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Oldest Old Mortality in China
Zeng Yi,Vaupel James W.
Demographic Research , 2003,
Abstract: We find that the Kannisto model, a two-parameter logistic formula, fits Han Chinese death rates at oldest-old ages better than the Gompertz and four other models. Chinese death rates appear to be roughly similar to Swedish and Japanese rates after age 97 for both males and females. Because reports of age seem to be serviceably reliable up to age 100 and perhaps age 105 in China, we think that this convergence may be mainly due to mortality selection in the heterogeneous Chinese population. We show that in China, as in developed countries, the rate of increase in mortality with age decelerates at very old ages.
Displacive Excitation of Coherent Phonons in YBa_2Cu_3 O_7: An Optical Evidence for the Van-Hove Singularity
W. -S. Zeng,J. Kuhl
Physics , 1996,
Abstract: The amplitude of displacive excitation of coherent phonons ({\it DECP}) in $YBa_2Cu_3O_7$ observed in time-resolved spectroscopy increases by a very large factor of 15 between 20 K (below $T_c$) and 100 K (above $T_c$). Microscopic modelling of phonon excitation reveals that these amplitude changes of the {\it $A_{1g}$} mode phonons are related to the existence of the {\it Van-Hove} singularity (VHS) below but very close to Fermi energy. PACS numbers: 78.47.+p, 74.25.Gz, 74.25.Jb, 71.15.Fv
Seasonal prediction of winter extreme precipitation over Canada by support vector regression
Z. Zeng, W. W. Hsieh, A. Shabbar,W. R. Burrows
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2011,
Abstract: For forecasting the maximum 5-day accumulated precipitation over the winter season at lead times of 3, 6, 9 and 12 months over Canada from 1950 to 2007, two nonlinear and two linear regression models were used, where the models were support vector regression (SVR) (nonlinear and linear versions), nonlinear Bayesian neural network (BNN) and multiple linear regression (MLR). The 118 stations were grouped into six geographic regions by K-means clustering. For each region, the leading principal components of the winter maximum 5-d accumulated precipitation anomalies were the predictands. Potential predictors included quasi-global sea surface temperature anomalies and 500 hPa geopotential height anomalies over the Northern Hemisphere, as well as six climate indices (the Ni o-3.4 region sea surface temperature, the North Atlantic Oscillation, the Pacific-North American teleconnection, the Pacific Decadal Oscillation, the Scandinavia pattern, and the East Atlantic pattern). The results showed that in general the two robust SVR models tended to have better forecast skills than the two non-robust models (MLR and BNN), and the nonlinear SVR model tended to forecast slightly better than the linear SVR model. Among the six regions, the Prairies region displayed the highest forecast skills, and the Arctic region the second highest. The strongest nonlinearity was manifested over the Prairies and the weakest nonlinearity over the Arctic.
Seasonal prediction of winter extreme precipitation over Canada by support vector regression
Z. Zeng,W. W. Hsieh,A. Shabbar,W. R. Burrows
Hydrology and Earth System Sciences Discussions , 2010, DOI: 10.5194/hessd-7-3521-2010
Abstract: For forecasting the maximum 5-d accumulated precipitation over the winter season at lead times of 3, 6, 9 and 12 months over Canada from 1950 to 2007, two nonlinear and two linear regression models were used, where the models were support vector regression (SVR) (nonlinear and linear versions), nonlinear Bayesian neural network (BNN) and multiple linear regression (MLR). The 118 stations were grouped into six geographic regions by K-means clustering. For each region, the leading principal components of the winter extreme precipitation were the predictands. Potential predictors included quasi-global sea surface temperature anomalies and 500 hPa geopotential height anomalies over the Northern Hemisphere, as well as six climate indices (the Ni o-3.4 region sea surface temperature, the North Atlantic Oscillation, the Pacific-North American teleconnection, the Pacific Decadal Oscillation, the Scandinavia pattern, and the East Atlantic pattern). The results showed that in general the two robust SVR models tended to have better forecast skills than the two non-robust models (MLR and BNN), and the nonlinear SVR model tended to forecast slightly better than the linear SVR model. Among the six regions, the Eastern Prairies region displayed the highest forecast skills, and the Arctic region the second highest. The strongest nonlinearity was manifested over the Eastern Prairies and the weakest nonlinearity over the Arctic.
Dual Band-Notched Antenna with the Parasitic Strip for UWB
W. X. Liu;Ying-Zeng Yin
PIER Letters , 2011, DOI: 10.2528/PIERL11052609
Abstract: A novel microstrip-fed ultra wideband (UWB) elliptical antenna with dual band-notched characteristics is proposed. Dual band-notched characteristics are achieved by employing a pair of U-shaped slots on the ground plane and a T-shaped parasitic strip on the backside of the substrate. The operation bandwidth of the designed antenna is from 2.9 to 12 GHz for voltage standing wave ratio (VSWR) less than 2, except two frequency stop-bands of 3.2-3.9 GHz for WiMAX system and 4.9-6.1 GHz for WLAN system. Moreover, the proposed antenna provides good radiation patterns across the working bands and a relatively flat gain over the entire frequency band excluding the rejected bands.
Generalized Concatenation for Quantum Codes
Markus Grassl,Peter W. Shor,Bei Zeng
Physics , 2009, DOI: 10.1109/ISIT.2009.5205592
Abstract: We show how good quantum error-correcting codes can be constructed using generalized concatenation. The inner codes are quantum codes, the outer codes can be linear or nonlinear classical codes. Many new good codes are found, including both stabilizer codes as well as so-called nonadditive codes.
The Structure of Barium in the hcp Phase Under High Pressure
W. -S. Zeng,O. Jepsen,V. Heine
Physics , 1996, DOI: 10.1088/0953-8984/9/17/001
Abstract: Recent experimental results on two hcp phases of barium under high pressure show interesting variation of the lattice parameters. They are here interpreted in terms of electronic structure calculation by using the LMTO method and generalized pseudopotential theory (GPT) with a NFE-TBB approach. In phase II the dramatic drop in c/a is an instability analogous to that in the group II metals but with the transfer of s to d electrons playing a crucial role in Ba. Meanwhile in phase V, the instability decrease a lot due to the core repulsion at very high pressure. PACS numbers: 62.50+p, 61.66Bi, 71.15.Ap, 71.15Hx, 71.15La
Duality between quantum and classical dynamics for integrable billiards
W. T. Lu,Weiqiao Zeng,S. Sridhar
Physics , 2006, DOI: 10.1103/PhysRevE.73.046201
Abstract: We establish a duality between the quantum wave vector spectrum and the eigenmodes of the classical Liouvillian dynamics for integrable billiards. Signatures of the classical eigenmodes appear as peaks in the correlation function of the quantum wave vector spectrum. A semiclassical derivation and numerical calculations are presented in support of the results. These classical eigenmodes can be observed in physical experiments through the auto-correlation of the transmission coefficient of waves in quantum billiards. Exact classical trace formulas of the resolvent are derived for the rectangle, equilateral triangle, and circle billiards. We also establish a correspondence between the classical periodic orbit length spectrum and the quantum spectrum for integrable polygonal billiards.
A q-Analogue of Faulhaber's Formula for Sums of Powers
Victor J. W. Guo,Jiang Zeng
Mathematics , 2005,
Abstract: Let $$ S_{m,n}(q):=\sum_{k=1}^{n}\frac{1-q^{2k}}{1-q^2} (\frac{1-q^k}{1-q})^{m-1}q^{\frac{m+1}{2}(n-k)}. $$ Generalizing the formulas of Warnaar and Schlosser, we prove that there exist polynomials $P_{m,k}(q)\in\mathbb{Z}[q]$ such that $$ S_{2m+1,n}(q) =\sum_{k=0}^{m}(-1)^kP_{m,k}(q) \frac{(1-q^n)^{m+1-k}(1-q^{n+1})^{m+1-k}q^{kn}} {(1-q^2)(1-q)^{2m-3k}\prod_{i=0}^{k}(1-q^{m+1-i})}, $$ and solve a problem raised by Schlosser. We also show that there is a similar formula for the following $q$-analogue of alternating sums of powers: $$ T_{m,n}(q):=\sum_{k=1}^{n}(-1)^{n-k} (\frac{1-q^k}{1-q})^{m}q^{\frac{m}{2}(n-k)}. $$
Multiple extensions of a finite Euler's pentagonal number theorem and the Lucas formulas
Victor J. W. Guo,Jiang Zeng
Mathematics , 2007, DOI: 10.1016/j.disc.2007.07.106
Abstract: Motivated by the resemblance of a multivariate series identity and a finite analogue of Euler's pentagonal number theorem, we study multiple extensions of the latter formula. In a different direction we derive a common extension of this multivariate series identity and two formulas of Lucas. Finally we give a combinatorial proof of Lucas' formulas.
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