Modelling, simulation and behaviour of sloshing liquid-tank-ship coupled system

Ph.DDOCTOR OF PHILOSOPH

Indoor assistance for visually impaired people using a RGB-D camera

In this paper a navigational aid for visually impaired people is presented. The system uses a RGB-D camera to perceive the environment and implements self-localization, obstacle detection and obstacle classification. The novelty of this work is threefold. First, self-localization is performed by means of a novel camera tracking approach that uses both depth and color information. Second, to provide the user with semantic information, obstacles are classified as walls, doors, steps and a residual class that covers isolated objects and bumpy parts on the floor. Third, in order to guarantee real time performance, the system is accelerated by offloading parallel operations to the GPU. Experiments demonstrate that the whole system is running at 9 Hz

Publications on COVID-19 from Vietnam during 2020 and 2021: A bibliometric analysis

Background: Following the outbreak of the COVID-19 pandemic, published research from Vietnam related to the pandemic was analysed using bibliometrics. Objectives: To examine the status of research on COVID-19 by authors from Vietnam. Methods: The following bibliometric aspects were considered in the analysis: international collaboration, institutions from Vietnam and their partner institutions worldwide, subjects and topics, types of documents, and individual authors. The basis of the study was data obtained from the Scopus database between 2020 and 2021. The data were analysed using Microsoft Excel, R, and VOSviewer, and the emerging trends illustrated through descriptive analysis and science mapping.  Results: Between 2020 and 2021, researchers from Vietnam co-authored 1034 documents related to COVID-19, amounting to 0.35% of the total of 296,148 such documents published worldwide as ascertained from the Scopus database. Vietnam’s top country collaborators in that research were USA, Australia, the United Kingdom, India, and Taiwan ROC. The top Vietnam institutions were Duy Tan University, Ton Duc Thang University, and the University of Economics Ho Chi Minh City. The research from Vietnam covered many subjects, from medicine and natural sciences to social sciences and economics. Eight clusters of topics related to COVID-19 were identified. In terms of citations, the most highly cited documents were the outcome of collaboration with international authors. Lastly, the study ranked top authors based on either the number of publications or the number of citations.  Conclusion: This study provides a preliminary picture of studies related to COVID-19 co-authored by researchers in Vietnam. The picture may help the Vietnam government in devising appropriate strategies for post-COVID-19 restoration of the country’s socio-economic status

A meshfree DLO formulation for yield line analysis of reinforced concrete slabs

The yield-line method of analysis is a powerful tool that can be used to rapidly estimate the limit load sustainable by a reinforced concrete slab. In recent years, it has been limited in use due to its difficulties to computerise. Consequently, the Discontinuity Layout Optimization (DLO) procedure has been proposed to provide a systematic means of automating the method. In the DLO formulation, the size of the underlying optimization is highly affected by the number of the potential yield-lines generated. In this paper the concept of domain of influence in the framework of mesh-free methods will be introduced to the DLO method, resulting an efficient DLO method that can provide accurate solutions compared with the original DLO method while the problem size is very much smaller

Dynamic Analysis of Mindlin Plates Resting on a Viscoelastic Foundation Subjected to Moving Loads During Abrupt Braking using Moving Element Method

The paper proposes a new computational approach using the moving element method (MEM) for simulating the dynamic responses of Mindlin plate resting on a viscoelastic foundation subjected to moving loads during abrupt braking. In this approach, the governing equations as well as the plate element mass, damping and stiffness matrices are formulated in a convected coordinate in which the origin is attached to the applied point of the moving load. Thus, the proposed method simply treats the moving loads as ‘stationary’ at the nodes of the plate to avoid updating the locations of moving loads due to the change of the contact points on the plate. The interaction between the moving load and the plate during abrupt braking is accounted for through the vertical force and tangential wheel-pavement friction force. The effects of wheel sliding, load deceleration magnitude, friction coefficient, and plate thickness on the dynamic responses of plate are investigated

The effect of track irregularity and wheel load on the dynamic response of a high-speed rail system

In this paper, a computational study using the moving element method (MEM) was carried out to investigate the dynamic response of a high-speed rail (HSR). A new formulation for calculating the structural matrices of the moving element is proposed. Two wheel-rail contact problems will be examined. One is linear and the other nonlinear. A parametric study is carried out to understand the effects of various factors on the response of the train-track system such as the severity of railhead roughness and the wheel load. In particular, the effect of above factors on the occurrence of the jumping wheel phenomenon, which occurs when there is a momentary loss of contact between the wheel and track, is considered

A moving element method using timoshenko’s beam theory for dynamic analysis of train-track systems

The paper presents a dynamic analysis of train-track systems supported by viscoelastic foundations by combining Timoshenko’s beam theory and moving element method (MEM). In the proposed method, a three-node beam element is utilized to get a high order approximation for the deflection of Timoshenko beam. The reduced integral method is applied in order to avoid the shear-locking phenomenon when computing the shear strain energy of the rail beam. In addition, the behavior of train-track system with respect to time is deduced by using Newmark’s constant acceleration method. Numerical results show that the proposed method is free of shear locking and gives a good agreement with Koh et al.’s method using Euler-Bernoulli beam theory

Multi-layer moving plate method for dynamic analysis of pavement structures subjected to moving loads

This paper presents a new approach, namely multi-layer moving plate method (MMPM), for the dynamic analysis of pavement structures subjected to moving load. The pavement resting on multi-layer foundation is modeled as a two-layer plate connected by a spring-damper system resting on a viscoelastic foundation. This model gives a accurately pavement structure model so that the dynamic responses of the surface slab and the base can be obtained. The governing equations as well as the plate element mass, damping and stiffness matrices are formulated in a convected coordinate with the idea of attaching its origin to the applied point of the moving load. The proposed method simply treats the moving load as ‘stationary’ at the node of the plate to avoid the updating of the location of moving load due to change of contact points on the plate. Numerical examples related to the dynamic analysis of the pavement structure subjected to a moving load are conducted to investigate the effects of various parameters such as concrete slab thickness, base thickness, foundation stiffness and the load’s velocity on dynamic responses of the pavement structure

Analyses of stiffened plates resting on the viscoelastic foundation subjected to a moving vehicle by a cell-based smoothed triangular plate element

Recently, a cell-based smoothed discrete shear gap method (CS-FEM-DSG3) based on the firstorder shear deformation theory (FSDT) was proposed for static and free vibration analyses of Mindlin plates. The CS-FEM-DSG3 uses three-node triangular elements that can be easily generated automatically for arbitrary complicated geometric domains. This paper further extends the CS-FEMDSG3 for static, free vibration, and dynamic response of the stiffened plate resting on viscoelastic foundation subjected to a moving vehicle. The viscoelastic foundation is modeled by discrete springs and dampers whereas the stiffened plate can be considered as the combination between the Mindlin plate and the Timoshenko beam elements. The moving vehicle is transformed into one concentrated load at its central point. Some numerical examples are investigated and numerical results show that the CS-FEMDSG3 overcomes shear-locking phenomena and has a fast convergence. The results also illustrate the good agreement of the CS-FEM-DSG3 for static and free vibration analyses of un-stiffened plate compared with the previous published methods. In addition, the numerical results for dynamic analysis of stiffened plates by the CS-FEM-DSG3 also show the expected property in which the deflection of the stiffened plate is much smaller than those of the un-stiffened plate

Elastic Scattering Time–Gated Multi–Static Lidar Scheme for Mapping and Identifying Contaminated Atmospheric Droplets

Numerical simulations are performed to determine the angular dependence of the MIe scattering cross-section intensities of pure water droplets and pollutants such as contaminated water droplets and black carbon as a function of the wavelength of the incident laser light, complex refractive index, and size of the scatterer. Our results show distinct scattering features when varying the various scattering parameters, thereby allowing the identification of the scattering particle with specific application to the identification of atmospheric pollutants including black carbon. Regardless of the type of scatterer, the scattering intensity is nearly uniform with a slight preference for forward scattering when the size of the particle is within 20% of the incident laser’s wavelength. The scattering patterns start to exhibit distinguishable features when the size parameter equals 1.77, corresponding to an incident laser wavelength of 0.355 μm and a particle radius of 0.1 μm. The patterns then become increasingly unique as the size parameter increases. Based on these calculations, we propose a time-gated lidar scheme consisting of multiple detectors that can rotate through a telescopic angle and be placed equidistantly around the scattering particles to collect the backscattered light and a commercially available Q-switched laser system emitting at tunable laser wavelengths. By using a pulsed laser with 10-ns pulse duration, our scheme could distinguish scattering centers that are at least 3 m apart. Our scheme called MIe Scattering Time-gated multi-Static LIDAR (MISTS–LIDAR) would be capable of identifying the type of atmospheric pollutant and mapping its location with a spatial resolution of a few meters.Mui L.V., Hung T.N., Shinohara K., et al. Elastic Scattering Time–Gated Multi–Static Lidar Scheme for Mapping and Identifying Contaminated Atmospheric Droplets. Applied Sciences (Switzerland) 13, 172 (2023); https://doi.org/10.3390/app13010172