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Variable stars in the field of open cluster NGC 2126

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Research in Astronomy and Astrophysics 2009年第7期9卷 791-802页

作者： shun-fang liu Zhen-Yu Wu Xiao-Bin Zhang Jiang-Hua Wu Jun Ma Zhao-Ji Jiang Jian-Sheng Chen Xu Zhou National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

We report the results of a time-series CCD photometric survey of variable stars in the field of open cluster NGC 2126. In about a one square degree field covering the cluster, a total of 21 variable candidates are detected during this survey, of which 16 are newly found. The periods, classifications and spectral types of 14 newly discovered variables are discussed, which consist of six eclipsing binary systems, three pulsating variable stars, three long period variables, one RS CVn star, and one W UMa or δ Scuff star. In addition, there are two variable candidates, the properties of which cannot be determined. By a method based on fitting observed spectral energy distributions of stars with theoretical ones, the membership probabilities and the fundamental parameters of this cluster are determined. As a result, five variables are probably members of NGC 2126. The fundamental parameters of this cluster are determined as： metallicity to be 0.008 Z, age log（t） = 8.95, distance modulus （m - M）0 = 10.34 and reddening value E（B - V） = 0.55 mag.

关键词： open clusters: individual (NGC 2126) - stars: variables (general) - bina- ties: general

Efficient electroreduction of nitrate via enriched active phases on copper-cobalt oxides

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Chinese Chemical Letters 2024年第4期35卷 204-209页

作者： Ling fang Sha Wang shun Lu Fengjun Yin Yujie Dai Lin Chang Hong liu Chongqing Institute of Green and Intelligent Technology Chinese Academy of SciencesChongqing 400714China University of Chinese Academy of Sciences Beijing 100049China

Electrochemical conversion of nitrate(NO_(3)~-) to ammonia(NH_(3)) can target two birds with one stone well, in NO_(3)^(-)-containing sewage remediation and sustainable NH_(3) production. However, single metalbased catalysts are difficult to drive high-efficient NO_(3)~- removal due to the multi-electron transfer ***, we present a tandem catalyst with simple structure, Cu-Co binary metal oxides(Cu-Co-O), by engineering intermediate phases as catalytic active species for NO_(3)~- conversion. Electrochemical evaluation,X-ray photoelectron spectroscopy, and in situ Raman spectra together suggest that the newly-generated Cu-based phases was prone to NO_(3)~- to NO_(2)~- conversion, then NO_(2)~- was reduced to NH_(3) on Co-based species. At an applied potential of -1.1 V vs. saturated calomel electrode, the Cu-Co-O catalyst achieved NO_(3)~- -N removal of 90% and NH_(3) faradaic efficiency of 81% for 120 min in 100 m L of 50 mg/L NO_(3)~- -N,consuming only 0.69 k Wh/mol in a two-electrode system. This study provides a facile and efficient engineering strategy for developing high-performance catalysts for electrocatalytic nitrate conversion.

关键词： NO_(3)^(-)-containing sewage remediation Electrocatalytic reduction Copper-cobalt oxides Tandem reactivity Enriched active phases

Recent advances in morphology control of platinum catalysts toward oxygen reduction reaction

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Frontiers in Energy 2024年第3期18卷 330-355页

作者： shun CHEN Yanru liu Xiaogang FU Wanglei WANG State Key Laboratory of Solidification Processing Atomic Control and Catalysis Engineering LaboratorySchool of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi’an 710072China State Key Laboratory of Oral and Maxillofacial Reconstruction and Regeneration National Clinical Research Center for Oral DiseasesShaanxi Key Laboratory of StomatologyDepartment of Dental MaterialsSchool of StomatologyThe Fourth Military Medical UniversityXi’an 710032China

Exploring advanced platinum (Pt)-based electrocatalysts is vital for the widespread implementation of proton exchange membrane fuel cells (PEMFCs). Morphology control represents an effective strategy to optimize the behavior of Pt catalysts. In this work, an attempt is made to comprehensively review the effect of morphology control on the catalytic behavior of catalysts in the oxygen reduction reaction (ORR). First, the fundamental physicochemical changes behind morphology control, including exposing more active sites, generating appropriate lattice strains, and forming different crystalline surfaces, are highlighted. Then, recently developed strategies for tuning the morphologies of electrocatalysts, including core-shell structures, hollow structures, nanocages, nanowires, and nanosheets, are comprehensively summarized. Finally, an outlook on the future development of morphology control of Pt catalysts is presented, including rational design strategies, advanced in situ characterization techniques, novel artificial intelligence, and mechanical learning. This work is intended to provide valuable insights into designing the morphology and technological innovation of efficient redox electrocatalysts in fuel cells.

关键词： morphology platinum catalysts electrocatalysis ORR PEMFC

Multiwavelength study of nearly face-on low surface brightness disk galaxies

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Research in Astronomy and Astrophysics 2010年第12期10卷 1223-1241页

作者： Dong Gao Yan-Chun Liang shun-fang liu Guo-Hu Zhong Xiao-Yan Chen Yan-Bin Yang Francois Hammer Guo-Chao Yang Li-Cai Deng Jing-Yao Hu National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China ycliang @ nao. cas. cn dgao @ nao. cas. cn Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China Graduate University of Chinese Academy of Sciences Beijing 100049 China GEPI Observatoire de Paris-Meudon 92195 Meudon France Department of Physics Hebei Normal University Shijiazhuang 050016 China

We study the ages of a large sample （1802） of nearly face-on disk low surface brightness galaxies （LSBGs） using the evolutionary population synthesis （EPS） model PEGASE with an exponentially decreasing star formation rate to fit their mul- tiwavelength spectral energy distributions （SEDs） from far-ultraviolet （FUV） to nearinfrared （NIR）. The derived ages of LSBGs are 1-5 Gyr for most of the sample no matter if constant or varying dust extinction is adopted, which are similar to most of the previous studies on smaller samples. This means that these LSBGs formed the majority of their stars quite recently. However, a small part of the sample （~2%-3%） has larger ages of 5-8 Gyr, meaning their major star forming process may have occurred earlier. At the same time, a large sample （5886） of high surface brightness galaxies （HSBGs） are selected and studied using the same method for comparisons. The de- rived ages are 1-5 Gyr for most of the sample （97%） as well. These results probably mean that these LSBGs have not much different star formation histories from their HSBGs counterparts. However, we should notice that the HSBGs are generally about 0.2 Gyr younger, which could mean that the HSBGs may have undergone more recent star forming activities than the LSBGs.

关键词： galaxies: evolution -- galaxies: formation -- galaxies: photometry --galaxies: spiral -- galaxies: statistics -- ultraviolet: galaxies

Removal of Cr(Ⅵ)by glutaraldehyde-crosslinked chitosan encapsulating microscale zero-valent iron:Synthesis,mechanism,and longevity

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Journal of Environmental Sciences 2024年第8期142卷 115-128页

作者： Yijun Duan fang liu Xiang liu Miao Li School of Environment Tsinghua UniversityBeijing 100084China Transportation Institute of Inner Mongolia University Hohhot 010070China

Microscale zero-valent iron(mZVI)has shown great potential for groundwater Cr(Ⅵ)***,low Cr(Ⅵ)removal capacity caused by passivation restricted the wide use of *** prepared mZVI/GCS by encapsulating mZVI in a porous glutaraldehydecrosslinked chitosan matrix,and the formation of the passivation layer was alleviated by reducing the contact between zero-valent iron *** average pore diameter of mZVI/GCS was 8.775 nm,which confirmed the mesoporous characteristic of this *** of batch experiments demonstrated that mZVI/GCS exhibited high Cr(Ⅵ)removal efficiency in a wide range of pH(2-10)and temperature(5-35℃).Common groundwater coexisting ions slightly affected m ZVI/*** material showed great reusability,and the average Cr(Ⅵ)removal efficiency was 90.41%during eight *** this study,we also conducted kinetics and isotherms ***-second-order model was the most matched kinetics *** Cr(Ⅵ)adsorption process was fitted by both Langmuir and Freundlich isotherms models,and the maximum Langmuir adsorption capacity of m ZVI/GCS reached243.63 mg/g,which is higher than the adsorption capacities of materials reported in most of the previous ***,the column capacity for Cr(Ⅵ)removal of a mZVI/GCS-packed column was 6.4 times higher than that of a mZVI-packed column in a 50-day ***,mZVI/GCS with a porous structure effectively relieved passivation problems of mZVI and showed practical application prospects as groundwater Cr(Ⅵ)remediation material with practical application prospects.

关键词： Chitosan Glutaraldehyde mZVI Cr(Ⅵ) Groundwater

Skill enhancement learning with knowledge distillation

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Science China(Information Sciences) 2024年第8期67卷 206-220页

作者： Naijun liu Fuchun SUN Bin fang Huaping liu Department of Computer Science and Technology Tsinghua University

Skill learning through reinforcement learning has significantly progressed in recent years. However, it often struggles to efficiently find optimal or near-optimal policies due to the inherent trial-and-error exploration in reinforcement learning. Although algorithms have been proposed to enhance skill learning efficacy, there is still much room for improvement in terms of skill learning performance and training stability. In this paper, we propose an algorithm called skill enhancement learning with knowledge distillation(SELKD), which integrates multiple actors and multiple critics for skill learning. SELKD employs knowledge distillation to establish a mutual learning mechanism among actors. To mitigate critic overestimation bias,we introduce a novel target value calculation method. We also perform theoretical analysis to ensure the convergence of SELKD. Finally, experiments are conducted on several continuous control tasks, illustrating the effectiveness of the proposed algorithm.

关键词： skill learning enhancement learning reinforcement learning knowledge distillation

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Fluorescence analysis of antibiotics and antibiotic-resistance genes in the environment: A mini review

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Chinese Chemical Letters 2024年第10期35卷 108-117页

作者： Yuxin Li Chengbin liu Qiuju Li shun Mao College of Environmental Science and Engineering State Key Laboratory of Pollution Control and Resource Reuse Tongji University Institute for Agri-food Standards and Testing Technology Shanghai Academy of Agricultural Sciences

Antibiotics, as widely used antibacterial drug, exist in various environmental media. Antibiotic residues can affect biological metabolism and lead to bacterial resistance and the formation of antibiotic-resistance genes, posing a threat to human health and ecological safety. Establishing efficient detection methods for antibiotics and antibiotic-resistance genes has great environmental significance. Fluorescence detection methods, due to their fast response, high sensitivity and specificity, and low-cost, are widely used in chemical and biological sensing. This review first summarizes the pre-treatment methods for different types of environmental samples, and then focuses on the recent advances of fluorescence methods for the detection of antibiotics and antibiotic-resistance genes. Finally, main challenges and future research directions of fluorescence methods for antibiotic and antibiotic-resistance genes detection are *** review highlights the promising prospect of fluorescence methods in-situ detection and monitoring of antibiotics and antibiotic-resistance genes, and provides guidance for the construction of overall risk assessment system of environmental media.

关键词： Antibiotic-resistance genes Antibiotics Environmental samples Fluorescence detection In-situ detection

Exploring battery material failure mechanisms through synchrotron X-ray characterization techniques

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Journal of Energy Chemistry 2024年第7期94卷 128-135页

作者： Lingzhe fang Xiaozhao liu Tao Li Department of Chemistry and Biochemistry Northern Illinois UniversityDeKalbIL 60115USA X-ray Science Division and Joint Center forEnergy Storage Research Argonne National LaboratoryLemontIL6439UA

Rechargeable battery cycling performance and related safety have been persistent *** is crucial to decipher the capacity fading induced by electrode material failure via a range of *** these,synchrotron-based X-ray techniques with high flux and brightness play a key role in understanding degradation *** this comprehensive review,we summarize recent advancements in degra-dation modes and mechanisms that were revealed by synchrotron X-ray ***,an overview of X-ray absorption spectroscopy and X-ray scattering techniques is introduced for charac-terizing failure phenomena at local coordination atomic environment and long-range order crystal struc-ture scale,*** last,we envision the future of exploring material failure mechanism.

关键词： Battery failure Synchrotron-based techniques X-ray scattering X-ray absorption spectroscopy

Modelling analysis embodies drastic transition among global potential natural vegetations in face of changing climate

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Forest Ecosystems 2024年第2期11卷 184-192页

作者： Zhengchao Ren Lei liu fang Yin Xiaoni liu School of Earth Science and Resources Chang’an UniversityXi’an710054China Research Center of Ecological Construction and Environmental Conservation in Gansu Province Gansu Agricultural UniversityLanzhou730070China State Key Laboratory of Tibetan Plateau Earth System Environment and Resources(TPESER)Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing100101China School of Land Engineering Chang’an UniversityXi’an710054China College of Pratacultural Science Gansu Agricultural UniversityLanzhou730070China

Potential natural vegetation(PNV)is a valuable reference for ecosystem renovation and has garnered increasing attention ***,there is limited knowledge on the spatio-temporal distributions,transitional processes,and underlying mechanisms of global natural vegetation,particularly in the case of ongoing climate *** this study,we visualize the spatio-temporal pattern and inter-transition procedure of global PNV,analyse the shifting distances and directions of global PNV under the influence of climatic disturbance,and explore the mechanisms of global PNV in response to temperature and precipitation *** achieve this,we utilize meteorological data,mainly temperature and precipitation,from six phases:the Last Inter-Glacial(LIG),the Last Glacial Maximum(LGM),the Mid Holocene(MH),the Present Day(PD),2030(20212040)and 2090(2081–2100),and employ a widely-accepted comprehensive and sequential classification sy–stem(CSCS)for global PNV *** find that the spatial patterns of five PNV groups(forest,shrubland,savanna,grassland and tundra)generally align with their respective ecotopes,although their distributions have shifted due to fluctuating temperature and ***,we observe an unexpected transition between tundra and savanna despite their geographical *** shifts in distance and direction of five PNV groups are mainly driven by temperature and precipitation,although there is heterogeneity among these shifts for each ***,the heterogeneity observed among different global PNV groups suggests that they may possess varying capacities to adjust to and withstand the impacts of changing *** spatio-temporal distributions,mutual transitions and shift tendencies of global PNV and its underlying mechanism in face of changing climate,as revealed in this study,can significantly contribute to the development of strategies for mitigating warming and promoting re-vegetation in degraded regions worldwide.

关键词： Potential natural vegetation Global warming Vegetation classification Predicted model CSCS