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1.
The superplastic formability of SP- lnconel 718 superalloy was evaluated using the argon blowing method. Relationships among
superplastic forming parameters (forming temperature, argon pressure, and forming time) and specific dome height (dome height/workpiece
diameter) were investigated, as were changes in material properties after superplastic forming. Experimental results showed
the optimum forming temperature range for SP- lnconel 718 to be between 975 and 995 °C. During the superplastic forming process,
5- phase precipitates formed at grain boundaries and limited the grain growth, which is considered beneficial for superplastic
deformation. On the other hand, increasing the forming deformation also increased the formation of cavities, which can be
attributed to the existence of niobium- rich inclusions. This degraded the superplasticity of the superalloy. Electrochemical
tests showed that the corrosion resistance of SP- lnconel 718 after superplastic forming worsened because of the existence
of both S- phase precipitates and niobium- rich inclusions. 相似文献
2.
The ordered f c c intermetallic compound Ni3Si was mechanically milled in a high-energy ball mill. The severe plastic deformation produced by milling induced transformations with increasing milling time as follows: ordered f c c disordered f c c nanocrystalline f c c. The structural and microstructural evolution with milling time was followed by X-ray diffraction, TEM, hardness tests, and differential scanning calorimetry (DSC). Complete disordering occurred at milling times of 2 h and kept the saturated H of the DSC peak in the range of estimated enthalpy even after 60 h milling. The structural development during milling of the f c c solid solution for Ni3Si was presumably dominated by the formation and refinement of a dislocation cell structure into microcrystallites which eventually reached nanometre dimensions. 相似文献
3.
A novel lotus plumule polysaccharide (LPPS) was administered to non-obese diabetic (NOD) mice for 15 weeks to evaluate the protective effects of LPPS on type 1 diabetes. After the 15-week feeding experiment, tumour necrosis factor (TNF)-α, interleukin (IL)-6 and IL-10 expressions in the spleen, liver and kidney of the experimental mice were measured using enzyme-linked immunosorbent assay or real-time quantitative polymerase chain reaction assay. The results showed that LPPS significantly (p < 0.05) decreased the absolute weights of the enlarged spleens in the NOD mice in a dose-dependent manner, inhibited pro-inflammatory TNF-α and IL-6 cytokine production and decreased the secretion ratio of IL-6/IL-10 in splenocyte cultures. LPPS markedly decreased the relative expression of pro-/anti-inflammatory cytokine genes (TNF-α/IL-10 and IL-6/IL-10) in the livers of NOD mice. Our results suggest that LPPS protected the spleen and liver from spontaneous inflammation in NOD mice by modulating pro-/anti-inflammatory cytokine gene expression. 相似文献
4.
Hao-Ming ChangChien-Wei Lin Min-Hsing Chang Huan-Ruei ShiuWen-Chen Chang Fang-Hei Tsau 《Journal of power sources》2011,196(8):3773-3780
This research investigates the optimal polytetrafluoroethylene (PTFE) content in the cathode gas diffusion layer (GDL) by evaluating the effect of compression on the performance of a proton exchange membrane (PEM) fuel cell. A special test fixture is designed to control the compression ratio, and thus the effect of compression on cell performance can be measured in situ. GDLs with and without a microporous layer (MPL) coating are considered. Electrochemical impedance spectroscopy (EIS) is used to diagnose the variations in ohmic resistance, charge transfer resistance and mass transport resistance with compression ratio. The results show that the optimal PTFE content, at which the maximum peak power density occurs, is about 5 wt% with a compression ratio of 30% for a GDL without an MPL coating. For a GDL with an MPL coating, the optimal PTFE content in the MPL is found to be 30% at a compression ratio of 30%. 相似文献
5.
Cortical local circuitry is important in epileptogenesis. Voltage-sensitive dyes and fast imaging were used to visualize the initiation of spontaneous paroxysmal events in adult rat neocortical slices. Although spontaneous paroxysmal events could start from anywhere in the preparation, optical imaging revealed that all spontaneous events started at a few confined initiation foci and propagated to the whole preparation. Multielectrode recording over hundreds of spontaneous events revealed that often two or three initiation foci coexisted in each preparation (n = 10). These foci took turns being dominant; the dominant focus initiated the majority of the spontaneous paroxysmal events during that period. The dominant focus and dynamic rearrangement of foci suggest that the initiation of spontaneous epileptiform events involves a local multineuronal process, perhaps with potentiated synapses. 相似文献
6.
We investigated a possible causal relation between exposure to organic solvents in Danish workers (housepainters, typographers/printers, carpenters/cabinetmakers) and onset of multiple sclerosis. Data on men included in the Danish Multiple Sclerosis Register (3,241 men) were linked with data from the 1970 census from the National Bureau of Statistics in Denmark, which has data on occupational status for 1,768,846 men between 15 and 74 years of age. From this census, we ascertained a group of 124,766 "solvent-exposed" men and an "unexposed" group of 87,501 male electricians, bricklayers, and butchers. Over a follow-up period of 20 years, we observed no increase in the incidence of multiple sclerosis among men presumed to be exposed to organic solvents. It was not possible to obtain data on potential confounders, and the study design has some potential for selection bias. Nevertheless, the study does not support existing hypotheses regarding an association between occupational exposure to organic solvents and multiple sclerosis. 相似文献
7.
William J. R. Gilbert Stephen J. Johnson Jyun‐Syung Tsau Jenn‐Tai Liang Aaron M. Scurto 《应用聚合物科学杂志》2017,134(10)
Polyacrylamides are often used in water‐based hydraulic fracturing for natural gas and oil production. However, residual polymer remaining in the fractured rock can limit production. A novel approach for degrading partially hydrolyzed polyacrylamide (HPAM) was investigated using hydrogen peroxide and horseradish peroxidase (HRP). This sustainable HRP/H2O2 system degraded the polymer in solution, reducing its viscosity in both pure water and brine solutions. Molecular weight measurements confirmed that the viscosity reduction was due to a significant degradation of the polymer backbone and not primarily by other mechanisms such as amide hydrolysis or rearrangement, and so forth. The reduction in viscosity and molecular weight was first order with respect to H2O2 concentration. The kinetics of viscosity reduction and molecular weight are closely correlated which would allow the quicker and simpler viscosity method to help engineer future processes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44560. 相似文献
8.
We demonstrate the development of a simply equipped displacement sensor utilizing spatially dispersive confocal technology. It feeds the amplified spontaneous emission (ASE) of a laser diode to a wavelength-selective feedback structure that corresponds to the position of a measured surface. The displacement sensor has a detecting range of 4 microm and precision of less than 2 nm, as proven by the analysis of the spectral shifts of the multipassed amplified output ASE. As compared with traditional sensors, the displacement sensor presented in our study requires fewer components and has as high precision as complex systems and a higher measurement rate due to the simpler strategy of displacement determination. 相似文献
9.
Ting-Chiang Tsai Jia-Hau Tsau Chun-Sheng Chen 《International Journal of Mechanical Sciences》2009,51(11-12):907-914
In this paper, governing equations of vibration for a beam with distributed internal viscous damping are established by using Timoshenko beam theory and Hamilton's principle. Then, the transfer matrix method is applied to obtain the frequency equations for the beam. The results reveal, when the internal viscous damping fully distributes along the beam, that the natural frequency decreases with the increasing damping and drops to a zero value at a certain critical damping. While the damping is locally distributed, damped frequency, mode shape and transient response time are affected most significantly by locating the damped segment at the position with maximum bending moment. The flexural amplitudes and phase angles of a beam excited by the resonant harmonic load can be effectively predominated by tuning the damping value. 相似文献
10.
Solid-state NaBH4/Ru-based catalyst composites have been fabricated for hydrogen generation through a high-energy ball-milling process, providing uniform dispersion of resin-supported Ru3+ catalysts among pulverized NaBH4 (SBH) particles, so as to increase the contacts of SBH with active catalytic sites. Consequently, the gravimetric hydrogen storage capacity as high as 7.3 wt% could be achieved by utilizing water as a limiting reagent to overcome the issue of deactivated catalysts whose active sites are often blocked by precipitates caused by limited NaBO2 solubility occurring in conventional aqueous SBH systems for hydrogen productions. Products of hydrolyzed SBH that greatly influence the gravimetric H2 storage capacity are found to be most likely NaBO2·2H2O and NaBO2·4H2O from SBH/H2O reacting systems with initial weight ratios, SBH/H2O = 1/2 and 1/10, respectively, according to the TGA and XRD analyses. 相似文献