ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

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Magnetic properties of Pb2Sr2PrCu3O8 studied by ac susceptibility : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)

Wu, S. Y. ; Chang, Y. C. ; Lee, K. C. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 83 (1998), S. 7318-7320

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: The magnetic responses of vacuum annealed polycrystalline Pb2Sr2PrCu3O8 to a magnetic field have been studied by ac magnetic susceptibility measurements, where both the in-phase component χ′ and the out-of-phase component χ″ were measured. Diamagnetic responses in χ′(T) below 60 K were clearly seen, showing the occurrence of superconductivity, but it is filamentary. This filamentary superconductivity was also evident in the χ″(T). Under an applied dc field, both the χ′(T) and χ″(T) behave as what are expected for a superconducting system. At lower temperatures, a well-defined peak associated with the Pr spin ordering is also clearly revealed at 5 K. Correspondingly, an anomaly is also seen in the specific heat data. © 1998 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.367592

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2

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Tilted antiferromagnetic ordering of Mn in Nd0.62Ca0.38MnO3 : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)

Wu, S. Y. ; Li, W.-H. ; Lee, K. C.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 83 (1998), S. 7345-7347

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: The magnetic ordering of the Mn spins in polycrystalline Nd0.62Ca0.38MnO3 has been investigated by means of neutron diffraction and ac magnetic susceptibility measurements. Three peaks around 230, 90, and 40 K were observed in the temperature dependence of the in-phase component of the ac susceptibility, χ′(T). Neutron diffraction measurements show that the peak at 90 K is associated with the ordering of the Mn spins, and that at 40 K is due to the reorientation of the Mn spins. Both ferromagnetic and antiferromagnetic coupling between the Mn spins were observed. The spins order at TN(approximate)130 K, with a spin structure consisting of ferromagnetically coupled, tilted antiferromagnetic sheets. No evidence was found from the neutron diffraction data to indicate that the peak around 230 K in χ′(T) is of magnetic origin, which suggests that it is associated with charge ordering. © 1998 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.367635

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3

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Alternating current susceptibility studies of Tb ordering in Pb2Sr2TbCu3O8 : The 40th annual conference on magnetism and magnetic materials (1996)

Wu, S. Y. ; Li, W.-H. ; Lee, K. C. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 79 (1996), S. 6571-6573

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: The magnetic response of the Tb spins in Pb2Sr2TbCu3O7 to the applied magnetic field have been studied by ac susceptibility measurements. Both the in-phase component χ′ and the out-of-phase component χ″ of ac susceptibility are found to be sensitive to the frequency but not to the strength of the driving field. At high temperatures χ′ exhibits Curie–Weiss behavior, it departs from this behavior as the magnetic correlations between the Tb spins develop, and a cusp which is typical of antiferromagnetic ordering is clearly revealed at lower temperatures. The correlated Tb spins respond "better'' to a driving magnetic field which has a lower frequency. The relative maximum of the dχ′/dT versus T plot matches to the TN determined using neutron diffraction measurements. This relative maximum continues to occur at the same temperature as the frequency of the driving field is varied. It, however, shifts to a lower temperature as a dc external field is applied, indicating the antiferromagnetic coupling between the Tb spins are weaken by the dc field. Moreover, the thermal behavior of χ″ exhibits a well-defined peak around the transition temperature, and a dc field of strength 5 kOe smears the peak. © 1996 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.361948

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4

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Cu spin reorientation in Tl(BaSr)PrCu2O7 : The 40th annual conference on magnetism and magnetic materials (1996)

Li, W.-H. ; Lin, Y. F. ; Wu, S. Y. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 79 (1996), S. 6568-6570

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: The Cu spins in TlBa2PrCu2O7 order at TN≈370 K with a spin structure that is collinear and is characterized by the {1/21/21} wave vector, where the nearest neighbor spins are aligned antiparallel along all three crystallographic directions. If 50% of the Ba atoms are randomly replaced by the smaller Sr atoms to form Tl(BaSr)PrCu2O7, the TN of the Cu spins reduces to 350 K but the magnetic structure that forms below TN is the same. However, at T≈20 K the Cu spins undergo a change in structure, and the spin arrangement is then characterized by the {1/21/21/2} wave vector below T≈12 K. The ground state spin structure of the Cu ions in Tl(BaSr)PrCu2O7 is hence noncollinear, where the spin directions of the nearest neighbor Cu ions in the ab plane remain collinear and antiparallel while along the c axis they are orthogonal. These results demonstrate that the atoms in the BaO layers are also actively participating in the coupling between the Cu ions. © 1996 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.361883

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5

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Magnetic order and spin reorientation in Nd0.45Ca0.55MnO3 (1999)

Li, W.-H. ; Wu, S. Y. ; Lee, K. C.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 85 (1999), S. 5588-5590

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: Neutron diffraction and ac magnetic susceptibility measurements have been performed to study the magnetic ordering of the Mn spins in polycrystalline Nd0.45Ca0.55MnO3. Three peaks around 260, 90, and 40 K were observed in the temperature dependence of the ac susceptibility. Structural analysis using high-resolution neutron diffraction patterns shows that the peak at 260 K is associated with the charge ordering of the Mn ions. Neutron magnetic diffraction shows that the peak at 90 K originates from the ordering of the Mn spins. Both ferromagnetic and antiferromagnetic couplings between the Mn spins were found. The spin structure in the basal plane consists of tilted ferromagnetic chains (along the [110] direction) aligned antiferromagnetically, whereas the interlayer coupling is ferromagnetic. A spin reorientation occurs below 15 K, which results in a change in the title angle. The Mn spins order at TN(approximate)120 K, and the moment saturated at 30 K at 〈μZ〉=2.29(4)μB. © 1999 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.369808

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6

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Relaxed Cutting Plane Method for Solving Linear Semi-Infinite Programming Problems (1998)

Wu, S. Y. ; Fang, S. C. ; Lin, C. J.

Springer

Journal of optimization theory and applications 99 (1998), S. 759-779

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ISSN: 1573-2878

Keywords: Linear semi-infinite programming ; cutting plane method

Source: Springer Online Journal Archives 1860-2000

Topics: Mathematics

Notes: Abstract One of the major computational tasks of using the traditional cutting plane approach to solve linear semi-infinite programming problems lies in finding a global optimizer of a nonlinear and nonconvex program. This paper generalizes the Gustafson and Kortanek scheme to relax this requirement. In each iteration, the proposed method chooses a point at which the infinite constraints are violated to a degree, rather than a point at which the violations are maximized. A convergence proof of the proposed scheme is provided. Some computational results are included. An explicit algorithm which allows the unnecessary constraints to be dropped in each iteration is also introduced to reduce the size of computed programs.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1021763419562

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7

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Combined Entropic Regularization and Path-Following Method for Solving Finite Convex Min-max Problems Subject to Infinitely Many Linear Constraints (1999)

Sheu, R. L. ; Wu, S. Y.

Springer

Journal of optimization theory and applications 101 (1999), S. 167-190

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ISSN: 1573-2878

Keywords: Min-max problems ; entropic regularization ; nonsmooth optimization ; interior-point methods ; path-following methods ; semi-infinite programming

Source: Springer Online Journal Archives 1860-2000

Topics: Mathematics

Notes: Abstract In this paper, we study the minimization of the max function of q smooth convex functions on a domain specified by infinitely many linear constraints. The difficulty of such problems arises from the kinks of the max function and it is often suggested that, by imposing certain regularization functions, nondifferentiability will be overcome. We find that the entropic regularization introduced by Li and Fang is closely related to recently developed path-following interior-point methods. Based on their results, we create an interior trajectory in the feasible domain and propose a path-following algorithm with a convergence proof. Our intention here is to show a nice combination of minmax problems, semi-infinite programming, and interior-point methods. Hopefully, this will lead to new applications.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1021727228957

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8

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Inexact algorithm for continuous complementarity problems on measure spaces (1996)

Wu, S. Y. ; Yao, J. C. ; Pang, J. S.

Springer

Journal of optimization theory and applications 91 (1996), S. 141-154

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ISSN: 1573-2878

Keywords: Continuous complementarity problems ; inexact solutions

Source: Springer Online Journal Archives 1860-2000

Topics: Mathematics

Notes: Abstract In this paper, we discuss a type of complementarity problem posed over a measure space. We give some conditions under which there exists a solution for the problem and work toward a new inexact algorithm for its solution. A general convergence proof for this algorithm is given and the advantage of using this approach is discussed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02192287

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9

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Whole-field residual stress measurement in rail using moiré interferometry and twyman/green interferometry via thermal annealing (1999)

Wang, B. S. ; Chiang, F. P. ; Wu, S. Y.

Springer

Experimental mechanics 39 (1999), S. 71-76

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ISSN: 1741-2765

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract A novel whole-field residual stress measurement technique is developed using moiré interferometry and Twyman/Green interferometry coupled with thermal annealing. The technique is successfully applied to residual stress measurement in rail. In the measurement, a high temperature resistant 1200-lines/mm cross grating is made on a rail transverse slice surface. The whole-field residual stress relief is achieved by thermal annealing. Moiré interferometry and Twyman/Green interferometry are employed to obtain the in-plane and out-of-plane deformations generated by the residual stress relaxation. The whole-field strain redistribution due to the residual stress relief is calculated, and the whole-field residual stress distribution, including the possible stress concentration, is then obtained. Because of the three-dimensional nature of the residual stress relaxation and the measurement, the three-dimensional residual stress reconstruction sometimes becomes possible based on some plausible assumptions. In this paper, the principle of the experimental theory, technique and procedures are described. Three-dimensional residual stress reconstruction in a rail using a transverse slice is shown. Its comparison to the hole-drilling method with moiré interferometry is also presented.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02329304

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