检索结果-南通市图书馆

Frontier studies on natural products:moving toward paradigm shifts

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2023年第4期66卷 928-942页

作者： Jin-Xin Zhao jian-min Yue State Key Laboratory of Drug Research Shanghai Institute of Materia MedicaChinese Academy of SciencesShanghai 201203China Shandong Laboratory of Yantai Drug Discovery Bohai Rim Advanced Research Institute for Drug DiscoveryYantai 264117China

1 Introduction Natural products(NPs)historically serve as a valuable and productive source of bioactive compounds for drug *** discovery of a range of alkaloids in the early1800s,including strychnine,morphine,etc.,her... 详细信息

关键词： alkaloids moving compounds

Observational signatures of close binaries of supermassive black holes in active galactic nuclei

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2020年第10期20卷 191-206页

作者： jian-min Wang Yan-Rong Li Key Laboratory of Particle Astrophysics Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China

Inspired by the General Relativity for many decades,experimental physicists and astronomers have a solid dream to detect gravitational waves(GWs)from mergers of black holes,which came true until the excellent performance of the Laser Interferometer Gravitational-Wave Observatory(LIGO)at hundreds ***-Hz GWs are expected to be radiated by close-binaries of supermassive black holes(CB-SMBHs;defined as those with separations less than^0.1 pc)formed during galaxy mergers and detected through the Pulsar Timing Array(PTA)*** of the writing,there remains no nano-Hz GWs *** for CB-SMBHs is also observationally elusive though there exist a number of possible *** this review,we focus on observational signatures of CB-SMBHs from theoretic expectations,simulations and *** signatures appear in energy distributions of multiwavelength continuum,long term variations of continuum,jet morphology,reverberation delay maps and spectroastrometry of broad emission lines,AGN type transitions between type-1 and type-2(changing-look),and gaseous dynamics of circumbinary disks,*** hundred-Hz GWs from stellar mass black hole binaries,the waveform chirping of nano-Hz GWs is too slow to detect in a reasonable human *** have to resort to electromagnetic observations to measure orbital parameters of CB-SMBHs to test nano-Hz GW *** mapping is a powerful tool for probing kinematics and geometry of ionized gas in the gravitational well of SMBHs(single or binary)and therefore provides a potential way to determine orbital parameters of *** particular,a combination of reverberation mapping with spectroastrometry(realized at the Very Large Telescope Interferometer)will further reinforce this *** Atacama Large Millimeter/submillimeter Array(ALMA)and the forthcoming Square Kilometre Array(SKA)are suggested to reveal dynamics of circumbinary disks through molecular emission lines.

关键词： galaxies:active quasars:supermassive black holes gravitational waves

15th Anniversary of Journal of Integrative Agriculture(JIA)

在线全文

学校读者我要写书评

暂无评论

Journal of Integrative Agriculture 2017年第12期16卷 2655-2656页

作者： WAN jian-min JIA Chinese Academy of Agricultural Sciences Chinese Academy of Engineering

The year 2017 marks the 15th anniversary of Joumal of Integrative Agriculture （JIA）, an official journal of the Chinese Academy of Agricultural Sciences （CAAS）. JIA has experi- enced a successful journey during the past 15 years. The 21 st century began with great challenges in global climate change, food safety, resource scarcity, and other key issues which are closely related to the agriculture sciences. Effec- tive solutions for agricultural problems require an internation- al exchange of experience via platforms such as academic journals. To contribute to these forums, the agriculture community in China sought to establish a scholarly journal published in English. In Jan. 2002, an agriculture journal in English was launched by CAAS and the first issue of the journal Agricultural Sciences in China was published. From the start, it has emphasized global concerns in multi-disci- plinary agricultural fields of crop science, horticulture, plant protection, animal science, veterinary medicine, agro-eco- system and environment science, food science and etc. And it is a peer-reviewed international journal published monthly in English. The first Editor-in-Chief was ZHAI Huqu, the president of CAAS at that time.

关键词： 15th Anniversary of Journal of Integrative Agriculture JIA

A preliminary study on photogrammetry for the FAST main reflector measurement

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2021年第7期21卷 23-30页

作者： Wei-min Li Liu-jian Zhou Department of Precision Machinery and Precision Instrumentation University of Science and Technology of ChinaHefei 230026China

The Five-hundred-meter Aperture Spherical radio Telescope(FAST) is the largest single-dish radio telescope in the world. In this paper, we apply photogrammetry to measure local area surface accuracy of the FAST main reflector. Contrast with the existing photogrammetric methods that need to stick the cooperation target on the panel. In this paper, we directly detect nodes according to their natural feature. Analyzing the FAST reflector composition, we propose a two-step Hough transform method for node detection. Due to the high similarity of the neighboring area around nodes, it is hard to match two images by the feature matching method. Therefore, we apply the nodes combination approach to obtain the homography matrix between two photos for nodes matching. After nodes detection and matching,triangulation and bundle adjustment algorithms are adopted for 3 D reconstruction. During the experiment,the adjusted node position deform a local area of the FAST main reflector into a spherical cap with a radius of 300 m. The experimental result shows that the measurement accuracy of the sphere with a radius of 300 m is 12.299 mm, indicating that it is feasible to apply photogrammetry for the FAST main reflector measurement.

关键词： FAST photogrammetry node detection bundle adjustment 3D reconstruction

Glomerular podocyte dysfunction in inherited renal tubular disease

在线全文

学校读者我要写书评

暂无评论

World Journal of Pediatrics 2021年第3期17卷 227-233页

作者： Li-min Huang jian-Hua Mao Department of Nephrology National Clinical Research Center for Child HealthThe Children’s HospitalZhejiang University School of Medicine#57 Zhugan LaneHangzhou 310006China

Background Hereditary renal tubular disease can cause hypercalciuria,acid-base imbalance,hypokalemia,hypomagnesemia,rickets,kidney stones,*** these diseases are not diagnosed or treated in time,they can cause kidney damage and electrolyte disturbances,which can be detrimental to the maturation and development of the *** involvement in renal tubular disease patients has only been considered *** We screened 71 papers(including experimental research,clinical research,etc.)about Dent's disease,Gitelman syndrome,and cystinosis from PubMed,and made *** Glomerular disease was initially underestimated among the clinical signs of renal tubular disease or was treated merely as a consequence of the tubular *** tubular diseases affect glomerular podocytes through certain mechanisms resulting in functional damage,morphological changes,and glomerular *** This article focuses on the progress of changes in glomerular podocyte function in Dent disease,Gitelman syndrome,and cystinosis for the purposes of facilitating clinically accurate diagnosis and scientific treatment and improving prognosis.

关键词： Cystinosis Dent disease Gitelman syndrome Podocyte Renal tubule disease

Optimum weighting-coefficient-pair in inter-carrier interference self-cancellation scheme of OFDM system

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

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第12期9卷 1676-1684页

作者： min-jian ZHAO Di ZHANG Bin CAI Department of Information Science and Electronic Engineering Zhejiang University Hangzhou 310027 China

As one of the most important components of the wideband wireless access technique, orthogonal frequency division multiplexing （OFDM） has a high usage rate of spectrum and combats inter-symbol interference （ISI） in multi-path fading channel. However, when there are frequency offsets during the signal transmission, the inter-carrier interference （ICI） is introduced, which significantly degrades the performance. The existing ICI self-cancellation schemes such as PCC-OFDM are not optimum to minimize the interference considering both noise and ICI. In this paper, a new metric named S1NR （signal-to-interference- and-noise ratio） is proposed. We discuss the optimization issue when a constant frequency offset exists and in time-varying channels. The optimum weighting-coefficient-pair （OWCP） is obtained, which maximizes SINR theoretically through the alternant iteration algorithm. Simulations show that the performance of OWCP-OFDM is better than that of PCC-OFDM, especially when the frequency offset is large. Although the ICI self-cancellation scheme suffers bandwidth inefficiency, from the simulation results we can also see that the performance of OWCP-OFDM is much better than that of the standard OFDM systems with the same bandwidth efficiency when a frequency offset exists. Moreover, since the redundant modulation provides the capability to suppress ICI as well as a receiving SNR gain, it can be considered as exchanging the bandwidth for SNR.

关键词： Orthogonal frequency division multiplexing (OFDM) Frequency offset Inter-carrier interference (ICI) Polynomial cancellation coding (PCC) Optimum weighting-coefficient-pair (OWCP)

Effects of dark matter on shadows and rings of Brane-World black holes illuminated by various accretions

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9期65卷 27-43页

作者： Xiao-Xiong zeng Ke-jian He Guo-Ping Li State Key Laboratory of Mountain Bridge and Tunnel Engineering Chongqing Jiaotong UniversityChongqing 400074China Department of Mechanics Chongqing Jiaotong UniversityChongqing 400074China College of Physics Chongqing UniversityChongqing 401331China Physics and Space College China West Normal UniversityNanchong 637000China

In this study, by taking the accretions into account, the observed shadows and rings cast by the Brane-World black hole were numerically investigated when the observer was located at the cosmological horizon. The results showed that the radius rpof the photon sphere increased with the cosmological parameter α and dark matter parameter β, while the impact parameter bpdecreased with α and increased with β. For thin disk accretion, the total observed intensity is mainly composed of direct ***, the lensing ring and photon ring have only small and negligible contributions, respectively. We also found that shadows and rings exhibit different and exciting features when the disk is located at different positions. For static and infalling spherical accretions, it is evident that the size of shadows is always the same for both accretions. This implies that shadows are only related to space-time geometry in this case. The luminosity of the shadow and photon sphere is closely associated with the Doppler effect and the emissivity per unit volume j(νe). In addition, the influence of dark matter and cosmological constant on the observed intensity of shadows and rings is carefully emphasized throughout this paper. Finally, we obtained the burring images of shadows and rings using the nominal resolution of the event horizon telescope. We also studied the upper limits of the X-clod dark matter parameter β using the data of the shadow of M87.

关键词： dark matter the accretion black hole shadow lensing and photon rings

Distributed Momentum-Based Frank-Wolfe Algorithm for Stochastic Optimization

在线全文

学校读者我要写书评

暂无评论

IEEE/CAA Journal of Automatica Sinica 2023年第3期10卷 685-699页

作者： Jie Hou Xianlin zeng Gang Wang jian Sun Jie Chen National Key Laboratory of Autonomous Intelligent Unmanned Systems School of AutomationBeijing Institute of TechnologyBeijing 100081China National Key Laboratory of Autonomous Intelligent Unmanned Systems School of AutomationBeijing Institute of TechnologyBeijing 100081 Beijing Institute of Technology Chongqing Innovation Center Chongqing 401120China School of Electronic and Information Engineering Tongji UniversityShanghai 200082and also with the National Key Laboratory of Autonomous Intelligent Unmanned Systemsthe School of AutomationBeijing Institute of TechnologyBeijing 100081China IEEE

This paper considers distributed stochastic optimization,in which a number of agents cooperate to optimize a global objective function through local computations and information exchanges with neighbors over a *** optimization problems are usually tackled by variants of projected stochastic gradient ***,projecting a point onto a feasible set is often *** Frank-Wolfe(FW)method has well-documented merits in handling convex constraints,but existing stochastic FW algorithms are basically developed for centralized *** this context,the present work puts forth a distributed stochastic Frank-Wolfe solver,by judiciously combining Nesterov's momentum and gradient tracking techniques for stochastic convex and nonconvex optimization over *** is shown that the convergence rate of the proposed algorithm is O(k^(-1/2))for convex optimization,and O(1/log_(2)(k))for nonconvex *** efficacy of the algorithm is demonstrated by numerical simulations against a number of competing alternatives.

关键词： Distributed optimization Frank-Wolfe(FW)algorithms momentum-based method stochastic optimization

Dynamic Spectrum Access Based on Prior Knowledge Enabled Reinforcement Learning with Double Actions in Complex Electromagnetic Environment

在线全文

学校读者我要写书评

暂无评论

China Communications 2022年第7期19卷 13-24页

作者： Linghui zeng Fuqiang Yao jianzhao Zhang min Jia The Sixty-third Research Institute National University of Defense TechnologyNanjing 210007China Communication Research Center School of Electronics and Information EngineeringHarbin Institute of TechnologyHarbin 150080China

The spectrum access problem of cognitive users in the fast-changing dynamic interference spectrum environment is addressed in this *** prior knowledge for the dynamic spectrum access is modeled and a reliability quantification scheme is presented to guide the use of the prior knowledge in the learning ***,a spectrum access scheme based on the prior knowledge enabled RL(PKRL)is designed,which effectively improved the learning efficiency and provided a solution for users to better adapt to the fast-changing and high-density electromagnetic *** with the existing methods,the proposed algorithm can adjust the access channel online according to historical information and improve the efficiency of the algorithm to obtain the optimal access *** results show that,the convergence speed of the learning is improved by about 66%with the invariant average throughput.

关键词： prior knowledge reinforcement learning anti-jamming communication spectrum access