Time filter

Source Type

Van Toan H.,Le Quy Don Technical University | Bao V.N.Q.,Posts and Telecommunications Institute of Technology
International Conference on Advanced Technologies for Communications | Year: 2016

In this paper, we consider a cognitive two-way relay system with multiple relay nodes and multiple primary receivers over Nakagami-m fading channels. Relay nodes process signal following selective decode-And-forward (DF) relay technique. The opportunistic relay selection is used to choose the best relay. We derive the exact closed-form expression of the overall outage probability over Nakagami-m fading channels. These analytical results are exactly verified by Monte-Carlo simulation. © 2016 IEEE.


Nguyen V.-G.,Le Quy Don Technical University
Optical Engineering | Year: 2016

Geometric parameters that define the geometry of imaging systems are crucial for image reconstruction and image quality in X-ray computed tomography (CT). The problem of determining geometric parameters for an offset flat-panel cone beam CT (CBCT) system, a recently introduced modality with a large field of view, with the assumption of an unstable mechanism and geometric parameters that vary in each view, is considered. To accurately and rapidly find the geometric parameters for each projection view, we use the projection matrix method and design a dedicated phantom that is partially visible in all projection views. The phantom consists of balls distributed symmetrically in a cylinder to ensure the inclusion of the phantom in all views, and a large portion of the phantom is covered in the projection image. To efficiently use calibrated geometric information in the reconstruction process and get rid of approximation errors, instead of decomposing the projection matrix into actual geometric parameters that are manually corrected before being used in reconstruction, as in conventional methods, we directly use the projection matrix and its pseudo-inverse in projection and backprojection operations of reconstruction algorithms. The experiments illustrate the efficacy of the proposed method with a real offset flat-panel CBCT system in dental imaging. © 2016 Society of Photo-Optical Instrumentation Engineers (SPIE).


Trung L.T.,Le Quy Don Technical University | Dinh N.Q.,Le Quy Don Technical University
International Conference on Advanced Technologies for Communications | Year: 2015

Recently, the Ultra-Wideband Multi-Input Multi-Output technique has draw the intention of many researchers as it is very promising for high data rate wireless communication systems. In this paper, a new ultra-wideband (UWB) antenna with the size of 15 mm × 26 mm × 1.6 mm is proposed. The antenna works as a magnetic dipole and has the working bandwidth from 3.1 GHz to 10.6 GHz with VSWR ≤ 2. The antenna parameters such as radiation pattern, maximal gain are also investigated. © 2014 IEEE.


Pham V.-B.,Le Quy Don Technical University
Transactions on Emerging Telecommunications Technologies | Year: 2015

The number of time slot (or symbols per slot in 3rd Generation Partnership Project language) in the long-term evolution frame structure for data transmission is not guaranteed to be an even number, so the Alamouti orthogonal space-time block code (STBC) can not be applied. Recently, Lei et al. (Institute of Electrical and Electronics Engineers Transactions on Wireless Communications, 2011) introduced a quasi-orthogonal space time block code (QOSTBC) for two transmit antennas and three time slots (which is named as L-QOSTBC in this paper). This code achieves two desirable properties as full rate and full diversity. However, the main disadvantage of the L-QOSTBC is high decoding complexity due to pair-symbol maximum likelihood decoding. In this paper, we propose a novel three-time-slot STBC (TTS-STBC) for two transmit antennas. The proposed TTS-STBC can achieve full-rate full-diversity transmission with single-symbol maximum likelihood decoding. In comparison to L-QOSTBC, the proposed TTS-STBC has lower decoding complexity and higher coding gain. In addition, a new decoding strategy for the proposed TTS-STBC that named as single-symbol quasi-maximum likelihood is also developed to overcome the performance degradation caused by time-varying fading channels. Simulation results show that the proposed TTS-STBC outperforms the L-QOSTBC in both quasi-static and time-varying fading channels. © 2014 John Wiley & Sons, Ltd.


Hiep P.T.,Le Quy Don Technical University | Hoang N.H.,Le Quy Don Technical University
International Conference on Advanced Technologies for Communications | Year: 2016

There have been increases in the elderly population worldwide, and this has been accompanied by rapid growth in the health-care market, as there is an ongoing need to monitor the health of individuals. Wireless body area networks (WBANs) consist of wireless sensors attached on or inside the human body to monitor vital health-related problems, e.g., electrocardiograms (ECGs), electroencephalograms (EEGs), and electronystagmograms (ENGs). With WBANs, patients' vital signs are recorded by each sensor and sent to a coordinator. However, because of obstructions by the human body, sensors cannot always send the data to the coordinator, requiring them to transmit at higher power. Therefore, we need to consider the lifetime of the sensors given their required transmit power. In the IEEE 802.15.6 standard, the transmission topology functions as a one-hop star plus one topology. In order to obtain a high throughput, we reduce the transmit power of the sensors and maintain equity for all sensors. We propose the multiple-hop transmission for WBANs based on the IEEE 802.15.6 carrier-sense multiple-access with collision avoidance (CSMA/CA) protocol. We calculate the throughput and variance of the transmit power by performing simulations, and we discuss the results obtained using the proposed theorems. © 2015 IEEE.


Nguyen V.H.,Le Quy Don Technical University | Pham P.X.,University of Sydney
Fuel | Year: 2015

Biodiesels, renewable fuels derived from biomass, animal fat, algae, wastes or residues, are amongst potential candidates to improve energy security and to reduce greenhouse gas emissions. Different from fossil diesel which mainly consists of hydrocarbons, biodiesels are oxygenated fuels. Oxygen contained in biodiesels, as an oxidizing enhancer, plays a crucial role in improving the auto-ignition quality. The oxygen enrichment coming from biodiesels causes the fuel-air mixture in the auto-ignition zone where the mixture is quite rich to become leaner, consequently improving combustion and emission quality. As such, a quantitative analysis of the impact of oxygen content in biodiesel-diesel blends in engine combustion and emission concentrations is crucial in giving key clues to fuel manufacturing as well as to internal combustion engine modeling. This study aims to establish a link between the oxygen content and engine performance as well as emission concentrations when using biodiesel blends B0, B10 and B20 (0%, 10% and 20% of biodiesel by volume in biodiesel-diesel mixtures, respectively). The biodiesel was derived from residues of the manufacturing process of palm cooking oil using methanol transesterification with the aid of a high hardness solid ceramic metal catalyst. The engine used in this test is a modern common-rail, single-cylinder engine operating under a fixed injection condition (injection timing, pressure and duration) but with a wide range of engine speeds. The results show that the oxygen enrichment coming from the fuel blends tested in this study lowers the engine power which is attributable to lower heating values of the biodiesel blends compared with that of the fossil diesel. However, the oxygen contained in the blends suppresses particle formation and decreases hydrocarbon and carbon monoxide concentrations. © 2015 Elsevier Ltd. All rights reserved.


Nguyen H.A.,Le Quy Don Technical University
Proceedings of the 2014 7th IEEE Symposium on Computational Intelligence for Security and Defense Applications, CISDA 2014 | Year: 2015

Biological pathways such as metabolic or signaling ones play an important role in understanding cell activities and evolution. A cost-effective method to discover such pathways is analyzing accumulated information about protein-protein interactions, which are usually given in forms of undirected networks or graphs. Previous findings show that orienting protein interactions can improve pathway discovery. However, assigning orientation for protein interactions is a combinatorial optimization problem which has been proved to be NP-hard, making it critical to develop efficient algorithms. In the previous report [1], we solved the problem of finding pathways in the protein-protein interaction networks using genetic algorithms. Our proposed algorithm was also compared with the ones of other authors and proved to be better. However, our algorithm gave out only one goal, which was maximizing the weight function of the interactive network, while ignoring the number of standard pathways in the network. Through exper-iments, we have realized that weight functions with high value do not always give the high number of standard pathways. As a result, this report introduces multi-objective generic algorithms to deal with two targets at the same time: Maximizing the weight and function, as well as calculating the number of standard pathways in the interaction network. To extend the previous report, we first studied the mathematical model of the interaction network orientation problem with multi-objective characteristic. Based on such model, we designed a multi-objective genetic algorithm to find the solutions for the problem. Many experimental runs were carried out on the yeasts protein interaction network data set to find the best answer. Results from Multi-Objective Genetic Algorithm (MOGA), when compared with those of our previous proposed GA algorithms (SOGA - Single-Objective Genetic Algorithm), turn out to better solve the problem. © 2014 IEEE.


Solovyev A.N.,Don State Technical University | Duong L.V.,Le Quy Don Technical University
International Journal of Applied Mechanics | Year: 2016

The power generation efficiency of piezoelectric energy harvesters is dependent on the coupling of their resonant frequency with that of the source vibration. The mechanical design of the energy harvester plays an important role in defining the resonant frequency characteristics of the system and therefore in order to maximize power density, it is important for a designer to be able to model, simulate and optimize designs to match new target applications. This paper gives a detailed calculation of piezoelectric energy harvesters that is in the form of a bimorph-circular plate fixed in the contour in the device frame by finite element (FE) analysis using the commercially available software package ANSYS, ACELAN. The piezoelectric bimorph is assumed to be driven into flexural vibration by an ambient acoustic source to convert the mechanical energies into electric energies. The optimal design was based on matching the resonant frequency of the device with the environmental exciting frequency, and balancing the output voltage. The simplified models of the account of a proof mass are offered. On the basis of calculations, the most effective construction of the device is offered that exhibit the targeted resonant frequency response chosen by the designer. © 2016 World Scientific Publishing Company.


Dinh N.Q.,Le Quy Don Technical University
International Conference on Advanced Technologies for Communications | Year: 2012

The normal mode helical antenna becomes an efficient radiator in the condition of the self resonance. When the antenna size is less than 0.03 wavelengths, the antenna input resistance becomes very small such as about 1 ohm. Therefore, the impedance matching structure is inevitable and its usefulness is required as well. © 2012 IEEE.


Ngo L.T.,Le Quy Don Technical University
Journal of Intelligent and Fuzzy Systems | Year: 2013

Triangulated irregular network (TIN) has used to represent 3-dimensional surfaces by dividing domain into irregular sub-triangles and approximately represent using piecewise linear functions. Hence, TIN are also used to approximately represent membership functions of general type-2 fuzzy sets for reducing computational complexity. To support speed-up in computation of operations of type-2 fuzzy sets, a refinement CTIN is proposed by combining contour model and constraint Delaunay criteria. So a type-2 fuzzy set is also represented by RCTIN in the same way. The paper deals with the use RCTIN to represent general type-2 fuzzy sets. On the basis of RCTIN representation theorem, algorithms for operations and general type-2 fuzzy logic systems (GT2FLS) are proposed. A T2FLS is designed and implemented in comparing previous approaches under an application of obstacle avoidance of robot navigation. © 2013 - IOS Press and the authors. All rights reserved.

Loading Le Quy Don Technical University collaborators
Loading Le Quy Don Technical University collaborators