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Study on Robot Grasping System of SSVEP-BCI Based on Augmented Reality Stimulus

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Tsinghua Science and Technology 2023年第2期28卷 322-329页

作者： Shangen Zhang Yuanfang chen Lijian Zhang Xiaorong Gao xiaogang chen School of Computer and Communication Engineering University of Science and Technology BeijingBeijing 100083China Beijing Institute of Mechanical Equipment Beijing 100854China Department of Biomedical Engineering School of MedicineTsinghua UniversityBeijing100084China Institute of Biomedical Engineering Chinese Academy of Medical Sciences and Peking Union Medical CollegeTianjin 300192China

Although notable progress has been made in the study of Steady-State Visual Evoked Potential(SSVEP)-based Brain-Computer Interface(BCI),several factors that limit the practical applications of BCIs still exist.One of these factors is the importability of the stimulator.In this study,Augmented Reality(AR)technology was introduced to present the visual stimuli of SSVEP-BCI,while the robot grasping experiment was designed to verify the applicability of the AR-BCI system.The offline experiment was designed to determine the best stimulus time,while the online experiment was used to complete the robot grasping task.The offline experiment revealed that better information transfer rate performance could be achieved when the stimulation time is 2 s.Results of the online experiment indicate that all 12 subjects could control the robot to complete the robot grasping task,which indicates the applicability of the AR-SSVEP-humanoid robot(NAO)system.This study verified the reliability of the AR-BCI system and indicated the applicability of the AR-SSVEP-NAO system in robot grasping tasks.

关键词： Steady-State Visual Evoked Potential(SSVEP) Brain-Computer Interface(BCI) Augmented Reality(AR) robot grasping system

Improving Operational Flexibility of Integrated Energy Systems Through Operating Conditions Optimization of CHP Units

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CSEE Journal of Power and Energy Systems 2023年第5期9卷 1854-1865页

作者： Shixing Ding Wei Gu Shuai Lu xiaogang chen Ruizhi Yu the School of Cyber Science and Engineering Southeast UniversityNanjing 210096China the School of Electrical Engineering Southeast UniversityNanjing 210096China Zhejiang Electric Power Corporation Hangzhou 310000China

As a type of energy system with bright application prospects,the integrated energy system(IES)is environmentally friendly and can improve overall energy efficiency.Tight coupling between heat and electricity outputs of combined heat and power(CHP)units limits IES operational flexibility significantly.To resolve this problem,in this paper,we integrate operating mode optimization of the natural gas combined cycle CHP unit(NGCC-CHP)into dispatch of the IES to improve flexibility of the IES.First,we analyze operational modes of the CHP units from the perspectives of thermal processes and physical mechanisms,including the adjustable extraction mode,backpressure mode,and switching mode.Next,we propose an explicit mathematical model for full-mode operation of the CHP units,in which the heat-electricity feasible region,switching constraints,and switching costs are all formulated in detail.Finally,a novel economic dispatch model is proposed for a heat and electricity IES,which uses the full-mode operation of CHP units to improve operational flexibility.The Fortuny-Amat transformation is used to convert the economic dispatch model into a mixed-integer quadratic programming model,which can then be solved using commercial solvers.Case studies demonstrate the proposed method can reduce operational costs and obviously promotes wind power utilization.

关键词： Adjustable extraction mode back pressure mode combined heat and power economic dispatch full-mode operations integrated energy system operational flexibility

Characterization of dissolved organic matter in submarine groundwater from a salt marsh in Chongming Island,China

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Journal of Oceanology and Limnology 2022年第1期40卷 128-141页

作者： Tangrong HE Fenfen ZHANG Yali WANG xiaogang chen Jinzhou DU State Key Laboratory of Estuarine and Coastal Research East China Normal UniversityShanghai 200241China Institute of Eco-Chongming(IEC) Shanghai 202162China Key Laboratory of Coastal Environment and Resources of Zhejiang Province School of EngineeringWestlake UniversityHangzhou 310024China

Salt marshes are research hotspots of the carbon cycle in coastal zones because large amounts of atmospheric carbon dioxide is fi xed by salt marshes vegetation and stored in its biomass and soil.Dissolved organic carbon(DOC)in submarine groundwater(well water and pore water)in salt marshes plays an important role in advective exchange between the salt marshes and coastal waters.However,the molecular characteristics of DOC in salt marsh groundwater are poorly understood because of the complex DOC structures and hydrodynamic process.In this study,fl uorescent components and refractory DOC(RDOC)in submarine groundwater from a salt marsh(Chongming Island,China)and adjacent coastal water were characterized by fl uorescence spectroscopy and nuclear magnetic resonance spectroscopy.The fl uorescent components identifi ed by parallel factor analysis indicated that humic-like substances dominated the chromophoric dissolved organic matter in the submarine groundwater.The chromophoric dissolved organic matter and dissolved organic matter in the submarine groundwater had non-conservative behaviors because of additions from terrestrial humic substances.The nuclear magnetic resonance spectra indicated that bioactive substances(carbohydrates)contributed only 13.2%-14.8%of the dissolved organic matter in the submarine groundwater but carboxyl-rich alicyclic molecules(CRAMs),the main components of RDOC,contributed 64.5%of the dissolved organic matter.Carbohydrates and CRAMs contributed 16.4%and 61.7%of the dissolved organic matter in the coastal water,similar to the contributions for submarine groundwater.The DOC concentration in submarine groundwater was 386±294μmol/L,which was signifi cantly higher than that in coastal water(91±19μmol/L).The high DOC concentrations and>60%relative RDOC content suggested that submarine groundwater may be an important source of RDOC to coastal seawater.This information will be helpful for estimating the climate eff ects of salt marsh blue carbon.

关键词： submarine groundwater dissolved organic carbon fl uorescence refractory dissolved organic carbon salt marsh Chongming Island

Linking bacterial and archaeal community dynamics to related hydrological,geochemical and environmental characteristics between surface water and groundwater in a karstic estuary

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海洋学报:英文版 2023年第8期42卷 158-170页

作者： xiaogang chen Qi Ye Jinzhou Du Neven Cukrov Nuša Cukrov Yan Zhang Ling Li Jing Zhang State Key Laboratory of Estuarine and Coastal Research East China Normal UniversityShanghai 200241China Key Laboratory of Coastal Environment and Resources of Zhejiang Province School of EngineeringWestlake UniversityHangzhou 310024China Division for Marine and Environmental Research Ruđer BoškovićInstituteZagreb 10000Croatia

Subterranean estuaries(STEs)are characterized by the mixing of terrestrial fresh groundwater and seawater in coastal aquifers.Although microorganisms are important components of coastal groundwater ecosystems and play critical roles in biogeochemical transformations in STEs,limited information is available about how their community dynamics interact with hydrological,geochemical and environmental characteristics in STEs.Here,we studied bacterial and archaeal diversities and distributions with 16S rRNA-based Illumina MiSeq sequencing technology between surface water and groundwater in a karstic STE.Principal-coordinate analysis found that the bacterial and archaeal communities in the areas where algal blooms occurred were significantly separated from those in other stations without algal bloom occurrence.Canonical correspondence analysis showed that nutrients and salinity can explain the patterns of bacterial and archaeal community dynamics.The results suggest that hydrological,geochemical and environmental characteristics between surface water and groundwater likely control the bacterial and archaeal diversities and distributions in STEs.Furthermore,we found that some key species can utilize terrestrial pollutants such as nitrate and ammonia in STEs,indicating that these species(e.g.,Nitrosopumilus maritimus,Limnohabitans parvus and Simplicispira limi)may be excellent candidates for in situ degradation/remediation of coastal groundwater contaminations concerned with the nitrate and ammonia.Overall,this study reveals the coupling relationship between the microbial communities and hydrochemical environments in STEs,and provides a perspective of in situ degradation/remediation for coastal groundwater quality management.

关键词： submarine groundwater discharge surface water and groundwater interaction algal bloom microbial ecology nutrient biogeochemistry ammonia-oxidizing archaea nitrate-utilizing bacteria Krka River Estuary

Seasonal metal fluxes derived by the interaction of surface water and groundwater in an aquaculture estuary

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海洋学报:英文版 2023年第8期42卷 113-124页

作者： Xiaoxiong Wang Jordi Garcia-Orellana xiaogang chen Jianan Liu Fenfen Zhang Jianguo Qu Zhuoyi Zhu Jinzhou Du State Key Laboratory of Estuarine and Coastal Research East China Normal UniversityShanghai 200062China ICTA-UAB Institut de Ciència i Tecnologia AmbientalsUniversitat Autònoma de BarcelonaBarcelona E-08193Spain Departament de Física Universitat Autònoma de BarcelonaBarcelona E-08193Spain Key Laboratory of Coastal Environment and Resources of Zhejiang Province School of EngineeringWestlake UniversityHangzhou 310024China School of Oceanography Shanghai Jiao Tong UniversityShanghai 200030China

Submarine groundwater discharge(SGD)plays a major role as a conveyor of metals to coastal waters.However,the seasonal change of metal fluxes derived through SGD is unclear.Here,we evaluated the behaviours and fluxes of trace metals(Mn,Fe,Ba,Pb,U,Cr,Zn,Cu)in an estuary under different seasonal conditions.The behaviours of trace metals revealed that SGD was the source of Mn(3.51 mmol/(m^(2)·d)),Fe(0.174 mmol/(m^(2)·d))and Ba(0.024 mmol/(m^(2)·d)),but the Cu sink(−0.55μmol/(m^(2)·d))and other metals exhibited a seasonal source‒sink conversion.The seasonal variation of dissolved organic matter and the fresh groundwater proportion in subterranean estuaries may have an important effect on metals fluxes especially for the Fe,Mn and Ba.Our result shows that the single seasonal metal fluxes estimation applied to the annual scale will cause a large deviation,up to 3.6 times for Fe,5.5 times for Mn,and 15 times for Ba.Therefore,the influence of seasonal fluctuations on SGDderived metal fluxes cannot be ignored,and our findings will be important for comprehending the metal budget and cycle in nearshore environment.

关键词： subterranean estuary seawater intrusion heavy metals seasonal changes coastal management

Effect of background luminance of visual stimulus on elicited steady-state visual evoked potentials

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Brain Science Advances 2022年第1期8卷 50-56页

作者： Shangen Zhang xiaogang chen School of Computer and Communication Engineering University of Science and Technology BeijingBeijing 100083China Institute of Biomedical Engineering Chinese Academy of Medical Sciences and Peking Union Medical CollegeTianjin 300192China

Steady-state visual evoked potential(SSVEP)-based brain-computer interfaces(BCIs)have been widely studied.Considerable progress has been made in the aspects of stimulus coding,electroencephalogram processing,and recognition algorithms to enhance system performance.The properties of SSVEP have been demonstrated to be highly sensitive to stimulus luminance.However,thus far,there have been very few reports on the impact of background luminance on the system performance of SSVEP-based BCIs.This study investigated the impact of stimulus background luminance on SSVEPs.Specifically,this study compared two types of background luminance,i.e.,(1)black luminance[red,green,blue(rgb):(0,0,0)]and(2)gray luminance[rgb:(128,128,128)],and determined their effect on the classification performance of SSVEPs at the stimulus frequencies of 9,11,13,and 15 Hz.The offline results from nine healthy subjects showed that compared with the gray background luminance,the black background luminance induced larger SSVEP amplitude and larger signal-to-noise ratio,resulting in a better classification accuracy.These results suggest that the background luminance of visual stimulus has a considerable effect on the SSVEP and therefore has a potential to improve the BCI performance.

关键词： steady-state visual evoked potential background lumimance visual stimulus brain-computer interface signal-to-noise ratio

A Numerical Study on the Propagation Mechanisms of Hydraulic Fractures in Fracture-Cavity Carbonate Reservoirs

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Computer Modeling in Engineering & Sciences 2021年第5期127卷 575-598页

作者： Fang Shi Daobing Wang xiaogang chen Jiangsu Key Laboratory of Advanced Manufacturing Technology Huaiyin Institute of TechnologyHuai’an223003China School of Mechanical Engineering Beijing Key Laboratory of Pipeline Critical Technology and Equipment for Deepwater Oil&Gas DevelopmentBeijing Institute of Petrochemical TechnologyBeijing102617China

Field data suggests that carbonate reservoirs contain abundant natural fractures and cavities.The propagation mechanisms of hydraulic fractures in fracture-cavity reservoirs are different from conventional reservoirs on account of the stress concentration surrounding cavities.In this paper,we develop a fully coupled numerical model using the extended finite element method(XFEM)to investigate the behaviors and propagation mechanisms of hydraulic fractures in fracture-cavity reservoirs.Simulation results show that a higher lateral stress coefficient can enhance the influence of the natural cavity,causing a more curved fracture path.However,lower confining stress or smaller in-situ stress difference can reduce this influence,and thus contributes to the penetration of the hydraulic fracture towards the cavity.Higher fluid viscosity and high fluid pumping rate are both able to attenuate the effect of the cavity.The frictional natural fracture connected to the cavity can significantly change the stress distribution around the cavity,thus dramatically deviates the hydraulic fracture from its original propagation direction.It is also found that the natural cavity existing between two adjacent fracturing stages will significantly influence the stress distribution between fractures and is more likely to result in irregular propagation paths compared to the case without a cavity.

关键词： Hydraulic fracturing fracture-cavity reservoir crack propagation XFEM

Cross-Target Transfer Algorithm Based on the Volterra Model of SSVEP-BCI

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Tsinghua Science and Technology 2021年第4期26卷 505-522页

作者： Jiajun Lin Liyan Liang Xu Han chen Yang xiaogang chen Xiaorong Gao Department of Biomedical Engineering School of MedicineTsinghua UniversityBeijing 100084China School of Electronic Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China Institute of Biomedical Engineering Chinese Academy of Medical Sciences and Peking Union Medical CollegeTianjin 300192China

In general, a large amount of training data can effectively improve the classification performance of the Steady-State Visually Evoked Potential(SSVEP)-based Brain-Computer Interface(BCI) system. However, it will prolong the training time and considerably restrict the practicality of the system. This study proposed a SSVEP nonlinear signal model based on the Volterra filter, which could reconstruct stable reference signals using relatively small number of training targets by transfer learning, thereby reducing the training cost of SSVEP-BCI. Moreover,this study designed a transfer-extended Canonical Correlation Analysis(t-eCCA) method based on the model to achieve cross-target transfer. As a result, in a single-target SSVEP experiment with 16 stimulus frequencies,t-eCCA obtained an average accuracy of 86.96%˙12.87% across 12 subjects using only half of the calibration time,which exhibited no significant difference from the representative training classification algorithms, namely, extended canonical correlation analysis(88.32%±13.97%) and task-related component analysis(88.92%±14.44%), and was significantly higher than that of the classic non-training algorithms, namely, Canonical Correlation Analysis(CCA) as well as filter-bank CCA. Results showed that the proposed cross-target transfer algorithm t-eCCA could fully utilize the information about the targets and its stimulus frequencies and effectively reduce the training time of SSVEP-BCI.

关键词： Steady-State Visual y Evoked Potential(SSVEP) Brain-Computer Interface(BCI) Volterra filter cross-target information transfer learning

Porewater-derived dissolved inorganic carbon and nutrient fluxes in a saltmarsh of the Changjiang River Estuary

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Acta Oceanologica Sinica 2021年第8期40卷 32-43页

作者： xiaogang chen Jinzhou Du Xueqing Yu Xiaoxiong Wang State Key Laboratory of Estuarine and Coastal Research East China Normal UniversityShanghai 200241China Key Laboratory of Coastal Environment and Resources of Zhejiang Province School of EngineeringWestlake UniversityHangzhou 310024China Institute of Advanced Technology Westlake Institute for Advanced StudyHangzhou 310024China Institute of Eco-Chongming(IEC) Shanghai 202162China

Saltmarshes are one of the most productive ecosystems,which contribute significantly to coastal nutrient and carbon budgets.However,limited information is available on soil nutrient and carbon losses via porewater exchange in saltmarshes.Here,porewater exchange and associated fluxes of nutrients and dissolved inorganic carbon(DIC)in the largest saltmarsh wetland(Chongming Dongtan)in the Changjiang River Estuary were quantified.Porewater exchange rate was estimated to be(37±35)cm/d during December 2017 using a radon(^(222)Rn)mass balance model.The porewater exchange delivered 67 mmol/(m^(2)·d),38 mmol/(m^(2)·d)and 2690 mmol/(m^(2)·d)of dissolved inorganic nitrogen(DIN),dissolved silicon(DSi)and DIC into the coastal waters,respectively.The dominant species of porewater DIN was NH_(4)^(+)(>99%of DIN).However,different with those in other ecosystems,the dissolved inorganic phosphorus(DIP)concentration in saltmarsh porewater was significantly lower than that in surface water,indicating that saltmarshes seem to be a DIP sink in Chongming Dongtan.The porewater-derived DIN,DSi and DIC accounted for 12%,5%and 18%of the riverine inputs,which are important components of coastal nutrient and carbon budgets.Furthermore,porewater-drived nutrients had obviously high N/P ratios(160–3995),indicating that the porewater exchange process may change the nutrient characteristics of the Changjiang River Estuary and further alter the coastal ecological environment.

关键词： porewater exchange coastal wetlands saltwater intrusion nitrogen cycle blue carbon Changjiang River Estuary