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Vortex shedding in free-flying beetles
Tien Van Truong,Hieu Trung Tran,Tuyen Quang Le,Hoon Cheol Park(박훈철),Doyoung Byun(변도영) 한국항공우주학회 2009 한국항공우주학회 학술발표회 논문집 Vol.2009 No.11
The detail of the field of air flow around the wings of free-flying beetle is presented by using smoke wire visualization technique. It is apparent that beetle is unusual in comparison with other insects, it has a pair of an elytron and a hind wing. Hence, vortices are generated by movement of both wings and wing-wing interaction. The images show that the vortex generated by eytron is strongly influence the vortex dynamic generated by hind wings. In forward flight, the leading edge vortex (LEV) of both wings grew in size and shed during downstroke, meanwhile the trailing edge vortex (TEV) is formed in supination. The formation of LEV on elytron highlights that total aerodynamic force of beetle can be improved by eytron.
Experimental and numerical studies of beetle-inspired flapping wing in hovering flight
Van Truong, Tien,Le, Tuyen Quang,Park, Hoon Cheol,Byun, Doyoung IOP Publishing 2017 Bioinspiration & biomimetics Vol.12 No.3
<P>In this paper, we measure unsteady forces and visualize 3D vortices around a beetle-like flapping wing model in hovering flight by experiment and numerical simulation. The measurement of unsteady forces and flow patterns around the wing were conducted using a dynamically scaled wing model in the mineral-oil tank. The wing kinematics were directly derived from the experiment of a real beetle. The 3D flow structures of the flapping wing were captured by using air bubble visualization while forces were measured by a sensor attached at the wing base. In comparison, the size and topology of spiral leading edge vortex, trailing edge vortex and tip vortex are well matched from experimental and numerical studies. In addition, the time history of forces calculated from numerical simulation is also similar to that from theforce measurement. A difference of average force is in order of 10 percent. The results indicate that the leading edge vortex due to rotational acceleration at the end of the stroke during flapping wing causes significant reduction of lift. The present study provides useful information on hover flight to develop a beetle-like flapping wing Micro Air Vehicle.</P>
Three-dimensional kinematics of beetle wings in free flight
Tien Van Truong,Hieu Trung Tran,Tuyen Quang Le,Hoon Choel Park,Doyoung Byun 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
In this study, the 3D kinematics parameters of of Allomyrina dichotoma has been obtained by using 3D reconstruction from two synchronized, the high speed cameras digitalized marked points on the wings. Wing tip trajectory, attack angle and camber deformation are presented. Beetle flaps at 38Hz with flapping angle of 165 degree, the angle of attack varies significant along the spanwise direction in free flight condition. In addition, camber deformation changes greatly with time at difference section. These characteristics highlight the extraordinary flexibility of beetle’s hindwing compared with other insects: honeybee, dragonfly. Furthermore, the interaction between the elytron and the hind wing through the leading edge vortex (LEV) and trailing edge vortex (TEV) generation and development are figured out through the smoke wire visualization technique.
Secrecy Performance of Energy Harvesting Wireless Networks in the Presence of Multiple Eavesdroppers
Tien-Vu Truong,Nhan-Van Vo,Dac-Binh Ha,Duc-Dung Tran 한국정보통신학회 2016 2016 INTERNATIONAL CONFERENCE Vol.8 No.1
This paper investigates the physical layer secrecy performance of radio frequency energy harvesting wireless networks over Rayleigh fading channels. The considered RF-EH system consists of a power transfer station, a source and a destination in the presence of multiple passive eavesdroppers. By using statistical characteristics of the signal-to-noise ratio (SNR), the exact closed-form expressions of existence probability of secrecy capacity is derived. Finally, simulation results are provided to confirm the correctness of our calculation.
Physical Layer Secrecy Performance of RF-EH Networks with Multiple Eavesdroppers
Truong, Tien-Vu,Vo, Nhan-Van,Ha, Dac-Binh,Tran, Duc-Dung The Korea Institute of Information and Commucation 2016 Journal of information and communication convergen Vol.14 No.3
In this study, we investigate the physical layer secrecy performance of RF energy harvesting (EH) networks over Rayleigh fading channels. The RF-EH system considered here consists of one power transfer station, one source, one destination, and multiple passive eavesdroppers. The source harvests energy from the power transfer station and transmits the information to the destination by using a time switching-based relaying protocol. The eavesdroppers try to extract the transmitted information without an active attack. By using the statistical characteristics of the signal-to-noise ratio (SNR), the exact closed-form expressions of the existence probability of the secrecy capacity and the secrecy outage probability are derived. Further, we analyze the secrecy performance of the system with respect to various system parameters, such as the location of the system elements and the number of eavesdroppers. Finally, the equivalent Monte Carlo simulation results are provided to confirm the correctness of our calculations.
Synthesis of Nano Titanium Dioxide and Its Application in Photocatalysis
Truong Van Chuong,Le Quang Tien Dung,Dinh Quang Khieu 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
This paper presents a simple way to synthesize titaniumdioxide nanotubes by using a microwave- assisted reaction of TiO2 particles and NaOH solution. The main advantage of the introduction of microwave into the reaction system is the extremely rapid kinetics for synthesis. This method is simple and easy to reproduce. Structural and microstructural characterizations of titania nanotubes were accomplished using X-ray diffraction (XRD), scanning-electron microscopy (SEM) and transmission-electron microscopy (TEM) techniques. The specific surface area was calculated using the Brunauer-Emmett-Teller model and was found to be 52 m2/g. A high photocatalysis of our TiO2 nanotubes was obtained. This paper presents a simple way to synthesize titaniumdioxide nanotubes by using a microwave- assisted reaction of TiO2 particles and NaOH solution. The main advantage of the introduction of microwave into the reaction system is the extremely rapid kinetics for synthesis. This method is simple and easy to reproduce. Structural and microstructural characterizations of titania nanotubes were accomplished using X-ray diffraction (XRD), scanning-electron microscopy (SEM) and transmission-electron microscopy (TEM) techniques. The specific surface area was calculated using the Brunauer-Emmett-Teller model and was found to be 52 m2/g. A high photocatalysis of our TiO2 nanotubes was obtained.