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- 저자 : HAIHUA ZHAO (검색결과 4 건)
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ONE-DIMENSIONAL ANALYSIS OF THERMAL STRATIFICATION IN THE AHTR COOLANT POOL
HAIHUA ZHAO,PER F. PETERSON 한국원자력학회 2009 Nuclear Engineering and Technology Vol.41 No.7
It is important to accurately predict the temperature and density distributions in large stratified enclosures both for design optimization and accident analysis. Current reactor system analysis codes only provide lumped-volume based models that can give very approximate results. Previous scaling analysis has shown that stratified mixing processes in large stably stratified enclosures can be described using one-dimensional differential equations, with the vertical transport by jets modeled using integral techniques. This allows very large reductions in computational effort compared to three-dimensional CFD simulation. The BMIX++ (Berkeley mechanistic MIXing code in C++) code was developed to implement such ideas. This paper summarizes major models for the BMIX++ code, presents the two-plume mixing experiment simulation as one validation example, and describes the codes’ application to the liquid salt buffer pool system in the AHTR (Advanced High Temperature Reactor) design. Three design options have been simulated and they exhibit significantly different stratification patterns. One of design options shows the mildest thermal stratification and is identified as the best design option. This application shows that the BMIX++ code has capability to provide the reactor designers with insights to understand complex mixing behavior with mechanistic methods. Similar analysis is possible for liquid-metal cooled reactors.
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ONE-DIMENSIONAL ANALYSIS OF THERMAL STRATIFICATION IN THE AHTR COOLANT POOL
Zhao, Haihua,Peterson, Per F. Korean Nuclear Society 2009 Nuclear Engineering and Technology Vol.41 No.7
It is important to accurately predict the temperature and density distributions in large stratified enclosures both for design optimization and accident analysis. Current reactor system analysis codes only provide lumped-volume based models that can give very approximate results. Previous scaling analysis has shown that stratified mixing processes in large stably stratified enclosures can be described using one-dimensional differential equations, with the vertical transport by jets modeled using integral techniques. This allows very large reductions in computational effort compared to three-dimensional CFD simulation. The BMIX++ (Berkeley mechanistic MIXing code in C++) code was developed to implement such ideas. This paper summarizes major models for the BMIX++ code, presents the two-plume mixing experiment simulation as one validation example, and describes the codes' application to the liquid salt buffer pool system in the AHTR (Advanced High Temperature Reactor) design. Three design options have been simulated and they exhibit significantly different stratification patterns. One of design options shows the mildest thermal stratification and is identified as the best design option. This application shows that the BMIX++ code has capability to provide the reactor designers with insights to understand complex mixing behavior with mechanistic methods. Similar analysis is possible for liquid-metal cooled reactors.
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Defang Zhao,Lichao Yu,Weiwei Guo,Xu Meng,Yinjiang Zhang,Haihua Zhan,Jianhan Hong,Huaizhong Xu 한국섬유공학회 2022 Fibers and polymers Vol.23 No.4
This paper reports a detailed study on the long-term mechanical and dynamic mechanical performance of carbonfiber (CF) plain-woven fabric-reinforced epoxy (CF/epoxy) laminates fabricated by the hot-compression molding technique. Water-sorption experiments, mechanical property tests, and dynamic mechanical analysis (DMA) tests were performed afterimmersion in de-ionized water at different temperatures (i.e., 25 oC, 60 oC, and 80 oC) for times up to 120 days. The resultsshow that weight-gain curves for the composites at elevated temperature (i.e., 80 oC) fit the theoretical Fickian diffusion curveduring the initial immersion time, but deviate substantially as time prolongs. The flexural properties and dynamic mechanicalproperties are highly susceptible to the effects of the hygrothermal environment, and the performance for both degrade withincreasing exposure temperatures and durations. The dynamic mechanical properties partly recover after the dryingtreatment, which is caused by the irreversible degradation in the interfacial region (i.e., fiber/matrix debonding) as evidencedby morphological images from scanning electron microscopy (SEM). Finally, the long-term degradation of the compositeswas estimated and the service life of the materials was also predicted using the Arrhenius degradation theory. The outputs ofthe research show that CF/epoxy laminates have flexural strength retention of 60 % for more than 2 years at the annualtemperature of Kyoto.
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Adaptive Correlation Noise Model for DC Coefficients in Wyner-Ziv Video Coding
Hao Qin,Bin Song,Yue Zhao,Haihua Liu 한국전자통신연구원 2012 ETRI Journal Vol.34 No.2
An adaptive correlation noise model (CNM) construction algorithm is proposed in this paper to increase the efficiency of parity bits for correcting errors of the side information in transform domain Wyner-Ziv (WZ) video coding. The proposed algorithm introduces two techniques to improve the accuracy of the CNM. First, it calculates the mean of direct current (DC) coefficients of the original WZ frame at the encoder and uses it to assist the decoder to calculate the CNM parameters. Second, by considering the statistical property of the transform domain correlation noise and the motion characteristic of the frame, the algorithm adaptively models the DC coefficients of the correlation noise with the Gaussian distribution for the low motion frames and the Laplacian distribution for the high motion frames, respectively. With these techniques, the proposed algorithm is able to make a more accurate approximation to the real distribution of the correlation noise at the expense of a very slight increment to the coding complexity. The simulation results show that the proposed algorithm can improve the average peak signal-to-noise ratio of the decoded WZ frames by 0.5 dB to 1.5 dB.
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