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Distribution and risk assessment of heavy metals in surface sediments of coastal mudflats on Leizhou Peninsula,China

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Acta Oceanologica Sinica 2023年第1期42卷 25-34页

作者： Tingting Li Lili Jia Xin ZHU Min Xu xinchang Zhang Key Laboratory of Ocean and Marginal Sea Geology South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou510301China University of Chinese Academy of Sciences Beijing100049China Guangdong Geological Survey Institute Guangzhou510080China State Key Laboratory of Isotope Geochemistry Guangzhou Institute of GeochemistryChinese Academy of SciencesGuangzhou510640China CAS Center for Excellence in Deep Earth Science Guangzhou510640China

Mudflats play a vital role in maintaining the dynamic balance between sea and land.To understand the characteristics,sources,and pollution risks of six heavy metals(As,Cd,Cr,Cu,Hg,and Pb)in the coastal mudflats on the Leizhou Peninsula,257 surface sediment samples were studied using mathematical statistics,correlation analysis,and factor analysis.The results show that the overall concentrations of these heavy metals are low although there are several high abnormal points in the local areas.The strong correlation between these heavy metals indicates that the sources of some of the metals are similar,yet their elemental combinations in different cities(counties)varied.According to the calculated enrichment factor(EF),anthropogenic activity-induced heavy metals were determined in order of decreasing influence:As,Cd,Pb,Cr,Cu,and Hg.The low EF values of Hg indicate that it does not present as a contaminant in the study area,while low values of Cr and Cu from the Lianjiang City suggest that these two metals were also attributed to natural sources.The presence of As,Cd,Cr,Cu,and Pb from the remaining cities(counties)should be influenced by anthropogenic activities.The overall potential ecological risk index indicates that the ecological risks posed by the six analyzed heavy metals to the Leizhou Peninsula mudflats,in order of decreasing risk,are Cd,As,Hg,Pb,Cu,and Cr.It is noteworthy that only Cd in Lianjiang City demonstrated substantial ecological risk.Other examined heavy metals in other cities of the study area showed slight ecological risk.

关键词： mudflat heavy metal ecological risk assessment source identification Leizhou Peninsula

Collision-aware interactive simulation using graph neural networks

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Visual Computing for Industry,Biomedicine,and Art 2022年第1期5卷 174-186页

作者： Xin ZHU Yinling Qian Qiong Wang Ziliang Feng Pheng‑Ann Heng College of Computer Science Sichuan UniversityChengdu 610065China Shenzhen Institute of Advanced Technology Chinese Academy of SciencesShenzhen 518055China Department of Computer Science and Engineering The Chinese University of Hong KongHong KongChina

Deep simulations have gained widespread attention owing to their excellent acceleration performances.However,these methods cannot provide effective collision detection and response strategies.We propose a deep interac-tive physical simulation framework that can effectively address tool-object collisions.The framework can predict the dynamic information by considering the collision state.In particular,the graph neural network is chosen as the base model,and a collision-aware recursive regression module is introduced to update the network parameters recursively using interpenetration distances calculated from the vertex-face and edge-edge tests.Additionally,a novel self-supervised collision term is introduced to provide a more compact collision response.This study extensively evaluates the proposed method and shows that it effectively reduces interpenetration artifacts while ensuring high simulation efficiency.

关键词： Deep physical simulation Collision-aware Continuous collision detection Graph neural network

Resource allocation optimization for SWIPT full-duplex relaying networks with practical energy harvester

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The Journal of China Universities of Posts and Telecommunications 2023年第1期30卷 39-46页

作者： Xu Siyang Song xin zhu Jiahui School of Computer and Communication Engineering Northeastern University at QinhuangdaoQinhuangdao 066004China

In this paper,the resource allocation optimization for the simultaneous wireless information and power transfer(SWIPT)full-duplex(FD)relaying networks is investigated,in which the power-constrained relay scavenges energy from the source signal and assists information transmission by FD operation.Taking into account non-linear energy harvesting(EH)hardware circuit characteristics of the relay,the information rate maximization problem is developed by jointly optimizing the time-switching(TS)factor and transmission powers of the source in two different phases.However,the formulated optimization is highly non-convex and difficult to solve.To cope with this problem,the primary problem is decomposed into two sub-problems with respect to the TS factor and transmission powers.After solving these two sub-problems,the final sub-optimal solutions can be obtained by alternating search.Simulation results prove that the optimization of both TS factor and transmission powers can effectively enhance the information rate for the considered networks.

关键词： resource allocation optimization full-duplex relaying networks energy harvesting information rate

Distortion minimization for multimedia transmission in NOMA HAP-UAV integrated aerial access networks

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Chinese Journal of Aeronautics 2022年第9期35卷 81-94页

作者： Guobin ZHANG zhu HAN Hang xin xin WEI Boya DI School of Electrical Engineering and Intelligentization Dongguan University of TechnologyDongguan 523808China Department of Electrical and Computer Engineering and Department of Computer Science University of HoustonTX77004USA School of Computer Science and Technology Dongguan University of TechnologyDongguan 523808China Department of Computing Imperial CollegeLondon SW72AzUK

Aerial access networks have been envisioned as a promising 6G solution to enhance the ground communication systems in both coverage and capacity. To better utilize the spectrum and fully explore different channel characteristics, this paper constructs an integrated network comprising the High Altitude Platform(HAP) and Unmanned Air Vehicles(UAVs) with the NonOrthogonal Multiple Access(NOMA) technology. In order to improve the transmission quality of images and videos, a power management scheme is proposed to minimize the distortion of the transmissions from the HAP and UAVs to the terminals. The power control is formulated as a non-convex problem constrained by the maximal transmit power and the minimal terminal rate requirements. The variable substitution and the first-order Tailor’s expansion is used to transform it into a sequence of convex problems, which are subsequently solved through the gradient projection method. Simulation demonstrates the signal distortion and error rate improvement achieved by the proposed algorithm.

关键词： Aerial Access Networks High Altitude Platform Non-Orthogonal Multiple Access Sixth-Generation Unmanned Air Vehicles

Effect of cerium on microstructure,eutectic carbides and Laves phase in electroslag remelted 15Cr-22Ni-1Nb austenitic heat-resistant steel

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Journal of Iron and Steel Research(International) 2023年第2期30卷 338-349页

作者： Xin ZHU Cheng-bin Shi Shi-jun Wang Peng Lan Jing Li State Key Laboratory of Advanced Metallurgy University of Science and Technology Beijing(USTB)Beijing100083China School of Metallurgical and Ecological Engineering University of Science and Technology Beijing(USTB)Beijing100083China

The dendrites,eutectic carbides,Laves phase and microsegregation of alloying element in electroslag remelted 15Cr-22Ni-1Nb austenitic heat-resistant steel with varying cerium contents were studied.The liquidus and solidus temperatures of the steel were determined to reveal the effect of cerium on solidification temperature interval and local solidification time of the steel.The secondary dendrite arm spacing decreases from 57.10 to 40.18μm with increasing the cerium content from 0 to 0.0630 wt.%.The eutectic NbC and Laves phase in as-cast ingots exhibit blocky and honeycomb morphology,respectively.The area fractions and sizes of eutectic NbC and Laves phase in as-cast ingots decrease with the increase in cerium content.The atomic percentage of Laves phase-forming element(Ni,Nb,Cr,Mo and Si)decreases with the increase in cerium content of the steel.The microsegregation of Mo,Ni,Si,Cr and Nb decreases with increasing the cerium content,which is favorable to reducing both the amount and sizes of eutectic NbC and Laves phase in as-cast ingots.The solidification temperature interval and local solidification time of the steel decrease as the cerium content is increased from 0 to 0.0630 wt.%,which inhibits the growth of dendrites,eutectic NbC and Laves phase.

关键词： Heat-resistant steel Rare earth cerium Eutectic NbC Laves phase Microsegregation Solidification characteristics

Asymptotic analysis of a nonlinear stochastic eco-epidemiological system with feedback control

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Applied Mathematics(A Journal of Chinese Universities) 2022年第3期37卷 317-339页

作者： ZHANG Sheng-qiang MENG xin-zhu College of Mathematics and Systems Science Shandong University of Science and TechnologyQingdao 266590China Business School University of Shanghai for Science and TechnologyShanghai 200093China

This paper proposes a new stochastic eco-epidemiological model with nonlinear incidence rate and feedback controls.First,we prove that the stochastic system has a unique global positive solution.Second,by constructing a series of appropriate stochastic Lyapunov functions,the asymptotic behaviors around the equilibria of deterministic model are obtained,and we demonstrate that the stochastic system exists a stationary Markov process.Third,the conditions for persistence in the mean and extinction of the stochastic system are established.Finally,we carry out some numerical simulations with respect to different stochastic parameters to verify our analytical results.The obtained results indicate that the stochastic perturbations and feedback controls have crucial effects on the survivability of system.

关键词： stochastic eco-epidemiological model stationary markov process feedback controls asymptotic behavior persistence in the mean

Complementary two-phase anode improving stability and conductivity for lithium storage performance

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Rare Metals 2023年第1期42卷 85-99页

作者： Xue-Fang Xie Guo-Zhao Fang Ying-zhu Hu xin-xin Cao Ting zhu An-Qiang Pan School of Materials Science&Engineering Central South UniversityChangsha410083China

Metal chalcogenides with multiple lithium ions storage capability have received extensive attentions in recent years;however,their practical application is restricted by the structural instability and poor reversibility.Herein,a unique structure of N and S co-doped C/TiO_(2)nanofibers is reported to support SnS nanosheets for fast and ultra-stable lithium storage.The incorporation of TiO_(2)can notably suppress the excessive uncontrollable growth of SnS and improve the structural stability of the electrode material.The effects of the ratios between Ti and Sn and the corresponding synthesis temperatures on the structure and electrochemical properties of the electrodes have been systematically studied.The interface charge transfer behavior of SnS and TiO_(2)composite heterostructure was clarified by density functional theory(DFT)calculation.The electronic interaction SnS and TiO_(2)can effectively reduce the energy band gap and form a built-in electric field at the interface of the two phases.This is beneficial for the adsorption of lithium ion and consequently accelerate the reaction kinetics of the electrode material.After the two phases are combined,the agglomeration of SnS is effectively suppressed,and the overall conductivity of the composite is greatly improved.Furthermore,the synergistic effect induced by SnS and TiO_(2)enables the good stability of the electrode in both lithium-ion half-cells and full cells.This work can provide new insights toward improving the performance of alloy-type anodes.

关键词： SnS TiO_(2) Structural stability Battery

Optical thermometry based on near-infrared luminescence from phosphors mixture

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Journal of Rare Earths 2022年第2期40卷 201-210,I0001页

作者： Wei Xu Xin ZHU Di Zhao Longjiang Zheng Fengkai Shang Zhiguo Zhang School of Electrical Engineering Yanshan UniversityQinhuangdao 066004China Key Lab of Measurement Technology&Instrumentation of Hebei Province Yanshan UniversityQinhuangdao 066004China Condensed Matter Science and Technology Institute Harbin Institute of TechnologyHarbin 150001China

Luminescence ratiometric thermometry based on rare earth(RE)ions has attracted great interest for the potential applications in many fields.But the improvement of the measurement sensitivity and accuracy is significantly restricted due to the small energy gap between thermally coupled levels(TCL).Here,a strategy striving for good thermometric properties of luminescent materials was designed by using the phosphors mixture composed of NaY(WO_(4))_(2):Nd^(3+)-Yb^(3+)and NaY(WO_(4))_(2):Er^(3+),which were prepared by secondary sintering method.Under the excitation of 980 nm lase r,the near-infrared(NIR)emissions(710-920 nm)from Nd^(3+)ions are effectively strengthened when the temperature increases from 304 to773 K,whereas Er^(3+)NIR luminescence centered at around 1536 nm is thermally quenched.The remarkably different response of NIR emissions to the thermal variation allows us to map temperature through the ratiometric method.By optimizing the dopant concentration of rare earth(RE)ions,a maximum sensitivity of 5.14%/K together with a measurement uncertainty of about 0.1 K is acquired at304 K,which is superior to the previously reported RE luminescence-based temperature sensors,indicating that the approach developed here can pave the way for achieving optical thermometry with desired properties.

关键词： NIR luminescence Thermometry NaY(WO_(4))_(2) Er^(3+)ions Nd3+ions Rare earths

Multistage Uncertain Random Linear Quadratic Optimal Control

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Journal of Systems Science & Complexity 2020年第6期33卷 1847-1872页

作者： CHEN xin zhu Yuanguo School of Science Nanjing University of Science and TechnologyNanjing 210094China

In this paper,linear quadratic(LQ)optimal control problems are investigated for two types of uncertain random systems which consider the coefficient of the perturbed term as a constant vector or a vector-valued function of state vector and control vector.First,the uncertain random optimal control model is established under expected value criterion.Second,based on Bellman’s principle,recurrence equations are presented for settling such problem.Then by applying the recurrence equations and chance theory,the analytical expressions of the optimal results for the LQ problems are derived.Furthermore,some examples and an application are given to show the effectiveness of our results.

关键词： Linear quadratic problem optimal control recurrence equations uncertain random system