Existence and Decay of Solutions of a Nonlinear Viscoelastic Problem with a Mixed Nonhomogeneous Condition

We study the initial-boundary value problem for a nonlinear wave equation given by u_{tt}-u_{xx}+\int_{0}^{t}k(t-s)u_{xx}(s)ds+ u_{t}^{q-2}u_{t}=f(x,t,u) , 0 < x < 1, 0 < t < T, u_{x}(0,t)=u(0,t), u_{x}(1,t)+\eta u(1,t)=g(t), u(x,0)=\^u_{0}(x), u_{t}(x,0)={\^u}_{1}(x), where \eta \geq 0, q\geq 2 are given constants {\^u}_{0}, {\^u}_{1}, g, k, f are given functions. In part I under a certain local Lipschitzian condition on f, a global existence and uniqueness theorem is proved. The proof is based on the paper [10] associated to a contraction mapping theorem and standard arguments of density. In Part} 2, under more restrictive conditions it is proved that the solution u(t) and its derivative u_{x}(t) decay exponentially to 0 as t tends to infinity.Comment: 26 page

MODELO DE CONSULTA ESCOLAR NO VIETNÃ: ESTUDO DE CASO DE PROFESSORES EM TEMPO PARCIAL

The school consultation model in Vietnam currently being implemented according to Circular No. 31/2017/TT-BGDDT effective from February 2, 2018, is the “Part-time teacher” model. The purpose of this exploratory study is to test the awareness of officials and teachers about the effectiveness of elements in the “part-time teacher” school consultation model in high schools in Ho Chi Minh City, Vietnam. The research sample was randomly selected from 4 high school heads and from teacher pedagogical training courses and management training classes, with 538 participants, of which teachers (69.0%), and managers (31.0%); in the study sample, there were (36.2%) participating in the school’s psychology team. Research subjects (28.6%) were trained in psychological consultation capacity by topic; (8.9%) training in psychological counseling capacity and granting training certificates; (5.4%) training for bachelor of psychology and master of psychology; (57.1%) had not studied through the psychological counseling competency program. The instrument’s validity and reliability were verified through the evaluation of Cronbach alpha analysis, and exploratory factor analysis (EFA). When analyzing the EFA factor, the results of the factors in the model have a positive correlation of 76.2% (R2 = 1.00), in the factors of personnel conducting consultations, policies for personnel participating in consultations, and policies for consulting personnel. Joining the school counseling team, the consultation process and the consultation room have not been paying attention.O modelo de consulta escolar no Vietname que está atualmente a ser implementado de acordo com a Circular n.º 31/2017/TT-BGDDT, em vigor a partir de 2 de fevereiro de 2018, é o modelo “Professor a tempo parcial”. O objectivo deste estudo exploratório é testar a sensibilização de funcionários e professores sobre a eficácia dos elementos do modelo de consulta escolar de “professores a tempo parcial” em escolas secundárias na cidade de Ho Chi Minh, Vietname. A amostra da pesquisa foi selecionada aleatoriamente entre 4 diretores de escolas de ensino médio e de cursos de formação pedagógica de professores e turmas de formação gerencial, com 538 participantes, sendo professores (69,0%) e gestores (31,0%); na amostra do estudo havia (36,2%) participantes da equipe de psicologia da escola. Os sujeitos da pesquisa (28,6%) foram capacitados em capacidade de consulta psicológica por tema; (8,9%) formação em capacidade de aconselhamento psicológico e concessão de certificados de formação; (5,4%) formação para bacharel em psicologia e mestre em psicologia; (57,1%) não haviam cursado o programa de competência em aconselhamento psicológico. A validade e a confiabilidade do instrumento foram verificadas por meio da avaliação da análise alfa de Cronbach e da análise fatorial exploratória (AFE). Ao analisar o fator AFE, os resultados dos fatores do modelo apresentam correlação positiva de 76,2% (R2 = 1,00), nos fatores pessoal que realiza consultas, políticas para pessoal participante de consultas e políticas para pessoal consultor. Juntando-se à equipe de aconselhamento escolar, o processo de consulta e o consultório não têm prestado atenção

Model Updating for Large-Scale Railway Bridge Using Grey Wolf Algorithm and Genetic Alghorithms

This paper proposes a novel hybrid algorithm to deal with an inverse problem of a large-scale truss bridge. Grey Wolf Optimization (GWO) Algorithm is a well-known and widely applied metaheuristic algorithm. Nevertheless, GWO has two major drawbacks. First, this algorithm depends crucially on the positions of the leading Wolf. If the position of the leaderis far from the best solution, the obtained results are poor. On the other hand, GWO does not own capacities to improve the quality of new generations if elements are trapped into local minima. To remedy the shortcomings of GWO, we propose a hybrid algorithm combining GWO with Genetic Algorithm (GA), termed HGWO-GA. This proposed method contains two key features (1) based on crossover and mutation capacities, GA is first utilized to generate the high-quality elements (2) after that, the optimization capacity of GWO is employed to seek the optimal solutions. To assess the effectiveness of the proposed approach, a large-scale truss bridge is employed for model updating. The obtained results show that HGWO-GA not only provides a good agreement between numerical and experimental results but also outperforms traditional GWO in terms of accuracy

Model Updating for Large-Scale Railway Bridge Using Grey Wolf Algorithm and Genetic Alghorithms

This paper proposes a novel hybrid algorithm to deal with an inverse problem of a large-scale truss bridge. Grey Wolf Optimization (GWO) Algorithm is a well-known and widely applied metaheuristic algorithm. Nevertheless, GWO has two major drawbacks. First, this algorithm depends crucially on the positions of the leading Wolf. If the position of the leaderis far from the best solution, the obtained results are poor. On the other hand, GWO does not own capacities to improve the quality of new generations if elements are trapped into local minima. To remedy the shortcomings of GWO, we propose a hybrid algorithm combining GWO with Genetic Algorithm (GA), termed HGWO-GA. This proposed method contains two key features (1) based on crossover and mutation capacities, GA is first utilized to generate the high-quality elements (2) after that, the optimization capacity of GWO is employed to seek the optimal solutions. To assess the effectiveness of the proposed approach, a large-scale truss bridge is employed for model updating. The obtained results show that HGWO-GA not only provides a good agreement between numerical and experimental results but also outperforms traditional GWO in terms of accuracy

The regularity and exponential decay of solution for a linear wave equation associated with two-point boundary conditions

This paper is concerned with the existence and the regularity of global solutions to the linear wave equation associated with two-point type boundary conditions. We also investigate the decay properties of the global solutions to this problem by the construction of a suitable Lyapunov functional.Comment: 18 page

Existence, blow-up and exponential decay estimates for a nonlinear wave equation with boundary conditions of two-point type

This paper is devoted to study a nonlinear wave equation with boundary conditions of two-point type. First, we state two local existence theorems and under suitable conditions, we prove that any weak solutions with negative initial energy will blow up in finite time. Next, we give a sufficient condition to guarantee the global existence and exponential decay of weak solutions. Finally, we present numerical resultsComment: 2

A Review of Occupational Stress among Certain Jobs in Vietnam

Background: Stress in the modern workplace is globally considered a risk factor for workers’ health and safety. However, a review of the prevalence and associated factors of occupational stress in developing countries like Vietnam was largely lacking. This review aimed to describe the situation of occupational stress among certain jobs from studies carried out in Vietnam. Methods: The review was implemented by using key words to search on online and offline, international and national database. After going through 2 stages of selections, total 25 eligible articles were chosen and used for this review. Results: The results showed the prevalence of occupational stress was varied and ranged from 6.4% to 90.4%. The study population focused on health workers, factory workers, students, academic staff and officers. The prevalence of each occupation ranged from 6.4% to 90.4% in health workers; 20.7% to 89.6% in factory workers; and 22.8% to 68.3% in students. Conclusions: In conclusion, the prevalence of occupational stress was very varied between and within each occupation. Therefore, a new way to develop in enhancing the occupational stress data, particularly in developing countries, is urgently needed

Large time behavior of differential equations with drifted periodic coefficients modeling Carbon storage in soil

This paper is concerned with the linear ODE in the form $y'(t)=\lambda\rho(t)y(t)+b(t)$, $\lambda <0$ which represents a simplified storage model of the carbon in the soil. In the first part, we show that, for a periodic function $\rho(t)$, a linear drift in the coefficient $b(t)$ involves a linear drift for the solution of this ODE. In the second part, we extend the previous results to a classical heat non-homogeneous equation. The connection with an analytic semi-group associated to the ODE equation is considered in the third part. Numerical examples are given.Comment: 18 page

Dynamic response analysis of truss bridges under the effect of moving vehicles

With the characteristics of heavy and concentrated loads, the influence of moving loads on the dynamic response of the bridges is significant. Therefore, in this paper, the dynamic response of a large-scale truss bridge is studied to consider the effect of the various parameters of moving loads. The considered main parameters consist of moving mass, moving velocity, and type of moving loads. The nonlinear dynamics of the bridge based on time history analysis are obtained using the Wilson-  method. four time history – based dynamic analysis method including modal superposition in frequency domain, modal superposition in time domain; direct time integration, and direct solution in the frequency domain are employed to analysis the obtained results. To compare the effectiveness of the aforementioned method. A large-scale railway truss bridge is employed for dynamic response analysis. The obtained results give more insight into the nature of the problem and help to determine the significant parameters of moving load affecting the bridge response