检索结果-南通市图书馆

Bare Strange Stars Might Not Be Bare

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 1998年第12期15卷 934-936页

作者： xu ren-xin qiao guo-jun Department of Geophysics Peking UniversityBeijing 100871 Chinese Academy of Sciences-Peking University Joint Beijing Astrophysical Center Beijing 100871

It is proposed that the bare strange matter stars might not be bare,and the observed pulsars might be in fact the bare strange *** intensely magnetized strange matter stars rotate,the induced unipolar electric fields would be large enough to construct *** situation is very similar to that discussed by many authors for rotating neutron ***,the strange stars with accretion crusts in binaries could act as x-ray pulsars or x-ray *** are some advantages if pulsars are bare strange stars.

关键词： stars crust accretion

Electric Character of Strange Stars

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics Letters 1999年第10期16卷 778-780页

作者： xu ren-xin qiao guo-jun National Astronomical Observatories Beijing Astronomical ObservatoryChinese Academy of ScienceBeijing 100012 CAS-PKU Joint Beijing Astrophysical Center and Department of Astronomy Peking UniversityBeijing 100871

Using the Thomas-Fermi model,we investigated the electric characteristics of a static non-magnetized strange star without *** exact solutions of electron number density and electric field above the quark surface are *... 详细信息

关键词： quark concerned exact

An Annular Gap Acceleration Model for γ-ray Emission of Pulsars

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Astronomy and Astrophysics 2007年第4期7卷 496-502页

作者： guo-jun qiao Ke-Jia Lee Bing Zhang hong-Guang Wang ren-xin xu Department of Astronomy Peking University Beijing 100871 Department of Physics University of Nevada Las Vegas Nevada 89154 USA Center for Astrophysics Guangzhou University Guangzhou 510400

If the binding energy of the pulsar＇s surface is not so high （the case of a neutron star）, both negative and positive charges will flow out freely from the surface of the star. An annular free flow model for 7-ray emission of pulsars is suggested. It is emphasized that：（1） Two kinds of acceleration regions （annular and core） need to be taken into account. The annular acceleration region is defined by the magnetic field lines that cross the null charge surface within the light cylinder. （2） If the potential drop in the annular region of a pulsar is high enough （normally the case for young pulsars）, charges in both the annular and the core regions could be accelerated and produce primary gamma-rays. Secondary pairs are generated in both regions and stream outwards to power the broadband radiations. （3） The potential drop grows more rapidly in the annular region than in the core region. The annular acceleration process is a key process for producing the observed wide emission beams. （4） The advantages of both the polar cap and outer gap models are retained in this model. The geometric properties of the 7-ray emission from the annular flow are analogous to that pre-sented in a previous work by qiao et al., which match the observations well. （5） Since charges with different signs leave the pulsar through the annular and the core regions respectively, the current closure problem can be partially solved.

关键词： pulsars: general - pulsars: - radiation mechanisms: non-thermal - stars:neutron - elementary particles

Particle Emission-Dependent Timing Noise of Pulsars

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2011年第1期28卷 230-232页

作者： LIU Xiong-Wei NA xue-Sen xu ren-xin qiao guo-jun School of Physics and State Key Laboratory of Nuclear Physics and Technology Peking University Beijing 100871

Though pulsars spin regularly, the differences between the observed and predicted ToA （tune of arrival）, known as ＂timing noise＂, can still reach a few milliseconds or more. We try to understand the noise in this study. As proposed by xu and qiao in 2001, both dipole radiation and particle emission would result in pulsar braking. Accordingly, possible fluctuation of particle current flow is suggested here to contribute significant ToA variation of pulsars. We find that the particle emission fluctuation could lead to timing noise which cannot be eliminated in timing process and that a longer period fluctuation would arouse a stronger noise. The simulated timing noise profile and amplitude are in agreement with the observed timing behaviors on the timescale of years.

关键词： Astrophysics and astroparticles

Coherent Inverse Compton Scattering Responsible for Pulsar Polarized and Unpolarized Emission

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics Letters 1999年第7期16卷 541-543页

作者： LIU Ji-feng qiao guo-jun xu ren-xin CAS-PKU Joint Beijing Astrophysics Center&Department of Geophysics Peking UniversityBeijing 100871 CCAST(World Laboratory) P.O.Box 8730Beijing 100080

A coherent inverse Compton scattering(ICS)mechanism is used to get polarization properties of radio emission of *** is found that particles moving along a ring with radius θ’=1/(√3γ)simultaneously contribute via coherent *** circular polarization can be easily gotten as well as linear polarization at the same *** theory releases the upper limit of Lorentz factor γ≤20 put by curvature radiation,and γ may take several thousands in ***,subpulse position angles do take diverse values,while mean position angle is associated with the projection of magnetic Geld *** it is natural to get commonly-seen S-shaped swing of mean position *** we present a simulation for position angle rotation,linear polarization,circular polarization of PSR1508+55,which means that the coherent ICS may be responsible for radio emission.

关键词： coherent circular polarized

A BiGRU joint optimized attention network for recognition of drilling conditions

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Petroleum Science 2023年第6期20卷 3624-3637页

作者： Ying qiao hong-Min xu Wen-jun Zhou Bo Peng Bin Hu xiao guo National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum UniversityChengdu610500SichuanChina School of Computer Science Southwest Petroleum UniversityChengdu610500SichuanChina Information Management Center of Sinopec Southwest Oil and Gas Branch Chengdu610500SichuanChina

The identification and recording of drilling conditions are crucial for ensuring drilling safety and efficiency. However, the traditional approach of relying on the subjective determination of drilling masters based on experience formulas is slow and not suitable for rapid drilling. In this paper, we propose a drilling condition classification method based on a neural network model. The model uses an improved Bidirectional Gated Recurrent Unit (BiGRU) combined with an attention mechanism to accurately classify seven common drilling conditions simultaneously, achieving an average accuracy of 91.63%. The model also demonstrates excellent generalization ability, real-time performance, and accuracy, making it suitable for actual production. Additionally, the model has excellent expandability, which enhances its potential for further application.

关键词： Drilling condition classification BiGRU Machine learning Attention mechanism

Braking PSR J1734–3333 with a possible fall-back disk

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2014年第1期14卷 85-92页

作者： Xiong-Wei Liu ren-xin xu guo-jun qiao Jin-Lin Han Hao Tong School of Physics China West Normal University School of Physics and State Key Laboratory of Nuclear Physics and Technology Peking University National Astronomical Observatories Chinese Academy of Sciences xinjiang Astronomical Observatory Chinese Academy of Sciences

The very small braking index of PSR J1734-3333, n = 0.9 ± 0.2, chal- lenges the current theories of braking mechanisms in pulsars. We present a possible interpretation that this pulsar is surrounded by a fall-hack disk and braked by it. A modified braking torque is proposed based on the competition between the magnetic energy density of the pulsar and the kinetic energy density of the fall-back disk. With this torque, a self-similar disk can fit all the observed parameters of PSR J1734-3333 with natural initial values of parameters. In this regime, the star will evolve to the re- gion having anomalous X-ray pulsars and soft gamma repeaters in the P -/5 diagram in about 20 000 years and stay there for a very long time. The mass of the disk around PSR J1734-3333 in our model is about 10M similar to the observed mass of the disk around AXP 4U 0142＋61.

关键词： pulsars: individual (PSR J1734-3333) - stars: evolution - stars: neutron

Experimental study on the moving characteristics of fine grains in wide grading unconsolidated soil under heavy rainfall

在线全文

学校读者我要写书评

暂无评论

Journal of Mountain Science 2017年第3期14卷 417-431页

作者： cui Yi-fei ZHOU xiao-jun guo Chao-xu Department of Civil and Environmental Engineering Hong Kong University of Science and TechnologyClear Water BayHong KongChina China Merchants Chongqing Communications Research&Design Institute Chongqing 400067China Fujian Academy of Building Research Pujian Key Laboratory of Green Building TechnologyFuzhou 350025China Fuzhou University Fuzhou 350108China

The initiation mechanism of debris flow is regarded as the key step in understanding the debrisflow processes of occurrence, development and damage. Moreover, migration, accumulation and blocking effects of fine particles in soil will lead to soil failure and then develop into debris flow. Based on this hypothesis and considering the three factors of slope gradient, rainfall duration and rainfall intensity, 16 flume experiments were designed using the method of orthogonal design and completed in a laboratory. Particle composition changes in slope toe, volumetric water content, fine particle movement characteristics and soil failure mechanism were analyzed and understood as follows: the soil has complex, random and unstable structures, which causes remarkable pore characteristics of poor connectivity, non-uniformity and easy variation. The major factors that influence fine particle migration are rainfall intensity and slope. Rainfall intensity dominates particle movement, whereby high intensity rainfall induces a large number of mass movement and sharp fluctuation, causing more fine particles to accumulate at the steep slope toe. The slope toe plays an important role in water collection and fine particleaccumulation. Both fine particle migration and coarse particle movement appears similar fluctuation. Fine particle migration is interrupted in unconnected pores, causing pore blockage and fine particle accumulation, which then leads to the formation of a weak layer and further soil failure or collapses. Fine particle movement also causes debris flow formation in two ways: movement on the soil surface and migration inside the soil. The results verify the hypothesis that the function of fine particle migration in soil failure process is conducive for further understanding the formation mechanism of soil failure and debris flow initiation.

关键词： Wide grading unconsolidated soil Fine particle migration Soil failure Landslide Debris flow initiation Flume test Heavy rainfall

How can FAST improve study of the pulsar emission mechanism and magnetospheric dynamics?

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2019年第2期19卷 55-64页

作者： hong-Guang Wang guo-jun qiao Yuan-Jie Du Ji-Guang Lu ren-xin xu Ke-Jia Lee Xiong-Wei Liu School of Physics and Electronic Engineering Guangzhou University Department of Astronomy Peking University Qian xuesen Laboratory of Space Technology China Academy of Space Technology National Astronomical Observatories Chinese Academy of Sciences School of Physics and Electronic Information China West Normal University

The Five-hundred-meter Aperture Spherical radio Telescope(FAST) has the potential to discover many new pulsars and new phenomena. In this paper we mainly concentrate on how FAST can impact study of the pulsar emission mechanism and magnetospheric dynamics. Several observational programs heading to this direction are reviewed. To make full use of the superior performance of FAST and maximize the scientific outcome, these programs can be arranged in different phases of FAST according to their demands for observational conditions. We suggest that programs can be performed following the test phase, which are observations of multifrequency mean pulse profiles, anomalous X-ray pulsars(AXPs)/soft gamma-ray repeaters(SGRs), mode changing, drifting subpulse and nulling. The long-term monitoring can be carried out for mode changing, AXPs/SGRs and precessional pulsars. Others programs, including polarization observations of radio and γ-ray pulsars, searching for weak pulse components, and multifrequency observations of subpulse drifting, microstructure and giant pulses, can be conducted in all the normal operating phases(the first and second phases). These programs will push forward the frontier in this field in different respects. The search for sub-millisecond pulsars and follow-up observations of their emission properties are very important projects for FAST, but they may be covered by other papers in this mini-volume; therefore,they are not discussed here.

关键词： pulsars:general pulsars: radio emission radiation mechanisms:non-thermal