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Control of fine particulate nitrate during severe winter haze in“2+26”cities

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Journal of Environmental Sciences 2024年第2期136卷 261-269页

作者： Chuang Qin Xiao Fu Tao wang Jian Gao Jiaqi wang Institute of Environment and Ecology Tsinghua Shenzhen International Graduate SchoolTsinghua UniversityShenzhen 518055China Department of Civil and Environmental Engineering Hong Kong Polytechnic UniversityHong Kong 99907China State Key Laboratory of Environmental Criteria and Risk Assessment Chinese Research Academy of Environmental SciencesBeijing 10084China

The“2+26”cities,suffering the most severe winter haze pollution,have been the key region for air quality improvement in China.Increasing prominent nitrate pollution is one of the most challenging environmental issues in this region,necessitating development of an effective control strategy.Herein,we use observations,and state-of-the-art model simulations with scenario analysis and process analysis to quantify the effectiveness of the future SO_(2)-NO_(X)-VOC-NH_(3) emission control on nitrate pollution mitigation in“2+26”cities.Focusing on a serious winter haze episode,we find that limited NO_(X)emission reduction alone in the short-term period is a less effective choice than VOC or NH_3emission reduction alone to decrease nitrate concentrations,due to the accelerated NO_(X)-HNO_(3)conversion by atmospheric oxidants and the enhanced HNO_(3)to NO_(3)^(-)partition by ammonia,although deep NO_(X)emission reduction is essential in the long-term period.The synergistic NH_(3) and VOC emission control is strongly recommended,which can counteract the adverse effects of nonlinear photochemistry and aerosol chemical feedback to decrease nitrate more.Such extra benefits will be reduced if the synergistic NH_(3) and VOC reduction is delayed,and thus reducing emission of multiple precursors is urgently required for the effective control of increasingly severe winter nitrate pollution in“2+26”cities.

关键词： Nitrate Winter haze pollution Emission reduction “2+26”cities

Modelling the formation and dissolution behavior of alumina agglomerate in the cryolite

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Particuology 2024年第3期86卷 211-222页

作者： Jiaqi wang Mao Li Benjun Cheng Hesong Li School of Energy Science and Engineering Central South UniversityChangsha410083China

The presence of alumina agglomerates seriously affects the current efficiency of the aluminum electrolysis process.Clarify the dynamic dissolution process of agglomerates is essential to improve the current efficiency of aluminum electrolysis.A mathematical model is proposed to describe the different phenomena from the formation until complete dissolution of agglomerates.Considering permeation and solidification processes of cryolite,a semi-analytical mathematical model is developed to formulate the formation,melting and dissolution processes of agglomerates,and the time duration for each stage is deduced.Porosity and heat mass transfer of agglomerates are explored based on the packing theory and mechanism of heat mass transfer in wet porous media.Dimensionless approach is applied to investigate the main factors affecting the dissolution stages and porosity of agglomerates.The results show that the superheat has a great influence on the formation and melting stage,the diameter of agglomerates can reach 14.93 mm for 200 particles agglomerated.The density decreases with the increase of agglomerated particle number,which varies in the range of 2.27-2.28 g/cm^(3).The average dissolution rate of agglomerates is about 1.83×10^(-5)-2.95×10^(-5) kg/s within the range of alumina concentration in this study.

关键词： Mathematical model Alumina agglomerate Porous media Packing theory Heatand mass transfer

Probabilistic movement primitive based motion learning for a lower limb exoskeleton with black-box optimization

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Frontiers of Information Technology & Electronic Engineering 2023年第1期24卷 104-116页

作者： Jiaqi wang Yongzhuo GAO Dongmei WU Wei DONG State Key Laboratory of Robotics and Systems Harbin Institute of TechnologyHarbin 150001China

As a wearable robot,an exoskeleton provides a direct transfer of mechanical power to assist or augment the wearer’s movement with an anthropomorphic configuration.When an exoskeleton is used to facilitate the wearer’s movement,a motion generation process often plays an important role in high-level control.One of the main challenges in this area is to generate in real time a reference trajectory that is parallel with human intention and can adapt to different situations.In this paper,we first describe a novel motion modeling method based on probabilistic movement primitive(ProMP)for a lower limb exoskeleton,which is a new and powerful representative tool for generating motion trajectories.To adapt the trajectory to different situations when the exoskeleton is used by different wearers,we propose a novel motion learning scheme based on black-box optimization(BBO)PIBB combined with ProMP.The motion model is first learned by ProMP offline,which can generate reference trajectories for use by exoskeleton controllers online.PIBB is adopted to learn and update the model for online trajectory generation,which provides the capability of adaptation of the system and eliminates the effects of uncertainties.Simulations and experiments involving six subjects using the lower limb exoskeleton HEXO demonstrate the effectiveness of the proposed methods.

关键词： Lower limb exoskeleton Human-robot interaction Motion learning Trajectory generation Movement primitive Black-box optimization

Using restored two-dimensional X-ray images to reconstruct the three-dimensional magnetopause

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Earth and Planetary Physics 2024年第1期8卷 133-154页

作者： RongCong wang Jiaqi wang DaLin Li TianRan Sun XiaoDong Peng YiHong Guo National Space Science Center Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing100049China Aerospace Information Research Institute Chinese Academy of SciencesBeijing 100094China

Astronomical imaging technologies are basic tools for the exploration of the universe,providing basic data for the research of astronomy and space physics.The Soft X-ray Imager(SXI)carried by the Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)aims to capture two-dimensional(2-D)images of the Earth’s magnetosheath by using soft X-ray imaging.However,the observed 2-D images are affected by many noise factors,destroying the contained information,which is not conducive to the subsequent reconstruction of the three-dimensional(3-D)structure of the magnetopause.The analysis of SXI-simulated observation images shows that such damage cannot be evaluated with traditional restoration models.This makes it difficult to establish the mapping relationship between SXIsimulated observation images and target images by using mathematical models.We propose an image restoration algorithm for SXIsimulated observation images that can recover large-scale structure information on the magnetosphere.The idea is to train a patch estimator by selecting noise–clean patch pairs with the same distribution through the Classification–Expectation Maximization algorithm to achieve the restoration estimation of the SXI-simulated observation image,whose mapping relationship with the target image is established by the patch estimator.The Classification–Expectation Maximization algorithm is used to select multiple patch clusters with the same distribution and then train different patch estimators so as to improve the accuracy of the estimator.Experimental results showed that our image restoration algorithm is superior to other classical image restoration algorithms in the SXI-simulated observation image restoration task,according to the peak signal-to-noise ratio and structural similarity.The restoration results of SXI-simulated observation images are used in the tangent fitting approach and the computed tomography approach toward magnetospheric reconstruction techniques,significantly improving the reconstruction results.Hence,the proposed te

关键词： Solar wind Magnetosphere Ionosphere Link Explorer(SMILE) soft X-ray imager magnetopause image restoration

Numerical simulation on magnetic confinement characteristics of internal vortex electrostatic cyclone precipitator under different working voltages

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Particuology 2023年第3期74卷 156-163页

作者： Jianping Zhang Jiaqi wang Peng Che Youqi wang Zhiyao Lu Zibing Qu School of Mechanical Engineering University of Shanghai for Science and TechnologyShanghaiChina College of Energy and Mechanical Engineering Shanghai University of Electric PowerShanghaiChina Sino-German College University of Shanghai for Science and TechnologyShanghaiChina

Aiming at improving the capture performance of internal vortex electrostatic cyclone precipitator(ECP),a theoretical model with mechanics-electric-magnetic coupling was established,the collection efficiency of magnetic confinement ECP under different working voltages was simulated,and the influence of magnetic flux intensity on the removal performance of submicron particles was explored.Results show that the number of particles escaped from the cyclone is greatly reduced after the introduction of magnetic field and electric field,indicating that charging effect and magnetic confinement are more conductive to trap submicron particles in the internal vortex ECP.The lower the working voltage is,the worse the charging lifting effect is,but the stronger the magnetic confinement characteristics are.Furthermore,the contributions of charging effect to collection efficiency and magnetic confinement characteristics are more obvious at a weaker magnetic flux density.The research results can provide a practical new idea for the innovative design of ECP.

关键词： Magnetic confinement characteristics Working voltage Internal vortex ECP Submicron particles Capture performance

Siamese transformer with hierarchical concept embedding for fine-grained image recognition

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Science China(Information Sciences) 2023年第3期66卷 188-203页

作者： Yilin LYU Liping JING Jiaqi wang Mingzhe GUO Xinyue wang Jian YU School of Computer and Information Technology Beijing Jiaotong University Beijing Key Lab of Traffic Data Analysis and Mining Beijing Jiaotong University Alibaba Group

Distinguishing the subtle differences among fine-grained images from subordinate concepts of a concept hierarchy is a challenging task. In this paper, we propose a Siamese transformer with hierarchical concept embedding(STr HCE), which contains two transformer subnetworks sharing all configurations,and each subnetwork is equipped with the hierarchical semantic information at different concept levels for fine-grained image embeddings. In particular, one subnetwork is for coarse-scale patches to learn the discriminative regions with the aid of the innate multi-head self-attention mechanism of the transformer. The other subnetwork is for finer-scale patches, which are adaptively sampled from the discriminative regions, to capture subtle yet discriminative visual cues and eliminate redundant information. STr HCE connects the two subnetworks through a score margin adjustor to enforce the most discriminative regions generating more confident predictions. Extensive experiments conducted on four commonly-used benchmark datasets, including CUB-200-2011, FGVC-Aircraft, Stanford Dogs, and NABirds, empirically demonstrate the superiority of the proposed STr HCE over state-of-the-art baselines.

关键词： fine-grained image recognition transformer hierarchical concept embedding adaptive sampling Siamese network

Temporal lobe epilepsy associated with human herpes virus 6

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Acta Epileptologica 2021年第1期3卷 71-76页

作者： Jiaqi wang Jinmei Li Department of Neurology West China HospitalSichuan UniversityChengdu 610041SichuanChina

Human herpes virus 6(HHV-6)is a ubiquitous and most common pathogen that affects humans.Human herpes virus 6B(HHV-6B)is a wide spread human herpesvirus that infects most people when they are children,establishes latent infections in the central nervous system(CNS),especially in the hippocampus and amygdala,and induces neurologic diseases.HHV-6 can establish a latent infection and be reactivated by various stimuli.Recently,viral genomic DNA of HHV-6B has been detected in surgically removed brain tissues of intractable epilepsy patients,suggesting the involvement of HHV-6B in the pathogenesis of epilepsy.Temporal lobe epilepsy(TLE)has been shown to be closely related with HHV-6B.TLE patients with HHV-6B in their brains suffer from reiterative attacks of febrile seizures and hippocampal sclerosis.However,the mechanisms underlying the contribution of this virus to the development of TLE remains unknown.The direct damage and immune activation caused by the virus are involved in the process of neuron damage,abnormal neural circuit formation and glial cell proliferation.In addition,some cytokines like interleukin-17A(IL-17A),nuclear factor-kappa B(NF-κb),transforming growth factor-β(TGF-β),mitogen-activated protein kinase(MAPK)and phospholipase A2 are up-regulated and involved in the pathological process of TLE.More studies are needed to clarify the mechanisms underlying the link between HHV-6B and epilepsy,and identify biomarkers to recognize different patient groups for anti-inflammatory or immunomodulatory therapies.

关键词： HHV-6 Epilepsy Mesial temporal lobe epilepsy Astrocytes Febrile seizures

Urea transport and hydrolysis in the rumen: A review

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Animal Nutrition 2021年第4期7卷 989-996页

作者： Samson Hailemariam Shengguo Zhao Yue He Jiaqi wang State Key Laboratory of Animal Nutrition Institute of Animal SciencesChinese Academy of Agricultural SciencesBeijing100193China Dilla University College of Agriculture and Natural ResourceDilla P.O.Box 419Ethiopia

Inefficient dietary nitrogen(N)conversion to microbial proteins,and the subsequent use by ruminants,is a major research focus across different fields.Excess bacterial ammonia(NH3)produced due to degradation or hydrolyses of N containing compounds,such as urea,leads to an inefficiency in a host’s ability to utilize nitrogen.Urea is a non-protein N containing compound used by ruminants as an ammonia source,obtained from feed and endogenous sources.It is hydrolyzed by ureases from rumen bacteria to produce NH_(3) which is used for microbial protein synthesis.However,lack of information exists regarding urea hydrolysis in ruminal bacteria,and how urea gets to hydrolysis sites.Therefore,this review describes research on sites of urea hydrolysis,urea transport routes towards these sites,the role and structure of urea transporters in rumen epithelium and bacteria,the composition of ruminal ureolytic bacteria,mechanisms behind urea hydrolysis by bacterial ureases,and factors influencing urea hydrolysis.This review explores the current knowledge on the structure and physiological role of urea transport and ureolytic bacteria,for the regulation of urea hydrolysis and recycling in ruminants.Lastly,underlying mechanisms of urea transportation in rumen bacteria and their physiological importance are currently unknown,and therefore future research should be directed to this subject.

关键词： Urea transporter Urea Urea hydrolysis Ruminal bacteria

Photodetection-induced relative timing jitter in synchronized time-lens source for coherent Raman scattering microscopy

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Journal of Innovative Optical Health Sciences 2017年第5期10卷 69-76页

作者： Jiaqi wang Ping Qiu Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province College of Optoelectronic Engineering Shenzhen University Shenzhen 518060 China College of Physics and Energy Shenzhen University Shenzhen 518060 China

Synchronized time lens source is a novel method to generate synchronized optical pulses to mode-locked lasers,and has found widespread applications in coberent Raman scattering microscopy.Relative timing jitter between the mode-locked laser and the synchronized time-lens source is a key parameter for evaluating the synchronization peformance of such synchronized laser sys-tems.However,the origins of the relative timing jitter in such systens are not fully determined,which in turn prevents the experimental efforts to optimize the synchronization perfornance.Here,we demonstrate,through theoretical modeling and mumerical simulation,that the photo-detction could be one physical origin of the relative timing jitter.Comparison with relative timing jitter due to the intrinsic timing jitter of the mode-locked laser is also demonstrated,revealing different qualitative and quantitative behavios.Based on the nature of this photo-detection-induced timing jitter,we further propose several strategies to reduce the relative timing jitter.Our thoretical results will provide guidelines for optimizing synchronization performance in experiments.

关键词： Synchronized time-lens source coherent Raman sca tering microscopy