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Search Results: 1 - 10 of 127129 matches for " Xiezhang Li "
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The Convergence of Two Algorithms for Compressed Sensing Based Tomography  [PDF]
Xiezhang Li, Jiehua Zhu
Advances in Computed Tomography (ACT) , 2012, DOI: 10.4236/act.2012.13007
Abstract: The constrained total variation minimization has been developed successfully for image reconstruction in computed tomography. In this paper, the block component averaging and diagonally-relaxed orthogonal projection methods are proposed to incorporate with the total variation minimization in the compressed sensing framework. The convergence of the algorithms under a certain condition is derived. Examples are given to illustrate their convergence behavior and noise performance.
A Reweighted Total Variation Algorithm with the Alternating Direction Method for Computed Tomography  [PDF]
Xiezhang Li, Jiehua Zhu
Advances in Computed Tomography (ACT) , 2019, DOI: 10.4236/act.2019.81001
Abstract: A variety of alternating direction methods have been proposed for solving a class of optimization problems. The applications in computed tomography (CT) perform well in image reconstruction. The reweighted schemes were applied in l1-norm and total variation minimization for signal and image recovery to improve the convergence of algorithms. In this paper, we present a reweighted total variation algorithm using the alternating direction method (ADM) for image reconstruction in CT. The numerical experiments for ADM demonstrate that adding reweighted strategy reduces the computation time effectively and improves the quality of reconstructed images as well.
A note on computing the generalized inverse of a matrix
Xiezhang Li,Yimin Wei
International Journal of Mathematics and Mathematical Sciences , 2002, DOI: 10.1155/s0161171202013169
Abstract: The generalized inverse A T,S (2) of a matrix A is a {2}-inverse of A with the prescribed range T and null space S. A representation for the generalized inverse A T,S (2) has been recently developed with the condition σ (GA| T)⊂(0,∞), where G is a matrix with R(G)=T andN(G)=S. In this note, we remove the above condition. Three types of iterative methods for A T,S (2) are presented if σ(GA|T) is a subset of the open right half-plane and they are extensions of existing computational procedures of A T,S (2), including special cases such as the weighted Moore-Penrose inverse A M,N † and the Drazin inverse AD. Numerical examples are given to illustrate our results.
Numerical Studies of the Generalized l1Greedy Algorithm for Sparse Signals  [PDF]
Fangjun Arroyo, Edward Arroyo, Xiezhang Li, Jiehua Zhu, Jiehua Zhu
Advances in Computed Tomography (ACT) , 2013, DOI: 10.4236/act.2013.24023
Abstract:

The generalized l1 greedy algorithm was recently introduced and used to reconstruct medical images in computerized tomography in the compressed sensing framework via total variation minimization. Experimental results showed that this algorithm is superior to the reweighted l1-minimization and l1 greedy algorithms in reconstructing these medical images. In this paper the effectiveness of the generalized l1 greedy algorithm in finding random sparse signals from underdetermined linear systems is investigated. A series of numerical experiments demonstrate that the generalized l1 greedy algorithm is superior to the reweighted l1-minimization and l1 greedy algorithms in the successful recovery of randomly generated Gaussian sparse signals from data generated by Gaussian random matrices. In particular, the generalized l1 greedy algorithm performs extraordinarily well in recovering random sparse signals with nonzero small entries. The stability of the generalized l1 greedy algorithm with respect to its parameters and the impact of noise on the recovery of Gaussian sparse signals are also studied.

Beneficial Experience from Teaching and Education to Research and Development  [PDF]
Li Li
Creative Education (CE) , 2012, DOI: 10.4236/ce.2012.37B039
Abstract:

Teaching and Education (T&E) constitute the most important activity in knowledge transfer from generation to generation. This can explain why government organizations consider the training of highly qualified personnel as one of the most important criteria in the selection of research and development (R&D) grant applications. A university professor should thus not only play the role of researcher, but also that of teacher. T&E and R&D combine to form an inseparable relationship for university professors. By shooting for excellence in T&E, we could get a new perception of a familiar field or initiate a brand new field altogether, which would in turn enhance our research. The quest for excellence in R&D leads to deeper and better understanding of materials taught, and progress in R&D enriches our T&E endeavors. Here, the author shares a beneficial experience from T&E to R&D.

A Causality Analysis of Coal Consumption and Economic Growth for China and India  [PDF]
Jinke Li, Zhongxue Li
Natural Resources (NR) , 2011, DOI: 10.4236/nr.2011.21007
Abstract: China and India are the two countries with the strongest economic growth in the world. Meanwhile they consume much of the global coal to fuel their economic development. With coal burning as a major factor contributing to global greenhouse gas emissions, China and India are confronted with a dilemma of economic growth and environment protection. Will coal consumption reduction cause economic shocks? Is there a causal relationship between coal consumption and economic growth in China and India? In this paper Granger causality tests were used to examine the relationship between coal consumption and GDP in China and India, using data for the period from 1965 to 2006. It was found that a unidirectional causality from GDP to coal consumption existed in China while a unidirectional causality from coal consumption to GDP did in India. Therefore, developing cleaner and more efficient technologies is essential to reduce their CO2 emissions to reach sustainable development.
An Investigation and Analysis of Information Overload in Manager's Work  [PDF]
Tao Li, Min Li
iBusiness (IB) , 2011, DOI: 10.4236/ib.2011.31008
Abstract: The problem of information overload in management field has been receiving increasing attention, while there are less empirical researches now. This paper proposes a conceptual model and some operational variables, in which information overload is as an intervening variable between the factors of causes and impacts. An investigation and analysis has been conducted from a selected sample of managers. This research suggests that work efficiency and work quality are both not strongly connected with information overload. We also find that the main causes of information overload are the work interruption and work time pressure but the amount of information.
Selection Advantage Pattern of International Sci-Tech Cooperation and Empirical Analysis  [PDF]
Li Li, Bin Yu
Journal of Service Science and Management (JSSM) , 2011, DOI: 10.4236/jssm.2011.41006
Abstract: Traditional international sci-tech cooperation theories mainly focus on the ability and advantage owned by cooperative parties, and according to which to guide the direction of international science and technology cooperation. Based on the integration of traditional theories of international science and technology cooperation and concrete practice, this paper proposes the selection advantage pattern and matching mechanism, which comprehensively take cooperator advantages, specification of project and change in circumstance into account and will play a guiding role in terms of determining the key country or region with which to prior carry out international science and technology cooperation. This paper also gives an analysis of the current status of industry development in Guangdong province and the research upon competitiveness evaluation of the world's related leading technology, puts forward corresponding countermeasures and suggestions on the science and technology cooperation patterns and approaches in terms of technological level and resources of Guangdong province.
Soil reinforcement by a root system and its effects on sediment yield in response to concentrated flow in the loess plateau  [PDF]
Peng Li, Zhanbin Li
Agricultural Sciences (AS) , 2011, DOI: 10.4236/as.2011.22013
Abstract: The importance of roots in soil conservation has long been underestimated due to a lack of sys-tematic studies conducted to evaluate root dis-tribution patterns and their effects on soil ero-sion. Current knowledge regarding root mor-phology and its impact on soil erosion by water is limited; therefore, detailed analysis of the role that root systems play in controlling soil ero-sion is needed. In this study, stratified runoff scouring at different soil depths in the field was conducted in a grassland area. The results in-dicated that both root biomass and soil wa-ter-stable aggregates decreased as soil depth increased at all three sites, while there was al-most no change in soil bulk density at 1.3g/cm3. Sediment yields under different runoff dis-charge at different sites showed similar trends, and the sediment yield increased as the soil depth increased at all three sites. Further analysis revealed that close relationships ex-isted between root biomass and the amount of water-stable aggregates and soil organic matter content, and that these factors greatly influ-enced soil erosion. Based on the data generated by the experiment, equations describing the relationship between sediment production at different soil depths and root biomass were determined.
Second-Order Volition and Conflict between Desires  [PDF]
Hengxi Li, Hengwei Li
Open Journal of Philosophy (OJPP) , 2012, DOI: 10.4236/ojpp.2012.21004
Abstract: In Freedom of the Will and the Concept of a Person, Harry Frankfurt put forward a theory that what is essential to be a person is second-order volition. The notion of second-order volition can be used as a key conceptual tool in understanding the conflict between desires. By means of the notion, this paper argues that the conflict between desires in our minds lies in the conflict between second-order volitions, other than the conflict between first-order desires. Based on this claim, this paper suggests that, due to the misunderstanding of the nature of the conflict between desires, the analysis of unwilling addict and wanton addict given by Frankfurt is thus wrong, and in his follow-up articles he made wrong description of the phenomenon concerning the conflict between desires.
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