FLUID COKING is a continuous process that thermally converts heavy hydrocarbons, such as oil sands bitumen, to lighter and higher‐value products by horizontal spray injection onto a fluidized bed of hot coke particles. The cyclone sections of commercial fluid coker reactors experience fouling during typical operation, which limits unit run lengths. The main objective of this work is to improve fluid coker reliability by proposing cyclone fouling mitigation strategies based on practical operation modifications. This study developed a process simulation in Aspen Plus to establish the combined impact of vapour‐liquid equilibrium, endothermic thermal cracking reactions, pressure changes, and overall fluid dynamics in the selected fluid coker control volumes. The hydrocarbon composition was defined by applying an assay characterization of distillation data for representative hydrocarbon streams. Case studies were performed to determine the sensitivity of the predicted temperatures and hydrocarbon condensate flow rates for: (a) the burner‐to‐fluid coker transfer line temperature; (b) the hot coke flow rate; (c) hot coke entrainment from the freeboard region; and (d) scouring coke flow rate in the horn chamber. The scouring coke flow rate was identified as the most promising process lever to mitigate fluid coker cyclone fouling. 相似文献
This research investigated how people’s perceptions of alternative water sources compare with their perceptions of other technologies, and identified significant predictors of comfort with different alternative water sources. We drew on data from four questionnaire survey studies with a total sample of more than 1200 Australian participants. Relative levels of comfort with the alternative water sources was consistent across the four studies: comfort was always highest for drinking rainwater and lowest for drinking recycled water, with comfort with drinking treated stormwater and desalinated water sitting between these two. Although comfort with drinking recycled water was always lowest of the four alternative water sources, participants were significantly more comfortable with drinking recycled water than they were with nuclear energy, or with using genetically modified plants and animals for food. In general, demographic variables were less important predictors of comfort with alternative water sources than were psychological variables; only age and gender emerged as relatively consistent predictors for recycled water, stormwater, and desalinated water, with older participants and males more comfortable with drinking these water sources. Of the psychological variables, participants’ comfort with technology in general, trust in science and trust in government emerged consistently as significant positive predictors of comfort with drinking recycled water, stormwater, and desalinated water.
Verbal protocols are the primary tool for understanding users' task-solving behaviors during usability testing. A qualitative study that examined the utility of combining a concurrent and retrospective think-aloud within the same usability test is described. The results indicate that although there was significant overlap between the types of utterances produced during each think-aloud, the retrospective phase produced more verbalizations that were relevant to usability analysis, for example, helpful self-assessments of performance, yielding insights into the impact of encountered difficulties. However, a small number of less desirable utterance types emerged: hypothesising, rationalizing, and forgetting. When used together, both methods contributed to an understanding of usability issues; the concurrent phase yielded more usability issues overall, and the retrospective data improved the understanding of these by (a) reinforcement: users highlighted the impact of an issue on their experience, (b) elaboration: users would provide causal explanations of encountered difficulties, and (c) context: users provided information about the product's context of use. 相似文献
ABSTRACT In April 2006, Alliance Library System and Online Programming for All Libraries partnered to start the Second Life Library 2.0 in the online world Second Life and in August 2006 purchased an island on the Teen grid of Teen Second Life. Second Life is a virtual world, a descendant of multiplayer online games. Educational institutions have recently been drawn into Second Life's robust economy and vibrant cultural life. The Second Life Library 2.0 works with librarians from around the world and with other educational partners such as TechSoup, WorldBridges, and the New Media Consortium. Second Life Library 2.0 provides “traditional” library services such as ready reference, book discussions, and search assistance, but, at heart, it explores what it means to be a virtual library in a virtual world. 相似文献
ABSTRACTGalleries, libraries, archives and museums (GLAMs) are increasingly using digital technologies for storytelling and creating mobile applications (apps) for cultural heritage content, but how apps are used in practice to communicate information to users has not been widely studied. A team of people from a heritage organisation, a university, and mobile app development group plan to create a bespoke heritage trail app for Ireland, but to date design conventions/recommendations for this genre are lacking. This article applies a systematic approach to digital narrative content analysis to better understand how apps are being used specifically for heritage trails with the aim of identifying what the common features are, which modalities and narrative techniques are used. The selected corpus included 55 apps downloaded from the Google Play Store. The results of this content analysis—based on the App Walkthrough Method (Light, B., Burgess, J., & Duguay, S. (2018). The walkthrough method: An approach to the study of apps. New Media & Society, 20(3), 881–900)—show that there is a gap between academic research themes/trends and how digital narrative is actually being communicated in the current market, and it aims to inform the future development of heritage trail apps by including a list of design and content features common to this genre. 相似文献
ABSTRACTIn this article, we review published literature that draws on autobiographical accounts of students' experiences learning mathematics. We summarize the main findings of the target literature and present recommendations for further research that will extend this field. Our review indicates that autobiographical and narrative methodological approaches have the potential to occasion important advances in our knowledge of students' experiences learning mathematics. However, relative to accounts of preservice teacher learning, there is a paucity of published research that documents the mathematics learning experiences of kindergarten to Grade 12 students. 相似文献
Wireless sensor networks (WSNs) deployed in hostile environments suffer from a high rate of node failure. We investigate the effect of such failure rate on network connectivity. We provide a formal analysis that establishes the relationship between node density, network size, failure probability, and network connectivity. We show that large networks can maintain connectivity despite a significantly high probability of node failure. We derive mathematical functions that provide lower bounds on network connectivity in WSNs. We compute these functions for some realistic values of node reliability, area covered by the network, and node density, to show that, for instance, networks with over a million nodes can maintain connectivity with a probability exceeding 95% despite node failure probability exceeding 53%. 相似文献
Studies have demonstrated that students prefer PowerPoint and respond favorably to classes when it is used. Few studies have addressed the physical structure of PowerPoint. In this study, students enrolled in several psychology classes on two campuses completed a 36 item questionnaire regarding their preferences for the use of PowerPoint in the classroom. Students preferred the use of key phrase outlines, pictures and graphs, slides to be built line by line, sounds from popular media or that support the pictures or graphics on the slide, color backgrounds, and to have the lights dimmed. It is recommended that professors pay attention to the physical aspects of PowerPoint slides and handouts to further enhance students’ educational experience. 相似文献