The high performance of IoT technology in transportation networks has led to the increasing adoption of Internet of Vehicles(IoV)technology.The functional advantages of IoV include online communication services,accide...The high performance of IoT technology in transportation networks has led to the increasing adoption of Internet of Vehicles(IoV)technology.The functional advantages of IoV include online communication services,accident prevention,cost reduction,and enhanced traffic regularity.Despite these benefits,IoV technology is susceptible to cyber-attacks,which can exploit vulnerabilities in the vehicle network,leading to perturbations,disturbances,non-recognition of traffic signs,accidents,and vehicle immobilization.This paper reviews the state-of-the-art achievements and developments in applying Deep Transfer Learning(DTL)models for Intrusion Detection Systems in the Internet of Vehicles(IDS-IoV)based on anomaly detection.IDS-IoV leverages anomaly detection through machine learning and DTL techniques to mitigate the risks posed by cyber-attacks.These systems can autonomously create specific models based on network data to differentiate between regular traffic and cyber-attacks.Among these techniques,transfer learning models are particularly promising due to their efficacy with tagged data,reduced training time,lower memory usage,and decreased computational complexity.We evaluate DTL models against criteria including the ability to transfer knowledge,detection rate,accurate analysis of complex data,and stability.This review highlights the significant progress made in the field,showcasing how DTL models enhance the performance and reliability of IDS-IoV systems.By examining recent advancements,we provide insights into how DTL can effectively address cyber-attack challenges in IoV environments,ensuring safer and more efficient transportation networks.展开更多
Using Bressan-Colombo results, concerning the existence of continuous selections of lower semicontinuous multifunctions with decomposable values, we prove a continuous version of Filippov's theorem for a fractional i...Using Bressan-Colombo results, concerning the existence of continuous selections of lower semicontinuous multifunctions with decomposable values, we prove a continuous version of Filippov's theorem for a fractional integro-differential inclusion involving Caputo's fractional derivative. This result allows us to obtain a continuous selection of the solution set of the problem considered.展开更多
BACKGROUND The coronavirus disease 2019(COVID-19)was perhaps the most severe global health crisis in living memory.Alongside respiratory symptoms,elevated liver enzymes,abnormal liver function,and even acute liver fai...BACKGROUND The coronavirus disease 2019(COVID-19)was perhaps the most severe global health crisis in living memory.Alongside respiratory symptoms,elevated liver enzymes,abnormal liver function,and even acute liver failure were reported in patients suffering from severe acute respiratory disease coronavirus 2 pneumonia.However,the precise triggers of these forms of liver damage and how they affect the course and outcomes of COVID-19 itself remain unclear.AIM To analyze the impact of liver enzyme abnormalities on the severity and outcomes of COVID-19 in hospitalized patients.METHODS In this study,684 depersonalized medical records from patients hospitalized with COVID-19 during the 2020-2021 period were analyzed.COVID-19 was diagnosed according to the guidelines of the National Institutes of Health(2021).Patients were assigned to two groups:those with elevated liver enzymes(Group 1:603 patients),where at least one out of four liver enzymes were elevated(following the norm of hospital laboratory tests:alanine aminotransferase(ALT)≥40,aspartate aminotransferase(AST)≥40,gamma-glutamyl transferase≥36,or alkaline phosphatase≥150)at any point of hospitalization,from admission to discharge;and the control group(Group 2:81 patients),with normal liver enzymes during hospitalization.COVID-19 severity was assessed according to the interim World Health Organization guidance(2022).Data on viral pneumonia complications,laboratory tests,and underlying diseases were also collected and analyzed.RESULTS In total,603(88.2%)patients produced abnormal liver test results.ALT and AST levels were elevated by a factor of less than 3 in 54.9%and 74.8%of cases with increased enzyme levels,respectively.Patients in Group 1 had almost double the chance of bacterial viral pneumonia complications[odds ratio(OR)=1.73,P=0.0217],required oxygen supply more often,and displayed higher biochemical inflammation indices than those in Group 2.No differences in other COVID-19 complications or underlying diseases were observed between groups.Preexisting hepatitis of a different etiology was rarely documented(in only 3.5%of patients),and had no impact on the severity of COVID-19.Only 5(0.73%)patients experienced acute liver failure,4 of whom died.Overall,the majority of the deceased patients(17 out of 20)had elevated liver enzymes,and most were male.All deceased patients had at least one underlying disease or combination thereof,and the deceased suffered significantly more often from heart diseases,hypertension,and urinary tract infections than those who made recoveries.Alongside male gender(OR=1.72,P=0.0161)and older age(OR=1.02,P=0.0234),diabetes(OR=3.22,P=0.0016)and hyperlipidemia(OR=2.67,P=0.0238),but not obesity,were confirmed as independent factors associated with more a severe COVID-19 infection in our cohort.CONCLUSION In our study,the presence of liver impairment allows us to predict a more severe inflammation with a higher risk of bacterial complication and worse outcomes of COVID-19.Therefore,patients with severe disease forms should have their liver tests monitored regularly and their results should be considered when selecting treatment to avoid further liver damage or even insufficiency.展开更多
The paper focuses on the optimal control of natural resources in mining industry. The purpose is to pro- pose an optimal extraction series of these resources during the lifetime of the Mine's maintenance. Fol- lowing...The paper focuses on the optimal control of natural resources in mining industry. The purpose is to pro- pose an optimal extraction series of these resources during the lifetime of the Mine's maintenance. Fol- lowing the proposed optimal control model, a sensitivity analysis has been performed that includes the interest rate impact on the optimal solution. This study shows that the increasing of the interest rate sti- mulates faster extraction of the resources. The discounting factor induces that the resource has to be extracted faster hut this effect is counterbalanced by the diminishing returns of the annual cash flow. At higher parameters of "alpha" close to one of the power function about 80% from the whole resource will be extracted during the first 4 years of object/mine maintenance. An existence of unique positive root with respect to return of investment has been proposed and proved by two ways: by the "method of chords" and by using specialized software.展开更多
The existence and uniqueness theorem of classical solutions of a coupled system of nonlinear parabolic PDEs arising in modelling of chemical reactions between two polymeric reactants over inhomogeneous surfaces with n...The existence and uniqueness theorem of classical solutions of a coupled system of nonlinear parabolic PDEs arising in modelling of chemical reactions between two polymeric reactants over inhomogeneous surfaces with nonclassical boundary conditions is proved and the long-time behaviour of the solution is studied.展开更多
Electron spectrum in doped n-Si quantum wires is calculated by the Thomas-Fermi (TF) method under finite temperatures. The many-body exchange corrections are taken into account. The doping profile is arbitrary. At the...Electron spectrum in doped n-Si quantum wires is calculated by the Thomas-Fermi (TF) method under finite temperatures. The many-body exchange corrections are taken into account. The doping profile is arbitrary. At the first stage, the electron potential energy is calculated from a simple two-dimensional equation. The effective iteration scheme is proposed there that is valid for multidimensional problems. Then the energy levels and wave functions of this quantum well are simulated from the Schrödinger equations. The expansion by the full set of eigenfunctions of the linear harmonic oscillator is used. The quantum mechanical perturbation theory can be utilized to compute the energy levels. Generally, the perturbation theory for degenerate energy levels should be used.展开更多
We introduce a common generalization of the L-R-smash product and twisted tensor product of algebras, under the name L-R-twisted tensor product of algebras. We investigate some properties of this new construction, for...We introduce a common generalization of the L-R-smash product and twisted tensor product of algebras, under the name L-R-twisted tensor product of algebras. We investigate some properties of this new construction, for instance, we prove a result of the type "invariance under twisting" and we show that under certain circumstances L-R- twisted tensor products of algebras may be iterated.展开更多
This paper describes the requirements for building accessible user interface for users with autism spectrum disorders (ASD) and presents the user interface (UI) of Open Book, a reading assistive tool for people with A...This paper describes the requirements for building accessible user interface for users with autism spectrum disorders (ASD) and presents the user interface (UI) of Open Book, a reading assistive tool for people with ASD. The requirements are extracted from both existing research on improving reading comprehension for people with ASD, and from the feedback of users and clinical professionals. The findings are applied in practice to create the user interface of Open Book tool. Key screens of the user interface are presented. It is implied that the features of the UI for people with ASD can be successfully applied to improving overall accessibility of any graphical user interface.展开更多
Let be a hypercube in Rn. We prove theorems concerning mean-values of harmonic and polyharmonic functions on In(r), which can be considered as natural analogues of the famous Gauss surface and volume mean-value formul...Let be a hypercube in Rn. We prove theorems concerning mean-values of harmonic and polyharmonic functions on In(r), which can be considered as natural analogues of the famous Gauss surface and volume mean-value formulas for harmonic functions on the ball in and their extensions for polyharmonic functions. We also discuss an application of these formulas—the problem of best canonical one-sided L1-approximation by harmonic functions on In(r).展开更多
The purpose of the paper is to develop a mobile Android application--"Car Log" that gives to users the ability to track all the costs for a vehicle and the ability to add fuel cost data by taking a photo of the cash...The purpose of the paper is to develop a mobile Android application--"Car Log" that gives to users the ability to track all the costs for a vehicle and the ability to add fuel cost data by taking a photo of the cash receipt from the respective gas station where the charging was performed. OCR (optical character recognition) is the conversion of images of typed, handwritten or printed text into machine-encoded text. Once we have the text machine-encoded we can further use it in machine processes, like translation, or extracted, meaning text-to-speech transformed, helping people in simple everyday tasks. Users of the application will be able to enter other completely different costs grouped into categories and other charges. Car Log application quickly and easily can visualize, edit and add different costs for a ear. It also supports the ability to add multiple profiles, by entering data for all ears in a single family, for example, or a small business. The test results are positive thus we intend to further develop a cloud ready application.展开更多
A bounded linear operator T on a complex Hilbert space H is called n-normal if T^(*)T^(n)=T^(n)T^(*).By Fuglede’s theorem T is n-normal if and only if T^(n)is normal.Let k,n∈N.Then a bounded linear operator T is sai...A bounded linear operator T on a complex Hilbert space H is called n-normal if T^(*)T^(n)=T^(n)T^(*).By Fuglede’s theorem T is n-normal if and only if T^(n)is normal.Let k,n∈N.Then a bounded linear operator T is said to be of typeⅠk-quasi-n-normal if T^(*k){T^(*)T^(n)-T^(n)T^(*)}T^(k)=0,and T is said to be of typeⅡk-quasi-n-normal if T^(*k){T^(*n)T^(n)-T^(n)T^(*n)}T^(k)=0.1-quasi-n-normal is called quasi-n-normal.We shall show that(1)typeⅠquasi-2-normal and typeⅡquasi-2-normal are different classes;(2)the intersection of the class of typeⅠquasi-2-normal and the class of typeⅡquasi-2-normal is equal to the class of 2-normal.We also give some examples of type I k-quasi-n-normal and typeⅡk-quasi-n-normal.We also show that Weyl’s theorem holds for this class of operators and every k-quasi-n-normal operator has a non trivial invariant subspace.展开更多
In this paper, we study the Poisson stability(in particular, stationarity, periodicity, quasiperiodicity, Bohr almost periodicity, almost automorphy, recurrence in the sense of Birkhoff, Levitan almost periodicity, ps...In this paper, we study the Poisson stability(in particular, stationarity, periodicity, quasiperiodicity, Bohr almost periodicity, almost automorphy, recurrence in the sense of Birkhoff, Levitan almost periodicity, pseudo periodicity, almost recurrence in the sense of Bebutov, pseudo recurrence, Poisson stability) of motions for monotone nonautonomous dynamical systems and of solutions for some classes of monotone nonautonomous evolution equations(ODEs, FDEs and parabolic PDEs). As a byproduct, some of our results indicate that all the trajectories of monotone systems converge to the above mentioned Poisson stable trajectories under some suitable conditions, which is interesting in its own right for monotone dynamics.展开更多
The Bogomolov multiplier B0 (G) of a finite group G is defined as the subgroup of the Schur multiplier consisting of the cohomology classes vanishing after restriction to all abelian subgroups of G. The triviality o...The Bogomolov multiplier B0 (G) of a finite group G is defined as the subgroup of the Schur multiplier consisting of the cohomology classes vanishing after restriction to all abelian subgroups of G. The triviality of the Bogomolov multiplier is an obstruction to Noether's problem. We show that if G is a central product of G1 and G2, regarding Ki ≤ Z(Gi),i = 1,2, and θ : G1 →G2 is a group homomorphism such that its restriction θ|K1 : K1 → K2 is an isomorphism, then the triviality of Bo(G1/K1), Bo(G1) and B0(G2) implies the triviality of Bo(G). We give a positive answer to Noether's problem for all 2-generator p-groups of nilpotency class 2, and for one series of 4-generator p-groups of nilpotency class 2 (with the usual requirement for the roots of unity).展开更多
We generalize Ekeland's Variational Principle for cyclic maps. We present applications of this version of the variational principle for proving of existence and uniqueness of best proximity points for different class...We generalize Ekeland's Variational Principle for cyclic maps. We present applications of this version of the variational principle for proving of existence and uniqueness of best proximity points for different classes of cyclic maps.展开更多
In this paper, an algorithm for computing some of the largest (smallest) generalized eigenvalues with corresponding eigenvectors of a sparse symmetric positive definite matrix pencil is presented. The algorithm uses a...In this paper, an algorithm for computing some of the largest (smallest) generalized eigenvalues with corresponding eigenvectors of a sparse symmetric positive definite matrix pencil is presented. The algorithm uses an iteration function and inverse power iteration process to get the largest one first, then executes m - 1 Lanczos-like steps to get initial approximations of the next m - 1 ones, without computing any Ritz pair, for which a procedure combining Rayleigh quotient iteration with shifted inverse power iteration is used to obtain more accurate eigenvalues and eigenvectors. This algorithm keep the advantages of preserving sparsity of the original matrices as in Lanczos method and RQI and converges with a higher rate than the method described in [12] and provides a simple technique to compute initial approximate pairs which are guaranteed to converge to the wanted m largest eigenpairs using RQL. In addition, it avoids some of the disadvantages of Lanczos and RQI, for solving extreme eigenproblems. When symmetric positive definite lira ear systems must be solved in the process, an algebraic multilevel iteration method (AMLI) is: applied. The algorithm is fully parallelizable. [ABSTRACT FROM AUTHOR]展开更多
This paper proves a Filippov type existence theorem for solutions of a boundary valueproblem for a Sturm-Liouville type differential inclusion defined by a nonconvex set-valued map.Themethod consists in application of...This paper proves a Filippov type existence theorem for solutions of a boundary valueproblem for a Sturm-Liouville type differential inclusion defined by a nonconvex set-valued map.Themethod consists in application of the contraction principle in the space of selections of the set-valuedmap instead of the space of solutions.展开更多
基金This paper is financed by the European Union-NextGenerationEU,through the National Recovery and Resilience Plan of the Republic of Bulgaria,Project No.BG-RRP-2.004-0001-C01.
文摘The high performance of IoT technology in transportation networks has led to the increasing adoption of Internet of Vehicles(IoV)technology.The functional advantages of IoV include online communication services,accident prevention,cost reduction,and enhanced traffic regularity.Despite these benefits,IoV technology is susceptible to cyber-attacks,which can exploit vulnerabilities in the vehicle network,leading to perturbations,disturbances,non-recognition of traffic signs,accidents,and vehicle immobilization.This paper reviews the state-of-the-art achievements and developments in applying Deep Transfer Learning(DTL)models for Intrusion Detection Systems in the Internet of Vehicles(IDS-IoV)based on anomaly detection.IDS-IoV leverages anomaly detection through machine learning and DTL techniques to mitigate the risks posed by cyber-attacks.These systems can autonomously create specific models based on network data to differentiate between regular traffic and cyber-attacks.Among these techniques,transfer learning models are particularly promising due to their efficacy with tagged data,reduced training time,lower memory usage,and decreased computational complexity.We evaluate DTL models against criteria including the ability to transfer knowledge,detection rate,accurate analysis of complex data,and stability.This review highlights the significant progress made in the field,showcasing how DTL models enhance the performance and reliability of IDS-IoV systems.By examining recent advancements,we provide insights into how DTL can effectively address cyber-attack challenges in IoV environments,ensuring safer and more efficient transportation networks.
基金supported by CNCS grant PN-II-ID-PCE-2011-3-0198
文摘Using Bressan-Colombo results, concerning the existence of continuous selections of lower semicontinuous multifunctions with decomposable values, we prove a continuous version of Filippov's theorem for a fractional integro-differential inclusion involving Caputo's fractional derivative. This result allows us to obtain a continuous selection of the solution set of the problem considered.
文摘BACKGROUND The coronavirus disease 2019(COVID-19)was perhaps the most severe global health crisis in living memory.Alongside respiratory symptoms,elevated liver enzymes,abnormal liver function,and even acute liver failure were reported in patients suffering from severe acute respiratory disease coronavirus 2 pneumonia.However,the precise triggers of these forms of liver damage and how they affect the course and outcomes of COVID-19 itself remain unclear.AIM To analyze the impact of liver enzyme abnormalities on the severity and outcomes of COVID-19 in hospitalized patients.METHODS In this study,684 depersonalized medical records from patients hospitalized with COVID-19 during the 2020-2021 period were analyzed.COVID-19 was diagnosed according to the guidelines of the National Institutes of Health(2021).Patients were assigned to two groups:those with elevated liver enzymes(Group 1:603 patients),where at least one out of four liver enzymes were elevated(following the norm of hospital laboratory tests:alanine aminotransferase(ALT)≥40,aspartate aminotransferase(AST)≥40,gamma-glutamyl transferase≥36,or alkaline phosphatase≥150)at any point of hospitalization,from admission to discharge;and the control group(Group 2:81 patients),with normal liver enzymes during hospitalization.COVID-19 severity was assessed according to the interim World Health Organization guidance(2022).Data on viral pneumonia complications,laboratory tests,and underlying diseases were also collected and analyzed.RESULTS In total,603(88.2%)patients produced abnormal liver test results.ALT and AST levels were elevated by a factor of less than 3 in 54.9%and 74.8%of cases with increased enzyme levels,respectively.Patients in Group 1 had almost double the chance of bacterial viral pneumonia complications[odds ratio(OR)=1.73,P=0.0217],required oxygen supply more often,and displayed higher biochemical inflammation indices than those in Group 2.No differences in other COVID-19 complications or underlying diseases were observed between groups.Preexisting hepatitis of a different etiology was rarely documented(in only 3.5%of patients),and had no impact on the severity of COVID-19.Only 5(0.73%)patients experienced acute liver failure,4 of whom died.Overall,the majority of the deceased patients(17 out of 20)had elevated liver enzymes,and most were male.All deceased patients had at least one underlying disease or combination thereof,and the deceased suffered significantly more often from heart diseases,hypertension,and urinary tract infections than those who made recoveries.Alongside male gender(OR=1.72,P=0.0161)and older age(OR=1.02,P=0.0234),diabetes(OR=3.22,P=0.0016)and hyperlipidemia(OR=2.67,P=0.0238),but not obesity,were confirmed as independent factors associated with more a severe COVID-19 infection in our cohort.CONCLUSION In our study,the presence of liver impairment allows us to predict a more severe inflammation with a higher risk of bacterial complication and worse outcomes of COVID-19.Therefore,patients with severe disease forms should have their liver tests monitored regularly and their results should be considered when selecting treatment to avoid further liver damage or even insufficiency.
文摘The paper focuses on the optimal control of natural resources in mining industry. The purpose is to pro- pose an optimal extraction series of these resources during the lifetime of the Mine's maintenance. Fol- lowing the proposed optimal control model, a sensitivity analysis has been performed that includes the interest rate impact on the optimal solution. This study shows that the increasing of the interest rate sti- mulates faster extraction of the resources. The discounting factor induces that the resource has to be extracted faster hut this effect is counterbalanced by the diminishing returns of the annual cash flow. At higher parameters of "alpha" close to one of the power function about 80% from the whole resource will be extracted during the first 4 years of object/mine maintenance. An existence of unique positive root with respect to return of investment has been proposed and proved by two ways: by the "method of chords" and by using specialized software.
基金supported by the Research Council of Lithuania(project No.S-MIP-17-65)
文摘The existence and uniqueness theorem of classical solutions of a coupled system of nonlinear parabolic PDEs arising in modelling of chemical reactions between two polymeric reactants over inhomogeneous surfaces with nonclassical boundary conditions is proved and the long-time behaviour of the solution is studied.
文摘Electron spectrum in doped n-Si quantum wires is calculated by the Thomas-Fermi (TF) method under finite temperatures. The many-body exchange corrections are taken into account. The doping profile is arbitrary. At the first stage, the electron potential energy is calculated from a simple two-dimensional equation. The effective iteration scheme is proposed there that is valid for multidimensional problems. Then the energy levels and wave functions of this quantum well are simulated from the Schrödinger equations. The expansion by the full set of eigenfunctions of the linear harmonic oscillator is used. The quantum mechanical perturbation theory can be utilized to compute the energy levels. Generally, the perturbation theory for degenerate energy levels should be used.
文摘We introduce a common generalization of the L-R-smash product and twisted tensor product of algebras, under the name L-R-twisted tensor product of algebras. We investigate some properties of this new construction, for instance, we prove a result of the type "invariance under twisting" and we show that under certain circumstances L-R- twisted tensor products of algebras may be iterated.
文摘This paper describes the requirements for building accessible user interface for users with autism spectrum disorders (ASD) and presents the user interface (UI) of Open Book, a reading assistive tool for people with ASD. The requirements are extracted from both existing research on improving reading comprehension for people with ASD, and from the feedback of users and clinical professionals. The findings are applied in practice to create the user interface of Open Book tool. Key screens of the user interface are presented. It is implied that the features of the UI for people with ASD can be successfully applied to improving overall accessibility of any graphical user interface.
文摘Let be a hypercube in Rn. We prove theorems concerning mean-values of harmonic and polyharmonic functions on In(r), which can be considered as natural analogues of the famous Gauss surface and volume mean-value formulas for harmonic functions on the ball in and their extensions for polyharmonic functions. We also discuss an application of these formulas—the problem of best canonical one-sided L1-approximation by harmonic functions on In(r).
文摘The purpose of the paper is to develop a mobile Android application--"Car Log" that gives to users the ability to track all the costs for a vehicle and the ability to add fuel cost data by taking a photo of the cash receipt from the respective gas station where the charging was performed. OCR (optical character recognition) is the conversion of images of typed, handwritten or printed text into machine-encoded text. Once we have the text machine-encoded we can further use it in machine processes, like translation, or extracted, meaning text-to-speech transformed, helping people in simple everyday tasks. Users of the application will be able to enter other completely different costs grouped into categories and other charges. Car Log application quickly and easily can visualize, edit and add different costs for a ear. It also supports the ability to add multiple profiles, by entering data for all ears in a single family, for example, or a small business. The test results are positive thus we intend to further develop a cloud ready application.
文摘A bounded linear operator T on a complex Hilbert space H is called n-normal if T^(*)T^(n)=T^(n)T^(*).By Fuglede’s theorem T is n-normal if and only if T^(n)is normal.Let k,n∈N.Then a bounded linear operator T is said to be of typeⅠk-quasi-n-normal if T^(*k){T^(*)T^(n)-T^(n)T^(*)}T^(k)=0,and T is said to be of typeⅡk-quasi-n-normal if T^(*k){T^(*n)T^(n)-T^(n)T^(*n)}T^(k)=0.1-quasi-n-normal is called quasi-n-normal.We shall show that(1)typeⅠquasi-2-normal and typeⅡquasi-2-normal are different classes;(2)the intersection of the class of typeⅠquasi-2-normal and the class of typeⅡquasi-2-normal is equal to the class of 2-normal.We also give some examples of type I k-quasi-n-normal and typeⅡk-quasi-n-normal.We also show that Weyl’s theorem holds for this class of operators and every k-quasi-n-normal operator has a non trivial invariant subspace.
基金supported by National Natural Science Foundation of China (Grant Nos. 11271151 and 11522104)the Startup and Xinghai Jieqing Funds from Dalian University of Technology
文摘In this paper, we study the Poisson stability(in particular, stationarity, periodicity, quasiperiodicity, Bohr almost periodicity, almost automorphy, recurrence in the sense of Birkhoff, Levitan almost periodicity, pseudo periodicity, almost recurrence in the sense of Bebutov, pseudo recurrence, Poisson stability) of motions for monotone nonautonomous dynamical systems and of solutions for some classes of monotone nonautonomous evolution equations(ODEs, FDEs and parabolic PDEs). As a byproduct, some of our results indicate that all the trajectories of monotone systems converge to the above mentioned Poisson stable trajectories under some suitable conditions, which is interesting in its own right for monotone dynamics.
基金Supported by Grant No.RD-08-82/03.02.2016 of Shumen University
文摘The Bogomolov multiplier B0 (G) of a finite group G is defined as the subgroup of the Schur multiplier consisting of the cohomology classes vanishing after restriction to all abelian subgroups of G. The triviality of the Bogomolov multiplier is an obstruction to Noether's problem. We show that if G is a central product of G1 and G2, regarding Ki ≤ Z(Gi),i = 1,2, and θ : G1 →G2 is a group homomorphism such that its restriction θ|K1 : K1 → K2 is an isomorphism, then the triviality of Bo(G1/K1), Bo(G1) and B0(G2) implies the triviality of Bo(G). We give a positive answer to Noether's problem for all 2-generator p-groups of nilpotency class 2, and for one series of 4-generator p-groups of nilpotency class 2 (with the usual requirement for the roots of unity).
基金The first author is partially supported by Scientific Research Fund of Sofia University,Contract 88/2014
文摘We generalize Ekeland's Variational Principle for cyclic maps. We present applications of this version of the variational principle for proving of existence and uniqueness of best proximity points for different classes of cyclic maps.
文摘In this paper, an algorithm for computing some of the largest (smallest) generalized eigenvalues with corresponding eigenvectors of a sparse symmetric positive definite matrix pencil is presented. The algorithm uses an iteration function and inverse power iteration process to get the largest one first, then executes m - 1 Lanczos-like steps to get initial approximations of the next m - 1 ones, without computing any Ritz pair, for which a procedure combining Rayleigh quotient iteration with shifted inverse power iteration is used to obtain more accurate eigenvalues and eigenvectors. This algorithm keep the advantages of preserving sparsity of the original matrices as in Lanczos method and RQI and converges with a higher rate than the method described in [12] and provides a simple technique to compute initial approximate pairs which are guaranteed to converge to the wanted m largest eigenpairs using RQL. In addition, it avoids some of the disadvantages of Lanczos and RQI, for solving extreme eigenproblems. When symmetric positive definite lira ear systems must be solved in the process, an algebraic multilevel iteration method (AMLI) is: applied. The algorithm is fully parallelizable. [ABSTRACT FROM AUTHOR]
文摘This paper proves a Filippov type existence theorem for solutions of a boundary valueproblem for a Sturm-Liouville type differential inclusion defined by a nonconvex set-valued map.Themethod consists in application of the contraction principle in the space of selections of the set-valuedmap instead of the space of solutions.