The composition and origination of particles from surface water in the Chukchi Sea, Arctic Ocean

Suspended particle samples were collected at 11 stations on the shelf and slope regions of the Chukchi Sea and the central Arctic Ocean during the fifth Chinese National Arctic Research Expedition (summer 2012). The particle concentration, total organic carbon (TOC), total nitrogen (TN) and the isotopic composition of the samples were analyzed. The suspended particle concentration varied between 0.56 and 4.01 mg.L-1; the samples collected from the sea ice margin have higher concentrations. The organic matter content is higher in the shelf area (TOC: 9.78%–20.24%; TN: 0.91%–2.31%), and exhibits heavier isotopic compositions (δ13C: –23.29‰ to –26.33‰ PDB; δ15N: 6.14‰–7.78‰), indicating that the organic matter is mostly marine in origin with some terrigenous input. In the slope and the central Arctic Ocean, the organic matter content is lower (TOC: 8.06% – 8.96%; TN: 0.46%–0.72%), except for one sample (SR15), and has lighter isotopic compositions (δ13C: –26.93‰ to – 27.78‰ PDB; δ15N: 4.13‰–4.84‰). This indicates that the organic matter is mostly terrestrially-derived in these regions. The extremely high amount of terrigenous organic matter (TOC: 27.94%; TN: 1.16%; δ13C: –27.43‰ PDB; δ15N: 3.81‰) implies that it was carried by transpolar currents from the East Siberian Sea. Material, including sea ice algae, carried by sea ice are the primary source for particles in the sea ice margins. Sea ice melting released a substantial amount of biomass into the shelf, but a large amount of detrital and clay minerals in the slope and the central Arctic Ocean

SVCV: segmentation volume combined with cost volume for stereo matching

Stereo matching between binocular stereo images is fundamental to many computer vision tasks, such as three‐dimensional (3D) reconstruction and robot navigation. Various structures of real 3D scenes lead stereo matching to be an old yet still challenging problem. In this study, the authors proposed a novel adaptive support weights technique which exploits the hierarchical information provided by multilevel segmentation to preserve the robustness to imaging conditions and spatial proximity in cost aggregation. Besides, a generalisable cost refinement strategy is designed to remove the matching ambiguity in large weakly textured regions. The proposed strategy utilises both the fluctuation of the filtered cost volume and the colour information to further improve the matching accuracy. Experimental results of 50 stereo images demonstrate the effectiveness and efficiency of the proposed method. Furthermore, a systematic evaluation is developed to assess the conventional steps in local stereo methods and then reliable suggestions are given to the beginners and researchers outside the stereo matching field

Tephra records from abyssal sediments off western Sumatra in recent 135 ka: evidence from Core IR-GC1

Three volcanic ash layers were identified in a deep-sea Core IR-GC1 from the north-eastern Indian Ocean, adjacent to western Indonesian arc. They were dominated by glass shards with minor mineral crystals, such as plagioclase, biotite, and hornblende. According to the morphology and major element compositions of the representative glass shards, combined with the 18O-based age, it is suggested that ash Layer A is correlated to the youngest Toba tuff (YTT), Layer B is supposed to be associated with a new eruption of Toba caldera in an age of 98 to 100 ka. Ash Layer C is different the geochemistry characteristics than those of Layer A and Layer B, suggesting that Layer C was not originated from Toba but registered another volcanic eruption event

Influence of temperature, pressure, and fluid salinity on the distribution of chlorine into serpentine minerals

Serpentinization produces serpentine minerals that have abundant water and fluid-mobile elements (e.g., Ba, Cs, and Cl). The dehydration of serpentine minerals produced chlorine-rich fluids that may be linked with the genesis of arc magmas. However, the factors that control the distribution of chlorine into serpentine minerals remain poorly constrained. We performed serpentinization experiments at 80-500 degrees C and pressures from vapor saturated pressures to 20 kbar on peridotite, orthopyroxene, and olivine with < 5% pyroxene. The results show that the concentrations of chlorine in serpentine minerals were up to 1.2 wt% at 200 degrees C, whereas they decreased slightly at 311-400 degrees C and 3.0 kbar and became significantly lower at 485 degrees C and 3.0 kbar, similar to 0.1 wt%. Fluid salinity greatly decreased chlorine concentrations of olivine-derived serpentine produced at 400 degrees C and 3.0 kbar, which was associated with a decrease in silica mobility during serpentinization. By contrast, influence of fluid salinity at 311 degrees C and 3.0 kbar is minor. Moreover, chlorine distribution into serpentine can be influenced by primary minerals of serpentine. Serpentine formed in olivine-only experiments at 311 degrees C and 3.0 kbar had 0.08 +/- 0.03 wt% Cl, which is significantly lower than chlorine concentrations of serpentine minerals (0.49 +/- 0.36 wt%) produced in orthopyroxene-only experiments. By contrast, for experiments at 311 degrees C and 3.0 kbar, olivine- and orthopyroxene-derived serpentine had comparable amounts of chlorine. In particular, olivine-derived serpentine had 0.16 +/- 0.09 wt% Cl that was slightly higher than chlorine concentrations of serpentine formed in olivine-only experiments, whereas orthopyroxene-derived serpentine had significantly lower chlorine concentrations than that formed in orthopyroxene-only experiments. The contrast may be associated with releases of aluminum and silica from pyroxene minerals, which possibly results in a decrease in chlorine concentrations of serpentine. The concentrations of chlorine in serpentine formed in experiments at 311 degrees C and 3.0 kbar were slightly lower than those in serpentine produced at 300 degrees C and 8.0 kbar, which may be associated with influence of pressure on the mobility of iron and silica. The experimental results of this study indicate that serpentine minerals are important carriers of chlorine in subduction zones. It also suggests that chlorine is significant for the redistribution of cations during serpentinization

Mineralogy and geochemistry of hydrothermal precipitates from Kairei hydrothermal field, Central Indian Ridge

The Kairei hydrothermal field was the first confirmed active submarine hydrothermal system on the Central Indian Ridge. It has been suggested to be related to mafic as well as ultramafic host rocks based on vent fluid composition and the presence of ultramafic rocks in its vicinity. In this study, detailed geochemical and mineralogical analyses have been carried out on the hydrothermal precipitates from the Kairei vent field in order to investigate the possible presence of indications for an ultramafic substrate at this vent site. The studied samples included fragments of sulfide chimneys, massive sulfides and talc-bearing and silicified breccias. Three mineralization stages were identified: (1) a high-temperature stage consisting largely of chalcopyrite, isocubanite, and pyrite; (2) a medium to low temperature stage characterized by the mineral assemblages of sphalerite and pyrite; and (3) a weathering stage characterized by secondary Cu-sulfides (bornite, digenite, covellite and idaite), Fe-oxihydroxides, Opal-A, and Cu-chloride (paratacamite and atacamite). The sulfide geochemistry is characterized by high concentrations of Cu and Zn (Cu + Zn up to 29.3 wt.%, n = 17) and Au (mean 5.28 ppm, n = 17), which is comparable to results from seafloor massive sulfides collected from ultramafic-hosted sites in the Atlantic Ocean, but differs from those of typical mafic-hosted deposits. The high concentrations of Cu and Au at the Kairei hydrothermal field could be an indication for the involvement of ultramafic rocks in the subseafloor. Ultramafic-hosted, Au-rich sulfide deposits may not be restricted to the Atlantic Ocean and may be common along all slow- and intermediate-spreading ridges

The production of iron oxide during peridotite serpentinization: Influence of pyroxene

Serpentinization produces molecular hydrogen (H2) that can support communities of microorganisms in hydrothermal fields; H2 results from the oxidation of ferrous iron in olivine and pyroxene into ferric iron, and consequently iron oxide (magnetite or hematite) forms. However, the mechanisms that control H2 and iron oxide formation are poorly constrained. In this study, we performed serpentinization experiments at 311 °C and 3.0 kbar on olivine (with <5% pyroxene), orthopyroxene, and peridotite. The results show that serpentine and iron oxide formed when olivine and orthopyroxene individually reacted with a saline starting solution. Olivine-derived serpentine had a significantly lower FeO content (6.57 ± 1.30 wt.%) than primary olivine (9.86 wt.%), whereas orthopyroxene-derived serpentine had a comparable FeO content (6.26 ± 0.58 wt.%) to that of primary orthopyroxene (6.24 wt.%). In experiments on peridotite, olivine was replaced by serpentine and iron oxide. However, pyroxene transformed solely to serpentine. After 20 days, olivine-derived serpentine had a FeO content of 8.18 ± 1.56 wt.%, which was significantly higher than that of serpentine produced in olivine-only experiments. By contrast, serpentine after orthopyroxene had a slightly higher FeO content (6.53 ± 1.01 wt.%) than primary orthopyroxene. Clinopyroxene-derived serpentine contained a significantly higher FeO content than its parent mineral. After 120 days, the FeO content of olivine-derived serpentine decreased significantly (5.71 ± 0.35 wt.%), whereas the FeO content of orthopyroxene-derived serpentine increased (6.85 ± 0.63 wt.%) over the same period. This suggests that iron oxide preferentially formed after olivine serpentinization. Pyroxene in peridotite gained some Fe from olivine during the serpentinization process, which may have led to a decrease in iron oxide production. The correlation between FeO content and SiO2 or Al2O3 content in olivine- and orthopyroxene-derived serpentine indicates that aluminum and silica greatly control the production of iron oxide. Based on our results and data from natural serpentinites reported by other workers, we propose that aluminum may be more influential at the early stages of peridotite serpentinization when the production of iron oxide is very low, whereas silica may have a greater control on iron oxide production during the late stages instead

A simplified statistic-based procedure for gas dispersion prediction of fixed offshore platform

© 2017 In explosion risk analysis, Frozen Cloud Approach (FCA) and Dimensionless Response Surface Method (DRSM) are both commonly used to achieve a balance between simulation workloads and accurate results. However, the drawbacks of these two approaches are obvious. FCA is not reliable for risk study of fuel-dominated regions. Whereas DRSM usually couples the dimensionless parameters and generates a large numbers of correlations to predict the flammable cloud size, which brings a heavy computation burden for engineers. Therefore, this paper aims to propose a simplified procedure which can quickly and accurately provide a large number of non-simulation data based on limited CFD simulation data. Full Factorial Design of Experiment (FFDOE) based RSM is adopted. Codification is applied to couple all the dimensional parameters into a single correlation. Automatically Selected Model Technology (ASMT) is used to easily determine the suitable structure of correlation. Compared to the conventional procedures, the simplified procedure is proven to be more robust. For subsequent Explosion risk analyses (ERAs) in the fuel-dominated regions, the simplified procedure becomes a superior alternative

High-efficiency WPT system for CC/CV charging based on double-half-bridge inverter topology with variable inductors

Efficiency remains a key challenge in wireless charging in academia and industry. In this article, a new wireless power transfer (WPT) system based on a double-half-bridge (DHB) inverter with two variable inductors (VIs) is proposed. Compared with conventional full-bridge (FB) inverters, the DHB inverter can reduce the current through the mosfets under the same output power and thus, reduce the conduction loss. Next, by adjusting the inductances of the VIs instead of using phase shift (PS) method, the output voltage or current can be controlled, while the circulating current can be eliminated and wide-range zero voltage switching operation can be achieved. Consequently, the power loss can be further reduced. Circuit analysis, VI design, as well as hardware implementation, are provided in detail. A laboratory prototype is built to verify the feasibility of the proposed method. Close agreement is obtained between simulation and experimental results. The maximum efficiency can reach 92.4%, which is 3.65% higher than traditional PS control. © 1986-2012 IEEE