Applying Bayesian networks in nuclear power plant safety analysis

AbstractOver the last decade, Nuclear energy has become one of important energy. Nuclear power systems become more complex and traditional safety methods are hard to be applied. This paper presents a novel approach for nuclear power plant safety analysis which called Bayesian Networks(BN). The BN model is constructed based on the combination of Failure Mode, Effect Analysis (FMEA) and Fault Trees Analysis(FTA). The probability of the model’s root nodes is estimated by Bayesian estimation method and Monte Carlo simulation. Bidirectional inference and sensitivity analysis of the model is also researched. At last, we use a case study to show the method’s advantages compared with traditional methods in nuclear power plant safety analysis

Non-orthogonal joint block diagonalization based on the LU or QR factorizations for convolutive blind source separation

This article addresses the problem of blind source separation, in which the source signals are most often of the convolutive mixtures, and moreover, the source signals cannot satisfy independent identical distribution generally. One kind of prevailing and representative approaches for overcoming these difficulties is joint block diagonalization (JBD) method. To improve present JBD methods, we present a class of simple Jacobi-type JBD algorithms based on the LU or QR factorizations. Using Jacobi-type matrices we can replace high dimensional minimization problems with a sequence of simple one-dimensional problems. The novel methods are more general i.e. the orthogonal, positive definite or symmetric matrices and a preliminary whitening stage is no more compulsorily required, and further, the convergence is also guaranteed. The performance of the proposed algorithms, compared with the existing state-of-the-art JBD algorithms, is evaluated with computer simulations and vibration experimental. The results of numerical examples demonstrate that the robustness and effectiveness of the two novel algorithms provide a significant improvement i.e., yield less convergence time, higher precision of convergence, better success rate of block diagonalization. And the proposed algorithms are effective in separating the vibration signals of convolutive mixtures

Oral Delivery of the Sj23LHD-GST Antigen by Salmonella typhimurium Type III Secretion System Protects against Schistosoma japonicum Infection in Mice

Schistosomiasis japonica is a zoonotic parasitic disease and occurs predominantly in Southeast Asia and China. Using a simple, cheap, yet efficient oral method to deliver the vaccine antigen would benefit to control its transmission in that the oral vaccine could be made into a preparation and mixed with feedstuffs of livestock hosts. In this study, we used an attenuated S. typhimurium strain VNP20009, whose safety has been demonstrated in phase I clinical trial, to express the bivalent Schistosoma japonicum antigen Sj23LHD-GST by an intracellular activated promoter (nirB) and deliver it to host cells through type III secretion system. After oral vaccination of this recombinant strain, efficient protection against S. japonicum challenge was induced in mice. Mean while, granuloma formation in the liver was improved significantly in the immunized mice. This protective immune response was Th1 specific type as evidenced by increase in the production of IL-12 and IFN-γ. This work provides an alternative S. japonicum vaccine for livestock and humans

Evolutionary Dynamics Analysis of Human Metapneumovirus Subtype A2: Genetic Evidence for Its Dominant Epidemic

Human metapneumovirus (hMPV) is a respiratory viral pathogen in children worldwide. hMPV is divided into four subtypes: hMPV_A1, hMPV_A2, hMPV_B1, and hMPV_B2. hMPV_A2 can be further divided into hMPV_A2a and A2b based on phylogenetic analysis. The typical prevalence pattern of hMPV involves a shift of the predominant subtype within one or two years. However, hMPV_A2, in particular hMPV_A2b, has circulated worldwide with a several years long term high epidemic. To study this distinct epidemic behavior of hMPV_A2, we analyzed 294 sequences of partial G genes of the virus from different countries. Molecular evolutionary data indicates that hMPV_A2 evolved toward heterogeneity faster than the other subtypes. Specifically, a Bayesian skyline plot analysis revealed that hMPV_A2 has undergone a generally upward fluctuation since 1997, whereas the other subtypes experienced only one upward fluctuation. Although hMPV_A2 showed a lower value of mean dN/dS than the other subtypes, it had the largest number of positive selection sites. Meanwhile, various styles of mutation were observed in the mutation hotspots of hMPV_A2b. Bayesian phylogeography analysis also revealed two fusions of diffusion routes of hMPV_A2b in India (June 2006) and Beijing, China (June 2008). Sequences of hMPV_A2b retrieved from GenBank boosted simultaneously with the two fusions respectively, indicating that fusion of genetic transmission routes from different regions improved survival of hMPV_A2. Epidemic and evolutionary dynamics of hMPV_A2b were similar to those of hMPV_A2. Overall, our findings provide important molecular insights into hMPV epidemics and viral variation, and explain the occurrence of an atypical epidemic of hMPV_A2, particularly hMPV_A2b

Voltammetry for quantitative determination of trace mercury ions in water via acetylene black modified carbon paste electrode

A sensitive acetylene black modified carbon paste electrode was fabricated for the determination of trace mercury ions in water samples. Nitric acid treatment of acetylene black (TAB) produced a porous structure with large surface area and defects, improving its performance as an electrode modifier. Under optimized conditions, the TAB/CPE showed good selectivity and sensitivity towards mercury ions. The peak current exhibited a linear relationship with mercury ion concentration from 10 nM to 0.1 mM, with a detection limit of 8.8 nM. The enhanced sensitivity results from a synergistic effect between the properties of TAB and carbon paste. The porous structure, large surface area and defects in TAB improve mercury ion adsorption and electron transfer kinetics. Meanwhile, the carbon paste provides a stable and conductive electrode base. The developed sensor showed good stability, repeatability and reproducibility, as well as acceptable recovery results when applied to detect mercury ions in simulated water samples. This simple and rapid electrochemical method holds potential for the determination of trace mercury ions in environmental water samples

Research Progress, Problems and Prospects of "Non-grain" of Cultivated Land in China

This study aims to sort out the relevant research results of the "non-grain" of cultivated land in China, summarize the research progress, and put forward questions and prospects, so as to provide theoretical reference for the research on solving the problem of "non-grain" of cultivated land to ensure food security and promote industrial development. Research methods: literature analysis and comparative analysis were adopted. Research results: most of the previous studies used the planting structure to measure the "non-grain" level of cultivated land, and few studies took changes in the quality and quantity of cultivated land as the breakthrough point. On the research scale, most of them were carried out in provinces and municipalities, and there were few multi-scale coupling studies that combined macro and micro scales. Driving factors and macro management and control strategies were the main research content, and there was little research on the construction of regional synergistic systems. In terms of research methods, most of them were quantitative analysis using mathematical statistical models, and few studies combined spatial analysis technology, model simulation and other methods. Research prospects: It is necessary to build a system for measuring the "grain" level of cultivated land, improve the accuracy of research results, strengthen multi-scale coupling research on "point, line, surface, and body", establish a regional collaborative governance mechanism, explore the application of 3S technology and geographic simulation, and grasp the temporal and spatial evolution and development trend of "non-grain" of cultivated land

Nickel-catalysed pyrolysis/gasification of biomass components

Hydrogen and syngas production have been investigated from the pyrolysis/gasification of biomass components (cellulose, xylan and lignin) in the presence of Ni-based catalysts by using a two-stage fixed-bed reaction system. Biomass samples were pyrolysed at the first stage and the derived products were gasified at the second stage. The Ni-Mg-Al and Ni-Ca-Al catalysts, prepared by co-precipitation, were applied in the gasification process. The lignin sample pyrolysed with more difficulty (56.0 wt.% of residue fraction) compared with cellulose and xylan at 500 °C, and therefore resulted in the lowest gas yield (42.7 wt.%) for the pyrolysis/gasification of lignin. However, the highest H concentration from the three types of feedstock (55.1 vol.%) was collected for the lignin sample in the presence of steam and catalyst. Carbon deposition was very low as indicated from the TPO and SEM analyses of the reacted Ni-Mg-Al catalyst. The investigation of reaction conditions showed that water injection rate (0.02 and 0.05 g min) had little influence on the gas production from the pyrolysis/gasification of lignin in the presence of the Ni-Ca-Al catalyst; however, the increase of gasification temperature from 700 to 900 °C resulted in a higher gas and hydrogen production due to the promotion of secondary reactions during the gasification process. Furthermore, coking was highest for the reacted Ni-Ca-Al catalyst at the gasification temperature of 800 °C (7.27 wt.%), when the temperature was increased from 700 to 900 °C. This work shows that the components of biomass have a significant influence on the catalytic gasification process related to hydrogen and syngas production