Browsing by Author "Liu, CJ"

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Common-acoustic-poles/zeros approximation of head-related transfer functions
(2001)
Liu, CJ
;
Hsieh, SF
;
電信工程研究所
;
Institute of Communications Engineering
Common-acoustic-poles/zeros (CAPZ) approximation is a more efficient way to model head-related transfer functions (HRTF's). In CAPZ approximation, a group of HRTF's can share a set of poles but use their own zeros. Previous CAPZ works, such as the Prony, Shanks and iterative prefiltering methods, were all based on the linearized least-square criterion. A new state-space approach, jointly balanced model truncation, is proposed by using singular value decomposition of a joint Hankel matrix. The proposed approach can choose the suitable order of IIR filters for HRTF's approximation according to the distribution of singular values but previous works can't. The proposed method is also modified to permit different orders for pole and zero. Computer simulations of these approaches are included for comparison.
Lateral migration of trapped holes in a nitride storage flash memory cell and its qualification methodology
(2004-09-01)
Zous, NK
;
Lee, MY
;
Tsai, WJ
;
Kuo, A
;
Huang, LT
The negative threshold voltage (V-t) shift of a nitride storage flash memory cell in the erase state will result in an increase in leakage current. By utilizing a charge pumping method, we found that trapped hole lateral migration is responsible for this V-t shift. Hole transport in nitride is characterized by monitoring gate induced drain leakage current and using a thermionic emission model. The hole emission induced V-t shift shows a linear correlation with bake time in a semi-logarithm plot and its slope depends on the bake temperature. Based on the result, an accelerated qualification method for the negative V-t drift is proposed.
Order parameter of MgB2: A fully gapped superconductor
(2001-10-15)
Yang, HD
;
Lin, JY
;
Li, HH
;
Hsu, FH
;
Liu, CJ
We have measured the low-temperature specific heat C(T) for polycrystalline MgB2 prepared by high pressure synthesis. C(T) below 10 K vanishes exponentially, which unambiguously indicates a fully opened superconducting energy gap. However, this gap is found to be too small to account for T, of MgB2. Together with the small specific heat jump DeltaC/gamma T-n(c) = 1.09, scenarios such as anisotropic s-wave or multicomponent order parameter are called for. The magnetic field dependence of gamma (H) is neither linear for a fully gapped s-wave superconductor nor H-1/2 for nodal order parameter. It seems that this intriguing behavior of gamma (H) is associated with the intrinsic electronic properties other than flux pinning.
Pressure effects on the transition temperature of superconducting MgCxNi3
(2003-09-01)
Yang, HD
;
Mollah, S
;
Huang, WL
;
Ho, PL
;
Huang, HL
The effect of hydrostatic pressure (P) up to 17 kbar on the superconducting transition temperature (T-C) of the newly discovered intermetallic nonoxide perovskite superconductor MgCxNi3 has been reported. T-C is found to increase with increasing P at a rate of dT(C)/dPsimilar to0.0134 to 0.0155 K/kbar depending on the value of carbon content x. The absolute value of dT(C)/dP for MgCxNi3 is about the same as that of intermetallic RNi2B2C (R denotes rare earth) and metallic superconductors but about one order of magnitude smaller than that of the most recently and intensively studied superconductor MgB2. However, the d ln T-C/dPsimilar to0.001 81 to 0.002 24 kbar(-1) and the rate of change of T-C with unit cell volume (V), d ln T-C/d ln Vsimilar to-3.18 to -2.58 of MgCxNi3 are having the comparable magnitude to that of MgB2 with opposite sign. The increase of T-C with P in MgCxNi3 can be explained in the framework of density of states (DOS) effect.