薄壁离心钢管混凝土结构及其质量控制

薄壁离心钢管砼结构发挥了钢及砼工种材料的特性 ,本文就此种管道结构的技术、经济特征、应用范围和生产质量等方面的内容展形评述。     

葛根素及其与金属离子的极谱行为研究

采用单扫描极谱法(LSP)研究了葛根素的极谱行为,在建立一种简单、快捷和灵敏的葛根素单扫描极谱分析方法的同时,考察了金属离子对于葛根素极谱波的影响及其相关性质.实验研究表明:在pH=12.40的乙二胺(1 mol/L)底液中,以滴汞电极(DME)为工作电极,Pt电极为对电极,饱和甘汞电极(vs·SCE)为参比电极的三电极系统,在-0.30 V～-0.80 V之间用LSP法扫描,发现葛根素在峰电位(Ep)为-0.58 V(V,SCE)处有一个灵敏的二阶导数的极谱峰,其浓度在0.M5～5.53mg/L时峰高(Ip)与浓度成很好的线性关系.标准曲线的相关系数为0.994 9,最小检测限为0.065mg/L.在最佳实验条件下,在葛根素溶液中加入金属离子Cu2 、Al3 、Pd2 、Fe3 进行LSP扫描,发现不同金属离子可使葛根素极谱峰的峰电位产生不同程度的负移和峰高增大现象,说明金属离子和葛根素有一定的络合反应发生,因此依据实验结果,计算得出金属离子Cu2 、Fe3 和葛根素络合反应的K稳.从样品分析的结果得出,利用葛根素在Ep为-0.58 V(vs·SCE)时的二阶导数极谱波对葛根素进行极谱分析的方法是可行的.     

Time‐of‐Flight Studies of Electron‐Collection Kinetics in Polymer:Fullerene Bulk‐Heterojunction Solar Cells

The charge‐collection dynamics in poly(3‐hexylthiophene:[6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (P3HT:PCBM) bulk heterojunctions are studied in thick (>1 μm) devices using time‐of‐flight measurements and external quantum‐efficiency measurements. The devices show Schottky‐diode behavior with a large field‐free region in the device. Consequently, electron transport occurs by diffusion in the bulk of the active layer. At high applied biases where the depletion region spans the entire active layer, normal time‐of‐flight transients are observed from which the electron mobility can be determined. Here, the electron mobility follows Poole–Frenkel behavior as a function of field. At lower applied biases, where the depletion region only spans a small portion of the active layer, due to a high density of dark holes, the recombination kinetics follow a first‐order rate law with a rate constant about two orders of magnitude lower than that predicted by Langevin recombination.     

The display of photographic-quality images on the Web: a comparisonof two technologies

Downloading medical images on the Web creates certain compromises. The tradeoff is between higher resolution and faster download times. As resolution increases, download times increase. High-resolution (photographic quality) electronic images can potentially play a key role in medical education and patient care. On the Internet, images are typically formatted as Graphics Interchange Format (GIF) or the Joint Photographic Experts Group (JPEG) files. However, these formats are associated with considerable data loss in both color depth and image resolution. Furthermore, these images are available in a single resolution and have no capability of allowing the user to adjust resolution as needed. Images in the photo compact disc (PCD) format have higher resolutions than GIF or JPEG, but suffer the disadvantage of large file sizes leading to long download times on the Web. Furthermore, native Web browsers are not currently able to read PCD files. The FlashPix format (FPX) offers distinct advantages over the PCD, GIF, and JPEG formats for display of high-resolution images on the Web. A Java applet can be easily downloaded for viewing FPX images. FPX images are higher resolution than JPEG and GIF images. FPX images offer rich resolutions comparable to PCD images with shorter download times     

Diagnosis of PTFE‐Nafion MEA degradation modes by an accelerated degradation technique

Cost and durability are central issues in the commercialization of proton‐exchange membrane fuel cells. This study used complex accelerated‐degradation protocols to diagnose the degradation modes of low‐cost polytetrafluoroethylene–Nafion membrane electrode assemblies (MEAs). Acceleration protocols included open‐circuit voltage, relative humidity cycling, and load cycling. Failure modes included measurements of cyclic voltammetry, linear sweep voltammetry, polarization curve, and AC impedance. The four modes (stages) of degradation were determined to be (i) catalyst aging, (ii) creep deformation, (iii) pinhole formation, and (iv) membrane failure. During catalyst aging, the maximum power density decreased by 0.117 mW cm^?2 cycle^?1. After the 280th cycle, creep deformation occurred, and the maximum power density decreased by 0.227 mW cm^?2 cycle^?1. Pinholes led to membrane failure and a final dramatic loss of performance (?0.453 mW cm^?2 cycle^?1). Therefore, membrane failure is the major factor in the failure of MEAs. Copyright © 2010 John Wiley & Sons, Ltd.     

Antiproliferative activity of peptides prepared from enzymatic hydrolysates of tuna dark muscle on human breast cancer cell line MCF-7

To produce and identify antiproliferative peptides, two commercial enzymes, papain (PA) and Protease XXIII (PR) were used to hydrolyse tuna dark muscle byproduct, and the protein hydrolysates were purified, before being evaluated for antiproliferative activities against human breast cancer cell line MCF-7. The results showed that the peptide fractions with the molecular weight ranging from 390 to 1400 Da possessed the greatest antiproliferative activity. The amino acid sequences of the two antiproliferative peptides isolated from PA and PR hydrolysates were Leu-Pro-His-Val-Leu-Thr-Pro-Glu-Ala-Gly-Ala-Thr (1206 Da) and Pro-Thr-Ala-Glu-Gly-Gly-Val-Tyr-Met-Val-Thr (1124 Da), whilst they show the dose-dependent inhibition effect of the MCF-7 cells with IC₅₀ values of 8.1 and 8.8 μM, respectively. We thus conclude that antiproliferative hydrolysates from tuna dark muscle byproduct may be useful ingredients in food and nutraceutical applications.     

Reduction in axle oil operating temperatures by fluids with optimized torque transfer efficiencies

Effective axle oils must efficiently transfer torque from the drive‐train to the wheels, while maintaining low axle oil operating temperatures. Previous studies have shown that fluids, which form thicker elastohydrodynamic (EHD) films and have lower EHD friction, have higher torque transfer efficiencies (TE) and lower axle oil operating temperatures (OT). In general, oils with higher viscosities form thicker films and those with lower viscosities have lower EHD friction. Therefore, optimizing oil's rheological properties to maximize TE and minimize OT is difficult. In this paper, we examine two approaches to maintaining high TE while reducing OT. One approach is to minimize boundary friction since previous studies have shown that the boundary frictional properties of oils influence OT and not TE. A second approach is to more thoroughly examine the effect of rheology on film thickness and EHD friction. Film thickness and EHD friction are related to the high temperature high shear viscosity and pressure‐viscosity coefficient of oils. We have found that oils with high pressureviscosity coefficients and low high temperature high shear viscosities will form thick films and have low EHD friction. This optimized combination of physical parameters, along with lowering the boundary friction coefficient of axle oils, results in oils with high TE and low OT. Copyright © 2006 John Wiley & Sons, Ltd.     

Interfacial Reactions of Sn, Sn-3.0Ag-0.5Cu, and Sn-9Zn Lead-Free Solders with Fe-42Ni Substrates

Interfacial reactions between Sn, Sn-3.0 wt.%Ag-0.5 wt.%Cu (SAC), and Sn-9 wt.%Zn (SZ) lead-free solders and Fe-42 wt.%Ni (alloy 42) substrates at 240°C, 255°C, and 270°C were investigated in this study. FeSn₂, (Fe,Ni, Cu)Sn₂, and (Ni,Fe)₅Zn₂₁ phases were formed, respectively, at the interface in the Sn/alloy 42, SAC/alloy 42, and SZ/alloy 42 couples. As the reaction time and temperature were increased, the layered intermetallic compound (IMC) assumed two distinct structures, i.e., a thicker layer and a pillar-shaped IMC, in all couples. The IMC thickness of these couples increased with the increase of reaction time and temperature. The IMC thickness was also proportional to the square root of the reaction time. The interfacial reaction mechanism of these couples was diffusion controlled.     

Effect of adding Sb on microstructure and adhesive strength of Sn-Ag solder joints

This study investigates the influence of adding Sb on the microstructure and adhesive strength of the Sn3.5Ag solder. Both solidus and liquidus temperatures increase as Sb additions increase. Adding 1.5wt.%Sb leads to the narrowest range (6.6°C) between the solidus and liquidus temperature of the solder. Adding Sb decomposes the as-soldered ringlike microstructure of Sn3.5Ag and causes solid-solution hardening. The as-soldered hardness increases with increasing Sb addition. For long-term storage, adding Sb reduces the size of the rodlike Ag₃Sn compounds. The hardness also increases with increasing Sb addition. Adding Sb depresses the growth rate of interfacial intermetallic compounds (IMCs) layers, but the difference between 1% and 2% Sb is not distinct. For mechanical concern, adding Sb improves both adhesive strength and thermal resistance of Sn3.5Ag, where 1.5% Sb has the best result. However, adding Sb causes a variation in adhesive strength during thermal storage. The more Sb is added, the higher the variation reveals, and the shorter the storage time requires. This strength variation helps the solder joints to resist thermal storage.