An implicit high order discontinuous Galerkin level set method for two-phase flow problems

International audienceAn implicit high order time (BDF) and polynomial degree discontinuous Galerkin (DG) level set method is presented in this talk. The major advantage of this new approach is an accurate mass conservation during the convection of the level set function, thanks to the implicit method. Numerical experiments are presented for the Zalesak and the Leveque test cases. The convergence rates versus time and space are investigated for both BDF and DG high orders. The capture of the zero level set interface is then improved by using an auto-adaptive mesh procedure. The problem is approximated by using the discontinuous Galerkin method for both the level set function, the velocity and the pressure fields

The Leadership Competency in Vietnam Public Administration

Globalization and technological development have changed people’s demand, which leads to many challenges for public and private sectors. Public administration can overcome the challenges by reforming their structure and performance. In this research, the authors affirmed the important roles of leaders in public administration. This research used the integrated leadership theory in the context of Vietnam public administration to build a framework of competency for leaders. The Key Informant Panel and the in-depth interview method were implemented to achieve the research objectives. Research findings have built a leadership competency framework for the public sector, which benefits both researchers and practioners. For researchers, the findings can add to leadership competency theories, especially in the public sector. For policy-makers, the findings can be solid foundations which they can rely on to work out policies for leadership development in Vietnam public sector

Integrated Flow Shop and Vehicle Routing Problem Based on Tabu Search Algorithm

We consider in this paper a m-machine permutation flow shop scheduling problem and vehicle routing problem (VRP) integrated [1]. The manufacturing workshop is a flow shop and there is only one vehicle available. We are interested in the minimization of the total tardiness. related to the delivery completion times. Therefore, we are faced to three interdependent problems: scheduling the jobs in the flow shop environment, batching the completed jobs, and routing the batches. Then, we present the resolution method based on Tabu search and the results that have been obtained. Computational experiments are performed on random data sets and show the efficiency of the methods. Finally, a conclusion and some future research directions are proposed

Binary-Continuous Sum-of-ratios Optimization: Discretization, Approximations, and Convex Reformulations

We study a class of non-convex sum-of-ratios programs which can be used for decision-making in prominent areas such as product assortment and price optimization, facility location, and security games. Such an optimization problem involves both continuous and binary decision variables and is known to be highly non-convex and intractable to solve. We explore a discretization approach to approximate the optimization problem and show that the approximate program can be reformulated as mixed-integer linear or second-order cone programs, which can be conveniently handled by an off-the-shelf solver (e.g., CPLEX or GUROBI). We further establish (mild) conditions under which solutions to the approximate problem converge to optimal solutions as the number of discretization points increases. We also provide approximation abounds for solutions obtained from the approximated problem. We show how our approach applies to product assortment and price optimization, maximum covering facility location, and Bayesian Stackelberg security games and provide experimental results to evaluate the efficiency of our approach

On a multistage discrete stochastic optimization problem with stochastic constraints and nested sampling

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English teachers’ perception and attitudes of scaffolding method in teaching academic writing: An exploratory study at universities in Vietnam

The primary aim of this research is to investigate the impact of utilizing the scaffolding method on teaching academic writing in the context of English as a Foreign Language (EFL) at universities in Vietnam. This mixed-method study examined the attitudes and perceptions of 88 EFL educators from diverse backgrounds and degree levels who were randomly selected for the research. Methodologically, data were gathered and analyzed using the appropriate methods for each instrument, including a questionnaire and focus group discussion (FGD). Theoretically, the study is a medley of relevant theories and approaches such as Vygotsky’s Sociocultural Theory of Learning, the Scaffolding theory, and the ‘High challenge - High support’ pedagogy. The results of this study suggest that participants used scaffolding to some extent and had strongly positive attitudes and perceptions regarding its practical aspects; however, the findings also revealed that the surveyed lecturers are deficient in the necessary knowledge and skills. In addition, the study's findings imply that EFL teachers need training on how to properly use scaffolding as a pedagogical strategy to facilitate teaching academic writing to EFL students

Applying diversity index and dominant species in research and selection of some indigenous plant species to absorb Pb, Zn

The study was carried out at Dai Dong and Chi Dao communes, Van Lam District, Hung Yen Province. The biological diversity indexes and dominance index of species were used to identify native plant species which have the ability to absorb Pb and Zn. The results were verified by applying methods such as plant classification, quadrat cell counting, biological indicators and chemical analysis. Results showed that there are five species of plants with the highest dominant index calculated due to number of individuals in the study area including Bidens pilosa L (33.03%), Acroceras munroanum (8.14%), Commelina coelestis (7.83%), Carex capillacea (5.41%), Ipomoea aquatic (5.26%). Verified results showed that Bidens pilosa L, Acroceras munroanum, Commelina coelestis, Ipomoea aquatic can be used to treat Pb with the absorption concentration of 380 mg/kg, 288 mg/kg, 270 mg/kg, 223 mg/kg, respectively. Only Commelina coelestis can absorb Zn with the highest concentration of 73mg/kg. In summary, Pb absorption of dominant species in the study area is higher than the absorption of Zn.Nghiên cứu được thực hiện tại hai xã Đại Đồng và xã Chỉ Đạo, huyện Văn Lâm, tỉnh Hưng Yên nhằm xác định một số loài thực vật bản địa có khả năng hấp thụ Pb, Zn bằng cách sử dụng chỉ số đa dạng sinh học và chỉ số ưu thế loài. Kết quả được kiểm chứng bằng các phương pháp như phân loại thực vật, đếm ô quadrat, sử dụng chỉ số sinh học và phân tích hóa học. Kết quả cho thấy có có năm loài thực vật có chỉ số ưu thế cao nhất tính theo số lượng cá thể trong khu vực nghiên cứu là: Đơn buốt (33,03 %), Cỏ lá tre (8,14 %), Thài lài (7,83 %), Kiết tóc (5,41 %), Rau muống (5,26 %). Kết quả phân tích kiểm chứng thấy Đơn buốt, Cỏ lá tre, Thài lài, Rau muống có khả năng xử lý Pb với giá trị lần lượt là 380 mg/kg, 288 mg/kg, 270 mg/kg, 223 mg/kg. Trong khi đó chỉ có Thài lài là có khả năng hấp thu Zn với giá trị cao nhất là 73 mg/kg. Nhìn chung khả năng hấp thu Pb của các loài ưu thế tại khu vực nghiên cứu cao hơn so với khả năng hấp thu Zn

LBM-MHD Data-Driven Approach to Predict Rayleigh–Bénard Convective Heat Transfer by Levenberg–Marquardt Algorithm

This study aims to consider lattice Boltzmann method (LBM)–magnetohydrodynamics (MHD) data to develop equations to predict the average rate of heat transfer quantitatively. The present approach considers a 2D rectangular cavity with adiabatic side walls, and the bottom wall is heated while the top wall is kept cold. Rayleigh–Bénard (RB) convection was considered a heat-transfer phenomenon within the cavity. The Hartmann (Ha) number, by varying the inclination angle (θ), was considered in developing the equations by considering the input parameters, namely, the Rayleigh (Ra) numbers, Darcy (Da) numbers, and porosity (ϵ) of the cavity in different segments. Each segment considers a data-driven approach to calibrate the Levenberg–Marquardt (LM) algorithm, which is highly linked with the artificial neural network (ANN) machine learning method. Separate validations have been conducted in corresponding sections to showcase the accuracy of the equations. Overall, coefficients of determination (R2) were found to be within 0.85 to 0.99. The significant findings of this study present mathematical equations to predict the average Nusselt number (Nu¯). The equations can be used to quantitatively predict the heat transfer without directly simulating LBM. In other words, the equations can be considered validations methods for any LBM-MHD model, which considers RB convection within the range of the parameters in each equation

The Relationship between Online Learning and Student Satisfaction with Training Quality in Private Universities during the COVID-19 Pandemic

This study aims to explore the relationship between the influential factors of online learning and the satisfaction of economics and business majors with the quality of their training in the context of the Covid-19 pandemic. A total of 900 students in private universities completed a questionnaire. The principal findings of this research are that the students are satisfied with their online learning and that learning conferencing software is the most important driving factor leading to the students’ satisfaction when compared with learning conditions and learning devices. Another interesting finding is that the experience of using learning conferencing software results in a slight difference in the students’ perceived level of satisfaction, adding that users with more than two years’ experience are more satisfied with their training quality than users with less than one year’s experience. However, the results also show that students want to switch to offline learning when the pandemic is over. This study should, therefore, be of value to higher education authorities wishing to understand their students’ perceptions of online learning. In addition, results from the study suggest more managerial approaches as well as improve the online teaching quality during the pandemic