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Shape optimization of acoustic lenses for underwater imaging
Quang Dat Tran,Gang-Won Jang,권휴상,조완호,조승현,Yo-Han Cho,Hee Seon Seo 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.10
Shape optimization of two-dimensional lenses for acoustic cameras used in underwater acoustic imaging is presented. To understand elastic shear wave effects of a lens on the pressure field of the medium, we couple two physics models, namely a pressure acoustics model and a linear elastic model and formulate it in the finite element analysis framework. As a result, the focal length of a lens is calculated to be longer than that in the absence of shear effects. The accuracy of our model is tested against experimental results, and compared with finite element analysis of a single physics model as well as the hybrid method - a method using geometrical acoustics and wave acoustics. Pressure at the focal point is optimized using geometric parameters for lens surfaces as design variables. Performance differences due to temperature change or obliquely incident waves are controlled using design constraints. The effectiveness of our optimization formulation is verified by solving single- and dual-lens design problems.
Tran, Si Bui Quang,Byun, Doyoung,Nguyen, Vu Dat,Kang, Tae Sam Published by the American Physical Society through 2009 Physical review. E, Statistical, nonlinear, and so Vol.80 No.2
<P>The electrohydrodynamic (EHD) spraying technique has been utilized in applications such as inkjet printing and mass spectrometry technologies. In this paper, the role of electrical potential signals in jetting and on the oscillation of the meniscus is evaluated. The jetting and the meniscus oscillation behavior are experimentally investigated under ac voltage, ac voltage superimposed on dc voltage, and pulsed dc voltage. Based on this in-depth study of the meniscus behavior under various signals, the optimal signal is implemented to an EHD inkjet head for drop-on-demand operation. For applied ac voltage and ac voltage superimposed on dc voltage, the jetting phenomenon is a dynamic process due to sequential opposite sign signals. The jetting occurs at the end of the oscillation cycle, where the meniscus oscillates upward and arrives at its highest position.</P>
Van-Dat Tran,Quang Huy Vu 사람과세계경영학회 2019 Global Business and Finance Review Vol.24 No.3
The purpose of this study is to clarify whether there are relationships among the four key factors contributing to the success of e-business: e-service quality, e-trust e-customer satisfaction and behavioral intentions, thus make a conclusion and provide better understanding in the field of e-service and e-marketing. This study method used to evaluate and test the scale and theoretical model in the study is quantitative research with sample size N = 476 through the survey to deliver questionnaire directly to subjects. This study examined the scale by confirmatory factor analysis (CFA) and the model of theoretical research by structural equation modeling (SEM). The results of analysis and verification of measurement scales and theoretical research models show that the research scales achieve unidirectional, reliability, convergent validity and high discriminant validity. The hypotheses are accepted at 95% reliability. The study has discovered the new indirect and positive impact of e-service quality on behavioral intentions through mediators e-trust and e-customer satisfaction, as well as other sub relationships, which can be used as foundation for future researches. At the end, managerial implications and recommendations plus contributions are proposed for e-commerce firms, e-marketers and researchers.
Fabrication of Polymer Inkjet Head for Electrohydrodynamic(EHD) Printing
Vu Dat Nguyen,Doyoung Byun(변도영),Si Bui Quang Tran 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
A polymer ink jet nozzle is designed and fabricated with 370 ㎛ outer diameter. Polymethyl-methacrylate (PMMA) is used for the nozzle, which can offer better wetting properties and low cost features Due to dynamic behavior of meniscus on the nozzle, it requires duration time for the meniscus to move from the initial position to the jet state. To improve drop-on-demand jetting speed, the effect of frequency of applied voltage is investigated.
Si Bui Quang Tran,Doyoung Byun(변도영),Vu Dat Nguyen,Tae Sam Kang(강태삼) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
The electrohydrodynamic (EHD) spraying technique has been utilized in applications such as inkjet printing and mass spectrometry technologies. In this paper, the role of electrical potential signals in jetting and on the oscillation of the meniscus is evaluated. The jetting and meniscus oscillation behavior are experimentally investigated under ac voltage, ac voltage superimposed on dc voltage, and pulsed dc voltage. Based on this in-depth study of the meniscus behavior under various signals. the optimal signal is implemented to an EHD inkjet head for drop-on-demand operation. For applied ac voltage and ac voltage superimposed on dc voltage, the jetting phenomenon is a dynamic process due to sequential opposite sign signals. Jetting occurs at the end of the oscillation cycle, where the meniscus oscillates upward and arrives at its highest position.