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16 results on '"Cao, Haiwen"'

3. Using List Decoding to Improve the Finite-Length Performance of Sparse Regression Codes

Author

Cao, Haiwen and Vontobel, Pascal O.

Subjects
Computer Science - Information Theory
Abstract

We consider sparse superposition codes (SPARCs) over complex AWGN channels. Such codes can be efficiently decoded by an approximate message passing (AMP) decoder, whose performance can be predicted via so-called state evolution in the large-system limit. In this paper, we mainly focus on how to use concatenation of SPARCs and cyclic redundancy check (CRC) codes on the encoding side and use list decoding on the decoding side to improve the finite-length performance of the AMP decoder for SPARCs over complex AWGN channels. Simulation results show that such a concatenated coding scheme works much better than SPARCs with the original AMP decoder and results in a steep waterfall-like behavior in the bit-error rate performance curves. Furthermore, we apply our proposed concatenated coding scheme to spatially coupled SPARCs. Besides that, we also introduce a novel class of design matrices, i.e., matrices that describe the encoding process, based on circulant matrices derived from Frank or from Milewski sequences. This class of design matrices has comparable encoding and decoding computational complexity as well as very close performance with the commonly-used class of design matrices based on discrete Fourier transform (DFT) matrices, but gives us more degrees of freedom when designing SPARCs for various applications., Comment: 12 pages, 8 figures, revised

Published
2020

16. Polarization screening-induced epitaxial growth and interfacial magnetism of BiFeO3/PbTiO3 nanoplates.

Author

Fu, Gangjie, Li, Wei, Cao, Haiwen, Chen, Xing, Wang, Shanpeng, Luo, Liang, Wu, Mengjiao, Tian, He, Ren, Zhaohui, and Han, Gaorong

Subjects
EPITAXY, MAGNETISM, ELECTRON spectroscopy, POLARIZED electrons, MAGNETIZATION, FERROMAGNETISM, HETEROSTRUCTURES
Abstract

In this work, single-crystal BiFeO3/PbTiO3 (BFO/PTO) nanoplates have been successfully synthesized via a hydrothermal method. It is interesting to find that BFO films selectively grew on the negative polar surface of PTO nanoplates with a saturation thickness of about 18–20 nm. Below such saturation size, the thickness of BFO films can be controlled in the range of 4–18 nm. An atomically sharp interface was identified to be formed between BFO and PTO with an epitaxial relationship of {012}BFO//{001}PTO. In particular, a room-temperature ferromagnetism in the nanoplates has been observed, where the saturation magnetization significantly decreased from to 0.029 to 0.003 emu g−1 upon the film thickness decreasing to 4 nm. Electron energy-loss spectroscopy (EELS) analysis on the interface suggests that the positive polar surface of BFO could be screened by both of the negative polarization and addition electrons in PTO. A mechanism of "screening balance broken and rebuilt" on the negative interface was proposed to explain the existence of selective growth, the saturation thickness and magnetism of the nanoplates. The findings suggest that a polar surface could be a powerful platform to realize the controllable epitaxial growth of perovskite oxide heterostructures with the intriguing interface functionality. [ABSTRACT FROM AUTHOR]

Published
2020
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