Browsing by Author "Lee, W. L."

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Disrupted long-range spin-spiral ordering and electric polarization in the Zn-substituted quantum helimagnet LiCu(2-x)Zn(x)O(2)
(2010-06-18)
Hsu, H. C.
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Lee, W. L.
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Lin, J. -Y.
;
Liu, H. L.
;
Chou, F. C.
Long-range spin-spiral ordering in quantum quasi-two-dimensional helimagnet LiCu(2)O(2) is destroyed by similar to 8% Zn(2+) substitution and a magnetic anomaly near similar to 14 K of different character emerges. Zn substitution may have introduced either a magnetic ground state of spin glass in nature, antiferromagnetic ordering with complex easy-plane anisotropy, or a gapped phase which is phase separated and proportional to the Zn substitution level on a short-range ordered background. The magnetic ground state is modified at the same time that the electric polarization disappears.
Disrupted long-range spin-spiral ordering and electric polarization in the Zn-substituted quantum helimagnet LiCu2-xZnxO2
(2010-06-18)
Hsu, H. C.
;
Lee, W. L.
;
Lin, J. -Y.
;
Liu, H. L.
;
Chou, F. C.
Long-range spin-spiral ordering in quantum quasi-two-dimensional helimagnet LiCu2O2 is destroyed by similar to 8% Zn2+ substitution and a magnetic anomaly near similar to 14 K of different character emerges. Zn substitution may have introduced either a magnetic ground state of spin glass in nature, antiferromagnetic ordering with complex easy-plane anisotropy, or a gapped phase which is phase separated and proportional to the Zn substitution level on a short-range ordered background. The magnetic ground state is modified at the same time that the electric polarization disappears.
Efficient passively Q-switched Nd:YLF TEM00-mode laser at 1053 nm: selection of polarization with birefringence
(2012-08-01)
Huang, Y. J.
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Tang, C. Y.
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Lee, W. L.
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Huang, Y. P.
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Huang, S. C.
"The natural birefringence of the Nd:YLF crystal is utilized to achieve a reliable TEM00-mode linearly polarized laser at 1053 nm in a compact concave-plano resonator. The efficient selection of the polarization relies on the combined effect of the difference in diffraction angle for sigma- and pi-polarization of a wedged laser crystal and the alignment sensitivity of an optical resonator. We further employ a Cr4+:YAG saturable absorber to perform the passively Q-switched operation. At an incident pump power of 12 W, the maximum average output power is up to 2.3 W with a pulse repetition rate of 8 kHz and a pulse width of 9 ns. The pulse energy and peak power are found to be 288 mu J and 32 kW, respectively."
Nonmagnetic impurity perturbation to the quasi-two-dimensional quantum helimagnet LiCu(2)O(2)
(2010-09-29)
Hsu, H. C.
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Lin, J. -Y.
;
Lee, W. L.
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Chu, M. -W.
;
Imai, T.
A complete phase diagram of Zn-substituted quantum quasi-two-dimensional helimagnet LiCu(2)O(2) has been presented. Helical ordering transition temperature (T(h)) of the original LiCu(2)O(2) follows finite size scaling for less than similar to 5.5% Zn substitution, which implies the existence of finite helimagnetic domains with domain boundaries formed with nearly isolated spins. Higher Zn substitution >= 5.5% quenches the long-range helical ordering and introduces an intriguing Zn-level-dependent magnetic phase transition with slight thermal hysteresis and a universal quadratic field dependence for T(c)(Zn > 0.055, H). The magnetic coupling constants of nearest-neighbor J(1) and next-nearest-neighbor J(2) (alpha = J(2)/J(1)) are extracted from high temperature series expansion fitting and N = 16 finite chain exact diagonalization simulation. We have also provided evidence of direct correlation between long-range helical spin ordering and the magnitude of electric polarization in this spin-driven multiferroic material.
Nonmagnetic impurity perturbation to the quasi-two-dimensional quantum helimagnet LiCu2O2
(2010-09-29)
Hsu, H. C.
;
Lin, J. -Y.
;
Lee, W. L.
;
Chu, M. -W.
;
Imai, T.
A complete phase diagram of Zn-substituted quantum quasi-two-dimensional helimagnet LiCu2O2 has been presented. Helical ordering transition temperature (T-h) of the original LiCu2O2 follows finite size scaling for less than similar to 5.5% Zn substitution, which implies the existence of finite helimagnetic domains with domain boundaries formed with nearly isolated spins. Higher Zn substitution >= 5.5% quenches the long-range helical ordering and introduces an intriguing Zn-level-dependent magnetic phase transition with slight thermal hysteresis and a universal quadratic field dependence for T-c(Zn > 0.055, H). The magnetic coupling constants of nearest-neighbor J(1) and next-nearest-neighbor J(2) (alpha = J(2)/J(1)) are extracted from high temperature series expansion fitting and N = 16 finite chain exact diagonalization simulation. We have also provided evidence of direct correlation between long-range helical spin ordering and the magnitude of electric polarization in this spin-driven multiferroic material.
Superconducting to spin-glass state transformation in beta-pyrochlore K(x)Os(2)O(6)
(2011-03-14)
Lee, C. C.
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Lee, W. L.
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Lin, J. -Y.
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Tsuei, C. C.
;
Lin, J. G.
beta-pyrochore KOs(2)O(6), which shows superconductivity below similar to 9.7 K, has been converted into K(x)Os(2)O(6) (x less than or similar to 2/3-1/2) electrochemically to show spin-glass-like behavior below similar to 6.1 K. A room-temperature sample surface potential versus charge transfer scan indicates that there are at least two two-phase regions for x between 1 and 0.5. A rattling model of superconductivity for the title compound has been examined using electrochemical potassium de-intercalation. The significant reduction of superconducting volume fraction due to minor potassium reduction suggests the importance of defect and phase coherence in the rattling model. Magnetic susceptibility, resistivity, and specific heat measurement results have been compared between the superconducting and spin-glass-like samples.
Superconducting to spin-glass state transformation in beta-pyrochlore KxOs2O6
(2011-03-14)
Lee, C. C.
;
Lee, W. L.
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Lin, J. -Y.
;
Tsuei, C. C.
;
Lin, J. G.
beta-pyrochore KOs2O6, which shows superconductivity below similar to 9.7 K, has been converted into KxOs2O6 (x less than or similar to 2/3-1/2) electrochemically to show spin-glass-like behavior below similar to 6.1 K. A room-temperature sample surface potential versus charge transfer scan indicates that there are at least two two-phase regions for x between 1 and 0.5. A rattling model of superconductivity for the title compound has been examined using electrochemical potassium de-intercalation. The significant reduction of superconducting volume fraction due to minor potassium reduction suggests the importance of defect and phase coherence in the rattling model. Magnetic susceptibility, resistivity, and specific heat measurement results have been compared between the superconducting and spin-glass-like samples.
UAV 3D modeling with multi-spectral imaging: An example of wax apple tree
(2019-01-01)
Shih, Ruei-Siang
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Li, Yi-Sheng
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Yan, Yung-Jhe
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Yu, Chun
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Huang, Wei-Tsang
As the Unmanned aerial vehicle (UAV) become ubiquitous, many early studies utilizing the UAV for three-dimensional (3D) modeling system are successively proposed as well. The advantage of using UAV successfully advances efficiency and reduces the cost time for simplifying the process of collecting data. Moreover, the characteristics of the light sized and suspension of new designed UAV could allow the users to gather the precise data from the rugged terrain and through a crowd of trees and may build a detail 3D and hyperspectral images. By those high-resolution 3D model data, the texture and shape of observation can be seen and brings research into further analysis. However, there are some limits that the information of 3D modeling data in RGB wide bands is not adequate to investigate vegetation research. The hyper spectrum collects the information of tens of bands with the narrow bandwidth could analyze the detail difference between abnormal and normal situations when the plant is growing. Therefore, how to combine hyperspectral data into a 3D modeling system would be important when researches want to attain the location data and spectral image simultaneously. In this study, the UAV will be loaded with two kinds of systems, and try to build the model include 3D modeling information and spectral information. As a result, it can monitor the growth condition of plants, their environment, also the precise location at the same time so that it can make vegetation analysis more complete.