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Energy and exergy analyses of the Kalina system integrated with a two-phase turbine
Nguyen Van Hap,Nguyen Minh Phu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.1
The Kalina power cycle can be integrated with a two-phase turbine as a substitute for the expansion valve to yield useful mechanical energy. An energy- and exergy-based mathematical model was formulated to analyze and evaluate the performance of the proposed cycle in this study. Independent parameters, including the base ammonia-water solution concentration, separator pressure, temperature difference in the recuperator, and vapor turbine outlet pressure, were used to analyze the sensitivity of efficiencies. The results show that the proposed cycle is efficient in terms of energy and exergy efficiencies. The two-phase turbine power is much larger than the solution pump power, and the exergy destruction of the turbine is much smaller than that of a throttle valve. The effect of the base solution concentration was dominant. At low concentrations, the energy and exergy efficiency improvements were 140 % and 160 %, respectively. At high concentrations, the substitution was not significant because the solution flow rate through the two-phase turbine was negligible. Furthermore, the efficiency enhancement was notable at a high vapor turbine outlet pressure.
A Magnetization Study of Prussian-blue Analogue Na<SUB>x</SUB>Mn<SUB>y</SUB>[Fe(CN)<SUB>6</SUB>]
Nguyen Van Minh,Phung Kim Phu,Nguyen Minh Thuan,In-Sang Yang 한국자기학회 2008 Journal of Magnetics Vol.13 No.4
In this report, we present the results of a study on the effects of the particle size on the properties of the Prussian blue (PB) analog NaxMny[Fe(CN)?]. A novel synthesis method of the NaxMny[Fe(CN)?] nano-particles using an organic solvent, formamide, is employed. The size of the PB particles is found to be 100-150 ㎚ for the samples prepared in the formamide solvent, which is much smaller than that of the samples prepared using water only. The broadening of the X-ray diffraction peaks of the nano-sized PB samples is attributed to the lattice disorder and a dramatic reduction in the particle size. The compositions of the samples are confirmed by an energy-dispersive X-ray analysis (EDAX), and the result proves that the samples are actually NaxMny[Fe(CN)?] Prussian blue. The UV-vis spectra show a broad intervalence charge-transfer (CT) band in the visible region between 400 and 700 ㎚, and the absorption decreases abruptly in the green region for the nano-sized PB sample. A divergence between the field cooled (FC) and zero field cooled (ZFC) magnetization curves is observed for the nano-sized PB sample at 11 K, indicating that nanoparticles in the sample are single domain superparamagnets with a blocking temperature of 11 K. Our results reveal that the nano-sized PB samples show significantly different optical and magnetic properties than those of the bulk PB samples.
NGUYEN, Phu Ha,NGUYEN, Phi-Hung,TSAI, Jung-Fa,NGUYEN, Thanh Tam,HO, Van Nguyen,DAO, Trong-Khoi Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.12
In accordance with huge demand for capital to meet the expansion of steel production, there are more and more steel companies who have officially listed their stocks in HOSE and HNX. One of the key issues in successful initial public offerings and seasonal offerings for these companies is how to make stocks of steel companies become more attractive in the eyes of investors. The purpose of this research is to analyze the determinants of share prices of listed steel companies in Vietnam. This study utilized macro-economic variables, ratios and indicators representing characteristics of steel industry collected from Quarter 1/2006 to Quarter 4/2019 in association with the panel data and the feasible generalized least square (FGLS) model to evaluate the degree of these factors on the share prices. The results of the research show that ROE, Cons_rate, and CO2_rate are three main factors affecting the share prices of listed steel companies. Among which, ROE and Cons_rate have a positive effect, while CO2_rate has a negative effect on the share prices of listed steel companies. It also confirms the relationship between the environmental factor, construction industry factor and the stock prices. This lays foundations for recommendations for the future policies towards environmental protection and sustainable development.