Risk analysis and maintenance decision making of natural gas pipelines with external corrosion based on Bayesian network

Buried natural gas pipelines are vulnerable to external corrosion because they are encased in a soil environment for a long time.Identifying the causes of external corrosion and taking specific maintenance measures is essential.In this work,a risk analysis and maintenance decision-making model for natural gas pipelines with external corrosion is proposed based on a Bayesian network.A fault tree model is first employed to identify the causes of external corrosion.The Bayesian network for risk analysis is determined accordingly.The maintenance strategies are then inserted into the Bayesian network to show a reduction of the risk.The costs of maintenance strategies and the reduced risk after maintenance are combined in an optimization function to build a decision-making model.Because of the limitations of historical data,some of the parameters in the Bayesian network are obtained from a probabilistic estimation model,which combines expert experience and fuzzy set theory.Finally,a case study is carried out to verify the feasibility of the maintenance decision model.This indicates that the method proposed in this work can be used to provide effective maintenance schemes for different pipeline external corrosion scenarios and to reduce the possible losses caused by external corrosion.

Hysteresis effect in current–voltage characteristics of Ni/n-type 4H-SiC Schottky structure

Hysteresis current–voltage(Ⅰ–Ⅴ) characteristics are often observed in a highly non-ideal(n > 2) as-deposited nickel(Ni)/4 H-SiC Schottky contact. However, we find that this kind of hysteresis effect also exists in an as-deposited Ni/n-type4 H-SiC Schottky structure even if the ideality factor(n) is less than 1.2. The hysteresis Ⅰ–Ⅴ characteristics is studied in detail in this paper by using the various measurements including the hysteresis Ⅰ–Ⅴ, sequentialⅠ–Ⅴ sweeping, cycle Ⅰ–Ⅴ,constant reverse voltage stress(CRVS). The results show that the hysteresis Ⅰ–Ⅴ characteristics are strongly dependent on the sweeping voltage and post-deposition annealing(PDA). The high temperature PDA(800℃) can completely eliminate this hysteresis. Meanwhile, the magnitude of the hysteresis effect is shown to decrease in the sequential Ⅰ–Ⅴ sweeping measurement, which is attributed to the fact that the electrons tunnel from the 4 H-SiC to the localized states at the Ni/ntype 4 H-SiC interface. It is found that the application of the reverse bias stress has little effect on the emission of those trapped electrons. And a fraction of the trapped electrons will be gradually released with the time under the condition of air and with no bias. The possible physical charging mechanism of the interface traps is discussed on the basis of the experimental findings.

Expressions and correlation of blood fibrinogen and IL-33 in patients with cerebral infarction combined with moderate-to-severe periodontitis

Objective:To observe the serum levels of Fibrinogen(Fg),Interleukin-33(IL-33)in patients with cerebral infarction and periodontitis,and to explore the relationship of cerebral infarction and periodontitis.Methods:104 subjects were included in this study.Among them,23 were patients with CI and CP(group CI+CP),28 with CI(group CI),28 with CP(group CP)and 25 were healthy volunteers(group H).The periodontal indexes and the serum levels of Fg and IL-33 were measured.Results:In groups of CI+CP,CP and CI the Fg and IL-33 were significantly higher than those in the group H(P<0.01).In groups of CI+CP the Fg and Il-33 was higher than group CI and CP(P<0.05).Conclusion:In patients with cerebral infarction with periodontitis,the levels of fibrinogen and interleukin-33 were both increased,and their concentrations were in direct proportion to the periodontal indexes。

TNF-α、IL-6、IL-1β Effect of omeprazole combined with amoxicillin on cytokines in gingival crevicular fluid of patients with periodontal disease

Objective:To investigate the TNF-α、IL-6、IL-1βeffect of omeprazole combined with amoxicillin on cytokines in gingival crevicular fluid of patients with periodontal disease.Methods:102 patients with periodontal disease who were treated in our hospital from June 2016 to March 2018 were selected.Randomly divided into two groups,the control group was treated with omeprazole alone,and the research group was treated with omeprazole combined with amoxicillin.The levels of inflammatory cytokines(TNF-α、IL-6、IL-1β),therapeutic effects and adverse reactions to drugs were compared between the two groups.Results:the levels of inflammatory factors(TNF-α、IL-6、IL-1β)in the study group were lower than those in the control group(P<0.05).The therapeutic effect(82.4%)of the control group was lower than that of the study group(96.1%)(P<0.05).The incidence of adverse reactions to drugs in the study group(3.8%)was lower than that in the control group(21.5%)(P<0.05).Conclusion:joint take omeprazole amoxicillin treatment of periodontal disease patients achieved ideal therapeutic efficacy.