Tuyhoa Industrial College

Vietnam, China

Tuyhoa Industrial College

Vietnam, China
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Tuan B.M.,Nanjing Southeast University | Tuan B.M.,Tuyhoa Industrial College | Chen Y.,Nanjing Southeast University
Dongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Southeast University (Natural Science Edition) | Year: 2014

The stress intensity factor (SIF) and stress fields at the crack tips of a center crack and an edge crack are investigated by the finite element method (FEM) and the nodal displacement method. With the use of the 8 node isoparametric quadrilateral element and the quarter singular element, the influence of meshing density and crack length on the calculation accuracy is studied. The nodal density in sub-region around the crack tips is improved, which can ensure the calculation accuracy and save computing time. The code for calculating and analyzing stress intensity factor, stress fields and displacement fields at the crack tips for mode I and mode II SIFs of plate is written in Matlab/Simulink. The results of the FEM-code are compared with those of the exact methods. The results show that this proposed method can improve the calculation accuracy and the converging speed. The algorithm is reasonable and the results can be used to improve the precision of simulation results and guide engineering design.


Minh Hau T.,Kunming University of Science and Technology | Minh Hau T.,Tuyhoa Industrial College | Yu X.,Kunming University of Science and Technology | Zhou D.,Kunming University of Science and Technology | And 4 more authors.
Optical Materials | Year: 2013

The Bi-Er co-doped lanthanum aluminosilicate glasses, which exhibited a broadband near-infrared emission, were developed and observed in using the optical absorption and photoluminescence spectra. A super broadband near-infrared emission extending from 1.0 to 1.8 μm with a full-width at half-maximum of 450 nm which covered the whole O, E, S, C and L bands, was observed in Bi-Er co-doped samples under 808 nm excitation, as a result of the overlap of the Bi-related emission band (1270 nm) and the emission from Er 3+ 4I13/2 → 4I15/2 transition (1545 nm). This report will discuss about a possible mechanism for energy transfer between Bi-related centers and Er3+ ion. © 2012 Elsevier B.V. All rights reserved.


Minh Hau T.,Kunming University of Science and Technology | Minh Hau T.,Tuyhoa Industrial College | Wang R.,Kunming University of Science and Technology | Yu X.,Kunming University of Science and Technology | And 5 more authors.
Journal of Physics and Chemistry of Solids | Year: 2012

The Bi-Tm-Er co-doped SiO 2-Al 2O 3-La 2O 3 (SAL) glasses, which exhibited a broadband near-infrared (NIR) emission, were investigated by the optical absorption and photoluminescence spectra. A super broadband NIR emission extending from 0.95 to 1.6 μm with a full-width at half-maximum (FWHM) of 430 nm which covered the whole O, E, S, C and L bands, was observed in Bi-Tm-Er co-doped samples under 808 nm excitation, as a result of the overlap of the Bi-related emission band (centered at 1270 nm) and the emission from Tm 3+ 3H 4→ 3F 4 transition (1450 nm) as well as Er 3+ 4I 13/2→ 4I 15/2 transition (1545 nm). In addition, a super broadband emission with amplitude relatively flat from 0.95 to 2.1 μm has been observed. The possible energy transfer between Bi-related centers, Tm 3+ ions and Er 3+ ions was proposed. © 2012 Elsevier Ltd. All rights reserved.


Dan H.K.,Kunming University of Science and Technology | Dan H.K.,Tuyhoa Industrial College | Zhou D.,Kunming University of Science and Technology | Wang R.,Kunming University of Science and Technology | And 5 more authors.
Optical Materials | Year: 2014

Transparent glass-ceramics SiO2-AlF3-BaF 2-TiO2-LaF3 (SABTL) containing Ba 2LaF7 nanocrystals were successfully prepared by heat treatment process through conventional melting method. The crystal size in the glass-ceramics increased gradually under the changing of heat treatment temperatures and times, which was confirmed by the results of XRD, TEM measurements. The intensity of the blue, green and red upconversion luminescence around 490 nm, 525 nm, 546 nm, 657 nm which originate from the transitions 5D4 → 7FJ (J = 6 and 5) of Tb3+ ions and (2H11/2, 4S 3/2, 4F9/2) → 4I15/2 transitions of Er3+ ions, respectively, were strongly observed after heat treatment under 980 nm laser diode excitation. The intensity of upconversion luminescence was increased gradually with the increase of Yb 3+ concentrations and reaches its maximum at 2.5 mol%. The upconversion luminescence and energy transfer process between Tb 3+, Yb3+ and Er3+ ions in the glass-ceramics were discussed. © 2013 Elsevier B.V. All rights reserved.


Dan H.K.,Kunming University of Science and Technology | Dan H.K.,Tuyhoa Industrial College | Zhou D.,Kunming University of Science and Technology | Wang R.,Kunming University of Science and Technology | And 7 more authors.
Journal of Non-Crystalline Solids | Year: 2013

The energy transfer and upconversion emission of Tm3 +/Tb 3 +/Yb3 + co-doped transparent glass-ceramics 50SiO 2-10AlF3-30BaF2-5TiO2-4LaF 3 (SABTL) containing Ba2LaF7 nanocrystals under the changing of heat treatment temperatures and concentrations of Tm 3 +/Tb3 +/Yb3 + ions were investigated. The structural investigation carried out by X-ray diffraction (XRD) and transmission electron microscopy evidenced the formation of cubic Ba2LaF 7 nanocrystals. The efficiency upconversion emission of Tm 3 +/Tb3 +/Yb3 + ions was observed in the glass-ceramics. The upconversion emission and energy transfer between Tm 3 + and Tb3 + ions were investigated with the Yb 3 + ions cooperatively upconversion emission, energy transfer between Tm3 + and Tb3 + ions. © 2013 Published by Elsevier B.V.


Dan H.K.,Kunming University of Science and Technology | Dan H.K.,Tuyhoa Industrial College | Zhoua D.,Kunming University of Science and Technology | Rongfei W.,Kunming University of Science and Technology | And 5 more authors.
Journal of Rare Earths | Year: 2013

The up-conversion of Er3+/Yb3+ co-doped transparent glass-ceramics 50SiO2-10AlF3-5TiO2-30BaF 2-4LaF3-0.5ErF3-0.5YbF3 containing Ba2LaF7 nanocrystals under the changing of heat treatment temperature and time were investigated. The Ba2LaF7 nanocrystals precipitated from the glass matrix was confirmed by X-ray diffraction (XRD). The structural investigation carried out by XRD and transmission electron microscopy (TEM) evidenced the formation of cubic Ba 2LaF7 nanocrystals with crystal size of about 14 nm. Comparing with the samples before heat treatment, the high efficiency up-conversion emission of Er3+/Yb3+ co-doped samples was observed in the glass-ceramics under 980 nm laser diode excitation. The increase in red emission intensity bands was stronger than the green bands when the crystal size increased. The mechanism for the up-conversion process in the glass-ceramics and the reasons for the increase of Er3+/Yb 3+ co-doped up-conversion intensity after heat treatment were discussed. © 2013 The Chinese Society of Rare Earths.


Dan H.K.,Kunming University of Science and Technology | Dan H.K.,Tuyhoa Industrial College | Zhou D.,Kunming University of Science and Technology | Zhou D.,Key Laboratory of Advanced Materials of Yunnan Province | And 10 more authors.
Ceramics International | Year: 2015

The transparent glass-ceramics SiO2-AlF3-BaF2-TiO2-CaCO3 containing BaF2 nanocrystals were successfully prepared by the conventional melting method. The effect of the AuNPs on the enhancement upconversion and near-infrared emission in Er3+/Yb3+ co-doped transparent glass-ceramics under 980 nm laser diode excitation were investigated. The transmission electron microscopy (TEM) micrograph showed the average diameter size of gold nanoparticles is estimated about 4-6 nm. Compared with the glass-ceramics sample without HAuCl4, the upconversion and near-infrared emissions intensity of SAB glass-ceramics samples with HAuCl4 were significantly increased. Particularly, the red UC emission intensity band centered at 850 nm strongly increased about twenty-fold with the increase of HAuCl4 concentration and reaches its maximum at 1.5 mol%, then decreases due to the self-quenching effect. The possible mechanism responsible for the enhancement of upconversion and near-infrared emission in Er3+/Yb3+ co-doped due to effectiveness of surface plasmon resonance were discussed. © 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.


Minh Hau T.,Kunming University of Science and Technology | Minh Hau T.,Tuyhoa Industrial College | Wang R.,Kunming University of Science and Technology | Zhou D.,Kunming University of Science and Technology | And 6 more authors.
Journal of Luminescence | Year: 2012

The BiTm co-doped SiO 2Al 2O 3La 2O 3 (SAL) glasses, which exhibited a broadband near-infrared (NIR) emission was investigated by the optical absorption and photoluminescence spectra. The super broadband near-infrared emission from 1000 to 2100 nm, which covered the whole O, E, S, C and L bands, was observed in the BiTm co-doped samples, as a result of the overlap of the Bi-related emission band (centered at 1270 nm) and the emission from Tm 3+ 3+H 4→ 3+F 4 transition (1440 nm) as well as Tm 3+ 3+F 4→ 3+H 6 transition (1800 nm). Relative luminescence intensity at 1270, 1440 and 1800 nm wavelength varied depending on the mixing ratio of Bi and Tm and the full-width at half-maximum (FWHM) extending from 1000 to 1600 nm could be 400 nm. These results indicated that BiTm co-doped SiO 2Al 2O 3La 2O 3 glasses could provide potential applications in tunable lasers as well as the broadband optical amplifiers in WDM system. © 2012 Elsevier B.V.


Tu T.D.,Nanjing Southeast University | Tu T.D.,Tuyhoa Industrial College | Guang C.,Nanjing Southeast University | Xin L.Y.,Nanjing Southeast University
2015 International Conference on Computing, Management and Telecommunications, ComManTel 2015 | Year: 2015

Modern botnets such as Zeus and Conficker com-monly utilize a technique called domain fluxing or a Domain Generation Algorithm (DGA) to generate a large number of pseudo-random domain names dynamically for botnet operators to control their bots. These botnets are becoming one of the most serious threats to the Internet security on a global scale. In this paper, we present a method based on analyzing the similar peri-odic time intervals series of DNS queries to identify DGA-bot infected machines. This method passively captures all DNS traffic from the gateway of monitor network. Firstly, we group queries of the same domain name that is requested by hosts, and then extracts time interval series between adjacent queries. Secondly, we measure the similar periodicity of DNS queries by calculating the squared Euclidean distance between each pair of their time interval series. Finally, we apply a hierarchical clustering algo-rithm to cluster high similar domain names. The experiment re-sults show that the domain names are generated by the same botnet or DGA would be grouped into the same cluster, thus all of the hosts that query to these clusters are marked as compro-mised hosts running a domain-flux botnet within monitor net-work. © 2015 IEEE.


Truong D.-T.,Nanjing Southeast University | Truong D.-T.,Tuyhoa Industrial College | Cheng G.,Nanjing Southeast University | Jakalan A.,Nanjing Southeast University | And 2 more authors.
Journal of Internet Technology | Year: 2016

Modern botnets such as Zeus, Conficker have started employing a technique called domain fluxing to prevent a naive blacklisting approach employed by network administrators. Domain fluxing bots generate a list of Pseudo-Random Domain names (PRD) or base on a predefined algorithm, called Domain name Generation Algorithm (DGA) for botnet operators to command and control (C&C) their bots. It is a pressing issue today to prevent or least reduce their destructive actions. In this paper, we focus on detecting domain-flux botnet within the monitored network based on DNS traffic features. First, we present a method to identify bot-infected machines based on the similar periodic time intervals series of DNS queries. Then, in order to detect C&C Server, we monitor the stream of active DNS queries from bot-infected machines, and introduce a method to extract related feature values aiming to distinguish bot-generated domain names from humangenerated ones base on a classifier model that we previously trained. We use five various machine learning algorithms to train classifier models and evaluate the effectiveness of detection. The experimental results showed that the proposed method achieves the highest detection efficiency for decision trees algorithms (J48) with the average overall accuracy up to 98.5% and false positive rate is 1.2%.

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