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Hydrogen Content (hydrogen + content)
Selected AbstractsPrediction of Hydrogen Content in Coal using Back Propagation Neural NetworkASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2005L. C. Ju This paper introduces the concept of sample study risk in neural network (NN), and studies the prediction of hydrogen content in coal using Back Propagation Neural Networks (BP NN). Targeting the problem of training convergence quality impaired by the interfering information of some samples in BP NN, the validity of the concept of sample study in NN, and the feasibility of analyzing chemical elements in coal using NN are discussed. [source] Effect of Decrease of Hydride-Induced Embrittlement in Nanocrystalline Titanium,ADVANCED ENGINEERING MATERIALS, Issue 8 2010M.A. Murzinova Abstract The room-temperature impact toughness, strength and ductility of nanocrystalline (NC) and microcrystalline (MC) titanium with hydrogen content ranging from 0.1 to 16,at.-% (0.002 to 0.450,wt.-%) are studied. NC titanium has higher strength and lower sensitivity to hydride-induced brittle fracture than the MC material. In contrast to MC titanium, the elongation and impact toughness in the NC material does not decrease dramatically with increasing hydrogen content. Moreover, the fracture toughness in hydrogenated NC condition is found to be higher than that in MC titanium. This unusual result may be associated with the precipitation of equiaxial nanoscale hydrides in the interior of ,-grains in the NC material, while platelet hydrides are formed in MC titanium. One can expect that the risk of hydride-induced embrittlement is lower in NC than in MC titanium, making the NC material attractive for potential application under conditions that may cause hydrogen saturation above the permissible level for MC titanium. [source] Effect of Hydrogen on Fatigue Strength of High-Strength Steels in the VHCF Regime,ADVANCED ENGINEERING MATERIALS, Issue 7 2009Yongde Li Diffusible hydrogen or non-diffusible hydrogen can decrease the fatigue strength of high-strength steels. The hydrogen influence factor f(C) describes the hydrogen damage level of fatigue strength. Fatigue strength decreases with increasing non-diffusible hydrogen content in the range 1 ppm,<,Ci,<,3.0,ppm. Fatigue strength decreases significantly with increasing diffusible hydrogen content in the range 1 ppm,<,Cr,<,3.0,ppm, but shows almost no obvious change in the range 3.0 ppm,<,Cr,<,10.0,ppm. [source] Nanoscopic fatigue and stress corrosion crack growth behaviour in a high-strength stainless steel visualized in situ by atomic force microscopyFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 11 2005K. MINOSHIMA ABSTRACT In situ atomic force microscope (AFM) imaging of the fatigue and stress corrosion (SC) crack in a high-strength stainless steel was performed, under both static and dynamic loading. The AFM systems used were (1) a newly developed AFM-based system for analysing the nanoscopic topographies of environmentally induced damage under dynamic loads in a controlled environment and (2) an AFM system having a large sample stage together with a static in-plane loading device. By using these systems, in situ serial clear AFM images of an environmentally induced crack under loading could be obtained in a controlled environment, such as in dry air for the fatigue and in an aqueous solution for the stress corrosion cracking (SCC). The intergranular static SC crack at the free corrosion had a sharp crack tip when it grew straight along a grain boundary. The in situ AFM observations showed that the fatigue crack grew in a steady manner on the order of sub-micrometre. The same result was obtained for the static SC crack under the free corrosion, growing straight along a grain boundary. In these cases, the crack tip opening displacement (CTOD) remained constant. However, as the static SC crack was approaching a triple grain junction, the growth rate became smaller, the CTOD value increased and the hollow ahead of the crack tip became larger. After the crack passed through the triple grain junction, it grew faster with a lower CTOD value; the changes in the CTOD value agreed with those of the crack growth rate. At the cathodic potential, the static SC crack grew in a zigzag path and in an unsteady manner, showing crack growth acceleration and retardation. This unsteady crack growth was considered to be due to the changes in the local hydrogen content near the crack tip. The changes in the CTOD value also agreed with those of the crack growth rate. The CTOD value in the corrosive environment was influenced by the microstructure of the material and the local hydrogen content, showing a larger scatter band, whereas the CTOD value of the fatigue crack in dry air was determined by the applied stress intensity factor, with a smaller scatter band. In addition, the CTOD value in the corrosive environment under both static and dynamic loading was smaller than that of the fatigue crack; the environmentally induced crack had a sharper crack tip than the fatigue crack in dry air. [source] Redshifted 21-cm observations of high-redshift quasar proximity zonesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008J. Stuart B. Wyithe ABSTRACT The introduction of low-frequency radio arrays is expected to revolutionize the study of the reionization epoch. Observation of the contrast in redshifted 21-cm emission between a large H ii region and the surrounding neutral intergalactic medium (IGM) will be the simplest and most easily interpreted signature. However, the highest redshift quasars known are thought to reside in an ionized IGM. Using a semi-analytic model we describe the redshifted 21-cm signal from the IGM surrounding quasars discovered using the i -drop-out technique (i.e. quasars at z, 6). We argue that while quasars at z < 6.5 seem to reside in the post-overlap IGM, they will still provide valuable probes of the late stages of the overlap era because the light-travel time across a quasar proximity zone should be comparable to the duration of overlap. For redshifted 21-cm observations within a 32-MHz bandpass, we find that the subtraction of a spectrally smooth foreground will not remove spectral features due to the proximity zone. These features could be used to measure the neutral hydrogen content of the IGM during the late stages of reionization. The density of quasars at z, 6 is now well constrained. We use the measured quasar luminosity function to estimate the prospects for discovery of high-redshift quasars in fields that will be observed by the Murchison Widefield Array. [source] Influence of laser crystallization on hydrogen bonding in poly-SiPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2008N. H. Nickel Abstract We investigate the influence of the hydrogen content in the amorphous starting material on hydrogen bonding and defect passivation in laser crystallized poly-Si using electron-spin-resonance and hydrogen effusion measurements. After laser dehydrogenation and crystallization the specimens contain a residual H concentration of 8×1021 cm,3 to 1.5×1022 cm,3. During a vacuum anneal at least 1.5×1021 cm,3 H atoms are mobile in the lattice, however, only about 3.7×1018 cm,3 H atoms passivate Si dangling-bonds. Our results show that the annealing treatment can cause the vast majority of H atoms to accumulate in H stabilized platelets. Since defect passivation preferentially occurs at grain boundaries and platelet nucleation and growth is confined to the interior of single crystal grains, H equilibration is governed by two spatially separated processes. Moreover, our data demonstrate that the hydrogen density-of-states distribution derived from H effusion data is dynamic and changes in response to experimental parameters. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of Technological Factors on Electrochemical Hydrogenation of LigninTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2002Jianan Zhang Abstract Lignin properties were improved by electrochemical hydrogenation. Various technological factors, such as cathode materials, temperature and concentrations of water, solvent, substrate, on the electrochemical hydrogenation of lignin in divided electrolytic cell were studied. The results showed that the hydrogen content (H %) and ratio of hydrogen to carbon (H/C) of hydrogenated lignin (HL) increased by 1.7 % and 0.04, respectively, and the softening point (SP) decreased by 24°C in comparison with lignin raw material. It was feasible for lignin to be electrochemically hydrogenated. Les propriétés de la lignine ont été améliorées par hydrogénation électrochimique. Divers facteurs technologiques, tels que le matériau des cathodes, la température et les concentrations de l'eau, du solvant, du substrat, sur l'hydrogénation électrochimique de la lignine dans une cellule électrolytique divisée, sont étudiés. Les résultats montrent que la teneur en hydrogène (H %) et le rapport entre l'hydrogène et le carbone (H/C) de la lignine hydrogénée (HL) augmente de 1,7% et 0,04, respectivement, et que le point d'adoucissement (SP) diminue de 24°C comparativement au matériau brut de la lignine. La lignine a pu être hydrogénée électrochimiquement. [source] Prediction of Hydrogen Content in Coal using Back Propagation Neural NetworkASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2005L. C. Ju This paper introduces the concept of sample study risk in neural network (NN), and studies the prediction of hydrogen content in coal using Back Propagation Neural Networks (BP NN). Targeting the problem of training convergence quality impaired by the interfering information of some samples in BP NN, the validity of the concept of sample study in NN, and the feasibility of analyzing chemical elements in coal using NN are discussed. [source] | ||||||||||||||||