Thai Nguyen, Vietnam
Thai Nguyen, Vietnam

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Nguyen M.T.,Oklahoma State University | Nguyen M.T.,Thai Nguyen University | Teague K.A.,Oklahoma State University
Proceedings - IEEE International Conference on Distributed Computing in Sensor Systems, DCOSS 2014 | Year: 2014

In this paper, we study the integration between Compressed Sensing (CS) and clustering methods in Wireless Sensor Networks (WSNs) that significantly reduce power consumption for the networks. In theory, a base station (BS) needs to collect M measurements from the network with N sensors, then applies CS to obtain precisely all N sensor readings. In clustered networks, a cluster-head (CH) collects data from non-CH sensors in its cluster, adds all received and its own data then send the combined measurement to the BS. We further analyze the clustered network with the measurement matrix created by clustering methods, and formulate the total power consumption. Finally, we suggest the optimal number of clusters for the networks consume the least power in practice. © 2014 IEEE.

Davydov O.,University of Strathclyde | Oanh D.T.,Thai Nguyen University
Computers and Mathematics with Applications | Year: 2011

We investigate the influence of the shape parameter in the meshless Gaussian radial basis function finite difference (RBF-FD) method with irregular centres on the quality of the approximation of the Dirichlet problem for the Poisson equation with smooth solution. Numerical experiments show that the optimal shape parameter strongly depends on the problem, but insignificantly on the density of the centres. Therefore, we suggest a multilevel algorithm that effectively finds a near-optimal shape parameter, which helps to significantly reduce the error. Comparison to the finite element method and to the generalised finite differences obtained in the flat limits of the Gaussian RBF is provided. © 2011 Elsevier Ltd. All rights reserved.

Davydov O.,University of Strathclyde | Oanh D.T.,Thai Nguyen University
Journal of Computational Physics | Year: 2011

We consider adaptive meshless discretisation of the Dirichlet problem for Poisson equation based on numerical differentiation stencils obtained with the help of radial basis functions. New meshless stencil selection and adaptive refinement algorithms are proposed in 2D. Numerical experiments show that the accuracy of the solution is comparable with, and often better than that achieved by the mesh-based adaptive finite element method. © 2010 Elsevier Inc.

This paper addresses the problem of adaptive tracking control for uncertain fully actuated dynamical systems with additive disturbance (FDSA) based on the sliding mode. We use the adaptive mechanism to adjust the uncertain parameters in sliding mode control law which can be switched to two modes depending on the sliding surface. By choosing appropriately the parameters in control law, the desired transient time can be obtained without effects of uncertain parameters and additive disturbances. The chattering phenomenon can be minimized by a chosen constant. This control method is applied to the angles tracking control of the twin rotor multi-input multi-output system (TRMS) which have nonlinear characteristics, the input torque disturbances and the coupling between the horizontal and vertical movements. The simulation and experimental results are presented that validate the proposed solution. © 2016 Chi Nguyen Van.

Linh N.K.,Thai Nguyen University | Muu L.D.,Institute of Mathematics VAST
RAIRO - Operations Research | Year: 2015

An important problem in distance geometry is of determining the position of an unknown point in a given convex set such that its longest distance to a set of finite number of points is shortest. In this paper we present an algorithm based on subgradient method and convex hull computation for solving this problem. A recent improvement of Quickhull algorithm for computing the convex hull of a finite set of planar points is applied to fasten up the computations in our numerical experiments. © EDP Sciences, ROADEF, SMAI, 2015.

Cuong N.D.,Thai Nguyen University
Proceedings - 2014 International Conference on Information Science, Electronics and Electrical Engineering, ISEEE 2014 | Year: 2014

This paper introduces an adaptive controller that designed based on Model Reference Adaptive System (MRAS) algorithm for motion systems using linear motors. For a given plant model the adaptive controller is designed such that the closed-loop control system has the characteristics of the desired dynamic system. The resulting controller is known as a combination between an adaptive PID controller and an adaptive feed-forward controller. Stability of the adaptive system is guaranteed by using Lyapunov stability theory for the design. The adaptive algorithm is quite simple, robust and converges quickly. Performances of the controlled system are studied through simulation in Matlab/Simulink environment. The effectiveness of the methods is demonstrated by numerical simulations. © 2014 IEEE.

Nguyen V.-D.,Thai Nguyen University | Woo K.-C.,University of Nottingham Malaysia Campus
Nonlinear Dynamics | Year: 2011

A variety of nonlinear dynamic responses for a new electro-vibro-impact system is presented, with indication of chaotic behavior. By mathematical modeling of the physical system, an insight is obtained to the global system dynamics. The modeling has established a good correlation with experimental data, and hence can be used as a numerical tool to optimize the system dynamics. In particular, with respect to impact forces and progression rate, may then be achieved with minimal computational cost. © 2010 Springer Science+Business Media B.V.

Oanh N.T.N.,Thai Nguyen University
Computers and Mathematics with Applications | Year: 2013

In this paper we propose a stable numerical method for an ill-posed backward parabolic equation with time-dependent coefficients in a parallelepiped. The problem is reformulated as an ill-posed least squares problem which is solved by the conjugate gradient method with an a posteriori stopping rule. The least squares problem is discretized by a splitting method which reduces the large dimensions of the discretized problem. We calculate the gradient of the objective functional of the discretized least squares problem by the aid of an adjoint discretized problem which enhances its accuracy. The algorithm is tested on several examples, that proves its efficiency. © 2012 Elsevier Ltd. All rights reserved.

Background: Vietnam shows a paradoxical situation where high contraceptive prevalence goes together with high abortion rates. This study examined the associations between self-reports of having received voluntary family planning (VFP) services and induced abortions.Methods: A cross sectional survey was conducted in Thai Nguyen province, covering a total of 1281 women. Data were derived from a sample of 935 married women aged 18-49 years who were ever-users (93.5%) and current users of contraceptives (84%), and had completed birth histories. The dependent variables were the likelihood of having an induced abortion and repeated (two or more) induced abortions. The main independent variable was having received the three VFP dimensions (counselling, broader information, and access to availability). The association was examined using multivariate logistic regressions, taking into account women's socio-demographic characteristics.Results: The overall induced abortion percentage was 19.4 per 100 pregnancies. None of the three VFP dimensions was significantly associated with the odds of having an induced abortion or having repeated induced abortions. Mother's age of 35 or older, having more than three living children, and ever used female contraception methods significantly doubled or more the odds of having an induced abortion and significantly tripled the odds of having repeated abortions.Conclusions: Results indicate that women receiving VFP services were not less likely to have induced abortions. The provision of family planning counselling, information on contraceptive method mix, and management skills to ensure availability, are in need of reinforcement in a new set of policy and program strategies in the future. © 2012 Nguyen and Budiharsana; licensee BioMed Central Ltd.

Gender-based violence (GBV) has profound adverse consequences on women's physical, mental, and reproductive health. Although Vietnam has high rates of induced abortion and GBV, literature examining this relationship is lacking. This study examines the association of GBV with induced abortion among married or partnered women of reproductive age in Thai Nguyen province, Vietnam. In addition, we explore contraceptive use and unintended pregnancy as mediators in the pathway between GBV and induced abortion. Data were drawn from a cross-sectional survey of 1,281 women aged 18-49 years in four districts of Thai Nguyen province. Bivariate and multivariate logistic regression analyses were applied to examine the associations between lifetime history of GBV, contraceptive use, unintended pregnancy, induced abortion, and repeat abortion, controlling for other covariates. One-third of respondents had undergone induced abortion in their lifetime (33.4%), and 11.5% reported having repeat abortions. The prevalence of any type of GBV was 29.1% (17.0% physical violence, 10.4% sexual violence, and 20.1% emotional violence). History of GBV was associated with induced abortion (OR=1.61, 95% CI: 1.20-2.16) and repeat abortion (OR=2.22, 95% CI: 1.48-3.32). Physical violence was significantly associated with induced abortion, and all three types of violence were associated with repeat abortion. Abused women were more likely than non-abused women to report using contraceptives and having an unintended pregnancy, and these factors were in turn associated with increased risk of induced abortion. GBV is pervasive in Thai Nguyen province and is linked to increased risks of induced abortion and repeat abortion. The findings suggest that a pathway underlying this relationship is increased risk of unintended pregnancy due in part to ineffective use of contraceptives. These findings emphasize the importance of screening and identification of GBV and incorporating women's empowerment in reproductive health and family planning programs.

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