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Search Results: 1 - 10 of 39264 matches for " Hong-kui Pang "
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On the correction equation of the Jacobi-Davidson method
Gang Wu,Hong-kui Pang
Mathematics , 2015,
Abstract: The Jacobi-Davidson method is one of the most popular approaches for iteratively computing a few eigenvalues and their associated eigenvectors of a large matrix. The key of this method is to expand the search subspace via solving the Jacobi-Davidson correction equation, whose coefficient matrix is singular. It is believed long by scholars that the Jacobi-Davidson correction equation is a consistent linear system. In this work, we point out that the correction equation may have a unique solution or have no solution at all, and we derive a computable necessary and sufficient condition for cheaply judging the existence and uniqueness of solution of the correction equation. Furthermore, we consider the difficulty of stagnation that bothers the Jacobi-Davidson method, and verify that if the Jacobi-Davidson method stagnates, then the corresponding Ritz value is a defective eigenvalue of the projection matrix. We provide a computable necessary and sufficient condition for expanding the search subspace successfully. The properties of the Jacobi-Davidson method with preconditioning and some alternative Jacobi-Davidson correction equations are also discussed.
Preconditioning the Restarted and Shifted Block FOM Algorithm for Matrix Exponential Computation
Gang Wu,Hong-kui Pang,Jiang-li Sun
Mathematics , 2014,
Abstract: The approximation of $e^{tA}B$ where $A$ is a large sparse matrix and $B$ a rectangular matrix is the key ingredient in many scientific and engineering computations. A powerful tool to manage the matrix exponential function is to resort to a suitable rational approximation such as the Carath$\acute{\rm e}$odory-Fej$\acute{\rm e}$r approximation, whose core reduces to solve shifted linear systems with multiple right-hand sides. The restarted and shifted block FOM algorithm is a commonly used technique for this problem. However, determining good preconditioners for shifted systems that preserve the original structure is a difficult task. In this paper, we propose a new preconditioner for the restarted and shifted block FOM algorithm. The key is that the absolute values of the poles of the Carath$\acute{\rm e}$odory-Fej$\acute{\rm e}$r approximation are medium sized and can be much smaller than the norm of the matrix in question. The advantages of the proposed strategy are that we can precondition all the shifted linear systems simultaneously, and preserve the original structure of the shifted linear systems after restarting. Theoretical results are provided to show the rationality of our preconditioning strategy. Applications of the new approach to Toeplitz matrix exponential problem are also discussed. Numerical experiments illustrate the superiority of the new algorithm over many state-of-the-art algorithms for matrix exponential.
Zan-Bin Wei,Zhi-Hong Liu,Jian-Liang Ye,Hong-Kui Zhang
Acta Crystallographica Section E , 2010, DOI: 10.1107/s1600536809054944
Abstract: The title compound, C6H5BrClN, is almost planar (r.m.s. deviation = 0.018 ). In the crystal, molecules are linked by intermolecular N—H...N and weak N—H...Br hydrogen bonds, generating sheets.
Study on weak signal detection of small shot in regional scale deep exploration

TANG Jie,WANG Bao-Shan,GE Hong-Kui,CHEN Yong,

地球物理学报 , 2008,
Abstract: 为了研究利用小当量震源进行远距离探测的可能性,通过现场试验进行了研究.野外实验采用1次大当量激发和16次小当量激发,研究结果表明:①有可能利用数十公斤当量的炸药实现200km距离的探测;②在激发条件相同(或相近)时,不同当量的激发波形滤波后存在一定的相似性;③依据人工震源可重复性采用以下的激发组合方式和处理方法能够有效提高信噪比:针对大当量激发与小当量激发波形的相似性,利用大当量激发的波形作模板与小当量激发的波形作相关,可判断台站是否接受到小当量激发的信号并检测其震相到时信息.针对小当量激发波形的相似性,采用小当量多次激发的方式,通过N次根加权叠加方法,能有效提高记录的信噪比和震相识别精度.
Seroprevalence of Toxoplasma gondii infection in slaughtered chickens, ducks, and geese in Shenyang, northeastern China
Yang Na,Mu Ming-Yang,Li Hong-Kui,Long Miao
Parasites & Vectors , 2012, DOI: 10.1186/1756-3305-5-237
Abstract: Background In recent years, investigations of Toxoplasma gondii infection in poultry (chickens, ducks, and geese) have been reported worldwide, including China. However, little is known about the prevalence of T. gondii infection in poultry in northeastern China. Therefore, the present study was performed to determine the prevalence of T. gondii infection in slaughtered chickens, ducks, and geese in Shenyang, northeastern China. Methods In the present study, the seroprevalence of T. gondii in 502 adult chickens, 268 adult ducks, and 128 adult geese was surveyed using the modified agglutination test (MAT). Results The seroprevalences of T. gondii were 5.8%, 7.8%, and 4.7% in chickens, ducks, and geese, respectively. Prevalence was higher in free-range groups (11.2%, 12.3%, and 8.9%) than caged groups (4.7%, 7.5%, and 6.0%), and there was a statistically significant difference only between free-range chickens and caged chickens, but no significant difference was found between free-range ducks, geese and caged ducks, geese. Conclusions The present study shows the prescence of T. gondii infection in slaughtered chickens, ducks, and geese in Shenyang, northeastern China, which suggests that consumption of poultry meat in Shenyang may pose a potential threat to human health and should be given attention.
Survey of the shallow structure on the northeast end of Wenchuan earthquake fault zone by artificial seismic

HUANG Wei-Chuan,GE Hong-Kui,YANG Wei,SONG Li-Li,

地球物理学报 , 2009,
Abstract: Fault zone is sensitive to the post-seismic stress state. We can get the fault healing process by monitoring the fault zone seismic velocity temporal variation. In order to get the shallow structure at the northeast end of Wenchuan earthquake fault zone, we carried out a shallow structure survey by artificial seismic sources. The strong shallow reflector and complex structure produced a complicated wave field and low signal to noise ratio data. Based on separated surface, reflection and refraction waves by f-k transform, we imaged the subsurface structure by refraction common middle point imaging, surface wave velocity inversion, and reflection wave stack imaging. An integrated interpretation was done combing the three imagine data and the shallow faults and velocity distribution were given. This work is helpful to post-seismic emergency monitoring of earthquake fault zone.
Process in precise measurement of seismic velocity variation by correlated detection

LUO Gui-chun,GE Hong-kui,WANG Bao-shan,HU Ping,CHEN Yong,

地球物理学进展 , 2008,
Abstract: To monitor interior stress's variation which is variety by time is an effective approach of seismic physical forecast.This paper reviewed the results concerning the precise measurement of seismic velocity variation and application, discussed the principle and application of the correlated detection.Making use of active seismic source,recording seismic signal by survey disposal,and combining the seismology with communication science,using correlated detection can get rid of disturb and uncertainty factor.The approach can resolve the problem about precise measurement of seismic velocity,and offer method for seismic physical forecast.Our group carried out a field experiment to attain seismic signal by active source,and we received seismic wave by instruments on the same ray.This field experiment lasted on 30 days to detect the velocity variation of p wave,the precision of the velocity variation achieved to 1.00E-05.
Ag-Cu Bimetallic Nanoparticles Prepared by Microemulsion Method as Catalyst for Epoxidation of Styrene
Hong-Kui Wang,Chao-Yong Yi,Li Tian,Wen-Juan Wang,Jian Fang,Ji-Hua Zhao,Wei-Guo Shen
Journal of Nanomaterials , 2012, DOI: 10.1155/2012/453915
Abstract: Ag/Cu bimetallic nanocatalysts supported on reticulate-like γ-alumina were prepared by a microemulsion method using N2H4·H2O as the reducing agent. The catalysts were activated by calcination followed with hydrogen reduction at 873K, and the properties were confirmed using various characterization techniques. Compared with metal oxides particles, Ag-Cu particles exhibited smaller sizes (<5 nm) after calcination in H2 at 873K. XPS results indicated that the binding energies changed with the Ag/Cu ratios, suggesting that increasing the copper content gave both metals a greater tendency to lose electrons. Furthermore, Ag-Cu bimetallic nanoparticles supported on γ-alumina showed better catalytic activity on the epoxidation of styrene as compared with the corresponding monometallic silver or copper. The styrene oxide selectivity could reach 76.6% at Ag/Cu molar ratio of 3/1, while the maximum conversion (up to 94.6%) appeared at Ag/Cu molar ratio of 1/1 because of the maximum interaction between silver and copper.
Study on large volume airgun source characteristics and seismic phase analysis

LIN Jian-Min,WANG Bao-Shan,GE Hong-Kui,TANG Jie,ZHANG Xian-Kang,CHEN Yong,

地球物理学报 , 2008,
Abstract: 利用大容量气枪震源在陆上水库进行地震波激发试验,研究陆上水库环境下激发气枪震源所产生的地震波特征及传播距离. 试验结果表明,大容量气枪震源是具有丰富的10 Hz以下低频信号的低频震源,其激发的地震波具有传播距离远,穿透深度深的特点. 在185 km长的测线上均记录到了气枪信号,成功检测到Pg,Pc,P2,PmP和Pn等多组震相,并在此基础上对地下深地壳结构进行了一维速度结构正演,讨论了该区域壳幔过渡带的低速结构. 气枪震源还具有一般炸药震源不具有的特征,如长期定点重复激发和有效转换S波的优点,是陆上进行长炮检距深穿透地下结构研究的一种优良人工震源.
Rapid algorithm of multi-block motion estimation for H.264

YAN Hong-kui,SHEN Yan-fei,ZHU Zhen-min,XIAO Jian-hua,

计算机应用 , 2008,
Abstract: The full search algorithm of H.264 multi-block motion estimation is highly time-consuming. The paper proposed a new multi-block algorithm by speculating motion estimation based on the characteristic of the image's spatial frequency. The results of the experiments show that our algorithm evidently reduces the complexity of motion estimation computing under the condition of keeping good image quality and high bit rate.
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