检索结果-南通市图书馆

Science China(Physics,Mechanics & Astronomy) 2018年第10期61卷 2-13页

作者： Qiang Yuan lei feng Key Laboratory of Dark Matter and Space Astronomy Purple Mountain ObservatoryChinese Academy of SciencesNanjing 210008China School of Astronomy and Space Science University of Science and Technology of ChinaHefei 230026China Center for High Energy Physics Peking UniversityBeijing 100871China

The DArk Matter Particle Explorer （DAMPE） is a satellite-borne, high-energy particle and 3,-ray detector, which is dedicated to indirectly detecting particle dark matter and studying high-energy astrophysics. The first results about precise measurement of the cosmic ray electron plus positron spectrum between 25 GeV and 4.6 TeV were published recently. The DAMPE spectrum reveals an interesting spectral softening arount 0.9 TeV and a tentative peak around 1.4 TeV. These results have inspired extensive discussion. The detector of DAMPE, the data analysis, and the first results are introduced. In particular, the physical interpretations of the DAMPE data are reviewed.

关键词： dark matter cosmic rays electrons plus positrons pulsars

The nanohertz stochastic gravitational wave background from cosmic string loops and the abundant high redshift massive galaxies

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2023年第12期66卷 11-19页

作者： Ziwei Wang lei lei Hao Jiao lei feng Yi-Zhong Fan Key Laboratory of Dark Matter and Space Astronomy Purple Mountain ObservatoryChinese Academy of SciencesNanjing 210023China School of Astronomy and Space Science University of Science and Technology of ChinaHefei 230026China Department of Physics McGill UniversityMontreal H3A 2T8Canada

Recently,pulsar timing array(PTA)experiments have provided compelling evidence for the existence of the nanohertz stochastic gravitational wave background(SGWB).In this work,we demonstrated that cosmic string loops generated from cosmic global strings offer a viable explanation for the observed nanohertz SGWB data,requiring a cosmic string tension parameter of log(Gμ)~-12 and a loop number density of log N~***,we revisited the impact of cosmic string loops on the abundance of massive galaxies at high ***,our analysis revealed challenges in identifying a consistent parameter space that can concurrently explain both the SGWB data and observations from the James Webb Space *** indicates the necessity for either extending the existing model employed in this research or acknowledging distinct physical origins for these two phenomena.

关键词： nanohertz stochastic gravitational-wave background cosmic string loop JamesWebb Space Telescope galaxy formation

Interpretation of the DAMPE 1.4 Te V peak according to the decaying dark matter model

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2018年第10期61卷 36-42页

作者： Xu Pan Cun Zhang lei feng Key Laboratory of Dark Matter and Space Astronomy Purple Mountain Observatory Chinese Academy of Sciences School of Physics Nanjing University

Highly accurate measurements of cosmic ray electron flux by the dark matter particle explorer （DAMPE） ranging between 25 GeV and 4.6 TeV have recently been published. A sharp peak structure was found at - 1.4 TeV. This unexpected peak structure can be reproduced by the annihilation/decay of a nearby dark matter （DM） halo. In this study, we adopt the decaying-DM model to interpret the - 1.4 TeV peak. We found that the decay products of the local DM subhalo could contribute to the DMAPE peak with mDM = 3 TeV and r - 10^28 s. We also obtain constraints on DM lifetime and the distance of the local DM subhalo by comparison with DAMPE data.

关键词： dark matter cosmic ray DAMPE

Modification of SDOF model for reinforced concrete beams under close-in explosion

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2023年第2期20卷 162-186页

作者： Wei Wei Yu-lei Zhang Jian-jun Su Yan Liu feng-lei Huang State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China Xi'an Modern Chemistry Research Institute Xi'an710065China

In this paper,a modified single-degree-of-freedom(SDOF)model of reinforced concrete(RC)beams under close-in explosion is proposed by developing the specific impulse equivalent method and flexural resistance calculation *** equivalent uniform specific impulse was obtained based on the local conservation of momentum and global conservation of kinetic ***,the influence of load uniformity,boundary condition and complex material behaviors(*** rate effect,hardening/softening and hoop-confined effect)was considered in the resistance calculation process by establishing a novel relationship between external force,bending moment,curvature and deflection *** accuracy of the proposed model was verified by carrying out field explosion tests on four RC beams with the scaled distances of 0.5 m/kg~(1/3)and 0.75 m/kg~(1/3).The test data in other literatures were also used for *** a result,the equivalent load implies that the blast load near the mid-span of beams would contribute more to the maximum displacement,which was also observed in the ***,both the resistance model and test results declare that when the blast load becomes more concentrated,the ultimate resistance would become lower,and the compressive concrete would be more prone to softening and ***,based on the modified SDOF model,the calculated maximum displacements agreed well with the test data in this paper and other *** work fully proves the rationality of the modified SDOF method,which will contribute to a more accurate damage assessment of RC structures under close-in explosion.

关键词： SDOF model Close-in explosion Specific impulse equivalent method Flexural resistance

Hemorrhagic hepatic cysts mimicking biliary cystadenoma

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2009年第36期15卷 4601-4603页

作者： You-lei Zhang lei Yuan feng Shen Yi Wang EasternHepatobiliary Surgery Hospital Second Military MedicalUniversity Shanghai 200438 China

The hemorrhagic simple hepatic cyst is extremely rare and can sometimes be confused with biliary cystadenoma or *** we present two cases of huge hemorrhagic simple hepatic cysts. Case 1 was a 43-year-old man with a cystic lesion measuring 13 cm×12 cm in the right hepatic lobe. Ultrasound and computed tomography showed several mural nodules on the irregularly thickened wall and high-density straps inside the *** 2 was a 60-year-old woman with a huge cyst measuring 15 cm ×14 cm in the central *** and magnetic resonance imaging showed the cystic wall was unevenly thickened and there were some flame-like prominences on the *** iconographic representations of the two cases mimicked biliary *** and left hepatectomy were performed for the two patients, *** patients recovered quickly after their operations and showed no recurrence.

关键词： Simple hepatic cyst Intracystic hemorrhage Biliary cystadenoma Diagnosis Treatment

Effect of interface behaviour on damage and instability of PBX under combined tension-shear loading

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2023年第5期23卷 137-151页

作者： Quan-zhi Xia Yan-qing Wu feng-lei Huang State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081PR China

To study the effect of interface behaviour on the mechanical properties and damage evolution of PBX under combined tension-shear loading, the present work establishes the numerical model of a PBX three-phase hybrid system, which introduces a nonlinear plastic damage cohesion model to study the mechanical response and damage process. The parameters in the model were fitted and *** the crack growth rate as the feature, the damage state in each stage was determined, and the damage instability criterion was given. The effects of interfacial tensile strength and shear strength on the damage process of PBX were studied. On this basis, serrated and hemispherical structures interface of PBX has been developed, which affects the damage process and instability during the loading *** results indicate that damage state response of PBX experiences the process of stable load bearing,unstable propagation, and complete failure. At the critical moment of instability, the overall equivalent effective strain of material reaches 3024 με and instability loading displacement reaches 0.39 mm. The increase of interfacial tensile strength and shear strength significantly inhibits the damage of PBX. The effect of interfacial shear strength on critical instability of PBX is approximately 1.7 times that of the interfacial tensile strength. Further, interface opening along the normal direction is the main damage form at the interface. Serrated and hemispherical rough interfaces can significantly inhibit propagation of cracks, and the load bearing capacity is improved by 22% and 9.7%, respectively. Appropriate improvement of the roughness of the interface structure can effectively improve the mechanical properties. It is significantly important to have a better understanding of deformation, damage and failure mechanisms of PBX and to improve our predictive ability.

关键词： PBX explosives Interface behaviour Damage Instability Crack propagation

Is the W-boson mass enhanced by the axion-like particle,dark photon,or chameleon dark energy?

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2022年第12期65卷 145-152页

作者： Guan-Wen Yuan lei Zu lei feng Yi-Fu Cai Yi-Zhong Fan Key Laboratory of Dark Matter and Space Astronomy Purple Mountain ObservatoryChinese Academy of SciencesNanjing210023China School of Astronomy and Space Science University of Science and Technology of ChinaHefei230026China Department of Astronomy School of Physical SciencesUniversity of Science and Technology of ChinaHefei230026China CAS Key Laboratory for Researches in Galaxies and Cosmology University of Science and Technology of ChinaHefei230026China

The W-boson mass(m W=(80.4335±0.0094)Ge V)measured by the Collider Detector at Fermilab Collaboration is greater than the standard model(SM)prediction at a confidence level of 7σ,strongly suggesting the presence of new particles or *** the literature,various new particles and/or fields have been introduced to explain the astrophysical and experimental data,and their presence,in principle,may also enhance the W-boson *** this study,we investigate axion-like particle(ALP),dark photon(DP),and chameleon dark energy(DE)models for a solution to the W-boson mass *** find that the ALP and DP interpretations have been significantly narrowed down by global electroweak *** possibility of attributing the W-boson mass anomaly to the chameleon DE is ruled out by other experiments.

关键词： W-boson mass axion-like particle dark photon chameleon dark energy

同方期刊数据库

Trade in goods among China,Japan,and South Korea and the road to a free trade area

在线全文

学校读者我要写书评

暂无评论

China Finance and Economic Review 2014年第2期3卷 114-128页

作者： feng lei National Academy of Economic Strategy Chinese Academy of Social SciencesBeijingChina

Trade in goods is of great importance to Northeast Asia,a region with highly developed manufacturing *** interdependency among China,Japan,and South Korea(CJK)is an important incentive and basis for the development of CJK free trade area(FTA)and cross-border *** 1991 to 2011,the value of bilateral trade as a share of total trade among China,Japan,and South Korea underwent significant ***’s imports increased but exports decreased,Japan’s imports and exports both increased,and South Korea’s exports increased but imports *** developments can help us understand the three countries’willingness of to continue the FTA negotiation process,in which commitment,environment,and demand uncertainty constitute disruptive factors in the CJKFTA negotiation *** CJKFTA can be realized directly or indirectly,depending on the will of China,Japan,and South Korea.

关键词： China Japan South Korea trade in goods trade independency FTA

Trigonometric Series with a Generalized Monotonicity Condition

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2014年第8期30卷 1289-1296页

作者： lei feng Vilmos TOTIK Song Ping ZHOU Institute of Mathematics Zhejiang Sci-Tech University MTA-SZTE Analysis and Stochastics Research Group Bolyai InstituteUniversity of Szeged Department of Mathematics and Statistics University of South Florida

In this paper,we consider numerical and trigonometric series with a very general monotonicity ***,a fundamental decomposition is established from which the sufficient parts of many classical results in Fourier analysis can be derived in this general *** the second part of the paper a necessary and sufficient condition for the uniform convergence of sine series is proved generalizing a classical theorem of Chaundy and Jolliffe.

关键词： Uniform convergence monotonicity mean value bounded variation decomposition

Application of split Hopkinson tension bar technique to the study of dynamic fracture properties of materials

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2012年第2期28卷 424-431页

作者： Ze-Jian Xu Yu-Long Li feng-lei Huang State Key Laboratory of Explosion Science and Technology Beijing Institute of Technology100081 BeijingChina School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China

A novel approach is proposed in determining dy- namic fracture toughness （DFT） of high strength steel, using the split Hopkinson tension bar （SHTB） apparatus, com- bined with a hybrid experimental-numerical method. The center-cracked tension specimen is connected between the bars with a specially designed fixture device. The fracture initiation time is measured by the strain gage method, and dynamic stress intensity factors （DSIF） are obtained with the aid of 3D finite element analysis （FEA）. In this approach, the dimensions of the specimen are not restricted by the connec- tion strength or the stress-state equilibrium conditions, and hence plane strain state can be attained conveniently at the crack tip. Through comparison between the obtained results and those in open publication, it is concluded that the ex- perimental data are valid, and the method proposed here is reliable. The validity of the obtained DFT is checked with the ASTM criteria, and fracture surfaces are examined at the end of paper.

关键词： Split Hopkinson tension bar Dynamic fracture toughness Hybrid experimental-numerical method High loading rate Failure mode