Academic literature on the topic 'Catastrophic melting'
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Journal articles on the topic "Catastrophic melting"
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Kokelaar, Peter. "Friction melting, catastrophic dilation and breccia formation along caldera superfaults." Journal of the Geological Society 164, no. 4 (July 2007): 751–54. http://dx.doi.org/10.1144/0016-76492006-059.
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Grund, Brigid Sky, and Snehalata V. Huzurbazar. "RADIOCARBON DATING OF TECHNOLOGICAL TRANSITIONS: THE LATE HOLOCENE SHIFT FROM ATLATL TO BOW IN NORTHWESTERN SUBARCTIC CANADA – ERRATUM." American Antiquity 83, no. 1 (January 2018): 184. http://dx.doi.org/10.1017/aaq.2017.72.
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The author affiliations appearing in Grund and Huzurbazar (2017) contain errors. The correct affiliations for the authors are as follows: Brigid Sky Grund ▪ Anthropology Department, University of Wyoming, Department 3431, 1000 E. University Avenue, Laramie, Wyoming 82071-2001.Snehalata V. Huzurbazar ▪ Department of Biostatistics, West Virginia University, P.O. Box 9190, One Medical Center Drive, Morgantown WV 26506, USA.Additionally, the sentence on page 5 reading, “Catastrophic melting events create palimpsest the upper layers of ice (Meulendyk et al. 2012), potentially introducing taphonomic bias” inadvertently omitted two words. The correct sentence is “Catastrophic melting events create a palimpsest in the upper layers of ice, potentially introducing taphonomic bias.”The publisher apologizes for these errors.
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Karasev, Valentin Petrovich, Sergey Vladimirovich Ryaboshuk, Pavel Valer'evich Kovalev, and Vitaliy Kulikov. "Phosphorus Removal Options at Induction Melting of Steel." Key Engineering Materials 822 (September 2019): 30–36. http://dx.doi.org/10.4028/www.scientific.net/kem.822.30.
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The main aspects of effective dephosphorization of steel under conditions of induction melting are presented. Regularities of scale growth on the surface of iron, as well as the conditions of its catastrophic oxidation, are considered. An industrial experiment was conducted to remove phosphorus from steel intended for brake discs.
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Bengus(a),, V. Z., E. D. Tabachnikova(a),, S. E. Shuinilin(a),, K. Csach(b),, P. Duhaj(c),, and J. Mishkuf(b),. "Local Melting in the Catastrophic Shear Band of Amorphous Alloy Ribbons." Journal of the Mechanical Behavior of Materials 5, no. 3 (June 1994): 315–24. http://dx.doi.org/10.1515/jmbm.1994.5.3.315.
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MacAyeal, Douglas R., and Olga V. Sergienko. "The flexural dynamics of melting ice shelves." Annals of Glaciology 54, no. 63 (2013): 1–10. http://dx.doi.org/10.3189/2013aog63a256.
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AbstractA conspicuous precursor of catastrophic ice-shelf break-up along the Antarctic Peninsula, reported widely in the literature, is the gradual increase in surface melting and consequent proliferation of supraglacial lakes and dolines. Here we present analytical and numerical solutions for the flexure stresses within an ice shelf covered by lakes and dolines, both isolated and arrayed. We conclude that surface water promotes ice-shelf instability in two ways: (1) by water-assisted crevasse penetration, as previously noted, and (2) by the inducement of strong tensile flexure stresses (exceeding background spreading stress by 10–100 times) in response to surface water mass loads and ‘hydrostatic rebound’ occurring when meltwater lakes drain.
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Sung, Si Young, and Young Jig Kim. "Melting and Casting of Titanium Alloys." Materials Science Forum 539-543 (March 2007): 3601–6. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.3601.
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Over the past decades, a large number of researchers have been trying titanium alloys in an attempt to combine most of their advantages, such as high specific yield strength, good corrosion resistance, excellent fatigue property and biocompatibility by casting route. However, the wide use of titanium alloys casting has been limited, since it is considered as only a near net shape forming process in titanium alloys due to the catastrophic reactivity of molten states, the alpha-case formations and the casting defects. In order to maximize the unique property of titanium alloys casting which are comparable to wrought products and quite often superior, it is necessary to take a close examination of titanium alloys casting procedure. Therefore, the merits and demerits of various melting devices, pouring methods and mold materials will be addressed with regard to improving titanium alloys casting.
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Akstinas, Vytautas, Diana Meilutytė-Lukauskienė, Jūratė Kriaučiūnienė, and Diana Šarauskienė. "Features and causes of catastrophic floods in the Nemunas River basin." Hydrology Research 51, no. 2 (July 18, 2019): 308–21. http://dx.doi.org/10.2166/nh.2019.147.
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Abstract The Nemunas River basin falls within the territories of five different countries – Belarus, Lithuania, Russia, Poland and Latvia. In general, the beginning of spring floods highly depends on rapid rise of air temperature, heavy precipitation and sudden snow melting in the analysed basin. In this paper, the conditions of formation and consequences of two catastrophic floods in 1958 and 1979 in the Nemunas River basin were studied regarding the hydrometeorological parameters (maximum snow water equivalent before the beginning of flood and precipitation amount during the flood) as well as runoff coefficients for each selected catastrophic flood. Differences between the main drivers and evolution of these floods were analysed. Spatial distribution of maximum snow water equivalent and precipitation, as well as runoff coefficient in different parts of the river basin, were identified as having the most significant impact on the formation of the studied catastrophic floods.
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Blown, Iain, and Michael Church. "Catastrophic lake drainage within the Homathko River basin, British Columbia." Canadian Geotechnical Journal 22, no. 4 (November 1, 1985): 551–63. http://dx.doi.org/10.1139/t85-075.
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Three distinct phenomena related to sudden lake drainage, which occurred in a restricted area within the southern Coast Mountains of British Columbia, are described: (i) moraine breaching by solitary wave action following an icefall into a lake; (ii) failure of a glacier ice dam by flotation and melting to produce a ‘glacier outburst’ flood or ‘jökulhlaup;’ (iii) debris torrent following a moraine breach. The possibility for a fourth failure phenomenon: moraine failure by piping, is discussed. A first attempt to develop practical hazard evaluation methods before the event, which relies on simple scale relations or index relations developed from experience of events elsewhere, is presented. Key words: dam break, debris flow, hazard evaluation, jökulhlaup, lakes, lake drainage.
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Gladish, Carl V., David M. Holland, Paul R. Holland, and Stephen F. Price. "Ice-shelf basal channels in a coupled ice/ocean model." Journal of Glaciology 58, no. 212 (2012): 1227–44. http://dx.doi.org/10.3189/2012jog12j003.
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AbstractA numerical model for an interacting ice shelf and ocean is presented in which the ice- shelf base exhibits a channelized morphology similar to that observed beneath Petermann Gletscher’s (Greenland) floating ice shelf. Channels are initiated by irregularities in the ice along the grounding line and then enlarged by ocean melting. To a first approximation, spatially variable basal melting seaward of the grounding line acts as a steel-rule die or a stencil, imparting a channelized form to the ice base as it passes by. Ocean circulation in the region of high melt is inertial in the along-channel direction and geostrophically balanced in the transverse direction. Melt rates depend on the wavelength of imposed variations in ice thickness where it enters the shelf, with shorter wavelengths reducing overall melting. Petermann Gletscher’s narrow basal channels may therefore act to preserve the ice shelf against excessive melting. Overall melting in the model increases for a warming of the subsurface water. The same sensitivity holds for very slight cooling, but for cooling of a few tenths of a degree a reorganization of the spatial pattern of melting leads, surprisingly, to catastrophic thinning of the ice shelf 12 km from the grounding line. Subglacial discharge of fresh water along the grounding line increases overall melting. The eventual steady state depends on when discharge is initiated in the transient history of the ice, showing that multiple steady states of the coupled system exist in general.
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Ahmad, Hafiz Haroon, Farhan Saleem, and Hania Arif. "Evaluation of catastrophic global warming due to coal combustion." Vol 3 Issue 4 3, no. 4 (December 31, 2021): 198–207. http://dx.doi.org/10.33411/ijist/2021030406.
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Coal is a carbon containing non-renewable fossil fuel and one of the major contributors of climate change and global warming. We used TANSO FTS instrument in order to obtain the level of atmospheric carbon dioxide through datasets obtained from GOSAT satellite. GIOVANNI was also used to obtain atmospheric concentration of various gases. Burning of coal causes emission of greenhouse gases (GHG) and black carbon (BC) in atmosphere which are responsible for nearly 0.3°C of 1°C rise in temperature. The annual average value of carbon emission for the year 2010 and 2019 is 388.4 ppm and 409 ppm respectively. Since the pre-industrial times CO2 concentrations have increased up to100 PPM (36%) in the last two and a half centuries (250 years).In South Asia Dhaka has the worst quality of air as CO2 concentration (6.7%) is higher than the country’s GDP (5.25%) and energy consumption (4.77%). While an increasing trend GHG has been observed in Lahore up to 5.5 %. This study concludes that the high concentration of carbon dioxide in atmosphere is responsible for average rise of 1.2 °C temperature annually. This temperature rise can lead to adverse climatic conditions i.e., melting of glaciers which will consequently rise the sea level various landmasses may disappear by 2050.
Dissertations / Theses on the topic "Catastrophic melting"
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Bockmann, K. L. "From Greenschist to Granulite: a mineral equilibria approach to melting and melt loss." Thesis, 2015. http://hdl.handle.net/2440/117961.
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This item is only available electronically.Melt loss during regional high-grade metamorphism has important consequences for interpreting the metamorphic evolution of the lower crust and for understanding processes leading to the chemical differentiation of the crust. However, melt loss typically modifies the protolith; making it difficult to reconstruct the conditions of prograde metamorphism and the extent to which melt loss modified the rock composition. The Reynolds Range in central Australia preserves a rare example where a single melt-prone stratigraphic unit can be traced from greenschist to granulite grade conditions. Using this as a natural laboratory, P–T mineral equilibria forward models have been calculated to explore melt loss and melt reintegration where both the protolith and the residuum compositions are preserved. Incremental melt loss modelling from the protolith composition along an isobaric heating path at 5 kbar shows that the residual granulite facies rock composition is consistent with around 18% melt loss from the protolith. Large-scale, one-step melt loss from a closed rock system that had built up 18% melt resulted in a similar residual composition to incremental melt loss. The fertility of the open (incremental) system and the closed system showed the closed system produced 5.4% more melt along a heating path from 700–800 °C. Determination of the concentrations of K–U–Th with increasing metamorphic grade shows that K and U concentrations decreased with increasing metamorphic grade. Conversely, Th concentrations increased, resulting in a slight overall increase in heat production from the protolith to the residuum, despite around 18% volume loss associated with melt extraction. An implication for this is that for melt prone rocks such as metapelites, melt loss during granulite facies metamorphism does not deplete the concentration of heat producing elements in the lower crust as is typically assumed.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2015
Books on the topic "Catastrophic melting"
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Taillant, Jorge Daniel. Glaciers. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780199367252.001.0001.
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Though not traditionally thought of as strategic natural resources, glaciers are a crucial part of our global ecosystem playing a fundamental role in the sustaining of life around the world. Comprising three quarters of the world's freshwater, they freeze in the winter and melt in the summer, supplying a steady flow of water for agriculture, livestock, industry and human consumption. The white of glacier surfaces reflect sunrays which otherwise warm our planet. Without them, many of the planet's rivers would run dry shortly after the winter snow-melt. A single mid-sized glacier in high mountain environments of places like California, Argentina, India, Kyrgyzstan, or Chile can provide an entire community with a sustained flow of drinking water for generations. On the other hand, when global temperatures rise, not only does glacier ice wither away into the oceans and cease to act as water reservoirs, but these massive ice bodies can become highly unstable and collapse into downstream environments, resulting in severe natural events like glacier tsunamis and other deadly environmental catastrophes. But despite their critical role in environmental sustainability, glaciers often exist well outside our environmental consciousness, and they are mostly unprotected from atmospheric impacts of global warming or from soot deriving from transportation emissions, or from certain types of industrial activity such as mining, which has been shown to have devastating consequences for glacier survival. Glaciers: The Politics of Ice is a scientific, cultural, and political examination of the cryosphere -- the earth's ice -- and the environmental policies that are slowly emerging to protect it. Jorge Daniel Taillant discusses the debates and negotiations behind the passage of the world's first glacier-protection law in the mid-2000s, and reveals the tension that quickly arose between industry, politicians, and environmentalists when an international mining company proposed dynamiting three glaciers to get at gold deposits underneath. The book is a quest to educate general society about the basic science behind glaciers, outlines current and future risks to their preservation, and reveals the intriguing politics behind glacier melting debates over policies and laws to protect the resource. Taillant also makes suggestions on what can be done to preserve these crucial sources of fresh water, from both a scientific and policymaking standpoint. Glaciers is a new window into one of the earth's most crucial and yet most ignored natural resources, and a call to reawaken our interest in the world's changing climate.
Book chapters on the topic "Catastrophic melting"
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Zank, Wolfgang. "The First World War — The Primary Catastrophe of the Century." In The German Melting-Pot, 139–42. London: Palgrave Macmillan UK, 1998. http://dx.doi.org/10.1057/9780230375208_12.
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V. Lebedeva, Ekaterina. "Catastrophic Processes in River Valleys of Volcanic Regions: Geomorphologist’s Point of View." In Updates in Volcanology - Linking Active Volcanism and the Geological Record [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.108141.
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The river valleys located in volcanic regions are prone to various catastrophic processes, including those catalyzed by eruptions. First, to be mentioned among them are volcanic mudflows known as lahars. They commonly result from melting of ice, snow on the mountaintop, and rainfalls immediately following the eruption. This sequence of catastrophic events—“eruption-volcanic mudflow”—is quite common and has been well studied. When viewed closely the mud and debris flow in the volcanic regions appears to be brought on by various causes, with many factors and agents involved. Quite commonly, an eruption triggers not a single endo- or exogenic event, but a sequence of interrelated catastrophes following one after another. The studied cases allow identifying and describing up to two tens of probable scenarios—successions of catastrophic events in river valleys of the volcanic regions. The specific chain in any particular case depends on volcanic activities and accompanying events, such as seismic shocks, changes in local topography, hydrothermal activity, and erosion. The river valleys and adjoining areas are the most hazardous and vulnerable areas within as much as a few kilometers from the eruption center as the erupted material tends to accumulate in valleys and rapidly transported downstream.
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Knapp Haraldsen, Trond. "Flood Damage on Agricultural Land and Methods for Restoration of Agricultural Soils after Catastrophic Floods in Cold Areas." In Floods - Understanding Existing and Emerging Risk Drivers in a Climate Change Context [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.109111.
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Catastrophic floods have large effect on agricultural land both in short and long term. In this chapter, examples of impact of floods of different size in cold regions with glaziers have been presented. The largest floods occur as combination of heavy rainfall and melting and snow and ice in the mountainous areas. Periods of waterlogging by cold running water resulted in decreased yields, but N-fertilization after the soil no longer was water saturated could reduce the yield loss considerably. Although the floods cause severe erosion and sedimentation, results show that it is possible to find measures for reconstruction of the soils with the same productivity as undamaged soils, while the average result was about 85% of the original productivity.
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Mallon, Christopher, Shai Y. Waisman, and Ray C. Schrock. "Emergency Sales in the US and the UK." In The Law and Practice of Restructuring in the UK and US. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198755395.003.0002.
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Any business that relies on confidence in its financial position, its brand name or goodwill, talented (but mobile) employees, or short-term contracts with customers or counterparties will be particularly hard hit by suggestions that it is or may soon be experiencing financial distress. Businesses of this type have been likened to ‘melting ice cubes’—once exposed to the heat of potential insolvency, value in the business melts away rapidly as customers and counterparties look to terminate relationships, key employees look to exit, and the goodwill and brand name of the business become tarnished. The catastrophic and rapid collapse during 2008 of famous Wall Street and the City of London names illustrated this in dramatic fashion, but businesses of almost every type will suffer negative effects once financial difficulties become more widely known.
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Gómez García, Wendy C., and Marleni R. Torres Núñez. "Cultural-Spiritual Guidance in Caring for Cancer Patients in the Dominican Republic, Dominican Republic." In Global Perspectives in Cancer Care, 446–53. Oxford University Press, 2022. http://dx.doi.org/10.1093/med/9780197551349.003.0044.
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The Dominican Republic is a melting pot of races and cultures. Its people perceive the diagnosis of cancer largely as a catastrophic event, not only from a scientific perspective but also from a magical/religious syncretism. Historically, the Dominican Republic has been influenced by dictatorial regimens (as have other Latin American countries), furthering the doctrine of medical paternalism to current generations. Its medical system strives daily to improve clinical protocols that would offer adequate psychosocial support for patients and their families. Still, many believe that a cure is contingent upon religious deities, and they are always hoping for some miracle or supernatural occurrence to intervene, regardless of their actual condition or stage of disease. Physicians in the Dominican Republic analyze all the clinical elements and sociocultural beliefs of their patients in an effort to offer appropriate interventions and search for better prognoses. National cancer care programs are encouraged to coordinate with the existing reality of the country, respecting family customs, faith, and beliefs which, far from being rejected, must be integrated into the psychoemotional vision of treatment, utilizing them as holistic supplements that contribute to the patient’s and their family’s strength and emotional support throughout the disease process.
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Hallam, Tony. "Climate change." In Catastrophes and Lesser Calamities. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780198524977.003.0010.
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Unlike the other factors that have been invoked to account for mass extinctions, climate change is manifest to us all, whether we travel from the tropics to the poles or experience the seasonal cycle. Over a longer timescale, the issue of global warming in the recent past and likely future, and its probable consequences for other aspects of the environment, has occupied a considerable amount of media attention. Those people who are unaware of the likely consequences of the burning of fossil fuels cannot count themselves as well educated. Over a longer timescale, geologists have been aware for many decades of significant climatic changes on a global scale leading to the appearance and disappearance of polar ice caps on a number of occasions. Steve Stanley, the distinguished palaeobiologist at Johns Hopkins University in Baltimore, has actively promoted the view that episodes of climatic cooling are the most likely cause of mass extinctions. However, we must consider also the significance of global warming, and for the continents, at any rate, the possible effects of changes in the humidity–aridity spectrum. Before examining the relationships between climatic change and mass extinctions we need to examine the criteria from the stratigraphic record that geologists use to determine ancient climates, or palaeo-climates. The most obvious way of detecting cold conditions in the past is to find evidence of the presence of ice. At the present day the sedimentary deposits associated with glaciers and ice sheets, which occur where melting ice dumps its rock load, range in grain size from boulders and pebbles to finely ground rock flour. Such deposits are known as boulder clay or till, and ancient examples consolidated into resistant rock as tillites. The surfaces of hard rock that have underlain substantial ice sheets bear characteristic linear striations indicating the former direction of ice movement, such as glaciers moving up or down a U-shaped valley. The striations are produced by pebbles embedded in the ice, and are a unique marker for glacial action. In the 1830s Louis Agassiz, the great Swiss naturalist, extrapolated from his knowledge of the margins of Alpine glaciers to propose that the whole of northern Europe had been covered by one or more ice sheets in the recent geological past.
Conference papers on the topic "Catastrophic melting"
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Ogura, Takahito, Junya Nakata, Mititsugu Mori, Hiroto Sakashita, and Shuichiro Miwa. "Performance Evaluation of SCS for AHTR and Time Assessment of Operation Procedures." In 2014 22nd International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/icone22-30790.
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The Advanced High-Temperature Reactor (AHTR) is a new nuclear power reactor concept being investigated in some countries including the United States. The coolant is a liquid salt with a melting point of 460°C and a boiling point of 1430°C. The AHTR uses Silo Cooling System (SCS) as the decay heat removal system in a Beyond-Design-Basis Accident (BDBA). SCS has two accident mitigations. The first component is low-cost, and thick steel rings which conduct heating up the silo wall for BDBA. The second component is an annular ring of an inexpensive, solidified BDBA salt, which is heated from the bottom and melts when the temperature of the salt increases above the melting point, then flows into the silo, and floods the whole silo to its top level. SCS could make AHTR free from catastrophic accidents, where core melting or vessel failure never takes place since the BDBA salt near the top of silo passively absorbs decay heat. On the other hand, AHTR decreases its heat removal ability to avoid freezing of the salt and blocking the flow of the liquid when the temperatures are low. We performed the numerical calculation of AHTR heat removal system and evaluated whether it has the ability to remove decay heat with the robustness for a long-time cooling operation after BDBA. Furthermore, we need to build up and optimize the operation plan of SCS in AHTR, taking its thermal characteristics of this system into account. It is essential to avoid severe accidents which we can suppose as the possible catastrophic scenario. In this paper, we calculated temperature distributions using the thermal-hydraulics code developed for AHTR, and assessed the performance in a long term cooling period under BDBA conditions. Finally, we investigated the temperature distributions of the whole plant, predicting the accident scenario without air-cooled passive decay heat-removal system. We obtained important conclusion about SCS of the AHTR that its heat removal ability was enough to avoid catastrophic accidents under Loss of Heat Sink (LOHS) conditions.
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Patil, Sandeep, Siddarth Chintamani, James Grisham, Ratan Kumar, and Brian H. Dennis. "Inverse Determination of Temperature Distribution in Partially Cooled Heat Generating Cylinder." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-52124.
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Inverse determination of the temperature distribution in the interior of a solid has been an area of interest in recent years. Conventional measurement devices, such as thermocouples or pyrometers, cannot be used to determine the interior temperature, but they can be used to determine the surface temperature. From this surface temperature, the temperature distribution in the interior can be estimated using an inverse method. If the maximum temperature is more than melting point of material then it may result in catastrophic accidents for some particular applications like nuclear fuel rods. Thus, knowledge of the temperature distribution on the interior is important. In this paper, numerical solution approach involving finite volume method along with MATLAB Optimization Toolbox is used to determine the temperature distribution in the interior of a solid object.
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De Los Santos, Nancy, Robert Jones, Constantine M. Tarawneh, Arturo Fuentes, and Anthony Villarreal. "Development of Prognostic Techniques for Surface Defect Growth in Railroad Bearing Rolling Elements." In 2017 Joint Rail Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/jrc2017-2262.
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Prevention of bearing failures which may lead to catastrophic derailment is a major safety concern for the railroad industry. Advances in bearing condition monitoring hold the promise of early detection of bearing defects, which will improve system reliability by permitting early replacement of failing components. However, to minimize disruption to operations while providing the maximum level of accident prevention that early detection affords, it will be necessary to understand the defect growth process and try to quantify the growth speed to permit economical, non-disruptive replacement of failing components rather than relying on immediate removal upon detection. The study presented here investigates the correlation between the rate of surface defect (i.e. spall) growth per mile of full-load operation and the size of the defects. The data used for this study was acquired from defective bearings that were run under various load and speed conditions utilizing specialized railroad bearing dynamic test rigs operated by the University Transportation Center for Railway Safety (UTCRS) at the University of Texas Rio Grande Valley (UTRGV). Periodic removal and disassembly of the railroad bearings was carried out for inspection and defect size measurement and documentation. Castings were made of spalls using low-melting, zero shrinkage Bismuth-based alloys so that a permanent record of the full spall geometry could be retained. Spalls were measured using optical techniques coupled with digital image analysis and also with a manual coordinate measuring instrument with the resulting field of points manipulated in MatLab™ and Solidworks™. The spall growth rate in area per mile of full-load operation was determined and, when plotted versus spall area, clear trends emerge. Initial spall size is randomly distributed as it depends on originating defect depth, size, and location on the rolling raceway. The growth of surface spalls is characterized by two growth regimes with an initial slower growth rate which then accelerates when spalls reach a critical size. Scatter is significant but upper and lower bounds for spall growth rates are proposed and the critical dimension for transition to rapid spall growth is estimated. The main result of this study is a preliminary model for spall growth which can be coupled to bearing condition monitoring tools to permit economical scheduling of bearing replacement after the initial detection of spalls.
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Burra, K. G., and A. K. Gupta. "Isothermal Splitting of CO2 to CO Using Cobalt-Ferrite Redox Looping." In ASME 2020 Power Conference collocated with the 2020 International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/power2020-16960.
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Abstract Rising atmospheric CO2 levels from significant imbalance between carbon emissions from fossil fuel utilization, especially for energy and chemicals, and natural carbon sequestration rates is known to drive-up the global temperatures and associated catastrophic climate changes, such as rising mean sea level, glacial melting, and extinction of ecosystems. Carbon capture and utilization techniques are necessary for transition from fossil fuel infrastructure to renewable energy resources to help delay the dangers of reaching to the point of positive feedback between carbon emissions and climate change which can drive terrestrial conditions to uninhabitable levels. CO2 captured from the atmosphere directly or from flue gases of a power plant can be recycled and transformed to CO and syngas for use as energy and value-added chemicals. Utilizing renewable energy resources to drive CO2 conversion to CO via thermochemical redox looping can provide a carbon negative renewable energy conversion pathway for sustainable energy production as well as value-added products. Substituted ferrites such as Co-ferrite, Mnferrite were found to be promising materials to aid the conversion of CO2 to CO at lower reduction temperatures. Furthermore, the conversion of these materials in the presence of Al2O3 provided hercynite cycling, which further lowered the reduction temperature. In this paper, Co-ferrite and Co-ferrite-alumina prepared via co-precipitation were investigated to understand their potential as oxygen carriers for CO2 conversion under isothermal redox looping. Isothermal reduction looping provided improved feasibility in redox conversion since it avoids the need for temperature swinging which improves thermal efficiency. These efforts alleviates the energy losses in heat recovery while also reducing thermal stresses on both the materials and the reactor. Lab-scale testing was carried out at 1673 K on these materials for extended periods and multiple cycles to gain insights into cyclic performance and the feasibility of sintering, which is a common issue in iron-oxide-based oxygen carriers. Cobalt doping provided with lowering of reduction temperature requirement at the cost of oxidation thermodynamic spontaneity that required increased oxidation temperature. At the concentrations examined, these opposing phenomenon made isothermal redox operation feasible by providing high CO yields comparable to oxygen carriers in the literature, which were operated at different temperatures for reduction and oxidation. Significantly high CO yields (∼ 750 μmol/g) were obtained from Co-ferrite isothermal redox looping. Co-ferrite-alumina provided lower CO yields compared to Co-ferrite. The oxygen storage was similar to those reported in the literature on isothermal H2O splitting, but with improved morphological stability at high temperature, especially compared to ferrite. This pathway of oxygen carrier development is considered suitable with further requirement in optimization for scaling of renewable CO2 conversion into valuable products.
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De Los Santos, Nancy, Constantine M. Tarawneh, Robert E. Jones, and Arturo Fuentes. "Defect Prognostics Models for Spall Growth in Railroad Bearing Rolling Elements." In 2018 Joint Rail Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/jrc2018-6214.
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Prevention of railroad bearing failures, which may lead to catastrophic derailments, is a central safety concern. Early detection of railway component defects, specifically bearing spalls, will improve overall system reliability by allowing proactive maintenance cycles rather than costly reactive replacement of failing components. A bearing health monitoring system will provide timely detection of flaws. However, absent a well verified model for defect propagation, detection can only be used to trigger an immediate component replacement. The development of such a model requires that the spall growth process be mapped out by accumulating associated signals generated by various size spalls. The addition of this information to an integrated health monitoring system will minimize operation disruption and maintain maximum accident prevention standards enabling timely and economical replacements of failing components. An earlier study done by the authors focused on bearing outer ring (cup) raceway defects. The developed model predicts that any cup raceway surface defect (i.e. spall) once reaching a critical size (spall area) will grow according to a linear correlation with mileage. The work presented here investigates spall growth within the inner rings (cones) of railroad bearings as a function of mileage. The data for this study were acquired from defective bearings that were run under various load and speed conditions utilizing specialized railroad bearing dynamic test rigs owned by the University Transportation Center for Railway Safety (UTCRS) at the University of Texas Rio Grande Valley (UTRGV). The experimental process is based on a testing cycle that allows continuous growth of railroad bearing defects until one of two conditions are met; either the defect is allowed to grow to a size that does not jeopardize the safe operation of the test rig, or the change in area of the spall is less than 10% of its previous size prior to the start of testing. The initial spall size is randomly distributed as it depends on the originating defect depth, size, and location on the rolling raceway. Periodic removal and disassembly of the railroad bearings was carried out for inspection and defect size measurement along with detailed documentation. Spalls were measured using optical techniques coupled with digital image analysis, as well as, with a manual coordinate measuring instrument with the resulting field of points manipulated in MatLab™. Castings were made of spalls using low-melting, zero-shrinkage bismuth-based alloys, so that a permanent record of the spall geometry and its growth history can be retained. The main result of this study is a preliminary model for spall growth, which can be coupled with bearing condition monitoring tools that will allow economical and effective scheduling of proactive maintenance cycles that aim to mitigate derailments, and reduce unnecessary train stoppages and associated costly delays on busy railways.