1,619 research outputs found
Towards closure of regional heat budgets in the North Atlantic using Argo floats and surface flux datasets
No full textThe upper ocean heat budget (0–300 m) of the North Atlantic from 20°–60° N is investigated using data from Argo profiling floats for 1999–2005 and the NCEP/NCAR and NOC surface flux datasets. Estimates of the different terms in the budget (heat storage, advection, diffusion and surface exchange) are obtained using the methodology developed by Hadfield et al. (2007a, b). The method includes optimal interpolation of the individual profiles to produce gridded fields with error estimates at a 10°×10° grid box resolution. Closure of the heat budget is obtained within the error estimates for some regions – particularly the eastern subtropical Atlantic – but not for those boxes that include the Gulf Stream. Over the whole range considered, closure is obtained for 13 (9) out of 20 boxes with the NOC (NCEP/NCAR) surface fluxes. The seasonal heat budget at 20–30° N, 35–25° W is considered in detail. Here, the NCEP based budget has an annual mean residual of ?55±35 Wm?2 compared with a NOC based value of ?4±35 Wm?2. For this box, the net heat divergence of 36 Wm?2 (Ekman=?4 Wm?2, geostrophic=11 Wm?2, diffusion=29 Wm?2) offsets the net heating of 32 Wm?2 from the NOC surface heat fluxes. The results in this box are consistent with an earlier evaluation of the fluxes using measurements from research buoys in the subduction array which revealed biases in NCEP but good agreement of the buoy values with the NOC fields
Near-Maximal Two-Photon Entanglement for Optical Quantum Communication at 2.1 mu m
No full textOwing to a reduced solar background and low propagation losses in the atmosphere, the 2- to 2.5-mu m waveband is a promising candidate for daylight quantum communication. This spectral region also offers low losses and low dispersion in hollow-core fibers and in silicon waveguides. We demonstrate near-maximally entangled photon pairs at 2.1 mu m that could support device-independent quantum key distribution (DIQKD), assuming sufficiently high channel efficiencies. The state corresponds to a positive secure-key rate (0.254 bits/pair, with a quantum bit error rate of 3.8%) based on measurements in a laboratory setting with minimal channel loss and transmission distance. This is promising for the future implementation of DIQKD at 2.1 mu m
D-1057b: 580 North 300 East, Logan, Utah, Norman and Elaine M. Hadfield residence. Lot 5 Block 52 Plat A
No full textD-1057b: 580 North 300 East, Logan, Utah, Norman and Elaine M. Hadfield residence. Lot 5 Block 52 Plat
Motivating learning / Jill Hadfield and Zoltan Dornyei.
No full textIncludes bibliographical references.viii, 307 p.
Comparative study of the mechanical and tribological properties of a Hadfield and a Fermanal steel
No full textIn this study, Fe-12.50Mn-1.10C-1.70Cr-0.40Mo-0.40Si-0.50(max)P-0.50(max)S (Hadfield alloy) and Fe-28.4Mn-0.86C-1.63Al-0.42Cu-1.80Mo- .59Si-0.60W (Fermanal alloy) (Wt. %) in the aged condition were compared in terms of its tribological and microstructural properties. The x-ray diffraction (XRD) patterns were refined with the lines of the austenitic γ -phase, Chromium Iron Carbide (Cr2Fe14C), Iron Carbide (Fe2C), and Iron Oxide (Fe0.974O (II)) for the Hadfield alloy, and the lines of the austenitic γ - phase, martensite (M), Mn1.1Al0.9 phase and iron carbide (Fe7C3) for the Fermanal alloy. Mossbauer spectra were fit with two sites for the Hadfield alloy, which displayed as a broad ¨ singlet because of the austenitic disordered phase, and had a magnetic hyperfine field distribution, which corresponds to the Cr2Fe14C ferromagnetic carbides found by XRD. There were two paramagnetic sites, a singlet, which corresponds to the austenite disordered phase, and a doublet, which can be attributed to the Fe7C3 carbide. The obtained Rockwell C hardness for aged Hadfield and Fermanal alloys were 43.786 and 50.018 HRc, respectivel
Maria Hadfield Cosway, catalogo della mostra (Lodi, Fondazione Maria Cosway, 23 settembre-27 novembre 2022)
No full textMaria Hadfield Cosway rimane una delle figure femminili più affascinanti della sua epoca, capace di intessere relazioni ed amicizie con personalità di rilievo internazionale nella storia politica, culturale e artistica tra la fine dell’Antico Regime e la Restaurazione. Tra di esse sono sicuramente da ricordare Thomas Jefferson, terzo Presidente degli Stati Uniti, e il suo fraterno amico, il generale polacco Tadeusz Kosciuszko, Louisa Stolberg contessa d’Albany con l’inseparabile Vittorio Alfieri, la famiglia Bonaparte, Giulia Beccaria e suo figlio Alessandro Manzoni, Ugo Foscolo, Luigi Marchesi di Inzago detto Marchesini (1754-1829), che studiò a Modena e divenne “allievo musico soprano” nella cattedrale di Milano, innumerevoli artisti tra cui Angelica Kauffman, Anne Damer Seymour, Antonio Canova, Jacques Louis David, Joseph-Marie Vien, Jean-Baptiste Regnault, Andrea Appiani, e tanti altri personaggi ancora. Di queste relazioni rimangono un ricco epistolario e diversi diari, che racchiudono importanti testimonianze storiche. Nella piena consapevolezza di non poter fornire una panoramica del tutto esaustiva dei molteplici aspetti che caratterizzarono la vita della Cosway, la mostra Maria Hadfield Cosway intende proporre al pubblico alcuni approfondimenti per la conoscenza e lo studio dell’artista, sia come pittrice sia come musicista, e dell’educatrice, oltre a presentare aperture su alcuni specifici temi del periodo, partendo dalla Firenze asburgica e dalla Londra di Giorgio III e del principe di Galles, affacciandosi sui nascenti Stati Uniti di Jefferson e sulla Parigi di Napoleone, per arrivare alla realtà di Lodi e della Lombardia dei primi decenni del XIX secolo
«I am susceptible and everything that surrounds me has great power to magnetise me» : Maria Cosway e l’ambiente romantico
No full textNel contributo, la ricca vicenda biografica di Maria Cosway è declinata a partire dai rapporti con insigni personalità preromantiche e romantiche: in primis Johan Heinrich Füssli e William Blake. Una contestualizzazione cruciale, che consente di valutare appieno la caratura e i connotati dell'apporto artistico della Hadfield fra Sette e Ottocento, intesi alla luce del sincretismo intellettuale, esistenziale, religioso e filosofico che tratteggia i salotti mondani frequentati in compagnia del marito Richard e il precipitato figurativo da essi derivato
Austenitic grain size refinement of Hadfield steel by the addition of Hf.
No full textO refino microestrutural tem sido amplamente estudado em materiais ferrosos que iniciam a solidificação com a fase ferrítica, assim como em ligas de alumínio, magnésio e ferros fundidos. Porém, existem poucos estudos para aços austeníticos, incluindo o aço Hadfield. Este trabalho consiste no estudo dos mecanismos envolvidos no refino do tamanho de grão austenitico do aço Hadfield através de adições controladas de Hf. Foram realizados cálculos termodinâmicos no software Thermo-calc para caracterizar a sequência de solidificação do aço Hadfield de referência (1,2%C; 13%Mn e 0,65%Si) e do aço Hadfield com adição de Hf (0,15%). Foram realizados experimentos de fundição para caracterizar a macroestrutura do aço Hadfield de referência (morfologia e tamanho dos grãos) e, na sequência, foi adicionado o Hf para a obtenção das amostras refinadas. Nas corridas experimentais, foram avaliados o efeito dos seguintes parâmetros no tamanho de grão austenítico: a desoxidação com Al, a temperatura de vazamento, o método de adição do Hf e o tempo entre a adição do Hf ao banho metálico e o vazamento. O aço Hadfield de referência possui três zonas macroestruturais de solidificação: zona coquilhada, colunar e equiaxial. O comprimento médio dos grãos colunares foi de aproximadamente 4000 m e o tamanho dos grãos equiaxiais médio foi de 2040 m. Na condição refinada (adição de Hf), a macroestrutura do lingote não possui as zonas coquilhada e colunar bem definidas, com tamanho médio dos grãos equiaxiais de 380 m, ou seja, redução de aproximadamente 5 vezes em relação a condição anterior. A combinação da adição de Hf e a desoxidação com 0,1%Al resultou em tamanhos de grão ainda menores (cerca de 340 m) em comparação às condições em que somente o Hf foi adicionado. A técnica de análise térmica (monitoramento da temperatura em função do tempo) foi utilizada para analisar o comportamento de solidificação do aço Hadfield de referência e com adição de Hf. A identificação e caracterização das partículas ricas em Hf foi realizada por: (a) microscopia eletrônica de varredura (EDS/WDS e EBSD); (b) microscopia de transmissão e (c) difração de raios X dos resíduos concentrados obtidos pela técnica de extração de precipitados por dissolução química. Essas técnicas indicaram a presença de partículas de óxido, carboneto, nitreto e carbonitreto, de Hf (HfO2, HfN, HfN2, HfCN, HfC), sugerindo que essas partículas desempenham uma função importante na nucleação heterogênea da austenita.Microstructural refining has been widely studied in ferrous materials that begin solidification with the ferritic phase, as well as in aluminum and magnesium alloys, and in cast iron. However, there are very few studies for austenitic steels, including Hadfield steels. This work consists of studying the mechanisms causing the refinement of the austenitic grain structure of an as-cast Hadfield steel by controlled additions of Hf. Simulations were performed in the Thermo-calc software to characterize the solidification sequence of a reference Hadfield steel (1.2%C, 13%Mn and 0.65%Si) and of a Hadfield steel with the addition of Hf. Casting experiments were carried out to characterize the macrostructure of the reference Hadfield steel (morphology and grain size), then Hf was added to obtain the refined specimens. In the casting experiments, the effect of Al deoxidation, pouring temperature and Hf addition method on the austenitic grain size were evaluated. The reference Hadfield steel ingot has three grain structure zones: chilled, columnar and equiaxed. The average columnar grain length is approximately 4000 m and the average equiaxed grain size is approximately 2040 m. In the refined condition (by the addition of Hf), the macrostructure of the specimen does not have well-defined chilled and columnar zones, with an average equiaxed grain size of 380 m. This represents a reduction in grain size by approximately 5 times in relation to the reference condition. The combination of Hf addition and 0.1%Al deoxidation resulted in Hadfield steel with even smaller grain sizes (about 340 m). Thermal analysis was used to investigate the solidification behavior of the ingots with and without Hf additions. Characterization and identification of Hf-rich particles was performed by: (a) scanning electron microscopy (EDS/WDS and EBSD); (b) transmission electron microscopy and (c) X-ray diffraction of residues with concentrated particles extracted from the samples by chemical dissolution. These techniques indicated the presence of Hf oxide, carbide, carbonitride and nitride particles (HfO2, HfN, HfN2, HfCN, HfC), suggesting that these particles might have played an important role in the heterogeneous nucleation of austenite
The North Atlantic heat budget: an Argo based study
No full textThe Argo dataset is used to obtain estimates of the heat storage and heat divergence withthe aim of the assessing the usefulness of the Argo array for investigating the NorthAtlantic heat budget. The accuracy of the Argo-based mixed layer heat storage variessignificantly throughout the North Atlantic. Errors are smallest, around 10-20 Wm-2 onmonthly timescales for 10° x 10° boxes, reducing to 5-10 Wm-2 on seasonal scales in thesubtropics and eastern basin. Heat storage errors over a fixed 300 m layer are higher, buttypically remain below 20 Wm-2 on seasonal timescales away from the western boundary.The heat budget is closed (using net heat fluxes from the NCEP climatology and NOCreanalysis) within the estimated error throughout the subtropical and eastern North Atlantic,indicating the value of the Argo dataset in studies of this nature. However, within thewestern boundary the heat budget residual typically exceeds 50 Wm-2, with the heat storageoverestimated or the heating from the net heat flux and/or advective and diffusivedivergence underestimated. Assuming that heat storage error estimates are accurate andconsidering results in the literature regarding the bias in net heat flux products, it is likelythat heating from divergence is underestimated. The heating contribution from this termmay be large on scales that cannot be resolved using Argo. In the eastern and subtropicalNorth Atlantic, the errors in the Argo-based heat budget terms are smaller than theuncertainty in the net heat flux products and can thus be used to provide insight into whichatmospheric dataset (the NCEP reanalysis or the NOC climatology) may be more accurate.The NOC net heat flux is more accurate than that from NCEP throughout the year in thesubtropics and during the first half of the year in the eastern mid-latitudes.The errors in the mixed layer heat storage are smaller than the interannual variability inthis term. Thus Argo can be used to investigate variability on this scale. While the currentArgo dataset is on the short side for studies of this nature, continued funding of the array isexpected to provide more insightful results
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