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Long-term surface water changes and driving cause in Xiong'an,China:from dense Landsat time series images and synthetic analysis

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Science Bulletin 2018年第11期63卷 708-716页

作者： Chunqiao Song Linghong ke Hang pan Shengan Zhan Kai Liu Ronghua Ma key Laboratory of Watershed Geographic Sciences Nanjing Institute of Geography and LimnologyChinese Academy of SciencesNanjing 210008China Department of Geography University of CaliforniaLos AngelesLos AngelesCA 90095United States School of Earth Sciences and Engineering Hohai UniversityNanjing 211100China Department of Geographic Information Science Nanjing UniversityNanjing 210023China

China＇s government statement recently reported the plan of constructing Xiong＇an New Area, which aims to phase out some extra capital functions from Beijing and to explore an innovative urban development mode with the priority in eco-environmental protection. The New Area is located in the semi-arid North China Plain （NCP） and is home to NCP＇s largest natural freshwater wetland, Baiyangdian Lake. A comprehensive realization of surface water dynamics would be crucial for policy-makers to outline a sustainable environment development strategy for New Area. In this study, we used a total of 245 time slices of cloud-free Landsat images to document the continuous changes of water bodies within Xiong＇an City dur- ing 1984-2016 and to provide detailed evidence of water presence and persistency states and changes under the influences of climate change and human actions. Our results reveal that the New Area water body areas varied dramatically during the past 33 years, ranging from 0.44 km^2 in April 1988 to 317.85 km^2 in February 1989. The change of surface water area was not characterized by a monotonically decreasing tendency. The evolution processes can be divided into four sub-stages： the first extreme desiccation in mid-1980s, the wet stage with the most extensive inundation areas and strong inter-annual fluctuations from late-1988 to late 1999, another desiccation stage in early 2000s, and the overall recovering stage between 2007 and 2016. We also mapped the maximum water inundation extents and frequencies of all-season, pre-wet season （February-May） and post-wet season （September-December） for the 33 years and different sub-periods. Although there is good agreement between time series of surface water area evolution in the New Area and station-based precipitation and evaporation variations, multipie lines of evidences reviewed in previous research indicate that the degraded Baiyangdian Lake was also tightly associated with human activities from various aspects, inc

关键词： Xiong'an New Area Surface water Baiyangdian Lake Remote sensing Climate change Landsat

Numerical Study on the Thermal Stress and its Formation Mechanism of a Thermoelectric Device

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Journal of Thermal Science 2018年第3期27卷 249-258页

作者： pan Tao GONG Tingrui YANG wei WU Yongjia Product Engineering Department Wuhan Branch of SAIC-GM ltd Wuhan 430200 China Microsystem and Terahertz Research Center China Academy of Engineering Physics Chengdu 610200 China Institute of Electronic Engineering China Academy of Engineering Physics Mianyang 621999 China Hubei Institute of Aerospace Chemical Technology Xiangyang 441000 China School of Mechanical Engineering Virginia Polytechnic Institute and State University Blacksburg 24060 USA

The strong thermo-mechanical stress is one of the most critical failure mechanisms that affect the durability of thermoelectric devices. In this study, numerical simulations on the formation mechanism of the maximum thermal stress inside the thermoelectric device have been performed by using finite element method. The influences of the material properties and the thermal radiation on the thermal stress have been examined. The results indicate that the maximum thermal stress was located at the contact position between the two materials and occurred due to differential thermal expansions and displacement constraints of the materials. The difference in the calculated thermal stress value between the constant and the variable material properties was between 3% and 4%. At a heat flux of 1 W·cm^(-2) and an emissivity of 0.5, the influence of the radiation heat transfer on the thermal stress was only about 5%; however, when the heat flux was 20 W·cm^(-2) and the emissivity was 0.7, the influence of the radiation heat transfer was more than 30%.

关键词： Solar Thermoelectric Power Generator Thermal Stress Thermal Radiation Numerical Simulation

Abnormal thermal expansion coefficients in(Nd_(1−x)Dy_(x))_(2)Zr_(2)O_(7) pyrochlore:The effect of low-lying optical phonons

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Journal of Advanced Ceramics 2023年第5期12卷 1001-1014页

作者： Zesheng Yang Yi Li wei pan Chunlei Wan State key Laboratory of New Ceramics&Fine Processing Tsinghua UniversityBeijing 100084China College of Mathematics and Physics Beijing University of Chemical TechnologyBeijing 100029China

Chemical doping is a normal strategy to tune thermal expansion coefficient(TEC)of ceramics in engineering applications,but the resultant TEC values usually follow Vegard’s law,as doping does not modify the nature of chemical bonding in ceramics and its *** this paper,we report abnormal TEC behavior in(Nd_(1−x)Dy_(x))_(2)Zr_(2)O_(7) ceramics,where the TEC values remarkably exceed the values predicted by Vegard’s law and even exceed the values obtained for two constituents Nd_(2)Zr_(2)O_(7) and Dy_(2)Zr_(2)O_(7).In addition to a reduction in lattice energy with an increasing molar fraction of Dy(x)value,we attribute the additional increase in the TEC to the high concentration of Dy dopants in a pyrochlore(P)region,which can soften low-lying optical phonon modes and induce strongly avoided crossing with acoustic phonon branches and enhanced *** believe that this finding can provide a new route to break through the restriction imposed by the conventional Vegard’s law on the TEC values and bring new opportunities for thermal barrier coatings(TBCs)or ceramic/metal composites towards realizing minimized thermal mismatch and prolonged service life during thermal cycling.

关键词： thermal barrier coating(TBC) thermal expansion first-principles calculations avoided crossing

Strategies for network security

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Science China(Information Sciences) 2015年第1期58卷 120-133页

作者： LI AngSheng LI XueChen pan YiCheng ZHANG wei State key Laboratory of Computer Science Institute of Software Chinese Academy of Sciences Beijing No.4 High School University of Chinese Academy of Sciences

Security of networks has become an increasingly important issue in the highly connected *** depends on attacks. Typical attacks include both cascading failure of virus spreading and of information propagation and physical attacks of removal of nodes or edges. Numerous experiments have shown that none of the existing models construct secure networks, and that the universal properties of power law and small world phenomenon of networks seem unavoidable obstacles for security of networks against attacks. Here, we propose a new strategy of attacks, the attack of rules of evolution of networks. By using the strategy, we proposed a new model of networks which generates provably secure networks. It was shown both analytically and numerically that the best strategy is to attack on the rules of the evolution of networks, that the second best strategy is the attack by cascading failure models, that the third best strategy is the physical attack of removal of nodes or edges, and that the least desirable strategy is the physical attack of deleting structures of the networks. The results characterize and classify the strategies for network security, providing a foundation for a security theory of networks. Equally important, our results demonstrate that security can be achieved provably by structures of networks, that there is a tradeoff between the roles of structures and of thresholds in security engineering,and that power law and small world property are never obstacles of security of networks. Our model explores a number of new principles of networks, including some topological principles, probabilistic principles, and combinatorial principles. The new principles build the foundation for new strategies for enhancing security of networks, and for new protocols of communications and security of the Internet and computer networks etc. We anticipate that our theory can be used in analyzing security of real systems in economy, society and technology.

关键词： complex networks security of networks strategy for network security cascading failure model of networks

Efficient removal of algae and turbidity from water by a composite coagulant composed of a cationic starch and attapulgite

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Science China(Technological Sciences) 2022年第12期65卷 2979-2989页

作者： JIN JiaSheng XIA wei HU pan YANG Hu State key Laboratory of Pollution Control and Resource Reuse School of EnvironmentNanjing UniversityNanjing 210023China Quanzhou Institute for Environmental Protection Industry Nanjing UniversityQuanzhou 362000China

Algae and suspended colloidal particles produced high turbidity in water,weakened water purification,and threatened the safety of the water *** this study,a series of composite coagulants(atp-st-CTA)composed of a cationic starch(st-CTA)and attapulgite(ATP)with different fed mass ratios were fabricated by a simple method to coagulate kaolin suspension with initial turbidity of 80.0 NTU and Chlorella suspension with 0.25 mg/L of chlorophyll a(chla),*** transform infrared spectroscopy and scanning electron microscopy investigated the structural characteristics of *** maximum turbidity and chla removal rates of atp-st-CTA were 92.2%and 100.0%,respectively,at natural pH *** effects of the fed mass ratio of st-CTA to ATP in the composites,dose,pH,and coexisting humic acid on the coagulation performance of atp-st-CTA were comprehensively *** on the apparent coagulation behaviors,the zeta potentials of the supernatants after coagulation,and the flocs properties,the coagulation mechanisms of atp-st-CTA were discussed in *** complete charge neutralization due to st-CTA and the enhanced sedimentation by ATP synergistically removed turbidity and algae from the water *** short,atp-st-CTA as a talented material has a notable prospect in applications of water treatment owing to its advantages of environmental friendliness,low cost,and high efficiency.

关键词： composite coagulant cationic starch attapulgite turbidity removal algae removal coagulation mechanism

Method for Predicting the Fatigue Life of Geometrically Discontinuous Structures Under Combined Bending and Torsion

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Acta Mechanica Solida Sinica 2019年第3期32卷 367-377页

作者： Jianhui Liu Xuemei pan Yaobing wei Youliang Wang School of Mechanical and Electronical Engineering Lanzhou University of Technology Lanzhou 730050 China

The fatigue damage model based on theory of damage mechanics is capable of predicting the fatigue life under multiaxial loading. Meanwhile, the application of critical plane method in the prediction of multiaxial fatigue life has made certain progress. According to the law of thermodynamics, a new damage evolution equation is developed in the present study to predict the fatigue life of geometrically discontinuous structure under tension-torsion loading based on damage mechanics and the critical plane method. The essence of this approach is tha t the st rain parame ter of the uniaxial nonlinear fatigue damage model is replaced with the equivalent strain, which consists of the releva nt parame ters of the critical plane. However, it is difficult to calculate the stress-strain status and the critical plane position of geometrically dis? continuous structure by theoretical methods because of the existence of stress concentration and the multiaxial nonproportional characteristics. Therefore, a new numerical simulation method is proposed to determine the critical plane of geometrically discontinuous structure under multiaxial loading by means of the finite element method and MATLAB software. The fatigue life of notched specimens subjected to combined bending and torsion is predicted using the proposed met hod, and the result is compared with t hose from the experimen ts and the Manson-Cfiffin law. The comparisons show that the proposed method is superior to the Manson-Coffin law and is capable of reproducing the experimental results reasonably when the geometry of the structure is complex. It completely meets the needs of engineering practice.

关键词： Damage mechanics Critical plane method Geometrically discontinuous structure Finite element method

Syndiospecific Polymerization of Styrene Catalyzed by Half-titanocenes Containing Monodentate Anionic Nitrogen Ligands

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Chinese Journal of Chemistry 2021年第10期39卷 2815-2822页

作者： Dan-Dan pan ke-Xin Fan Shu Zhang Yi-Xian Wu State key Laboratory of Chemical Resource Engineering Beijing University of Chemical TechnologyBeijing100029 China

Main observation and conclusion Styrene polymerization catalyzed by the half-titanocenes CpTiCl_(2)[1,3-R_(2)(CH_(2)N)_(2)C=N](6b:R=_(2),6-Me_(2)C_(6)H_(3),T_(4):R=_(2),4,6-Me_(3)C_(6)H_(2);T5:R=_(2),6-iPr_(2)C_(6)H_(3))was carried out in the presence of methylaluminoxane(MAO).Compared to the styrene conversion(31%)and syndiospecific index(45%)using reported 6b as precatalyst,T5 bearing ligand with isopropyl substitutes on the N-aryl-rings exhibits much higher styrene conversion(61%)and syndiospecific index(99%),indicating that the catalytic behavior could be improved obviously by the introduction of electronic donating and steric bulky *** N atom in imidazolin-_(2)-iminato ligand was replaced by O atom,affording half-titanocenes CpTiCl_(_(2))[3-C6H5(CH_(2)N)(CH_(2)O)C=N(T1)and CpTiCl_(_(2))[_(2),6-Me_(2)(C6H3O)(NiPr_(2))C=N](T_(2)).Compared to 6b,both higher styrene conversion and syndiospecific index are afforded by using half-titanocene T1 containing_(2)-imino-3-phenyloxazolidine *** the results illustrate that both the chemical structure and the nature of substituents of the ligand have obvious influence on the styrene conversion and syndiospecific index in the polymerization of *** the resulting syndiotactic polystyrenes(sPSs)are highly syndiospecific(rrr>99%).Correspondingly,the sPS prepared using T5/MAO catalytic system exhibits high melting point and narrow molecular weight *** results might show new light on designing more efficient half-titanocenes for styrene polymerization with both high styrene conversion and high syndiospecific selectivity.

关键词： Polymerization Metallocenes N ligands Syndiospecific polymerization Polystyrene

Modified Linggui Zhugan Decoction Ameliorates Glycolipid Metabolism and Inflammation via PI3K-Akt/m TOR-S6K1/AMPK-PGC-1α Signaling Pathways in Obese Type 2 Diabetic Rats

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Chinese Journal of Integrative Medicine 2022年第1期28卷 52-59页

作者： SUN Jia-pan SHI Lin WANG Fang QIN Jian ke Bin Department of Traditional Chinese Medicine the First Affiliated HospitalSun Yat-sen UniversityGuangzhou(510080)China Department of Traditional Chinese Medicine Zhujiang Hospital of Southern Medical UniversityGuangzhou(510280)China Department of Oncology the First Affiliated HospitalSun Yat-sen UniversityGuangzhou(510080)China Department of Traditional Chinese Medicine the Seventh Affiliated HospitalSun Yat-sen UniversityShenzhen(518107)Guangdong ProvinceChina Department of VIP Ward Sun Yat-sen University Cancer CenterGuangzhou(510060)China

Objective: To investigate the protective effects of modified Linggui Zhugan Decoction(MLZD), a traditional Chinese medicine formula, on obese type 2 diabetes mellitus(T2 DM) rats. Methods:Fifty Sprague-Dawley rats were randomly divided into 5 groups by a random number table, including normal, obese T2 DM(ob-T2 DM), MLZD low-dose [MLDZ-L, 4.625 g/(kg·d)], MLZD middle-dose [MLD-M,9.25 g/(kg·d) ] and MLZD high-dose [MLD-H, 18.5 g/(kg·d)] groups,10 rats in each group. After 4-week intervention, blood samples and liver, pancreas, muscle tissues were collected to assess the insulin resistance(IR), blood lipid, adipokines and inflammation cytokines. The alteration of phosphatidylinositol 3 kinase(PI3 K)-protein kinase B(PKB or Akt)/the mammalian target of rapamycin(mTOR)-ribosome protein subunit 6 kinase 1(S6 K1)/AMP-activated protein kinase(AMPK)-peroxisome proliferator-activated receptor gamma coactivator 1 alpha(PGC-1α) pathways were also studied. Results: MLZD dose-dependently reduced fasting blood glucose,fasting insulin, homeostasis model of assessment for IR index and increased insulin sensitive index compared with ob-T2 DM rats(Ppancreas(P<0.05 or P<0.01). Conclusions: MLZD ameliorated glycolipid metabolism and inflammation, which may be attributed to the regulation of PI3 K-Akt/mTOR-S6 K1/AMPK-PGC-1α pathways.

关键词： Chinese medicine obesity type 2 diabetes mellitus glycolipid metabolism adipokines inflammation

Proof of three conjectures on congruences

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Science China Mathematics 2014年第10期57卷 2091-2102页

作者： pan Hao SUN Zhi-wei Department of Mathematics Nanjing University

This paper proves three conjectures on congruences involving central binomial coefficients or Lucas *** p be an odd prime and let a be a positive *** is shown that if p=1（mod 4）or a〉1then [3/4pa]∑k=0≡（2/pa）（mod p^2）where（—）denotes the Jacobi *** confirms a conjecture of the second author.A conjecture of Tauraso is also confirmed by showing that p-1∑k=1 Lk/k^2≡0（mod p） provided p〉*** the Lucas numbers Lo,L1,L2,...are defined by L_0=2,L1=1 and Ln＋1=Ln＋Ln-l（n=1,2,3,...）.The third theorem states that if p=5 then Fp^a-（p^a/5）mod p^3 can be determined in the following way： p^a-1∑k=0（-1）^k（2k k）≡（p^a/5）（1-2F p^a-（pa/5））（mod p^3）which appeared as a conjecture in a paper of Sun and Tauraso in 2010.

关键词： congruences modulo prime powers Fibonacci numbers Lucas sequences