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Nguyen, Ngoc Hung,Kim, Jongrok,Hong, Seung-Hyun,Moon, Sang-Ki,Song, Chul-Hwa North-Holland Pub. Co 2017 Nuclear engineering and design Vol.325 No.-
<P><B>Abstract</B></P> <P>Coolability of the partially blocked core in a large break loss-of-coolant accident (LB LOCA) is one of the most important thermal-hydraulic concerns for nuclear reactor safety analysis. During blowdown phase and early stage of reflooding phase in the LB LOCA, the prevailing wall-to-vapor convective heat transfer plays an important role on the decay heat removal process. Experiments on single-phase convective heat transfer to vapor were conducted in 5×5 heater rod bundles containing 3×3 ballooned rods of 90% flow blockage ratio with consideration of fuel relocation phenomenon. The obtained experimental data were used to assess the single-phase heat transfer enhancement models of the COBRA-TF code. The assessment results showed underprediction of local heat transfer downstream of the flow blockage. Therefore, a new correlation has been proposed to improve the prediction capability of the conventional models by more accurately describing the flow blockage effect. The new correlation predicted the local heat transfer satisfactorily within a 20% discrepancy of the experimental data for various kinds of flow blockage configurations.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The wall-to-vapor convective heat transfer in partially blocked rod bundles is investigated. </LI> <LI> The COBRA-TF code underestimated local heat transfer downstream of flow blockage. </LI> <LI> A new correlation is developed to accurately describe the effect of flow blockage. </LI> <LI> Determination of reattachment point and maximum Nusselt number are critical for the new correlation. </LI> </UL> </P>
Hung-Ngoc Nguyen,김철홍,김종면 한국정보처리학회 2019 Journal of information processing systems Vol.15 No.2
This paper presents an optimal implementation of a Daubechies-based pipelined discrete wavelet packettransform (DWPT) processor using finite impulse response (FIR) filter banks. The feed-forward pipelined (FFP)architecture is exploited for implementation of the DWPT on the field-programmable gate array (FPGA). Theproposed DWPT is based on an efficient transpose form structure, thereby reducing its computational complexityby half of the system. Moreover, the efficiency of the design is further improved by using a canonical-signeddigit-based binary expression (CSDBE) and advanced functional sharing (AFS) methods. In this work, the AFStechnique is proposed to optimize the convolution of FIR filter banks for DWPT decomposition, which reducesthe hardware resource utilization by not requiring any embedded digital signal processing (DSP) blocks. Theproposed AFS and CSDBE-based DWPT system is embedded on the Virtex-7 FPGA board for testing. Theproposed design is implemented as an intellectual property (IP) logic core that can easily be integrated into DSPsystems for sub-band analysis. The achieved results conclude that the proposed method is very efficient inimproving hardware resource utilization while maintaining accuracy of the result of DWPT.
Nguyen, Ngoc Hung,Khan, Sheraz Ali,Kim, Cheol-Hong,Kim, Jong-Myon Elsevier 2018 Microprocessors and microsystems Vol.60 No.-
<P><B>Abstract</B></P> <P>The fast Fourier transform (FFT) algorithm is widely used in digital signal processing systems (DSPs); hence, the development of a high-performance and resource-efficient FFT processor that conforms to the processing and precision requirements of real-time signal processing is highly desirable. We propose an FFT processor for field programmable gate array (FPGA) devices, based on the radix-2-decimation-in-frequency (R2DIF) algorithm. An appropriately modified parallel double-path delay commutator (DDC) architecture for radix-2 with continuous dual-input and dual-output streams (CoDIDOS) is proposed to increase throughput and reduce latency in FFT computation. The chip-area of the proposed design is reduced by decreasing the memory footprint of the complex twiddle factor multipliers. A multiplication scheme based on a combination of the unrolled coordinate rotation digital computer (CORDIC) and the canonical signed digit-based binary expression (CSDBE) is used to multiply the complex twiddle factors without requiring memory blocks for their storage. The CSDBE technique is proposed to optimize the multiplication of constants in the architecture. The proposed FFT processor is implemented as an intellectual property (IP) core and tested on a Xilinx Virtex-7 FPGA. Experimental results confirm that the proposed design improves the speed, latency, throughput, accuracy, and resource utilization of computation on FPGA devices over existing designs.</P>
Ngoc Hung TRAN,Thi Thuy Hanh NGUYEN,Thi Phuong NGUYEN 한국유통과학회 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.7
This study aims to find out and measure the level of factors affecting the applicability of environmental management accounting (EMA) in Vietnamese automobile industry enterprises. Data was collected using both quantitative and qualitative methods. First, in general research, qualitative methodology was used to find out factors (variables) that can impact the possibility of implementing EMA in Vietnamese automobile enterprises. Second, in detailed research, all variables are measured using a quantitative method by collecting data through sampling and sending questionnaires. 500 questionnaires were sent to automobile enterprise managers and only 352 questionnaires met the criteria for the data analysis. The study used a mixed research design approach- a procedure for collecting, analyzing, and “mixing” both quantitative and qualitative research and methods in a single study to understand the research problem. Results show that 7 factors affect the possibility of implementing EMA in Vietnamese automobile industry enterprises. These factors are coercive pressure, normative pressure, mimetic pressure, business environmental uncertainty, environmental strategy, benefits when applying EMA, and task complexity. Based on the results of the study, promoting EMA in the automotive industry should depend mainly on the role of governmental departments.
Fiscal Decentralization, Corruption, and Income Inequality: Evidence from Vietnam
Hung Thanh NGUYEN,Thuy Hoang Ngoc VO,Duc Doan Minh LE,Vu Thanh NGUYEN 한국유통과학회 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.11
The objective of this research paper is to study the simultaneous relationship between fiscal decentralization, corruption, and income inequality among Vietnamese provinces. We use a balanced panel data set of 63 provinces/cities in Vietnam in the period from 2011 to 2018. The study used 3SLS-GMM (Three Stage Least Squares - Generalized Method of Moments estimator) and GMM-HAC (Generalized Method of Moments - Heteroskedastic and Autocorrelation Consistent estimator). Empirical evidence shows a strong simultaneous relationship: increased corruption will increase regional income disparities, income inequality, and increase fiscal decentralization. In addition, the results also suggest that an increase in per-capita income will reduce the level of corruption, or better control corruption of each province. The degree of increase in income inequality, which reduces fiscal decentralization, is the same for trade liberalization. All demonstrate that there is a simultaneous relationship between fiscal decentralization, corruption, and income inequality. In a region of high public governance quality, fiscal decentralization positively effects its economic growth. This issue will indirectly increase income inequality between provinces within a country. Our findings imply that a country’s fiscal decentralization strategy should be linked to improving corruption control and local governance effectiveness, indirectly improving income inequality between localities or regions.
Nguyen, Hung-Ngoc,Kim, Cheol-Hong,Kim, Jong-Myon Korea Information Processing Society 2019 Journal of information processing systems Vol.15 No.2
This paper presents an optimal implementation of a Daubechies-based pipelined discrete wavelet packet transform (DWPT) processor using finite impulse response (FIR) filter banks. The feed-forward pipelined (FFP) architecture is exploited for implementation of the DWPT on the field-programmable gate array (FPGA). The proposed DWPT is based on an efficient transpose form structure, thereby reducing its computational complexity by half of the system. Moreover, the efficiency of the design is further improved by using a canonical-signed digit-based binary expression (CSDBE) and advanced functional sharing (AFS) methods. In this work, the AFS technique is proposed to optimize the convolution of FIR filter banks for DWPT decomposition, which reduces the hardware resource utilization by not requiring any embedded digital signal processing (DSP) blocks. The proposed AFS and CSDBE-based DWPT system is embedded on the Virtex-7 FPGA board for testing. The proposed design is implemented as an intellectual property (IP) logic core that can easily be integrated into DSP systems for sub-band analysis. The achieved results conclude that the proposed method is very efficient in improving hardware resource utilization while maintaining accuracy of the result of DWPT.
AN IMPROVED HEAT TRANSFER CORRELATION FOR DEVELOPING POST-DRYOUT REGION IN VERTICAL TUBES
NGOC HUNG NGUYEN,문상기 한국원자력학회 2015 Nuclear Engineering and Technology Vol.47 No.4
A developing post-dryout region is characterized by significant heat transfer enhancements compared with the fully developed post-dryout region. The heat transfer enhancements are mainly due to upstream disturbance and entrained droplets in the region immediately downstream of the critical heat flux location. In this paper, an improved heat transfer correlation is developed for the developing post-dryout regions in vertical tubes over a wide range of flow conditions. The correlation represents a correction factor for the fully developed film-boiling look-up table to be applied to the developing post-dryout region. The new correlation significantly improves the heat transfer prediction in the developing post-dryout regions and provides very good agreement with the experimental data.