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Performance measurement of lab model 50W class Radio-frequency Ion Thruster
Hoai-Duc Vu,Huong Thi Thu Nguyen,Jichul Shin 한국항공우주학회 2021 한국항공우주학회 학술발표회 논문집 Vol.2021 No.7
A 50W radio frequency (RF) Ion Thruster – iU-50 was developed and fabricated in Applied Aerospace Research Laboratory at the University of Ulsan. A theoretical analysis model of the plasma discharge was established and put into the use of predicting plasma properties and thruster performances. Designs that utilized analysis model were simulated in a 2-D PIC-DSMC simulation and yields a good level of agreement. A laboratory model was fabricated and tested in the vacuum chamber. Experiments data show that the iU-50 generates stable discharge and ion beam at the flow rate of 3 (SCCM) and 50W power supply. Sub-systems for RF Ion Thruster including RF power supply system and Measurement system were developed and fabricated. The RF power supply system which consists of an RF Power amplifier and matching network operates stably at the predetermined frequency and power with a high power transfer efficiency (up to 85%). Measurements system including Faraday probe, RPA probe, and thrust stand will be used to evaluate ion beam characteristics and thruster performance. Measured data of the Faraday probe gives an estimate of the influence of flow rate, RF Power on ion beam current density at different positions.
Adaptive sliding mode control with backstepping technique for hydraulic manipulator
Duc-Thien Tran,Hoai Vu Anh Truong,Xuan Dinh To,Bomoon Seo,Kyoung Kwan Ahn 제어로봇시스템학회 2018 제어로봇시스템학회 국내학술대회 논문집 Vol.2018 No.5
In this paper, an adaptive sliding mode control with backstepping technique is proposed regarding to controlling position of a hydraulic manipulator in joint space. The proposed control is developed based on sliding mode control, backstepping technique, and radial basis function neural network (RBFNN). In the hydraulic manipulator, the primary torques are generated by hydraulic actuators, so it helps to extend load carrying capacity of the manipulator. But it brings some challenges, such as coupling issues, uncertainties in parameter, modeling, and external disturbance in mechanical and hydraulic dynamics. The properties of the proposed control can deal to these problems to guarantee the stability requirements and improve the precision. The sliding mode control with backstepping technique is used to handle the coupling issues and to ensure the stability and robustness. Additionally, two adaptive approximators based on RBFNN compensate the uncertainties and improve the precision. Some simulations are implemented and compared to other controllers to exhibit the effectiveness of the proposed control.
Hoai-An Trinh,Hoai Vu Anh Truong,Minh-Duc Pham,Tri Cuong Do,Hong-Hee Lee,Kyoung Kwan Ahn 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.2
Using renewable energy is becoming a new tendency for vehicular applications to reduce fossil fuel consumption and minimize greenhouse gas emissions. Well-known as an eco-friendly energy source, the proton exchange membrane fuel cell (PEMFC) is extensively used in hybrid power systems to achieve the objective of zero-emission and air protection. However, this type of fuel cell offers slow dynamics and cannot adapt to abrupt load variations when used as a primary energy source. To overcome this shortcoming, battery (BAT) and/or supercapacitor (SC) are supplemented as auxiliary sources. In this paper, an innovative energy management strategy (EMS) for a PEMFC/BAT/SC hybrid power source (HPS) is proposed to improve the accuracy of power distribution from energy sources to the load. In detail, according to different characteristics of energy sources, a frequency decoupling (FD) method is designed to determine the required currents for PEMFC, BAT, and SC based on the load power demand. Besides, an adaptive DC bus control loop is utilized to guarantee a stable DC output voltage by using the BAT. The proposed EMS is simulated in a MATLAB/Simulink environment and experimentally implemented with a real-time DSP TMS320F28379D controller board. Subsequently, a test bench of a 200 W PEMFC, 24 V–12 Ah battery, and 25 V–60 F supercapacitor is conducted for experimental validation. The obtained results show that the proposed EMS is effective to coordinate energy flows between the three used sources and enhance the fuel cell performance in a hybrid power system.
Duc-Thien Tran,Hoai Vu Anh Truong,Kyoung Kwan Ahn 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.3
The paper addresses an adaptive robust position control for tracking control of a manipulator under the presence of the uncertainties, such as variant payload, modeling error, friction, and external disturbance. The proposed control uses radial basis function neural networks (RBFNN)s to approximate and cancel the uncertainties. The nonsingular fast terminal sliding mode control (NFTSMC) of the proposed control is developed to guarantees a finite-time convergence and to solve the singular issue of the terminal sliding mode control. Moreover, the learning laws are derived from the Lyapunov approach to ensure the stability and robustness of the whole system. The proposed control is compared with other controllers through both simulations and experiments on a 3-DOF manipulator to exhibit its efficiency with the variant payload and the uncertainties.
Mortality following transarterial embolization due to hemorrhage after liver venous deprivation
Thanh Dung Le,Van Sy Than,Minh Duc Nguyen,Hoai Linh Vu,Xuan Hai Dao,Hong Son Trinh 소화기인터벤션의학회 2022 Gastrointestinal Intervention Vol.11 No.2
Liver venous deprivation (LVD) is considered to be a safe and effective method that induces more rapid and important liver hypertrophy before major hepatectomy in comparison with portal vein embolization (PVE) alone. Bleeding complications after LVD or PVE are rare, but can be a life-threatening event. Herein, we report a case of perihepatic and extended subcapsular hematoma of the liver after LVD. Transarterial embolization was performed using gelfoam to control the hemorrhage; however, the patient developed irreversible liver failure and passed away after 38 days of treatment. In patients with LVD or PVE, severe post-procedural bleeding poses a substantial challenge for treatment. Arterial embolization should be carefully considered to avoid liver failure and even death, regardless of whether temporary embolization is used.
Mortality following transarterial embolization due to hemorrhage after liver venous deprivation
Thanh Dung Le,Van Sy Than,Minh Duc Nguyen,Hoai Linh Vu,Xuan Hai Dao,Hong Son Trinh 소화기인터벤션의학회 2022 International journal of gastrointestinal interven Vol.11 No.2
Liver venous deprivation (LVD) is considered to be a safe and effective method that induces more rapid and important liver hypertrophy before major hepatectomy in comparison with portal vein embolization (PVE) alone. Bleeding complications after LVD or PVE are rare, but can be a life-threatening event. Herein, we report a case of perihepatic and extended subcapsular hematoma of the liver after LVD. Transarterial embolization was performed using gelfoam to control the hemorrhage; however, the patient developed irreversible liver failure and passed away after 38 days of treatment. In patients with LVD or PVE, severe post-procedural bleeding poses a substantial challenge for treatment. Arterial embolization should be carefully considered to avoid liver failure and even death, regardless of whether temporary embolization is used.
Phuc Nguyen Thien,Giang Nguyen Thi Huong,An Vu Nguyen Thien Truong,Nam Nguyen Thanh Hoai,Anh Ly Duc,Nguyen Huynh Cam,An Hoang,Phong Mai Thanh,Hieu Nguyen Huu 한국탄소학회 2023 Carbon Letters Vol.33 No.2
In this study, graphene oxide (GO) was synthesized by the improved Hummers’ method. The degree of oxidation from graphite (Gi) to GO was determined through interlayer spacing calculated from X–ray diffraction. Besides, the effect of KMnO4:Gi ratios (X1), H2SO4 volume (X2), oxidation temperature (X3), oxidation time of stage 1 (X4), and oxidation time of stage 2 (X5) was screened by the Plackett–Burman model. The simultaneous impact of three factors that influenced the degree of oxidation (X1, X2, and X3) was studied by the Box–Behnken experimental model of response surface methodology to achieve suitable conditions for the GO synthesis process. The characterization of GO product was investigated via the modern analytical methods: X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, UV–Vis spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. In addition, the study was also carried out on a pilot scale for orientation in industrial application with the yield of 14 g/batch.
Thanh-Tung Duong,Ta Quoc Tuan,Dang Viet Anh Dung,Nguyen Van Quy,Dinh-Lam Vu,Man Hoai Nam,Nguyen Duc Chien,윤순길,Anh-Tuan Le 한국물리학회 2014 Current Applied Physics Vol.14 No.12
Polyaniline nanowires (PANI NWs) were deposited onto fluorine-doped tin oxide (FTO) glass substrate using the cyclic voltammetric method with aniline monomer precursor in HCl aqueous solution. The secondary oxidation peak plays an important role in polymerization of aniline monomer and the optimization of catalytic activity of PANI-based counter electrodes was achieved by controlling the number of cycles. The photovoltaic performance of the dye-sensitized solar cells (DSSCs) with PANI NWs counter electrodes (CEs) was optimized at 4th cycles, and then following parameters were obtained: Jsc ¼ 17.2 mA cm2, Voc ¼ 0.71 V, FF ¼ 59.3%, and efficiency (h) ¼ 7.24%. While, Jsc ¼ 14.7 mA cm2, Voc ¼ 0.77 V, FF ¼ 70.6%, and efficiency (h) ¼ 7.98% in cells with Pt CEs. The PANI NWs were attractive as an alternative CEs for the low-cost DSSCs instead of Pt.