Ice-melt rates in liquid-filled cavities during explosive subglacial eruptions

Subglacial eruptions are often associated with rapid penetration of overlying ice and release of large flow rates of water as jökulhlaups. Observations of recent subglacial eruptions indicate rapid syn-eruptive ice melting within liquid-filled subglacial cavities, but quantitative descriptions of possible heat transfer processes need to be developed. Calculations of heat flux from the ice cavity fluid to the melting ice surface indicate that up to 0.6 MW m−2 may be obtained for fluids undergoing single-phase free convection, similar to minimum estimates of heat flux inferred from observations of recent eruptions. Our model of boiling two-phase free convection in subglacial cavities indicates that much greater heat fluxes, in the range 3–5 MW m−2, can be obtained in the vent region of the cavity and may be increased further by momentum transfer from the eruption jet. Rapid magma-water heat transfer from fragmented magma is needed to sustain these heat fluxes. Similar heat fluxes are anticipated for forced convection of subcooled cavity water induced by momentum transfer from an eruption jet. These heat fluxes approach those required to explain jökulhlaup flow rates and rapid ice penetration rates by melting in some, but not all recent eruptions

Beyond rote: Assessing mathematical thinking, not solely results

Arguably the greatest challenge in mathematics education is in fostering an understanding of what mathematicians would recognise as “mathematical thought.” Students are not encouraged to study mathematics simply to learn to answer specific questions correctly, rather to develop the transferable skills of abstraction, problem generalisation and scalability, which will be of value to a wide range of future problems. However, like many things in life – not just academia – we do not measure what we would like to, rather we measure what is easily measured and hope that this is a suitable proxy. In the case of mathematics education, this usually involves assessing only a numerical result or, at best, a numerical result along with a “show all of your working” statement. The danger of this is that we can encourage students to rely on rote learning of procedures or even results. If done well, students can obtain many correct answers (and hence usually high marks) even when their understanding of why the techniques work or where else they may be applicable is poorly developed. In this session, we will discuss some possible developments in curriculum and assessment design and how these can be tailored to minimise the potential for encouraging rote or shallow learning procedures. These will be considered in the context of many of the pressures associated with teaching a typical Australian undergraduate cohort, including both external influences (e.g. the diversity of school or tuition backgrounds students may have come from) as well as internal influences (e.g. the impacts of modern technology such as online assessment within university.) This will be an informal session with open discussion with all participants throughout. Sharing of experience, opinions and practice from all institutions is actively encouraged

Slipping between the cracks? Maximising the effectiveness of prerequisite paths in UTS Maths degrees

As with almost all degree programs at major Australian universities, the courses offered by the School of Mathematical Sciences at the University of Technology, Sydney consist of a number of individual subjects which together form several prerequisite paths. That is, certain subjects must be successfully completed by students before they may enrol in more advanced subjects in the same broad academic area. This attempts to ensure that those entering later subjects have the sufficient prior knowledge to succeed in their enrolled subjects. While this model is largely successful, it does have one potential 'loophole'. The minimum mark to pass a subject is 50%, meaning that students can potentially complete a prerequisite subject and advance through their course while demonstrating understanding of only half of the prior material. The implications of applying this pass criterion are generally poorly understood and little quantitative work has been undertaken to assess its efficiency and effectiveness. Here, we present quantitative analyses of recent (2008--2013) subject results and discuss a number of possible concerns and issues that these highlight. Furthermore, we draw conclusions and propose several future initiatives which are being used to inform future practice within the school, both in terms of subject development and assessment and also in providing targeted additional support to students whose prior subject performances suggest they may be at risk of future failure. References Belward, S., Mullamphy, D., Read, W. and Sneddon, G. Preparation of students for tertiary study requiring mathematics. ANZIAM J., 47:C840–C857, 2005. http://journal.austms.org.au/ojs/index.php/ANZIAMJ/article/view/1078 Keller, F. S., and Sherman, J. G. The Keller Plan handbook: Essays on a Personalized System of Instruction. Menlo Park, CA.: W. A. Benjamin, 1974. ISBN: 978-0805352399 Rylands, L. J. and Coady, C. Performance of students with weak mathematics in first-year mathematics and science. Int. J. Math. Edu. Sci. Tech., 40(6):741–753, 2009. doi:10.1080/00207390902914130 Tovey, J. Warning as pupils dump courses in 2-unit maths. Sydney Morning Herald, 6 November 2013. http://www.smh.com.au/national/education/warning-as-pupils-dump-courses-in-2unit-maths-20131105-2wzdm.html Varsavskya, C. Chances of success in and engagement with mathematics for students who enter university with a weak mathematics background.Int. J. Math. Edu. Sci. Tech., 41(8):1037–1049, 2010. doi:10.1080/0020739X.2010.49323

Ice-melt rates during volcanic eruptions within water-drained, low pressure subglacial cavities

Subglacial volcanism generates proximal and distal hazards including large-scale flooding and increased levels of explosivity. Direct observation of subglacial volcanic processes is infeasible; therefore, we model heat transfer mechanisms during subglacial eruptions under conditions where cavities have become depressurized by connection to the atmosphere.We consider basaltic eruptions in a water-drained, low-pressure subglacial cavity, including the case when an eruption jet develops. Such drained cavities may develop on sloping terrain, where ice may be relatively shallow and where gravity drainage of meltwater will be promoted. We quantify, for the first time, the heat fluxes to the ice cavity surface that result from steam condensation during free convection at atmospheric pressure and from direct and indirect radiative heat transfer from an eruption jet. Our calculations indicate that the direct radiative heat flux from a lava fountain (a “dry” end-member eruption jet) to ice is c. 25 kW m-2 and is a minor component. The dominant heat transfer mechanism involves free convection of steam within the cavity; we estimate the resulting condensation heat flux to be c. 250 kW m-2. Absorption of radiation froma lava fountain by steamenhances convection, but the increase in condensing heat flux is modest at c. 25 kW m-2. Overall, heat fluxes to the ice cavity surface are likely to be no greater than c. 300 kW m-2. These are comparable with heat fluxes obtained by single phase convection of water in a subglacial cavity but much less than those obtained by two-phase convection

Modelling the assembly and structure of microbial communities with applications to waste treatment strategies

The central premise of this thesis is that combining models in theoretical ecology with our newfound ability to observe and measure microbial systems will allow for a suite of laws to be developed which can describe and predict the assembly and structure of microbial communities. This would allow environmental engineers to modify and improve the design and efficiency of wastewater treatment systems. It is demonstrated here that there is significant evidence that microbial community assembly is at least partly a random process. A simple Neutral Community Model (NCM) is shown to replicate much of the variability observed in real systems as diverse as the waste water treatment plants, estuaries and the human lung. This is in contrast to the prevailing view in microbial ecology that community composition is shaped by deterministic processes. Molecular methods in microbial ecology yield very small, sometimes biased, samples from what are ostensibly very large communities. It is demonstrated, using published literature on taxa-area relationships for microorganisms that sampling effects have the capacity to significantly distort the true, underlying ecological patterns. In doing so, a potential reconciliation is offered between some seemingly contradictory published reports on the nature of taxa-area relationships for microorganisms. The effects of sampling are built directly into the NCM, which allows the model to be tested using the data which are typically collected by microbial ecologists. The model is calibrated using the taxa-abundance distribution observed in a small waterborne bacterial community housed in a bark lined tree hole in a beech tree. Using these parameters, unchanged, it is shown that the model can predict the taxa-abundance distributions and taxa-volume relationship observed in 26 other beech tree communities whose sizes span three orders of magnitude. This represents the strongest test, so far, for any biological community, microbial or otherwise, that NCMs provide a useful tool in predicting community composition

Ice-melt rates by steam condensation during explosive subglacial eruptions

Subglacial volcanism melts cavities in the overlying ice. These cavities may be flooded with meltwater or they may be fully or partially drained. We quantify, for the first time, heat transfer rates by condensation of steam on the walls and roof of a fully or partially drained subglacial eruption cavity. Our calculations indicate that heat fluxes of up to 1 MW m−2 may be obtained when the bulk vapor in the cavity is in free convection. This is considerably smaller than heat fluxes inferred from ice penetration rates in recent subglacial eruptions. Forcing of the convection by momentum transfer from an eruption jet may allow heat fluxes of up to 2 MW m−2, consistent with values inferred for the Gjálp 1996 subglacial eruption. Vapor-dominated cavities in which vapor-liquid equilibrium is maintained have thermal dynamic responses that are an order of magnitude faster than the equivalent flooded cavities

Favoritism and Corporate Law: The Confused Corporate Opportunity Doctrine in the Hyundai Motor Case

Core legal principles of U.S. corporate law are often met with perplexity in foreign jurisdictions – this is especially true when a particular principle remains controversial even in the U.S. This Article takes the corporate opportunity doctrine and examines how it has been exported to the civil law regime in Korea. Korean conglomerates such as Samsung Group and Hyundai Motor Group have become major players in the global market, but corporate law and practice in Korea have had a difficult time keeping up with the developments in the business sector. The Hyundai Motor Case demonstrates an ambitious but ill-fated attempt at adoption of U.S. corporate legal doctrine in Korea. This Article explains and analyzes the case and the new codified corporate opportunity doctrine rule in the Korean Commercial Code from a comparative perspective, and suggests that the dialogue surrounding the corporate opportunity doctrine in Korean legal and business communities are oriented in the wrong direction and that the new rule needs substantial refinement

Favoritism and Corporate Law: The Confused Corporate Opportunity Doctrine in the Hyundai Motor Case

Core legal principles of U.S. corporate law are often met with perplexity in foreign jurisdictions. This is especially true for legal principles that are controversial even in the U.S. This Article takes the corporate opportunity doctrine and examines how it has been exported to the civil law regime in Korea. Korean conglomerates such as Samsung Group and Hyundai Motor Group have become major players in the global market, but corporate law and practice in Korea have had a difficult time keeping up with developments in the business sector. The Hyundai Motor Case demonstrates an ambitious, but ill-fated, attempt at the adoption of U.S. doctrine in Korea. This Article explains and analyzes the case and the new codified corporate opportunity doctrine rule in the Korean Commercial Code from a comparative perspective, and suggests that the dialogue surrounding the corporate opportunity doctrine in Korean legal and business communities is oriented in the wrong direction and that the new rule needs substantial refinement

Favoritism and Corporate Law: The Confused Corporate Opportunity Doctrine in the Hyundai Motor Case

Core legal principles of U.S. corporate law are often met with perplexity in foreign jurisdictions. This is especially true for legal principles that are controversial even in the U.S. This Article takes the corporate opportunity doctrine and examines how it has been exported to the civil law regime in Korea. Korean conglomerates such as Samsung Group and Hyundai Motor Group have become major players in the global market, but corporate law and practice in Korea have had a difficult time keeping up with developments in the business sector. The Hyundai Motor Case demonstrates an ambitious, but ill-fated, attempt at the adoption of U.S. doctrine in Korea. This Article explains and analyzes the case and the new codified corporate opportunity doctrine rule in the Korean Commercial Code from a comparative perspective, and suggests that the dialogue surrounding the corporate opportunity doctrine in Korean legal and business communities is oriented in the wrong direction and that the new rule needs substantial refinement