检索结果-南通市图书馆

Cosmic-Ray Positrons Produced by Pulsar Winds from Mature Gamma-Ray Pulsars

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2001年第5期18卷 701-704页

作者：张力 k.s.cheng 梅冬成 Department of Physics Yunnan UniversityKunming 650091 Department of Physics University of Hong KongPokfulam RoadHongKong Yunnan Observatory Chinese Academy of SciencesKunming 650011

In the frame of theγ-ray pulsar outer gap model,e^(±)pairs in the pulsar magnetosphere are produced by the cascade of e^(±)pairs through synchrotron radiation of the return current from the outer *** pairs are accelerated mono-energetically to relativistic energies in the pulsar wind driven by low-frequency electromagnetic *** Monte Carlo simulations,we generate a sample of the matureγ-ray pulsars in our Galaxy and calculate the positron production rate from these *** a simple leaky box model,we calculate the ratio of cosmic-ray positron to total *** result indicates that the pulsar contribution to the cosmic ray positron peaks at about 40 GeV and the observed e^(+)/(e^(-)+e^(+))ratio can be explained by this model.

关键词： cosmic outer return

On the Light Curve and spectra of X-Rays and Gamma-Rays from the Crab Pulsar

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

Chinese Physics Letters 2000年第7期17卷 544-546页

作者：张力 k.s.cheng 梅冬成 Yunnan Astrophysics Center Yunnan UniversityKunming 650091 Department of Physics University of Hong KongPokfulam RoadHong Kong

We use a three-dimensional pulsar magnetosphere model to study the light curve and spectra of x-rays and gamma-rays from the Crab pulsar. In this model, the vertical size of the outer gap is first determined by a self-consistent model in which the outer gap is limited by pair production from collisions of thermal photons produced by polar cap heating of backflow outer gap current and curvature photons emitted by gap accelerated charged particles. The transverse size of the outer gap is determined by local pair production conditions. In principle, there are two topologically disconnected outer gaps present in the magnetosphere of a pulsar, and both incoming and outgoing particle flows are allowed. However, double-peak light curves with strong bridges are most common, Making use of the three-dimensional structure of the outer gap and its local properties, we compare the results of our model with the light curve and phase-resolved spectra of the Crab pulsar.

关键词： particles conditions outer

Gamma-Ray Bursts: Afterglows and Central Engines

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

Chinese Journal of Astronomy and Astrophysics 2001年第1期1卷 1-20页

作者： k.s.cheng T.Lu DepartmentofPhysics UniversityofHongKongPokfulamRoadHongKong DepartmentofAstronomy NanjingUniversit

Gamma-ray bursts (GRBs) are the most intense transient gamma-ray events in the sky; this, together with the strong evidence (the isotropic and inhomogeneous distribution of GRBs detected by BAsTE) that they are located at cosmological distances, makes them the most energetic events ever known. For example, the observed radiation energies of some GRBs are equivalent to the total convertion into radiation of the mass energy of more than one solar mass. This is thousand times stronger than the energy of a supernova explosion. some unconventional energy mechanism and extremely high conversion efficiency for these mysterious events are required. The discovery of host galaxies and association with supernovae at cosmological distances by the recently launched satellite of BepposAX and ground based radio and optical telescopes in GRB afterglow provides further support to the cosmological origin of GRBs and put strong constraints on their central engine. It is the aim of this article to review the possible central engines, energy mechanisms, dynamical and spectral evolution of GRBs, especially focusing on the afterglows in multi-wavebands.

关键词： gamma-rays: bursts - shock waves - IsM: jets and outflows- radiation mechanisms: non-thermal

Broad Band spectra of Pulsars and PWNe

在线全文

学校读者我要写书评

暂无评论

Broad Band Spectra of Pulsars and PWNe

Bed inventory balance and stability of dual circulating fluidized bed systems

中国天文学会2004年学术年会

作者： k.s.cheng Department of Physics University Hong kang

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Particuology 2024年第1期84卷 98-106页

作者： Yangjun Wei Leming cheng David Pallares Bo Leckner Institute for Thermal Power Engineering State Key Laboratory of Clean Energy UtilizationZhejiang UniversityHangzhou310027China Department of space Earth and EnvironmentChalmers University of TechnologyS-41296GöteborgSweden

Experiments and modelling are conducted for general understanding on the imbalance phenomenon and for discussion on the strategies to improve the bed inventory balance and stability of a dual circulating fluidized bed(DCFB)*** experiments are carried out in a 15.5 m high pilot-scale DCFB cold test system.A fluid-dynamic DCFB model is developed based on a 1.5-dimensional semi-empirical model of an industrial CFB boiler,validated by experimental *** effects of control methods and operation conditions on the bed inventory balance and on the stability of the pilot-and large-scale DCFB systems are discussed.A"stable-unbalanced"state,where the system reaches a steady state,consisting of un-balanced bed inventories,is observed in both experiments and model *** maintain a balanced state and similar bed inventory in the DCFB systems with similar cross-sectional areas,it is recom-mended to keep similar total pressure drops or gas velocities in both reactors.

关键词： Bed inventory balance stability Dual circulating fluidized bed(DCFB) Experiment Modelling

Reliability of a Multicomponent stress-strength Model Based on a Bivariate kumaraswamy Distribution with Censored Data

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 Mathematicae Applicatae sinica 2024年第2期40卷 478-507页

作者： Cong-hua cheng school of Mathematics and statistics Zhaoqing UniversityZhaoqing 526061China

In this paper,we consider a system which has k statistically independent and identically distributed strength components and each component is constructed by a pair of statistically dependent elements with doubly type-II censored *** elements(X1,Y1),(X2,Y2),…,(Xk,Yk)follow a bivariate kumaraswamy distribution and each element is exposed to a common random stress T which follows a kumaraswamy *** system is regarded as operating only if at least s out of k(1≤s≤k)strength variables exceed the random *** multicomponent reliability of the system is given by Rs,k=P(at least s of the(Z1,…,Zk)exceed T)where Zi=min(Xi,Yi),i=1,…,*** Bayes estimates of Rs,k have been developed by using the Markov Chain Monte Carlo methods due to the lack of explicit *** uniformly minimum variance unbiased and exact Bayes estimates of Rs,k are obtained analytically when the common second shape parameter is *** asymptotic confidence interval and the highest probability density credible interval are constructed for Rs,*** reliability estimators are compared by using the estimated risks through Monte Carlo simulations.

关键词： stress-strength model bivariate kumaraswamy distribution multicomponent reliability doubly Type-II censored scheme interval estimation

在线全文

学校读者我要写书评

暂无评论

多级薄层过滤机的洗涤

流体机械 1984年第5期 56-62页

作者： k.s.cheng ,F.M.Tiller ,Alex Bagdasarian ,时云天津化工修配厂

洗涤是固液分离过程中的一个重要部分。通过洗涤可以回收积存在滤渣内的有价值液体。另一方面,由于用洗涤水代替了母液,在滤渣中可溶质的浓度可以降低。在过滤过程中用清净的洗涤液通过过滤机中的滤渣,洗涤就能够顺利完成。由于母液被... 详细信息

洗涤是固液分离过程中的一个重要部分。通过洗涤可以回收积存在滤渣内的有价值液体。另一方面,由于用洗涤水代替了母液,在滤渣中可溶质的浓度可以降低。在过滤过程中用清净的洗涤液通过过滤机中的滤渣,洗涤就能够顺利完成。由于母液被洗涤液置换出来,所以在开始时效率是高的,

关键词：过滤速率滤渣料浆固体浓度过滤机洗涤液薄层地层

Equalizer Zero-Determinant strategy in Discounted Repeated stackelberg Asymmetric Game

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of systems science & Complexity 2024年第1期37卷 184-203页

作者： cheng Zhaoyang CHEN Guanpu HONG Yiguang key Laboratory of systems and Control Academy of Mathematics and Systems ScienceChinese Academy of SciencesBeijing 100190China school of Mathematical sciences University of Chinese Academy of SciencesBeijing 100049China school of Electrical Engineering and Computer science KTH Royal Institute of Technology10044 StockholmSweden. Department of Control science and Engineering Tongji UniversityShanghai 201804China shanghai Research Institute for Intelligent Autonomous systems Tongji UniversityShanghai 210201China

This paper focuses on the performance of equalizer zero-determinant(ZD)strategies in discounted repeated stackelberg asymmetric *** the leader-follower adversarial scenario,the strong stackelberg equilibrium(ssE)deriving from the opponents’best response(BR),is technically the optimal strategy for the ***,computing an ssE strategy may be difficult since it needs to solve a mixed-integer program and has exponential complexity in the number of *** this end,the authors propose an equalizer ZD strategy,which can unilaterally restrict the opponent’s expected *** authors first study the existence of an equalizer ZD strategy with one-to-one situations,and analyze an upper bound of its performance with the baseline ssE *** the authors turn to multi-player models,where there exists one player adopting an equalizer ZD *** authors give bounds of the weighted sum of opponents’s utilities,and compare it with the ssE ***,the authors give simulations on unmanned aerial vehicles(UAVs)and the moving target defense(MTD)to verify the effectiveness of the proposed approach.

关键词： Discounted repeated stackelberg asymmetric game equalizer zero-determinant strategy strong stackelberg equilibrium strategy

Nutrient transport following water transfer through the world's largest water diversion channel

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental sciences 2024年第1期135卷 703-714页

作者： Yuanhui cheng Hong Zhang Wei Yin state key Laboratory of Environmental Aquatic Chemistry Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085 China Changjiang Water Resources Protection Institute Wuhan 430051China University of Chinese Academy of sciences Beijing 100049China

Nutrient levels in the artificial channel constructed for the Middle Route Project are significant indicators of water quality safety and aquatic ecological integrity for this large,interbasin ***,the distribution and transport of nutrients along the channel were poorly *** on a time-series dataset as well as mass balance and material flow analysis methods,the water and nutrient transport fluxes in the Middle Route of the south-to-North Water Diversion Project were identified in this *** results indicate that the nutrient concentrations varied considerably with time,but there was no significant difference among the 30 stations of the main *** temperature difference was the major factor in the large fluctuations of water quality indicators over *** nutrient loadings varied with the water volume outputs from the main channel to the waterreceiving *** deposition was an important source of nutrients in the main channel,accounting for 9.13%,20.6%,and 0.635%of the nitrogen,phosphorus,and sulfur input from the Danjiangkou Reservoir,*** 2021,a net accumulation of 988 tons of N,29 tons of P,and 2,540 tons of s,respectively,were present in the main *** increase of these external and internal nutrient loadings would cause water quality fluctuation and deterioration in some local sections of the main *** study quantified the spatial and temporal patterns of nutrient transport in the Middle Route and revealed the ecological effects on the aquatic environment,assisting authorities on the project to develop effective water conservation strategies.

关键词： Nutrient transport spatiotemporal patterns The Middle Route The south-to-North Diversion Project Hydro-ecological effects Water-receiving cities