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Your search keyword '"Liu, Lifu"' showing total 94 results
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94 results on '"Liu, Lifu"'

1. Towards Large Scale Atomic Manufacturing: Heterodyne Grating Interferometer with Zero Dead-Zone

Author

Cui, Can, Gao, Lvye, Zhao, Pengbo, Yang, Menghan, Liu, Lifu, Ma, Yu, Huang, Guangyao, Wang, Shengtong, Luo, Linbin, and Li, Xinghui

Subjects
Physics - Optics, Electrical Engineering and Systems Science - Systems and Control
Abstract

This paper presents a novel heterodyne grating interferometer designed to meet the precise measurement requirements of next-generation lithography systems and large-scale atomic-level manufacturing. Utilizing a dual-frequency light source, the interferometer enables simultaneous measurement of three degrees of freedom. Key advancements include a compact zero Dead-Zone optical path configuration, significantly enhancing measurement reliability by mitigating the impact of light source fluctuations and air refractive index variations. A comprehensive crosstalk error analysis was conducted, resulting in a robust correction algorithm that reduces errors to below 5%. Performance testing of the prototype, size of 90mm*90mm*40mm, demonstrated exceptional resolution (0.25 nm in the XY-axis and 0.3 nm in the Z-axis), superior linearity (6.9e-5, 8.1e-5 and 16.2e-5 for the X, Y, and Z axes, respectively), high repeatability (0.8 nm/1000 nm for the three axes) and stability (20 nm for the XY-axis and 60 nm for the Z-axis over 1000 seconds). Comparative analysis with existing measurement sensors highlights the proposed method's significant advantages in integration, multidimensional capabilities, and is expected to be widely used in fields such as integrated circuits, atomic-level manufacturing and aerospace technology., Comment: 8 pages,11 figures

Published
2024

2. Joint Channel Estimation and Feedback with Masked Token Transformers in Massive MIMO Systems

Author

Zhao, Mingming, Liu, Lin, Liu, Lifu, Li, Mengke, and Tian, Qi

Subjects
Computer Science - Information Theory, Computer Science - Machine Learning
Abstract

The downlink channel state information (CSI) estimation and low overhead acquisition are the major challenges for massive MIMO systems in frequency division duplex to enable high MIMO gain. Recently, numerous studies have been conducted to harness the power of deep neural networks for better channel estimation and feedback. However, existing methods have yet to fully exploit the intrinsic correlation features present in CSI. As a consequence, distinct network structures are utilized for handling these two tasks separately. To achieve joint channel estimation and feedback, this paper proposes an encoder-decoder based network that unveils the intrinsic frequency-domain correlation within the CSI matrix. The entire encoder-decoder network is utilized for channel compression. To effectively capture and restructure correlation features, a self-mask-attention coding is proposed, complemented by an active masking strategy designed to improve efficiency. The channel estimation is achieved through the decoder part, wherein a lightweight multilayer perceptron denoising module is utilized for further accurate estimation. Extensive experiments demonstrate that our method not only outperforms state-of-the-art channel estimation and feedback techniques in joint tasks but also achieves beneficial performance in individual tasks., Comment: 10 pages

Published
2023

7. Hermite Expansion Model and LMMSE Analysis for Low-Resolution Quantized MIMO Detection

Author

Liu, Lifu, Ma, Yi, and Yi, Na

Subjects
Computer Science - Information Theory, Electrical Engineering and Systems Science - Signal Processing
Abstract

In this paper, the Hermite polynomials are employed to study linear approximation models of narrowband multiantenna signal reception (i.e., MIMO) with low-resolution quantizations. This study results in a novel linear approximation using the second-order Hermite expansion (SOHE). The SOHE model is not based on those assumptions often used in existing linear approximations. Instead, the quantization distortion is characterized by the second-order Hermite kernel, and the signal term is characterized by the first-order Hermite kernel. It is shown that the SOHE model can explain almost all phenomena and characteristics observed so far in the low-resolution MIMO signal reception. When the SOHE model is employed to analyze the linear minimum-mean-square-error (LMMSE) channel equalizer, it is revealed that the current LMMSE algorithm can be enhanced by incorporating a symbol-level normalization mechanism. The performance of the enhanced LMMSE algorithm is demonstrated through computer simulations for narrowband MIMO systems in Rayleigh fading channels., Comment: 16 pages

Published
2021

9. Massive MIMO signal reception with low-resolution quantizers

Author

Liu, Lifu and Ma, Yi

Subjects
Massive multiple-input multiple-output (mMIMO), analog-to-digital converter (ADC), quantization, second-order Hermite expansion (SOHE), contructive noise
Abstract

In massive multiple-input multiple-output (mMIMO) systems, the technique of using low-resolution analog-to-digital converters (ADCs) to quantize received signals can significantly reduce the receiver hardware cost as well as circuit power consumption. However, it incurs quantization noise in the digital domain which degrades the quality of signal reception. In particular, for 1- to 3-bit resolution quantizers, communication systems become very nonlinear and non-Gaussian. Quantization noise can be correlated to the received signal as well as the thermal noise. These are critical issues that can fundamentally change the way of receiver design and optimization, and thus they must be rigorously studied. The first contribution of this thesis lies in the use of Hermite polynomials to study the linear approximation model of low-resolution quantized mMIMO signal reception. Unlike other linear approximation models in the literature that assume the quantization noise to be white Gaussian and uncorrelated to the received signal, the proposed model, termed second-order Hermite expansion (SOHE), uses the second-order Hermite kernel to describe the quantization noise and the first-order Hermite kernel for the signal linear response. Novel mathematical theorems are established to explain key stochastic characteristics of the quantization noise. The SOHE theory results in an enhanced LMMSE channel equalizer which considerably improves the equalization performance particularly for mMIMO receivers using 2-bit quantizers. Another key contribution lies in an intensive study of the well-known dither effect of low-resolution quantizers, which explains the phenomenon of constructive noise in the mMIMO signal reconstruction. This study leads to a fundamental rethinking of mMIMO signal transmission strategy, operating signal-to-noise ratio (SNR) setup and more fundamentally the threshold optimization for low-resolution signal quantization. All of these provide theoretical support for the optimization of low-resolution quantized mMIMO. Finally, an outlook of major technical challenges and future direction of the lowresolution mMIMO research is presented.

Published
2021
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26. Massive MIMO Signal Reception with Low-Resolution Quantizers

Author

LIU, LIFU

Subjects
contructive noise, Massive multiple-input multiple-output (mMIMO), quantization, second-order Hermite expansion (SOHE), Computer Science::Databases, analog-to-digital converter (ADC)
Abstract

In massive multiple-input multiple-output (mMIMO) systems, the technique of using low-resolution analog-to-digital converters (ADCs) to quantize received signals can, significantly reduce the receiver hardware cost as well as circuit power consumption., However, it incurs quantization noise in the digital domain which degrades the quality, of signal reception. In particular, for 1- to 3-bit resolution quantizers, communication, systems become very nonlinear and non-Gaussian. Quantization noise can be correlated to the received signal as well as the thermal noise. These are critical issues that, can fundamentally change the way of receiver design and optimization, and thus they, must be rigorously studied., The first contribution of this thesis lies in the use of Hermite polynomials to study, the linear approximation model of low-resolution quantized mMIMO signal reception., Unlike other linear approximation models in the literature that assume the quantization, noise to be white Gaussian and uncorrelated to the received signal, the proposed model, termed second-order Hermite expansion (SOHE), uses the second-order Hermite kernel, to describe the quantization noise and the first-order Hermite kernel for the signal, linear response. Novel mathematical theorems are established to explain key stochastic, characteristics of the quantization noise. The SOHE theory results in an enhanced, LMMSE channel equalizer which considerably improves the equalization performance, particularly for mMIMO receivers using 2-bit quantizers., Another key contribution lies in an intensive study of the well-known dither effect, of low-resolution quantizers, which explains the phenomenon of constructive noise in, the mMIMO signal reconstruction. This study leads to a fundamental rethinking of, mMIMO signal transmission strategy, operating signal-to-noise ratio (SNR) setup and, more fundamentally the threshold optimization for low-resolution signal quantization., All of these provide theoretical support for the optimization of low-resolution quantized, mMIMO., Finally, an outlook of major technical challenges and future direction of the lowresolution mMIMO research is presented.

Published
2022
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28. Fruit, vegetable, and legume intake and the risk of all-cause, cardiovascular, and cancer mortality: A prospective study

Author

Liu, Weida, primary, Hu, Bo, additional, Dehghan, Mahshid, additional, Mente, Andrew, additional, Wang, Chuangshi, additional, Yan, Ruohua, additional, Rangarajan, Sumathy, additional, Tse, Lap Ah, additional, Yusuf, Salim, additional, Liu, Xiaoyun, additional, Wang, Yang, additional, Qiang, Deren, additional, Hu, Lihua, additional, Han, Aiying, additional, Tang, Xincheng, additional, Liu, Lisheng, additional, Li, Wei, additional, Chen, Chunming, additional, Zhao, Wenhua, additional, Yin, Lu, additional, Zhu, Jun, additional, Liang, Yan, additional, Sun, Yi, additional, Deng, Qing, additional, Jia, Xuan, additional, He, Xinye, additional, Zhang, Hongye, additional, Bo, Jian, additional, Wang, Xingyu, additional, Liu, Xu, additional, Gao, Nan, additional, Bai, Xiulin, additional, Yao, Chenrui, additional, Cheng, Xiaoru, additional, Li, Sidong, additional, Liu, Weida, additional, Lang, Xinyue, additional, Zhu, Yibing, additional, Xie, Liya, additional, Liu, Zhiguang, additional, Ren, Yingjuan, additional, Dai, Xi, additional, Gao, Liuning, additional, Wang, Liping, additional, Su, Yuxuan, additional, Han, Guoliang, additional, Song, Rui, additional, Cao, Zhuangni, additional, Sun, Yaya, additional, Li, Xiangrong, additional, Wang, Jing, additional, Wang, Li, additional, Peng, Ya, additional, Li, Xiaoqing, additional, Li, Ling, additional, Wang, Jia, additional, Zou, Jianmei, additional, Gao, Fan, additional, Tian, Shaofang, additional, Liu, Lifu, additional, Li, Yongmei, additional, Bi, Yanhui, additional, Li, Xin, additional, Zhang, Anran, additional, Wu, Dandan, additional, Cheng, Ying, additional, Xiao, Yize, additional, Lu, Fanghong, additional, Li, Yindong, additional, Hou, Yan, additional, Zhang, Liangqing, additional, Guo, Baoxia, additional, Liao, Xiaoyang, additional, Chen, Di, additional, Zhang, Peng, additional, Li, Ning, additional, Ma, Xiaolan, additional, Lei, Rensheng, additional, Fu, Minfan, additional, Liu, Yu, additional, Xing, Xiaojie, additional, Yang, Youzhu, additional, Zhao, Shenghu, additional, Xiang, Quanyong, additional, Tang, Jinhua, additional, Liu, Zhengrong, additional, Li, Xiaoxia, additional, Xu, Zhengting, additional, Aideeraili, Ayoupu, additional, and Zhao, Qian, additional

Published
2021
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30. A Low-Complexity Structure for Multi-user Massive MIMO with Binary Arrary-Receiver Based on Constructive Noise

Author

Liu, Lifu, Ma, Yi, Yi, Na, and Tafazolli, Rahim

Subjects
Computer Science::Information Theory
Abstract

In this paper, single-input multiple-output (SIMO) system when employing massive binary array-receiver has been investigated while constructive noise has been observed in the single user system to detect the higher-order QAM modulated signals. To fully understand the interesting phenomenon, mathematical model has been established and analyzed in this paper. Theorems of the signal detectability are studied to understand the best operating signal-to-noise ratio (SNR) range based on the error behaviours of the single user SIMO system. Within the observation and analysis, a novel new multiuser SIMO with binary array-receiver structure has been proposed and can be considered as a solution to deal with the high complexity problem that the traditional model has when using maximum likelihood (ML) detection. The key idea of this approach is to set up the multiuser multiple-input multiple-output (MIMO) model into a frequency division multiple access (FDMA) scenario and regard each user as single user SIMO to achieve the goal of decreasing the exponentially increased complexity of ML detection method to the number of users. It is shown by numerical results that each user in this system can achieve a promising error behaviour in the specific best operating SNR range.

Published
2020

41. Analysis of stope ground pressure by caving and filling in a mine.

Author

LIU Lifu, HUANG Jin, SUN Yuchao, XIONG Ke, and FENG Zhihao

Subjects
MINERAL industries, GROUND-cushion phenomenon, MINING methodology, MICROSEISMS, CAVING
Abstract

Sublevel caving method without bottom column and filling method were used for mining in a mine. This paper studied the change of stope ground pressure and stope stability when two mining methods were used simultaneously. FLAC3D numerical simulation technology was used to simulate the evolution law of stope ground pressure in this mine, and microseismic monitoring technology was used to verify the simulation results. The results showed that with the development of sublevel caving method, the stability of the lower consolidated backfill was significantly improved, and the force on the lower stope pillar was on the decline. After the mining of sublevel caving method, the vertical stress of the lower stope pillar decreased by about 35%. Thus, it was proved that the mining method of sublevel caving without bottom column can effectively relieve the ground pressure in the lower filling stope and is conducive to improving the stability of stope. [ABSTRACT FROM AUTHOR]

Published
2020
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42. Research on stability and optimal design of bedded rock slopes under deteriorated disturbance factors.

Author

XIONG Ke, HUANG Jin, SUN Yuchao, LIU Lifu, and FENG Zhihao

Subjects
ROCK slopes, SOIL degradation, EARTHQUAKES, RAINFALL, REDUCTION (Linguistics)
Abstract

The bedding rock slope is affected by natural geological structure and its stability is relatively poor. However, under the influence of strong degradation factors such as heavy rain, blasting and earthquakes, its stability is more threatened. Therefore, based on the strength reduction theory, this paper analyzed the stability of the bedding rock slope of a mine by numerical simulation. Meanwhile, this paper studied the position of the sliding surface of the rock slope, the lateral deformation and the stress change law of the rock slope under the bedding design and two optimization schemes under the three conditions of heavy rain, blasting and earthquake. The research results indicated that: the earthquake had the greatest impact on the stability of the bedding slope of the mine; in addition, the safety factor of the slope under the conditions of the proposed design scheme was lower than the standard value, and the slope was in an unstable state. Through the optimization study of the bedding slope of the mine, the optimal design plan of the mine was obtained. [ABSTRACT FROM AUTHOR]

Published
2020
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50. Real-time estimation of the pressure in the wheel cylinder with a hydraulic control unit in the vehicle braking control system based on the extended Kalman filter.

Author

Jiang, Guirong, Miao, Xiaolu, Wang, Yuehui, Chen, Jie, Li, Dalong, Liu, Lifu, and Muhammad, Fahad

Abstract

The pressure in the wheel cylinder plays an important role in the anti-lock braking system, but direct measurement usually needs expensive sensors. Therefore, estimation of the pressure in the wheel cylinder is of great significance to optimize the algorithm of the anti-lock braking system. There are two commonly used estimation methods: one is based on the hydraulic model, and the other is based on the equation for the tyre dynamics. Both of these, however, suffer from inadequacies. The former method is sensitive to the accuracy of the model in practical applications, and an accumulated error appears if some parameters of the process are not sufficiently accurate. In the latter method the pressure in the wheel cylinder is calculated for each cycle but, when the vehicle is running, the fluctuations in the deceleration are relatively large. To estimate the pressure more accurately, a novel method is proposed in this paper, which combines these two methods on the basis of the extended Kalman filter. The method can compensate for the inadequacies of the two methods mentioned above by using the variation in the wheel speed as the observation variable to modify the hydraulic model. It can decrease its sensitivity to the accuracy of the hydraulic model and improve the accuracy of the estimated magnitude of the pressure. The estimated results are compared with the real values which are obtained by using a pressure sensor on a typical low-friction road and on an asphalt road; in addition, the effectiveness of the novel method is validated by hardware-in-the-loop tests and vehicle tests. The results show that the proposed method can provide an accurate estimation of the pressure in the wheel cylinder during hydraulic control of the anti-lock braking system or any other brake control system. [ABSTRACT FROM AUTHOR]

Published
2017
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