Lead zirconate titanate (PZT)-based ceramics are used in numerous advanced applications, including sensors, displays, actuators, resonators, chips; however, the poor mechanical characteristics of ...these materials severely limits their utility in composite materials. To address this issue, we herein fabricate transgranular type PZT ceramic nanocomposites by a novel method. Thermodynamically metastable single perovskite-type Pb0.99(Zr0.52+xTi0.48)0.98Nb0.02O3+1.96x powders are prepared from a citrate precursor before both monoclinic and tetragonal ZrO2 nanoparticles ranging from 20 to 80 nm are precipitated in situ at a sintering temperature of 1260 °C. The effects of ZrO2 content on the microstructure, dielectric, and piezoelectric properties are investigated and the mechanism, by which ZrO2 toughened PZT is analyzed in detail. The ZrO2 nanoparticles underwent a tetragonal to monoclinic phase transition upon cooling. The fracture mode changed from intergranular to transgranular with increasing ZrO2 content. The incorporation of ZrO2 nanoparticles improved the mechanical and piezoelectric properties. The optimized piezoelectric properties (εT33/ε0 = 1398, tan δ = 0.024 d33 = 354 pC N−1, kp = 0.66 Qm = 78) are obtained when x = 0.02. Tc initially increased and subsequently decreased with increasing ZrO2 content. The highest Tc = (387 °C) and lowest εT33/ε0 was obtained at x = 0.01.
The Cretaceous tectonic evolution of South China is characterized by widespread extensional basin and dome generation, voluminous magma intrusion/eruption and associated polymetallic mineralization, ...all of which are of world-wide interests that have stimulated the attention of geologists for more than half a century. Due to the lack of a comprehensive understanding of regional tectonic evolution and geodynamics of South China, many controversies regarding the nature and origin of these features remain. This paper attempts to make a review by synthesizing existing structural, petrological, geochronological and geochemical data of the Cretaceous structures and magmas, which guides us to propose a three-stage tectono-thermal evolutionary history of South China during the Cretaceous period. The earliest Cretaceous (145–137Ma) tectonic stage was characterized by syn-orogenic shortening deformation and metamorphism under a NW–SE compressional setting, which generated voluminous porphyry Cu–Au ore-bearing adakitic rocks in the Lower Yangtze River Belt and gneissic granites in the coastal area. Its geodynamic origin was interpreted as combined effects of the Pacific–Izanagi ridge subduction beneath the Lower Yangtze River Belt and the Pacific subduction beneath the Cathaysia Block. This syn-orogenic shortening stage was followed by a post orogenic stage (136–86Ma) comprising two episodes of alternate extensional and shortening events. The extension (136–118Ma) in the earlier episode was dominated by a NW–SE extensional regime, it led to significant taphrogenesis manifested by large-scale extensional basins and voluminous magma intrusion/eruption; this extensional event was associated with a combination of the slab window opening during the ridge subduction and the rollback of the subducted Pacific slab. The subsequent NW–SE transpressional event led to cessation of active marginal magmatism and resulted in tectonic inversion of previous rift basins; this transpression lasted from 117Ma to 108Ma, and its driving mechanism was attributed to the collision between the eastern Asian margin and the West Philippine Block. The extension (107–86Ma) in the later episode was dominated by a WNW–ESE extensional regime, which led to a second phase of basin subsidence and produced numerous A- and I-type granites and bimodal volcanoes. The tectonic regime then changed at ca. 85Ma to WNW–ESE-oriented transpression, causing inversion of the Late Cretaceous rift basins and cessation of extension-related magmatism. The change of stress field from WNW–ESE extension to WNW–ESE transpression was related to the variations of the subducted slab dynamics, i.e., the transition from either the ESE-ward retreat to WNW-ward subduction of the Pacific slab, or the alternate stress during slab break-off. During the latest Cretaceous, a drastic change of regional tectonic stress orientation from WNW–ESE to N–S occurred in South China, the third stage predominated by N–S extension was developed, which caused a new phase of regional crustal subsidence along the youngest E–W trending extensional structures.
Abstract
Ceramifiable silicone rubber composites (CSR) are one of the most important industrially produced elastic technical materials. At present, there is a strong demand for CSR in the high-tech ...fields of high-speed rail, nuclear power, rocket and aerospace, which are still to be met. Many scholars have committed to the research work of improving the thermal stability, flame retardant, mechanical properties by changing the silicone rubber (SR) matrixes and filler, tremendous advances in CSR have been made for over the last decades where CSR intended for the high technology fields has evolved through different generations. In summary, the first-generation research is based on matrix reaction, the second-generation research is on reaction products, and the third-generation research is on fillers effects. In this review, the evolution of CSR and the synthesis routes, reaction mechanism, and degradation mechanism are introduced and analyzed; fillers, various types of CSR based composites as well as the flame retardancy and mechanical properties are reviewed. Finally, the problems of developing high-performance CSRs are proposed and discussed. This review provides a theoretical basis and supporting data for the application of high-performance CSR, as well as provides details on the fire prevention mechanism of CSR.
Silicone rubber has been widely used in electronic appliances, nuclear power cable, aerospace and so on, However, silicone rubber will continue to burn when exposed to flame, so flame retardant ...modification is required. In this work, aluminum hypophosphite (AHP) and Mica were used fluxing agent to make ceramizable silicone rubber material (CSR). The ceramization mechanism was investigated based on microstructure, mechanical and flame retardation properties. The scanning electron microscope result shows that the addition of AHP reduce the ceramization temperature effectively. AHP/Mica modified CSR have better flame retardation properties than pure silicone rubber, the addition of AHP increase LOI to 33.9%, and the LOI is 34.8% and the UL-94 is FV1 as 25 parts of Mica are added. When the 10 phr aluminum hypophosphite replaces Mica, the compression strength reach 14.46 MPa, increased by 42.5%. Moreover, the phenomenon of expansion into ceramics was founded and studied.
The Kunlun Orogen is generally divided into the East Kunlun Orogenic Belt (E-KOB) and the West Kunlun Orogenic Belt (W-KOB) by the Altyn Tagh fault. The E-KOB forms part of the western segment of the ...Central China Orogenic System (CCOS), and is considered to have formed by the collision between the Qaidam Block and Qiangtang or Bayanhar Terrane as a consequence of the closure of the Kunlun Ocean (branch of the Paleo-Tethyan Ocean). Based on a compilation recently published high-quality data, this contribution provides an overview of the composition, nature and ages of the principal tectonic elements, including ophiolitic mélanges and related volcanic rocks, intrusive plutons and sedimentary cover sequences in the E-KOB. According to multiple lines of evidence from these tectonic elements, we proposed herewith a Paleozoic–Triassic subduction and accretionary tectonic model to interpret the spatiotemporal tectonic framework, plate subduction polarity, and tectonic processes from accretion to collision of the E-KOB. Three main ophiolitic mélange zones are identified in the E-KOB, from north to south, they are the Qimantagh–Xiangride ophiolitic mélange zone (QXM), the Aqikekulehu–Kunzhong ophiolitic mélange zone (AKM) and the Muztagh–Buqingshan–Anemaqen ophiolitic mélange zone (MBAM). According to these ophiolitic mélange zones, the E-KOB is divided into four major tectonic units: the North Qimantagh belt, the Central Kunlun belt, the South Kunlun belt and the Bayanhar Terrane. Based on several lines of evidence from geology, geochemistry and geochronology, the South Kunlun belt is interpreted as a Paleozoic to Triassic fore-arc and accretionary complex related to northward subduction of the Kunlun Ocean during the Ordovician–Triassic time. The AKM, MABM and the South Kunlun belt constitute a wide accretionary complex along the Kunlun Suture zone that marks final closure of the major Paleo-Tethyan Ocean, while the QXM represents the best expression of another suture that records final closure of the Qimantagh back-arc basin. The Central Kunlun Belt, as a long-lived island-arc terrane from Ordovician to Triassic times, rifted from the Qaidam Block due to the spreading of the Qimantagh back-arc basin during the period of ca. 485–425Ma. Taken into all the geological, geochemical and geochronological lines of evidence together, a trench / arc / back-arc basin tectonic system in the E-KOB was built up, and evolved into a protracted and long-lived northward-subduction and accretion along the Kunlun Suture during Paleozoic and Triassic time.
•Sugar cane bagasse and orange peel can be recycled into biochar for wastewater treatments.•The rapid and high sorption capacities make them very promising alternative sorbent materials.•Sugar cane ...biochar (SC-BC) was more effective in removing Pb(II) than orange peel (OP-BC).•The morphological features determine the removal efficiency of biochar for Pb (II).
In this study sugar cane biochar (SC-BC) and orange peel biochar (OP-BC) were used to remove Pb(II) ions from aqueous solutions. To achieve this goal, biochars were produced by the pyrolysis of biomasses at temperature less than 500°C by using a small-scale biochar producing plant. Furthermore, batch adsorption studies have been performed, and the effects of several factors, i.e., pH, contact time, initial Pb(II) ions concentration and temperature were investigated on Pb(II) ions sorption mechanism and optimizing the removal efficiency of Pb. Boehm titration method and Fourier transform infrared (FTIR) spectroscopy were employed to quantitatively describe the major function groups on the surface of biochars. The obtained results revealed the presence of carboxyl, hydroxyl, and carbonyl groups, which are likely responsible for the adsorption of Pb(II) ions. Given the same chemical structure, SC-BC was more effective in removing Pb(II) ions than OP-BC, with the removal capacities of 86.96mg/g, much higher than those of OP-BC (27.86mg/g). The equilibrium data were well fitted with Langmuir model and the adsorption process was well fitted by pseudo-second-order model. We suggested the major adsorption mechanisms of Pb(II) ions through a specific ion-exchange mechanism, and surface precipitation. Results indicated that not only the chemical composition but also the morphological structure plays an important role in the sorption nature of biochar.
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In this work, we propose a novel adaptive spatially-regularized correlation filters (ASRCF) model to simultaneously optimize the filter coefficients and the spatial regularization weight. First, this ...adaptive spatial regularization scheme could learn an effective spatial weight for a specific object and its appearance variations, and therefore result in more reliable filter coefficients during the tracking process. Second, our ASRCF model can be effectively optimized based on the alternating direction method of multipliers, where each subproblem has the closed-from solution. Third, our tracker applies two kinds of CF models to estimate the location and scale respectively. The location CF model exploits ensembles of shallow and deep features to determine the optimal position accurately. The scale CF model works on multi-scale shallow features to estimate the optimal scale efficiently. Extensive experiments on five recent benchmarks show that our tracker performs favorably against many state-of-the-art algorithms, with real-time performance of 28fps.
Recently, fog computing has gained increasing attention in processing the computing tasks of the industrial Internet of things (IIoT) with different service popularity. In task-diversified fog ...computing-enabled IIoT (F-IIoT), the mismatch between expected computing efficiency and partitioned resources on fog nodes (FNs) may pose serious traffic congestion even large-scale industrial service interruptions. The existing works mainly studied offloading which type of computing tasks into FNs, but few studies enabled smart resource partitioning of FNs. In this paper, a service popularity-based smart resources partitioning (SPSRP) scheme is proposed for fog computing-enabled IIoT. We first exploit Zipf's law to model the relationship between popularity ranks and computing costs of IIoT services. Moreover, we propose an implementation architecture of the SPSRP scheme for F-IIoT, which decouples the computing control layer from data processing layer of IIoT through a specified SPSRP controller. Besides, a mobility and heterogeneity-aware partitioning algorithm is presented for extending SPSRP scheme to seamlessly support cross-domain resources partitioning. The simulations demonstrate that the SPSRP scheme can bring notable performance improvements on delay time, successful response rate and fault tolerance for fog computing to deal with the large-scale IIoT services.
In the Mesozoic, South China was situated along the convergent margin between the Asian and Pacific plates, providing an excellent laboratory to understand the interactions between deformation, ...sedimentation and magmatism in a retroarc environment. The crustal architecture of northwest South China is displayed along the ∼600-km-long SINOPROBE deep seismic reflection profiles and reveals from east to west: (1) highly folded and truncated reflectors in the upper crust of the Yangtze Fold Zone, which correspond to thin- and thick-skinned thrust systems, and document large-scale intraplate structural imbrication and shortening; (2) a crustal-scale flat-ramp-flat structure, termed the Main Yangtze decollement, which forms a weak, viscous layer to accommodate strain decoupling and material transport in the thin- and thick-skinned systems; and (3) nearly flat-lying reflectors in the Sichuan Basin, which support interpretation of the basin as a weakly deformed depocentre. The Yangtze Fold Zone and the Sichuan Basin represent a retro-arc foreland basin system that is >800 km away from the continental-margin magmatic arc. We suggest that tectonic processes across the arc and retro-arc systems, including arc magma flare-up, basin sedimentation, retroarc thrust propagation, lithosphere underthrusting, root foundering, and extension-related magmatism were interrelated and governed mass transfer. Age data and geological relations link the tectonic processes to evolving geodynamics of the subducting Paleo-Pacific plate.
•Deep seismic profiles reveal the crustal architecture of northwest South China.•A northwest-tapering retro-arc foreland system is traced in northwest South China.•Tectonic processes in the arc-retroarc system were linked and governed mass transfer.•Intraplate processes were related to subducting geodynamics of the Paleo-Pacific plate.
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