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Nguyen Tat Thanh University

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Nguyen M.-K.,Nguyen Tat Thanh University | Lim Y.-C.,Chonnam National University | Park S.-J.,Chonnam National University
IEEE Transactions on Power Electronics | Year: 2013

This paper deals with a new family of high boost voltage inverters that improve upon the conventional trans-Z-source and trans-quasi-Z-source inverters. The improved trans-Z-source inverter provides continuous input current and a higher boost voltage inversion capability. In addition, the improved inverter can suppress resonant current at startup, which might destroy the device. In comparison to the conventional trans-Z-source/-trans-quasi-Z-source inverters, for the same transformer turn ratio and input and output voltages, the improved inverter has a higher modulation index with reduced voltage stress on the dc link, lower current stress flow on the transformer windings and diode, and lower input current ripple. In order to produce the same input and output voltage with the same modulation index, the improved inverter uses a lower transformer turn ratio compared to the conventional inverters. Thus, the size and weight of the transformer in the improved inverter can be reduced. This paper presents the operating principles, analysis and simulation results, and compares them with those of the conventional trans-Z-source/-quasi-Z-source inverters. To verify the performance of the improved converter, a laboratory prototype was constructed based on a TMS320F2812digital signal processor with 100V $\rm dc input and 115V $\rm rms output voltage. © 1986-2012 IEEE.


Nguyen M.-K.,Nguyen Tat Thanh University | Lim Y.-C.,Chonnam National University | Kim Y.-J.,Chosun University
IEEE Transactions on Power Electronics | Year: 2012

A modified single-phase quasi-Z-source ac-ac converter is proposed in this paper. The proposed converter has the main features in that the output voltage can be bucked or boosted and be both in-phase and out-of-phase with the input voltage. The input voltage and output voltage share the same ground, the size of a converter is reduced, and it operates in a continuous current mode. A safe-commutation strategy for the modified single-phase quasi-Z-source ac-ac converter is used instead of a snubber circuit. The operating principles and a steady-state analysis are presented. A laboratory prototype, tested using a resistive load, a passive load, and a nonlinear load, was constructed that used an input voltage of 70 V$ \rm rms /60Hz in order to verify the performance of the modified single-phase quasi-Z-source ac-ac converter. The experimental results verified that the converter has a lower input current total harmonic distortion, a higher input power factor, and a higher efficiency in comparison to a conventional single-phase Z-source ac-ac converter. In addition, the experimental results show that the use of the safe-commutation strategy is a significant improvement, as it makes it possible to avoid voltage spikes on the switches. © 2011 IEEE.


Nguyen M.-K.,Nguyen Tat Thanh University | Lim Y.-C.,Chonnam National University | Kim Y.-G.,Chonnam National University
IEEE Transactions on Industrial Electronics | Year: 2013

A new family of single-stage high-step-up boost voltage inverters based on transformers is proposed, called TZ-source inverters. By replacing two inductors in the classical Z-source inverter with two transformers, the proposed inverter produces a very high boost voltage gain when the turn ratio of the transformers is larger than 1. Compared to the trans-Z-source inverters, the proposed TZ-source inverter uses a lower transformer turn ratio, which reduces the transformer's size and weight while producing the same output voltage gain. The extension of the proposed inverter topology to dc-link-type and embedded-type topologies is presented. The operating principles, analysis, and simulation results are shown. To verify the performance of the proposed TZ-source inverter, a laboratory prototype was constructed and operated with 60-V dc input. The simulation and experimental results verified that the converter has high-step-up inversion ability. © 1982-2012 IEEE.


Nguyen M.-K.,Nguyen Tat Thanh University | Lim Y.-C.,Chonnam National University | Cho G.-B.,Chosun University
IEEE Transactions on Power Electronics | Year: 2011

This paper deals with a new family of high boost voltage inverters called switched-inductor quasi-Z-source inverters (SL-qZSIs). The proposed SL-qZSI is based on the well-known qZSI topology and adds only one inductor and three diodes. In comparison to the SL-ZSI, for the same input and output voltages, the proposed SL-qZSI provides continuous input current, a common ground with the dc source, reduced the passive component count, reduced voltage stress on capacitors, lower shoot-through current, and lower current stress on inductors and diodes. In addition, the proposed SL-qZSI can suppress inrush current at startup, which might destroy the devices. This paper presents the operating principles, analysis, and simulation results, and compares them with those of the SL-ZSI. To verify the performance of the proposed converter, a laboratory prototype was constructed with 48 V dc input and an ac output line-to-line voltage of 120 V rms. The simulation and experimental results verified that the converter has high step-up inversion ability. © 2011 IEEE.


Phung-Van P.,Ton Duc Thang University | Nguyen-Thoi T.,National University of Civil Engineering | Luong-Van H.,Ho Chi Minh City University of Technology | Lieu-Xuan Q.,Nguyen Tat Thanh University
Computer Methods in Applied Mechanics and Engineering | Year: 2014

A cell-based smoothed three-node Mindlin plate element (CS-MIN3) based on the first-order shear deformation theory (FSDT) was recently proposed for static and dynamics analyses of Mindlin plates. In this paper, the CS-MIN3 is extended to geometrically nonlinear analysis of functionally graded plates (FGPs) subjected to thermo-mechanical loadings. In the FGPs, the material properties are assumed to vary through the thickness by a simple power rule of the volume fractions of the constituents. The nonlinear formulation is based on the C0-type high-order shear deformation plate theory (C0-HSDT) and the von Kármán strains, which deal with small strains and moderate rotations. In the analysis process, both thermal and mechanical loadings are considered and a two-step procedure is performed including a step of analyzing the temperature field along the thickness of the plate and a step of analyzing the geometrically nonlinear behavior of the FGPs subjected to both thermal and mechanical loadings. The accuracy and reliability of the proposed method is verified by comparing its numerical solutions with those of available other numerical results. © 2013 Elsevier B.V.


Nguyen-Thoi T.,Nguyen Tat Thanh University | Phung-Van P.,Nguyen Tat Thanh University | Nguyen-Xuan H.,Nguyen Tat Thanh University | Thai-Hoang C.,Ton Duc Thang University
International Journal for Numerical Methods in Engineering | Year: 2012

The cell-based strain smoothing technique is combined with discrete shear gap method using three-node triangular elements to give a so-called cell-based smoothed discrete shear gap method (CS-DSG3) for static and free vibration analyses of Reissner-Mindlin plates. In the process of formulating the system stiffness matrix of the CS-DSG3, each triangular element will be divided into three subtriangles, and in each subtriangle, the stabilized discrete shear gap method is used to compute the strains and to avoid the transverse shear locking. Then the strain smoothing technique on whole the triangular element is used to smooth the strains on these three subtriangles. The numerical examples demonstrated that the CS-DSG3 is free of shear locking, passes the patch test, and shows four superior properties such as: (1) being a strong competitor to many existing three-node triangular plate elements in the static analysis; (2) can give high accurate solutions for problems with skew geometries in the static analysis; (3) can give high accurate solutions in free vibration analysis; and (4) can provide accurately the values of high frequencies of plates by using only coarse meshes. © 2012 John Wiley & Sons, Ltd.


Cong Vinh P.,Nguyen Tat Thanh University
Future Generation Computer Systems | Year: 2015

New computing systems are currently at crucial point in their evolution: autonomic systems (ASs), which are inspired by the human autonomic nervous system. Autonomic computing (AC) is characterized by self-*such as self-configuration, self-healing, self-optimization, self-protection and more which run simultaneously in ASs. Hence, self-*is a form of concurrent processing in ASs. Taking advantage of categorical structures we establish, in this paper, a firm formal basis for specifying concurrency of self-* in ASs. © 2015 Elsevier B.V.


Vinh P.C.,Nguyen Tat Thanh University
Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering, LNICST | Year: 2016

Self-* is widely considered as a foundation for autonomic computing. The notion of autonomic systems (ASs) and self-* serves as a basis on which to build our intuition about category of ASs in general. In this paper we will specify ASs and self-* and then move on to consider products and coproducts of ASs. All of this material is taken as an investigation of our category, the category of ASs, which we call AS. © ICST Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2016.


Tung N.T.,Nguyen Tat Thanh University
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012

Sensor networks are deployed in numerous military and civil applications, such as remote target detection, weather monitoring, weather forecast, natural resource exploration and disaster management. Despite having many potential applications, wireless sensor networks still face a number of challenges due to their particular characteristics that other wireless networks, like cellular networks or mobile ad hoc networks do not have. The most difficult challenge of the design of wireless sensor networks is the limited energy resource of the battery of the sensors. This limited resource restricts the operational time that wireless sensor networks can function in their applications. Routing protocols play a major part in the energy efficiency of wireless sensor networks because data communication dissipates most of the energy resource of the networks. This paper studies the importance of considering neighboring nodes in the energy efficiency routing problem. After showing that the routing problem that considers the remaining energy of all sensor nodes is NP-complete, heuristics are proposed for the problem. Simulation results show that the routing algorithm that considers the remaining energy of all sensor nodes improves the system lifetime significantly compared to that of minimum transmission energy algorithms. © 2012 Springer-Verlag.


Vinh P.C.,Nguyen Tat Thanh University
Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering, LNICST | Year: 2016

Self-* is widely considered as a foundation for autonomic computing. The notion of autonomic systems (ASs) and self-* serves as a basis on which to build our intuition about category of ASs in general. In this paper we will specify ASs and self-* and then move on to consider finite limits and colimits in ASs. All of this material is taken as an investigation of our category, the category of ASs, which we call AS. © ICST Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2016.

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