检索结果-南通市图书馆

On the Geometry of Broad-Line Regions in BL Lac Objects

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Astronomy and Astrophysics 2006年第6期6卷 649-654页

作者： yun xu Xin-Wu Cao Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 Graduate School of Chinese Academy of Sciences Beijing 100049

The geometry of broad-line regions （BLRs） in active galactic nuclei （AGNs） is still controversial. We use a sample of BL Lac objects, of which the black hole masses Mbh are estimated from their host galaxy absolute magnitude at R-band, MR, by using the empirical relation between MR and black hole mass Mbh. The sizes of the broad-line regions for MglI are derived from the widths of MglI lines and the black hole masses. Compared with the empirical relation between BLR size RBLR and MgII line luminosity LMglI, it is found the BLR sizes in the BL Lac objects derived in this paper are 2-3 orders of magnitude higher. If the BLR geometry of these sources is disklike, then the viewing angle between the axis and the line of sight is in the range of - 2° - 15°, which is consistent with the unification scheme.

关键词： galaxies active BL Lacertae objects general-accretion, accretion disks- black hole physics

Community Governance in Urban Areas from the Perspective of Social Quality Theory

在线全文

学校读者我要写书评

暂无评论

学术界 2015年第4期 257-262页

作者： xu yun School of Law. Nanjing University of Finance and Economics Nanjing Jiangsu 210023

Social quality theory,as a new theory of social development research,is aim ed at studying the overall social situation through a series of social indicators system from which includes four elem ents: socio-econom ic security,social inclusion,social cohesion,social empowerment and participation. Community governance is the basic platform of society governance. The application of social quality approach to study community governance will give us not only a new analytical tool to assess the effect of com munity governance but also decision-making source to formulate community development policy,so as to give a future vision and direction to community development.

关键词：社会发展社区发展质量理论治理城镇指标体系经济安全社会和谐

COMPUTATION OF STRESS INTENsiTY FACTORS BY THE SUB-REGION MIXED FINITE ELEMENT METHOD OF LINES

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Solida sinica 2007年第2期20卷 149-162页

作者： Yuan si xu Yongjun WILLIAMS F W Department of Civil Engineering Tsinghua University Beijing 100084 China Institute of Mechanics Chinese Academy of Sciences Beijing 100080 China Structural Engineering Division Cardiff University Cardiff CF2 3TB UK

Based on the sub-region generalized variationM principle, a sub-region mixed version of the newly-developed semi-analytical ＇finite element method of lines＇（FEMOL） is proposed in this paper for accurate and efficient computation of stress intensity factors （siFs） of two-dimensional notches/cracks. The circular regions surrounding notch/crack tips are taken as the complementary energy region in which a number of leading terms of singular solutions for stresses are used, with the sought siFs being among the unknown coefficients. The rest of the arbitrary domain is taken as the potential energy region in which FEMOL is applied to obtain approximate displacements. A mixed system of ordinary differential equations （ODEs） and algebraic equations is derived via the sub-region generalized variational principle. A singularity removal technique that eliminates the stress parameters from the mixed equation system eventually yields a standard FEMOL ODE system, the solution of which is no longer singular and is simply and efficiently obtained using a standard general-purpose ODE solver. A number of numerical examples, including bi-material notches/cracks in anti-plane and plane elasticity, are given to show the generally excellent performance of the proposed method.

关键词： stress intensity factors finite element method of lines sub-region generalized variational principle ordinary differential equation solver

A DERIVATIVE-HILBERT OPERATOR ACTING FROM LOGARITHMIC BLOCH SPACES TO BERGMAN SPACES

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Scientia 2024年第5期44卷 1916-1930页

作者： Shanli YE yun xu School of Science Zhejiang University of Science and TechnologyHangzhou310023China

Letμbe a positive Borel measure on the interval[0,1).The Hankel matrix■with entriesμn,k=μn+k,whereμn=■[0,1)tndμ(t),induces,formally,the operator■where■is an analytic function *** characterize the measuresμfor which■is bounded(resp.,compact)operator from the logarithmic Bloch space■into the Bergman space■,where 0≤αsical Bloch space■.

关键词： derivative-Hilbert operator logarithmic Bloch space Carleson measure

Hochschild(Co)homology of Galois Coverings of Grassmann Algebras

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica sinica,English Series 2009年第10期25卷 1693-1702页

作者： yun Ge xu Xin TANG School of Mathematics and Computer Science Hubei University Wuhan 430062 P.R. China Department of Mathematics and Computer Science Fayetteville State University Fayetteville NC 28301 USA

Let ∧ be the Z2-Galois covering of the Grassmann algebra A over a field k of characteristic not equal to 2. In this paper, the dimensional formulae of Hochschild homology and cohomology groups of ∧ are calculated explicitly. And the cyclic homology of∧ can also be calculated when the underlying field is of characteristic zero. As a result, we prove that there is an isomorphism from i≥1 HH^i（∧） to i≥1 HH^i（∧）.

关键词： Galois covering Grassmann algebra Hochschild (co)homology minimal projective resolution

Effects of preparation methods on the performance of Cu-Mo-Fe-O_x in the hydrogen production from water

在线全文

学校读者我要写书评

暂无评论

Journal of Natural Gas Chemistry 2011年第5期20卷 553-557页

作者： si Chen Wei Chu xu Liu Dongge Tong College of Chemical Engineering Sichuan University Chengdu 610065 Sichuan China College of Materials and Chemistry ＆ Chemical Engineering Chengdu University of Technology Chengdu 610059 Sichuan China

Two Cu-Mo-Fe-Ox samples, which can store and supply pure hydrogen through repeated redox reaction （Fe3O4＋4H23Fe＋4H2O）, were prepared by co-precipitation （FCM-C） and impregnation （FCM-I） methods, respectively, and the performance of hydrogen production from water were investigated. Compared with the impregnated sample, the co-precipitation sample presented better catalytic activity. The samples were characterized by X-ray diffraction （XRD）, field emission scanning electron microscopy （FE-SEM）, X-ray photoelectron spectroscopy （XPS）, Fourier transform infrared spectroscopy （FT-IR） and temperature-programmed reduction （H2-TPR） techniques. XRD, FE-SEM and XPS results suggest that the FCM-C sample has smaller particle size and higher dispersion of iron oxide than that of FCM-I sample. In addition, FT-IR and H2-TPR analyses indicate that the weak interaction among metal oxides in FCM-C sample may induce facile reduction of active metal and superior property of hydrogen production by decomposing water in success

关键词： catalytic activity hydrogen production redox water decomposition

Operations Research in the Blockchain Technology

在线全文

学校读者我要写书评

暂无评论

Journal of the Operations Research Society of China 2022年第2期10卷 401-422页

作者： xu Wang Ling-yun Wu IAM MADISNCMISAcademy of Mathematics and Systems ScienceChinese Academy of SciencesBeijing 100190China School of Mathematical Sciences University of Chinese Academy of SciencesBeijing 100049China Department of Industrial Engineering Tsinghua UniversityBeijing 100084China

In the past decade,as a decentralized distributed database technology blockchain has developed rapidly at an unprecedented speed and been applied to a wide range of scenarios far beyond cryptocurrencies,for example,insurance,energy,risk management,and Internet of things(IoT).The blockchain technology combines the achievements from cryptography,computer science,economics,and operations research and has increasingly attracted attention from both academia and *** the operations research has been widely adopted in the blockchain technology,there is a lack of comprehensive survey on the operations research in blockchain-related *** order to fill the gap,we analyze the blockchain technology through the perspective of operations research and present a comprehensive review of the operations research problems from the aspects of security and stability,efficiency and performance,and resource *** paper aimed to help the relevant readers in the field of operations research find their own points of interest and conduct in-depth research on the blockchain technology,hoping to promote the rapid development and wider application of the blockchain technology in the near future.

关键词： Blockchain Operations research Security Efficiency Resource allocation

Improvement of mechanical properties, microscopic structures, and antibacterial activity by Ag/ZnO nanocomposite powder for glaze-decorated ceramic

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 Advanced Ceramics 2017年第3期6卷 269-278页

作者： Qian ZHANG Lv si xu Xiaoyan GUO College of Chemical Engineering Huaqiao University Xiamen China

With the increase in the international trade of ceramics, improvement in the physical and chemical properties of ceramics has become a market demand in recent years. The addition of nanomaterials in glaze can simultaneously improve the mechanical and corrosion resistance properties of ceramics. In this study, the effect of nano-sized Ag/ZnO in glazed ceramic was investigated considering the hardness, whiteness, and microscopic structures of the products. Results showed that the Ag/ZnO nanocomposite powder significantly affects the performance of glaze. Glaze hardness reached the highest value (96.6 HV) at the low sintering temperature of 1130 ℃ with the addition of 10% Ag/ZnO nanocomposite powder. Furthermore, the Ag/ZnO nanocomposite powder improved crack resistance and whiteness. Ag as AgO and Ag2O in the glaze was effective for antibacterial activity of ceramic. In addition, the Ag/ZnO nanocomposite powder could also promote the shrinkage of bubbles in the glaze layer and smooth the glaze. These results indicated that the nanoparticles could act as an active center for melting raw materials, which is crucial for ceramic properties.

关键词： Ag/ZnO nanocomposite powder sintering temperature performance microstructure antibacterial activity

Development and multicenter validation of a nomogram for preoperative prediction of lymph node positivity in pancreatic cancer(NeoPangram)

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

Hepatobiliary & Pancreatic Diseases International 2021年第2期20卷 163-172页

作者： Jie Hua xue-Min Chen yun-Jie Chen Bao-Chun Lu Jin xu Wei Wang si Shi Xian-Jun Yu Department of Pancreatic Surgery Fudan University Shanghai Cancer CenterShanghai 200032China Department of Oncology Shanghai Medical College of Fudan UniversityShanghai 200032China Shanghai Pancreatic Cancer Institute Shanghai 200032China Department of Hepatobiliary and Pancreatic Surgery The First People’s Hospital of ChangzhouChangzhou 213004China Department of Minimally Invasive Hepatobiliary and Pancreatic Surgery Ningbo No.2 HospitalNingbo 315010China Department of Hepatobiliary and Pancreatic Surgery Shaoxing People’s HospitalShaoxing 312000China

Background:Neoadjuvant therapy is associated with nodal downstaging and improved oncological outcomes in patients with lymph node(LN)-positive pancreatic *** study aimed to develop and validate a nomogram to preoperatively predict LN-positive ***:A total of 558 patients with resected pancreatic cancer were randomly and equally divided into development and internal validation *** logistic regression analysis was used to construct the *** performance was evaluated by discrimination,calibration,and clinical *** independent multicenter cohort consisting of 250 patients was used for external ***:A four-marker signature was built consisting of carbohydrate antigen 19–9(CA19–9),CA125,CA50,and CA242.A nomogram was constructed to predict LN metastasis using three predictors identified by multivariate analysis:risk score of the four-marker signature,computed tomography-reported LN status,and clinical tumor *** prediction model exhibited good discrimination ability,with C-indexes of 0.806,0.742 and 0.763 for the development,internal validation,and external validation cohorts,*** model also showed good calibration and clinical usefulness.A cut-off value(0.72)for the probability of LN metastasis was determined to separate low-risk and high-risk ***-Meier survival analysis revealed a good agreement of the survival curves between the nomogram-predicted status and the true LN ***:This nomogram enables the identification of pancreatic cancer patients at high risk for LN positivity who may have more advanced disease and thus could potentially benefit from neoadjuvant therapy.

关键词： Lymph node metastasis Pancreatic ductal adenocarcinoma Nomogram Neoadjuvant therapy