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The metal titanium (Ti) and its alloys have many attributes which are attractive as structural materials, but they also have one major disadvantage, high initial cost. Nevertheless, Ti and Ti alloys are used extensively in airframes, gas turbine engines (GTE), and rocket engines (RE). The high cost is a deterrent, particularly in airframe applications, in that the other alloys it competes with are, for the most part, significantly lower cost. This is less of a concern for GTE and RE where the cost of titanium is closer to and sometimes even lower than some of the materials it competes with for these applications. In spacecraft the weight savings are so important that cost is a lesser concern. Ti and its alloys consist of five families of alloys; α-Ti, near α-alloys, α + β alloys, β-alloys, and Ti-based intermetallic compounds. The intermetallic compounds of primary interest today are those based on the compound TiAl which, at this time, are only used for engine applications because of their higher temperature capability. These TiAl-based compounds are used in a relatively low, but growing, amounts. The first production application was for low pressure turbine blades in the GE engine (GEnx) used on the Boeing 787, followed by the GE LEAP engine used on A-320neo and B-737MAX. These air foils are investment cast and machined. The next application is for the GE90X which will power the Boeing B-777X. These air foils will be made by additive manufacturing (AM). Unalloyed titanium and titanium alloys are typically melted by vacuum arc melting and re-melted either once (2X VAR) or twice (3X VAR); however a new and very different melting method (cold hearth melting) has recently become favored, mainly for high performance applications such as rotors in aircraft engines. This process resulted in higher quality ingots with a significant reduction in melt-related defects. Once melted and cast into ingots, the alloys can be processed using all the standard thermomechanical working and casting processes used for making components of other types of structural alloys. Because of their limited ductility, the TiAl-based intermetallic compounds are quite difficult to process using ordinary wrought methods. Consequently, the low-pressure turbine blades currently in service are investment cast and machined to net shape. The AM air foils will require minimal machining, which is an advantage. This paper describes some relatively recent developments as well as some issues and opportunities associated with the production and use of Ti and its alloys in aerospace components. Included are new Ti alloys, new applications of Ti alloys, and the current status of several manufacturing processes including a discussion of the promise and current reality of additive manufacturing as a potentially revolutionary method of producing Ti alloy components.

The blast furnace campaign length is today usually restricted by the hearth life, which is strongly related to the drainage and behavior of the coke bed in the hearth, usually referred to as the dead man. Because the hearth is inaccessible and the conditions are complex, knowledge and understanding of the state of the dead man are still limited compared to other parts of the blast furnace process. Since a number of publications have studied different aspects of the dead man in the literature, the purpose of the current review is to compile the findings and knowledge in a comprehensive document. We mainly focus on contributions with respect to the dead man state, and those assessing its influence on the hearth performance in terms of liquid flow patterns, lining wear and drainage behavior. A set of common modeling approaches in this specific furnace area is also briefly presented. The aim of the review is also to deepen the understanding and stimulate further research on open questions related to the dead man in the blast furnace hearth.

Recent paleoanthropological studies have suggested that modern humans migrated from Africa as early as the beginning of the Late Pleistocene, 120,000 years ago. Hershkovitz et al. now suggest that early modern humans were already present outside of Africa more than 55,000 years earlier (see the Perspective by Stringer and Galway-Witham). During excavations of sediments at Mount Carmel, Israel, they found a fossil of a mouth part, a left hemimaxilla, with almost complete dentition. The sediments contain a series of well-defined hearths and a rich stone-based industry, as well as abundant animal remains. Analysis of the human remains, and dating of the site and the fossil itself, indicate a likely age of at least 177,000 years for the fossil—making it the oldest member of the Homo sapiens clade found outside Africa. Science , this issue p. 456 ; see also p. 389 Fossilized mouthparts indicate the presence of Homo sapiens in the Levant 160,000 years ago. To date, the earliest modern human fossils found outside of Africa are dated to around 90,000 to 120,000 years ago at the Levantine sites of Skhul and Qafzeh. A maxilla and associated dentition recently discovered at Misliya Cave, Israel, was dated to 177,000 to 194,000 years ago, suggesting that members of the Homo sapiens clade left Africa earlier than previously thought. This finding changes our view on modern human dispersal and is consistent with recent genetic studies, which have posited the possibility of an earlier dispersal of Homo sapiens around 220,000 years ago. The Misliya maxilla is associated with full-fledged Levallois technology in the Levant, suggesting that the emergence of this technology is linked to the appearance of Homo sapiens in the region, as has been documented in Africa.

Recycling iron-bearing solid wastes generated during iron and steelmaking processes is crucial for optimizing resource utilization and mitigating carbon emissions. The Rotary Hearth Furnace (RHF) has emerged as a promising alternative for sponge iron production from solid waste. This study developed a 3D computational fluid dynamics (CFD) model of a pilot-scale RHF using the FLUENT solver to investigate use of hydrogen as a fuel. The results indicated that substituting hydrogen for hydrocarbon-based fuels led to a remarkable reduction in fuel and air consumption, resulting in increased profitability for direct reduced iron (DRI) production. Optimum conditions for post-combustion of CO, air, and fuel rate and their preheat temperature were identified to minimize fuel rate and emission, maximizing heat transfer to pellet bed, and maintaining a reducing atmosphere over pellet bed to restrict reoxidation of metalized pellet with hydrogen as heat-producing fuel.

The effect of different lower air inlet tube inclinations on the gas dynamics, including concentration, fluid flow profile, temperature, and heat transfer potency, to the bottom part of a rotary hearth furnace (RHF), were investigated. The lower air-inlet tube inclination was varied from 5° to 25° upwards with the horizontal to maximize the burner efficiency. The inlet tube configuration with the lower two air-inlet tubes inclined at 10° upwards emerged as the most efficient tube orientation in the present burner system. This air inlet configuration of the burner produced the maximum heat transfer efficiency in transferring the combustion heat produced in the freeboard region to the bottom pellet layer region. Moreover, it was also able to produce better CO post-combustion efficiency.

The treatment of iron-bearing dusts and sludges by the rotary hearth furnace process has the advantage of sufficient utilization of valuable metals and a high impurity removal rate, but the lower strength of the metallized product needs to be addressed. The effects of quaternary basicity R 4 ( w (CaO + MgO)/ w (SiO 2  + Al 2 O 3 )) on the reduction behavior and physical and chemical properties of metallized pellets, including phase composition, compressive strength, microstructure and soft melting area, were investigated with FactSage thermodynamic software and experiments. The strength of metallized pellets depended on the gangue composition, such as CaO, MgO, Al 2 O 3 and SiO 2 , due to the altered chemical composition, physical phase composition, microscopic morphology and stability of the slag phase. The reduction of carbon-bearing pellets was significantly promoted by suitable basicity. The lower basicity ( R 4  < 1.4) facilitated the formation of low melting point iron-containing compounds from SiO 2 and Al 2 O 3 with FeO, resulting in increased liquid phase generation, but lower metallization rate, due to the hindered precipitation and growth of iron grains. Interestingly, the higher basicity ( R 4  > 1.8) also increased the amount of liquid phase and improved the strength of the pellets, due to the granular iron crystals bonded into sheets. Notably, the main component of the liquid phase in high-basicity conditions was calcium ferrite. Although the additional amount of liquid phase was beneficial to the strength of the metallized pellets, calcium disilicate was formed at R 4  = 1.6, resulting in a reduction in the compressive strength of the pellets to 1521.9 N/pellet.

Combustion features inform archaeologists about the prehistoric use of space, subsistence behaviors, and tempo of site visitation. Their study in the field is difficult because burned sediments are susceptible to reworking and diagenesis. Microarchaeological analyses, including micromorphology, are essential for documenting the composition, preservation, and function of hearths and other burned residues. These investigations focus on the description of fuels, depositional fabrics and structures, and mineralogy. As evidenced by a literature review, microarchaeological analyses have much to offer Paleolithic archaeologists, while applications of the techniques to Late Pleistocene and Early Holocene sites and in ethnographic or experimental contexts are presently rare.

Advanced deep learning methods combined with regional, open access, airborne Light Detection and Ranging (LiDAR) data have great potential to study the spatial extent of historic land use features preserved under the forest canopy throughout New England, a region in the northeastern United States. Mapping anthropogenic features plays a key role in understanding historic land use dynamics during the 17th to early 20th centuries, however previous studies have primarily used manual or semi-automated digitization methods, which are time consuming for broad-scale mapping. This study applies fully-automated deep convolutional neural networks (i.e., U-Net) with LiDAR derivatives to identify relict charcoal hearths (RCHs), a type of historical land use feature. Results show that slope, hillshade, and Visualization for Archaeological Topography (VAT) rasters work well in six localized test regions (spatial scale: <1.5 km2, best F1 score: 95.5%), but also at broader extents at the town level (spatial scale: 493 km2, best F1 score: 86%). The model performed best in areas with deciduous forest and high slope terrain (e.g., >15 degrees) (F1 score: 86.8%) compared to coniferous forest and low slope terrain (e.g., <15 degrees) (F1 score: 70.1%). Overall, our results contribute to current methodological discussions regarding automated extraction of historical cultural features using deep learning and LiDAR.

To realize the high value-added utilization of zinc hypoxide in a rotary hearth furnace, nano-ZnO was prepared by H2SO4 wet leaching combined with the Na2CO3 precipitation process. The effects of different process conditions on the leaching rate of Zn were analyzed, and the feasibility of preparing nano-ZnO from zinc hypoxide was discussed. The results showed that the optimal process conditions for H2SO4 leaching of zinc hypoxide in a rotary hearth furnace were as follows: H2SO4 concentration 2.0 mol·L−1, leaching temperature 60 °C, leaching time 90 min, and liquid-solid ratio 8:1. Under these conditions, the leaching rate of Zn reached 95%. The calculation results of leaching kinetics showed that the restrictive link of the H2SO4 leaching process was a chemical reaction process; the apparent activation energy was 14.45 kJ·mol−1; and the reaction order was 0.6. The precursor obtained by Na2CO3 precipitation treatment was Zn5(OH)6(CO3)2. After calcination at 400 °C, the nano-ZnO with a diameter of less than 100 nm and length greater than 1 μm was obtained. H2SO4 leaching combined with the Na2CO3 precipitation process provided a new approach for high value-added utilization of zinc hypoxide in a rotary hearth furnace.