Reduction and carburization of iron-ore in a fluidized bed by CO,H2 and CH4

The reduction and carburization of fine iron-ore (100 - 200 μm, Fe₂O₃ mass content of 98%) by gas mixtures containing CO, H₂ and CH₄ was investigated in a fluidized bed at temperatures of 400 up to 700°C. In this temperature range carbon is formed from CO via the Boudouard reaction as well as by the decomposition of methane. Yet, both reactions only occur in the presence of metallic iron and therefore only at reduction degrees of the DRI (direct-reduced iron) of more than 33%. As a contribution to the development of a DRI process without a costly hot briquetting, the influence of the C- and O-content of the DRI on its tendency to reoxidize was also investigated by means of the ignition point method. It was found that reoxidation (at 20°C) of a totally reduced DRI can be suppressed by carbon mass contents of more than 7%. With decreasing reduction degrees, this value decreases, until for reduction degrees of less than 80% no carbon is needed to suppress reoxidation. With regard to the final reduction of the DRI in the electric arc furnace, the molar C to O ratio should be one. The maximal reduction degree is then about 86% to stabilize carbon rich DRI (C mass content of 4%) against reoxidation.     

Routing for reliable manufacturing

The impact of spot defects on the susceptibility for electrical failure of a net is analyzed. Based on this analysis, a general routing cost function is presented, in which the manufacturability of a net is taken into account in conjunction with traditional routing objectives. The new cost function, relating the process spot defects to the routing procedure has been implemented. Failure probabilities are analyzed for the benchmark layouts obtained by our routing tool using both the original cost function and the new cost function. The results show that the failure probability of a layout is significantly decreased if the spot defect mechanism is taken into account in the routing procedure, while the area of the layout is kept constant     

Gravimetric determination of soluble phenolics including tannins from leaves by precipitation with trivalent ytterbium

A method for the gravimetric determination of soluble phenolics based on precipitation with trivalent ytterbium is described. Solutions of ytterbium-precipitated phenolics can be prepared in order to study u.v. absorbance, colorimetric assays for phenolics, protein precipitation and cellulase inhibition. The method was applied to mature leaves of 10 East African browse species in the diets of goats and camels. There was a large range in ytterbium-precipitated phenolics (Yb-ppt), from 50% dry matter (DM) in Acacia nilotica to less than 15% in Acacia brevispica and Cadaba farinosa. Results from u.v. absorbance and the Folin-Ciocalteu assay on solutions of ytterbium-precipitated phenolics indicated that ytterbium precipitates many types of phenolics including proanthocyanidins. The vanillin-HCl and n-butanol-HCl assays for proanthocyanidins separated the samples into two groups with high or low levels. The group with high levels of proanthocyanidins had greater protein precipitation capacity and cellulase inhibition at similar amounts of Yb-ppt. The results indicate that the method may be useful in nutritional studies involving browse and other forages. Gravimetric analysis avoids problems associated with colorimetric assays because it does not rely on the use of standards. The preparation of solutions of Yb-precipitated phenolics allows direct comparison between amount and nutritional effects such as protein precipitation and enzyme inhibition.     

Essential Oils as Natural Food Antimicrobial Agents: A Review

Food-borne illnesses pose a real scourge in the present scenario as the consumerism of packaged food has increased to a great extend. Pathogens entering the packaged foods may survive longer, which needs a check. Antimicrobial agents either alone or in combination are added to the food or packaging materials for this purpose. Exploiting the antimicrobial property, essential oils are considered as a “natural” remedy to this problem other than its flavoring property instead of using synthetic agents. The essential oils are well known for its antibacterial, antiviral, antimycotic, antiparasitic, and antioxidant properties due to the presence of phenolic functional group. Gram-positive organisms are found more susceptible to the action of the essential oils. Essential oils improve the shelf-life of packaged products, control the microbial growth, and unriddle the consumer concerns regarding the use of chemical preservatives. This review is intended to provide an overview of the essential oils and their role as natural antimicrobial agents in the food industry.     

Audibility of train horns in passenger vehicles

Studies of accident rates associated with train horn bans indicate that motorists rely on horns to warn them of approaching trains. However, researchers have not yet established the levels of horn sounds necessary for detection at railroad crossings. The purpose of this study was to obtain baseline measures of the auditory component of the motorist's detection task. Horn sounds recorded in three test vehicles were presented to 20 normal-hearing listeners in quiet and in four types of vehicle interior noise: engine idling, ventilation fan off; engine idling, fan on; vehicle moving at 30 miles/hr (mph), fan off; and vehicle moving at 30 mph, fan on. Thresholds of the horn sounds were determined by an adaptive procedure. Mean thresholds were lowest in quiet (1.8-4.4 dBA) and highest for the 30-mph, fan-on condition (49.7-58.4 dBA). Mean horn thresholds for all 12 noise conditions were more than 10 dB below the overall level of the vehicle interior noise. Our data are compared with those of previous studies and their implications are discussed. Actual or potential applications of this research include the establishment of a lower limit of signal-to-noise ratios required for the detection of horn sounds at highway-rail crossings.     

Catalytic Properties of Single Layers of Transition Metal Sulfide Catalytic Materials

Single layer transition metal sulfides (SLTMS) such as MoS₂, WS₂, and ReS₂, play an important role in catalytic processes such as the hydrofining of petroleum streams, and are involved in at least two of the slurry-catalyst hydroconversion processes that have been proposed for upgrading heavy petroleum feed and other sources of hydrocarbon fuels such as coal and shale oils. Additional promising catalytic applications of the SLTMS are on the horizon. The physical, chemical, and catalytic properties of these materials are reviewed in this report. Also discussed are areas for future research that promise to lead to advanced applications of the SLTMS.     

Dort solutions to the two-dimensional C5G7MOXbenchmark problem

We present a comprehensive study of the solution error for the C5G7MOXBenchmark problem using the two-dimensional transport code DORT. We set a stringent criterion that a successful solution to the benchmark exercise must satisfy, namely that at least for some of the benchmark quantities convergence to the reference solution with computational model refinement must be demonstrated. In the present exercise this amounts to examining the evolution of the DORT solution, e.g. the multiplication factor, with increasing angular quadrature order, decreasing computational cell size, and tighter representation of the curved rod-moderator interface for all circular rods in the core model. In addition we explored the effect of angular quadrature type, comparing solution accuracy for the fully symmetric and the Square Legendre-Chebychev quadratures establishing superiority of the latter. We establish the high quality of DORT's solution to this benchmark exercise by demonstrating that the multiplication factor asymptotically approaches the reference solution as stated in our self-imposed success criterion. High accuracy of the pin power distribution is also attained, however, convergence to the reference values is not realized. We conjecture that this is due to the lack of error information in the reference values. Our results also illustrate DORT's high accuracy on reasonable meshes and quadrature orders, as well as the sufficiency of a crude, square, geometric approximation of the rod-moderator interface to achieve high accuracy.     

Additive Manufacturing of Titanium Alloys for Orthopedic Applications: A Materials Science Viewpoint

Titanium‐based orthopedic implants are increasingly being fabricated using additive manufacturing (AM) processes such as selective laser melting (SLM), direct laser deposition (DLD), and electron beam melting (EBM). These techniques have the potential to not only produce implants with properties comparable to conventionally manufactured implants, but also improve on standard implant models. These models can be customized for individual patients using medical data, and design features, such as latticing, hierarchical scaffolds, or features to complement patient anatomy, can be added using AM to produce highly functional patient‐anatomy‐specific implants. Alloying prospects made possible through AM allow for the production of Ti‐based parts with compositions designed to reduce modulus and stress shielding while improving bone fixation and formation. The design‐to‐process lead time can be drastically shortened using AM and associated post‐processing, making possible the production of tailored implants for individual patients. This review examines the process and product characteristics of the three major metallic AM techniques and assesses the potential for these in the increased global uptake of AM in orthopedic implant fabrication.