Browsing by Author "Lee, JM"

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Behaviour of steel moment connections with a single flange rib
(2003-09-01)
Chen, CC
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Lee, JM
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Lin, MC
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土木工程學系
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Department of Civil Engineering
This paper presents a study of flange rib moment connections for use in steel moment-resisting frames. The connections are strengthened by welding a vertical rib to the beam flange and the column flange. The rib is characterized by an extension. Finite element analysis and experiments were conducted to elucidate the behaviour of lengthened rib reinforced connections. The results of the finite element analysis established the effectiveness of the lengthened rib in mitigating local stress concentrations and forming the plastic hinge zone in the beam. Two full-scale proof-test specimens behaved as observed by the analysis, and exhibited greater than 3% radians of plastic rotation under cyclic load. Without brittle fracture, both specimens developed a plastic hinge in the beam. Extensive yielding and local buckling occurred in the beam flanges and the web. The connections strengthened with a single flange rib were successfully verified by the test. (C) 2003 Elsevier Ltd. All rights reserved.
Dissociation dynamics of excited neutral fragments of gaseous SiCl4 following Si 2p and Cl 2p core-level excitations
(2005-09-01)
Chen, JM
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Lu, KT
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Lee, JM
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Ho, SC
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Chang, HW
State-specific dissociation dynamics for excited fragments of gaseous SiCl4 following Cl 2p and Si 2p core-level excitations were characterized by the dispersed UV/optical fluorescence spectroscopy. The core-to-Rydberg excitations at both Si 2p and Cl 2p edges lead to a noteworthy production of excited atomic fragments, neutral and ionic (Si-*,Si+*). In particular, the excited neutral atomic fragments Si-* are significantly reinforced. The core-to-valence excitation at the Si 2p edge generates an enhancement of excited molecular-ion SiCl4+. The experimental results provide deeper insight into the dissociation dynamics for excited neutral fragments of molecules via core-level excitation.
Electronic structure and transport properties of La0.7Ce0.3MnO3
(2005-10-01)
Chang, WJ
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Tsai, JY
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Jeng, HT
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Lin, JY
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Zhang, KYJ
X-ray absorption spectroscopy (XAS), optical reflectance spectroscopy, and the Hall effect measurements were used to investigate the electronic structure in La0.7Ce0.3MnO3 thin films (LCeMO). The XAS results are consistent with those obtained from LDA+U calculations. In that the doping of Ce has shifted up the Fermi level and resulted in marked shrinkage of hole pockets originally existing in La0.7Ca0.3MnO3 (LCaMO). The Hall measurements indicate that in LCeMO the carriers are still displaying the characteristics of holes as LDA+U calculations predict. Analyses of the optical reflectance spectra evidently disapprove the scenario that the present LCeMO might have been dominated by the La-deficient phases.
Hole distribution in YxPr1-xBa2Cu4O8 and YxPr1-xBa2Cu3O7 probed by X-ray absorption spectroscopy
(2004-08-01)
Chen, JM
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Liu, SJ
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Lee, JM
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Lin, JY
;
Gou, YS
Utilizing high-resolution O K-edge X-ray absorption spectra, we report a comparative study on the variation of hole states with Pr doping for Y-x Pr1-xBa2Cu3O7 and YxPr1-xBa2 Cu-4 O-8. The depletion rate of hole carriers in the CuO2 planes with Pr doping in YxPr1-xBa2Cu4 O-8 is considerably slower than that in YxPr1-xBa2Cu3O7. The oxygen content affects the depletion rate of hole carriers in cuprates with Pr doping. (C) 2004 Elsevier B.V. All rights reserved.
Hole states of X-Bi2Sr2CaCu2O8 [X=I, HgI2, and (Py-CH3)(2)HgI4] probed by OK-edge X-ray absorption spectroscopy
(2006-01-01)
Chen, JM
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Chang, SC
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Liu, RS
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Lee, JM
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Park, M
Hole states of X-Bi2Sr2CaCU2O8[X-Bi2212, X=I, HgI2, and (Py-CH3)(2)-HgI4, Py = pyridinel have been probed by O K-edge X-ray absorption near-edge structure (XANES) spectra. In the O 1s absorption edge of X-Bi2212, the pre-edge peak at similar to 528.3 eV is attributed to transitions into the 0 2p hole states located in the CuO2 planes. The hole concentration in the CuO2 planes of X-Bi2212 increases for X =I and HgI2, but decreases for X= (Py-CH3)(2)HgI4 as coMPared to pristine Bi2212. The variation of CuO2-plane hole concentration of Bi2212 is primarily responsible for the T-c variation upon intercalation. (c) 2005 Elsevier Ltd. All rights reserved.
Mapping spatial variations of the coercivity on patterned magneto-optical materials
(2003-05-15)
Wu, TH
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Ye, LX
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Lee, JM
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Wu, JC
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Shieh, HPD
The spatial variation of coercivity on patterned magneto-optical (MO) materials has been studied with a Kerr microscope. Our results show that the coercivity values on arrays made by holes are larger than those observed on the land regions. In contrast with nonpatterned MO media, which present a sharp Gaussian-like distribution, the coercivity distribution in the patterned material is much wider and shows an exponential-type distribution. This article maps the spatial variation of the coercivity on patterned magnetic materials with a spatial resolution of 0.1x0.1 mum(2). (C) 2003 American Institute of Physics.
Peculiar hole doping by Ca substitution in cuprate superconductors
(2003-05-01)
Lin, JY
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Chung, PC
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Liu, SJ
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Hsiang, CC
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Lin, PH
The doping effect of Ca substitution in Y0.7Ca0.3Ba2Cu3Oy has been studied for y=6.9 and 6 by the x-ray absorption near edge spectroscopy (XANES). While Ca doping leads to an obvious increase in hole concentration in the CuO2 planes in Y0.7Ca0.3Ba2Cu3O6.9, XANES indicates absence of this doping effect in Y0.7Ca6.3Ba2Cu3O6. These two contradict results suggest that the doping effect by Ca substitution could be sensitive to the oxygen content when y similar to6.0. Comparisons with others' works are made.
Pr-induced superconductivity suppression in YxPr1-xBa2Cu4O8 probed by soft-X-ray absorption spectroscopy: a comparative studies of YxPr1-xBa2Cu4O8 and YxPr1-xBa2Cu3O7
(2003-03-07)
Chen, JM
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Liu, SJ
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Lee, JM
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Hong, IP
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Lin, JY
The variation of hole states with Pr doping for YxPr1-x Ba2Cu3O7 and YxPr1-xBa2Cu4O8 has been investigated by O K-edge X-ray absorption spectroscopy. Upon Pr substitution, T-c suppression rate in YxPr1-xBa2Cu4O8 is slower than that in YxPr1-xBa2Cu3O7. For both systems, hole carriers in the CuO2 planes and CuO chains decrease monotonically with increasing Pr doping level. The depletion rate of hole carriers in the CuO2 planes with Pr doping in YxPr1-xBa2Cu4O8 is considerably slower than that in YxPr1-xBa2Cu3O7. The oxygen content affects the depletion rate of hole carriers in cuprates with Pr doping. (C) 2003 Elsevier Science B.V. All rights reserved.
Soft-x-ray absorption spectroscopy of heterostructured high-T-c superconducting nanohybrids: X-Bi2Sr2CaCu2O8 [X=I, HgI2, and (Py-CH3)(2)HgI4]
(2005-03-01)
Chen, JM
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Chang, SC
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Liu, RS
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Lee, JM
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Park, M
Unoccupied electronic states of X-Bi2Sr2CaCu2O8 [X-Bi2212, X=1, HgI2, and '(Py-CH3)(2)-HgI4, Py =pyridine] have been probed by O K-edge and Cu L-edge x-ray absorption near-edge structure (XANES) spectra using a bulk-sensitive x-ray-fluorescence-yield technique. In the 0 Is absorption edge of X-Bi2212, the pre-edge feature at similar to 528.3 eV is attributed to transitions into O 2p hole states located in the CuO2 planes. As deduced from 0 K-edge and Cu L-edge x-ray absorption spectra, the hole concentration in the CuO2 planes of X-Bi2212 increases for X=I and HgI2, but decreases for X= (Py-CH3)(2)HgI4, relative to pristine Bi2212. The present XANES results clearly demonstrate that the hole density within the CuO2 planes of intercalated Bi2Sr2CaCu2O8 can be not only decreased but also increased, depending on the chemical character of the intercalants.
Spectroscopic evidence of electron doping in La0.7Ce0.3MnO3
(2004-11-01)
Lin, JY
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Chang, WJ
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Juang, JY
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Wen, TM
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Wu, KH
X-ray absorption near edge spectroscopy was used to investigate the hole states in the La0.7Ce0.3MnO (LCeMO). A substantial decrease in the spectral weight of the e. orbital was observed in LCeMO compared to that in the hole-doped La0.7Ca0.3MnO. This directly proves that electron doping occurs in LCeMO. (C) 2004 Elsevier B.V. All rights reserved.
The electronic structure change induced by stripe phase formation in cuprates
(2004-08-01)
Lin, JY
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Huang, CW
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Lin, PH
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Sun, CP
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Lee, JM
It has been suggested that the stripe phase shows ID charge transport in the CuO2 planes instead of the 2D characteristics of the Zhang-Rice band. X-ray absorption near edge spectroscopy (XANES) has been used to study the electronic structure of the stripe phase compounds La2-xSrxCuO4, and La2-x-yNdySrxCuO4 for x around 1/8. The measurements were performed at both 300 and 28 K to examine the possible electronic structure change above and below the temperature of the stripe phase formation. (C) 2004 Elsevier B.V. All rights reserved.