This work aims the numerical modeling and characterization of as-welded microstructure of Ni-Cr-Fe alloys with additions of Nb, Mo and Hf as a key to understand their proven resistance to ductility-dip cracking. Part I deals with as-welded structure modeling, using experimental alloying ranges and Calphad methodology. Model calculates kinetic phase transformations and partitioning of elements during weld solidification using a cooling rate of 100 K.s?1, considering their consequences on solidification mode for each alloy. Calculated structures were compared with experimental observations on as-welded structures, exhibiting good agreement. Numerical calculations estimate an increase by three times of mass fraction of primary carbides precipitation, a substantial reduction of mass fraction of M23C6 precipitates and topologically closed packed phases (TCP), a homogeneously intradendritic distribution, and a slight increase of interdendritic Molybdenum distribution in these alloys. Incidences of metallurgical characteristics of modeled as-welded structures on desirable characteristics of Ni-based alloys resistant to DDC are discussed here. 相似文献
This study compares the hot corrosion performance of yttria-stabilised zirconia (7YSZ), and 7YSZ?+?Gd2O3 composite samples in the presence of molten mixture of Na2SO4?+?V2O5 at 1150°C. For 7YSZ, the reaction between NaVO3 and Y2O3 produces YVO4 and leads the transformation of tetragonal ZrO2 to monoclinic ZrO2. A high-density in sintered 7YSZ?+?Gd2O3 samples, led minor amounts of monoclinic ZrO2 and tetragonal GdVO4 as the hot corrosion products with only traceable amounts of YVO4, and a stable corroded layer was formed. Due to the synergic effect of doping of zirconia with Gd2O3, the 7YSZ?+?Gd2O3 sample has a much better hot corrosion crack resistance than 7YSZ. 相似文献
Visually impaired individuals often rely on assistive technologies such as white canes for independent navigation. Many electronic enhancements to the traditional white cane have been proposed. However, only a few of these proof-of-concept technologies have been tested with authentic users, as most studies rely on blindfolded non-visually impaired participants or no testing with participants at all. Experiments involving blind users are usually not contrasted with the traditional white cane. This study set out to compare an ultrasound-based electronic cane with a traditional white cane. Moreover, we also compared the performance of a group of visually impaired participants (N = 10) with a group of blindfolded participants without visual impairments (N = 31). The results show that walking speed with the electronic cane is significantly slower compared to the traditional white cane. Moreover, the results show that the performance of the participants without visual impairments is significantly slower than for the visually impaired participants. No significant differences in obstacle detection rates were observed across participant groups and device types for obstacles on the ground, while 79% of the hanging obstacles were detected by the electronic cane. The results of this study thus suggest that electronic canes present only one advantage over the traditional cane, namely in its ability to detect hanging obstacles, at least without prolonged practice. Next, blindfolded participants are insufficient substitutes for blind participants who are expert cane users. The implication of this study is that research into digital white cane enhancements should include blind participants. These participants should be followed over time in longitudinal experiments to document if practice will lead to improvements that surpass the performance achieved with traditional canes.
There has been a recent increase in both the production and consumption of ethanol due to the numerous environmental advantages that it offers, such as the fact that it can be produced from a variety of renewable materials, for instance corn and cellulose, or it can be obtained from sugarcane bagasse and biomass (2nd and 3rd generation ethanol). The result of this is that nowadays ethanol is widely seen as the dominant biofuel – or as a blend component in gasoline or pure fuel - in many countries.However, one disadvantage of the use of ethanol is the high corrosive behavior that occurs when its hygroscopic properties are exposed to a large number of materials. Xiaoyuan Lou and Preet Singh showed that the increase of water concentration in ethanol induces pitting and metal loss. Diamond-Like Carbon (DLC) films may be a solution to this problem due to the fact that they can be deposited inside tubes, offer good protection levels against corrosion, and reduce the friction coefficient and wear.This paper shows the tribocorrosion and corrosion studies of DLC films deposited on stainless steel grade 304 (SS304) substrates in order to gauge its appropriateness usage in the construction of pipelines and fuel storage tanks. The surface morphology was analyzed before and after 14 days of immersion. The tribocorrosion, friction coefficient, and wear rate were studied in ethanol to see the effects of water concentration. The films showed good adherence to the substrates. Corrosion and tribocorrosion results showed that for bare Stainless Steel 304 the increase of the water content increases the corrosion and the friction coefficient. DLC coated samples presented few points of delamination, and the friction coefficient and open circuit potentials were very low compared with the bare sample which was water concentration independent. 相似文献
The present study aimed to evaluate the potential use of whey to produce 2,3-BD via the fermentation of lactose and its monosaccharides, glucose and galactose, in a synthetic culture medium (medium 9, M9) using a modified strain of Escherichia coli K12 MG1655 (E. coli JFR12) at a 0.1 L/L (10 vol%) inoculum ratio, 37 °C, atmospheric pressure, an initial pH 7.4, and 100 rpm for 72 h varying the saccharide concentration from 12.5, 25, and 50 g/L. The 2,3-BD yield was ∼80 % of the theoretical yield using 25 g/L of glucose and lactose, corresponding to 0.38 g/g saccharides at a fermentation time of 48 h (glucose) and 72 h (lactose). However, the 2,3-BD yield was halved (0.19 g/g galactose), fermenting 25 g/L of galactose at 48 h. Taking into account these results, two important conclusions were determined: i) E. coli JFR12 could transform galactose into 2,3-BD although its yield was half of the yield observed with glucose at 48 h; and ii) E. coli JFR12 was as efficient as other natural 2,3-BD producers such as Klebsiella species fermenting lactose. However, the E. coli strain has the advantage of being an innocuous strain. To the best of our knowledge, there is no other study presenting the production of 2,3-BD from galactose and lactose with a genetically modified E. coli strain. 相似文献
Accurate identification of precipitating clouds is a challenging task. In the present work, Support Vector Machines (SVMs), Decision Trees (DT), and Random Forests (RD) algorithms were applied to extract and track mesoscale convective precipitating clouds from a series of 22 Geostationary Operational Environmental Satellite-13 meteorological image sub-scenes over the continental territory of Colombia. This study’s aims are twofold: (i) to establish whether the use of five meteorological spectral channels, rather than a single infrared (IR) channel, improves rainfall objects detection and (ii) to evaluate the potential of machine learning algorithms to locate precipitation clouds. Results show that while the SVM algorithm provides more accurate classification of rainfall cloud objects than the traditional IR brightness temperature threshold method, such improvement is not statistically significant. Accuracy assessment was performed using STEP (shape (S), theme (T), edge (E), and position (P)) object-based similarity matrix method, taking as reference precipitation satellite images from the Tropical Rainfall Measuring Mission. Best thematic and geometric accuracies were obtained applying the SVM algorithm. 相似文献
Microstructure evolution during friction stir welding (FSW) of mild steel and Ni-based alloy 625 was studied. Regarding the Ni-based alloy, the welding process led to grain refinement caused by discontinuous and continuous dynamic recrystallization, where bulging of the pre-existing grains and subgrain rotation were the primary mechanisms of recrystallization. In the steel, discontinuous dynamic recrystallization was identified as the recovery process experienced by the austenite. Simple shear textures were observed in the regions affected by the deformation of both materials. Although the allotropic transformation obscured the deformation history, the thermo-mechanically affected zone was identified in the steel by simple shear texture components. A new methodology for the study of texture evolution based on rotations of the slip systems using pole figures is presented as an approximation to describe the texture evolution in FSW. 相似文献
The importance of expressing composition of used catalysts in fresh basis is highlighted in this work. Since catalysts are subject to changes during processing, e.g. coking and metal deposition, their composition varies depending on their state (fresh, spent, regenerated) and to properly determine catalyst life, composition needs to be changed to fresh-basis. Previous works are commented to demonstrate the current confusion existing in the literature when reporting metal content of used catalyst, and a simple approach is developed to change catalyst metal composition to fresh-basis. 相似文献