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NURBS-based analyses of functionally graded carbon nanotube-reinforced composite shells
Nguyen, Tan N.,Thai, Chien H.,Nguyen-Xuan, H.,Lee, Jaehong Elsevier 2018 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.203 No.-
<P><B>Abstract</B></P> <P>We in this paper present an effective computational approach for static and free vibration analyses of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) shells. The governing equations are approximated based on the first-order shear deformation shell theory (FSDT) and non-uniform rational B-Spline (NURBS) basis functions. The advantage of NURBS in modeling exact geometries of shell structures is exploited. Material properties of FG-CNTRC shells are assumed to be graded through the thickness and estimated according to an equivalent continuum model based on the rule of mixture. The high accuracy and reliability of the present formulation is verified through several numerical examples in comparison with various reference solutions. In addition, some numerical results of FG-CNTRC panels and cylinders are provided. This may be useful for future references.</P>
NURBS-based postbuckling analysis of functionally graded carbon nanotube-reinforced composite shells
Nguyen, Tan N.,Thai, Chien H.,Luu, Anh-Tuan,Nguyen-Xuan, H.,Lee, Jaehong North-Holland Pub. Co 2019 Computer methods in applied mechanics and engineer Vol.347 No.-
<P><B>Abstract</B></P> <P>An investigation into the postbuckling and geometrically nonlinear behaviors of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) shells is carried out in this study. The discrete nonlinear equation system is established based on non-uniform rational B-Spline (NURBS) basis functions and the first-order shear deformation shell theory (FSDT). The nonlinearity of shells is formed in the Total Lagrangian approach considering the von Karman assumption. The incremental solutions are obtained by using a modified Riks method. In the present formulation, the rule of mixture is used to estimate the effective material properties of FG-CNTRC shells. Effects of CNTs distribution, volume fraction and CNTs orientation on the postbuckling behavior of FG-CNTRC shells are particularly investigated. Exact geometries of shells are modeled by using NURBS interpolation. Several verifications are given to show the high reliability of the proposed formulation. Especially, some complex postbuckling curves of FG-CNTRC panels and cylinders are first provided that could be useful for future references.</P> <P><B>Highlights</B></P> <P> <UL> <LI> NURBS-based postbuckling analysis of functionally graded carbon nanotube-reinforced composite shells is performed in this paper. </LI> <LI> The discrete nonlinear equation system is established based on non-uniform rational B-Spline (NURBS) basis functions and the first-order shear deformation shell theory (FSDT). </LI> <LI> The nonlinearity of shells is formed in the Total Lagrangian approach considering the von Karman assumption. </LI> <LI> Effects of CNTs distribution, volume fraction and CNTs orientation on the postbuckling behavior of FG-CNTRC shells are particularly investigated. </LI> <LI> Some complex postbuckling curves of FG-CNTRC panels and cylinders are first provided that could be useful for future references. </LI> </UL> </P>
Nguyen, Tan N.,Thai, Chien H.,Nguyen-Xuan, H.,Lee, Jaehong Elsevier 2018 Composite structures Vol.193 No.-
<P><B>Abstract</B></P> <P>This paper presents a novel formulation based on an improved moving Kriging (iMK) meshfree method and a refined plate theory (RPT) for geometrically nonlinear static and dynamic analyses of functionally graded material (FGM) plates. The nonlinearity of plates is formed in the total Lagrangian approach based on the von Karman strain assumptions. The present plate formulation has the following advantages: only four variables for each node, the tangential stress-zero boundary condition at the top and bottom surfaces of plates, and the stringent continuity requirement of the generalized displacements being simply treated without any additional variables. The novelty of the iMK meshfree method is to propose a quartic spline correlation function for establishment of basic shape functions. Thanks to this improvement, the solution of the iMK meshfree method is stable and no longer depends on an uncertain adjustment of correlation parameter θ . In addition, a simple rotation-free technique originated from isogeometric analysis (IGA) is successfully applied to the iMK meshfree method for enforcing the slopes of clamped boundary condition. Several numerical examples are provided to demonstrate high performance of the present method in comparison with other numerical methods.</P>
Time Switching for Wireless Communications with Full-Duplex Relaying in Imperfect CSI Condition
( Tan N. Nguyen ),( Dinh-thuan Do ),( Phuong T. Tran ),( Miroslav Voznak ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.9
In this paper, we consider an amplify-and-forward (AF) full-duplex relay network (FDRN) using simultaneous wireless information and power transfer, where a battery-free relay node harvests energy from the received radio frequency (RF) signals from a source node and uses the harvested energy to forward the source information to destination node. The time-switching relaying (TSR) protocol is studied, with the assumption that the channel state information (CSI) at the relay node is imperfect. We deliver a rigorous analysis of the outage probability of the proposed system. Based on the outage probability expressions, the optimal time switching factor are obtained via the numerical search method. The simulation and numerical results provide practical insights into the effect of various system parameters, such as the time switching factor, the noise power, the energy harvesting efficiency, and the channel estimation error on the performance of this network. It is also observed that for the imperfect CSI case, the proposed scheme still can provide acceptable outage performance given that the channel estimation error is bounded in a permissible interval.
Nguyen Huu Khanh Nhan,Tran Hoang Quang Minh,Tan N. Nguyen,Miroslav Voznak 한국광학회 2017 Current Optics and Photonics Vol.1 No.6
Due to optimal advances such as chromatic performance, durability, low power consumption, highefficiency, long-lifetime, and excellent environmental friendliness, white LEDs (WLEDs) are widely usedin vehicle front lighting, backlighting, decorative lighting, street lighting, and even general lighting. In thispaper, the remote packaging WLEDs (RP-WLEDs) with bi-layer red-emitting Sr2Si5N8: Eu2+ and yellowemittingYAG:Ce phosphor was proposed and investigated. The simulation results based on the MATLABsoftware and the commercial software Light Tools indicated that the color rendering index (CRI) of bi-layerphosphor RP-WLEDs had a significant increase. The CRI had a considerable increase from 72 to 94. Inconclusion, the results showed that bi-layer red-emitting Sr2Si5N8:Eu2+ and yellow-emitting YAG:Cephosphor could be a prospective approach for manufacturing RP-WLEDs with enhanced optical properties.
Determinants of Success of University Students in Vietnam: An Empirical Study
NGUYEN, Lan T.N.,THAN, Thao T.,NGUYEN, Tan G. Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.10
This paper investigates the determinants of students' success in Vietnam through conducting online interviews and surveys with 2,500 Vietnamese students at eight famous universities in Vietnam. By applying both SPSS 22 and STATA software, the study is to evaluate the impact of four driver factors, which affect GPA, language efficacy, and personal achievement. These factors are psychological perspective, home environmental, student demographic, and school environmental. The research results emphasize a positive effect of psychological and home-environmental determinants, but the negative effect of school environmental factors on the students' success. Besides, the relationship between demographics and student success was tested and indicated that male students have a better language learning ability, but a low level of academic achievement than female students. The results also point out the impact of religious affiliation and ethnicity on personal achievement. Non-religious students are better achievers than those having a religion or those in minority ethnicity. Moreover, accumulated schooling years are negatively associated with students' success. The more working experience students accrued, the higher possibility they are successful. Finally, the finding provides an insight into students' success that might be useful to government authorities and other universities in designing policies for enhancing the quality of education.
LE, Tri D.,NGUYEN, Tan T.,NGUYEN, Phuong N.D.,NGUYEN, Thi Quynh Trang Korea Distribution Science Association 2022 유통과학연구 Vol.20 No.11
Purpose: Increasing competition in the higher education sector has prompted universities to enhance their marketing efforts and understand their potential customers. The study aims to explore how information sources are used and changed among prospective Vietnamese students during the decision-making process. Research Design, Data, and Methodology: This study undertakes a longitudinal study involving multiple rounds of data collection to better understand the decision-making process of prospective students. Data was collected from 12th -grade students in Vietnam through two rounds of quantitative surveys with 251 students and one round of qualitative interviews, spanning the duration of their senior year. The three stages of the decision-making process correspond to the three stages of pre-purchase period. Results: Most students decide that attending open days, taking career assessments, and looking up information online are the most important information sources to consider. The WOM sources are more important in the early stages, while university-generated sources and events are important in the later stages. Conclusion: Implications from this study may contribute to the design of more effective marketing communications campaigns as university marketers gain a better understanding of the distribution of information sources utilized for each specific stage of the decision-making process.
Buckling resistance of axially loaded square concrete-filled double steel tubular columns
Junchang Ci,Mizan Ahmed,Viet-Linh Tran,Hong Jia,Shicai Chen,Tan N. Nguyen 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.43 No.6
Thin-walled square concrete-filled double steel tubular (CFDST) columns composed of the inner circular tube filled with concrete can be used to carry the large axial loads or strengthen existing CFST columns in composite constructions. This paper reports an experimental program carried out on short square CFDST columns loaded concentrically. The influences of important column parameters on the post-buckling performance of such columns are investigated. Test results exhibit that the inner circular tube significantly improves the ultimate loads and the ductility of such columns compared to conventional concrete-filled steel tubular (CFST) and double-skin CFST (DCFST) columns with an inner void. A mathematical model developed is used to simulate the ultimate strengths and load-strain curves of such columns loaded axially. Furthermore, the ultimate strengths of such columns are predicted using existing codified design models for conventional CFST columns as well as the formulas proposed by previous researchers and compared against a large database comprising 500 CFDST columns. Lastly, an accurate artificial neural network model is developed for the practical applications of such columns under axial loading.