Transient heat transfer and crust evolution during debris bed melting process in the hypothetical severe accident of HPR1000

Lv Chao,Li Gen,Gao Jinchen,Wang Jinshi,Yan Junjie 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.8

In the late in-vessel phase of a nuclear reactor severe accident, the internal heat transfer and crust evolution during the debris bed melting process have important effects on the thermal load distribution along the vessel wall, and further affect the reactor pressure vessel (RPV) failure mode and the state of melt during leakage. This study coupled the phase change model and large eddy simulation to investigate the variations of the temperature, melt liquid fraction, crust and heat flux distributions during the debris bed melting process in the hypothetical severe accident of HPR1000. The results indicated that the heat flow towards the vessel wall and upper surface were similar at the beginning stage of debris melting, but the upward heat flow increased significantly as the development of the molten pool. The maximum heat flux towards the vessel wall reached 0.4 MW/m2 . The thickness of lower crust decreased as the debris melting. It was much thicker at the bottom region with the azimuthal angle below 20 and decreased rapidly at the azimuthal angle around 20e50. The maximum and minimum thicknesses were 2 and 90 mm, respectively. By contrast, the distribution of upper crust was uniform and reached stable state much earlier than the lower crust, with the thickness of about 10 mm. Moreover, the sensitivity analysis of initial condition indicated that as the decrease of time interval from reactor scram to debris bed driedout, the maximum debris temperature and melt fraction became larger, the lower crust thickness became thinner, but the upper crust had no significant change. The sensitivity analysis of in-vessel retention (IVR) strategies indicated that the passive and active external reactor vessel cooling (ERVC) had little effect on the internal heat transfer and crust evolution. In the case not considering the internal reactor vessel cooling (IRVC), the upper crust was not obvious

Correlation of Liquid-Liquid Equilibrium of Four Binary Hydrocarbon-Water Systems, Using an Improved Artificial Neural Network Model

Lv, Hui-Chao,Shen, Yan-Hong Korean Chemical Society 2013 대한화학회지 Vol.57 No.3

A back propagation artificial neural network model with one hidden layer is established to correlate the liquid-liquid equilibrium data of hydrocarbon-water systems. The model has four inputs and two outputs. The network is systematically trained with 48 data points in the range of 283.15 to 405.37K. Statistical analyses show that the optimised neural network model can yield excellent agreement with experimental data(the average absolute deviations equal to 0.037% and 0.0012% for the correlated mole fractions of hydrocarbon in two coexisting liquid phases respectively). The comparison in terms of average absolute deviation between the correlated mole fractions for each binary system and literature results indicates that the artificial neural network model gives far better results. This study also shows that artificial neural network model could be developed for the phase equilibria for a family of hydrocarbon-water binaries.

Study on Calculation Method of Long Term Deformation of RAC Beam based on Creep Adjustment Coefficient

Chao Liu,Zhenyuan Lv,Chao Zhu,Guoliang Bai,Yu Zhang 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.1

The creep shrinkage of concrete is an important factor in the long-term deformation of concrete structures. It is also a key link for solving long-term deformation calculation accuracy and complex calculation forms. In this paper, a 1200-day long-term deformation test was conducted on beams with 0%, 50%, and 100% substitution ratios of recycled coarse aggregate. Meanwhile, based on the principle of virtual work, the creep coefficient of recycled concrete is introduced into the calculation of additional curvature of the beam section, and the formula for calculating the long-term deformation of recycled concrete is established. According to the size of recycled coarse aggregate, through the calculation of creep and shrinkage of concrete, the regeneration adjustment coefficient of concrete creep and shrinkage, the calculation results into three typical model of ordinary concrete creep and shrinkage, creep and shrinkage of concrete and regeneration model of deformation calculation of long period, the calculated and experimental results agree well; based on this, the deflection increase coefficient is proposed, which simplifies the long-term calculation formula. It not only can meet the calculation accuracy requirements, but also can be easily adapted to engineering promotion.

Modeling of the phase equilibria of aqueous two-phase systems using three-dimensional neural network

Hui-Chao Lv,Da Yong Tian 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.1

A three-dimensional neural network model has been designed for representing the phase equilibrium data related to aqueous two-phase systems. The polyvinyl pyrrolidone/phosphate/water system was selected as the model system to demonstrate the point of interest. The collected experimental data were categorized into two subsets, training and validation sets, not only to find the suitable network configuration but also to prevent the overfitting problem. Meanwhile, the weight comparison method was proposed to optimize the three-dimensional neural net. The results of accuracy comparison indicate that it outperforms the two-dimensional neural network on some details and can further enhance the calculation accuracy of the phase equilibrium data for these investigated aqueous two-phase systems. The development of the neural network in the three-dimensional space should be a research project of concern.

A newly developed tridimensional neural network for prediction of the phase equilibria of six aqueous two-phase systems

Hui-Chao Lv,Yong Zheng 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.57 No.-

A newly developed tridimensional neural network (TRDNN) has been utilized to represent the phaseequilibria of six polyethylene glycol (PEG)-inorganic salt aqueous two-phase systems (ATPSs).18 data setstotaling 108 experimental data in the temperature range (298.2–318.2 K) were categorized into training,test and validation sets in order to teach the model about the input-output relationships and validate itspredictive ability. The optimal configuration of the model was found to be {5, [3,4,5], 3} and the systemerror for the training process was determined as 0.0055. Results indicate that the TRDNN model hasbetter prediction performance as compared to the two-dimensional model. The standard deviationscorresponding to three data sets for the TRDNN model were 0.0057, 0.0068 and 0.0055, while those forthe two-dimensional model were 0.0065, 0.0078 and 0.0062, respectively. Moreover, it incorporates themolecular weight of polymer, salt type and temperature in one model and can reflect the effects of thesefactors on the phase behavior of these ATPSs correctly.

Prevalence and Genetic Characterization of Toxoplasma gondii in Pet Dogs in Central China

Wei-Feng Qian,Wen-Chao Yan,Tian-Qi Wang,Kai Zhai,Li-Fang Han,Chao-Chao Lv 대한기생충학열대의학회 2015 The Korean Journal of Parasitology Vol.53 No.1

The prevalence and genotype of Toxoplasma gondii infection in dogs in Henan Province, Central China was investigated. A total of 125 blood samples were collected from pet dogs during April to June 2013, and all samples were examined by indirect hemagglutination antibody test (IHA) and nested PCR. The overall T. gondii prevalence in pet dogs was 24.0% (30/125), with 20.8% (26/125) in IHA and 10.4% (13/125) in PCR, respectively. No statistical associations were found between animal gender and age and the prevalence of T. gondii infection. Thirteen positive DNA samples were genotyped using 11 PCR-RFLP markers, including SAG1, (3’+5’) SAG2, alt.SAG2, SAG3, BTUB, GRA6, c22-8, c29- 2, L358, PK1, and Apico. Of these, only 2 samples were genotyped with complete data for all loci, and a novel genotype (type III at SAG3 and GRA6 loci, and type I at other loci) was identified. This is the first report of genetic characterization of T. gondii infection in dogs in China.

Diffusion-Weighted Magnetic Resonance Imaging in the Diagnosis of Cerebral Venous Thrombosis : A Meta-Analysis

Lv, Bin,Jing, Feng,Tian, Cheng-lin,Liu, Jian-chao,Wang, Jun,Cao, Xiang-yu,Liu, Xin-feng,Yu, Sheng-yuan The Korean Neurosurgical Society 2021 Journal of Korean neurosurgical society Vol.64 No.3

Objective : A role of diffusion-weighted imaging (DWI) in the diagnosis of cerebral venous thrombosis (CVT) is not well-understood. This study evaluates the effectiveness of DWI in the diagnosis of CVT. Methods : Literature search was conducted in electronic databases for the identification of studies which reported the outcomes of patients subjected to DWI for CVT diagnosis. Random-effects meta-analyses were performed to achieve overall estimates of important diagnostic efficiency indices including hyperintense signal rate, the sensitivity and specificity of DWI in diagnosing CVT, and the apparent diffusion coefficient (ADC) of DWI signal areas and surrounding tissue. Results : Nineteen studies (443 patients with 856 CVTs; age 40 years [95% confidence interval (CI), 33 to 43]; 28% males [95% CI, 18 to 38]; symptom onset to DWI time 4.6 days [95% CI, 2.3 to 6.9]) were included. Hyperintense signals on DWI were detected in 40% (95% CI, 26 to 55) of the cases. The sensitivity of DWI for detecting CVT was 22% (95% CI, 11 to 34) but specificity was 98% (95% CI, 95 to 100). ADC values were quite heterogenous in DWI signal areas. However, generally the ADC values were lower in DWI signal areas than in surrounding normal areas (mean difference-0.33×10-3 ㎟/s [95% CI, -0.44 to -0.23]; p<0.00001). Conclusion : DWI has a low sensitivity in detecting CVT and thus has a high risk of missing many CVT cases. However, because of its high specificity, it may have supporting and exploratory roles in CVT diagnosis.

Analysis of Local Surface Plasmon Resonance in Multilayered Au/Ag/Graphene Nanoshells

Chao Liu,Zhaoting Liu,Jingwei Lv,Tao Sun,Qiang Liu,Haiwei Mu,Paul K. Chu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.5

"The localized surface plasmon resonance (LSPR) properties of Au/Ag/graphene nanoshells are studied by discrete dipole approximation (DDA). The coupled resonance wavelengths show a remarkable dependence on the graphene thickness as well as refractive index of the surrounding medium. The resonance wavelengths of Au/Ag/graphene nanoshells red-shift as the thickness of the graphene layer is increased, when the radii of the Au core and Ag interlayer are 40 nm and 45nm, respectively. Specifically, the longer wavelength red-shifts from 540 nm to 740 nm when the refractive index varies from 1.25 to 2.05. "

Analysis of Localized Surface Plasmon Resonance in Ag/ITO/CdS/SiO2 Multilayered Nanostructured Composite

Chao Liu,Jingwei Lv,Famei Wang,Qiang Liu,Haiwei Mu,Tao Sun,Qiang Liu,Paul K. Chu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2015 NANO Vol.10 No.8

Multilayered nanoshells have attracted much attention due to their unique optical, electronic and magnetic properties. In this work, numerical calculation using discrete dipole approximation (DDA) is conducted to investigate the quad-layered metal nanoshell consisting of a particle with a dielectric silica (SiO2) core, inner cadium sulfide (CdS) shell, middle indium tin oxide (ITO) shell and outer metal silver (Ag) shell. The phenomenon is interpreted by plasmon hybridization theory and the Ag–ITO–CdS–SiO2 multilayered nanoshells are studied by extinction spectra of localized surface plasmon resonance. The variation in the spectrum peak with nanoparticle thickness and refractive index of the surrounding medium is derived. The electric field enhancement contour around the nanoparticles under illumination is analyzed at the plasmon resonance wavelength. The |ω-->, |ω+->, and |ω-+> modes red-shift with the refractive index of the surrounding medium and increase in the layer thickness causes either blue-shift or red-shift as shown by the extinction spectra. The mechanism of the red-shift or blue-shift is discussed. The |ω--> blue-shifts and furthermore, the |ω-+> and |ω+-> modes of the Ag coated multilayered nanostructure are noticeable by comparing the extinction efficiency spectra of the Au–ITO–CdS–SiO2 and Ag–ITO–CdS–SiO2 multilayered nanoshells.

L² HARMONIC 1-FORMS ON SUBMANIFOLDS WITH WEIGHTED POINCARÉ INEQUALITY

Chao, Xiaoli,Lv, Yusha Korean Mathematical Society 2016 대한수학회지 Vol.53 No.3

In the present note, we deal with $L^2$ harmonic 1-forms on complete submanifolds with weighted $Poincar{\acute{e}}$ inequality. By supposing submanifold is stable or has sufficiently small total curvature, we establish two vanishing theorems for $L^2$ harmonic 1-forms, which are some extension of the results of Kim and Yun, Sang and Thanh, Cavalcante Mirandola and $Vit{\acute{o}}rio$.