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MAVEN observation of magnetosonic waves in the Martian magnetotail region

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Earth and Planetary Physics 2024年第2期8卷 317-325页

作者： ShangChun Teng JiCheng Sun JiaWei gao y.Harada Markus Fraenz DeSheng Han State Key Laboratory of Marine Geology School of Ocean and Earth ScienceTongji UniversityShanghai 200092China MNR Key Laboratory for Polar Science Polar Research Institute of ChinaShanghai 200136China Key Laboratory of Earth and Planetary Physics Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China Department of Geophysics Kyoto UniversityKyotoJapan Max-Planck-Institute for Solar System Research GoettingenGermany

Magnetosonic waves are an important medium for energy transfer in collisionless space plasma.Magnetosonic waves have been widely investigated in the upstream of the bow shock at Mars.These waves are believed to originate from pickup ions or reflected particles.By utilizing MAVEN spacecraft data,we have observed the occurrence of quasi-perpendicularly propagating magnetosonic emissions near the proton gyrofrequency in the Martian magnetotail region.These plasma waves are associated with a significant enhancement of proton and oxygen flux.The excited magnetosonic waves could possibly heat the protons through resonance and facilitate the ionospheric plasma escape.Our results could be helpful to better understand the Mars’magnetospheric dynamics and offer insights into possible energy redistribution between waves and plasma in the Martian nightside magnetosphere.

关键词： Martian magnetotail region magnetosonic waves proton escape

Weakly Supervised Object Localization with Background Suppression Erasing for Art Authentication and Copyright Protection

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Machine Intelligence Research 2024年第1期21卷 89-103页

作者： Chaojie Wu Mingyang Li ying gao Xinyan Xie Wing W.y.Ng Ahmad Musyafa School of Computer Science and Engineering South China University of TechnologyGuangzhou 511442China Guangdong Provincial Key Laboratory of Artificial Intelligence in Medical Image Analysis and Application Guangdong Provincial People's HospitalGuangzhou 510180China

The problem of art forgery and infringement is becoming increasingly prominent,since diverse self-media contents with all kinds of art pieces are released on the Internet every day.For art paintings,object detection and localization provide an efficient and ef-fective means of art authentication and copyright protection.However,the acquisition of a precise detector requires large amounts of ex-pensive pixel-level annotations.To alleviate this,we propose a novel weakly supervised object localization(WSOL)with background su-perposition erasing(BSE),which recognizes objects with inexpensive image-level labels.First,integrated adversarial erasing(IAE)for vanilla convolutional neural network(CNN)dropouts the most discriminative region by leveraging high-level semantic information.Second,a background suppression module(BSM)limits the activation area of the IAE to the object region through a self-guidance mechanism.Finally,in the inference phase,we utilize the refined importance map(RIM)of middle features to obtain class-agnostic loc-alization results.Extensive experiments are conducted on paintings,CUB-200-2011 and ILSVRC to validate the effectiveness of our BSE.

关键词： Weakly supervised object localization erasing method deep learning computer vision art authentication and copyright protection

Comparison Study of Constitutive Models for Overconsolidated Clays

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Acta Mechanica Solida Sinica 2020年第1期33卷 98-120页

作者： Z.Wan y.P.yao Z.W.gao Research Institute of Base and Foundation China Academy of Building ResearchBeijing 100013China School of Transportation Science and Engineering Beihang UniversityBeijing 100091China School of Engineering University of GlasgowGlasgow G128QQUK

Widely distributed in natural deposits,the overconsolidated(OC)clays have attracted extensive experimental investigations on their mechanical behaviors,especially in the 1960s and 1970s.Based on these results,numerous constitutive models have also been established.These models generally fall into two categories:one based on the classical plasticity theory and the other the bounding surface(BS)plasticity theory,with the latter being more popular and successful.The BS concept and the subloading surface(SS)concept are the two major BS plasticity theories.The features of these two concepts and the representative models based on them are introduced,respectively.The unified hardening(UH)model for OC clays is also based on the BS plasticity theory but distinguishes itself from other models by the integration of the reference yield surface,unified hardening parameter,potential failure stress ratio,arid transformed stress tensor.Modification is made to the Hvorslev envelop employed in the UH model to improve its capability of describing the behaviors of clays with extremely high overconsolidation ratio in this paper.The comparison among the BS model,SS model,and UH model is performed.Evidence shows that all these three models can characterize the fundamental behaviors of OC clays,such as the stress dilatancy,strain softening and attainment of the critical state.The UH model with the revised Hvorslev envelop has the fewest parameters which are identical to those of the modified Cam-Clay model.

关键词： Clay Overconsolidation Critical state Bounding surface Subloading surface Unified hardening model

不同蜜源植物蜂花粉游离和酯化三萜醇的成分研究

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不同蜜源植物蜂花粉游离和酯化三萜醇的成分研究

Utilizing Multilayer Design of Organic-Inorganic Hybrids to Enhance Wearable Strain Sensor in Humid Environment

作者： Xu X Gao Y 孙丽萍

蜂花粉含有丰富的三萜醇,并已被用作治疗良性前列腺增生症的植物药。游离和酯化的三萜醇用正己烷萃取,柱色谱法分离。采用气相色谱法-质谱/火焰离子化检测器（GC-MS/FID）对我国6种植物源蜂花粉中的三萜醇进行了综合分析。首次在蜂花粉...

蜂花粉含有丰富的三萜醇,并已被用作治疗良性前列腺增生症的植物药。游离和酯化的三萜醇用正己烷萃取,柱色谱法分离。采用气相色谱法-质谱/火焰离子化检测器（GC-MS/FID）对我国6种植物源蜂花粉中的三萜醇进行了综合分析。首次在蜂花粉中报道了6种4-去甲基甾醇、1种4-甲基甾醇、4种4-二甲基甾醇和3种三萜醇。不同植物源蜜蜂采集的花粉中游离和酯化三萜醇含量差异显著（p＜0.05）。研究发现,蜂花粉油馏分中总的三萜醇含量在2.6g/100 g和20.4 g/100 g之间变化。蜂花粉油中的三萜醇类以甾醇酯类为主（占67%）。目前,荷花蜂花粉油馏分中的酯化三萜醇主要由大量的环阿屯醇（11.2 g/100 g油）组成。

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Chinese Journal of Polymer Science 2023年第7期41卷 1037-1050页

作者： Chen-Chen Lu Wei-Chen gao Peng Li Wei Wu Robert K.y.Li Hui Zhao Guangxi Key Laboratory of Clean Pulp&Papermaking and Pollution Control School of Light Industry and Food EngineeringGuangxi UniversityNanning530004China Guangxi Key Laboratory of Calcium Carbonate Resources Comprehensive Utilization College of Materials and Chemical EngineeringHezhou UniversityHezhou542899China Department of Materials Science and Engineering City University of Hong KongTat Chee AvenueKowloonHong Kong999077China

Flexible strain wearable sensors have attracted considerable attention due to their advantages of low cost, lightweight, high sensitivity and good flexibility. However, the strain sensors are easy to be damaged in an extreme humidity environment or by the wearer’s sweat in the process of use, resulting in detection disorder or even a short circuit. Furthermore, preparation of sensors with stable properties under extreme environments is one of the most important research directions. To fill this gap, a flexible sensor was prepared by using polyurethane and carbon nanotubes, then modified by polydopamine and 1H,1H,2H,2H-perfluorodecane-mercaptan. A typical tunnel model was used to explain the working mechanism of the sensor, the sensitivity of the sensor is also explained and evaluated by the tunneling theory. The results show that the sensor has good sensitivity (the sensor has a stable sensing signal output under a strain range from 2% to 300%) and stability over 8500 cycles. At the same time, the sensor has good superhydrophobicity, the water contact angle reaches 152°, and it is still stable in a humid environment. Moreover, this sensor shows excellent performance in monitoring human joint motion (such as finger, elbow, wrist and knee) and physiological signals (such as speaking and drinking). This work provides an effective design method for the sensor which can be applied in a high humidity environment.

关键词： Wearable strain sensor Polyurethane Carbon nanotubes Superhydrophobicity

Rayleigh wave phase velocity tomography and strong earthquake activity on the southeastern front of the Tibetan Plateau

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Science China Earth Sciences 2014年第11期57卷 2532-2542页

作者： WANG Qiong Gao Yuan Institute of Earthquake Science China Earthquake Administration Institute of Geophysics China Earthquake Administration

To investigate the relationship between velocity structure and earthquake activity on the southeastern front of the Tibetan Plateau, we make use of continuous observations of seismic ambient noise data obtained at 55 broadband stations from the regional yunnan Seismic Network. These data are used to compute Rayleigh wave Green's Functions by cross-correlating between two stations, extracting phase velocity dispersion curves, and finally inverting to image Rayleigh wave phase velocity with periods between 5 and 34 s by ambient noise tomography. The results show significant lateral variations in crustal and uppermost mantle structures in the studied region. Phase velocity anomalies at short periods(5–12 s) are closely related to regional tectonic features such as sediment thickness and the depth of the crystalline basement. The Sichuan-yunnan rhombic block, enclosed by the Honghe, Xiaojiang and Jianchuan faults, emerges as a large range of low-velocity anomalies at periods of 16–26 s, that inverts to high-velocity anomalies at periods of 30–34 s. The phase velocity variation in the vicinity of the Sichuan-yunnan rhombic block suggests that the low-velocity anomaly area in the middle-lower crust may correspond to lower crustal channelized flow of the Tibetan Plateau. The spatial distribution of strong earthquakes since 1970 reveals that the yunnan region is inhomogeneous and shows prominent characteristics of block motion. However, earthquakes mostly occur in the upper crust, with the exception of the middle-yunnan block where earthquakes occur at the interface zone between high and low velocity as well as in the low-velocity zones, with magnitudes being generally less than 7. There are few earthquakes of magnitude 5 at the depths of 15–30 km, where gather earthquakes of magnitude 7 or higher ones which mainly occur in the interface zone between high and low velocities with others extending to the high-velocity abnormal zone.

关键词：速度层析成像地震活动青藏高原瑞利波川滇菱形块体速度异常中下地壳波相

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Multi-stage Sensitivity Analysis of Distributed Energy Systems: A Variance-based Sobol Method

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Journal of Modern Power Systems and Clean Energy 2020年第5期8卷 895-905页

作者： Shangshang Wei yiguo Li Xianhua gao Kwang y.Lee Li Sun Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education and Department of Energy and Environment Southeast UniversityNanjing 210096China IEEE Department of Electrical&Computer Engineering Baylor UniversityWacoTX 76798USA

In the face of the pressing environmental issues,the past decade witnessed the booming development of the distributed energy systems(DESs).A notable problem of DESs is the inevitable uncertainty that may make DESs deviate significantly from the deterministically obtained expectations,in both aspects of optimal design and economic operation.It thus necessitates the sensitivity analysis to quantify the impacts of the massive parametric uncertainties.This paper aims to give a comprehensive quantification,and carries out a multi-stage sensitivity analysis on DESs from the perspectives of evaluation criteria,optimal design and economic operation.First,a mathematical model of a DES is developed to present the solutions to the three stages of the DES.Second,the Monte-Carlo simulation is carried out subject to the probabilistic distributions of the energy,technical and economic parameters.Based on the simulation results,the variance-based Sobol method is applied to calculate the individual importance,interactional importance and total importance of various parameters.The comparison of the multi-stage results shows that only a few parameters play critical roles while the uncertainty of most of the massive parameters has little impact on the system performance.In addition,the influence of parameter interactions in the optimal design stage are much stronger than that in the evaluation criteria and operation strategy stages.

关键词： Sensitivity analysis uncertainty operation design optimization parameter characteristic distributed energy system(DES)

Four Late-type Galaxies with Double Radio Lobes and Properties of Such Galaxies

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Research in Astronomy and Astrophysics 2024年第4期24卷 84-90页

作者： Z.S.yuan X.y.gao Z.L.Wen J.L.Han National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China CAS Key Laboratory of FAST National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China School of Astronomy and Space Sciences University of Chinese Academy of SciencesBeijing 100049China

The triggering mechanism for radio lobes from late-type galaxies is not fully understood.More samples are desired for a thorough investigation and statistics.By utilizing the optical data from the newly released Dark Energy Spectroscopic Instrument imaging surveys and the radio sources from the NRAO VLA Sky Survey and the Faint Images of the Radio Sky at Twenty-centimeter,we identify four Late-type Galaxies with double Radio Lobes(La GRLs):J0217-3645,J0947+6220,J1412+3723 and J1736+5108.Including previously known La GRLs,we confirm the correlation between radio power P_(1.4GHz)and stellar mass M_(*)of host galaxies.Most(25/35)La GRLs belong to the blue cloud galaxies,while the newly identified cases in this work are located within the region of the red sequence.We find a clear correlation between the differential radio power,i.e.,the offset from the P_(1.4GHz)-M_(*)relation,and the galaxy color,indicating that bluer galaxies at a fixed M_(*)tend to host more powerful radio lobes.Furthermore,the majority(31/36)of La GRLs are either located in a galaxy group or displaying a disturbed morphology.We suggest that all of the galaxy mass,color and surrounding environment could play important roles in triggering radio lobes in late-type galaxies.

关键词： galaxies:active galaxies:jets galaxies:spiral radio continuum:galaxies

Tuning the microstructure for superb corrosion resistance in eutectic high entropy alloy

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Journal of Materials Science & Technology 2022年第14期109卷 197-208页

作者： S.Shuang Q.yua X.gao Q.F.He J.y.Zhang S.Q.Shi y.yang Department of Mechanical Engineering City University of Hong KongKowloon TongKowloonHong KongChina Department of Mechanical Engineering Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina Department of Materials Science and Engineering City University of Hong KongKowloon TongKowloonHong KongChina

In this work,we demonstrate that the corrosion resistance of the FeCrNiCoNb_(0.5) eutectic high entropy alloy(EHEA)can be tuned by controlling the size of its eutectic structure.Through microstructure refinement,the EHEA exhibits a superb corrosion resistance in 1 M NaCl in terms of a very low corrosion current density and an ultra-high transpassviation potential,which outperforms a variety of other HEAs and conventional metals and alloys.At the fundamental level,the microstructure refinement results in a rapid formation of a thick and compact passive film with less Cl-adsorption on the EHEA,which results in significant enhancement in its corrosion resistance.The outcome of our research provides important insights into the design of corrosion resistant chemically complex alloys.

关键词： Eutectic high entropy alloy Passivation Transpassivation potential Microstructure size