4,859 research outputs found
Numerical computation for parallel plate thermoacoustic heat exchangers in standing wave oscillatory flow
No full textA simplified computational method for studying the heat transfer characteristics of parallel plate thermoacoustic heat exchangers is presented. The model integrates the thermoacoustic equations of the standard linear theory into an energy balance-based numerical calculus scheme. Details of the time-averaged temperature and heat flux density distributions within a representative domain of the heat exchangers
and adjoining stack are given. The effect of operation conditions and geometrical parameters on the heat exchanger performance is investigated and main conclusions relevant for HX design are drawn as far as fin length, fin spacing, blockage ratio, gas and secondary fluid-side heat transfer coefficients are concerned. Most relevant is that
the fin length and spacing affect in conjunction the heat exchanger behaviour and have to be simultaneously optimized to minimize thermal losses localized at the HX-stack
junctions. Model predictions fit experimental data found in literature within 36% and 49% respectively at moderate and high acoustic Reynolds numbers
Adaptive Selbstlernaufgaben mit STACK
No full text<p>Die Beschäftigung mit Übungsaufgaben ist das wichtigste Lerninstrument für die Mathematik. An der Ruhr-Universität Bochum werden fächerübergreifend Studierenden zur eigenverantwortlichen Vor- und Nachbereitung digitale Mathematikaufgaben in einem eLearning-Kurs zum Selbststudium angeboten. Diese nutzen intensiv die Randomisierungs- und die differenzierten Feedback-Möglichkeiten des Aufgabentyps STACK. Erste Aufgaben wurden nun durch adaptive Aufgabenstellungen, die auch Zwischenschritte ermöglichen, ergänzt.</p>
Multi-step procedures in STACK tasks with adaptive flow control
No full textDigital exercises are increasingly becoming a mainstay of mathematics and engineering lectures worldwide. The time when digital tasks were only used to realize analog computational tasks with a schematic solution process and a check of the final result is long gone. In the meantime, didactically valuable and challenging tasks are being designed, with STACK taking a leading role in their realization. The further developments of STACK are correspondingly diverse and dynamic. One such further development, which is not yet part of the current STACK release, is the adaptive flow control of the solution process depending on the intermediate results in complex tasks. In this paper the technical realization is discussed, the added value is illustrated by two examples and finally an outlook on future planning is given.AlternativeReviewe
A Scenario-Based Review of IPv6 Transition Tools
No full textMomentum for IPv6 transition is on the rise, and many transition tools and techniques are available to ISPs, enterprise networks, and unmanaged networks. From a transitioning perspective, the ISP environment is interesting because the operators migration approaches will define, quite strictly, the extent of IPv6 services that their customers receive. As such, the ISPs (scalable) migration decisions have direct knock-on effects for customers. In the future, customers might require ISPs to offer value-added lPv6 services that not only have performance-based restrictions, but security and mobility considerations, as well
A portable stack-yard fence
No full textTitle from PDF caption (viewed on November 30, 2017).This archived document is maintained by the State Library of Oregon as part of the Oregon Documents Depository Program. It is for informational purposes and may not be suitable for legal purposes.Mode of access: Internet from the Oregon Government Publications Collection.Text in English
A dearth of legislative vetoes: why the Council and Parliament have been reluctant to veto Commission legislation
No full textSeveral reforms have taken place at the EU level to try and address the criticism that EU decision-making suffers from a democratic deficit. Drawing on recent research, Michael Kaeding and Kevin M. Stack assess one such reform: the provision of powers for the Council of the European Union and the European Parliament to veto so called ‘secondary legislation’ put forward by the European Commission. They find that the use of these veto powers has been extremely limited, although this does not necessarily mean the reforms have been ineffective, but rather that they may have impacted on the bargaining dynamics of informal negotiations between the institutions
Pollen-stack of combined sediment record ELSA
No full textPollen-stack of combined sediment record ELS
The green mirror image: An analysis of the self-portrayals of the German Green Party
No full textiii, 38 p.The author presents a history of the Green Party in Germany and analyzes how the party presents itself through the imagery and text of eleven posters between the years 1980 and 2016, showing the party’s evolution on key issues. The Green Party’s imagery is also compared and contrasted with the international activist group, Fridays for Future
EPA’S Value Engineering Approach for Gypsum Stack Closure
No full textEPA’s Value Engineering Approach for Gypsum Stack Closure Authors Mr. Michael Ayers - United States - Watershed Geo Mr. Craig Zeller - United States - US EPA Abstract In February 2017, US EPA Region 4 assumed responsibility for water treatment and daily operations for an unlined and open 350-acre gypsum stack located in Pascagoula, Mississippi. The gypsum stack contains approximately 15M cubic yards of phosphogypsum with elevated levels of nutrients and acidic pH. To the immediate east of the facility is one of the most biologically productive estuarine ecosystems in the Gulf of Mexico region. An uncontrolled and untreated release of contact water or leachate from the stack could have catastrophic effects on the Gulf of Mexico and its ecosystem. As a result of these potential risks, the US EPA endeavored to close the gypsum stack as quickly, cost effectively and with minimal impact to the surrounding environment. The two primary closure systems were evaluated and included a soil‐protected geomembrane cover (Traditional Cap) and synthetic turf geomembrane cover (ClosureTurf®). A value engineering study was performed to assess construction costs, operation and maintenance (O&M), environmental impacts, and constructability and ultimately resulted in the selection and installation of ClosureTurf®. The presentation will provide the results of the EPA’s study, key lessons learned from design through installation and discussion of how these same criteria apply to CCR projects
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