Capacitor‑assisted active‑switched quasi‑Z‑source inverters with high voltage gain

Anh-Tuan Huynh,Anh-Vu Ho,Tae-Won Chun 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.12

This paper presents a novel topology called the capacitor-assisted active-switched quasi Z-source inverter (CA/AS-qZSI). The proposed CA/AS-qZSI topology has a high ac voltage gain and low voltage and current stresses on the diodes and extra switch in the Z-network. The design guide of the passive elements used in the proposed topology and a comparative study of the proposed CA/AS-qZSI and four other topologies with an active-switched impedance network are addressed. A new pulse-width modulation (PWM) technique using a sawtooth carrier signal is also suggested to reduce the switching losses of the diodes and switches. Compared with the traditional simple boost control method, the efficiency of CA/AS-qZSI using the new PWM technique is improved by 4–4.6%. The experimental results utilizing a prototype made in the laboratory demonstrate the performance of the proposed CA/AS-qZSI and PWM technique.

Fabrication and characterization of n-IZO / p-Si and p-ZnO:(In, N) / n-Si thin film hetero-junctions by dc magnetron sputtering

Dao, Anh Tuan,Phan, Thi Kieu Loan,Nguyen, Van Hieu,Le, Vu Tuan Hung Institute of Korean Electrical and Electronics Eng 2013 전기전자학회논문지 Vol.17 No.2

Using a ceramic target ZnO:In with In doping concentration of 2%, hetero-junctions of n-ZnO:In/p-Si and p-ZnO:(In, N)/n-Si were fabricated by depositing Indium doped n - type ZnO (ZnO:In or IZO) and Indium-nitrogen co-doped p - type ZnO (ZnO:(In, N)) films on wafers of p-Si (100) and n-Si (100) by DC magnetron sputtering, respectively. These films with the best electrical and optical properties were then obtained. The micro-structural, optical and electrical properties of the n-type and p-type semiconductor thinfilms were characterized by X-ray diffraction (XRD), RBS, UV-vis; four-point probe resistance and room-temperature Hall effect measurements, respectively. Typical rectifying behaviors of p-n junction were observed by the current-voltage (I-V) measurement. It shows fairly good rectifying behavior with the fact that the ideality factor and the saturation current of diode are n=11.5, Is=1.5108.10-7 (A) for n-ZnO:In/p-Si hetero-jucntion; n=10.14, Is=3.2689.10-5 (A) for p-ZnO:(In, N)/n-Si, respectively. These results demonstrated the formation of a diode between n-type thin film and p-Si, as well as between p-type thin film and n-Si..

The Effects of Wing Mass Asymmetry on Low-Speed Flight Characteristics of an Insect Model

Anh Tuan Nguyen,한재흥,Thanh Trung Vu 한국항공우주학회 2019 International Journal of Aeronautical and Space Sc Vol.20 No.4

Wing asymmetries can be found in real insects and flapping-wing micro air vehicles. This paper investigates some characteristics, including the trim conditions, power requirements and passive open-loop dynamics of an insect model with the asymmetry in wing mass in low-speed flight. The motion of the insect model is obtained through a simulation framework that couples an unsteady vortex-lattice method and a multibody dynamics code. The results show that a heavier wing has to be moved with a larger stroke amplitude to compensate for the wing mass asymmetry. The power required by the heavier wing is also found greater. Moreover, we can observe the asymmetries in lateral dynamics while comparing dynamic responses due to rightward and leftward gust disturbances.

Flapping flight in the wake of a leading insect

Anh Tuan Nguyen,Thanh Dong Pham,Quoc Tru Vu 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.7

This study explores the wake effects of an upstream leading insect on the flight performance of a following one. The potential-flow based aerodynamic model, which combines the unsteady panel and unsteady vortex-lattice methods, is used to compute aerodynamic loads and simulate wake structures. The accuracy of the current aerodynamic model was confirmed in this study. The paper shows that the following insect does not cause any noticeable impact on the leading insect aerodynamics, while unfavorable effects due to the presence of the leading insect were found on the following counterpart. Nonetheless, by choosing a proper wing kinematic phase, the following insect may absorb the energy of the leading insect’s trailing wake, and therefore mitigate these negative effects. The variations of the required mechanical power of the following insect against the wing kinematic phase difference were shown to be related to the travel of the leading insect’s downstroke starting vortex.

Evaluation of grinding wheel wear in wet profile grinding for the groove of the ball bearing’s inner ring by pneumatic probes

Vu Toan Thang,Nguyen Anh Tuan,Nguyen Viet Tiep 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.3

Wear is one of the most influential factors in profile grinding. The measuring of grinding wheel wear is costly and time consuming. We introduce a new online wear measuring method in a wet profile grinding for the inner ring groove of ball bearing. The advantage of this method is the reduction of electromagnetic influence of workpiece as well as the impact of grinding debris and cutting lubricant. Two pneumatic gauging probes are positioned at two different locations with the biggest gap in the wear value on the curved edge surface of the grind stone. When the compressed air flow is blown onto the working surface of the grinding wheel, the back pressure in the measuring chamber corresponding to the gap between the probe and the working surface of the grinding wheel can be measured. Therefore, the radial wear value of grinding wheel can be determined. Based on theoretical calculations and the establishment of its dynamic characteristic curve, it is demonstrated that the first probe measuring wear at the top of the curved edge surface of the grinding wheel with the parameters of the probe d 1 = 0.85; d 2 = 1.5; P = 4 Bar has a measurement range of 200 µm, a maximum speed ratio of 0.01 Bar/µm. The second probe used to capture wear at the margin of the curved edge surface of the grinding stone with the parameters of the probe d 1 = 0.65; d 2 = 1.6; P = 4 Bar has a measurement range of 140 µm, a maximum speed ratio of 0.03 Bar/µm. The experimental results show that the grinding wheel wear value varies at different points of the curved edge surface of the grinding wheel. In profile grinding for the inner ring groove of the 6208 ball bearing, the wear value at the edge of the curved edge surface of the grinding wheel is usually bigger than that at the top of the curved edge surface of the grinding wheel.

Improving the electrochemical performance of anatase titanium dioxide by vanadium doping as an anode material for lithium-ion batteries

Anh, Ly Tuan,Rai, Alok Kumar,Thi, Trang Vu,Gim, Jihyeon,Kim, Sungjin,Shin, Eui-Chol,Lee, Jong-Sook,Kim, Jaekook Elsevier 2013 Journal of Power Sources Vol.243 No.-

<P><B>Abstract</B></P> <P>Undoped and 2 wt% vanadium (V<SUP>5+</SUP>) doped TiO<SUB>2</SUB> samples are prepared in polyol medium by low-temperature solvothermal method. The as-prepared samples are annealed at 400 °C for 5 h in an air atmosphere to increase the crystallinity. The XRD pattern shows that pure anatase TiO<SUB>2</SUB> is formed in both the doped and undoped samples. The maximum sizes of nanoparticles are found to be 300 nm and 15 nm with spherical shaped morphology for undoped TiO<SUB>2</SUB> and V<SUP>5+</SUP> doped TiO<SUB>2</SUB> samples respectively. In addition, 2 wt% V<SUP>5+</SUP> doped sample exhibits excellent electrochemical performance with high reversible specific capacity and excellent rate capability compared to the undoped case. This improvement can be attributed to the substitution of the Ti<SUP>4+</SUP> ions by V<SUP>5+</SUP> ions in the TiO<SUB>2</SUB> lattice and create more Ti<SUP>4+</SUP> vacancies in the lattice. This action may lead to the generation of apparently more number of free holes in the doped p-type semiconductor. Therefore, the increased hole concentration in the valence band can contribute to the electrical conductivity of the doped sample. Vanadium doping also influences the sample crystallinity and reduces the particle size, which provides a larger active surface area than that of undoped TiO<SUB>2</SUB>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A study on V<SUP>5+</SUP> doped TiO<SUB>2</SUB> as a high performance anode for lithium ion battery. </LI> <LI> V<SUP>5+</SUP> doping significantly influence the crystal structure and particle sizes. </LI> <LI> The electronic conductivity is largely improved through V<SUP>5+</SUP> doping. </LI> <LI> V<SUP>5+</SUP> doping greatly increased both the reversible capacity and cycling stability of TiO<SUB>2</SUB>. </LI> </UL> </P>

Chemical Constituents of the Morinda tomentosa Leaves and their α-Glucosidase Inhibitory Activity

Vu, Huong Giang,Ninh, Khac Ban,Nguyen, Xuan Nhiem,Phan, Van Kiem,Chau Van, Minh,Hoang, Le Tuan Anh,Pham, Hai Yen,Bui, Huu Tai,Nguyen, Xuan Cuong,Nguyen, Hoai Nam,Kim, Seung Hyun,Kwon, Young-In,Kim, Yo Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.5

Facial artery: anatomical variations in the perioral region in cadavers

Vu Hoang Nguyen,Lin Cheng-Kuan,Tuan Anh Nguyen,Trang Huu Ngoc Thao Cai Korean Cleft Palate-Craniofacial Association 2023 Archives of Craniofacial Surgery Vol.24 No.6

Background: In recent years, there has been an increase in reports of perioral vascular complications resulting from filler injections, such as necrosis of the lip or alar rim, occlusion, and in severe cases, blindness. Conversely, the use of perioral arterial flaps is becoming more prevalent in the treatment of cleft lips, cancer, and trauma. A thorough understanding of perioral arteries is essential to minimize complications and maximize the success of these flaps. However, the course of the facial artery (FA) in the perioral region remains incompletely understood. The aim of this study was to describe the variations of the FA in the perioral region. Methods: We dissected 52 embalmed and formaldehyde-fixed Vietnamese cadavers. We then studied the size and distribution of perioral arteries in 102 specimens. Results: The superior labial artery (SLA) was the most common branch, occurring in 87.25% of cadavers, followed by the inferior labial artery (ILA) at 78.43%. The SLA primarily originated above the mouth corner (cheilion), accounting for 91.01% of cases, and predominantly exhibited a tortuous course within the submucosa (78.65%). The ILA's branching pattern varied, but it was primarily located below the cheilion (91.25%). The ILA also followed a twisted path, generally within the submucosa. The ILA exhibited two patterns: the typical pattern, distributed at the vermilion border of the lower lip (8.82%), and the horizontal labiomental artery pattern, which ran horizontally in the middle of the lower lip area (69.61%). At their origin, the SLA and ILA had average external diameters of 1.29 mm and 1.28 mm, respectively. Conclusion: Numerous anatomical variations in the FA in the perioral region were found. A detailed anatomic description, suggested landmarks, and angiography before the procedure will be useful to help doctors avoid complications.

Effectiveness Analysis of Spin Motion in Reducing Dispersion of Sounding Rocket Flight due to Thrust Misalignment

Vu Dan Thanh Le,Anh Tuan Nguyen,Lac Hong Nguyen,Ngoc Thanh Dang,Ngoc Doan Tran,한재흥 한국항공우주학회 2021 International Journal of Aeronautical and Space Sc Vol.22 No.5

This paper explores the effectiveness of spin motion in mitigating the flight dispersion of a two-stage solid-propellant rocket model due to thrust misalignment. The aerodynamic coefficients of the rocket model are obtained by the use of a panel method and semi-empirical equations. A simulation program is developed to solve the equations of motion while considering the variations of the inertial parameters. Monte Carlo simulation techniques are applied to provide statistical data that are used to analyze the relationship between the spin motion and flight dispersion. The spin motion is generated by canting the fins to generate the axial aerodynamic moment. The results show that thrust misalignment at the first stage of the rocket has a great impact on the dispersion of rocket flight. By canting the first-stage fins at a relatively large angle to create the spin motion right after launch, the dispersion area of the payload-release location can be minimized considerably. However, thrust misalignment as well as the fin cant angle at the second stage appear to have insignificant effects on the rocket flight trajectory. On the other hand, canting the fins of the second stage at a large angle may lead to an increase in the spin rate, which may be harmful to the rocket operation. The paper also shows the variation of the dispersion characteristics of rocket flight when the fin size is modified.

Improvement of Protective Properties of Top Coatings Applied on Zinc-Rich Primer by 3-Aminopropyl-Triethoxysilan and 2-(Benzothialylthio) Succinic acid

( Trinh Anh Truc ),( To Thi Xuan Hang ),( Vu Ke Oanh ),( Nguyen Tuan Dung ) 한국부식방식학회(구 한국부식학회) 2004 Corrosion Science and Technology Vol.3 No.3