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Bakhtizin, R. Z.; Valeev, V. G. |
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Field evaporation stimulated by a coherent electromagnetic wave |
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1990 |
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Surface Science |
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Surf. Sci. |
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231 |
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1-2 |
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135-138 |
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Field Ion Microscopy |
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Abbreviated Series Title |
Laser-stimulated processes of constant field evaporation of surface atoms are described. It is shown that under certain conditions the application of a weak alternating field may enhance ion tunneling and result in a significant increase in ion current. The paper offers a numerical estimation of the expected results of such an experiment. |
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4324 |
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Sinnott, Susan; Mao, Zugang; Lee, Kiho |
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Computational Studies of Molecular Diffusions through Carbon Nanotubes Based membrances (Invited) |
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Journal Article |
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2002 |
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Computer Modeling in Engineering and Science |
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3 |
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5 |
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575-587 |
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Nanofluidics is an area that has been under study for some time in zeolites and idea nanoporous systems. Computational studies of the behavior of molecules in nanoporous structures have played an important role in understanding this phenomenon as experimental studies of molecular behavior in nanometer-scale pores are difficult to perform. in this paper computational work to study molecular motion and the separation of molecular mixtures in carbon nanotube systems is reported. The systems examined include organic molecules, such as CH4, C2H6, n-C4H10, and i-c4H10, and inorganic molecules, such as CO2. The interatomic forces in the molecular dynamics simulations are calculated using a classical reactive empirical bond order hydrocarbon potetial coupled to lernard-Jones and coulombic potentials. Molecules moving at thermal velocities corresponding to 300K are predicted to diffuse from areas of high density to areas of low density through the nanotubes. The simulations indicate how the structure and size of molecules and the nanotubes influence molecular diffusion through the nanotubes and the separation of the molecular mixtures. |
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NU @ z-mao2 @ |
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198 |
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Kim, Jeong Kil; Kim, Yeong Ho; Lee, Bong Ho; Kim, Kyoo Young |
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New findings on intergranular corrosion mechanism of stabilized stainless steels |
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Journal Article |
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2011 |
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Electrochimica Acta |
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ADVANCES IN CORROSION SCIENCE FOR LIFETIME PREDICTION AND SUSTAINABILITYSelection of papers from the |
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56 |
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4 |
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1701-1710 |
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Intergranular corrosion; Stainless steel; Stabilizer effect; Segregation; Chromium |
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Number of different sets of stabilized both ferritic and austenitic stainless steels with various alloying elements were evaluated to verify new findings on the intergranular corrosion mechanism. The intergranular segregation and precipitation were analyzed by using a transmission electron microscopy with an energy dispersive X-ray spectroscopy and a laser assisted three-dimensional atom probe. On the basis of the current result, it is newly proposed that the intergranular corrosion occurring in the stabilized both ferritic and austenitic stainless steels is induced by Cr-depletion due to segregation of un-reacted Cr atoms around carbides of stabilizer elements (Ti or Nb) along the grain boundary, but not due to formation of Cr-carbide. A prevention method for this type of intergranular corrosion is also suggested after critical evaluation on the effect of Cr, C, and Ni. |
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0013-4686 |
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NU @ karnesky @ |
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11057 |
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Chi, E. J.; Shim, J. Y.; Baik, H. K.; Lee, S. M. |
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Fabrication of amorphous-carbon-nitride field emitters |
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Journal Article |
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1997 |
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Applied Physics Letters |
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Appl. Phys. Lett. |
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71 |
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324-326 |
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Field Emission; Field emitters; Eutectic silicon; Electric currents; Carbon; Electron affinities |
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o improve siliconfield emitters, an amorphous-carbon-nitride (a-CN) coating was applied by helical resonator plasma-enhanced chemical vapor deposition. By this process, a-CN was very uniformly coated on silicon tips without any damage. Microstructural and electrical investigation of the silicon and a-CN coated field emitters were performed. a-CN coating lowered turn-on voltage and increased emission current. Negative electron affinity of carbon nitride is suggested for enhancing emission current. |
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NU @ karnesky @ |
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2540 |
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Rogozhkin, S.V.; Aleev, A.A.; Zaluzhnyi, A.G.; Nikitin, A.A.; Iskandarov, N.A.; Vladimirov, P.; Lindau, R.; Möslang, A. |
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Atom probe characterization of nano-scaled features in irradiated ODS Eurofer steel |
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Journal Article |
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2011 |
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Journal of Nuclear Materials |
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409 |
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2 |
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94-99 |
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ODS steel; ODS Eurofer; clusters; irradiation; fast neutron |
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Our previous investigations of unirradiated ODS Eurofer by tomographic atom probe (TAP) revealed numerous nano-scaled features (nanoclusters) enriched in vanadium, yttrium and oxygen. In this work the effect of neutron irradiation on nanostructure behaviour of ODS Eurofer (9%-CrWVTa) was investigated. The irradiation was performed in the research reactor BOR-60 (Dimitrovgrad, Russia) where materials were irradiated at 330°S to 32 dpa. TAP studies were performed on the needles prepared from parts of broken Charpy specimens. For all specimens except one, which was tested at 500°C, the Charpy tests were performed at temperatures not exceeding the irradiation temperature. A high number density 2÷4×1024 m-3 of ultra fine 1-3 nm diameter nanoclusters enriched in yttrium, oxygen, manganese and chromium was observed in the as-irradiated state. The composition of detected clusters differs from that for unirradiated ODS Eurofer. It was observed in this work that after neutron irradiation vanadium atoms had left the clusters, moving from the core into solid solution. The concentrations of yttrium and oxygen in the matrix, as it was detected, increase several times under irradiation. In the samples tested at 500°C both the number density of clusters and the yttrium concentration in the matrix decrease by a factor of two. |
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0022-3115 |
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NU @ karnesky @ |
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10946 |
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Aleev, A.A.; Iskandarov, N.A.; Klimenkov, M.; Lindau, R.; Möslang, A.; Nikitin, A.A.; Rogozhkin, S.V.; Vladimirov, P.; Zaluzhnyi, A.G. |
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Investigation of oxide particles in unirradiated ODS Eurofer by tomographic atom probe |
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Journal Article |
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2011 |
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Journal of Nuclear Materials |
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409 |
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2 |
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65-71 |
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Ods; atom probe tomography; precipitation |
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Oxide dispersion strengthened steels possess better high-temperature creep and radiation resistance than conventionally produced ferritic/martensitic steels. This behavior is mainly caused by the presence of highly dispersed and extremely stable oxide particles with diameters of a few nanometers. In this work the nanostructure of ODS Eurofer steel was investigated by means of tomographic atom probe and correlations with recent TEM and SANS studies were derived. The present investigation revealed nanoscaled clusters of typically 2 nm diameter containing not only yttrium and oxygen but also vanadium and nitrogen. Moreover, concentration of vanadium in particles was found to be higher than that of yttrium, which indicates the importance of these elements in cluster formation. The estimated average cluster number density is about 2×1024 m-3. These enriched zones might be evidently attributed to precursors of the larger precipitates observed by TEM. This conclusion is also supported by the similarities of the chemical composition inside enriched zones seen in both atomic probe and TEM data. |
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0022-3115 |
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NU @ karnesky @ |
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10951 |
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Knipling, Keith E.; Karnesky, Richard A.; Lee, Constance P.; Dunand, David C.; Seidman, David N. |
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Precipitation Evolution in Al-0.1Sc, Al-0.1Zr, and Al-0.1Sc-0.1Zr (at.%) Alloys during Isochronal Aging |
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Journal Article |
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2010 |
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Acta Materialia |
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58 |
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15 |
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5184-5195 |
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Aluminum alloys, Precipitation, Scandium, Zirconium, Atom-probe tomography; Al-Sc-Zr |
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Precipitation strengthening is investigated in binary Al-0.1Sc, Al-0.1Zr, and ternary Al-0.1Sc-0.1Zr (at.%) alloys aged isochronally between 200 and 600 °C. A pronounced synergistic effect is observed when both Sc and Zr are present. Above 325 °C, where peak microhardness (670 MPa) occurs in the binary Al-Sc alloy due to Al[sub:3]Sc (L1[sub:2]) nanometer-scale precipitates, Zr additions result in a secondary increase in strength due to additional precipitation of Zr-enriched outer shells onto these precipitates. The ternary alloy reaches a peak microhardness of 780 MPa at 400 °C, delaying overaging by >100 °C compared with the binary Al-Sc alloy and increasing strength compared with the binary Al-Zr alloy (peak microhardness of 420 MPa at 425–450 °C). Compositions, radii, volume fractions, and number densities of the Al[sub:3](Sc[sub:1-x]Zr[sub:x]) precipitates are measured directly using atom-probe tomography. This information is used to quantify the observed strengthening increments, attributed to dislocation shearing of the Al[sub:3](Sc[sub:1-x]Zr[sub:x]) precipitates. |
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NU @ karnesky @ |
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10705 |
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Lee, Thomas C. M. |
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ON ALGORITHMS FOR ORDINARY LEAST SQUARES REGRESSION SPLINE FITTING: A COMPARATIVE STUDY |
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Journal Article |
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2002 |
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Journal of Statistical Computation and Simulation |
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72 |
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8 |
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647-663 |
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Bivariate smoothing; Generalized cross-validation; Genetic algorithms; Regression spline; Stepwise selection |
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Regression spline smoothing is a popular approach for conducting nonparametric regression. An important issue
associated with it is the choice of a ‘‘theoretically best’’ set of knots. Different statistical model selection
methods, such as Akaike’s information criterion and generalized cross-validation, have been applied to derive
different ‘‘theoretically best’’ sets of knots. Typically these best knot sets are defined implicitly as the optimizers
of some objective functions. Hence another equally important issue concerning regression spline smoothing is
how to optimize such objective functions. In this article different numerical algorithms that are designed for
carrying out such optimization problems are compared by means of a simulation study. Both the univariate and
bivariate smoothing settings will be considered. Based on the simulation results, recommendations for choosing a
suitable optimization algorithm under various settings will be provided. |
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NU @ karnesky @ |
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860 |
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Park, Jin Ho; Kim, Jeong Kil; Lee, Bong Ho; Kim, Sang Seok; Kim, Kyoo Young |
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Three-dimensional atom probe analysis of intergranular segregation and precipitation behavior in Ti-Nb-stabilized low-Cr ferritic stainless steel |
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Journal Article |
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2013 |
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Scripta Materialia |
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68 |
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237-240 |
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3-D atom probe; Intergranular corrosion; Segregation; Precipitation; Stainless steel |
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Sequential phenomena of intergranular segregation and precipitation in Ti-Nb-stabilized 11 wt.% Cr ferritic stainless steel have been investigated. During aging, C and Ti diffuse into the grain boundary before Nb and Cr and form TiC preferentially. The solute Cr atoms segregate along the grain boundary, consequently resulting in Cr depletion in the vicinity of the grain boundary. |
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1359-6462 |
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NU @ karnesky @ |
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11426 |
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Tewari, S.N.; Vijayakumar, M.; Lee, J.E.; Curreri, P.A. |
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Solutal partition coefficients in nickel-based superalloy PWA-1480 |
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Journal Article |
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1991 |
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Materials Science and Engineering A |
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141 |
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1 |
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97-102 |
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Solutal profiles in dendritic single-crystal specimens of PWA-1480 nickel-base superalloy, which were directionally solidified and quenched, were examined on several transverse cross-sections to obtain the partition coefficients. Similar to their nickel-base binaries, the partition coefficients of tantalum, titanium, and aluminum were found to be less than unity; those of tungsten and cobalt were greater than unity. The partition coefficients were temperature independent in the range 1584-1608 K. The contribution of solid-state diffusion to microsegregation was observed to be negligible. |
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NU @ karnesky @ |
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9820 |
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