Statistical analysis of the arc behavior in dry hyperbaric GMA welding from 1 to 250 bar

In this paper, mathematical approaches were developed for predicting the hyperbaric GMAW process arc behavior and stability. The variation of stochastic parameters is related to the electrical stability that can be resolved into a number of varying parameters. The results show that most of the arc instability can be traced to the frequency domain of the voltage or current waveform. Uncorrelated current and voltage wave frequencies at higher pressures are found to have a great influence on process stability.     

Dynamic interface velocity for junction characterization

A dynamic velocity at the n-p junction interface has been introduced. Solar cell structures have been used as diode models. The relationship of the dynamic velocity with the technological parameters of solar cells and with the junction operating conditions has been considered. The variations of this dynamic velocity with the potential at the junction point out the influence of the base doping level and of the base width, and allow to differentiate the nature of the cell back contact.     

High-Resolution Electron Microscopy of Silicon Carbide-Whisker-Reinforced Alumina Composite Interfaces in Specimens Subjected to Elevated Temperatures

Interfaces of silicon carbide-whisker-reinforced alumina (SiC( w )/Al₂O₃) composites were examined using high-resolution electron microscopy (HREM). HREM specimens were prepared from the bulk of samples that were previously tested for fracture toughness at 25°, 1000°, 1200°, or 1400°C, in ambient air. The test temperature history served as an independent variable. It was found that the as-received material did not possess a distinct interfacial layer and that the test temperature history (which included a 30°C/min heating and cooling rate, a 30-min soak prior to specimen loading, and a typical test duration of 5–10 min) did not appreciably change the interface thickness at any of the elevated test temperatures.     

Biochemical changes induced by fenpropathrin in the sixth instar larvae of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

Sixth instar larvae of Tribolium castaneum were exposed to one of four sublethal concentrations i.e. 10, 20, 200 or 400 mg/L, of a synthetic pyrethroid, fenpropathrin, for 48 hr. The lactate dehydrogenase activity decreased 44, 15 and 10% after exposure to fenpropathrin at concentrations of 20, 200 and 400 mg/L respectively, while a significant increase was recorded in glutamate oxaloacetate transaminase (15, 16, 34 and 37%) and glutamate pyruvate transaminase (6, 20, 13 and 29%) activities respectively after exposure to 10, 20, 200 and 400 mg/L. The amylase and acid phosphatase activities remained unaffected. The trehalase activity increased 42, 72 and 149%, after 20, 200 and 400 mg/L, the isocitrate dehydrogenase activity increased 28 and 67% after 10 and 20 mg/L, white alkaline phosphatase activity increased 13 and 12% after 10 and 400 mg/L respectively. The weaker (10 and 20 mg/L) and stronger (200 and 400 mg/L) doses elicited two different types of responses. A dose of 20 mg/L resulted in increased soluble proteins (14%), lipids (49%), cholesterol (57%), RNA (18%), and DNA (32%) content per larva, while the stronger dose of 400 mg/L resulted in their decrease except for lipids. The total proteins, lipids and free amino acids content per larva were not affected by either concentration, while the glucose content per insect decreased with increasing concentration of fenpropathrin.     

High cycle fatigue life estimation of materials processed by laser powder bed fusion

The fatigue life of metal components is known to depend on the surface topography. For components made by laser powder bed fusion, the roughness of the as‐built surfaces depends on the orientation of the component surface with respect to the build plate. Surface topographies of AlSi10Mg and Inconel 718 specimens built at 0° to 90° inclination, with 15° increments, were characterised by white light interferometry. Two methods for calculating the stress concentration factor using the surface roughness data are proposed, and the results of each approach are presented and compared. Moreover, a finite element model was developed, in order to analyse the stress field when subsurface porosity is present. The fatigue lifetime estimates suggest that the lifetime of components may differ up to two orders of magnitude, depending on the build orientation.     

A Novel Actuator Fault-tolerant Control Strategy of DFIG-based Wind Turbines Using Takagi-Sugeno Multiple Models

International Journal of Control, Automation and Systems - In this paper, a new combined fuzzy observer-based fault-tolerant tracking control scheme is proposed for a doubly fed induction generator...     

Effect of Eryngium caeruleum essential oil on microbial and sensory quality of minced fish and fate of Listeria monocytogenes during the storage at 4°C

The present study investigated in vitro antimicrobial activity of Eryngium caeruleum essential oil (EEO) against five foodborne pathogenic bacteria based on microdilution and disk diffusion methods. Moreover, its effects on specific spoilage microorganisms, inoculated Listeria monocytogenes, and its sensory changes in minced fish were evaluated during 12 days of storage at refrigeration temperature. The results showed that Staphylococcus aureus and Escherichia coli were the most sensitive and the most resistant bacteria with a minimum inhibitory concentration of 0.125 and 1 mg/ml, as well as inhibition zones of 15.66 and 11.66 mm, respectively. Regarding the antimicrobial effect of EEO on the microbial profile and inoculated L. monocytogenes, treating with 0.4% EEO caused a significant decrease in the studied microorganisms when compared to the control group (p < 0.05). In addition, considering the sensory evaluation, the best scores were observed for the samples treated with 0.2% and 0.4% EEO. However, none of the groups obtained acceptable scores until the final day of storage except for the color attribute. In general, sensory evaluation and its correlation with microbial counting indicated that the treatment with 0.4% EEO was able to preserve the microbial quality of the minced fish at refrigeration temperature without any undesirable sensory effects.     

Photo-oxidation of phenol in aqueous solution: Toxicity of intermediates

The photodegradation of phenol was studied in a batch reactor system illuminated with a 400 W medium pressure mercury lamp. The effects of parameters such as pH, reaction time and initial phenol concentration on the photolytic degradation and toxicity assay have been studied. The experimental results have shown that lower pH and lower concentration of phenol favor the phenol degradation. The disappearance of phenol in each case approximately obeyed first-order kinetics with the apparent rate constants increasing with decreasing solute concentration. Bioassay tests showed that phenol was toxic to Daphnia magna and so resulted in quite low LC₅₀ values. Comparison of toxicity units (TU) between phenol and effluent toxicity has shown that TU value for effluent was 2.18 times lower than that obtained for phenol. Thus, photolysis is able to decrease the toxicity of by-products formed during the degradation of phenol.