Microstructural investigation of long-term degradation mechanisms in GFRP dowel bars for jointed concrete pavement

Steel dowel bar is used to transfer loads in concrete pavement slab. However, once the steel dowel bar corrodes, it may cause faults, such as joint freezing in concrete pavement, level differences resulting from spalling or decreased efficiency of load transfer, etc., which are the same problems experienced by typical reinforcing steel. This study evaluated the applicability of glass fiber-reinforced polymer (GFRP) dowel bar as a substitute for steel dowel bar. A microstructural analysis was conducted to examine the decrease in durability of GFRP dowel bar exposed to deterioration environments. To analyze the deterioration mechanism of GFRP dowel bar, scanning electron microscopy was employed and the porosity was measured by the gas absorption method. It was concluded that the longer the GFRP dowel bar was exposed to deterioration environments, the more the interlaminar shear stress decreased. This result was validated by the microstructural analysis. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The application of microencapsulated phase‐change materials to nylon fabric using direct dual coating method

The fabrication of functional textiles able to provide thermal regulation and comfort for the body has attracted increasing interest in recent years. This research investigated fabric coatings containing energy absorbing, temperature stabilizing, phase‐change material microcapsules (PCMMcs), and their methods of application. Specifically, a coated fabric was directly prepared by a dual‐type coating method, in which the PCMMcs were dispersed in a polyurethane coating solution with no binder. The thermal performances of the dual‐coated samples were evaluated by differential scanning calorimetry, and their physical characteristics were examined by scanning electron microscopy, thermal vision camera, porosity, water vapor transmission rate (WVTR), and water entry pressure (WEP) analyses. Furthermore, the microclimate characteristics of the thermally enhanced fabrics were investigated under experimental conditions using a human‐clothing‐environment (HCE) simulator system. The study results confirmed the superior performance of the dual‐coated fabrics in terms of thermal regulation and body comfort, compared with those coated by the dry or wet coating method, because of the improved WEP, WVTR, and thermal performance. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

NiCoFe/C cathode electrocatalysts for direct ethanol fuel cells

A direct ethanol fuel cell (DEFC), which is less prone to ethanol crossover, is reported. The cell consists of PtRu/C catalyst as the anode, Nafion^® 117 membrane, and Ni–Co–Fe (NCF) composite catalyst as the cathode. The NCF catalyst was synthesized by mixing Ni, Co, and Fe complexes into a polymer matrix (melamine-formaldehyde resins), followed by heating the mixture at 800 °C under inert atmosphere. TEM and EDX experiments suggest that the NCF catalyst has alloy structures of Ni, Co and Fe. The catalytic activity of the NCF catalyst for the oxygen reduction reaction (ORR) was compared with that of commercially available Pt/C (CAP) catalyst at different ethanol concentrations. The decrease in open circuit voltage (V_oc) of the DEFC equipped with the NCF catalysts was less than that of CAP catalyst at higher ethanol concentrations. The NCF catalyst was less prone to ethanol oxidation at cathode even when ethanol crossover occurred through the Nafion^®117 film, which prevents voltage drop at the cathode. However, the CAP catalyst did oxidize ethanol at the cathode and caused a decrease in voltage at higher ethanol concentrations.     

Thermal Stability of the Pigments Hydroxysafflor Yellow A, Safflor Yellow B, and Precarthamin from Safflower (Carthamus tinctorius)

ABSTRACT Three major yellow pigments were isolated from safflower petals ( Carthamus tinctorius ) and characterized as hydroxysafflor yellow A (1), safflor yellow B (2), and precarthamin (3) by ¹H-NMR, ¹H-¹H COSY, ¹³C-NMR, HMQC, and HMBC spectral analysis. Thermal degradation reactions of 3 yellow pigments 1 to 3 at temperatures of 70 to 90 °C were carried out at different pH levels within the range of 3.0 to 10.0 by UV-vis spectral measurements. First-order reaction kinetics was observed for the degradation of safflower yellow pigments (1 to 3) at pH 3.0 and 5.0. Activation energies of thermal degradation of 1-3 at pH 5.0 were calculated as 17.0, 15.4, and 20.1 kcal/mol, respectively. At neutral and alkaline conditions, yellow pigments 1-3 did not follow simple first-order kinetics.     

Measurements of coupling and reflection characteristics of butt-joints in passive waveguide integrated laser diodes

Amplified spontaneous emission (ASE) spectra of passive waveguide integrated lasers have been studied to estimate the coupling efficiency and the reflectivity at the butt-joints between active and passive waveguides. A new method has been proposed for the analysis of ASE to extract the coupling efficiency and reflectivity at the butt-joints. This method was applied experimentally to estimate the coupling and reflection of the passive waveguide integrated lasers with different amounts of vertical misalignments of active and passive waveguides.     

Structural system identification: from reality to models

The paper is an expository contribution on the subject of structural system identification, measured signal processing and their applications to model-based structural health detection. The materials covered in this paper are by and large extracted from the three theses of the first three authors. The paper focuses on the state-space oriented system identification theory as specialized to structural dynamics governing equations of motion, a judicious use of wavelet transformation techniques for extracting impulse response functions, various input-output combinations for multi-input and multi-output problems, robust ways of identifying both proportional and non-proportional damping parameters, and the use of localized identification theory for damage detection from measured response data. The authors then offer several outstanding challenges in structural system identification theory and their applications.     

Hierarchically Ordered Polymer Films by Templated Organization of Aqueous Droplets

Hierarchically ordered structures facilitate the incorporation of diverse functions simultaneously. The present report introduces a simple and novel strategy for producing hierarchically ordered polymeric films. Hierarchical ordering of aqueous droplets on a polymer solution is realized by the imposition of physical confinement via various shaped gratings. After drying of the solution, well‐ordered hierarchical structures were fabricated in the remaining polymer film. The size of the grating structure and the lattice size of spontaneous hexagonally packed aqueous pores comprise two different length scales, thereby offering multiscale ordering. Interfacial wetting of the polymer solution to the grating surface was crucial in terms of obtaining a highly ordered structure that can be tuned by dissolving a small amount of surfactant in the polymer solution. The present novel approach provides a new opportunity for lithography‐free fabrication of complex hierarchical structures.     

540kN力基准机砝码摆动的研究

日本国家计量研究院(National Research Laboratory of Metrology)540kN静重式力基准机中的振荡分量主要是由于砝码的摆动引起的。本文对砝码的动态特性做了详细的分析，给出了其摆动的轨迹图，并对由于砝码摆动引起的相对不确定度进行了评估。提出了一类采用传感器并联的叠加系统(以下称叠加系统)输出的力值信号来评估砝码动态特性的信号处理方法。它对研究静重式测力机砝码摆动提供了有效的分析方法。     

Epitaxial growth of GaN on (0001) Al<Subscript>2</Subscript>O<Subscript>3</Subscript> via solution-cast seed layer formation process using Ga(mDTC)<Subscript>3</Subscript>

This paper reports an alternative method for the growth of GaN epitaxial layer on (0001) Al₂O₃ substrate by hot-wall vapor phase epitaxy technique. Tris (N,N-dimethyldithiocarbamato)-gallium (III), Ga(mDTC)₃ was introduced as a precursor material for the seed layer formation in the growth of GaN. Optimal growth conditions with seed layers formed by the Ga(mDTC)₃ concentration of 0.047 mol/L were identified: Growth temperature was found to be 850 °C, and optimal distance between the reactant outlet and substrate was determined to be 12.5 cm. Characterization results showed that this growth method produce high-crystallinity GaN epitaxial layers at a relatively lower growth temperature compared to the existing growth techniques and simplify the growth process.