Browsing by Author "Chang, C. K."

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Antiferroelectric antiferromagnetic type-I multiferroic Cu9O2(SeO3)(4)Cl-6
(2019-12-11)
Wu, H. C.
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Denisova, K. N.
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Menzel, D.
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Kakarla, D. Chandrasekhar
;
Maximova, O. V.
We report that Cu9O2(SeO3)(4)Cl-6 is a new multiferroic compound. Comprehensive studies of this compound have been carried out on single crystals as well as polycrystalline samples. Magnetic susceptibility chi and specific heat C with H parallel to c axis both reveal an anomaly at T-N = 37 K associated with the long-range antiferromagnetic order. However, no signature of this phase transition is seen with the H parallel to b axis, providing evidence of the anisotropic nature of its magnetic properties. The results of chi measurements are consistent with the temperature evolution of the intensity of magnetic reflections from the neutron diffraction experiments. The magnetic structure derived from neutron scattering measurements shows that half of the Cu(5) ions carry no moments. Furthermore, an anomaly in the dielectric constant near T-N and observable magnetoelectric coupling below T-N are found. At high temperatures, a dielectric peak at T-E = 267 K is identified with no measurable spontaneous polarization below T-E, thereby suggesting an antiferroelectric order. A steplike anomaly seen in chi(T) at T-E hints the weak spin-lattice coupling. Concomitantly, high-resolution temperature-dependent synchrotron x-ray diffraction experiments elucidate a local structural distortion at T-E.
Excited Energy Attenuation Study Through Vibration Measurement and Spectrum Analysis
(2010)
Lin, S. Y.
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Chang, C. K.
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Chung, C. T.
;
Hsu, F. C.
;
Wang, C. C.
This paper presents the use of vibration measurement in conjunction with spectrum signal analysis to investigate the vibration phenomena and the dynamic response of the absorber system frame and rigid axle of a vehicle body under real road-driving conditions. Ford 1.6L sedan was selected as the vehicle body to carry out the experiments with different driving speeds. B&K PULSE dynamic signal analyzer was used to detect the vibration signal induced from the absorber system frame and rigid axle of the vehicle body in motion. The acquired on-line signals are then processed through the Fast Fourier Transform using the power spectrum density, the cepstrum method, and the overall analysis. The vibration energy attenuated from the absorber system is analyzed by comparing with that on the rigid axle excited from the road conditions corresponding to different driving speeds. Furthermore, the effects of various road conditions and driving speeds on oscillation of the vehicle body are studied. The corresponding results may be extensively treated as a guiding reference of the absorber system design and manufacturing for those vehicle manufacturing companies.