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Ho Chi Minh City, Vietnam

Bao V.N.Q.,Posts And Telecom Institute Of Technology | Phuong B.P.L.,International University | Thanh T.T.,Ho Chi Minh City University of Transport
2012 4th International Conference on Communications and Electronics, ICCE 2012 | Year: 2012

We first propose transmit antenna selection/selection combining (TAS/SC) based MIMO decode-and-forward (DF) relaying networks to simultaneously employ advantages offered by multi-hop relaying and TAS/SC. To investigate the system, we further propose to approximate the distribution of the end-to-end signal-to-noise ratio (SNR). The advantage of the proposed approximation resides mainly in the fact that it results in simple and mathematically tractable closed-form expression of the system performance metrics such as outage probability, ergodic capacity, symbol error rate and bit error rate thus offering clear insights on system behaviors. Monte-Carlo simulation results have been performed to cross-check the accuracy of the theoretical analysis showing that our proposed protocol outperforms the single-antenna-equipped multi-hop network in all range of operating SNRs. Under the constraint of spectral efficiency, the optimal number of hops is existed and a function of modulation schemes and path loss exponent. © 2012 IEEE. Source


Nguyen L.V.,University of Texas at Arlington | Tran H.-D.,Ho Chi Minh City University of Transport | Johnson T.T.,University of Texas at Arlington
IEEE Transactions on Energy Conversion | Year: 2014

In this paper, we present virtual prototyping of the distributed control for a modular multilevel inverter used as a grid-tie interface for photovoltaics. Due to the distributed control and inherent redundancy in the system composed of many panels and inverter modules, the system topology exhibits fault-tolerance capabilities that we study through virtual prototyping. The fault-tolerance is enabled by several distributed algorithms, such as services to identify which, if any, agents controlling inverter modules have failed. A distributed identifier algorithm allows the system to keep track of the number of operating panels to appropriately regulate the dc voltage output of the panels using buck-boost converters and determine appropriate switching times for H-bridges in the grid-tie. We evaluate the distributed inverter, its control strategy, and fault-tolerance through thousands of simulation scenarios in Mathworks Simulink/Stateflow. Our virtual prototyping framework allows for generating multilevel inverters composed of many inverter modules, and we evaluate inverters composed of five to dozens of inverter modules. Our analysis suggests the achievable total harmonic distortion of the modular multilevel inverter may allow for operating solar arrays in spite of failures of the power electronics, control software, and other subcomponents. © 2014 IEEE. Source


Dang T.,Ho Chi Minh City University of Transport | Bargstadt H.-J.,Bauhaus University Weimar
Journal of Construction Engineering and Management | Year: 2016

Four-dimensional (4D) schedules have proven successful in planning with their visualization capabilities allowing for coordination and time-space conflict detection. However, when considered in depth, internal aspects of 4D scheduling techniques have not made significant advances from traditional two-dimensional (2D) scheduling. What is missing from 4D scheduling? Why has the interaction between activities, their relationships, and three-dimensional (3D) components not been flexible and adaptive enough? In light of these questions, this paper analyzes the current state of 4D scheduling. The missing element in 4D scheduling is found to be 4D relationships (4DRs). A prototype of 4DRs has therefore been developed to improve 4D scheduling. Finally, guidance on the application of 4DRs in 4D scheduling is presented to help the users come to a thorough understanding of its advantages and disadvantages and potential applications. © 2015 American Society of Civil Engineers. Source


de Freitas J.A.T.,University of Lisbon | Cuong P.T.,University of Lisbon | Cuong P.T.,Ho Chi Minh City University of Transport | Faria R.,University of Porto
International Journal for Numerical Methods in Engineering | Year: 2015

A hybrid finite element formulation is used to model the hygro-thermo-chemical process of cement hydration in high performance concrete. The temperature and the relative humidity fields are directly approximated in the domain of the element using naturally hierarchical bases independent of the mapping used to define its geometry. This added flexibility in modeling implies the independent approximation of the heat and moisture flux fields on the boundary of the element, the typical feature of hybrid finite element formulations. The formulation can be implemented using coarse and, eventually, unstructured meshes, which may contain elements with high aspect ratios, an option that can be advantageously used in the simulation of the casting of concrete structural elements. The resulting solving system is sparse and well suited to adaptive refinement and parallelization. It is solved coupling a trapezoidal time integration rule with an adaptation of the Newton-Raphson method designed to preserve symmetry. The relative performance of the formulation is assessed using a set of testing problems supported by experimental data and results obtained with conventional (conform) finite elements. © 2015 John Wiley & Sons, Ltd. Source


Nguyen T.T.,Ho Chi Minh City University of Transport | Chan T.M.,Hong Kong Polytechnic University | Mottram J.T.,University of Warwick
Composite Structures | Year: 2015

This paper presents an investigation into the development of a design procedure for Pultruded Fibre Reinforced Polymers (PFRP) beams failing by the elastic buckling mode of Lateral-Torsional Buckling (LTB). The design procedure is based on the European design approach for uniform members in bending of structural steel. In particular, the calibration method adopts the general case 'resistance' formula in Eurocode 3 (EN 1993-1-1:2005), and follows a standard design from testing procedure given in Eurocode 0 (EN 1990:2002) when calibrating the 'design model' to determine the partial factor γM for a member instability check. The test population for calibration has 114 LTB buckling resistances using four PFRP section sizes of I and channel shapes. The non-dimensional slenderness parameter is defined using the local flange buckling strength instead of the yield strength. An imperfection factor of 0.34 and partial factor of 1.3 are shown to be appropriate for calculation of the LTB moment of resistance. © 2015 Elsevier Ltd. Source

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