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1
Problèmes de clique maximum avec applications à la coloration de graphe
Tez

Tez
Open Access
Kaynak :
The Dart-Europe
Dergi:
Université d'Angers
Yazar(lar) :
Qinghua Wu
Yıl :
2013
Qinghua Wu
Yayıncı Web Sitesi
Kaydet Alıntıla
Sınıflandırma :
2
The Approximate Solution of Fredholm Integral Equations with Oscillatory Trigonometric Kernels
Dergi Makalesi

Dergi Makalesi
Open Access
Kaynak 1:
Directory of Open Access Journals (DOAJ)
Kaynak 2:
Hindawi Limited
Dergi:
Journal of Applied Mathematics
Yazar(lar) :
Qinghua Wu
Yıl :
2014
Qinghua Wu
Piri Tam Metin Bulucu
Kaydet Alıntıla
A method for approximating the solution of weakly singular Fredholm integral equation of the second kind with highly oscillatory trigonometric kernel is presented. The unknown function is approximated by expansion of Chebychev polynomial and the coefficients are determinated by classical collocation method. Due to the highly oscillatory kernels of integral equation, the discretised collocation equation will give rise to the computation of oscillatory integrals. These integrals are calculated by using recursion formula derived from the fundamental recurrence relation of Chebyshev polynomial. The effectiveness and accuracy of the proposed method are tested by numerical examples.
DOI : 10.1155/2014/172327
Cilt: 2014
Sınıflandırma :
3
On graded meshes for weakly singular Volterra integral equations with oscillatory trigonometric kernels
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Journal of Computational and Applied Mathematics
Yayıncı:
Elsevier
Yazar(lar) :
Qinghua Wu
Yıl :
2014
Qinghua Wu
Yayıncı Web Sitesi
Tam Metin
Kaydet Alıntıla
We compare the collocation methods on graded meshes with that on uniform meshes for the solution of the weakly singular Volterra integral equation of the second kind with oscillatory trigonometric kernels. Due to, in general, unbounded derivatives at the left endpoint of the interval of integration, we should approximate the solution of the integral equation by collocation methods on graded meshes. However, we show that this non-smooth behavior of the solution has little effect on the approximate solution when the kernels of integral equation are highly oscillatory. Numerical examples are given to confirm the proposed results.
DOI : 10.1016/j.cam.2013.12.039
Anahtar Kelimeler : 65D32, 65D30, Volterra integral equation, Collocation methods, Weak singularity, Graded meshes, Oscillatory kernel, Filon-type method
ISSN: 0377-0427
Cilt: 263
Sayfa: 370-376
Sınıflandırma :
4
Self-assembly of poly(ethylene oxide)-b-polystyrene-b-poly(acrylic acid) triblock copolymers in solution
Tez

Tez
Open Access
Kaynak :
McGill University
Dergi:
McGill University
Yayıncı:
McGill University
Yazar(lar) :
Qinghua Wu
Konu :
Chemistry, Polymer.
Yıl :
2005
Qinghua Wu
Yayıncı Web Sitesi
Tam Metin
Kaydet Alıntıla
The self-assembly behavior of poly(ethylene oxide)-b-polystyrene- b-poly(acrylic acid) (PEO-b-PS-b-PAA) triblock copolymers in solution is the focus of this thesis. The triblock copolymers were synthesized by atom transfer radical polymerization (ATRP). The compositions of the block copolymers were determined by 1H NMR. The synthesized block copolymers have relatively low polydispersity indexes (PDI < 1.3) as proved by GPC. The influence of several factors on the ATRP of styrene or t-BA, such as temperature, catalyst and polymerization time, was also explored. The effects of several parameters on the self-assembly behavior of this triblock copolymer were investigated, including the nature and composition of the common solvent, PAA block length, pH, water content, and initial copolymer concentration. Multiple morphologies, such as spheres, vesicles, lamellae and rods have been prepared by varying the above parameters. In particular, vesicles with either PEO or PAA outside have been successfully prepared in dioxane/water. These vesicles may serve as carriers for potential encapsulation applications. The average size and corona chain composition of the triblock copolymer vesicles can be controlled by varying factors such as the PAA block length and pH. The polymer chains may have different arrangements in the vesicle wall, resulting in different corona chain compositions. The vesicles with PAA outside are stable in water, while the vesicles with PEO outside tend to flocculate. Nevertheless, the sediment can be redispersed under vigorous stirring.
5
A Simpler GMRES Method for Oscillatory Integrals with Irregular Oscillations
Dergi Makalesi

Dergi Makalesi
Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Dergi:
Advances in Mathematical Physics
Yazar(lar) :
Qinghua Wu , Meiying Xiang
Yıl :
2015
Qinghua Wu
Yayıncı Web Sitesi
 Piri Tam Metin Bulucu
Kaydet Alıntıla
A simpler GMRES method for computing oscillatory integral is presented. Theoretical analysis shows that this method is mathematically equivalent to the GMRES method proposed by Olver (2009). Moreover, the simpler GMRES does not require upper Hessenberg matrix factorization, which leads to much simpler program and requires less work. Numerical experiments are conducted to illustrate the performance of the new method and show that in some cases the simpler GMRES method could achieve higher accuracy than GMRES.
DOI : 10.1155/2015/103074
Cilt: 2015
Sınıflandırma :
6
THE CLINICAL AND ECHOCARDIOGRAPHIC ANALYSIS OF NONCOMPACTION CARDIOMYOPATHY IN MISDIAGNOSIS AND MISSED DIAGNOSIS
Dergi Makalesi

Dergi Makalesi
Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Dergi:
Российский кардиологический журнал
Yazar(lar) :
Yanna Liu , Qinghua Wu
Yıl :
2014
Qinghua Wu
Yayıncı Web Sitesi
 Piri Tam Metin Bulucu
Kaydet Alıntıla
Aim. Echocardiography has become the main mean in detection of noncompaction cardiomyopathy (NCC). However, misdiagnosis and missed diagnosis were common. The aim of this paper was to analyze the misdiagnosis and missed diagnosis of NCC, improve the diagnostic accuracy of this disease.Material and methods. We retrospectively analyzed the data of 56 subjects who had been clinically diagnosed with NCC in our institution, which included patients’ total echocardiographic data since the disease onset. Echocardiographic data and cardiac magnetic resonance (CMR) data were compared with each other.Results. 17 of the total subjects had been diagnosed with NCC after the first echocardiography at our institution. 39 subjects had not been diagnosed correctly until several times checking of echocardiography. 28 of them had been misdiagnosed as dilated cardiomyopathy (DCM) in local hospitals. All but 2 subjects were inconsistent between echocardiography measurement and CMR. The ratio of N/C was 2,63±0,49 by CMR, and 2,55±0,43 by echocardiography.Conclusion. Echocardiography can be the first choice of NCC assessment for its advantages of being non-radiative, real-time, economic and characteristic. When the echocardiographic image is not typical in the early stage of NCC, a combination with CMR is necessary.
DOI : 10.15829/1560-4071-2014-7-eng-34-41
Anahtar Kelimeler : noncompaction cardiomyopathy, echocardiography, cardiac magnetic resonance
Sayı: 7-eng
Sayfa: 34 - 41
Sınıflandırma :
7
Efficient BBFM-collocation for weakly singular oscillatory Volterra integral equations of the second kind
Dergi Makalesi

Dergi Makalesi
Kaynak :
Taylor and Francis
Dergi:
International Journal of Computer Mathematics
Yayıncı:
Informa UK Limited
Yazar(lar) :
Qinghua Wu , Weiwen Hou
Yıl :
2021
Qinghua Wu
Yayıncı Web Sitesi
Tam Metin
Kaydet Alıntıla
We present a fast and accurate numerical scheme for approximating weakly singular oscillatory Volterra integral equations (VIEs) of the second kind. The main idea is the combination of the black-box fast multipole method (FMM) and collocation methods that leads to a significant speed-up in CPU time for a given tolerance. The weakly singular oscillatory integrals, which arise from the evaluation of integral equations, are calculated using Clenshaw-Curtis Filon methods. Because the kernel function is approximated by a Chebyshev interpolation scheme, it is very useful for the kernel which is known analytically but is quite complicated. Compared with the method and the error estimates reported previously, the new scheme is suitable for more general kernel function and provide sharper estimates. The efficiency and accuracy of the new method are verified by numerical examples.
DOI : 10.1080/00207160.2021.1942460
Anahtar Kelimeler : Volterra integral equation, weakly singular oscillatory, Chebyshev expansion, black-box FMM, collocation methods, 65D32, 65D30
ISSN: 0020-7160
Sayfa: 1-19
8
Carbon emission reduction and product collection decisions in the closed-loop supply chain with cap-and-trade regulation
Dergi Makalesi

Dergi Makalesi
Kaynak :
Taylor and Francis
Dergi:
International Journal of Production Research
Yayıncı:
Informa UK Limited
Yazar(lar) :
Zhongrui Wang , Qinghua Wu
Konu :
Management Science and Operations Research, Strategy and Management, Industrial and Manufacturing Engineering
Yıl :
2020
Qinghua Wu
Yayıncı Web Sitesi
Tam Metin
Kaydet Alıntıla
Governments’ emission policies and consumers’ increasing environmental awareness have brought pressure on manufacturers. Particularly, governments are requiring manufacturers to manage their end-of-life products. Hence, the supply chain should consider environmental and economic performance comprehensively. This study considers strategies on carbon emission reduction and used product collection on the basis of cap-and-trade regulation in the closed-loop supply chain. Decentralised and centralised decision models are formulated, and the equilibrium solutions of these models are then derived. The impact of used product collection on carbon emission reduction is further analysed. Findings show that when the parameters meet a certain condition, the scenario where the manufacturer leads the collection is optimal for carbon emission reduction, used product collection, and profit generation; otherwise, the supply chain will select the retailer to collect used products. Under the special collection model with a fixed return rate, used product collection is beneficial for reducing carbon emissions. High initial carbon emissions are inconducive to carbon emission reduction and used product collection. Moreover, the government can affect supply chain decisions by regulating and controlling carbon trading prices.
DOI : 10.1080/00207543.2020.1762943
Anahtar Kelimeler : supply chain management, carbon emission reduction, cap-and-trade regulation, closed-loop supply chain, product collection
ISSN: 0020-7543
Sayfa: 1-25
9
A Review on the Synthesis and Bioactivity Aspects of Beauvericin, a Fusarium Mycotoxin
Dergi Makalesi

Dergi Makalesi
Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Dergi:
Frontiers in Pharmacology
Yazar(lar) :
Qinghua Wu , Qinghua Wu , Jiri Patocka , Jiri Patocka , Eugenie Nepovimova , Kamil Kuca
Yıl :
2018
Qinghua Wu Qinghua Wu
Yayıncı Web Sitesi
 Piri Tam Metin Bulucu
Kaydet Alıntıla
Beauvericin (BEA) is an emerging Fusarium mycotoxin that contaminates food and feeds globally. BEA biosynthesis is rapidly catalyzed by BEA synthetase through a nonribosomal, thiol-templated mechanism. This mycotoxin has cytotoxicity and is capable of increasing oxidative stress to induce cell apoptosis. Recently, large evidence further shows that this mycotoxin has a variety of biological activities and is being considered a potential candidate for medicinal and pesticide research. It is noteworthy that BEA is a potential anticancer agent since it can increase the intracellular Ca2+ levels and induce the cancer cell death through oxidative stress and apoptosis. BEA has exhibited effective antibacterial activities against both pathogenic Gram-positive and Gram-negative bacteria. Importantly, BEA exhibits an effective capacity to inhibit the human immunodeficiency virus type-1 integrase. Moreover, BEA can simultaneously target drug resistance and morphogenesis which provides a promising strategy to combat life-threatening fungal infections. Thus, in this review, the synthesis and the biological activities of BEA, as well as, the underlying mechanisms, are fully analyzed. The risk assessment of BEA in food and feed are also discussed. We hope this review will help to further understand the biological activities of BEA and cast some new light on drug discovery.
DOI : 10.3389/fphar.2018.01338
Anahtar Kelimeler : beauvericin, biosynthesis, bioactivity, anticancer, Fusarium
ISSN: 1663-9812
Cilt: 9
Sınıflandırma :
10
The factorization method for the inverse scattering problem from thin dielectric objects
Dergi Makalesi

Dergi Makalesi
Kaynak :
Springer Link
Dergi:
Computational and Applied Mathematics
Yazar(lar) :
Qinghua Wu , Guozheng Yan
Konu :
Applied Mathematics, Computational Mathematics
Yıl :
2015
Qinghua Wu
Yayıncı Web Sitesi
Tam Metin
Kaydet Alıntıla
We consider the inverse scattering problem of determining the shape and position of a thin dielectric infinite cylinder having an open arc as cross section from the knowledge of the related far field data. The mathematical analysis is given to prove the validity of the factorization method for reconstructing the shape of the arc. Some numerical examples are proposed to show the efficaciousness of the algorithms.
DOI : 10.1007/s40314-015-0285-5
Anahtar Kelimeler : Inverse scattering problem, Factorization method, Open arc, Primary 35C15, 35Q65, Secondary 78A45
ISSN: 0101-8205 1807-0302
Sayı: 2
Cilt: 36
Sayfa: 1099-1112
11
Existence results for nonlinear Schrödinger systems with electromagnetic fields in ℝN
Dergi Makalesi

Dergi Makalesi
Kaynak :
Taylor and Francis
Dergi:
Complex Variables and Elliptic Equations
Yayıncı:
Informa UK Limited
Yazar(lar) :
Dengfeng Lü , Qinghua Wu
Yıl :
2012
Qinghua Wu
Yayıncı Web Sitesi
Tam Metin
Kaydet Alıntıla
In this article, we deal with the following Schrödinger systems in ℝ N : where λ > 0 is a parameter, α > 1, β > 1, α + β < 2* and , for N ≥ 3, 2* = +∞, for N = 1, 2 is the Sobolev critical exponent. By exploiting the Nehari manifold method and the concentration compactness principle, we establish the existence of ground-state solutions when the parameter λ is sufficiently large.
DOI : 10.1080/17476933.2012.731399
Anahtar Kelimeler : Schrödinger systems, electromagnetic fields, variational method, ground-state solutions, 35J50, 35J10, 35Q60
ISSN: 1747-6933
Sayı: 2
Cilt: 59
Sayfa: 247-261
12
Health: a dream from reality to the future
Dergi Makalesi

Dergi Makalesi
Kaynak :
Springer Link
Dergi:
Frontiers of Medicine
Yazar(lar) :
Chunsong Hu , Qinghua Wu
Konu :
General Medicine
Yıl :
2016
Qinghua Wu
Yayıncı Web Sitesi
Tam Metin
Kaydet Alıntıla
This paper argues that health is a realistic productive force that may enhance the index of happiness. As the basis of all developments and the source of a person’s and his/her family’s happiness, health requires not only primary and secondary prevention, but also policy prevention, that is to say, grade-zero prevention. Therefore, people should pay more attention to Health in All Policies. As a new preventive strategy, the policy prevention will help improve people’s health significantly and promote the concepts of “Healthy China” and “the Chinese Dream” or “the World Dream” to realize a dream from reality to the future.
DOI : 10.1007/s11684-016-0444-0
Anahtar Kelimeler : health promotion, primary and secondary prevention, policy prevention, infectious disease, non-communicable disease
ISSN: 2095-0217 2095-0225
Sayı: 2
Cilt: 10
Sayfa: 233-235
13
Numerical solutions to Volterra integral equations of the second kind with oscillatory trigonometric kernels
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Applied Mathematics and Computation
Yayıncı:
Elsevier
Yazar(lar) :
Shuhuang Xiang , Qinghua Wu
Yıl :
2013
Qinghua Wu
Yayıncı Web Sitesi
Tam Metin
Kaydet Alıntıla
This paper explores quadrature methods for weakly singular Volterra integral equation of the second kind with highly oscillatory trigonometric kernels, and presents piecewise constant and linear collocation methods for approximation of the solution. The evaluation of the highly oscillatory kernels of integral equation will give rise to the computation of oscillatory integrals, which can be done by using efficient Filon-type methods. Moreover, by using asymptotic analysis of the solution, the convergence rates for piecewise constant and linear collocation methods, which show the higher the frequency the more accurate the numerical results. The effectiveness and accuracy of the proposed method are tested by numerical examples.
DOI : 10.1016/j.amc.2013.07.075
Anahtar Kelimeler : Volterra integral equation, Oscillatory kernel, Filon-type method, Weak singularity, Collocation methods
ISSN: 0096-3003
Cilt: 223
Sayfa: 34-44
Sınıflandırma :
14
Progress in genetic research on primary pulmonary hypertension.
Dergi Makalesi

Dergi Makalesi
Open Access
Kaynak :
PubMed
Dergi:
Zhonghua Yi Xue Yi Chuan Xue Za Zhi
Yazar(lar) :
Binbin Wang , Qinghua Wu
Yıl :
2018
Qinghua Wu
Yayıncı Web Sitesi
 Piri Tam Metin Bulucu
Kaydet Alıntıla
Primary pulmonary hypertension (PPH) consisting of hereditary pulmonary arterial hypertension and idiopathic pulmonary arterial hypertension is an obstructive pulmonary hypertension caused by primary pulmonary artery hyperplasia. Both environmental and genetic factors are involved in the pathogenesis of PPH. Genes associated with TGF-β signaling pathway including BMPR2, ALK1, ENG, SMAD8 and other genes including NFU1, CAV1, KCNK3 and TopBPl have been associated with PPH. In this review, the function and mechanism of the above genes in the pathogenesis PPH are summarized.
DOI : 10.3760/cma.j.issn.1003-9406.2018.04.031
Sınıflandırma :
15
Mathematical basis for a mixed inverse scattering problem
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Mathematics and Computers in Simulation
Yayıncı:
Elsevier
Yazar(lar) :
Qinghua Wu , Guozheng Yan
Yıl :
2016
Qinghua Wu
Yayıncı Web Sitesi
Tam Metin
Kaydet Alıntıla
In this paper we consider the scattering of an electromagnetic time-harmonic plane wave by an infinite cylinder having an open arc and a bounded domain in R2 as cross section. To this end, we solve a mixed scattering problem for the Helmholtz equation in R2 where the scattering object is a combination of a crack Γ and a bounded obstacle D, and we set suitable boundary conditions on Γ and ∂D ( ∂D∈C2). The boundary integral method is employed to study the direct scattering problem. The mathematical basis is given to reconstruct the shape of the crack and the obstacle by using the linear sampling method. The numerical examples are given to show the viability of the method.
DOI : 10.1016/j.matcom.2015.10.014
Anahtar Kelimeler : The linear sampling method, Inverse scattering problem, Mixed scattering problem
ISSN: 0378-4754
Cilt: 123
Sayfa: 37-52
Sınıflandırma :
16
Metabolic Pathway of Cyclosporine A and Its Correlation with Nephrotoxicity.
Dergi Makalesi

Dergi Makalesi
Open Access
Kaynak :
PubMed
Dergi:
Curr. Drug Metab.
Yazar(lar) :
Qinghua Wu , Kamil Kuca
Yıl :
2018
Qinghua Wu
Yayıncı Web Sitesi
 Piri Tam Metin Bulucu
Kaydet Alıntıla
Cyclosporine A (CsA) is widely used for organ transplantation and autoimmune disorders. However, CsA nephrotoxicity is a serious side effect that limits the clinical use of CsA. Notably, the metabolism of CsA has a close relationship with this disease in renal-transplant patients. The major metabolic pathways of CsA in humans are hydroxylation (AM1 and AM9) and N-demethylation (AM4N). Normally, these metabolites are relatively less toxic than CsA. However, the metabolism of CsA in the kidneys is much weaker than that in the liver, which explains why CsA is so toxic to the kidneys. CYP3A families, especially CYP3A4 and CYP3A5, play an important role in the biotransformation of CsA. Moreover, increased lines of evidence show that some metabolites (including AM19) associate directly with nephrotoxicity in CsA-treated organ-transplant patients. Therefore, it is important to understand the metabolic profiles of CsA in humans, especially in renal-transplant patients. However, the metabolic pathways of CsA and its metabolizing enzymes have rarely been comprehensively reviewed. Therefore, in this review, we have summarized the specific metabolic profiles of CsA in humans, especially renal-transplant patients. Moreover, the specific metabolizing enzymes and the potential roles that CsA metabolism plays in CsA nephrotoxicity were summarized and discussed. We hope that this review will help to further understand the metabolic activities of CsA in renal-transplant patients and cast some light on the mechanisms of CsA nephrotoxicity.
DOI : 10.2174/1389200219666181031113505
Anahtar Kelimeler : Cyclosporine A, metabolic pathways, metabolism, metabolizing enzymes, nephrotoxicity, renal-transplant patients
Sınıflandırma :
17
An adaptive multistart tabu search approach to solve the maximum clique problem
Dergi Makalesi

Dergi Makalesi
Kaynak :
Springer Link
Dergi:
Journal of Combinatorial Optimization
Yazar(lar) :
Qinghua Wu , Jin-Kao Hao
Konu :
Applied Mathematics, Computational Theory and Mathematics, Control and Optimization, Discrete Mathematics and Combinatorics, Computer Science Applications
Yıl :
2011
Qinghua Wu
Yayıncı Web Sitesi
Tam Metin
Kaydet Alıntıla
Given an undirected graph G=(V,E) with vertex set V={1,…,n} and edge set E⊆V×V. The maximum clique problem is to determine in G a clique (i.e., a complete subgraph) of maximum cardinality. This paper presents an effective algorithm for the maximum clique problem. The proposed multistart tabu search algorithm integrates a constrained neighborhood, a dynamic tabu tenure mechanism and a long term memory based restart strategy. Our proposed algorithm is evaluated on the whole set of 80 DIMACS challenge benchmarks and compared with five state-of-the-art algorithms. Computational results show that our proposed algorithm attains the largest known clique for 79 benchmarks.
DOI : 10.1007/s10878-011-9437-8
Anahtar Kelimeler : Tabu search, Maximum clique, Constrained neighborhood, Informed restart, Combinatorial optimization
ISSN: 1382-6905 1573-2886
Sayı: 1
Cilt: 26
Sayfa: 86-108
18
Insect Antimicrobial Peptides, a Mini Review
Dergi Makalesi

Dergi Makalesi
Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Dergi:
Toxins
Yazar(lar) :
Qinghua Wu , Jiří Patočka , Kamil Kuča
Yıl :
2018
Qinghua Wu
Yayıncı Web Sitesi
 Piri Tam Metin Bulucu
Kaydet Alıntıla
Antimicrobial peptides (AMPs) are crucial effectors of the innate immune system. They provide the first line of defense against a variety of pathogens. AMPs display synergistic effects with conventional antibiotics, and thus present the potential for combined therapies. Insects are extremely resistant to bacterial infections. Insect AMPs are cationic and comprise less than 100 amino acids. These insect peptides exhibit an antimicrobial effect by disrupting the microbial membrane and do not easily allow microbes to develop drug resistance. Currently, membrane mechanisms underlying the antimicrobial effects of AMPs are proposed by different modes: the barrel-stave mode, toroidal-pore, carpet, and disordered toroidal-pore are the typical modes. Positive charge quantity, hydrophobic property and the secondary structure of the peptide are important for the antibacterial activity of AMPs. At present, several structural families of AMPs from insects are known (defensins, cecropins, drosocins, attacins, diptericins, ponericins, metchnikowins, and melittin), but new AMPs are frequently discovered. We reviewed the biological effects of the major insect AMPs. This review will provide further information that facilitates the study of insect AMPs and shed some light on novel microbicides.
DOI : 10.3390/toxins10110461
Anahtar Kelimeler : antimicrobial peptides, Structure-activity relationship, modification, mechanism of action
ISSN: 2072-6651
Cilt: 10
Sayı: 11
Sayfa: 461
Sınıflandırma :
19
Existence and multiplicity of periodic solutions generated by impulses for second-order Hamiltonian system
Dergi Makalesi

Dergi Makalesi
Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Dergi:
Electronic Journal of Differential Equations
Yazar(lar) :
Dan Zhang , Qinghua Wu , Binxiang Dai
Yıl :
2014
Qinghua Wu
Yayıncı Web Sitesi
Kaydet Alıntıla
In this article, we study the existence of non-zero periodic solutions for Hamiltonian systems with impulsive conditions. By using a variational method and a variant fountain theorem, we obtain new criteria to guarantee that the system has at least one non-zero periodic solution or infinitely many non-zero periodic solutions. However, without impulses, there is no non-zero periodic solution for the system under our conditions.
Anahtar Kelimeler : Impulsive differential equations, critical point theory, periodic solution, variant fountain theorems
ISSN: 1072-6691
Cilt: 2014
Sayı: 121,
Sayfa: 1 - 12
20
Residual-Based Simpler Block GMRES for Nonsymmetric Linear Systems with Multiple Right-Hand Sides
Dergi Makalesi

Dergi Makalesi
Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Dergi:
Advances in Mathematical Physics
Yazar(lar) :
Qinghua Wu , Liang Bao , Yiqin Lin
Yıl :
2018
Qinghua Wu
Yayıncı Web Sitesi
 Piri Tam Metin Bulucu
Kaydet Alıntıla
We propose in this paper a residual-based simpler block GMRES method for solving a system of linear algebraic equations with multiple right-hand sides. We show that this method is mathematically equivalent to the block GMRES method and thus equivalent to the simpler block GMRES method. Moreover, it is shown that the residual-based method is numerically more stable than the simpler block GMRES method. Based on the deflation strategy proposed by Calandra et al. (2013), we derive a deflation strategy to detect the possible linear dependence of the residuals and a near rank deficiency occurring in the block Arnoldi procedure. Numerical experiments are conducted to illustrate the performance of the new method.
DOI : 10.1155/2018/1369707
Cilt: 2018
Sınıflandırma :
21
Coloring large graphs based on independent set extraction
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Computers & Operations Research
Yayıncı:
Elsevier
Yazar(lar) :
Qinghua Wu , Jin-Kao Hao
Yıl :
2012
Qinghua Wu
Yayıncı Web Sitesi
Tam Metin
Kaydet Alıntıla
This paper presents an effective approach (EXTRACOL) to coloring large graphs. The proposed approach uses a preprocessing method to extract large independent sets from the graph and a memetic algorithm to color the residual graph. Each preprocessing application identifies, with a dedicated tabu search algorithm, a number of pairwise disjoint independent sets of a given size in order to maximize the vertices removed from the graph. We evaluate EXTRACOL on the 11 largest graphs (with 1000 to 4000 vertices) of the DIMACS challenge benchmarks and show improved results for four very difficult graphs (DSJC1000.9, C2000.5, C2000.9, C4000.5). The behavior of the proposed algorithm is also analyzed.
DOI : 10.1016/j.cor.2011.04.002
Anahtar Kelimeler : Graph coloring, Independent set, Preprocessing, Tabu search, Memetic search
ISSN: 0305-0548
Sayı: 2
Cilt: 39
Sayfa: 283-290
22
Energy Balance Control of a Cascaded Multilevel Inverter for Standalone Solar Photovoltaic Applications
Dergi Makalesi

Dergi Makalesi
Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Dergi:
Energies
Yazar(lar) :
Lei Wang , Qinghua Wu , Wenhu Tang
Yıl :
2017
Qinghua Wu
Yayıncı Web Sitesi
 Piri Tam Metin Bulucu
Kaydet Alıntıla
This paper presents a clock phase-shifting (CPS) energy balance control (EBC) method for cascaded half-bridge multilevel inverters in standalone solar photovoltaic (PV) systems. It is based on the conservation of energy in each cascaded unit. By shifting the phase of the clock pulse of each cascaded unit, a staircase-like output voltage is obtained. The CPS EBC not only regulates the staircase-like output voltage of the cascaded multilevel inverters accurately under static conditions, but also suppresses the fluctuations of DC sources and improves its dynamic responses to load steps. Thus, the problems existing in solar PV systems using the cascaded multilevel inverters are avoided. Results obtained from simulations and experiments are presented to verify the feasibility and advantages of the proposed control method.
DOI : 10.3390/en10111805
Anahtar Kelimeler : solar photovoltaic systems, cascaded multilevel inverter, energy balance control
ISSN: 1996-1073
Cilt: 10
Sayı: 11
Sayfa: 1805
Sınıflandırma :
23
Solving the winner determination problem via a weighted maximum clique heuristic
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Expert Systems with Applications
Yayıncı:
Elsevier
Yazar(lar) :
Qinghua Wu , Jin-Kao Hao
Yıl :
2015
Qinghua Wu
Yayıncı Web Sitesi
Tam Metin
Kaydet Alıntıla
Combinatorial auctions (CAs) where bidders can bid on combinations of items is an important model in many application areas. CAs attract more and more attention in recent years due to its relevance to fast growing electronic business applications. In this paper, we study the winner determination problem (WDP) in CAs which is known to be NP-hard and thus computationally difficult in the general case. We develop a solution approach for the WDP by recasting the WDP into the maximum weight clique problem (MWCP) and solving the transformed problem with a recent heuristic dedicated to the MWCP. The computational experiments on a large range of 530 benchmark instances show that the clique-based approach for the WDP not only outperforms the current best performing WDP heuristics in the literature both in terms of solution quality and computation efficiency, but also competes very favorably with the powerful CPLEX solver.
DOI : 10.1016/j.eswa.2014.07.027
Anahtar Kelimeler : Winner determination, Combinatorial auctions, Tabu search, Maximum clique, Heuristics, Combinatorial optimization
ISSN: 0957-4174
Sayı: 1
Cilt: 42
Sayfa: 355-365
Sınıflandırma :
24
Improving the extraction and expansion method for large graph coloring
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Discrete Applied Mathematics
Yayıncı:
Elsevier
Yazar(lar) :
Jin-Kao Hao , Qinghua Wu
Yıl :
2012
Qinghua Wu
Yayıncı Web Sitesi
Tam Metin
Kaydet Alıntıla
Graph coloring is one of the most studied combinatorial optimization problems. This paper presents an improved extraction and expansion method (IE2COL), initially introduced in Wu and Hao (2012) [44]. IE2COL employs a forward independent set extraction strategy to reduce the initial graph G. From the reduced graph, IE2COL triggers a backward coloring process which uses extracted independent sets as new color classes for intermediate subgraph coloring. The proposed method is assessed on 20 large benchmark graphs with 900 to 4000 vertices. Computational results show that it provides new upper bounds for 6 graphs and consistently matches the current best-known results for 12 other graphs.
DOI : 10.1016/j.dam.2012.06.007
Anahtar Kelimeler : Graph coloring, Graph k-coloring, Independent set extraction, Memetic coloring, Progressive optimization
ISSN: 0166-218X
Sayı: 16-17
Cilt: 160
Sayfa: 2397-2407
Sınıflandırma :
25
A review on algorithms for maximum clique problems
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
European Journal of Operational Research
Yayıncı:
Elsevier
Yazar(lar) :
Qinghua Wu , Jin-Kao Hao
Yıl :
2015
Qinghua Wu
Yayıncı Web Sitesi
Tam Metin
Kaydet Alıntıla
The maximum clique problem (MCP) is to determine in a graph a clique (i.e., a complete subgraph) of maximum cardinality. The MCP is notable for its capability of modeling other combinatorial problems and real-world applications. As one of the most studied NP-hard problems, many algorithms are available in the literature and new methods are continually being proposed. Given that the two existing surveys on the MCP date back to 1994 and 1999 respectively, one primary goal of this paper is to provide an updated and comprehensive review on both exact and heuristic MCP algorithms, with a special focus on recent developments. To be informative, we identify the general framework followed by these algorithms and pinpoint the key ingredients that make them successful. By classifying the main search strategies and putting forward the critical elements of the most relevant clique methods, this review intends to encourage future development of more powerful methods and motivate new applications of the clique approaches.
DOI : 10.1016/j.ejor.2014.09.064
Anahtar Kelimeler : Maximum clique problems, Exact algorithms, Heuristics, Applications
ISSN: 0377-2217
Sayı: 3
Cilt: 242
Sayfa: 693-709
Sınıflandırma :
26
A hybrid metaheuristic method for the Maximum Diversity Problem
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
European Journal of Operational Research
Yayıncı:
Elsevier
Yazar(lar) :
Qinghua Wu , Jin-Kao Hao
Yıl :
2013
Qinghua Wu
Yayıncı Web Sitesi
Tam Metin
Kaydet Alıntıla
The Maximum Diversity Problem (MDP) consists in selecting a subset of m elements from a given set of n elements ( n>m) in such a way that the sum of the pairwise distances between the m chosen elements is maximized. We present a hybrid metaheuristic algorithm (denoted by MAMDP) for MDP. The algorithm uses a dedicated crossover operator to generate new solutions and a constrained neighborhood tabu search procedure for local optimization. MAMDP applies also a distance-and-quality based replacement strategy to maintain population diversity. Extensive evaluations on a large set of 120 benchmark instances show that the proposed approach competes very favorably with the current state-of-art methods for MDP. In particular, it consistently and easily attains all the best known lower bounds and yields improved lower bounds for 6 large MDP instances. The key components of MAMDP are analyzed to shed light on their influence on the performance of the algorithm.
DOI : 10.1016/j.ejor.2013.06.002
Anahtar Kelimeler : Maximum Diversity Problem, Solution combination, Local search, Constrained neighborhood, Population diversity
ISSN: 0377-2217
Sayı: 2
Cilt: 231
Sayfa: 452-464
Sınıflandırma :
27
A clique-based exact method for optimal winner determination in combinatorial auctions
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Information Sciences
Yayıncı:
Elsevier
Yazar(lar) :
Qinghua Wu , Jin-Kao Hao
Yıl :
2016
Qinghua Wu
Yayıncı Web Sitesi
Tam Metin
Kaydet Alıntıla
Given a set of items to sell and a set of combinatorial bids, the Winner Determination Problem (WDP) in combinatorial auctions is to determine an allocation of items to bidders such that the auctioneer’s revenue is maximized while each item is allocated to at most one bidder. WDP is at the core of numerous relevant applications in multi-agent systems, e-commerce and many others. We develop a clique-based branch-and-bound approach for WDP which relies on a transformation of WDP into the maximum weight clique problem. To ensure the efficiency of the proposed search algorithm, we introduce specific bounding and branching strategies using a dedicated vertex coloring procedure and a specific vertex sorting technique. We assess the performance of the proposed algorithm on a large collection of benchmark instances in comparison with the CPLEX 12.4 solver and other approaches. Computational results show that this clique-based method constitutes a valuable and complementary approach for WDP relative to the existing methods.
DOI : 10.1016/j.ins.2015.11.029
ISSN: 0020-0255
Cilt: 334-335
Sayfa: 103-121
Sınıflandırma :
28
An Improved Pigeon-Inspired Optimisation Algorithm and Its Application in Parameter Inversion
Dergi Makalesi

Dergi Makalesi
Open Access
Kaynak :
Directory of Open Access Journals (DOAJ)
Dergi:
Symmetry
Yazar(lar) :
Hanmin Liu , Xuesong Yan , Qinghua Wu
Yıl :
2019
Qinghua Wu
Yayıncı Web Sitesi
 Piri Tam Metin Bulucu
Kaydet Alıntıla
Pre-stack amplitude variation with offset (AVO) elastic parameter inversion is a nonlinear, multi-solution optimisation problem. The techniques that combine intelligent optimisation algorithms and AVO inversion provide an effective identification method for oil and gas exploration. However, these techniques also have shortcomings in solving nonlinear geophysical inversion problems. The evolutionary optimisation algorithms have recognised disadvantages, such as the tendency of convergence to a local optimum resulting in poor local optimisation performance when dealing with multimodal search problems, decreasing diversity and leading to the prematurity of the population as the number of evolutionary iterations increases. The pre-stack AVO elastic parameter inversion is nonlinear with slow convergence, while the pigeon-inspired optimisation (PIO) algorithm has the advantage of fast convergence and better optimisation characteristics. In this study, based on the characteristics of the pre-stack AVO elastic parameter inversion problem, an improved PIO algorithm (IPIO) is proposed by introducing the particle swarm optimisation (PSO) algorithm, an inverse factor, and a Gaussian factor into the PIO algorithm. The experimental comparisons indicate that the proposed IPIO algorithm can achieve better inversion results.
DOI : 10.3390/sym11101291
Anahtar Kelimeler : pigeon-inspired optimisation, particle swarm optimisation, pre-stack seismic data, amplitude variation with offset, parameter inversion
ISSN: 2073-8994
Cilt: 11
Sayı: 10
Sayfa: 1291
Sınıflandırma :
29
Memetic search for the max-bisection problem
Dergi Makalesi

Dergi Makalesi
Kaynak :
Science Direct
Dergi:
Computers & Operations Research
Yayıncı:
Elsevier
Yazar(lar) :
Qinghua Wu , Jin-Kao Hao
Yıl :
2013
Qinghua Wu
Yayıncı Web Sitesi
Tam Metin
Kaydet Alıntıla
Given an undirected graph G=(V,E) with weights on the edges, the max-bisection problem (MBP) is to find a partition of the vertex set V into two subsets V1 and V2 of equal cardinality such that the sum of the weights of the edges crossing V1 and V2 is maximized. Relaxing the equal cardinality, constraint leads to the max-cut problem (MCP). In this work, we present a memetic algorithm for MBP which integrates a grouping crossover operator and a tabu search optimization procedure. The proposed crossover operator preserves the largest common vertex groupings with respect to the parent solutions while controlling the distance between the offspring solution and its parents. Extensive experimental studies on 71 well-known G-set benchmark instances demonstrate that our memetic algorithm improves, in many cases, the current best known solutions for both MBP and MCP.
DOI : 10.1016/j.cor.2012.06.001
Anahtar Kelimeler : Max-bisection, Max-cut, Memetic search, Evolutionary computing, Tabu search, Optimization
ISSN: 0305-0548
Sayı: 1
Cilt: 40
Sayfa: 166-179

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