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Experiment on Nearest Level Modulation algorithm for FPGA based Modular Multilevel Converters
Tran Hung Cuong,Pham Viet Phuong,Tran Van Phuong,Tran Trong Minh 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
Modular Multilevel Converters (MMC) have many advantages in comparison with conventional multilevel converters in application to high voltage system. However, the control system of MMC requires a large amount of I/O signal ports which cannot be generated by a single digital signal processor (DSP) with maximum I/O port of 24. This paper fucuses on the experimental results of aMMC that uses a Field Programmable Gate Array (FPGA) in which embedge the Nearest Level Modulation (NLM) method and capacitor voltage balancing algorithm. The MMC consists of 12 Sub-Modules (SM) in each phase to generate a 13-level ac output voltage. Applying the NLM method and capacitor voltage balancing algorithm have significantly reduced the switching frequency and produced an ac output voltage with very low harmonic distortion. The experimental results have verified by a laboratory-scale prototype and compared with the simulation results.
Viet Hung Pham,정진석,Thanh Truong Dang,Tran Viet Cuong,Seung Hyun Hur,Byung-Seon Kong,김의정 한국화학공학회 2012 Korean Journal of Chemical Engineering Vol.29 No.5
We report the effect of temperature on the extent of graphene oxide reduction by hydrazine and the dispersibility of the resulting chemically converted graphene (CCG) in polar organic solvents. The extent of graphene oxide reduction at high temperatures was only slightly higher than at low temperatures (30-50 oC), while the dispersibility of the resulting CCG in organic solvents decreased markedly with increasing temperature. The low dispersibility of CCGs prepared at high temperatures was greatly affected by reduction and influenced by the formation of an irreversible agglomerate of CCG at high temperatures. The reduction of graphene oxide at low temperatures is necessary to prepare highly dispersible CCG in organic solvents. CCG prepared at 30 oC is dispersible in N-methyl-2-pyrrolidone concentrations as high as 0.71 mg/mL. The free-standing paper made of this CCG possessed an electrical conductivity of more than 22,000 S/m, one of the highest values ever reported.
An adaptive approach for the chloride diffusivity of cement-based materials
Bao-Viet Tran,Duc-Chinh Pham,Mai-Dinh Loc,Minh-Cuong Le 사단법인 한국계산역학회 2019 Computers and Concrete, An International Journal Vol.23 No.2
Adaptive schemes are constructed in this paper for modeling the effective chloride diffusion coefficient of cementbased materials (paste and concrete). Based on the polarization approximations for the effective conductivity of isotropic multicomponent materials, we develop some fitting procedures to include more information about the materials, to improve the accuracy of the scheme. The variable reference parameter of the approximation involves a few free scalars, which are determined through the available numerical or experimental values of the macroscopic chloride diffusion coefficient of cement paste or concrete at some volume proportions of the component materials. The various factors that affect the chloride diffusivity of cement-based material (porous material structure, uncertainty of value of the chloride diffusion coefficient in water-saturated pore spaces, etc.) may be accounted to make the predictions more accurate. Illustrations of applications are provided in a number of examples to show the usefulness of the approach.
유대황,Tran Viet Cuong,Viet Hung Pham,정진석,Nguyen Tri Khoa,김의정,한성홍 한국물리학회 2011 Current Applied Physics Vol.11 No.3
Photocatalytic TiO_2 films were prepared using RF magnetron sputtering and three kinds of graphene oxide (GO) solutions with different concentration of 0.05 mg GO, 0.03 mg GO, and 0.01 mg GO in 10 ml ethanol were coated on TiO_2 films, respectively. Structures and morphologies of the samples were examined by AFM, SEM, and Raman and photocatalytic properties under UV and visible irradiation were examined respectively. The efficiency of the photodegradation is enhanced when TiO_2 thin film was coated with GO, it is related to its giant π-conjugation system and two-dimensional planar structure and efficient charge separation by coating GO. The maximum photodegradation rate was observed for TiO_2thin film coated with 0.03 mg GO. It is attributed to the increase of absorbance and scattering of photons through excess carbon in the photosystem.
Application of ANFIS to the design of elliptical CFST columns
Ngoc-Long Tran,Trong-Cuong Vo,Duy-Duan Nguyen,Van-Quang Nguyen,Huy-Khanh Dang,Viet-Linh Tran Techno-Press 2023 Advances in computational design Vol.8 No.2
Elliptical concrete-filled steel tubular (CFST) column is widely used in modern structures for both aesthetical appeal and structural performance benefits. The ultimate axial load is a critical factor for designing the elliptical CFST short columns. However, there are complications of geometric and material interactions, which make a difficulty in determining a simple model for predicting the ultimate axial load of elliptical CFST short columns. This study aims to propose an efficient adaptive neuro-fuzzy inference system (ANFIS) model for predicting the ultimate axial load of elliptical CFST short columns. In the proposed method, the ANFIS model is used to establish a relationship between the ultimate axial load and geometric and material properties of elliptical CFST short columns. Accordingly, a total of 188 experimental and simulation datasets of elliptical CFST short columns are used to develop the ANFIS models. The performance of the proposed ANFIS model is compared with that of existing design formulas. The results show that the proposed ANFIS model is more accurate than existing empirical and theoretical formulas. Finally, an explicit formula and a Graphical User Interface (GUI) tool are developed to apply the proposed ANFIS model for practical use.
Study on the Melting of the Defective Interstitial Alloys TaSi and WSi with BCC Structure
Nguyen Quang Hoc,Tran Dinh Cuong,Bui Duc Tinh,Le Hong Viet 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.8
The statistical moment method is used to study the melting of defective interstitial AB alloys, where A is the main element and B is an interstitial atom, with a body-centered-cubic (BCC) structure. The melting temperature of the AB alloy with defects is obtained from the temperature of absolute stability for the crystalline state and the equilibrium vacancy concentration. Numerical calculations are performed for the interstitial alloys TaSi and WSi. Our calculated results are in good agreement with other calculations.
Effect of Dissolved Oxygen and Oxygen Scavenger on the Etch Rate of Polysilicon
Kyong-Ho Lee,Tran Viet Cuong,Chang-Hee Hong 대한전자공학회 2020 Journal of semiconductor technology and science Vol.20 No.1
The fabrication process has been modified to stabilize the product due to the miniaturization of the semiconductor. It is also necessary to change the material in accordance with the change in the manufacturing process. In this study, we systematically examine the problems caused by the increase of dissolved oxygen in the etching process of polysilicon through single tool equipment. To overcome this issue, surfactant and oxygen scavenger were exploited not only to reduce the surface roughness but also to increase the etch rate.