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Wet oxidation of 3C-SiC on Si for MEMS processing and use in harsh environments: Effects of the film thicknesses, crystalline orientations, and growth temperatures
No full textAn in-depth understanding of the formation of silicon dioxide (SiO2) on silicon carbide (SiC) in thermal oxidation is imperative for micro/nano fabrication processes, integration of electronic components, and evaluation of SiC device performance under extreme conditions. Herein, we report a comprehensive study on the effects of crystalline orientations, thicknesses, and growth temperatures of cubic SiC films on their wet oxidation properties. The oxidation rate and surface morphology were characterized using atomic force microscopy (AFM) and light reflectance measurement systems. Our experimental results revealed the role of defects in the SiC crystal on the oxidation that relates to SiC thickness, deposition conditions, crystal orientation and temperature of wet oxidation. Critically, the electrical properties of SiC films oxidized at 900 °C remained the same as the unoxidized film as confirmed by room-temperature current-voltage measurements, indicating a long-term service temperature of SiC. These findings are expected to provide crucial information on the effects of defects on the formation of SiO2\ua0on SiC films at different oxidation temperatures, which is highly essential for establishing a basic platform for the fabrication of high-performance SiC-based electronic devices
Callback2Vec: Callback-aware hierarchical embedding for mobile application
No full textAlthough numerous embedding approaches have been proposed for code representation of mobile applications, insufficient attention has been paid to its essential running nature: event-driven. As a result, the contextual semantics of event-driven callbacks re hardly captured. Existing solutions either discard the information of event callbacks such as their sequences, or simply treat event callbacks as ordinary APIs. Both of the solutions deviate from the actual running behavior of the applications and thus suffer from critical information loss of the callback contexts. To address the problem, in this paper, a callback based hierarchical embedding approach Callback2Vec is proposed, in which ordinary APIs and callbacks are distinguished and tackled at different levels in a top-down fashion. As such, the contextual semantics of callbacks can be reasonably represented by the embedding vectors. In particular, a fine-grained callback-sequence-generation algorithm is devised to capture the running behavior of callbacks. To evaluate the representation capability of Callback2Vec, a systematic analysis targeting at the embedding results is conducted, whereby the conventional embedding characteristics are rigorously investigated and new implications are identified. Of significance, the proposed embedding approach has been validated to be capable of providing novel solutions for typical downstream applications, through comprehensive experiments with large scale public datasets
Influences of negative pressure on air-leakage of coalseam gas extraction: Laboratory and CFD-DEM simulations
No full textComprehensive understandings of the influences of negative pressure on air-leakage and its driving mechanism are critical for controlling methane concentration during coal seam gas extraction. Laboratory experiments were conducted using an integrated apparatus to study the air-leakage process of coal seam gas extraction under different negative pressures. In addition, a coupled computational fluid dynamics-discrete element approach was used to simulate the process of air flow and particle transport in a natural coal fracture to understand the influential mechanism of negative pressure on air-leakage at the mesoscale. Experimental results show that with an increase in the absolute value of negative pressure, the air-leakage experiences three stages of increase, decrease and increase at Stage I, Stage II and Stage III, respectively. It is reported for the first time and in good agreement with field test data. From experimental and numerical results, at Stage I the air-leakage increases with the absolute value of negative pressure because there is no blockage in fractures around borehole. At Stage II, the further increased absolute value of negative pressure contributes to particles motion in fractures. It gradually leads to the formation of blockage structure composed of aggregated particles in fractures, and the decrease of fracture conductivity and air velocity. With the absolute value of negative pressure rising continuously, the contact forces between the aggregated particles increase. Therefore, the balance of the blockage structure tends to be broken, which helps to understand the air-leakage increase with the absolute value of negative pressure at Stage III. Between Stage II and Stage III, there is a valley point corresponding to the minimum air-leakage, which is important to the improvement of gas extraction performance. The contact forces on the aggregated soft particles are larger than those on the aggregated hard particles under the same negative pressure. Therefore, the blockage structure consisting of soft particles is much easier to be broken than that formed by hard particles. This explains why the absolute value of negative pressure corresponding to the valley point for hard coal model is larger than that for the soft coal model
Changes in global protein expression in sea turtle cells exposed to common contaminants indicates new biomarkers of chemical exposure
No full textNon-targeted protein expression at the cellular level can provide insights into mechanistic effects of contaminants in wildlife, and hence new and potentially more accurate biomarkers of exposure and effect. However, this technique has been relatively unexplored in the realm of in vitro biomarker discovery in threatened wildlife, despite the vulnerability of this group of animals to adverse sublethal effects of contaminant exposure. Here we examined the usefulness of non-targeted protein expression for biomarker discovery in green sea turtles (Chelonia mydas) by investigating differences in the response of primary cells from five different tissue types that were exposed to three contaminants known to accumulate in this species. Cells derived from C. mydas skin, liver, kidney, ovary and small intestine were exposed to 100 μg/L of either polychlorinated biphenyl 153 (PCB153), perfluorononanoic acid (PFNA) or phenanthrene for 24 h. The global protein expression was then quantitatively evaluated using sequential window acquisition of all theoretical mass spectra (SWATH-MS). Comparison of the global protein profiles revealed that, while a majority of proteins were mutually expressed in controls of all tissue types (~90%), the response to exposure in terms of protein expression strength was significantly different between tissue types. Furthermore, a comparison to known markers of chemical exposure in sea turtles from the literature indicated that in vitro response can reflect known in vivo responses. In particular, markers such as heat shock protein (HSP) 60, glutathione S-transferases (GSTs) and superoxide dismutases (SODs), cytochrome P450 and catalase were dysregulated in response to exposure. Furthermore, potential new markers of exposure were discovered such as annexin, an important protein in cell signalling processes. While this methodology proved promising further studies are required to confirm the accuracy of in vitro protein expression as a tool for biomarker discovery in wildlife
Betting on Bitcoin: how social collectives shape cryptocurrency markets
No full textMarket-shaping research assumes that firms are the primary actor to lead, manage, and respond to the formation of markets. This viewpoint is increasingly being challenged, but empirical insights explaining the roles, resources and actions of actors other than firms shaping markets remain limited. We address this gap in knowledge by drawing on insights from an in-depth ethnography of market-shaping in the context of cryptocurrency communities. Our theoretical and empirical contributions consist of a typology that highlights four distinct roles performed by individuals shaping cryptocurrency markets. We furthermore identify six micro-level market actions, and delineate a novel theoretical model and propositions outlining the pathways with which these actions impact market size, market offerings, as well as market functioning. This study thereby establishes an important avenue for future research, and offers managerial guidelines enabling practitioners attempting to benefit from cryptocurrencies
The effectiveness of advertising images in promoting experiential offerings: an emotional response approach
No full textThis research examines the role of advertising images in promoting experiential offerings. In particular, it investigates the congruence effect between the emotional responses evoked by advertising images and experiential offerings on consumers’ purchase likelihood in the tourism context. This congruence effect is tested in a series of four experimental studies using different advertising stimuli and manipulations of perceived certainty associated with the offerings. The findings show that advertising images eliciting awe have a more positive impact on purchase likelihood when combined with an experiential offering communicating a low level of certainty, whereas advertising images eliciting contentment have a more positive impact on purchase likelihood when combined with an experiential offering communicating a high level of certainty. Both the theoretical and managerial implications of the findings are discussed
Ecological restoration is not sufficient for reconciling the trade-off between soil retention and water yield: A contrasting study from catchment governance perspective
No full textEcological restoration program (ERP) is widely recognized as an effective measure to combat land degradation and improve environmental quality. However, inappropriate ERPs lead to trade-offs between soil retention and water yield as well as conflicts of soil and water resources between the midstream and the downstream of catchment. This study aims to assess the efficiency of ERPs in soil erosion control and identify the trade-offs between soil retention and water yield through the lens of runoff and sediment regimes in contrasting catchments of the Loess Plateau (LP) and the Karst Plateau (KP). Although favorable climate and rapid vegetation restoration substantially reduced water erosion in both these areas, the hydrological responses were not the same because of climate differences. In the arid LP, water and energy variables correlated closely with vegetation cover. Excessive afforestation programs in drylands increased vegetation transpiration and soil evaporation, further exhausting soil water resources, and eventually causing water yield reduction. However, soil and water conservation programs (SWCPs) in the humid KP reduced sediment yield substantially, and the runoff remained stable. Significant runoff reduction in the midstream of the Yellow River aggravated water scarcity and threatened the downstream water demand. Meanwhile, sediment load decline in the LP and the KP impacted sediment deposition in the downstream and estuary formation. From the perspective of integrated catchment governance, human interventions including ERP and SWCP should be more sustainable and consider not only the target process at the local scale (intracoupling effect), but also unprecedented non-target process at the regional scale (telecoupling effect). In addition, it should allow for the supply-demand balance of competing soil and water resources to achieve the coordinated development of resources, environment, and production
Biodegradable Zn–3Cu and Zn–3Cu–0.2Ti alloys with ultrahigh ductility and antibacterial ability for orthopedic applications
No full textZinc (Zn) and its alloys have been proposed as biodegradable implant materials due to their unique combination of biodegradability, biocompatibility, and biofunctionality. However, the insufficient mechanical properties of pure Zn greatly limit its clinical application. Here, we report on the microstructure, mechanical properties, friction and wear behavior, corrosion and degradation properties, hemocompatibility, and cytocompatibility of Zn–3Cu and Zn–3Cu–0.2Ti alloys under three different conditions of as-cast (AC), hot-rolling (HR), and hot-rolling plus cold-rolling (HR + CR). The HR + CR Zn–3Cu–0.2Ti exhibited the best set of comprehensive properties among all the alloy samples, with yield strength of 211.0 MPa, ultimate strength of 271.1 MPa, and elongation of 72.1 %. Immersion tests of the Zn–3Cu and Zn–3Cu–0.2Ti alloys in Hanks’ solution for 3 months indicated that the AC samples showed the lowest degradation rate, followed by the HR samples, and then the HR + CR samples, while the HR + CR Zn–3Cu exhibited the highest degradation rate of 23.9 μm/a. Friction and wear testing of the Zn–3Cu and Zn–3Cu–0.2Ti alloys in Hanks’ solution indicated that the AC samples showed the highest wear resistance, followed by the HR samples, and then the HR + CR samples, while the AC Zn–3Cu–0.2Ti showed the highest wear resistance. The diluted extracts of HR + CR Zn–3Cu and Zn–3Cu–0.2Ti at a concentration of ≤25 % exhibited non-cytotoxicity. Furthermore, both the HR + CR Zn–3Cu and Zn–3Cu–0.2Ti exhibited effective antibacterial properties against S. aureus
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