetron sputtering had been obtained. According to the theory of transmission line, the resistance of resonance is analyzed by MATLAB. This method is also applicable to the resistance solution of the homogeneous metal films at any position in the composite or frequency selective surfaces. The equivalent electromagnetic parameters of Al film and glass fiber reinforced resin matrix composite in simulation had been ascertained, and the simulation results agree well with the experimental results.     

A poly (ethylene oxide)/graphene oxide electrolyte membrane for low temperature polymer fuel cells

A novel method to prepare poly (ethylene oxide)/graphene oxide (PEO/GO) composite membrane aimed for the low temperature polymer electrolyte membrane fuel cells without any chemical modification is presented in this work. The membrane thickness is 80 μm with a GO content of 0.5 wt%. And SEM images show the PEO/GO membrane is condensed composite material without structure defects. Small angle XRD results for the membrane samples show that the d-spacing reflection (0 0 1) of GO in PEO matrix is shifted from 2θ = 11° to 4.5° as the PEO molecules intercalated into the GO layers during the membrane preparation process. FTIR tests show the typical -COOH vibration near 1700 cm⁻¹. Tensile tests show the resultant PEO/GO membrane tensile strength of 52.22 MPa and Young's modulus 3.21 GPa, and the fractured elongation was about 5%. The ionic conductivity of this PEO/GO membrane increases from 0.086 to 0.134 S cm⁻¹ when the operation temperature increases from 25 to 60 °C with 100% relative humidity. And further tests show the DC electronic resistance of this membrane is higher than 20 MΩ at room temperature with 100% relative humidity. Polarization curves in a single cell with this membrane give a maximum power density of 53 mW cm⁻² at the operation temperature around 60 °C, without optimizing the catalyst layer composition.     

锅炉包装入库发运管理系统

本系统采用Client/Server(C/S)模式,利用VB2005及MS SQL SERVER 2000为设计工具,实现了利用图纸明细表数据做锅炉包装清单设计以及工件入库、发运的信息化管理.该系统既解决了使用CAD做包装清单时容易丢件的问题,提高了设计效率,同时也解决了与工件入库、发运管理之间数据共享问题,大大提高了...     

Design of filament–wound domes based on continuum theory and non-geodesic roving trajectories

In this paper the optimal shapes and fiber architectures of non-geodesics-based domes for pressure vessels are determined upon the condition of equal shell strains. Based on the continuum theory and the non-geodesic law, the system of differential equations governing the optimal meridian profiles is derived. A specific function is chosen to describe the slippage coefficient distribution for the desired non-geodesic path, in order to ensure C¹ continuity of the roving paths when passing the dome–cylinder conjunction. Next, the meridian profiles are determined for various material anisotropies; the related winding angle developments of non-geodesic trajectories are also presented. The performance factors of non-geodesics-based optimal domes are obtained using various slippage coefficients and polar opening radii. The results show that the structural efficiency of the dome improves with increasing slippage coefficient. It is concluded that the non-geodesics-based dome designed using the present method gains better performance than the one relying on geodesics.     

Influence of strain amplitude on damping property of aluminum foams reinforced with copper-coated carbon fibers

Aluminum foams containing 0.35, 1.0, 1.7 vol.% copper-coated carbon fibers were fabricated by a melt route. The room temperature damping property of Al/C_f foam was studied at different strain amplitude in two directions. The experimental results show that the critical strain amplitude decreases and the damping capacity of Al/C_f foam increases with the copper-coated carbon fibers contents. It can be attributed to the interfacial micro-slip increasing with the C_f contents and the microplasticity deformation arises from the micro-crack among the C_f–Al interface. Moreover, the damping property in the transverse direction is higher than that in the longitudinal direction. The ratio of longitudinal loss factor to transverse loss factor is almost independent of the C_f contents and strain amplitude.     

Two Different Operation Regimes of Fiber Laser Based on Nonlinear Polarization Rotation: Passive Mode-Locking and Multiwavelength Emission

We have proposed and demonstrated a nonlinear polarization-rotation-based fiber laser with two different operation states: passive mode-locking and multiwavelength emission. The intensity-dependent transmission or loss induced by nonlinear polarization rotation accounts for the distinct operation regimes. Our experiment results indicate that both passively mode-locked pulses and continuous-wave multiwavelength can be generated from the same fiber laser just through adjusting polarizations. Another characteristic of the current multiwavelength laser is that the used periodic filter is a birefringence fiber filter, which facilitates all-fiber integration of the fiber laser, so it is a potential multifunction laser source with all-fiber configuration and convenient manipulation.