Littérature scientifique sur le sujet « Non polar Ice core »
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Articles de revues sur le sujet "Non polar Ice core"
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Legrand, Michel. « Ice–core records of atmospheric sulphur ». Philosophical Transactions of the Royal Society of London. Series B : Biological Sciences 352, no 1350 (28 février 1997) : 241–50. http://dx.doi.org/10.1098/rstb.1997.0019.
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Sulphate and methanesulphonate (MSA), the two major sulphur species trapped in polar ice, have been extensivelyh studied in Antarctic and Greenland ice cores spanning the last centuries, as well as the entire last climatic cycle. Data from the cores are used to investigate the past contribution of volcanic and biogenic emissions to the natural sulphur budget in high latitude regions of both Hemispheres. Sulphate concentrations in polar ice very often increased during one or two years after large volcanic eruptions. Sulphate records show that fossil fuel combustion has enhanced sulphate concentrations in Greenland snow by a factor of 4 since the beginning of this century, and that no similar trend has occurred in Antarctica. At present, sulphate in Antarctic snow is mainly marine and biogenic in origin and the rate of dimethyl sulphide (DMS) emissions may have been enhanced during pst developments of El Niño Southern Oscillations (ENSO). Marine biota and non–eruptive volcanic emissions represent the two main contributors to the natural high northern latitude sulphur budget. Whele these two sources have contributed equally to the natural sulphur budget of Greenland ice over the last 9000 years BP, non–eruptive volcanic emissions largely dominated the budget at the beginning of the Holocene. A general negative correlation is observed between surcace air temperatures of the Northern Hemisphere and Greenland snow MSA concentrations over the last two centuries. Positive sea–ice anomalies also seem to strengthen DMS emissions. A steady decrease of MSA is observed in Greenland snow layers deposited since 1945, which may either be related to decreasing DMS emissions from marine biota at high northern latitudes or a changing yield of MSA from DMS oxidation driven by modification of the oxidative capacity of the atmosphere in these regions. Slightly reduced MSA concentrations are obvserved in Greenland glacial ice with respect to interglacial levels. In contrast, sulphate and calcium levels are strongly enhanced during the ice age compared to the present day. These long–term variations in Greenland cores are opposite in sign to those revealed by Antarctic ice cores. Such a difference suggests that climate changes led to a quite different sulphur cycle response in the two Hemispheres.
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Shoji, Hitoshi, Atau Mitani, Kohji Horita et Chester C. Langway. « Crystal growth rates in polar firn ». Annals of Glaciology 18 (1993) : 208–10. http://dx.doi.org/10.3189/s0260305500011526.
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Continuous crystal-size measurements made on the G6 Antarctic ice core (100m deep) show enhanced growth rates above a depth of 30 m (Zone 1) and in the interval between 70 and 80 m (Zone 2). Crystal growth in Zone 1 most probably takes place by a process of sublimation and condensation. The higher growth rate in Zone 2 is most probably related to the pore close-off transformation process in which a non-uniform strain field is created to form air bubbles by plastic deformation and “cannibalization” of individual ice crystals.
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Shoji, Hitoshi, Atau Mitani, Kohji Horita et Chester C. Langway. « Crystal growth rates in polar firn ». Annals of Glaciology 18 (1993) : 208–10. http://dx.doi.org/10.1017/s0260305500011526.
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Continuous crystal-size measurements made on the G6 Antarctic ice core (100m deep) show enhanced growth rates above a depth of 30 m (Zone 1) and in the interval between 70 and 80 m (Zone 2). Crystal growth in Zone 1 most probably takes place by a process of sublimation and condensation. The higher growth rate in Zone 2 is most probably related to the pore close-off transformation process in which a non-uniform strain field is created to form air bubbles by plastic deformation and “cannibalization” of individual ice crystals.
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Tornow, Carmen, Ekkehard Kührt, Stefan Kupper et Uwe Motschmann. « Interaction between gas and ice phase in the three periods of the solar nebula ». Proceedings of the International Astronomical Union 5, S263 (août 2009) : 50–54. http://dx.doi.org/10.1017/s1743921310001493.
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AbstractWe simulate the chemical processes in the three evolution periods of the solar nebula, which are (i) the quasi-stationary prestellar cloud core, (ii) the gravitationally collapsing protostellar core, and (iii) the evolving gas-dust disk. Our purpose is to identify chemical parameters which reflect special aspects of the interactions between the gas and ice phase in the different periods, e.g. isotopic or molecular ratios. In this study we derive the D/H and 15N/14N ratio of selected compounds as well as the CO2/H2O ratio to measure the fraction of non-polar to polar ice in the grain mantles. The chosen ratios depend on the depletion-enrichment relation between the ice and gas phases driven by the thermal evolution in each period, especially during the collapse. Hence, we have made great efforts in order to derive realistic and compact hydrodynamic models to describe the evolutionary periods of the solar nebula.
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Shen, Liang, Yongqin Liu, Tandong Yao, Ninglian Wang, Baiqing Xu, Nianzhi Jiao, Hongcan Liu, Yuguang Zhou, Xiaobo Liu et Yanan Wang. « Dyadobacter tibetensis sp. nov., isolated from glacial ice core ». International Journal of Systematic and Evolutionary Microbiology 63, Pt_10 (1 octobre 2013) : 3636–39. http://dx.doi.org/10.1099/ijs.0.050328-0.
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A Gram-stain-negative, rod-shaped, aerobic, non-motile bacterium, designated Y620-1T, was isolated from a glacier on the Tibetan Plateau, China. The 16S rRNA gene sequence of the novel isolate shared 93.6–95.1 % similarity with type strains of species of the genus Dyadobacter . The major fatty acids of strain Y620-1T were summed feature 3 (C16 : 1ω7c and/or iso-C15 : 0 2-OH), iso-C15 : 0, C16 : 1ω5c and iso-C17 : 0 3-OH. The predominant isoprenoid quinone and polar lipid were MK-7 and phosphatidylethanolamine (PE), respectively. The DNA G+C content was 44.4±0.3 mol% (T m). Flexirubin-type pigment was produced. The novel isolate was classified in the genus Dyadobacter , but a number of phenotypic characteristics distinguished the novel isolate from type strains of species of the genus Dyadobacter . From these genotypic and phenotypic data, it is evident that strain Y620-1T represents a novel species of the genus Dyadobacter , for which the name Dyadobacter tibetensis sp. nov. is proposed. The type strain is Y620-1T ( = JCM 18589T = CGMCC 1.12215T).
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Kerch, Johanna, Anja Diez, Ilka Weikusat et Olaf Eisen. « Deriving micro- to macro-scale seismic velocities from ice-core <i>c</i> ; axis orientations ». Cryosphere 12, no 5 (23 mai 2018) : 1715–34. http://dx.doi.org/10.5194/tc-12-1715-2018.
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Abstract. One of the great challenges in glaciology is the ability to estimate the bulk ice anisotropy in ice sheets and glaciers, which is needed to improve our understanding of ice-sheet dynamics. We investigate the effect of crystal anisotropy on seismic velocities in glacier ice and revisit the framework which is based on fabric eigenvalues to derive approximate seismic velocities by exploiting the assumed symmetry. In contrast to previous studies, we calculate the seismic velocities using the exact c axis angles describing the orientations of the crystal ensemble in an ice-core sample. We apply this approach to fabric data sets from an alpine and a polar ice core. Our results provide a quantitative evaluation of the earlier approximative eigenvalue framework. For near-vertical incidence our results differ by up to 135 m s−1 for P-wave and 200 m s−1 for S-wave velocity compared to the earlier framework (estimated 1 % difference in average P-wave velocity at the bedrock for the short alpine ice core). We quantify the influence of shear-wave splitting at the bedrock as 45 m s−1 for the alpine ice core and 59 m s−1 for the polar ice core. At non-vertical incidence we obtain differences of up to 185 m s−1 for P-wave and 280 m s−1 for S-wave velocities. Additionally, our findings highlight the variation in seismic velocity at non-vertical incidence as a function of the horizontal azimuth of the seismic plane, which can be significant for non-symmetric orientation distributions and results in a strong azimuth-dependent shear-wave splitting of max. 281 m s−1 at some depths. For a given incidence angle and depth we estimated changes in phase velocity of almost 200 m s−1 for P wave and more than 200 m s−1 for S wave and shear-wave splitting under a rotating seismic plane. We assess for the first time the change in seismic anisotropy that can be expected on a short spatial (vertical) scale in a glacier due to strong variability in crystal-orientation fabric (±50 m s−1 per 10 cm). Our investigation of seismic anisotropy based on ice-core data contributes to advancing the interpretation of seismic data, with respect to extracting bulk information about crystal anisotropy, without having to drill an ice core and with special regard to future applications employing ultrasonic sounding.
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Weikusat, Ilka, Ernst-Jan N. Kuiper, Gill M. Pennock, Sepp Kipfstuhl et Martyn R. Drury. « EBSD analysis of subgrain boundaries and dislocation slip systems in Antarctic and Greenland ice ». Solid Earth 8, no 5 (6 septembre 2017) : 883–98. http://dx.doi.org/10.5194/se-8-883-2017.
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Abstract. Ice has a very high plastic anisotropy with easy dislocation glide on basal planes, while glide on non-basal planes is much harder. Basal glide involves dislocations with the Burgers vector b = 〈a〉, while glide on non-basal planes can involve dislocations with b = 〈a〉, b = [c], and b = 〈c + a〉. During the natural ductile flow of polar ice sheets, most of the deformation is expected to occur by basal slip accommodated by other processes, including non-basal slip and grain boundary processes. However, the importance of different accommodating processes is controversial. The recent application of micro-diffraction analysis methods to ice, such as X-ray Laue diffraction and electron backscattered diffraction (EBSD), has demonstrated that subgrain boundaries indicative of non-basal slip are present in naturally deformed ice, although so far the available data sets are limited. In this study we present an analysis of a large number of subgrain boundaries in ice core samples from one depth level from two deep ice cores from Antarctica (EPICA-DML deep ice core at 656 m of depth) and Greenland (NEEM deep ice core at 719 m of depth). EBSD provides information for the characterization of subgrain boundary types and on the dislocations that are likely to be present along the boundary. EBSD analyses, in combination with light microscopy measurements, are presented and interpreted in terms of the dislocation slip systems. The most common subgrain boundaries are indicative of basal 〈a〉 slip with an almost equal occurrence of subgrain boundaries indicative of prism [c] or 〈c + a〉 slip on prism and/or pyramidal planes. A few subgrain boundaries are indicative of prism 〈a〉 slip or slip of 〈a〉 screw dislocations on the basal plane. In addition to these classical polygonization processes that involve the recovery of dislocations into boundaries, alternative mechanisms are discussed for the formation of subgrain boundaries that are not related to the crystallography of the host grain.The finding that subgrain boundaries indicative of non-basal slip are as frequent as those indicating basal slip is surprising. Our evidence of frequent non-basal slip in naturally deformed polar ice core samples has important implications for discussions on ice about plasticity descriptions, rate-controlling processes which accommodate basal glide, and anisotropic ice flow descriptions of large ice masses with the wider perspective of sea level evolution.
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NG, Felix, et T. H. Jacka. « A model of crystal-size evolution in polar ice masses ». Journal of Glaciology 60, no 221 (2014) : 463–77. http://dx.doi.org/10.3189/2014jog13j173.
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AbstractIn the deep ice cores drilled at the GRIP, NGRIP and GISP2 sites in Greenland and at Byrd Station and the summit of Law Dome in Antarctica, the mean crystal size increases with depth in the shallow subsurface and reaches steady values at intermediate depth. This behaviour has been attributed to the competition between grain-boundary migration driven crystal growth and crystal polygonization, but the effects of changing crystal dislocation density and non-equiaxed crystal shape in this competition are uncertain. We study these effects with a simple model. It describes how the mean height and width of crystals evolve as they flatten under vertical compression, and as crystal growth and polygonization compete. The polygonization rate is assumed to be proportional to the mean dislocation density across crystals. Migration recrystallization, which can affect crystal growth via strain-induced grain boundary migration but whose impact on the mean crystal size is difficult to quantify for ice at present, is not accounted for. When applied to the five ice-core sites, the model simulates the observed crystal-size profiles well down to the bottom of their steady regions, although the match for Law Dome is less satisfactory. Polygonization rate factors retrieved for the sites range from 10–5 to 10–2 a–1. We conclude that since crystal size and dislocation density evolve in a strongly coupled manner, consistent modelling requires multiple differential equations to track both of these variables. Future ice-core analysis should also determine crystal size in all three principal directions.
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Sigl, M., T. M. Jenk, T. Kellerhals, S. Szidat, H. W. Gäggeler, L. Wacker, H. A. Synal et al. « Towards radiocarbon dating of ice cores ». Journal of Glaciology 55, no 194 (2009) : 985–96. http://dx.doi.org/10.3189/002214309790794922.
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AbstractA recently developed dating method for glacier ice, based on the analysis of radiocarbon in carbonaceous aerosol particles, is thoroughly investigated. We discuss the potential of this method to achieve a reliable dating using examples from a mid- and a low-latitude ice core. Two series of samples from Colle Gnifetti (4450 m a.s.l., Swiss Alps) and Nevado Illimani (6300 m a.s.l., Bolivian Andes) demonstrate that the 14C ages deduced from the water-insoluble organic carbon fraction represent the age of the ice. Sample sizes ranged between 7 and 100 μg carbon. For validation we compare our results with those from independent dating. This new method is thought to have major implications for dating non-polar ice cores in the future, as it provides complementary age information for time periods not accessible with common dating techniques.
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Schwikowski, Margit, Sabina Brütsch, Gino Casassa et Andrés Rivera. « A potential high-elevation ice-core site at Hielo Patagόnico Sur ». Annals of Glaciology 43 (2006) : 8–13. http://dx.doi.org/10.3189/172756406781812014.
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AbstractThe Patagonia icefields constitute a unique location in the Southern Hemisphere for obtaining non-polar paleo-records from ice cores south of 45°S. Nevertheless, no ice-core record with meaningful paleoclimate information has yet been obtained from Patagonia. This deficiency is due to extremely harsh field conditions, and to the fact that the main plateaus of both Hielo Patagónico Norte (HPN; northern Patagonia icefield) and Hielo Patagónico Sur (HPS; southern Patagonia icefield) are strongly affected by meltwater percolation. In order to explore the suitability of high-elevation glacier sites at HPS as paleoclimate archives, three shallow firn cores were retrieved covering the altitude range 1543−2300 ma.s.l. The glaciochemical records from the two lower sites confirm the presence of superimposed ice, a clear sign of meltwater formation and percolation. In the core from 2300 m, the glaciochemical signature appears to be preserved, indicating that no significant melting occurred. Although there might be problems associated with wind erosion and extreme melt events, there is good potential for well-preserved paleo-records within glaciers in the Patagonia icefields located higher than 2300 m.
Thèses sur le sujet "Non polar Ice core"
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MATTAVELLI, MATTEO. « Development of a Glaciological Spatial Data Infrastructure to assess glacier response to climatic fluctuation ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2016. http://hdl.handle.net/10281/102679.
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L’obiettivo del progetto di ricerca è creare una metodologia per ricercare, archiviare e diffondere dati glaciologici partendo dallo sviluppo di una infrastruttura di dati spaziali (SDI) che possa essere utile allo studio dell’evoluzione glaciale in relazione ai cambiamenti climatici. Questa ricerca è parte del progetto di interesse nazionale NextData (www.nextdataproject.it). Nei primi due anni è stato sviluppato un geodatabase contenente dati riguardanti la caratterizzazione chimico-fisica di carote di ghiaccio. La prima versione del geodb presentava delle criticità che sono state superate con l’implementazione della seconda versione dove sono stati applicati i seguenti miglioramenti: Sviluppata e applicata una metodologia di riposizionamento, aggiunta di differenti entità con informazioni riguardanti il progetto di perforazione, il sito di perforazione, le references dei dati e tutte le informazioni aggiuntive utili per la classificazione e la caratterizzazione delle ice cores. Durante il terzo anno di ricerca alla nuova struttura creata e chiamata IDB2 sono stati uniti diversi database glaciologici contenenti dati spaziali, geomorfometrici e informazioni su ghiacciai. E’ stata sviluppata una nuova parte dell’infrastruttura capace di accogliere dati derivanti da analisi geomorfologiche, nello specifico sono state aggiunte due entità chiamate rispettivamente Glacier_code_tab e Glacier_data_tab. La prima archivia l’unione tra differenti banche dati glaciologiche. Nello specifico gli ID del GLIMS, RGI, WGI, WGMS sono stati aggiunti e collegati ad ogni ghiacciaio perforato. La seconda contiene dati geomorfologici calcolati tramite un algoritmo GIS sviluppato durante il terzo anno. L’algoritmo sviluppato in ambiente GIS è stato chiamato GLACIER DATA MODULE (GDM). L’algoritmo è stato sviluppato per poter ricavare informazioni dettagliate per la calibrazione dei Minimal glacier model (MGM), una famiglia di modelli glaciologici per la predizione dell’andamento dei ghiacciai in risposta alle fluttuazioni climatiche. La procedura richiede per ogni ghiacciaio come input DTM, poligoni riportanti il confine glaciale e le linee di flusso del ghiaccio. Queste ultime sono state calcolate partendo dal risultato dell’algoritmo r.flow e dopo un attenta analisi geomorfologica è stata individuata la flow line principale del ghiacciaio analizzato. L’algoritmo è stato applicato a 34 ghiacciai della catena alpina con le più lunghe misurazione di bilanci di massa, parametro fondamentale per la calibrazione dei MGM. I dati di input per l’algoritmo sono stati ricavati dalla SDI IDB2 e come DTM è stato usato ASTER GDEMv2. I risultati del GDM sono stati usati per popolare IDB2 chiudendo così l’iteratività della SDI creata e sono stati usati per calibrare i MGM utili a valutare la risposta dei ghiacciai ai cambiamenti climatici. I dati geomorfologici ricavati dall’analisi spaziale sui ghiacciai sono anche stati usati per definire degli andamenti utili a definire la distribuzione dei ghiacci alpini lungo la catena montuosa.
Per concludere la creazione della SDI, un geoportale è stato sviluppato ed è disponibile al sito: http://geomatic.disat.unimib.it/home/geomatic/idb2/.
Concludendo, durante il mio dottorato ho sviluppato una SDI contenente dati glaciologici. La struttura ha permesso fino ad oggi di modellare la suscettibilità di ghiacciai non polari alla perforazione e di calibrare modelli glaciologici semplici come i MGM utilizzati per valutare la risposta dei ghiacciai ai cambiamenti climatici. La struttura verrà usata in futuro come base per lo sviluppo di banca dati riguardate tutti i proxy paleoclimatici utili alla ricostruzione del clima nella penisola italiana degli ultimi 2k anni.The aim of my Ph.D. research is to create a methodology for recovery, storage, access and disseminate glaciological data, starting from the development of a spatial data infrastructure (SDI) and use it to study the evolution of the glaciers in relation with climate change. My research is part of the project of interest Nextdata (www.nextdataproject.it). In the first two years a geodatabase for glaciological data was built. A new structure that can contain data about world non polar ice core characterization (IDB1) was implemented. To overlap IDB1 critical issues a new structure was set-up with this improvements: A repositioning methodology was set-up to increase the accuracy of coordinates of the ice cores, different entities with information about project of perforation, drilling-site, references of data and additional information about ice core were added to the structure. During the third year of research the new geodatabase IDB2 was linked with glaciological databases of glaciers containing spatial, geomorphometric and other information. A new part was developed to store data coming from geomorphological analysis. In particular two entities about glaciers were added: the first, Glacier_Code_tab stores the union between the different glaciers databases such as GLIMS, RGI, WGI, WGMS id for each perforated or not perforated glaciers. The second one, Glacier_Data_Tab contains the geomorphological parameters such as Flow line length, min and max elevation, averaged slope and aspect calculate using a GIS algorithm developed. A GIS module called GlacierDataModule (GDM) was developed also during the third year to provide detailed information to calibrate minimal glacier model (MGM) to assess glaciers response to climatic fluctuations and to linkage the geomorphological parameters with climate variability. The procedure requires for each glacier, as inputs DTMs, POLYGONs and FLOW LINEs. The flow lines was calculated starting from the results of r.flow algorithms and after a subjective evaluation based on morphological parameters the most important flow lines were digitalized. The algorithm was applied at 34 glaciers of great alpine region (GAR) that are the glaciers with the longest measurements of mass balance, the primary data needed to run the minimal model. Input data required to GDM were recovered from IDB2 and ASTER GDEMv2 was used as DEM input source. Results of GDM on GAR was used to populate IDB2 in an iterative way and used to calibrate the MGM to assess glaciers response to climatic fluctuations. Geomorphological data coming from the spatial analysis on glaciers was also used to compare the glaciers and find some behaviour useful to evaluate the glacier distribution along the GAR. The results of this analysis shows a clear climatic characteristic of the glaciers of GAR. Only 34 glaciers was evaluated but the results was comparable to the results presents by Evans in his study where 6561 glaciers on GAR were taken in account (Evans, I.S., 2006). A geoportal with a webgis available at: http://geomatic.disat.unimib.it/home/geomatic/idb2/ was developed to share this data. In conclusion during my Ph.D. a SDI contain glaciological data was set-up, drawn and implemented. SDI allowed until now at the scientific community to modelling the suitability for ice core drilling of mountains glaciers and provide a input parameters to run a GIS module developed. GIS Module is used to obtain geomorphological parameters to calibrate minimal model, evaluate the glaciers response at climatic fluctuations through the glacier distribution along the GAR. The IDB2 will be also used in the future to identify paleo-climatic proxy that could be useful, within the interaction of other paleo-climatic proxies (lake sediments; marine sediments; pollen and corals), to reconstruct the last 2K years of climate variability in Italy.
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Su, Yixiang. « Analyses of Two Ice Class Rules : for The Design Process of a Container Ship ». Thesis, KTH, Marina system, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-214992.
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During ice voyages, level ice and iceberg with huge inertia force can cause large deformation and even damage on the ship hull structure. Hence the hull structure for ice voyage requires higher strength than it for open water voyages. A container ship will be re-designed for ice voyages in the thesis. Generally, the ice strength is evaluated in ice class rules. IACS polar class and FSICR are adopted in this thesis. Ice class rules are based on experience and experiment data, but there has been no exact formula or parameters to described the ice properties so far. In other words, the results from ice class rules include uncertainties. In order to improve physical understanding, non-linear FE simulations will be processed after the re-design. In the simulations, the ship has a collision with different ice scenarios. The simulations are carried on ANSYS Workbench Explicit Dynamic using the solver of Auto-dyna. Afterwards, the results from the two designs schemes are compared and analysed.
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Huang, Po-yu, et 黃柏渝. « The photolysis difference between Polar and non-polar molecule in CH4-ice mixture ». Thesis, 2010. http://ndltd.ncl.edu.tw/handle/64394727286788084750.
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碩士國立中央大學
物理研究所
98
The astronomical observation in resent years shows that the main composition of those TNOs ice are H2O, CH4 and N2. We choose these species as the ice composition and compare their difference in reaction products after exposed to and altered by VUV photons. N2 : CH4 = 1 : 1, CH4 : H2O = 1 : 1 and N2 : CH4 : H2O = 1 : 1 : 1 mixtures were prepared in gas-phase before condensation on to a precooled (16K) substrate. We use the High Flux beamline at Synchrotron Radiation Research Cente as the VUV light source. New molecules produced during photolysis were identified on the basis of their characteristic infrared feature. Quadrupole mass spectrometer was employed to detect the desorbed products during ice warming. CH4 molecules being trapped within a comparably stable N2 species in the N2-containing ices. This will induce Matrix-isolated phenomenon which blocks the radicalradical interaction between CH3 molecules and reduces the destruction rate of CH4 durung photolysis. Therefore, less C2H6 and C3H8 reaction products were detected. Moreover, lots of H atoms detached form the CH4 molecures will recombine with CCCN molecules to form HNCCC. That’s why we can only find a weak Mid-IR absorbance band of CCCN at 2194 cm^-1, but a clear absorbance feature of HNCCC at 2205 cm^-1 wavenumber. We also used the hydrogen microwave discharge lamp as the VUV light souce in the laboratory(10.2 eV). And compare the reaction products difference with the High Flux beamline (4 ∼ 20 eV ) after solid N2 + CH4 + H2O mixtures were photolysized by them. However, we didn’t find any N-containing reaction products after the ice was photolyzed by hydrogen lamp. Supposedly, the hydrogen lamp already have enough photon energy to destruct the bonds in the N2 molecules which bonding energy is about 9.76 eV. After changing the experimental methodes by photolyzing and condensing the gas-phase mixtures onto the substrate at the same time, lots of new species and products yields are found by their IR feature. And the N-containing products also shown up in those products. So we infer that the bonding energy of N2 ice is higher than 10.2 eV at least. N2-containing ice was processed by UV-photons from the High Flux beamline light source. And we find the CN^-’s IR feature at 2082cm^-1 wavenumber. However, the product was only found during ice warming process in Moore and Hudson’s experiment. By comparing the behavior of the CN^-’s IR feature during warming, we confirmed that it’s the same species that also detected in Moore and Hudson’s experiment, and believe that the CN^- will forms after VUV photolysis, but the photochemistry procedurs still needs further study to confirm. There is also lots of Nitrile (R-CN) reaction products synthesized during N2 +CH4 mixtures were processed by UV-photons. However, if there are H2O in the ice mixtures. We can’t find any Nitrile or Isonitrile yields but OCN^- will show up instead. From the above results, we found that the non-polar molecules–N2 and the polar molecules–H2O will have different influences on the products of the CH4-containing ice after photolysis. By comparing to the astronomical observations and the related publications. We confirmed that those reactions and phenomenons occuring on the TNOs. The discoveries and analysis results in this work can be used as one of reference for TNOsrelated research and other ice simulated experiments in the future.
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Nedelcu, Aneta Florentina. « The microscopic dimension of paleoclimate in the EPICA-DML(Antarctica) deep ice core ». Doctoral thesis, 2011. http://hdl.handle.net/11858/00-1735-0000-000E-0CF1-C.
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Verpaelst, Manuel. « Mouvements de masse par solifluxion et dynamique syngénétique du pergélisol du Haut-Arctique ». Thèse, 2016. http://hdl.handle.net/1866/18727.
Texte intégralRésumé :
Le Haut-Arctique est caractérisé par de nombreux phénomènes climatiques et géomorphologiques extrêmes. Les températures très froides, les faibles précipitations et la couverture végétale disparate permettent une pénétration en profondeur du froid dans le sol. Ceci, combiné à un grand nombre de cycles de gel et de dégel, donne naissance à différentes formes de surface qui affectent les dynamiques d’évolution du pergélisol et induisent une variabilité verticale et latérale de la distribution des teneurs en glace dans le sol. Ce mémoire porte sur l’influence d’un lobe de solifluxion de type rocheux sur les dynamiques d’évolution du pergélisol sur l’île Ward Hunt, Nunavut (Canada). En utilisant une approche cryostratigraphique, les objectifs sont de caractériser la cryostratigraphie d’un lobe de solifluxion, ce qui permettra de proposer un modèle d’évolution du pergélisol en lien avec le déplacement de matériel par solifluxion. L’analyse cryostratigraphique a révélé que la formation du lobe de solifluxion a mené au développement syngénétique d’une couche de pergélisol avec une teneur en glace variant en fonction de la morphologie du lobe, et à l’enfouissement et la préservation d’un corps de glace massive préexistant en bas de pente. La succession verticale et latérale des cryofaciès fait état du déplacement du lobe et de l’impact que ce dernier a sur la variabilité spatiale et temporelle du pergélisol, et ce, tant sur les aspects d’aggradation liés à l’accumulation de matériel en surface que sur les aspects de dégradation associés aux réchauffements climatiques actuels.The high Arctic is characterized by many extreme climatic and geomorphologic phenomena. Very cold temperatures, low precipitation and sparse vegetation cover, permit a deep penetration of cold in the soil. The latter, combined with a great number of freeze-thaw cycles, give rise to different surface features which in turn affect permafrost evolution dynamics and induce a vertical and lateral variability of the ice content distributions in the soil. This thesis focusses on the influence of a stone-banked solifluction lobe on permafrost evolution dynamics on Ward Hunt Island, Nunvut (Canada). By using a cryostratigraphic approach, the objectives are first, to characterize the cryostratigraphy of a solifluction lobe and second, to propose an evolution model of permafrost in reaction to the downslope displacement of material by solifluction. The cryostratigraphic analysis revealed that the solifluction lobes formation lead to the development of a syngenetic layer of permafrost with an ice content that varied according to the morphology of the lobe, and to the burial and preservation of a pre-existing body of massive ice at the base of the slope. The vertical and lateral sequence of the cryofacies presents the displacement of the lobe and its impact on spatial and temporal variability of the permafrost, that being, the aspects of aggradation related to the accumulation of material at the surface as well as degradation due to the actual climatic warming.
Livres sur le sujet "Non polar Ice core"
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International Symposium on the Dome Fuji Ice Core and Related Topics (2001 Tokyo, Japan). Global scale climate and environment study through polar deep ice cores : Proceedings of the International Symposium on the Dome Fuji Ice Core and Related Topics, 27-28 February 2001, Tokyo. Tokyo : National Institute of Polar Research, 2003.
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Paolo, Laj, et United States. National Aeronautics and Space Administration., dir. Sulfur mass loading of the atmosphere from volcanic eruptions : Calibration of the ice core record on basis of sulfate aerosol deposition in polar regions from the 1982 El Chichon eruption, NASA grant NAG51304. Narragansett, RI : University of Rhode Island Graduate School of Oceanography, 1990.
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Sigurdsson, Haraldur. Sulfur mass loading of the atmosphere from volcanic eruptions : Calibration of the ice core record on basis of sulfate aerosol deposition in polar regions from the 1982 El Chichon eruption, NASA grant NAG51304. Narragansett, RI : University of Rhode Island Graduate School of Oceanography, 1990.
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Government, U. S., et U. S. Army Corps of Engineers (USACE). Fifty Years of Soviet and Russian Drilling Activity in Polar and Non-Polar Ice : A Chronological History - Polar Research, Antarctica, Arctic, Glaciers, Thermal Drills, Deep Core Holes. Independently Published, 2017.
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Stilwell, Jeffrey D., et John A. Long. Frozen in Time. CSIRO Publishing, 2011. http://dx.doi.org/10.1071/9780643104013.
Texte intégralRésumé :
No other continent on Earth has undergone such radical environmental changes as Antarctica. In its transition from rich biodiversity to the barren, cold land of blizzards we see today, Antarctica provides a dramatic case study of how subtle changes in continental positioning can affect living communities, and how rapidly catastrophic changes can come about. Antarctica has gone from paradise to polar ice in just a few million years, a geological blink of an eye when we consider the real age of Earth.
Frozen in Time presents a comprehensive overview of the fossil record of Antarctica framed within its changing environmental settings, providing a window into a past time and environment on the continent. It reconstructs Antarctica’s evolving animal and plant communities as accurately as the fossil record permits.
The story of how fossils were first discovered in Antarctica is a triumph of human endeavour. It continues today with modern expeditions going out to remote sites every year to fill in more of the missing parts of the continent’s great jigsaw of life.
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Bloom, Lisa E. Climate Change and the New Polar Aesthetics. Duke University Press, 2022. http://dx.doi.org/10.1215/9781478018643.
Texte intégralRésumé :
In Climate Change and the New Polar Aesthetics, Lisa E. Bloom considers the ways artists, filmmakers, and activists engaged with the Arctic and Antarctic to represent our current environmental crises and reconstruct public understandings of them. Bloom engages feminist, Black, Indigenous, and non-Western perspectives to address the exigencies of the experience of the Anthropocene and its attendant ecosystem failures, rising sea levels, and climate-led migrations. As opposed to mainstream media depictions of climate change that feature apocalyptic spectacles of distant melting ice and desperate polar bears, artists such as Katja Aglert, Subhankar Banerjee, Joyce Campbell, Judit Hersko, Roni Horn, Isaac Julien, Zacharias Kunuk, Connie Samaras, and activist art collectives take a more complex poetic and political approach. In their films and visual and conceptual art, these artists link climate change to its social roots in colonialism and capitalism while challenging the suppression of information about environmental destruction and critiquing Western art institutions for their complicity. Bloom’s examination and contextualization of new polar aesthetics makes environmental degradation more legible while demonstrating that our own political agency is central to imagining and constructing a better world.
Chapitres de livres sur le sujet "Non polar Ice core"
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Wolff, Eric W. « Nitrate in Polar Ice ». Dans Ice Core Studies of Global Biogeochemical Cycles, 195–224. Berlin, Heidelberg : Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-51172-1_10.
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Beer, J., M. Andrée, H. Oeschger, B. Stauffer, R. Balzer, G. Bonani, Ch Stoller, M. Suter, W. Wölfli et R. C. Finkel. « 10Be Variations in polar ice cores ». Dans Greenland Ice Core : Geophysics, Geochemistry, and the Environment, 66–70. Washington, D. C. : American Geophysical Union, 1985. http://dx.doi.org/10.1029/gm033p0066.
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Legrand, Michel. « Sulphur-Derived Species in Polar Ice : A Review ». Dans Ice Core Studies of Global Biogeochemical Cycles, 91–119. Berlin, Heidelberg : Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-51172-1_5.
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Legrand, M. « Ice Core Analysis in Arctic and Antarctic Regions ». Dans The Tropospheric Chemistry of Ozone in the Polar Regions, 205–17. Berlin, Heidelberg : Springer Berlin Heidelberg, 1993. http://dx.doi.org/10.1007/978-3-642-78211-4_14.
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Neftel, Albrecht, Roger C. Bales et Daniel J. Jacob. « H2O2 and HCHO in Polar Snow and Their Relation to Atmospheric Chemistry ». Dans Ice Core Studies of Global Biogeochemical Cycles, 249–64. Berlin, Heidelberg : Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-51172-1_14.
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Patterson, C. C., C. Boutron et R. Flegal. « Present status and future of lead studies in polar snow ». Dans Greenland Ice Core : Geophysics, Geochemistry, and the Environment, 101–4. Washington, D. C. : American Geophysical Union, 1985. http://dx.doi.org/10.1029/gm033p0101.
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Waddington, E. D. « Where are We Going ? The Ice Core — Paleoclimate Inverse Problem ». Dans Chemical Exchange Between the Atmosphere and Polar Snow, 629–40. Berlin, Heidelberg : Springer Berlin Heidelberg, 1996. http://dx.doi.org/10.1007/978-3-642-61171-1_34.
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De Angelis, Martine, et Michel Legrand. « Preliminary Investigations of Post Depositional Effects on HCl, HNO3, and Organic Acids in Polar Firn Layers ». Dans Ice Core Studies of Global Biogeochemical Cycles, 361–81. Berlin, Heidelberg : Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-51172-1_19.
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Koide, Minoru, et Edward D. Goldberg. « The historical record of artificial radioactive fallout from the atmosphere in polar glaciers ». Dans Greenland Ice Core : Geophysics, Geochemistry, and the Environment, 95–100. Washington, D. C. : American Geophysical Union, 1985. http://dx.doi.org/10.1029/gm033p0095.
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Talalay, Pavel G. « Geological and Scientific Offshore Drilling and Core Sampling in Ice-Covered Waters ». Dans Geotechnical and Exploration Drilling in the Polar Regions, 339–83. Cham : Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-07269-7_11.
Texte intégralActes de conférences sur le sujet "Non polar Ice core"
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Pilkington, Roger, Arno Keinonen et Igor Sheikin. « Ice Observations and Forecasting During the Arctic Coring Project, August - September 2004 ». Dans SNAME 7th International Conference and Exhibition on Performance of Ships and Structures in Ice. SNAME, 2006. http://dx.doi.org/10.5957/icetech-2006-171.
Texte intégralRésumé :
The Arctic Coring Expedition or ACEX was conducted as a special project under the Integrated Ocean Drilling Project. A review of the operational and ice management aspects of this project is provided in Keinonen et al (2006). This current paper reviews the ice observations and forecasting in more detail. Six scientists and naval architects were on board the IB Oden and Sovetskiy Soyuz to collect relevant ice data and forecast ice movement. The work involved the collection of ice data during transit and ice management, interpreting satellite imagery, ice forecasting, and providing the information to the vessels. The purpose of the project was to obtain a core from the seafloor to bed rock (420 m) on the Lomonosov Ridge, to study the paleo history of the polar cap region. This was achieved. The optimum transit route was determined using the Fengyun and Envisat satellite data which were showed the region of most leads. Once at the drill site at 88º north, Radarsat satellite data were used to identify regions of lighter ice. Ice thickness was generally 2.5 to 3.5 m, with mainly second year and old ice. Ice forecasting, using a very simple model, allowed the identification of any heavy ice expected to pass over the site and the regions where more information on ice severity was required. During the first two weeks at the drill site, the inertial oscillations of the ice were very small and not noticeable. Later the oscillations became much larger and the ice went through several complete loops, which created a minor problem for the drilling operation. Ice drift was measured by means of GPS buoys placed onto the ice and recovered by helicopter. This method worked well as the ice moved very slowly so that the buoys were within range for 2 to 3 days. A recent publication indicates that tropical conditions existed at the pole about 55 million years ago. Preliminary. Results indicated that the Polar Cap region was a shallow fresh water sea until about 15 million years ago. At that time, the region between Greenland and Norway opened, allowing the water from the Atlantic Ocean to flow north, with the result that the upper 15 million years of sediments are saline.
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Kvamme, Bjarte O., Jino Peechanatt et Ove T. Gudmestad. « Calculation of Time-to-Freeze for Liquids in Pipes ». Dans ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-62000.
Texte intégralRésumé :
In recent years, there has been unprecedented interest shown in the Arctic region by the industry, as it has become increasingly accessible for oil and gas exploration, shipping, and tourism. The decrease in ice extent in the Arctic has renewed the interest in the Northern Sea route, necessitating further research to evaluate the adequacy of the equipment and appliances used on vessels traversing in polar waters. In the oil and gas industry, exploration and production vessels and platforms are highly dependent on the piping facilities for rendering their intended function, and therefore, flow assurance is extremely crucial. If the winterization of pipes is not done properly, this could lead to massive cost overruns due to unplanned production shutdowns or even worse, accidents. A temperature drop between the different areas of the production facilities will change the thermodynamic properties of the fluids, and could cause the processing of the crude oil to become inefficient. The introduction of the Polar Code by the International Maritime Organization (IMO) attempts to mitigate some of the risks endangering the vessels in polar waters. The Polar Code is scheduled to take effect on 01.01.2017, and applies to all vessels traversing in polar waters. The Polar Code requires that all machinery installations and associated equipment required for the safe operation of ships shall be protected against the effect of freezing and increased viscosity of liquids, and that working liquids shall be maintained in a viscosity range that ensures the operation of the machinery. To account for this, the heat loss of pipes carrying liquid (water for fire extinguishing and hydraulic fluid amongst others) needs to be estimated and mitigating measures must be taken. In this study, methodology from the refrigeration industry is applied to calculate the estimated time to freeze for liquids in pipes. The methodology is adapted for use in the maritime industry, and results are presented in this study. The methodology used was found to be quite flexible, allowing for the calculation of complex scenarios and shapes, including the effect of varying degrees of insulation on pipes, and can easily be applied for approximating the best suitable method of insulating pipes to ensure flow assurance and maintain fluid properties at desired levels. Tables estimating the time-to-freeze for insulated pipes of different diameters and insulation thicknesses exposed to cross-winds of varying speeds are provided. The methodology is found to have great potential, and should be investigated further with experiments. The objective of the paper is thus to introduce the methodology for cold-climate engineering and use it for practical analysis of realistic estimates of insulated and non-insulated piping.
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Kujala, Pentti, Jorma Kämäräinen et Mikko Suominen. « Analysis of a suitable ice class of ship hull for Antarctic operations ». Dans SNAME 5th World Maritime Technology Conference. SNAME, 2015. http://dx.doi.org/10.5957/wmtc-2015-153.
Texte intégralRésumé :
Shipping in ice covered Polar waters is increasing and new ice classed ships are built to replace older ice strengthened fleet. Selection of suitable ice class for ships operation is an important but not simple task. The process of selecting an appropriate ice class is of high importance both from a safety as well as an economical perspective, but the selection process is still based on accumulated experience and traditions within the areas of existing operations. The increased exploitation of the Polar waters, both seasonal periods and geographical areas, as well as the introduction of new international design standards, reduces the relevancy of using existing experience as basis for the selection, and new methods and knowledge have to be developed. Based on the full scale measurements of ice loads during summer 2013-2014 in the Antarctica, the structural strength of the South African research vessel S.A. Agulhas II has been evaluated to assess the suitability of the chosen ice class of the vessel. The new polar code and especially the new Polar Operational Limit Assessment Risk Indexing System (POLARIS)is applied on this vessel to evaluate the suitable ice class. It is found the PC 3 is the most suitable ice class for ships navigating in harsh Antarctic ice conditions.
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Peechanatt, Jino, Bjarte O. Kvamme, Ove T. Gudmestad et Yaaseen A. Amith. « Heat Loss of Heated Deck Elements in Cross-Flow Wind ». Dans ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-61588.
Texte intégralRésumé :
In recent years, there has been unprecedented interest shown in the Arctic region by the industry, as it has become increasingly accessible for oil and gas exploration, shipping, and tourism. The decrease in ice extent in the Arctic has renewed the interest in the Northern Sea route, necessitating further research to evaluate the adequacy of the equipment and appliances used on vessels traversing in polar waters. The introduction of the Polar Code by the International Maritime Organization (IMO) attempts to mitigate some of the risks endangering the vessels in Polar waters. The Polar Code is scheduled to take effect on 01.01.2017, and applies to all vessels traversing in polar waters. One of the requirements in the Polar Code is that means shall be provided to remove or prevent accretion of snow and/or ice from escape routes, embarkation areas and access points. Even though, prior to the formulation of Polar Code, the requirement for de-icing the deck surfaces on vessels already exists, the suitability of the equipment currently in use is debatable. Large amounts of energy is required to maintain an ice-free surface, which is not desirable economically or environmentally, due to the substantial increase in fuel consumption. In this study, a heated deck element manufactured by GMC Maritime AS is subjected to cross flow wind of 5 m/s, 10 m/s and 15 m/s at various sub-zero temperatures in GMC Maritime AS’s climate laboratory in Stavanger, Norway. The deck element is rated to 1400 W / m2, and is one of the designs provided by GMC Maritime AS. The power consumption of the deck element is measured and compared to theoretical heat loss calculations. Large discrepancies between the measured power consumption and the theoretical heat loss were discovered, indicating the need for further studies on the matter. As part of SARex Spitzbergen 2016, a search and rescue exercise conducted off North Spitzbergen, heated deck elements on board the Norwegian Coast Guard Vessel KV Svalbard were studied and are discussed in this paper. The heating elements in the deck elements were designed to specifications at the time of commissioning, but proves insufficient when the vessel is in transit or exposed to slight winds, allowing snow and ice to accumulate on the surface. Finally, suggestions for a more energy efficient design of deck elements are made, as the current designs are found to have potential for improvement, especially due to the lack of insulation between the deck elements and the hull of the vessel.
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Liu, An, Zhigang Shan, Ting Shi et Weida Ni. « Numerical Simulation Research About the Influence of Nozzle Parameters on the Quality of Ice-Core in Hot-Water Ice-Drilling ». Dans ASME 2022 41st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/omae2022-80173.
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Abstract Ice sheets in the Arctic contain well-ordered accumulations of ancient ice that fell as snow years to millions of years ago. Ice-core data have become central to our understanding of climate change in the past, and to assessments of possible future climate change. Hot-water ice-coring drills are often used to recover ice-core samples from a desirable depth in conjunction with a full-scaled hot-water drilling systems. However, the recovered cores had the varying quality. In hot-water ice-coring drilling, many small nozzles are used to spray water out and melt out a cylindrical ice. Parameters of the nozzle, which mainly includes angle, diameter and quantity, are the most critical part of the drilling system. To improve the ice-core quality in hot-water ice-coring drilling, the influence mechanism of annular hot-water jets formed by nozzle with different parameters on ice-core quality was studied. Heat transfer law of annular jet on the ice-core was studied using the numerical simulation. Totally nine kinds of nozzle with different parameters were designed by using the orthogonal design method and the corresponding calculation domain model of ice was established. The ANSYS FLUENT software was used to analyze the heat flow field, variation trend of heat transfer to the ice-core with different nozzle parameters was researched. The result indicated that the heat transfer of hot water to ice core increased with the larger nozzle diameter while decreasing with the increase of nozzle quantity and nozzle angle. The result can help to give a reference for the design of hot-water ice-coring drill head used in the polar regions.
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Luping, Liu, Li Xin, Wu Xiao et Wu Bo. « Ice Model Tests for Semi-Submersible Platforms in Pack Ice Conditions ». Dans ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-95786.
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Abstract As development of the Arctic grows in intensity, semi-submersible platforms are one of promising type of offshore structures used for arctic oil exploitation. Generally a good ice management is equipped by a moored floating platform to reduce ice loads to manageable levels, thus the most common scenario for a polar operating semi-submersible platform is pack ice conditions. The resistance test of a 4-columns structure is performed in a normal towing tank in China using synthetic non-refrigerated material with similar density to model sea ice. Three component load cells on top of each column and a batch of single component load cells embedded in the surface of the columns near the waterline are used to measure indirect and direct ice loads on the structures. The effects of a series of parameters such as column shapes, orientations, column spacing ratios, ice floe shapes, ice drift speeds and ice concentrations are analyzed.
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Lande Andrade, Sthefano, Ahmed Elruby, Dan Oldford et Bruce Quinton. « Assessing Polar Class Ship Overload and Ice Impact on Low-ice Class Vessels using a “Quasi Real Time” Popov/Daley Approach ». Dans SNAME Maritime Convention. SNAME, 2022. http://dx.doi.org/10.5957/smc-2022-108.
Texte intégralRésumé :
The methodology presented in this work considers an impact’s available kinetic energy as balanced by the ice crushing energy as well as the structural deformation energy. The algorithm re-calculates the kinetic energy iteratively by subtracting the energy lost to structural deformation and ice crushing at specified time-intervals. The updated kinetic energy is then used to determine the current impact speed, which controls the indentation rate of ice on the structure. The result is a contactless ice load model which is intrinsically coupled to structural deformation. Accounting for structural deformation energy is important for overload of Polar Class ships, as well as any ice impact for non-ice class ships.
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Barz, Dominik P. J., Michael J. Vogel et Paul H. Steen. « Generation of Electrokinetic Flow in a Doped Non-Polar Liquid ». Dans ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels collocated with 3rd Joint US-European Fluids Engineering Summer Meeting. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30258.
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The presence of considerable amounts of free charge dispersed in a liquid is the basis for electrokinetic phenomena which are related to the existence of an electrical double layer (EDL). In polar liquids, the dissociation of electrolytes into ionic species is well understood and numerous electrokinetic phenomena are known; a good overview is given by e.g. Delgado et al. [1]. In nonpolar liquids it is known that electrical charges can exist as well. The presence of these electrical charges is utilized, for example, in colloid science to stabilize particle suspensions [2]. For this purpose, surfactants are added which enhance the zeta potential of the particles in order to prevent their agglomeration. Additionally to the manipulation of surface charges, it is reported that the electrical conductivity of nonpolar liquids essentially increases when surfactant is added and traces of water are present [3]. Such ternary solutions of nonpolar liquid-water-surfactant are known to contain surfactant agglomerations, so-called inverted micelles with a size of several nanometers, detectable for instance by quasielastic lightscattering measurements. Figure 1 sketches the generation and structure of an inverted micelle. In general, surfactants are macromolecules consisting of different functional groups, e.g. a polar “head” and a nonpolar “tail”. Above the critical micelle concentration (cmc), surfactant molecules attach with their polar head at a water droplet forming the inverted micelle. It is assumed that electrical charges are dissolved in the polar core of the inversed micelles enabling opposite charges to be held sufficiently far apart and preventing an agglomeration of different micelles [4].
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Papi, Francesco, Lorenzo Cappugi, Alessandro Bianchini et Sebastian Perez-Becker. « Numerical Modeling of the Effects of Leading-Edge Erosion and Trailing-Edge Damage on Wind Turbine Loads and Performance ». Dans ASME Turbo Expo 2020 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-16310.
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Abstract Wind turbines often operate in challenging environmental conditions. In hot and dusty climates, wind turbine blades are constantly exposed to abrasive particles that, according to many field reports, cause significant damages to the blade’s leading edge. On the other hand, in cold climates similar effects can be caused by prolonged exposure to hail and rain. Quantifying the effects of airfoil deterioration on modern multi-MW wind turbines is crucial to correctly schedule maintenance and to forecast the potential impact on productivity. Analyzing the impact of airfoil damage on fatigue and extreme loading is also important to improve the reliability and longevity of wind turbines. However, this is a topic that has not yet been extensively investigated. In this work, a blade erosion model is developed and calibrated using Computational Fluid Dynamics (CFD). The DTU 10MW Reference Wind Turbine (RWT) is selected as the case study for the analysis, as it is representative of the typical size of the future generation wind turbines. Lift and Drag polars are generated using the developed model and a CFD numerical set-up. Power and torque coefficients are compared in idealized conditions at two wind speeds, i.e. the rated speed and one below it. Full aero-servo-elastic simulations of the turbine are conducted with the eroded polars using NREL’s BEM-based code OpenFAST. Sixty-six ten-minute simulations are performed for each stage of airfoil damage, reproducing operating conditions specified by the IEC 61400-1 power production DLC-group, including wind shear, yaw misalignment and turbulence. Performance data, fatigue and extreme loads are compared for the aeroelastic simulations, showing maximum decreases in CP of about 12% as well as reductions in fatigue and extreme loading.
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Ahn, Jae-Woo, Joong-Hyo Choi, Sung-Gun Park et Sung-Kon Han. « Numerical Simulation of a Pre-Swirl Stator Collision With Sea Ice Incorporating Various Material Model Based on Experimental Study ». Dans ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/omae2018-77239.
Texte intégralRésumé :
The objective of this paper is to develop a realistic numerical model for ice–pre swirl stator (PSS) structure interaction problem under collision circumstance. PSS structure has been installed in front of a propeller of oil carrier or container vessel operating non-arctic region in order to increase efficiency of propulsion system, which was designed by Daewoo Shipbuilding and Marine Engineering (DSME). Recently, according to increase of port traffic in arctic region, it is being anticipated that market of PSS installed vessel operating in arctic region will be extended to pursue raised ship’s efficiency but in strength point of view, quantified assessment for dynamic interaction between PSS and sea ice is not specified in any design codes or classification rules. This standpoint will be led to an increased demand for the safe structural design of arctic vessel’s PSS structure subject to collision with sea ice. In this study, DSME’s PSS structure design will be introduced and five types of numerical model to represent ice crushing behavior which were well-known though previous study will be investigated. The parameters of each material model of ice will be defined and more realistic numerical model for ice will be proposed through comparison study with experimental results. After that, the results of numerical simulations for a collision between PSS and sea ice with five numerical models using LS-DYNA software will be represented. In here, dynamic responses of PSS and failure behaviors of each ice model at each load case will be thoroughly evaluated. Collision loading scenarios and ice dimension were properly assumed based on polar class rule for propeller-sea ice interaction. Consequently, simplified analytic method and proper numerical model for ice corresponding to PSS-sea ice collision simulation will be proposed and discussed, respectively.
Rapports d'organisations sur le sujet "Non polar Ice core"
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Ueda, Herbert T., et Pavel G. Talalay. Fifty Years of Soviet and Russian Drilling Activity in Polar and Non-Polar Ice : A Chronological History. Fort Belvoir, VA : Defense Technical Information Center, octobre 2007. http://dx.doi.org/10.21236/ada472548.
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Elbaum, Michael, et Peter J. Christie. Type IV Secretion System of Agrobacterium tumefaciens : Components and Structures. United States Department of Agriculture, mars 2013. http://dx.doi.org/10.32747/2013.7699848.bard.
Texte intégralRésumé :
Objectives: The overall goal of the project was to build an ultrastructural model of the Agrobacterium tumefaciens type IV secretion system (T4SS) based on electron microscopy, genetics, and immunolocalization of its components. There were four original aims: Aim 1: Define the contributions of contact-dependent and -independent plant signals to formation of novel morphological changes at the A. tumefaciens polar membrane. Aim 2: Genetic basis for morphological changes at the A. tumefaciens polar membrane. Aim 3: Immuno-localization of VirB proteins Aim 4: Structural definition of the substrate translocation route. There were no major revisions to the aims, and the work focused on the above questions. Background: Agrobacterium presents a unique example of inter-kingdom gene transfer. The process involves cell to cell transfer of both protein and DNA substrates via a contact-dependent mechanism akin to bacterial conjugation. Transfer is mediated by a T4SS. Intensive study of the Agrobacterium T4SS has made it an archetypal model for the genetics and biochemistry. The channel is assembled from eleven protein components encoded on the B operon in the virulence region of the tumor-inducing plasmid, plus an additional coupling protein, VirD4. During the course of our project two structural studies were published presenting X-ray crystallography and three-dimensional reconstruction from electron microscopy of a core complex of the channel assembled in vitro from homologous proteins of E. coli, representing VirB7, VirB9, and VirB10. Another study was published claiming that the secretion channels in Agrobacterium appear on helical arrays around the membrane perimeter and along the entire length of the bacterium. Helical arrangements in bacterial membranes have since fallen from favor however, and that finding was partially retracted in a second publication. Overall, the localization of the T4SS within the bacterial membranes remains enigmatic in the literature, and we believe that our results from this project make a significant advance. Summary of achievements : We found that polar inflations and other membrane disturbances relate to the activation conditions rather than to virulence protein expression. Activation requires low pH and nutrient-poor medium. These stress conditions are also reflected in DNA condensation to varying degrees. Nonetheless, they must be considered in modeling the T4SS as they represent the relevant conditions for its expression and activity. We identified the T4SS core component VirB7 at native expression levels using state of the art super-resolution light microscopy. This marker of the secretion system was found almost exclusively at the cell poles, and typically one pole. Immuno-electron microscopy identified the protein at the inner membrane, rather than at bridges across the inner and outer membranes. This suggests a rare or transient assembly of the secretion-competent channel, or alternatively a two-step secretion involving an intermediate step in the periplasmic space. We followed the expression of the major secreted effector, VirE2. This is a single-stranded DNA binding protein that forms a capsid around the transferred oligonucleotide, adapting the bacterial conjugation to the eukaryotic host. We found that over-expressed VirE2 forms filamentous complexes in the bacterial cytoplasm that could be observed both by conventional fluorescence microscopy and by correlative electron cryo-tomography. Using a non-retentive mutant we observed secretion of VirE2 from bacterial poles. We labeled the secreted substrates in vivo in order detect their secretion and appearance in the plant cells. However the low transfer efficiency and significant background signal have so far hampered this approach.