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Ho Chi Minh City, Vietnam

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. Source


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. Source


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. Source


Cong Vinh P.,Nguyen Tat Thanh University
Mobile Networks and Applications | 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 some universal constructions such as products, coproducts, finite limits and colimits of ASs. All of this material is taken as an investigation of our category, the category of ASs, which we call AS. © 2016 Springer Science+Business Media New York Source


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. Source

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