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Selective transmission and channel estimation in massive MIMO systems

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High Technology Letters 2016年第1期22卷 99-106页

作者：杨睿哲 Zong Liang Si Pengbo Ma Dawei Zhang Yanhua beijing Advanced innovation center for future Internet Technology Beijing University of Technology College of Electronics Information and Control Engineering Beijing University of Technology

Massive MIMO systems have got extraordinary spectral efficiency using a large number of base station antennas,but it is in the challenge of pilot contamination using the aligned *** address this issue,a selective transmission is proposed using time-shifted pilots with cell grouping,where the strong interfering users in downlink transmission cells are temporally stopped during the pilots transmission in uplink *** on the spatial characteristics of physical channel models,the strong interfering users are selected to minimize the inter-cell interference and the cell grouping is designed to have less temporally stopped users within a smaller ***,a Kalman estimator is proposed to reduce the unexpected effect of residual interferences in channel estimation,which exploits both the spatial-time correlation of channels and the share of the interference *** numerical results show that our scheme significantly improves the channel estimation accuracy and the data rates.

关键词： multiple-input multiple-output (MIMO) selective transmission time-shifted pilots Kalman

Virtual network embedding through node connectivity

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The Journal of China Universities of Posts and Telecommunications 2015年第1期22卷 17-23,56页

作者： Ding Jian Huang Tao Wang Jian Hu Wenbo Liu Jiang Liu Yunjie State Key Laboratory of Networking and Switching Technology Beijing University of Posts and Telecommunications future Network Industry innovation center of China

Virtual network embedding （VNE） is an essential part of network virtualization, which is considered as one of the most promising way for the future network. Its main object is to efficiently assign the nodes and links of a virtual network （VN） to a shared substrate network （SN）, The NP-hard and exiting studies have put forward several heuristic algorithms. However, most of the algorithms only consider the local resource of nodes, such as CPU and bandwidth （BW）, to decide the embedding, and ignore the significant impact of network attributes. Based on the attributes of entire network, a model of the connectivity between each pair of nodes was formulated to measure the resource ranking of the nodes, and a new two-stage embedding algorithm was proposed. Thereafter, the node mapping and link mapping can be jointly considered. Extensive simulation shows that the proposed algorithm improves the performance of VNE by increasing the revenue/cost ratio and acceptance ratio of VN requests while reducing the runtime.

关键词： virtual network virtualization VNE attributes of entire network connectivity

Intelligent Resources Management System Design in Information Centric Networking

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China Communications 2017年第8期14卷 105-123页

作者： Hengyang Zhang Shixiang Zhu Renchao Xie Tao Huang Yunjie Liu State Key Laboratory of Networking and Switching Technology Beijing University of Posts and TelecommunicationsBeijing 100876China beijing Advanced innovation center for future Internet Technology Beijing 100876China

Information centric networking(ICN) is a new network architecture that is centred on accessing content. It aims to solve some of the problems associated with IP networks, increasing content distribution capability and improving users' experience. To analyse the requests' patterns and fully utilize the universal cached contents, a novel intelligent resources management system is proposed, which enables effi cient cache resource allocation in real time, based on changing user demand patterns. The system is composed of two parts. The fi rst part is a fi ne-grain traffi c estimation algorithm called Temporal Poisson traffi c prediction(TP2) that aims at analysing the traffi c pattern(or aggregated user requests' demands) for different contents. The second part is a collaborative cache placement algorithm that is based on traffic estimated by TP2. The experimental results show that TP2 has better performance than other comparable traffi c prediction algorithms and the proposed intelligent system can increase the utilization of cache resources and improve the network capacity.

关键词： information centric networking traffi c estimation cache resources allocation time series analysis intelligent analysis

Unsupervised content-preserving transformation for optical microscopy

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Light(Science & Applications) 2021年第3期10卷 390-400页

作者： Xinyang Li Guoxun Zhang Hui Qiao Feng Bao Yue Deng Jiamin Wu Yangfan He Jingping Yun Xing Lin Hao Xie Haoqian Wang Qionghai Dai Department of Automation Tsinghua UniversityBeijing 100084China Tsinghua Shenzhen International Graduate School Tsinghua UniversityShenzhen 518055China Institute for Brain and Cognitive Sciences Tsinghua UniversityBeijing 100084China School of Astronautics Beihang UniversityBeijing 100191China beijing Advanced innovation center for Big Data and Brain Computing Beihang UniversityBeijing 100191China Department of Pathology Sun Yat-sen University Cancer CenterGuangzhou 510060China State Key Laboratory of Oncology in South China Guangzhou 510060China Collaborative innovation center for Cancer Medicine Guangzhou 510060China beijing innovation center for future chips Tsinghua UniversityBeijing 100084China

The development of deep learning and open access to a substantial collection of imaging data together provide a potential solution for computational image transformation,which is gradually changing the landscape of optical imaging and biomedical ***,current implementations of deep learning usually operate in a supervised manner,and their reliance on laborious and error-prone data annotation procedures remains a barrier to more general ***,we propose an unsupervised image transformation to facilitate the utilization of deep learning for optical microscopy,even in some cases in which supervised models cannot be *** the introduction of a saliency constraint,the unsupervised model,named Unsupervised content-preserving Transformation for Optical Microscopy(UTOM);can learn the mapping between two image domains without requiring paired training data while avoiding distortions of the image *** shows promising performance in a wide range of biomedical image transformation tasks,including in silico histological staining,fluorescence image restoration,and virtual fluorescence *** evaluations reveal that UTOM achieves stable and high-fidelity image transformations across different imaging conditions and *** anticipate that our framework will encourage a paradigm shift in training neural networks and enable more applications of artificial intelligence in biomedical imaging.

关键词： transformation preserving image

Length-dependent alignment of large-area semiconducting carbon nanotubes self-assembly on a liquid–liquid interface

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Nano Research 2023年第1期16卷 1568-1575页

作者： Haijian Wen Jian Yao Yijun Li Yahui Li Leitao Cao Wanquan Chi Yueyue Wang Hehua Jin Song Qiu Jianshi Tang Qingwen Li School of Physical Science and Technology ShanghaiTech UniversityShanghai 201210China Key Laboratory of Multifunctional and Smart Systems Division of Advanced MaterialsSuzhou Institute of Nano-Tech and Nano-BionicsChinese Academy of SciencesSuzhou 215123China School of Integrated Circuits Beijing Innovation Center for Future ChipsBNRistTsinghua UniversityBeijing 100084China

Aligned arrays of semiconducting carbon nanotubes(s-CNTs)with high homogenous density and orientation are urgently needed for high-performance carbon-based ***,a length-controlled approach using combined technologies was developed to regulate the s-CNT length and reduce the length *** impact of different lengths and length distributions was studied during aligned self-assembly on a liquid–liquid confined interface was *** results show that short s-CNTs with a narrow distribution have the best alignment uniformity over the large *** optimized and aligned s-CNT array can reach a density as high as 100 CNTs·μm−1 on a 4-inch *** field-effect transistor(FET)performance of these optimized s-CNT arrays was 64%higher than arrays without *** study clarified that rational control of s-CNTs with desired length and length distribution on the aligned self-assembly process within the liquid–liquid confined *** results illustrate a solid foundation for the application of emerging carbon-based electronics.

关键词： carbon nanotube aligned array length-controlled self-assembly liquid-liquid interface

Tuning the ferroelectricity of Hf0.5Zr0.5O2 with alloy electrodes

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Science China(Information Sciences) 2024年第8期67卷 321-330页

作者： Keqin LIU Bingjie DANG Zhiyu YANG Teng ZHANG Zhen YANG Jinxuan BAI Zelun PAN Ru HUANG Yuchao YANG beijing Advanced innovation center for Integrated Circuits School of Integrated Circuits Peking University School of Electronic and Computer Engineering Peking University center for Brain Inspired chips Institute for Artificial Intelligence Peking University center for Brain Inspired Intelligence Chinese Institute for Brain ResearchBeijing

Tuning ferroelectricity of Hf0.5Zr0.5O2is crucial for facilitating its practical applications in various fields, including in-memory and neuromorphic computing. Previous studies have revealed that the electrodes have a significant influence on ferroelectricity, and changing electrode materials can realize different but discrete ferroelectric polarization values. Here, we introduce an alloy-electrode method, in order to achieve gradual and accurate modulation of ferroelectric polarization, especially useful for matching the polarization charges at the interface of ferroelectric insulators and ferroelectric semiconductors. Au and W electrodes are chosen as baselines for realizing weak and strong ferroelectric polarization, where the intermediate states can be achieved by adjusting the ratio of metals in the Au-W alloy. To demonstrate the generality of this approach, the Cu-W alloy electrode is also realized for tuning ferroelectric polarization. The effect of alloy electrodes on device leakage current, endurance, and retention is evaluated. In addition, the temperature stability of ferroelectric capacitors is tested, where limited changes in both remnant polarization and coercive voltages are observed, showing the great potential of the ferroelectric hafnium oxide. Such gradual modulation of ferroelectric polarization could facilitate the application of Hf0.5Zr0.5O2in in-memory and neuromorphic computing.

关键词： ferroelectric hafnium oxide alloy electrode gradual modulation temperature stability

Navigation in virtual and real environment using brain computer interface:a progress report

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Virtual Reality & Intelligent Hardware 2022年第2期4卷 89-114页

作者： Haochen HU Yue LIU Kang YUE Yongtian WANG beijing Engineering Research center of Mixed Reality and Advanced Display School of Optics and PhotonicsBeijing Institute of TechnologyBeijing 100081China Advanced innovation center for future Visual Entertainment Beijing Film AcademyBeijing 100088China

A brain-computer interface (BCI) facilitates bypassing the peripheral nervous system and directly communicating with surrounding devices. Navigation technology using BCI has developed-from exploring the prototype paradigm in the virtual environment (VE) to accurately completing the locomotion intention of the operator in the form of a powered wheelchair or mobile robot in a real environment. This paper summarizes BCI navigation applications that have been used in both real and VEs in the past 20 years. Horizontal comparisons were conducted between various paradigms applied to BCI and their unique signal-processing methods. Owing to the shift in the control mode from synchronous to asynchronous, the development trend of navigation applications in the VE was also reviewed. The contrast between high level commands and low-level commands is introduced as the main line to review the two major applications of BCI navigation in real environments: mobile robots and unmanned aerial vehicles (UAVs). Finally, applications of BCI navigation to scenarios outside the laboratory;research challenges, including human factors in navigation application interaction design;and the feasibility of hybrid BCI for BCI navigation are discussed in detail.

关键词： Brain-computer interface Virtual reality Human-computer interface Navigation Motor imagery Steady-state visual evoked potential

An Analytical Method for Predicting Direct Tensile Creep Fracture in Brittle Solids Containing Initial Microcracks

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Acta Mechanica Solida Sinica 2022年第1期35卷 152-160页

作者： Xiaozhao Li Chengzhi Qi School of Civil and Transportation Engineering Beijing University of Civil Engineering and ArchitectureBeijing 100044China beijing Advanced innovation center for future Urban Design Beijing 100044China beijing International Scientific and Technological Cooperation Base of Construction of Urban Traffic Infrastructure Beijing 100044China

The tensile creep fracture behaviors in brittle solids are of great significance for the safety evaluation of brittle solid ***,micromechanics-based tensile creep fracture behavior is rarely *** this study,a micromechanics-based method for predicting direct tensile creep fractures is *** method is established by combining the suggested expression of the mode-I stress intensity factor,the subcritical crack growth law,and the relationship between wing crack length and axial *** suggested mode-I stress intensity factor is formulated by the use of the basic theory of fracture mechanics under different loading *** rationality of the proposed tensile creep fracture model is verified by comparing with the experimental *** correspondences of time-dependent axial strain,strain rate,wing crack length,and crack velocity are plotted under constant stress and stepping stress during tensile creep *** effects of the initial crack size,inclination angle and density on the crack initiation stress,tensile strength,tensile creep fracture time,steady-state strain rate,initial strain,crack coalescence strain,and failure strain are discussed.

关键词： Micromechanics Stress intensity factor Direct tensile creep Subcritical cracking Brittle solids

Decoupled Delay and Bandwidth Centralized Queue-Based QoS Scheme in OpenFlow Networks

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China Communications 2019年第7期16卷 70-82页

作者： Weihong Wu Jiang Liu Tao Huang State Key Laboratory of Networking and Switching Technology Beijing University of Posts and Telecommunications Beijing 100876 China beijing Laboratory of Advanced Information Networks Beijing 100876 China beijing Advanced innovation center for future Internet Technology Beijing 100124 China

There are an increasing of scenarios that require the independent bandwidth and delay demands. For instance, in a data center, the interactive message would not occupy much bandwidth, but it requires the rigorous demands for the delay. However, the existing QoS approaches are mainly bandwidth based, which are inappropriate for these scenarios. Hence, we propose the decoupled scheme in the OpenFlow networks to provide the centralized differential bandwidth and delay control. We leverage the mature HTB to manage the bandwidth. And we design the Queue Delay Management Scheme (QDMS) for queuing delay arrangement, as well as the Comprehensive Parameters based Dijkstra Route algorithm (CPDR) for the propagation delay control. The evaluation results verify the decoupling effectiveness. And the decoupled scheme can reduce the delay for high priority flows.

关键词： software-defined networks openflow quality of service decoupled delay and rate