Enhancement of hydrogen production rates in reformation process of methane using permeable Ni tube and chemical heat pump

Enhancement of the overall conversion efficiency from CH₄ to H₂ using a permeable-membrane Ni tube and temperature rise by a chemical heat pump system packed with hydrogen-absorbing alloys have been investigated in order to produce H₂ more efficiently using a high-temperature heat source. The two feasibilities to enhance the conversion efficiency are tested using their respective experimental apparatuses. Two things are experimentally proved that (1) Ni permeable-membrane tubes can provide measures to convert CH₄ to H₂ continuously without any deterioration in the course of partial oxidation or steam reformation and (2) two Zr(V_1−xFe_x)₂ alloys with different Fe displacement ratios can comprise a chemical heat-pump system working at higher-temperature conditions.     

Using rapid compression machines for chemical kinetics studies

Rapid compression machines (RCMs) are used to simulate a single compression stroke of an internal combustion engine without some of the complicated swirl bowl geometry, cycle-to-cycle variation, residual gas, and other complications associated with engine operating conditions. RCMs are primarily used to measure ignition delay times as a function of temperature, pressure, and fuel/oxygen/diluent ratio; further they can be equipped with diagnostics to determine the temperature and flow fields inside the reaction chamber and to measure the concentrations of reactant, intermediate, and product species produced during combustion.This paper first discusses the operational principles and design features of RCMs, including the use of creviced pistons, which is an important feature in order to suppress the boundary layer, preventing it from becoming entrained into the reaction chamber via a roll-up vortex. The paper then discusses methods by which experiments performed in RCMs are interpreted and simulated. Furthermore, differences in measured ignition delays from RCMs and shock tube facilities are discussed, with the apparent initial gross disagreement being explained by facility effects in both types of experiments. Finally, future directions for using RCMs in chemical kinetics studies are also discussed.     

Synthesis,structure and optical properties of x(CuO)/(1−x)Ni(OH)2 [x=0, 0.1 and 0.3] nanocomposites

The x(CuO)/(1−x)Ni(OH)₂ [x=0, 0.1 and 0.3] nanocomposites were prepared by the hydrothermal method in the presence of the surfactant polyethylenglycol-10000 (PEG-10000). X-ray diffraction (XRD), infrared (IR) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the as-prepared samples. The increase of the CuO content led to the increase of the crystallite size of both, the β-Ni(OH)₂ and the CuO. The increase in the crystallite size greatly affects the band gap energy of the as-prepared nanocomposites. The band gap energies of the x(CuO)/(1−x)Ni(OH)₂ nanocomposites were estimated by UV–vis spectroscopic method. UV–vis spectroscopic results showed an apparent decrease in the direct band gap energies. The x(CuO)/(1−x)Ni(OH)₂ [x=0, 0.1 and 0.3] nanocomposites show low band gap energies compared to the Ni(OH)₂ bulk materials. The enhanced optical properties lead to their possible use in photocatalytic and photovoltaic applications.     

Flow induced vibrations of a triangular tube array in various arrangements of orientation and natural frequency

Abstract

Crossflow induced vibrations of a triangular tube array with a pitch ratio 1.33 were investigated experimentally. The streamwise and cross‐stream displacements of a monitored tube in the array were simultaneously measured by two accelerometers to examine the tube response to the cross flow in a water tunnel. The experiment was aimed to study the effects of the array orientation, and the tube's natural frequency on the flow induced vibration of the tube array. It is shown by amplitude diagrams that fluid elastic vibrations exist when the reduced velocity is above a critical value. The critical reduced velocity is found to be sensitive to the orientation of the test array. Based on the measured data of critical reduced velocity, the tube array in a triangular pattern (at a 30‐deg orientation with respect to the flow direction in the experiment) is found to be more stable than when in a rotated triangular pattern (0‐deg orientation). Furthermore, it is illustrated that the discrepancy in natural frequency of the tubes delays the occurrence of the fluid elastic vibrations of the tube array. With all the tubes in the test array having the same natural frequency, the orbits of the tube that exhibits fluid elastic vibrations are an organized, elliptic shape. The corresponding spectra are line‐dominated with peaks at the natural frequency and its harmonics, suggesting that the tube vibration is an organized oscillator. Without the same natural frequency as the surrounding tubes, the monitored tube exhibits fluid elastic vibration at larger reduced velocity, vibrating in a relatively random orbit.     

Lonidamine Solid Dispersions: In Vitro and In Vivo Evaluation

ABSTRACT

Solid dispersions of lonidamine in PEG 4000 and PVP K 29/32 were prepared by the spray-drying method. Then, the binary systems were studied and characterized using differential scanning calorimetry, hot stage microscopy, and x-ray diffractometry. In vitro dissolution studies of the solid dispersed powders were performed to verify if any lonidamine dissolution rate or water solubility improvement occurred. In vivo tests were carried out on the solid dispersions and on the cyclodextrin inclusion complexes to verify if this lonidamine water solubility increase was really able to improve the in vivo drug plasma levels. Drug water solubility was increased by the solid dispersion formation, and the extent of increase depended on the polymer content of the powder. The greater increase of solubility corresponded to the highest content of polymer. Both the solid dispersions and the cyclodextrin complexes were able to improve the in vivo bioavailability of the lonidamine when administered per os. Particularly, the AUC of the drug plasma levels was increased from 1.5 to 1.9-fold depending on the type of carrier.     

大跨度拱形钢管桁架制作安装实例介绍

本文简要介绍了淮河防洪除涝减灾实体模型基地试验大厅工程大跨度钢管桁架的施工和施工方案的选择,重点分析了分件制作、现场拼装、双机抬吊、桁架整体就位主要过程的施工要点及注意事项.     

格构式柔性活动钢管结构支架设计研究

格构式柔性活动钢管结构支架是一种新型的钢结构形式。通过对一个实际工程的设计从结构的力学分析、稳定性验算、构件的截面选择和管节点的设计原则等方面阐述了钢管结构的计算方法和设计概念。     

Comparison of different methods for determination of Pt surface site concentrations for supported Pt electrocatalysts

Platinum surface atom (or site) concentrations for a series of commercially available 10, 20, and 40 wt% Pt/C electrocatalysts have been determined using X-ray diffraction (XRD), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), selective chemisorption, and cyclic voltammetry (CV) methods. Each method of analysis was repeated for a sufficient number of times to determine reproducibility and standard deviation limits. Comparison of the results shows that XRD and STEM methods give Pt surface site concentrations much higher than for chemisorption analysis due to assumptions regarding Pt particle shapes and particle size distributions. The results from CV analysis agree reasonably well with those from chemisorption if the sample amounts and methods of sample deposition preceding CV analysis can be well-controlled and there is no loss of surface exposure by the Nafion over-layer. Because both chemisorption and CV analyses more directly measure actual site concentrations with fewer assumptions, these methods should be considered superior to XRD and STEM analyses. Further, since chemisorption uses substantially larger sample sizes (up to 0.25 g) compared to CV (<0.01 g), reliability of chemisorption data is much more reliable and should be considered as the metric for surface Pt site determination.     

Giant dielectric response and mixed-valent structure in the layered-ordered double-perovskite ceramics

Origin of giant dielectric response in the layered-ordered double-perovskite La₂CuSnO₆ ceramics was investigated in the present work. Apart from the main layered-ordered double-perovskite La₂CuSnO₆ phase, minor La₂Sn₂O₇ secondary phase was detected. There were two dielectric relaxations in the curve of temperature dependence of dielectric properties of La₂CuSnO₆ ceramics. Both of dielectric relaxations were thermal activated process. The low temperature relaxation should be attributed to the mixed-valent structure (Cu²⁺/Cu³⁺) since the activation energy was similar to that of La₂CuTiO₆ ceramics. While the high temperature relaxation was closely related to the thermal activated hopping process of electrical conduction. After annealing the sample in N₂ and O₂ atmosphere, the trend of dielectric behaviors and ac conductivities were the same at high temperature. This result confirmed that the high temperature relaxation was closely related to the electrical conduction.     

Characterisation of the mechanical properties of pultruded fibre-reinforced polymer tube

This paper presents an investigation on the mechanical properties of pultruded fibre-reinforced polymer (FRP) tube. Unlike typical FRP tube, the investigated tube has additional ±45° glass fibre reinforcement making it suitable for several structural applications. Tests on coupons and full-scale specimens were undertaken to determine the mechanical properties of the tube. Moreover, a finite element (FE) analysis was carried to simulate the compressive and flexural behaviours of full-scale specimen. Experimental results showed that coupon and full-scale specimens exhibited linearly elastic up to failure. The maximum variation of the experimental data is up to 8% indicating that the reproducibility of the test is quite reasonable and that the experimental procedures were conducted within the acceptable margin of error. The comparison between the compressive and flexural peak load values obtained experiment and FE methods revealed that their difference is less than 5%. Furthermore, the compressive and flexure failure modes obtained from the experiment were fairly simulated in the FE analysis. These indicated that FE analysis predicted reasonably the actual compressive and flexural behaviours of the pultruded FRP tube.