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91.
Catalytic steam reforming of glycerol, a by‐product in biodiesel production, represents an attractive route to hydrogen. For the first time, the kinetics of the glycerol steam reforming reaction over a Pt/C catalyst was considered. Kinetic data, i.e., glycerol conversion vs. space time, were obtained experimentally by using a fixed‐bed reactor and were analyzed by the integral method of analysis. It was found that in the studied ranges of temperature from 623 to 673 K and space time from 0.39 to 1.56 g h/mol the investigated reaction is of the first‐order with respect to glycerol. The specific reaction rate constant at 673 K was determined to be 1.1·105 cm3/gcat h. The values of glycerol conversion predicted by the first‐order kinetic model were in good agreement with those obtained experimentally. The increase in temperature, space time, and initial water/glycerol ratio caused the expected increase in hydrogen yield. 相似文献
92.
The ability to measure the properties of thermal barrier coatings (TBCs) applied to engine components is challenging due to the complex geometry of parts and the difficulty of preparing samples suitable for conventional techniques. As a result, there is a shortage of information related to the morphology and thermal properties of coatings on engine components. Phase of photothermal emission analysis (PopTea) is a relatively new non-destructive technique that is suitable for measuring the thermal properties of coatings on serviceable engine parts. To demonstrate this capability, measurements are performed on an intact turbine blade coated with air plasma sprayed (APS) 7 wt.% Y2O3-stabilized ZrO2 (7YSZ). The average thermal diffusivity of the coating applied to the blade was ~ 0.5 mm2/s which is typical for thermal diffusivity previously measured on 7YSZ APS coatings made on test coupons with PopTea and laser flash. Furthermore, trends in thermal properties over the blade are studied and compared. It is discovered that variations in thermal properties are the result of differences in coating porosity. 相似文献
93.
Hailei Zhao Xue Li Feng Ju Uday Pal 《Journal of Materials Processing Technology》2008,200(1-3):199-204
The chemical stability and sinterability of nano- and micro-sized yttria stabilized zirconia (YSZ) powders were investigated, and the effect of Ta2O5 additive on the sinterability of YSZ electrolyte was also studied. Addition of Ta2O5 easily causes phase transformation of YSZ from cubic to monoclinic, and thus unfavorable for the improvement of ionic conductivity of YSZ electrolyte. Nano-sized YSZ easily causes abnormal grain growth and hence readily results in inhomogeneous microstructure of YSZ matrix, while micro-sized YSZ displays relatively low sinterability. Comparatively, mixture with 50 wt.% nano-sized and 50 wt.% micro-sized YSZ powders exhibits high sinterability and could be sintered to homogeneous microstructure, which can be used as starting materials to prepare dense YSZ electrolyte at low temperatures. 相似文献
94.
Maintenance is crucial to ensure production/output and customer satisfaction in the mining sector. The cost of maintenance of mechanised and automated mining systems is very high, necessitating efforts to enhance the effectiveness of maintenance systems and organisation. For effective maintenance planning, it is important to have a good understanding of the reliability and availability characteristics of the systems. Determining the Mean Residual Life (MRL) of systems allows organisations to more effectively plan maintenance tasks. In this paper, we use a statistical approach to estimate MRL and consider a Weibull proportional hazard model (PHM) with time-independent covariates to model the hazard function so that the operating environment could be integrated into the reliability analysis. The paper explains our methods for calculating the conditional reliability function and computing the MRL as a function of the current conditions. The model is verified and validated using data from the hydraulic system of LHD equipment in a Swedish mine. The results are useful to estimate the remaining useful life of such systems; the method can be used for maintenance planning, helping to control unplanned stoppages of highly mechanised and automated systems. 相似文献
95.
S. G. Song R. U. Vaidya A. K. Zurek G. T. Gray 《Metallurgical and Materials Transactions A》1996,27(2):459-465
Mechanical tests and microstructural examinations performed on a SiC-particle-reinforced 6061-A1 matrix composite indicate
that particle cracking during mechanical testing significantly affects the failure mechanisms of the composite. Microcracks
were observed to nucleate and propagate on stacking faults and interfaces between the 4H (or 3C) and 6H hexagonal phases within
the SiC particle reinforcements. These planar defects were the predominant defects seen in the SiC particles. Partial dislocations,
having a 1/3 (10άrc10) Burgers vector, were also observed bounding the stacking faults in the reinforcement phase. 相似文献
96.
Variations in semen analyses of 177 males over a 1 year period were assessed. The average means of total counts, motility, morphology, total motile count and non-motile % were determined for 5 classes of patients ranging from azoospermic to normospermic. Positive relationships between a falling sperm count, a decrease in motility and total motile counts were seen. Also, increasingly, abnormal forms were found with lower sperm counts. 相似文献
97.
K Hosoda LR Fitzgerald VA Vaidya GK Feussner PH Fishman RS Duman 《Canadian Metallurgical Quarterly》1995,48(2):206-211
The human CDX1 gene has been isolated from a small intestine cDNA library using a murine Cdx1 cDNA probe. The nucleotide sequence of CDX1 is 81% identical to murine Cdx1 and predicts a 265-amino-acid protein with 85% identity to the mouse protein (98% identity, including conservative amino acid changes). The CDX1 locus has been mapped to a cosmid contig from chromosome 5q31-q33, placing CDX1 approximately 100 kb distal to CSFIR. Expression of CDX1 in adults appears to be limited to the intestine and colon by Northern analysis, suggesting a possible role in the terminal differentiation of the intestine. Further analysis of CDX1 should elucidate the function of caudal-type homeobox genes in human development. 相似文献
98.
Porous polyester fibres with cotton-like dull characteristics were produced by salt leaching method. Polyester was synthesized in the presence of common salt. Fibres containing submicron size salt particles (0.5–1%) were prepared by melt spinning. The fibres were washed in hot water to remove the salt particles creating small craters of size 50–1000?nm. Partially oriented yarn (POY) and fully drawn yarn (FDY) were produced. POY samples were textured to produce polyester textured yarn containing salt particles. The influence of salt particles on polymer crystallization was investigated and found that the presence of salt significantly influences the rate of crystallization. The gloss values of porous FDYs were compared with standard semi-dull polyester yarns of same denier. The light scattering behaviour of the yarn has been enhanced due to porosity. This resulted in a fibre with better dullness characteristics. The light reflectance of porous yarn is lower in the 400–700?nm region compared to control FDY samples. The dyeability of the porous fibre was better than non-porous counterpart. 相似文献
99.
Sharma Faladrum Dixit Uday Shanker 《Journal of Mechanical Science and Technology》2019,33(9):4439-4449
A fuzzy set based cost model for additive manufacturing is proposed. The model is illustrated through an example of selective laser sintering (SLS), a commonly used additive manufacturing (AM) process. Initially, a deterministic cost model is developed. It is then converted to a fuzzy set based model by considering uncertainty in build time estimation and cost components. For the specific case of SLS, a build time estimation procedure is developed as a part of the cost model. A method to evaluate the reliability of the cost estimate in AM and its significance is also introduced. The cost model is illustrated through two examples of products manufactured by SLS.
相似文献100.