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Warping stresses of a rectangular single leaf flexure under torsion
Nghia Huu Nguyen,Ji-Soo Kim,이동연 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.59 No.3
We describe a stress analysis of a single leaf flexure under torsion in which the warping effect is considered. The theoretical equations for the warping normal stress (xx) and shear stresses (xz and xy) are derived by applying the warping function of a rectangular cross-sectional beam and the twist angle equation that includes the warping torsion. The results are compared with those of the non-warping case and are verified using finite element analysis (FEA). A sensitivity analysis over the length, width, and thickness is performed and verified via FEA. The results show that the errors between the theory of warping stress results and the FEA results are lower than 4%. This indicates that the proposed theoretical stress analysis with warping is accurate in the torsion analysis of a single leaf flexure.
Critical Compressive Strain of Concrete under a Long-Term Deformation Effect Part I. Experiments
Nghia, Tran Tuan,Chu, In-Yeop,Kim, Jin-Keun Korea Concrete Institute 2010 International Journal of Concrete Structures and M Vol.4 No.2
This paper focuses on the effect of creep on the critical compressive strain (CCS) of concrete. The strain of concrete corresponding to the peak compressive stress is crucial in the selection of the ultimate yield strength of the reinforcing bar used in reinforced concrete columns. Among the various influencing factors, such as the creep, shrinkage, loading rate and confinement, the effect of creep and shrinkage is the most significant. So far, investigations into how these factors can affect the CCS of concrete have been rare. Therefore, to investigate the effect of creep and shrinkage on CCS, an experimental (part I) and a parametric study (part II) were conducted, as presented in these papers (part I considers creep effect, part II considers effect of creep and shrinkage). In part I, experiments pertaining to the loading age, loading rate, loading duration and loading and creep levels were conducted to study the effect of these variables on the CCS of concrete. It was found that the effects of the loading rate, loading age, and level and duration on the CCS of concrete were negligible. However, it is very important to consider the effect of creep.
Real Time Control of an Induction Motor Using IMC Approach
Nghia, Duong Hoai,Nho, Nguyen Van,Bac, Nguyen Xuan,Lee, Hong-Hee The Korean Institute of Power Electronics 2009 JOURNAL OF POWER ELECTRONICS Vol.9 No.3
The paper presents a method for controlling induction motors using a nonlinear internal model control (IMC) approach. The process model and the inverse model are developed in the rotor flux coordinate. The main advantage of the proposed method is that it easily specifies the performance (steady state error, transient response, etc.) and the robustness of the controller by means of the IMC filters. Simulation results illustrate the effectiveness of the proposed method. Results on a real time system show that the control system has good performance and robustness against changes in motor parameters (rotor and stator resistances, rotor and stator inductances, rotor inertia).
Effect on TENG Performance by Phase Control of TiOx Nanoparticles
Nghia Dinh Huynh,박현우,정권범,최덕현 한국복합재료학회 2018 Composites research Vol.31 No.6
One of the critical parameters to improve the output power for triboelectric nanogenerators (TENGs) is the surface charge density. In this work, we modify the tribo-material of TENG by introducing the TiOx embedded Polydimethylsiloxane (PDMS) in anatase and rutile phase. The effect of dielectric constant and electronic structure of the TiOx on the capacitance of TENG and the output power as well are discussed. The surface charge density is increased as the control of the dielectric constant in difference weight percent of TiOx and PDMS. As the results of that, the 5% TiOx rutile phase and 7% TiOx anatase phase embedded PDMS exhibit the highest TENG output. The peak value of voltage/current obtained from TiOx rutile and anatase phase are ~180 V/8.2 μA and 211.6 V/8.7 μA, respectively, at the external force of 5 N and working frequency of 5 Hz, which gives over 12-fold and 15-fold power enhancement compared with the TENG based on the pristine PDMS film. This study provides a better understanding for TENG performance enhancement from the materials view.