Distribution of the Tax Burden across Companies in Vietnam: The Issue of Corporate Tax Avoidance

Kien Trung TRAN(Kien Trung TRAN ) 한국유통과학회 2023 유통과학연구 Vol.21 No.6

A New Approach for Micro-WEDM Control based on Real-Time Estimation of Material Removal Rate

Kien Trung Hoang,양승한 한국정밀공학회 2015 International Journal of Precision Engineering and Vol.16 No.2

This paper describes a new approach for controlling a micro wire electrical discharge machining (μ-WEDM) process. In thisapproach, the relative feedrate of electrodes was controlled based on the real-time estimation of material removal rate and theidentification of the workpiece height. An assisted vibration was applied to the workpiece, eliminating the limitation of a smalldischarge gap. This allows the electrode to be moved continuously, which cannot be performed in conventional WEDM. To verify theefficiency of the system, two workpieces with different shapes were used. For one workpiece, the height was varied linearly, whereasfor the other, the height was varied non-linearly. The discharge current, discharge voltage, and number of discharge pulses weremeasured using current and voltage probes. The signal was uploaded to a computer through data acquisition devices, and a LabVIEWprogram was developed to estimate the feedrate and control the stages. The experimental results showed that the developed systemworked effectively, with high machining stability and efficiency.

Improved object recognition performance of UWB radar according to different window functions

Trung Kien Nguyen,홍익표 한국전기전자학회 2019 전기전자학회논문지 Vol.23 No.2

In this paper, we implemented an Ultra-Wideband radar system using Stripmap Synthetic Apertrure Radar algorithm torecognize objects inside a box. Different window functions such as Hanning, Hamming, Kaiser, and Taylor functions toimprove image recognition performance are applied and implemented to radar system. The Ultra-Wideband radar system with3.1~4.8 GHz broadband and UWB antenna were implemented to recognize the conductor plate located inside 1m3 box. Toobtain the image, we use the propagation data in the time domain according to the 1m movement distance and use the RangeDoppler algorithm. The effect of different window functions to improve the recognition performance of the image areanalyzed. From the compared results, we confirmed that the Kaiser window function can obtain a relatively good image.

PR Controller Based Current Control Scheme for Single-Phase Inter-Connected PV Inverter

Trung-Kien Vu(부우충기엔),Se-Jin Seong(성세진) 한국산학기술학회 2009 한국산학기술학회논문지 Vol.10 No.12

최근 태양광 시스템에서는 기존의 태양광 시스템을 계통과 전원으로 상호 접속하는 것에 대한 연구에 관심 이 모아지고 있다. 단상, 삼상 시스템에 관계없이 태양광 시스템에서 태양광 인버터는 계통연계 동작에 중요한 역할 을 하기 때문에 전체 시스템에서 핵심요소로 고려된다. 태양광 인버터를 제어하기 위해서는 부하 전류 조절이 핵심요 소 중 하나이다. 일반적으로 태양광 인버터에서 이용되는 PI 제어기는 정상상태 오차와 왜란에 취약하다는 단점을 가 지고 있기 때문에 실제 시스템에 완벽하게 적용하기에는 무리가 있다. 특히, 이는 고주파영역에서의 PI와 PR 제어기 의 성능을 비교해보면 알 수 있다. 이 논문에서 제시된 PR 제어기는 무한 이득을 교류 기본파 성분에 넣을 수 있기 때문에 PR 제어기는 회전좌표계의 PI 제어기에서 사용되는 디커플링 기법과 복잡한 변환 없이 제로 정상상태오차에 도달할 수 있다. 그렇기 때문에 이 논문에서는 PI 제어기를 대체하는 이론적 분석을 통해 PR 제어기를 설계하였다. 논문에 제시되어 있는 이론을 바탕으로 한 PR 제어기를 고정 소수점 연산방식의 32비트 마이크로컨트롤러 DSP320F2812를 기반으로 한 3kW 프로토타입 태양광 인버터에 적용, 평가하였다. 또한 태양광 인버터의 제어 성능을 시뮬레이션과 실험결과를 통하여 보여주고 검증하였다. Nowadays, the PV systems have been focused on the interconnection between the power source and the grid. The PV inverter, either single-phase or three-phase, can be considered as the core of the whole system because of an important role in the grid-interconnecting operation. An important issue in the inverter control is the load current regulation. In the literature, the Proportional+Integral (PI) controller, normally used in the current-controlled Voltage Source Inverter (VSI), cannot be a satisfactory controller for an ac system because of the steady-sate error and the poor disturbance rejection, especially in high-frequency range. By comparison with the PI controller, the Proportional+Resonant (PR) controller can introduce an infinite gain at the fundamental ac frequency; hence can achieve the zero steady-state error without requiring the complex transformation and the dq-coupling technique. In this paper, a PR controller is designed and adopted for replacing the PI controller. Based on the theoretical analyses, the PR controller based control strategy is implemented in a 32-bit fixed-point TMS320F2812 DSP and evaluated in a 3kW experimental prototype Photovoltaic (PV) power conditioning system (PCS). Simulation and experimental results are shown to verify the performance of implemented control scheme in PV PCS.

Wage Differentials among Ownership Groups and Worker Quality in Vietnamese Manufacturing

Kien Trung Nguyen,Eric D. Ramstetter 연세대학교 동서문제연구원 2017 Global economic review Vol.46 No.3

Wholly foreign multinational enterprises (WFs), joint-venture multinationals (JVs), state-owned enterprises (SOEs) pay higher wages than domestic private firms in Vietnamese manufacturing. In large samples of medium–large (20+ employees) firms, conditional differentials accounting for worker education and occupation, as well as capital intensity, size, and shares of female workers, were substantially smaller, but positive and significant. Wage levels and differentials varied substantially among industries. Conditional differentials remained positive and significant for WFs and JVs in most of the 11 industries examined, but estimates of SOE-private differentials were insignificant in most industries. Robustness checks using 2007 data yielded similar results.

Seismic Demand Evaluation of Steel MRF Buildings with Simple and Detailed Connection Models

Kien Le-Trung,이기학,이재홍,이도형 한국강구조학회 2010 International Journal of Steel Structures Vol.10 No.1

A detailed connection model can take into account effects such as strength and stiffness degradation, pinching and brittle behavior while a simple one cannot. This study investigates the effects of using the detailed and simple connection models on the seismic behavior of steel moment resisting frame (MRF) buildings. The frame models designed by 1994 UBC and 2000IBC provisions involved the use of clear length dimensions of elements, panel zone models, and connection models subjected to suites of 20 accelerograms with 50/50, 10/50 and 2/50 hazard levels. The interstory drifts, column axial forces, and probability of building failure were investigated. The results show that the discrepancy of the building behaviors between using the detailed and simple connections became larger when the more severe seismic hazard levels and higher percentile values were considered. Therefore, the detailed connection models would be recommended to evaluate and predict seismic performance of steel MRF buildings.

Experimental Results on Lamellar-Type Solid Lubricants in Enhancing Minimum Quantity Lubrication Machining

Kien Nguyen, Trung,Park, Kyung-Hee,Kwon, Patrick Y. ASME International 2016 Journal of Manufacturing Science and Engineering Vol.138 No.10

Analysis and Simulation of Vector Control for PMSM using Matlab/Simulink

Trung-Kien Vu(부우충기엔),Hanju Cha(차한주) 대한전기학회 2008 대한전기학회 학술대회 논문집 Vol.2008 No.10

In this paper, the implementation of the Permanent Magnet Synchronous Machine (PMSMl model based on the Matlab/Simulink is described. Due to the analysis of the mathematical dq-modeling, a vector controlled PMSM drive simulation is approached. With the simulated system, unlike in black block models. all machine parameters are accessible for control and verification. Based on the Matlab/Simulink, the model of the PMSM with load torque is established, the simulation is studied and some conclusions are given.

A New On-Line Dead-Time Compensator for Single-Phase PV Inverter

Trung-Kien Vu(부우충기엔),Hanju Cha(차한주) 전력전자학회 2010 전력전자학술대회 논문집 Vol.2010 No.7

This paper presents a new software-based on-line dead-time compensation technique for single-phase grid-connected photovoltaic (PV) inverter system. To improve the mitigation of dead-time effect around the zero-crossing point of phase current, a selective harmonic elimination of instantaneous feedback current is used as an additional part of conventional current control scheme. Simulation and experimental results are shown to verify the effectiveness of proposed compensation method in the gridconnected power distributed generation systems.

맛 버섯 자실 체의 메탄올 및 열수추출물의 항산화 및 항염증 활성

( Trung Kien Nguyen ),신도빈 ( Do Bin Shin ),이수민 ( Su Min Lee ),임경환 ( Kyung Hoan Im ),이태수 ( Tae Soo Lee ),이우윤 ( U Youn Lee ) 한국균학회 2013 韓國菌學會誌 Vol.41 No.2

Pholiota nameko is an edible mushroom belonged to Family Strophariaceae of Agaricales, Basidiomycota. The purpose of this study was to investigate the antioxidant and anti-inflammatory activities for the methanol and hot water extracts prepared from fruiting bodies of Pholiota nameko. Besides measuring for 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity, a reducing power and a chelating activity on ferrous ions were also measured to evaluate the antioxidant activity for those extracts. To measure the anti-inflammatory activities for the extracts, nitric oxide(NO) production from lipopolysaccharide treated RAW 264.7 macrophage cells and carrageenan-induced acute hind paw edema of rats were investigated. The results showed that those extracts has a excellent chelating activity on the ferrous ions compared with positive controls. And it also turned out that extracts had a good DPPH activity and a reducing power. The NO production in LPS-treated RAW 264.7 macrophage cells were decreasing as we increased concentration of those mushroom extracts. Significant reduction of paw edema were also observed at 2~6 h after we treated methanol and hot-water extracts at the 50 mg/kg concentration to the rats which are induced acute hind paw edema by carrageenan treatment. The experimental results suggested that methanol and hot-water extracts of Pholiota nameko fruiting bodies might be used for potential source of antioxidant and anti-inflammatory agents.