Europium (Eu) in coal, coal combustion residues (e.g., fly ash), and sedimentary rocks in coal-bearing sequences has attracted much attention in recent years mainly because of its world-wide demand ...and use as a geochemical indicator of geological setting for coal deposit studies. This paper presents a method for accurately measuring the concentration of Eu in coal, fly ash, and sedimentary rocks by quadrupole-based inductively coupled plasma mass spectrometry (ICP-MS), plus the use of closed-vessel microwave digestion and a cation exchange resin. To significantly diminish the inference of Ba-based polyatomic ions (137Ba16O, 136Ba17O, 135Ba18O, and 134Ba18OH) on 153Eu in coal, fly ash, and sedimentary rock samples, a Bio-Rad AG50W-x8 cation exchange resin was used to separate Ba from digested solutions of solid samples. The AG50W-x8 cation exchange resin can effectively separate the barium from digested solutions and thus could diminish the inference of Ba on Eu. The determination of Ba and Eu in the National Institute of Standards Technology (NIST) standard references of coal and fly ash samples showed that the use of the AG50W-x8 cation exchange resin combined with quadrupole-based ICP-MS analysis can provide a reliable method for the accurate determination of Eu concentrations in coal and coal-related samples. The method detection limits for Ba and Eu are 0.030 μg/l and 0.006 μg/l, respectively, and the determination coefficient of their calibration curves (linearity range 0–100 μg/l) is >0.9999. A Ba/Eu value of 1000 in the samples is proposed for judging the interference of Ba on Eu. If Ba/Eu > 1000, then Ba in coal, fly ash, and sedimentary rocks significantly interferes with Eu and this interference then needs to be considered when interpreting the analytical results and their significance.
•Barium would interfere Eu using quadrupole-based ICP-MS for coal and coal-related materials.•The AG50W-x8 cation exchange resin can effectively separate the barium from Eu from digested solutions.•A method for accurately determining Eu concentrations was designed.•A Ba/Eu value of 1000 in the samples is proposed for judging the interference of Ba on Eu.
Comparison between the studied samples (including Dai et al., 2018, Guo et al., 2019) and their possible magmatic and metamorphic source rocks with the Al2O3/TiO2 vs. Sr/Y and La/Yb (modified after ...Dai et al., 2018).
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•The BS-22A Coal is enriched in As, Sb, Ge, Cs, and W.•The clastic materials of the Hunchun coals were dominantly from Mesozoic volcanic rocks and Paleozoic metamorphic rocks.•The Ge enrichments have been detected in some individual coal benches.•Tectonic activity and hybrid hydrothermal-weathering process elevated Ge in the coals.
The geochemistry and mineralogy of Palaeogene coals from the Hunchun Coalfield, Jilin Province, northeastern China, have been studied using X-ray fluorescence spectrometry, inductively coupled plasma mass spectrometry, scanning electron microscopy in combination with energy-dispersive X-ray spectrometry, and X-ray diffraction analysis of the low-temperature ash. The 22A Coal from the Banshi Mine is of subbituminous A to high volatile bituminous rank (0.53–0.56% Ro, ran) and has a low sulfur content (0.74% on average). The 22A Coal consists mainly of kaolinite, quartz, illite, and, to a lesser extent, plagioclase, siderite, and pyrite. As compared with the average world low-rank coals, the 22A Coal is enriched in As, Sb, Ge, Cs, and W.
Combined with the geochemical features of six other coal seams from the Hunchun Coalfield, the terrigenous materials of the Hunchun coals were dominantly from Mesozoic (mostly Lower Cretaceous) volcanic rocks and Paleozoic granites and associated metamorphic rocks surrounding the coal basin. A minor source was the Paleogene volcaniclastics including some adakitic rocks, which are characterized by higher Sr/Y and La/Yb ratios. The Ge enrichments that are detected in some individual coal benches from the Hunchun Coalfield were related to tectonic uplift of the crystalline rocks surrounding the basin and their following denudation. The oxidized meteoric waters episodically influenced by volcanic-related hot springs might extract Ge from the source rocks and then precipitate it as a result of bio-chemical reduction, forming the mineralization disseminated in the coals.
Over the last decade, there has been extensive research into the security and privacy of blockchain technology, from the use of ring signatures to ring confidential transactions. Although existing ...cryptographic methods perform well on traditional blockchain architectures, they do not provide complete privacy in a hierarchical blockchain architecture for Internet of Things (IoT) devices. The blockchain technology is centered at the gateway layer in the hierarchical blockchain architecture, which can easily reveal the transaction sender using network traffic information, thereby violating the sender’s anonymity. Furthermore, the gateway can perform eclipse attacks against transaction senders on a case-by-case basis. To this end, this paper proposes a novel security and privacy blockchain protocol that is better suited to the hierarchical blockchain architecture and thus more appropriate for the IoT environment. Specifically, it leverages the relationship among IoT devices at the perception layer of the hierarchical blockchain architecture for IoT, and constructs an overlay social IoT network by exploiting devices’ multi-agent capabilities. Furthermore, circuit establishment based on multilayered encryption is applied to conceal the transaction propagation path through the overlay social IoT. Theoretical analysis shows that our novel protocol is flexible, evades a malicious gateway, and is secure under the decisional Diffie-Hellman assumption.
By deviating from an honest mining strategy, attackers can obtain additional rewards through mining attacks. Selfish mining is the most well-known mining attack. It includes selfish mining (SM1), ...optimal selfish mining (∊-optimal), and bribed selfish mining (BSM), etc. The mining models addressed in prior studies, however, are based on the Nakamoto consensus. Therefore, this paper proposes the ESM model (Selfish Mining under Ecological model). Our new model is fully compatible with fewer resource expenditure requirements. Meanwhile, we also describe a novel selfish mining attack that allows the malicious pool to gain additional revenue by using an ESM attack rather than SM1 when its power is less than 25%. Furthermore, we present an EBSM (Bribery Selfish Mining under Ecological) attack that combines ESM together with the bribery attack. As a result, under EBSM, the malicious solo miner has a chance to gain additional revenue. Finally, we undertake quantitative analyses and simulations to assess the effectiveness of our attacks.
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