| 11. |
- Engquist, Björn, et al.
(author)
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Numerical methods for oscillatory solutions to hyperbolic problems
- 1993
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In: Communications on Pure and Applied Mathematics. - : John Wiley & Sons. - 0010-3640 .- 1097-0312. ; 46:10, s. 1327-1361
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Journal article (peer-reviewed)abstract
- Difference approximations of hyperbolic partial differential equations with highly oscillatory coefficients and initial values are studied. Analysis of strong and weak convergence is carried out in the practically interesting case when the discretization step sizes are essentially independent of the oscillatory wave lengths
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| 12. |
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| 13. |
- Guo, S.J., et al.
(author)
-
Improved single crystal growth in the Bi-Sr-Ca-Cu-O system using a sealed cavity technique
- 1990
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In: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 100:1-2, s. 303-308
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Journal article (peer-reviewed)abstract
- Bi-Sr-Ca-Cu-O single crystals obtained thus far commonly have a very small thickness in the c-axis because of the weak bonding between two adjacent BiO layers and the high vapour pressure of Bi2O3 at high temperature. To overcome these difficulties a presintered SrCaCu4O6 was used to seal the Bi-Sr-Ca-Cu-O melt from which the single crystals grew during slow cooling. In the SrCaCu4O6 sealed cavity the Bi loss through vaporization was prevented and Sr and Ca were enriched in the superconducting crystals. The resulting single crystals have a dimension of up to 3.0×1.5×0.7 mm3, which is two orders of magnitude thicker than those grown from alkali chloride flux. The composition of the crystals is Bi2.2Sr1.8Ca0.75Cu1.8Ox and they possess a zero resistance at temperature above liquid nitrogen
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| 14. |
- Guo, S.J., et al.
(author)
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Magnetic field dependence of the critical current density for the bismuth-based bulk high-Tc superconductors
- 1992
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In: Journal of Materials Science. - 0022-2461 .- 1573-4803. ; 27:11, s. 3043-3049
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Journal article (peer-reviewed)abstract
- Three types of bismuth-based bulk samples were prepared through uniaxial pressing at room temperature, hot isostatic pressing (HIP) and drawing and rolling. Transport current properties were characterized in a steady field up to 1.12 T at 77 K (T/T c=0.75). The Josephson weak-link decoupling fields have been found to be 5 mT for the cold-pressed pellet and 30 mT for the HIPed pellet and the rolled tape. At the decoupling field the transport critical current density,J c, drops 80% from 124 (OT) to 29 A cm-2 (5 mT) for the cold-pressed pellet, 80% from 582 (OT) to 126 A cm-2 (30 mT) for the HIPed sample and 50% from6500 (0 T) to 2850 A cm-2 (30 mT) for the rolled tape. In the flux flow regime, whereB is perpendicular to thec-axis a modified Kim's modelJ c=(α/B 0)/[(1+B/B 0)] n can be used to describe the field dependence of the critical current density, Jc, in the field range 0.2-1.12 T. The effective upper critical fields were estimated to be 0.98, 1.54 and 1.94 T for the three types of samples, respectively. An adjustable range ofB c2 for bismuth-based bulk highT c superconductors is given. Flux shear may operate in these materials. The prediction of this pinning mechanism is yielded from fitting the equation qualitatively. WhenB is parallel to thec-axis, the absence of strongly intragranular flux-pinning is emphasized by the poor flux flow regime for the rolled tape sample.
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| 15. |
- Gustafsson, Anders, et al.
(author)
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Reevaluation of blueshifts introduced by lateral confinement in quantum-well wire structures
- 1993
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In: Applied Physics Letters. - 0003-6951. ; 12:15, s. 1709-1711
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Journal article (peer-reviewed)abstract
- The luminescence from etched quantum-well wire structures often exhibits an unexpectedly large blueshift of the peak energy position. Further, the shift is usually quite independent of the width of the wires. In this letter we show that this blueshift can be explained as a decreased transfer of excitons between areas of different monolayer thicknesses within the single quantum wells, caused by a change in the exciton diffusion from being two-dimensional in the quantum wells to one-dimensional in the wires. This reduced transfer will result in a blueshift of the peak energy position if the monolayer splitting is unresolved.
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| 16. |
- Ioannidis, John, et al.
(author)
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Porting AIX onto the student electronic notebook
- 1991
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In: Proceedings of the 1991 ACM SIGSMALL/PC symposium on Small systems. - New York, NY, USA : Association for Computing Machinery. - 0897913965 ; , s. 76-82
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Conference paper (peer-reviewed)
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| 17. |
- Ioannidis, John, et al.
(author)
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Porting AIX onto the Student Electronic Notebook
- 1991
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In: ACM SIGSMALL/PC Notes. - : Association for Computing Machinery. - 0893-2875. ; 17:3-4, s. 5-11
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Journal article (peer-reviewed)abstract
- We describe the Student Electronic Notebook and the process of porting IBM's AIX 1.1 to run on it. We believe that portable workstation-class machines connected by wireless networks and dependent on a computational and informational infrastructure raise a number of important issues in operating systems and distributed computation (e.g., the partitioning of tasks between workstations and infrastructure), and therefore the development of such machines and their software is important. We conclude by summarizing our activites, itemizing the lessons we learned and identifying the key criteria for the design of the successor machines.
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| 18. |
- Ioannidis, John, et al.
(author)
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Porting AIX onto the Student Electronic Notebook
- 1990
-
Reports (other academic/artistic)abstract
- We describe the Student Electronic Notebook and the process of porting IBM’s AIX 1.1 to run on it. We believe that portable workstation-class machines connected by wireless networks and dependent on a computational and informational infrastructure raise a number of important issues in operating systems and distributed computation (e.g., the partitioning of tasks between workstations and infrastructure), and therefore the development of such machines and their software is important. We conclude by summarizing our activites, itemizing the lessons we learned and identifying the key criteria for the design of the successor machines.
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| 19. |
- Larker, Richard, et al.
(author)
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Diffusion bonding of Si3N4/TiN and Si3N4/TiB2 composites to Incoloy 909
- 1992
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In: 4th International Symposium on Ceramic Materials and Components for Engines. - London : Elsevier. - 1851667768 ; , s. 340-347
-
Conference paper (peer-reviewed)abstract
- Hot isostatic pressed (HIPed) mixtures of Si3N4/60%TiN and Si3N4 /50%TiB2 were joined to Incoloy 909 (42%Fe, 38%Ni, 12.9%Cr, 4.7%Nb, 1.5%Ti, 0.4%Si) by hot isostatic pressing at 927 deg.C and 200 MPa. Microstructure (TEM and STEM) and diffusion profiles are reported and discussed. The work is relevant to the use of graded ceramics to reduce thermomechanical stresses in silicon nitride /superalloy joints
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| 20. |
- Lindh, Roland, 1958-, et al.
(author)
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Accurate abinitio calculations of the quadrupole-moment of acetylene : a combined study of basis set, correlation, and vibrational effects
- 1991
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 94:6, s. 4356-4368
-
Journal article (peer-reviewed)abstract
- The quadrupole moment of acetylene has been studied at the multiconfiguration self-consistent field (MCSCF) and multireference single and double configuration interaction (MRSDCI) level of theory. At the MCSCF level the pi-CI complete active space SCF (CASSCF) and the valence-CI CASSCF were employed. The subsequent MRSDCI calculations were continued until the reference space included all configuration state functions (CSFs) of the MCSCF wave function with a coefficient larger than 0.01 [MRSDCI(0.01)]. The higher level basis sets in this study were all based on van Duijneveldt’s C(13s 8p) and H(6s) and extensions of that basis set. The study shows in a consistent way that both the one- and n-particle spaces are saturated at the highest level of theory. The study has revealed that in addition to the well known increase of the quadrupole moment due to the inclusion of polarizing functions in the basis (typically 0.20 a.u.), the inclusion of electronic correlation in the model wave function as well as vibrational corrections will decrease the quadrupole moment significantly more, -0.66, -0.49, and -0.36 a.u., for the correlation correction and zero-point correction for HCCH and DCCD, respectively. The most accurate computations predict the quadrupole moment of HCCH, including zero-point correction, to be 4.29 +/- 0.12 a.u., which discriminates the experimental estimates of 4.03 +/- 0.30, 4.28 +/- 0.30, and 4.57 +/- 0.30 a.u. (the first being the favored value). The quadrupole moment of DCCD is computed to 4.42 +/- 0.10 a.u. In the study it was observed that in contradiction to previous experiences the use of the model equilibrium geometries rather than the experimental geometry gives a smoother convergence as the level of theory is increased. The effects of basis set quality and electron correlation on the quadrupole moment are studied in detail. These effects are analyzed with reference to the redistribution of the electronic charge.
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