检索结果-南通市图书馆

A sample of active galactic nuclei with strong soft X-ray variabilities

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2015年第4期58卷 101-108页

作者： BI Da liu teng WANG JunXian CAS Key Laboratory for Research in Galaxies and Cosmology Department of AstronomyUniversity of Science and Technology of China

Large-amplitude X-ray variation is a special feature of AGN, reflecting possible extreme change in the central engine or the ab- sorption along the line of sight. Till now there are only a few relevant studies on individual sources or rather small samples. In this work we aim to perform a systematic study of AGNs with strong soft X-ray variations at timescale of 〉 10 years. To build the sample, we compare the soft X-ray fluxes of AGNs measured in ROSAT All-Sky Survey （RASS） during 1990-1991 with those measured by XMM-Newton during 2000-2009. This investigation bings forth to a sample of 13 AGNs, which appeared bright in RASS era, and went into low states （flux dropped by a factor of 〉 10） when they were caught by XMM-Newton. Most of the 13 sources are type I Seyfert galaxies. 5 of them are noticed to have strong X-ray vai＇iation for the first time. We study the nature of their variations through performing XMM-Newton spectral analyses and by collecting reports from the existing literature. We find the sample could be divided into three categories according to the possible causes of the strong X-ray variations. The variations in MRK 0478 and 1H 0419-557 are consistent with strong light-bending effect, i.e., the observed X-ray flux drops significantly as the X-ray emitting corona gets much closer to the central black hole. The variations in ESO 140-G043 and NGC 7158 are caused by absorption changes along the line of sight. For one special case MRK 0335, the variation can be explained by either light-bending or absorption variation. In the rest 8 sources （- 60%）, the strong soft X-ray variations are likely to exist due to intrinsic changes in the activities of the corona, although in some of them without high quality X-ray spectra we are unable to rule out alternative models. This sample provides good targets for future monitoring campaigns with more extensive studies.

关键词： soft X-ray active galactic nuclei variation

Recent advances in functional nanomaterials for X-ray triggered cancer therapy

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2020年第5期30卷 567-576页

作者： teng liu Kai Yang Zhuang liu State Key Laboratory of Radiation Medicine and Protection School of Radiation Medicine and Protection & School for Radiological and Interdisciplinary Sciences (RADX) Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions Soochow University Institute of Functional Nano & Soft Materials (FUNSOM) Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices Soochow University

X-ray is a form of ionizing radiation with high energy and strong tissue-penetrability, which has been widely used for cancer therapy, including radiation therapy(RT) as one of the mainstream cancer treatments and radiodynamic therapy(RDT) as an emerging treatment modality. However, the nonspecific absorption of X-ray and peculiar tumor microenvironment would lead to the unsatisfied therapeutic effect and severe damage to normal tissues. The fast progress of nanotechnology has provided great opportunities for the development of functional nanoparticles and strategies to solve these problems. In this review, we will summarize the recent advances in functional nanomaterials and the related strategies, discuss how they solve the challenges in order to improve the therapeutic efficacy and safety of RT and RDT, and moreover comment on the challenges and prospects for efficient X-ray triggered cancer therapy based on nanomedicine.

关键词： X-ray irradiation Nanomaterials Cancer therapy Radiation therapy Radiodynamic therapy

Microstructure and Mechanical Properties of Overcast 6101–6101 Wrought Al Alloy Joint by Squeeze Casting

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 Materials Science & Technology 2016年第4期32卷 298-304页

作者： teng liu Qudong Wang YudongSui Qigui Wang National Engineering Research Center of Light Alloys Net Forming and State Key Laboratory of Metal Matrix Composite Shanghai Jiao Tong University200030ShanghaiChina General Motors Global Powertrain Engineering 823 Joslyn AvenuePontiacMI 48340-2920USA

The wrought Al alloy-wrought Al alloy overcast joint was fabricated by casting liquid 6101 Al alloy onto 6101 Al extrusion bars and solidifying under applied pressure. The joint interfacial microstructure was investigated; the effect of applied pressure on the microstructure and mechanical properties was evalu- ated. The mechanism of joint formation and mechanical behaviors of both squeeze cast 6101 and 6101- 6101 overcastjoint material were analyzed. The results show that with the application of pressure during solidification process, wrought Al alloy 6101 could be cast directly into shape successfully. Excellent met- allurgical bonding was then formed in the overcast joint by electro-plating 6101 solid insert with a layer of zinc coating, and a transition zone formed in the joint region. During the tensile test, the fracture occurs in the 6101 solid insert part with the ultimate tensile strength （UTS） of 200 MPa, indicating that the strength of the overcast joint is higher than 200 MPa, and the tensile strength of overcast joint material is inde- pendent on the magnitude of applied pressure. For Al-Al overcast joint material, if a clean and high strength joint is formed, the UTS and yield strength （YS） are determined by the material with the lower value, while for EL, the value is determined by the length proportion and the stress-strain behavior of both components.

关键词： Aluminum alloyOvercastingSqueeze castingInterfaceMicrostructureMechanical properties

Condensation of eigen microstate in statistical ensemble and phase transition

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2019年第9期62卷 41-48页

作者： GaoKe Hu teng liu MaoXin liu Wei Chen XiaoSong Chen Key Laboratory of Theoretical Physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China School of Systems Science Beijing Normal UniversityBeijing 100875China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China State Key Laboratory of Information Photonics and Optical Communications & School of Science Beijing University of Posts and TelecommunicationsBeijing 100876China

In a statistical ensemble with M microstates, we introduce an M × M correlation matrix with correlations among microstates as its elements. Eigen microstates of ensemble can be defined using eigenvectors of the correlation matrix. The eigenvalue normalized by M represents weight factor in the ensemble of the corresponding eigen microstate. In the limit M →∞, weight factors drop to zero in the ensemble without localization of the microstate. The finite limit of the weight factor when M →∞ indicates a condensation of the corresponding eigen microstate. This finding indicates a transition into a new phase characterized by the condensed eigen microstate. We propose a finite-size scaling relation of weight factors near critical point, which can be used to identify the phase transition and its universality class of general complex systems. The condensation of eigen microstate and the finite-size scaling relation of weight factors are confirmed using Monte Carlo data of one-dimensional and two-dimensional Ising models.

关键词： statistical ensemble eigen microstate condensation phase transition finite-size scaling

Global Optimization Method Using SLE and Adaptive RBF Based on Fuzzy Clustering

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2012年第4期25卷 768-775页

作者： ZHU Huaguang liu Li LONG teng ZHAO Junfeng School of Aerospace Engineering Beijing Institute of Technology Beijing 100081 China

High fidelity analysis models,which are beneficial to improving the design quality,have been more and more widely utilized in the modern engineering design optimization ***,the high fidelity analysis models are so computationally expensive that the time required in design optimization is usually *** order to improve the efficiency of optimization involving high fidelity analysis models,the optimization efficiency can be upgraded through applying surrogates to approximate the computationally expensive models,which can greately reduce the computation *** efficient heuristic global optimization method using adaptive radial basis function（RBF） based on fuzzy clustering（ARFC） is *** this method,a novel algorithm of maximin Latin hypercube design using successive local enumeration（SLE） is employed to obtain sample points with good performance in both space-filling and projective uniformity properties,which does a great deal of good to metamodels *** method is adopted for constructing the metamodels,and with the increasing the number of sample points the approximation accuracy of RBF is gradually *** fuzzy c-means clustering method is applied to identify the reduced attractive regions in the original design *** numerical benchmark examples are used for validating the performance of *** results demonstrates that for most application examples the global optima are effectively obtained and comparison with adaptive response surface method（ARSM） proves that the proposed method can intuitively capture promising design regions and can efficiently identify the global or near-global design *** method improves the efficiency and global convergence of the optimization problems,and gives a new optimization strategy for engineering design optimization problems involving computationally expensive models.

关键词： global optimization Latin hypercube design radial basis function fuzzy clustering adaptive response surface method

Effect of Al_4C_3 Particle Size Distribution in a Al–2.5C Master Alloy on the Refining Efficiency of the AZ31 Alloy

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2017年第6期30卷 505-512页

作者： Yu-Zhen Zhao Xiao-teng liu Hai Hao Key Laboratory of Solidification Control and Digital Preparation Technology(Liaoning Province) School of Materials Science and EngineeringDalian University of TechnologyDalian 116024China

The Al-2.5C master alloy is prepared to investigate the effect of the Al4C3 particle size distribution on the refining efficiency of the AZ31 alloy. The results indicate that the Al4C3 particles are potent nucleation substrates for primary α-Mg grains. With 1.0 wt% master alloy addition, the grain size is reduced from 204 to 70 μm. The grain refining efficiency of the Al4C3 particles on the AZ31 alloy is calculated to be 0.04%-0.75%. Such low refining efficiency is mainly attributed to the size distribution of the Al4C3 particles. The particle sizes are in the range from 0.18 to 7.08 μm, and their distribution is well fitted by a log-normal function. The optimum particle size range for significant grain refinement is proposed to be around 5.0-7.08 μm in the present conditions.

关键词： Particle size distribution Grain refining efficiency Al-2.5C master alloy Magnesium alloys

Parallel Reinforcement Learning-Based Energy Efficiency Improvement for a Cyber-Physical System

在线全文

学校读者我要写书评

暂无评论

IEEE/CAA Journal of Automatica Sinica 2020年第2期7卷 617-626页

作者： teng liu Bin Tian Yunfeng Ai Fei-Yue Wang Department of Automotive Engineering Chongqing UniversityChongqing 400044 the Vehicle Intelligence Pioneers Inc. Qingdao 266109China the State Key Laboratory of Management and Control for Complex Systems Institute of AutomationChinese Academy of SciencesBeijing 100190China the School of Artificial Intelligence University of Chinese Academy of SciencesBeijing 101408China

As a complex and critical cyber-physical system(CPS),the hybrid electric powertrain is significant to mitigate air pollution and improve fuel *** management strategy(EMS)is playing a key role to improve the energy efficiency of this *** paper presents a novel bidirectional long shortterm memory(LSTM)network based parallel reinforcement learning(PRL)approach to construct EMS for a hybrid tracked vehicle(HTV).This method contains two *** high-level establishes a parallel system first,which includes a real powertrain system and an artificial ***,the synthesized data from this parallel system is trained by a bidirectional LSTM *** lower-level determines the optimal EMS using the trained action state function in the model-free reinforcement learning(RL)*** is a fully data-driven and learning-enabled approach that does not depend on any prediction and predefined ***,real vehicle testing is implemented and relevant experiment data is collected and *** results validate that the proposed EMS can achieve considerable energy efficiency improvement by comparing with the conventional RL approach and deep RL.

关键词： Bidirectional long short-term memory(LSTM)network cyber-physical system(CPS) energy management parallel system reinforcement learning(RL)

Phase Structure and Crystallization Behavior of Polyethylene in Its Blends with cis-1,4-Butadiene Rubber

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2015年第3期33卷 386-394页

作者： Hong Yao Jun-teng liu Li-qun Zhang 闫寿科 Beijing Key Laboratory of Membrane Science & State Key Laboratory of Chemical Resource Engineering Beijing University of Chemical Technology

Phase structure and crystallization behavior of polyethylene （PE） in its blends with cis-1,4-butadiene rubber （BR） at different blend ratios and sample preparation conditions were studied. The PE is finely dispersed in the BR matrix. For samples hot pressed at 145 ℃, circular PE microdomains with randomly oriented PE lamellar aggregates were produced. The domain size and number increase with increasing PE content. When the PE content is over 10 wt%, most of the PE domains impinged each other. The separated PE domains are connected by PE stripes with parallel arranged lamellar aggregates. For samples hot pressed at 140 ℃, elongated PE microdomains with oriented PE lamellar aggregates were obtained due to the shear flow. The crystallization of PE in the blends depends on the phase structure. Confined crystallization of PE occurs in small microdomains at relatively low temperature. With the increase of domain size, the crystallization ability of PE increases while the confined crystallization decreases.

关键词： Polyethylene cis-1,4-Butadiene rubber Blend Crystallization Morphology.

Crystallization Behavior of Disproportionately High and Low Molecular Weight PEO Blends

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2014年第9期32卷 1199-1209页

作者： Li Li Jun-teng liu Zhong-jie Ren 闫寿科 Department of Chemistry and Chemical Engineering Heze University Beijing Key Laboratory of Membrane Science & State Key Laboratory of Chemical Resource Engineering Beijing University of Chemical Technology

The crystallization behavior of PEOs with molecular weight of 1 Ok and 200k as well as their blends was studied in details. The results show that the lower molecular weight PEO crystallizes with faster crystallization rate as judged from a shorter time for completing the crystallization. On the other hand, the higher molecular weight PEO crystallizes at relatively higher temperature, indicating an early start of crystallization compared with the lower molecular weight one. The blends of these two PEOs with different blend ratios always cocrystallize during the cooling processes. It is confirmed that mixing of the 10k PEO with the 200k one is in favor of the crystallization of the system. This is not only demonstrated by the early start of the crystallization at higher crystallization temperature, and also a faster crystal growth of the blend with respect to the 200k PEO. The crystallization of the blends at higher temperature is caused by an early start of nucleation and an increment of nucleus density. This may originate from the density fluctuation of the blend and a reduction in energy barrier for nucleation. Moreover, it is found that the crystallinity of the 1 Ok PEO rich blends increases with increasing concentration of the 10k PEO. This is caused by the solvent effect of the 10k PEO toward the 200k PEO. On the other hand, the crystallinity of the 30/70 （10k/200k） PEO blend is decreased a little bit. This may be a balanced result of the improved crystallization of the 200k PEO at the expense of the high crystallization ability of the 1 Ok PEO.

关键词： PEO Molecular weight Blend Crystallization Morphology.