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Overfitting effect of artificial neural network based nonlinear equalizer: from mathematical origin to transmission evolution

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Science China(Information Sciences) 2020年第6期63卷 67-79页

作者： Zheng YANG Fan GAO Songnian FU Ming TANG deming LIU Wuhan National Laboratory for Optoelectronics School of Optical and Electronic InformationHuazhong University of Science and Technology Alibaba Infrastructure Service Alibaba Group

Overfitting effect of artificial neural network(ANN) based nonlinear equalizer(NLE) leads to a trap of bit error ratio(BEr) overestimation in optical fiber communication system, especially when the performance is evaluated by the commonly-used pseudo-random binary sequence(PrBS). First, we mathematically investigate the PrBS generation and Gray code mapping rules, in comparison with the use of Mersenne Twister random sequence(MTrS). Under the condition of a symbol erasure channel, we identify that ANN can recognize both the PrBS generation and symbol mapping rules, by increasing the weights of NLE at specific positions, whereas the MTrS is currently safe owing to the limited input length of current ANN based NLE. Then, we design four channel models of fiber optical transmission to experimentally examine various impairments on the evolution of overfitting effect. When both the additive white Gaussian noise(AWGN) channel and the bandwidth limited channel are considered, the mitigation of overfitting becomes possible by the use of pruned PrBS(P-PrBS) training set with removing the generation and mapping rules determined input symbols. However, as for both the chromatic dispersion(Cd) uncompensated channel and the Cd managed channel, the overfitting effect becomes serious, because both Cd and fiber nonlinearity induced inter-symbol interference(ISI) is beneficial for ANN to identify the PrBS symbol rules. Finally,possible solutions to mitigate the overfitting effect are summarized.

关键词： artificial neural network nonlinear equalizer pseudo-random binary sequence overfitting

Ab initio study of H/O trapping and clustering on U/Al interface

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Chinese Physics B 2018年第9期27卷 512-517页

作者： Wenhong Ouyang Wensheng Lai and Zhengjun Zhang Laboratory of Advanced Materials School of Materials Science and EngineeringTsinghua UniversityBeijing 100084China

Al coating on U surfaces is one of the methods to protect U against environmental corrosion. The behaviors of hydrogen and oxygen impurities near the Al/α-U interface have been studied in the density functional theory framework. It turns out that U vacancies tend to segregate to the interface with segregation energies of around 0.5-0.8 eV. The segregated U vacancy can act as a sink for H and O impurities, which is saturated when filled with 8 H or 6 O atoms, ***, the O impurities tend to stay in the Al layer while the H impurities prefer to diffuse into the U lattice, suggesting that the Al coating can play a significant role against oxidation but not against hydrogenation of U.

关键词： interface uranium aluminum density functional theory

Mechanisms of carbon storage and the coupled carbon, nitrogen and sulfur cycles in regional seas in response to global change

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Science China Earth Sciences 2017年第5期60卷 1010-1014页

作者： XIE ShuCheng CHEN JianFang WANG FengPing XUN LuYing TANG Kai ZHAI Weidong LIU JiHua MA WenTao State key Laboratory of Biogeology and Environmental Geology China University of Geosciences The Second Institute of Oceanography State Marine Administration of China Faculty of Life Science and Technology Shanghai Jiaotong University Institute of Oceanography Shangdong University College of Ocean and Earth Sciences Xiamen University School of Ocean and Earth Science Tongji University

*** challenges in scientific frontiers of marine carbon storage in the scenario of global change The marine carbon cycle is influenced by anthropogenic activities,affecting global climate change and casting a significant impact on ***,the complex spatiotemporal process of the marine carbon cycle results in the uncertainty in the estimation of marine carbon budget。

关键词： sulfur anthropogenic cycle scenario affecting microbial warming nutrients anaerobic Bohai

EnKF Assimilation of Satellite-retrieved Cloud Water Path to Improve Tropical Cyclone rainfall Forecast

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Journal of Tropical Meteorology 2021年第3期27卷 201-217页

作者： GAO Xiao-yu LIN Yan-luan YUE Jian Ministry of Education key Laboratory for Earth System Modeling Department of Earth System ScienceTsinghua UniversityBeijing 100084 China Center of Numerical Weather Predication China Meteorological AdministrationBeijing 100081 China

Tropical cyclone(TC) rainfall forecast has remained a challenge. To create initial conditions with high quality for simulation, the present study implemented a data assimilation scheme based on the EnKF method to ingest the satellite-retrieved cloud water path(C_(w)) and tested it in WrF. The scheme uses the vertical integration of forecasted cloud water content to transform control variables to the observation space, and creates the correlations between C_(w) and control variables in the flow-dependent background error covariance based on all the ensemble members, so that the observed cloud information can affect the background temperature and humidity. For two typhoons in 2018(Yagi and rumiba), assimilating C_(w) significantly increases the simulated rainfalls and TC intensities. In terms of the average equitable threat score of daily moderate to heavy rainfall(5-120 mm), the improvements are over 130%, and the dry biases are cut by about 30%. Such improvements are traced down to the fact that C_(w) assimilation increases the moisture content, especially that further away from the TC center, which provides more precipitable water for the rainfall,strengthens the TC and broadens the TC size via latent heat release and internal wind field adjustment.

关键词： tropical cyclone data assimilation EnKF cloud water path

Study on Ignition Proof AZ91d Magnesium Alloy Chips with Cerium Addition

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Journal of rare Earths 2005年第4期23卷 466-469页

作者：周宏李伟王明星赵宇 key Laboratory ofAutomobile Materials of Ministry of Education Department of Materials Science and Engineer-ing Jilin University Changchun 130025 China

The effect of Ce on ignition point of AZ91d magnesium alloy chips was studied. For the AZ91d and the AZ91d-xCe magnesium alloys, changing the sizes of the chips in the range of 58 - 270 μm has a limited influence on ignition point, however, the shift of the content of Ce has much effect on ignition point. Increasing the Ce content, x from 0.15 to 0.25, the ignition point increases with increasing of Ce; however, x from 0.25 to 0.45, the ignition point decreases with increasing of Ce. By the addition of Ce of 0.25 %. the ignition point is raised by 43℃.

关键词： metal materials ignition proof cerium chips magnesium alloy rare earths

Numerical study on the aerodynamic performance and safe running of high-speed trains in sandstorms

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2011年第12期12卷 971-978页

作者： Hong-bing XIONG Wen-guang YU da-wei CHEN Xue-ming SHAO department of Mechanics Zhejiang University Hangzhou 310027 China National Engineering Laboratory for System Integration of High-Speed Train （South） CSR Qingdao Sifang Co. Ltd. Qingdao 266111 China

The influence of sandstorms on train aerodynamic performance and safe running was studied in response to the frequent occurrence of sandstorm weather in north *** Eulerian two-phase model in the computational fluid dynamic (CFd) software FLUENT,validated with published data,was used to solve the gas-solid multiphase flow of a sandstorm around a *** train aerodynamic performance under different sandstorm levels and no sand conditions was then *** showed that in sandstorm weather,the drag,lift,side forces and overturning moment increase by variable *** on a numerical analysis of aerodynamic characteristics,an equation of train stability was also derived using the theory of moment balance from the view of dynamics.A recommended speed limit of a train under different sandstorm levels was calculated based on the stability analysis.

关键词： High-speed train Sandstorm Gas-solid multiphase Eulerian two-phase model Aerodynamic Safety Speed limit

Intelligent power distribution live‐line operation robot systems based on stereo camera

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High Voltage 2023年第6期8卷 1306-1318页

作者： Yutao Chen Yahao Wang Xuming Tang Kai Wu Shaolei Wu rui Guo Yu Feng Erbao dong department of Precision Machinery and Precision Instrumentation University of Science and Technology of ChinaHefeiChina State Grid Anhui Electric Power Company HefeiChina State Grid Anhui Electric Power Company Electric Power research Institute HefeiChina State Grid Intelligent Technology Co. LtdJinanChina

Maintenance tasks in distribution networks are often accompanied by hazards associated with high altitudes and high *** utilising robots instead of human operators to perform these tasks,potential risks can be avoided,while productivity can be *** research proposes an intelligent power distribution live‐line operation robot(PdLOr)system based on a stereo camera to replace human to complete *** PdLOr system consists of several key components,including dual manipulators,wireless tools,a visual perception system,an insulated bucket truck,and a ground control *** the task is confirmed,the real‐time vision system identification and posi-tioning enable the adjustment of the insulated bucket to position the robot correctly for its intended *** stereo camera plays a crucial role in accurately recognising and estimating the object's ***,a simplified reconstruction is performed within a virtual simulation environment,which aids in collision detection during path *** obtaining the optimal path,it is then communicated to the real manip-ulator for *** validate the feasibility of the PdLOr system,field experiments were conducted in actual distribution network *** results demonstrate that the PdLOr effectively completes single‐phase power‐line connection tasks within a remarkable 10‐min timeframe.

关键词： robot distribution stereo

Hydrogen-bonded organic framework-ionic liquid composite quasisolid electrolyte for high-performance lithium battery

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Nano research 2025年第1期18卷 332-340页

作者： Junmei Zhang Yatao Wu Chenye Wang Yong Liu Zhirong Yang Shiyue Zhou Wenpeng Li Wenjia Wu Jingtao Wang School of Chemical Engineering Zhengzhou UniversityZhengzhou 450001China

Ionic liquids(ILs)hold great promise as highperformance electrolyte material due to their unique advantages including nonvolatility,high thermal stability and high ionic ***,the IL-based electrolytes always suffer from serious ion aggregation and high viscosity at low temperatures,leading to significantly decline in ionic ***,hydrogen-bonded organic framework-ionic liquid composite quasi-solid electrolyte(high temperature treatment(HT)-HOF-IL CQSE)was prepared through confining the IL electrolytes(ILEs)into the pore of HOF lamellar *** weak hydrogen bonding interactions within HOF nanosheets,together with the generated interactions between ILE and HOF,enable uniform and continuous distribution of ILE in HOF lamellar *** effectively inhibits the ion migration of ILE,which meanwhile serves as Li+transfer sites,affording high ionic conductivity of 5.7×10^(-5)S·cm-1 at-60 ℃,with high lithium-ion transference number of 0.69,whereas ILEs usually lose ionic conduction ability at such low *** assembled Li symmetrical cell can stably cycle at 0.2 mA·cm^(-2)and^(-2)0 ℃ for more than 1500 *** LiFePO_(4)|HT-HOF-IL CQSE|Li cell shows excellent cycling performance at 0.5 C at a wide temperature range of^(-2)0 to 60 ℃.This work may pave a new avenue for the development of high-performance IL-based composite electrolytes.

关键词： ionic liquid hydrogen-bonded organic framework low-temperature ionic conductivity lithium-ion transference number quasi-solid electrolyte

Calculation of effective point reactor kinetic parameters combined with the Galerkin finite element method

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Nuclear Science and Techniques 2020年第7期31卷 65-75页

作者： Bao-Xin Yuan Wan-Kui Yang Song-Bao Zhang Bin Zhong Jun-Xia Wei Yang-Jun Ying Institute of Nuclear Physics and Chemistry China Academy of Engineering PhysicsMianyang 621900China Institute of Applied Physics and Computational Mathematics Beijing 100094China

Precise point reactor kinetic parameters are essential in the study of reactor *** reactor kinetic parameters include the effective delayed neutron fraction and prompt neutron *** this work,effective point reactor kinetic parameters,which can be applied to unstructured grids,were calculated based on the Galerkin finite element ***,two-dimensional and three-dimensional benchmarks were used to verify the calculation of steady-state neutronic ***,the Tehran research reactor core was divided into hexahedral meshes,and the forward flux and adjoint flux were ***,the effective point reactor kinetic parameters of the Tehran research reactor were obtained by comprehensively processing the steady-state neutronic parameters.

关键词： parameters element prompt