Search Results (89)

This paper extends the quasi-load insensitive (QLI) Class-E Doherty power amplifier (PA) design methodology to address Doherty PA combiners with complex load impedance trajectories. Additionally, the QLI operation is analyzed for generalized class-E output matching networks with input series inductors and finite DC-feed inductors. We demonstrate that the QLI class-E Doherty operation can be achieved for various Doherty combiners by selecting the appropriate combination of class-E outputs matching network resonance factors and input series inductances. Moreover, a modified class-E output network is proposed to overcome the frequency limitation that might be caused by the class-E network resonance factor choice. To validate the proposed methodology, two 40 W Doherty PAs are designed and simulated using commercial GaN HEMT transistors achieving more than 70% efficiency over a 6 dB output power back-off at 3.8 GHz. Full article

Understanding the mechanical properties of the constituent minerals of shales is of significance for gaining insight into the macroscopic mechanical behavior of shales. In this paper, a method combining nanoindentation with a TESCAN Integrated Mineral Analyzer (TIMA) was used to determine the mechanical properties of shale constituent minerals. The hardness and elastic modulus of five independent mineral phases and a mixed phase were detected. The order of the hardness of these five independent mineral phases is dolomite (4.90 ± 2.33 GPa) > wollastonite (4.84 ± 0.54 GPa) > ankerite (4.17 ± 1.37 GPa) > quartz (3.98 ± 0.67 GPa) > calcite (2.03 ± 0.29 GPa), and the order of the elastic modulus is dolomite (104.89 ± 11.25 GPa) > ankerite (103.70 ± 19.62 GPa) > wollastonite (100.78 ± 6.66 GPa) > quartz (88.04 ± 14.58 GPa) > calcite (78.20 ± 3.85 GPa). The mechanical properties of the shale mineral grain junctions are weaker than those inside the grains. When shale is subjected to an external load, it is more prone to intergranular failure. The proposed method in this study can rapidly and accurately probe the in situ mechanical properties of shale minerals. The results of this study enrich the database of in situ mechanical properties of shale minerals and provide a new insight into the macroscopy failure mode of shale. Full article

Physical attacks pose a significant threat to the security of embedded processors, which have become an integral part of our daily lives. Processors can be vulnerable to fault injection attacks that threaten their normal and secure behavior. Such attacks can lead to serious malfunctions in applications, compromising their security and correct behavior. Therefore, it is crucial for designers and manufacturers to consider these threats while developing embedded processors. These attacks may require only a moderate level of knowledge to execute and can compromise the normal behavior of the targeted devices. These attacks can be faced by developing effective countermeasures. This paper explores the main existing countermeasures against fault injection attacks in embedded processors, to understand and implement effective solutions against those threats. Subsequently, we further investigate solutions related to RISC-V, focusing on its hardware and architecture security. Full article

Coal fly ash (CFA) is a commercially viable source of alumina comparable to traditional bauxite deposits. Due to its high silica content and alumina in the refractory mullite phase, the most suitable processing technique is the sinter-H₂SO₄ leach process. However, this process is energy-intensive, has low selectivity for Al, and generates a secondary solid waste residue. To develop a sustainable process that is economically attractive, Al can be extracted with REEs, Ti, and Fe as saleable products, while secondary solid waste is regenerated for further applications to achieve high-value and high-volume utilisation of CFA. This study focused on the potential extraction of selected REEs (Ce, La, Nd, Y, and Sc), Al, Ti, and Fe, using dry magnetic separation and the sinter-H₂SO₄ leach process. XRD analysis showed that CFA is predominantly amorphous with crystalline mullite, quartz, and magnetite/hematite. Further analysis using SEM-EDS and TIMA showed Al-Si-rich grains as the predominant phase, with discrete REE-bearing grains (phosphates and silicates) and Fe-oxide (magnetite/hematite) grains. Traces of REEs, Ti, Ca, Si, and Fe were also found in the Al-Si-rich grains. Discrete Fe-oxide was recovered using dry magnetic separation, and up to 65.9% Fe was recovered at 1.05 T as the magnetic fraction (MF). The non-magnetic fraction (non-MF) containing quartz, mullite, and amorphous phase was further processed for preliminary leaching studies. The leaching behaviour of Al, Ti, Fe, and the selected REEs was investigated using the direct H₂SO₄ and sinter-H₂SO₄ leaching processes. The maximum extraction efficiency was observed using the sinter-H₂SO₄ leach process at 6 M H₂SO₄, a 1:5 solid-to-liquid ratio, 70 °C, and a residence time of 10 h, yielding 77.9% Al, 62.1% Fe, 52.3% Ti, and 56.7% Sc extractions. The extraction efficiencies for Ce, La, Nd, and Y were relatively lower at 23.2%, 27.6%, 11.3%, and 11.2%, respectively. Overall, the results demonstrate that the extraction of REEs using the sinter-H₂SO₄ leach process is strongly influenced by the complex CFA phase composition and the possible formation of insoluble calcium sulphates. Appreciable extraction of Al, Fe, Ti, and Sc was also observed, suggesting a potential two-step leaching process for the extraction of REEs as a feasible option for the industrial recovery of multiple saleable products. Full article

Hydrothermal alteration provides critical information for both the exploration and scientific research of hydrothermal uranium deposits. The Xiangshan uranium ore field, the largest volcanic-hosted uranium deposit in China, is characterized by different alterations, including hematitization, illitization, sericitization, chloritization, carbonation and silicification. However, the mineralogical and geochemical characteristics of hydrothermal alterations and their relationships with uranium mineralization remain unclear. In this study, we conducted detailed petrography, TIMA mapping, μ-XRF analyses, mass balance calculations and thermodynamic modeling on the hematitized and illitized porphyritic lava from the Zoujiashan deposit in the Xiangshan ore field. During hematitization, hematite and albite are produced, while quartz, K-feldspar, chlorite, sericite and biotite are consumed, consistent with the increase in Na₂O, Al₂O₃, Fe₂O₃-T, U, As, Pb, Cu, Sc, V, Zr, Y, Hf and Th and the loss of K₂O, MgO, Li, Zn, Ni and Ba. The production of hydrothermal hematite, illite and sericite indicates that the ore fluids are acidic and oxidized. Such physiochemical conditions are favorable for uranium transport as UO₂Cl₂(aq), UO₂SO₄(aq) and UO₂OH⁺. Geological processes such as fluid–rock interactions, fluid mixing and fluid boiling could cause fO₂(g) decrease, pH increase and temperature decrease and therefore result in the decrease in uranium solubility and mineralization. Full article

In this case study, exploratory techniques were applied for the selection of potential targets for rare-earth elements (REEs) in the Fazenda Buriti Mafic–Ultramafic Complex, part of the Goiás Alkaline Province. The results of the processing and interpretation of aeromagnetic and radiometric data associated with the direct measurements of magnetic susceptibility and radiometry in rock samples collected in the study area allowed for the characterization and delimitation of the geological units. The application of Boolean logic in the radiometric data of uranium (U), thorium (Th), and the U/Th ratio allowed for the generation of a prospective map with the delimitation of two exploration targets. A 100 m deep exploratory drill hole was drilled at the main target, intercepting REE mineralization and validating the developed prospective technique. The results contributed to the detailing of a 1:25,000 scale geological map and the interpretation of shallow and deep magnetic structures. Petrophysical data allowed for the estimation of the magnetite content in the main units of the study area. The delimitation of targets with the applied method proved to be efficient after positive geochemical results for REE from the drilled rocks. The total sum of ∑REEs reached 19,629 ppm in the superficial part of the hole and 3,560 ppm in the fresh rock. Mineralogical results in two follow-up drill core samples indicated that monazite was the main REE mineral. Total REE ranged from 34,746 ppm in HG1 to 30,017 ppm in HG2, with LREEs in its majority. The bulk and clay XRD analyses indicated that monazite consisted of 5.7% (HG1) and 5.1% (HG2). The mineral abundance from the TIMA-X analysis indicated 4.2% (HG1) and 4.4% (HG2) in monazite content. Full article

Several challenges arise during edge trimming of carbon fibre-reinforced polymer (CFRP) composites, such as the formation of machining-induced burrs and delamination. In a recent development, appropriate-quality geometric features in CFRPs can be machined using special cutting tools and optimised machining parameters. However, these suitable technologies quickly become inappropriate due to the accelerated tool wear. Therefore, the main aim of our research was to find a novel solution for maintaining the machined edge quality even if the tool condition changed significantly. We developed a novel mechanical edge-trimming technology inspired by wobble milling, i.e., the composite plate compression is governed by the proper tool tilting. The effectiveness of the novel technology was tested through mechanical machining experiments and compared with that of conventional edge-trimming technology. Furthermore, the influences of the tool tilting angle and the permanent chamfer size on the burr characteristics were also investigated. A one-fluted solid carbide end mill with a helix angle of 0° was applied for the experiments. The machined edges were examined trough stereomicroscopy and scanning electron microscopy. The images were evaluated through digital image processing. Our results show that multi-axis edge-trimming technology produces less extensive machining-induced burrs than conventional edge trimming by an average of 50%. Furthermore, we found that the tool tilting angle has a significant impact on burr size, while permanent chamfer does not influence it. These findings suggest that multi-axis edge trimming offers a strong alternative to conventional methods, especially when using end-of-life cutting tools, and highlight the importance of selecting the optimal tool tilting angle to minimize machining-induced burrs. Full article

The Cool Roof concept, known for its efficiency in summer due to high temperatures during this period, employs a light coating that covers the roof to prevent the absorption of heat and maintain lower indoor temperatures. This study integrates a chemical component with biomaterials to enhance performance and reduce CO₂ emissions. The composition investigated in this research is recognized for its durability and ability to lower outside temperatures, thereby mitigating the urban heat island effect. This experimental study evaluates the sustainability of CoolRoofs in a cold room located in Signes, France. Temperature measurements are conducted from 25 September 2023 to 27 July 2024, both with and without the coating, to assess energy performance and CO₂ emissions. The selection of the building type ensures optimal performance in both summer and winter. Results show that the maximum outside and inside surface temperatures for a Cool Roof are 48.7 °C and 25.6 °C, respectively, compared to 72.9 °C and 32.2 °C for an uncoated roof. Additionally, implementing a CoolRoof reduces thermal load through the cold room by 56%, while CO₂ emissions can be reduced by up to 27.31 kg CO₂/m² over a 20-year period. This study presents a solution for enhancing energy and environmental performance year-round using a resilient composite. Full article

With the development of the steel industry, China’s demand for niobium is increasing. However, domestic niobium resources are not yet stably supplied and are heavily dependent on imports from abroad (nearly 100%). It is urgent to develop domestic niobium resources. The Bayan Obo deposit is the largest rare earth element deposit in the world and contains a huge amount of niobium resources. However, the niobium resource has not been exploited due to the fine-grained size and heterogeneous and scattered occurrences of Nb minerals. To promote the utilization of niobium resources in the Bayan Obo deposit, we focused on the mineralogical and geochemical characterization of six types of ores and mineral processing samples from the Bayan Obo deposit, using optical microscopes, EPMA, TIMA, and LA–ICP–MS. Our results show that: (1) the niobium mineral compositions are complex, with the main Nb minerals including aeschynite group minerals, columbite–(Fe), fluorcalciopyrochlore, Nb–bearing rutile, baotite, fergusonite–(Y), fersmite, and a small amount of samarskite–(Y). Aeschynite group minerals, columbite–(Fe), and fluorcalciopyrochlore are the main niobium-carrying minerals and should be the primary focus of industrial recycling and utilization. Based on mineralogical and geochemical investigation, the size of the aeschynite group minerals is large enough for mineral processing. Aeschynite group minerals are thus a significant potential recovery target for niobium, as well as for medium–heavy REE resources. The Nb–rich aegirine-type ores with aeschynite group mineral megacrysts are suggested to be the most significant niobium resource for mineral processing and prospecting. Combined with geological features, mining, and mineral processing, niobium beneficiation efforts of aeschynite group minerals are crucial for making breakthroughs in the utilization of niobium resources at the Bayan Obo. Full article

The Sanhetun tellurium–gold (Te–Au) deposit, located in the Duobaoshan polymetallic metallogenic belt (DPMB) within the eastern section of the Central Asian Orogenic Belt (CAOB), is a newly discovered small-scale gold deposit. The mineralization, with a resource of ≥4 t Au, is mainly hosted in three NNE-trending alteration zones between Early Carboniferous granitic mylonite and Lower Cretaceous volcanogenic-sedimentary formations. The genesis of formation of this deposit is poorly constrained. Here, we report the results of petrographic studies, TESCAN Integrated Mineral Analyzer (TIMA), major and trace element concentrations, and in situ S isotopes of pyrite. The results show that there are four types of pyrite: coarse-grained euhedral Py1, fine-grained quartz-Py2 vein crosscutting Py1, anhedral aggregated Py3, and anhedral aggregated Py4. The pre-ore stage Py1 contains negligible Au, Te, and other trace elements and has a relatively narrow range of δ³⁴S values ranging from −1.20 to −0.57‰. Py2 has higher concentrations of Au and Te and distinctly high concentrations of Mo, Sb, Zn, and Mn with markedly positive δ³⁴S values of 4.67 to 14.43‰. The main-ore stage Py3 contains high Au and Te concentrations and shows narrow δ³⁴S values ranging from −5.69 to 0.19‰. The post-ore stage Py4 displays low Au concentrations with the δ³⁴S values ranging from 2.66 to 3.86‰. Tellurides are widespread in Py3 and Py4, consisting mainly of native tellurium, tetradymite, tsumoite, hessite, and petzite. Especially, tetradymite commonly coexists with native gold. This study highlights the role of Te–Bi–S melt as an important gold scavenger in As-deficient ore-forming fluids. Full article

As the global demand for tellurium (Te) increases, it is crucial to develop efficient recovery methods that consider existing supply streams. This research combines gravity separation and froth flotation processes to enhance the recovery of Te minerals from tailings produced during the beneficiation of copper porphyry ores. Prior to processing, a systematic and comprehensive characterization study of copper tailing (CT) samples was conducted to examine the deportment of Te minerals in different mineral phases and to understand their locking and liberation behavior. Characterization techniques included inductively coupled plasma mass spectrometry (ICP-MS) and TESCAN’s integrated mineral analysis (TIMA). Copper tailing characterization showed that minerals with gold (Au), silver (Ag), bismuth (Bi), and Te were present in various forms, including native Au, electrum, tellurides, and sulfosalts. TIMA revealed that >90% of these minerals were primarily hosted in pyrite as less than 10 µm inclusions in the CT. TIMA also revealed that Te minerals exhibited fine-grained liberation of less than 20 μm. Moreover, TIMA results showed that >80% of mica and other silicate minerals were concentrated in size fractions < 38 μm, suggesting that desliming processes would positively impact Te enrichment. The results from the processing tests showed a Te recovery rate of ~77% and a Te enrichment ratio of 13 when using the combination of gravity separation and froth flotation at 90 g/t xanthate collector and 50 g/t glycol frother. The findings from this study show a significant potential for Te recovery from unconventional sources if appropriate physical beneficiation approaches are adopted. Full article

AI systems have an increasing sprawling impact in many application areas. Embedded systems built on AI have strong conflictual implementation constraints, including high computation speed, low power consumption, high energy efficiency, strong robustness and low cost. Neural Networks (NNs) used by these systems are intrinsically partially tolerant to computation disturbances. As a consequence, they are an interesting target for approximate computing seeking reduced resources, lower power consumption and faster computation. Also, the large number of computations required by a single inference makes hardware acceleration almost unavoidable to globally meet the design constraints. The reported study, based on an integer version of LeNet, shows the possible gains when coupling approximation and hardware acceleration. The main conclusions can be leveraged when considering other types of NNs. The first one is that several approximation types that look very similar can exhibit very different trade-offs between accuracy loss and hardware optimizations, so the selected approximation has to be carefully chosen. Also, a strong approximation leading to the best hardware can also lead to the best accuracy. This is the case here when selecting the ApxFA5 adder approximation defined in the literature. Finally, combining hardware acceleration and approximate operators in a coherent manner also increases the global gains. Full article

Currently, the most advanced micromachined microphones on the market are based on a capacitive coupling principle. Capacitive micro-electromechanical-system-based (MEMS) microphones resemble their millimetric counterparts, both in function and in performance. The most advanced MEMS microphones reached a competitive level compared to commonly used measuring microphones in most of the key performance parameters except the acoustic overload point (AOP). In an effort to find a solution for the measurement of high-level acoustic fields, microphones with the piezoelectric coupling principle have been proposed. These novel microphones exploit the piezoelectric effect of a thin layer of aluminum nitride, which is incorporated in their diaphragm structure. In these microphones fabricated with micromachining technology, no fixed electrode is necessary, in contrast to capacitive microphones. This specificity significantly simplifies both the design and the fabrication and opens the door for the improvement of the acoustic overload point, as well as harsh environmental applications. Several variations of piezoelectric structures together with an idea leading to electrically controlled sensitivity of MEMS piezoelectric microphones are discussed in this paper. Full article

Mineralization characterized by Au, Hg, and Tl enrichment is rare, and research on Au, Hg, and Tl mineralization is limited. The Lanmuchang Au–Hg–Tl deposit is located in the “Golden Triangle” of Yunnan, Guizhou, and Guangxi Provinces in China. In this study, we used scanning electron microscopy (SEM), electron microprobe analysis (EPMA), and a Tescan integrated mineral analyzer (TIMA) to analyze the mineral composition and distribution of the different types of ores and identify the occurrence state and enrichment mechanism of ore-forming elements in the Lanmuchang deposit. The results show that the primary ore minerals in the Lanmuchang deposit are pyrite, cinnabar, and lorandite. Cinnabar is the primary carrier of Hg (>90%), and pyrite is the primary carrier of Tl (>60%). Gold, Hg, and Tl primarily occur as solid solutions in hydrothermal pyrite, whereas they primarily occur as nano-scale particles in diagenetic pyrite. The substitution of As for S in hydrothermal pyrite promotes Au enrichment. The coupled substitution of 2Fe²⁺ ⇔ Tl⁺ + As³⁺ may be a significant Tl incorporation mechanism and promotes the occurrence of Hg in pyrite. The As and Se contents and Cu/Au and Co/Ni ratios of the hydrothermal pyrite demonstrate that the ore-forming fluid was mostly in a low-temperature, low-salinity, almost-neutral pH, and nearly reducing environment. The results show that the mineralization of the Lanmuchang deposit is associated with the cooling, oxidation, water–rock interaction, and boiling processes of the ore-forming fluid(s). Full article

Selenium (Se) is an essential trace element for humans and animals, and an excess of or deficiency in Se is harmful to health. Research on the selenium enrichment zone began in the late 1970s in Shuang’an, Ziyang, southern Shaanxi Province. Naore village is only one selenosis area in Shuang’an, Ziyang, China. Different scholars have conducted systematic studies on the occurrence of selenium, its organic geochemistry and biomarkers, and its content and enrichment patterns in this area. This study applied the TIMA (TESCAN integrated mineral analyzer) for the first time to conduct detailed mineralogical work. The minerals included quartz, carbonate minerals (calcite and dolomite), feldspar (plagioclase, albite, and orthoclase), biotite and muscovite, clay minerals (chlorite and kaolinite), hematite, pyrite, and accessory minerals (almandine, olivine, zircon, and apatite) in Naore village, Ziyang, Shaanxi Province. The ATi index (100 × apatite/(apatite + tourmaline)) is used to determine the source of heavy minerals and the degree of heavy minerals’ weathering. The content POS (100 × (pyroxene + olivine + spinel)/transparent heavy mineral) of olivine, pyroxene, and spinel in heavy minerals can reflect the contribution of basic and ultrabasic rocks in the source area. The ATi and POS indexes for the heavy minerals in the research area were 91.83~99.96 and 0.01~18.75, respectively, reflecting the abundance of volcanic rock material in their source. In addition, the migration, transformation, bioavailability, and toxicity of selenium in the environment are closely related to its species. The species of selenium in various selenium-rich areas (Naore, Wamiao, and Guanquan) mainly include unusable residues and organic forms, followed by humic-acid-bound selenium. The proportions of water-soluble, exchangeable, and carbonate-bound selenium are relatively small, and the proportion of Fe-Mn oxide-bound selenium is the lowest. Full article